Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 09/14/22
Area Forecast Discussion
National Weather Service Gray ME
1139 PM EDT Tue Sep 13 2022
An area of low pressure will bring high coverage of showers and storms
through the area into the early overnight hours. Some of these
storms later this afternoon and evening may be strong to severe
with damaging winds and torrential downpours possible. This
system will be followed by much cooler, drier, and gusty
conditions for the end of the work week with high pressure
building into New England. The high remains in control through
the weekend, then drifts offshore by early next week with
ridging building across the Northeast.
.NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
Showers and scattered thunderstorms with heavy rain continue to
move east and weaken with time. This is reflected in the latest
In the meantime, fog will continue to break out before the
westerlies kick in with drier air later tonight. Low cloudiness
and fog will be most prevailent in Maine.
Have made minor adjustsments to the near term portion of the
forecast with temperatures, dew points and winds this updated
package. Also adjusted pops to account for latest radar imagery
and mesoscale models.
Continuing to monitor line of showers and thunderstorms
crossing through New Hampshire as of 2222Z. This system will
continue to be slow moving with training taking place in a
couple areas. This will elevate the threat of localized flooding
across portions of the forecast area with many flood advisories
already issued over western portions of New England.
The airmass will continue to gradually stabilize across portions
of the region as we head through this evening. Have updated the
near term portion of the forecast for temperatures, dew points
and winds. Also, fog will be problematic this evening,
especially across southern Maine. Drier air will enter the
region later tonight however on increasing westerly winds.
After some shower activity this morning and early afternoon, we
are in a temporary lull for a couple of hours before things get
active within the next few hours. So have lowered PoPs through
5 PM or so to account for this.
Otherwise, not much has changed with expectations for the rest of
this afternoon and into this evening. Latest CAM guidance continues
to show showers along with scattered storms developing and crossing
into western NH in the 5-7PM timeframe as an upper trough currently
centered over Lake Erie gradually approaches New England. While this
occurs, wind shear profiles will also increase as a 110 kt
250mb jet streak overspreads southern New England, putting most
of the forecast area in the left exit region. So while we will
have the lift and shear (0-6km shear approaching 40-50 kt this
evening), the question mark is the instability.
So while wind shear will be impressive over most of the area, the
latest runs of the HREF along and NAM are highlighting the southern
half of NH and more specifically southwestern NH with SBCAPE
approaching 1000 J/kg by early this evening. So the more favorable
shear/overlap will be across this area, suggesting the higher threat
for strong to severe storms with damaging wind gusts and torrential
downpours as the primary hazards. We also cannot rule out a brief
tornado with HREF ensemble means painting 0-1 km SRH across southern
Showers and storms will continue to push to the north and east
through the evening, but instability will be gradually waning with
time, especially with eastward extent. So while the threat for
strong to severe storms still exists across Maine, it does appear to
Convection will come to an end from west to east through the evening
and early overnight hours as drier air pushes into the area
while the upper trough and its surface low start to lift up the
St. Lawrence Valley. However, some upslope shower activity will
likely linger across the mountains.
.SHORT TERM /6 AM WEDNESDAY MORNING THROUGH WEDNESDAY NIGHT/...
The mid and upper levels dry out in response to a deepening W-NW
flow as the upper trough and associate surface low move up the St.
Lawrence River Valley. However, there will be quite a bit of low-
level moisture leftover toward the mountains, and with this moisture
and flow pattern, more cloud cover and scattered upslope showers
will continue through the day. Some of the clouds may work their way
down into the foothills and points farther south, but no precip
is expected across these areas with skies ranging from mostly
to partly sunny.
It will also be a breezy out with a tight pressure gradient and once
we start mixing down the higher winds from aloft by late morning and
into the early evening hours. Forecast soundings support gusts
generally around 25 mph, but we could see a few closer to 30
mph. Max temps will be warmest across coastal and southern
areas with the winds preventing a seabreeze, and these areas
will be in the upper 70s to around 80 degrees. A little farther
inland, temperatures will taper off into the low-mid 70s, and
toward the mountains, the clouds/showers will keep temperatures
cooler and in the 60s.
