Area Forecast Discussion
Issued by NWS Chicago, IL

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000
FXUS63 KLOT 301930
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
230 PM CDT SUN AUG 30 2015

.SHORT TERM...

TONIGHT AND MONDAY...

230 PM...PRIMARY FORECAST CONCERN IS DENSE FOG POTENTIAL TONIGHT
INTO MONDAY MORNING.

CLOUD COVER HAS BEEN SLOW TO SCATTER THIS AFTERNOON WITH SOME BREAKS
SHOWING UP ACROSS NORTHWEST IL AND OVER PORTIONS OF THE LAKE. CLOUD
COVER IS STEADILY ERODING FROM THE NORTHWEST ACROSS CENTRAL WI. THE
TREND FROM GUIDANCE IS FOR THIS SCATTERING AND POSSIBLE CLEARING TO
CONTINUE ACROSS THE AREA THIS EVENING AND HAVE MAINTAINED THIS IN
THE GRIDS BUT CONFIDENCE REGARDING CLEARING IS LOW. CLOUD TRENDS
WILL LIKELY HAVE A LARGE IMPACT ON FOG POTENTIAL TONIGHT. WINDS WILL
BECOME CALM IN MANY LOCATIONS TONIGHT AND IF CLOUDS DO SCATTER/CLEAR
THEN AS TEMPS DROP TO THE DEWPOINTS...AREAS OF FOG WILL DEVELOP BUT
MAY BECOME DENSE. CONFIDENCE REGARDING HOW WIDESPREAD DENSE FOG MAY
BECOME IS LOW AND SO NO MENTION AT THIS TIME...BUT TRENDS WILL NEED
TO BE MONITORED INTO THIS EVENING. IN ADDITION...WHILE FOG DID LIFT
OVER THE NEARSHORE WATERS...THERE STILL REMAINS SOME PATCHY FOG
WHICH MAY THICKEN AND THEN SPREAD INTO FAR NORTHEAST IL THIS EVENING.

CHANCE OF SHOWERS AND PERHAPS AN ISOLATED THUNDERSTORM THIS
AFTERNOON INTO THIS EVENING HAS SHIFTED A BIT FURTHER SOUTH AND MAY
JUST AFFECT THE FAR SOUTHERN CWA THRU EARLY EVENING. MAINTAINED LOW
CHANCE POPS FOR THIS POTENTIAL...BUT AFTER THIS EVENING...DRY
WEATHER CAN BE EXPECTED THRU MONDAY EVENING.

THE CLOUD COVER HAS HELD TEMPS DOWN THIS AFTERNOON...BUT TEMPS ARE
STILL WARMING THRU THE 70S AND SOME LOWER 80S MAY STILL BE POSSIBLE
WHERE THE SUN BREAKS OUT. IF THE FOG CAN BURN OFF FAIRLY QUICKLY
MONDAY MORNING WITH AT LEAST PARTLY CLOUDY SKIES...THEN MID 80S ARE
POSSIBLE WITH COOLER TEMPS NEAR THE LAKE. THESE TEMPS COMBINED WITH
DEWPOINTS IN THE UPPER 60S/LOWER 70S MAY PUSH HEAT INDEX VALUES INTO
THE LOWER 90S MONDAY AFTERNOON. CMS

&&

.LONG TERM...
329 AM CDT

TUESDAY THROUGH SATURDAY...

WARMTH CONTINUES ON TUESDAY...AND WILL CONTINUE THROUGH THE REST
OF THE WEEK AS UPPER LEVEL RIDGE SETTLES IN. THINK CONDITIONS WILL
LIKELY BE DRY FOR MOST AREAS...ALTHOUGH...GUIDANCE CONTINUES TO
ADVERTISE AFTERNOON THUNDERSTORMS ACROSS A PORTION OF THE AREA
THIS WEEK. AM NOT COMPLETELY SOLD ON THIS QUITE YET BUT WITH
INCREASING MOISTURE/INSTABILITY...WILL NEED TO CONTINUE TO MONITOR
FOR THE NEED FOR ADDITIONAL POPS. HOWEVER...RATHER WEAK FLOW ALOFT
WILL LIMIT ANY ORGANIZED DEVELOPMENT THIS WEEK.

