AP-WI--MSP-WI W Area Forecast Discussion, WI

000

FXUS63 KMPX 151058

AFDMPX

AREA FORECAST DISCUSSION

NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN

558 AM CDT WED JUL 15 2015

.UPDATED FOR 12Z AVIATION DISCUSSION...

ISSUED AT 548 AM CDT WED JUL 15 2015

&&

.SHORT TERM...(TODAY AND TONIGHT)

ISSUED AT 332 AM CDT WED JUL 15 2015

SHORT TERM FORECAST CONCERNS CENTERED AROUND THE PRECIP...MORE

SPECIFICALLY AMOUNT OF PRECIP TONIGHT INTO THURSDAY MORNING. THE

LARGE-SCALE MODELS SUCH AS SREF/NAM/GFS/GEM CONTINUE TO PAINT A

STRIP OF 2+ QPF FROM ROUGHLY SIOUX FALLS THROUGH THE TWIN CITIES.

THIS SEEMS UNREALISTIC IN THE HUMBLE OPINION OF THIS FORECASTER...AND

EXPECT THE PRECIP TO FALL ACROSS IOWA...NOT MN/WI.

THE MAIN WAVE RESPONSIBLE FOR TONIGHTS STORMS WAS LOCATED ACROSS

COLORADO AS OF 3 AM. AN AREA OF THUNDERSTORMS WAS ONGOING AHEAD OF

THIS WAVE ACROSS KS/NE. OVER THE NEXT 24 HOURS...H850 WARM ADVECTION

ACROSS THE SOUTHERN PLAINS WILL LEAD TO A TIGHTENING OF THE H850

THETA_E GRADIENT...WHICH SHOWS UP WELL ON THE GFS/GEM/ECMWF 15.00

RUNS BY 06Z THURSDAY. THIS THETA_E GRADIENT MATCHES UP WELL WITH THE

MODEL GENERATED QPF...AND SHIFTS NORTHEAST AS THE PARENT WAVE ROUNDS

THE CREST OF THE UPPER LEVEL RIDGE. AS A RESULT...THE MODEL

GENERATED QPF ALSO SHIFTS NORTHEAST ALONG THE AFOREMENTIONED TRACK

FROM SOUTHEAST MN INTO WEST CENTRAL WI.

HOWEVER...CONVECTION SHOULD DEVELOP ACROSS IOWA SOUTH OF THE FGEN

FORCING. THE 15.00 HIRES MODELS FOUND ON THE SPC STORM-SCALE

ENSEMBLE OF OPPORTUNITY...SPECIFICALLY HRW-WRFARW....NSSL-

WRFWARW...EMC-WRFNMM...AND HRW-NMMB ALL KEEP THE MAJORITY OF THE

CONVECTIVE ELEMENTS ACROSS IOWA...WITH SOME EVEN FOCUSING AS FAR

SOUTH AS I-80.

MEANWHILE...THE OPERATIONAL NAM 15.00 HAS 3+ INCHES ACROSS THE

FORECAST AREA AND IS ONE OF THE NORTHERN MOST SOLUTIONS.

ALSO...THE NAM-NEST WHICH IS ALSO FOUND ON THE SPC PAGE...LIFTS

THE PRECIP NORTHEAST INTO SOUTHERN MN...AND ALTHOUGH IT IS A BIT

MORE SOUTH THAN THE PARENT NAM MODEL...IT STILL DUMPS 1-2

INCHES...WITH LOCALIZED 4+ ACROSS THE SOUTHERN PART OF THE

FORECAST AREA. THE FORECAST SOUNDINGS OFF THE NAM ARE SCARY...WITH

PWATS OVER 2 INCHES AND 60-70 KT LOW LEVEL JET OVERNIGHT.

THEREFORE TRAINING THUNDERSTORMS IS A LEGIT CONCERN. HOWEVER...THE

MESOBETA ELEMENTS ARE GOING TO PROPAGATE SOUTHEAST. THEREFORE DO

NOT THINK THE NORTHERN SOLUTION OF THE NAM NEST...AND ESPECIALLY

THE NAM (ALONG WITH GFS/GEM/SREF) WILL COME TO FRUITION.

IN SUMMARY...THIS IS EERILY SIMILAR TO THE JUNE 11 CASE FROM EARLIER

THIS YEAR. AFTER COLLABORATING WITH BOTH NATIONAL GUIDANCE AND LOCAL

SURROUNDING OFFICES...THERE ARE DIFFERENCES BETWEEN THE TWO...MOST

NOTABLY THE PRESENCE OF INSTABILITY ACROSS MN...WHICH WAS NOT THE

CASE A MONTH AGO. ACKNOWLEDGING THESE DIFFERENCES DID LEAD US TO

SHIFT THE QPF FORECAST SLIGHTLY FARTHER NORTH TOWARD NORTHERN

IOWA...BUT STAY AWAY FROM THE PURE GFS/NAM/GEM BLEND.

.LONG TERM...(THURSDAY THROUGH TUESDAY)

ISSUED AT 332 AM CDT WED JUL 15 2015

SHOWERS AND THUNDERSTORMS WILL BE ONGOING THURSDAY MORNING FROM

IOWA AND SOUTHERN MN INTO WESTERN WI IN RESPONSE TO A 45-50 KT

LLJ ACROSS IOWA INTO SERN MN. A CLOSED LOW...ALBEIT LIKELY AIDED

IN PART BY CONVECTIVE FEEDBACK WILL SLOWLY DRIFT EAST ALONG THE

MN/IA BORDER THROUGH THE DAY. THE GFS/ECMWF REMAIN ON THE SLOWER

AND SOUTHERN SIDE OF CONSENSUS WITH THE NAM AND GEM A BIT FASTER

AND FURTHER NORTH. THINK SHOWERS AND SOME THUNDERSTORMS WILL

CONTINUE TO THE NORTH AND EAST OF THIS LOW INTO THE AFTERNOON.

