Area Forecast Discussion
Issued by NWS Billings, MT

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FXUS65 KBYZ 250910
AFDBYZ

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BILLINGS MT
310 AM MDT SAT OCT 25 2014

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

WATER VAPOR IMAGERY SHOWED A NICE COMMA HEAD DEVELOPING OVER THE
PACIFIC NW EARLY THIS MORNING WITH A STRONG VORTICITY CENTER ALONG
130W.

UPPER RIDGE WILL SLIDE ACROSS THE AREA TODAY...THEN THE FLOW ALOFT
WILL TURN SW TONIGHT AS THE PACIFIC SYSTEM MOVES INTO THE AREA.
SHORTWAVES AND ASSOCIATED Q-VECTOR CONVERGENCE WILL MOVE THROUGH
THE AREA AS WELL. AIRMASS WILL BE DRY TODAY THROUGH MUCH OF
TONIGHT. MOISTURE PROFILES SUPPORTED LEAVING A SLIGHT CHANCE OF
PRECIPITATION OVER THE SW MOUNTAINS LATE TONIGHT.

MADE ONLY SLIGHT ADJUSTMENTS TO THE HIGHS FOR TODAY BASED ON
LATEST MAV GUIDANCE.

THE TROUGH AXIS WILL MOVE INTO THE AREA ON SUN AND MOVE E THROUGH
THE AREA SUN NIGHT WITH ASSOCIATED Q-VECTOR CONVERGENCE. SOME JET
DIVERGENCE WAS FORECAST OVER THE AREA ON SUN AS WELL...AS JET
ENERGY MOVES AROUND THE BASE OF THE TROUGH. COLD FRONT WILL PUSH
THROUGH THE AREA SUN MORNING...BUT MOISTURE WILL REMAIN CONFINED
TO THE SW PORTION OF THE AREA...WHILE DOWNSLOPE FLOW KEEPS THE
REST OF THE AREA DRY. TRIMMED BACK THE EASTWARD EXTENT OF POPS
BASED ON THE DOWNSLOPING. MORE MOISTURE MOVES ACROSS THE AREA SUN
AFTERNOON...SUPPORTING MORE WIDESPREAD POPS...BUT DOWNSLOPE WILL
STILL INHIBIT THE AMOUNT OF PRECIPITATION. REDUCED POPS A LITTLE
OVER THE CENTRAL ZONES...AND RAISED THEM OVER THE SW MOUNTAINS.
TIME-HEIGHTS SHOWED DEEP INSTABILITY SUN AND SUN NIGHT...AND
BUFKIT SHOWED STEEP LAPSE RATES...SO ISOLATED THUNDER WOULD NOT
BE OUT OF THE QUESTION. MOISTURE CONTINUES TO INCREASE OVER THE
REGION SUN NIGHT AND FLOW TURNS NW AFTER 06Z MON. WILL CONTINUE
WITH THE SCATTERED POPS OVER LOW ELEVATIONS AND HIGHER POPS IN THE
MOUNTAINS. 700 MB TEMPERATURES DROP TO BELOW ZERO DEGREES C OVER
THE MOUNTAINS DURING SUN. EXPECT A FEW INCHES OF SNOW OVER THE
HIGHER ELEVATIONS SUN AND SUN NIGHT.

GOOD MIXING ON SUN COMBINED WITH STRONG WINDS ALOFT WILL MAKE FOR
WINDY CONDITIONS. WARMED UP SUN A LITTLE DUE TO THE GOOD
MIXING...BUT IT WILL BE A TOUGH CALL DUE TO THE FRONTAL PASSAGE.
ARTHUR

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

EXTENDED MODELS WERE IN MUCH BETTER AGREEMENT TODAY AND THIS
LEADS TO MORE CONFIDENCE IN THE FORECAST...DESPITE THE FAST FLOW
PATTERN. A COUPLE SHORTWAVES WILL SWING THROUGH THE AREA AND
GENERATE A FEW SHOWERS. THE FIRST ONE WILL BE ON THE BACK SIDE OF
THE TROUGH PASSING THROUGH ON SUNDAY. THIS WAVE WILL DRIFT DOWN IN
NORTHWEST FLOW AND WORK WITH AN UNSTABLE AIRMASS TO GENERATE
SCATTERED SHOWERS FOR THE MOUNTAINS AND SOME MOUNTAIN SNOW ON
MONDAY. MODELS WERE CONSISTENTLY HITTING THE EAST HARDER WITH THE
WAVE...AS THIS AREA WAS CLOSEST TO THE COLDEST AIR ALOFT AND THUS
MORE UNSTABLE. WILL PLACE HIGHER POPS EAST OF BILLINGS.

