Area Forecast Discussion
Issued by NWS Blacksburg, VA

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FXUS61 KRNK 261417
AFDRNK

Area Forecast Discussion
National Weather Service Blacksburg VA
1017 AM EDT Tue Mar 26 2024

.SYNOPSIS...
A cold front approaches from the west today, while low pressure
develops over the Gulf Coast states and moves into South
Carolina Wednesday morning. This front will slowly cross our
region into Wednesday before stalling in the Piedmont Thursday.
By Friday into the weekend, the system will be northeast of our
area with high pressure entering the region.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 1015 AM EDT Tuesday...

Key Messages:

1. Wind gusts have decreased over the western slopes, thus Wind
Advisory has been cancelled.
2. Rain chances increase through today into tonight.

Wind gusts have decreased, and wind speeds are mostly around 10
mph or less across the area, so the Wind Advisory has been
cancelled for the western tier of counties within the area.
Winds may become gusty later this evening along the higher
ridges in the southern Blue Ridge, as the main front crosses
the area, but will stay below advisory criteria.

Rain has reached the far southwestern portions of the area at
this time, and chances increase over the rest of the area
today through this evening, and rain will continue overnight.
Forecast remains on track for this morning`s update.

Previous discussion below...

Strong 8h jet will move across the TN Valley into the Central
Appalachians this morning, exiting to the north by midday. A few
gusts over 45 mph likely along the higher ridges of WV into far
SW VA and the Grayson Highlands, as well as in typical windy
spots like Tazewell, VA.

Southeast flow also increasing moisture along the southern
Appalachians this morning and could start to see some light
rain develop here by 8am.

Models are on track in terms of having front slowly shifting
east toward the Ohio Valley/TN Valley today while a low pressure
forms along another boundary in the Gulf Coast states. At the
moment, looks like moisture convergence stays south and west of
us this morining limiting any rain chances, but as we head to
the afternoon, appears better coverage will occur west of the
Blue Ridge. Sunshine will likely show itself through high clouds
in the Piedmont early on but clouds increase to limit sun this
afternoon. Some model difference in terms of cloud cover exist
but given extent of high clouds already moving across, think MAV
mos looks better with 40s in the southern Blue Ridge and
mountains of WV to 50s elsewhere west of the Blue Ridge into the
foothills, with lower 60s Piedmont.

There looks to be a lull in rain coverage around late
afternoon/early evening before better upper support arrives
ahead of the front, and at the same time the low pressure over
the Gulf Coast states moves into South Carolina. Better surge of
rain expected through the night although coverage per high-res
models still looks broken at times, so not everyone will see
rain and amounts overall look on the one tenth to quarter inch
range. Patchy fog also will be likely and could get dense along
the ridges late tonight as winds slacken. With cloud cover and
increased low level moisture, lows will be in the 40s most
areas.

Forecast confidence is moderate on rain chances and sky cover
and above average on winds and temperatures.

&&

.SHORT TERM /WEDNESDAY THROUGH FRIDAY NIGHT/...
As of 330 AM EDT Tuesday...

Key Messages:

1) Rain chances continue Wednesday, increasing going into
Thursday.

2) Temperatures near to slightly above normal through
this period.

The synoptic pattern features a broad upper trough anchored
across the central U.S. This trough will shift slowly east
through the later half of the week. Long fetched southerly flow
aloft will help to transport rich Gulf moisture northward.
However, the main dynamics associated with this upper trough
will track to our northwest. The initial associated frontal
boundary/baroclinic zone will drift through the region Tuesday
and then stall to our southeast. A southern stream short wave
within the base of the broad upper trough will help to include
an area of low pressure along the southeast coast, which will
then ridge northeast along the baroclinic zone. This will result
in rain increasing in intensity and coverage and spreading back
into the southeastern part of the CWA Thursday. The big
question which remains at this point is how far northwest will
this precipitation extend. Current thinking is that the bulk of
the associated heavier precipitation will remain mostly east of
U.S. 29, but light rain, and perhaps even areas of drizzle/fog
will be evident back into the western parts of the CWA. In fact,
the latest runs of the models show the heaviest rainfall
shifting a bit further east. WPC has shifted the "marginal" risk
of excessive rainfall east of our CWA as well. At this point,
rainfall amounts look to range from around 1/2 west to perhaps
as much as 1.25 to 1.50 inch along and east of the U.S. 29
corridor.

