Area Forecast Discussion
Issued by NWS Chicago, IL

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000
FXUS63 KLOT 271944
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
244 PM CDT FRI MAR 27 2015

.SHORT TERM...
242 PM CDT

THROUGH SATURDAY...

LAKE EFFECT SNOW IS FINALLY BEGINNING TO SHOW SIGNS OF WEAKENING ON
BOTH RADAR AND VISIBLE SATELLITE.  HAVE A DECREASING TREND THROUGH
THIS AFTN OVER NW INDIANA WITH UP TO A HALF INCH OF ADDITIONAL SNOW
EXPECTED. LOCALLY HIGHER AMOUNTS ARE POSSIBLE. EASTERN LAKE AND
PORTER COUNTIES WILL SEE THE MAJORITY OF THE SNOW.

HIGH PRESSURE CURRENTLY OVER THE SOUTHERN PLAINS AND UPPER MIDWEST
WILL SLIDE OVER THE REGION THIS EVENING. LAKE EFFECT CLOUDS WILL
SCATTER AND WINDS WILL LIGHTEN LEADING TO A QUIET AND CHILLY NIGHT.
WENT A BIT COLDER THAN THE PREVIOUS FORECAST GIVEN THE LOW DEWPOINTS
AND CALM CONDITIONS.  HAVE LOWS AROUND 20 DOWNTOWN AND THEN IN THE
TEENS IN THE OUTLYING AREAS.

THE HIGH HANGS AROUND TOMORROW AND BEGINS TO SLIDE SOUTHEAST IN THE
AFTERNOON. EXPECTING A HIGH AND DRY DAY WITH AMPLE SUNSHINE.  LIGHT
WINDS WILL BE OFF OF THE LAKE AND A LAKE BREEZE IS EXPECTED IN THE
AFTERNOON. SADLY TEMPERATURES WILL STILL BE WELL BELOW NORMAL WITH
HIGHS IN THE LOW TO MID 30S ALONG THE LAKE...AND IN THE UPPER 30S IN
THE OUTLYING AREAS.

JEE

&&

.LONG TERM...

SATURDAY THROUGH SUNDAY...

MAIN CONCERNS ARE WITH UNSEASONABLY CHILLY TEMPERATURES ON
SATURDAY...FOLLOWED BY LIGHT RAIN AND WINDY CONDITIONS ON SUNDAY.
A STRONG UPPER DISTURBANCE PUSHING INTO THE PAC NW WILL SHUNT THE
IMPRESSIVE WESTERN MID/UPPER RIDGE EAST...BRINGING HEIGHT
RISES...THOUGH COLD AIR MASS WILL BE SLOWER TO DEPART AND HIGH
PRESSURE OVER THE AREA WILL LIMIT MIXING. 850 MB TEMPS REMAINING
BELOW -10 CELSIUS UNTIL THE MID-LATE AFTERNOON SHOULD RESULT IN
HIGHS IN THE MID-UPPER 30S...WITH A FEW SPOTS REACHING 40. ONSHORE
FLOW SHOULD NOT RESULT IN MUCH OF A DIFFERENCE BETWEEN SHORE AND
INLAND TEMPS...AS LATEST LAKE SFC TEMP OBS ARE GENERALLY IN MID-
UPPER 30S OVER THE OPEN WATERS. THE SFC HIGH WILL BE OVERHEAD
SATURDAY NIGHT...ALLOWING TEMPERATURES TO DIP INTO THE 20S
OVERNIGHT. THE HIGH WILL QUICKLY SLIDE SOUTHEAST BY SUNDAY
MORNING...SO SOUTHERLY SURFACE FLOW AND WARM ADVECTION DUE TO
RAPID HEIGHT RISES SHOULD RESULT IN TEMPS RISING TOWARD DAYBREAK.

GUIDANCE IS IN GOOD OVERALL AGREEMENT ON A STRONG SURFACE LOW
MOVING THROUGH NORTHERN ONTARIO ON SUNDAY...WITH TRAILING COLD
FRONT APPROACHING AREA FROM THE WEST. IN ADDITION...A FAIRLY STOUT
BUT SHEARED MID LEVEL VORT MAX WILL DROP IN FROM THE NORTHWEST.
STRONG ISENTROPIC ASCENT/WAA AND AFOREMENTIONED SHORTWAVE WILL
RESULT IN PRECIP BLOSSOMING AHEAD OF COLD FRONT...LIKELY IN THE
FORM OF LIGHT RAIN BY THE TIME IT STARTS PER FORECAST SOUNDINGS.
THERE ARE SOME TIMING DIFFERENCES ON PROGRESSION OF COLD FRONT
THROUGH THE AREA...WITH ECMWF ON SLOWER SLIDE...BUT MOST PRECIP
SHOULD BE OVER BY THE EVENING. HAVE BUMPED UP TO HIGH END LIKELY
POPS...WITH LINGERING LOW CHANCES IN THE EVENING. OTHER CONCERN
ON SUNDAY IS WITH WINDY CONDITIONS DUE TO STRONG ISALLOBARIC
PRESSURE FALLS WITH DEPARTURE OF SFC HIGH AND APPROACH OF COLD
FRONTAL TROUGH. EVEN WITH CLOUD COVER...SOUTH-SOUTHWEST WINDS
COULD GUST TO 35 TO EVEN 40 MPH AT TIMES UNTIL FROPA. EXPECTING
HIGHS TO REACH THE MID TO UPPER 40S...BUT STRONG WINDS AND LIGHT
RAIN WILL MAKE FOR A RAW DAY.

