Area Forecast Discussion
Issued by NWS Billings, MT

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000
FXUS65 KBYZ 110333
AFDBYZ

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE BILLINGS MT
933 PM MDT THU JUL 10 2014

.UPDATE...
ISOLATED THUNDERSTORMS HAVE BEEN FORMING ALONG THE MT/WY BORDER
THIS EVENING...MAINLY FROM NEAR THE BIG HORNS W. STORMS WERE
FORMING IN RESPONSE TO WEAK VORTICITY MOVING THROUGH
WY...MONSOONAL MOISTURE SEEN ON WATER VAPOR IMAGERY...AND SOME
INSTABILITY. WEAK VORTICITY WILL CONTINUE MOVING THROUGH N WY
THROUGH THE NIGHT SO HAVE LIMITED POPS TO AREAS NEAR THE MT/WY
BORDER. THIS IDEA WAS SUPPORTED BY THE WRF AND HRRR.

TEMPERATURES WERE STILL IN THE 70S AND 80S AT 03Z. A COLD FRONT
HAS PUSHED THROUGH THE EASTERN ZONES PER PRESSURE RISES AND A
SURFACE WIND SHIFT TO THE N AND NE. NEW WRF SHOWED COLD ADVECTION
AT 850 MB OVERNIGHT WHICH WILL ALLOW TEMPERATURES TO REACH THEIR
FORECAST VALUES.

LAST COUPLE RUNS OF THE SREF HAVE TRENDED THE SEVERE THREAT IN THE
SE DOWN FOR FRI. CAPES WILL BE ON THE ORDER OF 500-1000 J/KG WITH
BULK EFFECTIVE SHEAR AROUND 30 KT. PRECIPITABLE WATERS WILL BE
AROUND AN INCH. WHILE THESE PARAMETERS SUPPORTED POSSIBLE SEVERE
THUNDERSTORMS...THERE WAS NO SHORTWAVE FORECAST TO MOVE THROUGH
THE AREA. THERE WILL BE THE RIGHT-REAR QUADRANT OF AN UPPER
JET...BUT NOT SURE THIS WILL BE ENOUGH TO TRIGGER AN OUTBREAK OF
SEVERE STORMS. WILL BRIEF THE NEXT SHIFT TO LOOK FURTHER AT THE
SITUATION. ARTHUR

&&

.SHORT TERM...VALID FOR FRI AND SAT...

WATER VAPOR SATELLITE SHOWING MONSOONAL MOISTURE MOVE NORTHWARD
INTO SOUTHERN MONTANA. SEVERAL WEAK EMBEDDED DISTURBANCES WHERE IN
THIS FLOW AND ARE EXPECTED TO BRING A FEW ISOLATED THUNDERSTORMS
LATE THIS AFTERNOON AND EVENING TO SOUTHERN MONTANA.

FRIDAY LOOKS TO BE A MORE ACTIVE WEATHER DAY AS EASTERLY SURFACE
FLOW SETS UP ACROSS THE AREA. EAST WINDS WILL ADVECT LOW LEVEL
MOISTURE INTO THE REGION WITH MID TO UPPER 50 DEW POINT
TEMPERATURES EXPECTED FROM HARDIN EAST THROUGH EKALAKA. THIS AREA
WILL SET BE UNDER RIGHT EXIT REGION OF THE JET AND WEAK Q VECTOR
FORCING. INCREASING LOW LEVEL MOISTURE WITH AFTERNOON HEATING WILL
CAUSE MLCAPE VALUES TO CLIMB TO AROUND TO 1500 J/KG. SHEAR WILL BE
AROUND 40KTS WITH STEEP MID LEVEL LAPSE RATES ALSO OVER THE AREA.
ONLY FLY IN THE OINTMENT IS A TRIGGERING MECHANISM. GFS BRINGS A
WAVE NORTHEASTWARD OUT OF UTAH TOMORROW WHILE THE EC/NAM/GEM KEEP
THIS WAVE OVER NORTHERN WYOMING. HAVE OPTED LEAN TOWARD THE GFS
AND MENTION SEVERE THUNDERSTORMS FROM HARDIN TO SHERIDAN AND EAST
TO EKALAKA FRIDAY AFTERNOON AND NIGHT GIVEN THE AMOUNT OF
INSTABILITY THAT WILL BE IN PLACE. THESE STORMS WILL HAVE THE
POTENTIAL TO PRODUCE HEAVY RAIN AND LARGE HAIL ALONG WITH STRONG
WINDS.

