Scientific Forecaster Discussion
fxus62 kcae 191838
Area forecast discussion
National Weather Service Columbia SC
238 PM EDT Thu Oct 19 2017
dry high pressure will hold over the forecast area through
Saturday. Moisture will increase Sunday and Monday ahead of an
approaching cold front and in an onshore flow associated with
the high shifting farther off the East Coast. The cold front
will move through the forecast area Tuesday followed by much
Near term /through tonight/...
this afternoon...fair weather continues. Upper ridge extending from
the west Gomex north into the Central Plains, with upper trough along
the eastern Seaboard. Embedded upper disturbance swinging through
producing mainly thin high cloudiness ahead of the shortwave trough.
The air mass remains very dry with precipitable water values a very
low 0.3-0.5 of an inch. Surface high pressure will remain centered
over the southern Appalachians. A slight warming trend to continue
as the air mass gradually modifies. Should see afternoon highs
ranging through the 70s.
Tonight...dry high pressure will remain over the region
supporting clear skies and light wind. Expect lows a few
degrees higher than last night because of air mass modification.
Strong net radiational cooling will occur. The in-house
radiation scheme supports the GFS MOS temperatures. Have
indicated overnight lows from the mid 40s to around 50 degrees.
Short term /Friday through Saturday night/...
surface high pressure will ridge into the forecast area from
the north or northeast through Saturday. The models have been
consistent with strong upper ridging over the region. It will
remain dry. Leaned toward the higher maximum temperature
guidance because of the strong upper ridging.
Long term /Sunday through Wednesday/...
moisture will be on the increase Sunday in an onshore flow
associated with the ridge off the mid-Atlantic coast. The models
also show weak isentropic lift. There may be considerable
cloudiness. Moisture should remain shallow with lingering upper
ridging. The guidance consensus supports just slight chance
pops. Also used the consensus for the temperature forecast.
Moisture should become deeper Sunday night and Monday ahead of the
cold front with the upper ridge shifting off the coast. The models
show the cold front moving through the area Tuesday. Deepest
moisture and greatest lift is depicted Monday night into Tuesday
morning and we have forecasted the highest pops during that period.
The models indicate considerable shear ahead of the strong cold
front with southerly h85 wind 40 to 50 knots Monday night into
early Tuesday. The shear supports possible severe thunderstorms
but the threat may remain limited because of weak instability.
Instability associated with the upper trough may help support
lingering showers Wednesday but the chance appears low because of
westerly low-level flow and little moisture behind the front. It
will turn much colder behind the front for Wednesday and Thursday.
Followed the guidance consensus for the temperature forecast.
Aviation /19z Thursday through Tuesday/...
VFR conditions are forecast through the 24-hour taf period, as
surface high pressure and a dry atmosphere remain over the region.
Localized ground fog near the Savannah River basin at fog-
prone ags possible late tonight/early Friday morning, but
confidence limited as air mass may remain a little too dry.
Extended aviation outlook...possibility of early morning fog
Saturday at ags and ogb. Increasing chances of fog/stratus
Saturday night/Sunday morning. Showers along with associated
restrictions late Sunday into Tuesday, with thunderstorms
possible Monday and Tuesday.