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March 20-21 Potential - STORM MODE THREAD

stormtracker

By stormtracker,
in Mid Atlantic

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Fozz

Fozz

Posted
Posted
4 minutes ago, supernovasky said:

Lol. It does, sorry. I'm really hoping I can cash in on being at 500' and catch the right end of a marginal temp event.

I think you will, especially when a better winter arrives, and maybe with this storm. I live at around 600' and I've lost count of the number of times mappy was surprised at my total even though her work place is just a few miles from my backyard (but also around 300' or so). A small difference like that can matter a lot in a marginal event.

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MillvilleWx

MillvilleWx

Posted
Posted
4 minutes ago, Bob Chill said:

Your area is pretty densely developed so all that asphalt and concrete does make a difference but with that being said there is no doubt over time that gburg does better than my yard. Unfortunately you moved just at the beginning of a really crappy stretch.  If you were here in 13-15 winters there would have been a noticeable difference compared to rockville, Bethesda, silver spring, etc.

Olney is pretty far removed from development and it really helps. It keeps getting better as you drive north on 97. Damascus is a jackpotville of MoCo. I worked in mt airy for 5 years and that 30 miles made a massive difference. I was working there during 12/5/09 and damn I'm glad I was. Double what I had at home. I watched the snow depth drop every like every mile south.

If it makes you feel any better, you'll prob do better than me this week. Lol

Rt 27 is pretty incredible, along with MD 108 in this regard as well. It's a stark difference at times from Germantown to where I live, and really gets interesting as you head north to Damascus. That run from Laytonsville on 124 to Damascus and up 27 to Mt Airy is special in marginal events. You can see the snowfall on ground increase like you mentioned. Two April's ago, there was a very borderline event in the area and I watched the rain change to snow as I was driving to GF's house. Temp drop like 2-3 degrees over a few miles. This area is extremely unique for micro climates and this is a system where this will be put to the test. I can see areas NW of Rockville start out as sleet/rain briefly, then change to all sleet before shifting to snow. How fast is key to potential accumulation. I really like Carroll, Northern Baltimore Co. and areas west out to WV in this one for best chance at jackpot. Westminster is probably in a solid spot this go around. 

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Fozz

Fozz

Posted
Posted
Just now, supernovasky said:

So right now, we've got the GEFS + EPS + Euro on one side (great for the cities, great for everyone involved), but the operational GFS is being dang stubborn. NAM is being NAM.

 

I have to think our chances are good and that the NWS/Cap Weather Gang are underselling it, right?

We've got a huge factor that's not on our side, and that is climo. I think that's why the forecasters are skeptical at this point, and it's completely understandable. But with time there will be watches and warnings if these trends start to lock in.

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ErinInTheSky

ErinInTheSky

Posted
Posted
1 minute ago, Fozz said:

We've got a huge factor that's not on our side, and that is climo. I think that's why the forecasters are skeptical at this point, and it's completely understandable. But with time there will be watches and warnings if these trends start to lock in.

Good point. It’s hard to bet against climo this season.

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Bob Chill

Bob Chill

Posted
Posted

I wouldn't read into the GEFS too much. Lower resolution is far inferior to the op with marginal temps. We're inside of the useful range at this point. The GEFS is very supportive of the ops qpf distribution so that piece of the puzzle is locking in good. But with marginal temps for at least part of the storm, those gefs members are no doubt too aggressive in general. 

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SomeguyfromTakomaPark

SomeguyfromTakomaPark

Posted
Posted
10 minutes ago, supernovasky said:

So right now, we've got the GEFS + EPS + Euro on one side (great for the cities, great for everyone involved), but the operational GFS is being dang stubborn. NAM is being NAM.

 

I have to think our chances are good and that the NWS/Cap Weather Gang are underselling it, right?

I wouldn’t say underselling it, I would say being prudent given the time of year, complex set up, and marginal temps around the metro areas. 

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Bob Chill

Bob Chill

Posted
Posted

These points can never be overlooked when comparing 10:1 snow maps:

  • It's going to rain first for quite a large portion of our sub
  • Temps will be above freezing leading into and at least part of the storm for most of our region so early snow will not stick
  • Meso and global soundings are showing a warm nose until after the low gets east of us
  • DGZ won't be optimal until after the low pressure is to our east
  • Omegas in the DGZ aren't looking all that great in general

Anyone thinking 10:1 even if it's all snow at their house is grossly overestimating how much will accumulate and this includes the northern tier. The wildcard is wave 2. IF there is a legit CCB/deform area then ratios could actually be above 10:1 but that piece of the puzzle is still very uncertain. 

 

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winterymix

winterymix

Posted
Posted
26 minutes ago, Fozz said:

We've got a huge factor that's not on our side, and that is climo. I think that's why the forecasters are skeptical at this point, and it's completely understandable. But with time there will be watches and warnings if these trends start to lock in.

The High Rez NAM (18Z) shows our area flipping to snow at hour 40 for five hours and then mixing.  The second impulse shows another period of snow for 3 to 5 hours and then another mix.  It seems that "the warm nose" is going to return twice.

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Bob Chill

Bob Chill

Posted
Posted
3 minutes ago, winterymix said:

The High Rez NAM (18Z) shows our area flipping to snow at hour 40 for five hours and then mixing.  The second impulse shows another period of snow for 3 to 5 hours and then another mix.  It seems that "the warm nose" is going to return twice.

