Scientific Forecaster Discussion
fxus62 kjax 221848
Area forecast discussion
National Weather Service Jacksonville Florida
248 PM EDT Mon may 22 2017
Near term.../through Tuesday/...
The region will be between high pressure to the east and a frontal
boundary to the northwest today into Tuesday. Most of todays
convection will initiate on the west and East Coast sea breeze
boundaries, with a convergence of these boundaries likely occuring
between interstates i95 and i75 around 20z. With the flow generally
from the southwest, expect this area of convection then to move
toward i95 corridor later this afternoon, before moving off the
Eastern Shore this evening. Could see showers and a few storms
linger through the night northwest closer to the frontal boundary.
The overall pattern will remain nearly the same into Tuesday.
However, a 500h short wave trough will move southeast into the
region in the afternoon. This energy, coupled with surface
instability and sea breeze interactions will result in scattered to
numerous showers and storms once again. The best chance for
convection Tuesday afternoon will be over southeast Georgia closer to the upper
Short term /Tuesday night through Wednesday night/...
Tuesday night...there may some linger convection along the first coast
and coastal southeast Georgia during the early evening with some
stratiform precip in the wake of the West Coast sea breeze
convection mainly north of I-10 and interior southeast Georgia through mid
evening. The convection will move well offshore during the late
evening as well as the stratiform rainfall. A couple hours after
midnight...increasing large scale ascent ahead of a large scale
trough...supplemented by diffluent flow aloft is quite favorable
to support widespread rainfall over the eastern Gulf of Mexico and
Florida's nature and sun coasts. This convection looks like it
will push into the Suwannee Valley during the predawn hours and
into interior southeast Georgia and into NE Florida. There may be some
initial heavy rain showers with embedded convection during the
morning commute early Wednesday morning which could be round #1.
Wednesday and Wednesday night...on Wed, upper level trof over the
mid south will extend into the Gulf of Mexico driving a frontal
boundary into the western Florida Panhandle and western Georgia
early in the day. Deep layer southwesterly wind and speed shear
will occur with surface winds strengthening at 15-25 mph with some
higher gusts while higher pre-frontal moisture overspreads the
area with precipitable water values 1.8" to 2.0". The deepness of
the trough suggests that a band of convection ahead of the front
could produce strong storms Wed afternoon into early Thu. The
sounding profile suggests a nearly saturated atmosphere.
Significant rainfall is possible, with day 3 wpc rainfall totals
of generally 2-3 inches, with substantially but locally higher
amounts are very feasible perhaps requiring a Flood Watch
Wednesday. Due to ample cloud cover and rainfall, instability does
decrease, but shear does increase with surface to 3km shear values at
35 knots. The wind profile will be unidirectional with ample
convective available potential energy of 1300-1600 j/kg. With this said, a couple rounds of strong
to severe weather will be likely across the region throughout the
day and into the evening hours ahead of the cold front, and along
the front itself. The main threat from the stronger to marginally
severe storms can be wind gusts of 45 to 65 mph, 1" hail with 5h
temps at -10. Storm Prediction Center has southeast Georgia in a marginal risk and
northeast Florida in a slight risk of severe weather on Wednesday.
The convective activity will likely linger through most of the
evening edging slowly eastward as the evening progresses with
shear values still pretty heightened east of Highway 301 with 40
knots of shear mid evening east of I-95 in NE Florida. The NAM does
show backing at the surface across northeast Florida with a
hodograph indicating some good directional shear in the lowest 1
km early to mid evening as frontal feature moves into Big Bend
region. Hence, a isold tornado can not be ruled out. Highs
Wednesday will generally range from upper 70s to lower 80s. Some
clearing expected over inland southeast Georgia and the western
Suwannee Valley by the predawn hours on Thursday as cold front
situates across our southern tier counties in north central Florida.
Lows will fall to the lower 60s interior southeast GA, and lows elsewhere
will remain in the mid to upper 60s.
Long term /Thursday through Memorial Day/...
the upper trough axis shifts through the region by Thursday
afternoon, with a surface cold front well ahead pushing east-
southeast through the north central southern tier zones by early
morning. The heavy rainfall threat will also end Thursday morning
behind the front. Drier air will filter into the region through
the day as the cold front pushes southward, with much more
pleasant dewpoints in the mid to upper 50s areawide by afternoon.
Friday morning lows will be cooler in the mid/upper 50s inland and
the low to mid 60s along the coast, around 5 degrees below
normal. Highs are forecast to also be cooler in the mid 80s. Upper
ridging will build northwest from the southwest Gulf late in the
week and into the weekend. Weak surface high pressure will then
build across central Florida through the end of the week and into
the weekend, with dry conditions continuing. Moisture may begin to
return Sunday and Monday, with 20-30% rain chances, highest
across southeast Georgia. However, models are not in agreement on
timing of moisture return this far out. Slightly below normal on
Thursday will quickly rebound to above normal in the upper 80s to
low 90s by the Memorial Day weekend, with lows in the mid 60s to
convection is expected to affect area taf sites this afternoon
into this evening. The convection will dissipate by around
midnight, then redevelop Tuesday morning. Restrictions in addition
to gusty winds can be expected in and near any storms.
Marine...high pressure will move from east of the region today to
the southeast Tuesday and Wednesday. A cold front will cross area
waters Wednesday night into Thursday. High pressure will build
from the west Thursday night into Friday. This ridge will be east
of area waters over the weekend.
Rip currents: low risk expected on Tuesday as offshore flow
Preliminary point temps/pops...
amg 71 80 69 79 / 70 70 70 80
ssi 73 83 73 81 / 70 60 60 80
jax 70 86 72 83 / 60 60 60 80
sgj 72 87 73 83 / 70 50 40 80
gnv 69 86 72 82 / 30 50 60 80
ocf 71 86 73 81 / 20 40 50 80