Area Forecast Discussion
Issued by NWS Chicago, IL

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000
FXUS63 KLOT 221928
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
228 PM CDT FRI MAY 22 2015

.SHORT TERM...
210 PM CDT

THROUGH SATURDAY NIGHT...

SURFACE HIGH PRESSURE OVER LAKE MICHIGAN THIS AFTERNOON CONTINUES TO
RESULT IN AN EAST-NORTHEASTERLY WIND COMPONENT OFF OF LAKE MICHIGAN.
THIS SURFACE HIGH IS EXPECTED TO SHIFT EASTWARD TOWARDS THE MID
ATLANTIC COAST ON SATURDAY...AND THIS WILL ALLOW WINDS TO BECOME
SOUTHERLY...EXCEPT NEAR LAKE MICHIGAN...WHERE A SOUTHEASTERLY
COMPONENT COULD ALLOW A LAKE BREEZE TO DEVELOP ACROSS PORTIONS OF
FAR NORTHEASTERN ILLINOIS SATURDAY AFTERNOON. IT DOES APPEAR THAT
SOME MID AND HIGH CLOUD COVER COULD RESULT IN PARTLY CLOUDY TO
PARTLY SUNNY DAY ACROSS THE REGION. OTHERWISE...IT APPEARS TO BE
ANOTHER GOOD LOOKING DAY ACROSS THE AREA. TEMPERATURES AT 925 MB ARE
EXPECTED TO BE 16-17 DEGREES CELSIUS AND THIS SHOULD SUPPORT HIGHS A
COUPLE OF DEGREES WARMER THAN TODAYS (INTO THE MID TO UPPER 70S FOR
MOST AREAS AWAY FROM LAKE MICHIGAN). MILD CONDITIONS WILL CONTINUE
SATURDAY NIGHT...WITH OVERNIGHT LOWS ONLY EXPECTED TO FALL INTO THE
MID TO UPPER 50S.

KJB

&&

.LONG TERM...
202 AM CDT

SATURDAY THROUGH THURSDAY...

SATURDAY THROUGH MEMORIAL DAY...
WEAK SFC RIDGING CENTERED OVER THE EASTERN OHIO VALLEY/MID-ATLANTIC
REGION...WILL CONTINUE TO DRIFT EAST SATURDAY MORNING...WITH LLVL
FLOW TURNING SOUTHEASTERLY TO SOUTHERLY. RETURN FLOW MOISTURE FROM
THE WESTERN GULF WILL BE ALREADY STREAMING NORTH THROUGH THE OZARKS
INTO THE PLAINS SATURDAY. FORTUNATELY HEIGHTS BEGIN TO INCREASE
SLIGHTLY SAT...SO EXPECT MUCH OF THE DAY/AFTN TO REMAIN DRY WITH
STEADILY INCREASING CLOUD COVER FROM SOUTHWEST TO NORTHEAST.

GUIDANCE CONTINUES TO PUMP ADDTL LLVL MOISTURE INTO THE
PLAINS...WITH THE MOIST AXIS EVENTUALLY SHIFTING EAST TOWARDS THE
WESTERN OHIO VALLEY AND GREAT LAKES LATE SAT NGT BUT MORE SO SUN
AFTN. DEW POINTS WILL BE STEADILY RISING SUN...WITH SOUTHERLY
FLOW...THIS WILL SETUP A WARM/HUMID DAY. THERMAL RIDGE OF 10-12 DEG
C WILL BE ADVECTING NORTH ACROSS THE REGION...HOWEVER EXPECT
ABUNDANT SOLAR SHIELDING TO DAMPEN HOW MUCH THE SFC CAN REALIZE THE
WARMTH ALOFT. AT THIS TIME WILL NUDGE TEMPS UP A FEW DEGREES BOTH
SAT AND SUN...WITH TEMPS NEARING THE MID/UPR 70S SUN AND POSSIBLY
ARND 80 IN THE FAR SOUTHERN CWFA. HOWEVER AS ELUDED TO EARLIER...THE
MOISTURE PLUME WILL BE STEADILY INCREASING SUN WITH PWAT VALUES
NEARING 30-40MM OR AROUND 1.5 INCHES. THIS WILL ALSO MAKE IT MORE
DIFFICULT TO WARM THE SFC...BY MOISTENING THE PARCELS.

