Area Forecast Discussion
Issued by NWS Chicago, IL

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000
FXUS63 KLOT 310912
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
412 AM CDT MON AUG 31 2015

.SHORT TERM...
320 AM CDT

THROUGH TONIGHT...

BIG FORECAST CHALLENGE THROUGH TONIGHT IS FOG EARLY THIS
MORNING...THEN SMOKE AND ITS POTENTIAL IMPACT ON TEMPS. DENSE SMOKE
WAS APPARENT SUNDAY AFTERNOON TO OUR WEST AND NORTHWEST OVER
WISCONSIN AND IOWA. TO SEE A MAP SHOWING SMOKE LOCATION AND DENSITY
CHECK OUT OUR TWITTER (@NWSCHICAGO) AND FACEBOOK (/NWSCHICAGO)
INCLUDING A LINK TO WHERE THAT MAP AND OTHER INFORMATION CAN BE
FOUND.

FOR TODAY EXPECT FOG TO BURN OFF RATHER QUICKLY THIS MORNING LEAVING
MOSTLY SUNNY SKIES (THOUGH LIKELY HAZY THANKS TO THE SMOKE) IN ITS
WAKE. HAVE LEANED TOWARD THE COOL SIDE OF GUIDANCE TODAY DUE TO
SMOKE...THOUGH IT IS UNCLEAR HOW DENSE SMOKE WILL BE TODAY. LESS
SMOKE MEANS TEMPS COULD BE A DEGREE OR TWO WARMER AND DENSER SMOKE A
BIT COOLER PERHAPS. GRADIENT LOOKS TO BE LIGHT ENOUGH TO ALLOW A
LAKE BREEZE TODAY WHICH SHOULD KEEP TEMPERATURES IN THE 70S ALONG
THE IMMEDIATE LAKEFRONT. SOME PATCHY FOG COULD DEVELOP AGAIN
TONIGHT...THOUGH AS LOW LEVELS SLOWLY DRY OUT A BIT WILL PROBABLY
SEE LESS FOG THAN THIS MORNING.

IZZI

&&

.LONG TERM...
320 AM CDT

TUESDAY THROUGH SUNDAY...

TODAY MAY BE THE LAST DAY OF METEOROLOGICAL SUMMER...BUT IT WOULD
APPEAR THAT MOTHER NATURE FAILED TO GET THE MEMO AS A STRETCH OF
VERY WARM TO ALMOST HOT WEATHER THROUGH NEXT WEEKEND WITH
UNUSUALLY STRONG UPPER LEVEL RIDGE OVER THE REGION. LINGERING
SLIGHT WEAKNESS IN THE UPPER RIDGE FROM INDIANA SOUTH TO THE LOWER
OHIO VALLEY COULD ALLOW FOR A SLIGHT CHANCE OF MAINLY
AFTERNOON/EARLY EVENING ISOLATED STORMS THROUGH TUESDAY...THOUGH
POPS OF 20 PERCENT OR LESS LOOK APPROPRIATE. MEDIUM RANGE GUIDANCE
HINTS AT POSSIBLE CONVECTION WITH VERY SUBTLE DISTURBANCES LATE IN
THE WEEK...BUT AGAIN KEPT POPS BELOW MENTIONABLE LEVELS GIVEN THE
WEAK FORCING AND INABILITY TO REALLY PINPOINT ANY ORGANIZED
FORCING AT THIS DISTANCE.

