Forecast Discussions mentioning any of
"ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 08/26/22
Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
641 PM CDT Thu Aug 25 2022
.SHORT TERM...
Issued at 208 PM CDT Thu Aug 25 2022
Through Tonight...
Overall, not too many changes in the going thinking for the rest
of today and into tonight. Stratus remains tenacious early this
afternoon, although seeing more openings around the periphery of
the main deck which is entrenched across northeast Illinois.
Showers have started developing across central and southern
Wisconsin closer to the core of cooler mid-level temperatures and
expect these to incrementally grow and expand in coverage as they
move south of the state line this afternoon. Additionally, noting
some slight additional vertical growth to cumulus from near
Galesburge, eastward towards the Kankakee River Valley in the
vicinity of a zone of differential heating which may serve as a
secondary area of isolated to scattered shower and thunderstorm
development over the coming hours. Deep shear will remain
appreciably weak, limiting storm organization and the attendant
severe risk. On top of this, subtle warming in the 700-600 mb
layer--corroborated by recent AMDAR soundings--will likely also
result in tempered instability profiles. As such, not expecting
prolific lightning producers today, but instead gradually-growing
showers with an eventually isolated-scattered threat for
lightning. The strongest cells today will be capable of producing
gusty winds, perhaps up to 40-50 mph, brief heavy rainfall, and
sharply reduced visibilities. Can`t discount the threat for a
funnel cloud or two as well near/south of the Kankakee River
Valley given the increasing low-level lapse rates/instability,
weak deep shear, and modest environmental vorticity along the
incoming cold front.
Activity should gradually dwindle this evening with the loss of
heating, although a trailing 500 mb vort may continue to force
some spotty showers across the region through the mid-late evening
hours.
Overnight there is some potential for patchy fog development,
mainly south of I-80 within a plume of deeper near-surface
moisture, although flow may remain just "strong" enough to
mitigate this threat and have left a formal mention out of the
gridded forecast for the time being.
Carlaw
&&
.LONG TERM...
Issued at 222 PM CDT Thu Aug 25 2022
Friday through Thursday...
High pressure quickly building into the area behind this
afternoon`s cold front/wave will usher in persistent N/NNE winds
of 15-20 mph on Lake Michigan late tonight into Friday afternoon.
This will promote dangerous swimming conditions (High Swim Risk)
along the Lake Michigan shore, especially from Chicago into
northwest Indiana.
The area will remain in the broader influence of surface high
pressure Friday night into Saturday night as an upper ridge drifts
eastward across region. Seasonable temps under partly cloudy
skies are expected during the day Saturday.
A broad mid-level trough stretching along the northern CONUS will
pick up a convectively enhanced mid-level wave lifting out of the
central High Plains on Saturday. Guidance has trended slower with
this wave, with dry conditions likely continuing area-wide
through at least daybreak Sunday. Shower and thunderstorm chances
will then increase through the day Sunday aided by diurnal heating
in the afternoon. The main wave will likely cross over or just
north of the CWA Sunday night. Pwats increasing to around 1.8
inches and freezing levels potentially surpassing 14kft combined
with poor mid-level lapse rates and deep forcing all support slow-
moving pockets of heavy rain, especially in and around the vort
max.
As mid-level lapse rates increase on Monday, deeper forcing with
a secondary wave will be shifting over the area in concurrence
with modest low-level drying. Shower and storm coverage will hinge
on the timing of the passage of the main trough axis, so will
maintain chances for showers and storms through the day.
A cold front associated with the Sunday-Monday wave is expected
to pass over the area on Tuesday, with a drying trend behind the
front as low-level capping increases and drier mid-level air
advects in the area. Significant model differences begin on
Tuesday due to the handling of a potential cutoff low over the
central Great Plains and the ultimate stalling location of the
cold front. Consensus guidance continues to suggest that the front
stalls just southwest of the CWA, yielding cooler and mostly dry
conditions Wednesday into the end of the week.
Kluber
&&
.AVIATION...
For the 00Z TAFs...
641 PM...Forecast concerns include...
Chance of thunderstorms early this evening.
Wind shift to north/northeast early this evening.
Low mvfr cigs overnight/Friday morning.
Isolated thunderstorms across far northern IL and over southern
Lake Michigan will continue through sunset. Coverage is expected
to remain isolated but these will continue drifting southeast and
may impact the Chicago terminals over the next hour or so. An
outflow boundary is located across far northeast IL and is
expected to move south over the next few hours, perhaps aiding by
the current shower and thunder activity. Low confidence for wind
directions with this shift, they may stay north/northwest but
given current directions behind the boundary, opted to shift winds
to the north/northeast. Speeds are expected to remain below 10kts.
