High Wind in Montana, March 31, 2015

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE BILLINGS MT
812 PM MDT TUE MAR 31 2015

.UPDATE...
COLD FRONT MOVED THROUGH LEWISTOWN AND LIVINGSTON LAST HOUR.
CURRENT TIMING SHOULD TAKE IT THROUGH BILLINGS AROUND 9 PM. DRY
LOW LEVELS HAVE SEVERELY LIMITED POP POTENTIAL WITH DEWPOINTS IN
THE TEENS AND 20S. MID LEVEL INSTABILITY CERTAINLY PRESENT AS
EVIDENCED ON SATELLITE IMAGERY AND FORECAST SOUNDINGS. HRRR
MAINTAINS SOME WEAK CAPE THROUGH THE EVENING AND THIS MAY BE ABLE
TO BE TAPPED INTO AFTER FRONTAL PASSAGE...SO WILL LEAVE POPS AND
MENTION OF ISOLATED THUNDER AS IS.

COLD FRONT WILL SWITCH WINDS TO THE NORTHWEST AS IT MOVES THROUGH
AND PRODUCE SOME GUSTS TO 35 MPH. THIS HANDLED WELL IN CURRENT
FORECAST PACKAGE. EVERYTHING LOOKS IN GOOD ENOUGH SHAPE. NO
CHANGES. TWH

&&

.SHORT TERM...VALID FOR WED AND THU...

AREAS OF FAIRLY THICK HIGH CLOUD HAVE KEPT OUR TEMPS AND MIXED
WINDS A BIT IN CHECK SO FAR THIS AFTERNOON...THOUGH AS OF 2 PM
TEMPS ARE IN THE UPPER 60S TO MID 70S. LATEST VISIBLE IMAGERY
SHOWS MTN WAVE CLOUDS CONTINUING TO DEVELOP IN THE LEE OF THE
BEARTOOTH ABSAROKAS IN SW FLOW ALOFT. THIS COULD HINDER OUR
PREFRONTAL TSTM POTENTIAL AS WELL...BUT WILL SUSTAIN ISOLD WORDING
INTO THE EVENING AS THE HRRR AND NAM HAVE BEEN HINTING AT. LOOKING
WEST...COLD FRONT IS CURRENTLY A LITTLE EAST OF MISSOULA WITH
PRESSURE FALLS IN EXCESS OF 1MB/HR NOTED FROM SALMON TO BUTTE AND
HELENA. SOME WEAK CONVECTION IS TRYING TO DEVELOP IN THIS AREA.

FRONT WILL PUSH INTO OUR WEST THIS EVENING. TIMING DEPICTED BY
MODELS IS A BIT SLOWER THAN PREVIOUSLY THOUGHT THOUGH PRESSURE
FIELDS ARE SOMEWHAT MUDDLED BY THE CONVECTION. H3 JET IS PARALLEL
TO FRONT IN CENTRAL MT WITH PRESSURE FALLS AS ALREADY
MENTIONED...AND IN FACT PRESSURE RISES ARE ALL THE WAY BACK IN
OREGON NOW...SO A SLIGHTLY SLOWER FROPA TIMING SEEMS REASONABLE.
EXPECT A FRONT TO LIVINGSTON BY AROUND 02Z...BILLINGS 04Z AND
MILES CITY/SHERIDAN 06Z. W-NW WIND GUSTS TO 40 MPH WILL ACCOMPANY
AND FOLLOW THIS FROPA. COULD SEE A LITTLE POST FRONTAL SHOWER
ACTIVITY ESPECIALLY CONSIDERING THE MID LEVEL INSTABILITY. BEST
CHANCE OF SHOWERS WILL BE OVER OUR WESTERN HIGH TERRAIN AS
SECONDARY PV MAX MOVES IN FROM THE WEST. THE BEARTOOTH ABSAROKAS
WILL SEE A LITTLE SNOWFALL AS 700MB TEMPS FALL TO NEAR -12C BY 12Z
WEDNESDAY. LIVINGSTON MAY ALSO WET BULB DOWN TO A RAIN/SNOW SHOWER
MIX BY LATE TONIGHT.

AS FOR THE RED FLAG WARNING WILL MAKE NO CHANGES AT THIS TIME.
FRONTAL PASSAGE AND WIND SHIFT TONIGHT WILL BE FOLLOWED BY GUSTY
W-NW WINDS THROUGH TOMORROW WITH GUSTS OF 35-50 MPH. WE WILL BE
VERY WELL-MIXED ON WEDNESDAY AND PER VERY DRY MID LEVELS EXPECT
SFC DEWPTS TO REALLY CRASH...PROBABLY SINGLE DIGITS FROM BILLINGS
WEST...RESULTING IN TEENS FOR AFTERNOON HUMIDITY DESPITE THE MUCH
COOLER AIRMASS. WINDS WILL BEGIN TO DIMINISH AND RHS WILL BEGIN TO
RECOVER WEDNESDAY NIGHT.

UNSTABLE NW FLOW ON TAP FOR THURSDAY AS UPPER TROF SLIDES TO OUR
EAST. SFC HIGH PUSHING INTO THE NORTHERN PLAINS WILL ACTUALLY
STABILIZE THE AIRMASS IN OUR EAST ON THURSDAY...BUT LIFTED INDICES
NEAR ZERO EXPECTED WEST OF BILLINGS. THIS ALONG WITH CONVERGENT
BOUNDARY LAYER FLOW WILL ALLOW FOR A GREATER CHANCE OF RAIN/SNOW
SHOWERS FROM BILLINGS WEST THURSDAY AFTERNOON AND EVENING. MTNS
WILL SEE A LITTLE MORE SNOW ACCUMULATION.

