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000
FXUS65 KBYZ 221520
AFDBYZ

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE BILLINGS MT
920 AM MDT WED MAY 22 2013

.UPDATE...

CURRENT FORECAST IS IN GOOD SHAPE AND HAVE ONLY MADE A MINOR
ADJUSTMENT TO SKY COVER WITH THIS UPDATE. SATELLITE SHOWING CLOUDS
ERODING QUICKLY ACROSS THE EAST FROM ROSEBUD COUNTY EAST AND
SOUTHEAST. HAVE REDUCED MORNING AND EARLY AFTERNOON CLOUDS TO
REFLECT MORE OF A PARTLY SUNNY DAY FOR THESE AREAS.
ELSEWHERE...COOL EASTERLY UPSLOPE FLOW HAS RESULTED IN THE
DEVELOPMENT OF A STRATUS DECK FOR THE CENTRAL AND WESTERN AREAS.
HAVE INCREASED CLOUD COVER FOR THE CENTRAL AREAS TO REMOVE THE
MOSTLY SUNNY WORDING. HOOLEY

&&

.SHORT TERM...VALID FOR TDY AND THU...

THE DEEP UPPER LOW OVER SOUTHWEST MINNESOTA WILL FINALLY LOSE ITS
GRIP ON THE EAST TODAY. LOW CLOUDS STILL PRESENT OVER THE EAST
THIS MORNING WITH EVEN SOME LIGHT SHOWERS OR SPRINKLES MOVING WEST
FROM NORTH DAKOTA INTO FALLON AND CARTER COUNTIES. WILL HAVE LOW
POPS IN THESE TWO COUNTIES THIS MORNING. RIDGING SHOULD MOVE INTO
THE EAST LATE THIS MORNING AND CLEAR THE CLOUD COVER OUT. THE
FOCUS THEN TURNS TO THE OTHER DEEP LOW OVER NORTH AMERICA...OVER
THE PACIFIC NORTHWEST.

THIS WESTERN LOW WILL EDGE SLOWLY EASTWARD TODAY AND INCREASE
UPPER DIVERGENCE OVER THE WESTERN PART OF THE FORECAST AREA. SHEAR
INCREASES OVER THE WEST...BUT CAPE SEEMS LIMITED. DEWPOINTS WERE
CURRENTLY IN THE UPPER 30S AT LIVINGSTON AND PROGGED TO ONLY RISE
INTO THE MID 40S THIS AFTERNOON. EASTERLY WINDS WILL BE PRESENT
OVER THE ENTIRE AREA TODAY AND THIS WILL PROVIDE A CAP ABOVE 750MB
INHIBITING SURFACE BASED CONVECTION. MID LEVEL CAPES WERE NOT THAT
HIGH DESPITE INCREASING SHEAR. DIVERGENCE AND MOUNTAINOUS TERRAIN
SHOULD TRIGGER CONVECTION OVER SOUTHWEST MONTANA TODAY AND LIFT
THE STORMS NORTHEAST THIS AFTERNOON. MODELS HAVE BEEN PERSISTENT
ON THAT. WILL KEEP HIGH POPS FOR THE WEST. PRECIPITABLE WATER
AMOUNTS AROUND .75 WOULD PRODUCE LOCALLY HEAVY RAINS...BUT STORM
MOTION SHOULD BE ENOUGH TO LIMIT FLOOD POTENTIAL. AS FAR AS SEVERE
POTENTIAL TODAY GOES...BELIEVE THERE IS A THREAT FOR SOME HAIL
GIVEN THE SHEAR...BUT CAP AND WEAK CAPE SHOULD KEEP MOST ACTIVITY
BELOW SEVERE LEVELS.

FOR THURSDAY...SOUTHEAST WINDS WILL INCREASE OVER THE EAST. IN
FACT...WIND GUSTS TO 50 MPH WILL BE POSSIBLE AT BAKER WITH
SUSTAINED WINDS UP TO 35 MPH AS A SURFACE LOW DEEPENS OVER THE
WEST. THESE WINDS WILL KEEP THE EAST CAPPED FROM CONVECTION.
ORDINARILY EAST TO SOUTHEAST WINDS WOULD BRING IN HIGHER DEWPOINTS
BUT THAT DOES NOT APPEAR TO THE BE THE CASE THIS TIME. DEWPOINTS
IN THE DAKOTAS WERE IN THE MID TO UPPER 40S...SO THAT LOOKS TO BE
THE LIMIT FOR THE FORECAST AREA ON THURSDAY. DEWPOINTS BELOW 50
WOULD LIMIT SEVERE POTENTIAL OVER CENTRAL AND WESTERN ZONES.
CONVECTION SHOULD TRIGGER WITH SHORTWAVES SPINNING OFF THE WESTERN
LOW AND IN AMONGST SOME SURFACE CONVERGENCE WITH THE LOW. CAPE
INCREASES OVER CENTRAL ZONES DURING THE AFTERNOON. THE CAP LOOKS
TO BE DISMISSED DURING THE AFTERNOON AS EAST WINDS DECREASE OVER
CENTRAL AND WESTERN ZONES. ABOUT 30-35KTS OF SHEAR SHOULD BE
PRESENT BUT AGAIN CAPES LOOK ON THE LOW SIDE DUE TO LOWER
DEWPOINTS. COULD BE A HAIL THREAT WITH SHEAR PRESENT. ANY SEVERE
CONVECTION SHOULD BE ISOLATED WITH THE MAIN THREAT BEING LOCALLY
HEAVY RAIN WITH...PWATS AROUND .75...AND HAIL DUE TO SHEAR. WILL
OPT TO NOT MENTION SEVERE IN THE ZONES BUT FOLKS SHOULD BE
PREPARED FOR THE POSSIBILITY OF STRONG THUNDERSTORMS BOTH TODAY
WEST AND THURSDAY OVER CENTRAL AND WEST. WILL KEEP MENTION OF
ISOLATED SEVERE IN THE HWO ALONG WITH THE STRONG SOUTHEAST WINDS
OVER FALLON AND CARTER COUNTIES THURSDAY. WARMER TEMPERATURES
EXPECTED THURSDAY AS THE CAP WEAKENS. TWH

