Area Forecast Discussion
Issued by NWS Chicago, IL

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640
FXUS63 KLOT 191306
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
806 AM CDT TUE MAY 19 2015

.UPDATE...
759 AM CDT

QUICK UPDATES THIS MORNING TO ADJUST SKY AND WEATHER THROUGH LATE
MORNING/MIDDAY. STRATUS CONTINUES TO SPILL SOUTH ACROSS MUCH OF
THE CWA THIS MORNING...AND HAVE TRENDED TOWARDS PREVIOUS THOUGHTS
ON THIS STRATUS WITH SKIES LIKELY CLOUDY OR PARTLY SUNNY THROUGH
MIDDAY. ALSO...WEAK RETURNS NOTED ON RADAR ACROSS SOUTHERN
WISCONSIN AND FAR NORTHERN ILLINOIS THIS MORNING ARE PRODUCING
SCATTERED SPRINKLES. HAVE ADDED THIS TO THE GRIDS THROUGH MID/LATE
MORNING MAINLY FOR NORTHERN ILLINOIS...BUT WITH ISOLATED SPRINKLES
NOT OUT OF THE QUESTION FOR THE REMAINING CWA.

RODRIGUEZ

&&

.SHORT TERM...
307 AM CDT

THROUGH WEDNESDAY...

PRIMARY FORECAST CONCERN IN SHORT RANGE IS WITH CLOUD COVER AND
TEMPS. DESPITE MODEL GUIDANCE INSISTENCE THAT IT ISN`T THERE...A
STRATUS BANK CONTINUES TO SPILL SOUTHEASTWARD ACROSS THE CWA EARLY
THIS MORNING. WHILE STRATUS WILL LIKELY HANG ON THROUGH EARLY
MORNING ANTICIPATE EROSION FROM THE EDGES AND HOLES LIKELY
DEVELOPING WITHIN IT BY MID-LATE MORNING AS STRONG LATE MAY SUN
WORKS ITS MAGIC AND BURNS IT OFF. NORTHWEST WINDS TODAY SHOULD
ALLOW FOR A HEALTHY LAKE BREEZE TO DEVELOP THIS AFTERNOON AND SEND
TEMPS FALLING EVEN FURTHER NEAR THE LAKE. ANTICIPATE SHORELINE
TEMPS WILL BE IN THE LOW/MID 40S BY EARLY EVENING...A FAR CRY FROM
THE RECENT 80 DEGREE TEMPS.

WHILE CLOUDINESS WILL BE ON THE DECREASE TODAY...HIGH AND EVENTUALLY
MID LEVEL CLOUDINESS WILL BEGIN STREAMING BACK INTO THE AREA TONIGHT
IN ADVANCE OF THE NEXT SHORTWAVE. SYSTEM WILL BE ENCOUNTERING A BIT
OF A CONFLUENT FLOW AND SHOULD WEAKEN AND TEND TO TURN MORE
SOUTHEAST AS IT PHASES WITH NORTHERN STREAM SHORTWAVE PIVOTING
AROUND THE LONGWAVE NE NOAM TROF. SUSPECT PRECIP WILL STRUGGLE TO
DEVELOP TOO FAR NORTH INTO OUR CWA WEDNESDAY WITH THIS WAVE AS DRY
AIR AND WEAKENING OF THE WAVE WOULD FAVOR MOST OF THE RAIN STAYING
SOUTH OF I-80 IF NOT FURTHER SOUTH THAN THAT WITH JUST PERHAPS SOME
SPRINKLES FROM A MID DECK POINTS NORTHWARD.

IZZI

&&

.LONG TERM...
307 AM CDT

WEDNESDAY NIGHT THROUGH MONDAY...

WESTERLY WINDS THURSDAY IN THE WAKE OF WEDNESDAY`S SYSTEM WILL ALLOW
FOR A HEALTHY REBOUND IN TEMPERATURES...PARTICULARLY ALONG THE LAKE
WHERE 24 HOUR TEMPERATURE CHANGES NEAR THE LAKE COULD EXCEED 25F AS
MID 40S WED PM REBOUND TO NEAR 70 THUR PM. SHORTWAVE TROUGH PIVOTING
AROUND UPPER LOW WELL TO OUR NORTHEAST OVER QUEBEC LOOKS TO ALLOW
WHAT WOULD NORMALLY BE A WEAK COLD FRONT SOUTHWARD ACROSS THE AREA
LATE THURS NIGHT/EARLY FRIDAY MORNING. SYNOPTIC AIR MASS BEHIND THE
FRONT IS NOT MUCH COLDER...BUT LAKE ENHANCEMENT OF THE FRONT WILL
KNOCK TEMPS ALONG THE LAKE DOWN SUBSTANTIALLY AGAIN FRIDAY WITH
AFTERNOON TEMPS NEAR OR PERHAPS JUST BELOW 50F AGAIN ALONG THE LAKE
WHILE POINTS WELL INLAND STILL CLIMB WELL INTO THE 60S.

BIG WESTERN CUT OFF LOW IS STILL PROGGED TO OPEN UP AND EJECT
EASTWARD INTO THE PLAINS OVER THE WEEKEND AND BRING US INCREASING
CHANCES OF SHOWERS AND THUNDERSTORMS DURING THE LATER HALF OF THE
UPCOMING HOLIDAY WEEKEND. WARMER AND MORE HUMID CONDITIONS ARE
ALSO EXPECTED FOR THE WEEKEND...THOUGH COULD SEE A SOUTHEAST WIND
CUTTING OFF THE LAKE AND KEEPING LAKE SIDE TEMPS COOLER. GLOBAL
MODELS HAVE A HABIT OF BEING TOO QUICK IN OPENING UP THESE TYPE OF
SYSTEMS AND KICKING THEM OUT TOO QUICKLY IN THE MEDIUM RANGE
PERIOD...SO IT IS POSSIBLE LATER RUNS WILL SLOW THE SYSTEM DOWN
AND FOR THAT REASON HAVE UNDERCUT BLENDED MODEL CONSENSUS POPS A
BIT.

IZZI

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 12Z...

* MVFR CIGS THIS MORNING.
* LAKE BREEZE TURNING WINDS NORTHEAST THIS AFTERNOON.

BMD

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

COLD CANADIAN HIGH WILL CONTINUE TO INCH INTO THE MIDWEST TODAY.
STRATUS DECK ASSOCIATED WITH THE COLD AIR IS IN PLACE ACROSS
NORTHERN ILLINOIS AND NORTHWEST INDIANA EARLY THIS MORNING WITH
CLOUD LEVELS GENERALLY BETWEEN 025 AND 035. ANTICIPATE MVFR CIGS
TO BE IN PLACE AT THE TERMINALS THROUGH MID MORNING...THEN CIGS
SHOULD BEGIN TO LIFT DIURNALLY...AND COVERAGE MAY ALSO THIN OUT
SOME. NORTHWEST WINDS WILL BE IN PLACE THIS MORNING AND EARLY
AFTERNOON...HOWEVER A LAKE BREEZE IS EXPECTED TO DEVELOP AND TURN
WINDS TO THE NE/ENE MID AFTERNOON. VFR CONDITIONS AND EASTERLY
FLOW ARE EXPECTED AFTER THE LAKE BREEZE AND THROUGH THE REMAINDER
OF THE FORECAST PERIOD.

BMD

//ORD AND MDW CONFIDENCE...UPDATED 12Z...

* MEDIUM-HIGH IN CIG TRENDS/TIMING.
* HIGH THAT A LAKE BREEZE WILL OCCUR...MEDIUM ON TIMING AT
  TERMINALS.

BMD

//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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