Scientific Forecaster Discussion
fxus61 kakq 181101
Area forecast discussion
National Weather Service Wakefield Virginia
701 am EDT Wed Sep 18 2019
surface high pressure builds into the region from the north
today through Thursday, and then settles over the region Friday.
Meanwhile, Hurricane Humberto is forecast to track well east of
the Carolina coast today and Thursday.
Near term /until 6 PM this evening/...
as of 350 am EDT Wednesday...
1027mb high pressure is centered over qb early this morning,
and extends swd into the Virginia Piedmont. Meanwhile, Hurricane
Humberto continues to track east-northeast well off the southeast coast.
Mostly clear early this morning, with some patchy fog over the
Piedmont. Temperatures range from the mid 50s to low 60s for
most of the area, with mid/upper 60s for coastal regions of southeast
Virginia and NE NC. Surface high pressure will build swd into nrn New
England today as Humberto continues to move away from the coast.
This will produce a modestly strong pressure gradient along the
coast, which will result in a NE wind of 15-20 mph with
occasional gusts to 25-30 mph. A NE wind will be lighter inland
and mainly 5-10 mph well away from the coast. Onshore flow off
relatively warm water should result in variably cloud cover from
late morning into the aftn with scattered-broken cumulus. Mild today, with
high temperatures ranging from around 70f/low 70s along the
coast, to the mid 70s inland.
Short term /6 PM this evening through 6 PM Thursday/...
as of 350 am EDT Wednesday...
Surface high pressure continues to build swd along the coast
tonight into Thursday. Mostly clear and cool tonight, with low
temperatures ranging from the low 50s from the Piedmont to the
Maryland ern shore to the upper 50s/around 60f over coastal southeast Virginia/NE
NC. Continued breezy Thursday although the wind should not be
quite as high as Wednesday. Partly cloudy along the coast with
scattered late morning and aftn cu, and mostly sunny inland. Pleasant
with high temperatures generally 70-75f, with upper 60s for the
Maryland Atlantic coast.
Long term /Thursday night through Tuesday/...
as of 350 am EDT Wednesday...
Cooler and drier conditions persist into the latter portion of
the week. Ridge of sfc high pressure will prevail over the mid-
Atlantic into the southeastern US for the late week period.
Aloft, the region will remain on the periphery of an upper level
ridge of high pressure, which will rebuild over the region from
the southwest during the upcoming weekend, bringing a gradual
warm- up late in the weekend into early next week.
Warm days and cool nights prevail later this week, with high
temperatures Friday ranging from 75-80f, after lows Thursday
night/Friday morning in the upper 40s over the Piedmont
(perhaps mid 40s in the northwest piedmont), around 50f/low 50s for the
interior coastal plain and Maryland ern shore, and mid 50s to around
60f for coastal southeast Virginia/NE NC. The warming trend begins Saturday
into early next week, with high pressure at the surface sliding
offshore and building heights aloft. Above average temperatures
likely prevail through this period with highs in the mid/upper
80s to around 90 degrees with early morning lows generally in
the 60s area wide.
Aviation /12z Wednesday through Sunday/...
as of 700 am EDT Wednesday...
High pressure was centered over qb as of 12z, and was building
into the mid Atlantic as Hurricane Humberto tracked east-northeast well off
the coast. The wind was NE 5kt or less inland, and NE 8-12kt
along the coast, and locally stronger at orf. Mostly clear
early this morning, with any lingering SC remaining well SW of
the taf sites. Some patchy fog is possible well inland, but
should remain west of ric. Onshore flow will continue today as high
pressure remains centered well north of the region. A NE wind is
expected to reach 12-15kt with gusts to 20-25kt closer to and
along the coast, and 8-12kt farther inland. Scattered-broken cumulus are
expected to develop late morning into the aftn. Mostly clear
tonight with an 8-12kt NE wind along the coast, and light out of
the NE farther inland.
Dry conditions are expected Thursday through Sunday as high
pressure slides across the region Thursday and Friday, and then
offshore Saturday and Sunday.
as of 350 am EDT Wednesday...
