Area Forecast Discussion
Issued by NWS Chicago, IL

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FXUS63 KLOT 030741
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
241 AM CDT FRI JUL 3 2015

.UPDATE...

909 PM CDT

FOR EVENING UPDATE...

MINOR ADJUSTMENTS PRIMARILY TO SKY COVER THIS EVENING...WITH
FAIRLY EXTENSIVE CIRRUS SHIELD OVER THE SOUTHWEST 2/3 OF THE CWA.
BUMPED HOURLY SKY COVER GRIDS...AND UPDATED ZFP ETC. COMBINATION
OF SLIGHTLY WARMER SFC TEMPS...SLIGHTLY DRIER LOW LEVEL MOISTURE
PROFILES AND HIGH CLOUDS SHOULD MINIMIZE LOW CLOUD/PATCHY FOG
POTENTIAL OVERNIGHT. OTHERWISE...FEW CHANGES MADE TO GOING
FORECAST.

MARINE WISE...DID HOIST A SMALL CRAFT ADVISORY FOR INDIANA
NEARSHORE WATERS EAST OF GARY THROUGH 4 AM CDT. WEAK SURFACE LOW
PRESSURE WAVE MOVING THROUGH OHIO VALLEY HAS HELPED TO TIGHTEN
GRADIENT SLIGHTLY OVER CENTRAL IL/IN WITH HIGH PRESSURE TO THE
NORTH ACROSS THE LAKE. THIS APPEARS TO HAVE HELPED KEEP NORTH-
NORTHEAST WINDS CLOSER TO 18-20 KT OVER TOWARD BURNS
HARBOR/MICHIGAN CITY AREAS AND HAVE NOTED WAVES BUILDING TO 4-4.6
FT AT THE NEARSHORE BUOY NEAR MICHIGAN CITY. SURFACE HIGH PRESSURE
RIDGE DRIFTS SOUTH ACROSS THE AREA FRIDAY... ALLOWING LIGHTER
WAVE/SMALLER WAVES AND BETTER SWIMMING/BOATING CONDITIONS GOING
INTO THE HOLIDAY WEEKEND.

RATZER

&&

.SHORT TERM...
131 PM CDT

THIS AFTERNOON THROUGH FRIDAY...

LOWER CLOUDS HAVE BEEN SLOW TO LIFT GIVEN THE PRESENCE OF A THERMAL
INVERSION AROUND 3000 FT...BUT GRADUALLY CONTINUE TO DO SO AND
SPREAD WESTWARD WITH THE MEAN 925-850 MB WIND. HIGH CLOUDS
CONTINUE TO STREAM IN FROM THE NORTHWEST. GIVEN A STIFF ONSHORE
WIND AND CLOUDS...HIGHS HOLD ONLY IN THE 60S TO LOW 70S.

THE WEATHER PATTERN IS CHARACTERIZED BY NW FLOW ALOFT ON THE BACK
SIDE OF DEEPER UPPER LEVEL LOW PRESSURE IN QUEBEC. THE TROUGH AXIS
WITH THIS SYSTEM WILL LINGER BACK OVER OUR AREA THROUGH THE SHORT
TERM. DISTURBANCES IN THIS FLOW PATTERN WILL LARGELY BE SHUNTED AWAY
FROM THE REGION AS SURFACE HIGH PRESSURE...CURRENTLY ANCHORED OVER
NORTH CENTRAL WISCONSIN DRIFTS SLOWLY SOUTHWARD. WE WILL SEE
CONTINUED HIGH CLOUDINESS/HAZE AS THESE WAVES TRACK THROUGH. AS THE
HIGH SINKS SOUTH ON FRIDAY...WE MAINTAIN A NE FLOW OFF THE
LAKE...THOUGH THE ONSHORE WIND COMPONENT DOES EASE A BIT. THE AIR
MASS WARMS SOME...SO STILL EXPECT A MILDER DAY ON FRIDAY WHICH
LESS IN THE WAY OF MORNING CLOUDINESS. HIGHS LOOKS TO TAG THE
UPPER 70S TO 80 IN OUTLYING AREAS...WITH COOLER UPPER 60S TO LOW
70S ALONG THE LAKE.

