Area Forecast Discussion
Issued by NWS Chicago, IL

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000
FXUS63 KLOT 010735
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
235 AM CDT SAT AUG 1 2015

.SHORT TERM...
222 PM CDT

THROUGH SATURDAY...

A BOUNDARY IS FINALLY EXITING THE SOUTHEAST CWA WITH A FEW ISOLATE
SHOWERS FIRING ALONG IT OVER NORTHWEST INDIANA. HIGH PRESSURE IS
SPREADING OVER THE UPPER MIDWEST WHILE LOW PRESSURE REMAINS OVER
HUDSON BAY.  BETWEEN AMPLE MIXING AND A TIGHTENED PRESSURE GRADIENT
BETWEEN THE HIGH AND LOW...WEST TO NORTHWEST WINDS ARE GUSTING UP TO
30 MPH THIS AFTERNOON. GUSTS WILL CONTINUE UNTIL MIXING EASES THIS
EVENING.  EXPECTING DRY CONDITIONS THROUGH THE NIGHT WITH LOWS
AROUND 60 EXCEPT FOR MID TO UPPER 60S DOWNTOWN.

THE NAM12 FEATURES A WEAK VORT STREAMER MOVING THROUGH SOUTHERN WI
AND NORTHERN IL EARLY SATURDAY MORNING. THE NAM ALSO INDICATES
ISOLATED SHOWERS AND MAYBE A THUNDERSTORM WILL FORM IN ASSOCIATION
WITH THE VORTICITY STREAMER. HAVE VERY LOW CONFIDENCE IN ANY PRECIP
OCCURRING AND COVERAGE...BUT ALSO DID NOT HAVE ENOUGH CONFIDENCE TO
GO DRY EITHER. SO A FEW ISOLATED LIGHT RAIN SHOWERS WITH PERHAPS A
COUPLE OF STRIKES OF LIGHTNING ARE POSSIBLE ALONG THE WI/IL STATE
LINE EARLY SATURDAY MORNING...THEN EAST OF A ROCKFORD TO MIDWAY
AIRPORT LINE MID TO LATE SATURDAY MORNING.  ANY LINGERING SHOWERS
WILL THEN MOVE SOUTHEAST OVER NW INDIANA EARLY SATURDAY AFTERNOON.
MY CONFIDENCE DECREASES RAPIDLY AFTER THE SUN COMES UP AS WE WARM
AND DRY DUE TO MIXING. THEREFORE...KEEP AN EYE OUT FOR A STRAY
SHOWER OR STORM SATURDAY MORNING OVER FAR NORTHEAST IL AND NW
INDIANA...BUT THE REST OF THE DAY TIME HOURS SATURDAY LOOK DRY.

RAISED HIGH TEMPS OVER WEST CENTRAL AND CENTRAL IL BY A DEGREE OR
TWO AS THE WARMEST LOCATIONS WILL BE UNDER THE WARMEST UPPER LEVEL
AIR. THE WHOLE WARNING AREA WILL SEE HIGHS IN THE MID TO UPPER 80S
WITH HEAT INDICES ABOUT THE SAME AS THE HIGH TEMPS.  WEST WINDS ARE
ONCE AGAIN EXPECTED BUT WITH THE WEAKER GRADIENT...GUSTS IN THE
AFTERNOON WILL ONLY BE UP TO 20 MPH.

JEE

&&

.LONG TERM...
234 AM CDT

SUNDAY NIGHT THROUGH FRIDAY...

THE ACTIVITY LEVEL WILL PERSIST FOR THE SECOND HALF OF THE
WEEKEND...AS THE 500MB TROUGH RETURNS TO THE GREAT LAKES WITH A
ROBUST SFC LOW QUICKLY LIFTING NORTHEAST ACROSS THE LOWER GREAT
LAKES REGION. ENSEMBLES CONTINUE A HIGH CONFIDENCE WITH PRECIP
SHIFTING EAST LATE SUN NGT...WITH ANTI-CYCLONIC FLOW BUILDING IN
FROM THE WEST. HAVE HELD ONTO PRECIP THRU DAYBREAK MON...HOWEVER
WITH THE NORTHWEST FLOW ARRIVING AND GENERALLY A MORE PROGRESSIVE
FLOW...IT IS POSSIBLE PRECIP MAY END SHORTLY AFTER MIDNIGHT SUN NGT.

