Area forecast discussion
National Weather Service Blacksburg Virginia
211 am EDT sun may 26 2013
Synopsis...
high pressure will continue to build into our area overnight and
Sunday... brining mainly dry conditions for the rest of the
weekend. Early next week a warm front lifts north across
US...reaching the Great Lakes by midweek. This will bring much
warmer temperatures and scattered afternoon showers and storms.
&&
Near term /until 6 am this morning/...
as of 900 PM EDT Saturday...
Infrared pics show that the earlier streamers of middle/high clouds have
faded crossing the mountains early this evening allowing temperatures to
fall off rather quickly in the western valleys. However have
another batch of a bit deeper moisture to the northwest with the middle
level wave over in/IL. This complex of cloudiness with a few embedded
-shra looks to also track southeast likely affecting the western areas
after midnight but to what extent iffy given dry air aloft off
evening radiosonde observations. Think the northern and eastern areas could stay
basically clear allowing temperatures to fall a bit lower. This should
still match up well with the going frost advisory where should be
well into the 30s in the northwest valleys so no adjusts to current
headlines. Elsewhere think the ridges and SW zones will see a bit more
wind per warm air advection along with cloud cover so bumped those areas up a
notch or so. Otherwise decreased sky grids a bit over the next few
hours and then increased western half after midnight but dry given
such arid low levels.
For Sunday a deep...but weaker...northwest flow will prevail. Weak
upper level disturbances moving through the west side of the
departing upper level low will continue to bring high clouds to the
area. The GFS continues to generate light precipitation across far
southwest Virginia/northwest NC...but this was discounted considering the depth
of dry air expected to persist tomorrow.
Guidance is very similar projecting highs a degree or two warmer
Sunday compared to today...and we did not stray far from these
values.
&&
Short term /6 am this morning through Tuesday night/...
as of 330 PM EDT Saturday...
As a warm front lifts north through the Ohio Valley...thunderstorm
remnants...which could be just scattered showers once they reach our
region...may hold together through southeast West Virginia and SW Virginia Monday. With
warm air advection and still some easterly component and clouds...temperatures may run a
few degrees cooler than guidance suggests...unless clouds leave
quicker during the day. By Tuesday...the warm front is north...but a
slight upslope component combined with increased dewpoints/maximum
T/instability can set off thunderstorms along the ridges....yet
still scattered. Tuesday night will be one of many warm and humid
evenings next week.
&&
Long term /Wednesday through Saturday/...
as of 330 PM EDT Saturday...
Heat wave possible through the end of next week as a 590dm upper
ridge closes off over the middle Atlantic in response to a Rex block
and closed low over the Continental Divide. Probability of precipitation decrease through
the week with sinking motion and the profile becoming too dry to
support anything more than the most isolated thunderstorm along
the highest peaks by end week. 90f looks possible in most of the
cities perhaps as early as Thursday. Upper air pattern may flatten
by the end of next weekend.
&&
Aviation /06z Sunday through Thursday/...
as of 200 am EDT Sunday...
VFR ceilings expected through the taf valid period. A series of northwest
flow disturbances on the back side of the deep NE U.S. Upper low
bringing middle/high clouds to the SW part of the forecast area. The
first such disturbance was moving across the region now. This will
move out shortly after daybreak...with another northwest flow
disturbance slated to arrive overnight into early Monday. All ceilings
with these should be at or above 100. VFR visibilities expected through the taf
valid period as well...with the possible exception lwb...where
some early morning ground fog is possible. However...right now
odds are against this because of current 6 degree f T/dew point spread.
Winds northwest 4-6kts across the County Warning Area through mid-morning...then northwest
6-8kts through the daytime. Winds will be notably lighter than the
past couple of days with little or no gust. Winds will be calm or
vrb03kt after 00z beginning a transition to the NE for Monday as the
surface high shifts east of the region.
Extended aviation discussion...moisture increases early in the
week as the surface high moves east and the upper ridge strengthens
over the Mississippi Valley. A weak warm front/baroclinic zone will
slide NE across the region early Monday-Tuesday ahead of the very
warm/moist air that will be pushing in from the SW. This will lead
to a slightly better shot at seeing a few rain showers/thunderstorms and rain Monday into
Tuesday with at least orographic driven convection for middle week.
Patchy late night fog also likely during the overnights espcly
valleys and where afternoon/evening rainfall occurs.
&&
Rnk watches/warnings/advisories...
Virginia...frost advisory until 8 am EDT this morning for vaz020.
NC...none.
WV...frost advisory until 8 am EDT this morning for wvz044-045.
&&
$$
Synopsis...ph
near term...jh/ph
short term...km
long term...km
aviation...rab
