FXUS65 KBYZ 232347
AFDBYZ
AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE BILLINGS MT
447 PM MST WED DEC 23 2009
.SHORT TERM...VALID FOR THU AND FRI...
PLAN TO EXPIRE/CANCEL ALL ADVISORIES EXCEPT FALLON...CARTER AND
POWDER RIVER WHERE WINDS MAY STILL CAUSE SOME BLOWING SNOW
PROBLEMS IN RURAL AREAS THIS EVENING. UPDATES OUT SHORTLY.
AM ANTICIPATING POSSIBLE WIND CHILL ADVISORIES OVER NIGHT IN EAST
BUT WILL ADDRESS THAT POSSIBILITY AT MID EVENING. BT
PREVIOUS DISCUSSION...
SNOW CONTINUES TO PUSH EAST THIS AFTERNOON AS BEST MOISTURE AND
DYNAMICS MOVE THROUGH. LOCAL HEAVY BAND OF SNOW SET UP OVER
MAINLY BILLINGS PRODUCING LOCALLY HEAVY SNOW. THERE ARE SIGNS OF
IT DISSIPATING SO THINK THAT TREND WILL CONTINUE FOR THE NEXT
COUPLE HOURS. WILL KEEP THE ADVISORY GOING FOR THE CENTRAL AND
EASTERN AREAS THIS AFTERNOON AND WILL CANCEL THE WESTERN AREAS.
CONTINUED HIGH POPS OUT EAST FOR THIS EVENING AS SOME SNOW SHOULD
CONTINUE THERE. CONTINUED THE DRYING TREND FROM WEST TO EAST
THROUGH THE NIGHT. GUSTY WINDS ACROSS THE EAST PRODUCING BLOWING
SNOW SO KEPT THAT GOING THROUGH THE NIGHT. LOW PRESSURE SYSTEM
MOVING OVER THE REGION TODAY WILL COMBINE WITH THE LOW PRESSURE
SYSTEM MOVING OUT OF THE ROCKIES AND PRODUCE A MAJOR SNOW STORM
FOR THE MIDWEST. THE EASTERN ZONES COULD SEE SOME WRAPAROUND
PRECIP FROM THIS SYSTEM SO HAVE KEPT SOME SCATTERED TYPE POPS
THROUGH FRIDAY NIGHT.
WINDS WILL PICK UP ACROSS THE WESTERN ZONES A LITTLE BIT FOR
THURSDAY AND FRIDAY AS THE ARCTIC TEMPS SLOWLY SHIFT OUT OF THE
AREA. AT THIS TIME DO NOT THINK ANY HIGHLIGHTS WILL BE NEEDED BUT
WILL BE SOMETHING TO WATCH. WINDS WILL ALSO PICK UP ACROSS THE
EASTERN ZONES ON FRIDAY AS A STRONG PRESSURE GRADIENT DEVELOPS
FROM THE BIG SYSTEM IN THE MIDWEST. HAVE INCREASED WINDS THERE A
LITTLE BIT. WILL NEED TO WATCH OUT FOR THE POTENTIAL FOR BLOWING
SNOW FOR THIS. SOLUM
.LONG TERM...VALID FOR SAT...SUN...MON...TUE...WED...
INHERITED A GOOD FORECAST FOR A RELATIVELY STABLE PATTERN IN THE
EXTENDED. GFS AND ECMWF AGREE WELL ON RIDGING TO START THE PERIOD.
DID INCREASE POPS IN THE SOUTHWEST MOUNTAINS CLOSER TO CLIMATOLOGY
ON MONDAY AND TUESDAY DUE TO SOUTHWEST FLOW. SOUTHWEST FLOW IS
TYPICALLY A GOOD REGIME FOR SHOWERS IN THE MOUNTAINS...HOWEVER
REMAINED BELOW CLIMATOLOGY BECAUSE IT DOES NOT HAVE A DIRECT TAP
INTO THE PACIFIC MOISTURE IN THE GFS. ECMWF IS MORE FAVORABLE FOR
A PACIFIC MOISTURE TAP.
