Area Forecast Discussion
Issued by NWS Chicago, IL

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FXUS63 KLOT 071646
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1046 AM CST SUN FEB 7 2016

.UPDATE...
1045 AM CST

NO BIG CHANGES TO GOING FORECAST. BREEZY AND MILD CONDITIONS ARE
IN PLACE IN THE WARM SECTOR OF THE CLIPPER LOW ALONG THE MN/CANADA
BORDER. BASED OFF PROGGED AND OBSERVED LOWER LEVEL THERMAL
PROFILES...ADJUSTED TEMPS UPWARD A DEGREE OR TWO IN MANY
LOCATIONS...WITH HIGHS AS WARM AS 48-49 FAVORED ALONG/EAST OF
I-55. ALSO MADE ADJUSTMENTS TO SKY COVER TRENDS...WITH A POCKET OF
SOME CLEARING IN THE MID/HIGH CLOUDS ESPECIALLY NORTH OF I-88
THROUGH EARLY AFTERNOON. LOOKING AHEAD TO SNOW SHOWERS TONIGHT
INTO EARLY MONDAY...TREND IS FOR A SLOWER ARRIVAL FROM THE
NORTHWEST AND PERHAPS BEST FOCUS INTO NORTH CENTRAL IL SOUTH OF
I-80. WILL ADDRESS THIS IN THE AFTERNOON FORECAST UPDATE.

RC

&&

.SHORT TERM...
322 AM CST

THROUGH TUESDAY...

ACCUMULATING SNOW TONIGHT THROUGH TUESDAY...PLEASE SEE THE SNOWFALL
TOTAL SECTION BELOW FOR SPECIFIC DETAILS. BELOW ZERO WIND CHILLS
FOLLOW THE SNOW TUESDAY NIGHT.

THE NEXT SYSTEM IS PUSHING INTO MINNESOTA THIS MORNING. A FEW LIGHT
ECHOES ARE ON RADAR...BUT NO PRECIP IS MAKING IT TO THE GROUND.  THE
UPPER LEVEL TROUGH WILL MOVE OVER THE UPPER MIDWEST TODAY AND THE
SURFACE LOW WILL BECOME CENTERED OVER WISCONSIN. WHILE A VORT
STREAMER ASSOCIATED WITH THE TROUGH WILL ROTATE THROUGH THIS
AFTERNOON AND EVENING...FORECAST SOUNDINGS ARE VERY DRY. THEREFORE
LOOKING AT A DRY DAY WITH SOUTHWEST WINDS AND WAA HELPING TEMPS RISE
INTO THE MID TO UPPER 40S.  DEFINITELY ENJOY IT BECAUSE THE PATTERN
WILL BE SHIFTING OVER THE NEXT COUPLE OF DAYS.

THE TROUGH AND SURFACE LOW SLOWLY SHIFT EAST THROUGH EARLY WEEK.
THIS WILL LEAD TO AN EXTENDED PERIOD OF LIGHT SNOW SHOWERS TONIGHT
THROUGH TUESDAY.  THE COLUMN SATURATES LATE THIS EVENING OVER NORTH
CENTRAL IL. PRECIP MAY INITIALLY FALL AS RAIN...BUT EXPECTING IT TO
QUICKLY TURN OVER TO SNOW AS THE COLUMN AND SURFACE COOLS.  SNOW
SPREADS EAST OVERNIGHT AND THERE COULD BE PERIODS OF LOW VISIBILITY
MONDAY DUE TO AN ABUNDANCE OF LARGE SNOWFLAKES. SNOWFALL RATES WILL
VARY...BUT A DEEP DGZ OF 5000-7000 FT WILL LIKELY LEAD TO LARGE
DENDRITES. THE LARGE FLAKES HAVE KNACK FOR REDUCING VISIBILITY
SIGNIFICANTLY...THEREFORE THOSE WITH TRAVEL PLANS MONDAY SHOULD PLAN
EXTRA TIME JUST IN CASE THEY ENCOUNTER POOR VISIBILITY.  STEADY SNOW
CONTINUES TUESDAY WITH HIGHS ONLY IN THE UPPER TEENS TO MID 20S.
GUSTY WINDS COULD RESULT IN AREAS OF BLOWING SNOW TUESDAY ESPECIALLY
IN OPEN AREAS.

THE TROUGH SHIFTS EAST TUESDAY AFTERNOON AND NIGHT LEADING TO A
GRADUAL WEST TO EAST END TO THE SNOW. SNOW WILL LINGER THE LONGEST
OVER PORTER COUNTY INDIANA DUE TO LAKE EFFECT SNOW.

SNOWFALL TOTALS...WEST OF I-39 WILL SEE 1-3 INCHES...THEN 2-4 INCHES
EAST OF I-39. LAKE AND PORTER COUNTIES IN INDIANA WILL HAVE THE
HIGHEST TOTALS OF 4-6 INCHES.  LOCALLY HIGHER AMOUNTS ARE POSSIBLE
ACROSS THE WARNING AREA TO DO MESOSCALE ENHANCEMENTS.

THE OTHER CONCERN IS ARCTIC AIR WILL REACH THE REGION TUESDAY NIGHT
AS THE HEART OF THE TROUGH SITS OVERHEAD.  LOW TEMPS WILL BE IN THE
SINGLE DIGITS AND WIND CHILLS WILL VARY BETWEEN 5 AND 15 BELOW
ZERO.

JEE

&&

.LONG TERM...
322 AM CST

WEDNESDAY THROUGH SUNDAY...

