Area Forecast Discussion
Issued by NWS Glasgow, MT

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42
000
FXUS65 KGGW 211532
AFDGGW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GLASGOW MT
832 AM MST FRI NOV 21 2014

.SHORT TERM...FOR NORTHEAST MONTANA...TODAY THROUGH SUNDAY...
NO UPDATE TO TEMPERATURES, TWEAKED SKY DOWN AND WINDS WERE MAINLY
LEFT UNTOUCHED.

BIGGEST CHALLENGES TODAY WILL BE TEMPERATURES...SKY AND WIND. THE
INVERSION THIS MORNING ACCORDING TO THE 12Z UPPER AIR LAUNCH WAS A
BIT THICKER THAN WHAT YESTERDAY/S MODELS WERE PREDICTING. BUT
TEMPERATURES WERE WARMER THAN EXPECTED THIS MORNING...SO WE`LL SEE
WHAT HAPPENS. MODELS ARE SHOWING IT TO BE RATHER SUNNY TODAY...SO
OUR FORECAST MAY BE ON THE PESSIMISTIC SIDE. HOWEVER...TRY TO PLAY
IT CONSERVATIVE IN SITUATIONS LIKE THIS AND KEEP TEMPS BELOW THE
POTENTIAL.

WILL HAVE TO LOOK AT FOG POTENTIAL FOR TONIGHT TOO. TFJ

PREVIOUS DISCUSSION...
A WINTRY MIX OF IS STILL ON TRACK FOR THIS WEEKEND WHICH MAY END
AS A PERIOD OF ACCUMULATING SNOW ACROSS NORTHEAST MONTANA...

EXPECT ZONAL FLOW ALOFT ACROSS THE NORTHERN HIGH PLAINS FOR TODAY
AHEAD OF THE NEXT VIGOROUS UPPER LEVEL SHORTWAVE FEATURE MOVING IN
FROM THE PACIFIC NORTHWEST. MAIN CHALLENGES THIS MORNING WILL BE
REFINING WX GRIDS FOR ANY LINGERING AM FOG. THERE WERE A FEW
OBSERVATIONS OVERNIGHT AND DEW POINT DEPRESSIONS REMAIN LOW IN
SOME SPOTS. HOWEVER...WINDS THIS MORNING ARE EXPECTED TO INCREASE
FROM THE WEST AND OVERALL EXPECT A NICE DAY ACROSS NORTHEAST
MONTANA WITH SUNSHINE AND HIGHS IN THE 30S TO LOW 40S.

EXPECT CLOUDS TO INCREASE OVERNIGHT AS THE SHORTWAVE APPROACHES ON
SATURDAY MORNING. PVA WILL PROVIDE DYNAMIC FORCING FOR ASCENT WITH
SOME MOISTURE IN THE VERTICAL TO PROVIDE PRECIPITATION CHANCES
ACROSS THE CWA. DO EXPECT THAT THE INITIAL ONSET MAY BE IN THE
FORM OF A WINTRY MIX...PERHAPS SLEET OR FREEZING RAIN. THIS HAS
SUPPORT FROM NAM BUFKIT SOUNDINGS WHICH SHOW MIDLEVEL WARMING BUT
SHALLOW COLD AIR REMAINING JUST NEAR THE SURFACE. DURING THE DAY
WAA WILL ALLOW TEMPERATURES TO SPRING DECIDEDLY ABOVE FREEZING
ACROSS MOST LOCATIONS AND A CHANGEOVER TO PLAIN RAIN SHALL ENSUE.
HOWEVER...SOME OF THE NORTHERN ZONES SEE PRECIPITATION REMAIN IN
THE FORM OF A WINTRY MIX. AT THIS TIME ICE ACCUMULATIONS APPEAR TO
BE MINIMAL FOR MOST OF THE REGION GIVEN LIGHT QPF IN THE MODEL
OUTPUT. THIS DOES BEAR WATCHING THOUGH AS IMPACTS TO TRAVEL AND IT
BEING A WEEKEND ARE TO BE KEPT IN MIND.

IN ANY EVENT...ATTENTION TURNS TO A COLD FRONT SATURDAY NIGHT
ALLOWING RAIN TO SWITCH BACK TO A WINTRY MIX AND QUICKLY OVER TO
SNOW. DO LOOK FOR PERHAPS SOME UPSLOPE/TERRAIN ENHANCED LIFT AND
SO WENT WITH QPF DISTRIBUTION FOLLOWING THAT IDEA. EXPECTATION IS
FOR UP TO AN INCH OF SNOWFALL ACCUMULATION BEFORE PRECIPITATION
WANES...WITH HIGHEST AMOUNT NEAR THE INTERNATIONAL BORDER AND
COMPLEX TERRAIN FEATURES. OTHER CONCERN GIVEN STRONG CAA BEHIND
THE FRONT AND SHARP PRESSURE GRADIENT FORCE WILL BE GUSTY WEST TO
NORTHWEST SURFACE WINDS...WHICH MAY ALLOW FOR BLOWING AND DRIFTING
OF ANY SNOW THAT ACCUMULATES. INCLUDED THIS MENTION IN THE WX
GRIDS WHERE AN INCH OF ACCUMULATION IS EXPECTED BUT COULD
CONCEIVABLY NEED TO EXPAND COVERAGE IN FUTURE SHIFTS.

