Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 08/25/24
Area Forecast Discussion
National Weather Service Boise ID
835 PM MDT Sat Aug 24 2024
.DISCUSSION...Showers have been most numerous this evening in
northern Malheur County/OR and the Weiser River Valley/ID, in
reasonable agreement with but slightly east of forecast. These
showers should taper off by midnight, but new showers should
move into south-central Idaho from Nevada overnight through
Sunday. Satellite loop supports these trends. Another area of
showers should develop Sunday afternoon and early evening in
the Boise Mountains and eastern Valley County/ID, right over
the most active fires. No showers are expected in eastern Oregon
Sunday. Patchy fog is expected Sunday morning in the currently
rainy valleys in Idaho. Latest HRRR model has less smoke than
previous forecast in south-central ID Sunday. No updates.
&&
.AVIATION...Mostly VFR with mid-level ceilings. MVFR/IFR and
mountain obscuration near wildfires. Scattered rain showers
decreasing by 25/05Z, except persisting for KTWF/KJER overnight.
Patchy mountain valley fog Sunday morning. Isolated showers/
thunderstorms over central Idaho mountains Sunday afternoon.
Surface winds: variable 5-10 kt, becoming W to NW 5-15 kt after
25/15Z. Winds aloft at 10kft MSL: variable 5-15 kt.
KBOI...VFR with scattered/broken mid level clouds. Surface winds:
light and variable overnight, then NW 7-12 kt with gusts to
15-20 kt after 25/16Z.
&&
.PREV DISCUSSION...
SHORT TERM...Tonight through Monday night...Showers and any
thunderstorm development will organize across SE Oregon and far
SW Idaho this afternoon/evening along the upper trough axis. The
wetter air mass could support locally heavier rainfall from
showers and storms, but with cooler air mass and lighter winds
aloft, outflow potential looks to max out around 30 mph. Also,
the storm motion across SE Oregon could be relatively slow
adding to the heavier rainfall potential. The focus of
precipitation development will shift to s-central Idaho
overnight, following the track of a closed low at the base of
the trough. The low lifts into e-central ID on Sunday keeping a
chance of showers in the ID mountains through early evening.
Gusty outflow winds to 30 mph will again be possible from
thunderstorms. Elsewhere, dry and relatively cool conditions
are backed by a northwest wind. Monday is dry with warming
temperatures responding to a short wave upper ridge pushing in
from the coast.
As winds aloft weaken tonight and Sunday, wildfire smoke will
begin to fill in across mtn valleys in w-central Idaho.
Smoke will return to SW Idaho later Sunday as circulation
around the upper low wraps it to the south and west. While smoke
may initially stay in layers aloft on Sunday, would not be
surprised to it draining into the Snake Plain Monday morning as
has been the case in recent days.
LONG TERM...Tuesday through Saturday...Strengthening southwest
flow will warm temperatures back to around normal on Tuesday.
This is in advance of a sharp upper trough that will push
through the Pac NW Tuesday night and Wednesday. An accompanying
dry cold front will cross SE Oregon and SW Idaho Tuesday night,
bringing gusty northwest winds. Wednesday is about 10 degrees
cooler than Tuesday with northwest flow keeping breezy winds,
especially through the middle Snake Plain. An upper ridge
rebuilds over the region to end the week, keeping it dry and
warming temperatures to around 5 degrees above normal for Friday
and Saturday.
&&
.BOI WATCHES/WARNINGS/ADVISORIES...
ID...None.
OR...None.
&&
$$
www.weather.gov/Boise
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DISCUSSION...LC
AVIATION.....SH
SHORT TERM...DG
LONG TERM....DG
Area Forecast Discussion
National Weather Service Cheyenne WY
931 PM MDT Sat Aug 24 2024
.KEY MESSAGES...
- Scattered to numerous showers and thunderstorms are expected
later today and again Sunday, some with locally heavy rainfall
and gusty winds. Isolated strong to severe thunderstorms will
be possible as well.
- Elevated to near critical fire weather conditions over
Converse, and Niobrara counties with gusty southwest winds
this weekend.
- Scattered showers and strong westerly winds gusting 40-50 mph
will be possible on Monday, then dry weather will develop for
Tuesday through Friday. The warmest days will be Tuesday and
Wednesday.
&&
.UPDATE...
Issued at 929 PM MDT Sat Aug 24 2024
Allowed the Red Flag Warnings for FWZ 417 and 418 to expire on
time at 9 PM. Winds have eased and humidity has climbed above
critical levels. Updates have been sent.
&&
.SHORT TERM /THROUGH MONDAY/...
Issued at 206 PM MDT Sat Aug 24 2024
Latest GOES WV imagery shows a large scale upper level low over
northern CA that continues little eastward progression with the
blocking pattern remaining in place across the central CONUS. A
channel of drier air aloft extends from the southwest CONUS through
central WY that has brought elevated to critical fire weather
conditions across portions of the CWA. So far have observed gusty
winds 30-40 mph, especially from Carbon Co through Converse Co, with
latest GOES imagery showing active wildfire behavior with ongoing
fires in the region, but outside of the CWA. Red Flag Warnings
continue through this afternoon for east-central WY where RHs have
dropped around 20 percent and could continue to drop with
downsloping southwesterly winds off the North Laramie Range.
Additionally, monsoonal moisture east of the I-25 corridor into the
NE panhandle will bring the chance of showers and thunderstorms
again later today into this evening with another shortwave passage.
However, instability remains fairly weak with latest RAP showing 500-
1000 J/kg of MLCAPE only in Morrill/Cheyenne Co where surface dew
points are currently around 60F degrees.
A few lingering overnight showers may persist through Sunday morning
before the next push of moisture from the south in western CO
arrives in Carbon Co by late morning Sunday. Expecting an increasing
coverage in showers and thunderstorms Sunday with favorable lift
from the upper level low finally progressing eastward as it phase in
with the subtropical jet. Widespread marginal instability (400-800
J/kg), especially west of the Laramie Range, with dry low-levels
will make gusty winds the main hazard.
The passage of the compact upper level low Monday will bring morning
to midday showers with gusty winds in the afternoon. Can expect
cooler temperatures in the 70s and 80s, though still near normal for
late August over the NE panhandle. 35-40 kt flow around the base of
the upper level trough across the Laramie Range would be supporting
of strong westerly winds across the I-25 corridor. Local in-house
guidance has been waking up to the idea of an early season wind
event, but has been keeping forecast wind gusts around 40-50
mph.
&&
.LONG TERM /MONDAY NIGHT THROUGH SATURDAY/...
Issued at 206 PM MDT Sat Aug 24 2024
Monday night/Tuesday...Isolated to widely scattered showers and
thunderstorms will end Monday evening across the Nebraska
Panhandle in the wake of the shortwave trough aloft. Drier air
aloft moves overhead for Tuesday, thus no precipitation
expected. With an increase in 700 mb temperatures, maximum
temperatures will be warmer.
