Area Forecast Discussion
Issued by NWS Spokane, WA

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
000
FXUS66 KOTX 270622
AFDOTX

Area Forecast Discussion
National Weather Service Spokane WA
1022 PM PST FRI DEC 26 2014

.SYNOPSIS...
A vigorous low pressure system will produce widespread
accumulating snow Saturday into Sunday. The heaviest snow
amounts will likely occur over the Idaho Panhandle where amounts
of 6 to 12 inches will be a good bet but far eastern washington
and the Cascades will also receive significant accumulating snow.
Bitterly cold northeast winds will develop by Monday morning.
Temperatures will be well below average most of next week as
arctic high pressure settles over the Inland Northwest.


&&

.DISCUSSION...

Evening update: 00z model guidance has made some minor adjustments
but overall thinking for the storm has not changed tremendously
at this point. Light snow will develop early Saturday morning
across most locations outside the deep Basin Snow picks up in
intensity Saturday afternoon and continues well into the evening
and night for the Idaho Panhandle and Cascade Crest while snow
activity lightens over Ern WA. Per this evening`s guidance, the
NAM remains a northern outlier with a quick surface low passage
and lighter snowfall amounts for locations across Northeastern WA
including Spokane to Republic and points north. The GFS continues
to illustrate a similar 1014-1016 mb surface low and lingers low
level convergence (ie light snow) across the eastern third of WA
well into Saturday night. This model is also struggling to bring
the dry slot to the ID border, a feature that would have brought
somewhat of a break Saturday evening.

The SREF appears to agree more with the GFS than NAM and looking
at 36 hour QPF suggest upwards of 0.42" across Spokane and Whitman
Counties with upwards of 0.60" for southeastern Spokane and
northeastern Whitman Counties. Utilizing a conservative 10:1
ratio, we could see upwards of 4+ inches in Spokane and 6+ inches
between Pullman and Rockford...assuming models are accurate.

For this we are looking for the 06z observations to come through
and give us an idea how models are handling the current surface
low which is just crossing Graham Island off the BC Coast.
For aloft, water vapor imagery indicates a potent upper-level
wave with the main circulation tracking just south of NAM/GFS/EC
initialization...and closest to the GEM which is remarkably close
to the EC/GFS solutions for storm total QPF.

So at this time, only changes were to trim off advisories near the
Cascades to only include the crest and nearby upper valleys and
raise concern that snow amounts for Spokane County could be
higher, not tremendously but a few more inches will be possible
after the moderate snow completes Saturday evening and could keep
light snow ongoing well into Sunday bringing snow totals up
between 4-6 inches. As with most winter storms, never a slam dunk
by any means but unlike the last few, this will definitely bring
several inches to most locations away from the lee of the
Cascades. /sb


&&

.AVIATION...
06Z TAFS: A winter storm will bring moderate snow accumulations
during the next 24 hours to Ern WA and Nrn ID. Little to no snow
will fall in the lee of the Cascades at Wenatchee and Moses
Lake. Stubborn fog between Spokane and Coeur D Alene will give way
to light snow btwn 13-15z with periods of moderate snow likely
in the afternoon and evening roughly 19-03z. Pullman, Spokane, and
Coeur D Alene will likely receive several inches of snow from
this storm system with potentially heavy amounts at Pullman and
Coeur D Alene. Although intensity decreases after 00z, periods of
light snow will be possible through Sunday. A surge of warmer air
could also bring a rain/snow mix or very heavy wet snow to Pullman
for a few hours Saturday afternoon. Restrictions of vis/cigs are
likely to fall into IFR/LIFR categories with some improvement to
MVFR at times. Gusty downslope winds off the Cascades should keep
rapid improvement to any short term restrictions develop in the
lee of the Cascades. /sb


&&

.PRELIMINARY POINT TEMPS/POPS...
Spokane        24  32  27  31  19  22 /  20 100 100  50  30  10
Coeur d`Alene  25  31  28  31  19  20 /  20 100 100  60  20  10
Pullman        25  33  28  30  16  23 /  10 100 100  80  50  10
Lewiston       27  37  31  36  24  28 /  10  50 100  60  50  10
Colville       25  32  24  32  20  24 /  30 100  60  40  30  10
Sandpoint      26  31  27  31  19  21 /  30 100 100  60  20  10
Kellogg        21  30  26  30  15  17 /  20 100 100  80  40  20
Moses Lake     27  36  27  36  25  29 /  10  30  10  10  30  20
Wenatchee      30  39  28  35  26  30 /  10  20  10  10  60  30
Omak           21  30  25  30  21  25 /  10  20  10  20  40  10

&&

.OTX WATCHES/WARNINGS/ADVISORIES...
ID...Winter Storm Warning from 4 AM Saturday to 4 PM PST Sunday for
     Central Panhandle Mountains.

     Winter Storm Warning from 7 AM Saturday to 4 PM PST Sunday for
     Lewis and Southern Nez Perce Counties.

     Winter Storm Warning from 4 AM Saturday to 10 AM PST Sunday for
     Coeur d`Alene Area-Idaho Palouse-Northern Panhandle.

WA...Winter Storm Warning from 7 AM Saturday to 4 PM PST Sunday for
     Northeast Blue Mountains.

     Winter Storm Warning from 4 AM Saturday to 10 AM PST Sunday for
     Northeast Mountains-Washington Palouse.

     Winter Weather Advisory from 4 AM Saturday to 4 AM PST Sunday
     for East Slopes Northern Cascades-Okanogan Highlands.

     Winter Weather Advisory from 4 AM Saturday to 10 AM PST Sunday
     for Spokane Area.

&&

$$



USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.