🚀 go-pugleaf

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1202 PM CST FRI FEB 22 2013

DISCUSSION...

926 AM...MORNING UPDATE...LIGHT SNOW CONTINUES TO SPREAD NORTHEAST
ACROSS NORTHWEST IL AS THE SURFACE LOW SLOWLY LIFTS NORTHEAST.
UPDATED POPS/GRIDS/ZFP FOR LIGHT SNOW WHICH WILL AFFECT MAINLY THE
NORTHERN THIRD OF THE CWA INTO THIS AFTERNOON. EXPECT ANY
ADDITIONAL ACCUMULATION TO BE UNDER AN INCH AND WHILE THIS MAY NOT
POSE ANY SIGNIFICANT IMPACTS WILL LET THE ADVISORY RIDE FOR NOW...
WHICH EXPIRES FOR THE SOUTHERN THIRD OF THE CWA IN A FEW HOURS.
LIKELY THAT THE ADVISORY WILL BE ABLE TO BE CANCELED PRIOR TO THE
00Z EXPIRATION TIME BUT PREFER TO SEE HOW THIS SNOW EVOLVES OVER
THE NEXT FEW HRS. CONFIDENCE ALSO FAIRLY LOW REGARDING DRIZZLE/
FREEZING DRIZZLE COVERAGE/POTENTIAL. CMS

//PREV DISCUSSION...
310 AM CST

TODAY...
LOW PRESSURE OVER NORTHEASTERN MISSOURI EARLY THIS MORNING WILL LIFT
ACROSS NORTH CENTRAL ILLINOIS INTO WISCONSIN EARLY THIS AFTERNOON.
AHEAD OF THE LOW...STRONG ISENTROPIC ASCENT FOCUSED OVER NORTHERN
ILLINOIS AND NORTHWEST INDIANA IS SUPPORTING MODERATE TO HEAVY AT
TIMES SNOW. THE BEST ASCENT WILL CONTINUE TO LIFT NORTH OUT OF THE
AREA THIS MORNING WHILE NOTABLE DRIER AIR ON WV IMAGE PUSHES INTO
THE SOUTHERN PORTIONS OF THE CWA. WEAKER ASCENT TO OUR SOUTH WILL
CONTINUE TO SUPPORT CHANCES OF PRECIP THROUGH THE DAY...HOWEVER THE
LOSS OF THE DEEPER MOISTURE WILL MAKE IT LESS LIKELY FOR ICE
CRYSTALS TO DEVELOP LEAVING US WITH DRIZZLE...FREEZING AT TIMES
DEPENDING ON SURFACE TEMPS. BASED ON SURFACE TEMPS...DRIZZLE WILL
BE TEETERING ON THE EDGE OF FREEZING POTENTIAL...WITH THE BEST
POTENTIAL MAINLY NORTH OF I-80 WHICH WILL BE SLOWER TO WARM ABOVE
FREEZING. WILL MAINTAIN THE CURRENT WINTER WEATHER ADVISORY WITH
EMPHASIS ON ACCUMULATING SNOWFALL ENDING AND TRANSITIONING TO
FREEZING DRIZZLE WITH LIGHT GLAZE OF ICE POSSIBLE. AS COLD AIR
ADVECTS IN FROM THE NORTHWEST BEHIND THE LOW THIS AFTERNOON...THE
TOP OF THE MOIST LAYER WILL PUSH -10 TO -12C WHICH SHOULD ALLOW
PRECIP TO TRANSITION BACK TO LIGHT SNOW/FLURRIES FROM THE
NORTHWEST LATER TODAY.

