🚀 go-pugleaf

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1215 PM CST FRI FEB 8 2013

DISCUSSION...
1007 AM CST

UPDATE FOR REST OF THIS MORNING THROUGH MID AFTERNOON...

HAVE INCREASED POPS AND ADDED SNOW ACCUMULATIONS TO LAKE COUNTY IN
AS WELL AS FAR EASTERN COOK AND EASTERN WILL COUNTIES. AN INCH OR
TWO EXPECTED IN THESE AREAS WITH LOCAL 3 INCH AMOUNTS POSSIBLE
FROM THE LAKE COUNTY SHORE AND A SHORT DISTANCE INLAND.

FORECAST THERMAL PROFILES OVER THE S END OF THE LAKE DO NOT LOOK
VERY CONDUCIVE TO LES BUT IT IS OCCURRING. WINDS THROUGH THE CLOUD
LAYER ARE PROGGED TO BACK A SMALL AMOUNT DURING THE AFTERNOON.
ALSO...THE HEIGHT OF THE INVERSION LOWERS ABOUT 1K FT BETWEEN 18Z
AND 00Z. THE SLIGHT BACKING WILL SHIFT THE WESTERN EDGE OF THE LES
THAT HAS BEEN BRUSHING DOWNTOWN CHICAGO S ACROSS THE S SIDE TO
EASTERN WILL COUNTY TO THE E DURING THE LATE MORNING AND EARLY
AFTERNOON...WHILE THE SUBSIDENCE LOWERING OF THE INVERSION WILL
DECREASE THE DEPTH OF THE LES CLOUDS DURING THE AFTERNOON
DECREASING IF NOT ELIMINATING ANY SIGNIFICANT LES.

TRS

//PREV DISCUSSION...

320 AM...MAIN FORECAST CONCERN/CHALLENGE THIS MORNING IS THE NEXT
STORM SYSTEM TO AFFECT THE AREA SUNDAY...WITH A CHANCE OF SOME
WINTRY PRECIP SUNDAY MORNING...RAIN SUNDAY...AND A WINDY MONDAY.

LAST OF THE LIGHT SNOW IS SHIFTING EAST OVER THE LAKE EARLY THIS
MORNING. SOME HOLES HAVE DEVELOPED IN THE OVERCAST AND THAT
COMBINED WITH COLD AIR ADVECTION AS ALLOWED TEMPS TO DROP INTO THE
LOWER 20S ACROSS PARTS OF NORTH CENTRAL IL. EXPECT THESE HOLES TO
FILL IN SOME THIS MORNING BUT OVERALL TREND WILL BE FOR DECREASING
CLOUDS BY LATE MORNING BUT ESPECIALLY THIS AFTERNOON. TEMPS OVER
THE DEEPER SNOW PACK PROBABLY WON/T GET OUT OF THE UPPER 20S...
EVEN WITH SOME SUNSHINE TODAY. BUT ELSEWHERE...HIGHS A LITTLE
TRICKY BASED ON HOW MUCH MID FEBRUARY SUNSHINE BREAKS THROUGH THE
CLOUDS. HUGE HIGH PRESSURE STRETCHING FROM QUEBEC SOUTHWEST ACROSS
THE LAKES TO THE ARKLATEX WILL THEN MOVE ACROSS THE REGION
TONIGHT. LIGHT WINDS AND CLEAR SKIES WILL PROVIDE GOOD RADIATIONAL
COOLING BUT SOME MODEST WARM AIR ADVECTION WILL BE ONGOING. THINK
TEMPS OVER THE DEEPER SNOW PACK COULD TANK INTO THE SINGLE DIGITS
BUT ELSEWHERE HAVE STAYED A BIT WARMER.

LOW PRESSURE WILL DEVELOP OVER COLORADO ON SATURDAY AND LIFT
NORTHEAST ACROSS THE NORTHERN PLAINS/UPPER MIDWEST SUNDAY INTO
SUNDAY NIGHT. TEMPS LIKELY TO DROP OFF SATURDAY EVENING BUT THEN
SHOULD HOLD STEADY INTO THE EARLY MORNING AND PERHAPS EVEN RISE A
FEW DEGREES TOWARD SUNRISE. BUT THINK MOST AREAS WILL DIP BELOW
FREEZING AND PERHAPS BY SEVERAL DEGREES. FAIRLY DEEP WARM LAYER
ALOFT DEVELOPS SUNDAY MORNING SO OTHER THAN A FEW ICE PELLETS
POSSIBLE AS THE COLUMN SATURATES...EXPECT THE BULK OF THE PRECIP
TO BE RAIN. ONSET OF PRECIP AND SURFACE TEMPS AT THAT TIME THEN
BECOME IMPORTANT FOR POTENTIAL FOR ANY FREEZING RAIN. THE BULK OF
THE PRECIP APPEARS TO HOLD OFF UNTIL AFTER SUNRISE AND PERHAPS
MORE MIDDAY INTO THE AFTERNOON. BUT STILL THE POTENTIAL FOR SOME
LIGHT PRECIP IN THE PREDAWN HOURS...ESPECIALLY ACROSS THE WESTERN
THIRD OR SO OF THE CWA. TEMPS AT THAT TIME FROM THIS DISTANCE ARE
UNCERTAIN AND WILL LIKELY BE NEAR FREEZING SO HAVE MAINTAINED
SLIGHT CHANCE OF FREEZING RAIN FOR A FEW HRS BEFORE SUNRISE AND
FOR A FEW HRS AFTER SUNRISE...MAINLY ALONG AND NORTH OF I-80. BUT
SURFACE TEMPS SHOULD QUICKLY RISE ABOVE FREEZING SUNDAY MORNING
ENDING THE THREAT OF ANY POSSIBLE FREEZING RAIN.

