FXUS65 KBYZ 051531
AFDBYZ
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BILLINGS MT
831 AM MST SAT DEC 5 2009
.SHORT TERM...VALID FOR TDY AND SUN...
MINOR UPDATE THIS MORNING TO WARM DAYTIME HIGHS...MAINLY IN THE
WEST THIS MORNING. WARM OVERNIGHT TEMPERATURES AND A FEW BREAKS IN
THE CLOUDS WILL ALLOW FOR SLIGHTLY WARMER TEMPS EARLY THIS MORNING
BEFORE THE COLD FRONT GETS INTO THE REGION. GILSTAD
...PREVIOUS DISCUSSION...
CURRENT FORECAST LOOKED IN REAL GOOD SHAPE AND DID NOT NEED TO
ADJUST MUCH. DEEP UPPER TROUGH WAS PUSHING INTO MONTANA THIS
HOUR. THE FORECAST AREA WAS STILL ON THE SOUTH SIDE OF THE LOW
AND UNDER THE INFLUENCE OF MID LEVEL DOWNSLOPE FLOW...SO NOT MUCH
HAPPENING AT THE MOMENT. THAT WILL CHANGE QUICKLY THIS MORNING.
AS THE UPPER TROUGH ADVANCES SOUTHWARD...THE FORECAST AREA WILL
LOOSE THE DOWNSLOPE INFLUENCES AND START TO GET INTO THE DEEP
ISENTROPIC LIFT CURRENTLY OVER NORTHERN MONTANA. SNOW HAS BEEN
FALLING FOR SEVERAL HOURS AT GREAT FALLS. KBLX RADAR SHOWING SOME
WEAK RETURNS MOVING INTO WHEATLAND COUNTY WITH LIGHT SNOW
REPORTED AT LEWISTOWN. THE SNOW WILL SPREAD IN THIS MORNING. THE
STRONGEST LIFT AND BEST INSTABILITY CORRELATED WITH THE BEST
DENDRITE GROWTH ZONE LOOKS TO BE THIS AFTERNOON AND EVENING. THIS
LINES UP WELL WITH THE ADVISORY AND WILL NOT CHANGE. WILL KEEP
THE WARNING IN PLACE FOR WHEATLAND COUNTY AS CUT BANK HAS BEEN
GUSTING TO 45 MPH OVERNIGHT AND THE PUSH OF COLD AIR SHOULD
CHANNEL THROUGH THE GAP QUITE READILY TODAY. WOULD EXPECT WINDS
TO BACK OFF TONIGHT AS THE ARCTIC SETTLES IN. SNOW AMOUNTS LOOK
REAL GOOD AND WILL NOT CHANGE. AREAS TO THE WEST WILL HAVE THE
BEST CHANCE OF HEAVIER ACCUMULATIONS AS THE STRONGEST FORCING IS
DIRECTED THERE. DAY CREW WILL HAVE TO KEEP A CLOSE WATCH ON THIS.
HIGHS TODAY WILL BE TRICKY WITH THE WARMEST AIR OVER THE AREA
THIS MORNING. STEADY TO SLOWLY FALLING TEMPERATURES ARE EXPECTED
THROUGH THE DAY AND TRIED TO REFLECT THAT IN THE GRIDS. THE
ARCTIC AIR PUSHES INTO THE AREA IN ERNEST TONIGHT. THE MID LEVELS
COOL DOWN DRAMATICALLY AND THIS PUTS THE STRONG DENDRITE GROWTH
ZONE ALL BELOW 750MB...WHICH IS PRETTY SHALLOW. WOULD EXPECT THE
SNOW FLAKES TO BECOME PRETTY SMALL AND DIMINISH ACCUMULATION
ABILITY OVERNIGHT TONIGHT. CLOUDS WILL HELP TO KEEP LOWS UP SOME
OVERNIGHT BUT WILL STILL HAVE READINGS FALLING TOWARD ZERO.
SUNDAY LOOKS QUITE CHILLY WITH HIGHS IN THE LOWER SINGLE DIGITS.
WEAK MID LEVEL WARM ADVECTION WILL BE OVER SOUTHERN MONTANA AND
NORTHERN WYOMING WITH 500MB FLOW TURNING SOUTH AS AN UPPER LOW
CUTS OFF OVER SOUTHERN OREGON. WOULD EXPECT CLOUDS AND LIGHT
SNOW...BUT NOT MUCH ACCUMULATION...PROBABLY ANOTHER INCH.
TEMPERATURES WILL NOT MOVE MUCH THROUGH THE DAY.
