Technical Discussion

Synopsis...

High pressure will build in from NW today allowing for drier conditions tonight and tomorrow.  Next storm system arrives during the day Thursday and will bring rain to the Commonwealth.  Much uncertainty exists however on exact track and strength of system.  Breezy conditions to follow on Friday with the weekend shaping up to be cool and crisp.

Near Term (Tues-Wed Night)...

Front will continue to sag southward today allowing skies to clear across the state.  Expect mostly-partly sunny skies by afternoon with a few more clouds in the usual mountain locales.  A few showers are still trekking through NE/SE zones at this hour but will continue to die out as they move farther south and east bringing only brief light rain to some areas in those regions.  As center of high pressure moves in tonight, the entire state will see clear skies with dry 700/850 RH values.  Clear skies and light winds will promote good radiational cooling conditions, allowing temperatures to drop into the 30s across the northern tier.  NWS has issued frost advisories and we have mentioned chilly in the wording for tonight.  This does not look to be a hard frost or freeze but it is one of the first of the season.  Expect a "Chamber of Commerce" type day tomorrow with clear skies and seasonable temperatures in the 60s across the state as high pressure remains in control.  By tomorrow night, the dome of high pressure will begin to retreat to the northeast as a shortwave trough at 500mb drops into Ohio Valley which will bring us our next storm system.

Long Term (Thurs-Sat)...

Tricky forecast for the upcoming system due to large model differences.  GFS is very bullish with coastal low forming Thursday night right over NYC as a second piece of energy dives into the trough.  WRF/CMC on the other hand have the second piece of energy diving into the trough later (Friday morning) which allows the sfc low to form farther north and east while being weaker.  This has a large impact on precip, especially across eastern zones.  The one thing that does look certain at this point is that we will see scattered showers across the state on Friday as the trough digs into our region.  What happens after that is up in the air (no pun intended).  We took the middle road and forecasted showers for Thurs/Thurs night/early Friday.  This forecast has a better chance of verifying in the western half of the state where they would not see much precip from a stronger and farther west coastal low.  However, if the GFS solution verifies, eastern zones would be in for an extremely wet and windy Thurs night as the low deepens to 988mb over New England.  This could be a nice Nor'Easter or just an ordinary low pressure system and the model solutions must be monitored over the next 2 days.  There is agreement on a breezy day Friday as the low pulls off to our north and east.  Skies will probably have a hard time completely clearing during the day due to the usual northwest flow regime we see in the state during fall and winter.  Saturday looks like a typical fall day with temperatures in the 50s and low 60s under sunny skies.  One other note is that we noticed the NWS has snow showers in their wording for Friday night and Saturday across the higher terrain of NE zones.  We did not add any mention of snow due to uncertainty at this time frame and localized nature of any frozen precip.  However, snow showers may have to be added to the wording across NE and NC mountains if a colder model solution emerges over the coming days.


-Dan DePodwin