FXUS65 KGGW 241254 AAA
AFDGGW
AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE GLASGOW MT
554 AM MST THU DEC 24 2009
UPDATED AVIATION DISCUSSION.
.SHORT TERM...FOR NORTHEAST MONTANA...TODAY THROUGH SATURDAY...
THE CLOSED OFF UPPER LEVEL LOW OVER NORTHEAST MONTANA THIS MORNING
WILL MOVE SOUTHEAST INTO THE CENTRAL PLAINS BY FRIDAY WHERE IT
WILL MERGE WITH A LOW THAT IS NOW MOVING THROUGH TEXAS. THIS WILL
SPIN UP INTO A LARGE CYCLONIC WINTER STORM AFFECTING MUCH OF
EASTERN CONUS. AS THE STORM STRENGTHENS IN THE EAST...THE WESTERN
EDGE WILL PRODUCE LOW CLOUDS AND LIGHT SNOW THAT AFFECTS OUR
EASTERN ZONES THROUGH MOST OF THE SHORT TERM. OTHERWISE AN UPPER
RIDGE BUILDS OVER THE WEST. SURFACE HIGH PRESSURE OVER CENTRAL
MONTANA AND SOUTHERN SASKATCHEWAN WILL GENERALLY KEEP CLOUD COVER
AND LIGHT SNOW CONFINED TO THE EASTERN ZONES.
TODAY AND TONIGHT...DIMINISHING WINDS IN THE WESTERN ZONES WILL
DROP WIND CHILLS BELOW HEADLINE CRITERIA...BUT EXPECT AROUND 10MPH
WINDS IN THE EAST TO REQUIRE AN ADVISORY THROUGH THE MORNING.
THE CLOSED UPPER LEVEL SLIPS INTO NORTHWESTERN SOUTH DAKOTA BY
00Z. ALSO BY 00Z THE SURFACE HIGH OVER SASKATCHEWAN WILL SLIP OVER
THE CWA RELAXING THE SURFACE GRADIENT...THUS MINIMIZING THE WINDS
IN THE WEST. 850MB TEMPERATURES TO -21*C WILL PREVENT HIGHS TODAY
FROM MOVING MUCH ABOVE ZERO. CONTINUED NORTHERLY UPPER FLOW WILL
ONCE AGAIN DROP TEMPERATURES TO THE TEENS BELOW ZERO OR LOWER
TONIGHT. WINDS OVER THE EASTERN ZONES COULD RUN AROUND 10 MPH SO
WIND CHILLS ARE A POSSIBILITY TONIGHT IF WINDS STAY UP. WILL LET
DAY SHIFT TAKE ANOTHER LOOKS AT WINDS TO DETERMINE IF ANOTHER WIND
CHILL ADVISORY IS NEEDED FOR TONIGHT. ALSO KEPT INHERITED LOW POPS
IN THE EAST FOR TONIGHT.
FRIDAY AND SATURDAY...THERE WILL BE A GRADUAL IMPROVEMENT IN
TEMPERATURES AS 850MB TEMPERATURES CREEP UP TO AROUND -6*C BY 00Z
SUNDAY. SO SATURDAY WILL BE THE WARMEST DAY BUT STILL BELOW
AVERAGE FOR LATE DECEMBER. OTHERWISE LOW CLOUDS AND SLIGHT CHANCE
POPS OVER THE EASTERN ZONES WILL NOT CHANGE MUCH. EXPECT NO
ACCUMULATION THROUGH THE SHORT TERM. SCT
.LONG TERM...SATURDAY NIGHT THROUGH THURSDAY...
STACKED LOW OVER THE MIDWEST WILL FINALLY MOVE TO THE EAST ON
SUNDAY ALLOWING AN UPPER RIDGE TO MOVE INTO MONTANA FROM THE WEST.
THIS RIDGE WILL BRING WARMER AIR ALOFT INTO THE FORECAST AREA ON
SUNDAY. HOWEVER...SHALLOW ARCTIC AIR WILL REMAIN NEAR THE SURFACE.
WITH SNOW COVER AND LIGHT WINDS...THE LOW LEVEL COLD AIR WILL
REMAIN OVER MOST OF THE FORECAST AREA. TEMPERATURES WILL MODERATE
WITH THE SOUTHWEST ZONES SEEING THE MOST WARMING FROM THIS RIDGE.
THE RIDGE WILL STAY OVER EASTERN MONTANA ON MONDAY AND GETS
FLATTENED SOMEWHAT BY A SHORTWAVE MONDAY NIGHT AND TUESDAY.
ALTHOUGH THE MODELS HAVE SOME DIFFERENCES IN HANDLING THIS
WAVE...IT HAS LIMITED MOISTURE WITH A WEAK COLD FRONT AT THIS
TIME. WILL MAINTAIN MAINLY DRY FORECAST.
BEYOND TUESDAY...WHILE THE ECMWF AND GFS DIFFER ON THEIR UPPER
LEVEL PATTERN...THEY AGREE ON A DRY FORECAST FOR WEDNESDAY. ECMWF
HAS A FAIRLY STRONG COLD FRONT ON NORTHWEST FLOW ALOFT FOR NEXT
THURSDAY THAT WAS PRESENT ON THE 18Z GFS BUT NOT THE 00Z GFS. WILL
NOT MAKE ANY SIGNIFICANT TEMPERATURES CHANGES BETWEEN WED AND THU
AT THE MOMENT AND SEE WHERE FUTURE MODEL RUNS TAKE THIS SYSTEM. FORRESTER
&&
.AVIATION...
THE TAF SITES WILL VARY FROM CLEAR TO CLOUDY TODAY WITH UPPER LOW
MOVING SOUTH THROUGH EASTERN MONTANA. LOW CLOUDS MOVING SOUTH OUT
OF SASKATCHEWAN THIS MORNING COULD BRING A PERIOD OF MVFR
CEILINGS TO TAF SITE TODAY. OTHERWISE...VFR CONDITIONS WILL
PREVAIL TODAY WITH NORTHWEST WINDS 5 TO 15 KNOTS. A MID OF LOW AND
MID CLOUDS ROTATING AROUND STACKED UPPER LOW TO THE EAST WILL
AFFECT NORTHEAST MONTANA TONIGHT WITH MVFR CEILINGS POSSIBLE AND A
CHANCE OF LIGHT SNOW MAINLY AT KSDY.
&&
.GLASGOW WATCHES/WARNINGS/ADVISORIES...
WIND CHILL ADVISORY UNTIL 11 AM MST THIS MORNING FOR CENTRAL AND
SOUTHERN VALLEY-DANIELS-SHERIDAN-WESTERN ROOSEVELT-MCCONE-
RICHLAND-DAWSON-PRAIRIE-WIBAUX-NORTHERN VALLEY-EASTERN ROOSEVELT.
&&
$$
WEATHER.GOV/GLASGOW