THE UPPER TROUGH DEEPENS OVER THE STATE SUNDAY NIGHT AS THE MAIN
LOW DROPS TOWARD SOUTHERN NEVADA. THIS WILL PULL THE COLDEST AIR
INTO THE FORECAST AREA WITH 850MB TEMPERATURES OF AROUND -20C
MOVING IN. LOWS WILL BE WELL BELOW ZERO. CLOUDS WILL STICK AROUND
WITH WEAK WARM AIR ADVECTION AT THE MID LEVELS AND THIS WILL
PREVENT READINGS FROM FALLING TOO FAR. THE AFOREMENTIONED WARM
AIR ADVECTION WILL KEEP LIGHT SNOW GOING SUNDAY NIGHT WITH
LIMITED ACCUMULATIONS. WOULD EXPECT THE LIGHT SNOW TO TAPER OFF
SOME LATE SUNDAY NIGHT AS THE 500MB FLOW VEERS TO THE SOUTHWEST
WITH THE UPPER LOW HEADING TOWARD NEVADA. HUMPHREY
.LONG TERM...VALID FOR MON...TUE...WED...THU...FRI...
MADE VERY FEW CHANGES TO THE EXTENDED FORECAST AS MODELS CONTINUE
TO BE IN FAIRLY GOOD AGREEMENT. GENERAL TROUGHINESS REMAINS OVER
THE FORECAST AREA ON MONDAY AND TUESDAY WITH THE BULK OF THE
ENERGY OVER THE FOUR CORNERS REGION. SOUTHERLY WINDS ALOFT DURING
THIS PERIOD WILL BRING WARM AIR ADVECTION TO THE REGION AND BRING
OVERRUNNING PRECIP. THE PRECIP LOOKS FAIRLY LIGHT BUT DID RAISE
POPS A LITTLE FOR THESE PERIODS GIVEN THESE DYNAMICS. TROUGH
SHIFTS OUT BY WEDNESDAY LEAVING A NORTHWEST FLOW OVER THE AREA
THROUGH THE END OF THE WEEK. HAVE KEPT IN LOW POPS FOR THESE
PERIODS...MAINLY OVER THE HIGHER ELEVATIONS.
TEMPERATURES CONTINUE TO LOOK VERY COLD FOR THIS PERIOD AND HAVE
ACTUALLY TRENDED DOWN TEMPS A LITTLE BIT FOR MONDAY AND TUESDAY.
TEMPS DO LOOK TO WARM A LITTLE BIT BY THE END OF NEXT WEEK AS
FLOW TURNS MORE SOUTHWESTERLY AT THE LOW LEVELS. SOLUM
&&
.AVIATION...
SNOW WILL CONTINUE TO INCREASE AND CEILINGS WILL CONTINUE TO LOWER ACROSS
THE REGION THROUGH THE DAY. EXPECT WIDESPREAD IFR CONDITIONS AND
MOUNTAIN OBSCURATIONS ACROSS MUCH OF THE REGION BY THIS AFTERNOON
AND CONTINUING INTO TONIGHT. GUSTY WINDS WILL ALSO CREATE AREAS OF
BLOWING SNOW AND REDUCED VISIBILITIES. FRIEDERS
&&
.PRELIMINARY POINT TEMP/POPS...
TDY SUN MON TUE WED THU FRI
-------------------------------------------------------
BIL 025 001/003 910/901 912/000 905/012 005/024 015/027
+/S +6/S 44/S 44/S 22/S 11/B 11/B
LVM 021 904/004 917/901 918/002 906/017 007/028 016/030
+/S +6/S 44/S 43/S 22/S 22/S 22/S
HDN 026 003/008 910/005 905/007 905/017 003/025 009/029
+/S +6/S 33/S 44/S 22/S 11/B 11/B
MLS 023 901/009 909/006 911/004 907/010 901/020 006/022
4/S 43/S 22/S 44/S 21/B 11/B 11/B
4BQ 026 002/011 906/009 905/010 906/014 001/026 007/029
5/S 64/S 22/S 44/S 21/B 11/B 11/B
BHK 021 001/009 908/007 906/005 907/013 000/021 007/022
3/S 32/S 22/S 33/S 11/B 11/B 11/B
SHR 023 002/008 910/007 908/008 908/018 901/028 006/031
8/S +6/S 34/S 44/S 22/S 22/S 22/S
&&
.BYZ WATCHES/WARNINGS/ADVISORIES...
MT...WINTER STORM WARNING IN EFFECT UNTIL 5 AM MST SUNDAY FOR
ZONES 28-63.
WINTER WEATHER ADVISORY IN EFFECT UNTIL 5 AM MST SUNDAY FOR
ZONES 29-34-35-38>42-56-57-64>66.
WY...WINTER WEATHER ADVISORY IN EFFECT UNTIL 5 AM MST SUNDAY FOR
ZONES 98-99.
&&
$$
WEATHER.GOV/BILLINGS
