Area Forecast Discussion
Issued by NWS Billings, MT

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
000
FXUS65 KBYZ 241557
AFDBYZ

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE BILLINGS MT
957 AM MDT TUE MAR 24 2015

.UPDATE...
UPDATED FORECAST TO FOLLOW RADAR TRENDS WITH PRECIPITATION
DECREASING OVER THE EAST WITH BOWMAN RADAR SHOWING WRAP AROUND
BAND PULLING OUT OF BAKER. BAKER HAD SNOW CHANGE BACK OVER TO
RAIN AND EVEN THE BACK EDGE OF THE LOW CLOUDS SHOULD BE
PROGRESSIVE THROUGH THE AREA. LOWERED CLOUD COVER IN CENTRAL ZONES
AS VISIBLE SATELLITE SHOWS A GOOD BREAK AHEAD OF THE
DESTABILIZATION FROM THE SYSTEM MOVING THROUGH IDAHO. DIURNAL
HEATING AND COOLING ALOFT WILL SUPPORT INCREASING CONVECTIVE
ACTIVITY THROUGH THE AFTERNOON WITH A SURFACE BOUNDARY SLIDING
THROUGH THE REGION IN THE EVENING. WHEN THIS BOUNDARY REACHES THE
FOOTHILLS AND MOUNTAINS IT WILL BECOME THE FOCUS FOR HEAVY SNOW
SHOWERS AND CURRENT HIGHLIGHTS LOOK GOOD. FURTHER NORTH ALONG THE
YELLOWSTONE RIVER VALLEY WILL SEE A RAIN SNOW MIX UNTIL MIDNIGHT
THOUGH RUC INDICATES SOME LOCAL FREEZING LEVEL LOWERINGS DUE TO
THE CONVECTIVE ACTIVITY. WITH WARM GROUND AND SHORT WIND FOR
SNOWFALL DO NOT EXPECT MUCH IN THE WAY OF ACCUMULATIONS LOWER
ELEVATIONS. BORSUM

&&

.SHORT TERM...VALID FOR TDY AND WED...

AN UNSETTLED WEATHER PATTERN IS EXPECTED TODAY AND WEDNESDAY WITH
THE HIGHLIGHT LIKELY BEING HEAVY SNOW SHOWERS IN THE BEARTOOTH AND
ABSAROKA MOUNTAINS AND THE RED LODGE FOOTHILLS...MAINLY TONIGHT.

TODAY...WRAP-AROUND MOISTURE IN THE FORM OF RAIN AND POSSIBLY EVEN
A MIX WITH SNOW WILL LINGER IN FAR SOUTHEASTERN MT...ESPECIALLY IN
THE BAKER AREA...THIS MORNING. OVERNIGHT RADAR AND MODEL DATA BOTH
SUGGEST A SLOWER AND DEEPER LOW- TO MID-LEVEL LOW MOVING NORTHEAST
INTO NORTH DAKOTA THIS MORNING IN SUPPORT OF THAT PRECIPITATION. A
COOLER AND BREEZY TO WINDY DAY IS EXPECTED IN THE WAKE OF THAT LOW
WITH CYCLONIC FLOW SUPPORTING LOW POPS MOST EVERYWHERE. HOWEVER...
FORECAST SOUNDINGS IN SOUTHEASTERN MT ARE NOT THAT UNSTABLE AND WE
DID NOT SEE MUCH SUPPORT FOR EVEN SHALLOW CONVECTION IN THE 00 UTC
HIGH-RESOLUTION MODEL OUTPUT...SO SLIGHT-CHANCE POPS MIGHT EVEN BE
TOO MUCH IN SOUTHEASTERN MT THIS AFTERNOON. BACK FURTHER WEST...WE
EXPECT INCREASING SHOWER ACTIVITY AFTER 18 UTC AS ANOTHER MID- AND
UPPER-LEVEL SHORTWAVE TROUGH BEGINS AFFECTING THE AREA. WE BEGAN A
WINTER STORM WARNING FOR THE BEARTOOTH/ABSAROKA RANGES AT NOON MDT
/18 UTC/ AS THAT WAVE APPROACHES AS SNOW SHOWERS SHOULD PICK UP IN
EARNEST AT THE HIGHER ELEVATIONS THIS AFTERNOON.

