Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 08/27/24
Area Forecast Discussion...UPDATED
National Weather Service Aberdeen SD
915 PM CDT Mon Aug 26 2024
.KEY MESSAGES...
- There is an enhanced risk (level 3 out of 5) for severe
thunderstorms, mainly from this afternoon through the evening
hours. the area of main concern will be Hwy 212 and south. All
modes of severe weather will be possible: Large hail, winds over
60 mph, as well as the potential for a few tornadoes.
- Additional thunderstorms are forecast for Wednesday afternoon
into Thursday. Some of these storms could be severe.
&&
.UPDATE...
Issued at 912 PM CDT Mon Aug 26 2024
Showers and thunderstorms have moved into central South Dakota
this evening. This area of precipitation will continue to track
eastward tonight, but it is beginning to look like the northern
part of the area will likely not see any severe weather, while
areas south of Highway 212 may still see a stronger storm or two.
No changes made to winds or temperatures at this time.
&&
.SHORT TERM /THIS EVENING THROUGH TUESDAY NIGHT/...
Issued at 321 PM CDT Mon Aug 26 2024
Showers have been ample on the cold side of the baroclinic zone
today. 18z sounding at KABR showed low CAPE and CIN around 150, so a
well-capped environment with little forcing is in place. Farther to
the east, stratus has held in all day long which is inhibiting
instability and a cap break. However, there has been some weak
convective development along the theta e gradient in west central MN
and into northeast Roberts county which prompted the issuance of a
severe watch. Keeping an eye on the towering cu that`s popping
through the stratus farther to the southwest especially given the 40
to 50 kts of bulk shear. CAPE is under 800 J/kg in that warm sector.
Still believe the best bet for discrete cell development will be
between 21z and 0z south of Hwy 212 and east of I-29 where there was
some minimal scouring of the stratus and closer to the sfc low and
the edge of the thermal boundary.
The second round of storms has developed over Wyoming this afternoon
and is moving east, approaching central SD by 0z. Hi-res, especially
the HRRR and NSSL-WRF have been consistent in dragging an MCS or bow
echo eastward across south central and this agrees with radar trends
in eastern Wyoming. There is some uncertainty regarding how far
north this line will get as it progresses east of the James, but
most guidance points to areas along and south of Hwy 14 being the
most likely to see strong winds, large hail, and perhaps a tornado
in a QLCS.
An upper trough digs in to the northern Plains Tuesday morning
bringing chances for some light showers and reinforcing caa. Highs
will top out in the 70s on Tuesday with temps falling into the 50s
Tuesday night.
&&
.LONG TERM /WEDNESDAY THROUGH MONDAY/...
Issued at 321 PM CDT Mon Aug 26 2024
Tuesday evening we start to move into more of an upper level ridge
pattern that will last at least through the morning hours of
Wednesday before a trough moves in from the west. The cold front
from this low looks to pass across the area Wednesday evening
through the overnight hours. Once the low moves north and east out
of the region we remain in northwesterly flow through the end of the
period.
The low and cold front Wednesday will bring the best chance for
showers and storms for the period. After some slight to low chance
(20 to 35%) PoPs during the afternoon, 40 to 60% PoPs move in for
the evening and overnight hours. Mid level lapse rates of 7 to 7.5
C/km in the NAM and Canadian seem to line up well with MLCAPE values
of around 2000 J/kg over central SD Wednesday evening. The EC and
GFS have the higher lapse rates completely separate from their
higher MLCAPE values closer to 1000 J/kg. So while storms are
expected to form, it is hard to say how likely it is for any to
become severe. That being said, SPC has put out a slight risk (2 out
of 5) for severe weather for most of the CWA. The rest of the period
looks to stay dry.
Wednesday is expected to be the warmest of the period, although not
overly so, with highs generally in the 80s with some low 90s
possible in central SD. The rest of the period should see highs in
the 70s to mid 80s. Gusts of 30 to 35 mph are still expected
Wednesday afternoon across the area and Thursday afternoon in north
central SD.
&&
.AVIATION /00Z TAFS THROUGH 00Z TUESDAY/...
Issued at 623 PM CDT Mon Aug 26 2024
Terminals KABR,KATY,KPIR,KMBG
A line of thunderstorms will track from west to east during the
evening into the overnight hours. The strongest storms will be
along and south of Highway 212, with large hail and strong wind
gusts in excess of 60 mph possible. By early Tuesday morning, the
storms will have exited the area. MVFR cigs may linger through mid
to late morning across the east, including at KATY. The remainder
of the area will see VFR conditions once the storms pass.
&&
.ABR WATCHES/WARNINGS/ADVISORIES...
SD...None.
MN...None.
&&
$$
UPDATE...Parkin
SHORT TERM...Wise
LONG TERM...Vernon
AVIATION...Parkin
Area Forecast Discussion
National Weather Service La Crosse WI
631 PM CDT Mon Aug 26 2024
.KEY MESSAGES...
- Severe Risk(15-30%)Tonight into Tuesday-Primary hazard will be
wind, with large hail and heavy rain possible. Multiple rounds
of storms possible, however greater chances are north of I90
late tonight into Tuesday morning and for parts of southern WI
Tuesday afternoon.
- Continued hot and humid for some Tuesday.
&&
.DISCUSSION...
Issued at 159 PM CDT Mon Aug 26 2024
Overview:
Morning water vapor satellite imagery, 500mb heights, and lightning
showed a decayed convective debris over Minnesota with a couple of
clusters of storms that were over South Dakota and southwest
Minnesota that developed overnight. A 500mb trough of low pressure
was over the northern Rockies with clusters of storms ahead of it
across MN/WY and the Dakotas. A ridge of 500mb high pressure was
centered over the central part of the country. 25.12Z 700mb raob
temperatures showed a solid 12-14 deg covering much of the region.
The MPX 25.12Z 700mb temp was close to 14 deg C., however the RAP
initialization seem slightly too cool at less than 13.5 deg C. At
18Z, surface low pressure was located over southern Minnesota into
northwest Iowa westward into northeast Colorado with a cold front
from central Minnesota into central Nebraska. Temperatures ahead of
the cold front and humidity have warmed into the 80s and 90s with
uncomfortable dewpoints in the 70s and lower 80s. The
combination of the heat and humidity is resulting in heat index
values with several locations 100 to 115 deg. F.
Several offices will be doing special soundings, thus this data
should become available around 3pm.
Severe Risk Tonight into Tuesday-Primary hazard will be wind, with
large hail and heavy rain possible:
Multiple rounds of storms are expected for the region through
Tuesday as a mid-tropospheric closed low over Idaho/associated 500mb
trough is forecast to migrate eastward flattening the ridge.
Forecast soundings initially show a strong cap in place, however
with time, heights lower, eroding the cap from north to south across
the region, allowing the potential for storms to progress
southeastward. Strong instability with MLCAPE build 3000-4500 J/kg
by 00Z...continues 2500-3500J/kg by 06Z...2000-3000J/kg by
12Z...then starts to increase again after 15Z across the southeast
portions of the forecast area 15Z and beyond Tuesday. Deep layer
shear (0-6km)...increases to 35-40kts north of I90 through 06Z, then
wanes overnight, increasing again after 12Z 35 to 60kts behind the
cold front.
There are a few different scenarios related to storms developing
over different parts of Minnesota and how the storms will progress.
Storms may develop over northern, central, and south central MN. The
Corfidi propagation vectors will try to take the storms northeast,
however depending on the moisture transport, instability and cold
pool development progresses this could alter their propagation.
Presently are leaning toward solutions with a strong cap in place.
It will be more difficult to push southward this evening with a
greater chance later tonight into Tuesday morning. For the first
round this evening into the early morning hours, we have the greater
risk for storms between the Twin Cities into central WI. We will
need to monitor MN storm development and should storms develop a
strong cold pool, they could push farther south than expected. Later
overnight, a stronger area of mid-level winds is forecast to track
into the forecast area. With the cooler mid-level temperatures
pushing southward, this brings the greater chance for storms
southward. Thus, have higher pops along and north of I90. The
upper level trough remains to the west of the area with flow
becoming more west and northwesterly. This could limit the greater
storm potential ahead of this wind shift across mainly our southern
counties.
Due to the very high instability and potential large downdraft CAPE
of 1600K/kg, damaging winds will be the primary severe weather risk.
Large hail would be possible with the more discrete storms, however
the deep layer shear does not seem to increase until after 15Z
behind the front. Due to the high precipitable water values in
excess of 1.75 or 2", locally heavy rain will be possible.
Heat and humidity continue for some Tuesday:
The heat and humidity will be suppressed to the south Tuesday, with
highs in the 90s near and south of I90. With dewpoints still in the
mid to upper 70s, continued the the excessive heat warning for
parts of eastern IA and southwest WI with a heat advisory north
toward I90, but limited farther northwest. Clouds and convection
could impact the temperatures, thus will need to monitor for
this.
&&
.AVIATION /00Z TAFS THROUGH 00Z WEDNESDAY/...
Issued at 627 PM CDT Mon Aug 26 2024
Thunder and fog are the primary concerns for aviation interests
over the next 24 hours. Up to three rounds of thunderstorm may
occur at LSE/RST with the most probable round arriving tomorrow
morning with the previous VCTS mentions being increased to
PROB30 mentions with this update. Another round may arrive this
evening with the potential for very strong wind gusts but the
chance for this activity persisting this far eastward - and far
enough south to impact LSE/RST - remains stubbornly unclear so
have covered this potential with VCTS for now. Should things
become more definite, expect amendments with a strong wind group
included as well. Otherwise, some fog may occur at both sites
before the thunderstorms arrive Tuesday morning but have kept
this out of the TAFs for now due to uncertainty about how the
radiational fog conditions will develop with the potential for
thunderstorm to greatly affect conditions.
