FXUS65 KBYZ 071022
AFDBYZ
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BILLINGS MT
322 AM MST MON DEC 7 2009
.SHORT TERM...VALID FOR TDY AND TUE...
ARCTIC AIR CONTINUES TO BE DRAWN IN WITH LOW SURFACE PRESSURE
OVER UTAH AND IDAHO. TEMPERATURES HAVE FALLING BELOW ZERO FOR
MOST LOCATIONS AND THERE WILL BE A STRUGGLE TO RECOVER ANY TODAY.
LOW LEVEL COLD ADVECTION WILL CONTINUE THIS MORNING WITH NEUTRAL
ADVECTION THIS AFTERNOON. 850MB TEMPERATURES OF -20C WILL BE OVER
THE ENTIRE AREA. CLOUDS WILL BE PRESENT ALL DAY TODAY AND THIS
WILL PREVENT MUCH WARMING FROM THE SUN. WILL BE THE COLDEST DAY
OF THE SEASON TODAY. GUSTY WINDS OVER THE FAR WEST AND NORTHWEST
ZONES HAVE DECREASED BELOW 10MPH. WINDS SHOULD STAY BELOW 10MPH
THE REST OF THE DAY...SO WILL DROP WIND CHILL ADVISORY. MID LEVEL
WARM AIR ADVECTION WAS PRODUCING PERSISTENT LIGHT SNOW OVER
CENTRAL AND WESTERN ZONES. EXPECT THIS TO CONTINUE THIS MORNING
SO RAISED POPS TO LIKELY. SNOW WILL BE VERY LIGHT WITH SUCH A
COLD AIRMASS...A HALF INCH EVERY 12 HOURS OR SO. 500MB FLOW TURNS
SOUTHWEST THIS AFTERNOON AND THIS SHOULD CUT DOWN ON THE COVERAGE
OF LIGHT SNOW.
AN UPPER TROUGH MOVES ACROSS MONTANA TONIGHT AND HEIGHTS FALL TO
AROUND 525DM. A SURFACE LOW WILL DEEPEN OVER UTAH AND CONTINUE
THE PULL OF ARCTIC AIR SOUTHWARD. TONIGHT WILL BE THE COLDEST
NIGHT. CLOUDS WILL HELP TO KEEP READINGS UP...BUT LOWS WILL STILL
BE 10 TO 20 BELOW ZERO ACROSS MOST OF THE AREA...WITH THE COLDEST
LOWS OVER THE WESTERN THIRD OF THE FORECAST AREA. WILL HAVE TO
WATCH WIND CHILLS TONIGHT FOR A POTENTIAL ADVISORY AS THE SURFACE
LOW TO THE SOUTH WRAPS UP AND PRODUCES INCREASING GRADIENTS FOR
EAST AND NORTHEAST WINDS OVER MAINLY THE SOUTHERN AND EASTERN
ZONES. WILL LET THE DAY CREW TAKE A CLOSER LOOK AT THIS...BUT AN
ADVISORY MAY BE NEEDED. A BATCH OF LIGHT SNOW WILL SPREAD ACROSS
THE SOUTHEAST HALF OF THE FORECAST AREA AS THE UPPER TROUGH MOVES
ACROSS THE STATE. RAISED POPS SOME.
TUESDAY WILL BE ANOTHER BITTERLY COLD DAY WITH THE ARCTIC AIR
SITTING RIGHT OVER THE STATE. TEMPERATURES WILL BE STARTING OUT
WELL BELOW ZERO. LOW LEVELS WILL NOT GET INTO DOWNSLOPE MODE
UNTIL TUESDAY NIGHT...SO THE ATMOSPHERE WILL NOT BE ABLE TO MIX
THE ARCTIC OUT. HIGHS WILL BE HARD PRESSED TO GET ABOVE ZERO
AGAIN ON TUESDAY. ALL THINGS CONSIDERED...LOWERED HIGHS A BIT.