MINIMAL SPREAD AMONGST THE ENSEMBLE MEMBERS CONTINUES IN THE
LONGWAVE PATTERN...WITH A HIGH AMPLITUDE RIDGE REMAINING ACROSS THE
WESTERN CONUS/ALASKA. THIS WILL ALLOW AN ANOMALOUSLY STRONG TROUGH
TO DIG INTO THE GREAT LAKES AND PRODUCE COOLER AIR FOR MUCH OF THE
REGION FROM TUE THRU FRI. OPERATIONAL SOLUTIONS INDICATE THE
SOUTHERN STREAM WILL BECOME SOMEWHAT ACTIVE...WITH A SERIES OF WAVES
RIDING ALONG A QUASI-STATIONARY BOUNDARY OVER THE TENN VALLEY NEXT
WEEK. CURRENTLY ANTICIPATE THE BULK OF THIS PRECIP WILL REMAIN
FURTHER SOUTH...HOWEVER A BUCKLE IN THE WAVE MAY OCCUR TUE INTO
EARLY WED AND COULD BRING A LOW CHC OF SHOWERS/THUNDER BACK TO THE
FORECAST AREA. FEEL THAT THIS MAY END UP TRENDING BACK SOUTH AS IT
APPEARS MORE FAVORABLE THAT NORTHERN IL WILL BE UNDER A STRONGER
INFLUENCE FROM THE SFC RIDGE.

MON APPEARS TO BE THE WARMEST DAY OF THE EXTENDED PERIOD...WITH
TEMPS GENERALLY IN THE LOW 80S. THEN THE 850MB THERMAL TROUGH
ARRIVES WITH WINDS SHIFTING NORTH/NORTHEAST...AND TEMPS FOR THE BULK
OF NEXT WEEK WILL BE IN THE MID/UPR 70S. LOWS WILL GENERALLY BE IN
THE UPR 50S TO LOW 60S THROUGHOUT THE EXTENDED.

BEACHLER

&&

.AVIATION...

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

* WEST WINDS BETWEEN 6-9KT THRU DAYBREAK...GUSTY WINDS DEVELOPING
  MID-MORNING THRU AFTERNOON. WEST GUSTS UP TO 22KT.

* A FEW MID-DECK CLOUDS AND POSSIBLE ISOLATED SPRINKLES MID-
  MORNING.

BEACHLER

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

HIGH PRESSURE CONTINUES TO INFLUENCE THE REGION...WITH NEAR
CLOUDLESS SKIES CONTINUEING THROUGH OVERNIGHT INTO DAYBREAK. WEST
WINDS WILL PERSIST...WITH BETTER MIXING DEVELOPING YET AGAIN
DURING THE DAYLIGHT HOURS AND PRODUCING GUSTS TO 22KT. THERE IS A
WEAK MID-LVL SYSTEM SLIDING SOUTHEAST FROM MINNESOTA THAT MAY
TOUCH OFF AN ISOLATED SHOWER OR A FEW SPRINKLES BETWEEN
14-17Z...HOWEVER FEEL THAT AT MOST JUST A FEW CLOUDS WILL DEVELOP
WITH THIS. THUS HAVE MAINTAINED A DRY TAF. WINDS DIMINISH AFTER
SUNSET...THEN BEGIN TO TURN SOUTHWESTERLY LATE THIS EVENING.

BEACHLER

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

* HIGH CONFIDENCE IN ALL FORECAST ELEMENTS.

BEACHLER

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

SUNDAY...CHANCE OF TSRA. SOUTHWEST WINDS.
MONDAY...MAINLY VFR. NORTHWEST WINDS.
TUESDAY...SLIGHT CHANCE OF SHRA. NORTHWEST WINDS BECOMING NORTHEAST.
WEDNESDAY...CHANCE OF SHRA/SLIGHT CHANCE OF TSRA. NORTHEAST
            WINDS.
THURSDAY...CHANCE OF SHRA. EAST WINDS.

MTF

&&

.MARINE...
234 AM CDT

WEST WINDS WILL PERSIST ACROSS THE LAKE AGAIN TODAY...AS
HIGH PRESSURE CENTERED OVER THE OHIO VALLEY. WINDS WILL BECOME GUSTY
AGAIN TODAY...BUT SHOULD REMAIN WITHIN A 15 TO 25 KT RANGE. SO WILL
NOT HOIST ANY SMALL CRAFT ADVISORY AT THIS TIME.

TONIGHT THE HIGH WILL SHIFT FURTHER EAST...ALLOWING WINDS TO SLOWLY
TURN SOUTHWESTERLY. A MUCH STRONGER LOW PRESSURE SYSTEM WILL ARRIVE
ACROSS THE WESTERN GREAT LAKES SUNDAY AND PASS OVER THE NORTHERN
PORTIONS OF THE LAKE SUN AFTERNOON/EVENING. THIS WILL PRODUCE A
TIGHT GRADIENT FOR THE SOUTHERN HALF OF THE LAKE...AND COULD ALLOW
GUSTS TO APPROACH 30KT WITH A FEW GALE FORCE GUSTS POSSIBLE. WILL
LIKELY NEED TO ISSUE A SMALL CRAFT ADVISORY FOR SUNDAY AND MAY
LINGER INTO SUNDAY NIGHT. THE LOW THEN QUICKLY LIFTS NORTHEAST BY
EARLY MONDAY...AS WINDS SHIFT NORTHWEST TO NORTH EARLY NEXT WEEK.
THEN WINDS WILL MAINLY BE FROM THE NORTH THROUGH MUCH OF THE
UPCOMING WEEK.

BEACHLER

&&

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

$$

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