Forecast Discussions mentioning any of
"ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 09/05/22
Area Forecast Discussion...UPDATED
National Weather Service Chicago/Romeoville, IL
859 PM CDT Sun Sep 4 2022
.UPDATE...
Issued at 859 PM CDT Sun Sep 4 2022
The main forecast tweak for overnight into Monday morning was to
boost sky cover.
Slow-moving showers and a couple good rain producing storms have
diminished or exited the forecast area. There have been sporadic
pinprick echoes dotting radar imagery at times this evening in
northeast Illinois and northwest Indiana more indicative of
sprinkles. Some of this is forced by residual influence of the
small mesoscale vorticity center noted in the earlier discussion
near the border Cook/Lake IN Counties, while it also may have been
partly due to light lake effect instability. Cannot rule out some
widely patchy sprinkles for the next few hours, but for the most
part precipitation should be done until a possible afternoon
expansion again in the southeast forecast area on Labor Day.
Chances and conditional coverage look less than today.
The stratus has expanded in area significantly since mid
afternoon. Recent aircraft soundings from ORD and MDW have sampled
the saturated layer with about a 2,500 ft depth and below a
couple degrees C inversion. So do not envision the clouds going
anywhere unless the dry push from the northeast seen over west
central Michigan is able to protrude into mainly far northern
Illinois. Several guidance members do indicate this and dew points
in southeast Wisconsin have dropped into the mid 50s. But the
pattern and the time of day would place that more on the unlikely
side of outcomes. So confidence is medium or so but enough at
least to boost sky cover. A low diurnal range was already well
covered in the forecast. See temperatures near the lake basically
not moving with a marine layer being advected in through tonight.
The northeast uptick in winds that occurred mid to late afternoon
resulted in another bump up in waves. Recent wave observations
are around 5 ft at Wilmette, IL and just under 4 ft at Michigan
City. Using these to calibrate wave output data from model
guidance does keep waves higher a smidge longer on the far
northwest Indiana shore, namely Lake County, but still looks like
waves overall will be just below high risk by late morning/midday
on Labor Day. The overnight shift will evaluate this further.
MTF
&&
.SHORT TERM...
Issued at 237 PM CDT Sun Sep 4 2022
Through Monday night...
What you see is what you will get in the short term as upper level
pattern remains pretty stagnant across the region. Upper low near
KSTL this afternoon is forecast to evolve into more of an
elongated shear axis embedded within the narrow, stationary upper
trough stretching from the eastern Great Lakes back into the
southern Plains.
A small scale mesoscale vorticity center has kept a pretty steady
rain going so far today over the southeastern Chicago suburbs into
northwest Indiana with some occasional lake effect showers into
Chicago to the north of this vort. Anticipate this feature will
weaken this afternoon with decrease in coverage of the associated
rain.
Farther south, some breaks in the cloud cover has allowed for a
bit of insolation to occur. Even with just a bit of heating,
atmosphere is becoming modestly unstable due to the unseasonably
moist boundary layer air mass with dewpoints around 70F.
Anticipate scattered showers and isolated thunderstorms to
continue through sunset with a decrease in coverage and intensity
of this activity this evening and only a small chance of showers
overnight into Monday morning.
Better boundary layer moisture and resultant instability looks to
be farther south Monday afternoon, so while we will likely see
scattered showers again Monday afternoon over about the
southern/southeastern half of the CWA the thunderstorm threat
Monday afternoon appears lower than this afternoon. Did maintain a
slight chance in the far southern counties where some weak
destabilization could allow for a couple lightning strikes, but
the better thunder chances appear to be south and east of our CWA.
- Izzi
&&
.LONG TERM...
Issued at 237 PM CDT Sun Sep 4 2022
Tuesday through Sunday...
