Forecast Discussions mentioning any of
"ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 08/22/23
Area Forecast Discussion
National Weather Service Denver/Boulder CO
948 PM MDT Mon Aug 21 2023
.UPDATE...
Issued at 947 PM MDT Mon Aug 21 2023
The forecast is performing well with only minor updates this
evening.
A daily record high temperature was set at Denver today, 99 F
(breaking 97 F of 2007). Our latest RERDEN is available with this
information online. The daily record high minimum temperatures
for today (67 F in 1946) and tomorrow (69 F in 1960) are both in
jeopardy as well (lowest temperature today was 72 F early in the
morning, temperature nearing the end of the evening is still 80
F).
We expired our Red Flag Warning and Heat Advisory this evening
shortly after sunset, as temperatures fell and humidity improved.
Otherwise, there is some cloudiness and light rainfall across the
high country but not much else for us. The 00Z synoptic analysis
shows the big ridge to our east has shifted a bit farther east,
now centered about over northern Missouri. The closest upstream
soundings (AMA and maybe ABQ) show a moderate 30 to 40 knot mid to
upper level flow with a bit more moisture (0.7 to 0.9 inches
precipitable water, some patchy cloud layers) and GOES water vapor
imagery shows some cloudiness coming around.
&&
.SHORT TERM...(This evening through Tuesday)
Issued at 236 PM MDT Mon Aug 21 2023
GOES-13 West GeoColor displays our current conditions nicely. Not
a cloud in the sky and dry conditions. Fear not, a few clouds
should develop in the mountains through southwesterly late this
afternoon giving relief to the heat. Daytime heating and
increasing mid-level moisture could create a weak high based
shower or two this evening across the northern mountains but with
such a warm airmass in place, any rainfall seems unlikely. Denver
ACARS soundings indicate weak instability, low PWATs, and strong
southerly flow from 700mb to the surface. As southerly flow
continues, wind gusts up to 25-35 mph could occur along the
plains. These conditions will continue through overnight into
Tuesday morning. Our low temperatures tonight should remain warm.
Consequently, the Denver record high and low temperature may be in
jeopardy especially given we`re at 98 currently. Tuesday,
afternoon temperatures remain slightly above normal but increasing
remnants of tropical moisture and MLCAPE values increase near 200
J/kg should allow scattered weak thunderstorms and showers to
occur through early Tuesday evening.
.LONG TERM...(Tuesday night through Monday)
Issued at 236 PM MDT Mon Aug 21 2023
Upper level high over Missouri, will slowly migrate southwestward
to the Central Plains. This will produce a deeper southerly flow
aloft and transport subtropical moisture into the area, including
the remnants of the tropical system tracking west across the Gulf
of Mexico. Precipitable water values climb above an inch across
the plains Wednesday and reach 0.75(in) to 1.00(in) over higher
elevations. Moisture continues to increase for Thursday and peak
on Friday with precipitable water values of 1.25 to 1.50(in) over
the plains and around an inch over the higher elevations. This
puts precipitable water values in the 175-225 percent of normal
range. Showers and thunderstorms will be capable of very heavy
rainfall by Friday. Friday is looking like the day with cool and
cloudy conditions with widespread rainfall as a (the old tropical
system) moves across northern Colorado.
Forecast becomes more uncertain beginning Saturday. The ECMWF
shows a second wave and keeps the airmass very moist, which
results in another round of widespread showers and storms. The GFS
shows some drying and not nearly as much precipitation. It will
remain on the cooler side at least. For PoPs, will have high
scattered to likely PoPs for Saturday. By Sunday, models generally
agree weak ridging will move across the region. This will dry the
airmass some, but again the GFS is about a quarter inch less with
precipitable water values. Should be enough moisture around, even
on the GFS for scattered showers and storms. Best moisture Sunday
and more so on Monday, transitions to the plains under a
northwest flow aloft. Precipitable water values will be around an
inch over the plains, but falls to a half inch or less over the
mountains.
&&
.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Issued at 608 PM MDT Mon Aug 21 2023
Expect VFR conditions through the period. Breezy southerly winds
should persist through this evening, and gradually shift from
south-southeasterly to south-southwesterly. Winds should calm a
bit in the morning, then breezy outflow from scattered convection
in the mountains likely by late afternoon. Storms and showers are
not expected in the vicinity of the terminals at this time, so the
outflow is being represented in a tempo without thunder or
precipitation. Breezy drainage winds likely after that.
