000
FXUS65 KBYZ 272205
AFDBYZ
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BILLINGS MT
305 PM MST MON DEC 27 2010
.SHORT TERM...VALID FOR TUE AND WED...
FORECAST CHALLENGES CONTINUE TO BE THE NEXT WINTER STORM TO MOVE
INTO THE AREA WEDNESDAY AND CONTINUE THROUGH THURSDAY. LEE-SIDE
TROUGHING WILL DEVELOP TONIGHT AS HIGH PRESSURE WILL BUILD OVER
SOUTHEAST IDAHO WHILE A SURFACE LOW WILL MOVE ACROSS SOUTHERN
BRITISH COLUMBIA. THIS WILL RESULT IN PRESSURE GRADIENTS
TIGHTENING AND ORIENTING THEMSELVES IN A FAVORABLE POSITION FOR
STRONG WINDS THROUGH THE EASTERN FOOTHILLS OF THE
BEARTOOTH/ABSAROKA MOUNTAINS SUCH AS LIVINGSTON AND NYE. LOOK FOR
WINDS TO INCREASE BY OR SHORTLY AFTER MIDNIGHT TONIGHT AND
CONTINUE THROUGH TUESDAY NIGHT. HOWEVER...BELIEVE IT WILL BE
CLOSER TO A 12 HOUR PERIOD WITH THE STRONGEST WINDS MORE IN THE
12Z TUESDAY THROUGH 06Z WEDNESDAY TIME FRAME. WIND ADVISORY FOR
THESE LOCATIONS WAS ISSUED EARLIER THIS MORNING.
UPCOMING WINTER STORM BEGINS TO ARRIVE ACROSS THE WESTERN ZONES
LATE TUESDAY NIGHT INTO WEDNESDAY MORNING. SURFACE LOW WITH AN
ASSOCIATED COLD FRONT WILL BLAST THROUGH THE WEST AND NORTHWEST
ZONES WEDNESDAY MORNING WHICH WILL BREAK THE STABLE LAYER ABOVE
LIVINGSTON RESULTING IN THE STRONG WINDS TO DECREASE. THIS LOW
AND COLD FRONT WILL MOVE EAST/SOUTHEAST AND BE THROUGH THE FAR
EASTERN PLAINS BY LATE AFTERNOON THEN BE POSITIONED OVER THE
GILLETTE AREA BY WEDNESDAY EVENING. AS THE LOW PASSES...EXPECT
GUSTY NORTH TO NORTHWEST WINDS ACROSS ALL OF THE PLAINS. A STRONG
FRONTOGENESIS BAND WILL ACCOMPANY THE FRONT AND BE MAINLY SET UP
ALONG A SHERIDAN TO BILLINGS LINE. STRONG DYNAMICS WILL ACCOMPANY
ALONG AND BEHIND THE FRONT AS TIME HEIGHTS SHOW A QUITE UNSTABLE
ATMOSPHERE LATE WEDNESDAY AFTERNOON THROUGH WEDNESDAY NIGHT FOR
MOST LOCATIONS ACROSS SOUTH CENTRAL AND SOUTHEAST MONTANA.
CONFIDENCE IS HIGH THAT MOST AREAS ON THE PLAINS WILL SEE 2 TO 4
INCHES. HOWEVER...HIGHER AMOUNTS ARE LIKELY ESPECIALLY THE RED
LODGE AREA WHICH WILL NEED TO BE MONITORED. CONFIDENCE IS ALSO
HIGH THAT ADVISORY AMOUNTS WILL BE MET AND POSSIBLY SOME WARNING
CRITERIA AS WELL. HOWEVER...EXACT LOCATIONS FOR HIGHER AMOUNTS
REMAINS UNCERTAIN. HAVE DECIDED TO HOLD OFF ON ANY HIGHLIGHTS AT
THIS TIME AS TIME STILL ALLOWS FOR SOME MORE EXACT LOCATIONS FOR
SNOW AMOUNTS. HOWEVER...WILL BE SENDING OUT A NOTIFICATION EMAIL
TO DES AND COUNTY CONTACTS. TEMPERATURES WEDNESDAY MORNING ARE
EXPECTED TO BE FAIRLY MILD AROUND FREEZING THEN FALL THROUGHOUT
THE DAY WHICH WILL RESULT IN SLUSHY ROADS QUICKLY FREEZING. WILL
CONTINUE TO FINE TUNE WITH LATER SHIFTS. HOOLEY
.LONG TERM...VALID FOR THU...FRI...SAT...SUN...MON...
