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Area forecast discussion 
National Weather Service Blacksburg Virginia
703 PM EDT Friday Jul 3 2015

a frontal boundary will work 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 655 PM EDT Friday...

Radar showed a bulk of the coverage of showers and isolated
thunderstorms in the far eastern County Warning Area and over the
North Carolina foothills. Will cancel the Flash Flood Watch in the
west since most of the widespread precipitation has moved out of
that region. Expecting only scattered showers and thunderstorms
for the rest of the evening.

Front extended from south of Bluefield to just north of Danville.
North of the boundary winds were still out of the east to
northeast. Warmest temperatures in the County Warning Area were in
the middle 70s....south of the warm front.

As of 300 PM EDT Friday...

Flash Flood Watch over southeast WV into the mountain Empire of SW Virginia until 8
am Saturday. Main concern is slower moving/repeating showers with
isolated storms through this evening as wavy front remains in the
general area. Think the latest high-res models showing better radar
trends of taking heavier rain to the northeast after the
watch may be cancelled early.

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 Saturday afternoon.

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
80s east.


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
the Piedmont.

Taper of probability of precipitation Monday night into Tuesday 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 /00z Saturday through Wednesday/...
as of 130 PM EDT Friday...

Stable layer airmass/weak wedge exists north of frontal boundary
over the Carolinas. Its very shallow so expect any fog/lower ceilings
to start to improve this afternoon with moderate to heavier
showers moving in.

The tafs followed a blend of the high res models hrrr/rap through
this evening...then more toward the gfslamp afterwards.

Needless to say...flying weather is not ideal this Holiday

Expect mostly sub VFR conditions through the period...worsening
again overnight with IFR or worse possible.

Before this...toned down thunder threat in the tafs as cloud
cover will limit thunder though upper dynamics favors some
scattered storms. For this kept thunderstorms in the vicinity in all tafs through early
evening. Confidence is higher for blf to have a small window of
thunderstorms per radar trends from 19-21z.

Models start to lift the showers away from US overnight with
potential for low ceilings/visibilities again with frontal boundary lingering
in vicinity of the Blacksburg forecast area. Winds should turn more SW then
west by 14-15z Saturday...with ceilings rising to at least MVFR.

Extended aviation discussion...

Poor aviation conditions likely to continue into early next
week...but windows of opportunity for VFR conditions increase as
we move 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.


near term...ams/wp
short term...kk
long term...kk

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