&&
.FIRE WEATHER...
Issued at 236 PM MDT Mon Aug 21 2023
Warm, southerly flow continues through Tuesday morning along
the eastern plains. Although relative humidities should increase
overnight recovering to 30-40 percent. Reg Flag conditions should
end near 7 PM MDT this evening.
&&
.HYDROLOGY...
Issued at 236 PM MDT Mon Aug 21 2023
Daytime heating and PWATs near 0.40 inches should support
afternoon thunderstorms across the mountains and valleys Tuesday.
This will lead to a limited flash flood threat over the burn
areas.
Moisture continues to increase for Wednesday and Thursday. By
Friday the airmass will be very moist with the remnants of the
tropical system currently in the Gulf of Mexico moving across
northern Colorado. Moisture should increase enough for a few
storms to produce heavy rain on Wednesday and Thursday. For Friday
and possibly Saturday, very heavy rainfall will likely accompany
the stronger storms. Flash flooding will be possible, mainly in
the flood prone areas. Friday appears to be the chance for
widespread and heavy rainfall. Scattered showers should prevail
this weekend, with Saturday possibly being another day with
widespread rainfall. Heavy rain and localized flooding will again
be the main weather concern.
&&
.BOU WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
UPDATE...EJD
SHORT TERM...AD
LONG TERM...Meier
AVIATION...EJD
FIRE WEATHER...AD
HYDROLOGY...AD/Meier
Area Forecast Discussion...UPDATED
National Weather Service Brownsville TX
635 PM CDT Mon Aug 21 2023
...New AVIATION...
.SHORT TERM...
(Tonight through Tuesday night)
Issued at 332 PM CDT Mon Aug 21 2023
Weather impacts in the short-term will be driven by newly formed
Tropical Depression Nine. ASCAT passes and aircraft recon have
recently found a closed circulation, with the intensity set at 30
knots. TD-9 is forecast to make landfall as a 40-45 knot tropical
storm along the Kenedy/Willacy county coast tomorrow morning. Due
to its broad structure and quick forward speed (currently moving
westward at 18mph), rapid intensification appears unlikely. While
the strongest winds will be on the north side of the center, the
most recent track has nudged south a bit, potentially bringing a
brief period of 40-50mph gusts to northern Kenedy county Tuesday
morning. Tropical Storm Warnings are in effect for all of the
barrier islands and coastal zones, along with inland Willacy and
Kenedy counties.
The main impact expected from TD-9 continues to be potentially
heavy rainfall, though much of this rain will be welcome. WPC has
delineated a Marginal Risk of excessive rainfall through early
tomorrow morning, mainly for areas east of I-69C/Highway 281.
Heavier rainbands should begin moving ashore around midnight, and
progress inland with time. For Tuesday, WPC has placed a Slight
Risk of excessive rainfall over the entire area. If you encounter
flooded roadways...turn around, don`t drown! There could be a
relatively tight gradient in the rainfall totals, with confidence
increasing that the bulk of the heaviest rainfall will pass north
of the Lower RGV. Still advertising up to 2 inches of rainfall for
the mid/Lower RGV, with 2-4 inches across the northern Ranchlands.
Isolated totals of 5-6 inches through Tuesday evening cannot be
ruled out. Isolated tornadoes in mini-supercell structures are
also possible across the northern Ranchlands in the right-front
quadrant of the circulation of TD-9.
Temps are tricky for tomorrow, but should be lower than they have
been for some time for most of the area, depending where main
precip shield/banding sets up. May not top 90F west of
I-69C/Highway 281. Brownsville/Harlingen metro could still rebound
to the lower-mid 90s if some sun can break out Tuesday afternoon,
as ridging aloft will already be nosing back into the region
toward evening. Residual moisture allows for scattered precip
Tuesday night, though amounts to be much lighter, in general.
Hazardous beach conditions are in store from tonight through
Tuesday as well, with a High Risk of Rip Currents, High Surf
Advisory, and Coastal Flood Advisory all in effect from 7PM this
evening through 7PM Tuesday. Local guidance suggests water level at
Brazos Santiago pass may exceed 2.5 ft. MHHW, with the added
swell energy from TD-9. Since the background astronomical tides
are rather low, most impactful time would be a few hours either
side of high tide early tomorrow morning, occurring at 5:38am
CDT. This is also roughly the time when the center of TD-9
approaches the Willacy/Kenedy County coast. The worst coastal
flooding should be north of the landfall point along Padre Island
National Seashore. After landfall, winds quickly re-acquire a
southerly component, which should reduce the coastal flooding
threat relatively quickly later on Tuesday.
