Winter Weather Advisory 20, NWS Missoula, MT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MISSOULA MT
353 AM MST FRI MAR 2 2012

.DISCUSSION...THERE ARE TWO FACES TO THE WEATHER THIS MORNING FOR
THE NORTHERN ROCKIES: THE FIRST BEING THE LIGHT AND INTERMITTENT
SNOW SHOWERS THAT CONTINUE ACROSS WEST CENTRAL MONTANA AND CENTRAL
IDAHO. THESE SNOW SHOWERS HAVE KEPT CLOUD COVER THICK ACROSS THIS
REGION. TO THE NORTHWEST IT IS ANOTHER STORY...SHOWERS HAVE
DISSIPATED ALTHOUGH AREAS OF FOG HAVE DEVELOPED IN THE TIME THAT
SKIES HAD CLEARED OVERNIGHT. EVEN WITH INCOMING CLOUD COVER
STREAMING INTO NORTHWEST MONTANA AT THIS HOUR...OBSERVATIONS
CONTINUE TO COME IN DEPICTING AREAS OF FREEZING FOG. EXPECT FOG IN
THE NORTHWEST TO LIFT TO STRATUS BY MID MORNING AS SNOW SHOWERS
REDEVELOP OVER THE TERRAIN.

SATURDAY...MOIST AIR OF TROPICAL ORIGIN MOVES OVER A RIDGE
BUILDING OVER THE WEST COAST. A SHALLOW LAYER OF INSTABILITY NEAR
THE SURFACE WILL CAUSE SCATTERED SNOW SHOWERS OVER THE MOUNTAINS
OF NORTHWEST MONTANA. SOME SHOWERS WILL MOVE OFF THE MOUNTAINS
OVER AREA VALLEYS IN NORTHWEST MONTANA CAUSING RAIN SHOWERS. IN
CENTRAL IDAHO AND SOUTH OF INTERSTATE 90 IN MONTANA SHOWERS WILL
MAINLY STAY CONFINED TO THE MOUNTAINS DUE TO INCREASING STABILITY
AND DOWNSLOPE WINDS. ALSO EXPECT BREEZY CONDITIONS SATURDAY WITH
STRONG MOUNTAIN TOP WINDS.

SUNDAY...A RIDGE MOVES IN CAUSING PARTLY SUNNY AND MILD CONDITIONS.

MONDAY WILL BE A WARM DAY AHEAD OF A FRONT THAT WILL IMPACT THE
AREA MONDAY NIGHT AND TUESDAY MORNING. COLD AIR ALOFT AND WELL
DEFINED COLD FRONT WILL MAKE IT VERY UNSTABLE AGAIN CAUSING WIDE
SPREAD SNOW SHOWERS WHICH WILL CAUSE INTERMITTENT MODERATE TO
HEAVY SNOW AND WINDY CONDITIONS LOWERING VISIBILITY AND IMPACTING
TRAVEL.

WEDNESDAY THROUGH NEXT WEEKEND...THERE IS LOW CONFIDENCE IN A
RIDGE OF HIGH PRESSURE BEING ADVERTISED RATHER SLOPPILY BETWEEN
THE FORECAST MODELS. HAVE TRENDED THE FORECAST DRIER...BUT STILL
HESITANT TO REMOVE PRECIPITATION CHANCES COMPLETELY UNTIL BETTER
AGREEMENT IS SEEN IN THE MODELS.

&&

.AVIATION...SHALLOW FOG WILL BE PRESENT IN VALLEYS OF NORTHWEST
MONTANA INCLUDING TERMINAL KGPI THROUGH MID MORNING...WITH ALL
OTHER TERMINALS REMAINING FOG-FREE. LATER TODAY EXPECT SNOW
SHOWERS TO REMAIN PERSISTENT IN THE HIGH TERRAIN...WITH A STRONG
BREEZE DEVELOPING THROUGH THE AFTERNOON. WINDS SHOULD DIE BY
SUNSET WITH PRECIPITATION MOVING IN WITH THE NEXT WEATHER SYSTEM
FOR TONIGHT THROUGH SATURDAY.

&&

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

DISCUSSION...ALLEGRETTO/LEACH
AVIATION...ALLEGRETTO