&&
.ARX WATCHES/WARNINGS/ADVISORIES...
WI...Excessive Heat Warning until 8 PM CDT this evening for
WIZ032>034-041>044-053>055-061.
Heat Advisory from 11 AM to 7 PM CDT Tuesday for WIZ041>044-
053.
Excessive Heat Warning from 11 AM to 7 PM CDT Tuesday for
WIZ054-055-061.
Heat Advisory until 8 PM CDT this evening for WIZ017-029.
MN...Excessive Heat Warning until 8 PM CDT this evening for MNZ079-
086>088-094>096.
Heat Advisory from 11 AM to 7 PM CDT Tuesday for MNZ096.
IA...Excessive Heat Warning until 8 PM CDT this evening for
IAZ008>011-018-019-029-030.
Heat Advisory from 11 AM to 7 PM CDT Tuesday for IAZ010-011-
029.
Excessive Heat Warning from 11 AM to 7 PM CDT Tuesday for
IAZ030.
&&
$$
DISCUSSION...Zapotocny
AVIATION...Ferguson
Area Forecast Discussion
National Weather Service Cheyenne WY
947 PM MDT Mon Aug 26 2024
.KEY MESSAGES...
- Strong to a severe thunderstorms are possible this afternoon,
with locally heavy rainfall, strong to severe winds, and
large hail.
- Dry weather will develop for Tuesday through Saturday, with a
chance of showers and thunderstorms on Sunday. The warmest
days will be Tuesday and Wednesday.
- Near critical fire weather is possible Tuesday, with RH values
in the low to mid-teens and wind gusts up to 25+ mph possible.
&&
.MESOSCALE...
Issued at 1200 PM MDT Mon Aug 26 2024
A surface cold front is draped from the southwest to northeast
across western CO/eastern UT toward northeast WY. The triple point,
or location of the surface low, of the surface front is
approximately near Gillette, WY as of 18Z this afternoon. The
surface warm front is draped to the east into central SD from the
surface low. That leaves the majority of our cwa in the warm sector,
and surface observations show a south to southwest wind as we have
had surface temperatures climb. Looking at some of the visible
satellite imagery, there is a clear delineation line across eastern
WY where the surface cold front can be interpreted. Cloud "streets"
have appeared as daytime instability has increased where limited
cloud cover was earlier today, with the general movement to the
northeast for steering flow. You can also see a vorticity maximum
across west-central WY as of 18Z, associated with the upper level
low (ULL). SPC Mesoanalysis has the H5/H3 upper level low centered
over northwest WY as of 18Z, and a jet streak max at H3 approaching
85-100 knots to the east over the eastern half of WY and the Black
Hills area of the Dakotas. All of this being said, we are beneath
the rear-entrance sector of the jet stream/streak. Thus, diffluent
flow aloft is being maximized across our cwa. Further RAP analysis
shows Effective Bulk Shear from 0-6km of 35-45 knots east of the
surface cold front, with an emphasis over the Laramie Range that is
elongated toward the Central Rockies of northwest CO. Steep lapse
rates of 8-9 degrees C/km are also co-located with the same region
of wind shear that has been maximized. DCAPE values are slightly
higher further to the east, with 800-1100 J/kg east of the Laramie
Range into western NE. Radar reflectivity as of 18Z is showing some
elevated convection popping up along the frontal boundary in Carbon
County and Converse County. RAP analysis shows that surface CAPE is
hovering around 1000 J/kg, so instability in the atmosphere still
has some work to do from daytime insolation before a higher threat
of severe wx becomes favored. Expect the main hazards to be elevated
to strong wind gusts in the next 1-3 hours, with the convection that
initializes likely being strongest as it approaches the SD/NE state
line. Hi-res analysis does hint at discrete thunderstorms becoming a
line segment by 21Z-0Z across western NE, but the highest concerns
of severe weather modes looks to stay north of NE where the
Slight/Enhanced Risk resides. Thunderstorm activity should wind down
quickly before sunset as it pushes to the east-northeast. Much
cooler temperatures expected behind the cold front overnight, with
lows in the upper 30s/40s for many areas of southeast WY, and low to
mid 50s for western NE.
&&
.UPDATE...
Issued at 943 PM MDT Mon Aug 26 2024
The severe thunderstorm watch has been allowed to expire on time
at 10PM MDT. Showers and thunderstorms have weakened and moved
out of the area.
&&
.SHORT TERM /THROUGH TUESDAY/...
Issued at 401 AM MDT Mon Aug 26 2024
Latest upper air analysis depicts the upper level high has continued
to push from the Central CONUS eastward towards the Great Lakes,
with the now longwave trough gaining some ground as it digs
into the Intermountain West. Under this setup, southwesterly
flow continues through the night with increased moisture
advection into the region. Observations throughout the night and
into the morning has seen the effects from this flow, with
dewpoints in the mid-50s for southeast Wyoming and further
eastward into the Nebraska Panhandle.
Some pretty good changes to the short term forecast, with the
continued moisture advection into the region, giving another day of
active weather for the CWA. Main changes revolve around the
progression of the upper level feature that developed off the
Pacific Northwest, and how it will interact with the blocking
pattern across the central CONUS. Latest changes have seen that
feature transition from a shortwave to more of a longwave trough
as it sets up on just the western fringes of the Intermountain
West. As would be expected, PWATs remain on the higher side,
with PWAT anomalies around 1.3 to 1.5 sigma above climatology,
and around the 75th to 90th percentile for this time of year. As
a result, portions of the Marginal Risk of Severe Thunderstorms
have been upgraded to a Slight Risk for the Converse, Niobrara,
Sioux, Dawes, and even into Box Butte Counties. Decent
instability exists across the zones with areas under the Slight
Risk showing MUCAPE around 1800 J/kg. Main threats will continue
to be a wind threat, with strong outflow boundaries pushing the
already elevated wind speed between the tightening gradients
upwards to criteria thresholds. In addition, could also see
warning level hail within the stronger storms, with decent
shear, lapse rates around 8.5 to 9.0C/km, and SHIP values on the
north side of 1.2. Went ahead and included large hail into the
forecast.
As the longwave trough continues to dig across the zone, will lose
some of its longwave features as it continues scraping across the
northern fringes of the blocking pattern, effectively pushing the
upper level feature further eastward. Zonal flow is expected to
ensue for the near term, effectively cutting off the moisture flow
into the CWA. PWATs mirror this solution, dropping anomalies to
around -1.5 sigma below climatology, and hovering below 0.5 inches
for the majority of areas. Will likely see a return to fire weather,
with RH minimums at or below critical thresholds and an increase to
wind speeds Tuesday afternoon.
&&
.LONG TERM /TUESDAY NIGHT THROUGH MONDAY/...
Issued at 401 AM MDT Mon Aug 26 2024
A large scale upper level low will continue its propagation across
the Canadian border Wednesday into Thursday with an associated cold
front that will sweep across the CWA Wednesday night. Looking at
700mb temps approaching 16C Wednesday afternoon supporting warm
afternoon highs in the upper 80s and 90s east of the Laramie Range.
Precipitation will be possible with the frontal passage Wednesday
night, mainly east of the I-25 corridor. However, based on the
position of the lee trough, the best southerly moisture advection
ahead of the front looks to be in central NE. While the colder air
mass will remain positioned well off to our north with the maturing
upper level system, Thursday temperatures will still drop ~5F
degrees below average for late August into the 70s to low 80s. The
remainder of the long term forecast will be quite dry with a gradual
warming trend headed into next weekend to near/slight above normal
with good ensemble agreement of 500mb height rises across the
western CONUS.
&&
.AVIATION /00Z TAFS THROUGH 00Z WEDNESDAY/...
Issued at 944 PM MDT Mon Aug 26 2024
Westerly flow aloft will continue. Clear skies will prevail.
Winds will gust to 22 knots at the Wyoming terminals after
16Z Tuesday at Cheyenne, and from 15Z to 01Z at Rawlins and
Laramie.
&&
.CYS WATCHES/WARNINGS/ADVISORIES...
WY...None.
NE...None.
&&
$$
MESOSCALE...BW
UPDATE...AM
SHORT TERM...MRD
LONG TERM...MB
AVIATION...RUBIN
Area Forecast Discussion
National Weather Service Des Moines IA
657 PM CDT Mon Aug 26 2024
...Updated for the 00z Aviation Discussion...
.KEY MESSAGES...
- Moderation in temp and humidity for most locations Tue into
Wed, although dangerous heat lingers southeast tomorrow
- Chances for storms west central and north tonight, and again
central tomorrow afternoon. Damaging winds would be the
primary concern.
- More appreciable cold frontal passage late Thu, with showers
and thunderstorms likely. Severe weather potential low for the
time being.
&&
.UPDATE...
Issued at 1233 PM CDT Mon Aug 26 2024
Upgraded Heat Advisory to Excessive Heat Warning. Only minor
changes in temp, dewpoint, and heat index values are anticipated
from previous forecast, but upgraded mainly to provide a more
consistent message across Iowa. Peak heat indices are still
expected to be 101 to 113 due to localized maxes and/or mins in
temp or dewpoint.
&&
.DISCUSSION...
