Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Wakefield Virginia
730 am EDT Sat Jul 4 2015
unsettled weather conditions will prevail through the Holiday
weekend as a frontal boundary oscillates north and south across
the region. The front finally lifts north of the area by Tuesday
ahead of the next cold front that should move into the local area
the middle of next week.
Near term /until 6 PM this evening/...
area of rain showers continuing to move through eastern Virginia/portions of lower Maryland Eastern
Shore next few hours. Surface warm fnt from about the lower ches Bay on west
through portions of the pdmnt in central Virginia at this time...and will continue to
make slo progress lifting NE of the region through middle/lt morning hours.
Weak surface low pressure will be tracking through northern Virginia to off the central
Delaware-Maryland-Virginia by this afternoon. Frontal boundary will again settle S into central/southern
Virginia lt today. Will have chance probability of precipitation (mnly 30-40%) into the this
afternoon...highest north and west portions of forecast area. More widespread rain showers/thunderstorms
expected lt today as the boundary from the north pushes S and combines west/ daytime
heating. Another rnd of MDT/heavy rain possible...especially in scntrl and/or southeast
Virginia/NE NC (some of these areas received 1-3 inches Friday eve). Not
considering any flood watches at this time...but will have to monitor
trends throughout the day. Additional average quantitative precipitation forecast of 1/2 inch from
central to southern Virginia...W/ lclly higher amts (1-2 inches) possible. Vrb
clouds to mostly cloudy today. Hi temperatures from the u70s-l80s north and northwest to
the u80s-around 90f S.
Short term /6 PM this evening through Monday/...
frontal boundary stalls in vicinity of Virginia/NC border tonight...then begins to move
back north once again lt sun into Monday as low pressure surface-aloft lifts NE from
the Gulf states to the central mountains there remain some model
inconsistencies in this scenerio...largely relating to timing and
where axis of highest quantitative precipitation forecast takes place.
Lingering rain showers/thunderstorms tonight far southern Virginia/NE NC while drying occurs
over north-northeast portions of the forecast area (esp after mdngt). The favored area of
additional rain showers/thunderstorms on sun likely to be from scntrl Virginia to far southeast
Virginia/NE NC in vicinity of stalled frontal boundary. Mostly cloudy S...partly cloudy
NE tonight through sun. Low temperatures from the M/u60s north to the u60s- l70s S.
Hi temperatures sun mainly in the l/m80s.
00z/06 NAM farther west west/ axis of significant precipitation Sun night into Monday as low
pressure moves into the central mountains will have probability of precipitation gradually incrsg
into central/interior eastern Virginia into Monday...while keeping probability of precipitation lower at
much of the CST. Most low temperatures Sun night in the u60s-l70s. Vrb
clouds-mostly cloudy Monday west/ hi temperatures in the l/m80s.
At this time...total quantitative precipitation forecast through Monday expected to average 1-1.5 inches central/scntrl
Virginia to interior NE NC...tapering to an average of about 1/2 inch over the
lower Maryland Eastern Shore. However...lclly much higher amts are certainly possible
due to hi precipitable waters (1.75-2 inches)/slo moving or repeating
shras/tstms. Will highlight ptntl in severe weather potential statement.
Long term /Monday night through Friday/...
the medium range period is characterized by continued low amplitude
upper troughing over the eastern conus, with gradual re-reemergence
of the subtropical ridge over the southern tier of the Continental U.S. By the
end of the week. Expect that with occasional upper
disturbances/perturbations pushing across the northern middle-Atlantic,
as weak surface trough persists in place overhead, mainly diurnally
driven showers/storms can be expected. Have kept probability of precipitation in the chance
range by day (near climatology norms), west/ slight chance or less overnight.
Forecast precipitable water values will also remain high through the
period...lingering around +2 S.D. Above normal. Accordingly, we'll
need to be on guard for heavy rainfall with any showers through the
period. Additionally, with this increased humidity/dewpoints through
the period, continued to ride on the low end of guidance with
forecast highs in the midweek period...generally favoring a typical
middle-July warm/moderately humid set up across the area through much
of next week. Look for daytime highs in the 80s to near 90 inland,
with early morning lows 65 to around 70.
Aviation /12z Saturday through Wednesday/...
a warm frontal boundary will lift just north of the region by around midday...as
low pressure moves north-northeast from southeast Virginia to just off the Delaware/Maryland CST. That low will
then track NE out to sea this afternoon into sun morng...pulling that
boundary back S into northern NC as a cold front. Scattered showers and thunderstorms
will continue to be possible today into sun morng...with the best
chances shifting from the entire region this morng...southward into southern Virginia
and northern/NE NC this eveng into sun morng. Expect mainly VFR/MVFR
conditions across the region for much of the time...with IFR
conditions possible at any taf site through sun morng...esply during
the morng hours.
west-southwest gusts have been to 20-25 kts near the mouth of the ches Bay
from around 0930z this morng...and will calm down to more like 15-20
knots gusts by 13z. So...since this will only last about 3 hours...have
not issued a Small Craft Advisory...and have winds at 15 knots for the forecast.
No headlines in the short term today through Sun night. Unsettled weather
conditions continue over the waters over the Holiday weekend.
Frontal boundary was lifting north across the waters early this morng...and
will lift just north of the area by around midday as low pressure moves north-northeast
off the Delaware/Maryland CST. Winds will shift from the east-southeast over the lower Maryland and
Virginia eastern shr...to the SW or west during this morng to around midday. The
front will then drop back S of the area this eveng into sun
morng...as surface low tracks NE out to sea. Waves average 1-2 feet...seas