Area Forecast Discussion
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FXUS61 KRNK 301626
Area Forecast Discussion
National Weather Service Blacksburg VA
1226 PM EDT MON MAY 30 2016
The remnants of Bonnie will linger along the South Carolina coast
this afternoon into tonight, slowly working northeast to the North
Carolina coast Tuesday. A cold front arriving from the west Friday
will finally boot Bonnie out to sea by the end of the week.
.NEAR TERM /THROUGH TONIGHT/...
As of 930 AM EDT Monday...
Much of the area remains in between the deeper tropical moisture
associated with Bonnie to the southeast per latest blended pwats,
and a weak upstream shear axis along a faint cold front just west
of the ridges. This has resulted in a weak convergence zone along
the Blue Ridge per north/ne flow around the tropical low and the
boundary approaching from the west. However latest short term
guidance indicates only very weak support aloft today, with
eastern showers driven via influx of tropical moisture from the
south, and more orographic aided convection over the west where
should see more heating once the remaining fog fades soon. This
along with better forecast instability west would support best
coverage across the far western mountains this afternoon, per
more clustering of shra/tsra, then heading east toward the Blue
Ridge late. Appears less out east where more spotty shra likely
given subsidence zone on the back of Bonnie which should factor in
per latest HRRR. Thus have cut back on pops central and east until
later while boosting to higher chances far west where may need
brief periods of likely pops pending later coverage. Again given
weak steering between low level northerly flow and sw flow aloft,
potential exists for bands to get stuck with some heavy rain
potential given decent pwats. Overall highs of 75-82 look on track
with perhaps the far east being the coolest pending clouds.
Previous discussion as of 330 AM EDT Monday...
Tropical depression Bonnie continues to track very slowly if at all
between Charleston and Myrtle Beach. Water vapor satellite shows a
plume of tropical moisture feeding into the NC coast then northward
across the Virginia piedmont. Drier air is situated across the
Appalachians with more moisture with a shortwave moving across the
Ohio Valley. Early this morning a narrow band of showers had formed
near I-77 in NC north along the Blue Ridge of Virginia. The 04z HRRR
seemed to be picking up on this fairly well with subsequent 06z run
also hitting the southern Blue Ridge into the NC foothills with best
threat of showers this morning with isolated to scattered coverage
to the east. At the same time fog was becoming dense where it had
cleared along and west of the Blue Ridge from Fancy Gap north toward
I-81 from Marion to Christiansburg. Think fog will be periodic based
on in and out lower clouds and possible showers but enough coverage
of lower visibilities to warrant a Special Wx Statement.
For today, any fog will be diminishing by 9am. Following the HRRR
into late morning and blending with the 00z GFS as it seemed to have
a decent handle on synoptic features gives us isolate to scattered
showers til lunchtime. Should see some sunshine enough to destablize
the airmass. More thunder is expected this afternoon, but not
expecting it to be widespread, as it will be dependent on how much
sunshine occurs. This afternoon, thinking the better low level
convergence stays near the Blue Ridge and the across the Piedmont
roughly east of a LYH-DAN line and moreso east of our forecast area.
Looking for high chance to even low likely pops along and either
side of the Blue Ridge this afternoon and then east of South Boston
to Charlotte Court House with low/scattered threat elsewhere. Given
the flow from the sfc-7h mb will be mainly light from the NNE should
see some heavy rain potential with slow moving storms and
precipitable water values of 1.5". At the moment will not highlight
this in the HWO as it will be isolated, but would not be surprised
that a flood advisory or even a flash flood warning is issued later
this afternoon for small scale area.
With a little more sunshine or breaks expected went close to MAV
guidance on highs with mainly upper 70s to lower 80s across a good
deal of the region. Slightly cooler in the lower to mid 70s along
the Southern Blue Ridge.
Tonight, remnants of Bonnie still situated near the NC/SC coast.
