Area Forecast Discussion
Issued by NWS Spokane, WA

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FXUS66 KOTX 271159
AFDOTX

Area Forecast Discussion
National Weather Service Spokane WA
459 AM PDT FRI MAR 27 2015

.SYNOPSIS...
Record warm temperatures will be possible today over much of the
Inland Northwest. A fast moving cold front will arrive tonight
bringing widespread showers, gusty winds, and the potential for
thunderstorms to southeast Washington and portions of eastern
Washington. Saturday will be quite windy with gusts of 40 mph
possible over Palouse, West Plains, and Upper Columbia Basin. The
weather Sunday and Monday should be mild and relatively dry.
Another fast moving front on Tuesday will bring more showers and
wind.

&&

.DISCUSSION...

Today: Unseasonably warm temperatures will be the main story for
today. A highly amplified upper level ridge/trough pattern will
increase deep southerly flow over the Pacific Northwest this
afternoon. Warm mid-level temperatures will be advected into the
region. The 850mb thermal ridge will extend from central Oregon
into the Idaho Panhandle during the afternoon with temperatures
as warm as 14-16C over southeast Washington and the southern
Panhandle. In May or June, 850mb temperatures of 14-16C would
yield highs in the low 80s, but the potential for some cloudiness
and the relatively low March sun angle suggest a more
conservative mid 70s for the L-C Valley is prudent. The mild
southerly flow will also destabilize the atmosphere ahead of
tonight`s cold front. At this time, it appears that there will
enough convective inhibition (mid-level capping) to impede showers
and thunderstorms this afternoon. The weakest capping according to
the GFS and NAM will be over northeast Oregon, southeast
Washington, and the southern/central Panhandle. A 20 percent
chance for showers and thunderstorms has been introduced after 2PM
followed by much higher chances this evening with the arrival of
strong frontal forcing.

Tonight and Saturday: A fast moving frontal system will collide
with our anomalously warm/moist air mass this evening. Widespread
showers will blossom along the frontal system by mid evening over
the eastern third of Washington and spread quickly into the Idaho
Panhandle by midnight.

* Thunderstorm potential: The front will probably not arrive early
  enough in the afternoon to tap into peak heating and maximum
  instability. However, given the tight thermal packing expected
  with the front, steep mid-level lapse rates, and abundance of
  mid/low level moisture, there should be a decent chance for
  thunderstorms. The increasing southwest surface pressure
  gradient combined with the potential for downdraft winds
  suggests a small threat for strong wind gusts this evening with
  thunderstorms. Cold advection and west winds undercutting the
  southwesterlies aloft on forecast hodographs do not fit the
  damaging wind prototype, so long-lived bowing segments will
  probably not be a likely scenario. A few small hail reports may
  be possible if the model soundings are accurate in their
  depiction of deep layer CAPE above the -10 to -20C layer.

* Post cold front winds: There is a decent probability that a Wind
  Advisory will be necessary for the Palouse, West Plains and
  portions of the Columbia Basin Saturday morning. Strong deep
  layer cold advection, 850mb winds of 40-50kts, and a tight
  surface pressure gradient suggest the potential for wind gusts
  of 40-45 mph over a good portion of east central and southeast
  Washington Saturday morning. Gradients are progged to relax a
  bit during the day, but gusty conditions will likely persist
  well into the afternoon hours on Saturday. /GKoch

Sunday through Thursday: The weather pattern will remain
progressive for much of next week. Initially, the later half of
the weekend will turn quieter and more stable as a flat ridge sets
up over the Inland Northwest. Pacific moisture will stream over
top of the ridge. This coupled with weak isentropic lift will give
way to plenty of cloud cover and the potential of light
precipitation across the higher terrain near the Canadian border.
Temperatures will remain mild and lighter winds anticipated, even
into Monday as the upper ridge amplifies and warm air funnels into
the region from the south. By Monday night and into Tuesday, a
vigorous cold front will sweep inland and bring the threat of
convection. Instability indices look too weak to introduce the
possibility of thunder, but it will need to be monitored. Winds
will turn breezy and gusty by Tuesday in the wake of the front
with gusts of up to near 35 mph. After this feature exits to the
east, on Wednesday another weather disturbance coupled with a
surface occluded front slides in from the northwest and brings
another round of showers. The main brunt will be mountains from
the Cascades to the Panhandle mountains. May see more breezy winds
across the Columbia Basin by Wednesday afternoon and evening. With
the passage of each of the weather disturbances, the storm track
slowly sags south and the jet stream creeps further into
Washington and north Idaho. By Thursday, another weather impulse
ripples through the region in addition to cold air aloft.
Instability values lower, leading to the potential for more
thunder Thursday afternoon and early evening. Also with each
passing impulse, temperatures cool slightly and snow levels lower
a bit, giving way to a better chance of mountain snow.
Temperatures which start above normal by this weekend, gradually
cool to more typically readings for late March. /rfox.

&&

.AVIATION...
12Z TAFS: Valley fog will impact ceilings and visibilities around
Spokane, Coeur D`Alene, Sandpoint, Bonners Ferry, and Colville
through 16z this morning. A vigorous early spring cold front will
collide with an unseasonbly warm and moist air mass tonight
bringing widespread showers and embedded thunderstorms to north
Idaho and the eastern third of Washington. Strong winds will also
develop behind the cold front after 07-09z and persist into Sunday
afternoon. Gusts of 30-35kts will be possible in Spokane, Coeur
D`Alene, Pullman, and Lewiston near the end of the TAF period
09-12z. /GKoch



&&

.PRELIMINARY POINT TEMPS/POPS...
Spokane        69  47  60  39  59  40 /   0  70  40   0  10  10
Coeur d`Alene  69  45  59  38  59  38 /  10  80  70   0  10  10
Pullman        71  46  58  40  58  41 /  10  90  40   0  10  10
Lewiston       75  51  64  41  63  42 /  10  90  20   0   0  10
Colville       70  44  63  39  60  39 /  10  50  50   0  10  10
Sandpoint      66  45  56  38  57  36 /  10  80  80   0  10  10
Kellogg        68  42  53  36  56  38 /  10  90  90   0  10  10
Moses Lake     74  48  66  40  65  39 /   0  20  10   0   0  10
Wenatchee      73  48  65  43  65  44 /   0  10  10   0  10  10
Omak           70  44  66  39  64  39 /   0  10  10  10  10  10

&&

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

$$



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