FRIDAY NIGHT THROUGH SUNDAY...
DEEPER MOISTURE WRAPPING AROUND THE DEPARTING LOW TO OUR NORTHEAST
WILL BEGIN TO SAG SOUTH INTO NORTHERN ILLINOIS TONIGHT INTO
SATURDAY...WHICH COUPLED WITH STEEP LOW LEVEL LAPSE RATES AND WEAK
FORCING FROM A PINWHEELING VORT LOBE WILL PROVIDE AT LEAST A
CHANCE OF SNOW SHOWERS OR FLURRIES. REMOVED POPS FROM SOUTH OF THE
INTERSTATE 80 CORRIDOR WHICH SHOULD REMAIN IN THE DRIER AIR. YET
ANOTHER LOBE OF ENERGY PIVOTS AROUND THE BACK SIDE OF THE LOW
SATURDAY AFTERNOON/EVENING BRINGING ANOTHER CHANCE FOR SOME
FLURRIES...MAINLY ACROSS THE NE HALF OF THE CWA. MEANWHILE...HIGH
PRESSURE BUILDING ACROSS THE CENTRAL PLAINS WILL SHIFT EAST ACROSS
THE MID TO UPPER MISSISSIPPI VALLEY SATURDAY EVENING WITH SKIES AT
LEAST PARTIALLY CLEARING FROM THE SOUTHWEST.

SUNDAY NIGHT THROUGH TUESDAY...
THIS MORNING...THERE IS A BUCKLE IN THE JET STREAM NOTED OVER THE
GULF OF ALASKA. MODELS INDICATE THIS TROUGH WILL DIG ACROSS THE
INTERMOUNTAIN WEST THROUGH THE WEEKEND...REACHING THE CENTRAL PLAINS
BY LATE IN THE WEEKEND AND DEEPENING A SURFACE LOW. CURRENTLY THERE
IS GOOD AGREEMENT AMONGST THE MODELS/ENSEMBLES OF A DEEPENING LOW
LIFTING FROM THE CENTRAL PLAINS ACROSS THE MID MISSISSIPPI VALLEY
MONDAY EVENING/NIGHT...THOUGH STILL IMPORTANT DIFFERENCES IN THE
TRACK AND TIMING OF THE LOW. THE ECMWF/GEM SOLUTIONS HAVE A
FAVORABLE TRACK FOR HEAVY SNOW ACROSS NORTHERN ILLINOIS AND
NORTHWEST INDIANA MONDAY NIGHT INTO TUESDAY...WHILE THE FASTER GFS
TRACKS THE LOW FARTHER NORTH OVER OUR AREA. THE GFS THERMAL PROFILE
MAY BE TOO COLD GIVEN THE TRACK OF THE LOW IT IS DEPICTING...AND
COULD SUPPORT A WINTRY MIX BEFORE EVENTUALLY CHANGING OVER TO
SNOW MONDAY. WITH THE OPERATIONAL GFS ON THE NORTHERN PERIPHERY OF
THE GEFS SOLUTION SPREAD...AND THE GEFS MEAN CLOSER TO THE ECMWF
TRACK...ALBEIT FASTER...FOR NOW WILL CONTINUE TO LEAN TOWARDS THE
POTENTIAL FOR PERIODS OF HEAVY SNOW WITH A MORE SOUTHERLY
TRACK...AS WELL AS FAVOR THE SLOWER TIMING OF THE ECMWF/GEM.
REGARDING MODEL PERFORMANCE OF LATE HOWEVER...THERE MAY YET BE
SIGNIFICANT SHIFTS IN THE TRACK/INTENSITY OF THE STORM AS THE
UPPER DISTURBANCE COMES ONSHORE THIS WEEKEND AND IS SAMPLED BY OUR
UPPER AIR NETWORK.

WEDNESDAY THROUGH THURSDAY...
OVERALL CONFIDENCE IN THE FORECAST BEYOND TUESDAY IS QUITE LOW.
GUIDANCE SUGGESTS A BLOCKING PATTERN WILL DEVELOP OVER THE ATLANTIC
WITH THE PROGRESSION OF THE EASTERN CONUS H5 LOW COMING TO A HALT.
AT THE SURFACE...THE LOW PRESSURE SYSTEM IS ALSO PROGGED TO STALL OR
EVEN RETROGRADE...BUT WHERE EXACTLY IS UNSURE. WILL MAINTAIN CHC/SLT
CHC POPS THROUGH THIS PERIOD AS THE LOW PRESSURE SYSTEM MAY LINGER
OVER THE GREAT LAKES REGION AND FILL AS A NEW LOW DEVELOPS OFF THE
EASTERN SEABOARD.

