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Cold Front, Wind and Snow I-95 Corridor Jan 29-31 2019


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Cold air and bitter winds seem inevitable. This Will produce a strong cold frontal passage. At this time precipitation types and amounts vary from 1-4 inches. Potential exist for a heavy squall with frontal passage.

 

Temperatures will bottom out from 0-5F along the corridor. North and West of I-95 could see temperatures -5 to -10F. Updates to follow.

 

Max snowfall map from CMS below. GFS 1-2, GFSV3 below.

 

fv3p_asnow_neus_18.png

 

 

gem_asnow_neus_16.png

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12z Euro showing 2-3 inches of snow with frontal wave, Washington to Baltimore. Starts as rain then quickly changes over.

 

Temps drop to 10F Wednesday morning but recover to 27 ahead of secondary front. This model showing low of 4F at BWI, Thursday morning. Highs of 11F NW wind 24mph, gust to 40.

 

That cold man...

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The operational GFS is the most bearish on this one, but I wouldn’t expect it to handle frontogenic forcing as well, especially at this range.

 

I do want to see what the 3km NAM projects, but it won’t be in range until tomorrow. I trust it more than the 12km version, which can (occasionally) have state independent convective biases.

 

I’m sure something will happen. Based on my 26 years of experience living here, Arctic fronts like this generally don’t cross quietly.

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Tuesday is shaping up to be an exciting weather day for Maryland, Virginia, along and NW of I-95. No major changes at 12z, except for more agreement. Below are GFS snowfall maps and GFSV3 temps Thursday morning.

 

Models are trending quicker, with a Tuesday afternoon show...

 

gfs_asnow_neus_13.png

 

 

fv3p_T2m_neus_17.png

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I miss living in Philly.

Move back, brother. We’d love to have you.

 

For what it’s worth, we’ve had a mega-HECS-filled winter during every 11yr solar minimum going back to at least the 1880s, so the odds favor either 2019/20 or 2020/21 being epic. ☃️

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It seems there will be a lot of, "nowcasting," with the Arctic frontal passage. Still uncertainty with thermal profiles just ahead, and precip onset times.

 

This morning dewpoints are diving in Maryland. The dynamics involved with these type of air masses can produce local anomalies in precip fields. These can produce local precip maximums.

 

I-95 will be the deviding line. Areas just south and east are involved. This will be a close one. 2-4 north and west, 1-3 just south and east. That's how much will fall. Accumulations will depend on rates and surface temps. Cars and grass for sure in the metro.

 

Behind front temps will drop rapidly with a flash freeze of residual moisture. Black ice the main threat. Outside activities on Thursday should be limited to those who have no choice.

 

nam3km_asnow_neus_46.png

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Yeah, I heard the wind pick up from the NW and watched the dewpoint crater from 30*F to 10*F. I wonder how much lower it will go..still mixing pretty good here.

 

The NWS forecast was for ~ 20*F right now, so we’re underneath that by a solid 10 degrees.

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Dewpoint 8F at BWI. This will help form an insitu CAD over Maryland that some models have been hinting. Impressive warm nose in central Indiana. Modified Arctic air continues to funnel down the east side of Appalachian Mountains. Surface obs in eastern Ohio will be a good bellwether for 500mb amplification this afternoon.

 

Good to be in the game....

 

NatLoop_Small.gif

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A Navy Chief said, "Never change your forecast. That way you can only be wrong once."

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Definitely agree re: in-situ CAD wedge, assuming it doesn’t advect out overnight/into tomorrow morning ahead of the precip shield.

 

That said, models usually underestimate it, if anything, and the trends have been colder/wetter across guidance, as LWX highlighted in their morning AFD.

 

I’m interested in this one. Nice early catch!

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As of 11:34AM, I’m still at 30.2*F/8*F with a N/NE wind and a cirrostratus deck filtering most of the insolation..only 211W/m^2 making it through according to my solar radiation sensor..and it’s peak heating right now.

 

Certainly much colder and drier than forecasted (so far).

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Temps, dewpoint, and relative humidity at my station today graphed below. Interesting how the dewpoint drop occurred in two distinct steps (tends to do that a lot here).

 

Station can be found on CWOP/Mesowest at this link:

 

https://mesowest.utah.edu/cgi-bin/droman/meso_base_dyn.cgi?stn=F3819&unit=0&timetype=LOCAL

 

bDjqjT1.png

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Water vapor image depicting mid level trof nicely. Radar depicts Overrunning of CAD. There has been some discussion obout overcoming a warm ground. The ground was frozen yesterday, and it is still frozen this morning. That is now a non-factor.

 

DC to Philly seems to be the sweet spot for accumulating snow. Someone along the corridor could get 4-5 inches.

IMGw_0.jpg

A Navy Chief said, "Never change your forecast. That way you can only be wrong once."

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Warm advection occurring in earnest early this AM, currently at 31.5/25, up from 27/15 before the cloud deck moved in. Awaiting precip, but some light returns are beginning to manifest aloft on LWX’s higher beams.

 

How much of the early/midday precip falls as snow vs sleet/zr/rain is the question in my mind (the late day precip will almost certainly be snow). I’m not as bearish as LWX on this one even with the S/SE winds to start the day. The airmass going into this is decent, all things considered, with a favorable diurnal start time.

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Precip has been underwhelming thus far, and most modeling doesn’t get it cranking until ~ 12-1pm. That said, even with surface temps above freezing, we’ve been getting off and on “snizzle” here even under the lightest of returns, so I’m not sure how much will actually end up falling as rain (if any), locally speaking.

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Yea, it's going to hit all at one time. Surface low trying to form near Greer SC. That should be what we need. NC mountains are about to get slammed. When the front breaches the mountains this wave will rocket NE.

Yeah, it’s gonna be an anafrontal type deal I think, w/ the majority of QPF now modeled behind the cold front.

 

If I’m extrapolating correctly, then light precip will begin to blossom between 11:30 and 12:30, w/ the front reaching the I-95 corridor ~ 2pm, which is when the heaviest stuff will begin to fall.

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You’re in a much better spot than me for this one, I think.

 

Had intermittent snizzle this morning but it’s pretty obvious we’re gonna miss out on the early part of the isentropic lift/jetmax. Will have to wait for the front itself.

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The main shield of precipitation is moving up into Central Virginia now, just about into Charlottesville now. Should really fill in over the next hour.

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Still oscillating between plain rain and sleet mixed with white missiles here, ahead of the cold front. Temp is dropping though, down a full degree over the last 45mins or so. Moderate snow reports about 5 miles west.

 

Front is approaching OKV/MRB based on velocity readings from LWX. So it’s a little ways away still, unless I’m reading too much into the near-surface flow. Winds are still SE here, but are N out there west of the BR (with stronger NW readings farther to the NW, out over the very high terrain).

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Can see a surge of NW winds approaching OKV on velocity..meanwhile light SE winds still ongoing here ahead of the front.

 

Convergence definitely increasing as this thing takes on a more negative tilt.

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Just had a burst of humongous snowflakes. Trying to flip over for good but not quite there yet.

 

You can peer up into the sky and see it’s filled with (what must be) gigantic snowflakes, just a few hundred feet off the ground. So the boundary layer is cooling..only a matter of time now.

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And just like that, we’ve flipped over, interestingly enough with a NW wind.

 

Still too warm for accumulation, but dynamic cooling is initiating. Currently 36.1/32.

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Coming down good now..solid SN with visibility down to about 1 mile. A dusting to a coating has accumulated on most surfaces except pavement.

 

34.1/31 as of 3:10pm

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