The upslope showers should continue into portions of the overnight
hours until a mid-level shortwave trough sends a strong but dry
reinforcing cold front through the area. A much cooler and drier
airmass will quickly advect in behind this front, and low
temperatures are expected to range from the upper 40s to lower
50s across the south the lower 40s across the north. A few spots
across northern areas may even reach the upper 30s.
.LONG TERM /THURSDAY THROUGH TUESDAY/...
Low pressure continues to move away from New England on
Thursday as high pressure builds in from the west, setting up
conditions for a breezy day. Winds ease Friday as the high
continues to build in on Friday. The high passes across New
England on Saturday, and then moves offshore on Sunday. Ridging
builds across the Great Lakes and the Northeast by late in the
weekend and early next, bringing a moderating trend and
seasonably warm temperatures back to the area. A weak system
brings an increased chance of POPs early next week, most likely
across northern areas.
The pressure gradient between the departing low pressure center
and the incoming high pressure brings northwesterly winds
gusting to near 30mph on Thursday. Combined with daytime highs
in the low 50s across the north and 60s across the coastal
plain, it will feel like the most fall-like day so far for many.
Temperatures then fall into the 30s and 40s across the area
Thursday night, with low to mid 40s expected all the way to the
As the high continues to build in on Friday the wind will ease
and temperatures moderate slightly, especially across northern
areas. As the high crosses overhead and winds settle Friday
night, temperatures fall into the 30s across most interior
areas. Frost is possible across northern zones and inland
Temperatures moderate further on Saturday as the high gradually
moves offshore. Temps climb back into the low to mid 70s across
the coastal plain, and mid to upper 70s by Sunday. As the ridge
builds, low 80s likely make a return to southern areas early
next week. A weak warm front gradually passes through New
England early next week, which brings the increased chance of
POPs with the warmer temperatures. The progression of this
system remains somewhat uncertain at this time, but either way
it doesn`t look to be a very potent system. Once this passes
through, the pattern signals building warmth into midweek as the
ridge continues to build.
.AVIATION /04Z WEDNESDAY THROUGH SUNDAY/...
Short Term...Areas of fog will continue to develop tonight.
However, VFR conditions should gradually return from west to
east from late this evening through tonight as drier air moves
into the area. The exception may be HIE, where scattered showers
and lower ceilings may linger into Wednesday afternoon.
Otherwise, west winds will gust to around 25 kt from Wednesday
morning into the early evening hours.
Long Term...Gusty northwest winds up to 30kts are likely on
Thursday. VFR conditions are expected at most terminals, but
MVFR ceilings are possible at HIE in the northwest flow. Winds
ease Thursday night with mainly VFR conditions expected through
the weekend. Some valley fog is possible at night Friday through
Monday. Scattered showers are possible early next week.
Short Term...Fog will remain possible across the waters into
most of tonight across the waters. Otherwise, conditions will
deteriorate late tonight as west to southwest winds increase
into Wednesday early afternoon. Gusts to around 25 mph are
expected along with seas building to around 5 ft. Conditions may
briefly fall below SCA levels later Wednesday afternoon, but
will likely need another SCA by Wednesday evening/night as
northwest winds ramp right back up behind a strong but dry cold
front crosses through waters.
Long Term...SCA conditions are likely on Thursday with gusty
northwest winds up to 30kts. Conditions then ease Thursday night
as high pressure builds across the waters and brings more
tranquil conditions for Friday and the weekend.
MARINE...Small Craft Advisory from 4 AM to 8 PM EDT Wednesday for
Area Forecast Discussion
National Weather Service Lincoln IL
1100 PM CDT Tue Sep 13 2022
Issued at 244 PM CDT Tue Sep 13 2022
The stretch of dry weather will continue through late week as
subsidence builds in behind a departing weather system. Meanwhile,
temperatures will exhibit a hearty warming trend through this
weekend as daily temperatures surge into the mid-to-upper 80s
beneath a strong, late-summer heat ridge.
Issued at 800 PM CDT Tue Sep 13 2022
00z surface map indicated broad high pressure stretched across the
Midwest and Ohio Valley. Under the ridge winds were light and
dewpoints were in the upper 50s to lower 60s. Latest IR satellite
imagery shows the cloud deck that had persisted over eastern IL
much of the day has almost completely pushed east of the state
Main forecast concern is fog potential late tonight. High resolution
guidance is pointing to areas east of I-57 for areas of fog, with
a low potential for dense fog along our far eastern row of
counties along the Indiana border. Conceptually this makes sense
since these areas did not mix out low level moisture this
afternoon, so have increased fog wording east of I-57. The primary
fog timing is from 3-8 am, and the eventual need for a Dense Fog
Advisory cannot be ruled out for the far eastern CWA. Farther
west, patchy shallow fog is possible but is not expected to have a
meaningful impact on visibility. Good radiational cooling will
promote another cool night, with lows in the low/mid 50s.
