Area Forecast Discussion
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FXUS62 KRAH 172359
Area Forecast Discussion
National Weather Service Raleigh NC
659 PM EST Fri Feb 17 2017
An upper level trough will approach from the west and cross the
southeastern U.S. Saturday and Saturday night. Surface high pressure
will otherwise extend across our region through the weekend.
.NEAR TERM /THROUGH TONIGHT/...
As of 140 PM Friday...
Earlier high clouds over the NE CWA are dwindling as the vorticity
maximum that was the primary driver of this cloudiness moves off the
NC coast. Heights aloft will continue to rise through tonight as the
deep longwave upper trough moves out over the Atlantic, followed by
shortwave ridging over the Southeast states, which will hold over
the region before moving to our east Sat morning. Expect generally
clear skies through much of the night, although high clouds will be
on the increase over our SW sections as an upper low now over OK/TX
shifts into the middle and lower Miss Valley, spreading warm-
advection high clouds into the forecast area from the SW. Expect
lows in the mid 30s to lower 40s, with the cooler readings in the
outlying areas. -GIH
.SHORT TERM /SATURDAY AND SATURDAY NIGHT/...
As of 220 PM Friday...
The mid level shortwave ridge axis is expected to be overhead at
sunrise Sat, after which time it will shift steadily off the coast
as the upper low crosses the Mid South Sat before then opening up a
bit as it crosses the Carolinas Sat night. Forecast soundings depict
relatively little moisture with this feature, focused primarily in
the mid to upper levels, with weak low level moisture transport, and
steady MSLP with ridging extending across the Southeast and a weak
lee trough over the Piedmont. Also, the initially-decent DPVA
weakens as this low/trough approaches and dampens, contributing to
reduced forcing for ascent as we head through Sat night. Model
output overwhelmingly supports little in the way of measurable
precip in central NC, including the SREF and NCAR ensemble which
show very low to no chance of measurable precip, and the operational
models which show only very light amounts barely scraping the NW and
SE corners of the CWA. Based on this limited moisture and lift, will
limit slight chances over just the SE and NW CWA Sat night. Expect
increasing and thickening clouds Sat, with thicknesses supporting
highs in the upper 60s to lower 70s. Lows in the mid-upper 40s. -GIH
.LONG TERM /SUNDAY THROUGH FRIDAY/...
As of 155 PM Friday...
An upper level disturbance will move west of the Appalachians on
Sunday while a surface low develops off of the southeast coast.
Model runs continue to trend drier for this system for central NC
and at this time there is a good chance that both of these systems
could pass us by with little to no rainfall across the area. This
will lead to cloudy skies early Sunday and clearing by afternoon.
This will allow max temps to rise towards the 70 degree mark.
Beyond Sunday a very strong upper level ridge will keep us warm and
dry through at least Tuesday night with highs in the upper 60s to
low 70s. A weak frontal system on Wednesday will give slight chances
for rain but nothing more than a few hundredths of an inch.
For the end of the week we will have slight chances for rain each
day as central NC resides under a southerly return flow regime with
high pressure out over the western Atlantic. As the same time a
strong low pressure system over the Midwest may help to enhance
moisture transport into the area. The whole time we will remain in
the warm sector with high temps in the low 70s, well above normal
for this time of year.
.AVIATION /00Z Saturday through Wednesday/...
As of 655 PM Friday...
Under the influence of dry surface high pressure over the
southeastern U.S., VFR conditions (with a high degree of confidence)
are expected through at least the first 20 or so hours of the TAF
period. The approach of an upper level trough, and associated mid to
to upper level lift, will result in a thickening and lowering of
clouds above 12 thousand feet Sat afternoon. Precipitation aloft
will accompany these clouds, but very dry air below the clouds
suggests most of the precipitation will evaporate before reaching
the ground, resulting in virga. Nonetheless, a few VFR sprinkles or
brief showers will be possible from west to east between 22Z Sat and
04Z Sun. Generally SWly surface winds will be light through early
Sat, then increase to between 8-15 kts --highest at eastern sites
and with occasional gusts to around 20 kts-- Sat afternoon.
Outlook: There will be a chance of showers, and perhaps brief MVFR
ceilings in SEly flow off the Atlantic, Tue night-Wed.