Forecast Discussions mentioning any of "ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 10/09/23

Area Forecast Discussion

National Weather Service Indianapolis IN

 1001 PM EDT Sun Oct 8 2023

.Forecast Update...
Issued at 1001 PM EDT Sun Oct 8 2023

Upper level energy is working with a weak surface low to generate
some sprinkles and very light showers this evening. Forcing will
increase some with these features into the early overnight, and this
will increase the coverage of showers and sprinkles (which is
already occurring as seen on radar).

However, these will continue to fight a dry lower atmosphere.
Current forecast had this pretty well covered by keeping PoPs in the
chance category, with highest PoPs in the I-74 corridor. Tweaked
these as needed based on latest trends seen on radar and hi-res
model data, but no significant changes were made.

Clouds will diminish some late tonight, mainly across the southwest.
However, if more clearing occurs than expected in the northwest,
temperatures could fall to colder than expected readings (and into
the upper 30s).

&&

.Short Term...(This evening through Monday)
Issued at 307 PM EDT Sun Oct 8 2023

Cloudy...cool afternoon ongoing with a few sprinkles drifting
southeast. Temperatures have been held down by the cloud deck today
with 50s common across much of the forecast and temps closer to 60
confined to the lower Wabash Valley.

Amplified flow pattern aloft across the country this afternoon
highlighted by a deep trough over the eastern half of the country
and ridging out west. The upper low will strengthen and pinwheel
south of James Bay through Monday...keeping a cool cyclonic flow
aloft across the Ohio Valley. Weak impulses aloft will drift across
the area through tonight as well and combine with a front to produce
an increase in coverage to light showers before dry weather returns
for Monday.

The moist layer has largely been confined to areas above 800mb so
far but recent ACARS soundings do show an expansion of moisture into
the boundary layer which should only increase over the next few
hours. Scattered sprinkles will continue for the remainder of the
afternoon but should see an uptick in precip coverage this evening
as a surface wave tracks into the mid Mississippi Valley and
moisture and lift increase slightly. The surface low will move
across the lower Ohio Valley tonight and pull the frontal boundary
across the forecast area through daybreak. Showers should end from
northwest to southeast during the predawn hours but clouds may
largely hold into Monday morning before fully scattering...
especially across the eastern half of the forecast area. Winds will
occasionally gust to 20-25mph through late day before dropping back
to light and variable tonight.

While the region will remain on the back side of the deepening upper
low and within a cyclonic flow regime aloft Monday...model soundings
and RH progs do show dry air advecting into the Ohio Valley as a
lobe of high pressure expands south from the northern Plains. This
will bring a return to mostly sunny skies for much of the day with
any diurnal cu largely confined to the northeast part of the
forecast area. W/NW winds will increase to 10-15mph for the
afternoon as boundary layer mixing deepens.

Temps...felt the overnight lows were too cold from the model blend
and may be due to clearing the cloud deck too quickly late tonight.
Nudged most areas up into the lower 40s. Warmer on Monday but still
another cool day as low level thermals support highs from the upper
50s north to the mid 60s south.

&&

.Long Term...(Monday night through Sunday)
Issued at 307 PM EDT Sun Oct 8 2023

A large upper low will be in place for the start of the long term,
centered of the Hudson Bay. This will keep the cooler temperatures
in place for Tuesday as we have NW flow aloft. The upper flow will
start to shift more westerly by midweek and then quickly turn
southwesterly for the end of the week. This shift will be caused by
a low pressure system moving in from the west, which will bring a
warm up in temps for a few days with highs in the 70s. It will also
bring a much needed and good chance of rain for the end of the week
and into the weekend.

Wednesday to Thursday, models show a boundary setting up over
northern Indiana which will bring PoPs for the northern half of the
forecast area for those days. As the eastward moving low approaches,
rain along the associated cold front will bring more widespread PoPs
for the end of the week, with best chances during the day Friday.
Should the northern boundary midweek shift southward, rain chances
for central Indiana will increase, but should it set up further
south we won`t see rain until late Thursday or Friday. Behind this
system confidence for rain is again low as models haven`t quite come
to an agreement yet. The low may stall just to the NE or E which
could keep light rain in the area throughout the weekend. There is
high confidence however in temperatures dropping behind the cold
front as highs this weekend look to stay in the 50s.

&&

.Aviation...(00Z TAF Issuance)
Issued at 733 PM EDT Sun Oct 8 2023

Impacts:

* Scattered showers possible near KIND/KBMG from 04-08Z tonight

* VFR conditions expected through the period, but brief MVFR
  visibilities cannot be ruled out with any showers tonight

Discussion:

Scattered showers are possible tonight near KIND/KBMG as a mid-level
disturbance moves through. Drier air will then advect into the
region towards daybreak Monday with showers and clouds diminishing.
VFR conditions are expected through the period, but brief MVFR
conditions cannot be ruled out with any showers tonight.

