Forecast Discussions mentioning any of
"ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 08/10/23
Area Forecast Discussion
National Weather Service La Crosse WI
1050 PM CDT Wed Aug 9 2023
.DISCUSSION...(This evening through Wednesday)
Issued at 228 PM CDT Wed Aug 9 2023
Key Messages:
- Isolated showers and storms this afternoon/evening. Cannot rule
out a stronger storm capable of small hail and gusty winds.
- Multiple rounds of showers and storms (50-80% chance) for Thu
night into Friday and then again Sunday.
- Seasonal temperatures for the remainder of the week, cooling
slightly for early next week.
This Afternoon/Tonight:
A modestly moist and unstable airmass exists across the forecast
area this afternoon with surface temps in the upper 70s to low 80s
and dewpoints in the low to mid 60s generating about 500-700 J/kg
of SBCAPE. The CAMs have all struggled to resolve the
thermodynamic profiles of this airmass, especially with their
dewpoint fields being 10+ degrees too low. As a result, the NAM--
of all the models-- is best depicting the boundary layer
conditions per a comparison with MSP ACARS soundings. Isolated
showers developed within this airmass by 17-18Z. However, the
boundary layer may dry further with daytime insolation and a
surface moist layer quite shallow, so updrafts will be fighting
narrow CAPE profiles and a dry lower troposphere that will act to
weaken updrafts through entrainment.
Effective shear values are only around 15-20 kts early this
afternoon, but do increase slowly through the afternoon as a 90-kt
jet and subtle shortwave wraps around a low north of Lake
Superior. With primarily linear hodographs through a lower hail
growth zone, one cannot rule out an organized cell capable of hail
up to around an inch in diameter. Upstream, a diffuse cold front
is sagging southward through central Minnesota and northwest
Wisconsin with several clusters of storms having fired along and
ahead of the boundary over the last few hours. These cells
propagate southeastward this afternoon, but confidence in how long
they will persist remains a near-term forecast challenge given
the current lack of deep shear. Convection should wane this
evening with the loss of daytime heating.
Thursday/Friday:
Upstream upper level ridging will keep pleasant and dry
conditions in place through the day on Thursday, though the ridge
axis does pass through by the afternoon and evening hours on
Thursday. Convection developing across the eastern Dakotas
propagates eastward into the western forecast area after midnight,
but will be on the decline as it begins to outruns the
instability corridor. The explicit CAM reflectivity outputs vary
in the coverage of the echos as they reach the forecast area, with
the northern locales showing the best likelihood of seeing
precipitation (60-80% chance).
The timing and evolution of the convection early Friday morning
will dictate the thunderstorm risk for Friday afternoon. A
seasonably strong upper tropospheric wave drives southeastward
through Minnesota Friday afternoon and should result in
redevelopment along and ahead of the surface cold front, but the
position of the front and the quality of the airmass over the
forecast area hinges heavily on how the previous event unfolds.
Some models try and develop convection back over southeast MN
while other solutions develop storms farther to the southeast over
WI and IL.
Saturday/Sunday:
Persistent northwest flow will result in a near carbon copy of
Thu/Fri for Sat/Sun. Saturday looks to be pleasant and dry ahead
of a low-amplitude shortwave ridge. A sharp trough digs
southeastward for Sunday, but confidence in the severe threat
remains low with the main question revolving around instability
profiles ahead of the wave and the timing of the wave itself.
Early Next Week:
The start of the week looks to feature a brief cool down behind
the Sunday cold front. Most ensemble members are pegging highs in
the mid-70s to around 80. This shot of cooler air will be short-
lived with a progressive pattern in place and shunting the upper
ridge eastward by Tuesday. This opens the door for another round
of showers and storms once cyclonic flow resumes on the backside
of the ridge late Tuesday into Wednesday.
&&
.AVIATION...(For the 06Z TAFS through 06Z Thursday night)
Issued at 1050 PM CDT Wed Aug 9 2023
CIGS: sct-bkn mid/upper level VFR clouds expected into Thu night.
