two part christmas weekend snow

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part 1:  a shortwave will bring a period of snow to the region from late friday afternoon into early christmas morning. The snow will develop by late afternoon from 1-65 west then into the 1-75 regions by early evening and further east after midnight. a general .1 to .2 qpf with local amounts of .25 qpf  are still expected yielding 1-3 inches of snow. However with the earlier timing highs in the mid 30’s south of the southern Kentucky parkway may allow for a mix with rain at the start. slick spots are still expected friday night and saturday and winter weather advisories will likely be issued. lighter snow flurries will linger into saturday evening.

short range ensemble qpf ( average of numerous nam and gfs runs)

this shows a high confidence in over .1 qpf of about 90%  from friday night into saturday

 but only a 30% chance of .25 qpf. thus the most likely outcome is for qpf between .1 and .25. This with ratios of 10:1 for the south and up to 15:1 for the north yields a 1-3 inch snowfall by christmas night.  the ecmwf has a general .1 to .25 as well with more amounts closer to .25 across the south. However the ECMWF has been suspect so far on qpf and will trend toward the sref, gfs and nam runs. If the ecmwf is correct my forecast totals would need to be increased for the south.

gfs qpf till christmas night

nam qpf till christmas night

both models indicate the snow band from the shortwave tracking from the upper midwest southeast then east along 1-64 with lighter snows around the band. 

updated snow map for PART 1 THROUGH SATURDAY NIGHT 

Now onto part 2: after flurries and light snow showers saturday night and upper level low begins to develop over the region as seen here on the 500 mb map

we’ll also see steeping lapse rates and colder air aloft which will be prime for the development of numerous snow showers throughout the day and into the night. snow ratios should also increase across the region and the latest model runs are picking up well on this snow shower activity. upslope flow kicks into full gear as well.

nam qpf

snow forecast PART 2 SUNDAY

day to day details are updated in the 14 day. for the long range take a look at this from the ecmwf ensembles for days 6-10 temperatures.

 ECMWF Ens

there is a nice map for those who want a warm-up. I often focus more on the snow and cold which I like. I’ll try not to forget those who want a winter thaw and that map is for you.

by day 10 the trough reaturns to the east but notice the flow coming straight off the pacfic, that is not favorable for well below temperatures in days 11-15 as suggested by the gfs ensembles. It appears the la-nina pattern may begin to assert it’sself but I don’t think winter is over and i don’t see a blowtoruch yet just more of a normal to slightly warmer than normal pattern.  I’m also not buying another version of the gfs arctic train for days 11-15 as on the 00z run.

next week we’ll have a few things to deal with

1. enough low level cold could linger mid week for some icing before a late week warm-up to end 2010.

2. new years could be a stormy and windy one with 50’s, could be another high shear low instability event. However I’m noticing the gfs is becoming less bullish on the warm-up likely sensing the arctic air in place and the arctic airmass in Canada.  It should be a very fun weekend in the plains to start 2010.

3.  colder with still some light snow by the 2nd or 3rd. a normal pattern for this time of the year still means rain or snow with storms for the first 10 days of january.

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One Response to “two part christmas weekend snow”

  1. tommy Says:

    Mitch please lets hope this thaw is erroroneous we need cold and snow!!!

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