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Area forecast discussion 
National Weather Service Spokane Washington
424 am PDT Sat Aug 1 2015

Synopsis....
expect a very hot weekend with afternoon temperatures in the mid
90s to near 105. The ongoing drought combined with high heat and
low humidity will raise concerns for wildfires the next several
days. A cold front will bring temperatures back closer to average
on Monday. Temperatures for Tuesday through Friday will likely be
at or below average.

&&

Discussion...
today through Sunday night: expect more of the same - the hot and
dry weather continues. A ridge of high pressure remains parked
over the inland northwest and will stay put through the weekend. A
surface trough stretches across the Columbia Basin will only
waiver slightly through the period.

Winds: downslope Cascade Gap winds that picked up last evening are
decreasing. The winds will remain light through the day but
appears west/northwest winds will prevail across the Cascades in
many spots, like Wenatchee valley. Terrain driven winds will be
found in more of the sheltered valleys, like the Methow Valley.
Surface pressure gradients tighten to about 5 mb this afternoon
and should see a repeat of gusty gap winds of 10 to 15 mph
especially from the Wenatchee valley onto the Waterville Plateau
into the evening hours. Afternoon gusts of 15 to 20 mph are also
possible across the Columbia Basin as the dry and unstable
atmosphere mixes. Sunday winds look to be slightly weaker with
speeds less than 10 mph with occasional gustiness.

Clouds/weather: the satellite fog product has been showing hot
spots from wildfires across the region and the hottest seems to be
the Wolverine in the northern Cascades. Anticipate plenty of smoke
over Lake Chelan and surrounding valleys this morning, possibly
spreading aloft as well. Initially the atmosphere will remain
starkly dry with a dry westerly flow aloft. But by tonight and
into Sunday, upper level moisture will filter in from the
southwest and south as it circulates around the dome of high
pressure. This moisture will raise pwats to over half an inch or
more by Sunday, but this moisture will be above 500mb and be
mainly a cirrus deck.

Temperatures/humidity: only subtle changes are anticipated with a
degree or two of cooling. That's still hot with readings from the
mid 90s to 105. Will continue the heat advisory for the lc valley
which will be hottest location. A few locations will be within a
couple degrees of record highs for again today. For Sunday, the
increase of cloud cover will help alleviate some of the heat,
although the low levels will remain very warm. A couple degrees of
cooling is anticipated for Sunday with highs in the lower 90s to
103. Humitidy values will still remain quite dry through the
weekend. /Rfox.

Monday and tuesday: the trough promising to bring US cooler
weather looks to be coming inland more fragmented than initially
progged by the models. The evening models runs are now bringing an
initial wave through Oregon and Washington on Monday. Shower
chances on Monday look to be mainly confined to Oregon since the
resident air mass in Washington is so exceedingly dry. Even the
NAM which is often generous with its cape, doesn't muster any
meaningful surface based instability. For Monday, the model
soundings from the GFS and NAM advertise the best moisture at or
above 12 thousand feet with marginal lapse rates aloft for any
high based showers. NAM and GFS sounding for Monday look like high
based clouds with virga. The good news for Monday is that the
latest model runs have decreased the potential for lightning. The
bad news is our chance for any meaningful precipitation on Monday
has also decreased.

Precipitation chances for Tuesday are marginally better than
Monday, however the models have trended drier over the last
several runs. The latest GFS and European model (ecmwf) track the upper trough
north of the Canadian border on Tuesday. This solution suggests
more wind and less shower activity. The increasing onshore flow
should establish a cross Cascade surface pressure gradient which
favors gusty gap winds along the east slopes of the Cascades. We
should see the continuation of a cooling trend on Tuesday as well
as rising humidity levels as maritime air gradually spreads across
the Cascades.

Wednesday through friday: the GFS and European model (ecmwf) reload the trough over
British Columbia on Wednesday and Thursday, but keep the trough
largely north of the Canadian border. There may be enough mid-
level cooling to produce widely scattered showers and
thunderstorms over the mountains, primarily along the Canadian
border. This pattern will likely perpetuate breezy conditions
along the east slopes of the Cascades into the Columbia Basin and
Palouse. Temperatures for the second half of the work week should
be cooler than average. /Gkoch

&&

Aviation...
12z tafs: VFR conditions can be expected over the taf sites for
the next 24 hours. Expect some smoke aloft with the best chance
for reduced surface visibilities around sunrise when the inversion
is the strongest...especially near Lake Chelan and in the Okanogan
Valley. High pressure across the region means only light diurnal
winds through the day. Some local gustiness is possible during the
afternoon. Gap winds will increase winds at keat after 00z. /Rfox

&&

Preliminary point temps/pops...
Spokane 99 63 97 67 90 63 / 0 0 0 0 10 10
Coeur D'Alene 98 58 96 61 90 60 / 0 0 0 0 10 10
Pullman 99 56 97 59 89 56 / 0 0 0 10 10 10
Lewiston 105 66 103 69 95 66 / 0 0 0 10 10 20
Colville 101 56 99 59 91 58 / 0 0 0 0 10 10
Sandpoint 97 50 95 56 87 56 / 0 0 0 0 10 10
Kellogg 96 58 95 58 90 58 / 0 0 0 10 10 20
Moses Lake 102 59 99 65 94 62 / 0 0 0 10 10 0
Wenatchee 101 68 98 72 93 67 / 0 0 10 0 10 10
Omak 102 60 100 65 95 61 / 0 0 0 0 10 10

&&

Otx watches/warnings/advisories...
Idaho...heat advisory until 8 PM PDT Sunday for Lewiston area.

Washington...heat advisory until 8 PM PDT Sunday for lower Garfield and
Asotin counties.

&&

$$

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