Area Forecast Discussion
Issued by NWS Chicago, IL

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000
FXUS63 KLOT 032016 AAA
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
216 PM CDT FRI JUL 3 2015

.SHORT TERM...
200 PM CDT

THROUGH SATURDAY NIGHT...

SHARP UPPER TROUGHING IN NORTHERN ONTARIO...WITH BROAD TROUGHING
EXTENDING SOUTHWEST THROUGH NORTHERN ILLINOIS AND INTO THE ARKLATEX
REGION. A MORE WELL DEFINED COLD FRONTAL BOUNDARY WILL SINK
SOUTHEAST THROUGH THE NORTHERN GREAT LAKES TONIGHT ASSOCIATED WITH
THE TROUGH AXIS IN CANADA. MEANWHILE... SHORTWAVE ENERGY IS
TRACKING TO THE SOUTH OF THE SOUTHERN EXTENSION OF THE 500 MB
HEIGHT DEPRESSION OVER CENTRAL ILLINOIS...CLOSER TO THE LOW LEVEL
SURFACE FRONT IN SOUTHERN ILLINOIS. ADDITIONALLY...SMOKE ALOFT
FROM FIRES IN CANADA CONTINUE TO DRIFT TOWARD THE AREA UNDER NW
FLOW ALOFT. UPSTREAM OBSERVATIONS IN NORTH DAKOTA/WESTERN
MINNESOTA DEPICTING HAZE...WITH SMOKE REPORTED IN OBSERVATIONS IN
SOUTHERN MANITOBA. THIS FLOW DIRECTION WILL CONTINUE TO DRIFT THIS
SMOKE/HAZE TOWARD THE GREAT LAKES THROUGH AT LEAST EARLY SATURDAY
BEFORE THE UPPER FLOW BACKS TO A WSW DIRECTION. MORE ON THIS ON
OUR SOCIAL MEDIA OUTLETS.

BACK TO THE SENSIBLE WX FORECAST...THE BROAD UPPER TROUGH SLOWLY SHIFTS
EASTWARD THROUGH TONIGHT...TAKING THE MORE EXTENSIVE CLOUDINESS
WITH IT AS UPPER LEVEL HEIGHT RISES/NEGATIVE VORTICITY ADVECTION
SHIFTS THROUGH THE GREAT LAKES REGION. LIGHT PRECIP MAINLY SOUTH
OF OUR FAR SOUTHERN ZONES WILL TAPER THIS AFTERNOON AND EVENING AS
WELL. FARTHER NORTH...THE COLD FRONT WILL DRIVE AN AREA OF
PRECIPITATION...BUT THIS SHOULD LARGELY REMAIN CONFINED INTO
WISCONSIN AND OVER NORTHERN AND CENTRAL LAKE MICHIGAN TONIGHT AS
LOW LEVEL RH PROFILES ARE DRY.

WE WILL LIKELY SEE SOME DISSIPATING CLOUDS WITH THIS FRONT IN THE
MORNING...OTHERWISE DAYTIME HEATING LOOKS TO LEAD TO DECENT WARMING
ON THE INDEPENDENCE DAY ALONG WITH SOME AFTERNOON CUMULUS CLOUDS OUT
AHEAD OF THE WEAKENING FRONT. MOST GUIDANCE DECAYS THE FORCING WITH
THIS FRONT BEFORE EXITING SOUTHERN WISCONSIN...BUT THERE IS A SMALL
CHANCE THAT A SHALLOW POP-UP SHOWER SNEAKS INTO FAR NORTHERN
ILLINOIS GIVEN SOME WEAK INSTABILITY PRESENT AS SUGGESTED BY THE GFS
AND SPC WRF...LIKELY OVERDONE ON THE GFS GIVEN HIGH DEWPOINTS IN THE
RAW MODEL FORECAST. LOW LEVEL WIND FIELDS ARE GENERALLY 10 KT OR
LESS...SUGGESTING A SE LAKE BREEZE IS STILL A LIKELY SCENARIO IN THE
AFTERNOON...THOUGH WITH MUCH LESS OF A MAGNITUDE OF LAKE COOLING AND
INLAND PROGRESSION ANTICIPATED GIVEN THE PREDOMINANT WESTERLY FLOW.
THE UPPER FORCING IS BENIGN...SO WILL BE RELYING ON ANY SURFACE
CONVERGENCE...POSSIBLY AIDED BY THE LAKE BREEZE...TO TRIGGER ANY
SHOWERS. IF ANYTHING OCCURS...IT WOULD BE ISOLATED IN NATURE...WITH
THE MORE LIKELY SCENARIO JUST AFTERNOON CUMULUS CLOUDS...AND HAVE
CONTINUED WITH A DRY FORECAST GIVEN THE WRF-NAM/4KM NAM HAS HIGH
DEWPOINTS AND HAS NO PRECIP. WOULD NOT BE SURPRISED IF SOME LOW POPS
ARE INTRODUCED IN THE NORTH GIVEN A SIGNAL IN THE GFS/SREF/CANADIAN
AND SOME HI-RES GUIDANCE. OTHERWISE A SPLENDID FORECAST WITH
READINGS IN THE 80S INLAND...70S NEAR THE LAKE...AND MODEST HUMIDITY
LEVELS. BENIGN CONDITIONS WILL RULE THE EVENING PERIOD WITH
TEMPERATURES FALLING THROUGH THE 70S AND CLEARING SKIES.

