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000
FXUS63 KLOT 101420
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
920 AM CDT MON MAR 10 2014

.DISCUSSION...

330 AM...PRIMARY FORECAST CONCERNS ARE RAIN CHANGING TO SNOW
TUESDAY EVENING WITH AN INCH OR TWO OF SNOW ACCUMULATION NORTH TO
PERHAPS SEVERAL INCHES ACROSS THE SOUTHERN CWA...THEN A SHORT
LIVED BLAST OF CHILLY TEMPS WEDNESDAY/WEDNESDAY NIGHT.

WARM AIR HAS SPREAD ACROSS THE REGION WITH TEMPS HOLDING STEADY IN
THE UPPER 30S/LOWER 40S. TEMPS MAY DROP A FEW DEGREES THROUGH
SUNRISE BUT BASICALLY STEADY. MID DECK CURRENTLY PASSING ACROSS
THE AREA MAY GENERATE A FEW SPRINKLES OVER THE NEXT FEW HOURS BUT
THE BACK EDGE OF THE HIGH CLOUDS IS QUICKLY PUSHING SOUTHEAST
THROUGH MN/WI AND SHOULD SEE MOSTLY SUNNY SKIES BY MID MORNING
WHICH WILL AID ALREADY MILD TEMPS TO WARM INTO THE 50S JUST ABOUT
EVERYWHERE. OVER THE DEEPER SNOWPACK ACROSS NORTHWEST IL...TEMPS
MAY ONLY BRIEFLY TOUCH LOWER 50S. ELSEWHERE MID/UPPER 50S ON TRACK
WITH THE POTENTIAL FOR SOME LOWER 60S ACROSS THE SOUTHERN CWA.

A FRONTAL BOUNDARY WILL SLOWLY SAG ACROSS SOUTHERN WI AND NORTHERN
IL LATE TONIGHT INTO TUESDAY MORNING. PRECIP WILL INITIALLY BE
RATHER LIGHT WITH A CONSENSUS OF KEEPING MUCH OF THE PRECIP NEAR
OR JUST NORTH OF THE STATE LINE THROUGH MIDDAY TUESDAY. THIS WILL
DRIFT SOUTH INTO NORTHERN IL DURING THE AFTERNOON WITH THERMAL
PROFILES SHOWING PRECIP TYPE SHOULD REMAIN LIGHT RAIN...THOUGH IT
WILL BE A CHILLY RAIN WITH TEMPS SLOWLY FALLING THROUGH THE 30S.
EVENTUALLY...PRECIP WILL TRANSITION TO LIGHT SNOW TUESDAY EVENING
WITH SOME LIGHT SNOW ACCUMULATIONS OF AN INCH OR SO POSSIBLE OVER
NORTHERN IL.

A DEVELOPING STORM SYSTEM OVER THE PLAINS TUESDAY WILL MOVE EAST
ACROSS THE OHIO VALLEY TUESDAY NIGHT WITH A BAND OF HEAVIER QPF
FALLING ACROSS CENTRAL IL INTO CENTRAL/NORTHWEST INDIANA TUESDAY
NIGHT INTO EARLY WEDNESDAY MORNING. EXACT PLACEMENT OF THIS
HEAVIER AXIS OF QPF IS STILL UNCERTAIN. IN ADDITION...PRECIP MAY
BEGIN AS RAIN OR A RAIN/SNOW MIX. ONCE IT CHANGES OVER TO ALL
SNOW...IT COULD BE RATHER WET WITH SNOW/WATER RATIOS AROUND OR
JUST UNDER 10:1. THIS ALL MAKES SNOW ACCUMULATIONS RATHER TRICKY.
THOUGH AS COLDER AIR SPREADS INTO THE REGION WEDNESDAY MORNING...
THE SNOW SHOULD BECOME A BIT DRIER WITH SOME BLOWING SNOW POSSIBLE
MAINLY OVER THE SOUTHERN THIRD OF THE CWA. BUT STORM TOTAL AMOUNTS
OF 1-3 INCHES ARE POSSIBLE ALONG A PNT TO VPZ LINE WITH MAYBE 3-5
INCHES ACROSS FAR SOUTHERN CWA BUT CHANGES ARE POSSIBLE AS TRENDS
BECOME MORE CLEAR.

WHILE TUESDAY WILL BE COOLER THAN TODAY OVER MUCH OF THE AREA...
WEDNESDAY WILL BE A BIG CHANGE FROM THE EXPECTED WARMER WEATHER.
HIGHS WILL LIKELY REMAIN IN THE 20S ACROSS MUCH OF THE AREA WITH A
NORTH WIND OF 15-25 MPH...PUSHING WIND CHILLS INTO THE LOWER TEENS
MAYBE EVEN SINGLE DIGITS BY LATE AFTERNOON. WINDS QUICKLY DIMINISH
WEDNESDAY EVENING AS HIGH PRESSURE MOVES ACROSS THE REGION. LOWS
EXPECTED IN THE TEENS WEDNESDAY NIGHT/THURSDAY MORNING BUT WITH
SOME WEAK WARMING ALOFT BY MORNING...COULD SEE STEADY OR SLOWLY
RISING TEMPS BY THURSDAY MORNING. TEMPS WILL MODERATE THURSDAY...
BACK INTO THE MID/UPPER 30S...BUT THIS IS COOLER THAN PREVIOUSLY
ADVERTISED AS WARMER AIR IS DELAYED AND TEMPS FRIDAY DEPENDENT ON
SPEED/TIMING OF A WEAK COLD FRONT THAT WILL PUSH ACROSS THE AREA
IN THE AFTERNOON. CMS

&&

.AVIATION...

