Area Forecast Discussion
Issued by NWS Billings, MT

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FXUS65 KBYZ 060219
AFDBYZ

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BILLINGS MT
819 PM MDT TUE MAY 5 2015

.UPDATE...
COLD FRONT HAS PUSHED THROUGH BILLINGS AND IS ALONG A PRYOR TO
INGOMAR LINE AS OF 02Z. BOUNDARY HAS AIDED BY CONVECTION WHICH IS
SCATTERED ACROSS OUR WEST HALF. WEAK PV COMING OUT OF THE GREAT
BASIN WILL INTERACT WITH MID LEVEL FRONTOGENESIS/VEERING FLOW TO
KEEP SHOWER ACTIVITY ACROSS OUR WEST GOING INTO TOMORROW
MORNING... ESPECIALLY ALONG THE FOOTHILLS...WITH A LITTLE SNOW
OVER THE HIGHER PEAKS AS 700MB TEMPS FALL BELOW ZERO. ENERGY
LIFTING UP THE HIGH PLAINS IS STILL WELL TO OUR SOUTH AND MAY NOT
REACH OUR SE PARTS TIL CLOSER TO 12Z...WITH BEST CHANCE OF PCPN
OVER OUR EAST TOMORROW.

FOR THE UPDATE THIS EVENING HAVE RAISED POPS A NOTCH ACROSS OUR
WEST...AND HAVE GIVEN BILLINGS A LIKELY POPS INTO TOMORROW
MORNING. HAVE ALSO SCALED BACK POPS IN OUR FAR EAST UNTIL AFTER
09Z TONIGHT. AS FOR THE COLD FRONT ITSELF...HAVE ADJUSTED WIND
GRIDS TO ACCOUNT FOR A FASTER TIMING THAN OPERATIONAL MODELS
SHOWED EARLIER TODAY. HRRR/RAP SEEM TO HAVE A FAIR HANDLE NOW.

JKL

&&

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

FORECAST AREA IS SITTING IN BETWEEN TWO UPPER LOWS...ONE OVER THE
PACIFIC NORTHWEST WITH THE SECOND OVER NORTHEAST COLORADO.
SOUTHWESTERLY JET STREAM IN BETWEEN THESE SYSTEMS WILL RIDE OVER
WESTERN MONTANA PUTTING GOOD DIVERGENCE AND PACIFIC MOISTURE OVER
THE AREA THIS AFTERNOON INTO THIS EVENING FOR ISOLATED TO
SCATTERED SHOWERS AND THUNDERSTORMS...MAINLY WEST OF A ROUNDUP TO
BILLINGS LINE. AS THIS ENERGY SHIFTS EASTWARD LATE TONIGHT A COLD
FRONT WILL PUSH THROUGH THE AREA ENHANCING LIFT AND SPREADING
PRECIPITATION INTO SOUTHEAST MONTANA. PRECIPITATION CHANCES WILL
INCREASE FROM CHANCE CATEGORY THIS EVENING TO CATEGORICAL FOR
WEDNESDAY MORNING WITH HIGHEST CHANCES OVER SOUTHEAST MONTANA.

PRECIPITATION WILL DIMINISH FROM NORTHWEST TO SOUTHEAST WEDNESDAY
AFTERNOON INTO WEDNESDAY NIGHT AS PLAINS ENERGY PULLS NORTHEAST
INTO MINNESOTA WITH DRIER LOW LEVEL NORTHWEST WINDS IN BEHIND IT.
EXPECTING A QUARTER TO A BIT OVER HALF AN INCH OF PRECIPITATION BY
LATE WEDNESDAY WITH THIS SYSTEM. THE HEAVIEST ACCUMULATIONS WILL
BE OVER SOUTHEAST MONTANA.

FOR THURSDAY...PACIFIC NORTHWEST LOW DROPS SOUTH INTO CALIFORNIA
PRODUCING SOUTHWEST FLOW OVER THE ARE. THIS WILL KEEP A CHANCE FOR
SHOWERS AND A FEW THUNDERSTORMS IN THE FORECAST FOR SOUTHERN AND
WESTERN ZONES...WITH MAINLY DRY CONDITIONS NORTH AND WEST.

