Forecast Discussions mentioning any of
"ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 08/12/19
Area Forecast Discussion
National Weather Service Houston/Galveston TX
633 PM CDT Sun Aug 11 2019
.AVIATION...
VFR most locations through the TAF period (could see some MVFR
ceilings/visibilities once again in/around the CLL area around
sunrise). Winds becoming SW up to around 10 knots in the morning
shifting to the S to SE at 5 to 10 knots in the afternoon. Maybe
a SHRA/TSRA or two in/around the Galveston Bay area during the day
tomorrow, but not confident enough to include in the TAF. 42
&&
.PREV DISCUSSION... /ISSUED 307 PM CDT Sun Aug 11 2019/
DISCUSSION...
- Heat advisory extended to Monday.
- Ridge may break down enough for a boundary to push into the area
midweek to lower max temps a couple of degrees.
SHORT TERM [Tonight and Monday]...
South to southwest winds today have allowed for another scorcher
with temps near 100F and heat index values well into heat advisory
territory. So with similar conditions expected tomorrow, we will
go with another heat advisory and a persistence forecast for max
temperatures and heat index values. Upper level ridge will still
be parked over Texas and limit convection. GOES 16 derived PWAT
imagery shows 2.0 inches of PWAT over the area but subsidence from
the ridge is just too much for convergence on the sea breeze to
over come. Looking at having 2.0 inches of PWAT tomorrow as well
but again think the ridge will be just too much to need any rain
chances in the forecast.
Overpeck
LONG TERM [Tuesday Through Sunday]...
The long term will start out with one last day of dry weather on
Tuesday as the ridge of high pressure continues to dominate our
weather. Daytime highs on Tuesday will again flirt with heat
advisory criteria with heat indices nearing 110 along the coast and
up towards Houston.
Wednesday is when things begin to change. The high that has been in
place over Texas weakens and retreats westwards towards the southern
Four Corners region as troughing increases near the Ohio River
Valley. A boundary along the trough will extend down through
northern Texas on Tuesday, then making its way towards our area on
Wednesday. The boundary passage will bring higher chances of showers
and thunderstorms beginning Wednesday afternoon into Thursday. The
timing of this passage does differ between the model solutions. The
NAM, Canadian, and GFS brings the front through sometime Wednesday,
but the EC is a bit later during Thursday morning. Moisture does
linger post front with the additional chance of showers and
thunderstorms during the heating hours on Friday. Things look to dry
out over the weekend with mostly sunny skies and some more hot
summer days.
Fowler
AVIATION [18Z TAF Issuance]...
Overall no real aviation concerns going the next 24 to 36 hours
under upper level ridging. Some of the short term guidance show a
few showers developing on the sea breeze near Houston so we will
need to watch for that. However AMDAR soundings are pretty dry
above 900mb to 600mb as well as pretty warm. Forecast will keep
TAFs dry with mainly subtle wind changes.
The only TAF site to worry about lower ceilings will be KCLL with
possibly some MVFR ceilings developing in the morning. We saw
similar conditions develop and may be a little later than the TAF
reflects in timing...14Z instead of 12Z.
Overpeck
MARINE...
Overall looking at light to moderate southerly winds for the week
and low/moderate seas as a result. A front may push into the area
mid week with a chance of thunderstorms and light/variable winds.
&&
.PRELIMINARY POINT TEMPS/POPS...
College Station (CLL) 78 102 79 103 79 / 0 0 0 0 10
Houston (IAH) 80 100 81 101 81 / 0 10 0 10 10
Galveston (GLS) 84 94 84 94 84 / 0 10 0 10 10
&&
.HGX WATCHES/WARNINGS/ADVISORIES...
TX...Heat Advisory until 7 PM CDT Monday for the following zones:
Austin...Brazoria Islands...Brazos...Burleson...Chambers...
Coastal Brazoria...Coastal Galveston...Coastal Harris...
Coastal Jackson...Coastal Matagorda...Colorado...Fort
Bend...Galveston Island and Bolivar Peninsula...Grimes...
