Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC-- Remove Highlighting --
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FXUS62 KRAH 282020
Area Forecast Discussion
National Weather Service Raleigh NC
320 PM EST Tue Feb 28 2017
A mild southwest flow will persist across central NC through
Wednesday. A strong cold front will cross the area Wednesday night,
followed by cooler temperatures for the later half of the week.
.NEAR TERM /THROUGH TONIGHT/...
As of 300 PM Tuesday...
Tonight...main forecast concern is the convective coverage.
Scattered-numerous showers and a few thunderstorms over eastern TN-
sw Virginia will continue to slide ne in a plume of favored moisture
transport/advection extending from western NC into western Virginia.
The air mass over the Piedmont and coastal plain is not as moist as
the atmosphere to the west, so should see a gradual decrease in
shower coverage/intensity as the system advances east from the
mountains. Still, should see a decent chance for showers after
sunset through the evening in the Triad vicinity, though coverage
will quickly dwindle to the south and east.
Closer to home, heating of a slightly unstable air mass along and
east of highway 1 may support an isolated shower late this afternoon-
Overnight, good potential for a deck of low clouds to develop as
strengthening sly flow pulls an increasingly moist air mass into our
region. The combination of overcast skies and a steady sly flow will
result in very mild overnight temperatures, primarily in the 60-65
.SHORT TERM /WEDNESDAY THROUGH WEDNESDAY NIGHT/...
-- Changed Discussion --As of 320 PM Tuesday...
A s/w dropping sewd out of the upper Midwest into the Great Lakes
will propel a lead s/w across the TN Valley Wednesday and into the
Carolinas Wednesday evening. This system will be accompanied by a
band of convection. A strengthening low level jet (50-60kts) will
support a strongly kinematic atmosphere. While the low level air
mass will be toasty with afternoon temps in the upper 70s-lower 80s.
Sfc dewpoints are forecast to be no worse than around 60-lower 60s.
This is supportive of a weakly unstable air mass but not supportive
of a widespread severe weather event. So, expect a band of
convection with locally strong/severe wind gusts to enter the western
Piedmont sometime close to or after sunset, then progress east into
the highway 1 corridor in the 9 PM-Midnight time frame. Expect
intensity of the showers/storms to diminish as it enters a
relatively more stable air mass.
Ahead of the showers and storms, southwest sfc winds will be
gusty/windy with sustained winds 15-20 mph and gusts 30-35 mph. A
deck of mid-high level clouds may deter insolation enough to prevent
optimal mixing, leading to slightly lower wind gusts. Conversely, if
more sunshine occurs than expected, wind gusts around 40 mph may
occur, prompting the need for a wind advisory.
Band of convection expected to progress east and exit our coastal
plain counties in the overnight hours. Low level flow from the nw
will advect a drier more stable air mass, leading to a decrease
cloud trend nw-se overnight. This clearing line will likely lie
across the Triangle region at daybreak, then progress swiftly se
early Thu morning.
Low level cold air advection will send temperatures tumbling north
and west of Raleigh, leading to min temps in the low-mid 40s. Later
arrival of the colder air will result in min temps in the 50s se of
-- End Changed Discussion --
.LONG TERM /THURSDAY THROUGH TUESDAY/...
As of 220 PM Tuesday...
Thursday and Thursday Night: The current timing of the cold front
may result in a slight chance of showers lingering over the far
southeast early Thursday morning, but the rest of Central NC should
be dry and beginning to clear. Skies will continue to clear through
the day, however the cold air advecting into the region behind the
front will likely limit highs to upper 50s NW to mid 60s south.
Winds will be northwesterly behind the front and remain quite strong
through the day Thursday afternoon with sustained winds up to 15 kts
with gusts to around 20 kts, diminishing late in the afternoon.
Expect winds of 5 kts or less overnight, backing slightly to more
westerly. The light winds combined with clear skies and continued
cold advection will yield lows generally in the mid 30s across the
area Thursday night.
