Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 08/22/23
AREA FORECAST DISCUSSION
National Weather Service Wakefield VA
750 PM EDT Mon Aug 21 2023
.SYNOPSIS...
A strong ridge aloft builds eastward today. A backdoor cold
front drops south early Tuesday. Dry conditions persist through
at least Thursday morning with higher potential for precip
Friday and Saturday ahead of the next cold front.
&&
.NEAR TERM /THROUGH TUESDAY/...
As of 750 PM EDT Monday...
Latest sfc analysis indicates high pressure (1026mb) centered
over the Great Lakes. Aloft, a large ridge extends from the
Gulf of Mexico to Canada, nudging into the SE US. Moisture aloft
has allowed for cirrus to move into the local area ahead of the
front, which helped moderate temperatures today. Temps as of 740
PM ranged from the upper 70s to mid 80s.
A backdoor cold front pushes S across the area late tonight into
Tues morning as high pressure builds into the NE from the Great
Lakes. Clouds increase ahead of and behind the front with HRRR
vertically integrated smoke indicating some smoke arrives with
the clouds, but similar to today, any smoke is expected to
remain aloft with VIS not impacted. Additionally, a brief period
of patchy fog is possible across the Eastern Shore between
12AM-4AM tonight. Given SCT cloud cover overnight, lows in the
lower 70s are expected for most with upper 60s possible for
rural areas. Behind the front, dewpoints drop from N to S, with
dewpoints in the 50s reaching the I-64 corridor as early as
mid- day. Temps will be a bit cooler as well, though still in
the mid-upper 80s for most and low 80s on the Eastern Shore and
immediately near the coast. N-NE winds will be breezy through
the day, especially near the coast with winds 10-15 mph and
gusts 20 mph inland and 20-25 mph closer to the coast.
&&
.SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY/...
As of 245 PM EDT Monday...
With cool high pressure building in and the ridge aloft retreating
west, expecting cooler conditions Wed. Lows Wed morning will be in
the low-mid 60s. Conditions look to be incredibly pleasant with
mostly sunny skies, highs in the low 80s, and dewpoints in the 50s.
High temps Thursday creep back into the mid and upper 80s for most
of the area with low 80s near the immediate coast. Expect a mostly
dry day but a few showers are possible NW of Richmond during the
afternoon and across the MD Eastern Shore in the
evening/overnight.
&&
.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
As of 245 PM EDT Monday...
The end of the week and the weekend look a little more unsettled
with rain chances returning, albeit low chances. The upper ridge
builds back eastward briefly on Friday before troughing over eastern
Canada digs southward. High temperatures rise back into the low/mid
90s Friday with afternoon heat index values potentially rising above
100 across the Piedmont. A shortwave in the NW flow aloft drops SE,
bring at least a slight chance for showers and thunderstorms to the
area (15-30%). There is some uncertainty regarding the weekend as
deterministic guidance shows differences in the pattern aloft
regarding timing and amplitude of the expected trough. Sticking
mostly to blended guidance for now, which shows chc PoPs for Sat and
mostly dry Sun. Highs in the upper 80s/low 90s Sat, then cooler Sun
with highs in the low 80s.
&&
.AVIATION /00Z TUESDAY THROUGH SATURDAY/...
As of 740 PM EDT Monday...
VFR conditions prevail through the 00z TAF period. Satellite
shows SCT-BKN high clouds lingering over the region with some
clearing to the N. A brief period of clearing may move into the
area this evening into early tonight before a backdoor cold
front pushes S late tonight into Tues morning. Clouds increase
ahead of and behind the front with mainly cirrus ahead and ~5000
ft stratus behind it. HRRR vertically integrated smoke
indicates some smoke arrives with the clouds, but similar to
today, any smoke is expected to remain aloft with VIS not
impacted. Additionally, a brief period of patchy fog is possible
across the Eastern Shore around 4-8z but confidence is not high
enough that it will impact SBY to include in the taf. Winds
become calm/light and variable tonight, becoming N 10 kt with
gusts to 20 kt behind the front. Winds increase to 10-15 kt with
gusts 20-25 kt Tues afternoon and become NNE near/along the
coast. High pressure builds in behind the front Tues night with
winds diminishing.
Dry and VFR conditions continue through the middle of the week,
as high pressure prevails over the area. The next chance for
scattered showers/storms arrives Fri-Sat.
&&
.MARINE...
As of 305 PM EDT Monday...
High pressure prevails off the Southeast coast this aftn ahead
of an approaching cold front. The wind is very light, and
locally variable, with 1-2ft seas and ~1 foot waves in the Bay.
The cold front will push S along the coast late tonight into
early Tuesday morning with a subsequent CAA surge as high
pressure builds from the Great Lakes to New England. The wind is
expected to become NNE Tuesday, then NE Tuesday night. There is
an initial surge Tuesday morning which primarily affects the
Bay with a NNE wind increasing to 15-20kt with gusts to 25kt,
then by Tuesday night the wind becomes more concentrated to the
lower Bay as high pressure nudges in from the N. As the wind
shift to NE seas should build to 4- 6ft off the coasts of SE
VA/NE NC, with the wind increasing to 15- 20kt for the Currituck
Sound. SCAs have been issued for the Bay, southern ocean zones,
and Currituck Sound where confidence is highest. The lower
James may eventually need a flag for later Tuesday aftn/Tuesday
night, and seas may briefly build to 4-5ft for the northern
ocean zones.
