Area Forecast Discussion
Issued by NWS Chicago, IL

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000
FXUS63 KLOT 280302
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1002 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...
254 PM CDT

SATURDAY NIGHT THROUGH FRIDAY...

STRONG SUBSIDENCE WILL BE IN PLACE SATURDAY NIGHT BEHIND DEPARTING
MID LEVEL TROUGH...HOWEVER ATTENTION TURNS BACK TO THE NORTHERN
PLAINS AND CANADIAN PRAIRIES WHERE A PAIR OF SHORTWAVES ARE PROGGED
TO MOVE ACROSS THE REGION. MAIN SURFACE LOW IS PROGGED TO MOVE
ACROSS NORTHERN ONTARIO THROUGH THE DAY SUNDAY WITH MODERATELY
STRONG SOUTHWEST FLOW DEVELOPING ACROSS PORTIONS OF THE MIDWEST
AHEAD OF AN APPROACHING COLD FRONT. A 50-60KT LOW LEVEL JET WILL
BE IN PLACE EARLY SUNDAY JUST A FEW THOUSAND FEET OFF THE SURFACE.
BUFKIT MOMENTUM TRANSFER ALGORITHM FROM BOTH THE NAM AND GFS SHOW
THE POTENTIAL TO MIX DOWN GUSTS IN THE 30 TO 40 MPH RANGE AHEAD OF
THE FRONT...WITH WINDS TAPERING MID AFTERNOON INTO THE EVENING AS
THE FRONT SWEEPS ACROSS THE REGION. THERMAL PROFILES SHOW DRY AIR
WITHIN THE DGZ BUT WITH TEMPERATURES HOVERING AROUND 0C ABOVE THE
BOUNDARY LAYER....WITH AT LEAST A PERIOD WHERE A WARM NOSE PUSHES
2C. THINK PRECIP TYPE WILL PRIMARILY BE RAIN BUT CANNOT RULE OUT A
FEW FLAKES MAINLY WITH THE ONSET OF PRECIP SUNDAY MORNING.

SUNDAY NIGHT THROUGH MONDAY NIGHT SHOULD GENERALLY BE QUIET AS HIGH
PRESSURE BUILDS ACROSS THE REGION. BY MIDDAY MONDAY WARM ADVECTION
SPREADS BACK OVERHEAD WHICH SHOULD BRING NEAR NORMAL TEMPERATURES
MONDAY...AND POSSIBLY A WARMER/ABOVE NORMAL STRETCH OF WEATHER
TUESDAY OR WEDNESDAY THROUGH THURSDAY WITH HIGHS AROUND 60 OR SO.
BEFORE THAT...THE ECMWF AND GFS BOTH BRING A QUICK HITTING CLIPPER
INTO THE REGION MONDAY NIGHT THOUGH THERE ARE CONSIDERABLE
DIFFERENCE IN THE TIMING AND TRACK. THE ECMWF IS FASTER AND
FARTHER SOUTH WITH THIS SYSTEM...AND MAY DELAY OUR WARMUP UNTIL
WEDNESDAY AS IT BRINGS A REINFORCING SHOT OF COLD AIR AND PRECIP.
TAKING THE MIDDLE GROUND FOR NOW WITH ONLY CHC/SLT CHC OF PRECIP.
INDIVIDUAL GEFS MEMBERS ALSO SHOW CONSIDERABLE SPREAD WITH SOME
MEMBERS SUPPORTING A TRACK CLOSER TO THE ECMWF AND THE OPERATIONAL
GFS ON THE NORTHERN EDGE OF THE SOLUTION ENVELOPE.

DESPITE THE UNCERTAINTY TUESDAY...THERE IS HIGHER CONFIDENCE IN
WARMER TEMPS BY WEDNESDAY. ECMWF AND GFS BOTH SHOW H85 TEMPS 10C+.
IF THIS PANS OUT...CURRENT FORECAST TEMPS MAY BE A BIT UNDERDONE.
ANOTHER COLD FRONT IS PROGGED THURSDAY WHICH WILL BRING SHOWERS AND
POSSIBLY THUNDERSTORMS.

BMD

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 03Z...

* LAKE BREEZE LIKELY SATURDAY AFTERNOON

IZZI

//DISCUSSION...UPDATED 00Z...

CLEAR/VFR CONDITIONS WILL PERSIST THROUGH THE TAF CYCLE. NORTHEAST
WINDS WILL EASE AND BECOME LIGHT THIS EVENING. LIGHT GRADIENT WILL
ALLOW HEALTHY LAKE BREEZE TO SURGE INLAND SATURDAY AFTERNOON
RESULTING IN A FRESHING UP OF THE NORTHEAST WINDS AT ORD/MDW WITH
SPEEDS AT OR ABOVE 10KT LIKELY FOR A AT LEAST A COUPLE/FEW HOURS
IN THE AFTERNOON.

IZZI

//ORD AND MDW CONFIDENCE...UPDATED 03Z...

* MEDIUM CONFIDENCE IN TIMING OF LAKE BREEZE SATURDAY AFTERNOON
  +/- AN HOUR
* HIGH CONFIDENCE IN REMAINING FORECAST ELEMENTS

IZZI

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

SUNDAY...MVFR CIGS DEVELOPING WITH A PERIOD OF RAIN.

MONDAY...PRIMARILY VFR DURING DAY. CHANCE OF SHRA AT NIGHT.

TUESDAY...CHANCE OF MVFR CIGS EARLY.

WEDNESDAY...VFR.

THURSDAY...CHANCE OF SHRA...OTHERWISE VFR.

IZZI

&&

.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.

     GALE WATCH...LMZ777-LMZ779...4 AM SUNDAY TO 7 PM SUNDAY.

&&

$$

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