Area Forecast Discussion
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FXUS61 KRNK 191959
Area Forecast Discussion
National Weather Service Blacksburg VA
259 PM EST Thu Jan 19 2017
High pressure centered over our region this afternoon will shift
east to the coast tonight as a warm front lifts north from the Gulf
Coast states into the southern Appalachians. The warm front will
swing north across Virginia and into the mid-Atlantic Friday, before
stalling. Another storm system moving across the southern U.S. will
impact our region Sunday into Monday.
.NEAR TERM /THROUGH FRIDAY/...
As of 200 PM EST Thursday...
Upper Ridge over our region this afternoon will slide east tonight
into Friday. Warm advection high clouds this afternoon will be
followed by increasing mid clouds starting to roll into the
southwest by dusk.
Low pressure over western Tennessee this afternoon will lift
northeast into the Ohio Valley tonight and reach Lake Erie by Friday
afternoon. A warm front trailing from the low will lift northward
tonight into Friday. Isentropic lift increases this evening across
the mountains of North Carolina and shift to the rest of the
forecast area overnight. With a dry airmass in place, slowed down
the onset of the rain this evening. Used a blend of HRRR and
HiResW-arw-east for pops this evening, then utilized a mix of NAM
and Continuity with pops tonight into Friday. The best chance for
rain is in the mountains with lower threat in the Piedmont. Lower
dewpoints in the evening combined with increasing moisture may
allow for temperature drop once the rain starts to fall tonight.
However, it should remain mild with low temperatures ranging from
the upper 30s in the Alleghanys and portions of the Greenbrier
Valley to upper 40s to about 50 degrees in Mountain Empire.
On Friday, the best lift will push quickly northeast through the
region. An upper level shortwave ridge will build over the Mid-
Atlantic region. The bulk of the rain will have moved northeast of
the area by the early to mid afternoon. Added the mention of fog to
isc grids. Lowered high temperatures a few degrees especially in the
north Friday with clouds and rain. High temperatures Friday will
vary from the upper 40s in the mountains to the lower 60s in the
south. Rainfall amounts overall will average around a quarter inch
with locally higher in the western mountains of Southwest Virginia
and North Carolina.
.SHORT TERM /FRIDAY NIGHT THROUGH SUNDAY/...
As of 300 PM EDT Thursday
Even with limited sunshine on Saturday the air mass will be
unseasonably warm, 15 to 25 degrees above normal. Deep moisture
begins to arrive back into the area from the southwest on Saturday
afternoon. But Bufkit not showing a saturated sounding until closer
to Sunday morning.
Models forecasting good lift Sunday with a strong vorticity maximum
crossing the central and southern Appalachians along with upper
diffluence. Winds at 850MB back to the southeast by 12Z/7AM Sunday
with good upslope and increasing inflow off the Atlantic first
along the Appalachians in northern North Carolina on the Sunday
morning gradually shifting north of Roanoke by the end of the
More significant differences in the guidance in the amount of
instability across southern Virginia and northern North Carolina on
Sunday all related to the location of the warm front. 12Z NAM/GFS
and latest RAP indicating enough of a secondary low developing
over eastern North Carolina that with the precipitation there
should be strong in-situ wedging. Large spread in location of
heaviest rain also so will lean toward WPC guidance. Wedge and
precipitation will keep temperatures on the cool side/or below
guidance for Sunday. Have added slight chance of thunder from
extreme southern Virginia into northern North Carolina but
confidence is low.
.LONG TERM /SUNDAY NIGHT THROUGH WEDNESDAY/...
As of 200 PM EDT Thursday
Precipitation will remain in the area through Monday with the
highest rain amounts on Sunday night and Monday, mainly along and
east of the Blue Ridge. Experimental Hydrologic ensembles
showed a least a small potential for 1 to 3 inches of rain.
Localized minor flooding is possible is this amount of
precipitation is realized.
Once the surface low is off the coast on Monday night and Tuesday,
precipitation will be confined to favored western upslope areas.
Enough colder air comes in Monday night that will have snow in the
forecast from southeast West Virginia into northwest North
Carolina. Winds will also increase Monday night and Tuesday.
There may be enough of a low level jet. cold air advection and
pressure rises for wind gusts in the 40 to 50 mph range.
By Wednesday and Thursday a long wave positively tilted upper trof
will extend from the Great Lakes across the central United States.
Prevailing deep southwest flow over the Mid Atlantic region
this time frame differences in the models on how fast any front
will progress east. For now WPC has surface front crossing the
region on Wednesday and Wednesday night. Behind this system is a
much colder air mass. More upslope snow showers in the
mountains are possible. At this time the models are showing any
snow showers on Thursday night.
.AVIATION /20Z THURSDAY THROUGH TUESDAY/...
As of 101 PM EST Thursday...
Low clouds eroded out of the Greenbrier valley this afternoon,
returning KLWB to VFR conditions. Under Mid and High clouds
VFR conditions will continue into this evening. As the high
pressure center shifts east tonight, a warm front will lift
north in the the southern Appalachians. As moisture increases
ceilings will lower from the Southwest tonight into Friday
morning. Looking at rain moving into BLF/LWB/BCB/ROA in the
08-12z time frame with MVFR cigs. Heavier bands of rain could
produce IFR conditions. Rain will spread east across the region
Friday with MVFR ceilings and local IFR/LIFR conditions in low
clouds,fog and rain.
Medium confidence in ceilings,visibilities and winds during the
Extended Aviation Discussion...
Rain moves out Friday afternoon with some improvement expected
briefly but next system will bring more lower cigs in Saturday
into Sunday with rain. This continues into Monday with poor
flying conditions expected across the Mid-Atlantic and
Southeast. Gusty northwest winds and mountain MVFR showers are
expected for Tuesday.