Area Forecast Discussion
Issued by NWS Chicago, IL

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary Off
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 301737
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1237 PM CDT SUN AUG 30 2015

.SHORT TERM...
329 AM CDT

THROUGH MONDAY NIGHT...

MAIN FORECAST CONCERNS/CHALLENGES ARE WITH PATCHY DENSE FOG EARLY
THIS MORNING...AND THEN WITH ISOLATED/WIDELY SCATTERED
THUNDERSTORMS POSSIBLE LATER THIS AFTERNOON.

SHOWER COVERAGE HAS DIMINISHED OVER THE LAST SEVERAL HOURS ACROSS
THE CWA WITH GENERALLY DRY CONDITIONS AT THIS TIME. THESE DRY
CONDITIONS WILL LIKELY CONTINUE THROUGH THIS MORNING...OUTSIDE OF
A BRIEF/ISOLATED SHOWER MAINLY WELL SOUTH OF INTERSTATE 80. LOW
STRATUS STILL IN PLACE EARLY THIS MORNING WITH RATHER MOIST
CONDITIONS IN PLACE ALLOWING FOR AREAS OF FOG...AND PATCHY DENSE
FOG. AT THIS TIME...ANY DENSE FOG CONTINUES TO REMAIN ISOLATED
OVER NORTH CENTRAL WITH LOCATIONS THAT DO BRIEFLY FALL BELOW 1
MILE QUICKLY IMPROVING. OTHER AREA OF CONCERN FOR DENSE FOG
CONTINUES TO BE NEAR THE LAKESHORE WHERE ITS STILL POSSIBLE FOR
THIS FOG TO SPREAD MORE INLAND THIS MORNING...WHILE OTHER DENSE
FOG EXPANDS. HOWEVER...ALL LOCATIONS NEAR THE SHORE CONTINUE TO
SHOW VIS ABOVE 1 MILE. WITH THE POSSIBILITY FOR ANY PATCHY DENSE
FOG TO EXPAND THIS MORNING...WILL NEED TO CONTINUE TO ASSESS THE
NEED FOR AN ADVISORY...BUT AM NOT ISSUING ONE AT THIS TIME.

FOG WILL DISSIPATE LATER THIS MORNING BUT WITH THIS STRATUS
LIKELY HOLDING A LITTLE LONGER. DO HAVE SKIES CLEARING LATER TODAY
BUT DONT THINK THAT WILL REALLY OCCUR UNTIL LATE MORNING/MIDDAY.
SUNNY TO PARTLY CLOUDY SKIES WILL THEN LIKELY BE OBSERVED THIS
AFTERNOON. DID LOWER MAX TEMPS SLIGHTLY TODAY WITH STRATUS
POSSIBLY LIMITING OVERALL DAYTIME HEATING. HOWEVER...THINK CLOUDS
WILL SCATTER IN TIME FOR HIGHS AROUND 80 UP NORTH AND LOWER 80S
DOWN SOUTH TO BE REALIZED THIS AFTERNOON. GUIDANCE CONTINUES TO
INDICATE THAT SCATTERED THUNDERSTORM DEVELOPMENT WILL BE POSSIBLE
LATER THIS AFTERNOON...ACROSS EAST CENTRAL ILLINOIS AND NORTHWEST
INDIANA SOUTH OF I80. THIS SEEMS REASONABLE WITH HIGH DEWPOINT AIR
IN PLACE...CLEARING SKIES ALLOWING FOR INCREASING
INSTABILITY...AND WITH LINGERING BOUNDARY IN PLACE.
HOWEVER...SHORT TERM GUIDANCE CONTINUES TO TREND THIS DEVELOPMENT
FURTHER SOUTH OF THE CWA TODAY AND CANT COMPLETELY ARGUE WITH
THIS...AS SURFACE CONVERGENCE WILL LIKELY REMAIN WEAK ALONG WITH
SUPPORT ALOFT LIKELY LACKING. NONETHELESS...DID KEEP SLIGHT
CHANCE/LOW CHANCE POPS BRIEFLY THIS AFTERNOON. IF THIS DEVELOPMENT
WERE TO OCCUR...COULD NOT RULE OUT AN ISOLATED STRONGER STORM
WHICH COULD PRODUCE GUSTY WINDS AND BRIEF HEAVIER DOWNPOURS. DRY
CONDITIONS THEN EXPECTED TONIGHT AND MONDAY WITH WARMING TREND
CONTINUING...WITH MID TO UPPER 80S LIKELY FOR MOST AREAS ON
MONDAY.

RODRIGUEZ

&&

.LONG TERM...
329 AM CDT

TUESDAY THROUGH SATURDAY...