LASTLY...ALTHOUGH TOTAL PRECIPITATION AMOUNTS LOOK LIGHT...AN
IMPORTANT CONSIDERATION MUST BE MADE IN TERMS OF WEEKEND PLANNING.
ANY RAIN/WINTRY MIX MAY MAKE FOR SLUSHY/WET ROAD CONDITIONS ON
SATURDAY...WHICH WILL TURN TO ICY CONDITIONS SATURDAY NIGHT AND
SUNDAY BEFORE BECOMING SNOW COVERED. WEEKEND TRAVEL WILL BE
IMPACTED AS A RESULT AND THOSE WITH INTERESTS SHOULD CONTINUE TO
MONITOR THE LATEST FORECAST FOR ANY NEW DEVELOPMENTS. MALIAWCO

.LONG TERM...SUNDAY NIGHT THROUGH FRIDAY...
MODELS IN QUITE GOOD AGREEMENT THROUGH MUCH OF THE PERIOD WITH
DIFFERENCES ONLY DEVELOPING BY THE MIDDLE OF NEXT WEEK. CLIPPER
SYSTEM FOR THIS WEEKEND EXITS EAST BY MONDAY MORNING WITH ONLY A
FEW LINGERING SNOW SHOWERS SUNDAY NIGHT.

AS NEXT SHORTWAVE BEGINS DROPPING OUT OF THE GULF OF ALASKA...
UPPER FLOW TURNS A LITTLE TO THE WEST...ALLOWING WARM AIR ACROSS
THE DIVIDE TO BEGIN SHALLOWING THE COLD AIR. MAIN MODEL
DIFFERENCE IS HOW FAR EAST DOES THE WARM AIR MIX AND DOES THE
WAVE PULL ANOTHER SURGE OF ARCTIC AIR INTO THE NORTHERN PLAINS. A
LITTLE OVERRUNNING PRECIPITATION POSSIBLE AS EARLY AS TUESDAY AS
THE BOUNDARY AND WARM AIR PUSHES EAST. THEN THE QUESTION BECOMES
DOES THE BOUNDARY SHIFT WESTWARD WITH A PUSH OF COLD AIR INTO THE
STATE AS PER PREVIOUS MODELS RUNS...OR AS THE TREND OF THE MOST
CURRENT MODELS INDICATES...DOES THE BOUNDARY REMAIN CLOSER TO
EASTERN MONTANA FOR A PERSISTENT BAND OF OVERRUNNING PRECIPITATION
OVER PART OF THE CWA THROUGH THE THANKSGIVING HOLIDAY. GIVEN THE
LOW CONFIDENCE WITH THE MODELS SHIFTING...MADE ONLY A FEW
ADJUSTMENTS TO GOING FORECAST. EBERT


&&

.AVIATION...

EXPECT VFR CONDITIONS WITH MID TO HIGH CLOUDS TODAY AND TONIGHT.

LIGHT WINDS UNDER THE SHALLOW INVERSION AND STRONGER WESTERLY
WINDS ABOVE THE INVERSION WILL CREATE POTENTIAL WIND SHEAR
PROBLEMS THROUGH LATE THIS MORNING. WIND SHEAR CONCERNS WILL
DIMINISH BY MID-DAY...WHEN THE INVERSION MIXES OUT. THE NEXT
STORM SYSTEM ARRIVES FROM THE WEST JUST BEYOND THE END OF THIS TAF
CYCLE. BMICKELSON


&&

.HYDROLOGY...
THE RIVER STAGES AT SIDNEY ON THE YELLOWSTONE RIVER HAVE BEEN ON
THE RISE AND THE LATEST FORECAST HAS IT ON THE PATH OF BEING LEVEL
WITH A SLIGHT STEADY RISE. WE WILL CONTINUE TO MONITOR BUT
FORECASTS FOR THIS LOCATION WILL BE DISCONTINUED FOR NOW. TFJ

&&

.GLASGOW WATCHES/WARNINGS/ADVISORIES...NONE.

&&

$$

WEATHER.GOV/GLASGOW




USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.