Area Forecast Discussion
Issued by NWS Chicago, IL

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FXUS63 KLOT 030606
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
106 AM CDT MON AUG 3 2015

.SHORT TERM...
151 PM CDT

.THROUGH TONIGHT...

A FEW ISOLATED SHOWERS/STORMS ARE WORKING THERE WAY EASTWARD ACROSS THE
AREA. THESE STORMS ARE HOLDING TOGETHER TO SOME DEGREE AS
INSTABILITY IS FAVORABLE. THE STORM IN DEKALB COUNTY HAS PRODUCED
SOME HAIL OF NICKEL TO QUARTER SIZE. THIS STORM WILL CONTINUE TO
PROPAGATE SOUTHEASTWARD ALONG THE INTERSTATE 88 CORRIDOR. SHEAR IS
WEAKER CLOSER TO THE LAKE...SO A DOWNWARD TREND IS POSSIBLE...BUT
IT WILL LIKELY HOLD ITS OWN FOR A BIT LONGER. THERE IS QUITE A BIT
OF INTER-CLOUD LIGHTNING WITH THIS STORM...WITH OCCASIONAL/FREQUENT
CLOUD TO GROUND LIGHTNING AS WELL.

WE DO STILL EXPECT AFTERNOON ACTIVITY TO REMAIN ISOLATED AS WATER VAPOR
IMAGERY SUGGESTS THE BETTER SHORTWAVE ENERGY IS PASSING THROUGH
CENTRAL ILLINOIS...AND EVEN MORE SO ACROSS WISCONSIN. STILL...WEAK
ENERGY IN THE NORTHWEST FLOW PATTERN KEEPS THE ISOLATED/WIDELY
SCATTERED STORM CHANCE IN PLACE IN AN UNCAPPED ATMOSPHERE. SHEAR
IS STILL LOW THIS AFTERNOON...SO THE SEVERE THREAT AT LEAST
THROUGH MID AFTERNOON APPEARS ON THE LOW SIDE...THOUGH THESE
STORMS COULD LOCALLY ENHANCE THE ALREADY SYNOPTICALLY MODEST WIND
FIELD AND MAY HAVE SOME MARGINALLY SEVERE HAIL.

FOR THE REST OF THE AREA...JUST WARM AND BREEZY CONDITIONS REMAIN
IN PLACE ACROSS THE AREA AND READINGS IN UPPER 80S/LOW 90S.
AFTERNOON MIXING IS KEEPING DEWPOINTS FROM GETTING OUT OF THE LOW
TO MID 60S...EXCEPT IN FAVORED OUTLYING AREAS WHERE AIDED
EVAPOTRANSPIRATION LOCALLY ENHANCES THE MOISTURE READINGS.

MORE ORGANIZED THUNDERSTORMS ARE EXPECTED TO SPREAD SOUTH AND EASTWARD
TOWARD THE AREA AHEAD OF BETTER HEIGHT FALLS AND A MODEST COLD
FRONT. STILL SOME CONCERNS OVER HOW WIDESPREAD THE CONVECTIVE
COVERAGE WILL BE THIS EVENING. BEST FORCING IS TIED TO THE COLD
FRONT WHICH WILL BE COMING THROUGH THE AREA JUST AFTER PEAK
HEATING TIME. FOR STORMS THAT DO FORM...AMPLE SHEAR AND
INSTABILITY WILL BE PRESENT FOR STORMS TO QUICKLY BECOME
SEVERE...AND OUTFLOW BOUNDARIES FROM STORMS TO OUR NORTH COUPLED
WITH THE COLD FRONTAL PUSH WILL COMPLICATE MATTERS. AIDED
CONVERGENCE/LIFT CAN POTENTIALLY BE ENHANCED CLOSER TO THE LAKE
WHERE ADDITIONAL MOMENTUM MAY KEEP THE HIGHER CHANCES FOR STORMS
NORTH AND EAST CLOSER TO THE LAKE...AND POTENTIALLY IN OUR
SOUTHWEST ZONES WHERE DEWPOINTS/INSTABILITY MAY BE A LITTLE
HIGHER. CONVECTIVE ALLOWING MODELS PAINTING QUITE A RANGE OF
SOLUTIONS FROM A FORWARD PROPAGATING MCS IN OUR SOUTHWEST AREAS
AND VERY LITTLE CLOSER TO CHICAGO...WITH ALTERNATE SOLUTIONS
SUGGESTING THE FORMER SCENARIO WITH LAKE ADJACENT COUNTIES
FAVORED. THE COLD FRONT WILL PUSH SOUTHEASTWARD THROUGH THE AREA
TONIGHT...WITH THUNDERSTORMS EXITING TO THE SOUTHEAST.

KMD

&&

.LONG TERM...
344 PM CDT

MONDAY THROUGH SUNDAY...

