Area Forecast Discussion Issued by NWS Raleigh/Durham, NC
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000
FXUS62 KRAH 191051
AFDRAH
Area Forecast Discussion
National Weather Service Raleigh NC
651 AM EDT Tue Mar 19 2024
.SYNOPSIS...
Canadian high pressure will build across the Southeast through
midweek. A dry cold front will move though the Mid-Atlantic late
Wednesday ahead of a low pressure system that will track
through the Southeast and offshore into the weekend.
&&
.NEAR TERM /THROUGH TONIGHT/...
As of 400 AM Tuesday...
...A Freeze Warning is in effect for portions of the Southern
Piedmont and Sandhills for sub-freezing temperatures this morning...
A vigorous mid/upper trough will shift offshore by this morning
with the secondary reinforcing surface cold front well offshore
and the Canadian airmass sufficiently deposited over the Mid-
Atlantic and a majority of the Southeast. Surface high pressure
over the ArkLaTex Region will gradually elongate across the Gulf
Coast states through the afternoon as a sub-1000mb low pressure
slides from central Ontario into the Great Lakes Region by this
evening. The result will back surface winds out of the
southeast through the afternoon with a continued tight pressure
gradient between the low to the north and the high to our south.
Incredibly strong subsidence on the backside of the departing
mid/upper trough on the order of 150-200m H5 height rises will
result in mostly clear skies across the area today with only
wisps of thin cirrus across northern NC into VA at the nose of a
100-120 kt northern stream upper jet.
Surface stirring should continue for most locations across central
NC given the pressure gradient across the area tonight and result in
lows in the upper 30s. However pockets of light winds with periods
of calm may allow temperatures to drop into the mid 30s. Enough
stirring should take place to avoid optimal radiational cooling and
prevent locations from reaching sub-freezing temperatures.
&&
.SHORT TERM /WEDNESDAY THROUGH WEDNESDAY NIGHT/...
As of 400 AM Tuesday...
The surface high draped out along the GOM states will continue to
weaken as the strongly convergent mid-level flow becomes more zonal
and the surface low over the Great Lakes continues its slow
march into southern Quebec Wed afternoon. At the same time,
Canadian high pressure over northern Saskatchewan/Alberta will
be nosing down through the central Plains and Upper Midwest and
help push a dry cold front through central NC late Wed into
early Thurs. Moisture return ahead of the front will be lacking
since the elongated area of high pressure to the south will
prevent much appreciable moisture into the area. Temperatures
will rise into upper 60s to low 70s within the southwesterly
surface flow and rising 1000-850mb thicknesses. Surface winds
will begin to increase during the early afternoon as the low-
level inversion gets completely eroded and a deeply mixed
boundary layer results in efficient momentum transfer up to 800
mb. This may result in sustained winds 10-20 mph with gusts up
to 30 mph, greatest towards the NC/VA border. Winds will relax
quickly after sunset as the boundary layer cools and a surface
inversion sets up.
Cooler air will filter in behind the cold front late Wed into early
Thurs morning and lows will be dependent on the amount of CAA
can occur at the surface before sunrise. Leaning on statistical
guidance results in the lows in the upper 30s (N) to low/mid 40s
(S).
&&
.LONG TERM /THURSDAY THROUGH MONDAY/...
As of 330 AM Tuesday...
Thursday and Thursday night: A strong, reinforcing high over SE
Canada will build south down the mid-Atlantic Seaboard and into the
Carolinas. Though clouds will increase Thursday night, it should
remain dry with slightly below normal temps.
Friday through Saturday night: A southern stream shortwave trough
over the Southern US Plains Thursday morning is forecast to eject
east through the Lower MS Valley and mid South Friday, across the
southern Appalachians Friday night and then traverse the SE US on
Saturday. The southern shortwave is expected to spur surface
cyclogenesis over the northern Gulf Coast region Friday with less
confidence in the exact track thereafter as it evolves eastward
through the SE US Friday night and Saturday, before moving offshore
Saturday night.
This system is shaping up to produce a wet end to the week with rain
chances increasing from the SW during the day on Friday, with the
wettest period being Friday night, potentially lingering across
eastern NC Saturday. Currently, expect rainfall amounts to range
from 0.50-1.0" west of US 1 to 1-2" east of US 1. The residual
continental airmass associated with a strong ~1030mb surface high
preceding the arrival of the surface low into the region should
greatly deter destabilization across the area. However, models do
indicate the development of some weak instability late Friday night
and into Saturday, mainly across SE portions of the forecast area.
As far as temperatures, while it will depend on the track of the
surface, the increasing likely development of an insitu CAD across
the NC Piedmont will favor a sharp NW to SE temperature gradient
across the area Friday. Highs potentially ranging from near 50 NW to
lower/mid 60s SE. Highs Saturday could be similarly challenging with
CAD likely to linger across the area and with secondary re-
development of rain as the upper trough crosses the area. Highs in
the upper 50s/near 60 north to lower/mid 60s elsewhere.
Sunday through Monday: Canadian high pressure building into the area
will bring cool below normal temps for early next week.
&&
.AVIATION /12Z TUESDAY THROUGH SATURDAY/...
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As of 650 AM Tuesday...
VFR conditions expected through the 24 hour TAF period. WNW surface
winds 5 to 10 kts with gusts up to 15 kts will back to SW through
the afternoon and strengthen to 10 to 15 kts with gusts 20 to 25
kts. As the winds relax later this evening and a surface inversion
sets up, a strong LLJ will overspread all terminals through the
night and weakening towards daybreak.
Outlook: A storm system approaches the area Fri afternoon into Sat
bringing widespread sub-VFR conditions within a CAD regime through
Sat night.-- End Changed Discussion --
&&
.FIRE WEATHER...
As of 400 AM Tuesday...
...Increased Fire Danger from 11 AM through 8 PM today...
Tuesday: Within the dry airmass deposited across central NC from
the cold frontal passage last night, dew points will be in the
teens to low 20s throughout the day. Surface winds will
increase by this afternoon to 15 to 25 mph and combine with
relative humidity values 20 to 30% and cause increased fire
behavior today. Refer to your local burn- permitting authority
on whether you may burn. If you do burn, exercise extreme
caution.
Wednesday: Ahead of a dry cold front, southwesterly winds have
the potential to increase to 10 to 20 mph sustained with gusts
up to 30 mph, especially across the Northern Piedmont and
Northern Coastal Plain. These winds may overlap with dry
antecedent conditions within the modifying continental airmass
with relative humidity values dropping into the 20s to 30s.
&&
.RAH WATCHES/WARNINGS/ADVISORIES...
Freeze Warning until 9 AM EDT this morning for NCZ073>076-083-
084.
&&
$$
SYNOPSIS...Swiggett
NEAR TERM...Swiggett
SHORT TERM...Swiggett
LONG TERM...CBL
AVIATION...Swiggett
FIRE WEATHER...Swiggett