🚀 go-pugleaf

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1157 AM CST SAT FEB 23 2013

DISCUSSION...
252 AM CST

MAIN CONCERN WILL BE LOOKING AHEAD TO THE NEXT SYSTEM TO IMPACT THE
REGION MONDAY NIGHT INTO TUESDAY...BRINGING A WINTRY MIX AND/OR
ACCUMULATING SNOW TO THE AREA.

THIS WEEKEND...
SLOWLY DEPARTING AREA OF LOW PRESSURE LOCATED OVER NORTHERN LAKE
MICHIGAN EARLY THIS MORNING WILL CONTINUE TO LIFT NORTHEAST TOWARDS
ONTARIO....HOWEVER CYCLONIC FLOW AS WELL AS PINWHEELING VORT LOBE
DROPPING SOUTH FROM WISCONSIN WILL KEEP THE CHANCE FOR LIGHT SNOW OR
FLURRIES IN THE FORECAST...MAINLY NORTH OF INTERSTATE 80 WHERE
BETTER MOISTURE IS LOCATED. BROAD STRATUS DECK NOTED ON IR IMAGERY
SPANS NORTHWEST/WEST ACROSS MUCH OF MINNESOTA AND IOWA...AND SOUTH
INTO CENTRAL ILLINOIS. WHILE A FEW HOLES HAVE DEVELOPED...EXPECT
MOSTLY CLOUDY/CLOUDY SKIES TO PERSIST MUCH OF TODAY NORTH OF I-80.
PARTIAL CLEARING SHOULD OCCUR THIS EVENING FROM THE SOUTHWEST AS HIGH
PRESSURE BEGINS TO BUILD INTO THE MID MISSISSIPPI VALLEY. DIMINISHING
WINDS...RECENT SNOWFALL...AND SCATTERING SKIES SATURDAY NIGHT WILL
HELP COOLING...ALLOWING TEMPS TO FALL INTO THE LOW TO MID TEENS
FOR MOST OF THE AREA...POSSIBLY STAYING PROPPED IN THE LOW 20S IN
THE URBAN HEAT ISLAND OF CHICAGO. SHOULD SEE SUNSHINE ACROSS THE
CWA SUNDAY BEFORE HIGH CLOUDS FROM AN APPROACHING LOW TO THE
SOUTHWEST BEGIN TO MOVE INTO THE AREA SUNDAY NIGHT. GRADUALLY
INCREASING WARM ADVECTION THROUGH THE DAY SUNDAY AS WELL AS LATE
FEBRUARY SUNSHINE SHOULD HELP PUSH TEMPERATURES ABOVE FREEZING
SUNDAY SOUTH OF I-80...THOUGH DEEPER SNOWPACK WILL LIKELY HOLD
TEMPS CLOSE TO THE FREEZING MARK IN THE NORTHERN COUNTIES.

MONDAY THROUGH TUESDAY...
THE UPPER TROUGH MOVING ONSHORE OVER THE PAC NW EARLY THIS MORNING
WILL BE THE SYSTEM THAT AFFECTS OUR REGION EARLY NEXT WEEK. THIS
TROUGH WILL DIG ACROSS THE GREAT BASIN SUNDAY THEN INTO THE SOUTHERN
HIGH PLAINS BY MONDAY. MEANWHILE...A SURFACE LOW WILL BEGIN TO
DEEPEN OVER OKLAHOMA/ARKANSAS MONDAY THEN LIFT NORTHEAST ACROSS THE
MID MISSISSIPPI VALLEY MONDAY NIGHT. EARLIER GEM/ECMWF GUIDANCE
SUGGESTED A SOUTHERLY TRACK OF THE LOW FROM ROUGHLY ST LOUIS TO FORT
WAYNE SUPPORTING BETTER HEAVY SNOW CHANCES FOR OUR AREA. WHILE
THE GEM STILL SUPPORTS A SOUTHERLY SOLUTION...THE 12Z ECMWF WAS A
NORTHERN OUTLIER //EVEN AS COMPARED TO THE ECENS MEAN// WHICH
LIFTS THE LOW NORTH ACROSS NORTHEASTERN ILLINOIS TUESDAY EVENING.
THE 00Z ECMWF CAME BACK IN LINE WITH A SOUTHERLY TRACK CLOSE TO
THE GEM.

