Area Forecast Discussion
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FXUS62 KRAH 210510
Area Forecast Discussion
National Weather Service Raleigh NC
1210 AM EST Tue Feb 21 2017
High pressure will extend along the East Coast through early Today.
An upper-level disturbance will cross the Southeast states Tonight
.NEAR TERM /THROUGH TONIGHT/...
As of 1050 PM Monday...
Scattered to broken coverage of cirrus existed across the region
late evening. Most of the high clouds were too thin to temper
cooling. The urban vs. rural locations were really noticeable given
the nearly calm conditions and thin cirrus. Readings at 1000 PM
ranged from 60 at the Winston-Salem urban located ASOS to 46 at the
rural Smithfield, Louisburg, and Roxboro AWOS`s. Some cirrus will
continue to override the strong ridge axis just to our west, leading
to partly cloudy skies overnight. Lows are expected to be in the
40s, with the large range in urban versus rural locations.
.SHORT TERM /TUESDAY AND TUESDAY NIGHT/...
As of 350 PM Monday...
The surface high will continue to extend southward through eastern
NC Tue as its center moves off the coast of New England. The mid
level ridge axis will also move offshore as the full-latitude trough
approaches from the west. This trough is currently phased but will
split on Tue, with the northern portion deamplifying as it
progresses through Quebec and the Northeast through Tue night,
while the southern portion drifts much more slowly along the Gulf
Coast. Improved overrunning flow as the 850 mb ridge axis shifts off
the Carolina coast Tue night along with falling heights will lead to
a chance for showers in western sections, mainly after midnight.
Forcing for ascent will initially be fairly weak however, as the
weakening mid level flow will lead to weaker DPVA, although upper
divergence will steadily improve. Low level moisture transport will
exhibit a small rise overnight over the western CWA, with rising
PWs. The NAM brings more substantial rain into our far NW Tue night
as compared to the GFS/ECMWF, with much higher PW. The more muted
and slower GFS/ECMWF solution is preferred based on its consistency,
the weaker low level mass convergence, and the strength of the
slowly departing ridge axis, so will only bring up pops into the
good chance range in the NW Tue night, with little to no pops
along/east of Highway 1. With the dip in thicknesses and increase in
clouds Tue, will have highs in the mid-upper 60s, still well above
normal. Lows Tue night in the mid 40s NE to lower 50s S. -GIH
.LONG TERM /WEDNESDAY THROUGH MONDAY/...
As of 247 PM Monday...
The pattern begins to change for midweek and although we stay warm,
a wetter pattern will bring more clouds and some chances for rain
late in the week. That being said no day looks like a washout at
this point and rainfall totals for the week look only to be about a
half an inch at the most with some locations receiving very little
rain. Temperatures will remain in the 60s and 70s throughout the
To break it down further, Wednesday will bring our fist chance for
rain as a low pressure system in the Gulf of Mexico dives
southeastward towards the Florida Peninsula. As a surface high
sinks southward, central NC will be on the northern fringes of this
system and any rain that does occur will be a result of some
isentropic lift and moisture advection from the south. Best chances
will be in the western part of the forecast area. On Thursday a
developing low pressure system to the west will establish a warm
front along our northern border and begin to advect northward. As a
result, best chances for any appreciable rain Thursday will be along
the VA border counties.
For the most part Friday looks dry as the low to the west tracks
northeastward into the Great Lakes. As it does so frontogenesis will
occur just west of the Appalachians as a cold front moves into North
Carolina Saturday morning and across our area by Saturday late
afternoon/evening. This may be our best chance for rain during the
long term with a non-zero chance of some Thunder, especially in the
southeast where some better instability may be allowed to develop.
Behind the front, high pressure moves in for Sunday signaling a
return to clear skies and dry weather.
.AVIATION /06Z TUESDAY THROUGH /...
As of 1210 AM Tuesday...
24-Hour TAF period: Fairly high confidence VFR conditions will
prevail through the TAF period. Low confidence in the development of
a brief period of low stratus/fog around daybreak, thus will keep
TAFs VFR. Broken to overcast cigs at 20-25 kft will persist through
the period, with few to scattered clouds at 3-4 kft developing
during the day Tuesday. Low stratus could develop at the very end of
the TAF period, but will keep it out at this issuance. Winds will be
calm to light and variable overnight, becoming predominantly
southeasterly around 5 kts during the day/evening. -KC
Looking ahead: We will see a chance for late-night and early-morning
sub-VFR fog/stratus repeat areawide each day through the remainder
of the week. MVFR to IFR conditions with a few showers are possible
late Tue night through Wed as an upper trough crosses the region. A
cold front will cross the area Sat, bringing a chance for showers
and MVFR cigs. -GIH