Area Forecast Discussion
Issued by NWS Chicago, IL

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000
FXUS63 KLOT 282306
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
606 PM CDT MON JUL 28 2014

.DISCUSSION...
244 PM CDT

MAIN FOCUS THROUGH THE FORECAST PERIOD REMAINS ON COOLER THAN NORMAL
WEATHER FOR LATE JULY AND EARLY AUGUST...AND LOW CHANCE POPS FOR
DAILY DIURNAL SHOWER/THUNDERSTORM POTENTIAL.

MORNING UPPER AIR ANALYSIS DEPICTS ANOMALOUSLY DEEP EASTERN NORTH
AMERICAN UPPER TROUGH WITH AN UPPER LOW OVER CENTRAL QUEBEC. THIS
FEATURE IS PROGGED TO SLOWLY RETROGRADE WESTWARD TOWARD JAMES BAY
THROUGH FRIDAY BEFORE EVENTUALLY OPENING UP AND LIFTING OUT TO THE
NORTHEAST OVER THE WEEKEND. THIS PERSISTENT UPPER AIR PATTERN WILL
KEEP THE WESTERN GREAT LAKES REGION IN PERSISTENT COOL NORTHWEST
FLOW ALOFT...WITH SERIES OF SHEARED MID-LEVEL SHORT WAVE FEATURES
ROTATING THROUGH THE WESTERN PERIPHERY OF THE UPPER LOW. THIS
PRESENTS A DAILY THREAT OF ISOLATED TO SCATTERED SHOWERS AND
THUNDERSTORMS DURING THE AFTERNOON/EVENING DIURNALLY FAVORED
INSTABILITY MAXIMA...WITH COVERAGE LIKELY LIMITED SOMEWHAT AND
TIED TO LOCALIZED BOUNDARY LAYER CONVERGENCE LINES. CURRENT
AFTERNOON GOES WATER VAPOR IMAGERY DEPICTS A WEAK MID-LEVEL SHORT
WAVE FEATURE DROPPING SOUTHWARD ACROSS WESTERN ONTARIO WHICH SHOULD
ARRIVE OVER THE AREA TUESDAY MORNING...AND MODELS INDICATE ANOTHER
SUCH FEATURE PASSING THROUGH WEDNESDAY. STRONGER HEIGHT FALLS OCCUR
FRIDAY INTO AS UPPER TROUGH RETROGRADES. GIVEN THESE CONTINUED
GUIDANCE TRENDS HAVE MAINTAINED GENERALLY LOW CHANCE POPS MAINLY FOR
AFTERNOON/EARLY EVENING PERIODS TUESDAY-THURSDAY...WITH SLIGHTLY
HIGHER POPS FRIDAY-SATURDAY WITH TROUGH OVERHEAD. TROUGH AXIS DRIFTS
OFF TO THE EAST SATURDAY NIGHT INTO SUNDAY INDICATING A RESPITE FROM
PRECIP THREAT BEFORE ANOTHER SHORT WAVE DIGS IN FROM THE NORTHWEST
ON MONDAY.

HIGH TEMPS HAVE STRUGGLED TO TOP 70 ACROSS NORTHEASTERN PARTS OF THE
FORECAST AREA TODAY...AND EVEN TO REACH THE MID 60S ALONG THE
INDIANA LAKE SHORE WITH STRONG GUSTY NORTH WINDS. DIMINISHING WINDS
AND A VERY GRADUAL MODERATION IN TEMPS ALOFT WILL HELP NUDGE TEMPS
INTO THE MID AND UPPER 70S OVER THE NEXT FEW DAYS. MORE OF A
NORTHWEST COMPONENT TO WIND TUESDAY SHOULD KEEP LAKE COOLING MAINLY
IN NORTHWEST INDIANA...AND WEAKER LAKE BREEZES OVER THE NEXT FEW
DAYS SHOULD ALLOW SHORE AREAS TO PEAK IN THE 70-75 DEGREE RANGE
MID-LATE WEEK. TEMPS NEAR 80 BY SUNDAY/MONDAY WILL AT LEAST BE ONLY
A FEW DEGREES FROM EARLY AUGUST NORMALS.