High pressure builds into the area Wednesday with the wind
remaining NE and diminishing to 10-15kt. High pressure slides
offshore Thursday into Friday with the wind becoming SSW
10-15kt. Seas subside to 3-4ft later Wednesday, but could linger
~5ft off the Currituck Outer Banks into Wednesday evening. Seas
remain 3-4ft Thursday into Friday. Another cold front
potentially pushes through the area Friday night into Saturday.
Rip currents: There is a moderate rip risk for Tuesday and
Wednesday as well, but the southern beaches will need to be
monitored for high Wednesday.
&&
.AKQ WATCHES/WARNINGS/ADVISORIES...
MD...None.
NC...None.
VA...None.
MARINE...Small Craft Advisory from 7 AM to 1 PM EDT Tuesday for ANZ630-
631.
Small Craft Advisory from 10 AM Tuesday to 4 AM EDT Wednesday
for ANZ632.
Small Craft Advisory from 1 PM Tuesday to 7 AM EDT Wednesday
for ANZ633.
Small Craft Advisory from 10 AM Tuesday to 10 AM EDT Wednesday
for ANZ634.
Small Craft Advisory from 4 PM Tuesday to 4 PM EDT Wednesday
for ANZ656-658.
&&
$$
SYNOPSIS...RHR
NEAR TERM...AM/RMM
SHORT TERM...AM/RHR
LONG TERM...AM/RHR
AVIATION...RMM
MARINE...AJZ
Area Forecast Discussion
National Weather Service Charleston SC
855 PM EDT Mon Aug 21 2023
.SYNOPSIS...
High pressure will build over the region through Tuesday,
followed by a weak boundary passing down through the region
midweek. High pressure then rebuilds for the latter half of the
week, with another front possible during the weekend.
&&
.NEAR TERM /UNTIL 6 AM TUESDAY MORNING/...
Hourly high-res output from both the H3R and RAP have been
consistent since mid-afternoon in showing the development of
isolated showers/tstms overnight as a weak lobe of vorticity
drops south along the coast. The best chances for isolated
convection will occur roughly along/east of the I-95 corridor.
Given the consistent trends noted in the guidance, 20% pops were
included in this area with the late evening update. Total cloud
cover was nudged upward. 22/00z KCHS raob was still fairly
unstable with plentiful MLCAPE. While the atmosphere will
moisten and stabilize overnight, enough instability looks to
hold to support a mention of tstms. Lows from from the mid 70s
well inland to the lower 80s at the beaches and Downtown
Charleston are still on target.
&&
.SHORT TERM /6 AM TUESDAY MORNING THROUGH THURSDAY/...
Pattern Synopsis/Forecast: Impressively large expanse of upper level
high pressure will remain centered over the Central Plains/mid
Mississippi River Valley region through midweek with 591+ DM heights
stretched across southeast South Carolina and southeast Georgia.
Some semblance of a backdoor front/shallow wedge is still looking to
sag down into the region late Tuesday night into Wednesday. Minimal
impact, but it will knock temps back down some off their current
very warm readings.
Tuesday: Continued subsidence/mid level warming should effectively
cap things off to convection with a nice warm nose noted in forecast
soundings under 700 MB. Suppose a very isolated shower is again
possible along the sea breeze during the afternoon. But plan is to
maintain a dry forecast.
Bigger concern resides with heat index readings. A bit warmer
temperatures anticipated on Tuesday with highs in the mid to upper
90s. This yields heat index values of 105F to 109F along with some
spotty 110F readings. Close...and we may eventually consider a Heat
Advisory for some...but will let overnight crew make that call.
Heading through midweek: As mentioned, some semblance of a surface
boundary will be dipping down through the region. Still not a lot
anticipated precip-wise, although there may be enough mid level
cooling to allow some convection to develop during the afternoon,
particularly down through the southern half of the CWA. But
otherwise, temperatures will get knocked back down into the upper
80s to lower 90s both Wednesday an Thursday, along with modestly
lower dewpoints.
&&
.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
Upper level ridging will remain the dominant player across the
southern and southeast CONUS through the latter half of the week,
maintaining overall quiet weather for southeast South Carolina and
southeast Georgia to end the work week. Heading into the weekend,
strong short-wave energy will dive through the Great Lakes and into
the mid Atlantic by Sunday, along with a boundary that settles
across inland areas through the weekend. This will bring an increase
in precip chances for the weekend, particularly during the daytime
heating cycle. Daytime temperatures will continue to run above
normal through the weekend and particularly on Saturday when mid and
upper 90s are anticipated along with elevated heat index values as
well.
Heading into next week: Larger scale troughiness is looking to
gradually develop across the southeast region. This will keep precip
chances going but also lead to cooler temperatures, possibly
slightly below normal for change.
&&
.AVIATION /01Z TUESDAY THROUGH SATURDAY/...
22/00z TAF discussion:
KCHS/KJZI/KSAV: VFR. There is a risk for isolated showers/tstms
overnight, but the chances for direct impact are too low to
justify a mention at this time.
Extended Aviation Outlook: VFR conditions will remain dominant
across the region through the week. The potential for flight
restrictions will increase into the weekend as shower and
thunderstorm chances increase.
&&
.MARINE...
Tonight: High pressure will remain the dominant weather feature
across the western Atlantic, extending across local waters with a
weak pressure gradient in place. The pattern will support conditions
well below Small Craft Advisory concerns. In general, south/southeast
winds will remain around 10 kt this evening, before gradually
turning more southwest overnight. Seas will average between 1-3 ft.