Winds may turn back to the north/northwest later this evening then
shift back to the north/northeast overnight or prior to sunrise
Friday morning. Northeast winds are then expected for the
remainder of the period.
Patchy mvfr cigs are possible this evening, especially with any
precip activity but more widespread low mvfr cloud cover is
expected overnight and may persist through mid/late Friday
morning. Ifr cigs are also possible but confidence too low to
include at this time. Some patchy fog is also possible, mainly in
the usual rural locations overnight. cms
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...Beach Hazards Statement...ILZ006-ILZ103-ILZ104...4 AM Friday to
midnight Saturday.
IN...Beach Hazards Statement...INZ001-INZ002...4 AM Friday to 4 AM
Saturday.
LM...Small Craft Advisory...LMZ740-LMZ741-LMZ742...4 AM Friday to
midnight Saturday.
Small Craft Advisory...LMZ743-LMZ744-LMZ745...4 AM Friday to 4
AM Saturday.
&&
$$
Visit us at weather.gov/chicago
Follow us on Facebook, Twitter, and YouTube at:
www.facebook.com/NWSChicago
www.twitter.com/NWSChicago
www.youtube.com/NWSChicago
Area Forecast Discussion
National Weather Service Los Angeles/Oxnard CA
751 PM PDT Thu Aug 25 2022
.SYNOPSIS...25/739 PM.
High pressure and above normal temperatures will remain over the
region through Friday. An upper low will cross northern California
on Saturday, bringing a cooling trend to the area along with
gusty onshore winds. Another significant warming trend is expected
by Tuesday or Wednesday of next week.
&&
.SHORT TERM (THU-SUN)...25/750 PM.
***UPDATE***
Latest satellite/surface observations indicate stratus/fog hugging
the coastal plain with clear skies elsewhere this evening.
Current AMDAR soundings indicate marine inversion near 900 feet
deep. No unusual winds are observed.
For the immediate short-term, main concern will be the marine
layer stratus/fog. Overnight, do not anticipate the depth of the
marine inversion to change much, so any stratus/fog issues should
remain confined to the coastal plain. Given the shallow nature of
the inversion, there may be some locally dense fog overnight
(especially north of Point Conception) and this will need to be
monitored overnight in case dense fog becomes more widespread.
Overall, current forecast has good handle on the immediate short
term. So, no significant updates are planned at this time.
***From Previous Discussion***
Low clouds lingered along the beaches of the Central Coast into
this afternoon, as well as along some of the beaches S of Point
Conception, with little change expected the rest of the day,
especially along the Central Coast. Mostly sunny skies will
prevail across the forecast area this afternoon, except for some
cu buildups over the VTU County mtns and the San Gabriel Mtns in
L.A. County.
Temps this afternoon will be near normal to several degrees above
normal. The warmest vlys and lower mtns should reach the mid to
upper 90s, except upper 90s to 102 in the Antelope Vly.
Some upper level ridging is forecast to linger over the region
this afternoon then slowly weaken thru Fri, but H5 heights on Fri
will still be quite high at around 590 dam. An upper level trof
will move into the state from the NW Fri night and Sat, with H5
heights over the fcst area falling to 585-586 dam by Sat
afternoon. A weak upper level low is forecast to develop off the
central CA coast Sat night and by Sun afternoon move either
inland over that area (GFS) or to a position just off the SBA
County coast (NAM). The EC does not fcst an upper level low at
all during this period, just a weak open trof. The EC/GFS mean
ensembles are even weaker with this feature and will lean more
toward these solutions.
The marine inversion is forecast to deepen slightly the next
couple of nights, and should be generally around 1000-1500 ft deep
from N-S tonight thru Sat, then deepen further to about 1500-2000
ft Sat night into Sun morning. It will be a quiet wx pattern for
the most part over the fcst area during the period. Varying
amounts of night and morning low clouds and fog are expected along
the coast, with some inland spread to the adjacent vlys Fri night
into Sat morning, and a further inland extent Sat night into Sun
morning. Low clouds and fog will be possible in the Salinas River
Vly by early Sun morning as well. Otherwise, mostly clear skies
are expected across the region tonight thru Sun, with any
monsoonal moisture over srn CA well east of the fcst area.
Temps will turn slightly cooler Fri but still be several degrees
above normal well inland, then more significant cooling should
occur on Sat and Sun as temps fall to several degrees below
normal for many areas. Highs in the warmest vlys and lower mtns on
Fri should be in the 90s except up to 102 in the Antelope Vly,
than lower on Sat and Sun into the 80s to low 90s, except mid to
upper 90s in the Antelope Vly.
