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AnalystwxCast Weather Center

Areal Thunderstorm Forecast

Issued: APRIL 10th 2011

...SLGT RISK FOR MID-ATLANTIC...

...PA,NY,WV,VA.MD...

Storms will be ongoing Monday morning across the Ohio Valley. In advance of this line of thunderstorms will be unstable conditions as temperatures push into the lower 70’s and lower 80’s. Cape values will reach 1000-2000 j/kg across a large portion on the risk area Monday afternoon. Shear will also be ample between 60-70 KTS which can support severe storms. At this time it looks like a few cells out ahead of the main line look likely early in the event and could pose a brief tornado threat before the main line takes over into the late evening with more of a damaging wind threat before dying out Monday night across the eastern portion of the risk area. KIPT soundings suggest a low level turning favorable for the risk of a few tornadoes around 18-00z.

FORECASTER: BRISKO/OUTTEN

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Here's the severe weather outlook for later today, these outlook maps are a dual effort from me as well as upstate NY poster and friend of mine CNYWxGuy. We used to put these out for events back when we primarily posted over on the AccuWx forums. Our percentage schemes for the various threats (wind, hail, tornado, etc) are the same as the SPC's. When the severe event is over, we normally tally up the severe weather reports on our maps to see how well our forecast did.

With that said, maps and disco below.

post-1507-0-10487600-1302507172.png

Overall, this looks to be the first traditional CPA severe outbreak of the season with the greatest threat being damaging winds. The best parameters with this system are definetely with the unidirectional high wind shear values, hence the heightened 30% wind threat. CAPE's should be pretty decent though not too ridiculous (don't foresee widespread 2000+), but still.. relatively impressive for our region this time of year. Couple the CAPE with Helicity values for the most part being in the 100-200 range, and it results in some areas of EHI values getting in the 1-2 range. If any individual storm cells manage to form ahead of the main action (which will likely be lots of clusters/line segments), they possess a heightened potential to also spin up a weak tornado.. so we highlighted a 5% region on our tornado threat. Don't really see a major hail threat today with aforementioned decent but not ridiculous CAPE values, relatively high freezing levels, and mid-level lapse rates that appear to be fairly meh. New SPC went widespread 15% over the region for hail but only did 5% as we only expect a sprinkling of hail reports here and there. Remember that the new guideline for severe hail is 1" or greater, and that's usually a bit harder for us to achieve.

To sum it up, pretty confident about this forecast. My biggest concern is with the widespread 30% wind region, specifically below about I-80 or so. The wildcard today is going to be cloudcover, if we get clouds spreading up from the SW during the day, it may cut back on heating and potentially limit development especially in the south and justify more of a 15% wind threat instead of 30%. The models seem to develop a second wave along the front further southwest and with the fast mid-upper level flow, it seems likely that would throw some cloudcover up into PA at some point. After originally starting with an even larger 30% area then what we have now, we then downsized to a 30% focused on only NE PA up into NY..where the 0z WRF had the best thunderstorm activity. Ultimately ended up expanding it back southwest some again in the end. We shall see how things go later today.

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Here's the severe weather outlook for later today, these outlook maps are a dual effort from me as well as upstate NY poster and friend of mine CNYWxGuy. We used to put these out for events back when we primarily posted over on the AccuWx forums. Our percentage schemes for the various threats (wind, hail, tornado, etc) are the same as the SPC's. When the severe event is over, we normally tally up the severe weather reports on our maps to see how well our forecast did.

With that said, maps and disco below.

post-1507-0-10487600-1302507172.png

Overall, this looks to be the first traditional CPA severe outbreak of the season with the greatest threat being damaging winds. The best parameters with this system are definetely with the unidirectional high wind shear values, hence the heightened 30% wind threat. CAPE's should be pretty decent though not too ridiculous (don't foresee widespread 2000+), but still.. relatively impressive for our region this time of year. Couple the CAPE with Helicity values for the most part being in the 100-200 range, and it results in some areas of EHI values getting in the 1-2 range. If any individual storm cells manage to form ahead of the main action (which will likely be lots of clusters/line segments), they possess a heightened potential to also spin up a weak tornado.. so we highlighted a 5% region on our tornado threat. Don't really see a major hail threat today with aforementioned decent but not ridiculous CAPE values, relatively high freezing levels, and mid-level lapse rates that appear to be fairly meh. New SPC went widespread 15% over the region for hail but only did 5% as we only expect a sprinkling of hail reports here and there. Remember that the new guideline for severe hail is 1" or greater, and that's usually a bit harder for us to achieve.

