Area Forecast Discussion
Issued by NWS Twin Cities, MN

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000
FXUS63 KMPX 031114
AFDMPX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN
614 AM CDT THU SEP 3 2015

.UPDATED FOR 12Z AVIATION DISCUSSION...
ISSUED AT 608 AM CDT THU SEP 3 2015

&&

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 415 AM CDT THU SEP 3 2015

THE UPPER LEVEL WAVE THAT BROUGHT EFFICIENT RAINFALL ACROSS
WESTERN WISCONSIN YESTERDAY WAS THE DRIVING FORCE BEHIND AN AREA
OF SHOWERS AND THUNDERSTORMS THAT LINGERED ACROSS EASTERN
WISCONSIN EARLY THIS MORNING. MEANWHILE ANOTHER PV ANOMALY WAS
EVIDENT ON WATER VAPOR ACROSS THE ARROWHEAD OF MINNESOTA. A FEW
SHOWERS AND THUNDERSTORMS MAY DEVELOP AHEAD OF THIS WAVE...BUT IF
THEY DO THEY WILL BE SOUTH AND EAST OF THE FORECAST AREA.

FOR CENTRAL MN AND WESTERN WI EXPECT ANOTHER MILD AND MUGGY DAY.
THE MORNING FOG AND STRATUS SHOULD QUICKLY MIX OUT PER THE
BUFKIT SOUNDINGS. AFTERNOON HIGHS IN THE MID 80S SHOULD BE
WIDESPREAD THIS AFTERNOON. LATER TONIGHT ANOTHER WAVE CURRENTLY
OVER THE 4-CORNERS REGION WILL LIFT NORTHEAST INTO THE DAKOTAS.
THIS WILL BE THE TRIGGER FOR ANOTHER MCS...WHICH COULD MAKE IT
INTO SOUTHWEST MINNESOTA. A FEW MEMBERS OF THE NCAR ENSEMBLE SHOW
THIS...AS WELL AS SOME OF THE LARGE SCALE GUIDANCE. HOWEVER THE
NAM NEST...WRFARW AND WRF NMM KEEP THE STORMS TO THE WEST. FOR NOW
CONTINUED WITH A DRY FORECAST...BUT EXPECT TO SEE AN INCREASE IN
POPS IF THIS WAVE SHIFTS EAST SINCE THERE WILL BE 2000 TO 2500
J/KG OF ELEVATED CAPE. THE WIND FIELD IS VERY LIGHT, SO DEEP LAYER
SHEAR IS NEGLIGIBLE...BUT THAT MAKES HEAVY RAIN THE PRIMARY
THREAT.

.LONG TERM...(FRIDAY THROUGH WEDNESDAY)
ISSUED AT 415 AM CDT THU SEP 3 2015

FRIDAY THROUGH SUNDAY...FRI WILL START OUT WITH THE CWFA ON THE
WRN FRINGES OF A DEPARTING LONGWAVE UPR LVL RIDGE WHILE A LARGE
CUTOFF LOW MOVES ONSHORE THE PAC NW. THE RIDGE WILL GRADUALLY MOVE
OFF TO THE E...ALLOWING A MORE PROGRESSIVE SW-NE FLOW TO MOVE ACRS
THE AREA. SEVERAL SHORTWAVE DISTURBANCES WILL RIDE ATOP THE AREA
STARTING LATE DAY FRI...MORE BUT PRONOUNCED SAT INTO SUN AS THE
UPR CUTOFF LOW BECOMES NEGATIVELY TILTED OVER THE NRN ROCKIES.
THIS LOW WILL THEN TRAVERSE ENE INTO SRN MANITOBA THRU SUN
NIGHT...BRINGING ALONG A SFC FRONT AND SFC LOW PRES SYSTEM WITH
IT. SCATTERED SHWRS/TSTMS CAN BE EXPECTED TO DEVELOP OVER MUCH OF
THE AREA OVER THE WEEKEND...PARTICULARLY SAT NIGHT THRU SUN NIGHT.
POCKETS OF HEAVY RAIN MAY ALSO DEVELOP AT TIMES AS A PROLONGED AND
PERSISTENT SURGE OF MOISTURE FROM THE GULF OF MEXICO WILL BRING
MUCH MORE MOISTURE TO THE REGION...TO THE TUNE OF DEWPOINTS AROUND
70 AND PWATS EASILY IN EXCESS OF 1.50 INCHES AND POSSIBLY AROUND 2
INCHES AT TIMES. THE SFC CDFNT WILL REACH THE ERN DAKOTAS BY SUN
MRNG THEN GRADUALLY TRAVERSE EWD SUN AND SUN NIGHT...MAKING THE
SAT NIGHT THRU SUN NIGHT TIME PERIODS THE MOST LIKELY FOR HAVING
PRECIP COVERING THE ENTIRE CWFA. AS FOR TEMPERATURES...THE LARGE
RIDGE COMBINED WITH THE AFOREMENTIONED DEEP SURGE OF MOISTURE WILL
KEEP WARM/HUMID CONDITIONS IN PLACE THRU THE WEEKEND...ESPECIALLY
FOR FRIDAY AND SATURDAY BEFORE DECENT PRECIPITATION COVERAGE
ARRIVES. HIGHS WILL CLIMB INTO THE MID-UPR 80S. WITH DEWPOINTS
INTO THE UPR 60S TO ARND 70...HEAT INDEX VALUES WILL HIT THE LWR
TO MID 90S FOR FRI AND SAT. IF TRENDS CONTINUE WHERE DEWPOINTS RUN
SLIGHTLY HIGHER THAN GUIDANCE HAS SHOWN...THEN HEAT INDEX
HEADLINES MAY WELL BE NEEDED.

