Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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FXUS62 KRAH 181755

Area Forecast Discussion
National Weather Service Raleigh NC
200 PM EDT Wed Oct 18 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 1020 AM Wednesday...

High pressure at the surface and aloft will provide central NC with
clear skies and seasonably cool temperatures through tonight. After
a chilly start to the day which saw morning slows down into the 30s
across much of the Piedmont, temperatures ate late morning had
recover into the 50s. Temperatures appear on track to reach the
forecast highs in the upper 60s to around 70. Under clear skies this
evening, temperatures will cool quickly after sunset, falling
through the 50s early this evening, and into the 40s across the
Piedmont after 10 PM. Min temps in the upper 30s-lower 40s common,
slightly warmer over the southern coastal plain where patchy low
clouds may develop prior to daybreak.


As of 300 AM Wednesday...

A quiet weather regime continues into Thursday and Thursday
night as surface high pressure remains in control. A short wave
trough pushes across the Carolinas on Thursday and offshore on
Thursday night resulting in some transient and patchy cirrus
clouds. Some shallow moisture could result in some patchy fog or
stratus across the Coastal Plain toward daybreak Friday.
Otherwise, skies should be generally clear. Highs on Thursday
will range in the lower to mid 70s with lows Thursday night in
the lower to mid 40s. -Blaes


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 120 PM Wednesday...

There is a high probability of VFR conditions to persist across
central NC through 00Z Friday as high pressure at the surface and
aloft controls the weather across central NC. The only exception
will be a brief instance of MVFR fog in proximity of KFAY and
possibly KRWI early Thursday morning, primarily between 10Z-12Z. As
the sfc high drifts offshore by the weekend, the instance of early
morning fog with visibilities predominately in the MVFR category may
occur. Surface winds through Friday will be light at less than 10
kts, and mostly from the east-northeast.

The next threat for widespread sub VFR parameters will occur early
next week ahead of an approaching cold front.




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