Area Forecast Discussion
Issued by NWS Billings, MT

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FXUS65 KBYZ 300234
AFDBYZ

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BILLINGS MT
834 PM MDT FRI APR 29 2016

.UPDATE...
DYNAMIC UPPER LOW IS WELL TO OUR SOUTH IN EASTERN COLORADO...BUT
MODEST ISENTROPIC ASCENT IS BEGINNING TO LIFT UP THRU WY INTO OUR
CWA THIS EVENING...FURTHER SUPPORTED BY A NEARLY STATIONARY AREA
OF PV ALONG THE WY/ID BORDER. THIS IS PRODUCING MAINLY INCREASING
HIGH CLOUDS SO FAR BUT THERE ARE A FEW WEAK ECHOES ON BLX RADAR IN
BIG HORN COUNTY UP THRU TREASURE COUNTY...AS WELL AS OVER OUR SW
MTNS. MAIN AREA OF LOW POPS OVER OUR MTNS/FOOTHILLS LOOKS GOOD FOR
TONIGHT BUT HAVE ADDED AN AREA OF SPRINKLES TO CENTRAL PARTS
INCLUDING BILLINGS. STRONGEST FORCING WILL REMAIN OUTSIDE OF OUR
CWA BUT OUR SOUTH WILL SEE AN INCREASED CHANCE OF PCPN BY
TOMORROW. FOR THE UPDATE THIS EVENING...IN ADDITION TO MINOR POP
ADJUSTMENTS...HAVE TWEAKED SKY COVER AND WINDS BASED ON CURRENT
CONDITIONS AND HAVE RAISED EXPECTED FORECAST LOWS JUST A BIT. JKL

&&

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

SATELLITE THIS AFTERNOON IS SHOWING AN UPPER LOW MOVING ACROSS
SOUTHEAST COLORADO AS BROAD TROUGHINESS REMAINS ACROSS THE ENTIRE
ROCKY MOUNTAIN REGION. THIS UPPER LOW CONTINUES TO ROTATE CLOUDS
NORTHWARD ACROSS WYOMING AND MONTANA. ALTHOUGH THERE ARE SOME
BREAKS IN THE CLOUDS...MOSTLY CLOUDY SKIES WILL PREVAIL FOR THE
REMAINDER OF THE AFTERNOON AND OVERNIGHT HOURS. HI RES MODELS
CONTINUE TO SHOW SOME SCATTERED SHOWERS OR PERHAPS SPRINKLES
ACROSS THE AREA THIS AFTERNOON BUT THE CHANCES ACROSS THE PLAINS
WILL QUICKLY DIMINISH BY EARLY EVENING BUT WILL CONTINUE THROUGH
THE NIGHT FOR THE MOUNTAINS AND ADJACENT FOOTHILLS.

BY SATURDAY...THIS LOW SLOWLY MOVES ACROSS SOUTHERN NEBRASKA
WHILE A SECOND UPPER LOW AND AREA OF VORTICITY TAKE SHAPE OVER THE
FOUR CORNERS REGION. THE FIRST LOW WILL EJECT A FEW AREAS OF
VORTICITY...AS WELL AS AN AREA OF PRECIP NORTHWEST ACROSS WYOMING
INTO SOUTHERN MONTANA DURING THE DAY SATURDAY. THE HEAVIEST PRECIP
LOOKS TO STAY SOUTH OF MONTANA MAINLY ACROSS EASTERN WYOMING TO
RAPID CITY AND AREAS SOUTH. AS A RESULT...HAVE PUT CHANCES FOR
SHOWERS ACROSS THE PLAINS EXCEPT FOR CUSTER AND FALLON COUNTIES.
IN ADDITION...GUIDANCE IS SHOWING LIKELY POPS FOR THE SHERIDAN
AREA SO WE HAVE INCREASED CHANCES TO LIKELY FOR SHERIDAN COUNTY
THROUGHOUT THE DAY. SHOWER ACTIVITY WILL QUICKLY DIMINISH AND
SHIFT SOUTH BY SATURDAY EVENING LEAVING JUST A CHANCE OVER THE
MOUNTAINS AND ADJACENT FOOTHILLS FOR SATURDAY NIGHT.

