Area Forecast Discussion
Issued by NWS Chicago, IL

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000
FXUS63 KLOT 260826
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE, IL
326 AM CDT TUE APR 26 2016

.SHORT TERM...
326 AM CDT

THROUGH WEDNESDAY...

WHEN IT COMES TO CHICAGO`S WEATHER...ESPECIALLY IN THE
SPRING...WHAT A DIFFERENCE A DAY CAN MAKE. OR...IF FOR AREAS
CLOSER TO THE LAKE...WHAT A DIFFERENCE A FEW MINUTES CAN MAKE. A
PNEUMONIA FRONT CAME BLASTING IN OFF THE LAKE A COUPLE HOURS AGO
WITH TEMP DROPS OF 20 DEGREES IN 15 MINUTES AND NOT TOO FAR FROM
30 DEGREES IN AN HOUR. LAKE ENHANCED FRONT WILL CONTINUE MOVING
ACROSS THE CWA THIS MORNING...THOUGH AS IT GETS FARTHER FROM THE
LAKE THE TEMP DROPS WILL BE LESS DRAMATIC AND THE FRONT SHOULD
HAVE A TENDENCY TO SLOW AS IT MOVES INTO CENTRAL IL THIS
AFTERNOON. LARGE BANK OF POST FRONTAL STRATUS BLANKETS MOST OF WI
AND POINTS NORTH. WHILE IT LAGS A BIT BEHIND THE SFC WIND SHIFT
BUT HAS BEEN STEADILY SEEPING SOUTHWARD AND ANTICIPATE IT TO
OVERSPREAD MOST OF THE CWA THIS MORNING. WHILE CIGS WILL LIKELY
INCH UPWARD TODAY...THINKING THAT STRATUS WILL PROBABLY HOLD
STRONG THROUGH THE DAY MOST AREAS...ESPECIALLY NORTH OF I-80 AND
NEAR THE LAKE. MOST OF THE NORTHERN 2/3RD OF THE CWA WILL PROBABLY
STRUGGLE TO GET OUT OF THE 50S TODAY AND AREAS NEAR THE LAKE WILL
LIKELY SPEND MOST OF THE DAY IN THE LOW TO MID 40S WITH LOW CLOUDS
AND A STIFF WIND OFF THE LAKE.

CLOUDY AND CHILLY CONDITIONS EXPECTED TO PERSIST THROUGH WEDNESDAY
WITH GRADUALLY INCREASING CHANCES FOR RAIN/SHOWERS AS THE DAY
WEARS ON WEDNESDAY AND POWERFUL SYSTEM AFFECTING THE CENTRAL AND
SOUTHERN PLAINS TODAY MOVES SLOWLY EAST TOWARD OUR AREA. A STEADY
FEED OF DRY AIR ADVECTING IN ON THE FAIRLY BRISK EASTERLY WINDS
WILL PROBABLY SLOW THE FORWARD PROGRESS OF RAIN ACROSS OUR
AREA...THOUGH STILL LOOKS LIKE MOST AREAS WILL SEE SHOWERS BY
WEDNESDAY AFTERNOON AND ESPECIALLY WEDNESDAY NIGHT. THE CYCLONE
WILL BE IN THE PROCESS OF BECOMING VERTICALLY STACKED AND
WEAKENING AS IT MOVES INTO THE AREA WEDNESDAY INTO WEDNESDAY NIGHT
WITH MAJORITY OF INSTABILITY PROGGED TO REMAIN SOUTH OF OUR
CWA...SO WHILE WE CANNOT TOTALLY RULE OUT A
THUNDERSTORM...ESPECIALLY SOUTH OF I-80...THE CHANCES OF THUNDER
LOOK PRETTY LOW.

IZZI

&&

.LONG TERM...
326 AM CDT

WEDNESDAY NIGHT THROUGH TUESDAY...

THE SAME SYSTEM WILL STILL BE IN THE AREA THURSDAY CONTINUING TO
WEAKEN AND FILL. ENOUGH COLD AIR ALOFT SHOULD BE PRESENT TO
SUPPORT A CONTINUED THREAT OF SHOWERS INTO THE DAY THURSDAY BEFORE
THIS SYSTEM FINALLY DISSIPATES AS IT MOVES EAST AWAY FROM THE AREA
THURSDAY NIGHT. A BREAK IN PRECIP CHANCES IS THEN EXPECTED FRIDAY
AND PROBABLY MOST IF NOT ALL OF SATURDAY AS WELL BEFORE THE NEXT
BIG SHORTWAVE/CLOSED EMERGES TO THE LEE OF THE ROCKIES AND HEADS
TOWARD THE MIDWEST BY LATER IN THE WEEKEND. HAVE TRIED TO SLOW
POPS A BIT FROM BLENDED MODEL GUIDANCE...BUT SUSPECT FURTHER
SLOWING IN THE ARRIVAL OF PRECIP COULD BE NEEDED AS MEDIUM RANGE
MODELS TEND TO SLOW THESE TYPE OF SYSTEMS EASTWARD PROGRESS AT
THIS DISTANCES. ONCE THE SYSTEM DOES EVENTUALLY ARRIVE LATER IN
THE WEEKEND LOOK FOR MORE RAIN AND PERHAPS SOME THUNDER CHANCES AS
WELL.

