Area Forecast Discussion
Issued by NWS Billings, MT

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FXUS65 KBYZ 100220
AFDBYZ

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE BILLINGS MT
820 PM MDT WED APR 9 2014

.UPDATE...

ONLY MINOR CHANGES WERE MADE TO THE OVERNIGHT FORECAST...NAMELY TO
LOWER POPS THE REST OF THE EVENING INTO THE 20 TO 3O PERCENT RANGE
FROM BROADUS TO EKALAKA SINCE RADAR IMAGES AS OF 02 UTC REVEAL THE
SHOWER ACTIVITY IN SOUTHEASTERN MT IS EXITING INTO SD. BACK ACROSS
SOUTH CENTRAL MT...THERE HAS ACTUALLY BEEN AN UPTICK IN SHOWERS AS
FAR NORTHWEST AS LAUREL AND ESPECIALLY FROM PRYOR DOWN TOWARD FORT
SMITH THIS EVENING. AN EARLIER OUTFLOW BOUNDARY THAT COULD BE SEEN
AS A FINE-LINE ON RADAR REFLECTIVITY IMAGES PROPAGATED WESTWARD TO
ABOUT THAT LINE AND IS LIKELY PARTIALLY RESPONSIBLE FOR THE SHOWER
DEVELOPMENT SINCE FORCING ALOFT IS WANING. WE DECIDED TO KEEP SOME
LIKELY POPS IN PLACE UNTIL 06 UTC FROM FORT SMITH SOUTHEAST TOWARD
SHERIDAN GIVEN ALL OF THIS...AND SOME 20 TO 30 PERCENT POPS BEYOND
06 UTC IN THOSE SAME AREAS.

OTHERWISE...WINDS ARE DECREASING WITH THE APPROACH OF A RIDGE AXIS
AT THE SURFACE AND A SLOWLY-DECOUPLING BOUNDARY LAYER...WHICH WILL
LEAD US INTO A RELATIVELY QUIET NIGHT. SCHULTZ

&&

.SHORT TERM...VALID FOR THU AND FRI...

THE COLD FRONT CONTINUES TO MOVE SOUTHEASTWARD THROUGH THE REGION
THIS AFTERNOON. LOW LEVEL MOISTURE IS LACKING AHEAD OF THE
FRONT...SO DESPITE THE STRONG FRONTAL FORCING AND STRONG UPPER
LEVEL DYNAMICS ASSOCIATED WITH THE SUPPORTING SHORTWAVE...WE HAVE
MAINLY SEEN SCATTERED SHOWERS. STILL...CANNOT RULE OUT A FEW
THUNDERSTORMS WITH MAYBE SOME SMALL HAIL ACROSS SOUTHEASTERN
MONTANA AND NORTH CENTRAL WYOMING THROUGH EARLY THIS EVENING. THE
BIGGER STORY IS THE WINDS. BOTH AHEAD OF AND BEHIND THE COLD
FRONT...WE HAVE SEEN NW WINDS GUSTING INTO THE 40 TO 50 MPH RANGE.
WE WILL CONTINUE TO SEE VERY WINDY CONDITIONS THROUGH THIS EVENING
DUE TO MIXING...COLD AIR ADVECTION...AND STRONG SURFACE PRESSURE
RISES BEHIND THE FRONT. WINDS WILL GRADUALLY TAPER OFF OVERNIGHT
AS WE LOSE MIXING AND THE FRONT MOVES WELL AWAY FROM THE REGION.
SOME SHOWER ACTIVITY IS STILL LIKELY THROUGH LATE THIS EVENING
OVER THE SOUTHERN HALF OF THE REGION DUE TO FRONTOGENESIS AND
SHORTWAVE ACTIVITY. TEMPS TONIGHT WILL COOL INTO THE 30S.

THURSDAY AND THURSDAY NIGHT...SHORTWAVE ENERGY IN NW FLOW ALOFT
WILL WORK WITH STEEP LAPSE RATES...DAYTIME HEATING...AND UPPER
LEVEL DIVERGENCE ASSOCIATED WITH STRONG JET ENERGY...TO GENERATE A
FEW SHOWERS...MAINLY IN THE MOUNTAINS AND ACROSS THE EASTERN HALF
OF THE AREA. TEMPERATURES WILL CONTINUE TO RUN A BIT ABOVE NORMAL
WITH HIGHS EXPECTED IN THE UPPER 50S EAST TO THE LOWER 60S
ELSEWHERE. MIXING WILL ALLOW W TO NW WINDS TO GUST TO THE 25 TO
30 MPH RANGE DURING THE DAY THURSDAY.

FLOW ALOFT BECOMES MORE ZONAL FRIDAY IN RESPONSE TO MORE
SHORTWAVE ENERGY MOVING INTO THE PACIFIC NW. FRIDAY SHOULD BE A
MOSTLY DRY DAY. WITH 850 MB TEMPS IN THE LOW TO MID TEENS ABOVE
C...IT WILL ALSO BE A FAIRLY WARM DAY. HIGHS WILL REACH THE MID
60S TO LOW 70S. FRIDAY NIGHT...THE SHORTWAVE ENERGY MOVES ACROSS
THE CWA...SUPPORTING A WEAK COLD FRONT AND AN INCREASING CHANCE OF
RAIN AND SNOW SHOWERS. LOWS FRIDAY NIGHT WILL BE IN THE MID 30S TO
AROUND 40. STC

