Area Forecast Discussion
Issued by NWS Tampa Bay Area, FL
FXUS62 KTBW 090013
Area Forecast Discussion
National Weather Service Tampa Bay Ruskin FL
713 PM EST Thu Dec 8 2016
00Z water vapor and H4 RAP analysis showing a rather unamplified
upper level pattern across the CONUS this evening with broad
longwave ridging over the western States...followed by broad
downstream troughing through the central and eastern portions of
the country. Sharpest troughing is pivoting through the Northeast
States this evening...delivering a shot of winter-time air to the
north-central and northeast part of the country. The base of this
eastern trough will pivot through the southeastern States and
Florida peninsula overnight and Friday morning. The weak influence
of this passing trough and associated mid/upper jet dynamics are
helping to bring general weak lift to the central and eastern Gulf
of Mexico. Have seen cooling and expanding clouds in satellite
imagery the past several hours...as the weak large-scale synoptic
lift is coupled with weak mid-level upglide over the Gulf. All
this...will add up to keep the clouds rolling overhead the next
12-24 hours...mainly above 7-10KFT. Most of the NWP guidance
members are producing just enough synoptic lift with the passing
upper trough/diffluent flow later tonight and Friday morning to
squeeze out scattered light showers. Most spots will likely see a
shower or two...especially from the I-4 corridor
southward...however...qpf totals are going to be very low.
Underneath all of this mid/upper level "action"...a cold front
will be slipping southward through the Florida peninsula during
the overnight. This front will not be delivering the degree or
cold air being experienced to our north...but it will be a good
shot of cool air for Florida. We will all notice the cooler air
settling in tomorrow...especially Friday night/Saturday morning.
All we talked about above slowly exits out of the region during
the second half of Friday...allowing high pressure and dry
conditions to dominate our forecast for Friday Night through the
upcoming weekend. Although it will be a good shot of cooler air
behind this front...the warmup will begin quickly during Saturday
afternoon and continue into the second half of the weekend.
Have a great rest of your evening everyone! Remember...you will
likely need to bundle up a bit if headed out early Saturday
morning. Plan accordingly.
Despite plenty of mid-upper level clouds in the forecast through
the TAF period...no significant restrictions are expected.
Forecast for all terminals will be prevailing VFR through Friday.
As mentioned...plenty of clouds aloft...with a few light showers
overnight into the first half of Friday...but no heavy rainfall
expected. Winds steady from the north and northeast through the
period and becoming gusty between 10-15 knots later tonight
.Prev Discussion... /issued 204 PM EST Thu Dec 8 2016/
SHORT TERM (Tonight - Friday)...
A closed upper low sits over central Quebec with troughing extending
through the Great Lakes region. The trough moves slowly eastward by
Friday afternoon and deepens over northern Florida. On the surface,
a disturbance develops along a stationary frontal boundary extending
over southern Florida and into the Gulf of Mexico. This will bring
our highest rain chances through the period with 20-30 POPs from
Tampa northward and 30-40 POPs south of Tampa. This boundary moves
south of Florida by late Friday as a 1036 MB high pressure center
over the central U.S. moves eastward and takes control of the
weather over Florida. The gradient between the boundary over
southern Florida and strong high pressure up north will produce
Small Craft Advisory winds and seas over the coastal waters by
starting Thursday evening and lasting through Saturday afternoon.
This will also allow for some of the coolest air we`ve seen this
season to advect into the region. The high and low temps on Friday
and Saturday will be 6-10 degrees below average for this time of
LONG TERM (Friday Night through Thursday)...
Broad cyclonic flow will engulf much of the eastern half of the
CONUS at the start of the medium range period, with a substantially
cold area of high pressure across much of the north central and
eastern U.S. Meanwhile...fast zonal flow will develop across the
northern and central Rockies...setting the stage for a number of
compact storm systems over the coming days.
Friday night will feature rather chilly overnight temperatures, as
high pressure settles into the southeastern states. While it will
certainly be cold, much of the coldest air will remain well to the
north of the Florida Peninsula, affecting mainly the Panhandle and
Georgia/Florida border regions. Temperatures over interior sections
of the Nature Coast and interior north Florida may fall to near
freezing or perhaps a degree or two below for a brief time Saturday
morning, but it currently looks that widespread freezing conditions
are unlikely. Further south, expect lows to only fall into the low
to mid 40s...with 50s south of I-4.
Within a progressive upper level flow pattern, we look to modify
rather quickly with temperatures rebounding into the 60s and low 70s
Saturday afternoon. The warming trend will continue into early next
week, as low to mid 70s return Sunday, and low 80s make a comeback
Monday and Tuesday. This will all occur as surface high pressure
slips eastward, and a return of moist east to southeast winds occurs
ahead of another cold front set to approach the region mid to late
VFR conditions will prevail through 06Z. At that time, cloudiness
will increase with a BKN deck around 3000 feet developing. Will also
bring in VCSH at the northern terminals after 06Z and the southern
terminals around 08Z. Winds will remain out of the north northeast
in the 5 to 10 knot range. No other aviation impacts expected.
A tightening gradient between a frontal boundary over southern
Florida and strong high pressure over the central U.S. will create
some hazardous boating conditions over the coastal waters starting
later this evening. Gusty north-northeast winds has prompted the
issuance of a Small Craft Advisory beginning later this evening and
continuing through Saturday afternoon. The gradient slackens at that
time, but will likely still remain at cautionary level for the outer
coastal waters through Sunday morning. As the high slips east off
the mid Atlantic coast, the winds will shift to the east southeast
and remain around 10-15 knots through the beginning of next week.
Drier air will filter into the northern half of the Florida
Peninsula by Friday afternoon. Relative humidity percentages will
drop into the mid 30s for a few hours over parts of the Nature
Coast, and into the mid to upper 40`s as far south as the Tampa Bay.
Elsewhere, relative humidity will only bottom out in the 50s and
60s. Relative humidity will then increase through the weekend with
no fire weather impacts expected.
.Preliminary Point Temps/PoPs...
TPA 53 63 50 71 / 30 30 0 0
FMY 55 67 57 76 / 20 30 10 10
GIF 52 62 49 70 / 20 30 0 0
SRQ 56 65 52 74 / 30 30 0 0
BKV 48 60 43 68 / 20 20 0 0
SPG 54 62 52 69 / 30 30 0 0
Gulf waters...Small Craft Advisory from 10 PM this evening to 1 PM EST
Saturday for Coastal waters from Bonita Beach to
Englewood FL out 20 NM-Coastal waters from Englewood
to Tarpon Springs FL out 20 NM-Coastal waters from
Tarpon Springs to Suwannee River FL out 20 NM-Waters
from Bonita Beach to Englewood FL out 20 to 60 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.