515
FXUS61 KRNK 030820
AFDRNK

Area Forecast Discussion
National Weather Service Blacksburg VA
420 AM EDT Fri May 3 2024

.SYNOPSIS...
Frontal system over the Ohio and Mid-Mississippi valleys will
move east, bringing clouds, scattered showers, and a few
thunderstorms to our region later today, these showers becoming
more prolific this weekend. Unseasonably warm temperatures today
will transition to somewhat cooler conditions this weekend as
clouds and an easterly wind become established over the forecast
area.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 300 AM EDT Friday...

Key Messages:

1. Continued unseasonably warm today.

2. Increasing clouds today with showers arriving across the
mountains during the afternoon.

3. Scattered showers areawide tonight with isolated
thunderstorms.

A cold front stretches from the Southern Plains into the
western Great Lakes with low pressure centered near Chicago. A
warm front extended east from the low across the northern Mid-
Atlantic. Within the warm sector temperatures were well above
the seasonal norm with both temperatures and dewpoints more like
late spring or early summer.

As we transition through the next 24 hours, the airmass will
get a little more humid as south winds ahead of the approaching
mid-west cold front bring higher dewpoints into the region.
There will be an increase in cloud cover to go along with the
increasing moisture and at some point, early-mid afternoon for
the mountains, we should begin to see development of shower
activity. Models suggest the best chance for showers today will
be west of I-77 from the NC High Country northward through Mount
Rogers and far southwest Virginia, and along and west of the
Appalachian Divide in West Virginia. There may also be some
showers along the warm front north of I-64. To the south and
east of these favored areas, most of the day should remain dry
with temperatures attempting a repeat of yesterday. Forecast
numbers reflect readings well above normal with highs in the
mid-upper 80s for the piedmont and upper 70s to lower 80s for
the mountains.

For tonight, the showers should begin to spill east of the Blue
Ridge with increasing chances as the front to our west gets
closer, in addition to areas to our northeast. As the upper
ridge near the Atlantic coast breaks down, expect warm front to
our north to become a back-door cool front, a northeast to
easterly surge of wind accompanying this feature as it moves
south through the piedmont early tonight. By Saturday morning,
all areas east of the mountains should transition to a cooler
northeast to easterly wind. In spite of the cooling trend,
overnight temperatures will continue to favor the warmer side
of normal.

Thunderstorm threat today and tonight looks minimal. Even with
daytime heating today, CAPE for our forecast area is not
expected to exceed 1000 j/kg. For now will advertise isolated
thunder threat, but nothing severe.

&&

.SHORT TERM /SATURDAY THROUGH MONDAY NIGHT/...
As of 345 AM EDT Friday...

Key Messages:

1) Significantly different weather conditions for the weekend
with cloudy, much cooler, breezy conditions, and with rain
likely through the weekend.

2) Warmer Monday with increasing chances for thunderstorms,

Compared to the past several days of bright sunny and very warm
conditions, the weekend will signal a drastic shift to cloudy,
dreary, damp, breezy, and chilly conditions thanks to a wedge of
cool maritime air flowing into the region from the east
underneath a slowly eastward progressing upper ridge. The cool
low-level wedge will spread west Friday night into Saturday
morning as a short wave from the Ohio Valley spreads east into
the region helping to spread showers and isolated thunderstorms
into the region. The remnant clouds and light precipitation will
be in place as the easterly maritime flow spreads into the area
and becomes firmly established by Saturday afternoon.

Once the wedge becomes established, it will be hard to dislodge
in a hurry thanks to the cloud cover and southwest flow aloft
helping to keep a series of weak disturbances riding over the
shallow surface wedge of cool/damp air which in turn will result
in spotty light rain, showers, and areas of drizzle, especially
along/near the Blue Ridge. Categorical pops are warranted as it
won`t take much with several positive features in place for
rain to generate a few hundredths but only weak dynamics and
limited thermodynamics over the Mid-Atlantic region through the
weekend, precipitation will be light through the weekend and
mostly around 1/2 inch for the two-day period. With this in mind
and after collaboration/discussion with WPC, the "marginal"
risk for excessive rain on Sunday has been removed with the
latest ERO updates.

As we move into Monday, the wedge begins to break down, but
exact timing at this point remains a bit uncertain as surface
winds only gradually veer from east to southeast by Monday and
no real change in the pattern aloft. The main weather player for
Monday appears to be a strong short wave moving into the region
from the west by Monday afternoon. Associated forcing will
likely result in a significant uptick in showers and
thunderstorms Monday afternoon as timing of the short wave looks
to line up well with maximum daytime heating. Intensity of the
thunderstorms will largely depend on how or if the wedge lingers
across the region, but certainly a more bonafide chance for high
rainfall amounts and perhaps even a strong storm or two.

