Special Weather Statement, NWS Missoula, MT

Area Forecast Discussion
National Weather Service Missoula MT
205 PM MDT Mon Aug 4 2014

...Slow-moving thunderstorms with heavy rain still possible from
central Idaho into southwest Montana today...

.DISCUSSION...Above normal atmospheric moisture continues to move
into the region. A wave that brought periods of light to moderate
rain over southeastern Idaho moved north towards Lemhi County and
has stalled and weakened a bit. This has allowed for portions of
northern Lemhi County, southeastern Idaho County east to southwest
Montana to receive more sunshine and warm into the 70s and 80s.
This will help thunderstorm growth and have seen this to be true
according to recent satellite and radar trends. Successive runs of
high resolution models have continued to show the heaviest cells
concentrated over the southern Bitterroot Mountains and near the
Mustang Burn Scar, over northern Lemhi County and also over
Granite to possibly Silver Bow County. Confidence is low, but there
remains the possibility that a few places could see rainfall rates
near 1" per hour threatening the burn scars and even steep terrain
in these areas. May have to issue a flash flood watch if
observations and radar trends become more impressive.

Another impact from the thunderstorms activity will be the
potential for gusty winds up to 40 mph across the Bitterroot
Valley and also east into southwest Montana.

The other area to watch will be across northwest Montana,
especially over Glacier National Park. An upper level wave is
currently tracking east across southeastern British Columbia and
will help to fire off a few showers and thunderstorms capable of
producing gusty winds, lightning and brief heavy rainfall. Those
hiking in the higher terrain should be aware that strong gusty
winds can all of a sudden develop even when showers and
thunderstorms are miles away.

Tuesday through Friday...The boundary of moist air mass and drier
air will hover around a line from the Salmon river in central
Idaho through the southern Bitterroots/Lemhi county and Southwest
Montana. Precipitation and thunderstorms are expected each day
south of this line. Thunderstorms that pop up in this area could
contain some pretty good precip amounts in a short period of time.
Impacts from these storms could be excessive rain on the burned
scars near the old Mustang fire.

Otherwise north of this line expect relatively dry conditions.  The
one exception would be along the Canadian Border into Glacier NP
and the continental divide where Isolated afternoon/evening
Isolated convection is possible as weak systems move through
southern Canada.  Little wind is anticipated.

Saturday through next Monday...Models continue to be in some
agreement of the development of a high pressure ridge over the
northern Rockies. This would keep temperatures well above normal in
the 90s. Ridging conditions will also increase inversions.

&&

.AVIATION...Developing showers and thunderstorms will be scattered
across the region through 05/0300. KMSO, KBTM and KSMN all have a
potential to be impacted by a storm. If one passes over one of
these terminals expect mainly heavy rain and lowering visibilities
for impacts.

&&

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

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SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE MISSOULA MT
258 PM MDT MON AUG 4 2014

MTZ006-007-043-042130-
BITTERROOT/SAPPHIRE MOUNTAINS-BUTTE/BLACKFOOT REGION-POTOMAC/SEELEY
LAKE REGION-
258 PM MDT MON AUG 4 2014

...SIGNIFICANT WEATHER ADVISORY FOR NORTHERN GRANITE COUNTY UNTIL 330
PM MDT...

AT 249 PM MDT...NATIONAL WEATHER SERVICE DOPPLER RADAR WAS TRACKING A
STRONG THUNDERSTORM 13 MILES NORTHWEST OF PHILIPSBURG...OR 24 MILES
SOUTHWEST OF DRUMMOND...MOVING SLOWLY NORTHEAST AT 10 MPH.

WIND GUSTS UP TO 40 MPH ARE EXPECTED WITH THIS STORM...ALONG WITH
HEAVY RAIN.

LOCATIONS NEAR THE PATH OF THIS STORM INCLUDE...MAINLY RURAL AREAS
OF CENTRAL GRANITE COUNTY.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

IF THREATENING WEATHER APPROACHES YOUR AREA...GO INDOORS AND STAY
AWAY FROM WINDOWS. IF YOU ARE CAUGHT OUTSIDE...MOVE TO A WELL
PROTECTED AREA.

&&

LAT...LON 4666 11342 4658 11322 4634 11353 4640 11364
TIME...MOT...LOC 2057Z 215DEG 7KT 4648 11348