Forecast Discussions mentioning any of "ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 09/30/21

Area Forecast Discussion

National Weather Service Green Bay WI

 1031 PM CDT Wed Sep 29 2021

Updated aviation portion for 06Z TAF issuance

.UPDATE...
Issued at 842 PM CDT Wed Sep 29 2021

Issued a dense fog advisory for the lake and bayshore counties.
It might need to be extended further west to the Fox Valley later
tonight.

Satellite pictures show cirrus increasing, but these clouds are
very high (35k feet based on 21z aircraft sounding at MKE and 00Z
GRB radiosonde) and should not stop surface air temperatures from
falling that much. Old rule of thumb is that if temperatures fall
3 or more degrees below lowest afternoon dewpoint you often get
dense ground fog. That should happen tonight. Mesoscale model
visibility forecasts also show fog forming in these areas tonight.
&&

.SHORT TERM...Tonight and Thursday
Issued at 238 PM CDT Wed Sep 29 2021

Fog potential late tonight into early Thursday is the main
forecast concern.

GRB CWA will remain on the western periphery of a large Great
Lakes high pressure system. A high-amplitude upper level ridge
will also be situated over the western Great Lakes region. These
features will keep the area dry through Thursday, with only a
gradual increase in high clouds anticipated. Mostly clear skies
and light winds will lead to fog development late tonight into
early Thursday morning, especially over far northeast WI. Lows
tonight are expected to be in the 40s and lower 50s. Highs on
Thursday should be similar to today, ranging from the upper 60s
and lower 70s near Lake Michigan to 75 to 80 well inland.

.LONG TERM...Thursday Night Through Wednesday
Issued at 238 PM CDT Wed Sep 29 2021

The stretch of dry and quiet weather will be coming to an end late
this weekend and weekend as we enter a more unsettled pattern.
Pleasant fall weather looks to return sometime early next week.
Temps will be well above normal through Saturday then drop back
closer to normal but no real cold air in sight for the foreseeable
future.

Thursday night...the quiet weather continues across the area as
ridging remains in control. High clouds will likely be present for
much of the night. Light winds and another strong inversion could
lead to some patchy ground fog. A few spots across northern WI
could drop into the 40s, but most of the area look to see lows in
the 50s.

Friday into Saturday...the quiet/dry fall weather will come to an
end as the ridge breaks down and shifts east of the region and a
trough and frontal boundary approach from the west. Still some
model differences on timing of the front/trough and arrival of the
shower chances. Models trending toward northern WI for the best
chance to see the activity Friday afternoon/evening, but the rest
of the area will still see at least a chance of some shower
activity. Better chances for showers will spread across the entire
area Friday night into Saturday as the front and trough push
across the area and PWATs climb to around 1.5" (near the 99th
percentile for this time of year). Instability will be weak
(skinny CAPE under 500 J/kg) and fairly weak lapse rates, but
could see some isolated storms. Temps look to warm up nicely ahead
of the front on Friday with most spots topping out in the middle
70s to lower 80s. We could approach a couple records. Friday
night is looking mild for early October with lows in the middle
50s to lower 60s. More clouds and shower activity will hold highs
on Saturday in the upper 60s and 70s but this is still above
normal.

Rest of the long term...as the front pushes east of the area on
Saturday night and Sunday, only a few lingering showers will be
possible as one upper trough departs and another digs across the
western Great Lakes. GFS the most aggressive with the second
through, painting more precip over the area, but this looks to be
mainly south of our area. For next week, models continue to
struggle with the overall pattern as how much the closed off upper
level low will retrograde west/south is handled differently. How
far this system is away from the area will determine precip
chances, along with cloud cover and temps. Will favor a dry
solution for now. Temps will settle back near normal for early
next week with more above normal readings looking likely for a
period next week.
&&

.AVIATION...for 06Z TAF Issuance
Issued at 1031 PM CDT Wed Sep 29 2021

Thin Cirrus clouds will continue to move in from the west tonight.
Areas of dense ground fog are expected, especially east of an IMT
to STE line. Ceilings and visibilities could be below minimums at
some airports.

The fog should dissipate by around 1400 UTC Thursday, with good
flying weather for the rest of the day and through the evening hours.
Ground fog is possible again late Thursday night and early Friday.
&&

.GRB WATCHES/WARNINGS/ADVISORIES...
Dense Fog Advisory until 9 AM CDT Thursday for WIZ022-040-050-
073-074.
&&

$$

UPDATE.........RDM
SHORT TERM.....Kieckbusch
LONG TERM......Bersch
AVIATION.......RDM



Area Forecast Discussion

National Weather Service Phoenix AZ

 507 PM MST Wed Sep 29 2021

.UPDATE...Updated Aviation discussion.

