Area Forecast Discussion
Issued by NWS Chicago, IL

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FXUS63 KLOT 022339
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
639 PM CDT SAT MAY 2 2015

.SHORT TERM...

TONIGHT THROUGH MONDAY NIGHT...

300 PM...FORECAST CONCERNS INCLUDE A CHANCE OF SHOWERS OVERNIGHT
INTO SUNDAY MORNING...THEN SHOWERS AND THUNDERSTORMS SUNDAY NIGHT
THRU MONDAY NIGHT.

IN THE SHORT TERM...A LAKE BREEZE HAS DEVELOPED WITH WINDS TURNING
ONSHORE IN NORTHWEST INDIANA...AND THEN SOUTHEASTERLY FROM
DOWNTOWN TO THE WI BORDER. SHORT TERM/HI RES GUIDANCE SUGGESTS
THIS BOUNDARY MAY CONTINUE MOVING INLAND THIS AFTERNOON BUT LOW
CONFIDENCE WITH 10+ MPH WINDS SPEEDS. COULD SEE THE LAKE BREEZE
REMAIN NEAR THE SHORE FOR THE NEXT FEW HRS THEN PUSH FURTHER
INLAND LATE THIS AFTERNOON/EARLY THIS EVENING AS WIND SPEEDS
DIMINISH SOME DIURNALLY.

UPPER WAVE OVER SOUTH CENTRAL IA/NORTHERN MO WILL MOVE NORTHEAST
TONIGHT AS IT SLOWLY WEAKENS. MODELS DIFFER ON HOW MUCH PRECIP
WILL REACH THE AREA. HAVE CONTINUED WITH SLIGHT CHANCE POPS FOR
MUCH OF THE AREA OVERNIGHT...DIMINISHING SUNDAY MORNING ACROSS
THE NORTH. ALSO REMOVED THUNDER AS INSTABILITY LOOKS RATHER LOW.
INCREASING MID/HIGH CLOUDS WITH THIS WAVE WILL ALSO HELP KEEP LOW
TEMPS RATHER MILD TONIGHT...GENERALLY IN THE 50S. AFTER ANY
MORNING SHOWERS...EXPECT AT LEAST PARTLY CLOUDY IF NOT MOSTLY
SUNNY SKIES SUNDAY AFTERNOON AND AFTER A WARMER START...HIGHS
SHOULD MAKE A RUN FOR THE LOWER 80S MOST AREAS. BREEZY SOUTHWEST
WINDS SHOULD PREVENT ANY LAKE COOLING WITH NO LAKE BREEZE
EXPECTED.

A FRONTAL BOUNDARY WILL MOVE ACROSS THE NORTHERN GREAT LAKES
SUNDAY EVENING...THEN SETTLE ACROSS AREA MONDAY. TIMING APPEARS TO
BE JUST A TAD SLOWER AND TRIMMED POPS SOME SUNDAY EVENING...WHICH
MAY END UP MAINLY DRY. SET UP STILL FAVORS THE POTENTIAL FOR HEAVY
RAIN BUT TRYING TO TIME INDIVIDUAL WAVES FOR BEST PRECIP TIMING IS
A BIT DIFFICULT. CONSENSUS SEEMS TO FOCUS ON MONDAY NIGHT AS THE
BEST TIME FOR WIDESPREAD SHOWERS/THUNDERSTORMS. MAINTAINED LIKELY
POPS SUNDAY NIGHT THRU MONDAY NIGHT...BUT THESE WILL LIKELY NEED
REFINEMENT WITH LATER FORECASTS.

PRECIP TIMING AND ASSOCIATED CLOUD COVER ALONG WITH FRONTAL
POSITION WILL ALL AFFECT HIGH TEMPS ON MONDAY...WHICH AT THIS
POINT IS SHAPING UP TO BE A BIT WARMER...WITH TEMPS IN THE 70S...
THOUGH CLOUD COVER AND EASTERLY WINDS COULD SIGNIFICANTLY LOWER
TEMPS ACROSS NORTHEAST IL AND THE LAKESHORE. CMS

&&

.LONG TERM...

TUESDAY THROUGH SATURDAY...