Issued at 300 PM CDT Mon Aug 26 2024
Central Iowa is still currently entrenched in the upper level
and thermal ridge with little in the way of cloud cover and 19z
heat indices from 100 to as high as 112 at Marshalltown so no
change to the current Excessive Heat Warning. The airmass is
quite anomalous with 12z OAX sounding 925mb and 850mb temps
33.2C and 28.6C respectively, both at the 99.9th percentile for
the day and time. The excessive heat is expected to remain in
place into the early evening with no precip through at least
that time. Current expectations are for surface based convection
to eventually develop by early evening in the 500m moisture
convergence axis, which is currently from north central NE to
just northwest of Sioux Falls. Projected storm motion would keep
most of this activity north and west of the forecast area,
however the CAM consensus is that some storms could reach
northern sections from either a SD/MN genesis region later this
evening, or more likely from a further upstream NE genesis
region later tonight. While the 19z surface analysis notes the
surface low along the central IA/MN border, this is likely at
least a hybrid thermal low with the true thermal/frontal
boundary trailing and more aligned with the aforementioned 500m
moisture gradient. This will result in plenty of instability
still available into the night with 3500 J/kg effective CAPEs
north lingering after midnight. Damaging winds are typically
the primary concern in this airmass, and projected DCAPEs
reflect that with values greater than 1000 J/kg. Convection
allowing models suggest there could be multiple episodes of
wind and severe weather through the night north and even just
past daybreak.
Looking ahead to tomorrow the heat will gradually break from NW
to SE as the front drifts through the state. MLCAPEs may still
reach 1500-2000 J/kg with QG forcing from the approaching
northern Plains upper level trough also providing additional
support. Unlike soundings overnight which have drier air aloft
and a moist boundary layer, RAP soundings tomorrow suggest a
trend to the opposite, more inverted V. This would still suggest
a damaging wind potential however with DCAPEs north of 1000
J/kg. 18Z HRRR runs have backed off a bit, but previous 06Z and
12Z runs noted a cluster of two of damaging winds central and
east from the morning into the afternoon. Other CAM solutions
are less robust, so the severe/damaging wind threat is somewhat
conditional. Confidence is not great, with precip, cloud debris,
synoptic frontal position, and convective outflow all in
question, but southeast sections may still see excessive heat
tomorrow, so have left that current Heat Advisory in place.
Storms may linger into the night, but with less severe potential
as effective shear values should be fairly low. Wednesday looks
mainly dry, and while the airmass will improve from the
previous two days, temps and dewpoints will still be above
seasonal levels.
More significant changes are anticipated to end the work week
with this progressive pattern bringing another cycle of a
northern stream trough Thursday, and associated stronger frontal
passage. More noted synoptic scale forcing, and an associated
cold front aloft, should result in showers and storms being
likely (70+% chances) by the afternoon and evening. Deep shear
should be fairly week, limited any severe weather potential. The
remainder of the forecast (Fri-Mon) looks mainly dry with more
seasonal temperatures driven by northwest flow aloft and surface
high pressure upstream.
&&
.AVIATION /00Z TAFS THROUGH 00Z WEDNESDAY/...
Issued at 657 PM CDT Mon Aug 26 2024
Mostly clear skies remain across the terminals this evening,
though will see increasing clouds mainly north as a boundary
moves into the state. Showers and storms are possible late
tonight into Tuesday morning over northern Iowa, though
uncertainty in the overall track and evolution of these storms
remains, so have left direct wording out at this time. Patchy
fog is again possible overnight into Tuesday morning across the
north as well, especially over KMCW. Winds are expected to shift
more northwesterly but generally remain on the light side.
&&
.DMX WATCHES/WARNINGS/ADVISORIES...
Excessive Heat Warning until 8 PM CDT this evening for
IAZ004>007-015>017-023>028-033>039-044>050-057>062-070>075-
081>086-092>097.
Heat Advisory from 1 PM to 8 PM CDT Tuesday for IAZ074-075-
084>086-095>097.
&&
$$
UPDATE...Small
DISCUSSION...Small
AVIATION...Bury
Area Forecast Discussion...UPDATED
National Weather Service El Paso Tx/Santa Teresa NM
556 PM MDT Mon Aug 26 2024
...New AVIATION...
.SYNOPSIS...
Issued at 1225 PM MDT Mon Aug 26 2024
An upper level disturbance over northern Mexico and attendant
trough extends northward west of the Divide. Scattered showers
and isolated thunderstorms are expected through the middle of the
week in mountain areas and west of the Divide. Temperatures are
expected to hover at or just above normal through Friday.
&&
.DISCUSSION...
Issued at 1225 PM MDT Mon Aug 26 2024
UL ridge centered over Missouri is expected to push eastward into
the Ohio River Valley by the middle of the week. This will allow
for east to southeast flow across the area to become briefly south.
A disturbance currently centered in the Gulf near Corpus Christ
will move across the RGV. The disturbance will pull deeper
moisture northward into the CWA and switch surface flow to the
southwest around the middle of the week. Both the GFS and ECMWF
continue to show some timing and placement issues of the
disturbance owing to a lower confidence forecast.
For the rest of this afternoon- An analysis of CAMS, particularly
the HRRR and HREF show scattered to numerous showers and
thunderstorm over the mountain region and west of the Divide. A
majority of the CAMS show activity lasting well into the evening
and could continue into the overnight hours across the area. THe
primary hazards with showers and storms will be periods of heavy
rainfall that could lead to flash flooding and gusty outflow wind
kicking up dust. A Flood Watch remains in effect until midnight
over the burn scar regions of the Sacramento Mountains.
For Tuesday and Wednesday-Deterministic models continue to
struggle with timing, strength, and placement of the disturbance
over the Gulf of Mexico as it moves west toward the CWA. Expected
scattered shower and thunderstorm activity to be within the
mountain areas and west of the Divide with lesser coverage
expected over the eastern part of the CWA on Tuesday. For
Wednesday, both the GFS and ECMWF model solutions show the feature
weakening with deeper moisture confined to areas west of the
Divide as ridging begins to expand into the eastern half of the
CWA.
Scattered showers and isolated showers are expected mainly west
of the Divide and the Gilas with more isolated coverage expected
for areas west of Deming. For the latter part of week into the
weekend- Deterministic guidance varies on how much monsoonal
moisture will be pulled northward into the CWA with passing
disturbances rotating around the ridge over the southern US
leading to chances for isolated to scattered showers and isolated
showers mainly across the mountain areas.
&&
.AVIATION...
(00Z TAFS)
Issued at 546 PM MDT Mon Aug 26 2024
Widespread shwrs and tstms will persist through much of the
critical TAF period, with the majority of the activity favoring
the Rio Grande Valley and centrl portion of the fcst area. Any
direct hits to terminals will likely result in brief MVFR/IFR
conditions by reductions to cigs/vsbys. Storms will be capable of
sudden outflows, some of which could products gusts btwn 30 and 40
kts. Convective activity will become more isold in nature aft
sunset, with drying conditions prevailing most areas by 27/07Z.
Aftn shwrs and tstms will return tomorrow, initiating over the
high terrain aft 27/17Z and increasing in coverage through the
remainder of the TAF period.
&&
.FIRE WEATHER...
Issued at 1225 PM MDT Mon Aug 26 2024
Monsoonal moisture will remain in place through the period leading
to a low fire risk across the area. Shower and thunderstorm
coverage will be the greatest particularly in the mountain areas
this afternoon and expand into the lowlands by tonight. Winds are
expected to remain light through the period except near
thunderstorms. Min RH values are expected to be in the upper 20s
to lower 30s through the middle of the week. Venting will range
from poor to good through the rest of the period.
&&
.PRELIMINARY POINT TEMPS/POPS...
El Paso 74 95 73 95 / 40 40 20 20
Sierra Blanca 65 87 65 87 / 20 20 10 20
Las Cruces 69 91 68 92 / 70 60 30 30
Alamogordo 65 89 65 90 / 50 60 10 40
Cloudcroft 49 65 49 65 / 50 80 10 60
Truth or Consequences 66 87 67 88 / 60 70 30 50
Silver City 60 82 60 80 / 60 80 60 80
Deming 68 91 67 90 / 60 60 50 40
Lordsburg 67 90 65 88 / 50 70 70 70
West El Paso Metro 73 92 73 92 / 40 40 20 20
Dell City 67 93 65 93 / 20 20 0 20
Fort Hancock 69 94 68 95 / 20 20 10 20
Loma Linda 66 86 65 85 / 30 40 10 30
Fabens 71 94 70 93 / 20 30 10 20
Santa Teresa 70 91 70 91 / 50 40 30 30
White Sands HQ 70 91 71 91 / 60 50 20 30
Jornada Range 67 89 67 90 / 70 70 30 40
Hatch 66 91 67 91 / 70 70 40 50
Columbus 70 91 68 89 / 50 50 40 40
Orogrande 67 89 65 90 / 50 50 10 30
Mayhill 53 78 52 78 / 40 80 10 60
Mescalero 52 77 52 78 / 60 80 10 60
Timberon 52 76 50 76 / 50 70 10 50
Winston 54 80 54 79 / 60 80 40 70
Hillsboro 61 87 62 86 / 60 70 50 60
Spaceport 64 88 64 89 / 60 70 30 50
Lake Roberts 55 80 54 79 / 60 90 60 90
Hurley 61 86 60 84 / 50 80 50 70
Cliff 60 91 60 89 / 50 90 50 80
Mule Creek 62 84 61 81 / 40 80 50 80
Faywood 63 84 63 83 / 60 80 50 70
Animas 67 91 65 88 / 50 70 70 70
Hachita 66 89 64 86 / 40 60 60 60
Antelope Wells 65 89 64 86 / 40 60 60 60
Cloverdale 62 84 61 82 / 40 70 70 80
&&
.EPZ WATCHES/WARNINGS/ADVISORIES...
TX...None.
NM...Flood Watch until midnight MDT tonight for NMZ415-416.
&&
$$
FORECASTER...40-Breitreiter
Area Forecast Discussion
National Weather Service Green Bay WI
703 PM CDT Mon Aug 26 2024
Updated aviation portion for 00Z TAF issuance
.KEY MESSAGES...
- Heat indices around 100 this evening will ease off the rest of
the night. Impactful heat continues on Tuesday for some, when
heat indices may reach 95 to 100 over parts of central Wisconsin
and the Fox Valley.
