FXUS65 KMSO 262140
AFDMSO
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MISSOULA MT
240 PM MST THU NOV 26 2009
.DISCUSSION...UPPER RIDGE CONTINUES TO FLATTEN AS AN APPROACHING
PACIFIC WEATHER SYSTEM MOVES INTO THE INTERMOUNTAIN REGION
TONIGHT. STILL HAVE INVERSIONS HOLDING STRONG OVER NORTHWEST
MONTANA VALLEYS AS CLOUDS HAVE INHIBITED HEATING/LIFTING OF THESE
INVERSIONS. PATCHY VALLEY FOG IS EXPECTED TO REDEVELOP AGAIN THIS
EVENING BEFORE THE PRECIPITATION MOVES IN. WARM AIR AHEAD OF THE
SYSTEM WILL KEEP PRECIPITATION MAINLY IN THE FORM OF RAIN WITH
HIGH ELEVATION SNOW. THE PRECIPITATION IS EXPECTED TO ENVELOP THE
INTERMOUNTAIN REGION BY FRIDAY MORNING...THEN TRANSITION TO SNOW
SHOWERS AS AN ASSOCIATED COLD FRONT MOVES THROUGH. BRUNT OF THE
PRECIPITATION WILL BE AHEAD OF THE COLD FRONT...THEREFORE SNOW
ACCUMULATIONS WILL BE CONFINED TO THE HIGHER ELEVATIONS WITH MOST
PASSES ONLY SEEING UP TO 4 INCHES.
AN UNSETTLED AND MOIST NORTHWEST FLOW BEHIND THE EXITING SYSTEM WILL
KEEP COOLER TEMPERATURES (MORE TOWARD NORMAL) AND A THREAT OF SNOW
SHOWERS IN THE FORECAST...ESPECIALLY WESTERN MONTANA...THROUGH
SATURDAY NIGHT. A LIGHT SURFACE FLOW AND MID LEVEL WINDS BODE WELL
FOR SNOW TO MAKE IT TO VALLEY FLOORS WITH THE THREAT OF
DOWNSLOPING BEING DRASTICALLY REDUCED. WILL HAVE TO WATCH FOR
PERSISTENT SNOW BANDS THAT MAY DEVELOP AND RESULT IN LIGHT
ACCUMULATIONS.
SUNDAY... SHOWERS WILL LINGER THROUGH SUNDAY AS A DIRTY...LOW
AMPLITUDE RIDGE WORKS ITS WAY INTO THE REGION.
MONDAY THROUGH THURSDAY...THE GFS HAS SHOWN SIGNIFICANT DIFFERENCES
BETWEEN THE CURRENT MODEL RUN AND ITS PREVIOUS SOLUTION WITH
RESPECT TO A LOW PRESSURE TROUGH MOVING INTO THE REGION STARTING
LATE MONDAY. THE GFS NOW HAS THE TROUGH WEAKER AND MUCH FARTHER TO
THE NORTH. AFTER COMPARING PREVIOUS MODEL RUNS TO THE
CURRENT...THIS NEW SOLUTION LOOKS TO BE AN OUTLIER. THE ECMWF ON
THE OTHER HAND HAS BEEN SHOWING A FAIR AMOUNT OF CONSISTENCY WITH
BOTH TIMING AND STRENGTH OF THE UPCOMING SYSTEM. SINCE THE ECMWF
IS MORE CONSISTENT...HAVE WEIGHTED THE FORECAST MORE HEAVILY IN
ITS DIRECTION. WHAT THIS MEANS FOR THIS WEEKS FORECASTS IS...THERE
WILL BE INCREASED SNOW CHANCES TUESDAY AND WEDNESDAY WITH COOLER
TEMPERATURES ESPECIALLY FROM WEDNESDAY ONWARD.
&&
.AVIATION...FOG STILL STRUGGLING TO LIFT ACROSS NORTHWEST MONTANA
DESPITE HIGH CLOUDS MOVING IN ADVANCE OF APPROACHING PACIFIC
WEATHER SYSTEM. THIS SCENARIO IS LESS COMMON FURTHER SOUTH WITH
KMSO BEING THE TRANSITION REGION. THE AFOREMENTIONED PACIFIC
WEATHER SYSTEM WILL CONTINUE TO INCREASE AND LOWER CLOUDS FROM
NORTHWEST TO SOUTHEAST OVERNIGHT. THE INVERSIONS OVER NORTHWEST
MONTANA WILL HOLD STRONG UNTIL PRECIPITATION BEGINS THIS EVENING.
MAY EVEN SEE SOME PATCHY FOG REDEVELOP EARLY THIS EVENING
OBSCURING LOWER TERRAIN. STRATIFORM RAIN AND HIGH ELEVATION SNOW
WILL TRANSITION TO SNOW SHOWERS BY EVENING AFTER A COLD FRONTAL
PASSAGE. THE FRONT IS EXPECTED TO MOVE THROUGH NORTHWEST MONTANA
FRIDAY AFTERNOON...THEN SOUTHWEST MONTANA BY THE EVENING.
&&
.MSO WATCHES/WARNINGS/ADVISORIES...
MT...NONE.
ID...NONE.
&&
$$
SHORT TERM...MEAD
LONG TERM....KITSMILLER
AVIATION...MEAD
