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Tuesday, March 25, 2014

Lucy and the Football

Some thoughts about forecasting.. and the MANY busts we've had this month. We've come such a long way and at times the public hardly recognizes it.

I must say that I totally enjoyed the 6 inches or so of snow that fell today. While I was a bit gun shy because of the last 2 busted events, I tried to convey "banding" and compare it to thunderstorms. There was also a sharp cut off where Farmville had NO snow just 50 miles east and Richmond was in the upper 40's early afternoon while we had heavy snow falling.

The computer models have gotten so much better, but just like you don't notice your children growing each day, you as the common person doesn't always notice or appreciate it.

We often use Jan 25, 2000 as a benchmark for busted storms. We had 7-12 from 5-6 miles west of LYH and DAN east that was 100% not forecasted in our region.  However, by 11pm, it was clear snow was coming and advisories were up for 2-4 inches. January 25, 2000 -- With that, the models were horrible and forecasters used now casting and radar to make a forecast. Everyone was watching radar with bated breath because the storm had taken on a classic "Negative tilt" look on radar. I had just gotten into reading models and local forecast office discussions and it was the NWS office out of State College who broke the silence around 8pm saying something big was up and talked about a foot or so. The model data had an incorrect Jet stream data and that was a 100 mile difference in the "track" of the storm. Not a dry slot, early change over-- track. I can't think of any storm "track" that was off by 100 miles in recent memory.

(For the record, I came home from work around 3pm that day and saw radar and told my roomates 6+ inches over night and at 5am we all had the front door open just amazed at 2-3 inch an hour snowfall on Jan 25, 2000)

With that, some amazing things the models did this month..

1. March 5 we were in the 70's and the models correctly showed within an hour or two we'd change to snow around 7 am Monday AM. I'm not sure even 10 years ago we'd of had a clue of that drastic drop in temps. The cold air actually hurt us because it blasted so far south, it pulled the forcing to our south and a band to our north leaving us in "sinking air" known as subsidence. Hence, a forecast of 5-8 inches ended up 1-2 inches.
2. March 17th- We were sitting at 48 degrees and drizzle when my kids and I walked out of lunch  and as modeled, by 4pm it was 35 and heavy snow. I doubt any model would have shown that accuracy 10 years ago.The models also showed the mix with sleet we had late evening and overnight. Had the stuff been heavier, we would have had more snow mixed in with the sleet and snow grains. So, a double whammy based on the "dry slot"

 Christmas Eve 2002, a surprise front running event to the Christmas Day storm (rain here, but snow to rain to snow in NOVA and a blizzard in upstate PA to NE) was very similar in that temps were WAY warm for snow but very dry air aided in the process. At that time, NO model showed snow south of the Mason Dixon line, but with dry air we had snow in NOVA, unforecasted on Christmas Eve.
3. March 25- The models did a very good job showing where this band would set up. Most data had it hugging the BR and LYH to CHO being close to the jack pot area, with ROA getting lesser amounts. Looking at the end results, you can see why it made sense.

BUT, NO forecaster followed that data because of the bast 2 busts, late season and the myriad of issues associate with that. (Warmth, rates, etc really matter in late season events, even when it's cold and below freezing)

Now, I feel like I conveyed well that "banding" would be an issue and somewhere would end up with more snow. Now, did I expect 6-7 inches-- NOT AT ALL, but did I think a surprise 4-5 inches was possibe? Yes! and I said that.  I'm a weather hobbyist with 300 readers. The NWS, WSET and everyone else who is a paid professional has to appeal to the "least common denominator" and on some levels that dumbs down forecast because they  have to. Some people just want to know how much, when and how will the roads be. Some what to a little more like how and potential and a crazy few like to know even more. So, a huge challenge is created because of these different needs.

So, my challenge to you as my readers is to NOT look at this as a month of Weathermen still getting paid to do their job despite the wrong forecasts, but look at the growth in the field. If you step back from the rough month, outlooks are getting better. Think of our "big" event from Feb 12-13-- we had a week lead time on that event and the window for start time was within 3-4 hours for about 3 days out. Despite some short term set backs, we are better off with Hurricane tracks, Tornadoes and severe weather and yes, even snowfall forecasts despite this challenging month. Forecasts are saving lives and making people aware of day to day conditions and we are getting better at doing it.

