FIRST CALL: quick heavy snowfall Thursday night regionwide

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Tongiht I’ll show some of the parameters I’m looking at tonight.  For modeling the 21z SREF ( ensembles of nam,wrf and gfs runs) was prefered because of the ability to generate probability forecasts within that model.

Overall an arctic front will move into the region thursday night with low pressure development to the south of this boundary. moisture will be drawn along and north of the boundary leading to a considerable amount of lift and the development of precipitation late Thursday afternoon and night.  By friday morning snow should be ending with a very cold friday.

– this precipitation may start out as a period of rain late Thursday afternoon. I feel the NAM is overdone on the WAA with the GFS underdone on WAA. the SREF allows for model biases to be accounted for.  the region in the southeast circled in with lines in the circle is where I think the precipitation starts as rain for an hour or two. After which my thinking is a process known as dynamical cooling ( heavy precipitation falling which aids in cooling the atmosphere) comes into play

and quickly changes the rain to snow.

i’m also thinking some thunderstorms develop ahead of the low which may actually work northeast around the north side of the low track, This will be something to watch that could lead to a heavier band of snow setting up. What is more likely to create a band of heavier snow is the amount of omega ( term to measure upward motion and thickness advection) lift in place just north of the low track.

The SREF indicates a high confidence for at least 2 inches of regionwide. I’ll use that as a base and I like the idea of a heavier snowband to the north of the low track as well.

low track black circle to the north is where heavy snow band would track.

FIRST CALL for accumulations

this will be a quick hitting system only lasting about 12 hours with moderate to heavy snow at times. winds may also pick up if the storm to develop quickly like the nam has.  I’ll have another update this afternoon likely to make revisions. winter storm watches could be issued tonight if trends continue to show these snow amounts.

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8 Responses to “FIRST CALL: quick heavy snowfall Thursday night regionwide”

  1. tornadolarkin Says:

    SREF omega lift still loks good this morning, along with the 6 hr precip it shows.

  2. mitchg Says:

    yup, general .25 to .5 qpf across the region this yields 3-5 snow. NAM faster now with the changeover with a smaller region seeing any rain. first band during the day thursday of lighter snow focused along Ohio river second band is heavier and tracks from southern MO into southern and eastern KY. my thinking would require winter storm watches later today though going into 4th forecasting period it may be another forecast shift away.

    Also I surprised by the dry forecasts for Monday GFS and ECMWF showing over .1 qpf of rain/snow

  3. mitchg Says:

    12z gfs ensembles match up well with sref with .25-.5 regionwide.

  4. mitchg Says:

    nws forecast seems mainly weighted on the ecmwf for what reason i don’t know. I think the ecmwf has been lagging behind for several days now. I’ve done pretty well using sref in the past and will stick with it despite the 1-3 nws has. I will say 3 looks more likely than 5 for many regions.

  5. james Says:

    Mitch, do you think any chance of watch being extended down to Lexington tomorrow?

  6. tornadolarkin Says:

    Man Mitch, check out latest run of sref. Omega lift looks great!!!

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