Forecast Discussions mentioning any of
"ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 08/09/22
Area Forecast Discussion
National Weather Service Indianapolis IN
956 PM EDT Mon Aug 8 2022
.Forecast Update...
Issued at 956 PM EDT Mon Aug 8 2022
Busy evening in progress across the northwest half of central
Indiana as clusters of thunderstorms have develop along and ahead of
a slowly southward moving frontal boundary. 0130Z temperatures
ranged from the lower 70s in rain cooled air to the lower 80s.
Overall forecast is in good shape for the overnight with the evening
update focused on providing more detail going forward. Convection to
this point this evening has been relatively slow moving and confined
to locations within the forecast area along and north of I-70.
Starting to see isolated development further south along with an
expanding area of convection into the lower Wabash Valley. With the
frontal boundary still located over far northern portions of the
forecast area...expect continued convective development into the
overnight with the focal area gradually setting up near and south of
I-70 where low level westerly flow will be slightly more enhanced
and potentially favorable for backbuilding showers and storms.
Several of the pulsing cells near the Indy metro have exhibited
stronger velocity signatures this evening...indicative of smaller
wind cores underneath collapsing cores. Wind gusts have peaked at 40-
50mph briefly within these storms and may do so for a bit longer as
lapse rates within the boundary layer weaken. By far the greatest
concern from convection overnight will be torrential rainfall and
localized flooding. PWATs off LAPS sounding this evening are at 2.15
to 2.25 inches indicative of a copious amount of moisture in the
lower levels. in addition...freezing levels in excess of 15kft and
soundings showing a saturated airmass up over 500mb strongly support
efficient warm rain processes in play overnight. Will maintain the
Flood Watch over the southwest counties where moisture is deepest
and convection may linger the longest through the night. But there
will be a localized flood risk from any storm over the forecast area
tonight.
Zone and grid updates out.
&&
.Short Term...(This evening through Tuesday night)
Issued at 319 PM EDT Mon Aug 8 2022
...FLASH FLOOD WATCH IS IN EFFECT FROM THIS EVENING THROUGH LATE
TONIGHT FOR SOUTHWEST CENTRAL INDIANA...
Current visible satellite imagery shows an expansive cloud deck
just northwest of the CWA as an approaching shortwave provides
weak large scale ascent. A surface low associated with the trough
is currently over Michigan with a cold front stretching back into
Missouri. ACARS soundings suggest daytime heating and dewpoints in
the mid 70s have contributed to moderate instability this
afternoon. Furthermore, deep moisture with PWATs near 2.20 inches
is present across central Indiana. This combined with low level
convergence along the front will lead to the development of
numerous showers and thunderstorms this evening. Weak tropospheric
flow should limit the overall severe weather risk. Although,
steep low level lapse rates may lead to an isolated damaging wind
gust, mainly across northwest portions of central Indiana before
sunset.
Flooding is a greater concern tonight as the front slowly sags
south. Models are in general agreement the surface boundary will
stall over south central Indiana by tomorrow morning as mean flow
becomes parallel to it. High PWATs and near moist adiabatic profiles
may lead to efficient rain producers. This combined with the
potential for training storms along the slow moving front will lead
to an elevated flood threat tonight, mainly across SW counties
where heavy rain has fallen over the past few weeks. Showers and
storms will be possible through the day Tuesday with the surface
boundary stalled across southern counties.
By Tuesday night, the front will push just south of the CWA with
surface high pressure building in. Weak subsidence aloft behind
the cold front may begin to break up clouds overnight. This
combined with surface moisture and light winds may lead to patchy
fog in spots.
Expect below average highs tomorrow due to clouds across the south
with northerly surface flow behind the front. Lows will be near
average tonight and fall below climatological average tomorrow night
as cooler air filters in. Especially across NW counties where lows
could drop into the 50s.
&&
.Long Term...(Wednesday through Monday)
Issued at 319 PM EDT Mon Aug 8 2022
The cold front should be just south of central Indiana to start the
long term. The proximity of the front and the upper trough moving
through from the west support small mainly early day PoPs over the
southern tier. Models were indicating from 250-500 J/Kg mixed CAPE
there, so would not rule out a rumble or two of thunder. Meanwhile,
PWATs will still be in the 75% moving average, a moderate to heavy
shower not out of the question. By Wednesday night, drier air will
briefly work in as the front settles south. However, sharp trough
will pivot over Ontario and the Great Lakes which will send a
secondary front south across the area Thursday. With weak
instability and PWATs over 1.75 inches, can not rule out a PM
thunderstorm.
