Area Forecast Discussion
Issued by NWS Billings, MT

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000
FXUS65 KBYZ 250929
AFDBYZ

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BILLINGS MT
329 AM MDT WED MAR 25 2015

.SHORT TERM...VALID FOR TDY AND THU...

UNSETTLED WEATHER WILL CONTINUE TODAY...BUT START MOVING EASTWARD
ALONG WITH A LOW- TO MID-LEVEL WARM FRONT TONIGHT INTO THURSDAY.

DURING THE NIGHT...CONVERGENT LOW-LEVEL FLOW PERSISTED RIGHT NEAR
A LINE FROM HARLOWTON TO BILLINGS AND LAUREL SOUTHEASTWARD TO FORT
SMITH AND SHERIDAN. THAT WEAK FRONTAL ZONE ACTED WITH AN UNSTABLE
AIR MASS TO PRODUCE SNOW SHOWERS WITH ACCUMULATIONS OBSERVED EVEN
IN BILLINGS AS OF 3 AM MDT. HOWEVER...THIS BOUNDARY NEVER DID MAKE
IT INTO THE FOOTHILLS OF THE BEARTOOTH/ABSAROKAS LIKE WE HAD
EXPECTED...LEAVING RED LODGE AND COMPANY WITH MUCH LESS SNOW THAN
FORECAST. RECENT MODEL GUIDANCE LIKE THE HRRR CAPTURES THIS SIGNAL
WELL AND SUGGESTS PRECIPITATION WILL WEAKEN QUICKLY BEFORE SUNRISE
AND SO WE CANCELLED THE WINTER STORM WARNING FOR THE BEARTOOTH AND
ABSAROKA MOUNTAINS AND THE RED LODGE FOOTHILLS.

WE DID DECIDE TO CARRY A MENTION OF PATCHY FOG IN AROUND BILLINGS
THROUGH MID MORNING IN RESPECT TO OVERNIGHT MOISTURE...AND A WIND
FIELD THAT WILL WEAKEN AND LIKELY TURN BACK LIGHT SOUTHWEST EARLY
THIS MORNING AS THE FRONTAL ZONE WASHES OUT.

FOR TODAY...WEAKLY UNSTABLE CONDITIONS WILL CONTINUE ACROSS SOUTH
CENTRAL MT AND NORTH CENTRAL WY UNDER CYCLONIC FLOW ALOFT. THAT IS
SUPPORTIVE OF A SMALL RAIN AND SNOW SHOWER CHANCE...BUT WE DECIDED
TO CAP POPS AROUND 20 PERCENT IN MOST LOWER-ELEVATION LOCATIONS AS
THE OVERNIGHT CONVECTION-ALLOWING MODEL GUIDANCE SUGGESTS LITTLE
IN THE WAY OF ACTIVITY IN MOST AREAS. A WINTER WEATHER ADVISORY IS
STILL IN EFFECT FOR THE NORTHEAST BIGHORN MOUNTAINS UNTIL NOON MDT
SINCE THEY WILL CATCH A BIT MORE ACCUMULATION THIS MORNING. WE ARE
CALLING FOR HIGHS MAINLY IN THE 40S AND 50S F TODAY...BUT THERE IS
AN EXTENSIVE AREA OF STRATUS /LOW CLOUDS/ OBSERVED IN SOUTHEASTERN
MT EARLY THIS MORNING AND RECENT MODEL GUIDANCE EXPECTS THAT LOWER
CLOUD DECK TO NOT BREAK OVER MILES CITY UNTIL MIDDAY OR EVEN EARLY
THIS AFTERNOON...AND NOT UNTIL LATER IN BAKER...SO FORECAST HIGHS
IN BAKER ARE BELOW MOST 00 UTC GUIDANCE...AND IN THE UPPER 30S F.

TONIGHT...A WEAK LOW- AND MID-LEVEL WARM FRONT WILL MOVE EASTWARD
INTO SOUTHEASTERN MT...TAKING A SMALL SHOWER CHANCE ALONG WITH IT.

THURSDAY...THE 00 UTC MODEL SIMULATIONS SUGGEST THAT WARM FRONT IS
GOING TO STALL OUT IN SOUTHEASTERN MT...SO WE HAVE LINGERED A LOW-
END CHANCE OF SHOWERS THROUGH THURSDAY THERE. HOWEVER...THE DRYING
ON THE WARM SIDE OF THAT BOUNDARY SHOWN IN THAT MODEL GUIDANCE WAS
ENOUGH FOR US TO SWITCH TO A DRY FORECAST IN SOUTH CENTRAL MT AND
NORTH CENTRAL WY...WHERE A WARM-UP WILL COMMENCE WITH HIGHS AGAIN
ABOVE 60 F IN MANY AREAS PER THE 00 UTC MULTI-MODEL BLEND. SCHULTZ

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

STRONG UPPER RIDGE ALONG THE PAC COAST WILL SLIDE EAST AND OVER
THE NORTHERN ROCKIES FRIDAY. THIS WILL RESULT IN SIGNIFICANT
DOWNSLOPE WARMING OVER OUR AREA. 700MB TEMPS RISING TO NEAR +2C SHOULD
YIELD HIGHS INTO THE LOWER 70S EVERYWHERE EXCEPT NEAR THE DAKOTAS
BORDER.