PERIOD WILL BEGIN WITH SURFACE TROUGH/FRONTAL BOUNDARY DEPARTING
TO THE EAST...WITH ASSOCIATED PRECIP LIKEWISE DEPARTING TO THE
EAST. COOLER AND DRIER CONDITIONS STILL APPEAR LIKELY FOR THE
BEGINNING OF THIS UPCOMING WEEK AS LARGE UPPER LEVEL LOW SETTLES
INTO SOUTHERN CANADA AND THE NORTHEAST CONUS. NO PRECIP EXPECTED
MONDAY INTO TUESDAY...WITH TEMPS IN THE LOW 80S LIKELY BOTH DAYS.
MODELS QUICKLY DIVERGE WITH APPROACHING SYSTEM BY MIDWEEK...WITH
THE GFS THE OUTLIER BRINGING STRONGER/MORE DEFINED LOW CLOSER TO
THE CWA. THIS WOULD PROVIDE A FURTHER NORTHWARD PUSH OF PRECIP
AXIS ESPECIALLY DURING THE WEDNESDAY TIME FRAME. WITH UNCERTAINTY
IN PLACE AND WITH SOME GUIDANCE KEEPING THE CWA DRY...HAVE MADE
LITTLE CHANGES TO THE GOING FORECAST AND KEPT LOW CHANCE POPS FOR
THE SOUTHERN HALF OF THE CWA. AFTER THIS POSSIBLE PRECIP...A DRIER
TREND IS LOOKING LIKELY TOWARDS THE END OF THE WORK WEEK WHILE
BELOW NORMAL TEMPS OCCUR.

RODRIGUEZ

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 06Z...

* MAINLY NORTHWEST WINDS BUT AT TIMES VARIABLE...SPEEDS WILL
  REMAIN BETWEEN 3-6KT OVERNIGHT. SPEEDS INCREASE BEGIN TO
  INCREASE AFTER DAYBREAK...GUSTS NEARING 20KT BY 16Z.

* A COUPLE PATCHES OF BKN CIGS ARND 4KFT AGL THRU 09Z...IMPROVING
  TO THIN CIRRUS AND VFR CONDS AFT 9Z.

BEACHLER

//DISCUSSION...UPDATED 06Z...

LINE OF STORMS HAVE PUSHED SOUTH OF THE TAF SITES WITH THE FRONTAL
BOUNDARY SLOWLY SLIDING SOUTHEAST. WINDS HAVE MAINLY SWITCHED TO
NORTHWEST BEHIND THE BOUNDARY AND DIMINISHED TO LESS THAN 9KT.
WINDS MAY BECOME VARIABLE FOR A PERIOD EARLY THIS MORNING...THEN
SOLIDIFY FROM THE NORTHWEST BY DAYBREAK. MIXING WILL INCREASE BY
16Z AND GUSTS NEARING 20KT THROUGH THIS AFTERNOON. MIXING WILL
DECREASE SHORTLY AFT SUNSET...BUT REMAIN NORTHWEST. CLOUDS LOOK TO
REMAIN MINIMAL AS WELL...WITH ONLY A COUPLE AREAS OF BKN CIGS AT
4KFT AGL THRU 9Z. THEN DRY AIR WILL CONTINUE TO POUR SOUTH AND
LIMIT CLOUDS DURING THE DAY TO ONLY A FEW/SCT DECK AT 2500-3000FT
AGL.

BEACHLER


//ORD AND MDW CONFIDENCE...UPDATED 06Z...

* HIGH CONFIDENCE IN WIND DIR/SPEED...AND HIGH ON TIMING OF GUSTS
  DEVELOPING AND DURATION OF GUSTS.

* HIGH CONFIDENCE IN CIGS FORECAST.

BEACHLER

//OUTLOOK FOR ORD/MDW FOR 12Z TUESDAY-12Z SUNDAY...UPDATED 00Z...

TUESDAY...VFR. NORTHWEST WINDS.
WEDNESDAY...MAINLY VFR. CHANCE OF SHOWERS LATE.
THURSDAY...VFR. CHANCE OF SHRA/TSRA.
FRIDAY AND SATURDAY...VFR.

LENNING

&&

.MARINE...
440 PM CDT

STRONG SOUTHWEST WINDS WILL CONTINUE LATE THIS AFTERNOON INTO THE
EVENING ACROSS MUCH OF THE LAKE INCLUDING THE NEARSHORE AREAS...AS
STRONG LOW PRESSURE MOVES THROUGH THE GREAT LAKES REGION. HIGHEST
SPEEDS ARE OCCURRING ACROSS THE SOUTHERN HALF OF THE LAKE AND
ESPECIALLY ALONG THE NEARSHORE WHERE A FEW GALE FORCE GUSTS ARE
ALSO POSSIBLE. THIS WILL PERSIST BEFORE WINDS DIMINISH LATE THIS
EVENING AND INTO THE OVERNIGHT HOURS AS THIS LOW EXITS TO THE
EAST...WITH WINDS BECOMING MORE WEST NORTHWEST.

RODRIGUEZ

&&

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

$$

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