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Office: SEW

FXUS66 KSEW 170349
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
849 PM PDT Tue Aug 16 2022

.SYNOPSIS...
A strong ridge of high pressure will build into the Pacific
Northwest over the next several days. This will provide well above
temperatures with highs well into the 90s in many areas. The hot
weather will continue for a few days before the upper level ridge
shifts east by the weekend with temperatures dropping back closer
to normal.

&&

.SHORT TERM /TONIGHT THROUGH FRIDAY/...A quiet evening weather
wise across Western Washington. Under mainly clear skies this
evening temperatures remain still in the 60s and 70s. Expecting a
comfortable night with lows into the 50s to low 60s overnight. The
warming trend will be noticed tomorrow, however, as highs should
be some 5-10 degrees warmer than today. This will give a decent
run at 90 degrees in the Seattle metro area, probabilities for
Seattle remain around 25% for a high of 90 or higher. So the
forecast remains with an expected high in the upper 80s, but much
hotter especially across the interior valleys of the Cascades
where temperatures will reach well into the mid and upper 90s.
850mb temps around 18C this evening will warm all the way to the
20-25C range by late tomorrow. Fortunately there is no strong
offshore wind component to drive temperatures even higher this
time. Heat Advisories and Excessive Heat Warnings remain in effect
for the next couple days.

Thursday looks to be the hottest day in the interior with
high temperatures in the low 90s in the Central Sound and even mid
90s South of the sound. The hottest locations will be the Cascade
valleys where temperatures will hover in the upper 90s and even
close to 100.

Guidance shows some mid-level instability within the Cascade mountains,
and some ensembles are picking up on traces of a thunder threat.
Confidence is low on any storms firing off due to the lack of
sufficient moisture in the region, but if anything does indeed
form, it will be super high based and likely will not last long.

Conditions look to cool down 5 to 10 degrees on Friday as the
ridge axis moves eastward and an upper level trough nears Western
Washington. The marine layer will deepen and in conjunction
strengthening the onshore flow, providing a cool down into the
weekend.

Johnson/Mazurkiewicz

&&

.AVIATION...Upper level ridge over the area. Light flow aloft
becoming southerly Wednesday morning. In the lower levels light
onshore flow through Wednesday.

Clear skies over the area tonight with stratus offshore. Stratus
moving to the coastline around 09z but not making it very far
inland. Ceilings with the stratus less than 1000 feet. Stratus
retreating back off the coast 16z-18z. Clear skies for the
remainder of the area through Wednesday.

KSEA...Clear skies. Northerly wind 4 to 8 knots increasing to 8 to
12 knots around 22z Wednesday. Felton

&&

.MARINE...Onshore flow continues over W WA waters as
high pressure influences the coastal water zones and lower pressure
continues east of the Cascade Crest. Winds will remain rather benign
over the waters tonight.

Weaker onshore flow/marine pushes Wednesday and Thursday will keep
the greatest extent of the stratus over the coastal waters. This
will also result in either the absence of, or very marginal westerly
small craft advisory level winds down the Strait.

Onshore flow will then strengthen Friday and into the weekend, with
stronger pushes each evening down the Strait. Models remain
consistent in putting Small Craft Advisory winds for the Strait
during this timeframe and possibly spilling over into the adjacent
waters of Admiralty Inlet and the Northern Inland Waters. Seas
through the forecast period will generally remain 3-5 feet near the
Coast and offshore and 1-2 feet in the interior waters (2-4 feet in
the Strait during small craft advisory level winds).

18

&&

.FIRE WEATHER...Hot and dry conditions continue to develop the next
few days. This, in combination with receptive fuels and very
unstable (Haines 6) conditions lead to critical fire weather
conditions in the Cascades the next few days. As a result, have
issued a Red Flag Warning for zones 658 and 659 for Wednesday and
Thursday. There may be some modest, but generally poor recoveries
across the zones Wednesday night. Elsewhere across the lowlands,
expect that some marine influence will yield better recoveries and
somewhat higher daytime RHs above critical values. The adjacent
foothills zones (specifically: 656, 657, and parts of 655), however,
may approach critical values, so will have to closely monitor the
forecast in these areas. The next fire weather concern would be the
potential for thunderstorm activity. There's some slight chance that
late Thursday could see some monsoonal moisture work north to near
the crest, but this does not look favorable at this time. A better
chance would be around Sunday with the breakdown of the upper ridge.
Cullen

&&

.HYDROLOGY...The daily hydrology discussion has ended until the
start of the next rainy season; it will only be updated as needed.

