Area Forecast Discussion
Issued by NWS Blacksburg, VA-- Remove Highlighting --
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FXUS61 KRNK 260548
Area Forecast Discussion
National Weather Service Blacksburg VA
148 AM EDT Fri Aug 26 2016
High pressure will be the dominant weather feature through the
upcoming weekend...becoming centered directly overhead by
.NEAR TERM /THROUGH TODAY/...
As of 845 PM EDT Thursday...
Despite the return of ample low level moisture per dewpoints/pwats,
convection has remained quite isolated into early this evening
given only a weak residual surface trof along the Blue Ridge to
focus on. Also subsidence aloft across the west in the wake of the
passing wave very efficient in removing most cloudiness as
evidenced via the very dry air aloft over a weak mid level cap off
the RNK evening sounding. This along with building heights under
the ridge aloft and forecast subsidence seen off latest models in
conjunction with loss of heating supports going dry overnight.
Still might see an isolated low topped shower redevelop from outflow
along the VA/NC border given lingering instability but overall
mostly clear. This along with low level moisture and favorable
fog parameters off guidance raobs should allow for more widespread
fog in the valleys by dawn, and espcly southern sections that saw
earlier heavy downpours. Otherwise will be back to the warm and
muggy scenario overnight with lows mid/upper 60s mountains to
around 70/low 70s east.
Previous discussion as of 330 PM EDT Thursday...
A few showers and storms across the foothills of VA/NC shown by the
high-res models to shift eastward through late afternoon. As such
will keep very low chance pops mainly from just east of the Blue
Ridge through early evening, then should see dry wx. As we head
overnight skies should be mostly clear. With dewpoints in the upper
60s to lower 70s and a light wind, should see some fog mainly in
river valleys, and where it rained this afternoon. Low temps will be
in the mid to upper 60s west to lower 70s east.
Friday will be drier as upper center of high moves across Virginia.
Slight chance of storms will be mainly over the southern Blue Ridge.
A hotter day but heat indices in the Piedmont should stay just below
the century mark. Highs will be in the lower to mid 90s east of the
Blue Ridge including Roanoke and Lexington, VA, with the mountains
reaching the mid to upper 80s.
.SHORT TERM /TONIGHT THROUGH SUNDAY NIGHT/...
As of 350 PM EDT Thursday...
Strong subtropical ridge of high pressure (5H heights advertised
near 597 dm) will be centered over the region this weekend. This
feature will ensure that summertime heat will prevail with daytime
temperatures of 4 to 7 degrees above normal and overnight lows
averaging a full 10 degrees above normal. There will be an
isolated threat for diurnally driven showers/storms, but this
activity is expected to be mainly confined to the mountains west
of the Blue Ridge.
.LONG TERM /MONDAY THROUGH THURSDAY/...
As of 450 AM EDT Thursday...
The upper-level ridge will begin to weaken as we progress into the
mid part of next week but will also be the key to steering a
tropical system that is forecast by most models to track into
south Florida early in the week. Although the track is now
relatively similar among the models, there are vast differences in
the intensity. While the GFS shows a weak tropical low drifting
slowly north to northeast across FL into southeast GA and
eventually the Carolinas through the week, the ECMWF develops a
tropical storm/hurricane, which it similarly moves northeast,
albeit much quicker than the weaker GFS system. Meanwhile, as the
upper high weakens and shifts south of our area, another weak
front is progged to drift into the region by midweek. Much of the
time, our region will likely remained sandwiched in between the
frontal precipitation to our north/west and the tropical system to
our south. However during the later part of the week, the tropical
system could begin to impact at least the southeastern parts of
our CWA and with the pattern in place, there is always at least
some concern of a predecessor rain event. At any rate, considerably
uncertainty remains and such considerations still remain just
beyond this forecast period. Therefore, will continue the trend
established in the short term period of slight chance to low
chance diurnally driven pops and well above normal temperatures
moderating only slightly closer to normal by the end of the period
as cloud cover and moisture increase, the upper high weakens, and
850mb temps drop back a few degrees.
.AVIATION /06Z FRIDAY THROUGH TUESDAY/...
-- Changed Discussion --As of 148 AM EDT Friday...
High pressure both surface and aloft will control our weather
today and tonight. Outside of morning fog and isolated convection,
great flying weather is expected. This morning, the combination
of light winds and low level moisture has produced patches of fog.
Patchy dense fog and localized IFR- LIFR vsbys/cigs may occur
especially KLWB and perhaps KBCB. KLYH and KDAN along with KBLF
may also see a period of MVFR fog. morning low clouds and fog will
burn off by mid morning, expecting mainly scattered cumulus
through the afternoon with any convection very isolated at best.
This will be too isolated to include mention in any taf site.
winds will remain light and variable Friday afternoon. Clear to
partly cloudy conditions are expected Friday night with another
round of late night patchy fog in the valleys. KLWB could drop to
IFR/LIFR once again Saturday morning.
High confidence in ceilings,winds and winds during the taf
Extended aviation discussion...
Strong ridging to hold tight on Saturday with continued VFR and
again only isolated late day mountain shra/tsra resulting in
possible brief MVFR.
A weak front will drift into the area Sunday. Isolated to
scattered diurnal showers and thunderstorms still possible into
Sunday evening. Coverage will be limited in area and duration.
Monday high pressure bubbles in but still a very humid airmass to
keep isolated mountain storms around in the afternoon, but mainly
VFR. Another front situated north of us Tuesday could enhance
convective threat, mainly over the mountains and north of ROA/LYH.
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