FIRST POSSIBILITY OF SEVERE WEATHER FOR THE SEASON LIKELY WEDNESDAY AFTERNOON AND EVENING:
The Storm Prediction Center in Norman, Oklahoma has placed most of the area, especially south of Route 6, in a slight risk zone for severe weather, usually indicating that we have a 15-30% chance of seeing any type of severe weather within 10 or so miles of any given location. By the usual standards of probability within the atmosphere, this is fairly significant (although the chance is much higher farther south and west).
At this time, there are still too many model discrepancies to make a sound judgement of the forecast, but the best guess at this time is that DISCRETE SUPERCELLS are possible. Why? Because low level helicity (rotating winds in reference to a storm-relative framework with height in the atmosphere) will be on the increase (due to our proximity to the warm front), deep-layer shear will be rather strong (in the 40-50 knot; ideal for classic supercells), and instability will range from 1500-2000 J/kg on Wednesday afternoon (J/kg is a measure of the amount of potential energy in the atmosphere; another way of measuring atmospheric instability). What is a discrete supercell? A discrete cell is a storm that is rather isolated and scattered. There may be numerous in a region, but a discrete storm is one that can be differentiated from other storms (and is therefore not part of a storm complex or system such as a squall line). They can be violent producers of severe weather, and have been known to do quite a bit of damage in this area. Any type of severe weather will be possible from these storms, from damaging winds and large hail, to frequent lightning and tornadoes. Tornadoes look to be a problem, especially if they interact with the warm front. Hail will not be as much of a concern unless CAPE increases, and moisture amounts decrease. This doesn't look to happen, so I would elevate the tornado and wind risks over the hail risks. Widespread damaging winds would be more likely if the squall line from the west arrives earlier. This doesn't appear all that likely at this time, but it is possible. Damaging winds in these discrete supercells could be threatening, especially if evaporational cooling and momentum transfer can occur with steeper-lapse rates in the low levels. Dry air will be non-existent from this storm, so I would not be as worried about intense downbursts or microbursts. At this time, the most prevalent "danger" might be tornadoes and damaging winds. This will be monitored.
Forecast soundings from the NAM indicate a fairly moist, and moderately unstable atmosphere on Wednesday afternoon, precluding the possibility of such dangerous storms. At this time though, the NWS and SPC believe that the NAM may be reflecting its bias towards more instability, and thus, should probably be disregarded. It is possible that we see this kind of instability, then we WILL see some intense thunderstorms, but its highly unlikely right now.
Before you get the idea that we have a high chance of severe weather, let me emphasize that it is still early in the season, and it may be that the NAM model is overestimating instability and thunderstorm coverage. If so.. The thunderstorm threat, and especially severe threat, will be greatly diminished. REMEMBER, I do NOT expect widespread severe weather. Only the POSSIBILITY of severe weather. As we get closer to Wednesday, details will become clearer in regards to the type of weather, and the possiblities.
Other than that, if severe weather doesn't happen, expect scattered thunderstorms to become more likely as the afternoon progresses Wednesday. Temperatures will likely approach the mid-70's, especially south of Route 6, making for a very warm, and humid day. Thunderstorms will become numerous to widespread during the evening and overnight hours, producing heavy rain, and frequent lightning. It appears that rainfall amounts may approach 1 to 2 inches, but most areas will likely see 0.5 to 1 inch of rain.
Rain will continue on Thursday as well as the system exists the region. By Friday, conditions will continue to clear as cooler air arrives. But don't worry, temperatures will begin to rebound by the end of the weekend and next week.
The Storm Prediction Center in Norman, Oklahoma has placed most of the area, especially south of Route 6, in a slight risk zone for severe weather, usually indicating that we have a 15-30% chance of seeing any type of severe weather within 10 or so miles of any given location. By the usual standards of probability within the atmosphere, this is fairly significant (although the chance is much higher farther south and west).
At this time, there are still too many model discrepancies to make a sound judgement of the forecast, but the best guess at this time is that DISCRETE SUPERCELLS are possible. Why? Because low level helicity (rotating winds in reference to a storm-relative framework with height in the atmosphere) will be on the increase (due to our proximity to the warm front), deep-layer shear will be rather strong (in the 40-50 knot; ideal for classic supercells), and instability will range from 1500-2000 J/kg on Wednesday afternoon (J/kg is a measure of the amount of potential energy in the atmosphere; another way of measuring atmospheric instability). What is a discrete supercell? A discrete cell is a storm that is rather isolated and scattered. There may be numerous in a region, but a discrete storm is one that can be differentiated from other storms (and is therefore not part of a storm complex or system such as a squall line). They can be violent producers of severe weather, and have been known to do quite a bit of damage in this area. Any type of severe weather will be possible from these storms, from damaging winds and large hail, to frequent lightning and tornadoes. Tornadoes look to be a problem, especially if they interact with the warm front. Hail will not be as much of a concern unless CAPE increases, and moisture amounts decrease. This doesn't look to happen, so I would elevate the tornado and wind risks over the hail risks. Widespread damaging winds would be more likely if the squall line from the west arrives earlier. This doesn't appear all that likely at this time, but it is possible. Damaging winds in these discrete supercells could be threatening, especially if evaporational cooling and momentum transfer can occur with steeper-lapse rates in the low levels. Dry air will be non-existent from this storm, so I would not be as worried about intense downbursts or microbursts. At this time, the most prevalent "danger" might be tornadoes and damaging winds. This will be monitored.
Forecast soundings from the NAM indicate a fairly moist, and moderately unstable atmosphere on Wednesday afternoon, precluding the possibility of such dangerous storms. At this time though, the NWS and SPC believe that the NAM may be reflecting its bias towards more instability, and thus, should probably be disregarded. It is possible that we see this kind of instability, then we WILL see some intense thunderstorms, but its highly unlikely right now.
Before you get the idea that we have a high chance of severe weather, let me emphasize that it is still early in the season, and it may be that the NAM model is overestimating instability and thunderstorm coverage. If so.. The thunderstorm threat, and especially severe threat, will be greatly diminished. REMEMBER, I do NOT expect widespread severe weather. Only the POSSIBILITY of severe weather. As we get closer to Wednesday, details will become clearer in regards to the type of weather, and the possiblities.
Other than that, if severe weather doesn't happen, expect scattered thunderstorms to become more likely as the afternoon progresses Wednesday. Temperatures will likely approach the mid-70's, especially south of Route 6, making for a very warm, and humid day. Thunderstorms will become numerous to widespread during the evening and overnight hours, producing heavy rain, and frequent lightning. It appears that rainfall amounts may approach 1 to 2 inches, but most areas will likely see 0.5 to 1 inch of rain.
Rain will continue on Thursday as well as the system exists the region. By Friday, conditions will continue to clear as cooler air arrives. But don't worry, temperatures will begin to rebound by the end of the weekend and next week.
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