Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 08/21/23
AREA FORECAST DISCUSSION
National Weather Service Wakefield VA
737 PM EDT Sun Aug 20 2023
.SYNOPSIS...
High pressure moves slowly offshore this afternoon. A strong
ridge aloft builds eastward today into Monday. A backdoor cold
front drops south early Tuesday. Dry conditions persist through
at least Thursday with some potential for precip Friday and
Saturday.
&&
.NEAR TERM /UNTIL 6 AM MONDAY MORNING/...
As of 735 PM EDT Sunday...
Evening sfc analysis reveals high pressure (~1020mb) centered
offshore. Aloft, a trough pulls farther offshore as a strong
ridge (centered over the central CONUS) builds into the local
area. Skies become clear this evening through most of tonight.
HRRR vertically integrated smoke does indicate that skies could
become slightly hazy this evening/overnight as NW flow brings
in wildfire smoke aloft. However, not expecting much, if any,
to mix down to the surface. Additionally, guidance indicates
there may be some patchy fog over the Eastern Shore late tonight
into early tomorrow morning. Temps as of 730 PM ranged from the
upper 70s to upper 80s. Given clear skies, light/calm winds, and
high pressure centered just offshore tonight, expect lows
in the mid 60s inland in rural areas, upper 60s to around 70F in
urban areas, and lower 70s along the coast.
&&
.SHORT TERM /6 AM MONDAY MORNING THROUGH TUESDAY NIGHT/...
As of 300 PM EDT Sunday...
Ridge aloft continues to nose eastward into the local area on
Monday, resulting in the warmest temperatures of the forecast
period. Guidance shows a bit more moisture aloft which argues for at
least some clouds Monday afternoon. Models continue to trim down max
highs for Monday by a degree or two. Forecasting highs around 93/94
inland with low 90s near the coast. Do expect dew points to mix out
somewhat during the afternoon but remaining generally in the mid 60s
to low 70s, resulting in afternoon max heat indices around 100 in
the SE and upper 90s elsewhere. Lows Monday night in the low
70s despite the passage of a backdoor cold front as surface high
pressure to the NW builds into the region.
12z guidance generally agrees that the front will have cleared the
southern portion of the area around daybreak on Tuesday. Cooler air
lags behind the front initially so high temperatures will still rise
into the mid 80s to low 90s (lowest NE and highest S and SW). Some
drier air does mix in from N to S during the afternoon. Rain-free
period continues with PoPs below 15%. Lows overnight will fall into
the mid 60s N to the low 70s in the far S.
&&
.LONG TERM /WEDNESDAY THROUGH SUNDAY/...
As of 300 PM EDT Sunday...
The upper ridge continues to retreat back to the west on Wednesday
with flow aloft remaining out of the NW. High temps Wednesday in the
low 80s NE to the mid 80s in the far SW. Flow aloft continues out
of the NW through the end of the work week with only slight chance
PoPs. Some upper troughing noted on the ensembles as we move into
next weekend so will introduce slight chance/chance PoPs for
Saturday ahead of a potential cold front. Temperatures top out in
the 80s Thursday and rise back into the upper 80s to low 90s Friday
and Saturday with overnight lows in the 60s to low 70s.
&&
.AVIATION /23Z SUNDAY THROUGH FRIDAY/...
As of 730 PM EDT Sunday...
Skies continue to clear this evening as high pressure slowly
pushes offshore. HRRR vertically integrated smoke does indicate
that skies may become slightly hazy this evening and overnight
due to NW flow aloft bringing in smoke from wildfires. However,
not expecting this to mix down to the surface and cause
visibility issues. Otherwise, clear skies and light/calm winds
should allow for some patchy fog near/around SBY between 9-12z
Mon. Apart from SBY, terminals remain VFR through the 00z taf
period. A weak boundary pushes S Mon morning allowing for high
clouds to move in (cirrus/stratus). This will allow for SCT-BKN
cloud cover through most of the day Mon. Winds this afternoon
were SE/S 5-10 kt, become light and variable overnight, and
remain variable but increase to 5-10 kt Mon due to a combination
of the boundary moving S and sea/bay breeze interactions.
Dry and VFR conditions continue through the middle of next
week, as high pressure prevails over the area.
&&
.MARINE...
As of 300 PM EDT Sunday...
Generally benign conditions are expected to continue this evening
through tonight. Winds are generally SSE ~10 to 15 knots this
afternoon. A few gusts to 20 knots will be possible at the elevated
sites later this afternoon into the first part of the night,
especially across portions of the Lower Bay, James, and York Rivers.
Similar conditions on Monday afternoon. Waves 1 to 2 feet, seas 2
to 3 feet through Monday evening.
A dry cold front will drop south across the region in "back door"
fashion late Monday night/Tuesday morning through midday on Tuesday.
An abrupt post-frontal wind shift is expected around or just before
sunrise Tuesday morning, with NNE winds increasing slightly to ~15
kt Tuesday morning. Winds strengthen a bit more later Tuesday
afternoon and evening, as E-NE winds continue and cool air advection
ensues. SCA headlines may be needed over the lower bay and lower
James as soon as late Tuesday afternoon, but are more likely late
Tuesday night into Wednesday. SCA headlines may also be needed over
the coastal waters Tuesday night through midweek as choppy NNE wind
waves drive seas up to 4-5 ft offshore later Tue night and
Wednesday.
