Area Forecast Discussion
Issued by NWS Billings, MT

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000
FXUS65 KBYZ 120926
AFDBYZ

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BILLINGS MT
326 AM MDT SAT JUL 12 2014

.SHORT TERM...VALID FOR TDY AND SUN...

SEASONABLY WARM AND IN MANY PLACES DRY WEATHER WILL BE THE WEEKEND
THEME. EARLY-MORNING SHOWERS AND STORMS ACROSS SOUTHEASTERN MT ARE
EXPECTED TO EXIT INTO THE DAKOTAS BY 18 UTC...AND THE WEAKER BATCH
OF MOISTURE OVER SOUTH CENTRAL MT NEAR LIVINGSTON AT 09 UTC SHOULD
WEAKEN LONG BEFORE THAT /LIKELY AROUND DAYBREAK...IF NOT SOONER/.

FLOW ALOFT WILL TURN MORE SHARPLY NORTHWEST AS AN ANOMALOUSLY DEEP
500-MB LOW CONSOLIDATES NEAR HUDSON BAY AND DROPS INTO THE MIDWEST
DURING THE NEXT 48 HOURS. THIS WILL ASSURE MONSOONAL MOISTURE GETS
SUPPRESSED SOUTH AND WEST FOR THE MOST PART...MEANING THAT DIURNAL
/AFTERNOON AND EVENING/ SHOWER AND STORM CHANCES THE NEXT TWO DAYS
WILL MAINLY BE RELEGATED TO NEAR THE HIGHER TERRAIN. SUBSIDENCE IN
THE MID-LEVELS SEEN IN MODEL-FORECAST SOUNDINGS OVER THE PLAINS IS
EXPECTED TO KEEP THINGS DRY THERE WITH HIGHS MAINLY IN THE 80S F.
ACTUALLY...BY SUN COLD AIR ADVECTION ALOFT WILL PROBABLY BE ENOUGH
TO KEEP HIGHS IN THE 70S F IN FAR SOUTHEASTERN MT LIKE AT BAKER.

WE FOLLOWED THE 00 UTC MULTI-MODEL CONSENSUS CLOSELY WHEN BUILDING
THE SHORT TERM FORECAST WITH NO NOTABLE REASON TO DEVIATE FAR FROM
THAT NORMALLY-WELL-PERFORMING SET OF GUIDANCE WITH THIS RELATIVELY
LOW-KEY/LOW-IMPACT WEATHER PATTERN. FORECAST HIGHS ON FRI WERE TOO
WARM IN MANY AREAS BECAUSE WE HAD LEANED ON THE WARMER EDGE OF THE
GUIDANCE ENVELOPE...BUT EASTERLY WINDS AND CONVECTIVELY-COOLED AIR
EMANATING FROM CONVECTION OVER NORTHERN MT THU NIGHT PREVENTED THE
TEMPERATURES FROM REACHING THE FULL POTENTIAL OF THE AIR MASS. THE
FLOW WILL TURN A BIT MORE NORTHERLY TODAY AND SUN THOUGH...SO THAT
ISSUE MAY BE LESS PREVALENT WITH TIME...ALBEIT PROBABLY REAL AGAIN
TODAY IN PARTS OF SOUTHEASTERN MT IN THE WAKE OF TONIGHT/S STORMS.
SCHULTZ

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

MODELS WERE ADVERTISING SIMILAR SOLUTIONS THROUGH MID WEEK BUT
DIVERGE FROM THURSDAY ONWARD. THIS WAS THE CASE YESTERDAY AND THE
DIFFERENCES LOOK SIMILAR IN THAT THE GFS DOES NOT BREAK DOWN THE
UPPER RIDGE OVER THE GREAT BASIN AS AGGRESSIVELY AS THE ECMWF
DOES. THE ECMWF WAS COOLER FROM FRIDAY ONWARD AS IT LOWERS HEIGHTS
DUE TO A BROAD TROUGH WORKING INTO THE NORTHERN ROCKIES. THE GFS
SUPPRESSES THE RIDGE TO THE SOUTH A BIT AND DOES NOT CRASH IT DOWN
OVER WYOMING AND COLORADO LIKE THE ECMWF. THIS CAUSES A SHARPER
AMPLITUDE TROUGH TO MOVE INTO BRITISH COLUMBIA AND MAINTAINS
HIGHER MID LEVEL HEIGHTS INTO EARLY FRIDAY. HAVE SIDED WITH THE
GFS AS IT MAKES MORE SENSE CLIMATOLOGICALLY.