To sum it up, pretty confident about this forecast. My biggest concern is with the widespread 30% wind region, specifically below about I-80 or so. The wildcard today is going to be cloudcover, if we get clouds spreading up from the SW during the day, it may cut back on heating and potentially limit development especially in the south and justify more of a 15% wind threat instead of 30%. The models seem to develop a second wave along the front further southwest and with the fast mid-upper level flow, it seems likely that would throw some cloudcover up into PA at some point. After originally starting with an even larger 30% area then what we have now, we then downsized to a 30% focused on only NE PA up into NY..where the 0z WRF had the best thunderstorm activity. Ultimately ended up expanding it back southwest some again in the end. We shall see how things go later today.

Nice post guys!:thumbsup: The sun will play a big role in today's action. Further east here we will have that marine layer knocking things down. Watch out for those discrete cells just ahead of the front.

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Here's the severe weather outlook for later today, these outlook maps are a dual effort from me as well as upstate NY poster and friend of mine CNYWxGuy. We used to put these out for events back when we primarily posted over on the AccuWx forums. Our percentage schemes for the various threats (wind, hail, tornado, etc) are the same as the SPC's. When the severe event is over, we normally tally up the severe weather reports on our maps to see how well our forecast did.

With that said, maps and disco below.

post-1507-0-10487600-1302507172.png

Overall, this looks to be the first traditional CPA severe outbreak of the season with the greatest threat being damaging winds. The best parameters with this system are definetely with the unidirectional high wind shear values, hence the heightened 30% wind threat. CAPE's should be pretty decent though not too ridiculous (don't foresee widespread 2000+), but still.. relatively impressive for our region this time of year. Couple the CAPE with Helicity values for the most part being in the 100-200 range, and it results in some areas of EHI values getting in the 1-2 range. If any individual storm cells manage to form ahead of the main action (which will likely be lots of clusters/line segments), they possess a heightened potential to also spin up a weak tornado.. so we highlighted a 5% region on our tornado threat. Don't really see a major hail threat today with aforementioned decent but not ridiculous CAPE values, relatively high freezing levels, and mid-level lapse rates that appear to be fairly meh. New SPC went widespread 15% over the region for hail but only did 5% as we only expect a sprinkling of hail reports here and there. Remember that the new guideline for severe hail is 1" or greater, and that's usually a bit harder for us to achieve.

To sum it up, pretty confident about this forecast. My biggest concern is with the widespread 30% wind region, specifically below about I-80 or so. The wildcard today is going to be cloudcover, if we get clouds spreading up from the SW during the day, it may cut back on heating and potentially limit development especially in the south and justify more of a 15% wind threat instead of 30%. The models seem to develop a second wave along the front further southwest and with the fast mid-upper level flow, it seems likely that would throw some cloudcover up into PA at some point. After originally starting with an even larger 30% area then what we have now, we then downsized to a 30% focused on only NE PA up into NY..where the 0z WRF had the best thunderstorm activity. Ultimately ended up expanding it back southwest some again in the end. We shall see how things go later today.

Nice maps and write-up! In regards to your fears about the clouds, I can tell you that if a sustained SW winds gets going, then areas in the lee of the blue Ridge and Appalachian Mts. will definitely break out with full sun macros. In fact the clearing is ongoing across the greater Lancaster area as I type.

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Nice maps and write-up! In regards to your fears about the clouds, I can tell you that if a sustained SW winds gets going, then areas in the lee of the blue Ridge and Appalachian Mts. will definitely break out with full sun macros. In fact the clearing is ongoing across the greater Lancaster area as I type.

It's clearing up here also, breaking that stubborn low clouds.

Nam and GFS both show over an inch from later tonight into Wednesday. Everything is still really satured here. Hopefully i can get my grass mowed, over seed and fertilize this evening after practice.

I planted cool season stuff in our veggie garden yesterday even though the ground was saturated. Needed to get them in and given how cool and wet it looks going forward, figured now was a good time.

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Speaking of severe, the miserable communications failure that is the terminology "slight risk" reared it's ugly head again today. I mentioned the storms and several people said today "but the National Weather Service said just a slight risk so I guess it's not likely we get any storms."

:axe:

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It's clearing up here also, breaking that stubborn low clouds.

I planted cool season stuff in our veggie garden yesterday even though the ground was saturated. Needed to get them in and given how cool and wet it looks going forward, figured now was a good time.

My wife and i decided to plant a garden. (the decision was made yesterday) We are going to start small, 8x10... i have to scramble now to get the lumber, etc. My dad had a big garden, but i never have, so it should be an experience.

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Probably won't be a really popular post, and to be clear, I'm not knocking the opinion of many, but I'm not into the whole severe storm thing. I like thunderstorms, but I just can't get into storms that generate property damage or personal injury. Yeah, I know that can happen in raging blizzards as well, but most of us don't think of snow as being as personally threatening to lives or property like we do with severe storms.

Last May a hailstorm here in Maytown set me back a lot of money to get my vehicle fixed...I wasn't thrilled with that.

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