AREA FORECAST DISCUSSION…updated for near term discussion
NATIONAL WEATHER SERVICE TALLAHASSEE FL
628 AM EDT Thu Jul 19 2012

NEAR TERM [THRU this morning]…
NOCTURNAL land breeze began early with marine CONVECTION developing
overnight. During the predawn hours, satellite PIX showed vort MAX
rounding base of area TROUGH igniting marine convection which was
increasing AS it moved ENE and brushed adjacent coastlines.
Conversely, convection across our NRN counties aligned with surface
trough decreased with loss of heating.

&&

.SHORT TERM [Today Through Saturday]…

SYNOPSIS…The persistent large scale longwave pattern is
highlighted by a trough along West Coast with CUTOFF LOW over Nrn
CA, strong ANTICYCLONE that covers much of CNTRL Rockies and SRN
Plains, trough over ERN states, a HIGH/RIDGE over Atlc with ridging
SWWD to over Gulf of MEX. Weak upper low over E/Cntrl GA opening up
into base of ERN trough with ample MID/high clouds along and east of
low.

At surface subtropical ridge extends from WRN Atlc WWD to across Nrn
Gulf of Mex. Trough extends from low along PA coast swwd to across
Cntrl GA/S/Cntrl AL. Second minor trough over FL Peninsula. All this
continues to place local area in a broad area of HEIGHT weakness and
assocd with upper low and between deep layer ridges to our west,
east and south. Light SW FLOW continues to favor moist airmass with
DEW points in the lower 70s and PWs above 2 inches.

TODAY THRU TONIGHT, Both the Rockies/Plains ridge and NE trough will
amplify and the broad CIRCULATION around low at base of weakening
trough will continue to favor a moist airmass and high PWs and
influence the weather across the region. While the low is PROGGED to
further weaken and open up, the deep MOISTURE and general cyclonic
mid-level flow will remain in place. Weak impulses will continue to
rotate around low enhanced by DEEPENING trough which will interact
with Gulf seabreeze. RAIN across mainly marine area and coastal
counties this morning with rain spreading inland during the AFTN
aided by proximity to GA surface trough and outflows. This will keep
POPS at or above summertime CLIMO. With light steering flow and high
PWs, cant discount locally heavy rain. Per local confidence and CAM
tools, the threat of severe weather quite low with focus over waters
and adjacent SE Big Bend. SPC places only our wrn counties in 5%
convective WIND OUTLOOK” onClick=”return popup(this, ‘notes’)”>OUTLOOK and cant discount ISOLD PULSE STORM and will
put gusty winds in GRIDS there. Will go with 50-60% POPs today,
30-40% tonight. With the expected rain and CLOUD coverage, high
temperatures should remain at or below climo, mid 80s coast to
around 90 inland. Lows low 70s inland to mid-upper 70s coast.

FOR FRI, amplified trough and moist airmass remain. the threat of
severe WX even lower with only SPC see text. Will go 40-60% S-N POP
GRADIENT and Highs upper 80s coast to low 90s inland.

FOR FRI NIGHT INTO SAT, the Rockies/Plains ridge will hold but the
Ern trough will begin to weaken and move offshore with the ridge to
our south amplifying NWWD with drier AIR/SUBSIDENCE filtering in.
At surface, upper trough shifts offshore and Gulf ridge builds NWD.
Hence precip coverage and intensity will commence to decrease from
SE-NW. TEMPS will rise to at or above NORMAL especially across FL
more distant from trough and with fewer clouds. Will go 30-40% POP
gradient Fri night and 20-50% SE-NW POP gradient on Sat. Lows low
70s inland to upper 70s coast. Highs upper 80s coast to low-mid 90s
inland.

&&

.LONG TERM (Saturday night through next Thursday)…
As the upper trough continues to deamplify, the ridge to the west
and the Bermuda high will merge over the local region on Sunday.
Then, Bermuda ridge weakens early next week with a digging TROF off
the eastern seaboard through the remainder of the extended period.
This puts the local area on the eastern periphery of the upper ridge
centered over the Mississippi Valley. Surface ridging will extend
from the Western Atlantic across the Gulf with the axis over or
south of our coastal waters. Despite the deep layer ridging, time
height cross sections continue to show sufficient moisture along
with a FEW embedded impulses to provide at least SCATTERED DIURNAL
convection. Temps will be a few degrees above seasonal levels.

&&

.AVIATION…
ISOLATED convection is getting an early start this morning. Most
activity is over the coastal waters with some showers moving onshore
as of 07z. Expect VFR conditions to persist through much of the
overnight hours with only localized MVFR vsbys concerns before
SUNRISE at all sites but ECP. We should see an ACTIVE day with
convection. All convective tempo groups are for this afternoon but
if trend continues we may need an additional tempo group in the
morning for ECP and TLH.

&&

.FIRE WEATHER…
Low level onshore flow will continue to feed abundant moisture into
the region. Minimum afternoon relative HUMIDITY levels are forecast
to stay well above critical levels along with rain chances each day
through the upcoming weekend and beyond.

&&

.MARINE…
The subtropical ridge will remain situated just south of the waters
over the next several days. The gradient has tightened up just a bit
and will remain so through Friday night. During this time winds will
edge up to 10-15 KT with SEAS up to 3 FT. However, no headlines are
anticipated through the forecast period.