695
FXUS61 KRNK 151743
AFDRNK

Area Forecast Discussion
National Weather Service Blacksburg VA
143 PM EDT Mon Jul 15 2024

.SYNOPSIS...
High pressure and unseasonably warm temperatures will cover the Mid
Atlantic and southeast states tonight and Tuesday. A cold front will
track out of the Ohio Valley, reaching the area late Wednesday into
Thursday with showers and thunderstorms. The front, along with
cooler temperatures, and a continued daily chance of precipitation
will remain in the region into the weekend.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 1250 PM EDT Monday...

Key messages:

    - May be issuing a Heat Advisory for Tuesday in the piedmont of
      Virginia and North Carolina

Stratocumulus has developed over the mountains. Convective allowing
models show coverage of any showers and thunderstorms as isolated.
The most likely locations are in the Mountain Empire area and along
the Blue Ridge south of Roanoke. Expect to see storms pop up by 4PM
as the cap breaks. A majority of the precipitation will
dissipate after sunset and as a shallow surface based inversion
forms.

Surface dew points remain mainly in the 60s overnight. Similar, to
past few days, some record warm low temperatures may be be in
jeopardy. Highs on Tuesday are a degree or two warmer than this
afternoon. This is enough to push the max heat index to around 105
for a few hours in the afternoon. Coverage of thunderstorms Tuesday
afternoon will be isolated.

&&

.SHORT TERM /TUESDAY THROUGH THURSDAY NIGHT/...
As of 1230 PM EDT Monday...

Key Points:

1. Cold front crosses the region Wednesday into Wednesday night.
2. Locally heavy rain possible from showers and storms.
3. Cooler temperatures Thursday with values around or slightly above
normal.

A look at the 15 July 00Z NCEP Ensemble Mean 500 mb Geopotential
heights shows a persistent upper ridge extending from western CONUS
across the southern half of CONUS Wednesday and Thursday. An upper
trough will be centered over the central Great Lakes and Lower Ohio
Valley regions on Wednesday and the Mid-Atlantic region on Thursday.
However, on Thursday, the position of this trough via the ensemble
averaging becomes a bit more broad in its depiction, even trailing
southwest into the mid-Mississippi Valley, also suggesting a slowing
of the system. At the surface, on Tuesday night, low pressure will
be centered over southern Quebec. An associated cold front will
trail southwest into the Midwest. As time progresses, this front is
expected to cross our region on Wednesday. Wednesday night through
Thursday night, the parent low makes progress eastward as high
pressure moves into the Upper Mississippi Valley/Great Lakes region.
This will have result of the front over/near our region losing its
forcing factor, and result in a stalling of the front over or just
south of the region.

Output from the 15 July 00Z Ensemble Situational Awareness Table
shows 850mb temperatures falling from their high values on Tuesday
to numbers closer to +18C to +21C over the area by Wednesday
afternoon. While these numbers are lower, areas east of the
Interstate-81 corridor will still have values that fall within the
90 to 97.5 percentile of the 30-year climatology. By Thursday
afternoon, the numbers continue to decrease reaching the +16C to
+18C range. Precipitable Water (PW) slowly climb Tuesday night into
Wednesday with values by the afternoon ranging from 1.75 to a little
over 2.00 inches across the area with the highest end of the range
across southeast sections of the area. Regions with PW of 2.00 and
higher will fall within the 90 to 97.5 percentile of the 30-year
climatology. On Thursday, drier air will start entering the region,
but result in primarily strengthening the nw-se PW gradient. Values
in the far northwest are expected to be around 1.00 to 1.25 inches
with values in the far southeast between 1.75 and 2.00 inches.

Given the above weather pattern, very warm weather will continue
through Tuesday night, with limited chances of showers and storms.
Any that occur will likely be dissipating activity for a few hours
in the evening from what transpires Tuesday afternoon. Additionally,
towards daybreak Wednesday, there isolated coverage may occur across
western sections with the approach of a cold front. This same cold
front is expected to continue progressing towards, and then crossing
the region sometime during the late afternoon and evening hours.
Look for much better coverage of showers and storms as compared to
recent days, and with PW reaching 2.00 inches for parts of the
region, locally heavy rain will be possible. Thursday into Thursday
night, the cold front`s parent low is expected to outpace the speed
of the front, leaving an orphaned front lying somewhere across the
VA/NC/SC. This feature will continue to severe as the focus for
additional showers and storms through this period. With a better
probability than not of the boundary being south of our region,
plenty of cloud cover, and the potential for precipitation,
temperatures will be notably cooler than previous days on Thursday.

