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 131357
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
857 AM CDT SUN JUL 13 2014

.DISCUSSION...
245 AM CDT

TODAY THROUGH TONIGHT...
EARLY THIS MORNING THE CONVECTIVE LINE HAS CONTINUED TO PUSH FURTHER
SOUTH...LOCATED ALONG THE SOUTHERN FORECAST AREA STRETCHING
NORTHEAST AND CLIPPING A PORTION OF NORTHWEST INDIANA. THIS BOUNDARY
WILL SLOWLY SAG FURTHER SOUTH/EAST THROUGH THE MORNING HOURS. BEHIND
THE FEATURE...PRECIP HAS COME TO AN END AND THE BULK OF THE DAY IS
EXPECTED TO BE DRY FOR MUCH OF THE CWFA. THE EXCEPTION WILL BE THRU
THIS MORNING FOR THE SOUTHERN PORTIONS...ALTHOUGH IF THE BOUNDARY
CAN MAINTAIN A CURRENT FORWARD SPEED PRECIP MAY END JUST AFT
DAYBREAK.

THEN THE NEXT CHALLENGE WILL RESIDE WITH HOW WARM THE SFC WILL
BECOME. THE LACK OF A GRADIENT BEHIND THE INITIAL CONVECTIVE
BOUNDARY WILL AID IN KEEPING DEW PTS SLIGHTLY ELEVATED IN THE
MID/UPR 60S. SKIES SHUD BEGIN TO THIN BY MIDDAY...AND EXPECT HIGHS
TO PUSH BACK TO ARND 80 TO PSBLY THE LOW 80S.

A HANDFUL OF THE HI-RES SOLUTIONS SUGGEST THAT SOME STEEPENING IN
THE LAPSE RATES THIS AFTN COULD PAINT A FEW SHOWERS. THEN ONCE WE
LOSE THE DIURNAL COMPONENT...PRECIP WILL DIMINISH. OVERNIGHT LOWS
WILL LIKELY FALL INTO THE UPR 50S/LOW 60S.

MONDAY THROUGH TUESDAY...
ROBUST 500MB VORT/TROUGH WILL CONTINUE TO PIVOT SOUTHEAST ACROSS THE
UPPER MIDWEST TOWARDS THE GREAT LAKES REGION MON...WITH TEMPS
STEADILY COOLING ALOFT AND EVENTUALLY REACHING THE SFC. GUIDANCE
CONTINUES TO HINT THAT SOME WEAK INSTABILITY MAY DEVELOP...AND WITH
SOME BREAKS IN THE CLOUD COVER MARGINAL SFC INSTABILITY COULD
WARRANT AN ISOLATED THUNDERSTORM GENERALLY SOUTH OF I-80. TEMPS MON
WILL LINGER IN THE 70S. SOME HEIGHT RISES SHUD CREEP EAST INTO THE
AREA MON NGT AND BRING AN END TO THE ISOLATED CONVECTION...WITH SOME
BREAKS IN CLOUDS AND ALLOW TEMPS TO RADIATE INTO THE LOW 50S. IT IS
POSSIBLE THAT THE TRADITIONALLY COOL SPOTS COULD DIP INTO THE UPR
40S MON NGT.

WRAP AROUND MOISTURE WILL BE DIVING SOUTH/SOUTHEAST ACROSS WISC MON
NGT...AND SHUD CLIP THE NORTHEAST PORTIONS OF THE CWFA TUE MIDDAY
THRU EARLY EVE. THERE IS SOME DIFFERENCES IN THE LATEST SOLUTIONS
THAT ARE BEGINNING TO SUGGEST THE UPPER LEVEL TROUGH THAT ARRIVES
COULD REMAIN PROGRESSIVE...WHICH MAY ALLOW TEMPS TO BE A LITTLE
WARMER FOR TUE. HAVE NUDGED TEMPS UP A DEG TO ARND 70 TUE...AND IF
THE SOLUTIONS CONTINUE TO AGREE THAT A SLIGHTLY MORE PROGRESSIVE
TROUGH DOES OCCUR THEN TEMPS TUE COULD BE GENERALLY IN THE LOW 70S
AND PERHAPS END UP WITH A DRY DAY.

CONFIDENCE...HIGH.

