Area Forecast Discussion
Issued by NWS Billings, MT

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FXUS65 KBYZ 300318 AAB
AFDBYZ

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE BILLINGS MT
918 PM MDT MON JUN 29 2015

.UPDATE...

SHOWERS AND THUNDERSTORMS HAVE WEAKENED AS EXPECTED NOW THAT THE
SUN IS SETTING AND THE BOUNDARY LAYER IS STABILIZING. GUSTY WINDS
ASSOCIATED WITH THE COLD POOL TIED TO THAT ACTIVITY WILL DIMINISH
BY MIDNIGHT AS WELL. SOME ADDITIONAL...BUT WEAK SHOWERS AND STORMS
OVER WESTERN MT AND ID MAY REACH SOUTH CENTRAL MT AFTER 06 UTC AND
SO WE DID INCREASE POPS A BIT INTO THE CHANCE RANGE OVER PARTS OF
SOUTH CENTRAL MT AFTER MIDNIGHT WITH THIS UPDATE. WE ALSO ADJUSTED
HOURLY TEMPERATURES FOR THE NEXT FEW HOURS TO ACCOUNT FOR OBSERVED
COLD-POOL-INDUCED TEMPERATURE REDUCTIONS ACROSS SOUTH CENTRAL MT.
SCHULTZ

PREVIOUS UPDATE...ISSUED 652 PM MDT MON JUN 29 2015...

WE UPDATED THE FORECAST TO INCREASE THE CHANCE OF EVENING SHOWERS
AND STORMS OVER SOUTH CENTRAL MT IN ORDER TO ACCOUNT FOR TRENDS IN
RADAR DATA WITH THE ACTIVITY APPROACHING HARLOWTON AND BIG TIMBER
AS OF 645 PM MDT. LOW HUMIDITY IN THE BOUNDARY LAYER IS PROMOTING
STRONG WIND GUSTS WITH THAT ACTIVITY...WITH ENHANCEMENT THANKS TO
THE TERRAIN IN PLACES LIKE LIVINGSTON WHERE A GUST TO 63 MPH WAS
OBSERVED EARLIER. WE INCREASED POPS TO 40 PERCENT AS FAR EAST AS
BILLINGS THIS EVENING...THOUGH THE ACTIVITY SHOULD WEAKEN AS IT
APPROACHES THE CITY SINCE INSTABILITY WILL BE DIMINISHING WITH
SUNSET. SCHULTZ

&&

.SHORT TERM...VALID FOR TUE AND WED...

HOT TEMPERATURES WILL CONTINUE FOR AT LEAST THE NEXT COUPLE OF
DAYS...ALTHOUGH TODAY LOOKS TO BE THE HOTTEST DAY OF THE WEEK. THE
LARGE DOME OF HIGH PRESSURE THAT HAS BEEN OVER THE NORTHERN
ROCKIES WILL GET FLATTENED SOMEWHAT AND SHIFTED EAST TONIGHT INTO
TUESDAY AS A WEAK COLD FRONT AND UPPER LEVEL WAVE MOVE ACROSS THE
AREA. THE FRONT AND UPPER DISTURBANCE WILL APPROACH OUR WESTERN
ZONES THIS AFTERNOON INTO THIS EVENING RESULTING IN INCREASED
CHANCES FOR A THUNDERSTORM. VISIBLE SATELLITE CURRENTLY IS SHOWING
THUNDERSTORMS DEVELOPING ACROSS WESTERN AND SOUTHWESTERN
MONTANA...AS WELL AS CENTRAL IDAHO. EXPECT THIS ACTIVITY TO MOVE
INTO OUR SOUTHWEST MOUNTAINS AND FAR WESTERN COUNTIES BY MID TO
LATE AFTERNOON. THE ACTIVITY MAY ADVANCE AS FAR EAST AS A ROUNDUP-
BILLINGS-SHERIDAN LINE THIS EVENING INTO THE OVERNIGHT HOURS. AS A
RESULT...WILL MAINTAIN A SLIGHT THUNDERSTORM CHANCE ALONG AND WEST
OF THIS LINE THROUGH TONIGHT.

MODELS BRING THE FRONT THROUGH LATE TONIGHT INTO TUESDAY MORNING.
THUNDERSTORM CHANCES WILL MAINLY SHIFT EAST OF BILLINGS DURING THE
AFTERNOON AND EVENING ON TUESDAY. HOWEVER...GUSTY NORTHWEST WINDS
WILL USHER IN BEHIND THE FRONT ACROSS MOST OF OUR AREA.
TEMPERATURES WILL ONLY BE A FEW DEGREES COOLER BEHIND THE FRONT
TUESDAY WITH READINGS STILL CLIMBING WELL INTO THE 90S.