Wednesday...Continued dry with southwest flow aloft and a relatively
dry airmass overhead. The warming trend continues with 700 mb
temperatures near 14 Celsius.
Thursday-Saturday...The lower and mid levels look to remain
relatively dry looking at precipitable water values, thus we will
continue a dry forecast. Somewhat cooler on Thursday in the wake of
a passing cold front and 700 mb temperatures near 11 Celsius, with a
warming trend for Friday and Saturday.
&&
.AVIATION /00Z TAFS THROUGH 00Z MONDAY/...
Issued at 527 PM MDT Sat Aug 24 2024
Concern tonight with the 00Z TAFs will be convection in the
Panhandle. Latest HRRR/RAP short term guidance does not show
much convection this evening. Looking at latest radar...there
are a few cells developing. So continued VCTS wording in TAFs
for a couple hours. Other concern will be possibility of
stratus in the Panhandle. KAIA...KSNY and KBFF have all gone
down the previous 3-4 mornings. Believe tonight will be the
exception as we do have westerly downsloping winds. Did not
include low clouds in these TAFs overnight based on the
downsloping winds. But will continue to monitor and will adjust
as needed.
&&
.CYS WATCHES/WARNINGS/ADVISORIES...
WY...None.
NE...None.
&&
$$
UPDATE...GCC
SHORT TERM...MB
LONG TERM...RUBIN
AVIATION...GCC
Area Forecast Discussion
National Weather Service Green Bay WI
1102 PM CDT Sat Aug 24 2024
Updated aviation portion for 06Z TAF issuance
.KEY MESSAGES...
- Heat and humidity will build from Sunday into early next week.
Monday looks to be the warmest day across the entire area, with
highs in the upper 80s to mid 90s. The heat will continue across
central and east central WI on Tuesday when heat indices in the
mid to upper 90s are expected, with some locations across
exceeding 100 degrees at times.
- Next chance for storms will arrive late Monday into Tuesday.
Will continue to monitor the potential for some strong to severe
storms.
&&
.DISCUSSION...
Issued at 312 PM CDT Sat Aug 24 2024
Short Term...Tonight and Sunday
The latest RAP analysis and satellite/radar imagery show shortwave
energy moving across northern Lake Superior while a beefy mid-
level ridge is building over the Great Plains. Enhanced moisture
within a thetae axis and south of the shortwave energy mentioned
above has produced scattered to broken mid-level clouds over
northern WI and the Upper Peninsula. No showers have developed
within the zone, but a few showers could pop along lake breezes of
the U.P. Looking upstream, a warm front is positioned over
northeast Kansas into Missouri where a thunderstorm complex
impacted the area this morning. The chance of impactful weather
remains low over the next 24 hours, but concerns include fog and
shower potential from late tonight into Sunday.
Fog Potential: Clouds across northern WI will dissipate this
evening, which will leave clear conditions across the region for a
time until warm advection clouds arrive into central WI towards
daybreak. The clear skies and light winds will promote ground fog
after midnight as temps approach the cross-over temp. Locally
dense fog is possible, particularly over the sandy soil areas of
far northern WI. The fog should lift by 8-9 am.
Shower Potential: As a potent mid-level ridge builds northeast,
the warm front will surge towards the western Great Lakes. An area
of elevated moisture and instability will precede the surface
front late tonight into Sunday. Most unstable capes will rise into
the 500-800 j/kg range by 7 am Sunday morning over central WI
where the CAMS develop a broken line of light showers. Will leave
a small chance in the forecast.
Additional waves of moisture advection are expected through Sunday
afternoon, but most models are dry after about 9 am. This is
likely due to a developing cap in the 8-9 kft area. As a result,
will remove pops from mid-morning onwards.
Temperatures: Readings will be trending warmer on Sunday with
highs in the mid to upper 80s expected in the afternoon. It will
feel more humid as well with some low 90s heat indices expected
over central WI to the southern Fox Valley.
Long Term...Sunday Night Through Saturday
Main forecast concerns in the long term continue to be how hot
and humid it will get early next week and if/when/where showers
and storms (some possibly strong/severe) will occur.
Heat & Humidity:
The heat and humidity will build into early next week as ridging
over the Plains builds/expands north/east into the western Great
Lakes. 850mb temps forecast to peak out between 20-25C Monday and
Tuesday, allowing temps to soar into the mid 80s to low 90s, with
some mid 90s not out of the question in central or east central
WI, where a couple record highs could be in jeopardy. With a
slower arrival of the front, expect Tuesday to be similar to
Monday in the Fox Valley, with the one caveat being if/where any
storm complex tracks, which could keep more clouds around. Only
spot not seeing the hot temps will be near Lake Michigan where
highs look to remain mainly in the 80s. Dewpoints likely to
remain/climb into the low to mid 70s, pushing heat index readings
into the 90s, with some low triple digits likely mainly across
central and east central WI. A little skeptical of the dewpoints
in the upper 70s, especially with not much evidence of anything
upstream and the evapotraspiration likely limited to our
south/west as the corn crop is getting pretty late in the season.
But some higher dewpoints could pool ahead of the frontal
boundary. Low temps Sunday and Monday nights will only drop into
the lower 70s across much of central and east central WI. The
combination of the heat, humidity and little recover at night,
will likely lead some some heat related health issues for heat-
sensitive groups. Still too early for any heat headline, but heat
advisories looking more and more likely for Monday and/or Tuesday.
Will continue to highlight in the HWO and social media posts.
Cooler and less humid air will arrive on Wednesday and continues
through the end of the week, but it will still feel summer-like
with highs mainly in the mid 70s to mid 80s.
Shower/Storm & Severe Wx Potential:
A few models trying to generate some shower/storm activity
overnight Sunday into early Monday associated with the push of
WAA, but the capping inversion should keep things pretty limited
and will go with a dry forecast. It is going to be nearly
impossible to get anything to develop during the day on Monday as
strong capping remains in place, with convective temps around 40C!
Cap could break over north-central WI in the evening or some
elevated convection could get going, but that threat looks low at
times time. Will need to watch upstream across MN as a LLJ, front
and shortwave will likely kick off an area of storms, likely
forming into a MCS. This activity could make a run at central and
north central WI late Monday into early Tuesday (where SPC has a
slight risk out for Day 3) as it will be moving into a rather
impressive pool of instability as MUCAPE looks to remain between
1000-2000 J/kg through the night. Tuesday is looking like a boom
or bust day as impressive severe parameters will be in place, with
CAPEs to ~4000 J/kg, deep layer shear to ~50 kts, steep lapse
rates, and high 0-3 km SRH bringing all severe threats into play.
