Area Forecast Discussion
Issued by NWS Chicago, IL

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000
FXUS63 KLOT 242202
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
502 PM CDT THU APR 24 2014

.DISCUSSION...
311 PM CDT

SYNOPSIS...SHOWERS AND POSSIBLY A COUPLE OF THUNDERSTORMS MOVE
THROUGH THIS AFTERNOON WITH ADDITIONAL SHOWERS EXPECTED OVERNIGHT.
FRIDAY WILL BE DRY AND WARM WITH RAIN POSSIBLE FRIDAY NIGHT. THEN
CHANCES OF RAIN INCREASE FOR SATURDAY NIGHT THROUGH MOST OF NEXT
WEEK.  IN ADDITION TEMPS BEGIN A SLOW DECLINE FROM LATE THIS WEEKEND
THROUGH NEXT WEEK WITH BELOW NORMAL TEMPERATURES EXPECTED FOR MOST
OF NEXT WEEK.

THROUGH TONIGHT...
THE UPPER LEVEL RIDGE HAS PUSHED EAST OF THE CWA WHILE A TROUGH IS
OVER THE PLAINS.  THE TROUGH WILL MOVE OVERHEAD TONIGHT. AT THE
SURFACE LOW PRESSURE IS OVER SOUTHWEST MO AND IT WILL MOVE OVER
CENTRAL IL TONIGHT.  A WARM FRONT LIES WEST AND SOUTH OF THE CWA
WITH SHOWERS STRETCHING FROM WI THROUGH MO. THE BEST CAPE VALUES
REMAIN SOUTH OF THE CWA WHERE MORE LIGHTING IS BEING SEEN...BUT HAVE
SEEN A FEW STRIKES IN THE SCATTERED CONVECTION MOVING INTO THE FAR
WESTERN CWA. GIVEN THE WEAK INSTABILITY...WENT WITH A SLIGHT CHANCE
OF THUNDER WEST OF A HARVARD TO PONTIAC LINE THIS AFTERNOON.  AS THE
LOW PASSES TO OUR SOUTH THIS EVENING...THINKING THE SLIGHT CHANCE OF
THUNDER WILL SHIFT EAST AND COVER MOST OF NORTHERN IL.
HOWEVER...WITH ONLY MINOR AMOUNTS OF INSTABILITY TO WORK WITH...ONLY
EXPECTING ISOLATED CLAPS OF THUNDER AT BEST.

SHOWERS ON THE OTHER HAND ARE VERY LIKELY THROUGHOUT THE NIGHT WITH
STORM TOTAL QPF VALUES RANGING FROM AROUND 0.75 INCHES ACROSS NORTH
CENTRAL IL TO 0.3-0.5 INCHES OVER NW INDIANA.  WINDS TURN NW BEHIND
THE LOW AND OVERNIGHT MIN TEMPS WILL BE IN THE MID 40S TO AROUND 50.

FRIDAY AND SATURDAY...
THE UPPER LEVEL CLOSED LOW ASSOCIATED WITH THE TROUGH LAGS BEHIND
THE TROUGH A BIT AND PASSES OVER LAKE SUPERIOR AND FAR NORTHERN LAKE
MI TOMORROW.  THE SURFACE LOW SHIFTS EAST INTO THE OHIO RIVER VALLEY
TOMORROW WITH RAIN ENDING EARLY IN THE MORNING.  A RIDGE THEN BUILDS
IN DURING THE AFTERNOON AND OVERNIGHT.  AS SUCH LOOKING AT SKIES
CLEARING AND A GOOD MIXING DAY WITH NW TO W WINDS GUSTING 25 TO 30
MPH IN THE AFTERNOON.  STILL THINKING WE COULD HAVE DRIER MIX DOWN
TO THE SURFACE SO KEPT DEWPOINTS BELOW GUIDANCE.

MAX TEMPS WILL BE IN THE UPPER 60S TO LOW 70S AND THEN LOWS WILL BE
IN THE 40S WITH INCREASING CLOUD COVER. A WEAK SHORTWAVE MAY PRODUCE
A FEW SHOWERS FRIDAY NIGHT AND HAVE A SLIGHT CHANCE OF POPS IN FOR
THAT. CONFIDENCE IS LOW IN THE SHOWERS OVERNIGHT.