&&
.AKQ WATCHES/WARNINGS/ADVISORIES...
MD...None.
NC...None.
VA...None.
MARINE...None.
&&
$$
SYNOPSIS...RHR
NEAR TERM...AM/RMM
SHORT TERM...AM/RHR
LONG TERM...AM/RHR
AVIATION...RMM
MARINE...AJB/MAM
Area Forecast Discussion
National Weather Service Denver/Boulder CO
834 PM MDT Sun Aug 20 2023
.UPDATE...
Issued at 817 PM MDT Sun Aug 20 2023
Winds have diminished across the region this evening, leading to
a mild but quiet overnight period. We may see winds pick up again
across portions of the Palmer Divide and the southeast side of the
metro later this evening/overnight, which should keep overnight
lows above normal.
Outside of a few minor grid updates, little change has been made
in this evening update. We did allow the Red Flag Warning to
expire, as winds and RH have improved over the past couple of
hours.
&&
.SHORT TERM...(This evening through Monday)
Issued at 236 PM MDT Sun Aug 20 2023
Lots of filtered sunshine this afternoon with a mixture of smoke
and haze. Gusty southeast winds will continue this afternoon.
For this evening, gusty southerly winds will persist east and
southeast of Denver with gusts of 35 to 40 mph possible. Very mild
temperatures overnight, as the wind will decrease but linger
overnight. Low temperatures in those areas will only fall into the
mid/upper 60s.
On Monday, the 600 decameter ridge will remain centered over Kansas
will a dry southerly flow aloft over northeast CO. High
temperatures on Monday will be in the mid/upper 90s. The record
high temperature in Denver is 97 in 2007, and expect it to be
reached. No moisture to work with another thunderstorm free
afternoon on tap. Critical to near critical fire danger again an
issue especially along and south of Palmer Divide with a combination
of gusty winds and low relative humidity.
.LONG TERM...(Monday night through Sunday)
Issued at 236 PM MDT Sun Aug 20 2023
Upper level high to be centered over the middle part of the
country for the upcoming week and next weekend. On Monday night
and Tuesday, the high will be centered over Missouri. It slowly
retrogrades southwest, making it over New Mexico and west Texas
for Friday and next weekend. This will result in a south to
southwest flow aloft over Colorado. Monsoon moisture will slowly
increase over the area Tuesday and Wednesday. As the moisture
increases, temperatures slow decrease. It will still be very warm
for Tuesday with highs in the mid 90s across northeast Colorado.
By Thursday, highs cool to the upper 80s to lower 90s. Chances for
storms will slowly increase as well. For Tuesday and Wednesday,
some question how far east convection will make it. Best monsoon
moisture will be over the mountains and this is where the best
chances for storms will be.
While most eyes are on Tropical Storm Hilary, the next weather
system expected to move across Colorado is currently over the
eastern part of Gulf of Mexico. Westerly winds around the large
high parked in the middle of the country will push this system
westward across the Gulf. The high will then slowly direct the
tropical wave across Texas and northern Mexico Tuesday and
Wednesday. Colorado begins to see moisture from it Thursday, but
more so Friday and Saturday. Model precipitable water values climb
to 180-200 percent of normal for Friday and Saturday. Will have
high PoPs and cooler temperatures for this. With this system many
days away, strength, timing, and amount moisture with it will
likely change some. By next Sunday, this system should be
northeast of Colorado, but enough moisture will likely be around
for a chance of showers and storms.
&&
.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
Issued at 540 PM MDT Sun Aug 20 2023
Gusty southerly winds will continue across DEN/APA through the
next few hours, with a gradual weakening trend after sunset.
Still, drainage flow should be a bit stronger than normal. There
may be a brief period of weaker winds Monday morning, before
stronger south-southeasterlies develop again in the afternoon.
HRRR Smoke forecasts do show a brief, slight increase in near
surface smoke Monday AM, with a more well defined push of deeper
smoke Monday evening. Concentrations are generally light and I`m
not sure this would cause any direct impacts, though some reduced
slant-range visby would be possible if smoke ends up thicker than
forecast.
&&
.FIRE WEATHER...
Issued at 236 PM MDT Sun Aug 20 2023
Red flag conditions will continue into this evening for portions of
the northeast plains of Colorado due to gusty southerly winds and
low relative humidities in the mid teens. Conditions will start to
gradually recover by mid evening. Hot, dry and breezy weather will
return on Monday afternoon with critical fire conditions possible
over the Palmer Divide east and southeast of Denver in the
afternoon. Consequently, a Fire Weather Watch was issued for those
locations.
&&
.HYDROLOGY...
Issued at 236 PM MDT Sun Aug 20 2023
No thunderstorm are expected this evening or Monday with no
flash flood threat.
Moisture will slowly increase this upcoming week. Storms are
expected to be on the weak side for Tuesday with limited moisture
and instability. For Wednesday, moisture should increase enough
for a few of the storms to produce heavy rain. For Thursday
through Saturday, the remnants of a tropical system/wave over the
Gulf of Mexico are expect to track across the region. This is
expected to bring a period of widespread rainfall, possibly heavy.
Best chance for this looks to be in the Friday and Saturday time
frame.
&&
.BOU WATCHES/WARNINGS/ADVISORIES...
Fire Weather Watch Monday afternoon for COZ245-246-249.
