345  
FXUS63 KLOT 260748  
AFDLOT  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE, IL  
248 AM CDT THU APR 26 2018  
   
SHORT TERM
 
 
210 AM CDT  
 
THROUGH TONIGHT...  
 
ANOTHER QUIET WEATHER DAY IS IN STORE ACROSS THE AREA AS A SURFACE  
AND MID-LEVEL RIDGE SLOWLY EXIT TO THE EAST. EXPECT MOSTLY SUNNY  
SKIES THIS MORNING TO GIVE WAY TO FILTERED SUNSHINE THIS AFTERNOON  
AS WIDESPREAD CIRRUS SPREAD ACROSS THE AREA. TEMPS TODAY WILL BE A  
FEW DEGREES WARMER THAN ON WEDNESDAY, WITH MID TO UPPER 50S ALONG  
THE IMMEDIATE LAKE MICHIGAN SHORE TO THE MID 60S INLAND.  
ADDITIONALLY, WITH RATHER DRY CONDITIONS ALOFT, DAYTIME MIXING  
SHOULD PRODUCE MINIMUM RH VALUES OF 25-30% ACROSS MUCH OF THE  
AREA.  
 
A COLD FRONT AND ASSOCIATED MID-LEVEL TROUGH AXIS EXTENDING FROM  
HUDSON BAY TO THE CENTRAL HIGH PLAINS WILL TRACK SOUTHEASTWARD  
ACROSS THE CWA DURING THE EARLY MORNING HOURS FRIDAY. GIVEN A VERY  
DRY ANTECEDENT AIR MASS AND LIMITED DEEP FORCING, ONLY SOME VERY  
ISOLATED LIGHT SHOWERS/SPRINKLES ARE EXPECTED FOR AN HOUR OR TWO  
ALONG THE FRONT. OTHERWISE, CONDITIONS WILL BE MOSTLY CLOUDY WITH  
NNW WINDS GUSTS OF 20 MPH TO POSSIBLY 25 MPH OVERNIGHT.  
 
KLUBER  
 

 
   
LONG TERM
 
 
244 AM CDT  
 
FRIDAY THROUGH WEDNESDAY...  
 
AMPLIFIED UPPER LEVEL PATTERN IN PLACE WILL BRING LARGE  
TEMPERATURE SWINGS DURING THE EXTENDED TIMEFRAME. INITIAL COLD  
FRONT THAT PUSHES ACROSS THE REGION THURSDAY NIGHT INTO FRIDAY  
SHOULD PASS THROUGH MAINLY DRY GIVEN THE UNFAVORABLE DIURNAL  
TIMING. EXPECT A MODEST COOL-DOWN WITH THE FIRST FRONT. NORTH  
FLOW THROUGH THE DAY FRIDAY WILL KEEP TEMPERATURES IN THE UPPER  
50S TO LOW 60S ACROSS NORTHERN ILLINOIS AND NORTHWEST INDIANA,  
EXCEPT FOR LOW TO MID 50S NEAR THE LAKE WITH ONSHORE FLOW THROUGH  
THE DAY. MEANWHILE, A VIGOROUS SHORTWAVE WILL DIG INTO THE WESTERN  
GREAT LAKES FRIDAY AFTERNOON AND EVENING BRINGING A REINFORCING  
SHOT OF COLD AIR. STEEP LOW LEVEL LAPSE RATES WILL BE IN PLACE  
WITH PASSAGE OF THE UPPER LEVEL DISTURBANCE WHICH SHOULD ALLOW FOR  
SCATTERED SHOWERS TO FORM AND COULDN'T RULE OUT AN ISOLATED LOW-  
TOPPED THUNDERSTORM OR TWO AS WELL. COLD AIR MASS BEHIND THE FRONT  
WILL PUSH ACROSS THE OHIO VALLEY SATURDAY ENCOMPASSING THE ENTIRE  
MIDWEST. LOCALLY, EXPECT HIGHS ONLY IN THE LOW TO MID 50S FOR  
MUCH OF THE CWA, BUT AGAIN COOLER BY THE LAKE WITH PERSISTENT  
ONSHORE FLOW THAT WILL LIMIT TEMPS IN THE 40S. AN EXPANSIVE  
SURFACE HIGH WILL BUILD ACROSS THE UPPER MIDWEST ON SATURDAY  
RESULTING IN A MODEST NORTHERLY BREEZE LOCALLY, BUT OTHERWISE  
EXPECT DRY AND SUNNY CONDITIONS.  
 
