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Sunday - Monday storm now trending more 'normal'

Which can be good or bad, depending on your perspective...

Good Saturday morning everyone :-)

Today is going to be great-- so be sure to get out there and make the most of it, because beyond this one those temperatures won't nearly be as cooperative for the spring weather lovers.

HPC - Surface Map - Saturday

High pressure is departing the Carolina coastline, but is still able to get us enough rain-free time to have our temperatures bump up toward 50. Low pressure lurks to our south and west, and will converge on the area Sunday. As noted in our last blog installment, this presents a lot of out-of-season issues for the tri-state, although now things are settling down a little bit.

It Starts Sunday

NAM - Sunday Morning NAM - Sunday Afternoon

At first arrival, the storm system advances eastward across the Ohio and Tennessee Valleys, though now oriented a little more north of its previous trajectory. This puts a mix of rain and snow along and north of a line that roughly includes the east-west part of the Ohio River. The eastern WV mountains are in for an icy start to the day-- not fun for Palm Sunday church goers. The rest of us from the Kanawha Valley southwestward into Kentucky will instead be seeing a chilly rain, although the right-hand map above is indicating some downsloping will occur. I've drawn in the general windflow using two arrows. The first blue one indicates we'll have cold air dammed in against the WV mountains and spreading west across the northern part of West Virginia. Whatever makes it over the mountains will then rush down the otherside, compressing (and warming) the air that's already there. It looks likely that our friends toward Richwood, WV may not get out of the 20s on Sunday and yet at the same time those who live west of the Big Sandy River might well get pushed to the 50-degree mark again.

This first part of the storm will end when the tri-state enters somewhat of a "dry slot" later Sunday. The no-man's land between one storm that is fading, and a new one that will be strengthening.

Sunday Night Transition

NAM - Early Monday NAM - Monday Afternoon

Two things are happening as we get to Monday: (1) Our first storm is fading as a new storm develops off the Virginia coastline; (2) As this system fills in and weakens, it will retain a portion of its remnant circulation sufficient to keep part of the River-Cities area out of the snow category for a while longer, and of course have part of that dry-slot still aligned through our region until the colder air riding in from the west can cause more moisture to squeeze out of the clouds above. The right-hand map above shows the dual-circulation wind field of such a scenario. This is also why the WV Mountain counties may well clean up again in terms of snowfall as there's no mechanism for the warm air to override.

If you are a more regular follower of the blog, you should recognize this pattern, because we've dealt with it not too long ago (and indeed it happens all the time). Check these out from another storm earlier this month. One particular map "jumps" out at you:

NAM - Clouds / Surface Pressure - Monday Morning Surface Pressure - March 6th, 2013 - Morning

Every storm is unique, but these are pretty close :-)

The mid-upper level dynamics of this system are what separates it from the one earlier this month. As I've said at other times, a good mechanism to identifying the best zone of snowfall potential in these large cyclonic storm systems is to watch what is happening at the 700mb level (cloud level / 10,000feet). This works well as a ball-park methodology and naturally can't account for surface features like the mountains. Anyway, here's the view from the air up there, courtesy of the GFS:

GFS - 700mb Chart - Early Monday GFS - 700mb Chart - Monday Afternoon

The 700mb Low comes right toward the tri-state Monday morning, allowing us to expect that change-over to snow for everyone. It is oriented farther north of the March 6th system, so we'll focus the better snowfall up that way as well. Instead of progressing evenly through West Virginia, the center of the low as it appears on the 700mb chart will "jump" to the coast, deepening there while filling in over the Mountain State (sound familiar?) However, since we'll be firmly entrenched in the cold air by then we'll still be getting snowflakes-- just not the steadier snow that folks over toward New Jersey will be seeing. It is also not lost on me that this action is once again heading toward the Philly / Harrisburg / Washington DC area [a region that has been giving meteorologists fits for forecasting snow, with multiple busts on forecasts that have been making viewers angry].

The Numbers...

In accordance with the increasing clarity (and shifting) of the storm, the models have been painting a different picture of the storm compared to the dire-ness of before. Here's what they are putting out...

NAM - Snowfall Forecast GFS - Snowfall Forecast

(Click on either of the above maps for a larger pop-out)

A couple things I see right away--

1. The snowfall axis indeed shifts north, and I am comfortable with that.
2. The mountains still get their fair share (ski resorts may stay open into April on this one)
3. The donut-hole is back! Of course...

The GFS is advertising a better total snowfall than the NAM, but it has been a more volatile model. My own thinking would be to give the most weight to the solution that brings the least amount of snow. Simple climatology states that these events should be rare, and the amount of times they get forecasted ends up being a much larger number than the ones that get verified.

Nevertheless, any time late March brings a snowfall it should be considered interesting. There may well be school delays and/or cancellations Monday morning, and not quite the welcome-back from Spring Break that college students had been looking for.

Regional Radar/Satellite with Warnings Tracking

Accuweather Radar

From the Storm Prediction Center (below): Click For a Larger Image

Activity Overview Storm Outlook Watches Potential Watches Storm Reports
Temperatures HD Doppler Radar Estimated Rainfall Active Warnings
Current Temperatures HD Doppler Radar Estimated Rainfall Active NWS Warnings
Click For Larger Click For Interactive Radar Click For Larger Click For Larger

Have a great day everyone!

-B

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