BIG STORY THIS WEEK WILL BE THE WELL ADVERTISED HEAT WAVE THAT
SHOULD GET GOING IN FULL FORCE TOMORROW. ECMWF/NAM/GFS ALL PROG
925MB TEMPS AROUND 25-26C WHICH IS PUSHING THE LIMITS OF CLIMO FOR
EARLY SEPTEMBER. USING THE NEW SPC SOUNDING CLIMO TOOL
(WWW.SPC.NOAA.GOV/EXPER/SOUNDINGCLIMO) THE 7 DAY RUNNING AVERAGE
925MB FOR THIS WEEK IS AROUND 19-20C WITH 24C THE 90TH PERCENTILE.
OUR 925MB TEMPS ARE PROGGED TO BE CLOSE TO 3 STANDARD DEVIATIONS
ABOVE AVERAGE WITH CLIMO SUPPORTING HIGHS IN THE LOW/MID 90S WITH
925MB TEMPS OF 25C...HOWEVER DEWPOINTS LOOK TO BE A BIT HIGHER
THAN NORMAL FOR A SEPTEMBER HEAT WAVE AND ALSO THERE IS THE BIG
SMOKE WILDCARD...SO KEPT TEMPS A BIT BELOW WHAT 925MB TEMP CLIMO
WOULD SUPPORT.

SURFACE GRADIENT COULD BE STRONG ENOUGH TO PREVENT ANY SIGNIFICANT
LAKE BREEZE TUES AND WED ALLOWING THE HEAT TO REACH RIGHT UP TO
THE BEACHES...WEAKER GRADIENT LOOKS TO ALLOW SOME LAKE COOLING
LATE IN THE WEEK AND POSSIBLY OVER THE WEEKEND. OUTSIDE OF ANY
LAKE COOLING TEMPS LOOK LIKELY TO REMAIN IN THE UPPER 80S/NEAR 90
THROUGH THE UPCOMING WEEKEND.

IZZI

&&

.AVIATION...

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

* FOG THIS MORNING...WITH MVFR/IFR VIS LIKELY.

RODRIGUEZ

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

HIGH PRESSURE CENTERED ACROSS THE REGION WILL HELP FOR DRY/VFR
CONDITIONS WITH LIGHT WINDS THIS FORECAST PERIOD. HOWEVER...FOG
IS DEVELOPING OVER MUCH OF THE AREA EARLY THIS MORNING AND EXPECT
THIS TO PERSIST THROUGH THE MORNING. DO THINK VIS WILL RANGE FROM
1-3 MILES...BUT WILL NEED TO MONITOR VIS POSSIBLY DROPPING BELOW
THIS FOR A TIME LATER THIS MORNING. FOG WILL DISSIPATE BEFORE MID
MORNING...WITH LIGHTER WINDS MAKING WAY FOR A WIND SHIFT TO THE
EAST WITH LAKE INFLUENCE. SPEEDS WILL REMAIN WELL BELOW 10 KT
THOUGH.

RODRIGUEZ

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

* MEDIUM HIGH CONFIDENCE WITH FOG/VIS.

* HIGH CONFIDENCE WITH WIND SPEED/DIRECTION.

RODRIGUEZ

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

TUESDAY THROUGH THURSDAY... VFR. SOUTH TO SOUTHWEST WIND.
FRIDAY THROUGH SATURDAY...VFR. SOUTH TO SOUTHEAST WIND.

BMD

&&

.MARINE...
406 AM CDT

AS A LARGE RIDGE OF HIGH PRESSURE REMAINS NEARLY STATIONARY OVER
THE EASTERN THIRD OF THE COUNTRY THROUGH THIS WEEK WITH ANY LOW
PRESSURE SYSTEMS TRACKING NORTH OF THE LAKE...SOUTHERLY WINDS WILL
BE OBSERVED OVER THE LAKE.

RODRIGUEZ

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...DENSE FOG ADVISORY...ILZ003-ILZ004-ILZ005-ILZ006-ILZ008-ILZ010-
     ILZ011-ILZ012-ILZ013-ILZ014-ILZ020-ILZ021-ILZ022-ILZ023
     UNTIL 9 AM MONDAY.

IN...DENSE FOG ADVISORY...INZ001-INZ002-INZ010-INZ011 UNTIL 9 AM
     MONDAY.

LM...DENSE FOG ADVISORY...NEARSHORE WATERS
     UNTIL 10 AM MONDAY.

&&

$$

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