266
FXUS62 KRAH 201715
AFDRAH

Area Forecast Discussion
National Weather Service Raleigh NC
115 PM EDT Sat Jul 20 2024

.SYNOPSIS...
The combination of a weak nearly stationary front sitting over North
Carolina and Virginia, a very moist air mass in place, and a series
of upper level disturbances tracking southwest to northeast over the
region will bring continued unsettled weather through Tuesday.

&&

.NEAR TERM /TODAY THROUGH TONIGHT/...
As of 945 AM Saturday...

Ongoing forecast looks pretty good. Primary tweak this morning was
to nudge rain chances downward for the next few hours across the N,
following radar trends. A few convective clusters and attendant MCVs
are evident in both radar and satellite imagery over the region this
morning, including one just NW of the Triad in NW NC/SW VA (near and
north of a quasi-stationary sfc frontal zone), one just ENE of ATL
in NE GA, and a third over central AL, with additional budding MCVs-
to-be over and just S of the FL Panhandle. It remains deeply moist
over the area, as noted by layer WV imagery and 12z soundings, the
latter showing PWs near or over 2". A few isolated showers have
popped up this morning in our NE and skirting into our extreme NW,
but otherwise we`re in a brief relative lull attm with the more
organized convection just to our NW and well to our SW. But we
should see an uptick in coverage esp across the S and W later this
morning through the afternoon as the NE GA activity spreads into the
area, coupled with some heating over our area (albeit modest in the
NW half due to high cloud cover there) to support at least scattered
convection outside of the incoming MCV. Will continue to depict pops
trending upward today, first in the S and W but with good chance to
likely pops everywhere at some point. The risk of a few strong to
severe storms persists, given the uptick in deep layer bulk shear
today to 25-35 kts, although the higher shear (mainly NW) may not
spatially coincide with the greatest SBCAPE (mainly SE). Lastly,
have opted to hold off on any kind of flood watch for now, given
that the area most likely to see downpours today was mostly spared
from the heaviest rain yesterday. But HREF probabilities of one or
two inches or more is indeed highest across our N, so will continue
to monitor CAM and radar trends. Highs still expected to range from
around 80 N to the mid 80s to around 90 central/SE. -GIH

Earlier discussion from 356 AM:
The lead MCV which induced stratiform rain over much of central NC
early this morning has shifted off to our east.  Lingering light
rain over northern areas will continue to dissipate through sunrise.
Aloft, a strong short-wave will eject through the Mid-
Atlantic/northeast through tonight. An associated strong mid-level
impulse currently over Alabama/Georgia will ride along the
Appalachians inducing convection across our area this afternoon.

As the short-wave ejects northeastward, increasing mid-level flow
will induce upwards of 25 to 35 kts of shear across the northern
half of our CWA.  As such, a few organized/stronger storms will be
possible this afternoon and evening (primarily over the
Piedmont/Coastal Plain).  Forecasted hodographs are generally
straight and thus any stronger storm that develops would primarily
be capable of producing localized damaging wind gusts. The only
caveat is that some guidance suggests sfc backing of winds could be
possible across the Piedmont/Coastal Plain later today. As such,
there is a non-zero chance for a supercell or a two to develop.
While tornadoes wouldn`t be expected, any mid-level rotation could
overcome poor mid-level lapse rates and promote the potential for
isolated hail. Overall though, the main severe weather potential
today remains localized damaging wind gusts.

Similar to recent days, given the persistent, anomalously moist
airmass, as well as the potential for west-east training cells,
isolated flash flooding will be possible. Best chances for flash
flooding would likely be along the NC/VA border, where due to recent
rainfall, 1 hr FFG is only about 1 to 2 inches.  HREF rain rate
exceedance probabilities peak just north of the border in AKQ`s CWA,
but the actual heavier rain rates could easily slip into our
northeast instead.

Highs will reach the upper 80s to around 90 in the south. Overnight
lows in the lower to mid 70s are expected.

&&

.SHORT TERM /SUNDAY THROUGH SUNDAY NIGHT/...
As of 305 AM Saturday...

The front that is lingering over the region appears as if it should
spend most of the day south of the forecast area. While all
locations still have likely pops in the forecast, did bump up
southern counties to categorical being closer to the focus area of
the front. Highs should again be close to normal, ranging from 85 to
90. Conditions will remain muggy, although even with high humidity
values, temperatures in the 80s should minimize the amount of triple
digit heat index coverage.

&&

.LONG TERM /MONDAY THROUGH FRIDAY...
As of 305 AM Friday...

There is minimal change to the long term forecast. A longwave trough
will extend from Quebec south into the Gulf of Mexico, and warm,
moist advection will persist across much of the eastern United
States. Will continue with likely pops during this time period. In
addition, heavy rainfall rates means that isolated flash flooding
will continue to be a threat across the entire area despite the area
being in a drought. Highs should remain near climatology in the
upper 80s and lower 90s.

&&

.AVIATION /18Z SATURDAY THROUGH THURSDAY/...
As of 115 PM Saturday...

Sct-bkn MVFR clouds persist across central NC, although cigs
continue to lift, and the current pace of this lift would suggest
that all TAF sites will be VFR by 19z. INT/GSO has seen a band of
showers with brief IFR conditions pass over during the last couple
of hours, and while these particular showers are exiting, there is a
chance for additional scattered to numerous showers and storms to
develop through mid afternoon. These are most likely to impact
INT/GSO/RDU first, between 18z and 22z, before reaching RWI within
an hour later as the showers and storms increase in number, and
finally reaching FAY after 22z. Isolated wind gusts over 40 mph will
be possible in and near any storms, along with erratic speeds and
directions and brief sub-VFR cigs/vsbys. FAY will see a trend from
storms to mostly scattered showers overnight, while other sites
should trend to dry weather from mid evening onward. We should see a
redevelopment of sub-VFR conditions, mainly MVFR cigs (except mainly
IFR at INT) with patchy MVFR vsbys after 07z tonight, with the
highest confidence across the W. Cigs will again be slow to rise
Sun, likely not lifting and breaking up to VFR until after 16z.
Surface winds will be under 10 kts and mostly from the SW through
Sun.

Looking beyond 18z Sun, cigs should have lifted to mostly VFR by
18z, however another round of numerous slow-moving showers and
storms is expected across all terminals Sun afternoon through Sun
night. There will be a high chance for showers and storms each day
through Thu, as we stay in a moist and unsettled pattern. The chance
for late-night-through-mid-morning sub-VFR clouds and briefly sub-
VFR vsbys will also continue through mid week. -GIH

&&

.CLIMATE...
Record High Minimum Temperatures:

July 20: KGSO: 75/2019 KRDU: 76/2020

July 21: KGSO: 76/2011 KRDU: 78/1932 KFAY: 80/2017

July 22: KRDU: 78/2011

July 23: KRDU: 78/2011

July 24: KRDU: 79/2011 KFAY: 79/1945

July 25: KFAY: 78/2016

July 26: KGSO: 76/2016 KRDU: 77/2010

&&

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

&&

$$

SYNOPSIS...Hartfield
NEAR TERM...Hartfield/Luchetti
SHORT TERM...Green
LONG TERM...Green
AVIATION...Hartfield
CLIMATE...RAH