SUNDAY NIGHT THROUGH THURSDAY...

MUCH MILDER CONDITIONS ARE IN STORE AS WE TRANSITION INTO MORE OF
A ZONAL FLOW PATTERN WITH THE PRIMARY STORM TRACK ALONG THE
NORTHERN TIER AND SOUTHERN CANADA. HAVE MAINLY LOW/SLIGHT CHC
POPS WITH A POSSIBLE SYSTEM NEARBY ON MONDAY NIGHT. MOST
GUIDANCE/ENSEMBLES ARE NOT TOO EXCITED ABOUT THIS SYSTEM WITH
EXCEPTION OF 00Z CANADIAN...WHICH SEEMS TO BE AN OUTLIER AT THIS
TIME. NEXT SYSTEM/FRONT LOOKS TO BE LATER WEDNESDAY INTO WEDNESDAY
NIGHT. IF DEWPOINTS CAN SURGE INTO 50S AS SHOWN ON OPERATIONAL
GFS...MAY NEED TO ADD THUNDER TO FORECAST...BUT FOR NOW HAVE JUST
RAIN SHOWER CHANCES IN THIS TIME PERIOD. TEMPERATURES WILL WARM
FROM THE 50S ON MONDAY TO PRIMARILY 60S ON TUESDAY THROUGH
THURSDAY...THOUGH ONSHORE FLOW IS LIKELY LATER TUESDAY AND THEN
ONTO IL SHORE ON WEDNESDAY...KEEPING SHORE TEMPS COOLER.

RC

&&

.AVIATION...

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

* NORTH-NORTHEAST WINDS GUSTING NEAR 20 KT GRADUALLY DIMINISHING
  LATE THIS AFTERNOON/EARLY EVENING.

RATZER

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

LAKE EFFECT SNOW SHOWERS HAVE MOVED EAST OF THE TERMINALS THIS
MIDDAY...THOUGH BROKEN MAINLY VFR CIGS STILL POSSIBLE AT ORD/MDW
AND GYY THROUGH THIS AFTERNOON. WINDS FROM THE NORTH-NORTHEAST
WILL BE GUSTY TO AROUND 20 KT EXCEPT AT GARY...WHERE FETCH RIGHT
OFF OF THE LAKE WILL ALLOW GUSTS CLOSER TO 25-30 KT EARLY.

HIGH PRESSURE BUILDING IN FROM THE NORTHWEST WILL ALLOW WINDS TO
DECREASE AND BECOME NORTHEAST TONIGHT...WITH A FEW/SCT VFR CLOUDS
STILL MOVING INLAND OFF THE LAKE. LIGHT MAINLY NORTHEAST WINDS
WILL LIKELY BECOME MORE EASTERLY AT ORD/MDW SATURDAY AFTERNOON
WITH LAKE BREEZE INFLUENCE IN LIGHT GRADIENT.

RATZER

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

* MEDIUM-HIGH IN WIND TRENDS.
* HIGH ALL OTHER ELEMENTS.

RATZER

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

SATURDAY NIGHT...VFR. SOUTHEAST WINDS.
SUNDAY...MVFR WITH RAIN. IFR POSSIBLE. SOUTHWEST WINDS.
MONDAY...SLIGHT CHANCE OF RAIN. WEST WINDS.
TUESDAY...VFR. NORTH WINDS.
WEDNESDAY...CHANCE OF RAIN SHOWERS. SOUTHEAST WINDS.
THURSDAY...SLIGHT CHANCE OF RAIN. WEST WINDS.

MTF

&&

.MARINE...
242 PM CDT

WINDS ARE COMING DOWN AS HIGH PRESSURE SLIDES EAST TOWARD THE
WESTERN LAKES.  HOWEVER WAVES WILL REMAIN HAZARDOUS TO SMALL CRAFT
INTO SATURDAY MORNING.  THE HIGH SHIFTS SOUTHEAST OVER THE OHIO
VALLEY SATURDAY EVENING WITH WINDS BECOMING SOUTHWEST TO 30 KT
OVERNIGHT.  THE NEXT LOW PASSES OVER ONTARIO SUNDAY AND WINDS
INCREASE TO GALES ACROSS THE LAKE.  MAX GUSTS OF 45 KT WILL BE OVER
THE NORTHERN END OF THE LAKE...AND WILL ISSUE A GALE WATCH FOR ALL
OF THE OPEN WATERS. GALES ARE POSSIBLE OVER THE NEARSHORE WATERS AS
WELL BUT WILL HOLD OFF ON ISSUING A WATCH AS CONFIDENCE IN NOT HIGH
ENOUGH FOR A WATCH AT THIS POINT.  THE LOWS COLD FRONT SWINGS OVER
THE LAKE SUNDAY EVENING WITH WINDS DIMINISHING AND BECOMING WEST TO
30 KT.  A WEAK RIDGE PASSES OVER THE LAKE MONDAY WITH A SURFACE LOW
MOVING OVER THE LAKE TUESDAY MORNING.  ANOTHER HIGH PRESSURE SYSTEM
REACHES THE WESTERN LAKES MID WEEK THEN A STRONG LOW SLIDES NORTH OF
THE LAKE THURSDAY.

JEE

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WATERS
     UNTIL 10 AM SATURDAY.

&&

$$

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