Area Forecast Discussion
Issued by NWS Chicago, IL

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674
FXUS63 KLOT 040836
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
236 AM 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...
218 PM CST

SATURDAY THROUGH WEDNESDAY...

FOR THE WEEKEND...SFC HIGH PRESSURE IS EXPECTED TO SETTLE INTO THE
OHIO AND TENNESSEE VALLEY WHILE A SERIES OF WEAK CLIPPER-TYPE
SYSTEMS TRACK THROUGH THE UPPER GREAT LAKES.  THE FIRST IN THE
SERIES SHOULD TRACK TOO FAR NORTH TO HAVE ANY IMPACT ON THE LOCAL
AREA...BUT THE LONGER RANGE GUIDANCE IS SUGGESTING THAT THE SECOND
WAVE IN THE SERIES WILL TRACK A LITTLE FARTHER TO THE
SOUTH...BRINGING A CHANCE FOR PCPN BY SUNDAY EVENING.  WITH WARMING
AHEAD OF THE SYSTEMS...TEMPERATURES ON SATURDAY AND SUNDAY SHOULD
TOP OUT IN THE UPPER 30S TO MIDDLE 40S.  WITH SFC TEMPS WELL ABOVE
FREEZING INTO SUNDAY EVENING...ANY PCPN SHOULD START OUT AS
RAIN...BUT AS COOLER AIR FILTERS ACROSS THE REGION OVERNIGHT PCPN
SHOULD GRADUALLY CHANGE OVER TO A RAIN/SNOW MIX AND THEN ALL SNOW
LATE SUNDAY NIGHT INTO MONDAY MORNING.  THE LONGER RANGE GUIDANCE IS
ALSO ADVERTISING THAT A DEEP LOW PRESSURE SYSTEM WILL DEVELOP OFF
THE EAST COAST EARLY NEXT WEEK...WHICH WOULD ACT TO BLOCK THE
PROGRESSION OF THE SYSTEM DROPPING THROUGH THE WESTERN GREAT
LAKES...CAUSING THE SYSTEM TO STALL OUT OVER THE WRN GREAT LAKES.
THIS WOULD SET UP AN EXTENDED FETCH OF COLD AIR OUT OF CANADA
THROUGH MIDWEEK...KEEPING A CHANCE FOR SCATTERED LIGHT SNOW SHOWERS
ACROSS THE REGION WITH TEMPERATURES DROPPING INTO THE SINGLE DIGITS
TO LOWER TEENS BY TUESDAY NIGHT INTO WEDNESDAY MORNING WHILE HIGHS
SHOULD ONLY BE IN THE LOWER 20S.

KREIN

&&

.AVIATION...
FOR THE 06Z TAFS...

ANY LINGERING LIGHT SNOW SHOWERS ARE CURRENTLY EXITING TO THE EAST
OF THE TERMINALS...WITH PRIMARILY GYY BEING IMPACTED OVER THE NEXT
SEVERAL HOURS. MVFR CEILINGS WILL REMAIN IN PLACE FOR MOST OF
TONIGHT...BUT CLEARING LINE CAN BE SEEN PUSHING EAST TOWARDS RFD.
HAVE SPEED UP TIMING OF CLEARING LATE TONIGHT AND EARLY THURSDAY
MORNING FOR ALL THE TERMINALS...WITH ONLY VFR CEILINGS THEN
EXPECTED FOR THE REMAINDER OF THE FORECAST PERIOD. WESTERLY WINDS
WILL FURTHER DIMINISH OVERNIGHT INTO THURSDAY...GRADUALLY BECOMING
SOUTHWEST THURSDAY AFTERNOON.

RODRIGUEZ

&&

.MARINE...

131 PM...LOW PRESSURE NORTHEAST OF LAKE HURON WILL CONTINUE INTO
QUEBEC TONIGHT. A RIDGE OF HIGH PRESSURE WILL MOVE ACROSS THE LAKE
THURSDAY WITH ANOTHER WEAK TROUGH QUICKLY MOVING ACROSS THE LAKE
THURSDAY NIGHT. NORTHWEST WINDS TO 30 KT THIS EVENING WILL
DIMINISH TONIGHT AND TURN SOUTHWESTERLY THURSDAY AND THEN INCREASE
THURSDAY EVENING AHEAD OF THE WEAK TROUGH. ITS POSSIBLE THERE
COULD BE A BRIEF PERIOD OF 30KTS BUT WINDS SHOULD DIMINISH INTO
FRIDAY MORNING...SHIFTING MORE WEST/NORTHWEST. A LARGER HIGH WILL
THEN BUILD ACROSS THE SOUTHERN LAKES AND OHIO VALLEY FRIDAY...
EVENTUALLY MOVING OFF THE EAST COAST SUNDAY. ANOTHER WEAK LOW WILL
MOVE ACROSS ONTARIO FRIDAY NIGHT FOLLOWED BY HIGH PRESSURE
SATURDAY THAT WILL MOVE INTO QUEBEC SUNDAY. STRONG LOW PRESSURE IS
EXPECTED TO MOVE FROM SOUTHERN CANADA SATURDAY NIGHT TO THE
WESTERN LAKES SUNDAY NIGHT AND THEN POSSIBLY REMAIN NEARLY
STATIONARY OVER THE LAKES REGION INTO MONDAY NIGHT AS A STRONG LOW
MOVES NORTH...JUST OFFSHORE OF THE EAST COAST. CMS

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...INDIANA NEARSHORE WATERS UNTIL 3 AM THURSDAY.

&&

$$

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