-- Discussion containing changed information from previous version are highlighted. --
584
FXUS61 KRNK 050905
AFDRNK

Area Forecast Discussion
National Weather Service Blacksburg VA
505 AM EDT Sun May 5 2024

.SYNOPSIS...
An upper level trough of low pressure is slowly moving across
the Mid-Atlantic region, resulting in mostly cloudy skies,
areas of rain and rain showers, and a few thunderstorms.
Rainfall amounts will be highly variable, with the heaviest
occuring along and east of the Blue Ridge. Daily afternoon
showers and thunderstorms are possible through much of the
upcoming week.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 330 AM EDT Sunday...

Key Messages:

1. Widespread rain east of the Blue Ridge this morning.

2. Cool easterly wind this morning transitions to a warmer
southerly wind this afternoon.

3. Scattered afternoon and evening showers and thunderstorms.

Upper level trough is slowly working its way across the forecast
area. Best lift for widespread rain will occur along and east of
the Blue Ridge this morning...with opportunity for a quarter to
three quarters of an inch of rain before the church bells ring.
Dynamic support becomes more diffuse this afternoon, so think
we transition from stratiform rain to a more showery
environment, rainfall amounts becoming more variable. Breaks in
the cloud cover should lead to warmer temperatures,increasing
CAPE, and a better opportunity for a rumble of thunder. The
easterly low level flow should transition to more of a
southerly flow this afternoon, so look for temperatures to test
70 degrees this afternoon.

Tonight, showers will wane, but lingering moisture will maintain
a good bit of cloud cover along with patchy fog. Most of the fog
that we have been experiencing is coming from the low level
stratus coming in contact with the ground. So in this situation,
the higher elevations have the greater opportunity for fog where
the cloud base intersects the terrain.

&&

.SHORT TERM /MONDAY THROUGH WEDNESDAY NIGHT/...
-- Changed Discussion --
As of 445 AM EDT Sunday...

Key Messages:

1) Warmer temperatures Monday trending to well above normal for
Tuesday and Wednesday.

2) Quite unsettled weather pattern through the period with
scattered showers and a few thunderstorms Monday and Tuesday.

3) Strong to severe thunderstorms possible late Wednesday into
Wednesday evening as a strong cold front approaches from the
northwest.

The wedge of cool/maritime air that has prevailed across the
region this weekend will erode in earnest Monday as ridging
aloft and warmer temperatures aloft spread into the region from
the south. The remnant frontal boundary/baroclinic zone will
lift north closer to the PA/MD...Mason-Dixon line. Most, if not
all of the CWA, will be located within the warm sector.
Precipitation will become less numerous as a result of
increasing subsidence and warm air aloft. However, moisture
content will be abundant with dewpoints creeping into the 60s
across much of the region. Therefore, instability and
thermodynamics will support isolated to scattered showers and a
few thunderstorms both days with the best focus across the
western mountains and along/north of I-64 closer to the frontal
boundary. Temperatures Monday will warm into the 70s west to as
warm as the lower to mid 80s Piedmont.

By Wednesday, the upper ridge will begin to break down as a
broad and persistent upper trough in the central U.S. begins to
progress slowly east. A northern stream short wave diving south
from the Great Lakes will help to deepening the central U.S. low
and also contribute to its eastward progression. The flow aloft
will consequently become much more progressive with a vigorous,
highly kinematic short wave embedded within the flow slated to
track across the region late Wednesday into Wednesday night.
While there remain uncertainties for sure with the timing of
this wave, there certainly appears to be at least some threat
for strong to severe thunderstorms approaching from the west
late Wednesday/Wednesday evening, potentially linger into the
overnight hours, then redeveloping Thursday afternoon along/east
of the Blue Ridge. Again, timing of this event is quite
uncertain at this point and there is definitely the potential
for morning convection/cloud cover Thursday to greatly limit
severe potential for much of the CWA. However, the window for
the strong to severe threat is fairly large stretching roughly
from 18Z Wednesday to 00Z Friday thus resulting in increased
possibilities for some strong to severe activity in parts of
the CWA during this time frame. Both WPC and SPC have noted this
potential as well in their extended outlook products.

Temperatures on Wednesday will be quite warm and rival those of
the warmest day we saw last week with highs in the 85-90 range
outside the mountains and closing in on the 80 degree mark
across the higher terrain in the west above 3000 ft. Warm air
aloft will result in poor lapse rates Wednesday, but as the
upper trough and front approach from the west late in the day,
lapse rates will become more favorable as well as dynamics.

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

&&

.LONG TERM /THURSDAY 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 /09Z SUNDAY THROUGH THURSDAY/...
As of 330 AM EDT Sunday...

LIFR cigs and IFR/LIFR vsbys expected through this morning.
Improvement expected this afternoon as surface winds transition
from easterly to southerly. Widespread rain ongoing east of the
Blue Ridge will transition to scattered showers and
thunderstorms this afternoon and evening. Mean wind aloft is
from the SSW, so expect storm cell movement this afternoon to be
from SW-NE. Probability for thunderstorms is too low to add to
any of the TAFS attm.

Lingering moisture tonight will result in areas of stratus and
fog, so look for cigs to lower again tonight following any
improvement we get this afternoon.

Confidence above average for today, and below average for
tonight. Not sure how widespread the fog and stratus will be
tonight.

Extended Aviation Outlook...

Unsettled weather is expected for much of the upcoming week.
Daily threat of SHRA/TSRA Monday through Thursday. This will
bring periods of MVFR/IFR ceilings and visibilities at times.
Winds Monday through Wednesday will favor a SW direction and
may be gusty at times.

&&

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

&&

$$

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