Area Forecast Discussion
Issued by NWS Billings, MT

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000
FXUS65 KBYZ 230314
AFDBYZ

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE BILLINGS MT
914 PM MDT FRI MAY 22 2015

.UPDATE...
DISORGANIZED LOW-TOPPED CONVECTION HAS BEEN OCCURRING OVER THE
CENTRAL AND WESTERN ZONES THIS EVENING. THE CONVECTION WAS THE
RESULT OF A WEAK WAVE MOVING W IN THE WEAK FLOW ALOFT COMBINED
WITH UPSLOPE FLOW AND DAYTIME HEATING. PRECIPITABLE WATERS WERE
ALSO ON THE ORDER OF /0.6/ TO /0.8/ INCHES OVER THE AREA DUE TO
MOIST SE FLOW. MESOANALYSIS SHOWED THAT CAPES WERE DECREASING OVER
THE AREA OVER THE LAST FEW HOURS...BUT THE MID-LEVEL LAPSE RATES
WERE AROUND 6.5 DEG C/KM...SUPPORTING CONTINUED LIGHTNING STRIKES.

WEAK ENERGY WILL REMAIN OVER THE AREA TONIGHT ALONG WITH HIGH
PRECIPITABLE WATERS. UPSLOPE FLOW WILL CONTINUE BUT STABILITY WILL
INCREASE DUE TO LOSS OF HEATING. THUS ADJUSTED POPS LOWER THROUGH
06Z BASED ON LATEST RADAR IMAGERY...AND LOWERED THEM A BIT
OVERNIGHT AS WELL. LEFT THUNDER OUT OF THE FORECAST OVERNIGHT.
MODELS WERE INDICATING POSSIBLE LOW CEILINGS OR FOG OVERNIGHT.
GIVEN THE LARGE AMOUNT OF CLOUD COVER ALREADY OVER THE
AREA...FOG DOES NOT SEEM LIKELY. HOWEVER...THERE COULD BE
SCATTERED TO BROKEN LOW CLOUDS ADVECTING INTO THE AREA
OVERNIGHT. INCREASED WIND SPEEDS OVER KLVM AND KSHR WHERE THE E TO
SE WINDS HAVE BEEN GUSTY THIS EVENING.

BROAD TROUGH OVER THE WESTERN U.S. WAS FORECAST TO CONSOLIDATE
INTO A BROAD UPPER LOW FROM MT TO THE FOUR CORNERS REGION ON SAT.
WITH PLENTY OF WAVES AND MOISTURE OVER THE AREA...EXPECT MORE
SHOWERS AND THUNDERSTORMS...WHICH WILL CONTINUE THROUGH SUN AS THE
SYSTEM WILL REMAIN ALMOST STATIONARY. ARTHUR

&&

.SHORT TERM...VALID FOR SAT AND SUN...

AN UPPER LOW MOVING NORTHEAST OUT OF COLORADO THIS AFTERNOON IS
RESULTING IN AREAS OF RAIN ACROSS WESTERN NEBRASKA AND SOUTHEAST
WYOMING. SOME OF THIS PRECIP IS SLOWLY SHIFTING NORTH RESULTING IN
ISOLATED TO SCATTERED SHOWERS ACROSS NORTHERN WYOMING INTO
SOUTHERN/SOUTHEASTERN MONTANA. THERE IS ANOTHER UPPER LOW THAT IS
CURRENTLY MOVING OUT OF SOUTHERN CALIFORNIA INTO THE FOUR CORNERS
AREA. THESE TWO LOWS ARE WRAPPING MOISTURE WEST AND NORTH ACROSS
THE GREAT BASIN AREA. LIGHTING DATA IS SHOWING THUNDERSTORMS
POPPING UP ALL ACROSS THE WEST EAST OF THE ROCKIES. WATER VAPOR
IMAGERY ALONG WITH THE LIGHTING DATA LOOK TO BE WHAT WE WOULD
TYPICALLY SEE DURING THE MONSOON SEASON OF LATE JULY/EARLY AUGUST.

THESE LOWS WILL SLOWLY MOVE EAST AND NORTHEAST THROUGH THE
WEEKEND WITH PIECES OF ENERGY GETTING EJECTED ACROSS OUR AREA. AS
A RESULT...WILL KEEP A CHANCE FOR SHOWERS AND ISOLATED
THUNDERSTORMS IN THE FORECAST THROUGH THE WEEKEND. AS THE UPPER
LOW OVER THE FOUR CORNERS REGION MOVES INTO THE WESTERN HIGH
PLAINS SUNDAY INTO SUNDAY NIGHT...IT WILL WRAP MOISTURE AROUND THE
BACK SIDE OF IT ACROSS SOUTHEAST MONTANA BRINGING THE LIKELIHOOD OF
NUMEROUS SHOWERS OR POSSIBLY A LIGHT STEADY RAIN. AS A RESULT...I
INCREASED POPS TO LIKELY FOR OUR FAR SOUTHEAST COUNTIES LATE
SATURDAY NIGHT INTO EARLY MONDAY MORNING.

