Friday, December 11, 2009

My Weekend Outlook & Some Upcoming Pattern Thoughts.

For The Delaware Valley Region.
Date: 12/11/09
Issued: Friday PM

Cold and Dry for Saturday, followed by a Brief wintry mix to rain on Sunday !

The coldest airmass of the season has settled into the region, and this cold weather will continue into Saturday. Strong High Pressure now over the lower Midwest, will move east to the M/A coast by Saturday Night. This will provide us with very cold temperature for tonight, and another cold, but less windy day on Saturday. Lows tonight will dip into the upper teens and low 20's, under mainly clear skies. Saturday will be Mostly sunny and continued quite cold, Highs will be in the upper 30's.

As we approach Sunday, things begin to change as this High moves off the Delmarva coast and heads off shore on Sunday. The return flow around this High will switch our wind direction to the SE, and bring in a milder onshore flow from the mild Atlantic Ocean. Moisture will increase quickly as a weak warm front and wave of low pressure approach from the SE States. This front will then push northward through the area Sunday afternoon and night.

Just enough cold air will be in place on Sunday morning, that a brief period of snow and sleet will occur at the onset of this advancing precip shield, in what looks too be a rainy day for Sunday afternoon and evening. I expect no snow/sleet accumulation on Sunday morning, as this light wintry mix, will then quickly change to a cold rain by afternoon. This will mainly be for points north of PHL.

So overall, expect a Cloudy but Chilly day for Sunday, with a wintry mix during the mid and late morning hours, then turning to a rain during the afternoon. Highs will be in the low to mid 40's. north, and the mid to upper 40's south of PHL. This rain should continue into Sunday evening, then taper off later Sunday night. Lows will be in the Upper 30's.

Early next week we should be near seasonable to slightly above normal in temperatures. For Monday expect P.Sunny with highs in the mid to upper 40's. On Tuesday we can expect a milder day with Highs near 50. Some showers will move in during the day Tuesday, as a strong cold front approaches from the Midwest and Great Lakes. A wave of low pressure will develop in the GOM and then move NE along the front. This low pressure system and cold front will have a pretty good amount of moisture to work with, so the showers move in on Tuesday, and much milder air piles up ahead of this strong Cold front.

This front will then blast through the area on Tuesday night, as much colder air returns and the winds increase as well. It's possible that just enough cold air filters in to change the rain to some flurries before ending during Tuesday night. So I'll keep an eye on that chance, but this doesn't look like a big deal for the snow hounds to get excited about !

Some Upcoming Pattern Thoughts !

Where are we headed for the second half of December > Some Christmas Weather thoughts ???

As I've always said, let the fun begin ! We'll that's if you like the cold and snow. Overall the second half of December will remain quite cold, and become more active and stormy. Most LR models see this cold continuing, and yes I can agree on this 100%, but I'm surprised at the lack of storms and details at the surface. It appears these LR models are having some serious problems in picking up on this pattern. IMO they are not handling certain features well, and cannot be trusted past 5 days with surface details.

Ok here's why I disagree with these LR details that are lacking storms or an active pattern: I'm sure most of you always hear me talking about teleconnections in the mid and Long Range Forecasts. These include the AO/NAO/PNA and each of these teleconnections control the weather in certain/specific regions. These are three of the major pattern drivers for the CONUS, and our part of the Northern Hemisphere. I'm going to keep this very simple, as this could become a book if I get too carried away here, LOL

The combination of the following teleconnections during the winter months, will in most cases signify a cold and stormy pattern for the Eastern CONUS.

1. (NEG) - AO
2. (NEG) - NAO
3. (POS) + PNA

Ok, Guess what the signals are now, and the ensemble forecasts also continue these same signals for the next 2-3 weeks, Ahhh, You guessed it, A Neg NAO / Near tanked and very NEG AO / and a POS PNA. So this would suggest a cold and stormy pattern for the SE, Mid-Atlantic, and Northeast States during the second half of December.

So, for the Delaware Valley Region and NYC Area, I'm forecasting the second half of the month to be as follows

Overall Temps:
Slightly Below to Below Normal.
-1.0 F to -3.0 F

Snowfall Potential:

(1 or 2) Minor snow events of 2" or Less.

(1) Snow event that will be in the 2" to 5" range.

I do think We'll have a White Christmas this year, with at least some snow on the ground. As I've outlined, all signs/signals are very favorable.

IMO, The bigger 2"-5" snow event will have the best chance to occur, near or close to Christmas. So, for all of you snow lovers, it's time to start dreaming of a White Christmas. I do think we have a very decent shot this year !

Take Care,


Anonymous said...

Hi what does CONUS mean???



CONUS = Continental United States

Anonymous said...