-- Discussion containing changed information from previous version are highlighted. --
874
FXUS62 KRAH 230653
AFDRAH

Area Forecast Discussion
National Weather Service Raleigh NC
255 AM EDT Sun Jun 23 2024

.SYNOPSIS...
A weak upper level trough will move across the Mid Atlantic region
through the rest of the weekend. A stronger trough and accompanying
surface cold front will cross North Carolina Monday and Monday
night. The front will then weaken and dissipate over the Carolinas
through mid week.

&&

.NEAR TERM /TODAY THROUGH TONIGHT/...
-- Changed Discussion --
As of 225 AM Sunday...

Another day of anomalously hot weather along with increasing
humidity will be the main weather story today. A heat advisory will
be issued for today for central and eastern portions of central NC.

We will remain within a hot and increasingly muggy air mass today,
with low level thicknesses forecasted to be 3-5 m higher than
yesterday morning. Strong mid level ridging centered over the Desert
Southwest and Southern Plains continues to extend eastward into the
Southeast, although by tonight we`ll start to see the influence of
potent northern stream shortwave troughing shifting through the
Great Lakes region, reflected at the surface by a cold front that
will drop SE through MI into the Ohio Valley by this evening. After
areas of stratus mainly across the S and E early this morning burns
off, we should see a period of considerable sunshine lasting well
into the afternoon. Our deep layer shear will be quite low and our
PW initially rather modest with limited CAPE due to the mid level
warmth, however we will have increasing PW late in the day to near
2" which should support isolated storms this afternoon into early
evening despite the lack of a definitive focus, other than perhaps
an inland-moving sea breeze and/or subtle differential heating
boundaries. Coverage may be slightly better in the far NE where deep
layer shear and surface heating may be a bit higher.

Regarding the heat, while we will see a good SSW/SW breeze today and
the forecast heat index is slightly lower than what we`ve typically
seen prompting a heat advisory, several other factors exist which
support a need for an advisory. These include the successive days of
hot weather (RDU and FAY saw highs on 6/21-22 of 96/98 and 94/96,
respectively, with mid-upper 90s expected again today); increasingly
warm lows (low-mid 70s this morning and solidly mid 70s tonight)
that make it difficult to cool off and exacerbate the heat illness
threat; and the exceptionally high HeatRisk for much of central NC,
which factors in the above (warm lows + long duration of heat) along
with the temps being unusually high for this time of year and the
correlation to high impacts (high observed heat mortality under such
conditions in the past). After coordination with neighbors, will
issue a heat advisory for much of our central and eastern areas. The
only spots with lower confidence is our far SE, where a sea breeze
could cut temps back slightly during the late afternoon, but they
should still have a few hours of high heat index there. Expect highs
of 92-98 and a peak heat index of 96-104.

With loss of heating further cutting down an already-meager CAPE,
any isolated to scattered storms should dwindle by mid evening,
leaving low pops overnight and a chance of stratus mainly across the
NE. Lows in the mid 70s. -GIH
-- End Changed Discussion --

&&

.SHORT TERM /MONDAY AND MONDAY NIGHT/...
-- Changed Discussion --
As of 255 AM Sunday...

Mon will still be fairly hot across our SE, however we will start to
see some relief especially across the N and W. The potent shortwave
trough tracking over the western St Lawrence Valley late tonight
will continue to push E into the Northeast states Mon, resulting in
slight cooling aloft and a strengthening cyclonic mid level flow
over NC, which will take the cold front SE through much of the CWA
during the afternoon and early evening. Mid level lapse rates will
be 1-1.5 deg C higher than today, with improving upper divergence
over E NC, although strong prefrontal heating and possible deep
mixing may limit SBCAPE a bit. PW is expected to be aoa 2" over the
E (along and E of Hwy 1), so expect at least scattered to numerous
showers and storms, mostly in the SE Coastal Plain. Expect highs in
the low 90s NW and mid to isolated upper 90s SE. Pops should push to
our SE in the evening, with dry weather overnight as NW low level
flow takes over and draws in lower surface dewpoints post-front.
Lows in the mid 60s to lower 70s with clearing skies. -GIH
-- End Changed Discussion --

&&

.LONG TERM /MONDAY THROUGH SATURDAY/...
As of 330 PM Saturday...

