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.LONG TERM /SATURDAY THROUGH WEDNESDAY/...
A coastal low pressure system continues to bring plenty of
uncertainty to the forecast for the upcoming weekend into early next
week. Synoptically, we will remain in a split flow pattern
caught between the northern and southern branches of the jet
stream. Surface high pressure will gradually push east from
southern New England into the western Atlantic through the
weekend while an area of low pressure pushes north along a
stalled boundary at the southeast U.S. coast. Meanwhile, closed
low pressure looks to dig south from the Great Lakes/Ohio River
Valley into the Mid-Atlantic during the weekend timeframe.
Deterministic and ensemble model solutions continue to exhibit
large spread when it comes to how these features interact,
although some consistency has been noted in the latest 12z
solutions. The biggest question overall is to how far south the
closed low feature digs into the region and its overall
placement to interact with the incoming coastal low.
The 12z EPS continues to favor a solution where the cutoff low
pressure system has some interaction with the incumbent
shortwave/cutoff low over the Northeast. The 12z GEFS also favors
some interaction between the cutoff low and coastal low, especially
toward the back half of the weekend into early next week. Both
solutions suggest increasing rain chances late Saturday into
Sunday, especially in locations east of the Blue Ridge and
toward the I-95 corridor. Some shower activity may push toward
the mountains, but is highly dependent on the timing/placement
of the coastal feature and interaction with the closed
low/shortwave feature which looks to pass just over/north of the
region. Either way, this is a highly volatile forecast with
many moving parts that will have to be closely monitored. A
blend of the solutions would suggest increased cloud cover,
seasonable temperatures, and blustery conditions (especially by
the waters) for the upcoming weekend ahead. Precipitation
chances look to increase from the southeast Saturday afternoon
and evening as the influence of high pressure kicks further into
the western Atlantic, and coastal low pressure moves toward the
Carolinas. Rain chances will continue to increase for all
locations with an emphasis for those east of US-15 Sunday into
Monday as low pressure lifts up toward the Delmarva, and the
shortwave trough/cutoff low nears. Rain chances will decrease
Tuesday as the cutoff low/shortwave trough pushes east, and the
coastal low retrogrades back south toward the Carolinas. High
pressure returns thereafter for the middle part of next week.
Persistent east to northeasterly flow will lead to below normal
temperatures through early next week. Highs should remain in the 60s
with overnight lows in the 40s to mid 50s. Rainfall chances are
generally confined to areas along and east of I-95, and generally
capped at 30 to 50 percent. There is certainly room for this to
change based on the track of the coastal feature. Expect wind gusts
of 20 to 25 mph over land Sunday with gale gusts possible over
the waters. Stay tuned and check back at weather.gov/lwx for the
latest.