Forecast Discussions mentioning any of
"ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 08/19/22
Area Forecast Discussion...UPDATED
National Weather Service Brownsville TX
645 PM CDT Thu Aug 18 2022
...New AVIATION...
.SHORT TERM...
(This evening through Friday night)
Issued at 246 PM CDT Thu Aug 18 2022
The short term will bring another 36 hours of seasonal weather. A
tropical wave will emerge into the Southwest Gulf of Mexico (Bay
of Campeche) on Friday where an area of low pressure could form.
The disturbance will then move North toward the Lower RGV. Rain
chances will eventually increase, but I really don`t see much
increase so far in the short term. The system does have low...30
percent chance of developing into a tropical system in the next 48
hours.
Sea breeze activity this afternoon has been weak today. PWAT values
will remain in the 1.6 to 1.8 inch range on Friday, with guidance
supporting silent PoPs. High temps on Friday will range from the
lower 90s east to a few degrees above the century mark for Starr and
Zapata Counties. Heat index values there will range from 102 to 107
degrees. Beach high temperatures will be in the upper 80s to near 90
degrees. Overnight lows will range from the mid 70s to near 80
degrees. Cloud cover will be mostly clear to partly cloudy and winds
will remain out of the southeast, becoming moderate to breezy on
Friday.
&&
.LONG TERM...
(Saturday through next Wednesday)
Issued at 246 PM CDT Thu Aug 18 2022
The primary concern at the start of the long-term period will be
the much anticipated tropical wave/mid-level low, which is currently
moving across Central America. Latest consensus of the 12z
deterministic model suite (GFS/ECMWF/Canadian/NAM) continues to
indicate very little development with the tropical wave after it
enters the Bay of Campeche on Friday. Really, only the ECMWF hints
at a brief closed low on Saturday morning, with pressure
bottoming out around 1011 mb, with all other keeping the feature
an open wave. Nevertheless, the NHC has a 30% chance of the wave
developing into tropical cyclone over the next 48 hours before
moving inland across northeast Mexico either Saturday evening or
night. An Air Force Reserve Hurricane Hunter aircraft is scheduled
to investigate the system on Friday, if necessary.
As far as rainfall, models have been trending back on amounts
with this system for Deep South Texas. This might be due to a
combination of them developing a weaker system and a quick-
building mid-level ridge over South Texas beginning on Saturday.
Best chances of rain will be mostly concentrated offshore and
locations closer to the coast, with best timing being as it moves
inland Saturday night into Sunday. But overall, general rainfall
amounts look to be less than half an inch through the weekend;
some showers/storms may be heavy and produce higher amounts of
rain in isolated spots.
Both Monday and Tuesday look to be mostly dry, warmer, and humid
as mid-level ridging continues to build in over the region.
Isolated shower activity cannot be ruled out during the afternoon
hours, especially along the seabreeze. A very weak cold front will
slowly push into the northern part of the state Monday/Tuesday as
a vigorous mid/upper-level trough digs into the Southern CONUS.
The front likely won`t reach this far south, but could
potentially create a convergent zone/produce outflow boundaries
in favor of isolated chances of showers/thunderstorms on
Wednesday. This forecast will be fine-tuned in later updates.
&&
.AVIATION...
(00Z TAFS)
Issued at 635 PM CDT Thu Aug 18 2022
VFR through the period with breezy winds becoming calmer
overnight. Clouds should dissipate by midnight with skies
becoming mostly clear. Southeast winds start to increase becoming
breezy again by Friday morning.
&&
.MARINE...
Issued at 246 PM CDT Thu Aug 18 2022
Now through Friday Night...Moderate to fresh southeast to south
winds and low to moderate seas will prevail with high pressure
over the Western Gulf of Mexico. A tropical wave will emerge into
the Southwest Gulf of Mexico (Bay of Campeche) on Friday where an
area of low pressure could form. The disturbance will then move
North toward the Lower Texas Coastal Waters. That said, impacts to
the Lower Texas Coastal Waters should be minimal through Friday
night.
Saturday through Tuesday...The tropical wave is forecast to move
onshore across northeast Mexico Saturday evening/night. This will
likely produce scattered showers and thunderstorms, especially on
the Gulf waters Saturday and Sunday. A moderate to strong
pressure gradient will be in place on Saturday and on Sunday.
