Area Forecast Discussion
Issued by NWS Billings, MT

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000
FXUS65 KBYZ 200927
AFDBYZ

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BILLINGS MT
327 AM MDT SAT SEP 20 2014

.SHORT TERM...VALID FOR TDY AND SUN...

WEAK VORTICITY MOVING SE THROUGH THE AREA COMBINED WITH MID-LEVEL
MOISTURE WAS PRODUCING SOME CLOUDS OVER THE REGION EARLY THIS
MORNING. THIS ENERGY WILL PUSH E OF THE AREA EARLY TODAY AS UPPER
RIDGING SLIDES E. THERE WAS A PIECE OF STRONGER ENERGY OVER S
SASKATCHEWAN PRODUCING SOME SHOWERS. MODELS KEPT THESE SHOWERS NE
OF THE AREA THIS MORNING...SO WILL BE LOOKING FOR A DRY DAY ACROSS
THE REGION.

UPPER RIDGE WILL BE OVER THE AREA TONIGHT AND SUN. UPPER LOW OVER
CENTRAL CA ON WATER VAPOR IMAGERY THIS MORNING...WILL PUSH SOME
ENERGY TOWARD THE FORECAST AREA LATE ON SUN. MODELS WERE IN GOOD
AGREEMENT IN MOVING THE LOW TO S ID/W WY BY 12Z MON. GFS TIME-
HEIGHT CROSS SECTIONS SHOWED SOME MOISTURE OVER THE NE BIG HORNS
AND THE KSHR AREA AFTER 06Z MON WHICH WOULD SUPPORT A LOW POP.
OTHERWISE THE MOISTURE LOOKS AS THOUGH IT WILL STAY MAINLY S OF
THE BEARTOOTHS AND ABSAROKAS. THUS WILL LOWER THE INHERITED POPS
OVER THIS AREA.

MIXING TO BELOW 700 MB DUE TO EASTERLY FLOW OVER MOST OF THE AREA WILL
HAMPER TEMPERATURE RISES SOMEWHAT TODAY. WILL HAVE A SIMILAR
SITUATION ON SUN. GOING TEMPERATURE FORECAST WAS ON TRACK AND IN
LINE WITH LATEST GUIDANCE. IT WILL BE WINDY IN THE EASTERN ZONES
TODAY DUE TO LINGERING STRONG NW FLOW ALOFT...BUT WINDS IN
FORECAST SOUNDINGS AND FORECAST PRESSURE RISES DID NOT LOOK
STRONG ENOUGH TO SUPPORT A HIGH WIND WARNING. ARTHUR

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

ISSUES HAVE ARISEN WITH THE EXTENDED FORECAST MODELS AND THIS
LENDS TO DECREASING CONFIDENCE IN THE FORECAST LATE IN THE PERIOD.
THE MAJORITY OF THE FORECAST LOOKS IN GOOD SHAPE AND MODELS WERE
IN DECENT AGREEMENT ON. MADE SOME CHANGES IN THE MONDAY THROUGH
TUESDAY TIME PERIOD AND THIS INVOLVED RAISING POPS A BIT MORE FOR
SOUTHERN MONTANA AND NORTHERN WYOMING...AND ALSO BRUSHING SOME
POPS FARTHER NORTH. MODELS WERE TOGETHER IN PUSHING THE RELATIVELY
WEAK UPPER LOW OVER SOUTHERN CALIFORNIA INTO NORTHERN WYOMING ON
MONDAY. MODELS WERE GRABBING ONTO SOME DECENT MID LEVEL MOISTURE
AS PRECIPITABLE WATERS RISE ON THE ORDER OF AN INCH TO AN INCH AND
A QUARTER. FORCING WAS PRETTY WEAK WITH THIS SYSTEM BUT THERE
SHOULD BE SOME INSTABILITY ALONG WITH ADEQUATE MOISTURE...SO
SHOULD BE ABLE TO GET SHOWERS TO FORM...ESPECIALLY OVER SOUTHERN
LOCATIONS.

THE SYSTEM MOVES OUT AND INTO THE PLAINS TUESDAY AS AN UPPER
RIDGE TAKES OVER ON WEDNESDAY. THE UPPER RIDGE WILL HOLD OVER THE
ROCKIES THROUGH THURSDAY AND HAVE RAISED TEMPERATURES WITH THIS IN
PLACE. THE GFS WAS MORE AGGRESSIVE IN SHIFTING THE NEXT UPSTREAM
TROUGH INTO THE WESTERN UNITED STATES LATE IN THE WEEK. THE ECMWF
KEEPS THE TROUGH OFF SHORE THURSDAY...WHILE THE GFS BRINGS IT
INLAND. THIS DISCREPANCY CONTINUES FRIDAY AND SATURDAY. THE GFS
CUTS OFF A LOW AND MOVES IT INTO IDAHO AND UTAH SATURDAY...WHILE
THE ECMWF KEEPS IT OVER WESTERN NEVADA. THE GFS WOULD BE MUCH
COOLER AND WETTER AS THE ECMWF WOULD BE WARM AND DRY. WILL NOT
MAKE ANY CHANGES PAST THURSDAY AND SEE HOW THE MODELS TRY TO
RESOLVE THEIR DIFFERENCES. TWH
&&

.AVIATION...

EXPECT VFR FLYING WEATHER TODAY ACROSS SOUTHERN MONTANA AND
NORTHERN WYOMING. WEST TO NORTHWEST WINDS WILL GUST TO 25-30 KTS
OVER EASTERN MONTANA BY LATE MORNING. THIS WILL IMPACT KMLS AND
KBHK. THE WINDS WILL DECREASE LATE THIS AFTERNOON AND EARLY THIS
EVENING. TWH
&&

.PRELIMINARY POINT TEMP/POPS...

    TDY SUN     MON     TUE     WED     THU     FRI
-------------------------------------------------------
BIL 073 049/075 051/078 055/083 055/085 056/087 057/080
    0/U 00/U    13/T    21/B    11/U    11/B    11/U
LVM 076 041/077 048/077 049/080 048/083 051/084 052/077
    0/U 00/U    13/T    21/B    10/U    01/B    22/T
HDN 076 045/078 048/079 052/083 052/087 054/087 055/082
    0/U 00/U    13/T    21/B    11/U    11/B    11/U
MLS 073 045/076 048/081 055/083 054/086 055/088 056/083
    0/N 00/U    02/T    11/B    11/U    11/U    11/U
4BQ 076 046/076 049/080 054/081 052/085 054/088 055/083
    0/N 00/U    03/T    32/T    11/U    11/U    11/U
BHK 071 040/073 044/078 051/078 050/082 052/084 053/082
    0/N 00/U    01/U    22/T    11/U    11/U    11/U
SHR 074 046/077 049/075 049/079 049/083 052/085 053/081
    0/U 00/U    24/T    42/T    10/U    00/U    11/U

&&

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

&&

$$
WEATHER.GOV/BILLINGS


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