Area Forecast Discussion
Issued by NWS Blacksburg, VA

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FXUS61 KRNK 200658

Area Forecast Discussion
National Weather Service Blacksburg VA
258 AM EDT Fri Apr 20 2018


A large high will cover much pf the eastern United States today
through Saturday. Low pressure over the Lower Mississippi Valley on
Sunday will track northeast to the Virginia coast by Wednesday. This
will bring widespread rain and below normal temperatures to the Mid
Atlantic region Monday and Tuesday.


As of 225 AM EDT Friday...

No changes to Frost Advisory and Freeze Warning for this morning.

Surface high pressure from teh Great Lakes to the Carolina today and
tonight. Dry air mass in place with little cloud cover expected.
Warm air advection at 850mb, dry air and a lot of sun will mean a
large rise in temperatures today. Similarly, dry air and surface dew
points in the 20s will result in sharp drop in temperatures after
sunset. Winds in the valleys will decouple with ideal radiational
cooling conditions. Will headline more frost east of the Blue Ridge
along with a Freeze Watch for a few counties north of Route 460
again tonight.


As of 230 AM EDT Friday...

Surface high pressure centered along the Virginia coast, will weaken
some on Saturday, but still keep the area dry. An inverted surface
trough is expected to emerge west of the Appalachains and should only
develop a few fair weather cumulus clouds Saturday afternoon across
the mountains. Mostly sunny skies with a light east to southeast
flow will allow for highs in the upper 50s to mid 60s areawide,
coolest in the higher ridges.

A back-door front will stall across north-central Virginia Saturday
night. This front will bring more clouds than previously thought
into the area overnight. These clouds will help keep overnight
temperatures mild in the upper 30s to lower 40s. The back-door front
washes out on Sunday while clouds stick around through the day. If
these clouds remain thick and with a southeasterly flow,
temperatures Sunday maybe similar to Saturday (upper 50s to mid

A slow moving closed low is expected to track from Arkansas Sunday
morning to eastern Tennessee late Sunday night. Models have a strong
short wave out ahead of this low moving up the southern Appalachian
Mountains Sunday night. With high pressure to the north and the low
to the southwest, southeast flow will increase and transport of Gulf
and Atlantic moisture should reach the southern Blue Ridge and
adjacent foothills of NC into far southwest VA by dawn Monday.
Latest models are coming around toward a wet Monday, but the weekend
stays dry.


As of 200 PM EDT Thursday...

Not a lot of confidence in the models as they continue to shift back
and forth with track of upper and surface low across the Gulf Coast
States early next week, then offshore by Wednesday followed by
another front Wednesday-Wed night. Ensembles are leaning toward a
wetter solution similar but not as wet as the 12z GFS. The 0z ECM
appears driest early on. Will increase pops Mon-Tuesday but cap pops
in the likely range with best coverage over our southern CWA.

High pressure over the mid-Atlantic coast then offshore will provide
an easterly fetch and in-situ wedge which could hold temps down
quite a bit Monday, with 40s in the mountains of NC/far southern VA
but due to uncertainty on northern shield of rain will have temps a
little milder but still at or just under mex mos elsewhere.

Low tracks to the GA coast by Tuesday morning, then northeast off
the NC coast by Wednesday morning as northern stream wave allows
another front to cross Wednesday night.

So in essence most of the extended period will hold a threat of rain
with best chance Mon-Monday night into early Tuesday, possibly a
break Tue-Tue night but will not have sub-30 percent pops at this
time. Should be drier by later Thu-Thu night.


As of 120 AM EDT Friday...

High confidence of VFR conditions today and tonight across the
Mid Atlantic region.

Extended Aviation Discussion...

VFR conditions into Saturday as high pressure slowly builds in
from the northwest.

Clouds will begin to creep back into the area on Sunday in
advance of an approaching low in the Lower Mississippi River
Valley. However, cigs should remain VFR even while the ceiling
heights lower and clouds thicken. SCT MVFR showers are possible
in southern Virginia and northern North Carolina Sunday night
with rain becoming more widespread across the Mid Atlantic
region on Monday. MVFR/IFR ceilings and visibilities are
possible Tuesday due to rain.


VA...Frost Advisory until 9 AM EDT this morning for VAZ022-023-
     Freeze Warning until 9 AM EDT this morning for VAZ024-035.
NC...Frost Advisory until 9 AM EDT this morning for NCZ003>006-019-


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