Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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FXUS62 KRAH 182204
AFDRAH

Area Forecast Discussion
National Weather Service Raleigh NC
605 PM EDT Fri Aug 18 2017

.SYNOPSIS...
A weak surface trough will extend from the western Piedmont of
Virginia south into the Piedmont of the western Carolinas. A
cold front will move across the southern Appalachians this
evening and into the Piedmont of the Carolinas and Virginia
overnight. The front will slow across the Coastal Plain on
Saturday before pushing off the coast on Sunday.
&&

.NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...
As of 605 PM Friday...

Main adjustment to the near term forecast was to increase the PoPs
this evening across the southern Piedmont where convective coverage
potential appears better than a few hours ago. The approach of a mid
level trough and a band of instability extending from upstate SC
into the NC Piedmont should cause scattered convection to develop
through 00Z. This batch of scattered showers and storms may reach as
far east as the highway 1 corridor by mid-late evening before
gradually diminishing. Unlike the past few weeks, the storms this
evening have the potential to produce abundant lightning. A few
showers and storms may linger into the overnight as a weak sfc cold
front approaches from the northwest.

Otherwise hot/muggy conditions will persist this evening as
temperatures generally remain above 80 degrees through 10 or 11 PM.
Overnight temperatures generally in the mid-upper 70s.

&&

.SHORT TERM /6 AM SATURDAY MORNING THROUGH SATURDAY NIGHT/...
As of 300 PM Friday...

The cold front reaches the Coastal Plain Saturday morning and
slowly slips east and moves off the coast by daybreak Sunday.
An upper level trough approaches the region from the OH Valley
on Saturday afternoon with the trough axis moving across central
NC toward daybreak Sunday. A much drier air mass moves into the
region with precipitable water values dropping into the 1.1
(west) to 1.6 (east) range by Saturday afternoon. While a small
threat for a shower or storm lingers across the Coastal Plain
and Sandhills near the cold front, generally dry conditions are
expected elsewhere. The air mass cools slightly with highs
ranging between 88 to 94 degrees Saturday afternoon. Drier air
moves into the area from the northwest Saturday night, and dew
points fall into the mid to upper 60s across the Piedmont and
the lower 70s in the Coastal Plain. This will support much more
comfortable lows in the upper 60s in the Piedmont and lower 70s
in the Coastal Plain. -Blaes &&

.LONG TERM /SUNDAY THROUGH THURSDAY/...
As of 244 PM Friday...

Dry weather is expected on Sunday across all of central NC with a
dissipating front now progged well to our south and rather inactive
westerly flow aloft.  Given the steady-state airmass combined with
ample sunshine, we should easily see highs into the low 90s.

On Monday we`ll see heights rise as the ridge off the SE coast
builds northward.  The sfc pattern will be fairly typical for this
time of year with the sfc high over the western Atlantic promoting a
southerly low level flow over our area.  Forecast soundings show a
notable inversion around H7 with dry air in the mid-levels, and in
some cases (particularly across our southern and eastern counties) a
fair amount of moisture above H4.  Thus with heating, the forecast
soundings suggest a decent amount of shallow cu may form below the
inversion across much of central NC as the afternoon progresses.  To
make matters worse, the soundings also suggest a veil of cirrus, esp
the farther south you go.  If there is any good news, these
soundings do not support rain or deep convection, so will keep PoPs
well below climo for Monday.  So in summary for the eclipse weather,
neither clear nor completely overcast, but rather partly cloudy with
cu briefly obscuring the sun at times, along with some high clouds.
Keep in mind that if you spend any substantial time outside, be
ready for highs in the low-mid 90s with heat index values in the
upper 90s.

Tuesday should be mostly dry as the ridge slowly moves east, but
then rain chances will increase on Wednesday as the next northern
stream short wave moves south and east and pushes a cold front
across our area.  The longwave trough will continue to deepen over
the East, so look for cooler temps by late next week, and perhaps
even a brief break from the high humidity for next weekend.

&&

.AVIATION /19Z FRIDAY THROUGH WEDNESDAY/...
As of 230 PM Friday...

VFR conditions across central NC this afternoon will give way
to scattered showers and thunderstorms this evening. The
convection will largely be associated with an eastward
advancing cold front. Look for the greatest chances of adverse
aviation conditions in the Triad (KINT and KGSO terminals) from
21 to 02Z, in the Triangle (KRDU terminal) from 23 to 03Z and
in the east and southeast (KRWI and KFAY terminals). An isolated
shower or storm is possible across the Piedmont and especially
the Coastal Plain overnight. Don`t expect much in the way of
late night or early morning low-level stratus although a BKN
layer of clouds is expected overnight at around 6kft. Generally
fair weather with SCT-BKN cumulus with bases around 4kft is
expected on Saturday, with some scattered afternoon storms
across the Coastal Plain and Sandhills impacting the KFAY
terminal. Southwest winds at 5 to 10kts this afternoon will
become light west overnight behind the front and light
northwesterly on Saturday.

Looking beyond 18Z Saturday....generally VFR conditions are
expected on Saturday and Sunday with just a few showers or
storms across the Coastal Plain on Saturday and dry weather
on Sunday. The threat late-day storms and some early-morning
fog and stratus increases on Monday into tuesday. -Blaes
&&

.RAH WATCHES/WARNINGS/ADVISORIES...
None.

&&

$$
SYNOPSIS...BLAES
NEAR TERM...WSS
SHORT TERM...BLAES
LONG TERM...NP
AVIATION...BLAES


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