BY SUNDAY, SURFACE HIGH WILL BUILD SOUTHEAST TOWARDS THE OHIO  
VALLEY WITH WINDS FLIPPING TO SOUTHWEST ACROSS THE CWA WHICH  
WILL HELP MODERATE TEMPERATURES CLOSER TO, BUT STILL LIKELY BELOW  
THE SEASONAL NORMS. THIS BEGINS TO CHANGE AS WE HEAD INTO THE  
UPCOMING WEEK, THOUGH, AS STRONG UPPER RIDGE TRANSLATES EAST  
ACROSS THE PLAINS INTO THE GREAT LAKES. LOW-MID LEVEL FLOW  
INCREASES OUT OF THE SOUTHWEST AS THIS TRANSITION OCCURS WHICH  
WILL TRANSPORT AN INCREASINGLY WARM AND MOIST AIR MASS INTO  
PORTIONS OF THE MIDWEST. AFTER A WARMING TREND WITH NICE WEATHER  
MONDAY INTO AT LEAST PART OF TUESDAY WHEN TEMPERATURES COULD TOP  
OUT NEAR THE 80F MARK, A MORE ACTIVE PATTERN SETS UP MIDWEEK.  
SURFACE HIGH SETTLES OVER THE SOUTHEAST ALLOWING AMPLE GULF  
MOISTURE TO STREAM NORTH INTO THE MIDWEST. MEANWHILE, A SERIES OF  
SHORTWAVES ROUNDING THE BASE OF THE UPPER TROUGH OVER THE  
SOUTHERN PLAINS AND LIFTING INTO THE MID/UPPER MISSISSIPPI VALLEY  
WILL RESULT IN PERIODIC CHANCES FOR SHOWERS AND THUNDERSTORMS. WAY  
TO EARLY TO GET INTO THE DETAILS WITH THESE LOW AMPLITUDE WAVES,  
BUT LARGE SCALE PATTERN DOES LOOK STORMY WITH POTENTIAL FOR STRONG  
TO SEVERE STORMS IN OR NEAR THE LOCAL AREA.  
 
DEUBELBEISS  
 

 
   
AVIATION
 
 
FOR THE 06Z TAFS...  
 
VFR CONDITIONS ARE EXPECTED THROUGH THIS EVENING AT ALL SITES. LIGHT  
WINDS WILL BECOME SW LESS THAN 10KTS THIS AFTERNOON AS A SURFACE  
RIDGE SHIFTS TO THE EAST. A LAKE BREEZE MAY MOVE FAR ENOUGH INLAND  
TO BRIEFLY REACH MDW EARLY THIS AFTERNOON BEFORE INCREASING SW WINDS  
PUSH THE LAKE BREEZE EAST OF THE TERMINAL BY LATE AFTERNOON. A COLD  
FRONT WILL THEN REACH RFD LATE THIS EVENING AND ORD/MDW DURING THE  
EARLY OVERNIGHT HOURS FRIDAY, BRINGING A PERIOD OF GUSTY N WINDS AND  
MVFR CEILINGS. AN ISOLATED -SHRA WILL BE POSSIBLE FOR AN HOUR OR TWO  
WITH THE COLD FRONT PASSAGE.  
 
KLUBER  
 

 
   
MARINE
 
 
244 AM CDT  
 
LIGHT FLOW IS IN PLACE ACROSS LAKE MICHIGAN THIS MORNING UNDER  
THE INFLUENCE OF HIGH PRESSURE JUST SOUTH OF THE LAKE, BUT  
SOUTHWEST TO SOUTH WINDS WILL GRADUALLY PICK UP THROUGH THE  
AFTERNOON AHEAD OF AN APPROACHING COLD FRONT. THE FRONT WILL SWEEP  
DOWN THE LAKE THIS EVENING AND OVERNIGHT LEAVING NORTH WINDS  
GUSTING TO 30 KT IN ITS WAKE. CONDITIONS APPEAR BRIEFLY CLOSE TO  
SMALL CRAFT CRITERIA LATE TONIGHT INTO EARLY FRIDAY, MAINLY FOR  
THE INDIANA NEARSHORE ZONES WHERE THE FETCH IS LONGEST, BUT WILL  
NOT HOIST ANY HEADLINES AT THIS TIME. A STRONGER COLD FRONT WILL  
PUSH DOWN THE LAKE FRIDAY EVENING AND NIGHT AND WILL PROVIDE  
ANOTHER PERIOD OF NORTH WINDS GUSTING TO 30 KT THAT WILL GRADUALLY  
EASE THROUGH THE DAY SATURDAY. A SMALL CRAFT ADVISORY WILL LIKELY  
BE NEEDED FOR THIS TIME FRAME. WINDS SHOULD DIMINISH LATER IN THE  
DAY SATURDAY AS HIGH PRESSURE BUILDS TOWARDS THE REGION AND  
REMAIN LIGHT ON SUNDAY.  
 
BMD  
 

 
   
LOT WATCHES/WARNINGS/ADVISORIES
 
 
IL...NONE.  
IN...NONE.  
LM...NONE.  

 
 

 
 
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