- There is a slight risk of severe thunderstorms through Tuesday.
At this time, it appears the greatest risk will occur after
midnight tonight through early Tuesday morning. Damaging winds
will be the primary concern. Another round is possible Tuesday
afternoon into Tuesday evening; however, confidence is lower for
this second round.
- Temperatures will be at or below normal starting Wednesday.
- Rain and thunderstorm return late Thursday into Friday.
Probabilities of getting at least 1 inch of rain range from
20-50%.
&&
.DISCUSSION...
Issued at 347 PM CDT Mon Aug 26 2024
Short Term...Tonight and Tuesday
The latest RAP analysis and satellite/radar imagery show a strong
mid-level ridge axis centered from the mid-Mississippi Valley,
across Wisconsin, to Lake Superior early this afternoon. With
daytime heating, a widespread cumulus field develop over central
and north-central Wisconsin by late this morning. Temperatures
have warmed into the middle to upper 80s. Combined with dewpoints
in the middle 70s, heat indices are reaching into the middle to
upper 90s. Looking upstream, a cold front is draped across western
to north-central Minnesota.
Satellite imagery shows shallow cumulus clouds developing across
northern Wisconsin this afternoon as a substantial capping
inversion exists between 750 mb and 800 mb. Upstream
thunderstorms are developing across Minnesota, which is progged
to track through the area later tonight. CAMs models are still
all over the place, with some models developing storms across
north-central Wisconsin later this evening, while others wait
until the thunderstorms across Minnesota develop further and ride
the ridge in place across the western Great Lakes region. Given
the substantial capping inversion in place, the later scenario
with the ridge riders seems mostly likely. That being said, the
model discrepancies do not lend a high level of confidence to the
forecast. Any storms that do develop will likely be organized
into a line, taking advantage of 1500-3000 J/kg of MUCAPE, with
straight line winds being the main severe weather threat.
Any storms that track through late tonight could linger well into
Tuesday morning, depending on the CAMs model. The forecast for
Tuesday is even more murky as lingering cloud cover would likely
mute high temperatures, whereas any clearing would pose a threat
for afternoon thunderstorms as instability soars to 1500 to
2500 J/kg. If there is enough clearing and instability, all forms
of severe weather will be on the table given steep low level
lapse rates and surface based convection as the cold front sweeps
through the area. That being said, lingering cloud cover would
likely keep the severe weather threat to a minimum. If there is
enough clearing, high temperatures will likely get into the low
90s with heat index values well into the 90s and approaching
100 degrees. Given the uncertainty regarding this cloud cover,
will not extend the Heat Advisory into Tuesday at this time.
Long Term...Tuesday Night Through Monday
Lots of uncertainty at the start of the long term period beginning
00Z/Wed. Many CAMs show precip/thunderstorms south or east of the
area by this time; however, recent runs of the NAMNest in
particular show another round of convection Tuesday evening. Given
the surface front will still be departing, and a 500mb wave has
yet to clip far northern Wisconsin, will carry chance/likely PoPs
Tuesday evening, and then gradually lower PoPs into Wednesday
morning, hanging around longest in northern WI. Instability will
theoretically wane Tuesday evening, but given the complex nature
of everything to happen before this time, severe storms could
still be possible, especially north.
The cold front will be past the area by Wednesday, bringing
cooler and slightly less humid air to northeast WI. High temps on
Wednesday will range from the upper 60s to upper 70s, coolest in
far north- central Wisconsin.
Rain/thunderstorm chances return Thursday afternoon into Friday
ahead of an approaching shortwave and frontal system. Timing is
not certain, but the current depictions show the best timing is
overnight, which would be less favorable for strong or severe
thunderstorms. Pwats climb as high as 2.0 inches which will bring
a heavy rain threat. Precip-free days appear most favorable from
midday Friday into next Monday; although some weak shortwave
energy could produce some spotty showers this weekend.
Temperatures will be near normal Thu-Sat, and then fall a few
degrees below normal Sun-Mon. This generally means highs in the
upper 60 to low 80s, and lows in the 40s and 50s.
&&
.AVIATION...for 00Z TAF Issuance
Issued at 657 PM CDT Mon Aug 26 2024
Focus through Tuesday afternoon is on thunderstorm potential.
Quiet at this time. Isolated storms stretch from northwest WI to
western Upper Michigan, but these should remain north of RHI.
Cluster of storms over central MN just west of MSP are poised to
push into western WI 01z-03z. If these hold together they would
reach western TAF sites (CWA, AUW and RHI) after 05z, then make
it to east-central WI TAFs after 09z. Have shaped updated TAFs
this way for now. Brief IFR conditions will occur during
thunderstorms. Given how humid it is already, mainly MVFR cigs
and/or vsby would likely linger a few hours even after the storms
exit. No thunderstorm wind gusts highlighted at this time, but
will monitor as the evening progresses and add them if needed.
Once this round of storms moves out 11z-13z Tuesday, there
remains questions on whether more storms will form during peak
heating of the day as there may be a lot of debris clouds around
in wake of the storms. Even so, there will be abundant instability
present ahead of cold front and maybe enough time for recovery to
develop additional storms mid to late afternoon. For now, placed
a small mention of storms in the western TAFs closer to the cold
front.
&&
.GRB WATCHES/WARNINGS/ADVISORIES...
Heat Advisory until 8 PM CDT this evening for WIZ018-020-030-031-
035>039-045-048-049-074.
&&
$$
DISCUSSION.....Kurimski/KLJ
AVIATION.......JLA
Area Forecast Discussion...Updated
National Weather Service Lincoln IL
801 PM CDT Mon Aug 26 2024
.KEY MESSAGES...
- Dangerously hot and humid conditions will persist through
Wednesday. The highest heat index readings potentially in excess
of 110 degrees will occur Tuesday afternoon along and north of
the I-72 corridor.
- A marginal risk for severe weather exists Tuesday night into
Wednesday as an approaching cold front triggers scattered
thunderstorms.
- Much cooler and less humid weather is on tap for the upcoming
weekend as high temperatures drop back into the lower to middle
80s.
&&
.UPDATE...
Issued at 800 PM CDT Mon Aug 26 2024
Today`s heat headlines were allowed to expire at 8 pm, but
overnight heat index values will only drop into the mid to upper
70s in areas along and west of I-55. 8 pm surface map shows dew
points remain in the 75-80 degree range in this area, but should
drop back about 5 degrees overnight. Skies will remain clear over
the forecast area through the night, as cirrus blowoff from a
large MCS currently near Minneapolis should stay to our north.
Geelhart
&&
.SHORT TERM...(Tonight through Tuesday)
Issued at 301 PM CDT Mon Aug 26 2024
The heat has underperformed a bit today...as 19z/2pm heat index
values have just now reached Heat Advisory criteria west of the
Illinois River. As upper heights rise, air temperatures will be a
few degrees higher on Tuesday with widespread middle to upper 90s
anticipated. The main question will be exactly how high the
dewpoints will climb. The HRRR continues to indicate deep-layer
mixing, resulting in dewpoints initially in the lower to middle
70s during the morning decreasing into the middle to upper 60s by
peak heating. Meanwhile the NAM Nest is considerably higher with
readings mostly in the middle to upper 70s. While lower dewpoint
air is currently seen across the Ozarks into the Ohio River
Valley, think this well-mixed airmass will remain largely south of
central Illinois on Tuesday. As a result, am siding with the more
bullish NAM Nest with dewpoints well into the 70s across at least
the northern half of the KILX CWA. Corresponding heat index values
peak at or above 110 degrees along/north of the I-72 corridor
where we have upgraded the Excessive Heat Watch to an Excessive
Heat Warning. Further south, heat index values generally remain
near 105, so have continued the Heat Advisory everywhere south of
I-72.
A cold front currently analyzed from Minnesota into eastern
Nebraska will slowly approach from the northwest by late Tuesday.
Most model solutions keep the associated convection W/NW of
central Illinois through the day, then spread/develop storms
further east into the CWA by evening. At this point, will carry
slight chance PoPs (20%) along/west of the Illinois River by late
Tuesday afternoon...then have gone with chance PoPs (30-40%)
along/north of I-72 Tuesday night. According to the 12z HREF, the
probability of SBCAPEs exceeding 500J/kg and 0-6km shear greater
than 30kt remains less than 30% across central Illinois. Am
therefore not expecting widespread severe weather with any storms
that fire along the front Tuesday evening...although isolated
damaging wind gusts cannot be ruled out with the strongest cells.
.LONG TERM...(Wednesday through Next Monday)
Issued at 301 PM CDT Mon Aug 26 2024
Wednesday will be another hot and humid day: however, whether Heat
Advisory or Warning criteria will be met remains in question.
Outflow from thunderstorms across Iowa/Wisconsin Tuesday night
will drop southward through at least parts of central Illinois. In
addition, the synoptic cold front is expected to sag into the area
and become stationary. End result will be slightly cooler
temperatures in the lower 90s across all but locations along/south
of I-70 where middle to upper 90s will persist. Despite the lower
air temperatures, moisture pooling immediately along the boundary
will result in pockets of dewpoints in the upper 70s to near 80
degrees. Therefore think a Heat Advisory will eventually be needed
across much of the area. Scattered thunderstorms will develop
along the front, especially during the afternoon/evening: however,
areal coverage may remain fairly sparse. Will carry 30-40 PoPs in
the vicinity of the front, but this may be too generous as per the
latest CAMs.
The initial frontal boundary will lift back northward on Thursday
in response to a short-wave approaching from the west. Upper
heights will be considerably lower than now, so temperatures will
not get as hot. Even still, am expecting highs in the lower to
middle 90s with heat index values flirting with advisory criteria
once again.
