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