Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Wakefield Virginia
159 am EDT Wednesday may 27 2015
high pressure remains anchored off the middle Atlantic coast into
the weekend. A trough of low pressure remains nearly stationary
east of the mountains through Friday.
Near term /until 6 am this morning/...
offshore ridge dominates overnight but expect an increase in cloud
cover by morning. Warm and humid with lows 65-70.
Short term /6 am this morning through Friday/...
offshore Bermuda ridge continues the Summer heat/humidity through
the period. Models continue to show a persistent trough which when
combined with the apprchg moisture from the west-southwest will likely be the
trigger for scattered convection. Timing rather problematic given low
confidence of short wave energy ejecting NE from dsptg mcs's....but the
emphasis of this forecast will be for mainly diurnally driven
convection each day. Highest probability of precipitation (40-50%) will be across the northwestern
third of forecast area...20-30% rest of forecast area expect the NE corner of NC where little
if any support seen for precipitation. Threat will be for lclly heavy downpours
given the precipitable waters at or above 1.5 inches...deep temperatures in the 60s and relatively
weak steering currents. Highs each day in the l-m80s...xcpt 70s at
the beaches. Lows 65-70.
Long term /Friday night through Tuesday/...
long term period starts off Sat with an upper-level ridge breaking
down over the eastern Seaboard as a cold front drops into the medium Atlantic
region. There is still some differences amongst models in regards
to when the front makes it into the local area which would affect
timing of precipitation...with the 12z GFS faster than the 12z ecwmf. For
now with this still several days out will forecast 20-30% probability of precipitation Sat
increasing to 30-50% sun with the front in the vicinity. Expect
above normal temperatures both days with highs avgg in the middle to upper
80s. Chance of rain continues into Erly next week with temperatures not
quite as warm as the weekend...highs only in the upper 70s to lower
80s on average.
Aviation /06z Wednesday through Sunday/...
high pressure has centered off the middle-Atlantic coast early this
morning...as low pressure locates over the Great Lakes region. The
result is a S-SW wind 5-15 knots...strongest near the coast. Latest
satellite indicates broken-overcast MVFR deck (1500-2000 feet agl)
expanding across south central Virginia. MVFR conditions have spread northward
into kric. Abundant low-level moisture in tandem with an upper
level disturbance will result in the continued expansion of this
cloud deck...but due to sub-cloud layer mixing...do not anticipate
IFR ceilings like some guidance indicates. Combination of cloud
cover...mixing and relatively dry soils will inhibit fog
development this morning.
For today...expect MVFR deck to erode by middle-morning as high
pressure remains over the region. S-SW winds of 10-15 knots persist
today with occasional gusts around 20 knots. Isolated-widely
scattered showers/thunderstorms possible after 18z...mainly over
the Piedmont into central Virginia.
High pressure dominates into the weekend...resulting in diurnally
driven showers and thunderstorms. VFR conditions will prevail
outside of thunderstorms.
Small Craft Advisory issued this morng for the Bay continues through this eveng. With a
similar pattern as yesterday which had frequent gusts to 20 knots
expect S winds to pick up to 15-20 knots later this afternoon and eveng. Sub-
Small Craft Advisory conds over the other waters with 15-20 knots winds over coastal waters and
10-15 knots over the rivers and sound. S flow continues into Wednesday with
strong surface hi pressure offshore. Expect similar winds as today with waves
over the Bay at 2-3 feet and seas over coastal waters at 2-4 feet. Pressure
gradient weakens a bit on Thursday...and winds should be a few knots less
overall. Winds look to remain southerly avgg 10-15 knots for the most part
into the upcoming weekend.