Scientific Forecaster Discussion

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Area forecast discussion 
National Weather Service San Juan PR
1103 am AST Thursday Apr 24 2014

Update...clear to partly cloudy skies prevailed this morning across
the local islands as a generally fair and stable weather continued
across the region. In agreement with this reasoning...the Doppler
weather radar detected no precipitation across the region so far
this morning. However...the limited moisture across the local
islands will combine with daytime heating...sea breeze and other
local effects to induce the development of some showers mainly
across parts of the north and central sections of Puerto Rico this
afternoon. The prevailing southeast low level wind flow will promote
warmer than normal temperatures mostly across the northern part of
Puerto Rico.

&&

Aviation...mostly VFR conditions are expected across the local
flying area for the next 24 hours. Latest tjsj sounding indicated
a light and variable wind flow all the way from the surface to 15k
feet...becoming from the west and stronger above 15k feet. Vcsh
possible for tjmz and tjbq between 24/17z and 24/22z with clouds
increasing causing mountain obscurations and ceilings at around fl030-040
across western PR.

&&

Marine...trade winds will turn a little more from the
east-southeast tonight while weakening a little as high pressure
northeast of local islands move farther into central Atlantic.
Across the coastal waters...seas of 4 feet or less and winds of
15 knots are expected.

&&

Previous discussion... /issued 435 am AST Thursday Apr 24 2014/

Synopsis...broad trough aloft will dominate the western Atlantic into
Greater Antilles through early next week with upper level ridge
expected to build middle to late next week.

Discussion...mostly clear to partly cloudy skies prevailed across
the local islands overnight...with showers observed across portions
of north central Puerto Rico. Temperatures were in the lower 80s
at lower elevations with light and variable winds.

A generally fair and mainly stable weather pattern will continue to
prevail across Puerto Rico and the US Virgin Islands today...as a
zonal flow continues to dominate the northeastern Caribbean...
creating and maintaining overall subsidence and mostly dry conditions
aloft. However...due to a weak southeast low level wind flow...better
local sea breeze variations are anticipated...resulting in some
diurnally induced showers and possibly a late afternoon thunderstorm
mainly across parts of the north and central sections of Puerto
Rico. As the aforementioned southeast flow prevails...warmer than
normal temperatures will continue.

GFS and WRF continue to suggest a slight increase in moisture Friday
and into early next week. This slight increase is associated with
a series of troughs moving north of the area. This along with local
and diurnal effects will allow for better chances of afternoon
convection inland Friday through early next week.

Upper level ridging gradually builds middle to late next week as troughs
deepen over the central Atlantic and eastern Continental U.S....bringing once again dry
and stable weather conditions.

Aviation...VFR conditions are expected across the local terminals
for the next 24 hours. Light and variable winds until 24/11z...east-southeast
winds at around 10 knots thereafter with sea breeze variations. Vcsh
possible for tjmz and tjbq between 24/17z and 24/22z with clouds
increasing causing mountain obscurations and ceilings at around fl030-040
across western PR.

Marine...broad trough north of the area will prevail through Friday
maintaining a weak pressure gradient with light to moderate trade
winds. Moderate north swells will begin affecting the Atlantic coastal
waters Saturday with seas building up to 6 feet.

&&

Preliminary point temps/pops...
sju 90 79 90 79 / 10 10 20 10
stt 85 79 85 79 / 10 20 20 20

&&

Sju watches/warnings/advisories...
PR...none.
Vi...none.
Coastal waters...none.
&&

$$

72/12