LAKE EFFECT SNOW MAY LINGER OVER NW INDIANA WEDNESDAY...BUT
EXPECTING DRY AND COLD CONDITIONS OTHERWISE. COULD SEE A FEW BREAKS
IN THE CLOUDS AND THE FRESH SNOWPACK COULD RESULT IN COLDER THAN
FORECAST TEMPERATURES.  WEDNESDAY NIGHT ALSO LOOKS COLD WITH WIND
CHILLS BETWEEN 5 AND 10 BELOW ZERO. OVERNIGHT TEMPS COULD BE EVEN
COLDER IF CLOUDS CLEAR OUT AS THE SURFACE HIGH BUILDS IN.

THE REST OF THE WEEK LOOKS DRY WITH ONLY A SLIGHT CHANCE OF LAKE
EFFECT SNOW OVER NW INDIANA.  GUIDANCE DIFFERS GREATLY IN THE UPPER
LEVEL PATTERN. THE GFS SUGGESTS WE WOULD WARM ALOFT THROUGH SATURDAY
WHILE THE ECMWF HOLDS A TROUGH AND ARCTIC AIR OVERHEAD. DID NOT
ADJUST SUPERBLEND TEMPS SINCE THE TEMPS ARE BETWEEN THE TWO
SOLUTIONS.

JEE

&&

.AVIATION...
FOR THE 12Z TAFS...

THE CONCERNS FOR THE TAFS ARE NEAR LLWS CRITERIA WINDS OFF THE
DECK EARLY THIS MORNING...THEN OF BROADER CONCERN MVFR CIGS LATE
TONIGHT INTO MONDAY WITH SCATTERED TO NUMEROUS IFR SNOW SHOWERS IN
THE REGION.

SOUTHWEST SURFACE WINDS WILL QUICKLY INCREASE AFTER DAYBREAK
HELPING TO EASE ANY SHARP VERTICAL INCREASE AND LLWS. GUSTS OF
20-25 KT ARE EXPECTED THIS MORNING THROUGH MID-AFTERNOON.
OTHERWISE TODAY AND THIS EVENING WILL BE FAIRLY QUIET FOR AREA TAF
SITES. AN INITIAL COLD FRONT WILL PASS LATE TONIGHT USHERING IN
MVFR CIGS WITH HIGH CONFIDENCE. THE PROFILES BEHIND THIS FRONTAL
PASSAGE SUPPORT PROBABLE SNOW SHOWERS...SOME OF WHICH COULD
BE BRIEFLY ROBUST IN INTENSITY. CONFIDENCE IN TIMING IS MEDIUM-
HIGH BUT IN COVERAGE AND HOW LOW THE VISIBILITY WILL DROP IS MORE
LOW-MEDIUM. THE WEST WINDS BEHIND THIS FRONT WILL NOT PICK UP
MUCH...BUT AFTER A SECONDARY PUSH OF COLDER AIR MONDAY MORNING
THEY WILL...WITH GUSTS OF 20 KT OR HIGHER.

OVERALL IT APPEARS AREAS OF SNOW SHOWERS WILL EXIST FROM LATE
TONIGHT THROUGH TUESDAY...THOUGH VARYING DEGREES OF COVERAGE.
LIGHT ACCUMULATION IS LIKELY WITH ANY SNOW SHOWERS AS
TEMPERATURES COOL. A LONG DURATION SNOWFALL TOTAL OF 1 TO 3
INCHES IS PRESENTLY EXPECTED AT ORD AND MDW.

MTF

&&

.MARINE...
148 AM CST

THE LAKE MICHIGAN WEATHER FROM TODAY THROUGH WEDNESDAY WILL BE
ENTIRELY INFLUENCED BY A STRONG LOW PRESSURE DIVING IN FROM CANADA
LATER TODAY THAT WILL THEN DRIFT EAST OVER THE GREAT LAKES. THE
SOUTHWEST WINDS AHEAD OF THIS WILL BE AROUND OR A TAD ABOVE 30 KT
THIS MORNING OVER THE OPEN WATER...AND SOME 22-25 KT GUSTS IN THE
ILLINOIS AND INDIANA NEARSHORE. AT THIS TIME AM LEANING ON NOT
HAVING A SMALL CRAFT ADVISORY TODAY DUE TO LACK OF DURATION OF
THESE WINDS AND THE CONFIDENCE IN DEGREE OF MIXING BEING LOWER
THAN TYPICAL FOR A FORECAST ONLY 6 TO 12 HOURS FROM NOW. WILL
ASSESS TRENDS THROUGH DAYBREAK THOUGH AND IF THEY ARE OUTPACING
THE FORECAST THEN WILL ISSUE AN ADVISORY.

AS THE NORTHWEST FLOW ON THE BACKSIDE OF THE LOW BEGINS TO WRAP IN
ON MONDAY...SMALL CRAFT CRITERIA IS VERY LIKELY TO BE SEEN IN THE
NEARSHORE. AS FOR THE OPEN WATER...THE POTENTIAL FOR GALES
DEFINITELY EXITS FOR AT LEAST TIMES IN THE MONDAY NIGHT THROUGH
TUESDAY NIGHT WINDOW. THE LOW IS FORECAST TO SLOW DUE TO A VERY DEEP
LOW LIFTING NORTHWARD OFF THE EASTERN U.S. SEABOARD. SO THIS THROWS
CONTINUED UNCERTAINTY ON HOW FAST THE LOW WILL MOVE EASTWARD AND
THUS THE DEGREE OF PRESSURE GRADIENT AND COLD ADVECTION COUPLED OVER
THE OPEN WATERS FOR GALES. WILL NOTE SOME GALES IN THE GLF AND
CONTINUED LIGHT FREEZING SPRAY CHANCES.

MTF

&&

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

$$

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