733
FXUS61 KRNK 292320
AFDRNK

Area Forecast Discussion
National Weather Service Blacksburg VA
720 PM EDT Wed May 29 2024

.SYNOPSIS...
Cold front pushes to the coast tonight. Dry and cooler high
pressure will build in for Thursday and Friday with below
normal temperatures. The next chance of rain will be late this
weekend.

&&

.NEAR TERM /THROUGH THURSDAY/...
As of 710 PM EDT Wednesday...

Key message:

   - Lowered pops this evening and cut back on fog.

Precip is mainly isolated and confined to north of a line from
BKW-LWB-SHD. Should see showers fade by late evening though
could see some linger toward western Greenbrier til around
midnight.

As we head through the late night may see some ground fog where
it rained or possibly along rivers, but opposing factors will
be the drier air working in along with some wind, so for now
backing off on fog in the forecast from previous forecast.

Previous discussion

MSAS and LAPS analysis of Lifted Index and CAPEs showed the
greatest instability from Lynchburg northeast into northern
Virginia. The areal coverage of showers and thunderstorms will
be in that area this afternoon and evening, but much of the rest
of southwest Virginia, northwest North Carolina and southeast
West Virginia will have a lower probability of precipitation
until the front crosses through the upper short wave axis moves
to the east. As of 18Z/2PM the front was over the mountains.
Model guidance had the front and associated upper lift near the
East Coast by midnight.

A bulk of the showers and thunderstorms will dissipate with the loss
of lift and heating by late this evening. Some upslope cloud cover
is possible along the western slopes of the central Appalachians.
Also expecting fog formation overnight in the mountain and
river valleys. Similar to Wednesday morning,the fog will be
shallow and dissipate quickly Thursday morning.

850MB temperatures drop into the +6 to +8 range overnight. Winds
will stay mixed for much of the evening and a low level jet of 40 to
50 knots over the southern Blue Ridge will keep gusty winds at
higher elevations. As high pressure moves closer to the area on
Thursday, wind speeds will diminish and drier air will cover much of
the region.

Another well-defined short wave tracks out of the Great Lakes and
across the Mid Atlantic region Thursday. Models were very limited
with any precipitation, but will not rule out an isolated shower in
the afternoon.

&&

.SHORT TERM /THURSDAY NIGHT THROUGH SATURDAY NIGHT/...
Issued at 240 PM EST Wed May 29 2024

Key Message:

- Generally quiet weather and below normal temperatures expected
  through the end of the week.

The big story for the end of the week will be below normal
temperatures for early June. An upper-level trough should gradually
move eastward across the Mid-Atlantic and Northeast U.S. through the
end of the week. As this occurs, a surface high will be pushed
across the region. With a northerly flow through the boundary layer,
continued low-level cold air advection will continue through the end
of the week, as weak perturbations continue rounding the base of the
upper trough. This, combined with a continued dry airmass, will
allow below normal temperatures to be seen.

Deterministic guidance for this period remains on the lower end of
the statistical guidance spectrum during this period, with most
values appearing to hover between the 10th and 25th percentile. This
is true especially for overnight lows. Based on everything I`m
seeing, I plan on going below the guidance mean for temperatures
this afternoon. In other words, we`re already doing this in the
forecast and I see no reason to buck the trend. It looks like the
coldest night will be Thursday night/Friday morning.

The upper trough axis should shift offshore Friday night, allowing
shortwave ridging to build into the region from the west. While we
still might see a weak north to northeast low-level flow heading
into the weekend, temperatures will begin to moderate. By the time
Saturday rolls around, winds should become southerly as the surface
high shifts east of our area. With low-level moisture increasing,
expect more cloud cover to join the slowly warming temperatures.

&&

.LONG TERM /SUNDAY THROUGH WEDNESDAY/...
Issued at 245 PM EST Wed May 29 2024

Key Messages:

- Precipitation probabilities return to the forecast area.

- Temperatures return to near normal levels for early June.

An atmospheric disturbance is forecast to move from the Upper
Midwest into the Great Lakes Sunday. There should be some flattening
of the upper-level flow in response, with the boundary layer flow
becoming southwesterly - or maybe west-southwesterly - and
precipitable water levels increasing to near normal for this time of
year (which is somewhere around an inch). The added moisture,
combined with slightly better forcing, should allow cloud cover, as
well as shower probabilities, to return to our area at some point
Sunday. Right now, I`ve got a fairly low confidence in the timing of
any precipitation Sunday. But it looks like areas east of the Blue
Ridge will have greater odds in the afternoon, with no one
particular time of day favored for showers west of the Blue Ridge.

Beyond Sunday, about the best I can say is that it looks like
unsettled weather conditions could continue. Overall, though, I
have fairly low confidence in the overall evolutionary details
of the forecast. The upper-level flow should more-or-less remain
zonal through early next week. This will allow quick-moving
shortwave troughs in the northern stream to dart across (or at
least very close) to the region. Boundary layer moisture should
remain ample for convection through Day 7, with precipitable
water values at or above normal for early June. In fact, there
is some indication in ensemble guidance of values approaching 2
standard deviations above normal (98th percentile). We`ll see
what happens, though. Regardless of the details, it looks like
scattered convection will be seen through the middle of next
week.

Temperature-wise, it looks like there will be gradual warmup through
the long term portion of the forecast. I`m pretty confident that
temperatures will go above seasonal levels, but I`m not sure to what
extent. At this stage, I`ll stick pretty close to the national
blend, which has highs by Wednesday around 80 in the mountains and
in the upper 80s across the Piedmont/Southside Virginia.

&&

.AVIATION /23Z WEDNESDAY THROUGH MONDAY/...
As of 710 PM EDT Wednesday...

Showers will be in vicinity of LWB through 01z, otherwise VFR
with winds from the west-northwest diminishing.

Confidence in fog is low but cannot rule out some IFR or lower
at LWB and BCB, but especially LWB as they had showers in and
near there this afternoon. However, drier air working in behind
the front and some wind may prevent fog from lingering too long,
so just a tempo group for now.

Otherwise, once any fog burns off on Thursday morning, the rest
of the day will be VFR.

Above average confidence on ceilings and wind, moderate
confidence on vsbys.

EXTENDED AVIATION OUTLOOK...

VFR much of the week, aside from potential fog at LWB/BCB early
in the mornings. Storms may bring sub-VFR Sunday afternoon
through Monday but low confidence.

&&

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

&&

$$

SYNOPSIS...AMS/WP
NEAR TERM...AMS/WP
SHORT TERM...DB
LONG TERM...DB
AVIATION...AMS/WP