Area Forecast Discussion
Issued by NWS Chicago, IL

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000
FXUS63 KLOT 222205
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
505 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...
307 PM CDT

SUNDAY THROUGH FRIDAY...

SUNDAY THROUGH MONDAY...PRIMARY CONCERN IS WITH PRECIP/THUNDER
CHANCES. MAIN FEATURE OF NOTE TO WATCH IS DEEP MID/UPPER TROUGH
DIGGING INTO SOUTHWEST. THIS WILL FORCE STRONG DOWNSTREAM HEIGHT
RISES OVER THE MIDWEST AS THE TROUGH SETTLES INTO THE
INTERMOUNTAIN WEST OVER THE WEEKEND BEFORE LIFTING GRADUALLY
NORTHWARD...WITH SFC CYCLOGENESIS IN THE CENTRAL PLAINS.
CONVECTIVELY ENHANCED DISTURBANCE/S FORMING OVER THE PLAINS WILL
LIFT NORTHEAST...BUT PLACEMENT OF 582 DM 500 MB HEIGHTS OVER
NORTHERN IL ON MUCH OF GUIDANCE SUGGESTS BEST FORCING WITH THE
UPPER WAVES AND LOW LEVEL JET CONVERGENCE WILL BE NORTH AND
NORTHWEST OF CWA ON SUNDAY. OPERATIONAL ECMWF MODEL HAS STARTED TO
TREND IN THIS DIRECTION AS WELL. THINKING IS THAT THIS TREND WILL
CONTINUE AND SUNDAY COULD END UP BEING A WARM AND BREEZY DAY WITH
PERHAPS SOME SCATTERED SHOWERS/ISOL`D TSRA MAINLY IN FAR
NORTH/NORTHWEST CWA AND GEARED POPS IN THIS DIRECTION. THERE DOES
LOOK TO BE A FAIR AMOUNT OF MID CLOUD COVER WHICH WILL LIMIT
WARMING SOME...BUT MID 70S NORTH TO AROUND 80 FARTHER SOUTH SHOULD
STILL BE ATTAINABLE FOR HIGHS. STRENGTHENING SOUTH- SOUTHEAST FLOW
SHOULD PREVENT MUCH OF A LAKE BREEZE EXCEPT ALONG LAKE COUNTY
SHORE...WHERE HIGHS SHOULD BE LIMITED TO THE 60S.

THE RIDGE AXIS WILL GRADUALLY GET SHUNTED EAST ON SUNDAY
NIGHT...SO EXPECTING INCREASING SHRA COVERAGE WITH CHANCE TSRA AS
STRONG LOW LEVEL JET STARTS TO INCREASE ELEVATED INSTABILITY. VERY
MILD NIGHT IS LIKELY WITH STEADY AND OCCASIONALLY GUSTY SOUTH
WINDS KEEPING LOWS IN MID-UPPER 60S. LOW PRESSURE WILL TRACK NORTH
OF THE AREA ON MEMORIAL DAY...KEEPING US IN GUSTY SOUTH WINDS IN
THE WARM SECTOR...WITH GUSTS UP TO 30 MPH OR POSSIBLY HIGHER. WE
WILL REMAIN IN FAVORED AREA FOR ADDITIONAL SHORT WAVE DISTURBANCES
TO RIDE INTO AREA IN SOUTHWEST FLOW ALOFT...SO PAIRED WITH STEEPER
LAPSE RATES/BETTER INSTABILITY...HAVE GONE WITH LIKELY POPS AREA
WIDE FOR SHRA/TSRA. STILL WOULD NOT EXPECT THE WHOLE DAY TO BE A
WASHOUT AND IT WILL BE WARM AND HUMID WITH 850/925 MB TEMPS
SUPPORTIVE OF HIGHS IN THE UPPER 70S-LOWER 80S ALONG WITH
DEWPOINTS WELL INTO THE 60S.

MONDAY NIGHT THROUGH FRIDAY...THEME OF THIS PERIOD WILL BE
CONTINUED WARM AND UNSETTLED. COLD FRONT TRAILING FROM LOW
PRESSURE WILL WASH OUT OVER THE AREA BY TUESDAY...THEN PERIODIC
SHOWER/TSRA CHANCES CONTINUE AS WE REMAIN POSITIONED UNDER
DISTURBED WEST-SOUTHWEST MID/UPPER FLOW. 850 MB TEMPS IN MID-UPPER
TEENS CELSIUS AND 925 MB TEMPS IN LOWER 20S CELSIUS BY LATE IN THE
WEEK COULD SPELL AT LEAST LOW-MID 80S FOR HIGHS ON FRIDAY. A DAY
OR TWO COULD HAVE ONSHORE FLOW INTO AT LEAST A PORTION OF THE
LAKEFRONT.

RC

&&

.AVIATION...

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

* EASTERLY WINDS AT/AROUND 10 KT THROUGH SUNDOWN.

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

MTF

//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 22Z...

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

* HIGH WITH ALL OTHER ELEMENTS.

MTF

//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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