Area Forecast Discussion
Issued by NWS Billings, MT

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FXUS65 KBYZ 052113
AFDBYZ

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

.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...

ISOLATED TO SCATTERED SHOWERS AND THUNDERSTORMS WITH LOCAL MVFR
CONDITIONS AND MOUNTAIN OBSCURATIONS WILL CONTINUE THROUGH THIS
EVENING IN SOUTH CENTRAL MT AND NORTH CENTRAL WY. THE CHANCE OF
THUNDERSTORMS WILL DIMINISH AFTER 06 UTC...BUT A MORE WIDESPREAD
AREA OF SHOWERS AND MVFR CEILINGS WILL DEVELOP OVER SOUTHEASTERN
MT /AND LIKELY AS FAR WEST AS KBIL AND KSHR/ WEDNESDAY MORNING.
SCHULTZ

&&

.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
    45/W    21/C    23/W    77/W    64/W    32/W    22/W
LVM 045/059 036/052 033/051 035/046 034/049 032/062 037/068
    63/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
    46/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
    49/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
    49/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
    57/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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