Tuesday through Saturday: Overall lighter flow will persist
across the coastal waters through Tuesday, with the usual sea
breeze development and tendency for stronger winds during the
day. The pressure gradient will tighten along the mid Atlantic
coast and into the Southeast Coast during the mid to late week
period, which will result in stronger northeasterly flow and
increasing seas across the coastal waters. A Small Craft
Advisory may be eventually be needed. Winds and seas subside for
late week and into the weekend.
&&
.CLIMATE...
The low observed so far today in Downtown Charleston (KCXM) is
82 degrees. If this low holds through 1 AM EDT, it will tie the
record high minimum for the date, last set in 1900.
&&
.CHS WATCHES/WARNINGS/ADVISORIES...
GA...None.
SC...None.
MARINE...None.
&&
$$
Area Forecast Discussion
National Weather Service Green Bay WI
1003 PM CDT Mon Aug 21 2023
Updated aviation portion for 06Z TAF issuance
.SHORT TERM...Tonight and Tuesday
Issued at 252 PM CDT Mon Aug 21 2023
The latest RAP analysis and satellite/radar imagery show a warm
front stretching from southwest Minnesota to northern Illinois
early this afternoon. The front is mostly inactive early this
afternoon except for areas north of the boundary across eastern
Minnesota and western Wisconsin when broken strato-cu prevails. A
few showers have popped up at times in a fgen zone over northeast
Minnesota to north-central WI. Given weak warm advection, don`t
see these clouds dissipating and therefore lowered high temps
this afternoon. Meanwhile, high pressure over the Lake Superior
region is funneling a relatively drier/cooler airmass into the
region via northeast or east winds. As the warm front surges north
into the region, thunderstorm and severe weather potential are
the main forecast concerns through Tuesday.
Tonight...The warm front will gradually lift north across the
northern Mississippi Valley and western Wisconsin. A 30-40 kt low
level jet will increase through the evening with the nose pointed
at northeast Minnesota and northwest Wisconsin. While mid-level
lapse rates and instability are modest (6.5 C/km 700-500mb lapse
rates and up to 1000 j/kg of most unstable cape), strong 500mb
flow of 40-50 kts could lead to some rotating updrafts as storms
progress southeast across northern Wisconsin. Marginally severe
hail appears possible in the strongest storms. Timing of the
storms has slowed somewhat, with most convective allowing models
bringing in convection to north-central WI around 08-09z
timeframe. Lows will range from the middle 50s to middle 60s.
Tuesday...The warm front will continue to slowly bow north into
Wisconsin with showers and storms dropping southeast across
northeast Wisconsin during the morning. With weakening moisture
convergence, thunderstorm intensity should weaken through the
morning hours and possibly depart by midday. The exception could
be near the U.P. border where mid-level fgen will persist through
the afternoon. Temps are challenging due uncertainties revolving
around warm front movement and track/timing of showers and storms.
Increased highs a degree or two over central WI, closest to heat
dome and least likely to be impacted by precip. With the later
precip timing, lowered high temps over far NE WI. There will be a
large range of high temps from the upper 60s to near 90 degrees
across the region.
.LONG TERM...Tuesday Night Through Monday
Issued at 252 PM CDT Mon Aug 21 2023
A jet streak moving around the edge of the upper ridge, and a
weak warm front near the Upper Michigan border could produce some
thunderstorms in far northeast Wisconsin late Tuesday night and
early Wednesday. A few strong or marginally severe storms are
possible.
Wednesday looks to be hot and humid, with high temperatures from
the upper 80s in the northeast to middle 90s in parts of central
Wisconsin. Dewpoints in the upper 60s to mid 70s should create
heat indices of 100 to 105 in central and east central Wisconsin.
A heat advisory will likely be issued for those areas.
Thursday should not be quite as hot, thous it will still be very
warm and humid in central and east central Wisconsin. A cold front
will move across the region Friday, possibly accompanied by
showers and thunderstorms. Cooler and drier weather should follow
for Saturday and Sunday.
&&
.AVIATION...for 06Z TAF Issuance
Issued at 955 PM CDT Mon Aug 21 2023
VFR stratocumulus covered most of the forecast area, in response
to a warm front lifting toward the region. This scenario will
persist into the first few hours of the new TAF period, along
with mainly dry conditions.
Showers and thunderstorms remain on track to overspread the
northeast half of the region overnight into Tuesday morning, with
an arrival time around 08z-09z/Tue in NC WI. The RHI TAF site
appears to be the only one with a high probability of storms, as a
capping inversion could prevent convection from firing along and
south of Hwy 29. Will likely remove the mention of storms at
AUW and GRB, as the positioning of the capping inversion and
latest meso-model trends keep most of the convection farther
north. Storms will be elevated and initially have VFR ceilings,
but ceilings may lower to MVFR in N WI late tonight into early
Tuesday. Heavier downpours with thunderstorms could drop VSBYs to
MVFR/IFR at times. Most thunderstorms should depart far NE WI by
midday Tuesday, but it is possible that another round will develop
in far NE WI Tuesday night.
&&
.GRB WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
SHORT TERM.....MPC
LONG TERM......RDM
AVIATION.......Kieckbusch
Area Forecast Discussion
National Weather Service Hanford CA
1254 PM PDT Mon Aug 21 2023
.SYNOPSIS...
Remnants of Tropical Storm Hilary will continue to bring
widespread rainfall to the area through this morning and into
tonight. Thunderstorms are also possible this afternoon. The
system is expected to exit our area Tuesday morning and dry
conditions will begin to prevail Wednesday with some showers
along the Sierra Nevada crest possible on Thursday and Friday.
