Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

FXUS61 KRNK 191355

Area Forecast Discussion
National Weather Service Blacksburg VA
955 AM 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 715 AM EDT Tuesday...

Bands of low clouds will continue to slowly increase from the
north and east early this morning as low level moisture wraps
around Jose passing well offshore. These cloud swaths along with
areas of fog should make for a wide range of conditions from
LIFR in fog/stratus in some of the valleys to MVFR under
strato-cu over the northern and eastern sections. Thus will have
either prevailing sub-VFR conditions through mid morning to
start or TEMPO in brief lower cigs/vsbys in spots where appears
low conditions wont linger too long. 

Fog/stratus should burn off around 14z/10A, with perhaps some
lower sub-VFR cigs lingering where bands persist until around
midday espcly along/east of the Blue Ridge. Otherwise expecting
enough heating along with a drier northerly flow to allow for
diminishing low level moisture through the morning with all 
sites becoming VFR going into the afternoon under a SCT- BKN 
cumulus field similar to the past few days. A few showers may 
develop late in the afternoon, but none should deter flight 
plans given isolated nature, so wont mention at this point.

A weak upper disturbance approaches from the west this evening 
which could bring more clouds and added showers and even an 
isolated storm to far western sections early tonight. Otherwise
expecting another round of fog/stratus to redevelop late once 
any shallow convection ends and clouds diminish by daybreak 

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 diurnal showers possible mainly 
Wednesday and Thursday afternoons as upper level energy slides 





National Weather Service Glossary of Abbreviations