Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Raleigh NC
150 PM EDT Monday Jul 6 2015
Synopsis...a weak front near the Virginia border will lift north
today as an upper low and associated weak surface low over West
Virginia lift off to the northeast. Building high pressure over the
southeast states and Carolinas beginning tonight will bring a trend
to warmer and drier weather through the middle and end of the work
Near term /through tonight/...
as of 1120 am Monday...
Visible satellite imagery shows an upper level vortex centered in
southwest Virginia lifting northeast. Morning stratus across central NC
has dissipated and the initiation of cumuliform cloudiness is
underway. Scattered showers across the northwest Piedmont and triad
area are in response to DPVA and are lifting away from The Triad.
Scattered convection is likely to develop this afternoon as boundary layer
destabilization increases and localized forcing for ascent is driven
by spokes of vorticity emanating from the upper low and in
southwest-northeast convergence zones resulting from differential
heating from morning stratus in the eastern Piedmont and with
convergence along a weak surface trough in the western Piedmont. The
convection will have a storm motion to the northeast with the larger
convective lines gradually shifting east. Current forecast highs in
the 86 to 92 range look great.
Convection this evening should largely diminish with sunset but given
the proximity of the the upper trough...would not be surprised to see
a few storms linger into the overnight. But a general drying of the
atmosphere should limit coverage overnight and bring convective
activity to an end late. Lows will range in the upper 60s to lower
Short term /Tuesday and Tuesday night/...
as of 330 am Monday...
Afternoon showers and storms should be mainly isolated Tuesday as
the upper low shears to our north and just a weak Piedmont trough
remains amidst relatively weak instability. Models do show a very
shallow upper shear level shear axis...above 500 mb...drifting
overhead...but instability looks to be low for this feature to
trigger much convection. Thus...will maintain just slight chance
probability of precipitation...with highs couple degrees warmer than today in the lower
90s. Lows Tuesday night in the 69-73 range.
Long term /Wednesday through Monday/...
as of 150 PM Monday...
Gradual westward regression of subtropical ridging will lift the
westerlies and persistent frontal zone north of the area in the
midweek. The frontal zone makes a southerly jog on Friday as the
ridge begins to amplify into the central Continental U.S....with ensuing
northwest flow and a gradual uptick in heights over the East Coast
through the weekend.
The riding will limit convection through Friday...with slight
chances...primarily diurnally driven...across the northern tier due
to proximity with the active westerlies zone across the Ohio Valley.
Highs will range from 90 across the north to 95 in the south after
morning lows in the lower 70s.
Over the weekend...deep northwest steering flow will increase the
chance that upstream mesoscale disturbances wander in to initiate
convection across the area. Will thus maintain chance (30-40)
probability of precipitation...shaded towards maximum heating each day...on Saturday through
Monday. Highs will be a couple of degrees warmer...mostly in the middle
90s...with potential for some upper 90s across the southern tier.
Aviation /12z Monday through Friday/...
as of 650 am Monday...
A couple areas of IFR stratus...one over the western Piedmont and
impacting kgso/kint...and the other over the coastal plain impacting
krwi...will begin to lift by 12-13z and VFR conditions are expected
by 15z. A brief period of IFR ceiligs is still possible at krdu and
kfay. Scattered showers and storms are expected to develop by early
afternoon and last through early evening as they move off to the
northeast. While a thunderstorms is possible at eastern
terminals...confidence is too low to pin down a small time
frame...so vcsh will be included in the current taf. All activity
is expected to end by 00-03z and VFR conditions are expected
Outlook...a subtropical ridge will build over the southeast US this
week...which will limit afternoon storms to mainly isolated
coverage. VFR conditions are expected to be predominate this week.