Area Forecast Discussion
Issued by NWS Spokane, WA

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FXUS66 KOTX 291828
AFDOTX

Area Forecast Discussion
National Weather Service Spokane WA
1115 AM PDT FRI MAY 29 2015

.SYNOPSIS...
Scattered showers and thunderstorms will continue today. A few
storms in the Cascades and northern mountains could become strong
with heavy rain and hail.  Expect a warming trend into the
weekend, with highs in the 80s, with a lingering threat of mainly
mountain showers and thunderstorms. The next best chance of
showers and thunderstorms arrives by next Monday and Tuesday with
the potential for some stronger storms and the return of cooler
temperatures.

&&

.DISCUSSION...
Morning update: We have issued a flash flood watch for the East
Slopes of the Cascades. We anticipate similar afternoon
instability to setup across the region today...but with subtle
differences. One will be a slightly stronger corridor of winds
coming across the Cascades. This will increase 0-6km shear from
10kts observed on Thur to 20-25kts this afternoon. In addition,
there will be a "kicker" or shortwave currently present on
satellite over NW Washington. So confidence is increasing for
thunderstorms; especially north of Hwy 2. So the potential is
there for deep convection producing heavy rain and hail...with
most uncertainty related to storm motion. It is likely that storms
will be moving more than yesterday given the mean wind in the
layer but the intensity may be stronger. Additionally, the air
mass remains quite moist with PWATS near 0.75" over the Cascades and
0.80" over NE WA and Nrn ID which is roughly 120-170% of normal.

My other concern for this afternoon will be the potential for
strong storms over the Northern Mtns zones of WA/ID. Given above
reasoning and potential for the shortwave passage during peak
heating, I imagine storms will be a bit more organized or deeper
than what we saw yesterday. This will increase the risk for
hail...with sizes generally ranging from dime to nickels but a few
stronger storms may approach hail to the size of quarters. These
storms will also bring heavy rainfall but should be moving a bit
quicker today. Outflow winds toward 40 mph will be possible and
could complicate the thunder forecast, especially in the upper
reaches of the Columbia Basin.  /sb

&&

.AVIATION...18Z TAFS: We anticipate an active thunderstorm day
across the northern mountains...with emphasis north of Hwy 2.  There
is a small chance that outflow from these storms initiate storms
vcnty of the terminals from Wenatchee to Coeur D Alene but confidence
is low.  As these storms depart/dissipate around sunset...focus will
turn toward a secondary weak disturbance traversing the region btwn
6-15Z.  There is some uncertainty on coverage but model trends is to
develop widely scattered elevated showers and thunderstorms east of a
line from Moses Lake to Republic.  /sb



&&

.PRELIMINARY POINT TEMPS/POPS...
Spokane        82  60  83  59  80  58 /  10  30  30  10  10  20
Coeur d`Alene  82  58  82  56  80  56 /  10  30  30  10  10  20
Pullman        81  58  79  57  79  55 /  10  30  30  10  20  40
Lewiston       88  63  86  62  87  61 /  10  40  30  20  30  30
Colville       83  55  84  54  83  55 /  50  40  30  20  10  10
Sandpoint      81  53  81  53  78  53 /  30  30  30  20  10  20
Kellogg        81  55  80  54  81  53 /  20  30  40  20  20  30
Moses Lake     89  59  89  58  86  61 /  10  20  10   0  10  20
Wenatchee      89  62  89  60  84  62 /  20  10  10   0  10  20
Omak           87  57  89  53  85  56 /  40  20  20  10  10  10

&&

.OTX WATCHES/WARNINGS/ADVISORIES...
ID...None.
WA...Flash Flood Watch from 1 PM this afternoon to 8 PM PDT this
     evening for East Slopes Northern Cascades.

&&

$$


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