Forecast Discussions mentioning any of
"ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 10/21/21
Area Forecast Discussion
National Weather Service Northern Indiana
703 PM EDT Wed Oct 20 2021
.SYNOPSIS...
Issued at 621 PM EDT Wed Oct 20 2021
Scattered showers and a few storms will persist tonight into
early Thursday, with a few lingering showers persisting into
Thursday afternoon across northern Indiana and southern Lower
Michigan. Turning cooler otherwise through the weekend with dry
conditions expected Friday into Saturday. Rain chances return
Sunday into early next week.
&&
.SHORT TERM...(This Evening through Thursday)
Issued at 240 PM EDT Wed Oct 20 2021
An uptick in mid level clouds, southwest winds, and possibly a few
showers will be the story into this evening as a corridor of
isentropic ascent and elevated moisture transport shifts east into
the area in advance of an approaching low pressure system. Better
prospects for scattered showers will arrive later tonight into early
Thursday morning as the main/narrow pre-frontal pwat axis moves
through under increased forcing via DCVA and height falls. There
also could be some embedded thunder and brief heavier rain rates
during this time given the stronger forcing and overspread of
steeper mid level lapse rates. With that said, coverage continues
to look somewhat limited by poor moisture return and quick
progression of the system cold front with light rainfall amounts
expected for most.
The center of low pressure will track into central MI/Lk Huron
tomorrow. This will likely provide a relative lull in precip for
much of the day as the system dry slot works in post-frontal. The
trailing secondary trough/deformation does collapse back south
through the area later Thursday into Thursday evening. A few showers
or drizzle may accompany this feature, especially across northern
zones mid-late afternoon. Cooler otherwise on Thursday with temps
steady or falling in the 50s to low 60s.
&&
.LONG TERM...(Thursday Night through Wednesday)
Issued at 240 PM EDT Wed Oct 20 2021
Thermal troughing on the southern fringe of a deep closed low near
the Quebec/Ontario border will result in cooler than normal temps
Friday into this weekend. There will be a few weak perturbations in
this broad/cyclonic wnw flow, especially Friday before sfc ridging
builds in for Saturday under increasing confluence aloft. Held with
a dry forecast regardless given the overall dearth of moisture and
weak forcing.
Periodic rain chances return to the forecast Sunday into early next
week as low pressure develops across the Central Plains Sunday, then
gradually weakening east through the region early next week. Models
continue to struggle with timing/track with PoPs held in the mid
chance range for most periods. Temps may gradually warm otherwise
during this time as the low level thermal trough retreats.
&&
.AVIATION...(For the 00Z TAFS through 00Z Thursday Evening)
Issued at 621 PM EDT Wed Oct 20 2021
A surface low was near the MN and IA border near MCW. This system
was moving east and was trying to occlude. Farther to the east, a
narrow band of moisture was spreading northeast toward northern
Indiana ahead of an associated front. Showers and isolated storms
were occurring in this band. The lightning detection network
indicated a few flashes mainly near the Indiana/Illinois border.
BUFKIT and aircraft soundings showed fairly dry conditions in the
lower atmosphere along with virtually no instability. Added
vicinity thunder at the SBN terminal for the first few hours of
the TAF period. MVFR clouds will follow behind the front Thursday
morning. Included a MVFR ceiling at SBN after 16Z. FWA may go down
briefly with MVFR ceilings, but for now have them VFR through the
TAF period except for a TEMPO MVFR visibility group before
daybreak.
&&
.IWX WATCHES/WARNINGS/ADVISORIES...
IN...NONE.
MI...NONE.
OH...NONE.
LM...Small Craft Advisory from 8 AM Thursday to 5 AM EDT Friday for
LMZ043-046.
&&
$$
SYNOPSIS...Steinwedel/Skipper
SHORT TERM...Steinwedel
LONG TERM...Steinwedel
AVIATION...Skipper
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Area Forecast Discussion
National Weather Service Phoenix AZ
439 PM MST Wed Oct 20 2021
.UPDATE...
