FXUS65 KTFX 221054
AFDTFX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
354 AM MST TUE DEC 22 2009
.DISCUSSION...
TODAY THROUGH THURSDAY...COMPLICATED WEATHER PATTERN WILL CONTINUE
TO CAUSE PROBLEMS ACROSS THE REGION THROUGH MID-WEEK. LOW CLOUDS
AND AREAS OF FOG REMAIN ENTRENCHED ACROSS MUCH OF NORTH CENTRAL
MONTANA THIS MORNING. HOWEVER...WIDESPREAD DENSE FOG HAS ENDED FOR
NOW DUE TO INCREASED NORTH WINDS AS LOW PRESSURE FORMS SOUTH OF
THE STATE. AT THIS TIME IT APPEARS THAT DENSE FOG SHOULD NOT
REFORM...SO WILL GO AHEAD AND CANCEL THE ADVISORY. MOISTURE WILL
CONTINUE TO STREAM OVER THE ARCTIC AIRMASS AND IS EXPECTED TO
SQUEEZE OUT SCATTERED SNOW SHOWERS THIS MORNING. AS THE NORTHERLY
SURFACE WINDS INCREASE AND UPSLOPE FLOW DEVELOPS ALONG THE NORTH
SLOPES OF THE ISLAND RANGES IT APPEARS THAT NUMEROUS SNOW SHOWERS
COULD DEVELOP ACROSS CENTRAL MONTANA THIS AFTERNOON. HOWEVER...
SNOW ACCUMULATIONS ARE EXPECTED TO BE GENERALLY LIGHT. A MORE
WIDESPREAD AND HEAVIER SNOW EVENT WILL TAKE SHAPE OVERNIGHT AS AN
UPPER LEVEL TROUGH SWEEPS ACROSS THE NORTHERN ROCKY MOUNTAINS AND
DRAGS AN ARCTIC FRONT INTO NORTH CENTRAL MONTANA. SNOW WILL
DEVELOP IN MY FAR NORTHWEST ZONES THIS EVENING AND SPREADS ACROSS
ALL OF CENTRAL MONTANA BY MORNING...BEFORE QUICKLY EXITING THE
FORECAST AREA WEDNESDAY AFTERNOON. WILL ISSUE A WINTER WEATHER
ADVISORY FOR SNOW FOR ALL OF NORTH CENTRAL AND CENTRAL MONTANA FOR
TONIGHT AND WEDNESDAY. THE CHANCE FOR WIDESPREAD PRECIPITATION AND
ADVISORY CRITERIA SNOW AMOUNTS IN SOUTHWEST MONTANA DOES NOT
APPEAR FAVORABLE FOR HIGHLIGHTS AT THIS TIME. THE ARCTIC AIR WILL
REMAIN OVER THE FORECAST AREA WEDNESDAY NIGHT AS SKIES CLEAR AND
TEMPERATURES DROP BELOW ZERO ONCE AGAIN. HOWEVER...THIS OUTBREAK
WILL NOT BE AS COLD AS THOSE SEEN EARLIER THIS MONTH. ON THURSDAY
THE ARCTIC AIRMASS IS EXPECTED TO BEGIN MOVING EAST WITH WINDS
SHIFTING TO THE WEST AND SOUTHWEST ACROSS WESTERN PORTIONS OF MY
FORECAST AREA AND TEMPERATURES WARMING BACK INTO THE TEENS ABOVE
ZERO. MPJ
CHRISTMAS EVE THROUGH TUESDAY...AN UPPER-LEVEL RIDGE OF HIGH
PRESSURE BEGINS TO BUILD OVER THE PACIFIC NORTHWEST ON CHRISTMAS DAY
WITH DRY NORTHERLY FLOW AND MODERATING TEMPERATURES. OVERALL...A
QUIETER PATTERN IS ANTICIPATED FOR THE FORECAST PERIOD WITH THE
STRONG UPPER RIDGE PERSISTING OVER THE WESTERN U.S. THROUGH THE
HOLIDAY WEEKEND. THOUGH TEMPERATURES WILL TREND TOWARDS AVERAGE...A
FRESH SNOWPACK MAY STILL KEEP READINGS AROUND TO SLIGHTLY BELOW
SEASONAL AVERAGES. RIDGE AXIS WILL MOVE EAST BY SUNDAY WITH WESTERLY
FLOW DEVELOPING. DRY CONDITIONS ARE EXPECTED TO CONTINUE THROUGH
MONDAY...WITH INCREASING PACIFIC MOISTURE BY MONDAY NIGHT INTO
TUESDAY AS OUR NEXT SHORTWAVE APPROACHES. MLS
&&
.AVIATION...