Saturday and Sunday will be dramatically cooler than the 80s of
the past few days. Not only will you want to keep a rain coat or
umbrella handy for the weekend, but you will likely want to have
a light jacket or sweater on hand as well. Temperatures Saturday
and Sunday will be a good 25-30 degrees cooler across much of
the forecast area, especially east of the I-77 corridor where
highs will likely only reach the upper 50s to lower 60s Saturday
and Sunday with cloudy skies, east winds 10-15 mph with some low
end gusts, and sprinkles and drizzle interspersed with periods
of light rain and a few heavier showers. Monday should see
temperatures climbing back closer to the normal 70 degrees for
early May.

/Confidence Levels in Forecast Parameters/
- Moderate to High Confidence in Temperatures,
- Moderate to High Confidence in Precipitation Probabilities,
- Moderate to High Confidence in Wind Direction and Speed,
- Low to Moderate Confidence in Thunderstorm Potential.

&&

.LONG TERM /TUESDAY THROUGH THURSDAY/...
As of 400 AM EDT Friday...

Key Messages:

1) Quite unsettled through the period with scattered to numerous
showers and thunderstorms at times.

2) Can`t rule out an isolated strong to severe thunderstorm
Monday and again on Thursday.

3) Repeated rainfall events increase the chance for minor
flooding issues through the week, but much of the area is below
normal on rainfall after a rather dry April.

4) Temperatures trend back to above normal levels during the
later half of the week.

An increasingly unsettled weather pattern will evolve through
the week as a baroclinic zone settles across the region from the
north with a series of vigorous upper-level disturbances riding
through the southwest to west-southwest flow aloft. With the
wedge finally eroding for the most part Monday, the atmosphere
across the region will also become increasingly unstable. This
combined with improved dynamics increases the chance for
thunderstorms. A strong short wave will track from OH/KY to the
northern Mid- Atlantic Monday bringing the first round of
showers and thunderstorms for the week. While not outlooked,
Brooks-Craven parameters suggest some potential for an isolated
strong to severe storm Monday afternoon. The next short wave of
concern arrives WEd-Thu and appears to be rather potent. Rounds
of showers and thunderstorms are possible with this system and
again there is the chance for locally heavy rain and one or two
strong to severe thunderstorms or two. At this point, there is
too much uncertainty to include in the HWO/gHWO and SPC has not
yet outlooked the region for Day4-Day8.

With dewpoints creeping into the mid 60s during the later half
of the week and high temperatures encroaching on 80-degrees
during the afternoon lower elevations and 70s mountains, it will
feel more like June than early May. Lows at night will remain on
the mild/muggy side mostly in the 60s.

/Confidence Levels in Forecast Parameters/
- High Confidence in Temperatures,
- Moderate to High Confidence in Precipitation Probabilities,
- Moderate Confidence in Wind Direction and Speed,
- Moderate Confidence in Thunderstorm Potential.

&&

.AVIATION /08Z FRIDAY THROUGH TUESDAY/...
As of 300 AM EDT Friday...

Widespread VFR conditions at all terminals this morning, with
VFR expected through most of the day. Cirrus will be on the
increase today with scattered afternoon high based cumulus. At
some point the cumulus may form a lower cloud base with
opportunity for showers later in the afternoon. An isolated
thunderstorm or two cannot be ruled out along and west of the
Blue Ridge.

Showers will gradually overspread the entire region tonight in
addition to a few thunderstorms. Sever weather is not
anticipated, but do expect lowering cloud bases tonight with
transition to MVFR and possibly IFR by daybreak Saturday
morning.

Light/calm winds expected early this morning, becoming south
southwesterly late morning and early afternoon 5-8kts. A
backdoor cold front will introduce a northeast wind across areas
east of the mountains tonight.

Extended Aviation Outlook...

Rain showers and the potential for isolated thunderstorms are
expected through the weekend. This will bring periods of
MVFR/IFR TSRA/SHRA at times. There is also a chance for LIFR
associated with development of easterly upslope wind vcnty of
the Blue Ridge which may impact terminals for Saturday and
Sunday.

Unsettled weather is expected next week. Scattered mainly
afternoon and evening SHRA/TSRA continue Monday and Tuesday with
periods of MVFR ceilings/ visibilities.

Easterly winds this weekend will shift back around to the south
and southwest for Monday and Tuesday.

&&

.RNK WATCHES/WARNINGS/ADVISORIES...
VA...None.
NC...None.
WV...None.

&&

$$

SYNOPSIS...PM
NEAR TERM...PM
SHORT TERM...RAB
LONG TERM...RAB
AVIATION...PM