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

* GUSTY SOUTHWEST WINDS TODAY.
* CHANCE FOR FOG TONIGHT AND MVFR CIGS TUE MORNING.
* WIND TURNING NORTH NORTHEAST LATE THIS EVE OR OVERNIGHT.

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

THE WIND WILL CONTINUE FROM THE SOUTHWEST TODAY AS LOW PRESSURE
SCOOTS EAST ACROSS SOUTHERN CANADA. GUSTS TO 20 KT ARE EXPECTED AT
TIMES GIVEN SOME MIXING...ESPECIALLY AS SUNSHINE BECOMES MORE
APPARENT BY MID TO LATE MORNING. THE WIND WILL SHIFT
NORTHWESTERLY THIS EVE AS A WEAK SURFACE TROUGH PASSES. WIND
SPEEDS WILL ALSO DIMINISH QUICKLY THIS EVE IN A WEAKENING PRESSURE
GRADIENT. GIVEN SNOW MELT AND SUBLIMATION THROUGH TODAY...THIS
SETUP TONIGHT LOOKS FAVORABLE AT LEAST MVFR FOG...AND POTENTIALLY
AS EARLY AS AN HOUR OR TWO AFTER SUNDOWN. WITH THICKENING MID-
LEVEL CLOUDS...THE FOG IS NOT ANTICIPATED TO BECOME TOO
AGGRESSIVE TONIGHT...ALTHOUGH TO AT LEAST IFR IS CERTAINLY
POSSIBLE. WINDS WILL TURN MORE NORTHEAST OVERNIGHT ESPECIALLY FOR
CHICAGOLAND SITES NEAR THE LAKE. SPEEDS ARE EXPECTED TO INCH
UPWARD OVER 10 KT BY LATER TUE MORNING. THE FLOW OFF THE ICE-
COVERED LAKE MAY FURTHER AID IN SATURATION WITH THE MOIST
CONDITIONS OVER LAND. THIS COULD LEAD TO BOTH MVFR VISBYS AND CIGS
THROUGHOUT TUE MORNING. RAIN IS ALSO EXPECTED TO DEVELOP INTO FAR
NORTHERN ILLINOIS LATE TUE MORNING AND INTO ORD AND MDW TUE
AFTERNOON. THIS WILL CHANGE TO A WET SNOW LIKELY DURING EARLY TUE
EVE OR SO WITH ONE TO THREE INCHES OF FORECAST ACCUMULATION.

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

* HIGH IN SOUTHWEST WINDS TODAY AND MEDIUM IN GUST MAGNITUDE.
* HIGH IN AT LEAST MVFR VISIBILITY DEVELOPING TONIGHT BUT LOW IN
  HOW FAR VISIBILITY WILL DROP.
* LOW IN TIMING OF WIND SHIFT TO NORTHEAST TONIGHT.
* LOW IN MVFR CIGS TUE MORNING.

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

TUESDAY NIGHT...RAIN/SNOW CHANGING TO ALL SNOW DURING THE EVE AND
                PERSISTING OVERNIGHT.
WEDNESDAY...SLGT CHC OF SNOW. MVFR LIKELY IN THE MORNING. GUSTY
            WINDS NEAR DUE NORTH IN DIRECTION.
THURSDAY-FRIDAY...VFR LIKELY.
SATURDAY...SLGT CHC OF SNOW DURING THE NIGHT.
SUNDAY...SLGT CHC OF RAIN/SNOW.

MTF/RODRIGUEZ

&&

.MARINE...
225 AM CDT

AN ACTIVE AND PROGRESSIVE PATTERN IN THE MIDDLE OF THE COUNTRY WILL
PRESENT NUMEROUS PERIODS OF AT LEAST MODEST WINDS OVER LAKE
MICHIGAN. WHILE A FEW SOUTHWEST WIND GUSTS TO AROUND 30 KT WILL
BE SEEN THROUGH DAYBREAK OVER THE FAR SOUTHERN PART OF THE
LAKE...MOST OF THE SOUTHWEST GUSTS SEEN TODAY WILL BE 20 KT OR
LESS. AS LOW PRESSURE MOVES EAST ACROSS ONTARIO TONIGHT...A WEAK
COLD FRONT WILL TURN THE WIND NORTHWEST OVER THE LAKE.

THE WIND WILL TURN MORE NORTHERLY ON TUESDAY AS LOW PRESSURE
DEVELOPS ALONG THE AFOREMENTIONED FRONT IN THE SOUTHERN PLAINS.
AS THIS LOW ADVANCES UP THE OHIO RIVER VALLEY LATER TUESDAY NIGHT
INTO WEDNESDAY...NORTHERLY WINDS WILL FURTHER INCREASE OVER THE
LAKE WITHIN A TIGHT PRESSURE GRADIENT. GALE POTENTIAL REMAINS
ACROSS THE SOUTHERN PART OF THE LAKE...INCLUDING THE ILLINOIS AND
INDIANA NEARSHORE FOR LATE TUESDAY NIGHT AND WEDNESDAY. DID
CONSIDER A WATCH AS OVERALL SYNOPTIC SIGNATURE IS GOOD FOR
GALES...WITH A LOW PASSING TO THE SOUTH AND A PRESSING HIGH TO THE
NORTH. WITH STILL JUST BEYOND 48 HOURS...HAVE OPTED TO HOLD BACK
AT THIS TIME...AS SOME SHIFTING OF THE LOW PATH MAY OCCUR. LATE IN
THE WEEK...ANOTHER PACIFIC/CLIPPER TYPE SYSTEM IS FORECAST TO
APPROACH THE LAKE FROM THE NORTHWEST AND WOULD FAVOR A PERIOD OF
AGAIN MODEST SOUTHWEST TO WEST WINDS.

MTF

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&

$$

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