THE EXTENDED STARTS OUT UNDER AN UPPER LEVEL LOW THAT EXITS
THE REGION THURSDAY WITH THE HEAVIEST PRECIPITATION TO THE EAST OVER
THE DAKOTAS. GFS CURRENTLY INDICATES A DESCENDING DRY-SLOT OVER
EXTREME SOUTHEAST MONTANA WITH LIGHT PRECIPITATION ACROSS THE
EASTERN HALF OF THE CWA. THE ECMWF IS MUCH SLOWER AND WETTER
PULLING THE SYSTEM OUT...WITH PRECIPITATION ENDING FRIDAY EVENING.
LEFT SLIGHT CHANCE POPS IN THE EAST ON FRIDAY EVENING TO ACCOUNT
FOR THE DIFFERENCE IN THE MODELS.
HIGH PRESSURE BUILDS IN BEHIND WITH COLD AIR AND EVENTUALLY ANCHORS
OVER EASTERN IDAHO AND WESTERN WYOMING WITH WEAK DOWNSLOPE FLOW
COMING INTO THE AREA. THE REMAINDER OF THE EXTENDED LOOKS
RELATIVELY DRY AFTER SNOW CEASES BY FRIDAY MORNING. THE AREA REMAINS
UNDER NORTHWEST FLOW WITH SHORTWAVES ALOFT...BUT AS OF YET NONE OF
THE SHORTWAVES TARGET THE CWA WITH ANY SIGNIFICANT MOISTURE. MODELS TRY
TO WARM THE FORECAST SIGNIFICANTLY BY THE END OF SATURDAY...BUT IT IS
MORE LIKELY THAT COLD AIR WILL PERSIST BENEATH THE SOUTHWEST FLOW
SINCE THERE IS NEVER A STRONG PUSH THAT COULD CLEAN IT OUT. WINDS
ARE A CONCERN WITH THE HIGH PRESSURE OVER WYOMING AND
IDAHO...HOWEVER A LEESIDE TROUGH NEVER DEVELOPS TO REALLY TIGHTEN
THE GRADIENT. LEACH
&&
.AVIATION...
VFR AND WINDY CONDITIONS EXPECTED ACROSS THE AREA TONIGHT. GUSTY
SOUTHWEST WINDS WITH GUSTS OF 40 KNOTS OR MORE WILL IMPACT KLVM
AND THE BEARTOOTH FOOTHILLS THIS EVENING AND INCREASE TO OVER 50
KNOTS TONIGHT. WINDS WILL BE GUSTY BUT WEAKER FARTHER EAST WITH
GUSTS FROM 20 TO 30 KNOTS AT KMLS AND ON THE PLAINS. LOW LEVEL
WIND SHEAR IS A CONCERN AT KMLS AND EASTERN TERMINALS WHERE
SURFACE WINDS WILL DECREASE TO 5 TO 15 KNOTS AT TIMES WITH 35
KNOTS OR GREATER AT 2000 FEET. LOW CLOUDS AND ISOLATED SNOW
SHOWERS WILL CAUSE PARTIAL MOUNTAIN OBSCURATIONS. LEACH
&&
.PRELIMINARY POINT TEMP/POPS...
TUE WED THU FRI SAT SUN MON
-----------------------------------------------------------
BIL 021/037 024/031 010/011 905/007 902/017 007/024 014/028
01/N 26/S 88/S 33/S 11/B 11/B 11/B
LVM 022/036 024/031 008/010 907/008 904/014 000/021 008/025
12/W 46/S 88/S 32/S 11/B 11/B 11/B
HDN 019/038 023/034 011/012 905/009 906/017 002/023 008/029
00/B 24/O 68/S 33/S 11/B 11/B 11/B
MLS 016/034 017/029 009/008 910/003 908/012 000/018 009/024
00/B 16/S 68/S 43/S 21/E 11/B 11/B
4BQ 018/039 020/034 009/007 906/005 904/015 003/022 007/028
00/B 12/S 46/S 43/S 21/B 11/B 11/B
BHK 014/034 014/031 006/010 909/003 908/009 000/016 006/023
00/B 16/S 77/S 44/S 21/B 11/B 11/B
SHR 013/037 018/034 010/011 906/009 905/017 003/026 009/030
00/B 12/S 48/S 42/S 11/B 11/B 11/B
&&
.BYZ WATCHES/WARNINGS/ADVISORIES...
MT...WIND ADVISORY IN EFFECT FROM MIDNIGHT TONIGHT TO 6 AM MST
WEDNESDAY FOR ZONES 65-66.
WY...NONE.
&&
$$
WEATHER.GOV/BILLINGS
