Special Weather Statement, NWS Missoula, MT

Area Forecast Discussion
National Weather Service Missoula MT
235 PM MDT Fri Aug 1 2014

.DISCUSSION...Showers and thunderstorms are beginning to develop
in the region this afternoon as the next wave of monsoon
moisture approaches. Showers and thunderstorms are forecast by
high resolution model guidance to pass through north central Idaho
and western Montana from the southwest to the northeast through
this afternoon and evening. Relatively dry air ahead of the
monsoon push will promote storms with gusty winds initially but
as more moist air arrives brief heavy rain will become more
common especially by the evening. The associated shortwave trough
will linger in northwest Montana tonight so showers, isolated
thunderstorms, and cloud cover will linger through tonight in the
Glacier Region and decrease in areas to the southwest. An easterly
gradient will also develop from Kalispell eastward late this
evening so east winds are going to increase overnight.

Saturday will be similar to today with valley temperatures in the
upper 80s and 90s and afternoon thunderstorms.

The northern Rockies will remain under the this pattern for
several days. A ridge pattern for the northern Rockies will keep
temperatures at or above average for next week. However, moisture
associated with the southwest monsoon will continually move north
over the southern reaches of the northern Rockies. Isolated
mountain thunderstorms can be expected on a daily basis, with
storms occasionally moving out over the valleys.

Some days will be much stormier than others, though it is very
difficult to predict which days will be stormier due to the
relatively weak disturbances moving through the ridge causing the
showers.

One feature of interest is a broad, weak low pressure system
moving under the ridge early next week. Models have been very
inconsistent with the path of this disturbance, and ensembles do
not yet agree well on a path. If the Northern Rockies were to
take a direct hit, this would cause several slow moving, very wet
storms. It is the perfect scenario for heavy rain and flash
floods. Confidence remains below average for this system, but the
potential impacts necessitate us to keep a close watch on how this
evolves.

&&

.AVIATION...Showers and thunderstorms are developing through north
central Idaho and southwest Montana this afternoon, but are
mostly stationary over the terrain. A shortwave approaching from
Oregon will help storms to have better storm motion and high
resolutions model guidance have thunderstorms to pass from the
southwest to northeast during this afternoon and evening. Most of
the convective activity will decrease late this evening but
showers, isolated thunderstorms, and cloud cover are anticipated
through northwest Montana overnight. An easterly pressure gradient
will develop mainly from KGPI and east, so easterly winds can be
expected through Saturday morning. The active monsoon pattern will
continue on Saturday so showers and thunderstorms are to return in
the afternoon.

&&

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

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SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE MISSOULA MT
634 PM MDT FRI AUG 1 2014

MTZ002-020115-
WEST GLACIER REGION-
634 PM MDT FRI AUG 1 2014

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

AT 624 PM MDT...NATIONAL WEATHER SERVICE DOPPLER RADAR WAS TRACKING A
STRONG THUNDERSTORM NEAR GOING-TO-THE-SUN ROAD IN GLACIER PARK...OR
38 MILES NORTHEAST OF EVERGREEN...MOVING NORTH AT 10 MPH.

HAIL UP TO ONE-HALF INCH IN DIAMETER AND WIND GUSTS UP TO 50 MPH ARE
EXPECTED WITH THIS STORM...ALONG WITH HEAVY RAIN.

LOCATIONS NEAR THE PATH OF THIS STORM INCLUDE...GOING-TO-THE-SUN ROAD
IN GLACIER PARK.

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 4885 11379 4881 11375 4877 11375 4874 11370
      4862 11374 4862 11387 4882 11397 4886 11385
TIME...MOT...LOC 0034Z 161DEG 10KT 4871 11383