SUN NGT THE LLVL JET IS PROGGED TO INCREASE FROM THE
SOUTHWEST...WITH GUIDANCE PROGGING A WEAK LOBE OF MID-LVL VORTICITY
LIFTING NORTH ACROSS THE OZARKS. HAVE NUDGED POPS UP TO LIKELY SUN
NGT...WHICH SEEMS TO LINE-UP WELL GIVEN THE ENVIRONMENTAL SETUP.
CURRENT THINKING IS THAT COVERAGE OF CONVECTION COULD BE LIMITED
GIVEN THE MAIN FOCUS WILL BE WELL WEST/NORTHWEST OF THE REGION. SO
ANY THUNDERSTORMS WOULD LIKELY BE EMBEDDED OR SCATTERED AT BEST.

TEMPS SUN NGT WILL REMAIN VERY MILD...IN THE MID/UPR 60S. BUT COULD
SEE A FEW LOCATIONS NOT DIP BELOW 70 ALONG THE KANKAKEE VALLEY.

UNFORTUNATELY CHANCES FOR SHOWERS AND POSSIBLY A THUNDERSTORM
CONTINUES INTO MEMORIAL DAY...HOWEVER AS HAS BEEN THE CASE WITH
OTHER SYSTEMS...THE PATTERN IS SIMILAR AND COULD PRODUCE LIMITED
COVERAGE OF SHOWERS DURING THE DAY. GUIDANCE IS HINTING THAT A DRY
SLOT MAY DEVELOP ACROSS THE SOUTHERN PLAINS AND QUICKLY LIFT
NORTHEAST TOWARDS NORTHERN IL LATE MON AFTN/EARLY EVE. IF THIS CAN
MESH TOGETHER...DRY CONDS MAY END UP DEVELOPING FOR THE SECOND HALF
OF MEMORIAL DAY. WARM MOIST CONDS CONTINUE INTO MON WITH TEMPS
GENERALLY IN THE MID/UPR 70S...BUT WITH DEW POINTS IN THE MID
60S.

TUESDAY THROUGH THURSDAY... HIGH AMPLITUDE RIDGING REMAINS ACROSS
WESTERN CANADA/ALASKA...WITH THE DOWNSTREAM TROUGH SLOWLY MODERATING
AND BLENDING INTO THE DAMPENING RIDGE OVER THE ATLANTIC. THEN BY
TUE/WED THE DOWNSTREAM RIDGE WILL CONSOLIDATING INTO A SLIGHTLY
STRONGER RIDGE ACROSS THE SOUTHEASTERN CONUS. THIS PATTERN WILL
LIKELY TRANSLATE INTO A SOUTH/SOUTHWEST FLOW ACROSS THE CENTRAL
CONUS TOWARDS THE MIDDLE OF NEXT WEEK...WITH TEMPS GENERALLY IN THE
UPR 70S TO LOW 80S WITH PERIODIC CHANCES FOR AFTN
SHOWERS/THUNDERSTORMS.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 18Z...

* EASTERLY WINDS THROUGH THE DAY UP AROUND 10 KT AT TIMES THIS
  AFTERNOON WITH LAKE BREEZE PUSH.

* POSSIBILITY OF A LAKE BREEZE ON SATURDAY AFTERNOON...WITH A
  SOUTHEASTERLY WIND SHIFT.

