Area Forecast Discussion
Issued by NWS Twin Cities, MN

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FXUS63 KMPX 241820
AFDMPX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN
120 PM CDT SUN MAY 24 2015

.UPDATE...
ISSUED AT 119 PM CDT SUN MAY 24 2015

CHANGES THAT HAVE BEEN MADE TO THE FORECAST DURING THE MORNING
WERE TO ONE...REMOVE THUNDER MENTION FROM THE GRIDS THROUGH
TONIGHT...AS SREF CALIBRATED THUNDERSTORM PROBS DO NOT EVEN START
TO SHOW UP UNTIL MONDAY MORNING...SO FEEL CONFIDENT IN JUST RAIN
THROUGH TONIGHT. ALSO CUT BACK ON QPF AMOUNTS ACROSS THE WRN HALF
OF MN AS THE BEST MOISTURE TRANSPORT AND HEAVIEST RAIN TODAY HEAD
FOR WI. NEXT UP FOR THE GRIDS IS TO DO SOME SIGNIFICANT
RECONFIGURING OF POPS FOR TONIGHT THROUGH MONDAY...WILL BE
TRENDING TOWARD A BLEND OF THE GFS/CANADIAN/MPXWRF WITH ACTIVITY
CURRENTLY IN SW MISSOURI COMING UP THROUGH WRN WI...WHILE THE
DEFORMATION PRECIP STAYS ANCHORED UP OVER CENTRAL MN...SO BIGGEST
CHANGES /IN THE DOWNWARD DIRECTION/ WILL BE NEEDED FOR THE SW
QUADRANT OF THE MPX CWA.

UPDATED TO INCLUDE 18Z AVIATION DISCUSSION BELOW.

&&

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 345 AM CDT SUN MAY 24 2015

TODAY AND TONIGHT...SFC ANALYSIS DEPICTS SEVERAL WEAK LOW PRES
CENTERS OVER THE SRN PLAINS WHILE A DEEP UPR LVL LOW ROTATES OVER
THE 4-CORNERS REGION /SHOWING UP NICELY ON WV IMAGERY THIS MRNG/.
IN ADDITION...A LARGE SUBTROPICAL RIDGE OVER THE SERN CONUS WILL
BE A MAJOR PLAYER IN FORCING COPIOUS AMOUNTS OF WRN GOMEX MOISTURE
INTO THE UPR MISS RIVER VALLEY OVER THE WEEKEND. THIS DEEP UPR LVL
LOW WILL ALSO HELP THE CONGLOMERATION OF WEAK SFC LOWS INTO AN
ORGANIZED SFC LOW PRES SYSTEM LATER TDA...AND HELP SLOWLY NUDGE IT
SLOWLY NNE THRU TMRW. ISENTROPIC LIFT HEIGHTENS GREATLY THIS MRNG
IN ADVANCE OF THIS SYSTEM...HELPING SPREAD PRECIPITATION CURRENTLY
MOVING INTO FAR SWRN MN NWD AND ENCOMPASSING MUCH OF THE WFO MPX
CWFA BY MIDDAY TDA. HAVE GONE ALONG WITH THE CONSENSUS OF THE
HOPWRF/HRRR/SREF/ARW-E IN SLOWING DOWN THE INITIATION OF THE
PRECIP INTO THE CWFA...MORE TOWARDS THE 12Z HR FOR SRN PORTIONS
AND TO 17Z FOR THE ENTIRE CWFA TO BE IN THE LIKELY POP RANGE. MUCH
OF THIS INITIAL PRECIP SURGE LOOKS TO BE WITH A PRE-WARM-FRONTAL
TROF WHICH SHOWS UP IN THE H7 THRU H5 PRES LEVELS...INDICATING A
MIDLVL DISTURBANCE RIDING AROUND THE ERN PERIPHERY OF THE DEEP
LOW. ONCE THIS DISTURBANCE MOVES THRU...THE MODELS DO SHOW A
DIMINISHING OF THE PRECIP COVERAGE IF NOT A TEMPORARY BREAK IN THE
ACTION. HAVE DEPICTED THIS BY A LOWERING OF POPS BACK TO THE CHC
CATEGORY APPROACHING 00Z THIS EVENING. MORE WIDESPREAD PRECIP
COMMENCES BY LATE THIS EVENING INTO THE OVERNIGHT HRS AS THE WMFNT
ITSELF PUSHES INTO IA TONIGHT AND NUDGES UP AGAINST THE IA/MN
BORDER BY DAYBREAK MON MRNG. THERE IS THE POTENTIAL FOR POCKETS OF
HVY RAIN AS PWATS INCREASE TO ARND 1.50 INCHES LATER TDA THRU TNGT
AND THE OVERALL PROGRESS OF THIS SYSTEM CONTINUES TO BE ON A
SLOWING TREND. AS FOR CONVECTIVE POTENTIAL... THE CONTINUED LACK
OF INSTABILITY AS EVIDENCED BY NO BONA FIDE PERIODS OF SUNSHINE
AND MEAGER PROGGED CONVECTIVE PARAMETERS WILL MITIGATE GOOD
THUNDERSTORM POTENTIAL. CANNOT RULE IT OUT COMPLETELY SO HAVE
MAINTAINED SLGT CHC THUNDER FOR THIS AFTN THRU TNGT BUT ANY TSTM
DEVELOPMENT IS NOT EXPECTED TO BE STRONG/SEVERE. AS FOR
TEMPS...HAVE NUDGED TEMPS DOWN SLIGHTLY FROM INHERITED
VALUES...ESP OVER SRN MN...DUE TO EXTENSIVE CLOUD COVER AND THE
LACK OF INSOLATION. IN SOME CASES...MAX TEMPS MAY WELL HAVE
ALREADY BEEN REACHED AND TEMPS MAY REMAIN STEADY OR EVEN FALL A
DEGREE OR TWO THROUGHOUT THE DAY TDA. THAT SAID...MIN TEMPS EARLY
MON MRNG ARE EXPECTED TO BE WARMER THAN CURRENT VALUES THIS MRNG
DUE TO SLIGHT WAA WITH THE APPROACH OF THE WMFNT LATE TNGT AND
DEEP SWLY FLOW FROM THE UPR LVL PATTERN. WILL LOOK FOR LOWS IN THE
55-60 DEGREE RANGE MON MRNG.

