Area Forecast Discussion
Issued by NWS Chicago, IL

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613
FXUS63 KLOT 192011
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
311 PM CDT TUE MAY 19 2015

.SHORT TERM...
301 PM CDT

THROUGH WEDNESDAY...

MAIN FORECAST CHALLENGES/CONCERNS ARE WITH INCREASING CHANCES FOR
SHOWERS WEDNESDAY...AND BELOW NORMAL TEMPS.

PERSISTENT STRATUS IS FINALLY ERODING AS IT SLOWLY DRIFTS
SOUTHEAST THROUGH THE CWA. EXPECT CLEARING TO OCCUR FROM NORTHWEST
TO SOUTHEAST OVER THE NEXT SEVERAL HOURS...WITH FAR NORTHEAST
ILLINOIS AND NORTHWEST INDIANA OBSERVING THIS CLOUD COVER THE
LONGEST. CLEARER SKIES WILL BE IN PLACE BY EARLY THIS EVENING
WHILE QUIET/DRY CONDITIONS WILL BE OBSERVED. MADE MINOR
ADJUSTMENTS TO LOW TEMPS TONIGHT WITH UPPER 30S TO LOW 40S
EXPECTED ACROSS THE CWA.

CLOUD COVER WILL INCREASE LATER TONIGHT INTO WEDNESDAY MORNING
WITH MID/HIGH CLOUDS SPREADING NORTHEAST ACROSS THE REGION. THIS
WILL OCCUR OUT AHEAD OF UPPER LEVEL SYSTEM OVER THE PLAINS
SHIFTING EAST/NORTHEAST TOWARDS THE AREA. CURRENT PRECIP OVER THE
PLAINS WILL LIFT ACROSS THE REGION WEDNESDAY MORNING...BUT WITH
GUIDANCE STILL VARYING TO THE EXTENT OF THE NORTHWARD PUSH. DID
INCREASE POPS TO LIKELYS FOR THE SOUTHERN CWA LATE WEDNESDAY
MORNING INTO THE EARLY AFTERNOON BUT DID LIMIT POPS ACROSS THE
NORTHERN THIRD OF THE CWA. ALTHOUGH BEST CHANCES FOR SHOWERS WILL
BE ALONG AND SOUTH OF INTERSTATE 80...DID BRING AT LEAST SLIGHT
CHANCE POPS TO AREAS FURTHER NORTH WITH THE POSSIBILITY FOR A MORE
NORTHWARD MOVEMENT. HOWEVER...IF THIS WERE TO OCCUR ACROSS THE
NORTHERN CWA...IT WOULD LIKELY ONLY BE IN THE FORM OF AN ISOLATED
SHOWER OR TWO. LITTLE TO NO INSTABILITY WILL LIMIT ANY POTENTIAL
FOR THUNDERSTORMS...AND HAVE CONTINUED MENTION OF ONLY RAIN. WITH
SOME UNCERTAINTY AS TO THE EXTENT OF THE PRECIP ON
WEDNESDAY...MADE ONLY SLIGHT CHANGES TO GOING MAX TEMPS. CURRENT
FORECAST MAX TEMPS IN THE LOW TO MID 50S COULD BE ON THE HIGH SIDE
IF MORE EXPANSIVE PRECIP SHIELD PRESENTS ITSELF...WITH THE
POSSIBILITY FOR SOME AREAS TO NOT RISE OUT OF THE 40S.

RODRIGUEZ

&&

.LONG TERM...
310 PM CDT

WEDNESDAY NIGHT THROUGH TUESDAY...

