7/31/09 Severe Weather Discussion/Forecast

Friday 7/31/09 Day 1 Outlook

Tomorrow could be a very active day for parts of Mid Atlantic if the atmospheric conditions and parameters corroperate. This day could be very interesting in severe weather and if we get the right conditions, this could be a great severe weather event for us. The 00z GFS has CAPE values of 500-2000 over portions of the Mid Atlantic, LI values of -2 to -6 over portions of the Mid Atlantic, and 500mb shear of 35 to 55 over most of the Mid Atlantic and Northeast. The 00z NAM has CAPE values of 500-1500 over portions of the Mid Atlantic, LI values of -2 to -5 over portions of the Mid Atlantic, and 500 mb Shear of 30 to 60 over most of the Mid Atlantic and Northeast. The culprit is a front that is going to move up toward our area, bringing us rainfall and potential severe weather. Temperatures will be in the 80s near the coast and the major cities, it could be nearing 90 on the MD/VA coasts, while inland will have temperatures in the 70s because of them having more cloud cover. The coastal areas back to the Interstate 95 area should wake up to some sunshine possible, hence there will be instability with this, inland instability will be harder to get. Humidity will be ample tomorrow everywhere which means rain and storms will be widespread and could contain a lot of rain in them. For tomorrow, I am about 70% confident in this forecast, the main problems that could go wrong is where the front is and especially how much cloud cover is there in the morning. I am seeing that the main factor for severe storms will be Shear and that will be helpful for producing thunderstorms. I believe the best threat area will be in a 15% risk zone in the delmarva area, extending into NJ this area will have CAPE of 1000-1500, LI of -3 to -6, and decent 500mb Shear, this zone will have a slight possibility for tornadoes. The 10% zone will consist of CAPE of 500-1000, LI of -2 to -4, and decent 500mb Shear. The 5% zone will consist of CAPE of 0-500, LI of -1 to -4, and decent 500mb Shear. I am expecting more storms forming in a line then Wednesday and a higher MCS potential. So the main threats Tomorrow will be Damaging Winds, Small Hail, with a slight risk of Tornadoes in the Mid Atlantic, and a flood threat for most of the area.

Comments would be appreciated.