Weather Turns Cooler and Unsettled, then Snow?

I have been watching models for several days now seeing if one run would show the potential of snow for a few areas across the Ohio Valley region past October 20th. Needless to say, the GFS has went that way. As stated many times models will flip back and forth but the overall message I take from any modelling is a trend to look for as we come closer to that time frame.

To review, since it has been over six months, when looking at the thicknesses you want the number and dash lines to be blue. The general rule of thumb is if you have that thickness number below 540 decameters (DM) then the potential exists that the column of air is cold enough to support snow. With the time of year only being late October being at 540 or just under might not be cold enough but it will be close.

Another feature to look at is the 850 millibar (MB) level. Currently the temperature at that level appears to be a tad too warm for snow but I will watch it. A bona fide surge of Arctic origin air appears to be poised to come down and great the region post October 20th so be prepared for that potential in about 10 days. Until then moderate temperatures and a few rain chances will exist.

Coming back to the near term, the mostly sunny days and pleasant temperatures are about to come to an end. High and mid level clouds from the disturbance just off the Florida coast is responsible for blocking full sunshine. The recent post the other day mentioned that the storm system could plague eastern portions of the region and it appears it will have some affect.

Wednesday Map Indicated Rain East, Rain West, Dry in the Middle; Courtesy of NCEP

This is a look at the surface features on Wednesday afternoon. Low pressure over the Delmarva region will throw moisture from the Atlantic back west far enough to provide a threat of rain for eastern Ohio, western Pennsylvania, and West Virginia. Back farther west cold front will be inching eastward that a few showers could affect the western part of the region that same day. It appears that Wednesday could be a split between systems across the Ohio Valley. Rain from a tropically influenced low pressure system to the east and a cold front and its associated features from the west.

Thursday looks to be a pretty good bet of rain, region wide as the cold front swings through the Ohio Valley. Showers and a few thunderstorms will be possible for most of the day. Right now the rain should move out by late Thursday in the west but will linger for most of the day Friday in the far east. The good news is that the weekend appears to be dry at this time.

Speaking of temperatures, highs in the mid 70s to lower 80s should stick around one more day, Tuesday, but drop a few degrees through the weekend. Wednesday should be predominantly low to perhaps a few upper 70s, Thursday upper 60s to low 70s, and Friday featuring upper 50s to mid 60s. As for the weekend, Saturday should range from the upper 50s north and east to near 70 south and west, while Sunday should be a bit warmer with low 60s north and east to low 70s south and west.

The last area of focus is still in the tropics. Without trying to beat a dead horse over and over, upward motion patterns appear favorable for a storm to come out of the pattern when the Midwest, Great Lakes, Ohio Valley, and Northeast flip back to a colder weather regime. As always stated, this is not in stone and is not a forecast, this is based on teleconnection patterns and what should occur. This weekend’s tropical disturbance off the Florida Coast and now the Carolina’s and Mid-Atlantic I believe is a warning shot telling us to pay attention. This is still several days out and will have plenty of time to watch but it is something I will keep my eye on.

In the near term, go out and try to enjoy the rest of the day and tomorrow because the days are numbered for 2011 before the real cold sets in and then you will have to wait until the Spring of 2012 to have weather like this.

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By Weather Specialist Josh Ketchen