Forecast Discussions mentioning any of
"ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 09/19/20
Area Forecast Discussion...UPDATED
National Weather Service Corpus Christi TX
1059 PM CDT Fri Sep 18 2020
Latest aircraft measurements indicate that Tropical Storm Beta`s
max sustained winds has strengthened to near 60 mph. Tropical
Storm Beta`s track has slightly shifted to the north from the
previous forecast. Beta is currently moving toward the north-
northeast across the western Gulf with a slow westward motion
expected to begin late Saturday. Beta is expected to reach
hurricane status Sunday morning and continue to slowly approach
the northwestern Gulf Coast. Due to the increase in winds, a
Hurricane Watch has been issued for the coastal regions and over
portions of the Gulf waters north of Port Aransas. South of Port
Aransas, a Tropical Storm Watch has been issued. In addition, seas
will also build to hazardous levels and tides are expected to run
well above normal. For this, a Storm Surge Watch has been issued
from Baffin Bay to Port O`Connor with 2-4 feet inundation
.PREV DISCUSSION... /Issued 621 PM CDT Fri Sep 18 2020/
Update for 00Z Aviation.
VFR conditions will persist through the period. Rain chances will
continue to diminish this evening with a slim chance for developed
around LRD for the next hour or two. Otherwise, light
northeasterly winds will continue tonight with winds picking up
throughout the day tomorrow across ALI, CRP and VCT.
PREV DISCUSSION... /Issued 239 PM CDT Fri Sep 18 2020/
SHORT TERM (Tonight through Saturday Night)...
This afternoon/evening should be similar to yesterday with an upper
level trough remaining in the area and PWATs above 2 inches.
Isolated to scattered showers and thunderstorms will form and move
southwest through the area. A few storms could be strong.
Drier air will move in later tonight as the trough drifts away from
the area giving us a brief respite from the rain. Saturday should be
fairly pleasant, with normal temperatures for mid-September, partly
cloudy skies, and only a slight chance of showers over the Coastal
Bend and over the waters. Cloud cover and the chances for
precipitation will begin to creep back in Saturday night as moisture
from Tropical Depression 22 pours into the area.
A Coastal Flood Advisory remains in effect through Saturday morning
as tide levels continue to run high with persistent, moderate to
strong northeast flow. A Coastal Flood Watch has been issued in
response to the approach of TD22. Moderate coastal flooding will be
possible with inundation values up to 2 to 4 feet MHHW.
LONG TERM (Sunday through Friday)...
The NHC forecast of current Tropical Depression Twenty-Two (TD22)
essentially controls the long-term forecast. The official track of
the tropical cyclone (TC)is based on the expectation of an upper
ridge over the SRN Plains/SERN CONUS, resulting in a westward
movement of the TC Sunday/Monday toward the TX coast, followed by a
developing quasi-zonal upper pattern, resulting in the northward
movement of the TC Tuesday/Wednesday. Satellite-based PWAT values
depict the copious moisture associated with the TC. The GFS predicts
this moisture to advect onshore Sunday. Expect copious moisture to
contribute to scattered/numerous convection Sunday. Expect rainbands
associated with the TC to result in numerous/widespread
precipitation Monday/Tuesday over the ERN CWA. Assuming the TC
continues to move NWD, anticipate isolated/scattered convection over
the CWA Wednesday-Friday. The track/scale of the TC, along with
deterministic WaveWatch output, suggest an enhanced risk of rip
currents/coastal flooding at least Sunday-Tuesday.
Moderate to strong north to northeast winds will continue through
Saturday night. Wave heights will rapidly build as Tropical
Depression 22 approaches the area, with seas reaching near 16 feet
by late Saturday night. A Small Craft Advisory has been issued for
both winds and hazardous seas through Saturday afternoon. Tropical
storm conditions may be possible beginning as early as Saturday
night. The tropical cyclone is expected to maintain
numerous/widespread showers, and isolated/scattered thunderstorms,
during the Sunday- Tuesday period. A gradual decrease in the
coverage/intensity of convection expected Wednesday-Friday. Wind
forecast Sunday-Wednesday reflects the NHC forecast. Wave height
forecast Sunday-Wednesday for the coastal waters primarily
reflects Wavewatch output.
.PRELIMINARY POINT TEMPS/POPS...