Winds will be light and variable tonight. Expect a resumption of
northwest winds on Monday.


&&

.IND WATCHES/WARNINGS/ADVISORIES...
None.
&&

$$

Update...50
Short Term...Ryan
Long Term...KH
Aviation...Melo



Area Forecast Discussion

National Weather Service Phoenix AZ

 431 PM MST Sun Oct 8 2023

.Update...Updated Aviation

&&

.SYNOPSIS...
Above normal temperatures will continue through first half of the
week before a gradual cooling trend brings readings back closer to
the seasonal normal during the latter half of the week. While an
isolated shower and perhaps an embedded thunderstorm will be
possible through Monday, dry weather with clear skies will dominate
the region the remainder of the week.

&&

.DISCUSSION...
A blocked Conus flow pattern continues this afternoon with high
amplitude ridging centered over the Rockies and a deep, cold core
cyclone wobbling across the Great Lakes. While this configuration
would typically portend warm, quiet weather over the Southwest, an
active subtropical jet and embedded disturbances undercutting the
western ridge were supporting forced ascent acting on modest
midlevel moisture profiles. While both in-situ ACARS data and model
forecast sounding only depict 6-7 g/kg mixing ratios and low level
T/Td spreads in excess of 40F, near saturation in a 600-500mb layer
was yielding elevated MUCape up to 500 J/kg. As a result, isolated
convective elements should be common the remainder of the day and
even into the overnight hours as the region remains in favorable
cyclonic, divergent flow aloft. However, the dry subcloud layer will
likely limit any accumulations across lower elevations, but rather
encourage erratic, evaporationally forced outflows near any more
robust activity.

HREF membership highlights isolated showers and embedded storms
redeveloping Monday as the synoptic pattern remains favorable for
large scale ascent amidst marginal moisture profiles. While the vast
majority of activity should be focused over mountainous areas outside
the forecast area, some cells could leak into foothill and higher
elevations of the CWA. Thus, bumped required NBM POPs initialization
very slightly towards broader HREF output. Thereafter, strong
Pacific jet energy will break into the NW Conus as the western
hemisphere blocking pattern starts to realign. The subtropical jet
and weak waves influencing the current weather will quickly be
absorbed downstream with the SW Conus falling under subsident anti-
cyclonic flow on the equatorward side of the incoming jet streak
during the midweek period.

During the latter half of the week, ensemble members are in very
good agreement depicting the incoming shortwave intensifying and
inducing lee cyclogenesis through the central high plains. Remaining
on the anti-cyclonic side of the jet will ensure dry weather, though
H5 heights eroding to around 576dm and Great Basin surface pressure
rises aiding cooler air filtering south will result in temperatures
retreating close to the seasonal normal. Otherwise, the tightened
gradient should result in a period of breezy conditions though the
limited height falls and jet energy dipping into the CWA will keep
gusts reasonable for this time of year. Ensemble trends through the
end of the week suggest some form of shortwave ridging returning to
the SW Conus though moderate uncertainty exists regarding the
magnitude and duration of this pattern. Regardless, at least a brief
period of temperatures returning to a slightly above normal category
appears likely over the weekend.

&&

.AVIATION...Updated at 2330Z.

South-Central Arizona including KPHX, KIWA, KSDL, and KDVT:
No major aviation concerns are expected during the TAF period. A
few virga showers are possible through the evening hours which
could produce brief periods of gusty and erratic winds. However,
the majority of the shower activity should continue to remain to
the N and E of metro terminals. SCT mid-level clouds will be
present over the region through tonight, with bases ranging 12-15
kft.

Southeast California/Southwest Arizona including KIPL and KBLH:
No aviation concerns are expected during the TAF period. Winds at
IPL will follow diurnal tendencies, with speeds remaining below 10
kts through the period. At BLH, NW winds late this evening through
early tonight will give way to more variability for the remainder
of the period. Besides a FEW mid-level clouds, skies will be
mostly clear through the forecast period.

&&

.FIRE WEATHER...
Temperatures will remain slightly above normal over the next couple
of days before retreating close to the seasonal normal during the
latter half of the week. An isolated light shower with perhaps an
embedded thunderstorm will be possible in eastern districts through
Monday with dry weather thereafter. Wetting rainfall should not be
expected. Minimum afternoon humidity levels will fall mostly in a 15-
25% range as fair to good overnight recovery in a 30-60% range
deteriorate to a poor to fair 20-45% range late in the week. Winds
should begin to strengthen towards the middle of the week as a
weather system passes north of the area, though remaining below
critical thresholds.

&&

.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...None.
CA...None.
&&

$$

DISCUSSION...18
AVIATION...RW
FIRE WEATHER...18