AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BILLINGS MT
913 PM MDT WED JUN 19 2013
.UPDATE...
THUNDERSTORM ACTIVITY HAS SHIFTED TO OUR NORTH AND AS OF 03Z IS
LOCATED OVER MUSSELSHELL COUNTY AND SHIFTING SLOWLY EASTWARD ALONG
NOSE OF EASTERLY LOW LEVEL JET. SATELLITE IMAGERY SHOWS VERY
IMPRESSIVE DIFFLUENCE AS DYNAMIC SHORTWAVE LIFTS THRU SOUTH
CENTRAL MT. 700MB TEMPS ON THE ORDER OF 12-14C PROVIDING A VERY
STRONG CAP ACROSS OUR EAST TO THIS POINT...AND SURGE OF DRY WY
AIR ALREADY PREVENTED CONVECTION IN OUR SOUTH INCLUDING THE PRYORS
AND BIG HORNS. CONVECTION CURRENTLY APPROACHING NW ROSEBUD COUNTY
IS MOVING INTO THE CAPPED AIRMASS...BUT AS MID LEVEL TEMPS COOL
AND SFC FRONT PUSHES EAST...CONVECTIVE CHANCES WILL INCREASE
ACROSS OUR NORTH CENTRAL TO NORTHEAST PARTS AS THE NIGHT
PROGRESSES...AND CERTAINLY LOW LEVEL SHEAR/INSTABILITY ARE
FAVORABLE PER EAST WINDS AND DEW PTS IN THE UPPER 50S. WILL KEEP
WITH RISK OF TSTMS MENTIONED ACROSS OUR NORTH INCLUDING
FORSYTH...MILES CITY AND BAKER...THOUGH DO NOT THINK CONVECTION
WILL REACH AS FAR EAST AS FALLON COUNTY UNTIL AFTER 06Z...AND TSTM
COVERAGE WILL BE GREATER TO OUR NORTH. OTHERWISE... SUBSIDENCE
AND STRONG LOW LEVEL DOWNSLOPING ARE ALLOWING FOR WX TO QUIET DOWN
FROM LIVINGSTON TO BILLINGS AND SOUTHWARD. HAVE CLEANED OUT POPS
CONSIDERABLY IN THESE AREAS... AND THERE IS NO MORE RISK OF SEVERE
WX HERE. GUSTY POST FRONTAL W-NW WINDS WILL CONTINUE THROUGH THE
NIGHT AS PACIFIC AIRMASS SURGES INTO THE REGION. JKL
&&
.SHORT TERM...VALID FOR THU AND FRI...
POTENTIAL FOR SEVERE THUNDERSTORMS THIS AFTERNOON AND EVENING
WILL BE MORE WIDESPREAD THAN PREVIOUSLY THOUGHT AS DEWPOINTS WERE
IN THE 50S OVER MUCH OF THE AREA. SHEAR WILL INCREASE FROM W TO E
ACROSS THE AREA THIS AFTERNOON AND EVENING. DEWPOINTS IN THE 50S
WERE HELPING TO FEED HIGH CAPES...ESPECIALLY IN THE E. SURFACE
CAPES RANGED FROM 500 TO 2000 J/KG FROM W TO E ACROSS THE AREA AT
19Z. WILL HAVE PLENTY OF LIFT FROM DIFFLUENT FLOW ALOFT...COLD
FRONT MOVING THROUGH W MT...AND STRONG SHORTWAVE SEEN IN WATER
VAPOR IMAGERY...ROTATING AROUND THE BASE OF THE NEGATIVELY TILTED
TROUGH OVER THE PACIFIC NW. A SEVERE THREAT WILL PROGRESS FROM W
TO E ACROSS THE REGION THROUGH THE EVENING AS DYNAMICS MOVE E.
ONLY HINDRANCE TO SEVERE WEATHER WILL BE WHERE THE S TO SW FLOW
WILL ADVECT DRIER AIR INTO THE REGION. GUSTY WINDS WILL BE
POSSIBLE IN THESE AREAS...CURRENTLY EXPECTED FROM KBIL S AND
E...BUT WILL NEED TO WATCH THIS EVOLVING SITUATION CAREFULLY THIS
AFTERNOON. EXPECT SEVERE WEATHER TO EXIT THE AREA AFTER 06Z AS
COLD FRONT MOVES E. BUFKIT SOUNDINGS HAD A STRONG WIND SHIFT
BEHIND THE FRONT WITH WIND SPEEDS WELL INTO THE 30S.