The shortened work week begins with a broad low-mid level Low
centered over south-central Illinois. Most guidance has a scattered
to widespread swath of showers developing across the northern
periphery of the system and falling on the CWA. Whereas there was
quite a bit of discrepancy in shower coverage with the Low
yesterday, guidance has come to a somewhat fair consensus that
at least some isolated showers will probably be in the area on
Tuesday, particularly Tuesday afternoon. The amount of instability
that we`ll build up is still a hot topic among models but it
seems like I-88 is a very rough cutoff for instability. Therefore,
thunder chances were limited to areas south of I-88, though at
this point it appears that anywhere north of I-80 will heavily
struggle to develop any thunderstorms. Even further south in the
CWA, skinny, elongated CAPE profiles with weak flow aloft favor
run-of-the-mill pop-up convection that should collapse on itself
just as quickly as it spins up, similar to what much of the area
saw on Friday.
The latter half of the work week will be rather quiet as our very
uneventful synoptic pattern continues. The CWA will spend one more
day in the 70`s before most areas climb back into the 80`s by
Wednesday. At the moment, there doesn`t appear to be much to write
home about until next weekend when a potent upper level trough is
slated to push across the north-central CONUS. This translates to
strong surface Low trekking across central Canada and an associated
cold front expected to move across the Midwest bringing weekend rain
chances to the area, primarily on Saturday. The GFS and Euro have a
very not-so-summer-like airmass moving in behind the front possibly
giving us our first real taste of a transition to fall early next
week.
Doom
&&
.AVIATION...
For the 00Z TAFs...
Aviation weather challenges for the 00Z TAFs:
* Continued low MVFR ceilings through tonight and into Monday
afternoon.
* Gusty northeasterly winds Monday afternoon.
Winds remain northeasterly throughout this TAF period, with some
gusty winds early this evening quickly dropping down to or below 10
kt. Extensive MVFR ceilings between 1000 to near 2000 ft stretch
upstream as far as Michigan and even into Quebec. Aircraft-based
soundings show this deck is a couple of thousand feet thick, with a
strong inversion above it, so this MVFR ceiling is expected to
remain in place throughout this evening and into tomorrow afternoon.
Guidance indicates that ceilings will climb up above MVFR Monday
afternoon, with wind gusts picking up to the upper teens. Ceilings
are forecast to continue to increase throughout the late afternoon
into the early evening as northeasterly winds decrease again to
around 10 kt in the evening.
BKL
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...Beach Hazards Statement...ILZ006-ILZ103-ILZ104 until 10 AM
Monday.
IN...Beach Hazards Statement...INZ001 until 4 AM Monday.
Beach Hazards Statement...INZ002 until 10 PM Sunday.
LM...Small Craft Advisory...IL nearshore waters until 4 AM Monday.
&&
$$
Visit us at weather.gov/chicago
Follow us on Facebook, Twitter, and YouTube at:
www.facebook.com/NWSChicago
www.twitter.com/NWSChicago
www.youtube.com/NWSChicago
Area Forecast Discussion
National Weather Service Phoenix AZ
442 PM MST Sun Sep 4 2022
.UPDATE...Updated 00Z Aviation section.
&&
.SYNOPSIS...
Thunderstorm potential will remain seasonally low through at
least the middle of the week as strong high pressure expands
across the region. As a result, heat will be the greater concern
with above normal temperatures. An excessive heat warning remains
in place for many lower desert locations. Late in the week, clouds
and moisture should increase rapidly across the area with better
shower and thunderstorm chances returning.
&&
.DISCUSSION...
Strong midlevel high pressure remains entrenched over western UT
early this afternoon while the remnants of Javier continue to
drift west of the Baja. Visible satellite reveals that a few
tenuous clouds are continuing to drift across SE California and
far SW Arizona on the outer reaches of the remnants of Javier, but
little to no precipitation is expected today. Continued dry
easterly flow through much of the troposphere is persisting with
a corresponding gradual drying of the lower atmosphere. Surface
mixing ratios are still a reasonable 10 g/kg in Phoenix per the
latest ACARS soundings, but drier air persists just above the
surface leading to very limited convective chances for most
locations in south-central AZ. Further west along the Colorado
River Basin moisture remains somewhat elevated, with mixing ratios
of 12-14 g/kg. Wind shear is elevated for portions of this area,
such as the Blythe to Parker corridor with plenty of MUCAPE
present. HREF guidance shows a fairly strong possibility of a
cluster of showers and thunderstorms developing and moving into La
Paz and Riverside Counties from the northeast in the early
evening today along a weak shortwave. This conceptually makes
sense given the favorable convective environment. HREF guidance
also shows a 70-90% chance of 30+ kt winds but a minimal chance
of 50+ kt winds, meaning gusty winds are likely but they will
probably remain sub severe. This implies that blowing dust will
be a concern for these same locations. A second shortwave may kick
off a shower over Gila County (5-10% chance) but given the drier
air this seems unlikely to occur with an even lower probability of
moving into the valleys (<5% chance).
