FXUS65 KTFX 070531
AFDTFX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
1031 PM MST SUN DEC 6 2009
...UPDATE TO AVIATION
.DISCUSSION...
UPDATE FORTHCOMING. HAVE MADE SOME ADJUSTMENTS TO SKY GRIDS TO
BETTER ALIGN WITH A FORECAST OF VERY COLD OVERNIGHT LOWS AND THE
POSSIBILITY OF PATCHY FOG FORMING. OVERNIGHT LOWS CONTINUE TO BE
TRICKY AS SATELLITE IMAGERY INDICATES MORE CLOUDS PRESENT THAN
PREVIOUSLY ANTICIPATED. HOWEVER...ANY BREAKS IN THE CLOUD COVER WILL
SEND TEMPERATURES PLUMMETING. WILL LEAVE TEMPERATURES ALONE AS WELL
AS CONTINUE THE WIND CHILL ADVISORY. EMANUEL
&&
.AVIATION...
UPDATED 0531Z.
VFR CONDITIONS ARE EXPECTED FOR MUCH OF THE TAF SITES FOR THE NEXT
24 HOURS. THERE IS A SLIGHT POSSIBILITY OF SOME FOG OR LOW STRATUS
AT SOME TAF SITES THAT COULD QUICKLY REDUCE CIGS/VIS CONDITIONS BACK
DOWN TO IFR/LIFR CONDITIONS. HAVE INDICATED THIS POSSIBILITY WITH A
SCT GROUP AT THE LOWER ELEVATION. MOUNTAIN OBSCURATIONS ARE
POSSIBLE WITH THE PATCHY STRATUS AND FOG. SUK
&&
.PREV DISCUSSION...ISSUED 312 PM MST SUN DEC 6 2009
TONIGHT THROUGH TUESDAY...VERY COLD AIRMASS IS CONTINUING TO MOVE
OVER THE AREA WITH FLURRIES AND LIGHT SNOW SHOWERS CONTINUING
ACROSS PORTIONS OF THE AREA...ESPECIALLY OVER FAVORED UPSLOPE
AREAS ACROSS CENTRAL MONTANA. OVERNIGHT...PATCHY FREEZING FOG IS
POSSIBLE BUT WILL MAINLY BE PROMINENT DURING THE EVENING HOURS
WHEN SOME LOW-LEVEL MOISTURE WILL BE PRESENT. LITTLE ADDITIONAL
SNOW ACCUMULATION IS EXPECTED THROUGH MONDAY. CLOUDS WILL BREAK UP
A BIT TONIGHT BUT AM EXPECTING A LOW STRATUS DECK TO PERSIST BEFORE
MORE CLEARING TAKES PLACE ON MONDAY. WINDS HAVE ALSO DECREASED
ACROSS THE REGION...BUT EVEN WITH LIGHT WINDS AS THE MODIFIED
ARCTIC AIRMASS MOVES SOUTH WIND CHILLS ARE EXPECTED TO DROP TO
NEAR 40 BELOW FOR SOME LOCATIONS. HIGH TEMPERATURES ON MONDAY WILL
REMAIN BELOW ZERO WITH OVERNIGHT LOWS FALLING TO 20 AND 30 BELOW
ZERO AND VERY LOW WIND CHILLS ONCE AGAIN. MLS
TUESDAY NIGHT THROUGH SUNDAY...MODELS IS REASONABLY GOOD AGREEMENT
FOR THE MID-RANGE AND EXTENDED FORECAST PERIODS IN SHOWING GRADUAL
WEAKENING AND EASTWARD SHIFT OF THE DEEP LONGWAVE TROF OVER THE
ROCKIES. THIS WILL EVENTUALLY BRING AN END TO THE BITTERLY COLD
ARCTIC CONDITIONS BUT NOT BEFORE A FEW MORE FRIGID DAYS THROUGH
MIDWEEK. MOISTURE SWINGING SOUTH ALONG THE BACKSIDE OF THE UPPER
LEVEL TROF WILL BRING PERIODS OF LIGHT SNOW ON WED AND THURS...
MAINLY OVER CENTRAL AND NORTH CENTRAL MT...BUT ACCUMULATIONS SHOULD
BE ONLY A FEW INCHES AT MOST AS QPF VALUES ARE LOW. FLOW ALOFT
BEGINS TO SHIFT FROM NORTHWEST TO MORE WESTERLY DIRECTION ON FRI AS
WEAK UPPER LEVEL RIDGING BUILDS OVER THE GREAT BASIN. FRIDAY SHOULD
BE DRY OVER THE REGION BUT MOISTURE AND CHANCES OF LIGHT SNOW
INCREASE AGAIN ACROSS SOUTHWEST MT ON SAT AS NEXT WEATHER SYSTEM
MOVES FROM THE PACIFIC INTO CA/OR. MOISTURE WILL BE SLOW TO SPREAD
EAST OF THE DIVIDE SO PARTS OF CENTRAL MT MAY ONLY SEE INCREASING
CLOUDINESS ON SUN WITH LITTLE/NO SNOW. AS FOR TEMPERATURES...THE
ARCTIC AIRMASS WILL LINGER OVER THE CWA EARLY IN THIS PERIOD. WITH
FAIR AMOUNT OF SNOW COVER PRESENT AND LOW SEASONAL SUN ANGLE...HAVE
ADJUSTED OVERNIGHT LOWS DOWNWARD A FEW DEGREES...KEEPING BELOW ZERO
CONDITIONS THRU WED NIGHT. WIND CHILLS MAY AGAIN REACH 20 DEGREES
BELOW ZERO OR LESS ON TUES NIGHT. GRADUAL WARMUP STARTS ON THURS
BUT IT WILL TAKE A FEW DAYS TO COMPLETELY ERODE THE AIRMASS SO
EXPECT TEMPS TO REMAIN BELOW NORMAL ON THURS & FRI...BUT FINALLY GET
CLOSE TO SEASONAL AVERAGES NEXT WEEKEND. WARANAUSKAS
&&
.PRELIMINARY POINT TEMPS/POPS...
GTF -21 -10 -25 -6 / 40 10 10 10
CTB -25 -11 -35 -6 / 30 0 10 0
HLN -15 -2 -23 -2 / 20 10 10 10
BZN -18 0 -24 -1 / 30 20 20 20
WEY -35 4 -38 3 / 30 40 30 30
DLN -16 -3 -24 1 / 20 10 10 10
HVR -13 -6 -20 -1 / 20 0 10 10
LWT -15 -3 -20 -2 / 40 20 20 20
&&
.TFX WATCHES/WARNINGS/ADVISORIES...
WIND CHILL ADVISORY UNTIL 5 AM MST MONDAY FOR MTZ008>015-044>055.
&&
$$
SHORT TERM...EMANUEL/MLS
LONG TERM...WARANAUSKAS
AVIATION...SUK
WEATHER.GOV/GREATFALLS
