Area Forecast Discussion
Issued by NWS Billings, MT

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FXUS65 KBYZ 280324
AFDBYZ

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BILLINGS MT
924 PM MDT WED APR 27 2016

.UPDATE...
TEMPS HAVE FALLEN TO THE LOWER/MID 30S AND WE ARE SEEING A
TRANSITION TO LIGHT SNOW ACROSS MOST OF THE CWA AS OF 9PM. WATER
VAPOR IMAGERY SHOWS ENERGY IN WESTERN SD APPROACHING OUR SE PARTS.
EXPECT PCPN TO BE ENHANCED IN OUR SOUTHEAST FOR THE NEXT FEW
HOURS...THEN IT SHOULD BECOME LIGHTER AS ASCENT BEGINS TO
WEAKEN IN THIS AREA...AS MODEL QPF SUGGESTS AFTER 06Z. AN AREA OF
PV IN NORTH CENTRAL WY REMAINS IN A FAVORABLE LOCATION TO ALLOW
ASCENT TO STRETCH FROM EAST TO WEST ACROSS OUR CWA...AND HAVE
RAISED POPS A BIT MORE IN OUR WEST THRU THE NIGHT. HAVE ALSO
RAISED POPS IN OUR NW AT 12-18Z THURSDAY AS DEEP EASTERLY UPSLOPE
WINDS WILL FAVOR THIS AREA INTO TOMORROW. COULD SEE A COUPLE
INCHES OF SNOWFALL IN THE HARLOWTON AREA. HAVE ALSO LOWERED
FORECAST LOWS A BIT PER CURRENT VALUES. JKL

PREVIOUS DISCUSSION ISSUED 520 PM...
WESTERN EXTENT OF A RATHER LARGE AREA OF MOSTLY LIGHT
PRECIPITATION CONTINUES TO PUSH WEST AND IS TO A HARLOWTON TO
COLUMBUS LINE...IE WEST OF BILLINGS...WITH RAIN/SNOW CONTINUING
ALL THE WAY TO THE DAKOTAS BORDER. ASCENT WILL BE STRONGEST THIS
EVENING BUT SHOULD PERSIST THROUGH THE NIGHT...WITH WEAK AREA OF
PV IN NORTH CENTRAL WY IN AN IDEAL LOCATION FOR WET CONDITIONS IN
OUR CWA...SO WITH CONFIDENCE HAVE RAISED POPS MANY AREAS TONIGHT.
THIS INCLUDES BILLINGS WHERE A RAIN/SNOW MIX MAY LAST THRU THE
NIGHT. WOULD EXPECT AREAS OF LIGHT PCPN TO LAST INTO THURSDAY
MORNING AS WELL. THERE WILL BE SOME SNOW ACCUMULATION OVER THE
HILLS...PROBABLY ON THE ORDER OF 1-2 INCHES OF SLUSHY SNOW...AND
AN INCH OR SO IS POSSIBLE UP IN OUR NW PARTS AS UPSLOPE FLOW
DEEPENS EAST OF THE CRAZY MTNS THRU THE NIGHT. HAVE RAISED SNOW
AMOUNTS SLIGHTLY UP NEAR HARLOWTON AND JUDITH GAP. FOR BILLINGS...
WOULD EXPECT A LITTLE ACCUMULATION OVER THE SURROUNDING HILLS AS
TEMPS FALL TO THE LOWER 30S. A DUSTING IS EVEN POSSIBLE ON THE
GRASS IN THE CITY BY SUNRISE THURSDAY. JKL

&&

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

MODELS ARE IN PRETTY GOOD AGREEMENT OVER THE NEXT 12 TO 24 HRS
WITH PLACEMENT OF QPF ALONG STRETCHED OUT DEFORMATION ZONE
INDUCED BY THE UPPER LOW OVER THE GREAT PLAINS. OUR MAIN FORECAST
CONCERN IS WITH REGARDS TO ACCUMULATING SNOW AND IMPACTS IN THE
FAR EASTERN ZONES THROUGH TONIGHT.

DEFORMATION BAND HAS NICE EASTERLY FLOW AND ISENTROPIC LIFT ALONG
IT EXTENDING FROM SOUTH DAKOTA INTO NORTH CENTRAL MONTANA. WAVES
OF PRECIPITATION ALONG THIS BAND CONTINUE TO AFFECT OUR CWA
OVERNIGHT AND INTO THURSDAY BEFORE SLOWLY WEAKENING AND
DISSIPATING TOMORROW NIGHT. MY CONCERN IS CENTERED AROUND THE
850MB PROGS SHOWING AN AXIS OF -2C EXTENDING OVER OUR EASTERN
ZONES. WHAT WE HAVE TO WEIGH IS FACT THAT WHILE SNOW IS MORE
LIKELY TO ACCUMULATE AFTER DARK...NOT MUCH SNOW IS ACCUMULATING AT
THIS TIME AND MODELS SUGGEST BEST PRECIPITATION RATES ARE THROUGH
THIS AFTERNOON...LETTING UP A BIT BY TONIGHT. SO UNLESS WE SEE A
BURST OF SNOWFALL THAT PILES UP /VIA WEBCAMS OR SPOTTER
REPORTS/...WE WILL LIKELY JUST CONTINUE TO USE THE HAZARDOUS
WEATHER OUTLOOK AND SOCIAL MEDIA AS A HEADS UP FOR FOLKS OUT EAST
THAT THEY MAY SEE SOME SLUSHY ROADS TONIGHT AND EARLY THURSDAY.