ELSEWHERE ACROSS THE FORECAST AREA...SCATTERED SHOWERS AND
ISOLATED THUNDERSTORMS CAN BE EXPECTED THROUGH THE WEEKEND. GIVEN
THE LIGHT WINDS ALOFT/LITTLE SHEAR...THUNDERSTORMS ARE NOT
EXPECTED TO BE SEVERE OR EVEN STRONG BUT THEY MAY PRODUCE SOME
BRIEF HEAVY RAIN. WITH THE EXCEPTION OF FAR SOUTHEAST MONTANA
SUNDAY...THE WEEKEND FOR THE MAJORITY OF OUR AREA IS NOT EXPECTED
TO BE A WASHOUT. TEMPERATURES WILL BE BELOW NORMAL IN THE LOWER
60S FOR MOST AREAS BUT NOT AS COOL AS THE PAST COUPLE OF WEEKENDS.
HOOLEY

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

A BROAD TROUGH WILL BE OVER THE EASTERN HALF OF THE NORTHERN AND
CENTRAL ROCKIES MONDAY INTO TUESDAY. THE FLOW ALOFT WILL BE WEAK
AS THE MAJORITY OF THE JET ENERGY WILL BE TO OUR NORTH AND SOUTH
OF OUR FORECAST AREA. THERE WILL BE ENOUGH INSTABILITY AROUND TO
WARRANT A CHANCE FOR A SHOWER OR THUNDERSTORM MONDAY AND TUESDAY.
850MB TEMPERATURES WILL BEGIN TO WARM FROM WEST TO EAST MONDAY AND
WITH READINGS AROUND 15-18C SPREADING EAST ACROSS THE ENTIRE AREA
TUESDAY RESULTING IN TEMPERATURES WARMING TO NORMAL TO SLIGHTLY
ABOVE NORMAL VALUES.

MODELS BRING AN UPPER LOW OVER THE PACIFIC NORTHWEST EASTWARD
ACROSS MONTANA WEDNESDAY INTO THURSDAY RESULTING IN INCREASING
CHANCES FOR SHOWERS AND ISOLATED THUNDERSTORMS. A COLD FRONT IS
PROGGED TO DROP SOUTH ACROSS THE FORECAST AREA THURSDAY NIGHT INTO
FRIDAY KEEPING SHOWER AND THUNDERSTORM CHANCES IN THE FORECAST.
TEMPERATURES LOOK TO BE AROUND NORMAL THROUGH THE PERIOD UNTIL
FRIDAY WHEN READINGS WILL COOL SLIGHTLY BEHIND THE COLD FRONT.
HOOLEY
&&

.AVIATION...

ISOLATED TO SCATTERED SHOWERS AND THUNDERSTORMS WILL PERSIST INTO
THE LATE EVENING HOURS TONIGHT. LOCAL MVFR OR LOWER CONDITIONS CAN
BE EXPECTED NEAR THIS ACTIVITY WITH BRIEF HEAVY RAINFALL. RESIDUAL
VFR CLOUD COVER WILL PERSIST ONCE CONVECTION DISSIPATES. THERE IS
SOME INDICATION SOME MVFR CEILINGS COULD DEVELOP BETWEEN 11Z-15Z
TOMORROW MORNING AT KSHR...KLVM AND KBIL. CONFIDENCE AT THIS TIME
IS NOT VERY HIGH THIS WILL OCCUR OR BE WIDESPREAD. LOOK FOR MORE
SCATTERED SHOWERS TOMORROW. BT

&&

.PRELIMINARY POINT TEMP/POPS...

    SAT     SUN     MON     TUE     WED     THU     FRI
-----------------------------------------------------------
BIL 046/063 045/060 045/070 047/072 049/071 050/071 048/066
    23/T    23/T    32/T    23/T    33/T    33/T    33/T
LVM 045/061 041/061 039/067 043/068 044/066 045/069 043/065
    56/T    33/T    33/T    34/T    44/T    43/T    33/T
HDN 045/065 046/061 045/071 046/074 049/074 049/074 048/069
    23/T    33/T    32/T    23/T    33/T    33/T    33/T
MLS 047/064 045/062 047/067 046/073 050/072 050/071 049/067
    13/T    44/T    44/T    42/T    23/T    33/T    33/T
4BQ 043/059 046/058 046/065 045/072 049/071 049/070 048/068
    16/T    67/T    43/T    33/T    33/T    33/T    33/T
BHK 043/058 045/060 045/065 043/069 047/070 048/069 046/066
    16/T    67/T    66/T    63/T    33/T    33/T    33/T
SHR 045/059 043/058 042/065 042/070 046/070 046/069 045/068
    25/T    46/T    33/T    34/T    43/T    33/T    33/T

&&

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

&&

$$
WEATHER.GOV/BILLINGS



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