After that, surface high pressure will provide subsidence and
combined with a dry column and north and northeast winds, will
result in tranquil weather with seasonably cool temperatures and
comfortable humidity levels with afternoon highs in the upper 70s to
lower 80s and overnight lows mostly in the 50s.
As the surface high shifts to the east coast late in the weekend,
modest southerly flow around the high will gradually bring in higher
moisture. In addition, central Indiana will be under northwest flow
aloft overtop a Rockies ridge. This setup puts the area potentially
in the path of upper Midwest MCS activity.
&&
.Aviation...(00Z TAF Issuance)
Issued at 650 PM EDT Mon Aug 8 2022
Impacts:
* Convective coverage will increase through the evening and continue
overnight
* Restrictions possible within showers and storms this
evening...otherwise mainly VFR
* MVFR ceilings developing overnight with IFR conditions possible
towards daybreak Tuesday
* Low ceilings persisting Tuesday along with scattered convection
Discussion:
Scattered convection that had fired within the moist and unstable
air across the southern half of central Indiana during the afternoon
has largely diminished early this evening. Convection however is
increasing over northern Indiana and eastern Illinois near and just
behind a cold front. This trend will continue through the evening as
the boundary drops into the region from the north and showers and
storms increase in coverage and begin to impact the terminals.
Periodic showers and storms will continue overnight with ceilings
lowering to MVFR then eventually to IFR towards daybreak Tuesday.
Lower ceilings will linger into Tuesday afternoon before lifting
back to VFR as the increasingly diffuse boundary drifts south
towards the Ohio River by late day. Scattered convection will
continue as well...gradually focusing south of the terminals by mid
to late afternoon.
Southwest winds will veer to N/NW overnight as the front slides into
the region. Expect variable wind directions into Tuesday until later
in the day as the boundary pushes south of the area and a more
uniform N/NE wind develops.
&&
.IND WATCHES/WARNINGS/ADVISORIES...
Flood Watch until 5 AM EDT Tuesday for INZ051>053-060>062-
067>070.
&&
$$
Update...Ryan
Short Term...Melo
Long Term...MK
Aviation...Ryan
Area Forecast Discussion
National Weather Service Phoenix AZ
539 PM MST Mon Aug 8 2022
.SYNOPSIS...
The main storm chances for today will begin in the eastern
Arizona high terrain and parts of the western deserts this
afternoon before possibly spreading into the lower deserts and
Phoenix this evening and tonight. Storm chances will increase
noticeably tomorrow and then remain elevated through next weekend
and into early next week due to abundant moisture and an active
Monsoon pattern in place. Occasionally heavy rainfall, localized
flash flooding, gusty winds and localized blowing dust remain
likely through early next week. High temperatures will also remain
slightly below to near normal through early next week.
&&
.DISCUSSION...
The H5 Monsoon ridge is ideally positioned near the 4-Corners with
moist E flow through the mid-upper levels aloft. GOES WV imagery
indicated a very moist airmass across the region with inverted
disturbances pushing W into SE CA where GOES imagery and radar
also indicated an area of scattered showers and storms/MCS where
localized flash flooding is happening this afternoon including
near I-10 and JTNP. Early afternoon radar also showed widely
isolated to scattered distant thunderstorms across the high
terrain of N, E and S AZ. The E AZ storms were associated with
additional E wave vort clusters advancing from NM. The latest
ACARS soundings shows an increasingly moist airmass with PW
having climbed to 1.7->1.9" while mesoscale analysis indicated PW
>2" across SW AZ and into SE CA. MU and SB CAPE had also increased
to >2-3K j/kg.
