Area Forecast Discussion
Issued by NWS Tampa Bay Area, FL

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FXUS62 KTBW 120809

Area Forecast Discussion
National Weather Service Tampa Bay Ruskin FL
309 AM EST Tue Dec 12 2017

.SHORT TERM (Today - Wednesday)...
Aloft - A ridge reaches from CA/NV to the Yukon Territory, Canada
while a low spins above the Baja Peninsula. A broad trough
dominates the eastern U.S. from Hudson Bay to the Gulf of Mexico.
The trough contains a short wave trough that rotates through the
Ohio Valley region today then lifts up into northern New England
by Wed afternoon. Surface - High pressure in the central Plains
early this morning drops down into the Rio Grande Valley during
the day...which along with the short wave trough aloft will shove
a dry cold front eastward. The front moves off the eastern
seaboard by tonight...with the southern end dragging across Fl.
The front exits to the open Atlantic Wed as the Rio Grande high
pressure builds into the Gulf of Mexico region.

The front arrives with a swath of deeper moisture ahead of it...but
with PWAT values only in the 0.5 to 0.8 inch range. This precludes
any significant rainfall but will bring some occasional cloudiness
later this morning and during the afternoon. Dry air follows the
front in with PWAT of 0.5 inches or less for tonight into Wed. The
timing of the front should allow the highs to warm to almost
normal this afternoon. Then cool dry northwest to north flow will
keep overnight lows and Wed afternoon highs below normal. Can not
rule out patchy frost in sheltered Nature Coast locations but the
dry air and some wind will limited widespread frost. Some robust
and gusty winds are expected with the front but these will
primarily be beach and marine concerns. The onshore component of
the winds will bring elevated water levels at the coast with a
high risk of rip currents today...a coastal hazard statement will
be in place.

.LONG TERM (Wednesday Night - Monday)...
The highly amplified upper air pattern featuring strong upper level
ridging over the western U.S. and strong upper level troughing over
the eastern U.S of late will de-amplify and become more progressive
in nature toward the end of the week and continuing through early
next week.

At the start of the period a zonal flow aloft and surface high
pressure building across the Gulf and Florida will maintain pleasant
cool dry weather with clear skies across the entire forecast area
Wednesday night into Thursday with temperatures Wednesday night
falling into the upper 30s to around 40 across the Nature Coast,
lower to mid 40s central and southern interior zones, and upper 40s
to lower 50s along the immediate Gulf coast with highs on Thursday
in the upper 60s to around 70.

During Thursday night the high will shift east-southeast into the
Atlantic as another short wave trough and attendant cold front
approach from the northwest. The GFS and Canadian continue to show
this front moving south through the forecast area on Friday with
decent rain chances, while the Euro now is even slower than previous
solutions, and keeps the front to the north of the area through
Friday night, then sinks its remnants south into the north-central
peninsula on Saturday with much lower rain chances compared to the
GFS and Canadian solutions. Given the differences in the models and
fact that the GFS and Canadian have been a bit more consistent with
this front, have opted to use a blend of the models for now with a
bit more weight given to the GFS/Canadian solutions. With this in
mind will depict rain chances increasing into the 20 to 30 percent
range during Thursday night, then 40 to 60 percent from south to
north on Friday as the front moves south through the area. Pleasant
dry weather with seasonably cool temperatures will return Friday
night through Saturday night as surface high pressure builds in over
the region in the wake of the front.

The high will shift east into the Atlantic on Sunday as the next
front approaches from the northwest on Monday. Pleasant dry weather
with moderating temperatures can be expected during Sunday and
Sunday night, with the next rain chance (Pops 20 to 30 percent)
expected across the northern Nature Coast on Monday as the front
sinks south toward the area during the day, while dry conditions
will continue across central and southern portions of the forecast
area. Temperatures during the latter part of the weekend and into
early next week will continue to modify with overnight lows
generally in the 50s, with daytime highs climbing into the lower and
middle 70s.


12/06Z TAFs. SKC gives way to FEW-SCT CU under SCT-BKN CI with dry
FROPA late morning-early afternoon...with just FEW CI behind it. The
front shifts SW winds to NW...and gusty in the afternoon.


A dry cold front tracking southward over the waters will being
increasing winds and seas...with a small craft advisory starting
this morning in the north and early afternoon for central and
southern zones. High pressure builds in Wed with winds shifting
and diminishing. However another cold front will arrive Fri and
increase winds and seas until high pressure builds back in for
the weekend.


The frontal passage today will result in strong enough 20 foot and
transport wind speeds for high dispersions this afternoon and also
begin to usher in drier air. The driest air reaches the area Wed
with 5 to 7 hours of critical RH levels. However low ERC values and
slackening winds will preclude any red flag warnings. The atmosphere
begins to moisten Thu with RH levels staying above critical levels.


.Preliminary Point Temps/PoPs...
TPA  72  45  62  50 /   0   0   0   0
FMY  75  48  66  47 /  10   0   0   0
GIF  73  42  62  42 /   0   0   0   0
SRQ  72  47  63  50 /  10   0   0   0
BKV  72  37  61  42 /   0   0   0   0
SPG  71  50  61  52 /   0   0   0   0


FL...High Rip Current Risk from 10 AM EST this morning through
     this evening for Coastal Charlotte-Coastal
     Hillsborough-Coastal Lee-Coastal Manatee-Coastal

Gulf waters...Small Craft Advisory from 10 AM this morning to 7 AM EST
     Wednesday for Coastal waters from Tarpon Springs to
     Suwannee River FL out 20 NM-Waters from Englewood to
     Tarpon Springs FL out 20 to 60 NM-Waters from Tarpon
     Springs to Suwannee River FL out 20 to 60 NM.

     Small Craft Advisory from 1 PM this afternoon to 7 AM EST
     Wednesday for Charlotte Harbor and Pine Island Sound-
     Coastal waters from Bonita Beach to Englewood FL out
     20 NM-Coastal waters from Englewood to Tarpon Springs
     FL out 20 NM-Tampa Bay waters-Waters from Bonita
     Beach to Englewood FL out 20 to 60 NM.



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