&&
$$
UPDATE...Hiris
SHORT TERM...Cooper
LONG TERM...Meier
AVIATION...Hiris
FIRE WEATHER...Cooper
HYDROLOGY...Meier
Area Forecast Discussion
National Weather Service Billings MT
738 PM MDT Sun Aug 20 2023
.UPDATE...
Satellite imagery shows a very moist subtropical flow extending
from CA to MT, with anomalously high heights associated with
strong ridging over the central CONUS. Despite today`s cool & wet
weather, our region is actually underneath rising heights...over
590dam over southeast MT. As a result, greatest precip chances
will remain over our west & north and will continue to shift in
that direction over the next 24 hours. There is a downslope
signature developing on BLX radar in the lee of the Beartooth-
Absarokas...and indeed our VAD winds show 25-30 knots at ~700mb.
HRRR continues to show a fairly weak band of convection developing
later this evening into the overnight hours over our east (near
Colstrip, Miles City & Baker). This may or may not happen
(elevated instability is quite modest), but latest mesoanalysis
shows healthy 850mb moisture transport as southeasterly low level
jet is forming over far southeast MT. So isolated storms are
possible. Otherwise, precip tonight will stay generally light.
Despite the cloud cover, the boundary layer is plenty moist for at
least a risk of fog for a good portion of the night, especially
west and central parts where wind is lighter. In fact, several
ASOS sites are currently showing a little reduction in vsby, which
may be just fog or perhaps a mix of fog and smoke.
JKL
&&
.DISCUSSION...
Today through Monday...
Mostly cloudy skies, cool temperatures, and widespread light
beneficial rain showers will persist through the day today over
central and western zones. Monday will be much different as
temperatures rebound back up into the upper 80s to lower 90s with
clearing skies and gusty south winds in the mountains.
Current temperature readings this afternoon have much of the area
remaining in the upper 50s to 60s under mostly cloudy skies.
While high temperatures are forecast in the 60s to 70s, many areas
today may struggle to get above 70 as long as the cloud cover and
light rain showers persist. Precipitable water values as of 2PM
were analyzed between 1.1 to 1.3 inches across the area, with some
increase still expected into the afternoon. This moisture will
aid the rain showers through the evening, but limited lift and
instability will continue to prevent heavier rain from occuring.
The persistent nature of the light rain may add up in some areas
though, especially west of Billings. Outside of this light
activity, some high resolution models are picking up on isolated
thunderstorms developing over far eastern MT this evening under
some clearing before moving into the Dakotas. This will be
dependent on clearing and models have not grasped the eastern
extent of the rain very well today. Therefore, confidence is low.
On Monday, the remnants of Hurricane Hilary will push north
through the western CONUS. While this will bring heavy
precipitation to many areas in the northwest, the large ridge over
the central CONUS will build heights back into our area keeping
much of this precipitation to the west. With that said, areas west
of Billings still have a low (20-40%) chance for showers and a
weak thunderstorm. Strong mid-level winds will also push up into
our region Monday from Hilary bringing 30-40 mph wind gusts to the
higher elevations and over the Beartooth Pass. Arends
Tuesday through Saturday night...
Main forecast concerns in the extended period are on heat building
back into the area and low chances for showers and thunderstorms.
A large ridge center over the central CONUS will back into the
forecast area this week. WPC clusters are in good agreement with
high confidence in this pattern. We aren`t expecting record heat
but high temperatures exceeding 90 degrees are likely (87 percent
chance at KBIL on Tuesday). This ridge will act to shunt the remnant
moisture from Hilary mainly to the west and north of the forecast
area. High temperatures then look to drop just slightly late this
week, closer to normal values for this time of year, as the ridge
flattens. Embedded weak shortwaves could bring small chances for
showers and thunderstorms at times. Ridging then looks to return
across the Rockies by early next week.
&&
.AVIATION...
Widespread light rain will persist into the overnight hours
mainly north and west of KBIL. A few isolated light rain showers
are possible at KSHR and KMLS, however, confidence is lower. This
rain, along with low clouds, will bring about periods of MVFR
conditions and mountain obscurations into Monday morning. Smoke
will continue to reduce slant- range visibilities today as it
slowly dissipates into tomorrow. Arends/TS
&&
.PRELIMINARY POINT TEMP/POPS...
Mon Tue Wed Thu Fri Sat Sun
-----------------------------------------------------------
BIL 057/087 064/095 064/091 060/086 058/085 061/090 062/092
21/B 21/B 21/U 10/U 12/W 21/U 11/U
LVM 055/085 061/087 057/085 052/084 050/082 054/087 055/089
73/T 21/B 11/U 11/U 13/T 33/T 22/T
HDN 055/090 060/098 061/093 057/086 054/086 057/090 059/092
30/B 10/U 31/U 21/U 12/W 21/U 11/U
MLS 059/087 063/096 067/092 062/085 057/083 061/090 062/092
40/B 00/U 21/U 21/U 12/W 22/W 21/U
4BQ 059/093 066/099 067/093 063/086 058/083 061/088 062/091
20/U 00/U 20/U 31/U 22/W 32/T 21/U
BHK 055/085 061/095 065/092 059/085 054/080 056/085 059/089
40/B 00/U 11/U 21/U 21/U 22/W 21/U
SHR 055/094 061/095 060/089 057/083 054/081 056/086 057/089
10/U 01/U 21/U 22/T 23/T 32/T 21/U
&&
.BYZ WATCHES/WARNINGS/ADVISORIES...
