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000
FXUS63 KLOT 112152
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
452 PM CDT TUE MAR 11 2014

.DISCUSSION...
355 PM CDT

HEADLINES...UPGRADED THE SOUTHEASTERN COUNTIES FROM A WINTER STORM
WATCH TO A WINTER STORM WARNING. OTHERWISE NO CHANGES WERE MADE TO
THE HEADLINES.

REST OF TODAY THROUGH WEDNESDAY AFTERNOON...
AN UPPER LEVEL TROUGH AXIS STRETCHES FROM HUDSON BAY THROUGH THE
NORTHERN ROCKIES...WITH ANOTHER WEAK SHORTWAVE IS MOVING INTO NORTH
DAKOTA AND NORTHERN MINNESOTA.  THE SURFACE LOW IS OVER SOUTHEASTERN
KANSAS AND IS BEGINNING TO DEEPEN.

A STATIONARY FRONT IS OVER THE FAR SOUTHERN SECTION OF THE CWA...AND
STRETCHING FROM NORTHERN MO THROUGH LOGANSPORT INDIANA.  TEMPS HAVE
BEEN RATHER IMPRESSIVE TODAY GIVEN THE CLOUD COVER.  EVERYWHERE
JUMPED TO AT LEAST 40 WITH AREAS SOUTH OF I-88 REACHING INTO THE
UPPER 40S TO AROUND 60 IN CENTRAL IL.  EVEN SEEING 40 DEGREE TEMPS
THROUGHOUT SOUTHERN WI DESPITE THE NORTHERLY WINDS.  AS WINDS BECOME
NORTH ACROSS THE CWA WILL SEE TEMPS START TO FALL THIS AFTERNOON.
MAY HAVE TOO QUICK OF A TREND IN THE GRIDS...BUT EXPECTING TEMPS TO
FALL PRETTY QUICKLY.

THE LOW WILL CONTINUE TO DEEPEN AS IT CROSSES OVER SOUTHERN IL AND
CONTINUES EAST INTO THE UPPER OHIO RIVER VALLEY TOMORROW AFTERNOON.
HIGH PRESSURE IS CENTERED OVER MANITOBA AND IT WILL MOVE OVER SW
ONTARIO BY TOMORROW MORNING.  AS SUCH THE PRESSURE GRADIENT WILL
TIGHTEN OVERNIGHT RESULTING IN STRONG WINDS. IN GENERAL WINDS WILL
BE 20-30 MPH WITH GUSTS UP TO 40 MPH. THE STRONGEST GUSTS...UP TO 45
MPH...WILL BE ALONG THE LAKESHORE.

RIGHT NOW THERE IS A BAND OF LIGHT RAIN OVER SOUTHERN WI AND A FEW
STRAY ECHOES OVER NW ILLINOIS.  EXPECTING THAT BAND TO SLOWLY SHIFT
SOUTH INTO NORTHERN IL LATE THIS AFTERNOON AND INITIALLY FALL AS
RAIN.  EXPECTING SNOW TO SPREAD ACROSS THE CENTRAL AND SOUTHWESTERN
PORTIONS OF THE CWA THIS EVENING AS THE LOW MOVES OVER SOUTHERN IL.
AT THE SAME TIME...THE MAIN TROUGH AXIS AND ASSOCIATED VORT STREAMER
WILL BE MOVING OVER THE MISSISSIPPI RIVER BRINGING IMPRESSIVE
FORCING TO THE REGION.  GUIDANCE INDICATES THERE WILL BE A BAND OF
FRONTOGENESIS ASSOCIATED WITH NEGATIVE EPV ROUGHLY ALONG THE I-55
CORRIDOR.  ADDITIONAL FORCING WILL BE PROVIDED BY THE UPPER LEVEL
JET. WE WILL BE UNDER THE LEFT EXIT REGION OF THE JET STREAK
ASSOCIATED WITH THE DEEPENING LOW...AND THEN AT THE NOSE OF THE JET
PUSHING IN FROM THE NORTH. ALL OF THIS FORCING IS OVER THE
DGZ...WHICH VARIES FROM 100MB TO 200MB DEEP. THEREFORE...KEPT THE
SAME IDEA AS THE PREVIOUS FORECAST WITH THE MAJORITY OF SNOW FALLING
OVERNIGHT TONIGHT.  RATES OF 1-2 INCHES PER HOUR ARE EXPECTED ALONG
AND EAST OF I-55.

