Forecast Discussions mentioning any of
"ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 10/04/21
Area Forecast Discussion
National Weather Service Houston/Galveston TX
835 PM CDT Sun Oct 3 2021
.SHORT TERM [Tonight through Tuesday]...
Quick update to lower rain chances over the coastal counties where
the seabreeze collided with the prefrontal trough producing storms
earlier this evening but have since pushed into the coastal waters
and weakened. Upper troughing to the west will keep the high level
moisture streaming overhead tonight and at least through late
morning Monday. In addition the presence of lingering lower-mid
level moisture evident in observations with sct/bkn deck of
5000-13000 ft being reported and present in the AMDAR soundings.
This level will be slow to dry out with the 800-700mb drying out
very slowly in the short term guidance which makes it possible
that scattered clouds could linger well into Monday evening.
Drying in the low levels though will continue as the cold front
pushes through the coastal counties this evening and into the Gulf
A pleasant and dry day expected Monday with northerly flow of
around 10 mph with gusts of 15 to 20 mph at times.
45
&&
.AVIATION [00Z TAF Issuance]...
VFR. Mid clouds of 5k-10k will be possible through 18z then should
see some further scattering. Northerly winds wobbling about from
around 340-030.
45
&&
.PREV DISCUSSION /Issued 341 PM CDT Sun Oct 3 2021/...
.LONG TERM [Wednesday Through Sunday]...
Not a whole lot to discuss in the long term as mid/upper level
ridging becomes established over the region. This will bring
seasonably warm and dry weather for southeast TX through next
weekend. While a tad warm with afternoon highs topping out around
90F for some areas, light winds and sunny skies will make for a
nice week/weekend. Although most areas will see morning lows more
normal for October given the relatively dry airmass in place with
lows in the low/mid 60sF away from the immediate coast. Surface
winds will become a bit more onshore next weekend, so expect
humidity and overnight lows to creep upwards next weekend.
Evans
.MARINE...
We will have a cool front push offshore tonight, taking with it a
few showers and usher in a period of offshore flow and clear
skies. Light to occasionally moderate winds and mainly low seas
behind this front can be expected to start the week, along with
dry weather.
Evans
&&
.PRELIMINARY POINT TEMPS/POPS...
College Station (CLL) 66 89 60 88 59 / 0 0 0 0 0
Houston (IAH) 69 87 64 87 62 / 10 0 0 0 0
Galveston (GLS) 74 86 73 85 73 / 20 0 0 0 0
&&
.HGX WATCHES/WARNINGS/ADVISORIES...
TX...None.
GM...None.
&&
$$
SHORT TERM...45
LONG TERM...41
Area Forecast Discussion
National Weather Service Phoenix AZ
454 PM MST Sun Oct 3 2021
.UPDATE...
Updated Aviation discussion.
&&
.SYNOPSIS...
Expect seasonably warm and dry conditions through tomorrow with
gradually increasing clouds. A low pressure system will bring
increasing chances for showers and a few thunderstorms late
Monday and into Tuesday. Slightly cooler and dry weather will
take place Wednesday and Thursday. The forecast becomes more
murky late in the week with another weather system potentially bringing
additional rain chances to the area.
&&
DISCUSSION...
Near to slightly above normal temperatures will continue through
Monday as our area remains under the influence of shortwave ridging
today into the first part of tomorrow. Afternoon high temperatures
will top out in the mid to upper 90s across the lower deserts today
and tomorrow with chances of reaching 100 degrees generally less
than 15% for most locations. Afternoon Phoenix ACARS sounding showed
dry conditions through the column with PWATs less than 0.75" across
the CWA, while mesoanalysis data showed richer moisture confined
near the southern half of the Baja Peninsula. We`ll see this change
over the next couple of days as an upper level low, currently
situated over the eastern Pacific, progresses through the
Southwest during the latter half of Monday into Tuesday.
As the aforementioned upper level low progresses toward the east
tomorrow, it will pull moisture up from the south into the
forecast area with PWAT values climbing into the 1.00-1.30" range
(above the 90th climatological percentile). Heading into tomorrow
afternoon and evening, increasing moisture and difluence will
help in developing showers and embedded thunderstorms across
southeast California and southwest Arizona. Model soundings show
CAPE values remaining marginal during the afternoon/evening
timeframe, so thunderstorm activity does not look to be
widespread, but a few isolated thunderstorms will be possible.
The main impacts with any thunderstorms that manage to develop
will be gusty winds, blowing dust, and locally heavy rain.
