Area Forecast Discussion
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FXUS62 KRAH 251518
Area Forecast Discussion
National Weather Service Raleigh NC
1115 AM EDT SUN SEP 25 2016
A cold front will move into northern South Carolina and stall
this evening and overnight. High pressure will build south into
our region from New England this afternoon and tonighyt. The
front will return north as a warm front late Monday.
.NEAR TERM /THIS AFTERNOON/...
As of 1115 AM Sunday...
Surface high pressure (1025+ MB) was centered over NY state this
morning. The high pressure was building south into North Carolina,
behind a cold front that was pushing into southern sections of the
state late morning. The front separated two seasons, with
summer to the south and fall to the north. Low stratus has spread
behind the front across much of NC and the cloudiness has become
thicker and more widespread with time this morning from VA into
much of our region. The only sunshine was noted near the NC/SC border
from near Charlotte to Lumberton. Temperatures at late morning ranged
from the mid 60s north of the front into the upper 70s around
Wadesboro and Charlotte.
For the rest of the afternoon, the high pressure to the north will
extend south into NC and SC as the cold front stalls over northern
SC. Areas near the front will see a few breaks in the overcast,
otherwise expect a low overcast through the afternoon as lift is
forecast to continue between the surface up through 2500 feet or so
from east to west, just north of the low level boundary. Very
little in the way of sprinkles or spotty very light rain may
occur, but conditions are not favorable for anything widespread.
Highs are expected to hold around 70 NE and range into the
lower 80s around Wadesboro where some sunshine will continue.
.SHORT TERM /TONIGHT THROUGH MONDAY NIGHT/...
As of 305 AM Sunday...
Expect partly cloudy skies tonight east (much weaker to absent moist
upglide and slightly drier low levels) and mostly cloudy to cloudy
west with patchy light rain or drizzle possible. Lows from around 60
near the VA border to upper 60s SW.
The work week will start with the cool surface ridge centered over
SE Canada nosing south/southwestward through the NC Piedmont, capped
by mid level shortwave ridging between deep shortwave troughing over
the upper Midwest and off the Canadian Maritimes. The remaining low
level stable pool will hold firm for the first half of the day, then
slowly erode throughout the afternoon as the parent high eases
eastward and weakens, with fairly dry mid levels allowing for some
wedge-dissolving isolation. This dry air will be quickly supplanted
however as moisture ramps up and deepens by late in the day, as the
mid level trough axis and surface cold front approach from the WNW.
Jetting on the east side of the upper level trough will result in
improving upper divergence across western/central VA/NC late Mon
into Mon night, with rebounding prefrontal PW to over 1.75". Will
hold onto slight chance pops east (longer-lasting dry air) and
better chances east, trending upward slightly through the late day
and night as large scale forcing for ascent ramps up. Expect highs
Mon from the upper 70s to lower 80s, followed by lows in the mid-
upper 60s Mon night. -GIH
.LONG TERM /Tuesday through Saturday/...
As of 310 AM Sunday...
A cold front will make its way through the state on Tuesday as the
parent low pressure system becomes stacked over the Great Lakes. At
this point it looks like there will be hardly any punch at all with
this system and thus expect most of the precipitation to be in the
form of convective showers with isolated thunder possible Tuesday
afternoon, particularly across the south but otherwise instability
is lacking. The effects on temperature will not be seen until
Wednesday and beyond so expect highs on Tuesday near 80 degrees with
upper 70s across the north.
The real curiosities in the long term center around how the stacked
low will evolve over time. The GFS solution has the low remaining
embedded in the upper level flow and gradually moves eastward
keeping the end of the week dry. The ecmwf solution is much
different and is beginning to gain a little consistency with the
upper low cutting off from the mean flow and dropping south along
the Appalachians and hovering there for several days. This would
greatly increase precipitation chances over our area for the end of
the week and needs to be watched because the latest run of the GFS
is showing a bit of a trend toward that upper low dropping further
south although it has not cut it off yet. For now will keep the
forecast dry outside of slight chances for showers across the east
on Thursday but if this trend in the forecast continues, then pops
will need to be increased significantly for the end of the week.
Temperatures will drop back into the mid 70s for highs for the rest
of the week with lows in the middle 50s.
.AVIATION /12Z SUNDAY THROUGH THURSDAY/...
As of 645 AM Sunday...
All central NC terminals have seen a trend toward IFR to LIFR cigs
over the last several hours, as stratus pours in behind a backdoor
cold front pushing toward the SSW through NC this morning. The
exception is in the NE including RWI, which has seen earlier IFR
cigs rebound to MVFR as some drier air has worked into this area.
Elsewhere, the stratus will hold over central NC through mid
morning, followed by a slow lift to MVFR areawide by midday, with
lowest cigs holding at INT/GSO, then to VFR at RWI/RDU/FAY by 19z
while MVFR cigs hold at INT/GSO, through sunset. MVFR conditions are
expected to slip back to IFR at INT/GSO after 08z tonight, with MVFR
or VFR cigs elsewhere late tonight through 12z Mon morning. A few
light showers or sprinkles are possible at all sites today, with
little to no risk of thunder. Winds will remain light under 10 kts
from the ENE or NE.
Looking beyond 12z early Mon morning, a trend to VFR conditions
areawide is expected by late Mon morning, holding through the
afternoon/evening. IFR conditions are expected to develop late Mon
night, trending to MVFR Tue morning with improving rain chances, as
a cold front approaches slowly from the west. A period of sub-VFR
conditions is likely late Tue into Wed as the front moves through
with scattered to numerous showers and a few storms. Conditions will
improve to VFR from west to east Wed night, lasting through Thu
behind the front. -GIH