Area Forecast Discussion
Issued by NWS Billings, MT

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FXUS65 KBYZ 240237
AFDBYZ

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BILLINGS MT
837 PM MDT WED APR 23 2014

.UPDATE...
WINDS ARE DIMINISHING ACROSS THE ENTIRE AREA THIS EVENING. NIGHT
TIME TEMPERATURE INVERSION IS SETTING UP AND WINDS ALOFT ARE
ALREADY DECOUPLING FROM THE SURFACE. MAIN FORCING WITH THE UPPER
LEVEL TROUGH OF LOW PRESSURE HAS SHIFTED INTO THE DATKOA`S THIS
EVENING. THERE REMAINS WEAK JET DYNAMICS OVER THE AREA WITH LEFT
EXIT REGION OF THE JET. EXPECT A FEW ISOLATED SHOWERS TO CONTINUE
ACROSS OUR FAR NORTHERN ZONES FOR SEVERAL MORE HOURS. ISOLATED
SNOW SHOULD CONTINUE OVER THE SOUTHWEST MOUNTAINS WITH THE WEAK
LIFT ALOFT AND OROGRAPHIC LIFTING. AIR MASS DRYING OUT LATE
TONIGHT AS A RIDGE OF HIGH PRESSURE BEGINS TO BUILDS IN OVER THE
FORECAST AREA. OTHER CHANGE TO THE GOING FORECAST WAS SOME MINOR
TWEAKS TO TEMPERATURES. RICHMOND

&&

.SHORT TERM...VALID FOR THU AND FRI...

GUSTY WINDS WILL CONTINUE FOR THE REMAINDER OF THE AFTERNOON AND
INTO THE EARLY EVENING HOURS BEHIND THE STRONG PACIFIC FRONT THAT
MOVED THROUGH OUR FORECAST AREA LAST NIGHT. PLENTY OF SUBSIDENCE
BEHIND THE FRONT WITH STRONG WINDS ALOFT HAVE BEEN MIXING DOWN TO
THE SURFACE THIS AFTERNOON. MANY AREAS HAVE BEEN GUSTING IN THE 30
TO 40 MPH RANGE WITH A FEW HIGHER GUSTS. SATELLITE CURRENTLY
SHOWING THIS SUBSIDENCE AS WELL AS SKIES HAVE BECOME PARTLY TO
MOSTLY SUNNY ACROSS OUR CENTRAL AND WESTERN AREAS. AN ISOLATED
SHOWER WILL BE POSSIBLE INTO THIS EVENING BUT MAINLY ACROSS THE
EAST TOWARD THE DAKOTA BORDERS. HAVE REMOVED POPS FOR TONIGHT AS
LOSS OF DAYTIME HEATING WILL ELIMINATE SHOWER CHANCES EXCEPT FOR
THE POSSIBILITY OVER AND THE NEAR THE MOUNTAINS.

HIGH PRESSURE RIDGING BUILDS BACK ACROSS THE FORECAST AREA FOR
THURSDAY INTO FRIDAY RESULTING IN MOSTLY DRY CONDITIONS AND WARMER
TEMPERATURES. SOME WEAK INSTABILITY WILL UNDERCUT THE RIDGE
HOWEVER BRINGING A SLIGHT CHANCE FOR A SHOWER THURSDAY NIGHT AND
FRIDAY ALONG AND WEST OF A SHERIDAN-BILLINGS-ROUNDUP LINE. A
SURFACE LOW DEVELOPS ON THE MONTANA/WYOMING BORDER FRIDAY NIGHT
PLACING A WARM FRONT ACROS THE CENTER OF OUR FORECAST AREA. MODELS
PUT A LARGE AREA OF PRECIP ALONG THE FRONT LATE FRIDAY NIGHT INTO
SATURDAY MORNING. HAVE PUT LIKELY POPS FOR THIS TIME PERIOD FOR
ALL BUT THE FAR SOUTH AND SOUTHEAST AREAS OF OUR FORECAST AREA.
TEMPERATURES LOOK WARM ENOUGH FOR PRECIP TO BE RAIN OR A RAIN/SNOW
MIX EXCEPT FOR THE BEARTOOTH/ABSAROKA MOUNTAINS AND FOOTHILLS
WHERE SOME MINOR SNOW ACCUMULATIONS MAY OCCUR. TEMPERATURES WILL
BE AT TO SLIGHTLY ABOVE NORMAL THURSDAY AND FRIDAY WITH READINGS
IN THE LOWER TO MIDDLE 60S. HOOLEY

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

THE GFS HAD BEEN SHOWING A WARMER AND DRIER SOLUTION FOR THE
WEEKEND WHEN COMPARED TO THE WETTER AND COLDER ECMWF. IN
ADDITION...MODEL DETAILS HAVE VARIED FROM RUN-TO-RUN WITH QPF
PLACEMENT AND 850 MB TEMPERATURE VALUES. HOWEVER...THE NEW ECMWF
HAS COME IN FAIRLY SIMILAR TO THE GFS IN TERMS OF SHOWING A WARMER
AND DRIER WEEKEND SOLUTION. THUS HAVE TRENDED THE FORECAST TOWARD
A BLEND OF THE TWO MODELS.