Updated Aviation discussion.
&&
.SYNOPSIS...
Dry tranquil conditions are expected over the next several days
with temperatures warming to around normal starting Thursday and
lasting through the weekend. A slight cool down and breezy
to possibly windy conditions will be likely early next week as a
strong low pressure system tracks mostly to the north of our
region. This system may also bring a chance of precipitation to
the region at some point early next week, but chances may be
limited to higher terrain areas.
&&
.DISCUSSION...
Weak quasi-zonal flow is in place across the area with passing
high clouds. Aircraft and RAP soundings show a few degrees of
warming below 700 mb from this time yesterday, which should result
in afternoon highs a few degrees warmer than yesterday. Height
rises over the region, as ridging amplifies downstream of an
active trough pattern in the northeast Pacific, should yield
another few degrees of warming through Thursday. NBM MaxTs for
both Thursday and Friday are in the upper-80s across the lower
deserts with 20-40% chance of reaching 90 degrees each day most
places. Conditions will also remain dry with light winds through
the end of this week as well.
Around midday Friday the first of a couple of strong and dynamic
troughs will move inland in the PacNW. While this first wave will
remain well north of the local area, heights will be suppressed
slightly which should lead to a few degrees of cooling heading
into the weekend, along with some breezier conditions. NBM
forecast MaxTs for this weekend are in the mid-80s across the
lower deserts both days. The second, more prolific trough will
take shape late this weekend and begin pushing inland in the
northwest CONUS late-Sunday into Monday. Greatest impacts from
this trough are still expected in the coastal states through early
next week. WPC cluster analysis still shows moderate variance
among global members mostly in terms of how far south the trough
will dig and timing. Models continue to support a strong
atmospheric river with this trough, so the amplitude of the trough
will certainly have an influence on precipitation chances for the
local area. It is still too early to say with confidence what the
chances are, but latest NBM still has a 10-20% chance for rain in
south-central AZ, favoring high terrain, around Tuesday. In
addition to the rain chances, this trough will also likely result
in breezy conditions across the region. There is still
uncertainty in magnitudes, but the ECMWF EFI is showing the
potential for unseasonably high winds Monday into Tuesday mainly
north of the local area. Lastly, much cooler temperatures will be
possible with the magnitude of cooling again dependent on the
evolution of the trough.
&&
.AVIATION...Updated at 2339z.
South-Central Arizona including KPHX, KIWA, KSDL, and KDVT; and
Southeast California/Southwest Arizona including KIPL and KBLH:
Light winds surface and aloft (favoring westerly directions above
Fl120 and south/southeasterly below that) will continua through
Thursday except for some modest strengthening above FL210. Surface
winds will be light and follow familiar diurnal patterns overall.
But, there may be a period this evening over the Phoenix area
with light northerly directions during the transition between
early evening westerly and late evening onset of downvalley/drainage
winds (favoring easterly directions). Skies will be mostly clear
tonight followed by another batch of cirrus during the day
Thursday.
&&
.FIRE WEATHER...
Friday through Tuesday:
High pressure in place early in the period will shift to broad
troughing early next week as a strong low pressure system impacts
most of the Western U.S. Moisture levels are likely to increase
modestly late in the weekend into early next week with the weather
system, but precipitation chances are likely to be very limited
for the lower deserts to slightly better over the high terrain.
Near normal temperatures are expected for the bulk of the period
with light winds on Friday becoming breezy during the daytime
hours over the weekend. Even stronger winds will be likely for
Monday when widespread gusts of 20-30 mph will be possible. Min
afternoon RH values will improve through the period starting out
in the teens on Friday, rising to 20-30% for Sunday-Tuesday.
Overnight recoveries will mostly reach between 35-60% through the
period.
&&
.SPOTTER INFORMATION STATEMENT...
Spotters should follow standard reporting procedures.
&&
.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...None.
CA...None.
&&
$$
DISCUSSION...Benedict
AVIATION...17
FIRE WEATHER...Kuhlman