However, wind speeds and wave heights don`t really increase
dramatically this weekend, with winds reaching high-end SCEC
(possibly low-end SCA) and waves increasing to only about 3 to 5
feet through Sunday. Winds and seas will begin to subside Sunday
night, with high pressure building in and mostly tranquil marine
weather continuing through Tuesday.
&&
.PRELIMINARY POINT TEMPS/POPS...
BROWNSVILLE 80 96 80 92 / 0 10 10 40
HARLINGEN 77 95 78 92 / 0 10 0 30
MCALLEN 78 100 78 95 / 0 10 0 30
RIO GRANDE CITY 78 100 77 97 / 10 0 0 20
SOUTH PADRE ISLAND 81 88 81 87 / 0 0 10 30
BAYVIEW/PORT ISABEL 79 92 79 91 / 0 0 10 30
&&
.BRO WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
SHORT TERM...65-Soria
LONG TERM....67-Hallman
AVIATION...65-Soria
Area Forecast Discussion
National Weather Service Phoenix AZ
454 PM MST Thu Aug 18 2022
.UPDATE...Updated Aviation Discussion.
.SYNOPSIS...
Temperatures will fall to slightly below normal today with scattered
afternoon thunderstorms moving off of the high terrain. For the
remainder of the week, deep Monsoon moisture will gradually increase
across the region with much improved chances for showers and
thunderstorms. Heavy rainfall and localized flooding are likely with
chances peaking Friday afternoon through Sunday morning.
Temperatures are also forecast to cool to well below normal with
highs across a good portion of the lower deserts falling into the
nineties by Friday and possibly the upper eighties by Saturday.
Temperatures warm to near 100 degrees for the rest of next week with
scattered storms over the higher terrain each day.
&&
.DISCUSSION...
High pressure over Arizona is quickly retreating as an upper level
trough is developing over the Great Basin and edging southeast.
Meanwhile the upper level low south of Arizona continues to slowly
travel westward. Visible satellite imagery shows mostly clear skies
from Phoenix and points west. Building instability across the higher
terrain of eastern and northern Arizona is apparent with increasing
cloud and shower coverage at this time. ACARS soundings continue to
show a very moist airmass with PWAT near 2". The wind profile is
improved over yesterday with easterly flow of 10-20 kts in the 800-
500 hPa layer and westerly flow above 250 hPa. MLCAPE of 500-1500
J/Kg is present with MUCAPE of 1500-3000 J/Kg. There is still a cap
near 850 hPa but this will continue to erode with daytime heating.
HREF guidance is handing the current progression so far, and
indicates that convective coverage will continue to increase across
the higher terrain into the afternoon. There is some variability in
the timing, intensity, and placement, but showers and thunderstorms
are possible across the lower deserts of Arizona with PoPs
increasing to 30-70% this evening with lower PoPs west of the
Colorado River. The corridor with the highest potential for
thunderstorms and the corresponding wind/dust threat appears to be
west of Phoenix and east of the Colorado River, with a secondary
corridor south and east of Phoenix. HREF shows that these areas will
see a 40-70% chance of winds in excess of 30 kts. Similar to
yesterday, storms will move from northeast to southwest and congeal
with time. An isolated flash flood producing storm is possible, but
quick storm motions and some residual dry air in the boundary layer
should keep that risk relatively low.
The forecast still appears to be on track for Friday and into the
weekend with a surge of anomalously deep monsoonal moisture and a
corresponding increase in the rain and flash flood threat. WPC has
maintained a moderate risk for flash flooding for much of south-
central Arizona for Friday into Saturday and again for portions of
Gila County on Saturday into Sunday. Compared to yesterday, models
have slightly tapered expectations for Friday into Saturday with the
ensemble mean precipitation dropping slightly and less individual
ensemble members showing extreme precipitation totals. However, the
ensemble mean has also ticked up Saturday into Sunday which may
ultimately prologue the rain threat. For now the Flood Watch remains
in effect from Friday late morning through Saturday night. It is
possible that this may need to be extended further into Sunday
morning.
In terms of the forecast analysis, it still looks like a trough will
set up to the northwest of the area with a jet streak well
positioned to induce upper level difluence over southern Arizona.
