Forecast Discussions mentioning any of
"ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 08/03/22
Area Forecast Discussion
National Weather Service Louisville KY
713 PM EDT Tue Aug 2 2022
...Updated Aviation Discussion...
.Short Term...(This evening through Wednesday)
Issued at 326 PM EDT Tue Aug 2 2022
...Peak Heat Indices Around/Just Over 100 Degrees Wednesday...
The upstream convective complex has continued to diminish this
afternoon, and remnant outflow continues to push southward across
Grayson and Ohio counties. Confidence on afternoon/evening
convection isn`t all that high given convective temps in the low 90s
and the lack of any notable triggers outside of remnant
outflow/differential heating. Will keep some low chance pops in the
forecast for a few popcorn showers or storms, but overall these
would be in an environment with little shear and mostly pulse in
nature. If a stronger storm does get going, then some gusty winds
would be possible given the higher DCAPE values brought on by the
lower dew points this afternoon. Best location for that to occur
would be south and east of the outflow boundary from Ohio county, to
E-town, and up through just east of Louisville. Any storm north of
the boundary would have a strong stable layer (evident on recent
AMDAR soundings) limiting gusty wind potential at the surface.
Dew points have fallen into the mid 60s for most, and expect things
to stay that way for the remainder of the daylight hours, before
they begin to rise back into the low to mid 70s for tomorrow. Given
the increased moisture, and temps expected to reach into the lower
90s for many, heat indices are expected to peak in that 100 to 105
degree range tomorrow afternoon. Have elected to issue a Special
Weather Statement to cover the hot and humid temperatures, but
expect we fall just shy of actual criteria (105) for most.
The only other near term issue will be potential for some
valley/river valley fog overnight, especially if we clear out some.
Otherwise, look for a pretty quiet night with muggy lows in the low
to mid 70s.
.Long Term...(Wednesday night through Tuesday)
Issued at 305 PM EDT Tue Aug 2 2022
Long term period should feature warm and humid conditions with
additional PoPs through the rest of the week and into the weekend.
Low level sfc winds are expected to remain south-southwesterly into
next week, so there likely won`t be a change in airmass anytime
soon. Aloft, a shortwave trough will be located over the Great Lakes
on Thursday, with a sfc frontal boundary stretching across MO to the
Great Lakes and into eastern Ontario and southern Quebec. We should
get a decent slug of moisture advected northward on Thursday, aiding
in showers and storms. Temps in the mid to upper 80s and dewpoints
in the mid 70s will support moderate destabilization, though overall
wind fields appear weak, helping to keep storms a bit unorganized.
The upper trough looks to slightly amplify on Friday, and additional
rounds of precip are expected as we remain in a warm SW sfc flow
pattern with PWATs up to 2 inches. Model soundings for Friday are
similar to Thursday, and should be another day of diurnally-enhanced
convection as peak heating ramps up destabilization. Wind profiles
remain weak, so overall effective shear will be very limited.
The cold front boundary is expected to wash out north of the Ohio
River by Saturday, so we should remain in SW flow into the weekend.
To our east, a Bermuda high pressure will retrograde back towards
the East Coast, which will help keep warm return flow and enhanced
moisture advection funneling into the Ohio Valley. Diurnally-driven
PoPs are needed through much of the weekend, with model soundings
showing similar CAPE and shear profiles as noted in the days prior.
Besides the rain chances, daily max temps are forecast to be in the
mid to upper 80s each day of the long term. With high dewpoints in
the mid 70s each day as well, it`s possible for heat indices to
approach the mid to upper 90s each day. Though overall confidence is
low given the daily PoPs, which any increased coverage of storms
along with lingering convective debris could hinder temps from
reaching the current forecast, but that might not be such a bad
thing anyway.
&&
.Aviation...(00Z TAF Issuance)
Issued at 713 PM EDT Tue Aug 2 2022
VFR conditions to prevail through the TAF period. Expect mostly
clear skies overnight with just a few passing mid and high clouds
while winds will generally be light and variable. For Wednesday,
winds will pick up out of the SSW during the mid-late morning hours
with speeds around 10 kts and occasional gusts to 20 kts possible
mainly at KHNB and KSDF.