Corpus Christi 71 88 69 80 71 / 10 20 60 60 80
Victoria 68 87 66 80 70 / 0 20 50 50 70
Laredo 69 88 66 83 69 / 20 0 20 20 50
Alice 69 88 67 83 69 / 10 20 50 50 70
Rockport 74 90 72 80 74 / 10 20 60 70 90
Cotulla 68 88 66 84 69 / 0 0 20 20 50
Kingsville 69 87 67 83 70 / 20 20 60 60 80
Navy Corpus 77 89 72 79 74 / 20 30 70 70 80
TX...Tropical Storm Watch For the following zones: Coastal Kleberg...
Coastal Nueces...Coastal San Patricio...Kleberg Islands...
Storm Surge Watch For the following zones: Aransas Islands...
Calhoun Islands...Coastal Aransas...Coastal Calhoun...
Coastal Kleberg...Kleberg Islands...Nueces Islands.
Hurricane Watch For the following zones: Aransas Islands...
Calhoun Islands...Coastal Aransas...Coastal Calhoun...
GM...Tropical Storm Watch For the following zones: Bays and Waterways
from Baffin Bay to Port Aransas...Coastal waters from
Baffin Bay to Port Aransas out 20 NM...Waters from Baffin
Bay to Port Aransas from 20 to 60 NM.
Small Craft Advisory until 4 PM CDT Saturday For the following
zones: Coastal waters from Baffin Bay to Port Aransas out
20 NM...Coastal waters from Port Aransas to Matagorda Ship
Channel out 20 NM...Waters from Baffin Bay to Port Aransas
from 20 to 60 NM...Waters from Port Aransas to Matagorda
Ship Channel from 20 to 60 NM.
Hurricane Watch For the following zones: Bays and Waterways from
Port Aransas to Port O`Connor...Coastal waters from Port
Aransas to Matagorda Ship Channel out 20 NM...Waters from
Port Aransas to Matagorda Ship Channel from 20 to 60 NM.
Area Forecast Discussion
National Weather Service Los Angeles/Oxnard CA
827 PM PDT Fri Sep 18 2020
Temperatures will cool through Monday then warm again into next
weekend. There will be gusty northerly winds across southern
Santa Barbara County through Saturday morning. Overnight and
morning low clouds and fog will expand into most coastal and
lower valley areas by Monday.
.SHORT TERM (FRI-MON)...18/823 PM.
The marine inversion early this evening ranged from near 500 ft
deep at LAX to near 800 ft deep at VBG. Low clouds were expanding
along the Central Coast this evening and should push into the
Santa Ynez Vly later tonight. Low clouds should also develop over
the SoCal Bight later tonight and move into the immediate coast
of L.A.County by daybreak or so. With the shallow marine
inversion, there should also be patchy dense fog with any low
clouds overnight. Otherwise, mostly clear skies can be expected
across the region thru the night.
Good northerly pressure gradients this evening across SBA County
(NAM fcst SBA-SMX -3.6 mb at 06Z) will continue strong and gusty
NW to N canyon winds across the SBA County S coast and Santa Ynez
Mtns mainly from San Marcos Pass westward. Gusts up to 50 mph
have been observed at the SCE San Augustin automated wx station
west of Gaviota, with gusts up to 48 mph at the Refugio RAWS.
These wind gusts will likely persist overnight into early Sat. A
Wind Advisory is in effect for this area overnight thru mid-
morning Sat. Please see the latest Non-Precipitation Weather
Message (LAXNPWLOX) for further details.
***From Previous Discussion***
A cooling trend will continue through the weekend and into Monday
along with a deepening marine layer. The latest AMDAR soundings
from KLAX indicate a marine layer depth closer to 600 feet deep.
The marine layer depth should deepen to near 1000 feet deep by
Saturday morning, possibly thinning slightly for Sunday morning,
then deepening again on Monday. Middle and high level cloudiness
from what used to be tropical storm Karina will continue to thin
out across the region tonight which should allow for better
With the trough moving over the region, the smoke that has been
in place the last couple of weeks will clear out over a majority
of the area. Increasing southwest flow in the boundary layer will
increase transport winds and the trough should enhance mixing.
The smoky skies should continue to improve across the area,
except for portions of Los Angeles County where the Bobcat Fire is
still actively burning at this time.