Confidence in the above weather scenario is moderate to high. The
biggest question is just where the font takes up residency after
Wednesday night and its influence on our sensible weather.

&&

.LONG TERM /FRIDAY THROUGH SUNDAY/...
As of 1230 PM EDT Monday...

Key Points:

1. Daily chances of showers and storms, especially southern sections.
2. Locally heavy rain possible, especially southeastern sections.
3. Around or slightly cooler than average temperatures.

A look at the 15 July 00Z NCEP Ensemble Mean 500 mb Geopotential
heights shows a ridge-trough-ridge blocking pattern developing
across CONUS. This trough portion of this configuration is expected
to be positioned from Quebec southwest into the Central Plains
States. This would place our region within a persistent southwest
flow aloft. At the surface, there is notable uncertainty as to the
evolution of the front that arrived on Wednesday. Ensemble averaging
show a nebulous area of surface high pressure to our north, and a
slight weakness generally to our south. Without any strong steering
flow to impact the surface features, we are expecting the front, or
at least some form of remnant boundary, to remain over or near our
region through Monday.

Output from the 15 July 00z Ensemble Situational Awareness Table
shows 850mb temperatures on Friday will average +16C to +17C across
the area. For Saturday through Monday, +17C to +18C will be common.
PW values on Friday will range from roughly 1.25 across northeast
sections to a little over 1.75 inches the southeast. Through Monday
these values and nw-se gradient change only slightly.

Given the above, this portion of the forecast could provide for
daily chances of showers and storms, especially over southern
portions of the region, while a cold front, or its status as simply
a weakening boundary, fluctuates somewhere over the region of
VA/TN/NC/SC. Far southeast sections are still expected to have PW
numbers close to 2.00 inches, so locally heavy rain cannot be ruled
out for any day, again especially for this southeast portion of the
area. We also will have to wonder about northern sections. Drier air
is working its way into the Ohio Valley in association with a nearly
stationary surface high. Our pattern could be one where there is an
absence of precipitation across the far northern sections, with the
focus closer to the VA/NC border. However, given the uncertainties
is just where the remnant front will be positioned, at this time it
would be unwise to suggest such a binary forecast. Our forecast will
reflect a better chance of precipitation south, with lesser amounts
south. Also, given the uncertainties, even for southern sections,
our forecast will reflect no location with a likely, 55-74 percent,
probability of precipitation. Finally, given no notable changes in
the overall pattern, temperatures are expected to be around or
slightly cooler than normal thanks to being on the north side of the
boundary, likely abundant cloud cover, and better chances of
precipitation than recent days.

Confidence in the overall synoptic pattern and expected temperature
trend is moderate. Confidence in the finer details of the location
of the greatest coverage of precipitation is low.

&&

.AVIATION /18Z MONDAY THROUGH SATURDAY/...
As of 140 PM EDT Monday...

VFR Stratocumulus has developed over the mountains. Convective
allowing models show coverage of any showers and thunderstorms
as isolated. The most likely locations are in the Mountain
Empire area and along the Blue Ridge south of Roanoke. Expect to
see storms pop up between before 4PM as the cap breaks. A
majority of the precipitation will dissipate after sunset and as
a shallow surface based inversion forms.

Average confidence for ceiling,visibility, and wind.


AVIATION OUTLOOK...

Coverage of thunderstorms Tuesday afternoon will be isolated.

Better chance SHRA/TSRA chances arrive Wednesday and Thursday along
with potential sub-VFR, with shower/storm chances lingering

Lower confidence on location of the front and coverage of
showers and thunderstorms for Friday and Saturday.

&&

.CLIMATE...
As of 300 AM EDT Monday...

Temperatures may come close to record high temperatures and/or
record warm low temperatures for July 15 and July 16.

Below you are table that list these values for 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   |
+=============================================+

&&

.EQUIPMENT...
As of 140 PM AM EDT Monday...

The KFCX 88-D radar has returned to service

&&

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

&&

$$

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