But will have to break the cap that will be in place. Thinking the
combination of the frontal boundary and trough/shortwave will be
enough to get storms to initiate, but timing of the shortwave and
front still to be pinned down as differences remain. This could
determine how much of the area will be impacted by the storms,
along with how intense the storms will be.
Things quiet down on Wednesday, with additional chances for
shower and storms arriving Thursday into early Friday.
&&
.AVIATION...for 06Z TAF Issuance
Issued at 1102 PM CDT Sat Aug 24 2024
VFR conditions will dominate the early overnight hours, but some
patchy fog may reduce flight categories at a few locations shortly
after 06Z. Near the Lake Michigan shoreline, some marine fog may
work its way across the area, so made a mention in the MTW TAF.
Additional ground fog will be possible across portions of the
northwoods, affecting areas from Rhinelander to Iron Mountain. The
latest trend keeps visibility up over central WI, so removed the
fog with the 06Z TAFs.
Sunday, scattered afternoon cloud cover will cross the region as
showers decay to our west, but no impactful aviation hazards are
expected.
&&
.GRB WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
DISCUSSION.....MPC/Bersch
AVIATION.......Uhlmann
Area Forecast Discussion
National Weather Service Grand Rapids MI
1115 PM EDT Sat Aug 24 2024
.KEY MESSAGES...
- Warming continues through weekend, slight chance storms Sunday
- Hot and humid Monday through Wednesday
- Not quite as hot late in the week
&&
.UPDATE...
Issued at 1115 PM EDT Sat Aug 24 2024
Quick update to add slight chance POPs across the southern zones
overnight as mid level warm advection and moisture return is
allowing isolated showers to develop in the vicinity of southwest
forecast area adjacent Lake Michigan currently. These showers will
spread east overnight but are expected to remain isolated through
Sunday morning and into the afternoon. Some thunder is possible by
Sunday afternoon.
&&
.DISCUSSION...
Issued at 300 PM EDT Sat Aug 24 2024
- Warming continues through weekend, slight chance storms Sunday
Heights continue to rise over the weekend as upper high over OK
expands northeastward, resulting in a continued warming trend
and highs Sunday pushing 90. Lwr MI remains in an area of
PWAT/moisture "minimum" this afternoon although higher values do
begin to creep in from the southwest later tonight and especially
on Sunday, as do the juicier sfc dew points.
A few isolated showers may develop along the leading edge of
those higher PWATs; mainly south of I-96 where weak low level
convergence may be present along a sfc trough/warm front. There
could be a tstm or two Sunday afternoon once instability builds
and MLCapes rise to near 1000 J/KG. Interestingly though the
latest RAP guidance suggests that the higher sfc dew pts on Sunday
may get no farther north than about a RQB to LAN line.
Convection over Missouri today has been forming on the immediate
edge of the building/expanding heat dome and on the nose of a 30
kt low level jet. Southward propagation has been occurring on the
east side of the upper high and in alignment with deep layer
thickness. A similar set up occurs later tonight along the
Mississippi River in the vicinity of LSE/DBQ/MLI and those storms
also propagate south on Sunday. Some of the synoptic ingredients
supporting these tstm clusters on the edge of the heat dome should
be in our area by late Sunday night and seems worthy of a 20 pop
in wrn sections at this time.
- Hot and humid Monday through Wednesday
An upper level ridge will gradually build in and bring hot and humid
wx early to midweek with high temps reaching the upper 80s to lower
90s Monday through Wednesday. In the increasingly warm and humid and
unstable airmass isolated showers and storms are possible early to
midweek.
Several upper level disturbances embedded in the mid to upper level
flow could be triggering mechanisms for isolated pcpn but subsidence
under the ridge will tend to suppress this. Some of the medium range
guidance has also backed off a bit in terms of how warm h7 temps
will get meaning a little less potential for a strong cap as an
inhibiting factor. All things considered mostly dry and hot and
humid conditions are still expected early to midweek with little
more than an isolated shower or storm.
- Not quite as hot late in the week
High temps will settle back into the 80s late week as the upper
ridge breaks down in advance of the upper trough moving east across
the upper midwest. This pattern shift will also result in potential
for a few showers and storms late Thursday into Friday.
&&
.AVIATION /00Z TAFS THROUGH 00Z SUNDAY/...
Issued at 707 PM EDT Sat Aug 24 2024
Scattered to broken high clouds are expected through the period. A
weak warm front moving north tonight across southern Lower may
kick off a few showers after 06z as an increase in low level
moisture develops. Otherwise, VFR expected.
&&
.MARINE...
Issued at 300 PM EDT Sat Aug 24 2024
Light synoptic flow continues over Lk MI for the rest of weekend
keeping winds/waves on the low side. Southerly flow could
increase a bit for late Sunday night and Monday but likely not
enough to warrant any marine headlines. The cold water which had
been present along the coast from upwelling earlier in the week
has recovered into the 60s but there still may be some haze over
the waters as the warmer and more humid air mass arrives.
&&
.GRR WATCHES/WARNINGS/ADVISORIES...
MI...None.
MARINE...None.
&&
$$
UPDATE...Ostuno
DISCUSSION...Meade/Laurens
AVIATION...04
MARINE...Meade
Area Forecast Discussion
National Weather Service Wilmington NC
856 PM EDT Sat Aug 24 2024
.SYNOPSIS...
Cooler and drier than normal conditions will continue this
weekend, especially inland, before warmer temperatures return
starting early next week. Rain chances may increase towards the
end of the work week and into the weekend as high pressure slips
offshore.
&&
.UPDATE...
Not much change from previous fcst thinking and persistence.
Isolated POPs, up to 24% along the immediate coast, possible,
per latest KLTX 88D and surrounding radar trends and the latest
HRRR guidance. Some tweaking to the individual elements a
given, but no categorical changes applied.
Across the coastal waters, NE-ENE winds 15 to occasionally 20 kt
with a modest gradient west of the coastal trof extending
across the local waters. Seas 3 to 4 ft, with a few 5 footers
out there, and mainly a mix of NE 4 to 6 second wind wave and an
identifiable ESE-SE 7+ second period swell. Isolated to
scattered showers and an isolated tstorm remains possible
overnight.
352pm edt Update...
The Coastal Flood Advisory for the Lower Cape Fear River near
Downtown Wilmington has been cancelled as it is forecasted to
remain below minor flood levels tonight. Minor coastal flooding
along the river is forecasted again during Sunday and Monday
high tides.
&&
.NEAR TERM /THROUGH SUNDAY/...
With low level winds more easterly than northerly, we will start
to see a warming trend beginning Sunday. Coastal trough is
still just offshore, with associated showers remaining over the
waters as they are falling apart quickly as they approach the
coast with low level subsidence and dry air aloft over land.
