665  
FXUS63 KLOT 191107  
AFDLOT  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE, IL  
607 AM CDT FRI APR 19 2019  
   
SHORT TERM
 
 
331 AM CDT  
 
THROUGH SATURDAY...  
 
GOES DIFFERENTIAL WATER VAPOR RGB SHOWS DEEP TROUGH DIGGING SOUTH  
TO THE NORTHWEST GULF OF MEXICO WITH A PAIR OF VORT MAX AND  
ASSOCIATED JET STREAK STILL DIGGING SOUTH DOWN THE WESTERN FLANK  
OF THE UPPER TROUGH. NUMERICAL GUIDANCE HAS THIS ENERGY CLOSING  
OFF A MID-UPPER LEVEL LOW OVER THE SOUTHEAST U.S. TODAY BEFORE  
BEGINNING A SLOW TURN NORTHEAST AND NORTHWARD TONIGHT INTO  
SATURDAY. ASSOCIATED STRONG SURFACE LOW WILL TRACK NORTH INTO THE  
OHIO VALLEY TONIGHT AND THE MEANDER AROUND A BIT SATURDAY BEFORE  
THE ENTIRE SYSTEM BEGINS MOVING EAST.  
 
SHOWERS ON THE NORTHWEST FLANK OF THE TROUGH, AFFECTING OUR  
SOUTHEASTERN CWA, ARE EXPECTED TO PUSH EAST TODAY, BUT RAIN  
CHANCES WILL INCREASE AGAIN SATURDAY MORNING AS THE ENTIRE DEEP  
TROPOSPHERIC CIRCULATION WOBBLES WEST A BIT. SOUTHEAST CWA WILL  
STAY SOCKED IN WITH CLOUD COVER TODAY WHILE SKIES LOOK TO CLEAR  
FROM THE NORTHWEST THIS AFTERNOON. THE BIGGER IMPACT FROM THIS  
SYSTEM WILL BE STRONG NORTHERLY WINDS TODAY THROUGH MUCH OF THE  
DAY SATURDAY. FORECAST SOUNDINGS FOR THIS AFTERNOON SUPPORT GUSTS  
WELL INTO THE 30 MPH RANGE WITH SOME GUSTS OVER 40 MPH A DECENT  
BET. CAN'T RULE OUT BRIEFLY TAGGING WIND ADVISORY CRITERIA TODAY,  
BUT FOR MOST PART SHOULD STAY JUST BELOW, SO NO HEADLINE PLANNED  
AT THIS TIME.  
 
THE STRONG NORTHERLY WINDS AND CLOUD COVER WILL KEEP TEMPS FROM  
REBOUNDING MUCH FROM CURRENT READINGS NEAR THE LAKE AND IN  
NORTHWEST INDIANA. POINTS FARTHER NORTHWEST, WHERE SKIES WILL  
CLEAR OUT SOME TODAY SHOULD SEE TEMPS REBOUND INTO THE 50S THIS  
AFTERNOON. TEMPS SHOULD MODERATE SOME SATURDAY WITH CLOUD COVER  
AND STRONG NORTHERLY WINDS CONTINUING TO RESULT IN THE CHILLIEST  
TEMPS OVER NORTHWEST INDIANA AND NEAR THE LAKE.  
 
NO CHANGES PLANNED TO THE LAKESHORE FLOOD ADVISORY WITH NORTHERLY  
GALES LIKELY TO RESULT IN VERY LARGE AND BATTERING WAVES. IN  
ADDITION, LAKE LEVELS CONTINUE TO RISE (AND ARE APPROACHING LEVELS  
NOT SEEN IN QUITE SOME TIME) AND WITH NORTHERLY WINDS DOWN THE  
FULL FETCH OF THE LAKE SHOULD SEE WATER PILING UP (STORM SURGE)  
OVER THE SOUTHERN PORTIONS OF THE LAKE. A BIT OF UNCERTAINTY WITH  
RESPECT TO HOW LARGE THE WAVES GET DUE TO MARGINAL STABILITY  
PROFILES IN THE MARINE LAYER RESULT IN A BIT OF UNCERTAINTY  
REGARDING HOW LARGE WAVES WILL BUILD UP TODAY. NEARSHORE BUOYS  
HAVE BEEN DEPLOYED, SO DAY SHIFT WILL BE ABLE TO SEE HOW WAVE  
FORECAST IS VERIFYING, IF THE WAVE FORECAST VERIFIES THEN  
LAKESHORE FLOOD ADVISORY WILL NEED TO BE EXTENDED FOR NORTHWEST  
INDIANA INTO SATURDAY AND PERHAPS FOR COOK COUNTY AS WELL GIVEN  
THE WIND TRAJECTORY.  
 
- IZZI  
 

 
   
LONG TERM
 
 
331 AM CDT  
 
SATURDAY NIGHT THROUGH THURSDAY...  
 
AS DEEP CYCLONE MOVES EAST OF THE REGION, LOOK FOR SOUTHERLY WINDS  
AND STRONG WARM AIR ADVECTION TO RESULT IN ANOTHER BIG WARM UP IN  
TEMPS SUNDAY. A BIT CONCERNED THE CUT OFF LOW COULD END UP BEING A  
BIT SLOWER TO MOVE OUT THAN FORECAST, SO DIDN'T MAKE ANY CHANGES  
TO THE BLENDED MODEL GUIDANCE, HOWEVER, SHOULD THE LOW MOVE OUT AS  
FAST OR FASTER THAN FORECAST THAN SOME UPPER 70S TO NEAR 80 WEST  
FOR HIGHS ARE POSSIBLE SUNDAY.  
 