.SHORT TERM...(This evening through Wednesday)
ISSUED AT 244 PM CDT Tue Sep 13 2022
While the large upper low was centered near Buffalo NY early this
afternoon, the fringes of the circulation continues to bring cloud
cover east of I-57, though it has appeared more diurnal as of late.
However, RAP layer humidity plots show this should largely be east
of the Indiana border by sunset.
Forecast soundings in eastern Illinois do suggest the possibility of
some ground fog after midnight, with latest NBM probabilities
showing 20-30% chances of visibility below 3 miles. Will include a
mention of patchy fog in the two columns of counties along the
Indiana border, as well as north of Peoria where some of the heavier
rain occurred over the weekend. Otherwise, clear skies to prevail
overnight, with lows mainly in the lower 50s. Can`t rule out some
upper 40s in the western fringes of the forecast area, where dew
points this afternoon have dropped into the 40s.
High pressure will slowly drift east through Wednesday, keeping our
weather quiet. The thicker smoke layer to our west will make an
eastward push, though vertically integrated smoke forecasts off the
HRRR favor more of an impact across northern Illinois, thus any
corrections to sky cover projections have been fairly minimal for
this forecast package. With more of a southeast flow setting up,
temperatures should reach the lower 80s for highs.
.LONG TERM...(Thursday through Tuesday)
ISSUED AT 244 PM CDT Tue Sep 13 2022
Low-level winds will veer southerly by Thursday as the upper-level
ridge axis builds across the Mid-Mississippi Valley and the center
of surface high pressure drifts eastward. This process will help
boost temperatures into the low-to-mid 80s as the return flow
advects warmer air in from the Southern Plains.
The stretch of dry and progressively warmer temperatures will
continue through this weekend as mid-level ridging remains locked in
place over the SE U.S. This feature will help keep central Illinois
entrenched in southwesterly flow, and ultimately on the periphery of
any convective activity as the majority of shortwave impulses look
to skirt by to the north and west. Trends over the past couple
forecast cycles have decreased PoPs and QPF over our CWA, with the
better signal coming over SE Iowa and N Illinois; closer to the
The main message into early next week is the continued unseasonably
warm temperatures. NBM guidance is offering daily highs near 90
each day Sunday through Tuesday as heat builds beneath an anomalous
late-summer ridge. The forecast also calls for breezy and continued
dry conditions as the stubborn ridge helps deflect convective
activity north and west of our area.
It`s not until the middle-to-late stages of next week that the ridge
shows signs of breaking down. About 1/3 of the members of the grand
ensemble cluster toward a solution that keeps the heat ridge
anchored over the Deep South. This would keep central Illinois hot
and dry into late next week. Meanwhile, the other 2/3 of members
cluster toward a solution that sends robust shortwave energy digging
through the Plains, effectively breaking down the ridge as an
approaching front brings on a wetter and cooler period into late
.AVIATION...(For the 06Z TAFS through 06Z Wednesday night)
Issued at 1100 PM CDT Tue Sep 13 2022
Guidance has trended toward more widespread fog late tonight,
with higher probabilities of IFR fog at KCMI. This is where the
lowest visibilities are forecast and have a TEMPO group for 1SM
at KCMI. Higher visibilities are forecast farther west, but at
least a few periods of MVFR conditions are possible, centered
around 09-13z. Otherwise, clear skies and light/variable winds
prevail next 24 hours under a high pressure ridge.
...UPDATED AVIATION FORECAST DISCUSSION...
.SHORT TERM...(This evening through Wednesday night)
Issued at 247 PM CDT Tue Sep 13 2022
Continued quiet weather is anticipated tonight before a change in
the weather pattern occurs on Wednesday. An upper level ridge,
currently centered over the High Plains, will progress east tonight.
