Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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529
FXUS62 KRAH 270114
AFDRAH

Area Forecast Discussion
National Weather Service Raleigh NC
910 PM EDT Wed Apr 26 2017

.SYNOPSIS...
High pressure will be overhead tonight and early Thursday. A
weakening cold front will approach the mountains from the west on
Thursday, then dissipate over central and eastern NC Thursday night.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 910 PM Wednesday...

The skies had cleared across NC this evening. High pressure will be
overhead tonight with light winds. There may be a bit more patch fog
around sunrise that currently forecast due to the saturated ground
under clear skies and light winds. We may have to add some patchy
ground fog for later tonight, especially in the fog prone and soaked
valley areas near the lakes, rivers, and even smaller creeks. The
temperature / dew point spreads were already 5 degrees or less in
many areas. Lows should fall into the 60-65 range, except upper 50s
over the northern Piedmont.

&&

.SHORT TERM /Thursday and Thursday Night/...
As of 335 PM Wednesday...

Skies will be generally sunny for much of Thu morning, with the mid
level ridge axis sliding to our east, although high clouds will be
increasing as the weakening line of convection approaches from the
west, along with a weakening surface trough that brushes our W and N
sections late Thu through Thu night before lifting up into the Mid
Atlantic region. Warm and stable 850-600 mb air will inhibit
convection in our area through early afternoon, despite surface
dewpoints within a few degrees of 60, and this is further supported
by the latest hi-res WRF-ARW/NMM runs which stay dry in our area
through 18z. By mid afternoon, however, a weakened version of the
convective line will be moving into the western CWA, accompanying a
30-40 kt 850 mb SSW jetlet, weaker than its previous state but still
enough to support low level mass convergence over central NC, mainly
from very late afternoon until shortly after midnight. Forecast
soundings show mostly elevated instability increasing by evening,
peaking in the 800-1200 J/kg range, and deep layer shear ranging
from around 40 kts west to around 20 kts east, with column
moistening as high PW values of 1.5-1.75" advect in from the SW.
Detrimental to maintenance of this convection will be the lack of
dynamic forcing for ascent, as any weak DPVA will track well to our
NW, although models do indicate a pocket of enhanced upper
divergence tracking NE through the area Thu evening, which may
support greater storm coverage. For now, will hold onto low-end
likely pops west, with lower chances through the central CWA and
just small chances east, where deep layer shear and dynamic forcing
for lift will be weaker closer to the departing ridge. With
thicknesses higher than yesterday tempered by the increase in
clouds, expect highs from near 80 NW to the mid 80s SE. Lows Thu
night ranging from the low 60s NW to the upper 60s SE. -GIH

&&

.LONG TERM /Friday through Tuesday/...
As of 325 PM Wednesday...

A weak surface tough associated with dying overnight convection is
forecast to stall over the coastal plain and then retreat back to
the west on Friday as the subtropical ridge amplifies off the
Southeast coast.  The ridge, and associated rising thicknesses will
peak on Saturday (thicknesses of 1410-1420m), with highs accordingly
peaking in the upper 80s to lower 90s, just short of record highs.
Convection each day should mainly be tied to the seabreeze and higher
terrain in southwesterly flow and no strong forcing.  However, with
strong instability forecast, owing to a plume of steep mid-level
lapse rates off the Mexican Plateau, there could be a large hail and
damaging wind threat, more so on Saturday when models suggest a
shallow tropopause disturbance/jet moving lifting through the Deep
South that could aid in triggering storms.  Confidence in this
feature and whether or not storms will be able to develop is still
low at this point.

The ridge will hold on Sunday and then give a little to a strong
upper low forecast to lift from the Southern Plains to the Great
Lake by Monday.  POPs will increase on Monday as the associated cold
front advances east across the mountains.  Shear looks favorable for
severe weather, but instability is questionable on Monday.  Temps
will accordingly be knocked back toward normal for the middle of
next week.

&&

.AVIATION /00Z THURSDAY THROUGH MONDAY/...
As of 820 PM Wednesday...

24 Hour TAF Period: VFR conditions are generally expected to
continue through the 24 hour TAF Period.

Mid level ridging is expected to shift to the east of the area
overnight, allowing for a cold front to approach the area tonight
into Thursday. This will allow for a south to southwesterly 5 to 10
mph wind overnight, increasing to 10 to 15 mph by mid morning
tomorrow, with gusts in the afternoon of 20 to 25 mph. Very late in
the TAF period, we could see a few showers and storms affect
KGSO/KINT, possibly resulting in sub-VFR conditions.

Outlook: Any storms that move into the area late afternoon/early
evening Thursday will weaken as they moves into central NC. Other
isolated storms will be possible Sat and Sun afternoon/early
evening, especially at KINT/KGSO, with a better chance areawide Mon
as a cold front approaches. Sub-VFR fog and shallow stratus
will be possible each late-night/early-morning as well.

&&

.HYDROLOGY...
As of 230 PM Wednesday...

High water in area creeks and drainage ditches continues to recede
today, with residual scattered road closures appearing to be more
infrastructure-related than hydrological. Main stem river flooding
will likely persist for several more days, particularly over north
central and northeast sections.

See
water.weather.gov/ahps2/index.php?wfo=rah for the latest forecasts
and additional information.

&&

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

&&

$$

SYNOPSIS...Badgett
NEAR TERM...Badgett
SHORT TERM...Hartfield
LONG TERM...Smith
AVIATION...BSD/Hartfield
HYDROLOGY...WFO RAH



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