Area Forecast Discussion
Issued by NWS Chicago, IL

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000
FXUS63 KLOT 282337
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
537 PM CST SAT FEB 28 2015

.SHORT TERM...
318 PM CST

MAIN CONCERNS ARE WITH SNOW POTENTIAL THIS EVENING THROUGH SUNDAY
WITH THE FOCUS FOR MORE ACCUMULATING SNOW SOUTH OF I-80...AND THEN
WITH ANOTHER SYSTEM VARYING PRECIP MONDAY NIGHT INTO TUESDAY.

THROUGH MONDAY...

LATEST RADAR IMAGERY DEPICTING LARGE AREA OF LIGHT TO MODERATE
SNOW PUSHING NORTHEAST THROUGH PORTIONS OF THE PLAINS AND MID
MISSISSIPPI VALLEY...STEADILY APPROACHING CENTRAL ILLINOIS AT THIS
TIME. THIS AREA OF SNOW IS RIDING ALONG A FAIRLY ENERGETIC SHORT
WAVE...AND STRONG/BROAD WAA. AS THIS WAVE LIFTS NORTHEAST THIS
AFTERNOON AND EARLY EVENING THE FOCUS OF THIS WAA WILL LIKELY WISE
SHIFT EAST...WITH THIS LIGHT SNOW TO AT TIMES MODERATE SNOW
SPREADING OVER MOST OF NORTHERN ILLINOIS AND NORTHWEST INDIANA BY
EARLY TO MID EVENING. WHILE THE BEST FORCING WILL REMAIN ACROSS
THE SOUTHEAST HALF OF THE CWA THROUGH THIS EVENING...BROAD ASCENT
SHOULD STILL BRING AT LEAST A PERIOD OF LIGHT SNOW FOR EVEN AREAS
NEAR THE ILLINOIS/WISCONSIN BORDER. SO DO HAVE LIKELY POPS FOR
AREAS UP NORTH AND THEN CATEGORICAL POPS SOUTHERN HALF OF THE CWA
BY THIS EVENING. WHILE A PERIOD OF LIGHT SNOW IS EXPECTED THIS
EVENING DO FEEL THAT BRIEF BURSTS OF MODERATE SNOW COULD FALL AT
TIMES AND WHILE MORE THAN LIKELY A LOW QPF EVENT...A DEEP DGZ WILL
RESULT IN FAIRLY EFFICIENT SNOW WITH A DUSTING UP TO AN INCH OF
SNOW LIKELY ALONG AND NORTH OF INTERSTATE 88...AND 1 TO 2 INCHES
SOUTH BY AROUND MIDNIGHT TONIGHT. WITH REGARDS TO START
TIMES...PONTIAC SHOULD START OBSERVING SNOW BY 23-00Z WITH AREAS
FROM ROCKFORD TO CHICAGO...TO VALPARAISO BY THE 2-3Z TIME FRAME.
DO EXPECT A 3-4 HOUR WINDOW OF THIS SNOW BEFORE THIS SNOW LIKELY
EXITS.

THERE WILL LIKELY BE A WINDOW WHEN THE SNOW STOPS AND THEN MOVES
BACK ACROSS THE SOUTHERN CWA LATE TONIGHT INTO EARLY SUNDAY
MORNING...WITH THE SNOW THIS EVENING AND THEN ADDITIONAL SNOW
TOMORROW ALMOST TWO SEPARATE EVENTS. INCREASING FLOW ALOFT AND
ADDITIONAL SHORTWAVE ENERGY SHOULD ALLOW THE SNOW TO RETURN BUT
WITH THE FOCUS FROM THIS POINT FORWARD TO REMAIN SOUTH OF
INTERSTATE 80...AND WITH AREAS TO THE NORTH LIKELY ONLY OBSERVING
ADDITIONAL FLURRIES...IF THAT. ONCE AGAIN EXPECT A PERIOD OF LIGHT
SNOW WITH THE POSSIBILITY FOR BRIEF HEAVIER SNOWFALL WITH ANY
POTENTIAL FGEN BANDING THROUGH AT LEAST MIDDAY SUNDAY WITH ANY
REMAINING SNOW EXITING INTO THE AFTERNOON. THE HIGHEST SNOWFALL
AMOUNTS DO REMAIN FAIRLY SIMILAR TO THE PREVIOUS FORECAST AS WELL
AS EVEN THE LOCATION. THROUGH SUNDAY AFTERNOON...TOTAL SNOWFALL IS
EXPECTED TO RANGE FROM A DUSTING UP TO 2 INCHES NORTH OF THE I-80
CORRIDOR WITH 2 TO 5 INCHES SOUTH. HOWEVER...SOUTHERN PORTIONS OF
FORD... IROQUOIS...AND BENTON COUNTIES MAY STILL SEE ISOLATED
AMOUNTS NEAR 6 INCHES IF THE BETTER BANDING WERE MATERIALIZE. THE
LONG DURATION OF THIS LIGHT SNOW AS WELL AS THE ANTICIPATED BREAK
IN SNOWFALL TONIGHT BEFORE STARTING UP ONCE AGAIN SUNDAY MORNING
SHOULD HELP TO LIMIT IMPACTS...AND SO HAVE NOT ISSUED ANY
HEADLINES AT THIS TIME BUT WILL CONTINUE THE SPS.

RODRIGUEZ

&&

.LONG TERM...
318 PM CST

MONDAY NIGHT THROUGH SATURDAY...