MT...None.
WY...None.
&&
$$
weather.gov/billings
Area Forecast Discussion
National Weather Service Grand Rapids MI
927 PM EDT Sun Aug 20 2023
LATEST UPDATE...
Update
.UPDATE...
Issued at 927 PM EDT Sun Aug 20 2023
The surface front has cleared Fremont and Alma, on its way south
with drier air. The dew point at Big Rapids and Mount Pleasant
dropped 9 degrees in 2 hours. This evening`s NBM has come in a
degree or two warmer with Monday`s high temperatures, perhaps
owing to slightly increased expectation for insolation through
high clouds.
&&
.SHORT TERM...(This evening through Monday night)
Issued at 258 PM EDT Sun Aug 20 2023
No significant weather in the near term. The next chance for rain
does not come until late Monday night as an MCS is expected to
form across northern Wisconsin and move southeast into northern
Lower Michigan in large scale NW flow while diminishing as it
translates away from the LLJ. We will have slight chance POPs for
the northern zones for these showers between 06Z and 12Z Tuesday.
.LONG TERM...(Tuesday through Sunday)
Issued at 258 PM EDT Sun Aug 20 2023
Deterministic and ensemble guidance appears to be locking in on the
idea of one or more elevated nocturnal tstm clusters/MCSs impacting
the area Tuesday night into Wednesday morning. This is on the nose
of a 30+ kt low level jet and just north of an advancing warm front.
Will have to watch for the possibility of locally heavy rainfall due
to the potential for training cells in deeply uniform nw flow on the
edge of the heat dome/upper high over the center of the CONUS. Also
a tropical connection will be present. The east Pacific tropical
moisture plume (in which TS Hilary is embedded) can be seen on water
vapor imagery already riding up and around the northern periphery of
the big upper high.
If early day convection does not hold back the incoming warm front,
highly unstable conditions with capes in excess of 3000 J/KG would
develop Wednesday afternoon as 70+ dews points return. This may
bring another round of later day diurnal storms although potential
for strong capping in arriving warm sector could be limiting factor.
We may be looking at heat advisory criteria on Thursday as H8 temps
peak around 25C before gradually cooling off Friday as the upper
high retreats southwest. Of course if occasional "ridge rider/ring
of fire" convective activity persist then the low 90s temps and 70-
75 dew pts may have trouble nudging in here from the west midweek.
Overwhelming support in ensemble guidance for a cooler, more
comfortable air mass arriving for next weekend with highs in the low
to mid 70s and dew pts dropping into the 50s/40s.
&&
.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
Issued at 738 PM EDT Sun Aug 20 2023
A few patches of ceilings at 3,500 feet lingering around Battle
Creek / Jackson are expected to scatter out tonight, and higher-
altitude cirrus clouds are moving in. Light winds from the
northwest will become more from the north-northeast overnight
into much of Monday. A layer of smoke -- modeled by the HRRR to
be between 5,000 and 10,000 feet -- could partially mix down to
the ground late tonight into Monday morning, though confidence is
low that MVFR visibility will occur.
&&
.MARINE...
Issued at 258 PM EDT Sun Aug 20 2023
Winds will have a mostly offshore component the next few days with
wave heights generally in the one to two foot range. There could
be rounds of showers and thunderstorms Tuesday night and Wednesday
night along a slow moving front.
&&
.GRR WATCHES/WARNINGS/ADVISORIES...
MI...None.
LM...None.
&&
$$
UPDATE...CAS
SHORT TERM...Ostuno
LONG TERM...Meade
AVIATION...CAS
MARINE...Ostuno
Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
1018 PM EDT Sun Aug 20 2023
.SYNOPSIS...
Hot high pressure will continue to dominate the Southeast through
Tuesday, resulting in climbing temperatures and continued dry
conditions. A weak, dry cold front will push in from the northeast
during midweek, bringing only temporary slightly cooler
temperatures. Hot high pressure brings back the much above normal
temperatures on Friday which will continue into Saturday.
&&
.NEAR TERM /THROUGH MONDAY/...
As of 1015 PM EDT: No major changes were needed as the forecast
remains on track. Otherwise, 500 mb height fields from the RAP
continue to show a tremendous 600 dm heat dome centered over KS/MO,
with the sprawling ridge nosing east across the Appalachian mountain
chain. This feature will dominate the near term portion of the
forecast, with a strong subsidence inversion negating any convective
potential despite the modifying airmass resulting from redeveloping
southerly flow at low levels. The main impact of the slowly
improving boundary layer moisture will be the continued likely of
mountain river valley fog forming overnight, with a secondary area
of fog possible out along the Catawba River region. Overnight mins
will be about a category above climatology.
The flattened cumulus field may see slightly better coverage on
Monday as dewpoints modestly improve, but not enough to
significantly trim insolation. Temperatures will thus rise to about
8 to 10 degrees above climo during the afternoon in warming
thicknesses. Heat Index values will likely max out in the 100 to 102
range along and southeast of I-85, so no Heat Advisories are needed
at present.
&&
.SHORT TERM /MONDAY NIGHT THROUGH WEDNESDAY/...
As of 200 pm Sunday: Upper ridge extending from an anticyclone over
the central Conus will remain over our region through the period.
