000
FXUS63 KLOT 231603
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1103 AM CDT THU MAY 23 2013

.DISCUSSION...
240 AM CDT

TODAY...
FORECAST CHALLENGES FOR TODAY RESIDE WITH HIGH TEMPS...AND PRECIP
CHANCES THIS MORNING.

IR IMAGERY EARLY THIS MORNING SHOWS CONSIDERABLE CLOUD COVER
REMAINING ACROSS THE WESTERN GREAT LAKES...EXTENDING SOUTH THROUGH
THE MID-MISSISSIPPI VALLEY. ALONG THE WESTERN PERIPHERY OF THE CLOUD
COVER LIES THE LEADING EDGE OF THE STRONG SFC RIDGE...BEGINNING TO
PUSH INTO THE UPPER MIDWEST/NORTHERN PLAINS. MOISTURE HAS BEEN
CONSISTENTLY PEELING OFF TO THE NORTHEAST...NOTED IN THE STEADILY
LOWERING DEW POINTS. DEW POINTS ACROSS CENTRAL WISC HAVE ALREADY
FALLEN INTO THE UPR 40S...AND EXPECT THIS TREND TO EVENTUALLY ARRIVE
ACROSS NORTHERN IL/NORTHWEST IN. A BROAD SFC TROUGH WAS ANALYZED
ACROSS NORTHEAST IL STRETCHING INTO SOUTHCENTRAL LOWER MI. AS A
RESULT SFC WINDS ACROSS THE CWFA HAVE MAINLY BEEN FROM THE
WEST/SOUTHWEST...HOWEVER JUST NORTH OF THE CWFA INTO WISC WINDS HAVE
ALREADY SHIFTED TO THE NORTHWEST/NORTH. LOCATIONS ADJACENT TO LAKE
MICHIGAN WILL SEE WINDS FLOP OVER TO THE NORTHEAST THIS
MORNING...ALLOWING THE MUCH COOLER MARINE ENVIRONMENT TO READILY
FLOW ACROSS THE LAND.

REGIONAL RADAR EARLY THIS MORNING SHOWS AN AREA OF SHOWERS ACROSS
CENTRAL WISC...SLOWLY SLIDING SOUTHEAST. HI-RES GUIDANCE SUGGESTS
THIS CHANNEL OF PRECIP WILL EVENTUALLY ARRIVE ACROSS NORTHERN IL
JUST BEFORE DAYBREAK. AS A RESULT OF THE INCREASED CONFIDENCE IN
PRECIP...HAVE NUDGED THE 12-15Z TIMEFRAME TO LIKELY POPS FOR FAR
NORTHEAST IL.

DRY AIR CONTINUES TO POUR INTO THE REGION MID-MORNING...AND SHOULD
BRING AN END TO THE PRECIP FROM NORTHWEST TO SOUTHEAST ACROSS THE
CWFA BY EARLY THIS AFTERNOON. THE STEADY PUSH OF DRY AIR WILL ALSO
AID IN ERODING THE CLOUD COVER...AND BY LATE THIS AFTERNOON EXPECT
MOSTLY SUNNY SKIES TO DEVELOP. COLD AIR ADVECTION WILL DOMINATE THE
DAY...COUPLED PRECIP AND CLOUDS...EXPECT MUCH COOLER TEMPS FOR THIS
AFTERNOON. GUIDANCE HAS CONTINUED TO SUGGEST TEMPS WILL STRUGGLE TO
WARM BEYOND THE LOW 60S FOR THE FAR WESTERN CWFA...MEANWHILE FURTHER
EAST TEMPS WILL ONLY WARM A FEW DEGREES FROM THEIR STARTING POINT.
THIS WILL MOST LIKELY LEAD TO AREAS EAST OF I-39 ONLY WARMING INTO
THE MID/UPR 50S. LOCATIONS IMMEDIATELY ADJACENT TO LAKE MICHIGAN
COULD SEE TEMPS STRUGGLE TO WARM BEYOND 50 DEGREES.

CONFIDENCE IN PRECIP ENDING TIME...MEDIUM/HIGH.
CONFIDENCE IN TEMPERATURES...HIGH.

