Area Forecast Discussion
Issued by NWS Chicago, IL

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000 FXUS63 KLOT 061522 AFDLOT AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE, IL 1022 AM CDT FRI MAY 6 2016 .UPDATE...
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1014 AM CDT THE ONLY CHANGE TO THE FORECAST TODAY WAS TO ADD IN SOME SPRINKLES THROUGH THE REST OF THE MORNING...AS SOME ISOLATED VERY LIGHT SHOWERS CONTINUE TO DEVELOP OVER THE AREA IN ASSOCIATION WITH STRONG WARM AIR ADVECTION. THIS ACTIVITY SHOULD SHIFT EAST OF THE AREA THIS AFTERNOON...WITH TEMPERATURES STILL EXPECTED TO TOP OUT AROUND 80 IN THE CHICAGO AREA...AND INTO THE LOWER 80S OUT BY ROCKFORD. WHILE THERE REMAINS A SMALL CHANCE THAT A LAKE BREEZE COULD DEVELOP THIS AFTERNOON ALONG THE LAKE SHORE...IT APPEARS THE WEST-SOUTHWEST WINDS COULD BE JUST STRONG ENOUGH TO KEEP IT FROM SHIFTING VERY FAR INLAND. AS A RESULT...THERE MAY NOT BE MUCH LAKE COOLING ON THE LAKESHORE TODAY. KJB
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&& .SHORT TERM... 327 AM CDT THROUGH SATURDAY NIGHT... MAIN FORECAST CONCERNS/CHALLENGES ARE WITH CLOUD COVER AND HIGH TEMPS TODAY...INCREASING CHANCES FOR SHOWERS AND THUNDERSTORMS SATURDAY...AND THEN WITH PERIODIC CHANCES FOR SHOWERS AND THUNDERSTORMS NEXT WEEK. RELATIVELY QUIET THIS MORNING WITH SURFACE RIDGE AXIS SITUATED ACROSS THE REGION/CWA. SKIES HAVE REMAINED CLEAR OVERNIGHT BUT LOOKING UPSTREAM ACROSS WISCONSIN...CAN SEE AN EXPANDING AREA OF MID LEVEL CLOUDS RAPIDLY PUSHING SOUTH INTO THE CWA. SOUTHWARD DROPPING SPEED MAX AND STRONG WAA LIKELY OWING FOR THIS EXPANSION AND DONT SEE WHY THIS WILL DIMINISH AS IT PUSHES THROUGH THE CWA. SO HAVE INCREASED CLOUD COVER THIS MORNING BUT MAY NEED TO DO SOME LAST MINUTE ADJUSTMENTS TO FURTHER INCREASE...WITH A PERIOD OF AT LEAST PARTLY SUNNY SKIES LIKELY THIS MORNING FOR MOST AREAS IN NORTHERN ILLINOIS AND NORTHWEST INDIANA. CAN SEE A STEADILY MOVING BACK EDGE TO THIS MID LEVEL MOISTURE WHICH IS CONSISTENT WITH SHORT TERM GUIDANCE INDICATING THIS WILL EXIT TO THE SOUTH/SOUTHEAST BY AROUND MIDDAY...WITH SUNNY TO PARTLY CLOUDY SKIES THEN LIKELY IN THE AFTERNOON. ALSO UP NORTH ARE SOME WEAK RETURNS ON RADAR AT THIS TIME BUT DONT THINK THIS IS REALLY REACHING THE GROUND. HAVE MAINTAINED A DRY FORECAST THIS MORNING BUT AN ISOLATED SPRINKLE COULD BE POSSIBLE. WARMER TEMPS STILL EXPECTED TODAY DESPITE THIS CLOUD COVER. ALTHOUGH IT MAY INITIALLY HINDER TEMP TRENDS IN THE MORNING...THE STRONG WAA WILL USHER IN A MUCH WARMER AIRMASS THAT WILL STILL ALLOW TEMPS TO RISE TO THE 80S IN NORTHERN ILLINOIS AND MID TO UPPER 70S ACROSS NORTHWEST INDIANA. WITH