FOCUS NEXT WEEK CONTINUES TO BE WITH LARGER SYSTEM TO AFFECT MUCH
OF TH REGION EARLY NEXT WEEK THROUGH MID WEEK...AND LOCALLY MONDAY
NIGHT INTO TUESDAY. HIGHLY AMPLIFIED PATTERN STILL ANTICIPATED
WITH APPROACHING LONGWAVE THROUGH EXPECTED TO STEER A SURFACE LOW
ACROSS THE AREA MONDAY NIGHT INTO TUESDAY. WARM/MOIST ADVECTION
OUT AHEAD OF THIS SYSTEM WILL HELP SPREAD PRECIP ACROSS THE CWA
LATE MONDAY NIGHT AND EARLY TUESDAY MORNING. LATEST GUIDANCE TODAY
INDICATING THAT INITIAL PROFILES WILL BE SUPPORTIVE OF SNOW AT THE
ONSET...AND THEN WITH A WINTRY MIX LIKELY ACROSS THE ENTIRE CWA
THROUGH TUESDAY MORNING. A TRANSITION OVER TO ALL RAIN IS STILL
EXPECTED THROUGHOUT THE DAY ON TUESDAY BUT SOME GUIDANCE HINTING
AT A POSSIBLE COLDER SOLUTION FOR THE CWA. IF THIS WERE TO
MATERIALIZE...THEN LESS OF THE CWA...LIKELY FAR NORTHERN
ILLINOIS...WOULD OBSERVE LESS RAIN AND MORE FROZEN TYPE PRECIP.
THIS WOULD ALSO RESULT IN MORE A TRANSITION OVER TO ALL SNOW BY
TUESDAY AFTERNOON. HOWEVER THIS PANS OUT...TUESDAY MORNING IS
STILL A PERIOD TO MONITOR CLOSELY WITH THE VARYING PRECIP TYPE AND
THEN STILL POSSIBLE HYDRO ISSUES WITH RAIN AND SNOW MELT.

RODRIGUEZ

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 00Z...

* PERIOD OF LIGHT SNOW AND IFR VSBY DEVELOPING LATER THIS EVENING
* MVFR CIGS OVERNIGHT INTO SUNDAY MORNING

IZZI

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

AN UPPER LEVEL DISTURBANCE WILL MOVE ACROSS THE AREA TONIGHT
BRINGING A GLANCING BLOW OF SNOW TO THE TERMINALS LATER THIS
EVENING...POSSIBLY JUST MISSING RFD TO THE SOUTH. BASED ON
UPSTREAM OBS WOULD APPEAR A PERIOD OF IFR VSBY WILL OCCUR WITH THE
LIGHT SNOW THOUGH ONLY EXPECTING MINOR ACCUMS AT THE TERMINALS.
MVFR CIGS WILL DEVELOP WITH THE SNOW AND LIKELY LINGER THROUGH
SUNDAY MORNING BEFORE PROBABLY TRENDING TOWARD LOW END VFR SUNDAY
AFTERNOON.

IZZI

//ORD AND MDW CONFIDENCE...UPDATED 00Z...

* MEDIUM CONFIDENCE IN SNOW AND ASSOCIATED VSBY TONIGHT
* MEDIUM CONFIDENCE IN CIGS OVERNIGHT/SUNDAY
* HIGH CONFIDENCE IN REMAINING FORECAST ELEMENTS

IZZI

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

MONDAY...VFR.

TUESDAY...RAIN...FREEZING RAIN...OR SNOW. IFR PROBABLE.

WEDNESDAY...MVFR CIGS POSSIBLE.

THURSDAY AND FRIDAY...MAINLY VFR.

IZZI

&&

.MARINE...
249 PM CST

VISIBLE SATELLITE IMAGERY TODAY SHOWS THAT MUCH OF THE LAKE IS ICE
BOUND EXCEPT FOR A NARROW CORRIDOR FROM THE SOUTH CENTRAL PORTION TO
JUST NORTHWEST OF MANISTEE HARBOR. THE ICE IS LIKELY TO FURTHER
EXPAND THROUGH MONDAY NIGHT AS A COLD AIR MASS REMAINS OVER THE LAKE.
SOUTH-SOUTHWEST WINDS WILL REACH 20-25 KT AT TIMES THROUGH SUNDAY
AFTERNOON OVER THE CENTRAL AND NORTHERN PORTIONS OF THE LAKE. A COLD
FRONT WILL THEN CROSS THE LAKE SUNDAY EVENING...WITH A BRIEF PERIOD
OF NORTHWEST WINDS UP TO 30 KT ON THE SOUTHERN PORTION OF THE LAKE.
ANOTHER LARGE HIGH PRESSURE WILL APPROACH ON MONDAY...RESULTING IN
DIMINISHING WINDS. THE HIGH WILL SHIFT EAST ON MONDAY NIGHT INTO
TUESDAY AS LOW PRESSURE APPROACHES FROM THE CENTRAL PLAINS...RESULTING
IN SOUTHERLY WINDS PICKING UP TO 20 TO 25 KT BY TUESDAY MORNING.
MOST MODEL GUIDANCE HAS TRENDED WEAKER WITH SYSTEM OVERALL. THIS
WOULD MAKE TOP END NORTHWEST WIND SPEEDS TO 30 KT OVER THE CENTRAL
AND SOUTHERN PORTION OF THE LAKE MORE LIKELY THAN GALES TUESDAY
NIGHT AND WEDNESDAY BEHIND THE LOW. IF THE LOW IS STRONGER...GALES
WOULD STILL BE POSSIBLE. YET ANOTHER EXPANSIVE HIGH PRESSURE AREA
WILL MOVE TO THE MID MISSISSIPPI VALLEY BY THURSDAY...WITH
INCREASING SOUTHWEST WINDS AS THE HIGH SLIDES SOUTHEAST THURSDAY
NIGHT.

RC

&&

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

$$

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