Area Forecast Discussion
Issued by NWS Billings, MT

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000
FXUS65 KBYZ 222113
AFDBYZ

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BILLINGS MT
313 PM MDT FRI AUG 22 2014

.SHORT TERM...VALID FOR SAT AND SUN...

BROAD UPPER TROUGH OVER THE PACIFIC NW WILL CONTINUE TO PRODUCE
AN UNUSUALLY COOL AND WET PERIOD ACROSS OUR REGION THE NEXT COUPLE
OF DAYS. IF I WERE TO PICK A WETTEST PERIOD...IT WOULD BE TONIGHT
INTO SATURDAY MORNING AS PLENTY OF LIFT IS PROGGED OVER OUR
FORECAST AREA. ASSOCIATED JET DYNAMICS AND STRONG ISENTROPIC LIFT
OUT IN FRONT OF THE UPPER TROUGH WILL LIKELY PRODUCE WIDESPREAD
RAIN AND EMBEDDED THUNDER OVER THE AREA. SOME DISCRETE STRONG
THUNDERSTORM CELLS ARE ALSO POSSIBLE FROM SHERIDAN TO CARTER
COUNTY THIS EVENING AS EFFECTIVE SHEAR INCREASES ACROSS THIS AREA
WITH A JET STREAK ALOFT. ONE OR TWO STRONG TO SEVERE STORMS ARE
POSSIBLE IN THIS AREA DUE TO THE INCREASING POSSIBILITY OF
SUSTAINED UPDRAFTS. LOOK FOR A VERY MOIST ATMOSPHERE WITH AREAS OF
FOG AND LIGHT RAIN OVERNIGHT.

SATURDAY...NEGATIVE TILT TROUGH WORKS INTO THE REGION FROM THE
WEST AND MAY PRODUCE SOME STRONG TO SEVERE STORMS IN THE SE CORNER
OF THE STATE DUE TO STRONG SHEAR AND INSTABILITY/LIFT. SEVERAL
POCKETS OF LIFT WILL PRODUCE AREAS OF RAIN...MAINLY OVER THE
NORTHERN AND EASTERN ZONES THROUGH SATURDAY. BY SATURDAY EVENING
AS THE UPPER LOW MOVES OVER THERE IS SOME HINT OF DOWNSLOPE DRYING
FROM HARLOWTON TO YELLOWSTONE COUNTY DUE TO NORTH/NORTHWEST FLOW
WRAPPING AROUND THE LOW PRESSURE SYSTEM. THE ECMWF WANTS TO KEEP A
CLOSED UPPER LOW OVER SE MONTANA WHILE THE GFS LIFTS THE SYSTEM
NORTH. THE ECMWF VERSION IS MUCH WETTER THAN THE GFS. THERE IS NO
REAL WAY TO DISCERN WHICH SOLUTION IS MOST ACCURATE AT THIS TIME
...THOUGH THE GFS HAS SUPPORT FROM THE NAM...AND GFS ENSEMBLE
SPREADS ARE NOT THAT WIDE. THEREFORE...I HAVE BLENDED THE WET/DRY
SOLUTIONS BUT LEANED A BIT MORE ON THE LESS WET GFS SOLUTION GOING
INTO SUNDAY. LOOK FOR A BLUSTERY SATURDAY NIGHT AND SUNDAY WITH
NORTH WINDS 15 TO 25 MPH COMBINED WITH THE RAINY CONDITIONS.

BY SUNDAY NIGHT THE UPPER LOW IS TRACKING ACROSS NORTH DAKOTA WITH
A MID LEVEL ZONAL FLOW SPREADING OVER MONTANA AND GENERALLY
BRINGING MOST OF THE PRECIPITATION TO AN END OVER OUR FORECAST
AREA. BT


.LONG TERM...VALID FOR MON...TUE...WED...THU...FRI...

