Area Forecast Discussion
Issued by NWS Chicago, IL

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000
FXUS63 KLOT 300912
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
412 AM CDT SUN AUG 30 2015

.SHORT TERM...
329 AM CDT

THROUGH MONDAY NIGHT...

MAIN FORECAST CONCERNS/CHALLENGES ARE WITH PATCHY DENSE FOG EARLY
THIS MORNING...AND THEN WITH ISOLATED/WIDELY SCATTERED
THUNDERSTORMS POSSIBLE LATER THIS AFTERNOON.

SHOWER COVERAGE HAS DIMINISHED OVER THE LAST SEVERAL HOURS ACROSS
THE CWA WITH GENERALLY DRY CONDITIONS AT THIS TIME. THESE DRY
CONDITIONS WILL LIKELY CONTINUE THROUGH THIS MORNING...OUTSIDE OF
A BRIEF/ISOLATED SHOWER MAINLY WELL SOUTH OF INTERSTATE 80. LOW
STRATUS STILL IN PLACE EARLY THIS MORNING WITH RATHER MOIST
CONDITIONS IN PLACE ALLOWING FOR AREAS OF FOG...AND PATCHY DENSE
FOG. AT THIS TIME...ANY DENSE FOG CONTINUES TO REMAIN ISOLATED
OVER NORTH CENTRAL WITH LOCATIONS THAT DO BRIEFLY FALL BELOW 1
MILE QUICKLY IMPROVING. OTHER AREA OF CONCERN FOR DENSE FOG
CONTINUES TO BE NEAR THE LAKESHORE WHERE ITS STILL POSSIBLE FOR
THIS FOG TO SPREAD MORE INLAND THIS MORNING...WHILE OTHER DENSE
FOG EXPANDS. HOWEVER...ALL LOCATIONS NEAR THE SHORE CONTINUE TO
SHOW VIS ABOVE 1 MILE. WITH THE POSSIBILITY FOR ANY PATCHY DENSE
FOG TO EXPAND THIS MORNING...WILL NEED TO CONTINUE TO ASSESS THE
NEED FOR AN ADVISORY...BUT AM NOT ISSUING ONE AT THIS TIME.

FOG WILL DISSIPATE LATER THIS MORNING BUT WITH THIS STRATUS
LIKELY HOLDING A LITTLE LONGER. DO HAVE SKIES CLEARING LATER TODAY
BUT DONT THINK THAT WILL REALLY OCCUR UNTIL LATE MORNING/MIDDAY.
SUNNY TO PARTLY CLOUDY SKIES WILL THEN LIKELY BE OBSERVED THIS
AFTERNOON. DID LOWER MAX TEMPS SLIGHTLY TODAY WITH STRATUS
POSSIBLY LIMITING OVERALL DAYTIME HEATING. HOWEVER...THINK CLOUDS
WILL SCATTER IN TIME FOR HIGHS AROUND 80 UP NORTH AND LOWER 80S
DOWN SOUTH TO BE REALIZED THIS AFTERNOON. GUIDANCE CONTINUES TO
INDICATE THAT SCATTERED THUNDERSTORM DEVELOPMENT WILL BE POSSIBLE
LATER THIS AFTERNOON...ACROSS EAST CENTRAL ILLINOIS AND NORTHWEST
INDIANA SOUTH OF I80. THIS SEEMS REASONABLE WITH HIGH DEWPOINT AIR
IN PLACE...CLEARING SKIES ALLOWING FOR INCREASING
INSTABILITY...AND WITH LINGERING BOUNDARY IN PLACE.
HOWEVER...SHORT TERM GUIDANCE CONTINUES TO TREND THIS DEVELOPMENT
FURTHER SOUTH OF THE CWA TODAY AND CANT COMPLETELY ARGUE WITH
THIS...AS SURFACE CONVERGENCE WILL LIKELY REMAIN WEAK ALONG WITH
SUPPORT ALOFT LIKELY LACKING. NONETHELESS...DID KEEP SLIGHT
CHANCE/LOW CHANCE POPS BRIEFLY THIS AFTERNOON. IF THIS DEVELOPMENT
WERE TO OCCUR...COULD NOT RULE OUT AN ISOLATED STRONGER STORM
WHICH COULD PRODUCE GUSTY WINDS AND BRIEF HEAVIER DOWNPOURS. DRY
CONDITIONS THEN EXPECTED TONIGHT AND MONDAY WITH WARMING TREND
CONTINUING...WITH MID TO UPPER 80S LIKELY FOR MOST AREAS ON
MONDAY.

