Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 09/22/22
Area Forecast Discussion...UPDATED
National Weather Service Aberdeen SD
624 PM CDT Wed Sep 21 2022
.UPDATE...
Issued at 623 PM CDT Wed Sep 21 2022
The forecast remains on track this evening. No major changes are
planned.
&&
.SHORT TERM...(This Evening through Thursday Night)
Issued at 241 PM CDT Wed Sep 21 2022
Main story for the short term is the patchy frost across northern
SD for the overnight hours. Latest run shows just thin to no clouds
across northern SD where frost outputs show patchy frost early
Thursday morning. Thicker clouds across the southern/SW CWA will
keep temperatures warmer, therefore, frost should not be an issue.
In the areas where high clouds/clear skies will be, I used NBM 25%
and areas of clouds...straight NBM. This puts lows in the mid-upper
30s (across northern/northeastern CWA) to the lower 40s in our
southern area. A frost advisory has been issued for Corson and east
through Marshall Counties from 08Z-14Z Thursday. I was hesitant at
this point to add counties further south to this advisory due to
cloud cover/warmer temps. This may need to be adjusted later on
tonight if anything changes.
Models continue to show the large troughing pattern pushing east
across Canada and the northern U.S with a cooler airmass behind this
trough as winds aloft are out of the northwest. An elongated surface
high pressure system is currently dominating the area. 850mb winds
will decrease through the late afternoon with more of a gentle
pressure gradient overhead. With a closed low/trough out west over
the Pacific Coast, this will put a quick ridging pattern overhead
for Thursday. This ridge/high moves east late Thursday into early
Friday as the trough/low out west, starts to move over the area with
winds aloft out of the southwest. A surface low will push west to
east during this time and its associated fronts. A LLJ moves back in
late Thursday into early Friday, which will bring gusts back up as
models show this LLJ max on the southeastern side of the 850mb low
with speeds up to 45-50kts. This is also seen on RAP bufkit,
especially in western CWA. Along with steeper pressure gradients
with the exiting high and incoming low I also mixed in a little
NBM/90th to show for this. A wind advisory has been issued for
Corson and Dewey counties as output shows advisory level winds in
this area Thursday afternoon and evening.
The good news is the chance of widespread rain! ECMWF has the precip
chances across the western CWA starting around Thursday evening
while GFS/NAM has it starting a few hours later. Anyways, widespread
rain pushes west to east and looks to be out of the area by 12Z with
ECMWF hanging on to some precip across western MN a little longer.
Not a lot of instability with this low, just enough for maybe some
isolated thunder. NBM QPF indicates anywhere from a trace-0.30 of an
inch with this system. Highs for Thursday will still be cool as CAA
is dominant with temps ranging in the 60s.
.LONG TERM...(Friday through Wednesday)
Issued at 241 PM CDT Wed Sep 21 2022
Friday, a closed low system will be tracking across the northern
plains/Canada. The overall synoptic scale pattern is well agreed upon
by models with really no significant outliers in the cluster maps. It
is a pretty strong system with 12-hour height falls on the order of
10+ dam as well coupled q-vector convergence, frontogenesis and warm
air advection. Soundings also show a quick saturation of the column
by Friday morning. All in-all, the high POP/low QPF forecast
persistence seems to be on track. The eastern CWA generally has 10-
15% probabilities of more than a half inch of rain, but more likely
is storm total precipitation totals in the tenth to quarter inch
range.
Northwest flow aloft will follow for the weekend into early next
week while the long wave trough lingers over the eastern CONUS. The
GFS ensemble members move the trough east much more quickly as
compared to the EC/Canadian ensemble members. As such, the GFS
solutions move the next ridge/warm air overhead more quickly. The
resultant maximum temperature spread is 10+ degrees for some
locations heading into mid to late week. Solutions will have to
converge to build confidence in the out periods. The overall blended
guidance does maintain dry conditions and seasonal to just below
normal temperatures from the weekend through the end of the period.
&&
.AVIATION...(For the 00Z TAFS through 00Z Thursday Evening)
Issued at 623 PM CDT Wed Sep 21 2022
Terminals KABR,KATY,KPIR,KMBG
VFR conditions are expected through Thursday afternoon. Winds will
shift to the southeast and become breezy on Thursday.
&&
.ABR WATCHES/WARNINGS/ADVISORIES...
SD...Frost Advisory from 3 AM to 10 AM CDT Thursday for SDZ003>007-
009-010.
Wind Advisory from 10 AM to 7 PM CDT Thursday for SDZ003-015.
MN...None.
&&
$$
UPDATE...Wise
SHORT TERM...MMM
LONG TERM...Serr
AVIATION...Wise
Area Forecast Discussion
National Weather Service Cheyenne WY
744 PM MDT Wed Sep 21 2022
.UPDATE...