The first in a series of short wave troughs passing over the
southern Canada through the northern Conus will sweep off the
Northeast Coast Tue/Tue night, with surface high pressure building
into New England in its wake. Attendant weak frontal boundary will
push south across the Eastern Seaboard, likely pushing into our
forecast area by Wed. The GFS remains the odd-model-out in
developing a weak qpf response within somewhat unstable air along
the leading edge of the boundary. As such, will maintain just a
small token PoPs for mountain convection during the
afternoon/evening. Otherwise, the short term will be dry and hot,
with max temps expected to average a good 7-8 degrees above normal.
Apparent temps in the Piedmont are generally expected in the 99-102
range, but some spotty areas could reach Heat Advisory criteria Tue
afternoon, esp across the upper Savannah River Valley. The front
should otherwise cool things down a bit for Wed, mainly across
northern areas, where temps should find their way to near-normal.
&&
.LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/...
As of 220 pm Sunday: Sprawling anticyclone is expected to retrograde
toward the Four Corners, as the wave train continues across southern
Canada and the far northern Conus. However, the latest consensus
trend in the global models is evolution to an omega blocking
pattern, with a deepening trough/upper low over the East, and the
ridge holding strong across the Rockies and Plains. With the upper
ridge slowly-but-surely expected to relinquish its grip over our
area, the potential for spotty diurnal, mainly mountain convection
will begin creeping into the forecast during the latter half of the
week, with chance PoPs advertised for much of the CWA by Saturday.
Chances may be enhanced by Day 7, as a frontal boundary associated
with height falls/developing eastern trough may become more of a
player in convective development. After starting off the period
near-normal, temperatures are expected to rebound to around 5
degrees above climo for Fri/Sat as the post-frontal air mass (such
as it is) quickly modifies. Temps may cool off substantially by
early next week due to increasing precip chances/clouds and the
possible arrival of a respectable front.
&&
.AVIATION /02Z MONDAY THROUGH FRIDAY/...
At KCLT and elsewhere: A large upper high pressure system will
continue to extend across the Southeast through the 00Z TAF forecast
period leading to dry and VFR conditions. Winds will gradually
become light and variable this evening into the overnight hours.
Mountain valley fog and low stratus is expected to develop again
overnight, so maintained the IFR fog mention at KAVL this update.
Since KHKY saw fog and low stratus develop early this morning, will
go ahead with a persistence forecast for the terminal for early
Monday morning. Winds will remain light Monday, with wind direction
generally N/NW at KAVL, W/WSW across the SC terminals, and W/WNW at
the NC terminals. VFR cu will develop again across the
terminals Monday afternoon.
Outlook: Relatively dry air should remain over the region through
Tuesday. A cold front may drop south across the area by Wednesday,
but it will be accompanied by limited moisture as well. Continued
modification of the airmass will permit diurnal isolated to
scattered thunderstorms, mainly over the mountains, to return late
in the week. Mountain valley fog and low stratus look likely around
daybreak each morning.
&&
.GSP WATCHES/WARNINGS/ADVISORIES...
GA...None.
NC...None.
SC...None.
&&
$$
SYNOPSIS...DEO
NEAR TERM...AR/HG
SHORT TERM...JDL
LONG TERM...JDL
AVIATION...AR
Area Forecast Discussion
National Weather Service Elko NV
344 PM PDT Sun Aug 20 2023
.SYNOPSIS...Remnants from tropical storm Hilary bring widespread
showers with isolated heavy rain through Monday.
&&
.SHORT TERM...Tonight through Monday night...
Tropical storm Hilary lifting northward, accelerating and merging
with the upper low west of San Francisco. Steady stream of deep
layered moisture advecting northward over central and eastern
Nevada. Rainfall rates at Tonopah and Ely has increased during the
past 1-2 hours. Appears that KLRX radar is underestimating
rainfall and the office has elected to change to the radar into
tropical Z/R mode given the anomalous environment that currently
covers the region.
Many short term concerns for the next 18-24 hours. Extensive
cloud cover has inhibited any convective towers from forming, but
any cloud breaks may provide the trigger for isolated
thunderstorms to develop. The special 18Z upper air sounding
measured precipitable water at 1.19”. As Hilary moves northward,
mid level gradient flow increases substantially with 700 mb winds
of 50+ knots. Occasionally these winds will reach the surface and
the High Wind Warning continues. These winds will occur later
tonight (highest threat from midnight to 6 am). Mid level winds
will generally be from the SSE; resulting in the best orographic
component will be on the steeper eastern slopes of the Ruby
Mountains. For the central Nevada mountains, including the Snake
Range, many small rivers and streams are flashy with fast
response rates. Combined that the highest rainfall rates will
occur during the nighttime hours, hazards will be extremely
difficult to observe. In the HRRR models, still seeing amounts in
the 2-4 inch range across the high terrain of Nye County, and the
extreme southern end of Lander, Eureka, and White Pine County.
Monday afternoon and night, what remains of Hilary will be north
of Nevada. Air mass remains moist, although less so but still
above climatology. With increased surface heating, areal coverage
for thunderstorms will be favorable. Excessive rainfall show a
slight risk of flash flooding, except for the northeast Nevada
corner. Synoptic scale gusty winds will be waning Monday morning.
.LONG TERM...Tuesday through next Sunday.
