HAMweather.com Area Forecast Discussion for County Warning Area TFX

Thu, 16 Feb 2012 12:30:33 GMT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
450 AM MST THU FEB 16 2012

UPDATED AVIATION SECTION

.DISCUSSION...
TODAY THROUGH SATURDAY...LATEST SATELLITE IMAGERY INDICATES
INCREASING CLOUDS OVER NORTH-CENTRAL MONTANA THIS MORNING AS WEAK
UPPER-LEVEL RIDGING BECOMES SUPPRESSED WITH APPROACHING SHORTWAVE.
WINDS WILL INCREASE TODAY AND BE GUSTY AT TIMES...HOWEVER HIGH
WINDS ARE NOT ANTICIPATED. DOWNSLOPING WINDS OVER THE PLAINS WILL
KEEP DRY CONDITIONS OVER THE PLAINS WITH SNOW SHOWERS IN THE
HIGHER ELEVATIONS ALONG THE ROCKY MOUNTAIN FRONT. THE SHORTWAVE
WILL DESCEND OVER NORTHERN MONTANA THIS AFTERNOON AND INTO CENTRAL
AND SOUTHWEST MONTANA OVERNIGHT. THOUGH MOISTURE IS LIMITED...THERE
SHOULD BE ENOUGH FOR SOME LIGHT SNOW SHOWERS ACROSS THE AREA. SNOW
AMOUNTS WILL BE VERY LIGHT WITH LESS THAN A HALF INCH OVER THE
PLAINS AND A FEW INCHES IN THE MOUNTAINS THROUGH FRIDAY MORNING.
THE WAVE QUICKLY EXITS FRIDAY MORNING AND A RIDGE OF HIGH PRESSURE
WILL REBUILD YIELDING DRY CONDITIONS AND NEAR AVERAGE
TEMPERATURES. THE PROGRESSIVE PATTERN WILL CONTINUE INTO THE FIRST
HALF OF THE WEEKEND AS A MORE PRONOUNCED SHORTWAVE TROUGH DIGS
INTO THE PACIFIC NORTHWEST AND NORTHERN ROCKIES. SOUTHWEST FLOW
AND INCREASING PACIFIC MOISTURE WILL BRING INCREASING CLOUDS WITH
A SLIGHT CHANCE OF RAIN/SNOW SHOWERS IN THE PLAINS AND LIKELY SNOW
IN THE MOUNTAINS...PARTICULARLY ALONG THE CONTINENTAL DIVIDE AND
SOUTHWEST MONTANA. AT THIS TIME SNOW ACCUMULATIONS IN THE
MOUNTAINS SHOULD BE LIMITED TO A FEW INCHES DURING THE DAY ON
SATURDAY WITH LITTLE TO NO SNOW ACCUMULATION OVER THE PLAINS AND
VALLEYS. MLV

SATURDAY NIGHT THROUGH THURSDAY...THE GENERAL TRENDS OF THE MODELS
CONTINUE THE SAME AS YESTERDAY. AN UPPER TROUGH WILL AFFECT THE
AREA EARLY IN THE PERIOD. THIS WILL BE FOLLOWED BY NORTHWEST FLOW
ALOFT WITH INCREASING MOISTURE. MODELS DIVERGE BY THURSDAY WITH
THE ECMWF CONTINUING THE NORTHWEST FLOW ALOFT. THE CANADIAN AND
GFS MODELS ON THE OTHER HAND BACK THE FLOW ALOFT TO A MORE
WESTERLY DIRECTION. DID NOT MAKE ANY BIG CHANGES TO THE INHERITED
CHANCE OF PRECIPITATION FORECASTS AS MODEL TRENDS CONTINUE THE
SAME. SO EXPECT SNOW OVER THE MOUNTAINS WITH A SLIGHT CHANCE OR
CHANCE OF SNOW FOR THE LOWER ELEVATIONS SATURDAY NIGHT INTO
SUNDAY. SUNDAY NIGHT THROUGH MONDAY ANY THREAT OF PRECIPITATION
SHOULD BE CONFINED TO THE MOUNTAINS. THEN THE THREAT OF
PRECIPITATION OVER THE FORECAST AREA FROM TUESDAY ON WILL INCREASE 
IN LINE WITH MODELS TREND OF INCREASING MOISTURE. A CONCERN
DURING THE PERIOD WILL BE THE THREAT OF HIGH WINDS OVER THE ROCKY
MOUNTAIN FRONT AND POSSIBLY FARTHER EAST AROUND TUESDAY. MODELS
DIFFER ON THIS THREAT SO RIGHT NOW CONFIDENCE IS ON THE LOW SIDE
FOR HIGH WINDS. THE MOUNTAINS OF THE ROCKY MOUNTAIN FRONT WILL
LIKELY SEE PERIODS OF SNOW FROM MONDAY NIGHT ON. AT THIS TIME DO
NOT SEE HEAVY SNOW FOR THIS AREA BUT WILL ADD BLOWING SNOW FOR THE
MOUNTAINS WITH THE THREAT OF STRONG WINDS. BLANK

.AVIATION...
UPDATED 1150Z.
EXPECT GENERALLY VFR CONDITIONS. MOISTURE WILL BE INCREASING THIS 
AFTERNOON AND EVENING FROM THE NORTHWEST. SNOW WILL DEVELOP OVER 
THE ROCKY MOUNTAIN FRONT LATER THIS AFTERNOON WITH MOUNTAINS 
BECOMING OBSCURED. THIS SNOW WILL SPREAD TO THE SOUTHWEST MOUNTAINS 
THIS EVENING WITH AREAS OF MOUNTAIN OBSCUREMENT DEVELOPING. FOR THE 
LOWER ELEVATIONS WITH THE EXCEPTION OF NORTH CENTRAL MONTANA EXPECT 
CEILINGS ABOVE 15000 FEET TO LOWER TO BETWEEN 4000 FEET AND 8000 
FEET LATE THIS AFTERNOON AND EVENING WITH SCATTERED SNOW SHOWERS 
DEVELOPING. WITH THESE SCATTERED SNOW SHOWERS EXPECT AT LEAST LOCAL 
MVFR CEILINGS AND VISIBILITIES WITH IFR CEILINGS AND VISIBILITIES 
NOT OUT OF THE QUESTION. OVER NORTHCENTRAL MONTANA CEILINGS ARE 
EXPECTED TO STAY ABOVE 15000 FEET INTO THIS AFTERNOON. THERE ARE 
SIGNIFICANT MODEL DIFFERENCES TONIGHT OVER NORTH CENTRAL MONTANA 
INCLUDING THE KHVR TAF WITH SOME GUIDANCE KEEPING CONDITIONS VFR AND 
OTHER GUIDANCE FORECASTING CONDITIONS AS LOW AS LIFR CEILINGS AND 
VISIBILITIES IN FREEZING FOG. THINK THERE IS A LITTLE BETTER THAN A 
50/50 CHANCE OF LIFR CEILINGS AT KHVR SO WENT THIS WAY WITH THE TAF 
FORECAST. BLANK 

.PRELIMINARY POINT TEMPS/POPS...
GTF  42  21  40  24 /  10  30  10   0 
CTB  37  17  39  21 /  10  20  10   0 
HLN  37  18  34  20 /  10  30  20  10 
BZN  39  17  39  17 /  10  40  20   0 
WEY  26   2  29   7 /  10  60  40  20 
DLN  38  18  38  19 /  10  20  20  10 
HVR  36  11  40  15 /  10  20  10   0 
LWT  37  19  37  20 /  10  30  30  10 

.TFX WATCHES/WARNINGS/ADVISORIES...
NONE.