Area Forecast Discussion
Issued by NWS Blacksburg, VA

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FXUS61 KRNK 242313
AFDRNK

Area Forecast Discussion
National Weather Service Blacksburg VA
613 PM EST Sat Feb 24 2018

.SYNOPSIS...
Low pressure was over Arkansas with a warm front extending into the
Mid Atlantic region. The low will move northeast tonight and Sunday
which pushes the warm front into New England and a cold front across
much of the eastern United States on Sunday. High pressure will be
over the area on Tuesday.

&&

.NEAR TERM /THROUGH SUNDAY/...
As of 545 PM EST Saturday...

Updating PoPs based on radar trends with showers across the
mountains. These showers will move north and out of the area by
900 pm.


As of 215 PM EST Saturday...

Primary axis of precipitation this evening will extend from central
New Jersey to southern Indiana to central Arkansas with scattered
showers in the warm sector. Will have higher probability of
precipitation this evening when the models bring a band of deeper
moisture across southwest Virgina, northwest North Carolina, and
southeast West Virginia. Expecting a lull in the precipitation late
tonight. Any chance of thunderstorms this afternoon and evening will
be largely driven by daytime heating.

Widespread showers and isolated thunderstorms will reach the area on
Sunday morning along with the cold front. Bath county to Buckingham
County will be close to the surface warm front this evening so will
be trending temperatures down a couple of degrees in that area.
Otherwise temperatures will remain mild and above normal overnight
ahead of the front.  Clouds and precipitation will hold down warming
on Sunday. Even with a minimal heating potential on Sunday,
Convective Available Potential Energy forecast to be around 500 J/KG
Sunday afternoon so may keep threat of isolated thunderstorms
in east of the Blue Ridge. Overall timing of front was very
similar in all the guidance.

&&

.SHORT TERM /SUNDAY NIGHT THROUGH TUESDAY NIGHT/...
As of 215 PM EST Saturday...

Cold front expected to move through a large part of the forecast
area will continue to largely govern sensible weather conditions
Sunday night into a part of Monday as well. By majority of today`s
12z NWP solutions, this front will tend to get hung up or stall from
the VA Tidewater region southwest into north-central NC and into the
Deep South. A weak mid-level trough coming out of the southern
Rockies/Plains region should induce a weak low/wave to form on the
frontal zone Sunday night, rippling along the stalled boundary into
the first half of Monday. Still is some level of uncertainty on the
exact position of the frontal zone Sunday night, which mostly
affects the northward extent of rain chances on the cool side of the
boundary; that said, it`s reasonable enough to expect some brief
northward return of the stalled front Monday as the weak low/wave
moves across. Though showers may extend as far north as Route 460,
highest confidence of rain is from Route 58 in southern VA into
northern NC where frontal boundary may linger. It`s also a little
less certain on when rain chances are greatest - the NAM and 00z
ECMWF suggests it rains a good part of this period, with the
GFS/Canadian shows the best period of rain being in the after-
midnight timeframe. While the ECMWF is considerably wetter than most
guidance, that the rain will probably be falling on the cold side of
the front should keep rain rates more gradual, so not anticipating
any hydrologic issues at this stage. Best chance of clearing and
cooler nighttime temperatures is toward the northwest due to cool
advection and some radiational cooling from building ridge. These
areas also should see at least peeks of sun on Monday as well versus
the cloudier southern tier. Will show lows in the 40s/lower 50s, but
in the southern areas will show little significant rise in temps
Monday into the upper 50s. Highs elsewhere are also in the upper
50s, despite starting off cooler with better prospects for sun here.

Passage of the weak low along the front then pushes the front into
the Carolinas Monday night with the center of an expansive ridge
settling over the Canaan Valley in WV. This is pretty much ideal
radiational cooling which should help to plummet temperatures into
the 30s, perhaps near 40 in the northern NC Piedmont. Though I`m not
overly confident as yet to put in the grids, with the likelihood of
wet ground and developing radiation inversion, may have some
overnight patchy fog with best chance perhaps where it rained Sunday
night/Monday.