A dying boundary north of the region will move south and tighten
the northerly pressure gradient through Sunday. Marginally gusty
Sundowner winds are already occurring this afternoon and will
increase across southern Santa Barbara County later and linger
into Saturday morning. A wind advisory remains in effect from 4 pm
PDT this afternoon through 9 am PDT Saturday morning. Gusts up to
45 mph are possible, especially west of Goleta out toward the
Gaviota area. If traveling across this area, gusty cross winds are
possible on Highways 101 and 154 this afternoon and tonight. If
planning any outdoor recreational activities this afternoon and
evening, such as kayaking out near Gaviota and Refugio, it might
be best to delay these activities when these winds may not present
hazardous weather and/or sea conditions.
A tricky cloud forecast is on tap for tonight. Cold air advection
could make for little marine layer induced stratus south of Point
Conception. The previous forecast was scaled back for a later
arrival. Little, if any stratus should make into the Ventura
County Coast or the Santa Barbara South Coast. Better confidence
exists for the Central Coast and the Santa Ynez Valley. Night
through morning low clouds and fog should start to expand into
Saturday night and Sunday as the eddy circulation should allow for
Zonal flow should setup for Sunday between troughs as the trough
along the southern Oregon coast lifts out and another trough dips
in behind it. The marine influence should continue to win out for
the coast and lower valley, keeping a cooling trend going. Less
confidence for the mountains and desert as these areas could end
.LONG TERM (TUE-FRI)...18/138 PM.
The influence of the trough should linger into Tuesday and keep
cooler temperatures in place. The deepest marine layer of the week
should be in place between Monday and Tuesday, then ridging aloft
should start to build into the region and thin the marine layer.
A warming trend will develop for the latter half of the week. By
Thursday or Friday, stratus coverage could be minimal as weak
offshore flow develops. For the current time, no gusty offshore
winds are expected, but this will need to be monitored closely for
At 2330Z at KLAX...The inversion was about 500 feet deep. The top
of the inversion was around 2500 feet with a temperature of about
28 degrees C.
Moderate confidence in the 00Z TAFs for KPRB, KSBP, KSMX and KLGB
due to uncertainties with regard to the timing and extent of low
clouds and LIFR/IFR conditions at these airfields from this
evening along the Central Coast to late tonight into Sat morning
elsewhere. The timing of the onset and dissipation of the low
clouds may be off +/- an hour or two. There is also a 20%-30%
chance of no low clouds and fog development at KPRB and KLGB.
Otherwise and elsewhere, there is hi confidence in VFR conditions
thru Sat afternoon.
KLAX...Generally hi confidence in the 00Z TAF with VFR conditions
expected thru Sat evening. However, there is still a 10%-20%
chance of low clouds and LIFR conditions late tonight and early
KBUR...Hi confidence in the 00Z TAF with VFR conditions expected
through Sat afternoon.
Across the outer waters... Small Craft Advisory (SCA) level wind
will continue through Saturday night and there is a forty percent
chance of it continuing through Sunday night. SCA level winds will
develop again Tuesday and Wednesday. The strongest winds will be
in the afternoon and evening hours. Otherwise, conditions will
remain below SCA level through the forecast period.
Across the nearshore waters of the Central Coast... There is a
forty percent chance of SCA level wind during the afternoon and
evening hours through Saturday night. Otherwise, conditions will
remain below SCA level through the forecast period.
Across the inner waters south of Point Conception... SCA level
wind will continue across the western portion of the Santa
Barbara Channel through Saturday night. Otherwise and elsewhere,
conditions will remain below SCA level through the forecast
Patchy fog will continue into next week across the coastal waters.
The poorest visibility and most widely spread conditions will
occur in the overnight and morning hours.
CA...Wind Advisory in effect until 9 AM PDT Saturday for zones
39-52. (See LAXNPWLOX).
PZ...Small Craft Advisory in effect until 3 AM PDT Sunday for
zones 650-670-673-676. (See LAXMWWLOX).
.HAZARD POTENTIAL OUTLOOK (MON-FRI).
No significant hazards expected.
