Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 07/26/23
Area Forecast Discussion
National Weather Service La Crosse WI
650 PM CDT Tue Jul 25 2023
.UPDATE...Tonight
Issued at 650 PM CDT Tue Jul 25 2023
Based on the latest CAMs delayed the onset of the storms tonight.
Unlike earlier runs which had multiple lines of convection moving
through the area, they are now showing more scattered convection
associated with the shortwave trough as it moves east through the
region. At this time, it looks like the convection will move into
the western areas between 25.07z and 25.08z.
&&
.DISCUSSION...(Tonight through Tuesday)
Issued at 200 PM CDT Tue Jul 25 2023
Key Messages:
- Showers and storms overnight into Wed morning. Some could be
strong with hail, wind and locally heavy rain.
- Above normal temperatures through Friday with highs in the lower
to middle 90s. Heat indices around 100 for some locations. Hottest
day Thursday.
- Seasonable temps return for the weekend. Also looking dry for
most.
* SHOWERS/STORMS OVERNIGHT-EARLY WED MORNING
Upper level shortwave trough in concert with 850 mb jet/moisture
transport expected to spark a thunderstorm complex across ND late
this afternoon. Consensus via most of the CAMS and the HopWRF is to
roll the complex southeast, tracking with the shortwave and in the
plume of highest instability. Track could take the heart of the MCS
just along the west/southwest flanks of the forecast area (SE MN/NE
IA), but additional convective develop is expected northward along
associated cool front/upper level shortwave. Some hints in the
models that the convective focus would shift north by mid morning
(northern WI) with the heart of the shortwave and return focus of
the low level jet/moisture transport.
Ample instability overnight (1500-2000 J/kg MUCAPE) for the
convection to tap into. Mixed signals in short term guidance on
shear profiles. Hodographs more straight line, but not long. Storms
likely elevated by the time they move in and RAP 1-7 km shear
suggests 20-30 kts to aid any storm development. Not a lot, but when
added to the lift/instability could see some hail and stronger wind
gusts (depending on storm mode) with stronger storms. Moreso, warm
cloud depths from 4-4.5 kft and PWs around 2" will support locally
heavy rain. No training evident and pcpn looks to be fairly
transitory. Could see local 1+" amounts.
* SUMMER HEAT THIS WEEK - but more seasonable for the weekend. Thu
shaping up to be the "hottest" day with heat indices around 100
for most.
The much talked about upper level ridge is currently setup up across
the plains and will ease east over the next few days. The ridge
flattens as it shifts over the upper mississippi river, thanks to a
few west-east moving shortwaves topping it across southern Canada.
GFS remains the odd model out with too much mixing, drying out and
amping up the heat. 925 mb temps for 00z Fri push +32 in GFS
(suggestive of record/near record heat) while the NAM and EC
continue to hold around +27-28 C. Further, EC EFI sits around
.85 for Tmax with shift of tails close to zero - saying it`s warm,
but not anomalously so. Will continue to hold the forecast closer to
the NAM/EC and other short term guidance. Model blend has trended
down a bit as more of the short term guidance has been incorporated.
Thu still shaping up to be the hottest day with low to mid 90s for
all. Dewpoints in the upper 60s/around 70 push heat indices to
around 100 for many/most. A Heat Advisory for a portion of the
forecast area may be needed for Thu afternoon, generally south of I-
94.
With nocturnal/early morning convection expected tonight and Thu
night, the rainfall will provide another source of moisture to
evaporate, juice up the atmosphere. Could push heat indices up a
bit. Also of note is that said rain could temper back ambient temps
if realized during the daytime hours. Latest short/medium range
indicate some chances for this Friday.
Come the weekend, pattern shift continues to be favored with ridge
reamplifying and moving back to the west, allowing for northwest
flow to redevelop locally. Temps should fall back to more seasonable
normals in this scenario.
* MORE STORM CHANCES LATE THU NIGHT INTO FRI...BUT DRIER
WEEKEND FAVORED.
GFS/EC suggest another storm complex could spark over the northern
plains Thu night, tracking across the upper mississippi river valley
overnight/Fri morning. Some support from their various ensemble
members, but a few are also dry. Not a clear-cut signal, but
generally favoring the chances. While a few more bits of upper level
energy/rain producers could slip across the region through the day
Friday, current consensus is that the activity will push a west-east
sfc front south of the forecast area Fri night, keeping the bulk of
any further convective chances generally southward for the weekend.
Add in the cooler, more seasonable temps...and it`s shaping up to be
a fairly nice weekend weather-wise (if scenario holds).
&&
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 650 PM CDT Tue Jul 25 2023
Adjusted the TAF timing of the onset of showers and thunderstorms
a bit to align more with the timing in the CAMs. Now have the
showers and storms at KRST between 26.08z and 26.12z and KLSE
between 26.09z and 26.13z. Otherwise, did not make too many
changes from the 25.18z TAFs.
&&
.ARX WATCHES/WARNINGS/ADVISORIES...
WI...NONE.
MN...NONE.
IA...NONE.
&&
$$
UPDATE...Boyne
DISCUSSION...Rieck
AVIATION...Boyne
Area Forecast Discussion
National Weather Service Cheyenne WY
529 PM MDT Tue Jul 25 2023
.SHORT TERM...(This evening through Wednesday)
Issued at 200 PM MDT Tue Jul 25 2023
The convective threat this afternoon appears greatly diminished
from prior forecast cycles thanks to a stronger push of dry
westerly flow early this afternoon. GOES visible satellite shows
only modest convective growth even over the higher terrain as of
20z. This, combined with surface Tds running a few degrees below
guidance, and persistent morning cloud cover that held back
temperatures by an hour or two along and to the east of I-25, have
resulted in enough confidence to lower the PoP forecast. Kept a
mention of a few isolated showers and possibly a rumble of
thunder along the far eastern edge of the CWA including the SNY
area, as a few HREF ensemble members do still fire weak, high-
based convection here after 23z. However, given the trends in
surface obs, satellite, and recent HRRR runs, even this now
appears unlikely this afternoon. Afternoon high temperatures will
continue to run around 5 to 7 degrees above average across most
locations in southeast Wyoming and western Nebraska today.
Subtle changes in the upper-level pattern will result in a
slightly more active day of convection on Wednesday. A trough
passing through the Pacific Northwest will act to compress the
southwest CONUS ridge a bit, with subtle height falls noted over
the central and northern Rockies in 500mb progs during the
morning and afternoon hours. At the same time a plume of deeper
moisture from the southwest, noted by PWAT normalized anomalies
climbing into the 1-1.5 sigma range, will push north and eastward
across southern Wyoming/northern Colorado. Forecast soundings from
various short-term guidance support PWAT values in the 0.6" to
0.7" range generally, with convective initiation occurring in the
noon-1pm timeframe. The most favored area for convection will be
over the higher terrain of eastern Wyoming with thunderstorms
drifting eastward through the afternoon and early evening hours.
Heavy downpours will be the primary threat, however cant entirely
rule out some gusty outflow winds as well. This will be especially
true later in convective mode given inverted V soundings with
DCAPE in the 900-1100 range. Plentiful moisture in the mid-levels
of forecast soundings may also aid in outflow wind gusts,
increasing mass acceleration in locations where repeated outflows
can pool and head east. A few HREF ensemble members do indicate
the potential for some lingering shower activity overnight, west
of the Laramie Range. Elevated surface moisture values from
daytime convection and a few weak embedded vort max impulses in
southwest flow aloft supports the shower threat through around 06z
Thursday morning.
.LONG TERM...(Wednesday night through Tuesday)
Issued at 200 PM MDT Tue Jul 25 2023
Main Weather Highlights:
1) Daily thunderstorm chances can be expected across most areas east
of the Laramie Range with better chances for area wide coverage on
Friday and into the weekend.
2) There is a Marginal Risk for severe weather for the southeastern
corner of the Nebraska Panhandle on Thursday.
3) Staying unsettled for the start of next week as the monsoon
moisture should begin to impact the overall weather over the Front
Range. Scattered to widespread showers and thunderstorms are
possible.
4) Temperatures trending slightly cooler over the weekend but
staying near seasonal normals.
Overview: Minimal changes made in the long term forecast package as
the overall weather pattern remains on track. A gradual flattening
and breakdown of ridging pattern will open the door for more
organized shower and thunderstorm activity Thursday and Friday, this
will transition to a monsoonal influence which will increase both
PoP chances and coverage over the weekend and into next week. Model
parameters are hinting at the potential for more organized severe
weather to impact the region on Saturday.
Discussion: As mentioned above, the ridge will begin to transition
and flatten out as it slowly retrogrades to the west. In response
the flow aloft will gradually shift toward a more west-northwesterly
flow and allow for some weak vorticity perturbations to transverse
aloft increasing both the chances and coverage for showers and
thunderstorms. Temperatures will trend slightly cooler with the
increase in cloud coverage and the main thermal ridge associated
with the ridge weakens and shifts to the west, but we should hold on
to temperatures near seasonal normals for most areas.
The main days of concern will be Friday and again on Saturday.
Leeside development of a surface high pressure should shift the
surface flow more to the south and east and allow for modest
moisture advection and increase dewpoints across much of eastern
Wyoming and the Nebraska Panhandle. Surface heating prior to CI
should allow for modest CAPE values to develop and with ejecting
shortwaves aloft, organized convection seems probably on Friday and
Saturday, with Saturday being the day of most concerns as some
models are showing high CAPE values with adequate 0-6km shear to help
support thunderstorm longevity.
Sunday is shaping up to be a transitional day as the ridge begins to
amplify and move back toward the east allowing for some drying in
the mid-levels to occur and shift the flow aloft toward a drier
westerly flow. With a residual moist boundary layer still in place
can`t rule out the threat of some diurnal convection during the
afternoon hours.
