Area Forecast Discussion
Issued by NWS Chicago, IL

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000
FXUS63 KLOT 280837
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
337 AM CDT TUE APR 28 2015

.SHORT TERM...
321 AM CDT

THROUGH THURSDAY...

ANOTHER QUIET WEATHER DAY IS EXPECTED ACROSS THE REGION AS A SURFACE
RIDGE AXIS RESULTS IN A LIGHT NORTHEASTERLY WIND OVER THE AREA. AN
AFTERNOON LAKE BREEZE SHOULD PUSH INLAND...WITH A SLIGHT WIND
INCREASE AND TEMPERATURE DROP FOLLOWING ITS PASSAGE.
OVERALL...TEMPERATURES LOOK TO TOP OUT A FEW DEGREES WARMER THAN
YESTERDAYS HIGHS. THIS SHOULD PUT ALL AREAS INLAND FROM THE LAKE
INTO THE LOWER 60S...WITH MID TO UPPER 60S ACROSS NORTH CENTRAL
PORTIONS OF THE STATE. AREAS ALONG THE LAKE MICHGAN SHORES WILL
LIKELY REMAIN IN THE UPPER 40S TO LOW 50S DUE TO THE ONSHORE FLOW.

THE MAIN CHANGE TO THE GOING FORECAST WAS TO ADD IN A MENTION OF
SHOWERS AND THUNDERSTORMS WEDNESDAY AFTERNOON AND EVENING...MAINLY
FOR INLAND AREAS. IT APPEARS THAT A SIGNIFICANT MID-LEVEL IMPULSE
AND AN ASSOCIATED UPPER JET MAX WILL DIG SOUTHWARD ALONG THE EASTERN
PERIPHERY OF A SHARPENING UPPER LEVEL JET AXIS OVER THE WESTERN
CONUS. FORECAST GUIDANCE SUGGESTS THAT THIS SYSTEM WILL QUICKLY
DEVELOP A COLD POOL IN THE MID-LEVELS (500 MB TEMPERATURES AROUND
-24 C) AS IT MOVES OVER THE AREA LATE WEDNESDAY AND WEDNESDAY NIGHT.
WITH SURFACE TEMPERATURES LIKELY TO REACH INTO THE MID TO UPPER 60S
INLAND BENEATH THIS POCKET OF COLD MID-LEVEL AIR...LAPSE RATES
SHOULD BECOME STEEP ENOUGH...THOUGH A DEEP ENOUGH LAYER TO SUPPORT
AT LEAST SOME SCATTERED SHOWER AND THUNDERSTORM DEVELOPMENT OVER
PORTIONS OF NORTHERN ILLINOIS WEDNESDAY AFTERNOON. IT CURRENTLY
APPEARS THE BEST CHANCE FOR THIS WILL BE AREAS INLAND FROM LAKE
MICHIGAN...MAINLY FROM THE WESTERN CHICAGO SUBURBS WESTWARD ACROSS
NORTH CENTRAL ILLINOIS. AN AFTERNOON LAKE BREEZE IS AGAIN LIKELY
WEDNESDAY AND THIS COULD HELP FOCUS SOME OF THE DEVELOPMENT AS IT
BECOMES COMPLEMENTED BY THE LARGER SCALE FORCING FOR ASCENT
ASSOCIATED WITH THE DEEPENING MID-LEVEL SYSTEM AND THE LEFT EXIT
REGION OF AN UPPER JET. NO SEVERE WEATHER IS EXPECTED WITH THIS
ACTIVITY...THOUGH WITH LOWER FREEZING HEIGHTS...SOME SMALL HAIL
COULD BE POSSIBLE WITH ANY STRONGER UPDRAFTS THAT DEVELOP.

SHOWERS LOOK TO LINGER OVER SOUTHERN PORTIONS OF THE AREA
WEDNESDAY NIGHT AS THE UPPER SYSTEM CLOSES OFF OVER THE AREA.
TEMPERATURES WILL BE COOLER ON THURSDAY AS A COLDER LOW LEVEL
AIR MASS SHIFTS OVER THE AREA. EXPECT TEMPERATURES TO MAINLY BE
IN THE UPPER 50S TO LOW 60S INLAND AND IN THE UPPER 40S LAKESIDE.

