Area Forecast Discussion
Issued by NWS Spokane, WA

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FXUS66 KOTX 051209

Area Forecast Discussion
National Weather Service Spokane WA
509 AM PDT THU MAY 5 2016

Several rounds of showers and storms will be possible across the
region today. Some storms will be capable of heavy
rainfall...hail...and gusty winds. Improving but breezy conditions
will begin on Friday, lasting through the weekend. More unsettled
and cooler weather is expected next week.




Today through Friday: Active weather will continue across the Inland NW
for the next 24-36 hours then look for abrupt drying trend into
Friday as gusty north/northeast winds develop.

A trof of low pressure will migrate into the Wrn US today.  The southern
branch of the low will evolve into a closed low over CA/NV while the
northern branch weakens but ushers a cold front in from the north.
The last 36 hours of southerly flow ahead of the approaching trof
has brought deep moisture into the Inland NW and following last
night`s convective cluster, dewpoints have climbed into the upper
40s to lower 50s. As the region warms this afternoon, the air mass
will become quite unstable leading to widely scattered showers and
thunderstorms, some which may be strong. The cold front will push
into the Okanogan Valley early Thursday and continue toward the
south and southeast through the day. The front should make up for
the lack of shortwaves and assist in parcel displacement through
the CIN layer...ultimately resulting in convective towers and mix
of showers and thunderstorms. Drier air will accompany the post
frontal air mass so confidence is moderate that the Okanogan
Valley will be left out of the action following this morning`s
cluster of rain. On the contrary, the boundary will interact with
the instability early afternoon in the East Slopes, Waterville
Plateau, Okanogan Highlands, and Western Basin. This activity will
need to be monitored closely as storm motion will be slowing down
yet PWATS remain around a 0.75". It looks as if the trends in
instability will be on the decline toward the peak heating hours
so we do not anticipate strong storms in these locations but the
possibility for small hail and heavy downpours.

For the remainder of NE WA and N ID, look for scattered light showers
through much of the morning hours followed by the potential for a
lull in the action Thursday morning. The front presses through
during the late afternoon with scattered showers and t-storms
developing. Intensity of these storms carry some uncertainty due
to uncertainty with cloud cover and exactly how much CAPE will be
present as the lift comes through. Small hail and gusty winds will
be possible with any t-storm activity.

Of bigger concern is to the southeast across extreme southeastern WA
and lower ID Panhandle where we find a marginal risk for severe
weather. CAPE values look quite impressive in the late afternoon
with values ranging between 1000-2000 J/kg along and south of a
line from Mullan to Pullman to the Blue Mtns. Clouds could very
well keep these numbers lower and also result in a lull of shower
or t-storm activity through much of the afternoon but when and if
storms develop...they will have the potential to be strong to
locally severe producing large hail and damaging winds along with
heavy rainfall and frequent lightning. Some models suggest the
threat will be delayed until after 5PM but cannot rule out
isolated activity sooner which generally leads to lower confidence
on exact timing.

As the weak northern branch shortwave tracks east of the region, the
atmosphere will become drawn to the deep low over CA/NV and gusty
N/NE winds will increase Thursday night and linger into Friday.
Look for an abrupt end to precipitation from north to south
Thursday evening with just a few showers or thunderstorms
lingering around the Camas Prairie and Blue Mtns overnight into
Friday morning. Most of this activity will diminish well before
Friday afternoon.

Winds will be quite gusty Thursday night and Friday, especially
down the Okanogan Valley, Purcell Trench, and across the open
Columbia Basin. Sustained speeds 15-20 mph with gusts 25-40 mph
are a strong possibility however temperatures will already be
rebounding on Friday with highs warming back into the mid 70s. /sb

Friday night through Wednesday...Latest model runs are in fairly
good agreement through the beginning of next week at least. After
some residual showers and possible garden variety thunderstorms
over the Idaho Panhandle Friday evening...the forecast area will
come under the drying influence of a building positively tilted
upper ridge which will keep conditions dry and once again warmer
than normal for Saturday at least. Breezy north to northeast winds
will be the most noticeable weather as dry low level air invades
the region from Canada through the Okanogan Valley and Purcell
trench. Possibly as early as Sunday but certainly by early next
week the weather pattern will become more progressive as a trough
carves out of western Canada producing an initial breezy cold
front Sunday...but with not a lot of moisture...followed by an
increasing chance of showers Monday through Tuesday as the upper
trough settles into the region with a commiserate cooling of
temperatures back toward seasonal normals. This unsettled period
may begin to improve Tuesday night and Wednesday as the next ridge
builds over the region. /Fugazzi


12Z TAFS: The next 12 hours have the potential to be active across
the region as a cold front interacts with an unstable air mass in
place. The main aviation impacts this morning will be areas of
MVFR stratus between Pullman and Spokane coupled with spotty light
showers littering much of the region. After 20z...focus will
switch to the t-storm potential as the frontal boundary slides
down from the north. Storms will be capable of small hail, gusty
winds, and heavy downpours. Isolated stronger storms capable of
of large hail and damaging winds are a possibility along an axis
stretching frm KALW to KMLP and points south btwn 23-03Z. /sb


Spokane        73  54  77  54  81  55 /  50  20  10  10   0   0
Coeur d`Alene  73  49  76  50  81  52 /  60  20  10  10  10   0
Pullman        71  49  75  49  78  51 /  60  20  10  10  10   0
Lewiston       76  53  81  54  83  56 /  60  30  20  10  10  10
Colville       73  45  81  47  85  48 /  60  20  10  10   0   0
Sandpoint      71  47  74  44  79  46 /  60  30  10  10   0   0
Kellogg        73  45  73  44  79  46 /  60  30  10  10  10   0
Moses Lake     76  52  83  53  86  52 /  30  20  10   0   0   0
Wenatchee      75  54  82  57  86  58 /  40  20  10   0   0   0
Omak           73  48  81  53  85  52 /  50  10  10   0   0   0



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