FXUS65 KBYZ 302253
AFDBYZ
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BILLINGS MT
353 PM MST MON NOV 30 2009
.SHORT TERM...VALID FOR TUE AND WED...
CONCERNS FOR THE DAY ARE STRONG WINDS OVER WESTERN VALLEYS
TONIGHT...AND SNOW ACCUMULATIONS/BLOWING SNOW ASSOCIATED WITH A
STRONG COLD FRONT TUESDAY MORNING. ISSUED A WIND ADVISORY FOR THE
BEARTOOTH FOOTHILLS THIS MORNING AND HAVE SEEN WINDS OF 40 TO 45
MPH WITH GUSTS TO 60 MPH IN LIVINGSTON AND NYE THIS AFTERNOON. AS
THE COLD FRONT APPROACHES THE AREA OVERNIGHT EXPECT THESE WINDS TO
CONTINUE...FINALLY WEAKENING BELOW ADVISORY CRITERIA EARLY TUESDAY
MORNING AS THE FRONT MOVES THROUGH.
ISSUED A WINTER WEATHER ADVISORY FOR SOUTHWEST AND SOUTH CENTRAL
ZONES FOR TUESDAY INTO TUESDAY EVENING. AS THE STRONG COLD FRONT
MOVES THROUGH THE AREA TUESDAY MORNING SNOW IS EXPECTED TO
DEVELOP. MODEL PROGS SHOW STRONG INSTABILITY AND LIFT FOR A SHORT
PERIOD WITH THIS SYSTEM AS IT MOVES THROUGH. IN ADDITION THE
DENDRITIC GROWTH ZONE DROPS INTO A FAVORABLE ELEVATION ONCE THE
FRONT MOVES THROUGH PROVIDING ENHANCED SNOW GROWTH. ONLY EXPECT A
3 TO 6 HOUR WINDOW OF SNOWFALL BEHIND THE FRONT...BUT GIVEN THE
DYNAMICS COULD SEE 1 TO 2 INCH PER HOUR SNOWFALL
RATES...ESPECIALLY IN THE NORTHERN FOOTHILLS OF THE BEARTOOTH AND
BIG HORN MOUNTAINS WHERE 10 TO 20 MPH NORTHERLY WINDS WILL PROVIDE
UPSLOPE ENHANCEMENT. NORTHERLY WINDS OF 10 TO 20 MPH WILL CAUSE
ANY SNOWFALL TO BLOW AROUND FOR MUCH OF THE DAY RESULTING IN AREAS
OF REDUCED VISIBILITY. ROADWAYS ARE WARM THIS AFTERNOON AND WITH
TEMPERATURES REMAINING ABOVE FREEZING FOR MOST OF THE NIGHT THERE
COULD BE SOME PROBLEMS WITH SNOW MELTING AND THEN FREEZING AS
TEMPERATURES DROP BEHIND THE FRONT.
THE BILLINGS AREA IS JUST ON THE NORTHERN FRINGE OF THE HEAVIER
SNOW POTENTIAL. HOWEVER WITH THE MOST INTENSE SNOWFALL COMING
RIGHT AROUND RUSH HOUR TUESDAY MORNING THERE IS THE POTENTIAL FOR
SLICK ROADS TO CAUSE ADDITIONAL PROBLEMS...SO EXTENDED THE
ADVISORY INTO YELLOWSTONE COUNTY WITH 1 TO 2 INCHES OF SNOWFALL
EXPECTED. SNOW WILL QUICKLY DIMINISH TUESDAY AFTERNOON FROM
NORTHWEST TO SOUTHEAST AS THE FRONTOGENESIS BAND MOVES INTO
CENTRAL WYOMING.
HIGH TEMPERATURES TUESDAY WILL OCCUR IN THE MORNING WITH STEADY OR
FALLING TEMPS THROUGH THE DAY. BY LATE AFTERNOON MOST AREAS SHOULD
BE IN THE 20S. WITH SKIES CLEARING SOMEWHAT TUESDAY NIGHT ALONG
WITH FRESH SNOWFALL EXPECT LOWS TO DROP INTO THE SINGLE DIGITS AND
TEENS WEDNESDAY MORNING. HIGHS WEDNESDAY WILL BE IN THE 20S AND
LOWER 30S WITH CANADIAN HIGH PRESSURE OVER THE AREA. A FEW WEAK
DISTURBANCES WILL MOVE ACROSS EASTERN AREAS WEDNESDAY BRINGING A
CHANCE OF LIGHT SNOW OR FLURRIES AND KEEPING CLOUD COVER IN PLACE
THERE. ANOTHER COLD NIGHT IS ON TAP WEDNESDAY NIGHT WITH MOST
PLACES IN THE SINGLE DIGITS AND LOWER TEENS. CHAMBERS
.LONG TERM...VALID FOR THU...FRI...SAT...SUN...MON...
AN ARCTIC INTRUSION OF COLD AIR IS THE MAIN WEATHER HIGHLIGHT FOR
THIS PARTICULAR EXTENDED PERIOD.
