FXUS65 KBYZ 240411
AFDBYZ
AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE BILLINGS MT
911 PM MST WED DEC 23 2009
.SHORT TERM...VALID FOR THU AND FRI...
TROUGH AXIS ALOFT HAS PUSHED TO MILES CITY AREA THIS EVENING.
THERE IS STILL SOME LINGERING Q VECTOR FORCING PRODUCING LIGHT
SNOW EAST OF THIS AXIS...BUT WILL GRADUALLY SHIFT EAST BY
MIDNIGHT. THERE IS ALSO ANOTHER WEAK WAVE DROPPING SOUTH FROM
NORTH CENTRAL MONTANA INTO OUR CENTRAL ZONES THIS EVENING WHICH
MAY PRODUCE SOME LIGHT SNOW YET IN THE BILLINGS VICINITY...BUT
MORE LIKELY JUST SOME FLURRIES AND CLOUD COVER. IN
ADDITION...CALLS TO COUNTY OFFICIALS OUT EAST SUGGEST ANY BLOWING
OR DRIFTING SNOW PROBLEM IS MINIMAL. THEREFORE...WILL CANCEL
WINTER WEATHER ADVISORIES IN EAST.
MAIN CONCERN FOR THIS UPDATE PACKAGE IS POSSIBILITY OF WIND CHILL
ADVISORY CRITERIA IN THE EAST. OVERNIGHT LOWS WILL BE TRICKY DUE
TO WIDESPREAD BOUNDARY LAYER MOISTURE BATTLING WITH POCKETS OF
DRIER MID LEVEL AIR TRYING TO MIX IN WITH BRISK WINDS JUST OFF
SURFACE. SURFACE WINDS WILL DECREASE SOME OVERNIGHT IN THE EAST
WHICH MAY OFFSET SOME DROP IN TEMPS. IT APPEARS RIGHT NOW WE MAY
ONLY PUSH WIND CHILL CRITERIA IN FALLON AND CARTER COUNTIES AND
THIS IS WHERE WINDS LIKELY TO REMAIN BRISK INTO EARLY THURSDAY.
WILL ISSUE WIND CHILL ADVISORY IN THESE AREAS THROUGH MID MORNING
THURSDAY. WILL ALSO BE LOWERING FORECAST LOWS A BIT IN MANY AREAS.
BT
.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...
AS A WEAK DISTURBANCE MOVES THROUGH THE REGION OVERNIGHT...OCCASIONAL
SNOW SHOWERS AND MVFR CEILINGS AND VISIBILITY CAN BE EXPECTED FROM
THE KLVM AREA EASTWARD TO KBIL. OTHERWISE...MAINLY VFR CONDITIONS
CAN BE EXPECTED ACROSS THE REGION. ANOTHER DISTURBANCE DROPPING
SOUTHWARD WILL LIKELY BRING LIGHT SNOW AND MVFR CONDITIONS TO MOST
OF THE REGION...INCLUDING KMLS...KBIL AND KSHR BEGINNING LATE
THURSDAY MORNING. ALSO...AN INCREASING PRESSURE GRADIENT WILL
INCREASE WSW WINDS TO THE 25 TO 35 KT RANGE IN THE KLVM REGION BY
THURSDAY MORNING. MOUNTAIN OBSCURATIONS WILL CONTINUE ACROSS THE
AREA. CAMPBELL/TESAR.
&&
.PRELIMINARY POINT TEMP/POPS...
THU FRI SAT SUN MON TUE WED
-----------------------------------------------------------
BIL 903/013 001/020 006/034 009/033 013/028 014/030 015/028
30/B 00/B 01/U 11/B 11/B 11/B 21/B
LVM 002/016 001/024 003/031 014/035 015/030 016/030 019/031
30/N 00/N 01/U 11/B 11/B 12/S 22/S
HDN 901/013 906/019 904/030 005/032 008/029 006/029 010/030
30/B 00/B 01/U 11/B 11/B 11/B 22/S
MLS 907/008 908/009 906/019 901/026 004/024 005/024 008/023
30/E 22/S 01/B 11/B 11/B 11/B 21/B
4BQ 903/009 904/017 902/023 002/030 004/028 005/028 008/030
42/S 22/S 01/B 11/B 11/B 11/B 21/B
BHK 909/006 907/011 904/016 000/025 005/023 005/021 007/025
43/S 32/S 21/B 11/B 11/B 11/B 21/B
SHR 901/012 902/021 901/028 006/032 003/030 004/032 007/029
42/S 02/S 01/U 12/S 12/S 22/S 22/S
&&
.BYZ WATCHES/WARNINGS/ADVISORIES...
MT...WIND CHILL ADVISORY IN EFFECT UNTIL 10 AM MST THURSDAY FOR
ZONES 33-37.
WY...NONE.
&&
$$
WEATHER.GOV/BILLINGS
