Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 09/02/24
See below for an aviation forecast discussion for the 00Z TAFs.
&&
.SHORT TERM /THIS EVENING THROUGH MONDAY NIGHT/...
Issued at 337 PM CDT Sun Sep 1 2024
Surface high pressure over the region late this afternoon will
eventually shift east into Wisconsin by Monday morning. As the high
departs, the pressure gradient tightens ahead of an approaching warm
front, as warm air advection and increasing southerly winds also
develop. As this ramps up overnight, low temps should be a few
degrees warmer than this mornings readings, but will still see most
areas in the 50s.
Focus for tomorrow turns to fire weather as hotter and drier air
begin working in, along with gusty southerly winds. With the tight
pressure gradient in place, many areas will see south winds gusting
from 25 to 40 mph, especially along and west of the James River and
into central SD. Winds aloft from 850-700mb are not overly strong
during the day, perhaps only maxing out around 30 knots, so don`t
expect gusts to get out of hand by any means. Given the dry
soundings and good mixing, dewpoints were lowered a bit from the
NBM. This did bring forecast RH values from Corson south through
Jones counties down to between 15 to 30 percent from west to east.
Therefore, went ahead and issued a Fire Weather Watch, even though
fuels may be marginal. Certainly better cured fuels over the western
third of SD, with a bit of transition zone over the Missouri Valley
area, before greenness picks up east of the Missouri River. Forecast
RH still shows quite a gradient across the west-river counties, but
felt the forecast wind/RH parameters and marginal/progressively
curing fuels were enough to hoist the watch.
Low-level jet kick in Monday night with models showing around 40
knots at 850mb. With the warm front moving through the region Monday
night and sustained southerly winds all night, lows will stay on the
mild side and may struggle to cool lower than 60 degrees for many
areas.
&&
.LONG TERM /TUESDAY THROUGH SUNDAY/...
Issued at 337 PM CDT Sun Sep 1 2024
Ensembles continue to agree on the ridge and high pressure system
pushing east of the area as a shortwave will be over the Northern
Rockies and a vort max over ID/MT early Tuesday morning. This wave
will continue to push east and over the Northern Plains and Upper
Midwest through Thursday. To the north of this, a longwave trough
and several embedded shortwaves will be over central Canada with one
of the waves dipping into the upper Midwest/Ontario on
Thursday/Friday. Clusters 3 (12 members GEFS=40%) and Clusters 4 (12
members EC, 3 GEFS) show a quicker more subtle wave, staying over
Canada, with Clusters 1/2 showing more of a deeper wave over the
Upper Midwest and slower track. Behind this wave, a ridge will
amplify over the western CONUS as a low deepens over the northern
Pacific. Well into the extended for the weekend into next week, this
ridge will push east and over the central CONUS. At this point in
time, overall Clusters agree on this synoptic setup but there are
differences between the members on intensity and timing of the ridge
as it pushes east.
850mb trough will continue to be positioned over the lee side of
Rockies and western Dakotas Tuesday with a weak surface low just to
the north over MT/ND. With a steeper pressure gradient between this
and the exiting high, winds will still be gusty out of the
south/southeast with sustained winds between 15-25kts and gusts to
35kts Wednesday before diminishing. Increased fire concerns are
possible with this as Min RH will range in the 20-30% range around
and west of the Missouri River with GFDI in the high category for
our western continues. This trough pushes east/northeast over SD
through Wednesday evening along with a secondary cold front moving
in from the northwest Wednesday/Thursday (associated with the wave
mentioned above from Canada). Precip wise, models are not too
excited on much moisture (if any) with pops ranging from 15-25% for
these days. Otherwise, a high moves in keeping the area quiet for
the end of the week into the weekend.
Ahead of the trough, 850mb temps for Tuesday will range between 21-
28C with forecasted highs ranging in the 80s to the mid/upper 90s,
warmest west river. Highs range in the 80s for Wednesday, warmest
over central SD. CAA becomes dominant for the end of the week with
the incoming high with forecasted highs in the 60s and 70s, making
it really feel like fall! However NBM spread in temps is quite large
due to model variability at this point in time, so lower confidence
exists on exact temps later on in the week.
&&
.AVIATION /00Z TAFS THROUGH 00Z MONDAY/...
Issued at 606 PM CDT Sun Sep 1 2024
Terminals KABR,KATY,KPIR,KMBG
VFR conditions are forecast through the TAF valid period.
&&
.ABR WATCHES/WARNINGS/ADVISORIES...
SD...Fire Weather Watch from Monday afternoon through Monday evening
for SDZ003-015-033-045.
MN...None.
&&
$$
UPDATE...Dorn
SHORT TERM...TMT
LONG TERM...MMM
AVIATION...Dorn
Area Forecast Discussion
National Weather Service Amarillo TX
643 PM CDT Sun Sep 1 2024
...New AVIATION...
.SHORT TERM...
(This evening through Tuesday night)
Issued at 142 PM CDT Sun Sep 1 2024
As of 1 PM, a weak upper-level low can be seen spinning in the
northeastern part of the Mexican state of Sonora (south of
southeastern Arizona). This upper-level low is part of a Rex Block
with a upper-level high situated over the Central Rockies. This is
leading to fair weather today for most of the Panhandles except the
far southeast Texas Panhandle where some quick showers and isolated
thunderstorms have been passing through. Expect clear skies through
this afternoon, though some clouds may begin to move in from the
south this evening.
Monday through Monday night.... the previously mentioned upper-level
low will slowly move eastward and begin to move into far
southwestern Texas. As one should expect with a blocking pattern
featuring a weak upper-level low, there is great uncertainty
regarding the speed and track of the low. Some guidance suggests
showers associated with the low may move into the far southern Texas
Panhandle, continuing and spreading east through the night. Other
guidance, which includes most operational models, keeps the rain
south of the Panhandles throughout the night. This leads to a lack
of confidence regarding the forecast, thus have ensured PoPs remain
between 10-25% in the southeastern Texas Panhandle. Rain chances taper
off throughout the day Tuesday and clouds will clear for most of the
Panhandles with the exception of the far southeastern Texas
Panhandle.