WX/vsby: CAMS continue to suggest some late night shra could spark
along a sfc front slowing sinking southward across the region. Very
isolated activity via latest radar imagery, showing a decreasing
trend. Meanwhile, some of the short term guidance trigger a few
showers Thu morning/early aft from a shortwave moving southeast out
of the northern plains. Issues with saturation and amount of forcing
lowers confidence in possible impacts for the TAF sites. Will hold
with a dry forecast for now.
Next shot for shra/ts will come with an upper level shortwave/sfc
warm front Thu night/early Fri morning.
Shifting gears back to late tonight, low T/Td spread and light sfc
winds will promote fog in the mississippi river valley. However,
SCT/BKN mid level clouds moving in overnight and the near sfc wind
goes light north at KLSE by 12z (bad for fog pushing onto the
airport). Depth of the light wind layer has been increasing in the
RAP over its lasts few runs...upwards of 2 kft. HRRR/NAM12 are
lower. As it sits, the clouds might be the biggest deterrent to 1/2SM
or less FG at KLSE. For now, will likely roll with BCFG and adjust
as the cloud/wind trends become more evident.
WINDS: generally westerly this evening, becoming more
northwest/north with passage of a sfc front near 06z. Speeds less
than 10kts through the period.
&&
.ARX WATCHES/WARNINGS/ADVISORIES...
WI...NONE.
MN...NONE.
IA...NONE.
&&
$$
DISCUSSION...Skow
AVIATION.....Rieck
Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
1103 PM EDT Wed Aug 9 2023
.AVIATION...
Upper level low pressure across portions of central Canada and an
attendant upper level jet maximum will dig through Southeast
Michigan during the next 24 hours. VFR conditions are expected to
persist tonight with a combination of cloud cover and surface
gradient winds limiting the fog potential Thursday morning. Did
include a climo 6SM in hz for the northern taf sites. Main item that
will be monitored for the tafs will be shower and potential
thunderstorm chances that will occur north to south ahead of an
approaching cold front. Chances appear to be early for MBS 12-14Z
with additional initiation then at the Detroit taf sites between
19-21Z. Decided on TEMPO groups for SHRA with too low of confidence
on coverage of TSRA. Mixed boundary layer is expected to lead to NW
winds of 10 to 20 knots late Thursday afternoon post cold front.
.DTW THRESHOLD PROBABILITIES...
* Low for ceilings below 5000 feet tonight. Moderate Thursday
afternoon.
* Low for thunderstorms between 19-21Z Thursday.
&&
.PREV DISCUSSION...
Issued at 316 PM EDT Wed Aug 9 2023
DISCUSSION...
Upper level cloud debris is shedding off the earlier convective
complex that was over Missouri and expanding across southern
Michigan. There are at least a couple weaker mid level short wave
impulses over Iowa and northern Illinois, north of the stronger MCV
now over Missouri. The wave now advancing across nrn Illinois will
slide across the srn Mi border this evening. A stout mid level dry
layer will limit the extent of rain on the north side of this wave,
warranting just low chance pops. Recent ACARS soundings offer some
support for model soundings which have showed a little warmer temps
around 700mb, which may offer some capping and thus also limit the
coverage of evening convection.
A cold front now extending across Upper Michigan will be driven
south toward the Saginaw Valley by daybreak before becoming a little
weaker, less well defined, as it extends across Se Mi by afternoon.
This front is associated with the upper low now churning over
northern Ontario. Upper level divergence within the exit region of
an upper jet streak and respectable mid level convergence will
support a chance of convection Thursday, with current models
suggesting the best forcing occurring in the 15Z to 21Z time frame.
There will be a strong mid level wind field across Lower Mi on
Thursday, supporting 0-6k Bulk Shear values of 40 to 45 knots. With
instability forecast to be weak (ML CAPE of just a few hundred
J/kg), Se Mi is not outlooked for severe weather. If there is an
overachievement on instability, particularly if temps reach low 80s
and dewpoints are able to remain in the low 60s, an isolated severe
wind threat can not be ruled out. Based on the current timing
projections, the best chances for the forcing to occur concurrent
with the peak in instability will be across the eastern third of the
forecast area.
Mid level confluence/subsidence will expand across the region
Thursday night into Friday morning as the upper low rotates into
Quebec, bringing a period of subsidence and fair weather to Se Mi.