Heading into next week, models are in fairly good agreement for much
of the Front Range to be influenced by a monsoonal push of moisture
that will increase the rain and thunderstorm chances next week.
Details are still unclear and these moisture plumes heavily rely on
source point and advection path but all indicators point toward the
weather staying unsettled for the first half of next week.
&&
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 521 PM MDT Tue Jul 25 2023
Wyoming Terminals... Isolated showers and a couple thunderstorms
are present across southeast Wyoming. VCSH continues for KCYS and
KLAR with VCTS at KRWL for the thunderstorms over south-central
Wyoming. Winds and wind gusts are expected to decrease over the
next 3 hours before becoming calm overnight. Winds will pick back
up tomorrow afternoon along with increased chances for showers and
thunderstorms. Included VCTS for all Wyoming sites starting at
18Z tomorrow, but timing will be further narrowed down over the
next several hours.
Nebraska Terminals... VFR conditions with breezy winds and mostly
clear skies across all Nebraska sites. Winds will decrease over
the next 3 hours before becoming calm overnight. Winds increase
again tomorrow afternoon, with several sites gusting around 15 to
20 kts. Isolated showers and thunderstorms will be possible across
western Nebraska tomorrow, so included VCSH beginning at 18Z for
KBFF, KSNY, and KAIA. Showers and thunderstorms likely to begin
after the 00Z TAF period for KCDR. Some thunderstorms may be
severe tomorrow with a threat for strong winds and hail.
&&
.FIRE WEATHER...
Issued at 101 PM MDT Tue Jul 25 2023
Fire weather concerns will be centered on any lightning that may
evolve from thunderstorms over the next few days. RH values and wind
speeds will remain above any fire weather criteria. However, a few
instances of dry thunderstorms have occurred over the past few
days and this will again be possible on Wednesday through the end
of the week. Most storms will produce heavy downpours later in their
lifecycle, but early afternoon storms may be drier and thus pose
a greater `dry` lightning threat.
&&
.CYS WATCHES/WARNINGS/ADVISORIES...
WY...None.
NE...None.
&&
$$
SHORT TERM...MAC
LONG TERM...AW
AVIATION...AM
FIRE WEATHER...MAC
Area Forecast Discussion
National Weather Service Des Moines IA
635 PM CDT Tue Jul 25 2023
...Updated for the 00z Aviation Discussion...
.DISCUSSION.../Tonight through Tuesday/
Issued at 252 PM CDT Tue Jul 25 2023
Key Messages:
--Strong to severe storms possible overnight into early Wednesday,
mainly across the north half of Iowa.
-- Warmest temps of the season thus far still expected Wednesday
through Friday
-- Heat Advisory in effect on Wednesday for portions of central/southern
Iowa
Late this afternoon into Tonight:
Area of elevated showers and isolated thunderstorms continues to
move across portions of central and southern Iowa this afternoon.
While sfc based instability remains moderate/strong /1500-2500
J/kg/, these showers have remain rooted well above the PBL due to
strong capping in place across the area. There is a low
probability that an isolated strong storm is possible late this
afternoon and early this evening, although most of the guidance
suggests all of the activity should remain weak and elevated.
Tonight...a seasonally strong upper shortwave with modest H5
height falls is expected to move across northern Iowa this evening
and overnight. This is expected to induce a moderate 40-50kt LLJ
after 03Z with scattered strong to severe storm initiating over
parts of SD/MN. Most models indicate these storms will expand and
grow upscale in the 06Z to 12Z Wed timeframe moving e/sewd along
the stout instability gradient over IA with MUCAPE values >2000
J/kg. The big question is how far south the storms will be able
to progress? Mid-level thermal advection today has allowed H7
temps to warm, with the +12C contour running west to east
generally along the IA/MN border then arcing swd into eastern
Iowa. Typically storms struggle to maintain/survive south of this
+12C contour due to stronger capping, unless a strong and deep
cold pool can become established. Currently, a majority of the
12Z suite of CAM solutions agree on developing a well defined MCS
tracking across northwestern and northern IA after midnight,
diminishing with swd extend towards the US30 corridor. It should
be noted that the latest HRRR runs have consistently showed much
less convection, with almost no convective activity over Iowa. If
capping is stronger, this is also a possibility. If an MCS can
develop, the primary threat would be strong winds, with several
CAM solutions showing peak hourly wind speeds > 50 kts.
Wednesday and Wednesday night:
Linger showers and thunderstorms may be ongoing early Wednesday
morning, mainly across northern and eastern Iowa, with all
precipitation shifting east of the area by 15Z. Skies should then
become sunny to partly cloudy with a northerly low level flow
becoming established. This will result in a rather tricky
temperature forecast on Wednesday, Several model clusters /ECMWF/
show H8 temps cooling quite a bit into the teens Celsius, whereas
other models show more limited cooling with H8 temps still in the
20s Celsius. Additionally, the drier N/NWLY flow may actually permit
better vertical mixing then we`ve seen the past few days, thus
temperatures might actually be quite a bit warmer. Similar
uncertainty with Tds /will they hold in the 70s or mix out into
the 60s?/. After coordination with neighboring WFOs, decided to
issue a Heat Advisory for generally I-80 and south, including Polk
County. Although we may struggle to reach our HI criteria of 105F
/thinking more 100F to 105F/ we will have a high number of
vulnerable people outdoors on Wednesday. Dry conditions will
continue on Wednesday night, with mild overnight lows in the 60s
north to 70s south.
Thursday through Monday:
Another surge of strong WAA occurs on Thursday, and continues into
Friday. H8 temps are forecast to rise in the +23C to +27C range,
likely yielding highs of 95-100F. With sfc Td values in the 60s
to low 70s, HI values near or exceeding 105F are again possible.
Additionally low temps are also likely to remain very warm
overnight, especially across central and southern Iowa, with MinT
values only falling into the mid 70s. Additional heat headlines
are possible in this period. There will again be chances for
thunderstorms on Thursday night, and again on Friday and Friday
night as a frontal boundary gradually shifts swd.
Slightly cooler temperatures will prevail into the upcoming
weekend, with just slight chances of showers and storms.
&&
.AVIATION.../For the 00Z TAFS through 00Z Wednesday evening/
Issued at 630 PM CDT Tue Jul 25 2023
VFR expected for most terminals within the next 6 hours with
showers and localized MVFR possible for KOTM. Thunderstorms to
impact northern terminals after 06z with gusty winds and MVFR
conditions possible. Winds become northwesterly tomorrow after an
area of low pressure passes across the area in the morning.
&&
.DMX WATCHES/WARNINGS/ADVISORIES...
Heat Advisory from noon to 8 PM CDT Wednesday for IAZ057>060-
070>075-081>086-092>097.
&&
$$
DISCUSSION...Fowle
AVIATION...Jimenez
Area Forecast Discussion
National Weather Service Quad Cities IA IL
707 PM CDT Tue Jul 25 2023
...AVIATION UPDATE...
.SHORT TERM...(This evening through Wednesday)
Issued at 230 PM CDT Tue Jul 25 2023
Key Messages:
1. Heat advisory has been issued along and south of a Fairfield to
Galesburg line from 11 AM to 8 PM.
2. Potential for two round of showers and storms. The first this
evening and the second from 3 to 9 AM on Wednesday. Isolated severe
storms are possible.
Discussion:
High pressure has shifted eastward into Michigan and Indiana early
this afternoon. To our west, an MCV is shifting southeastward from
Nebraska into western Iowa with showers and isolated thunderstorms
moving into southwestern Iowa. Across eastern Iowa, northwest
Illinois and far northeast Missouri temperatures have warmed into
the mid to upper 80s with sites in far southeast Iowa around 90
degrees. Dewpoints across the area were in the upper 60s to lower
70s.
In the near term, an MCV and showers and storms continue to move
eastward across southern Iowa. This forecast to move eastward
across the area in the 21 to 03 UTC time frame. This MCV is moving
into a destabilizing environment with building CAPE. The +12*C at
700 MB continues to move eastward this afternoon ahead of the MCV
which may largely cap convection late this afternoon and into this
evening. Have placed 20%T chances of showers and storms across the
area in the 4 to 10 PM timeframe. There is a chance that any storms
that become surface based would produce a damaging wind and hail
threat. The area remains in a marginal or level 1 risk for severe
storms this evening.
A second, stronger, shortwave is forecast to move southeastward
across Minnesota and into northern Illinois in the 08 to 14/15 UTC
timeframe. The HRRR continues to back off on moving convection
across the area overnight while the 12 UTC NAM Nest continues to
show a weak MCS moving across the area. Upper level divergence and
theta-e advection in larger scale models would place the better
lift to our north across Minnesota into Wisconsin.
Temperatures on Wednesday are largely dependent on the coverage
storms and cloud cover Wednesday morning. The highest likelihood of
heat indices above 100 is along and south of a Fairfield to
Galesburg line. This area is showing heat indices of 100 to 104 for
several hours on Wednesday. In collaboration with neighboring
offices, have issued a heat advisories for these areas. High
temperatures on Wednesday were decreased slightly north of
Interstate 80 were highs are range from 90 to 95 with highs of 94 to
98 to the south. Dewpoints across the area will be in the upper 60s
to around 70.
.LONG TERM...(Wednesday night through Tuesday)
Issued at 230 PM CDT Tue Jul 25 2023
A brief but slight respite from the heat over the weekend before
heat starts building again next week. Media, refer to the climate
section as to when the six main climate sites last reached 100.
Wednesday night/Thursday
Assessment...high confidence on excessive temperatures
The heat dome builds further into the area resulting in hot and dry
conditions. The probability is high that heat headlines will be
needed for Thursday. Attention then turns to Thursday night and
Friday.
Thursday night through Friday night
Assessment...high confidence on hot and humid conditions. Medium
confidence on rain chances
The model solutions vary on timing but the expected cold front will
slowly begin entering the area either late Thursday night or
sometime during the day on Friday. The main push of the front into
the area looks to be Friday night before it stalls out and begins to
dissipate.
