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Jan 21 event


Ian

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Not sure if you were asking me or him - I'm in Baltimore County, right at the Hereford zone line.

Both actually.

I am rather impressed at the cold air locked in east of the mountains. Dewpoints are in the single digits across a good portion of the LWX CWA which denotes the true arctic nature of this air mass.

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Have to say, I like the look of the NAM. Maybe it is just because I've seen a number of situations where the p-type didn't change in the middle of the precipitation, but while there was a break. Here, the NAM is really showing two distinct parts of the system, the more broad-scale forcing on the front end which is our snowfall from midnight to 4am or so, and then the more "energetic" part of the system which shows up around 7-10am. In those places still below freezing, we could see some quick moderate freezing rain accumulation.

I still think I mix with the 1st batch....but it is a hard call...NAM is snow for sure at 6z...GFS even at 6Z has a 750MB temp of -0.8 and an 800mb temp of +0.1 even with the 850 line 50 miles to the south...this doesn't inspire a lot of confidence in remaining snow much past 1-2am....I think the key for me and probably you too in Falls Church is getting precip early as possible....a 9-11pm start would be awesome....

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Both actually.

I am rather impressed at the cold air locked in east of the mountains. Dewpoints are in the single digits across a good portion of the LWX CWA which denotes the true arctic nature of this air mass.

Well he is in AA county

Yeah, I just mentioned that in the short range discussion thread - the temp at home has dropped a few degrees since I woke up this morning. 25 at home with a dp of 9

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I have a hunch that the NAM may be right with temps at 2M, I'm not trying to be weenie but CAD situations seem to almost always underplayed even by mesoscale models, to an extent. January 2011, we didn't go above freezing until maybe 5-7hrs after even the coldest model had forecast. Not a very scientific post but I think this might be the case..

yes...agreed for the most part...a 32 degree contour on a model in a CAD situation means nothing to me...It can be in southern PA and there will still be areas that are below freezing....You have to lean toward climo here....I think some areas that are more favored in CAD probably stay below freezing the entire event and perhaps all day

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10:00 am

MRB: 24/6

HGR: 22/7

IAD: 28/3

Morgantown: 15/8

PIT: 11/8

This is good stuff....LWX....should have a winter storm warning up soon....will be curious what they do with Loudoun/Moco...probably WWA and then play catch up later

I would agree with regards to the WSW. I can't recall a time where they immediately went to a WSW (I'm sure it's happened and I'm just drawing a blank). LWX has always been big on the catch up. Though I wonder if they will just let an advisory ride for the entire event except for the places where there already is a watch up.

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10:00 am

MRB: 24/6

HGR: 22/7

IAD: 28/3

Morgantown: 15/8

PIT: 11/8

This is good stuff....LWX....should have a winter storm warning up soon....will be curious what they do with Loudoun/Moco...probably WWA and then play catch up later

Zones look polar opposites (updated at 9:30 AM)

Loudoun has up to 1/4" ice tonight and 1/10" tomorrow... while Montgomery is trace and trace

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based on current information, what would justify warnings east of the Blue Ridge (except for across northern Maryland)? I don't think out here we'll actually reach warning criteria even if one is issued.

I would think there's a small chance to hit warning criteria on ice (1/4 inch). You will likely hit warning on ice. Definitely not snow though...advisory level on snow pretty much area wide I'd say.

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I would agree with regards to the WSW. I can't recall a time where they immediately went to a WSW (I'm sure it's happened and I'm just drawing a blank). LWX has always been big on the catch up. Though I wonder if they will just let an advisory ride for the entire event except for the places where there already is a watch up.

hopefully they don't wait until later this evening when HGR is like 14 degrees and decide it might be a good idea.....Wheeling WV was 28 at 11pm last night....they are currently 9/5....I am going to go ahead and take the under on modeled sfc temps

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based on current information, what would justify warnings east of the Blue Ridge (except for across northern Maryland)? I don't think out here we'll actually reach warning criteria even if one is issued.

From LWX

A Winter Storm Warning is issued when a significant combination of hazardous winter weather is occurring or imminent.

Significant and hazardous winter weather is defined as a combination of:

1) Over 5 inches of snow/sleet

AND/OR

2) Glaze accumulation (freezing rain) of 1/4 inch or more

AND/OR

3) Enough ice accumulation to cause damage to trees or powerlines.

AND/OR

4) a life threatening or damaging combination of snow and/or ice

accumulation with wind.

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hopefully they don't wait until later this evening when HGR is like 14 degrees and decide it might be a good idea.....Wheeling WV was 28 at 11pm last night....they are currently 9/5....I am going to go ahead and take the under on modeled sfc temps

outside DC, temps are falling into the 20's now on all wxbug stations inside the beltway, on the westside at least. All except 1 station are at 29 or below.

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We are running the op NAM fire wx nest over DC because neither OPC/HPC are requesting points. Hourly progs here for those interested:

http://www.emc.ncep..../mmbpll/firewx/

Thanks!

looks like the big warm push at 850mb is between 8z and 10z and the big warm push at the surface between 14z and 16z

the 1st slug is mostly 6z to 8z or maybe a bit after and then a distinct lull before the heavier stuff...that 9am to noon period will be interesting wrt surface temps

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Thanks!

looks like the big warm push at 850mb is between 8z and 10z and the big warm push at the surface between 14z and 16z

the 1st slug is mostly 6z to 8z or maybe a bit after and then a distinct lull before the heavier stuff...that 9am to noon period will be interesting wrt surface temps

For us that lull is the kiss of death. It doesn't look like the 06Z to 08Z stuff is that heavy. the real good stuff comes with the second wave if I'm reading it right.

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From LWX

A Winter Storm Warning is issued when a significant combination of hazardous winter weather is occurring or imminent.

Significant and hazardous winter weather is defined as a combination of:

1) Over 5 inches of snow/sleet

AND/OR

2) Glaze accumulation (freezing rain) of 1/4 inch or more

AND/OR

3) Enough ice accumulation to cause damage to trees or powerlines.

AND/OR

4) a life threatening or damaging combination of snow and/or ice

accumulation with wind

AND/OR

5)A Petition signed by at least 100 whining weenies

Missed one.

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Hit my low-of-day about 20 minutes ago. Slight rebound since, but only 31.

outside DC, temps are falling into the 20's now on all wxbug stations inside the beltway, on the westside at least. All except 1 station are at 29 or below.

DC stations are now running 28-30 after a midnight-1am high of 38-40....Children's hospital just dropped to 27.....I'm pretty sure Sterling's point and click highs of 40 for DC and northern VA last night will not be reached....

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10:00 am

MRB: 24/6

HGR: 22/7

IAD: 28/3

Morgantown: 15/8

PIT: 11/8

This is good stuff....LWX....should have a winter storm warning up soon....will be curious what they do with Loudoun/Moco...probably WWA and then play catch up later

My house 36.5 degrees so there is a big temp gradient., My humidity is 29%.

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