FXUS65 KGGW 142036
AFDGGW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GLASGOW MT
236 PM MDT SUN MAR 14 2010

.SHORT TERM...FOR NORTHEAST MONTANA...TONIGHT THROUGH TUESDAY...
A WEAK SHORTWAVE TROUGH AND COLD FRONT WILL SLOW THE EXIT OF LOW
STRATUS TO THE EASTERN AREAS TONIGHT. ALTHOUGH TEMPERATURES WERE
A BIT COOL TODAY DUE TO THE NORTHWEST FLOW BEHIND THE FRONT THERE
WAS SUFFICIENT SNOW-MELT TO MOISTEN UP THE SURFACE LAYER FOR
ANOTHER ROUND OF FOG TONIGHT. THE FORMATION OF FOG WILL BE
ENHANCED BY CLEARING SKIES FROM THE WEST AND DIMINISHING WINDS.
BUT SINCE PATCHY BARE AREAS ARE GROWING IN NUMBER AND SIZE...WILL
KEEP FOG ONLY AT PATCHY IN THE GRIDS.

MONDAY THROUGH TUESDAY... A LARGE SCALE RIDGE IS ANTICIPATED TO
BUILD INTO THE AREA WITH CONDITIONS WARMING ABOVE NORMAL BY
TUESDAY. 1000MB-500MB THICKNESS HEIGHTS WILL RAMP UP FROM AROUND
540DM LATE THIS AFTERNOON TO ABOUT 555DM BY LATE TUESDAY
AFTERNOON. APPROACHING THE VERNAL EQUINOX HAS CONTINUED TO
INCREASE THE TIME THAT THE SUN REMAINS OVERHEAD TO AID THE SNOW
MELT. AREAS SUCH AS PETROLEUM COUNTY AND THE MISSOURI BREAKS ARE
ANTICIPATED TO MAKE IT INTO THE 50S AND POSSIBLY EVEN THE 60S FOR
HIGHS MONDAY. BY TUESDAY A WEAK CHINOOK EVENT IS ANTICIPATED TO
MOVE THROUGH THE REGION WITH SOUTHWEST WINDS AND TEMPERATURES FROM
THE UPPER 40S TO MID 50S SHOULD BE ABLE TO SPREAD ACROSS MUCH OF
THE REGION. THEREFORE WILL CONTINUE TO SLOWLY RAMP DOWN THE
BLENDING OF BIAS CORRECTED MOS WITH STANDARD MOS GUIDANCE. SCT


.LONG TERM...TUESDAY NIGHT THROUGH SUNDAY...
THE PERIOD BEGINS ON TUESDAY NIGHT WITH A HIGH AMPLITUDE UPPER
RIDGE EXTENDING FROM THE DESERT SOUTHWEST NORTHEASTWARD TO
SASKATCHEWAN. CONDITIONS OVER EASTERN MONTANA WILL REMAIN WARM
AND DRY INTO WEDNESDAY AS THE UPPER RIDGE DOMINATES. A PACIFIC
TROUGH EFFECTIVELY BREAK DOWN THE UPPER RIDGE ON WEDNESDAY
NIGHT...SENDING A MAINLY DRY COLD FRONT THROUGH THE REGION.

THURSDAY INTO FRIDAY THE UPPER LEVEL TROUGH WILL MAKE FOR
COOL...UNSETTLED CONDITIONS. ALTHOUGH THERE IS A BIT BETTER
CONSISTENCY IN THE LATEST SET OF MODEL RUNS...THERE REMAINS SOME
UNCERTAINTY REGARDING INDIVIDUAL DISTURBANCES ASSOCIATED WITH THE
UPPER TROUGH. THUS WILL CONTINUE THE GOING BROADBRUSHED FORECAST
FOR THURSDAY INTO FRIDAY.

