Area Forecast Discussion
Issued by NWS Chicago, IL

Home | Current Version | Previous Version | Graphics & Text | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
000
FXUS63 KLOT 051924
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
224 PM CDT SUN JUL 5 2015

.UPDATE...
1123 AM CDT

THE DEVELOPING LAKE BREEZE HAS STARTED TO BRING COOLER LOW 70S
TEMPERATURES ONSHORE IN AREAS IMMEDIATELY ADJACENT TO THE LAKE.
SOUTHERLY FLOW AT LOCATIONS FARTHER OUT IS HELPING WARM MOST OF
THE AREA INTO THE UPPER 70S AND LOWER 80S AS OF LATE MORNING.
SCATTERED TO BROKEN CUMULUS HAVE ALSO STARTED BREAKING OUT OF THE
THIN HAZY OVERCAST. LATEST ACARS SOUNDINGS FROM AIRCRAFT AT ORD
SHOW A WELL MIXED LAYER FROM THE SFC TO ABOUT 875 MB AND THEN A
WARM CAPPING LAYER ABOVE THAT. DEWPOINTS LOCALLY ARE IN THE LOW TO
MIDDLE 60S...WHILE MUCH FARTHER WEST ACROSS IOWA THEY ARE REACHING
VALUES IN THE UPPER 60S TO MIDDLE 70S. OVERNIGHT SHOWERS IN THAT
AREA HAVE MOSTLY DISSIPATED...BUT SHORT TERM RAP GUIDANCE SUGGESTS
PRONOUNCED MOISTURE FLUX INTO THAT AREA WILL SUPPORT RENEWED
CONVECTION IN THE SPC SLIGHT TO ENHANCED RISK FOR THE NORTH
CENTRAL CONUS TODAY. IN THE LOCAL AREA...THE WARM CAPPING LAYER
ALOFT AND LACK OF MOISTURE CONVERGENCE AT LOW LEVELS WILL PROVIDE
FOR A QUIET AND SEASONABLY WARM AFTERNOON AND EVENING.

LENNING

&&

.SHORT TERM...
328 AM CDT

THROUGH MONDAY NIGHT...

FAIRLY QUIET CONDITIONS ACROSS THE AREA POST INDEPENDENCE DAY
CELEBRATIONS...THE EXCEPTION BEING SOME LINGERING HAZY SKIES
POSSIBLY MIXED WITH SOME PATCHES OF FOG. SPLIT FLOW REGIME IN PLACE
UPSTAIRS WITH MORE DOMINANT UPPER JET HEADING NORTH TOWARD HUDSON
BAY AND WITH ANOTHER WEAKENING JET HEADED SOUTH INTO THE CENTRAL AND
SOUTHERN PLAINS THANKS TO A MID LEVEL RIDGE MOVING EAST THROUGH THE
REGION. VERY DRY UPPER AIR SOUNDINGS AT KDVN AND KILX AND UPSTREAM
SUGGEST LITTLE IN THE WAY OF CLOUDINESS TODAY..THOUGH SOME HIGH
CLOUDS FROM LOW PRESSURE IN THE OHIO VALLEY WILL CLIP THE AREA ALONG
WITH LINGERING SKY OBSCURATION DUE TO CANADIAN WILDFIRE SMOKE.

AT THE SURFACE...FRONTS LIE WELL AWAY FROM THE AREA WITH ONE
BOUNDARY IN SOUTHERN ILLINOIS...AND ANOTHER WELL NORTHWEST BACK IN
THE UPPER MIDWEST.  STRONG LOW LEVEL LAPSE RATES WITH AN INVERSION
AROUND 850 MB STILL LOOKS TO SUPPORT SOME SHALLOW AFTERNOON CUMULUS
TODAY AS WELL. 850/925 TEMPS GET A 2-3C DEGREE BOOST AND WITH THE
MIXING DOES SOLIDLY SUPPORTS MID TO UPPER 80S.  LOCAL CLIMO
SUGGESTING A 90 NOT IMPOSSIBLE IN THE FAR WEST...BUT KEPT TEMPS
UNDER THAT GIVEN THE SMOKE STILL PRESENT IN THE AREA. AGAIN A LAKE
BREEZE SEEMS A GOOD BET...BUT WITH MIXING TO 850 TAPPING SLIGHTLY
HIGHER WINDS...FEELING AT THIS POINT THAT IT REMAINS EAST OF
ORD/MDW. ENOUGH TO KEEP LAKESHORE AREAS AT OR BELOW 80.

