-- Discussion containing changed information from previous version are highlighted. --
965
FXUS61 KRNK 240828
AFDRNK

Area Forecast Discussion
National Weather Service Blacksburg VA
428 AM EDT Fri May 24 2024

.SYNOPSIS...
-- Changed Discussion --
A front stalled across the Ohio Valley will result
in multiple days with showers and thunderstorms over
the area. Then a low pressure system crossing the Great Lakes
will push a cold front through the Mid Atlantic region early
Tuesday. This will lead in drier and cooler weather for the
middle of next week.
-- End Changed Discussion --

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 245 AM EDT Friday..

Key message:

   - Best probability of precipitation is this morning

Water vapor satellite images showed a well defined short wave along
the Ohio River between Ohio and Kentucky early this morning. This
feature was tracking northeast along with clusters of showers and
thunderstorms over the Mid Atlantic region.  HRRR bring showers and
thunderstorms across southeast West Virginia and the Alleghany
highlands closer to the upper wave this morning. The upper trough
with this wave will be along the east coast by afternoon.

Surface and low level winds turn to the northwest to northeast
during the day and the air mass will not be more stable this
afternoon and tonight. This will limit the areal coverage and
intensity of any showers and thunderstorms and removes the area from
the marginal risk of severe weather and excessive rainfall.

Bufkit forecast soundings show mid and upper levels drying out
behind the short wave. But with lingering low level moisture and
some westerly component to the wind will not get rid of much cloud
cover. The combination of light wind and near surface moisture may
result in patchy fog overnight.

No significant changes planned to temperatures in this time frame.
Still above normal, especially for the lows.

&&

.SHORT TERM /SATURDAY THROUGH MONDAY NIGHT/...
As of 145 AM EDT Friday...

Key Points:

1. Scattered showers and storms for Saturday.
2. A brief dry period late Saturday night and early Sunday.
3. Better chances of showers and storms Sunday afternoon through
Monday night with the approach and passage of a cold front.
4. Above average temperatures through the period.

A look at the 23 May 12Z NCEP Ensemble Mean 500 mb Geopotential
heights shows our region on Saturday within a nearly zonal flow.
However, even with ensemble averaging, a weak shortwave trough is
depicted crossing our area within this flow. Across the Rockies, a
stronger low/trough is developing. On Sunday, a shortwave ridge now
is depicted over our region, with a shortwave trough over the mid-
Mississippi River valley. The broader trough across western CONUS is
expected to move closer to central CONUS and lose a bit of its
amplification. By Monday morning, the central CONUS trough shows
signs of deepening closer to the Mississippi Valley. By late Monday
night, this trough trends a bit negatively tilted as its axis swings
into the Southern Appalachians. At the surface, on Saturday morning,
a cold front is expected to extend from the central Great Lakes
region south into the Ohio Valley. By Sunday morning, this front
will have moved through our region and be located along eastern
VA/NC. An area of low pressure will also be located across the
Central Plains states. By Monday morning, this same low is expected
to be over the mid-West with an associated cold front trailing
southwest across the Lower Ohio and Tennessee Valleys. By late
Monday night, the low will be near the Ontario/Quebec border with
the front located east of our region.

Output from the 23 May 12Z Ensemble Situational Awareness Table
shows 850mb temperatures across the area are expected to be around
+16C Saturday, +16C to +17C Sunday and Monday. Those areas touching
+17C will see values within the 90 to 97.5 percentile of the 30-year
climatology. Precipitable Water values on Saturday will average 1.25
inches across the area, 1.00 to 1.25 inches on Sunday, and 1.00 to
1.50 inches on Monday, with the high end of this range across
eastern parts of the region.