KMD

&&

.LONG TERM...
229 PM CDT

FRIDAY NIGHT THROUGH THURSDAY...

A LARGE SCALE UPPER TROUGH WILL SHIFT EAST OF THE AREA SATURDAY AND
BE REPLACED BY AN UPPER RIDGE WHICH WILL BE AMPLIFYING ACROSS THE
WESTERN GREAT LAKES AND ONTARIO AHEAD OF A LARGER UPPER TROUGH OVER
WESTERN CANADA. THE RIDGING WILL BROADEN AND SHIFT TO THE EAST
SUNDAY WHILE THE UPPER TROUGH ADVANCES EAST-SOUTHEAST. THE PASSAGE
OF THIS TROUGH EARLY NEXT WEEK WILL USHER IN A MORE ZONAL BUT STILL
BROADLY TROUGHED UPPER FLOW.

AS FOR THE DETAILS...PLEASANT CONDITIONS WILL PERSIST THROUGH THE
WEEKEND AS SURFACE HIGH PRESSURE SETS UP RIGHT OVER THE AREA BY
SATURDAY MORNING. A WEAK COOL FRONTAL BOUNDARY WILL TRAIL A SURFACE
TROUGH MOVING ACROSS EASTERN ONTARIO/WESTERN QUEBEC AND DROP DOWN
LAKE MICHIGAN SATURDAY MORNING. THIS BOUNDARY LOOKS TO LOSE
DEFINITION AS IT APPROACHES THE SOUTHERN SHORES OF THE LAKE AS ITS
PARENT LOW PULLS OFF TO THE NORTHEAST AND IT ENCOUNTERS THE HIGH.
GIVEN THE PRESENCE OF THE HIGH...WINDS WILL BE LIGHT SO A LAKE
BREEZE IS LIKELY. THIS WILL KEEP LAKESHORE AREAS IN THE LOW TO MID
70S SATURDAY. HAZY SKIES FROM THE WILD FIRE SMOKE WILL PROBABLY
STILL BE IN PLACE DURING THE DAY BUT SHOULD START TO PEEL OFF TO THE
NORTH AS UPPER LEVEL FLOW SHIFTS SOUTHWESTERLY WITH THE ARRIVAL OF
THE RIDGE LATER IN THE DAY. SUNDAY WILL SEE A STEADIER SOUTHERLY LOW
LEVEL FLOW SO LAKE COOLING WILL BE MORE CONFINED TO SHORELINE AREAS.
OTHERWISE HIGHS WILL BE SIMILAR TO SATURDAY. A COLD FRONT WILL BE
WORKING ITS WAY TOWARDS THE AREA MONDAY AS THE UPPER TROUGH MOVES
ACROSS CENTRAL CANADA. STRONGER SOUTHERLY FLOW WILL BRING MORE HUMID
CONDITIONS TO THE AREA. THE SPEED OF THE FRONT IS STILL IN QUESTION
AND WESTERN AREAS MAY SEE SHOWER/THUNDER CHANCES LATER MONDAY
AFTERNOON ON THE EARLY SIDE. AM LEANING TOWARD A SLOWER PROGRESSION
BRINGING BETTER CHANCES MONDAY NIGHT AND FIRST THING TUESDAY BUT
WILL HAVE TO WATCH. THE FRONT WILL LIKELY STALL OUT SOMEWHERE SOUTH
OF THE AREA AND WHERE THIS OCCURS WILL DICTATE WHERE POPS MAY LINGER
THROUGH TUESDAY OR EVEN TUESDAY NIGHT. SOME MINIMAL POPS MAY BE
NEEDED WEDNESDAY/THURSDAY AS THE FLOW WILL BE FAVORABLE FOR
SHORTWAVE PASSAGES BUT SURFACE HIGH PRESSURE MAY WIN OUT. MONDAY
WILL BE THE WARMEST DAY WITH COOLER TEMPS TUESDAY AND WEDNESDAY
THANKS TO NORTHERLY LOW LEVEL WINDS. IT BECOMES INCREASINGLY
DIFFICULT TO PIN DOWN THE UPPER FLOW PATTERN BY LATE NEXT WEEK BUT
IT DOES APPEAR THAT PRECIP CHANCES MAY INCREASE DURING THAT TIME.