As the short-wave and its associated cold front get closer,
showers and thunderstorms will become more numerous Thursday night
into Friday. Once the front passes, much cooler and less humid
conditions will be on tap by next weekend. High temperatures will
drop back into the lower to middle 80s while overnight lows dip
into the 50s and 60s from Saturday through Monday.
Barnes
&&
.AVIATION... (For the 00z TAFs through 00z Tuesday Evening)
Issued at 603 PM CDT Mon Aug 26 2024
Little in the way of cloud cover expected through the TAF period,
though a general increase in high clouds will take place from the
northwest in the afternoon. Some small potential for a few
thunderstorms near KPIA toward the end of the period, though
better chances appear to be after 00Z and thus no mention will be
included at this time. Southerly winds overnight will switch to
the southwest again on Tuesday, increasing to near 10 knots by
late morning.
Geelhart
&&
.CLIMATE...
Issued at 600 PM CDT Mon Aug 26 2024
Record & Forecast Highs for Tues Aug 27
Record | Forecast
Peoria......... 98 in 1899 | 98
Lincoln........ 98 in 1936 | 97
Springfield.... 97 in 1983 | 97
Bloomington.... 102 in 1899 | 96
Decatur........ 101 in 1983 | 96
Champaign...... 96 in 1953 | 97
Mattoon........ 98 in 1953 | 95
Record Warm Lows & Forecast Lows for Tues Aug 27
Record | Forecast
Peoria......... 78 in 1886 | 75
Lincoln........ 75 in 1921 | 73
Springfield.... 77 in 1936 | 75
Bloomington.... 75 in 1977 | 73
Decatur........ 76 in 2018 | 74
Champaign...... 73 in 2020* | 73
Mattoon........ 75 in 2004* | 73
* - occurred in several years, most recent shown.
&&
.ILX WATCHES/WARNINGS/ADVISORIES...
Excessive Heat Warning from 11 AM to 8 PM CDT Tuesday for
ILZ027>031-036>038-040>051-053.
Heat Advisory from 11 AM to 8 PM CDT Tuesday for ILZ052-054>057-
061>063-066>068-071>073.
&&
$$
Area Forecast Discussion
National Weather Service Northern Indiana
622 PM EDT Mon Aug 26 2024
.KEY MESSAGES...
- Hot and humid with temperatures in the 90s continuing through
Wednesday and a few parts may see 90 degrees on Thursday as
well. Heat indices in the 100s will be common Tuesday and
potentially Wednesday. Relief can be expected by this weekend
at the latest.
- Periodic chances for showers and thunderstorms between Tuesday
night and Friday is forecast. The greatest chances are late
Tuesday night and Friday afternoon. Strong gusty winds will be
possible in addition to locally heavy rain. Severe weather may
be most possible with a cold frontal passage Friday.
&&
.DISCUSSION...
Issued at 237 PM EDT Mon Aug 26 2024
The moisture axis across Michigan and NW OH moved eastward this
morning away from the area. Meanwhile, another area of moisture
slowly moves in from the west. Surface dew points have been slow to
surpass 70 degrees and models delay the arrival of that humidity
until Tuesday morning. That may be able to allow temperatures to
bottom out closer to 70 degrees as opposed to 75 tonight. After
sunrise, better low level lapse rates take shape at least east of IN-
15 earlier in the day, arriving farther west during the afternoon.
This provides a picture of how much heating can take place Tuesday.
The mid level ridge buckles southward as a stronger shortwaves
within the broad area of low pressure moves eastward into Michigan
and both the ECMWF and the GFS have precipitation output across the
area early Tuesday morning whereas the NAM, HRRR, and RAP do not. If
this activity does occur, lingering debris clouds could restrict
surface heating. The HRRR and RAP both do have showers and storms
arriving in the evening. This allows more time in the sun, but may
also provide a ceiling to temperatures in the north and west where
the storms come in from, if this happens. In this area, he HRRR
still has mixing up to 850 mb where low to potentially mid 20s
Celsius resides allowing for highs in the 95 to potentially 100
degree range. That paired with the humidity will allow for heat
indices above 100 degrees with Indiana and southwest Lower Michigan
attaining heat indices well above 100 away from Lake MI. Am
fairly skeptical of the afternoon activity Tuesday given the
12C 700 mb capping temperatures.
Tonight, an upper low moves northeastward from the Northern
Rockies towards the Northern Great Lakes Tuesday night into
early Wednesday and shears out. With the extra forcing around
and lingering heat and humidity, would not be surprised if
showers and thunderstorms are around, Wednesday, especially
with the boundary approaching our north Wednesday evening/night.
Given their time of arrival and relative lack of shear, think
any severe potential would be limited with it, but gusty winds
may be possible with the likely dying cluster/line of storms.
Once again, this may spread debris clouds across the area, at
the very least, potentially affecting warming for Wednesday.
Additionally, there is some model agreement on pop showers and
storms being possible south of US-30 during the afternoon.
Locally heavy rain and gusty winds are the main threats with
these storms.
Both Tuesday and Wednesday have the potential to see at least
100 degree max heat indices over parts of the area and the
morning heat indices level out around the low to mid 70s. An
excessive heat warning and heat advisory has been issued for
Tuesday for parts of the area and another heat advisory may be
need for Wednesday, but the rain/cloud cover may cut into a few
areas seeing high heat during Wednesday. Of course with schools
returning to session now and those with heat-affected illnesses
and the lack of cooling recovery taking place, wanted to
highlight the Tuesday period despite the lower confidence for
Wednesday.
Thursday, the MaxTs are expected to be cooler with mid 80s to low
90s as opposed to upper 80s to mid 90s, but the humidity will still
be around. As a result, heat indices across our southern 2 tiers of
counties will have the greatest chance to attain mid to maybe upper
90s heat indices, which is just below heat advisory threshold. Once
again, showers and storms may be around with capping now gone, but
nailing down when still comes with low confidence.
Better agreement compared to yesterday exists with respect to timing
of the cold front Friday afternoon or Friday night. With the low
level jet nearby, a better chance for strong to severe thunderstorms
exists. This evolution means it is likely that the weekend sees
relief from the high heat with more like highs in the upper 70s to
mid 80s and dew points back in the 60s.
&&
.AVIATION /00Z TAFS THROUGH 00Z WEDNESDAY/...
Issued at 621 PM EDT Mon Aug 26 2024
VFR this period as heat dome aloft holds overhead.
&&
.IWX WATCHES/WARNINGS/ADVISORIES...
IN...Air Quality Alert from midnight EDT /11 PM CDT/ tonight to
midnight EDT /11 PM CDT/ Tuesday night for INZ005-012>015-
020-022-023-103-104-116-203-204-216.
Excessive Heat Warning from 11 AM EDT /10 AM CDT/ to 10 PM EDT
/9 PM CDT/ Tuesday for INZ005-012>015-020-022>024-103-104-
116-203-204-216.
Heat Advisory from 11 AM to 10 PM EDT Tuesday for INZ006>009-
017-018-025>027-032>034.
OH...Heat Advisory from 11 AM to 10 PM EDT Tuesday for OHZ001-002-
004-005-015-016-024-025.
MI...Air Quality Alert from midnight tonight to midnight EDT
Tuesday night for MIZ078-177-277.
Excessive Heat Warning from 11 AM to 10 PM EDT Tuesday for
MIZ078-177-277.
Heat Advisory from 11 AM to 10 PM EDT Tuesday for MIZ079>081.
MARINE...None.
&&
$$
DISCUSSION...Roller
AVIATION...T
Area Forecast Discussion
National Weather Service North Platte NE
1050 PM CDT Mon Aug 26 2024
.KEY MESSAGES...
- Strong to severe thunderstorms are probable this evening for
much of western and central Nebraska with large hail and
damaging winds the main concerns though a tornado cannot be
ruled out.
- Rain and thunderstorm chances return Wednesday and Thursday
with a strong storm possible Wednesday across north central
Nebraska.
- Conditions generally dry out for the weekend into early next
week with near to slightly above normal values expected
through the timeframe.
&&
.SHORT TERM /THROUGH TONIGHT/...
Issued at 422 PM CDT Mon Aug 26 2024
Early afternoon satellite analysis shows an arching line of
thunderstorms tracking east across northern Wyoming. Closer to home,
a progressive backdoor cool front has entered northern Nebraska from
South Dakota. Moisture pooling behind this feature has propelled dew
points in the area to the low to middle 70s as modest northerly flow
maintains slight cool air fetch which has held afternoon highs in
check to the middle to upper 80s. Further south, general westerly
flow across the southern Sandhills into southwest Nebraska has
allowed for much warmer temperatures though more limited surface
mugginess has made the warmer temperatures much more comfortable
relatively speaking.
For tonight, the southward diving cool front has yielded strong low-
level lift and allowed an isolated weak thunderstorm to develop near
ANW-ONL. While instability is moderate to strong, lift when removed
from the low-level convergence zone is weak but also hampered by
strong capping thanks to h85 temperatures in the low to middle 20s.
Still, concern is non-zero that a storm in the locally juiced
environment could support itself. With MLCAPE values exceed 2000
j/kg and 0-6km BWD values of 40+ knots, the environment would be
more than supportive of an organized severe threat. This region
should remain more on the isolated side given the aforementioned
weak lift and strong capping. Further west, ongoing convection
across Wyoming and South Dakota continues to shift east. Latest hi-
res guidance suggests we`re still 2-4 hours away from activity
reaching our western zones and timing of echoes lends support to
this idea. The background environment supports organized storms with
1500-2500 j/kg of MLCAPE and 40-50 knots of 0-6km BWD. Merging cold
pools with eastward progression should favor more linear storm mode
but line-normal 0-3km shear approaching 25 to 30 knots could support
a modest tornado threat in addition to the damaging wind threats.
