Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Raleigh NC
325 am EDT Friday may 29 2015
Synopsis...high pressure centered over the western Atlantic will
extend into the region through Saturday. A cold front will drop into
the middle Atlantic and southern Appalachians on Sunday and move
into the Carolinas on Monday and Tuesday.
Near term /through tonight/...
as of 255 am Friday...
Middle to upper level ridge is expected to remain over the area
today... with Bermuda surface high pressure offshore allowing for
continued warm and humid conditions for late may. With the middle to
upper level ridge now back in place across the area.... convection
will be generally driven by lingering outflow boundaries from
yesterday... the seabreeze and any differential heating boundary
left from areas of stratus. The latest cam's continue to point to
the western and northern Piedmont as having the best chance for
seeing some showers and storms today... with potentially some
activity developing on the seabreeze as well. However... cant
completely rule out some showers developing across the central
Piedmont as well... especially as activity along the seabreeze is
expected to track northeastward after developing. Still think the
coverage will be generally isolated to widely scattered... to
locally numerous with the axis of higher precipitable waters pivoting north and
westward today. Thus... plan to carry slight chance probability of precipitation for all
locations except the northwest Piedmont... where we will carry low
end chance probability of precipitation. Any severe threat will again be quite limited...
with very weak deep layer shear and only modest instability at best.
Expect high temperatures similar to yesterday... in the middle to upper 80s
across the area.
Any lingering convection is expected to die off by middle to late
evening again... with the potential again for some patchy to areas
of early morning stratus and fog. Overnight lows will continue to
run several categories above normal... in the middle to upper 60s.
Short term /Saturday and Saturday night/...
as of 3 am Friday...
More of the same is expected on Saturday... with perhaps even a
lesser chance of seeing some isolated afternoon and evening showers
and/or storms... best chance northwest Piedmont. Expected similar
highs and lows from today and tonight... highs in the middle to upper
80s and lows in the middle to upper 60s.
Long term /Sunday through Thursday/...
as of 325 am Friday...
..increasing chances of some much needed rain early next week...
The large scale pattern during the long term features the breaking
down of the Southeast Ridge and decreasing heights as troughing
develops across the Tennessee Valley and deep south. At the
surface...Atlantic high pressure will retreat as a cold front drops
south into NC late Sunday and Monday and lingers across the region
for several days before shifting offshore as high pressure builds in
toward middle week.
Convective coverage will increase somewhat on Sunday afternoon and
evening ... across the northwest Piedmont and near the Virginia
border with scattered showers and thunderstorms associated with the
approaching cold front and upper trough. The threat of precipitation
will be very limited from U.S. 1 eastward. Highs Sunday will range
in the upper 80s to near 90.
The cold front will drop into NC late Sunday and is expected to move
slowly southward across the state on Tuesday and Wednesday. This
unusual pattern has support from both the ec and the GFS. The front
will provide a focus for scattered to possibly numerous showers and
storms on Monday and Tuesday with the greatest coverage gradually
shifting south during the period. Temperatures will cool during the
period as cloud cover and the arrival of cooler air on Monday and
especially Tuesday pushes highs into the upper 70s north to middle 80s
south on Tuesday afternoon.
Will decrease probability of precipitation on Wednesday and Thursday as the front weakens
and shifts away from central NC and confidence in forecast details
slip. A 1025 mb area of high pressure will extend into the area from
the northeast on Wednesday and Thursday with a cool northeast flow.
Highs will range in the upper 70s to lower 80s on Wednesday and
Quantitative precipitation forecast forecasts typically are not as skillful in the warm season as
the cool season and there is still some uncertainty in the forecast
details but there is an increasing potential for at least some much
needed rain over the long term with the greatest confidence an
expected precipitation amounts across the western and northwestern
Piedmont locations...especially on Monday and Tuesday. &&
Aviation /06z Friday through Tuesday/...
as of 130 am Friday...
24-hour taf period: convection continues to wane/dissipate across the
region early this morning... with no activity near any central NC
taf sites. However... a lingering outflow boundary in vicinity of The Triad
could allow for an isolated showers or two in vicinity of kgso/kint early
this morning... though confidence is way too low to include in the
tafs. Otherwise... aside from a potential for sub-VFR fog or
ceilings during the pre-dawn and early morning hours (08-15z)...and
a potential for isolated convection this after/evening (19-00z)... best
chance at the kint/kgso terminals...VFR conditions will prevail
through the taf period in associated/west an upper level ridge along the
Looking ahead: status quo. Expect a continued potential for early
morning fog/stratus and late after/evening isolated convection through the
weekend...primarily at the int/gso terminals. Expect chances thereof
to increase at all terminals by early next week as the ridge aloft
weakens and a slow-moving upper level trough approaches from the