LEFT THUNDERSNOW OUT OF THE FORECAST BECAUSE DO NOT HAVE ENOUGH
CONFIDENCE IN IT.  FORECAST SOUNDINGS FEATURE MINIMUM CAPE
VALUES...LESS THAN 50 J/KG. MAY SEE A RANDOM STRIKE OF LIGHTNING
ASSOCIATED WITH THE HEAVY SNOW...BUT NOT EXPECTING AN ABUNDANCE OF
THUNDERSNOW.

THEREFORE THE WINTER STORM WARNING IS FOR PERIODS OF HEAVY SNOW AND
NEAR BLIZZARD LIKE CONDITIONS WITH THE GUSTY WINDS.  VISIBILITIES AT
OR BELOW A QUARTER OF A MILE ARE POSSIBLE OVERNIGHT AND INTO THE
PRE-DAWN HOURS WEDNESDAY MORNING.  THE MORNING COMMUTE WILL PROBABLY
BE IMPACTED BY THE LINGERING SNOW AND GUSTY WINDS.  EVEN IF IT IS
NOT SNOWING THAT HARD DURING THE COMMUTE...THE GUSTY WINDS WILL
LIKELY BE BLOWING SNOW AROUND AND REDUCING VISIBILITY.

SNOW INTENSITY DWINDLES TOMORROW MORNING AS FORCING AND SATURATION
IN THE DGZ BOTH DIMINISH.  AS THE TROUGH MOVES THROUGH...THE SNOW
ENDS FROM WEST TO EAST.  MAY SEE SOME LIGHT SNOW PERSIST OVER
NORTHWEST INDIANA AFTER THE WARNING EXPIRES...BUT THINKING THE MAIN
SHOW WILL BE OVER.  SNOW TOTALS WILL VARY FROM 2 TO 4 INCHES ACROSS
THE IL/WI STATE LINE TO 4 TO 8 INCHES ALONG AND SOUTH OF I-88.  MAY
SEE A FEW LOCALLY HIGHER TOTALS ESPECIALLY IF WE SEE SOME
THUNDERSNOW.

WINDS WILL BE DUE NORTH DOWN THE LAKE AND MAY SEE A FEW LIGHT SNOW
SHOWERS PRIMARILY OVER NORTHWEST INDIANA IN THE AFTERNOON. DO NOT
THINK THE SHOWERS WILL AMOUNT TO MUCH WITH THE EXTENSIVE ICE COVER
OVER THE LAKE.  ALSO MAY SEE A FEW STRAY LIGHT SNOW SHOWERS OVER THE
WESTERN CWA LATE WEDNESDAY MORNING INTO EARLY WEDNESDAY AFTERNOON AS
ANOTHER VORT STREAMER MOVES THROUGH THE REGION.  CONFIDENCE IS LOW
WITH THESE SNOW SHOWERS AS THE FORCING AND MOISTURE DO NOT LOOK
OVERLY IMPRESSIVE AT THIS TIME.

AS MENTIONED ABOVE...TEMPS WILL FALL LATER THIS AFTERNOON THROUGH
THIS EVENING WITH OVERNIGHT LOWS IN THE 20S.  WITH THE STRONG
WINDS...WIND CHILLS WILL BE IN THE SINGLE DIGITS TONIGHT.  TEMPS WILL
NOT REBOUND MUCH TOMORROW WITH THE HIGH TEMP BEING REACHED IN THE
MORNING.  THE COLD AIR ASSOCIATED WITH THE TROUGH MOVES OVER THE
REGION DURING THE DAY...SO HIGH TEMPS WILL BE IN THE 20S. WIND
CHILLS WILL MAKE IT FEEL LIKE +10 OR LOWER.

WEDNESDAY NIGHT AND THURSDAY...
THE TROUGH SHIFTS EAST WEDNESDAY NIGHT AND UPPER LEVEL TEMPS BEGIN
TO RISE.  OVERNIGHT LOWS WILL BE IN THE SINGLE DIGITS...EXCEPT 10-15
DEGREES OVER THE CITY.  WIND CHILLS WILL BE AROUND ZERO WITH SOME
OUTLYING AREAS GETTING AS LOW AS -5.

THERE IS A SLIGHT CHANCE OF LIGHT SNOW NORTH OF I-88 THURSDAY
MORNING AS A WEAK WARM FRONT MOVES INTO THE REGION.  FORCING DOES
NOT LOOK IMPRESSIVE WITH THE FRONT SO HAVE LOW CONFIDENCE IN THIS
CHANCE OF SNOW.