THE ARCTIC HIGH SHIFTS EAST TUESDAY NIGHT AND SETS UP LOW LEVEL
DOWNSLOPE GRADIENTS. THE ARCTIC WILL TRY TO SHALLOW AND PUSH EAST
WITH INCREASING WEST WINDS. MAY NEED A WIND CHILL ADVISORY FOR
TUESDAY NIGHT IN THIS SCENARIO. HUMPHREY
.LONG TERM...VALID FOR WED...THU...FRI...SAT...SUN...
VERY FEW CHANGES MADE TO THE EXTENDED FORECAST THIS MORNING AS
MODELS IN GOOD AGREEMENT EARLY ON BUT THEN DIVERGE TOWARDS THE
WEEKEND.
ARCTIC AIR TO REMAIN OVER THE FORECAST AREA ON WEDNESDAY AND
THURSDAY WITH TEMPERATURES IN THE SINGLE DIGITS AND TEENS. MODELS
HAVE TRENDED COLDER WITH THESE TWO DAYS AND HAVE TRENDED THE
FORECAST A LITTLE COOLER AS A RESULT. UNSTABLE NORTHWEST FLOW
OVER THE AREA AS WELL DURING THIS PERIOD AND KEPT SLIGHT CHANCE
POPS GOING FOR NOW. FRIDAY DOES LOOK A LITTLE WARMER AS MODELS
SHIFT THE COLDER AIR FURTHER EAST. DIFFERENCES IN THE MODELS SHOW
UP ON SATURDAY AND SUNDAY AS THE ECMWF BRINGS ANOTHER ARCTIC
BLAST INTO THE AREA WHICH WOULD BRING TEMPS BACK INTO AT LEAST
THE SINGLE DIGITS IF NOT COLDER. THE GFS HOWEVER ACTUALLY WARMS
THINGS UP A LITTLE MORE INTO THE 20S AND LOW 30S. SO THIS IS
QUITE A BIG DIFFERENCE BETWEEN THE MODELS. HAVE KEPT THE WARMER
TREND WE HAVE BEEN GOING WITH THE PAST FEW DAYS FOR NOW AND WILL
CONTINUE TO MONITOR THE MODELS OVER THE NEXT FEW DAYS. SOLUM
&&
.AVIATION...
LIGHT SNOW WILL CONTINUE ACROSS MUCH OF THE FORECAST TODAY.
EXPECT WIDESPREAD MVFR CONDITIONS WITH IFR CONDITIONS IN AND
AROUND AREAS OF HEAVIER SNOWFALL. LOCAL MOUNTAIN RANGES WILL ALSO
REMAIN OBSCURED THROUGH THE DAY. SOLUM
&&
.PRELIMINARY POINT TEMP/POPS...
TDY TUE WED THU FRI SAT SUN
-------------------------------------------------------
BIL 000 912/000 908/011 903/017 002/017 012/027 018/031
6/S 44/S 02/S 22/S 22/S 20/B 00/B
LVM 901 918/002 909/011 902/018 001/024 015/031 018/034
5/S 32/S 02/S 22/S 22/S 22/S 22/S
HDN 004 911/006 909/016 902/021 901/023 006/030 009/031
6/S 44/S 02/S 22/S 22/S 20/B 00/B
MLS 007 911/004 910/012 906/015 906/014 001/025 006/022
2/S 34/S 02/S 22/S 22/S 20/B 00/B
4BQ 007 907/008 911/014 906/019 902/021 005/030 009/034
3/S 65/S 02/S 22/S 22/S 20/B 00/B
BHK 005 910/006 911/012 904/015 902/016 004/023 008/023
1/E 24/S 02/S 22/S 22/S 20/B 00/B
SHR 005 910/007 911/013 906/020 905/025 005/031 009/034
4/S 54/S 02/S 22/S 22/S 20/B 00/B
&&
.BYZ WATCHES/WARNINGS/ADVISORIES...
MT...NONE.
WY...NONE.
&&
$$
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