388
FXUS61 KAKQ 211017
AFDAKQ

AREA FORECAST DISCUSSION
National Weather Service Wakefield VA
617 AM EDT Fri Jun 21 2024

.SYNOPSIS...
High pressure off the Mid Atlantic coast slowly shifts south
through the end of the week, leading to an extended period of
hot weather this weekend and again next week. There is a small
chance for rain Sunday evening into Monday, and again on
Thursday, but many places will stay dry.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 615 AM EDT Friday...

Key Message:

- Remaining dry and very warm today. High temperatures will inch up
a few degrees compared to the previous few days.

The ongoing stretch of dry and seasonably warm weather continues
today. At the surface, the synoptic pattern will be dominated
by offshore high pressure that will be slowly drifting south.
Aloft, the flow is very weak with a ~596dm ridge centered over
TN. Low- level thickness values and 850 mb temps inching up a
few degrees support highs 3-5 deg F higher than the previous few
days. With mainly weak southerly flow, still expecting some
degree of sea breeze development this afternoon. This will keep
coastal localities a few degrees cooler (upper 80s/low 90s) than
those inland (mid 90s). Dew points will again drop off into the
low- mid 60s this afternoon owing to BL mixing. Thus, the
humidity will keep the heat index in check with heat indices
very similar to the air temp. Skies stay sunny or mostly sunny
through the day. Overnight lows also inch up a few degrees and
look to be in the upper 60s or lower 70s (warmest in the urban
corridors and near the coast).

&&

.SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/...
As of 330 AM EDT Friday...

Key Messages:

- Hot temperatures expected Saturday and Sunday with maximum
temperatures both days in the mid/upper 90s to around 100 F.

- Highest heat indices (105+ F) expected Sunday, with heat
advisories probable for most of the area.

The hottest temps are still expected Saturday and Sunday. On
Saturday, the high pressure system will shift further offshore to
our SE. This will shift the sfc flow to the SSW. While the ridge
gradually begins to break down, 850 mb temps of 20-23C will be
common across the area. This yields highs in the upper 90s to around
100 F inland and mid 90s closer to the coast. In fact, most of the
recent guidance suggests Saturday may end up being the day with the
hottest air temperatures. The one thing to stress is that dew points
again look to mix out into the mid 60s (some guidance even suggests
lower 60s). This will again act to mitigate excessively high heat
indices. At this time, the heat index looks to peak in the 100-104 F
range Saturday. Still cannot rule out a marginal heat advisory for
parts of the area, but this is looking quite unlikely as of now.
Overnight lows in the mid-upper 70s will not provide much relief
from the heat.

The core of the heat is expected to shift SE some for Sunday, though
hot temps will remain over the entire forecast area with 850 temps
remaining in the 20-23C range. Recent trends in the guidance
(including the NBM) have been for slightly "cooler" highs and higher
afternoon dew points. Probabilities from the NBM for 100 F have
generally dropped by 20-50% compared to the previous forecast
packages. Will continue to reflect highs in the upper 90s for most
of the area, with temps around 100 F still probable around the
Richmond metro and surrounding I-95 corridor. The higher dew points
are in response to increasing moisture with strengthening
southwesterly sfc flow. The flow aloft also shifts more W/WSW and
700 mb RH fields show a noticeable increase in moisture across the
area. This is likely to prevent the degree of afternoon mixing seen
today (Fri) and Saturday. In this realm, dew points only drop into
the upper 60s-low 70s in the afternoon, producing heat indices well
into heat advisory range (105-110 F) for most of the area. While a
few locations could near 110 F, not enough confidence at this point
for any excessive heat watches. Wet bulb globe temperatures (WBGT)
in the upper 80s to around 90 also suggest the potential for
significant heat stress for those outdoors and especially those
participating in strenuous activities. Sun night lows will remain
very mild and in the 70s.

The other part of the forecast Sunday is any potential for later
afternoon/evening convection. Those higher dew points support higher
sfc-based instability and upper-level height falls from an
approaching shortwave could set off isolated storms, especially
later in the day. With the hot temps, steep low-level lapse rates
and high DCAPE could support a damaging wind threat if any storm can
develop. SPC has introduced a marginal risk for our northern tier of
counties. Shear is weak so not expecting much in the way of
organized svr wx. With uncertainty in coverage very high, PoPs are
only 10-20% for the area. Will want to keep an eye on the various
CAMs as they come into range over the next 24-36 hrs. A weak cold
front slowly pushes through the area Sun night suggesting perhaps
some higher coverage of showers or storms. Have chance PoPs for most
of the area overnight (highest coverage expected N). Still, this
does not look to be a widespread beneficial rainfall to alleviate
the developing drought over the area.

&&

.LONG TERM /MONDAY THROUGH THURSDAY/...
As of 330 AM EDT Friday...

Key Messages:

- Another hot day Monday with higher humidity. Scattered storms
also possible across the southeast.

- The heat builds again midweek, with temperatures again increasing
well into the 90s to near 100.

- Flash drought conditions developing.

It remains hot Monday, but air temps will not be as high as Sat/Sun.
However, the humidity levels will be even higher as dew points stay
in the low-mid 70s for most of the area. Heat indices of 100-105 F
are expected for most of the area, though SE VA and NE NC could near
heat advisory criteria (105 F). The one caveat is potential
afternoon convection developing along the "cold" front in these same
areas which could mute the upper end temp potential. As of now,
going with highs in the mid 90s areawide. Regarding convection, most
guidance is honing in on ern VA and NE NC for thunderstorms and will
continue high-end chance PoPs here (likely PoPs along the Albemarle
Sound). Little to no coverage is expected W of I-95 with the frontal
boundary E/SE of these areas, though will maintain a 20% PoP there
in case models trend slower. Model instability fields show high
MLCAPE (2000+ J/kg) ahead of the boundary. Weak shear will again
prevent much in the way of storm organization, though the high CAPE
and DCAPE again suggests damaging downburst winds and frequent
lightning as potential threats.