Houston...Inland Brazoria...Inland Galveston...Inland
Harris...Inland Jackson...Inland Matagorda...Madison...
Matagorda Islands...Montgomery...Northern Liberty...Polk...
San Jacinto...Southern Liberty...Trinity...Walker...
Waller...Washington...Wharton.
GM...NONE.
&&
$$
Area Forecast Discussion...UPDATED
National Weather Service Los Angeles/Oxnard CA
842 PM PDT Sun Aug 11 2019
.SYNOPSIS...11/840 PM.
Afternoon temperatures increase notably through the week with many
locations above 100 degrees again by Wednesday. Temperatures cool
on Friday and into the weekend but remain warm. Overnight and
morning coastal low clouds will continue through Wednesday morning
then become very patchy.
&&
.SHORT TERM (TNT-WED)...11/830 PM.
The latest satellite imagery shows an upper-level ridge of high
pressure over north Texas, and an upper-level trough of low
pressure over central Montana. The trough to the northeast of the
region will continue to lift out over the ridge, while the ridge
builds west into Far West Texas and the Borderland region of New
Mexico. A warming and drying trend will take shape over the next
couple of days with hot temperatures likely for the middle portion
of the work week. Onshore flow will generally weaken each day
through Wednesday, while 500 mb heights climb and 950 mb
temperatures warm. There is an outside chance of dangerously hot
conditions developing between Wednesday and Thursday.
The stratus pattern is somewhat patchy this evening as northerly
surface pressure gradients keep ahold of the surface pattern.
Muddled stratus coverage this evening should become more
entrenched late tonight and into Monday morning. The latest AMDAR
soundings from KLAX indicate a marine layer depth near 900 feet
deep currently. A weak eddy circulation developing across the
southern California bight could deepen the marine layer to around
1200 feet deep on Monday morning. The stratus coverage has been
expanded somewhat in the latest update to push low clouds and fog
into the lower valley areas such as the San Gabriel and Santa Ynez
Valleys. The weak eddy circulation could also push lower clouds
into the Santa Barbara area after daybreak Monday.
With the lingering northerly gradient, locally gusty Sundowner
winds are possible across southern Santa Barbara County through
late tonight, and locally gusty northerly winds are possible
through the Interstate 5 Corridor. Winds are being monitored
closely this evening, but no wind advisory issuance is expected.
An update was issued to the forecast previously and no additional
updates are planned.
***From Previous Discussion***
An upper level trof over CA will weaken thru Tue as a large upper
level high from Texas to northern Mexico expands into srn CA. H5
heights are expected to increase from 587-588 dm today to about
591 dm by Tue afternoon. The ridging will then build further into
srn CA for Wed with H5 heights up to 594 dm.
The marine inversion will gradually lower to 1000 ft or so Mon
night, and down to 700 ft or even lower Tue night into Wed morning
as the boundary layer heats up. Low clouds and fog are expected
to affect the Central Coast, the coastal plain of VTU/L.A.
Counties and just into the San Gabriel Vly tonight into Mon
morning, and just the Central Coast and the VTU/L.A. County
coastal areas Mon night into Tue morning. Low clouds with possible
dense fog will then be mainly confined to the immediate Central
Coast and far southern L.A. County coast Tue night into Wed
morning. Otherwise, mostly clear skies will prevail across the
forecast area thru Wed.
Onshore gradients are forecast to increase to +7.2 mb LAX-DAG Mon
afternoon, then lower to +6.4 mb Tue afternoon and +5.5 mb Wed
afternoon per the 12Z NAM. These onshore gradients will continue
to bring some gusty afternoon and early evening S to W winds to the
foothills, mtns and deserts. For the SBA County S coast and mtns,
the SBA-SMX gradient is forecast to be around -1.9 mb this evening.
This will bring locally gusty sub-advisory level NW to N sundowner
winds to areas below and thru the passes and canyons mainly W of
Goleta this evening.