Recent CAM guidance including HRRR/NAM Nest carries much of the
greatest storm intensity immediately north of the state line but
areas along and north of Highway 20 should be cognizant of the
threat for severe weather tonight. Further southwest yet, a third
area of rain and thunderstorms is anticipated to develop. This is
occurring in an area of weak surface convergence/a quasi-warm front.
A definite density gradient is apparent with 87 at IML yet 95 at ADT
as of ~21z. Fgen at h85 has notched up and recent satellite and
radar images shows growing cu field/towers. While instability and
shear is weaker down here, the threat for severe weather will also
exist with MLCAPE values nearing 1000 j/kg and near 25 to 35 knots
of deep layer shear. NAM Nest has been most aggressive in this area
developing multiple supercells that track north and east through the
evening into central Nebraska. While the HRRR is less bullish, it
still advertises clusters of multicells which would be capable of
isolated large hail and damaging wind gusts. All storms will remain
fairly progressive given strong steering flow aloft. That said,
precipitable water values are running nearly 150% of normal as
indicated by 12z RAOB data. This suggests all storms will be capable
of locally heavy rainfall. As typical with convection, QPF will be
splotchy with fairly isolated pockets of heavier amounts. More
widespread wetting rains are likely north of Highway 2 as late night
convection marches west to east across these areas. Most locations
should fall short of 0.50" but isolated instances closer to 1.00"
cannot be ruled out. Expect activity to gradually wane overnight
with most if not all activity having departed to the east by sunrise
Tuesday.
&&
.LONG TERM /TUESDAY THROUGH MONDAY/...
Issued at 422 PM CDT Mon Aug 26 2024
Tuesday/Tuesday Night...a dry day is expected across the area for
Tuesday. Behind the passing frontal boundary from Monday night,
reinforcing high pressure will nose in from the northeast. While the
central high pressure will remain will north and east of the area,
pressure rises and veering winds will promote fairly quiet
conditions. A warm front will again take shape near or just north of
Interstate 70 across western Kansas. This will provide the focus for
thunderstorm development but overall NWP guidance is confidently
keeping this feature well to our south and out of our hairs. One of
the bigger question marks for Tuesday focuses on temperatures.
Statistical guidance varies by 10 degF and this is likely due to
influence and progression of the high pressure. For now, played
middle ground which produced low to middle 80s across the area.
Rapid height rises/subsidence behind the main h5 trough will keep
conditions dry in the local area. Dry conditions continue overnight
with lows falling into the lower 60s.
Wednesday and beyond...broad northern stream trough will track east
along the Canadian border with impressive upper-level dynamics. This
will likely stay north of the area but introduce another notable
cool front into the area late Wednesday and early Thursday. PoPs
increase markedly as a result, capping around 50% across the
Sandhills. The Storm Prediction Center has introduced a Marginal
Risk (level 1 of 5) for our far north central zones and overall have
no qualms with this. As daytime highs once again climb into the
middle to upper 90s, moderate instability will develop. Shear is
generally limited to 20 to 25 knots but strong forcing along the
frontal boundary should lead to a few thunderstorms of which a few
could be strong to briefly severe. Must stronger high pressure will
bully itself in late Thursday and early Friday which will again
drive daytime temperatures lower but keep PoPs at bay. This will
likely continue into the weekend though temperatures should moderate
into early next week as broad ridging develops upstream and subtle
height rises build in from the west. Ridging continues to strengthen
upstream but northwesterly flow will provide support for fleeting
disturbances to dive southeast and bring some rain and thunderstorm
chances. NAEFS extended outlook supports above normal temperatures
and some weak signals for above normal precipitation. So continued
near to above normal temperatures and recurring thunderstorm chances
should be expected as we turn the calendars to September.
&&
.AVIATION /06Z TAFS THROUGH 06Z WEDNESDAY/...
Issued at 1045 PM CDT Mon Aug 26 2024
Scattered thunderstorms will be located across the region
tonight. Winds will be locally gusty and variable in the
vicinity of any thunderstorm activity. Otherwise VFR conditions
are expected to persist through Tuesday. The exception will be
across portions of north central Nebraska from VTN eastward,
where a period of MVFR low ceilings are expected through the
late morning hours.
&&
.LBF WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
SHORT TERM...NMJ
LONG TERM...NMJ
AVIATION...Taylor
Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
910 PM CDT Mon Aug 26 2024
.KEY MESSAGES...
- Dangerous heat and humidity will continue through Tuesday
where heat indices could exceed 110. Excessive Heat Warning
issued for all northeast IL counties, Heat Advisory issued for
northwest IN counties.
- Potential for scattered thunderstorms Tuesday afternoon/evening,
a few of which could be strong to severe.
- Chances (20 to 40 percent) for showers and storms, mainly south
of I-80 on Wednesday
- Additional shower and storm chances Thursday into Friday as a
cold front moves from NW to SE over the region
- Cool and dry expected over Labor Day weekend
&&
.UPDATE...
Issued at 909 PM CDT Mon Aug 26 2024
The going forecast is in good shape for the remainder of the
night, with only minor refinements made to precip potential
overnight. This evening, a bowing MCS is crossing from east-
central MN into northwest WI. This appears to be clinging to the
northern fringe of a defined instability gradient oriented
across central WI. Recently, an outflow boundary had developed
along the southern edge of the bowing segment but we haven`t
seen much in the way of southward development, despite the
boundary extending into a region of even higher MLCAPE with
little to no capping according to latest RAP mesoanalysis.
Whereas some earlier model runs depicted a good chunk of this
system impacting the far northern CWA tonight, it looks like
we`re seated just far enough underneath the ridge to keep the
brunt of it safely up to our north. Nonetheless, did decide to
maintain a corridor of slight chance PoPs along and north of
I-88 tonight to account for anything that may go up on the
outflow. Building low level stability should make that
increasingly difficult with time. But, given the impressive mid
level thermal profiles, anything that can overcome that
stability could be thunderous. This low-end potential should
move off to our east well before morning. No changes in the
thinking for the heat tomorrow or storm potential tomorrow
evening at this time.
Doom
&&
.DISCUSSION...
Issued at 330 PM CDT Mon Aug 26 2024
Through Tuesday Night:
A stout upper-level ridge continues to reside across the
Midwest this afternoon which is making for a rather hot and
humid afternoon. While some earlier cloud cover slowed diurnal
heating a bit, temperatures have still managed to work their way
into the lower 90s across most of northeast IL and northwest
IN. These temperatures in combination with steadily increasing
dew points into the lower 70s has resulted in peak heat indices
well into the 100 to 105 range areawide. Therefore, the Heat
Advisory continues for portions of northern IL along and east of
I-55 except for Cook County where an Excessive Heat Warning
remains in effect for this threat.
Temperatures will gradually cool this evening, but the
aforementioned low to mid-70s dew points will keep overnight
lows well into the 70s with the potential for temperatures to
remain near 80 degrees in downtown Chicago. As a result, the
warm and humid night will offer little relief before
temperatures begin to rebound on Tuesday. However, a cluster of
thunderstorms is expected to develop across SD and southern MN
this evening and track into southern WI overnight. While this
trajectory should keep the bulk of the storms north of the IL-WI
line, there is the potential for an outflow boundary to surge
south into northern IL after midnight. Given the warm and humid
airmass expected to be in place, this outflow could kick off
some isolated to scattered thunderstorms across our northern
tier of counties (roughly for areas north of I- 90) a few of
which could be strong to severe with a threat for gusty winds.
Though, forecast soundings continue to show a stout cap in place
overhead tonight which could prevent storms from even
developing so this remains a low confidence forecast.
Regardless of thunderstorm coverage tonight, temperatures are
expected to rebound into the mid to upper 90s Tuesday afternoon
resulting in another hot and humid day for us. In fact, with dew
points forecast to be in the low to mid-70s heat indices will
likely be near 110 degrees across most of the area. The
exception though will be in northwest IN where dew points could
mix down a bit a result in slightly lower heat indices in the
105 to 110 range. Therefore, the previous Heat Watch was
upgraded to an Excessive Heat Warning across all of north and
northeastern IL and to a Heat Advisory for northwest IN for
Tuesday afternoon.
Though there are a couple of caveats that could break the
forecast in spots. The first is a lake breeze that is forecast
to develop and move inland across northeast IL and northwest IN.
While guidance continues to show the lake breeze making little
inland progress due to elevated synoptic winds, it could still
result in some localized relief Tuesday afternoon for areas
along the immediate lakeshore. The second caveat is the
potential for more scattered thunderstorms Tuesday afternoon
along the aforementioned outflow boundary. Given that there is a
good deal of uncertainty where (if at all) this boundary will
stall in northern IL, confidence remains low on where any storms
may materialize. If and where any storms develop could also see
localized relief from the heat and result in temperatures and
heat indices than forecast.
Finally, a better coverage of thunderstorms is expected to
develop Tuesday evening as a frontal boundary begins to move
into northern IL from IA. While wind shear will be somewhat
limited, the combination of the heat and humidity will make for
a very unstable airmass (MLCAPE around 3500 to 4000 J/kg) and
will support the potential for any storms to become strong to
severe. Any storms that do become strong to severe will have the
primary threat of damaging winds, but the steep mid-level lapse
rates will also support instances of large hail as well.
Additionally, the high moisture content of the air (PWATs around
2.0 inches) will also make any thunderstorms heavy rain
producers which may lead to ponding in poor drainage areas.
Thunderstorm coverage should gradually diminish heading into
Wednesday morning, but it will also aid in providing some relief
with cooler overnight temperatures in the low to mid- 70s.