The cold front does very little to provide any heat relief as temps
Tuesday remain in the low-mid 90s. Even hotter Wednesday and we
again could be talking about temps nearing 100 F. This ultimately
makes sense given the downslope NW flow and still warm 850 mb temps
around 21-24C per the 00z/21 GFS. It will be drier, however, with
dew points perhaps dropping back in the mid 60s as compared to the
low-mid 70s seen on Monday. By Thursday, another cold front
approaches from the NW and will continue chance PoPs for the area,
favoring the higher coverage across the S and SE. While this front
looks to have a little more moisture to work with, the chances for
widespread rainfall remain low. Temps may drop back into
mid/upper the 80s to end the week.

On that note, it continues to not look promising for widespread
rainfall, as many places will see little to no rain through the
period. The latest NBM probabilities are not optimistic either with
the probability for at least 0.50" of total rainfall through the
midweek period 10-20% across the W/NW and 30-50% across the E/SE.
This will only exacerbate the recent dry conditions and set us up
for what can be considered a "flash drought". More information on
this can be found on CPC`s Probabilistic Hazards Outlook page at
www.ncep.cpc.noaa.gov or drought.gov.

&&

.AVIATION /10Z FRIDAY THROUGH TUESDAY/...
As of 615 AM EDT Friday...

VFR is expected all of today and through most of the weekend.
Noting some very patchy ground FG/BR this morning, but vsbys
are mainly MVFR or greater. Either way, expecting this to remain
away from the terminals and dissipate shortly after sunrise. A
few CU may develop this aftn, but most areas stay sunny. Light
S/SSW winds this morning become S/SSE 5-10 kt this aftn. Winds
could briefly become 10-15 kt at ORF as the sea breeze becomes
established. Light S flow continues tonight w/ generally SKC.

Outlook: Dry and VFR conditions are expected to prevail through
Sunday afternoon as high pressure remains centered off the
coast. There is a low chance for some isolated to widely
scattered storms Sun evening and again Mon afternoon into Mon
evening.

&&

.MARINE...
As of 330 AM EDT Friday...

Key Messages:

- Sub-SCA marine conditions expected through Saturday morning.

- An elevated southerly wind is forecast to develop late Saturday
through Sunday night. The best chance for SCA conditions is later
Sunday afternoon into Sunday night.

- Moderate rip current risk at all areas beaches continues Friday.
At least a moderate risk continues through the weekend.

High pressure remains centered off the Mid-Atlantic coast early this
morning. The wind is primarily S 5-10kt and locally S 10-15kt in the
middle Ches. Bay. Seas range from 3-4ft S to 2-3ft N. High pressure
remains centered off the coast today into tonight. The wind will
mainly be S to SE 5-10kt this morning into early aftn. A SSE wind is
expected to increase to ~15kt with gusts up to 20kt for the Ches.
Bay and ocean N of Cape Henry later this aftn and evening, and 10-
15kt elsewhere. By later this evening and into tonight the wind is
expected to become SW and diminish to 8-12kt. Seas are expected to
be ~3ft today into tonight, with 1-2ft waves in the Ches. Bay, which
will briefly build to 2-3ft with the late aftn/evening diurnal
increase in wind.

High pressure settles off the Southeast coast Saturday into Sunday.
A SSW wind will generally be 5-10kt Saturday morning into early
aftn, with a late aftn/early evening diurnal shift to SSE and
increase to ~15kt for the Ches. Bay and ocean N of Cape Henry (10-
15kt elsewhere). Seas build to 3-4ft N (mainly 2-3ft S) with waves
in the Ches. Bay building to 2-3ft with the diurnal shift and
increase in wind. A weakening cold front slowly approaches from the
NW later Saturday night through Sunday night. A SW wind potentially
increases to 15-20kt for the Ches. Bay and northern ocean later
Saturday night into early Sunday, with marginal SCA conditions
possible in the Ches. Bay. The pressure gradient tightens over the
ocean Sunday aftn/evening with a ~20kt SSW wind possible, which
could result in seas building to 4-6ft N of Cape Charles later
Sunday aftn into Sunday night. Additionally, a SW wind potentially
increases to 15-20kt for the Ches. Bay Sunday night with marginal
SCA conditions possible. The pressure gradient slackens Monday into
Tuesday as the weakening cold front settles into the area and washes
out. High pressure rebuilds offshore by the middle of next week with
sub-SCA southerly flow returning. Seas will mainly be 2-3ft Monday
into the middle of next week with 1-2ft waves in the Ches. Bay.

Rip currents: A moderate rip risk will continue today for all
beaches with some SE swell ~3ft with ~8s periods. An elevated rip
risk likely continues through the weekend. Confidence of moderate is
higher for the northern beaches Saturday and Sunday, but southerly
flow and a longshore current may preclude a high risk.

&&

.AKQ WATCHES/WARNINGS/ADVISORIES...
MD...None.
NC...None.
VA...None.
MARINE...None.

&&

$$

SYNOPSIS...SW
NEAR TERM...SW
SHORT TERM...SW
LONG TERM...SW
AVIATION...SW
MARINE...AJZ