-- Discussion containing changed information from previous version are highlighted. --
835
FXUS61 KRNK 220642
AFDRNK

Area Forecast Discussion
National Weather Service Blacksburg VA
242 AM EDT Wed May 22 2024

.SYNOPSIS...
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Isolated thunderstorms are expected again this afternoon as the
region remains between high pressure over the western Atlantic and
low pressure in the central United States. This low crosses the
Great Lakes and will drape a front across the Ohio and
Tennessee Valleys by Thursday bringing showers and
thunderstorms, along with a chance of heavy rain to the region
Thursday and Friday. The wet weather pattern continues through
the beginning of next week with yet another front crossing
through the area.
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&&

.NEAR TERM /THROUGH TONIGHT/...
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As of 215 AM EDT Wednesday...

Key messages:

   - No significant changes to probability of precipitation
   - Confidence high for above normal temperatures today and tonight

Fog had developed in the headwaters of the New River Valley but
Night Fog satellite images showed much of the fog was confined to
the eastern Virginia and North Carolina. High clouds off of upstream
thunderstorms were over the southern Appalachians. The high clouds
will gradually fill in over the region throughout the day.

Scattered to broken stratocumulus develops this afternoon. Models
have isolated thunderstorms mainly along the Blue Ridge this
afternoon. With little to upper support, main trigger for
storms will be topography. Storms will erode with the loss of
heating this evening. As a cold front slowly approaches late
tonight, the probability of precipitation increases in central
and northern West Virginia.

Air mass will still support maximum temperatures in the 70s and 80s
today, aided by a westerly downsloping component to the mean flow.
Expect highs to be a few degrees warmer than on Tuesday in the
foothills and piedmont. Lows remain mild, 5 to 15 degrees above
normal.
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&&

.SHORT TERM /THURSDAY THROUGH SATURDAY NIGHT/...
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As of 1230 AM EDT Wednesday...

Key Points:

1. Showers and storms expected each day.
2. Locally heavy rain possible.
3. Well above normal temperatures.

A look at the 21 May 00Z NCEP Ensemble Mean 500 mb Geopotential
heights shows the region Thursday through Friday with a generally
southwest flow across the region. However, within this flow regime
will be periodic shortwave troughs passing either over or north of
the region. On such feature is expected to be over roughly the
Ontario/Quebec border, south into PA Thursday evening. Another is
expected to move trough the Ohio Vally on Friday. On Saturday,
another is expected to be over the Great Lake region. At the
surface, a cold front is expected to cross the area on Thursday. By
Friday, the front is only expected minor progression southeast of
the area. By Saturday, the front is expected to lose its strength as
a front, yet remain near eastern/southeastern parts of the area as a
lee side trough. During these three days, low pressure will be
across central CONUS and a ridge of high pressure will be across the
western Atlantic. Another low will cross the Great Lakes region on
Saturday with an associated cold front trailing southwest into the
mid-Mississippi River Valley.

Output from the 21 May 12Z Ensemble Situational Awareness Table
shows 850mb temperatures around +16C for Thursday and Friday, and
milder yet for Saturday at +16C to +18C. For Saturday, this range is
well within the 90 to 97.5 percentile for the 30-year climatology.
Precipitable Water values for Thursday are expect to be around or a
bit over 1.50 inches, which falls within the 90 to 97.5 percentile
of the 30-year climatology. This value dips a bit for Friday to the
1.25 to 1.50 range. Values decrease a bit more on Saturday to around
1.25 inches.

The above weather scenario places our region in a pattern conducive
to consecutive days of likely or better chances of showers and
storms for at least parts of our region. With the front crossing our
area on Thursday, and then essentially stalling somewhere over or
close to the region, all while maintaining a good southerly fetch of
moisture into the area, with well above normal Precipitable Water
values, this could set the stage for some locally heavy rainfall
amounts. Temperatures will be well above normal for this time of
year.

Confidence in the above weather scenario is moderate to high.
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&&

.LONG TERM /SUNDAY THROUGH TUESDAY/...
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As of 1230 AM EDT Wednesday...

Key Points:

1. Additional rounds of showers and storms each day.
2. Continued above normal temperatures.

A look at the 21 May 00Z NCEP Ensemble Mean 500 mb Geopotential
heights shows a developing longwave trough across Northern Plains
states on Sunday which is expected to head east. By Tuesday evening,
the feature is expected to be more amplified and centered over the
Mississippi Valley. At the surface, a broad region of low pressure
will be across the Southern and Central Plains States. A piece of
energy from this region of low pressure will eject as its own low
pressure on Monday moving into the Ohio Valley. By Tuesday this same
low pressure is expected to over OH/PA/MD/VA with an associated cold
front crossing our region.

Output from the 21 May 12Z Ensemble Situational Awareness Table
shows 850mb temperatures for Sunday and Monday within the +16C to
+18C range. This range falls with the 90 to 97.5 percentile for the
30-year climatology. For Tuesday, values decrease to +14C to +16C.
Precipitable Water values will average 1.25 to 1.50 inches on Sunday
and Monday and dip to around 1.00 to 1.25 inches for Tuesday.

Rather than a stalled boundary being the focus for various rounds of
showers and storms, the daily passage of shortwave troughs over or
near the region, along with our region remaining within moisture
laden atmosphere, will keep our forecast on the wet side into early
next week. Additionally, temperatures will also continue trending on
the warm side of normal.

Confidence in the above weather scenario is moderate.
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&&

.AVIATION /07Z WEDNESDAY THROUGH SUNDAY/...
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As of 235 AM EDT Wednesday...

Fog had developed in the headwaters of the New River Valley but
Night Fog satellite images showed much of the fog was confined to
the eastern Virginia and North Carolina. High clouds off of upstream
thunderstorms were over the southern Appalachians. The high clouds
will gradually fill in over the region throughout the day.

Fog will fill in along the New and Greenbrier Rivers this
morning. KLWB may have LIFR conditions and KBCB MVFR/IFR fog
before 12Z/8AM this morning. Any fog will be shallow and will
dissipate quickly after sunrise.

Scattered to broken stratocumulus, around 4000ft agl according
to the 3km NAM Bufkit, will form this afternoon. Models have
isolated thunderstorms mainly along the Blue Ridge this
afternoon. With little to upper support, main trigger for
storms will be topography. The clouds and thunderstorms will
dissipate with the loss of heating shortly after sunset.

As a cold front slowly approaches late tonight, mid and high
clouds and the probability of precipitation increases in
central and northern West Virginia.

Average confidence for cloud bases, wind, and visibility.


EXTENDED AVIATION OUTLOOK...

A cold front will approach the area Thursday bringing increasing
chance for showers and thunderstorms. This front will stall by
Friday across the Mid Atlantic.

Waves of low pressure riding along this weak boundary will
trigger more showers and thunderstorms and increase the
likelihood of MVFR conditions Friday through Sunday.
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&&

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

&&

$$

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