Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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FXUS62 KRAH 231814

Area Forecast Discussion
National Weather Service Raleigh NC
214 PM EDT Fri Mar 23 2018

Cold high pressure will extend across the region today, then move
offshore late tonight. An area of low pressure will approach from
the west Saturday and cross our region Saturday night and Sunday
bringing unsettled weather and the chance for some winter
precipitation across northern portions of the forecast area. Chilly
high pressure will build southward into the Carolinas Sunday and


As of 215 PM Friday...

Quiet day weather wise across central NC as surface high pressure
over the Gulf Coast is keeping skies clear with seasonably cool
temperatures over the area. This surface high, coupled with an upper
level trough with the axis just offshore are keeping winds
northwesterly through the column this afternoon with some gusting to
15 kts possible. Off to the west, a surface low over Missouri will
start to bring clouds into the area from the west after 6z Saturday.
Precipitation however is expected to hold off until after 12z.
Temperatures overnight will drop in to the mid to upper 30s across
the southwest Piedmont with lower 30s across the northern Piedmont
and Coastal Plain.


As of 215 PM Friday...

As a low pressure system moves in from the west, chances for winter
precipitation are increasing across the VA border counties and areas
northwest of I-85. There is very high confidence in a wet weekend
with all portions of the forecast area expecting as much as an inch
of rain in places. The northern coastal plain may fall short of this
number, closer to a half of an inch. This will occur beginning
around or just after 12z in the Triad and then pushing eastward
across the CWA by 18Z. From this time onward expect precipitation to
be occurring until at least 18z Sunday if not a little longer.

Latest model guidance does not give much clarity as to the type of
winter P-type that may fall in areas north of US-64 this weekend.
The event may begin as some brief snow on Saturday morning in the
Triad before turning over to all rain for much of the day.
The best chance for any accumulating snow will be in the northern
portions of the Triad and VA border counties, similar to last event.
The favored window for timing will be after 00Z Sunday through 15Z
Sunday. Forecast soundings indicate a few hours of very good omega
coupled with a saturated dendritic growth zone but that saturated
area comes and goes over the course of the evening leaving lots of
uncertainty as whether or not precip will be falling as snow or
sleet. Nomograms aren`t much help as they also indicate more of a
wintry mix through much of the event. There is the chance however
for some bursts of heavy snow that could lead to some accumulation
on the ground Sunday morning. At this time the forecast calls for as
much as an inch of snow accumulation in the northern portions of the
VA border and Triad counties with a half an inch or less through
much of the I-85 corridor. Further south to US-64 expect a mix of
snow and sleet with little to no accumulation and no impacts to
travel. In fact, there will likely be no impacts to travel except
maybe for some slushy areas in the northern portions of those VA
border and Triad counties.

Temperatures for the weekend will be cold, with highs Saturday and
Sunday likely in the low to mid 40s with some southern locales
squeaking out 50 degrees.


As of 200 PM Friday...

Dry and cool weather is expected during the first part of the work
week. A few low clouds may hang on through Mon morning in the
western CWA as the semi-anchored surface high, centered over SW
Quebec into the Maritimes, ridges SSW through NC, generating a weak
wedge air mass over central NC. Nocturnal stabilization and a local
increase in shallow moist upglide may result in patchy drizzle over
the W Piedmont Mon night. Mid level ridging will steadily build over
the East Coast through mid week, between deep closed lows over the
Desert Southwest and over the NW Atlantic, ensuring a lack of
forcing for ascent and continued tranquil weather (albeit with
periodic cloudiness, particularly with SW-to-NE passage of a warm
frontal zone aloft through the region). The GFS/ECMWF weaken the
Desert Southwest low and track it eastward into the Southern Plains
by Thu, which nudges the ridge axis offshore and leads to increasing
moist SW flow into the area, prompting a rising chance for showers
late in the week. This is supported by the GEFS and EPS, although
both the ECMWF and EPS lag a bit, closer to the slow Canadian
solution. Will opt for the ECMWF`s compromise but slower solution,
introducing low shower chances Thu with slightly better chances Fri,
but still just near climatology. Surface temps will continue to
modify through the week, with soaring 850 mb temps, supporting a
trend of highs from the upper 40s to upper 50s Mon to the upper 60s
to mid 70s by Fri. -GIH


As of 1140 AM Friday...

VFR conditions will hold through tonight, with gradual deterioration
thereafter. An upper level trough just off the Eastern Seaboard
today will continue shifting eastward through tonight, while a
surface high centered over E Canada and extending southward through
NC weakens as a frontal zone approaches from the SW. Little more
than scattered high-based flat cu are expected through late
afternoon. An upper level disturbance moving in from the WNW will
bring increasing clouds starting this evening, and rising chances
for precipitation, starting near daybreak at INT/GSO and slowly
spreading to RDU and then FAY/RWI toward the end of the TAF valid
period. High and mid clouds will overspread the state from the west
this evening through tonight, with lowering bases, although it will
remain VFR at all central NC terminals through 12z Sat. INT/GSO will
trend to MVFR 12z-15z, followed by RDU 15z-18z. INT/GSO will see a
chance for rain or snow after 15z Sat.

Looking beyond 18z Sat: The trend down to MVFR will spread to
eastern terminals after 18z, while western terminals trend to IFR. A
band of mostly light precip, rain mixed with a little wet snow, will
overspread northern terminals Sat afternoon, with a lower chance at
FAY. Starting late Sat afternoon, all locations will become IFR/LIFR
with a solid area of heavier precip, mostly rain with a little sleet
at FAY and a wintry mix or mainly snow/sleet at INT/GSO/RDU/RWI.
This will continue through Sat night into early Sun morning. Dry
weather is expected after 15z Sun, but cigs should remain IFR into
Sun evening. RDU/RWI/FAY should trend to MVFR Sun night, while
fog/stratus may redevelop at INT/GSO overnight, with a potential pre-
and post-dawn period of IFR conditions. All locations should become
low-end VFR by Mon afternoon, and VFR conditions will then dominate
through Wed as deep high pressure settles over and just offshore of
the Carolinas. -GIH





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