Have limited slight chance pops to the immediate coastline
through tonight with broken low-mid clouds across coastal
counties and high clouds inland. Lows tonight in the low 60s
near I-95 and upper 60s/70 along the coast. While low level
ridge persists over the East Coast through tomorrow, a mid level
ridge over the central US builds slightly eastward Sunday. This
will push mid level dry air into the area from the west and
lead to decreasing PWATs during the day. Less cloud cover on
Sunday, with only minimal pops across coastal NE SC. Highs
Sunday in the mid to upper 80s.
&&
.SHORT TERM /SUNDAY NIGHT/...
High pressure remains inland through the period with a boundary
offshore. Activity should remain offshore with the boundary
which will be pushed south of the area Monday. Dry conditions
with mostly clear skies and warming temperatures will hold
through the period. Highs near 90 Monday then in mid 90s for
Tuesday. Lows in the mid 60s Sunday night and then upper 60s
Monday night.
&&
.LONG TERM /MONDAY THROUGH SATURDAY/...
Dry conditions persist until Thursday. The high should slip
offshore by then with an upper level disturbance and surface
cold front approaching from the north. PWATs should increase
ahead of this feature, but it doesn`t look like it moves through
the CWA. We then look to move into a diurnal pattern with low
precip chances possible during the afternoon/evenings through
the end of the period.
&&
.AVIATION /01Z SUNDAY THROUGH THURSDAY/...
VFR dominates the 24 hr TAF issuance period. The only fly in
the ointment will be possible and periodic onshore movement of
MVFR clouds from off the Atlantic as pcpn and clouds associated
with the coastal trof offshore continues to churn away thru the
night and into Sunday. SCT-BKN Scu/Cu at 4k-6k ft to dominate
the coastal terminals Sun with SCT diurnal Cu 5k+ inland. Will
keep coastal terminals above the 3k MVFR cloud deck. Followed
previous fcst thinking and kept the BR threat out from all
terminals. Northeasterly winds persist through TAF period. The
onshore -shra movement looks too isolated via 88D loops and
latest HRRR runs, with majority of the onshore movement well
south of MYR. Current ENE winds back to NNE-NE 4 to 8 kt tonight
at the coastal terminals, inland terminals to remain NE 5 kt or
less tonight. Sun, NE around 10 kt except becoming ENE-E 10g15
kt at the coastal terminals during Sun aftn.
Extended Outlook...VFR conditions expected.
&&
.MARINE...
Through Sunday...With broad high pressure over the East Coast
and persistent offshore coastal front, northeast winds 15-20
kts continue to prevail across the coastal waters through
Sunday. 3-4 ft seas tonight and Sunday will be a mix of NE wind
chop and SE swell. Scattered showers will continue across the
waters tonight into tomorrow, before coverage decreases tomorrow
afternoon as mid level dry air moves in and front moves further
from the coast, with isolated thunder possible.
Sunday Night through Thursday...The boundary keeping activity
over the waters should move away from the area Monday through
Tuesday, with high pressure keeping dry conditions in play until
it slides offshore Thursday. NE winds will become SW Tuesday
night with speeds 10-15 kts. Seas 2-3 ft with a SE swell at 7-9
seconds.
&&
.ILM WATCHES/WARNINGS/ADVISORIES...
NC...Beach Hazards Statement from 6 AM EDT Sunday through Sunday
evening for NCZ106-108.
SC...Beach Hazards Statement from 6 AM EDT Sunday through Sunday
evening for SCZ056.
MARINE...None.
&&
$$
SYNOPSIS...ILM
UPDATE...VAO/DCH
NEAR TERM...VAO
SHORT TERM...LEW
LONG TERM...LEW
AVIATION...DCH
MARINE...VAO/LEW
Area Forecast Discussion...Updated
National Weather Service Lincoln IL
735 PM CDT Sat Aug 24 2024
.KEY MESSAGES...
- Above normal temperatures are expected well into the upcoming
work week, with dangerous heat and humidity on Monday and
Tuesday. On those days, heat indices as high as 115 degrees are
possible.
- There is a chance (20-40%) of showers/storms late tonight into
early Sunday, mainly west of I-55, but chances have trended
lower compared to previous forecasts. While not all areas will
see storms, those that do could experience locally heavy
rainfall.
- After a hot stretch, below normal temperatures are favored
(40-60% chance) during the first week of September.
&&
.UPDATE...
Issued at 735 PM CDT Sat Aug 24 2024
Regional radar is fairly quiet this evening, with a remnant MCV
west of St. Louis. Still quite a bit of high clouds lingering in
our area from the earlier convective cluster over Missouri.
Evening balloon sounding is not overly moist in most of the
column, and latest RAP guidance continues to focus the main LLJ
well to the west. Most recent runs of the NAM-Nest and the HRRR
try and trigger a few showers across central Illinois as early as
9 pm, though most of the focus still looks to be toward 3-4 am or
so. Overall PoP placement hasn`t been changed too much, though
actual values were toned down a bit. If storms do manage to form,
there remains plenty of precipitable water to work with, and
midday HREF run shows areas of 30% chances of 3-hour rainfall
greater than half an inch near and west of the Illinois River.
Geelhart
&&
.DISCUSSION...
Issued at 243 PM CDT Sat Aug 24 2024
Dangerous heat and humidity remain the top concern for this
forecast period, particularly on Mon-Tues. As of 2pm/19z Saturday
afternoon, the synoptic pattern was defined by a large upper ridge
which was centered over the southern Plains with its ridge axis
extending northward through MN. A decaying convective complex
continued to sag south across southern MO. While some cirrus
associated with this complex has spilled into west-central IL, the
bulk of the cirrus shield has slowed its eastward progression and
no longer appears likely to push into the ILX CWA. The rest of
the daytime hours on Saturday will feature modest southerly winds,
temps in the upper 80s/low 90s, and perhaps some diurnal Cu.
Before turning attention to the upcoming heat wave, will quickly
touch on the precip chances for tonight/early Sun. CAMs have
backed off quite a bit on storm coverage tonight, which seems
appropriate given weak LLJ forcing. The strongest LLJ forcing and
greater instability both seem positioned west of the ILX CWA as
well, further reducing confidence that we see meaningful storm
coverage locally. The latest forecast calls for a 20-40% chance of
showers/storms west of I-55 tonight. While storm coverage appears
limited, where the rain does occur it could be locally heavy as
PWATs approach 2". The latest HREF depicts some localized areas of
1.5-3" of rain, and there is a marginal risk (level 1 of 4) of
excessive rainfall west of the IL River.
The robust upper ridge over the southern Plains will gradually
shift NE over the next several days, eventually becoming centered
over MO/IL on Mon-Tues. Concern is growing that life-threatening
heat and humidity will develop as a result of this feature. As
noted yesterday, the forecast 500mb heights (>5970m) are near the
max of the ILX sounding climatology, and similarly, the forecast
925mb temps (approaching +30 degC) are also near the max of the
ILX sounding climo. With that in mind, it is a not a surprise that
NBM forecast high temps have been trending warmer, now into the
upper 90s (west of I-55 on Mon, area-wide on Tues). Such values
would threaten high temp records (see climate AFD for more
details).