SKIES WILL CLEAR WEDNESDAY NIGHT BEHIND THE DEPARTING
WAVE...YIELDING CHILLY CONDITIONS TO START THURSDAY. THIS WILL
QUICKLY CHANGE THURSDAY...WITH NORTHWESTERLY WAA...WEST NORTHWEST
WINDS AND DEEP MIXING IN THE DRY AIRMASS ALLOWING TEMPERATURES TO
WARM TO AROUND 70. SOME HIGH-BASED CU MAY DEVELOP AT THE TOP OF THE
MIXED LAYER...WHICH MAY REACH 750 MB. A BACKDOOR COLD FRONT WILL
DROP SOUTH THURSDAY NIGHT...TURNING WINDS ONSHORE BY DAYBREAK
FRIDAY. AIRMASS FRIDAY WILL BE SUPPORTIVE OF HIGHS IN THE LOW 70S
INLAND UNDER PLENTY OF SUN...BUT LAKESHORE SHOULD BE KEPT IN THE 50S
BY ONSHORE FLOW.

MID/UPPER PATTERN WILL SHIFT TO SOUTHWESTERN TROUGHING AND EASTERN
RIDGING OVER THE HOLIDAY WEEKEND AS DEEP UPPER LOW NEAR HUDSON BAY
GETS SHUNTED EAST. EXPECTING A QUIET DAY ON SATURDAY...WITH EC
SEEMING TO BE OUTLIER IN BREAKING OUT PRECIP DURING THE AFTERNOON.
THERMAL FIELDS SUPPORT HIGHS IN THE 70S...EXCEPT EAST-SOUTHEAST
ONSHORE FLOW IS LIKELY TO LIMIT THE IL SHORE TO THE 60S. MULTIPLE
DISTURBANCES IN SOUTHWEST FLOW ALOFT WILL MOVE ACROSS THE AREA
SUNDAY THROUGH TUESDAY. IN ADDITION...LOW PRESSURE OVER THE
CENTRAL PLAINS SHOULD PASS NORTH OF THE AREA ON MEMORIAL DAY. GOOD
MOISTURE RETURN WILL SEND DEWPOINTS BACK INTO THE 60S SUNDAY
NIGHT...ALONG WITH PWAT VALUES CLIMBING TO ~1.5 TO 1.75 INCHES.

STAYED GENERALLY CLOSE TO CONSENSUS BLEND FOR POPS SUNDAY THROUGH
TUESDAY...WITH SUNDAY NIGHT AND MEMORIAL DAY CURRENTLY FAVORED FOR
POTENTIALLY MORE WIDESPREAD CONVECTION. WOULD NOT EXPECT THE WHOLE
PERIOD TO BE A WASHOUT...BUT WILL NEED TO WATCH FOR HEAVY
DOWNPOURS IN SEASONABLY MOIST AIRMASS. COLD FRONT LOOKS TO MOVE
ACROSS THE AREA ON TUESDAY...BUT SIGNS POINT TO THE PATTERN
REMAINING ACTIVE BEYOND DAY 7. REGARDING TEMPERATURES...LOCAL
CLIMO FOR 850 MB AND 925 MB TEMPS IN THE TEENS CELSIUS SUPPORTS AT
LEAST WELL INTO THE 70S INLAND ON SUNDAY AND UPPER 70S-LOWER 80S
MONDAY AND TUESDAY. READINGS COULD END UP WARMER IF WE GET MORE
SUN THAN CURRENTLY FORECAST. WITH INCREASING DEWPOINTS...THE
SECOND HALF OF MEMORIAL DAY WEEKEND WILL TURN RATHER MUGGY.
ONSHORE FLOW LOOKS LIKELY INTO NORTHEAST ILLINOIS ON SUNDAY...BUT
THEN OFFSHORE FLOW EXPECTED THE REST OF THE PERIOD.

RC

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 20Z...

* LAKE BREEZE TURNS WIND E ARND 10 KT THIS AFTN. NE TO E WINDS
  ARND 10 KT EXPECTED AGAIN WEDNESDAY.

* CHANCE OF -SHRA WEDNESDAY AFTN.

