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000
FXUS63 KLOT 070301
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
901 PM CST FRI DEC 6 2013

.DISCUSSION...
704 PM CST

MADE MINOR ADJUSTMENTS TO THE FORECAST THIS EVENING...WITH THE
MAIN ONE BEING CLOUD COVER. CLOUDS THINNED AND PUSHED EAST A LOT
QUICKER THAN ORIGINALLY THOUGHT SO WENT WITH MOSTLY CLEAR
OVERNIGHT IN MOST PLACES. AREAS ALONG AND EAST OF I-57 STILL HAVE
BROKEN TO OVERCAST SKIES THAT WILL SLOWLY CONTINUE TO SHIFT EAST.

ADJUSTED TEMPS TO REFLECT CURRENT OBS BUT MADE NO OTHER MAJOR
CHANGES. DID WONDER IF WE ARE PERHAPS A DEGREE OR TWO TOO WARM
OVERNIGHT TONIGHT...BUT DID NOT HAVE ENOUGH CONFIDENCE TO GO
COLDER.

JEE

//PREV DISCUSSION...
334 PM CST

MAIN FORECAST CONCERNS ARE WITH CONTINUED COLD TEMPS AND LOW WIND
CHILLS TONIGHT...AND POTENTIAL REMAINING FOR ACCUMULATING SNOW
SUNDAY INTO SUNDAY NIGHT.

PERSISTENT COLD AIR ADVECTION ACROSS THE REGION MAKING FOR SOME
RATHER CHILLY CONDITIONS TODAY AND WITH A 10 TO 20 MPH NORTHWEST
WIND...RESULTANT WIND CHILLS HAVE BEEN IN THE SINGLE DIGITS TO
LOWER TEENS. ALTHOUGH A STRONGER SHORT WAVE TROUGH LIFTING
NORTHEAST JUST SOUTH OF THE AREA TODAY HAS HELPED TO TIGHTEN THE
THERMAL GRADIENT AND THEN INCREASE THE SUBSEQUENT FRONTOGENETICAL
FORCING...THIS MID LEVEL FRONTOGENESIS HAS BEEN RATHER WEAK ACROSS
THE CWA AND NOT ENOUGH FOR ANY LONG LIVED SATURATION. BETTER LOW
LEVEL FRONTOGENESIS HAS BEEN OCCURRING TO THE SOUTHEAST...AND WILL
REMAIN THIS WAY FOR THE REMAINDER OF THE AFTERNOON INTO THE
EVENING. DESPITE SOME SHORT TERM GUIDANCE TRYING TO HINT AT THIS
PRECIP AXIS INCHING FURTHER NORTH TOWARDS THE BENTON COUNTY
INDIANA AREA...FEEL THIS GUIDANCE IS A BIT AGGRESSIVE WITH THIS
PRECIP AXIS....ESPECIALLY THE 00HR FORECAST ALREADY OFF WITH
REGARDS TO PLACEMENT AT THE TIME. SO DID LOWER AND CONFINE LOW
CHANCE POPS FOR THE REMAINDER OF THE AFTERNOON FOR THE BENTON
COUNTY AREA...WITH THE IDEA THAT MAYBE STRAY LIGHT SNOW OR
FLURRIES COULD OCCUR BRIEFLY...BUT DONT EXPECT ANY SNOW
ACCUMULATION. THE PREVIOUSLY MENTIONED MID LEVEL WAVES WILL DEPART
TO THE EAST THIS EVENING...WITH ANY LINGERING PRECIP THEN SHIFTING
TO THE EAST. PERSISTENT CLOUD COVER TODAY WILL FINALLY EXIT AS THE
STREAM OF MID/HIGH LEVEL CLOUD LIKEWISE EXITS TO THE EAST. DESPITE
SOME ADDITIONAL MID/HIGH LEVEL CLOUD COVER MOVING NORTHEAST ACROSS
SOUTHERN IOWA...AM EXPECTING THIS TO ERODE AS IT LIFTS NORTHEAST
THIS EVENING. WITH SURFACE RIDGE TO THE WEST BUILDING EAST ACROSS
THE REGION AND CLEARING SKIES TONIGHT...EXPECT VERY COLD TEMPS
AGAIN WITH TONIGHT BEING ONE OF THE COLDER NIGHTS THIS WEEK.
DESPITE A NORTHWEST WIND AROUND 10 TO 15 MPH REMAINING IN PLACE
TONIGHT...DO EXPECT MOST LOCATIONS TO OBSERVE SINGLE DIGIT LOWS
TONIGHT. ALTHOUGH RESULTANT WIND CHILLS WILL NOT BE LOW ENOUGH FOR
ANY HEADLINES...WIND CHILLS OF 5 TO 15 BELOW ARE STILL FORECAST
TONIGHT.

