🚀 go-pugleaf

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1231 PM CST MON FEB 4 2013

DISCUSSION...
1230 PM CST

HAVE OPTED TO EXTEND THE ADVISORY FOR LAKE AND COOK COUNTIES IN
NORTHEAST IL DUE TO LAKE INDUCED SNOW BAND MOVING TOWARD SHORE
EARLY THIS AFTERNOON.

THE MAIN SYNOPTIC EVENT THAT BROUGHT TWO TO FOUR INCHES OF SNOW
EARLIER THIS MORNING HAS EXITED...BUT WITH ITS DEPARTURE AND
NORTHEAST FLOW HAS DEVELOPED LAKE EFFECT SNOW. A PRONOUNCED BAND
FIRST SEEN ON VISIBLE SATELLITE NOW IS BECOMING BETTER DEFINED ON
THE TMKE RADAR. REFLECTIVITY HAS BEEN AS HIGH AS 30 DBZ AT TIMES
WITH THIS INDICATING LIKELY GOOD BURSTS OF SNOW. THE CONVERGENCE
SEEN ON SATELLITE AND RADAR LINES UP WELL WITH RAP AND NAM
DEPICTING IN THE LOWER LEVELS AND THE TREND HAS BEEN TO SLOW THIS
REORIENTING EASTWARD TOWARD NORTHWEST IN. THUS A FEW HOURS OF
SNOWFALL THIS AFTERNOON ARE FAVORED INTO EASTERN LAKE AND COOK
COUNTIES. EQUILIBRIUM LEVELS ARE SOMEWHAT LOW BEING AROUND
5000-6000 FT AND WIND SHEAR IN THE CLOUD DEPTH IS ALSO A LITTLE
HIGH /GREATER THAN 30 KT/...WHICH TOGETHER WILL LIKELY LIMIT
HEAVIER RATES FROM BEING WIDESPREAD OR TO MAKE IT FAR INLAND.
OTHER FACTORS SUCH AS THE CONVERGENCE...MOISTURE...AND INSTABILITY
ARE CONDUCIVE THOUGH FOR THE SNOW TO AT LEAST MAKE IT ONSHORE. SO
UNCERTAINTIES ON INTENSITY WOULD NORMALLY MEAN HOLDING OFF A
HEADLINE...HOWEVER THE WINTER WEATHER ADVISORY HAD BEEN ALLOWED TO
GO TO NOON ORIGINALLY FOR THE THREAT OF AT LEAST TEMPORARY
HEAVIER RATES AND BRINGING ADDITIONAL SNOWFALL TO WHAT HAS FALLEN.
WITH THE BAND/AREA OF SHOWERS OF SNOW MOVING INTO FAR NORTHEAST
ILLINOIS SHORTLY...SEE IT AS MORE PRUDENT TO CONTINUE ADVISORY.

MTF

&&

//PREV DISCUSSION...
419 AM CST

MAIN CONCERN FOR THE NEXT FEW DAYS WILL BE THE CONTINUED PERIODIC
CHANCES FOR SNOW.

BEGINNING TO FEEL LIKE A BROKEN RECORD...REMEMBER RECORDS?...TALKING
ABOUT CLIPPERS BRINGING LIGHT SNOW TO NORTHERN ILLINOIS AND
NORTHWESTERN INDIANA...BUT THE MAIN CONCERN FOR THE REMAINDER OF THE
NIGHT AND INTO THE MORNING HOURS WILL BE THE ONGOING SNOW FALLING
OVER PORTIONS OF THE AREA. WHILE THE LOT RADAR IS STILL READING TOO
HIGH DUE TO MECHANICAL ISSUES...IT DOES INDICATE AN AREA OF SNOW
FALLING NORTH OF A LINE ROUGHLY FROM DIXON...TO JOLIET...TO
VALPARAISO.  THIS SNOW IS ASSOCIATED WITH A MID LEVEL VORT MAX
TRACKING THROUGH THE AREA.  WHILE LIGHT...TO OCCASIONALLY MODERATE
SNOW HAS BEEN FALLING SINCE EARLY LAST EVENING...THERE IS A VERY
SHARP CUTOFF TO THE SNOW WITH LITTLE OR NO SNOW FALLING SOUTH OF THE
AFOREMENTIONED LINE.  EXPECT THIS TREND TO CONTINUE ACROSS THE AREA
THROUGH THE REMAINDER OF THE NIGHT AND INTO THE MORNING HOURS...BUT
AS THE MID LEVEL IMPULSE AND THE ASSOCIATED WEAK SFC LOW BEGIN TO
MOVE EAST OF THE AREA...SOME LIGHT SNOW SHOULD BEGIN TO SPREAD
SOUTHWARD...PERHAPS JUST SOUTH OF THE ILLINOIS AND KANKAKEE RIVERS.
HAVE RECEIVED ONLY A FEW SNOWFALL REPORTS THIS MORNING...BUT WHAT
OBSERVATIONS HAVE BEEN RECEIVED INDICATE THAT 2 TO 3 INCHES HAVE
FALLEN OVER NORTH-CENTRAL ILLINOIS...WHERE THE SNOW HAS BEEN FALLING
THE LONGEST...WITH LESSER AMOUNTS TO THE EAST.  WITH ACCUMULATING
SNOW EXPECTED TO CONTINUE OVER MUCH OF THE AREA UNTIL UNTIL LATE
MORNING BEFORE TAPERING OFF TO FLURRIES BY EARLY AFTERNOON...THE
MORNING RUSH HOURS FOR TRAVELERS WILL BE HAZARDOUS...ESPECIALLY ON
UNTREATED OR UNPLOWED ROADS.  WHEN ALL IS SAID AND DONE FOR THE
SYNOPTIC SNOW...GENERALLY EXPECT TOTALS OF 2 TO 4 INCHES NORTH OF
THE DIXON...TO JOLIET...TO VALPARAISO LINE AND LESSER AMOUNTS TO THE
SOUTH.

