FXUS61 KRNK 200036

Area Forecast Discussion
National Weather Service Blacksburg VA
836 PM EDT Mon Aug 19 2019

High pressure will remain over the region tonight into Tuesday
resulting in a continuation of the hot and humid weather. A cold
front approaches by the middle of the week bringing increasing
chances of showers and storms Wednesday into Thursday. This front
should finally work southeast through the area by the weekend.


As of 800 PM EDT Monday...

The Bermuda high pressure will remain in the Atlantic ocean tonight
into Tuesday. The very hot and humid airmass will continue with
scattered diurnal showers and thunderstorms.

Monday's deep convection is fading per loss of daytime heating.
A few showers may linger longer in the east where temperatures
were the warmest. Patchy fog is possible late tonight and
Tuesday morning, otherwise will be another muggy sort of night
with little or no threat for precipitation. Low temperatures
tonight will range from the upper 50s in the deeper mountains
valleys to around 70 degrees in the piedmont.

The hot and humid weather pattern will continue Tuesday with the
opportunity for more scattered afternoon and evening
thundershowers. Weak upper level shortwave energy will combine
with low level instability, orographic effects, convergence and
surface boundary interactions to generate scattered showers and
thunderstorms. The slowly approaching cold frontal boundary off
to the northwest may enhance the convective environment. The
SPC Day 2 convective outlook indicated marginal severe
thunderstorms are possible in the west. Outflow boundary
interactions and clustering of cells may create pulse severe
thunderstorms especially during the afternoon and evening hours.
Also anticipate some heavy downpours and potential localized
hydro issues will remain a concern in the moist environment.
High temperatures Tuesday will vary from the lower 80s in the
mountains to the lower 90s in the piedmont. Heat index in the
piedmont will be near the century mark Tuesday afternoon.


As of 345 PM EDT Monday...

The synoptic pattern changes little from Tuesday into Wednesday
with numerous weak and subtle short waves moving across the
Appalachians across the top of a broad subtropical ridge
anchored across much of the southern U.S. Meanwhile, a Bermuda
high remains parked offshore. Hot and humid conditions will
continue through midweek. These hot/humid conditions will fuel
ample instability for a continuation of largely pulse drive
thunderstorms with diurnal heating, thus favoring mid-afternoon
through the early evening hours. As we near the end of this
period, a weak west-east oriented frontal boundary will begin to
slowly approach from the north. This will likely enhance the
areal coverage and perhaps the intensity of storms during the
later half of the week. Thus isolated severe storms will be
possible, but most are expected to be non-severe given the weak
dynamics aloft. Some heavy downpours and potential localized
flooding issues may begin to develop after several days of this
pattern, but overall rainfall recently has been spotty and
evaporation of soil moisture has been high in the hot
temperatures and lack of general rainfall in recent weeks. Most
areas could really use a good soaking. Grass is dried up and
brown in many areas around the forecast area. So, rain will be
welcome in most areas. However, any persistent and repetition of
storms in the same areas could result in localized flooding
concerns. At this point, Thursday looks to be the best day for
widespread showers and thunderstorms as well as the severe and
flood threat. Pops also reach into the likely range by Thursday.

With 850mb temperatures hovering in the +20C to +22C range
through the next several days, don't look for any cooling this
period with highs in the 80s west to 90s east and lows mostly in
the upper 60s to lower 70s, except for the cooler decoupled
values at night. Dewpoints will remain close to 70 in many
areas, limiting the cooling at night for sure.


As of 345 PM EDT Monday...

A pattern change will slowly evolve into the weekend as an upper
trough centered across the Great Lakes continues to deepen and
help push a west-east oriented cold front slowly south through
the area. Models disagree on the speed with which the front will
drift south of the area enough to shut off precipitation
changes. At this point, that does not appear with strong enough
potential to remove pops from any forecast period within this
time frame. In fact, the weekend could be quite wet and
unsettled as the front slowly drifts southward through the area. This
front will eventually stall across the Southeast by the weekend.

Given time of year and the overall lack of good upper-level
support to push the front south, have kept high chance to even
periods of likely pops across the southern two thirds of the
region into the weekend. It appears from the viewpoint of most
models that drying will be limited to northern areas, generally
near and north of the I-64 corridor.

Temperatures are expected to be a bit closer to normal as 850mb
temperatures drop back into the mid and upper teens and clouds
and precipitation remain abundant. Northern areas may eventually
end up being warmer during the daytime than southern areas by
the weekend, as clouds and precipitation will be more abundant
south/east of the Blue Ridge. Nighttime low temperatures will
likely remain at or above normal during the period, especially
across southern areas.


As of 800 PM EDT Monday...

Mainly VFR anticipated with the exception of patchy late night
fog and scattered afternoon and evening showers/thunderstorms.
Fog may be accompanied by a layer of stratus in the mountain
valleys with between 3AM-9AM promoting local IFR/LIFR. Scattered
thunderstorms Tuesday afternoon will promote local MVFR/IFR but
not widespread enough to place in the TAFs at time. VCNTY TS/CB
will be advertised. Mean wind aloft is forecast under 15 kts,
so storm cells that develop should be slow moving.

Medium confidence on cloud bases,visibilities and winds during
the taf period.

.Extended Aviation Discussion...

The airmass will remain unchanged through mid-week with daily
threat for showers and thunderstorms. A front will approach from
the northwest later in the week, resulting in an uptick in
shower/storm activity with potential for organized deep
convection across the Ohio Valley which may move downstream and
into the Mid-Atlantic region as an MCS or series of MCSs.

Improving conditions with more in the way of VFR will be
possible for the weekend, pending just how far south of the
area the front makes it.


As of 810 PM EDT Monday...

No records today. Got within 1 degree of the record at LYH and
within 2 degrees at BCB.

Record Daily Maximum Temps:

Monday 8/19:
ROA: 98/1914
BLF: 91/2007
DAN 102/1988
LYH 98/1914
BCB 93/1988

Tuesday 8/20:
ROA: 104/1983
BLF: 92/1914
DAN: 101/1925
LYH: 102/1983
BCB: 92/1983

Wednesday 8/21:
ROA: 105/1983
BLF: 94/1936
DAN: 104/1983
LYH: 101/1983
BCB: 98/1983




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