SVR WEATHER TO THREATEN MIDDLE ATLANTIC TOMORROW!

[yoda]

...THERE IS A SLGT RISK OF SVR TSTMS OVER THE MIDDLE ATLANTIC
REGION...

...MIDDLE ATLANTIC...

UPPER TROUGH AXIS WILL SHIFT EWD ACROSS THE APPALACHIANS BY THE END
OF THE PERIOD AS STRONGEST FLOW ALOFT...H5 SPEEDS IN EXCESS OF
90KT...DEVELOPS ON THE DOWNSTREAM SIDE OF THE TROUGH AXIS...THEN
LIFTS NWD ACROSS THE MIDDLE ATLANTIC REGION. NEEDLESS TO
SAY...IMPRESSIVE VERTICAL SHEAR PROFILES WILL FAVOR STORM ROTATION
AND QUICK MOVEMENT FOR ANY THUNDERSTORMS THAT MANAGE TO INITIATE AND
ROOT WITHIN/CLOSE TO THE BOUNDARY LAYER.

PROSPECT FOR SEVERE THUNDERSTORMS ACROSS THE MIDDLE ATLANTIC REGION
ON DAY2 IS PREDICATED ON BOUNDARY LAYER RECOVERY AHEAD OF UPPER
TROUGH. ONGOING WIDESPREAD PRECIPITATION ATOP VERY COOL LOW LEVEL
AIRMASS SHOULD MAINTAIN ELY COMPONENT TO LOW LEVEL FLOW...THUS
SLOWING THE RETURN OF MODIFIED MARITIME AIRMASS ACROSS THE CAROLINAS
INTO VA. LATEST MODEL GUIDANCE SUGGESTS STRONGEST INSTABILITY WILL
DEVELOP ALONG AN AXIS JUST EAST OF THE MOUNTAINS FROM CENTRAL NC
INTO NRN VA. WHILE THE MODELS MAY BE SOMEWHAT FAST IN THIS
MODIFICATION...THE AXIS OF INSTABILITY APPEARS TO BE PLACED
CORRECTLY WITH COASTAL PORTIONS EXPECTED TO ONLY MARGINALLY
DESTABILIZE...OR DO SO VERY LATE.

THUNDERSTORMS SHOULD DEVELOP ALONG WRN PORTIONS OF THE INSTABILITY
AXIS THEN RACE NEWD IN THE FORM OF LINE SEGMENTS WITH BOW-SHAPED
STRUCTURES. IF SUFFICIENT INSTABILITY CAN MATERIALIZE...SUPERCELL
STRUCTURES CAPABLE OF PRODUCING [b]TORNADOES CAN BE EXPECTED. [/b]
OTHERWISE...DAMAGING WINDS WILL BE THE MAIN SEVERE THREAT.

Shall be an interesting day tomorrow, maybe we will get a watchbox. Any thoughts or comments from anyone, especially those that live in the MA region?

[Stephanie]

Gotta wait and see. They have been saying locally that we will be getting thunderstorms this week.

[yoda]

Yes, we will have to wait and see, but I would like to see a few severe storms for us tomorrow.

[WEATHER53]

So far most of this has been overblown. and not materializing. Fact is for DC area specifically and mid atlantic in general, temps in 50's and 60's are not going to generate damaging thunderstorms. Sunday's deluge was a no show, radar is impressive but nothing special.

[yoda]

true, true. But we still have to wait and see. I am not getting my hopes up just yet, but maybe for once this will be our time?

[Allexpert Mike]

Damaging winds would be the main concern if this threate were to pan out. The threaten vicinity is in the confluent entrance region of a strong LLJ with strong ll WAA/isentropic lifting. This will help increase thermodynamic profiles,,,,,,,but will have a solid cloud cover in place through most of the day limiting diurnal heating.......thus not allowing instability to rise. Strongest instability will be measured in VA with SBCAPE values around 1000j/kg. Uni-directional hsear profiles will favor linear convection with possible small scale bow echo segments with the damaging wind threats. Slow moving fornt with mid level winds parallel to frontal boundry allowing training to occur so flooding is also a major concern.

Strong exit region of a upper level jet streak (110-120KTS) will enhance upward vertical motuion along with BL-6km shear profiles. Strong deep layer shear will support some strong storms and with the strong speed shear allowing for healthy environment for updraft growth may allow it to tap into the chilly mid level temps to produce a minimal hail threat. Damaging winds and flash flooding main threats.

