000
FXUS63 KLOT 161944
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
244 PM CDT THU MAY 16 2013

.DISCUSSION...
330 AM CDT

SURFACE FRONT LIES JUST SOUTH OF THE CWA THIS MORNING AND PROBABLY
WONT MOVE MUCH THE NEXT COUPLE OF DAYS...ONLY TRENDING SLOWLY
NORTHWARD OVER THE WEEKEND. POPS THE NEXT COUPLE OF DAYS WILL BE A
CHALLENGE AS MAIN BELT OF WESTERLIES IS NORTH OF THE AREA AND UPPER
LOW OVER TEXAS OPENS UP AND MOVES INTO THE OHIO VALLEY LEAVING OUR
CWA IN A REGION OF RELATIVELY WEAK FORCING. CERTAINLY PLAUSIBLE THAT
CONVECTION COULD LIGHT UP NEAR AND JUST NORTH OF THE STALLED OUT
BOUNDARY AT JUST ABOUT ANY POINT THE NEXT COUPLE DAYS WITH THE BEST
CHANCES ACROSS FAR SOUTHERN CWA SLOWLY SPREADING NORTH INTO THE
REMAINDER OF THE AREA LATE FRIDAY INTO EARLY SATURDAY. DOES LOOKS
LIKE WE PRECIP CHANCES WILL DECREASE LATER SATURDAY THROUGH SUNDAY
AS UPPER RIDGE BUILDS INTO THE AREA AND FRONT MOVES NORTH OF THE
REGION.

TEMPERATURES PROBABLY WONT FLUCTUATE MORE THAN A FEW DEGREES FROM
WEDNESDAY`S READINGS TODAY THROUGH SATURDAY. DAILY LAKE BREEZES
SHOULD HOLD TEMPS IN THE 60S ALONG THE LAKE WITH UPPER 70S TO LOW
80S EXPECTED INLAND...THOUGH MORE CLOUD COVER ON FRIDAY COULD KEEP
IT A BIT COOLER INLAND. BIGGER WARM UP IS ANTICIPATED SUNDAY AS H8
TEMPS SORE INTO THE MID TEENS AND 925MB TEMPS GET INTO THE UPPER
TEENS WHICH SHOULD ALLOW TEMPS TO SOAR WELL INTO THE 80S AND
POSSIBLY AROUND 90 WITH ENOUGH SUNSHINE. MODELS SUGGEST THE SRF
GRADIENT WILL BE SOUTHEAST WHICH WOULD KEEP CHICAGO LAKE FRONT AND
NORTH SHORE AREAS COOLER...BUT AT THIS DISTANCE THE DETAILS ON THE
GRADIENT AND RESULTANT WIND FLOW COULD CHANGE SO STAY TUNED.

BIG WESTERN UPPER TROUGH THAT WE`VE BEEN TALKING ABOUT FOR DAYS
STILL LOOKS LIKE IT WILL MOVE TOWARD THE UPPER MISSISSIPPI VALLEY
EARLY NEXT WEEK. AFTER WHAT LOOKS TO BE A COUPLE ACTIVE SEVERE
WEATHER DAYS OUT IN THE CENTRAL CONUS THIS WEEKEND...THE MORE ACTIVE
WEATHER WILL SHIFT EAST INTO OUR AREA EARLY NEXT WEEK. GENERALLY
SPEAKING THE SYNOPTIC PATTERN LOOKS REASONABLY FAVORABLE FOR A
SEVERE WEATHER THREAT IN THE REGION MONDAY AND/OR TUESDAY...BUT
OBVIOUSLY A LOT WILL HINGE ON THE SMALLER SCALE DETAILS THAT WONT BE
RESOLVED FOR DAYS TO COME STILL. OF POTENTIALLY GREATER CONCERN IS
THE THREAT FOR HEAVY RAINFALL AND FLOODING...GFS/ECMWF/GEM ALL SHOW
UPPER LOW CLOSING OFF OVER THE NORTHERN PLAINS AND UPPER MISSISSIPPI
VALLEY DURING THE FIRST HALF OF THE WEEK WITH A WIDE OPEN GULF OF
MEXICO PROVIDING AMPLE MOISTURE. PROBABLY A BIT EARLY TO DO AN ESF
BUT IF THE MODEL REMAIN CONSISTENT THE NEXT RUN OR TWO LATER SHIFTS
MAY NEED TO CONSIDER AN ESF FOR THE THREAT OF MULTIPLE ROUNDS OF
SHOWERS/STORMS DURING THE FIRST HALF OF NEXT WEEK.

IZZI

&&

.AVIATION...

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

* NONE.