Some HREF members still favor pronounced convection with locally
heavy rainfall developing this afternoon across the across S Gila
Cty and near Globe and burn scar areas before descending into the
lower deserts and parts of the Phoenix Metro around 04Z. The HRRR
however is an outlier and has recently backed off on that notion
by both delaying and weakening the convection coming off of the
high terrain this evening. However all members continue to favor a
gusty E outflow this evening pushing into the Phoenix metro and N
Pinal. The potential for patchy blowing dust moving west remains
possible, although most likely for N Pinal Cty and the SE-E Phx
Metro Valley
For tomorrow the HREF and ensembles are in agreement on an uptick in
storm chances and coverage from E to W across the region with POPs
increasing to near 50% for Phoenix and the lower deserts, to 60-70%
for the E AZ high country, and 20-30% for SW AZ and SE CA. WPC Day
2 ERO also features a "slight risk" over much of the region for
tomorrow. Some HREF members start with some shower activity W of
Phoenix in the Tue morning hours moving in from in S-SE AZ.
However the main convection will likely start in E-SE AZ
associated with the next E wave(S) and will push into the Phoenix
Metro and the lower deserts Tue evening. Good (>50% for >35 mph
gusts) chances of strong gusty winds, from both the S-SW and E and
locally dense blowing dust will likely be followed by locally
heavy rainfall and localized flash flooding in the high country
and the lower deserts.
Going through the rest of the week and possibly beyond, ensembles
continue to be in very good agreement that the subtropical high
pressure will remain situated northeast of the four corners
region. This overall positioning of the high will be favorable for
continuous moisture advection into the desert southwest with PWAT
values across the lower elevations ranging between 1.7 and 2.0
inches. In addition to the continuous moisture advection, there
will be periodic easterly waves that will migrate into the region,
which will aid in increasing the storm coverage. However,
determining the timing of each individual wave as it approaches
the region is difficult this far in advance. NBM PoPs through the
period range between 25-50% in the lower elevations and between
40-70% across the higher terrain. With the increased moisture and
potential cloud cover from convective debris, high temperatures
during the next several days will remain near to slightly below
normal.
&&
.AVIATION...Updated 0039Z.
South-Central Arizona including KPHX, KIWA, KSDL, and KDVT:
The environment over Phoenix is still capped this afternoon with
FEW to SCT small cumulus. There are storms surrounding the area
with storm motion to the west. There are a couple outflows moving
toward the metro area with the closest one to the northwest that
could provide a light northwest wind shift at KDVT. The more
favorable outflow(s) will be from showers and storms moving toward
the metro from the east this evening. Most favorable timing of an
outflow is still around 4-6Z. Probability of outflow gusts
exceeding 30 kts is around 30-40%, which could also generate
blowing dust at these magnitudes. There is also a 30% for showers
and storms to survive into or redevelop in the metro this evening
with the outflow(s), although most hi-res models weaken the
activity the further west they push. Storm chances in the metro
will be higher Tuesday afternoon and evening. Lowest cloud bases
will mostly be around 10 kft, but could dip to 7-8 kft with a
storm. Greatest cloud coverage will be during the evening and
overnight.
Southeast California/Southwest Arizona including KIPL and KBLH:
Westerly winds at KBLH now are expected to eventually shift back
southerly or become variable this evening and overnight. East to
southeast winds at KIPL will prevail for at least the next hour or
so, but storms over the mountains to the west may eventually push
a gusty outflow through the Imperial Valley with winds shifting to
the west. There is a low chance (10-15%) for VCSH or VCTS at KIPL
with an outflow this afternoon and evening. Winds should
eventually turn back easterly tonight after any outflow. There
will be another chance for VCSH and VCTS Tuesday morning, better
at KBLH (10-20%), as hi-res models suggest elevated convection
moving through SW AZ. FEW to SCT clouds based around 10 kft will
be common, with SCT to BKN higher clouds, through the period.
&&
.FIRE WEATHER...
Active monsoon storm conditions are expected during the next
several days as moisture levels remain elevated across the area.
With the elevated moisture levels in place, MinRHs will range
between 25-40% with excellent overnight recoveries. Therefore, the
fire danger threat is expected to remain low for the foreseeable
future. Winds for the most part will remain light, with the
exception of thunderstorm outflows generating stronger gusts.
&&
.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...None.
CA...None.
&&
$$
DISCUSSION...Sawtelle/Lojero
AVIATION...Benedict
FIRE WEATHER...Lojero