.LONG TERM...(MONDAY THROUGH SATURDAY)
ISSUED AT 345 AM CDT SUN MAY 24 2015

MONDAY WILL START OFF WET WITH THE SURFACE LOW LIFTING NORTH
THROUGH NORTH CENTRAL IOWA AND DEFORMATION ZONE PRECIPITATION
EXPANDING ACROSS MUCH OF THE FA. AT THIS TIME...EXPECTING A BAND
OF HEAVIEST PRECIP JUST ON THE BACK SIDE OF THE SURFACE LOW
THROUGH MONDAY AFTERNOON...BUT THERE REMAINS VARIABILITY IN THE
GUIDANCE ON WHERE EXACTLY THIS BAND SETS UP. THE 00Z RUNS OF THE
GFS AND NAM CAME IN WITH GOOD AGREEMENT THAT THE AREA JUST WEST OF
THE TWIN CITIES THROUGH THE MILLE LACS LAKE AREA COULD SEE THE
HEAVIEST AMOUNTS ON MONDAY /UPWARDS OF AN INCH/.
HOWEVER...CONFIDENCE MUST BE SOMEWHAT LIMITED BECAUSE THE
EC...WHICH HAS BEEN ONE OF THE LEADING MODELS IN THE HANDLING OF
THIS SYSTEM AS IT HAS COME CLOSER IN TIME...IS INDICATING A
SURFACE LOW TRACK FARTHER EAST THROUGH WESTERN WISCONSIN AND WANTS
TO PLACE THAT HEAVIEST BAND OF PRECIP FROM RED WING THROUGH NEW
RICHMOND. IN OUR FA...THE MOST UNCERTAIN AREA FOR PRECIP IS
WESTERN WI AT THIS TIME...BECAUSE IF THE GFS/NAM SOLUTIONS END UP
BEING MORE ACCURATE...THAT COULD INTRODUCE A DRY SLOT OVER EAU
CLAIRE AND REALLY LIMIT PRECIP THERE. SO...MUCH OF HOW MEMORIAL
DAY TURNS OUT WILL DEPEND ON THE TRACK OF THE SURFACE LOW. AS IS
USUAL WITH SURFACE LOWS...AREAS EAST OF THE TRACK WILL BE MAINLY
LIMITED TO THE WARM AIR ADVECTION PRECIP BAND WHICH TYPICALLY MOVE
THROUGH QUICKLY...THEN BATTLE THE DRY SLOT. MEANWHILE...AREAS
IMMEDIATELY WEST OF THE SURFACE LOW COULD SEE SEVERAL HOURS OF
DECENT RAINFALL RATES AND OVER AN INCH IS CERTAINLY POSSIBLE.

