767  
FXUS63 KLOT 211133  
AFDLOT  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE, IL  
633 AM CDT SAT APR 21 2018  
   
SHORT TERM
 
 
224 AM CDT  
 
THROUGH TONIGHT...  
 
HIGH PRESSURE WILL REMAIN OVER THE CENTRAL AND EASTERN GREAT  
LAKES TODAY AND TONIGHT RESULTING IN FAIR WEATHER AND A LIGHT  
EASTERLY BREEZE ACROSS NORTHERN ILLINOIS AND NORTHWEST INDIANA. TO  
OUR WEST, BAROCLINIC LEAF IS NOTED ON SATELLITE IMAGERY WITH  
CLOUD COVER INCREASING ACROSS THE LOCAL AREA AS THIS FEATURE  
SLOWLY SHIFTS EAST ACROSS THE GREAT PLAINS TODAY. GFS CONTINUES TO  
DEVELOP A NARROW CORRIDOR OF LIGHT PRECIPITATION TODAY, AND NOW  
THE NAM AND SEVERAL HIGH-RES MODELS HAVE JOINED THE GFS CAMP.  
FORCING IS NOT OVERLY IMPRESSIVE, MAINLY IN THE FORM OF BROAD  
DIFFLUENCE ALOFT IN ADVANCE OF THE UPPER LOW TO OUR WEST AND  
MODEST COMPACT SHORTWAVE. MEANWHILE, VERY DRY ANTECEDENT  
CONDITIONS ARE IN PLACE. 00Z KDVN RAOB RECORDED 0.21 INCHES PWAT  
AND SHOWS VERY DRY CONDITIONS BELOW 500MB. NO LOW/MID LEVEL  
MOISTURE ADVECTION INTO THE REGION IS EXPECTED UNDER THE INFLUENCE  
OF THE 850MB HIGH PRETTY MUCH OVERHEAD THROUGH THE MORNING, SO  
WOULD ANTICIPATE THE DRY LAYER WILL BE VERY HARD TO OVERCOME. MAY  
SEE SOME ECHOES ON RADAR BUT THINK MOST PRECIP WOULD EVAPORATE  
BEFORE REACHING THE GROUND. MID-HIGH LEVEL LAPSE RATE ARE POOR,  
WHICH SHOULD PREVENT ANY CONVECTION. AT MOST, PERHAPS A FEW HIGH  
BASED SPRINKLES WILL BE POSSIBLE, BUT LIKELY NOT ENOUGH TO FULLY  
WET THE GROUND. WILL CARRY SILENT 10-14 POPS TODAY AND INTRODUCE A  
SLIGHT CHANCE FOR SOME SPRINKLES. CLOUD COVER WILL LIMIT MIXING  
THIS AFTERNOON AND LIKELY TRIM A COUPLE DEGREES FROM OUR HIGH  
TEMPS COMPARED TO YESTERDAY, BUT STILL EXPECT NEAR SEASONABLE  
WARMTH THIS AFTERNOON WITH HIGHS IN THE MID TO UPPER 50S. ONSHORE  
FLOW WILL KEEP TEMPERATURES IN THE 40S NEAR THE LAKE MICHIGAN  
SHORES.  
 
DEUBELBEISS  
 

 
   
LONG TERM
 
 
224 AM CDT  
 
SUNDAY THROUGH SATURDAY...  
 
QUIET WEATHER IS EXPECTED TO CONTINUE SUNDAY INTO MONDAY AS  
MID/UPPER CLOSED LOW MOVES FROM THE CENTRAL GREAT PLAINS TO THE  
TENNESSEE VALLEY. EXPECT THE LOCAL AREA TO FALL ON THE NORTHERN  
PERIPHERY OF THE CLOUDS FROM THIS SYSTEM, BUT DRY WEATHER WILL  
PREVAIL WITH TEMPERATURES EXPECTED TO BE NEAR THE SEASONAL NORMS.  
 
UPPER LOW WILL MEANDER NORTH TOWARDS THE OHIO VALLEY TUESDAY AND  
SOME MODELS SHOW AREAS EAST OF THE I-57 CORRIDOR GETTING SOME  
LIGHT RAIN ON TUESDAY. MEANWHILE, ANOTHER DISTURBANCE IS PROGGED  
TO DIG FROM THE NORTHERN PLAINS TUESDAY ACROSS THE MID MISSISSIPPI  
VALLEY LATE WEDNESDAY. MORE WIDESPREAD SHOWERS APPEAR POSSIBLE  
SOMEWHERE IN THE REGION, BUT THERE ARE LARGE DISCREPANCIES IN  
LOCATION, SO FOR NOW WILL MAINTAIN SLIGHT CHANCE/LOW CHANCE POPS  
TUESDAY NIGHT INTO WEDNESDAY.  
 
YET ANOTHER WAVE TAKES AIM ON THE AREA LATE IN THE WEEK WITH A  
MORE ORGANIZED COLD FRONT EXPECTED TO SWEEP ACROSS THE REGION  
THURSDAY NIGHT BRINGING ANOTHER CHANCE FOR SHOWERS. LOOKS LIKE  
ONLY A GLANCING BLOW OF COOLER TEMPS WILL OCCUR FRIDAY THEN  
TEMPERATURES MODERATE AGAIN BY SATURDAY. BROAD UPPER TROUGHING  
SETS UP BEHIND THE FRONT OVER THE GREAT LAKES NEXT WEEKEND SO THE  
COLD AIR WON'T BE TOO FAR AWAY NEXT WEEKEND.  
 
DEUBELBEISS  
 

 
   
AVIATION
 
 
FOR THE 12Z TAFS...  
 
SURFACE HIGH PRESSURE WILL CONTINUE TO PREVAIL OVER THE LOCAL  
AIRPORTS TODAY, KEEPING WINDS MAINLY LIGHT APART FROM A LAKE  
INFLUENCE INTO THE CHICAGO SITES. THIS SHOULD PUSH NORTHEAST  
WINDS THIS AFTERNOON TO 7-8 KT WITH SPORADICALLY HIGHER.  
 
AS MID CLOUDS CONTINUE TO THICKEN AND LOWER, VIRGA AND PATCHY  
SPRINKLES WILL LIKELY DEVELOP OVER FAR NORTHERN ILLINOIS THIS  
MORNING. THE VERY DRY LOW-LEVELS SHOULD PREVENT ANY VISIBILITY  
RESTRICTIONS OR SIGNIFICANTLY LOWERING CEILINGS.  
 
MTF  
 

 
   
MARINE
 
 
101 AM CDT  
 
CONTINUED QUIET WEATHER OVER LAKE MICHIGAN THROUGH MONDAY NIGHT  
WITH HIGH PRESSURE PREVAILING. THIS WILL PRESENT A VARIABLE WIND  
DIRECTION AT TIMES BUT WITH MINIMAL SPEEDS. A COLD FRONT WILL MOVE  
SOUTHWARD ACROSS THE LAKE DURING OR AROUND TUESDAY NIGHT BRINGING  
NORTHERLY WINDS IN ITS WAKE. THIS MAY PRESENT SMALL CRAFT  
ADVISORY CRITERIA CONDITIONS IN THE ILLINOIS AND INDIANA  
NEARSHORES INTO WEDNESDAY.  
 
MTF  
 

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

 
 

 
 
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