PRECIPITABLE WATER VALUES REACH AS HIGH AS 0.7 TO 0.9 INCHES BY
EARLY SUNDAY AFTERNOON AND LATEST MODEL QPF IS NOW APPROACHING A
HALF INCH. COULD BE SOME CONVECTIVE ELEMENTS AS WELL WITH A RUMBLE
OF THUNDER ALSO POSSIBLE. HAVE BUMPED UP QPF AMOUNTS IN THE GRIDS
WITH A HALF INCH CERTAINLY REASONABLE. PRECIP SHOULD QUICKLY END
BY SUNDAY EVENING AS IT LIFTS NORTHEAST. TRACK OF THE SURFACE LOW
SHOULD SWING THE DRY SLOT ACROSS THE AREA LATER SUNDAY EVENING
WITH COLDER AIR SPREADING IN OVERNIGHT INTO MONDAY MORNING. WRAP
AROUND LIGHT SNOW WILL SPREAD EAST ACROSS NORTHERN IA AND SOUTHERN
WI. APPEARS SOME OF THIS COULD AFFECT NORTHERN IL INTO MONDAY BUT
JUST CHANCE POPS FOR NOW. WINDS WILL BEGIN TO INCREASE SUNDAY
NIGHT AS THE COLD AIR ARRIVES BUT FORECAST SOUNDINGS SUGGEST THAT
MONDAY WILL BE QUITE WINDY WITH GUSTS PERHAPS AS HIGH AS 40 MPH.

WEAK HIGH PRESSURE REMAINS ACROSS THE REGION/OHIO VALLEY THROUGH
THE MIDDLE OF NEXT WEEK WITH SEASONAL TEMPS AND NO SIGNIFICANT
SYSTEMS. BY THURSDAY NIGHT/FRIDAY...APPEARS THERE COULD BE SOME
CLIPPER LIKE SYSTEM MOVING THROUGH THE LAKES REGION BUT A BIT
EARLY FOR ANY SPECIFICS. CMS

&&

AVIATION...

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

* LOW END MVFR CEILINGS PERSISTING EARLY THIS AFTERNOON...THEN
  SLOWLY LIFTING BUT REMAINING MVFR THROUGH TONIGHT.

* LIGHT LAKE EFFECT SNOW SHOWERS TO CONTINUE THROUGH EARLY
  AFTERNOON...VIS OF 5SM-6SM EXPECTED PRIMARILY OVER MDW.

* NORTH/NORTHWEST WINDS GUSTING TO AROUND 20 KT EARLY THIS
  AFTERNOON.

RODRIGUEZ

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

LOW END MVFR CEILINGS AND ONGOING LAKE EFFECT SNOW SHOWERS ARE THE
MAIN CONCERN EARLY THIS FORECAST PERIOD...BUT WITH A SLOW
IMPROVING TREND EXPECTED THROUGH THE FORECAST PERIOD TODAY. LATEST
RADAR IMAGERY DEPICTING THE MAIN SNOW SHOWERS CONTINUING TO SLOWLY
MOVE EAST OF THE TERMINALS EARLY THIS AFTERNOON...AND EXPECT THIS
TREND TO CONTINUE THROUGH THE REMAINDER OF THE AFTERNOON. BEFORE
THIS OCCURS...EXPECT MDW AND GYY TO LIKELY OBSERVE PERIODIC LIGHT
SNOW BUT WITH GYY OBSERVING THE LOWER VIS. THEN...LAKE EFFECT SNOW
SHOWERS SHOULD CONTINUE TO DIMINISH INTO THE EARLY EVENING. MAIN
STRATUS DECK REMAINS OVERHEAD BUT WITH SOME HOLES BEGINNING TO
DEVELOP AS HIGHER PRESSURE CONTINUES TO BUILD ACROSS THE REGION.
EXPECT THIS STRATUS TO SLOWLY ERODE THROUGH THE REMAINDER OF THE
AFTERNOON WITH RFD/DPA LIKELY OBSERVING SCT SKIES LATER THIS
AFTERNOON...BUT WITH ORD/MDW/GYY OBSERVING A LONGER PERIOD OF MVFR
CEILINGS DUE TO FLOW OFF THE LAKE. HAVE GONE MORE PESSIMISTIC WITH
THESE LOW CLOUDS EXITING THE TERMINALS WITH FLOW OFF THE LAKE TO
CONTINUE USHERING IN A GOOD AMOUNT OF MOISTURE OFF OF THE LAKE.
ITS NOT UNTIL LATER TONIGHT THAT SKIES SHOULD SCATTER...AND REMAIN
ON THE CLEARER SIDE THROUGH THE REMAINDER OF THE FORECAST PERIOD.