Flooding will continue to impact the area as the water from
yesterday`s excessive rainfall recedes.
&&
.DISCUSSION...
Current satellite imagery shows a broad area of low pressure
spinning off the California coastline. Abundant moisture and
instability from Hilary are present over our CWA with Surface
Based CAPE sitting over 1000 J/kg. The HRRR runs this morning have
been showing quite an active afternoon with thunderstorms firing
off by noon (which are ongoing as we speak) and trekking across
the valley this afternoon into the evening hours. Expect hail of
at least 1/2 inch and strong winds to 50 mph with some of these
storms capable of producing larger hail and stronger winds.
Rotation has been observed on radar already this afternoon and
funnel clouds and/or brief touchdowns of tornadoes is certainly
possible.
With the amount of rainfall some areas received yesterday, any
precipitation with showers or thunderstorms today could help to
exasperate more flooding concerns. Be weary of any standing water
you encounter and always head on the side of caution and avoid
driving through any amount of water in roadways.
After this afternoon, expect conditions to begin to taper back to
seasonal norm for our area with temperatures rebounding back to
near normal and much drier conditions present. Longer range models
are showing a possible heat up by next Tuesday.
&&
.AVIATION...
Widespread MVFR and areas of mountain obscuring IFR conditions in
and near showers and thunderstorms across Kern County mountains
and Sierra Nevada. Showers and thunderstorms will also impact the
remainder of the Central CA interior with areas of MVFR.
&&
.AIR QUALITY ISSUES...
ISSUED: 08/20/2023 13:29
EXPIRES: 08/21/2023 23:59
None.
&&
.CERTAINTY...
The level of certainty for days 1 and 2 is medium.
The level of certainty for days 3 through 7 is medium.
Certainty levels include low...medium...and high. Please visit
www.weather.gov/hnx/certainty.html for additional information
and/or to provide feedback.
&&
.HNX WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
JMC
weather.gov/hanford
Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
700 PM CDT Mon Aug 21 2023
.SHORT TERM...
Issued at 154 PM CDT Mon Aug 21 2023
Through Tuesday...
A generally seasonable day today for late August will begin to
transition to oppressive heat by mid-week as the edge of a
building heat dome drifts toward the area on Tuesday. The low-
level moisture gradient in the region is nicely demarcated by
growing cumulus south of a line from Valpo to Pontiac, with a
secondary region of higher moisture extending northwestward toward
Dixon. Upstream flow with persistent NE winds has maintained weak
dry air advection through the day. With the counteraction of ET,
low-level moisture profiles have been rather steady north of the
aforementioned boundary.
Overall flow will not change considerably over the next 24 hours,
though a weak surface ridge nosing southward into Wisconsin
tonight may perturb wind direction overnight (if winds do not
become calm instead). With all that said, plenty of low-level
moisture and associated strato-cumulus trapped under a subsidence
inversion has been evident upstream across Lower Michigan this
afternoon. This may complicate the temp forecast for Tuesday if
status expands and advects toward the CWA overnight, similar to
what occurred early this morning over east-central Illinois.
Additionally, patchy shallow fog will be possible late tonight
across much of the southern CWA, but especially northwest Indiana
into east-central Illinois.
Temps today in the CWA and upstream have underperformed, so with
that in mind along with the increasing chance for lingering
stratus Tuesday morning, have nudged down temps another degree or
two through Tuesday afternoon. This puts the Heat Advisory in
question for the eastern tier of active counties (roughly Boone to
Will to Benton). Opted to keep the headline for now as very warm
conditions are still expected, but any further downward
adjustments (i.e. more morning clouds) will necessitate canceling
at least some parts of the advisory.
Kluber
&&
.LONG TERM...
Updated at 700 PM CDT Mon Aug 21 2023
Tuesday night through Thursday night
Overview:
A period of dangerous heat and humidity is expected to build
across the region, peaking on Wednesday and Thursday. An Excessive
Heat Watch remains in effect to highlight the potential for a
two-day episode of very dangerous heat and humidity, but some
failure modes and caveats remain (see below).
The core of a sprawling and unusually strong mid-upper level
ridge will meander across southern Illinois on Wednesday, making
its closest approach to our region. While the main theta-e axis
will migrate a bit farther west for Tuesday (see short term
discussion), this looks to solidly slosh back across our area on
Wednesday. Based on how dewpoints behaved on Sunday, guidance such
as the NAM, NAMNest, HiresARW, NSSL WRF, and ECMWF continue to
vastly outperform the GFS, RAP, and HRRR which continue to
aggressively deepen PBLs way too much. In fact, dew points
continue to verify some 20 degrees higher than advertised during
peak heating by the GFS, so we continue to discount it (and it`s
extremely hot air temperatures) from our forecast.
Wednesday and Thursday:
Wednesday continues to look like it will end up featuring the
highest heat indices of the two-day stretch as we`ll remain on the
southeastern flanks of the main surface pressure trough. Robust
subsidence inversion aloft should continue to suppress deep(er)
mixing, and we continue to suspect that dewpoints will rise
through the upper 70s, if not tagging 80-81 during the afternoon.
Combined with air temperatures crawling their way into the upper
90s, peak heat indices around or over 110 F appear likely, with
peak heat indices in some areas reaching 115 to 120 F looking
increasingly plausible for at least some locations (particularly
in rural areas in close proximity to farm fields).
