Area Forecast Discussion
Issued by NWS Chicago, IL

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000
FXUS63 KLOT 291803
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
103 PM CDT SAT AUG 29 2015

.SHORT TERM...
328 AM CDT

THROUGH SUNDAY NIGHT...

MAIN FORECAST CHALLENGES/CONCERNS ARE WITH PRECIP TRENDS ACROSS
THE ENTIRE CWA THIS MORNING INTO THE AFTERNOON...WITH PRECIP
CHANCES LINGERING TONIGHT INTO SUNDAY ACROSS A PORTION OF THE
AREA.

LATEST RADAR IMAGERY DEPICTING AN AREA OF LIGHT TO AT TIMES
MODERATE SHOWERS MOVING THROUGH NORTH CENTRAL ILLINOIS EARLY THIS
MORNING. THIS IS IN RESPONSE TO MID/UPPER LEVEL TROUGH AND SURFACE
REFLECTION SLOWLY PUSHING EAST ACROSS THE REGION...WITH FAIRLY
ENERGETIC WAVES LIFTING OUT AHEAD OF IT. WITH THE DEPARTURE OF A
STRONGER WAVE/BETTER FORCING...THE INTENSITY OF THESE SHOWERS HAS
DIMINISHED AND WHILE INSTABILITY AXIS REMAINS TO THE WEST OF THE
CWA...LIGHTNING HAS BEEN LIMITED JUST TO THE WEST OF THE CWA.
NONETHELESS...A SOLID AREA OF SHOWERS CONTINUES TO SLOWLY MOVE
EAST THIS MORNING...SLOWLY OVERCOMING DRIER AIR IN PLACE. WITH
UPSTREAM ENERGY TO REINFORCE LIFT THIS MORNING THROUGH
MIDDAY...EXPECT THIS PRECIP TO CONTINUE MOVING INTO REMAINING
AREAS IN NORTHEAST ILLINOIS AND THEN EVENTUALLY NORTHWEST INDIANA.
HAVE CAT POPS FOR AREAS IN NORTHERN ILLINOIS THROUGH MID TO LATE
MORNING WITH CHANCE TO LIKELY POPS ELSEWHERE...BUT THEN LOWER TO
HIGH CHANCE POPS ACROSS THE ENTIRE AREA BY EARLY AFTERNOON. WHILE
THE MID/UPPER LEVEL TROUGH FURTHER DAMPENS TODAY LARGE SCALE
FORCING WILL STILL BE PRESENT...BUT WONDER IF IT WILL BE ENOUGH TO
SUSTAIN SUCH A WIDE AREA OF PRECIP INTO THE AFTERNOON. THINK MORE
SCATTERED DEVELOPMENT WILL LIKELY BE THE TREND LATER TODAY...THUS
THE LOWERING OF POPS...WITH BEST CHANCES FOR PRECIP SHIFTING MORE
EASTWARD. GUIDANCE STILL INDICATING AN INCREASE IN INSTABILITY
THROUGH MIDDAY AND THE AFTERNOON...AND HAVE MAINTAINED MENTION OF
SLIGHT CHANCE FOR THUNDER. HOWEVER...WITH WEAK LAPSE RATES IN
PLACE...NOT EXPECTING ANY STRONG/SEVERE DEVELOPMENT TODAY. DESPITE
A WARMING AIRMASS...CLOUDS/PRECIP IN PLACE TODAY WILL LIMIT
WARMING AND HAVE LOWERED HIGH TEMPS FOR TODAY. HAVE LOWER 70S
NORTH AND THEN MID TO UPPER 70S ACROSS THE SOUTHERN CWA...BUT MAY
HAVE NOT LOWERED ENOUGH AS ITS POSSIBLE THAT SOME LOCATIONS MAY
NOT MAKE IT OUT OF THE 60S TODAY.

FURTHER WEAKENING OF THIS SYSTEM WILL OCCUR TONIGHT INTO SUNDAY
BUT WITH THIS CONTINUED SLOW EXIT...PRECIP CHANCES MAY LINGER FOR
THE EASTERN CWA TONIGHT. THIS COULD CONTINUE ON SUNDAY WITH
GUIDANCE STILL ADVERTISING FOR REDEVELOPMENT OF SHOWERS AND
THUNDERSTORMS ON SUNDAY...MAINLY SOUTH OF INTERSTATE 80. SUNDAY
WILL BE MUCH WARMER WITH HIGHS IN THE LOW TO MID 80S. MID TO UPPER
80S COULD BE REALIZED IN SOME LOCATIONS BUT WITH POTENTIAL FOR
CLOUDS/PRECIP...DID NOT GO HIGHER AT THIS TIME.

RODRIGUEZ

&&

.LONG TERM...
328 AM CDT

MONDAY THROUGH FRIDAY...