The HRRR vertically integrated smoke model shows that while the
smoke will not be as dense as it was today, it will still linger
aloft. Very little should be at the surface and major impacts are
not expected. This smoke should help prevent some radiational
cooling overnight. A surface trough along the front range will
remain in place and cause winds to shift to the south, drawing
warm air from Texas north into Nebraska through the night. These
factors combined with forecasted daytime highs in the 90s this
afternoon will moderate overnight temperatures with lows in the
Warm temperatures are on tap again tomorrow as southerly warm air
advection carries on. However, this morning`s sounding showed 850 mb
temperatures of 29 degrees Celsius, but model soundings for tomorrow
show 850 mb temperatures closer to 22 Celsius in the morning and
weaker low level lapse rates. The advancing surface trough will also
bring greater cloud cover. Therefore, temperatures will be slightly
lower than today but still around 10 degrees above normal. A
tightening pressure gradient between the surface trough in eastern
Colorado and high pressure over the Indiana/Ohio will create
stronger southerly winds tomorrow, gusting to 30 knots in some
areas. Hot temperatures, low relative humidity, and stronger winds
do create some fire weather concerns for tomorrow. Please see the
fire weather discussion for more details.
Southerly to southwesterly flow will bring a subtle increase in
moisture into Nebraska, some of which originated from the remnants
of tropical storm Kay in the Pacific. An upper level shortwave
trough ahead of a low over the Pacific Northwest will move east over
the Rockies and reach Nebraska by the afternoon. As the surface
trough and upper level support converge, the possibility for
thunderstorms returns to the forecast area. Severe storms are not
expected as CAPE is less than 1000 J/kg and surface to 6 km shear
less than 20 knots, but some storms may be strong. One limiting
factor may be moisture as advection may not be strong enough for
widespread storm development. Surface relative humidity will be
between 20 and 35 percent for most areas with dew points in the 40s
to 50s. Rain chances do appear to improve later in the night as the
trough advances east into areas of better moisture.
.LONG TERM...(Thursday through Tuesday)
Issued at 247 PM CDT Tue Sep 13 2022
Additional rainfall chances exist Thursday through Saturday as an
upper level trough deepens over the West Coast and several
shortwave troughs will move east ahead of this feature. A surface
trough will slowly move east through Nebraska, providing a lifting
mechanism for storm development. The possibility for severe
weather appears low at this time, although there is an indication
of increased CAPE on Friday and Saturday which may be the best
chances for stronger thunderstorms.
Exceptionally hot weather is possible again early next week. A
trough over the western United States will continue to draw warm air
into the Great Plains. Long range guidance is picking up on highs 20
to 30 degrees above normal, through these temperatures are
moderated in the forecast through bias correction. Temperatures
should begin to cool once again on Tuesday as a cold front
approaches from the northwest.
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 620 PM CDT Tue Sep 13 2022
VFR conditions are expected to prevail through tomorrow evening.
Scattered thunderstorms are anticipated across much of western and
north central Nebraska tomorrow afternoon, though confidence
remains too low for any TS mention at both LBF and VTN for now.
Winds remain southerly and increase tomorrow afternoon, with gusts
of 25 to 30kts anticipated.
Issued at 256 PM CDT Tue Sep 13 2022
The return of summer-like temperatures and high pressure overhead
have resulted in very dry air today, especially across western
Nebraska where humidity values fell into the lower teens. The lack
of gusty winds precludes any critical fire weather concerns.
Elevated fire weather continues tomorrow, but mainly for gusty
winds. Moisture begins streaming into the region, which holds
humidity above critical thresholds, but southerly winds will gust
above 30 mph at times. Isolated to scattered thunderstorms will
affect the Sandhills from late afternoon through the late evening
hours, then again on Thursday and Friday. Potential for wetting
rain seems to be localized, although more widespread precipitation
is possible Thursday evening across north central Nebraska (zone
209, eastern 208). A cool front will also result in a rapid wind
shift from south to northwest on Thursday. Looking ahead,
temperatures rebound and humidity drops again Sunday into Monday.
Depending on winds, critical conditions are possible, especially
Area Forecast Discussion
National Weather Service San Francisco Bay Area
535 PM PDT Tue Sep 13 2022
.SYNOPSIS...Cooler than normal temperatures are expected to persist
across the region through late week with breezy onshore winds at
times. There will also be the potential for light rainfall late in
the weekend followed by the development of offshore winds and
slightly warmer temperatures early next week.