On Wed, temps will soar to 5 to 10 deg above normal for many
areas away from the coast as 950 mb temps and boundary layer temps
increase substantially, and 1000-500 mb thicknesses increase to
582 to 585 dm. The warmest vlys and foothills should reach the mid
90s to around 100 on Mon, and upper 90s to around 102 on Tue, and
upper 90s to 104 on Wed. Temps on Wed may be warm enough to
warrant a heat advisory for the vlys and mtns. This will be looked
at more closely as we draw closer to mid week.
.LONG TERM (THU-SUN)...11/207 PM.
The upper level ridge will slowly break down Wed night and Thu, then
a large upper level trof will move into the W coast Fri. Upper level
troffiness should then persist over srn CA Sat thru Sun with
increasing onshore flow and much cooler temperatures.
Night and morning low clouds and fog are expected for some
portions of the coastal plain Thu thru Fri, then the marine layer
should deepen quite a bit into the weekend with more extensive
night and morning low clouds and fog for the coast into some of
the adjacent vlys. Otherwise, mostly clear skies will continue
across the region.
Temps will continue much above normal away from the coast Thu, then
a cooling trend will take place Fri thru Sun. The warmest vlys and
lower mtns should have highs in the upper 90s to 104 on Thu, then
drop into the 90s Fri and generally mid 80s to lower 90s Sat and
Sun. The forecast high temps for next weekend are several degrees
below normal for this time of year.
&&
.AVIATION...12/0041Z.
At 2341z at KLAX...the marine layer was 1100 feet deep. The top
of the inversion was around 2600 feet with a temperature of 22C.
Some stratus with low MVFR to high IFR conds will affect immediate
beach areas for a couple of hours early this evening. Otherwise,
expect widespread stratus to affect all coastal areas tonight with
the possibly exception of the south coast of SBA County. Status
will likely push into the Santa Ynez Valley, the San Gabriel
Valley and the lower valleys of VTU County. Conds will be mostly
LIFR to VLIFR north of Pt Conception, and low MVFR or high IFR
south of Pt Conception. Skies should clear by mid morning in the
valley and late morning on the coastal plain.
KLAX...Low confidence in the 00Z TAFs. There is a 20% chance that
current cigs will persist through the night. If they do dissipate
as expected by 03Z, there is a 30% chance that will arrive as
early as 07Z. There is a 30% chance of cigs will be in the MVFR
category rather than the forecast IFR category.
KBUR... High confidence in the 00Z TAF. There 10% chance of
IFR cigs between 13z and 17z.
&&
.MARINE...11/804 PM.
For the Outer Waters, Small Craft Advisory (SCA) level winds will
likely continue across the outer waters through late tonight and
will likely continue through at least late Tuesday night in the
northern and central outer waters. There is a 60 percent chance
that SCA level winds will linger into late Wednesday in the
northern and central outer waters. There is a 40-50 percent
chance of SCA conditions (winds and seas) for the outer waters on
Thursday.
For the nearshore waters north of Point Sal, winds will continue
to diminish tonight across the nearshore waters. There is a 40
percent chance that SCA level winds will redevelop Monday
afternoon and evening. Winds will be a bit weaker Tuesday and
Wednesday, then there is a 40 percent chance of SCA level winds
on Thursday.
For the Inner Waters south of Point Conception, local gusts to 25
knots are possible across the western portion of the Santa Barbara
Channel. There is a 30 percent chance of SCA level winds for the
western portion of the Santa Barbara Channel again on Thursday.
Otherwise, conditions will remain below SCA levels.
&&
.FIRE WEATHER...11/330 PM.
Weaker sundowner winds are expected to occur later this afternoon
and evening across western portions of the Santa Barbara south coast
and adjacent foothills, with gusts generally in the 25 to 35 mph
range (strongest near Gaviota). As an upper level high pressure
system begins to build westward, there will be a warming and drying
trend across Southwest California Monday through Thursday,
especially interior sections. Triple digit temperatures are expected
across warmest interior valleys, mountains, and deserts Tuesday
through Thursday, with the warmest days expected to be Wednesday and
Thursday. Single digit humidities are expected to return to the
Antelope Valley and Los Angeles mountains by Tuesday, becoming more
widespread across interior areas by Wednesday and Thursday.
