FXUS65 KGGW 010447 AAA
AFDGGW

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE GLASGOW MT
947 PM MST MON NOV 30 2009

.SHORT TERM...FOR NORTHEAST MONTANA...TONIGHT THROUGH WEDNESDAY...
A COLD FRONT IS IN THE PROCESS OF CROSSING NORTHEAST MONTANA THIS
EVENING. UP TO THIS POINT WIND SPEEDS HAVE BEEN RATHER
UNIMPRESSIVE AND THIS IS LIKELY DUE TO THE FACT THAT THE STRONGEST
COLD AIR ADVECTION AND PRESSURE GRADIENT IS WELL BEHIND THE
LEADING EDGE OF THE FRONTAL ZONE. TEMPERATURES WILL STEADILY FALL
BEHIND THE FRONT...BUT MIXING ALONG THE LEADING EDGE OF THE FRONT
HAS PRODUCED INTRIGUING BRIEF TEMPERATURE INCREASES WITH VALUES
JUMPING INTO THE 50S BEFORE FALLING. GOES WATER VAPOR IMAGERY
REVEALS A VIGOROUS SHORTWAVE TROUGH DIGGING SOUTHEAST ACROSS
MONTANA. THE TROUGH IS BEGINNING TO SHOW SIGNS OF BECOMING A
CLOSED LOW WITH AN AXIS OF MOIST AIR BEING LIFTED AND DRAWN
CYCLONICALLY AROUND THE NORTHERN PERIPHERY OF THE SYSTEM. THIS HAS
RESULTED IN WIDESPREAD SNOW ACROSS SOUTHERN SASKATCHEWAN AND
ALBERTA. CURRENT SATELLITE AND RADAR TRENDS INDICATE THIS SNOW
WILL CLIP THE NORTHERN ZONES LATE TONIGHT AND EARLY TOMORROW
MORNING HENCE POPS WERE INCREASED TO LIKELY FOR THE FAR NORTH
LATE TONIGHT AND NORTHEAST FOR TOMORROW MORNING. ACCUMULATION OF NO
MORE THAN ONE INCH IS EXPECTED DUE TO THE SPEED OF THE UPPER LEVEL
SYSTEM. AJZ

PREVIOUS SHORT TERM DISCUSSION...
A RETURN TO REALITY IS EXPECTED FOR THE BEGINNING OF DECEMBER AS A
STRONG COLD FRONT PLOWS THROUGH NORTHEAST MONTANA BRINGING AN END
TO THE MILD CONDITIONS OF THE PAST MONTH AND TRIGGERING A PATTERN
CHANGE THAT COULD SEND TEMPERATURES PLUMMETING WELL BELOW SEASONAL
AVERAGES AS ARCTIC AIR RETURNS TO NORTH AMERICA.

THE UPPER LEVEL TROUGH CURRENTLY MOVING OVER THE CANADIAN ROCKIES
WILL DIVE THROUGH MONTANA ON ITS WAY OUT OVER THE CENTRAL PLAINS.
THIS MOVEMENT WILL SEND A COLD FRONT SOUTH THROUGH THE LOCAL AREA
TONIGHT. A CLOSED SURFACE LOW SLIDES SOUTH INTO NORTH DAKOTA WHICH
WILL ESTABLISH A TIGHT PRESSURE GRADIENT ACROSS THE LOCAL ZONES.
850MB AND 700MB WIND STRENGTH WILL RANGE AROUND 35KT TO 45 KTS OUT
OF THE NW. THESE UPPER WINDS WILL LIKELY MIX TOWARDS THE SURFACE IN
THE AREA AROUND THE COLD FRONT...REINFORCING THE SURFACE WINDS.
WILL ISSUE A LWA. WITH NOT MUCH MOISTURE TO WORK
WITH...PRECIPITATION WILL BE LIMITED WITH THE SYSTEM. THE MAIN
STORM ENERGY WILL REMAIN TO THE NORTH IN SASKATCHEWAN AND
MANITOBA. HOWEVER LOW CLOUDS ASSOCIATED WITH THE SYSTEM WILL
BLANKET MUCH OF THE AREA...ESPECIALLY THE NORTHEASTERN ZONES WHERE
THERE WILL BE ENOUGH DYNAMICS TO GENERATE LIGHT SNOW. ANOTHER
ACTIVE AREA FOR PRECIPITATION WILL BE THE CENTRAL AND SOUTHEAST
REGIONS OF THE STATE. SOME OF THIS MIGHT SLIP ACROSS THE
SOUTHWESTERN ZONES TONIGHT. A GOOD HEAD START IN TEMPERATURES
TODAY WILL PREVENT LOWS TONIGHT FROM PLUNGING TOO FAR DOWN...SO
LOWS WILL BE SIMILAR TO THOSE OF LAST NIGHT.