THE HIGH SHIFTS EAST ON SATURDAY WITH SKY COVER INCREASING IN THE
AFTERNOON AND OVERNIGHT.  A BACKDOOR COLD FRONT SLIDES DOWN THE LAKE
WITH WINDS TURNING OFF OF THE LAKE.  THIS WILL LEAD TO HIGH TEMPS
ALONG THE LAKE ONLY GETTING INTO THE UPPER 40S TO LOW 50S.  OUTLYING
AREAS SHOULD WARM NICELY INTO THE 60S AND MAYBE EVEN LOW 70S.  KEPT
SATURDAY DRY SINCE THE RIDGE IS MOVING OVERHEAD. HOWEVER GUIDANCE
CONTINUES TO FEATURE AN UPPER LEVEL WAVE MOVING IN WITH PRECIP
FORMING SATURDAY EVENING AND NIGHT.  CONFIDENCE IS MEDIUM IN THE
TIMING AND LOCATION OF PRECIP SO CAPPED POPS AT CHANCE.

SUNDAY THROUGH NEXT WEDNESDAY...
NEXT WEEK STILL LOOKS RAINY AND COOL WITH A CUT OFF LOW HANGING OUT
OVER THE REGION.  THE UPPER LEVEL LOW BEGINS OVER THE SW US SATURDAY
AFTERNOON AND THEN CUTS OFF OVER THE PLAINS SUNDAY AFTN/EVE. IT THEN
MOVES OVER THE MIDWEST TUESDAY EVENING AND REMAINS OVER THE REGION
THROUGH THURSDAY BEFORE FINALLY SHIFTING EAST.  AT THE SURFACE...A
LOW FORMS OVER THE PLAINS SATURDAY NIGHT AND REMAINS OVER THE PLAINS
INTO MONDAY BEFORE MOVING OVER THE REGION MONDAY NIGHT. THE LOW THEN
STALLS OVER THE REGION THROUGH MOST OF NEXT WEEK.  GUIDANCE HAS THE
LOW FINALLY SHIFTING EAST LATE ON THURSDAY OR FRIDAY.

CUT OFF LOWS ARE NOTORIOUS RAIN PRODUCERS WITH LOBES OF VORTICITY
CIRCLING AROUND THEM BUT NOT HELPING TO ADVANCE THE PATTERN OR
SYSTEM.  AS SUCH...HAVE A CHANCE OR BETTER OF RAIN FROM SUNDAY
THROUGH WEDNESDAY.  THE 7 DAY TOTAL QPF OUTLOOK FROM WPC HAS 2-3
INCHES OF RAIN. NOTE THIS DOES INCLUDE THE RAIN WE RECEIVE THIS
AFTERNOON AND TONIGHT...BUT IT STILL IS A SUBSTANTIAL AMOUNT OF RAIN
NONETHELESS.

NOT OVERLY IMPRESSED WITH OUR THUNDER CHANCES...BUT THINK THE BEST
CHANCE FOR THUNDER IS MONDAY.  HOWEVER AS THE LOWS WARM FRONT HANGS
OUT SOUTH OF THE CWA SUNDAY...HAVE A SLIGHT CHANCE OF THUNDER IN
ALONG AND SOUTH OF I-80. THEN HAVE A CHANCE OF THUNDER IN FOR MONDAY
ALONG AND SOUTH OF I-80. THINKING THE THREAT OF THUNDER WILL THEN
SLOWLY DIMINISH MONDAY NIGHT INTO TUESDAY AS THE LOW MOVES ACROSS
CENTRAL IL.

THE JET STILL SWINGS WELL SOUTH WHICH ALLOWS COLDER AIR TO WRAP
AROUND THE LOW.  THERE WILL BE A COOLING TREND THROUGH NEXT WEEK
WITH HIGHS ON SUNDAY IN THE MID 50S ALONG THE LAKE TO AROUND 70
ACROSS THE SOUTHERN CWA.  BY WEDNESDAY WE ARE LOOKING AT HIGHS IN
THE 50S ACROSS THE CWA AND LOWS POSSIBLY DIPPING INTO THE UPPER 30S
OVERNIGHT.

JEE

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 22Z...

