Area Forecast Discussion
Issued by NWS Chicago, IL

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FXUS63 KLOT 010524
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1224 AM CDT WED JUL 1 2015

.UPDATE...
943 PM CDT

FOR EVENING UPDATE...

MINOR TWEAKS TO GOING FORECAST THIS EVENING...MAINLY WITH RESPECT TO
HOURLY GRIDS FOR WIND AND TEMPS...AS WELL AS SKY COVER WITH EARLIER
LAKE BREEZE/SECONDARY COLD FRONTAL BOUNDARY.

WEAK SURFACE LOW PRESSURE WAS PULLING AWAY FROM THE FORECAST AREA
ACROSS THE CENTRAL GREAT LAKES THIS EVENING. PRIMARY TRAILING COLD
FRONT EXTENDED SOUTHWEST ACROSS SOUTHERN IN/IL...WHILE A COMBINED
LAKE BREEZE/SECONDARY COLD FRONT HAD SURGED INLAND ACROSS NE IL/NW
IND AND EAST CENTRAL IL SINCE LATE AFTERNOON. WHILE COOLER AND DRIER
AIR WAS SPREADING INTO THE AREA ON NORTH-NORTHEAST WINDS...AN AREA
OF FOG HAD INITIALLY DEVELOPED BEHIND THE BOUNDARY ACROSS THE LAKE
AND BRIEFLY IMPACTED AREAS NEAR THE LAKE SHORE. WEB CAMERAS INDICATE
THAT FOG HAS LARGELY DISSIPATED...LIFTING INTO A LOW CEILING AND
SCATTERING AS LOWER DEW POINT AIR ARRIVES. 11-3.9 MICRON IR IMAGERY
INDICATES ONLY SCATTERED LOW CLOUDS AROUND THE SOUTH END OF THE LAKE
AT THIS HOUR...WITH MORE EXTENSIVE CLOUDINESS LIMITED TO THE
NORTHERN HALF OR SO. FARTHER WEST...CIRRUS WAS SPILLING INTO THE
MISSISSIPPI VALLEY IN ASSOCIATION WITH THE UPPER JET STREAK ENTERING
THE WESTERN SIDE OF THE UPPER TROUGH OVER THE EASTERN CONUS...WHICH
WILL LIKELY KEEP SKIES PARTLY CLOUDY IN NATURE THROUGH THE NIGHT.

SURFACE HIGH PRESSURE SPREADING INTO THE NORTHERN GREAT LAKES AND
UPPER MIDWEST WILL BUILD SOUTH INTO THE MIDWEST WEDNESDAY...SETTING
THE STAGE FOR A FEW DAYS OF DRY WEATHER.

RATZER

&&

.SHORT TERM...
210 PM CDT

THROUGH WEDNESDAY...

DECIDED TO REDUCE THE PRECIPITATION OUTLOOK SIGNIFICANTLY FOR THIS
AFTERNOON. THE MAIN UPPER LEVEL WAVE IS WELL TO OUR EAST OVER
EASTERN MI AND OHIO AND THICK CLOUD COVER IS NORTH OF I-80.  WAS
ORIGINALLY THINKING A FEW SHOWERS WOULD DEVELOP ALONG THE LAKE
BREEZE...BUT THE CLOUD COVER WILL LIKELY LIMIT ANY VERTICAL GROWTH
ESPECIALLY SINCE MOST PLACES HAVE NOT WARMED AS QUICKLY AS
ORIGINALLY THOUGHT.  KEPT A SLIGHT CHANCE OF THUNDERSTORMS ACROSS
SOUTHERN FORD...IROQUOIS...AND BENTON COUNTIES THIS AFTERNOON
ALTHOUGH WITHOUT ANY CLEAR FORCING...HAVE LOW CONFIDENCE IN ANY
SHOWERS OR STORMS FORMING.  THE LATEST RAP ANALYSIS DOES FEATURE
AROUND 1500 J/KG OF CAPE SOUTH OF I-80 SO IF ANY FORCING DOES
DEVELOP...STORMS ARE POSSIBLE.

EXPECTING DRY CONDITIONS THROUGH WEDNESDAY AS THE NEXT CONVECTIVE
SYSTEM WILL PASS TO OUR SOUTH OVER CENTRAL ILLINOIS.  TO PLAY IT
SAFE...PUT A SLIGHT CHANCE OF STORMS SOUTH OF A PONTIAC IL TO FOWLER
INDIANA LINE LATE WEDNESDAY AFTERNOON...BUT HAVE MEDIUM-LOW
CONFIDENCE IN STORMS GETTING THAT FAR NORTH TOMORROW.

DID NOT MAKE ANY MAJOR CHANGES TO TEMPS FOR TONIGHT AND TOMORROW.
WITH INCREASING CLOUD COVER OVERNIGHT AND DEWPOINTS IN THE MID 50S
TO LOW 60S...LOW TEMPS WILL GET INTO THE MID TO UPPER 50S. FLOW WILL
BE OFF OF THE LAKE TOMORROW RESULTING IN UNSEASONABLY COOL TEMPS
WITH HIGHS IN THE 70S. LOCATIONS ALONG THE LAKE WILL LIKELY STAY IN
THE LOW TO MID 60S.

JEE

&&

.LONG TERM...
313 PM CDT

WEDNESDAY NIGHT THROUGH TUESDAY...

