Area Forecast Discussion
Issued by NWS Twin Cities, MN

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000
FXUS63 KMPX 210911
AFDMPX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN
411 AM CDT THU AUG 21 2014

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 411 AM CDT THU AUG 21 2014

IT IS SHAPING UP TO BE A VERY BUSY DAY WEATHERWISE WITH MULTIPLE
THREATS TO BE CONCERNED ABOUT. THE FIRST IS SEVERE WEATHER AND
FLASH FLOODING. AT 4 AM...DEEP MOISTURE CONTINUES TO ADVECT INTO
THE AREA...AIDED BY A TROPICAL CONNECTION TO LARGE TROPICAL STORM
LOWELL IN THE EASTERN PACIFIC. TWO THUNDERSTORM COMPLEXES ARE
BEGINNING TO CONGEAL OVER ERN SODAK AND WRN MN ON THE NOSE OF A
40-50 KT LLJ. IN ADDITION...OBSERVATIONS INDICATE A POTENT
MESOSCALE AREA OF LOW PRESSURE IS DEVELOPING OVER SOUTHEASTERN
SODAK AS THESE TWO COMPLEXES MERGE. THE HEAVIEST THUNDERSTORMS ARE
OCCURRING TO THE NORTH AND EAST OF THIS LOW WHERE MOISTURE
CONVERGENCE IS MAXIMIZED. THERE IS A RELATIVELY GOOD RISK FOR
FLASH FLOODING IN THIS DEFORMATION ZONE REGION AS THUNDERSTORMS
CONTINUE TO DEVELOP AND TRAIN OVER THE SAME AREAS. THE MESO LOW
WILL CONTINUE PUSHING EAST AS THE LLJ VEERS EARLY THIS
MORNING...WITH THE HEAVY RAIN AND FLASH FLOODING THREAT SHIFTING
FROM WRN MN TO CENTRAL AND ERN MN AND FAR WESTERN WI DURING THE
NEXT FEW HOURS. WIDESPREAD RAINFALL OF 1 TO 3 INCHES ARE
EXPECTED...WITH HIGHER TOTALS OF 3 TO 6 INCHES POSSIBLE IN THE
DEFORMATION BAND/TRAINING CELL REGION EXTENDING ALONG A LINE FROM
NEAR MORRIS TO WILLMAR...THE TWIN CITIES...AND RED WING MN. SHOULD
THE HIGHER END TOTALS FALL IN THE TWIN CITES PROPER...SERIOUS
FLASH FLOOD CONCERNS COULD DEVELOP. LUCKILY...THE CONVECTION SEEMS
SOMEWHAT DISORGANIZED AND CONTINUOUS TORRENTIAL RAIN HAS NOT YET
MATERIALIZED. HOWEVER...IT WILL CONTINUE TO BE MONITORED. TO THE
NORTH AND EAST OF THIS MAX POTENTIAL REGION...A LARGE AREA OF
MODERATE TO OCCASIONALLY HEAVY STRATIFORM RAIN WILL CONTINUE WITH
A LESSER THREAT FOR FLASH FLOODING. SEVERE THREAT EARLY THIS
MORNING IS DIMINISHING AS THUNDERSTORMS BECOME MORE WIDESPREAD AND
DESTRUCTIVE INTERFERENCE OCCURS. STILL...SOME OF THE MORE DISCRETE
CELLS COULD PRODUCE MARGINALLY SEVERE HAIL. THE AREA MOST
SUSCEPTIBLE TO THIS IS SOUTH OF THE MN RIVER AND ALONG I-90.

THE LLJ WILL WEAKEN BY MID MORNING AND THE LARGE AREA OF SHOWERS
AND THUNDERSTORMS WILL BEGIN TO DIMINISH. THERMAL RIDGING WILL
BUILD NORTHEAST THIS AFTERNOON AND SET UP AT LEAST ACROSS SRN MN.
TOUGH TO SAY HOW FAR NORTH AND EAST THIS WILL REACH GIVEN THE
ONGOING CONVECTION WHICH WILL IMPACT IT TO SOME DEGREE...AND THE
POTENTIAL FOR REDEVELOPMENT THROUGH THE DAY. TEMPERATURES UNDER
THE THERMAL RIDGE WILL LIKELY REACH THE 90S. IN ADDITION...AND
PERHAPS MORE IMPORTANTLY...DUE TO THE JUICY AIRMASS THE BOUNDARY
LAYER WILL HAVE A HARD TIME MIXING AWAY DEW POINTS AND VALUES MAY
REMAIN IN THE LOW TO MID 70S THROUGHOUT THE AFTERNOON. THIS WOULD
SEND HEAT INDICES INTO THE LOW 100S. HOWEVER...HELD OFF ON A HEAT
ADVISORY FOR NOW UNTIL THE IMPACTS FROM MORNING THUNDERSTORMS
BECOME CLEARER.

A COLD FRONT WILL SAG SOUTH TONIGHT AND TAKE WITH IT THE RESIDUAL
THUNDERSTORM CHANCES.

