Scientific Forecaster Discussion
fxus62 kilm 191140
Area forecast discussion
National Weather Service Wilmington NC
740 am EDT Thu Oct 19 2017
mostly clear skies and a warming trend are expected into the
weekend, as a dry upper ridge builds across the region. An
approaching cold front will bring a few showers on Tuesday,
before moving offshore Wednesday.
Near term /through tonight/...
as of 211 am Thursday...though a moderate trough axis and
vorticity center crosses the region today, the column is simply
too dry for any notable meteorological effects as the result of
any lift it provides. At the surface high pressure will remain
centered to our north bringing a NE wind, though the high will
be closer than recent days and the wind lighter. Low level
baroclinicity is very weak so the paltry sense of cold advection
in the NE flow will be offset by insolation and afternoon
temperatures will warm into the upper 70s. With lighter winds
tonight however temperatures will be a bit cooler than those of
today's predawn lows.
Short term /Friday through Saturday night/...
as of 211 am Thursday...a dry and warm short-wave upper ridge
of notable amplitude will migrate east, and anchor off the coast
this period. Associated subsidence will maintain a particularly
dry column, while promoting a daytime warming trend into 80s
over many inland spots Friday and Saturday. The aridity will
sustain large diurnal temperature ranges, as clearing overnight
leads to efficient radiational cooling and seasonably cool fall
mornings, with surface high pressure nearly overhead. As the
center of the high slips offshore late Saturday, return air flow
off the Atlantic will bring increasing low level moisture and
marine clouds into very early Sunday, and minimums at daybreak
will be considerably higher than previous dawns. Patchy fog
along the coastal interior seems plausible early on Sunday.
Long term /Sunday through Wednesday/...
as of 300 PM Wednesday...a highly amplified 500 mb pattern will
prevail at the onset of the long term period with ridging across
the eastern United States. At the surface, high pressure will
also continue to ridge across the forecast area as it departs
the mid-Atlantic region. As a result, dry weather will continue
as temperatures warm a few categories above normal through the
weekend into early next week. Eventually the 500 mb and surface
ridges lose control as an upper trough and surface low push
eastward. Give this system's current progression it appears that
there will be a good chance of storms during Tuesday with a
lowering in temperatures Tuesday night into Wednesday as surface
high pressure builds back into the region.
Aviation /12z Thursday through Monday/...
as of 12z...high confidence of VFR through 20/00z. Some
stratocumulus cigs this morning for a few hours near kilm otherwise
clouds will be sct through this taf valid period. North-NE winds
at 5-10 kts expected, except becoming east kcre/kmyr this afternoon.
After 00z, with clear skies and light winds conditions will be
favorable for fog development. Moisture is very limited and will
just indicate MVFR vsbys for now at the most favorable times 10-12z.
Fog could certainly develop sooner at coastal stations where
moisture is more favorable.
Extended outlook...tempo MVFR/showers Mon. Otherwise VFR.
near term /through tonight/...
as of 612 am Thursday...the Small Craft Advisory was replaced with a scec for
the 0-20 nm waters. Seas up to 5 ft offshore and gusts to 20 kt
will be common this morning.
As of 211 am Thursday...long fused NE surge to finally abate
today as high pressure sinks southward and a little closer to
the region. This should ease the gradient sufficiently to allow
the advisory- worthy 6 ft seas to exit the 20 nm coastal waters forecast boundary
and no changes to the headlines are planned. Wind to remain out
of the NE during the overnight hours and may even settle to
around 10kt. Wind wave energy will wane allowing for a continued
settling of waves though wna continues to show a dominant
period of 8-9 seconds in the NE swell.
Short term /Friday through Saturday night/...
as of 211 am Thursday...an improving marine trend, as winds and
seas decrease, generally NE-east through the period. Winds will
veer to east in the afternoons inshore, then back to NE at night
generally 15 kt or less. Wave energy from the east with dominant
periods of 8-9 seconds. A dry atmosphere remains in place so no
thunderstorms this period.
Long term /Saturday through Monday/...
as of 300 PM Wednesday...high pressure is expected to shift
farther off the mid-Atlantic coast Sunday, allowing the flow to
veer onshore. Southeast flow will further turn becoming
southerly during Monday as an area of low pressure treks from
the Gulf Coast to the western Carolinas. Small Craft Advisory
conditions may be reached late Monday in the strengthening
southerly flow. Seas will be 3-4 ft through much of the period
given the duration and size of the onshore fetch around the
periphery of the aforementioned high pressure.
as of 211 am Thursday...Spring tides to continue to lead to
very marginal minor flooding close to this month's new moon,
which comes today. Yesterday morning guidance was almost a half-
foot over done on the Cape Fear River at downtown. Was tempted
to not hoist advisory this morning but given the full moon think
we have the 80 percent confidence level to go ahead. At
Wrightsville Beach the current forecast is for tide to barley
just reach the 6.0 MLLW value needed for an advisory. Given the
positive error of guidance recently however any error with this
tide will keep the water level shy of minor flooding so will not
issue for the beach at this time.
NC...coastal flood advisory until 11 am EDT this morning for ncz107.