Thursday will also afford another day of potentially dangerous
heat, and possibly even record high temperatures. While the core
of the ridge will wobble farther south, the 925mb and 850mb
thermal ridge will settle south into our CWA and encourage deeper
mixing compared to Wednesday. In fact, 925 mb temperature
climatology supports the potential for triple-digit air temps.
Such temperatures would be contingent on surface dew points
mixing lower, possibly to the lower 60s in spots. Temperatures at
or above 100 degrees are rare in Chicago and to a lesser extent
Rockford. That`s not to say it can`t happen on Thursday (frankly
it very well may happen), but a conservative approach to
temperatures continues to be our strategy. Besides, highs in the
lower 100s with upper 60 degree dew points feels pretty much the
same as highs in the mid 90s and dew points in the upper 70s/lower
80s. So, dangerous heat appears poised to continue into Thursday
even if humidity levels aren`t as high compared to Wednesday.
Potential caveats:
As we`ve mentioned several times already, very rarely do we see
excessive heat episodes here without some potential for
unanticipated convection, outflow boundaries, extra cloud cover,
etc. delaying or entirely suppressing high-end heat episodes.
This remains the case this time around, and is something we
continue to be mindful of. Guidance continues to fire convection
late Tuesday night into Wednesday morning as the eastern fringes
of a region of very steep mid-level lapse rates intercepts a
nocturnally-intensifying low-level jet and warm advection to our
north. The 00z NAMNest, while perhaps a bit too far south with
initiating convection, is a good visual depiction of the concern:
a maturing MCS has the potential to barrel down the lake, sending
rain-cooled outflow across NE IL and NW IN resulting in notably
cooler conditions.
The other failure mode is on Thursday, most guidance is now
pushing a lake-enhanced cold front across lake-adjacent areas.
Timing varies, but it`s not uncommon for models to be too slow
with lake enhanced fronts. An earlier arrival would mean day 2 of
the high heat indices would likely be out of reach for parts of
the region, most notably near the lake, including the heart of the
Chicago metro area and portions of Lake and Porter Counties in
Indiana.
Our local criteria for an Excessive Heat Warning is for a two
day/48 hour stretch of maximum heat indices of 110 F or greater,
except in Cook county which requires only 1 day of a 110+ heat
index. To be frank, we try to reserve Excessive Heat Warnings for
the worst of the worst heat waves, as it`s the strongest product
we can issue for dangerously hot temperatures. With that in mind,
as well as the aforementioned caveats, we opted not to upgrade
the inherited Excessive Heat Watch to an Excessive Heat Warning
yet. With that said, if the airmass remains undisturbed, a two-day
period of nasty and potentially deadly conditions will unfold
across part if not all of our region. Even if it is just
Wednesday that reaches its full potential for heat, then an
Excessive Heat Warning will be needed for Cook Co and may be
justifiable (impact-based rather than criteria-based) elsewhere
given the extreme nature of the one day heat spell.
Thursday night and beyond:
A big time cool down looks to be on the way, particularly into the
weekend as Canadian high pressure builds into the region.
Surprisingly, we`re not seeing a signal for convection with the
incoming front in model guidance, although we suspect we`ll have
to contend with at least a brief period of higher shower and
thunderstorm chances as the heat dome breaks down.
NWS Chicago
&&
.AVIATION...
For the 00Z TAFs...
Generally light and northeasterly winds will continue after
sunset, before gradually veering throughout the morning and
settling on a south to southwesterly direction tomorrow afternoon.
At ORD/MDW/GYY, a lake breeze should arrive tomorrow morning before
winds veer south or southwesterly, keeping the direction with an
easterly component through the TAF period.
High resolution model guidance offers hints that IFR to MVFR
stratus may develop overnight as a surface warm front attempts to
lift northward over the terminal airspace. However, coverage and
exact location remains stubborn to pin down. Even along the
lakeshore, filaments of IFR clouds have ebbed and flowed over the
past few hours, confirming the difficulty in pinpointing when and
where clouds may develop overnight. For now, opted to use the
HREF as a guide and advertise FEW to SCT015 at all terminals
centered on the 10-15Z timeframe. If stratus really does develop
and expand over the terminals, it may be closer to a BKN to OVC
800-1200ft situation.
Borchardt
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...Heat Advisory...ILZ003-ILZ004-ILZ008-ILZ010-ILZ011-ILZ012-ILZ019-
ILZ020-ILZ021-ILZ023-ILZ032-ILZ033-ILZ039-ILZ106-ILZ107-
ILZ108...11 AM Tuesday to 9 PM Tuesday.
Excessive Heat Watch...ILZ003-ILZ004-ILZ005-ILZ006-ILZ008-ILZ010-
ILZ011-ILZ012-ILZ013-ILZ019-ILZ020-ILZ021-ILZ023-ILZ032-
ILZ033-ILZ039-ILZ103-ILZ104-ILZ105-ILZ106-ILZ107-
ILZ108...11 AM Wednesday to 8 PM Thursday.
IN...Excessive Heat Watch...INZ001-INZ002-INZ010-INZ011-INZ019...11
AM Wednesday to 8 PM Thursday.
Heat Advisory...INZ010-INZ019...11 AM Tuesday to 9 PM Tuesday.
LM...None.
&&
$$
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Area Forecast Discussion
National Weather Service Spokane WA
711 PM PDT Mon Aug 21 2023
.SYNOPSIS...
Widespread wildfire smoke should gradually improve early this
week as the weather pattern and wind shifts. Rain chances continue
to be focused on the eastern third of Washington and the Idaho
Panhandle with Hilary moisture. Warmer than normal temperatures
return late this week.
&&
.DISCUSSION...