NEXT SHORTWAVE TROUGH WILL MOVE ACROSS THE REGION WITH SOME SHOWER  
AND THUNDERSTORM CHANCES PERHAPS AS EARLY AS SUNDAY NIGHT, BUT  
MORE LIKELY MONDAY INTO MONDAY NIGHT. SEASONABLY COOL AND DRY  
WEATHER IS EXPECTED IN THE WAKE OF THAT SYSTEM MIDWEEK BEFORE  
TEMPS BEGIN TO REBOUND LATE IN THE WEEK.  
 
- IZZI  
 

 
   
FIRE WEATHER
 
 
505 AM CDT  
 
STRONG NORTHERLY WINDS TODAY, POSSIBLY GUSTING TO 40 MPH AT TIMES,  
WILL RESULT IN A SOMEWHAT HEIGHTENED FIRE DANGER. THIS IS  
PARTICULARLY THE CASE OVER WESTERN CWA WHERE LESS RAIN FELL AND  
LOWER RH AND HIGHER TEMPS ARE EXPECTED TODAY DUE TO MORE SUNSHINE.  
WHILE STRONG WINDS WILL OCCUR OVER EASTERN IL AND NORTHWEST IN,  
COOLER TEMPS, WETTER FUELS, AND HIGH RH SHOULDN'T MITIGATE THE  
FIRE DANGER.  
 
SATURDAY WILL BE ANOTHER DAY OF STRONG NORTHERLY WINDS. MILDER  
TEMPERATURES AND LOWER RELATIVE HUMIDITY VALUES COMPARED TO TODAY  
WILL RESULT IN A GREATER FIRE DANGER. THE DRIEST FUELS ON SATURDAY  
WILL AGAIN BE ACROSS NORTH CENTRAL IL, WHICH IS WHERE THE WINDS  
ARE FORECAST TO BE LIGHTER. WINDS AND MIN RELATIVE HUMIDITY  
VALUES COULD BOTH APPROACH RED FLAG WARNING CRITERIA OVER EASTERN  
IL AND POSSIBLY OVER NORTHWEST INDIANA DEPENDING ON THE EXTENT OF  
CLOUD COVER. HOWEVER, THIS AREA SAW MORE SIGNIFICANT RAINFALL  
THURSDAY AND FUELS WILL LIKELY NOT HAVE HAD SUFFICIENT TIME TO DRY  
BY SATURDAY, SO NO FIRE WEATHER WATCH IS PLANNED.  
 
- IZZI  
 

 
   
AVIATION
 
 
FOR THE 12Z TAFS...  
 
WINDS WILL REMAIN NORTH THROUGH THE PERIOD, WITH A FAVORED DIRECTION  
AROUND AROUND 010. WIND SPEEDS WILL CONTINUE TO INCREASE THROUGH MID-  
MORNING AND GUST OVER 30 KNOTS AREA-WIDE THROUGH MUCH OF THE DAY.  
WHILE GUSTS ARE EXPECTED TO REMAIN UNDER 35 KNOTS, THERE REMAINS A  
POTENTIAL FOR GUSTS SURPASSING 35 KNOTS DURING THE AFTERNOON. THE  
GUSTY WINDS WILL CONTINUE INTO THIS EVENING, BUT GRADUAL DECOUPLING  
WILL SUPPORT A DECREASE IN SPEED. THIS SHOULD RESULT IN LLWS BY LATE  
EVENING AS WIND SPEEDS REMAIN 40 KNOTS OR HIGHER AROUND 1 KFT.  
 
OTHERWISE, MVFR CEILINGS WILL PERSIST EARLY THIS MORNING, BUT  
WILL QUICKLY CLEAR FROM WEST TO EAST DURING THE MID-MORNING TO  
EARLY AFTERNOON AS MUCH DRIER AIR ADVECTS INTO THE AREA.  
 
KLUBER/KJB  
 

 
   
MARINE
 
 
321 AM CDT  
 
NORTHERLY GALES WILL PERSIST ACROSS THE SOUTHERN LAKE MICHIGAN  
NEAR SHORES TODAY, BEFORE EASING A BIT TONIGHT. THE GRADIENT OVER  
SOUTHERN LAKE MICHIGAN WILL REMAIN RATHER TIGHT ON SATURDAY AS  
WELL, SO SOME BREEZY NORTHERLY WINDS AROUND 30 KT ARE LIKELY TO  
PERSIST THROUGH SATURDAY BEFORE WINDS FINALLY DIMINISH SATURDAY  
EVENING. WE ALSO CAN'T RULE OUT ANOTHER PERIOD OF GALE FORCE GUSTS  
OVER SOUTHERN LAKE MICHIGAN ON SATURDAY. THE GALE WARNING  
CURRENTLY RUNS THROUGH THIS EVENING. A SMALL CRAFT ADVISORY WILL  
LIKELY BE ISSUED FOLLOWING THE GALE AND LASTING THROUGH SATURDAY  
EVENING FOR STRONG WINDS AND HIGH WAVES.  
 
KJB  
 

 
   
LOT WATCHES/WARNINGS/ADVISORIES
 
 
IL...LAKESHORE FLOOD ADVISORY...ILZ006-ILZ014 UNTIL 1 AM SATURDAY.  
 
IN...LAKESHORE FLOOD ADVISORY...INZ001-INZ002 UNTIL 1 AM SATURDAY.  
 
LM...GALE WARNING...NEARSHORE WATERS UNTIL  
10 PM FRIDAY.  
 

 
 

 
 
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