000
FXUS63 KMPX 300357
AFDMPX
AREA FORECAST DISCUSSION...UPDATED FOR 06Z TAFS
NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN
1050 PM CDT FRI AUG 29 2008
.DISCUSSION...
/ISSUED 254 PM CDT FRI AUG 29 2008/
THE FORECAST CHALLENGES ARE WINDS AND DRY CONDITIONS THIS
WEEKEND AND THEN THUNDERSTORM CHANCES DURING THE EXTENDED PORTION
OF THE FORECAST.
SFC ANALYSIS SHOWS WELL DEFINED TROUGH DRAPED FROM NRN MN INTO SW
MN MOVING EAST. LOW TDS HAVE PREVENTED MUCH MLCAPE TO FORM ALONG
THIS...AND LIKEWISE HARDLY ANY CLOUDS IN OUR FORECAST AREA. THIS
TROUGH IS FORECAST TO WEAKEN THIS EVENING AND ALMOST WASH OUT IN
THE FLOW. COMBINED WITH THE CLEAR SKIES THIS WILL ALLOW
TEMPERATURES TO FALL TO NEAR THIS MORNINGS LOWS. HAVE ADAPTED
PREVIOUS FORECAST WITH THIS MORNINGS MINS...ALL TOGETHER ENDING UP
SEVERAL DEGREES BELOW MOS GUIDANCE.
HIGH PRESSURE IN THE GREAT LAKES TO OHIO VALLEY WILL STRENGTHEN
THIS WKND IN CONCERT WITH PERSISTENT CYCLOGENSIS OVER THE NRN
PLAINS. THIS WILL FORCE A STRONG MSLP GRADIENT TO SHAPE UP OVER
MN. ON SUNDAY THIS WILL HAVE A BETTER ISALLOBARIC COMPONENT AS
TRUE PRESSURE FALLS MOVE EASTWARD INTO WRN MN. MIXING LOOKS DEEP
ON BOTH AFTERNOONS...AND HAVE GUIDED BY THE NAM PREDICTED 200 FT
WIND FOR SUSTAINED AND NEAR THE TOP OF THE MIX DOWN LAYER FOR
GUSTS. CONDITIONS WILL BE CLOSE TO A WIND ADVISORY IN WRN MN ON
SUN. DRY AIR GRADUALLY ADVECTING IN THIS AFTN WILL BE IN PLACE ON
SAT WITH THE SRLY WINDS OFFERING LITTLE MOIST ADVECTION AT FIRST.
MINIMUM RELATIVE HUMIDITIES ARE FORECAST TO BE IN THE 25-35 PERCENT
RANGE ACROSS THE FORECAST AREA ON SAT. COME SUN...MOIST FETCH
BEGINS TO GRADUALLY WORK INTO WRN MN...WHICH AGAIN IS THE AREA
WITH THE STRONGEST WINDS. VERY DRY CONDITIONS THOUGH WILL
CONTINUE TO PREVAIL IN ERN MN AND WRN WI. SEVERE FIRE WEATHER
CONDITIONS THEREFORE ARE LIKELY TO DEVELOP DURING SAT AFTN IN FAR
WEST CTRL MN AND POSSIBLE ACROSS MUCH OF THE AREA ON SUN.
WITH THE SUNSHINE...MIXING...AND WARM AIR ADVECTION...TEMPS WILL
ALSO BE INCHING UP THIS HOLIDAY WEEKEND...TAKING THE MOST NOTABLE
JUMP FROM TODAY TO SAT. HIGHS ON SAT ARE EXPECTED TO BE IN THE MID
TO UPPER 80S. AS THE GROUND DRIES FROM OUR RECENT RAIN AND THE
925-700MB LAYER CONTINUES TO WARM...HIGH TEMPS WILL CLIMB TO OR
EVEN SLIGHTLY ABOVE 90 IN PLACES BY SUN AND THE FIRST DAY OF
METEOROLOGICAL AUTUMN...LABOR DAY. DEW POINTS ARE FORECAST TO
ASCEND GRADUALLY INTO THE LOWER TO MID 60S BY LABOR DAY.
GFS AND ECMWF CONSISTENCY CONTINUES WITH REGARD TO AN UPPER
TROUGH COMING EWRD ACROSS THE NRN CONUS ON TUES INTO WEDS.
MID-LEVEL TEMPS DO NOT LOOK TO BREAK DOWN UNTIL TUES AND MORESO
TUES NIGHT. LONG RANGE PROBABILISTIC GUIDANCE HAS BEEN CONSISTENT
ENOUGH TO CONTINUE TO RAISE POPS ON TUES NIGHT...WITH UPPER TROUGH
ACQUIRING A NEGATIVE TILT IN THE DAKOTAS AND STRONG THICKNESS
DIFLUENCE OVERSPREADING THE FORECAST AREA. THE FRONT LOOKS TO
PUSH THROUGH THE FORECAST AREA BEFORE BECOMING STRETCHED OUT AND
BECOMING STATIONARY JUST TO OUR SOUTHEAST.
WEDS THROUGH THU ARE FAIRLY UNCERTAIN DUE TO THE PATTERN GETTING
HUNG UP WITH POTENTIAL INCOMING TROPICAL ACTIVITY. THE ECWMF HAS
BEEN CONSISTENT ITS PAST TWO RUNS ON BRINGING A BULK OF THE
MOISTURE FROM GUSTAV UP TO IA...ERN MN...AND WI. A QUICK GLANCE
AT THE TRACKS OF REMNANT LOWS OF HURRICANES SHOW IT IS HIGHLY
UNLIKELY THIS WOULD MAKE IT THAT FAR NORTH AND WEST ESPECIALLY
WITH AN NHC AND HPC PREDICTED SLOW DOWN SOMETIME DURING THE MON-
WEDS TIME FRAME. THIS UNCERTAINTY COUPLED WITH WHERE EXACTLY THE
FRONT WILL WIND UP LEAD TO SLIGHT CHC/CHC POPS IN THE FORECAST
FROM NW TO SE ACROSS THE LOCAL AREA. TEMPS DO LOOK TO BE NORMAL TO
SLIGHTLY BELOW NORMAL DURING THAT TIME AS 12Z GFS ENSEMBLE H8 TEMP
ANOMALIES GRADUALLY SWING FROM POSITIVE TO NEGATIVE. ...MTF...
&&
.AVIATION.../06Z TAF ISSUANCE/
WKNG SFC TROUGH FROM NW WI TO NR KMSP WL SLIDE THRU EAU LT
TNGHT..BUT WNDS VRY LGT. T/TD SPRDS DCRSG ENUF THAT LCL FOG MAY
FORM LT...MAIN THREAT PRBLY AT EAU WHRE BIT HIER DPTS VCNTY FNT.
INCRSG PRES GRAD MAINLY W SITES LT MRNG. WL PRBLY AFTN GUSTS 20 KTS
OR BIT STGR AXN AND RWF.
&&
.MPX WATCHES/WARNINGS/ADVISORIES...
MN...NONE.
WI...NONE.
&&
$$