As of 7 PM, the first wave of precipitation with remnants of
Hurricane Hilary continues to move through the central and
southern Idaho Panhandle. Rain bands are not as heavy as they were
earlier in the day, and it looks like there is a back edge of
persistent rain near Lewiston. The heaviest bands clipped Idaho,
Clearwater, and southern Shoshone counties where observing
stations received between a half and three quarters of an inch of
rain. Measurable rain reached as far north as Benewah, northern
Whitman and eastern Kootenai counties, but missed Spokane and the
fires close to the metro.
The forecast has been updated to lower precipitation chances for
the evening across eastern Washington, but there will be
additional opportunities for rain. A upper level disturbance with
moisture from Hilary`s remnants will move through Oregon this
evening and spread into eastern Washington overnight. It won`t
produce widespread rain amounts as high as those that fell in the
southern Idaho Panhandle today, but the HREF produces a swath of
a quarter to half inch of rain from Walla Walla to Cheney to
Northport by mid morning (Tuesday). Satellite and land based
lightning detection shows widely scattered lightning activity with
the showers in southern Oregon, and there is a good chance that
lightning will spread into eastern Washington overnight into
Tuesday morning with this wave. Negative theta-e lapse rates and
mid-level CAPE is advertised by the NAM within the axis of highest
precipitation. And members of the HREF indicate convection in
their simulated radar reflectivity suggesting the likelihood of
lightning and brief heavy downpours. Even the Crater Creek fire
on the boundary between British Columbia and Okanogan county will
have a shot at morning rain showers and additional wet
thunderstorms Tuesday afternoon and evening. /GKoch
.PREVIOUS DISCUSSION...
Today and tomorrow: Tropical moisture has brought precipitable water
values as high as 300 percent of normal over northeast Oregon.
Spokane area sounding will likely show values around 200% of normal.
A very dry boundary layer has led to lackluster precipitation
totals as of 2 PM. Lewiston has 0.07 inches of precipitation while
Pullman only has 0.02 inches. Expecting this round of stratiform
rain to barely clip Spokane with a 40% chance of 0.01 inches
through midnight.
The more substantial rain comes tomorrow morning with up
to a 70-90% chance of a quarter inch through 2 pm in Eastern WA/ID
Panhandle, a 20-40% chance of a quarter inch in north central WA.
Some temporarily improvements in air quality will come with
precipitation. The best chance for 1" remains in the flood watch
with up to a 60% chance. Tomorrow`s rain could present a flash flood
risk given the more convective nature of the rain in the watch.
An upper low will bring a dry front dropping our precipitable water
around 50% of normal tomorrow afternoon and evening. This will
squash any precipitation rather quickly tomorrow night. /Butler
Wednesday: A trough/low pressure system will move along the
US/Canadian border Wednesday. Through the morning there is a
chance of showers across the Camas Prairie and up towards Lookout
Pass, as well as the Cascade crest and northern WA/ID (mainly
along the border). By the afternoon much drier air will move into
portions of central and southern WA and the ID Panhandle. Along
the Canadian border enough moisture continues along with some
instability to have showers and thunderstorms continue. Winds will
pick up in the afternoon 10 to 15 mph sustained with gusts 15 to
25 mph. Probabilities of gusts above 25 mph is about 40% for the
northern Columbia Basin mainly north of Highway 2, and about 60%
south of Omak on the Okanogan Valley into portions of the
Waterville Plateau. Winds and humidity levels do not look to be in
the critical fire weather levels Wednesday.
Thursday through Monday: The next low will move out of the Gulf of
Alaska and move down the eastern Pacific. This will provide warmer
south to southwesterly flow into the region. We will see about 4
to 9 degrees of warming. Humidities will continue to lower, and
likely be the lowest readings for the week. Fortunately, winds do
not look particularly strong. Friday we will see an increase in
moisture from the south as the low that has been sitting off the
central CA coast moves inland. This will provide a round of
sprinkles or light showers to the region on Friday. Currently
instability isn`t terribly strong, and just have mention of
afternoon thunderstorms for the southeast corner of WA extending
towards Lookout Pass. The remainder of the weekend actually
remains dry as the low off the west coast (that moved down Thur)
sits and spins. There are some discrepancies as to how close to
the coast the low comes. 70% of ensemble models keep it west of
130W, with only 30% bringing it closer to the coast. The ridge
will pump up and our temperatures warm. By next Sunday/Monday we
will be looking at widespread temperatures in the 90s, which is 9
to 14 degrees above average for the end of August. /Nisbet
&&
.AVIATION...
00Z TAFs: Smoke improvements are being seen and will continue to
improve as increasing clouds and precipitation arrive from the
southeast. Moses Lake and Wenatchee along with Omak and the Methow
Valley however may not totally clear out per the latest HRRR
smoke model and given the east-southeast winds. A second round of
precipitation is expected regionwide starting at 06Z-12Z with
chances of heavy showers and thunderstorms in KLWS through at
least 00Z Wednesday.
&&
.PRELIMINARY POINT TEMPS/POPS...
Spokane 59 74 51 75 49 83 / 60 80 20 0 0 0
Coeur d`Alene 61 75 51 75 49 83 / 80 70 40 10 0 0
Pullman 53 70 47 72 43 80 / 100 70 50 10 0 0
Lewiston 64 79 58 82 55 88 / 100 80 70 10 0 0
Colville 52 72 41 74 40 83 / 60 70 30 20 0 0
Sandpoint 56 74 48 72 45 81 / 90 70 50 10 0 0
Kellogg 60 74 55 71 52 81 / 100 80 60 10 0 0
Moses Lake 60 77 49 79 50 85 / 20 30 0 0 0 0
Wenatchee 60 79 55 79 56 83 / 10 10 0 0 0 0
Omak 62 81 54 80 53 85 / 20 40 20 10 0 0
&&
.OTX WATCHES/WARNINGS/ADVISORIES...