Models show deeper moisture well east of us but will still be in a
tropical like airmass and think showers will linger all night, though
coverage will lessen as will thunderstorm threat. Will go with
isolated coverage most of the night and still looks like areas near
the Blue Ridge may stay in more of a favorable low level convergence
zone to keep isolated showers here through the overnight. Drier air
will try to make it at least to the WV/VA border south toward the
NC/TN border. This gradient will likely enhance fog potential with
fog likely most areas overnight.
.SHORT TERM /TUESDAY THROUGH THURSDAY/...
As of 210 AM EDT Monday...
Tropical Depression Bonnie will continue to linger over the
Carolinas through Thursday. While Bonnie is inland, she will
continue to weaken, losing her closed circulation aloft. However,
she will maintain and generate spiral bands of convection,
especially during the afternoon, fading in the evening. These bands
will likely move east over the piedmont, possibly making it to the
Blue Ridge each afternoon. Even if these bands do not track that far
east, afternoon heating and easterly upslope in a tropical air mass
should be enough to generate scattered showers and an isolated
thunderstorm along and west of the Blue Ridge Tuesday and Wednesday
afternoon. By Thursday, a closed low is expected to move over the
Great Lakes and its associated cold front will enter the Ohio
Valley. This front will give Bonnie a nudge out to sea. This cold
front and remaining tropical moisture will bring a good chance for
widespread showers Thursday and Thursday night.
Temperatures will continue to warm by a degree or two each day until
the front moves east of the area Thursday night into Friday.
Temperatures will generally warm into the upper 70s to lower 80s.
Overnight lows will remain muggy and in the 60s.
.LONG TERM /THURSDAY NIGHT THROUGH SUNDAY/...
As of 400 PM EDT Sunday...
A cold front Friday will result in an increased threat for
showers/storms...its passage bringing a less humid airmass to the
region for the weekend.
Until the frontal passage at the end of the week, temperatures,
especially the overnight lows, will favor above normal readings.
After the frontal passage, lower dewpoints and clearing skies will
support lower nightime lows. Daytime highs are advertised to be close
.AVIATION /16Z MONDAY THROUGH FRIDAY/...
As of 1220 PM EDT Monday...
Overall VFR conditions will prevail along/west of the Blue Ridge
to start this afternoon with a gradual increase in cumulus
buildups as bands of convection develop along the western ridges.
This may bring periods of sub-VFR in shra/tsra but any lower
conditions are expected to be brief so will keep a vicinity
mention going and amend if convection nears a particular airport.
East of the mountains still looking at bands of lower clouds
associated with the remnants of Bonnie with MVFR expected to
linger at times around KDAN and perhaps KLYH with KROA remaining
VFR outside of any showers. However appears that a band of
convection may shift east across the Blue Ridge before sunset and
perhaps push east affecting the eastern locations into this
evening ahead of a weak cold front. Thus kept in some shra/tsra
mention from KROA east to around midnight with clearing over the
west. Dense fog is then likely across the valleys including
KLWB/KBCB, with MVFR to IFR fog out east. Locations such as KBLF
and KROA remain iffy in regards to fog pending rainfall later
today and any mixing overnight. For now will keep these locations
mainly MVFR with potential for more fog/stratus and IFR at KBLF at
Should see conditions improve to VFR by midday Tuesday although
low cigs may linger out east around KDAN longer with low level
moisture with Bonnie still around. Repeat scenario then likely
Tuesday afternoon with heating resulting in bands/clusters of
convection over the mountains and lingering lighter showers with
tropical moisture in the east. This likely to occur mainly after
the valid taf period so will bring most locations excluding KDAN
up to VFR by early Tuesday afternoon without any mention of
convection for now.
Similar setup from tonight again Tuesday night with more fog
around along with low clouds after any evening convection ends.
Appears convection may be more isolated Wednesday as the area
slides in between the next upstream cold front and the remnants of
Bonnie near the coast. Thus more potential to see more widespread
VFR Wednesday with exceptions over the east and with any pop up
storms across the mountains.
Finally an stronger upper trough will kick what is left of Bonnie
out to sea Thursday-Friday. Thursday may be our driest day with
frontal showers and storms not arriving until late in the day, then
more widespread showers Thursday night into Friday making for
periods of sub-VFR.