Scientific Forecaster Discussion
fxus62 krah 210016
Area forecast discussion
National Weather Service Raleigh NC
815 PM EDT sun Oct 20 2019
weak high pressure will move over the area tonight and Monday.
A cold front will cross the region Tuesday afternoon, followed by
high pressure building in from the west on Wednesday.
Near term /tonight/...
as of 640 PM Sunday...
The remnants of Nestor have moved off the Delmarva Peninsula. While
partial clearing has made its way into The Triad, the eastern half
of the state remains socked in under low clouds. Expect that
clearing will occur tonight with weak ridging, but the clearing
skies, light wind, and wet top of the ground should lead to areas of
ground fog later tonight. Areas of dense fog appear likely, with
locations across The Triad having the best chance due to more
moisture available from last night's rainfall. Lows generally in the
mid 40s to lower 50s.
Short term /Monday and Monday night/...
as of 215 PM Sunday...
Monday will start with lingering stratus and areas of fog. Weak high
pressure will move overhead during the afternoon. The skies will
become partly sunny, but delayed somewhat by the very light wind.
Highs generally in the upper 60s to lower 70s.
We will see increasing high clouds again in the afternoon, ahead of
the next frontal system. This front will be approaching from the Tennessee
Valley region by late Monday night. Dew points/low level moisture
will increase with the southerly flow. We will increase the chance
of showers late, mainly over the western third of the region
including the Piedmont. Lows in the upper 50s NE to mid 60s SW.
Long term /Tuesday through Sunday/...
as of 4 PM Sunday...
A deep mid/upper level trough will progress eastward into the
eastern U.S. At the start of the period on Tuesday. The main stacked
area of low pressure associated with the system will lift northward
from the upper Midwest into the Great Lakes region and southern
Canada. Meanwhile, the trailing cold front is expected to move
eastward and across the area. However, a secondary mid level
perturbation is expected to lift northeastward out of the deep south
and across central NC on Tuesday, which will allow for the
development of a secondary area of low pressure along the front as
it cross our area on Tuesday. Given deep shear is expected to be
strong, generally in the 45 to 55 kt range, and the potential for at
least some surface instability (~500 j/kg across the south and east)
Storm Prediction Center has all of central NC in a marginal risk for severe storms (with
the best chance across the southern and eastern portions of the
area). High temps are expected to range from around 70 north/northwest to
around 80 S/se.
Dry weather is expected behind the front as surface high pressure
builds into the area Tuesday night. The dry weather will continue
until at least Thursday night into Friday. The GFS and European model (ecmwf)
continues to struggle with the evolution of the mid/upper level flow
pattern across the Continental U.S. On late week into the weekend. The GFS
continues to support a more progressive pattern, with a front moving
across the area late week into the weekend, with the European model (ecmwf) has a
mid/upper level low develop over the Southern Plains late next
week/weekend, which would delay any precip chances for our area
until late weekend at best. Ensemble guidance is more in line with
the progressive GFS, though confidence remains rather low at this
time. Temps during this time frame will be near to slightly below
Aviation /00z Monday through Thursday/...
as of 815 PM Sunday...
Abundant low level moisture in the wake of Nestor and clearing skies
will lead to widespread fog tonight. Low clouds, mostly MVFR level,
are slowly clearing from west to east, yielding VFR at gso and int
already. Fay should be VFR by 02z and rdu by 03-04z, lasting longer
at rwi. With dry air aloft and surface high pressure stretching
from New England into central NC, fog seems almost certain as winds
go clam. Confidence is highest at gso and int, with LIFR vsbys or
lower by 08-09z, perhaps closer to 10z at rdu and Fay. Some
uncertainty in conditions being optimal at rwi, but conditions don't
always have to be optimal at rwi to get dense fog.
Fog and any low clouds will scour through the morning hours, with
MVFR or VFR by 15z. Light southeasterly winds will persist through
the day, turning to more southerly late in the day as a strong cold
front approaches from the central US.
Looking beyond 00z tuesday: su-VFR conditions are expected Monday
night and Tuesday as a cold front and associated rain across the
region. VFR is expected to return for the middle of the week.