The timing and amplitude of short wave features advancing across the
Great Lakes Friday into Saturday continue to carry some degree of
forecast uncertainty, particularly with respect to the strength and
coverage of potential convection. The 12Z model suite at least have
some semblance of agreement in showing a lead wave advancing across
Lower Mi Friday afternoon/evening. Much of the ascent may outpace
the advection of the stronger instability along a trailing warm
front. There is at least enough model support to suggest some degree
of elevated instability will advect into Se Mi Friday night,
supporting a good chance for convection. Broad upper level troughing
across the Great Lakes region this weekend will support temperatures
on the cool side of normal by the end of next weekend and into next
week.
MARINE...
Weak southwest wind continues through the afternoon and evening
ahead of a cold front slowly sagging across the northern Great
Lakes. Scattered showers and storms are most likely across northern
and central Lake Huron through the rest of today ahead of this
front. There will be just a slight chance of a shower or storm for
Lake St. Clair and western Lake Erie tonight as a low pressure
system tracks up the Ohio Valley. Coverage of showers and storms
then expands across the region on Thursday as the front makes it way
through. Northwest wind increases late Thursday in its wake with
some gusts to 20-25 kt possible at times over Lake Huron. At this
time it looks most likely that the wind and waves will remain below
Small Craft Advisory for the nearshore zones. A brief period of
quiet conditions follows for early Friday before the next low
pressure system arrives from the west. This will bring the next
round of showers and storms as well as gusty southeast winds Friday
night.
&&
.DTX WATCHES/WARNINGS/ADVISORIES...
MI...None.
Lake Huron...None.
Lake St Clair...None.
Michigan waters of Lake Erie...None.
&&
$$
AVIATION.....CB
DISCUSSION...SC
MARINE.......TF
You can obtain your latest National Weather Service forecasts online
at www.weather.gov/detroit.
AREA FORECAST DISCUSSION
National Weather Service Kansas City/Pleasant Hill MO
633 PM CDT Wed Aug 9 2023
.Discussion...
Issued at 341 PM CDT WED AUG 9 2023
Key Messages:
- Limited Storm Chances in the Southern CWA
- Seasonable Temperatures Thursday, Warming This Weekend
- Precipitation Very Late Thursday; More Likely Friday Morning
Discussion:
The updated discussion at 1028am provided details on redevelopment,
primarily concerned for our southern counties. The clearing brought
in behind the MCV has increased insolation and increased instability
for areas south of Interstate 70, with MLCAPE values ranging between
750-1000 J/kg. Unfortunately MCI is a bit far north, and there have
not been any ACARS observations further south to get an idea of how
the boundary layer lapse rates have been responding, particularly in
our south. The H5 short-wave trough axis has been digging further
into the High Plains, and the surface cyclone has deepened and is
centered along the OK-TX Red River Valley, with surface troughing
extending ahead of this into southwest Missouri. Deep layer shear is
still present ahead of the mid-level vort max with 0-6km bulk shear
still around 40-45 kts. While there has been some level of
thermodynamic recovery in area of stronger shear, it appears that
the clearing did bring in some drier air around 700mb which perhaps
provided cap. On GOES Day Cloud Convection, there do appear to be a
few updrafts trying to initiate from Vernon to Benton County, MO,
but are failing to reach deep depths. This may confirm that there is
still a cap in place above a destabilizing boundary layer. While
there is still a decent environment in place from Linn [KS] to
eastern Henry [MO] Counties, it appears the better forcing with the
surface troughing is moving south of the forecast area. Subsequent
HRRR cycles since 15z today continue to push stronger updraft
initiation further south toward Interstate 44. The satellite trend
currently observed seems to support this. Therefore, only holding
onto slight chance POPs in our far south. While there is plenty of
CAPE and shear around, thinking the severe threat is extremely
limited for our area, as the storms will need time to mature and
will move out of the forecast area before becoming strong enough.