The temperature forecast for Friday is highly dependent upon where
the front is located. The potential for convection `could` suppress
temperatures but the increase in dew points `may` overcome any
temperature suppression.
The model consensus has slight chance to chance pops Thursday night
and Friday with chance to likely pops Friday night. The highest pops
during the entire time frame are along and north of I-80.
As mentioned earlier, temperatures and heat index values are
dependent upon clouds and rain. The probability of continuing a heat
advisory into Thursday night and Friday is high. IF the front is
delayed until late Friday or Friday night then the probability of
headlines for a heat warning for Friday increases considerably.
Saturday/Saturday night
Assessment...medium confidence on rain chances
The models vary on where the front stalls but all agree that the
front will slowly dissipate. The trends with the models have been to
lower the overall areal coverage of rain the first half of the
weekend.
The model consensus has slight chance pops Saturday morning with
mainly dry conditions Saturday afternoon and night.
With the front over the area, temperatures will be somewhat cooler
on Saturday.
Sunday
Assessment...medium to high confidence
The model consensus has very warm and dry conditions for the area as
the weak high behind the front moves into the Great Lakes. The plus
side is that dew points will be much lower than Saturday.
Sunday night through Tuesday
Assessment...high confidence on warming temperatures. Low to
medium confidence on rain chances
Early next week the model consensus begins to rebuild the heat dome
northward as an upper level high pushes north into the northern
Rockies. At the same time an upper low will move further south along
the east coast. The resulting pattern places the area under
northwest flow aloft.
The models agree that there will be two upper level disturbances
moving through in the flow aloft. Right now the timing of the
disturbances suggest the potential for nocturnal storms across the
area that may be in the form of an organized thunderstorm complex.
The model consensus suggests this with the evening hours dry each
day. The highest pops (which are currently chance) are late Sunday
night/Monday morning and again late Monday night into Tuesday
morning.
&&
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 658 PM CDT Tue Jul 25 2023
Quiet conditions will continue through this evening and most of
tonight with prevailing VFR. There is a chance for a few showers
or storms late into early Wednesday morning. The best chance for
a brief period of thunder is at DBQ. Then for the remainder of the
day on Wednesday, expect dry and hot conditions with steady W to
NW winds.
&&
.CLIMATE...
Issued at 230 PM CDT Tue Jul 25 2023
Here are the dates the last time the six main climate sites
reached 100 degrees:
StationDateHigh
Burlington, IA9/09/2013 100
Cedar Rapids, IA 8/30/2013100
Davenport, IA7/07/2012100
Dubuque, IA7/25/2012101
Iowa City, IA9/10/2013101
Moline, IL 7/25/2012102
&&
.DVN WATCHES/WARNINGS/ADVISORIES...
IA...Heat Advisory from 11 AM to 8 PM CDT Wednesday for Des Moines-
Henry IA-Jefferson-Lee-Van Buren.
IL...Heat Advisory from 11 AM to 8 PM CDT Wednesday for Hancock-
Henderson-McDonough-Warren.
MO...Heat Advisory from 11 AM to 8 PM CDT Wednesday for Clark-
Scotland.
&&
$$
SHORT TERM...Cousins
LONG TERM...08
AVIATION...Uttech
CLIMATE...08
AREA FORECAST DISCUSSION
National Weather Service Sioux Falls SD
630 PM CDT Tue Jul 25 2023
.SHORT TERM...(This Evening through Wednesday)
Issued at 253 PM CDT Tue Jul 25 2023
Key Messages:
1. Scattered storms expected mid/late evening into the overnight
with some strong to severe storms possible. Confidence is low in
timing and location.
2. Heat and humidity lead to dangerous heat indices through
Thursday.
3. Periodic but uncertain shower/storm chances over the next
week.
_______________________________________________________________
Short Term Discussion:
A few clouds around, mainly associated with convection.
Temperatures continue to climb along with the humidity early this
afternoon. Through 19z/2 PM CDT, we`re already seeing temps in
the upper 80s to mid 90s with heat index values in the upper 90s
to lower 100s. Dew points are in the upper 60s to mid 70s.
Maintained previously issued heat advisory, although shifted the
start time earlier to 2 PM. Did not expand in area, but have seen
some periodic obs of heat index over 100 elsewhere. Folks should
limit time outdoors, especially during peak heating. Take
precautions to prevent heat illness if you have to be outside.
South to southeasterly winds gusting around 25 mph are likely not
bringing much relief to those outside, given the increasing
humidity.
Main challenge of the forecast has been convection and convective
evolution. Since this morning`s forecast, models have slowed the
progression of the wave (and thus storm chances). Satellite shows
that the main wave is still presently (as of 19z/2 PM CDT) in
eastern MT/WY toward the far western portions of ND/SD with showers
ahead of it. This wave is expected to be the catalyst for convection
later this afternoon through tonight as it progresses
east/southeastward. Convection should pop up over the north central
SD/central ND as the wave interacts with the hot and humid air mass.
Convection is expected to develop as discrete cells. Main threats
with discrete cells would be large hail around 2 inches (mid
level lapse rates ~7.5 deg C/km, 0-6km bulk shear near 30 kts) and
damaging winds to 70 mph (DCAPE near 1000 J/kg). As these
discrete cells trek southeastward along the instability gradient,
expect them to form a line and continue to track southeasterly,
becoming more parallel to bulk shear. Thus, expect a transition to
a severe wind threat with isolated large hail. With DCAPE
continuing to be at or exceed 1000 J/kg and dry sub cloud layer,
wind gusts to 70 mph in the strongest portions of the line are the
main threat. Tornadoes are unlikely, with convection and cloud
bases generally more elevated. Heavy rain is also a threat with
PWATs over an inch (approaching two inches for some folks), which
could lead to localized ponding of water but widespread flooding
impacts are not expected.
Now, where does the uncertainty come in to play? For one, hi res
guidance has continued to slow down the progression of convection,
but there are still a few outliers (NSSL WRF) running 2-3 hours
ahead of the majority. Additionally, the HRRR and RAP have
persistently shown convection hitting the strong cap over our area
and promptly dissipating, nearly splitting our forecast area
entirely. Some models do have the instability/theta-e gradient a
bit further north, which may be why some of the hi res guidance
keeps the convection further north.
Temperatures through the overnight fall into the upper 60s to
near 70. For Wednesday, surface high pressure slides overhead,
which should lead to lighter winds even when peak mixing occurs
in the afternoon. Another hot and humid day is on tap, with highs
in the 90s to lower 100s. Expect heat indices in the upper 90s to
lower 100s, with a Heat Advisory likely for portions of the area.
.LONG TERM...(Wednesday Night through Tuesday)
Issued at 253 PM CDT Tue Jul 25 2023
Flow aloft shifts more zonal late Wednesday, with a subtle wave
tracking through the northern Plains as surface high pressure slides
to the southeast. Can`t rule out some isolated showers/storms in the
evening/overnight Wednesday into Thursday, but confidence is low
given the subtly of the wave. Lows again in the upper 60s to lower
70s.
More of the same on Thursday, with zonal flow aloft and another
wave progged to swing through during the afternoon/evening hours.
Again, could see scattered showers/storms later in the day/night
Thursday, but with variance in the timing of the wave by 6-12
hours, confidence in pops is low. Have much higher confidence in
the heat and humidity once again Thursday, with another day of
heat headlines likely for portions of the area as heat indices
climb toward 105. Highs again climb into the 90s and lower 100s.
Relatively cooler high pressure with northwesterly flow aloft builds
in for the end of the week and the weekend. Zonal flow early in the
weekend gives way to a building ridge by the second half of the
weekend and early next week. Temperatures should stay closer to but
still above normal for most of the time. Periodic waves will bring
occasional shower/storm chances to the region, but confidence in
details is low. Given low confidence and focus on the short term,
have left NBM as is.
&&
.AVIATION...(For the 00Z TAFS through 00Z Wednesday Evening)
Issued at 628 PM CDT Tue Jul 25 2023
Still a lot of question marks regarding convective development
this evening. Scattered strong to severe thunderstorms in central
SD towards the James Valley from about 1-5z starting to look like
the better bet with additional scattered strong to severe storms
possible in southwest MN later, from about 4z to 9z. Between these
two areas activity should be much more isolated. The main threats
from the strongest storms will be 2 inch hail and wind gusts to 70
mph. Outside of the thunderstorms VFR conditions are expected.
&&
.FSD WATCHES/WARNINGS/ADVISORIES...
SD...Heat Advisory until 8 PM CDT this evening for SDZ050-057-063.
MN...None.
IA...None.
NE...None.
&&
$$
SHORT TERM...SG
LONG TERM...SG
AVIATION...08
Area Forecast Discussion
National Weather Service Goodland KS
802 PM MDT Tue Jul 25 2023
.UPDATE...
Issued at 800 PM MDT Tue Jul 25 2023
With temperatures dropping in tandem with sunset over the past
hour, heat indices have dropped below criteria. Have allowed the
Advisory to be canceled/expire as a result.
&&
.SHORT TERM...(This evening through Wednesday)
Issued at 133 PM MDT Tue Jul 25 2023
18Z water vapor imagery and RAP analysis indicated large H4 ridge
centered over the southern High Plains. Some semblance of an
embedded short wave trough was departing the CWA to the southeast.
At the surface, hot and humid airmass in place across the CWA with
a few remnant boundaries/convergent areas noted.
Main concern will be dangerously hot conditions this afternoon
followed by thunderstorm chances tonight and tomorrow.
Current heat advisory looks on track as afternoon dewpoints have
been slow to mix out, allowing for higher apparent temperatures to
occur further west than expected. Current forecast is on track so
do not expect any further changes to advisories.
