Forecast Discussions mentioning any of
"ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 10/05/21
Area Forecast Discussion
National Weather Service Honolulu HI
332 PM HST Mon Oct 4 2021
.SYNOPSIS...
Locally breezy trades will become strong by the end of the week.
Clouds and showers will tend to focus over windward and mauka
areas throughout this time.
&&
.DISCUSSION...
The return of a weak subsidence inversion at Lihue per this
afternoon`s sounding indicates that the stability gradient that
was established over the state for the last few days is beginning
to diminish. The weakly capped nature of the environment over & in
the vicinity of Kauai means that any pockets of deeper moisture
will still be capable of producing locally taller showers and
heavier rainfall, mainly over Windward Kauai. However, judging
from regional visible imagery the lack of any organized stratocu
upstream suggests that the probability for any heavy rain is quite
low - much lower than last night. The general expectation is
therefore for breezy trades to support a typical trade wind
pattern through mid-week.
Global model consensus remains strong that the evolving pattern
over the north central Pacific will force strong high pressure
south of 40N causing trades to ramp up Wednesday into Thursday,
further strengthening during the weekend. The overall message for
this period is that Wednesday through Friday will feature a
steady strengthening of trade winds with windy conditions likely
for the balance of the weekend. Although showers will tend to be
focused over windward and mauka areas during this time, the
strengthening trades will tend to carry showers leeward with
greater efficiency, particularly overnight.
&&
.AVIATION...
Conditions are primarily VFR across the state. Occasional MVFR
ceilings and brief MVFR visibilities are possible across windward
sections from areas of moisture embedded in the low-level trade
wind flow.
Radar VWPs and recent AMDAR soundings continue to show 25 knots
of wind in the mixed layer and the 00z soundings from both Lihue
and Hilo show an inversion around 6kft. Earlier this afternoon we
issued an AIRMET for moderate low-level turbulence in the lee of
the mountains. These conditions are expected to continue through
the night and potentially through the week.
&&
.MARINE...
High pressure north of the area will continue to produce moderate
to fresh trade winds into Wednesday. A Small Craft (SCA) is
currently posted for the typically windy waters around Maui
County and the Big Island. A stronger high will build in north of
the area late Wednesday and on into the weekend resulting in
stronger trades winds. The SCA will likely be expanded across most
other coastal waters at that time.
A small, long period west northwest swell will continue to fill
in tonight, peak Tuesday through early Wednesday, then lower
gradually through the remainder of the week and on through the
weekend. A series of small, mainly background south swells can be
expected through Thursday. A slightly larger long period south
swell is expected to fill in by Friday, peak on Saturday, then
lower slowly on into Sunday. Easterly trade winds will continue to
produce short period choppy surf along east facing shores through
Wednesday. With the expected increase in trade winds over and
upwind of the island beginning Wednesday, surf heights are
expected in increase later in the week and on into the weekend.
&&
.HFO WATCHES/WARNINGS/ADVISORIES...
Small Craft Advisory until 6 PM HST Wednesday for Maalaea Bay-
Pailolo Channel-Alenuihaha Channel-Big Island Leeward Waters-Big
Island Southeast Waters.
&&
$$
DISCUSSION...JVC
AVIATION...Bravender
MARINE...Burke
Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
855 PM CDT Mon Oct 4 2021
.UPDATE...
855 PM CDT
Minor tweaks to the forecast this evening, mainly to expand low
chance pops for isolated showers this evening east of the I-55
corridor. Also bumped winds up a bit mainly along/over Lake
Michigan this evening where a few marine observation platforms
have tagged a few 25-30 mph gusts. Otherwise, going forecast
appears to be on track.
Evening surface analysis placed gradually weakening 1015 mb low
to our east near Toledo OH. Meanwhile, slowly strengthening
surface high pressure was to our north/northwest over the upper
Mississippi Valley and northern Lakes. Between these two pressure
centers, a broad area of low level north-northeasterly low level
winds were maintaining mild/moist conditions across the region,
with occasional spits of sprinkles/showers beneath our old upper
trough which remains focused just to our east while slowly
weakening. Mid-evening radar imagery indicates some light showers
mainly across the southeast parts of Chicago and the IL/IN state
lake area, wrapping southwestward. These should affect primarily
areas along/east of I-55 through the remainder of the evening, and
have expanded/increased our low chance pops across this area for
the remainder of the evening hours. Weak low level moisture
transport on northeast low level winds will continue to produce
the potential for spotty light sprinkles or showers overnight
early Tuesday, mainly across the Chicago metro area near Lake
Michigan. Shower chances should decrease from the north Tuesday as
surface high pressure continues to build across the northern
Lakes, though diurnally-driven isolated to scattered showers are
likely again by afternoon south mainly south of I-80.