The combination of hotter temperatures, low humidities, and locally
gusty onshore winds will bring a return of elevated to brief critical
fire weather conditions to interior sections of Southwest
California Monday through Thursday. In addition, the hotter
temperatures will bring the potential for large vertical plume growth
across wind sheltered interior sections Tuesday through Thursday,
with potential afternoon mixing heights ranging between 10,000 and
15,000 feet. An upper level trough is expected to bring a cooling
trend Friday into Saturday, but increased onshore winds could
bring potential fire weather concerns.
&&
.LOX WATCHES/WARNINGS/ADVISORIES...
CA...NONE.
PZ...Small Craft Advisory in effect until 9 PM PDT this evening
for zone 645. (See LAXMWWLOX).
Small Craft Advisory in effect until 3 AM PDT Wednesday for
zones 670-673. (See LAXMWWLOX).
Small Craft Advisory in effect until 3 AM PDT Monday for zone
676. (See LAXMWWLOX).
&&
.HAZARD POTENTIAL OUTLOOK (WED-SUN).
Significantly above normal temperatures away from the coast
Wednesday and Thursday may prompt the issuance of Heat Advisories
for the valleys and mountains. Otherwise, no significant hazards
are expected through Sunday.
&&
$$
PUBLIC...Hall/Sirard
AVIATION...DB
MARINE...Hall
FIRE WEATHER...Gomberg
SYNOPSIS...Kj
weather.gov/losangeles
Area Forecast Discussion...Updated
National Weather Service Phoenix AZ
445 PM MST Sun Aug 11 2019
.UPDATE...Updated aviation discussion.
&&
.SYNOPSIS...
Much drier and warmer conditions are expected this week as high
pressure expands over the region, pushing thunderstorm chances
east into New Mexico. Excessive heat with high temperatures
between 110 and 115 degrees is expected on Tuesday through
Thursday for lower desert locations in southeast California and
Arizona including the Phoenix metro. Temperatures will decrease
slightly on Friday and Saturday with a brief increase in moisture,
with isolated thunderstorms mainly confined to Gila County.
&&
.DISCUSSION...
Fair weather shallow cumulus clouds continue to develop over
south central Arizona where lingering boundary layer moisture is
in place. Although convection is trying to develop, aircraft
soundings into PHX from the west suggest significant capping is in
place between 600-700 mb below the melting layer as dry air aloft
continues to filter in from the west with the broader trough off
the Pacific coast. Therefore, convection is not expected from
Phoenix west towards southeast California aside from maybe a rogue
convective cell between Gila Bend and Ak-Chin. Although some
instability is present further east of Phoenix if weak capping
and a midlevel stable layer erode, it looks like subsidence on
the backside of the trough that is now in northern New Mexico is
generally winning out to suppress convection. Thus, we should only
see isolated convection over the higher terrain of Gila County
with deeper convection capable of producing more than a few
lightning strikes is generally not expected. Drier air will
continue to advect eastward overnight and tomorrow, preventing
convection from developing anywhere except maybe a rogue cell
over far southeast Gila County.
Attention turns to the increasing likelihood of another excessive
heat episode later this week. Models have been consistent in
showing the subtropical high quickly rebuilding to our southeast
over the next few days while drifting westward. The position of
the high will allow for persistent dry southwesterly flow through
all Arizona as afternoon dew points fall into the 40s. The
building ridge will bring 500mb heights of 592-595dm in by late
Tuesday with 850 mb temperatures increasing to 30-32 deg C. The
combination of the greater than 90% of climo heights and the
unseasonably dry boundary layer should allow for lower desert
temperatures to top out at around 110 degrees beginning Tuesday.