&&

.PREV DISCUSSION... /issued 307 PM PDT Tue Aug 16 2022/


LONG TERM /SATURDAY THROUGH TUESDAY/...Temperatures go back to
near seasonal normals for the weekend as upper heights begin to
fall due to the approaching upper level trough in our region.
With this trough, unstable southerly flow will be present
throughout the weekend. Ensembles are continuing to trend more on
the dry side for now, but the pattern does look favorable for
some convection Sunday through Monday in the mountains. Will need
to continue to monitor the trend for any potential changes.

Mazurkiewicz


&&

FIRE WEATHER...Hot and dry conditions continue to develop the next
few days. This, in combination with receptive fuels and very
unstable (Haines 6) conditions lead to critical fire weather
conditions in the Cascades the next few days. As a result, have
issued a Red Flag Warning for zones 658 and 659 for Wednesday and
Thursday. There may be some modest, but generally poor recoveries
across the zones Wednesday night. Elsewhere across the lowlands,
expect that some marine influence will yield better recoveries and
somewhat higher daytime RHs above critical values. The adjacent
foothills zones (specifically: 656, 657, and parts of 655), however,
may approach critical values, so will have to closely monitor the
forecast in these areas. The next fire weather concern would be the
potential for thunderstorm activity. There's some slight chance that
late Thursday could see some monsoonal moisture work north to near
the crest, but this does not look favorable at this time. A better
chance would be around Sunday with the breakdown of the upper ridge.
Cullen

HYDROLOGY...The daily hydrology discussion has ended until the
start of the next rainy season; it will only be updated as needed
until then.

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...Heat Advisory from noon Wednesday to midnight PDT Thursday night
     for Bellevue and Vicinity-Bremerton and Vicinity-East Puget
     Sound Lowlands-Everett and Vicinity-Hood Canal Area-Lower
     Chehalis Valley Area-Seattle and Vicinity-Southwest
     Interior-Tacoma Area-Western Skagit County-Western Whatcom
     County.

     Excessive Heat Warning from noon Wednesday to midnight PDT
     Thursday night for West Slopes North Cascades and Passes-
     West Slopes North Central Cascades and Passes-West Slopes
     South Central Cascades and Passes.

     Red Flag Warning from 11 AM Wednesday to 10 PM PDT Thursday for
     West Slopes of the Central Cascades Generally above 1500
     Feet-West Slopes of the North Cascades Generally above 1500
     Feet.