QUIET WEATHER WITH SUNNY CONDITIONS ARE EXPECTED ON SATURDAY AND
AS TONIGHT BEING ONE OF THE COLDER NIGHTS...SATURDAY WILL BE
ANOTHER COLD DAY WITH TEMPS STRUGGLING TO GET OUT OF THE TEENS.
ABOUT THE ONLY DIFFERENCE WITH TOMORROW ARE WITH SLIGHTLY LIGHTER
WIND SPEEDS...WITH SURFACE RIDGING CONTINUING. UPPER LEVEL TROUGH
WILL BE MOVING THROUGH THE WESTERN CONUS DURING THE DAY
SATURDAY...SLOWLY APPROACHING THE REGION SATURDAY NIGHT. AS THIS
OCCURS...SURFACE HIGH WILL SHIFT EAST ACROSS THE GREAT LAKES WITH
LOW LEVEL FLOW VEERING FROM THE NORTHWEST TO THE NORTHEAST AND
EAST SATURDAY NIGHT. ALTHOUGH EQUILIBRIUM HEIGHTS WONT BE THE
GREATEST...850MB DELTA TS OVER THE LAKE WILL BE MORE THAN
SUFFICIENT FOR LAKE EFFECT CLOUD COVER/SNOW TO DEVELOP ACROSS THE
SOUTHERN END OF THE LAKE MORE TOWARDS EARLY SUNDAY MORNING.
ALTHOUGH ANY LAKE GENERATED PRECIP WONT BE THE
HEAVIEST...FAVORABLE THERMODYNAMIC CONDITIONS COINCIDING WITH
MODEL GUIDANCE HINTING AT DECENT LOW LEVEL CONVERGENCE AXIS
SWINGING ACROSS NORTHEAST ILLINOIS...FEEL THAT AT LEAST A PERIOD
OF LIGHT SNOW WILL DEVELOP ESPECIALLY GOING INTO SUNDAY MORNING
WITH CONVERGENCE INCREASING.

WHILE THIS IS OCCURRING...FAIRLY STOUT MID LEVEL FEATURE WILL
EJECT NORTHEASTWARD OUT AHEAD OF APPROACHING LONG WAVE TROUGH.
WITH WINDS CONTINUING TO VEER MORE SOUTHERLY...WARM ADVECTION WILL
BEGIN TO KICK IN DURING THE DAY SUNDAY WITH MID/HIGH LEVEL CLOUD
COVER CONTINUING TO STREAM OUT AHEAD OF IT. ADVECTION SNOW SHOULD
BEGIN TO OVERSPREAD THE CWA SUNDAY AFTERNOON AS THE COLUMN
SUFFICIENTLY SATURATES. DID INCREASE POPS SUNDAY AFTERNOON...WITH
THE THINKING THAT GUIDANCE MIGHT BE UNDER DONE WITH THIS TOP DOWN
SATURATION. ALTHOUGH SUNDAY AFTERNOON SHOULD ONLY OBSERVE LIGHT
SNOW AND GENERALLY LIGHT ACCUMULATION...AREAS ALONG AND NORTH OF
I-88 SHOULD BEGIN TO OBSERVE BETTER ACCUMULATION. BEST FORCING
ACROSS THE CWA DOES ARRIVE BY THE 00Z TIME FRAME SUNDAY
NIGHT...WITH THE BETTER FORCING STILL RESIDING MORE ACROSS THE
NORTHERN HALF OF THE CWA. FROM THE 00-06Z TIME FRAME...MOST AREAS
SHOULD LIKELY OBSERVE A PERIOD OF LIGHT-MODERATE SNOW. HAVE MADE
LITTLE CHANGES TO PREVIOUS SNOWFALL TOTALS...ONLY INCREASING
SLIGHTLY. FEEL THAT SEVERAL INCHES OF SNOW ARE STILL POSSIBLE MORE
TOWARDS THE ILLINOIS/WISCONSIN BORDER...WITH SNOWFALL TOTALS
LOWERING FURTHER SOUTH ACROSS THE CWA...AND AT AN INCH OR LESS
ACROSS THE SOUTHERN CWA. ANY LAKE EFFECT SNOWFALL EARLY SUNDAY
INTO SUNDAY AFTERNOON COULD HELP TO PROVIDE ISOLATED HIGHER
AMOUNTS...AND WILL NEED TO MONITOR THIS POTENTIAL. GUIDANCE STILL
INDICATING THE DEEPER MOISTURE WILL BE LOST ACROSS EAST CENTRAL
ILLINOIS AND NORTHWEST INDIANA GOING INTO THE 6Z PERIOD SUNDAY
NIGHT. THIS LOSS OF MOISTURE/CRYSTALS SHOULD THEN RESULT IN A
PERIOD OF EITHER LIGHT FREEZING DRIZZLE OR LIGHT SNOW. WEAK LIFT
WITH THIS NOW SHEARED OUT WAVE COULD RESULT IN CONTINUED LIFT INTO
EARLY MONDAY MORNING...BUT WITH ANY ACCUMULATION BECOMING LESS
LIKELY DURING THIS PERIOD.

