000
FXUS63 KDLH 272040
AFDDLH
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DULUTH MN
340 PM CDT WED AUG 27 2008
.DISCUSSION...A COLD FRONT WILL SLOWLY MOVE ACROSS THE UPPER
MIDWEST TONIGHT AND TOMORROW. THIS FRONT...ALONG WITH AN UPPER
LEVEL SHORTWAVE...WILL BE THE MAIN FORCING MECHANISM FOR THE
DEVELOPMENT OF SHOWER AND THUNDERSTORMS ACROSS OUR FCST AREA
THROUGH TOMORROW. ALL OF THE OPERATION MODELS GENERATE A SWATH OF
HEAVIER RAINFALL ACROSS OUR CENTRAL AND ERN ZONES DURING THIS TIME
FRAME...ALTHOUGH THE GFS DIFFERS FROM THE OTHERS SOMEWHAT BY
SHUNTING THE PRECIP OFF TO THE EAST MORE QUICKLY. SOME MODELS ARE
FORECASTING RAIN AMOUNTS OF OVER AN INCH. BUT FEEL MORE CONFIDENT
IN MENTIONING 0.5 TO 1 INCH AMOUNTS SINCE THESE HIGHER AMOUNTS
SHOULD BE LOCALIZED. THE FRONT WILL PROPAGATE EAST OF OUR CWA BY
THURSDAY NIGHT...ALTHOUGH A FEW SHOWERS MAY LINGER ACROSS THE
NORTHLAND AS THE UPPER LEVEL WAVE ROTATES OVER THE CWA. DRIER AIR
WILL FILTER IN ACROSS THE REGION BY FRIDAY AS HIGH PRESSURE FROM
THE PLAINS MOVES OVER THE UPPER MIDWEST.
EXTENDED...SUN THRU TUESDAY..MEDIUM RANGE GUIDANCE SUPPORTS GENERAL
IDEA OF LARGE SCALE RIDGE AMPLIFYING OVER ERN GRT LAKES. THIS OCCURS
IN RESPONSE TO A PROGRESSIVE M/L TROF OVER NRN ROCKIES.SOME
DIFFERENCE BETWEEN EC/GFS WITH EC MAINTAINING RIDGE OVER CWA
LONGER..ALLOWING WARMING TO CONTINUE INTO TUESDAY AFTERNOON.GFS
IS ABOUT 12HRS FASTER BREAKING DOWN RIDGE...ALLOWING PRECIP TO PUSH
FARTHER EAST. EC/CMC IN STRONG AGREEMENT ON SLOWER MOVEMENT OF MAIN
FEATURES. GFS ENSEMBLE MEMBERS ARE MUCH LESS PRONOUNCED WITH TROF
AMPLITUDE BY 12Z TUESDAY...SUPPORTING EC/CMC SOLUTION OF HOLDING OFF
ON PRECIP TIL EARLY TUESDAY OVER WRN CWA...AND THEN EDGING EAST BY
WEDNESDAY MORNING. HAVE TOSSED MEX MOS CONSIDERING IT IS TOO
COOL..AND LEANED MORE WITH EC/HPC VALUES...CONSIDERABLY HIGHER MAXES
MONDAY.
&&
.AVIATION...MAINLY MVFR-IFR CONDITIONS CAN BE EXPECTED THROUGH
THIS EVENING AND OVERNIGHT...EXCEPT WEST OF A LINE FROM
KCDD...TO KGPZ..TO KPWC...WHERE VFR WILL PREVAIL. PLENTY OF LOW
AND MID LEVEL MOISTURE WILL CONTINUE TO FEED NORTH AND EAST ALONG
A COLD FRONT THAT WILL ONLY SLOWLY PROGRESS EASTWARD...RESULTING
IN CEILINGS GENERALLY 2K FT AGL OR BELOW. WHILE PRECIPITATION WILL
BE MINIMAL THROUGH 00Z...RAIN AND THUNDERSTORM CHANCES WILL
INCREASE EARLY TONIGHT AS AN AREA OF ENHANCED LIFT AND INSTABILITY
APPROACHES THE REGION IN RESPONSE TO THE SHORTWAVE CURRENTLY OVER
NORTH DAKOTA. WHILE TIMING IS A BIT OF A CHALLENGE...THE HIGHEST
RISK FOR SHRA/TSRA...AND THE LOWEST CEILINGS...APPEARS TO BE FROM
04Z-10Z. HOWEVER...AREAS OF FOG MAY DEVELOP DURING THE OVERNIGHT
HOURS AND PERSIST THROUGH ABOUT 13Z...RESULTING IN LOCAL LIFR-
VLIFR CONDITIONS. EXPECTING IMPROVEMENT TO VFR IN MUCH OF NE
MINNESOTA BY 14Z THURSDAY...WHILE SHOWERS WILL STILL BE POSSIBLE
OVER MUCH OF NORTHWEST WISCONSIN INCLUDING KHYR THROUGH ABOUT 18Z.
THE POTENTIAL FOR CONVECTION WILL ALSO PERSIST IN THIS
AREA...ESPECIALLY DUE TO STRONG FLOW ALOFT/SHEAR...BUT THE HIGHEST
SBCAPE...LIFTED INDICES...AND GREATEST ASCENT WILL LIKELY BE JUST
TO THE SOUTH OVER CENTRAL AND SOUTHERN WISCONSIN.
&&
POINT TEMPS/POPS...
DLH 72 54 72 52 / 30 70 20 10
INL 74 48 72 46 / 10 20 30 20
BRD 76 54 75 48 / 30 60 20 10
HYR 76 56 76 48 / 30 70 30 10
ASX 76 58 76 52 / 30 70 30 20
&&
.DLH WATCHES/WARNINGS/ADVISORIES...
MN...NONE.
WI...NONE.
LS...NONE.
$$
BERDES/BETTWY