AN UNSEASONABLY DEEP UPPER LOW IS PROGGED TO DIVE INTO MINNESOTA
MONDAY AND THIS WILL SEND COOLER AIR SLIDING INTO EASTERN MONTANA.
AIRMASS DOES NOT LOOK QUITE AS UNSEASONABLY COOL AS IT DID ON RUNS
YESTERDAY...BUT STILL HAS 850MB TEMPERATURES OF 12C ENTERING FAR
EASTERN MONTANA EARLY MONDAY. THIS WILL CAUSE HIGHS TO BE LIMITED
TO THE UPPER 70S TO LOWER 80S ON MONDAY. TUESDAY WILL BE NOT SEE
MUCH MODERATION WITH LOW LEVEL NORTHEASTERLY FLOW CONTINUING WITH
NORTHWEST FLOW ALOFT. WEAKENING UPPER ENERGY IS PROGGED TO SLIDE
OVER THE TOP OF THE WESTERN RIDGE AND DROP INTO WESTERN AND
CENTRAL ZONES MONDAY AFTERNOON THROUGH TUESDAY NIGHT. MODELS HAVE
MOISTENED UP THE ATMOSPHERE A BIT MORE WITH THIS RUN AND HAVE THUS
RAISED POPS FOR THIS.

AN UPPER RIDGE BUILDS IN FROM THE SOUTHWEST ON WEDNESDAY AND
STARTS THE MODERATION PROCESS. WEDNESDAY LOOKS DRY WITH DRIER AIR
ALOFT SLIDING IN WITH SUBSIDENCE UNDERNEATH THE RIDGE AXIS. THINGS
SHOULD WARM BACK UP INTO THE LOWER 90S THURSDAY AND FRIDAY AND MID
LEVEL DOWNSLOPE FLOW INCREASES WITH A BRITISH COLUMBIA UPPER
TROUGH SLIDING INTO NORTHERN IDAHO. HEIGHTS WILL FALL ENOUGH TO
INTRODUCE LOW POPS AS THE THROUGH MOVES IN. TWH

&&

.AVIATION...

WEAKENING SCATTERED SHOWERS AND THUNDERSTORMS WILL IMPACT AREAS
WEST OF BILLINGS THIS MORNING. BRIEF MVFR TO IFR CONDITIONS ARE
EXPECTED IN THE HEAVIER SHOWERS. MOUNTAINS WILL BE FREQUENTLY
OBSCURED THIS MORNING. ALSO...ISOLATED SHOWERS AND THUNDERSTORMS
WILL SHIFT ACROSS FAR EASTERN MONTANA AND IMPACT BAKER AND EKALAKA
EARLY THIS MORNING WITH BRIEF MVFR TO IFR CONDITIONS. BOTH AREAS
OF SHOWERS AND STORMS WILL DECREASE AS THE MORNING WEARS ON. MORE
SHOWERS AND THUNDERSTORMS ARE EXPECTED THIS AFTERNOON WEST OF A
LINE FROM BIG TIMBER TO SHERIDAN. LOCAL HEAVY RAIN WILL CAUSE
LOCAL MVFR TO IFR CONDITIONS IN THE HEAVIER STORMS. TWH

&&

.PRELIMINARY POINT TEMP/POPS...

    TDY SUN     MON     TUE     WED     THU     FRI
-------------------------------------------------------
BIL 085 059/087 058/081 056/081 056/087 058/093 060/089
    1/B 11/U    01/U    22/T    22/T    22/T    22/T
LVM 085 052/085 051/082 050/080 050/084 052/089 054/086
    3/T 31/U    12/T    23/T    33/T    22/T    22/T
HDN 087 058/089 056/082 056/082 056/087 059/094 061/091
    1/B 10/U    01/U    22/T    22/T    22/T    22/T
MLS 086 059/084 054/078 056/082 056/086 060/093 063/090
    1/U 10/U    01/U    11/U    11/U    12/T    22/T
4BQ 085 059/085 053/078 055/079 055/084 058/091 062/091
    2/T 11/U    01/U    11/U    12/T    21/U    12/T
BHK 083 054/079 048/072 051/076 052/081 056/088 060/088
    3/T 10/U    01/U    11/U    11/U    11/U    12/T
SHR 084 054/086 053/079 053/078 051/080 054/088 057/087
    2/T 22/T    12/T    23/T    32/T    22/T    22/T

&&

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

&&

$$
WEATHER.GOV/BILLINGS



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