Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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FXUS62 KRAH 190637

Area Forecast Discussion
National Weather Service Raleigh NC
237 AM EDT Thu Oct 19 2017

Surface high pressure over the Mid-atlantic will extend across
the region into the weekend. A cold front will approach the
area from the west early next week.


As of 220 AM Thursday...

A weak mid/upper level disturbance is currently moving across the
region this morning. However, with generally a dry atmo in place,
only a scattering of high cirrus is accompanying the weak
disturbance this morning. Otherwise, surface high pressure will
remain in place with slowly moderating temperatures. Model guidance
has trended cooler with high temps today, and have such lowered
highs by a couple of degrees from previous forecasts. Thus, expect
high temps will generally be in the lower to mid 70s today.

Mid level ridging will begin to build eastward and into the area
tonight, with surface high pressure holding over the area. This will
result in a continuation of dry and cool conditions with clear
skies. Low temps are expected to range from around 40 in the coldest
rural locations to the mid to upper 40s in the urban areas and far


As of 235 AM Thursday...

Mid level ridge axis will build overhead on Friday into Friday
night, resulting in little change in the weather across central NC,
other than temps will be a bit warmer. Expect high temps will
generally be in upper 70s to around 80. Lows temps are expected to
range from the mid 40s in the cold spots to the lower 50s in the
urban areas and SE.


As of 200 PM Wednesday...

Glorious "fair" weather will continue through the weekend as the
upper ridge axis shifts east and over the area Friday and Saturday,
then offshore Sunday. The dry surface high follows suit, with low
level easterly flow gradually veering more southerly through the
weekend. Expect sunny skies with light winds and highs reaching the
mid to upper 70s each day. Morning lows will be nippy, but warming a
bit, with Saturday morning`s lows mostly in the upper 40s warming to
the lower 50s for Sunday morning, and further to the mid 50s Monday

By Sunday night, the low level winds will be southeast and
increasing as a strong cold front edges east towards the mountains.
Upslope flow will produce increasing cloudiness spreading in from
the west Sunday night, with showers developing as far east as the
western Piedmont (Charlotte and the Triad) by Monday morning. Shower
coverage will increase throughout the day, enhanced by the approach
of stronger upper dynamic support associated with an upper level
short wave which will be moving east across the area Monday night.
While still subject to error, the timing of the deepest moisture,
low level forcing, and upper dynamics which would favor stronger
convection align best Monday night into early Tuesday, missing out
on our strongest diurnal instability. Highs Monday prior to frontal
passage should reach mid and upper 70s, with warm air advection
offsetting the lessened insolation.

There is considerably more uncertainty as to whether we have a
relatively clean cold frontal passage on Tuesday with drying to
quickly follow, or whether we might have a more vigorous upper short
wave move across to produce more widespread convection during the
day, and will maintain ~50% PoPs. The cold air surge behind the
front will be delayed until later in the day, and highs Tuesday
should have a chance to reach upper 60s to lower 70s. The colder,
drier air will be settling into the area Tuesday night and
Wednesday, with mins falling into the 40s Tuesday night, and highs
stalling mostly in the lower 60s on Wednesday.


As of 220 AM Thursday...

24-Hour TAF period: VFR conditions will generally continue for the
24 hour TAF period. The one exception will be at fog prone KRWI,
where some pre-dawn fog is expected this early this morning. Visbys
at KRWI are expected to range from MVFR-LIFR early this morning
through around sunrise. Otherwise, VFR conditions will continue with
light and variable to calm winds and mostly clear/clear skies, as
surface high pressure remains over the region.

Looking ahead: VFR conditions will prevail through the first half of
the weekend, with brief periods of sub-vfr conditions in the pre-
dawn hours possible near KRWI. Upslope flow in the west late Sunday
night or Monday ahead of an approaching cold front could result in
some sub-VFR conditions. However, the next chance for widespread sub-
vfr conditions will come with pre-frontal convection between Monday
afternoon and Tuesday night as the front moves into and through the




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