-- Discussion containing changed information from previous version are highlighted. --
828
FXUS62 KRAH 121745
AFDRAH

Area Forecast Discussion
National Weather Service Raleigh NC
145 PM EDT Sun May 12 2024

.SYNOPSIS...
High pressure will build across the Southeast and Mid Atlantic
region today, then shift off the Southeast coast tonight through
Monday. A storm system will move in from the west Monday night
through Wednesday, bringing unsettled weather. Weak high pressure
moving in briefly for Thursday will be quickly followed by another
storm system arriving Friday.

&&

.NEAR TERM /TODAY THROUGH TONIGHT/...
As of 910 AM Sunday...

A quiet, dry, and seasonable day ahead. Mostly sunny skies are
likely to hold today with incoming surface high pressure. A few mid
clouds associated with a weak shear axis aloft will track through
far N and NE sections over the next few hours, and high thin clouds
will stream from the Mid South across our SW sections, plus we`ll
see a few high base flat cu this afternoon. All in all, though,
quite a bit of sunshine is expected today. Morning thicknesses are
about 15-18 m below normal, but modifying air balanced with abundant
insolation favors near-normal highs of 74 to 82, with a few gusts
around 15-20 mph. Very dry air is noted aloft (0C at 925 mb on the
12Z GSO sounding), and with good mixing expected today, we should
see very low RH well down into the 20-30% range this afternoon. -GIH

Earlier discussion from 330 AM: Radar echos have finally completely
dissipated across the Sandhills and southern Coastal Plain, with
just a deck of clouds there that will exit in the next couple hours.
Elsewhere there will be clear skies the rest of the night. A few
sites have reported reduced visibilities from fog/mist, but the rain
that fell this evening was so light that the fog/mist should stay
very isolated.

Dry NW flow will prevail today across central NC between ridging
over the lower-mid MS Valley and a closed mid/upper low that water
vapor imagery depicts currently spinning over Lake Erie. At the
surface, low pressure will move SE from Upstate NY and weaken, as
high pressure drifts east from the TN Valley to stretch from VA/NC
to off the NJ coast on Monday morning. PW values today are only
modeled to be around half an inch (40-50% of normal) with good
mixing and downsloping helping dew points bottom out in the lower-to-
mid-40s. Statistical guidance even shows upper-30s dew points in the
far NW Piedmont. A dry and very pleasant Sunday will result, with
only some scattered cumulus below the subsident inversion at about
700 mb. NW winds could gust up to 15-25 mph during the day. Today`s
1000-850 mb thicknesses will be about 10 m higher than yesterday,
supporting high temperatures from the mid-70s to lower-80s.

As winds diminish to mostly calm Sunday evening/night, decent
radiational cooling conditions will help lows drop to the mid-40s to
lower-50s, though high clouds spreading in from the SW could inhibit
cooling a bit.

&&

.SHORT TERM /MONDAY NIGHT THROUGH TUESDAY NIGHT/...
-- Changed Discussion --
As of 145 PM Sunday...

A closed upper trough over MO Mon night will become an open wave as
it tracks eastward Tue and Tue night into the lower OH valley and
parts of KY/TN. At the surface, guidance shows a Miller B low
pressure tracking from east-central MO into the OH valley during
this period. Downstream of the low, a warm front over GA/SC is
forecast to lift northward Tue night. While there remain some
differences with respect to track/intensity, models show a secondary
low tracking NE along the NW Piedmont and along the VA border at
this time.

Rain chances will overspread the region overnight Mon night and
especially Tue morning/afternoon as moisture transport and
isentropic ascent maximize over the region. Precipitable water
values increase to near record daily maximum values of 1.75 to 2.0
inches. While not a classic setup, there are some indications of a
weak in-situ wedge that could set up over the NW Piedmont Tue as the
secondary low tracks through. As such, most of the forcing north of
the warm front will be isentropically driven but some thunder
chances will exist across our southern zones, mainly south/east of
US-64/US-1 in closer proximity to some surface based instability.
Highs could be tricky in the NW with lots of low clouds/rain around.
We lowered highs to the upper 60s in the NW and mid 70s in the far
SE, but these may need to be lowered if trends favor a wedge setup.

Rain chances appear to lessen Tue evening/overnight into early Wed
as a dry slot moves in from the mid-level shortwave. However,
lingering low-level saturation should favor drizzle/shower chances
over portions of the area, and perhaps some fog. Lows will be in the
low to mid 60s. Rainfall totals could range from half an inch to
three quarters of an inch in the NW to three quarters of an inch to
1.25 inches in the SE by Wed morning.
-- End Changed Discussion --

&&

.LONG TERM /TUESDAY THROUGH SATURDAY/...
As of 305 AM Sunday...

Surface low pressure should be over southern Illinois at the
beginning of the extended forecast and precipitation will extend
well to the east, with rain increasing in coverage through the day.
Models begin to diverge with the surface feature Tuesday night, with
the 00Z GFS showing two low centers by Wednesday morning (over KY/TN
and DE) while the 00Z ECMWF has one broad center over OH. Regardless
of which scenario plays out, think that a bit of a dry slot will
develop over the Carolinas Tuesday night and there should be a bit
of a lull in shower coverage. The last two runs of the ECMWF are
suggesting that the upper trough helping to support the surface low
could close off into an upper low over the mid-Atlantic on
Wednesday, helping to intensify the surface low as it passes to the
north. While some rain could linger Wednesday evening, conditions
should then dry out as high pressure settles over Quebec and a ridge
extends along the eastern seaboard on Thursday. Meanwhile, the next
system will be developing in the Plains, and with models indicating
it may move east a little more slowly, have removed all pops from
the forecast Thursday night. Had enough confidence to add likely
pops across western counties Friday, but the models diverge too much
after this to go with anything higher than chance pops through
Saturday. Tuesday remains the coolest day in the forecast with
widespread highs in the 70s and possibly even upper 60s near the
Virginia border, otherwise temperatures should be near climatology,
around 80 and 60 degrees.

&&

.AVIATION /18Z SUNDAY THROUGH FRIDAY/...
As of 135 PM Sunday...

VFR conditions are likely, with high confidence, for the next 24
hours across central NC. Dry weather will continue, and after
scattered to briefly broken high-base cumulus this afternoon
dissipates, fair skies will prevail this evening through Mon,
although high clouds will steadily spread in and thicken Mon
afternoon. Surface winds will be from the WNW or NW through this
afternoon at 10-15 kt gusting to around 20 kt, diminishing to light
and variable after 22z.

Looking beyond 18z Mon, VFR conditions are expected through Mon
evening, although light sprinkles will begin spreading into the
western Piedmont during the evening hours. Widespread rain with a
high chance of sub-VFR conditions and increasing/shifting winds
aloft will overspread the area from SW to NE starting Mon night,
lasting through Tue afternoon. Rain should become lighter and more
patchy Tue evening/night, but sub-VFR fog and low clouds should
linger through Wed morning. A band of showers with brief sub-VFR
conditions is expected to swing through Wed afternoon/evening. Areas
of sub-VFR clouds are possible early Thu morning, otherwise VFR
conditions will dominate Thu. Scattered sub-VFR showers and storms
are possible Fri afternoon. -GIH

&&

.RAH WATCHES/WARNINGS/ADVISORIES...
None.

&&

$$
SYNOPSIS...Hartfield
NEAR TERM...Hartfield/Danco
SHORT TERM...Kren
LONG TERM...Green
AVIATION...Hartfield