Area Forecast Discussion
Issued by NWS Chicago, IL

Home | Current Version | Previous Version | Graphics & Text | 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 210912
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
412 AM CDT SUN SEP 21 2014

.DISCUSSION...
936 PM CDT

LATEST RADAR IMAGERY DEPICTING SCATTERED SHOWER AND THUNDERSTORM
DEVELOPMENT PERSISTING MAINLY ACROSS THE FAR SOUTHERN PORTIONS OF
THE CWA...WHILE ISOLATED DEVELOPMENT CONTINUES ELSEWHERE. THIS
LINE OF SHOWERS/THUNDERSTORMS ARE DEVELOPING ALONG LOW LEVEL
CONVERGENT AXIS STRETCHED ACROSS CENTRAL ILLINOIS WITHIN MODERATE
INSTABILITY...WHILE ISOLATED DEVELOPMENT IS FORMING NEAR ANY
BETTER LOW LEVEL CONVERGENCE. HEIGHTS OF THESE STORMS HAVE NOT
BEEN OVERLY GREAT...LIKELY DUE TO LACK OF ANY STEEP LAPSE RATES.
WILL LIKELY OBSERVE A SOUTHWARD TREND WITH THIS PRECIP OVER THE
NEXT COUPLE OF HOURS...WITH ISOLATED SMALL HAIL OR GUSTY WINDS
STILL NOT OUT OF THE QUESTION WITH ANY STRONGER STORMS. LARGE VORT
MAX WILL CONTINUE TO SWING EAST/SOUTHEAST ACROSS THE UPPER MIDWEST
AND GREAT LAKES REGION TONIGHT...WHILE COLD FRONT/SURFACE TROUGH
SHIFT SOUTHEAST THROUGH THE CWA. CURRENT PRECIP OVER SOUTHWEST
WISCONSIN WILL SHIFT SOUTHEAST THROUGH THE NORTHERN THIRD OF THE
CWA ALONG THESE FEATURES...BUT DO EXPECT BEST DEVELOPMENT TO
REMAIN IN WISCONSIN. A THUNDERSTORM OR TWO WILL BE POSSIBLE BUT
DONT EXPECT COVERAGE TO BE OVERLY GREAT...AS INSTABILITY AXIS WILL
SHIFT SOUTHEAST WITH TIME THROUGH EARLY SUNDAY MORNING.

RODRIGUEZ

//PREV DISCUSSION...

329 PM...MAIN FORECAST CONCERNS ARE SEVERE POTENTIAL THROUGH
EARLY THIS EVENING THEN COOLER TEMPERATURES WITH RAIN SHOWERS FOR
SUNDAY.

LINE OF THUNDERSTORMS FROM NORTHWEST INDIANA BACK THROUGH WEST
CENTRAL IL MOVING INTO RATHER MOIST AND UNSTABLE AIR AND THIS WILL
BE THE BEST LOCATION...SOUTHERN/SOUTHEASTERN THIRD OF THE CWA...
FOR SEVERE WEATHER INTO EARLY THIS EVENING. FURTHER NORTH...PRECIP
IS MORE SHOWERY WITH EMBEDDED THUNDER AND THE BACK EDGE OF THIS
PRECIP SHOULD BE THROUGH MUCH OF THE NORTHERN HALF/TWO THIRDS OF
THE CWA BY EARLY EVENING.

AN UPPER WAVE MOVING SOUTHEAST ACROSS THE UPPER MIDWEST WILL MOVE
ACROSS THE WESTERN LAKES LATER THIS EVENING WITH PRECIP WITH THIS
FEATURE LIKELY REMAINING MAINLY NORTH OF THE CWA BUT SOME SHOWERS
OR AN ISOLATED THUNDERSTORM IS STILL POSSIBLE LATER THIS EVENING.

A STRONG COLD FRONT WILL THEN MOVE SOUTH ACROSS THE LAKES REGION
OVERNIGHT REACHING NORTHERN IL SUNDAY MORNING. THIS WILL SHIFT THE
WINDS NORTH/NORTHEAST BY AFTERNOON WITH A PERIOD OF SHOWERS
POSSIBLE FROM MID MORNING THROUGH MID/LATE AFTERNOON. SOME
UNCERTAINTY REGARDING COVERAGE BUT POTENTIAL IS HIGH ENOUGH FOR
CHANCE POPS FOR MUCH OF THE DAY. PRECIP AND CLOUD COVER ALONG WITH
COLDER AIR SPREADING INTO THE REGION WILL KEEP TEMPS COOLER AND
ONLY HAVE HIGHS IN THE 60S.

AS HIGH PRESSURE MOVES ACROSS THE AREA SUNDAY AND MONDAY...LIGHT
WINDS WILL LIKELY ALLOW TEMPS TO COOL TO THE DEWPOINTS WITH FOG
POSSIBLE. THE REST OF THE PERIOD IS EXPECTED TO BE DRY WITH TEMPS
STILL IN THE 60S MONDAY...THEN WARMING A FEW DEGREES THROUGH THE
70S EACH DAY THROUGH THE END OF THE WEEK. CMS

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 09Z...