Otherwise, had also bumped wind/gust speeds up a bit for this
evening primarily along/south of the Lake Michigan shore from
the City into northwest IN, where some 25-30 mph gusts have been
noted likely due to a slight tightening of the pressure gradient
south of the strengthening high to our north. Forecast appears
otherwise on track through the rest of the overnight hours, with
breeze north-northeast winds and mostly cloudy skies maintaining
fairly uniform temps from around 60 to the lower 60s.
Ratzer
&&
.SHORT TERM...
246 PM CDT
Through Tuesday night...
While we have had a bit of sun peak through the low clouds early
this afternoon, widely scattered showers have been developing
across inland sections of northern IL. This appears to be the most
focused along a lower level confluence zone located from north to
south across the far western suburbs of Chicago. While these
showers will produce some brief heavy downpours in the areas they
impact, it appears unlikely we will see much in the way of
lightning from them, especially north of I-80. Recent aircraft
soundings out of ORD and MDW indicate that profiles across
northern IL are less favorable to charge separation then they
have been the previous few days, with little to no surface based
instability reaching above the -10C level. Recent radar imagery
also suggests that these are low topped showers, with generally
remaining below 16,000 feet. For this reason, any thunder
potential this afternoon will be confined to areas south of I-80
across central IL into IN.
While these diurnal showers will dissipate across the area early
this evening, it appears we will continue to see low clouds across
the area tonight into at least Tuesday morning. With the low
level flow shifting off the lake and marginal lake induced
thermodyamics, we could see a few lake induced light showers or
sprinkles at times tonight into early Tuesday morning across
northeastern IL. However, these should not result in any real
impacts should they materialize. Thereafter, some additional
scattered showers will be possible later Tuesday morning into the
afternoon as a large mid- level low sets up across the Lower
Mississippi Valley. It appears the best chances for these
scattered diurnal showers will largely remain south of I-80, along
the northern periphery of the upper low.
KJB
&&
.LONG TERM...
246 PM CDT
Wednesday through Monday...
The closed upper low across the southern Mississippi Valley will
begin to lift northward toward the Lower Great Lakes Wednesday
into Thursday bringing additional chances for showers and some
embedded thunderstorms to the area. At this time coverage looks
more scattered in nature Wednesday afternoon mainly south of I-80
with precipitation lifting north and west through the evening and
overnight hours, gradually expanding in coverage. Precip chances
peak Thursday afternoon with the closed low expected to be
overhead. The upper low eventually gets pulled eastward by the
upper jet on Friday bringing a brief break in precip chances
Friday night into Saturday.
Temperatures through the extended period will continue to be
above normal with highs in the mid to upper 70s with low 80s
possible over the weekend in some areas as ridging builds overhead
in the wake of the departing upper low. Overnight temperatures
will also be well above normal in the upper 50s and 60s.
Confidence in the placement and timing of the various
waves/closed lows rounding the western CONUS trough is on the
lower side, but in general the pattern looks to remain active
early next week.
Petr
&&
.AVIATION...
For the 00Z TAFs...
Forecast concerns for area terminals...
*Ceilings lowering to low MVFR/IFR overnight
*Ceilings return to higher MVFR towards mid to late morning
*Northeast winds persist through Tuesday.
Forecast is a bit quieter tonight compared to the past few days
with just a few lingering showers across the CWA. There is a batch
of showers over southern Lake Michigan that is moving southwest
towards MDW and GYY where some light showers can be expected
this evening. We decided to leave showers out of the ORD TAF due
to low confidence in it reaching the airport, but will continue to
monitor radar trends for changes.
Otherwise the main concern is for lower ceilings overnight.
Current observation trends have been for ceilings to come down to
lower MVFR conditions this evening with guidance indicating some
IFR conditions possible especially closer to the lake later
tonight. Ceilings are expected to lift through the morning
tomorrow with MVFR and even potentially VFR conditions by the
afternoon and evening, especially for inland terminals.
Winds will be northeasterly and gusty this evening with speeds 10
to 15 kts and gusts around 20 kts. Gusts will weaken overnight
along with the speeds to around 10 kts before increasing again
tomorrow afternoon to 10 to 15 kts. A slight wind shift to a more
easterly direction can also be expected later tomorrow evening.
Yack
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...None.
IN...None.
LM...Small Craft Advisory...Gary to Michigan City IN until 4 AM Tuesday.
Small Craft Advisory...Winthrop Harbor to Gary IN until 10 AM
Tuesday.