A SPLIT UPPER TROUGH WILL CROSS THE WESTERN U.S. THROUGH MON. THE
MODELS CONTINUED TO CUTOFF A LOW WELL TO THE S OF THE REGION AND
ROTATE IT INTO THE CENTRAL/SOUTHERN PLAINS ON MON. THE FORECAST
AREA WILL BE AFFECTED BY THE NORTHERN STREAM OF THE TROUGH WHICH
BRINGS A SURFACE LOW INTO S MT ON SAT. MUCH OF THE PRECIPITATION
WAS FORECAST TO MOVE N OF THE AREA WITH THE SYSTEM/S WARM FRONT ON
SAT MORNING...WHILE OTHER PRECIPITATION MOVES INTO WESTERN AREAS.
SE MT WILL BE IN THE WARM SECTOR SAT AFTERNOON. HAVE SCALED BACK
POPS OVER THE E BASED ON THESE SOLUTIONS AND ADDED A CHANCE OF
THUNDER TO THE FORECAST FOR SAT AFTERNOON AND EVENING SUPPORTED BY
CAPES ON THE GFS. ALSO RAISED TEMPERATURES ON SAT...ESPECIALLY
FROM KBIL E. INVERTED SURFACE TROUGH WILL BE OVER THE AREA SAT
NIGHT SUPPORTING THE INHERITED LIKELY POPS. THE WARM 850 MB
AIRMASS WILL SUPPORT RAIN OR A RAIN/SNOW MIX. A QUARTER TO A HALF
INCH OF PRECIPITATION WILL BE POSSIBLE SAT NIGHT FROM KBIL W BASED
ON THE LATEST MODEL RUNS.

THE INVERTED TROUGH SHIFTS E DURING SUN WHICH WILL ALLOW
PRECIPITATION CHANCES TO DECREASE OVER THE W. PRECIPITATION
AMOUNTS COULD EXCEED A HALF INCH OVER SE MT. NUDGED TEMPERATURES
HIGHER ON SUN AS WELL. PRECIPITATION WILL GRADUALLY TAPER OFF FROM
W TO E SUN NIGHT THROUGH MON AS THE NORTHERN BRANCH WEAKENS OVER
THE AREA. DEFORMATION OVER THE AREA WILL BRING A SLIGHT CHANCE OF
SHOWERS TO THE REGION MON NIGHT INTO TUE. KEPT THE FORECAST MAINLY
DRY FOR WED FOR NOW EVEN THOUGH THERE WAS SOME MODEL DISAGREEMENT
WITH THE PATTERN. MON WILL BE A COOLER DAY BUT THERE WILL BE A
WARMING TREND FOR TUE AND WED. ARTHUR
&&

.AVIATION...

OVERALL...SURFACE WINDS ARE EXPECTED TO REMAIN FAIRLY LIGHT THE
REST OF TONIGHT...THOUGH W TO SW GUSTS OVER 25 KTS ARE STILL
POSSIBLE IN THE KLVM AREA. LOW LEVEL WIND SHEAR MAY BE A PROBLEM
ACROSS THE EAST TONIGHT...INCLUDING KMLS AND KBHK. MOSTLY VFR
CONDITIONS WILL PREVAIL THROUGH THURS MORNING. THURS
AFTERNOON...THE AIRMASS WILL BECOME MORE UNSTABLE AS A DISTURBANCE
GENERATES SCATTERED SHOWERS FROM KBIL WEST. A FEW THUNDERSTORMS
ARE ALSO POSSIBLE OVER WESTERN MOUNTAINS THURS AFTERNOON. STC

&&

.PRELIMINARY POINT TEMP/POPS...

    THU     FRI     SAT     SUN     MON     TUE     WED
-----------------------------------------------------------
BIL 037/062 040/063 039/061 042/051 035/054 036/060 039/063
    12/W    22/W    64/T    66/W    32/W    22/W    11/U
LVM 037/055 034/063 035/059 039/055 034/055 034/064 036/067
    12/W    23/W    66/T    65/W    32/W    22/W    11/U
HDN 034/061 038/063 037/067 037/051 032/055 032/060 031/064
    11/B    22/W    44/T    66/W    42/W    22/W    11/U
MLS 036/062 039/061 038/065 040/048 032/054 032/055 034/063
    11/N    21/B    65/T    77/W    74/W    32/W    11/U
4BQ 034/060 037/058 038/071 041/051 032/054 032/054 031/062
    11/N    11/B    34/T    77/W    64/W    32/W    11/U
BHK 033/058 038/060 036/058 036/046 029/049 028/051 030/056
    11/N    11/B    65/T    67/W    75/W    32/W    11/U
SHR 032/060 035/065 039/068 039/050 034/052 033/057 032/063
    11/B    22/W    43/T    66/W    43/W    22/W    21/U

&&

.BYZ WATCHES/WARNINGS/ADVISORIES...
MT...NONE.
WY...NONE.

&&

$$
WEATHER.GOV/BILLINGS



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