* STRONG/GUSTY SOUTHEAST WINDS THROUGH EARLY THIS EVENING.
* CHANCE OF SHOWERS THIS EVENING WITH THE BEST CHANCE OF SHOWERS
  FROM LATE EVENING THROUGH EARLY MORNING.
* MVFR CIGS WITH POSSIBLE IFR CIGS LATE THIS EVENING/OVERNIGHT.
* WIND SHIFT TO THE NORTHWEST OVERNIGHT.
* STRONG/GUSTY WEST/NORTHWEST WINDS FRIDAY. CMS

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

A BROAD AREA OF LOW PRESSURE LIES OVER THE PLAINS THIS AFTERNOON.
AHEAD OF THE LOW THIS AFTERNOON AND EVENING...EXPECT GUSTY SOUTHEAST
WINDS TO CONTINUE ACROSS NORTHERN ILLINOIS...WITH GUSTS PUSHING 30
KT AT TIMES. THIS LOW WILL CONSOLIDATE AS IT MOVES EAST ACROSS
CENTRAL ILLINOIS LATE THIS EVENING/TONIGHT. SHOWERS ALONG WITH
LOWERING CIGS WILL ACCOMPANY THE LOW THIS EVENING. CIGS ARE EXPECTED
TO LOWER TO MVFR...AND CANNOT COMPLETELY RULE OUT IFR AT THIS
TIME...THOUGH THERE ARE BETTER CHANCES FOR CIGS BOTTOMING OUT IN THE
010-015 RANGE. WINDS MAY GO VARIABLE FOR A BRIEF PERIOD AS AN
INVERTED TROUGH PUSHES ACROSS THE AREA...THEN EXPECT WINDS TO BECOME
NNW TO NW BEHIND THE TROUGH WITH CONDITIONS QUICKLY RETURNING TO VFR.

BMD

//ORD AND MDW CONFIDENCE...UPDATED 22Z...

* MEDIUM FOR WIND SPEEDS/GUSTS/DIRECTIONS THROUGH THE PERIOD.
* LOW FOR SHOWERS THIS EVENING...MEDIUM FOR SHOWERS LATE THIS
  EVENING AND OVERNIGHT.
* HIGH FOR MVFR CIGS...LOW FOR IFR CIGS. CMS

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

FRIDAY NIGHT...SLIGHT CHANCE OF SHOWERS...OTHERWISE VFR.

SATURDAY...CHANCE OF SHOWERS LATE...OTHERWISE VFR.

SUNDAY...CHANCE OF SHOWERS...OTHERWISE VFR.

MONDAY...CHANCE OF SHOWERS...OTHERWISE VFR.

TUESDAY...CHANCE OF SHOWERS...OTHERWISE VFR.

WEDNESDAY...CHANCE OF SHOWERS...OTHERWISE VFR.

RODRIGUEZ

&&

.MARINE...
158 PM CDT

TWO WEAK LOW PRESSURE CENTERS WERE LOCATED WEST OF LAKE MICHIGAN.
ONE WAS STEADILY WEAKENING OVER CENTRAL IOWA...WHILE A SECOND WAS
BEGINNING TO STRENGTHEN ACROSS CENTRAL MISSOURI. THE TWO LOW
PRESSURES ARE EXPECTED TO CONSOLIDATE THIS EVENING...THEN STEADILY
LIFT NORTHEAST/EAST ACROSS CENTRAL ILLINOIS OVERNIGHT. IN THE
MEANTIME...WINDS WILL GENERALLY REMAIN EASTERLY TO SOUTHEASTERLY.
A TIGHT GRADIENT DOES EXIST...WHICH HAS RESULTED IN WINDS AT TIMES
GUSTING TO 30KT THIS AFTN. GUIDANCE HAS BEEN CONSISTENT IN
DEPICTING WINDS DIMINISHING TONIGHT...THEN WINDS WILL TURN
WEST/NORTHWEST. THIS WILL ALLOW THE WAVES TO SUBSIDE ACROSS THE
NORTH/NORTHWEST PORTIONS OF THE LAKE...WHILE WAVES BEGIN TO BUILD
ONCE AGAIN FOR THE INDIANA NEARSHORE WATERS FRIDAY MIDDAY THROUGH
FRIDAY NIGHT.

HIGH PRESSURE WILL SLIDE EAST ACROSS MANITOBA TO NORTH OF LAKE
SUPERIOR EARLY SATURDAY. THIS WILL ALLOW WINDS TO TURN NORTHERLY
EARLY SATURDAY THEN NORTHEAST TO EASTERLY ACROSS THE LAKE BY
SATURDAY AFTERNOON. THEN A PROLONGED PERIOD OF GENERALLY EASTERLY
WINDS IS EXPECTED ACROSS THE LAKE SUNDAY THROUGH TUESDAY.

BEACHLER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WATERS UNTIL 10 PM THURSDAY.

&&

$$

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