10-19-2011 Technical Discussion

Technical Discussion

Synopsis:

A large early season storm will affect the region starting Wednesday morning. Expect showers to develop early Wednesday morning and continue throughout the day. The western and extreme eastern part of the state may see some steadier rains. Some isolated showers will linger into Wednesday night and the winds will start to pick up. Thursday looks to be a blustery day with mostly cloudy skies and possible light showers. Things should calm down on Friday as the storm system departs the region.

Short-term (Tuesday night-Wednesday night):

A sharp deep in the jet stream has spun a low pressure over Tennessee Valley tracking northeast toward the Commonwealth. This low is expected to intensify even further as the 500mb trough becomes negatively tilted and cuts-off over Ohio-Tennessee Valley, down to approximately 988mb by late Wednesday night. Meanwhile, a second low pressure will develop off Florida Panhandle Tuesday evening in response to the strong positive vorticity advection brought forth by the deepening trough. The water vapor imagery is already showing a robust system forming at the time of this writing. This second low is expected to track north-north-eastward along the southeast coast Tuesday night and Wednesday morning and tap in tropical moisture from remnants of tropical disturbance 95L. As it does so, parts of the southeastern states will see much needed rain to fall Tuesday night. However, the rain is not expected to reach the northeast later Tuesday night or early Wednesday morning. The commonwealth should see the first drops from this coastal storm to fall sometime early Wednesday morning, especially over the eastern half of the state. However, the aforementioned primary low over the Ohio Valley will also intensify rapidly as the upper-level trough occludes. This storm is expected to bring rain showers to the western parts of the state late Wednesday night. For the central portion of the state there is a concern that a dry slot developing behind the upper-level trough may significantly cut down the precipitation amount on Wednesday. As Wednesday night approaches, most of the rains should have moved out of the region except for the western half of the states as the Ohio low brings more moisture into the region. The winds are also expected to intensify behind the storm system.

Mid-term (Thursday-Friday)

Blustery conditions will linger into Thursday as the winds pick up behind the passage of the storm. Expect mostly cloudy skies with some possible showers on Thursday, especially over the western half of the state on the windward side of the storm, where some orographically lifted precipitations are possible. However, the eastern half of the state should only see isolated showers, otherwise, partly to mostly cloudy skies with windy conditions. The winds should gradually calm down across the state on Friday as the storm weakens over Canada.

Long-term (Saturday)

Despite the 500mb low lingering over the eastern half of the nation, the upper-levels of the atmosphere should start to dry up as the day progresses. Expect partly cloudy skies for most parts of the state. Some counties near the lake may see more clouds and possible light drizzles.

Written-by

David Wang