000
FXUS65 KGGW 200405
AFDGGW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GLASGOW MT
905 PM MST WED NOV 19 2008
.SHORT TERM...FOR NORTHEAST MONTANA...TONIGHT THROUGH FRIDAY...
UPDATE...POLAR HIGH PRESSURE CONTINUES TO PUSH IN FROM
SASKATCHEWAN. SOME LOW STRATUS UNDER THE HIGH IS EVIDENT ON
SATELLITE ACROSS SOUTHERN SASK...PUSHING INTO NORTHERN
VALLEY...DANIELS...AND SHERIDAN COUNTIES. FLURRIES ARE ALSO BEING
EXPERIENCED IN WEYBURN. EXPECT THIS STRATUS TO PUSH MORE TO THE
EAST AFTER MIDNIGHT AS UPPER RIDGING BUILDS IN. UPDATED SKY AND WX
TO REFLECT SAID DEVELOPMENTS. GILCHRIST
PREVIOUS DISCUSSION...COOLER AIRMASS TO STAY WITH US THROUGH THE
PERIOD. PERIOD STARTS OFF DRY BUT A SYSTEM IS EXPECTED TO IMPACT
THE AREA BY FRIDAY WITH SNOW ESPECIALLY IN THE SOUTHERN ZONES.
SURFACE CHARTS SHOWING A POLAR FRONT STALLED OUT FROM SW MT TO
NORTHEAST COLORADO WHILE AN ARCTIC FRONT IS STALLED FROM CENTRAL
MINNESOTA TO SE SASK. A 1044MB SURFACE HIGH IS EXPECTED TO PRESS
SOUTH INTO THE AREA TONIGHT...ALLOWING FOR CLEAR SKIES AND LIGHT
WINDS. THIS WILL RESULT IN THE COOLEST TEMPS THAT WE HAVE SEEN YET
THIS SEASON (COLDEST SO FAR IN GLASGOW WAS 14 ON 10/27)...WITH TEMPS
DROPPING AT LEAST INTO THE TEENS ACROSS THE CWA.
THE NEXT SYSTEM IS CURRENTLY MOVING THROUGH THE GULF OF ALASKA. THE
MODELS HAVE BEEN IN DISAGREEMENT WITH IT AS IT MOVES THROUGH MONTANA
AND A GFS/ECMWF BLEND WAS USED WITH THIS FORECAST PACKAGE. INCREASED
POPS TO HIGH CHANCE FOR THE SOUTHERN ZONES AND IF MODEL AGREEMENT
CONTINUES...SOME LIGHT ACCUMULATION (ABOUT AN INCH) IS A GOOD
POSSIBILITY FOR THIS AREA. JAMBA
.LONG TERM...FRIDAY NIGHT THROUGH WEDNESDAY...
OPERATIONAL MODELS AND GFS ENSEMBLES ARE IN DECENT AGREEMENT THROUGH
THIS WEEKEND. A SHORTWAVE TROUGH WILL BE EXITING THE AREA FRIDAY
NIGHT WITH DRIER AIR MOVING IN FROM THE WEST. ANOTHER SHORTWAVE
WILL QUICKLY FOLLOW ON SATURDAY. GFS/ECMWF/CANADIAN DIFFER
SOMEWHAT WITH THE TRACK...BUT THEY ALL DEVELOP A CLOSED LOW
CENTERED OVER THE SOUTHERN HALF OF MANITOBA BY SUNDAY. NONETHELESS
THE CHANCE OF PRECIPITATION OVER THE LOCAL FORECAST AREA IS VERY
MINIMAL WITH ONLY A FEW SNOW SHOWERS OR FLURRIES WITH CYCLONIC
NORTHERLY FLOW ALOFT SATURDAY NIGHT AND SUNDAY. TEMPERATURES
FRIDAY NIGHT THROUGH SUNDAY SHOULD AVERAGE SLIGHTLY ABOVE SEASONAL
AVERAGES.
