Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Wakefield Virginia
350 PM EDT Monday Sep 22 2014
high pressure advances east into the middle Atlantic region tonight
into Tuesday. A coastal low pressure system will bring chances of
rain back to the area for middle to late week.
Near term /until 6 am Tuesday morning/...
latest surface analysis reveals ~1026 mb hi pressure centered over the
Midwest with a stationary frontal boundary located off the Carolina
CST. The hi will spread east into the middle Atlantic region leading to
a cool and mostly clear night. Did include prtly cloudy skies across
extreme southeast Virginia/NE NC where moist southwesterly flow continues aloft ahead of
an approaching short wave trough. Not enough moisture/lift expected to
produce any rain. Light north winds tonight with overnight low temperatures ranging from
the upper 40s over the Piedmont to the middle/upper 50s near the
CST...about five degrees below normal for late sept.
Short term /6 am Tuesday morning through Thursday/...
short term period will be characterized by a return to NE flow and
tricky forecast with regards to chances of rain. For Tuesday...surface hi
pressure remains locked in place across the NE and Middle Atlantic States
while a trough of low pressure aloft cuts off from the mean flow. The
uncertainty regarding the strength and location of this cutoff
low and an associated developing coastal trough will complicate the
precipitation forecast across the area. Kept conditions dry daytime Tuesday
with any precipitation expected to stay S of the forecast area. Then slowly
increased probability of precipitation from S to north Tuesday night through Wednesday. 12z European model (ecmwf)...for the
third day in a row...continues to be more aggressive with bringing
the precipitation nwrd into the area...while 12z GFS continues to favor
drier conditions as it keeps the coastal trough farther offshore than
the European model (ecmwf). Continue to think European model (ecmwf) is overdone however with some
guidance such as the sref trending wetter...will forecast at least
chance probability of precipitation over the area Wednesday/Wednesday night/Thursday with likely probability of precipitation near
As for temperatures...readings wil continue to be below normal...with highs
avgg in the low to middle 70s and lows in the 50s to lower 60s.
Long term /Thursday night through Monday/...
model differences continue to make for a rather low confidence
extended period. Not quite buying the extended wet period (cut-off low)
European model (ecmwf) has painted across the area (given time of year and previous
performances) so have gone with the dryer GFS / Canadian solution. Gist
is that oceanic moisture will be battling the dry air from the high
prs to the north. Last time this happened...the high won out except
along coastal sections. Have trended this forecast in the same
manner meaning the best chances for precipitation will be along coastal sctns
with mainly dry conditions west of the ches Bay through the weekend.
Coolest day Friday. Highs in the l-m70s. 75-80 both Sat & sun. Lows
Next trough of low pressure moves east across the mts Monday. Low chance
probability of precipitation with this feature for now. Highs 75-80.
Aviation /20z Monday through Saturday/...
VFR conditions will prevail through the 18z taf period. 15-20kt
NE wind gusts will subside ~21/22z. High pressure builds in from
the northwest tonight into Tuesday as a cold front stalls off the
Low pressure forms along the front and attempts to nudge northward
Wednesday into Thursday. This will bring the potential for
occasional rain along with reduced visibility and low ceilings. A modestly
strong NE wind is also expected...especially along the coast.
secondary (shallow) cold air advection surge prognosticated Tuesday morning with guidance suggesting
about a 4 hour prd (8-12z) where a few gusts to 20 knots may occur over
the ches Bay. Given such a small (time) window and marginal event...
decided to hold off on any Small Craft Advisory headlines but word forecast as incrsg to
15 kts. Tuesday appears to be an in between day as high prs builds over the
region. No headlines expeceted. North-NE winds at or below 15 kts. Seas 3-4 feet.
High pressure builds across New England Tuesday night through Thursday.
Meanwhile...low pressure develops along the old frontal boundary and
nudges northward along the coast. The pressure gradient tightens
particularly Wednesday/Wednesday night bringing a 20-25kt NE wind to
the ocean/mouth of the Bay/sound...and 15-20kt elsewhere. Gusts to
30 knots. Seas are expected to build Wednesday into Wednesday night
potentially reaching 8-10ft out near 20 nm...and 5-6ft nearshore.
Small Craft Advisory conditions are expected to develop late Tuesday night and Wednesday
and will likely last for an extended period of time. Will hold off on
any headlines with this forecast package given a late third / fourth prd
starting time. NE flow continues through the end of the week...and
seas will likely be slow to subside.
Plan on keeping a moderate rip current risk Tuesday...but will likely
see a high threat for rip currents develop by Wednesday.
persist NE flow is expected to develop Tuesday night and strengthen
Wednesday into Thursday as high pressure remains anchored over New
England...and low pressure develops off the Carolina coast. Current
guidance suggests tidal departures rise to between 1-1.5ft above normal
Wednesday night into Thursday. This would put several locations right
around the minor flooding thresholds.
Maryland...moderate rip current risk through Tuesday evening for mdz025.
NC...moderate rip current risk through Tuesday evening for ncz102.
Virginia...moderate rip current risk through Tuesday evening for