UPDATED 0600Z.
A VERY SHALLOW LAYER OF COLD AND MOIST AIR NEAR THE SURFACE WITH
WARMER AIR ALOFT HAS REMAINED IN PLACE OVER MUCH OF NORTH CENTRAL
AND CENTRAL MONTANA. PRECIPITATION HAS DIMINISHED ACROSS MOST OF
CENTRAL MONTANA BUT SOME SHOWERS CONTINUE TO MOVE NORTHEAST ACROSS
NORTHERN MONTANA. DENSE FOG AND SURFACE BASED STRATUS REMAINS A
CONCERN DUE TO THE COLD MOIST AIR. RESTRICTING FOG WILL DIMINISH
LATER TONIGHT AS A NORTHERLY WIND SHIFT HELPS CLEAR OUT THE TRAPPED
LOWER LEVEL MOISTURE. ANOTHER WINTER STORM IS ON THE HORIZON THOUGH.
EXPECT SNOW TO MOVE INTO THE REGION TOMORROW DURING THE DAY AT MOST
PLACES. EXPECT SEVERAL INCHES ACROSS THE PLAINS AND VALLEYS...WITH
HIGHER TOTALS AT HIGHER ELEVATIONS...THROUGH THURSDAY WHEN SNOW WILL
COME TO AN END. THE POTENTIAL FOR AT LEAST TEMPORARY MVFR AND
POSSIBLY IFR CONDITIONS LOOKS LIKELY AT THIS POINT. MOUNTAIN
OBSCURATIONS DURING THE STORM ARE ALMOST A CERTAINTY ACROSS NORTH
CENTRAL AND CENTRAL MONTANA AS WELL.
&&
.PRELIMINARY POINT TEMPS/POPS...
GTF 27 5 9 -6 / 60 80 80 10
CTB 20 0 7 -11 / 50 90 40 10
HLN 30 13 15 -6 / 50 70 70 10
BZN 34 15 21 -7 / 40 60 70 20
WEY 31 9 22 -11 / 60 50 80 30
DLN 33 14 24 -6 / 70 50 60 10
HVR 20 4 9 -13 / 40 80 80 10
LWT 36 7 9 -10 / 40 80 80 20
&&
.TFX WATCHES/WARNINGS/ADVISORIES...
WINTER WEATHER ADVISORY FROM 11 PM THIS EVENING TO 11 AM MST
WEDNESDAY FOR EASTERN TETON...SOUTHERN ROCKY MOUNTAIN FRONT.
WINTER WEATHER ADVISORY FROM 11 PM THIS EVENING TO 5 PM MST
WEDNESDAY FOR BLAINE...CASCADE...CHOUTEAU...FERGUS...HILL...
JUDITH BASIN...LIBERTY...MEAGHER.
WINTER WEATHER ADVISORY FROM 5 PM THIS AFTERNOON TO 11 AM MST
WEDNESDAY FOR EASTERN GLACIER...EASTERN PONDERA...NORTHERN ROCKY
MOUNTAIN FRONT...TOOLE.
&&
$$
SHORT TERM...MPJ
LONG TERM...MLS
AVIATION...GUSTAFSON
WEATHER.GOV/GREATFALLS
