Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Blacksburg Virginia
748 PM EDT Monday Jul 28 2014
an upper trough of low pressure will remain centered over the East
Coast through the middle of the week. Likewise...cool high
pressure will settle over the region through Wednesday. During the
latter half of the week and heading into the weekend...the upper
trough will retrograde westward...and allow for an increase in
moisture...moderating temperatures...and potential for showers
Near term /through Tuesday/...
as of 700 PM EDT Monday...
Northwest flow in the low levels along with shortwave aloft in the mean
trough across the middle Atlantic and central Appalachians noted
across US this early evening. Acting more like fall out there with
stratocu in the mountains spilling over into the foothills and
Piedmont. Isolated rain showers over the mountains per support aloft. Going
into this evening think the coverage of rain showers dissipated with loss
of heating...though cannot rule out a few sprinkles in the higher
terrain. The rest of the forecast looks on track...just updated
some wind and sky cover to account for the gusty conditions in the
mountains winds should subside a bit after dusk.
Previous valid discussion...
Low temperatures tonight will be on the cool side for this time
of the year...with most areas forecast within five degrees of
records. The forecast low of 55 at Bluefield would tie the
record. Specific records are in the climate section of this
On Tuesday...our cool pattern will continue with the axis of the
upper trough still over our region...and the center of surface high
pressure will approach from the west. Embedded with the main upper
trough pattern...model guidance offer a solution with a weak
disturbance within the main flow crossing mainly the southern half
of the area on Tuesday. Will continue to allow for isolated showers
in the forecast across the southwestern part of the area...in the
path of the disturbance and within a zone of weak upslope 850 mb
flow. High on Tuesday are expected to average around five degrees
cooler than those realized today. Low to middle 70s are forecast across
the mountains with upper 70s to near 80 across the Piedmont.
Short term /Tuesday night through Thursday/...
as of 345 PM EDT Monday...
By Wednesday morning surface high pressure is centered over the
forecast area. A very weak pressure gradient remains in place
through Thursday. Precipitable water values gradually increase back
up into the 1.0 to 1.5 inch range by late Thursday.
BUFKIT forecast soundings for Wednesday show enough mixing to bring
dew points down into the 40s for much of the area during the
afternoon. Will stay close to cooler guidance for lows on both
Tuesday night and Wednesday night. Record lows are still possible
Tuesday night with lows 5 to 15 degrees below normal.
Long term /Thursday night through Monday/...
as of 345 PM EDT Monday...
Upper 500 mb trough over the northeast United States amplifies on
Friday and Saturday with a significant short wave over the Ohio
Valley. Models similar in showing height falls on the southern end
of the trough and what may eventually be a cut off low over the lower
Mississippi Valley or southeast United States Monday.
Moisture begins to increase across the area on Friday but little in
the way of any organized lift to trigger any precipitation aside
from daily threat of airmass type showers and thunderstorms. With
little change in the air mass there will be minimal changes in high
and low temperatures each day. Temperatures will be near normal. Not
anticipating any extremes.
Aviation /00z Tuesday through Saturday/...
as of 730 PM EDT Monday...
Inclined to keep the northwest flow SC in the west through most of the
evening...with models showing downward trend in ceilings at lwb/blf
and possibly bcb overnight with MVFR/IFR ceilings. In addition fog
will be an issue...if any clearing takes place despite the dry
airmass...due to warm waters/cooler air...at lwb/bcb and perhaps
blf. Blf will be more due to lower clouds in the mountains than
radiation fog as winds stay up there.
Further east VFR expected.
Any sub-VFR conditions will rapidly improve to VFR Tuesday
Extended aviation discussion...
Persistent trough pattern in the east will gradually retrograde
west by the end of the week. Mainly VFR conditions are expected
through at least Thursday save for some late night/early morning
patchy MVFR fog in the mountain and river valleys. After
Thursday...with the trough axis farther west...this will allow for
a return of Atlantic moisture and a greater abundance of
showers...and potentially storms...in the forecast heading into
the weekend. This also will allow for increased chances of sub-VFR
conditions within the area of the showers...and then again
overnight in the form of light fog or stratus as boundary moisture
gets trapped under the nocturnal inversion.
July 29th record lows:
July 30th record lows:
July 31st record lows:
the National oceanic and atmospheric administration weather radio at Wytheville Virginia...wz2500...broadcasting
on a frequency of 162.450 mhz...is off the air...due to phone line
issues. Phone company is working on it. No estimated time for
return to service.
short term...air mass
long term...air mass