Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Jacksonville Florida
304 PM EST sun Nov 23 2014
..strong to severe thunderstorms possible late this afternoon
through early evening for inland southeast Georgia and the western
..warm and humid conditions continue tonight and Monday...Turning
sharply colder and rainy on Tuesday and Wednesday...
afternoon surface analysis depicts a warm front extending west to
east across southern Alabama and Georgia. Low pressure (999
millibars) was located over the lower Mississippi Valley...while
high pressure (1028 millibars) was retreating eastward towards
Bermuda. Aloft...a negatively tilted shortwave trough was pivoting
northeastward into the Tennessee Valley. With strong ridging
positioned over the western Atlantic...cyclonic flow is increasing
over our region...with a strong veering profile noted on the
morning soundings at Tallahassee and Jacksonville...featuring a
low level southerly jet of 45-50 kts in a layer from 925-850
millibars (2500-5000 feet). A squall line is moving rapidly east-
northeastward across the Florida Panhandle and southeastern
Alabama. An unseasonably moist air mass prevails in the warm
sector...with temperatures ranging from the middle 70s to the lower
80s and dewpoints near 70. Low-topped showers are developing over
much of northeast Florida and far southern Georgia well in advance of the
squall line...due to strengthening isentropic lift and a
saturated atmosphere. Temperatures and dewpoints north of the warm
front are in the 60s...mainly along the immediate Georgia coast.
Near term (this afternoon through monday)...
the main focus will be the progression of the squall line into
interior southeast Georgia and the western Suwannee Valley late this
afternoon. With plenty of deep-layer wind shear in
place...damaging wind gusts and isolated tornadoes will be
possible in these locations through the early evening hours. The
threat is higher in interior southeast Georgia...closer to the warm
front...where enhanced helicity values are still being analyzed.
Categorical probability of precipitation were inserted into the forecast grids for areas
west and northwest of a Gainesville...Jacksonville...and Saint
Simons Island. High resolution models also indicate convection
increasing ahead of the squall line over the rest of northeast and
north central Florida as well as coastal southeast Georgia. Heavier activity
in these locations will be capable of producing wind gusts of
30-40 miles per hour...but severe weather is not anticipated.
The squall line should decrease in intensity after sunset as the
shortwave trough moves quickly northeastward and away from our
region. Scattered showers and thunderstorms will move into coastal
southeast Georgia this evening...with gradually decreasing rain
chances in northeast Florida after midnight. A cold front will remain
well west of our region...and we expect an extensive deck of low
stratus to develop over much of our area overnight given the very
moist conditions and strong southerly flow just off the surface.
Lows tonight will average about 15-20 degrees above late Nov
climatology...with middle/upper 60s expected. These values are near record
warm minimum temperatures
The cold front will move slowly eastward across the Florida
Panhandle and southwest Georgia on Monday. Unseasonably warm and
humid conditions will prevail within deep southwest flow. With
minimal forcing due to a lack of shortwave energy aloft...we
expect isolated to widely scattered showers and perhaps a few
embedded thunderstorms to gradually move eastward across our
region along and ahead of the cold front. Southwest winds of 10-15
miles per hour will boost highs into the upper 70s to the lower 80s. Temperatures
could be even higher if breaks develop in the morning cloud deck.
Short term (monday night through wednesday)...
Monday night...quiet conditions during the evening will be
followed by slowly increasing rain chances after midnight as next
shortwave in the southwest flow approaches the region. Mild temperatures
in the 50s/60s expected.
Tuesday & Tuesday night...moist southwest flow aloft along and north of old
frontal boundary across central Florida will continue to increase rain
chances in overrunning rainfall scenario with storm total rainfall
amounts of 1-2 inches expected area-wide. Enough lift/instability
aloft will trigger isolated thunderstorm activity but surface based
convection is not expected as highs only expected to remain in the
upper 50s/60s across southeast Georgia/NE Florida as cool north flow develops across
the forecast area.
Wednesday...trailing cold front pushes through during the day with
rainfall ending from west to east during the middle of the day.
Brisk northwest flow will develop and maximum temperatures only expected to top
out in the 50s despite clearing skies during the late afternoon
Long term (thursday through sunday)...
cool high pressure builds in for Thursday/Friday with sunny skies and highs
in the lower 60s and cool/clear nights with lows in the 30s inland
and 40s along the coast. Freeze is not expected but some patchy
frost will be possible. High pressure will settle over the region
for the Holiday weekend with mostly sunny skies and temperatures warming
close to 70 degrees for highs and in the 40s for lows.
chance for thunderstorms in the vicinity to develop in the late afternoon ahead of the main
line approaching from the west at crg...jax...and vqq. Expect
IFR/MVFR ceilings to return after dusk as front approaches. Front gets
hung up over the area keeping ceilings and visible restrictions in the
forecast through the pre-dawn hours.
small craft advisories have been extended through late this
evening for the near shore waters evening and through Monday
in the offshore waters. South winds of 20-25 kts will subside to
caution levels in the near shore waters by sunset...but seas in the
5-7 feet range will take a few more hours this evening to subside to
caution levels overnight. Seas offshore will peak in the 7-10 feet
range this evening. Southerly winds will subside to caution
levels in the offshore waters on Monday...but seas will remain
in the 6-8 feet range through at least the middle-afternoon hours.
Light to moderate southwest flow Monday night becomes north on
Tuesday and increases to around 20 knots by the afternoon and
evening hours with Small Craft Advisory headlines likely needed
again that will continue into Wednesday as northwest winds at 20-25
knots are expected behind the cold frontal passage then slowly
subsiding winds/seas Thursday into Friday.
Rip currents: high risk continues through this evening today...with
breakers currently peaking around 6 feet and slowly decreasing to
4-5 feet late this afternoon. Moderate risk expected Monday as
winds shift from southerly to southwesterly...with a lingering
long period easterly swell.
widespread 1 to 2 inches of rainfall across southeast Georgia last night will
make for sharp river rises but at this point river levels expected
to stay below action stages along the Altamaha and Satilla river
record highs for November 23rd...
jax 84/1992...gnv 88/1906...amg 82/2010...ssi 82/1992
Record warm minimums for November 24th...
jax 67/1992...gnv 68/1957...amg 65/1977...ssi 67/1998
Record highs for November 24th...
jax 85/1967...gnv 86/1948...amg 83/1986...ssi 83/1967
Preliminary point temps/pops...
amg 65 77 53 58 / 80 30 20 50
ssi 65 76 59 60 / 70 30 40 60
jax 67 81 58 63 / 60 30 50 60
sgj 68 79 62 67 / 40 30 40 70
gnv 66 79 60 65 / 60 30 50 70
ocf 66 81 63 69 / 50 30 40 70
Florida...high rip current risk until 7 PM EST this evening for Duval-
Georgia...high rip current risk until 7 PM EST this evening for coastal
Am...Small Craft Advisory until 4 PM EST Monday for Altamaha Sound Georgia
to Fernandina Beach Florida 20 nm to 60 nm offshore-Fernandina
Beach to St Augustine Florida 20 nm to 60 nm offshore-St
Augustine to Flagler Beach Florida 20 nm to 60 nm offshore.
Small Craft Advisory until 11 PM EST this evening for Altamaha
Sound Georgia to Fernandina Beach Florida out 20 nm-Fernandina Beach
to St Augustine Florida out 20 nm-St Augustine to Flagler Beach
Florida out 20 nm.