National Weather Service San Juan PR
525 AM AST Thu Feb 29 2024
.SYNOPSIS...
Northeasterly winds will continue to steer shallow shower activity
over windward sectors through the weekend, with limited afternoon
shower development over portions of southwest Puerto Rico. Another
increase in moisture is forecast for Sunday onwards. Marine and
coastal conditions will deteriorate and become hazardous due
increasing northeast winds and a northerly swell Friday night
through the first half of the next workweek.
&&
.SHORT TERM...Today through Saturday...
Partly cloudy skies prevailed through the overnight hours across the
islands. Passing showers under northeasterly steering winds were
noted over land areas, leaving less than a quarter of an inch in
general. Minimum temperatures were from the mid 60s across the higher
elevations to the mid and upper 70s across the lower elevations. Wind
gusts were between 18 and 22 mph near showers. For today, mostly sunny
to partly cloudy skies are expected to prevail across the islands.
Passing trade wind showers could reach once again portions of the USVI
and the north/eastern sections of PR through the morning hours. Later
in the afternoon, the combination of the limited moisture content with
daytime heating and the sea breeze convergence should cause showers to
develop over portions of the SW quadrant of PR.
For the rest of the short term period, a building mid-to upper-level
ridge from the west will continue to promote drier air aloft and
stable conditions in general across the local area. In response, a
gradual warming of the 500 mb temperature is expected from -10C
yesterday to around -6C by Friday morning. The precipitable water
content (PWAT) is forecast to gradually erode from around 1.30 inches
today to below 1.00 inch on Saturday morning. Therefore, shallow level
moisture transport will promote isolated to scattered showers at times
across the windward areas of the islands, with limited afternoon shower
development each afternoon over portions of SW PR.
At lower levels, northeasterly trades will prevail across the
northeastern Caribbean as a weak surface high over the western
Atlantic gets replaced by a stronger one by Friday. This will
promote breezy conditions from Friday evening through Saturday,
and mainly across the local waters. Near normal temperatures
should continue across the islands each day.
&&
.LONG TERM...Sunday through Wednesday...
Based on the latest model guidance, the broad surface high
pressure will continue to move northeastward and will be located
over the north-central Atlantic by Sunday. Winds are forecast to
remain from the northeast for the beginning of this forecast
period, then become more from the east on Monday and eventually
southeast by midweek. During Sunday, patches of moisture due to an
inverted trough will be moving across the region, increasing
precipitable values to near normal range. With the easterly flow,
available moisture, and local effects expect isolated to scattered
showers, mainly across eastern sections of PR and the U.S. Virgin
Islands during the morning hours, with some areas of afternoon
convection across the western and southwest quadrant of Puerto
Rico. An upper-level trough should be crossing our forecast area
by early next week increasing instability and allowing better
chances for convection development.
&&
.AVIATION...
(06Z TAFS)
Issued at 525 AM AST Thu Feb 29 2024
Mainly VFR conditions are expected to prevail across all terminals
during the next 24 hours. However, showers embedded in the northeast
trades should cause mostly VCSH and brief -RA periods across the
area terminals. ENE winds at 12-16 kt with higher gusts at times.
&&
.MARINE...
Current CARICOOS buoy observations near Rincon, Arecibo and San
Juan indicate seas up to 4.2, 4.9, and 4.4 ft, respectively.
CARICOOS buoys north of Vieques, south of Ponce, and south of St.
John, indicate 4.1, 3.0, and 2.6 ft, respectively. Small Craft
Should Exercise Caution over the Atlantic Waters due to seas up
to 6 ft, and over sectors of the Caribbean waters and the Mona
Passage due to winds.
As a shearline north of the region continues to meander and weaken
and an upper trough moves away from the islands, weather
conditions should generally improve through the day. Gentle to
moderate northeasterly winds are forecast for today. Brief showers
steered by east northeast winds will still reach portions of the
local waters and passages during the morning hours. Northeasterly
winds are expected to increase moderate to fresh tonight through
the weekend as the latest model guidance suggests a broad surface
high pressure will move northeastward across the Western Atlantic
during the next several days and spread into the North Central
Atlantic. Hazardous marine and coastal conditions are anticipated
due to increasing northeast winds and a northerly swell coming by
Friday night through the first half of the next workweek.
&&
.BEACH FORECAST...
There will be a moderate risk of Rip Currents today across the
northern coastline of Puerto Rico; from Rincon to Fajardo,
Culebra, and St. Thomas. During the weekend, the risk of Rip
Currents is anticipated to go from moderate to high risk on
beaches with northerly exposure due to increasing northeast winds
and a northerly swell.