HIGH TEMPS ON THURSDAY WILL BE IN THE 30S DUE TO WAA ASSOCIATED WITH
THE FRONT.  THE WARMING TREND CONTINUES OVERNIGHT WITH LOWS AROUND
30.

JEE

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 22Z...

* NORTHEAST WINDS INCREASING TODAY AND TONIGHT WITH GUSTS OF
  30-35 KT LIKELY TONIGHT INTO WEDNESDAY MORNING.

* RAIN/SNOW MIX BY MID EVENING...RAPIDLY CHANGING OVER TO ALL SNOW
  SOON THERE AFTER.

* RAPIDLY DETERIORATING CONDITIONS IN SNOW WITH VIS/CEILINGS
  FALLING TO LIFR/VLIFR.

* PERIOD OF HEAVY SNOW WITH SIGNIFICANTLY REDUCED VIS LIKELY AFTER
  MIDNIGHT.

* BLOWING SNOW OVERNIGHT INTO WEDNESDAY MORNING.

RODRIGUEZ/KB

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

VFR CONDITIONS AND AN INCREASING NORTHEAST WIND IN PLACE OVER THE
TERMINALS EARLY THIS AFTERNOON AS APPROACHING LOW TO THE SOUTHWEST
CONTINUES TO WORK ITS WAY TOWARDS THE AREA. WINDS WILL STEADILY
INCREASE THROUGH THE AFTERNOON AND EVENING WITH HIGHEST GUSTS
EXPECTED OVERNIGHT INTO WEDNESDAY MORNING. VFR CEILINGS WILL LOWER
THIS AFTERNOON BUT THEN QUICKLY DETERIORATE AS BETTER FORCING
ARRIVES THIS EVENING WITH MVFR CONDITIONS BECOMING IFR SOON THERE
AFTER...WITH THESE CEILINGS THEN LIKELY FOR MOST OF THE NIGHT. A
RAIN/SNOW MIX WILL SPREAD OVER THE TERMINALS THIS EVENING BUT
EXPECT A RAPID CHANGE OVER TO ALL SNOW BASICALLY WITHIN AN HOUR OF
ONSET. NO REAL CHANGES TO EXPECTED SNOW TONIGHT AND TIMING WITH
THE 6-10Z TIME FRAME STILL THE BEST TIME FOR MORE MODERATE TO
HEAVY SNOW. HAVE LEFT THE LOWEST VIS AT 1/2 MILE FOR ALL THE
TERMINAL SITES...BUT WITH THEM LIKELY OBSERVING PERIODS OF 1/4
MILE OR EVEN LESS AT TIMES. EXPECT THIS HEAVIER SNOW TO BE MORE
TIED TO CONVECTIVE ASPECTS...WITH UNCERTAINTY TO EXACT TIMING AND
DURATION OF THIS HEAVIER SNOW ASSOCIATED WITH THIS FEATURE.
MDW/GYY WOULD LIKELY HAVE THE BEST CHANCES FOR 1/4 MILE OR LESS
VISIBILITY AS WELL AS FOR A LONGER DURATION AS THIS WILL BE A MORE
FAVORED LOCATION FOR THE BEST SNOWFALL DEVELOPMENT. BUT ONCE
AGAIN...WITH SOME UNCERTAINTY REMAINING...HAVE OPTED TO LEAVE OUT
OF THE TAF AT THIS TIME BUT COULD SEE THIS LOWER VIS IN HEAVY SNOW
ADDED LATER THIS EVENING. BEST SNOW DEVELOPMENT SHOULD EXIT THE
TERMINALS BY EARLY WEDNESDAY MORNING...TAPERING OFF THROUGH THE
MORNING WITH A SLOW IMPROVING TREND WITH CEILINGS.

RODRIGUEZ

//ORD AND MDW CONFIDENCE...UPDATED 22Z...

* MEDIUM HIGH CONFIDENCE WITH WIND SPEED/DIRECTION...AND RESULTANT
  BLOWING SNOW.

* MEDIUM HIGH CONFIDENCE WITH RAIN/SNOW MIX TIMING AND CHANGE OVER
  TO SNOW.

* MEDIUM CONFIDENCE WITH VIS/CEILING TRENDS.

* MEDIUM HIGH CONFIDENCE WITH HEAVY SNOW...LOW MEDIUM CONFIDENCE
  WITH TIMING/DURATION.

RODRIGUEZ/KB

//OUTLOOK FOR ORD/MDW FOR 00Z THURSDAY-12Z TUESDAY...UPDATED 12Z...

