660  
FXUS61 KILN 291050  
AFDILN  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE WILMINGTON OH  
650 AM EDT MON MAY 29 2017  
   
SYNOPSIS
 
 
A SLIGHTLY DRIER AIR MASS IS IN PLACE IN THE MIDDLE OHIO VALLEY  
BEHIND A COLD FRONT. ANOTHER WEAK FRONT WILL MOVE THROUGH THE  
AREA TONIGHT, WHICH COULD BRING A FEW SHOWERS OR THUNDERSTORMS.  
UPPER LEVEL LOW PRESSURE WILL REMAIN IN PLACE OVER THE NORTHERN  
GREAT LAKES THROUGH THE MIDDLE OF THE WEEK, WITH SEASONABLE  
CONDITIONS OVER THE OHIO VALLEY.  
 

 
   
NEAR TERM /THROUGH TONIGHT/
 
 
IT IS NOT EASY TO SAY EXACTLY WHERE THE SURFACE TROUGH/FRONT IS  
LOCATED EARLY THIS MORNING, AS THERE IS LITTLE DEFINITION TO  
THE WIND SHIFT. DEWPOINTS PROBABLY TELL THE STORY THE BEST, WITH  
A DROP FROM THE LOWER 60S TO UPPER 50S, BUT EVEN THIS IS NOT  
ESPECIALLY WELL DEFINED. REGARDLESS, THERE ARE CLEAR SIGNS OF A  
DRIER AIR MASS ADVECTING INTO THE REGION, WHICH WILL BE THE  
BIGGEST CHANGE IN THE WEATHER FROM YESTERDAY TO TODAY -- SIMILAR  
TEMPERATURES, BUT LESS HUMIDITY AND CLEARER SKIES.  
 
WITH THE DRIER AIR IN PLACE, MODEL SOUNDINGS SHOW MUCH DEEPER  
MIXING TODAY, PERHAPS TO AROUND 5KFT-6KFT. WIND FLOW, HOWEVER,  
IS NOT VERY STRONG -- LIMITING GUST POTENTIAL TODAY TO MAYBE  
AROUND 20 KNOTS. THE LOW-END CHANCES FOR PRECIPITATION THIS  
EVENING WILL BE DISCUSSED IN THE SHORT TERM AFD SECTION BELOW.  
 

 
   
SHORT TERM /TUESDAY/
 
 
THE DOMINANT FEATURE IN THE LARGE-SCALE WEATHER PATTERN EARLY  
THIS WEEK WILL BE THE UPPER LOW CENTERED NORTH OF LAKE SUPERIOR.  
ON THE SOUTHERN PERIPHERY OF THIS LOW, PSEUDO-ZONAL FLOW IS  
EXPECTED OVER THE ILN CWA, BUT WITH SOME INTRUSION OF VERY WEAK  
SHORTWAVE FORCING AT TIMES. ONE SUCH INSTANCE WILL OCCUR THIS  
EVENING, WITH A VERY WEAK VORTICITY MAXIMA MOVING EAST THROUGH  
THE CWA BETWEEN 00Z AND 06Z. LOOKING AT WINDS AND THETA-E, THERE  
IS ALSO EVIDENCE OF A WEAK FRONT AT 925MB-850MB. THIS IS NOT AN  
ESPECIALLY STRONG AMOUNT OF FORCING, AND THE AIR MASS IT WILL BE  
INTERACTING WITH IS FAIRLY DRY. AT MOST, SOUNDINGS ARE  
DEVELOPING SBCAPE VALUES OF AROUND 500 J/KG -- SHALLOW AND  
HIGH-BASED. THUS, NOT SEEING A REASON (AT LEAST THIS FAR OUT IN  
THE FORECAST PROCESS) TO INCREASE POPS ABOVE THE 20-30 PERCENT  
CHANCES CURRENTLY IN THE FORECAST. THESE CHANCES WILL END AFTER  
06Z AS THE WEAK TROUGH MOVES ONWARD TO THE EAST.  
 
OWING TO THE SLIGHT DECREASE IN 925MB-850MB TEMPERATURES,  
TEMPERATURES ARE LIKELY TO DROP SLIGHTLY FROM MONDAY TO TUESDAY,  
EVEN THOUGH IT WILL BE ANOTHER DAY WITH A REASONABLE AMOUNT OF  
INSOLATION AND MIXING. WITH 850MB TEMPERATURES FALLING BY 2-3  
DEGREES C, THE MAX T FORECAST WILL SHOW A 3-5 DEGREE F DROP  
FROM MONDAY TO TUESDAY.  
 

 
   
LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/
 
 
THE CENTER OF AN UPPER LEVEL CLOSED LOW OVER ONTARIO WILL CONTINUE TO  
ELONGATE AND ROTATE NORTHEAST TUESDAY NIGHT INTO WEDNESDAY. A COUPLE  
OF EMBEDDED DISTURBANCES ROTATING AROUND THE BASE OF THIS LOW ACROSS  
OUR REGION, COUPLED WITH A WEAK COLD FRONT/TROF AXIS, REQUIRES  
KEEPING LOW CHANCE POPS GOING DURING THIS PERIOD. THE WEAK FRONT  
SHOULD EXIT THE EASTERN CWFA BY WEDNESDAY EVENING WHEN THE THREAT  
FOR PCPN SHOULD COME TO AN END. AFTER LOWS IN THE LOWER TO MID 50S  
WEDNESDAY MORNING, HIGHS ON WEDNESDAY WILL RANGE FROM THE LOWER TO  
MID 70S.  
 