Should a robust updraft manage to start further north, strong winds
and hail around 1 inch could be possible, but expectations for this
are very low. As for the rest of the CWA north of Interstate 70,
expecting an area of H5 height rises and AVA behind the MCV that
should gradually clear out the stratiform cloud cover. A few light
showers could be possible given the increase in moisture from early
precipitation and convection, but north of Interstate 70 the forcing
is drastically decreasing. One final note for this evening and into
Thursday morning, clear skies with cooler temperatures, an increase
surface moisture, and calm winds will lead to fog potential across
much of the CWA. Will continue to monitor trends on GOES Nighttime
Microphysics Imagery as the evening progresses.
Thursday morning, expecting clear skies (though likely at least
patchy fog around). The main H5 trough that has been driving the
surface cyclone and active weather in the Ozarks Region to Tennessee
Valley will shift eastward. Eventually should see winds pick up a
bit ahead of this trough axis that should mixout patchy fog by the
late morning hours. Even with the brief H5 height rises and AVA
Wednesday Night, the subtle height falls with the main trough axis
passage may provide some passing clouds heading into Thursday
afternoon. Surface ridging though should extend eastward from the
developing high into the area, which will keep the forecast dry for
most of Thursday afternoon with relatively seasonable temperatures
across the area.
Late Thursday Night and into Friday morning, another H5 short-wave
trough is progged to drop out of the Northern Plains and increase
kinematic forcing across the middle and lower Missouri River Valley.
With previous H5 ridging, WAA will likely start late Thursday in the
evening and then continue into Friday. Therefore, a warm-moist
airmass may again be in place ahead of this feature that will
present the opportunity for rain shower and thunderstorm
development. GEFS probabilities for MUCAPE above 1000 J/kg are above
90 percent heading into Friday morning, especially for far northern
reach of the CWA. With a stronger vorticity maximum, potential for
deep layer shear will also be there. This may lead to the potential
for a few strong to severe storms. In the SWODY2 outlook, areas
along and north of Hwy. 136 are in the marginal, with the SWODY3
placing marginal risk across a large portion of the area. This is
shaped this way with convection crossing the 12z timeframe between
the Day 2 and Day 3 outlooks. For our area, this may become more of
a Friday morning event rather than Thursday late night, as current
GEFS and other ensemble probabilities focus greatest chances for at
least 0.10 inches of QPF between 12-15z Friday. However, the
propagation speed of the progged short-wave may change, and if it
speeds up could produce more prior to 12z Friday morning. This
mornings`s cycle of the 12z HREF mean with respect to QPF are also
in the same realm that most of this if favored after 12z Friday
morning. While the mid-level flow will likely be tad more
northwesterly, there is another short-wave perturbation in the
southwesterly CONUS that results in a surface cyclone, and turns low-
level flow southwesterly across much of the Southern Plains into the
middle Mississippi River Valley. This creates a WAA regime that will
send temperatures back into the upper 80s and potentially lower 90s,
along with increasing dewpoints. NBM probabilities for temperatures
at least 85F or higher are about 70 percent, with the 90th
percentile values Friday into Saturday around 93F across most of the
area. With increasing humidity, this may send heat index values into
the triple digits. One factor though will be cloud cover moving in
with the Friday vort max. But any areas of clearing may get quite
warm and muggy again.
Sunday into Monday, a stronger PV anomaly is progged to drop south
out of Canada with a strong H5 trough will bring active weather to
portions of the Upper Midwest. Would expect seasonably high values
of deep layer shear to be present with a warm unstable airmass
across the region that could support organized activity. This is
highlighted in the Day 5 portion of the extended severe weather
outlook. At this point, cannot pinpoint exact mesoscale details.
Synoptic scale ensembles though are indicating higher probabilities
for SBCAPE to exceed 1000 J/kg along with stronger convergence.
Depending on the exact track, these probabilities likely shift over
the next few days, but currently anticipate active weather
especially in northern and northeastern portions of the CWA Sunday
into Monday. Beyond the weekend, deterministic GFS/ECMWF have a
594dam high progged across the Southern Plains. However it does look
like flow across our region may be more zonal above the H5 ridge.
Temperatures more likely would remain seasonable, but if the ridge
were to amplify could see increasing temperatures. Toward the end of
next week, the 25th-75th percentile spread in the NBM for max
temperatures is between the lower 80s and the mid 90s, indicative of
the dependence on the amplification of the pattern.