DEUBELBEISS

&&

AVIATION...

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

* LIFR CIGS ARND 400FT AGL WILL CREEP BACK TO 600FT THIS AFTN.
  CIGS MAY LIFT TO 1000FT AGL LATE THIS AFTN/EARLY EVE.

* VSBYS WILL REMAIN ARND 1SM THRU THIS AFTN...THEN BEGIN TO LIFT
  TOWARDS 5SM BY 19-20Z.

* LIGHT SNOW MIXED WITH A LIGHT WINTRY MIX WILL CONTINUE THRU 21Z.


* FLURRIES/LIGHT SNOW SHOWERS LATE THIS EVENING...THRU EARLY SAT
  MORNING.


BEACHLER

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

LOW PRESSURE STEADILY LIFTING OVER NORTHERN IL/NORTHWEST IN
AIRFIELDS AT THIS TIME...ALLOWING WINDS TO SLOWLY TURN FROM
EAST/SOUTHEAST TO SOUTH/SOUTHWEST. THE GRADIENT REMAINS
LIGHT...THUS EXPECT FOR THE NEXT SEVERAL HOURS SPEEDS TO HOVER
ARND 10KT OR JUST UNDER 10KT. ABUNDANT LLVL MOISTURE HAS LINGERED
AND ADDITIONAL LIGHT SNOW HAS DEVELOPED ACROSS NORTHERN IL LATE
THIS MORNING. LIGHT SNOW WILL CONTINUE TO LIFT NORTHEAST ACROSS
RFD/DPA/ORD/MDW AIRFIELDS THRU 21Z...THEN COME TO AN END. WITH
DEW POINTS HOVERING ARND FREEZING OVER THE FRESH SNOW...AND
ABUNDANT LLVL MOISTURE...VSBYS WILL REMAIN LOW AS WELL AS CIGS.
EXPECT VSBYS TO HANG ARND 1SM THRU 20Z...THEN SHOW SOME SLOW
IMPROVEMENTS BACK TO MVFR VSBYS. CIGS WILL BE SLOWER TO
IMPROVE...HOLDING ONTO THE LIFR CIGS AT 300FT AGL THRU 21Z. THEN
EXPECT IFR CIGS TO DEVELOP AND HOLD THRU THE EARLY
EVENING...BEFORE SOME DRY AIR WILL PUSH IN FROM THE SOUTHWEST.
THEN CIGS MAY TOUCH MVFR CONDS OVERNIGHT. THE GRADIENT DOES
INCREASE THIS EVENING AND WINDS WILL TURN TO THE SOUTHWEST...WITH
GUSTS DEVELOPING UP TO 20KT. LATEST FORECAST GUIDANCE HAS
INDICATED GUSTS WILL THEN CONTINUE THRU DAYBREAK SAT...POSSIBLY
INTO THE MID-MORNING TIMEFRAME SAT.

BEACHLER


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

* HIGH CONFIDENCE IN CIGS FORECAST.

* MEDIUM CONFIDENCE ON ENDING TIME OF LIGHT SNOW.

* HIGH CONFIDENCE IN WIND DIR/SPEED FORECAST.

* MEDIUM CONFIDENCE IN VSBY FORECAST.

BEACHLER

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

SATURDAY NIGHT AND SUNDAY...VFR.

MONDAY...VFR EARLY...THEN BECOMING MVFR WITH SNOW LIKELY MONDAY
NIGHT. IFR POSSIBLE AT NIGHT.

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

WEDNESDAY...CHANCE OF SNOW. MVFR POSSIBLE.

