FXUS65 KBYZ 111701
AFDBYZ
AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE BILLINGS MT
1001 AM MST FRI DEC 11 2009
.SHORT TERM...VALID FOR TDY AND SAT...
BREEZY AND WARMER TODAY BUT WINDS OVER THE SOUTHEAST MONTANA
VALLEYS SHOWING AN EASTERLY RESPONSE AND KEEPING COOLER
TEMPERATURES THIS MORNING. PRESSURE GRADIENTS EXPECTED TO DECREASE
FROM KIDA-KLWT DURING THE LATE MORNING HOURS AND WHILE NYE AND LIVINGSTON
ARE STILL HITTING CRITERIA SUSPECT THAT BY 11 A.M. THEY SHOULD BE
DIMINISHING. WILL ISSUE A LATE UPDATE TO ZONES TO COVER THIS SCENARIO.
BACKING FLOW ALOFT BRINGING MORE OF A WESTERLY ORIENTATION TODAY
WHICH IS GENERATING DOWNSLOPE AND DEWPOINT DEPRESSIONS AGAIN ARE
FALLING BELOW 15 DEGREES WHICH WILL KEEP AREA DRY UNTIL SOME TIME
LATER ON SATURDAY.TEMPERATURES ARE ALREADY IN THE 20S IN MANY
AREAS BUT LOOKING AT YESTERDAYS OBSERVATIONS IT WAS DIFFICULT FOR
READINGS TO CLIMB MUCH HIGH THAN THAT ALONG THE ROCKY MOUNTAIN
FRONT SO HIGHS IN THE UPPER 20S TO NEAR 30 LOOK GOOD ACROSS THE
WESTERN AND CENTRAL ZONES...WHILE EASTERN STATIONS MAY STAY IN THE
TEENS. CURRENTLY SOUTH WIND AT EKALAKA AND SOUTHEAST AT MILES CITY
AND THIS MAY REFLECT HOW TEMPERATURE GRADIENTS MAY SET UP ALONG
THE SURFACE TROUGH THAT LIES ACROSS SOUTHEAST MONTANA. BORSUM
.LONG TERM...VALID FOR SUN...MON...TUE...WED...THU...
MAIN FORECAST ISSUE IN THE EXTENDED CONTINUES TO BE SURGE OF
ARCTIC AIR WHICH SEEMS TO BE A CERTAINTY NOW IN THE SUN/MON TIME
FRAME. MODELS COMING TOGETHER NOW BUT STILL DEPICT SOME SLIGHT
TIMING ISSUES. CONSENSUS IS FOR STRONG COLD ADVECTION BEHIND
ARCTIC FRONT TO KICK IN NO LATER THAN EARLY SUNDAY. AS FOR
POPS...BEST FORCING/OVERRUNNING AND POTENTIAL FOR SNOWFALL APPEARS
TO BE LATE SUNDAY INTO MONDAY AS UPPER WAVE SWINGS THROUGH THE
AREA. THIS ARCTIC WILL BE MUCH SHALLOWER THAN THE LAST EPISODE...
AND FORECAST SOUNDINGS SHOW AN ELEVATED DENDRITIC LAYER SHOULD BE
PRESENT DURING TIME OF PCPN. THUS WOULD EXPECT MANY PLACES TO GET
A QUICK INCH OR TWO OR SNOWFALL...PERHAPS A BIT MORE IN UPSLOPE
AREAS...SOMEWHAT TYPICAL WITH AN ARCTIC. HAVE RAISED POPS TO
LIKELY ACROSS A LARGE PORTION OF THE FORECAST AREA SUNDAY NIGHT
AND MONDAY. PCPN SHOULD TAPER OFF MONDAY AFTERNOON OR EVENING AS
DESCENT WORKS IN FROM THE NW. AS FOR TEMPS THIS IS SHAPING UP TO
BE AN EVEN COLDER AIRMASS THAN THE ONE THAT JUST EXITED. COLD AIR
CURRENTLY ASSOCIATED WITH DEEP UPPER LOW IN THE NORTHWEST
TERRITORIES IS ON THE ORDER OF -30F TO -40F...AND THIS IS THE
AIRMASS WE WILL BE TAPPING INTO...ALBEIT BRIEFLY. MAIN ISSUE WITH
TEMPERATURE FORECASTS IS TIMING. SUNDAY HIGHS SHOULD BE EARLY IN
THE DAY...WITH TEMPS FALLING THROUGHOUT...AND BELOW ZERO READINGS
A GOOD BET BY SUNDAY NIGHT IF NOT SOONER. MONDAY SHOULD BE COLDEST
DAY WITH HIGHS LIKELY BELOW ZERO ACROSS OUR CENTRAL AND EAST...AND
THIS MAY EVEN BE TOO OPTIMISTIC IF GFS FORECAST OF -26C AT 850MB
HOLDS TRUE. OTHER MODELS ARE A BIT WARMER THAN THIS. WITH THE
INCREASED CONFIDENCE HAVE LOWERED TEMPS EACH PERIOD SUNDAY THROUGH
MONDAY NIGHT. MONDAY NIGHT COULD BE PARTICULARLY COLD IN OUR EAST
AS SFC RIDGE SETTLES IN...AND AT THIS POINT WOULD EXPECT LOWS NEAR
20 BELOW AT LEAST FROM MILES CITY TO BAKER AND EKALAKA. GUSTY NW
WINDS ON MONDAY WILL LIKELY LEAD TO BITTER WIND CHILLS AS WELL.
