Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
FXUS62 KRAH 291902

Area Forecast Discussion
National Weather Service Raleigh NC
302 PM EDT Wed Mar 29 2017

Weak high pressure will move over central NC today and remain in
control through Thursday before low pressure brings unsettled
weather to the area for Friday and Friday night.


As of 1250 pm Wednesday...

Central NC will be under the influence of a very remote surface high
centered over northern Ontario with building heights aloft as
shortwave ridging shifts overhead. Widespread stratus with ceilings
between 2 to 4kft, has overspread the area, as depicted by the HRRR
and NAM, within the stable low-level NELY flow. Expect these low
ceilings to lift and eventually scatter out into a stratocu layer.

High temperatures ranging from mid to upper 60s NE , to mid/upper
70s southwest.

It should start out mostly clear this evening, but an area of
expanding stratus, developing within the 925-850mb SELY upslope flow
along the higher terrain, is expected to spread into the western and
possibly central piedmont between 06 to 12z. Lows ranging from the
mid 40s NE to mid 50s SW.


As of 405 AM Wednesday...

Thursday will be quiet during the day as a meso-high develops over
the Delmarva Peninsula which will throw temperatures into question a
bit for Thursday afternoon. if flow remains southeasterly over the
area, we should see temps near 60 degrees across the north with
highs closer to 70s in the south. If flow remains more northeasterly
temps could come in quite a bit cooler, especially across the north.

By Thursday night, the first waves of precipitation associated with
an approaching low pressure system will begin to overspread at least
the western portions of the CWA, and perhaps everywhere by 12z
Friday. Diurnal timing should keep most of this activity limited to
convective showers as instability is non-existent. That being said,
model soundings show every strong veering with height and wind
profiles suggest bulk shear of 50 knots or so with a large heaping
pile of helicity in the lowest levels of the atmosphere. Will
certainly keep an eye on these details as they evolve. Lows Thursday
night mainly in the 50s.


.LONG TERM /Friday through Wednesday/...
As of 300 PM Wednesday...

Fri-Fri Night: The 12Z GFS/ECMWF are in fairly close agreement
showing the upper low tracking ENE through the OH valley during the
day Friday, progressing into western PA late Friday into Friday
night. However, differences in timing persist between the GFS/ECMWF,
and the 12Z NAM (an outlier) shows the upper low tracking east
through KY into WV Fri/Fri night (much closer than the GFS or
ECMWF). Forecast confidence remains lower than normal, esp given
uncertainty in the evolution of upstream convection across the Deep
South Thu/Thu night in addition to uncertainty in the strength/
extent/evolution of the CAD wedge expected to develop over central
NC on Thu. Although confidence in precipitation chances remains
high, forecast specifics such as precip amounts, temperatures and
intensity/mode of convection remain relatively low. With the latest
guidance in mind, will indicate highs ranging from the mid 60s in
the Triad to the mid 70s in the Sandhills/SE Coastal Plain. Expect
precipitation to end from SW-NE as early as late Friday aft/eve,
with skies clearing in the wake of a cold frontal passage Fri night.
Lows Sat morning will depend primarily upon fropa timing, ranging
from the upper 40s/lower 50s (N/NW) to mid 50s (S/SE). The 12Z
GFS/ECMWF suggest a lower potential for severe weather given an
upper low track further to the north and a slightly faster
progression of the system. The 12Z NAM would suggest a more robust
potential for severe weather due to the closer proximity of the
upper low and slightly slower progression of the system which would
result in favorable diurnal timing, as well. Uncertainty remains too
high to say much more w/regard to the severe weather potential.

Sat-Sun night: Expect dry conditions and a warming trend over the
weekend as a shortwave ridge builds east across the Mid-Atlantic and
Carolinas. Expect highs in the lower/mid 70s Sat and mid 70s Sunday
as a shortwave ridge aloft tracks across the region from the west.

Mon-Wed: Expect increasing cloud cover during the day Monday and a
chance for convection Mon Night through Tue as the next upper level
low /attendant sfc cyclone/ approach from the west. -Vincent


As of 200 PM Wednesday...

24 Hour TAF Period:   High pressure will wedge south into the area
tonight and into the day on Thursday. The stable low-level NELY
flow has advected a shallow marine layer into the area, producing
ceilings between 3 to 4kft. GOES-R 16 visible imagery shows these
low-end VFR ceilings quickly morphing into a scattered to broken
stratocu deck.

There is medium confidence to high confidence that an area of MVFR
stratus will at KINT and KGSO, within the 925-850mb SELY upslope
flow along the eastern slopes of the higher terrain. Though
confidence is not as high, ceilings at KRDU, KRWI and KFAY are
expected to remain VFR, with the potential that KRDU could be
on the eastern periphery of the sub-VFR ceilings. A strong mid-level
subsidence inversion over the area on Thursday will result in slow
lift/improvement of the stratus layer, with a high likelihood that
sub-VFR ceilings at KGSO and KINT could linger into the mid to late

Long term: A warm front associated with a low pressure system
tracking through the Middle MS Valley will bring the chance for
showers and thunderstorms Thursday night late Thursday night through
mid to late morning hours on Friday.  High pressure with VFR
conditions should return Friday afternoon and will persist
through the weekend. The next storm system is expected to impact
the area on Monday.





LONG TERM...Vincent
AVIATION...CBL is the U.S. government's official web portal to all federal, state and local government web resources and services.