Welcome to the 1st day of meteorological spring!
Yesterday definitely felt like spring. But today we've returned to that feel of winter; with very chilly temperatures as the cold front pushed across the region. Currently the snow showers associated with that cold front Is sitting over far eastern New England.
Behind this high pressure is going to build in. Temperatures are going to continue to drop during the day. The next couple of days are gonna see temperatures slightly below to below average for this time of year. I think the slightly below to average temperatures will last into the weekend And then we will start to see a change to a warmer trend. For the weekend and into next week I think we're gonna see 5-6 days where temperatures are well above average. The models are probably doing a fairly decent job with temperatures across the northern Middle Atlantic. But across New York State into northern and central New England where there is a deeper snowpack. I think the models are overdoing it.
Tomorrow we will have a system to our south. The high pressure is going to suppress this south. But it could brush Pennsylvania south of Pittsburgh down across west Maryland and southeast Maryland with a bit of a snow mix. Accumulations should be fairly light. But it doesn't cause take a lot of freezing rain to cause issues.
Tuesday Into Wednesday we will be dealing with an over running event. We're going to have precipitation advancing north and east across the region. Across Pennsylvania Maryland Delaware and New Jersey This is looking to likely start as freezing rain and sleet and then as warm temperatures continue to build in; it will likely change over to plain rain. Snow and mix will likely be working into central New York State and the New York State Capital District during the late morning into the afternoon. For the most part Any snow south of I90 will generally be a dusting to less than 3". North of I-90 across northern New York State and across the southern half of Vermont 3-6 "will be possible The higher elevations like the Adirondacks and Greens could end up with a bit more than that. Northern Vermont Into northern New Hampshire Could see a dusting to perhaps 3". Southern New Hampshire into southeast Maine could also see 3-6 " for Tuesday into early Wednesday morning. As the storm moves through the rest of Maine could pick up D-3". Sleet and ice accretion could be a bigger deal across the southern tier of New York State and especially across Pennsylvania into northwest New Jersey. I think for the most part southern Maryland, Delaware and southern New Jersey will see mainly rain. While the rest of New Jersey, New York City, Long Island into southern New England will be dealing with that snow mix, It will likely start as a snow before changing over to that mix. Accumulation should be fairly light. I will have more details on this tomorrow!
The Storm Prediction Center (SPC) convective outlook is changing.
With the severe season quickly approaching I wanted to go over some changes with the convective outlook.
I think most of y'all are familiar with the storm prediction centers Convective weather outlook That comprised of level 1 through level 5 risk. The convective outlook is the first notice that indicates the possibility of severe weather containing damaging winds, Hail and Possibly tornadoes are possible. Several years ago they made a major change with the outlooks. And on March 3 of this year they are going to introduce a new change to hopefully convey the dangers of the severe weather set up in an improved way. The latest update represents the most significant change in the mapping system in years.
Historically SPC maps have focused on the probability of a tornado occurring within 25 miles of a point. While affective this system occasionally struggled to deviate between a day with many weak short lived storms and a day with a single devastated violent tornado.
A post I did back in 2013 that talked about the convective outlooks
Then in 2014 I issued a new post that covered the last time there was a major change to the convective outlook
Last Convective outlook Change
The old single hatch System had many drawbacks. High-end severe weather like violent tornadoes caused by far the greatest loss of life The new system will allow meteorologists to highlight days where the specific threats are more likely even if the overall coverage probability is low.
The old system
The hatching represented a possibility of a EF2+ tornados, hail 2"+ and wind of 74+ miles an hour.
The way the system work was problematic EF2 tornado was treated the same as an EF5 tornado The hazard significance was tied to coverage. The way the hatching worked implied 10% coverage. which means all tornadoes were expected to be EF2 + in a given 10% hatched area. The system was very simplistic and did not convey the actual intent of what the SPC was trying to communicate. There was no way to differentiate between the risk of an EF2 tornado and an EF5 tornado. And as we know that's a big difference indeed.
The new system
In the latest change the Storm Prediction Center will utilize a tiered hatching system to convey the dangers more completely. To accomplish this the SPC is going to be adding conditional intensity groups (CIG). This will allow the convective outlook to move beyond simple probabilities to explicitly highlight the environment and the potential for things like violent long track tornadoes.
An example of how the CIG will look
There are three SIG for tornadoes and wind and two SIG for hail
CIG 2 (double hatch) will indicate a probability of violent tornadoes (EF4 and EF5)
CIG 3 (triple hatch) Will indicate extreme setups where there is a the possibility of long track violent tornadoes.
If the convective outlook is indicating the possibility of tornadoes but there is no intensity level and no hatching marks. The expected outcome would be a possibility for mostly weak EF0 to EF1 Tornadoes.
If there was a CIG1 intensity level listed dotted hashmarks, The SPC would be saying it's reasonable to assume that the maximum intensity of tornadoes that might develop would be most likely be EF2.
If there was a CIG2 intensity level listed with the solid hash marks. The SPC is indicating the possibility of EF3 tornadoes. That doesn't mean there couldn't be stronger tornadoes; it just means that the reasonable maximum intensity would be expected to be EF3.
In the rare instance where there would be a CIG3 intensity level With the double criss cross hash marks It would indicate the possibility of EF4 and EF5 violent long track tornadoes. This would only be used when there is a danger for a historic high-end outbreak.
For wind events
The same hatching system will be used for wind events as well
If the CPC Is indicating a possibility for damaging winds If there is no intensity level listed and no hatching is seen on the map That would mean Mostly wind gust up to 73 mph.
With a CIG1 Intensity level indicated it would mean there would be the danger of wind gust of 74+miles an hour.
CIG2 To intensity level is indicating the possibility of wind gust of 84+ miles an hour.
A CIG3 intensity level What would indicate a possibility of very extreme wind gust are expected to be 94+ miles per hour. This would be used when the SPC is expecting a very powerful violent derecho.
For hail
If there is a probability of hail but no intensity level or hatching was present it would mean the expected outcome would be hail less than 2" in diameter.
Under CIG1 It would indicate the possibility of hail of 2" or greater in diameter
CIG2 will indicate there is a possibility For hail 3.5" in diameter or larger
That covers the changes that are going to occur for this year's convective outlook. These changes should make it easier for the public to understand the risk better. Since we're talking about severe weather. If you haven't got one, now is the time to buy a NOAA Weather Radio. They are the best way to remain safe during severe weather events.
