Weather Service Report


189 
FXUS66 KOTX 310541
AFDOTX

Area Forecast Discussion
National Weather Service Spokane WA
1040 PM PDT THU OCT 30 2014

.SYNOPSIS...
A slow moving frontal system will slowly move through the region
over the next 24 hours. Rain will push up against the Cascades
tonight...before tracking across the region Friday and Friday
night. Rain in the Idaho Panhandle will likely linger into
Saturday. Cool and unsettled weather is expected to continue into
next week.


&&

.DISCUSSION...
Quick update this evening to modify chance of precipitation
through the evening and into tomorrow morning. Radar showing some
very light showers across northeast WA and north ID. These showers
should move out of the area in the next 2 hours or so, with this
area then remaining dry the rest of the night. Other change made
was to split the chance of precipitation tomorrow morning into an
early morning and mid morning period. Models seem to agree that
the Spokane area shouldn't see any rain through the morning
commute at least...and therefore decreased chance of precip
throughout Spokane county and areas to the east and north. /Nisbet


&&
.PREV DISCUSSION... 
Tonight through Friday night...Afternoon
satellite imagery shows a deep low pressure system in the eastern
Pacific out near 135W. Current model guidance is matching up
pretty well. The low is expected to split tonight as a a short
rounds the bottom of the trough courtesy of a 130+ kt jet. With
the jet parallel to the low forward movement has been slowed. The
accompanying cold front isn't expected to cross the Cascades until
Friday evening between 00z-03z. As the trough digs the steering
flow will become increasingly southerly. The warm front eased in
from the west- northwest overnight...but as the flow becomes
increasingly southerly the warm front will retrograde back to the
west and tuck up against the east slopes of the Cascades this
evening...before slowly pushing through the forecast area Friday
afternoon.

The cold front then tracks across the remainder of the forecast
area Friday night and stalls over the Idaho Panhandle. This puts
the focus for the best precipitation to the Idaho Panhandle. The
stratiform precipitation will change to showers with the
atmosphere drying from west to east.

Precipitation: I kept the chances for precipitation west of a
line from about Republic south to about Saddle mountain Wildlife
area for most of tonight and Friday. Aiding in the precipitation
production will be light east to southeast winds which will add an
orographic lift. Rain fall amounts will range from .10 to .15 for
the lower east slopes and the deep basin to around an inch near
the Cascade crest over the next 24 hours. Snow levels are pretty
high, around 6k feet and are not expected to drop below 5k feet
until after the frontal passage Friday night. By this time the
heaviest precipitation will be winding down. But the area near the
Cascade crest could certainly pick up several inches of fresh snow
in the showers following the cold front. Further to the east
precipitation will begin later but not be quite as wet. QPF from a
couple hundredths in the deep basin to around a third of an inch
in the Blue mountains and the central Panhandle mountains early
Saturday morning. Again snow levels will start out very high in
the warm sector precipitation and not drop below 5k feet until
later Saturday morning. So precipitation should be as mostly rain.

Temps and Wind: Temperatures will bump up 3-5 degrees Friday with
southerly winds and warm air advection. Pre-frontal winds from the
east-southeast will come around to the south-southwest Friday
afternoon and increase slightly. Winds 5-10 mph with gusts to 15
mph will be common as this is not expected to be a big wind event.
/Tobin

Saturday and Sunday: A trough pattern will slowly traversing
through the region during this period. Models are in good
agreement of timing and moisture associated with this system. With
strong cyclonic flow around the apex of the trough in NW Nevada, a
strong moist flow will push into the Idaho Panhandle and western
Montana. This is expected to bring precip to the Idaho Panhandle
and extreme eastern Washington. The bulk of the precip is expected
to fall on Saturday with snow levels above 5000 feet. Areas could
receive rain totals of at least a quarter of an inch in the Cams
Prairie area and around one inch near Mullan Pass. Snow levels
drop to around 4000 feet late Saturday but the bulk of moisture
and the trough will shift further East. This will allow for light
snow accumulation in the higher elevations near Lookout Pass. The
Cascades during this period are expected to fairly dry. Spill over
from the western Washington along the Cascades will bring some
light showers to the eastern side of the Cascades but precip
amounts will fairly small. The Columbia Basin is expected to be
dry during this weekend. Temperatures for this will period will be
near the season normals. Highs will range in the upper 40s to low
50s. Lows are expected to around mid 30s with some locations
expected to cross into freezing temperatures. /JDC