The above weather scenario suggestion the following forecast for the
area. Saturday will be a day with scattered showers and storms
thanks to the passing shortwave trough. However, by late Saturday
night into the first part of Sunday, we may have a break in the
activity with the quick passage of the shortwave ridge. However, by
the afternoon, the influence of the next advancing system will be
noted by an increase in shower and storm activity heading into the
evening hours, especially western parts of the area. Sunday night
into Monday precipitation probabilities will continue to be greatest
across western parts of the area with the approach of a strong cold
front. Either late Monday afternoon or early Monday night, the cold
front is expected to cross our region. Behind the front, winds shift
northwest and become gusty. Some guidance offers 850mb winds around
30kts Monday night. These winds and perhaps a reinforcing front will
allow for isolated to scattered showers across the mountains late
Monday night. Temperatures during this portion of the forecast are
expected to be well above normal for this time of year.

Confidence levels for this section of the forecast are moderate.

&&

.LONG TERM /TUESDAY THROUGH THURSDAY/...
As of 145 AM EDT Friday...

Key Points:

1. Residual showers across SE WV Tuesday and Wednesday
2. Trending cooler through the period.

A look at the 23 May 12Z NCEP Ensemble Mean 500 mb Geopotential
heights shows a slow progression eastward of an upper longwave
trough. The feature will extend from the central Great Lakes region
to eastern TN Tuesday morning, have made little progress eastward by
Wednesday morning, and by Thursday morning be centered from NY south
to eastern SC. At the surface, a cold front will be located east of
the region with a northwest flow regime behind it over our area.
High pressure will be over the Central Plains. As we progress into
Thursday, the center of the high progresses into the Mississippi
River Valley while the front hugs the Atlantic Coast.

Output from the 23 May 12Z Ensemble Situational Awareness Table
shows 850mb temperatures trending lower than recent days, with
numbers more in the +12C to +14C range on Tuesday. For Wednesday and
Thursday, the downward trend continues with values around +10C.
Precipitable Water values will average 0.75 to 1.00 inch on Tuesday,
0.75 inch on Wednesday, and 0.75 inch or slightly less on Thursday.

The above weather scenario suggests a trend these three days with
decreasing chances of showers and storms as high pressure progresses
towards the area from the west. However, with a persistent northwest
flow between the approaching high and the departing low, we may see
at least scattered showers over parts of Southeast West Virginia.
Additionally, with the axis of the upper trough slow to progress
across the region, we will likely maintain some degree of steep
lapse rates aloft helping to promote instability, perhaps helping to
generate some showers east of the Blue Ridge, especially on Tuesday.
Temperatures during this portion of the forecast will begin a few
degrees above normal. By Wednesday, values a few degrees below
normal are expected.

Confidence levels for this section of the forecast are moderate.

&&

.AVIATION /09Z FRIDAY THROUGH TUESDAY/...
As of 310 AM EDT Friday..

Scattered MVFR showers this morning then VFR this afternoon.

Water vapor satellite images showed a well defined short wave
along the Ohio River between Ohio and Kentucky early this
morning. This feature was tracking northeast along with clusters
of showers and thunderstorms over the Mid Atlantic region. HRRR
bring showers and thunderstorms across southeast West Virginia
and the Alleghany highlands closer to the upper wave this
morning. The upper trough with this wave will be along the east
coast by afternoon. Another batch of MVFR showers is expected
for KBLF and KLWB through 15Z/11AM.

Surface and low level winds turn to the northwest to northeast
during the day and the air mass will not be more stable this
afternoon and tonight. This will limit the areal coverage and
intensity of any showers and thunderstorms and removes the area from
the marginal risk of severe weather and excessive rainfall.

Bufkit forecast soundings show mid and upper levels drying out
behind the short wave. But with lingering low level moisture and
some westerly component to the wind will not get rid of much cloud
cover. Do have VFR ceilings lifting and becoming sct gradually
throughout the day.

The combination of light wind and near surface moisture may
result in patchy MVFR to IFR fog overnight.

Average confidence for ceiling, wind, and visibility

EXTENDED AVIATION OUTLOOK...

Periods of showers and thunderstorms, especially each afternoon
and evening, will continue through Monday. MVFR remain likely
with any of the thunderstorms.

A front will cross through the area early Tuesday turning winds
to the northwest and eventually bringing drier air in the area.

&&

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

&&

$$

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