&&
$$
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Area Forecast Discussion
National Weather Service Memphis TN
952 PM CDT Mon Oct 4 2021
.UPDATE...Evening Update
It is another relatively quiet evening across the Mid-South.
Current temperatures are in the mid 60s to low 70s. Latest GOES
water vapor imagery shows the upper low now approaching the
ArkLaMiss region. This low is forecast to close off by Tuesday
afternoon as it is centered over the ArkLaMiss. Patchy fog will
be possible again tonight mainly for areas east of the MS River.
Overnight temperatures will be in the 60s. Forecast is on track,
no major changes made.
17
&&
PREV DISCUSSION... /issued 326 PM CDT Mon Oct 4 2021/
.DISCUSSION...
GOES water vapor imagery showed a developing upper low digging
south into the Red River valley at midafternoon. A well-defined
dry slot/subsidence band was evident around the southern periphery
of the low, while the beginnings of a baroclinic leaf were
evident in the downstream diffluent flow over the Midsouth.
Showers had thus far failed to materialize outside of northeast
MS. MEM aircraft soundings this afternoon showed a stout inversion
above 750mb, capping deep convection.
Similar to last night, clouds will partially clear, allowing for
patchy radiative fog formation in low-lying areas and river valleys.
Over northeast MS, fog may be more in the form of elevated stratus,
northwest of an inverted surface trof from east central MS to north
central AL.
By Tuesday afternoon, the upper will have closed off and reached
peak strength, centered over the Arklamiss region. An elevated
warm conveyor belt will extend through AL, into the TN River
valley and west TN. Precipitable water values will peak near 1.5
inches over this region through Tuesday evening. A Marginal Risk
will exist for large hail Tuesday afternoon over east central MS.
Instability will taper off rather quickly further north into
northeast MS.
The upper low will lift into north central AR Wednesday afternoon,
with a dry slot wrapping into north MS, and the low level warm
conveyor belt displaced to the east over AL. As stated in previous
discussions, a few cold air funnels can`t be ruled out Wednesday,
given the dry slot wrapping into the delta, over a nearly stationary
surface pressure trof east of the upper low center.
On Thursday, the upper low will begin to open up become more
influenced by the westerlies, arriving to central IL by midafternoon.
A few showers will remain possible over northwest TN and the MO
bootheel, but drying will have already begun for most of the Midsouth.
Upper level ridging remains on track for the early weekend, as a
5920m 500mb ridge expands northeast. Latest guidance depict this
ridge to be more transitory and to our east by Sunday afternoon.
However, given the brief and significant height increases,
official forecasted highs for Friday and Saturday reflect a slight
bump over the NBM.
PWB
&&
.AVIATION...
VFR conditions are expected to continue through the morning hours.
A few rain showers may move into portions of north Mississippi
and southwest Tennessee Tuesday morning. Coverage will increase
through the day and thunderstorms may develop across northeast
Mississippi. Have added vicinity showers and storms at several
sites for Tuesday afternoon. Winds will be mainly from the
northeast at around 5 knots for much of the forecast period.
&&
.MEG WATCHES/WARNINGS/ADVISORIES...
AR...None.
MO...None.
MS...None.
TN...None.
&&
$$
Area Forecast Discussion
National Weather Service Phoenix AZ
541 PM MST Mon Oct 4 2021
.UPDATE...Updated Aviation Discussion.
&&
.SYNOPSIS...
Increasing coverage of showers and embedded thunderstorms will
occur this evening into the overnight hours in response to a
weather system moving into the region. Chances for thunderstorms
will increase going into Tuesday afternoon with some thunderstorms
potentially becoming strong to severe. The main threats with
stronger thunderstorms will be strong winds and localized blowing
dust along with hail. Cooler temperatures will also set in with
many places remaining near or below 90 degrees tomorrow. Below
normal temperatures will continue through the rest of the week
with dry conditions most likely, though forecast uncertainty
increases drastically this weekend.
&&
DISCUSSION...
An approaching upper level low situated off the coast of the
northern Baja Peninsula is helping to force some isolated shower and
thunderstorm activity currently across southern portions of the
state this afternoon. Mesoanalysis data shows limited CAPE values so
much of this is expected to remain in the form of showers with
coverage remaining isolated. Rainfall amounts with these will remain
low with the dry subcloud layer helping to consume some of the rain
that falls. Gusty winds will be possible with any thunderstorms this
afternoon/evening as DCAPE values are upwards of 1,500 J/kg. Phoenix
ACARS soundings this afternoon showed increasing mid-level moisture
with PWATs around 0.75". Moisture will continue to increase across
the region through tomorrow as the upper level low pulls rich
moisture in from the south where objective analysis already shows
PWATs in excess of one inch across northern Mexico. Afternoon highs
today will peak in the mid to upper 90s with some of the warmest
lower desert locales potentially eclipsing 100 degrees.
