Scientific Forecaster Discussion
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Area forecast discussion
National Weather Service Raleigh NC
925 PM EDT Sat Apr 19 2014
Synopsis...low pressure will slowly move east off the the southeast
US coast through the weekend.
Near term /through Sunday night/...
as of 925 PM Saturday...
vertically stacked low along the southeast coast will move slowly
eastward off the coast tonight and into the day on Sunday. While the
deep subtropical feed has shifted offshore...continued easterly
overrunning flow will support periods/occasional light rain and or
drizzle overnight...with the deformation band of moderate precipitation
currently across the southern Piedmont/foohtills and mountains
likely to pivot eastward in concert with the eastward moving broad
cyclonic circulation center. Localized 0.25 to 0.50" is still
possible underneath this heavier precipitation band. Otherwise...expect
light amounts of generally only a few hundredths.
Sunday and Sunday night... a model consensus is for precipitation to slowly
shift south and east and out of the area through late morning/early
afternoon hours with gradual clearing from the north-northwest as
the strengthening surface high builds in from New England.
However... if the cyclonic flow lingers along the I-95 corridor...
as some models hint... the cloudiness may be slower to clear. Skies
becoming partly sunny northwest... and variably cloudy elsewhere Sunday.
Highs generally in the lower to middle 60s...with the warmest readings
across the northwest Piedmont where we will more sunshine. Most areas
should become mostly clear west of I-95 Sunday night. Lows in the
Short term /Monday through Tuesday night/...
as of 200 PM Saturday...
Monday and Monday night: high confidence that Monday and Monday
night will be dry as the coastal low moves away from the Carolinas.
Surface high pressure will continue to ridge in from the northeast
while ridge also builds in aloft. Expect highs around 70 degrees
and overnight lows around 50 degrees.
Tuesday through Tuesday night: an upper level trough will approach
the area early Tuesday. The surface trough amplifies the surface low
over the Great Lakes moves east-northeast and deepens on Tuesday. Rain chances
will increase Tuesday afternoon as the cold front approaches.
Although southwest flow is expected to advect in some warm moist air
ahead of the front...the duration is relatively short...limiting the
available moisture and potential rainfall totals. As of the last
couple of model runs...the GFS appears wetter than the European model (ecmwf) with
this system...not helping to improve confidence. The warm southwest
flow will help high temperatures reach the middle to upper 70s across
the area. Given the projected marginal shear and instability Tuesday
aft/eve...an isolated strong/severe storm cannot be ruled out...but
the best upper level support is well to the north...which should
help limit the threat. Regardless...expect the cold front to move
through central NC Tuesday eve/night...with dry air advecting into
the middle level behind it helping cut off any remaining precipitation.
Though it will be dependent on timing of the front...for now expect
lows around 50 degrees northwest to middle 50s southeast Tuesday night.
Long term /Wednesday through Saturday/...
as of 215 PM Saturday...
High pressure builds in behind the front and remain in place through
Thursday night...yielding dry weather and temperatures within a few
degrees of normal...highs in the low to middle 70s and lows increasing
from middle 40s Wednesday night to low 50s Thursday night. Another low
pressure system traversing eastward across the northern U.S. At the
end of the week will gradually push the high offshore and yield the
return of southwest flow and increasing rainfall chances for Friday
and Saturday. Again with this system the models differ...with the
GFS being the wetter of the two...thus will continue to indicate a
slight chance for rain...although confidence in the timing and
amounts is not particularly high at this time. Expect highs in the
middle 70s to around 80 degrees and lows in the middle to upper 50s Friday
night...decreasing into the low to middle 50s for Saturday night.
Aviation /00z Sunday through Thursday/...
as of 730 PM Saturday...
Periods of light rain or drizzle will continue through the overnight
hours as low pressure slowly moves east off the southeast coast.
Despite the expected precipitation...mostly VFR conditions will prevail
with the main exception being across the southeast (kfay) where MVFR
to IFR conditions will likely prevail until Sunday morning or early
afternoon. Other taf sites may see brief periods of MVFR conditions
within heavier bands of precipitation...but that is almost impossible to
time out. Skies will begin to clear out from northwest to southeast
throughout the day on Sunday. Northeasterly winds will remain rather
brisk through the period...with periodic gusts US to 20-25 miles per hour...
especially across the east.
Outlook...VFR conditions are expected to dominate through Monday
night. Then the next system will impact the area on Tuesday...
bringing another chance for rain and associated adverse aviation
conditions. However this will be a much more progressive system with
conditions improving to VFR late Tuesday night into Wednesday...with
VFR conditions then persisting through Thursday as high pressure