Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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FXUS62 KRAH 201603

Area Forecast Discussion
National Weather Service Raleigh NC
1100 AM EST Tue Nov 20 2018

A surface cold front will move offshore this afternoon. High
pressure will then build in tonight and Wednesday bringing chilly
weather to the region, with below normal temperatures continuing
through Friday. A new storm system will bring a chance of rain on


As of 1100 AM Tuesday...

The cold front extended from near Richmond to Raleigh to Charlotte
with the late morning observations. The light SW wind at 5-10 mph
continued out ahead of the front over eastern NC. Winds shift to the
NW and increase to 10-15 mph with gusts to 20 mph behind the front.
Henderson, Roxboro, Siler City, and the Triad cities were all behind
the front as of the 1100 am observations. Late morning temperatures
were in the 40s over the Mountains ranging into the 50s in the
Piedmont, and lower 60s down east.

Jet stream cirrus/cirrostratus were rather thick over the coast,
with clearing skies noted across western and central NC. Mountain
induced waves in bands of stratocumulus were common over the
Mountains into the Foothills and western Piedmont.

Expect skies to become partly to mostly sunny this afternoon as the
front passes. Winds will shift to the NW at 10-15 mph with gusts to
20 mph. Highs generally in the lower 60s NW, ranging into the mid to
upper 60s SE.

As weak high pressure builds in tonight, winds will die off and
skies will be mainly clear. Lows generally in the 30-35 range


As of 410 AM Tuesday...

During the day Wednesday the upper level trough axis will remain
stationed south of the Hudson Bay with weak surface high pressure
overhead in NC. 850 MB temperatures Wednesday fall to around 3
degrees C and with skies clear will support high temperatures in the
mid 50s. Wednesday night the upper level trough axis will nudge east
with a cold front pushing through New England. A strong surface high
pressure located in New England will cause the pressure gradient to
tighten keeping winds elevated. This will allow lows slightly warmer
Wednesday night compared to tonight. Still though, temperatures will
be in the mid 30s.


As of 430 AM Tuesday...

A highly amplified, progressive, split flow pattern will prevail
across the CONUS through the medium range. Within this energetic
pattern, a couple significant cyclones are forecast to affect the
ern US - the first a Miller A coastal low track, and the second one
west of the Appalachians/into the Great Lakes, with secondary triple
point development in the lee of the srn and cntl Appalachians.

At the start of the period (Thu), Arctic surface high pressure will
be migrating across the Great Lakes and Northeast, and ridging swd
in classical damming fashion in the lee of the Appalachians.
Associated chilly nely flow, CAA, and steady or falling afternoon
temperatures are expected in cntl NC on Thu, with widespread 20s
likely Thu night, and more 40s as the cold, dry air ridge becomes
firmly established by Fri.

The high will move offshore in the aforementioned progressive flow
aloft, such that an in-situ damming regime will develop over the srn
middle Atlantic states as warm, moist advection returns atop the
surface ridge Fri night-Sat, in response to the approach of a
negatively-tilted trough aloft from the mid MS valley to the middle
Atlantic states. Wet-bulbing of the dry air ridge will cause
temperatures to evaporatively cool into the 30s to low 40s, as rain
becomes widespread, Fri night. Similar to the most recent event,
there may be a marginal threat of freezing rain over the nw Piedmont
Sat morning, but likely a degree or three shy of freezing and
another near miss, and instead another widespread, soaking rain
event for most.

Lingering in-situ damming, low clouds, and patchy light rain or
drizzle will continue into Sun, ahead of the next system scheduled
to affect cntl NC Sun night-Mon. While another potentially-dynamic
system, with lower than average predictability given model spread in
timing and amplitude of the flow aloft, it appears at this time that
the air mass will be incompletely modified over cntl NC, with the
poleward return of maritime Tropical air from the Gulf likely to get
shunted off the sern US coast. As such, the severe weather threat
would be muted in cntl NC, as it would appear at this time.


As of 1100 AM Tuesday...

24 Hour TAF Period: VFR conditions are expected today through 18z/Wed.
Winds will become NW at 10-15kt this afternoon, with a few gusts
to 20kt. Winds will die off this evening.

High pressure will then build in from the west this evening
allowing for a continuation of VFR conditions.

Long Term: Arctic high pressure will move south and extend into
the region Friday morning. A potential MVFR deck looks to form
towards KINT and KGSO Friday. IFR conditions will then be
possible Saturday as widespread rain moves over the terminals.




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