Over the next few days the high pressure area will strengthen and
expand, putting the lid on convective chances for at least a few
days. 500 hPa heights will reach a record breaking (for this time
of year) 600 dm over the Great Basin and may reach as high as 597
dm or so over the Phoenix CWA, which is above the 90th percentile
on the NAEFS climatology. ECMWF EFI values are not as notable for
maxT with values of 0.5 to 0.7. The entire atmospheric column
will warm, but as implied by the differences in the EFI and NAEFS
climatology, not all of the upper level warming will be realized
at the surface. Still, high temperatures will creep up to around
109-113 by Tuesday. High temperatures will then begin to gradually
cool as the upper level high starts to diminish midweek. Based on
this, the Excessive Heat Warning will continue through Tuesday
for SE California and Wednesday for the Phoenix metro area where
the onset of cooling will be delayed slightly.
The next forecast challenge will be the influence of a newly
developed tropical depression well to the south off of the coast of
Mexico. The official NHC track strengthens this system into a
hurricane before it parallels the coast of Baja starting next
Thursday. Ensemble guidance then suggests that this system will
weaken as it approaches southern California and possibly turn out to
sea towards next weekend. There is some potential that moisture
from this system could result in heavy rainfall, especially over
southeast California, but it would be irresponsible to speculate
on the details given the multitudes of uncertainties at this lead
time. However, similar systems have resulted in higher impact rain
events in the past so we will be keeping a close eye on it in the
days ahead.
&&
.AVIATION...Updated 2340Z.
South-Central Arizona including KPHX, KIWA, KSDL, and KDVT:
No aviation concerns expected through the period. East to
southeast winds with speeds around 10 kts will prevail through
sunset before weakening afterwards through the overnight period
into early tomorrow morning. A westerly wind shift is anticipated
by late tomorrow afternoon with speeds of around 10 kts. Generally
mostly clear skies can be expected through the period.
Southeast California/Southwest Arizona including KIPL and KBLH:
KBLH- No aviation weather concerns expected through the period.
Generally easterly winds with speeds aob 10 kts expected, however,
some thunderstorm activity currently across Mohave County
may send an outflow boundary towards the terminal early this
evening causing some gusty winds from the northeast, however, no
direct thunderstorm impact expected at this time.
KIPL-No aviation weather concerns expected through the period.
Westerly winds with speeds aob 10 kts will prevail through the
evening hours, becoming light and variable during the overnight
and continuing into tomorrow morning. Winds will generally be
southeasterly during the late morning through the afternoon with
speeds aob 10 kts.
&&
.FIRE WEATHER...
Above normal temperatures will persist through the middle of the
week as strong high pressure maintains its intensity over the
region. In addition, thunderstorm potential will be nearly
eliminated in all but the most favorable high terrain areas. This
drier regime should also lower minimum afternoon humidity levels
fall into a 10-25% range, while overnight recovery only becomes fair
to good in a 25-60% range. Winds should not pose any significant
concerns with the typical diurnal upslope gusts. An abrupt switch to
a cooler and much more humid pattern will begin during the end of
the week though specifics on which districts may have the best
opportunity for wetting rains remains very uncertain.
&&
.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...Excessive Heat Warning until 8 PM MST Tuesday for AZZ530.
Excessive Heat Warning until 8 PM MST Wednesday for AZZ537-
540>544-546-548>551.
CA...Excessive Heat Warning until 8 PM MST Tuesday for CAZ560>570.
&&
$$
DISCUSSION...Hodges
AVIATION...Lojero
FIRE WEATHER...18