Area Forecast Discussion
Issued by NWS Spokane, WA

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FXUS66 KOTX 172332
AFDOTX

Area Forecast Discussion
National Weather Service Spokane WA
432 PM PDT Thu Aug 17 2017

.SYNOPSIS...
The warm and dry weather is expected to persist through at least
the early part of next week. Breezy and dry winds on Friday will
raise concerns for wildfires. Our weather on Monday should be
favorable for good views of the eclipse with mainly clear skies.
Areas of smoke will continue. There is the potential for mountain
thunderstorms in North Idaho by middle of next week.

&&

.DISCUSSION...
Tonight through Saturday: Dry westerly flow will remain over the
Inland Northwest with seasonably warm temperatures. Few cumulus
over the Panhandle mountains will dissipate early this evening,
meanwhile bands of smoke aloft will most likely spread in from the
northwest. A weak ridge aloft will flatten tonight into Friday as
a dry cold front swings inland. This feature will push east of the
Cascades Friday afternoon and reach north Idaho by early evening.
Winds ahead of the front will steadily increase, and become breezy
with the frontal passage with gusts of 20 to 25 mph. This may stir
up area fires and cause more smoke. Temperatures will cool
slightly Friday night as wind dissipate. The cooling will continue
into Saturday will less wind. Some mountain cumulus may develop
over northeast Washington and north Idaho, although precipitation
chances are very low. /rfox.

Saturday night through Tuesday...Strong model agreement exists
for this period featuring dry zonal flow on Saturday...a weak
troffy pattern on Sunday with the forecast area under the dry
northern branch region of a broad western US split flow
trough...and then a building ridge and warm up for Monday and
Tuesday as a trough digs offshore. No precipitation is expected
through this period. Temperatures will begin the weekend slightly
above normal and then increase on Monday and Tuesday. Smoke
infiltration from BC and local smoke from eastern Washington fires
will mainly impact the northern zones on Saturday and Sunday and
probably retrograde to the north as flow becomes more
southwesterly on Monday. The eclipse viewing will probably be
through mostly clear skies Monday...or at worse through some thin
cirrus. All in all there is high confidence that it will be a
benign and seasonably warm weekend and early work week.

Wednesday and Thursday...Model differences become noticeable by
Wednesday and forecast confidence degrades. The GFS suggests the
offshore will kick inland and through the region during this
period with a thunderstorm threat mainly on Wednesday ahead of
it...then a breezy cold front passage Thursday. The ECMWF suggest
a deeper and slower trough arrival suggesting another warm day
Thursday with a longer period of thunderstorm threat in moist
southerly flow. Given the recent pattern shift to a more
progressive flow regime and the anomalous nature for high summer
of the EC solution...will hedge toward the more progressive GFS
model...which also has some loose support from the latest
Canadian model run. This argues for at least a small threat of
thunderstorms somewhere over the forecast area on Wednesday
followed by a slightly cooler...dry and breezy period on Thursday.
/Fugazzi

&&

.AVIATION...
00Z TAFS: Locally breezy northwest winds will develop around
Wenatchee tonight...otherwise light terrain driven winds will be
in place through 18Z Fri. The next dry cold front to bring the
next increase in winds late Friday afternoon and evening with
speeds on the order of 15-20 mph coupled with gusts to 25 mph.
Mainly passing high clouds expected with the frontal passage. /sb

&&

.FIRE WEATHER...
The dry cold front will bring gusty winds across the region for
Friday. The wind speeds of 15 to 20 mph will be the strongest
from the Cascade valleys into the western Columbia Basin Friday
late afternoon and early evening, while relative humidities drop
into the teens. The winds and dry conditions will lead to
increased fire spread. The timing of the strongest winds and low
humidity`s seems to meet the best in the Wenatchee valley,
although it will be a short window. Humidities will be on the rise
through the evening despite the breezy winds persisting
overnight. The Fire Weather Watch will be upgraded to a Red Flag
warning for the East Washington Central Cascade Valleys (Zone 677)
for late Friday afternoon and early evening. Low level
instability will be elevated with the front that may make current
fires more active. Winds will be lighter through the weekend,
although occasional gap winds are expected in the Cascade valleys.
/rfox.

&&

.PRELIMINARY POINT TEMPS/POPS...
Spokane        57  85  58  82  58  83 /   0   0   0   0   0   0
Coeur d`Alene  54  85  55  81  54  82 /   0   0   0   0   0   0
Pullman        53  85  54  80  53  80 /   0   0   0   0   0   0
Lewiston       62  93  62  88  61  88 /   0   0   0   0   0   0
Colville       52  88  52  85  51  85 /   0   0   0   0   0   0
Sandpoint      49  84  50  80  47  81 /   0   0   0   0   0   0
Kellogg        52  81  52  77  51  79 /   0   0   0   0   0   0
Moses Lake     59  90  59  87  55  87 /   0   0   0   0   0   0
Wenatchee      64  88  63  86  62  88 /   0   0   0   0   0   0
Omak           60  92  59  87  58  89 /   0   0   0   0   0   0

&&

.OTX WATCHES/WARNINGS/ADVISORIES...
ID...None.
WA...Red Flag Warning from 4 PM to 8 PM PDT Friday for East
     Washington Central Cascade Valleys (Zone 677).

&&

$$



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