HEIGHTS BEGIN TO BUILD DURING THE DAY SUNDAY AS HIGH PRESSURE
RIDGING ACTUALLY BUILDS IN FROM THE NORTHWEST BRINGING PARTLY
SUNNY SKIES AND DRY CONDITIONS ACROSS THE ENTIRE FORECAST AREA.
MODELS DIVERGE GREATLY BY LATE SUNDAY NIGHT INTO MONDA AS THE
ECMWF BRINGS AN UPPER LOW AND VORT MAX SOUTH OUT OF CANADA INTO
NORTH DAKOTA THEN SOUTHWEST ACROSS SOUTHERN MONTANA/NORTHERN
WYOMING MONDAY...WHEREAS THE GFS TAKES THE LOW AND VORT AREA INTO
MINNESOTA. POPS WERE NOT ADDED INTO OUR EASTERN AREAS SUNDAY NIGHT
BUT THIS WILL NEED TO BE WATCHED AS SHOWER CHANCES MAY NEED TO BE
ADDED WITHIN THE NEXT FEW FORECAST ISSUANCES. TEMPERATURES WILL
REMAIN BELOW NORMAL FOR THE WEEKEND WITH LOWER TO MIDDLE 50S
SATURDAY AND MIDDLE 50S TO POSSIBLY 60 DEGREES FOR SOME LOCATIONS
ON SUNDAY. HOOLEY

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

UPPER-LEVEL HIGH PRESSURE IS EXPECTED TO DOMINATE WITH DRY AND
MILD WEATHER THROUGH THURSDAY. 12Z OPERATIONAL ECMWF DOES SHOW A
SHORTWAVE WITH SHOWERS WORKING NORTHEAST-TO-SOUTHWEST ACROSS OUR
CWA ON MONDAY, BUT AT THIS TIME AM LEANING MORE TOWARDS 12Z GFS
OPERATIONAL/ENSEMBLES AND WPC GUIDANCE...WHICH SHOW A DRY
SCENARIO.

SURFACE FLOWS BECOME A BIT MORE SOUTHERLY ON TUESDAY AND THE REST
OF THE WEEK PROMOTING BETTER MIXING AND TEMPERATURES MOVING INTO
THE 70S OR BETTER FOR THE LATTER HALF OF THE WEEK. NEXT UPPER-
LEVEL LOW LOOKS TO ARRIVE ON THE CALIFORNIA COAST ON THURSDAY,
WITH PERHAPS SOME SHOWERS AFFECTING OUR WESTERN ZONES LATE
THURSDAY, EXPANDING EASTWARD THURSDAY NIGHT-FRIDAY. SOME MODEL
DIFFERENCES EXIST WITH THE EASTWARD EXTENT OF SHOWERS FOR THU-FRI,
SO ONLY HAVE LOW CHANCE POPS FOR NOW. WINDS LOOK LIGHT FOR MUCH OF
THE PERIOD. RMS/HOOLEY

&&

.AVIATION...

MID LEVEL CLOUD COVER WILL REMAIN EXTENSIVE ACROSS THE REGION
TONIGHT INTO SATURDAY. ISOLATED SHOWERS AND A FEW LIGHT SPRINKLES ARE
POSSIBLE GENERALLY WEST AND SOUTH OF KBIL THIS EVENING...EXPANDING
TO MUCH OF SOUTHERN MONTANA LATE TONIGHT INTO SATURDAY. MVFR TO
TO IFR CIGS ARE POSSIBLE SOUTH AND WEST OF KMLS LATE TONIGHT.
BEST CHANCES FOR -SHRA WILL BE VC KSHR ON SATURDAY. EXPECT
MOUNTAIN OBSCURATIONS TO CONTINUE ACROSS SOUTHERN MONTANA AND
NORTHERN WYOMING TONIGHT INTO SATURDAY. RMS/STP

&&

.PRELIMINARY POINT TEMP/POPS...

    SAT     SUN     MON     TUE     WED     THU     FRI
-----------------------------------------------------------
BIL 038/053 036/060 039/065 041/071 044/074 046/075 047/072
    13/W    10/U    01/U    10/U    00/U    11/U    22/W
LVM 034/051 032/057 032/065 036/071 039/074 041/074 042/070
    22/W    21/B    00/U    11/U    11/U    12/W    22/W
HDN 035/056 034/061 035/066 037/071 039/075 041/076 044/074
    13/W    10/U    01/U    10/U    00/U    11/U    22/W
MLS 039/059 036/063 039/067 040/072 044/075 046/075 048/073
    11/E    00/U    00/U    10/U    00/U    11/U    12/W
4BQ 035/055 032/059 034/064 037/071 040/074 042/075 044/075
    23/W    10/U    01/U    11/U    00/U    11/U    12/W
BHK 036/056 032/060 036/065 037/070 041/072 042/073 043/070
    01/B    00/U    00/U    00/U    00/U    11/U    12/W
SHR 035/050 028/058 032/060 034/066 036/070 038/073 040/071
    36/W    31/B    01/U    11/U    00/U    11/U    22/W

&&

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

&&

$$
WEATHER.GOV/BILLINGS



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