&&
.LMK WATCHES/WARNINGS/ADVISORIES...
IN...None.
KY...None.
&&
$$
Short Term...BJS
Long Term...CJP
Aviation...JML
Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
802 PM CDT Tue Aug 2 2022
.SHORT TERM...
Issued at 246 PM CDT Tue Aug 2 2022
Through Tonight...
Quiet, warm and muggy conditions are expected through tonight,
with an increasing southerly breeze. Have been monitoring the
seemingly never-ending narrow corridor of elevated convection from
western Illinois to downstate Illinois this afternoon. However,
the lack of any Cu development over the CWA speaks to the
plentiful dry air aloft and thus capped air mass over the area
(nicely sampled by recent aircraft soundings. Near term model
forecasts indicate some dry advection from the west-northwest into
this evening into the ongoing area of thunderstorms near PIA.
Thus, while the storms are not far from southwest CWA locales,
feel reasonably confident in the dry forecast.
The area will be entrenched in the warm sector tonight as a warm
front continues to lift north. Temperatures should warm a bit for
Illinois shore locations after the lake breeze retreats back over
the lake due to increasing southerly flow aloft. A robust and low-
based low level jet will ramp up tonight, resulting in increasing
southerly winds at the surface and some gustiness, especially in
the late evening and overnight. Based on forecast soundings, some
gusts up to 30 mph are feasible, particularly over the heart of
the Chicago metro. After any temperature drop this evening,
foresee steady or rising temps overnight providing a springboard
for the hot and humid conditions on Wednesday and the fuel for the
severe weather threat, all discussed below.
Castro
Wednesday through Thursday...
An active Wednesday is in store with heat and severe
thunderstorms in focus across much of the area.
Synopsis: A longwave trough with a relatively sharp embedded
trough axis will move across the western Great Lakes on Wednesday,
with a corresponding cold front lagging the wave by up to six
hours Wednesday evening. Guidance is now in fairly good agreement
that the trough will shift across northern Illinois mid-afternoon,
with rapid destabilization leading to convective initiation by
mid-afternoon. A result effective outflow will surge southeast of
the CWA by mid- evening, with the trailing cold front possibly
initiating isolated convection early in the evening across
northwest Illinois into the northwest CWA. The cold front will
finally clear most of the CWA by mid-morning Thursday, with
continued shower and embedded storm chances across mainly the
south half of the CWA well into Thursday.
Heat: A low inversion combined with increasing dew points
Wednesday morning will result in heat index values surpassing 100F
as early as late morning south of I-80. With expected heat index
values of 105+ ahead of the convection, a Heat Advisory has been
issued for the southern CWA. The advisory may need to be expanded
northward into the southern Chicago metro depending on location
and timing of convective initiation.
Severe storms: Capping from the nocturnal inversion as well as
WAA aloft will limit low-level mixing through at least the morning
hours. Dew points should therefore surge well into the 70s from
both the limited mixing as well as advection from now-saturated
central Illinois. Daytime heating and the moisture increase along
with approaching wave will quickly erode the low-level capping by
early afternoon. Mixing heights will rapidly increase early
afternoon, the the environment likely going from little to no
cumulus to initiation of deep convection in as little as one hour.
MLCAPE values in excess of 3000 J/kg and steep lapse rates below
600 hPa will support explosive convective growth. Even with the
slight southward shift in stronger mid-level flow, effective bulk
shear will be modest at best at under 25 knots. However, the
thermo profiles will offset this deficiency. With storm tops
likely pushing 50kft and DCAPE values nearing 2000 J/kg, storms
will quickly develop an inherent damaging wind risk. Storm mode
will likely transition from pulsing storms with localized
downbursts to congealing clusters with swaths of damaging winds
across the southeast half of the CWA through late afternoon. This
is are has been upgraded to a Slight Risk for severe storm per
coordination with SPC.