TUESDAY INTO WEDNESDAY LEFT POPS NEAR CLIMATOLOGY SINCE GEFS
CONTINUES TO SHOW THE POSSIBILITY OF A COLD FRONT COMING THROUGH
AT THAT TIME. GFS INDICATES A SURFACE TROUGH AT THIS TIME BUT NO
PRECIPITATION OR SIGNIFICANT TEMPERATURE GRADIENT. ECMWF DEPICTS
A LEE-SIDE TROUGH OVER ALBERTA AND NORTHERN MONTANA.
FOR TEMPERATURES MADE VERY FEW ADJUSTMENTS. LAST FORECAST TRENDED
WARMER AS MODEL AND GUIDANCE TRENDS CONTINUED WARM. HOWEVER...12Z
GUIDANCE WAS COOLER THAN THE FORECAST BY A FEW DEGREES...AND HIGHS
WERE A FEW DEGREES WARMER THAN GEFS MEAN 850 MB TEMPERATURES
SUGGEST. CONSIDERING RECENT MODEL TRENDS...THIS IS A GOOD PLACE
FOR THE FORECAST. SO FAR MODELS ARE NOT SHOWING A GOOD DOWN-SLOPE
AND LEE-SIDE TROUGH PATTERN EARLY NEXT WEEK...SO DO NOT WANT TO GO
TOO FAR ABOVE GUIDANCE IN THE WEST. LEACH/SOLUM.
&&
.AVIATION...
LIFR TO MVFR CONDITIONS WILL PERSIST AT KBIL AND MOST TERMINALS
EAST OF THERE. LOW CEILINGS IN A COLD SHALLOW AIR-MASS WILL BE THE
MAIN IMPACT. THROUGHOUT THE NIGHT CONDITIONS SHOULD IMPROVE FROM
LIFR TO IFR OR MVFR. KSHR WILL SEE SNOW SHOWERS THROUGHOUT THE NIGHT
BUT SHOULD REMAIN MVFR. KLVM SHOULD ALSO REMAIN MVFR TO VFR WITH
CEILINGS TONIGHT. MOUNTAIN OBSCURATIONS WILL CONTINUE ACROSS THE
AREA TO THE SHALLOWNESS OF THE COLD MOIST AIR-MASS. LEACH/SOLUM.
&&
.PRELIMINARY POINT TEMP/POPS...
THU FRI SAT SUN MON TUE WED
-----------------------------------------------------------
BIL 002/013 001/020 006/034 009/033 013/028 014/030 015/028
20/B 00/B 01/U 11/B 11/B 11/B 21/B
LVM 901/016 001/024 003/031 014/035 015/030 016/030 019/031
20/N 00/N 01/U 11/B 11/B 12/S 22/S
HDN 001/013 906/019 904/030 005/032 008/029 006/029 010/030
50/B 00/B 01/U 11/B 11/B 11/B 22/S
MLS 904/008 908/009 906/019 901/026 004/024 005/024 008/023
70/E 22/S 01/B 11/B 11/B 11/B 21/B
4BQ 902/009 904/017 902/023 002/030 004/028 005/028 008/030
93/S 22/S 01/B 11/B 11/B 11/B 21/B
BHK 906/006 907/011 904/016 000/025 005/023 005/021 007/025
83/S 32/S 21/B 11/B 11/B 11/B 21/B
SHR 002/012 902/021 901/028 006/032 003/030 004/032 007/029
82/S 02/S 01/U 12/S 12/S 22/S 22/S
&&
.BYZ WATCHES/WARNINGS/ADVISORIES...
MT...WINTER WEATHER ADVISORY IN EFFECT UNTIL 5 AM MST THURSDAY FOR
ZONES 33-36-37.
WY...NONE.
&&
$$
WEATHER.GOV/BILLINGS