RODRIGUEZ

&&

.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 09Z...

* IFR STRATUS AND FOG THROUGH EARLY THIS MORNING
* CHANCE OF FOG AGAIN TONIGHT

IZZI

//DISCUSSION...UPDATED 09Z...

VSBY HAVE LARGELY HELD STEADY AT THE TERMINALS THE LAST SEVERAL
HOURS AND WITH CIGS ACTUALLY TRENDING UPWARD A BIT THINKING THE
THREAT OF DENSE FOG IS DIMINISHING. HAVE TRENDED CIG/VSBY TRENDS
HIGHER IN THE TAFS...THOUGH STILL A CHANCE THAT VSBY COULD BRIEFLY
DROP AROUND SUNRISE.

IZZI

UPDATED 06Z...

VERY MOIST AIR MASS IN PLACE WITH LIGHT WINDS HAS ALLOWED STRATUS
TO FESTER AND SLOWLY BUILD DOWN WITH SOME FOG ALSO DEVELOPING. FOG
HAS BEEN MORE PREVALENT NEAR THE LAKE AND WITH LIGHT WINDS NOT
EXPECTING LAKE INFLUENCE TO REACH ORD/MDW. VSBY HAS BEEN FAIRLY
STEADY AND IT IS POSSIBLE THAT THE STRATUS DECK MAY PREVENT DENSE
FOG FROM FORMING AT THE TERMINALS...THOUGH WILL NEED TO WATCH FOR
STRATUS BUILDING DOWN TO SURFACE. TRENDED CONDITIONS A BIT MORE
OPTIMISTIC IN THE TAFS OVERNIGHT...BUT ADMITTEDLY CONFIDENCE IS
LOW. STILL HIGH SUN ANGLE SHOULD RESULT IN FAIRLY QUICK
IMPROVEMENT TO VFR AFTER SUNRISE DESPITE THE LIGHT WINDS. COULD BE
A WEAK LAKE BREEZE THIS AFTERNOON BUT OTHERWISE EXPECTING
GENERALLY CALM OR LIGHT/VARIABLE WINDS THROUGH THE TAF CYCLE.
COULD SEE SOME LIGHT FOG REDEVELOP AGAIN TONIGHT WITH NOT MUCH
DRYING EXPECTED TODAY AND CONTINUED LIGHT WINDS WITH CLEAR OR
CLEARING SKIES.

IZZI

//ORD AND MDW CONFIDENCE...UPDATED 09Z...

* MEDIUM CONFIDENCE IN GENERAL VSBY/CIG TRENDS
* HIGH CONFIDENCE IN IMPROVEMENT TO MVFR/VFR BY MID-LATE MORNING
* LOW-MEDIUM CONFIDENCE IN SOME VSBY RESTRICTIONS DEVELOPING AGAIN
  TONIGHT
* HIGH CONFIDENCE IN REMAINING ELEMENTS

IZZI

//OUTLOOK FOR ORD/MDW FOR 12Z MONDAY-12Z SATURDAY...UPDATED 00Z...

MONDAY...VFR. SOUTH WINDS.
TUESDAY...VFR. SOUTHWEST WINDS.
WEDNESDAY...SLT CHC TSRA. PRIMARILY VFR. SOUTH WINDS.
THURSDAY...SLT CHC TSRA. PRIMARILY VFR. SOUTHEAST WINDS.
FRIDAY...SLT CHC TSRA. PRIMARILY VFR. SOUTHEAST WINDS.

BMD

&&

.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...DENSE FOG ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-LMZ745-
     LMZ777-LMZ779 UNTIL 9 AM SUNDAY.

&&

$$

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