Area Forecast Discussion
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FXUS62 KRAH 291726
Area Forecast Discussion
National Weather Service Raleigh NC
125 PM EDT Sat Apr 29 2017
A warm moist southerly flow will continue through the weekend, as a
strong high pressure remains anchored off the Southeast U.S. coast.
.NEAR TERM /THROUGH TONIGHT/...
As of 955 AM Saturday...
No significant changes to forecast. The strong mid level anticyclone
will hold over coastal NC with above-normal heights over the CWA,
leading to weak but deep subsidence, limited moisture, and a very
low chance of convection, despite HRRR-projected peak MUCAPE values
of 3000-4000 J/kg this afternoon. The stratus across the area has
been slowly dispersing with heating, although thicker and more
stubborn stratus has held in over the Triad and Roxboro areas, and
these areas will see clouds lingering longer. Eastern sections,
however, will likely see a bit better coverage of flat cumulus this
afternoon given better heating there. And areas across the north
will likely see greater coverage of high cirrus blown off the
expansive convection line to our NW, stretching from OH to N TX.
Despite the slight reduction in insolation, low level thicknesses
are near 40 m above normal this morning, with temps pacing a few
degrees above this time yesterday, supporting highs in the upper 80s
to lower 90s. Heat index values will peak in the mid 90s for all but
the NW CWA this afternoon. Have chosen to go with a dry forecast for
the rest of today/tonight, following persistence with similar
conditions to yesterday, including a pronounced cap near 850 mb and
the lack of any forcing for ascent with the strong ridge over the
area. PW is a bit higher than yesterday, though, so we may see
isolated cells over the higher terrain to our west, but the steering
flow should deflect these away from our area. -GIH
Earlier discussion from 340 AM: It will definitely feel like summer
today as central NC as an area of high pressure at the surface and
aloft extends across our region. This abnormally strong high for
this time of year will support high temps a solid 10-15 degrees
above normal ranging from the upper 80s-lower 90s. The heating of
the marginally moist and unstable air mass may trigger an isolated
shower or storm in vicinity of the Yadkin/Pee Dee River Valley,
though a mid level subsidence inversion will provide a decent cap to
prevent convection from popping across the region.
Another night of warm/muggy conditions anticipated tonight. Skies
will start out mostly clear-partly cloudy though expect a deck of
low clouds to overspread the region from the south late this evening
into the overnight. Min temps upper 60s-near 70. -WSS
.SHORT TERM /Sunday and Sunday night/...
As of 340 AM Saturday...
Main adjustment to the Sunday-Sunday night period was to adjust max
temps up a few degrees from the previous forecast. Finding it
difficult to justify high temps as much as 7-8 degrees, primarily
over the western Piedmont, Sunday afternoon with little notable
change in the low level air mass. Surface and upper level ridge does
weaken with upper heights 30-50m lower than today, but warm/moist
sly flow will maintain the summer-like air mass. Morning clouds will
slowly depart in the afternoon, which should allow for at least
partial sun in the western Piedmont by mid afternoon. With
temperatures starting out near 70, should see temps recover into the
mid 80s across the west, upper 80s-near 90 in the east.
Some weakening of the mid level subsidence inversion and slightly
deeper moisture and instability will support isolated convection in
the late afternoon-early evening across the western half of central
May see an uptick in isolated showers late Sunday night, mainly
across the far west, as a s/w approaches from the southwest. This
system will may enhance convective coverage on Monday. Continued
warm and muggy with overnight temperatures once again in the 60s to
.LONG TERM /MONDAY THROUGH FRIDAY/...
As of 330 AM Saturday...
A shift in the longwave pattern next week will ultimately result in
lower heights over the eastern US and a ridge over the west. The
sub-tropical ridge over the Southeast this weekend will shift east
Monday as a deep upper low lifts from the Southern Plains to the
Great Lakes. The associated cold front and convective line will be
crossing the mountains early Monday, encountering more favorable
heating/instability in the west Monday afternoon before undergoing a
general downward trend in intensity as it progresses east Monday
night owing to a loss of better forcing and heating. Still expect
PW over 1.5" and 60-80m height falls to support at least scattered
showers through central NC Monday night before moving to the coast
early Tuesday. Highs Monday in the upper 70s to mid 80s. Lows in
the mid 50s to lower 60s.
Temps will be knocked back top near normal briefly on Tuesday, but
with the secondary polar front holding to the north across VA, temps
will rebound into the mid 80s and above normal Wednesday. the next
shortwave moving through the longwave trough is forecast to strongly
amplify over the Deep South Thursday, with medium range guidance
showing the potential for another cut off low near Tenn Thursday
night. Models diverge quickly regarding out the eventual track of
the low, but the pattern will favor widespread precip late Thursday
and Friday, some of which could be heavy if the low slows and tracks
closer to the Southern Ablutions. Temps are most likely to be
below normal int he upper 60s and low/mid 70s.
.AVIATION /18Z Saturday through Thursday/...
As of 125 PM Saturday...
Cigs have improved to VFR across central NC, with unrestricted
vsbys, and these conditions will hold through this evening, as deep
high pressure extends across the region, deflecting any weather-
making disturbances and deep moisture away from our area. Scattered
to broken VFR flat cumulus clouds will dissipate during the early
evening hours with loss of heating. With abundant low level moisture
in place, confidence is high that we`ll see development of another
round of IFR (perhaps low-end MVFR in some spots) after 06z tonight,
lasting until gradual lifting and partial clearing trends terminals
up to VFR during the 15-17z time frame Sunday. Winds will hold from
the S or SW at 10-15 kts through sunset, with infrequent gusts to 15-
20 kts, falling to 4-7 kts overnight.
Looking beyond 18z Sun, VFR conditions and dry weather will hold
through Sun evening, with development of MVFR to IFR stratus once
again after midnight, lasting through sunrise Mon with slow
improvement to VFR Mon morning. A band of showers and storms
expected to cross the area late Mon afternoon through Mon evening
may bring a period of sub-VFR conditions and breezy/gusty winds from
the SSW. Dry weather and VFR conditions should follow behind a front
late Mon night through Wed. Chances will increase for showers/storms
and sub-VFR conditions Wed night and especially Thu. -GIH