Area Forecast Discussion
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FXUS62 KRAH 011547
Area Forecast Discussion
National Weather Service Raleigh NC
1050 AM EST Wed Mar 1 2017
Warm southwest flow will continue across the region today ahead
of a strong cold front approaching from the west. The cold front
will cross the area tonight, followed by cool high pressure for
the latter half of the week.
.NEAR TERM /THROUGH TONIGHT/...
As of 1050 AM Wednesday...
Potential for severe storms with damaging wind gusts appears
slightly higher, primarily west and north of Raleigh late this
afternoon into the evening hours.
Early morning analysis depicts a conditionally stable air mass as
12Z GSO sounding depicts a strong cap between 850-750mb. In
addition, very strong winds noted just off the surface with 40kts
observed at 1000 ft. As temperatures rise to around 70, breaking the
sfc based inversion, should see an increase in the sfc winds with
gusts 30-40 mph. Plan to handle gusts with a SPS but may need to
issue a short fuse wind advisory by mid day.
While a few showers may skirt the northwest Piedmont early this
afternoon, the better forcing for scattered-numerous showers and
storms appears to arrive in our region after 21Z. Sfc dewpoints this
morning are in the upper 50s-lower 60s west and low-mid 60s east.
These values are a few degrees higher than projected. In addition,
low stratus absent across much of the northwest Piedmont, allowing
this region to warm faster than earlier thinking. The expected
string heating late this morning-early afternoon along with the
approach of a slightly cooler air mass aloft may be enough to
erode/break the 850-750mb cap, leading to a better potential for
strong/severe storms. This threat appears most likely across the
western piedmont into the far northern Piedmont along the Virginia
Still some uncertainty as to the probability of severe storms in the
RDU metro area and points east-se as system projected to go through
mid-late evening hours when the near sfc air mass will begin
nocturnal stabilization. If storms arrive in the Raleigh area closer
to 7 or 8 PM, the threat for locally damaging winds will increase.
Afternoon temperatures near 80 NW to the low-mid 80s SE still appear
.SHORT TERM /THURSDAY THROUGH THURSDAY NIGHT/...
As of 400 AM Wednesday...
After lingering mid level ceilings and perhaps a few sprinkles over
the far sern counties early Thu, cirrostratus within the axis of a
150 kt WSWly gradually edge Swd and out of central NC throughout the
day. Downslope NWly flow will help offset waning CAA. Highs in the
upper 50s to lower-middle 60s, with gusts up to 25 mph until midday-
early afternoon, before CAA diminishes by afternoon.
Surface high pressure will ridge overhead from the SW in advance of
a clipper frontal system approaching from the NW, so temperatures
will have the potential cool into the upper 20s to lower-middle 30s.
.LONG TERM /FRIDAY THROUGH TUESDAY/...
As of 355 AM Wednesday...
A progressive pattern aloft will result in a transition from a
departing trough in the eastern U.S. Fri-Sat, to ridging
through early next week. The trough will reach maximum amplitude
as a shortwave trough in NW flow aloft amplifies across the
Middle Atlantic states during the day Fri. This trough will be
followed by a less amplified/shear vorticity maximum that will
migrate through the NW flow, with a brief period mid level WAA
cloudiness, on Sat.
At the surface, a clipper surface wave accompanying the
aforementioned shortwave trough in NW flow aloft will track
across the nrn Middle Atlantic states, while the trailing nrn
stream surface cold front will sweep across central NC during
the day Fri. Given both 1) a tendency for the models to advect
cold air across the Appalachians too quickly, and 2) the
prevalence of a downslope/compressional warming flow component
throughout the day, temperatures are expected to recover into
the middle 50s to lower 60s. Cold and dry advection within a
deeply mixed (800-750 mb) boundary layer will support afternoon
wind gusts up to 25-30 mph, which will make it feel cooler.
Incoming cP surface high pressure behind the front on Fri will
result in a hard freeze Fri night-Sat morning, when
temperatures are expected to fall into the lower-middle 20s over
the Piedmont, to upper 20s to around 30 degrees over the
Sandhills, srn Coastal Plain, and urban areas. Temperatures
will gradually moderate thereafter, as the surface ridge moves E
and modifies, with 50s on Sat replaced by 60s-70s by early next
After a dry weekend as the ridge moves overhead and offshore,
the approach of the next frontal system will result in a chance
of showers late Mon-Tue.
.AVIATION /12Z WEDNESDAY THROUGH SUNDAY/...
As of 640 AM Wednesday...
Strong winds expected today, with storms late this evening...
MVFR and IFR ceilings from RCZ to FAY to RWI will continue to
drift slowly north and lift through mid morning, evolving into a
deck of MVFR to low end VFR cumuli by midday. Confidence in
sub-VFR ceilings this afternoon is medium and strongest at INT
and GSO based on latest hires model guidance. Meanwhile,
southwesterly wind gusts to 30-35kt are expected, with winds
increasing after 15Z as a cold front moves through the Tenn
Valley and across the mountains this afternoon. A line of storms
will cross central NC this evening, likely at INT/GSO by 00-02Z,
RDU by 02Z and RWI/FAY by 03-05Z. The storms have the potential
to be severe with gusts to 50kt or higher. Behind the
convection, low-level drying will return conditions to VFR as
winds turn to northwesterly, though winds may continue to gust
to around 20kt.
Outlook: Skies will clear out for Thursday with VFR conditions
and NW winds. VFR conditions will continue through Sunday under
As of 550 AM Wednesday...
Critical, or nearly so, fire weather conditions still probable Thu
and especially Fri.
Much drier air will overspread central NC following a cold frontal
passage, and accompanying line of showers and storms, tonight. The
drier air, combined with afternoon temperatures in the upper 50s to
middle 60s on Thu, will result in minimum relative humidity values
between 20 and 25 percent Thu afternoon. However, NWly winds, which
will gust between 20-25 mph through 1 PM, will subside during the
afternoon (when critical RH values are met). Nonetheless, there may
be a several hour period centered around noon Thu when marginally
critical relative humidity values between 25-35 percent overlap with
the aforementioned stronger winds; and increased fire danger may
These conditions will also set the stage for Fri, when daytime
heating and a secondary cold frontal passage during the afternoon
will result in critical RH values for several hours during the
afternoon. In addition, breezy Wly to NWly surface winds are
forecast to be sustained between 15-20 mph, with 25-30 mph gusts.
These conditions for increased fire danger to red flag will likely
be coordinated with the NCFS later today and/or on Thu.
Record highs for March 1st:
RDU: 82 (set in 1997)
GSO: 77 (set in 2012)
FAY: 87 (set in 1918)