* WEST WINDS VEERING NORTHWEST BY DAYBREAK. SPEEDS GENERALLY ARND
  10-14KT WITH GUSTS DEVELOPING AFT DAYBREAK TO 20-24KT.

* MVFR CIGS DEVELOPING ARND 10Z AND LIKELY PERSISTING THRU EARLY
  AFTN.

BEACHLER

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

ACROSS WISCONSIN MVFR CIGS HAVE DEVELOPED AND WILL CONTINUE TO
SLIDE SOUTHEAST TOWARDS NORTHERN IL AIRFIELDS...BUT HOLD OFF UNTIL
ARND DAYBREAK. WINDS HAVE MAINLY BECOME WESTERLY WITH SPEEDS ARND
10-14KT...AND AS DAYBREAK NEARS GUSTS WILL BE DEVELOPING TO NEAR
20-24KT. GUIDANCE INDICATES THAT WITH THE MID-LVL SYSTEM DROPPING
SOUTHEAST TOWARDS THE TAF SITES...MVFR CIGS WILL BE DEVELOPING AND
LIKELY PERSIST THUR EARLY AFTN. IN ADDITION IT APPEARS SOME VCSH
OR LGT SHRA WILL ACCOMPANY THE LOW CIGS LATER THIS MORNING THRU
EARLY AFTN. WINDS WILL ALSO BE TURNING NORTHWEST THEN NORTH BY
THIS AFTN. THEN DRIER AIR WILL ARRIVE AND SCOUR THE LOW CLOUDS BY
SUNSET.

BEACHLER

//ORD AND MDW CONFIDENCE...UPDATED 09Z...

* HIGH CONFIDENCE IN WIND DIR/SPEED/GUSTS.

* MEDIUM CONFIDENCE IN PRECISE TIMING OF CIGS...HIGH CONFIDENCE IN
  MVFR CIGS DEVELOPING THOUGH.

* MEDIUM CONFIDENCE IN TIMING AND PLACEMENT OF SHRA LATER TODAY.

BEACHLER

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

MONDAY AND TUESDAY...VFR.

WEDNESDAY THROUGH FRIDAY. VFR. SOUTHEAST WINDS.

KMD

&&

.MARINE...
313 AM CDT

LOW PRESSURE HAS MOVED INTO LOWER MICHIGAN AND WILL CONTINUE TO
SLIDE EAST THROUGHOUT THE AFTERNOON...REACHING THE EASTERN GREAT
LAKES REGION BY THIS EVENING. MEANWHILE THE PRESSURE GRADIENT
ALONG THE WESTERN PERIPHERY OF THE LOW HAS TIGHTENED...AND WAS
EXPECTED TO MOVE ACROSS LAKE MICHIGAN THIS MORNING. GUIDANCE HAS
CONTINUED TO INDICATE THAT GALE FORCE WINDS WILL DEVELOP...HOWEVER
IT APPEARS TO BE MARGINAL WITH GUSTS GENERALLY AROUND 35 KT TO
POSSIBLY A FEW GUSTS UP TO 38KT IN THE SOUTHERN HALF OF THE LAKE.
HAVE GONE AHEAD AND UPGRADED THE GALE WATCH TO A GALE
WARNING...BUT ALSO TRIMMED THE END TIME AS IT APPEARS GALE
CONDITIONS WILL QUICKLY COME DOWN BY THIS AFTN. THE OTHER
CHALLENGE HAS BEEN HOW TO HANDLE THE GALE WATCH THAT WAS IN EFFECT
FOR THE INDIANA NEARSHORE WATERS. THIS APPEARS TO BE SLIGHTLY LESS
FAVORABLE SO HAVE MIGRATED THE GALE WATCH TO A SMALL CRAFT
ADVISORY...BUT FEEL AN OCCASIONAL GALE FORCE GUST IS POSSIBLE LATE
THIS MORNING THROUGH THE AFTERNOON. WHILE THE GRADIENT WILL
QUICKLY DIMINISH TONIGHT...WAVES WILL LIKELY REMAIN ELEVATED FOR
THE SOUTHERN HALF OF THE LAKE. HAVE NUDGED THE END TIME TO THE
SMALL CRAFT ADVISORY FOR THE INDIANA NEARSHORE INTO MON AFTN. HIGH
PRESSURE ACROSS THE CENTRAL PLAINS WILL CONTINUE TO BUILD EAST
TONIGHT...THEN REMAIN OVER LAKE MICHIGAN THROUGH WEDNESDAY BEFORE
DRIFTING EAST. THIS WILL MAINTAIN MUCH LIGHTER WINDS AND LOWER
WAVES FOR TUESDAY AND WEDNESDAY.

BEACHLER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WARNING...LMZ080-LMZ567-LMZ669-LMZ671-LMZ673-LMZ675-LMZ777-
     LMZ779-LMZ868-LMZ870-LMZ872-LMZ874-LMZ876-LMZ878...9 AM
     SUNDAY TO 3 PM SUNDAY.

     SMALL CRAFT ADVISORY...ILLINOIS NEARSHORE WATERS UNTIL 10 AM MONDAY.

     SMALL CRAFT ADVISORY...INDIANA NEARSHORE WATERS UNTIL 5 PM MONDAY.

&&

$$

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

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
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.