250
FXUS63 KMPX 161939
AFDMPX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN
239 PM CDT WED MAY 16 2012
DISCUSSION
SEVERAL WX CONCERNS OVER THE NEXT FEW DAYS AS THE ATMOSPHERE
BEGINS TO MOISTEN UP AND A FRONTAL BOUNDARY MOVES CLOSE TO THE
REGION...AND THEN EVENTUALLY THROUGH THE AREA BY LATE IN THE
WEEKEND.
CHC OF TSRA/SHRA OVERNIGHT REMAINS PROBLEMATIC IN TERMS OF AREAL
COVERAGE DUE TO LIMITED MOISTURE IN THE BOUNDARY LAYER. EVEN IF
TSRA/SHRA DEVELOP...THE HEIGHT OF WHICH THESE STORMS DEVELOP WILL
LIKELY BE ABV 70H AS LCL/S REMAIN FAIRLY HIGH UNTIL WE GET MORE
MOISTURE FROM THE GULF...OR AS SHRA/TSRA DEVELOP...THE BOUNDARY
LAYER WILL SLOWLY MOISTEN UP BASED ON SATURATION FROM ABV. OVER
THE PAST SEVERAL MODEL RUNS...AND OVER THE PAST FEW DAYS...THE
ORIENTATION OF THE LLJ AND THE NOSE OF THE FEATURE WILL BE THE
MAIN INITIATION TOOL FOR DEVELOPMENT. SOME OF THE LOCAL MODEL RUNS
HAVE SHRA/TSRA DEVELOPING NEAR EC SD AFT 3Z...THEN SLOWLY TAKING
THIS COMPLEX E/NE ACROSS WC...INTO CENTRAL MN BY DAYBREAK.
EVENTUALLY...THIS COMPLEX WILL LIKELY TAKE A MORE E/ESE
ORIENTATION AFT 12Z THU. EARLIER FORECAST WITH 30/50 POPS ACROSS
THE FA...SEEMS REASONABLE BASED ON COVERAGE AND THE LLJ.
ANOTHER ELEMENT WHICH HAS BEEN CONSISTENT IN THE MODEL RUNS IS THE
85H HEIGHT RISES ACROSS THE EASTERN GREAT LAKES. THIS WILL LEAD TO
A SLOWER MOVEMENT OF THE FRONTAL BOUNDARY OVER THE WEEKEND...AND
THE POSSIBILITIES OF HOLDING ONTO POPS LONGER IN THE WEST...AND
HOLDING OFF ON THE POPS IN THE EAST FOR THE FIRST PART OF THE
WEEKEND. ANOTHER ASPECT TO AN ANTICIPATED STRONG SOUTHERLY WND
DEVELOPING LATER TONIGHT...AND LASTING THRU SAT IS HOW THIS WILL
AFFECT THE OVERALL MIXING IN THE LOWEST 1K IN THE ATMOSPHERE. SOME
OF THE MODELS...IF YOU MIX DOWN FROM ARND 85-80H BOTH TOMORROW AND
FRI...HAVE WIDESPREAD 90S ACROSS THE WESTERN 2/3 OF THE FA. EVEN A
FEW UPPER 90S IN WC MN ARE NOT OUT OF THE QUESTION IF WE GET FULL
SUNSHINE ON FRI. AGAIN...IF WE GET MORE CLOUD COVER THAN FORECAST
FOR THU AND FRI...THEN THESE TEMPS WILL NOT MATERIALIZE...BUT
SOMETHING TO THINK ABOUT FOR THE NEXT FORECAST SHIFT.
AS FOR RAINFALL...AFT TONIGHT CHC/S OF PRECIPITATION WILL BE
LIMITED UNTIL THE FRONT GETS CLOSER TO THE REGION. A CAPPING
INVERSION IS LIKELY ABV THE MIXING LAYER WHICH WILL BE FAIRLY HIGH
BASED ON THE DISCUSSION INDICATED BEFORE.
AFT SUNDAY...THE FORECAST IS HIGHLY BASED ON HOW STRONG THE 85H
HEIGHTS DEVELOP ACROSS THE GREAT LAKES...AND WHAT HAPPENS TO AN
UPPER LOW DEVELOPING ACROSS THE SE U.S. BASED ON THE OVERALL
MEAN...THERE SHOULD BE A DRY PERIOD AFT SUNDAY WITH SLIGHTLY
RIDGING DEVELOPING OVER THE UPPER MIDWEST AND A LONG WAVE TROUGH
ALONG THE WEST COAST. ..JLT..
AVIATION
/18Z TAF ISSUANCE/
VFR FLYING CONDITIONS THROUGH THE PERIOD. WARM FRONT STILL PROGGED
TO LIFT NORTHEAST OVER THE REGION LATE TONIGHT AND INTO NORTHERN
PORTION OF THE FA BY MIDDAY THURSDAY. AT LEAST SCT -SHRA EXPECTED
WITH THE STRONG WAA DEVELOPING ALONG AND NORTH OF FRONT. WILL
CONTINUE TREND OF -SHRA AT MN TAF LOCATIONS WITH VCSH INTO WEST
CENTRAL WI THU MORNING. SURFACE HIGH DRIFTING EAST THIS AFTERNOON
WITH SOUTHEAST TO SOUTH WINDS INCREASING BY MID MORNING THU AND
BECOMING GUSTY.
MSP...CONTINUE VFR CONDITIONS. CEILINGS DEVELOPING LATER TONIGHT
DROPPING TO AROUND 9K FEET BY MORNING WITH SCT -SHRA IN VCNTY.
CONTINUED THIS TREND INTO THE MORNING AND EXITING THE AREA WITH WARM
FROPA AFTER 16Z. LIGHT EAST TO SOUTHEAST WIND INTO TONIGHT AND THEN
BECOMING SOUTH AND INCREASING/BECOMING GUSTY BY MID MORNING
THU.
OUTLOOK...
THU AFT-FRI...SLIGHT CHANCE OF SHRA/TSRA...MVFR CEILINGS POSSIBLE.
SAT-SUN...SHRA/TSRA LIKELY WITH MVFR/IFR POSSIBLE.
MPX WATCHES/WARNINGS/ADVISORIES
MN...NONE.
WI...NONE.
JLT/DWE
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