Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Wakefield Virginia
410 am EDT Wednesday Aug 5 2015
a cold front stalls across North Carolina today and tonight as
high pressure moves east from the Great Lakes. The front lifts
back north as a warm front Thursday with low pressure moving east
along it Thursday night and Friday. High pressure slowly returns
over the weekend.
Near term /until 6 PM this evening/...
cold front now pushing south through the County Warning Area...temperatures and dew points
have dropped into the 60s across the far north...with 70s elsewhere.
Thunderstorms across the Eastern Shore finally diminishing/exiting offshore now
with the front pushing south. For today...surface high pressure
centered over the upper Midwest will shift east-southeast into the Great
Lakes by this aftn/evening. Somewhat drier airmass to overspread
the region today...with dew points mixing out into the 60s most
areas...despite temperatures remaining very warm. Best moisture and
support for any precipitation later today should be confined to NC (will
maintain just a 20% pop across these areas this aftn). Partly to
mostly sunny and less humid as deep temperatures drop. Highs generally in the
low to middle 90s...with drier airmass afternoon heat index values to
remain below 100 f.
Short term /6 PM this evening through Friday/...
frontal boundary begins to move back north as a warm front tonight but
still prognosticated across NC at 12z Thursday. Some warm air advection at 850 mb noted to
produce slght chance probability of precipitation across southern most counties aftr midnight.
Otw...pt cloudy with lows m60s north to around 70 f south (lwr 70s
Warm front lifts north into the akq forecast area on Thursday...GFS the fastest
while the European model (ecmwf) is generally the slowest to overspread deeper moisture
into the area. The exact location and timing still a bit uncertain
but overall trends indicate that Thursday afternoon will be wet over much of
the County Warning Area...have raised probability of precipitation to likely across western/central zones...will
keep probability of precipitation in chance range across the E/se. Depending on the onset of
rain...temperatures could be hard pressed to get out of the 70s in some
areas...though will not forecast readings as cool as the GFS/mav
numbers are currently indicating. For now will go with highs
ranging from the upper 70s far west/northwest (due to earlier onset of low
clouds/rain) to around 90f NE NC where skies remain partly sunny
into midday and precipitation is slower to arrive. Likely probability of precipitation all areas
Thursday night as low pressure deepens along the slowly advancing
warm front. Heavy rain possible and will mention in the severe weather potential statement. Lows
in the upper 60s to lower 70s.
Models differing on Friday with respect to how fast the systm exits off the coast.
Splitting the difference keeps likely probability of precipitation across the area into
early afternoon tapering off to chance probability of precipitation drng the afternoon. A rare Summer
wedge possible Friday across the northwest Piedmont where temperatures will be hard
pressed to get much above the upper 70s/around 80 f. Otw...highs
in the Lower-Middle 80s. A widespread rainfall appears likely with
additional qpf's around one inch...higher along the coast.
Long term /Friday night through Tuesday/...
long term period starts off Friday night with a middle-level shortwave
trough and associated surface low pressure pulling offshore. Will hold on to
some lingering probability of precipitation Friday night with decreasing cloudiness and low
temperatures in the middle 60s to lower 70s. Weekend then shaping up to be dry
and comfortable with surface hi pressure building into the area. Expect a
prtly cloudy sky with fairly low humidity and hi temperatures only in the low
to middle 80s both days. Next chance of rain comes Monday and Tuesday as more
upper-level energy approaches from the west. Will cap probability of precipitation at 30% at this time with
this being several days out.
Aviation /08z Wednesday through Sunday/...
cold front has settled just north of the local area this morning.
Showers/thunderstorms currently impacting ksby will push east of
the site by the 05/06z taf issuance. Another isolated shower
impacted kphf...but has since moved out over the Bay. Expect the
remainder of the overnight to be dry...outside of an isolated
shower near the coast. Otherwise...southwesterly surface winds generally at or below 10
knots with broken high clouds at or above 25k feet above ground level.
For today...cold front slowly drops across the region
today. Little more than a wind shift to the northwest late today and scattered
afternoon cumulus expected with the frontal passage. Dry forecast will
More unsettled conditions arrive later Thursday into Friday as
low pressure and its associated cold front affect the area. High
pressure builds in from the north Saturday and Sunday.
cold front has settled over the northern waters early this
morning...marked by a wind shift to the west-northwest. Earlier gusts to 20 knots
in the Lower Bay and lower James River have diminished thanks to a
weakening pressure gradient. However...a few gusts to 20 knots still
possible in the Lower Bay through 6 am EDT. Seas generally 2-3 feet (4 feet
buoy 44009) and waves 2 feet. Cold front slowly drops across the
waters today...stalling near the Virginia/NC border late today into early
tonight. Winds generally westerly (depending on where the front settles)
at or below 15 knots this afternoon...and then northerly tonight at or below 10 knots. An area
of low pressure prognosticated to develop along the frontal boundary
Thursday as high pressure builds into New England. The result will
be onshore flow Thursday at or below 15 knots. Gradient strengthens Thursday night as
the low deepens in the vicinity of eastern NC. Spatial differences
still remain in the short term models with respect to the low
placement and resultant frontal location. However...there is
increasing confidence for Small Craft Advisory conditions Friday into Saturday due to
strength of the pressure gradient and NE flow. Seas
respond...building to 4 t0 5+ feet Friday night though Sat. Low prognosticated
to lift away from the coast Sat night into sun...allowing the
gradient to relax and winds/seas to diminish/subside.