LOWERED CONFIDENCE EXISTS IN THE FORECAST FOR THE WEEKEND.
OPERATIONAL 12Z ECMWF...GFS...AND GEM MODELS ARE NOW REASONABLY
CONSISTENT WITH QUICKLY BUILDING IN A RIDGE FROM THE WEST...WITH A
STALLED FRONTAL BOUNDARY OVER NORTHEAST MONTANA. PREVIOUS
OPERATIONAL RUNS ALONG WITH SEVERAL GFS ENSEMBLE MEMBERS AND THE
12Z DGEX AGREE IN WRAPPING SOME ADDITIONAL ARCTIC AIR DOWN UNDER
THE POLAR VORTEX. GIVEN THE UNCERTAINTY MADE ONLY MINOR TWEAKS TO
THE GOING FORECAST WHICH FAVORS NEAR CLIMO POPS AND COOLER
CONDITIONS FOR NOW. GILCHRIST

PREVIOUS LONG TERM DISCUSSION...OVERALL MODEL CONSISTENCY FAIRLY
GOOD FOR THE EXTENDED FORECAST ALTHOUGH DIFFERENCES DEVELOPING IN
THE LATE PERIODS REGARDING THE STRENGTH OF THE ARCTIC AIRMASS
MOVING INTO THE NORTHERN PLAINS.

UPPER RIDGE OVER THE REGION AT THE START OF THE EXTENDED PERIOD
BEGINS TO BREAK DOWN WITH AN UPPER TROF MOVING INTO WESTERN CANADA
TUESDAY NIGHT. THIS WAVE WILL PUSH A COLD FRONT INTO NORTHERN
MONTANA LATE WEDNESDAY. TROF DEEPENS ALONG THE FRONT RANGE AS
ADDITIONAL SHORTWAVE DIVE SOUTH...PULLING COLDER AIRMASS SOUTHWARD
AS WELL. TIMING OF THE VARIOUS WAVES DIFFERENT AMONG THE MEDIUM
RANGE MODELS BUT WITH COLD AIR ADVECTION...A GENERAL UNSETTLED
PERIOD WITH BROADBRUSHED POPS FROM THURSDAY NIGHT INTO SATURDAY
SEEMS REASONABLE.

LARGER MODEL DIFFERENCES BEGIN TO DEVELOP ON SATURDAY WITH RIDGE
PUSHING OVER THE WEST COAST. ECMWF AND GEM FURTHER EAST WITH THE
RIDGING THAN THE GFS AND PUSH WARM AIR INTO MONTANA ON SATURDAY.
ALL THE MODELS DO BRING ANOTHER SHORTWAVE ALONG THE CANADIAN
BORDER IN THIS TIME PERIOD WHICH BRINGS COLDER AIR BACK SOUTHWARD
JUST THE GFS REMAINS COLDER THROUGHOUT. FOR NOW HELD OFF ON ANY
WARMING FOR THE WEEKEND AS THIS IS A CHANGE FROM PREVIOUS MODEL
RUNS. EBERT



&&

.AVIATION...
IFR LOW CLOUDS AND FOG SOUTH OF A KJDN TO KGDV LINE WILL CONTINUE
TO RETREAT TO THE SOUTHEAST THROUGH THE EVENING HOURS. OTHERWISE
EXPECT VFR CONDITIONS AT THE FOUR TAF TERMINALS UNDER CLEAR SKIES.
NORTHWEST WINDS WILL CONTINUE AT 10-15KTS THROUGH EARLY
EVENING...BEFORE GOING LIGHT AND VARIABLE AT LESS THEN 5 KTS. WITH
RECENT SNOWMELT...THERE REMAINS SOME POTENTIAL FOR PATCHY FOG TO
DEVELOP IN THE MILK...MISSOURI...AND YELLOWSTONE RIVER VALLEYS
LATE TONIGHT INTO EARLY MONDAY. SAID FOG COULD POSSIBLY LOWER
CEILINGS AND OR VISIBILITIES BELOW VFR LEVELS. GILCHRIST

&&

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

&&

$$

WEATHER.GOV/GLASGOW


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