010
FXUS61 KRNK 211634
AFDRNK

Area Forecast Discussion
National Weather Service Blacksburg VA
1234 PM EDT Tue May 21 2024

.SYNOPSIS...

High pressure passing overhead to the east will provide dry
weather for most locations through tonight. Increasing moisture
pooling ahead of an approaching cold front will bring widely
scattered showers and thunderstorms for Wednesday and Thursday.
This activity will increase in coverage through the weekend as
the low pressure system tracks toward the eastern United States.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 1215 PM EDT Tuesday...

Key messages:

   - Confidence moderate for isolated thunderstorms this afternoon
   - Confidence high for above normal temperatures today and tonight

Satellite imagery depicts scattered fair weather clouds across
the region this afternoon, with more pronounced development
along the higher ridges west of the Blue Ridge. Still, abundant
sunshine has allowed temperatures to warm into the 70s for most
of the region, with a few 80 degree observations across the
Southside area.

Rapid update weather models still hinting at the development of
a few showers and isolated thunderstorms developing across the
mountains after 3 pm. This activity is expected to remain
progressive, resulting in relatively brief periods of rainfall,
with mainly a tenth of an inch or less in accumulation where it
does manage to develop. Most of the lower Mid-Atlantic area
will top out in the upper 70s to the low 80s for highs.

For tonight, showers will fade quickly with the loss of daytime
heating as sunset approaches. With light winds and mostly clear
skies overtop moist soils from recent rainfall, patchy fog will
redevelop after midnight, particularly in the river valleys.
Overnight lows will bottom out in the mid 50s to around 60
degrees.

&&

.SHORT TERM /WEDNESDAY THROUGH FRIDAY NIGHT/...
As of 200 AM EDT Tuesday...

Key Points:

1. Well above normal temperatures for this time of year.
2. Scattered showers and storms Wednesday mainly across the mountains.
3. Robust coverage of showers and storms Thursday and Friday, especially
during the afternoon hours over the mountains.

A look at the 20 May 00Z NCEP Ensemble Mean 500 mb Geopotential
heights shows for Wednesday high pressure in the western Atlantic,
off the coasts of the Carolinas and a shortwave trough extending
form MN southeast into IN. By Thursday, this axis of the shortwave
trough will be over our region, and by Friday, it will be over the
Canadian Maritimes. At the surface, on Wednesday, low pressure will
be centered near the Ontario/Quebec border with an associated cold
front curving southwest into parts of MI/WI/IA. By Thursday, the low
shifts into northern Quebec with the cold front crossing our region.
On Friday, the low makes additional progress eastward, but its front
is not as progressive and begins to stall over the region.

Output from the 20 May 12Z Ensemble Situational Awareness Table
shows 850mb temperatures around +16C across the area Wednesday and
Thursday, or values with the 90 to 97.5 percentile of the 30-year
climatology. On Friday, values are slightly cooler in the +14 to
+16C range. On Wednesday Precipitable Water values will range from
1.00 to 1.25 inches, for Thursday, 1.50 inch which falls with the 90
to 97.5 percentile of the 30-year climatology, then back to around
1.25 inches by Friday.

The above weather scenario will offer increasing chances of showers
and storms on Wednesday, especially across the mountains. By
Thursday into Friday, look for robust coverage across the region,
especially across the mountains during peak heating of the day as a
cold front crosses and then stalls over the area. Given the above
normal PW values over the are on Thursday, expected rainfall
Thursday into Friday may need to be monitored for locally heavy rain
concerns, especially if the same locations have repeated heavy rain.
Temperatures will be well above normal for this time of year.

Confidence in the above weather pattern is moderate to high.

&&

.LONG TERM /SATURDAY THROUGH MONDAY/...
As of 200 AM EDT Tuesday...

Key Points:

1. Temperatures continue above normal for this time of year.
2. Potential for daily chance of showers and storms
3. Confidence in the specific timing and location of the precipitation
is low.

A look at the 20 May 00Z NCEP Ensemble Mean 500 mb Geopotential
heights shows the region in a general southwest flow pattern as a
trough deepens across central CONUS. Concurrently, heights will
trend slightly higher each day over the region. At the surface,
indications are the surface front that began to stall over the area
on Friday, continues over or near the area on Saturday as the parent
low races away to south of Greenland. Sunday and Monday, the
averaging process of the ensemble solution washes out its earlier
weak signature of a front over the area. However, there are good
signs of a generally troughiness across the central US.

Output from the 20 May 12Z Ensemble Situational Awareness Table
shows 850mb temperatures average +16C through the period.
Precipitable Water values will average 1.25 inches through the
period.

The above weather scenario may present a continuation of daily
chances of showers and storms. The challenge in just where the
frontal boundary from Friday moves to, or doesn`t move.
Additionally, the prevailing southwest flow aloft could help escort
shortwave troughs across the region from the generally area of
troughiness across the center of the nation. While this general
pattern may end up being accurate, at this time, nailing down the
details in the timing of the best chances of precipitation each day
is the biggest question mark. As such, confidence in this portion of
the forecast is low on these details. There is better confidence in
the continuation of above normal temperatures

&&

.AVIATION /16Z TUESDAY THROUGH SATURDAY/...
As of 640 AM EDT Tuesday...

Patchy IFR to MVFR fog covered much of Virginia and North
Carolina this morning. LIFR stratus moving onshore in eastern
Virginia is expected to stay east of KLYH and KDAN this morning.

The shallow fog will dissipate by 14Z/10AM, then scattered to
broken VFR stratocumulus will develop this afternoon over the
mountains and foothills. Isolated showers and thunderstorms are
expected, especially along the southern Blue Ridge. Because the
coverage will be isolated, local TAF sites may not be impacted
by these storms. For now only have VCSH mentioned at KBLF and
KLWB.

Any showers and thunderstorms will erode this evening, after
00Z/8PM with the loss of heating. MVFR/IFR fog will form again
overnight in the piedmont.


Average confidence for ceiling, wind, and visibility.


EXTENDED AVIATION OUTLOOK...

VFR conditions will continue into Wednesday with the wind turning
to the southwest. The chance of showers and thunderstorms will
gradually increase in the mountains by Wednesday afternoon and
become more widespread by Thursday as a front arrives.

This front will stall by Friday across the Mid Atlantic and
linger through Saturday. Waves of low pressure riding along this
boundary will spark more showers and thunderstorms and increase
the likelihood of low ceilings during this time.

&&

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

&&

$$

SYNOPSIS...AMS
NEAR TERM...AMS/NF
SHORT TERM...DS
LONG TERM...DS
AVIATION...AMS