Area Forecast Discussion
Issued by NWS Blacksburg, VA

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FXUS61 KRNK 191735

Area Forecast Discussion
National Weather Service Blacksburg VA
135 PM EDT Tue Sep 19 2017

High pressure will remain over the region the remainder of this
week resulting in mainly dry and mild weather during the next
few days. Jose should track north, off the east coast today
through Tuesday, before sliding just east of New England on


As of 955 AM EDT Tuesday...

Low clouds and fog will gradually mix out or lift this morning
into this afternoon. Adjusted temperatures with surface obs,
trends and GLAMP for late morning into this afternoon. A mixture
of clouds and sunshine will warm afternoon temperatures to
highs from the upper 60s in the mountains to the lower 80s in
the piedmont. Low level convergence, heating and orographic
lift may generate some isolated shallow convection this
afternoon. Enjoy the pleasant weather !

As of 240 AM EDT Tuesday...

Area remains under dry air aloft, per water vapor loop, between Jose
passing well offshore and the next upstream axis of deeper moisture
associated with a cluster of mid level shortwave energy in the
Midwest. Expect this overall trend to continue today as subsidence
is maximized espcly east as a drier but weak north/northwest
trajectory develops behind the passing Jose. Guidance continues to
try and develop shallow convection mountains with heating but
convergence looks even weaker this afternoon given less northeast
flow. Thus trimmed back going pops to just an isolated shower
mention Blue Ridge without any thunder despite slightly higher
instability beneath a lingering strong inversion aloft. This mainly
in the mid to late afternoon hours when strong heating is maximized.
May also be looking at less fog to start the morning per lingering
low clouds around which could fill in and delay heating a little
longer espcly if fog does develop around dawn.

Otherwise appears rather similar to the past few days with low level
moisture early fading to afternoon north to south cumulus bands
later on. Heating of slightly drier air after a warmer start should
also boost highs a bit more today, with some warming aloft west
leading to highs 75-82 mountains, and low/mid 80s east.

Models show the upstream energy aloft associated with a weak surface
cold front to the northwest slowly edging east into western sections
by late tonight. However moisture will again be running into
subsidence including leftover dry air aloft so expect most showers
to fade upon approach into the mountains after loss of heating. This
could at least result in more cloud cover which may put a damper on
widespread fog late, so only including some patchy coverage in the
valleys toward daybreak. Otherwise keeping it mainly clear east to
partly cloudy west with only an isolated pop far western ridges
late. Lows mainly 55-60 west and 60-65 east pending degree of
clouds/fog late.


As of 300 AM EDT Tuesday...

Our persistent pattern featuring an eastern ridge and western trof will
become amplified through the end of the week as a closed low digs into
the northwest. While this will provide us with rather uneventful
weather through the end of the workweek, it will also open the east
coast to effects from tropical systems moving across the Atlantic.
Current and future tropical systems will continue to be monitored
closely for any potential impacts in our neck of the woods.

Capping in the strong ridge aloft will be weakening with time and
upstream short wave energy will be undercutting the ridge and moving
through the region. Expect the result will be a diurnal pattern for
scattered showers/thunderstorms generally along and west of the Blue
Ridge, with a trend toward decreasing coverage and drier conditions
by Friday as upper support slowly sinks off to the south

Expect little change in the temperature regime with a continuation of
above normal warmth. Look for highs generally in the low to mid 80s
east of the Ridge with mid 70s/near 80 to the west. Lows will generally
be in the low to mid 60s east, mid/upper 50s west with some cooler
readings in the valleys.


As of 330 PM EDT Monday...

Upper ridge becomes even more dominant in the extended period with a
large a dome of high pressure covering the eastern CONUS and
extending north into southern Canada right through the weekend. The
upper low out west digs even further south into the Great Basin as
short-wave energy continues to drop into the long-wave trough. At
the same time whatever is left of Jose may be lingering in the
western Atlantic with models continuing to struggle with how
blocking to the north may affect future movements. Meanwhile,
tropical system Maria, likely still a hurricane, will be entering
the picture but still well off the southeast coast. Temperatures
thought the extended period will remain at about 5F to 10F
above mid- to late September climatology and chances for
significant precipitation will remain low beneath the strong
and persistent ridge.


As of 135 PM EDT Tuesday...

SCT to BKN MVFR clouds possible this afternoon into tonight.
A few showers may develop late in the afternoon, but none
should deter flight plans given isolated nature. The best
chances will occur across the higher terrain. A weak upper
disturbance approaches from the west this evening into tonight
which could bring more clouds and some showers and even an
isolated storm to far western sections tonight. The question is
whether the drier air in place will dry up convection. Some
clearing expected overnight leading to another round of
fog and stratus to develop late once any shallow convection
ends. Similar to recent morning expect fog to mix out by 14z
Wednesday morning. By Wednesday afternoon expect some scattered
MVFR/VFR convection to form with the best chances along and west
of the Blue Ridge mountains. Light winds tonight will become
west around 10 mph Wednesday afternoon.

Medium confidence in ceilings,visibilities and winds during the
taf period.

Extended Aviation Discussion...

Overall persistence forecast to prevail for the rest of the
upcoming week into the weekend with strengthening high pressure
remaining in place between exiting Jose offshore and a weak
cold front approaching from the west. This should maintain good
flying weather outside of early morning fog/stratus through late
next week, with only isolated to scattered diurnal showers
possible Wednesday evening and Thursday afternoon as upper
level energy slides across. Isolated MVFR convection is
possible Friday in the southwest mountains. Dry weather is
expected Saturday and Sunday.




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