The other factor contributing to the sweltering conditions will be
the humidity. As noted yesterday, there is still some uncertainty
about the impact that evapotranspiration will ultimately have on
the dewpoints. During internal collaboration, NWS Chicago shared
that during a similar heat event late last August, the dewpoint
forecasts were too low and underestimated the contributions from
evapotranspiration, but that NAM guidance actually performed well
in its dewpoint forecasts. That trend has also been realized so
far this weekend, with blended guidance underperforming the actual
dewpoints while the NAM has done better. Accordingly, an effort
was made to increase dewpoints on Mon/Tues based on the NAM/ECMWF
forecasts. This change resulted in peak heat indices of 105-115F
west of I-55 on Monday, then area-wide on Tuesday.
If dewpoints wind up higher than currently forecast, it would
likely mean the forecast high temps are too warm, or vice versa,
but regardless how these two variables play out, there is high
confidence that dangerous heat will be present Mon-Tues. Heat
headlines will eventually be needed for those days. Beyond
Tuesday, there is spread among the models as to how quickly
conditions cool off, with the spread due to a difference in the
placement of a boundary. The latest blended guidance has trended
warmer, with highs in the 90s through Thursday. Lower dewpoints
result in less aggressive heat indices on Wed-Thurs, although I
would wager that if that boundary stays north of the area that
forecast dewpoints will eventually trend higher as the NAM starts
to capture the latter half of the week.
While precip chances are not zero throughout the week, it will be
difficult for any development beneath such a robust thermal ridge.
A better chance for precip arrives late in the work week as a
stronger cold front arrives. After a hot week, a cool down is
still on track into the start of September, with the CPC 8-14 day
outlook favoring (40-60% chance) below normal temperatures. Normal
temps during the first week of September include highs in the low
80s and lows in the upper 50s.
Erwin
&&
.AVIATION... (For the 00z TAFs through 00z Sunday Evening)
Issued at 624 PM CDT Sat Aug 24 2024
VFR conditions expected the next 24 hours, with mainly high level
ceilings. However, some showers approaching KPIA/KSPI after 09Z
may lower ceilings down to around 6-7kft for a few hours.
Southerly winds will pick up mid to late morning Sunday to around
10 knots.
Geelhart
&&
.CLIMATE...
Issued at 311 PM CDT Sat Aug 24 2024
Record & Forecast Highs for Mon Aug 26
Record | Forecast
Peoria......... 98 in `36/`03 97
Lincoln........ 101 in 1936 | 95
Springfield.... 103 in 1936 | 96
Bloomington.... 97 in 2014 | 94
Decatur........ 103 in 1936 | 95
Champaign...... 98 in 2003 | 94
Mattoon........ 102 in 1943 | 93
Record & Forecast Highs for Tues Aug 27
Record | Forecast
Peoria......... 98 in 1899 | 99
Lincoln........ 98 in 1936 | 97
Springfield.... 97 in 1983 | 98
Bloomington.... 102 in 1899 | 97
Decatur........ 101 in 1983 | 98
Champaign...... 96 in 1953 | 98
Mattoon........ 98 in 1953 | 98
Record Warm Lows & Forecast Lows for Mon Aug 26
Record | Forecast
Peoria......... 75 in `83/`93 73
Lincoln........ 74 in 1948 | 70
Springfield.... 77 in 1943 | 73
Bloomington.... 74 in `59/`03 72
Decatur........ 74 in 2018* | 70
Champaign...... 73 in 2018* | 70
Mattoon........ 75 in 2018 | 70
Record Warm Lows & Forecast Lows for Tues Aug 27
Record | Forecast
Peoria......... 78 in 1886 | 76
Lincoln........ 75 in 1921 | 74
Springfield.... 77 in 1936 | 74
Bloomington.... 75 in 1977 | 74
Decatur........ 76 in 2018 | 74
Champaign...... 73 in 2020* | 74
Mattoon........ 75 in 2004* | 73
* - occurred in several years, most recent shown.
&&
.ILX WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
Area Forecast Discussion
National Weather Service Key West FL
1030 PM EDT Sat Aug 24 2024
...New DISCUSSION, MARINE, AVIATION...
.DISCUSSION...
Issued at 1030 PM EDT Sat Aug 24 2024
After another very active day across the Florida Keys and
surrounding coastal waters, with scattered to numerous showers and
thunderstorms, quiet conditions have returned to the area this
evening, with radars currently detecting just a few showers over
the offshore Gulf waters. Temperatures along the island chain are
hovering in the lower 80s, with dewpoints in the mid to upper
70s, and winds on land from the northeast to east at 5 to 10 mph.
Surface analysis depicts a weak trough just east of Florida,
extending southward to just west of Andros Island. Aloft, a well-
defined mid/upper level low continues to spin over the central
Gulf. The 00Z Key West sounding sampled a very moist airmass, with
PW of 2.14 inches (near the 90th percentile for the date). MIMIC-
TPW satellite imagery shows copious tropical moisture continuing
to move west across the area, with estimated PWs of 2.0 to 2.3
inches extending eastward to near Andros Island.
The overnight forecast is tricky. There certainly is plenty of
moisture available, with the combination of the mid/upper trough
to our west and the trough/tropical wave axis to our east
providing potential sources for forcing. However, the complete
lack of any convection in our area thus far during the evening
suggests that the atmosphere is quite worked over and may take
some additional time to recover. Also, the latest HRRR and
experimental HRRR-Caribbean CAM guidance suggest that convection
will not reinitiate across our area until around sunrise, and the
legacy GFS/NAM MOS guidance is not especially bullish on overnight
rain chances. Have elected to nudge overnight PoPs down just a
notch to 50 percent. Otherwise, expect partly to mostly cloudy
skies to continue, with temperatures remaining in the lower 80s
for the rest of the night outside of any downpours.
&&
.MARINE...
Issued at 1030 PM EDT Sat Aug 24 2024
Evening observations show NE/E winds of 5 to 10 knots along the
reef and at Long Key C-MAN, with seas at Satan Shoal running just
over 2 feet. Expected overnight winds were eased down a notch
with the late evening forecast update. Otherwise, no significant
changes were made.
&&
.AVIATION...
(00Z TAFS)
Issued at 1030 PM EDT Sat Aug 24 2024
Unsettled conditions will prevail at the EYW and MTH terminals
through Sunday afternoon, with greater than normal chances for
periods of sub-VFR conditions due to scattered to numerous showers
and thunderstorms. After the quiet period this evening, uncertainly
as to the timing of convective reinitiation remains high, but at
this time the best chance for the next round of widespread
convection appears to run from around sunrise Sunday through at
least early Sunday afternoon. Expect frequent short-term
amendments based primarily on radar trends once convection
redevelops. Outside of convection, surface winds will remain
generally from the northeast to east at 5 to 10 knots.
