Scientific Forecaster Discussion
fxus62 kcae 271731
Area forecast discussion
National Weather Service Columbia SC
131 PM EDT Mon Mar 27 2017
a series of troughs will move through the area through early
Tuesday and possibly trigger some showers and a few thunderstorms.
A cold front will move through the area Tuesday night. High
pressure will build into the region Thursday from the north
while moisture increases across the area. This may set up
unsettled conditions for the later half of the week with below
normal temperatures possible Thursday but warmer than normal
over the weekend.
Near term /through tonight/...
old weak front/surface trough, and band of slightly enhanced
moisture with precipitable water around 1 inch, remains stretched across the
forecast area (fa). Though models projecting weak to moderate
instability this afternoon, lack of upper trigger with weak
ridging aloft, and some mid level capping, expected to preclude
thunder threat today for the most part though isolated thunder
possible, but diurnal heating and any convergence along the
trough, possibly aided by sea breeze, expected to result in
scattered mainly afternoon showers. Upper trough, and surface
front, to approach the forecast area tonight. Lead impulse to move through
tonight, with main upper trough riding by mainly just to our
north late tonight. This could provide a chance of showers
tonight, with some thunder possible, mainly across northern
areas. S to south-southwest low level flow will promote above normal temps.
Short term /Tuesday through Wednesday night/...
upper level low will be moving east across North
Carolina/Virginia with trough axis through SC through midday.
The stronger dynamics remain northeast of the area but scattered
showers and a few thunderstorms expected. A weak surface front
will be approaching from the northwest late in the day but
moisture ahead of the front will be limited and upper level
ridge developing. So little in the way of showers expected by by
20z. Expect clearing late Tuesday evening as both the upper
trough and surface front push through and slightly drier air
moves into the area. Pre-frontal conditions Tuesday and warm
advection. Air mass modifies quickly under ridge Wednesday with
subsidence. Expect temperatures to be near or slightly above MOS
guidance for Max temperatures. Guidance looks good for overnight
min temperatures. Temperatures remaining above normal with
highs in the lower to mid 80s and lows in the middle to upper
Long term /Thursday through Monday/...
the Thursday and Friday periods remain the most unsettled
through the expected. Upper ridge into the southeastern states
through Thursday then shifts east Thursday night as deep upper
level low moves from the Mississippi Valley to the east. Still
the possibility of a weak cold air damming wedge Thursday as
ridge builds south from the north but the ridge appears to be
off the New England coast resulting in more east low level flow
in the region. So confidence remains low and in fact the latest
models suggest weaker wedge scenario...especially in the Pee Dee
and east midlands where drier air may be present. Models
indicate moisture may be shallow and the strongest isentropic
lift and low level convergence remains along stalled front in
the csra and upstate regions. Still think temperature guidance
may be too high given the pattern but may little change to
current forecast. Highest pops in the csra Thursday. Warm front
may move north Thursday night and occluded front approaches from
the west early Friday. Strong deep layer shear possible but
instability appears weak. Still potential for strong
thunderstorms through Friday afternoon. Dry conditions over the
weekend although moisture may return early next week.
Temperatures remain above normal.
Aviation /17z Monday through Friday/...
VFR expected today outside of any scattered afternoon showers.
Surface trough with diurnal heating and sufficient moisture
could provide scattered mainly afternoon showers. Will handle
with vcsh for now, and introduce greater inclusion if/when
confidence warrants. Upper trough moving towards the region
tonight could promote a continued shower chance, but main
thunder threat expected to remain north of the terminals. Moist
low levels could promote diurnal restrictions late
tonight/Tuesday morning, but possibility of mid/high level
cloudiness along with a normally unfavorable SW low level wind
direction, along with mixed results in latest guidance, leads to
low confidence. Will include restrictions in later taf
issuances if/when confidence warrants.
Extended aviation outlook...showers, and a possible thunderstorm,
Tuesday. Ceiling/visibility restrictions possible in weak wedgelike
conditions, along with a chance of showers, Thursday/Thursday
night. Thunderstorms possible late Thursday night and Friday.