FXUS65 KBYZ 041040
AFDBYZ
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BILLINGS MT
340 AM MST FRI DEC 4 2009
.SHORT TERM...VALID FOR TDY AND SAT...
NORTHERLY FLOW OVER THE AREA TONIGHT WITH CLEAR SKIES AS SOUTHERN
MONTANA AND NORTHERN WYOMING ARE AWAITING THE ARRIVAL OF A SHOT OF
WINTER WEATHER STARTING SATURDAY. GAP FLOW AND DRAINAGE WINDS ARE
OCCURRING TONIGHT WITH LEESIDE PRESSURE FALLS OCCURRING IN ADVANCE
OF A WAVE HEADING SOUTHWARD THROUGH ALBERTA. GAP FLOW WINDS ARE
STRUGGLING TO GET STEAM GOING AS STRONG SURFACE HIGH PRESSURE OVER
IDAHO AND SOUTHWEST MONTANA ARE KEEPING WINDS TURNED A BIT MORE
WESTERLY THAN FAVORED DIRECTIONS. HOWEVER...EXPECT PRESSURE FALLS
TO DRIVE LEESIDE TROUGHING DEEPER INTO CENTRAL MONTANA AND THIS
SHOULD CAUSE GAP FLOW WINDS TO INCREASE...AND REPORTS AROUND 3
A.M. ALREADY INDICATED GUSTS TO 55 MPH AT LIVINGSTON AT NYE. NO
BLOWING SNOW HAS BEEN REPORTED AND HAVE DROPPED THE WINTER
WEATHER ADVISORY IN FAVOR OF A WIND ADVISORY. DESPITE THE WINDIER
CONDITIONS TEMPERATURES ARE IN THE TEENS AT BILLINGS AT LIVINGSTON
AND SINGLE DIGITS ELSEWHERE. LOWERED TEMPERATURES AS DIURNAL
WARMING SHOULD NOT HAVE A DRAMATIC EFFECT WITH LOW SUN ANGLES AND
AIRMASS ALREADY IS SHOWING MIX DOWN DOES NOT HAVE A LOT OF WARMER
AIR ALOFT TO WORK WITH. PRESSURE GRADIENTS BECOME LESS FAVORABLE
THIS EVENING AS THE SURFACE TROF SHIFTS EASTWARD WHILE THE BC
SYSTEM ENTERS NORTHWEST MONTANA AND CAUSES THE FLOW ALOFT TO
BECOME WESTERLY AND THEN SOUTHWESTERLY OVERNIGHT. MODELS BEGIN TO
MOISTEN UP THE ATMOSPHERE OVERNIGHT BUT MODELS SHOW DRY AIR AT THE
LOW LEVELS WHICH SHOULD SLOW PRECIP DEVELOPMENT OVER THE PLAINS.
MOUNTAINS WILL PICK UP SNOW SHOWER ACTIVITY TONIGHT AND SNOWFALL
WILL BECOME MORE WIDESPREAD ACROSS THE AREA ON SATURDAY. COLD
FRONT TO BRING REINFORCING SHOT OF ARCTIC AIR INTO THE STATE
DURING THE DAY AND DO NOT EXPECT TEMPERATURES TO REALLY DO MUCH ON
SATURDAY BEFORE FALLING DURING THE AFTERNOON HOURS. WITH THE PUSH
OF COLDER AIR UPSLOPE BEGINS TO BECOME A BETTER FORCING MECHANISM
AND EVEN THROUGH PRECIPITATION AMOUNTS WILL BE LIGHT...EXPECT SNOW
RATIOS OF 20 TO 1 TO BE PREVALENT SO ACCUMULATIONS OF 1 TO 2 INCHES
ARE POSSIBLE FROM BILLINGS WEST WITH GREAT AMOUNTS OVER THE
FOOTHILLS. UPSLOPE AND COLD AIR PUSHING INTO THE AREA TO CONTINUE
SATURDAY NIGHT WITH TEMPERATURES HEADING TOWARDS ZERO FOR MANY
AREAS. EXPECT ANOTHER 1 TO 2 INCHES OF SNOW TO FALL...AGAIN FROM
BILLINGS WESTWARD. ANY SNOW THAT ACCUMULATES WILL SET THE STAGE
FOR BITTERLY COLD TEMPERATURES TO DEVELOP LATER IN THE WEEKEND AND
EARLY NEXT WEEK. BORSUM
.LONG TERM...VALID FOR SUN...MON...TUE...WED...THU...
