Scientific Forecaster Discussion
fxus61 krnk 180058
Area forecast discussion
National Weather Service Blacksburg Virginia
858 PM EDT Mon Jun 17 2019
a stationary front will linger over the mid Atlantic this week.
Waves of low pressure should track eastward along this front,
which will provide a daily threat of showers and thunderstorms.
Warm and humid conditions should continue through this time.
Near term /through Tuesday/...
as of 900 PM EDT Monday...
Clusters of showers and isolated thunderstorms continue to
linger across southern/southwest sections this evening, mostly
in areas that have not been worked over from earlier convection.
Also appears that a convectively induced wave looks to be
lingering along the foothills per broad turning seen on radar
loops. Latest hrrr keeps some of this convection going for a few
more hours before loss of heating/instability finally cause most
showers to fade around midnight. However can see some of this
continuing to spread east via redevelopment given the current
lingering axis of higher cape values in the southeast. Expect
these mostly to be heavy rain produces per pwats nearing 1.5
inches this evening. Therefore keeping likely pops going in
spots over the south with low chances north to Highway 460 attm.
Muggy lows in the 60s with some staying above 70 with some
patchy fog around.
Previous discussion as of 200 PM EDT Monday...
The 12z rnk sounding reveals a precipitable water of 1.20 inches
and a considerably high freezing level. Wind shear is rather
light, so the threat for any severe weather this afternoon
appears marginal. However, thunderstorms that develop will be
quite efficient in producing rainfall. Cape should exceed 2,000
j/kg during the next couple hours, which will increase the
expected coverage of storms.
By tonight, the showers and thunderstorms should wane as
instability decreases. Leftover cloudiness from earlier
convection and the humid air mass will keep low temperatures in
the 60s. More showers and thunderstorms appear likely for
Tuesday as a shortwave upper level trough moves overhead. As a
result, pops were increased across the County Warning Area. Again, heavy
rainfall will likely occur in the storms due to the high
freezing levels and above average precipitable water. Storm Prediction Center also
maintains a marginal threat of severe weather for Tuesday.
Short term /Tuesday night through Thursday night/...
as of 300 PM EDT Monday...
Showers/storms associated with upper level shortwave trough are
expected to move east of the forecast area after midnight
Tuesday, increasing stability and west-northwest downslope wind
bringing an end to the convective threat. Will maintain slight
chance pops to account for any lingering showers late Tuesday
night into Wednesday morning but think overall chance for rain
will end with passage of the shortwave and onset of negative
vorticity advection (nva).
Wednesday will likely be a down day with respect to thunderstorm
threat as we will be in the wake of the departing short wave.
Surface heating and may initiate some isolated showers/storms
Wednesday, but coverage sub-par since forcing mechanism limited
to just the heating of the day. Better opportunity for
showers/storms is expected to occur Thursday associated with
dynamic lift from another short wave trough...this trough moving
quickly from west to east via modest zonal flow.
Elevated pwats of 1.25 to 1.75 are forecast the entire week, so
showers/storms that do occur will be rain efficient. Surface
dewpoints are also forecast to remain at or above 65 so it will
remain muggy, temperatures ranging from the 60s at night to the
80s during the day.
Long term /Friday through Monday/...
as of 330 PM EDT Monday...
Expect a drying trend for Friday and Friday night as winds
likely to remain northwesterly in the wake the passage of
thursday's short wave trough. Plenty of mid level drying
progged as well, so shower/storm activity would be
unfavorable. Can't rule out a rogue shower far west for any
upstream activity which may cross the Ohio Valley, but think
Friday as a whole for our forecast area will be dry.
The drying is expected to be short-lived however as upper ridge
builds in again by Saturday along with return of deeper
moisture for the entire weekend. Thus chances of showers/storms
increase Saturday and more so into Sunday. Near seasonal
temperatures and increasing humidity as well through next
weekend. Generally pretty good agreement in the guidance for
these trends through the upcoming weekend.
Aviation /01z Tuesday through Saturday/...
as of 710 PM EDT Monday...
Showers and isolated thunderstorms will continue to linger into
this evening before slowly fading to mainly VFR with the
exception of patchy fog overnight. Thus plan to continue either
a vicinity mention or tempo in some lower conditions in residual
showers espcly south and west through about midnight. Expect
areas of MVFR to IFR conditions in fog/stratus overnight espcly
in spots that received earlier heavy rain. However debris clouds
as well as upstream cloud cover could inhibit it to some
VFR conditions should resume for Tuesday morning, but showers
and thunderstorms appear likely to fire again in the afternoon
as a wave of low pressure passes overhead. Coverage of this
convection could become rather widespread with the potential for
MVFR conditions, gusty winds, and turbulence at all taf sites.
Therefore given higher confidence included either prevailing
showers/storms or vicinity mention for convection Tuesday
Extended aviation discussion...
A stationary front over the mid Atlantic along with waves of low
pressure tracking eastward along this boundary should keep an
active weather trend through Thursday. Showers and thunderstorms
will likely develop each afternoon and evening, which will
produce areas of MVFR and heavy rainfall. MVFR or IFR conditions
from fog or low clouds may also occur during the late night
hours due to increasing moisture. By Friday, a cold front should
shove the stalled boundary offshore, and drier air from high
pressure will bring VFR conditions through Saturday.