Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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FXUS62 KRAH 181815

National Weather Service Raleigh NC
215 PM EDT Tue May 18 2021

High pressure will strengthen over the Carolinas and southern
Appalachians through Friday.


As of 1100 AM Tuesday...

1030 mb surface high pressure currently centered near the VA coast
will move SW across the southern Mid-Atlantic tonight. A weak vort
max aloft stretching from south-central VA into northern NC is
resulting in widespread clouds across much of the forecast area this
morning (outside of the far NE), along with some very light
sprinkles/showers from portions of the northern Piedmont into the
Sandhills. As this disturbance weakens and another one currently
evident on water vapor imagery moves into western NC, slight
precipitation chances shift to the NW Piedmont this afternoon and
early evening, but any showers will still be light, and the
environment is too stable for any thunder. Widespread clouds will
keep highs today in the lower-to-mid-70s in the NW Piedmont,
increasing to near 80 in far SE zones. Any showers will diminish
everywhere tonight, with cloud cover gradually lessening from NE to
SW, as the mid-level ridge moves directly overhead and dry air and
subsidence take over. This will allow temperatures to drop into the
lower-50s NE to mid-to-upper-50s elsewhere.


As of 350 AM Tuesday...

The surface high will continue sliding southward along the Carolina
coasts on Wednesday, shifting inland Wednesday night. Meanwhile
aloft, the ridge will persist, with high pressure centered over the
southern Appalachians by Wednesday night. Partly cloudy/mostly clear
skies and dry weather are expected, with highs in the low to mid 80s
and lows in the mid 50s.


As of 355 AM Tuesday...

An anomalously strong ridge, initially ~3 sigma above average at 700
mb over the cntl Appalachians, will drift swd and weaken through
early next week. Associated nwly flow aloft by the weekend will at
least present an opportunity for some weak forcing for ascent across
the srn middle Atlantic Sat-Mon.

At the surface, equally, anomalously strong, and continental-sourced
high pressure initially over the srn Appalachians, will also weaken
and drift swd, and ultimately yield to an Appalachian-lee trough by
the weekend.

Despite the opportunity for disturbances in nwly flow aloft Sat-Sun,
residual warm air and capping aloft, and continental air in the low
levels, will limit instability and chances for convection to just 10-
15% each afternoon-evening. As such, the long term will be mainly
dry, and increasingly hot, as afternoon temperatures reach the upr
80s to lwr-mid 90s Fri onward.


As of 200 PM Tuesday...

24 hour TAF period: Multi-layered broken cloud cover will continue
across much of central NC (outside of the far east including RWI)
this afternoon. However, ceilings are expected to remain VFR.
Isolated very light sprinkles are possible this afternoon across the
western Piedmont (including INT/GSO), but confidence is too low to
include in the TAFs. Cloud cover will lessen from east to west this
evening into tonight, with only few to scattered high clouds
expected overnight. Models are hinting at the possibility of
scattered low stratus and MVFR visibilities around daybreak
tomorrow, with the best chance in the east where coverage of high
clouds will be least, so added a TEMPO group for this potential at
RDU, FAY, and RWI.

Looking beyond 18z Wednesday: VFR conditions and mainly dry weather
will prevail from the rest of Wednesday through Sunday, with only a
very slight chance of showers this weekend.





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