For thunderstorms tonight, strong capping inversion was apparent
in morning soundings along with a deep layer of very dry air. This
will likely make any storm development unlikely away from the
higher terrain despite the presence of persistent convergence
zones as even if cap could be overcome, dry air entrainment would
likely keep storms from developing fully. Decent signal that area
of storms will move off of higher terrain and into CWA in the
00-04Z time period, although coverage should be very spotty. Could
see some impacts regardless of the rain amounts as pattern
favorable for strong wind gusts and a few lightning strikes.
For Wednesday, temperatures aloft cool a few degrees celsius as
weak cold front slides over area. With slightly cooler temps aloft
and more cloud cover, will see some minor relief from the heat but
not by much. Similar pattern for thunderstorms expected although
with slightly weaker capping storms will likely be possible in the
late afternoon into the evening. As was the case today, expect
spotty coverage with strong winds and lightning the main threat.
.LONG TERM...(Thursday through Tuesday)
Issued at 1235 PM MDT Tue Jul 25 2023
Essentially a persistence forecast. Long range guidance continues
to indicate that a robust upper level ridge.. situated over the
4-Corners, Rockies and Central/Southern Plains.. will persist
through the upcoming weekend into next week. The location and
orientation of the ridge (per latest GFS/ECMWF guidance) suggest
that the mid-latitude westerlies (and any small amplitude waves
therein) will largely be relegated to higher latitudes (e.g. north
of I-80, Dakotas). While isolated/scattered diurnal convection may
develop on the lee slopes of the Colorado Front Range and adjacent
portions of the Palmer Divide during the late afternoon hours on
any given day.. synoptic environments characterized by weak
steering flow tend to confine/anchor such development in close
proximity to the mountains. With moderate high-based instability
and strong to extreme DCAPE over the region throughout this
period, downstream propagation into the Tri-State area cannot be
ruled out, mainly from the northwest and north (e.g. WY/SD and NE
Panhandle) -- in closer proximity to the westerlies -- where some
degree of convective organization and outflow consolidation are
[relatively] more likely to arise. With the above in mind, above
average temperatures and below average chances for precipitation
(convection) are anticipated throughout the long term period.
&&
.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 456 PM MDT Tue Jul 25 2023
Both terminals will see VFR conditions through the forecast
period.
Winds for KGLD, west-southwest around 10kts through 11z
Wednesday, then northwest. By 19z, southeast around 10kts.
Winds for KMCK, light/variable through 06z Wednesday then west
around 10kts. By 12z light/variable becoming southeast at 10kts
by 17z.
&&
.GLD WATCHES/WARNINGS/ADVISORIES...
KS...NONE.
CO...NONE.
NE...NONE.
&&
$$
UPDATE...JN
SHORT TERM...JRM
LONG TERM...Vincent
AVIATION...JN
Area Forecast Discussion
National Weather Service Grand Rapids MI
947 PM EDT Tue Jul 25 2023
LATEST UPDATE...
Update
.UPDATE...
Issued at 947 PM EDT Tue Jul 25 2023
No changes of note for this update. Convection around Green Bay
already appears to be splashing out, so there is very little risk
of that activity crossing Lake Michigan into the Ludington area.
Visibility restrictions in smoke and haze continue to hold sway
across the area and this will likely persist well into Wednesday.
A peek at the 00Z HRRR guidance suggests convection moving onshore
around noon tomorrow with little in the way of preceding warm
advection showers and storms. This would mean a more pristine
preconvective environment that will be even more supportive of
strong to severe convection. It`s true that other CAM guidance
remains highly disparate in their solution details. However,
taking the broader view, tomorrow we will have seasonably strong
dynamics and thermodynamics combined with strong QG forcing from a
tight PV maximum, as well as fairly close temporal alignment with
diurnal peak instability. Given all of this, it`s hard to imagine
our area emerging unscathed from severe weather.
&&
.SHORT TERM...(This evening through Wednesday night)
Issued at 247 PM EDT Tue Jul 25 2023
...Severe Weather Wednesday...
While there is a chance for a few isolated showers this afternoon
and evening, the main focus of the next 24+ hours is the severe
weather risk for Wednesday. The Storm Prediction Center has
continued the Enhanced Risk for severe weather for Wednesday
afternoon and evening with those near and south of I-96 having the
greatest risk. Plenty of potential for damaging winds and a few
tornadoes though some questions do remain on whether that
potential will be realized for all of lower Michigan. Hail is a
lesser threat but still could be a concern in some storms.
At this time it still looks as through the worst weather can be
expected early afternoon through early evening with some hint
that the worst could develop near or east of US-131 and near/south
of I-96. Best wind profiles and the development of instability
should be better in southeast Michigan where more sunshine and
deeper southerly flow will be in place for much if not all of the
day. Supercells could develop at the onset of storms as a
shortwave moves across the state...with a more organized line of
storms late in the afternoon and evening as the storms progress to
the east/southeast. Limiting factor for further western
initiation will be how much cloud cover and/or lingering light
showers will be in place Wednesday morning over lower Michigan
from convection currently over the Dakotas.
With the southerly flow also comes a great deal of moisture
advection ahead of storms. Couple that with the potential of
the broader storm system pivoting over central michigan...and prolonged
periods of heavy rainfall may occur over the same areas. Generally
this type of set up means urban areas would be at most risk for
some flooding though any area that sees prolonged heavy rain could
see some localized impacts.
System exits quickly in the evening with a quiet yet warm and
muggy overnight Wednesday Night expected.
.LONG TERM...(Thursday through Tuesday)
Issued at 247 PM EDT Tue Jul 25 2023
An upper low across southwest Canada moves east during the period
and initially causes heights to rise across the Great Lakes on
Thursday into Friday. It merges with troughing across eastern Canada
by the weekend and re-establishes troughing across the Great
Lakes.
The effect on sensible weather will be a break in the convection
under shortwave ridging on Thursday into Friday bringing two days of
heat and humidity with no cooling influence of afternoon convection
expected on Thursday. Storms should be on the increase on Friday
across northern and central Lower Michigan as heights begin to fall
and a cold front sags south into the northern and central forecast
area.
The front continues to move slowly south on Saturday and cooler and
drier weather builds in for Sunday and into early next week with
Canadian sfc high bringing much lower temperatures and dew points in
the fabulous 50s.
&&
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 750 PM EDT Tue Jul 25 2023
MVFR visibility restrictions in a combination of smoke and haze will
continue overnight. IFR restrictions seem less likely overall,
especially prior to 06Z. A chance for thunderstorms will enter far
southwest Lower Michigan around sunrise tomorrow, hence the VCTS
mention at AZO and BTL. Any thunderstorms that develop will
feature heavy rain and very temporary IFR visibility restrictions.
More significant thunderstorms with the potential for widespread
severe winds are possible after 18Z Wednesday and could bring
substantial impacts to aviation operations.
&&
.MARINE...
Issued at 334 PM EDT Tue Jul 25 2023
South winds are expected to increase tonight and could touch Small
Craft Advisory criteria by Wednesday morning or afternoon. In
addition to this, thunderstorms could generate locally higher
winds and waves during Wednesday. We will hold off on issuing a
SCA or Beach Hazards Statement at this point, given continued low
confidence in how timing of convection will affect the synoptic
wind. Southwest winds on Thursday could build some higher waves
as well.
&&
.GRR WATCHES/WARNINGS/ADVISORIES...
MI...None.
LM...None.
&&
$$
UPDATE...TJT
SHORT TERM...Maczko
LONG TERM...Ostuno
AVIATION...TJT
MARINE...Ostuno
Area Forecast Discussion
National Weather Service Gray ME
1118 PM EDT Tue Jul 25 2023
.SYNOPSIS...
A brief dry period is expected on Wednesday as high pressure
builds in. It will then become very warm and uncomfortably humid
for much of the remainder of the work week, with a return of
showers and thunderstorms.
&&
.NEAR TERM /THROUGH WEDNESDAY/...
11:15pm Update... The last of the thunderstorms are coming to an
end. A few remnant showers are moving through the area, and are
expected to gradually diminish through the overnight. Patchy fog
is expected to continue developing through the overnight hours,
especially in areas that saw rain today. Otherwise a fairly
quiet and warm night looks to be on track at this point.
7PM Update...Quick update this evening to increase pops and
thunder chances in Maine along the line of convection.
Considerable urban flash flooding has occurred in the
Lewiston/Auburn area with 2 to 4" of rain recorded in an hour of
half. Expect the thunderstorm and heavy rain activity in Maine
to diminish over the next few hours as daytime instability is
lost along with the low level convergence along the sea breeze
front.
Water vapor imagery shows a compact short wave over PA/NY that will
trek across the forecast area through this evening. This wave will
continue to trigger thunderstorms through this evening with a few
storms capable of strong winds and isolated instances of flash
flooding. Similar to yesterday, there isn`t much of a front for
storms to organize along. This is creating some variance amongst the
12Z CAM suite as to where storms will initiate as well as how strong
storms will become. A broad consensus focuses storms along the
western Maine foothills towards the Maine coastline with a
secondary area of focus across southern New Hampshire into far
SW Maine later this evening.
The convective parameter spaces is currently characterized by 1000
to 1500 J/kg of ML CAPE and 25 to 30 kts of effective shear. This
will be sufficient enough for a few strong updrafts that could lead
to some gusty outflow winds or potentially a strong to severe
downburst if any storms collapse. Modest mid level lapse rates
around 6C/km could also lead to some hail, and there is a non zero
risk for some marginal severe hail.
