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-- Discussion containing changed information from previous version are highlighted. --
000
FXUS61 KRNK 241401
AFDRNK

Area Forecast Discussion
National Weather Service Blacksburg VA
1001 AM EDT Sun Sep 24 2017

.SYNOPSIS...
High pressure over the eastern United States will continue to
bring mainly warm and dry weather to the region through the
first part of the week, while Hurricane Maria stays just off
the east coast. A cold front is forecast to cross through the
area on Thursday.

&&

.NEAR TERM /THROUGH TONIGHT/...
-- Changed Discussion --
As of 1000 AM EDT Sunday...

A fine Sunday is underway with warm temperatures and plenty of
sunshine to be had. Highs will be in the mid 80s/near 90 east of
the Blue Ridge, low/mid 80s west. Enjoy!

Previous discussion...

Mid Atlantic region will be firmly beneath the upper ridge today and
tonight. Cirrus was filling over Virginia and North Carolina early
this morning. This cloud cover and the temperature/dew point spread
will result in less extensive fog than on Saturday morning. Typical
valleys from Greenbrier into the NRV will still have patchy dense
fog around sunrise.

Day to day persistence has been verifying well for maximum
temperatures. Highs today will be similar to Saturday. Used bias
corrected MAV/MET guidance as a base for low temperatures tonight.
-- End Changed Discussion --

&&

.SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/...
As of 350 AM EDT Sunday...

Deep-layer ridge broadly centered over the Southern Tier of NY will
continue to provide subsidence and dry conditions to the region
Monday into part of Tuesday. 00z deterministic and ensemble NWP
shows the ridge beginning to break down and weaken later Tuesday as
Maria makes an approach to coastal NC. Weak ridging should prevail
Wednesday across the western third of the forecast area, with the
00z GFS and ECMWF solutions do show an increased pressure gradient
for locales east of the Blue Ridge and into the VA/NC Piedmont as
Maria makes her closest approach to the Carolina coast Wednesday.
Latest forecast calls for Maria`s center to likely remain off the
coast with the only effect on our forecast area being a modest
increase in northeasterly to north wind speeds midweek. For more
details specific to Maria, consult the latest forecast and
advisories from the National Hurricane Center.

The chief guidance differences in this period is the extent of cloud
cover Monday and Tuesday with an influence on temperatures. The 00z
NAM generally advects much more RH in northeast flow back westward
than either the GFS or the ECMWF show. Should see partly to mostly
sunny skies each dry conditions Monday. On Tuesday afternoon, the
NAM also shows some light QPF along the eastern slopes of the
Appalachians and the Blue Ridge associated with slightly better
moisture convergence. Both the NAM and the GFS show some low-level
convective instability - being capped above 700 mb. Did include 15-
20% PoPs Tuesday on the eastern lee side of the terrain for showers.
Shallow convective depth should preclude any thunder so kept as
light showers. For Wednesday, expecting more variable cloudiness
greatest with eastern extent - particularly east of a rough line
from Appomattox to Rockingham Counties where cloudiness associated
with Maria`s far northwestern circulation could overspread. Partly
to mostly sunny skies should exist further west. What should be a
noticeable trend through each day in the period is a gradual
increase in northeast winds, greatest on Wednesday. With that said,
gusts are no higher than 25 mph.

As for temperatures...warmest day still appears to be Monday with
highs in the upper 70s to mid/upper 80s. Kept high temperatures in
the mid 80s Tuesday and Wednesday given at least some partial
cloudiness. Lows Monday night are in the mid 50s to mid 60s, but are
about 3 degrees warmer with some clouds around and increased wind
speeds than experienced recently.

&&

.LONG TERM /WEDNESDAY THROUGH SATURDAY/...
As of 147 PM EDT Saturday...

Just minor changes to the previous forecast this period as we watch
Hurricane Maria track northward off the east coast. An upper ridge
over the northeast will slow Maria down some, and as it lifts
northeast a slight heading to the northwest toward the Outer Banks
looks likely before the stronger upstream 5h trough shifts Maria
back east and out to the sea into Friday/Saturday.

For our weather still looking fairly dry with warmer than normal
temperatures Thu, then some cooling trend Friday-Saturday as
front and upper trough shift across. However, the front lacks
moisture so shower chances are very low, as we continue a drier
than normal trend. Model trends beyond 7 days continues to paint
us mainly dry, but temperatures should be a little closer to or
below normal.

&&

.AVIATION /14Z SUNDAY THROUGH THURSDAY/...
As of 715 AM EDT Sunday...

Fog was not nearly as extensive as the past few mornings, mainly
due to high thin clouds. Could still see some fog along the New
and Greenbrier Rivers but it had not spilled into the KBCB and
KLWB airports as of 11Z/7AM. Have pulled all the morning fog out
of area TAFs. Once the river valley fog burns off, VFR
conditions are expected for the rest of the day.

Clearing anticipated with sunset with good radiational cooling
and a calm to light and variable wind, potentially supporting
fog in the favored river valleys, most likely after 09Z/5AM.

Extended Aviation Discussion...

Overall persistence forecast early this week as strong high
pressure aloft builds in from the northwest keeping tropical
moisture offshore. VFR conditions should prevail in the daylight
hours, along with late night/early morning IFR/LIFR radiation
fog through Wednesday morning.

An overall dry cold front crosses the region Wednesday night
into Thursday as Maria passes off the Outer Banks. These
features likely to cause increasing northerly winds Wednesday
into Thursday as the pressure gradient between the two tightens
on Wednesday, and then due to cold advection behind the front
on Thursday.

&&

.RNK WATCHES/WARNINGS/ADVISORIES...
VA...None.
NC...None.
WV...None.

&&

$$
SYNOPSIS...MBS
NEAR TERM...MBS/AMS
SHORT TERM...AL
LONG TERM...WP
AVIATION...AL/AMS