This, in conjunction with the closest approach of the upper level
low, will overlay copious moisture in the same location as the
enhance diffluence aloft. As a result, we still expect thunderstorms
with heavy rain to develop on Friday afternoon. There is some
indication of a 700 hPa convergence zone in the vicinity of Phoenix
at this time, which could focus rainfall into a narrow corridor
while other nearby areas see much less. This is the general picture
presented by the HREF guidance, but the individual members disagree
on the exact location and timing of the rainfall. Regardless, any
storms that do develop in this environment will have the potential
to produce very heavy rainfall and flash flooding. A secondary jet
streak will reinvigorate storm chances Saturday into Sunday, but
rainfall will probably focus more towards Gila County and points
east or south as the upper low to the south of Arizona will be
moving east by that time. Storm total accumulations may vary
considerably, as some areas could fail to see even a half inch of
rain while others could see two inches or more.
High temperatures will drop into the low 90s or upper 80s for
Saturday and Sunday before climbing back to near 100 F for much of
next week. NBM probability of reaching 100F at Phoenix will hover at
around 40-55% each day. With PWAT remaining elevated, mountain
showers and thunderstorms will be possible each day with a low risk
(15-30%) of impacting the valleys.
&&
.AVIATION...Updated 2354Z.
South-Central Arizona including KPHX, KIWA, KSDL, and KDVT:
Light westerly winds are expected to continue into the early evening
hours. Latest high-res model output continues to show thunderstorms
that are over the high terrain north and east of Phoenix to move
into the valley during the 02Z-03Z timeframe. Confidence remains low
in exact outflow directions given the potential for multiple
outflows from various directions. For now, have left an E to NE
outflow as suggested by several CAMs. Chances for outflows to exceed
30 kts climb to around 30-40% this evening. As outflows travel
through the Phoenix area, additional thunderstorm development will
be possible, which may lead to strong gusty erratic winds in
addition to blowing dust, lightning and locally heavy rainfall. We
may see SCT-BKN clouds dip down to around 7-8 kft with any
thunderstorms. T-storm activity is expected to move off to the
west/southwest by 05Z-06Z with lighter SHRA activity persisting for
a couple of hours thereafter. More typical easterly drainage winds
are expected to become established sometime after midnight,
persisting thru Friday morning. Winds then expected to once again
become westerly Friday afternoon with another good chance (40-60%)
of t-storms moving into the Phoenix area from the east/northeast by
Friday evening.
Southeast California/Southwest Arizona including KIPL and KBLH:
Winds at KIPL will mostly favor the E to SE through the period, with
some gusty E winds possible later tonight/early Friday morning. At
KBLH, winds will mostly favor the S outside of any thunderstorm
outflows. CAMs suggest a strong outflow coming from the N to NE this
evening and reaching KBLH. May see additional thunderstorm
development as this occurs near the terminal. Gusty erratic winds
along with blowing dust and lightning will be possible with
thunderstorms near KBLH. Chances for exceeding 30 kts climbs to
around 30-40% this evening. Expecting rather quiet conditions with
winds favoring a southerly direction at KBLH and a southeasterly
direction at KIPL during the day on Friday. Chances (30-40%) for t-
storms return to the KBLH Friday evening.
&&
.FIRE WEATHER...
Isolated shower and thunderstorm activity today will likely increase
and become scattered as storm chances and CWR ramp-up to 40-70% from
late afternoon and evening through Fri and Fri evening-night across
S-Cent AZ. Slight 10-30% storm chances for SW AZ and SE CA today
will also improve to 20-40% Fri. Very elevated moisture with min RH
values >30% today and >40% Fri with excellent overnight recovery of
>75-80%. Winds on average will be light, with the exception of any
thunderstorm outflows generating stronger gusts. Below normal highs
today fall to well below normal by tomorrow as upper level
disturbances with deep Monsoon moisture are expected to impact much
of AZ through the remainder of the week and into the weekend, likely
peaking Fri into Sat. This will provide even more widespread wetting
rains and cooler below, to well below normal highs across the area,
especially for S, SE, S-Cent and E AZ. Impacts from thunderstorm
activity will include locally strong winds, rounds of heavy rainfall
and localized flooding well into the weekend. Winds through the
majority of the period will remain light, with the exception of
nearby thunderstorms or thunderstorm outflow generating stronger
gusts.
&&
.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...Flood Watch from Friday morning through Saturday evening for
AZZ531-533>563.
CA...None.
&&
$$
DISCUSSION...Hodges
AVIATION...Percha/Smith
FIRE WEATHER...Sawtelle