PZ...None.
&&

$$

www.weather.gov/seattle



Office: OTX FXUS66 KOTX 170457 AFDOTX Area Forecast Discussion National Weather Service Spokane WA 957 PM PDT Tue Aug 16 2022 .SYNOPSIS... Another heatwave will occur across the Inland Northwest this week with triple digit heat returning to central Washington, the Lewiston area, and parts of eastern Washington Wednesday through Friday. The forecast for the weekend into early next week should be a few degrees cooler with afternoon temperatures in the 90s. && .DISCUSSION... ...EXCESSIVE HEAT WARNINGS AND HEAT ADVISORIES ARE IN EFFECT WEDNESDAY THROUGH FRIDAY EVENING FOR CENTRAL AND EASTERN WASHINGTON AND PARTS OF THE IDAHO PANHANDLE... Tonight through Friday: Upper level ridging begins to amplify this evening as a deep upper level low in the Gulf of Alaska sends a shortwave trough into the far eastern Pacific. Models are in good agreement that 850mb temperatures will warm to around 26-28C through at least Friday. This corresponds to high temperatures across the Inland Northwest well into the mid 90s to low 100s which is about 15 degrees above normal for mid-August. The warmest locations will be in the lee of the Cascades and into the Columbia Basin and the Okanogan Valley where high temperatures above 100 degrees will be likely Wednesday through Friday. As the ridge amplifies over the Western US, a deep southerly flow aloft will allow for monsoonal moisture from the southwestern US to migrate into the region. As a result, cloud cover will begin to increase Thursday afternoon. Thursday has the potential to be the warmest day of the week, with about a 55% chance for Spokane to reach 100 degrees. Clouds cover looks to arrive late enough in the afternoon to not affect high temperatures, but an earlier arrival could keep Thursday cooler than currently forecasted. The increase in clouds will keep low temperatures very warm Thursday night with lows Friday morning in the 60s to mid 70s. Anyone without air conditioning will receive little relief from the warm temperatures of the day. A weak impulse will move through the northwest Thursday afternoon and another, stronger one will move through Thursday night through Friday. Given the very dry boundary layer both days, confidence on the overall storm development is quite low. There may be enough elevated instability and elevated moisture to allow for isolated thunderstorms mainly across the Cascades Thursday afternoon and again late Friday morning/early afternoon. Friday will be warm again with highs in the upper 90s to low 100s. Saturday through Tuesday: Models begin to differ heading into the weekend on the end time of the heatwave as an upper level trough progresses toward the Pacific Northwest. Temperatures look to stay relatively warm for Saturday and Sunday as this trough works to re-amplify the ridge over the region. Depending on the speed of the approaching trough, heat products may need to be extended into the weekend. By the beginning of next week, models are suggesting that the upper level trough may begin to move onshore with temperatures trending back to near average values and an increasing potential for precipitation. The arrival of this trough will need to be monitored closely, with models suggesting better chances for scattered thunderstorms Monday afternoon and early evening across eastern Washington and the Idaho Panhandle. vmt && .AVIATION... 06Z TAFs: VFR conditions will continue through Wednesday, with mainly light diurnally driven winds. The exception could be slightly stronger winds draining through the COE area in the morning. Smoke from area wildfires should largely stay aloft and/or away from TAF sites. A potential exception will be near EAT as some Cascade wildfire smoke could bring brief MVFR conditions. However confidence is low. /Cote' && .PRELIMINARY POINT TEMPS/POPS... Spokane 60 98 64 99 68 98 / 0 0 0 0 0 0 Coeur d'Alene 58 96 61 98 64 97 / 0 0 0 0 0 0 Pullman 57 95 59 96 62 93 / 0 0 0 0 0 0 Lewiston 65 103 67 103 73 101 / 0 0 0 0 0 0 Colville 53 98 56 100 58 99 / 0 0 0 0 0 0 Sandpoint 55 94 58 95 61 94 / 0 0 0 0 0 0 Kellogg 64 94 66 95 70 94 / 0 0 0 0 0 0 Moses Lake 60 101 65 103 68 102 / 0 0 0 0 0 10 Wenatchee 68 100 73 102 75 100 / 0 0 0 0 0 10 Omak 64 101 66 103 68 104 / 0 0 0 0 0 10 && .OTX WATCHES/WARNINGS/ADVISORIES... ID...Heat Advisory from noon Wednesday to 11 PM PDT Friday for Coeur d'Alene Area-Idaho Palouse-Lewis and Southern Nez Perce Counties-Lewiston Area-Northern Panhandle. WA...Excessive Heat Warning from noon Wednesday to 11 PM PDT Friday for Central Chelan County-Moses Lake Area-Okanogan Valley- Upper Columbia Basin-Waterville Plateau-Wenatchee Area. Heat Advisory from noon Wednesday to 11 PM PDT Friday for Lower Garfield and Asotin Counties-Northeast Blue Mountains- Northeast Mountains-Okanogan Highlands-Spokane Area- Washington Palouse-Western Chelan County-Western Okanogan County. Red Flag Warning from 11 AM Wednesday to 10 PM PDT Thursday for East Washington Central Cascades (Zone 696). && $$