What is more of a concern is the increase in PWATs to around 1.5
inches and the potential for slow moving storms along a convergence
zone near the Maine foothills and another convergence zone across MA
that could shift into southern NH later this evening. Storms
have already developed over east-central Oxford County in line
with most runs of the HRRR since early this morning. Similar to
yesrday`s storm that produced flash flooding, the HRRR suggest
these storms will be slow moving. The 12Z HREF 3-hour max QPF
shows isolated pockets of up to 3-4 inches suggesting this is
the high end of heavy rainfall potential. Looking at the 12Z
HREF 3-hour ensemble mean only tops out around 0.5 inches
indicating the isolated nature of heaviest rainfall. Thus, the
greatest threat appears to be isolated instances of flash
flooding followed by strong winds and possibly some small to
near severe hail stones.
Convection wanes between 8 and 10 PM this evening with clearing
skies overnight. Fog will be likely across areas that do see
rainfall and along sheltered valleys with patchy fog elsewhere.
Lows will range from the upper 50s north to mid 60s south.
&&
.SHORT TERM /WEDNESDAY NIGHT THROUGH 6 PM WEDNESDAY/...
Fair weather looks to be in store for Wednesday as high pressure
builds in from the southwest. SW flow will allow for temperatures to
climb into the mid to upper 80s, while some onshore wind component
will keep the beaches several degrees cooler than the interior.
&&
.LONG TERM /WEDNESDAY NIGHT THROUGH TUESDAY/...
The big picture in the long term will be the potential for an
organized convective/MCS on Thursday with heavy rain/severe
storms accompanied and followed by sultry heat that will
increase into Friday. This will be followed by a welcome cool
down Sunday into next week.
Wednesday night will be quiet across the area in the wake of the
passing ridge. Meanwhile a pair of shortwave troughs and
associated frontal system will be progressing eastward out of
NY. Concern is growing for strong/severe storms and torrential
rainfall with this system. The LLJ around 40-50kt will be
paralleling the warm front as it noses into New England late
Thursday morning. PWATs are projected to surge over 2" with warm
cloud depths >12kft. The trends have favored a track from NY
and into NH/ME by midday Thursday, however a lot of uncertainty
remains with this exact location/track which could have great
impacts on our forecast. For now, have added the pops/clouds
expected with the convection, which will have the effect of
limiting our potential heating for the day. If not for the
convection, temperatures would shoot up into the upper 80s to
low/mid 90s as 850H temps climb to 17-19C. SPC Day 3 outlook has
the southern half of the forecast area in a slight risk, and a
marginal risk elsewhere. The WPC Excessive Rainfall Outlook
(ERO) has the area in a marginally risk for flash flooding.
Confidence in the track could lead to adjustments in these
categories. Something to closely monitor with future forecast
packages.
Showers and thunderstorms could linger Thursday evening, but as
the best jet dynamics weaken and push east with the wave expect
coverage to lessen. It will be a warm and muggy night with
dewpoints in the 70s. This will support a rapid warm up on
Friday, with heat inidices near to just below headline
criteria in southern areas. Some scattered convection is
possible, but not widespread enough to limit heat with cloud
coverage. Once again there will be concerns for heavy rainfall.
Attention then turns to an approaching cold front Friday Night
into Saturday morning, continuing rain chances. Looking at a
notable cool down Sunday
This front will also bring a significant cool down to the
region. While 850H temps +8C-10C. This will translate to high
temperatures in the mid 70s, with the higher terrain areas
possibly seeing highs only in the upper 60s. This cooler weather
will continue into Monday as the upper level trough lingers
over Quebec.
&&
.AVIATION /03Z WEDNESDAY THROUGH SUNDAY/...
Short Term... Valley and coastal fog will likely bring LIFR
conditions to KLEB, KHIE, and KRKD tonight and there is
potential for IFR to LIFR at KAUG. Patchy fog may impact
remaining TAF sites although confidence is lower. VFR prevails
under high pressure Wednesday.
Long Term...The ridge will break down on Wednesday night
allowing a shortwave into New England, which will bring sct to
numerous TSRA to the terminals from west to east. Mainly VFR
conditions expected Friday apart from fog possible.
&&
.MARINE...
Short Term...SW flow prevails tonight through Wednesday with
winds and seas remaining below SCA thresholds. High pressure
builds into the waters late tonight into WEdnesday.
Long Term...The Bermuda High builds offshore late
Wednesday through the latter half of the week bringing
predominately S to SW winds around 10 to 15 kt, then
veers to the NW Saturday evening after a cold front pushes
offshore. Seas will be around 2-3 ft.
&&
.GYX WATCHES/WARNINGS/ADVISORIES...
ME...None.
NH...None.
MARINE...None.
&&
$$
NEAR TERM...Clair/Schroeter
SHORT TERM...Schroeter
LONG TERM...Jamison
Area Forecast Discussion...Updated
National Weather Service Lincoln IL
844 PM CDT Tue Jul 25 2023
.SYNOPSIS...
Issued at 827 PM CDT Tue Jul 25 2023
Hot and humid weather will build over the next few days, peaking
on Friday when highs near 100 degrees are likely over central and
southeast Illinois. The heat index is expected to reach 100 to 105
Wednesday afternoon and 105 to 110 degrees on Thursday and Friday
afternoon. Some relief from the high heat and humidity will
arrive to parts of central IL with a cold front bringing showers
and thunderstorms Friday night, though this front may not reach
much further than I-72, and areas south of there may see the heat
linger into Saturday.
&&
.UPDATE...
Issued at 845 PM CDT Tue Jul 25 2023
Updated the forecast to address increasing chances of showers and
thunderstorms during this evening. The 01Z/8 pm surface map shows
a warm front lifting ne into central IL and extends from a 1003 mb
surface low in south central SD through northern Iowa into central
IL just sw of Galesburg, Lincoln, Decatur and Effingham. Very
moist and unstable air mass over central IL with PW values of 1.5
to 2.2 inches (highest sw CWA) and SB Capes of 2500-4500 j/kg.
Effective bulk shear is 3-40 kts, highest in southeast IL. (ILX
00Z sounding had PW of 1.74 inches, SB CAPE of 4582 j/kg and 0-6
km wind shear values of 37 kts.
A weak short wave was also moving se into ne and east central MO
and west central IL and combined with a sw low level jet from the
central plains helping produce this isolated convection. Strongest
cell currently east of Taylorville in eastern Christian county
which may have small hail. SPC Day1 outlook has marginal risk of
severe storms tonight nw of the IL river for wind, but will also
need to monitor hail over much of CWA rest of this evening. CAMs
not in the best agreement with evolotion of convection rest of
tonight, but generally show an uptick in showers and thunderstorms
over central IL rest of this evening and then diminishing from
the west during overnight between 06-12Z (1-7 am). Muggy dewpoints
in the low to mid 70s (even 77 in Lincoln and Decatur and 80 at
Macomb which have come up a few degrees past few hours). Lows
overnight mostly in the mid 70s and to transition into a hot and
humid day in the mid 90s on Wed afternoon with heat indices
100-105F common during Wed afternoon. Heat advisory starts at 11
am Wed from McLean, DeWitt, Macon and Christian counties westward.
07
&&
.DISCUSSION...
Issued at 310 PM CDT Tue Jul 25 2023
Key Messages:
* Heat Advisory has been issued beginning midday Wednesday west of
a Bloomington-Taylorville line, but may need to be expanded east
depending on overnight convective debris.
* Hottest day likely to be on Friday, but some potential for the
heat to linger into Saturday south of I-72.
* Temperatures return closer to normal Sunday/Monday, with
potential for warming again before the middle of next week.
Convective concerns tonight and Wednesday:
Afternoon satellite/radar imagery showing remnants of a central
Plains convective cluster tracking southeast into northern
Missouri. The high-reso lution models have been advertising this
feature grazing the southwest forecast area toward 6 pm or so. It
has also been suggesting some development further north this
evening with a remnant MCV, but this has been more uncertain and
the hourly HRRR has been inconsistent with this potential. With
upwards of 4000 J/kg of CAPE to play with, completely dropping the
PoP`s would not be wise. Best focus would likely be near and
north of I-74 closer to the MCV track, and will go with 30-40%
PoP`s toward midnight and afterward in that area. The overnight
MCS development over the northern Plains now looks to be tracking
more closer to the Illinois/Wisconsin border, and the SPC Day2
outlook has significantly scaled back on severe potential this far
south. However, some isolated development in the afternoon can`t
be ruled out as residual boundaries push through the area.
Temperature concerns:
We have gone ahead and issued a Heat Advisory for Wednesday-Friday
in areas roughly west of US-51 (Bloomington to Taylorville
westward). Heat index of 100-105 degrees appears more likely in
that area beginning tomorrow afternoon. Areas east of there are
more uncertain with any overnight convective debris, but if this
should not end up being the case, then an expansion into that area
may be needed later. Thursday and Friday look highly probable for
heat index values 105-110 degrees, and Saturday may also be above
100 heat index if the late week front doesn`t push as far south as
expected.
Temperatures are a bit of a challenge Thursday and Friday. The
unreasonably hot GFS an d even its ensembles appear to be driving
the NBM guidance too high on Friday. 2-meter temperatures from the
GFS would suggest widespread 110 degree highs, which would be
near all-time records if that were to occur. Experience has shown
that it is difficult to get widespread 100`s in this area outside
of a severe drought, and the last time that did occur (2012), we
indeed were in extreme drought conditions. This time, there has
been some drought recovery that has taken place over the last few
weeks, but will it be enough? 8 inch soil moisture analysis shows
percentiles at 20-30% of normal mainly west of a Galesburg-
Effingham line, which did not get quite as much drought relief as
areas further east. Soils in the Illinois River valley are also
sandier, and are more likely to support the triple digit
temperatures. Overall though, highs near 100 will be possible in
west central Illinois Thursday, and over most of the CWA Friday.
Some brief relief from the heat (mainly in the form of drier air)
arrives later in the weekend with the front, but ridging builds
across the central Plains once again early next week. This puts us
into more of a "ridge-rider" pattern where potential MCS`s start
to complicate the forecast. No changes were made to the
temperatures in the Monday/Tuesday time frame, still near or above
90 degrees.