STRONG ASCENT THROUGH MONDAY MORNING ON THE BACK SIDE OF THE SURFACE
LOW IS SUPPORTED BY THE VERY STRONG DIFFERENTIAL DIVERGENCE
INDICATED BY THE DETERMINISTIC GUIDANCE AS WE ARE IN A PRIME REGION
OF RIGHT ENTRANCE REGION INDUCED LIFT OF THE UPPER JET. SOME
INSTABILITY AND PWAT VALUES EXCEEDING 1.5" SUPPORT THE IDEA OF
SEEING SOME DECENT RAINFALL TOTALS IN THAT DEFORMATION BAND THAT
WILL PIVOT IN THE VICINITY OF EASTERN MN AND WESTERN WI. MUCH OF THE
AREA WILL LIKELY DRY OUT MONDAY AFTERNOON...ESPECIALLY SOUTH. WEST
CENTRAL MN HOWEVER MAY STILL BE PLAGUED BY LIGHT PRECIP RIGHT
THROUGH THE AFTERNOON. BY MONDAY NIGHT...THE LOW WILL HAVE MOVED OFF
INTO THE NORTHERN GREAT LAKES AND THE FA MAY HAVE A FEW SCATTERED
SHOWERS. IT LOOKS LIKE A SECOND TROUGH AND ASSOCIATED SURFACE LOW
WILL THEN PUSH INTO THE MIDWEST BUT MOST OF THE PRECIP ASSOCIATED
WITH THAT FEATURE SHOULD REMAIN SOUTH OF THE FA. SO...CUT POPS BACK
MONDAY NIGHT.

THE TRACK OF THE SECOND LOW SHOULD REMAIN SOUTHEAST OF OUR AREA
THROUGH WEDNESDAY...BUT IT MAY SPREAD LIGHT PRECIP AS FAR WEST AS
EASTERN MN AND WESTERN WI...SO HAVE INCLUDED SOME LOW POPS TUESDAY
DURING THAT TIME. EXPECTING A DRY DAY WEDNESDAY BEFORE MORE POPS
COME BACK WEDNESDAY NIGHT THROUGH FRIDAY. A MESSY PATTERN INDEED
FOR THE LATTER HALF OF THE WEEK AS A MODEST FEED OF MOISTURE AND
INSTABILITY LOOKS TO GIVE BROAD CHANCES FOR THUNDERSTORM
DEVELOPMENT DURING THAT PERIOD.

LITTLE CHANGE FOR THE END OF THE WEEK AND NEXT WEEKEND. THE EC/GFS
STILL AGREE THAT A CONTINENTAL POLAR AIR MASS FROM THE NORTH WILL
PUSH INTO THE UPPER MIDWEST WITH COOLER AND DRIER CONDITIONS
EXPECTED. HOWEVER...NAILING DOWN THE EXACT TIMING OF THE FROPA
IS TOUGH THIS FAR OUT.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z MONDAY AFTERNOON)
ISSUED AT 119 PM CDT SUN MAY 24 2015

WHAT IS A CERTAINTY IS RAIN AT ALL TERMINALS FOR THE FIRST 6 HOURS
OF THE TAF. RAIN SHIELD MOVING ACROSS THE AREA NOW WILL BECOME
ANCHORED TONIGHT FROM WC MN TOWARD NW WI...WITH PRECIP LIKELY
ENDING AFTER 6Z FOR RWF AND POSSIBLY MSP. ALSO A CERTAINTY ARE
CIGS GOING UNDER VFR AND EVENTUALLY IFR OVERNIGHT. CURRENT TAFS
ARE PROBABLY A BIT OPTIMISTIC ON WHEN MVFR/IFR CIGS MOVE IN...AS
MVFR/IFR CIGS ARE STARTING TO MAKE A BIT MORE NRN PROGRESS INTO
SRN MN. WIND DIRECTIONS WILL BE A BIT DIFFICULT OVERNIGHT AS A
SFC LOW BY MONDAY MORNING WILL BE CENTERED NEAR EAU. WITH THE LOW
PASSING OVERHEAD...WINDS WILL REMAIN LIGHT...BUT DIRECTION WILL
GET A BIT TRICKY TO PIN DOWN...BUT FOLLOWED THE TREND OF THE SREF
FOR DIRECTIONS WITH THE 18Z TAFS.

KMSP...SREF PROBS FOR IFR CIGS AFTER 6Z INCREASE TO ALMOST
100%...SO FEEL CONFIDENT IN CIGS STARTING OFF MONDAY UNDER 1K FT.
CONFIDENT IN RAIN FALLING AS WELL THROUGH ABOUT 4Z...BUT AFTER
THAT IT MAY BE MOSTLY DRY AT MSP FOR THE REST OF THE TAF PERIOD AS
PRECIP STAYS NORTH AND EAST OF THE FIELD.

/OUTLOOK FOR KMSP/
TUE...VFR. WINDS SW 10 KTS.
WED...VFR. WINDS SW 5-10 KTS.
THU...VFR. CHC SHRA/-TSRA. WINDS SE 5-10 KTS.

&&

.MPX WATCHES/WARNINGS/ADVISORIES...
MN...NONE.
WI...NONE.
&&

$$

UPDATE...MPG
SHORT TERM...JPC
LONG TERM...SPD
AVIATION...MPG



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