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000
FXUS63 KLOT 081409
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
809 AM CST SAT MAR 8 2014

.DISCUSSION...

328 AM...FORECAST CONCERN IN THE SHORT TERM IS POTENTIAL FOR A
MIX OF WINTRY PRECIP CHANGING TO SNOW OVER THE NEXT FEW HOURS.
LONGER TERM CONCERNS ARE TEMPERATURES THROUGH THE NEXT 7 DAYS AND
THE POTENTIAL FOR ANOTHER PERIOD OF RAIN CHANGING TO SNOW TUESDAY
NIGHT INTO WEDNESDAY MORNING.

A COLD FRONT WILL MOVE SOUTH OF THE CWA OVER THE NEXT FEW HOURS AS
COLDER AIR SLOWLY SPREADS ACROSS THE AREA. AIR TEMPS REMAIN AT OR
JUST ABOVE FREEZING EXCEPT NEAR THE WI STATE LINE. PRECIP NOW
DEVELOPING FROM WESTERN IL INTO THE WESTERN CWA WILL CONTINUE INTO
THE MID/LATE MORNING AS IT SLOWLY DRIFTS SOUTHEAST. EVENTUALLY THE
COLUMN WILL COOL SUFFICIENTLY FOR PRECIP TO CHANGE TO ALL SNOW.
HOWEVER...PRIOR TO THAT OCCURRING...A MIX OF WINTRY PRECIP COULD
OCCUR WITH SOME LIGHT FREEZING RAIN POSSIBLE DEPENDING ON SURFACE
TEMPERATURES. CONFIDENCE IS RATHER LOW FOR SPECIFIC PRECIP TYPES
AND TRENDS WILL NEED TO BE MONITORED OVER THE NEXT FEW HOURS. WITH
THE BULK OF THE PRECIP EXPECTED TO TRANSITION TO SNOW...SOME AREAS
MAY RECEIVE UP TO AN 1 INCH...PRIMARILY OVER THE CENTRAL CWA WITH
LESSER AMOUNTS NORTH AND SOUTH. BUT AGAIN...IF PRECIP FALLS AS A
MIX OR EVEN AS SOME RAIN...THEN SNOWFALL COULD BE MUCH LESS.

TEMPS STILL IN THE LOWER 30S ACROSS SOUTHERN WI AND WHILE TEMPS
WILL DROP A FEW DEGREES WITH PRECIP...ESPECIALLY SNOW...TEMP
TRENDS TODAY ARE ALSO UNCERTAIN. HIGHS COULD BE SET AT 12Z WITH
CURRENT TEMPS AT THAT TIME...BUT ALSO POSSIBLE FOR SOME MINOR
RECOVERY IN TEMPS LATER THIS AFTERNOON WITH SOME SUN. REGARDLESS...
TEMPS WILL BE MUCH COOLER TODAY. HIGH PRESSURE BUILDS ACROSS THE
REGION TONIGHT WITH TEMPS LIKELY TO TANK IN THE EVENING AND COULD
THEN BECOME STEADY OR EVEN RISE A FEW DEGREES OVERNIGHT. COULD BE
QUITE A SPREAD FROM SINGLE DIGITS IN THE USUAL COLD SPOTS TO MID
MAYBE UPPER TEENS IN THE IMMEDIATE METRO AREA/DOWNTOWN.

WARM AIR ADVECTION REALLY INCREASES SUNDAY ON THE BACKSIDE OF THE
DEPARTING HIGH. WITH AMPLE SUNSHINE...TEMPS COULD EASILY REACH
BACK INTO THE LOWER/MID 40S AND CURRENT TEMPS MAYBE A BIT COOL.
TEMPS ALOFT CONTINUE TO WARM SUNDAY NIGHT INTO MONDAY. THUS TEMPS
MAY REMAIN QUITE MILD SUNDAY NIGHT...IN THE LOWER/MID 30S...MAYBE
WARMER IN THE CITY. THESE WARMER TEMPS OVERNIGHT WILL FURTHER
ASSIST HIGHS REACHING WELL INTO THE 50S MONDAY OVER THE SOUTHERN
HALF OF THE CWA AND INTO THE METRO AREA WITH TEMPS NEAR 50
POSSIBLE EVEN OVER THE NORTHWEST CWA. AGAIN MADE NO CHANGES TO
THIS TIME PERIOD WITH LOWER 60S ADVERTISED ACROSS THE SOUTHERN CWA.