Regarding the uncertainties... it is worth noting that the 15z
RAP is initializing best with respect to the low`s position, and
it also turns out to be one of the wetter guidance. However, with
the seemingly unpredictable nature of cut-off lows, not confident
that it will handle the track and speed correctly through the next
48 hours. Another point of interest to note is that the 12z GEFS
mean gives the southeastern Texas Panhandle between 0.2" to 0.5"
through Tuesday night. Looking at the individual ensemble members,
there are some highly anomalous members that are tipping the mean
upward... though most GEFS members do give the southeastern Texas
Panhandle rain totals of around 0.1" or less. Therefore... while
it is not out of the realm of possibilities that the southeastern
Texas Panhandle gets some very beneficial rain, unfortunately, it
looks very unlikely (<10%).
Vanden Bosch
&&
.LONG TERM...
(Wednesday through next Saturday)
Issued at 142 PM CDT Sun Sep 1 2024
Wednesday starts with an upper-level trough moving into the Central
Rockies, moving southeastward through the day. This leads to
increasing northwesterly flow aloft for the Panhandles through the
day and nighttime hours. This favors the potential for some showers
or thunderstorms to develop in the higher terrain and move into the
Panhandles, but instability looks meager at this time. A cold front
is favored to move into the Panhandles Thursday morning.
As the shortwave departs, a longwave trough dips into the Upper
Midwest/Great Lakes on Thursday with more northwesterly or north-
northwesterly flow aloft. Showers and thunderstorms would be
possible Thursday afternoon and into the evening hours. The longwave
trough sets up over the Great Lakes leading to northwesterly or
northerly flow aloft. If the flow is more northwesterly, there will
be a better chance for showers and thunderstorms on a nocturnal
basis. If the flow is more northerly, this coming weekend would
likely be dry.
Vanden Bosch
&&
.AVIATION...
(00Z TAFS)
Issued at 637 PM CDT Sun Sep 1 2024
For the 00Z TAFs, VFR conditions are forecast to prevail at KGUY,
KDHT, and KAMA through late Monday afternoon.
02
&&
.PRELIMINARY POINT TEMPS/POPS...
Amarillo TX 60 83 58 81 / 10 10 10 10
Beaver OK 57 83 53 85 / 0 0 0 0
Boise City OK 55 82 51 83 / 0 0 0 0
Borger TX 60 87 59 86 / 0 0 10 10
Boys Ranch TX 58 84 56 83 / 0 0 0 10
Canyon TX 59 81 55 78 / 10 10 10 10
Clarendon TX 61 82 59 78 / 10 10 20 20
Dalhart TX 55 81 52 82 / 0 0 0 0
Guymon OK 55 83 51 85 / 0 0 0 0
Hereford TX 59 81 55 81 / 10 10 10 10
Lipscomb TX 59 85 58 85 / 0 0 0 10
Pampa TX 58 82 57 82 / 0 0 10 10
Shamrock TX 62 84 59 81 / 10 10 20 20
Wellington TX 63 85 61 81 / 10 10 30 30
&&
.AMA WATCHES/WARNINGS/ADVISORIES...
TX...None.
OK...None.
&&
$$
SHORT TERM...52
LONG TERM....52
AVIATION...02
Area Forecast Discussion
National Weather Service La Crosse WI
1009 PM CDT Sun Sep 1 2024
.KEY MESSAGES...
- Seasonable temperatures are expected through the middle of the
week with highs in the 70s to lower 80s.
- Conditions remain relatively dry with some returning rain
chances on Thursday (20-40%).
- Cooler temperatures expected late this week and into the
weekend with many locations seeing highs in the 60s by
Saturday.
&&
.DISCUSSION...
Issued at 207 PM CDT Sun Sep 1 2024
Gradually Warming Into Mid-Week:
The general synoptic pattern that will maintain our pleasant weather
for can be seen on GOES-16 water vapor imagery and 01.12z RAP 500mb
heights this afternoon with an amplified upper-level trough situated
to our east with a building upper-level ridge. Consequently, our
region is subjected to northwesterly flow allowing for some
maintaining of the cold air advection regime behind a cold frontal
passage yesterday. As a result, the coolest day over the next few
days will likely be today with highs in the lower to middle 70s.
With surface high pressure moving overhead tonight, light surface
winds and clear skies will allow temperatures to fall into the 40s
to around 50 for much of the region, perhaps a few upper 30s in cold
drainage areas of central Wisconsin that can manage calm winds for
an extended period. Additionally, with the aforementioned clear
skies and light winds, seems like a fairly conducive morning for
valley fog in the Mississippi River and its tributaries along with
the Wisconsin River.
The first half of the upcoming work week will feature gradual
warming with the aforementioned 500mb ridge moving eastward and
ending the northwesterly flow pattern. Consequently, temperatures
will slowly increase through the first half of the week with median
high temperatures by Wednesday reaching to around 80 degrees for
much of the region in the 01.12z grand ensemble (GEFS/EC
ensemble/Canadian ensemble) with minimal variance in the inter-
quartile range.
Rain Chances For Thursday:
As we head into late week, deterministic guidance (EC/GFS/Canadian)
features a broad upper-low beginning to descend into the
northern portions of the CONUS. As this occurs, pieces of
shortwave energy will aid a surface cold front to push through
the region providing some lift for precipitation as it passes.
Some uncertainty remains between various operational guidance
with how the wave and embedded shortwave pieces behave later
into the upcoming week. However, instability and moisture with
this wave appear limited with median precipitable waters of
around 1 inch in the 01.12z grand ensemble (GEFS/EC
ensemble/Canadian ensemble). As a result, generally lighter
rainfall amounts are currently shown in ensemble guidance with
only moderate probabilities (40-60%) for over 0.1" of
precipitation in the recent GEFS/EC ensemble with a some (about
10-20%) increase in probabilities from the 01.06z to 01.12z runs
of the GEFS.
Cooler Temperatures Late Week & Weekend:
After the aforementioned cold front progresses through, there is a
fairly strong signal that temperatures will trend below normal late
week and into the weekend with the 01.00z EFI showing values of -0.7
and a shift of tails of 0 across portions of the area, particularly
on Saturday. This is reflected in the median temperatures in the
01.00z grand ensemble with median high temperatures by Saturday in
the lower to middle 60s across much of the region with roughly 10
degrees of inter-quartile spread. This would suggest that the 25th
to 75th percentile of members trend high temperatures anywhere from
the upper 50s to lower 70s for Saturday in the local area, a
consequence of uncertainty still on how the aforementioned broad
synoptic upper-low amplifies into our region. Regardless,
certainly is a reminder that fall is just around the corner!
