Jump to content
  • Member Statistics

    17,587
    Total Members
    7,904
    Most Online
    LopezElliana
    Newest Member
    LopezElliana
    Joined

December 13-14th Winter Storm


Chicago Storm

Recommended Posts

  • Replies 988
  • Created
  • Last Reply

DTX with a great write up again, if slightly more pessimistic. Calling for 11:1 ratios, but with good reasoning laid out

 

AS FOR AMOUNTS, THE LACK OF NOTEWORTHY MESOSCALE FORCING HAS

RESULTED IN GREAT AGREEMENT AMONG THE GUIDANCE IN TERMS OF QPF.
HOWEVER, MODELED CROSS-SECTIONS AND FORECAST SOUNDINGS DO OFFER SOME
REASON FOR PAUSE IN TERMS OF OVERALL EFFICIENCY. DESPITE A HEALTHY
200MB DEEP DENDRITE GROWTH LAYER, THERE WILL BE VERY LITTLE FORCING
FOR ASCENT WITHIN THIS LAYER AND EVEN LESS BENEATH IT. THIS WILL
MAKE IT HARD OR IMPOSSIBLE TO ACHIEVE THE NECESSARY CONDITION OF
SUPERSATURATION FOR OPTIMAL DENDRITE FORMATION. ALSO, WITH THE BULK
OF ASCENT TAKING PLACE ABOVE THE DGZ WHERE IT IS MUCH COLDER WITH
LESS ABSOLUTE MOISTURE CONTENT, A PLETHORA OF NEEDLE GENERATION
SEEMS LIKE A GOOD BET - PERHAPS BECOMING MODIFIED TO SOME EXTENT AS
THEY FALL THROUGH THE DGZ OR EVEN EXPERIENCE A BIT OF RIMING AS THE
SUB-850MB LAYER WARMS LATER IN THE DAY. GIVEN THIS INFORMATION,
EVENT-AVERAGE SNOW RATIOS OF AROUND 11:1 SEEM APPROPRIATE. FORECAST
AMOUNTS THEREFORE REMAIN SIMILAR TO YESTERDAY: 3 TO 6 INCHES WITH
LESS TO THE NORTH AND MORE TO THE SOUTH. THE GENERAL REGIME OF BROAD
SCALE ASCENT AND MODERATE ISENTROPIC LIFT OCCURRING IN THE ABSENCE OF
SIGNIFICANT MESOSCALE FORCING WILL FAVOR LIGHT SNOWFALL RATES ON THE
ORDER OF A QUARTER TO HALF INCH PER HOUR - A TRUE GRINDER EVENT.

Link to comment
Share on other sites

DTX with a great write up again, if slightly more pessimistic. Calling for 11:1 ratios, but with good reasoning laid out

 

The one thing I have noticed over there years is there is normally a band on the northern part of these systems that has high ratios.  Not saying they are wrong rather I would not be surprised if there is an area that over performs snow wise but has same or even less QPF than other areas.

Link to comment
Share on other sites

IWX has some interesting comments on possible phasing not being picked up by models as they share their afternoon update.

HAVE BEEN WATCHING THE INTERACTION BETWEEN THE MAIN SHORT WAVE ANDTHE ONE DIGGING IN ON THE BACKSIDE THIS AFTERNOON AND THERE SEEMS TOBE SOME PHASING ALREADY TAKING PLACE. MODELS HAVE GENERALLY KEPTTHESE WAVES SEPARATE SO THIS IS CERTAINLY SOMETHING TO WATCH THISEVENING. MORE PHASING WOULD LEAD TO STRONGER WAVE AND A MORENEGATIVE TILT TO SYSTEM...LEADING TO A MORE IMPRESSIVE COMMA HEADAND POTENTIAL FOR STRONGER BANDING. DESPITE THIS...MODELS INAGREEMENT ON STRONG ISENTROPIC SURGE TONIGHT WITH 3 TO 4 G/KG MIXINGRATIOS ADVECTING ACROSS THE CWA WITH STRONG ISENTROPIC LIFT. GARCIAMETHOD INDICATES 4 TO 6 INCHES ALONE IF THIS STRONG LIFT VERIFIES.HIRES GUIDANCE TENDENCY IS TO BE OVERDONE WITH WARM AIR ADVECTIONPCPN BUT RADAR MOSAIC IN CENTRAL CONUS AND PACIFIC MOISTURE PLUMELEND CREDENCE TO THIS HIGHER SCENARIO. CAUTIOUSLY TEMPERED OVERALLAMOUNTS TO THE 3 TO 5 INCH RANGE TONIGHT WITH THIS FORCING.MODEST SURFACE REFLECTION SHOWN IN MODELS WITH A RELATIVELY BROADSURFACE LOW MOVING THROUGH THE OHIO VALLEY SATURDAY WITH INVERTEDTROUGH THROUGH CWA AS LOW LEVEL FOCUS FOR CONVERGENCE. 850-700MBFRONTOGENETICAL FORCING PIVOTS THROUGH CENTRAL CWA OVER THIS TROUGHAND THIS EXPECTED TO BE FOCUS FOR ADDITIONAL 2 TO 4 INCHES ONSATURDAY BEFORE EXITING EASTERN AREAS LATE IN AFTERNOON. COBB METHODALSO REMAINS CONSISTENT AMONG GFS AND NAM ACROSS THE AREA WITHBUFKIT SNOW AMOUNTS IN LINE NICELY WITH OTHER MODEL OUTPUT. LATESTSREF QPF/SNOW PLUME DIAGRAMS AND 18Z NAM COMING IN AND REMAINCONSISTENT LENDING MORE CONFIDENCE TO EXPECTED SITUATION.THE RESULT IS AN EXPECTED SWATH OF 5 TO 7 INCH SNOWFALL ACROSSWARNING AREA WITH BANDING PRODUCING THE EXPECTED HIGHER END 6 TO 8INCHES WITHIN THE WARNING AREA. SOME ISOLATED HIGHER AMOUNTS WOULDNOT BE OUT OF QUESTION WITH ANY STRONGER BANDING THAT PIVOTS OVER ACERTAIN LOCATION. HOWEVER...NO WAY TO NAIL DOWN THAT KIND OFDETAIL.
Link to comment
Share on other sites

