Area Forecast Discussion
Issued by NWS Chicago, IL

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FXUS63 KLOT 280519
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1219 AM CDT TUE APR 28 2015

.SHORT TERM...
250 PM CDT

THROUGH THURSDAY...

A QUIET FORECAST CYCLE CONTINUES WITH A SLOW MOVING UPPER PATTERN
AND THUS SURFACE REFLECTION ACROSS THE AREA. THIS IS PREVENTING
TEMPERATURES FROM CLIMBING BACK TO NORMAL AT A MORE SPEEDY RATE
ACROSS MOST OF THE FORECAST AREA WITH NORTHERLY LOW-LEVEL WINDS
PERSISTING AND THUS LAKE INFLUENCE CONTINUING MODIFY THE AIR MASS
SOME. A 16 DEGREE RANGE IS SEEN ACROSS THE FORECAST AREA AS OF 230
PM THIS AFTERNOON FROM LAKESIDE OF 47 DEGREES TO 63 OUT IN PARTS
OF NORTH CENTRAL ILLINOIS. THIS SIMILARLY IS EXPECTED TO RESULT A
GOOD PART OF THE WORKWEEK.

GIVEN THE ANTICIPATED SURFACE RIDGE PLACEMENT LATER TONIGHT FROM THE
U.P. OF MICHIGAN THROUGH EASTERN IOWA...LESS WIND IS FORECAST THAN
LAST...ALTHOUGH STILL A SLIGHT COMPONENT IS EXPECTED THIS EVE.
CONDITIONS WARRANT A SLIGHTLY BETTER FROST POTENTIAL THAN LAST
NIGHT IN EXPOSED AREAS...BUT CONSIDERING THAT TEMPERATURES DID NOT
DROP AS FAR LAST NIGHT IN MANY PLACES AS ANTICIPATED...STILL
MARGINAL CONFIDENCE FOR AN ADVISORY. PATCHY TO SOME AREAS OF FROST
ARE MENTIONED IN THE FORECAST ALONG WITH OUR OTHER MESSAGING WHICH
SHOULD SUFFICE.

GUIDANCE HAS TRENDED STRONGER WITH A BUCKLE IN THE NORTHERN FLOW OF
THE JET STREAM ON WEDNESDAY. THE FORCING FOR ANY RAIN REMAINS
WEAK...BUT THE LOW-LEVEL REFLECTION OF COOLER AIR ADVECTING IN
LOOKS MORE PRONOUNCED WEDNESDAY NIGHT INTO THURSDAY AS A CLOSED
UPPER LOW IS FORECAST NOW OVER LAKE MICHIGAN DROPPING SOUTHWARD.
THIS PATTERN SHOULD RESULT IN MORE CLOUDS DURING THAT
PERIOD...ESPECIALLY AS LOW-LEVEL LAPSE RATES STEEPEN DURING THE
AFTERNOON. HAVE HIGHS ON THURSDAY SIMILAR TO WHAT THEY WERE TODAY
WITH SYNOPTIC NORTHEAST WINDS.

MTF

&&

.LONG TERM...
300 PM CDT

THURSDAY NIGHT THROUGH MONDAY...

AS WE FLIP THE CALENDAR FROM APRIL TO MAY...THE DRY BENIGN
CONDITIONS AT THE END OF APRIL WILL TRANSITION TO A WARMER...MORE
HUMID...AND POTENTIALLY ACTIVE PATTERN. MID AND UPPER PATTERN WILL
BECOME GENERALLY ZONAL. WHILE STRONGER FLOW ALOFT WILL REMAIN NEAR
OR NORTH OF THE CANADIAN BORDER...MIDLEVEL SHORTWAVE ENERGY SHOULD
STILL PROPAGATE ACROSS THE REGION IN WARM ADVECTION REGIME ALSO
ACCOMPANIED BY LOW PRESSURE SYSTEMS DEVELOPING OVER PLAINS AND
WORKING THEIR WAY EAST-NORTHEAST. BETTER MOISTURE RETURN WILL ALSO
OCCUR AROUND PERIPHERY OF HIGH PRESSURE EXPECTED TO SETUP NEAR OR
OFF SOUTHEAST COAST OVER THE WEEKEND INTO EARLY NEXT WEEK.

END RESULT IN SENSIBLE WEATHER IS GENERALLY DRY DAY ON FRIDAY
WITH ONSHORE FLOW...BUT START OF WARM-UP WITH HIGHS OF ABOUT 65 TO
70 INLAND. MODEL THERMAL PROGS AND LOCAL CLIMO SUPPORTS HIGHS
INTO 70S SATURDAY THROUGH MONDAY...AND POSSIBLY WELL INTO 70S AT
THAT. GIVEN PROGGED MOISTURE RETURN/50+ DEWPOINTS IN THIS
PERIOD...SHOULD BE ENOUGH INSTABILITY TO SUPPORT OCCASIONAL
THUNDER CHANCES IN DISTURBED FLOW OVER THE WEEKEND INTO NEXT
WEEK...BUT POPS WILL UNDOUBTEDLY BE REFINED IN LATER FORECASTS.
UNCERTAINTY WITH HOW WARM TEMPERATURES MAY GET OVER THE WEEKEND
INTO EARLY NEXT WEEK WILL LIKELY BE TIED TO IMPACT OF CLOUDS AND
PRECIP...AND ANY DAYS THAT HAVE ONSHORE FLOW.

RC

&&

.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...
212 PM CDT

HIGH PRESSURE WILL CONTINUE TO EXPAND OVER THE NORTHERN UNITED
STATES IN THE COMING DAYS. WINDS WILL LIGHTEN UP SOME AS THIS
OCCURS...WHICH SHOULD ALLOW WAVES TO SUBSIDE ALONG THE SOUTHERN
TIP OF THE LAKE. WAVES HAVE BEEN HOLDING AROUND 4-5 FT ALONG THE
NEARSHORE...SO WILL LET THE ADVISORY RIDE THROUGH THE EVENING. THE
CORE OF HIGH PRESSURE WILL REMAIN NORTH OF THE AREA THROUGH
MIDWEEK. MEANWHILE...LOW PRESSURE WILL MOVE EAST ALONG THE GULF
COAST THROUGH THURSDAY. THEN NORTHEAST ALONG THE ATLANTIC COAST
THURSDAY INTO FRIDAY. THIS WILL MAINTAIN NORTH-NORTHEAST WINDS
ACROSS THE LAKE MOST OF THE WEEK...WITH AN UPTICK EXPECTED ON
THURSDAY AS THE SOUTHERN LOW DEEPENS SLIGHTLY. THE HIGH WILL MOVE
OVERHEAD FRIDAY FOR A LAKE BREEZE CIRCULATION DOMINATED WIND
FIELD.

KMD

&&

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

$$

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