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 030750
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
250 AM CDT MON AUG 3 2015

.SHORT TERM...
248 AM CDT

THROUGH TUESDAY...

COMPLEX OF THUNDERSTORMS HAS PRESSED SOUTHEAST OF THE FORECAST AREA
EARLY THIS MORNING...MAINLY ACROSS CENTRAL INDIANA. THE FRONTAL
BOUNDARY WILL SLOWLY PROGRESS SOUTHEAST THROUGHOUT THE MORNING.
THE GRADIENT BEHIND THE BOUNDARY REMAINS VERY MINIMAL...HOWEVER BY
LATE MORNING THE MIXING HEIGHTS WILL INCREASE AND PRODUCE GUSTS TO
NEAR 20MPH.

MID-LVL TROUGH AXIS WILL REMAIN OVER THE GREAT LAKES
REGION...KEEPING THE SFC RIDGE AXIS DISPLACED WEST AND STRETCHING
FROM THE CANADIAN ROCKIES SOUTHEAST THROUGH THE MID-MISSOURI VALLEY.
BAROCLINIC ZONE WILL BE MUCH FURTHER SOUTH...AS COOLER AIR ALOFT
BEGINS TO FILTER SOUTH ACROSS THE FORECAST AREA. DRIER AIR WILL
CONTINUE TO ADVECT ACROSS THE REGION WITH ABUNDANT SUNSHINE
EXPECTED. MOST LOCATIONS SHOULD HAVE AFTN TEMPS WARM INTO THE UPPER
70S TO THE LOW 80S.

WEAK LOBE OF VORTICITY PIVOTS AROUND THE TROUGH LATE TONIGHT...BUT
IT APPEARS THE ASSOCIATED MOISTURE/PRECIP WILL REMAIN WELL
NORTH/NORTHEAST OF THE FORECAST AREA. PLENTY OF DRY AIR REMAINS WITH
A CONTINUED INFLUENCE FROM THE ANTI-CYCLONIC FEATURE LOCATED TO THE
WEST. TEMPS SHUD EASILY RADIATE INTO THE MID/UPR 50S AWAY FROM LAKE
MICHIGAN...AND LIKELY REMAIN IN THE LOW 60S CLOSER TO THE LAKE.

TUESDAY...
500MB TROUGH AXIS BEGINS TO RELAX TO THE NORTH...WHICH
WILL ALLOW THE SFC RIDGE ACROSS THE MID-MISSOURI VALLEY TO SHIFT
EAST DURING THE DAY. THIS WILL ALLOW A LIGHT GRADIENT AND MINIMAL
MIXING FOR TUE. AS A RESULT EXPECT SFC WINDS TO TURN NORTH AND
LIKELY SEE A LAKE BREEZE DEVELOP IN THE LATE AFTERNOON HOURS. HIGHS
WILL APPROACH 80 TO THE LOW 80S...HOWEVER CLOSER TO THE LAKE
MICHIGAN SHORE HIGHS WILL HINGE UPON THE TIMING OF THE LAKE BREEZE.
CURRENT INDICATIONS ARE THAT THE TIMING FOR ONSHORE WINDS WILL BE
BEYOND PEAK HEATING...HOWEVER IF THIS OCCURS EARLIER IN THE DAY THEN
TEMPS MAY STRUGGLE TO WARM BEYOND THE MID 70S ALONG THE LAKESHORE.

BEACHLER

&&

.LONG TERM...
344 PM CDT

MONDAY THROUGH SUNDAY...