BY MONDAY...LARGER MODEL SPREAD DEVELOPS...BUT IT IS PRIMARILY IN THE
POSITION AND STRENGTH ON AN UPPER RIDGE. 12Z ECMWF HAS INTRODUCED
A PROGRESSIVE SHORTWAVE WITH LITTLE MOISTURE MONDAY NIGHT WITH THE
UPPER RIDGE QUICKLY REBOUNDING TUESDAY. TEMPERATURES SHOULD BE
WELL ABOVE AVERAGE THROUGH THIS PERIOD. BY THE MIDDLE OF NEXT WEEK
SPLIT FLOW ALOFT DEVELOPS ACROSS NORTH AMERICA...WHICH KEEPS ANY
ARCTIC AIR TRAPPED WELL TO THE NORTH.
OVERALL FORECAST WAS IN GOOD SHAPE WITH ONLY A FEW TWEAKS FOR
COORDINATION PURPOSES. AJZ
PREVIOUS LONG TERM DISCUSSION...
GFS AND ECMWF ARE NOW IN GOOD AGREEMENT WITH WHAT SHOULD BE A
CONTINUATION OF GENERALLY QUIET FALL WEATHER. LITTLE IN THE WAY OF
PRECIP AND NO REALLY COLD TEMPS IN SIGHT. OTHER FORECAST MODELS
STILL SHOWING SOME VARIATION...MAINLY IN REGARD TO INCOMING
SHORTWAVE TROUGH FROM THE WEST SAT NIGHT/SUN. IT FORMS A CLOSED
UPPER LOW CENTER TO OUR N-NE AS IT DOES SO. WITH THE SURFACE LOW
TO OUR N AS WELL...MOST MOISTURE MISSES OUR AREA...WITH THERE
BEING JUST A SLIGHT CHANCE OF SNOW SHOWERS FOR ONE OR TWO FORECAST
PERIODS. POTENTIAL FOR WINDY WEATHER AT TIMES WITH THIS SYSTEM AS
850 MB WINDS ARE AS HIGH AS 45 KT ON MODELS SAT NIGHT AND
SUN...WITH MODERATE COLD ADVECTION.
FOLLOWING THIS SYSTEM...DRYING AND COOLING IN NW FLOW WITH A
SURFACE HIGH OF N PACIFIC ORIGIN MOVING ESE ACROSS S CANADA. THE
COOLING FROM THIS WILL BE SHORT LIVED AND SIMILAR TO WHAT WE HAVE
EXPERIENCED A FEW TIMES THIS MONTH ALREADY. THE CLOSING OFF OF THIS
SYSTEM MARKS A RETURN TO A MORE AMPLIFIED PATTERN AGAIN...AND AGAIN
A RATHER STRONG UPPER RIDGE OVER THE WESTERN STATES. THE COOL
SURFACE HIGH MOVES OUT OF THE AREA BY TUE...LEAVING BEHIND A PATTERN OF
WEAK SURFACE PRESSURE GRADIENTS. THICKNESSES ARE NOT TOO FAR FROM
YESTERDAYS...WHICH PRODUCED THE RECORD HIGHS. THIS WILL RESULT IN
AT LEAST TWO MILD DAYS...BUT LACK OF WIND WILL HELP PREVENT ANYTHING
UNUSUALLY WARM. SIMONSEN
&&
.AVIATION...
A GENERALLY BROKEN MVFR LOWER CLOUD LAYER AT 25 HUNDRED FT AGL
WILL BE MOVING SE FORECAST AREA TONIGHT. THIS WILL MAINLY EFFECT
VALLEY...ROOSEVELT...DANILES...SHERIDAN...AND RICHLAND COUNTIES
INCLUDING TAF SITES GGW...OLF..AND SDY. THIS STRATUS SHOULD MOVE
EAST OUR OF THE AREA AROUND 12Z THU MORN...FOLLOWED BY HIGH
CLOUDS MOVING IN FROM THE WEST. A 10-15 KT N WIND WILL STEADILY
VEER TO THE SOUTHEAST BY THURSDAY AFTERNOON AND GENERALLY BECOME
LIGHT...EXCEPT FOR KGGW...WHICH WILL INCREASE TO 12-15 KT. AJZ/SIMONSEN
&&
.GLASGOW WATCHES/WARNINGS/ADVISORIES...NONE.
&&
$$
WEATHER.GOV/GLASGOW
