Area Forecast Discussion
Issued by NWS Chicago, IL

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000
FXUS63 KLOT 041922
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
222 PM CDT TUE AUG 4 2015

.SHORT TERM...
221 PM CDT

THROUGH WEDNESDAY

A WEAK SURFACE TROUGH REMAINS IN PLACE ACROSS SOUTHERN LAKE MICHIGAN
THIS AFTERNOON...WITH HIGH PRESSURE TO OUR WEST...AND A STATIONARY
FRONT STRETCHED FROM THE SOUTHERN PLAINS AND EASTWARD ACROSS THE
OHIO/TENNESSEE VALLEYS. ALOFT...NW FLOW PERSISTS ON THE BACK SIDE OF
THE UPPER LOW JUST SOUTH OF HUDSON BAY...RIDGING ACROSS THE CENTRAL
PLAINS INTO THE UPPER MIDWEST...WITH A DISTURBANCE UNDER CUTTING THE
RIDGE CLOSER TO THE SURFACE FRONT.

THUNDERSTORMS ARE ONGOING THOUGH WEAKENING CLOSER TO THE
WAVE/SURFACE FRONT...BUT WITH HIGH PRESSURE JUST TO OUR WEST...WE
ARE JUST SEEING SOME HIGH CLOUDS FROM THIS ACTIVITY...ALONG WITH
SOME DAYTIME HEATING INDUCED CUMULUS ASSOCIATED WITH THE UPPER
LOW. THE UPPER LOW WILL PULL EAST TONIGHT INTO
WEDNESDAY...ALLOWING THE UPPER RIDGE TO SLIDE OVERHEAD TOMORROW.
PRECIPITATION ASSOCIATED WITH THE DISTURBANCE UNDERCUTTING THE
RIDGE WILL REMAIN TO OUR SOUTH AS SURFACE HIGH PRESSURE MOVES
ALONG AND EAST OF LAKE MICHIGAN AND ANCHORING THE SURFACE FRONT
ACROSS CENTRAL AND SOUTHERN ILLINOIS. THIS WILL MEAN DRY
CONDITIONS FOR THE FORECAST AREA TOMORROW DURING THE DAYTIME
HOURS. WITH THE HIGH EAST OF THE LAKE...ONSHORE FLOW WILL KEEP
LAKE ADJACENT AREAS COOLER IN THE 70S...WHILE AREAS INLAND STAY
CLOSE TO WHERE THEY ARE PEAKING TODAY IN THE LOW 80S.

KMD

&&

.LONG TERM...
238 AM CDT

WEDNESDAY NIGHT THROUGH MONDAY...

THE MID/UPPER LEVEL SHORT WAVE DISTURBANCE...CURRENTLY NOTED IN
WATER VAPOR IMAGERY ACROSS WY...IS EXPECTED TO SHIFT EAST-
SOUTHWARD ACROSS LOWER MISSOURI VALUE THROUGH WEDNESDAY NIGHT.
FORECAST GUIDANCE CONTINUES TO SUGGEST THAT THIS FARTHER SOUTH
TRACK WILL KEEP ANY DECENT MOISTURE RETURN WITH THIS SYSTEM
LARGELY SOUTH OF MY AREA. THEREFORE...I HAVE GONE DRY ACROSS ALL
BY MY FAR SOUTHERN COUNTIES WEDNESDAY NIGHT INTO EARLY THURSDAY
MORNING...THOUGH IT EVEN APPEARS THE BETTER FOCUS FOR RAIN MAY END
UP SOUTH OF THESE AREAS.

AFTER WHAT LOOKS TO BE A NICE DRY DAY ON THURSDAY...ANOTHER MID
LEVEL DISTURBANCE IS FORECAST TO SHIFT EASTWARD ACROSS THE UPPER
MIDWEST AND WESTERN GREAT LAKES REGION BY FRIDAY. THIS COULD PRODUCE
OR NEXT LOW END CHANCE FOR SOME SHOWERS AND THUNDERSTORMS FOR
FRIDAY. THEN...LOOKING AHEAD TO THE WEEKEND...THERE WILL BE SOME
SLIGHT CHANCES FOR THUNDERSTORMS ACROSS THE AREA AS THE MID LEVEL
WEATHER PATTERN LOOKS TO REMAIN DISTURBED ACROSS THE CENTRAL PORTION
OF  THE COUNTRY. HOWEVER...CONFIDENCE IS LOW ON WHERE THE BETTER
FOCUS AND ACTUAL TIMING OF ANY CONVECTIVE ACTIVITY MIGHT END UP. SO
NO BIG CHANGES WERE MADE TO CHANCES FOR STORMS NEXT WEEKEND.
HOWEVER...SOME OF THESE SLIGHT CHANCES MAY BE ABLE TO BE PULLED OUT
OF THE FORECAST ALL TOGETHER AS WE GET A BETTER HANDLE ON WHERE THE
FOCUS AREAS WILL END UP.