&&
.LONG TERM...
(Wednesday through next Monday)
Issued at 332 PM CDT Mon Aug 21 2023
Long-term period appears to be relatively quiet. On Wednesday,
with the center of the H5 high lying across the Red River valley,
the atmospheric column continues drying from east-to-west, though
there should be sufficient moisture for a few residual rain
showers. As winds go slack early Thursday morning, patchy fog
could develop inland in spots that pick up significant rainfall
from TD-9. A weak inverted trough is progged by the GFS pass to
our south on Friday (a bit closer in the ECMWF), which should be
enough for isolated sea-breeze convection. Max heat indices may
approach advisory criteria, as temps march back to near- or
slightly above normal levels. Heading into the weekend, the H5
high center again takes up residence near the Four Corners region,
though with an axis extending back toward Texas. Rain likely to
be sparse, though isolated sea-breeze showers may occur again
Sunday into Monday.
&&
.AVIATION...
(00Z TAFS)
Issued at 628 PM CDT Mon Aug 21 2023
Conditions deteriorate, in term of rain and thunderstorms,
overnight as Tropical Depression Nine approaches. These should
generally be MVFR for ceilings and visibility, though they could
briefly drop to IFR in heavier downpours, mainly toward sunrise
Tuesday. Winds back from current NE direction, to more N
overnight and becoming a little gustier. Further backing to the
NW is expected tomorrow morning as the center of TD-9 passes
about 50 miles north of the RGV terminals. Current forecast shows
improvement tomorrow afternoon, but timing adjustments are likely
in future updates. If TD-9 tracks further south than currently
forecast, winds may be stronger than indicated in the current TAF.
Low-level wind shear may be a factor at BRO and HRL from 12-18Z on
Tue due to the passage of TD-9 to the north. Have not included in
TAF at this time, but may be needed in future issuances.
&&
.MARINE...
Issued at 332 PM CDT Mon Aug 21 2023
Now through Sunday...
Tropical Depression Nine has formed in the western Gulf of Mexico
and is forecast to make landfall as a tropical storm in the
general vicinity of Port Mansfield on Tuesday morning. Tropical
Storm Warnings remain in effect for all of the Lower Texas coastal
waters. Wind gusts on the northern Laguna Madre may reach 45
knots, with very rough bad conditions. Gulf waters north of Pt.
Mansfield could see gusts briefly up to 50-55 kt on Tuesday, with
seas of 6-11 ft. Small Craft Advisories, at least on the Gulf, are
likely to follow up the Tropical Storm Warning for Tuesday night,
as seas are likely to remain agitated.
Boating conditions will deteriorate tonight into Tuesday morning
across the coastal waters due to the approach of TD-9. Strong
gusty winds, high seas, widespread showers and thunderstorms, and
isolated waterspouts will prevail into Tuesday afternoon.
Gradually improving, though still hazardous, conditions are
expected by Tuesday evening, with the trend continuing through
Wednesday. Modest surface high pressure takes hold over the Gulf
from Thursday onward, leading to more favorable conditions.
&&
.PRELIMINARY POINT TEMPS/POPS...
BROWNSVILLE 78 92 79 93 / 80 50 50 50
HARLINGEN 75 92 76 94 / 80 80 50 50
MCALLEN 77 91 78 95 / 80 90 50 50
RIO GRANDE CITY 76 87 77 93 / 80 90 50 50
SOUTH PADRE ISLAND 78 86 81 87 / 90 50 50 40
BAYVIEW/PORT ISABEL 76 90 79 92 / 90 60 50 40
&&
.BRO WATCHES/WARNINGS/ADVISORIES...
TX...Tropical Storm Warning for TXZ251-254-351-354-355-451-454-455.
Coastal Flood Advisory until 7 PM CDT Tuesday for TXZ451-454-455.
High Rip Current Risk through Tuesday evening for TXZ451-454-455.
High Surf Advisory until 7 PM CDT Tuesday for TXZ451-454-455.
GM...Tropical Storm Warning for GMZ130-132-135-150-155-170-175.
&&
$$
SHORT TERM...53-Schroeder
LONG TERM....53-Schroeder
AVIATION...53-Schroeder