National Weather Service Area Forecast Discussion
567
FXUS61 KRNK 050028
AFDRNK
Area Forecast Discussion
National Weather Service Blacksburg VA
828 PM EDT Sat May 4 2024
.SYNOPSIS...
An upper level trough of low pressure will move across the Mid-
Atlantic Region through Sunday, resulting in mostly cloudy
skies, widespread showers, and a few thunderstorms. Rainfall
amounts will be highly variable, ranging from a quarter of an
inch, to more than an inch. Temperatures rebound into the 70s
for Sunday. Daily afternoon showers and thunderstorms are
possible through the week.
&&
.NEAR TERM /THROUGH SUNDAY/...
As of 815 PM EDT Saturday...
For the near term update this evening, expecting areas of light
rain and showers to continue through much of the overnight as
strong isentropic upglide overrides the CAD wedge. Any
attainable instability should be mainly confined to the south
and west of the CWA so there is no thunder mention through
tonight. Areas of fog should also develop across much of the
area. Not expecting much dense coverage but there could be some
spots that bounce around the 1/4 SM vsby at times. Forecast
largely on track and previous discussion follows...
As of 200 PM EDT Saturday...
Key Messages:
1. Isolated thunder possible mainly for western and southern
sections of the forecast area this afternoon/evening.
2. Rainy and foggy conditions continue, with a large area of
rain moving through tonight.
3. Wedge of cool/damp air begins to erode slowly on Sunday with
scattered showers and thunderstorms.
Scattered to numerous rain showers continue through this
evening. The eastern portion of our VA counties were embedded
in a wedge of high pressure supported by easterly surface winds.
This was keeping temperatures cool and thunderstorms out of
that region. The western side of the wedge was bounded by a
warm/backdoor front, and to the west of this we were seeing
heavier showers and an uptick in thunderstorms this afternoon.
The western edge of the forecast area will see the best chance
for thunder where there have been breaks in cloud cover.
Elsewhere, the wedge stays in place and will keep the weather
damp and foggy. Tonight, isentropic lift increases as moisture
rides over the wedge ahead of a short wave, as does
frontogenesis associated with the residual warm/backdoor front.
This will culminate in a large area of stratiform rain moving
from the Deep South north towards the Mid Atlantic.
As this occurs, PWATs will hover around 1.5 inches, and warm
cloud depths will reach 10 kft. A LLJ of about 20 to 25 kts and
slow storm motion will support training and urban and small
stream flood concerns. So far, precipitation amounts have varied
widely, but southern and southeastern sections of our area have
seen close to an inch or more. These locations will be monitored
for flood/flash flooding potential. As this large slug of rain
moves out in the morning, the wedge of cool air begins to
retreat to the northeast. Tomorrow`s rain and thunderstorm chances
look more widely scattered and centered on the higher terrain.
Temperatures should rebound somewhat in southerly flow tomorrow,
reaching the upper 60s to mid 70s.
Confidence in the near term is moderate.
&&
.SHORT TERM /SUNDAY NIGHT THROUGH TUESDAY NIGHT/...
As of 130 PM EDT Saturday...
Key Messages:
1. Warming trend in temperatures for beginning of the week.
2. Chances for showers and storms each day.
Rain and thunderstorm chances continue each day through this
short term period of the forecast as a front stalls to the
north and west of the area. Late Monday, a 500mb shortwave rides
over the ridge and provides some additional upper forcing for
ascent over the area, which could result in some showers and
storms. The surface front lifts northward Tuesday, putting the
area in a broad warm sector, with the surface low still over the
north central US, bringing in warmer air and more moisture.
With the front moving farther from the area early Tuesday,
expecting more breaks in the clouds than on Monday, and so
daytime heating will increase the instability over the area
later in the day, and will lead to showers and thunderstorms
again Tuesday afternoon.
Weak ridging at 500mb will spread over the southeast US and Mid
Atlantic into the beginning of the work week. Increasing heights
will lead to a warming trend in temperatures through Tuesday,
with increasing positive 850mb temperatures anomalies through
the middle of the work week. High temperatures will gradually
increase from the low 70s to upper 70s in the west, near 80 to
mid 80s in the east, through Tuesday. Lows will be mild, in the
mid to upper 50s in the west and low 60s in the east.
&&
.LONG TERM /WEDNESDAY THROUGH SATURDAY/...
As of 200 PM EDT Saturday...
Key Messages:
1. Showers and storms possible each day, highest probability
Thursday.
2. Warming temperatures through Wednesday, cooler for the
weekend.
Mid level ridging builds back in over the southeast and Mid
Atlantic in response to a trough deepening over the central
US. This keeps broad southwesterly flow at mid levels over the
area into the second half of the work week, but slowly
flattening and becoming more zonal into the weekend, as the main
500mb low tracks across southern Canada. A surface low pressure
system moves eastward across the Great Lakes by Thursday, with
a cold front extending south and another boundary extending
west-east across the upper Mid Atlantic. With this increased
large scale forcing, probabilities for thunderstorms are highest
on Thursday. Deterministic long range models show some
differences in the timing of the actual frontal passage, some
bringing it through the area late Thursday and others not until
Friday, which brings some uncertainty into duration of
precipitation with the front.
The warming trend in temperatures will continue through the
middle of the work week. Rain and cloud cover will keep
Thursday a couple degrees cooler as well, but not quite as cool
as the weekend, as a cooler and drier airmass settles into the
area behind the front.
&&
.AVIATION /00Z SUNDAY THROUGH THURSDAY/...
As of 820 PM EDT Saturday...
Most sites should stay with LIFR cigs and IFR/LIFR vsbys (possibly
lower) through the overnight along with areas of RA/SHRA and
possible fog. There could be a lull in precip coverage Sunday
morning after sunrise though the low cigs and vsbys could
continue through much of the morning with eventual improvement
after about 17/18z (perhaps sooner for the western sites). TSRA
chances could increase for Sunday afternoon but coverage of
precip overall should be less than today. Winds initially east
to SE under 10 kts then mainly shift more south to SW/west
during the day Sunday.
Extended Aviation Outlook...
SHRA/TSRA with periods of BR yielding MVFR/IFR/LIFR conditions
continue through Sunday evening. More diurnally driven -SHRA/TSRA
are expected Monday through Wednesday. This will bring periods
of MVFR ceilings and visibilities at times. Winds Monday through
Wednesday will be SSW and gusty at times.
&&
.RNK WATCHES/WARNINGS/ADVISORIES...
VA...None.
NC...None.
WV...None.
&&
$$
SYNOPSIS...PM/SH
NEAR TERM...SH/AB
SHORT TERM...AS
LONG TERM...AS
AVIATION...SH/AB
NWS RNK Office Area Forecast Discussion