Tuesday by and large is uneventful. In-situ CAD profile will
probably begin the day with easterly flow against the southern Blue
Ridge, perhaps leading to some scattered lower clouds but it`s
otherwise a largely dry, mostly sunny forecast. CAD then erodes by
afternoon with southerly/veering low-level profile. This will spread
increased cloud cover in the western Appalachians/southern Blue
Ridge Tuesday night. Appears best chance for light rain is along the
southern Appalachians in GA/southwestern NC, but will carry lower
Chance PoPs for the pre-dawn Wednesday hours up to Ashe County.
Highs Tuesday should have no trouble reaching at least the upper
50s, and areas in Southside/Piedmont should reach the mid 60s again.
For temps Tuesday night, sided on cool side of guidance given at
least some radiational cooling before clouds overspread Tuesday
night - with lows in the upper 30s to mid 40s.

&&

.LONG TERM /WEDNESDAY THROUGH SATURDAY/...
As of 100 PM EST Friday...

12z global guidance points to a more active weather pattern late in
the week. A southern stream mid-level trough and organizing surface
low coming out of the southern Plains will be the source of this
active weather period, and at least on a synoptic scale, may not be
too dissimilar to the one underway today (Saturday). This
should be a potentially wet period overall at least for the end
of the week, before conditions begin to trend somewhat drier and
more typical for late February/early March.

Elongated warm front pushes across the region on Wednesday/Wednesday
night. This will focus at least steady light showers through
Wednesday. The most active day at this point appears to be on
Thursday, as a powerful digging shortwave with good 500 mb height
falls/diffluence aloft combines with warm, moist warm sector (PWATs
> 1 inch) and approaching cold front to lead to high chances for
rain. Good veering profile from surface southeasterlies to southwest
500 mb winds along with the aforementioned height falls/forcing
could support potential for thunder as well for part of the region.
Beyond that, it`s too early to speculate on any further potential
impact though. Thursday is nonetheless a day to keep close tabs on
in the upcoming workweek. Will indicate high Likely to low
Categorical PoPs with this system.

The southern stream trough then phases with northern energy and
evolves into a closed upper low Thursday night into Friday. This
will lead to precipitation becoming more orographic/NW flow variety
as the surface low becomes nearly stationary off Southern New
England. Though much of region should trend cooler and generally
drier, may see some rain or upslope, elevation-dependent wet snow in
the western mountains Friday (850 temps fall to 0 to -4C).

Temperatures should continue to run above to well above normal
through the rest of the workweek, then begin to trend closer to
normal into the upcoming weekend.

&&

.AVIATION /00Z SUNDAY THROUGH THURSDAY/...
As of 613 PM EST Saturday...

Flight conditions will be VFR into tonight across southwest
Virginia, northwest North Carolina and southeast West Virginia.
Isolated to scattered showers are expected through the evening.
Probability of occurrence was too low to include in area TAFs
except LWB.

MVFR of lower ceilings are possible north of a warm front
tonight. NAM, RAP, and GFS all keep the boundary north of KLYH
but only medium confidence overall with the forecast position of
this front.

The main cold front crosses into the region from the west on
Sunday. High confidence of widespread showers after 12Z with
occasional MVFR visibility.

Extended:

Sub-VFR conditions may extend through Monday and Monday night as
the front stalls to the south allowing for showers to linger
across southern Virginia into much of North Carolina throughout
the day. High pressure builds over the region into Tuesday
which should bring drier conditions and VFR, at least
temporarily. By Thursday rain and MVFR to IFR ceilings may
return to the region.

&&

.CLIMATE...
Records For...

Feb 24th

Site MaxT/Year    Warm Min/Year
 BLF  71/2017        53/2017
 DAN  79/2012        51/1996
 LYH  79/2012        53/1985
 ROA  80/1985        52/1943
 RNK  73/1975        49/1975

&&

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

&&

$$
SYNOPSIS...AMS
NEAR TERM...AMS/RCS
SHORT TERM...AL
LONG TERM...AL
AVIATION...AMS/RCS
CLIMATE...PM



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