The increasing moisture across the region will help push PWATs to
around 1.00-1.30", which is above the 90th climatological percentile
for this time of year. Hi-Res guidance shows shower coverage
increasing across the forecast area this evening through the
overnight hours. Much of this activity is expected to come in the
form of showers with a few embedded thunderstorms with associated
QPF remaining low for most places.
As the upper level low ejects across Arizona on Tuesday, steepening
lapse rates, along with increased PVA, instability, and shear, will
enhance the threat for a few organized strong to severe
thunderstorms going into tomorrow afternoon through early evening.
Hi-Res guidance shows CAPE values increasing upwards of 1,000-1,500
J/kg around midday tomorrow as daytime heating increases. Meanwhile,
0-6 km bulk shear will increase to around 40-50 kts tomorrow. With
these shear parameters along with the increasing CAPE and upper
level support, organized thunderstorms will be possible with an
isolated supercell not out of the question; the main threats with
these would be strong wind gusts/blowing dust and severe hail. SPC
highlights the severe weather potential with a Marginal Risk for a
good portion of our CWA east of the Lower Colorado River Valley.
Strong steering flow will help to limit the flash flooding potential
as it will act to decrease the residence time thunderstorms will
have over a given location. However, training thunderstorms are
possible, which would lead to enhanced locally heavy rainfall and
the potential for some flooding concerns. The best potential for any
flash flooding looks to remain across southern Gila County,
particularly the burn scars, where the greater chances for enhanced
rainfall amounts are expected to reside. WPC has southern Gila
County along with the northern fringes of Maricopa County in a
Marginal Risk for the Excessive Rainfall Outlook tomorrow.
In terms of rainfall amounts, QPF has trended down with low amounts
across much of the lower desert areas, especially across southeast
California. NBM QPF continues to indicate that the better rainfall
totals will remain across the Phoenix area and areas to the north
and east. The highest amounts will likely remain confined to the
high terrain areas such as southern Gila County. NBM 90th percentile
QPF shows amounts across Phoenix upwards of 0.80" with amounts
closer to around one inch across southern Gila County. Areas that
see multiple/training thunderstorms would stand the best chance at
achieving these higher amounts.
Aside from the rain, temperatures are forecast to fall below normal
starting tomorrow as afternoon highs are only expected to top out in
the mid to upper 80s across the Valley while the warmer desert
locations may climb into the low 90s.
.PREVIOUS DISCUSSION...
The system will quickly exist to the northeast Tuesday night, and
Wednesday looks to be a quiet day with a developing trough axis
along the coast. By Thursday/Friday, a strong southwest jet streak
develops ahead of the trough axis, yielding passing clouds and
very slightly warmer temperatures. NAEFS and EPS mean winds are
100-120 kt within the jet, unusually strong for this latitude and
time of year (95-99th percentile). Cluster analysis reveals one
solution where an embedded shortwave moves through the trough
axis and across our forecast area, generating light showers as it
does (other solutions maintain the axis further west with no
precipitation).
Heading into the weekend, still quite a bit of uncertainty
regarding troughing energy across the Southwest. Ensembles cluster
into various slower/faster and deeper/shallower solutions. As an
example, the absolute spread in 700 mb temperatures over Phoenix
on Saturday afternoon is +8C to +24C, with a grand ensemble mean
of +17C. The equates to high temperatures on Thursday ranging
from the upper 70s/lowers 80s at the 10th percentile to upper
80s/lower 90s at the 90th percentile. The latest CPC 6-10 Day
Outlook does heavily favor below normal temperatures across the
western US, with a minor dry signal along the US/MEX border.
&&
.AVIATION...Updated at 0040Z.
South-Central Arizona including KPHX, KIWA, KSDL, and KDVT:
Mid v high CIGs will persist through the period with breezy W
winds during early evening with gusts in the low-mid 20 kt range.
Showers east of the Phoenix will begin to move into the area
later this evening (after 03Z). Showers then continue on and off
across Phoenix area from 06-14Z, with more widespread showery
activity, lower CIGs and occasional light embedded thunderstorms
10-14Z as per the tempo group. There is a decent chance (20-30%)
few embedded thunderstorms during another round of afternoon
showers/storms with a PROB 30 thunderstorm group starting 23Z.
Occasionally gusty N component storm outflows with gusts in the
upper teens are currently favored for Tue by mid morning.
