Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000
FXUS61 KRNK 181509
AFDRNK

Area Forecast Discussion
National Weather Service Blacksburg VA
1009 AM EST Sun Feb 18 2018

.SYNOPSIS...
High pressure will move across the area today. A warm front
will move north into the southeast tonight into Monday bringing
another shot of rain to the area. Afterwards, a strong ridge
will set up off the southeast coast providing much above normal
temperatures through much of the week.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 1009 AM EST Sunday...

High pressure will build east across the region this afternoon
into tonight. Adjusted temperatures with latest observations,
their trends and shaped towards GLAMP. Morning low clouds and
fog are mixing out and lifting.


As of 310 AM EST Sunday...

Expect a clearing trend today, but low clouds are expected to linger
in the upslope areas through late morning, with the lower clouds in
the piedmont scouring out around 8am.

High pressure will be over KY this morning, then shift east off the
mid-Atlantic coast this evening. Warm frontal boundary draped over
the deep south advances northward tonight as southwest flow
increases. Isentropic lift overrunning this boundary should serve to
bring a some rain to the area overnight. Temperature profiles stay
above freezing and not expecting any ptype issues in our forecast
area. Temperatures will be about 10 degrees warmer than Saturday
with mid 40s to around 50 west, to lower to mid 50s east, except
some upper 50s across the NC piedmont into southside VA.

Tonight, the rain will move into the drier air with evap cooling
knocking temps into the 30s overnight, except around 40 southwest VA
west of Bluefield to Marion, and into the NC foothills/piedmont.
Rainfall amounts overnight will be under a quarter inch, with best
coverage over southeast WV into the Alleghanys.

&&

.SHORT TERM /MONDAY THROUGH WEDNESDAY/...
As of 307 AM EST Sunday...

Amplified mid-level height pattern through the balance of this
period across much of CONUS. The two main large-scale height
features being a 2-2.5 standard deviation above-normal subtropical
ridge west of Bermuda, and a sharp digging trough into the Desert
Southwest/southern Rockies. Given the implied height gradient
between the two features, a cold front progged across the mid-
Mississippi Valley - serving as the focus for repeated rounds of
early-week rain in the middle of the country given a favorable tap
of moisture off the western/central Gulf - will be very slow to
advance eastward toward the western Appalachians by late Wednesday.

Main highlights in the period are well above normal high/low temps
Tuesday and Wednesday with springlike humidity levels. Couple
chances for precip in the period - as a warm front makes
northeastward progress Monday, and in a weakly unstable environment
Wednesday.

Warm front from Sunday night will make a slow advance northeast,
with leftover showers continuing into the early afternoon north of
Route 460. Given the timing of the front and the likelihood of
leftover clouds behind the front, am not optimistic that the
Piedmont in VA/NC gets out of the mid 50s in terms of highs, despite
850 temps pushing +11C. Southeast WV and into the New River Valley
stands the best chance of reaching the low/mid 60s given southwest
surge of milder air from the TN Valley. Any afternoon showers would
be mainly in the southern Blue Ridge in NC/VA and would depend
highly on enough southeast-south wind convergence to generate any
showers. Am not optimistic this will occur but kept a token 15-20%
PoP in for these areas.

Warming trend areawide begins Tuesday where guidance has begun to
trend less cloudy. It will begin to turn more humid by mid-Feb
standards as well w/dewpoints commonly in the 50s. Subsidence again
largely keeps the forecast area dry. Partly cloudy skies should push
most areas into the lower 70s, except along the ridges with mid 60s.
While the first half of Tuesday night looks dry, moisture begins to
increase per 00z NWP against the Blue Ridge and have carried 15-30%
PoPs for the after-midnight period. Still looks like the best chance
at rain Tuesday night is into the southern Appalachians.

Cold front begins to approach central/eastern KY on Wednesday, with
another day of anomalously mild, humid conditions by mid-Feb
standards. Noticed the 00z ECMWF and 00z GFS generate warm-sector
QPF mainly from the Blue Ridge foothills west, in a regime of weak
instability (LI`s of -1 and showalters of -1 per GFS) with PWATs of
1-1.25". Kept PoPs at Chance levels Wednesday, but opted to
introduce slight chance thunder. And by slight chance thunder, this
really translates to a few rumbles here or there. Best convergence
still lags the region but given the progged thermo environment,
couldn`t say thunder is out of the question. Rain chances diminish
the further east of the Ridge one goes, with QPF a few hundreths to
as much as a quarter-inch. Highs should again top out in the lower
70s with mid 50s to lower 60s dewpoints.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH SATURDAY/...
As of 300 PM EST Saturday...

Synoptic pattern features a strong subtropical ridge of high
pressure parked along the southeast Atlantic Coast with 590+ heights
at 500 mb. Relative to climatology, this is 2 to 2.5 standard
deviations above normal.

This set-up favors much above normal temperatures for the Southeast
States with the baroclinic zone forced to reside on the west side of
the Appalachians from East Texas to the Ohio Valley and into the
eastern Great Lakes. Repetitive rainfall is likely within this
corridor during the second half of the week with our forecast area
far enough east of the boundary to escape anything significant.
Toward the end of the week, models hint that a surface front will
impinge on the forecast area, but overall weather conditions for mid
week feature above normal warmth and only a chance for showers
pending any instability within the warm subtropical airmass.

Temperatures Wednesday night are expected to be 10-20 degrees
above normal with lows in the 40s. Models suggest potential for
a backdoor front to impinge from the north-northeast Thursday,
so somewhat cooler/wetter conditions are favored for Thursday.

&&

.AVIATION /15Z SUNDAY THROUGH THURSDAY/...
As of 620 AM EST Sunday...

Keeping some MVFR cigs early at BLF/LWB and LIFR vsbys at DAN
but should see all sites at VFR by 14-16z. Gusty northwest winds
will drop off to the light winds by midday as high pressure
works overhead.

Clouds increase this evening ahead of a warm front with rain
moving in late tonight. Ceilings and visibilities overall will
be MVFR to at times IFR especially in the mountains.

Extended Aviation Discussion...

The area will stay situated in a sub-VFR pattern with rain through
at least early afternoon Monday before we start to dry out. We
may clear out enough Monday night for fog to form. High
pressure strengthens offshore resulting in a return to overall
VFR Tuesday ahead of the next cold front well west of the
Appalachians. Scattered MVFR showers are expected Wednesday into
Thursday.

&&

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

&&

$$
SYNOPSIS...WP
NEAR TERM...KK/WP
SHORT TERM...AL
LONG TERM...PM
AVIATION...WP


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