TONIGHT...
ANTI-CYCLONIC FLOW WILL CONTINUE TO BUILD OVERHEAD EARLY THIS
EVENING...AND ERODE ANY LINGERING CLOUDS BY MIDNIGHT. DEW POINTS AS
A RESULT WILL CONTINUE TO DRY...BOTTOMING OUT IN THE MID 30S IN MANY
LOCATIONS. THE COMBINATION OF NEAR CLOUDLESS SKIES...LIGHT NORTH TO
AT TIMES CALM WINDS...AND RECENT RAINFALL...WILL SET THE STAGE FOR
NOT ONLY STRONG RADIATIONAL COOLING BUT PATCHY FROST AWAY FROM LAKE
MICHIGAN. GUIDANCE CONTINUES TO PROG TEMPS FALLING OVERNIGHT INTO
THE MID/UPR 30S FOR AREAS WEST OF WAUKEGAN TO KANKAKEE. FAR SOUTHERN
PORTIONS OF THE CWFA SHOULD HAVE TEMPS HOLD ARND 40 DEGREES
OVERNIGHT...HOWEVER A FEW LOW-LYING AREAS COULD SEE SPOTTY FROST. AT
THIS POINT IT DOES NOT APPEAR TO BE A WIDESPREAD FROST SETUP...SO
WILL HOLD OFF ON ANY HEADLINES AT THIS POINT.

CONFIDENCE...HIGH.

FRIDAY...
SFC HIGH PRESSURE WILL DOMINATE THE REGION FOR THE END OF THE
WEEK...AND MORE THAN LIKELY ONLY ALLOW A FEW DIURNAL CLOUDS TO
DEVELOP. A LIGHT NORTHEAST FLOW OFF OF LAKE MICHIGAN WILL CONTINUE
TO KEEP ADJACENT AREAS MUCH COOLER IN THE MID/UPR 50S...MEANWHILE
INLAND LOCATIONS WILL BEGIN TO WARM INTO THE LOW/MID 60S.

WITH HIGH PRESSURE STILL IN CONTROL FRIDAY NIGHT...EXPECT ANOTHER
NIGHT OF STRONG RADIATIONAL COOLING. THE ONLY DIFFERENCE FOR FRI
NIGHT WILL BE THE RIDGE AXIS WILL HAVE SHIFTED EAST. THIS WILL ALLOW
THE LIGHT WINDS TO BEGIN TURNING SOUTHEASTERLY AFTER MIDNIGHT...AND
COULD SLOW THE RATE OF COOLING. HAVE MAINTAINED TEMPS IN THE LOW 40S
FOR MANY AREAS. COULD SEE A FEW OF THE TRADITIONAL COOL SPOTS DIP TO
THE UPR 30S EARLY SAT MORNING...HOWEVER AT THIS POINT NOT
ANTICIPATING FROST FORMATION.

CONFIDENCE IN TEMPERATURES...HIGH.

SATURDAY...
DISCREPANCIES BEGIN TO EMERGE AMONGST SOLUTIONS FOR SAT...WITH
RESPECT TO PLACEMENT/TIMING OF A MOIST BOUNDARY. GFS HAS CONTINUED
TO BE THE MORE PROGRESSIVE SOLUTION...BRINGING THIS CHANNEL OF
MOISTURE/PRECIP INTO THE REGION AND STRETCHES FROM THE NORTHERN
PLAINS SOUTHEAST THROUGH THE OHIO VALLEY. MEANWHILE THE EC HAS
MAINTAINED THE SFC RIDGE...AND SUPPRESSING THE MOIST CHANNEL TO THE
SOUTHWEST OF THE CWFA.

THE LARGEST WEATHER PLAYER IS THE DOWNSTREAM 500MB RIDGE LOCATED
ACROSS THE WESTERN ATLANTIC. THIS WILL ACT AS A BLOCK...SLOWING THE
DEPARTURE OF THE MID-LVL TROUGH ACROSS THE MID-ATLANTIC REGION. THEN
FURTHER UPSTREAM YET ANOTHER 500MB RIDGE WAS PROGGED TO ARRIVE
ACROSS THE CENTRAL CONUS...AND DOES SHOW SOME SIGNS OF
AMPLIFICATION. BASED ON THIS SETUP IT IS BECOMING MORE EVIDENT THAT
SAT COULD END UP BEING DRY...AND POSSIBLY EXTEND INTO SUN. AT THIS
POINT HAVE ONLY ADJUSTED POPS SAT MARGINALLY...TO SLIGHT CHANCE
WORDING.

