FXUS65 KTFX 220553
AFDTFX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
1100 PM MST MON DEC 21 2009
UPDATED AVIATION
.UPDATE...
AN UPDATE IS PLANNED. WARMER AIR SOUTH OF A FRONTAL SYSTEM FROM
SOUTH OF GREAT FALLS TO NEAR LEWISTOWN IS SLOWLY CREEPING
NORTHWARD THIS EVENING. DENSE FOG PREVAILS IN MANY AREAS NORTH OF
THIS FRONT. THE DENSE FOG ADVISORY WILL REMAIN IN EFFECT. ALSO...WEAK
DISTURBANCES ARE MOVING THROUGH THE FLOW PRODUCING A FEW LIGHT
SNOW/RAIN SHOWERS AND POSSIBLY DRIZZLE IN SOME OF THE AREAS THAT
REMAIN BELOW FREEZING. THIS WILL CONTINUE TO ADD A LIGHT GLAZE
LAYER TO AREAS ALREADY AFFECTED BY THE FREEZING RAIN FROM EARLIER
TODAY. DID RAISE TEMPERATURES ACROSS SECTIONS OF THE SOUTHWEST AND
OTHER AREAS IN THE SOUTHERN HALF OF THE CWA. THESE AREAS ARE IN
THE WARMER AIR. OTHER THAN SOME MINOR TWEAKS TO THE WINDS...THE
INCREASE IN TEMPS OVER SOUTHERN PORTIONS WAS THE BIGGEST CHANGE. DB
&&
.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.
&&
.PREV DISCUSSION...
/ISSUED 530 PM MST MON DEC 21 2009/
TODAY THROUGH TUESDAY...A COLD MOIST AIRMASS IS MORE ENTRENCHED
THAN PREVIOUSLY FORECASTED AND HAS PERSISTED THROUGH THE DAY ALONG
THE ROCKY MOUNTAIN FRONT AND INTO CENTRAL MONTANA. AREAS OF DENSE
FOG OVERNIGHT WILL RETURN TO THE SECTIONS OF NORTH CENTRAL AND
CENTRAL MONTANA THAT DID CLEAR OUT TODAY. THERE IS STILL A WARM
TONGUE OF AIR ALOFT IN THE MODEL PROFILES THAT SUGGESTS ANY PRECIP
THAT OCCURS OVER CENTRAL MONTANA TONIGHT HAS A SLIGHT CHANCE TO
START OUT AS FREEZING RAIN BEFORE TRANSITIONING INTO SNOW. THERE
ALSO IS A WEAK UPPER LEVEL DISTURBANCE CURRENTLY MOVING ACROSS
NORTHERN IDAHO THAT COULD POSSIBLY LEAD TO AREAS OF PRECIPITATION
ACROSS CENTRAL AND NORTH CENTRAL MONTANA TONIGHT. BY TUESDAY
MORNING A COLD FRONT WILL START TO MOVE SOUTH OUT OF CANADA
HOPEFULLY WITH STRONG ENOUGH SURFACE WINDS TO MIX OUT THE FOG
ALONG THE HIGH PLAINS. SNOW SHOULD START TO FALL BY MIDDAY TUESDAY
ACROSS MUCH OF THE AREA...WITH SOUTHWESTERN MONTANA LAGGING A FEW
HOURS BEHIND NORTH CENTRAL AND CENTRAL MONTANA. BECAUSE OF THE
ON GOING HAZARD FROM THE FOG A DENSE FOG ADVISORY HAS BEEN ISSUED
FOR CENTRAL AND NORTH CENTRAL MONTANA UNTIL 11 AM TUESDAY. SUK
TUESDAY NIGHT THROUGH WEDNESDAY NIGHT...AN UPPER LOW PRESSURE AREA
OVER ALBERTA TUESDAY NIGHT WILL DROP SOUTH OVER THE FORECAST AREA
WEDNESDAY NIGHT. THERE WILL BE AN ARCTIC SURGE AHEAD OF THE UPPER
LOW WHICH WILL SPREAD SOUTH OVER THE AREA TUESDAY NIGHT AND EARLY
WEDNESDAY. HAVE INCREASED THE CHANCES OF SNOW ASSOCIATED WITH THIS
SYSTEM. COMING UP WITH SEVERAL INCHES OF SNOW OVER MOST OF THE LOWER
ELEVATIONS EXCEPT FOR FAR SOUTHWEST MONTANA. LOWERED HIGH
TEMPERATURES FOR WEDNESDAY OVER THE PLAINS. ALSO LOWERED LOWS FOR
WEDNESDAY NIGHT OVER MOST OF THE PLAINS. TEMPERATURES COULD BE
SIGNIFICANTLY LOWER IN OTHER AREAS AS WELL BUT AM NOT SURE IF SKIES
WILL CLEAR OUT. BLANK
CHRISTMAS EVE...NORTHERLY FLOW WILL DOMINATE AS THE LOW MOVES OUT OF
THE AREA WITH LIGHT SNOW STILL POSSIBLE IN THE MOUNTAINS OF
SOUTHWEST AND CENTRAL MONTANA. TEMPERATURES WILL CONTINUE WELL BELOW
NORMAL.
CHRISTMAS DAY THROUGH MONDAY...A QUIETER PATTERN IS ANTICIPATED FOR
THE REMAINDER OF THE FORECAST PERIOD AS A BUILDING RIDGE OF HIGH
PRESSURE DOMINATES OVER THE WESTERN U.S. TEMPERATURES THROUGH THE
PERIOD WILL REMAIN NEAR TO SLIGHTLY ABOVE SEASONAL AVERAGES. MLS
AVIATION...
UPDATED 0030Z.
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 KEEPING SOME LIGHT FREEZING RAIN POTENTIAL.
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. NORTHERN AIRFIELDS HAVE A HIGH CHANCE OF SEEING
RESTRICTING FOG TONIGHT WITH KHLN AND KBZN BEING THE EXCEPTIONS.
ANOTHER STORM IS ON THE SHORT TERM HORIZON. EXPECT SNOW TO MOVE INTO
THE REGION TOMORROW STARTING AROUND THE MIDDLE OF THE DAY. EXPECT
SEVERAL INCHES ACROSS 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 ARE
ALMOST A CERTAINTY ACROSS NORTH CENTRAL AND CENTRAL MONTANA AS WELL.
&&
.PRELIMINARY POINT TEMPS/POPS...
GTF 19 24 6 8 / 30 70 70 80
CTB 13 17 1 7 / 40 50 90 80
HLN 18 28 14 15 / 30 70 70 70
BZN 21 32 16 20 / 20 60 60 70
WEY 15 29 13 19 / 60 60 50 80
DLN 21 32 14 19 / 30 60 50 60
HVR 10 19 4 8 / 40 60 70 70
LWT 23 33 7 9 / 20 50 70 90
&&
.TFX WATCHES/WARNINGS/ADVISORIES...
DENSE FOG ADVISORY UNTIL 11 AM MST TUESDAY FOR BLAINE...
CASCADE...CENTRAL AND SOUTHERN LEWIS AND CLARK...CHOUTEAU...
EASTERN GLACIER...EASTERN PONDERA...EASTERN TETON...FERGUS...
HILL...JUDITH BASIN...LIBERTY...MEAGHER...NORTHERN ROCKY
MOUNTAIN FRONT...SOUTHERN ROCKY MOUNTAIN FRONT...TOOLE.
&&
$$
SHORT TERM...DB
LONG TERM...MLS
AVIATION...GUSTAFSON
WEATHER.GOV/GREATFALLS