 

IWX has some interesting comments on possible phasing not being picked up by models as they share their afternoon update.

HAVE BEEN WATCHING THE INTERACTION BETWEEN THE MAIN SHORT WAVE ANDTHE ONE DIGGING IN ON THE BACKSIDE THIS AFTERNOON AND THERE SEEMS TOBE SOME PHASING ALREADY TAKING PLACE. MODELS HAVE GENERALLY KEPTTHESE WAVES SEPARATE SO THIS IS CERTAINLY SOMETHING TO WATCH THISEVENING. MORE PHASING WOULD LEAD TO STRONGER WAVE AND A MORENEGATIVE TILT TO SYSTEM...LEADING TO A MORE IMPRESSIVE COMMA HEADAND POTENTIAL FOR STRONGER BANDING. DESPITE THIS...MODELS INAGREEMENT ON STRONG ISENTROPIC SURGE TONIGHT WITH 3 TO 4 G/KG MIXINGRATIOS ADVECTING ACROSS THE CWA WITH STRONG ISENTROPIC LIFT. GARCIAMETHOD INDICATES 4 TO 6 INCHES ALONE IF THIS STRONG LIFT VERIFIES.HIRES GUIDANCE TENDENCY IS TO BE OVERDONE WITH WARM AIR ADVECTIONPCPN BUT RADAR MOSAIC IN CENTRAL CONUS AND PACIFIC MOISTURE PLUMELEND CREDENCE TO THIS HIGHER SCENARIO. CAUTIOUSLY TEMPERED OVERALLAMOUNTS TO THE 3 TO 5 INCH RANGE TONIGHT WITH THIS FORCING.MODEST SURFACE REFLECTION SHOWN IN MODELS WITH A RELATIVELY BROADSURFACE LOW MOVING THROUGH THE OHIO VALLEY SATURDAY WITH INVERTEDTROUGH THROUGH CWA AS LOW LEVEL FOCUS FOR CONVERGENCE. 850-700MBFRONTOGENETICAL FORCING PIVOTS THROUGH CENTRAL CWA OVER THIS TROUGHAND THIS EXPECTED TO BE FOCUS FOR ADDITIONAL 2 TO 4 INCHES ONSATURDAY BEFORE EXITING EASTERN AREAS LATE IN AFTERNOON. COBB METHODALSO REMAINS CONSISTENT AMONG GFS AND NAM ACROSS THE AREA WITHBUFKIT SNOW AMOUNTS IN LINE NICELY WITH OTHER MODEL OUTPUT. LATESTSREF QPF/SNOW PLUME DIAGRAMS AND 18Z NAM COMING IN AND REMAINCONSISTENT LENDING MORE CONFIDENCE TO EXPECTED SITUATION.THE RESULT IS AN EXPECTED SWATH OF 5 TO 7 INCH SNOWFALL ACROSSWARNING AREA WITH BANDING PRODUCING THE EXPECTED HIGHER END 6 TO 8INCHES WITHIN THE WARNING AREA. SOME ISOLATED HIGHER AMOUNTS WOULDNOT BE OUT OF QUESTION WITH ANY STRONGER BANDING THAT PIVOTS OVER ACERTAIN LOCATION. HOWEVER...NO WAY TO NAIL DOWN THAT KIND OFDETAIL.

Very interesting.. 

Link to comment
Share on other sites

My final call: 4" IMBY in northeast Scarborough.

Im going with a general 10-15cm (4-6") across the GTA up until King city. Areas north of that but south of Barrie closer to 5-10cm (3-6").

As of now areas like Mississauga and west towards Hamilton have a good shot at seeing 15-25cm (6-10"), however it will depend on how the winds align up. Some models, in particular, the EURO, is more robust in Toronto and has a different wind alignment.

It"ll be interesting to see how the short term models depict this when it comes into range.

For now that's my thinking.

Link to comment
Share on other sites

Archived

This topic is now archived and is closed to further replies.

Guest
This topic is now closed to further replies.
  • Recently Browsing   0 members

    • No registered users viewing this page.

×
×
  • Create New...