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000
FXUS63 KLOT 180916
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
416 AM CDT TUE JUN 18 2013

.DISCUSSION...
330 AM CDT

PRIMARY FORECAST CHALLENGE THIS MORNING IS WITH PRECIP CHANCES
TODAY AND INTO THE WEEKEND...ALONG WITH POTENTIAL BIG WEEKEND WARM
UP.

SOMEWHAT DIFFUSE COLD FRONT...AIDED BY SOME LAKE ENHANCEMENT...HAS
PUSHED SOUTH OF THE CWA THIS MORNING WITH NORTH TO NORTHEAST WINDS
ADVECTING IN COOLER AND DRIER AIR MASS. HOWEVER...VIGOROUS SHORTWAVE
TROUGH OVER MN THIS MORNING IS PROGGED TO DROP SOUTHEAST TOWARD THE
AREA RESULTING IN A STEEPENING UP OF THE LOW AND ESPECIALLY MID
LEVEL LAPSE RATES RESULTING IN SOME INSTABILITY DEVELOPING.
INSTABILITY WILL BE MOST PRONOUNCED...ALBEIT LIKELY WEAK
STILL...WELL WEST AND SOUTH OF THE LAKE AS STABLE MARINE BOUNDARY
LAYER WILL BLEED WELL INLAND. NO REAL CHANGES MADE TO POPS TODAY
WITH EXPECTATION THAT THE GREATEST CHANCES OF CONVECTION WILL BE
FROM NC IL SE INTO SOUTHERN PORTIONS OF THE CWA. GIVEN THE STEEP
LAPSE RATES CAN NOT RULE OUT SOME SPRINKLES FALLING FROM SOME
ACCAS/MID DECK OVER CHICAGO AREA...BUT CHANCES LOOK TOO SLIM TO ADD
TO FORECAST.

A COUPLE OF TRULY SPECTACULAR WEATHER DAYS EXPECTED WEDNESDAY
AND PROBABLY INTO THURSDAY AS WELL. WEDNESDAY SHOULD FEATURE FULL
SUNSHINE AND BELOW AVERAGE TEMPERATURES WITH 70S INLAND AND 60S
LAKESIDE. TEMPS WILL WARM A COUPLE DEGREES ON THURSDAY...BUT
EXPECT SOME INCREASE IN MID-HIGH LEVEL CLOUDINESS IN THE AFTERNOON
AS REMNANTS OF DECAYING MCS POTENTIALLY MOVE INTO THE AREA. SOME
MODELS ARE SUGGESTING SOME PRECIP COULD MAKE IT INTO THE CWA
THURSDAY...ESPECIALLY WEST...BUT THINKING THAT CONVECTIVE ACTIVITY
SHOULD DRY UP PRETTY QUICKLY AS IT TRIES TO PENETRATE EASTWARD
INTO DRY CANADIAN AIR MASS OVER THE AREA.

FRIDAY THROUGH THE WEEKEND INTO EARLY NEXT WEEK LOOK PRETTY SUMMER
LIKE ON THE WHOLE. UPPER RIDGE IS PROGGED TO SPREAD EAST INTO THE
CENTRAL AND EVENTUALLY EASTERN CONUS...WITH OUR CWA LIKELY TO BE ON
THE NORTHERN FRINGES OF THIS RIDGE. THIS CERTAINLY COMPLICATES THE
FORECAST WITH RING OF FIRE PATTERN LIKELY TO SET UP ON THE PERIPHERY
OF THE RIDGE AND WITH OUR CWA LYING PRECARIOUSLY CLOSE TO THE EDGE
OF THE RIDGE AND STRONGER BELT OF WESTERLIES THE FORECAST IS A LOW
CONFIDENCE ONE. SYNOPTICALLY...IT WOULD APPEAR THE FRONT SHOULD LIE
NORTH OF THE CWA PUTTING US IN THE HOT AND HUMID AIR MASS WITH HIGHS
AROUND IF NOT INTO THE LOWER 90S. HOWEVER...SHOULD PARADE OF MCS
ACTIVITY NUDGE THE FRONT SOUTHWARD INTO THE AREA THEN TEMPS WOULD BE
COOLER WITH CLOUDS AND THUNDER POTENTIAL. UNFORTUNATELY AM LEFT WITH
LITTLE CHOICE OTHER THAN TO PAINT DAY AFTER DAY WITH CHANCES OF
SHOWERS AND THUNDERSTORMS...WHEN IN REALITY THE MAJORITY OF THE FRI
THROUGH MON PERIOD WILL BE DRY WITH A WORST CASE SCENARIO LIKELY
BEING ONE OR TWO ROUNDS OF THUNDERSTORMS.

IZZI

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 09Z...

* POTENTIAL FOR LOW CIGS OVERNIGHT.