.LONG TERM (MON-THU)...25/201 PM.
There are some differences in the synoptic features of the GFS/EC
deterministic over the E pac into CA while there is much better
agreement in the mean ensembles so discussion will focus on these.
The upper level trof over CA will weaken quickly thru Mon as
upper-level high pressure starts to build back into the area. The
SW periphery of the upper-level high will be firmly entrenched
over srn CA by Tue with H5 heights around 593 dam. This upper high
will persist over the region Wed and Thu with very slow weakening.
The marine layer pattern will persist thru the extended period,
altho the extent of the night and morning low clouds will shrink
back to the coastal plain as the marine inversion lowers. By mid-
week the marine inversion will likely be below 1000 ft deep. It
also looks like onshore gradients will weaken by mid week, and
some offshore gradients to the N will be possible by Thu morning.
This should help to limit the low clouds S of Point Conception to
mainly the immediate L.A. County coast by Wed morning. Otherwise,
the mostly clear skies will continue Mon thru Thu.
The building ridge will help to boost temps over the region, with
highs as much as 5-10 deg above normal away from the coast by mid
week. Highs for the warmest vlys and lower mtns are expected to
reach the mid to upper 90s by Tue, except as high as 103 in the
Antelope Vly. The peak of the heat should be Wed and Thu when
these areas reach the upper 90s to 106, hottest in the deserts.
&&
.AVIATION...25/2326Z.
At 2250Z, the marine inversion at KLAX was based near 800 feet.
The top of the inversion was 3600 feet with a temperature of
27 degrees Celsius.
Overall, low to moderate confidence in 00Z coastal TAFs and high
confidence in valley/desert TAFs. Lower confidence for coastal
sites due to uncertainty in the behavior of the marine layer
stratus: arrival/dissipation times and flight categories.
KLAX...Overall, moderate confidence in 00Z TAF. High confidence in
return of CIG/VSBY restrictions, but only moderate confidence in
timing of arrival (could be +/- 2 hours of current 02Z forecast)
and dissipation (could be +/- 2 hours of current 17Z forecast) and
flight category (equal chance of IFR and LIFR conditions). No
significant easterly wind component is expected.
KBUR...High confidence in 00Z TAF as CAVU conditions are
anticipated through the period.
&&
.MARINE...25/748 PM.
High confidence that winds and seas will remain under Small Craft
Advisory (SCA) level through Friday morning. By Friday afternoon,
there is a 40% chance of low-end SCA level winds from Point
Conception to San Nicolas Island and around the western Channel
Islands. Lower confidence of winds making it into the Santa
Barbara Channel, so keeping winds below SCA levels there for now.
A return of more widespread, potentially SCA level NW winds from
the waters offshore from the Central Coast to San Nicolas Island
is likely Saturday afternoon and evening. Sunday afternoon, SCA
winds are likely to affect the waters near and southwest of Point
Conception.
Patchy dense fog is expected over the coastal waters again
tonight into Saturday morning, especially along the Central Coast
and the waters west of that area.
&&
.LOX WATCHES/WARNINGS/ADVISORIES...
CA...NONE.
PZ...NONE.
&&
$$
PUBLIC...Sirard
AVIATION...Thompson
MARINE...Smith
SYNOPSIS...Smith
weather.gov/losangeles
Experimental Graphical Hazardous Weather Outlook at:
https://www.weather.gov/erh/ghwo?wfo=lox
Area Forecast Discussion
National Weather Service Phoenix AZ
525 PM MST Thu Aug 25 2022
.UPDATE...00Z AVIATION DISCUSSION.
.SYNOPSIS...
The weather pattern will shift into a drier regime through the
weekend with chances for showers and thunderstorms gradually
lowering, then migrating exclusively into higher terrain regions.
Storm activity early next week may be extremely limited before
better moisture possibly begins to return during the latter half of
the week. Temperatures will hover slightly below normal through the
weekend before a warming into a near to above normal range next
week.
&&
.DISCUSSION...
Early afternoon WV satellite imagery and objective analysis shows
the predominant H5 subtropical high has consolidated over northern
Chihuahua placing the forecast area under deepening westerly flow.
Additional ridge dampening and somewhat stronger westerly winds
through the atmospheric column should be the trend through early
next week as a series of northern stream shortwaves traverse the
Great Basin. Although this west wind pattern will result in a
protracted drying process, current copious low level moisture
profiles will be more difficult to completely scour away resulting
only a slow downtrend to deep convective potential. Thus, terrain
forced storms will be common the next couple days before moisture
content falls to levels only marginally supportive for mountain
storms early next week.
