Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC
FXUS62 KRAH 272349
Area Forecast Discussion
National Weather Service Raleigh NC
740 PM EDT Thu Apr 27 2017
A cold front will over the Mountains this evening will drift into
the central Piedmont overnight, then dissipate. A strong high
pressure will build off the southeast coast Friday and linger into
Saturday. A moist southerly return flow on the western periphery of
the strengthening Bermuda high will prevail Friday through the
.NEAR TERM /THROUGH TONIGHT/...
As of 748 PM Thursday...
Central and eastern parts of our region, essentially east of the
Triad region eastward are in the clear for now, and expected to be
so for the evening. The air mass continued to be rather stable and
not favorable for convective development. To the west, as previously
mentioned the cold front was drifting into the Mountains. Conditions
were more unstable and favorable for convective showers/iso
thunderstorms in this region. However, the most unstable air did
reside along the boundary over the Mountains and the forecast is for
the boundary layer east of the mountains to cool and stabilize
further as the the evening unfolds. Therefore, the scattered showers
and isolated thunderstorms tracking NE over the Mountains,
Foothills, and western Piedmont should weaken with time this
evening. We will maintain the highest POP (likely) over the Winston-
Salem area, with lower POP (chance of shower) from Greensboro and
Lexington eastward to Burlington for the next few hours. Otherwise,
no POP in the east. Then later tonight and early in the morning, the
cold front will slowly advance east toward the central Piedmont. As
this occurs, the latest HRRR and other hi-res models suggest only a
low chance of showers associated with the front. Otherwise, simply a
partly cloudy evening and overnight with warm temperatures. Lows
should be in the mid to upper 60s (or a good 15-18 degrees above
.SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/...
As of 330 PM Thursday...
In the wake of the upper wave lifting through the Great Lakes,
the sub-tropical ridge will expand across the Southeast Friday
into the weekend. Strong heating, with thicknesses approaching
1420m on Saturday, will leave to highs in the upper 80s Friday
and upper 80s/low 90s on Saturday. A strong cap will limit any
convection to the seabreeze on Friday, where the cap will be
weaker owing to strong heating, but dry air will ultimately
limit the coverage storms. Lows Friday night in the mid to upper
Strong instability will develop on Saturday as an elevated
mixed layer advectS across the region, deflect to the north a
bit by the mid-level ridge. MLCAPE as high as 3000 J/KG is
forecast by both the NAM and GFS. The threat of severe storms
will be conditions upon convective development, which will be
hindered by dry mid-level air (which will also support 1000 J/KG
of DCAPE) and the lack of a focus, other than the terrain induced
differential heating. Models do indicate a shallow tropopause
disturbance/jet emerging off the GOMEX saturday, which given the
strong instability could be enough to offer some forcing.
However, confidence is low at this point. Lows Sat night will be
in the upper 60s.
.LONG TERM /SUNDAY THROUGH THURSDAY/...
As of 330 PM EDT Thursday...
The subtropical ridge will retreat a bit on Sunday and
especially Monday as an upper low lifts of the southern Plains.
the associated cold front and convection are forecast to move
into central NC Monday night, later than in prior forecasts,
with limited instability and and forcing as it moves east. The
front will also serve to knock temps back to more seasonal
values, with highs in the 70s and lows in the 50s for midweek.
Some uncertainty develops midweek, as the front is forecast to
stall over the region and may be the focus for some unsettled
weather as another shortwave or two swing through the longwave
trough generally over the eastern US.
.AVIATION /19Z THURSDAY THROUGH TUESDAY/...
As of 115 PM Thursday...
VFR conditions prevail this afternoon with a 8-12kt southwest wind
gusting to near 20kt in some spots. An area of showers and storms
out ahead of a cold front will move into central NC from the west
this evening,and while the intensity and coverage should weaken as
they move east, there may be continued development of showers all
the way east to RDU/RWI/FAY overnight as the primary cold front
finally tracks east across the area. Brief MVFR/IFR conditions can
be expected in any shower or storm, with low confidence in timing
and location. IFR stratus looks to also be a possibility late
VFR is expected to return by mid-morning Friday as strong high
pressure aloft expands over the region.
Outlook: A very summer-like pattern through the weekend with sub-VFR
stratus possible during the early morning hours, scattering out by
15Z, and isolated afternoon convection being focused mainly around
GSO/INT. Otherwise, expect the best overall potential for convection
Monday evening/night in assoc/w a cold front /squall line/ progged
to track eastward through the Carolinas.