BY THIS AFTERNOON...THE FOCUS WILL SHIFT TO LAKE EFFECT SNOW
POTENTIAL FOR NORTHWESTERN INDIANA.  SOME OF THE HIGH RESOLUTION
MODEL GUIDANCE INDICATES THE POTENTIAL FOR A MESO-VORTEX TO FORM
OVER THE SOUTHERN LAKE MICHIGAN WITH A CONVERGENCE ZONE EXTENDING
NORTHWARD.  HAVE GENERALLY FOLLOWED THIS IDEA AND BACKED OFF ON THE
LAKE EFFECT SNOW POTENTIAL FOR FAR NERN ILLINOIS AND CONCENTRATED
THE LAKE EFFECT SNOW FORECAST OVER NWRN INDIANA...SINCE THE
MESO-VORTEX WOULD SHIFT WINDS INVOF THE ILLINOIS SHORE OF LAKE
MICHIGAN TO AN OFF-SHORE DIRECTION.  GIVEN THE HIGHLY LOCALIZED
NATURE OF LAKE EFFECT SNOW ASSOCIATED WITH THESE TYPES OF
FEATURES...HAVE SOMEWHAT BROAD BRUSHED THE LAKE EFFECT
POTENTIAL...WITH THE POTENTIAL FOR A COUPLE INCHES OF LAKE EFFECT
SNOW AND LOCALLY HIGHER AMOUNTS POSSIBLE.

THE UPPER LEVEL PATTERN IS FINALLY SHOWING INDICATIONS OF DECREASING
AMPLITUDE AS PACIFIC SHORT WAVE ENERGY BEGINS TO BREAK DOWN THE WEST
COAST RIDGE.  ALSO...THE EAST COAST TROUGH IS BROADENING AND
FLATTENING.  HOWEVER...THE LOCAL AREA IS STILL UNDER FAST NWLY FLOW
ALOFT AND THE NEXT IS THE SERIES OF CLIPPERS IS EXPECTED TO IMPACT
THE REGION ON TUESDAY.  THIS SYSTEM IS STILL BEING ADVERTISED TO BE
A BIT LESS FOCUSED AND SHOULD TAKE A MORE NORTHERLY TRACK ACROSS
THE MIDWEST AND GREAT LAKES REGIONS.  SO...STILL EXPECT THE HEAVIEST
SNOWFALL AMOUNTS TO BE WELL NORTH OF THE WISCONSIN BORDER.  AS FOR
TIMING...EXPECT THE INITIAL SNOW TO MOVE INTO THE FAR NORTHERN
PORTIONS OF THE CWA EARLY TUESDAY MORNING AND THEN SPREAD SOUTH AND
EAST.  AGAIN...IT LOOKS LIKE THE FAR SOUTHERN COUNTIES OF THE CWA
WILL SEE LITTLE OR NO SNOW WHILE THE FAR NORTHERN COUNTIES MAY SEE 1
TO 2 INCHES BEFORE COMING TO AN END IN THE LATE AFTERNOON HOURS.

FOR THE LONGER TERM...FROM WEDNESDAY THROUGH NEXT WEEKEND...THE
LONGER RANGE MODEL GUIDANCE IS STILL IN VERY GOOD AGREEMENT ON
BREAKING DOWN THE UPPER LEVEL LONG WAVE PATTERN AND BECOMING MORE
PROGRESSIVE.  THIS WILL ALLOW FOR TEMPERATURES TO MODERATE WITH
HIGHS IN THE UPPER 30S TO MIDDLE 40S...WITH SOME UPPER 40S POSSIBLE
OVER THE SOUTHERN PORTIONS OF THE CWA.  ALSO...AS THE UPPER LEVEL
PATTERN FLATTENS...MORE PACIFIC SHORT WAVE ENERGY WILL BE ABLE TO
IMPACT THE AREA...BRINGING PERIODIC CHANCES FOR RAIN AS WELL AS SOME
SNOW...BUT WITH THE WARMING TREND...ANY SNOW SHOULD BE ON THE
WET...SLUSHY SIDE.

