National Weather Service Weather Forecast Office

• Home
• Site Map
• News
• Organization
• Search for: NWS All NOAA 

000
FXUS63 KLOT 181837
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
137 PM 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 18Z...

* GUSTY NORTHEAST WINDS INTO THIS EVENING. CMS

//DISCUSSION...UPDATED 18Z...

IFR/LIFR CIGS STILL PERSISTING SOUTH OF MDW FROM IGQ TO GYY EAST
ALONG THE INDIANA SHORELINE. CLEARING FROM THE EAST ALONG WITH
EROSION FROM THE SOUTHWEST SEEMS TO HAVE SLOWED IN THE PAST HR OR
SO. WHILE VFR CONDITIONS ARE NOW EXPECTED AT ORD/MDW...WILL NEED
TO MONITOR TRENDS FOR GYY THROUGH THE AFTERNOON. SOME CU ALONG
WITH MID CLOUDS POSSIBLE THROUGH EARLY EVENING...THEN SKC EXPECTED
FOR THE REMAINDER OF THE PERIOD.

NORTHEAST WINDS WILL REMAIN IN THE 10-15KT RANGE WITH GUSTS IN THE
16-20KT RANGE INTO THIS EVENING WITH WINDS DIMINISHING UNDER 10KTS
BY MID/LATE EVENING THEN TURNING MORE EASTERLY WEDNESDAY MORNING.

AS A WEAK WAVE MOVES SOUTH OF THE TERMINALS THIS AFTERNOON...THERE
COULD BE SOME SHOWERS AND POSSIBLY AN ISOLATED TSRA BUT ANY
ACTIVITY THAT DEVELOPS IS EXPECTED TO REMAIN SOUTH OF ALL THE
TERMINALS. CMS

//ORD AND MDW CONFIDENCE...UPDATED 18Z...

* MEDIUM CONFIDENCE REGARDING WIND SPEEDS/GUSTS THROUGH THE
  PERIOD. CMS

//OUTLOOK FOR ORD/MDW FOR 00Z THURSDAY-12Z TUESDAY...UPDATED 12Z...

WEDNESDAY NIGHT THROUGH THURSDAY NIGHT...VFR.
FRIDAY THROUGH MONDAY...PERIODIC CHANCES FOR THUNDERSTORMS...ELSE VFR.

BMD

&&

.MARINE...
137 PM CDT

A SURFACE RIDGE OF HIGH PRESSURE ACROSS THE UPPER GREAT LAKES
REGION...WILL SHIFT EASTWARD TOWARDS NEW ENGLAND BY WEDNESDAY
EVENING. MEANWHILE...LOW PRESSURE IS EXPECTED TO TAKE SHAPE ACROSS
THE PLAINS STATES. THIS PRESSURE PATTERN WILL REMAIN IN PLACE FOR A
FEW DAYS INTO THE WEEKEND. OVERALL...THIS WILL RESULT IN A PROLONGED
PERIOD OF SOUTHERLY WINDS ACROSS THE LAKE. WIND MAGNITUDES GENERALLY
LOOK TO BE IN THE 10 TO 20 KT RANGE...WITH A FEW PERIODS OF 15 TO 25
KT SOUTHERLY WINDS...ESPECIALLY LATER IN THE PERIOD.

THERE WILL ALSO BE INCREASING CHANCES FOR A FEW PERIODS OF
THUNDERSTORM ACTIVITY FRIDAY AND INTO THE WEEKEND OVER THE LAKE. A
FAIRLY ACTIVE WEATHER PATTERN LOOKS TO SETUP UP ACROSS THE GREAT
THE NORTHERN CONUS AND GREAT LAKES REGION.

IN THE SHORTER TERM...I HAVE EXTENDED THE SMALL CRAFT ADVISORY INTO
THIS EVENING FOR THE ILLINOIS SHORES AND MAINTAINED THE ADVISORY
THROUGH LATE TONIGHT FOR THE INDIANA SHORES. LOCAL BUOY OBS INDICATE
WAVES AROUND 4 FT...AND WITH THE ONSHORE FLOW CONTINUING TO BE IN THE
15 TO 20 KT RANGE AHEAD OF THE SURFACE HIGH...I DO NOT SEE ANY
IMPROVEMENT IN THE WAVE CONDITIONS FOR SEVERAL MORE HOURS.

KJB

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...BEACH HAZARDS STATEMENT...ILZ006-ILZ014 UNTIL 4 AM WEDNESDAY.

IN...BEACH HAZARDS STATEMENT...INZ001-INZ002 UNTIL 4 AM WEDNESDAY.

LM...SMALL CRAFT ADVISORY...NEARSHORE WINTHROP HARBOR TO NORTHERLY IS UNTIL 10 PM TUESDAY.

     SMALL CRAFT ADVISORY...NEARSHORE NORTHERLY IS TO MICHIGAN CITY IN UNTIL 4 AM
     WEDNESDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO