Area Forecast Discussion
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FXUS62 KRAH 010005
Area Forecast Discussion
National Weather Service Raleigh NC
705 PM EST Tue Feb 28 2017
A warm and blustery southwest flow will continue across the region
through Wednesday. A strong cold front will cross the area Wednesday
night, followed by clearing skies and cooler temperatures for the
latter 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/...
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
.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 /00Z Wednesday through Sunday/...
As of 705 PM Tuesday...
A band of showers will cross central NC this evening, bringing a
brief period of MVFR vsbys, although cigs should remain
predominantly VFR. Then, clouds will thicken and lower within a
strengthening low level flow from the SW, and a period of MVFR cigs
is likely at all sites later tonight (most likely 09z-13z), with
some spots potentially seeing a short period of IFR cigs. Cigs
should then lift to VFR gradually between 13z and 15z, remaining VFR
through the end of the TAF valid period. Surface winds, currently
from the S or SSW under 10 kts, will strengthen from the SW
overnight, increasing to around 15 kts toward daybreak, then to
sustained 15-25 kts with frequent gusts to 25-35 kts starting mid
morning. These deeply strong winds may induce mechanical turbulence
which could bring about difficulty handling some smaller aircraft.
Looking beyond 00z Thu (early Wed evening), a line of showers and
strong thunderstorms is expected to cross central NC Wed evening,
bringing a high chance of sub-VFR conditions and a threat of
damaging wind gusts (on top of the already-strong and -gusty winds).
This convection will be ahead of a cold front that will sweep
through the area Wed night, mainly after midnight. Skies will clear
out for Thu with VFR conditions and NW winds. VFR conditions will
hold Thu through Sun as high pressure builds over the area. -GIH
As of 445 PM Tuesday...
A cold front will cross central NC Wednesday night. Out ahead of the
boundary, south-southwest 15-20 mph expected with gusts 30-40 mph.
Minimum RH values Wednesday afternoon should bottom out 45-50
Scattered convection should occur Wednesday night, though
precip will be in the form of showers, and fall in less than an
hour. This will not allow the rain to soak into the dry/dead
grasses/leaves. Minimum RH values Thursday afternoon will fall to
near the critical level of 25 percent. Gusty NW winds are expected
Thursday morning though the winds are expected subside Thursday
afternoon (at the time when the RH reaches the critical level).
A secondary cold front is expected to cross central NC Friday
afternoon. Again, RH values will bottom out around 25 percent. Sfc
winds may gusts 20-25 mph out of the NW by Friday afternoon. These
parameters may result in increased fire danger over the region. This
may require the issuance of fire weather statements, per
coordination with the NC Forestry Service.