Issued at 738 PM MDT Wed Sep 21 2022
Latest radar imagery has shown rain expanding across southeast WY
since 6 PM MDT. Overall, rain has been fairly light with KCYS ASOS
only reporting 0.01", but should see more as we head into later
this evening. Latest WYDOT webcams between Cheyenne and Laramie
before sunset showed low clouds/fog over the I-80 Summit and
Vedauwoo areas with near zero visibility. SREF probability of
visibility less than 1 SM only increases and expands through the
night in these areas with the moist low levels. With the Dense Fog
Advisory already issued for later tonight, decided to start the
South Laramie Range and Foothills zones now based on current
conditions. Use caution if traveling between Cheyenne and Laramie
this evening and Thursday morning as these conditions look to
persist through mid-morning!
&&
.SHORT TERM...(This evening through Friday)
Issued at 225 PM MDT Wed Sep 21 2022
The current weather setup begins with the discussion of the large
dome of high pressure stacked aloft across the Southern Plains,
which is assisting with the large plume of moisture transport from
the Four Corners region and an ULL coming onshore from the CA
coastline. This moisture transport has resulted in increasing
coverage of rain showers and non-severe thunderstorms arriving
from UT/CO. The plume of heaviest rain shower activity is expected
to be mainly west of I-25, and along the I-80 corridor from the
Summit to Rawlins this afternoon and evening. However, the rain
showers will push north and east as the day presses on. Expect
mostly cloudy conditions with continued cool temperatures through
this evening.
Overnight, expect rain showers to sweep across the area quickly.
Areas that have had more persistent rain showers will see areas of
dense fog develop. The HRRR and NamNest have pinpointed the
Summit, South Laramie Range Foothills, and portions of Laramie
County to the east for very low visibility. Due to this
persistently advertised feature on the 12Z and 18Z model runs,
have gone with a Dense Fog Advisory from 6Z-15Z Thursday. Given
the trends, the potential for the dense fog to persist through
late morning does exist. Have gone with mostly a persistence
forecast for the daytime highs on Thursday. Areas west of the
Laramie Range will see partly cloudy skies, and this will help
allow for a few rumbles of thunder across the region where
forecast MUCAPE sounding values between 200-400 J/kg become
present in Carbon County. Breaks in the cloud cover will slowly
push to the east as a pronounced upper level wave scoots to the
north and east aloft. Daytime highs will range from the 50s east
of I-25, and in the 60s west of the Laramie Range. A few locations
may see highs reach 70 degrees if sunshine breaks out a couple
hours earlier than forecast.
Thursday night into Friday will usher in our first stretch of high
winds for the season. We managed to stretch it out for
approximately 3.5 months since our last High Wind headlines. The
Arlington and Elk Mountain region have a continued strong signal
of mountain wave activity advertised via the GFS omega fields at
the earliest point Thursday night, thus have gone with a High Wind
Warning for that area. We will likely see wind gusts up to
60-65mph along the wind prone corridor of I-80 overnight, and
continuing into Friday afternoon before winding down. Additional
areas of concern will be the Bordeaux, I-80 Summit, and South
Laramie Range Foothills that depict mountain wave activity
occurring as well. Have gone with a High Wind Watch for these
weather zones due to the threat of 60+ mph winds being possible
from the early Friday morning hours through the afternoon.
Conditions will remain dry for Friday, with warmer afternoon highs
due to downslope westerly winds. Will likely see daytime highs in
the 70s to near 80 east of I-25, and in the 60s west of the
Laramie Range. The high winds will dissipate by the late afternoon
time period as we begin to see a prolonged dry period.
.LONG TERM...(Friday night through Wednesday)
Issued at 225 PM MDT Wed Sep 21 2022
Overall, no major weather highlights in the long term forecast with
little to no precipitation expected and temperatures climbing to
above normal through midweek. The upper level closed low is progged
to slowly eject further eastward, ultimately being inhibited from
digging southward by the continued blocking pattern just to the
south. This feature keeps the upper level closed low just off to the
north, skirting the US/Canadian border, and ushering in a brief
period of quasi-zonal flow across the Pacific Northwest through the
CWA. Mostly dry conditions expected by the early portion of the
weekend with better moisture advection just south of the Four
Corners in response to the location of the blocking feature, and
further northward from some moisture transport across the Pacific
Northwest. By Saturday afternoon/early evening, a short wave trough,
and its associated cold front, will dig quickly southeast across the
high plains along the backside of the upper level closed low now
just north of the Great Lakes. Still not expecting much from the
system, with little moisture along the boundary as PWATs remain
below 0.50, outside of a decent cooldown towards seasonal averages.
