Forecast Discussions mentioning any of "ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 07/27/22

Area Forecast Discussion

National Weather Service Denver/Boulder CO

 620 PM MDT Tue Jul 26 2022

.UPDATE...
Issued at 618 PM MDT Tue Jul 26 2022

Recently ACARS soundings indicate a supportive environment for
isolated thunderstorms with MLCAPE near 1200 J/kg and 0-35km shear
near 35kts. These isolated thunderstorms will begin to dissipate
this late evening. Forecast remains on track thus there limited
changes in this update. Increased PoPs now through 04Z for the
eastern plains.

&&

.SHORT TERM...(This evening through Wednesday)
Issued at 122 PM MDT Tue Jul 26 2022

A few showers and thunderstorms were beginning to develop over the
Front Range/foothills as of 1 PM aided by a surface convergence
boundary, and these will continue to shift eastward through the
afternoon and evening into the plains, where MLCAPE values locally
exceeding 2,000 J/Kg will provide for more favorable
strengthening. Some CAMs do show convection lingering through late
evening and into tonight for portions of the plains as well.

Tomorrow, the high pressure axis will shift farther eastward and
allow for a notable increase in moisture. PWAT values look to rise
to between 1.10-1.30" in the plains by the afternoon, and to a
modest 0.60-0.70" over the high country. East/northeast surface
flow will permit good moisture advection at the surface as well,
with dewpoints into the 60`s in the plains. Steering level flow
will be on the decline, with forecast soundings indicating
west/northwest winds in the range of 5-20 kts between 700 and
300mb. Given the increasing moisture and weaker winds aloft, the
threat for burn scar flash flooding will be a little higher
Wednesday.

However, the bulk of the convective activity for the lower
elevations doesn`t appear to start until later in the evening (see
discussion below), when conditions will become increasingly
favorable for more widespread and potentially strong to severe
thunderstorm activity.

.LONG TERM...(Wednesday night through Tuesday)
Issued at 230 PM MDT Tue Jul 26 2022

Wednesday evening, storm development should be decreasing over
the high terrain as storms moving southeasterly across the plains.
Shear favors multicellular convection which may potentially
organize into an mesoscale convective system through the evening.
There should also be a few embedded severe storms bringing
marginal wind and hail threats primarily to the northeast plains.
The main impact will be locally heavy rainfall from slow-moving
storms which may linger on the plains overnight

Thursday, there will be northwesterly flow aloft and surface high
pressure moving over the Central Plains. Easterly to
southeasterly surface flow around that high will advect low level
moisture and models have surface dew points up to the 50s and 60s
across the plains. The moisture also has good depth and
precipitable water values will be 150 to 200 percent above normal
across most of the area by evening. High temperatures should be
down well below normal: in the 70s across the plains and and 50s
to 70s in the high country. The airmass will be more stable and
the best chance of storms will be over the high terrain and
adjacent plains through the urban corridor during the afternoon,
but still expect scattered to widespread showers across northeast
Colorado through evening. Forecast soundings show long, skinny
CAPE again through the evening, up to around 1000 to 1500 J/kg in
some areas. With good moisture, moderate instability and weak
winds aloft there will be a greater threat of heavy rainfall and
an elevated threat of burn area flash flooding, especially in the
afternoon. A few marginally severe storms are also possible
favoring the northern plains near the best shear.

Friday, there will be persistent northwesterly flow aloft and
surface flow turning more southerly across the plains as that high
moves away east. There will still be good moisture in place.
Expect another round of widespread showers through the afternoon
and evening, bringing moderate to heavy rainfall across most of
the area. Instability will again be quite low and shear decreasing
as well, which limits the threat of severe storms. Temperatures
similar to those Thursday, maybe even a bit cooler.

Saturday and Sunday, the ridge will build and gradually shift
eastward. Flow aloft will be decreasing as it turns more
northerly. There will still be quite a bit of moisture around and
scattered showers and storms over the higher terrain, lower
chances across the plains. A warming trend will bring high
temperatures back into the 80s and 90s across the plains.

&&

.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 618 PM MDT Tue Jul 26 2022

Winds will shift into the southeast direction this evening.
Isolated thunderstorms will decrease in coverage for all terminals
this evening. Outflows may produce brief wind gusts up to
20-25kts but it is the unlikely outcome. Typical drainage will
occur through Wednesday morning with sustained winds reaching
12kt. Wednesday evening, CAMs show scattered thunderstorms near
all sites thus adding VCTS late Wednesday evening.

&&

.HYDROLOGY...
Issued at 230 PM MDT Tue Jul 26 2022

Scattered thunderstorms are expected to develop in the mountains
after midday Wednesday. Weaker winds aloft and increasing moisture
will result in a higher threat for flash flooding for area burn
scars relative to Tuesday, although in general the threat will
remain limited. Some elevated concerns may exist for easternmost
portions of the Cameron Peak burn scar as well as Calwood.

The threat of burn area flash flooding will increase significantly
Thursday and Friday with cooler temperatures, increasing
moisture and decreasing flow aloft. Expect an elevated threat for
all burn areas both days, then at least a limited threat seems
likely through the weekend.

&&

.BOU WATCHES/WARNINGS/ADVISORIES...
None.
&&

$$

UPDATE...AD
SHORT TERM...Rodriguez
LONG TERM...EJD
AVIATION...AD
HYDROLOGY...Rodriguez/EJD



Area Forecast Discussion

National Weather Service Phoenix AZ

 526 PM MST Tue Jul 26 2022

.UPDATE...Updated 00Z Aviation Discussion.

