Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC-- Remove Highlighting --
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FXUS62 KRAH 261827
Area Forecast Discussion
National Weather Service Raleigh NC
227 PM EDT Sun Mar 26 2017
A weakening upper level disturbance will pivot northeast across our
region this afternoon. Bermuda high pressure will otherwise extend
west into the southeastern U.S. through Mon.
.NEAR TERM /THROUGH TONIGHT/...
As of 1045 AM Sunday...
Little change required to the near term forecast.
12Z upper air analysis depicts a deep south-southwest flow over
central NC. The mid levels of the atmosphere remain quite dry and
will remain so. Meanwhile, the lower levels are marginally moist and
expected to change little through early Monday. A weakening mid-
upper level trough will lift newd across the region this afternoon.
This system may spread or trigger a few showers in vicinity of the
NW Piedmont including the Triad region. Showers expected to be
spotty due to limited moisture and weakening support. Current
forecast of the highest PoPs confined to the western half of the
Triad appears on target at this time.
Otherwise, expect a mixture of cloud/sun through this afternoon. Any
showers that occur along and east of highway 1 will be isolated and
too remote to mention in the forecast at this time. The moderating
air mass coupled with peeks of sun will boost afternoon temperatures
into the low-mid 70s this afternoon. If sun becomes more prominent
this afternoon, could see a few upper 70s over the Sandhills and
coastal plain. ~WSS
While shortwave ridging aloft behind the departing mid level trough
will likely yield dry conditions tonight, the mid level moist axis
accompanying the trough will be left behind; and this may support a
lingering shower or two over the wrn Piedmont tonight. Low
temperatures centered in the middle 50s. ~MWS
.SHORT TERM /MONDAY THROUGH MONDAY NIGHT/...
As of 405 AM Sunday...
A kicker shortwave trough now over the Four Corners, and a trailing
lower amplitude perturbation near the Baja of CA, will both move
generally Ewd across the MS Valley on Mon, and into the Carolinas
Mon night. Lapse rates aloft will steepen into the 6.5-7 C/km range
first Mon by a modified EML plume preceding the troughs, then as the
associated cool pool aloft accompanying the troughs moves overhead
Mon night, with an associated increase in (still-weak) instability
of around 500-1000 J/kg over the Carolinas Mon afternoon and night.
The models indicate the perturbation now over the Baja will slightly
outpace the main shortwave trough over the Four Corners, such that
the associated forcing for ascent accompanying the perturbation will
spread E and interact with the weak instability axis over the
Carolinas, and consequently result in scattered showers and storms
Mon afternoon, particularly along and west of U.S. 1, where diurnal
timing of the forcing for ascent will be maximized.
The chance of showers and storms will increase overnight, as the
parent shortwave trough and preceding forcing for ascent cross the
Appalachians. The aforementioned steep lapse rates aloft, and
relatively cool thermal profiles/low freezing level around 10 k ft,
and 30-35 kts of mid level flow, may support the development of
small hail in the storms. Instability would appear to be too limited
to support any severe hail threat, however.
It will again be warm, in the middle 70s to around 80 degrees, with
lows in the middle to upper 50s.
.LONG TERM /Tuesday Night through Sunday/...
-- Changed Discussion --As of 230 PM Sunday...
Wed-Wed Night: With a shortwave ridge aloft, expect mostly sunny to
partly cloudy skies with above normal highs in the mid/upper 70s.
Thu: High pressure is expected to extend southward into the
Carolinas Thu morning (in the form of a backdoor cold frontal
passage) in association with height/pressure rises in the wake of an
upper level low moving offshore New England into the Canadian
maritimes. With low-level NE flow emanating from the cool Labrador
current in NE portions of the state and an increased likelihood for
cloud cover in SW portions of the state, temps Thu afternoon could
be as much as 15-20F cooler than Wed afternoon. With the above in
mind, have decreased highs to the mid/upper 50s west to lower 60s
Thu night: Expect an increasing potential for rain from west-east
between midnight and sunrise Fri as an upper level low progresses
from the central MS river valley to the Ohio valley and low level
flow backs/strengthens downstream over the Carolinas and Mid-
Atlantic. Lows in the mid 40s to lower 50s, depending on rain
Fri-Fri Night: Confidence in the evolution of the aforementioned
upper level low, attendant sfc cyclone and associated warm/cold
fronts at this range is low to begin with, let alone when a CAD
wedge may be in place at the beginning of the period. All guidance
continues to indicate precipitation, thus have increased precip
chances to high likely (60-70%). From a pattern recognition
standpoint, a potential for severe weather cannot be ruled out,
however, little more can be said at this range in the forecast. The
temperature forecast on Fri/Fri night is challenging to say the
least. At this time will show the coolest temps in the Triad (highs
in the low 60s) and warmest temps in the Sandhills and SE Coastal
Plain (lower 70s). Expect clearing skies in the wake of a cold
frontal passage Fri night, with lows in the upper 40s to mid 50s.
Sat-Sun night: Expect a warming trend with dry conditions Sat in the
wake of the aforementioned upper level low progressing offshore the
Mid-Atlantic coast. A continued warming trend with dry conditions is
expected on Sun as a shortwave ridge aloft tracks into the region
from the west. -Vincent
-- End Changed Discussion --
.AVIATION /18Z SUNDAY THROUGH FRIDAY/...
As of 115 PM Sunday...
Varying degrees of cloudiness will result in periods of MVFR
ceilings across central NC through 00Z Tuesday, primarily in
vicinity of the Triad terminals. In addition, pockets of fog may
reduce the visibility into the IFR category at KFAy and KRWI early
In the near term, a few showers may cross the Triad terminals
through 21Z, though the showers are expected to be light with
limited adverse affects to aviation aside from slightly lower
A marginally moist and conditionally unstable air mass will result
in periods of MVFR ceilings across the region through Wednesday. The
lower ceilings will most likely occur between 10Z and 16Z. There is
the possibility of a few showers and thunderstorms Monday afternoon,
and again late Monday night through early Tuesday afternoon.
Near the heavier showers and storms, expect MVFR ceilings and
A cold front will drop southward through central NC Wednesday, then
stall to our south. The approach of an upper level low will increase
sly flow a few thousand feet above of the cool stable dome of air at
the surface, leading to widespread MVFR/IFR parameters due to low
clouds and areas of rain late Thursday into Friday.