Area Forecast Discussion
Issued by NWS Spokane, WA

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FXUS66 KOTX 070947
AFDOTX

Area Forecast Discussion
National Weather Service Spokane WA
247 AM PDT TUE JUL 7 2015

.SYNOPSIS....
Another weather system drops in from Canada today, with a threat
of showers and thunderstorms across the north. Drier conditions
return Wednesday with hot temperatures through Thursday. The
remainder of the week will see a cooling trend with and increased
chance of showers.

&&

.DISCUSSION...
Today through Wednesday: Water vapor imagery shows the next wave
dropping down from BC. This wave has already created some showers
just north of the Canadian border and into NW Montana, with a
couple of lightning strikes. This activity is expected to continue
and increase across northeast WA and the northern Panhandle this
morning. We still expect surface-based convection to develop in
this area this afternoon/evening. Instability should also result
in some thunderstorm activity over the north Cascades.

I don`t expect any of these storms to be severe since the shear is
too weak. Also flooding is not a concern given the relatively
modest amount of moisture available. The main threat from these
storms will be the potential gusty outflow wind. The WRF-ARW
continues to suggest that an organized gust front will propagate
southward from the convection over the northeast mountains. I`ve
tried to depict this in the forecast, with gusty northeast winds
moving through the Spokane metro area and into the Basin during
the evening hours. The remnants of all this shower activity could
propagate out into the Basin in the evening before dying off, so
I`ve added some low precip chances in the Basin. Wednesday
weather should be quiet and warmer.  RJ

Wednesday night through Tuesday...Model guidance is coming together
through the forecast period. Wednesday night into Thursday a weak
ridge will track through southern B.C. Meanwhile the closed low
currently off the NORCAL coast will move into central California.
This will result in another day of warm and dry conditions with
light and variable winds. However there is also agreement that
moisture will wrap around the low and move as far north as the
Blue mountains and the Camas Prairie Thursday afternoon. Some low
end pops were already in the forecast for the southeast zones as
far north as southern Shoshone county. Pattern recognition says
that the region will indeed see increased moisture...but maybe
just not quite this quick. The forecast stays with the low end
pops for late in the day Thursday, but confidence is wavering that
this will verify.

Friday that closed low will move north as a deeper trough moves
just off the Washington coast. The resultant southerly flow will
definitely allow the moisture to make it up into the region. A
short wave disturbance moving through the region will be the
focusing point for late afternoon convection likely continuing
well into Friday evening. Southerly flow will keep temperatures
well above normal for yet another day.

The trough off the coast will then take the remainder of the
weekend and into the first of next week to slowly move through
the region. This puts the region in an extended period of very
moist southerly flow. Multiple weak waves combined with a very
moist atmosphere and day time heating will result in widespread
late day showers and thunderstorms. At this time the best chances
for thunderstorms will remain in the mountains, but as the
moisture deepens through the weekend it is very likely that all
locations east of the Cascades will see thunderstorms. PWATs are
impressive and rise to well over an inch which is well over 200
percent of normal. So thunderstorms will likely result in short
periods of very heavy rain. With this much rain in short periods
of time, flooding and debris flows will be possible. The 2013-2014
and 2015 burn scars will be the most likely locations, but
flooding and debris flows will be possible across the entire
region. Heavy rain will not preclude new fire starts, but with as
much rain as expected this may not be a huge concern. This pattern
should also bring a cool down with temperatures falling back into
the 80s and approaching seasonal normals. /Tobin

&&

.AVIATION...
12Z TAFS: Showers and isolated thunderstorms will affect the
mountains north and east of Spokane this morning, and increase in
coverage during the afternoon. Some of this activity could move
over the KGEG/KSFF/KCOE sites late in the afternoon or early
evening. Additionally, a thunderstorm gust front is possible for
these TAF sites, but the likelihood is too low to depict it in the
TAFS. KEAT and KWMH have a very small chance of seeing
thunderstorm activity late in the day, too low to mention in the
TAF. KPUW and KLWS should be VFR today and tonight.  RJ


&&

.FIRE WEATHER...
The Fire Weather Watch has been upgraded to a Red Flag Warning for
the Okanogan Highlands, northeast Washington, and the northern
Panhandle areas. Given the current fuel states, any lighting has a
good potential to ignite new wild fires. Additionally, these
thunderstorms could produce gusty winds which could hamper fire
fighting on existing wild fires.

The Watch for the north Cascades has been canceled. Isolated
thunderstorms may still develop, but the coverage of lightning
should not be abundant.  RJ

&&

.PRELIMINARY POINT TEMPS/POPS...
Spokane        92  66  94  66  96  70 /  10  20   0  10  10  10
Coeur d`Alene  89  62  92  61  95  64 /  30  30   0  10  10  10
Pullman        91  56  92  57  94  61 /   0  10   0  10  20  20
Lewiston       98  68  99  69 100  72 /   0  10   0  10  20  20
Colville       91  60  97  61 100  62 /  30  20   0   0  10  10
Sandpoint      84  54  90  54  94  57 /  50  30   0  10  10  10
Kellogg        87  56  91  57  93  61 /  30  30   0  10  10  10
Moses Lake    100  69 100  67 102  71 /   0  10   0   0  10  10
Wenatchee      99  74 101  73 102  74 /  10  20   0   0  10  10
Omak           98  66 100  67 102  68 /  20  20   0   0  10  10

&&

.OTX WATCHES/WARNINGS/ADVISORIES...
ID...Red Flag Warning from Noon today to 9 PM PDT this evening for
     Northern and Central Idaho Panhandle (Zone 101).

WA...Red Flag Warning from Noon today to 9 PM PDT this evening for
     East Washington Northeast (Zone 686)-East Washington
     Okanogan Highlands (Zone 687).

&&

$$


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