SFC TEMPS WILL REMAIN UNSEASONABLY COOL IN THE LOW/MID 60S...WITH
AREAS ADJACENT TO LAKE MICHIGAN BEING EVEN COOLER THAN THIS. DESPITE
THE EXPECTED SOUTHEAST COMPONENT TO THE SFC WINDS...ENOUGH HEATING
COULD ALLOW A LAKE BREEZE TO FORM AND ALLOW WINDS TO BECOME MORE
EASTERLY FOR LOCATIONS ADJACENT TO LAKE MICHIGAN. THIS WILL MOST
LIKELY RESULT IN THOSE AREAS IMMEDIATELY NEXT TO THE LAKE REMAINING
IN THE 50S SAT AFTN.

CONFIDENCE...MEDIUM.

SUNDAY THROUGH WEDNESDAY...
FOR THE EXTENDED PERIODS GUIDANCE HAS CONTINUED TO DEMONSTRATE
MINIMAL CHANGES FROM PREVIOUS SOLUTIONS...HOWEVER OPERATIONAL
ECMWF/GFS CONTINUE TO DIFFER ON THE PLACEMENT/TIMING OF PRECIP. THE
ECMWF CONTINUES TO SUGGEST THE SFC RIDGE FROM LATE IN THE WEEK WILL
HOLD TOUGH AND KEEP NORTHERN IL/NORTHWEST IN DRY THRU THE WEEKEND
AND INTO EARLY NEXT WEEK. MEANWHILE THE GFS IS STILL MORE
PROGRESSIVE AND BRINGS THE BOUNDARY OVERHEAD AND BECOMES
QUASI-STATIONARY THRU THE FIRST HALF OF NEXT WEEK.

ENSEMBLES CONTINUE TO INDICATE THE WESTERN ATLANTIC MID-LVL RIDGE
WILL WEAKEN...ALLOWING THE 500MB TROUGH TO FINALLY EJECT EAST. IN
ADDITION THE UPSTREAM RIDGE WILL BEGIN TO FLATTEN...LEADING TO A
SOMEWHAT PROGRESSIVE FLOW OF SYSTEMS FROM WEST TO EAST TOWARDS THE
MIDDLE OF NEXT WEEK. THUS PRECIP CHC WILL BE ON THE INCREASE TOWARDS
THE FINAL FEW PERIODS OF THE CURRENT EXTENDED FORECAST.

BY TUE/WED OF NEXT WEEK...TEMPS COULD EASILY BE BACK INTO THE UPR
70S TO LOW 80S.

CONFIDENCE IN PRECIPITATION...LOW.
CONFIDENCE IN TEMPERATURES...HIGH.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 16Z...

* VARIABLE MVFR/IFR CIG SLOWLY IMPROVING AOA 1500 FT AROUND 17Z.
  VFR/CLEARING BY MID AFTN.

* NORTH WIND WITH GUSTS TO AROUND 30 KT CONTINUING THROUGH AFTN.

ALLSOPP/BMD

//DISCUSSION...UPDATED 12Z...

MAIN CONCERN THIS MORNING IS CIG TRENDS...THEN THIS AFTERNOON
FOCUS WILL BE ON STRONG GUSTY NNE WINDS. LOW PRESSURE WAS OVER
THE EASTERN GREAT LAKES WITH A COLD FRONT TRAILING WESTWARD INTO
NORTHERN IL. AT 11Z THE FRONT WAS FROM ABOUT IKK-VYS. BASED ON
NAM AND HRRR MODEL SOUNDINGS...CIGS SHOULD SLOWLY IMPROVE TO
AROUND 1000-1200 FT IN THE NEXT COUPLE HOURS. THIS SEEMS
REASONABLE WITH STRONGER WINDS MIXING COLDER AND SLIGHTLY DRIER
AIR DOWN FROM THE NORTH. ALSO SPOTTY LIGHT RAIN/DRIZZLE WILL BE
DIMINISHING/MOVING OUT AND THAT MAY ALSO HELP IMPROVE CIG AND VSBY
A BIT THIS MORNING. AS OF 11Z THE BACK EDGE OF THE MAIN BAND OF
RAIN ASSOCIATED WITH THE COLD FRONT WAS LINED UP FROM DKB-DPA-
MDW-GYY AND SINKING VERY SLOWLY S. THERE WERE SOME VSBY
RESTRICTIONS DOWN TO 2-3 MILES IN THIS BAND OF RAIN...BUT IT HAS
PUSHED SOUTH OF THE TERMINALS. FURTHER NORTH INTO SOUTHERN WI
THERE WERE SOME PATCHES OF LIGHT RAIN/DRIZZLE..BUT THIS WAS VERY
LIGHT. SHORT RANGE/HI RES MODELS SUGGEST THIS SPOTTY LIGHT RAIN
WILL BE DRYING UP AND MOVING SE OUT OF THE AREA BY MID TO LATE
MORNING. THEREFORE DONT EXPECT ANY SIGNIFICANT VSBY RESTRICTIONS
BELOW 5 OR 6 MILES THE REST OF THE MORNING. AS STRONG NORTH WINDS
CONTINUE TO PUSH COLDER DRIER AIR DOWN...EXPECT CLOUDS TO LIFT TO
1500 FT OR BETTER BY NOON AND BREAK UP THIS AFTERNOON WITH
CLEARING MID TO LATE AFTN.

