Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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FXUS62 KRAH 212004

Area Forecast Discussion
National Weather Service Raleigh NC
404 PM EDT Sun Apr 21 2019

A mid and upper level low will redevelop southeastward across the
southern middle Atlantic states through early Monday. Following
surface high pressure will expand across the southeastern US through


As of 340 PM...

A mid-upr trough axis stretching from Quebec swd across and offshore
the Carolinas will drift slowly ewd, to offshore the middle Atlantic
coast, through early Mon. Embedded within that trough, a well-
defined vort center (in afternoon WV satellite imagery) directly
over cntl NC (near TTA) will pivot a trailing trough axis --an
increasingly negatively-tilted one-- across ern/nern NC through this
evening. A mid-upr low center will likely reform/wobble from the
cntl Appalachians/middle Atlantic, sewd to near the mouth of the
Chesapeake Bay, by 12Z Mon.

At the surface, an elongated low center analyzed at 19Z from near
IAD ssewd to ECG will drift slowly ewd, while becoming absorbed by a
frontal wave now developing about 200 nm ese of ILM. The latter,
dominant low center will track generally nwd to nnewd past the Outer
Banks tonight, and offshore the DelMarVA by 12Z Mon. A trough axis
trailing the elongated low over VA and nern NC will move off the NC
coast through this evening. High pressure centered at 1024 mb over
the nrn Gulf of Mexico, and extending nwd to the lwr Great Lakes,
will otherwise build east into the Appalachians by 12Z Mon.

While a shower or two will remain possible over the far ne Piedmont
and nrn Coastal Plain this afternoon, that potential will be better
over ern NC, along the aforementioned surface trough/convergence
axis and where temperatures have warmed into the mid 60s-near 70
degrees, with surface dewpoints around 50 F.

A better (slight-small) chance of light rain/showers will exist
early tonight in cntl NC/over the nrn Coastal Plain, as the main mid-
upr low center reforms sewd. An accompanying area of mixed phase
saturation, coincident with the center of the cold pool aloft, will
likely result in the development of an area of mixed character
(stratiform/cellular) rain between 00-06Z Mon over nern NC,
including as far west as the nrn Coastal Plain.

With a light to calm wind, as the surface ridge axis builds ewd and
nears cntl NC, good radiational cooling will favor lows in the lwr-
mid 40s, except mid-upr 40s where clouds are apt to linger over the
nrn Coastal Plain for much of the night, in closest proximity to the
mid-upr low.


As of 400 PM Sunday...

Shortwave ridging aloft, and underlying 1020-1022 mb surface high
pressure, will build across the Carolinas through Mon night. Aside
from mainly scattered, diurnal/afternoon cumulus over ern and e-cntl
NC, skies should be clear. Temperatures will moderate, into the low-
mid 70s on Mon, though with another cool night with strong
radiational cooling mostly into the upr 40s-lwr 50s.


As of 400 PM Sunday...

Surface high pressure will be centered over South Carolina
Tuesday morning with the upper level low exiting northeast. Low
level thermal profiles Tuesday quickly respond to the rising
heights with 850 mb temperatures around 13 degrees C and
1000/850 mb thicknesses around 1395 m. Simultaneously Tuesday
heights will continue to fall across Arizona and New Mexico with
northern stream energy heading east over Ontario. A surface cold
front in association with the northern stream energy will move
across Virginia Wednesday before washing out around the NC/ VA
border Thursday morning. Depending on how quickly the front
heads south, Wednesday or Thursday will be the warmest days of
the entire forecast period. Mid to upper 80s looks likely over
the Coastal Plain and Sandhills mid week.

The closed low over New Mexico will eject east over southeast
Texas Thursday morning with weak PVA starting across the western
Piedmont. Upper level lift for the most part Thursday looks
weak, but with PWATs on the rise (between 1.2" and 1.3")
forecast soundings do start to weakly destabilize. An upper
level shortwave will then head southeast across Michigan and
begin to amplify helping to open up the southern stream wave
over Mississippi Friday morning. As this occurs, resultant weak
height falls along with DCVA will induce upper level lift. The
main band of DCVA and height falls will likely split North
Carolina, but will be more than sufficient to support high end
chance PoPs.

Friday evening the dual upper level disturbances will push east
and drag the corresponding surface cold front through central
North Carolina. The GFS is slightly stronger and faster with the
front than the ECMWF while the CMC is a compromise. The main
concern for the weekend will be if the southern stream energy
ends up getting absorbed or not. The 21.00z run of the ECMWF
stalls the upper level low over South Carolina helping to
promote the chance of rain over the southern zones. The latest
run of the ECMWF keeps the low moving very slowly. For now have
kept the forecast dry, or more aligned with the GFS/ CMC


As of 220 PM Sunday...

VFR ceilings between 3500-6500 ft will persist area-wide through
this evening, then linger overnight at RWI and perhaps RDU, in
association with a mid-upr low and associated moist axis that will
pivot across srn VA/nern NC through Mon morning. Patches of light
rain/showers will also develop from VA swd into nern NC, including
around the RWI vicinity late this afternoon through this evening. No
related sub-VFR conditions are expected, however.

Outlook: A frontal zone will settle into and linger over VA/NC late
Wed-Fri, with a related chance of a mainly afternoon shower/storm




LONG TERM...Haines
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