KMD

&&

.LONG TERM...
313 AM CDT

SATURDAY NIGHT THROUGH THURSDAY...

SUNDAY LOOKS TO BE QUITE WARM AND GUIDANCE HAS ALL TRENDED WARMER
WITH 925MB TEMPS NOW PROGGED TO BE IN THE 22-24C RANGE SUNDAY
AFTERNOON WHICH WOULD SUPPORT HIGHS IN THE UPPER 80S. ONCE AGAIN
GRADIENT MAY BE TOO WEAK TO TOTALLY SUPPRESS LAKE BREEZE...ESPECIALLY
ALONG ILLINOIS SHORE...BUT LAKE INFLUENCE SHOULD BE MUCH LESS WITH
TEMPS PROBABLY MANAGING TO HIT 80 FOR AT LEAST A TIME ALONG THE
LAKE. STRONGER SOUTHERLY WINDS EXPECTED TO PREVENT LAKE COOLING
MONDAY AHEAD OF THE APPROACHING COLD FRONT. BLENDED MODEL GUIDANCE
HAS HIGHS IN THE MID 80S MONDAY...THOUGH IF CLOUD COVER IS NOT TOO
EXTENSIVE WE COULD EASILY BE PUSHING AT LEAST UPPER 80S MONDAY.

COLD FRONT LOOKS TO ARRIVE MONDAY NIGHT/TUESDAY TIME FRAME WITH
ASSOCIATED SHOWER/T-STORM CHANCES ACCOMPANYING THE FRONT. BLENDED
MODEL GUIDANCE WOULD MAINTAIN PERIOD AFTER PERIOD OF POPS TUESDAY
ONWARD...BUT ECMWF AND GFS SUGGEST FRONT CLEARS THE AREA AND SHOULD
ALLOW FOR DRY CONDITIONS TUES NIGHT THROUGH WED EVENING BEFORE FRONT
POTENTIALLY TRIES TO CREEP BACK NORTH AS A WARM FRONT LATER NEXT
WEEK WITH A RETURN OF PRECIP CHANCES.

IZZI

&&

.AVIATION...

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

* EAST TO NORTHEAST WINDS SPORADICALLY REACHING 10-11 KT BUT
  PRIMARILY LESS THAN 10 KT THIS AFTERNOON.

* LIGHT WESTERLY WINDS SATURDAY BUT POSSIBLE SHIFT TO EAST OR
  SOUTHEAST LATER SATURDAY AFTERNOON WITH LAKE BREEZE.

MDB

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

HIGH PRESSURE ACROSS THE REGION CONTINUES TO RESULT IN LIGHT AND
VARIABLE WINDS...WITH AN EASTERLY DIRECTION FAVORED. LAKE
INFLUENCE MAY REINFORCE EAST TO NORTHEAST WINDS AT ORD/MDW BY MID
AFTERNOON SO A SLIGHT UPTICK IN WIND SPEEDS MAY OCCUR BUT SPEEDS
LOOK TO BE UNDER 10 KT THE MAJORITY OF THE TIME. GYY SHOULD SEE A
STEADIER NORTHEAST WIND THROUGH THE AFTERNOON. WINDS WILL DIMINISH
AND TURN SOUTHEASTERLY EARLY THIS EVENING THEN TREND TO THE WEST
AND SOUTHWEST LATE TONIGHT. LIGHT WEST WINDS ARE EXPECTED SATURDAY
AND A LAKE BREEZE IS EXPECTED TO DEVELOP. THERE IS SOME
INDICATION IT MAY BE MORE OF A SOUTHEASTERLY LAKE BREEZE WHICH
WOULD HAVE A TOUGHER TIME REACHING ORD/MDW BUT WITH SUCH A WEAK
FLOW REGIME A MORE TYPICAL EASTERLY LAKE BREEZE WITH A FURTHER
INLAND PUSH MAY RESULT. WILL KEEP A LIGHT WESTERLY WIND AT ORD FOR
SATURDAY AFTERNOON FOR NOW BUT THERE IS POTENTIAL FOR AN EAST TO
SOUTHEAST SHIFT...THOUGH SPEEDS WOULD PROBABLY BE UNDER 10 KT.

MDB

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

* HIGH CONFIDENCE IN WINDS REACHING 10-11 KT THIS AFTERNOON AND
  MEDIUM- HIGH CONFIDENCE THAT IT WILL BE SPORADIC WITH SPEEDS
  MAINLY UNDER 10 KT.

* LOW CONFIDENCE THAT LAKE BREEZE WIND SHIFT WILL ARRIVE AT
  ORD/MDW SATURDAY AFTERNOON.

MDB

//OUTLOOK FOR ORD/MDW FOR 00Z SUNDAY-12Z FRIDAY...UPDATED 12Z...

SATURDAY NIGHT...DRY. VFR. S WINDS.
SUNDAY...DRY. VFR. S WINDS. LAKE BREEZE PSBL.
MONDAY...TSRA LIKELY LATE. SW WINDS.
TUESDAY...CHC TSRA. NW WINDS BECOMING NE.
WEDNESDAY...DRY. VFR. E WINDS.
THURSDAY...CHC TSRA. NW WINDS.

BMD

&&

.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...NONE.
IN...NONE.
LM...NONE.
&&

$$

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