TUESDAY...WIND STRENGTH WILL BE MAINTAINED TUESDAY MORNING...BUT
AS MIXING IMPROVES THE GRADIENT BEGINS TO RELAX AS THE SURFACE LOW
SLIDES FARTHER EAST. INCREASING LOW CLOUDS FROM THE NORTH COULD
MODERATE ANY MIXING. 850MB TEMPERATURES TODAY OF +1*C TO +8*C WILL
PLUNGE DOWN TO -10*C TO -8*C IN 24 HOURS ON TUESDAY AFTERNOON. THE
VIGOROUS CAA WILL LIMIT TMAX TO NEAR NORMAL...RANGING FROM THE
UPPER 20S TO MID 30S. THE STRONG NW WINDS...INCREASING LOW CLOUDS
AND COLDER TEMPERATURES WILL MAKE FOR AN UNCOMFORTABLE DAY
OUTSIDE. LIGHT SNOW...MAINLY IN THE NORTHEAST...REMAINS A
POSSIBILITY AS MOISTURE CONTINUES TO WRAP AROUND THE LOW CENTER.

TUESDAY NIGHT AND WEDNESDAY...WINDS PROGRESSIVELY WEAKEN AS THE
SURFACE LOW MOVES INTO THE GREAT LAKES REGION. HOWEVER THE UPPER
LOW CENTERED OVER ONTARIO WILL CONTINUE TO DIRECT A STRONG FLOW
ALOFT DIRECTLY OUT OF THE NORTH OVER THE FORECAST AREA. WITH THE
PREVIOUS DAY HIGHS NEAR NORMAL...THE TUESDAY NIGHT LOWS CAN EXPECT
TO BE NEAR NORMAL...IN THE TEENS. IN ADDITION...LOW CLOUDS WITH
ENHANCED VORTICITY COULD GENERATE VERY LIGHT SNOW OR FLURRIES
THROUGH WEDNESDAY. WITH CONTINUED NORTHERLY FLOW WEDNESDAY...850MB
TEMPERATURES AT -12*C TO -15*C AND LOW OVERCAST 1000MB-500MB
THICKNESS HEIGHTS ALL THE WAY DOWN TO ABOUT 510DM...TMAX WILL DROP
TO TO AROUND 10 DEGREES BELOW NORMAL. 