SURFACE RIDGE AXIS AND LIGHTER FLOW AROUND...AM A LITTLE CONCERNED FOR A PERIOD OF ONSHORE FLOW TODAY AND DID LOWER TEMPS NEAR THE LAKE. HAVE MORE LOW TO MID 70S FOR AREAS NEAR THE LAKE. AS ONE UPPER LEVEL LOW/TROUGH EXITS TO THE EAST...ANOTHER UPPER LEVEL SYSTEM WILL DROP SOUTH INTO THE UPPER MIDWEST AND GREAT LAKES REGION TONIGHT INTO SATURDAY. THIS WILL ALLOW SURFACE LOW AND FRONTAL BOUNDARY TO DROP SOUTH THROUGH WISCONSIN TONIGHT AND AS THIS OCCURS...UPSTREAM MOISTURE/INSTABILITY AXIS WILL SWING THROUGH. GUIDANCE FAIRLY CONSISTENT WITH THIS AND EXPECT INCREASING CHANCES FOR SHOWERS AND THUNDERSTORMS EARLY SATURDAY MORNING. HAVE INCREASED POPS DURING THIS TIME BUT KEPT AT HIGH CHANCE OWING TO LOWER CONFIDENCE ON COVERAGE. HOWEVER...ITS APPEARING THAT MOST LOCATIONS WILL OBSERVE AT LEAST A SMALL WINDOW OF PRECIP SATURDAY MORNING. THUNDER DOES APPEAR POSSIBLE SATURDAY MORNING BUT AM NOT ANTICIPATING ANYTHING SEVERE DURING THAT TIME. AM MONITORING THE SATURDAY AFTERNOON PERIOD FOR POSSIBLE ADDITIONAL THUNDERSTORM DEVELOPMENT...SOME OF WHICH COULD BE STRONG. ALTHOUGH THE SIGNAL FOR STRONG THUNDERSTORMS APPEARS TO BE HIGHER FURTHER TO THE SOUTH OF THE CWA...MOISTURE POOLING AHEAD OF THIS FRONT AND INCREASING INSTABILITY AHEAD OF APPROACHING SPEED MAX COULD ALLOW FOR SOME ISOLATED STRONG STORMS SOUTH OF A PONTIAC IL TO FOWLER INDIANA LINE. THIS POTENTIAL SHOULD QUICKLY END BY THE EARLY EVENING WITH THE ARRIVAL OF DRIER AIR...BUT WITH SHOWERS STILL POSSIBLE FOR AREAS OVER THE FAR SOUTHERN CWA. RODRIGUEZ && .LONG TERM... 327 AM CDT SUNDAY THROUGH FRIDAY... THE END OF THE WEEKEND WILL BE DRY BUT AN ACTIVE PATTERN WILL REMAIN IN PLACE OVER THE CONUS. GUIDANCE SHOWING ANOTHER LARGE UPPER LEVEL SYSTEM WORKING ITS WAY TOWARD THE REGION SUNDAY NIGHT INTO MONDAY WITH SHOWERS AND THUNDERSTORMS INCREASING ONCE AGAIN LATE IN THE NIGHT INTO MONDAY MORNING. LOW CONFIDENCE WITH EXACTLY HOW MONDAY WILL EVOLVE GIVEN ANTICIPATED ONGOING SHOWER/THUNDERSTORM ACTIVITY BUT GIVEN INCREASING MOISTURE/INSTABILITY BEHIND LIFTING FRONTAL BOUNDARY AND PERSISTENT FORCING ALOFT...WILL NEED TO MONITOR ANOTHER PERIOD FOR POSSIBLE STRONG THUNDERSTORMS SOMEWHERE ACROSS THE REGION. GIVEN THE ANTICIPATED CLOSED NATURE OF THIS NEXT SYSTEM AM NOT OVERLY CONFIDENT WITH MODEL SOLUTIONS AT THIS TIME. NONETHELESS...AN ACTIVE PERIOD IS APPEARING PROBABLY EARLY NEXT WEEK WITH THIS SYSTEM LIKELY TO LINGER AROUND THE CWA ON TUESDAY AS WELL. IF THIS WERE TO OCCUR...THUNDERSTORM DEVELOPMENT WILL AGAIN BE POSSIBLE. RODRIGUEZ && .AVIATION... FOR THE 12Z TAFS... HIGH PRESSURE REMAINS OVERHEAD...HOWEVER A WEAK MID-LEVEL SYSTEM WAS SLIDING SOUTH AND