Tropical system Hilary will no longer be a concern as two weather
patterns dominate. Offshore trough results in drier conditions
for the western half of the forecast area. Eastern Nevada will be
on the western periphery of monsoonal moisture plume for diurnally
driven thunderstorms.
&&
.AVIATION...
Mountains mostly obscured with widespread showers, areas of heavy
rainfall (primarily between KTPH and KELY). Areas of 3-5SM in mist
with local IFR vis below 3SM, especially during periods of
moderate/heavy rainfall. Some improvement after 18Z Monday with
rising ceilings, but scattered showers/thunderstorms continue.
&&
.FIRE WEATHER...
Fuel status likely changes given the amount of rainfall that has
occurred and expected to occur. Current pattern does not indicate
any critical thresholds to be approached. No immediate fire
weather concerns for the coming week.
&&
.LKN Watches/Warnings/Advisories...
Flood Watch through late Monday night Humboldt County...
Northeastern Nye County...Northern Elko County...Northern Lander
County and Northern Eureka County...Northwestern Nye County...
Ruby Mountains and East Humboldt Range...South Central Elko
County...Southeastern Elko County...Southern Lander County and
Southern Eureka County...Southwest Elko County...White Pine
County.
High Wind Warning from 10 PM this evening to 8 PM PDT Monday
Humboldt County...Northwestern Nye County.
High Wind Warning until 8 PM PDT Monday Northeastern Nye
County...Northern Elko County...Northern Lander County and
Northern Eureka County...Ruby Mountains and East Humboldt
Range...South Central Elko County...Southeastern Elko County...
Southern Lander County and Southern Eureka County...Southwest
Elko County...White Pine County.
&&
$$
88/88/88/88
Area Forecast Discussion
National Weather Service Spokane WA
850 PM PDT Sun Aug 20 2023
.SYNOPSIS...
Widespread smoke should gradually improve early this week as the
weather pattern shifts. The chance for rain will increase across
Southeast Washington into the Idaho Panhandle on Monday. Our best
chances for significant rain will be Monday and Tuesday as a
remnants from Hurricane Hilary track through. The precipitation
will be focused in Idaho and the eastern third of Washington.
Warmer than normal temperatures return late this week.
&&
.DISCUSSION...
Evening update: What is now Tropical Storm Hilary is moving into
southern California producing heavy rain. Moisture from Hilary
will continue to stream north over the next couple days. Latest
model data combined with radar trends suggest a slower onset to
the shower chances over Eastern Washington and north Idaho and
thus have made some updates to the POP`s into Monday mainly
through the morning. Have also delayed the start time of the
Flood Watch until Monday afternoon.
Models continue to show a significant increase in precipitable
water, with the axis of highest values of 250 percent of normal on
Monday afternoon stretching from NE Oregon, into SE Washington,
the southern ID Panhandle, and NW Montana. There is good agreement
in the models of wetting rains in these areas. This includes areas
from Pullman to Kellogg and points south and east. Greater
uncertainty exists further to the north and west of this axis.
Some models show a short wave developing along the plume with a
westward enhancement to the rain Monday evening over the eastern
third of Washington, while other solutions show less development
and keep the majority of eastern Washington dry including Spokane.
With two active fires in Spokane county a closer look at
precipitation potential for Monday was analyzed. Looking at all
100 members of the GFS/ECMWF/Canadian ensemble members for Spokane
35 percent are dry through Monday evening, 45 percent showing
less than a tenth of an inch, with the remaining 20 percent having
a wetting rain. However if the first round doesn`t give the area
rain, there will be another opportunity on Tuesday as another mid
level wave tracks through the area. This cloud shield may limit
thunderstorms chances over SE Washington and the ID Panhandle on
Monday. Increasing dynamics and some weak mid level instability
from a large closed low dropping to off the Washington coast by
Monday evening may provide another focus area of showers over
North Central Washington by Monday evening. However surface based
instabilty will be limited by all the smoke and could limit shower
and thunderstorm potential in this area.
Speaking of smoke, updated the forecast from the latest HRRR smoke
model. No big changes here. Already seeing improving air quality
and visibility from Sandpoint to Coeur d`Alene with even some good
air quality readings on the Camas Prairie just southeast of
Lewiston as of 8 pm. With increasing southeast winds tonight and
tomorrow additional improvement is shown by the HRRR for North
Idaho and much of Eastern Washington. Central Washington
improvement carries lower confidence as the easterly winds may not
penetrate that far west. JW
&&
.AVIATION...
00Z TAFs: Prevailing north to northeast winds with visibility
reductions due to smoke for all airports will continue for the
next 18-24 hours. Ceilings will be impacted as well, MVFR or IFR
conditions for airports across eastern Washington and north Idaho.
HRRR smoke models has been used heavily and UW WRF wind model for
improvements. A wind shift is expected from the east- southeast
late tonight which should further improve smoke, visibility, and
ceilings from southeast (Lewiston) to northwest (Omak) with
increasing cloud cover and moisture. An outflow boundary moving NW
could bring gusty southeast winds to KGEG-KLWS-KPUW-KMWH around
18-00Z. /butler
&&
.PRELIMINARY POINT TEMPS/POPS...