Geelhart
&&
.AVIATION... (For the 00z TAFs through 00z Wednesday Evening)
Issued at 659 PM CDT Tue Jul 25 2023
An area of showers and isolated thunderstorms over central and
northeast MO and into far west central IL near the MS river is
tracking ESE and is projected to move over central IL during
mid evening. There is some support from low level jet with
unstable air mass ahead of this convection so think this will
maintain itself as it tracks into central IL. Have 6 hour period
of VCTS over central IL airports starting from 02-04Z and going
til 08-10Z. There could be MVFR conditions with thunderstorms that
occur and will need to monitor this. Otherwise SSE to SE winds
5-10 kts will turn south overnight and increase to 9-14 kts. Winds
veer SW during Wed morning and increase to 15-20 kts with gusts
25-30 kts by late Wed morning and continue thru Wed afternoon.
Latest models are keeping convection north and ne of central IL
airports during daytime hours on Wed.
07
&&
.CLIMATE...
Issued at 310 PM CDT Tue Jul 25 2023
Last occurrences of highs 100 degrees or above:
Champaign 8/02/2012 (101 degrees)
Charleston 7/26/2012 (100 degrees)
Decatur 7/25/2012 (101 degrees)
Galesburg 7/26/2012 (100 degrees)
Jacksonville 7/26/2012 (101 degrees)
Lincoln 7/25/2012 (101 degrees)
Normal 6/15/2022 (102 degrees)
Olney 8/02/2012 (100 degrees)
Peoria 7/25/2012 (102 degrees)
Springfield 7/31/2012 (101 degrees)
Geelhart
&&
.ILX WATCHES/WARNINGS/ADVISORIES...
Heat Advisory from 11 AM Wednesday to 7 PM CDT Friday for
ILZ027>031-036>038-040>043-047>053.
&&
$$
Area Forecast Discussion
National Weather Service North Platte NE
625 PM CDT Tue Jul 25 2023
...UPDATED AVIATION DISCUSSION...
.SYNOPSIS...
Issued at 328 PM CDT Tue Jul 25 2023
Key Messages:
- Severe weather chances this afternoon and evening hinge around
isolated to perhaps scattered storms forming across swrn and
ncntl Nebraska. Storm development is uncertain.
- Additional isolated severe storms are possible Wednesday across
much of wrn and ncntl Nebraska.
- Storms will be capable of locally heavy rainfall which may cause
flooding in some areas.
- Heat advisory conditions are possible Thursday and Friday.
&&
.SHORT TERM...(This evening through Wednesday night)
Issued at 328 PM CDT Tue Jul 25 2023
The remnants of a MCV is moving through wrn Nebraska this afternoon.
If this weak trigger is strong enough to break the 14C-15C cap at
h700mb, 5000-7000 J/KG of MUCAPE (3000-4000 MLCAPE) could be
released. The focus is a weak sfc trof, east of highway 83 drifting
toward cntl Nebraska.
Despite the trigger and instability, the models are mostly silent
with storm development. The forecast leans on the most aggressive
models like the NAMnest and HRRR which suggest isolated to low-end
scattered coverage late this afternoon and this evening. Damaging
wind gusts, large hail and locally heavy rainfall are the hazards.
PWAT will increase to 1.40 inches south and higher across northern
Nebraska.
Whatever storms develop should move east and southeast this evening
and exit by about 05z.
The next storm chance develops Wednesday afternoon and evening. In
the wake of the storm system tonight, a fairly strong outflow
boundary from the storms across the Dakotas should sweep into wrn
and ncntl Nebraska dropping dew points into the 60s. By late
afternoon, south winds should be underway across wrn Nebraska
causing the atmosphere to become unstable. The focus once again, is
a sfc trof aligned from southwest Nebraska northeast into ncntl
Nebraska. The dynamics, or upper level support are nebulous, perhaps
an UA disturbance across srn CA/NV this afternoon. POPs for this
potential event are limited to 30 percent for this reason. Still,
the NAMnest shows storms forming. In fact, the model shows more
storm coverage Wednesday than Tuesday.
Overall, it is worth noting several important ingredients for storm
development will remain over Nebraska. The region will remain under
a plume of subtropical upper level moisture, winds aloft will remain
strong and low level moisture will be focused and plentiful.
The forecast concludes the expected outflow boundary tonight will be
sufficient to lower temperatures and dew points. No Heat advisory is
planned for Wednesday.
.LONG TERM...(Thursday through Tuesday)
Issued at 328 PM CDT Tue Jul 25 2023
There is not much change in the extended forecast philosophy.
Wrn and ncntl Nebraska will remain under a plume of subtropical
moisture operating around the periphery of a strong upper level
ridge of high pressure located over NM. The ridge will slowly
migrate east into the srn Plains this week and next. Isolated to low-
end scattered POPs are in place during the next 7 days. Moisture
will be plentiful during this time but rain chance will be dependent
upon upper level forcing. A strong cap will be in place through
Friday which could certainly limit rain chances.
The model consensus suggests modest cooling will occur Saturday and
perhaps last into Sunday before the onset of another heat wave
Monday and beyond. The heat wave next week is the result of the
upper level ridge migrating east into the srn Plains and a long wave
trof impinging upon srn CA. This could flush a fresh batch of hot
air across the Rockies and into Nebraska.
Between now and Friday, Heat advisory conditions are contingent on
the dew point forecast. Thus far, forecast skill in handling the
70F+ dew points has been poor. If dew points continue to rise into
the 70s, heat advisories would likely be needed daily. The strong
cap in place during this time could certainly trap moisture
presenting ultra humid weather to the region.
&&
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 624 PM CDT Tue Jul 25 2023
VFR conditions are expected to prevail this forecast period,
although with the caveat of the challenging convective portion of
the forecast.
A very unstable airmass remains in place east of a line from
Valentine to North Platte. As such, if any larger scale forcing
mechanism can force strong enough convergence on any surface
boundaries left behind from previous convection, isolated strong
to severe storms would develop. This would most likely affect the
KLBF TAF site from 01-04Z, but confidence in this occurring is low
due to a lack of shear and very warm temperatures aloft. Therefore
it has been left out of the forecast at this time.
&&
.LBF WATCHES/WARNINGS/ADVISORIES...
Heat Advisory until 10 PM CDT /9 PM MDT/ this evening for
NEZ005>010-025>029-036>038-057>059-069>071.
&&
$$
SYNOPSIS...CDC
SHORT TERM...CDC
LONG TERM...CDC
AVIATION...Stoppkotte
Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
907 PM CDT Tue Jul 25 2023
.UPDATE...
Issued at 907 PM CDT Tue Jul 25 2023
The near term forecast remains in good shape and have only
re-trended hourly parameters and continued the mention of haze
through the overnight hours based on observational trends.
An area of ACCAS, which had been drifting northeastward out of
western Illinois has recently started to sprout elevated
convective elements with the arrival of sufficient 850-700 mb
moisture to drive reductions in CIN for parcels lifted above about
850 mb. This activity is developing on the northeastern periphery
of the EML plume which is evident on the ILX evening sounding with
a general steepening of the mid-level lapse rates and drying just
under 500 mb. As 310-315 K upglide increases with the arrival of a
nocturnally-intensifying LLJ, suspect we`ll continue to pop
additional elevated convection, perhaps all the way back into
parts of NE Iowa. Some of this activity appears set to drift into
parts of our area after 11 PM-midnight or so. While upper level
winds aren`t particularly strong, significant turning/veering with
height looks to yield perhaps just enough effective deep layer
shear amidst increasing MUCAPE to support a few more rambunctious
cells capable of producing some marginally severe hail. Just how
widespread this activity becomes remains unclear given
inconsistent CAM output. However, based on the slow increase in 5
to 7 kft cloud cover up to Moline, it seems plausible that guidance
like the HRRR and the incoming 00z NAMNest aren`t showing enough
convection. Think coverage may remain scattered enough to limit
the training/flash flood threat, but conceptually, high-level
flow would support some degree of backbuilding overnight as the
LLJ intensifies.
Still in a holding pattern regarding a potential morning MCS,
with activity just getting going upstream. While MLCIN will
continue to build, downstream deep layer shear profiles and a
theta-e/MUCAPE gradient sloshing NE with time would support MCS
sustenance into our region *if* robust upscale growth occurs.
Haven`t quite seen sustained signs of that just yet, although
recent radar and satellite trends across extreme NE South Dakota
may be showing signs of MCV development.
Carlaw
&&
.SHORT TERM...
Issued at 250 PM CDT Tue Jul 25 2023
Through Wednesday night...
Regional water vapor imagery augmented by 13 km RAP analysis data
depict a pair of upper-level shortwaves/convectively invigorated
vort maxes west of our area. The first moving along the IA/MO
borders and the second moving across the Dakotas. Both are moving
east-southeastward along the gradients in mid-level lapse rates, 850-
500mb thickness, and low-level moisture within the the eastern
periphery of an expanding central Plains ridge. Closer to home, our
area remains just on the outside edge of the heat dome and low-level
moisture gradient, though filtered sunshine is nevertheless
contributing to a hot day with current temperatures in the upper 80s
to lower 90s. With all forcing and moisture remaining outside of our
area through sunset, the remaining daylight hours will be quiet (but
warm).
Confidence in our forecast from sunset onward remain lower than
average. Conceptually speaking, the lead shortwave currently in Iowa
should follow the 850-500mb thickness gradient into central Illinois
overnight perhaps "outrunning" the leading edge of a a developing
broad southwesterly LLJ induced by the approach of the secondary
shortwave. Even behind the leading shortwave, increasing low-level
confluence along the leading edge of the intensifying southwesterly
LLJ may provide focus for a relatively confined area of elevated
convection somewhere in the region. With a healthy reservoir of
MUCAPE > 2000 J/kg, 2-8 km shear (e.g. elevated parcels) of 20-25
kt, relatively steep mid-level lapse rates of 7 K/km, and PWATs of
1.6-1.7", any storm overnight may produce frequent lightning,
torrential downpours, and damaging hail (1-1.5" in diameter). At
this point, oped to maintain "chance" PoPs (30-40%) areawide
overnight with the opportunity for refinement as trends (or clues)
can be identified after dark.
