Area Forecast Discussion
Issued by NWS Chicago, IL

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FXUS63 KLOT 190751
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
251 AM CDT SAT APR 19 2014

.DISCUSSION...

250 PM...FORECAST CONCERNS INCLUDE WARMING TEMPS THIS WEEKEND
ALONG WITH LAKE COOLING...CHANCE OF SHOWERS MONDAY...LAKE COOLING
MID WEEK AND A CHANCE OF THUNDERSTORMS AHEAD OF A COLD FRONT
THURSDAY.

NORTHEASTERLY WINDS WILL STRENGTHEN A TAD GOING INTO THIS EVENING
AS HIGH PRESSURE DRIFTS SOUTHEAST ACROSS THE NORTHERN LAKES. WHILE
TEMPS HAVE WARMED INTO THE UPPER 50S/LOWER 60S WELL INLAND...TEMPS
WILL BEGIN TO DROP ACROSS MUCH OF THE METRO AREA AS COOLER AIR
SPREADS IN FROM THE LAKE. OTHERWISE...DRY WEATHER IS EXPECTED THIS
EVENING WITH THIN HIGH CLOUDS.

AS THE FLOW TURNS SOUTHERLY SATURDAY...TEMPERATURES WILL REBOUND
WELL INTO THE 60S WITH LOWER 70S EXPECTED ACROSS PARTS OF CENTRAL
IL UNDER MOSTLY SUNNY SKIES. SOUTHEASTERLY WINDS WILL KEEP THE
ILLINOIS SHORE MUCH COOLER HOWEVER. WINDS TURN A BIT MORE
SOUTHWESTERLY AND STRENGTHEN SOME ON SUNDAY. HIGHS SUNDAY SHOULD
REACH THE LOWER TO MID 70S EVERYWHERE...PERHAPS SOME UPPER 70S
SOUTH. FOR NOW HAVE MAINTAINED WARMER TEMPS ALL THE WAY TO THE
LAKESHORE...BUT COULD BE A WEAK LAKE BREEZE RIGHT ALONG THE SHORE
FROM DOWNTOWN NORTH. ANY ONSHORE FLOW WOULD LEAD TO SIGNIFICANTLY
LOWER TEMPS.

A FRONTAL BOUNDARY WILL MOVE ACROSS THE UPPER MIDWEST AND NORTHERN
LAKES REGION SATURDAY AND THEN VERY SLOWLY MOVE SOUTH SATURDAY
NIGHT AND SUNDAY. PRECIPITATION WITH THIS FRONT WILL REMAIN WELL
NORTH OF THE AREA THROUGH SUNDAY EVENING WHEN WEAK LOW PRESSURE
DEVELOPS OVER IOWA AND THEN SHIFTS EAST ACROSS THE AREA ON MONDAY.
HAVE SCALED BACK POPS THROUGH SUNDAY EVENING...GOING DRY AND MAY
END UP BEING DRY MUCH OF SUNDAY NIGHT UNTIL PRECIP FINALLY ARRIVES
WITH MAIN SURFACE LOW AND WHILE THERE MAY BE SOME PERIODS OF DRY
WEATHER ON MONDAY HAVE BUMPED POPS TO LOW END LIKELY. END TIME
MONDAY EVENING/MONDAY NIGHT STILL A BIT UNCERTAIN BUT MUCH OF
MONDAY NIGHT...ESPECIALLY ACROSS THE WESTERN CWA MAY END UP BEING
DRY.

AS A RIDGE OF HIGH PRESSURE PASSES TUESDAY INTO WEDNESDAY...TEMPS
WILL DROP BACK TO SEASONAL LEVELS FOR MID APRIL BUT WITH EASTERLY
FLOW...MUCH COOLER TEMPS CAN BE EXPECTED ALONG THE LAKE.

STRONGER LOW PRESSURE WILL MOVE ACROSS THE NORTHERN PLAINS
THURSDAY AND THEN ACROSS THE LAKES REGION TOWARD THE END OF THE
WEEK. HELD ONTO CHANCE POPS FROM WEDNESDAY NIGHT THROUGH FRIDAY.
HOWEVER...THERE WILL BE MANY DRY HOURS DURING THIS PERIOD AND
EXPECT THE BEST CHANCE OF SHOWERS AND THUNDERSTORMS TO BE
ALONG/AHEAD OF A COLD FRONT FROM THURSDAY AFTERNOON INTO THURSDAY
NIGHT. ADDITIONAL TIMING CAN BE ADDED AS THIS TIME PERIOD
APPROACHES BUT DID LOWER POPS ON FRIDAY AS EVEN COOLER WRAP AROUND
SHOWERS MAY ONLY BRUSH NORTHERN IL. TEMPS THEN TURN MUCH COLDER
GOING INTO NEXT WEEKEND. CMS

&&

.AVIATION...