Through midweek, temperatures will begin to rebound under an upper
level ridge developing across the western CONUS and a deep trough
pushing eastward across the Eastern Seaboard. Should see
temperatures climb above seasonal averages with areas of of I-25 in
the low to mid-80s, and lower off to the west. Main area of concern
next week is targeted for Tuesday with a possible stronger winds
developing across southeastern Wyoming from the GFS locking onto a
minor shortwave disturbance pulsing across central to southeastern
Wyoming. Confidence is low at this time to increase wind speeds on
Tuesday, but will need to keep an eye on it in future model runs.
&&
.AVIATION...(For the 00Z TAFS through Thursday evening)
Issued at 545 PM MDT Wed Sep 21 2022
Pacific storm system and associated cold front is forecast to push
into Wyoming tonight and Thursday. Well out ahead of this system, an
area of light to occasionally moderate rainfall is expected to lift
northeast into Wyoming this evening. Expect periods of rain for most
terminals through tonight with patchy fog or drizzle at times.
Conditions are not expected to improve until late Thursday morning
or Thursday afternoon for a few terminals.
HAZARDS/WEATHER TRENDS: Current radar loop shows a large band of
rainfall lifting north into Wyoming this evening. MVFR and
eventually IFR/LIFR conditions expected after 02z this evening, with
the exception of KRWL which should remain VFR. KCYS, KSNY, and
eventually KBFF and KAIA have the highest probability of seeing LIFR
CIGS with also a good chance for locally dense fog later tonight and
into early Thursday morning. A few thunder showers are possible, but
confidence with timing and coverage is very low.
&&
.FIRE WEATHER...
Issued at 225 PM MDT Wed Sep 21 2022
Fire weather concerns will remain low for today and Thursday as
cool temperatures and rain showers continue to impact the area.
We begin to see an increase in fire weather concerns on Friday
as strong wind are likely in FWZs west of I-25, with breezy
winds likely continuing into the weekend as the area becomes dry.
&&
.CYS WATCHES/WARNINGS/ADVISORIES...
WY...High Wind Watch from late Thursday night through Friday
afternoon for WYZ106-116-117.
High Wind Warning from midnight Thursday night to 3 PM MDT
Friday for WYZ110.
Dense Fog Advisory until 9 AM MDT Thursday for WYZ116-117.
Dense Fog Advisory from midnight tonight to 9 AM MDT Thursday
for WYZ118.
NE...None.
&&
$$
UPDATE...MB
SHORT TERM...BW
LONG TERM...MRD
AVIATION...TJT
FIRE WEATHER...BW
Area Forecast Discussion
National Weather Service Dodge City KS
1047 PM CDT Wed Sep 21 2022
...Updated Synopsis...
.SYNOPSIS...
Issued at 1044 PM CDT Wed Sep 21 2022
Scattered showers and thunderstorms are moving across portions of
southwest and north central Kansas. A 500 mb shortwave combining
with cold air advection from a frontal boundary along the Kansas-
Oklahoma border is leading to the lift for the stratiform showers
and storms. This area of rain should continue until around sunrise
as the upper level energy moves out. Rainfall amounts will range
from 0.10-0.25 inch with potentially higher amounts locally under
the stronger storms.
&&
.UPDATE...
Issued at 556 PM CDT Wed Sep 21 2022
Updated short term grids based on radar trends and model guidance.
An area of stratiform rain south of Dodge City will continue to
spread eastward this evening with light rainfall amounts. A few
lightning strikes remain possible with this activity through
7 pm. After 7 pm, models depict near zero CAPE across the CWA, so
removed all thunder from the grids. Radar indicates rain
intensifying quickly from Trego to northern Lane counties, where
areas of moderate rain are being observed. Highest pops in the
definite/categorical range of 80% were focused along the I-70
corridor including Hays through tonight. Rain coverage will
diminish rapidly with southward extent, as shown by 18z NAM, and
trimmed pops accordingly. Am confident that widespread stratus
will overspread SW KS in the post frontal environment by sunrise
Thursday, with areas of drizzle possible. This stratus will be
very stubborn to budge daylight Thursday, especially with upslope
flow and especially north of US 50. Across these northern zones,
temperatures are expected to remain in the 50s Thursday, and
lowered the max T grid accordingly. Allowed for minimal warming
adjacent to Oklahoma, where temperatures should approach 70 by
late afternoon with some clearing.
