Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Wakefield Virginia
346 am EDT Sat Aug 2 2014
a frontal boundary remains nearly stationary along the middle Atlantic
coast through Monday. Areas of low pressure will track northeast
along this boundary...keeping unsettled conditions in place into
early next week.
Near term /today/...
latest msas showing mesoscale low tracking NE along Delaware-Maryland-Virginia peninsula.
In its wake...a mini in-situ cool wedge has developed resulting in
more of a stratiformed light rain/drizzle regime across the Piedmont.
Models show the short wave moving NE and away from the forecast area by late morning
with a second low tracking NE across NE NC/servn Virginia this afternoon and
evening. Not much of a trigger seen for widespread precipitation in between systms
for a several hour prd late this am and Erly afternoon...however tsctns/soundings
show plnty of ll moisture around the region especially ivof stalled boundary
along the coast. Combine this with some heating results in periodic
precipitation chances through out the day with the highest probability of precipitation along the coast.
Dual pole radar estimates from lasts nights rainfall ranged between 1-2
inches along i95 and rt 360 corridors. Some sporatic inch+ amts
along the coast except for a narrow band of 2-3 inches across southeastern
Virginia assctd with the convection assctd with the mesoscale low as it crossed
that area. Given high precipitable waters...setup favorable for some training echoes
across coastal areas later today. Lclly heavy downpours are still possible...
but widespread flooding not anticipated at this time. So given the sporatic
nature to the heavy rainfall past 12 hours / the time lag between S/w's & ffg
guidance between 2-3 inches per hour...decided to not issue any flood watches
with this package. Highs 75-80.
Short term /tonight through Monday/...
next short wave prognosticated to track NE across southeastern Virginia / Delaware-Maryland-Virginia tonight.
Thus likely probability of precipitation will be maintained across eastern half of forecast area...chance
across the west. Lows m60s-l70s.
Little change seen in overall pattern sun/Sun night with yet anthr
short wave enhancing rainfall ptntl along coastal sections. Latest guidance
suggests some breaks in overcast possible along and west of i95 corridor Sun afternoon.
A bit warmer as precipitation should become a bit more spotty in nature.
Highs u70s-l80s. Lows Sun night 65-70 with highest precipitation chances along
Precipitation coverage starts to diminish west to east Monday as the front
gets pulled offshore by tropical cyclone Bertha. Kept chance probability of precipitation all
areas with highs M-u80s.
Long term /Monday night through Friday/...
the nearly stationary front and associated plume of Atlantic
moisture should finally nudge offshore Monday night as a final
wave of low pressure lifts NE along the boundary. This wave then
pulls off the coast Tuesday. 30-40% probability of precipitation will be maintained over
southeast portions in closer proximity to the surface boundary. A brief
dry period is expected Tuesday night into early Wednesday as
shortwave ridging passes overhead. A cold front then approaches
from the northwest Wednesday and drops into the area Wednesday night.
This will bring a chance of afternoon/evening showers/tstms. The
front is prognosticated to drop into NC Thursday. 20-30% probability of precipitation will be
included for southern portions to account for any uncertainty with
respect to the frontal location. The front should eventually lift
back north later in the week...but confidence with respect to timing
and location is low...so minimal probability of precipitation will be continued. Highs
Tuesday should average in the upper 80s...with upper 80s/
around 90 Wednesday ahead of the front. Highs should drop back
into the middle/upper 80s Thursday and Friday behind the front. Low
temperatures should average from the middle 60s to low 70s.
Aviation /07z Saturday through Wednesday/...
as of 06z...light to moderate rain will continue to push north
through the region through 12z. The rain will be the steadiest at ksby.
Rain should end at kric by 07z. IFR/MVFR conditions will remain in
place for most taf sites through 14z.
Outlook...threat for showers/thunderstorms persist today/sun as moisture with
stalled boundary along/just inland from the coast. Periodic flight
restrictions will be possible in heavier showers/thunderstorms both days.
Overall coverage of precipitation will gradually diminish Monday/Monday night.
a frontal boundary will remain in vicinity of the middle-Atlantic coast through
the weekend. No flags are expected as wind speeds should remain at or below
15kt (direction averaging east/se) and seas/waves should remain below
5ft/4ft. Nevertheless...persistent onshore flow should keep seas
around 3ft...with occasional 4ft seas out near 20nm. Waves in the
Bay will average 1-2 feet. The front pushes offshore early next week as
high pressure returns to the region. A cold front approaches from
the northwest during the middle of next week. Overall sub-Small Craft Advisory conditions
are expected to prevail during the early to middle portion of next
week. However...some long period swell could encroach the area
depending on the strength/track of ts Bertha. Current 02/00z
wavewatch guidance brings 3-4ft swell out near 20nm Tuesday and
Wednesday of next week.
periodic rainfall along a slow-moving frontal boundary will
continue to bring accumulating precipitation to the region today
through Monday. Highest accumulations focused over NE NC and southeast
Virginia with addntl quantitative precipitation forecast amts between 1-2 inches (lclly higher in training
echoes) next 48 to 72 hours.
This may result in minor flooding of urban areas...areas of poor
drainage...low lying areas...and to rises of small streams/creeks.
Will continue to highlight locally heavy rainfall potential in
the severe weather potential statement.
Maryland...moderate rip current risk from 8 am EDT this morning through
this evening for mdz025.
NC...moderate rip current risk from 8 am EDT this morning through
this evening for ncz102.
Virginia...moderate rip current risk from 8 am EDT this morning through
this evening for vaz098>100.