Early this morning, Hurricane Humberto was continuing to move east-northeast
several hundred miles off the SC coast while ~1026 mb high pressure
was centered over far nrn New England/srn Quebec. Humberto is
forecast to slowly transition into an extratropical cyclone during
the next couple of days as it interacts with a frontal system. The
pressure gradient between Humberto and the high is leading to NE
winds of 15-20 kt north/20-25 kt S of the Virginia-NC border. Waves are ~2 ft
across the Northern Bay and 3-4 ft across the south. Seas have
increased to 5-6 ft north/6-9 ft S.
High pressure builds south-southwest toward central Virginia/NC today and tonight as
Humberto continues to track to the east-northeast. Even though Humberto will
continue to slowly move away from the Atlantic coast, the pressure
gradient between Humberto and the aforementioned high will increase.
Therefore, expect a slight uptick in winds before peaking during the
00z-06z (thu) timeframe. Sustained winds will increase to 20-25 kt
on the ches Bay/23-27 kt on the ocean by 00z Thu. At least a few
gusts to ~30 kt are likely on the lower ches Bay, srn coastal
waters, and the Currituck Sound this aftn through the first part of
tonight. Occasional gusts to ~20 kt are likely on the upper rivers
later today-06z Thu. A few gusts to 25 kt are possible on the lower
part of the York river, so went ahead and issued an Small Craft Advisory from 1 PM
today-1 am Thu. Not sure that 20 kt gusts will be frequent enough to
warrant scas for the Rappahannock/upper James, so left these two
zones out of any headlines attm. Seas build to 7-8 ft north/8-10 ft S by
late this evening. Will maintain the high surf advisory for Virginia
Beach/ern Currituck (through 7 PM thu). Scas remain in effect
through 7 am Thu for the ches Bay, lower James River, and Currituck
Sound. The Small Craft Advisory for the ocean is now in effect through 7 am Fri (due
to very high confidence in seas remaining aoa 5 ft).
On Thursday, the high is expected to build south-southwest toward the area, and
Humberto will be far enough offshore to allow the pressure gradient
to relax some. As a result, NE winds slowly diminish from early Thu
am through the day on Thu. The current forecast has wind gusts
dropping below Small Craft Advisory thresholds by early Thu afternoon. The high is
expected to settle into the region from Fri-Sat before moving to the
southeast of the area by sun. Winds turn to the north then northwest on Fri before
becoming SW by early Sat am. Sustained winds will remain aob 12 kt
from Fri through the weekend. However, seas (and waves near the
mouth of the bay) will be slow to diminish. Scas may need to be
extended for the mouth of the ches Bay through Fri am/ocean through
Sat (due to waves/seas) in future forecast packages.
as of 530 am EDT Wednesday...
Tidal anomalies have risen to 1-1.5 ft above normal in areas
adjacent to the ches Bay/rivers. Nuisance to minor tidal
flooding is expected in areas from the lower Maryland ern shore to the
srn shore of the ches Bay/upper James River during today's high
tide. Therefore, coastal flood statements/advisories have been
issued accordingly. With the persistent NE wind, tidal
anomalies will remain elevated/slowly rise through Thursday. As
a result, additional statements/advisories will be needed for
both tonight and thursday's high tide cycles. At this time, it
looks like any tidal flooding from today-Thu will mainly be
minor. However, water levels may come very close to moderate
flood thresholds at bishop's head, Lewisetta, and Jamestown
during the high tide cycle Thu aftn. Tidal anomalies slowly fall
from Thu night-Fri as winds continue to diminish. However,
lingering nuisance to (low-end) minor tidal flooding is possible
The current forecast keeps water levels just below minor flood
thresholds along the Atlantic coast of MD, VA, and NC. However,
there is a very slight chc that water levels exceed minor flood
thresholds on the Oceanside of the Virginia ern shore/NC during the
higher astronomical tides today/Thu.
A high rip current risk is forecast for today, and will likely
continue into Thursday, as swell from Humberto propagates toward
NC...high surf advisory until 7 PM EDT Thursday for ncz102.
Virginia...coastal flood advisory from 11 am this morning to 8 PM EDT
this evening for vaz075-077-078-089-090-093-096-524.
High surf advisory until 7 PM EDT Thursday for vaz098.
Marine...Small Craft Advisory until 7 am EDT Friday for anz650-652-654-
Small Craft Advisory until 7 am EDT Thursday for anz630>634-
Small Craft Advisory from 1 PM this afternoon to 1 am EDT
Thursday for anz636.