Area Forecast Discussion
Issued by NWS Chicago, IL

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FXUS63 KLOT 200508
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1208 AM CDT SUN APR 20 2014

.DISCUSSION...

250 PM...FORECAST CONCERNS INCLUDE HIGHS BACK IN THE 70S SUNDAY
AND MONDAY...ALONG WITH POSSIBLE LAKE COOLING. SHOWERS ALONG WITH
A CHANCE OF THUNDERSTORMS MONDAY AFTERNOON/EVENING...ADDITIONAL
SHOWERS FOR THE END OF THE WEEK.

DESPITE THE CENTER OF HIGH PRESSURE NOW OVER THE EASTERN LAKES
AND PUSHING INTO WESTERN QUEBEC...THE GRADIENT REMAINS WEAK OVER
LAKE MICHIGAN AND THIS IS AIDING COOLER EASTERLY FLOW WITH TEMPS
ALONG THE IL LAKESHORE ONLY IN THE 40S. TEMPS WARM QUICKLY INTO
THE 60S INLAND. THIS EASTERLY FLOW WILL SLOWLY TURN SOUTHEASTERLY
AS THE GRADIENT GRADUALLY TIGHTENS OVERNIGHT. LOWS TONIGHT ARE A
BIT TRICKY...DEWPOINTS WILL GRADUALLY CREEP UP...PERHAPS INTO THE
LOWER 40S BY MORNING. AIR ALOFT WILL ALSO BE WARMING. LOWS MAY END
UP OCCURRING IN THE LATE EVENING OR EARLY OVERNIGHT THEN BECOME
STEADY OR SLOWLY RISE TOWARD MORNING. BUT USUAL COOL SPOTS MAY DIP
INTO THE LOWER 40S.

SUNDAY WILL BE DRY AND WARMER AS HIGHS SHOULD EASILY REACH THE
LOWER TO MID 70S WITH SOME UPPER 70S POSSIBLE ACROSS PARTS OF
CENTRAL IL. HOWEVER...THE GRADIENT NOW APPEARS TO BE JUST WEAK
ENOUGH FOR A LAKE BREEZE TO FORM FROM DOWNTOWN NORTH TO THE WI/IL
STATE LINE AND IT WILL LIKELY REMAIN RIGHT ALONG THE SHORE...
MAKING THE TEMP FORECAST DIFFICULT. TEMPS COULD STAY IN THE UPPER
40S/LOWER 50S RIGHT AT THE SHORE LINE...QUICKLY WARMING INTO THE
LOWER 70S JUST A FEW MILES INLAND.

A FRONTAL BOUNDARY WILL SLOWLY SAG ACROSS THE NORTHERN LAKES
TONIGHT INTO SUNDAY AND THEN BECOME STATIONARY INTO SUNDAY NIGHT
AS LOW PRESSURE MOVES ACROSS THE UPPER MIDWEST AND NORTHERN GREAT
LAKES REGION MONDAY. PRECIP TIMING CONTINUES TO SLOW AND MUCH OF
THE AREA SHOULD REMAIN DRY THROUGH DAYBREAK MONDAY WITH ONLY THE
WESTERN THIRD OF THE CWA POTENTIALLY SEEING SOME SHOWERS MONDAY
MORNING. BEST CHANCE OF SHOWERS AND PERHAPS A FEW THUNDERSTORMS
WILL BE ALONG/AHEAD OF A TRAILING COLD MONDAY AFTERNOON INTO
MONDAY EVENING. WITH LOWS ONLY FALLING BACK INTO THE 50S SUNDAY
NIGHT/MONDAY MORNING...HIGHS ON MONDAY WILL LIKELY BE ABLE TO
REACH THE LOWER 70S...ESPECIALLY EASTERN TWO THIRDS OF THE CWA
AND BUMPED TEMPS UP A FEW DEGREES.