3 AM update

One of those nights where I dozed off at 10:30 or so and woke up at 1 am thinking it was 5am..and it was only 1AM.

Our storm looks good up close now, after 2 bad forecasts on March 3 and March 17th, hopefully this one pans out. The clipper has a little punch and radar looks to be developing like the more aggressive models. With that, I'm hedging a bit low because it's late March, some melting as it falls..etc. Most models show 3-4 inches across most the region, but I'm going to put up 1-3 inches, with a potential for a bit more, especially the higher elevations. If everything goes crazy, a few spots could see 5 inches.

New Map..
General 1-3, with local higher amounts. Should see several hours of moderate
to even heavy snow at times and flurries linger to late afternoon in our area. 

This radar out of NE TN shows our precipitation moving NE.. the more aggressive models have all shown our precipitation forming down here.

Monday, March 24, 2014

Tune in for the season finale!

I think??

Crazy winter in both Lynchburg and Roanoke that outside of the BIG snow on Feb 12-13, neither place has a snowfall over 2 inches.

So, if by some chance, LYH gets 2.1 inches tomorrow, it will be our second biggest storm of the year. And, there is legit shot at that, albeit not the greatest.

The big storm idea died late last week and while I wanted to update, work was killing me Friday-Saturday. We are left with a clipper system taking a good track for us as it begins to interact with low pressure off the east coast. These two systems will phase, but that won't really impact our part of the storm. There will be a wide area of precipitation with some embedded areas of heavier snow. Now, like Thunderstorms we can choose an area, but can give EXACT details when it comes to this banding.

Most places in VA get a general coating to an inch. The MTS get an additional 1-2 because they are the MTS.

Here is my general idea-- anyone north and east of the black line has the best chance of some heavier burst of snow, but with such strong energy aloft, everywhere has a risk.

We should be just about out of snow chances after this. With that, last year in April 5-6 some snow fell in our region. Looking forward to next year, an "el nino" watch issued recently. Moderate, west based el ninos are historically our best winters. So, if we get that type of  El Nino, which is what we had back in 09-10 I went 25-30 in LYH, 30-35 Roanoke and 40-45 in Blacksburg. I think they were CLOSE to being accurate that winter. Also, the pre summer el nino's are often cooler then normal and wet. Just some ideas for now, we have spring and summer to watch this develop. 

Thursday, March 20, 2014

I will gladly pay you Tuesday...

For a great Friday and Saturday..

There has been a bunch of chatter on social media and other outlets about a possible event next week on Tuesday/Wednesday Time frame.

I've been on the verge of posting, but once I start my investment time, it can be very taxing going over data with a fine tooth comb to get the best forecast possible. For a blog that peaks at 600 readers when a storm approaches, that's not a wise use of my time. (But you know I do really enjoy it) Maybe a little late season fatigue because we've had so much to track with a Winter Type advisory or warning EVERY month since November. March has been rough with 2 bad forecasts and the March 6 now cast that was less than accurate. It happens. Sundays event unfolded as expected, with super dry air, we went from 48 and rain to 40 and rain snow mix in an hour. The bulk of the storm was frozen, we just got dryslotted. When it filled, we had changed to sleet. Had that been heavier, it would have been a snow/sleet mix.  So, had we pulled 2-3 inches up front then flipped, my forecast would have been good. But, I digress...

Another spring event? Palm Sunday 13 was a historic event, being the largest spring storm in LYH in 40 years. We could literally match or exceed if the trends continue.

The never ending abundance of arctic air makes another charge at us while ANOTHER short wave spins a low in the gulf. As of now, the low stays decentl off show and this being early spring makes it an ideal track for snow from Western NC up the East coast. Now, we are still 5 days out but the data has been consistent and that matters. Here is the Euro ensembles. (Ensembles are more skilled at this point because they run the data OVER AND OVER, which weeds out bias errors from the runs)

This run on the Euro Ensembles shows a 1007 low amping up to 987 in 24 hours, not quite a bomb but getting deeper fast.

Compliments of Wxrisk.. a good follow on FB. 

Now, the model data shows more liquid along 95, but my guess is if something like that pans out, we'd see the 1inch liquid line back to the BR. With that, March 25th sun--etc, it won't be 10-1 ratio snow stuff.

But, as of now-- if we set the bench mark at the "official" 6.5 inches that fell Palm sunday, I'd say we have  25% chance of breaking that next week. 