ANOTHER FRONTAL BOUNDARY WILL MOVE ACROSS THE AREA TUESDAY AS LOW
PRESSURE THEN DEVELOPS OVER THE PLAINS AND MOVES EAST ACROSS THE
OHIO VALLEY TUESDAY NIGHT. SIMILAR SITUATION TO THIS MORNING AS
TEMPS AHEAD OF THE FRONT WILL BE QUITE MILD ALLOWING FOR PRECIP TO
INITIALLY FALL AS RAIN THEN TRANSITION TO SNOW. BULK OF THE PRECIP
LOOKS TO REMAIN SOUTH OF THE AREA. COLDER AIR BEHIND THIS FRONT
WILL BE SHORT LIVED AS THE PATTERN QUICKLY TRANSITIONS BACK TO
SOUTHWESTERLY FLOW. HAVE BUMPED TEMPS UP INTO THE 40S FOR THURSDAY
AND INTO THE 50S FOR FRIDAY...THOUGH ANOTHER FRONTAL BOUNDARY AND
POTENTIAL CLOUD COVER WILL BE POSSIBLE FRIDAY. CMS

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 14Z...

* LIGHT SNOW ENDING AROUND 1430Z ORD 1530-16Z MDW.
* MVFR CIGS LINGERING AFTER THE SNOW THROUGH MID AFTERNOON.
* NORTHEAST WINDS WITH SPORADIC GUSTS TO AROUND 20 KT PERSISTING
  INTO THIS AFTERNOON.
* POSSIBLE FOG OVERNIGHT.

//DISCUSSION...UPDATED 12Z...

WHILE THE SURFACE COLD FRONT PASSED OVER THE AREA LAST
EVENING...THE ELEVATED COLD FRONT IS PRESENTLY DOING SUCH. AS IT
DOES SO IT WILL CONTINUE TO BRING LIGHT PRECIPITATION. THIS HAS
MAINLY TRANSITIONED TO SNOW AT ALL TAF SITES ALREADY BY 1130Z...AND
EVEN LIKELY ENDED FOR GOOD AT ROCKFORD. THE FORCING FOR SNOW IS
MAINLY LIGHT...BUT COMBINED WITH ALREADY SOME FOG PRESENT...IFR
VISBYS ARE TEMPORARILY POSSIBLE AND HAVE BEEN OBSERVED IN SNOW
THROUGH 14Z. THE PRECIPITATION WILL END FROM NORTH TO SOUTH
THROUGH MID MORNING...HOWEVER MVFR CLOUDS ARE FAVORED TO LINGER
INTO THE AFTERNOON AS DRYING HAPPENS ALOFT MORE SO THAN IN THE
BOUNDARY LAYER. THE LOW CLOUDS SHOULD DISSIPATE BY EVE AND THAT
MAY OFFER THE POSSIBILITY OF FOG AS WINDS FALL OFF WITH NEARBY
HIGH PRESSURE.

THE NORTHEAST WINDS ARE FAVORED TO LAST INTO THE AFTERNOON WITH
EVEN SOME 25 KT GUSTS EARLY THIS MORNING FOR CHICAGOLAND SITES
NEAR THE LAKE. LATE THIS AFTERNOON INTO EARLY THIS EVE...THE HIGH
PRESSURE CENTER SHOULD MOVE FAR ENOUGH SOUTH THAT IT ALLOWS FOR
MORE OF A NORTHWEST WIND COMPONENT TO EVOLVE...ALONG WITH SPEEDS
DROPPING OFF. SUNDAY LOOKS TO SEE GUSTY SOUTHWEST WINDS AS THE
AREA BECOMES UNDER THE INFLUENCE OF QUICK-MOVING LOW PRESSURE NEAR
THE CONUS BORDER.

