Area Forecast Discussion
Issued by NWS Chicago, IL

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000
FXUS63 KLOT 091920
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
220 PM CDT WED JUL 9 2014

.DISCUSSION...
335 AM CDT

LOW HUMIDITY AND MILD CONDITIONS ON TAP THROUGH MUCH OF THE
REMAINDER OF THE WORK WEEK BEFORE A TRANSITION TOWARD WARMER...MORE
HUMID...AND UNSETTLED CONDITIONS JUST IN TIME FOR THE WEEKEND.

WEAK BACK DOOR FRONT IS WORKING ITS WAY DOWN THE LAKE EARLY THIS
MORNING WITH A WIND SHIFT TO NORTHEAST AND A DECENT PUSH OF MARINE
COOLING AND SOME LOW CLOUDS AND FOG NEAR THE LAKE. GIVEN THE DRIER
AIR MASS UPSTREAM...ANTICIPATE ANY LAKE CLOUDS/FOG SHOULD MIX OUT
PRETTY READILY BY MID TO LATE MORNING...THOUGH WINDS OFF THE LAKE
THROUGH THE DAY SHOULD KEEP TEMPS IN THE 60S AT THE BEACHES TODAY
WHILE INLAND TEMPS REBOUND INTO THE 70S. MINUS THE LAKE CLOUDS AND
PERHAPS BEING A COUPLE DEGREES WARMER...THURSDAY LOOKS TO BE A
CARBON COPY OF TODAY.

THE MAJORITY OF GUIDANCE HAS LARGELY SLOWED THE DEPARTURE OF THE
UPPER TROUGH AND RETURN OF BETTER MOISTURE AND INSTABILITY LATER THIS
WEEK. THIS COULD RESULT IN MOST OF FRIDAY POTENTIALLY ENDING UP
DRY...ESPECIALLY EASTERN CWA. RAIN CHANCES WILL RAMP UP FRIDAY NIGHT
AND CONTINUE AT TIMES THROUGH THE WEEKEND WITH A PERTURBED
WEST-NORTHWESTERLY FLOW ALOFT. TEMPERATURES OVER THE WEEKEND
GENERALLY LOOK WARMER WITH MORE HUMIDITY...THOUGH ILL-TIMED MCS
AND/OR DEBRIS CLOUD COVER CERTAINLY COULD PLAY A ROLE IN KEEPING
TEMPS COOLER.

GFS/ECMWF BOTH REMAIN IN GOOD AGREEMENT ON AMPLIFYING AND
UNSEASONABLY DEEP UPPER TROUGH OVER THE REGION NEXT WEEK PROVIDING
FOR A PERIOD OF UNSEASONABLY COOL TEMPERATURES. ECMWF HAS BEEN
DROPPING 850MB TEMPS INTO THE MID SINGLE DIGIT RANGE BY TUES/WED
WHICH IS GETTING TO THE LOWER BOUNDS OF WHAT WE SEE AROUND HERE IN
JULY. NOT UNCOMMON FOR MODELS TO BE A BIT TOO AGGRESSIVE WITH COLD
SNAPS IN THE DAYS 6 AND BEYOND RANGE...BUT REGARDLESS IT LOOKS LIKE
BELOW AVERAGE TEMPS NEXT WEEK ARE QUITE LIKELY.

IZZI

&&

.AVIATION...

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

* LAKE BREEZE TIMING...NORTHWEST WINDS SHIFTING TO THE EAST
  NORTHEAST WITH SPEEDS AT OR ABOVE 10KT.

RODRIGUEZ

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

QUIET CONDITIONS ACROSS THE TERMINALS AT THIS TIME WITH THESE
QUIET AND VFR CONDITIONS EXPECTED TO REMAIN THROUGH THE REST OF
THE FORECAST PERIOD. THE ONLY CONCERN IS WITH THE LAKE BREEZE AND
TIMING THIS AFTERNOON. MOVEMENT OF THE LAKE BREEZE HAS BEEN
VARIABLE OVER THE LAST HOUR...WITH LOWER LEVEL SPEEDS STILL ON THE
HIGHER SIDE. EXPECT THESE STRONGER WESTERLY WINDS TO DIMINISH
EARLY THIS AFTERNOON WHILE THE CURRENT SLOW WESTWARD MOVEMENT
INCREASES. CONFIDENCE IS HIGHER WITH LAKE BREEZE TIMING FOR MDW
WITH IT RAPIDLY APPROACHING AT THIS HOUR. WILL CONTINUE TO MONITOR
TIMING FOR ORD...ESPECIALLY WITH SOME INCREASE IN THIS MOVEMENT
ANTICIPATED.

RODRIGUEZ

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

* HIGH CONFIDENCE IN VFR CONDITIONS.

* HIGH CONFIDENCE OF LAKE BREEZE WIND SHIFT...MEDIUM HIGH
  CONFIDENCE WITH SPEEDS...MEDIUM CONFIDENCE WITH EXACT TIMING.

RODRIGUEZ

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

THURSDAY NIGHT...VFR

FRIDAY THROUGH SUNDAY...GENERALLY VFR WITH A CHANCE OF SHOWERS
AND THUNDERSTORMS EACH DAY.

MONDAY AND TUESDAY...VFR.

KJB

&&

.MARINE...
218 PM CDT

LOW PRESSURE CONTINUES TO PULL AWAY ACROSS QUEBEC THIS
AFTERNOON...WITH A WEAK SURFACE TROUGH SAGGING SOUTH ACROSS THE
NORTHERN GREAT LAKES. THIS TROUGH WILL MOVE SOUTHEAST ACROSS THE
LAKE THROUGH TONIGHT...THOUGH THE GRADIENT WILL WEAKEN SIGNIFICANTLY
WITH THE APPROACH OF SURFACE HIGH PRESSURE FROM THE WEST. THIS HIGH
WILL MOVE ACROSS LAKE MICHIGAN TONIGHT INTO THURSDAY...WITH WINDS
BECOMING GENERALLY LIGHT/VARIABLE WITH LAKE BREEZES ALONG THE
SHORES. THE SURFACE RIDGE WILL DRIFT EAST OF THE LAKE FRIDAY...
ALLOWING SYNOPTIC SOUTH-SOUTHEAST FLOW TO DEVELOP AND EVENTUALLY
STRENGTHEN INTO FRIDAY NIGHT AS A TROUGH OF LOW PRESSURE ADVANCES
FROM THE PLAINS. SOUTH WINDS WILL INCREASE INTO THE 20 KT RANGE
FRIDAY AFTERNOON INTO SATURDAY MORNING...ESPECIALLY ACROSS THE
NORTHERN PORTION OF THE LAKE...BEFORE DECREASING AGAIN LATER
SATURDAY AS THE GRADIENT BECOMES WEAKER IN THE VICINITY OF THE
APPROACHING TROUGH AXIS. WIND DIRECTION MAY BE A BIT VARIABLE IN THE
BAGGY GRADIENT OF THE TROUGH AXIS...BEFORE THE TROUGH ACTUALLY MOVES
PAST THE LAKE AND WINDS SHIFT WEST-NORTHWEST LATE SUNDAY NIGHT AND
MONDAY.

RATZER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&

$$

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