Spokane 60 81 59 75 52 76 / 10 40 60 60 30 10
Coeur d`Alene 60 80 59 75 54 75 / 10 50 70 60 50 10
Pullman 57 72 52 72 47 72 / 10 80 70 70 60 10
Lewiston 68 79 65 80 60 82 / 10 90 70 80 70 10
Colville 47 83 50 74 42 75 / 10 10 70 60 30 10
Sandpoint 54 79 54 74 51 74 / 10 40 80 70 60 10
Kellogg 64 74 61 75 57 71 / 10 90 80 70 60 10
Moses Lake 58 86 59 77 50 80 / 0 10 30 30 10 0
Wenatchee 64 84 62 79 57 79 / 0 10 20 20 0 10
Omak 58 85 62 82 55 80 / 0 20 40 30 20 10
&&
.OTX WATCHES/WARNINGS/ADVISORIES...
ID...Flood Watch from Monday afternoon through Tuesday evening for
Central Panhandle Mountains-Idaho Palouse-Lewis and
Southern Nez Perce Counties-Lewiston Area.
WA...Flood Watch from Monday afternoon through Tuesday evening for
Lower Garfield and Asotin Counties-Northeast Blue Mountains.
&&
$$
Area Forecast Discussion
National Weather Service Las Vegas NV
858 PM PDT Sun Aug 20 2023
.SYNOPSIS...The remnants of Hilary will lift up through
through southeast California and western Nevada tonight with
widespread rain and instances of significant flash flooding. Strong
winds will also accompany this storm system with gusts of 50-60 mph
primarily confined to exposed hills and ridges at elevations above
4000 feet. Decreasing shower coverage is expected Monday but daily
chances for showers and thunderstorms will persist through the week
with temperatures remaining below normal.
&&
.UPDATE...The center of Hilary was located just northwest of Los
Angeles at 8 PM and moving quickly northward. Widespread moderate to
heavy rain was confined to San Bernardino and Inyo counties in the
northeast quadrant of the system though the eastern periphery of the
circulation will continue brushing Clark and southern Nye counties
through this evening. Lightning has been very sparse in this
tropical environment, but radar was indicating discrete convective
cells over Clark County were moving toward the north-northwest
around 60 mph. So, any heavy rain they produce will be very short
lived over any particular spot and it will take considerable
training of cells to produce significant flash flooding around the
Las Vegas Valley. However, minor urban flooding can be expected
through this evening around Las Vegas. After midnight, the latest
HRRR indicates preciptation will be confined to our zones west and
northwest of the Las Vegas Valley...including the Pahrump Valley,
much of Nye, Esmeralda and Inyo counties followed by a narrowing
band of precipitation continuing Monday morning over southeast Inyo
County and much of Nye County. -Adair
&&
.PREV DISCUSSION...
.SHORT TERM...The Rest of Today through Monday.
Continuing to watch as the historic event unfolds.
This afternoon will feature two areas of differing concerns and
impacts.
Area 1: In Inyo County, Nye County, Esmeralda, and far western San
Bernardino County (including areas such as the Western Mojave
Preserve, the Morongo Basin, Daggett Barstow), the main threat
through this evening will be heavy rain and flash flooding. An 300mb
jet will provide continued upper level support while PWATs will
continue to increase...therefore expecting an widespread and
continuous rain area to develop and sit over this region. Moderate
rain with embedded thunderstorms and heavier rain are expected. HREF
3hr PMMs bullseyes Inyo County with high probabilities for 3hr
rainfall totals over 1.00 inch through 5PM tonight. Embedded
thunderstorms will be possible, especially with any upsloping in the
terrain, however the continued highest risk with storms in this
region today will be heavy rain.
Area 2: Further east in Clark, Lincoln, much San Bernardino, and
Mohave counties, precipitation this afternoon and evening should be
more scattered and convective in nature. Instability will increase
to 500-1500 J/Kg through the afternoon with the highest instability
over southern areas such as Twentynine Palms, the southern Colorado
River Valley, and southern Clark. Deep layer shear will be a lot to
overcome as 50-70KT of 0-6km shear being shown on mesoanalysis.
However, storm initiating of the edge of the moisture push acting
much like a warm front should have enough instability to tap into
to result in strong to severe thunderstorms today. The main
threat will be heavy downpours as the atmosphere is super moist.
Along with that, strong winds will be possible as sounding show
strong winds just above the surface that could easily transfer
down with rapid storm motion or heavy rain. Continuing to watch
the threat for a few tornadoes. While a low chance, the atmosphere
is primed for it as LCLs are very low and 0-3km shear is high.
For the rest of the day, ensure you have multiple ways to receive
weather warnings and updates. Take all forecasts and warnings
seriously. The small scale details of this forecast continue to
change and are hard to pinpoint. Even if its not raining now or
flooding isn`t occurring at this moment- the weather will rapidly
change and impacts will develop quickly if intense weather hits your
location. Not every location will see high impact weather today, but
all locations have some risk of high impact and dangerous
conditions. As meteorologists, our main goal is ensure everyone
remains safe.
For tonight...Tropical system Hilary will continue it`s
northward track tonight and Monday, bringing heavy rain and strong
winds to the region. Flash flooding remains a concern overnight,
especially in San Bernardino, Inyo, and southern Nye counties.
High winds with gusts over 60MPH are possible tonight with
widespread moderate to high wind impacts possible.
FLASH FLOOD THREAT: Overall, the forecast for rainfall remains on
track from previous forecast. Increasing forcing as Hilary lift
north through the night along with extreme moisture advecting into
the region will result in heavy rain at times for many areas.