RODRIGUEZ

&&

.AVIATION...

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

* NONE.

KJB

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

QUIET WEATHER CONDITIONS ARE EXPECTED TO CONTINUE THROUGH THE PERIOD
AT THE TERMINALS AS HIGH PRESSURE SLOWLY BUILDS EASTWARD TOWARDS THE
AREA ON SATURDAY. SKIES SHOULD REMAIN MOSTLY CLEAR AND WINDS SHOULD
REMAIN LIGHT OUT OF THE NORTHWEST.

KJB

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

* NONE.

KJB

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

SUNDAY...SNOW...MAINLY IN THE LATE AFTERNOON AND EVENING. IFR
CONDITIONS DEVELOPING LATE.

MONDAY...MVFR OR LOWER EARLY IMPROVING DURING THE DAY.

TUESDAY THROUGH THURSDAY...VFR.

KJB

&&

.MARINE...
245 PM CST

.SYNOPSIS...W TO NW FLOW WILL PERSIST ACROSS LAKE MI TONIGHT AND
INTO SAT EVENING. WEAKENING LOW PRESSURE E OF JAMES BAY CONTINUES
NE AND MERGES WITH ANOTHER LOW OFF OF THE NEW FOUNDLAND COAST THIS
EVENING. A LARGE STRONG RIDGE OF HIGH PRESSURE SPRAWLED FROM
WESTERN CANADA SE AND S TO THE SOUTHERN GREAT PLAINS CONTINUES TO
MOVE VERY SLOWLY SE AND SLIGHTLY WEAKENS AS IT BECOMES CENTERED
OVER SOUTHERN MN BY SAT EVENING. WINDS DIMINISH TO 10 KT OR LESS
OVERNIGHT SAT AS THE CENTER OF THE HIGH MOVES E OVER THE GREAT
LAKES. LOW PRESSURE WILL DEVELOP OVER THE SOUTHERN ROCKIES SAT
AFTERNOON AND REACH NE KS BY SUN EVENING. WINDS BECOME SE AND
FRESHEN DURING SUN AS THIS LOW APPROACHES THE UPPER MIDWEST AND
WESTERN GREAT LAKES. WINDS BECOME SW OVERNIGHT SUN AND THEN W AND
INCREASING TO STRONG BREEZES DURING MON AS THE LOW MOVES NNE FROM
THE U.P. OF MI INTO ONTARIO SWEEPING A COLD FRONT E ACROSS LAKE
MI. WINDS BACK TO OUT OF THE SW AND SLACKEN SOMEWHAT DURING MON AS
A RIDGE OF HIGH PRESSURE MOVES E ACROSS THE LAKE. WINDS BECOME W
AGAIN AND INCREASE TO NEAR GALE FORCE...POSSIBLY LOW END GALES...
TUE AS LOW PRESSURE MOVES E ACROSS LAKE SUPERIOR PULLING ANOTHER
COLD FRONT ACROSS THE WESTERN GREAT LAKES. THE STRONG WINDS...HIGH
WAVES AND COLD AIR ADVECTION ACROSS THE LAKE WILL LIKELY RESULT
IN FREEZING SPRAY ACROSS MUCH OF THE LAKE TUE AND TUE NIGHT.

TRS

&&

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

$$

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