Area Forecast Discussion
Issued by NWS Billings, MT

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000
FXUS65 KBYZ 310518
AFDBYZ

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE BILLINGS MT
1118 PM MDT SUN AUG 30 2015

.UPDATE...

WE WILL BE MAKING A QUICK UPDATE LATE THIS EVENING TO CANCEL THE
RED FLAG WARNING THAT WAS IN EFFECT UNTIL MIDNIGHT FOR OUR CENTRAL
AND WESTERN AREAS. THE COLD FRONT HAS MOVED THROUGH THIS AREA AND
WINDS HAVE SWITCHED TO THE NORTHWEST AND WERE GUSTY FOR A BRIEF
TIME BUT HAVE SINCE RELAXED INTO THE 10 TO 20 MPH RANGE. IN
ADDITION...HUMIDITIES HAVE RISEN ABOVE 30 PERCENT ACROSS THE
AFFECTED AREA. HOOLEY

&&

.SHORT TERM...VALID FOR MON AND TUE...

A SEASONABLY STRONG COLD FRONT WILL CROSS THE REGION TONIGHT AND
LEAD INTO A PERIOD OF QUIET WEATHER MONDAY AND TUESDAY.

TONIGHT...THE 12 UTC MODELS AND MORE CONTEMPORARY HRRR MODEL RUNS
ARE IN GENERAL AGREEMENT IN SHOWING THE COLD FRONT MOVING THROUGH
THE LIVINGSTON AREA BETWEEN 6 PM AND 9 PM MDT...BILLINGS BETWEEN 7
PM AND 11 MDT...SHERIDAN BETWEEN 11 PM AND 3 AM MDT...AND MILES
CITY AND BAKER AFTER MIDNIGHT. WE EXPECT A SHIFT TO WEST-NORTHWEST
WINDS BEHIND THE FRONT WITH GUSTS TO 45 MPH BASED ON THE DEGREE OF
LOW- AND MID-LEVEL COLD AIR ADVECTION AND THERMAL GRADIENT IN THE
FRONTAL ZONE. THAT/S SUPPORTED BY MOS STATISTICAL OUTPUT /THE MAV
AND MET/ AS WELL. FORECAST SOUNDINGS DO SUGGEST THE BOUNDARY LAYER
MAY BE A BIT TOO DECOUPLED FOR FULL MOMENTUM TRANSFER OF THE 40 KT
WINDS THAT ARE SIMULATED WITHIN 3000 FT AGL OF THE GROUND...BUT WE
BELIEVE THE COLD AIR ADVECTION WILL OVERCOME THAT TENDENCY. A RED
FLAG WARNING CONTINUES THROUGH THE EVENING TO CONVEY THE RISK THIS
COLD FRONTAL PASSAGE WILL PRESENT FOLLOWING LATE-AFTERNOON MIX-OUT
OF GUSTY SOUTHWEST WINDS AND DRYING IN SOUTH CENTRAL MT.

WHERE PRECIPITATION IS CONCERNED...ISOLATED SHOWERS AND STORMS ARE
POSSIBLE WITH THE SHORTWAVE TROUGH PASSAGE DRIVING THE COLD FRONT
EASTWARD...MAINLY THIS EVENING. STRONG MID-LEVEL WINDS SUGGEST A
STRONG STORM IS POSSIBLE...BUT WE FEEL THAT RISK WILL GENERALLY BE
MITIGATED BY A LACK OF STRONGER INSTABILITY.

MONDAY...THE POST-FRONTAL AIR MASS WILL BE COOLER...DRIER...AND
STABLE. HIGHS WILL BE NEAR 80 F WITH AFTERNOON HUMIDITIES AROUND
20 PERCENT PER THE 12 UTC MULTI-MODEL CONSENSUS WE USED TO DERIVE
THE OFFICIAL FORECAST...BUT WIND/S WILL NOT BE ANYTHING TO WRITE
HOME ABOUT.

