Wednesday December 20 2017

Back to reality today with temperatures staying in the 40s on this last day of Autumn. Yesterday did reach 60ºF at Baltimore’s BWI, but a quiet cold font moved through and you will notice the chill today. We have one more warm up this weekend before the pattern changes again. This will bring in rain Saturday that may get you wet at the Ravens game. The next surge of cold air looks faster on the computer models, but I have my suspicions about the accuracy of what that means. See more below.

Stats For December 20

Normal High: 44ºF

Record High: 67ºF in 1877

Normal Low: 27ºF

Record Low: 6ºF in 1942

Snow Record: 3.0″ in 1966

Sunrise: 7:22 AM

Sunset 4:47 PM

*Bay Water Temperature = 44ºF at Thomas Pt. Light House

Snow To Date (at BWI): 3.8″

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Weekend Rain

This large scale system is ahead of the arctic front. Low Pressure will ride along the mountains to our west. This is a pattern I identified in my winter outlook as one of the primary tracks. This brings warmer air ahead of it, so we will get only rain this weekend.

Storm Animation

This animation shows the rain moving in Saturday morning, then out Saturday night. There may be some breaks as the warmer air tends to push the rain up along the mountain ridges… but plan on a soggy Saturday if you go to the Ravens game or another outdoor event.

Christmas Day

I Don’t Believe This Map

It is going to be colder for sure! In fact, the consensus among computer modeling now is a faster cold front that moves off of the coast and takes much of the moisture with it. The thing is, we still have 5 days and I don’t think this is fully accurate. Remember the last snow event we had last Friday? Also the one the weekend prior? Both were initially expected to be too far off of the coast, and only came back in line with our region that day or two beforehand.

Models tend to have bias or errors and this is the one I have identified in my winter outlook. The trend was for systems to verify farther east from the original forecast. Well, we have that now from what initially looked like Christmas rain. Now, I expect this to creep back west in the next few days of model runs. We still have time to prepare.

Jet Stream

One thing I can almost promise at this point: It will get MUCH COLDER on Christmas Day! This is the start of a pattern change, and there will be reinforcing cold shots through the first week of 2018.

Jet Stream Animation

Temperature Outlook

The big cool down will be really big to close out the month. Whenever it arrives, it will be stronger and last longer that the previous arctic push.

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