RATZER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 00Z...

* SMALL POTENTIAL FOR WIND SHIFT TO EASTERLY WITH LAKE BREEZE LATE
  TUES AFTERNOON
* CHANCE OF ISOLD SHRA/POSSIBLE TSRA LATE TUES AFTERNOON INTO
  EARLY TUES EVENING

IZZI

//DISCUSSION...UPDATED 00Z...

WINDS WILL CONTINUE TO DIMINISH AND BECOME LIGHT/VARIABLE THIS
EVENING BEFORE PICKING UP A BIT FROM THE NORTHWEST BY MID-LATE
MORNING TUESDAY. SPEEDS LOOK TO BE IN THE 8-10KT RANGE WHICH
SHOULD ALLOW A LAKE BREEZE TO FORM...BUT PROBABLY ENOUGH TO HOLD
IT JUST EAST OF ORD/MDW. CONVERGENCE ALONG THE LAKE BREEZE ALONG
WITH COLD AIR ALOFT COULD BE ENOUGH TO ALLOW ISOLD SHOWERS AND
PERHAPS EVEN A THUNDERSTORM IN THE AFTERNOON. LOW LEVEL MOISTURE
IS LIMITED AND ONLY WEAK LARGE SCALE FORCING...SO CONFIDENCE IN
THE OCCURRENCE OF AND SUBSEQUENT COVERAGE OF ANY SHRA/TSRA IS LOW
AND ONLY JUSTIFIES A PROB30 AT THIS POINT.

IZZI


//ORD AND MDW CONFIDENCE...UPDATED 00Z...

* LOW CONFIDENCE IN SHRA/POSSIBLE TSRA CHANCES LATE TOMORROW
  AFTERNOON/EARLY TOMORROW EVENING
* MEDIUM CONFIDENCE IN LAKE BREEZE REMAINING EAST OF ORD/MDW TUES
  PM
* HIGH CONFIDENCE IN REMAINING FORECAST ELEMENTS

IZZI

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

WEDNESDAY THROUGH SUNDAY...PREDOMINANTLY VFR...THOUGH A BRIEF
SHRA/TSRA CANNOT BE RULE OUT (MAINLY AFTERNOON/EARLY EVENING)

IZZI

&&

.MARINE...
124 PM CDT

NORTHERLY WINDS CONTINUE UP AROUND 25 KT ACROSS THE SOUTHERN HALF OF
THE LAKE EARLY THIS AFTERNOON...AND THIS IS CONTINUING TO RESULT IN
BUOY OBSERVATIONS OF 8 TO 10 FOOT WAVES. THESE WINDS WILL GRADUALLY
EASE LATE THIS AFTERNOON AND EVENING...AND EVEN BECOME WESTERLY
TONIGHT AS THE GRADIENT WEAKENS. HOWEVER...WAVE HEIGHTS WILL BE SLOW
TO SUBSIDE...WITH 4+ FOOTERS EXPECTED ACROSS SOUTHERN LAKE MICHIGAN
THROUGH MUCH OF TONIGHT. NO CHANGES ARE PLANNED TO THE CURRENT
ENDING TIMES OF THE SMALL CRAFT ADVISORIES.

FOLLOWING TODAY`S WIND AND WAVE EVENT...IT APPEARS THE WEATHER WILL
BE SOMEWHAT QUIET ACROSS THE LAKE DURING THE WEEK. AN UPPER LEVEL
LOW OVER QUEBEC WILL CONTINUE TO LEAD TO A WEST NORTHWESTERLY FLOW
PATTERN...ALBEIT LIGHT...ACROSS THE LAKE THROUGH MUCH OF THE PERIOD
AS A COUPLE OF WEAK COLD FRONTAL BOUNDARIES DROP SOUTHWARD OVER THE
LAKE.

KJB

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...BEACH HAZARDS STATEMENT...ILZ014 UNTIL 4 AM TUESDAY.

     BEACH HAZARDS STATEMENT...ILZ006 UNTIL 10 PM MONDAY.

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

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

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

&&

$$

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