GIVEN THE CONTINUED UNCERTAINTY IN THE LOW TRACK...HARD TO NAIL
PRECIP TYPE AND POTENTIAL SNOW ACCUMULATIONS. LOOKED TO GFS GUIDANCE
WHICH TAKES THE LOW FROM ST LOUIS THROUGH DANVILLE AND WAS WELL
CLUSTERED WITHIN THE SOLUTION ENVELOPE TO GET SOME SENSE OF THE
THERMAL PROFILE. THERE IS STILL SUPPORT FOR PARTIAL MELTING ALOFT
ESPECIALLY SOUTH/EAST OF THE I-55 CORRIDOR WITH H8-H9 LAYER MAX WET
BULB TEMPS MARGINALLY ABOVE FREEZING LEADING TO SLEET AND MAYBE
FREEZING RAIN. NORTHWESTERN AREAS...INCLUDING ROCKFORD HAVE THE BEST
CHANCE FOR ALL SNOW THIS EVENT. CONTINUE TO LEAN SLIGHTLY COOLER
THAN MODEL CONSENSUS TEMPS TO ACCOUNT FOR THE 12Z ECMWF BEING TOO
WARM AND FAVORING A SOUTHERLY TRACK OF THE LOW. AS MENTIONED
EARLIER...THE UPPER WAVE IS NOW MOVING ONSHORE...SO SHOULD HAVE
BETTER SAMPLING WITH THE 12Z RAOB NETWORK FOR THE NEXT MODEL SUITE
AND HOPEFULLY A BETTER SENSE OF P-TYPE.

WEDNESDAY THROUGH FRIDAY...
MODELS CONTINUE TO ADVERTISE BLOCKING PATTERN DEVELOPING OVER THE
ATLANTIC WEDNESDAY THOUGH THE END OF THE WEEK WITH H5 LOW STALLING
ACROSS THE EASTERN GREAT LAKES REGION. AT THE SURFACE...MODELS SHOW
THE LOW SLOWLY FILLING AS IT MEANDERS OVER THE EASTERN LAKES...WITH
COLD AIRMASS AND CYCLONIC FLOW LOCKING IN PLACE OVER THE WESTERN
GREAT LAKES. THIS WILL SUPPORT BELOW NORMAL HIGHS AND ONGOING
CHANCES FOR LIGHT PRECIP AS WELL AS LAKE EFFECT SNOW GIVEN THE
MODEST INSTABILITY THAT DEVELOPS OVER THE LAKE.

DEUBELBEISS

&&

AVIATION...

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

* MVFR CIGS ARND 2500-3000FT AGL WILL SLOWLY LIFT TO BORDERLINE
  VFR/MVFR CONDS...THEN SCT TO 4KFT AGL ARND 4Z. VFR CONDS WILL
  THEN PREVAIL.

* W/SW WINDS WILL PERSIST WITH OCCASIONAL GUSTS TO 15KT. WINDS
  WILL DIMINISH AFT SUNSET TO LESS THAN 10KT.

* WINDS WILL SLOWLY TURN SOUTHERLY SUN MORNING THEN SOUTHEAST.

BEACHLER

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

HIGH PRESSURE SLOWLY BUILDING IN FROM THE SOUTHWEST. THIS WILL AID
IN PUSHING THE MVFR CLOUDS AND LINGERING PATCHES OF FLURRIES TO
THE EAST. CIGS WILL SLOWLY LIFT TO VFR AND THEN SCT. EXPECT
FEW/SCT CONDS THRU THE OVERNIGHT HOURS...THEN WITH ENOUGH DRY AIR
AROUND IT IS POSSIBLE FOR A PERIOD OF TIME SUN SKIES COULD BECOME
SKC. VFR CONDS WILL PREVAIL OVERNIGHT THRU SUN...WITH WINDS SLOWLY
TURNING SOUTHERLY THEN SOUTHEASTERLY LATE SUN AFTN/EVE.

