FXUS65 KTFX 222155
AFDTFX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
255 PM MST TUE DEC 22 2009
.DISCUSSION...
TONIGHT THROUGH WEDNESDAY NIGHT...A PROGRESSIVE WEATHER SYSTEM WILL
MOVE INTO THE NORTHWEST ZONES LATE TONIGHT THEN MOVE EAST THROUGH
THE REMAINDER OF THE AREA WEDNESDAY MORNING AND EARLY AFTERNOON.
MODELS ARE FASTER WITH THIS SYSTEM THAN THEY WERE ON MONDAY. IN LINE
WITH THIS HAVE LOWERED SNOW ACCUMULATIONS OVER THE PLAINS FROM 2 TO
5 INCHES TO 2 TO 3 INCHES. THE ARCTIC SURGE ASSOCIATED WITH THE
WEATHER SYSTEM WILL MOVE INTO THE NORTHERN ZONES THIS EVENING THEN
SPREAD SOUTH OVER ALL BUT FAR SOUTHWEST MONTANA BY WEDNESDAY
MORNING. WINDS ASSOCIATED WITH THIS SURGE IN COMBINATION WITH VERY
COLD TEMPERATURES WILL CAUSE WIND CHILLS OF 10 BELOW ZERO TO 20
BELOW ZERO ON WEDNESDAY. EVEN THOUGH EXPECTED SNOW ACCUMULATIONS ARE
LESS THAN WAS EARLIER THOUGHT...THE COMBINATION OF THE SNOW AND VERY
COLD WIND CHILL TEMPERATURES WILL STILL NECESSITATE THE CONTINUATION
OF THE WINTER WEATHER ADVISORY. SINCE THE SYSTEM IS EXPECTED TO BE
FASTER WILL DROP THE WINTER WEATHER ADVISORY EXCEPT IN THE FAR EAST
FOR WEDNESDAY AFTERNOON. BLANK
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 1800Z.
LOW CLOUDS AND AREAS OF DENSE FREEZING FOG REMAIN ACROSS PORTIONS OF
CENTRAL MONTANA THIS MORNING BUT ARE BEGINNING TO SHOW SIGNS OF
IMPROVING. SPECIFICALLY KGTF AND KLWT TERMINALS ARE THE HARDEST HIT
WHERE IFR AND OCCASIONAL LIFR CONDITIONS CONTINUE. AS NORTHERLY
WINDS INCREASE SO SHOULD CIGS/VIS AT CURRENTLY LOW SITES. THE NEXT
WINTER STORM IS HEADED INTO MONTANA THIS AFTERNOON THOUGH...BRINGING
WIDESPREAD SNOW FROM NORTH TO SOUTH. LIGHT SNOW IS EXPECTED TO BEGIN
THIS AFTERNOON AT KCTB AND KHVR...AND LATER THIS EVENING FOR THE
REST. CONDITIONS WILL ONCE AGAIN DROP TO MVFR AND POSSIBLY IFR WITH
MOUNTAIN OBSCURATION PRETTY MUCH A GUARANTEE. SNOW ACCUMULATIONS OF
2 TO 5 INCHES ARE EXPECTED IN THE PLAINS AND VALLEYS...WITH HIGHER
AMOUNTS IN THE MOUNTAINS. DRIFTING SNOW IS LIKELY AS NORTHERLY WINDS
INCREASE BUT WINDS SHOULD NOT BE VERY STRONG SO VISIBILITIES SHOULD
MOSTLY BE AFFECTED BY SNOW AND LOW CLOUDS. EXPECT VIS LESS THAN A
MILE AT TIMES OVER THE REGION. SNOW WILL END THURSDAY AFTERNOON.
&&
.PRELIMINARY POINT TEMPS/POPS...
GTF 6 8 -6 17 / 80 80 10 0
CTB 0 4 -9 16 / 90 30 0 0
HLN 15 16 -5 16 / 50 50 10 0
BZN 17 18 -7 15 / 50 50 10 10
WEY 10 19 -13 12 / 60 80 20 10
DLN 13 23 -5 14 / 40 40 10 0
HVR 4 5 -16 3 / 90 80 10 0
LWT 8 9 -7 9 / 80 80 10 10
&&
.TFX WATCHES/WARNINGS/ADVISORIES...
WINTER WEATHER ADVISORY FROM 11 PM THIS EVENING TO 11 AM MST
WEDNESDAY FOR CASCADE...CHOUTEAU...EASTERN TETON...HILL...JUDITH
BASIN...LIBERTY...MEAGHER...SOUTHERN ROCKY MOUNTAIN FRONT.
WINTER WEATHER ADVISORY FROM 11 PM THIS EVENING TO 5 PM MST
WEDNESDAY FOR BLAINE...FERGUS.
WINTER WEATHER ADVISORY UNTIL 11 AM MST WEDNESDAY FOR EASTERN
GLACIER...EASTERN PONDERA...NORTHERN ROCKY MOUNTAIN FRONT...
TOOLE.
&&
$$
SHORT TERM...BLANK
LONG TERM...GUSTAFSON
AVIATION...GUSTAFSON
WEATHER.GOV/GREATFALLS
