FXUS65 KBYZ 080343
AFDBYZ
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BILLINGS MT
843 PM MST MON DEC 7 2009
.SHORT TERM...VALID FOR TUE AND WED...
A VERY LIGHT SNOW SPREADING/EXPANDING NORTHWARD OUT OF SOUTHEAST
IDAHO AND WYOMING THIS EVENING. COLDER IR TOPS AND EXPANSION OF
RADAR ECHOES INDICATIVE OF THE BACKING WINDS/WARM ADVECTION THAT
HAS DEVELOPED OVER THE PAST FEW HOURS. DESPITE THE WARM
ADVECTION...ARCTIC AIR IS FIRMLY ENTRENCHED ACROSS THE AREA...AND
WITH NO DENDRITIC LAYER TO SPEAK OF THE SNOW WILL REMAIN VERY
LIGHT. COULD NONETHELESS SEE UP TO A HALF INCH OR SO TONIGHT...
INCLUDING AT BILLINGS WHERE THE SNOW SHOULD PERSIST INTO TUESDAY.
HAVE OPTED TO RAISE POPS ABOVE FLURRY LEVEL FOR MUCH OF THE
AREA...AND HAVE ALSO UPPED POPS IN OUR EAST TOMORROW AS ENERGY
SPREADS EASTWARD. WATER VAPOR CLEARLY SHOWS ENERGY MOVING
SOUTHWARD THRU THE PAC NW ON BACK SIDE OF LONGWAVE TROF...ALLOWING
FOR GREAT BASIN ENERGY TO LIFT AND AFFECT US...GIVING CONFIDENCE
TO INCREASE POPS. MODELS ALSO SEEM TO HAVE A HANDLE ON THIS
SCENARIO.
OTHERWISE THE MAIN STORY IS THE CONTINUED COLD. COLDEST PART OF
CWA TONIGHT WILL BE OUR FAR NW WHERE LIGHT PCPN SHOULD AVOID AND
SKIES MAY STAY MOSTLY CLEAR. CURRENT OBSERVATIONS SHOW TEMPS
ALREADY IN THE MINUS TEENS AT WILSALL...LIVINGSTON AND JUDITH
GAP...WITH NEAR -20F OVER THE MTNS. SO HAVE DROPPED EXPECTED LOWS
A BIT IN OUR WEST. CLOUDS/SNOWFALL WILL KEEP THINGS SOMEWHAT IN
CHECK TO OUR EAST AND HAVE RAISED TEMPS A TAD THERE. BRRR.
UPDATE COMING SHORTLY.
JKL
.LONG TERM...VALID FOR THU...FRI...SAT...SUN...MON...
MODELS IN GOOD AGREEMENT WITH EACH OTHER IN BRINGING A COLDER
ARCTIC BLAST ACROSS THE FORECAST AREA THIS WEEKEND. 00Z EC SHOWED
ANOTHER ARCTIC BLAST FOR THIS WEEKEND BUT THE 00Z GFS WAS
ACTUALLY RETREATING THE CURRENT ARCTIC AND BRINGING WARMER
TEMPERATURES. HOWEVER...THE 12Z GFS IS NOW IN LINE WITH THE 12Z
EC IN AGREEMENT WITH A SECOND ARCTIC SURGE. AS A
RESULT...CONFIDENCE IS HIGHER NOW IN MUCH COLDER TEMPERATURES FOR
THE WEEKEND SO HAVE LOWERED SATURDAY AND SUNDAY HIGHS SEVERAL
DEGREES. HOWEVER...THIS PROBABLY IS STILL NOT COLD ENOUGH BUT
DIDN'T WANT TO GO TOO DRAMATIC THIS FAR OUT. IN ANY CASE...DID
LOWER HIGHS AND LOWS FOR THE WEEKEND A GOOD 5 TO 8 DEGREES ACROSS
THE BOARD. IN THE MEANTIME...A COLD NORTHERLY FLOW WILL CONTINUE
THURSDAY AND FRIDAY WITH ONLY A SLOW MODERATION IN TEMPERATURES.
WILL CONTINUE WITH A SLIGHT CHANCE OF FLURRIES EACH DAY DUE TO
WARM AIR ALOFT OVERRUNNING COLD ARCTIC AIR AT THE SURFACE. BEST
CHANCE FOR SNOW WILL BE SATURDAY INTO SUNDAY WITH INCOMING ARCTIC
FRONT ALONG WITH POSSIBLE OVERRUNNING MOISTURE MOVING IN FROM THE
PACIFIC NORTHWEST. HOOLEY
&&
.AVIATION...
MVFR TO IFR CONDITIONS WILL BE COMMON THROUGHOUT THE NIGHT FROM
KBIL AND KSHR EASTWARD WITH SOME VFR CONDITIONS EXPECTED NEAR
KLVM. A DISTURBANCE LIFTING OUT OF WYOMING WILL PRODUCE LOW
CEILINGS AND LIGHT SNOW ACROSS SOUTHEAST MONTANA THROUGH MID-DAY
TUESDAY. SNOW IS EXPECTED TO LIGHTEN UP AFTER 18Z ACROSS MUCH OF
THE REGION AS A TROUGH APPROACHES FROM THE NORTHWEST. MOUNTAIN
OBSCURATIONS ARE LIKELY THROUGH THE PERIOD. CAMPBELL/LESTER
&&
.PRELIMINARY POINT TEMP/POPS...
TUE WED THU FRI SAT SUN MON
-----------------------------------------------------------
BIL 912/902 909/006 905/015 001/017 012/023 014/027 018/031
12/J 02/J 22/J 22/J 22/S 22/S 11/B
LVM 918/000 910/006 904/016 000/024 015/027 014/030 018/034
22/J 02/J 22/J 22/J 22/S 22/S 22/J
HDN 911/004 910/011 904/019 902/023 006/026 005/027 010/031
13/J 02/J 21/E 11/B 22/S 22/S 21/B
MLS 911/002 911/007 908/013 907/014 001/021 002/018 007/022
13/J 02/J 21/E 11/B 22/S 22/S 11/B
4BQ 907/006 912/009 908/017 903/021 005/026 005/030 008/034
65/J 02/J 21/B 21/B 11/B 11/B 11/B
BHK 910/004 912/007 907/013 903/016 004/019 004/020 007/023
24/J 02/J 21/B 11/B 22/S 21/B 11/B
SHR 910/005 912/008 908/018 906/025 005/027 005/030 009/034
44/J 02/J 22/J 22/J 11/B 12/S 12/J
&&
.BYZ WATCHES/WARNINGS/ADVISORIES...
MT...NONE.
WY...NONE.
&&
$$
WEATHER.GOV/BILLINGS