BEACHLER


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

* HIGH CONFIDENCE IN ALL FORECAST ELEMENTS.

BEACHLER

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

SUNDAY NIGHT...VFR.

MONDAY...MAINLY VFR...EXCEPT CHANCE OF SNOW/SLEET LATE MONDAY
NIGHT WITH MVFR/IFR POSSIBLE BY 12Z TUES.

TUESDAY...SNOW...POSSIBLY MIXED WITH SLEET/RAIN. IFR/LIFR
PROBABLE.

WEDNESDAY...CHANCE OF SNOW. MVFR/IFR POSSIBLE.

THURSDAY AND FRIDAY...CHANCE OF SNOW SHOWERS/FLURRIES. MVFR
POSSIBLE ESPECIALLY THURSDAY.

RATZER

&&

MARINE...
231 AM CST

LOW PRESSURE WAS OVER NORTHERN LAKE MICHIGAN EARLY THIS MORNING...
RESULTING IN A FAIRLY SHARP CONTRAST FROM LIGHT WINDS IN THE BAGGY
GRADIENT IN THE VICINITY OF THE LOW CENTER TO THE MORE GUSTY
WEST-SOUTHWEST WINDS IN THE TIGHTER GRADIENT SOUTH OF THE LOW ACROSS
THE SOUTHERN PART OF THE LAKE. THE LOW WILL SLOWLY DRIFT OFF TO THE
NORTHEAST INTO ONTARIO THROUGH THIS AFTERNOON ALLOWING
WEST-SOUTHWEST WINDS TO COME UP A BIT ACROSS THE NORTH. AS THE LOW
CONTINUES TO MOVE AWAY TONIGHT...HIGH PRESSURE WILL SPREAD IN FROM
THE SOUTHWEST...AND WILL ALLOW WINDS TO DIMINISH ACROSS THE ENTIRE
LAKE INTO SUNDAY.

THE SURFACE HIGH PRESSURE RIDGE WILL THEN DRIFT OFF ACROSS THE
EASTERN LAKES BY EARLY MONDAY...AS ANOTHER AREA OF LOW PRESSURE
DEVELOPS ACROSS THE FAR SOUTHERN PLAINS OF TEXAS. VARIOUS MODEL
FORECASTS CONTINUE TO DEEPEN THIS LOW AND MOVE IT NORTHEAST THROUGH
THE MIDWEST AND EASTERN GREAT LAKES DURING THE MONDAY NIGHT THROUGH
WEDNESDAY PERIOD. TRENDS FROM THESE MODEL RUNS AT THIS TIME SUGGEST
THE LOW WOULD TRACK THROUGH SOUTHEAST MISSOURI INTO SOUTHERN IL AND
INDIANA...AND EVENTUALLY ACROSS THE EASTERN LAKES. THIS WOULD RESULT
IN INCREASING EAST-NORTHEAST WINDS ACROSS LAKE MICHIGAN BEGINNING
LATE MONDAY NIGHT AS THE LOW APPROACHES. HAVE SLOWED THE INCREASE IN
WINDS JUST A BIT OVER PREVIOUS FORECAST...THOUGH IT APPEARS THAT
WINDS IN THE 25-30 KT RANGE WILL BECOME LIKELY BY SUNRISE TUESDAY
ESPECIALLY ACROSS THE SOUTHERN PORTION OF THE LAKE. EAST-NORTHEAST
GALES ARE POSSIBLE. WINDS WILL THEN LIKELY SLOWLY BACK TO THE
NORTH-NORTHWEST MID-WEEK AS THE LOW MOVES SOUTH AND THEN EAST OF THE
LAKE.

RATZER

&&

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

$$