KJB

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

QUIET CONDITIONS CONTINUE WEATHER WISE AT THE TERMINALS THIS
AFTERNOON AS A SURFACE RIDGE OF HIGH PRESSURE DOMINATES ACROSS THE
WESTERN GREAT LAKES. SHOWER AND THUNDERSTORM ACTIVITY WILL STAY
SOUTH OF THE TERMINALS THIS AFTERNOON ACROSS CENTRAL PORTIONS OF
ILLINOIS...IN CLOSE PROXIMITY TO A STALLED OUT SURFACE BOUNDARY.
LIGHT EASTERLY FLOW IS EXPECTED THROUGH MUCH OF THE PERIOD.

A SERIES OF UPPER LEVEL DISTURBANCES...CURRENTLY ACROSS WESTERN
NEBRASKA AND THE OZARKS VIA WATER VAPOR IMAGERY...ARE EXPECTED TO
PROGRESS EASTWARD ACROSS THE MID MISSISSIPPI VALLEY ON FRIDAY. THIS
WILL LIKELY LEAD TO ADDITIONAL SHOWER AND THUNDERSTORM
DEVELOPMENT...ESPECIALLY FRIDAY AFTERNOON. HOWEVER...AT THIS TIME IT
APPEARS THE BETTER CHANCES WILL BE WEST AND SOUTH OF THE
TERMINALS...SO NO MENTION HAS BEEN ADDED TO THE NEW 30 HOUR ORD
TAF...BUT THIS WILL NEED TO BE WATCHED AS CONVECTIVE ACTIVITY COULD
BE CLOSE TO THE TERMINALS FRIDAY AFTERNOON.

KJB

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

* HIGH FOR ALL FORECAST ELEMENTS.

KJB

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

FRIDAY NIGHT...SLIGHT CHANCE OF TSRA...OTHERWISE VFR.

SATURDAY...SLIGHT CHANCE OF TSRA...OTHERWISE VFR.

SUNDAY...CHANCE OF TSRA...OTHERWISE VFR.

MONDAY...CHANCE OF TSRA...OTHERWISE VFR.

TUESDAY...CHANCE OF TSRA...OTHERWISE VFR.

WEDNESDAY...CHANCE OF TSRA...OTHERWISE VFR.

RODRIGUEZ

&&

.MARINE...
228 PM CDT

RIDGING FROM HIGH PRESSURE CENTERED OVER WESTERN ONTARIO EXTENDS
ACROSS LAKE MICHIGAN THIS AFTERNOON. WEAK LOW PRESSURE WILL DEVELOP
AND MOVE UP THE OHIO RIVER VALLEY FRIDAY WITH ADDITIONAL LOW
PRESSURE DEVELOPING ACROSS THE CENTRAL HIGH PLAINS. EAST TO
NORTHEAST FLOW OVERALL WILL CONTINUE ACROSS THE LAKE...WITH ONSHORE
FLOW IN AREAS WHERE THE PRESSURE GRADIENT IS WEAKER CAUSING SOME
ERRATIC DIRECTIONS AT TIMES. STEADIER AND MORE UNIFORM WINDS WILL
DEVELOP WITH TIME THROUGH TOMORROW WITH MORE OF AN EAST TO SOUTHEAST
TREND. THE STRONGEST WINDS WILL OCCUR FRIDAY EVENING/NIGHT
COINCIDENT WITH THE STRONGEST PRESSURE GRADIENT THANKS TO THE LOW
PASSING TO THE SOUTHEAST. THE GRADIENT WEAKENS DURING THE DAY
SATURDAY AS THE LOW DEPARTS TO THE EAST. LOW PRESSURE STRENGTHENS
ACROSS THE CENTRAL/NORTHERN HIGH PLAINS INTO SUNDAY WHICH WILL
GRADUALLY TIGHTEN THE PRESSURE GRADIENT ACROSS THE LAKE. THIS WILL
ALLOW A STEADY SOUTH TO SOUTHEAST WIND TO DEVELOP ACROSS MOST OF THE
LAKE...WITH A MORE EASTERLY DIRECTION ACROSS THE FAR NORTH WHERE A
WARM FRONTAL BOUNDARY IS EXPECTED TO SET UP. THE MAIN LOW WILL
MEANDER NORTHWARD BEFORE BEING PUSHED EASTWARD ACROSS MINNESOTA/IOWA
SOMETIME TUESDAY OR WEDNESDAY WHICH WILL LIKELY PUSH THE FRONTAL
BOUNDARY FURTHER SOUTH ACROSS THE LAKE LEADING TO EAST TO NORTHEAST
WINDS NORTH AND SOUTH TO SOUTHWEST WINDS SOUTH BY MID WEEK. THE MAIN
CONCERN WILL BE THE POTENTIAL FOR INCREASED GUSTINESS ACROSS THE
NORTH AS COLDER AIR SETTLES IN ALLOWING SLIGHTLY INCREASED MIXING.
OTHERWISE...GENERALLY STABLE LOW LEVEL AIR ACROSS THE LAKE WILL KEEP
GUSTS TO A MINIMUM FROM TONIGHT THROUGH THE WEEKEND.

MDB

&&

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

$$

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