Wednesday and Thursday look to be the hottest days of the week
with highs likely reaching 111-115 degrees across the lower
deserts. Forecast temperatures Tuesday to Thursday are toward the
upper quartile of available guidance due to the cool bias models
have had with other recent heat events. Confidence on meeting
excessive heat thresholds on Tuesday remains low to moderate, but
is very high for Wednesday and Thursday. Due to the uncertainties
for Tuesday, we have continued the Excessive Heat Watch instead of
upgrading to a Warning, which should happen in the next 12-24
hours depending on how the potential for Tuesday looks. Aside from
adding in a few zones on the far east and southeast sides of the
Phoenix metro and southeast Yuma County, the previous watch area
and timing remains in tact.
By Thursday, the center of the high begins to shift back to the
east slightly as another Pacific trough moves into the Pacific
Northwest. Models generally agree that monsoonal moisture will
seep back into portions of southern and eastern Arizona beginning
Thursday night through Saturday, with slightly lower heights aloft
and increasing moisture decreasing temperatures back down below
110 degrees by Friday. There is still some indication that a weak
inverted trough loosely associated with a PV fracture that splits
off from the longwave trough and front over the eastern half of
the U.S. mid-week may eventually move west along the southern
fringe of the ridge to improve rainfall chances over Arizona on
Friday or Saturday. However, models continue to trend south and
east with the position of the ridge over Texas and Mexico which
would keep storm chances limited to areas east of Phoenix. Drier
and warmer conditions appear to filter in behind that, so this may
be our only chance of rainfall over the next 10-14 days.
&&
.AVIATION...Updated at 2345 UTC.
South-Central Arizona including KPHX, KIWA, KSDL, and KDVT:
Dry southwest flow aloft, thinning moisture in low levels,
subsidence behind the exiting shortwave and weak SW steering flow
will all result in no showers/storms in the Phoenix area this
evening. Any storms that develop will focus over high terrain well
east of Phoenix, mostly from Globe eastward. There will be FEW-SCT
cumulus around 8k feet early this evening which will dissipate
leaving generally clear skies behind by about 03-04z. Maybe a few
high based cu again tomorrow afternoon but likely less than what was
observed today.
Given the afternoon sunshine, expected clearing overnight and light
surface/mid level gradients, expect winds to attempt to weakly
follow typical diurnal tendencies with light SW to W winds this
evening, tapering off after midnight and turning to the
east/southeast after 09z. Winds then become light SW again Monday
afternoon. However, expect lots of light/variable mixed in at the
terminals, including KPHX.
Southeast California/Southwest Arizona including KIPL and KBLH:
Dry southwest flow aloft will result in generally clear skies over
the western deserts next 24 hours. Winds/gradients are weak so do
not expect winds of consequence. They should favor the south to
southwest at KBLH with maybe a few gusts into the teens Monday
afternoon. Winds to favor the west for part of tonight, then
becoming light and eventually SE by late Monday morning.
Aviation Discussion not updated for amended TAFs.
&&
.FIRE WEATHER...
Wednesday through Sunday:
A much drier and warmer pattern is expected through at least
Thursday with very few thunderstorms expected even over higher
terrain locations. Temperatures will warm several degrees above
normal amidst the drier air mass, with winds following typical
diurnal trends. Humidity values will generally drop into the upper
single digits to mid-teens across the lower deserts while
remaining above 15 to 20 percent over the higher terrain areas of
Gila County. Overnight recovery will be poor to fair except at
higher elevations where better recovery is expected. Moisture will
briefly increase on Friday and Saturday as moist southerly flow
aloft and isolated thunderstorms at higher elevations return, but
wetting rains are generally not expected anywhere.
&&
.SPOTTER INFORMATION STATEMENT...
Spotters should follow standard reporting procedures.
&&
.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...Excessive Heat Watch from Tuesday morning through Thursday
evening for AZZ530>546-548>551-553>556-559-560.
CA...Excessive Heat Watch from Tuesday morning through Thursday
evening for CAZ565>567-569-570.
&&
$$
DISCUSSION...Hopper/Kuhlman
AVIATION...CB
FIRE WEATHER...Hopper