Moderate rain with embedded thunderstorms and heavier rain is
expected through tonight. The main change from the previous forecasts
is an increase in rainfall amount in northern areas of Inyo. The
latest WPC day 1 excessive rainfall forecast has been extended the
high risk for flash flooding further north to include this area
while continuing to highlight San Bernardino and southern Nye
counties. Through this area, HREF shows high probabilities for 3hr
rainfall totals over 1.00 inch . Also of note, HREF probabilities
has low chances (10%-20%) for 3 hour rainfall amounts over 3.00
inches a between 5pm and 8pm PT in San Bernardino, and between 8pm
and 11pm in Inyo County. Areas further east may see waves of
rainfall with varying intensity and impacts tonight as opposed to a
large, widespread swath of continuous rain like areas further west.
Main unknown for eastern areas tonight will be how long
thunderstorms will continue into tonight before transition to just
rain. Currently expecting thunderstorm activity through at least
10pm in most areas of Clark, Mohave, Lincoln, and eastern San
Bernardino counties. No changes were made the the flash flood
watches as we continue to see a risk for heavy rain and flooding
through tonight.
STRONG WINDS: As Hilary moves north, models continue to show
increasing south to southeast winds this evening and overnight.
There is still uncertainty on how strong the winds will get as
ensembles showing varying probabilities for winds over 60MPH. There
is at least a high risk for impactful wind gusts after 40MPH so will
not make changes to the High Wind Warning that is in place. Expect a
sharp increase in winds as Hilary moves through, with the strongest
winds located closest to the center of the low,, lasting 3 to 6
hours before then before slowly tapering off the rest of the night
and Monday morning. The highest probability for wind gusts over 60MPH
will be southern Nevada, eastern San Bernardino, and the Colorado
River Valley where ensembles paint at least 40%-50% probabilities.
By Monday, Hilary will be a thing of the past but widespread low
level moisture will remain well entrenched across the area. This
will keep the forecast rather moist and unstable with numerous
showers and thunderstorms, especially in the higher terrain. While
coverage will decrease from past days, storms will remain very
efficient rain producers and flash flooding will remain a
possibility. There is low confidence in the precipitation
probability forecast as models show varying solutions on where
precipitation may develop, if they will be convective or not, and how
widespread the scattered precipitation may cover.
.LONG TERM...Tuesday through Saturday.
Broad ridge will remain over the central US steering at least low
to moderate grade monsoonal moisture northward around its perifery
through next weekend. This will keep shower and thunderstorm
activity in the forecast, especially across southern Nevada and
Northwest Arizona. Meanwhile, temperatures will remain on the cool
side of normal thanks to wet soils, persistent moisture feed, and
scattered storm activity in the area, though temperatures will
slowly be trending upward each day.
&&
.AVIATION...For Harry Reid...Adverse conditions are forecast through
most of the TAF period as the remnants of Hilary track across the
area. Light scattered showers early this afternoon will ll transition
to thunderstorms this afternoon through early tonight. Rain this
afternoon and evening may not be continuous, instead expecting waves
of rain with rapidly deteriorating conditions as the precipitation
moves through. High confidence for lightning, heavy rain, reduction
in visibility to 4SM, and CIGs to 5000ft with the rounds of
precipitation this afternoon. Low probability for sudden gusty winds,
CIGS below 3000ft, and visibility less than 3SM with afternoon
convection. Thunderstorm risk and convective driven impacts will
decrease after 06Z tonight, but continued showery activity is likely
through at least Monday morning. Low confidence in precipitation
forecast Monday afternoon as showers and thunderstorms will be
possible in and around LAS, however not expecting as widespread of
activity and unsure if precipitation will directly impact the
terminals.
Northeast winds around 10KT will become southeast and rapidly
increase late this afternoon and tonight. Increasing confidence for
wind gusts over 40KT, especially between 03Z to 09Z. Low
probability (20%) for wind gusts over 50KT, mainly centered around
06Z. Southeast wind gusts will slowly decrease after 09Z, with wind
gusts dropping below 35KT by 12Z, then dropping below 25KT
sometime after 15Z. Elevated south to southeast winds are expected
through MOnday afternoon with speeds 10-15KT but little to no gusts.
For the rest of southern Nevada, northwest Arizona and southeast
California...Poor aviation conditions expected through much of the
TAF period across the region. Widespread areas of moderate to
locally heavy rainfall can be expected as the remnants of Hilary
pass across the region with the heaviest precipitation is expected
across far western Nevada and the Mojave Desert in California. Winds
this afternoon should generally be 10KT or less from an east-to-
south direction before rapidly increasing south to southeast winds
arrive late this afternoon and tonight. Gusts to 50KT are possible,
especially in the lower Colorado River Valley. The gusts should then
diminish south to north overnight into Monday morning. During
periods of heavier precipitation today, CIGs may fall below 2kft,
and visibilities may be reduced to 3mi or less. Outside of the
heavier rain, prevailing CIGs around 5kft can be expected.&&
.SPOTTER INFORMATION STATEMENT...Heavy rain, high winds or wind
damage, and flash flooding reports are requested through the
weekend as the remains of Hurricane Hilary lift through the
area.
&&
$$
SHORT TERM/AVIATION...Nickerson
LONG TERM...Outler
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