.DISCUSSION...as of 02:01 PM PDT Tuesday...Mostly sunny sky
conditions prevail over the region with a few to scattered low-
level clouds bumping up again the North Bay and San Mateo County
coastlines as well as the East Bay Hills. Satellite imagery is
showing even these clouds beginning to dissipate as conditions
begin to dry out in the boundary layer. Even with the abundant
sunshine, temperatures are running a few to as much as 10 deg F
cooler compared to 24 hours ago. This is in response to the
cooling air mass aloft as a mid/upper level low pushes inland over
A similar pattern will persist into Wednesday with temperatures
below seasonal averages, generally running in the mid/upper 60s at
the coast to mid 70s inland. Additionally, the HRRR and other short-
range guidance do show low-level clouds developing once again late
tonight before spreading locally inland. Breezy onshore winds are
also likely to persist through midweek, with gusty winds in the
favor passes and coastal gaps. Only slight warming is anticipated on
Thursday and Friday with a few interior locations peaking in the
lower 80s as broad troughing persists over the region.
By Saturday the mid/upper level pattern will begin to change with a
low pressure system developing over the Bay of Alaska. The forecast
models are becoming better aligned with the track of the mid/upper
level low dropping down the Pacific Northwest coast and eventually
down the California coast this weekend. As such, a frontal system is
likely to push southward into northern California and interact with
precipitable water values close to an inch. With enough forcing,
may see light precipitation spread from north to south across the
region on Sunday. Currently, it looks as though rainfall amounts
will range from a few hundredths of an inch to a tenth of an inch in
the coastal hills. This is still an evolving pattern with details
likely to change in the coming days.
The next impact of note would be once the aforementioned mid/upper
level system shifts inland early next week. Forecast models continue
to indicate a reinforcing trough dropping into the Pacific Northwest
and then down the intermountain West as an inside slider. This
pattern would be favorable for the development of offshore winds
across the greater San Francisco Bay Area (thinking North Bay and
East Bay hills/mountains). The timing of this still appears to be in
the Tuesday to Wednesday timeframe with the details on strengthen of
potential offshore winds still in question. The good news is we have
a few days to monitor and fine tune the forecast.
.AVIATION...as of 5:00 PM PDT Tuesday...For the 00Z TAFs. Mainly
clear skies prevail this afternoon with the exception of a few
patches of stratus lingering along the coast. A deep marine layer
coupled with a moderately strong onshore gradient will result in
the return of stratus a bit sooner, between 04z-06z this evening
and the expectation of a later burn-off, around 16z-18z tomorrow
morning. Coastal terminals may see stratus linger till around
Vicinity of KSFO...VFR conditions persist across area terminals
with patchy stratus spreading inland through coastal gap.
Anticipate a slightly earlier return of the status this evening
with gusty onshore flow. MVFR cigs expected to return to area
terminals between 04Z-06Z with winds easing overnight. A deep
marine layer and onshore flow may keep cigs around through
Wednesday morning before clearing in the afternoon.
KSFO Bridge Approach...Similar to KSFO.
Monterey Bay...VFR conditions prevail through the evening,
with stratus redeveloping tonight. MVFR likely but IFR possible.
Breezy NW winds this afternoon, easing by evening. Late clearing
.MARINE...as of 03:08 PM PDT Tuesday...Some strong gusty winds
through the Golden Gate, along coastal jet regions south of Pigeon
Point, and along the Big Sur coast through tonight. Hazardous
conditions for smaller vessels can be expected where the stronger
winds develop. Winds will diminish tonight into Wednesday, but
then redevelop Thursday through the end of the week. A southerly
swell of 2 to 4 feet at 12 to 14 seconds continues.
.Tngt...SCA...SF Bay until 9 PM
SCA...Mry Bay until 9 PM
SCA...Pigeon Pt to Pt Pinos 0-10 nm until 9 PM
SCA...Pt Pinos to Pt Piedras Blancas 0-10 nm until 3 AM
PUBLIC FORECAST: RGass
Visit us at www.weather.gov/sanfrancisco
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...Updated Aviation Forecast Discussion...
Issued at 321 PM CDT Tue Sep 13 2022
Upper-level ridging will continue to move over the central CONUS.