WARMTH CONTINUES ON TUESDAY...AND WILL CONTINUE THROUGH THE REST
OF THE WEEK AS UPPER LEVEL RIDGE SETTLES IN. THINK CONDITIONS WILL
LIKELY BE DRY FOR MOST AREAS...ALTHOUGH...GUIDANCE CONTINUES TO
ADVERTISE AFTERNOON THUNDERSTORMS ACROSS A PORTION OF THE AREA
THIS WEEK. AM NOT COMPLETELY SOLD ON THIS QUITE YET BUT WITH
INCREASING MOISTURE/INSTABILITY...WILL NEED TO CONTINUE TO MONITOR
FOR THE NEED FOR ADDITIONAL POPS. HOWEVER...RATHER WEAK FLOW ALOFT
WILL LIMIT ANY ORGANIZED DEVELOPMENT THIS WEEK.

RODRIGUEZ

&&

.AVIATION...

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

* MVFR LIFTING TO VFR BY EARLY AFTERNOON.

* MVFR/IFR VSBY IN FOG LATE TONIGHT.

KREIN

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

HIGH PRESSURE REMAINS CENTERED OVER THE ERN CONUS WITH RIDGING
EXTENDING WEST TO THE MIDDLE MISSISSIPPI VALLEY WHILE A TROUGH OF
LOW PRESSURE DEVELOPS OVER THE WESTERN PLAINS. NRN IL/IN REMAINS
UNDER THE INFLUENCE OF THE HIGH WITH LIGHT AND VARIABLE WINDS. THE
STRATUS THAT DEVELOPED LAST NIGHT HAS BEEN SLOW TO IMPROVE THOUGH
VISIBILITY HAS IMPROVED TO VFR AT ALL OF THE TERMINALS. A
PERSISTENT INVERSION BASED AT ARND 2500FT HAS HELPED KEEP BKN-OVC
CIGS...THOUGH BASES HAVE LIFTED TO MVFR THROUGH THE MORNING. HAVE
BACKED OFF ON THE TIMING OF SKIES SCATTERING UNTIL 21Z AS THE
LATEST VIS SATELLITE IMAGERY HAS SHOWED SOME THINNING OF CLOUD
COVER TO THE SOUTH OF THE TERMINALS...BUT HAVE SOME RESERVATIONS
ABOUT THE NEW 21Z TIMING FOR SCATTERING. THE LATEST MODEL
SOUNDINGS STILL INDICATE THAT THE INVERSION SHOULD WEAKEN BY EARLY
EVENING AND THAT SKIES SHOULD STILL BE ABLE TO CLEAR OVERNIGHT...
BUT HAVE DECREASING CONFIDENCE IN THE INVERSION WEAKENING ENOUGH
TO ALLOW FOR DRIER AIR TO MIX TO THE LOWER LEVELS OF THE
ATMOSPHERE. HOWEVER...CONFIDENCE IS ALSO NOT HIGH ENOUGH TO MAKE
SGFNT CHANGES AT THIS TIME...SO WILL CONTINUE THE TREND OF BR
DEVELOPING AGAIN TONIGHT AS WINDS SHOULD BE WEAK TO NEAR CALM WITH
A VERY WEAK PRESSURE GRADIENT REMAINING IN PLACE. PLUS IF SKIES DO
CLEAR...RADIATIONAL COOLING SHOULD ALLOW FOR BR/FG TO DEVELOP
OVERNIGHT.

KREIN

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

* MEDIUM CONFIDENCE IN TIMING OF CONDITIONS IMPROVING TO VFR.

* LOW-MEDIUM CONFIDENCE IN VSBY TONIGHT.

* HIGH CONFIDENCE IN ALL OTHER FORECAST ELEMENTS.

KREIN

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

MONDAY NIGHT THROUGH SATURDAY...VFR. PRIMARILY SOUTH/SOUTHWEST
WINDS.

IZZI

&&

.MARINE...
221 AM CDT

STAGNANT WEATHER PATTERN EXPECTED TO SET UP THROUGH THE UPCOMING
WEEK WITH HIGH PRESSURE OVER THE EASTERN US AND TROUGHING OVER THE
HIGH PLAINS. GENERALLY SOUTHERLY FLOW IS EXPECTED THROUGH THE PERIOD
OVER THE LAKE WITH SOME LAKE BREEZE INFLUENCE TO THE FLOW DURING THE
AFTERNOON...ESPECIALLY SOUTHERN PORTIONS OF THE LAKE. NORTHERN
PORTIONS OF THE LAKE WILL OCCASIONALLY SEE SOUTHERLY WINDS FRESHEN
UP A BIT AS GRADIENT PERIODICALLY TIGHTENS ON THE NORTHWEST FRINGE
OF THE HIGH PRESSURE RIDGE AS LOWS TRACK ACROSS CANADA.

IZZI

&&

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

$$

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.