KJB

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

HIGH PRESSURE WILL CONTINUE TO SHIFT DOWN LAKE MICHIGAN THROUGH
THE AFTERNOON...AND THIS WILL RESULT IN AN EASTERLY FLOW AT THE
TERMINALS. WIND SPEEDS WILL LIKELY REMAIN IN THE 6 TO 10 KT RANGE
INTO THE EARLY AFTERNOON. HOWEVER...A STRONGER PUSH OF WIND OFF
THE LAKE THIS AFTERNOON WITH A LAKE BREEZE...COULD PUT SPEEDS UP
IN THE 10 TO 12 KT RANGE FOR A PERIOD AT THE EASTERN TERMINALS.
OTHERWISE...VFR CONDITIONS ARE EXPECTED THROUGH THE PERIOD.

WINDS WILL TURN SOUTH-SOUTHEASTERLY TONIGHT INTO EARLY SATURDAY
MORNING AS THE SURFACE HIGH SHIFTS OVER THE EASTERN STATES. IT
APPEARS THAT ANOTHER LAKE BREEZE COULD DEVELOP AND POSSIBLY RESULT
IN AN EAST-SOUTHEASTERLY WIND SHIFT AT THE EASTERN TERMINALS LATE
IN THE DAY...THOUGH SPEEDS MAY STRUGGLE TO REACH 10 KT.

KJB

//ORD AND MDW CONFIDENCE...UPDATED 18Z...

* LOW ON LAKE BREEZE SIGNIFICANTLY IMPACTING THE EASTERN TERMINALS
  ON SATURDAY AFTERNOON.

* HIGH WITH ALL OTHER ELEMENTS.

KJB

//OUTLOOK FOR ORD/MDW FOR 00Z SUNDAY-12Z FRIDAY...UPDATED 12Z...

* SATURDAY NIGHT...DRY/VFR. SOUTH WINDS.
* SUNDAY...SHRA LIKELY/CHANCE OF TSRA. MVFR POSSIBLE. SOUTH-
  SOUTHEAST WINDS.
* MONDAY AND TUESDAY...CHANCE OF SHRA/TSRA. GUSTY SOUTHWEST
  WINDS.
* WEDNESDAY AND THURSDAY...CHANCE OF SHRA/TSRA. SOUTHWEST WINDS.

&&

.MARINE...
228 PM CDT

SURFACE HIGH PRESSURE CENTERED OVER LAKE MICHIGAN IS RESULTING IN AN
ONSHORE WIND COMPONENT AROUND THE LAKE DUE TO LAKE BREEZE
INFLUENCES. THIS HIGH WILL SHIFT TOWARDS THE MID ATLANTIC COAST ON
SATURDAY AS LOW PRESSURE TAKES SHAPE ACROSS THE HIGH PLAINS. THIS LOW
IS FORECAST TO SOMEWHERE OVER THE UPPER MIDWEST BY LATE MONDAY OR
TUESDAY. OVERALL...THIS WILL SET UP INCREASING CHANCES OF SHOWERS
AND THUNDERSTORMS OVER THE LAKE LATE SUNDAY AND INTO EARLY NEXT
WEEK. IN ADDITION...SOUTHERLY WINDS WILL LIKELY BE ON THE INCREASE
OVER THE LAKE SUNDAY NIGHT AND MONDAY AND COULD REACH UP INTO THE 25
TO PERHAPS AS HIGH AS 30 KT. THIS WILL LIKELY RESULT IN SMALL CRAFT
ADVISORY CONDITIONS FOR THE ILLINOIS AND INDIANA NEAR SHORES ON
MONDAY.

FOG MAY ALSO BECOME AN INCREASING CONCERN LATE SUNDAY INTO
MONDAY...ESPECIALLY ACROSS THE NORTHERN HALF TO TWO THIRDS OF THE
LAKE. HIGH DEW POINT AIR IS EXPECTED TO BE TRANSPORTED OVER THE COLD
LAKE SURFACE WATERS...AND WITH THE BUOYS REPORTING MID TO UPPER 30
DEGREE WATER TEMPERATURES IN THE OPEN WATERS OF THE LAKE...THIS
COULD SUPPORT THE DEVELOPMENT OF AREAS OF DENSE MARINE FOG FOR A
PERIOD INTO EARLY NEXT WEEK.

KJB

&&

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

$$

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