THURSDAY...CHANCE OF FLURRIES. MVFR POSSIBLE.

RATZER

&&

MARINE...
221 AM CST

MAIN MARINE CONCERNS FOCUS ON GUSTY EASTERLY WINDS TODAY AHEAD OF AN
AREA OF LOW PRESSURE LIFTING TOWARD THE WESTERN LAKES FROM MISSOURI.
THE POTENTIAL FOR ANOTHER DEEP LOW TO AFFECT THE WESTERN LAKES
APPEARS TO COME IN THE MONDAY-TUESDAY TIMEFRAME OF EARLY NEXT WEEK.

SURFACE LOW PRESSURE WAS OVER NORTHWEST MISSOURI EARLY THIS MORNING
WITH SURFACE PRESSURE FALLS DEVELOPING AHEAD OF IT ACROSS MUCH OF
THE UPPER MIDWEST AND WESTERN GREAT LAKES REGION. EAST WINDS HAVE
BEEN GUSTING AROUND 30 KTS ACROSS CENTRAL/SOUTHERN LAKE MICHIGAN
OVERNIGHT...AND THESE STRONGER WINDS ARE EXPECTED TO SPREAD TO THE
NORTH TODAY AS THE LOW MOVES INTO FAR NORTHWEST IL THROUGH MIDDAY.
THE GRADIENT WILL EVENTUALLY WEAKEN AS THE LOW APPROACHES THIS
AFTERNOON...WITH WINDS VEERING FROM EAST TO SOUTHWEST ON ALL BUT THE
FAR NORTHERN PART OF THE LAKE AS THE LOW PASSES NORTHEAST ACROSS THE
CENTRAL/NORTHERN PART LAKE MICHIGAN LATE THIS AFTERNOON INTO THIS
EVENING. MODEST WEST-SOUTHWEST FLOW WILL THEN AFFECT MUCH OF THE
LAKE THROUGH SATURDAY AS THE LOW DRIFTS SLOWLY ACROSS THE NORTHERN
LAKES. WINDS WILL DIMINISH MORE SUBSTANTIALLY SUNDAY AS WEAK HIGH
PRESSURE RIDGE SPREADS NORTHEAST ACROSS THE AREA.

VARIOUS FORECAST MODELS CONTINUE TO DEPICT ANOTHER FAIRLY DEEP LOW
DEVELOPING ACROSS THE PLAINS SUNDAY...AND MOVING INTO THE MIDWEST
AND GREAT LAKES REGION MONDAY-TUESDAY OF NEXT WEEK. CONSIDERABLE
SPREAD CURRENTLY EXISTS IN THE MODEL SOLUTIONS OF BOTH THE TRACK AND
INTENSITY OF THE LOW PRESSURE SYSTEM...THOUGH IT APPEARS LIKELY THAT
A DEEP LOW WILL MOVE INTO IL/IN BY MONDAY NIGHT/TUESDAY...AND WILL
LIKELY PRODUCE A PERIOD OF GUSTY NORTH-NORTHEAST WINDS ON THE LAKE
DURING THIS TIME.

SMALL CRAFT ADVISORY CONDITIONS WILL EASE OVER THE INDIANA NEARSHORE
WATERS AS WINDS DIMINISH THIS MORNING...BUT ARE EXPECTED TO LINGER
INTO THIS AFTERNOON ACROSS THE ILLINOIS NEARSHORE WATERS.

RATZER

&&

LOT WATCHES/WARNINGS/ADVISORIES...
IL...WINTER WEATHER ADVISORY...ILZ003-ILZ004-ILZ005-ILZ006-ILZ008-
     ILZ010-ILZ011-ILZ012-ILZ013-ILZ014-ILZ020-ILZ022 UNTIL 6 PM
     FRIDAY.

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

LM...SMALL CRAFT ADVISORY...ILLINOIS NEARSHORE WATERS UNTIL 4 PM FRIDAY.

&&

$$