Area Forecast Discussion

FXUS61 KRNK 240714
Area Forecast Discussion
National Weather Service Blacksburg VA
314 AM EDT Mon Jun 24 2019
A warm front will slowly lift north through our area today. A
cold front will sweep across our area this evening with high
pressure building in behind this system for Tuesday and
.NEAR TERM /Through Monday Night/...
As of 315 AM EDT Sunday...
A warm front across our region early this morning will lift
north today allowing much higher dew points and a more
summerlike airmass to overtake the region. Meanwhile in the
upper levels of the atmosphere, an impressive upper level trof
becomes negatively-titled and pushes through the great lakes by
Tuesday morning. This will help drive a cold front through our
region Monday evening. 
In advance of the cold front, the mean 00Z HREF forecast 
SBCAPES exceed 1500 J/KG this afternoon. With forecast soundings
showing no capping in place, expect thunderstorm to fire late
this morning/early this afternoon, especially in areas with
differiental heating such as the Blue Ridge. With forecast
soundings hinting at an inverted-v signal and DCAPE values
forecast to exceed 400 J/KG, damaging winds are looking more
likely today and added 'gusty wind' wording in grids for
The CAMs are in good agreement bringing a more organized line of
thunderstorms into the western portion of our forecast area
around or after 00Z (8 PM Monday). This timing is slightly
slower than earlier forecasts, so kept chance for storms in the
east until around 06Z. With 0-6km bulk shear values 25-35 knots,
this line of storms should continue well into our forecast area
before gradually fading with loss of heating. Damaging winds and
locally heavy rains are also expected with this line.
With a nice surge in 850mb temps and winds becoming southwest in
the wake of a warm front, leaned toward the warmer guidance for
temps today and pushed highs up a degree or two.
In the wake of the cold front tonight, gusty west to northwest
winds are expected, so wind speeds were adjusted slightly upward
tonight with lows staying toward the warmer end of guidance.
.SHORT TERM /Tuesday through Thursday night/...
As of 230 AM EDT Monday...
The cold front will be passing offshore by Tuesday morning. Model 
soundings show a 30-40 kt jet at 850 mb with the NAM showing a 
stronger jet than the GFS. Thus, the winds and wind gusts have been 
bumped upward due to the expected mixing from the boundary layer 
into that low-level jet during sunrise and through the remainder of 
the day. This jet will weaken by the afternoon, and winds should 
eventually subside toward evening as high pressure builds overhead. 
Although confidence is high that nothing should reach wind advisory 
criteria, there may be gusts over 30 kt in the highest elevations. 
Temperatures will warm up considerably across the Piedmont due to 
downsloping winds from the west-northwest. With drier air being 
depicted in the models for Tuesday night into Wednesday morning, 
dewpoints and low temperatures were nudged a few degrees downward.
Wednesday and Thursday should start as pleasant with plentiful 
sunshine. The upper air pattern during those days will flatten as a 
broad upper level ridge takes hold from east of the Rocky Mountains 
all the way to the East Coast. This ridge combined with surface high 
pressure across the Mid Atlantic should place a good cap overhead 
that will limit any organized convective development. PoPs were 
decreased for Wednesday as the cap appears to be the strongest on 
this day, so it will be difficult for even an isolated shower or 
thunderstorm to pop up along the northwest North Carolina mountains. 
Confidence is a little better that some convection may fire on 
Thursday afternoon as the heat and humidity continue to increase, so 
chance PoPs were included along the southern Blue Ridge in North 
Carolina and Virginia. This activity should dissipate by early 
Thursday night. Elsewhere, it will likely stay dry.
.LONG TERM /Friday through Sunday/...
As of 300 PM EDT Sunday...
During most of this portion of the forecast, an upper level ridge 
will be centered over the Central Plains States, with its eastern 
edge over our region. Closer to the surface, high pressure will 
start this period over our region, and trend eastward through 
Saturday. The result will an airmass across our region that will 
average about five degrees above normal, and become progressively 
more moist throughout the depth of the column as low level winds 
trend more southerly. With limited, if any, upper level dynamics to 
help initiate vertical motion, any precipitation will be confined to 
diurnal/differential heating based showers and storms, with their 
focus near the higher peaks and ridges of the mountains, and, or, 
southern sections of the area where dew points will be higher than 
those of northern sections.
Heading into Sunday, we may see a backdoor cold front head south 
toward, or into, the area as the upper level low over southeast 
Canada shift farther south into New England and possibly parts of 
the mid-Atlantic region. It's impacts are expected to be more 
noticable on Monday in the form of cooler temperatures, a day past 
the valid seven-day time period of this afternoon's forecast package.
Confidence in the above section of the forecast is moderate.
As of 140 AM EDT Monday...
At 0530Z (130 AM EDT), a warm front bisected our area with
south/southwest winds generally west of I-77 ushering in higher
dew points and thus lower clouds and vsbys with IFR and LIFR
conditions in some spots. For our TAF sites, the most likely
areas to experience MVFR to IFR cigs early this morning will be
KLWB and KBCB. Any low clouds and fog will erode after 9 AM 
As the warm front lifts north of our area today, a surge in
moisture will help trigger scattered thunderstorms across the
region, but for now left VCTS in all taf sites after 17Z, with
later times for KDAN and KLYH. The probability of thunderstorms
increases with a cold front that will reach KBLF around 00Z (8
PM EDT), and sweep east exiting our region by 06Z (2 AM
EDT/Tuesday). Any storms today will have the potential to bring
gusty winds. Continued VCTS for this later period until a more 
precise time can be pinpointed. 
.Extended Aviation Discussion...
The cold front will cross the Mid Atlantic region by Tuesday 
morning. High pressure tries to build into the area later 
Tuesday into Thursday. Other than some late night/early morning 
patchy fog, VFR conditions are expected for the bulk of this 
time period.
Confidence in the above aviation forecast discussion is