Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC
FXUS62 KRAH 291848
Area Forecast Discussion
National Weather Service Raleigh NC
250 PM EDT Sat Apr 29 2017
A warm moist southerly flow will continue through the rest of the
weekend, as a strong high pressure remains anchored off the Carolina
coast. A cold front will cross the region Monday afternoon and
.NEAR TERM /THROUGH TONIGHT/...
As of 250 AM Saturday...
A quiet but warm/muggy night ahead. Experimental GOES-16 red visible
band imagery reveals cloud streets over the western and southern
CWA, and batches of thin cirrus that emanated from the now-
dissipating MCS activity just north of the Ohio River. But cloud
cover remains mostly scattered/thin, allowing for strong heating and
temps soaring to well above normal readings. The strong mid level
anticyclone centered just off the Carolina coast combined with the
Bermuda high pressure extending across the Southeast continues to
prompt mean subsidence and a fairly dry column, so despite decent
lapse rates around 7 C/km and current MLCAPE of 3000-4000 J/kg, any
convection chances for the rest of the day appear slim. With the
strong cap holding in place in the 950-850 mb layer, we`ll have
another round of stratus form overnight, leading to a trend to
mostly cloudy skies and patches of fog. We should once again see
lows in the upper 60s to lower 70s, over 15 degrees above normal
.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