WIND CHILLS COULD DROP TO NEAR 40 BELOW ON MONDAY. BRRR.
THIS ARCTIC WILL BE SHORT-LIVED AS RIDGING AND INCREASED DOWNSLOPE
FLOW BEGIN ON TUESDAY AND WILL LEAD TO A RAPID WARM UP. WEDNESDAY
AND THURSDAY SHOULD BE MOSTLY DRY AND WARMER WITH HIGHS ABOVE
FREEZING AND POSSIBLY INTO THE 40S. MODELS IN GOOD AGREEMENT HERE.
WILL PROBABLY HAVE GAP WIND CONCERNS THESE DAYS WITH THE FLOW
GENERALLY WESTERLY. THOUGH THIS IS SEVERAL DAYS OFF YET HAVE
PAINTED FAIRLY STRONG WINDS AT LIVINGSTON AND NYE ACCORDINGLY.
JKL
&&
.AVIATION...
STRONG SOUTHWEST WINDS WILL GUSTS TO 50KTS THIS MORNING AT KLVM.
THE WINDS WILL DECREASE EALRY THIS AFTERNOON. WINDS WILL ALSO
GUSTS TO 30KTS AT KBIL THIS MORNIG. THESE WINDS WILL ALSO
DECREASE EARLY THIS AFTENROON. OTHERWISE...EXPECT VFR FLYING
WEATHER WITH SOME MID LEVEL CLOUDS FLOATING THROUGH. THERE WILL
BE A SLIGHT CHANCE OF SNOW SHOWERS OVER THE MOUNTAINS CAUSING THE
MOUNTAIN TOPS TO OCCASIONALLY BE OBSCURED. HUMPHREY
&&
.PRELIMINARY POINT TEMP/POPS...
TDY SAT SUN MON TUE WED THU
-------------------------------------------------------
BIL 026 012/030 012/019 903/000 907/024 020/035 026/042
0/N 01/E 25/S 66/S 11/B 11/B 11/N
LVM 028 015/034 018/024 004/010 007/031 024/037 027/042
0/N 02/J 25/S 66/S 21/E 11/N 11/N
HDN 025 005/028 009/020 903/000 908/022 009/035 014/040
0/B 01/B 24/S 65/S 11/B 11/B 11/B
MLS 021 901/023 002/015 908/903 916/015 005/028 012/033
0/B 11/E 33/S 53/S 11/B 11/B 11/B
4BQ 025 003/027 006/020 904/000 916/018 006/032 015/037
0/B 01/B 22/S 55/S 11/B 11/B 11/B
BHK 019 902/022 001/013 908/903 920/013 003/026 010/030
0/B 12/J 22/S 43/S 11/B 11/B 11/B
SHR 026 007/033 012/028 001/008 908/025 010/037 015/040
0/B 01/B 23/S 66/S 21/B 11/B 11/B
&&
.BYZ WATCHES/WARNINGS/ADVISORIES...
MT...WIND ADVISORY IN EFFECT UNTIL 11 AM MST THIS MORNING FOR
ZONES 65-66.
WY...NONE.
&&
$$
WEATHER.GOV/BILLINGS