&&
.Aviation...(For the 00Z TAFS through 00Z Thursday Evening)
Issued at 631 PM CDT WED AUG 9 2023
Abundant low level moisture, clear skies and light winds will lead
to the development of fog overnight. Fog is expected to buirn off
after 14Z Thursday with light winds.
&&
.EAX WATCHES/WARNINGS/ADVISORIES...
KS...NONE.
MO...NONE.
&&
$$
Discussion...Krull
Aviation...BT
Area Forecast Discussion
National Weather Service Indianapolis IN
952 PM EDT Wed Aug 9 2023
.Forecast Update...
Issued at 952 PM EDT Wed Aug 9 2023
The most concentrated and heaviest rain was now moving across areas
south of I-70, closer to the highest PWATs of around 1.8 inches and
within the higher remaining instability / 250-500 J/kg CAPE) as the
atmosphere north of I-70 has been worked over good from the heavier
rain earlier. CAMS also suggest this area will see the bulk of the
waning activity overnight before it ends from west to east toward
daybreak. Lingering cloud cover should keep any fog development
limited to patchy with only a slight temperature drop and overnight
lows in the 60s.
Loss of instability and marginal shear supports the marginal risk
for severe weather being pulled and reduced chance of thunder. Will
let the flood watch ride based on any lingering flooding and
potential for isolated flooding over the southeastern counties due
to heavier convection there.
&&
.Short Term...(This evening through Thursday)
Issued at 302 PM EDT Wed Aug 9 2023
-Flash flooding is possible in areas along and south of I-74 through
the overnight hours.
-A few storms this evening may become marginally severe, with
damaging winds the most likely hazard.
-More rain appears likely to fall overnight, with flooding most
likely in areas that see repeated rounds of heavy rainfall.
Rest of Today and Tonight:
Current satellite imagery and METAR observations across Central
Indiana depict classic signs of low level moisture and warm air
advection, with surface winds strengthening and shifting to more
southerly components as time progresses. Temperatures have begun to
approach the 80 degree threshold, and their dewpoint counterparts
have risen into the upper 60s/lower 70s across the forecast area.
This corresponds to a modest clearing trend and the development of
some towering cumulus clouds in the sky. Combined, this has allowed
thunderstorms to develop across eastern Illinois and west central
Indiana. These storms may take advantage of the tall/skinny CAPE
profile depicted in recent Indianapolis ACARS soundings and a dry
slot aloft to produce damaging wind gusts as they push ENE across
the area. High freezing levels and modest lapse rates should limit
the hail threat, and the primary threat with this system appears to
be heavy rainfall.
Given the relatively low LCLs, high freezing levels, and deep parcel
trajectories shown in forecast soundings, storms that develop are
anticipated to be particularly efficient rain producers. Thick warm
cloud layers will promote collision-coalescence micro-physical
processes within these storms, and rainfall rates greater than 2
inches an hour appear possible. The aforementioned and strengthening
low level moisture/WAA will increase PWATS through the overnight
hours towards values upwards of 2.00 inches in western and southern
portions of the county warning area, further exemplifying the
potential for a flash flooding event in our area. This threat is
likely to be maximized in a corridor south of I-74, where a
mesoscale boundary is likely to establish. This, coupled with the
approach of a parent upper level trough and its vorticity maxima,
should provide enough lift for multiple rounds of
convection/rainfall overnight. The strength of storms and intensity
of their rainfall decreases with time overnight, but given fairly
saturated soils from previous days` activity and the fairly high
confidence in heavy rainfall this evening, areas that see multiple
rounds of rainfall will need to be carefully watched for flooding as
this event unfolds.
Rainfall chances should wean off from the NW to the SE overnight,
and by daybreak, most precipitation should be clearing out of the
area. Cloud coverage lingers overnight and limits the influence of
the traditional diurnal curve as it applies to low temperatures and
winds. Overnight lows will remain in the mid to upper 60s under said
cloud coverage, and winds should not calm to the slower speeds of
the last few nights. As such, widespread fog is unlikely tonight,
but the elevated ground-level moisture from fallen precipitation may
produce patchy fog in geographically predisposed localities
during the morning commute.