Heavy rain/Flooding: The more progressive nature of the storms
compared to the past couple days has somewhat reduced the flash
flood risk across the area. However, an expansive area of Pwats
over 2" will allow for substantial rain rates with any convection.
a quick 1 to locally 2" in an hour or less is likely under these
storms. Flooding concerns may increase across the southeast CWA
Wednesday evening in the event the result cold pool slows as the
LLJ increases.
Swim risk Thursday: A NNE surge of wind behind the cold front
Thursday morning will build waves along the southern Lake Michigan
shoreline. With guidance again trending stronger and earlier with
the highest winds, dangerous swimming conditions may exist
through much of the day Thursday and into Thursday night.
Kluber
&&
.LONG TERM...
Issued at 300 PM CDT Tue Aug 2 2022
Thursday through Tuesday...
Forecast concerns include shower and thunderstorm chances through
the period and hot and humid conditions on Saturday, with heat and
humidity likely to continue on Sunday.
The dominant feature into next week will be strong 500 mb ridging
centered from the southern High Plains to the Mid South, which
places our area on the commonly active northeast flank.
Mainly dry weather is expected Thursday night through Friday and
probably Saturday as the upper ridge builds back into the region.
Minor exception Friday will be low PoPs for southeast 1/3 or 1/4
of the CWA closer to the quasi-stationary front and moderate-
strong instability axis. Highs on Friday will be in the 80s,
slightly cooler near the lake due to onshore winds favored by high
pressure over the local area.
By Saturday, highs will be back into the lower 90s, perhaps mid
90s. With dewpoints back into low/mid 70s, afternoon peak heat
indices may be in the 100-105 range, if not a bit higher if dew
points overperform (such as via ET from maturing crops). There has
been noteworthy run to run variability regarding progression of a
cold front that will move across the area over the weekend. A
faster frontal approach could result in late Saturday into
Saturday night being impacted by thunderstorms, while the current
favored timing (Sunday) would make Sunday the more active day.
Pattern for Sunday isn`t dissimilar to the forecast for Wednesday,
though with shear more on the sub-marginal side, rather than
marginal as forecast for for Wednesday, so isolated pulse
downbursts may be the severe threat if any.
All in all, there`s plenty of uncertainty from this distance as
would be expected. A slow enough frontal approach on Sunday
(similar to 12z GFS) would also potentially necessitate heat
headlines for portions of the area, given dew points into the 70s.
Beyond Sunday, the pattern remains unsettled and chance pops
warranted for the remainder of the extended for periodic shower
and thunderstorm potential, though there will likely be many dry
periods. Signs point toward high pressure over the northern Great
Lakes and north that would be expected to nose southward behind
frontal passages.
Castro/cms
&&
.AVIATION...
For the 00Z TAFs...
There is considerable uncertainty regarding the details for
tomorrow, though high confidence that the local airspace will see
increasing thunderstorm coverage during the afternoon. Various
sources of model guidance are showing quite a bit of disagreement
in the timing of thunderstorm development, but the early to mid
afternoon period appears to be the best bet at this time given the
expected position of the initiating surface trough and the
increasing warmth and humidity. One potential deviation could be a
brief late morning line that moves through in association with
outflow from activity across Wisconsin overnight. This appears to
be a lower probability scenario, but could slightly delay later
development if it does occur.
After the leading line of storms moves through, there could also
be an extended period of showers and occasional thunderstorms
behind the leading trough and ahead of the main cold front. This
is conveyed in the longer VCTS group, with the shorter TEMPO group
providing an estimate of the most likely window of more
significant coverage.
Lenning
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...Heat Advisory...ILZ023-ILZ032-ILZ033-ILZ039...10 AM Wednesday to
7 PM Wednesday.
IN...Heat Advisory...INZ001-INZ002-INZ010-INZ011-INZ019...10 AM
Wednesday to 7 PM Wednesday.
LM...Small Craft Advisory...IL nearshore waters until 7 PM Wednesday.