TONIGHT...A WEAK SOUTHWARD-MOVING FRONTAL PUSH IS EXPECTED AS THAT
SHORTWAVE TROUGH DROPS ACROSS WY. THAT WILL TURN LOW-LEVEL FLOW TO
A MORE NORTHERLY AND UPSLOPE TRAJECTORY AND THAT WILL COMBINE WITH
THE CYCLONIC FLOW ALOFT AND STEEP MID-LEVEL LAPSE RATES OF 7 C/KM
TO PRODUCE HEALTHY PRECIPITATION OVER AND NEAR THE HIGHER TERRAIN
OF SOUTH CENTRAL MT AND NORTH CENTRAL WY. THIS TYPE OF LARGE-SCALE
PATTERN FAVORS HEAVY SNOW ON THE NORTH SLOPES OF THE BEARTOOTH AND
ABSAROKAS AND IN THE FOOTHILLS AT RED LODGE...AND USING A BLEND OF
00 UTC HIGH-RESOLUTION WRF-NMM AND WRF-ARW MODEL DATA WITH A DASH
OF INPUT FROM A LOCALLY-RUN WRF-NMM PRODUCED AT NWS RIVERTON GAVE
LIQUID-EQUIVALENT MOISTURE TOTALS OF 0.70 TO 1.00 ON SLOPES WHICH
ARE FAVORED BY THE EXPECTED WIND DIRECTIONS. IT/S A BIT UNCLEAR AS
TO WHEN RAIN WILL CHANGE OVER TO SNOW DOWN TO RED LODGE...BUT NONE
OF THE MODEL GUIDANCE SUGGESTS IT WON/T DO SO BY LATE EVENING. OUR
FORECAST IS THUS A RELATIVELY HIGH-CONFIDENCE ONE IN SUPPORT OF 8
TO 14 INCHES OF SNOW OVER THE MOUNTAINS AND HIGHER...NORTH-FACING
SLOPES AND 5 TO LOCALLY 10 INCHES AROUND RED LODGE. WE THUS ISSUED
A WINTER STORM WARNING FOR THE RED LODGE FOOTHILLS AS WELL BETWEEN
6 PM MDT THIS EVENING AND 9 AM MDT WEDNESDAY...WHEN WE ALSO ENDED
THE WARNING FOR THE MOUNTAINS. THE HIGH-RESOLUTION MODEL GUIDANCE
WE USED TO BUILD THE FORECAST SUGGESTED LOWER TOTALS JUST BENEATH
ADVISORY-LEVEL CRITERIA IN THE BEARTOOTH FOOTHILLS LIKE AT MCLEOD
AND OVER THE NORTHEASTERN BIGHORN MOUNTAINS...AND SO CONFIDENCE IN
GETTING HEADLINE-WORTHY SNOW WASN/T HIGH ENOUGH FOR US TO ISSUE A
WINTER WEATHER ADVISORY IN THOSE LOCATIONS JUST YET. THERE WILL BE
SNOW IN THOSE PLACES THOUGH AND A LATER FORECAST MAY NEED TO ADD
IN SOME ADDITIONAL HEADLINES THERE.

OTHERWISE...WE ALSO HAVE CHANCE-STYLE POPS ELSEWHERE IN THE LOWER
ELEVATIONS OF SOUTH CENTRAL MT AND NORTH CENTRAL WY TONIGHT AS
WELL IN RESPECT TO THE SAME SCENARIO...ALBEIT WITH WEAKER FORCING
IN SUPPORT OF ONLY LIGHT MOISTURE TOTALS IN SPOTS LIKE BILLINGS.

WEDNESDAY...CYCLONIC FLOW WILL CONTINUE AND SO WILL SOME CHANCE
OF SHOWERS IN MOST AREAS. IT WILL ALSO STAY RELATIVELY COOL WITH
HIGHS ONLY IN THE 40S TO LOWER 50S F. SCHULTZ

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

MOIST NW FLOW WILL CONTINUE OVER THE REGION THURSDAY BUT LATEST
TRENDS ARE TO KEEP THE SFC TROF A BIT EAST OF BILLINGS AS RIDGE
BEGINS TO BUILD IN FROM THE WEST. THIS WILL RESULT IN WARMER AND
DRIER CONDITIONS IN OUR WEST HALF...WITH MUCH BETTER CHANCE OF
SHOWERS TO THE EAST ESPECIALLY AS WEAK BACKDOOR COOLING INCREASES
LOW LEVEL BAROCLINICITY. EXPECTING SOME MORE SNOW ACCUMULATION
OVER THE NW FLOW FAVORED BIGHORN MTNS...BUT LOWER ELEVATION
SNOWFALL SHOULD BE MINIMAL OR NONEXISTENT DUE TO MILD SFC TEMPS.
IT IS ALSO POSSIBLE THAT PARTS OF OUR EAST COULD MIX WITH A LITTLE
LIGHT FREEZING RAIN EITHER EARLY THURSDAY MORNING OR THURSDAY
NIGHT BEFORE PCPN ENDS AS WARM ADVECTION OVERRUNS THE
AFOREMENTIONED BACKDOOR COOL FRONT. AS FOR TEMPS...HAVE RAISED
THURSDAY HIGHS AND THURSDAY NIGHT LOWS SIGNIFICANTLY ESPECIALLY
FROM BILLINGS WEST. SHOULD SEE HIGHS ON THURSDAY BACK NEAR 60F OUT
WEST...AND ONLY IN THE 40S ALONG THE DAKOTAS BORDER.

