Thursday, November 18, 2010

The smooth roller coaster ride, is about to take a dive after Thanksgiving into the first week of December. A Colder Pattern is on the way !

Full Discussion and Forecast:
Issued: 11/18/2010 (Thursday 5:00 PM)

My Mid-Range Call:
Nov 19th through Dec 5th.

Issued For:
The Delaware Valley Region and Northern M/A States.

Full Discussion:
This is my first full, in depth discussion, to start off the 2010-2011 Winter Season. As we all know, the smooth roller coaster ride has been going on since the end of October, and has continued into much of November. We have experienced both Mild and Chilly temperature, from slightly above normal to slightly below normal, but nothing really that extreme so far.

As of today, much of the M/A and the PHL region, are near normal with temperature for the month. The same goes for overall precipitation amounts. This same pattern will continue through near Thanksgiving, then things will change rather quickly with the overall u/l (Upper level) pattern, which will then transfer to the surface, and start effecting our weather, down here in the Zoo.

The ENSO > La Nina signal is doing her typical thing so far this Fall season, and is pretty much on target. But She's about to get her tracks buckled after Thanksgiving ! The combined timing of a typical seasonal step down, and favorable teleconnections, are about to set things into motion. All teleconnections have been rather flat over the past few months, but both the AO and NAO are slowly heading negative, and could really take a more sharp dip between Nov 27th and the first week of December.

A large and rather strong PV (Polar Vortex) will begin to take shape over "North Central Canada" early next week. This will then send down colder air, and carve a trough over the Central US during early next week. This PV and trough will then slowly slide east later in the week towards Thanksgiving, and then this trough becomes parked thereafter, over the Eastern US, as blocking develops near Greenland as a NEG NAO/AO couplet develops.

This PV will then have no where to go, but east and setup near a Newfoundland 50/50 position. If this all sets up accordingly, then additional shortwaves and troughs will continue to develop, over the Central and Eastern US, as we head into the first week of December. This should produce a much colder pattern over these Regions along with a couple Clipper type systems or disturbances during this timeframe. A more pronounced ridge will be prevolant over the Western CONUS, so milder conditions can be expected there during this period.

So to sum it all up, much of the Central and Eastern CONUS, will begin to see a pattern change to colder weather and some increasing storm activity, which starts before Thanksgiving in the Central US then moves east and effects points east of the Mississippi from near Thanksgiving into the first week of December. All these Regions will see below normal temperature as an Anomoly, from Nov 22nd through Dec 5th, with the best chance over the Central/Northern Plains, The Midwest, The G/l's and much of the NE/MA States. I'm not forecasting any bitter cold temperatures, or well below normal temps with this pattern change, just >>> "Slightly Below" to "Below Normal"

The Deep South and SE States, will see "Near" to "Slightly Below Normal" temperatures during this period, with a couple of days getting quite chilly during the Thanksgiving weekend.

My Forecast for the Delaware Valley and NYC Areas !!!

Expect a chilly weekend with Mostly Sunny skies for both Saturday and Sunday, At night expect fair and cold conditions. Highs will be near 55 on Saturday and near 50 on Sunday. Lows in the Upper 20's to mid 30's.

Early next week we rebound to the Upper 50's on Monday and then approach 60-65 for both Tuesday and Wednesday. This will be the last time we see the low to mid 60's for quite a while. A strong Cold front and trough moves in on Wednesday and Thanksgiving. A low pressure system will develop on this front over the lower Midwest and Ohio Valley on Tuesday night and Wednesday, then move ENE to the Northern M/A coast on Thanksgiving. This will likely bring a round of rain and some showers for Wednesday into much of Wednesday night, then a few leftover showers on Thanksgiving day, some clearing is possible during the afternoon.

Temps will begin to drop during the day Thursday (Thanksgiving) into the Upper 40's, then followed by some much colder weather for later next week into the weekend, with Highs only in the lower to mid 40's, and lows in the mid 20's and lower 30's. I want to also mention the possibility of some flurries or snow showers between the 28th and 30th from CAA (Cold Air Advection) along with a possible s/w (Shortwave) disturbance moving through the Northern M/A and Southern New England. It's really too early for detail until we get closer to this time frame, but worth a mention, due to the pattern I see coming.

As we head into the first week of December or (through the 5th), we can expect a continuation of cold weather (Below to Slightly Below Normal Temps) and some minor systems, that could bring some rain and or wet snow. I'll also update on this possibility as we get closer. Winter is knocking at the door !


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