Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Blacksburg Virginia
1041 PM EDT Friday Jul 3 2015
a frontal boundary will work slowly northeast through the area
tonight into Saturday followed by a cold front. The cold front
will hang up just south of US Saturday nigh into Monday. This will
keep our area in an unsettled pattern through the Holiday weekend.
Near term /through Saturday/...
as of 1030 PM EDT Friday...
Radar showed another large area of moderate to heavy showers
moving into southwest Virginia and southeast West Virginia. Have
adjusted probability of precipitation to account for latest radar
Warm front extended from near Bluefield to near Danville. North
of the boundary winds were still out of the east to northeast with
low clouds and dew point depression near zero. Little drop in
temperature is expected overnight. Have added patchy fog in the
forecast tonight for a large part of the County Warning Area. As
the front drifts north clouds and fog will lift...but it may be
middle morning before the Alleghany Highlands and areas north of
Route-460 get out of the stratus and fog.
As of 300 PM EDT Friday...
The models seem to be in general agreement in the pattern taking
wavy front north of US Saturday morning. Until then expect showers
and some thunderstorms this afternoon into the evening...with one
upper wave passing by. A window of somewhat dry weather occurs
overnight before the another weak wave moves across the NC mountains
overnight into Saturday morning. This second wave once it moves
east of US midday Saturday will be followed by a "cold" front
This will be the focus for more showers and storms. Given the flow
turns more SW then west the probability of precipitation were for more scattered to numerous
coverage and not everyone will see rain Saturday but half to 3/4 of
you will at least from late morning into early evening.
With clouds around tonight...and high moist surface conditions kept lows
as we have had them the past few nights lower to middle 60s west to
upper 60s/near 70 east.
May see some sunshine Saturday so highs will be a few degrees warmer
than today ranging from the middle to upper 70s west to lower or middle
Short term /Saturday night through Monday night/...
as of 300 PM EDT Friday...
The unsettled weather will continue into the Holiday weekend. A wave
of low pressure along the frontal boundary will lift northeast
Saturday evening into Saturday night. This will push the front south
as low center moves away from our area. Low temperatures Saturday
night will range from around 60 degrees in the northwest mountains
to near 70 degrees in the Piedmont.
The front get hung up on Sunday across the south as cutoff low takes
shape over North Carolina. Widespread showers and thunderstorms are
likely...but the extensive cloud cover will hinder instability.
Localized heavy rainfall will be the main concern...but given that
the heaviest rainfall should remain mostly east of the
mountains...this further reduces concerns of flooding. With cloud
cover and rain...leaned highs towards the cooler MOS. High
temperatures Sunday will be below normal with readings from around
70 degrees in the mountains to the lower 80s in the Piedmont.
The best chance of convection Sunday will be in the east. Scattered
showers will linger Sunday night. Low temperatures Sunday night will
generally be from around 60 degrees to the upper 60s.
The cloudy wet weather continues Monday as the remnant upper low
drifts into northern Virginia. The best coverage of precipitation will be
located across the eastern sections...but differential heating
across the mountains should result in an increase of afternoon
convection compared to Sunday. Will hold on to high chance to likely
probability of precipitation for Monday. Instability appears marginal and the main concern
will remain that of localized heavy rainfall. High temperatures
Monday will vary from the middle 70s in the mountains to the middle 80s in
Taper of probability of precipitation Monday night into Tuesday morning...as shown on GFS
and European model (ecmwf). Low temperatures Monday night will drop into the upper
50s in the northwest mountains to the upper 60s in the Piedmont.
Long term /Tuesday through Friday/...
as of 300 PM EDT Friday...
On Tuesday...shortwave across northern Virginia will lift northeast
toward New England. At the same time...another shortwave and
associated front will approach from the northwest Tuesday. High
temperatures on Tuesday will warm into the lower 80s in the
mountains t0 the upper 80s in the Piedmont. Cold front pushes
southeast through the Ohio Valley...while surface trough will push
east to the Atlantic Tuesday night. Lows Tuesday night will
generally be in the 60s.
The front drifts south Wednesday and stalls by Wednesday night.
Highs on Wednesday will average from the middle 70s in the mountains to
the upper 80s in the Piedmont. This boundary will remain across our
region Thursday into Friday night.
How far south the boundary GOES is different depending on model
choice. The European model (ecmwf) pushing the cold front farther south with some
supportive upper troughiness compared to GFS.
Once again waves of low pressure are expected to form and ride along
the front keeping a good chances of diurnal showers and
thunderstorms across the region. High temperatures for Thursday and
Friday will moderate to around 80 degrees in the mountains to the
middle to upper 80s in the Piedmont. Low temperatures will range from
middle 60s in the mountains to around 70 degrees in the Piedmont.
Aviation /03z Saturday through Wednesday/...
as of 1030 PM EDT Friday...
Stable layer airmass/weak wedge exists north of frontal boundary
over the Carolinas. Front will lift slowly northeast tonight and
Saturday. North of the front expect widespread IFR to LIFR
ceilings and patchy MVFR to IFR fog. As areas of moderate to heavy
showers track across the region...visibilities may briefly
improve. Moderate confidence in the timing of the warm front. It
may not be until middle morning that ceiling and visibility at klyh
Winds should turn more SW then west by noon/16z Saturday...with
ceilings rising to at least MVFR. Lower confidence about the coverage
of showers and thunderstorms in the afternoon ahead of the cold
front. For now have kept any thunderstorms and rain/rain showers out of the tafs.
Extended aviation discussion...
Poor aviation conditions to continue into next week...but windows
of opportunity for VFR conditions increase into Mon/Tue. Upper
low/trough will linger west of the Virginia/NC coastal plain into the
southeast states through the weekend...then begin to drift into
northern Virginia by Monday. Meanwhile...a cold front will approach from
the Ohio Valley by Wednesday. This leaves a very unsettled/wet pattern
across the region through the period.
Expect widespread late night/early morning low clouds/fog with
IFR-LIFR cigs/vsbys. Overall...conditions should improve to MVFR-
VFR outside rain showers/thunderstorms and rain activity during the afternoons. At this
point...Tuesday appears to offer the best opportunity for more
widespread VFR conditions.