Area Forecast Discussion
Issued by NWS Billings, MT

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FXUS65 KBYZ 250257
AFDBYZ

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BILLINGS MT
857 PM MDT THU APR 24 2014

.UPDATE...
NIGHTTIME INVERSION SETTING UP QUICKLY THIS EVENING AND
PRECIPITATION OVER OUR WESTERN ZONES HAS DIMINISHED. ONLY SOME
ISOLATED POPS EXPECTED FROM BILLINGS TO MILES CITY TONIGHT BUT
THAT CHANCE WILL BE ENDING BY MIDNIGHT. STEEP LAPSE RATES AND WEAK
ENERGY MOVING BENEATH A RIDGE OF HIGH PRESSURE IS CAUSING THE
LIGHT PRECIPITATION. TWEAK TEMPERATURES SLIGHTLY ACROSS THE AREA
TONIGHT AND ALSO ADJUSTED WINDS IN THE LIVINGSTON AREA TO A WEST
DIRECTION. RICHMOND

&&

.SHORT TERM...VALID FOR FRI AND SAT...

WEAK HIGH PRESSURE RIDGE WILL CONTINUE TO BE OVER THE FORECAST
AREA INTO FRIDAY MORNING. HOWEVER...AN UPPER LEVEL WAVE AS NOTED
ON WATER VAPOR IMAGERY CURRENTLY MOVING ACROSS WASHINGTON STATE IS
PROVIDING FOR INCREASING CLOUDS ALONG WITH SOME ISOLATED SHOWER
ACTIVITY ACROSS OUR AREA THIS AFTERNOON. TEMPERATURE/DEWPOINT
SPREADS ARE AROUND 25 TO 30 DEGREES SO THE MAJORITY OF ANY SHOWER
ACTIVITY IS CONSISTING OF A FEW SPRINKLES ALONG WITH SOME GUSTY
WINDS. IN ADDITION...WINDS ALOFT HAVE MIXED DOWN TO THE SURFACE
THIS AFTERNOON RESULTING IN A WINDY AFTERNOON ACROSS THE ENTIRE
AREA...BUT NOT NEARLY AS WINDY AS YESTERDAY. WILL CONTINUE TO KEEP
A SLIGHT SHOWER CHANCE IN THE FORECAST THROUGH THE EVENING EAST OF
BILLINGS...AS WELL AS OVER AND NEAR THE MOUNTAINS. AREAS IN
BETWEEN SUCH AS BILLINGS WILL SEE MORE OF A DOWNSLOPE EFFECT.

HIGH PRESSURE RIDGE WILL CONTINUE OVER THE FORECAST AREA FOR MOST
OF FRIDAY BUT THE AXIS GETS SHIFTED EAST IN RESPONSE TO A STRONG
UPPER LOW THAT MOVES ONTO THE CALIFORNIA COAST. THIS LOW WILL
PROVIDE FOR A SOUTHWEST FLOW ALOFT ALONG WITH SOME UPPER LEVEL
DIVERGENCE. SHOWER CHANCES WILL INCREASE FROM WEST TO EAST DURING
THE AFTERNOON INTO THE EVENING. AT THE SAME TIME...A SURFACE LOW
DEVELOPS ACROSS EASTERN WYOMING DURING THE AFTERNOON RESULTING IN
WINDS BECOMING EAST AND SOUTHEAST ADVECTING SOME LOW LEVEL
MOISTURE INTO THE AREA. THIS SURFACE LOW WILL PLACE A WARM FRONT
ACROSS OUR FORECAST AREA AND THIS WILL BE THE FOCUS AREA FOR THE
BEST PRECIP CHANCES. THE LOW DRIFTS A BIT NORTH FRIDAY NIGHT
TAKING THE BULK OF THE SHOWER ACTIVITY WITH IT.

THE 500MB LOW OVER CALIFORNIA MOVES INTO THE FOUR CORNERS REGION
SATURDAY AND INTO EASTERN COLORADO SATURDAY NIGHT. A DOUBLE-
BARRELED SURFACE LOW TAKES SHAPE ACROSS EASTERN WYOMING AND
NORTHEAST COLORADO PROVIDING FOR A TIGHT PRESSURE GRADIENT AND
ACROSS SOUTHEAST MONTANA. A STRONG EASTERLY FLOW WILL BE IN STORE
ACROSS OUR EASTERN ZONES WITH A NORTH TO NORTHWEST SURFACE WIND
ACROSS OUR CENTRAL AND WESTERN AREA. MODELS BRING INCREASING
PRECIP INTO THE AREA SATURDAY AFTERNOON AND EVENING. ENOUGH
INSTABILITY WILL BE ON TAP TO WARRANT AN ISOLATED THUNDERSTORM
SATURDAY AFTERNOON WITH THE BEST CHANCES BEING ACROSS SOUTHEAST
MONTANA WHERE BETTER SHEAR EXISTS. TEMPERATURES LOOK TO BE WARM
ENOUGH SATURDAY NIGHT FOR THE SHOWERS TO BE IN LIQUID FORM.
HOWEVER...CAN`T RULE OUT A RAIN/SNOW MIX OR WET SNOW FOR THE
MOUNTAIN FOOTHILLS OF SHERIDAN AND RED LODGE WHERE A COUPLE INCHES
COULD OCCUR BUT MAINLY ON GRASSY SURFACES. HOOLEY