Going into Tuesday, favorable dynamic support will increase across
Arizona and yield increasing coverage of showers and thunderstorms
across the state. NBM PoPs reflect the expected increase in coverage
with PoPs increasing to 70-80% across south-central Arizona by
Tuesday morning. Hi-Res guidance indicates increasing CAPE values
across the forecast area by Tuesday morning into Tuesday afternoon.
Thus, increased thunderstorm activity will be possible which may
lead to gusty winds and locally heavy rainfall, including the burn
scars, so some flooding issues will be possible.
NBM QPF data show minimal rainfall amounts across the western CWA
with WPC QPF keeping storm totals below 0.10" for most places.
Even with the 95th percentile NBM QPF, amounts across southeast
California and southwest Arizona remain below 0.50". Higher
amounts are more likely to remain near the Phoenix area with the
highest totals remaining over the high terrain north and east of
the metro. WPC QPF currently keeps the Phoenix area between
0.25-0.40", while higher amounts above 0.50" to near an inch in a
few localized places will be possible across parts of southern
Gila County. NBM QPF shows 90th percentile amounts over an inch
across southern Gila County, which could potentially happen in a
few localized places with any heavier thunderstorms that develop.
WPC currently has Phoenix and areas north and east in a Marginal
Excessive Rainfall Outlook for Tuesday. Aside from the rain,
temperatures will fall below normal on Tuesday as afternoon highs
remain in the 80s across the lower deserts of south-central
Arizona and low 90s along and west of the Lower Colorado River
Valley.
.PREVIOUS DISCUSSION...
Rain chances should quickly and as the system moves northeast
Tuesday night. The quiet weather in its wake will last Wednesday
and Thursday, slight warming temperatures. Another deep trough is
appearing more likely late in the week off the California coast,
though with considerable uncertainty. Ensemble clusters vary on
how far off or close to the southern California coast it will be
Thursday, then if it moves onshore or not Friday/Saturday. The
spread becomes quite pronounced among EPS/GEM/GEFS members, with
500 mb heights over Phoenix varying from roughly as low as 568 dm
in the more progressive/deep trough scenario to as high as 596 dm
in the slower scenario (low stays off the coast and amplifies a
substantial downstream ridge over the Southwest). While rain
chances seem scant in the various scenarios, temperature spreads
will be very large with highs in the upper 90s in the
amplified/high height scenario to the lower 80s in the deeper
trough scenario.
&&
.AVIATION...Updated at 2354Z.
South-Central Arizona including KPHX, KIWA, KSDL, and KDVT:
An upper low centered west-southwest of KSAN is spreading cirrus
over the forecast area. This will continue the rest of the night
and into day Monday (with fluctuating thickness). Surface winds
the rest of the afternoon and evening will generally be light but
have some variability in direction - especially at KPHX. In the
lower levels above the surface, the winds will be southeasterly.
After midnight, familiar nocturnal surface wind patterns can be
expected. Anticipate surface winds to favor the southeast quadrant
for much of the daytime Monday with possibly a period of modest
gustiness over the East Valley (including KIWA) between 16Z-20Z.
By late afternoon, south-southwesterly directions will be common.
As the low advances eastward, it will begin advecting additional
moisture northward leading to some isolated showers over the
higher terrain east and northeast of the Phoenix area Monday
afternoon. Ceilings will go from cirrus level to around FL100
Monday evening at the TAF sites with scattered to numerous showers
developing late Monday night through Tuesday.
Southeast California/Southwest Arizona including KIPL and KBLH:
An upper low centered west-southwest of KSAN will spread
increasing cirrus over the forecast area the rest of the night.
Winds will be light and favor familiar nocturnal patterns. Winds
will favor southerly directions at KBLH during the afternoon with
more variable directions at KIPL. As the low advances eastward,
scattered showers and isolated thunderstorms will develop over the
higher terrain of San Diego County and far northern Baja by
midday Monday and slowly expand eastward during the afternoon.
Thus, inserted mention of PROB30 for -SHRA at KIPL after 21Z.
Shower chances arrive just after the current TAF period at KBLH.
&&
.FIRE WEATHER...
Tuesday through Saturday:
A storm system will be passing through Tuesday, with wetting rains
possible all areas. Greatest rainfall amounts are likely in the
foothills and mountains north and east of Phoenix. Temperatures
will be much cooler and humidity values much higher. Wednesday
into Saturday, temperatures will trend a bit warmer and humidity
values back down.
&&
.SPOTTER INFORMATION STATEMENT...
Spotters should follow standard reporting procedures.
&&
.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...None.
CA...None.
&&
$$
DISCUSSION...Smith
PREVIOUS DISCUSSION...Iniguez
AVIATION...AJ
FIRE WEATHER...Iniguez