Area Forecast Discussion
Issued by NWS Billings, MT

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197
FXUS65 KBYZ 281541
AFDBYZ

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE BILLINGS MT
941 AM MDT THU APR 28 2016

.UPDATE...

A WEAK DEFORMATION AREA REMAINS ACROSS THE FORECAST AREA AS A
STUBBORN UPPER LOW OVER THE IOWA/MINNESOTA BORDER SLOWLY
RETROGRADES NORTHWEST. AS A RESULT...A VERY COOL AND MOIST
EASTERLY FLOW WILL CONTINUE ACROSS THE AREA TODAY. AN AREA OF
Q-VECTOR CONVERGENCE WILL MOVE ACROSS THE AREA THIS MORNING BUT
WEAKEN THIS AFTERNOON. CURRENT RADAR IS SHOWING BANDS OF LIGHT
SNOW MOVING EAST TO WEST MAINLY ACROSS OUR CENTRAL AND WESTERN
AREAS. HOWEVER...NO ADDITIONAL ACCUMULATION IS EXPECTED. PRECIP
CHANCES WERE CATEGORICAL THROUGH MID MORNING BUT I DID CONTINUE
100 PERCENT POPS FROM ROSEBUD COUNTY WEST AND NORTH THROUGH THE
REMAINDER OF THE MORNING. THE PRECIP WILL GRADUALLY TAPER OFF BY
LATE MORNING WITH JUST SCATTERED RAIN SHOWERS EXPECTED THIS
AFTERNOON. THE OTHER ADJUSTMENT TO THE FORECAST WAS TO TWEAK HIGH
TEMPERATURES IN A FEW LOCATIONS AS READINGS ARE ONLY EXPECTED TO
BE IN THE LOWER TO MIDDLE 40S TODAY. UPDATED FORECAST HAS BEEN
SENT. HOOLEY

&&

.SHORT TERM...VALID FOR TDY AND FRI...

COMPLEX PATTERN CONTINUES TODAY OVER THE AREA. BROAD UPPER TROF
COVERS THE WESTERN HALF OF THE U.S. WITH A TRIO OF UPPER VORTICITY
CENTERS EMBEDDED WITHIN IT. ONE IS OVER EASTERN NEBRASKA THIS
MORNING AND IS DIMINISHING AS IT BLEED ENERGY INTO FASTER
NORTHWEST FLOW OVER THE GREAT LAKES. THIS IS THE MAIN LOW AT THE
MOMENT AND IS CONTROLLING THE FLOW OF MOISTURE FROM THE PLAINS
INTO THE AREA. THE SECOND IS OVER CENTRAL CALIFORNIA AND THIS
SYSTEM WILL DEEPEN BECOMING THE MAIN LOW TOMORROW. THIS SYSTEM MAY
IMPACT SOUTHERN MONTANA/NORTHERN WYOMING THIS WEEKEND. THE THIRD
IS WEAKER AND IS DEVELOPING IN AN AREA OF DEFORMATION/DIFFLUENCE
OVER SOUTHWEST MONTANA. EASTERLY LOW TO MID LEVEL FLOW WILL
CONTINUE TO PUSH INTO THE AREA FOR THE NEXT SEVERAL DAYS AS THE
UPPER TROF REMAINS IN PLACE...WHICH WILL KEEP LOW LEVEL MOISTURE
AND BELOW AVERAGE TEMPERATURES IN PLACE.

MOIST EASTERLY UPSLOPE FLOW WILL KEEP CHANCE TO LIKELY POPS IN
PLACE TODAY THROUGH TONIGHT. BEST CHANCES FOR PRECIPITATION TODAY
WILL BE OVER THE WESTERN HALF OF THE FORECAST AREA AS DYNAMICS
ASSOCIATED WITH DEVELOPING VORTICITY CENTER ALOFT COMBINE WITH
UPSLOPE FLOW AND MODERATE INSTABILITY IN THE LOW LEVELS.
PRECIPITATION POTENTIAL WILL BE HIGHEST THIS MORNING...TAPERING TO
CHANCE POPS THIS AFTERNOON. COULD SEE A FEW BREAKS IN THE CLOUD
COVER THIS AFTERNOON...BUT THEY SHOULD BE BRIEF GIVEN THE LOW
LEVEL MOISTURE AROUND WHICH WILL ALLOW CUMULUS TO FILL IN THOSE
HOLES QUICKLY. TEMPERATURES SHOULD BE 4 OR 5 DEGREES WARMER THAN
YESTERDAY GIVEN SOME WARM ADVECTION AT 850MB.

