991
FXUS61 KRNK 141744
AFDRNK

Area Forecast Discussion
National Weather Service Blacksburg VA
144 PM EDT Sun Jul 14 2024

.SYNOPSIS...
Well above normal to near record warm temperatures will be found
across the region through Tuesday. Only an isolated shower or storm
is expected this afternoon, with scattered storms possible Monday
and Tuesday as moisture builds across the region. The best chance
for showers and storms will be on Wednesday and Thursday as a cold
front dips south through our area.

&&

.NEAR TERM /THROUGH MONDAY/...
As of 130 PM EDT Sunday...

1. High confidence for well above normal temperatures through the
period with near record high minimum temperatures possible Monday
morning at Roanoke.

2. Thunderstorm chances look low today, and only slightly
higher for Monday afternoon.

Much of the eastern CONUS was in full sunshine today, with some
daytime cumulus forming over our Blue Ridge. Otherwise, it was
hot, with much of the area in the upper 80s to low/mid 90s.
Organized convection was ongoing over the Midwest, in response
to mid level energy near Chicago. A few isolated showers and a
rumble of thunder may be possible this afternoon and early
evening along our higher terrain initially, and may drift SE
towards the Piedmont before weakening.

Deep westerly flow was keeping plenty of dry air in our
vicinity, as seen on mid level water vapor and BUFKIT. This,
along with moist adiabatic profiles and weak capping have led to
low instability and suggest any convection that forms will be
brief and have a hard time reaching glaciation level to produce
lightning. Brief heavy rain will continue to be a localized
concern. Tonight, lows will be in the 60s to low 70s.

850mb temperatures remain around 20-21C over the southern
Appalachians through Monday, and along with westerly downsloping
winds and at least partly sunny skies, will result in
high temperatures a couple degrees warmer than today. That will
put Roanoke and parts of the Piedmont of VA and NC around 100F
for highs, with heat index values just a degree or 2 higher.
GEFS probability of heat index over 105F is very spotty and
under 15% for most of the Mid Atlantic, therefore a heat
advisory is not needed at this time. A couple sites come with a
degree or two for record high minimums. Record highs will be
harder to break. See Climate section below.

Tomorrow, a weak ripple in the flow aloft will arrive for the
afternoon, and should create scattered convection in the
vicinity of lee troughing. Instability looks slightly higher
tomorrow than today, and forecast soundings show plenty of dry
air in the lower levels for downbursts. Shear remains weak, with
less than 10 kts up through 15 kft/500mb. Isolated instances of
damaging winds along with heavy rain will be possible for a few
hours. SPC only has us in general thunder, likely because we
will have debris clouds in the morning which will lower
available instability.

&&

.SHORT TERM /MONDAY NIGHT THROUGH WEDNESDAY NIGHT/...
As of 1215 PM EDT Sunday...

Key Points:

1. Hot on Tuesday with Heat Index values potentially surpassing 105F
across portions of the Piedmont.
2. Cold front arrives Wednesday into Wednesday night providing
for abundant showers and storms with locally heavy rainfall
possible.

A look at the 14 July 00Z NCEP Ensemble Mean 500 mb Geopotential
heights shows a persistent latitudinal upper ridge axis across the
southern half of the US. A shortwave trough over the Upper
Mississippi Valley on Tuesday is expected to shift east into the
Great Lakes and Lower Ohio Valley by Wednesday. On Tuesday, a cold
front will extend from the eastern Great Lakes region southwest into
the mid-Mississippi River region and then into central Kansas. By
Wednesday, this front will pass through our region, and curve into
the Tennessee and farther west into the Arklatex area.

Output from the 14 July 00Z Ensemble Situational Awareness Table
shows 850mb temperatures around +22C for much of the area on
Tuesday. This corresponds to the entire area being within the 97.5+
percentile of the 30-year climatology with over half within the 99+
percentile. On Wednesday, numbers dip a little, with the region
averaging about +19C to +21C in the southeast. Areas at or a little
above +20C fall within the 90 to 97.5 percentile range. Precipitable
Water (PW) on Tuesday are expected to average around 1.50 to 1.75
inches. For Wednesday, higher values in the 1.75 to 2.00 inch range
are expected. Those locations that do touch 2.00 inches will reach
the low end of the 90 to 97.5 percentile of the 30-year climatology.

The above weather pattern will mean a continuation of well above
normal temperatures on Tuesday. Our forecast will continue with some
locations across the Piedmont touching the century mark for high
temperatures and portions of the NC/VA Piedmont potentially seeing
Heat Index values surpass 105F. With the approach of a cold front,
however not the actual arrival, shower and thunderstorm chances will
increase a little bit as compared to Monday. Come Wednesday into
Wednesday night, shower and storms chances notably increase with the
arrival of a cold front. More cloud cover and better chances of
precipitation will allow for cooler temperatures as compared to
Tuesday. However, values will still be above normal. With PW values
on the high end of normal, any shower or thunderstorm that develops
will have the potential of producing some locally heavy rainfall.