WINDS WILL REMAIN OUT OF THE NORTHWEST BEFORE SLOWLY SHIFTING MORE
NORTH WHILE DIMINISHING. THEN EXPECT WINDS TO REALLY DIMINISH
OVERNIGHT LIKELY BECOMING MORE LIGHT AND VARIABLE.

RODRIGUEZ


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

* MEDIUM HIGH CONFIDENCE WITH CEILING TRENDS THROUGH THIS
  AFTERNOON...MEDIUM CONFIDENCE WITH CEILING TRENDS TONIGHT.

* HIGH CONFIDENCE WITH LAKE EFFECT SNOW SHOWERS TIMING/TRENDS THIS
  AFTERNOON.

* HIGH CONFIDENCE WITH WIND SPEED AND DIRECTION.

RODRIGUEZ

//OUTLOOK FOR ORD/MDW FOR 00Z SUNDAY-12Z FRIDAY...UPDATED 12Z...

SATURDAY NIGHT...VFR.

SUNDAY...CHANCE FZRA EARLY THEN RA. MVFR LIKELY WITH IFR POSSIBLE.

MONDAY...MVFR IMPROVING TO VFR. GUSTY WEST TO SOUTHWEST WINDS.

TUESDAY THROUGH THURSDAY...VFR.

MDB

&&

MARINE...
304 AM CST

LOW PRESSURE OVER NORTHERN OHIO WILL CONTINUE TO MOVE NORTHEAST INTO
NORTHERN PENNSYLVANIA TODAY AND MERGE WITH DEEPENING LOW PRESSURE
CURRENTLY OFF THE CAROLINA COAST. THIS NEWLY COMBINED LOW WILL DEEPEN
TO AROUND 28.8 INCHES OFF CAPE COD BY SATURDAY MORNING. NORTH TO
NORTH-NORTHEAST WINDS WILL REMAIN GUSTY THROUGH THE MORNING HOURS
WITH A TIGHT PRESSURE GRADIENT IN PLACE. EXPECT SPEEDS AROUND 30 KT
WITH A FEW GALE FORCE GUSTS TO AROUND 35 KT POSSIBLE THROUGH THE
MORNING...ESPECIALLY ACROSS CENTRAL PORTIONS OF THE LAKE. WINDS
WILL STEADILY DIMINISH AND TURN MORE NORTHEASTERLY LATER ON TODAY
AS HIGH PRESSURE SETTLES IN FROM THE DAKOTAS. THE HIGH SHIFTS EAST
SATURDAY NIGHT AS LOW PRESSURE DEVELOPS ACROSS SOUTHEAST COLORADO
AND LIFTS NORTHEASTWARD. SOUTHERLY WINDS WILL INCREASE SUNDAY WITH
WARMER AIR STREAMING IN ALOFT. THIS WILL LEAD TO AN INVERSION
WHICH WILL PREVENT GUSTS FROM BEING TERRIBLY STRONG SUNDAY BUT
SOME GALES ARE POSSIBLE. BY MONDAY...THE LOW WILL BE CROSSING THE
U.P. OF MICHIGAN ALLOWING COLDER AIR TO WRAP IN BEHIND IT AND
SETTING UP A BETTER SCENARIO FOR MIXING. THIS MAY RESULT IN A
PERIOD OF LOW TO MID-RANGE GALES ACROSS CENTRAL AND SOUTHERN
SECTIONS OF THE LAKE MONDAY. THE LOW EXITS THE REGION EARLY
TUESDAY AS SEVERAL WEAK UPPER LEVEL IMPULSES CROSS THE AREA BEFORE
HIGH PRESSURE RETURNS FROM THE SOUTH WEDNESDAY NIGHT.

MDB

&&

LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WATERS
     UNTIL 4 AM SATURDAY.

&&

$$