MONDAY LOOKS TO BE THE BEST CHANCE AT ECLIPSING THE 90 DEGREE MARK.
THE FRONTAL BOUNDARY DOWN IN SOUTHERN ILLINOIS GETS A NORTHWARD
SHOVE IN RESPONSE TO SOUTHERLY FLOW AHEAD OF LOW PRESSURE
EAST/NORTHEASTWARD THROUGH THE UPPER MIDWEST AND INTO THE NORTHERN
GREAT LAKES. SOME MID LEVEL FORCING IN THE LATE MORNING/EARLY
AFTERNOON MOVES THROUGH AS THE MID LEVEL FRONTAL BOUNDARY SHIFTS
NORTHWARD...BUT SOUNDINGS GENERALLY PRETTY DRY DURING THIS TIME.
GUSTY SOUTH/SOUTHWEST WINDS SHOULD HOLD A LAKE BREEZE AT BAY.

ATTENTION FOCUSES ON THE APPROACHING COLD FRONT FROM THE NORTHWEST
MONDAY LATE AFTERNOON AND MONDAY NIGHT. SEVERAL LOW PRESSURE WAVES
RIDING ALONG THE FRONT LOOK TO SLOW ITS PROGRESS DOWN FROM ITS
SPEEDIER CURRENT TRACK...AS THE UPPER JET INITIALLY REMAINS PARALLEL
TO THE LOWER LEVEL FRONT. THE FRONT WORKS ITS WAY THROUGH MONDAY
NIGHT INTO EARLY TUESDAY...BRINGING A DECENT SHOT OF
RAIN/THUNDERSTORMS AREA WIDE...SLOWEST IN THE SOUTHEAST. THE STRONG
LOW LEVEL WIND SPEEDS AND HIGH PWAT AIR MASS SHOULD ALLOW FOR SOME
RELATIVELY EFFICIENT RAINFALL PRODUCTION AND GUSTY
WINDS...COINCIDENT WITH A MARGINAL RISK FOR SEVERE STORMS MONDAY
LATE AFTERNOON AND EVENING.

KMD

&&

.LONG TERM...
328 AM CDT

TUESDAY THROUGH SATURDAY...

THERE COULD BE SOME LINGERING PRECIP BEHIND THE FRONT TUESDAY
MORNING BEFORE HIGH PRESSURE MOVES BACK IN. NORTHERLY FLOW WILL
USHER IN A MUCH COOLER AIR MASS AS ADDITIONAL COOL AIR CONTINUES
TO POUR IN OFF THE LAKE. TEMPS GRADUALLY MODULATE THROUGH THE
REMAINDER OF THE WEEK.

THE SOUTHEASTERN U.S. RIDGE ATTEMPTS TO REESTABLISH ITSELF...WHILE
TROUGHING SETS UP IN THE SOUTHWESTERN U.S. INITIALLY DRY AND
COOLER STABLE AIR WILL LIMIT PRECIP CHANCES THROUGH TUESDAY
NIGHT...BUT LATER WEDNESDAY THROUGH WEEKS END LOOK FOR OCCASIONAL
WAVES TO BRING OCCASIONAL CHANCES OF SHOWERS/STORMS.

KMD

&&

.AVIATION...

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

* LAKE BREEZE TO REMAIN EAST OF ORD/MDW TODAY.

* SOUTH WINDS GUSTING TO 25KT MONDAY AFTERNOON.

