High Wind in Wyoming, January 13, 2002

SOUTH CENTRAL AND SOUTHEAST MONTANA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BILLINGS MT
230 AM MST SUN JAN 13 2002

.SHORT TERM...VALID FOR TDY...MON...TUE...
DEEP UPPER LOW PUSHING ACROSS SOUTHERN SASKATCHEWAN AT THE MOMENT. THE
SURFACE REELECTION OF THIS ENERGY HAS A 995MB LOW MOVING INTO NORTHWEST
NORTH DAKOTA. STRONG INITIAL PUSH OF COLD FRONT PRODUCED VERY STRONG
WINDS OVER SOUTH CENTRAL MONTANA SATURDAY EVENING. THE STRONGEST WINDS
SHOULD PUSH INTO SOUTHEAST MONTANA AND SHERIDAN COUNTY WYOMING THIS
MORNING AND CONTINUE INTO EARLY AFTERNOON. SURFACE PRESSURE GRADIENT
WILL REMAIN STRONG. PREFERRED THE ETA MODEL FOR THIS EVENT BASED ON
WATER VAPOR AND STRENGTH OF THE SURFACE LOW MENTIONED ABOVE.

STRONG COLD AIR ADVECTION FROM 850-700MB TO BE OVER THE AREA TODAY.
POTENTIAL INSTABILITY WILL BE PRESENT UP TO 700MB INTO THE AFTERNOON.
ETA BRINGS 45KT WINDS AT 850MB INTO THE SOUTHEAST THIS MORNING WITH
60KTS AT 700MB. THESE TWO FORCES SHOULD BE ENOUGH TO VERIFY HIGH WIND IN
AT LEAST THE SUSTAINED CATEGORY WITH 40MPH. HIGH WIND GUSTS MAY BE
HARDER TO REACH BUT SHOULD BE CLOSE. LIMITING FACTOR WILL BE OMEGA OVER
THE AREA. POTENTIAL INSTABILITY SHOULD AID IN MIXING WINDS NEAR 850MB
WHICH WOULD PUT THE AREA UNDER HIGH WINDS. SURFACE PRESSURE GRADIENT
WILL SLACKEN UP THIS AFTERNOON...SO WILL WINDS SHOULD DIE DOWN THEN.
SOUTH CENTRAL WILL ALSO BE WINDY...BUT THE STRONGER WINDS ALOFT SHIFT
EAST THIS MORNING...SO WILL KEEP THEM OUT OF HIGH WIND WARNING. SHERIDAN
IS ONE OF THE BORDERLINE AREAS WITH BROAD LIFT THROUGH EARLY AFTERNOON.
CLOSE ENOUGH TO KEEP WARNING GOING HOWEVER. WILL ALSO INCLUDE SOUTHERN
BIG HORN COUNTY IN HIGH WIND WARNING AS SOME HIGHER TERRAIN IN THIS AREA
SHOULD GET THE SAME TYPE OF WINDS AS SHERIDAN. A SLUG OF MOISTURE WAS
SPREADING SOUTH OVER NORTHEAST MONTANA. WILL BREAK OFF THE NORTHERN PART
OF SOUTHEAST MONTANA WITH LIKELY POPS AND GO SCATTERED FARTHER SOUTH.
THE REST OF THE FORECAST AREA WILL BE UNDER SCATTERED POPS. WILL TRY TO
TIME THINGS OUT FOR HIGHS TODAY AS COLD AIR ADVECTION SHOULD PREVENT
MUCH RECOVERY.

