Area Forecast Discussion
Issued by NWS Chicago, IL

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000
FXUS63 KLOT 042033
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
233 PM CST THU FEB 4 2016

.SHORT TERM...
232 AM CST

THROUGH SATURDAY NIGHT...

THE SHORT TERM PERIOD FEATURES RELATIVELY PROGRESSIVE NW FLOW...BUT
GENERALLY COOL AND QUIET CONDITIONS WITH VARIABLE CLOUDINESS.
CURRENT WATER VAPOR IMAGERY DEPICTS AN UPPER LEVEL SHORTWAVE
EMBEDDED IN A FAIRLY BROAD UPPER LEVEL TROUGH JUST EAST OF THE
AREA...WITH SEVERAL ADDITIONAL DISTURBANCES EMBEDDED IN THE NW
FLOW ON THE BACK EDGE OF THE UPPER TROUGH. A SURFACE HIGH IS
FOCUSED OVER THE SOUTHERN PLAINS...WITH A RIDGE EXTENDING THROUGH
THE MID MISSOURI VALLEY NORTH AND THROUGH MUCH OF THE UPPER
MISSISSIPPI VALLEY AS WELL. THERE IS A WEAK SURFACE TROUGH WHICH
IS HEADING EAST OF THE LOCAL AREA EARLY THIS MORNING. AHEAD OF THE
UPPER LOW AND IN WEAKLY CONVERGENT LOW LEVELS...A FEW ECHOES STILL
CONTINUING SUGGESTIVE OF SOME PASSING FLURRIES...WITH SOME LAKE
ENHANCEMENT OUT OVER THE OPEN WATERS.

THE LEADING SHORTWAVE WILL PASS EAST THIS MORNING WHICH SHOULD BRING
AN END TO MOST OF THE FLURRY ACTIVITY...WITH SOME LAKE EFFECT SNOW
SHOWERS LARGELY IMPACTING LOCATIONS IN SOUTHWEST MICHIGAN. THIS IS
ALSO SUPPORTED BY A DISTINCT CLEARING LINE IN 11-3.9 MICRON
SATELLITE IMAGERY. THE SURFACE RIDGE MOVES OVERHEAD THIS MORNING
WHICH WILL PROMOTE A PERIOD OF CLEARING SKIES...BUT IT WILL QUICKLY
TRANSLATE EASTWARD. THIS IS DUE TO A SECONDARY SHORTWAVE/CLIPPER IN
NW FLOW THAT WILL INCREASE CLOUD COVER AGAIN THIS AFTERNOON. IN
SPITE OF SOME SUNSHINE THIS MORNING...IT WILL BE A COLDER DAY WITH
HIGHS IN THE UPPER 20S TO LOW 30S. SINCE WE STAY ON THE NORTHERN
FRINGE OF THE RIDGE...WEST WINDS REMAIN ELEVATED MAKING IT FEEL A
BIT COLDER.

THIS SECONDARY WAVE AND ASSOCIATED WEAK SURFACE TROUGH MAY BRING A
FEW FLURRIES AND SOME CLOUDS TONIGHT...BUT IMPACTS WILL BE MINOR.
THE UP AND DOWN CONTINUES FRIDAY AS SURFACE RIDGING BUILDS
IN...ONLY TO BE FOLLOWED BY A SIMILAR INCREASE IN CLOUDS AND A
POSSIBLY SLIGHTLY STRONGER SHORTWAVE FRIDAY NIGHT. MODEL GUIDANCE
DEPICTS THAT ENERGY IN THIS TROUGH WILL NOT REMAIN
CONSOLIDATED...BUT BECOME SPLIT WITH SOME PASSING THROUGH
WISCONSIN WHILE A PORTION OF THE FORCING SHIFTS ALONG THE BASE OF
THE TROUGH AXIS FRIDAY NIGHT. WITH THIS IN MIND...MOST GUIDANCE
KEEPS THE LOCAL AREA DRY WITH BETTER CHANCES FOR SNOW SHOWERS
NORTH. THE NAM DOES DRIVE SOME OF THE SOUTHERN ENERGY THOUGH NE
ILLINOIS AND NW INDIANA...BUT AT THIS POINT HAVE HELD TO A GLOBAL
CONSENSUS FOR MOSTLY DRY CONDITIONS BUT WILL CARRY FLURRIES. AND
JUST LIKE CLOCKWORK...THE PATTERN REPEATS ITSELF SATURDAY NIGHT
INTO EARLY SUNDAY WITH HIGH PRESSURE RETURNING.

KMD

&&

.LONG TERM...
334 AM CST

SUNDAY THROUGH THURSDAY...