Yack
Wednesday through Monday:
The weather pattern across the central portion of the county will
remain supportive of periodic chances for showers and
thunderstorms through late week as a series of weather impulses
track eastward into the Lower Great Lakes. Fortunately, however,
this threat looks to come to an end following the passage of a
cold front late Friday. This will thus set the stage for what
looks to be a great period of dry and cooler weather through the
upcoming Holiday Weekend.
The threat and coverage of thunderstorms on Wednesday into
Wednesday night may ultimately be dependent upon how far south
Tuesday night`s convective activity drives an effective cold
frontal boundary into northern IL into Wednesday morning. While a
chance of storms exists areawide at this time for Wednesday
afternoon and evening, the primary focus for more substantial
storms may ultimately end up south of I-80. Locally heavy
rainfall and localized strong wind gusts would be the primary
threats from these storms. Otherwise, temperatures will remain
very warm and humid Wednesday, especially to the south of the
effect cold front. However, it appears peak heat indices will
remain at or below 100.
Warm and humid weather continues Thursday into Friday, with the
chances for showers and thunderstorms during this period peaking
ahead of the approaching cold front late Thursday night into
Friday. In the wake of this frontal boundary, expect drier and
cooler weather to filter in across the area for the weekend.
KJB
&&
.AVIATION /00Z TAFS THROUGH 06Z TUESDAY/...
Issued at 630 PM CDT Mon Aug 26 2024
Key Messages:
- Low confidence in wind trends Tuesday
- Potential for severe thunderstorms Tuesday evening
Expect winds to gradually ease with sunset this evening though
sporadic gustiness will remain possible through the overnight
hours. Winds will be generally SSW over the Chicago metro with
light S to SSE possible at times at RFD through the overnight
hours.
Looking ahead to Tuesday, confidence in wind directions
decreases markedly, which will ultimately be dependent upon
upstream mesoscale convective trends. At this time, storms are
expected to remain north of the local area overnight, though any
storms that move across Wisconsin could still throw out an
outflow boundary which could at least briefly turn winds north
to northeast Tuesday morning. If this feature develops and is a
bit slower to arrive, it could aid in a faster inland surge of
the lake breeze turning winds solidly easterly by mid-late
afternoon at ORD/MDW. Confidence in this occurring remains too
low to including the TAFs, however, and will maintain a westerly
direction in the TAFs with this update.
As is typical in this weather pattern, confidence in convective
trends on Tuesday remains low. In spite of this there is still
a strong enough signal to maintain PROB30 groups for TSRA during
the late afternoon through early evening period (~23-03Z) and
incorporates a gusty northwest wind shift. Expect this time
window to get refined with later updates. If/when storms
develop, the environment will be favorable for damaging wind
gusts.
Petr
&&
.CLIMATE...
Issued at 330 PM CDT Mon Aug 26 2024
Record Max Temperatures and High Minimum Temperatures for early
Tuesday and Wednesday this week:
Record Max/YearRecord High Min/Year
Chicago:
Tue Aug 27th.........97 in 1973...........78 in 2020.
Wed Aug 28th.........97 in 1955...........77 in 2020.
Record Max/YearRecord High Min/Year
Rockford:
Tue Aug 27th.........97 in 1953...........74 in 2018.
Wed Aug 28th.........97 in 1955...........76 in 1928.
Ratzer/Yack
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...Excessive Heat Warning from noon to 10 PM CDT Tuesday for
ILZ003-ILZ004-ILZ005-ILZ006-ILZ008-ILZ010-ILZ011-ILZ012-
ILZ013-ILZ019-ILZ020-ILZ021-ILZ023-ILZ032-ILZ033-ILZ039-
ILZ106-ILZ107-ILZ108.
Air Quality Alert until midnight CDT Tuesday night for ILZ005-
ILZ006-ILZ012-ILZ013-ILZ020-ILZ021-ILZ103-ILZ104-ILZ105-
ILZ106-ILZ107-ILZ108.
Excessive Heat Warning until 10 PM CDT Tuesday for ILZ103-
ILZ104-ILZ105.
IN...Air Quality Alert until midnight CDT Tuesday night for INZ001-
INZ002-INZ010-INZ011.
Heat Advisory from noon CDT /1 PM EDT/ to 10 PM CDT /11 PM
EDT/ Tuesday for INZ001-INZ002-INZ010-INZ011-INZ019.
LM...None.
&&
$$
Visit us at weather.gov/chicago
Area Forecast Discussion
National Weather Service Morristown TN
1019 PM EDT Mon Aug 26 2024
...New UPDATE...
.UPDATE...
Issued at 1006 PM EDT Mon Aug 26 2024
A dry and warm evening across the east Tennessee Valley and
Southern Appalachians after highs reached the lower to mid 90s
earlier today. Upper level ridging moving east and surface high
overhead with a dry airmass holding strong. Temperatures late
this evening had cooled into the 70s to around 80 with only a few
clouds and dewpoints generally in the mid 50s to mid 60s.
Temperatures are near to a few degrees warmer than Sunday night at
this time. Expect lows to be in the upper 50s to upper 60s with a
few localized areas of fog. This is what is currently forecast so
no changes to current forecast.
&&
.SHORT TERM...
(This evening through Tuesday)
Issued at 233 PM EDT Mon Aug 26 2024
Key Messages:
1. Dry weather and dry air once again tonight and Tuesday with
high pressure and ridging across the region.
2. Temperatures warm another 1 to 3 degrees as 850mb temperatures
warm beneath the upper ridge.
Discussion:
The upper-level 596 dam 500mb upper-level ridge will gradually
shift eastward across the Ohio Valley on Tuesday with continues
northerly upper-level flow and subsidence across the Tennessee
Valley and Southern Appalachians. This will result in dry weather
and dry, warming boundary layer conditions. We don`t expect to
reach record highs on Tuesday, but we will be close. Once again,
we went with lower than NBM dew points by blending with HRRR because
of the subsidence pattern that supports drier afternoon dew
points across our region.
Daily Record High Maximum Temperatures
Date Chattanooga Knoxville Tri-Cities Oak Ridge
08-27 102(1936) 101(1943) 95(2016) 97(2007)
&&
.LONG TERM...
(Tuesday night through next Monday)
Issued at 233 PM EDT Mon Aug 26 2024
Key Messages:
1. Mostly dry conditions and record heat is expected Wednesday to
Friday with temperatures rising far into the 90s to the lower 100s.
2. Chances for storms increase by Saturday with a front bringing
drier and cooler conditions by Labor Day or possibly later on.
Tuesday Night through Friday
At the start of the period, very strong ridging will be over the
area with a record high 500mb high of 5,950m. Surface high pressure
will also remain centered to our east. This pattern will continue
the dry and progressively hotter trend. Conditions at the surface
will still be fairly dry due to mixing and limited overall moisture.
This will limit heat index values but allow actual air temperatures
to rise far into the 90s area-wide. Wednesday night into Thursday,
this upper high will become centered directly over the area. Maximum
heating is indicated with 850mb temperatures rising to record high
values of 22 Celsius or higher. With some weak moisture return, very
limited chances for storms exist over the higher terrain. But more
broadly, this moisture return will likely be sufficient for heat
index values to rise above the actual air temperature, which will
likely be higher than the day before. By Friday, the upper high
begins to weaken some but still remains centered nearly directly
over the area. Some further moisture return will be sufficient for
another slight increase in PoPs outside of the mountains. Otherwise,
the heat and humidity will be similarly as concerning with near
record values possible again.
Daily Record High Maximum Temperatures
Date Chattanooga Knoxville Tri-Cities Oak Ridge
08-28 100(1990) 98(1936) 94(1953) 98(1995)
08-29 100(1993) 102(1948) 96(1953) 99(1948)
08-30 98(1993) 96(1995) 95(1953) 99(1995)
Regardless of if criteria for heat products is met, the length and
magnitude of this heat wave will be on par with what was seen
earlier this Summer. We continue to emphasize the need to stay
hydrated, look before you lock, and limit exposure in direct
sunlight as much as possible.
Saturday through Monday
Heading into Saturday, the upper-level high will shift further east
with shortwave troughing noted further north. This will allow for
increased moisture across the area, along with chances for storms.
With a lot of the better forcing further north, convection will
likely be more terrain-focused with a reduction from NBM guidance.
Some guidance does indicate a weak jet streak traversing to our
north, which may give enough divergence for better coverage. By
Sunday, the shortwave will move further east, putting the region in
a more northwesterly flow pattern aloft. Frontogenesis will be noted
to our northwest ahead of a surface high diving south from Canada.
Rain chances will remain as this front approaches towards Labor Day.
The main question is when the front will move through, which will
usher in cooler and drier conditions, likely by early next week.
&&
.AVIATION...
(00Z TAFS)
Issued at 734 PM EDT Mon Aug 26 2024
VFR conditions and light winds continue across the region with
high pressure in control of our weather. Patchy areas of fog will
be possible in the vicinity of terminals late tonight into Tuesday
morning so have included a few hours of MVFR fog at TRI as model
guidance is showing some before sunrise and with a brief decrease this
morning.
&&
.PRELIMINARY POINT TEMPS/POPS...
Chattanooga Airport, TN 67 98 67 98 / 0 0 0 10
Knoxville McGhee Tyson Airport, TN 66 95 66 96 / 0 0 0 10
Oak Ridge, TN 66 95 66 96 / 0 0 0 10
Tri Cities Airport, TN 61 92 63 92 / 0 0 0 10
&&
.MRX WATCHES/WARNINGS/ADVISORIES...
NC...NONE.
TN...NONE.
VA...NONE.
&&
$$
SHORT TERM...TD
LONG TERM....BW
AVIATION...TD
Area Forecast Discussion
National Weather Service Springfield MO
600 PM CDT Mon Aug 26 2024
.KEY MESSAGES...