.LONG TERM...(FRIDAY THROUGH WEDNESDAY)
ISSUED AT 411 AM CDT THU AUG 21 2014

FRIDAY LOOKS LIKE A CONTINUED WARM AND HUMID DAY...BUT THE MAIN
THERMAL RIDGING WILL BE DOWN TO THE SOUTH. ALSO LOOKS DRY UNTIL
OVERNIGHT WHEN THE FRONT LIFTS BACK NORTH AND A 40-50 KT LLJ
DEVELOPS ANOTHER ROUND OF THUNDERSTORM ACTIVITY ALONG IT. MOST OF
THIS WILL BE SOUTH OF MN FRIDAY NIGHT...BUT WILL EXPAND NORTHWARD
SATURDAY ACROSS MUCH OF THE REGION AS LOW PRESSURE DEVELOPS OVER
THE CENTRAL PLAINS. ANOTHER NEARLY STATIONARY BOUNDARY...WHICH THE
LOW WILL TRACK NORTH ALONG...WILL BE THE FOCUS FOR CONTINUED
THUNDERSTORM DEVELOPMENT THROUGH SUNDAY NIGHT. SUNDAY COULD BE A
RATHER WARM DAY IF SUNSHINE CAN MAKE AN APPEARANCE WITH THE LOW
PASSING TO THE WEST. AS THE LOW PASSES BY TO THE WEST...THE FRONT
WILL BEGIN TO MAKE EASTWARD PROGRESS AND MONDAY CURRENTLY LOOKS
DRY POST FRONTAL.

BY THE MIDDLE OF NEXT WEEK...MODELS STILL HINT AT THE FRONT
STALLING AND LIFTING BACK AS A WARM FRONT AS ANOTHER LOW FORMS
OVER THE PLAINS. THIS MAY BRING ANOTHER ROUND OF HEAVY RAIN
PRODUCING THUNDERSTORMS IN THE TUESDAY/WEDNESDAY TIME FRAME.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z THURSDAY NIGHT)
ISSUED AT 1127 PM CDT WED AUG 20 2014

THE MAIN CONCERN CONTINUES TO BE TIMING OF THE HEAVIEST
RAINFALL/TSRA DURING THE NEXT 6 HRS WITH TSRA/SHRA ALREADY
DEVELOPING ACROSS FAR EASTERN SD AND WC MN AS OF 430Z. THESE
STORMS WERE DEVELOPING ON THE NOSE OF THE LLJ WHICH IS PROGGED TO
CONTINUE OVERNIGHT AND VEER MORE SW WITH THE BULK OF THE SHRA/TSRA
MOVING FROM THE EAST EARLY...THEN MORE SE ACROSS SOUTHERN MN THRU
MID MORNING. PREVIOUS TAFS WERE MODIFIED FOR SOME TIMING
DIFFERENCES...BUT AGAIN ANY HEAVY RAINFALL WILL BE SHORT LIVED
WITH PREVAILING VSBYS ARND 3-5 SM WITH AN OCCASIONAL 1/2 TO 2 SM
IN +TSRA/+SHRA THRU 15Z. CIGS WILL BE MORE OF A REFLECTION OF
HEAVIER RAINFALL RATES...WITH SOME LOWERING DURING THE TYPICAL
MORNING HRS FROM 10-15Z...WITH CIGS LIFTING BY 15-18Z TO VFR. MORE
SHRA/TSRA WILL BE POSSIBLE DURING THE AFTN ACROSS WC WI...BUT
TIMING AND COVERAGE IS TOO LOW FOR CONTINUING VCSH/VCTS DURING THE
AFTN. WINDS WILL BE GENERALLY FROM THE SE/S OVERNIGHT...THEN MORE
S/SW THURSDAY MORNING...BEFORE BECOMING LIGHT AND VARIABLE DURING
THE LATE AFTN/EVENING.

KMSP...

BASED ON THE LATEST SHORT TERM MODEL INFORMATION...THE BEST TIME
FRAME FOR SHRA/TSRA TO AFFECT KMSP WILL OCCUR AFT 8Z...WITH 10-14Z
THE BEST TIME FRAME OF HEAVY RAINFALL WITH IFR CONDS. A GRADUAL
IMPROVEMENT IS EXPECTED BETWEEN 15-18Z WITH VFR CONDS EXPECTED BY
THE AFTN. WINDS WILL BE GENERALLY FROM THE E/ESE OVERNIGHT...THEN
MORE SE/S THURSDAY MORNING...WITH A SHIFT TO THE SW/W IN THE AFTN
BEFORE BECOMING LIGHT AND VARIABLE IN THE EVENING.

/OUTLOOK FOR KMSP/

FRI...VFR WITH MVFR/TSRA LATE. WINDS NE AT 10 KTS.
SAT...MVFR WITH IFR/+TSRA POSSIBLE. WINDS E AT 10G15 KTS.
SUN...VFR WITH MVFR/TSRA POSSIBLE. WINDS NW 10 KTS.

&&

.MPX WATCHES/WARNINGS/ADVISORIES...
MN...FLASH FLOOD WATCH UNTIL 10 AM CDT THIS MORNING FOR MNZ041-
     047>049-051-055>063-065>070-075>078-083>085.

WI...FLASH FLOOD WATCH UNTIL 10 AM CDT THIS MORNING FOR WIZ023-024.

&&

$$

SHORT TERM...BORGHOFF
LONG TERM...BORGHOFF
AVIATION...JLT








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