033
FXUS65 KBYZ 191513
AFDBYZ
AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE BILLINGS MT
913 AM MDT WED JUN 19 2013
UPDATE
SEVERE THUNDERSTORMS WILL BE POSSIBLE N OF A KLVM TO KBIL LINE
THIS AFTERNOON AND EVENING. IF CONVECTION INHIBITION CAN BE
OVERCOME OVER SE MT...SEVERE WEATHER WILL BE POSSIBLE THERE TOO.
PLENTY OF FACTORS WILL CONTRIBUTE TO LIFT OVER THE AREA THROUGH
TONIGHT. DIFLUENT FLOW WAS EVIDENT ON WATER VAPOR IMAGERY THIS
MORNING. UPPER LOW WAS ALSO SEEN ON IMAGERY NEGATIVELY TILTING
INTO THE PACIFIC NW. A STRONG 500 MB FLOW W OF THE AREA AT 12Z
WILL MOVE E DURING THE DAY BRINGING INCREASING SHEAR. SHORTWAVE
ENERGY WILL ROTATE INTO THE AREA TODAY THROUGH TONIGHT...BRINGING
Q-VECTOR CONVERGENCE. A LOW-LEVEL JET WILL STRENGTHEN OVER THE
EASTERN ZONES TODAY AS WELL. MORE LIFT WILL BE PROVIDED BY STRONG
JET DIVERGENCE OVER THE WESTERN ZONES TONIGHT.
THERE WILL NOT BE A LOT OF MOISTURE TO WORK WITH THROUGH THIS
EVENING AS MOISTURE TRANSPORT VECTORS SHOWED THE BEST MOISTURE
BEING TRANSPORTED FROM THE CENTRAL PLAINS INTO THE NE PART OF MT.
REMAINDER OF THE AREA WILL RECEIVE MOISTURE FROM WY/SE ID/UT WHERE
PRECIPITABLE WATERS WERE AROUND /0.30/ INCHES WHICH WAS DRY AIR.
AS FOR INSTABILITY...HIGH CAPES AND HELICITIES WILL BE E OF KBIL
THIS AFTERNOON AND EVENING SO STORMS THAT DO FORM WILL NEED TO
MONITORED CLOSELY FOR SEVERE POTENTIAL. STORMS THAT FORM ALONG
THE NORTHERN TIER WILL BE IN A HIGH CAPE/INCREASING SHEAR
ENVIRONMENT AND WILL NEED TO BE WATCHED AS WELL. THE AREAS WHERE
SEVERE STORMS AND DRY THUNDERSTORMS WERE MENTIONED WERE IN GOOD
SHAPE PER THE ABOVE.
NOTE THAT THE 12Z HRRR HAS NOTHING DEVELOPING UNTIL 22Z THIS
AFTERNOON. SEE NO NEED TO CHANGE GOING FORECAST. THE SYSTEM/S COLD
FRONT WILL MOVE INTO THE WESTERN ZONES BY 00Z TONIGHT AND CROSS
THE AREA OVERNIGHT. SPC SSEO FROM 00Z LAST NIGHT SHOWED ACTIVE
WEATHER EXITING THE AREA BETWEEN 06-09Z TONIGHT.
ONLY TEMPERATURE ADJUSTMENT WAS TO LOWER READINGS INTO THE 80S IN
FAR SE MT WHERE MIXING WILL BE JUST ABOVE 850 MB. ARTHUR
SHORT TERM...VALID FOR TDY AND THU
..TODAY
AN APPROACHING UPPER LEVEL LOW WILL PIVOT A NEGATIVELY
TILTED SHORTWAVE ACROSS WESTERN MONTANA THIS AFTERNOON. THIS WILL
PUSH A SURFACE LOW...CURRENTLY POSITIONED ACROSS SOUTHEAST
IDAHO...ACROSS THE FORECAST AREA INTO EASTERN MONTANA BY TONIGHT.
