Scientific Forecaster Discussion
fxus62 kcae 290740
Area forecast discussion
National Weather Service Columbia SC
340 am EDT Sat Apr 29 2017
high pressure ridging into the forecast area from the Atlantic
will dominate through Sunday and help keep any thunderstorms
mainly associated with heating isolated. The next cold front
will bring showers and thunderstorms Monday. Mainly dry weather
is forecast behind this front Tuesday and Wednesday. Another
significant weather system will impact the region Thursday and
Near term /through tonight/...
satellite trends and the hrrr indicate low cloudiness affecting
mainly the East Part of the forecast area early this morning.
The low-level moisture is shallow and it should diminish later
this morning because of heating and mixing. Ridging extending
into the area from the east will dominate through tonight. The
NAM and GFS display moderate to strong instability with
surface-based Li values -5 to -8 today with the greater
instability in the west section where the upper ridging will be
slightly weaker. The thunderstorm chance should remain low
because of shallow moisture and mid-level capping. However, we
did forecast slight chance pops in the west section because of
the strong instability plus high-resolution models displays a
few storms in that area. If thunderstorms do develop then
damaging wind and hail would be possible because of the strong
instability. Followed the higher temperature guidance based on
Short term /Sunday through Sunday night/...
the upper ridge will weaken a bit Sunday and Sunday night as a
cold front approaches from the west. Heating may help support
thunderstorms Sunday afternoon. The moisture increase and
convergence ahead of the front may also help cause thunderstorms
late Sunday night. The chance should be limited because of
shallow moisture Sunday and nocturnal cooling Sunday night. The
guidance consensus supported slight chance pops. Followed the
guidance consensus for the high temperature Sunday. Mixing ahead
of the front supported the higher low temperature guidance
Long term /Monday through Friday/...
the models show a deep closed upper low lifting north into the
Great Lakes region Monday with an associated cold front pushing
into the forecast area Monday afternoon and evening bringing
the chance for thunderstorms which could possibly be severe.
Several ingredients come together Monday including precipitable
water values rising to near 1.7 inches with strong moisture
advection into the region with southerly 850 mb winds around 40
knots and upper dynamics in the form of forced ascent in the
right entrance region of the upper jet. Breezy south-southwest
winds and areas of heavy rain can also be expected.
Stable and dry conditions return behind the front for Tuesday,
and temperatures will be slightly cooler with highs only in the
mid 70s to low 80s. There is a slight chance of showers and
thunderstorms late Wednesday with a warm front ahead of the
next system. As a deep low digs south, ample Gulf of Mexico
moisture will be advected into the region Thursday and Friday,
and there will be a chance for moderate rain, as well as
another round of potentially severe thunderstorms.
Aviation /07z Saturday through Wednesday/...
latest satellite loop indicating some lower clouds moving into the
eastern midlands early this morning. Latest hrrr seems to indicate
that these low clouds will continue to spread westward during the
early morning hours. IFR conditions possible at all taf sites during
before sunrise which may persist until around 14z-15z. Restrictions
will be mainly due to cigs given a 25 knot low level jet which
should inhibit widespread fog development. Should see conditions
improving to VFR mid to late morning as bounday layer mixing
commences. Will once again see afternoon cumulus development with
bases 5kft to 6kft and southerly winds around 10 knots.
Extended aviation outlook...early morning fog/stratus expected
to bring MVFR or lower conditions Sunday and Monday. Gusty winds
and restrictions in thunderstorms expected Monday as a cold
front moves through the region.