494
FXUS62 KRAH 181959
AFDRAH

Area Forecast Discussion
National Weather Service Raleigh NC
359 PM EDT Fri Apr 18 2025

.SYNOPSIS...
A backdoor cold front will move south through VA and northeastern NC
on Sunday, while warm high pressure will otherwise extend from near
Bermuda westward across the South Atlantic states through the
weekend.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 300 PM Friday...

A sub-tropical, mid-level high will strengthen and expand from the
nrn Gulf newd and across GA and the Carolinas tonight. Surface high
pressure beneath and just downstream the ridge will drift to near
Bermuda, while extending wwd across the South Atlantic states. After
continued breezy and gusty swly winds this afternoon, winds will
diminish to a light but steady breeze tonight. Low temperatures will
be about 15-20 F above those of this morning and mostly in the upr
50s-lwr 60s.

&&

.SHORT TERM /SATURDAY AND SATURDAY NIGHT/...
As of 250 PM Friday...

* Very warm, with temperatures ~15-20 F above average

A strong mid-level, sub-tropical high, with standardized 700-500 mb
height anomalies of 2-3 sigma, will migrate across and just offshore
the South Atlantic states through the first half of the weekend, as
will a plume of dry air and steep lapse rates accompanying an
expansive elevated mixed layer. While the EML will be overspread by
periods of cirrus and cirrostratus in high-level wswly flow, the
column will otherwise remain a dry one.

Surface high pressure beneath and just downstream of the sub-
tropical ridging aloft will extend across the swrn N. Atlantic from
near Bermuda to the South Atlantic states. Meanwhile, a cold front
will move through the OH Valley and Middle Atlantic, then settle in
backdoor fashion swd and into cntl or srn VA by 12Z Sun. Breezy and
gusty swly surface winds with daytime heating/mixing Sat, and very
warm temperatures, will result between the two and over the
Carolinas/srn Middle Atlantic.

While very warm and mostly in the upr 80s, high temperatures should
fall several degrees shy of daily records in the lwr-mid 90s. Low
temperatures mainly in the lwr-mid 60s will be close to daily record
high minimums for 4/20 at RDU and GSO.

&&

.LONG TERM /SUNDAY THROUGH FRIDAY/...
As of 355 PM Friday...

A weakening surface high centered WSW of Bermuda will slowly
retrograde back toward the Southeast US coast on Sunday and Sunday
night. Meanwhile, a deepening mid/upper low and surface low will
move east across the Canadian Maritimes on Sunday and Sunday night.
This will push a backdoor cold front SW into the mid-Atlantic on
Sunday, and some guidance indicates it may try to creep into our far
NE zones on Sunday evening/night. However, it will have a hard time
getting too far with the surface high still anchored to our SE. Even
if it does make it, it will be mainly dry, with the only effect
being a brief slight drop in temperatures and dew points behind it.
Can`t completely rule out an isolated shower with it in the far
north near the VA border, and GFS/CMC ensemble probabilities of
measurable precipitation are 10-20%, but keep forecast POPs below
15% at this time. During this period, a second mid/upper low and
associated surface low will eject NE from around the TX panhandle
and OK to WI and the UP of MI, dragging a cold front to its south
and beginning to weaken/suppress the Southeast US ridging. Despite
this and some high clouds beginning to spill into the area, Sunday`s
temperatures should continue to be very warm with highs in the mid-
to-upper-80s. Lows Sunday night will be in the upper-50s to lower-
60s.

The Great Lakes mid/upper low will then open up into a wave as it
pushes E/NE into southern Ontario and Quebec on Monday and Tuesday,
really flattening out by Wednesday. The associated weakening cold
front still looks to reach central NC at some point, but there is
still a lot of uncertainty regarding the front`s timing and
placement, as the GFS, ECMWF and CMC along with their ensembles have
been trending slower for days. The GFS and ECMWF now depict the
front beginning to reach central NC on Tuesday night/early Wednesday
before stalling across our northern counties and eventually washing
out mid to late week as the mid-level flow really weakens. The CMC
no longer even brings the front this far south at all. Regardless,
while there will be increased PW values in the 1-1.5 inch range in
proximity of the front, forcing for precipitation does not appear
great which should somewhat limit overall coverage. This is due to
the weakening of the front and the mid/upper low tracking so far to
our north. As a surface high moves east of New England, another
backdoor cold front may try to reach our NE on Thursday and/or
Friday, but effects look limited and similar to the one on Sunday
night.

In terms of sensible weather, with the slower timing, Monday now
looks dry and still quite warm, but not quite as warm as this
weekend with the ridge further breaking down. The earliest
measurable precipitation even looks possible for central NC is in
the NW on Monday night, with better chances each afternoon and
evening from Tuesday through Friday, less each night. Went a bit
below NBM to cap POPs in the chance range due to the aforementioned
factors, decreasing a bit on Thursday and Friday as ridging may
start to build back in. A few storms can`t be ruled out as there
will be weak to perhaps moderate instability each afternoon/evening,
in the 500-1500 J/kg range (highest south). The best day for any
severe threat would be Tuesday, as the shear and mid-level flow turn
minimal for the rest of the week. Ensemble mean QPF is less than a
half inch and mostly a tenth to a quarter inch each day, but locally
higher amounts will be possible where storms do occur, and they
could be slow moving. As for temperatures, Tuesday still looks warm
ahead of the front with highs in the 80s, and there will only be a
slight drop in temperatures on Wednesday and Thursday with highs in
the upper-70s to lower-80s. Southerly return flow may begin to
increase temperatures again on Friday. Cloud cover and moisture
should help keep lows very mild each night, in the upper-50s to
lower-60s.

&&

.AVIATION /18Z FRIDAY THROUGH WEDNESDAY/...
As of 200 PM Friday...

High pressure and lingering dry/continental air will favor a high
probability of VFR conditions in cntl NC through Sat. Any exception
to VFR will be a chance of 500-1500 ft cloud bases near and
especially west of INT around 12-13Z Sat. Otherwise, breezy and
gusty swly surface winds this afternoon will diminish after sunset,
then be followed by the development of a 35-45 kt low-level jet and
risk of marginal low-level wind shear centered from the NC Piedmont
newd across the Middle Atlantic coast overnight-Sat morning. Daytime
heating and mixing by 13-14Z Sat will promote a return to breezy and
gusty swly surface winds and an end of the earlier risk of LLWS.

Outlook: A backdoor cold front will be accompanied by a band of post-
frontal, IFR-MVFR ceilings over sern VA and nern NC late Sun-Sun
night, some of which may advance to near and especially just
northeast of RWI Sun night. A front and next chance of convection
and flight restrictions will settle over NC next Tue-Wed.

&&

.CLIMATE...
Record High Temperatures:

April 19:
KGSO: 92/1917
KRDU: 93/1941
KFAY: 94/1941

April 20:
KGSO: 94/1917
KRDU: 93/1896
KFAY: 94/1917

Record High Minimum Temperatures:

April 20:
KGSO: 65/1941
KRDU: 67/1896
KFAY: 69/2011

April 21:
KGSO: 64/1927
KRDU: 70/1896
KFAY: 68/2017

April 22:
KGSO: 63/1967
KRDU: 66/1909
KFAY: 64/1963

&&

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

&&

$$
SYNOPSIS...MWS
NEAR TERM...MWS
SHORT TERM...MWS
LONG TERM...Danco
AVIATION...MWS
CLIMATE...RAH