&&
.AVIATION /00Z TAFS THROUGH 00Z MONDAY/...
Issued at 1009 PM CDT Sun Sep 1 2024
Continue to monitor trends this evening for fog...especially IFR
valley fog at KLSE. Cooling has taken place but most
observations suggest fog would not be below about a mile. Winds
above the surface per the radar are still in the 20 kt range at
1kft. At the surface on the ridge surrounding KLSE, winds are
nearly calm so cooling and drainage is expected into the valley
as the inversion strengthens. Have again decided to keep the
current TAF forecast as is for TEMPO IFR and 1SM at KLSE.
Otherwise some fog may be around away from the river valleys,
more likely in central WI at preferred localized areas. But
overall, local or patchy fog would be the rule area wide.
&&
.ARX WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...None.
IA...None.
&&
$$
DISCUSSION...Naylor
AVIATION...Baumgardt
Area Forecast Discussion
National Weather Service Bismarck ND
958 PM CDT Sun Sep 1 2024
.KEY MESSAGES...
- Much warmer temperatures are expected Labor Day and Tuesday
with widespread highs back into the 80s and 90s. A few lower
triple digit readings will be possible southwest.
- There is a low chance (20 percent) of showers and
thunderstorms southwest Tuesday night through Wednesday
morning. There is a low chance (20 to 30 percent) of showers
across all of the west and central Wednesday night.
- A cooling trend is expected mid week with average to below
average highs possible by the end of the week and into the
weekend.
&&
.UPDATE...
Issued at 958 PM CDT Sun Sep 1 2024
Quiet weather continues this evening, with lows tonight in the
upper 40s to upper 50s. Skies are clear at the moment, with
nighttime satellite imagery showing some high clouds in Montana
that are slowly drifting our way.
Although we did not make any substantial grid changes with this
update, it`s worth noting that we will likely see an increase
in smoke aloft on Labor Day, as smoke from wildfires from our
west filters into the region. The latest HRRR smoke model run is
not showing any smoke near the surface, so not expecting any
visibility reductions, but if smoke aloft ends up as thick as
model guidance looks then would expect to see pretty hazy, milky
skies across the area.
UPDATE
Issued at 636 PM CDT Sun Sep 1 2024
Surface high pressure is centered over eastern North Dakota
into Minnesota, with a tightening pressure gradient across
western North Dakota leading to winds becoming a bit breezy.
Satellite imagery shows completely clear skies across western
and central North Dakota. No changes needed with this update.
&&
.DISCUSSION...
Issued at 242 PM CDT Sun Sep 1 2024
An expansive surface high continues to slide east southeast
across the northern Plains this afternoon, currently centered
near the North Dakota/South Dakota/Minnesota border. This
pattern will mean a nearly cloudless sky for western and
central North Dakota through the rest of today and tonight. The
one exception may be across the northwest or north central
overnight, when some mid to high clouds could make their way
down from Canada. The rest of this afternoon should be pleasant
with highs right around or below seasonal averages (lower 70s
northeast to the lower 80s southwest). An upper level ridge axis
will approach the Montana/North Dakota border overnight, so
lows will not be as chilly as last night, mainly in the 50s.
As the ridge axis moves over the west on Labor Day, we will see
a drastic increase in highs across much of the west and
central, but especially the southwest. The latest NBM raw output
is advertising highs in the mid to upper 90s across the
southwest on Monday afternoon. Under a cloudless sky, highs in
the lower triple digits are not out of the question here.
Elsewhere, highs will range from the upper 70s and lower 80s
east, to the upper 80s and lower 90s central and northwest.
The ridge axis will slowly advance a bit further east on
Tuesday, leading to well above average high temperatures for
most of western and central North Dakota. The NBM currently
advertises highs ranging from the mid to upper 80s east, to the
90s west. A few lower triple digit readings will be possible
again southwest, but there will be some increasing cloud cover
which could keep temperatures lower than currently forecast
depending on timing. Fortunately, afternoon dewpoints will only
be in the lower 40s to lower 50s where the hottest temperatures
are forecast. Thus, apparent temperatures should remain well
below advisory criteria, maxing out in the low to mid 90s on
Monday and Tuesday.
With the ridge axis sliding towards the Minnesota border, most
of our area will transition back into southwest flow aloft as a
weak shortwave trough approaches from the west. Most solutions
have the bulk of the shortwave energy remaining to our west and
south, but we could see a glancing blow. A cold front will cross
the state Tuesday afternoon and night. Any interaction of the
upper wave and cold front may lead to low chances (20 percent or
less) of showers and thunderstorms along and behind the front.
For now, it appears the most likely area for a stray shower or
storm would be across the southwest. Instability and shear will
be limited so severe weather is not expected, if isolated storms
can even develop in the first place.
Highs will be cooler on Wednesday behind the cold front,
ranging from the mid 70s to lower 80s, much more in line with
seasonal averages. Another wave approaches within the parent
trough Wednesday night, leading to a low chance (20 to 30
percent) of showers across the west and central.
After the trough moves off to our east by late Thursday, we
transition into amplified northwest flow aloft by the end of the
week and into the weekend. This should lead to much cooler
temperatures. NBM highs on Thursday range from the low to mid
60s across the Turtle Mountains, to the upper 60s to mid 70s
elsewhere. Highs on Friday and Saturday are forecast to mainly
be in the lower 60s to lower 70s. That being said, it is
important to note that NBM temperature spread starts to get
fairly high on Friday and Saturday so the ensemble systems are
still having a tough time resolving the eventual pattern. Much
will depend on how amplified the ridge to our west becomes, and
for now there doesn`t seem to be a clear consensus within the
guidance.
&&
.AVIATION /00Z TAFS THROUGH 00Z TUESDAY/...
Issued at 636 PM CDT Sun Sep 1 2024
VFR conditions at all terminals through the period. Southerly
winds will generally be light through tonight, but will become
breezy Monday afternoon. Expect sustained winds around 15 to 20
knots, strongest at KBIS/KJMS.