MM

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

TERMINAL DOPPLER RADAR INDICATES LAKE BREEZE MAKING WEAK INROADS
ATTM. EXPECT THE LAKE BREEZE FRONT TO STAY JUST EAST OF MDW AND
ORD TODAY AS THE SYNOPTIC SOUTH WINDS SHOULD SHUNT THE LAKE BREEZE
FURTHER NORTH. THIS WILL CONFINE THE EAST WINDS TO WITHIN 5 MILES
OF THE SHORE. FAIR WEATHER CUMULUS CLOUDS HAVE DEVELOPED AND
REMAIN AT 4-5KFT TODAY. THEY MAY OCCASIONALLY GATHER INTO A BROKEN
DECK THIS AFTERNOON BEFORE DISSIPATING AFTER 00Z THIS EVENING.

QUIET CONDITIONS ARE EXPECTED OVERNIGHT...THEN WINDS START TO
RAMP UP MONDAY AFTERNOON. LOW PRESSURE APPROACHING FROM THE WEST
WILL INCREASE SOUTH WINDS AS THE PRESSURE GRADIENT INCREASES.
DECENT MIXING TO 850MB WILL ALLOW 25KT WIND GUSTS TO REACH THE
SURFACE MONDAY AFTERNOON...WITH GUSTY CONDITIONS EXPECTED THROUGH
FROPA LATER MONDAY NIGHT.

MM

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

* MEDIUM IN LAKE BREEZE STAYING EAST OF TAF SITES.

* HIGH IN ALL OTHER FORECAST ELEMENTS.

MM

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

MONDAY NIGHT...TSRA LIKELY.

TUESDAY...CHANCE MORNING TSRA. NORTH-NORTHEAST WINDS.

WEDNESDAY...SLIGHT CHANCE SHRA.

THURSDAY...CHANCE TSRA.

FRIDAY...CHANCE TSRA.

SATURDAY...CHANCE TSRA.

RODRIGUEZ

&&

.MARINE...
220 PM CDT

WITH HIGH PRESSURE DEPARTING THE LAKES REGION AND A LOW PRESSURE
TAKING SHAPE IN THE HIGH PLAINS...SOUTHERLY WINDS WILL CONTINUE TO
STRENGTHEN ACROSS THE LAKE. ON THESE WINDS WILL COME HIGHER DEW
POINT AIR. WEBCAM IMAGERY FROM AROUND THE LAKE INDICATES HAZE THAT
MAY BE A LITTLE MORE THICKER ALREADY OVER THE WATER. CONCERNS WITH
DENSE FOG WILL INCREASE DURING THE DAY AND EVENING ON MONDAY WHEN
DEW POINTS OF 10-20 DEGREES HIGHER THAN THE LAKE WATER TEMPERATURES
MOVE OVER THE LAKE.

THE OFFSHORE SOUTHWESTERLY WINDS ON MONDAY AFTERNOON AND EVENING
LOOK TO REACH SMALL CRAFT ADVISORY CRITERIA ALONG THE ILLINOIS SHORE
AND IT IS POSSIBLE ALONG THE INDIANA SHORE. WILL GO AHEAD AND ISSUE
A SMALL CRAFT ADVISORY ON THIS SHIFT FOR THE ILLINOIS SHORE. AS FOR
THE OPEN WATERS...THE STABILITY WILL KEEP GUSTS FAR BELOW WHAT THEY
COULD BE MONDAY AFTERNOON...AS WINDS JUST OFF THE DECK /WITHIN
700 FT/ ACROSS THE NORTHERN PART OF THE LAKE ARE FORECAST TO BE
40-50 KT. WILL MENTION A FEW GALE FORCE GUSTS POSSIBLE ACROSS THE
NORTH AND THAT WILL BE PARTICULARLY TRUE FROM THE AREA OF THE
NORTH BUOY TO THE U.P. SHORE.

THE SYSTEM COLD FRONT WILL MOVE SOUTHWARD DOWN THE LAKE OVERNIGHT
MONDAY NIGHT. THE ONSHORE FLOW FROM THIS ON TUESDAY...IF A LITTLE
STRONGER THAN FORECAST...COULD BRING WAVES TO NEAR SMALL CRAFT
ADVISORY CRITERIA ALONG MAINLY THE INDIANA SHORE.

MTF

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742...NOON MONDAY TO 10
     PM MONDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO



USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.