Small Craft Advisory...LMZ743-LMZ744-LMZ745...3 AM Wednesday to
7 PM Wednesday.
&&
$$
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Area Forecast Discussion
National Weather Service Great Falls MT
754 PM MDT Tue Aug 2 2022
.SYNOPSIS...
Dry conditions and gusty northwesterly winds across North Central
Montana with isolated showers across Southwest Montana through early
Tuesday evening. Above normal temperatures are expected tomorrow
through Thursday for the High Plains region.
&&
.UPDATE...
Continuing westerly cross-barrier flow favors some stronger winds
than originally forecast; therefore, have increased winds in the
short term, accordingly. Other than this increase in wind speed/gust
grids, no other changes are made, at this time.
- Fogleman
&&
.DISCUSSION...
A weak upper level trough continues to make its way just north of
the area today, bringing gusty winds to most of North-Central and
Southwestern Montana this afternoon. While a surface boundary
associated with this trough has brought some additional surface
moisture to parts of the area, RH values still remain in the 20s
to near 30 percent north of this boundary. Where the boundary has
yet to push through, which includes the higher elevations of the
Rocky Mountain Front and south of a Great Falls to Lewistown line,
RH values remain in the teens, which continues to result in
critical fire weather danger. In addition to the dry and breezy
conditions, a few showers and thunderstorms are beginning to
develop across Southwestern MT, which could produce gusty winds
and little to no lightning, so this may be an area to watch for
new fire starts in the coming days.
Behind this upper level trough, somewhat zonal flow will return,
which will result in continued warm, dry, and breezy conditions
across the area through Thursday. That said, a more potent upper
level trough will begin to move into the area on Thursday, which
will bring a threat of some thunderstorms to the higher terrain.
Given the dry environment, some of the storms may produce very
little rainfall, and therefore any areas that the storms move
through will need to be watched closely for new fire starts.
The upper level trough will move overhead to close out the week,
which will bring some slightly cooler temperatures and continued
thunderstorm chances, which will still pose a fire risk even if
they are a little wetter than their counterparts on Thursday. This
system will linger through Saturday, but zonal flow will return to
start next week, bringing a return to the warm, dry, and breezy
conditions to the area. Ludwig
&&
.AVIATION...
607 PM MDT Tue Aug 2 2022 (03/00Z TAF period)
Expect VFR conditions at all airfields throughout this TAF period.
Periods of breezy to gusty winds are forecast at all airfields.
These winds impact light aircraft ops, especially near mountains or
through mountain valleys. Expect to encounter reduced visibility in
haze/smoke enroute. Hot temperatures continue to place a focus on
density altitude issues.
- Fogleman
Refer to weather.gov/zlc for more detailed regional aviation weather
and hazard information.
&&
.FIRE WEATHER...
A red flag warning remains in effect until 9 PM Thursday across all
fire weather zones. Breezy, dry, and warm conditions are expected
each afternoon through Thursday evening, which in combination with
receptive fuels, would make any fire starts difficult to put out.
Cooler temperatures and lighter winds are expected Friday and
Saturday. -AM
&&
.PRELIMINARY POINT TEMPS/POPS...
GTF 91 56 93 58 / 0 0 0 0
CTB 83 54 85 57 / 0 0 0 0
HLN 93 59 94 60 / 0 0 0 0
BZN 94 52 92 55 / 10 0 0 10
WYS 76 43 79 43 / 60 30 20 10
DLN 87 51 87 53 / 10 0 10 0
HVR 86 56 92 62 / 0 0 0 0
LWT 89 54 90 56 / 0 0 0 0
&&
.TFX WATCHES/WARNINGS/ADVISORIES...
Red Flag Warning until 9 PM MDT Thursday Central and Eastern
Lewis and Clark National Forest Areas...Chouteau and Fergus
Counties...Eastern Glacier/Toole/Central/Eastern
Pondera/Liberty...Helena and Townsend Ranger Districts of the
Helena National Forest...Hill and Blaine Counties...Lewis and
Clark National Forest Rocky Mountain District-Rocky Mountain
Front...Lincoln Ranger District of the Helena National Forest.
&&
$$
http://www.weather.gov/greatfalls