A long stretch of hot temperatures, ~5-10 F above average and in the
90s, will result throughout the forecast period, though seasonable
to seasonably low surface dewpoints/humidity values will
regulate/temper Heat Index values until at least Wed.

A nrn stream shortwave trough/compact closed cyclone now centered
over srn Saskatchewan will amplify modestly while progressing sewd
and across the Great Lakes through this weekend, then across and
offshore the Middle Atlantic Mon-Mon night. Glancing and weak (10-20
m/12 hr) mid-level height falls, and the passage of a surface cold
front, will result over cntl and ern on Mon. Scattered convection
will accompany the front, with the relative greatest concentration
from the Coastal Plain to the coast.

Shortwave ridging and marked mid-level drying and warming will
follow and expand across the srn Appalachians and Carolinas Tue-Tue
night, during which time weak high pressure and dry but still hot
conditions will build across the srn Middle Atlantic.

A couple of additional shortwave perturbations are otherwise
forecast to migrate ewd and across the Canada/US international
border and Great Lakes mid-late week and support an associated weak
cold frontal passage across the srn Middle Atlantic late Thu-early
Fri. Low-level moisture/humidity will increase ahead of the front
and favor a renewed, ~30-50% chance of diurnal convection Wed and
especially Thu.

A broad and strong mid-level high/ridge will then restrengthen from
the srn Plains and Southeast to the w-cntl Atlantic through next
weekend. A related surface high will expand from the cntl Atlantic,
near and east of Bermuda, wwd and across the South Atlantic states,
while an Appalachian-lee trough will extend across the srn Middle
Atlantic Foothills/wrn Piedmont. The presence of the ridge and
warming aloft should tend to keep the chance of diurnal convection
near or slightly below climo probabilities (~20-30%).

&&

.AVIATION /06Z SUNDAY THROUGH THURSDAY/...
As of 111 AM Sunday...

The main aviation concern early this morning remains the good chance
for MVFR stratus across our SE 09z-13z this morning, highest
confidence at FAY and just slightly lower chances at RDU/RWI, where
the stratus may be more patchy and/or more short-lived. INT/GSO have
an even lower, but non-zero, chance of MVFR stratus for an hour or
so this morning. Any sub-VFR cigs are likely to lift and burn off by
13z, leaving VFR conditions through tonight, with high clouds
increasing from the NW late in the period. Isolated storms are
possible mainly this afternoon, however coverage should be low and
the risk at any given TAF site is too low to include at this time.
Surface winds will be from the SSW or SW, light until 13z then 10-14
kts gusting to 16-19 kts until 23z, then light from the S or SSW
tonight.

Looking beyond 06z Mon, there is a chance of some sub-VFR stratus
mainly across NE sections of central NC early Mon morning, mainly
affecting RDU/RWI. An approaching cold front will bring a good
chance of showers and storms mainly in the E (RDU/RWI/FAY) Mon
afternoon into early evening. Expect mostly dry weather late Mon
night through Tue night with VFR conditions. Isolated late day
storms are again possible mainly west Wed, followed by a better
chance of afternoon/evening showers and storms Thu. -GIH

&&

.CLIMATE...

-- Changed Discussion --
Record High Temperatures:

June 23:
KRDU: 100/1986

June 24:
KRDU: 99/2010
KFAY: 102/1914

June 25:
KRDU: 100/1952
KFAY: 102/1914

June 26:
KRDU: 102/1952
KFAY: 101/1951

June 27:
KFAY: 102/1998


Record High Minimum Temperatures:

June 23:
KGSO: 74/2015
KRDU: 77/1890
KFAY: 77/2017

June 24:
KGSO: 76/2015
KRDU: 76/1888
KFAY: 79/2010

June 25:
KFAY: 75/1952

June 26:
KGSO: 74/2010
KRDU: 76/1902
KFAY: 76/1997

June 27:
KGSO: 76/1969
KRDU: 76/1952
KFAY: 77/1998

June 28:
KGSO: 76/1969
KRDU: 76/1952
KFAY: 78/1914
-- End Changed Discussion --

&&

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

&&

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