Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Raleigh NC
954 PM EST sun Feb 1 2015
Synopsis... a strong cold front will approach from the west tonight
and swing across central NC on Monday. Highs pressure will then
build over the region through midweek.
Near term /through tonight/...
as of 954 PM Sunday...
The initial band of showers has been light and has shifted quickly
east of the region. This has been handled well by the latest hi-res
models. The main band of showers was rapidly developing/expanding
across the Tennessee Valley to the Appalachians. It is this band
that will bring the categorical pop and quantitative precipitation forecast of 0.25 to 0.50 later
tonight and Monday as it pushes through the region. Warm air advection and maa from
the south will bring temperatures and dew points up through the night.
Expect temperatures to remain steady or slowly rise from the upper
40s and lower 50s... well into the 50s to lower 60s late tonight.
Categorical showers expected to overspread the region from west to
Short term /Monday through Monday night/...
as of 300 PM Sunday...
Ongoing showers Monday morning are expected to progress east to the
coastal plain by 15z as an upper trough and cold front swing across
the area. While the bulk of the precipitation will be to the east...the
NAM and some of the cams suggest another band of low-topped showers
accompany the actual front between 15-21z. If these
materialize...some enhanced wind gusts will be possible in addition
to the 30-35kt westerly Post-frontal wind gusts already expected.
30-35kt wind gusts are below Wind Advisory criteria so no advisory
is needed...but this possible final band will need to be monitored
for locally enhanced winds. Highs ranging from 51 to 58 will likely
occur during the early morning hours before crashing during the
afternoon and the strong winds and cold advection surge across the
area. Final low tamps are a little uncertain given how far they
they are expected to fall through the day...but there is some
general model consensus of middle 20s for much of the area and upper
20s in the coastal plain.
Long term /Tuesday through Sunday/...
as of 310 PM Sunday...
Surface high pressure will be in place across the area on Tuesday...
before moving off the East Coast on Wednesday. A low amplitude
shortwave will cross the area on Tuesday... with little more than
enhanced middle and upper level cloudiness... as the antecedent airmass
remains quite dry at low levels. Return flow will provide a brief
warm up Wednesday... with highs reaching in to the low 50s.
Agreement does exist in more recent runs of both the European model (ecmwf) and
GFS... as both remain more suppressed with a southern stream wave
and resultant low over the northern Gulf early Thursday... with a
wave developing off the southeast coast... potentially bringing some
precipitation into the coastal plain. The northern stream wave diving out
of the northwest on Wednesday and into the area Thursday is now
playing a larger part... however moisture return in advance of the
associated cold front is weak... and models have backed off
considerably on precipitation chances. Given inconsistencies in model
solutions... will continue with the general flavor of the past few
days forecast... with no greater than slight chance probability of precipitation over the
area on Thursday.
High pressure will settle over the area for the remainder of the
period. Temperatures will remain below normal.
Aviation /18z Sunday through Friday/...
as of 105 PM Sunday...
Conditions are currently VFR across central central NC with cloud
bases at or above 10k feet and a light south-southwesterly wind. The
pressure gradient will continue to strengthen this afternoon ahead of
a low pressure system moving into the Ohio Valley...and as surface
winds increase to 8-12kt...a few wind gusts to 15-20kt may
occur...mainly from krdu west to kint/kgso.
Precipitation associated with the aforementioned low pressure system looks
to be ahead of the forecast by an hour or two...so will introduce
MVFR ceilings and a chance of rain in the tafs just a little
earlier. Expect ceilings to be near MVFR (3-4k ft) by 03z at
kgso/kint and more toward 06z from krdu east. The main rain band
with this system will cross the area between 06z and 15z...with
predominately IFR ceilings possible during this period. Southerly
winds will increase to 15-20kt and gust to near 30kt overnight as
the precipitation and cold front approach....then shift to west-
northwesterly and gust into the 30-35kt range behind the front on
Outlook... northwest breeze at 10-15 knots will persist Monday night as high
pressure builds toward the region from the west. VFR conditions will
rule through middle-week as dry high pressure builds over the Carolinas.