MOST OF THE REMAINING FORECAST PERIOD WILL LIKELY SEE BELOW
NORMAL TEMPS AND WITH DRIER CONDITIONS. THIS WILL BE THE CASE
WEDNESDAY NIGHT AS EXPECTED SHOWERS/THUNDERSTORMS ACROSS THE
CENTRAL PLAINS LIKELY DRIFT EAST SOUTHEAST TOWARDS A MORE
MOIST/UNSTABLE AIRMASS...WHILE DRIER AIR AND LITTLE TO NO
INSTABILITY ARE PRESENT ACROSS THE CWA. DID LEAVE SLIGHT CHANCE
POPS FOR SHOWERS ACROSS THE FAR SOUTHERN CWA FOR SOME VARIABILITY
IN GUIDANCE TRYING TO INCH THIS PRECIP CLOSER TO THE CWA.
HOWEVER...A MORE LIKELY SCENARIO IS FOR THIS DEVELOPMENT TO REMAIN
TO THE SOUTH. THURSDAY AND THURSDAY NIGHT WILL LIKELY BE DRY AS
HIGH PRESSURE DOMINATES THE REGION...BUT THERE STILL IS SOME
VARIABILITY AMONG MODEL GUIDANCE HANDLING OF AN APPROACHING UPPER
LEVEL TROUGH AND ASSOCIATED SURFACE REFLECTION...AND ASSOCIATED
PRECIP ON FRIDAY. ALTHOUGH THE BEST PRECIP AXIS SHOULD REMAIN JUST
SOUTH OF THE CWA...DID LEAVE SLIGHT CHANCE OF SHOWERS FOR THE
SOUTHERN HALF OF THE CWA DUE TO THIS UNCERTAINTY. THE REMAINDER OF
THE WEEKEND IS LOOKING DRY FOR MOST AREAS BUT TOWARDS SUNDAY AND
ESPECIALLY BY EARLY NEXT WEEK...A RETURN TO SOUTHERLY FLOW WILL
ALLOW A WARMER AND MORE MOIST ENVIRONMENT TO SPREAD BACK NORTH
ACROSS THE REGION. ISOLATED TO SCATTERED SHOWER/THUNDERSTORM
DEVELOPMENT IS APPEARING MORE PROBABLE ON SUNDAY...BUT WITH
CONTINUED MOIST ADVECTION AND INCREASING FLOW ALOFT EARLY NEXT
WEEK...MORE WIDESPREAD DEVELOPMENT WILL BECOME MORE LIKELY. TIMING
AND PLACEMENT ISSUES ARE PRESENT DURING THIS TIME....BUT MORE
ORGANIZED DEVELOPMENT DOES APPEAR POSSIBLE IN THE MONDAY TO
TUESDAY TIME FRAME.

RODRIGUEZ

&&

.AVIATION...

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

* MVFR CIGS DEVELOPING OVERNIGHT.

BMD

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

HIGH PRESSURE WILL REMAIN OVER THE UPPER MIDWEST THROUGH MUCH OF
THE TAF PERIOD PROVIDING NORTHEAST WINDS AND DRY WEATHER. SOME
MODELS HINT AT THE POSSIBILITY OF MVFR CIGS OVERSPREADING THE
TERMINALS OVERNIGHT INTO EARLY WEDNESDAY AND THERE ARE PATCHY MVFR
OBS UPSTREAM...SO WILL HAVE TO KEEP AN EYE ON TRENDS OVERNIGHT.
NOT CONFIDENT ENOUGH AT THE MOMENT TO INCLUDE...BUT 10Z-16Z SEEMS
LIKE THE MOST LIKELY TIMEFRAME IF IT DOES OCCUR. A LAKE BREEZE
WEDNESDAY AFTERNOON IS EXPECTED TO DRIVE WIND AOA 10 KT UNTIL THE
EVENING WHEN WINDS SHOULD BEGIN TO TAPER AGAIN.

BMD


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

* LOW CONFIDENCE IN MVFR CIGS.

BMD

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

* THURSDAY THROUGH SATURDAY...DRY/VFR. NORTHEAST WINDS.
* SUNDAY...SLIGHT CHANCE OF TSRA. EASTERLY WINDS.
* MONDAY...CHANCE OF TSRA. SOUTHWEST WINDS.

&&

.MARINE...
404 PM CDT

AS LOW PRESSURE DEPARTS THE LAKE THIS AFTERNOON...WINDS ARE
QUICKLY SHIFTING TO THE NORTH. AS THIS OCCURS...SPEEDS ARE ALSO
QUICKLY INCREASING TO THE 15 TO 25 KT RANGE OVER MUCH OF THE LAKE.
THESE SPEEDS WILL LIKELY SPREAD THROUGH THE REMAINING SOUTHERN
PORTIONS OF THE LAKE THROUGH EARLY THIS EVENING. ALTHOUGH THE
STRONGEST SPEEDS SHOULD REMAIN AWAY FROM THE NEARSHORE...DO THINK
10 TO 20 KT WINDS WILL BE POSSIBLE IN THESE AREAS THIS
AFTERNOON/EVENING. WITH HIGH PRESSURE SPANNING THE GREAT LAKES
REGION THROUGH THE END OF THE WORK WEEK...NORTHERLY WINDS WILL
PREVAIL.

RODRIGUEZ

&&

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

$$

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