&&

.SYNOPSIS...
A weather system will provide slight to moderate chances for
showers and isolated thunderstorms later today and into Thursday,
especially from Phoenix eastward. After continued below normal
temperatures through Friday, increasing high pressure over the
weekend should bring readings back to around normal by Sunday.

&&

.DISCUSSION...
Water vapor imagery shows the southern extension of a trough over
the eastern Great Basin through the lower Colorado River Valley.
Area of cloudiness and modest ascent is resulting some weak
showers across central Arizona this afternoon. Although some
drying has occurred over the past 48 hours, surface dewpoints are
holding in the 50s across the lower deserts, and objective
analysis and ACARS soundings are showing PW values near or just
under one inch over the southern half of Arizona. A few showers
and thunderstorms are possible across La Paz/western Maricopa
Counties this afternoon and evening closer to a low-level moisture
access, but coverage should remain fairly limited. More widespread
activity is expected to develop overnight, primarily from the
Phoenix metro area eastward, as the upper trough continues to
progress eastward. Latest HREF and HRRR runs are very consistent
in highlighting this area overnight, with the main uncertainty
being how far westward the area of showers and thunderstorms will
extend. Precipitation amounts on average should range between 0.10
and 0.25 of an inch, but the HREF maximum precip fields suggest
some isolated locations could receive over 0.50 of an inch. Gusty
outflow winds are also possible in the vicinity of any
thunderstorms, with the HREF highlighting a 10-30% chance that
30 kt winds affect the Phoenix area overnight. This may be enough
to kick up some localized blowing dust in Pinal County.

By daybreak Thursday, the bulk of the activity should shift
eastward primarily into southern Gila County, with drier air
overspreading the lower deserts. Wrap around moisture accompanying
the main upper-level circulation may spread southward off the
higher terrain towards northern Maricopa County during Thursday
afternoon, but expecting any additional precipitation to remain
isolated. The upper low will begin to accelerate late Thursday
east of the region, bringing modest height rises to the Southwest
by Friday. Temperatures will remain below normal and only expected
to reach the upper 80s through Friday in Phoenix, and lower to mid
90s in southeast California.

Temperatures will gradually warm through the weekend closer to
seasonal normal, reaching the upper 90s in many locations Sunday
and Monday. NBM guidance is even suggesting there`s some chance
for triple-digit readings, peaking Monday at 19% in Phoenix and
32% in El Centro. The next feature of interest will be an intense
and well-defined cutoff low near the coast of northern Baja
California, that is forecast to rapidly shift northeastward across
the Southwest Tuesday and Wednesday of next week. The orientation
of this feature is not expected to be too favorable for
significant moisture advection and precipitation across the lower
deserts, but perhaps moreso across northern Arizona. However,
given the potential intensity of this system, some outlying
members are highlighting higher QPF amounts. The 95th percentile
24-hour QPF values of the NBM range between 0.25-0.5 inch for
south-central Arizona, while the 50th percentile values are 0.
Trends will certainly be worth monitoring. Otherwise, a slight
decrease in temperatures into the low 90s along with breezier
afternoons can be expected by mid-week.

&&

.AVIATION...Updated at 0000Z
South-Central Arizona including KPHX, KIWA, KSDL, and KDVT:

Showers and thunderstorms are expected to develop overnight
across portions of south-central Arizona. Latest radar and model
trends are suggesting a more active late evening and overnight
period, and 00z TAFs were adjusted to include VCTS and ceilings
down to 7k feet for the Phoenix sites beginning around 07z. Severe
storms are not anticipated, however the strongest storms will be
be capable of producing wind gusts above 35 kt. Conditions are
expected to improve during the 12z-15z period as the trough axis
pushes slowly eastward through the Valley.

Southeast California/Southwest Arizona including KIPL and KBLH:

No aviation weather impacts expected. Mostly clear skies and
northerly winds occasionally up to 12 kt will prevail through
Thursday at KIPL and KBLH.

&&

.FIRE WEATHER...
Friday through Tuesday:
Conditions will dry out and warm up through the weekend and early
next week. Sunday will be the hottest and driest day with
afternoon highs reaching the mid to upper 90s while minimum RH`s
drop into the 15-25% range. Min RH`s will be slightly wetter on
other days. Overnight RHs will rise into the 40-60% range for most
areas on most nights. Otherwise, winds will be fairly light with
directions favoring local diurnal/terrain influences.

&&

.SPOTTER INFORMATION STATEMENT...
Spotters should follow standard reporting procedures.

&&

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

$$

DISCUSSION...Rogers
AVIATION...Hirsch
FIRE WEATHER...12