&&

.SYNOPSIS... With plentiful moisture over the Southwest, widely
scattered showers and storms are forecast to continue over the next
several days. Heavy rainfall and briefly gusty winds will accompany
the stronger showers and storms that develop through the work week.
Areas that see repeated rounds of heavy rain will be monitored for
flash flooding. However, the nature of the activity will keep some
areas from seeing significant rainfall, and many hours will be spent
rain- free. Due to thicker clouds and rain in the vicinity, high
temperatures will remain at or below normal, but it will also be
rather muggy.

&&

.DISCUSSION...
Current satellite/radar imagery continues to show scattered showers
and a few t-storms continuing across south-central/SW AZ at this
hour. The most active area this afternoon appears to be over
Pinal/eastern Maricopa/southern Gila County, which missed out on
late last night/early this morning`s rainfall, which saw some areas
of western Maricopa County measure as much as 2 inches of rain. The
MCV that triggered last night`s rainfall has stalled over south-
central AZ. This feature will provide the lift to trigger more
showers/t-storms through this evening. Current ACARS soundings are
showing a very wet atmosphere today, with PWATS all the way into the
2.10-2.20 inch range, which is a near-record levels for this time of
year. The worked-over nature of the atmosphere over western
Maricopa/eastern La Paz/Yuma Counties will likely continue to
inhibit convective active over these regions thru the evening hours,
but areas across eastern Maricopa/Pinal/southern Gila Counties look
like they will have more activity, with the latest SPC showing an
axis of 1000-1500 J/Kg of CAPE extending across those regions. Storm
motion will be quite slow. with mid-level winds remaining quite
light. Combined with high rainfall rates (1-2 inches/hour),
localized flash flooding with be the main issue.

As far as the forecast for tonight thru Thursday is concerned,
latest high-res HRRR and HREF models are suggesting a bit of a break
late this evening, then an increase in convective activity over SW
and the western portion of South-Central AZ as another MCV possibly
rotates southwestward from NW AZ into that region. Again, the main
impacts will likely be locally heavy rain/flooding as well. The
activity appears it will shift to the higher terrain north and east
of Phoenix by Wednesday afternoon as the flow aloft becomes light
easterly, importing a bit drier air into the region ahead of another
weak disturbance that will be moving into SE AZ. Another round of
nocturnal convection appears possible late Wednesday night over the
western lower deserts as the airmass remains very moist (PWAT`s aoa
1.70 inch) with yet another disturbance dropping southern into the
region. Given the continuing threats for convection/very moist
airmass, decided to extend the FLood Watch until 12Z Thursday for
most of our CWA east the the Colorado River. WPC continues to
highlight much of AZ in a slight risk for excessive rainfall
through Wednesday.

Peering out into the extended forecast period, there is not a lot
of change to speak of. The upper ridge axis will continue to
extend from GA - TX - UT, allowing occasional weak disturbances a
path into the Sonoran Desert while no mechanisms will be in place
to scour out our antecedent monsoon moisture. This will keep
20-40% storm chances over Central Arizona and even higher coverage
over the higher terrain at least into the upcoming weekend, and
likely even longer.

This enhancement of the monsoon pattern will continue to give us
a break from the intense heat. Lower deserts will see high
temperatures ranging from 98-105 the next several days, hottest the
farther west you go into SW AZ/SE CA where less clouds/rain are
forecast. Muggy to occasionally humid conditions will also prevail.

&&

.AVIATION...Updated 0026Z.

South-Central Arizona including KPHX, KIWA, KSDL, and KDVT:
Showers and storms this afternoon have developed mostly around the
metro area so far, however at anytime outflows from the
surrounding convection, most favorably from the north to
northwest, could generate new showers and storms. Thus, have
maintained VCSH through this evening. The environment will remain
favorable for isolated to scattered convection through Wednesday
morning. Although confidence in hi-res models is low, majority of
members support most of the overnight convection focusing more
through western Maricopa, perhaps just outside the metro. Primary
threats will be heavy rain, occasional lighting, and brief gusty
winds with magnitudes most likely less than 30 kts. Wind
directions will be driven by vicinity showers and any distant
outflows, but diurnal trends will continue to favor a west through
the day and east overnight. Cloud bases as low as 4-5 kft will be
possible through tonight, but CIGs will mostly be aoa 7-8 kft.

Southeast California/Southwest Arizona including KIPL and KBLH:
Persistent southeast to south winds are expected. At KBLH, there
is a somewhat higher chance of storms late this afternoon through
early Wednesday morning, though probabilities and confidence
remain low. Skies will be a bit clearer at KIPL with showers and
storms not expected into the Valley.

&&

.FIRE WEATHER...
MinRH values will feature a gradient from 20-30% near and west of
the CO River to 35-45% near Phoenix and points eastward. Overnight
recovery will remain good. Heavy rain potential will be best
through tonight and a Flood Watch is in effect for districts east
of the Lower Colorado River Valley (except southern Yuma County).
From mid-week onward, the highest rain and storm chances will
become relegated to the higher elevations with 20-40% chances into
the eastern lower deserts (lower out west). Apart from
thunderstorm outflows, winds will favor familiar warm season
patterns. High temperatures will be below normal through at least
Wednesday over south- central AZ (less so further west) followed
by gradual warming (little change further west).

&&

.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...Flood Watch through late Wednesday night for AZZ533-534-537>563.

     Flood Watch through late tonight for AZZ531.

CA...None.
&&

$$

DISCUSSION...Percha/Heil
AVIATION...Benedict/Feldkircher
FIRE WEATHER...Heil/AJ