Flash Flood Warning 8, NWS Missoula, MT

465 
WGUS75 KMSO 050517
FFSMSO

FLASH FLOOD STATEMENT
NATIONAL WEATHER SERVICE MISSOULA MT
1117 PM MDT WED SEP 4 2013

IDC059-050527-
/O.CAN.KMSO.FF.W.0008.000000T0000Z-130905T0600Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
LEMHI ID-
1117 PM MDT WED SEP 4 2013

...THE FLASH FLOOD WARNING HAS BEEN CANCELLED FOR NORTHWESTERN LEMHI
COUNTY...

LAT...LON 4546 11456 4541 11433 4528 11451 4532 11459

$$

Area Forecast Discussion
National Weather Service Missoula MT
243 PM MDT Wed Sep 4 2013

...Strong thunderstorms possible Thursday...

.DISCUSSION...High pressure has added some stability to the
atmosphere today. However, daytime heating is sufficient to
overcome some of this stability and support a few showers and
thunderstorms into this evening. The most probable area for
thunderstorms into this evening is from Grangeville to Orofino and
eastward to the Bitterroots. Within this area, a few of the storms
could produce brief heavy rain...mainly over Idaho.

A low pressure system is expected to begin shifting inland into
Oregon and approach north central Idaho and western Montana
Thursday into Friday. This will place much of the region under a
very favorable wind profile and unstable environment for showers
and possible strong thunderstorms. The initial storm development
should be across the entire region from Orofino and Grangeville
eastward across western Montana Thursday afternoon. A few of the
stronger storms could produce hail, high winds, and very heavy
rain. As the low pressure system becomes more wrapped up, in terms
of moisture, the main shower and thunderstorm threat will actually
shift westward into north central Idaho and mainly northwest
Montana (Missoula northward) Thursday night into Friday. Again, a
few of these storms could be quite strong and produce heavy rain,
hail and strong winds. This looks to be an unusual active period
for thunderstorms for early September.

The low pressure system may then temporarily stall over eastern
Washington Friday night through Saturday keeping mainly northern
Idaho and northwest Montana under the threat of showers and
thunderstorms. During this period, it could become quite breezy,
but generally remain dry in far southwest Montana and Lemhi
County.

There is still quite a bit of uncertainty in where the low
pressure system may finally track. Current thinking and majority
of the guidance has the low tracking east across northern Idaho
and far northwest Montana Sunday. This track should provide cooler
temperatures for the northern Rockies, but keep some of the
heaviest showers north of the border in Canada. However, still
some showers are possible as far south as about Orofino and
Missoula.

In addition to all the impacts listed above, the terrain of
Glacier Park may become quite soaked in rain and obscured in
clouds at times Friday into the weekend. The higher mountain peaks
could also see some small accumulations of wet snow. Those
planning a weekend in the backcountry should prepare for quite
cool and moist conditions.

High pressure and drier conditions may return early next week.

&&

.AVIATION...Main threats for today will be the scattered
thunderstorms developing in southwest Montana and north central
Idaho this afternoon. These storms will be capable of producing
heavy rain, lightning, gusty winds, and small hail. Storms are
expected to linger through the late evening/overnight hours. Lower
ceilings and occasional obscuration of higher terrain is expected
under precipitation. Thursday, we will see a very active day for
thunderstorms.

&&

Bauck

.MSO WATCHES/WARNINGS/ADVISORIES...
MT...None.
ID...None.
&&

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