WEDNESDAY THROUGH SATURDAY...
ENSEMBLES CONTINUE TO DEMONSTRATE HIGH CONFIDENCE IN THE EXTENDED
PERIODS WITH THE TROUGH AXIS LIFTING NORTHEAST BY THUR...AND FLOW
UPSTREAM BEGINNING TO BECOME FLAT. THERE IS SOME HINT THAT A WEAK
TROUGH MAY BEGIN TO DEVELOP OVER THE CANADIAN ROCKIES THUR/FRI...AND
ARRIVE OVER THE GREAT LAKES REGION LATER NEXT WEEKEND.

DESPITE THE STEADY LIFTING OF THE TROUGH AXIS...BROAD SFC RIDGING
WILL LINGER OVERHEAD THRU FRI BUT BE DRIFTING EAST BY THE WEEKEND.
GUIDANCE HAS BEEN CONSISTENT IN BRINGING A STEADY MODERATING TREND
AND A RETURN TO MORE SEASONAL AIR BY WEEKS END.

CONFIDENCE...HIGH.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 14Z...

* MVFR CIGS SCATTER OUT THIS MORNING.

* SMALL CHANCE FOR SHRA LATE THIS AFTERNOON/EVENING.

JEE

//DISCUSSION...UPDATED 12Z...

OBSERVATIONS HAVE BEEN SHOWING A TREND TO LIFT CEILINGS ACROSS
THE TERMINALS...BUT DEWPOINT DEPRESSIONS REMAIN LOW ENOUGH BEHIND
A WEAK COOL FRONT TO KEEP AREAS OF MVFR AND IFR CEILINGS AND
ISOLATED MVFR VSBYS. MOST SHORT TERM GUIDANCE IS INDICATING MVFR
WITH POCKETS OF IFR CONDITIONS LINGERS THROUGH 15Z AND THEN LIFTS TO
VFR. THEREFORE WILL HANG ONTO A MENTION OF MVFR CEILINGS FOR A
SHORT TIME THIS MORNING. IF IFR OCCURS IT SHOULD BE SHORT LIVED
AND NOT PREDOMINANT. CONFIDENCE IS MEDIUM AS TO WHEN THESE WILL
LIFT.

WINDS HAVE TURNED TO THE W AND NW. EXPECT SOME GUSTS INTO THE MID
TEENS TODAY AS A COLD FRONT SAGS SOUTH. THERE COULD BE A FEW
SHOWERS WITH THE FRONT BUT CONFIDENCE IS NOT HIGH GIVEN THE WEAK
FORCING...SO KEPT THE TAFS DRY.

KMD

//ORD AND MDW CONFIDENCE...UPDATED 14Z...

* HIGH CONFIDENCE IN MVFR CIGS SCATTERING...MEDIUM-HIGH CONFIDENCE
  IN VFR CONDITIONS BY 15Z.

* LOW CONFIDENCE IN SHRA THIS AFTN/EVE.

* HIGH CONFIDENCE IN ALL OTHER FORECAST ELEMENTS.

JEE

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

MONDAY NIGHT...VFR LIKELY.
TUESDAY...CHANCE OF SHRA. MAINLY VFR.
WEDNESDAY-FRIDAY...VFR LIKELY.
SATURDAY...SHRA/TSRA POSSIBLE.

KMD

&&

.MARINE...
357 AM CDT

SHOWERS AND THUNDERSTORMS HAVE CLEARED THE LAKE...AND LOW PRESSURE
HAS NOW SHIFTED EAST TO LAKE HURON. WINDS HAVE GENERALLY TURNED
WESTERLY...WITH SLIGHTLY STRONGER SPEEDS ACROSS THE NORTH HALF OF
THE LAKE. EXPECT THE WEST NORTHWEST WIND ACROSS THE LAKE ON
TO CONTINUE THROUGH THE WEEKEND...AS A SECONDARY TROUGH/FRONT MOVE
SOUTHEAST THROUGH THE GREAT LAKES REGION...THEN AS HIGH PRESSURE
BUILDS INTO THE NORTHERN PLAINS...A STRONGER COLD FRONT SPREADS
DOWN THE LAKE MONDAY AFTERNOON AND EVENING WITH GUSTY NW WINDS 15
TO 25 KT. HIGH PRESSURE THEN SHIFTS OVER THE GREAT LAKES REGION
THROUGH MID WEEK FOR QUIET CONDITIONS.

KMD

&&

.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/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.