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

A FEW MINOR CHANGES TO THE EXTENDED PERIOD...BUT OVERALL FORECAST
LOOKS LIKE IT SHOULD BE IN PRETTY GOOD SHAPE.

MODELS APPEAR IN PRETTY GOOD AGREEMENT THROUGH ABOUT
SUNDAY...WITH UPPER LEVEL LOW PRESSURE SYSTEM OVER THE PACIFIC
NORTHWEST LIFTING SLOWLY TO THE NORTHEAST. THIS WILL KEEP THE
REGION IN PERSISTENT SOUTHWEST FLOW ALOFT. EASTERLY SURFACE FLOW
DEVELOPS BY SATURDAY...WITH LLJ TAKING SHAPE IN EASTERN ZONES AND
STRENGTHENING THROUGH SUNDAY. THIS SHOULD BRING ADDED INSTABILITY
AND MOISTURE TO THE SYSTEM AS WELL. MODELS THEN FAVOR A TROF...IN
SOME SHAPE...PUSHING ACROSS THE REGION FOR MONDAY THROUGH
WEDNESDAY. THE GFS IS LEANING TOWARD A DEEPER SLOW MOVING TROF...
WHILE EC FAVORS A MORE SHALLOW...SOMEWHAT NEGATIVELY TILTED TROF
THAT KICKS THROUGH THE REGION MUCH MORE QUICKLY...BUT KEEPS
SOUTHWEST SLOW INTACT ACROSS THE REGION. HAVE KEPT CLIMO TYPE...TO
SLIGHTLY HIGHER POPS IN PLACE ACROSS THE REGION THROUGHOUT THE
BULK OF THE PERIOD.

AS FOR TEMPERATURES...EXPECT TO SEE SLIGHTLY ABOVE NORMAL TEMPS
THROUGH THE PERIOD. MODELS CAME IN WARMER THROUGH MUCH OF THE
PERIOD...SO TRENDED TEMPS UP SLIGHTLY. AAG

&&

.AVIATION...

SHOWERS AND THUNDERSTORMS WILL BE ON THE INCREASE FROM KMLS TO
KSHR W THIS AFTERNOON AND EVENING. THE BEST CHANCES FOR
PRECIPITATION WILL BE FROM HARLOWTON TO RED LODGE W. ISOLATED TO
SCATTERED SHOWERS WILL OCCUR FROM KMLS TO KSHR W OVERNIGHT AND THU
MORNING. EXPECT MAINLY MVFR TO IFR CEILINGS TODAY THROUGH THU
MORNING WITH LOWER CEILINGS AND REDUCED VISIBILITIES IN
PRECIPITATION. SURFACE WINDS WILL BE E 10 TO 20 KT THROUGH THU
MORNING. SE WINDS WILL INCREASE TO 25 TO 35 KT E OF KBIL THU
MORNING. ARTHUR
&&

.PRELIMINARY POINT TEMP/POPS...

    TDY THU     FRI     SAT     SUN     MON     TUE
-------------------------------------------------------
BIL 066 046/073 050/078 048/077 053/081 053/077 051/078
    2/T 33/T    43/T    22/T    22/T    33/T    33/T
LVM 066 043/065 041/071 040/078 041/082 042/078 041/076
    5/T 65/T    44/T    32/T    23/T    33/T    33/T
HDN 070 048/077 050/081 048/079 053/082 052/080 051/080
    1/N 22/T    23/T    22/T    23/T    33/T    33/T
MLS 065 046/072 051/081 051/079 057/084 058/079 054/080
    1/N 11/N    23/T    23/T    33/T    44/T    33/T
4BQ 065 046/074 052/082 050/081 055/087 052/081 052/082
    1/N 11/N    13/T    22/T    33/T    33/T    33/T
BHK 061 042/066 048/078 050/073 056/079 056/077 052/077
    1/N 11/N    13/T    24/T    43/T    33/T    33/T
SHR 066 045/075 047/079 046/079 048/085 048/079 046/077
    2/T 22/T    23/T    22/T    22/T    23/T    33/T

&&

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

&&

$$
WEATHER.GOV/BILLINGS