TUESDAY...DEEPER MIXING TO 700 MB OR MORE AND WARMING TEMPERATURES
ALOFT WITH SOUTHWEST FLOW WILL PROMOTE A WARM-UP INTO THE UPPER
80S AND LOWER 90S F. ATMOSPHERIC MOISTURE CONTENT WON/T CHANGE
TOO MUCH AND THE RESULT WILL BE EVEN LOWER HUMIDITIES WELL DOWN
INTO THE TEENS...THOUGH WINDS AREN/T EXPECTED TO BE STRONG ENOUGH
FOR ANY RED-FLAG-TYPE CONDITIONS. SCHULTZ

.LONG TERM...VALID FOR WED...THU...FRI...SAT...SUN...

UPPER TROUGH OVER THE PACIFIC NORTHWEST WILL MOVE INLAND ON
WEDNESDAY AND THIS SETS UP DEEP SOUTHWEST FLOW OVER SOUTHERN
MONTANA AND NORTHERN WYOMING. HIGHS WILL APPROACH 90 DEGREES ON
WEDNESDAY AHEAD OF COLD FRONT. THIS FRONT WILL MOVE THROUGH
WEDNESDAY NIGHT AND BRING COOLER WEATHER FOR THE END OF THE WEEK.
IN FACT...THIS WILL MARK A DRAMATIC PATTERN CHANGE AS THE WESTERN
TROUGH SWINGS OVER THE NORTHERN ROCKIES THIS WEEKEND. THIS WILL
END THE WARM AND DRY REGIME AND PROVIDE COOLER TEMPERATURES AND A
CHANCE OF PRECIPITATION. SOME OF THE MOUNTAIN TOPS COULD EVEN SEE
A LITTLE SNOW SATURDAY AND SUNDAY...ALTHOUGH THE STRONGER FORCING
AND MOST LIKELY PRECIPITATION PLACEMENT...WOULD BE OVER NORTHERN
MONTANA. TWH

&&

.AVIATION...

STRONG SOUTHWEST WINDS WILL CONTINUE AT KLVM THIS AFTERNOON WITH
SOME GUSTS TO 35KTS. WIDELY SCATTERED SHOWERS AND THUNDERSTORMS
WILL DEVELOP THROUGH THIS EVENING AS A COLD FRONT APPROACHES. SOME
OF THE STORMS NORTHWEST OF BILLINGS COULD BE STRONG WITH WIND
GUSTS TO 45KTS. A COLD FRONT WILL MOVE THROUGH CENTRAL LOCATIONS
FROM KBIL TO KLVM FROM 02-04Z...KSHR 03-05Z AND KMLS AND KBHK
05-07Z. NORTHWEST WINDS WILL GUST TO 35KTS BEHIND THE FRONT.
TWH/AAG

&&

.PRELIMINARY POINT TEMP/POPS...

    MON     TUE     WED     THU     FRI     SAT     SUN
-----------------------------------------------------------
BIL 054/082 054/089 059/090 055/075 048/069 047/070 045/071
    20/U    00/U    01/U    11/B    23/T    33/T    22/T
LVM 045/080 046/086 051/085 048/072 041/067 038/069 039/073
    20/K    00/K    01/B    23/T    44/T    44/T    32/T
HDN 054/083 053/092 057/094 056/080 048/075 048/072 046/073
    20/U    00/U    11/U    11/B    22/T    22/T    22/T
MLS 057/082 055/092 059/097 059/081 051/077 049/073 047/072
    30/U    00/U    00/U    11/B    22/T    22/T    22/T
4BQ 056/080 055/092 059/096 058/082 053/079 051/071 049/070
    30/U    00/U    00/U    01/U    12/T    22/T    22/T
BHK 055/079 054/091 057/095 058/081 051/080 049/073 046/070
    30/N    00/U    10/U    11/U    12/T    22/T    22/T
SHR 051/083 049/091 054/092 053/082 046/076 044/070 042/071
    30/U    00/U    10/U    01/B    12/T    22/T    22/T

&&

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

&&

$$
WEATHER.GOV/BILLINGS



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