//ORD AND MDW CONFIDENCE...UPDATED 14Z...

* HIGH IN LIGHT SNOW BEING MAINLY MVFR WITH ONLY TEMPORARY IFR
  CONDITIONS. MEDIUM-HIGH CONFIDENCE IN END TIME
* LOW IN END TIME OF MVFR CLOUDS THIS AFTERNOON
* HIGH IN WIND DIRECTION AND SPEED THROUGH EARLY AFTERNOON. MEDIUM
  ON 23Z SHIFT BACK TO NORTHWEST
* LOW ON WHETHER FOG DEVELOPS OVERNIGHT.

//OUTLOOK FOR ORD/MDW FOR 00Z MONDAY-12Z SATURDAY...UPDATED 12Z...

SUNDAY NIGHT-MONDAY...VFR LIKELY.
TUESDAY...SLGT CHC OF RAIN DURING THE DAY AND CHC OF SNOW DURING
          THE NIGHT. IFR POSSIBLE.
WEDNESDAY...SLGT CHC OF SNOW.
THURSDAY-FRIDAY...VFR LIKELY.

MTF

&&

.MARINE...
144 AM CST

NORTHERLY WINDS ACROSS THE LAKE THIS MORNING WILL CONTINUE INTO THIS
AFTERNOON. SUCH A SYNOPTIC PATTERN AND WIND SPEEDS WOULD NORMALLY
PROVIDE WAVE HEIGHTS SUFFICIENT FOR A SMALL CRAFT ADVISORY ALONG THE
INDIANA AND POSSIBLY EVEN ILLINOIS SHORE...BUT DUE TO THE EXTENT OF
ICE COVERAGE WAVES WILL BE A MOOT POINT. A FEW GUSTS AROUND 25 KT
ARE POSSIBLE IN NEARSHORE AREAS EARLY TODAY. OTHERWISE WINDS
SHOULD DIMINISH LATE IN THE DAY AND ESPECIALLY THIS EVENING WITH
NEARBY RIDGING TO THE SOUTHWEST.

A PROGRESSIVE PATTERN ALONG THE NORTHERN CONUS BORDER DURING
SUNDAY INTO MONDAY WILL STEER A COUPLE LOW PRESSURE SYSTEMS ACROSS
LAKE SUPERIOR. THE FIRST OF THESE WILL TIGHTEN THE PRESSURE
GRADIENT QUICKLY BY SUNDAY AFTERNOON AND OFFER SOUTH SOUTHWEST
WINDS LIKELY TO GALE FORCE ACROSS THE NORTH FOR A 6-9 HR PERIOD.
FOR THAT REASON HAVE ISSUED A GALE WATCH FOR SUNDAY AFTERNOON AND
EARLY EVE. THE NEXT SYSTEM ON MONDAY WILL BE DEEPER BUT BECAUSE
SO CLOSELY ON THE HEELS TO ITS PREDECESSOR WILL NOT HAVE AS STRONG
OF ISALLOBARIC COMPONENT. SO LESS WINDS SPEEDS ARE ANTICIPATED FOR
MONDAY. AN ACCOMPANYING COLD FRONT WILL OOZE ITS WAY DOWN THE LAKE
MONDAY NIGHT INTO EARLY TUESDAY AND SHIFT WINDS NORTHERLY. HIGH
PRESSURE IS FAVORED TO MOVE OVER THE LAKE DURING MIDWEEK.

THE LARGE AMOUNT OF ICE EXTENT WILL CONTINUE TO SUPPRESS WAVES IN
MANY AREAS...HOWEVER SOME ICE MOVEMENT/BREAK-UP IS LIKELY ON SUNDAY
AND SUNDAY NIGHT WITH WARMER AIR AND TURBULENT FLOW.

MTF

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WATCH...LMZ261-LMZ362-LMZ364-LMZ366-LMZ563-LMZ565-LMZ567-
     LMZ868...NOON SUNDAY TO 9 PM SUNDAY.

&&

$$

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