Scientific Forecaster Discussion
fxus62 ktae 211955
Area forecast discussion
National Weather Service Tallahassee Florida
355 PM EDT Sat Oct 21 2017
Near term [through tonight]...
At upper levels, the ridge will remain parked off the southeast U.S.
Coast and move little as an upstream trough deepens across the Great
Plains. Surface high pressure centered over the mid Atlantic states
will slide a bit further to the east as winds on its southern
periphery veer slightly from the east-northeast to the east-southeast over our forecast
area. Isolated showers will move west from the Atlantic overnight,
but are not expected to reach as far east as out zones. However,
some lower clouds are expected to make it into our Georgia zones. It will
be another mild night with lows generally in the mid 60s.
Short term [sunday through Monday night]...
Deep layer moisture will increase from Sunday through Monday
morning as southeasterly to southerly flow brings a warm, moist
airmass northward from the Gulf into our area. Precipitable water values are
expected to exceed 1.5" by Sunday evening, and will increase to
around 2" on Monday morning. Throughout this period, a sharp upper
level trough will move eastward toward our area, with a well-
defined cold front also pushing eastward under the leading flank
of this feature. As a result of the increasing moisture and
forcing, rainfall will become more likely from west to east on
Sunday night, with periods of showers expected from Monday morning
through the afternoon. Isolated thunderstorms are also possible,
although thunderstorm coverage and intensity could be limited by
modest instability. However, SBCAPE could increase to 500-1500
j/kg along and just ahead of the front on Monday late morning and
afternoon, with ample 0-6 km bulk shear (40 kts or greater)
present due to the potent trough moving into our area. As a
result, severe thunderstorms cannot be ruled out during this time.
Chances of showers and storms will decrease from west to east on
Monday night as the front continues to push eastward, and in its
wake much cooler and drier air will push into our area. Highs will
be in the mid-upper 80s on Sunday with lows in the upper 60s and
lower 70s Monday morning. After highs ranging from the upper 70s
northwest to mid 80s southeast on Monday, temperatures will drop
into the 50s overnight across most of our area.
Long term [tuesday through saturday]...
Much cooler and drier air will continue to settle in across our
area behind the cold front mentioned in the short term discussion.
As high pressure builds across our region from Tuesday through
Thursday, generally clear skies will prevail each day. Highs will
remain in the 70s, with some inland areas possibly remaining in
the upper 60s on Wednesday as a secondary cold front pushes across
our area. Under ideal radiational cooling conditions, lows will
dip to the mid-upper 40s inland on Wednesday and Thursday morning.
Late in the week through the weekend, increasingly mild and moist
conditions will return to our area ahead of another potent upper
level trough approaching our area. Chances of showers and
thunderstorms will increase on Saturday as the leading edge of
this upper trough moves into our region and another cold front
approaches our area. Highs in the upper 70s and lows in the 50s
are expected from Friday through Saturday.
Aviation [through 18z sunday]...
VFR conditions will prevail for the most part. We will see a
scattered cumulus deck at 4-6 kft this afternoon dissipate
overnight. Most guidance indicates an MVFR deck moving in from the
east during the pre-dawn hours and we have shown this for aby and
vld. Winds will be out of the east, generally 10 kt or less.
Increasing easterly winds tonight will result in choppy seas and
advisory level conditions across all but our eastern nearshore
zones. Small craft will need to continue exercising caution
through early next week as a cold front moves across our area,
resulting in persistent elevated winds and choppy seas.
Hazardous fire weather conditions are not expected over the
next several days. Rain is expected on Sunday and especially
on Monday with an upcoming frontal passage.
Coverage of showers and isolated thunderstorms will increase from
Sunday evening through Monday as a cold front moves into our
area. Widespread amounts from 1 to 2 inches are expected across
our area, with isolated totals up to 3 inches possible. These
amounts are unlikely to cause widespread flooding.
Spotter information statement...
Spotter activation is not requested. However, spotters are always
encouraged to safely report significant weather conditions when they
occur by calling the office or tweeting US @nwstallahassee.
Preliminary point temps/pops...
Tallahassee 66 87 72 82 59 / 10 40 50 80 40
Panama City 69 83 72 79 60 / 10 30 70 80 20
Dothan 64 86 70 77 54 / 10 20 70 80 20
Albany 63 87 69 79 56 / 10 20 50 80 40
Valdosta 65 87 70 83 59 / 10 30 30 80 60
Cross City 67 88 71 84 63 / 10 40 40 60 70
Apalachicola 71 83 72 81 61 / 10 40 70 70 30
Florida...high rip current risk until 6 PM CDT this evening for south
GM...Small Craft Advisory from 8 PM this evening to 6 am EDT Sunday
for coastal waters from Ochlockonee River to Apalachicola
FL out to 20 nm-coastal waters from Apalachicola to Destin
Florida out 20 nm-waters from Suwannee River to Apalachicola Florida
from 20 to 60 nm-waters from Apalachicola to Destin Florida from
20 to 60 nm.