LES is More

Big time lake effect snow event along the windward shore of Lake Ontario this past week with historic snowfalls recorded at some stations.

The observed conditions @ Watertown, NY on February 4 are of particular interest.

METAR KART 041756Z AUTO 28014G18KT M1/4SM +SN FZFG VV001 M12/M14
METAR KART 041856Z AUTO 27012G31KT M1/4SM +SN FZFG VV001 M11/M13
SPECI KART 041942Z AUTO 25015G33KT M1/4SM +SN FZFG M11/M13
METAR KART 041956Z AUTO 27019G31KT M1/4SM +SN FZFG M11/M13
SPECI KART 042014Z AUTO 26017G29KT M1/4SM +SN FZFG VV001 M11/M13
SPECI KART 042051Z AUTO 26016G24KT M1/4SM +SN FZFG M11/M13
METAR KART 042056Z AUTO 27012G22KT M1/4SM +SN FZFG M11/M13

From 1756z until 2056z...there was considerable falling or blowing snow. Visibility was frequently reduced to less than 1/4 SM. The wind frequently gusted to above 35 MPH (30 KTS). These observations depict near-blizzard conditions from lake-effect snow. Had these conditions lasted a little while longer...they would have meet the three hour threshold for a blizzard.

The theta diagram shown below shows deep layer instability from the surface up to ~750 mb.

The SkewT-logP diagram shows the vertical temperature profile is nearly dry adiabatic from the surface to ~750 mb...moist adiabatic from the LCL near 900 mb...and deep moisture in the column up to ~700 mb. With such an unstable sounding and cold temperatures aloft...it/s surprising there were no reports of +TSSN. Also note the low tropopause height near 350 mb (~25K')


More interesting and extreme LES obs from Buffalo, NY
SPECI KBUF 032210Z 24029G38KT 0SM R23/0600V2200FT +SN FZFG BLSN VV001 M08/M09
[...]
SPECI KBUF 032359Z 24032G40KT 0SM R23/1800VP6000FT +SN FZFG BLSN SCT004 BKN015 OVC040 M09/M12

Zero visibility although runway visual range reported a low value of 600' (~0.1 SM). Wind gusts to 46 MPH.