684
FXUS62 KRAH 061039
AFDRAH

Area Forecast Discussion
National Weather Service Raleigh NC
640 AM EDT Mon May 6 2024

.SYNOPSIS...
An upper level trough and accompanying parade of disturbances will
approach from the west today and will traverse the area this evening
and tonight. A strengthening upper level ridge will bring a period
of unseasonable warm conditions mid week, before a cold front
approaches late in the work week.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 330 AM Monday...

A shortwave trough over the middle MS Valley will deamplify as it
advances eastward, progged to reach the central and southern
Appalachians this evening and then across NC and the mid-Atlantic
States tonight. A weak area of low pressure is expected to develop
over Va during the afternoon and evening, with a surface trough
taking shape in the lee of the mountains. Renewed SWLY moisture
advection ahead of this trough will lead to a resurgence of
anomalous moisture into the region with PWATs 1.6-1.8, near record
daily maximum.

A parade of upper disturbances will move through the region during
the period. And based on upstream radar observations, there is a
high probability that a prominent MCV or two will emerge to support
a west to east moving band of deep moist convection(DC), potentially
multiple bands, through the afternoon and evening.

Compared to previous days, more robust instability of 1000-1500 J/Kg
should develop across the area, likely maximized east of US 1 where
strongest insolation  is expected. Shear will increase slightly,
with models indicating a pocket of enhanced shear of 25-30kts into
western NC late this afternoon and evening. Thus, cannot rule out an
isolated severe cluster or two Monday afternoon and evening. As
we`ve seen the past few days, the anomalous high moisture in place
will also support an isolated flooding threat, primarily in urban
and poor drainage areas.

Rain chances should decrease by the late evening, though some
lingering isolated convection overnight owing to the dampening upper
trough moving through the region.

Highs ranging from upper 70s/near 80 north to lower/mid SE. Lows in
the lower to mid 60s.


&&

.SHORT TERM /TUESDAY AND TUESDAY NIGHT/...
As of 330 AM Monday...

The aforementioned dampening trough will move off the mid-Atlantic
coast during mid to late morning. Synoptic scale subsidence will
overspread the area in it`s wake, with a westerly downslope
component noted over the area. However, moisture/PWATS will remain
exceptionally high as strong insolation fuels moderate instability
during the afternoon. Discernible forcing is weak, limited to
daytime heating, weak sfc convergence along a lee side trough across
the area, and quite possibly a subtle upper perturbation with the
back/anticyclonic side of the exiting trough. If storms do develop,
sufficient deep layer shear of 30-35 kts could support an isolated
severe storm, with damaging winds the primary threat. Warmer with
highs ranging from mid 80s north to upper 80s/near 90 south.


Convection will dissipate after sunset. Lows 65-70.


&&

.LONG TERM /WEDNESDAY THROUGH SUNDAY/...
As of 250 AM Monday...

The extended continues to focus on the potential for heat Wed/Thu,
but more importantly the threat of severe weather Wed/Thu. Drier
weather looks favored for the weekend, along with temperatures near
to below normal.

Wed will feature weak ridging aloft transitioning to WSW flow. A
trough over the Plains and Upper MS valley will aid perturbations
tracking across the TN valley and Carolinas in the late afternoon
and evening/overnight. A broad SW flow will exist at the surface,
with a lee trough during the day. With rising thicknesses,
temperatures should rise into the upper 80s to lower 90s. Dewpoints
in the upper 60s to low 70s will result in heat indices in the
mid/upper 90s in the Triangle/Sandhills. While there is no clear
discernible boundary on Wed, broad 850-700 mb WAA coupled with a
surface low moving into the OH valley as a cold front reaches
western TN will aid impulses of energy tracking through in the SW
flow. The Carolinas look to be on the nose of the left-exit region
of a jet streak over SC. This pattern should favor the chance of
disorganized showers/storms both Wed aftn across the south and Wed
night along/north of US-64. Coverage and location is difficult to
determine thus far in the WAA flow, but some storms could be severe
with models showing 1500-2000 J/kg of MLCAPE, DCAPE over 1000 J/kg,
and 25-30 kt of shear, supportive of a hail/wind threat.

Thu/Fri: Thu still looks warm in the mid 80s to low 90s, warmest in
the Sandhills to Coastal Plain, but the main concern is the severe
risk. Deterministic and ensemble data, including the CSU/CIPS severe
analogs, continue to highlight a consistent severe potential Thu
aftn/eve. The low pressure from Wed (over OH valley Thu) is forecast
to bring a strong cold front through the area as early as Fri
morning. Ahead of the front, increasing SW flow aloft will combine
with moisture-rich air with low 70s dewpoints to promote another
round of showers/storms. Models appear to depict a line of storms
tracking east from eastern TN/western NC in the aftn/eve, though
early morning convection from Wed night could complicate things. The
environment ahead of the storms shows upwards of 2000 J/kg of MLCAPE
and 2500 J/kg of SBCAPE, along with low/deep layer shear favorable
for all hazards. We will continue to monitor this as we get closer,
but it appears models are honing in on the best severe potential on
Thu/Thu night. Some recent model/ensemble trends has been for the
cold front to move through early Fri, shunting the severe/storm risk
south/east of the area. However, a few ensemble members from the
GEFS/EPS/GEPS still show the front held up over the Carolinas, so we
kept low chance PoPs for Fri aftn.

Sat/Sun: A drier pattern is still looking favored for the weekend as
a WNW flow takes over at mid-levels with troughing over the Mid-
Atlantic. However, some ensemble solutions show energy building back
in for Sun with troughing over the Midwest/OH valley. For now, have
leaned on a drier forecast until there is better model agreement.
Temperatures will be more seasonal to slightly below normal with mid
to upper 70s and humidity much more bearable with dewpoints in the
40s to low 50s.

&&

.AVIATION /11Z MONDAY THROUGH FRIDAY/...
As of 640 AM Monday...

24-hour TAF period: The widespread LIFR and IFR restrictions in low
clouds will lift to MVFR and then VFR from south to north through
the morning and into the early afternoon, slowest  lowest to improve
in the Triad.

Scattered to numerous showers and storms are expected to develop
from late morning on, with some TAF sites potentially experiencing
multiple rounds of storms and restrictions through the late evening.
Widely scattered showers could linger well into the overnight hours
with the continued moist airmass likely to support the re-
development of IFR to MVFR restrictions between 06 to 12z.

Outlook: Rain chances decrease for Tuesday and Wednesday with
showers and storms more isolated/widely scattered in nature.
However, storm coverage coverage should increase on Thursday. With a
moist airmass in place, areas of fog and stratus are possible on
Tuesday morning with reduced chances during mid week.

&&

.CLIMATE...

Record High Minimum Temperatures:

May 8: KGSO: 66/1938 KRDU: 68/1930 KFAY: 70/2003

May 9: KGSO: 68/2002 KRDU: 70/1936 KFAY: 71/2009

&&

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

&&

$$

SYNOPSIS...CBL
NEAR TERM...CBL
SHORT TERM...CBL
LONG TERM...Kren
AVIATION...CBL
CLIMATE...RAH