&&
.BIS WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
UPDATE...Jones
DISCUSSION...ZH
AVIATION...Jones
Area Forecast Discussion
National Weather Service Des Moines IA
634 PM CDT Sun Sep 1 2024
...Updated for the 00z Aviation Discussion...
.KEY MESSAGES...
- Beautiful early September weather with warming trend Monday into
Wednesday
- Cold front brings 20-30% chance of rainfall, mainly on Thursday
- Cooler conditions - mainly 70s for highs - behind the front
&&
.DISCUSSION...
Issued at 208 PM CDT Sun Sep 1 2024
The main weather themes over the next week have not changed
much since this time yesterday - pleasant and dry weather today into
Labor Day with a warm up into the middle of the week with the next
chance of any rain being around Thursday. Early afternoon GOES-East
GeoColor has shown the high level smoke drifting over Minnesota and
portions of Iowa. Latest HRRR and RAP high level smoke products look
to match up fairly well as does the near surface smoke when compared
to the US EPA air quality PM2.5 monitors. However, not noting any
surface impacts to visibility and given low concentrations in the
models, will not have any impact on the forecast other than perhaps
a hazy sunset this evening. The smoke largely drifts away from the
state tonight.
The northwesterly flow that Iowa has been beneath will weaken and
become more nebulous in direction as a mid-level ridge over the
western US eases eastward through the week pushed along by an
upstream trough. This trough will help to turn our low level flow
more out of the south bringing in warmer air from Monday through the
middle of the week and highs returning well into the 70s if not 80s
across much of the state by Wednesday afternoon. A cold front
associated with the approaching trough will be the focus and
potential for rainfall mainly on Thursday. Chances peak around 20 to
30% at this point with much of the moisture with the front being of
Pacific origins with any contribution from the Gulf being cut off as
a shortwave moves over the Ozarks into the Ohio Valley. While QPF
amounts look to be light given the aforementioned limited moisture,
the deterministic ECMWF and its experimental AIFS is more bullish on
QPF than the deterministic GFS and the rest of the ensemble
guidance. While there may be sufficient instability for storms, flow
and resulting deep layer shear is not remarkable for severe weather
at this time. This is supported by Colorado State University`s
machine learning random forest outlook, which does not highlight an
area. As the front clears the area Thursday night, the upper level
pattern diverges and the only thing that can be said with a fair
amount of confidence is that late week into next weekend will likely
have below normal temperatures.
&&
.AVIATION /00Z TAFS THROUGH 00Z TUESDAY/...
Issued at 634 PM CDT Sun Sep 1 2024
VFR conditions will prevail through the period. Winds will shift
on Monday morning to out of the south at northern sites and out
of the east and central and southern sites, remaining under 10
knots.
&&
.DMX WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
DISCUSSION...Ansorge
AVIATION...Hagenhoff
Area Forecast Discussion
National Weather Service Grand Forks ND
628 PM CDT Sun Sep 1 2024
.KEY MESSAGES...
- The probability for weather impacts over the next 7 days is
low.
&&
.UPDATE...
Issued at 627 PM CDT Sun Sep 1 2024
Quiet conditions this evening across the region, with clouds
slowly diminishing as the sun sets. Forecast remains on track.
&&
.DISCUSSION...
Issued at 213 PM CDT Sun Sep 1 2024
...Synopsis...
A flattening 500mb ridge will move east over the Northern Plains
starting tomorrow. There is pretty strong warm advection, so
Labor Day will be warmer than today. The RAP and HRRR show more
upper level smoke moving into the area later Monday into
Tuesday, so will have to monitor that (also see if any of it can
make it down to the surface). This smoke is not coming from
fires to the northwest in Canada, it is from fires in the Idaho
area.
Ridging over the area on Tuesday will bring the warmest temperatures
of the week. High temperatures will top out in the 80s across the
FA. While highs will be about 10 degrees above average for early
September, we will not break records, as those are still in the 90s.
A tight pressure gradient between the departing high pressure over
the Great Lakes and a low over the Canadian Rockies on Tuesday will
cause breezy southerly winds, with gusts up to 35 mph. A cold front
is still pegged to cross the region late Wednesday. This will bring
a few showers, but soundings continue to show dry air in the low
levels, so accumulations should be limited both in areal coverage
and magnitude. Temperatures will cool to end the week, with highs in
the 60s and lows in the 40s. Depending on how clear skies and light
winds are, we may see a few upper 30 degree readings Saturday
morning.
&&
.AVIATION /00Z TAFS THROUGH 00Z TUESDAY/...
Issued at 627 PM CDT Sun Sep 1 2024
Clouds continue to diminish this evening, with VFR ceilings
continuing. Winds remain light and variable through mid morning
tomorrow. Around 15-16z winds become sustained out of the south,
with gusts reaching 25kts 19z through the end of the TAF period for
all sites, but BJI. Clouds redevelop tomorrow afternoon, but
ceilings remain VFR.
&&
.FGF WATCHES/WARNINGS/ADVISORIES...
ND...None.
MN...None.
&&
$$
UPDATE...Spender
DISCUSSION...Godon
AVIATION...Spender
Area Forecast Discussion
National Weather Service Missoula MT
103 PM MDT Sun Sep 1 2024
.DISCUSSION...An area of smoke, comprising of a mix from local
wildfires and those in Idaho, is currently the most prominent
feature on satellite imagery over the Northern Rockies. The HRRR
smoke model indicates that this area of smoke will continue to
spread northward, with elevated smoke levels expected to become
widespread across Idaho and western Montana. Near-surface smoke
concentrations are also forecast to increase in west-central
Montana, including the Missoula and Bitterroot valleys, later
this evening and tonight.
A trough off the west coast is still projected to move into the
region on Monday, which will lead to increased moisture in the
mid-levels of the atmosphere. The combination of this trough and
dry conditions in the lower levels will heighten the likelihood of
thunderstorms producing strong gusty outflow winds. High-
resolution ensemble models indicate a 30-70% probability of
outflow wind gusts exceeding 40 mph by Monday evening, and up to a
30% probability for gusts over 50 mph. If you have outdoor plans
on Monday, be prepared for these gusty winds. This development is
being monitored closely due to its potential impact to ongoing
fires in the area.