I thought about that but I'm skeptical. The whole event is morphing into a more cohesive evolution. My guess is that any "second" warm nose will only be around during light precipitation when it won't matter much anyways. If we don't get much of a lull then everyone but SE of town is probably good once they flip to snow. 

I will say that I thought the euro temps were too aggressive on the cold side but even the 3k drops the surface for most areas below freezing before 18z. Which is counter-intuitive because temps at sunrise are above freezing everywhere. This is very unsual for a mid day march storm. The HP pressing down couldn't be more perfect honestly. 

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Kmlwx

Kmlwx

Posted
Posted
3 minutes ago, Eskimo Joe said:

I would be shocked to wake up to a watch for anyone east of I-81.  Too marginal of an event.  Probably advisory by noon and maybe we get lucky and an upgrade to a warning last minute.

I mean...isn't that the whole point of a *watch* - to show POTENTIAL? We've seen them plenty of times go with a watch and then go to advisory once trends are clear. 

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clskinsfan

clskinsfan

Posted
Posted
6 minutes ago, Bob Chill said:

I thought about that but I'm skeptical. The whole event is morphing into a more cohesive evolution. My guess is that any "second" warm nose will only be around during light precipitation when it won't matter much anyways. If we don't get much of a lull then everyone but SE of town is probably good once they flip to snow. 

I will say that I thought the euro temps were too aggressive on the cold side but even the 3k drops the surface for most areas below freezing before 18z. Which is counter-intuitive because temps at sunrise are above freezing everywhere. This is very unsual for a mid day march storm. The HP pressing down couldn't be more perfect honestly. 

And it is about time. For two years we have had LP's over the lakes during our events. It is refreshing to finally have a good setup. I wish we could have had this setup in January or February.

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WxUSAF

WxUSAF

Posted
Posted
17 minutes ago, Bob Chill said:

I thought about that but I'm skeptical. The whole event is morphing into a more cohesive evolution. My guess is that any "second" warm nose will only be around during light precipitation when it won't matter much anyways. If we don't get much of a lull then everyone but SE of town is probably good once they flip to snow. 

I will say that I thought the euro temps were too aggressive on the cold side but even the 3k drops the surface for most areas below freezing before 18z. Which is counter-intuitive because temps at sunrise are above freezing everywhere. This is very unsual for a mid day march storm. The HP pressing down couldn't be more perfect honestly. 

Interesting that the 3k NAM is one of the coldest at the surface, but also has the strongest warm nose.  I wouldn't be surprised if both get muted a bit in the next 2-3 runs.  If Euro keeps the thermals looking like 12z today over the next 2 runs and the 3k also holds firm, that will be an interesting forecast decision come tomorrow afternoon. 

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dallen7908

dallen7908

Posted
Posted
11 minutes ago, Eskimo Joe said:

Has to be at least a 50% (60%?) confidence level.

Not sure if this has changed because of the Weather Ready Nation Initiative but this is one description of the difference in categories. 

Outlook - Winter weather that may cause significant impact in the day 3 to 7 forecast time period and eventually lead to the issuance of a watch or warning is contained in the Hazardous Weather Outlook. More scientific discussion on the event can also be found in the Area Forecast Discussion. Forecasts in the day 3 to 7 time period typically have a lot of forecast uncertainty. Uncertainty is generally in the 30 to 50% range that the event will occur and reach warning criteria. It is intended to provide information to those who need considerable lead time to prepare for the event.

Watch - A watch is generally issued in the 24 to 72 hour forecast time frame when the risk of a hazardous winter weather event has increased (50 to 80% certainty that warning thresholds will be met). It is intended to provide enough lead time so those who need to set their plans in motion can do so. A watch is issued using the WSW Winter Weather Message product and will appear as a headline in some text products such as the Zone Forecast. It will change the color, as shown in the table below, of the counties on the NWS front page map according to what type of watch has been issued.
 

Warning - These products are issued when a hazardous winter weather event is occurring, is imminent, or has a very high probability of occurrence (generally greater than 80%). A warning is used for conditions posing a threat to life or property.  Warnings are issued using the WSW Winter Weather Message product and will appear as a headline in some text products such as the Zone Forecast. It will change the color, as shown in the table below, of the counties on the NWS front page map according to what type of warning/advisory has been issued.

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winterymix

winterymix

Posted
Posted
28 minutes ago, Bob Chill said:

I thought about that but I'm skeptical. The whole event is morphing into a more cohesive evolution. My guess is that any "second" warm nose will only be around during light precipitation when it won't matter much anyways. If we don't get much of a lull then everyone but SE of town is probably good once they flip to snow. 

I will say that I thought the euro temps were too aggressive on the cold side but even the 3k drops the surface for most areas below freezing before 18z. Which is counter-intuitive because temps at sunrise are above freezing everywhere. This is very unsual for a mid day march storm. The HP pressing down couldn't be more perfect honestly. 

 

9 minutes ago, WxUSAF said:

Interesting that the 3k NAM is one of the coldest at the surface, but also has the strongest warm nose.  I wouldn't be surprised if both get muted a bit in the next 2-3 runs.  If Euro keeps the thermals looking like 12z today over the next 2 runs and the 3k also holds firm, that will be an interesting forecast decision come tomorrow afternoon. 

I realize that forecast soundings are only as good as the underlying model.  Attached below is the 18Z GFS sounding for Tuesday afternoon, IAD.  The next 3 hour period shows the column as frozen. Until then it seems that precipitation should be some sort of a mix.

 

gfssoundingforecast.jpg

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