Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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FXUS62 KRAH 240652

Area Forecast Discussion
National Weather Service Raleigh NC
250 AM EDT Tue Oct 24 2017

A cold front will shift off the North Carolina coast early this
morning. A secondary cold front will move eastward through the
region this evening and tonight. A strong upper level disturbance
will cross the area Wednesday night, otherwise surface high pressure
will build in from the southwest from Wednesday through the end of
the week.


.NEAR TERM /today and tonight/...
As of 230 AM Tuesday...

The showers and storms have exited all but the far NE portions of
the CWA, and everywhere should be dry prior to daybreak as the cold
front shifts slowly eastward to coastal NC. With a light wind regime
right behind the front and dewpoints remaining elevated with a clear
or clearing sky, pockets of fog and stratus have already formed over
the NW Piedmont. Following the observed trends as well as high res
model output, particularly the HRRR, we should see the stratus and
fog envelope much of the northern Piedmont during the remainder of
the overnight extending to just beyond daybreak. With higher level
clouds largely absent, the resultant heating from above along with a
light breeze from the SW should allow for a lifting and dissipation
of the stratus through mid morning. Expect plenty of sunshine today,
with a dry column and no lift mechanisms between the departing cold
front and ahead of the secondary cold front this evening into the
early overnight hours. This latter feature will bring a few clouds
and little else given the overall lack of both deep moisture and
mechanisms to force ascent, although a shift of surface winds to W
or WNW is anticipated. With near normal thicknesses, highs should
follow suit, with readings of 69-77. The secondary frontal passage
and drop in thicknesses to readings 25 to 35 m below normal by
sunrise suggests lows ranging from 41 NW to 50 SE, with winds
staying up a big overnight. -GIH


.SHORT TERM /Wednesday through Wednesday night/...
As of 250 AM Tuesday...

The axis of the amplified mid level trough, and its corresponding
shearing vorticity lobe, will cross the Carolinas Wed. But moisture
remains absent, and warming/stabilizing mid levels will follow.
Expect generally sunny skies, albeit with some high cloudiness. With
the chilly morning and cold air advection during the day, expect
highs in the low-mid 60s. A potent vorticity max is expected to dive
southeastward through the Carolinas Wed night. While PW remains
quite low, forecast soundings do depict moistening between 800 mb
and 400 mb, particularly on the NAM and ECMWF as well as the SREF
mean, which all squeeze out a few hundredths of an inch with this
feature. The chance of anything measurable looks very low despite
the strength of the DPVA and the upper divergence max in the left
exit region of the upper jet core extending from MI into W NC/SC, as
it remains quite dry below 850 mb. But both the forcing for ascent
and the potential for moisture aloft are sufficient to including a
few sprinkles across the NW CWA Wed night. Low level cold air
advection will increase late Wed night with passage of the 850-925
mb trough, suggesting lows of 37-43. Surface winds should stay just
stirred enough with the influx of lower dewpoints to limit frost
development. -GIH


As of 240 AM Tuesday...

Thursday will begin another gradual warmup across central NC as
surface high pressure centered over the Gulf Coast will bring winds
back around to southwesterly and remain there as that surface high
moves northeastward and runs up the east coast. This will keep NC on
the warm side of the high through Saturday as high temperatures rise
from the low to mid 60s on Thursday up into the low 70s by Saturday.
Overnight lows during this time will moderate slightly from the low
to upper 40s. No precipitation is expected during this time.

The next real weather maker will enter the picture late Saturday as
a low pressure system moves up the coast ahead of a cold front that
is progged to cross the area later on Sunday. Aloft a deep trough
will push the system through the area and start to become negatively
tilted as it does so. It is still too early for details but at this
point the surface low strengthens over central NC which could cause
a significant rain event but current model runs still range anywhere
from a half an inch over the area to as much as 2 inches. Will have
to look for the possibility of severe wx as well but currently best
shear and instability do not quite align with the upper jets
trailing the system. Certainly high shear will be present, the
question will be can we get some instability to go with it. Stay
tuned. Highs Sunday back into the upper 50s to upper 60s from NW to

Cooler airmass will move in behind the system for Tuesday and
Wednesday with highs near 60 degrees and lows in the mid 30s to near
40 degrees with a dry forecast in place.


As of 155 AM Tuesday...

The showers and storms associated with the cold front now sweeping
through eastern NC have mostly ended over central NC, although
lingering showers will affect RWI until around 07z. With the moist
ground and light winds, areas of IFR/LIFR fog and stratus have
already formed at INT/GSO, and this is likely to persist through
13z, and should spread eastward to RDU through daybreak, with IFR
conditions expected there 10z-13z. Confidence in sub-VFR conditions
is lower at RWI/FAY, but patchy fog and stratus can`t be ruled out
at these locations either. Conditions at all sites are expected to
trend to VFR by 13z at INT/GSO, but may linger until 14z at RDU. VFR
conditions are likely from late this morning through this afternoon,
with surface winds from the SW at 7-10 kts and infrequent gusts to
11-14 kts possible but not dominant. With passage of a secondary
cold front this evening, surface winds will veer to be from the W or
WNW starting 00z-02z this evening.

Looking beyond 06z Wed, VFR conditions will rule through Sat as
surface high pressure builds into and over the region. Passage of a
strong but somewhat moisture-starved upper level disturbance Wed
night may bring a period of MVFR cigs at INT/GSO/RDU. A strong upper
level trough and corresponding surface cold front will approach from
the west late Sat. -GIH




NEAR TERM...Hartfield
SHORT TERM...Hartfield
AVIATION...Hartfield is the U.S. government's official web portal to all federal, state and local government web resources and services.