UNSTABLE NORTHWEST FLOW SETTING UP OVER THE AREA SATURDAY WHICH
WILL BRING ISOLATED SHOWERS AND THUNDERSTORMS TO THE AREA.
TEMPERATURES REMAINING NEAR SEASONAL VALUES WITH HIGHS IN THE MID
80S. RICHMOND

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

VERY MINOR CHANGES TO THE EXTENDED FORECAST PERIOD...AS SPECIFICS
OF AMPLIFYING RIDGE OVER WESTERN MONTANA AND UPPER LEVEL LOW
DROPPING SOUTH INTO MINNESOTA REMAIN SOMEWHAT UNCERTAIN THROUGH
THE PERIOD. THE MAJORITY OF CHANGES CENTERED AROUND COLLABORATION
ISSUES...BUT RESULTING IN A GENERAL TREND TO SLIGHTLY COOLER TEMPS
THROUGH THE EARLY AND MIDDLE PORTIONS OF THE EXTENDED PERIOD.

A LARGE UPPER LEVEL LOW IS PROGGED TO DROP SOUTH FROM NORTHERN
MANITOBA INTO NORTHERN MINNESOTA...AND SLOWLY PUSH EAST SOUTHEAST
THROUGH ABOUT TUESDAY. THIS PATTERN KEEPS NORTH TO NORTHEAST FLOW
ACROSS THE REGION. THE SYSTEM IS QUITE COOL...AND SHOULD RESULT
IN RELATIVELY COOL TEMPS IN THE EAST...WITH A STRONG THERMAL
GRADIENT SETTING UP SOMEWHERE OVER THE REGION AS THE UPPER LEVEL
RIDGE IN THE WEST SHIFTS EASTWARD. THE QUESTION REMAINS AS TO HOW
FAR WEST THE COOLER AIR WILL REACH AND WHERE THE THERMAL GRADIENT
WILL SET UP. THIS SYSTEM ALSO HAS THE POTENTIAL TO SET UP UPSLOPE
FLOW INTO THE BIGHORN AND BEARTOOTH MOUNTAINS. THIS SHOULD RESULT
IN BEST POTENTIAL FOR SHOWERS AND ISOLATED THUNDER IN THE HIGH
TERRAIN...WITH LITTLE CHANCE FOR MOVEMENT OFF THE MOUNTAINS DUE TO
LIMITED MOISTURE AVAILABILITY. THIS HOLDS TRUE UNTIL TUESDAY WHEN
THE EVERYTHING BEGINS TO SHIFT MORE READILY EASTWARD AND A
SHORTWAVE IS PROGGED TO SLIDE SOUTHEAST ALONG THE THERMAL GRADIENT
THROUGH THE HEART OF THE CWA. UNCERTAINTY REMAINS SIGNIFICANT WITH
VARIABILITY OF THE TRACK OF THE LOW...THIS APPEARS TO BEST CHANCE
FOR MORE WIDESPREAD PRECIPITATION AND THUNDER POTENTIAL. SHOWERS
AND THUNDER MAY LINGER THROUGH WEDNESDAY...WITH SLIGHTLY SLOWER
PROGRESSION FORECAST IN THE ECMWF...SO INTRODUCED SOME SLIGHT POPS
THROUGH WEDNESDAY.

MINOR MODELS DISCREPANCIES IN TIMING CONTINUE THROUGH THE END OF
THE PERIOD...BUT GENERALLY KEEP UNSTABLE NORTHWEST FLOW ACROSS THE
REGION WITH UPPER LEVEL RIDGE ANCHORED IN THE PACIFIC NORTHWEST.
AAG

&&

.AVIATION...

ISOLATED SHOWERS AND THUNDERSTORMS WILL LINGER OVER AND NEAR THE
MOUNTAINS ALONG THE MONTANA/WYOMING BORDER TONIGHT. THERE IS A
SLIGHT CHANCE OF SOME LIGHT SHOWERS DEVELOPING AFTER 04Z AND
TRACKING ACROSS SOUTH CENTRAL MONTANA OVERNIGHT. VFR CONDITIONS
WILL PREVAIL. BT
&&

.PRELIMINARY POINT TEMP/POPS...

    FRI     SAT     SUN     MON     TUE     WED     THU
-----------------------------------------------------------
BIL 061/085 062/085 061/085 061/081 058/080 056/082 057/087
    12/T    32/T    21/U    12/T    22/T    22/T    21/U
LVM 052/082 052/082 052/086 052/079 050/076 049/083 049/086
    13/T    33/T    31/U    22/T    33/T    33/T    21/U
HDN 060/088 059/087 061/087 059/082 056/081 056/084 056/088
    12/T    32/T    21/U    12/T    22/T    22/T    21/U
MLS 062/086 063/087 063/081 060/079 056/081 057/082 058/086
    11/B    22/T    21/U    11/U    12/T    22/T    21/U
4BQ 062/089 059/086 062/087 060/080 056/079 056/081 056/085
    12/T    32/T    21/U    12/T    22/T    22/T    21/U
BHK 058/084 059/083 060/079 056/073 050/077 053/078 054/083
    11/B    42/T    21/U    11/U    12/T    22/T    21/U
SHR 057/084 056/081 056/084 055/079 052/077 051/080 053/083
    24/T    43/T    32/T    22/T    23/T    33/T    31/U

&&

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

&&

$$
WEATHER.GOV/BILLINGS



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