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

THE FOCUS IN THE EXTENDED FORECAST REMAINS THE QUICK-MOVING
WEATHER SYSTEM FOR SATURDAY INTO SUNDAY. MODELS ARE STARTING TO
CONVERGE ON A SOLUTION FOR THE WAVE CROSSING THE FORECAST AREA
SATURDAY NIGHT...WITH THE BEST CHANCE OF PRECIPITATION SATURDAY
AFTERNOON THROUGH SATURDAY NIGHT AND TAPERING OFF SUNDAY MORNING.
THE MAIN ELEMENTS TO THIS SYSTEM...WHICH PROMISE TO BRING THE MOST
IMPACT TO THE FOOTHILLS...ARE THE QG FORCING MOVING ACROSS THE
AREA...COUPLED WITH DEEP UPSLOPE FLOW AS 850 MB AND 700 MB WINDS
BEND AROUND TO THE NORTHEAST LATE SATURDAY INTO SATURDAY NIGHT.
SOME MODEST INSTABILITY WILL ALSO HELP TO INCREASE PRECIPITATION
RATES ALONG THE FOOTHILLS. AS WITH ANY SPRING STORM
SYSTEM...TEMPERATURES WILL BE AN ISSUE FOR THE RAIN TO SNOW
TRANSITION SATURDAY AFTERNOON AND EVENING. FOR THE HIGHER
ELEVATIONS ALONG THE FOOTHILLS...PRECIPITATION COULD START OFF AS
A RAIN/SNOW MIX THEN QUICKLY TRANSITION TO ALL SNOW. FOR THE REST
OF THE LOWER ELEVATIONS...INCLUDING BILLINGS...PRECIPITATION WOULD
LIKELY FALL AS RAIN SATURDAY AND SATURDAY EVENING...SWITCHING TO
ALL SNOW BY AROUND MIDNIGHT. THUS THE BEST CHANCE FOR ACCUMULATING
SNOWFALL FOR THIS SYSTEM WILL BE ALONG THE FOOTHILLS AND NE FACING
MOUNTAINS FROM MELVILLE TO LIVINGSTON TO RED LODGE...AND FROM FORT
SMITH TO DAYTON TO SHERIDAN WYOMING. OTHERWISE...ANY ACCUMULATIONS
ACROSS THE PLAINS WILL BE LATE SATURDAY NIGHT AND SHOULD ONLY
AMOUNT TO AN INCH OR TWO.

FOR SUNDAY AND BEYOND...TEMPERATURES WILL REMAIN COOL ON SUNDAY
BEHIND THE STORM WITH LIGHT EASTERLY FLOW PREVAILING AS THE
SURFACE HIGH SLIDES BY. RIDGING WILL PUSH IN DURING THE DAY
MONDAY...WITH SOME MODEL DIFFERENCES IN JUST HOW QUICKLY.
NEVERTHELESS...MONDAY WILL BE DRY AND FOLLOW A WARMING TREND.
HOWEVER...BEYOND MONDAY...MODELS CONTINUE TO STRUGGLE WITH THE
OVERALL SYNOPTIC PATTERN. THE IDEA SEEMS TO BE A TRANSITION TO
SOMEWHAT ZONAL FLOW WITH PACIFIC DISTURBANCES MOVING THROUGH. THUS
DON/T EXPECT TO SEE ANY EXTREMELY WARM OR COOL DAYS...AND COULD
SEE CHANCES OF PRECIPITATION THROUGH THE MIDDLE TO END OF NEXT
WEEK.

CHURCH

&&

.AVIATION...

SCATTERED SHOWERS CONTINUE ACROSS SOUTH CENTRAL AND SOUTHEAST
MONTANA...AND NORTHERN WYOMING...BUT ARE DIMINISHING IN COVERAGE.
LOCALIZED MVFR CONDITIONS CAN BE EXPECTED IN SHOWERS...OTHERWISE
VFR CONDITIONS WILL PREVAIL. MOUNTAINS ALSO CONTINUE TO BE
OBSCURED AT TIMES. SKIES WILL CONTINUE TO CLEAR OVERNIGHT. AAG

&&

.PRELIMINARY POINT TEMP/POPS...

    THU     FRI     SAT     SUN     MON     TUE     WED
-----------------------------------------------------------
BIL 034/062 038/068 039/049 027/044 030/058 037/056 033/047
    21/B    10/B    36/R    63/S    11/U    12/W    23/W
LVM 030/060 035/066 036/049 025/049 026/057 034/055 030/046
    22/W    10/N    36/R    63/S    11/U    13/W    33/W
HDN 035/064 034/069 039/051 028/045 028/059 033/056 033/048
    42/W    10/B    36/R    63/S    11/U    12/W    22/W
MLS 031/062 035/068 038/051 026/045 027/056 032/055 033/047
    12/W    10/B    24/R    31/B    11/U    12/W    22/W
4BQ 034/063 034/070 039/054 027/045 026/056 032/056 032/045
    22/W    10/B    34/R    52/S    11/U    12/W    22/W
BHK 029/058 032/065 036/050 025/042 024/051 026/051 029/044
    12/W    10/B    24/R    31/B    11/U    12/W    22/W
SHR 034/061 033/068 038/051 026/042 024/055 032/055 031/046
    62/W    10/B    26/R    76/S    21/U    12/W    33/W

&&

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

&&

$$
WEATHER.GOV/BILLINGS



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