166
FXUS65 KGGW 091601
AFDGGW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GLASGOW MT
901 AM MST TUE FEB 9 2010
SHORT TERM...FOR NORTHEAST MONTANA...TODAY THROUGH THURSDAY
UPDATE...PATCHY FOG WILL LINGER THROUGH MIDDAY ACROSS THE
YELLOWSTONE RIVER VALLEY...AND AREAS NORTH OF THE MILK AND
NORTHERN MISSOURI RIVER VALLEYS. THUS UPDATED TO PUT MENTION IN.
THERE COULD ALSO BE A FEW FLURRIES THAT FALL OUT OF SOME
RETREATING STRATUS EAST OF A PLENTYWOOD TO MEDICINE LAKE TO US2
LINE.
THE WIND CHILL ADVISORY FOR VALLEY AND PHILLIPS COUNTIES
LOOKS ON TRACK WITH ITS NOON EXPIRATION. OTHERWISE CLEAR SKIES
WILL DOMINATE WITH TEMPS RISING INTO THE SINGLE DIGITS ABOVE ZERO
ACROSS THE NORTH...WITH DOUBLE DIGITS ABOVE ZERO SOUTH. GILCHRIST
PREVIOUS DISCUSSION...DOUBLE-CENTERED ARCTIC HIGHER EXTENDING
FROM MB INTO E MT. RIDGING ALOFT IS TO OUR W. THIS COMBINATION
GIVING CLEAR SKIES...BUT COLD TEMPS. UPPER FLOW REMAINS
SPLIT...MAIN JETSTREAM STAYING WELL TO OUR S. WEAKER NORTHERLY
BRANCH OF THE JET WILL HAVE JUST SOME WEAK DISTURBANCES IN IT TO
INFLUENCE OUR AREA.
OVERCAST STRATUS OVER W ND HAS BACKED INTO OUR EXTREME E
OVERNIGHT...BUT STALLED PROGRESS SINCE MIDNIGHT. MODELS HAVE
HANDLED THIS POORLY...BUT LATEST RUC APPEARS MORE REASONABLE...NOT
CHANGING LOCATIONS OF STRATUS MUCH UNTIL LATE MORN...THEN QUICKLY
MOVES IT OUT. ELSEWHERE...ENOUGH LOW LEVEL MIXING...DRY AIRMASS
JUST OFF SURFACE...AND NOT A WELL-DEVELOPED ENOUGH
INVERSION...DISCOURAGES MUCH CHANCE OF FOG.
E WIND RESULTING IN 30 TO 40 BELOW WIND CHILLS THIS MORN IN AT
LEAST PARTS OF THE PHILLIPS AND VALLEY COUNTY ADVISORY AREA...NOT
EXPECTED TO DIMINISH THIS MORN...SO EXTENDING THE ADVISORY TIL
NOON. WINDS ELSEWHERE TO STAY ON THE LIGHT SIDE TODAY.
SLOW WARMING OF THE AIRMASS THRU THU...BUT DEEP SNOW COVER AND
WEAKENING PRESSURE GRADIENTS WILL GREATLY SLOW WARMING FOR THE
VALLEYS AGAIN...ESPECIALLY LOWER MILK AND LOWER MISSOURI...AS HAS
HAPPENED OFTEN LATELY. WILL STAY BELOW MOS ON HIGHS.
THERE WILL ALSO BE MORE CLOUDINESS LATE TONIGHT THRU THU AS 3 WEAK
SHORTWAVES ARRIVE FROM THE NW ARRIVE. PRECIP CHANCES SLIM FROM ANY...AND
WILL LEAVE POPS QUITE LOW. MODELS HAVE MOST TROUBLE WITH THE 3RD
SHORTWAVE ARRIVING THU AFTERNOON. MIXING POOR WITH THESE
THOUGH...BUT MORE CLOUDINESS SHOULD SOMEWHAT BALANCE THE MORE
FAVORABLE CONDITIONS FOR PATCHY VALLEY FOG...SO NO MENTION.
SIMONSEN
LONG TERM...THURSDAY NIGHT THROUGH TUESDAY
NORTHWEST FLOW ALOFT WILL CONTINUE INTO THE WEEKEND WITH MAINLY
DRY SHORTWAVES AND COLD FRONT. THE COLD FRONTS WILL LIMIT ANY
SIGNIFICANT WARMING FROM THE WEST TO MOVE INTO THE FORECAST AREA.
THE GFS AND ECMWF DIFFER SOMEWHAT ON THE TIMING OF THE INDIVIDUAL
SHORTWAVES AND COLD FRONT. AT THIS POINT...IT LOOKS LIKE ONE OF
THE WAVES AND FRONTS IN THE EXTENDED PERIOD WILL BE EITHER FRIDAY
NIGHT (ECMWF) OR SATURDAY (GFS). THE COLD FRONT WILL BRING
SOMEWHAT COLDER TEMPERATURES.
BOTH MODELS BRING AN UPPER RIDGE INTO THE AREA ON SUNDAY.
HOWEVER...THE NEW ECMWF TURNS THE FLOW ALOFT BACK TO THE NORTHWEST ON
MONDAY WITH A COLD FRONT AND SHORTWAVE MOVING THROUGH NORTHEAST
MONTANA ON MONDAY. THE GFS IS WEAKER WITH BOTH THE WAVE AND COLD
FRONT AND HAS THE FLOW ALOFT GOING ZONAL. WILL KEEP THE FORECAST
DRY AT THIS POINT AS THE SYSTEM HAS LIMITED MOISTURE. FORRESTER
AVIATION
A BRISK SOUTHEASTERLY WIND OF 15 KTS HAS PICKED LOOSE SNOW CAUSING
DRSN (LOW DRIFTING SNOW) AROUND KGGW. IN ADDITION...THE MORNING
SOUNDING INDICATED HIGH RH IN THE BOUNDARY LAYER UP TO 500FT. THIS
HAS CREATED PATCHY LIGHT FOG AND HAZE AROUND THE AREA. THERE ALSO
HAS BEEN LOW STRATUS AND FLURRIES BEING GENERATED AROUND THE
MONTANA- NORTH DAKOTA BORDER THIS MORNING WHICH COULD AFFECT KSDY
AND KGDV. OTHERWISE EXPECT A SOUTHEASTERLY BREEZE AROUND 10KTS OR
LESS AND CLEAR SKIES...EXCEPT FOR HIGH THIN SCATTERED CIRRUS. AN
UPPER LEVEL CLIPPER WILL AFFECT THE AREA TONIGHT AND WEDNESDAY
WITH INCREASING MID-LEVEL CLOUDS AND THE POSSIBILITY OF LIGHT SNOW
OR FLURRIES WEDNESDAY. SCT
GLASGOW WATCHES/WARNINGS/ADVISORIES
WIND CHILL ADVISORY UNTIL NOON MST TODAY FOR CENTRAL AND
SOUTHEAST PHILLIPS-CENTRAL AND SOUTHERN VALLEY-NORTHERN PHILLIPS-
SOUTHWEST PHILLIPS-NORTHERN VALLEY.
WEATHER.GOV/GLASGOW
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