FXUS65 KBYZ 010417 AAA
AFDBYZ
AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE BILLINGS MT
916 PM MST MON NOV 30 2009
.SHORT TERM...VALID FOR TUE AND WED...
COLD FRONT WAS PUSHING INTO CENTRAL MONTANA AS ENTERED GREAT
FALLS AROUND 8 PM MST. WOULD EXPECT FRONTAL PASSAGE IN BILLINGS
BY 3 AM MST. THIS FRONT WAS PRODUCING IMPRESSIVE SURFACE PRESSURE
RISES OF AROUND 2MB PER HOUR AS IT MOVES THROUGH. WINDS SHOULD
GUST UP TO 45 MPH AS THE FRONT DRIVES THROUGH. WINDS HAVE GUSTED
TO NEAR 50 MPH AT CUT BANK WITH PASSAGE OF THE FRONT. TIMING
LOOKS PRETTY MUCH ON TRACK WITH FORECAST. SURFACE PRESSURE RISES
BEHIND THE FRONT WAS CAUSING THE SURFACE GRADIENT TO TURN TO A
NON FAVORABLE ORIENTATION FOR STRONG WINDS OVER THE UPPER
YELLOWSTONE VALLEY. WINDS HAVE NOT HIT ADVISORY CRITERIA SINCE
THIS AFTERNOON AT LIVINGSTON. HAVE HAD A PICK UP IN WIND SPEEDS
THE LAST COUPLE OF HOURS BUT WOULD EXPECT A DECREASE SHORTLY AS
SURFACE PRESSURE DIFFERENCES WERE DECREASING FROM IDAHO FALLS TO
LEWISTOWN. WILL CANCEL THE WIND ADVISORY FOR THE UPPER
YELLOWSTONE AND UPPER STILLWATER RIVER VALLEYS.
WINTER WEATHER ADVISORY LOOKS FINE AND WILL NOT ADJUST. SNOW WAS
TIMING AROUND 3 HOURS AFTER FRONTAL PASSAGE WHICH WOULD PUT THE
SNOW IN BILLINGS CLOSE TO RUSH HOUR. VISIBILITIES WILL BE REDUCED
BY THE SNOW AND WIND...SO TRAVEL WILL BE IMPACTED. WILL NOT
ADJUST POPS AS FORECAST TIMING OF PRECIPITATION LOOKS IN GOOD
SHAPE. ONE CONCERN IS JUDITH GAP WITH WIND AND SNOW...BUT AGREE
WITH DAY SHIFT IN QUICK MOVING NATURE OF FORCING SHOULD LIMIT
IMPACTS. SITUATION WILL BE MONITORED CLOSELY HOWEVER. HUMPHREY
.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...
MVFR TO IFR CONDITIONS ARE POSSIBLE TONIGHT AND INTO THE MORNING
HOURS AS A COLD FRONT PASSES THROUGH THE AREA. GUSTY WINDS IN THE
WEST AHEAD OF THE FRONT...ESPECIALLY AT KLVM...WILL CEASE AFTER
FRONTAL PASSAGE. MOUNTAIN OBSCURATIONS WILL ALSO BE A PROBLEM WITH
THE POTENTIAL FOR TERRAIN ENHANCED SNOW SHOWERS. LEACH/HUMPHREY.
&&
.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.
WY...WINTER WEATHER ADVISORY IN EFFECT FROM 5 AM TO 9 PM MST
TUESDAY FOR ZONE 99.
&&
$$
WEATHER.GOV/BILLINGS