UPPER RIDGE SHIFTS EAST ALLOWING FOR MUCH WARMER TEMPERATURES
FRIDAY AND SATURDAY. GIVEN H5 HEIGHTS INTO THE 570S AND 700MB
TEMPS ABOVE 0C WE WILL SEE TEMPS GET BACK TO THE UPPER 60S AND
70S. A BREAK DOWN OF THIS RIDGE IS IN STORE FOR SATURDAY BUT THERE
ARE TIMING ISSUES WHICH WILL SIGNIFICANTLY IMPACT HOW WARM IT MAY
GET ON SATURDAY. A QUICKER FRONTAL PASSAGE WILL OBVIOUSLY BEGIN A
COOL DOWN ON SATURDAY...BUT IF THE SLOWER ECMWF VERIFIES WE COULD
BE LOOKING AT SOME MID TO UPPER 70S IN A STRONG DOWNSLOPE AND
PREFRONTAL REGIME AHEAD OF A FROPA EITHER SATURDAY AFTERNOON OR
EVENING. A FEW HOURS COULD MAKE A BIG DIFFERENCE HERE.

SHOULD SEE AT LEAST SOME LIGHT SHOWER ACTIVITY ASSOCIATED WITH
WEAK WEEKEND CLIPPER...ALONG WITH A MODEST COOL DOWN INTO SUNDAY.
THIS IS EXPECTED TO BE A WEAK SYSTEM AND HEIGHTS REMAIN NEAR
570DAM ON SUNDAY...SO IMPACTS WILL BE MINIMAL. COULD SEE SOME
RESIDUAL SHOWERS OVER THE MOUNTAINS MONDAY BUT OTHERWISE MODEL
CONSENSUS IS FOR BROAD UPPER RIDGING. TEMPS WILL REMAIN ABOVE
NORMAL SUNDAY/MONDAY.

LOOKING A BIT FURTHER AHEAD...THERE IS POTENTIAL FOR A STRONGER
TROF AND INCREASED PCPN CHANCES BY NEXT TUESDAY/WEDNESDAY...BUT
PLENTY OF MODEL SPREAD EXISTS BOTH WITH THIS FEATURE AND FLOW IN
THE NORTHEAST PACIFIC. STAY TUNED.

JKL
&&

.AVIATION...

LIGHT PRECIPITATION AND IFR CONDITIONS WILL SLOWLY MOVE OUT OF
KBHK THIS MORNING. CONDITIONS SHOULD RISE TO VFR BY EARLY
AFTERNOON. THE REST OF THE AREA WILL HAVE VFR FLYING CONDITIONS.
SHOWERS WILL DEVELOP THIS AFTERNOON...ESPECIALLY IN THE MOUNTAINS.
SOME OF THE SHOWERS COULD CAUSE LOCAL MVFR CONDITIONS. THE
MOUNTAINS WILL BE OBSCURED. TWH
&&

.PRELIMINARY POINT TEMP/POPS...

    TDY WED     THU     FRI     SAT     SUN     MON
-------------------------------------------------------
BIL 055 030/052 038/060 040/071 048/076 040/065 041/070
    4/W 53/W    32/W    10/B    02/W    22/W    11/B
LVM 048 029/049 033/060 040/071 048/071 038/065 040/068
    5/W 83/W    22/W    10/B    02/W    22/W    21/B
HDN 059 028/053 032/059 032/073 040/078 035/066 035/072
    3/W 53/W    32/W    10/B    02/W    22/W    11/B
MLS 055 027/048 030/050 033/067 040/075 034/061 037/068
    2/W 11/B    22/W    10/B    02/W    21/B    11/U
4BQ 057 026/048 030/050 029/068 040/077 035/064 036/070
    2/W 11/B    24/W    20/B    02/W    21/B    11/B
BHK 046 024/042 024/045 027/061 036/073 032/059 033/065
    7/W 11/B    22/W    21/E    02/W    21/U    11/U
SHR 054 027/046 030/053 032/068 039/076 036/065 035/070
    3/W 54/W    34/W    20/B    02/W    22/W    11/B

&&

.BYZ WATCHES/WARNINGS/ADVISORIES...
MT...WINTER STORM WARNING IN EFFECT FROM 6 PM THIS EVENING TO 9 AM
      MDT WEDNESDAY FOR ZONE 56.
     WINTER STORM WARNING IN EFFECT UNTIL 9 AM MDT WEDNESDAY FOR
      ZONE 67.
WY...NONE.

&&

$$
WEATHER.GOV/BILLINGS


USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.