&&
.SHORT TERM...(This evening through Thursday)
Issued at 218 PM CDT Wed Sep 21 2022
At 18z a cold front was moving south though the area, and had
reached a line from near Elkhart and northeastward roughly
following the Ark river valley. Widely scattered thunderstorms are
likely to develop ahead of the surface convergence and in the
still very warm and higher CAPE air. Shear is increasing along
and behind the boundary but still rather limited out ahead of the
front. HRRR model has been consistent all day in developing
strong, but largely sub severe thunderstorms outflow along the
highway 54 corridor late this afternoon into the very early
evening as the cold front overtakes the convective development
and/or the storms propagate farther south into Oklahoma. Farther
north, more organized rain bands are modeled shifting southward
into Kansas as a roughly 700 mb frontogenetic zone plays out. The
zone either side of the smoky Hill Valley will be the target of
best rainfalls across our area of concern, which although
convective in nature, should bring widespread light measurable
amounts of a tenth of an inch on average with higher amount to a
half inch. Areas in the far southeast of the forecast area like
Medicine lodge will remain in the heat for the balance of the day
while falling temperatures will ensue for the northwest 2/3rds of
the area.
Tonight, aided by 850-700 mb frontogenesis, rain and embedded
thunderstorms will expand south from northern Kansas. The best
rainfall coverage will be across the I-70 corridor to the K-96
corridor or so and as the forcing wanes during the overnight, more
scattered showery nature precipitation will be found southward to
DDC and the OK line by the 12ish timeframe. Breezy northeast post
frontal winds are likely to weaken in the overnight setting up
Thursday light to moderate easterly surface winds. Thursday brings
pleasantly cooler temperatures with highs only reaching the 60s
in most areas, while a large range between 50s at Hays to 70s at
Elkhart is more probabilistic.
.LONG TERM...(Thursday night through Wednesday)
Issued at 245 PM CDT Wed Sep 21 2022
There is a large amount of uncertainty with respect to synoptic
boundary placement in the extended. All global models EC/GFS and
Canadian flatten out the large southern Plains subtropical high
pressure by the end of the week with northwest flow aloft
redeveloping. This spells another warm up Friday into Saturday
with a relatively high confidence in the another round of cooler
northeast winds developing Saturday night into Sunday. Beyond that
a very large amount of uncertainty exists in the synoptic
pattern and thus the thermodynamic fields heading into Monday and
Tuesday.
&&
.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 457 PM CDT Wed Sep 21 2022
The strong cold front had cleared most of SW KS as of 2145z,
passing through P28. Strong NEly post frontal winds will continue
to gust 30-35 kts through about 00z Thu, with NE winds gradually
decreasing overnight. Weak convection east of LBL and south of DDC
at 2150z will remain away from those terminals, so kept those
TAFs dry. Highest confidence of rain coverage is at HYS 06-12z
Thu, but even here, much of the rain may remain north of the
airport. High confidence that flight categories will degrade
tonight and early Thursday, with widespread IFR ceilings in post-
frontal stratus expected by 12z Thu. Stratus will very slowly
erode daylight Thursday, most efficiently at LBL, where confidence
is highest that VFR will return. Expect stratus to hold all day
at HYS, with ceilings gradually improving from IFR to MVFR. Winds
will veer to light easterly through Thursday afternoon.
&&
.PRELIMINARY POINT TEMPS/POPS...
DDC 51 66 52 87 / 40 30 20 0
GCK 48 65 51 84 / 40 20 30 0
EHA 51 74 56 90 / 10 20 20 10
LBL 52 72 54 90 / 10 10 10 0
HYS 48 56 49 77 / 90 40 60 10
P28 55 68 54 87 / 40 40 10 10
&&
.DDC WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
UPDATE...Turner
SYNOPSIS...Tatro
SHORT TERM...Russell
LONG TERM...Russell
AVIATION...Turner
Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
925 PM EDT Wed Sep 21 2022
.SYNOPSIS...
For the last day of summer, dry weather conditions to persist as an
area of high pressure dominates through the Southeast, keeping
temperatures well above normal. A change comes about on Thursday
night as a cold front sweeps through the area, with the slight
possibility of an isolated shower or two. Cooler temperatures and
drier air will bring Fall like weather to the region over the
weekend ahead of a second cold front expected to arrive early next
week.
&&
.NEAR TERM /THROUGH THURSDAY/...
Evening Update...Winds weak to calm across the area as stg ridging
persists aloft. Expect good rad cooling, but no sigfnt fog threat
outside the mtn valleys overnight as drainage flow may help to lower
rather high sfc tdd/s. Made some minor upward tweaks to sfc td/s
mainly across the Upstate and into the nrn NC fthills.
As of 200 PM EDT Wednesday: The upper-level ridging across the
CFWA will gradually breakdown through the period with associated
height falls. A digging upper trough will sink into the Great
Lakes region with an attendant cold front through Thursday. Decent
radiational cooling conditions and a residual subsidence inversion
will support a mostly clear night, but mountain valley fog/low
stratus will be in store once again, especially in the Little TN
Basin. Overnight lows will be at or slightly above normal. The
encroaching cold front will be mostly moisture starved, especially
with a downsloping 850mb wind. Better forcing and dynamics will
reside north and east of the CFWA as well, which is why the
marginal risk for severe on Day 2 is in central NC through the
Mid-Atlantic and out of the CFWA. Expect the front to enter from
the northwest throughout the daytime period Thursday. Disagreement
between the CAMs makes this a challenging forecast, especially
for convective initiation. The HRRR basically has a dry forecast,
while the NAMNest produces a broken line of convection south and
east of I-85, with every other high res model being somewhere in
between. Modest instability will be available, but the better shear
parameters lag behind the frontal boundary. Expect isolated showers
and thunderstorms during peak heating as there should be enough
moisture and low-level convergence to support isolated initiation,
but the better PoPs will stay confined to the mountain zones.
