Area Forecast Discussion
Issued by NWS Chicago, IL

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FXUS63 KLOT 031928
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE, IL
228 PM CDT TUE MAY 3 2016

.SHORT TERM...
228 PM CDT

THROUGH WEDNESDAY...

BIG CHANGES ARE IN STORE IN THE SHORT TERM. HIGH PRESSURE IS SLOWLY
SHIFTING SOUTH AS LOW PRESSURE AND A COLD FRONT DROP SOUTH OUT OF
ONTARIO.  EXPECTING A PLEASANT AFTERNOON AND EVENING WITH WEST WINDS
AND FAIR WEATHER CUMULUS CLOUDS.  SHOWERS HAVE ALREADY FORMED AHEAD
OF THE COLD FRONT OVER THE U.P. OF MICHIGAN. REALLY LIKING THE RAP/S
TIMING SO LEANED HEAVILY IN ITS DIRECTION...WITH THE NAM BEING A
SLOWER SOLUTION.  HAVE SLIGHT CHANCE TO CHANCE POPS OUT AHEAD OF THE
MAIN FRONTAL PRECIP JUST IN CASE A FEW STRAY SHOWERS FORM THIS
EVEING. KEPT THE PREVIOUS FORECASTS IDEA OF NUMEROUS SHOWERS WITH A
FEW EMBEDDED THUNDERSTORMS. SEVERE STORMS ARE NOT EXPECTED AS CAPE
VALUES WILL BE MINIMAL AT BEST.

THE BIGGER STORY WILL BE WINDS SHIFTING OUT OF THE NORTH AND GUSTING
TO 30 MPH BEHIND THE FRONT. WINDS WILL BE EVEN GUSTIER ALONG THE
SOUTHERN END OF LAKE MICHIGAN ESPECIALLY ALONG THE INDIANA SHORE.
MUCH COOLER TEMPERATURES FOLLOW THE FRONT WITH HIGHS IN THE LOW TO
MID 50S AWAY FROM THE LAKE.  HIGHS ALONG THE LAKE WILL BE IN THE
UPPER 40S TO MAYBE 50.  THE BACK END OF THE UPPER LEVEL LOW ROTATES
THROUGH TOMORROW AND EXPECTING SCATTERED SHOWERS TO FORM.  FORECAST
SOUNDINGS SHOW VERY SHALLOW CAPE...BUT ANY CONVECTION WOULD BE VERY
LOW TOPPED.  FREEZING LEVELS ARE ALSO LOW AROUND 3000 FT SO THINKING
THE LOW CAPE AND STEEP LAPSE RATES WILL LEAD TO GRAUPEL INSTEAD OF
THUNDER.  NOT EXPECTING A TON OF RAIN...MORE ALONG THE LINES OF
DREARY CONDITIONS WITH OCNL LIGHT RAIN AND POSSIBLY GRAUPEL.

JEE

&&

.LONG TERM...
322 AM CDT

THURSDAY THROUGH MONDAY...

THE EXTENDED PORTION OF THE FORECAST FEATURES A LATE-WEEK WARM-UP
FRIDAY INTO THE WEEKEND...THOUGH ANOTHER COLD FRONT WILL SAG
ACROSS THE AREA SATURDAY. THIS WILL TEMPER THE WARM-UP ALONG LAKE
MICHIGAN AND ACROSS FAR NORTHERN IL SUNDAY AND MONDAY AS WINDS
TURN OFF THE LAKE...AND WILL ALSO PRESENT THE POTENTIAL FOR
PERIODIC SHOWERS AND THUNDERSTORMS.

SURFACE HIGH PRESSURE RIDGING WILL SPREAD EAST INTO THE MIDWEST
ON THURSDAY AS THE UPPER TROUGH OVER THE EASTERN CONUS DRIFTS AWAY
TO THE EAST. NORTHERLY FLOW WILL INITIALLY MAINTAIN COOL
TEMPERATURES ESPECIALLY NEAR AND DOWNWIND OF LAKE MICHIGAN INTO
NORTHWEST INDIANA. SUNSHINE WILL RETURN HOWEVER...AS DRY/SINKING
AIR HELPS TO CLEAR OUT ANY LINGERING CLOUDS. AFTERNOON TEMPS
THURSDAY SHOULD CLIMB TO THE LOW-MID 60S ACROSS NORTHERN IL AWAY
FROM THE LAKE...WHILE HOLDING IN THE 50S ACROSS NORTHWEST INDIANA.
BETTER THINGS ARE IN STORE HOWEVER AS THE UPPER RIDGE OVER THE
CENTRAL CONUS BUILDS EAST THURSDAY NIGHT INTO FRIDAY...ALLOWING
TEMPERATURES TO SURGE WELL INTO THE 70S AND POSSIBLY TO THE 80
DEGREE MARK IN A FEW SPOTS ON FRIDAY. MODEST WEST TO SOUTHWEST
WINDS WILL LIKELY ALLOW A WEAK LAKE BREEZE TO DEVELOP BY
AFTERNOON...COOLING IMMEDIATE SHORE AREAS A BIT.