THE UP AND DOWN PARADE WILL TAKE A TURN SUNDAY INTO THE COMING
WEEK AS A MASSIVE RIDGE BUILDS ACROSS THE WEST. DOWNSTREAM
TROUGHING WILL LEAD TO AT LEAST A COUPLE DAY INTRUSION OF CANADIAN
AIR. SEVERAL PERIODS OF LIGHT SNOW APPEAR ON TAP FOR
SUNDAY...MONDAY...AND POSSIBLY TUESDAY. IT WILL GENERALLY BE ON
THE CLOUDIER SIDE AND BREEZY AS WELL INITIALLY...MAKING IT FEEL A
BIT MORE UNCOMFORTABLE. THE GFS IS MORE AGGRESSIVE WITH THE
COOLING...SNOW SHOWER COVERAGE...AND WIND SPEEDS THAN THE ECMWF AT
THIS POINT...BUT THE THEME IS FOR COLDER CONDITIONS WITH POSSIBLE
LIGHT SNOW AS ENSEMBLES INDICATE DECENT CONFIDENCE IN THIS DEEP
EASTERN CONUS TROUGH EVOLUTION DESPITE DISAGREEING SOME ON ITS
STRENGTH AND BREAKDOWN.

KMD

&&

.AVIATION...
FOR THE 18Z TAFS...

A WEAK STORM SYSTEM OVER THE UPPER MIDWEST WILL BE THE MAIN WEATHER-
MAKER ACROSS NORTHERN ILLINOIS AND NORTHWEST INDIANA THROUGH THE 18Z
TAF PERIOD.  A TRAILING WARM FRONT CURRENTLY OVER EASTERN IOWA WILL
SPREAD MID-LEVEL CLOUDS INTO THE AREA LATE THIS AFTERNOON AND
EVENING.  BASED ON SATELLITE TIMING TOOLS, VFR CEILINGS WILL ARRIVE
AT KRFD BY 21Z...THEN FURTHER EAST TO KORD AND KMDW BY 23Z.  WINDS
WILL INITIALLY BE FROM THE W/NW AT 10KT THEN WILL BACK TO THE S/SW
TOWARD EVENING.  WINDS WILL THEN VEER BACK TO THE W/NW LATE TONIGHT
INTO FRIDAY MORNING AS A COLD FRONT PASSES THROUGH THE REGION.
LATEST SATELLITE IMAGERY AND UPSTREAM OBS ARE SHOWING A NARROW BAND
OF MVFR CEILINGS IMMEDIATELY ALONG/BEHIND THE COLD FRONT.  BOTH THE
NAM AND RAPID REFRESH SUGGEST THESE LOWER CLOUDS WILL SPREAD ACROSS
THE KLOT TERMINALS LATE TONIGHT.  FORECAST SOUNDINGS ARE SHOWING
MVFR CEILINGS ARRIVING AT KRFD AT 08Z...THEN FURTHER EAST TO KORD
AND KMDW BY 11Z.  THESE CLOUDS WILL THEN CLEAR FROM WEST TO EAST
LATE FRIDAY MORNING INTO FRIDAY AFTERNOON.


BARNES

&&

.MARINE...
232 PM CST

BROAD SURFACE HIGH PRESSURE STRETCHES FROM THE TENNESSEE VALLEY
NORTH THROUGH CENTRAL ONTARIO...RESULTING IN A LIGHT WEST FLOW
ACROSS LAKE MICHIGAN THIS AFTERNOON. SURFACE RIDGE WILL SHIFT EAST
FRIDAY...ALLOWING ANOTHER LOW PRESSURE SYSTEM TO SLIDE EAST ACROSS
THE UPPER MIDWEST TO NORTH OF LAKE SUPERIOR FRIDAY NIGHT INTO
SATURDAY. THIS WILL LIKELY INCREASE THE GRADIENT AND WINDS FROM THE
WEST TO SOUTHWEST...WITH SPEEDS INCREASING TO AROUND 25 TO 30 KT
ACROSS THE NORTHERN HALF OF THE LAKE THROUGH SAT MORNING. FURTHER
SOUTH THE GRADIENT ARRIVES AFTER DAYBREAK SAT WITH SPEEDS BETWEEN 20-
25KT SAT. THEN A WEAK GRADIENT SLIDES BACK ACROSS THE LAKE SATURDAY
NIGHT THROUGH EARLY SUNDAY...BEFORE A MUCH STRONGER LOW PRESSURE
SYSTEM DIVES SOUTHEAST FROM CENTRAL CANADA SUNDAY AFTERNOON. THIS
SYSTEM WILL BRING COOLER AIR TO THE WESTERN GREAT LAKES SUNDAY
EVENING...ALONG WITH WINDS INCREASING FROM THE SOUTHWEST BETWEEN 20-
25KT AND POSSIBLY NEARING 30 KT ACROSS THE NORTHERN HALF OF THE LAKE
BY SUNDAY EVENING THROUGH MONDAY MORNING. THE LOW PRESSURE WILL THEN
SLIDE SOUTHEAST ACROSS CENTRAL WISCONSIN AND SLOW AS IT APPROACHES
CENTRAL LAKE MICHIGAN MONDAY EVENING...ALLOWING THE BRIEF LULL IN
THE GRADIENT THROUGH MONDAY NIGHT...BEFORE INCREASING AND TURNING
NORHT/NORTHWEST HEADING INTO TUESDAY AND NEARING 30KT WITH A FEW
GALES POSSIBLE.

BEACHLER

&&

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

$$

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