TEMPERATURES WEDNESDAY AND THURSDAY WILL BE IN THE 55 TO 65 DEGREE
RANGE IN MOST AREAS. HOWEVER THERE WILL BE COLD AIR IN PLACE
ACROSS THE HIGHER ELEVATIONS WITH 20S FOR LOWS IN THE MOUNTAINS
AND 30S FOR HIGHS. A FEW INCHES OF WET SNOW CAN BE EXPECTED ABOVE
7000 FEET OVER THE NEXT FEW DAYS. CHAMBERS

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

THE HIGHEST PROBABILITY OF WETTING MOISTURE ACROSS SOUTHERN MT AND
NORTH CENTRAL WY DURING THE LONG TERM FORECAST PERIOD WILL LIKELY
BE FROM LATE FRIDAY THROUGH THE DAYTIME ON SATURDAY. IT IS DURING
THAT PERIOD THAT DIFFLUENCE IN SOUTH-SOUTHWEST FLOW ALOFT TIED TO
A DYNAMIC 500-MB TROUGH DIGGING INTO THE GREAT BASIN APPEARS TO BE
MAXIMIZED. MOREOVER...GUIDANCE SUGGESTS LOW-LEVEL WINDS WILL HAVE
AN UPSLOPE /EAST-NORTHEAST/ TRAJECTORY IN THAT TIME FRAME AND THAT
WILL LIKELY ASSIST PRECIPITATION PRODUCTION. THE 12 UTC ECMWF AND
GFS SUGGEST THAT ONE-QUARTER TO ONE-HALF INCH OF MOISTURE MAY FALL
IN THAT TIME FRAME /AND IT WILL COME AS SNOW OVER THE MOUNTAINS/.
HOWEVER...BY LATER SATURDAY INTO SUNDAY...THE CLOSED 500-MB LOW
IS /AND HAS BEEN FOR THE LAST 24/ HOURS SIMULATED TO EJECT INTO
THE CENTRAL PLAINS...WHICH WOULD KEEP THE HEAVIEST AND LONGEST-
LIVED PRECIPITATION SOUTH OF OUR LOCAL AREA.

WE RELIED HEAVILY ON THE 12 UTC MULTI-MODEL CONSENSUS TO BUILD THE
FORECAST TODAY...CALLING FOR COOL TEMPERATURES MAINLY IN THE 50S F
EARLY IN THE PERIOD AND A WARMING TREND BACK TO THE 60S F BY EARLY
NEXT WEEK ONCE MID-LEVEL HEIGHTS REBOUND SOME BEHIND THE WEEKEND
TROUGH. HOWEVER...WE ARE STILL ADVERTISING A LOW-END SHOWER CHANCE
IN MOST AREAS SUNDAY THROUGH TUESDAY...BOTH DUE TO THE POSSIBILITY
THAT THE WEEKEND TROUGH ENDS UP EJECTING FURTHER NORTHWEST AND/OR
MORE SLOWLY...AND IN RESPECT TO THE POTENTIAL FOR WEAKER SHORTWAVE
TROUGHS TO CROSS THE REGION EARLY NEXT WEEK. SCHULTZ

&&

.AVIATION...

SHOWERS AND ISOLATED TSTMS WILL CONTINUE ACROSS THE REGION AND
SPREAD SLOWLY EAST THROUGH THE NIGHT. POTENTIAL FOR LOCAL MVFR
CONDITIONS WILL INCREASE LATER TONIGHT INTO TOMORROW MORNING...
AND MOUNTAINS WILL BE FREQUENTLY OBSCURED. SHOWERS WILL BECOME
MORE WIDESPREAD OVER FAR SOUTHEAST MT ON WEDNESDAY...ALONG AND
EAST OF A MLS-4BQ LINE...WITH A GOOD CHANCE OF MVFR IN THIS AREA.
WIND GUSTS TO 30 KTS WILL FOLLOW A COLD FRONTAL PASSAGE WHICH IS
ALREADY EAST OF BIL AND WILL IMPACT SHR...MLS AND BHK LATER
TONIGHT AND WEDNESDAY. JKL

&&

.PRELIMINARY POINT TEMP/POPS...

    WED     THU     FRI     SAT     SUN     MON     TUE
-----------------------------------------------------------
BIL 050/061 039/056 040/054 039/046 036/051 036/065 043/069
    66/W    21/C    23/W    77/W    64/W    32/W    22/W
LVM 044/059 036/052 033/051 035/046 034/049 032/062 037/068
    73/W    43/W    35/W    66/W    63/W    33/W    33/W
HDN 051/059 039/058 040/058 040/049 036/054 034/066 041/072
    56/W    21/E    13/W    66/W    64/W    32/W    22/W
MLS 054/058 041/059 039/057 040/053 035/054 036/063 041/068
    38/W    41/B    12/W    55/W    53/W    32/W    22/W
4BQ 051/056 041/058 037/057 040/049 033/049 033/061 040/066
    39/T    52/W    12/W    66/W    64/W    32/W    22/W
BHK 053/060 042/055 036/056 036/050 032/050 033/058 035/064
    39/T    82/W    12/W    44/W    43/W    32/W    22/W
SHR 047/052 038/054 035/056 039/045 034/047 031/060 037/067
    47/W    42/W    23/W    77/W    75/W    42/W    22/W

&&

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

&&

$$
WEATHER.GOV/BILLINGS


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