By Monday night, as the atmosphere continues to moisten,
conditions will become more favorable for rain, especially in
areas from north-central Idaho through west-central and southwest
Montana. Thunderstorm activity is expected to persist through
Tuesday in these regions.
High pressure is forecast to build back into the region on
Wednesday, initiating a warming and drying trend that will last
through the rest of the week.
&&
.AVIATION...Smoke in the region is expected to spread further
across Idaho and western Montana by this evening, with increased
concentrations likely in the valleys. This may lead to reduced
visibilities, particularly in west-central Montana, by Monday
morning. The incoming trough is expected to bring thunderstorms
and gusty outflow winds on Monday afternoon and evening.
&&
.MSO WATCHES/WARNINGS/ADVISORIES...
MT...Red Flag Warning from noon to 10 PM MDT Monday for Bitterroot...
Deerlodge/West Beaverhead...East Beaverhead.
ID...&&
$$
Area Forecast Discussion
National Weather Service Spokane WA
525 PM PDT Sun Sep 1 2024
.SYNOPSIS...
The arrival of a cold front Monday night into Tuesday will bring
breezy conditions and the chance for showers and thunderstorms.
Hot temperatures look to return over the Inland Northwest for the
latter half of next week as the ridge of high pressure rebounds.
&&
.DISCUSSION...
Today and tomorrow:
-Hot and dry conditions continue today with Moderate to Major
HeatRisk. Elevated wildfire risk due to dry fuels today.
-Chance of showers and thunderstorms in the Inland Northwest Monday.
Elevated wildfire risk due to lightning tomorrow.
The ridge axis has shifted eastward into Northwest Montana tomorrow,
signaling the peak of the warmth this Labor Day weekend. A compact
shortwave will bring a threat of showers and thunderstorms to much
of the region Monday. Southeast Washington and the Idaho Panhandle
has a 20-40% chance of a wetting rain (0.10 or more) Monday morning
through Tuesday morning. Elsewhere has a 5-15% chance of wetting
rains. As the low departs, there is an additional 30-50% chance of
showers and thunderstorms in SE WA and North Idaho Tuesday morning.
/Butler
Tuesday through Saturday: There is good agreement on the overall
pattern for the upcoming week. As the trough exits the region,
lingering showers with potential isolated thunderstorm threat
continues over Southeast Washington and Lower Idaho Panhandle. The
shower activity through the morning. Highs for Tuesday will be
cooler than previous days but will quickly rebound for the rest of
the week. A ridge pattern will fuel the snap pack. It will bring a
warm, dry trend. Tuesday highs will be in the 80s. The rest of the
week can expect highs in the upper 80s and 90s. Models do begin to
breakdown the ridge late Friday as Gulf of Alaska Low begins to
press into the region. For now, models are only showing weak
instability for the weekend. /JDC
&&
.AVIATION...
00Z TAFS: An upper low moving will move inland over southern
Oregon Monday afternoon. As mid and high level moisture spreads
north, HREF and NBM probabilities of measurable precipitation are
only 20 to 30 percent for southeast Washington and the southern
Idaho Panhandle between 18-24z Monday. Forecast soundings are very
dry below 10 thousand feet with marginal instability aloft which
is a good indication of a band of virga with embedded convective
showers for Lewiston, Pullman, Spokane, Couer d`Alene, and Moses
Lake beginning around 18z at Lewiston and Pullman and spreading
toward the metro around 20-22z.
FORECAST CONFIDENCE AND/OR ALTERNATE SCENARIOS: Increasing
southerly flow aloft and easterly winds draining down the high
terrain in Idaho suggests that smoke from central ID fires will
spread into eastern Washington. The HRRR Surface Smoke forecast
pushes increasing smoke concentrations into southeast Washington
and the Idaho Panhandle overnight. Forecasting visibility
reductions from smoke is challenging. There is low confidence in
the 5SM and 6SM FU in the TAFs, but confidence is high that
visibility Monday will be reduced compared to Sunday at Lewiston,
Spokane, and Coeur d`Alene. Pilots should also be prepared for
convective downdrafts Monday afternoon from showers and virga.
Rain evaporating in a warm, dry airmass will create cool
downdrafts. /GKoch
-----------------------
Confidence descriptors:
Low - Less than a 30 percent chance
Moderate - 30 to 70 percent
chance High - Greater than a 70 percent chance
For additional probabilistic information for NWS Spokane airports,
please refer to the Aviation Dashboard on our webpage:
https:/www.weather.gov/otx/avndashboard
&&
.PRELIMINARY POINT TEMPS/POPS...
Spokane 60 90 57 83 55 88 / 0 20 20 10 0 0
Coeur d`Alene 58 90 56 81 54 85 / 0 20 30 10 0 0
Pullman 58 87 54 78 51 85 / 0 30 50 30 0 0
Lewiston 65 93 63 86 60 92 / 0 30 50 30 0 0
Colville 53 92 50 85 48 87 / 0 20 20 0 0 0
Sandpoint 56 87 53 78 51 83 / 0 20 30 10 0 0
Kellogg 64 90 58 77 57 82 / 0 20 40 30 0 0
Moses Lake 61 92 56 87 53 90 / 0 20 10 0 0 0
Wenatchee 71 93 64 87 62 89 / 0 20 10 0 0 0
Omak 66 96 60 90 58 92 / 0 20 20 0 0 0
&&
.OTX WATCHES/WARNINGS/ADVISORIES...
ID...Heat Advisory until 9 PM PDT this evening for Central Panhandle
Mountains-Coeur d`Alene Area-Idaho Palouse-Lewiston Area-
Northern Panhandle.
WA...Heat Advisory until 9 PM PDT this evening for Central Chelan
County-Lower Garfield and Asotin Counties-Moses Lake Area-
Northeast Mountains-Okanogan Highlands-Okanogan Valley-
Spokane Area-Upper Columbia Basin-Washington Palouse-
Waterville Plateau-Wenatchee Area-Western Chelan County-
Western Okanogan County.
