Area Forecast Discussion
Issued by NWS Spokane, WA

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632
FXUS66 KOTX 190001
AFDOTX

Area Forecast Discussion
National Weather Service Spokane WA
401 PM PST Wed Jan 18 2017

.SYNOPSIS...
Freezing rain, sleet, and snow will create treacherous driving
conditions over much of the Inland Northwest today. Temperatures
will gradually warm this afternoon and much of the region will be
above freezing on Thursday. Several rounds of precipitation are
expected through the weekend with seasonable cool temperatures.


&&

.DISCUSSION...
Tonight through Friday night: The Inland NW will remain in a wet
and, in some places, wintry pattern especially through early
Thursday. Tonight a long-wave trough off the Pacific Northwest
coast will be moving onshore. The moist southwest flow, combined
with some isentropic ascent in the 290-295K layer and synoptic
lift associated in the LFQ of the jet will lead to another round
of precipitation. This precipitation is expected to increase
across the area from west/southwest to northeast through the
evening. Before about 7-8 PM the best threat will be re-developing
around the Cascades/western Columbia Basin into southeastern WA
and the lower Panhandle. The threat will expand northeast after
this time frame.

* Precipitation-type and Highlights: it has warmed up nicely
  across the upper Columbia Basin east and northeastward. So much
  of these areas will see just rain, though some of the sheltered
  valleys could still see some pockets of sleet/freezing rain. The
  better wintry threat remain across the western Columbia Basin
  into the Cascades and some of the northern mountains. These
  colder areas will continue to be under the potential for snow,
  sleet, and freezing rain. Freezing rain and sleet will be more
  likely toward the lower lee of the Wenatchee Area/Waterville
  Plateau/Moses Lakes area. A Winter Weather Advisory is being
  issued for these areas for this mixture, with the potential for
  some slick conditions from additional ice from freezing rain and
  accumulations from sleet. The main impacts are expected to
  develop this evening, before winding down overnight. Elsewhere
  Winter Storm Warnings continues for the Cascades, Okanogan
  Valley and Highlands: here a mixture snow and sleet and possible
  pockets of freezing rain will be the main threat. I cut back the
  Winter Storm Warnings across the northeastern WA and north ID
  zones, relegating them to mainly areas above 3000 feet.
  Temperatures below 3000 feet have warmed into the lower 30s.
  There may still be some mixed precipitation below 3000 feet,
  especially closer to the Canadian border but the risk of
  significant impacts has diminished.

* Flooding: we continue to highlight the threat of flooding in the
  urban/small stream/poor drainage areas due to rain and melting
  snow. This will continue to be a concern through at least next
  couple days with the milder temperatures. There have been
  reports of significant ponding of water on roads around some of
  city locations across the east and even heading up into the
  Idaho Panhandle along I-90.

Going into Thursday the upper trough shifts inland and the deeper
moisture plume starts to shift east. Precipitation will remain
likely across the Cascades, eastern third of WA and the ID
Panhandle in the morning. However as the day passes the main
threat will shift into the mountains. Drier weather starts to
develop across the east going into Thursday night and Friday
night, but another system will be approaching the west coast and
increasing precipitation chances again the Cascades through
western Columbia Basin. Some light snow/rain threat will return to
these areas. The best chance will be within the Cascades and
nearby valleys, but compared to recent systems the accumulations
do not look relatively light.

We will have to watch for a fog threat Thursday night into Friday
morning and again Friday night, especially over the northeastern
basin and sheltered valleys. /J. Cote`

Saturday through Tuesday: On Saturday, a weak push of moisture
associated with a extinct Low will push through the region on
Saturday bringing a dusting of snow of a few tenths to most of the
region with a couple of inches in the Cascades. A more potent
system is expected on Sunday. Models are bringing a decent amount
of moisture with this system and with temperatures expected to be
hovering around the snow/rain line could bring around another inch
of snow for the Colombia Basin and a couple of inches for the
higher terrains. By the Monday afternoon, a ridge is beginning to
build into the region and precip off across the region. This
stable airmass could create periods of freezing fog in the morning
hours. Temperatures for the weekend will be mid 30s for highs and
mid 20s for lows leading to a possible freeze/thaw cycle. A
cooling trend is expected to begin on begin on Monday with highs
in the mid 20s and lows in the mid teens for the remainder of the
period. /JDC

&&

.AVIATION...
00Z TAFS: The next round of precip is moving into southern WA
late this afternoon. IFR conditions are expected at KEAT and KMWH
this evening into the early overnight hours as precip increases.
KMWH has warmed above freezing with -FRZA considered to be less of
a threat. Light snow will be the dominant precip type at KEAT.
LIFR conditions with fog will be possible at KEAT Thursday morning
as snow moves out of that area. The rest of the TAF sites KLWS,
KPUW, KGEG, KSFF and KCOE) will see a gradual lowering of cigs
and vis through the night with rain increasing after 02Z. KPUW
and KLWS will bounce around between VFR and MVFR conditions. IFR
condtions will be possible for the Spokane/Coeur d`Alene corridor
once surface winds swing southwesterly during the morning
Thursday. /SVH

&&

.PRELIMINARY POINT TEMPS/POPS...
Spokane        33  41  27  35  24  33 /  90  60  10  10  10  30
Coeur d`Alene  33  41  26  36  24  34 /  90  70  20  10  10  30
Pullman        34  40  27  35  25  34 / 100  70  20  10  20  20
Lewiston       37  44  30  37  28  37 /  90  50  10  10  20  20
Colville       32  39  28  35  24  32 /  90  50  30  10  10  30
Sandpoint      32  39  28  37  25  34 /  90  80  40  10  10  30
Kellogg        31  41  25  34  23  32 /  90  80  30  10  10  30
Moses Lake     29  38  25  34  22  33 /  80  20  10  10  30  20
Wenatchee      25  35  23  31  25  31 /  70  20  30  50  60  30
Omak           28  35  26  36  25  33 /  90  30  40  40  30  50

&&

.OTX WATCHES/WARNINGS/ADVISORIES...
ID...Winter Storm Warning until 8 AM PST Thursday for Northern
     Panhandle.

WA...Winter Storm Warning until 8 AM PST Thursday for East Slopes
     Northern Cascades-Northeast Mountains-Okanogan Highlands-
     Okanogan Valley.

     Winter Weather Advisory from 6 PM this evening to 4 AM PST
     Thursday for Moses Lake Area-Waterville Plateau-Wenatchee
     Area.

&&

$$



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