Tactical Decision Aids
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955 PM CDT TUE APR 15 2014 //ORD AND MDW CONCERNS...UPDATED 03Z..

* LIGHT SOUTH-SOUTHEAST WINDS OVERNIGHT BECOMING STRONG SOUTH WEDNESDAY...WITH GUSTS 30-35 KT POSSIBLE IN THE AFTERNOON

* POTENTIAL FOR LLWS LATE WEDNESDAY EVENING AS GUSTS DIMINISH...WITH WINDS 20045-50KT AROUND 2000 FT AGL

RATZER //DISCUSSION...UPDATED 00Z..

SURFACE HIGH PRESSURE RIDGE ALONG IL/IN BORDER AND OVER SOUTHERN LAKE MICHIGAN WILL CONTINUE TO DRIFT EAST THIS EVENING WILL ALLOW DECREASING WESTERLY WINDS TO SHIFT TO THE SOUTHEAST OVER THE NEXT 1-3 HRS. LAKE BREEZE HAD DEVELOPED AND MOVED AS FAR INLAND AS MDW BEFORE RETREATING A BIT...BUT DEPARTURE OF RIDGE AXIS TO EAST SHOULD ALLOW FOR A LARGE SCALE SHIFT TO SOUTHEAST WINDS ACROSS THE AREA

FOCUS THEN SHIFTS TO STRONG SOUTH WINDS EXPECTED WEDNESDAY IN RESPONSE TO AN AREA OF LOW PRESSURE DEVELOPING INTO THE UPPER MIDWEST. TIGHTENING PRESSURE GRADIENT APPEARS TO SUPPORT SUSTAINED WINDS AROUND 20 KT BY AFTERNOON...WITH GUSTS INTO THE 30-35 KT RANGE POSSIBLE PER FORECAST SOUNDINGS DEPICTING MIXING TO 4000-5000 FT AGL. SURFACE LOW LIFTS INTO WESTERN WISCONSIN WEDNESDAY EVENING ALLOWING THE GRADIENT TO EASE SLIGHTLY. DEGREE OF BOUNDARY LAYER DECOUPLING SOMEWHAT UNCERTAIN AFTER SUNSET WITH STRONG WINDS CONTINUING...THOUGH BY LATE EVENING EXPECT DECREASED GUSTS. THIS SETS UP THE POTENTIAL FOR NON-CONVECTIVE LOW LEVEL WIND SHEAR HOWEVER...WITH MODELS DEPICTING LOW LEVEL JET FROM ABOUT 200 DEGREES AT 45-50KT AT 2000 FT AGL

OTHERWISE...CURRENT VFR STRATOCU DECK EXPECTED TO ERODE QUICKLY EARLY THIS EVENING WITH STRONG SUBSIDENCE DEVELOPING AND DRY AIR IN PLACE. MID/HIGH VFR CLOUDS ALREADY RACING SOUTHEAST ACROSS THE NORTHERN PLAINS SHOULD RESULT IN INCREASING MID-CLOUDS LATER TONIGHT. MODEL TIME/HEIGHT DEPICTIONS INDICATE VFR MID DECK WILL REMAIN ACROSS AREA IN 10-15 KFT RANGE THROUGH WEDNESDAY. LOW CLOUDS WILL BE ABSENT...WITH SOUTHERN PORTION OF SURFACE HIGH PRESSURE RIDGE EFFECTIVELY BLOCKING MOISTURE RETURN FROM THE GULF OF MEXICO

RATZER //ORD AND MDW CONFIDENCE...UPDATED 03Z..

* MEDIUM CONFIDENCE IN GUSTS ABATING AND TRUE LLWS CONDITIONS DEVELOPING WEDNESDAY EVENING

* HIGH CONFIDENCE ALL OTHER ELEMENTS

RATZER //OUTLOOK FOR ORD/MDW FOR 12Z THURSDAY-12Z TUESDAY...UPDATED 00Z..

THURSDAY...CHC RA LATE AFTN/NGT. MAINLY VFR

FRIDAY...CHC RA/MVFR EARLY...THEN VFR

SATURDAY...VFR

SUNDAY...CHC RA

MONDAY...SLGT CHC RA

RATZER
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