SYSTEM MOVES EAST TONIGHT AND THE WINDS SHOULD DECREASE. NORTHWEST FLOW
TO SEND SHEARED VORTICITY THROUGH THE EAST THIS EVENING. THE ATMOSPHERE
DOES STABILIZE...BUT LINGERING LOWER LEVEL MOISTURE ALONG WITH WIND
SPEED CONVERGENCE IS ENOUGH TO MENTION A SLIGHT CHANCE OF SNOW SHOWERS.
WILL CONFINE THIS TO THE EAST AS SOUTH CENTRAL MONTANA DRIES OUT
QUICKER. ATTENTION THEN TURNS TO NEXT SYSTEM THAT IS FORECAST TO CUT OFF
OVER OREGON MONDAY. THIS SYSTEM IS HANDLED DIFFERENTLY BY THE MODELS.
THE ETA IS FARTHER NORTH AND THUS A LITTLE WETTER. THE AVN IS FARTHER
SOUTH AND EVENTUALLY SWINGS THE SYSTEM DOWN INTO SOUTHERN WYOMING BEFORE
SHEARING IT APART TUESDAY NIGHT AS NEW CUT OFF FORMS OVER CALIFORNIA.
WILL INTRODUCE SLIGHT POPS MONDAY NIGHT AND TUESDAY FOR SOUTH CENTRAL
MONTANA FOR THIS SYSTEM AS UPSLOPE DEVELOPS. WILL INCLUDE SCATTERED POPS
IN SHERIDAN AS WILL BE CLOSEST TO UPPER DIVERGENT PATTERN AS LOW SHIFTS
OUT OF IDAHO AND INTO WYOMING. WILL COOL TEMPERATURES THROUGH THE PERIOD
ON NORTHWEST FLOW. HUMPHREY

.LONG TERM...VALID FOR WED...THU...FRI...SAT...
MODELS CONTINUE TO SHOW MEAN UPPER LEVEL RIDGE SETTING UP OVER THE
EASTERN PACIFIC. THIS WILL PUT THE FORECAST AREA IN A NORTHERLY FLOW
ALOFT. AVN BRINGS A SHORT WAVE EMBEDDED IN THIS FLOW OVER THE WESTERN
AREAS OF THE BILLINGS FORECAST AREA ON WEDNESDAY. MODELS ARE NOT VERY
CONSISTENT BEYOND WEDNESDAY. NUMEROUS SHORTWAVES WILL BE MOVING THROUGH
THE NORTHERLY FLOW THURSDAY THROUGH SATURDAY BUT TIMING AND STRENGTH OF
WAVES WILL BE DIFFICULT. MRF MEAN ENSEMBLE REFLECTS THIS WITH VERY LOW
CONFIDENCE. WITH NORTHERLY FLOW SET UP OVER THE AREA THROUGH THE
PERIOD...TEMPERATURES SHOULD BE SLIGHTLY BELOW NORMAL AND WILL MAKE
ADJUSTMENTS FOR WEDNESDAY AND THURSDAY. WILL NOT MAKE ANY CHANGES FOR
THURSDAY AND FRIDAY DUE TO MODEL UNCERTAINTY. RICHMOND

    TDY MON     TUE     WED     THU     FRI     SAT
-------------------------------------------------------
BIL 038 018/030 012/022 020/028 025/030 025/035 024/037
    3/N 00/E    22/J    20/B    02/E    23/J    22/E
LVM 037 015/028 010/022 016/026 022/029 020/030 021/035
    3/N 00/E    22/J    22/B    22/E    23/J    22/E
HDN 038 016/030 010/022 018/027 023/030 021/036 022/038
    3/N 00/E    22/J    20/B    02/E    23/J    22/E
MLS 037 017/029 009/021 018/025 018/029 023/033 021/035
    6/N 20/E    00/B    20/B    02/E    23/J    22/E
4BQ 037 017/029 009/021 019/024 019/028 025/034 022/036
    4/N 20/E    00/B    20/B    02/E    23/J    22/E
BHK 035 015/027 007/019 016/022 016/027 018/030 018/032
    6/N 20/E    00/B    20/B    02/E    23/J    22/E
SHR 038 014/027 008/019 018/029 023/035 023/033 022/035
    3/N 00/E    23/J    20/B    02/E    23/J    22/E

.BYZ...HIGH WIND WARNING TODAY FOR A SMALL PART OF SOUTH CENTRAL MONTANA
       ALL OF SOUTHEAST MONTANA AND SHERIDAN COUNTY WY.