Forecast Discussions mentioning any of
"ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 04/19/19
Area Forecast Discussion
National Weather Service Honolulu HI
340 PM HST Thu Apr 18 2019
.SYNOPSIS...
Moderate to locally breezy trade winds will prevail through much
of the week as surface high pressure holds north of the state.
Rather stable conditions will remain in place, leading to a
typical pattern of mainly windward and mauka showers.
&&
.DISCUSSION...
A stable, moderate to locally breezy trade wind flow remains in
place. The trades are being driven by a 1027 mb high passing
about 1,100 miles north-northeast of the state. A mid level ridge
is building over the islands from the west, leading to rather
stable conditions. Afternoon soundings and recent aircraft data
show the inversion settling between 5,000 and 7,000 ft, and
precipitable water (PW) across the area is running near to below
April normal. A small pocket of moisture in the trade wind flow
produced active showers (totals mainly around 1/4 of an inch) over
windward Big Island and east Maui this morning. Otherwise, modest
rainfall, generally less than 1/10 of an inch, has been recorded
at remaining windward gages, while leeward areas have been mostly
dry.
Overall, a typical trade wind weather pattern is expected through
the upcoming week. The surface high will settle to the northeast
of the state, while its associated surface stalls about 300 to 500
miles north of the islands. We could see an uptick in trade winds
during the weekend as the ridge briefly strengthens. Stable
conditions will dominate through much of the week as the mid level
ridge will remain parked overhead. Generally, precipitable water
will be near normal, suggesting that showers will be modest and
confined to windward slopes. As random pockets of low level
moisture move through on the trade wind flow, expect brief and
localized increases in showers. Aside from afternoon showers on
the Kona slopes of the Big Island, leeward areas will be mostly
dry.
&&
.AVIATION...
Strong high pressure far north of the islands will support a
locally brisk trade wind pattern through twenty-four hours and
beyond. Light sea breezes across leeward Big Island this
afternoon will taper off after sunset, but are expected to
redevelop on Friday.
Clouds and light showers will favor island interiors through this
evening, then windward slopes and coasts late tonight and Friday
morning. Isolated moderate showers over inland portions of the Big
Island will remain possible through late this evening.
AIRMET Tango for mechanical turbulence below 8k feet will
remain in effect, possibly for several days.
&&
.MARINE...
Fresh to strong easterly trade winds associated with a strengthening
ridge north of the islands will continue through early next week.
A Small Craft Advisory is in effect for the Pailolo and Alenuihaha
channels, Maalaea Bay, and over the waters around South Point of
the Big Island through Sunday where the strongest winds are expected.
A small, north northwest swell will build down the island chain
tonight, peak Friday and then slowly decline through the weekend.
A small, west northwest swell from a compact gale that has
developed east of Japan will be possible early next week.
Surf along south facing shores will remain small through the weekend
with mainly background south southwest pulses moving through. An
upward trend is anticipated early next week, beginning as early as
Sunday night due to activity south to southeast of New Zealand
over the past few days. Guidance depicts this source peaking at
Pago Pago Saturday, which should correlate to above average south
shore surf continuing into midweek.
Surf along east facing shores will rise slightly on Friday
through the weekend due to fresh trades locally and just upstream.
Expect this trend to continue early next week.
&&
.HFO WATCHES/WARNINGS/ADVISORIES...
Small Craft Advisory until 6 PM HST Sunday for Maalaea Bay-
Pailolo Channel-Alenuihaha Channel-Big Island Leeward Waters-Big
Island Southeast Waters.
&&
$$
DISCUSSION...Wroe
AVIATION...Bedal
MARINE...Foster
Area Forecast Discussion
National Weather Service San Diego CA
200 PM PDT Thu Apr 18 2019
.SYNOPSIS...
Strengthening high pressure aloft across California will continue
the warming trend this afternoon with the warming continuing in the
deserts Friday. The marine layer will return late tonight with low
clouds and fog, with local dense fog possible, in coastal areas. The
marine layer will deepen Friday through Sunday with low clouds
spreading to the coastal mountain slopes Saturday night. A low
pressure system will move across California late Saturday and early
Sunday and will bring substantial cooling over the weekend and a
slight chance of light showers. Stronger onshore flow will bring
gusty west winds to the mountains and deserts with strongest winds
Saturday afternoon and night. High pressure will rebuild across
California next Monday through Thursday and bring a return to fair
warm weather.
&&
.DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE...
SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO
COUNTIES...
High pressure aloft is peaking today and bringing warm weather to
the region, with Thermal Airport up to 96 at 1 PM, and quite a few
places approaching 90 in the Inland Empire (92 at Lake Elsinore).
Models indicate a shallow marine layer developing tonight, with some
stratus and fog near the immediate coast. Local dense fog could form
over higher coastal terrain, such as the mesas. Latest observation
at San Clemente Island (NUC) has broken clouds at 500 feet above
ground level (around 700 feet above sea level), and aircraft
soundings have shown similar inversion heights, so elevations below
about 700 feet could get fog tonight. Due to the developing marine
layer, Friday should be a little cooler in coastal areas, though
with 850 MB temps peaking in the deserts then despite the height
falls, the mountains and deserts should have their warmest day of
this week then.
A weak shortwave will move through the region Friday night and help
to deepen the marine layer, then a longwave trough will move through
Saturday night and Sunday. NAM and local WRF both have some light
precipitation, mainly from the valleys to the west mountain slopes,
and given the nocturnal passage of the main vorticity maximum with
the system, I added slight chances of showers to the forecast in the
afternoon package. Temperatures will be lower, mostly about 5
degrees below seasonal normals over the weekend. As is typical for
low pressure troughs during the spring, strong gusty winds will
develop over the mountains and deserts, with gusts likely over 50
MPH in the usual windy spots, especially Saturday afternoon and
evening. High pressure will rebuild next week and bring fair warmer
weather again, with the possibility of 100 degree temps in the
hottest parts of the lower deserts.
&&
.AVIATION...
182010Z...Coast/Valleys...SCT-BKN high clouds expected today with
bases AOA 20000 FT MSL. High confidence in low clouds returning to
coastal areas tonight. Low confidence in exact timing but cigs most
likely to form after 06Z Fri, with bases 500-1000 ft MSL. Reduced
vis of 3 miles or less will be possible due to fog over higher
coastal terrain. SCT conditions expected by 15Z Fri at coastal TAF
sites.
Mountains/Deserts...Mostly clear skies and unrestricted vis expected
through Friday afternoon.
&&
.MARINE...
A brief period of NW winds 12-18 kt over the outer coastal waters
expected Friday afternoon-Friday night. NW winds 10-15 kt gusting 20-
25 over the outer waters late Saturday night into Sunday. These
conditions may become hazardous to small craft.
&&
.SKYWARN...
Skywarn activation is not requested. However weather spotters are
encouraged to report significant weather conditions.
&&
.SGX WATCHES/WARNINGS/ADVISORIES...
CA...NONE.
PZ...NONE.
&&
$$
PUBLIC...Maxwell
AVIATION/MARINE...CO