Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC-- Remove Highlighting --
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FXUS62 KRAH 240720
Area Forecast Discussion
National Weather Service Raleigh NC
320 AM EDT SAT SEP 24 2016
Weak high pressure will hold over the area today. A backdoor cold
front will approach from the north early tonight, and then move
southward through the area late tonight through Sunday morning.
A cooler air mass will push in from the north Sunday morning through
Monday. The front will move back northward as a warm front late
Monday, with brief high pressure following, before a cold
front crosses the region west to east late Tuesday.
.NEAR TERM /today through tonight/...
As of 305 AM Saturday...
Today: Once the areas of shallow fog wear off an hour or two after
daybreak, a fairly quiet and warm day is expected with plenty of
sunshine. The latest surface analysis shows the remains of the weak
trough just off the coast, with weak high pressure covering the rest
of the region, although weak Piedmont trough development is
anticipated this afternoon. Pronounced ridging is noted throughout
the mid and upper levels centered just to our west, with a weak mid
level flow from the NW or NNW over our area, and observed PW
according to blended TPW imagery is low (1.0-1.4"). With deeply dry
and stable air in residence and upstream, expect mostly sunny skies
today. Thicknesses are expected to be 10-20 m above normal, favoring
highs in the 86-90 range, highest west.
Tonight: Warm conditions will hold through the evening, then the
backdoor front currently stretching across central IN/central OH/
southern PA will push southward into NE NC overnight, propelled by
cool dense high pressure to the north and flow around a strong
vortex over SE Canada. Plenty of low stratus is currently found near
and north of this front, and see no reason why this won`t hold as
the front drops into NC. Models agree on light precip near the front
with considerable low level moisture pooling taking place, and will
hold onto low chance pops over the NE and far N CWA tonight, with
low QPF overall given the shallow nature of the incoming moisture.
Lows in the mid-upper 60s. -GIH
.SHORT TERM / /...
As of 320 PM Friday...
To be updated shortly.
.LONG TERM /MONDAY THROUGH FRIDAY/...
-- Changed Discussion --As of 320 AM Saturday...
Model solutions are very much in step for the beginning of the long
term with surface high pressure over New England heading out to sea
on Monday and a deep low pressure system over the northern Great
Lakes bringing a front over the Appalachians which will approach the
forecast area Monday night into Tuesday. The best vorticity and jet
dynamics will remain well to the north with this system. Couple that
with nocturnal timing and there is not a lot going for the system as
far as any kind of deep convection. Despite that, rain showers and
some thunderstorms will be possible Monday night and Tuesday. There
is some debate over how quickly the front will move through the
area, so will keep slight chance pops in for the east through
Wednesday but most of the forecast area should start to clear out by
Tuesday night. Highs near 80 degrees Monday and Tuesday, dropping
into the upper 70s Wednesday. Lows in the 60s.
After Wednesday, the forecast is expected to be generally dry and
cool for Thursday and Friday. There is a caveat, however, that the
latest run of the ECMWF model has put a new wrinkle in the forecast
and that is a strong upper low becoming cutoff from the main flow
and sinking southward along the NC/TN border. If this were to
happen, the dynamic support would be enough to bring precipitation
into the region late in the week, however this is an anomalous
scenario at this point so we will watch it but for now have decided
to stay with the dry and cool forecast which will feature highs in
the mid to upper 70s with lows in the upper 50s to low 60s.
-- End Changed Discussion --
.AVIATION /06Z SATURDAY THROUGH WEDNESDAY/...
As of 150 AM Saturday...
IFR/LIFR conditions will hold over the NE CWA including RWI through
daybreak, while at RDU/FAY, a trend to IFR conditions by 09z are
less certain but still likely. VFR conditions are likely to hold
over the western CWA including INT/GSO. Any sub-VFR conditions will
trend to VFR by 14z this morning, mixed out by dry air aloft. Dry
weather and very few clouds are expected areawide from mid morning
through the evening. As a backdoor front moves in from the NNE, cigs
will trend to IFR at RWI/RDU after 04z, with light/variable surface
winds becoming light from the ENE or NE.
Looking beyond 06z early Sun morning, sub-VFR cigs (likely IFR or
LIFR) will spread over all of central NC late tonight as the
backdoor front progresses toward the SSW through the area. Patchy
light rain or drizzle is possible. These low cigs will trend slowly
to MVFR during Sun, with a slight chance of light rain lingering,
especially over the west and south at INT/GSO/FAY. The chance for
light rain will increase in the west (INT/GSO) Sun night with IFR
conditions, while MVFR conditions are expected elsewhere. A trend
back to VFR conditions are expected Mon as the front starts to head
back northward as a warm front. MVFR to IFR fog is expected late Mon
night into early Tue morning. VFR conditions will dominate Tue into
Wed, although passage of a cold front late Tue or Tue night will
bring shifting winds from light/variably to N and NE. -GIH