The air mass will remain mild and moist for late March in this
region. However, extensive cloud cover and precipitation will
hold temperatures down, especially across the eastern parts of
the CWA. Consequently, temperatures will remain relatively close
to just a bit above normal equating to highs in the 50s and 60s
with lows mainly in the 40s, with some 30s in the slightly less
moist/cooler areas to the northwest.

/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.

&&

.LONG TERM /SATURDAY THROUGH MONDAY/...
As of 345 AM EDT Tuesday...

Key Messages:

1) Rain from the southeastern U.S. system moves out of the area
by Friday.

2) Northwest flow disturbance brings potential showers/isolated
thunderstorms to the area, mainly north of U.S. 460, over the
weekend.

The upper flow becomes more progressive during this period as
the southeastern U.S. system finally moves out to sea Friday. By
the weekend, the upper trough has drifted off the coast and the
flow aloft trends toward a more zonal pattern overall across the
U.S, but maintains a slight northwest tilt across the eastern
U.S.

The focus during this period will be on a northwest flow
disturbance and an associated baroclinic zone/west-east oriented
frontal boundary focused just to the north of the CWA. Latest
runs of the models continue to depict a convective complex
developing over the Ohio Valley Saturday afternoon. The remnants
of this system drifts into the northwestern/northern parts of
the CWA Saturday night and Sunday. The associated convection
helps push the baroclinic zone further south toward the I-64
corridor, in essence setting up very close to the I-64
corridor. The boundary will tend to linger in this region into
early next week as ridging aloft negates much further southward
movement. Consequently, showers will tend to develop along and
near the boundary throughout the remainder of the weekend. The
best forcing will remain across the western parts of the region.
Confidence in this pattern is increasing thanks to consistency
among the models from day-to-day.

Temperatures are also problematic, but at this point should be a
bit above normal with westerly flow in advance of any frontal
boundary across the region or just to the north of the CWA.
However, clouds and precipitation could play havoc with any
appreciable warm temperatures, so feel the ECMWF MOS guidance is
more reliable than the warmer NBM/GFS MOS.

/Confidence Levels in Forecast Parameters/
- Moderate Confidence in Temperatures,
- Moderate Confidence in Precipitation Probabilities,
- Low to Moderate Confidence in Wind Direction and Speed.

&&

.AVIATION /14Z TUESDAY THROUGH SATURDAY/...
As of 656 AM EDT Tuesday...

VFR conditions this morning for most, though some MVFR cigs
creeping across the mountains may occur at times. Rain and MVFR
ceilings will arrive at BLF in the afternoon, reaching other
terminals shortly thereafter, except possibly LYH. Rain likely
will bring ceilings down to under 1kft from TNB/GEV up to BLF
Tuesday evening. Vsbys with rain also could drop to IFR.

Prior to the rain, southeast winds will be gusty across the BLF
area with 30-40kts possible this morning. At the same time low
level wind shear looks like an issue across the mountains as
well through 12-15z.

Winds will start to slacken by the afternoon at BLF with gusts
dropping under 20kt by evening.

Rain will be mainly east of the Blue Ridge after midnight with
IFR or lower cigs at all terminals.

EXTENDED AVIATION OUTLOOK...

Through Thursday, conditions will trend to primarily IFR/MVFR
for most locations as a front slowly crosses the region, with
rain chances remaining.

Conditions return to VFR by Thursday night into Friday,
accompanied by gusty northwest winds.

A front may drop down from the north Saturday with possible
showers, but overall appears mainly VFR.

&&

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

&&

$$

SYNOPSIS...DS/WP
NEAR TERM...WP/AS
SHORT TERM...RAB
LONG TERM...RAB
AVIATION...SH/WP


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