What to look for:

1. Track of the low-- the close to the coast the more moisture back towards the  Mts. 
2. Amount of cold-- We still need WELL below normal temps for snow. Our average high now is like 62 or so.  
3. Speed and timing of system. Now, last year snow laid just fine on March 25th, but it was nice and cold aloft. Some snow falling before sunrise Tuesday would be ideal in "insulating" the warmth. 
4. Strength of system. If this phases 2 jets, stronger systems tend to hug the coast and we could eventually have sleet and dry slot issues. 

The good thing is we are not HOPING cold gets here right as the snow shows up like March 3 and Sunday this past week. 

As I said, Wxrisk is an excellent mid range forecaster and will update per model run. He is "woofing" which is what he says when models show a "big dog" AKA big storm

Wxsouth-- has had a phenomenal winter. 

Just remember these guys forecast BROAD areas, so look to the for broad ideas, but fine details are better found from your local NWS and Media outlets. 

Sean Sublette from WSET has a nice blog and has already touched on this system 2x.

Sunday, March 16, 2014

Game time & Storm day!

I think the bust potential is higher than being conveyed to the public. NWS has a warning for 460 corridor from Roanoke to Lynchburg for 4-7 inches. While I have a map from yesterday that says 2-5, and said a few times on FB I lik 3-6, I'm going to hold with my initial map of 2-5 and just added an area of 6+  possible along 81 in north of Lexington.

Here is my map again..

We have NO room for error along 460- NONE. As in, 10 miles south of LYH, rain to sleet mixed with snow is expected and only an inch or two. Having tracked way to many storms, expecting perfection on a model is NOT reasonable. This is a probability map from the WPC about the risk of 4 inches or more. We are on the 50-60% shade, but look how quikcly it drops off to our south. 

So, a 50% or so risk, that up over 80% northern Amherst County and down to 10% risk in Brookneal to 
SML area.  My gut is telling me 1-3 because we just battle too much sleet and rain, but I"ll leave this 2-5 up.

Timing: Rain develops early to mid afternoon and pretty quickly mixes with snow and maybe sleet. Late evening, we may have more issues with sleet mixing in. Temps should fall pretty quickly to the low to mid
30's once rain starts and be mid to upper 20's by this time sunrise tomorrow. 

Once the storm ends, we should have freezing drizzle and flurries from late tonight into the day tomorrow. Round two may not be what my map was, but it's fluid and will change. Chance of freezing drizzle and sleet exists till maybe mid day Tuesday. 

Frequent updates on FB and Twitter. 

7 AM temps are 38 LYH and 40 ROA. 

Saturday, March 15, 2014

Initial Map thoughts

This could end up being a 2 part event.

My confidence for my forecast for round one is about 75%.. It's been charging south, but that has to bottom out soon. Any changes could mean less sleet and rain in Lynhcburg/Roanoke and more snow. Of course, the north trend could appear late and we get more rain and sleet. I will amend these ideas as needed.

I think this map is pretty stable, will need to watch Roanoke to Lynchburg for change from sleet to snow. If everything goes right, we could eek out 6-7 inches along 460. 2-5 is a nice place to start 

Round 2 is not a lock to happen. The remainder of the upper air energy is strong and creates another round of precipitation. We have a ton of cold air below 5k feet, but it's eroding above that. It may be some snow to start, but will transition to sleet and eventually freezing rain. Since most falls overnight, ice CAN build up, especially at night. Confidence is about 40-50% on this round. 

I'll tweet/FB mid day model updates.

St Paddy special?

Well, I'd been tracking this event all week and truly thought it would end up a rain event here. Even commented today that I wasn't "jazzed"--

This AM my thoughts were best snows, a NICE event from the Mason Dixon line up through central PA-- aligned east west so to speak.

What changed?

The entire piece of energy isn't coming out and the confluence, as marked on this map by L up in New Foundland is pushing cold air in faster than I had thought. This am, I could have believed we ended as a little snow and sleet. now, we may be looking a good bit of snow and sleet. The low is shunted due east as cold air filters in. Also, there COULD be a round 2 Monday Afternoon into overnight because all the energy isn't coming out phase 1.

I'll put an early outlook map out tomorrow AM..I think sleet and even freezing rain this late in the year will have to be watched as well as what happens, if anything with round 2.