Tomorrow:
Tomorrow`s weather will be characterized by a clearing trend as the
parent features eject out of the Ohio Valley into the Mid Atlantic.
In their wake, flow shifts to a more northwesterly direction,
allowing drier air to seep into the column. Some cloud coverage
associated with lingering moisture is expected, but no significant
impacts are anticipated. If cloud coverage is more stubborn and
widespread by tomorrow afternoon, afternoon highs may need to be
adjusted downwards in future forecasts, but for now, expect highs in
the upper 70s to low 80s under gradually clearing skies for your
Thursday forecast.
&&
.Long Term...(Thursday night through Wednesday)
Issued at 302 PM EDT Wed Aug 9 2023
A northwest flow pattern will persist from the northern Plains
through the Ohio Valley for much of the extended period as strong
ridging reestablishes near the south-central CONUS. This will keep
the region within a somewhat active regime as multiple shortwaves
move through the region and bring periodic chances for convection.
Uncertainty remains in exact timing/evolution of these features, but
models show two primary opportunities for convection through the
middle of next week.
Thursday night through Friday...
The beginning of the period will start off quiet with weak surface
high pressure in place. Patchy fog may develop Thursday night due to
expected rainfall tonight and optimal radiational cooling. The best
chance appears to be south of I-70 closer to the surface high where
winds will be nearly calm. Look for temperatures to fall towards
dewpoints in the low-mid 60s Friday morning. Dry conditions will
continue through the day Friday. A shortwave trough moving across
the region could lead to increasing high clouds, but no
precipitation is expected due to the dry airmass across the area.
Partly cloudy skies and increasing southwesterly flow will help warm
temperatures into the mid 80s for most.
Friday night through Wednesday...
A shortwave trough is expected to track across the region late
Friday night into Saturday with the potential for a few rounds of
convection. Models show strong low-level theta-e advection ahead of
this system will promote large amounts of CAPE during this period.
The first round of convection could arrive late overnight Friday as
a strong nocturnal LLJ leads to an MCS or cluster of storms
developing across IL and propagates towards the area. Uncertainty in
the speed of the trough limits confidence in this potential
scenario. Large amounts of CAPE and sufficient shear would pose some
risk for severe weather if storms were to develop. These storms
should move out early Saturday morning. Guidance then suggests a
strong cap will limit thunderstorm chances thereafter for part of
the day. Daytime heating and low-level theta-e advection should
eventually erode the cap during the afternoon or evening. Isolated
to scattered storms are expected to develop within this uncapped
environment, but weak overall forcing should limit greater coverage.
If thunderstorms fire up in this weakly forced environment, moderate-
strong instability and favorable deep-layer shear would support
organized convection. While confidence in this scenario is low,
severe weather potential cannot be ruled out on Saturday. Confidence
should improve as higher resolution models begin to realize the
environment.
Weak surface high pressure moves in again on Sunday behind the
previously mentioned system, providing quiet weather conditions.
Some lingering low-level moisture may be enough to support a few
diurnal showers. A deep trough moving through late Sunday into
Monday will likely bring another round of showers and storms.
Guidance begin to diverge beyond this point, but dry and seasonably
cool conditions are expected next week.
&&
.Aviation...(18Z TAF Issuance)
Issued at 505 PM EDT Wed Aug 9 2023
Impacts:
- Thunderstorms will be widespread enough along a boundary this
evening to include thunder either prevailing or VC
- MVFR and worse flying conditions possible in convection and
after convection dissipates overnight through 17z-19z Thursday
Discussion:
Convection will become widespread this evening along a boundary and
ahead of a convectively induced wave and waves ahead of a Missouri
Valley trough. Plenty of instability for thunder through the late
night. MVFR and worse flying conditions possible in thunderstorms and
likely overnight into Thursday morning.
Winds will from WSW mostly less than 10 knots and switch to WNW less
than 10 knots before daybreak.
&&
.IND WATCHES/WARNINGS/ADVISORIES...
Flood Watch until 4 AM EDT Thursday for INZ028>030-035>037-039-
043>048-051>057-060>065-067>072.
&&
$$
Update...MK
Short Term...Updike/Marcus
Long Term...Melo
Aviation...MK