&&
.KEY WATCHES/WARNINGS/ADVISORIES...
FL...None.
GM...None.
&&
$$
Public/Marine/Fire...Jacobson
Aviation/Nowcasts....Jacobson
Data Acquisition.....DR
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Area Forecast Discussion
National Weather Service Marquette MI
741 PM EDT Sat Aug 24 2024
.KEY MESSAGES...
- 20-40% chance of a brief shower or storm for the interior
central and east through sunset today.
- Warm Sunday in the west half and Monday across the interior UP
as temperatures climb to near 90 and the heat index climbs
into the 90s.
- Chances for showers and thunderstorms Monday into Tuesday and
again Thursday into Friday. The west half of the UP is under
a Marginal (category 1 of 5) risk of severe weather Monday
evening.
&&
.SHORT TERM /THROUGH SUNDAY NIGHT/...
Issued at 215 PM EDT Sat Aug 24 2024
Early afternoon water vapor and RAP analysis shows a 597 dam 500 mb
anticyclone centered near the TX/OK border, with anomalous ridging
extending northward through the Upper Mississippi Valley and further
north toward western Hudson Bay. There is also some weak troughing
extending into SE Ontario extending from a cutoff low over southeast
Hudson Bay. Northwest flow over the local area with dry air noted on
the low-level water vapor channel. Surface pressure pattern is
fairly ill-defined over Upper Michigan. Notable pressure features
are leeside low pressure over the northern/central Plains and an
anticyclone encompassing much of the Eastern Seaboard. Dewpoints in
the mid/upper 60s are common with temps in the upper 70s/low 80s
giving a summer-y feel to the day. Low-level moisture has mixed into
a broken cu/sc deck. Expect this to diminish somewhat through the
afternoon as mixing deepens. MLCAPE has increased to around 500 J/kg
over the eastern UP where the cu appear a bit more agitated,
especially along the Superior lake breeze. Isolated to scattered
showers are expected to develop here, mainly from Luce westward to
the Marquette/Delta/Menominee junction, with more coverage the
further east one goes. Forecast soundings show very dry air at
mid/upper levels, which should limit coverage this afternoon. Severe
weather is not expected, although an isolated thunderstorm or two
cannot be ruled out. Any activity should diminish around sunset.
Tonight, low-level moisture remains elevated with a weak pressure
gradient and dissipating diurnal clouds. This should lead to areas
of fog developing, especially over the central and eastern UP and
Keweenaw. Lows, mainly mid-50s interior to low 60s shorelines.
Sunday, midlevel ridging expands northeastward, with 500 mb height
standardized anomalies reaching +2 to +3 over the west half. 850 mb
temps will increase accordingly on modest warm advection, reaching
the upper teens. Instability builds, but so does capping, and
without much of a trigger, precip is not expected. Heat will build
as well, especially for the west half with mid-80s to near 90
expected, and apparent temps maybe a couple degrees warmer. An
easterly/onshore component to the winds should keep the eastern half
not quite as warm, with low/mid 80s expected (except for the
Michigan/Green Bay shorelines, which may remain in the upper 70s).
Likely enough influence from the ridging to hold with a dry forecast
Sunday night, although a few ensemble members drift some upstream
shower/storm activity into our western zones, so will roll with NBM
slight chance PoPs there. Lows range through the 60s.
&&
.LONG TERM /MONDAY THROUGH SATURDAY/...
Issued at 341 PM EDT Sat Aug 24 2024
A progressive pattern aloft will bring multiple chances for active
weather for the upcoming week. Monday morning, ridging over the
central CONUS extending northeast over the UP and into Ontario and
Quebec will be eroded by a pair of troughs, one over the western end
of the Hudson Bay and one over the central Rockies. The further
north trough will weaken the ridging over the Upper Great Lakes and
northern Ontario to pave the way for the trough over the Rockies to
advance over the Upper Midwest Tuesday. Ridging will briefly build
back in over the UP to provide a patch of dry weather in the midweek
before a deep trough will transit across the US/Canada border and
provide another wave of showers late Thursday and Friday.
Uncertainty grows significantly going into September, but ensemble
means show ridging preferred over western North America which should
allow for a pattern of cooler and slightly drier conditions under
continental northwesterly flow, which is reflected in the CPC
outlooks.
The past 24 hours of guidance have provided some increased
confidence in the track of the troughing and resulting surface low
Monday into Tuesday. Confidence is high in a ~1010mb low near Sioux
Falls, SD by 18Z Monday and reaching the Upper Great Lakes around
18Z Tuesday with most member lows over the UP. Some uncertainty
still exists in how far ahead of the parent low the extent of
showers will be, but some isentropic ascent is present in the NAM
along with broad 850mb warm advection, so a couple of (albeit weak)
lifting mechanisms could be present. Warm, moist flow will allow
high temperatures to climb to near 90 for many interior UP spots,
and with even NBM10th percentile dew points over 70, heat indices
could climb to the mid 90s and above. One complicating factor is
that the NAM Nest shows a decaying MCS moving over the western UP in
the morning hours, which could act to increase boundary layer
moisture or keep cloud cover over the western UP during peak
heating. That is if the placement of the MCS is accurate at all as
it is not uncommon for large placement errors in similar features at
that time frame. If sufficient forcing is present, the atmosphere
looks to be quite unstable, as the LREF shows probabilities of over
2000 J/kg of SBCAPE to be over 50% along the MI/WI state line and up
to 25% as far north as Baraga and as far east as Ishpeming. There
will be some shear present though not tons, around 20-30kt of bulk
shear. Because of the overwhelming instability, present shear, and
plausible forcing, the SPC has issued a Marginal (category 1 of 5)
risk of severe weather over the west half of the UP with the
Ironwood vicinity being in a Slight (category 2 of 5) risk for
Monday evening. Shower chances will pass through the UP Tuesday and
potentially into Wednesday morning, though the spread increases in
how quickly the low will pass, thus decreasing confidence in severe
weather on Tuesday.
A dry midweek period will follow as the trough departs to the east
and a trough over western Canada kicks a ridge over the Upper Great
Lakes, though high temperatures in the low 70s will be near-normal
for late August. The western trough will arrive over the Upper Great
Lakes in the late-week period into the weekend, once again bringing
PoPs up to near 60% with thunder potential. Uncertainty is even
higher with this period of weather than the early week period, but
it is looking increasingly likely that next weekend will have a wet
beginning.
&&
.AVIATION /00Z TAFS THROUGH 00Z MONDAY/...