300 PM...MAIN FORECAST CONCERN ARE PRECIP CHANCES AND HIGH TEMPS.

WITH THE EXPECTATION THAT THE BEST CHANCE FOR PRECIP MAY END UP
BEING MONDAY NIGHT...POSSIBLY LINGERING INTO TUESDAY MORNING...
LOWERED POPS TUESDAY AND THESE MAY STILL BE TOO HIGH AS THE FOCUS
SHIFTS NORTH OF THE AREA. DECENT AGREEMENT THAT THE FRONTAL
BOUNDARY WILL STILL BE LOCATED ACROSS THE AREA TUESDAY AND THIS
WILL MAINTAIN COOLER EASTERLY FLOW OFF THE LAKE...BUT SOUTH OF
WHEREVER THIS BOUNDARY LIES...TEMPS WILL BE WELL INTO THE 70S. THE
FRONT WILL MOVE NORTH AS A WARM FRONT TUESDAY NIGHT INTO
WEDNESDAY. NOT MUCH TO FOCUS PRECIP DEVELOPMENT BUT MAINTAINED LOW
CHANCE POPS THRU WEDNESDAY MORNING. BY THE TIME THE FRONT LIFTS
NORTH...PRECIP CHANCES SHOULD END WITH GENERALLY DRY CONDITIONS
THRU THURSDAY. PRECIP CHANCES BEGIN TO INCREASE LATE IN THE WEEK
WITH PERHAPS THE BEST CHANCES FRIDAY NIGHT INTO SATURDAY.

HIGH TEMPS SHOULD CLIMB BACK INTO THE LOWER 80S SOUTH OF THE WARM
FRONT WED/THURS/FRI...WITH PERHAPS SOME ONSHORE WINDS/COOLER TEMPS
WEDNESDAY AS THE FRONT LIFTS BACK NORTH. CMS

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 00Z...

* NONE

IZZI

//DISCUSSION...UPDATED 00Z...

VFR THROUGH THE PERIOD. SOUTH-SOUTHWEST WINDS WILL INCREASE SUNDAY
MORNING AND LIKELY GUST TO BETWEEN 18-24KT AT TIMES THROUGH SUNDAY
AFTERNOON.

IZZI


//ORD AND MDW CONFIDENCE...UPDATED 00Z...

* HIGH CONFIDENCE ALL ELEMENTS

IZZI

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

MONDAY THROUGH TUESDAY...PERIODIC SHRA/TSRA WITH MVFR AND BRIEF
IFR POSSIBLE.

WEDNESDAY THROUGH FRIDAY...PRIMARILY VFR.

IZZI

&&

.MARINE...
217 PM CDT

HIGH PRESSURE CENTERED OVER THE MIDDLE ATLANTIC REGION COVERS A
LARGE PORTIONS OF THE EASTERN GREAT LAKES...AND STILL INFLUENCING
LAKE MICHIGAN THIS EVENING. WINDS ARE GENERALLY FROM THE SOUTH TO
SOUTHWEST...HOWEVER THE GRADIENT REMAINS JUST LIGHT ENOUGH TO ALLOW
A LAKE BREEZE TO DEVELOP BUT HUG THE SHORELINE THIS AFTERNOON. A LOW
PRESSURE OVER HUDSON BAY HAS A FRONTAL BOUNDARY EXTENDING SOUTHWEST
ACROSS THE CENTRAL PLAINS. VERY MILD AIR CONTINUES TO ADVECT NORTH
ACROSS LAKE MICHIGAN THIS AFTERNOON...SO DESPITE THE WINDS ABOVE THE
SURFACE BETWEEN 10 TO 20 KT IT DOESN/T APPEAR WAVES WILL BUILD MUCH
THIS EVENING. ALONG THE FAR NORTHERN PORTIONS OF THE LAKE WAVES MAY
BE EASIER TO BUILD...CLOSER TO A 3 TO 5 FT RANGE.

THE FRONTAL BOUNDARY ACROSS THE CENTRAL PLAINS WILL SLOWLY SLIDE
EAST SUNDAY...WHICH WILL ALSO ALLOW THE GRADIENT OVER LAKE MICHIGAN
TO TIGHTEN WITH WINDS INCREASING TO 15 TO 25 KT. IT IS POSSIBLE A
SMALL CRAFT ADVISORY MAY BE NEEDED...HOWEVER ANOTHER VERY MILD DAY
IS EXPECTED OVER LAND SUN...WHICH COULD RESULT IN A TOUGHER TIME
MIXING DOWN THE WINDS TO THE LAKE SFC BEYOND 1NM OFFSHORE. SO AT
THIS TIME WILL HOLD OFF ON A SMALL CRAFT ADVISORY FOR SUN.

THE FRONTAL BOUNDARY WILL SAG SOUTH ACROSS THE LAKE SUN NGT INTO
EARLY MON...WITH WINDS TURNING NORTH/NORTHEAST. SOUTH OF THE
BOUNDARY THE SOUTHERN TIP OF THE LAKE MAY SEE WINDS TURN EAST MON
AFTERNOON. THEN THE BOUNDARY IS EXPECTED TO STALL JUST SOUTH OF THE
LAKE MONDAY NIGHT WITH NORTHERLY WINDS BEHIND IT THEN BECOMING
EASTERLY INTO TUESDAY. THEN THE BOUNDARY WILL DEVELOP NORTH DURING
THE MIDDLE OF THE WEEK WITH SOUTHERLY WINDS INCREASING IN SPEED
THROUGH THE LATTER PART OF THE WEEK.

BEACHLER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&

$$

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