Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Raleigh NC
1045 am EDT Thursday may 28 2015
Synopsis...Bermuda high pressure centered over the western Atlantic
will be the dominant feature affecting our weather into the weekend.
Near term /through tonight/...
as of 1045 am Thursday...
Morning update...lingering showers in the southern coastal plain
will be diminishing as a weak shortwave continues to move east.
Meanwhile...morning stratus/fog hanging tough across The Heart of
the area into late morning...and could have a suppressive affect on
convection due to the hour or two lag in heating it will cause
across the area. Expect rapid warming and temperatures will catch up once
breaks occur...so we should still approach ongoing forecast maximum
temperatures in the middle to upper 80s in most areas. Low chance pop
convection will be possible about anywhere across the area as
instability climbs this afternoon. Focusing mechanisms are about
none...a weak western Piedmont trough to perhaps elevate probability of precipitation a bit in
Short term /Friday and Friday night/...
as of 258 am Thursday...
Generally a persistence forecast for Friday. Model soundings
indicate cap of warm air aloft will suppress
destabilization...generally 500 j/kg of MLCAPE or less. Thus rain
chances look to be isolated-slight chance(10 to 20 percent) at best.
Highs in the middle to upper 80s. Lows in the middle to upper 60s.
Long term /Saturday through Wednesday/...
as of 315 am Thursday...
A summertime pattern is apparent at the beginning of the long term
on Saturday as the main westerlies are near the U.S. Canadian border
with a ridge aloft near the typical Bermuda high position. A short
wave ridge centered off the New England coast extends into the
eastern Carolinas. This setup should greatly limit diurnal
convection. Have accordingly cut back probability of precipitation with just a limited area
of slight chance probability of precipitation across the southern sandhills where middle level
lapse rates are not as inhibitive and both the GFS/ec suggest a
ribbon of enhanced moisture extending northward from the savanah
river. High temperatures will range between 85 and 88 degrees.
The westerlies sink southward across the Great Lakes and northeast
on Sunday with a developing short wave trough developing over the
Missouri Valley. A southwest to northeast oriented cold front drops
into the middle Atlantic and Tennessee Valley on Sunday and Monday as a
weak area of low pressure associated with the upper trough develops
in the western Tennessee Valley. The result will be an increased
potential for scattered...mainly afternoon and evening convection.
Coverage on Sunday afternoon should be confined to the northwest
Piedmont and the NC/Virginia border area...much of the remainder of
central NC should be dry. Chances of convection increase on Monday
as the front drifts southward a bit and the upper tough axis slips
eastward. While scattered convection is possible across all of
central NC on Monday afternoon and evening...the greatest coverage
will be across the western and northern Piedmont. Highs on Sunday
will likely be a few degrees warmer than Saturday as low level
thickness values increase 5-10m. Highs Sunday should range in the 87
to 91 range. A good deal of uncertainty with the highs on Monday as
the cold front drifts south and may reach into northern NC. The
airmass will cool noticeably behind the front...the question is
whether the front makes it into the rah County Warning Area. For example...the 12z
European model (ecmwf) ensemble guidance for Henderson NC has highs ranging from 70
to 86 on Monday. For now will have highs ranging from near 80 at the
Virginia border to 88 at the SC border.
Uncertainty increases toward the middle of next week as the short
wave trough over the western Tennessee Valley closes off and becomes cut
off from the westerlies and drifts south across the Mississippi
Valley. The cold front lingers in the region but most likely
persists just to our north as the axis of deeper moisture from the
Gulf remains just to our southwest. Given the pattern will include a
good deal of cloudiness along with scattered mainly afternoon and
evening convection. Expect near seasonable high temperatures in the lower
to middle 80s. -Blaes
Aviation /12z Thursday through Monday/...
as of 630 am Thursday...
Areas of sub-VFR fog/stratus should lift to VFR 15-16z. Expect
isolated to widely scattered showers and thunderstorms this
afternoon. Probability appears too low to mention in the terminal
forecast at this time.
Outlook: the threat for restrictions in early morning fog/stratus
will continue into the weekend as Bermuda high pressure holds over
the area. Rain chances will begin to decrease some into the weekend
as the upper level ridge retrogrades west over the area.