THE NEXT WAVE TO DRIFT THROUGH WILL MOVE IN TUESDAY NIGHT AND
WEDNESDAY. THIS WAVE WAS VERY DISORGANIZED WITH THE MAJORITY OF
THE LIFT CONFINED TO WESTERN AND SOUTHERN ZONES. A COLD FRONT WILL
PUSH THROUGH WITH THIS WAVE AND ENHANCE THE LOW LEVEL LIFT...SO
WILL MAINTAIN SCATTERED POPS AND HIT SOUTHERN LOCATIONS THE
HARDEST. THE MOUNTAINS WILL SEE ANOTHER COUPLE INCHES OF SNOWFALL
FROM HEAVIER SNOW SHOWERS WITH THIS ENERGY. AN UPPER RIDGE WILL
THEN BUILD IN FOR THE END OF THE WEEK.

THE OTHER THING TO HIGHLIGHT WITH THIS FORECAST IS THE WINDY
PERIODS EXPECTED. MONDAY WILL BE WINDY...ESPECIALLY EARLY IN THE
DAY. WINDS WILL INCREASE OVER THE FAVORED SOUTHWEST VALLEYS
TUESDAY NIGHT INTO EARLY WEDNESDAY. WINDS WILL SPREAD ACROSS
WESTERN AND CENTRAL ZONES TUESDAY NIGHT AND EARLY WEDNESDAY.
INCREASING SOUTHEAST WINDS ARE EXPECTED THURSDAY NIGHT OVER
SOUTHEAST MONTANA AS A SURFACE TROUGH SETS UP OVER CENTRAL ZONES.
BUMPED WINDS UP FOR ALL THESE PERIODS AND LOCATIONS.

TEMPERATURES WILL BE SEASONAL FOR MONDAY AND TUESDAY BEFORE A
WARM UP KICKS IN FOR MID WEEK. THE MAIN WARM UP WILL BE LATE IN
THE WEEK AS THE UPPER RIDGE BUILDS BACK IN. TWH
&&

.AVIATION...

VFR FLYING CONDITIONS ARE EXPECTED TODAY. SOUTHWEST WINDS WILL
INCREASE AT KLVM EARLY THIS AFTERNOON WITH SOME GUSTS TO 30KTS.
TWH
&&

.PRELIMINARY POINT TEMP/POPS...

    TDY SUN     MON     TUE     WED     THU     FRI
-------------------------------------------------------
BIL 070 048/066 038/052 031/055 037/059 035/059 034/063
    0/U 02/T    33/W    11/B    23/W    10/B    00/B
LVM 070 043/059 034/046 029/051 034/054 034/057 032/059
    0/N 13/T    33/W    11/N    34/W    10/B    00/B
HDN 072 047/070 035/053 030/056 033/060 033/060 032/064
    0/U 02/T    33/W    11/B    22/W    10/B    00/B
MLS 071 047/067 037/050 029/054 033/059 031/057 030/060
    0/U 02/T    23/W    10/U    11/B    00/B    00/B
4BQ 073 048/069 037/050 029/054 032/059 033/057 033/063
    0/U 02/T    43/W    10/U    11/B    00/B    00/B
BHK 067 045/068 034/046 027/048 029/056 029/052 029/058
    0/U 02/T    33/W    10/U    11/B    00/B    00/B
SHR 073 050/069 030/050 028/054 029/059 029/060 030/062
    0/U 02/T    44/W    11/U    22/W    10/B    00/B

&&

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

&&

$$
WEATHER.GOV/BILLINGS



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