Smoke originating from fires across the northwestern U.S. will
continue to pass overhead but according to the recent runs of HRRR
near-surface smoke, is not anticipated to mix down to the
surface. This should create some photogenic sunrises and sunsets
over the next couple of days.
Temperatures will remain about 10 degrees above normal for this time
of the year through the next 7 days. Upper/mid-level flow becomes
southwesterly by late in the week as a broad trough moves into the
the western U.S. This will send a series of weak disturbances into
the region with off and on chances for showers and thunderstorms
beginning as early as Wednesday night and continuing into the
weekend. QPF through the period does not look overly impressive and
certainly not a drought-buster by any means. Better precipitation
chances look possible into next week as a large western upper trough
begins to eject into the central U.S. pushing a strong cold front
into the central Plains.
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 616 PM CDT Tue Sep 13 2022
VFR conditions will prevail through the forecast period with LLWS
expected from around midnight into mid-morning on Wednesday. From
late morning through afternoon, southerly surface winds will
strengthen to 12-15 kt with gusts of 20-25 kt.
Area Forecast Discussion
National Weather Service Spokane WA
439 PM PDT Tue Sep 13 2022
Clusters of slow moving thunderstorms will develop over north
central Washington this afternoon and spread into eastern
Washington and north Idaho overnight. Locally heavy rain will be
possible over the steep terrain of the north Cascades and Okanogan
Highlands. Redevelopment of showers and thunderstorms is likely
Wednesday along the Canadian border. The combination of rain, cool
temperatures, and a subtle increase in west winds should bring
gradual improvements to our air quality Wednesday into Thursday.
The weekend will be cooler with daytime temperatures in the 60s
and morning lows in the 40s and a few 30s.
This evening and through the night: Showers and thunderstorms over
north central Washington will increase late in the afternoon into
the evening as an upper low over the Olympic Peninsula (as of 2
PM) slowly migrates east through the night. Through the night,
look for scattered showers and thunderstorms to spread into
eastern Washington and north Idaho. While our precipitable water
values and surface dewpoints aren`t particularly high, the
combination of upper level difluence and weak mid-level flow will
contribute to an environment conducive for slow moving showers and
thunderstorms, mainly in north central Washington. A Flash Flood
Watch is in place for Chelan, Okanogan, Ferry, and Stevens
counties this afternoon into Wednesday. Widespread flooding is not
anticipated, but slow moving cells that develop over flood prone
areas may cause problems with rock/mud slides and rapid rises on
creeks and streams. Steep terrain, urban areas, and burn scars are
a particular concern. While the rain may cause some localized
problems, precipitation will benefit our region which has been
very dry since mid July.
Wednesday: During the day Wednesday, our slow moving upper low
will pivot across northeast Washington into southern British
Columbia. High resolution models predict a lull in shower activity
in the morning with a redevelopment for our counties along the
Canadian border during the afternoon. Similar to today,
atmospheric moisture and instability will be sufficient for
thunderstorms development. Once again, slow moving cells capable
of locally heavy rain will be monitored closely in Okanogan,
Ferry, and Stevens counties.
Thursday and Friday: A weak upper level trough will persist over
the Pacific Northwest Thursday and Friday. With the departure of
our upper low Wednesday night, precipitation chances will be very
low on Thursday with a slight increase up to 20 percent along the
Canadian border on Friday afternoon. Seasonal temperatures will be
on tap with highs in the 70s and lows in the 40s and 50s.
Saturday through Wednesday: The upper level weather pattern
begins to take on a more Fall-like pattern as we head into the
weekend. The trajectory of where this upper level trough is
originating in the Gulf of Alaska will bring southward much cooler
air. The weather system has little signature of moisture with the
percentile of precipitable water showing about normal for this
time of year.
The cluster analysis of ensemble members by Sunday is a three-way
tie between deepening the Low off shore, a weaker longwave trough
down the West Coast, or a digging trough into Oregon. The EC
ensemble favors more of the longwave trough extending southward
and swinging through the Great Basin over the weekend; a more
progressive solution. The GFS and Canadian ensembles would be more
in favor of a deeper, cut-off Low off the California coast. What
would this mean for our sensible weather in the Inland Northwest?