MDB

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 06Z...

* WIND SPEEDS OUT OF THE NE/ENE FRIDAY AFTERNOON.

BMD

//DISCUSSION...UPDATED 06Z...

HIGH PRESSURE STRETCHES FROM CENTRAL WISCONSIN TO CENTRAL
MICHIGAN TONIGHT AND WILL GRADUALLY SLIDE SOUTH THROUGH THE TAF
PERIOD. LIGHT WINDS WILL BE IN PLACE OVERNIGHT THROUGH MIDDAY
FRIDAY...OUT OF THE NORTHEAST. WINDS WILL LIKELY PICKUP WITH A
LAKE BREEZE FRIDAY AFTERNOON. MODELS KEEP WINDS SPEEDS BELOW 10KT
BEHIND THE BOUNDARY. EXPECT VFR CONDITIONS THROUGH THE FORECAST
PERIOD.

BMD

//ORD AND MDW CONFIDENCE...UPDATED 06Z...

* MEDIUM IN WINDS STAYING BELOW 10 KT.
* HIGH IN REMAINING FORECAST ELEMENTS.

BMD

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

SATURDAY AND SUNDAY...VFR. LAKE BREEZE POSSIBLE.

MONDAY...VFR THEN SHRA/TSRA AND VSBY IMPACTS LIKELY LATE
MONDAY/MONDAY NIGHT.

TUESDAY...CHANCE SHRA/TSRA...ESPECIALLY EARLY. WIND SHIFT TO
NORTH-NORTHEAST.

WEDNESDAY...SLIGHT CHANCE TSRA...OTHERWISE VFR. NORTHEAST WINDS.

RC

&&

.MARINE...
240 AM CDT

A RIDGE STRETCHES FROM WISCONSIN ACROSS SOUTHERN LAKE MICHIGAN
INTO MICHIGAN THIS MORNING RESULTING IN LIGHT AND VARIABLE WINDS
ACROSS THE SOUTH HALF OF THE LAKE...AND SOUTHWEST WINDS ACROSS THE
NORTH. THE NORTHERN HALF OF THE LAKE WILL SEE WINDS INCREASING
INTO THE 15 TO 25 KT RANGE THIS AFTERNOON AND EVENING AHEAD OF AN
APPROACHING FRONT. MEANWHILE...THE SOUTH HALF WILL CONTINUE TO
SEE LIGHT WINDS WITH LAKE BREEZES RESULTING IN ONSHORE FLOW THIS
AFTERNOON. THE FRONT WILL BEGIN TO SAG ACROSS THE NORTH HALF OF
LAKE MICHIGAN LATE TONIGHT...DROPPING TO AROUND MIDLAKE
SATURDAY...THEN LIFTING NORTH AGAIN. SOUTH WINDS FRESHEN UP ACROSS
THE LAKE AGAIN SUNDAY NIGHT INTO MONDAY AHEAD OF A STRONGER COLD
FRONT PROGGED TO SWEEP ACROSS THE LAKE MONDAY NIGHT.

BMD

&&

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

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

LM...SMALL CRAFT ADVISORY...NEARSHORE GARY TO MICHIGAN CITY IN UNTIL 4 AM FRIDAY.

&&

$$

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