Suchan Says: Big Pattern Change Ahead

As my headline states, you and I should be expecting quite a shift in the overall pattern but it will not be Thanksgiving week.  Instead, it’s the following week as we round out November and head into early December where strong signals abound for an absolute flip of the pattern we’ve seen for October and most of November.

Weeks ago I had talked about roughly Nov. 16th – 20th bringing cooler temperatures.  That materialized with highs in the 40s to near 50 and morning lows in the 20s.  Certainly nothing to write home about but it did represent a shift away from 60s and 70s which have been all to common over the past 4 to 6 weeks.

A true flip in the pattern appears ready to unfold the week after Thanksgiving as a large trough digs into the western United States and carves across the central and southern Plains.  A strong jet streak will accompany this trough as well as it digs into the Plains.  This will induce an area of low pressure most likely near our region.

My confidence is actually fairly high in seeing an area of low pressure late November (29th-30th) to December 1st.  Computer modeling is remarkably in good agreement on this scenario.  Differences are confined to exact track, strength of low at this point and that should surprise no one 8 to 10 days out!

Reviewing the GFS, ECMWF and Canadian at this point show rain with a potential rain mixed with snow zone setting up over the northern or northwestern part of the area.  System would then pass by with wrap around cold switching everything over to snow showers or flurries before ending.

If you love snow… what you need to see happen with modeling ahead is a trend of developing the storm a bit further south than currently advertised.  Wouldn’t hurt to see a deeper low as well versus a weak baggy system.

BUT here’s the deal in the end, this system opens the door to an extended period of colder temperatures from Canada plus we’ll likely see developing snowpack across the northern tier of the country to keep cold air masses refrigerated as they slide south.  December still looks colder than normal to me when all is said and done.  A far cry from this autumn we’ve experienced.

Here are some computer model images with notations made in the panels.

avn_189_500

GFS 500mb vorticity… Monday the 28th

avn_210_500

GFS 500mb Vorticity… Tuesday the 29th

avn_213_850

GFS 850mb Temperatures…. can see the “thermal low” of the system passing a bit to far north for ideal track but it’s close

avn_240_850

Final day of November… system moves away and much colder air is setting in

ecmwf

ECMWF (European) surface map for Tuesday the 29th…. it’s similar to the GFS on track

sef_210_850

Canadian 850mb Temperatures Tuesday the 29th… thermal low in this panel is a bit further south which brings better chance for some snow into the area compared to the GFS & ECMWF. Low is not particularly strong however

sef_213_vv

Canadian… deep layer lift / vertical velocities (rising or sinking air). Image is for Tuesday 29th

avn_total_snow_accum_240

GFS keeps bulk of accumulating snow just north to northwest of us

ec_snow

European snow is much heavier w/ stronger system but like the GFS, primarily to our north & northwest (but not by much!)

Chris Suchan
Meteorologist
KCTV5/KSMO

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