* WEDNESDAY NIGHT...DRY/VFR.
* THURSDAY...DRY/VFR. GUSTY SOUTHWEST WINDS.
* FRIDAY...DRY/VFR. GUSTY WESTERLY WINDS.
* SATURDAY...DRY/VFR.
* SUNDAY...SLIGHT CHANCE OF SNOW.
* MONDAY...DRY/VFR.

&&

.MARINE...
210 PM CDT

LOW PRESSURE OVER THE CENTRAL PLAINS WILL CONTINUE TO DEEPEN AS IT
TRACKS EAST ACROSS SOUTHERN ILLINOIS TONIGHT AND INTO THE OHIO
VALLEY WEDNESDAY.  AS THE LOW TRACKS SOUTH AND THEN SOUTHEAST OF THE
LAKE...HIGH PRESSURE WILL ALSO BUILD ACROSS THE UPPER GREAT LAKES
REGION...SETTING UP STRONG NORTH WINDS.  THE COMBINATION OF A STRONG
GRADIENT AND STRONG COLD ADVECTION WILL LEAD TO WINDS QUICKLY
INCREASING TO GALES BY LATE THIS EVENING.  THE LATEST GUIDANCE HAS
BEEN RELATIVELY CONSISTENT IN INDICATING THE POTENTIAL FOR HIGH END
GALES BY LATE WEDNESDAY MORNING AND EARLY AFTERNOON...WITH THE
STRONGEST GALES OVER THE SOUTHERN PORTIONS OF THE LAKE...INCLUDING
THE NEARSHORE WATERS.  BY WEDNESDAY EVENING...THE HIGH PRESSURE WILL
BEGIN TO SPREAD ACROSS LAKE MICHIGAN ALLOWING WINDS TO SUBSIDE BELOW
GALE FORCE.  BY THURSDAY NIGHT...THE HIGH WILL PUSH TO THE SOUTHEAST
OF THE LAKE AS A CLIPPER DROPS OUT OF NORTHERN ALBERTA AND SWINGS
JUST NORTH OF THE UPPER GREAT LAKES ON FRIDAY.  WITH THE SFC HIGH
SAGGING OFF THE SERN COAST...A PERIOD OF SWLY WINDS WILL DEVELOP
AHEAD OF AN APPROACHING COLD FRONT TRAILING FROM THE CLIPPER.
ANTICIPATE A PERIOD OF BRISK SLY TO SWLY WINDS FOR THURSDAY NIGHT
THROUGH FRIDAY...BUT MORE GALES ARE NOT EXPECTED AT THIS TIME.  AS
THE CLIPPER TURNS NEWD INTO QUEBEC...IT WILL DRAG A WEAK COLD FRONT
DOWN THE LAKE WITH ANOTHER ARCTIC HIGH BUILDING IN BEHIND THE
FRONT.  25-30KT NORTH WINDS WILL SET UP FOLLOWING THE FROPA FOR
SATURDAY NIGHT AND SUNDAY...BUT AS THE HIGH SPREADS ACROSS THE GREAT
LAKES SUNDAY NIGHT...WINDS SHOULD BECOME MORE LIGHT AND VARIABLE.

KREIN

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...WINTER STORM WARNING...ILZ013-ILZ014-ILZ019-ILZ020-ILZ021-ILZ022-
     ILZ023-ILZ032...10 PM TUESDAY TO 1 PM WEDNESDAY.

     WINTER STORM WARNING...ILZ033-ILZ039...1 AM WEDNESDAY TO 1 PM
     WEDNESDAY.

     WINTER WEATHER ADVISORY...ILZ006-ILZ008-ILZ010-ILZ011-
     ILZ012...10 PM TUESDAY TO 10 AM WEDNESDAY.

IN...WINTER STORM WARNING...INZ001-INZ002...10 PM TUESDAY TO 1 PM
     WEDNESDAY.

     WINTER STORM WARNING...INZ010-INZ011-INZ019...1 AM WEDNESDAY TO
     1 PM WEDNESDAY.

LM...GALE WARNING...LMZ080-LMZ669-LMZ671-LMZ673-LMZ675-LMZ740-LMZ741-
     LMZ742-LMZ743-LMZ744-LMZ745-LMZ777-LMZ779-LMZ870-LMZ872-
     LMZ874-LMZ876-LMZ878...MIDNIGHT WEDNESDAY TO 10 PM
     WEDNESDAY.

     GALE WARNING...LMZ261-LMZ362-LMZ364-LMZ366-LMZ563-LMZ565-LMZ567-
     LMZ868...MIDNIGHT WEDNESDAY TO 7 PM WEDNESDAY.

&&

$$

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