STRONGER WESTERLIES WILL BE SITUATED WELL NORTH OF THE REGION
BEGINNING OF THE PERIOD...WITH RIDGING/WEAKER FLOW ACROSS THE
AREA. CONTINUED WARMING TREND WILL CONTINUE EARLY NEXT WEEK WITH
MID TO UPPER 80S LIKELY ON MONDAY...WITH TEMPS LIKELY APPROACHING
90 FOR MOST LOCATIONS ON TUESDAY AND WEDNESDAY. WITH INCREASING
MOISTURE/INSTABILITY DURING THE PERIOD...AFTERNOON THUNDERSTORMS
DO APPEAR POSSIBLE THROUGHOUT THE WEEK. HAVE TRIED TO INDICATE
BEST CHANCES DURING THIS NEXT WEEK...BUT WITH THESE POPS LIKELY
BEING REFINED WITH LATER FORECASTS. HOWEVER...WOULD THINK MOST
LOCATIONS WILL REMAIN ON THE DRY SIDE WITH ANY DEVELOPMENT MORE
THAN LIKELY ISOLATED TO WIDELY SCATTERED.

RODRIGUEZ

&&

.AVIATION...

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

* SCATTERED SHOWERS ISOLATED THUNDER NEAR ORD/MDW THRU 19Z.

* LGT SOUTH WINDS BECOMING VARIABLE AFT 00Z TO NORTHEAST LESS THAN
  4KT.

* CIGS LOWERING TO IFR AND POSSIBLY LIFR. IN ADDITION FOG IS
  EXPECTED TO DEVELOP AND LOWER VSBYS TO ARND 1SM.

BEACHLER

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

VISIBLE SATELLITE IMAGERY SHOWS CONSIDERABLE CLOUD COVER ACROSS
THE REGION...WITH SURFACE OBSERVATIONS INDICATING VERY LIGHT
WINDS. A WEAK FRONTAL BOUNDARY WAS ORIENTED ACROSS NORTHEAST IL
STRETCHING SOUTHWEST...WITH WIND DIRECTIONS BECOMING VARIABLE ON
EITHER SIDE OF THIS BOUNDARY THIS AFTERNOON. A FEW SHOWERS
CONTINUE TO LINGER WITH SOME EMBEDDED THUNDER NEAR ORD...HOWEVER
IT APPEARS THUNDER WILL BE ENDING BY 20Z AND SHOWERS WILL SLOWLY
DISSIPATE IN COVERAGE THROUGH THE REMAINDER OF THE AFTERNOON.
GUIDANCE INDICATES CIGS WILL QUICKLY LOWER ARND 00Z OR SHORTLY
AFT...NEARING IFR AND POSSIBLY TRENDING FURTHER TOWARDS LIFR.
WINDS WILL REMAIN LIGHT OVERNIGHT...WHICH WILL ALLOW FOG AND LOW
CIGS TO LINGER THRU DAYBREAK. AREAS OF DENSE FOG ARE EXPECTED TO
DEVELOP AS WELL...BUT SHOULD REMAIN WEST OF ORD/MDW. AT THIS TIME
HAVE OPTED TO INCLUDE MENTION OF 1/4SM FOG AT DPA/RFD IN CURRENT
TAF.

BEACHLER


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

* HIGH CONFIDENCE IN WIND DIR/SPEED.

* HIGH CONFIDENCE IN CIGS LOWERING TOWARDS IFR...MEDIUM CONFIDENCE
  IN TIMING AND LIFR CIGS DEVELOPING.

* MEDIUM/HIGH CONFIDENCE IN PRECIP ENDING AT ORD/MDW BY 20Z.

* MEDIUM/HIGH CONFIDNECE IN VSBYS LOWERING TO MVFR...LOW
  CONFIDENCE IN VSBYS LOWERING TO IFR.

BEACHLER

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

SUNDAY NIGHT THROUGH FRIDAY...PRIMARILY VFR. MOSTLY LIGHT
SOUTHERLY WINDS...THOUGH AFTERNOON LAKE BREEZES COULD SHIFT WINDS
TO EAST OR SOUTHEAST DURING AFTERNOONS.

IZZI

&&

.MARINE...
207 AM CDT

NARROW RIDGE OF HIGH PRESSURE STRETCHING FROM NEAR DETROIT TO
GREEN BAY COMBINED WITH WEAKENING LOW PRESSURE OVER IOWA WILL
RESULT IN A NARROW RIBBON OF STRONGER EASTERLY WINDS EARLY THIS
MORNING OVER PORTIONS OF CENTRAL LAKE MICHIGAN BEFORE BACKING MORE
SOUTHEAST LATER THIS MORNING THEN ULTIMATELY EASING THIS
AFTERNOON. WEAK LOW OVER IOWA WILL DISSIPATE TONIGHT AND REMAINDER
OF THE UPCOMING WEEK WILL SEE WEATHER OVER THE LAKE DOMINATED BY
HIGH PRESSURE ANCHORED OVER THE MID ATLANTIC AND NORTHEAST.

IZZI

&&

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

$$

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