UPPER LOW WILL ROTATE SLOWLY INTO THE REGION THU THROUGH FRI
NIGHT. DOWNSLOPE FLOW WILL COMPETE WITH UPPER DYNAMICS FOR
PRECIPITATION CHANCES ON THU. CONTINUED THE LOW CHANCES OVER AND
NEAR THE MOUNTAINS WITH JUST A SLIGHT MENTION OF THUNDER AS
AIRMASS WILL BE MUCH MORE STABLE THAN TODAY/S AIRMASS. A SECONDARY
COLD FRONT WILL PASS THROUGH THE AREA THU NIGHT WHICH WILL BRING
SCATTERED SHOWERS TO THE AREA. MODELS DIFFERED ON PLACEMENT OF
PRECIPITATION FRI THROUGH FRI NIGHT. DYNAMICS ALOFT AND INVERTED
SURFACE TROUGH OVER THE E WILL BRING A CHANCE OF SHOWERS AND
THUNDERSTORMS TO THE AREA. LEANED ON THE SREF FOR POP FORECAST.
TEMPERATURES WILL BE AROUND SEASONABLE VALUES THU AND FRI. ARTHUR
.LONG TERM...VALID FOR SAT...SUN...MON...TUE...WED...
EXTENDED MODELS IN FAIRLY GOOD AGREEMENT SO DID NOT MAKE ANY
SIGNIFICANT CHANGES WITH THIS FORECAST ISSUANCE. LARGE UPPER LOW
CURRENTLY OVER THE PACIFIC NORTHWEST WILL SLOWLY SHIFT EAST ACROSS
THE CANADIAN BORDER SATURDAY AND SATURDAY NIGHT AND BE SITUATED
JUST NORTH OF NORTH DAKOTA DURING THE DAY SUNDAY. AT THE SAME
TIME...A FEW DISTURBANCES WILL GET PULLED NORTHEAST WITH A
SOUTHWEST FLOW ALOFT BRINGING VERY GOOD CHANCES FOR SHOWERS AND
THUNDERSTORMS TO THE ENTIRE FORECAST AREA SATURDAY AND SATURDAY
NIGHT. BEST CHANCES WILL BE NEAR THE DAKOTA BORDERS WHERE CHANCES
HAVE BEEN INCREASED TO LIKELY SATURDAY INTO SATURDAY NIGHT. THE
UPPER LOW SHIFTS FURTHER EAST SUNDAY LEAVING OUR FORECAST AREA IN
A BROAD SOUTHWEST FLOW ALOFT. AT THIS TIME...NO BIG DISTURBANCES
LOOK TO INFLUENCE OUR AREA RESULTING IN MAINLY DRY CONDITIONS WITH
POSSIBLY AN ISOLATED SHOWER/THUNDERSTORM THROUGH THE PERIOD.
TEMPERATURES WILL BE AT OR SLIGHTLY BELOW NORMAL FOR THE WEEKEND
BEFORE WARMING TO ABOVE NORMAL READINGS BY EARLY TO MID NEXT WEEK.
HOOLEY
&&
.AVIATION...
THUNDERSTORM ACTIVITY HAS ENDED AT KLVM AND KBIL...BUT COULD SEE
ISOLD ACTIVITY REACH KMLS AND KBHK LATER TONIGHT. BRIEF MVFR TO
IFR CAN BE EXPECTED IN THE THUNDERSTORMS. OTHERWISE VFR WILL
PREVAIL WITH GUSTY W-NW WINDS ACROSS THE LOWER ELEVATIONS BEHIND A
PACIFIC COLD FRONT. THESE WINDS WILL CONTINUE INTO THURSDAY...WITH
A WEAKENING TREND THROUGH THE AFTERNOON. JKL
&&
.PRELIMINARY POINT TEMP/POPS...
THU FRI SAT SUN MON TUE WED
-----------------------------------------------------------
BIL 051/077 052/073 052/069 051/078 054/082 058/082 059/082
11/U 33/T 34/T 41/B 11/B 22/T 21/U
LVM 042/070 041/072 042/067 046/079 046/082 051/081 054/085
23/T 34/T 35/T 40/B 22/T 22/T 21/U
HDN 051/078 052/074 050/072 050/078 052/082 054/083 058/083
10/U 33/T 24/T 41/B 11/B 22/T 21/U
MLS 058/078 055/077 056/076 055/080 056/083 059/083 061/085
20/U 34/T 34/T 42/T 11/B 22/T 21/B
4BQ 055/080 055/076 054/075 053/079 054/084 057/084 059/086
10/U 34/T 46/T 42/T 11/B 22/T 21/U
BHK 059/077 054/078 055/074 054/076 054/084 059/082 062/085
30/U 25/T 56/T 42/T 22/T 22/T 21/U
SHR 048/078 048/075 048/073 047/076 049/081 052/082 053/084
01/U 24/T 34/T 41/B 11/B 22/T 21/U
&&
.BYZ WATCHES/WARNINGS/ADVISORIES...
MT...NONE.
WY...NONE.
&&
$$
WEATHER.GOV/BILLINGS