HIGHS IN THE 50S WEDNESDAY SHOULD FALL TO THE MID 40S TO LOWER 50S
ON THURSDAY AS WE CONTINUE TO WEAKLY COLD ADVECT AS THE FLOW TURNS
NORTHWESTERLY. A GOOD CHANCE OF BELOW FREEZING TEMPS MANY AREAS
THURSDAY NIGHT. JKL

.LONG TERM...VALID FOR FRI...SAT...SUN...MON...TUE...

THE PATTERN FOR THE EXTENDED PERIOD IS SHAPING UP TO BE COOLER
AND MORE UNSETTLED THAN THE PATTERN OF RECENT DAYS. A SHORTWAVE
RIDGE WILL BE OVER THE AREA FRI AND FRI NIGHT. A DEPARTING
SHORTWAVE OVER E MT WILL BRING A SLIGHT CHANCE OF SHOWERS TO THAT
AREA ON FRI. FRI WILL HAVE HIGHS IN THE 50S UNDER A COOLER
AIRMASS. THE RIDGE WILL FLATTEN ON SAT ALLOWING PACIFIC ENERGY TO
MOVE INTO THE AREA. A COLD FRONT WILL PUSH S THROUGH THE REGION.
TEMPERATURES WERE SOMEWHAT UNCERTAIN DUE TO FRONTAL TIMING
DIFFERENCES BETWEEN THE MODELS. MODEL COMPROMISE GAVE HIGHS IN THE
50S TO AROUND 60 DEGREES. SW FLOW WILL APPROACH THE AREA SAT NIGHT
AND WILL MOVE OVER THE AREA ON SUN. CHANCES FOR SHOWERS WILL BE
CONFINED TO MAINLY WESTERN AND CENTRAL AREAS SAT THROUGH SUN.
HIGHS ON SUN WILL BE SLIGHTLY LOWER...IN THE UPPER 40S AND 50S.

FOR SUN NIGHT THROUGH TUE...MODELS AGREED ON AN UPPER TROUGH
MOVING THROUGH THE REGION. MODELS HAD DRY-SLOTTING PUSHING UP INTO
THE AREA FROM LOW PRESSURE IN WY SUN NIGHT INTO MON. CONTINUED
CHANCE POPS OVER MOST OF THE AREA DURING THIS TIME...BUT THE DRY
SLOT WILL NEED TO BE WATCHED IN CASE POPS ARE A BIT TOO HIGH.
CONTINUED SLIGHT CHANCE/CHANCE POPS OVER THE AREA THROUGH THE REST
OF THE PERIOD. HAD HIGHS IN THE 50S FOR MON AND TUE. TUE LOOKS A
LITTLE WARMER THAN MON DUE TO THE DEPARTING SYSTEM. ARTHUR
&&

.AVIATION...

A COLD FRONT WILL CROSS KBIL AROUND 04Z...KMLS AROUND 06Z AND
KSHR AROUND 05Z. SURFACE WINDS WILL SHIFT TO THE NW BEHIND THE
FRONT WITH GUSTS OF 25 TO 35 KT. WINDS WILL GUST IN THE 30S AND
40S FROM THE NW ON WED. OTHERWISE...THERE WILL BE A SLIGHT CHANCE
OF THUNDERSTORMS AROUND KLVM...AND OVER AND NEAR THE WESTERN
MOUNTAINS THROUGH 06Z. ISOLATED TO SCATTERED SHOWERS WILL OCCUR
OVER THE AREA TONIGHT WITH MAINLY VFR CONDITIONS CONTINUING. THERE
WILL BE A CHANCE OF SHOWERS OVER AND NEAR THE MOUNTAINS ON WED.
MOUNTAIN OBSCURATIONS WILL OCCUR TONIGHT AND PERSIST INTO EARLY
WEDNESDAY. ARTHUR/TWH

&&

.PRELIMINARY POINT TEMP/POPS...

    WED     THU     FRI     SAT     SUN     MON     TUE
-----------------------------------------------------------
BIL 042/056 033/049 031/056 033/059 034/056 035/055 033/056
    31/N    13/W    31/B    01/B    22/W    33/W    32/W
LVM 035/050 027/047 025/053 031/054 028/052 030/050 028/052
    54/W    24/W    31/B    12/W    23/W    33/W    32/W
HDN 040/058 030/050 028/058 030/062 033/059 034/058 031/059
    31/N    12/W    21/B    01/B    21/B    22/W    32/W
MLS 041/058 031/049 028/055 030/060 032/058 033/055 031/055
    21/N    02/W    12/W    01/B    11/B    33/W    32/W
4BQ 041/057 031/048 025/054 028/061 031/058 032/057 031/057
    21/N    02/W    11/B    01/B    12/W    22/W    32/W
BHK 039/056 029/045 024/052 026/058 028/054 028/049 028/050
    21/N    02/W    12/W    01/B    11/B    33/W    32/W
SHR 037/054 028/047 025/052 026/059 029/057 032/055 030/055
    22/W    13/W    21/B    01/B    12/W    22/W    32/W

&&

.BYZ WATCHES/WARNINGS/ADVISORIES...
MT...RED FLAG WARNING IN EFFECT UNTIL 9 PM MDT WEDNESDAY FOR ZONES
      28>42-56>58-63>68.
WY...RED FLAG WARNING IN EFFECT UNTIL 9 PM MDT WEDNESDAY FOR ZONES
      98-99.

&&

WEATHER.GOV/BILLINGS