000
FXUS63 KMPX 080336
AFDMPX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN
1036 PM CDT SUN SEP 7 2008
.DISCUSSION...
SHORTWAVE ENERGY ASSOCIATED WITH THE BROAD UPPER TROUGH STRETCHED
ACROSS THE NORTHERN CONUS...HAS ASSISTED IN THE GENERATION OF
WIDELY SCATTERED CONVECTION ACROSS PARTS OF CENTRAL AND SOUTHERN
MN AND WEST CENTRAL WI THIS AFTERNOON...WHERE MID LEVEL TEMPS ARE
AROUND -22C. THE GREATEST THUNDER POTENTIAL IS EXPECTED FROM
EAST/SOUTH CENTRAL MN INTO WEST CENTRAL WI...GENERALLY EAST OF
INTERSTATE 35...WHERE MU/SFC CAPES HAVE INCREASED TO BETWEEN
500 AND 1000 J/KG ALONG/AHEAD OF THE SURFACE BOUNDARY. WITH THE
COLD MID LEVEL TEMPS...CANNOT RULE OUT SMALL HAIL ACROSS THE
EASTERN HALF OF THE CWA...WHERE EFFECTIVE BULK SHEAR VALUES ARE
AROUND 30 KNOTS. THE ACTIVITY SHOULD WANE AFTER SUNSET...WHEN
ATTENTION WILL SHIFT TO A STRONGER SHORTWAVE APPROACHING FROM THE
WEST. THIS FEATURE...EVIDENT OVER SOUTHERN MT ON 19Z WATER VAPOR
IMAGERY...WILL DIVE ACROSS THE NORTHERN/CENTRAL PLAINS TONIGHT.
THE 12Z NAM PROGGED IMPRESSIVE 600-700MB FRONTOGENESIS TO OCCUR
ACROSS SOUTHERN MN ON MONDAY MORNING...AS UPPER DIVERGENCE IN THE
ENTRANCE REGION OF THE UPPER JET ALSO DEVELOPS. THE 12Z GFS ALSO
FEATURED THESE ELEMENTS...BUT WITH A SLIGHTLY FURTHER SOUTH
PLACEMENT CENTERED MORE OVER NORTHERN IA. REGARDLESS...EXPECT RAIN
SHOWERS TO DEVELOP IN AREAS ALONG THE IOWA BORDER ON MONDAY
MORNING...WHERE SREF PROBABILITIES OF A HUNDREDTH ARE BETWEEN 60
AND 80 PERCENT. ON MONDAY AFTERNOON...THE REMAINDER OF THE CWA
WILL HAVE THE OPPORTUNITY TO EXPERIENCE WIDELY SCATTERED
SHOWERS...DUE TO MORE DIURNALLY DRIVEN COLD POOL ACTION.
LOW LEVEL RIDGING WILL BUILD IN ON TUESDAY...AND BRING DRY
CONDITIONS. WIDESPREAD LOW TEMPERATURES TUESDAY MORNING WILL
LIKELY DIP INTO THE MID TO UPPER 30S. TEMPERATURES WILL
MODERATE ON TUESDAY...BUT REMAIN BELOW NORMAL...WITH HIGHS IN THE 60S
ANTICIPATED.
SOUTHERLY FLOW AND SLIGHTLY WARMING TEMPERATURES ARRIVE FOR
WEDNESDAY...AS SURFACE CYCLOGNESIS ENSUES OVER THE
NORTHERN/CENTRAL PLAINS. ALTHOUGH SOME RAIN SHOWERS MAY ARRIVE
DURING THE DAY ON WEDNESDAY...THE 00Z THURSDAY TO 00Z FRIDAY
TIMEFRAME CONTINUES TO APPEAR TO BE THE MAIN WINDOW WITH THE HIGHEST
POTENTIAL FOR PRECIPITATION. HAVE INCLUDED 50-60 POPS FOR
WEDNESDAY EVENING THROUGH THURSDAY MORNING.
CONFIDENCE DECREASES DRAMATICALLY NEXT WEEKEND...AS MODEL
SOLUTIONS ATTEMPT TO FORECAST THE FATE OF HURRICANE IKE.
HOWEVER...HAVE INTRODUCED LOW CHANCE POPS FOR SATURDAY...AS BOTH
GFS AND ECMWF MODELS FORECAST A SHORTWAVE TROUGH /IN SOME FORM OR
FASHION/ MOVING ACROSS THE AREA.
&&
.AVIATION.../06Z TAF ISSUANCE/
WEAK UPPER RIDGE HAD BUILD OVER THE AREA THIS EVENING. CLOUDS HAD
SCOURED OUT OVER THE NORTHERN TWO THIRDS OF THE MN AND NORTHERN
WISCONSIN. MAINLY CLEAR SKIES OVERNIGHT WITH SOME PATCHY FOG
DEVELOPING IN FOG PRONE AREAS AND RIVER/SMALL STREAMS BOGS.
MEANWHILE...A SHORTWAVE TROUGH OVER THE NORTHERN PLAINS...WILL MOVE
EAST OVER THE UPPER MIDWEST BY DAYBREAK MONDAY AND MOVE ACROSS THE
UPPER MIDWEST. MOST OF THE DYNAMICS ASSOCIATED WITH THIS SHORTWAVE
TROUGH...WILL STAY WELL SOUTH OF MAIN TAF SITES. CLOUDS ARE EXPECTED
TO THICKEN OVER THE TAF SITES DURING THE DAY ON MONDAY. CEILINGS AND
CLOUD HEIGHTS WILL LOWER TO 4-5K FEET AGL. SFC WINDS WILL BE
NORTHWEST AT 5 TO 10 MPH THEN BECOMING LIGHT AND VARIABLE OR UNDER 6
KNOTS BY SUNSET MONDAY.
&&
.MPX WATCHES/WARNINGS/ADVISORIES...
MN...NONE.
WI...NONE.
&&
$$
LS/JVM