Factoring in the aforementioned downslope wind and warm thicknesses,
temperatures will be 10-15 degrees F above normal for highs on
Thursday, especially east of the mountains. Temperatures at GSP will
flirt with record highs, but shouldn`t threaten CLT and AVL. After
the fropa at the very end of the forecast period, expect much cooler
weather to develop in short-term.
&&
.SHORT TERM /THURSDAY NIGHT THROUGH SATURDAY/...
As of 210 PM EDT Wednesday: For the first day of the Fall season, a
dome of high pressure over the Southern Plains will begin to weaken
as it spreads eastward. The remnants of the high pressure will keep
maximum temperatures well above normal with higher thickness values.
However, these warm temperatures will be wiped out as an upper level
trough dips southward, supporting a surface cold front from the
northwest. This boundary will bring cooler and drier air Thursday
evening, setting the stage for a pleasant weekend. Expect
temperatures on Friday and Saturday to be closer to climo. For the
cooler air mass, given the added forcing associated with the front
and lingering moisture, any precipitation that could occur will
likely be limited to the mountain areas, though confidence on
showers is extremely low. Model guidance shows lower PWAT values
behind the front, which should keep rainfall activity to a minimum
throughout the weekend.
&&
.LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...
As of 215 pm EDT Wednesday: Dynamics become a bit more active
Saturday night through Sunday as an upper-level jetlet passing just
north of the region brings divergence over the forecast area, and
upstream heights fall sharply from the Ohio River Valley to the
southern Appalachians. An associated surface cold front will
approach from the northwest through Sunday and cross the area Sunday
night. A mid-level speed maximum will accompany the system Sunday
evening, which will lead to a sharp uptick in deep-layer shear, with
about 50 kt of sfc to 6 km bulk shear possible circa 00Z Monday.
Instability remains the question mark given modest dewpoint recovery
through the weekend, but isolated severe storms cannot be ruled out
for Sunday and Sunday night given the forcing.
The GFS has been more progressive with the H5 trough departing the
East Coast early next week, while the ECMWF solution lingers a broad
trough axis along or west of the Appalachians. Either way, post-
fropa dry surface high pressure should build in from the west on
Monday, settle over the Appalachians on Tuesday, and migrate off the
eastern seaboard Wednesday. Greater uncertainty begins to arise
midweek given the differences in the mid-level flow pattern, but no
sensible weather differences are evident yet. Temperatures will be
fairly near climatology, except for cooler than climo over the
higher terrain.
&&
.AVIATION /02Z THURSDAY THROUGH MONDAY/...
At KCLT and elsewhere: VFR conds will continue this evening with low
end VSBY restrictions possible before daybreak at KAVL. Winds remain
light as stg hipres makes for stagnant flow overnight. By daybreak,
the pressure gradient will tighten as a weak frontal system
approaches from the northwest. Winds will align generally sw/ly to
w/ly across non-mtns and nw/ly at KAVL. Expect a wind shift to nw/ly
outside the mtns by early afternoon as trof axis crosses area. With
downslope warming, convection will be hard to develop east of the
mtns and have included a Prob30 -SHRA only at KAVL beg at 19z. High
surface temps will make for deep afternoon mixing, so have included
low-end gusts into the evening across most TAF sites.
Outlook: High pressure builds back in behind the departing front
Friday into Saturday. Low stratus and/or fog will remain a concern
each morning, primarily in the mountain valleys.
&&
.CLIMATE...
RECORDS FOR 09-22
MAX TEMPERATURE MIN TEMPERATURE
STATION HIGH LOW HIGH LOW
------- ---------- ---------- ---------- ----------
KAVL 91 1931 61 1913 67 1992 35 1918
1926
KCLT 98 1895 54 1897 74 1931 43 1918
KGSP 95 1940 62 1897 73 1931 40 1983
1931 1913
&&
.GSP WATCHES/WARNINGS/ADVISORIES...
GA...None.
NC...None.
SC...None.
&&
$$
SYNOPSIS...CP
NEAR TERM...CAC/SBK
SHORT TERM...CP
LONG TERM...HG
AVIATION...SBK
CLIMATE...