Tomorrow morning, all eyes will be on the second upper-level
shortwave as it approaches from our northwest. Conceptually
speaking, we see two forecast scenarios:
(1) Overnight convection in the Dakotas and Minnesota grows upscale
in an organized bowing cluster. If this occurs, the MCS would likely
track southeastward through the early morning hours and right into
northern Illinois after daybreak along the gradient in mid-level
thickness, lapse rates, and low-level moisture. Even at an
unfavorable timing, a deep cold pool would have no problem lifting a
near-surface static stable layer to unlock 2000-3000 J/kg of MUCAPE
supporting a damaging wind threat, perhaps greater than 70 mph. Such
a scenario would take place between 8 AM and 12 PM primarily
northwest of a line from Freeport, IL to Kouts, IN. Along the
backside of the MCS, strong southwesterly flow (partially augmented
by gravity wave action?) would lead to mixing of surface dew points
even as surface temperatures rise by early-afternoon, leading to a
warm but not necessarily dangerously hot afternoon.
(2) Overnight convection in the Dakotas and Minnesota fails to grow
upscale. In this scenario, scattered convection across Wisconsin
would move into Michigan keeping our area dry tomorrow morning. As a
result, the majority of our area would have a threat for dangerous
heat developing as surface temperature rise into the low to mid 90s
and surface dew points remain in the lower 70s. Peak heat index (wet
bulb globe) temperatures would thus soar above 100 F (88 F), raising
concern for heat-related illnesses without preventative measures.
However, a backdoor cold front (convective outflow from Michigan)
with help from a lake breeze may serve as a focus for severe
thunderstorm develop in the afternoon and evening hours primarily
northeast of a line from Crystal Lake, IL to Valparaiso, IN. With a
much smaller footprint of convection and less opportunity to mix
away low-level moisture, parts of our area would need heat advisory
tomorrow if this scenario plays out. We will hold off and let the
midnight shift see how convection is evolving upstream of our area.
Whatever happens tomorrow morning/afternoon, confidence is
cautiously high that Wednesday night should be dry as any and all
convection moves east of our area. Overnight lows should fall into
the lower to mid 70s.
Borchardt
&&
.LONG TERM...
Issued at 250 PM CDT Tue Jul 25 2023
Thursday through Tuesday...
Key Messages:
* High temperatures late in the week bring about concerns for heat
related illnesses. Thursday and Friday are expected to be the
warmest days, although the potential for storms on Friday could
limit the high temperatures
* The potential for thunderstorms continues with the best chance
for higher thunderstorms coverage, some threat for severe
weather, and flash flooding being late Friday through Friday
evening or the early overnight
* Temperatures will trend back to near normal for the weekend into
early next week, coolest lakeside
* Thunderstorm chances may return early next week
Discussion:
The ridge that currently covers the western CONUS will push slightly
east, bringing high temperatures to the area Thursday and Friday.
Temperatures are expected to climb into the 90s with some areas
reaching as high as the upper 90s (mainly south of I-80). With dew
points expected to rise into the low-to-mid 70s outside of the
Chicago urban heat island (possibly maximized over farming areas
due to evapotranspiration), heat indices are expected to be above
100 degrees Fahrenheit in many areas, with wet bulb globe
approaching dangerous levels of 90-95F (!) for interior sections.
Heat indices this high raise concerns about heat related
illnesses and we may need a Heat Advisory for much of the area
away from lake cooling influence. Weak synoptic flow starting
onshore will allow an early lake breeze to develop and push inland
on Thursday, limiting the high temperatures along the lakeshore
and in the downtown Chicago area. These areas could see
temperatures 10-15 degrees Fahrenheit cooler than areas further
inland.
Thursday as alluded to above looks to remain hot and humid with
the potential for storm development being near-zero due to very
dry air in the mid-levels and a lack of forcing. Late Thursday
night, we`ll have to monitor for a lower chance/lower predictability
scenario of an MCS over northern Plains/upper MS Valley area
riding northwest flow and thickness and instability gradient
southeastward into area. Should this not come to pass, the best
chance for storms to return comes on Friday, although it is also
very dependent on the development of a shortwave upstream of our
CWA bringing a plume of steep lapse rates with it. Mid-level
moisture will advect into the area on Friday, allowing for a
building reservoir of MLCAPE to develop. If these storms do fire,
they could easily become severe with deep layer shear values
looking pretty good (~30+kts). However, confidence on the
development of these storms remains lower than usual due to the
reliance on the development of an upstream shortwave. This will
continue to be monitored closely through the remainder of the
week.
The timing of any storms on Friday will impact the high
temperatures. Model guidance shows the timing of storms to be in
evening hours Friday (possibly as early as after 3-4pm north of
I-80) into Saturday morning. This will allow temperatures to
still reach their maximum during the day on Friday, however if the
storms do fire earlier, temperatures may not be as extreme. Friday
will certainly have the potential to require a Heat Advisory for
parts of the area, as convective trends (or lack thereof during
peak heating) become more apparent.
Moving into the weekend, the hot and humid weather is expected to
break, along with convective chances shifting south of the area.
Temperatures will cool as the ridge in the west begins to weaken
slightly and a trough develops over the eastern CONUS. The
magnitude of the cooling is still uncertain as that is dependent
on where the trough develops and how strong it is. As of now it
appears that temperatures will cool back to, or even potentially
just below, average along with dry conditions for the weekend. The
next chance for rain returns to the forecast on Monday with
another shortwave expected to pass over the area.
Carothers/Castro
&&
.AVIATION...
For the 00Z TAFs...
Aviation forecast concerns for the current TAF period include:
* Potential for multiple rounds of showers and thunderstorms from
late overnight through tomorrow afternoon, though confidence is
low in exactly how everything will play out.
* Near-surface wildfire smoke lingering around into tonight.
The main forecast concern for this TAF period revolves around the
potential for thunderstorms. While confidence is low in the exact
specifics of how things will play out, there appear to be three
potential opportunities for convection to affect the terminals
over the next 24-30 hours.
The first opportunity would be during the late overnight hours
tonight. The latest indications in forecast guidance and
observations are that if these overnight showers and storms were
to come to fruition (and this is not a guarantee), it appears that
they would remain southwest of the terminals. Thus, there is
currently no prevailing or TEMPO group for SHRA or TSRA in any of
the TAFs through daybreak, but trends will continue to be
monitored.
The second opportunity is expected to come after daybreak tomorrow
morning. This opportunity hinges heavily upon how ongoing
convection presently in the eastern Dakotas and Minnesota evolves
over the next several hours. If the storms in that region were to
organize and grow upscale into an MCS, then there would be an
appreciable chance for a large thunderstorm complex with strong to
damaging wind gusts to impact (or at least get close to) the
terminals at some point tomorrow morning. However, if this does
not occur, then a wide range of outcomes remains on the table for
tomorrow morning ranging from scattered thunderstorms occurring
near the terminals to all of our TAF sites remaining dry through
tomorrow morning. There appear to be enough signs pointing to at
least some convection occurring near the terminals tomorrow
morning to warrant the introduction of a VCSH mention and to keep
a PROB30 group for TSRA going through much of the morning, but
confidence in the forecast is still far too low to pin down
anything more specific than that at this point.
The third opportunity for showers/thunderstorms would come during
the late morning or afternoon. Whether this final potential round
of convection materializes near the terminals will depend on how
the morning plays out. Most guidance currently appears to favor
the terminals remaining dry during this time frame, so opted to
not formally introduce any afternoon shower or storm mentions
into the TAFs for now, but if little to no convection occurs here
locally during the morning, then the odds of convection occurring
near the terminals tomorrow afternoon will increase.
Otherwise, near-surface Canadian wildfire smoke has lingered
around longer than indicated in available smoke forecast guidance,
so have opted to keep a HZ mention going in the TAFs through
tonight with at least occasional reductions to MVFR visibility
appearing to be possible until any showers or storms arrive.
Ogorek
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...None.
IN...None.
LM...None.
&&
$$
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Area Forecast Discussion
National Weather Service Pendleton OR
853 PM PDT Tue Jul 25 2023
.EVENING UPDATE...A broad upper trough remains over the Pacific
Northwest this evening with a dry westerly flow over our area.
Skies remain clear for the most part. Some cumulus clouds remain
over the Washington Cascade crest and in Deschutes and Wallowa
Counties but they are dissipating as we get later into the
evening. Smoke from several wildfires around the region remains
the main issue this evening. Satellite imagery shows widespread
smoke streaming into central Oregon and the Ochoco-John Day
Highlands and from the Newell Road Fire near Goldendale across the
Columbia Basin. A dark smoke layer aloft is visible to the north at
the NWS office in Pendleton as this is being written. This is
causing some air quality and visibility issues around the areas
though elevated surface particulate values are only occurring in
central Oregon and to a lesser extent in the Ochoco-John Day
Highlands. Did make a few sky cover changes overnight to match the
HRRR smoke model forecasts. Winds are dropping off this evening
though winds are expected to remain at 10 to 20 mph at Ellensburg
through the night. Made some minor wind changes tonight and tomorrow
morning. Otherwise, the forecast was in good shape and no other
chances were made. Forecast update is already out. Perry/83
&&
.PREV DISCUSSION... /issued 539 PM PDT Tue Jul 25 2023/
AVIATION...00Z TAFs...VFR conditions are generally expected through
the TAF period, except for RDM and BDN which are being impacted by
wildfire smoke. Those two sites will see MVFR conditions and
possibly lower at times, mainly in the evening and morning.