MINIMAL UPDATES THIS AFTERNOON FOR THE INHERITED EXTENDED
FORECAST...WITH MODELS IN GOOD AGREEMENT THROUGHOUT THE
PERIOD.

A SECONDARY LOBE OF THE BROAD UPPER TROF IS STILL VERY SLOW TO
PUSH OFF TO THE EAST. THE TROF AXIS WILL BEGIN SLOW PROGRESSION
EASTWARD MONDAY. THIS WILL BRING ANOTHER ROUND OF PRECIP THROUGH
THE REGION BEGINNING MONDAY...AND LINGERING THROUGH MUCH OF
TUESDAY. THE DYNAMICS FOR THIS SYSTEM APPEARS MUCH WEAKER...SO
EXPECT SHOWERS AND THUNDERSTORMS TO BE MORE SCATTERED IN NATURE.
THE SLOW MOVEMENT OF THE TROF WILL KEEP TEMPS WELL BELOW SEASONAL
AVERAGE...WITH HIGHS IN THE LOW TO MID 70S EACH DAY.

AN UPPER LEVEL RIDGE BEGINS BUILDING INTO THE REGION OVERNIGHT
TUESDAY NIGHT...AND IS THEN FOLLOWED BY ZONAL FLOW DEVELOPING LATE
THURSDAY. THEREFORE EXPECT WARMER AND DRIER CONDITIONS TO PREVAIL
THROUGH THE REMAINDER OF THE EXTENDED PERIOD. TEMPERATURES WILL
SLOWLY TREND UPWARD...BUT GENERALLY REMAIN AROUND SEASONAL AVERAGE.
AAG

&&

.AVIATION...

SHOWERS AND ISOLATED THUNDERSTORMS WILL CONTINUE TO INCREASE IN
COVERAGE THROUGH THIS EVENING...AS A STRONG UPPER LOW MOVES INTO
THE REGION. EXPECT MANY AREAS TO HAVE MVFR TO IFR CONDITIONS AT
TIMES THROUGHOUT THE DAY. MOUNTAIN OBSCURATIONS WILL PERSIST
THROUGHOUT THE REMAINDER OF THE DAY AS WELL. STRONG GUSTY WINDS
ARE POSSIBLE WITH THUNDERSTORMS ACTIVITY...WITH STRONGEST GUSTS
EXPECTED SOUTH OF A LINE FROM KSHR TO EKALAKA. WIDESPREAD
RAIN...HEAVY AT TIMES...IS EXPECTED OVERNIGHT. LOW CIGS ARE
POSSIBLE INTO THE EARLY MORNING HOURS...WITH LIFR/VLIFR CONDITIONS
POSSIBLE. AAG

&&

.PRELIMINARY POINT TEMP/POPS...

    SAT     SUN     MON     TUE     WED     THU     FRI
-----------------------------------------------------------
BIL 056/063 049/065 048/071 050/075 053/082 057/087 061/085
    86/T    44/T    23/T    32/T    11/U    01/U    11/U
LVM 051/060 045/064 042/070 044/075 048/083 051/086 051/084
    86/T    43/T    25/T    52/T    11/B    01/U    12/T
HDN 057/068 050/066 046/074 050/077 051/083 055/088 059/088
    86/T    55/T    13/T    32/T    11/U    01/U    11/U
MLS 060/067 052/062 047/071 051/074 053/082 057/087 062/090
    98/T    86/T    22/T    22/T    11/U    11/U    11/B
4BQ 060/071 051/064 046/071 052/073 051/081 056/087 060/089
    78/T    63/T    22/T    33/T    11/U    11/U    11/U
BHK 056/066 050/061 046/069 047/071 048/078 053/083 059/086
    87/T    86/T    22/T    23/T    11/U    11/U    11/B
SHR 055/070 047/065 044/073 048/074 048/081 051/087 055/089
    76/T    53/T    13/T    43/T    11/U    01/U    11/U

&&

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

&&

$$
WEATHER.GOV/BILLINGS


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