PRECIPITATION GENERALLY SHUT OFF BY FRIDAY MORNING WHILE NEXT
UPPER LOW TRACKS THROUGH SOUTHERN COLORADO...AND APPEARS TO FAR
SOUTH TO AFFECT OUR CWA. SO STILL LOOKING FOR A LITTLE WARMER AND
CERTAINLY  DRIER CONDITIONS FRIDAY...THOUGH A FEW SHOWERS ARE
POSSIBLE IN THE HIGH COUNTRY BY EVENING AS NEXT UPPER LOW DROPS
INTO THE GREAT BASIN AND SPREADS SOME PACIFIC MOISTURE OUR WAY
AGAIN. BT

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

THE UPCOMING WEEKEND WILL CONTINUE THE OVERALL TREND OF BEING
COOL AND SHOWERY. MODELS ARE IN AGREEMENT IN KEEPING A LARGE
TROUGH OVER MOST OF THE WESTERN U.S. HOWEVER...DIFFERENCES EXIST
IN THE MODELS WITH SEVERAL UPPER LOWS. ON SATURDAY...BOTH THE GFS
AND ECMWF HAVE AN UPPER LOW OVER THE NEBRASKA AREA...AS WELL AS
SOUTHERN UTAH/CALIFORNIA. BY SUNDAY...THE UPPER FLOW ACROSS THE
NORTHERN AND CENTRAL ROCKIES BECOMES MORE STAGNANT AS THE JET
ENERGY WILL BE WELL NORTH ACROSS CANADA AND WELL SOUTH ACROSS THE
SOUTHERN STATES. AS A RESULT...THE GENERAL TROUGHINESS LOOKS TO
STAY IN PLACE THROUGH SUNDAY NIGHT WITH PIECES OF VORTICITY
WOBBLING AROUND THE REGION. THIS WILL RESULT IN CONTINUED CHANCES
FOR SHOWERS ACROSS THE FORECAST AREA WITH THE HIGHEST CHANCES
ACROSS OUR SOUTHERN AREAS ALONG THE MONTANA/WYOMING BORDER...BUT
ALL AREAS WILL HAVE A CHANCE FOR SHOWERS. TEMPERATURES OVER THE
WEEKEND WILL REMAIN BELOW NORMAL WITH READINGS IN THE UPPER 40S TO
MIDDLE 50S.

THE LARGE SCALE PATTERN BEGINS TO SLOWLY BREAK APART MONDAY.
HOWEVER...MODELS ARE NOT IN GOOD AGREEMENT THIS FAR OUT AS THE GFS
KEEPS SOME TROUGHINESS OVER THE NORTHERN ROCKIES WHILE THE ECMWF
TRIES TO BRING A RIDGE OVER THE AREA. MODELS DO...HOWEVER...TRY TO
BUILD SOME BRIEF RIDGING OVER THE STATE TUESDAY AND WEDNESDAY IN
RESPONSE TO ANOTHER TROUGH APPROACHING THE WEST COAST. THIS WOULD
ALLOW CONDITIONS TO DRY AND TEMPERATURES TO WARM TO NORMAL OR
SLIGHTLY ABOVE NORMAL. HOOLEY
&&

.AVIATION...


WIDESPREAD MVFR TO IFR CONDITIONS WILL PERSIST ACROSS THE AREA
TONIGHT AS RAIN AND SNOW CONTINUE OVER THE REGION. LOCALIZED LIFR
CONDITIONS ARE POSSIBLE...WITH SOME LOWERING CIGS AND HEAVIER
PRECIP OVERNIGHT. CONDITIONS ARE EXPECTED TO IMPROVE FROM EAST TO
WEST BEGINNING LATE THURSDAY MORNING. GILSTAD

&&

.PRELIMINARY POINT TEMP/POPS...

    THU     FRI     SAT     SUN     MON     TUE     WED
-----------------------------------------------------------
BIL 032/044 034/055 037/055 040/056 039/061 041/066 042/069
    +5/S    21/B    14/W    44/W    22/W    11/B    11/U
LVM 032/046 031/056 035/056 036/055 035/060 036/066 040/069
    63/O    32/W    23/W    44/W    22/W    22/W    22/W
HDN 032/046 031/056 035/054 036/056 036/061 037/066 039/069
    +4/O    21/B    14/W    44/W    22/W    11/B    11/U
MLS 032/048 034/055 037/054 037/057 038/062 039/066 043/068
    +5/O    21/E    13/W    22/W    11/B    11/U    10/U
4BQ 031/043 029/052 035/049 036/053 036/059 037/063 039/067
    +5/S    31/E    16/W    44/W    22/W    11/B    11/U
BHK 030/045 030/051 034/052 034/055 036/059 038/063 040/065
    +4/S    11/E    14/W    22/W    11/B    11/B    10/U
SHR 031/044 029/053 033/050 033/052 035/057 036/062 038/064
    93/S    21/E    24/W    44/W    32/W    22/W    21/B

&&

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

&&

$$
WEATHER.GOV/BILLINGS


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