Area Forecast Discussion
National Weather Service Phoenix AZ
425 PM MST Fri Sep 18 2020
A gradual cooling trend begins today persisting into the weekend
with highs dipping below 105 across most desert areas. A weak
disturbance moving through the area early next week will be on the
dry side, but an isolated shower or thunderstorm over high terrain
north and east of Globe is possible. High temperatures will continue
to fall off early next week with some desert locations approaching
only 100 degrees Monday and Tuesday.
The UL plots show lingering elevated heights at H5 although the
ridge is already starting to flatten and shift east with the
anticyclonic circulation seen to the east, and cyclonic flow noted
across N Baja. 850mb temperatures were still elevated, around 27C,
within a BL thermal ridge lingering across the area. The BL also
remained dry in spite of the southeasterly flow. The stable Phx 12Z
sounding and recent ACARs also indicated a more moist airmass than
yesterday with PW`s near 0.7" due to moistening in the mid to upper
levels. Satellite imagery also confirmed this uptick in mid and
upper level WV. With early afternoon temperatures running up to 3
degrees cooler than yesterday, the gradual cooldown into early next
week is now underway with highs expected from 104-107 degrees today
for the Phoenix and nearby deserts.
The NE PAC progressive low pressure system will push across the PAC
NW and through the N Rockies into the weekend. As it passes to the
north it will continue to flatten the ridge and shift it even
further south and east. This pattern shift will support the current
gradual cooling trend through early next week as heights continue to
decrease and moisture slightly increases. Models still show slightly
below normal PWs approaching seasonal norms tonight and tomorrow,
but this will not prevent mostly dry conditions from prevailing.
Early next week ensembles bring a fairly dry and weak shortwave
disturbance in from the west as PW`s once again trend slightly
higher and possibly closer to, or slightly above seasonal norms of
0.8-0.9", and maybe even near 1.0". Again it appears that conditions
will remain marginally too dry for any significant chance of rain as
supported by ensembles and NCEP/WPC cluster 24H QPF. Although a
slight chance of isolated showers and thunderstorms across the
Mogollon rim and the eastern and southeastern high country are
possible for early next week. However there continues to be much
better confidence that temperatures will bottom out in the low 100s,
only slightly above seasonal norms around Tuesday with very little
The 5 and 6 day NCEP/WPC 500 mb heights clusters indicate similar
variations on a theme of strong high pressure returning to the
Southwest and Central US by Wednesday and Thursday next week. They
also suggest a minor rebound of high temperatures of only 2 or 3
degrees going into midweek.
.AVIATION...Updated at 1725Z.
South-Central Arizona including KPHX, KIWA, KSDL, and KDVT:
Only minor aviation weather concerns will exist through Saturday as
a thin layer of lofted smoke remains positioned across the area and
could create slantwise visibility issues. Winds this evening will be
highly variable potentially not truly complete the traditional
westerly switch and remaining 140v210 before returning back to an
easterly configuration mid/late evening. Towards sunrise, a stronger
pressure gradient should create some 25kt SE winds above the
boundary later around 2K ft AGL, albeit well below LLWS criteria.
Some of this momentum may be mixed to the sfc late morning in the
form of gusty east winds. Confidence is good east winds will prevail
much of the day, with lower confidence in the ability for the
typical westerly wind shift to occur Saturday afternoon.
Southeast California/Southwest Arizona including KIPL and KBLH:
No major weather concerns through Saturday other than some wafting
high level smoke that could create slantwise visibility issues. Wind
trends will be nearly identical to the past couple days with
directions switching to SW at KIPL later this evening before
returning to easterly by sunrise. The typical period of light
northerly drainage wind is likely at KBLH Saturday morning with
afternoon southerly winds likely somewhat stronger than today.
Monday through Friday:
Cooler high temperatures will remain a few degrees above normal
through the period. Minimum humidities will mostly be in the 10
to 15 percent range across the lower deserts through the period.
Higher terrain areas will also stay below 20 percent. Max RH will
see a slightly better upward trend of roughly 10% most places and
reach about 30-50% by the middle of next week before dropping back
down again late in the week. Thunderstorms are expected to remain
outside of the forecast area. However, the Mogollon Rim and the
eastern and southeastern high terrain areas will have a slight
chance of storms for early next week. Winds will generally be
light except for some modest afternoon breeziness.
.SPOTTER INFORMATION STATEMENT...
Spotters should follow standard reporting procedures.