THE ACCOMPANYING SURGE OF SOUTHWESTERLY WIND BEHIND THE LOW WILL
PUSH VERY DRY AIR ACROSS THE SOUTHERN PORTIONS OF THE FORECAST
AREA BY THIS AFTERNOON...WITH THE MOIST GULF MOISTURE TAP WRAPPING
AROUND THE NORTHERN SIDE OF THE LOW INTO THE GGW AND TFX FORECAST
AREAS. EXPECT TO SEE DEW POINTS CRASH INTO THE 30S AND 40S ACROSS
SOUTHERN PORTIONS OF THE FORECAST AREA AS MIXING BECOMES
ESTABLISHED IN THE LATE MORNING. OUR NORTHERN TIER OF COUNTIES
WILL REMAIN ON THE GRADIENT BETWEEN THE DRY AIR AND MUCH MORE
MOIST AIR AND SHOULD RETAIN DEW POINTS IN THE 50S. THESE HIGHER
DEW POINTS WILL SUPPORT THE BETTER POTENTIAL FOR CONVECTION AND
EVEN SOME SEVERE WEATHER IN THE FORM OF HAIL AND STRONG WINDS.
HOWEVER...FARTHER SOUTH TOWARD BILLINGS THE LCLS WILL BE ALMOST
15K FEET WITH ALL THE CAPE EXTREMELY ELEVATED. CURRENT THINKING IS
THAT THE BEST CHANCE OF STRONG TO SEVERE THUNDERSTORMS WILL
PROGRESS FROM THE CRAZY MOUNTAINS TO HARLOWTON TO ROUNDUP TO
NORTHERN ROSEBUD COUNTY BY THIS EVENING. HOWEVER FOR THE SOUTHERN
TIER OF THE FORECAST AREA...EXPECT ONLY ISOLATED DRY THUNDERSTORMS
WHICH COULD PRODUCE SOME GUSTY WINDS. EXPECT THE CONVECTIVE THREAT
WILL END ACROSS THE FORECAST AREA BY 03 TO 06Z AS THE THREAT
SHIFTS NORTH.
..TONIGHT AND THURSDAY
THE SURFACE COLD FRONT WILL PROGRESS ACROSS THE FORECAST AREA
FROM THE LATE AFTERNOON IN THE WEST TO AFTER MIDNIGHT IN THE EAST.
COOLER AIR WILL PUSH IN BEHIND THE FRONT BRINGING ALLOWING
TEMPERATURES TO BE COOLER THAN LAST NIGHT IN CENTRAL AND WESTERN
ZONES. WINDS WILL STAY UP OVERNIGHT IN THE EAST KEEPING OVERNIGHT
LOWS IN THE MID TO UPPER 50S. TEMPERATURES WILL BE COOLER TOMORROW
IN THE POST FRONTAL ENVIRONMENT WITH 700MB TEMPERATURES CRASHING
AROUND +13C TO DOWN TO AROUND +5C. THUS EXPECT HIGH TEMPERATURES
TO STAY MAINLY IN THE 70S THURSDAY. THE UPPER LEVEL LOW WILL STILL
BE POSITIONED TO OUR WEST ON THURSDAY AND A NEW SURFACE LOW WILL
DEVELOP OVER NORTHERN WYOMING GOING INTO THURSDAY EVENING. THIS
ALLOWS EASTERLY LOW LEVEL WINDS TO INCREASE THE MOISTURE OVER
SOUTHEAST MONTANA. THIS COMBINED WITH THE INVERTED SURFACE TROUGH
ACROSS EASTERN MONTANA...EXPECT TO SEE AN INCREASED CHANCE OF
DEVELOPING SOME SHOWERS BY THURSDAY EVENING.
CHURCH
LONG TERM...VALID FOR FRI...SAT...SUN...MON...TUE
SLOWING TREND OF TRANSIT OF THE UPPER LOW THROUGH THE AREA IS
BRINGING INCREASING CHANCES FOR SHOWERS AND THUNDERSTORMS SATURDAY
AND SUNDAY BUT HELPING MAKE LATER PERIODS DRIER. FRIDAY WILL STILL
BE SEEING LOW LEVEL MOISTURE RECOVERING SO THERE IS A THREAT OF
CONVECTION BUT PRECIP AMOUNTS WILL BE LIGHT.
