Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Raleigh NC
1022 am EDT Tuesday may 5 2015
Synopsis...Bermuda high pressure will extend into our region
through middle week. An area of low pressure will form near the Bahamas
and meander off the southeast coast during the middle of the week.
Near term /through tonight/...
as of 1020 am Tuesday...
High pressure over eastern NC this morning will continue to ridge
westward into central NC...even as the high shifts offshore. 12z
surface analysis shows a surface trough to the west...along the Lee
of the mountains...which will be the focus for any showers or storms
should they develop this afternoon. Central NC is expected to remain
dry with plentiful sunshine. 12z upper air analyses show high
pressure over the Carolinas at 850 mb and 700 mb...with a weak trough at 500 mb
and h25. Do not expect much out of the upper level wave...except
possibly a few clouds developing later in the day. With little to no
warm air advection into the region from yesterday and clear skies overhead...expect
temperatures near to slightly higher than yesterday. Highest in the
low 80s and lows in the middle to upper 50s.
Short term /Wednesday and Wednesday night/...
as of 300 am Tuesday...
To our north...a cold front over the Middle-Atlantic States will likely
stall and eventually washes out as it tries to slip south into
southern Virginia. Meanwhile to our south-southeast...models are
hinting at low pressure development off the southeast coast. In
between these two features...central NC should remain largely under
the influence of a weakening Bermuda high and ridging aloft which
will should help maintain warm and mostly dry conditions. The
exception may be across the far northern zones...near the NC-Virginia
state line where an isolated shower or two may develop in closer
proximity to the front. However...lack of moisture and sufficient
instability will act to suppress convective development and thus
will leave out any rain chances.
With no change in airmass...highs again in the lower 80s. Lows
Wednesday night a tad warmer...especially across the north where
there models suggest increasing middle/upper level moisture/clouds.
Lows in the upper 50s-lower 60s. &&
Long term /Thursday through Monday/...
as of 247 am Tuesday...
There is high confidence in the overall pattern of upper level
ridging over the eastern United States late this week through the
weekend... the troughing out west. However... models still likely do
not have a good handle on the evolution of the potential coastal
storm that would develop under the ridge. It still appears that most
models keep the significant rains offshore associated with the system
exclusively. HPC continued to favor a blend of the two camps of
models to ensure continuity of current forecasts. This is accepted
as the best starting point for our late week forecast.
Our chance of rain may end up mostly coming from a scattering of
mainly diurnal showers and thunderstorms that may focus along or
near the expected backdoor front Thursday and then what is left of
the boundary Friday. In addition... some moisture may eventually
come into play from the low pressure - but the details continue
sketchy at best. Until that process improves... we will continue to
forecast above normal temperatures especially at night as the dew
points should become 60+ by Friday and linger into the weekend.
Sensible weather for now will be partly sunny to mostly cloudy each
day. A chance of mainly afternoon and early nighttime showers and
thunderstorms. Lows 60-65. Highs 78-85.
Aviation /12z Tuesday through Saturday/...
as of 730 am Tuesday...
High confidence of VFR conditions persisting through the current taf
period as Bermuda high pressure continues to ridge westward into the
region. Diurnal cumulus will develop once again on Tuesday during the
afternoon hours with southerly winds between 5 to 8kt.
Outlook...VFR conditions are expected through at least Wednesday as
Bermuda high in place gradually weakens. A back-door cold
front is expected to stall and eventually stall just north of the
area late Wednesday night/early Thursday. Moisture is limited along
the front and thus rain chances will be small with little to no
aviation impacts. Models continue to show the development of an area
of low pressure area north of the Bahamas Wednesday/Thursday time
frame. Model spread remains high with the eventual evolution track
of this system as it enters a region of weak flow off the southeast
coast...where it could meander for several days. This system could
result in some adverse aviation impacts late in the work week and
into the weekend...especially across coastal sections of North
Carolina. Additionally...enhanced easterly onshore flow from this
system could bring an increase threat for morning stratus/fog.