Special Weather Statement, NWS Missoula, MT

Area Forecast Discussion
National Weather Service Missoula MT
225 PM MDT Thu Aug 8 2013

.DISCUSSION...

Tonight...Isolated to widely scattered thunderstorms will be
developing across Lemhi County and southwest Montana through the
remainder of the afternoon and into the evening. This convective
activity will be decreasing with the setting of the sun. Higher
surface pressure diving out of central Canada and into eastern
Montana will be tightening an easterly winds flow across western
Montana and the Idaho Panhandle tonight. Strong winds are expected
through the typical gaps of the divide, then spilling into the
northern Flathead and Missoula valleys.

Friday through Saturday...The upper ridge pattern will remain
over the Northern Rockies through the period. However, the atmosphere
is already very unstable and moisture will be increasing during the
next 24 hours from the southeast. As a result, the threat of
thunderstorms will be increasing, as well as expanding farther
north with time. Since the lower atmosphere will remain somewhat
dry, the potential impacts will center around strong downdrafts and
outflows from storms, lightning, as well as small hail with some
storm cells.

Sunday through late next week...Southwest flow aloft is expected
to develop over the Northern Rockies. Precipitation chances
remain relatively high over northwest Montana each afternoon. Some
weather models depict weak weather features moving within the
flow, however there is low confidence on the timing of these
features. Regardless, this pattern will be mostly unsettled and
keep daytime temperatures slightly above the seasonal average.

&&

.AVIATION...Moisture has been increasing from the south this
afternoon with isolated thunderstorms expected across Lemhi
county and into southwest Montana. KSMN and KBTM are likely to be
the most impacted by storms through the early evening hours.
Elsewhere, cumulus clouds were developing over the higher terrain
this afternoon, but should dissipate again later this evening. The
ridge pattern currently over central Idaho and western Montana
will see a greater influx of moisture from the south during the
next 24 hours. The threat of thunderstorms will expand to cover
all of western Montana Friday afternoon with scattered coverage in
most areas. The greatest concerns with storms will lightning and
strong downdraft winds with some stronger storms capable of
producing small hail.

&&

.FIRE WEATHER...A Red Flag Warning has been issued for the Nez
Perce, Clearwater, Bitterroot, and Beaverhead-Deerlodge National
Forests (Zones 102,103,109,110,111) for lightning and strong gusty
winds from thunderstorms valid Friday afternoon through Friday
evening. Storms will be capable of producing frequent lightning
and with dry fuel conditions there is a real potential for new
fire starts and critical fire conditions. Some storms will produce
wetting rainfall, however, we are not expecting widespread
rainfall by any stretch.

&&

.MSO WATCHES/WARNINGS/ADVISORIES...
MT...RED FLAG WARNING from 2 PM to 10 PM MDT Friday
     Bitterroot/Sapphire Mountains...Butte/Blackfoot Region.

     RED FLAG WARNING from 2 PM to 10 PM MDT Friday
     Missoula/Bitterroot Valleys.

ID...RED FLAG WARNING from 1 PM to 9 PM PDT Friday Northern
     Clearwater Mountains...Orofino/Grangeville Region.

     RED FLAG WARNING until 11 PM MDT this evening Eastern Lemhi
     County...Western Lemhi County.

     FIRE WEATHER WATCH from Friday afternoon through Friday evening
     Eastern Lemhi County...Western Lemhi County.

     RED FLAG WARNING from 11 AM Friday to 5 AM PDT Saturday Lower
     Hells Canyon/Salmon River Region...Southern Clearwater
     Mountains.

     RED FLAG WARNING until 5 AM PDT Friday Southern Clearwater
     Mountains.

&&

MSJ/Zumpfe

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SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE MISSOULA MT
701 PM MDT THU AUG 8 2013

MTZ002-090145-
WEST GLACIER REGION-
701 PM MDT THU AUG 8 2013

...SIGNIFICANT WEATHER ADVISORY FOR NORTHERN FLATHEAD COUNTY UNTIL
745 PM MDT...

AT 655 PM MDT...NATIONAL WEATHER SERVICE DOPPLER RADAR WAS TRACKING A
STRONG THUNDERSTORM 14 MILES WEST OF GOING-TO-THE-SUN ROAD IN GLACIER
PARK...OR 35 MILES NORTH OF EVERGREEN...MOVING SOUTHEAST AT 20 MPH.

WIND GUSTS UP TO 50 MPH ARE EXPECTED WITH THIS STORM...ALONG WITH
FREQUENT DANGEROUS LIGHTNING.

LOCATIONS NEAR THE PATH OF THIS STORM INCLUDE...LAKE MCDONALD.

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 4860 11374 4849 11391 4873 11421 4879 11410
TIME...MOT...LOC 0101Z 318DEG 17KT 4870 11405