Area Forecast Discussion
National Weather Service Nashville TN
727 PM CDT Wed Sep 21 2022
...New UPDATE...
.UPDATE...
Issued at 716 PM CDT Wed Sep 21 2022
After another record setting day of heat across Middle Tennessee
with Nashville hitting a toasty 100 degrees, temperatures have
cooled down somewhat but are still quite warm at this hour
ranging from the low 70s on the Plateau to the low 90s in our
northwest counties. Also had a few very isolated showers pop up
late this afternoon, but that activity has dissipated and removed
precip chances for this evening.
Tonight will be another warm and muggy night with lows only
falling into the upper 60s to low 70s while dewpoints remain in
the 60s to low 70s. However, the long heralded Autumn cold front
is currently approaching STL and is still on track to push through
the midstate Thursday morning, reaching Stewart County around
10-11Z and exiting Grundy County by 17-18Z per latest NAM and
HRRR models. Guidance has also consistently shown isolated
showers with the fropa so expanded the slight chance pop for
tomorrow areawide. No other changes were made to the forecast.
&&
.SHORT TERM...
(This afternoon through Thursday Night)
Issued at 147 PM CDT Wed Sep 21 2022
It`s another scorcher across the region. Nashville has broken the
daily record hitting 98 degrees already. Now, the question is can
we reach 100 degrees which would be the latest in the year we`ve
ever done that. Stay tuned!
Relief is on the way. A cold front will drop through the area
after 3 am in the northwest and clearing the southern counties by
late morning on Thursday. Models show some light shower activity
is possible with the fropa, but qpf will likely only be a
hundredth or two at most. Behind the front, dew points will drop
into the 40s by tomorrow night.
&&
.LONG TERM...
(Friday through next Wednesday)
Issued at 147 PM CDT Wed Sep 21 2022
After the upper 90 temperatures today, it will feel a touch on
the chilly side Friday morning with lows in the mid 40s to lower
50s. With high pressure centered over the Midwest, Friday will be
a nice fall day with highs in the 70s across the area. Friday
night will be another pleasant night with lows in the 50s.
Southerly winds will return along with 80s on Saturday ahead of a
shortwave that will pass through Saturday night. GFS has some qpf
Saturday night, but seems to be the outlier at the moment.
Slightly higher pops look warranted as a larger scale trough axis
and another fall-like cold front passes through the area on Sunday.
Behind the front, highs will be back in the 70s and lows will be
upper 40s and 50s to start the work week.
&&
.AVIATION...
(00Z TAFS)
Issued at 613 PM CDT Wed Sep 21 2022
Frontal boundary positioned across central IL and central MO at
this time. This feature is on the move with the fropa expected
between the 06Z and 10Z time period. The boundary is generally
moisture starved and cape values are rather limited in its
advance. That said, will include a window of vcsh from roughly 06Z
to 17Z. After the fropa, cooler weather will prevail. Looks like
partial sunshine with scattered decks between 7kft and 10 kft. NW
surface wind will amp up a touch by afternoon.
&&
.PRELIMINARY POINT TEMPS/POPS...
Nashville 72 82 53 77 / 10 20 0 0
Clarksville 68 79 48 75 / 10 20 0 0
Crossville 67 76 45 71 / 10 20 0 0
Columbia 71 83 52 78 / 0 20 0 0
Cookeville 69 78 47 73 / 10 20 0 0
Jamestown 66 76 46 70 / 10 20 0 0
Lawrenceburg 70 82 50 77 / 0 20 0 0
Murfreesboro 70 83 50 78 / 0 20 0 0
Waverly 68 80 50 77 / 10 20 0 0
&&
.OHX WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
UPDATE.......Shamburger
SHORT TERM...Reagan
LONG TERM....Reagan
AVIATION.....21
Area Forecast Discussion
National Weather Service Phoenix AZ
440 PM MST Wed Sep 21 2022
.UPDATE...
Updated Aviation
&&
.SYNOPSIS...
Scattered showers and thunderstorms will continue through the rest
of this afternoon, mainly in Arizona, with stronger activity capable
of producing flash flooding. Rain chances will shift focus mostly to
the northern Arizona high terrain and southeast Arizona the next
couple days, but any storm that develops will still be capable of
heavy rain. Expansive cloud cover will yield well below normal
temperatures the next couple days followed by readings warming back
towards the seasonal normal into the weekend.
&&
.DISCUSSION...
Deep southerly to south-southwesterly moisture advection through AZ
has led to scattered to widespread showers and storms today. Most of
the heaviest rain fell in northwestern Maricopa county through the
morning, with many areas picking up more than 0.5" and some spots up
to around 1.5". Early this afternoon the focus of the heavier rain
is shifting more to southwest Maricopa county and Pinal county.