JEE

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

HIGH END MVFR TO LOW END VFR STRATUS IS SLOWLY LIFTING. STRATUS
HAS CLEARED OVER SW WI AND FAR NW IL...AND EXPECTING THE
SCATTERING TO SLOWLY SPREAD OVER NORTH CENTRAL IL. THINKING
EASTERN TERMINALS WILL NOT SEE SCATTERED CLOUDS UNTIL THE LAKE
BREEZE PUSHES THROUGH. DID NOT ADJUST THE TIME OF THE LAKE BREEZE
AS BUOYS ALONG SOUTHERN LAKE MI ARE BEGINNING TO TURN...SO THE
CURRENT TIMING LOOKED REASONABLE. STILL EXPECTING 10 KT E TO NE
WINDS BEHIND THE LAKE BREEZE.

WINDS SHIFT TO NE ACROSS THE TERMINALS THROUGH THIS EVENING AS
HIGH PRESSURE MOVES OVERHEAD AND THE LAKE BREEZE PUSHES WEST.
WINDS DIMINISH TO LESS THAN 10 KT THIS EVENING BUT EXPECTING NE TO
E WINDS TO PICK UP TO ARND 10 KT AGAIN WEDNESDAY MORNING. AN UPPER
LEVEL WAVE WILL BRING SHOWERS TO THE REGION WEDNESDAY AFTERNOON.
THE MAJORITY OF SHOWERS SHOULD PASS SOUTH OF THE TERMINALS...BUT
THERE IS A CHANCE OF SHOWERS REACHING THE TERMINALS. FOR NOW JUST
HAVE A PROB30 AT ORD WITH LOW CONFIDENCE.

JEE

//ORD AND MDW CONFIDENCE...UPDATED 20Z...

* HIGH CONFIDENCE IN CIG TRENDS...MEDIUM-HIGH CONFIDENCE IN
  TIMING.

* HIGH CONFIDENCE IN LAKE BREEZE...MEDIUM-HIGH CONFIDENCE IN 10
  KT...MEDIUM ON TIMING.

* HIGH CONFIDENCE IN NE TO E WINDS TOMORROW...MEDIUM-HIGH
  CONFIDENCE IN SPEEDS ARND 10 KT.

* MEDIUM LOW CONFIDENCE IN -SHRA TIMING AND IF THEY MAKE IT TO
  ORD WEDNESDAY AFTN.

JEE

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

WEDNESDAY NIGHT THROUGH SATURDAY...PRIMARILY VFR.
SATURDAY NIGHT THROUGH MONDAY...PERIODIC CHANCES FOR TSRA.

BMD

&&

.MARINE...
309 AM CDT

A COLD FRONT HAS PUSHED ACROSS LAKE MICHIGAN WITH WEST WINDS EARLY
THIS MORNING VEERING TO THE NORTH THROUGH THE DAY AS HIGH PRESSURE
BUILDS DOWN INTO THE UPPER MIDWEST. WINDS WILL BEGIN TO DIMINISH
THIS AFTERNOON ALLOWING A LAKE BREEZE TO DEVELOP. THE RIDGE AXIS
WILL START TO SLIDE ACROSS SOUTHERN LAKE MICHIGAN WEDNESDAY WITH A
LAKE BREEZE ONCE AGAIN DEVELOPING ACROSS THE SOUTH END OF THE LAKE.
MEANWHILE...SOUTHWEST WINDS WILL FRESHEN UP ACROSS THE NORTH. WEST
WINDS WILL BE IN PLACE ACROSS THE ENTIRE LAKE ON THURSDAY AS A SLOW
MOVING TROUGH STARTS TO WORK DOWN THE LAKE...EVENTUALLY CLEARING THE
SOUTH END OF THE LAKE BY FRIDAY. WINDS TURN BACK NORTHEASTERLY
BEHIND THE TROUGH. DO NOT ANTICIPATE ANY HEADLINES OVER THE OPEN
WATERS THROUGH THE REMAINDER OF THE WEEK INTO THE WEEKEND...THOUGH
CONDITIONS MAY BE CLOSE TO SMALL CRAFT CRITERIA TODAY MAINLY OVER
THE INDIANA NEARSHORE WATERS.

BMD

&&

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

$$

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