Weather Service Report


978 
FXUS66 KOTX 300955
AFDOTX

Area Forecast Discussion
National Weather Service Spokane WA
255 AM PDT SAT MAY 30 2015

.SYNOPSIS...
Strong thunderstorms will be possible in the Idaho Panhandle and
in the Northeast Mountains this afternoon; large hail, gusty
outflow winds and heavy rain will be potential threats.
Thunderstorm chances will lesson on Sunday and are expected to be
more confined across the southeast portion of the forecast area.
Meanwhile most locations will see very warm temperatures with
highs in the 80s through the weekend. Thunderstorm chances will
increase markedly on Monday into Tuesday as a strong upper level
trough moves in from the south. Some of the storms on Monday could
be strong and may produce large hail and strong winds. Unsettled
and cooler weather will persist into the remainder of the work
week with a threat of showers and thunderstorms each day.


&&

.DISCUSSION...

...ISOLATED STRONG TO SEVERE THUNDERSTORMS POSSIBLE IN THE CENTRAL
TO NORTHERN PANHANDLE AND NORTHEAST MOUNTAINS THIS AFTERNOON...

Today: An upper level low pressure system will sit over central
BC. The eastern half of the region will remain unstable today, but
the wester portion of the region will dry out as drier air pushes
through the Cascade gaps. This will keep the active weather
northeast of a line from Omak to Walla Walla. Much of the eastern
portion of the region is very moist early this morning with P-wats
up over 0.90 inches. Although these P-wats will see a slight
downward trend through this afternoon, the atmosphere will remain
moist across this portion of the region. There is a lot of cloud
cover this morning with isolated to scattered showers and
thunderstorms developing from the Okanogan Highlands down to the
Camas Prairie. Much of these showers are very wet with heavy rain
being observed underneath the stronger cores. These showers will
keep the primer pumped for more afternoon thunderstorms in the
afternoon. Dew point temps are expected to be in the mid 50s in
the Panhandle and over the Northeast Mtns. Clouds are also
expected to be clearing to the east by the late morning, which
should allow for good surface heating. Models are indicating some
impressive looking surface based CAPEs of between 1000-2000 J/KG.
There will also be a modest amount of shear of around 30 kts
between 0-6 kms. Winds also will veer with height, which will help
to generate some rotation with any thunderstorms that develop.

There is a limiting factor for developing convection and that is
there is no discernible kicker. In other words, there isn't a
shortwave that will pushing across the region to help generate
convection like what was observed yesterday. With the upper level
low in central BC, it may be close enough to generate some weak
divergence across the northern mtns. In addition, there will be a
weak jet streak that sets up from northwest WA to the Central
Panhandle Mtns. This would also help to create some additional
lift in the left exit region across the northeast portion of the
region (albeit weak). With that said, surface based CAPEs off of
the models are strong for this portion of the region this time of
year. There will also be little to no CIN to overcome as well.
This alone should be sufficient to get convection going. Some of
these storm are expected to become strong and isolated severe
thunderstorms is not out of the question. The primary hazard will
be for large hail and gusty outflow winds. Heavy rain is also
expected, but storms should also be moving at a decent pace to the
northeast. This should limit the possibility for flash flooding
impacts.

Tonight into Sunday morning: Convection should wane quickly with
sunset. This will result in more benign weather overnight. There
will be the possibility for some fog developing by early Sunday
morning depending on how much additional rainfall is observed
today. Best potential for fog would be in the Northern Panhandle
and in the Northeast Mtns. /SVH

Sunday through Saturday: Monday will be the potentially big wx
day as far as thunder potential as a tongue of high theta-e air
surges northward ahead of the ejecting vort max that will lift N
up the Pacific Nw coast. This conveyor belt of higher theta-e air
will provide favorable ingredients that will combine with the
large- scale lift of the ejecting short- wave trough to
potentially initiate strong thunderstorms that will expand NE
through Ern Oregon and into N Idaho and Ern Wa. Uncapped CAPE of
500-1000 j/kg will combine with modest deep lyr shear of 20-30kts.
This should be plenty sufficient to produce bands of embedded
strong thunder comparable to what we saw last afternoon and
evening...though farther east closer to N Idaho. SREF guidance
also supports this slightly farther E corridor of highest thunder
threat favoring hail and gusty winds. Tues, however, will be a
tougher thunder fcst as most model guidance brings the low far
enough inland that the deepest instability from Mon is quickly
shunted E into Wrn Montana. The Tues through Fri period will
resemble closely the wx regime we experienced earlier this week
with the upper low overhead...with a resurgence of showers and
thunder every afternoon where it's not already showering. There's
no way we can get around broad-brushing this type of regime given
the high level of confidence we have that pattern recognition
supports the heaviest showers every afternoon. bz


&&

.AVIATION...06Z TAFS: Another weather disturbance traveling
through the forecast area tonight 6-15Z is producing forced
elevated nocturnal showers and thunderstorms in the aviation area.  
Daytime heating Saturday morning should allow for their
dissipation if they have not already exited the area which may
take as long as 18Z Saturday for it to occur. /Pelatti

&&

.PRELIMINARY POINT TEMPS/POPS...
Spokane        82  57  83  59  77  51 /  40  10  10  10  60  70 
Coeur d'Alene  81  55  82  57  77  51 /  50  30  10  10  60  70 
Pullman        79  55  82  56  75  49 /  30  10  10  20  70  60 
Lewiston       87  62  89  63  82  56 /  30  20  20  20  70  70 
Colville       82  53  86  56  80  52 /  60  20  10  10  60  80 
Sandpoint      74  52  80  54  76  50 /  80  50  10  10  70  80 
Kellogg        77  53  80  55  74  48 /  60  30  20  20  70  80 
Moses Lake     90  57  88  62  83  55 /  10   0   0  10  50  50 
Wenatchee      89  60  86  63  80  55 /  10   0   0  10  60  70 
Omak           89  52  85  56  81  52 /  20  10   0  10  70  80 

&&

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

$$

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Western Regional Climate Center, wrcc@dri.edu