Otherwise, a few cumulus at 060-120 will continue through 05Z.
Beyond that, skies will be SKC-FEW250 through 00Z tomorrow
afternoon. Winds will continue at 10-20 kts with gusts to 30 kts at
KDLS through 04Z-06Z. After that winds will remain below 12 kts with
KDLS having some gusts to 20 kts after 21Z tomorrow afternoon.
Perry/83
PREV DISCUSSION... /issued 214 PM PDT Tue Jul 25 2023/
SHORT TERM...
Tonight through Thursday night...No fire weather highlights are
planned at this time for the short term period, but there are a
few noteworthy concerns. An Air Quality Advisory is in effect for
Deschutes County due to the Bedrock Fire in the Willamette NF. Air
quality in this area is in the unhealthy category near Sisters
and unhealthy for sensitive groups in Redmond. Based on the HRRR
near surface smoke products, boundary layer winds shifting from
the SW to WNW will push the thick smoke southward tonight and
Wednesday for improving conditions over most of Deschutes County.
Westerly winds today have been sustained around 15-20 mph gusting
to 30 mph and RHs are in the 20s and 30s across the Lower
Columbia Basin and surrounding valleys...strong enough winds to
alert the public of rapidly spreading fires but the threat for
both wind and RH is below criteria for Red Flag Warnings.
Gradients relax more on Wednesday, and any breezy winds will be
localized to the typical windy areas in the eastern Cascade
valleys and CR Gorge but also a little breezy in the Grande Ronde
Valley and central Oregon. The main concern for Wednesday will be
the flat upper level trough moving onshore that will cause the
westerly flow to buckle slightly and increase the SW flow aloft
over eastern OR. A weak wave embedded in the flow will have a
slight chance (15%) of thunderstorms over far southeast Oregon
that includes Baker County and far southern Wallowa County
Wednesday night and Thursday. There will be elevated instability
during the night. It could only be ACCAS development overnight,
but the NAMNest is advertising a line of weak convection around
12Z Thursday.
The rest of Thursday and Thursday night looks quiet weather wise,
although the continued cross-Cascade gradient will keep breezy
winds through the Cascade gaps once again. It will be warmer on
Thursday with highs in the upper 70s to upper 80s for most areas.
Fortunately, the WSW flow aloft will limit the amount of heating
that would occur with the 850mb thermal ridge suppressed to the
south. Afternoon RHs will be back down into the teens to mid-20s
which is nothing unusual for late July but still worth noting for
continued fire weather concerns. Wister/85
LONG TERM...
Friday through Tuesday...The extended forecast is dry, with several
troughs moving across or close to the region. The first will occur
on Friday when a low moves into southern British Columbia. Dry,
southwest flow will continue ahead of this trough. A second trough
will move onshore on Sunday. Dry westerly flow will follow behind
the trough. Ridging will then build in from the southeast beginning
around Tuesday.
There will be diurnal breezy conditions each day, but potentially a
bit higher winds on Sunday, especially across the western Gorge and
Basin on Sunday as the trough moves through. However, at this time
wind gusts still look to be 20 to 25 mph, with gusts to 30 mph in
these areas.
Probabilities of winds greater than 25 mph are very high both
Saturday and Sunday (70-90%) and in some places (>90%) in the Basin
and the Gorge. However, probabilities decrease when looking at wind
gusts greater than 39 mph are between about 20-50% on Saturday and
20-60% on Sunday in the Basin and Gorge, though the areal coverage
is also greater on Sunday as well.
Overall, the deterministic guidance is in good agreement, with some
minor difference in the timing and position of both troughs, with
the ECMWF generally being slower.
Temperatures look to be close to seasonable through much of the
period, warming up to above normal by the the end of the extended.
High temperatures will be in the mid 80s to lower 90s on Friday,
perhaps rising a degree or two on Saturday. High temperatures will
likely be a bit cooler on Sunday with the trough moving across the
area. Highs will then rebound Monday and by Tuesday, highs will
range from the low 90s in central Oregon to the mid to upper 90s in
the Basin. Overnight lows will mainly be in the 50s, rising to the
50s and 60s by Tuesday morning.
&&
.PRELIMINARY POINT TEMPS/POPS...
PDT 52 84 54 86 / 0 0 0 0
ALW 54 87 57 89 / 0 0 0 0
PSC 59 88 59 90 / 0 0 0 0
YKM 53 85 56 88 / 0 0 0 0
HRI 55 88 58 90 / 0 0 0 0
ELN 52 82 56 86 / 0 0 0 0
RDM 47 83 48 84 / 0 0 0 0
LGD 52 84 53 86 / 0 0 0 0
GCD 51 88 52 88 / 0 0 0 0
DLS 57 87 58 86 / 0 0 0 0
&&
.PDT WATCHES/WARNINGS/ADVISORIES...
OR...None.
WA...None.
&&
$$
EVENING UPDATE...83
SHORT TERM...85
LONG TERM....87
AVIATION...83
Area Forecast Discussion
National Weather Service Las Vegas NV
113 PM PDT Tue Jul 25 2023
.SYNOPSIS...Afternoon and evening thunderstorm potential today will
be highest across the eastern Mojave Desert and northeastern Arizona
before moisture retreats through the remainder of the week.
Temperatures will remain above-average each afternoon until
monsoonal moisture returns over the weekend, which will allow
temperatures to drop to around normal.
&&
.SHORT TERM...Today.
An area of high pressure centered over New Mexico will allow
temperatures to remain 4-6 degrees above seasonal normals. Anomalous
PWATs for the region (albeit... sub-1 inch) coupled with
differential heating and orographic lift will support isolated
convection this afternoon in southern Nevada and northwestern
Arizona. In fact, this can already be seen on the Hualapai Mountains
in southern Mohave County where a storm has trained over an area
stretching from the northern edge of the mountain range to
Interstate 40 east of Kingman. Due to the dry low levels, this cell
required a bit of training before precipitation was measured beneath
it. As of this discussion, highest measured rain rate with this
storm has been 0.25 inches in 10 minutes. Primary concerns today
will be cloud-to-ground lightning, gusty winds, and localized
flooding. Storms that train over mountain ranges will have the best
opportunities for flood impacts. The 12Z HRRR indicated convective
activity over the McCullough Range south of Las Vegas and the Sheep
Mountains in northern Clark County... both of which have seen radar
returns within the last half hour, so these will be other points of
interest for localized flooding. Otherwise, due to the dry low
levels, gusty winds will be the primary concern, with DCAPE values
between 1500 and 2000 J/kg in southeastern California, southern
Nevada, and northwestern Arizona.
Otherwise, an Excessive Heat Warning went into effect this morning
at 10am PDT for the Colorado River Valley including Lake Mead, lake
Mohave, and Lake Havasu, where HeatRisk will remain in the Major-to-
Extreme category due to afternoon high temperatures approaching 118
coupled with morning low temperatures only dropping to the upper-80s
to mid-90s. With long-duration heat events, the lack of cooling
overnight has the most impact, because those without access to air-
conditioning are unable to sufficiently cool off. As such,
vulnerable populations such as the elderly and individuals
experiencing homelessness are the most at-risk.
.LONG TERM...Wednesday through next Tuesday.
Through the week, the aforementioned area of high pressure will
slowly meander eastward. By midweek, a dry southwesterly flow will
set up aloft due to the placement of this high, resulting in
shortwave passages and gusty afternoon southwest winds between 25
and 35 mph Wednesday and Thursday. Temperatures will vary only
slightly, with each day-to-day forecast remaining within a couple
degrees of each other. The highest heat impacts will be focused down
the Colorado River Valley where the Excessive Heat Warning currently
in effect will continue through Thursday evening.
By the weekend, the high pressure will meander its way back westward
toward the Four Corners, which will allow moisture to funnel into
our forecast area once again. Timing of this westward shift seems to
be slowing somewhat. If this trend continues, then temperatures may
remain elevated Friday afternoon as well, which could warrant an
extension of the Excessive Heat Warning for the Colorado River
Valley.
Ensemble means continue to suggest the approach of an inverted
trough stretching across northern Mexico, with a strong signal for
anomalous PWAT returning to our forecast area. That said, the GEFS
mean is a bit more ambitious with regard to moisture than the ECMWF
ensemble mean, but both indicate a surge of 125-200% PWAT into the
Mojave Desert and southern Great Basin by the start of next week.
This moisture surge will return thunderstorm chances to the eastern
Mojave and southeastern Great Basin and drop temperatures areawide
toward normal readings.
&&
.AVIATION...For Harry Reid...Generally, southerly winds with
occasional wind gusts to 20kts are likely this afternoon and early
evening before turning to the southwest and decreasing around
sunset. Model guidance continues to show isolated areas of
convection developing after 21Z south and east of the field. The
chances of direct impacts to the field remain low (20%), with
outflow winds from storms that do develop the primary concern.
Similar wind patterns are expected on Wednesday, with little to no
convective activity in the valley. Away from storms, FEW to SCT
clouds AOA 12kft are likely through the TAF period.
For the rest of southern Nevada, northwest Arizona and southeast
California...Scattered showers and thunderstorms are expected again
this afternoon and evening across western Arizona, with more
isolated activity possible across southern Nevada and eastern
California. No direct impacts are likely at area terminals except
for gusty outflow winds from distant storms. Away from convective
activity, winds will follow typical diurnal patterns with breezy
conditions in the afternoon and evening and lighter winds at most
sites overnight. Similar conditions are expected tomorrow,
although thunderstorm activity should be more limited and confined
to western Arizona. Away from storms, FEW to SCT clouds AOA 12kft
are likely through the TAF period.
&&
.SPOTTER INFORMATION STATEMENT...Spotters are encouraged to report
any significant weather or impacts according to standard operating
procedures.
&&
$$
DISCUSSION...Varian
AVIATION...Planz
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