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

* NONE.

RATZER

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

SURFACE HIGH PRESSURE RIDGE OVER LAKE MICHIGAN AND NORTHEAST
ILLINOIS EARLY THIS AM WILL MOVE EAST TODAY...WITH WINDS GRADUALLY
VEERING MORE EAST-SOUTHEAST DURING THE MORNING HOURS. LAKE BREEZE
IS EXPECTED TO DEVELOP AND MAY RESULT IN A WIND SHIFT MORE TO THE
EAST ACROSS ORD AND POSSIBLY MDW/GYY. WHILE EXACT DIRECTION
SOMEWHAT UNCERTAIN...SOME EASTERLY OR EAST-SOUTHEAST COMPONENT IS
EXPECTED. OTHERWISE...VERY DRY CONDITIONS WITH VFR CONDITIONS
THROUGH THE PERIOD.

RATZER

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

* LOW CONFIDENCE IN EXACT WIND DIRECTION SATURDAY AFTERNOON...BUT
  HIGH CONFIDENCE IT WILL BE GENERALLY EAST-SOUTHEAST.
* HIGH CONFIDENCE IN ALL OTHER FORECAST ELEMENTS.

RATZER

//OUTLOOK FOR ORD/MDW FOR 12Z SUNDAY-12Z FRIDAY...UPDATED 00Z...

SUNDAY...VFR.

MONDAY...SCT`D SHRA...MAINLY IN AFTERNOON.

TUESDAY THROUGH THURSDAY...VFR.

IZZI

&&

.MARINE...
251 AM CDT

HIGH PRESSURE RIDGE OVER THE WESTERN LAKES EARLY THIS MORNING WILL
DRIFT OFF TO THE EAST TODAY...WHILE A PAIR OF SURFACE LOW PRESSURE
CENTERS OVER THE NORTHERN PLAINS AND CANADIAN PRAIRIES CONSOLIDATE
INTO A SINGLE LOW NORTH OF THE BORDER. SOUTH-SOUTHEAST WINDS WILL
GRADUALLY INCREASE TODAY INTO TONIGHT AS THE LOW MOVES EAST INTO
ONTARIO AND THE GRADIENT TIGHTENS IN ADVANCE OF A COLD FRONT WHICH
WILL TRAIL THIS LOW INTO THE CENTRAL AND SOUTHERN PLAINS. SOUTHERLY
WINDS MAY APPROACH 30 KT ON THE NORTHERN PORTION OF THE LAKE TONIGHT
AS THE LOW PASSES BY TO THE NORTH. THE GRADIENT WILL THEN WEAKEN
SUNDAY AS THE LOW CONTINUES TO TRACK EAST TOWARDS JAMES BAY... AND
THE FRONT SAGS SOUTHEAST ACROSS THE LAKE. THE COLD FRONT WILL NOT
COMPLETE ITS TRANSIT OF THE LAKE AT THAT TIME HOWEVER...AS ANOTHER
WEAKER AREA OF LOW PRESSURE DEVELOPS OVER THE SOUTHERN PLAINS SUNDAY
AND LIFTS NORTHEAST ALONG THE FRONT INTO THE GREAT LAKES REGION ON
MONDAY. THIS LOW WILL PULL THE COLD FRONT SOUTHEAST OF THE LAKE BY
MONDAY EVENING. NORTHERLY WINDS WILL THEN INCREASE AS THE GRADIENT
TIGHTENS AHEAD OF AN AREA OF HIGH PRESSURE BUILDING EAST ACROSS THE
PLAINS AND UPPER MIDWEST INTO TUESDAY. THE HIGH PRESSURE RIDGE WILL
MOVE ACROSS THE WESTERN LAKES WEDNESDAY MORNING...WHILE ANOTHER DEEP
LOW TAKES SHAPE TO THE WEST ACROSS THE NORTHERN HIGH PLAINS. STRONG
SOUTH WINDS ARE ANTICIPATED AGAIN THURSDAY AS THIS LOW ALSO MOVES
EAST.

RATZER

&&

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

$$

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