BMD

//DISCUSSION...UPDATED 09Z...
BLOSSOMING AREA OF STRATUS IS MOVING ONSHORE FROM LAKE MICHIGAN THIS
HOUR AND MAY IMPACT THE CHICAGO TERMINALS IN THE NEXT HOUR OR SO.
SOME OF THE NEAR-SHORE OBSERVING PLAFORMS ARE INDICATING 007-012
CIGS. RAP/NAM WHICH SEEM TO HAVE HANDLED THE DEVELOPMENT WELL SHOW
CIGS SCATTERING OUT SOMEWHERE BETWEEN 14Z AND 16Z.

PREVIOUS DISCUSSION...06Z...
A COLD FRONT HAS DROPPED SOUTH ACROSS THE
TERMINALS LEAVING NORTHEAST FLOW OVER NORTHERN ILLINOIS AS HIGH
PRESSURE BUILDS ACROSS THE PLAINS AND NORTHERN LAKES REGION. THE
HIGH IS EXPECTED TO VERY GRADUALLY CONSOLIDATE AND SINK SOUTH
TOWARDS NORTHERN LAKE MICHIGAN THROUGH THE DAY TUESDAY LEADING TO
VERY LITTLE CHANCE IN THE WEATHER THROUGH THE FORECAST PERIOD.
WINDS WILL PICK UP WITH ONSET OF MIXING DURING THE DAY
TUESDAY...THEN SHOULD DIMINISH AFTER SUNSET. VFR CLOUDS EXPECTED
THROUGH THE PERIOD...BUT CONTINUE TO MONITOR CLOSELY THE CHANCE
FOR LOWER CIGS DEVELOPING OVERNIGHT INTO THE EARLY MORNING HOURS.
NAM/RAP SOUNDINGS CONTINUE TO ADVERTISE THE POTENTIAL FOR IFR CIGS
TO DEVELOP AS THE COLUMN COOLS...BUT SEE NO SIGN OF THIS YET
UPSTREAM AND OTHER MODELS AS LESS BULLISH ON THE DEVELOPMENT. NAM
HAS A TENDENCY TO OVERDO LOW LEVEL MOISTURE SO FOR NOW WILL
MONITOR CLOSELY. IF LOW CIGS DO DEVELOP THE BEST TIME FRAME WOULD
BE ROUGHLY 09-14Z.

BMD

//ORD AND MDW CONFIDENCE...UPDATED 09Z...

* HIGH CONFIDENCE IN LOW CIGS DEVELOPING.
* HIGH CONFIDENCE IN OTHER FORECAST ELEMENTS.

BMD

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

WEDNESDAY...VFR.

THURSDAY...VFR.

FRIDAY...VFR EARLY...CHANCE OF TSRA OVERNIGHT.

SATURDAY AND SUNDAY...PERIODIC CHANCES FOR TSRA.

LENNING

&&

.MARINE...
300 AM CDT

A COLD FRONT HAS PUSHED SOUTH OF LAKE MICHIGAN AND HIGH PRESSURE
OVER THE NORTHERN LAKES REGION THIS MORNING WILL GRADUALLY SETTLE
SOUTHEAST OVER LAKE MICHIGAN TONIGHT AND WEDNESDAY. FRESH NORTHERLY
WINDS THIS MORNING WILL CONTINUE THROUGH TODAY AND THE PERSISTENT
AND LONG FETCH IS EXPECTED TO ALLOW WAVES TO BUILD ACROSS THE FAR
SOUTH PORTIONS OF THE LAKE AND NEARSHORE WATERS TO OR ABOVE 5
FT...THUS WILL ISSUE A SMALL CRAFT ADVISORY FOR THE INDIANA AND
EASTERN MOST ILLINOIS NEARSHORE ZONES. AS THE HIGH BUILDS SOUTH
OVERNIGHT WINDS AND WAVES SHOULD BEGIN TO DIMINISH. EXPECT LAKE
BREEZES TO DOMINATE THE WIND PATTERN WEDNESDAY AFTERNOON/EVENING.
LOW PRESSURE WILL BEGIN TO TAKE SHAPE OVER THE PLAINS AND THE
DEPARTING HIGH WILL ALLOW SOUTHERLY WINDS TO OVERTAKE THE LAKE
THURSDAY THROUGH THE WEEKEND. BMD

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...BEACH HAZARDS STATEMENT...ILZ006-ILZ014...1 PM TUESDAY TO 4 AM
     WEDNESDAY.

IN...BEACH HAZARDS STATEMENT...INZ001-INZ002...1 PM TUESDAY TO 4 AM
     WEDNESDAY.

LM...SMALL CRAFT ADVISORY...LMZ742-LMZ743-LMZ744-LMZ745...1 PM
     TUESDAY TO 4 AM WEDNESDAY.

&&

$$

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