[yoda]

So you believe that there will be no chance for tornadoes tomorrow in the MA?

[Allexpert Mike]

Well theres always a chance,,,but I think there will be no reports of any tornadoes,,,,just wind and possibily a few hail reports.

[Colin]

Agreed...too early for tornadoes IMO across the Middle Atlantic.

[ColdFront77]

There is technically no such thing as, "too early for tornadoes." I am sure there have been tornado reports in early to mid April across the Mid-Atlantic states.

[WEATHER53]

DC metro certainly in for a good soaking on order of 1-2" and warm front moves through overnight such that if we can pop some sun into the 65+ range for temps Tue/Wed then thunderstorms are on the table but most of the time, around here at this time of year we really just cannot get the instability warming into gear.

[Stormsfury]

The wedge currently in place should be able to be broken down ... this isn't January and the wedge is fairly weak at best. So far, further down south in the Tornado watch box #70, Thunderstorms have not materialized so far, despite favorable wind profiles, and such ... but a decent cap and the series of MCS's down in the GOM continue to rob moisture upstream ...

Good overrunning moisture later tonight/tomorrow as the warm front lifts northward (as Weather53 stated) should be able to generate a decent swath of steady rains and imbedded thunder, but during this time, any convection should remain elevated.

SF

[ColdFront77]

You would think the SPC can see this cap and wouldn't of issued Tornado Watch box #70 for central South Carolina and eastern Georgia.

[Stormsfury]

You would think the SPC can see this cap and wouldn't of issued Tornado Watch box #70 for central South Carolina and eastern Georgia.

Well ... I can't fault them either, and they can easily extend the watch later if need be, but the fact of the matter is a thin mid/upper level deck of clouds (from the MCS further south) continues to keep things kinda bottled up despite the fact that it's very warm and unstable ... but the atmosphere takes time to recover especially after a pretty good convective complex came through this morning really stablizing things after it moved NE out of the area.

And last night, the convection easily broke out during the early morning as the mid levels cooled off (with the swinging of an h5 disturbance) and hence the cap broken. I believe the same thing will likely happen tonight with a little more in the way of dynamics/shear to work with.

SF

[Stormsfury]

Also SPC did mention that when they issued a mesoscale discussion regarding tornado watch #70 earlier this afternoon.

[ColdFront77]

Dewpoints were only in the 50's last evening here (they felt higher), at 7:05 pm, the dewpoint temperature was 66°, air temperature at the same time was 72°.

[Scott_inVA]

Very little to suggest sufficient insolation (clearing) today in VA to enhance widespread SVR. Probably exception is I-95 north of RIC and perhaps DC west along I-66. TOR parameters ATTM marginal, maybe some wind, even small hail.

Having a cold pool is sometimes good but if the Low occludes here it's just another soggy rotten day.

Scott

tons of VA info here: http://www.wrel.com/weather.htm

PS...after saying all that, if we get an F3 I'll be ticked

[Brett Adair]

I agree. I don't see too much in the way of diurnal heating in that area today. I think the threat will be rather limited across the area. Stronger cells will contain strong damaging winds/large hail at best with dangerous cloud-to-ground lightning.

[WEATHER53]

Pretty much panning out the way I thought, the warm air usually does not make it into DC metro with this set up and at this time of year, would need strong sw-wsw winds and anything east of 180 degrees is going to have too much ocean air influence which is still very chilly.

[Scott_inVA]

Pretty much panning out the way I thought, the warm air usually does not make it into DC metro with this set up and at this time of year, would need strong sw-wsw winds and anything east of 180 degrees is going to have too much ocean air influence which is still very chilly.

Yep. This is a dandy wedge for mid-April
http://www.ems.psu.edu/wx/automet2/surf ... t/temp.gif

WREL's mesomap has an interesting temp presentation today:
http://www.wrel.com/mesomap.htm
Andrews AFB is 120° but if you ignore that you'll see the line of shallow cold.

Winds over eastern VA are now beginning to respond (progged and part of my thinking behind the I-95 idea) This also nicely depicts our sorta CAD:
http://www.ems.psu.edu/wx/automet2/surf ... stream.gif

Maybe after 5PM but sat doesn't offer much convective hope.

Scott