Monday and Tuesday: Shortwave ridge of higher pressure breaks down
and allows another moist Pacific storm system to push across the
region. This storm system will ride a 150 +kt jet streak directed
toward Vancouver Island. Much of the upper level dynamics
associated with the jet and vorticity maximum will remain north
of the region. This will result in a surface low that tracks
across central and northern BC from Monday night into Tuesday.
Precip will develop during the day on Monday with some decent
isentropic ascent ahead of the cold front. The cold front will
then swing across the region Tuesday morning. This is will result
in approximately 12-18 hours of light to moderate precip from
Monday afternoon into Tuesday morning. All areas will see a good
chance for at least some light precip. Best accumulations are
expected across the Northeast Mtns over into the ID Panhandle with
storm totals of between 0.50 to 1.00 inches. Totals will be a bit
less out into the greater basin area with 0.25 to 0.50 inches
expected in the Spokane Area and on the Palouse; and up to a
quarter of an inch for most other locations around the region.
Snow levels will generally be up around 5,000 feet. They sill
start out a bit lower early Monday and then increase as the precip
moves in through Monday night.

Wednesday through Thursday: There will be another storm system
that moves through toward the end of the work week. A warm front
will push north across the region on Wednesday. This will result
in some light precip across the region. We may then see a little
bit of a break in the precip before the cold front pushes through
around Thursday. Models show a quick hitting cold front passage.
Strong upper level dynamics aloft looks to spin up a deepening
surface low pressure system from southern BC into southern
Alberta. This would create good packing of isobars across the
region for Thursday afternoon. Expect breezy to windy conditions
with this front. Wind highlights may be needed depending on how
strong this surface low gets. The 12Z model runs are the first to
show such strong cyclogenesis, so confidence at this point in
wind strength is low.

Expect fall like temperatures next week. Overnight low temperatures
will moderate out from the chilly temperatures expected this
weekend. /SVH

AVIATION...
06Z TAFS: Light rain will continue at KEAT through Friday morning.
Conditions will very widely at KEAT the next 12 hours from VFR to
IFR and back. Precipitation and a lower deck will make it to KMWH
by 17z but conditions are expected to remain VFR. Further to the
east the remainder of the TAF sites will not see precipitation
begin until aft 20z Friday...again with lowering decks but
conditions mainly VFR.

&&

.PRELIMINARY POINT TEMPS/POPS...
Spokane        45  56  42  48  34  49 /  10  50  50  20  10  10 
Coeur d'Alene  43  58  43  46  34  48 /   0  40  50  70  40  10 
Pullman        46  59  42  46  35  48 /   0  30  60  70  40  10 
Lewiston       48  65  46  48  40  53 /   0  20  70  80  40  10 
Colville       42  55  41  50  33  50 /  40  80  50  10  10   0 
Sandpoint      39  57  41  47  35  47 /  10  40  60  70  40  20 
Kellogg        42  59  41  45  35  44 /   0  20  70 100  60  30 
Moses Lake     45  55  41  54  35  54 /  40  60  10  10  10   0 
Wenatchee      46  55  39  55  39  56 / 100  90  10  10   0  10 
Omak           43  52  37  51  34  52 /  90  90  20  10  10  10 

&&

.OTX WATCHES/WARNINGS/ADVISORIES...
ID...None.
WA...None.
&&


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Western Regional Climate Center, wrcc@dri.edu