MODELS CONTINUE TO ADVERTISE A REDUCTION IN TEMPERATURES BY
PUSHING UPPER LEVEL ENERGY WESTWARD TOWARD OREGON. THIS ALLOWS
THE DEEP ARCTIC OVER THE NORTHERN TERRITORIES TO PENETRATE THE
ENTIRE NORTHERN ROCKIES AND POOL THE COLDEST AIR ALONG THE GREAT
DIVIDE. THIS AIR WILL GET PULLED DOWN WITH LOWERING HEIGHTS
THROUGH THE DAY SUNDAY. DROPPED HIGHS AGAIN AS 850MB TEMPERATURES
TO NEAR -20C WILL BE SITTING OVER THE FORECAST AREA SUNDAY
THROUGH MONDAY. THE COLDEST LOCATIONS LOOK TO BE OVER CENTRAL AND
WESTERN ZONES WITH THE ORIENTATION OF THE UPPER FEATURES. HIGHS
WILL STRUGGLE IN THE SINGLE DIGITS SUNDAY AND HAVE A HARD TIME
GETTING ABOVE ZERO ON MONDAY. DYNAMICS WERE LOOKING A LITTLE
BETTER THIS RUN FOR SNOW SUNDAY INTO MONDAY WITH THE UPPER LOW
DROPPING INTO NEVADA AND SETTING UP WEAK OVER RUNNING. THE UPPER
TROUGH WILL PUSH SLOWLY ACROSS THE ROCKIES AND THIS WILL KEEP THE
CHANCE OF SNOW HIGH THROUGH MONDAY NIGHT. THE STRONGEST Q VECTOR
FORCING STAYS SOUTH...BUT CONFIDENT LIGHT SNOW WILL LINGER INTO
TUESDAY MORNING SO RAISED POPS FURTHER. AMOUNTS SHOULD BE LIGHT
AS THE AIRMASS WILL BE SO COLD THAT FLAKE SIZE WILL BE QUITE
SMALL AND THEREFORE NOT ACCUMULATE READILY. GOING FOR AROUND AN
INCH EVERY TWELVE HOURS LOOKS LIKE A GOOD BET. SLOWED DOWN THE
WARM UP WITH MORE ENERGY STREAMING IN BEHIND THE MAIN TROUGH
TUESDAY NIGHT AND REINFORCING NORTHERLY FLOW. LOW LEVELS RESPOND
WEDNESDAY AFTERNOON OVER WESTERN ZONES...BUT MODERATION WILL BE
SLOW. HIGHS SHOULD STAY BELOW SEASONAL AVERAGES THROUGH THE
ENTIRE WEEK. LOWS COULD BE MUCH COLDER THEN FORECAST IF WE CLEAR
OUT SOME. THE PLACEMENT OF THE UPPER TROUGH SHOULD KEEP LOWS FROM
FALLING TOO FAR OFF THE TABLE WITH CLOUD COVER...BUT WILL NEED TO
BE WATCHED. THE COLDEST NIGHT LOOKS TO BE MONDAY NIGHT WITH LOWS
WELL BELOW ZERO. HUMPHREY
&&
.AVIATION...
STRONG WEST TO SOUTHWEST WINDS WILL BE OVER CENTRAL AND WESTERN
ZONES THIS MORNING. THE STRONGEST WINDS WILL BE OVER KLVM WITH
GUSTS TO 50KTS THIS MORNING. KBIL WILL HAVE GUSTS TO 25KTS. THE
WINDS WILL DECREASE THIS AFTERNOON. OTHERWISE...VFR FLYING
WEATHER IS ANTICIPATED TODAY WITH SOME MID TO HIGH LEVEL CLOUDS
WORKING IN. HUMPHREY
&&
.PRELIMINARY POINT TEMP/POPS...
TDY SAT SUN MON TUE WED THU
-------------------------------------------------------
BIL 032 015/024 003/005 907/001 911/006 903/018 009/029
0/N 17/S 86/S 43/S 22/S 22/S 11/B
LVM 029 008/019 905/005 914/001 917/008 902/022 011/032
0/N 27/S 86/S 44/S 22/S 22/S 22/S
HDN 032 011/027 003/010 904/007 904/013 904/021 006/030
0/B 15/S 76/S 33/S 22/S 22/S 11/B
MLS 030 010/024 002/011 905/008 910/007 905/016 902/025
0/U 13/S 33/S 22/S 22/S 22/S 11/B
4BQ 030 011/028 004/012 902/011 904/014 904/022 004/028
0/B 13/S 44/S 22/S 22/S 22/S 11/B
BHK 025 008/023 002/013 903/009 905/013 905/016 001/022
0/B 12/B 32/S 22/S 22/S 22/S 11/B
SHR 032 007/028 002/010 906/009 907/013 907/021 003/033
0/B 14/S 76/S 33/S 32/S 22/S 22/S
&&
.BYZ WATCHES/WARNINGS/ADVISORIES...
MT...WIND ADVISORY IN EFFECT UNTIL 5 PM MST THIS AFTERNOON FOR
ZONES 65-66.
WY...NONE.
&&
$$
WEATHER.GOV/BILLINGS