This could lead to cooler, more unstable weather over the weekend
with a dry boundary layer and high level moisture (partly cloudy
While uncertainty is quite large for exactly which model solution
to lean harder on, the overall agreement to a more troughy and
cooler pattern seems probable. CPC has introduced a slight chance
for below normal temperatures as we head out into the far extended
(next week). This time of year, mid September, brings normal
daytime high temperatures in the low 70s and right now the
forecast is showing upper 60s. /Dewey
.AIR QUALITY AND SMOKE...
The combination of precipitation, higher humidity, and
temperatures trending cooler than they were the last few weeks
should bring gradual improvements to air quality for much of the
Inland Northwest. Over the next 24 to 36 hours, parts of Idaho,
southern British Columbia, northern Washington, and northeast
Oregon should experience enough shower activity to wet a
significant number of our active fires. And a persistent upper
level trough should lead to several days of a prevailing west or
southwest flow. While late summer morning inversions will be slow
to break leading to thick smoke near fires, in general the
combination of wetter and cooler conditions and a cleaner west
flow should lead to gradual improvements in our smoky skies this
week into the weekend. /GKoch
00Z TAFs: Scattered showers and thunderstorms will accompany the
passage of a slow moving upper low this evening through the
overnight. VCSH have been included at most TAF sites this evening.
High resolution models predict the development of a band along the
WA/ID border between 10-15z which is enough to include prevailing
showers at Pullman and Coeur d`Alene. A gradual improvement in the
visibility is predicted through the night as the upper low crosses
the Cascades leading to a cleaner west wind through the night and
into the day Wednesday. Visibility forecasting with smoke is a
low confidence endeavor. The HRRR smoke model is frequently better
at forecasting the arrival of smoke than the departure of it.
.PRELIMINARY POINT TEMPS/POPS...
Spokane 53 74 50 77 50 74 / 40 20 0 0 0 0
Coeur d`Alene 52 74 50 77 48 73 / 40 40 0 0 0 0
Pullman 47 73 45 73 43 71 / 40 40 0 0 0 10
Lewiston 59 80 56 80 54 78 / 30 30 0 10 0 10
Colville 43 73 41 78 41 75 / 50 60 10 0 10 10
Sandpoint 48 71 45 74 45 71 / 30 50 10 0 10 10
Kellogg 55 71 53 73 52 71 / 20 50 10 0 10 10
Moses Lake 50 78 49 80 48 76 / 40 10 0 0 0 0
Wenatchee 56 76 57 78 54 74 / 40 10 0 0 0 0
Omak 54 78 53 80 52 78 / 70 40 10 10 0 10
WA...Flood Watch through Wednesday evening for Central Chelan County-
Okanogan Highlands-Okanogan Valley-Upper Columbia Basin-
Wenatchee Area-Western Chelan County-Western Okanogan
Flood Watch through Wednesday evening for Northeast Mountains.
Area Forecast Discussion
National Weather Service Reno NV
147 PM PDT Tue Sep 13 2022
Smoke from the Mosquito fire will continue to produce air quality
and visibility impacts across portions of western Nevada and
northeast California. Shower and thunderstorm chances will shift
eastward this afternoon and tomorrow with localized areas of heavy
rainfall possible from Mono County into the eastern extents of
Pershing and Churchill counties. Seasonably cool temperatures with
freezes possible in mountain valleys each morning. An early
season cold front this weekend is expected to bring below average
temperatures, gusty winds along with low elevation rain and
mountain snow showers.
.SHORT TERM (Through Wednesday Night)...
* The main topic of discussion will continue to be the degraded
air quality from the Mosquito Fire burning in western Placer and
El Dorado counties. While it`s safe to conclude that not
everyone in the region will experience smoke impacts, the
location of the fire and prevailing winds will keep many of our
larger metropolitan areas along the I-80 corridor in a favorable
location for haze/smoke as long as the fire keeps burning. In
the near term, while we will see some improvement early this
afternoon due to afternoon mixing, an uptick in fire behavior
due to peak afternoon heating along with an increase in
southwest transport winds will likely transport a concentrated
smoke plume from Placer Co north into SE Plumas by mid/late
afternoon. Around sunset, we should see the smoke establish
itself into portions of western Nevada - primarily impacting
southern Washoe (including Reno/Sparks) before traversing
eastward into portions of the Basin and Range. Check out
fire.airnow.gov for the latest air quality in your area
including short-term AQI forecast for specific locations.
