Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Wakefield Virginia
503 am EDT Thursday may 7 2015
a weak frontal boundary dissipates over the local area this
morning. High pressure builds over the region today. Low pressure
off the coast of northern Florida and Georgia...will slowly lift
northward and will spin off or near the southeast coast through
Near term /until 6 PM this evening/...
weak backdoor front has located over the northern local area and Eastern
Shore early this morning...marked by slightly cooler temperatures and
dewpoints. Showers have dissipated over the local area...so have
dropped probability of precipitation to silent due to the lack of appreciable forcing and
instability along the front. Patchy fog has developed over portions
of the Piedmont and northern Virginia where rainfall was recorded last evening.
Any remaining fog will quickly burn off/lift after sunrise.
For today...area continues to be under the influence of an upper
level ridge resulting in light flow aloft. Cut-off low remains
nearly stationary under the ridge off the SC coast. At the
surface...high pressure slides off the NE/northern middle-Atlantic coast as the
backdoor front washes out. Onshore flow and warming temperatures around
700mb will result in stable conditions across the region. Large
scale subsidence and a lack of appreciable forcing will keep much of
the local area dry today. The exception will be across NE NC where a
slight chance of showers and thunderstorms was retained due to the
close proximity of better forcing and dynamics associated with the
cut-off low. However...expect best chances for measurable precipitation to
remain south of the local area today. Low-level thicknesses drop off
slightly today compared to previous days due to aforementioned
onshore flow. The result will be slightly cooler temperatures...but
remaining above normal. Highs around 80 inland. Dropped temperatures along
the coast...with highs only expected in the low to middle 70s. Along
the immediate coast...highs only in the middle-upper 60s. A partly
cloudy sky is expected today as middle-upper level moisture spreads northward
from the cut-off low.
Short term /6 PM this evening through Saturday/...
local area remains under the influence of an upper level ridge and
light flow through the short term. Surface high pressure remains centered
over the western Atlantic...ridging westward over the local area. The result
will be a continuation of above normal temperatures. Remaining cooler along
the coast as onshore flow persists. Models coming into good
agreement with handling the cut-off along the southeast coast. Through the
short term period (thurs night through sat)...models forecast the surface low
center to move roughly 80 miles to the west northwest...remaining
just off the SC coast. Sensible weather impacts for the local
area will be tied to occasional waves of deeper moisture and
modest lift affecting mainly the southern 1/2 of the local area Friday-
Sat. Even with warm temperatures and Theta-E advection...instability will
be limited due to subsidence/warm temperatures aloft. Precipitable waters prognosticated to be
around 1 to 1.25 inches...which combined with only modest dynamics
over the local will limit total quantitative precipitation forecast amounts. Have maintained
chance probability of precipitation mainly Friday and Sat afternoons for scattered showers
and a slight chance for thunder. Confidence is simply not there to
increase probability of precipitation based on amount of subsidence and timing of the
deeper moisture and lift. For more information on the low becoming
subtropical...please refer to the National Hurricane Center
Highs Friday and Sat remain slightly above normal...generally around 80
inland and the middle-upper 70s near the coast. Immediate coast may
only warm into the middle-upper 60s. Lows generally upper 50s to low
60s through the short term. Skies average partly cloudy...with periods of
mostly cloudy-cloudy across the southeast.
Long term /Saturday night through Wednesday/...
the overall pattern for late this weekend and early next week keeps
a ridge of high pressure in place across the eastern Continental U.S. For
continued warm temperatures. The uncertainty in the forecast has to
do with low pressure currently off the southeast coast...its eventual
track...and how much of an impact it has on the local area. Stayed
close to wpc/NHC forecasts for the end of the weekend/first of next
week which brings the center of the low up into eastern NC on
Monday...then off the Virginia coast on Tuesday in advance of a cold front
that sweeps through the local area Tuesday night/Wednesday morning.
Will allow for scattered shower/thunderstorm chances over the local area sun-
Tuesday...then dry again next Wednesday behind the cold front. Highs through
Tuesday in the 80s...except cooler 70s immediate coast. Lows in the
Aviation /09z Thursday through Monday/...
VFR conditions through forecast prd as subsidence around dvlpng coastal
low off southeastern coast results in mainly high level moisture. Diurnal cumulus
develops today...but any shower activity remains west of akq terminals.
S-southeast winds at or below 10 kts today slowly become east-southeast by Friday.
Low pressure lingers off the southeast coast through the weekend...bringing
chances for showers / tstrms to southeast Virginia/NE NC Friday through sun.
no headlines in short term as the marine area remains in between high
prs over the NE and low prs spinning off the southeastern coast. Model data
continues to indicated a slow movmnt of the coastal storm toward the
Carolina coast keeping the strongest winds and highest seas S of
Cape Hatteras. This leaves the akq marine area with a general Erly
wind flow into the weekend with speeds at or below 15 kts. Seas will slowly
increase to 3-4 feet due to the persistant Erly flow...but should remain
below 5 feet within 20 nm of the shore. Offshore seas will slowly build
especially closer to the Gulf Stream wall.