RODRIGUEZ

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 18Z...

* MVFR LIFTING TO VFR BY EARLY AFTERNOON.

* MVFR/IFR VSBY IN FOG LATE TONIGHT.

KREIN

//DISCUSSION...UPDATED 18Z...

HIGH PRESSURE REMAINS CENTERED OVER THE ERN CONUS WITH RIDGING
EXTENDING WEST TO THE MIDDLE MISSISSIPPI VALLEY WHILE A TROUGH OF
LOW PRESSURE DEVELOPS OVER THE WESTERN PLAINS. NRN IL/IN REMAINS
UNDER THE INFLUENCE OF THE HIGH WITH LIGHT AND VARIABLE WINDS. THE
STRATUS THAT DEVELOPED LAST NIGHT HAS BEEN SLOW TO IMPROVE THOUGH
VISIBILITY HAS IMPROVED TO VFR AT ALL OF THE TERMINALS. A
PERSISTENT INVERSION BASED AT ARND 2500FT HAS HELPED KEEP BKN-OVC
CIGS...THOUGH BASES HAVE LIFTED TO MVFR THROUGH THE MORNING. HAVE
BACKED OFF ON THE TIMING OF SKIES SCATTERING UNTIL 21Z AS THE
LATEST VIS SATELLITE IMAGERY HAS SHOWED SOME THINNING OF CLOUD
COVER TO THE SOUTH OF THE TERMINALS...BUT HAVE SOME RESERVATIONS
ABOUT THE NEW 21Z TIMING FOR SCATTERING. THE LATEST MODEL
SOUNDINGS STILL INDICATE THAT THE INVERSION SHOULD WEAKEN BY EARLY
EVENING AND THAT SKIES SHOULD STILL BE ABLE TO CLEAR OVERNIGHT...
BUT HAVE DECREASING CONFIDENCE IN THE INVERSION WEAKENING ENOUGH
TO ALLOW FOR DRIER AIR TO MIX TO THE LOWER LEVELS OF THE
ATMOSPHERE. HOWEVER...CONFIDENCE IS ALSO NOT HIGH ENOUGH TO MAKE
SGFNT CHANGES AT THIS TIME...SO WILL CONTINUE THE TREND OF BR
DEVELOPING AGAIN TONIGHT AS WINDS SHOULD BE WEAK TO NEAR CALM WITH
A VERY WEAK PRESSURE GRADIENT REMAINING IN PLACE. PLUS IF SKIES DO
CLEAR...RADIATIONAL COOLING SHOULD ALLOW FOR BR/FG TO DEVELOP
OVERNIGHT.

KREIN

//ORD AND MDW CONFIDENCE...UPDATED 18Z...

* MEDIUM CONFIDENCE IN TIMING OF CONDITIONS IMPROVING TO VFR.

* LOW-MEDIUM CONFIDENCE IN VSBY TONIGHT.

* HIGH CONFIDENCE IN ALL OTHER FORECAST ELEMENTS.

KREIN

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

MONDAY NIGHT THROUGH SATURDAY...VFR. PRIMARILY SOUTH/SOUTHWEST
WINDS.

IZZI

&&

.MARINE...
221 AM CDT

STAGNANT WEATHER PATTERN EXPECTED TO SET UP THROUGH THE UPCOMING
WEEK WITH HIGH PRESSURE OVER THE EASTERN US AND TROUGHING OVER THE
HIGH PLAINS. GENERALLY SOUTHERLY FLOW IS EXPECTED THROUGH THE PERIOD
OVER THE LAKE WITH SOME LAKE BREEZE INFLUENCE TO THE FLOW DURING THE
AFTERNOON...ESPECIALLY SOUTHERN PORTIONS OF THE LAKE. NORTHERN
PORTIONS OF THE LAKE WILL OCCASIONALLY SEE SOUTHERLY WINDS FRESHEN
UP A BIT AS GRADIENT PERIODICALLY TIGHTENS ON THE NORTHWEST FRINGE
OF THE HIGH PRESSURE RIDGE AS LOWS TRACK ACROSS CANADA.

IZZI

&&

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

$$

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