A RIDGE OF HIGH PRESSURE WILL MOVE ACROSS THE REGION TUESDAY AND
TUESDAY NIGHT ALLOWING FOR SEASONAL TEMPS ALONG WITH EASTERLY FLOW
KEEPING THE LAKESHORE AREAS COOLER. AS THE HIGH DEPARTS...A BRIEF
PERIOD OF SHOWERS APPEAR POSSIBLE WEDNESDAY AFTERNOON INTO
WEDNESDAY EVENING AS WARMER AIR SPREADS ACROSS THE REGION BUT THIS
SHOULD BE FAIRLY SHORT-LIVED WITH THE REST OF WEDNESDAY NIGHT AND
THE FIRST PART OF THURSDAY MOSTLY DRY. TEMPS RISE BACK TO THE MID/
UPPER 60S THURSDAY AND WHILE WINDS LOOK FAIRLY BREEZY...THEY WILL
BE MAINLY SOUTHERLY...SO SOME LAKE COOLING ALONG THE IL SHORE WILL
BE POSSIBLE. THE BEST CHANCE OF SHOWERS AND THUNDERSTORMS WILL BE
ALONG/AHEAD OF A COLD FRONT LATER THURSDAY AFTERNOON INTO THURSDAY
EVENING. CMS

&&

.AVIATION...

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

* NONE.

RATZER

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

SOUTHEAST WINDS NEAR 10 KT WILL VEER SOUTH SUNDAY MORNING AND
INCREASE SLIGHTLY...WITH A FEW OCCASIONAL GUSTS 15-20 KT POSSIBLE
DURING THE AFTERNOON HOURS. DRY VFR CONDITIONS WILL CONTINUE...
WITH SCT MID/HIGH CLOUDS INCREASING AND EVENTUALLY FORMING A MORE
SOLID MID-LEVEL DECK SUNDAY NIGHT.

RATZER


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

* HIGH CONFIDENCE ALL FORECAST ELEMENTS.

RATZER

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

MONDAY...AFTERNOON SHRA LIKELY. BRIEF MVFR POSSIBLE.

TUESDAY AND WEDNESDAY...VFR.

THURSDAY...CHANCE SHRA/TSRA...MAINLY AT NIGHT.

FRIDAY...VFR PROBABLE.

IZZI

&&

.MARINE...
151 PM CDT

LOW PRESSURE TRACK FROM SOUTHERN MANITOBA EAST-NORTHEASTWARD TO NEAR
THE JAMES BAY BY LATE SUNDAY. THIS WILL SYSTEM WILL PRODUCE A PERIOD
OF STIFF SOUTHERLY WINDS UP AROUND 25 KT ACROSS THE LAKE TONIGHT
INTO SUNDAY. HOWEVER...THE STRONGEST OF THESE WINDS SHOULD REMAIN
OVER THE OPEN WATERS OF THE LAKE. A COLD FRONTAL
BOUNDARY...ASSOCIATED WITH THIS LOW...IS FORECAST TO MOVE ACROSS THE
FAR NORTHERN PORTION OF THE LAKE SUNDAY NIGHT...THEN AS A SECOND
AREA OF LOW PRESSURE MOVES OVER THE LAKE MONDAY...THE FRONT WILL BE
DRIVEN ACROSS THE ENTIRE LAKE BY MONDAY EVENING. IT APPEARS THAT A
PERIOD OF STRONG NORTHERLY WINDS (25 TO 30 KT) MAY SET UP FOR A
PERIOD IN THE WAKE OF THIS FRONT FOR MONDAY NIGHT AND
TUESDAY...BEFORE HIGH PRESSURE BEGINS TO BUILD ACROSS THE LAKE BY
MIDWEEK.

THE LATER PORTION OF THE UPCOMING WEEK APPEARS TO REMAIN ACTIVE
ACROSS THE GREAT LAKES REGION...AS WEATHER SYSTEMS REMAIN VERY
PROGRESSIVE. IT APPEARS THAT ANOTHER SIGNIFICANT AREA OF LOW
PRESSURE WILL IMPACT THE UPPER MIDWEST AND THE GREAT LAKES REGION
LATE IN THE WEEK AND INTO EARLY NEXT WEEKEND. THIS SYSTEM COULD
PRODUCE THUNDERSTORMS ACROSS THE LAKE AND ALSO ADDITIONAL PERIODS OF
SIGNIFICANT WINDS.

KJB

&&

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

$$

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