Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 04/27/24
Area Forecast Discussion
National Weather Service La Crosse WI
651 PM CDT Fri Apr 26 2024
.KEY MESSAGES...
- Scattered showers and storms continue tonight with gusty winds
blowing 40-50 mph at times.
- Conditions trending drier on Saturday. Strong to severe
storms could develop Saturday evening in northeast Iowa into
far southwest Wisconsin. Large hail and damaging wind are the
primary threats.
- Widespread showers and storms likely on Sunday with a healthy
dose of rainfall on tap.
&&
.DISCUSSION...
Issued at 315 PM CDT Fri Apr 26 2024
Showers and Storms Tonight:
Broad cyclonic flow exists this afternoon across the western and
central CONUS with a compact negatively-tilted shortwave ejecting
northeastward through the central Missouri River valley. A maturing
991-mb surface cyclone was positioned near Hastings, NE at 18Z and
is progged to lift northeast into central Minnesota by sunrise on
Saturday. The leading wave of showers rooted along the attendant 700-
mb theta-e advection wing lifting through our area decayed through
the morning as they outran the axis of supportive MUCAPE, but enough
evaporative cooling occurred on the backside of these dissipating
showers to transport a 50-60-kt LLJ down to the surface west of the
Mississippi River, producing surface wind gusts of 45-55 mph in
their wake.
The next round of showers rooted closer to 850 mb warm frontal nose
have started developing over central Iowa and lift through the
region this afternoon and evening, once again outrunning the axis of
elevated upright instability but the possibly still putting out
lightning as the move through given the low static stability.
Attention then turns to the line of linear/quasi-linear convection
working northward from western Iowa towards the 03-06Z timeframe.
There is some uncertainty with how far north the surface warm front
will lift and the exact timing of these storms in relation to this
frontal progression will dictate the possibility any QLCS tornadoes
over northeastern Iowa. Surface wind profiles and hodograph
trajectories within the warm sector and along the front would be
supportive of QLCS tornadoes--if the warm sector makes it this far
north. The latest few runs of the HRRR have been hinting at a
northward push of the warm sector ahead of this line, so the
evolution of this mesoscale environment bears watching through the
evening. The severe weather threat wanes steadily once the storms
overrun the front north of Iowa.
The mid-level dry slot cuts across the forecast area in the wake of
this overnight convection, bringing an end to the precipitation by
sunrise on Saturday morning.
Severe Storm Threat Saturday Afternoon/Evening:
Confidence is increasing for a drier Saturday than previously
forecast thanks to weak upper-level ridging and the aforementioned
dry slot. Gusty winds hold on through the first half of the day, but
gradually subside Saturday afternoon as the pressure gradient
relaxes. Southeast gusts look to top out in the 30-35 mph range area
wide with sustained winds of 20-25 mph.
Despite the broader synoptic-scale environment lacking organized
ascent, thunderstorm chances increase across northeast Iowa into far
southwest Wisconsin Thursday evening. Weak shortwave perturbations
in the mid-level flow provide the best forcing with this system, as
frontal boundaries in the area lack baroclinicity. Furthermore, an
elevated mixed layer is present in model soundings. The CIN
associated with the EML increases as you move northward across the
forecast area. A few Dubuque, Iowa model soundings show the
potential to tap into 1500-2000 J/kg of CAPE as the EML erodes in
the evening, but as you move northward the chance of eroding enough
CIN to freely convect decreases rapidly. The chance of convective
initiation will be highly correlated with how much daytime heating
is achieved tomorrow afternoon with differences remaining across
models, especially when it comes to cloud cover.
If storms are able to initiate, a narrow corridor of CAPE 1500+ J/kg
and deep-layer sheer over 40 knots across northeast Iowa into far
southwest Wisconsin could lead to storms quickly becoming strong to
severe. Large hail and damaging wind are the main threats, but a
tornado or two cannot be ruled out if storms are surface based.
As the evening progresses, the atmosphere will stabilize putting an
end to the severe weather threat. Showers and sub-severe storms will
likely increase in coverage as potential vorticity advection
increases across the Upper Mississippi Valley.
Soaking Rain Sunday:
Widespread showers and storms take hold on Sunday as a low pressure
system approaches from the southwest. Heavy rain is the primary
threat with NAFES precipitable water values at our above the 95th
percentile for this time of year. This will result in 1-1.5" of rain
area wide, with locally higher amounts possible. As it stands, the
area can take this much rain with minimal impacts but we will
continue to monitor the potential for urban street flooding and
minor river/stream rises as this system approaches.
Looking Ahead To Next Week:
An active weather pattern continues into the new week with
shortwaves propagating in the primarily zonal upper-level flow. This
pattern supports periodic preciptiation chances and seasonable
temperatures. More details to come after we get through this
weekend`s push of precipitation.
&&
.AVIATION /00Z TAFS THROUGH 00Z SUNDAY/...
Issued at 652 PM CDT Fri Apr 26 2024
MVFR/IFR cigs are expected through the morning hours on Saturday as
low stratus hangs onto the region. Light showers will continue to
progress north of the region through rest of the evening hours.
The next set of TAF concerns comes overnight with much of the
deterministic CAMs pushing a round of showers and storms through
the region. Still a fair amount of disagreement in exact
coverage but opted to hold onto -SHRA and VCTS mention to
account of this potential. As morning approaches, conditions
should begin to improve with MVFR cigs, perhaps low VFR in
spots.