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

A FAIR AMOUNT OF PRECIPITATION WAS IN STORE FOR AREAS E OF KBIL
FOR THE EXTENDED PERIOD PER THE LATEST MODEL RUNS. A STRONG
PACIFIC JET WILL CARVE OUT A POSITIVELY TILTED PACIFIC TROUGH OVER
THE WESTERN U.S. ON SUN. AN UPPER LOW OVER E CO WILL ROTATE NE
INTO THE CENTRAL PLAINS ON MON. THIS CUTOFF LOW WILL THEN PHASE
WITH A GREAT LAKES LOW ON TUE AND ROTATE OVER THE MIDWEST THROUGH
THU LEAVING THE FORECAST AREA UNDER CYCLONIC FLOW. GULF OF MEXICO
MOISTURE WILL BE DRAWN INTO THE SYSTEM AND THERE WILL BE AN
INVERTED TROUGH OVER EASTERN PORTIONS OF THE FORECAST AREA...EXTENDING
FROM THE SYSTEM/S SURFACE LOW...INTO MON.

THE ABOVE FACTORS WILL BRING HEAVY PRECIPITATION TO EASTERN
PORTIONS OF THE AREA...MAINLY E OF KBIL. THE CYCLONIC FLOW ALOFT
WILL THEN BRING SCATTERED SHOWERS TO THE AREA MON NIGHT THROUGH
THU. CONTINUED WITH THE HIGH POPS OVER THE E SUN THROUGH MON.
AROUND AN INCH OF PRECIPITATION WILL BE POSSIBLE OVER SE MT
THROUGH MON. IN ADDITION...THE SYSTEM WILL DRAW COLD AIR INTO THE
AREA FROM THE N WHICH WILL CAUSE A RAIN/SNOW MIX. A FEW INCHES OF
ACCUMULATION WILL BE POSSIBLE OVER SE MT...ESPECIALLY SUN NIGHT.
TRENDED TEMPERATURES DOWN SUN AND MON...ESPECIALLY OVER THE E.

OTHERWISE WENT WITH ISOLATED TO SCATTERED POPS MON NIGHT THROUGH
WED. THE MODELS HAD THU DRYING OUT. EXPECTING ONLY A SLOW WARMUP
THROUGH THE WEEK AS MODELS KEEP THE COLD 850 MB AIR OVER THE AREA
INTO WED. ARTHUR
&&

.AVIATION...

MOSTLY VFR CONDITIONS WILL BE THE RULE THROUGH FRI MORN.
HOWEVER...A COUPLE OF LINES OF SHOWERS WILL IMPACT WESTERN AND
CENTRAL AREAS THROUGH 05Z...INCLUDING KLVM AND KBIL...WITH
BRIEF...ERRATIC...GUSTY WINDS...AND BRIEF MVFR CONDITIONS. CANNOT
RULE OUT AN ISOLATED THUNDERSTORM THROUGH 05Z EITHER. MORE
SHOWERS AND ISOLATED THUNDERSTORMS ARE EXPECTED ACROSS WESTERN AND
CENTRAL ROUTES BY FRI AFTERNOON AS SURFACE WINDS BECOME EASTERLY.
MVFR CONDITIONS MAY ACCOMPANY THE SHOWERS/STORMS. MOUNTAIN
OBSCURATION IS POSSIBLE THROUGH FRI EVE. STC

&&

.PRELIMINARY POINT TEMP/POPS...

    FRI     SAT     SUN     MON     TUE     WED     THU
-----------------------------------------------------------
BIL 039/063 041/059 041/052 034/052 034/052 036/058 036/062
    23/W    66/T    87/W    43/W    33/W    22/W    11/U
LVM 038/056 036/053 035/052 033/052 032/055 035/059 035/065
    26/W    68/T    85/W    32/W    22/W    11/U    11/U
HDN 034/064 039/064 040/051 032/051 030/051 032/057 032/063
    22/W    44/T    78/W    65/W    33/W    22/W    11/B
MLS 039/067 045/065 040/048 032/046 030/047 033/052 033/057
    21/B    63/T    78/W    86/W    43/W    22/W    11/B
4BQ 036/068 042/070 040/048 032/046 030/045 032/050 032/057
    11/B    33/T    78/W    86/W    53/W    22/W    11/B
BHK 037/066 043/063 038/046 032/043 028/043 030/048 031/055
    10/B    63/T    78/W    86/W    53/W    32/W    11/B
SHR 035/064 039/065 040/048 033/048 031/048 030/053 032/061
    23/W    43/T    68/W    65/W    33/W    22/W    11/B

&&

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

&&

$$
WEATHER.GOV/BILLINGS



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