OTHERWISE...SEASONABLE TEMPERATURES...MAINLY IN THE LOWER 80S...ARE
EXPECTED TO CONTINUE THROUGH THE PERIOD.

KJB

&&

.AVIATION...

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

* WNWLY-WLY WINDS AROUND 10-12KT WITH GUSTS BETWEEN 18-20KT
  THROUGH SUNSET...THEN BECMG LGT/VRBL OVERNIGHT.

* WINDS BECOMING NORTHEAST 8-10KT WEDNESDAY MORNING.

KREIN

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

HIGH PRESSURE WILL CONTINUE ACROSS NORTHERN IL/NORTHWEST
IN WHILE LOW PRESSURE SITS OVER NRN QUEBEC. THIS WILL KEEP WLY-
WNWLY WINDS OVER THE REGION. DEEP LAYER MIXING WILL ALLOW GUSTS
UP TO ARND 20KT THROUGH SUNSET. THESE WINDS SHOULD BE STRONG
ENOUGH WINDS TO PREVENT A LAKE BREEZE FROM PUSHING INLAND. WINDS
WILL DIMINISH ARND SUNSET...AND BECM LGT/VRBL DURG THE EARLY
MORNING HOURS. DRY AIR WILL CONTINUE TO LIMIT THE CLOUD COVER
TODAY...WITH JUST SOME STRATOCU GENERATED BY CYCLONIC CURVATURE TO
THE UPPER LEVEL PATTERN AND SOME CIRRUS BLOW-OFF FROM
THUNDERSTORMS OVER THE UPPER MISSOURI VALLEY.

AS HIGH PRESSURE SHIFTS EAST OVERNIGHT...WINDS WILL TURN NORTHEAST
SHORTLY AFTER DAYBREAK WEDNESDAY AND THEN MORE ELY DURG THE
AFTERNOON. WIND SPEEDS SHOULD SLOWLY INCREASING TO 8-10 KT BY
TOMORROW AFTERNOON.

KREIN

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

* HIGH CONFIDENCE IN ALL FORECAST ELEMENTS.

KREIN

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

WEDNESDAY NIGHT THROUGH THURSDAY...VFR.

FRIDAY...MAINLY VFR. CHANCE OF SHOWERS AND THUNDERSTORMS.

SATURDAY THROUGH MONDAY...MAINLY VFR. SLIGHT CHANCE OF
SHOWERS/THUNDERSTORMS.

BEACHLER

&&

.MARINE...
258 AM CDT

A SURFACE RIDGE OF HIGH PRESSURE WILL SHIFT OVER THE LAKE TODAY INTO
WEDNESDAY...RESULTING IN MAINLY LAKE BREEZE DRIVEN WINDS OVER THE
LAKE LATER TODAY AND ON WEDNESDAY. HOWEVER...ANOTHER AREA OF LOW
PRESSURE IS EXPECTED TO SHIFT EASTWARD SOUTH OF THE LAKE BY
THURSDAY...WITH A SECOND AREA LOW PRESSURE EXPECTED TO SHIFT OVER
THE UPPER MIDWEST LATER INTO WEEK. THESE LOW PRESSURE SYSTEMS COULD
RESULT IN A PERIOD OR TWO OF SOME STRONGER EASTERLY FLOW OVER LAKE
MICHIGAN. HOWEVER...AT THIS TIME THE ACTUAL SPEEDS AND WIND
DIRECTIONS ARE A BIT UNCERTAIN DUE TO UNCERTAINTIES ON THE TIMING AND
TRACKS OF THESE LOWS.

KJB

&&

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

$$

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