GUIDANCE HAS TRENDED FASTER WITH A SHORT WAVE TROUGH WHICH TOPS
THE RIDGE FRIDAY NIGHT INTO SATURDAY...INDUCING A SURFACE LOW
WHICH MOVES ACROSS THE NORTHERN LAKES AND TRAILS A COLD FRONT INTO
THE CWA DURING THE DAT SATURDAY. THUS WHILE TEMPS WILL ONCE AGAIN
REACH THE MID-UPPER 70S ACROSS WESTERN AND SOUTHERN PARTS OF THE
CWA SATURDAY...IT APPEARS THAT THE COLD FRONT WILL SHIFT WINDS
ONSHORE NEAR THE LAKE. WITH THIS SCENARIO IN MIND HAVE LIMITED
TEMPS TO THE MID-UPPER 60S ALONG THE IL SHORE AND MAY SEE FALLING
TEMPS NEAR THE LAKE SATURDAY AFTERNOON. INCREASED CLOUD COVER AND
SCATTERED SHOWERS AND THUNDERSTORMS WILL ALSO LIKELY ACCOMPANY THE
FRONT WHICH PUSHES INTO DOWNSTATE IL/IN SATURDAY NIGHT BEFORE
BECOMING STATIONARY. WEAK HIGH PRESSURE SPREADS ACROSS THE GREAT
LAKES NORTH OF THE FRONT AND PRODUCES COOLER ONSHORE WINDS SUNDAY
AND MONDAY...WITH THE ELEVATED BAROCLINIC ZONE NORTH OF THE
SURFACE FRONT CONTINUING TO BE A FOCUS FOR INCREASED CLOUD COVER
AND POTENTIAL SHOWERS/THUNDERSTORMS. BOTH DAYS WILL FEATURE A
CONTRAST IN TEMPERATURES FROM NEAR 60 UP NEAR WAUKEGAN TO THE LOW-
MID 70S ACROSS THE FAR SOUTHERN PARTS OF THE CWA. SUNDAY COULD BE
RELATIVELY DRY WITH THE FRONT WELL TO THE SOUTH... WITH POPS
INCREASING MONDAY AS THE FRONT BEGINS TO LIFT BACK NORTH AS A WARM
FRONT.

RATZER

&&

.AVIATION...
FOR THE 18Z TAFS...

THE REMAINDER OF THIS AFTERNOON SHOULD BE QUIET WITH HIGH PRESSURE
SLOWLY DRIFTING SOUTH. VFR CU AND NORTHWEST TO WEST WINDS ARE
EXPECTED. THE LOW OVER ONTARIO AND ITS ASSOCIATED COLD FRONT WILL
SHIFT SOUTH THIS EVENING AND OVERNIGHT. SHOWERS AND A FEW EMBEDDED
THUNDERSTORMS WILL MOVE THROUGH AHEAD OF THE FRONT. HAVE MUCH
HIGHER CONFIDENCE IN SHOWERS THAN THUNDER. THUNDER WILL BE AROUND
BUT DO NOT HAVE  ENOUGH CONFIDENCE IN LOCATION...COVERAGE...AND
EXACT TIMING TO INCLUDE THUNDER IN THE TAF. CIGS WILL FALL TO IFR
BEHIND THE FRONT. HAVE A LITTLE LOWER CONFIDENCE IN IFR AT RFD.
ALSO RAISED NORTH WIND SPEEDS WITH GUSTS TO 25 KT EXCEPT FOR
GUSTS TO 30 KT AT GYY. CIGS IMPROVE TO MVFR BY MID MORNING...BUT
ALSO EXPECTING SCATTERED SHOWERS AS THE BACK END OF THE UPPER
LEVEL SYSTEM ROTATES THROUGH. NOT EXPECTING RAIN ALL DAY
TOMORROW...BUT THE SHOWERS SHOULD BE SCATTERED ENOUGH TO JUSTIFY A
VCSH.

JEE

&&

.MARINE...
221 AM CDT

HIGH PRESSURE IS OVER THE REGION EARLY THIS MORNING PROVIDING
LIGHT FLOW ACROSS LAKE MICHIGAN...HOWEVER A COLD FRONT IS EXPECTED
TO MOVE SOUTH ACROSS LAKE MICHIGAN LATE THIS EVENING AND OVERNIGHT
BRINGING NEAR GALE FORCE NORTHERLY WINDS. SOUTHWEST FLOW WILL
INCREASE THROUGH THE DAY TODAY AHEAD OF THE FRONT. SHOWERS AND A
FEW THUNDERSTORMS ARE ALSO EXPECTED TO OCCUR IMMEDIATELY ALONG AND
AHEAD OF THE FRONT...THEN WINDS WILL TURN NORTHERLY AND INCREASE
WITH GUSTS TO AROUND 30 KT EXPECTED BEHIND THE FRONT. WINDS WILL
REMAIN STRONG THROUGH THE DAY WEDNESDAY...THEN GRADUALLY COME DOWN
THROUGH THE DAY THURSDAY. A SMALL CRAFT ADVISORY WILL LIKELY BE
NEEDED FOR THE ILLINOIS AND INDIANA NEARSHORE WATERS THROUGH THIS
TIMEFRAME. WINDS DIMINISH ENOUGH FOR LAKE BREEZES BY LATE THURSDAY
AFTERNOON AS HIGH PRESSURE ONCE AGAIN MOVES OVERHEAD...THEN
SOUTHWESTERLY FLOW RETURNS THURSDAY NIGHT AS THE RIDGE AXIS SAGS
SOUTHEAST OF THE LAKE. ANOTHER COLD FRONT IS EXPECTED TO PUSH
ACROSS LAKE MICHIGAN OVER THE WEEKEND.

BMD

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WARNING...LMZ743-LMZ744-LMZ745-LMZ777-LMZ779...5 AM
     WEDNESDAY TO 4 AM THURSDAY.

     SMALL CRAFT ADVISORY...LMZ743-LMZ744-LMZ745...4 AM THURSDAY TO 3
     PM THURSDAY.

     SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742...5 AM WEDNESDAY TO
     10 AM THURSDAY.

&&

$$

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