KREIN

&&

AVIATION...

//ORD AND MDW CONCERNS...UPDATED 18Z...

* WINDS GRADUALLY SHIFTING FROM EAST TO NORTHEAST AND THEN NORTH-
  NORTHWEST THIS AFTERNOON. SPEEDS UP TO 12-14 KT.

* AREAS OF LAKE-ENHANCED SNOW IN THE CHICAGO METROPOLITAN AREA
  EXPECTED TO REMAIN EAST OF ORD AND MDW.

PAW

//DISCUSSION...UPDATED 18Z...

LOW PRESSURE CENTER IN CENTRAL IL WILL MOVE EAST THIS AFTERNOON.
THIS WILL ALLOW WINDS TO SHIFT MORE TO THE NORTHEAST AND THEN
NORTH-NORTHWEST DURING THE AFTERNOON. THE EASTERLY WINDS FROM
THIS MORNING ARE SUPPORTING SOME BANDS OF LAKE-ENHANCED SNOW OVER
THE CHICAGO METROPOLITAN AREA AT MIDDAY. AS WINDS SHIFT AROUND
THESE AREAS WILL MOVE CLOSER TO THE LAKE AND THEN INTO NORTHWEST
INDIANA. AT THIS TIME IT APPEARS THAT ONLY GYY WOULD BE VULNERABLE
TO SEEING SOME OF THIS SNOW AND EVEN THERE CONFIDENCE IS LOW.

ANOTHER IN THE SERIES OF CLIPPER SYSTEMS WILL BE MOVING ACROSS THE
TERMINALS ON TUESDAY. THIS ONE WILL BE FURTHER NORTH AND SO THE
THE TERMINALS SHOULD BE ON THE FRINGE OF THE SNOW AREAS THIS TIME.

PAW

//ORD AND MDW CONFIDENCE...UPDATED 18Z...

* HIGH CONFIDENCE IN WIND TREND. MEDIUM CONFIDENCE IN TIMING.

* MEDIUM CONFIDENCE IN SNOW AREAS REMAINING EAST OF ORD AND MDW.

PAW

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

TUESDAY NIGHT...VFR PSBL MVFR WITH LIGHT SNOW.

WEDNESDAY...VFR.

THURSDAY...PSBL MVFR WITH LIGHT RAIN/SNOW.

FRIDAY...VFR.

SATURDAY...VFR. PSBL MVFR WITH RAIN IN THE AFTN.

SUNDAY...MVFR. CHANCE OF RAIN.

BEACHLER

&&

MARINE...
257 AM CST

ANOTHER AREA OF LOW PRESSURE WAS SLIDING EAST ACROSS IOWA INTO THE
OHIO VALLEY TODAY...WHICH WILL ALLOW A SLIGHT INCREASE IN THE WIND
GRADIENT FOR THE SOUTHERN HALF OF LAKE MICHIGAN. HIGH PRESSURE
WILL THEN QUICKLY BUILD IN FROM THE WEST AND PROVIDE RELATIVELY
QUIET WEATHER FOR LAKE MICHIGAN...BEFORE YET ANOTHER LOW PRESSURE
SLIDES INTO THE UPPER MIDWEST LATE TONIGHT/EARLY TUESDAY AND
ARRIVES ACROSS THE WESTERN GREAT LAKES TUESDAY AFTERNOON/EVENING.
THE GRADIENT DOES APPEAR TO INCREASE PRIOR AND JUST AFTER THIS
SYSTEM...THEN ANOTHER RIDGE OF HIGH PRESSURE IS FORECAST TO PUSH
INTO THE WESTERN GREAT LAKES REGION FOR WEDNESDAY. THIS RIDGE OF
HIGH PRESSURE WILL THEN SLIDE EAST TO THE EASTERN OHIO VALLEY
WEDNESDAY NIGHT...WITH AN INCREASING GRADIENT AND SOUTHERLY FLOW
FOR EARLY THURSDAY ACROSS LAKE MICHIGAN. THE GRADIENT THEN
INCREASES FURTHER ACROSS THE FAR NORTHERN PORTION OF THE LAKE
MIDDAY THURSDAY AS A WEAK LOW PRESSURE SLIDES OVER THE SOUTHERN
PORTION OF THE LAKE.

BEACHLER

&&

LOT WATCHES/WARNINGS/ADVISORIES...
IL...WINTER WEATHER ADVISORY...ILZ006-ILZ014 UNTIL 4 PM MONDAY.

IN...WINTER WEATHER ADVISORY...INZ001-INZ002 UNTIL 6 PM MONDAY.

LM...NONE.
&&

$$