ID...Flood Watch through Tuesday evening for Central Panhandle
Mountains-Idaho Palouse-Lewis and Southern Nez Perce
Counties-Lewiston Area.
WA...Flood Watch through Tuesday evening for Lower Garfield and
Asotin Counties-Northeast Blue Mountains.
&&
$$
Area Forecast Discussion...UPDATED
National Weather Service Pueblo CO
250 PM MDT Mon Aug 21 2023
.SHORT TERM...(This evening through Tuesday)
Issued at 250 PM MDT Mon Aug 21 2023
Key messages:
1) Isolated showers and thunderstorms will be possible over areas of
the higher terrain throughout the evening, mainly over the southern
mountains.
2) Still hot tomorrow for the plains and slightly above average
elsewhere. Triple digits are expected in the lower Arkansas River
Valley.
3) Isolated to scattered thunderstorms will develop tomorrow
afternoon over the higher terrain with slightly better coverage. A
few could move out into the San Luis Valley and adjacent plains.
4) There will be spotty fire weather conditions over portions of the
plains and I-25 corridor for a couple of hours during the afternoon,
although not widespread enough to warrant the issuance of a Red Flag
Warning.
Detailed discussion:
Tonight...
Currently there are a few showers and thunderstorms beginning to
develop over the southern Sangres
Latest CAMs show that there will be some areas of showers and
thunderstorms still possible through the evening hours, mainly over
the eastern San Juan Mountains. There will be the highest amount of
CAPE over the Sangres with values as high as 800 J/kg for some
areas, and because of this there will be a slight chance of one or
two of the storms becoming stronger and perhaps produce some brief
torrential rainfall, gusty winds greater than 40 mph, and small
hail. A few of the CAMs, such as the HRRR and NamNest, does show a
few showers lingering just after midnight over the Sangres, although
it is more likely with the stabilizing of the mid-levels and overall
subsidence in place over the region that all showers should come to
an end before midnight.
Mostly cloudy skies over the higher terrain will begin to clear
going into the early morning hours tomorrow and it will be clear
over the plains, although the southerly flow will keep temperatures
somewhat modified and relatively warmer. Lows tonight will drop down
into the mid 60s to low 70s for most of the plains. For high
country, lows will generally be in the 40s to low 50s.
Tomorrow...
As the ridge to the east nearly remains in place but begins to break
down slightly, it will allow for the monsoonal moisture to be
shifted a little further east and over the region tomorrow.
Therefore, there will be slightly better convective activity
developing over the higher terrain during the afternoon hours, and
some of these showers and thunderstorms will possibly move off the
mountains and over the valleys and adjacent plains with some better
southwesterly shear in the mid to upper levels. CAPE will be similar
to what it was today, although with some added moisture content at
the 700 mb level, there should be more in the way of thunderstorm
development and strengthening given the better effective bulk shear
in place of nearly 30 kts over the Sangres. Moreover, the better
shear could also allow for some of the storms to become strong over
this area, with the main threats being gusty outflow winds to 50 mph
and possibly up to a half inch hail.
The southerly surface winds over the plains are going to result in
another hot day, with temperatures likely getting up over 100 for
some locations in the lower ArkRvr Valley. In addition to the heat
will be low RH values and some gusty winds which will bring about
spotty critical fire weather conditions over some portions of the
plains and I-25 corridor for a couple of hours during the afternoon,
although not widespread enough to warrant the issuance of a Red Flag
Warning. Expect for high temperatures to also be slightly above
average across all other areas of the CWA. -Stewey
.LONG TERM...(Tuesday night through Monday)
Issued at 250 PM MDT Mon Aug 21 2023
Key Messages:
1) Atmospheric moisture on the increase starting Wednesday.
2) Widespread precipitation possible for Friday and Saturday, with
periods of moderate to heavy rainfall.
3) Above normal temperatures through Thursday, then cooler.
A large upper high located over the central US will shift through
the extended period, while remnant moisture from TC9 rotates around
the high and eventually impacts Colorado. This will play a deciding
role in realized temps and precipitation for the forecast area.
Tuesday night and Wednesday...The upper high will be centered over
MO Tue evening, while the remnant moisture of TC9 tracks northwest
along the Rio Grande. The upper high will sink to the south and
center over AR on Wed, while the moisture pushes up into southern AZ
and UT, with a notable increase in precipitable water entering
western CO. This will result in a noticeable increase in convection
over the higher terrain, and especially along the Continental Divide
Wed late morning through the aftn and into the evening. It still
looks like the shower and thunderstorm chances will remain over the
higher terrain however, with the plains remaining dry. As for temps,
overnight lows in the 50s and 60s for most locations Tue night, then
another warm one for Wed with highs in the 80s for the high valleys,
and 90s to near 100F for the plains.
Thursday...This looks like the transition day as the upper high
slides slowly to the west over OK, and the remnant tropical
moisture pushes well up into UT and northwestern CO. Forecast
temperatures are expected to be very similar to the day before, so
still at or above normal for this time of year, but the change is
the potential shower and thunderstorm activity with the increasing
available moisture. Isolated showers along the Continental Divide
through the morning will increase in coverage and intensity through
the afternoon, covering all of the mts and high valleys, with
isolated activity possibly spilling over to the I-25 Corridor.
