Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Wakefield Virginia
1041 PM EDT Monday Jul 27 2015
high pressure remains offshore through midweek...with the next
cold front crossing the area by Thursday night.
Near term /until 6 am Tuesday morning/...
latest regional radar mosaic depicts lingering isolated showers
over the northwest counties late this evening. Elsewhere...earlier
showers and thunderstorms have diminished. While loss of daytime
heating has limited instability...will maintain slight chance probability of precipitation
overnight due to warm/moist air mass and passing upper wave.
However...most places will remain dry. Skies still partly to
mostly cloudy with low temperatures in the upper 60s to low 70s.
Short term /6 am Tuesday morning through Thursday/...
upper level ridging expands a bit farther east into the Tennessee Valley
on Tuesday...as a weak frontal boundary dissolves over southern
Maryland. Northwest flow does continue and so expect any afternoon convection to be
initiated over the higher terrain to the northwest of the forecast area and drifting
eastward during the late aftn/eve. Will carry 30-40% probability of precipitation
west...lowering to slight chance (20%) probability of precipitation along the coast.
Overall...maximum temperatures will be similar or slightly warmer than today
because of cloud cover. Highs in the 80s to around 90. Mainly dry
Wednesday night as precipitation will wane after sunset. Lows in the 60s to low
upper level ridging will continue to expand eastward from the
Southern Plains. This will help to limit any afternoon convection while
maximum temperatures warm a couple of degrees. Have slight chance probability of precipitation (20%)
along and west of I-95. Partly sunny and more humid with highs in
the upper 80s to low 90s...with low/middle 80s at the beaches. Milder
Wednesday night with lows in the low to middle 70s.
upper ridging retrogrades a bit Thursday as a trough moves across
the Great Lakes and pushes a cold front into the middle-Atlantic
region by late in the day. Due to the late arrival of the
front...chance probability of precipitation (30-40%) will remain across western areas during
the afternoon...lowering to ~20% at the coast. It will also allow maximum
temperatures to reach into the low/middle 90s...except 80s at the immediate
Long term /Thursday night through Monday/...
pattern initially begins with a middle/upper level ridge
centered over the SW Continental U.S. And an upper level low persisting across
Hudson Bay Canada. GFS/European model (ecmwf) in decent agreement that an upper
trough axis will extend south into the Great Lakes Fri/Sat...then
flatten out sun/Mon. Across the deep south/Gulf Coast states...models
show a general persistence of a weak upper level trough. Appears
that a surface cold front will push through at least some of the area
later Thursday night into Friday...question is with regard to how far south
it makes it before stalling/dissipating. For now will go with a
climatology-type of scenario where the front stalls and weakens over far
southern Virginia/NC late Friday into the weekend. Best chance for precipitation looks to be
Thursday night/early Friday am with the front...then will keep chance probability of precipitation (30-
40%) across mainly southern parts of the forecast area Friday-sun with the front
stalled to our south and the opportunity for low pressure to move
northward along the front. Typical summertime temperatures can be
expected with highs mainly ranging from the middle/upper 80s to lower 90s
and lows generally ranging from the middle 60s northwest to the lower 70s southeast.
Aviation /03z Tuesday through Saturday/...
should see lots of dry air aloft slide through the area. The GFS
shows more clear conditions than the NAM...and while there could
be some patches of clouds...should see less clouds than more...but
in all cases...suspect conditions will be VFR. Sby could see some
fog though after getting nearly 1.5" of rain this morning. The VFR
conditions will continue into the day on Tuesday with the
traditional daytime cumulus forming between 15z and 16z.
VFR conditions should prevail until Thursday when a cold front
arrives late in the day and convection should be more prevalent
with MVFR to IFR conditions possible.
weak surface high pressure remains along/just off the coast with
weak surface troughing inland across the coastal plain. S/southeast winds average 10-
15 knots this evening/overnight...and will generally be a bit lighter
Tuesday/Wednesday as surface high pressure re-establishes itself over the area.
Waves over the Bay through midweek will average 1-2 feet...W/ 2-3 feet seas
over coastal waters. A weak cold front approaches the waters late
Thursday...then stalls south of the area by late in the week. South-southwest winds
at or below 15 knots expected Thu-Fri. Waves 1-2 feet and seas 2-4 feet.