Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000
FXUS62 KRAH 200212
AFDRAH

Area Forecast Discussion
National Weather Service Raleigh NC
1010 PM EDT Sat Aug 19 2017

.SYNOPSIS...
A cold front across the eastern Carolinas will linger overnight,
then dissipate on Sunday. A strong cold front will approach the area
on Wednesday and reach the coast on Thursday.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 1010 PM Saturday...

Little if any changes required to the near term forecast.

At the surface, a stalled, weak sfc front was wavering across the
eastern counties of central NC. With the setting sun, sfc dewpoints
have recovered as dewpoints at or above 70 degrees were observed
over all but the northwest Piedmont. In the mid levels of the
atmosphere, a trough was exiting our region, leaving a drier air
mass in its wake.

Overnight, expect tranquil weather conditions under mostly clear
skies. Could see a few pockets of fog or low clouds by daybreak in
the Sandhills or coastal plain but most locations will have clear
skies. Overnight, the stalled sfc front will gradually wash out as
the mid/upper level trough lifts east-newd. This will allow a weak
high pressure system to nose into our region by Sunday. Under mostly
clear skies, overnight temperatures will generally be in the 70-75
degree range.


&&

.SHORT TERM /SUNDAY THROUGH SUNDAY NIGHT/...
As of 250 PM Saturday...

A shearing short wave trough at 500 hPa shifts across the eastern
Carolinas on Sunday morning with increasing heights on Sunday
afternoon and Sunday night. The cold front that stalled near the
coast will retreat inland and washout during the day. The light and
variable low-level flow to start the day becomes southeasterly on
Sunday afternoon and southerly on Sunday night. A drier atmosphere,
ridging aloft, and limited forcing for ascent should keep central NC
generally convection free on Sunday. It`s worth noting that the
exception will be some isolated convection that develops across the
higher elevations of NC that drifts east, weakens and likely
dissipates as it approaches the NW Piedmont late in the
afternoon/early evening. An isolated shower or storm is possible
across the southern and southeastern tier in proximity to the cold
front. Feel that warm mid-levels and ridging aloft will keep
coverage very limited and will not include a PoP at this time. Low-
level thickness values increase a few meters over Saturday and would
support highs between 90 and 95. Dew points in the mid 60s to around
70 will result in heat index values less than 100 degrees. The
southerly flow will allow nocturnal dew points to creep up and
result in lows in the 69 to 75 range. -Blaes

&&

.LONG TERM /MONDAY THROUGH SATURDAY/...
As of 400 PM Saturday...

Mon: The surface front over ern NC this afternoon will have stalled
and begun to retreat nwwd, into srn and sern NC on Mon. The retreat
of this by-then-diffuse boundary, marked by the leading edge of
surface dewpoints in the lower-middle 70s, and which will be in the
vicinity of a sea breeze that will likely make quick and deep inland
progress owing to prevailing onshore low level flow, will favor a
relative maximum in diurnal cumulus --some of which will grow into
widely scattered showers and storms-- from the Sandhills to the
Coastal Plain. In addition, a perturbation in wly flow aloft is
forecast to amplify as it drifts east of the Appalachians early in
the day; and this feature will also serve to stream a veil of cirrus
newd across the ern Carolinas, including areas mostly east of I-95.
As such, the relative best eclipse viewing will likely occur over
the nwrn half of the RAH forecast area, from the Triangle to the
Triad. Even where both the cirrus and diurnal cu noted above are
likely to be maximized over the sern counties, the eclipse may still
be visible, but more dimly so due to the high level moisture.
Frankly, it will only take one cumulus cloud to obscure the view, so
if you happen to be in an unlucky and untimely location even over
the nwrn Piedmont, the eclipse could be obscured. It will otherwise
be warm-hot, with high temperatures in the lower to middle 90s.
Dry and seasonably mild Mon night, with lows 70-75.

Tue-Sat: The pattern aloft will transition to a relatively amplified
one, with a trough across ern NOAM by mid-late week. A slow sewd-
moving surface cold front will mark the leading edge of the
associated height falls aloft, and settle across central NC late Wed
through Thu, with an associated high chance of convection during
that time. Cooler and drier, post-frontal high pressure will follow
for the end of the week into next weekend, with temperatures likely
to peak in the lower to middle 80s in most locations Thu-Sat.

&&

.LONG TERM /MONDAY THROUGH FRIDAY/...
As of 244 PM Friday...

Monday: As continental high pressure begins to merge with an
offshore surface high the question for Monday will be how much
moisture is in the weak southerly return flow and what will that
result in as far as cloud cover for the eclipse viewing. Partly
cloudy skies look likely but there should be enough breaks in the
clouds to get a decent view of the moon passing between us and our
closest star situated some 93,000,000 miles away. While temperatures
are expected to rise into the lower 90s there will be a break in the
heat from roughly 1:30 to 3:30 PM. A scattered shower or
thunderstorm cant be ruled out, especially in the southern tier of
the area.

Rest of the week: Relative dry but warm weather continues through
Tuesday before the next frontal system passes through the area on
Wednesday in association with a low pressure system moving across
southern Canada. High rain chances Wednesday will continue through
Thursday in the east and possibly into Friday as the front begins to
stall near the coast. Temperatures in the low 90s Tuesday and
Wednesday will fall back into the mid 80s for Thursday and maybe
into the low 80s by Friday. With that, some dewpoints in the lower
60s should make for some very comfortable weather heading into the
weekend.

&&

.AVIATION /00Z SUNDAY THROUGH THURSDAY/...
As of 810 PM Saturday...

24 Hour TAF Period: VFR conditions expected to continue this evening.
However, with a weakening stalled surface front located across
eastern portions of the area, we may see at least some patchy fog
and low stratus at KFAY/KRWI and possibly even KRDU. Given
confidence is low, will only include a mention in a tempo group at
KFAY/KRWI for IFR conditions and KRDU for MVFR conditions.

The stalled front is generally expected to dissipate on Sunday, with
any patchy morning sub-VFR conditions dissipating/lifting by mid
morning. VFR conditions and dry weather are expected for Sunday
afternoon.

Outlook: The threat of mainly afternoon and evening showers or
thunderstorms and late night/early morning fog/stratus is expected
to increase a bit on Monday and Tuesday. A strong cold front is
expected to approach the area on Wednesday and reach the coast on
Thursdays bringing a greater chance of adverse aviation conditions
in showers and thunderstorms.

&&

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

&&

$$
SYNOPSIS...BLAES
NEAR TERM...WSS
SHORT TERM...BLAES
LONG TERM...MWS
AVIATION...BSD/BLAES


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