Southeast California/Southwest Arizona including KIPL and KBLH:
A storm system will pass across the area during the period with
shower activity gradually developing later tonight after 07-08Z
and becoming more widespread mid morning tomorrow. CIGs will
remain AOB 090 kft though may briefly lower to 5-7 kft in heavier
showers and thunderstorms from mid to late morning and early
afternoon. Gusty SW-NW component outflows from showers and
embedded storms with gusts upwards of 20 kt are also favored
during the later half of the morning. Areas of patchy blowing dust
with reduced slant-wise visibilities are also possible near
showers/storms.
&&
.FIRE WEATHER...
Wednesday through Sunday:
An unsettled weather pattern will remain in place, most likely
resulting in slightly below normal temperatures and typical
humidity values (afternoon values of 20-40% and morning values of
40-60%).
&&
.SPOTTER INFORMATION STATEMENT...
Spotters should follow standard reporting procedures.
&&
.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...None.
CA...None.
&&
$$
DISCUSSION...Smith
PREVIOUS DISCUSSION...Iniguez
AVIATION...Sawtelle/Percha
FIRE WEATHER...Iniguez
Area Forecast Discussion
National Weather Service San Diego CA
200 PM PDT Mon Oct 4 2021
.SYNOPSIS...
An upper level low pressure system off the northern Baja California
coast will move slowly northeast across the area through Tuesday.
This will bring cooling and periods of scattered showers and
isolated thunderstorms this afternoon into Tuesday. The cooling
trend will continue through Friday with additional chances of
precipitation on Thursday and Friday with gusty southwest winds in
the mountains and deserts. Dry warmer weather will return next
weekend.
&&
.DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE...
SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO
COUNTIES...
Scattered light showers and isolated thunderstorms were moving
north over San Diego County and the adjacent coastal waters at early
afternoon. The lower layers of the atmosphere remained dry with mid-
morning AMDAR soundings with low humidity below 750 MB, and dry
conditions continue as there is a lot of virga and only minor
amounts of precipitation reaching the ground. The highest precip
amount so far has been Granite Hills at 0.03". Temperatures were
lower versus Sunday, generally by 3 to 10 deg F.
The upper low will move northeast across far SoCal, and with a lot
of instability aloft tonight, more showers and isolated
thunderstorms will occur. Some rainfall amounts could reach one-half
inch (0.50") through Tuesday, though most locations will receive one-
tenth (0.10") to one-quarter (0.25") of an inch, but amounts will be
quite variable due to the convective nature of the precip. The
precip should exit to the northeast Tuesday afternoon, if not sooner.
A long-wave trough of low pressure will develop over the West Coast
Wed/Thu with the trough axis likely moving through around Fri,
though with some uncertainty in timing. Despite some indications of
a weak atmospheric river possible either in SoCal or far northern
Baja California, ensembles show rather light precip amounts, mostly
less than one-half inch but with great variability (0 to over an
inch) in the ensemble output. Thursday night/Friday is the most
favorable period, but the rain could come as early as Thursday
morning. This trough will bring continued cooling as well, with
daytime temperatures likely 5-15 deg F below normal by Friday. Due
to the increasing height gradients aloft, a round of gusty southwest
winds will likely occur in the mountains and deserts, most likely
Thursday night. Fair weather should return next weekend with a
warming trend.
&&
.AVIATION...
041945Z...VCSH and slight chance of Isold TSRA moving from south to
north through 07Z Tue with cloud bases lowering to 5000-8000 ft MSL.
Increasing chance of ISOLD/SCT SHRA/TSRA, 07-11Z Tue. Isold TSRA
will have lightning and could contain +RA reducing vis 1-5SM along
with erratic winds. After 11Z Tue, VCSH expected through 15Z.
After 15Z Tue... SCT-BKN clouds AOA 10,000 ft MSL.
&&
.BEACHES...
Lightning strikes are possible at the beaches through early Tuesday
morning. Thunder and lightning are most likely overnight tonight.
Please check with your local authorities on potential beach closures
for hazardous water conditions caused by the oil spill.
&&
.MARINE...
A Marine Weather Statement is in effect for possible thunderstorms
that produce lightning and/or gusty erratic winds through early
Tuesday morning. Otherwise, no hazardous marine weather is expected
through Saturday.
&&
.SKYWARN...
Skywarn activation is not requested. However weather spotters are
encouraged to report significant weather conditions.
&&
.SGX WATCHES/WARNINGS/ADVISORIES...
CA...Beach Hazards Statement through Tuesday morning for Orange
County Coastal Areas-San Diego County Coastal Areas.
PZ...NONE.
&&
$$
PUBLIC...Maxwell
AVIATION/MARINE/BEACHES...CO