These areas have seen greater destabilization through the day, with
more solar heating, and analyzed MLCAPE values have risen to around
2000 J/kg. Continued clustering and training of storms in this area
will be capable of very heavy rainfall and is highlighted as the
greatest area of concern for flooding impacts through the rest of
the afternoon by HREF. The 12Z sounding from Phoenix this morning
showed a deep warm cloud layer, around 10,000 feet deep, which
supports the very efficient warm rain process. Stronger storms this
morning near Buckeye had measured rainfall rates up to or just above
2"/hr. A flood control gauge on Bender Wash east of Gila Bend early
this afternoon measured 1.61" in 30 minutes. HRRR sub-hourly model
runs support the 2"+/hr max rain rates from the most robust updrafts
in the area south of Phoenix. Considerable flash flooding is likely
where any high rain rate storms train over the same areas. A Flood
Watch remains in effect through 11 PM MST tonight.
Moderate to locally heavy rain will still be possible in the Phoenix
area and to the east in the higher terrain, which could impact flood-
prone burn scars, but the greatest rainfall is expected to remain
mostly south of the metro. Further west there is more dry air
entrainment, but deep layer shear is greater to the west to support
more organized storm development. There is a non-zero, but very low,
chance for an isolated severe storm in this area with the marginal
CAPE and high EBWD (30-40 kts). An isolated supercell cannot be
ruled out. Small to severe hail and strong winds will be the most
probable impact from a severe storm, although a funnel cloud also
cannot be ruled out. Coverage overall will be lower in the western
areas and there is a rather sharp moisture gradient near the Lower
CO River. The dew point difference between Blythe and Desert Center
is around 25-30 degrees. So, storms are not expected to develop very
far into Southeast CA. Storms across the region are expected to
gradually diminish later this evening and into the overnight hours,
with some lingering activity in the high terrain north of Phoenix.
Shower and thunderstorm activity will continue into Thursday but
will become increasingly tied to the higher terrain. While upper
levels will begin drying with the increased southwesterlies, the PBL
will take a little longer to dry and localized flash flooding will
still be possible with any storms that develop, especially where any
showers or storms train over the same areas. Convective coverage
will continue to wane into the weekend with any remaining activity
ending by Sunday. Temperatures will run well below normal through
Thursday but will pop back up to near normal Friday and onwards as
upper level ridging returns to the area and the boundary layer dries
out significantly.
&&
.AVIATION...Updated 2340Z.
South-Central Arizona including KPHX, KIWA, KSDL, and KDVT:
Showers with the potential for a few embedded storms this evening
will be the primary weather concern with more tranquil conditions
overnight through Thursday afternoon. Confidence is lowering that
storms will actually survive into the Phoenix terminals this
evening, though the most likely time frame for any activity is 01Z-
03Z. Isolated showers may persist into mid/late evening, and chances
fall below 10% by sunrise.
North winds influenced by showers could switch to a southerly
direction briefly in the evening as showers/storms approach.
Confidence in specific wind shifts and timing is very low with
better confidence of easterly winds finally becoming established
after midnight. Winds trends Thursday should follow the more
traditional diurnal behavior.
Southeast California/Southwest Arizona including KIPL and KBLH:
Only minimal weather concerns will exist through Thursday afternoon
with periods of 7K-10K ft cigs early this evening eroding fairly
quickly. Showers and storms will be common in Arizona during the
evening, and should remain just outside an operational influence at
KBLH. Winds may be variable for extended periods, but generally be
similar to the past several days.
&&
.FIRE WEATHER...
A large moisture surge today through Thursday will result in a 30-
70% chance of rain for areas east of the Colorado River and 5-20%
chance west of the river. These factors along with elevated RH
values will lead to minimal fire weather concerns. A gradual drying
trend begins on Thursday afternoon but a few storms will remain
possible into Friday or Saturday. Min RH will fall to 15-25% by the
weekend with mostly light diurnal winds and high temperatures
approaching 100 degrees once again in the lower deserts.
&&
.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...Flood Watch until 11 PM MST this evening for AZZ533-534-537>563.
CA...None.
&&
$$
DISCUSSION...Benedict
AVIATION...18
FIRE WEATHER...Hodges
Area Forecast Discussion
National Weather Service Las Vegas NV
645 PM PDT Wed Sep 21 2022
.SYNOPSIS...Gusty winds and isolated thunderstorms are the main
focus of the forecast through tonight, then our low pressure
system will shift off to the northeast and shift the focus to a
warmer/dryer forecast through the rest of the week and into the
weekend. A return of above average temperatures looks likely as
well.
