Area Forecast Discussion
Issued by NWS Blacksburg, VA

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FXUS61 KRNK 191949

Area Forecast Discussion
National Weather Service Blacksburg VA
249 PM EST Mon Feb 19 2018

A warm front will lift north of the region overnight and a strong
ridge will then set up off the southeast coast providing much
above normal temperatures through the week. Chances for rain
increase late Wednesday into Thursday.


As of 235 PM EST Monday...

The big weather story in the near term (and beyond) is in fact
the development of a very big ridge off the southeast U.S. coast
which all the global models have been consistently showing with
somewhat varying amplitude for at least several days and short-
term models now in agreement. WPC model diagnostic discussion
favors the EC and EC ensembles for the strength of the ridge
which is a little less extreme than the UKMET and CMC but still
highly anomalous. Heights more typical of summer with 594 dm
heights at h5 building over the Carolinas by midday Tuesday will
allow for unusually warm temperatures expected both overnight
and Tuesday (see Climate section below for details on possible
records). 850 mb temps are near +15C by Tuesday afternoon and
with more sun than today would not be surprised if some records
highs are at least challenged, although at this point only
Bluefield is currently forecast at a record for tomorrow.
Overnight lows will not fall off much tonight especially in the
east where lingering overcast impedes diurnal cooling. Patchy
fog is likely tonight and some very light drizzle possible
mainly along the Blue Ridge where ceilings may be quite low at
times. Clouds will continue to diminish tomorrow with temps
maxing out in upper 60s to low 70s, some 20 to 30 degrees above
normal for this date.


As of 200 PM EST Monday...

Surface high pressure over Bermuda and a strong 595 dam upper level
ridge just off the East Coast will provide a strong warm air
advection pattern for Tuesday night and Wednesday. Meanwhile, a cold
front will try to move eastward across the Ohio River Valley. Model
guidance continues to show well above normal temperatures for
Wednesday that could put records in jeopardy, which are further
discussed in the Climate section. The only caveats going against
this record warmth are cloud cover and a chance of afternoon
showers. A slight threat of a thunderstorm exists over southeast
West Virginia, but model soundings reveal quite weak instability
with CAPE only reaching 100 to 200 J/kg. The latest GFS solution has
a little more cloud and shower coverage than the NAM and ECMWF
models. There is a consensus that some morning clouds could linger
along the southern Blue Ridge until the afternoon, but temperatures
could soar significantly once the clouds break up.

The chance of rain will increase during Wednesday night and Thursday
as the cold front tries to edge closer. Models portray the upper
level ridge slowly flattening and sagging southward, but it will
still resist the eastward progression of the cold front.
Temperatures should remain well above normal for the middle of
February, but highs should run a little cooler for Thursday due to
surface high pressure passing over eastern Canada and beginning to
wedge southward along the eastern side of the Appalachian Mountains.
Eventually, the cold front will fold over and set up as a nearly
stationary baroclinic zone over northern Virginia. Thus, this
forecast keeps the highest probability of rain north of Interstate
64. Shower coverage should also increase west of Interstate 81 later
in the afternoon. With the cool wedge in place by Thursday night,
lows should be notably cooler compared to Wednesday night.


As of 200 PM EST Monday...

The cool wedge should weaken as surface high pressure heads offshore
on Friday. However, the latest GFS shows a slower weakening trend
compared to the ECMWF model. Another area of low pressure will try
to develop over the southern Gulf Coast as an upper level trough
progresses eastward from the Rocky Mountains. More clouds and
chances of rain seem likely for the upcoming weekend as this area of
low pressure pushes eastward. Meanwhile, the upper level ridge over
the Southeast should finally give way and heads toward Florida. That
pattern change should free up the atmospheric flow to allow a cold
front passage over the Mid Atlantic toward Sunday night. High
pressure should allow drier conditions by Monday. Despite the
overall trend of more clouds and rain, temperatures still should
remain considerably above normal with no anticipated threat of
freezing temperatures.


As of 1245 PM EST Monday...

TAF conditions are quite variable early this afternoon with the
best CIGS/VSBYs in the west where the skies have partially
cleared. Terminals along and east the Blue Ridge remain in a
weak wedge situation with lower clouds and ceilings persisting
but also variable. This general pattern will continue overnight
with the lowest CIGS/VSBYs in the east. Also the possibility of
patchy fog and drizzle in the early morning hours but
confidence not enough for prevailing.

Improving conditions expected on Tuesday as the ridge builds
across the area and the air mass dries out somewhat under
southerly flow at the surface and aloft.

Scattered MVFR showers are expected Wednesday into Thursday
with the approach of a cold front. This front lifts back north
Friday with continued threat of showers and potential low


As of 330 AM EST Monday...

Tuesday and Wednesday will feature well-above normal temperatures
that may approach or eclipse daily record highs and daily record
high minimum temperatures. It`s also possible that all-time warmest
February minimum temperatures could be approached or broken in this

Following are daily records, as well as the all-time warmest minimum
temperatures recorded in the month of February, for our five
climate sites with long-established periods of record:

Tuesday 2/20/2018
Site    MaxT Year   HiMin Year
BLF       67 2017      48 1994
DAN       74 1971      51 1949
LYH       76 1930      59 1939
ROA       75 1939      54 1971
RNK       69 2017      47 1991

Wednesday 2/21/2018
Site    MaxT Year   HiMin Year
BLF       65 1996      54 1997
DAN       75 2011      55 1953
LYH       75 1930      50 1981
ROA       73 1930      48 1997
RNK       71 1986      49 1953

Warmest HiMin - February:
Site   HiMin Date
BLF       57 Feb  5 2008
DAN       60 Feb 18 2008
LYH       59 Feb 20 1939
ROA       57 Feb 12 1932
RNK       52 Feb 16 1990




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