.LONG TERM...WEDNESDAY NIGHT THROUGH MONDAY...
TRENDING COLDER. MODELS ARE IN AN EXPECTED SHAKEDOWN PROCESS AS
THEY ATTEMPT TO DEAL WITH A MAJOR PATTERN CHANGE. A VERY AMPLIFIED
PATTERN DEVELOPS. GFS PAST FEW RUNS HAS SHOWED A SHORTWAVE FROM
THE GULF OF AK MOVING SE AND CLOSING OFF OVER MT FRI NIGHT...WITH
A FAST COLD FRONT ARRIVAL AS WELL...MUCH QUICKER THAN ANY OTHER
MODEL. ECMWF CONTINUES MUCH FARTHER W WITH THE CLOSED LOW...AND
MUCH SLOWER WITH THE COLD FRONT FROM THE NW. CMC IS A MIDDLE
GROUND...AND NOGAPS NOT SHOWING MUCH CONSISTENCY. SEVERAL OF THE
GFS ENSEMBLES LEAN TOWARD THE ECMWF...AS THE ECMWF SOLUTION LOOKS
JUST AS REASONABLE AS THE GFS...HOWEVER GFS HAS ALSO ROUTINELY
BEEN THE BETTER MODEL COMPARED TO THE ECMWF AND APPEARS MOST
CONSISTENT. THINK THAT A MODEL MIDDLE GROUND OR ENSEMBLE MEAN IS
THE WAY TO GO AT THIS TIME. WITH CONFIDENCE REMAINING LOW
THOUGH...WILL STAY WITH THE ONGOING FORECAST POPS WHICH HAS A FEW
LATER PERIODS OF ONLY 10 PCT OR SO...THEREFORE NOT SHOWING IN ANY
TEXT PRODUCTS.

FOR TEMPS...WHILE THERE ARE SIGNIFICANT TIMING AND SURFACE
PRESSURE DIFFERENCES...ALL MODELS APPEAR TO TREND TOWARD COLDER
WEATHER LATE IN THE PERIOD WITH INCREASING ARCTIC AIR. GFS HAS
BEEN LOOKING MOST BLEAK IN THAT REGARD WITH A STRONG ARCTIC HIGH
INTO MT BY THE END OF THE PERIOD...SOME 850 MB TEMPS DOWN TO
-21C...SO WOULD EXPECT SOME BELOW ZERO LOWS BY SUN NIGHT. SIMONSEN

PREVIOUS LONG TERM...WEDNESDAY NIGHT THROUGH MONDAY...COLD AIR
LINGERS OVER THE AREA WEDNESDAY NIGHT WITH UPPER TROUGH OVER NORTH
DAKOTA. MODEL HAVE DIFFERENT TIMING WITH A SHORTWAVE RIDGE LATE IN
THE WEEK WITH THE GFS BRINGING IT IN ON THURSDAY... THE CANADIAN
ON FRIDAY AND ECMWF ON SATURDAY. THEY ALL FOLLOW THE RIDGE WITH A
STRONG COLD FRONT A DAY LATER. GFS IS LIKELY TOO FAST WITH THE
PROGRESSION OF THE SYSTEM. WILL TREND FORECAST TOWARDS SLOWER
ECMWF FOR NOW AND TIME THE COLD FRONT SATURDAY NIGHT. MUCH COLDER
AIR MASS DROPS SOUTH FOR EARLY NEXT WEEK. WITH LIMITED MOISTURE AT
THE MOMENT... WILL KEEP FORECAST DRY. FORRESTER

&&

.AVIATION...
VFR WITH BROKEN CLOUD LAYER 10K FT AGL TONIGHT. LATE TONIGHT...
BETWEEN 2 AND 5 AM...MVFR OVERCAST CEILINGS DOWN AS LOW AS 1K
FT...WILL SPREAD SE ACROSS THE AREA. THIS WILL BE ACCOMPANIED BY
FLURRIES...BUT EMBEDDED ISOLATED SNOW SHOWERS COULD DROP
VISIBILITY BRIEFLY DOWN TO IFR...AROUND 2 MILES...FOR A SHORT
TIME. EXPECT THESE CONDITIONS...WITH MVFR OVERCAST CEILINGS...WITH
ISOLATED LIGHT SNOW SHOWERS OR FLURRIES THE REMAINDER OF THE DAY
TUE. IT WILL BE VERY WINDY LATE TONIGHT AND TUE AS WELL...NW
25-30KT WITH GUSTS TO 40 KT. SIMONSEN

&&

.GLASGOW WATCHES/WARNINGS/ADVISORIES...
LAKE WIND ADVISORY UNTIL 5 PM MST TUESDAY FOR FORT PECK LAKE.

&&

$$

WEATHER.GOV/GLASGOW