* However, we obviously cannot forget about the topic of showers
and thunderstorms as well! Not much change in forecast thinking
from the overnight hours... High resolution CAM guidance
continues to be in good agreement on scattered to numerous
showers and storms firing up this afternoon along the eastern
Sierra and portions of western Nevada, primarily south of US-50
and outside of Reno/Carson (although chances aren`t zero).
Despite ample moisture (PWATs 0.75-1.00 inches), HREF
neighborhood probabilities keep the chances of exceeding 1hr
flash flood guidance generally 5-10% across southern Mono and
Mineral counties due to the storm motion of around 15 knots.
Nevertheless, quick but high rain rates on burn scars or steep
terrain always creates a concern for flooding due to their
localized lower thresholds. Finally, any convection that does
sneak north of US-50 in eastern Churchill/Pershing will have a
higher likelihood of strong outflows due to higher DCAPE values
off to the north. Another round of convection can be
anticipated Wednesday afternoon, but more isolated to scattered
in nature and generally along or east of US-95 and US-6. Quicker
storm motion (around 20kts) compared to today will lower the
chance for flash flooding even further as well. Oh yes, if you
happen to be hiking above 11,000-12,000 feet, some snow showers
will be possible through the period in places like the White
Mountains and high eastern Sierra; expect minimal accumulation -
if any ...
* Nothing unusual in terms of temperatures in the short term period.
Well, compared to what we`ve seen lately, I guess below average is
something to write home about! On Wednesday, highs around 80 in
western Nevada Valleys with low 70s in Sierra Valleys will feel
rather pleasant. A freeze is possible tonight in some of our
colder Sierra valleys, but more widespread sub-freezing temps can
be expected Wednesday night as several valleys in the Sierra will
dip into the upper 20s. Hooray for the taste of Fall!
.LONG TERM (Thursday Onward)...
For Thursday and Friday, we`ll maintain a cool, southwest to
zonal flow aloft. This will provide the area with slightly below
normal temperatures with mostly low 80s for the valleys and low
70s in the Sierra. There still is a slight 15% chance of lingering
showers in Mono and Mineral counties on Thursday due to left over
moisture. The big question for the region will be possibility of
continued poor air quality due to surrounding wildfires.
Unfortunately, there is no simple answer to this question. While
near-term models show light west to southwesterly winds (which
would transport smoke into western NV/Tahoe), it`s very dependent
on the amount of smoke generated by the Mosquito Fire.
For those of you tired of summer (my hand is raised), a big pattern
change is in store by the weekend through the end of the forecast
period Tuesday. The long-term ensembles are in favor a deep trough
dropping south from the Gulf of Alaska into the western U.S. But,
the latest WPC Cluster analysis shows considerable differences
between the ensembles in timing and strength of the aforementioned
trough, especially after Saturday. What is for certain, temperatures
will fall well below average by Sunday, and remain below average
through the at least the middle of next week. Southwest winds will
increase ahead of this trough, with the strongest gusts possible
(35+ mph) on Saturday and Sunday. Finally, precipitation chances
will increase between 25-35% from Saturday through Monday. Given
the considerable drop in temperatures, some of this precipitation
could fall as snow for the higher elevations (~7,500-8,000ft).
Stay tuned to the upcoming changes! -McKellar
* The latest HRRR smoke model is not as aggressive with the smoke as
the past couple of afternoons, with the KRNO-KTRK terminals on the
southern edge of the main plume trajectory. We are looking at the
potential for primarily VFR conditions for KTRK-KRNO (but
degraded conditions at KRTS). While there may be some slantwise
visibility concerns, areas to the north and south including
KTVL/KCXP/KMEV/KMMH and KSVE also appear to remain VFR with much
less dense smoke than recent days.
* The shower and t-storm potential has shifted eastward this
afternoon-evening, with west central NV around 35-45% chance at
KLOL/KNFL, southward to KHTH-KMMH about 60% chance and less than
20% elsewhere. Primary concerns will be MVFR-IFR conditions from
heavy rain and localized dust/smoke, outflow wind gusts to 40
knots, and lightning. By Wednesday, the potential for storms
trends down with about a 25% chance for KMMH-KHTH and 10% or less