MONDAY THROUGH WEDNESDAY...WITH THE SRN CANADIAN SYSTEM BECOMING
VERTICALLY STACKED BY MON MRNG AND ITS ASSOCIATED CDFNT NEAR LAKE
MICHIGAN...ANY PRECIPITATION WILL SHIFT OFF TO THE E COME MON
MRNG. HIGH PRES WILL SETTLE IN...BUT ONLY FOR THE DAY ON MON AS
UPR LVL FLOW BECOME PREDOMINANTLY E-W ZONAL...MEANING THAT HIGH
PRES ON MON WILL GIVE WAY TO A DEVELOPING SYSTEM FOR TUE INTO WED.
WHILE THE MAIN LOW PRES WILL REMAIN ANCHORED IN THE PLAINS...A
WEAK SFC TROF IN ADVANCE OF THE SFC LOW WILL EXTEND ENEWD INTO THE
UPR MISS RIVER VALLEY. THIS MAY WELL PROMOTE SCTD SHWRS ACRS THE
REGION...AND POSSIBLY A FEW TSTMS...BUT THE SETUP LOOKS TO BE MORE
OF A STRATIFORM/ISENTROPIC SETUP RATHER THAN CONVECTIVE. TSTM
CHANCES ARE DOWNPLAYED BUT DO NOT HAVE THE CONFIDENCE TO ELIMINATE
IT ALTOGETHER SO HAVE CAPPED TSTMS AS SLGT CHC. THE BIGGER CHANGE
WILL BE TEMPERATURES AS MUCH COOLER AIR WITH NOTICEABLY LOWER
DEWPOINTS WILL PREVAIL OVER THE REGION. HIGHS WILL RANGE FROM THE
UPR 60S TO MID 70S WHILE LOWS BOTTOM OUT IN THE 50S FOR THE FIRST
HALF OF NEXT WEEK.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z FRIDAY MORNING)
ISSUED AT 608 AM CDT THU SEP 3 2015

LOW STRATUS AND FOG HAS BLANKETED THE REGION ONCE AGAIN...WITH
WIDESPREAD LIFR CONDITIONS. FORECAST SOUNDINGS SHOW THESE
CONDITIONS IMPROVING BY MID MORNING...WITH VFR CONDITIONS THE REST
OF THE DAY. LATER TONIGHT EXPECT ANOTHER ROUND OF
FOG/STRATUS...BUT ONLY WENT MVFR SINCE IT IS TOWARD THE END OF THE
TAF PERIOD.

KMSP...
AN IFR/LIFR CLOUD BACK TO THE SOUTH OF KMSP HAS NOW CREPT UP TO
MSP...AND SHOULD LINGER AROUND THROUGH THE EARLY MORNING RUSH.
CONDITIONS SHOULD QUICKLY IMPROVE THIS MORNING...WITH VFR
CONDITIONS THE REST OF THE DAY. ANOTHER ROUND OF FOG AND STRATUS
IS POSSIBLE FRIDAY MORNING...BUT DID NOT HAVE CONFIDENCE TO GO
BELOW VFR AT THIS TIME.

/OUTLOOK FOR KMSP/
FRI...VFR. WIND S AT 10G20KT.
SAT...VFR WITH MVFR AND SHRA/TSRA POSSIBLE LATE. WIND S AT
10G20KT.
SUN...VFR WITH MVFR/IFR TSRA POSSIBLE. WIND S AT 15G20KT.

&&

.MPX WATCHES/WARNINGS/ADVISORIES...
MN...DENSE FOG ADVISORY UNTIL 9 AM CDT THIS MORNING FOR MNZ047-048-
     054>058-064>070-073>078-083>085.

WI...DENSE FOG ADVISORY UNTIL 9 AM CDT THIS MORNING FOR WIZ015-016-
     024>028.

&&

$$

SHORT TERM...JRB
LONG TERM...JPC
AVIATION...JRB



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