Friday through Sunday Night: This period is expected to remain dry.
Highs Friday will be in the mid 50s NW to mid 60s South, though they
will be somewhat dependent upon the timing of a reinforcing dry cold
front expected to push through late Friday/Friday night. Highly
confident the coldest temperatures will occur Saturday morning as a
result of the aforementioned cold air (mid to upper 20s), as well as
the surface high moving overhead. With the high overhead and
continued northerly flow, highs Saturday will struggle to recover,
maxing out in the low to mid 50s. Expect moderating temperatures
once again through Sunday night as southerly flow sets up once
again. Lows Saturday night in the low to mid 30s, increasing into
the mid 40s by Sunday night and highs Sunday in the mid 60s.
Monday and Tuesday: The surface high will shift off to the southeast
as yet another low pressure system develops out west. The warm
southerly flow increases over the Carolinas Monday and Tuesday as
the aforementioned system moves east toward the Mid-Atlantic. There
are still issues with timing of this system, thus confidence is
somewhat low in that regard, but expect a chance for showers ahead
of the front as it moves into the region early to mid week. As
expected, temps will increase ahead of the front and decrease in its
wake, however the timing is uncertain at this time.
.AVIATION /18Z TUESDAY THROUGH SUNDAY/...
As of 125 PM Tuesday...
Pockets of low end VFR/high end MVFR ceilings will persist across
parts of the coastal plain and sandhills this afternoon. The MVFR
ceilings may briefly occur at KRWI and KFAY. A mid/upper level
disturbance lifting east-ne across the TN Valley into the central
Appalachians this evening. This feature may produce a few showers in
the vicinity of the Triad terminals between 00Z-06Z. The showers
should be more concentrated to the north of the Triad.
The sly low level flow will continue to advect moisture into our
region. After 03Z, this added moisture should lead to the
development of IFR/LIFR ceilings over most of our region, most
likely between 09Z-13Z.
The IFR/LIFR ceilings will lift/dissipate by 14Z-16Z. In its wake,
expect abundant mid-high level clouds and windy sfc conditions.
Southwest winds Wednesday will likely gusts 30-35 mph with a few
gusts topping 40 mph.
A strong cold front will approach from the west late Wednesday and
cross our region Wednesday night. Ahead of the sfc feature, expect
and 15-30 mile wide band of showers and thunderstorms, producing
MVFR/IFR conditions. The stronger storms may produce wind gusts 45-
The convection threat will rapidly decrease west-to-east between 04Z-
08Z as the front sweeps across the region. Breezy sfc winds will
occur early Thursday with gusts generally 25 kts. Otherwise expect
VFR conditions late Wednesday night through Sunday.
As of 500 AM Tuesday...
Critical fire weather conditions are expected on Friday, after a day
Thu with low RH and drying fuels, and marginal NWly winds.
Behind a cold front that will cross central NC Wed night, surface
dewpoints will fall into upper teens over the NW Piedmont to 20s
elsewhere on Thu. When combined with afternoon temperatures in the
upper 50s to middle 60s, relative humidity values between 20 and 25
percent will result. However, NWly winds will be strongest between
10 AM and 1 PM - prior to the lowest humidity values being met
during the afternoon hours. In addition fuel moisture values will
probably be residually elevated after a round of showers and storms
accompanying the cold front Wed evening-night.
Nonetheless, the low RH will at least set the stage for Fri, when a
reinforcing cold front and following NWly winds and low RH will
result in critical fire weather conditions. Cold and dry air
advection behind the cold front, and associated deep mixing up to 7
or 8 thousand ft, will favor the development of breezy NWly
sustained winds of 14-19 mph, with 25-30 mph gusts. Afternoon
surface temperatures and dewpoints in the 50s to around 60 degrees,
and teens to lower 20s, respectively, will yield minimum RH values
between 20-25 percent. Rapid/explosive fire growth may result; and a
Fire Weather Watch may be coordinated with NCFS on Wed.