INTENSITY WILL BE WANING WITH THE LLJ BY MID MORNING THURSDAY.

WESTERN MN WILL LARGELY BE DRY...ALTHOUGH A WEAK MID LEVEL TROUGH

MAY ALLOW A FEW STORMS TO PUSH IN FROM THE DAKOTAS DURING THE LATE

AFTERNOON AND EARLY EVENING BEFORE DIMINISHING AFTER SUNSET. LIGHT

WINDS AND CROSSOVER TEMPS LIKELY TO BE EXCEEDED BY SEVERAL

DEGREES WILL ALLOW FOR AREAS OF FOG TO DEVELOP THURSDAY NIGHT OVER

MUCH OF THE AREA.

THE RIDGE TO THE SOUTH WILL BUILD NORTH SOMEWHAT FRIDAY. WARMER

AND MORE HUMID CONDITIONS WILL BEGIN TO PUSH IN AS 850 MB TEMPS

REACH +20 TO +23C. HIGHS IN THE UPPER 80S TO LOW 90S A GOOD BET

ACROSS MN...WITH LOW TO MID 80S IN WI WHERE THE THERMAL RIDGING IS

JUST OUT OF REACH. COMBINED WITH DEW POINTS CREEPING BACK TO

70...HEAT INDICES WILL PEAK AS HIGHS AS THE MID/UPPER 90S ALONG

THE MN RIVER.

BY FRIDAY NIGHT...A WEAK MID LEVEL SHORT WAVE IN CONJUNCTION WITH

STRONGER LOW LEVEL WAA WILL FACILITATE SCATTERED ELEVATED THUNDERSTORM

DEVELOPMENT FROM THE DAKOTAS INTO CENTRAL/SOUTHERN MN. A COUPLE OF

THESE STORMS MAY BECOME SEVERE WITH LARGE HAIL BUT LACK OF SHEAR

WILL LIMIT THE THREAT.

THERMAL RIDGING WILL BUILD BACK SATURDAY WITH HOT AND VERY HUMID

AIR RETURNING. EVAPOTRANSPIRATION AIDED BY THE POTENTIAL FOR RAIN

THE NIGHT BEFORE WILL SEND DEW POINTS BACK INTO THE MID AND UPPER

70S BY AFTERNOON. HEAT INDICES WILL RANGE FROM 95 TO 105 AGAIN AS

TEMPERATURES CLIMB INTO THE UPPER 80S TO LOWER 90S. HEAT

ADVISORIES WILL LIKELY BE NEEDED IN SOME AREAS...PARTICULARLY

SOUTH OF I-94. DESPITE MUCAPE EXCEEDING 5000 J/KG...THUNDERSTORM

ACTIVITY SHOULD BE LIMITED SATURDAY DUE TO LACK OF FORCING AND

CAPPING. THE BEST CHANCE FOR A FEW STORMS WOULD BE NORTH OF I-94

WHERE THE CAP IS SOMEWHAT WEAKER UNTIL THE FRONT ARRIVES SATURDAY

NIGHT WHEN STORMS BECOME MORE WIDESPREAD.

FOR THE REST OF THE PERIOD...WEST NORTHWEST FLOW WILL BRING COOLER

AND LESS HUMID CONDITIONS BACK. REMOVED CHANCES FOR STORMS BEYOND

SUNDAY WITH BROAD HIGH PRESSURE ENCOMPASSING THE UPPER MIDWEST.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z THURSDAY MORNING)

ISSUED AT 548 AM CDT WED JUL 15 2015

GENERALLY VFR CONDITIONS...WITH MVFR/IF -RA/TSRA LATE TONIGHT.

MAIN ITEM OF INTEREST IS SHOWERS AND THUNDERSTORMS...WHICH WILL

DEVELOP LATER TONIGHT. THE BEST CHANCE FOR MVFR/IFR IS AT

KAXN...AND DOWN SOUTH NEAR KRWF. MOST LOCATIONS SHOULD SEE

RAIN...BUT THE MOST INTENSE WILL BE AT THOSE OTHER 2 LOCATIONS.

KMSP...

LATEST FORECAST TRENDS OF THE HIRES MODELS SUGGEST THAT THE

HEAVIEST STORMS/RAINFALL WILL REMAIN TO THE SOUTH IN IOWA. STILL

EXPECT PRECIP TO DEVELOP LATE TONIGHT/EARLY THURSDAY MORNING...BUT

NOT ANTICIPATING SIGNIFICANT IMPACTS.

/OUTLOOK FOR KMSP/

THU...MVFR WITH SHRA/TSRA LIKELY EARLY. THEN VFR. WINDS SE 10-15

AT KT

FRI...VFR WITH MVFR/-TSRA POSSIBLE LATE. WINDS SSW 5-10 KT

SAT...VFR. SLIGHT CHC SHRA/TSRA. WINDS SSE 5-10 KT

&&

.MPX WATCHES/WARNINGS/ADVISORIES...

MN...NONE.

WI...NONE.

&&

$$

SHORT TERM...JRB

LONG TERM...BORGHOFF

AVIATION...JRB

Delivered by Weather Underground Inc. Wed Jul 15 2015 6:59AM EDT