Flood and Heavy Rain in Florida, May 25 to 26, 2020

Area Forecast Discussion
National Weather Service Jacksonville FL
857 PM EDT Mon May 25 2020

.UPDATE...

Forecast remains on track as low pressure system over South FL
tracks slowly up the FL Peninsula overnight and into NE FL by
Tuesday Morning. This will continue scattered shower activity
along the coastal areas through the night with more heavier shower
activity breaking out towards morning along the NE FL coastal
counties of Flagler/Putnam/St Johns around sunrise and track
northward along the I-95 corridor into the JAX metro area by the
mid-late morning hours. Locally heavy rainfall still possible but
still looks too disorganized to pinpoint and significant flood
threat areas, but still on track for 1-2 inches with locally
higher amounts possible. Mild overnight lows in the upper 60s
inland and lower to middle 70s closer to the coast. Onshore winds
will increase to 15 to 25 mph with gusts of 30-40 mph possible
along the immediate beaches Tuesday Morning as the low pressure
tracks northward along the I-95 corridor.

&&

.PREV DISCUSSION [736 PM EDT]...

.NEAR TERM [Through Tuesday]...

Troughing advancing northward over the Florida peninsula will
consolidate into a weak low pressure center along or just east of
Cape Canaveral after midnight tonight. The initial wave of
isentropic lift and mostly light to moderate rainfall will likely
exit our region this evening, followed by additional waves of
showers and a few embedded thunderstorms expected to overspread
coastal northeast Florida from south to north during the predawn
hours on Tuesday. Activity at inland locations should become
isolated to widely scattered in coverage overnight. Our local
pressure gradient will begin to tighten towards midnight as weak
low pressure takes shape to our south, resulting in gradually
strengthening onshore winds later tonight at coastal locations.
Cloud cover and rainfall will keep lows mostly in the upper 60s
inland and lower 70s at coastal locations.

Short-term, high resolution guidance indicates that low pressure
will continue to move northward on Tuesday morning over the near
shore waters adjacent to northeast Florida that will move into the
Georgia coastal waters towards sunset. A burst of heavier rainfall
on the western periphery of this system's circulation should
progress northward along the I-95 corridor during the morning
hours, providing beneficial rainfall amounts up to one inch for
coastal locations, while more scattered coverage inland results in
rainfall amounts of only one quarter to one half inch for most
locations west of U.S. Highway 301. Easterly winds sustained at
15-25 mph east of I-95 will shift to northeasterly by the mid-
morning hours in northeast Florida and then northerly with
decreasing speeds by late afternoon, with breezy easterly and then
northeasterly winds continuing throughout the day for coastal
southeast Georgia. Breaks in the afternoon cloud cover will
develop from south to north, allowing highs to climb to the mid
80s in north central Florida, while clouds and rainfall persisting
for most of the day keeps highs in the mid to upper 70s for most
of southeast Georgia.

.SHORT TERM [Tuesday Night Through Thursday Night]...

Low pressure will continue progressing northward towards coastal
South Carolina on Tuesday night, with decreasing coverage of
showers early in the evening area-wide and winds quickly subsiding
after sunset. Fog formation may be possible along the Interstate
10 corridor early on Wednesday morning, with lows again ranging
from the upper 60s inland to the lower 70s at coastal locations.

Troughing diving over the southern Plains states on Tuesday will
become cutoff near the Arklatex region and the Ozarks on Wednesday
and Thursday as ridging aloft builds off the Mid-Atlantic coast.
This weather pattern will result in a loose local pressure
gradient that will promote scattered to numerous afternoon and
evening convection along sea breeze boundaries. Southeast Georgia
and the I-95 corridor in northeast FL should be favored on
Wednesday and Wednesday evening as deep southwesterly low and mid
level flow prevails in the wake of departing low pressure over
the Carolinas. Summertime temperatures and humidity levels will
return by midweek, with highs climbing to the lower 90s at most
inland locations, while an active Atlantic sea breeze moving
inland keeps highs in the mid to upper 80s at coastal locations. A
few storms may pulse during the late afternoon hours along
colliding Gulf and Atlantic sea breeze boundaries to the east of
U.S. Highway 301, with downburst winds of 40-50 mph and frequent
lightning strikes being the main threats within any heavier
activity.

Sea breezes should collide near or just west of U.S. Highway 301
on Thursday afternoon as light southerly flow prevails over our
region, with highs again soaring to the lower 90s inland, while
the sea breeze keeps coastal highs in the mid to upper 80s. Lows
will continue to range from the upper 60s inland to the lower 70s
at coastal locations.

.LONG TERM [Friday Through Sunday Night]...

