Area Forecast Discussion
Issued by NWS Chicago, IL

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000
FXUS63 KLOT 231935
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
235 PM CDT WED JUL 23 2014

.DISCUSSION...
248 AM CDT

TODAY THROUGH TONIGHT...
EARLY THIS MORNING IR IMAGERY DEPICTS A CHANNEL OF COOLER CLOUDS
STRETCHING FROM FORD COUNTY NORTHEAST THROUGH NORTHWEST INDIANA.
RADAR CONTINUES TO SHOW A RAGGED LINE OF CONVECTION UNDER THESE
CLOUDS...WHICH SHOULD CONTINUE TO SAG SOUTHEAST AS THE FRONTAL
BOUNDARY PUSHES SOUTH ACROSS THE FORECAST AREA THIS MORNING.
INSTABILITY ALONG AND SOUTH OF THE BOUNDARY REMAINS...WITH MOST OF
THE CONVECTION BEING ROOTED IN THE MID-LVLS AS LAPSE RATES CONTINUE
TO REMAIN RATHER STEEP. FORTUNATELY THOUGH THE INTENSITY OF THE
STORMS SHUD CONTINUE TO REMAIN SUB-SEVERE AND PERHAPS ANOTHER SPS
WILL BE NEEDED BEFORE ACTIVITY PUSHES SOUTH OF THE FORECAST AREA.

OTHERWISE HIGH PRESSURE WILL BUILD INTO THE REGION TODAY...WITH
WINDS SHIFTING NORTHERLY TO SLIGHTLY NORTHEASTERLY. THIS WILL
PROVIDE AN INVERSE AIRMASS FROM THE PAST 48 HOURS...TO A MUCH DRIER
AND SUB-SEASONAL TEMPS. THE PRESSURE GRADIENT WILL REMAIN TIGHT ON
THE LEE-SIDE OF THE SFC RIDGE...RESULTING IN A STRONGER MARINE
INFLUENCE ON TEMPS ALONG THE IMMEDIATE SHORELINE TODAY. THUS IT IS
LIKELY THAT AFTN HIGHS MAY STRUGGLE TO TOUCH 70...MEANWHILE INLAND
AREAS WILL BE GENERALLY IN THE LOW/MID 70S.

TONIGHT HIGH PRESSURE WILL BE OVERHEAD WITH JUST A LIGHT NORTHERLY
FLOW AND PERHAPS WINDS WILL BECOME CALM FOR THE NORTHERN CWFA. TEMPS
SHUD EASILY RADIATE INTO THE LOWER 50S. A FEW LOCATIONS COULD DIP
INTO THE UPR 40S JUST BEFORE SUNRISE THUR...MAINLY ACROSS THE FOX
VALLEY.

THURSDAY...
ANTI-CYCLONIC FLOW WILL CONTINUE TO DOMINATE THE REGION THRU
THUR...WITH MINIMAL CLOUD COVER AND TEMPS GENERALLY IN THE MID 70S.
THE EXCEPTION WILL BE LOCATIONS ADJACENT TO LAKE MICHIGAN WHERE A
LAKE BREEZE/ONSHORE FLOW WILL KEEP TEMPS ARND 70.

MID-LVL TROUGH AXIS BEGINS TO PIVOT EAST THUR NGT...WITH THE SFC
RIDGE DRIFTING EAST AND ALLOWING WINDS TO SLOWLY TURN SOUTHERLY
AHEAD OF THE NEXT WAVE SET TO ARRIVE FRI.

CONFIDENCE...HIGH.

FRIDAY THROUGH TUESDAY...
MID-LVL RIDGE CENTERED OVER THE SOUTHERN PLAINS WILL BEGIN TO
FLATTEN ALONG THE NORTHERN FRINGES...ALLOWING FOR AN EASE OF SYSTEMS
TO TRAVERSE THE NORTHERN TIER STATES EAST ACROSS THE GREAT LAKES
REGION. GUIDANCE HAS CONTINUED TO POINT TOWARDS A WEAK SFC WAVE
SLIDING EAST FROM THE CENTRAL PLAINS FRI...ARRIVING OVER THE
FORECAST AREA WITH SOME ENHANCEMENT TO THE PRECIP OUTPUT DUE TO WARM
AIR ADVECTION AND ASCENT TO PARCELS. THUS HAVE NUDGED POPS UP
SLIGHTLY DURING THE DAY FRI...WITH THE FOCUS LIKELY MIDDAY THRU
EARLY EVENING.

A MID-LVL VORT PROGGED TO BE OVER THE CANADIAN PRAIRIES FRI...WILL
SLOWLY MOVE EAST FRI NGT BEFORE SLIDING SOUTHEAST ACROSS THE GREAT
LAKES REGION LATER IN THE WEEKEND. ENSEMBLES CONTINUE TO POINT
TOWARDS ANOTHER PATTERN ADJUSTMENT OVER THE SECOND HALF OF THE
WEEKEND INTO EARLY NEXT WEEK...AS THE NORTH ATLANTIC RIDGE RETURNS
AND PREVENTS THE AFOREMENTIONED UPPER MIDWEST SHORTWAVE FROM
DEPARTING. IN ADDITION A HIGH AMPLITUDE RIDGE CONTINUES TO BE
PROGGED ACROSS THE WESTERN CONUS...KEEPING THE MID-LVL TROUGH OVER
HUDSON BAY/GREAT LAKES THRU MON/TUE.