Issued at 740 PM EDT Sat Aug 24 2024
Not too many changes made to the 00z TAF issuance. Confidence is
fairly high, moreso at SAW and CMX, that patchy dense fog will
develop sometime after midnight. Current dewpoints are sitting in
the mid-upper 60s with 70-80% RHs, light winds, and diurnal cu
starting to diminish. This will allow good radiational cooling and a
quick turnover to soupy low levels. Opted to keep TEMPOs for
possible LIFR vis at SAW and CMX in the 8-12z timeframe. Fog will
scour with the sunrise and no forecast concerns for Sunday as skies
will be fairly clear with light S-SE winds.
&&
.MARINE...
Issued at 341 PM EDT Sat Aug 24 2024
Wind gusts will be below 20 kts for much of the forecast. The
exceptions will come in the form of a pair of disturbances next
week, though uncertainty in the track and timing of these
disturbances are high. The first looks to pass near Lake Superior
Monday into Tuesday with the highest chances of gusts exceeding 20
kt coming behind the system Tuesday afternoon through midday
Wednesday with northeasterlies between Isle Royale and the Keweenaw
Peninsula. The second disturbance will arrive approximately Thursday
evening. Gales are unlikely with either system. Significant wave
heights are forecast to be under 4 feet except for Tuesday night
into Wednesday between Isle Royale and the Keweenaw Peninsula with 4-
5 ft waves.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
None.
Lake Superior...
None.
Lake Michigan...
None.
&&
$$
SHORT TERM...Thompson
LONG TERM...GS
AVIATION...BW
MARINE...GS
Area Forecast Discussion
National Weather Service Morristown TN
1036 PM EDT Sat Aug 24 2024
...New UPDATE...
.UPDATE...
Issued at 1027 PM EDT Sat Aug 24 2024
No changes needed to the immediate forecast. High pressure and
calm conditions, especially overnight, will prevail with >1020 mb
dominating at the sfc. There is the chance of isolated patchy
fog.
KS
&&
.SHORT TERM...
(This evening through Sunday)
Issued at 312 PM EDT Sat Aug 24 2024
Key Messages:
1. Another dry day with gradually warming temperatures.
2. Ridging across the Great Plains and Mississippi Valley
continues to result in strong subsidence with clear sky conditions
and lower dew points across our region.
Discussion:
Upper-level 597 dam 500mb ridge across the Great Plains and mid-
Mississippi Valley continues to place us within northwest flow
aloft with subsidence and clear sky conditions. This will continue
to result in dry air aloft mixing into the boundary layer during
the afternoon hours with locally lower RH values. Blended in HRRR
with NBM values to lower forecast dew points based on the pattern
and current observations/trends this afternoon. Otherwise, 850mb
heights will continue to rise with warming boundary layer
temperatures resulting in max temperatures 3 to 4 degrees warmer
than today.
&&
.LONG TERM...
(Sunday night through next Saturday)
Issued at 312 PM EDT Sat Aug 24 2024
Key Messages:
1. Near-record heat is expected mid-week with highs well into the
90s to near 100 in southern areas.
2. Late in the week and into the weekend, rain chances increase with
some moderation in temperatures.
Discussion:
At the start of the period, a near-record 500mb ridge will be
centered to our west with surface high pressure continuing across
the eastern U.S. Heading into Monday, this setup will continue the
dry and warming trend we have seen in the past couple of days with
500mb heights reaching a record 5,950m. However, the more impressive
heat in the lower levels is noted by Tuesday and Wednesday as the
ridge sets up overhead. The model consensus suggests 850mb
temperatures to reach in excess of 22 Celsius, which is at or above
record values for this time of the year. As such, near record high
temperatures (shown below) are increasingly likely. By Thursday, the
ridge will begin to shift further east with some moisture return
into the area. Overall, low-level temperatures will remain nearly as
high around record values, but a low-end chance for rain will be
introduced. Below are the record high temperatures and most
recent year of occurrence.
Daily Record High Maximum Temperatures
Date Chattanooga Knoxville Tri-Cities Oak Ridge
08-27 102(1936) 101(1943) 95(2016) 97(2007)
08-28 100(1990) 98(1936) 94(1953) 98(1995)
08-29 100(1993) 102(1948) 96(1953) 99(1948)
Late in the week and into the weekend, a further breakdown in the
ridge and increasing moisture is indicated. This will allow for a
further increase in rain chances and some moderation of temperatures
back below record values. The pattern still remains uncertain, but
hopefully some rain is seen after many days of hot/dry conditions
and climatological decrease in rain potential.
&&
.AVIATION...
(00Z TAFS)
Issued at 726 PM EDT Sat Aug 24 2024
VFR under high pressure expected to continue. SKC-SCT sky
conditions with light & variable winds expected. Low chance of
brief fog at TRI just before sunrise. Added a no VSBY restriction
TEMPO to reflect this chance.
&&
.PRELIMINARY POINT TEMPS/POPS...
Chattanooga Airport, TN 65 94 66 95 / 0 0 0 0
Knoxville McGhee Tyson Airport, TN 64 92 65 93 / 0 0 0 0
Oak Ridge, TN 64 91 65 93 / 0 0 0 0
Tri Cities Airport, TN 60 88 62 89 / 0 0 0 0
&&
.MRX WATCHES/WARNINGS/ADVISORIES...
NC...NONE.
TN...NONE.
VA...NONE.
&&
$$
SHORT TERM...JB
LONG TERM....BW
AVIATION...KS
Area Forecast Discussion
National Weather Service Salt Lake City UT
345 PM MDT Sat Aug 24 2024
.SYNOPSIS...Warm, dry and windy to very windy conditions can be
expected across western Utah today ahead of an approaching cold
front. Lingering moisture and instability will bring the threat of
strong thunderstorms across eastern Utah Sunday afternoon and
evening. A cold front will bring much cooler temperatures to
northern and central Utah for Sunday while the south remains mild.
&&
.SHORT TERM (Through 12Z Monday)...Strong winds continue across
western Utah this afternoon, with occasional gusts up to 65 mph.
Early afternoon upper air and satellite analysis indicates a very
cold upper level trough is crossing into the western Great Basin.
A strong upper level ridge remains across the southern Plains.
Very critical fire weather conditions continue across western
Utah, with humidities near single digits and winds gusting up to
65 mph. At least one wildfire has been reported. Please be very
careful in these areas with any potential ignition sources. Red
Flag Warnings continue across western Utah. High wind warnings
and wind advisories also continue for many locations across the
state through midnight. Winds should decrease later this
evening...so do not anticipate any extensions.
By Sunday, broad upper level diffluence will remain across
eastern Utah. This combined with the upper level trough shifting
across the region, SBCAPE near 1000-1500 J/kg, and deep layer
shear around 40-50kts will support the potential for a few strong
thunderstorms. Of note, the last few runs of the HRRR have
actually shifted the best forcing for convection east of the CWA,
while the NAMNEST and other CAMS shift this area of convection
further west, largely between the I-15 corridor and the Colorado
River. The 00Z runs may increase confidence in either scenario.