BREAK DOWN OF THE RIDGE PER PASSAGE OF A WEAK PACIFIC SHORTWAVE
WILL OCCUR ON SATURDAY...THOUGH THERE REMAINS UNCERTAINTY BOTH
WITH THE TIMING AND STRENGTH OF THIS ENERGY. THE GFS REMAINS A BIT
FASTER THAN THE ECMWF...AND THE 00Z RUN OF THE LATTER IS NOW
SHOWING A SHARPER TROF WITH LESS SPLITTING OCCURRING IN THE
EASTERN PACIFIC. BOTH WILL PRODUCE PLENTY OF WIND BUT THE ECMWF
SUGGESTS A BETTER CHANCE OF SHOWERS ALONG WITH A BIT STRONGER POST
FRONTAL COOLING. A SLOWER FRONTAL TIMING WOULD ALLOW FOR STRONG
PREFRONTAL WARMING WHICH WOULD INCREASE THE THERMAL GRADIENT ALONG
THE FRONT. WARM AND DRY CONDITIONS FOLLOWED BY A COLD FRONTAL
PASSAGE WITH STRONG WINDS WILL BE OF CONCERN TO THOSE WITH FIRE
WEATHER INTERESTS...AND WILL HIGHLIGHT THIS DAY IN THE MORNING
FIRE WEATHER FORECAST. AS FOR TEMPS AND POPS...HAVE LOWERED
EXPECTED HIGHS A BIT IN OUR NW BUT RAISED THEM SLIGHTLY IN OUR SE
WITH EXPECTATION OF A LATE MORNING TO MID AFTERNOON FROPA. COULD
SEE UPPER 70S FOR HIGHS AT SUCH PLACES AS SHERIDAN AND BROADUS.
WILL KEEP POPS BROADBRUSHED AT ISOLD TO SCATTERED SATURDAY
AFTERNOON AND NIGHT.

SUNDAY AND MONDAY WILL BE MOSTLY DRY DAYS WITH TEMPS REMAINING
ABOVE NORMAL. EXPECT HIGHS INTO THE 60S ON SUNDAY AND NEAR 70F ON
MONDAY UNDER SHORTWAVE RIDGING.

IT APPEARS THE NEXT SYSTEM OF INTEREST WILL IMPACT US NEXT
TUESDAY WITH ANOTHER PACIFIC SHORTWAVE AND FRONTAL PASSAGE.
CURRENT INDICATIONS ARE THIS WILL BE VERY PROGRESSIVE ENERGY
WITHOUT MUCH AMPLITUDE...WHICH WOULD PRODUCE A BRIEF CHANCE OF
SHOWERS ALONG WITH WIND.

JKL

&&

.AVIATION...

A BAND OF SNOW SHOWERS FROM K3HT-KBIL-KSHR WILL PRODUCE IFR TO
LIFR CONDITIONS THRU AROUND 12Z. A STEADY IMPROVEMENT TO VFR WILL
THEN OCCUR AFTER SUNRISE AS PRECIPITATION TAPERS OFF. THERE IS A
RISK OF LOCALIZED FOG THRU AROUND 15Z IN AREAS THAT RECEIVED
NIGHTTIME PRECIPITATION...INCLUDING KBIL. FURTHER EAST...A LARGE
AREA OF MVFR CIGS WILL PERSIST AT KMLS AND KBHK THROUGH 18Z BEFORE
IMPROVING TO VFR IN THE AFTERNOON. SOME LIGHT PRECIPITATION WILL
IMPACT THE MTNS AND AREAS MAINLY EAST OF KBIL TONIGHT...WITH LOCAL
MVFR POSSIBLE. MOUNTAINS WILL BE FREQUENTLY OBSCURED IN SNOW
SHOWERS TODAY AND TONIGHT. JKL

&&

.PRELIMINARY POINT TEMP/POPS...

    TDY THU     FRI     SAT     SUN     MON     TUE
-------------------------------------------------------
BIL 051 039/063 043/073 049/073 040/065 041/070 045/065
    2/W 21/N    10/B    02/W    21/B    11/B    13/W
LVM 050 037/062 042/072 049/067 037/065 040/068 042/058
    2/W 21/N    10/N    02/W    21/B    11/B    24/W
HDN 054 032/064 037/074 040/074 035/066 035/072 039/068
    2/W 21/E    10/B    02/W    21/B    11/B    13/W
MLS 049 030/057 038/070 041/074 034/063 037/069 038/067
    1/E 22/W    10/B    02/W    21/B    00/U    12/W
4BQ 048 029/057 036/070 040/076 035/064 036/070 039/069
    1/E 22/W    10/B    02/W    21/B    00/U    12/W
BHK 039 025/048 031/064 037/073 033/061 033/066 037/066
    1/E 32/W    21/E    02/W    20/U    00/U    12/W
SHR 047 031/058 038/070 039/076 035/065 035/070 038/069
    3/W 22/W    10/B    02/W    21/B    11/B    13/W

&&

.BYZ WATCHES/WARNINGS/ADVISORIES...
MT...NONE.
WY...WINTER WEATHER ADVISORY IN EFFECT UNTIL NOON MDT TODAY FOR
      ZONE 98.

&&

$$
WEATHER.GOV/BILLINGS


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