The midday update from the Storm Prediction Center office of the National Weather Service upgraded all of our viewing area to a Level 2 of 5 risk of severe storms for tomorrow (Friday) with the main focus for severe storm potential in our local area being in the afternoon and early evening. We are giving an overall timeframe for this risk of around 1:00 PM until 8:00 PM, and this will be an event where storms will be widely scattered, and we won't be able to break down timing into specific smaller segments because of that. The afternoon risk of severe storms is NOT a guarantee, but IF they are able to form, they could have all hazard types with them: 50-60 mph wind gusts, quarter to half-dollar size hail, and even a tornado threat.
There will be an initial morning round of widespread heavy rain and thunderstorms. These will be moving through between 4 or 5 AM and around 10-11 AM. The overall risk of severe storms in this first morning round is extremely low, if not near zero. The main concerns are widespread heavy rain with localized street flooding, lightning, and maybe some pea size hail or 30-40 mph winds in one or two of the embedded storms. These storms will be moving through when the air at the surface is cool and stable, and that means the tornado threat will be as close to zero during this time as it possibly can be.
It is the period during the afternoon and evening, AFTER the morning storms move out, that we are concerned about the potential for severe storms... but it depends on how much the air mass is able to heat up and recover behind those morning storms and how much lift there will be ahead of the approaching cold front to get storms going. If the morning storms linger for too long, and the atmosphere can't destabilize enough, then afternoon redevelopment and severe weather potential would be very low to possibly even zero. However, we have been getting more indications in the data that the sun will be able to break out behind the morning storms and ahead of the cold front. This would allow temperatures to climb into the 70s and dewpoints into the mid 60s or higher, making the atmosphere unstable. Then, IF there is still enough lift ahead of the cold front, the atmosphere would be supportive of individual supercell thunderstorms that would be capable of all severe weather hazard types, including a tornado risk. There are just question marks on whether these storms will be able to form, and we might not have a definite "yes" or "no" type answer to that until we get to around midday tomorrow. If the storms are able to form, not everyone would get them, but for those that do, severe thunderstorm warnings and a few tornado warnings would be possible. The main timeframe opens up as early as 1:00 PM, and the cold front starts exiting our eastern counties around 8:00 PM or so. Again, this will NOT be a line of storms where everybody has a cute little time window of an hour. These will be scattered individual storms if they are able to develop.
It is very possible that the afternoon storms do not materialize, but because of the environment they will have available to them if they do, you need to make sure you are ready to deal with warnings tomorrow. Make sure you have multiple reliable ways of hearing warnings no matter where you are. Also make sure you have your severe weather plans set, or work now to formulate one if you don't already have one. Above are some safety guidelines to use to help you formulate your severe weather safety plan, as well as information on multiple ways you can stay in touch with us for severe weather coverage tomorrow.