Area Forecast Discussion
Issued by NWS Chicago, IL

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FXUS63 KLOT 130940
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
440 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 09Z...

* IFR/MVFR CIGS LINGERING INTO THE MORNING

* SMALL CHANCE FOR SHRA/TSRA LATE THIS AFTERNOON/EVENING

KMD

//DISCUSSION...UPDATED 09Z...

CHALLENGING FORECAST THIS MORNING AS A MIX OF IFR AND MVFR
CEILINGS CONTINUE EARLY THIS MORNING. DEWPOINTS ARE FALLING SLIGHTLY
AS A SUBTLE COLD FRONTAL BOUNDARY BRINGS IN SLIGHTLY COOLER
DEWPOINTS WHICH HAS ALLOWED IFR TO LIFT TO LOW END MVFR AT
TIMES...BUT IT HAS GENERALLY NOT OFFSET THE IFR CONDITIONS. HIGH
CLOUDS ARE DEVELOPING OVER THE LOW CLOUDS WHICH SHOULD ENABLE
VISIBILITIES TO REMAIN HIGHER. EXPECT IFR OR MVFR TO LINGER
THROUGH DAYBREAK..,POSSIBLY LONGER.

WINDS SHOULD GENERALLY CONTINUE TO TURN TO THE W AND NW BEHIND THE
INITIAL COOL FRONT THAT IS MOVING THROUGH NOW.  A SECONDARY STRONGER
FRONT WILL MOVE THROUGH LATE IN THE DAY SUNDAY. THIS COULD TRIGGER A
FEW SHOWERS OR STORMS...THOUGH THERE IS LIMITED FORCING SO KEPT THE TAFS
DRY.

KMD

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

* HIGH THAT IFR/MVFR CONDITIONS WILL LINGER INTO THE MORNING WITH
  CEILINGS BOUNCING RIGHT AROUND 1000 FT. LOW IN PRECISE DEPARTURE
  TIME LATER THIS MORNING.

* LOW IN ANY SHRA/TSRA SUNDAY AFTERNOON/EARLY SUNDAY EVE.

KMD

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

MONDAY...CHANCE OF AFTERNOON TSRA.
TUESDAY...CHANCE OF SHRA.
WEDNESDAY-FRIDAY...VFR LIKELY.

MTF

&&

.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...FLASH FLOOD WATCH...ILZ033-ILZ039 UNTIL 10 AM SUNDAY.

IN...FLASH FLOOD WATCH...INZ019 UNTIL 10 AM SUNDAY.

LM...NONE.
&&

$$

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