Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC-- Highlight Changed Discussion --
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FXUS62 KRAH 211724
Area Forecast Discussion
National Weather Service Raleigh NC
Issued by National Weather Service Blacksburg VA
1224 PM EST Tue Feb 21 2017
High pressure will extend along the East Coast through early today.
An upper-level disturbance will cross the Southeast states tonight
.NEAR TERM /THROUGH TONIGHT/...
As of 950 AM Tuesday...
Forecast pretty much on track. Seeing a bit of high level warm
advection clouds streaming across the skies this morning. Models
are in agreement that there will be intervals of sunshine mixed
in with a high level cloud cover. As such will keep forecast
highs similar to the previous forecast, ranging from the lower
60s in the northeast Piedmont, to near 70 in the Sandhills.
Previous discussion from 700 AM...
North Carolina will be under the influence of ridging aloft and
ridging at the surface from a high centered over the New England
coast. A closed low aloft is expected to break away from the
northern stream trough by 12Z this morning over the ARKLATEX region.
The aforementioned low will slide southeast over the Gulf Coast
through tonight as the weak remnants of the northern stream trough
approach Central NC. The surface ridge will linger until late in the
day/evening, with the southeasterly return flow increasing as the
center of the high slides southeast off the Mid-Atlantic coast and
the ridging over the area weakens. Much of the precipitation
associated with this system will be displaced well south of the area
and the northern stream energy won`t pass overhead until Wednesday.
As a result, have kept the forecast dry through this evening, with a
slight chance of showers developing over the far west late tonight.
Temperatures will be largely dependent on the return flow around the
high as it slides southward, but for now expect temperatures to top
out in the mid 60s to around 70 degrees this afternoon. Lows should
range from the mid 40s northeast to low 50s southwest.
.SHORT TERM /WEDNESDAY THROUGH WEDNESDAY NIGHT/...
As of 245 AM Tuesday...
The closed low aloft will slide further southeast through the
eastern Gulf of Mexico and over FL through Wednesday night, taking
the best moisture with it. There is still a chance for some light
rain to occur over Central NC on Wednesday as the weakened northern
stream trough passes overhead, but exactly where the rain will fall
is somewhat uncertain. Regardless, skies will be cloudy throughout
the day and rainfall totals are not expected to be very high. The
highs on Wednesday (like the temperatures the previous 24 hours)
will depend on the return flow into the region from the high
offshore. For now, expect a 10-15 degree temperature gradient from
NW to SE (60 degrees NW to low-mid 70s SE). There will be enhanced
east-southeasterly flow into the southeast U.S. to southern Mid-
Atlantic coast Wednesday night as a result of being sandwiched
between the Gulf low and the high over Bermuda. Though the best
warm, moist advection will be south of the NC coast, expect a
continuation of the above normal temps and overnight lows warmer
than the previous night (low to mid 50s NW to SE).
.LONG TERM /THURSDAY THROUGH MONDAY/...
As of 325 AM Tuesday...
The upper air pattern across central NC will continue to support
very warm conditions though the atmosphere will be slightly
unsettled. A strong cold front will cross our region this weekend
followed by a slightly cooler and tranquil weather regime.
A s/w ridge will build into our region Thu=Fri in response to the
departure of an upper level low off of south FL. These rising upper
heights will maintain very warm conditions across our region. Closer
to the surface, low level southerly flow will gradual increase the
moisture content of the column, yielding variably cloudy skies. With
weak speed convergence occurs, a few stray showers will likely
develop. This scenario appears more plausible over the western
Piedmont both Thursday and Friday though most locations will remain
rain free. With surface based CAPE approaching 1000 j/kg Thursday
afternoon, a thunderstorm may be possible. Temperatures will remain
a solid 15-20 degrees above normal though still a couple of degrees
shy of record warmth.
A mid-upper level s/w crossing the Great Lakes Fri-Sat will drive a
sfc cold front southeastward into the Carolinas Saturday. This front
will encounter a adequately sheared and slightly unstable air mass
to support broken bands of showers and thunderstorms Saturday
afternoon, primarily along and east of highway 1. Cannot rule out
the possibility of a few strong/severe storms as mixed layer CAPE
approaches 1000 j/kg though low level helicity is lacking.
Blustery nw winds behind the front Saturday night/Sunday will usher
a cooler/drier air mass into central NC. While air mass is cooler,
afternoon temperatures will still average 4-6 degrees above normal
for late February. Dry weather anticipated Saturday night into
Monday as deep wly flow will limit precipitation chances.
.AVIATION /17Z TUESDAY THROUGH SATURDAY/...
-- Changed Discussion --As of 1210 PM Tuesday...
Expect VFR conditions through this evening with mainly mid and
high clouds increasing from the southwest.
Tonight, low pressure will move into the Gulf Coast states,
sending low level moisture northward to the Triad/Triangle and
eventually the coastal plains. Will start to see sub-VFR cigs
and vsbys working to most terminals after 06z with best threat
of any rain over INT/GSO, with drizzle toward RDU and RWI after
08z. With high pressure keeping flow off the Atlantic will see
some fog as well, so vsbys could drop to IFR, though confidence
is not high enough to add in the terminals except INT closer to
As we head into Wednesday will be tough to dislodge the lower
cigs but models favor most sites going to VFR after 15z, though
in-situ damming over the Triad should keep INT/GSO IFR til the
end of this taf period.
Looking ahead: Expect cigs in the MVFR/low end VFR range to persist
through Wednesday afternoon, mainly west of RDU. With continued
southeast flow through Friday, the early-morning sub-VFR cigs
and visbys will likely be a reoccurring theme. Low clouds may
scatter out enough during the daytime hours for a return to VFR.
Winds will slowly veer through the period ahead of the
approaching cold front. Showers and sub-vfr conditions will also
be possible ahead of the front, which is expected to move
through Central NC on late Saturday.
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