PERIOD WILL BEGIN WITH SURFACE TROUGH/FRONTAL BOUNDARY DEPARTING
TO THE EAST...WITH ASSOCIATED PRECIP LIKEWISE DEPARTING TO THE
EAST. COOLER AND DRIER CONDITIONS STILL APPEAR LIKELY FOR THE
BEGINNING OF THIS UPCOMING WEEK AS LARGE UPPER LEVEL LOW SETTLES
INTO SOUTHERN CANADA AND THE NORTHEAST CONUS. NO PRECIP EXPECTED
MONDAY INTO TUESDAY...WITH TEMPS IN THE LOW 80S LIKELY BOTH DAYS.
MODELS QUICKLY DIVERGE WITH APPROACHING SYSTEM BY MIDWEEK...WITH
THE GFS THE OUTLIER BRINGING STRONGER/MORE DEFINED LOW CLOSER TO
THE CWA. THIS WOULD PROVIDE A FURTHER NORTHWARD PUSH OF PRECIP
AXIS ESPECIALLY DURING THE WEDNESDAY TIME FRAME. WITH UNCERTAINTY
IN PLACE AND WITH SOME GUIDANCE KEEPING THE CWA DRY...HAVE MADE
LITTLE CHANGES TO THE GOING FORECAST AND KEPT LOW CHANCE POPS FOR
THE SOUTHERN HALF OF THE CWA. AFTER THIS POSSIBLE PRECIP...A DRIER
TREND IS LOOKING LIKELY TOWARDS THE END OF THE WORK WEEK WHILE
BELOW NORMAL TEMPS OCCUR.

RODRIGUEZ

&&

.AVIATION...

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

* MAINLY NORTHWEST WINDS BUT AT TIMES VARIABLE...SPEEDS WILL
  REMAIN BETWEEN 3-6KT OVERNIGHT. SPEEDS INCREASE BEGIN TO
  INCREASE AFTER DAYBREAK...GUSTS NEARING 20KT BY 16Z.

* A COUPLE PATCHES OF BKN CIGS ARND 4KFT AGL THRU 09Z...IMPROVING
  TO THIN CIRRUS AND VFR CONDS AFT 9Z.

BEACHLER

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

LINE OF STORMS HAVE PUSHED SOUTH OF THE TAF SITES WITH THE FRONTAL
BOUNDARY SLOWLY SLIDING SOUTHEAST. WINDS HAVE MAINLY SWITCHED TO
NORTHWEST BEHIND THE BOUNDARY AND DIMINISHED TO LESS THAN 9KT.
WINDS MAY BECOME VARIABLE FOR A PERIOD EARLY THIS MORNING...THEN
SOLIDIFY FROM THE NORTHWEST BY DAYBREAK. MIXING WILL INCREASE BY
16Z AND GUSTS NEARING 20KT THROUGH THIS AFTERNOON. MIXING WILL
DECREASE SHORTLY AFT SUNSET...BUT REMAIN NORTHWEST. CLOUDS LOOK TO
REMAIN MINIMAL AS WELL...WITH ONLY A COUPLE AREAS OF BKN CIGS AT
4KFT AGL THRU 9Z. THEN DRY AIR WILL CONTINUE TO POUR SOUTH AND
LIMIT CLOUDS DURING THE DAY TO ONLY A FEW/SCT DECK AT 2500-3000FT
AGL.

BEACHLER

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

* HIGH CONFIDENCE IN WIND DIR/SPEED...AND HIGH ON TIMING OF GUSTS
  DEVELOPING AND DURATION OF GUSTS.

* HIGH CONFIDENCE IN CIGS FORECAST.

BEACHLER

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

TUESDAY...VFR. NORTHWEST WINDS.
WEDNESDAY...MAINLY VFR. CHANCE OF SHOWERS LATE.
THURSDAY...VFR. CHANCE OF SHRA/TSRA.
FRIDAY AND SATURDAY...VFR.

LENNING

&&

.MARINE...
440 PM CDT

STRONG SOUTHWEST WINDS WILL CONTINUE LATE THIS AFTERNOON INTO THE
EVENING ACROSS MUCH OF THE LAKE INCLUDING THE NEARSHORE AREAS...AS
STRONG LOW PRESSURE MOVES THROUGH THE GREAT LAKES REGION. HIGHEST
SPEEDS ARE OCCURRING ACROSS THE SOUTHERN HALF OF THE LAKE AND
ESPECIALLY ALONG THE NEARSHORE WHERE A FEW GALE FORCE GUSTS ARE
ALSO POSSIBLE. THIS WILL PERSIST BEFORE WINDS DIMINISH LATE THIS
EVENING AND INTO THE OVERNIGHT HOURS AS THIS LOW EXITS TO THE
EAST...WITH WINDS BECOMING MORE WEST NORTHWEST.

RODRIGUEZ

&&

.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.