Morning sounding data and in situ ACARS sampling depict boundary
layer mixing ratios still 12-14 g/kg and total column PWATs above
1.75 inches yielding weakly capped MLCape above 1000 J/kg. However,
generalized subsidence behind an exiting MCV has precluded stronger
vertical development despite the otherwise favorable thermal
profiles. 12Z HREF output continues to support previous iterations
indicating preferred thunderstorm development over the typical
initiation points (i.e. JTNP, Kofas, Table Top Wilderness, etc.), but
little sustenance and survival into lower elevations. Certainly
given the thermodynamic situation, a couple isolated lower elevation
storms are possible, however even NBM POP trends have been
deteriorating with now well less than a 25% chance of storms removed
from their terrain induced development.
The drying westerly flow pattern will become even more established
Friday and Saturday as sfc-H7 mixing ratios fall closer to a 10-12
g/kg range and PWATs tumble below 1.50 inches. Terrain outcroppings
should once again become the focal point for storm initiation though
becoming more focused into Arizona with activity completely waning
in SE California. Several models indicate the southern extent of
shortwave forcing clipping into northern and central AZ which could
conceivably aid in greater synoptic scale ascent. Various CAMs
indicate a few storms potentially clipping portions of the Phoenix
area as well as other lower elevations, however chances do not
dictate POPs much higher than 20-30%. In addition given the W/SW
steering flow, the bulk of activity would have a tendency to remain
north and east of the CWA.
The ensemble majority eventually indicates the drier westerly flow
will reach a point early next week where rainfall chances may be
precluded through virtually the entire forecast area. Forecast BUFR
soundings show mixing ratios falling below 10 g/kg while
midtropospheric temperatures begin increasing as stronger ridging
builds north into the region. Isolated afternoon storms over
southern Gila County may still continue, however mandated NBM POPs
even fall below 20% during the entire Mon-Wed time frame. During
this transition, there is growing evidence of retreating H5 ridging
allowing heights to build close to 594dm resulting in a return to
above normal temperatures. Ensemble means point towards afternoon
highs nearing or exceeding 110F by the middle of the week and
HeatRisk surging back into a moderate category.
Forecast confidence deteriorates during the latter half of next week
as ensembles diverge on the pattern evolution downstream which
eventually could influence the magnitude of return easterly flow and
moisture re-introduction. Some members (including recent operational
GFS iterations) indicate a large cutoff low stalling/retrograding
over the southern plains and allowing a better moisture return up
the Rio Grande valley. However, other members (including the 12Z
ECMWF) maintain a progressive eastern Conus pattern while
intensifying high pressure ridging over central/northern AZ and
sequestering quality moisture into northern Mexico. If this latter
solution comes to fruition, the stronger high pressure and lack of
storm activity could also easily result in a late season heat event
with a return to more widespread 110F temperatures and high
HeatRisk.
&&
.AVIATION...Updated 0025Z.
South-Central Arizona including KPHX, KIWA, KSDL, and KDVT:
Current light/variable winds to become light westerly in next hour
or so as weak outflows from t-storm remains to SW move into the
Phoenix area. Latest high-res models are now showing westerly winds
to continue well into the night, then switch to light easterly late
tonight/towards daybreak. There is still a remote (10%) chance that
an isolated -SHRA or t-storm could approach a Phx area terminal earl
this evening, but confidence is far too low to include any mention
in the TAFs. Winds to pivot back to westerly late Friday afternoon.
Once again, there is only a slight chance (10-20%) that t-storms
will impact the terminals Friday afternoon/evening, but confidence
is once again to include any mention of them in the TAFs.
Otherwise...expect FEW to SCT coverage aoa 12 kft through the TAF
period.
Southeast California/Southwest Arizona including KIPL and KBLH:
Winds at both locations will generally remain below 10 kts and favor
a southerly to southeasterly direction with periods of variable wind
directions. Lower level cloud decks will continue to thin out with
FEW-SCT coverage persisting above 12 kft. No thunderstorm activity
is expected.
&&
.FIRE WEATHER...
A gradual decline in storm chances will take place from west to east
beginning today, but the high terrain north and east of Phoenix
should remain fairly active into the weekend with good chances for
daily thunderstorms through Saturday. Substantial drying will spread
across the area starting Sunday, essentially ending rain chances
across the lower deserts and then likely even over the Arizona high
terrain for early next week. MinRH values will generally remain in a
30-35% range over lower elevations to 40-50% over the higher terrain
through Sunday, before lowering starting Monday. Apart from
thunderstorms, winds will follow familiar diurnal patterns.
&&
.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...None.
CA...None.
&&
$$
DISCUSSION...18/Kuhlman
AVIATION...Percha/Feldkircher
FIRE WEATHER...Kuhlman