Area Forecast Discussion
Issued by NWS Billings, MT

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410
FXUS65 KBYZ 281158
AFDBYZ

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BILLINGS MT
558 AM MDT THU APR 28 2016

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

UPDATED FORECAST TO ADJUST PRECIPITATION CHANCES FOR CURRENT RADAR
TRENDS. INCREASED POPS CENTRAL AND WEST TO 100 PERCENT THROUGH
9AM. WITH TEMPERATURES NOW IN THE LOW 30S ADDED MENTION OF LIGHT
SNOW ACCUMULATIONS FOR THE LOWER ELEVATIONS. BRIDGES AND
OVERPASSES MAY GET A BIT ICY FOR THE NEXT COUPLE OF HOURS GIVEN
TEMPERATURES AROUND FREEZING. MAIN ROADWAYS SHOULD REMAIN WET FOR
ALL BUT THE FOOTHILLS ABOVE 5000 FEET WHERE LIGHT SNOW/SLUSH CAN
BE EXPECTED. CHAMBERS

PREVIOUS DISCUSSION...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
    +/O 32/W    22/W    22/W    11/B    10/U    00/U
MLS 049 034/053 037/056 037/059 038/065 041/069 043/070
    7/O 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 047 032/051 036/055 033/057 034/063 038/066 039/067
    6/O 22/W    22/W    11/B    01/B    10/U    00/U
SHR 045 028/050 033/049 033/053 033/060 034/065 037/068
    +/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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