-- Discussion containing changed information from previous version are highlighted. --
227
FXUS61 KRNK 030803
AFDRNK

Area Forecast Discussion
National Weather Service Blacksburg VA
403 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/...
-- Changed Discussion --
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 chance 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. The
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 gets into place, 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.
-- End Changed Discussion --

&&

.LONG TERM /TUESDAY THROUGH THURSDAY/...
As of 130 PM EDT Thursday...

Key Messages:

1) Confidence is moderate for ongoing chances of showers and
thunderstorms each day.

2) Temperatures will trend warmer as the week progresses.

With a stalled frontal boundary draped across the Mid Atlantic,
several waves of low pressure will track eastward to bring a
daily chance of showers and thunderstorms. Some upper level
ridging should occur by the middle of the week, which will push
temperatures above normal but fuel more instability for
convection. Deciphering which days will be the most active for
showers and thunderstorms remains difficult due to the subtle
timing differences of these waves of low pressure in the models.
The frontal boundary may budge northward as a warm front
towards Tuesday and Wednesday. Even though a cold front may
arrive by Thursday, there does not appear to be any appreciable
change in the air mass to end this unsettled pattern.

&&

.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