Cutoff troughing over the Ozarks will on Thursday evening will
open and lift northeastward through the Tennessee and Ohio Valleys
as a potent shortwave trough glides eastward across the northern
Great Lakes region. This shortwave will dig a full fledged trough
over the eastern third of the nation by late in the weekend.
Southwesterly flow will develop late this week in advance of this
approaching trough, with deeper moisture advecting into our region
on Friday afternoon. This should result in scattered to numerous
mainly afternoon and evening convection along a dominant Gulf
coast sea breeze, with a few pulsing storms possible along the
I-95 corridor by late Friday afternoon. Higher coverage may focus
over inland southeast Georgia on Saturday afternoon ahead of an
approaching frontal boundary, but hot and humid conditions will
keep at least scattered diurnal coverage in place for northeast
and north central Florida. High pressure building over the Ohio
Valley should then push this decaying frontal boundary towards the
Florida/Georgia border by Sunday afternoon, accompanied by at
least scattered convection. A drier air mass advecting southward
in the wake of this frontal boundary may limit convective coverage
across inland southeast Georgia by late Sunday afternoon. Highs
will continue to climb to the upper 80s to lower 90s, with lows in
the upper 60s to lower 70s through the weekend.

.AVIATION...
[Through 00Z Wednesday]

Brief lull in the rain shield this evening and into the early
overnight hours will lead to mainly VFR conds with TEMPO MVFR
CIGS/VSBYS at times. In the 10-14z time frame Tuesday Morning the
northward moving low pressure center along the NE FL coast will
bring widespread IFR/MVFR conds to all TAF sites with best chances
of lower CIGS/VSBYS/WINDS along the coastal TAF sites of CRG/SGJ
and SSI later in the morning. For now have just placed VCTS
starting from 12-16z time frame since timing of storms still too
uncertain at this time. NE winds will gust to 25-30 knots for the
coastal NE FL TAF sites as well as SSI by the 16z time frame. Have
tried to show some improvement in TAF conds to MVFR CIGS and just
VCSH at NE FL TAF sites for the later afternoon time frame as some
better conds should develop in the 18-22z time frame as low lifts
into the SE GA waters by later in the day.

.MARINE...

A trough over southeast Florida this afternoon will move northward
and consolidate into a weak low pressure center along the east
central Florida coast overnight. Winds and seas will increase
after midnight from south to north, with occasional Gale Force
gusts possible over the northeast Florida waters by the predawn
hours on Tuesday. Small Craft Advisory conditions over the
northeast Florida waters tonight will then overspread the
southeast Georgia waters towards sunrise on Tuesday, with seas
building to 5-7 feet for the near shore Florida waters and 6-9
feet offshore after midnight. Low pressure will continue to move
northward on Tuesday, with onshore winds increasing over the
Georgia waters during the early morning hours, where occasional
Gale Force wind gusts will be possible. Seas over the near shore
Georgia waters will build to 5-7 feet on Tuesday and 7-10 feet
offshore. Low pressure will then approach the South Carolina
coast by late Tuesday night, resulting in decreasing shower
activity, accompanied by winds shifting to an offshore direction
and gradually subsiding seas. The axis of Atlantic ridging will be
positioned across central Florida late this week, with prevailing
light southerly winds and active afternoon sea breezes for the
near shore waters.

.FIRE WEATHER...

Numerous showers and a few embedded thunderstorms will continue to
overspread our region early this evening, with heavier activity
shifting to coastal areas overnight. Breezy easterly surface and
transport winds will continue overnight and Tuesday morning, with
winds then shifting to northeasterly and northerly with gradually
decreasing speeds on Tuesday afternoon. Showers and a few
thunderstorms over coastal northeast Florida on Tuesday morning
will shift northward over southeast Georgia, with scattered
afternoon and evening showers and thunderstorms possible inland.
Surface and transport winds will then shift to southwesterly
overnight on Tuesday night through Wednesday, with an active
Atlantic sea breeze boundary expected to slowly push inland on
Wednesday afternoon, where scattered to numerous afternoon and
early evening showers and thunderstorms are expected to develop.

&&

.PRELIMINARY POINT TEMPS/POPS...

AMG  69  78  67  88  70 /  30  60  20  60  30
SSI  72  78  71  85  74 /  40  70  30  50  40
JAX  70  80  69  90  71 /  50  70  20  60  30
SGJ  71  81  71  87  73 /  80  70  20  60  30
GNV  68  81  69  92  70 /  50  50  10  40  10
OCF  68  85  70  91  70 /  50  50  10  40  10

&&

.JAX WATCHES/WARNINGS/ADVISORIES...
FL...High Rip Current Risk through Tuesday evening for Coastal Duval-
     Coastal Flagler-Coastal Nassau-Coastal St. Johns.

GA...High Rip Current Risk through Tuesday evening for Coastal Camden-
     Coastal Glynn.

AM...Small Craft Advisory until 6 PM EDT Tuesday for Coastal waters
     from Fernandina Beach to St. Augustine FL out 20 NM-Coastal
     waters from St. Augustine to Flagler Beach FL out 20 NM-
     Waters from Fernandina Beach to St. Augustine FL from 20 to
     60 NM-Waters from St. Augustine to Flagler Beach FL from 20
     to 60 NM.

     Small Craft Advisory from 5 AM Tuesday to midnight EDT Tuesday
     night for Coastal waters from Altamaha Sound to Fernandina
     Beach FL out 20 NM-Waters from Altamaha Sound GA to
     Fernandina Beach FL from 20 to 60 NM.

&&