- Heat Advisory is in effect for the western and northern
portions of the area from 12 to 9 PM today, and from 12 to 9
PM Tuesday for counties toward central Missouri.
- Conditional chance (15-25%) for showers and thunderstorms
Tuesday morning, and again late Tuesday afternoon. Wind gusts
of 40-50 mph possible with any storm that does form Tuesday
afternoon.
- Daily Heat Index values of 100 to 105 will continue to occur
across portions of the area into the middle of the week.
- A front will bring greater shower and thunderstorm chances
(40-70%) to the region late this week into the weekend along
with cooler conditions.
&&
.SHORT TERM /THROUGH TUESDAY NIGHT/...
Issued at 330 PM CDT Mon Aug 26 2024
Current mesoanalysis depicts the center of a broad upper-level
high centered right over our heads. Water vapor imagery depicts
well the deep shortwave trough moving NE across the northern
Rockies, and a mid- and upper-level tropical disturbance
exiting the Gulf and inching into central TX. As per usual with
a broad upper-level high, the surface pattern around our area
consists of weak winds west of a broad surface high pressure.
Clear skies are also dominating our region. This is leading to
hot temperatures today with many places in the lower to middle
90s and Heat Index values in the 95-110 F range. As such, the
Heat Advisory continues until 9 PM today for areas along the
Missouri-Kansas/Oklahoma border and up into central Missouri.
Weather tonight will be quiet and mild with lows in the lower to
middle 70s, calm winds, and clear skies.
Low-end chance (15-25%) for showers and thunderstorms Tuesday:
There is a very conditional potential for showers and
thunderstorms across the area Tuesday morning and again Tuesday
afternoon. This means there could be rain across portions of
the area, but also absolutely nothing. Tuesday morning, models
like the RAP and GFS depict a very subtle pre-frontal trough
dropping through SW MO Tuesday morning. RAP soundings suggest
that elevated 850/700 mb moisture content should be enough to
erode inhibition enough for the vertical motion to produce some
showers and perhaps a thunderstorm Tuesday morning between the
7 AM and 1 PM timeframe. However, other models and CAMs do not
handle such a subtle feature well. And additionally, there is
low confidence in whether the cap will break at all. Therefore,
there is only a 15-25% chance.
The next chance comes later in the day Tuesday, mainly across
our northern counties toward central MO. The 12Z HREF suite
depicts 1500-2500 J/kg SBCAPE across the areas. Deep-layer shear
will be quite minimal (<10 kts), but with dewpoints in the lower
70s, and mid-level RH in the 60-80% range, the environment is
primed for pulse thunderstorms. With little in the way of
synoptic or mesoscale forcing, the main uncertainty becomes if
storms can initiate from ample solar heating that can break
through any inhibition. As of right now, the RAP/HRRR do show
convection breaking out, and the HREF mean does suggest < 25
J/kg CIN. But given these models overmix, the convective
temperature may be being reached too easily in these models.
As such, confidence and chances are low (15-25%) Tuesday
afternoon. Given steep low and mid-level lapse rates at 7-8
C/km with inverted V profiles noted in HREF sounding plumes,
downburst wind gusts of 40-50 mph are possible if storms do
form.
Heat Advisory in effect from 12-9 PM Tuesday:
The upper-level high will shift east during the day Tuesday.
This will also shift the greatest heat threat eastward. Heat
Index values across the area are still expected to reach around
100 F as highs continue in the middle to upper 90s and dewpoints
around 70 F. The greatest Heat Index values will be toward
central MO. These will be in the 103-108 F range and a Heat
Advisory has been issued for Morgan, Miller, Maries, and Camden
counties to account for such. Even with only a small area within
advisory status, widespread areas of 95-104 F Heat Index values
will still create threatening circumstances for those who work
outside and/or have little in the way of cooling. Please
continue to practice applicable heat safety.
Lows Tuesday night will continue to be mild in the lower 70s.
&&
.LONG TERM /WEDNESDAY THROUGH MONDAY/...
Issued at 330 PM CDT Mon Aug 26 2024
Daily Heat Index values up to 100-105 F through midweek:
As the week continues, the upper-level ridge/high will continue
to shift eastward and break down as potent troughs traverse the
northern CONUS. This will slightly decrease high temperatures
through Thursday. Highs Wednesday and Thursday will continue to
be in the mid-90s with widespread Heat Index values around 100
F, though some localized pockets of 100-103 F will still be
possible. Lows will also continue to hover around 70 F,
generally cooler in the eastern Ozarks. Once again, please
continue to practice heat safety by drinking plenty of fluids,
taking frequent breaks in the shade and air conditioning, and
checking on family and friends.
Cooler conditions and rain chances late week into the weekend:
A deep trough will traverse the northern CONUS late this week.
An attending cold front will drop through the region bringing
shower and thunderstorm chances as well as cooler conditions to
the area, especially Friday. The trough will break down the
mid-level ridge Thursday, which will open up the Gulf and allow
a more humid airmass across the eastern CONUS. This may allow
for some pulse thunderstorms Thursday afternoon/evening before
the front arrives (20-30% chance).
The front is currently forecast to arrive Friday. Ensemble
clusters do point at a slight timing discrepancy, though many
are in agreement for the passage to occur Friday. As the front
pushes through the muggy airmass, showers and thunderstorms
appear likely (40-70% chances now, likely to increase as the
time nears). As the trough and mid-level wind speed max will
stay well north of our area, shear will be minimal, so severe
weather is not expected with these storms at this time.
After the frontal passage, highs will cool into the lower to
middle 80s Thursday through Monday with lows in the lower to
middle 60s (below 50 in the eastern Ozarks over the weekend).
There are additional 15-30% chances for rain Saturday through
Monday to close out Labor Day weekend, however, model spread is
quite high. Ensemble QPF clusters have either widespread rain,
or bone dry values. This is due to some members depicting a
tropical disturbance lifting out from Mexico, while others do
not. Some members have the cold front stalling just south of our
area which could force daily chances of isolated/scattered
showers and thunderstorms. Bottom line is that uncertainty is
too high at the moment. Check back for updates to the Labor Day
Weekend forecast.
&&
.AVIATION /00Z TAFS THROUGH 00Z WEDNESDAY/...
Issued at 600 PM CDT Mon Aug 26 2024
High confidence in VFR conditions prevailing through the TAF
period. Light south to southwest winds at 5 to 10 knots. Some
scattered high level cloud cover at times.
&&
.SGF WATCHES/WARNINGS/ADVISORIES...
KS...Heat Advisory until 9 PM CDT this evening for KSZ073-097-101.
MO...Heat Advisory until 9 PM CDT this evening for MOZ055>058-
066>069-077>080-088-089-093-101.
Heat Advisory from noon to 9 PM CDT Tuesday for MOZ056>058-069.
&&
$$
SHORT TERM...Price
LONG TERM...Price
AVIATION...Perez
Area Forecast Discussion
National Weather Service Tucson AZ
156 PM MST Mon Aug 26 2024
.SYNOPSIS...Isolated showers and thunderstorms today with an
increase in thunderstorms Tuesday and Wednesday followed by a
decrease in storms into this weekend. High temperatures are
expected to remain near normal.
&&
.DISCUSSION...An MCV from overnight convection in Sonora is just
south of Douglas slowly moving north. Showers have formed along
the northern periphery of the MCV with isolated thunderstorms
starting to form over the Sky Islands. Dry air is evident on
water vapor imagery from Tucson westward with a trough moving into
Wyoming, high pressure over Missouri, and an easterly wave over
Texas. The latest HRRR run shows continued isolated thunderstorm
development mainly on the western and northern periphery of the
MCV on the edge of this morning`s cloud cover. Cochise County will
likely just see showers as its seen very little surface heating.
Instability is somewhat limited with MLCAPE around 500 J/kg.
Because of this storms won`t be especially strong but will still
be capable of wind gusts to 45 kts and locally heavy rainfall.
Tuesday and Wednesday are expected to be more active as mid-level
flow turns southerly allowing more moisture to return to southeast
Arizona. PWAT values increase to 125 percent of normal for most of
the CWA with plenty of instability for storms to tap into. The
latest HREF shows scattered showers and thunderstorms mainly from
central Pima County eastward Tuesday afternoon and evening. The
severe threat looks limited right now but storms will be capable
of strong outflow winds and heavy rainfall. Wednesday looks to
have a similar set up in terms of moisture, storm chances, and
coverage. However ensembles are hinting at the possibility of
overnight convection Tuesday night. HREF members don`t show much
activity past midnight, so there is still some uncertainty with
how Tuesday night will play out. If there is nocturnal activity
this could lead to Wednesday seeing reduced storm coverage and
intensity.
Starting Thursday moisture begins to decrease for areas out west
which will decrease storm chances and limit coverage to areas from
Tucson south and eastward again. By the weekend storm chances are
between 20-40 percent and confined to areas east of Tucson.
&&
.AVIATION...Valid through 27/18Z.
BKN-OVC clouds mainly above 8k-12k ft AGL from KTUS south and
eastward this afternoon and evening. ISOLD SHRA/TSRA this
afternoon/evening mainly south and east of KTUS. Visibility
restrictions, wind gusts up to 45 kts, heavy rain, small hail, and
mountain obscurations possible with any thunderstorm. Outside of
thunderstorm wind gusts, SFC winds SWLY to NWLY in direction
generally 8-12 kts becoming SELY overnight 5-10 kts. Aviation
discussion not updated for TAF amendments.
&&
.FIRE WEATHER...Low end chance for storms today with an increase
in areal coverage of storms tomorrow into Wednesday, then a
gradual decrease into next weekend. Outside of any thunderstorm
outflow winds, 20-foot winds will generally be 15 mph or less,
with afternoon/early evening gusts to 20-25 mph and light winds
overnight.
&&
.TWC WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
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