&&
$$
Area Forecast Discussion
National Weather Service Pocatello ID
234 PM MDT Sun Sep 1 2024
.SHORT TERM...Satellite imagery shows center of upper low off
northern California coast, shifting east toward the coastal states
this afternoon. Moisture already streaming north through Nevada,
with convective cloud shield and weak radar returns already
forming in northeast Nevada/southwest Idaho. 18Z model runs
indicating an outside shot at some weak convection potentially
impacting the southwest corner of the forecast area this evening,
but best chances arrive during the day Monday. Convection could
get started by mid-morning, but coverage really picks up during
the afternoon/evening. HRRR indicating potential for isolated
50+kt gusts. Convection continues into the overnight, particularly
along the Montana border and along/east of I-15. Upper low shifts
across East Idaho Tuesday night/early Wednesday. DMH
.LONG TERM...Tuesday through next Sunday.
Come Tuesday morning, the center of the low will be shifting
eastward from Oregon into Idaho with the greatest chances for
showers and thunderstorms remaining across the central mountains and
E/SE Highlands. Only very limited measurable precipitation is
expected across this region, where the current forecast only
includes around 0.05 or less. At this time, thunderstorm activity
looks to predominately be isolated with a more localized area of
scattered coverage along our border with Wyoming. Gusty outflow
winds to around 50 mph will continue to be a threat with the
strongest storms. Breezy winds will accompany the front, with gusts
ranging 20 to 30 mph. As the trough continues eastward, showers will
shift into Montana during the day with high pressure rebuilding from
the west on Wednesday. Temperatures will return to right around
normal Thursday and remain there through the end of the extended.
Cropp
&&
.AVIATION...
Southwest winds will turn slightly breezier this afternoon as the
ridge breaks down and a Pacific low moves inland. Gusts should
remain around 15 kts or less this evening but will increase to
around 25 mph Monday afternoon outside of any thunderstorm outflow
winds. High clouds will also increase from west to east this evening
into tomorrow. Showers and thunderstorms will lift into south-
central Idaho tonight before overspreading the region further
northeast and increasing in coverage during the afternoon and
evening hours on Monday. Scattered thunderstorms are expected near
all terminals and gusty outflow winds to around 50 kts are possible.
Cropp
&&
.FIRE WEATHER...Upper ridge beginning to break down as shortwave
feature shifts into the region from the west. Moisture already
beginning to surge north through Nevada, as seen on satellite
imagery. There is still a very very low (< 10%) chance of a dry
thunderstorm this evening or overnight mainly Southern Sawtooth,
but high-res models place activity just to the west. Much better
chances occur on Monday into Monday night as weak shortwave axis
lifts north through the region. Convective initiation could start
during the morning, but best chances occur during the afternoon
and evening for most areas. There is a small chance that coverage
is slightly overdone for portions of the Snake Plain, but outflows
will likely still impact these areas. Speaking of those, high-res
models indicate potential for 50+ mph gusts. Will upgrade the
Fire Weather Watch to a Red Flag Warning for all areas. Models
continue precipitation into the overnight, and then into Tuesday
and possibly Tuesday night as the shortwave feature slides across
the region. Wednesday through Saturday should see shifting of next
ridge axis across the region, for dry and gradually warming
conditions. DMH
&&
.AIR QUALITY...
An Air Quality Advisory remains in effect for Custer County through
Tuesday afternoon, where smoke from the Wapiti fire is keeping air
quality degraded. Air quality is currently "Moderate" to "Unhealthy
for Sensitive Groups" but forecast to improve across portions of the
area tomorrow as southwesterly flow aids in advecting smoke further
north. Cropp
&&
.PIH WATCHES/WARNINGS/ADVISORIES...
Red Flag Warning from noon to 10 PM MDT Monday for IDZ410-411-
413-422-425-427-475-476.
&&
$$
Area Forecast Discussion
National Weather Service Reno NV
140 PM PDT Sun Sep 1 2024
.SYNOPSIS...
* Gusty winds will produce critical fire weather conditions and
impact both aviation and outdoor activities on Labor Day.
* There is a 10 to 15% chance of showers and thunderstorms near
the Oregon border and west-central Nevada expected today and
tomorrow.
* Above normal temperatures are expected during the middle of the
week before cooling back towards seasonal averages by the weekend.
Otherwise, generally quiet weather after Labor Day.
&&
.DISCUSSION...
The latest upper air RAP analysis shows an upper air cyclone
residing off the coast of northern CA with the CWA having a south-
southwesterly flow aloft this afternoon. The latest surface
observations and radar imagery report dry conditions across the
region with some isolated showers and thunderstorms outside the
CWA in central and eastern NV. Going through the remainder of
today, forecast guidance projects the upper air low progressing
slowly eastward and going ashore the CA/OR coast overnight
allowing for the south-southwesterly flow over the CWA to
continue. At the surface, dry conditions look to continue through
most of the region through the day with CAMs showing around a 10%
chance of isolated showers developing in eastern portions of
Churchill and Pershing Counties during the afternoon. However, do
not have the greatest confidence for precipitation to reach the
ground due to drier air in the area. Slightly better
precipitation chances (~15%) are seen in northern portions of the
CWA closer to the OR border starting around midnight that continue
into the morning hours of Monday. Not much QPF is expected with
this with Northern Washoe County possibly seeing around 0.01
inches. Chances for thunder with these showers today and tonight
look to be rather low (less than 10%), but there could be some
gusty outflow winds should a storm develop. As for the low
temperatures tonight, the valley portions of the region expect to
range between the middle 50s and middle 60s while the higher
elevations look to be in the lower 40s to lower 50s.
For Labor Day, ensemble guidance shows the upper air low opening
into a trough and passing over the the CWA during the evening hours.
At the surface, the CWA expects an approaching cold front during the
day associated with this system. The CWA will see some pretty windy
conditions as a result throughout the day with southwesterly to
westerly winds gusting up to around 40 mph beginning in the late
morning hours and continuing through the afternoon and evening
hours. Ridgetop wind gusts still look to increase to around 50-70
mph by tomorrow morning and last through the day and overnight.
These winds will allow for critical fire weather conditions (see Red
Flag Warning and Fire Weather Section for more information), choppy
waters on area lakes (see Lake Wind Advisory for more information),
aviation impacts, and blowing dust near desert areas. Additionally,
CAMs suggest the potential for showers and thunderstorms once again
along and east of US-95 during the afternoon hours of Labor Day,
however confidence continues to be low on westward extent of
convection at this time. Please be sure to plan your holiday
activities accordingly and to frequently check the latest forecast
with these conditions. Cooler overnight lows are expected
tomorrow night with the cold frontal passage.