EXTENDED PERIOD BEGINS THURSDAY WITH THE REGION UNDER NORTHERLY
FLOW AS A POSITIVELY TILTED TROUGH DEEPENS OVER THE CENTRAL UNITED
STATES. GFS AND ECMWF ARE IN GOOD AGREEMENT EARLY ON IN THE PERIOD
WITH THE PLACEMENT OF THIS TROUGH. HOWEVER...THE SIMILARITIES
QUICKLY END THERE. ONE THING IS CLEAR...THERE IS A SOURCE OF
ENERGY THAT WILL BE MOVING INTO MONTANA FROM OFF OF THE NORTHERN
PACIFIC COAST SOMETIME FRIDAY. THE GFS SOLUTION IS QUICK TO DEVELOP
THIS ENERGY INTO A DEEPENING TROUGH OVER THE WESTERN US...WHILE
THE ECMWF TAKES MORE TIME TO ALLOW THE SYSTEM TO MATURE.
DECIDED TO SIGNIFICANTLY REDUCE MAXIMUM TEMPERATURES NEXT
SUNDAY AND MONDAY AS MODELS HAVE BEEN CONSISTENTLY INCREASING COLD
AIR OVER SOUTHERN CANADA. GFS IS PROJECTING VERY COLD AIR
MASS...WITH 850 MB TEMPERATURES NEARING 28 DEGREES BELOW ZERO IN
SOUTHERN SASKATCHEWAN. THE ECMWF IS NOT NEARLY AS COLD...SO
DECIDED TO BLEND BOTH MODELS FOR A SOLUTION. WAS TEMPTED TO GO
EVEN COLDER...BUT DECIDED TO WAIT UNTIL THE AIR MASS HAS A CHANCE
TO MODIFY ITSELF. HOW COLD WE GET WILL DEPEND ON HOW MUCH SNOW IS
ON THE GROUND IN NORTHERN CANADA AND WEATHER OR NOT CLOUD COVER IS
SIGNIFICANT.
FEEL THE NEED TO ONCE AGAIN MENTION THE HPC ANOMALIES ARE SHOWING
AN EVEN STRONGER TREND TOWARDS THE COLD...WITH A -3.5 PROBABILITY
VALUE OVER ALASKA LATE IN THE PERIOD. THIS FURTHER ENHANCES
CONFIDENCE THAT MAX TEMPERATURES WILL BE VERY COLD.
DECIDED NOT TO CHANGE POPS VERY MUCH DURING THIS PERIOD. BEST
CHANCE FOR ANY SNOW WILL BE IN THE HIGHER ELEVATIONS OUT WEST
FRIDAY THROUGH MONDAY. SINGER
&&
.AVIATION...
PRETTY GUSTY AFTERNOON ACROSS THE REGION...ESPECIALLY NEAR KLVM.
EXPECTING WINDS TO DIE DOWN AS FRONT PASSES THROUGH THE REGION
LATER TONIGHT. WINDS SHOULD TAKE A MORE NORTHERLY DIRECTION AFTER
FRONTAL PASSAGE. EXPECTING SNOW SHOWERS NEAR KLVM TONIGHT AND A
SLIGHT CHANCE FOR SNOW OVER THE EASTERN PLAINS. VISIBILITIES MAY
BE REDUCED TO EITHER MVFR OR VFR DURING SNOW...SO PLEASE USE CAUTION.
SINGER
&&
.PRELIMINARY POINT TEMP/POPS...
TUE WED THU FRI SAT SUN MON
-----------------------------------------------------------
BIL 034/036 015/030 011/031 020/036 020/026 016/020 009/015
28/S 00/B 01/B 11/B 11/B 11/B 11/B
LVM 032/034 007/026 005/030 011/035 017/026 009/016 006/015
49/S 00/N 01/N 11/B 12/J 22/J 22/S
HDN 035/037 016/030 013/032 018/034 019/025 014/021 008/018
06/S 00/B 01/B 11/B 11/B 11/B 11/B
MLS 031/037 018/028 013/029 016/034 018/025 013/018 006/013
02/S 22/S 21/B 11/B 11/B 11/B 11/B
4BQ 031/037 016/027 012/027 015/034 017/025 012/020 006/018
02/S 22/S 21/B 11/B 11/B 11/B 11/B
BHK 030/035 016/025 010/026 012/030 012/026 008/019 004/016
02/S 22/S 21/B 11/B 11/B 11/B 11/B
SHR 031/034 013/027 010/029 018/038 019/027 014/024 011/017
08/S 20/B 01/B 11/B 22/J 22/J 22/S
&&
.BYZ WATCHES/WARNINGS/ADVISORIES...
MT...WINTER WEATHER ADVISORY IN EFFECT FROM 5 AM TO 5 PM MST
TUESDAY FOR ZONES 34-35-39-41-56-64>66.
WINTER WEATHER ADVISORY IN EFFECT FROM 5 AM TO 9 PM MST
TUESDAY FOR ZONE 38.
WIND ADVISORY IN EFFECT UNTIL 5 AM MST TUESDAY FOR ZONES
65-66.
WY...WINTER WEATHER ADVISORY IN EFFECT FROM 5 AM TO 9 PM MST
TUESDAY FOR ZONE 99.
&&
$$
WEATHER.GOV/BILLINGS
