Area Forecast Discussion
Issued by NWS Chicago, IL

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000
FXUS63 KLOT 240753
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
253 AM CDT FRI APR 24 2015

.SHORT TERM...
252 AM CDT

THROUGH SATURDAY...

QUIET WEATHER ON TAP FOR MOST OF TODAY AS RIDGE AXIS CENTERED JUST
TO OUR EAST EARLY THIS MORNING SLOWLY SLIDES EAST ALLOWING RETURN
FLOW TO SPREAD MOISTURE UP ALONG WITH MISSISSIPPI RIVER VALLEY
AND INTO THE FORECAST AREA TONIGHT AHEAD OF LOW PRESSURE OVER THE
CENTRAL PLAINS. IN THE MEANTIME...EXPECT MORNING SUNSHINE TO GIVE
WAY TO INCREASING HIGH AND MID LEVEL CLOUD COVER. LIGHT WINDS IN
PLACE TODAY WILL ALLOW A LAKE BREEZE TO DEVELOP THIS AFTERNOON
ALONG THE INDIANA AND ILLINOIS SHORES. TEMPERATURES WILL WARM INTO
THE UPPER 50S TO AROUND 60 INLAND...BUT TEMPERATURES WILL LIKELY
STAY IN THE MID TO UPPER 40S ALONG THE LAKE FRONT.

CHANCES FOR PRECIP WILL INCREASE STARTING AROUND MID EVENING TONIGHT
AS SURFACE LOW MOVES INTO KS/NE AND LEADING EDGE OF MOISTURE PUSHES
INTO NORTHERN ILLINOIS ALONG WITH 850MB BAROCLINIC ZONE AND BROAD
WARM ADVECTION PROVIDING MODERATE ASCENT. DRY AIR BELOW 800MB WILL
HAVE TO BE OVERCOME BEFORE PRECIP REACHES THE SURFACE MAINLY LENDING
TO SOME UNCERTAINTY IN TIMING ONSET OF PRECIP. BY SATURDAY MORNING
EXPECT THE COLUMN TO BE SATURATED WITH DEEP MOISTURE IN PLACE AND
PWATS AROUND AN INCH. NAM INDICATES VERY MODEST INSTABILITY MAINLY
SOUTH OF A DIXON TO RENSSELAER LINE. VERY SKINNY CAPE PROFILES ARE
NOTED HOWEVER AND IT MAY BE DIFFICULT TO REALIZE THE FULL
POTENTIAL...SO WILL INTRODUCE ONLY A SLIGHT CHANCE OF THUNDER FOR
SOUTHWESTERN/SOUTHERN COUNTIES IN THE FORECAST AREA.

EXPECT RAIN ACROSS THE CWA MOST OF SATURDAY MORNING...THEN CHANCES
WILL BEGIN TO WIND DOWN THROUGH THE AFTERNOON AS THE SURFACE LOW
TRACKS ACROSS DOWNSTATE ILLINOIS AND BOUNDARY LAYER FLOW LOCALLY
COMES AROUND TO NORTHEASTERLY. PASSAGE OF THE MID LEVEL WAVE
SATURDAY EVENING AND ARRIVAL OF MID-LEVEL HEIGHT RISES SHOULD MARK
THE END OF PRECIP.

DEUBELBEISS

&&

.LONG TERM...
252 AM CDT

SATURDAY NIGHT THROUGH THURSDAY...

GENERALLY DRY CONDITIONS WITH A GRADUAL WARMING TREND IS EXPECTED TO
CLOSE OUT THE WEEKEND AND CONTINUE THROUGH MOST OF THE UPCOMING
WEEK. LOW PRESSURE THAT WILL BRING RAIN TO THE AREA FRIDAY
NIGHT/SATURDAY WILL MOVE TOWARDS THE MID ATLANTIC COAST SUNDAY WITH
HIGH PRESSURE BUILDING DOWN FROM THE CANADIAN PRAIRIES INTO THE
UPPER MIDWEST. NORTH/NORTHEAST FLOW IN THE MID-LEVELS WILL PUSH THE
BAROCLINIC ZONE BACK TO OUR SOUTH SUNDAY WITH H85 TEMPS FALLING TO
AROUND -6C TO -8C...ALBEIT BRIEFLY. THE HIGH WILL GENERALLY REMAIN
IN PLACE THROUGH MIDWEEK THOUGH WEAKENS THROUGH THIS PERIOD WITH THE
AIRMASS BECOMING INCREASINGLY MODIFIED BY LATE APRIL INSOLATION.
THIS SHOULD ALLOW TEMPS ONLY IN MID 50S SUNDAY TO GRADUALLY WARM
THROUGH THE UPCOMING WEEK WITH TEMPS PUSHING THE 70 MARK BY
THURSDAY. THE EXCEPTION THROUGH THE PERIOD WILL BE NEAR THE LAKE
FRONT WHERE ONSHORE FLOW IS EXPECTED THROUGH AT LEAST THE FIRST HALF
OF THE WEEK KEEPING CONDITIONS COOLER.