NORTH WINDS HAVE PICKED UP AND WINDS WILL CONTINUE TO INCREASE TO
20 TO 30 KT BY MID MORNING. DIRECTION MAY VARY SOME FROM 350-030
BUT WILL BE PREDOMINANTLY JUST E OF N TODAY. PRESSURE GRADIENT
SLOWLY BEGINS TO RELAX LATE THIS AFTERNOON AND WINDS MAY DIMINISH
SLIGHTLY DURING THE LATE AFTN. ATMOSPHERE SHOULD BEGIN TO DECOUPLE
THIS EVENING AS PRESSURE GRADIENT CONTINUES TO RELAX.

OUTLOOK FOR FRIDAY IS VFR WITH LIGHT NORTHEAST WINDS.

ALLSOPP

//ORD AND MDW CONFIDENCE...UPDATED 16Z...

* MEDIUM-HIGH CONFIDENCE IN CIG TRENDS THIS MORNING.

* MEDIUM CONFIDENCE IN TIMING OF CLEARING THIS AFTN.

* HIGH CONFIDENCE IN WIND FORECAST. DIRECTION MAY VARY FROM
  350-030.

ALLSOPP/BMD

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

FRIDAY NIGHT AND SATURDAY...VFR. WX NIL.

SUNDAY AND MONDAY...VFR. CHC SHRA SLIGHT CHC TSRA.

TUESDAY AND WEDNESDAY...CHC TSRA.

ALLSOPP

&&

.MARINE...
147 AM CDT

EARLY THURSDAY MORNING AN ELONGATED AREA OF LOW PRESSURE WAS FROM
THE EASTERN GREAT LAKES BACK TO NORTHERN ILLINOIS...WHILE A STRONG
AREA OF HIGH PRESSURE WAS CENTERED OVER NORTHERN MANITOBA WITH A
RIDGE EXTENDING SOUTHWARD INTO THE NORTHERN PLAINS. AS THE TROF
SWINGS EAST AND THE RIDGE BUILDS INTO THE WESTERN GREAT LAKES
TODAY...GALE FORCE NORTH WINDS WILL DEVELOP OVER LAKE MICHIGAN.
THE GALES WILL DEVELOP OVER CENTRAL LAKE MICHIGAN EARLY THIS
MORNING AND SPREAD TO THE SOUTH END BY MID OR LATE MORNING. WINDS
WILL DIMINISH OVERNIGHT AS THE HIGH SETTLES OVER THE WESTERN GREAT
LAKES AND THE LOW MOVES UP THE EAST COAST. THE HIGH WILL THEN BE
NEARLY STATIONARY OVER THE GREAT LAKES THROUGH THE WEEKEND WITH
LIGHT EAST TO SOUTHEAST FLOW OVER THE LAKE. LOW PRESSURE WILL MOVE
FROM THE CENTRAL PLAINS TO THE UPPER MISSISSIPPI VALLEY MONDAY AND
TUESDAY WHICH WILL CAUSE WINDS TO BECOME SOUTHERLY OVER LAKE
MICHIGAN.

ALLSOPP

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WARNING...LMZ080-LMZ671-LMZ673-LMZ675-LMZ740-LMZ741-LMZ742-
     LMZ743-LMZ744-LMZ745-LMZ777-LMZ779-LMZ872-LMZ874-LMZ876-
     LMZ878 UNTIL 9 PM THURSDAY.

     GALE WARNING...LMZ366-LMZ565-LMZ567-LMZ669-LMZ868-LMZ870 UNTIL 3
     PM THURSDAY.

&&

$$

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