254 
FXUS65 KMSO 271716
AFDMSO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MISSOULA MT
1016 AM MST WED JAN 27 2010

.UPDATE...KEPT SNOW LINGERING ACROSS LEMHI COUNTY IDAHO AND
SOUTHWEST MONTANA THROUGH THE AFTERNOON. 


&&

.DISCUSSION...A WEAK MID LEVEL BOUNDARY AND LOW LEVEL MOISTURE
WILL KEEP AREAS OF LIGHT SNOW OVER LEMHI COUNTY...THE SOUTHERN
BITTERROOT VALLEY AND MOUNTAINS AND THE THE BUTTE REGION THROUGH
THIS AFTERNOON. FURTHER NORTH DRIER AIR IS MOVING INTO THE REGION
AND SKIES ARE BEGINNING TO CLEAR. STILL HAVE SOME AREAS OF FOG
THIS MORNING AND THIS IS NOT EXPECTED TO BURN OFF UNTIL THE
CLOUDS DECREASE A BIT MORE TOWARD AFTERNOON. TEMPERATURES LOOK
VERY SIMILAR TO YESTERDAY ACROSS MUCH OF WESTERN MONTANA WITH A
FEW LOCATIONS A DEGREE OR TWO COOLER. A FEW ADJUSTMENTS WERE MADE
TO ACCOUNT FOR THIS. 


&&

.AVIATION...A MID LEVEL BOUNDARY AND AMPLE LOW LEVEL MOISTURE WILL
KEEP LIGHT SNOW AND AREAS OF FOG OVER KBTM AND KSMN FOR MUCH OF
THE DAY. MOUNTAINS AND VALLEYS WILL BE OBSCURED AS A RESULT.
FURTHER NORTH...DRIER AIR IS MAKING ITS WAY INTO THE INTERMOUNTAIN
REGION. MID AND HIGH LEVEL CLOUDS WILL BE DECREASING FROM NORTH TO
SOUTH THIS AFTERNOON. THE QUESTION WILL BE WHETHER OR NOT THE LOW
LEVEL CLOUDS WILL COMPLETELY BURN OFF. EXPECT KMSO AND KGPI TO SEE
IMPROVING CONDITIONS WITH AFTERNOON WITH THE POSSIBILITY OF LOW
CLOUDS AND FOG REDEVELOPING TONIGHT AS THE RIDGE BUILDS IN. 


&&

.PREV DISCUSSION... /ISSUED 628 AM MST WED JAN 27 2010/ 

UPDATE...INCREASED POP AND SNOW AMOUNTS IN PORTIONS OF WESTERN
MONTANA THIS MORNING

DISCUSSION...RECENT RADAR AND SATELLITE ENHANCEMENTS ARE PRODUCING
LIGHT SNOWS ACROSS PORTIONS OF THE BITTERROOT MOUNTAINS AND WEST
CENTRAL MONTANA. EVEN THOUGH THE SNOWFALL IS LIGHT...ACCUMULATIONS
UP TO AN INCH ARE POSSIBLE OVER THE NEXT FEW HOURS.

AVIATION...A NEWLY DEVELOPED AREA OF SNOW WILL IMPACT KMSO
THROUGH 27/16Z WITH UP TO AN INCH OF SNOW POSSIBLE. AREAS OF VALLEY
FREEZING FOG IS EXPECTED THROUGH THE MORNING HOURS...ESPECIALLY IN
NORTHWEST MONTANA AND THE BITTERROOT VALLEY. EXPECT LOWERING
VISIBILITIES AND CEILINGS. 

PREV DISCUSSION... /ISSUED 413 AM MST WED JAN 27 2010/ 

DISCUSSION...

FOG HAS DEVELOPED ACROSS MANY OF THE VALLEYS IN THE NORTHERN
ROCKIES AND SHOULD PERSIST THROUGH MID MORNING WHICH WILL IMPACT
THE MORNING COMMUTE. FOG WILL BE MOST EXTENSIVE IN THE LOWER
VALLEYS OF EXTREME NORTHWEST MONTANA WHERE VISIBILITIES MAY BE
BROUGHT DOWN TO 1/4 MILE AT TIMES.  IN ADDITION A WEAK AND SLOW
MOVING WEATHER DISTURBANCE AND WEAK WEST/NORTHWEST FLOW CONTINUES
TO BRING VERY LIGHT SNOW ACROSS CENTRAL IDAHO...WESTERN
MONTANA...AND SOUTHWEST MONTANA. EXPECT WIDESPREAD LIGHT SNOW TO
PERSIST THROUGH MUCH OF THE MORNING WITH ONLY VERY LITTLE SNOW
ACCUMULATIONS. PERHAPS UP TO AN INCH IN THE MOUNTAINS AND A TRACE
TO HALF INCH IN THE VALLEYS AT BEST...WHICH MAY CAUSE SOME
DIFFICULT TRAVEL FROM SLICK ROADS IN AREAS.

THIS MORNING'S WEAK WEATHER DISTURBANCE WILL EXIT THE REGION BY
LATE THIS AFTERNOON AND EVENING. THE REMAINDER OF THE WEEK WILL
THEN BE LARGELY UNDER THE INFLUENCE OF A DEVELOPING RIDGE OVER THE
REGION. THIS WILL BE A DIRTY RIDGE WITH CONSIDERABLE HIGH TO MID
CLOUDS OVER THE REGION. MORNING FOG IS ANTICIPATED UNDER THIS
RIDGE WITH LOW LEVEL MOISTURE IN PLACE. THERE IS SOME UNCERTAINTY
WITH THE POTENTIAL EXTENT OF THE FOG AT THIS TIME WHICH IS
DEPENDENT ON THE PLACEMENT OF THE RIDGE AXIS AND EXTENT OF CLOUD
COVER.

SATURDAY THROUGH MONDAY...UPPER LEVEL TROUGH WILL MOVE INTO THE
PACIFIC NORTHWEST...INTRODUCING SOUTHWEST FLOW AND MOISTURE TO
NORTH CENTRAL IDAHO AND WESTERN MONTANA. BULK OF THE 500MB LOW
ENERGY WILL DIVE INTO THE GREAT BASIN...WITH A WEAKER 500MB WAVE
REMOVED TO THE NORTH. THIS SPLIT FLOW IS TYPICAL OF THE UPPER
LEVEL PATTERN OBSERVED THIS WINTER...AND TYPICAL ESPECIALLY UNDER
EL NINO CONDITIONS. GREATEST PRECIPITATION AMOUNTS WITH THIS
SYSTEM ARE FOCUSED OVER THE CLEARWATER MOUNTAINS IN NORTH CENTRAL
IDAHO AND THE WEST FACING SLOPES OF THE BITTERROOTS. A WEAKER SECONDARY
SHORTWAVE PROGGED TO TRACK BEHIND THIS SYSTEM FOR THE BEGINNING OF
NEXT WEEK. NORTHWEST FLOW REMAINS OVER THE AREA...AS A
PROGRESSIVE...ZONAL FLOW ENCOMPASSES THE REGION.


&&

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

$$

UPDATE/AVIATION...MEAD
PREVIOUS DISCUSSION....RPN/NOLTE