WITH CUTOFF ENERGY LINGERING OVER AREAS WEST OF BILLINGS TONIGHT
WILL KEEP LOW CHANCE POPS IN THE FORECAST TONIGHT THERE. FOR THE
REST OF THE AREA WILL KEEP SLIGHT CHANCE POPS GOING MAINLY FOR
SOME VERY LIGHT PRECIPITATION DUE TO SATURATED BOUNDARY LAYER
CONDITIONS IN UPSLOPE EASTERLY FLOW. ANY PRECIPITATION TONIGHT
SHOULD ONLY AMOUNT TO A HUNDREDTH OR TWO.

EASTERLY FLOW WILL CONTINUE OVER THE AREA FRIDAY AS SW MONTANA
UPPER LOW DRIFTS NORTHWARD AND CALIFORNIA SYSTEM PUSHES INTO NORTHERN
COLORADO. UPPER LEVEL FLOW BECOMES SOUTHERLY AND DIFFLUENT DURING
THE DAY. SOME BREAKS IN THE CLOUD COVER SHOULD PUSH TEMPERATURES
INTO THE 50S RESULTING IN STEEP LOW LEVEL LAPSE RATES. COMBINE THE
MOISTURE RECENT PRECIPITATION...EASTERLY UPSLOPE FLOW...STEEP LOW
LEVEL LAPSE RATES AND DIFFLUENCE ALOFT AND WILL LIKELY SEE
ISOLATED TO SCATTERED LIGHT INSTABILITY SHOWERS DEVELOP FRIDAY
AFTERNOON. CHAMBERS

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

MODELS HAVE TRENDED DRIER SO HAVE FOLLOWED SUIT AND GONE LOWER WITH
FORECAST POPS. A DOUBLE UPPER LOW WILL BE WELL S OF THE AREA ON
SAT. THE EASTERN LOW WILL MOVE FURTHER AWAY FROM THE REGION ON SUN
WHILE THE WESTERN LOW WILL BE OVER THE WESTERN PORTION OF THE
FOUR-CORNERS REGION. E TO SE FLOW WILL BRING MOISTURE INTO THE
AREA ON SAT MAINLY ACROSS THE SOUTHERN AND WESTERN ZONES. THUS HAD
CHANCE POPS IN THOSE AREAS WITH SLIGHT CHANCE ELSEWHERE. THE
MOISTURE SINKS S OUT OF THE AREA DURING SUN SO JUST LEFT A LOW
CHANCE OVER SOUTHERN AND WESTERN AREAS. TEMPERATURES WILL HOLD IN
THE 50S OVER THE WEEKEND. REX BLOCK TYPE RIDGING THEN STRENGTHENS
OVER THE FORECAST AREA ON MON...THEN AN OMEGA BLOCK DEVELOPS WITH
THE RIDGE REMAINING ANCHORED OVER THE FORECAST AREA. WENT WITH A
DRY FORECAST THROUGH THE REMAINDER OF THE PERIOD. THERE WILL BE A
WARMING TREND...WITH TEMPERATURES REACHING THE 70S BY MIDWEEK.
ARTHUR

&&

.AVIATION...

A MIX OF RAIN AND SNOW WILL PERSIST OVER THE AREA THROUGH THE
MORNING BRINGING WIDESPREAD MVFR TO IFR CONDITIONS. THE MIXED
PRECIPITATION WILL CHANGE TO MAINLY RAIN THIS AFTERNOON...THEN MIX
WITH SNOW AGAIN THIS EVENING. THE MVFR TO IFR CONDITIONS WILL
CONTINUE THROUGH THIS EVENING. WIDESPREAD MOUNTAIN OBSCURATIONS
WILL DECREASE SOMEWHAT THIS AFTERNOON. ARTHUR

&&

.PRELIMINARY POINT TEMP/POPS...

    TDY FRI     SAT     SUN     MON     TUE     WED
-------------------------------------------------------
BIL 045 032/052 036/054 038/057 038/064 042/069 043/071
    +/O 32/W    22/W    22/W    11/B    10/U    00/U
LVM 045 028/050 033/054 035/056 033/064 037/070 039/071
    +/O 43/W    33/W    32/W    11/U    10/U    00/U
HDN 047 031/054 036/054 035/058 035/065 037/069 040/072
    8/S 32/W    22/W    22/W    11/B    10/U    00/U
MLS 047 034/053 037/056 037/059 038/065 041/069 043/070
    7/R 22/W    12/W    11/B    01/B    10/U    00/U
4BQ 044 032/050 035/051 034/056 035/063 039/068 041/070
    7/O 22/W    24/W    32/W    11/B    10/U    00/U
BHK 046 032/051 036/055 033/057 034/063 038/066 039/067
    4/R 22/W    22/W    11/B    01/B    10/U    00/U
SHR 043 028/050 033/049 033/053 033/060 034/065 037/068
    4/O 32/W    24/W    42/W    11/B    10/U    00/U

&&

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

&&

$$
WEATHER.GOV/BILLINGS



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