AS THE MAIN MID LEVEL TROUGH AXIS SHIFTS EAST WEDNESDAY NIGHT,  
CONFLUENT FLOW IN THE MID LEVELS WILL RESULT IN SURFACE HIGH  
PRESSURE BUILDING INTO THE OHIO VALLEY. SKIES WILL CLEAR AND WINDS  
WILL BECOME LIGHT TO CALM. IT WILL LIKELY BE THE COOLEST LOW  
TEMPERATURES OF THE EXTENDED GIVEN RADIATIONAL COOLING. LOWS WILL  
DROP INTO THE UPPER 40S TO THE LOWER 50S.  
 
WE WILL TRY TO SQUEEZE OUT A DRY DAY ON THURSDAY. HOWEVER, RETURN  
MOIST FLOW AROUND DEPARTING HIGH AND A PSEUDO WARM FRONT APPROACHING  
THE REGION FROM THE WEST MAY BRING CLOUDS AND A LOW CHANCE OF  
SHOWERS AND THUNDERSTORMS TO OUR FAR WESTERN CWFA BY THURSDAY  
EVENING. HIGHS ON THURSDAY WILL RANGE FROM THE MID 70S NORTH TO NEAR  
80 SOUTH.  
 
LONG RANGE MODELS ARE IN DECENT AGREEMENT AS WE HEAD INTO THE FIRST  
PART OF THE WEEKEND, BUT THEN DIVERGE AS WE GO INTO NEXT WEEK.  
ANOTHER UPPER LEVEL CLOSED LOW IS FORECAST TO DIG SOUTHEAST INTO  
SOUTHEAST CANADA AND THE NORTHERN GREAT LAKES FRIDAY INTO SATURDAY.  
AS THIS OCCURS, A COLD FRONT WILL SLOWLY PUSH SOUTH ACROSS THE GREAT  
LAKES, AND THEN IT MAY GET HUNG UP SOMEWHERE ACROSS OUR AREA ON  
SATURDAY. CHANCES OF SHOWERS AND THUNDERSTORMS WILL INCREASE ON  
FRIDAY WITH THE HIGHEST CHANCES LIKELY COMING FRIDAY NIGHT INTO  
SATURDAY MORNING.  
 
THE REMAINDER OF THE EXTENDED, AS STATED, BECOMES MUDDLED AS MODELS  
CAN NOT AGREE IF UPPER LEVEL CLOSED LOW WILL PUSH OFF TO OUR EAST OR  
ADDITIONAL ENERGY WILL DIG SOUTHWARD FROM SOUTH CENTRAL CANADA INTO  
THE GREAT LAKES. HAVE BROAD BRUSHED THE FORECAST DURING THIS PERIOD  
AS FRONT MAY BE SLOW TO DEPART TO OUR EAST/SOUTHEAST. THUS, KEPT AT  
LEAST A CHANCE OF SHOWERS AND THUNDERSTORMS ACROSS THE SOUTH, BUT  
DID ALLOW THE FAR NORTH TO DRY OUT. HIGH TEMPERATURES WILL REMAIN IN  
THE 70S FOR THE WEEKEND.  
 

 
   
AVIATION /12Z MONDAY THROUGH FRIDAY/
 
 
SOME AREAS OF FOG AND STRATUS HAVE DEVELOPED THIS MORNING,  
PRIMARILY AFFECTING THE CVG/LUK/ILN AIRPORTS. A RANGE OF MVFR TO  
LIFR CONDITIONS CAN BE EXPECTED FOR ANOTHER HOUR OR TWO, BEFORE  
THESE CONDITIONS IMPROVE BY MID-MORNING. ONCE THIS HAS OCCURRED,  
VFR CONDITIONS ARE EXPECTED THROUGH THE REST OF THE DAY, WITH  
JUST SOME HIGH/MID CLOUDS AND PERHAPS A FEW CUMULUS.  
 
THERE MAY BE A CHANCE FOR A FEW SCATTERED SHOWERS OR  
THUNDERSTORMS THIS EVENING, BUT CONFIDENCE IS TOO LOW TO  
INCLUDE IN THE TAFS AS OF NOW. A VCSH WILL BE USED AT TDAY.  
 
OUTLOOK...THUNDERSTORMS WILL BE POSSIBLE ON FRIDAY.  
 

 
   
ILN WATCHES/WARNINGS/ADVISORIES
 
 
OH...NONE.  
KY...NONE.  
IN...NONE.  
 

 
 

 
SYNOPSIS...HATZOS  
NEAR TERM...HATZOS  
SHORT TERM...HATZOS  
LONG TERM...HICKMAN  
AVIATION...HATZOS  
 
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