Friday and Saturday...A strong upper low crossing the Great lakes
region Friday morning will force a cold front south across the
eastern CO plains, and will actually help to push the upper ridge of
high pressure over OK to the west, finally coming to a stop directly
over NM and CO by Sat. The remnant tropical moisture over the Great
Basin will cross the northern half of the ridge and directly affect
CO, bringing the possibility of widespread moderate to heavy
rainfall to the eastern 2/3 of the state Fri afternoon overnight
into Sat morning due to PWAT values 150%-200% of normal. Another
round of convection is expected to light up once again over the
higher terrain Sat afternoon and evening. As for temps, finally some
relief with highs both days in the 70s to near 80F for the high
valleys. Across the plains, plan on upper 70s to lower 90s for Fri,
then upper 70s to upper 80s for Sat.
Sunday and Monday...Extended models indicate that the upper ridge
will continue a bit further west, centering over the Four Corners to
finish the weekend. Residual moisture trapped under the high will
get recycled over the region, leading to isolated to scattered
afternoon and evening showers and thunderstorms for most locations
both days, and convection likely over the highest peaks. Temps will
remain near normal for the high valleys, 70s to around 80F, and
slightly below normal for the plains. Moore
&&
.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Issued at 250 PM MDT Mon Aug 21 2023
VFR conditions are expected to prevail for all TAF sites (KALS,
KCOS, and KPUB) throughout the forecast period. Winds will be mainly
diurnally driven at all terminals. They could be rather gusty during
the afternoon and early evening hours for all stations, with gusts
around 25 kts. There is a slight chance of VCSH/VCTS for KALS this
evening and tomorrow, towards the end of the forecast period. If
SHRA/TSRA does develop and move over KALS, it could temporarily
reduce CIGs and VIS to MVFR/IFR criteria. It could also result in
periodic windshifts and temporary increased wind speeds. There is a
lesser chance of VCSH/VCTS to occur at KCOS and KPUB.
&&
.PUB WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SHORT TERM...STEWARD
LONG TERM...MOORE
AVIATION...STEWARD
Area Forecast Discussion
National Weather Service Tucson AZ
132 PM MST Mon Aug 21 2023
.SYNOPSIS...Daily rounds of scattered showers and thunderstorms
this week. Cooler than normal temperatures Wednesday then warming
to above normal next weekend.
&&
.DISCUSSION...Latest satellite imagery shows a small cumulus field
developing over Cochise County and a little bit in Pima County.
There is mid level clouds that is inhibiting some of the
development of the cumulus clouds over Pima County and to the
west. There is plenty of moisture in the air and instability
within the region. The better instability is closer to Cochise
County which there are a few cumulus are starting to build more
into towers. The mid level clouds are taking a little longer to
clear out for the cumulus clouds to really build and the better
access for surface heating. The latest 19z HRRR run still shows
thunderstorms developing this afternoon, starting around 2 pm MST.
That may get delayed a bit more if there is still higher cloud
cover to limit growth, but the eastern edge of the cloud field
(western Cochise County) will likely to be the first action item
of the afternoon. Especially when the CAPE values are in the 2000
J/kg range which is higher than in Pima or Santa Cruz County. SPC
still has the area under a marginal risk for thunderstorms with
the threat of wind and hail. The upper level does support strong
thunderstorm potential and it can make the storms move fairly
quickly due to the 30kt steering flow at the 700mb. 12Z HREF has a
strong signal for strong gusty winds that can lead to blowing
dust along the high traffic corridor. Plus, there is plenty of
moisture to create brief heavy rainfall within a short amount of
time. Expect flows in washes and localized significant ponding of
water and other localized flooding challenges.
Later in the evening, there could be another quick round of
showers and thunderstorms based on the latest HRRR. Showers and
thunderstorms will taper off through the rest of the night.
Tomorrow, temperatures will be around normal with breezy
conditions for mainly in the eastern counties of the CWA. The
better chances for thunderstorms will be west of Tucson in the
afternoon.
By Wednesday, a trof or a tropical wave from the Gulf of Mexico
that will bring more moisture and upper level dynamics. This will
increase the chances for showers and thunderstorms as well as
keep temperatures slightly below normal.
Rest of the week, there will be a daily chance of showers and
thunderstorms due to the lingering moisture. The moisture will
slowly erode away through the weekend. Temperatures will warm up
to a few-several degrees above normal through the weekend.
&&
.AVIATION...valid through 23/00z.
SCT SHRA/TSRA with bases SCT-BKN 9-12k ft MSL, ISOLD MVFR
CIGS/VSBYS, MT obscurations and gusts 35-45kts through 22/02z. Areas
of BLDU from KAVQ to KCGZ. SHRA/TSRA diminishing overnight then
redeveloping Tuesday afternoon mainly W of KTUS/KOLS. Outside of
thunderstorms SFC winds mainly SE-ly 8-18 kts. Gusts to 25 kts this
evening and Tuesday afternoon VCNTY KDUG and KSAD. Aviation
discussion not updated for TAF amendments.
&&
.FIRE WEATHER...Scattered afternoon and evening showers for much
of the work week with day-to-day variability in areal coverage of
storms. Gusty southeast winds into this evening and again Tuesday,
especially east of Tucson. Later this week through the weekend, it
looks like we could see two or three consecutive days of warmer
temperatures/lower humidities and limited thunderstorm coverage.
&&
.TWC WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
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