NOW THAT WINDS ARE SHIFTING TO NORTHEAST BEHIND THE FRONT MOVING
THROUGH THE AREA EARLY THIS MORNING...LOOK FOR THE NORTHEAST OR
EAST WIND REGIME TO REMAIN LOCKED IN THROUGH THE UPCOMING WEEKEND.
THE EASTERLY WINDS AND FREQUENT BOUTS OF CLOUD COVER AND RAIN WILL
KEEP TEMPS BELOW AVERAGE THROUGH THE UPCOMING WEEKEND. NO WHERE
WILL THAT BE THE CASE MORESO THAN NEAR THE LAKE WHERE TEMPERATURES
PROBABLY WONT REACH 50 DEGREES AGAIN THROUGH THE REST OF THE AND
POSSIBLY THROUGH THE WEEKEND AS WELL.

IZZI

&&

.AVIATION...
FOR THE 06Z TAFS...

THUNDERSTORMS NO LONGER POSE A THREAT TO THE TERMINALS. HOWEVER
THE COLD FRONT IS STEADILY ADVANCING SOUTH. YOU CAN SEE THE FRONT
ON RADAR PUSHING SOUTHWEST. WINDS BECOME NE LESS THAN 10 KT
BEHIND IT INITIALLY BUT EXPECTING WIND SPEEDS TO INCREASE TO 10-15
KT THIS MORNING. LIFR STRATUS IS ALSO LAGGING BEHIND THE FRONT.
LUCKILY THE STRATUS AND FOG OVER THE LAKE ARE REMAINING OVER THE
LAKE AND NOT SPREADING TOO FAR ONSHORE. EXPECTING AN INITIAL WIND
SHIFT TO NE WITHIN THE NEXT FEW HOURS AT THE EASTERN
TERMINALS...AND THEN THE STRATUS SHOULD BUILD IN A FEW HOURS
LATER. GYY AND RFD ARE THE EXCEPTION. THINKING THE LAKE STRATUS
WILL MOVE OVER GYY WITH THE WIND SHIFT TO N OR NNE EARLY THIS
MORNING. ALSO THINKING THE STRATUS AND WIND SHIFT WILL OCCUR
SIMULTANEOUSLY AT RFD. I HAVE HIGH ENOUGH CONFIDENCE TO GO WITH
500 FT CIGS INITIALLY. COULD SEE EVEN LOWER CIGS AS MANY SITES IN
WI ARE BELOW 500 FT. NOT EXPECTING ANY FOG AT THE TERMINALS.

GUIDANCE DIFFERS ON HOW CIGS WILL BEHAVE TODAY. LEANING TOWARD A
MORE PESSIMISTIC OUTLOOK WITH CIGS RISING TO MVFR LATE THIS
MORNING AND REMAINING MVFR THROUGH THE PERIOD. IT IS POSSIBLE THAT
CIGS RISE TO VFR THIS AFTN OR EVENING. HAVE HIGH CONFIDENCE IN
THICK CLOUD COVER AND CIG TRENDS THROUGH THE PERIOD...BUT ONLY
MEDIUM CONFIDENCE IN MVFR THIS AFTN AND EVENING AS WE MAY BE VFR.

JEE

&&

.MARINE...
317 AM CDT

HEADLINES...GUSTS ARE BELOW GALE FORCE OVER THE NORTHERN END OF THE
LAKE SO CANCELLED THE GALE WARNING EARLY.  LEFT THE SMALL CRAFT
ADVISORIES AS IS.  THE LATEST WAVE MODEL SUGGESTS THE SCY FOR THE IL
WATERS NEEDS TO BE EXTENDED. ALSO CONSIDERED EXTENDING THE SCY FOR
POINTS BETWEEN CALUMET HARBOR AND GARY. DO NOT HAVE ENOUGH
CONFIDENCE TO EXTEND EITHER OF THOSE SCY/S JUST YET.

THE LOW IS OVER SOUTHWEST MICHIGAN AND IT WILL CONTINUE EAST. ITS
COLD FRONT IS NOW SOUTH OF THE LAKE WITH WINDS NORTH TO NORTHEAST
ACROSS THE LAKE.  WINDS WILL VARY BETWEEN NORTH AND EAST THROUGH
EARLY NEXT WEEK. THE NEXT LOW FORMS OVER THE PLAINS THIS AFTERNOON
AND PASSES OVER CENTRAL IL THURSDAY. THE SOUTHERN EDGE OF HIGH
PRESSURE CENTERED OVER HUDSON BAY SWINGS THROUGH FRIDAY WITH ANOTHER
LOW FORMING OVER THE PLAINS SATURDAY. GUIDANCE DIFFERS ON THE PATH
OF THE LOW...BUT THE MAIN MODELS BRING IT INTO NORTHERN IL EARLY
NEXT WEEK.

JEE

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742...10 AM TUESDAY TO
     10 PM WEDNESDAY.

     SMALL CRAFT ADVISORY...LMZ743-LMZ744-LMZ745...4 PM TUESDAY TO 4
     PM WEDNESDAY.

&&

$$

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