HIGH PRESSURE RIDGING TRIES TO BUILD BACK ACROSS THE AREA TUESDAY
NIGHT INTO WEDNESDAY...MAINLY ACROSS OUR WEST...AS ANOTHER
DISTURBANCE DROPS SOUTH OUT OF CANADA AND MOVES ACROSS THE
NORTHEASTERN PORTIONS OF THE STATE. THIS WILL BRING A SLIGHT
CHANCE FOR A SHOWER/THUNDERSTORM ACROSS OUR FAR EASTERN COUNTIES
LATE INTO THE AFTERNOON INTO THE EVENING. AFTERNOON TEMPERATURES
WILL BE A FEW DEGREES COOLER ESPECIALLY ACROSS THE EAST WITH
READINGS IN THE UPPER 80S TO LOWER 90S WITH POSSIBLY LOWER 80S
ALONG THE DAKOTA BORDER. HOOLEY

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

UNDER NW FLOW ALOFT AND AN ADDITIONAL SHORTWAVE...THURSDAY WILL BE
THE COOLEST DAY IN AWHILE WITH HIGHS EXPECTED TO STAY UNDER 90
DEGREES. WILL KEEP SHOWER/TSTM CHANCES CONFINED TO OUR EAST AND
THE MTNS AS WAVE WILL BE PASSING OUT OF OUR CWA IN THE MORNING.
GFS/ECMWF DO SHOW A WEAKER AREA OF PV BY THURSDAY NIGHT BUT WITH A
DRIER AIRMASS IN PLACE NOT SURE IF THIS WILL GENERATE ACTUAL
SHOWERS.

SHOULD SEE A PERIOD OF DRY WX FRIDAY INTO SATURDAY AS WE UNDERGO
FLAT SHORTWAVE RIDGING AHEAD OF A CLIPPER DROPPING THROUGH BC.
THUS EXPECT A WARMING TREND FRIDAY AND SATURDAY WITH POTENTIAL FOR
A VERY WARM PRE-FRONTAL DAY ON THE LATTER. HAVE EXPANDED CLIMO
POPS ACROSS OUR CWA SATURDAY AFTERNOON AND EVENING AS THIS CLIPPER
AND A COLD FRONT PASS THROUGH THE REGION. THERE ARE SOME
SIGNIFICANT DIFFERENCES BETWEEN THE ECMWF AND GFS WITH THE FORMER
SUGGESTING A STRONGER THERMAL GRADIENT AND A COOLER POST-FRONTAL
DAY ON SUNDAY. SOMETHING TO KEEP WATCH OF MOVING FORWARD.

WILL SUSTAIN CLIMO POPS AND SLIGHTLY ABOVE NORMAL TEMPS FOR SUNDAY
AND MONDAY. MODELS DIVERGE QUITE A BIT BY DAY 7 BUT THERE IS
POTENTIAL FOR MORE PACIFIC SHORTWAVE ACTIVITY IN A GENERALLY
WESTERLY FLOW ALOFT...AND ABOVE NORMAL HEIGHTS.

JKL

&&

.AVIATION...

GUSTY W TO NW SURFACE WINDS OF 35 TO 45 KT WILL AFFECT AREAS FROM
AROUND KBIL TO NEAR A KMLS TO BROADUS LINE THROUGH 04Z.
OTHERWISE...ISOLATED TO SCATTERED SHOWERS AND THUNDERSTORMS WILL
BE OVER THE REGION FROM KMLS TO KSHR W OVERNIGHT. MVFR CONDITIONS
ARE POSSIBLE IN THUNDERSTORMS AND HEAVIER SHOWERS. EXPECT AREAS OF
MOUNTAIN OBSCURATION OVER THE CRAZYS...BEARTOOTHS AND ABSAROKAS
WITH LOCALIZED OBSCURATION OVER THE NE BIGHORNS. ISOLATED SHOWERS
AND THUNDERSTORMS WILL AFFECT THE ENTIRE AREA ON TUE WITH
ACCOMPANYING MVFR/IFR CONDITIONS. EXPECT LOCALIZED MOUNTAIN
OBSCURATION. ARTHUR

&&

.PRELIMINARY POINT TEMP/POPS...

    TUE     WED     THU     FRI     SAT     SUN     MON
-----------------------------------------------------------
BIL 070/096 063/091 062/086 061/091 065/093 061/086 062/090
    42/T    11/U    21/U    11/U    12/T    22/T    22/T
LVM 062/093 053/091 053/088 052/093 055/092 052/088 054/089
    52/T    11/U    11/U    11/U    12/T    22/T    22/T
HDN 065/098 060/093 061/088 057/093 060/095 059/089 059/093
    32/T    11/U    21/U    11/U    12/T    22/T    22/T
MLS 068/097 064/089 062/085 059/089 064/094 059/086 060/090
    12/T    11/U    32/T    11/U    12/T    22/T    22/T
4BQ 065/094 063/087 061/085 058/087 062/092 058/085 060/089
    12/T    11/U    22/T    11/U    12/T    22/T    22/T
BHK 062/093 060/082 057/081 056/083 059/090 057/082 058/085
    12/T    22/T    32/T    11/U    12/T    22/T    22/T
SHR 060/093 058/089 058/083 054/085 057/092 056/084 057/088
    22/T    21/U    22/T    11/U    12/T    22/T    22/T

&&

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

&&

$$
WEATHER.GOV/BILLINGS


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