&&
.UPDATE...With wind speeds on the decrease as we approach sunset,
have allowed the wind advisories to expire on schedule across
Lincoln County and the Spring Mountains. Also went ahead and
cancelled the Flash Flood Watch for northern Mohave County a few
hours early. That region remains devoid of any shower activity and
increasingly dry mid level air continues to surge eastward as
sampled by the 00z VEF sounding with precipitable water dropping
below a third of an inch. If we do see any additional convection
this evening, it will most likely be across far southern Mohave
county, through storms moving north out of La Paz county have
repeatedly died upon crossing the Mohave county border. As such,
not anticipating anything too exciting for the remainder of the
evening.
&&
.SHORT TERM...Today and Tomorrow.
A complex and interesting forecast for today and tonight across
the eastern 1/3 of the CWA. The low pressure system off the
California coast will begin its trek eastward on shore today and
shift some impressive upper level dynamics with it to the east as
well. At the same time, this system is advecting good moisture up
into Arizona from Baja California, setting the stage for heavy
rain across the state of Arizona and more of a severe
thunderstorms concern farther north into Utah and eastern Nevada.
In fact, SPC has outlines these areas in a marginal/slight risk
and WPC with marginal slight risks as well.
From a flash flood perspective, the feature to watch is a quasi-
dry line situation that is set up over the CRV and how much wobble
westward it can make. This feature is seen quite well on RAP
analysis and implied in WV/VIS satellite. With the CRV and Mohave
in the RER of a 250 mb jet and some meager instability available,
there is a marginal heavy rainfall threat with PWATs still well
above normal across Mohave, especially if cells train over the
same areas, but the storm motions should be rather quick with the
level of shear and 40+kt mean wind.
Perhaps more concerning is the conditional severe threat at hand
this afternoon. The aforementioned quasi-dry line is also a point
of interest for additional low to mid level convergence given
925-700 mb flow being quite strong and nearly parallel to this
line. HREF instability parameters are meager at best, but given
the quite favorable dynamical lifting mechanisms, instability will
be a bonus for additional updraft strength. CU fields are already
forming over Mohave County so keeping an eye on that through the
rest of the afternoon. So if differential low level convergence
along the moisture gradient couples with afternoon instability and
the RER above, we could get a couple discrete cells as far south
as Laughlin. With these, the main concerns will be hail and
damaging outflow winds, especially along and east of the CRV from
Lake Mead to Laughlin, northeast to Colorado City.
Contemplated expanding the Flash Flood Watch to include southern
Mohave, and while the highest QPF is currently south of the
Hualapais, all of this higher values come from one discrete cell
in the HREF members, and this cell has been inconsistently
modeled, and not agreed upon the HREF suite. Should it occur, it
will be in the highest PWAT environment indeed, but given this is
based off one storm and misses the most vulnerable areas in
southern Mohave, opted to leave this out for now unless later
runs change the thinking.
The low begins its transition into an open wave, moving farther
east tomorrow. This pushes the PWAT values east and south
tomorrow, leaving PoPs only to the area south of I-40 and east of
93.
.LONG TERM...Friday through the early next week.
The flow aloft will become more zonal by Friday and Saturday
resulting in a drying trend with fairly seasonable temperatures and
light winds. By Sunday and into early next week, an amplified ridge
will begin to build across the West, prompting a warming trend
heading into next week. Current NBM deterministic guidance places
most of the lower deserts below 2000 feet back into triple digit
territory by Sunday and there is at least a low probability of a
stray 100 degree day or two next week into the Las Vegas Valley. The
calendar may suggest the arrival of fall, but the heat isn`t ready
to let up just yet.
&&
.AVIATION...For Harry Reid...25 knot southwesterly gusts will
continue throughout the afternoon and into the evening hours. Around
03Z gusts will drop off and winds will become more westerly with
sustained speeds of 10 knots or less. Sustained speeds will decrease
throughout the overnight hours with winds becoming light and
variable around 09Z. Breezy southwesterly winds will return tomorrow
afternoon around 21Z.
For the rest of southern Nevada, northwest Arizona and southeast
California...Southwesterly gusts, with a magnitude of around 25
knots, will continue at KVGT and KHND through later this evening.
Around 03Z gusts are expected to drop off with winds favoring a
south/southwesterly direction at the Las Vegas Valley TAF sites.
KBIH will experience south-southwesterly gusts of around 15-20 knots
through approximately 00Z, when winds will briefly become more
westerly before shifting to the north at 03Z. KDAG will favor a
westerly direction with 25-30 knot gusts expected to pick up later
this afternoon. KEED and KIFP will favor a southerly direction
though later this evening when winds will become light and variable.
Wind gusts, around 25 knots, are expected to persist throughout the
afternoon with gusts dropping of around 02/03Z at the Colorado River
Valley TAF sites.
&&
.SPOTTER INFORMATION STATEMENT...Spotters are encouraged to report
any significant weather or impacts according to standard operating
procedures.
&&
$$
SHORT TERM...TB3
LONG TERM...Outler
AVIATION...Stessman
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