National Weather Service San Juan PR
454 AM AST Sat Apr 30 2022
.SYNOPSIS...
Today as an inverted low to mid-level trough moves though the
region, rainy conditions will prevail across most local Islands
with the risk of urban and minor stream flooding and even
thunderstorms. This weather will persist into Sunday yet will
begin to improve as the weekend ends. Climatologically average
moisture values will provide a week of typical weather with a
drying trend beginning on the weekend. As a northerly swell is
still in the local waters, marine hazardous remain.
&&
.SHORT TERM...TODAY THROUGH MONDAY...
Weather conditions will deteriorate today as a wetter air mass moves
from the Caribbean Sea into the islands of Puerto Rico and the U.S.
Virgin Islands. The following factors: abundant moisture, an
inverted low to mid-level trough, an upper-level trough, local
topography, and low-level convergence will promote showery
conditions today. Although rainy conditions will prevail across most
islands, model guidance is now backing up or indicating less
rainfall accumulation than previous simulations. However, the risk
for urban and minor stream flooding will remain high across the
islands today. We could not rule out flash flooding across some
spots today. Some of these showers could have moderate to heavy
rain, increasing the risk of flooding. The strongest activity is
expected across eastern PR, Vieques, Culebra, and the U.S. Virgin
Islands. There is a potential to observe areas with 3 to 5 inches of
rain totals; elsewhere, between 1 and 3 inches will remain possible
through Sunday.
Although the potential for showers and even thunderstorms will
persist on Sunday, the activity should slowly erode across the
islands. The main concern continues to be on how fast this drying
trend will occur. Nevertheless, weather conditions should improve
throughout the day on Sunday.
A more seasonal weather pattern with an easterly wind flow,
combinations of clouds and sunshine, and a few passing showers in
the night and morning hours, followed by afternoon convection across
the interior and western portions, will return by Monday.
.LONG TERM...Tuesday through Sunday...
At the surface, a high pressure system in the Western Atlantic
promotes breezy easterly flow throughout the week. This flow will
advect patches of moisture into the region with Wednesday and
Thursday morning appearing with the best precipitable water values
according to the GFS. The previous expected wet trend starting
around the end of the week is not present in the current GFS model
run with the precipitable water and columnar RH values much lower
than previous simulations. However, GFS 250 mb heights still
indicate that an upper level trough will pass through the region
on Friday which could enhance instability.
On the contrary to previous model runs, the end of the week shows
the beginning of a drying trend that continues on past Sunday
with light winds from the southeast. A lack of moisture during the
weekend is consistent between the latest GFS and ECMWF model
runs. Therefore, A predictable weather pattern is expected
throughout the week with passing showers along windward regions
and afternoon development in the western side of Puerto Rico and
if model guidance holds true, next weekend will have fair, dry
weather as moisture values reach below climatological averages.
&&
.AVIATION...Unstable weather, cloudy skies and rainy conditions
will prevail today. -SHRA/SHRA are expected across most of the
local flying area. Prds of MVFR conds likely with BKN-OVC clds
lyrs nr FL025...FL050... FL100 and wdly SCT SHRA/ISOLD TSRA. SFC
wnds will continue calm to light and VRB bcmg ESE-SE at 10 to 15
knots with higher gusts and sea breeze variations aft 30/13Z.
Higher wind gusts btw 20-25 kts will accompany Isold/Sct-TSRA and
+SHRA.
&&
.MARINE...A weakening northerly swell has raised wave heights up to
7 feet. Moderate winds from the east continue to cause choppy
seas. As a trough moves through the region today, expect winds
from the southeast with numerous showers and isolated
thunderstorms over the local waters. There are Small Craft
Advisories in effect and a High Risk of Rip Currents Remain for
beaches of Puerto Rico and the U.S. Virgin Islands.
&&
.PRELIMINARY POINT TEMPS/POPS...
SJU 84 73 82 74 / 90 70 50 40
STT 83 72 83 75 / 90 90 70 30