Area Forecast Discussion
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FXUS63 KLOT 281944
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
244 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 20Z...

* GUSTY N-NNE WINDS EASING LATE AFTERNOON THEN DIMINISHING EARLY EVENING.

* LOW CHANCE FOR SOME SCATTERED THUNDERSTORMS TUESDAY AFTERNOON.

MDB

//DISCUSSION...UPDATED 20Z...

LAKE BOUNDARY IS NOW WELL WEST OF MDW AND RIGHT NEAR THE WEST END
OF ORD AT 1935Z. THE BOUNDARY CONTINUES TO WOBBLE BACK AND FORTH
AT ORD WHICH IS LIKELY ACCOUNTING FOR THE ERRATIC WIND SPEEDS.
DIRECTIONAL CHANGE IS MINIMAL AND RANGES FROM ABOUT 360 TO 030
DEGREES. WIND TRENDS LATE THIS AFTERNOON WILL BE A
CHALLENGE...ESPECIALLY DETERMINING WHEN SPEEDS WILL BEGIN TO
DIMINISH. HAVE MADE SOME ADJUSTMENTS TO TRY AND DETAIL THE CHANGES
WITH THE 20Z TAF UPDATE. IF THE BOUNDARY REMAINS IN CLOSE
PROXIMITY TO ORD THEN SPEEDS COULD DROP OFF MORE QUICKLY AS THE
BOUNDARY DISSIPATES AND MIXING WINDS DOWN INTO THE EVENING. IF IT
STAYS WEST THEN SPEEDS WOULD STAY UP A BIT LONGER.

FROM 18Z...

STRONG PRESSURE GRADIENT CONTINUES ACROSS THE TERMINALS WITH GUSTS
IN THE 20-25 KT RANGE ACROSS IL AND PUSHING 30 KT AT TIMES NEAR
THE LAKE MICHIGAN SHORE OF NW INDIANA. THE DIRECTION CONTINUES TO
FLUCTUATE BETWEEN N AND NNE AND WILL LIKELY CONTINUE TO DO SO
THROUGH AFTERNOON. THE PRESSURE GRADIENT SLACKENS LATE THIS
AFTERNOON SO SPEEDS SHOULD EASE BUT THIS MAY TAKE SOME TIME INTO
THE EVENING. WIND DIRECTION MAY BECOME VARIABLE THIS EVENING WITH
A LIGHT NORTHWEST DIRECTION EXPECTED OVERNIGHT. A STEADIER
NORTHWEST WIND IS EXPECTED TUESDAY. A LAKE BREEZE MAY TURN WINDS
NORTHEAST AT GYY TUESDAY AFTERNOON BUT WILL KEEP THE LAKE BREEZE
EAST OF ORD/MDW FOR NOW.

A SERIES OF UPPER WAVES WILL CROSS THE AREA THE NEXT FEW DAYS WITH
ONE WAVE PASSING OVERNIGHT POTENTIALLY BRINGING SOME MID CLOUDS.
WEAK ASCENT WILL BE IN PLACE TUESDAY WHICH MAY TRIGGER SOME ISOLD-
SCT SHRA/TSRA DURING THE AFTERNOON. THREAT IS TOO LOW TO MENTION
IN THE TAF AT THIS TIME. OTHERWISE SHOULD SEE AN INCREASE IN
DIURNAL CLOUDS.

MDB

//ORD AND MDW CONFIDENCE...UPDATED 20Z...

* HIGH CONFIDENCE IN WIND TRENDS THROUGH MID AFTERNOON. MEDIUM
  CONFIDENCE IN NNE WINDS BECOMING NE LATE THIS AFTERNOON WITH
  SPEEDS EASING INTO EARLY EVENING.

* HIGH CONFIDENCE THAT TSRA CHANCES ARE LOW TUESDAY AFTERNOON AND
  COVERAGE WOULD BE ISOLATED TO SCATTERED.

MDB

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

TUESDAY NIGHT...SLIGHT CHANCE OF AN EVE STORM.
WEDNESDAY-SATURDAY...MAINLY VFR. SLIGHT CHANCE OF AFTERNOON TSRA.
SUNDAY...VFR.

MTF

&&

.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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