.LONG TERM (After 12Z Monday), Issued 401 AM MDT... Weather-wise,
a somewhat benign week is expected. The period will begin with a
trough of low pressure existing the Great Basin, with a flat ridge
of high pressure shifting across the region on Tuesday. This
pattern will ensure dry weather across the forecast area both
days. High temperature readings, on the order of 10 degrees below
normal on Monday, will moderate on Tuesday.
Ensemble solutions generally favor a trough of low pressure moving
across the Northern Rockies on Wednesday, though with roughly a
50/50 split with depth of trough, along with some timing
differences. The more amplified trough would produce stronger winds
across the forecast area, primarily the northern half of Utah and
extreme southwest Wyoming. Coupled with marginally low relative
humidities, some potential (less than 20 percent chance) exists for
critical fire weather conditions Wednesday afternoon and evening.
As the trough progresses eastward on Thursday, generally dry
conditions will prevail, with temperatures a few degrees below
normal.
Ensembles depict a ridge of high pressure building over the Great
Basin on Friday, with roughly 80 percent of the solutions offering a
more amplified ridge. Dependent upon location of ridge axis, this
could lead to moisture advecting back into southern Utah by Friday
afternoon, justifying current low (20-30 percent) chances for
showers and thunderstorms.
&&
.AVIATION...
KSLC...Strong southerly winds around 40 knots will continue
through 00-01Z. A wind shift to the northwest is possible as early
as 01Z, or as late as 03-04Z, depending on how quickly the
northwest wind can undercut the stronger southerly winds aloft.
Lighter south winds will then return by 06-08Z. Southerly winds
will increase again Sunday morning before turning to the northwest
with a cold front passage midday. Visibility restrictions due to
blowing dust and smoke from a wildfire near the Juab/Tooele line
are likely through this evening.
.REST OF UTAH AND SOUTHWEST WYOMING...Strong southwesterly winds
will continue across much of the area with widespread gusts to
30-40kts, and locally up to 50kts. Areas of blowing dust are
expected, especially across western Utah from these winds.
Isolated showers and thunderstorms will continue across
southeastern Utah this afternoon, with an additional round
possible overnight into Sunday morning.
&&
.FIRE WEATHER...Widespread, very critical fire weather conditions
will continue across western Utah as an anomalously cold upper
level trough crosses the Great Basin into the Rocky Mountain
States through Monday. A cold front with a northwest wind shift
will cross northwest Utah Sunday morning, gradually shifting
through the remainder of the state Sunday evening into Sunday.
Significantly cooler and moister conditions will build into the
state Sunday into Monday. By Tuesday, high pressure will move into
the area, bringing drier, warmer conditions once again.
&&
.SLC WATCHES/WARNINGS/ADVISORIES...
UT...Red Flag Warning until midnight MDT tonight for UTZ478-492-495.
High Wind Warning until 10 PM MDT this evening for UTZ101-102-
115-122.
Wind Advisory until 10 PM MDT this evening for UTZ103>106-116-
119>121-126-129-130.
WY...Red Flag Warning until 9 PM MDT this evening for WYZ277.
&&
$$
Kruse/Church/Barjenbruch
For more information from NOAA`s National Weather Service visit...
http://weather.gov/saltlakecity
Area Forecast Discussion
National Weather Service Tucson AZ
138 PM MST Sat Aug 24 2024
.SYNOPSIS...Scattered showers and thunderstorms will continue this
weekend with daily chances all next week. High temperatures are
expected to remain near normal.
&&
.DISCUSSION...Still some lingering light showers and cloud cover
along the AZ/NM border with clear skies elsewhere. The MCV is no
longer apparent in visible imagery but is likely just north of
Douglas at this time. Visible satellite also shows cumulus clouds
have begun to form over the mountains. Aloft, southeast Arizona
is in between high pressure over the southern Plains and a trough
over the Great Basin and Pacific Northwest. Dry air ahead of the
trough covers most of western Arizona including western Pima
County. This will keep convection mainly from Tucson eastward over
the next few days.
For today recent CAM models including the HRRR have backed off
some on the coverage of storms. RAP mesoanalysis still shows a
weak cap in place likely due to less surface heating from this
morning`s shower activity and cloud cover. Once the CIN is eroded
any storms that form will have 500-1000 J/kg of MLCAPE to tap
into along with PWAT values around normal for this time of year.
Storm initiation is expected to start in eastern Pima County and
Pinal County then expand south and east along outflows. However,
areas east of Tucson may struggle to get rid of the CIN. Because
of this storms will likely be more isolated in nature but still
capable of strong outflow winds and locally heavy rainfall.
Tomorrow into Monday the trough begins to move northeastward with
the dry air remaining in place over western Pima County. PWAT
values will be around normal from Tucson eastward which is where
the 24/12Z HREF keeps storm activity. With today`s storms looking
more subdued, the atmosphere tomorrow should be able to support
scattered storm coverage. Storms will be capable of strong outflow
winds and locally heavy rainfall. Monday models hint that the dry
air could make it as far of Tucson which would push thunderstorm
activity further east, but right now Tucson looks to be on the
western periphery of storm chances Monday.
After Monday the trough moves into the northern Plains leaving
southeast Arizona under southerly to southeasterly flow in the
mid-levels. This will allow more moisture back into the region
especially for areas west of Tucson. Ensembles keep this southerly
flow in place through the work week along with PWAT values around
normal to slightly above normal. So can expect daily thunderstorm
activity for most of the CWA next week with normal day to day
variations. Temperatures will stay around normal through next
week.
&&
.AVIATION...Valid through 26/00Z.
Isolated to scattered SHRA/TSRA mainly east of a Picacho-TUS-OLS
line after 24/21Z. Visibility reductions, wind gusts up to 45
kts, heavy rain, small hail, and mountain obscurations possible
with any thunderstorm. Outside of thunderstorm wind gusts, winds
generally 15 kts or less with a southwest to northwesterly
direction. Scattered thunderstorms with similar impacts again aft
25/20Z Sunday primarily east of San Carlos Airport-TUS-OLS.
&&
.FIRE WEATHER...Isolated to scattered thunderstorms through Monday
mainly from Tucson eastward. Drier air pushing in will act in
lowering minimum relative humidities to around 18-28 percent
through Monday, though areas east of Tucson to Nogales should keep
higher values. Daily thunderstorms chances each day next week for
most of southeast Arizona. Outside of any thunderstorm outflow
winds, 20-foot winds will generally be 15 mph or less, with
afternoon/early evening gusts to 20-25 mph and light winds
overnight.
&&
.TWC WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
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