Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Raleigh NC
1220 PM EDT Wednesday Oct 7 2015
high pressure centered along the Appalachians this morning will
build overhead through tonight and to the coast by Thursday evening.
Meanwhile...a cold front will approach from the northwest and cross
the region Friday night through early Saturday.
Near term /through tonight/...
as of 1033 am Wednesday...
Dry weather with seasonable temperatures expected this afternoon as
weak surface high pressure extends across central NC. A relatively
dry atmosphere will keep cloud cover to a minimum...limited to a
scattering of fair weather stratocumulus. Afternoon temperatures will be a
shade above normal for this time of year with most locations within
a degree of 80.
Tonight...a weak short wave in the northern stream will scoot across New
England and offshore. This system will drag a weak backdoor cold
front toward the Virginia border this evening...possibly drifting south
into our NE Piedmont/northern coastal plain before stalling. A few
clouds may accompany this feature but little if any precipitation should
occur as the moisture layer is thin and enough lift to generate
precipitation anemic. With variably cloudy skies north and mostly clear-
partly cloudy skies south...overnight temperatures should be fairly uniform
in the low-middle 50s.
Short term /Thursday and Thursday night/...
as of 355 am Wednesday...
A weak backdoor cold front with only very modest cooling behind it
will settle south into the NE Piedmont and northern coastal plain
early Thursday...before the surface ridge axis drifts to the coast and
promotes a light southerly flow throughout central NC by Thursday
afternoon. Weak convergence and an uptick in surface dewpoints to
near 60 degrees (and associated weak and shallow cape) may support
an isolated to widely scattered very light shower/sprinkle over the
northern Piedmont Thursday afternoon...but the associated probability of
occurrence is less than 15 percent. Cloud cover will be greater than
previous days...but still generally partly sunny on average amidst both
4-5 thousand feet cumulus and passing cirrus in westerly/quasi-zonal
Highs in the upper 70s to lower 80s...coolest NE. Not as cool with
light southerly stirring...and lows in the upper 50s to around 60
degrees - coolest in the coastal plain where periods of calm in
closet proximity to the surface ridge near the coast are most
Long term /Friday through Tuesday/...
as of 310 am Wednesday...
Models continue to converge towards a consensus concerning the
evolution of a short wave digging into the Ohio Valley late week
into the weekend. Initially...clouds will be on the increase from
the northwest with southwest flow low level flow ahead of the short
wave and its associated surface front. Highs will benefit from a
warm start and the warm air advection to reach into the upper 70s
northwest to lower 80s southeast. Will have slight probability of precipitation northwest by
middle day Friday increasing to chance probability of precipitation for showers across the area
Friday night and through the day Saturday as the upper short wave
cuts off over the Carolinas. Will hold off thunder with minimal
instability due to unfavorable diurnal timing Friday night. Later
forecasts can evaluate deeper convection potential Saturday once the
cutoff position is more clear. Highs Saturday will be cooler Post
frontal passage...and could end up even cooler than the upper 60s to lower 70s
in the current forecast.
Showers Saturday night (perhaps lingering into sunday) will be more
widespread nearer the coast where the surface front will stall or at
least slow dramatically parallel to the shoreline. Meanwhile showers
should be spottier north of the cutoff over central NC. Heavy
cloudiness will be widespread with highs Sunday mostly in the middle to
upper 60s after a morning low in the middle 50s. High pressure builds
in on Monday as the coastal system lifts northeast. Temperatures
moderate towards normal...mostly low and middle 70s...Monday and
Tuesday...with our next front (which looks dry at this point) moves
Aviation /18z Wednesday through Monday/...
as of 1220 PM Wednesday...
A weak area of high pressure extending across the region through
Friday will cause VFR conditions. Expect few to scattered clouds
this afternoon-evening with bases 3500-5000ft. A few surface front will
drift into the northeast counties late tonight. This feature may
enhance the cloudiness a bit but VFR will prevail.
An approaching low pressure system will increase the cloudiness and
the threat for rain showers across central NC late Friday night into
Saturday. This may cause a period of MVFR ceilings across central NC
Saturday through early Sunday. Improving weather conditions are
anticipated in Monday.