KJB

&&

.LONG TERM...
321 AM CDT

THURSDAY NIGHT THROUGH MONDAY...

TEMPERATURES BEGIN A WARMING TREND BY FRIDAY THROUGH THE UPCOMING
WEEKEND. IT ALSO APPEARS THAT AREAS ALONG THE LAKE SHORES WILL BE
ABLE TO JOIN IN ON THIS WARMTH THIS WEEKEND AS THE SURFACE FLOW
BECOMES OFFSHORE. IT LOOKS LIKE TEMPERATURES WILL BE WELL INTO THE
70S FOR THE WEEKEND. THE UPPER-LEVEL PATTERN IS EXPECTED TO
TRANSITION TO A QUASI-ZONAL FLOW PATTERN OVER MUCH OF THE COUNTRY BY
THE WEEKEND...THEN TO MORE OF A WEST-SOUTHWESTERLY ORIENTATION LATER
IN THE WEEKEND AS A BROAD UPPER TROUGH SETS UP OVER CANADA AND THE
NORTHWESTERN CONUS. THIS COULD SET THE STAGE FOR A BIT MORE ACTIVE
PERIOD OF WEATHER...WITH A FEW PERIODS OF SHOWERS AND THUNDERSTORMS
LOOKING POSSIBLE SATURDAY NIGHT THROUGH MONDAY.

KJB

&&

.AVIATION...

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

* LAKE BREEZE TIMING TUESDAY AFTERNOON.

BMD

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

HIGH PRESSURE WILL BE IN PLACE ACROSS NORTHERN ILLINOIS AND
NORTHWEST INDIANA THROUGH MUCH OF THE DAY TUESDAY PRODUCING LIGHT
WINDS...GENERALLY OUT OF THE NORTH OR NORTHEAST BUT POSSIBLY
VARIABLE AT TIMES. A LAKE BREEZE IS EXPECTED TO DEVELOP TUESDAY
AFTERNOON WITH WINDS PICKUP UP TO AROUND 10-12 KT OUT OF THE
NORTHEAST. WINDS WILL BECOME LIGHT AND VARIABLE TUESDAY EVENING
AND OVERNIGHT. EXPECT VFR CONDITIONS THROUGH THE PERIOD.

BMD

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

* HIGH.

BMD

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

WEDNESDAY...VFR. NORTH-NORTHEAST WINDS.

THURSDAY...BRIEF PERIOD OF MVFR CIGS POSSIBLE...OTHERWISE VFR.
NORTH-NORTHEAST WINDS.

FRIDAY...VFR. CHANCE OF SHOWERS FRIDAY NIGHT. WEST WINDS...EAST
LAKE BREEZE WINDS POSSIBLE IN THE AFTERNOON.

SATURDAY...VFR. SLIGHT CHANCE OF THUNDERSTORMS. SOUTHWEST WINDS.

SUNDAY...PRIMARILY VFR. CHANCE OF THUNDERSTORMS. SOUTH-SOUTHEAST
WINDS.

RATZER

&&

.MARINE...
305 AM CDT

QUIET WEATHER CONTINUES ACROSS LAKE MICHIGAN TODAY AS HIGH
PRESSURE LIES JUST TO THE WEST OF THE LAKE. EXPECT LIGHT NORTH
WIND TO GIVE WAY TO LAKE BREEZES THIS AFTERNOON WITH WINDS TURNING
ONSHORE. LOW PRESSURE MOVING ACROSS THE GULF OF MEXICO TODAY WILL
LIFT ACROSS THE SOUTHEASTERN STATES WEDNESDAY RESULTING IN A
MODEST INCREASE IN NORTHERLY FLOW ACROSS LAKE MICHIGAN WEDNESDAY
AND THURSDAY. THE RIDGE AXIS WILL MOVE OVER LAKE MICHIGAN FRIDAY
WITH WINDS TURNING SOUTH/SOUTHWEST BUT REMAINING RELATIVELY LIGHT
FRIDAY NIGHT INTO SATURDAY. BMD

&&

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

$$

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