On Tuesday, the latest forecast guidance shows the upper air trough
departing eastward away from CWA while a ridge trails it coming in
from the west. This ridge is forecast to move over the western CONUS
on Wednesday and Thursday governing the general upper air pattern. A
weak trough is then seen moving over the northern CA coast on Friday
and Saturday which then changes the CWA`s upper air flow to more
south-southwesterly. With this evolution of the upper air pattern, a
brief cooldown in temperatures along with dry conditions are in the
forecast on Tuesday following the cold frontal passage. This is
followed by a return to seasonably warm temperatures for the
remainder of the work week along with closer to normal temperatures
by the weekend. Precipitation chances look to possibly return for
portions of the CWA on Friday going through the weekend along with
possible breezier winds on Friday due to this change in the upper
air pattern. -078
&&
.AVIATION...
VFR conditions are expected at all REV TAF sites today with winds
gusting up to around 20-25 kts ending around 02/02Z-03Z. FL100 winds
will increase to 25-35 kts this evening and will remain elevated
through Monday across the Sierra and western NV, inducing moderate
turbulence and LLWS issues. Surface gusts strengthen to 25-35 kts
Monday afternoon for Sierra and western NV terminals.
There is a very slight chance (~10%) of showers and isolated storms
across west-central NV near KHTH/KNFL/KLOL later this afternoon as
well as Monday afternoon. Portions of the area near the OR border
may also see some light shower chances as well beginning at 02/06Z
that last through 02/12Z. The latest HRRR near-surface smoke product
continues to show some smoke from the Coffee Pot Fire moving into
southern Mono County after midnight and into the early Monday
morning hours. Not anticipating a reduction in visibility for KMMH
at this time, but will monitor and amend TAF if needed. -078
&&
.FIRE WEATHER...
Changes: The Fire Weather Watch has been upgraded to a Red Flag
Warning for all existing zones and expanded to CA zones 271, 272 and
NV zones 421, 423.
Southwesterly winds are expected to pick up late this afternoon as a
closed low approaches the northern California coast. As this system
makes its way inland overnight, increased instability and meager
moisture may allow a few showers and an isolated thunderstorm to
develop between midnight and 6 am Monday, mainly over northern
Washoe county. Though the threat for dry lightning strikes isolated
and low probability given the shallow nature of this nocturnal
convection, any ground strikes are risk given gusty winds expected
over the area on Monday.
Speaking of winds on Monday, latest high resolution guidance has
prompted the issuance of a Red Flag Warning for northeast California
and portions of western Nevada. An extended period of wind gusts to
30-40 mph is expected from late morning to the evening hours on
Monday, coinciding with low relative humidity. Minimum RH will be in
the single digits to low teens across western Nevada and northeast
California. While the Tahoe Basin and southern Sierra Front aren`t
solidly hitting critical RH values, with minimum RH between 20-25%,
recent hot and dry conditions with the addition of increased holiday
recreation have prompted these areas to be included. Whitlam
&&
.REV Watches/Warnings/Advisories...
NV...Red Flag Warning from 11 AM to 8 PM PDT Monday
NVZ420-421-423-458.
Lake Wind Advisory from 11 AM to 8 PM PDT Monday NVZ002-003.
Lake Wind Advisory from 2 PM to 8 PM PDT Monday NVZ001-004.
CA...Red Flag Warning from 11 AM to 8 PM PDT Monday CAZ270>272-278.
Lake Wind Advisory from 11 AM to 8 PM PDT Monday CAZ071>073.
&&
$$
Area Forecast Discussion
National Weather Service Great Falls MT
850 PM MDT Sun Sep 1 2024
.UPDATE...
Satellite imagery through this evening showed a substantial amount
smoke advecting northward from active wildfires in SW MT west of
the continental divide and central ID. Very warm, dry and
unstable conditions this afternoon across Southwest MT likely
contributed to the increased fire activity with many locations
there seeing single digit (%) minimum humidity after poor
overnight recovery last night (830 pm RH at KDLN was still only
9%). Recent HRRR-smoke modeling indicates a greater concentration
of smoke/haze spilling east of the continental divide late
tonight with some potential for visibility degradation to 5 miles
or less as far east as Helena and Dillon. Incorporated latest
HRRR guidance expanding the coverage of smoke/haze across the
area through tomorrow morning with forecast otherwise on track for
quiet conditions through Monday morning. Hoenisch
&&
.SYNOPSIS...
An area of smoke will continue to drift northward through North
Central MT this evening, otherwise expect a quiet night. For Labor
Day, expect hot temperatures at lower elevations over North Central
and Southwest MT, with some areas approaching 95 degrees. There will
also be a chance for a passing thunderstorm, some of which will
produce strong wind gusts over Central and Southwest MT. It will not
be has hot Tue and Wed, with small chance for a passing storm once
again on Tue.
&&
.AVIATION...
02/00Z TAF Period
Some locally gusty winds are possible through early this evening
across SW MT before the airmass stabilizes and scattered cumulus
across those areas dissipate. Otherwise, generally light winds and
scattered high clouds will persist through early Monday afternoon.
Smoke generated by more active wildfires across western MT and
central ID will spread east across central and SW MT overnight. Much
of this is likely to remain aloft, but there is some potential for
lower level smoke to affect visibility at KHLN and KDLN early Monday
morning. Widely scattered thunderstorm development is expected by
late Monday afternoon across SW MT with potential for strong wind
gusts being the primary risk into Monday evening. Hoenisch
Refer to weather.gov/zlc for more detailed regional aviation
weather and hazard information.
&&
.FIRE WEATHER...
A Red Flag Warning has been issued for the Helena/Bozeman areas
because of low humidity, dry conditions and the potential for
thunderstorms late Monday afternoon into Monday evening. Some of
these storms could produce strong wind gusts, with some of the
storms also producing little rainfall. There is the potential for
more thunderstorms on Tuesday, however humidity looks higher and
there is a small potential that the storms on Tuesday could
produce higher rainfall amounts. Brusda
&&
.PREV DISCUSSION...
