National Weather Service San Juan PR
508 AM AST Tue Mar 6 2018
.SYNOPSIS...Large area of low pressure continued to move farther
eastward into the north central Atlantic, as a high pressure ridge
builds across the southwest Atlantic and north of the region.
This will induce a light northwest to north wind flow through
tonight. An upper level ridge will establish across the region by
the end of the week.
&&
.SHORT TERM...Today through Friday..
Sunny to partly cloudy skies will prevail across the area today with
a slight chance for an isolated shower. Skew T sounding shows
precipitable water value of 1.0 inch this tell us that drier air is
in place. The direr air is depicted by the sounding image which
shows drier air from 800 to 200 mb this drier air will thwart most
shower activity today. The frontal boundary that move trough the
region on Sunday will continue to weaken and washout but the strong
low pressure system in central Atlantic will remain until Wednesday.
Wednesday a mid to upper ridge will build to the north of Puerto
Rico and the U.S. Virgin ahead of another front that will move into
North Atlantic waters. The ridge of high pressure will pull tropical
moisture from the east Atlantic over Puerto Rico and the U.S. Virgin
Islands on Wednesday a result precipitable water values and rain
chances will increase through the end of the week. This is seen on
the GFS and NAM cross sections which shows increase in relative
humidity, vorticity and potential temperature late Wednesday through
Friday.
Currently at the surface winds are out of the east to northeast these
northeast winds are bringing in cooler air from the North Atlantic
waters and, causing dew point temperatures to remain in the low to
mid 60s. Wednesday surface winds will veer to the east southeast so
you can expect an increase in temperatures and dew point Wednesday
through Thursday.
Friday, the plume on moisture will decrease due to drier air filtering
in from the east but with southerly flow across the islands
scattered showers will be possible across most of Puerto Rico and
the U.S. Virgin Islands.
.LONG TERM...Saturday through Wednesday...An upper level ridge
will build across the Northeast Caribbean. As a result, very dry
weather conditions are forecast for this period. A cold front is
forecast to approach the local region, inducing a southerly flow
across the region by mid next week.
&&
.AVIATION...VFR conditions will continue to prevail through
06/22z TAF period. Sfc winds out of the west northwest at 5 to 15
kts with winds turning to the west greater than alf ranging from 25
to 50 kts from 10 kft to 45 kft.
&&
.MARINE...Latest buoy observations continued to indicated seas
between 12-15 feet. As a result, kept and extended the coastal
flood warning through 6PM tonight as breaking wave of 18 feet or
more are expected to continue. A slow improvement in marine
conditions are expected later tonight into Wednesday. However,
hazardous marine conditions will prevail for most of the week.
&&
.FIRE WEATHER...An elevate fire danger is expected across the
southwestern slopes of Puerto Rico today as very dry conditions
will maintain relative humidity values at critical values.
&&
.PRELIMINARY POINT TEMPS/POPS...
SJU 80 71 82 73 / 10 10 20 20
STT 82 69 83 74 / 10 10 30 30