757  
FXUS63 KIWX 301042  
AFDIWX  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE NORTHERN INDIANA  
642 AM EDT WED JUL 30 2014  
   
SYNOPSIS
 
 
ISSUED AT 450 AM EDT WED JUL 30 2014  
 
A STRONG LOW PRESSURE SYSTEM WILL REMAIN ANCHORED OVER JAMES BAY  
CANADA REACHES SOUTH THROUGH WESTERN LAKE ERIE. THIS WILL RESULT  
IN CONTINUED COOL WEATHER IN OUR AREA WITH SCATTERED...PRIMARILY  
AFTERNOON SHOWERS AND THUNDERSTORMS THROUGH THE NEXT FEW DAYS.  
HIGHS TODAY WILL GENERALLY REACH INTO THE MID 70S...THOUGH ONLY  
NEAR 70 CLOSE TO LAKE MICHIGAN. LOWS TONIGHT WILL DROP BACK INTO  
THE LOWER TO MIDDLE 50S.  
 

 
   
SHORT TERM
 
(TODAY AND TONIGHT)  
ISSUED AT 446 AM EDT WED JUL 30 2014  
 
ANTICIPATE SIMILAR SCENARIO AS SEEN YESTERDAY GIVEN HIGHLY BLOCKED  
LONGWAVE PATTERN WITH DEEP LAYER TROF AXIS HOLDING FROM JAMES BAY  
ANCHOR SOUTHWARD TO WESTERN LAKE ERIE. CONTINUED NWRLY PERTURBED  
FLOW AMID STEEP 0-3KM LAPSE RATES PEAKING AT 7.5-8.25C/KM  
MIDDAY/AFTERNOON WITH SFC/5H DIFFERENTIALS AGAIN IN UPPER 30C TO  
NEAR 40C RANGE SHOULD BE SUFFICIENT FOR RENEWED CONVECTIVE  
DEVELOPMENT BY LATE MORNING/MIDDAY. SURFACE DEWPOINTS HAVE CREPT  
UPWARDS PER BOTH YESTERDAYS ISOLATED TO SCATTERED CONVECTION AS WELL  
AS GENEROUS EVAPOTRANSPIRATION THROUGH CORN BELT. MODIFIED NAM12  
POINT SOUNDINGS YIELD GENERALLY 600-800 J/KG WITH MID 70S/MID  
50S...SAVE FOR ONLY ABOUT 250 J/KG DOWNWIND OF SOUTHEAST LAKE  
MICHIGAN. WITH GREATER CONVERGENCE/INSTABILITY WELL INLAND AND ALONG  
SOUTHEAST EXTENSION OF NERN IL/NWRN IN LAKE SHADOW...WILL OFFER SOME  
SPATIAL DETAIL WITH COVERAGE TYPE WORDING...AND LOWER POPS AS WELL  
AS NIX TSRA MENTION IN NWRN CWA CONCAVITY. AGAIN LITTLE LCL/LFC  
DIFFERENTIAL SHOULD PROVIDE FAIRLY RAPID LOW TOPPED CONVECTIVE  
DEVELOPMENT AND WET BULB ZERO HEIGHTS AROUND 9 KFT SUGGEST SMALL  
HAIL WITHIN STRONGEST STORMS POSSIBLE. WEAKENING GRADIENT FLOW AND  
REMNANT LOW LEVEL THERMAL TROF SUGGESTS ANOTHER GOOD LONGWAVE  
RADIATIONAL EVENING/EARLY WED NIGHT AND LOWERED TEMPS  
SLIGHTLY...ESPECIALLY AT KBEH WITH ANTICIPATED LAND BREEZE/DRAINAGE  
WIND.  
 

 
   
LONG TERM
 
(THURSDAY THROUGH TUESDAY)  
ISSUED AT 446 AM EDT WED JUL 30 2014  
 
CONTINUED SEASONALLY COOL MID LEVEL TEMPS ON THURSDAY WILL ALLOW  
AFTERNOON LAPSE RATES TO STEEPEN WITH DAYTIME HEATING...AND SHOULD  
ALLOW FOR A SLIGHT CHANCE FOR THUNDERSTORMS AS WEAK UPPER LEVEL  
DISTURBANCES MOVE ACROSS THE AREA. WEAK UNIDIRECTIONAL WIND FLOW BUT  
WITH LOW WET BULB ZERO HEIGHTS COULD ALLOW FOR SOME VERY SMALL HAIL  
FROM A STORM OR TWO. THEREFORE...HAVE KEPT A SLIGHT CHANCE FOR  
THUNDERSTORMS THURSDAY AFTERNOON. KEPT A LOW CHANCE OR SLIGHT CHANCE  
FOR SHOWERS OR STORMS FRIDAY THROUGH SATURDAY AS THIS PATTERN  
CONTINUES WITH ADDITIONAL WEAK SHORT WAVE ENERGY ROTATING AROUND THE  
UPPER LOW THAT SHOULD BE OVER JAMES BAY EARLY THIS WEEKEND. THE  
UPSTREAM UPPER LEVEL RIDGE SHOULD FLATTEN EARLY NEXT WEEK AND ALLOW  
A MORE PROGRESSIVE UPPER LEVEL PATTERN. LOW LEVEL THETA E SHOULD  
INCREASE TUESDAY...AND ALONG WITH WEAK LOW LEVEL FORCING...SHOULD  
ALLOW FOR A SMALL CHANCE FOR THUNDERSTORMS TUESDAY. AS FOR  
TEMPERATURES...FAVOR THE COOLER GFS MEAN ENSEMBLE TEMPERATURES WHICH  
SEEM TO SUPPORT COOL 850 MB TEMPERATURES FOR THIS TIME OF YEAR.  
 

 
   
AVIATION
 
(FOR THE 12Z TAFS THROUGH 12Z THURSDAY MORNING)  
ISSUED AT 642 AM EDT WED JUL 30 2014  
 
LITTLE CHANGE TO LATEST 12 UTC TAFS FOR NORTHERN INDIANA. PRIMARILY  
VFR MET CONDITIONS THROUGH THE FORECAST PERIOD SAVE FOR MVFR  
VSBSY NEAR DAYBREAK INVOF KFWA. OTHERWISE...SIMILAR SCENARIO AS  
SEEN YDAY WITH MID TROPOSPHERIC COLD POOL REMAINING FROM NORTH OF  
LAKE SUPERIOR INTO NWRN OH WITH SOLD/SCT CONVECTION POTENTIAL  
INCREASING BY MIDDAY...AND HAVE ADDED MENTION OF VCTS AT KFWA 16-23  
UTC GIVE HIGHER DEGREE OF CONFIDENCE...AND WILL MONITOR TRENDS  
FOR POSSIBLE TEMPO INCLUSION LATER. SUFFICIENT INLAND SCOUR  
DOWNWIND OF LAKE MICHIGAN SHOULD PRECLUDE SHRA/TSRA OCCURRENCE AT  
KSBN.  
 

 
   
IWX WATCHES/WARNINGS/ADVISORIES
 
 
IN...NONE.  
MI...NONE.  
OH...NONE.  
LM...NONE.  

 
 

 
 
SYNOPSIS...MURPHY  
SHORT TERM...MURPHY  
LONG TERM...SKIPPER  
AVIATION...MURPHY  
 
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