FRIDAY NIGHT THE UPPER LOW DIGS INTO SOUTHWESTERN MONTANA AND
REALLY GIVES A CHANCE FOR MOISTURE TO DEEPEN ACROSS CENTRAL AND
EASTERN MONTANA AT THE LOWER LEVELS DESPITE SOUTHWESTERLY FLOW
ALOFT STILL TRYING TO ADVECT IN DRIER AIR. WITH STRONG DIFFLUENCE
AND PLAINS MOISTURE WRAPPING BACK INTO THE YELLOWSTONE VALLEY
LOOKS LIKE A GOOD CHANCE TO GET WET. SATURDAY IN PARTICULAR WILL
HAVE TO BE WATCHED FOR THE STRENGTH OF STORMS WITH FAVORABLE SHEAR
BUT INSTABILITY MAY BE LIMITED DUE TO COOL BOUNDARY LAYER
TEMPERATURES.
SUNDAY THE UPPER LOW EJECTS INTO EASTERN MONTANA AND WRAP AROUND
MOISTURE CONTINUES TO BRING A THREAT OF SHOWERS AND THUNDERSTORMS
TO MAINLY THE EASTERN HALF OF THE AREA. TEMPERATURES ON FRIDAY
THROUGH SUNDAY COULD RUN 10 DEGREES BELOW NORMAL ESPECIALLY IF
CLOUDS DOMINATE AND ENOUGH DYNAMIC COOLING OCCURS.
MONDAY AND BEYOND IS DRYING AS FLOW BECOMES WESTERLY AND NEXT
UPSTREAM SYSTEM IS PROGGED TO EJECT TO THE NORTH AND WEST OF
MONTANA. BORSUM
AVIATION
ISOLATED THUNDERSTORMS WILL DEVELOP OVER THE MOUNTAINS BY EARLY
THIS AFTERNOON WITH A FEW THUNDERSTORMS MOVING ONTO THE PLAINS
WEST OF BILLINGS BY MID AFTERNOON. THE MAJORITY OF THE
THUNDERSTORM ACTIVITY IS EXPECTED TO BE NORTH AND WEST OF KBIL.
STRONG GUSTY WINDS WILL BE THE MAIN THREAT WITH ANY THUNDERSTORM.
A COLD FRONT WILL MOVE ACROSS THE FORECAST AREA THIS EVENING INTO
THE OVERNIGHT HOURS. HOOLEY
PRELIMINARY POINT TEMP/POPS
TDY THU FRI SAT SUN MON TUE
-------------------------------------------------------
BIL 093 052/077 052/072 052/069 051/078 054/082 056/082
1/T 11/B 23/T 34/T 41/B 11/B 22/T
LVM 085 043/072 041/069 042/067 046/079 046/082 049/081
3/T 22/T 23/T 35/T 50/B 02/T 22/T
HDN 095 053/078 052/074 050/072 050/078 052/082 052/083
1/T 11/B 32/T 34/T 41/B 11/B 22/T
MLS 096 058/081 055/076 056/076 055/080 056/083 057/083
1/N 21/B 44/T 34/T 43/T 11/B 11/B
4BQ 095 054/081 055/076 054/075 053/079 054/084 055/084
1/N 11/B 44/T 34/T 52/T 11/B 22/T
BHK 087 057/080 054/076 055/074 054/076 054/080 057/082
1/N 21/B 36/T 55/T 53/T 11/B 22/T
SHR 090 048/078 050/073 048/073 047/076 049/081 050/082
1/T 11/B 32/T 24/T 41/B 11/B 11/B
BYZ WATCHES/WARNINGS/ADVISORIES
MT...NONE.
WY...NONE.
WEATHER.GOV/BILLINGS
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