DEUBELBEISS

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 06Z...

* EASTERLY WINDS THIS AFTERNOON AND TONIGHT.
* CHANCE OF SHOWERS TONIGHT.

KJB

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

CLEAR SKIES AND NEARLY CALM WINDS ARE OCCURRING OVER MUCH OF THE AREA
UNDER THE INFLUENCE OF SURFACE HIGH PRESSURE. THIS SURFACE HIGH WILL
SHIFT EAST TODAY WHILE LOW PRESSURE OVER THE HIGH PLAINS BEGINS TO
CONSOLIDATE ACROSS WESTERN KANSAS BY THIS EVENING. AS THIS
OCCURS...LIGHT SOUTH-SOUTHEASTERLY WINDS THIS MORNING WILL BECOME
EASTERLY THROUGH THE AFTERNOON. WIND SPEEDS LOOK TO GENERALLY REMAIN
LIGHT THROUGH MUCH OF THE DAY. HOWEVER...EASTERLY WINDS UP AROUND 10
KT COULD DEVELOP BY MID TO LATE AFTERNOON...WITH A CONTINUED
INCREASE IN SPEED LIKELY TONIGHT AS THE SURFACE LOW PROGRESSES
EASTWARD TOWARDS THE LOWER AND MIDDLE MISSOURI VALLEY.

THE CHANCES FOR RAIN WILL GRADUALLY INCREASE ACROSS THE AREA
TONIGHT...BUT THE BEST CHANCE FOR WIDESPREAD RAIN WILL BE ON
SATURDAY. WARM AIR ADVECTION WILL INCREASE MID-LEVEL MOISTURE
THROUGH THE DAY...LEADING TO AN INCREASE IN VFR CLOUD COVER ABOVE
7000 FEET. A FEW SHOWERS MAY DEVELOP OVER THE AREA LATER THIS
EVENING AND TONIGHT...BUT LOW CIGS AND MORE WIDESPREAD RAIN LOOKS TO
OCCUR JUST BEYOND THE CURRENT TAF PERIOD. THEREFORE...LATER TAF
FORECASTS WILL LIKELY NEED TO HIT THE RAIN CHANCES AND LOW CIGS
HARDER FOR THE DAYLIGHT HOURS SATURDAY.

KJB

//ORD AND MDW CONFIDENCE...UPDATED 06Z...

* HIGH FOR WINDS THRU THE PERIOD.
* MEDIUM FOR SCT SHOWERS TONIGHT.

KJB

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

* SATURDAY...RAIN. IFR/LIFR. STRONG/GUSTY EAST/NORTHEAST WINDS.
* SUNDAY THROUGH WEDNESDAY...DRY/VFR. NORTH/NORTHEAST WINDS.

&&

.MARINE...
138 AM CDT

LIGHT AND VARIABLE WINDS EARLY THIS MORNING OVER THE LAKE WILL
BECOME EASTERLY LATER TODAY AND TONIGHT AS AN AREA OF LOW PRESSURE
CONSOLIDATES ACROSS WESTERN KANSAS. WIND SPEEDS ARE LIKELY TO
INCREASE INTO SATURDAY AS THIS AREA OF LOW PRESSURE TRACKS EASTWARD
ACROSS SOUTHERN ILLINOIS BY EARLY EVENING...THEN OVER THE OHIO
VALLEY SATURDAY NIGHT. EASTERLY WINDS OF 25 TO 30 KT LOOK LIKE A
DECENT BET ON SATURDAY...ESPECIALLY ACROSS THE SOUTHERN HALF OF THE
LAKE. THIS WILL LIKELY RESULT IN SMALL CRAFT CONDITIONS FOR ILLINOIS
AND INDIANA NEAR SHORES...WITH WAVES LIKELY TOPPING 5 FEET. WINDS
GRADUALLY SWITCH AROUND OUR OF THE NORTH FOR SUNDAY AND REMAIN GUSTY
UP TO 25 TO 30 KT AS SURFACE HIGH PRESSURE BEGINS TO BUILD BACK
SOUTHWARD ACROSS THE UPPER MIDWEST.

PERIODS OF LIGHTER WINDS...LIKELY DOMINATED MORE BY LAKE AND LAND
BREEZE INFLUENCES LOOK TO BE ON TAP FOR AT LEAST THE FIRST PORTION
OF NEXT WEEK AS SURFACE HIGH PRESSURE DOMINATES THE GREAT LAKES
REGION.

KJB

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...FROST ADVISORY...ILZ003-ILZ004-ILZ005-ILZ006-ILZ008-ILZ010-
     ILZ011-ILZ012-ILZ013-ILZ014-ILZ019-ILZ020-ILZ021-ILZ022-
     ILZ023-ILZ032-ILZ033-ILZ039 UNTIL 8 AM FRIDAY.

IN...FROST ADVISORY...INZ001-INZ002-INZ010-INZ011-INZ019 UNTIL 8 AM
     FRIDAY.

LM...NONE.
&&

$$

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