Confidence in the above weather scenario is high.

&&

.LONG TERM /THURSDAY THROUGH SUNDAY/...
As of 1215 PM EDT Sunday...

Key Points:

1. A potentially wavering frontal boundary over or just south of the
area will keep showers/storms in the forecast each day.
2. Temperatures will trend to readings around or slightly below normal
for this time of year.

A look at the 14 July 00Z NCEP Ensemble Mean 500 mb Geopotential
heights shows the western extent southern US ridge axis buckling
north across the Rockies on Thursday. In response, a Great
Lakes/Ohio Valley trough slows its eastward momentum heading into
Friday. Over the weekend, the upper synoptic pattern shows little
signs of change, keeping our region on the southeast side of an
upper trough with southwest aloft over the region. At the surface,
Thursday into Friday, the front that crossed the region on
Wednesday, will take up residency just south of the area as high
pressure builds into the Great Lakes region. Saturday into Sunday,
the ensemble averaging washed out any indications of a cold front to
the south while maintain some suggestion of high pressure to our
north. A look at various deterministic guidance and forecast WPC
frontal positions, suggest the front to the south will either remain
just to our south or inch back north across our region.

Output from the 14 July 00z Ensemble Situational Awareness Table
shows 850mb temperatures on Thursday averaging +16C to +18C over the
region. For Friday, these numbers cool slightly to an average of
+16c. For Saturday, numbers creep a little higher to around +17C to
+18C with similar numbers for Sunday. PW values on Thursday will
fall along and nw-se gradient across the region with values slightly
over 1.25 inches in southeast West Virginia to values just shy of
2.00 inches over Southside Virginia. This configuration and range
hold nearly steady through Sunday.

With a cold front slow to head south of the region, and then
potentially stalling to our south and/or heading back north across
the region, the latter half of the week and the weekend will have
daily chances of showers and storms. The highest probabilities will
continue to be advertised across the southern half of the region. As
the upper level flow trends into a stagnant pattern with ridging in
the west, and troughing in the east confidence is moderate in this
forecast from the synoptic scale. However, at the local level,
confidence is more on the low side regarding where the best chances
will be given the notable uncertainty in the daily position of the
front. Although, in general terms, southern sections should have
greater chances than northern sections.

Temperatures are expected to take a downward trend with values on
Friday and Saturday potentially slightly below normal, only to be
closer to normal again by Sunday.

&&

.AVIATION /15Z SUNDAY THROUGH THURSDAY/...
As of 130 PM EDT Sunday...

VFR conditions will persist through the TAF period. Isolated
showers and storms this afternoon will primarily be focused
along the southern Blue Ridge and the probability of this
isolated activity impacting any TAF sites today are extremely
low. West to southwest winds less than 10 knots are expected
through 18Z Monday.

VFR conditions continue tonight, with the exception of patchy
IFR to LIFR conditions due to fog at KLWB for a couple of hours
early Monday morning.

AVIATION OUTLOOK...

SHRA/TSRA chances return during the afternoons and evenings
Monday and Tuesday, before dissipating after sunset. A front
crosses the region Wednesday and Thursday, bringing widespread
SHRA/TSRA and sub-VFR conditions.

&&

.CLIMATE...
As of 215 PM EDT Sunday...

Temperatures may come close to record high temperatures and/or
record maximum low temperatures Monday, July 15, and Tuesday,
July 16. Below you will find a table that lists these values
for different locations in our region and the years those
records were set.

************* RECORDS FOR July 15 *************
+=============================================+
|  LOCATION   | RECORD HIGH  | RECORD MAX LOW |
| Blacksburg  |  99 in 1954  |   72 in 1954   |
| Bluefield   |  91 in 1951  |   72 in 1942   |
| Danville    | 104 in 1936  |   79 in 1922   |
| Lynchburg   | 101 in 1936  |   77 in 1988   |
| Roanoke     | 103 in 1936  |   74 in 1995   |
+=============================================+



************* RECORDS FOR July 16 *************
+=============================================+
|  LOCATION   | RECORD HIGH  | RECORD MAX LOW |
| Blacksburg  |  93 in 1983  |   70 in 2020   |
| Bluefield   |  96 in 1988  |   71 in 1980   |
| Danville    | 102 in 1934  |   77 in 1920   |
| Lynchburg   | 103 in 1934  |   76 in 1937   |
| Roanoke     | 100 in 1988  |   74 in 2020   |
+=============================================+

&&

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

&&

$$

SYNOPSIS...PH/SH
NEAR TERM...SH
SHORT TERM...DS
LONG TERM...DS
AVIATION...SH
CLIMATE...DS