Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Wakefield Virginia
907 PM EDT Wednesday Apr 1 2015
high pressure will build over the area tonight...then gradually
shift off the coast on Thursday. The next cold front approaches
from the northwest on Friday...and crosses the region Friday night
into Saturday morning. High pressure returns from Saturday
afternoon through Easter Sunday.
Near term /until 6 am Thursday morning/...
clear skies and lght winds resulting in good radiational cooling this
evening as temperatures have dropped some 10-15 degrees in some areas since sunset.
Given the current deep temperatures...lows should drop into the m30s most areas
xcpt l30s in the normally colder spots along the rt 460 corridor
east of ptb and inland sections of the Eastern Shore.
A frost adsy remains in effect for most of the zones that have
started the growing season today (april 1st). This includes the
NE NC counties from Chowan east to the Atlantic coast / Chesapeake /
Virginia Beach. Kept Norfolk and coastal/Outer Banks Currituck out of
it due to slightly warmer temperatures west/ a few knots of wind anticipated.
It should be noted that counties in the adsy along the sound and
along the Atlantic coast (va beach oceanfront) will likely be a few
degrees warmer and frost is unlikely...just that we do not have
the ability to issue polygon-based frost advisories. Patchy frost
also possible farther inland in NC and Virginia...but these zones do not
start the growing season until April 8th or later.
Short term /6 am Thursday morning through Saturday/...
with surface high pressure axis offshore by middle/late thus morning and
a weather disturbance approaching the region from the SW...the area
will be within a warming airmass as breezy south winds develop by
the afternoon. Most inland locations should reach around 70 f under
mostly sunny skies...with highs in the l/m60s at the immediate
Increasing clouds Thursday night as upper ridge axis shifts off the
coast and a more moist SW flow aloft develops. In general...models
remain slower at bringing in deep moisture and the northern stream and
southern stream are slower to phase. Will continue west/ highest probability of precipitation on Friday
to north-northwest 1/3rd of forecast area by early Friday am through Friday afternoon. Very mild
Thursday night in south-southwest flow and increasing clouds...lows in the 50s to
possibly as warm as 60f in a few spots. Warm/variably cloudy Friday
with 20-30% chance for -shra and perhaps some late day thunderstorms as the
surface front moves closer to the region. Highs mainly in the
M/u70s to around 80f (u60s/l70s on the eastern shore). Main rain
event looks to hold off until Friday night...as the actual front
moves through the County Warning Area from northwest to southeast from 06-12z. Not a long period
of deep moisture and lift with this front however...and given some
continued model discrepancies regarding these features will keep
probability of precipitation in the high chance range Friday night...except likely across the
north. Lows Friday night mainly in the 50s. Dry air moves in from northwest
to southeast Sat morning...and most areas should be dry after 15z. Temperatures
aloft cool...but a downslope west-northwest flow should allow for highs
mainly 60-65 f under afternoon sunshine.
Long term /Saturday night through Wednesday/...
high pressure builds across the Tennessee Valley and into the southeastern
states/middle Atlantic region Sat night into sun...sliding off the
Carolina coast by sun evening. Aside from some breezy northwest winds
along the immediate coast Sat night...the middle Atlantic region will
experience relatively quiet and dry conditions Sat night through
early next week. Highs will begin at to slightly below average on
sun (upper 50s to low-middle 60s) and then warm 3-5 degrees each
consecutive day with forecast highs generally in the lower 70s
(mid-upper 60s at the immediate coast) by Tuesday. Overnight lows will
experience the same gradual warming trend with lows in the upper
30s to lower 40s Sat night...warming roughly 5 degrees each night
with lows in the low-middle 50s forecast for Tuesday night. Timing varies
regarding when the next chance for precipitation is expected to
occur. The GFS model brings intermittent periods of light rain
showers to the area Monday evening through Wednesday...while the European model (ecmwf)
model does not bring rain to the area until Wednesday. Went with a long
range model blend to average out rain chances during the
Aviation /01z Thursday through Monday/...
calm to light winds will prevail overnight as high pressure will
remain centered over the region. The high slips off the coast for
Thursday with gusty S/SW winds by midday. Low dew points will prevent
fog formation for Thursday morning. A mainly clear sky is
indicated with only scattered high clouds.
Outlook...the passage of a cold front will bring a chance for
showers and thunderstorms late Friday and Friday night. Otherwise a
dry forecast is in place through Monday.
Small Craft Advisory flags cancelled for southern coastal waters now that seas are
finally falling below 5ft as high pressure settles over the waters
through tonight. Light northerly winds veer around to the south after
midnight tonight and remain light (aob 10kt). High pressure slides
off the coast by Thursday afternoon and the surface pressure gradient begins to
tighten ahead of an approaching cold front. Breezy S winds begin
to increase in northern waters Thursday afternoon and then become widespread
across all waters by Thursday evening. Speeds will average 15-20kt with
gusts of 20-25kt (up to 30 knots in northern coastal waters). A new round
of Small Craft Advisory flags have been issued for the northern coastal waters from
Fenwick Island to Parramore Island and all of ches Bay beginning
Thursday afternoon through at least Friday afternoon. Coastal waters from Parramore
Island to the Virginia/NC border may briefly reach Small Craft Advisory gusts of 25kt Thursday
evening...but the duration anticipated is not long enough to
justify Small Craft Advisory flags at this time. Waves will average 2-3ft Thursday afternoon through
Thursday night. Seas will average 2-3ft...building to 3-5ft northern coastal
waters Thursday evening.
A cold front approaches the waters on Friday and pressure gradient
winds tighten further with SW winds averaging 20kt with gusts of
25-30kt throughout the day. Waves average 3-4ft and seas build to
3-5ft all coastal waters by early Friday evening. The front crosses
the waters late Friday night into Sat morning...resulting in a quick
surge of winds/seas with the frontal passage. Conditions remain
well-rooted in Small Craft Advisory flags on Sat in the Post-front environment as
winds/gusts become northwesterly and seas average 4-6ft north of Cape
Charles and 3-5ft south of Cape Charles. Ongoing Small Craft Advisory flags from
Thursday will likely be extended through Sat...and any waters not
within Small Craft Advisory flags will likely be in them by early Friday morning
(beginning roughly around daybreak). High pressure builds back
into the region by Sat evening and all conditions (winds/waves/seas)
are expected to diminish below Small Craft Advisory criteria. High pressure settles
over the waters sun through early Monday with southerly winds remaining
at or below 15kt.
the combination of low relative humidities and gusty south to
southwest winds will produce an increased fire danger threat
Thursday afternoon. Sustained winds of 15 to 20 miles per hour with gusts to
25 miles per hour and relative humidity levels dropping between 20 to 30
percent are expected during the afternoon hours.
NC...frost advisory from 3 am to 8 am EDT Thursday for ncz015>017-
Virginia...frost advisory from 3 am to 8 am EDT Thursday for vaz097-098.
Marine...Small Craft Advisory from 2 PM Thursday to 8 PM EDT Friday for
Small Craft Advisory from 5 PM Thursday to 8 PM EDT Friday for