PRODUCING SOME SPRINKLES AND CLOUDS AROUND 8-12KFT AGL. BASED ON LATEST GUIDANCE SPRINKLES SHOULD ONLY LAST THROUGH ABOUT 15Z AND REMAIN VERY MINIMAL IN COVERAGE. WINDS WILL START OUT FROM THE WEST WITH SPEEDS AROUND 5 TO 7KT...THEN AS THE DAY PROGRESSES WINDS SHOULD INCREASE SLIGHTLY AND TURN SOUTHWESTERLY. WINDS ALOFT SHOULD REMAIN STRONG ENOUGH FROM THE SOUTHWEST TO PREVENT A LAKE BREEZE FROM MOVING INLAND...SO HAVE HELD ONTO THE SOUTHWEST WINDS THROUGH THIS AFTERNOON. HIGH PRESSURE WILL STEADILY DRIFT SOUTH AS A FRONTAL BOUNDARY BEGINS TO SLIDE SOUTH ACROSS NORTHERN WISCONSIN LATE TONIGHT. THIS FRONTAL BOUNDARY WILL LIKELY NOT ARRIVE ACROSS NORTHERN ILLINOIS UNTIL CLOSER TO DAYBREAK WITH WINDS BEGINNING TO TURN NORTHWESTERLY AND EVENTUALLY NORTH...ALONG WITH INCREASING IN SPEEDS. THERE WILL BE A CHANCE FOR A FEW THUNDERSTORMS SHORTLY AFTER DAYBREAK SATURDAY. BEACHLER && .MARINE...
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258 AM CDT HIGH PRESSURE CONTINUES TO BE IN CONTROL OF MUCH OF THE GREAT LAKES REGION TODAY...STRETCHING SOUTH THROUGH THE GULF OF MEXICO. HOWEVER THIS RIDGE OF HIGH PRESSURE WILL STEADILY DRIFT SOUTH WHILE A LOW PRESSURE WILL SLIDE EAST ACROSS WESTERN ONTARIO TOWARDS QUEBEC BY EARLY SATURDAY. THIS WILL PRODUCE A TRAILING FRONTAL BOUNDARY THAT WILL SAG SOUTH ACROSS LAKE MICHIGAN EARLY SATURDAY FOR THE NORTHERN HALF OF THE LAKE...THEN STEADILY PUSH SOUTH TO THE SOUTHERN HALF OF LAKE MICHIGAN. WINDS WILL REMAIN RELATIVELY LIGHT THIS MORNING...BUT INCREASE THROUGHOUT THE AFTERNOON FROM THE SOUTH/SOUTHEAST TO 15 TO 25 KT. THIS WILL RESULT IN WAVES BUILDING ALONG THE NORTHERN HALF OF LAKE MICHIGAN...HOWEVER WITH THE MUCH WARMER AIR FLOWING OVER THE LAKE WAVES WILL LIKELY NOT BUILD MUCH BEYOND 3 TO 5 FT. THE WEAK GRADIENT MAY TURN WINDS SOUTHEASTERLY WITHIN THE ILLINOIS NEARSHORE WATERS THIS AFTERNOON...BUT THEN AS THE FRONTAL BOUNDARY SAGS SOUTH OVERNIGHT/EARLY SATURDAY...WINDS WILL INCREASE FROM THE SOUTH AND THEN BEHIND THE FRONT QUICKLY TURN NORTHWESTERLY TO NORTHERLY. WAVES WILL BE INCREASING SATURDAY FOR THE SOUTHERN HALF OF THE LAKE...AND COULD COME CLOSE TO SMALL CRAFT HAZARDS FOR THE INDIANA NEARSHORE WATERS. WINDS WILL THEN BEGIN TO DIMINISH LATER SATURDAY EVENING...THEN TURN EASTERLY. BEACHLER
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&& .LOT WATCHES/WARNINGS/ADVISORIES... IL...NONE. IN...NONE. LM...NONE. && $$ VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE) FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT: WWW.FACEBOOK.COM/NWSCHICAGO WWW.TWITTER.COM/NWSCHICAGO WWW.YOUTUBE.COM/NWSCHICAGO

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