230
FXUS63 KBIS 070929
AFDBIS
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BISMARCK ND
329 AM CST SAT NOV 7 2009
SHORT TERM...TODAY TROUGH MONDAY NIGHT
FORECAST HIGHLIGHTS IN THE SHORT TERM PERIOD WILL BE CONTINUED MILD
TEMPERATURES INTO EARLY NEXT WEEK. WILL USE A GENERAL MODEL BLEND.
CURRENTLY...A S/WV MID LEVEL TROUGH IS PUSHING EAST ACROSS SOUTH
CENTRAL CANADA...AHEAD OF 100KT UPPER LEVEL JET STREAK EXTENDING
FROM THE PACIFIC NORTHWEST INTO THE WESTERN DAKOTAS. SURFACE COLD
FRONT HAS PUSHED WELL EAST OF THE LOCAL AREA...NOW OVER WESTERN MN.
IN THE WAKE OF THIS COLD FROPA BREEZY WESTERLY WINDS (15-30 MPH)
CONTINUE OVER WESTERN AND CENTRAL ND...MAINLY ACROSS MY NORTHERN
COUNTIES WHERE THE BEST MOMENTUM TRANSFER IS OCCURRING WITH
850-700MB WINDS 45-50KTS (VAD WIND PROFILE FROM KMBX INDICATES
50-65KT WINDS 3-4K FEET OFF THE SFC). NOCTURNAL INVERSION WILL
PREVENT THESE STRONGER WINDS FROM MIXING DOWN TO THE SFC...WITH
THESE MID LEVEL WINDS GRADUALLY DIMINISHING THROUGHOUT THIS SAT
MORNING.
COOLER TODAY BEHIND YESTERDAY'S COLD FRONT...BUT STILL MILD WITH
HIGHS FORECAST INTO THE 50S WITH THE COLDER AIR REMAINING IN CANADA
NORTH OF THE UPPER JET. BREEZY WESTERLY WINDS LOOK TO
CONTINUE/REDEVELOP ACROSS THE NORTH AND AROUND THE JAMES RIVER
VALLEY AREA THIS MORNING/AFTERNOON WHERE PRESSURE RISES CONTINUE AND
WHERE THE STRONGER MID LEVEL WINDS (25-30KTS) WILL RESIDE.
MODELS ARE DEPICTING AN EMBEDDED S/WV IMPULSE SLIDING EAST-NORTHEAST
INTO THE DAKOTAS TONIGHT...COINCIDING WITH A WEAK SFC BOUNDARY OVER
MY SOUTHERN COUNTIES. LOOKS TO BE ENOUGH SFC AND MID LEVEL FORCING
FOR PRECIPITATION DEVELOPMENT...HOWEVER IT WILL BE DIFFICULT FOR ANY
MEASURABLE PRECIPITATION AT THE SURFACE WITH A DRY ATMOSPHERE BELOW
750MB. NONETHELESS WILL THROW IN SLIGHT CHANCES FOR LIGHT RAIN SOUTH
TONIGHT AND INTO THE DAYTIME AM HOURS OF SUNDAY OVER MY SOUTHEAST.
ANOTHER S/WV TROUGH EMBEDDED IN WESTERLY FLOW ALOFT APPROACHES AND
MOVES THROUGH THE NORTHERN PLAINS SUNDAY AND SUNDAY NIGHT. THIS WILL
BE ANOTHER DRY FRONTAL PASSAGE WITH A CONTINUED DRY AIRMASS IN PLACE
AND LITTLE IF ANY SFC FORCING. A S/WV RIDGE WILL THEN BUILD ACROSS
THE REGION MONDAY/MONDAY NIGHT BRINGING A REINFORCED SHOT OF WAA
INTO THE WESTERN DAKOTAS...ALTHOUGH NOT TO THE DEGREE OF OUR RECORD
SETTING TEMPS ON FRIDAY.
LONG TERM...TUESDAY THROUGH SATURDAY
A PROGRESSIVE UPPER LEVEL PATTERN CONTINUES TO BE INDICATED BY THE
LONG TERM MODELS THROUGH THE PERIOD. SOME AGREEMENT DOES EXIST
BETWEEN THE GFS AND ECMWF IN A 500 HPA RIDGE OVER THE NORTHERN
PLAINS ON TUESDAY WITH RETURN SOUTH TO SOUTHWESTERLY FLOW ACROSS THE
NORTHERN PLAINS RAISING TEMPERATURES BACK ABOVE AVERAGE DURING THE
DAY. LONG TERM MODEL AGREEMENT BEGINS TO ERODE VERY QUICKLY AFTER
THAT WITH A TROUGH THAT SETS UP IN THE WESTERN UNITED STATES.
PREDICTABILITY OF ANY DISTURBANCES WITHIN THIS TROUGH REMAINS VERY
LOW THIS FAR OUT MAKING TIMING DIFFICULT AT THIS TIME.
AVIATION
SYNOPTIC FEATURES THIS SATURDAY MORNING INCLUDE A COLD FRONT MOVING
THROUGH MINNESOTA WITH A BROAD NORTHWEST ANTICYCLONIC FLOW ACROSS
MONTANA...NORTH DAKOTA ND THE PRAIRIE PROVINCES OF CANADA. ONE
CONCERN WILL BE LOW LEVEL WIND SHEAR FOR THE MORNING HOURS. 1 TO 3
THOUSAND MSL WINDS LIKELY TO BE 35 TO 45 KTS ACROSS MUCH OF WESTERN
AND CENTRAL ND...ESPECIALLY NORTH. AFTER THE MORNING HOURS THE WINDS
MIX OUT AND DIMINISH. I HAVE INCLUDED SOME WIND SHEAR IN THE
ISN-MOT-BIS TAFS.
FIRE WEATHER
THE RANGELAND FIRE DANGER INDEX WILL RANGE FROM THE MEDIUM TO HIGH
CATEGORY WEST AND CENTRAL TODAY. SFC DEWPOINT TEMPS WILL STAY LOW IN
THE 20S...HOWEVER DAYTIME HIGHS LOOK TO BE 15-20 DEGREES COOLER FROM
YESTERDAY PUTTING DAYTIME MIN RH VALUES MAINLY 25-40 PERCENT WEST
AND CENTRAL. SOME UNCERTAINTIES WITH WIND MAGNITUDES ON SUNDAY AS
ANOTHER MID LEVEL DISTURBANCE SLIDES INTO THE NORTHERN PLAINS.
ALTHOUGH SPC (STORM PREDICTION CENTER) HAS WESTERN ND IN THE 'SEE
TEXT' FOR FIRE WEATHER...LATEST NAM/GFS BUFFER SOUNDINGS ARE EITHER
INDICATING RELATIVELY LIGHT WINDS AROUND 15KTS (NAM BUFFER) OR WEAK
LAPSE RATES PREVENTING STRONGER WINDS FROM MIXING TO THE SFC (GFS).
WILL CONTINUE TO MONITOR.
BIS WATCHES/WARNINGS/ADVISORIES
NONE.
SHORT TERM...NH
AVIATION/LONG TERM...DC/WAA
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