STORM2K

within rather impressive deep layer shear regime, w/ boundary layer-6 KM shear in excess of 60 KT over WW 249 as lift increases due to approaching s/w from the west.

Further downstream over the rest of NB, northern KS, western IA, instability is FAR nore impressive with increasing NCAPE values suggesting a CAPE profile favorable for large parcel accelerations which in combination with favorable deep layer vertical shear, STEEP mid level (700-500mb) lapse rates generally between 8 and 8.5 DEG C/km, 4-6 KM S-R winds of up to 30 KT will support further convective/suprecell development after 21z as LLJ intensifies to ~50 KT over the next few hours.

Main threat given very strong instability, impressive vertical shear through a deep layer, and lowering LCL heights over eastern NB, KS, and western IA, tornadoes (some POTENTIALLY very strong), and large hail given very strong updraft intensity.

Over across the lower lakes, 19 UTC mesoanalys shows area of impressive Low Level shear (manifested in 0-3 KM SRH values of 150-300 m^2/s^2, surface-1 KM vertical shear between 15-30 KT, and 0-2 KM SR inflow >20 KT). BLYR-6 KM shear is not as impressive over the lower lakes as it is across the western plains, however nonetheless, would be supportive of suprecells with values generally between 30-45 KT. Instability is also plentyful, w/ SB CAPE values over southern Michigan around 3000 J/kg. Mid level Lapse rates however are borderline, only about 6-6.5 DEG C/km, however strong instability, and good low level shear should make up for it.

Areas across WRN/central NY, PA and some parts of New England will want to pay close attention to convection developing upstream over the lower lakes and ohio valley for late this evening and into the overnight hours. outflow boundaries assoiated w/ whatever may be left of today's convection should provide a focus for convective initiation over the northeast once again tomorrow.

Nothing developing right now across the PA/NJ area...the slight risk that SPC issued for today, I would consider a bust. Not one thunderstorm in the KDIX/KCCX radars.

Colin wrote:Nothing developing right now across the PA/NJ area...the slight risk that SPC issued for today, I would consider a bust. Not one thunderstorm in the KDIX/KCCX radars.

The SPC was concerned earlier that convection MAY develop along the lake breeze boundary as it pushed inland over WRN PA/NY, although that really has not materialized. the threat for PA and NY later on tonight depends on whether the activity over the OH VLY region organizes into an MCS, which it is showing signs of doing so at this time.

Instability remains very good over the region with lowest 100mb Mixed layer CAPE generally >1500 J/kg over most of OH and PA. Only problem I really see is that the best deep layer vertical shear (0-6 KM) is not co-located with the area of best instability. per SPC mesoanalysis at 20 UTC the best vertical shear through a deep layer (>35 kt over the lowest 6KM) was located mainly north of the Michigan/OH and PA/NY borders --- while the best instability (I.E. ML CAPE >1000 J/kg) was south of the MI/OH and PA/NY borders. 4-6 KM winds were also generally 15-20 KT, which is borderline for being able to make a clear distinction between multi-cellular convective modes and suprecells, vertical shear over the lowest 1 KM depth was similarly borderline AOA 10-15 KT over much of PA.

We'll have to see what happens with loss of diurnal heating, as to how quickly the downstream airmass over PA and NY stabilizes in order to get an idea if the area of convection over the OH VLY which appears to be organizing into an MCS (which should follow close to the peak of the theta-e ridge) is able to survive into PA and NY.