/ISSUED 555 PM MDT Sun Sep 1 2024/
Tonight through Labor Day...Quiet weather conditions are expected
over the CWA tonight. The only concern is an area of smoke aloft
moving northward through North Central MT this evening. Little
impacts are expected, since the smoke is quite high. For Labor
Day, an upper level disturbance will approach Southwest MT by mid
afternoon. This will result in a some thunderstorms developing.
With hot temperatures expected, inverted ` V ` type soundings are
expected, which will result in the potential for strong wind
gusts with any passing thunderstorm. The HREF has a few storms
with wind gusts approaching 60 mph late Monday afternoon and into
early Monday evening. Thus there is the potential that SPC could
change the current risk of general thunderstorms to a marginal
risk on later updates. For areas along the Highway 2 corridor,
from East Glacier Park to Harlem, they should be far enough north
that little to no impacts from thunderstorms are expected on
Monday.
Tuesday through Wednesday...A second upper level disturbance will
move through the CWA on Tuesday. Precipitable water will be a bit
higher, around 0.90 inches, resulting in a slightly more unstable
air mass. Thus much of Southwest and Central MT is in both a
marginal risk for severe storms and excessive rainfall. Afternoon
temperatures will not be as hot as they have been for Tue/Wed.
Thursday through Sunday...An upper level ridge of high pressure
will once again rebuild over the CWA during this period. The
chances for precipitation will be quite low, but do expect another
period of warm temperatures to redevelop. By next weekend,
afternoon temperatures will generally be in the mid to upper 80s,
along with light winds.
&&
.PRELIMINARY POINT TEMPS/POPS...
GTF 55 93 58 84 / 0 0 20 40
CTB 51 89 56 79 / 0 0 10 30
HLN 56 94 57 83 / 0 10 30 70
BZN 50 92 53 82 / 0 10 40 70
WYS 34 80 43 73 / 0 10 50 60
DLN 49 86 49 74 / 0 20 40 70
HVR 54 93 59 88 / 0 0 10 10
LWT 55 91 58 84 / 0 0 10 40
&&
.TFX WATCHES/WARNINGS/ADVISORIES...
Red Flag Warning from 2 PM to 10 PM MDT Monday for Helena and
Townsend Ranger Districts of the Helena National Forest.
&&
$$
http://www.weather.gov/greatfalls
Area Forecast Discussion
National Weather Service Las Vegas NV
839 PM PDT Sun Sep 1 2024
.SYNOPSIS...Isolated thunderstorms can be expected this afternoon
and evening and again Monday afternoon and evening over Mohave,
Lincoln, and the mountains of Clark County. High pressure building
overhead will then push temperatures higher, and an Excessive Heat
Watch is in effect for lower elevations of the Mojave Desert
Wednesday through Friday. Weak low pressure moving in from the
Pacific could increase thunderstorm chances and decrease
temperatures next weekend.
&&
.UPDATE...Isolated showers and a few brief thunderstorms that
have been occurring over far northern Mohave County will gradually
dissipate through the evening with no significant impacts expected.
The latest HRRR indicates better potential for isolated showers or a
thunderstorm over the mountains around southern Nevada Monday
afternoon as mid-level moisture increases slightly. This supports
the inherited forecast with 15-20 percent PoP grids and no immediate
changes are needed. -Adair
&&
.PREV DISCUSSION...
135 PM PDT Sun Sep 1 2024
.SHORT TERM...through Monday night. Early afternoon satellite loop
showed scattered cumulus mainly over the higher terrain. No
lightning had been detected in our CWA as of yet, which is
consistent with the forecast of fewer and less intense thunderstorms
today vs yesterday. Later this afternoon, Mohave County is expected
to be the main focus for thunderstorm development, where lifted
indices were already 0 to -2 and up to 500 J/kg of surface-based
CAPE is forecast later. Farther north, Lincoln County could see a
few dry thunderstorms, but coverage will be too low to justify a Red
Flag Warning. For Labor Day, increasing pressure gradients
associated with low pressure moving inland over southwest Oregon
will lead to increased southerly winds, mainly over Inyo, Esmeralda,
and Nye counties. Agree with previous shift that while this will
increase fire danger, the winds will not meet Red Flag Warning
criteria. Temperatures will remain solidly above early September
normals, with little day to day change from yesterday to today to
Labor Day, except in areas which see thunderstorms.
.LONG TERM...Tuesday through Saturday.
The shortwave trough responsible for the breezy start to the week
will lift northeast into the northern Intermountain West on Tuesday.
This will allow for a ridge of high pressure to make itself at home
over the Southwestern US. With persistent ridging in place directly
overhead, we will see temperatures gradually warm up a degree or two
each day through the end of the work week. As temperatures heat up
to 5 to 10 degrees above normal during the second half of the week,
we will see the return of Major to Extreme HeatRisk across the lower
elevations of the Mojave Desert. In coordination with neighboring
offices, issued an Excessive Heat Watch for lower elevation zones
Wednesday through Friday. Temperatures will eventually cool back
down as an incoming trough erodes and displaces the upper-level
ridge. However, much uncertainty remains as to when exactly this
cooling will begin and how much we will cool down. This uncertainty
is due to interensemble discrepancies regarding the timing and
strength of this system.
&&
.AVIATION...For Harry Reid...Diurnal winds with speeds of less than
10 knots are expected through Monday morning. FEW to SCT mid-level
clouds stream across the area as well. We will see an increase in
southeast winds after 18z with speeds 8-10kts with gusts up to 15kts
at times. A few isolated thunderstorms will be possible affecting
the Mormon Mesa and Peach Springs corridors.
For the rest of southern Nevada, northwest Arizona and southeast
California...Diurnal winds with speeds of less than 10 knots are
expected through the forecast period for most locations. Exceptions
include KBIH where gusty southerly winds up to 20 knots develop this
afternoon and again Monday afternoon. At KDAG, southwesterly winds
will reach over 10 knots this evening. Showers and thunderstorms
develop in the afternoon over northwest Arizona outside the vicinity
of any terminal with a low chance of any outflow winds impacting the
TAF sites. FEW to SCT mid level clouds around 12k feet will be seen
across the area through the forecast period.
&&
.SPOTTER INFORMATION STATEMENT...Spotters are encouraged to report
any significant weather or impacts according to standard operating
procedures.
&&
$$
SHORT TERM...Morgan
LONG TERM...Stessman/Morgan
AVIATION...Gorelow
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