THE OVERALL THEME CONTINUES TO BE A BRIEF RETURN TO SEASONAL TEMPS
FOR THE WEEKEND IN THE LOW 80S...HOWEVER ONCE THE TROUGH RETURNS TO
THE GREAT LAKES REGION SO WILL THE UNSEASONABLY COOLER AIR. TEMPS BY
EARLY NEXT WEEK WILL MAINLY BE IN THE MID/UPR 70S.

CONFIDENCE...HIGH.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 20Z...

* GUSTY NNE/NE WINDS THROUGH THIS EVENING.

* LAKE BREEZE WITH ENELY WINDS ARND 10KT TOMORROW AFTERNOON.

KREIN

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

A COLD FRONT HAS PUSHED ACROSS THE REGION WITH BRISK NLY TO NELY
WINDS COVERING THE REGION. THE STRONGEST WINDS WILL BE NEAR THE
LAKEFRONT WITH GUSTS APPROACHING 30KT THROUGH INTO THE EARLY
EVENING. WINDS WILL TAPER OFF FARTHER INLAND...BUT ORD/MDW/DPA
SHOULD STILL SEE AT LEAST OCCASIONAL NELY GUSTS TO 25KT THROUGH
SUNSET. WITH HIGH PRESSURE BUILDING ACROSS THE REGION TONIGHT AND
TOMORROW...WINDS WILL DIMINISH TO 5KT OR LESS OVERNIGHT. A VERY
WEAK PRESSURE GRADIENT IN PLACE ACROSS THE REGION TOMORROW SHOULD
ALLOW LAKE BREEZE DEVELOPMENT...WITH WINDS BECOMING ENELY TO ARND
10KT BY EARLY AFTERNOON. OTHERWISE...NO SIG WX EXPECTED THROUGH
THE PERIOD.

KREIN

//ORD AND MDW CONFIDENCE...UPDATED 20Z...

* HIGH IN WIND DIRECTION AND SPEED...MEDIUM IN TIMING OF GUSTS
  DIMINISHING THIS EVENING.

* MEDIUM CONFIDENCE IN TIMING/SPEED/DIRECTION OF LAKE BREEZE
  TOMORROW.

* HIGH CONFIDENCE IN ALL OTHER FORECAST ELEMENTS.

KREIN

//OUTLOOK FOR ORD/MDW FOR 00Z FRIDAY-12Z WEDNESDAY...UPDATED 12Z...

THURSDAY NIGHT...VFR.
FRIDAY THROUGH SUNDAY...PERIODIC CHANCES FOR THUNDERSTORMS.
MONDAY THROUGH TUESDAY...SLIGHT CHANCES FOR SHOWERS.

BMD

&&

.MARINE...
220 PM CDT

WINDS REMAIN IN THE 20 TO 25 KT ACROSS MUCH OF LAKE MICHIGAN EXCEPT
IN THE FAR NORTH BEHIND A STRONG COLD FRONT WHICH IS NOW WELL SOUTH
OF THE GREAT LAKES. SIGNIFICANT WAVE HEIGHTS PEAKED EARLIER TODAY
WITH 10 FT OBSERVED NEAR MICHIGAN CITY...AND WE ARE STILL SEEING 6
TO 8 FT WAVES ALONG THE SOUTHERN HALF OF THE LAKE WHERE RIP CURRENT
ACTIVITY HAS BEEN REPORTED ALONG THE INDIANA SHORELINE. A SMALL
CRAFT ADVISORY REMAINS IN EFFECT FOR THE INDIANA AND ILLINOIS
NEARSHORE WATERS DUE TO THE ELEVATED WINDS AND WAVES.

HIGH PRESSURE IS NOSING INTO THE UPPER MIDWEST...AND IT WILL
CONTINUE SLIDING SOUTH AND EAST ACROSS LAKE MICHIGAN TONIGHT ALLOWING
WINDS TO SUBSIDE OVERNIGHT INTO THURSDAY. WINDS WILL GENERALLY
REMAIN NORTHERLY OVER THE SOUTHERN HALF OF THE LAKE WITH ONSHORE
WINDS ON THE INDIANA AND ILLINOIS SHORES WHILE WINDS BEGIN TO TURN
SOUTHERLY ALONG THE NORTH HALF OF THE LAKE.  THE HIGH WILL DEPART TO
THE EAST AS LOW PRESSURE MOVES OUT OF THE NORTHERN ROCKIES INTO THE
PLAINS ON FRIDAY ALLOWING WINDS TO HAVE A SOUTHERLY COMPONENT ACROSS
THE LAKE.

THE NEXT ORGANIZED COLD FRONT WILL PASS THROUGH ON SUNDAY. THE
SURFACE LOW ASSOCIATED THIS FRONT WILL DEEPEN IN THE EASTERN LAKES
ON MONDAY WHILE HIGH PRESSURE AGAIN BUILDS SOUTH INTO THE UPPER
MIDWEST. THIS WILL CREATE A PERIOD OF GUSTY NORTHWEST TO NORTH WINDS
WHICH REACH 25 TO 30 KT.

KMD

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...BEACH HAZARDS STATEMENT...ILZ006-ILZ014 UNTIL 10 AM THURSDAY.

IN...BEACH HAZARDS STATEMENT...INZ001-INZ002 UNTIL 10 AM THURSDAY.

LM...SMALL CRAFT ADVISORY...NEARSHORE WATERS
     UNTIL 10 AM THURSDAY.

&&

$$

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