Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Raleigh NC
317 PM EDT Friday may 29 2015
Synopsis...high pressure centered over the western Atlantic will
extend into the region through Saturday. A cold front will drop into
the middle Atlantic and southern Appalachians on Sunday and move
into the Carolinas on Monday and Tuesday.
Near term /through tonight/...
as of 315 PM Friday...
Near term: through tonight: surface high pressure really dominating
the pattern the past few days and today is really no different. With
virtually no forcing aloft (as evidenced by forecast soundings which
are showing less than 10 kts all the way up through 30 kft) all of
the action will be surface based with much of it occurring northwest of the
forecast area. The Triad will continue to have showers and possibly
a weak thunderstorm in the area for the remainder of the afternoon
and possibly into this evening. Rap and NAM forecast soundings show
the best instability occurring right now and actually diminishing
through the afternoon so what is out there now could be the peak of
it but will require watching through the afternoon. Anything that
forms has been slowly drifting northward and out of the area. Highs
this afternoon should top out in the middle to upper 80s with the
sandhills receiving the highest temperatures. High resolution models
also hinted at some showers forming on the sea breeze but so far
these have been very minimal and confined to the coast.
Overnight tonight expect a chance for some low stratus...especially
in The Triad where ceilings as low as IFR could show up for a few
hours around 12z. Elsewhere MVFR ceilings are more likely. Return to
VFR is expected after 15z on Saturday morning. Lows overnight in the
Short term /Saturday and Saturday night/...
as of 315 PM Friday...
Saturday and Saturday night: surface high pressure builds back in a
little further than recent days and the upshot is possibly a drier
day in The Triad than previous afternoons. Will still carry a slight
chance of showers in the west tomorrow but continued minimal shear
and even less instability than today dont Bode well fore convection
prospects. This is backed up by cams which show minimal activity
tomorrow afternoon. Instead expect another day of warm return flow
with highs again mostly in the upper 80s. Lows Saturday night in the
middle 60s once again.
Long term /Sunday through Thursday/...
as of 325 am Friday...
..increasing chances of some much needed rain early next week...
The large scale pattern during the long term features the breaking
down of the Southeast Ridge and decreasing heights as troughing
develops across the Tennessee Valley and deep south. At the
surface...Atlantic high pressure will retreat as a cold front drops
south into NC late Sunday and Monday and lingers across the region
for several days before shifting offshore as high pressure builds in
toward middle week.
Convective coverage will increase somewhat on Sunday afternoon and
evening ... across the northwest Piedmont and near the Virginia
border with scattered showers and thunderstorms associated with the
approaching cold front and upper trough. The threat of precipitation
will be very limited from U.S. 1 eastward. Highs Sunday will range
in the upper 80s to near 90.
The cold front will drop into NC late Sunday and is expected to move
slowly southward across the state on Tuesday and Wednesday. This
unusual pattern has support from both the ec and the GFS. The front
will provide a focus for scattered to possibly numerous showers and
storms on Monday and Tuesday with the greatest coverage gradually
shifting south during the period. Temperatures will cool during the
period as cloud cover and the arrival of cooler air on Monday and
especially Tuesday pushes highs into the upper 70s north to middle 80s
south on Tuesday afternoon.
Will decrease probability of precipitation on Wednesday and Thursday as the front weakens
and shifts away from central NC and confidence in forecast details
slip. A 1025 mb area of high pressure will extend into the area from
the northeast on Wednesday and Thursday with a cool northeast flow.
Highs will range in the upper 70s to lower 80s on Wednesday and
Quantitative precipitation forecast forecasts typically are not as skillful in the warm season as
the cool season and there is still some uncertainty in the forecast
details but there is an increasing potential for at least some much
needed rain over the long term with the greatest confidence an
expected precipitation amounts across the western and northwestern
Piedmont locations...especially on Monday and Tuesday. &&
Aviation /18z Friday through Wednesday/...
as of 145 PM Friday...
24 hour taf period: expecting mostly VFR conditions through the taf
period with a possible couple exceptions. The first is with
afternoon convection. The Triad sites will be most vulnerable to
this as showers and thunderstorms have developed along a boundary
running from Charlotte to Richmond which clips The Triad but storms
forming here will move north and away from the area. To the south
there is a slight chance of some sea breeze shower activity that
would be brief and occur later this afternoon/early evening.
Otherwise light southeasterly winds with broken ceilings in the 4-6
kft range expected.
There will be a chance for some low stratus on early Saturday
morning with triad sites possibly receiving a couple of hours of IFR
ceilings with mostly MVFR possible at other sites. After 15z
conditions are expected to return to VFR for the remainder of the
Long term: pattern remains the same for much of the long term with a
slightly eastward shift early next week. Mainly look for diurnal
convection with chances for fog/low stratus during the early morning
hours each day.