Area Forecast Discussion
Issued by NWS Melbourne, FL
FXUS62 KMLB 202027
Area Forecast Discussion
National Weather Service Melbourne FL
327 PM EST Fri Jan 20 2017
...Threat for Severe Storms Sunday Afternoon/Evening...
...Very Hazardous Boating Conditions Sunday Afternoon-Monday...
Tonight...High pressure ridge over the north/central Bahamas will
continue a southerly wind flow and slowly elevate dew points.
Satellite doesn`t show a lot of mid or high level cloudiness
upstream so skies look clear to partly cloudy for a time. GFS MOS
continues to show a low visibility and ceiling from metro
Orlando northward to Lake and Volusia counties. Boundary layer
winds may favor stratus over dense fog, but will leave current
forecast that has areas of fog over the north and patchy fog over
the south. Low temperatures should moderate a few degrees and be
in the upper 50s to lower 60s.
Saturday...Continuing southerly flow will gradually moisten the airmass.
The GFS indicates a pocket of higher moisture working north/northeast
over the eastern Gulf and moving across the northern peninsula.
At the same time, a mid level impulse is shown intersecting that
higher moisture band. MOS has 20-30 POPs across northern
sections. Not sure of the timing of these two features so have
only put small afternoon shower chances in the far north. Otherwise
it will be another warm day with highs in the lower to mid 80s.
MODIFIED PREVIOUS DISCUSSION...
Sunday...Models remain in good agreement regarding a higher than
usual threat of "dry-season" severe weather during the afternoon and
evening hours. A robust cut off low moving eastward through the
southern U.S. and 100-120kt 250mb jet across the southeast states
will aid the intensification of a low pressure system over Georgia
and the Carolinas. An organized pre-frontal squall line is expected
to take shape over the eastern Gulf of Mexico and move rapidly east
between 40 to 50 mph, impacting east central Florida in the
afternoon and evening.
Temps reaching the low 80s ahead of this band of convection and
dewpoints in the mid-upper 60s will result in more than sufficient
instability across the area as it moves through. A 50-knot low level
jet is forecast to overspread the region into the afternoon ahead of
the front, favoring strong to severe straight line winds as the main
threat with the squall line. Also, helicity values up to 200-300
m2/s2 will produce the potential for a few tornadoes, especially
with any supercells that can develop out ahead of the main line.
Monday-Thursday...Axis of low aloft will swing through the state
early Monday and may continue to enhance lift for light
rain/showers in the morning. Otherwise a strong westerly flow
will usher in cooler/drier air behind the front early next week,
with rain chances ending and temperatures returning to more normal
values for this time of year (highs upper 60s/low 70s and lows in
the upper 40s/low 50s). Temperatures will then slowly climb
through mid week, with highs in the mid to upper 70s Wed/Thu.
VFR until after midnight then there is a chance for IFR-LIFR due
to fog/stratus. Have only brought conditions down to IFR for now
as boundary layer flow looks to favor more stratus than dense fog.
Stratus and any fog should dissipate 14-15z Sat.
Tonight-Sat...High pressure will gradually push east of the
northern/central Bahamas, which should cause the local pressure
gradient to tighten slightly on Sat. Expect speeds over the cooler
Continental shelf to be around 10 knots tonight and nudge to
10-15 knots Sat, but over the Gulf Stream, speeds look about 5 mph
higher and an exercise caution for small craft operators might be
necessary later in the day.
Sunday-Wednesday...Boating conditions will deteriorate through the
weekend becoming hazardous to very hazardous Sunday/Sunday night
ahead of a passing frontal boundary and pre-frontal squall line
pushing offshore through the afternoon/evening hours. Southwest
winds will increase up to 20-30 knots, with a Gale Watch/Warning
potentially needed for the offshore waters Sunday night through
Monday as a strong westerly breeze continues behind the front.
This strong westerly flow will keep highest seas farther offshore,
up to 9-11 feet through Monday night.
Winds gradually decrease out of the west-northwest into mid week,
but seas will be slow to subside, remaining poor to hazardous
through Tuesday night.
Temperatures Sat might might approach record highs at a few spots:
DAB 21-Jan 83 1990
MCO 21-Jan 87 1929
MLB 21-Jan 85 1963
VRB 21-Jan 86 1990
.PRELIMINARY POINT TEMPS/POPS...
DAB 63 81 65 81 / 10 20 20 80
MCO 63 83 66 81 / 10 10 20 80
MLB 61 84 66 83 / 0 10 10 60
VRB 60 84 67 83 / 0 10 10 50
LEE 63 81 67 79 / 10 10 30 80
SFB 63 83 66 81 / 10 10 20 80
ORL 65 82 66 81 / 10 10 20 80
FPR 58 83 65 83 / 0 0 10 40