Winds through the TAF period will remain fairly breezy at around 15-
20 kts with gusts of up to 30 kts from the southeast. There remains
some questions in valley locations for LLWS, with some
deterministic soundings showing the potential for decoupling
overnight allowing for wind gusts to diminish. As a result, will
need to monitor to reintroduce LLWS into the TAF for KLSE if
this potential is realized. Otherwise, winds will swing to
westerly by the end of the TAF period.
&&
.ARX WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...None.
IA...None.
&&
$$
DISCUSSION...KAA/Skow
AVIATION...Naylor
Area Forecast Discussion
National Weather Service Des Moines IA
644 PM CDT Fri Apr 26 2024
...Updated for the 00z Aviation Discussion...
.KEY MESSAGES...
* Additional strong/severe storms expected this evening, now
arriving across the western forecast area, translating NW/W
through evening. While all modes of severe possible, a few
tornadoes (strong possible) and large hail remain primary
threats.
* Threat for additional severe storms Saturday, appears primarily
over southern half of Iowa or so. All modes possible again, with
primary threats for very large hail and a few tornadoes. Some
heavy rain threat concerns linger.
* Another round possible Sunday, however details uncertain with
preceding rounds of convection to play some role.
* Quieter start to next week, additional precipitation activity mid-
late week.
&&
.MESOSCALE...
Issued at 528 PM CDT Fri Apr 26 2024
As of 545pm, a broken line of severe storms is approaching the
western edge of the forecast area. Several tornadoes, a few
strong, have already occurred across the NWS Omaha Forecast
area. A relatively warm and moist axis characterized by temps in
the 60s and 70s along with dewpoints in the low 60s extends nwd
along the Missouri River valley up through about Sioux City.
The environment in this area is characterized by MLCAPE values
of 1000-2000 J/kg with MLCIN generally less than -50 J/kg. The
kinematic parameter space at 22-23z remains very impressive
with 0-1km bulk shear values around 30kts and effective SRH
values from 200-400 m2/s2, most of which is confined in the
lowest 0.5-1km above the sfc. The questions that remain are how
long storms can remain discrete or semi-discrete and how long
can the storms remain in the more volatile atmosphere? The
latest guidance suggests that at least scattered severe storms
will impact the western counties for the next few hours, with
all modes of severe weather possible including tornadoes. As we
get further into the evening, after 00z, the latest guidance
suggests storms may congeal into a more linear QLCS mode.
However, even then isolated to scattered severe storms may
continue, especially across the south half of Iowa where
soundings show the boundary layer is less likely to become
capped. This could continue right into the early overnight hours
before storms eventually outrun the instability access to the
east and north.
&&
.DISCUSSION...
Issued at 230 PM CDT Fri Apr 26 2024
Morning convection progressed about as expected, if not a bit weaker
than original thoughts, moving across and out of the area by later
morning to early afternoon. In addition to already gusty background
winds, sporadic wind gusts in excess of 50kts were seen on the
backside of showers, producing wake low-like effects, as seen
in/around KOTM/KOOA/KEBS/KMCW. Additional scattered convection
across the area has been seen/experienced from late morning into the
early afternoon. All of which has been highly elevated with a strong
850-800mb warm nose in place, limiting severe hail potential. Of
note, CAMs have struggled with this convection, generally depicting
little to nothing until the later severe threat. This convection is
not expected to have adverse effects on the potential later today.
As of the time of this writing, dry line back across portions of
south-central Nebraska and north-central Kansas has begun initiating
strong surface based convection, including a confirmed tornadic
storm in Nebraska along the nose of the dry slot and triple point.
This activity is a couple of hours sooner than the HRRR has recently
advertised, but aligns with recent NAMnest and ARW core runs. Timing
for western Iowa remains largely unchanged with arrival around 23z.
By this time, some clearing and the 850-800mb warm nose will have
been eroded, allowing for surface based convection to take hold.
Parameter space remains strongly in favor of tornadic potential and
large hail, especially over western areas where SBCAPE and 0-3km
CAPE values will be at their greatest. Hodographs continue to depict
text book low level curvature yielding 0-1km SRH values approaching
300 m2/s2, efficient streamwise vorticity ingestion, and supportive
streamwise vorticity values. Improved mid-level lapse rates increase
the hail threat with SBCAPE values in excess of 2000 J/kg. Earlier
convective initiation west calls into some question what storm modes
may be by the time activity reaches the CWA, but HRRR runs continue
to suggest a few isolated supercells possible with some weak CIN
lingering, which would continue the threat for a stronger tornado or
two in addition to large hail. Should upscale growth become
prevalent/dominant, multi-cell or QLCS processes may still yield
tornadoes with proper orientation to low level shear, but
predominantly weaker and shorter lived in nature. Same for hail,
threat would remain, but likely lesser. As activity translates
eastward, nightfall will attempt to stabilize low levels, but strong
background winds to limit that, keeping surface based potential
going into the evening as storms approach I-35. Strong dynamics as
the upper wave and surface lows will continue the previously
mentioned tornado and hail threats as well. SPC Day 1 Enhanced area
remains well placed from this perspective.
A period of quieter conditions will settle in after 06z tonight or
so as the first upper wave and surface low exit northeastward. In
its wake will be a frontal boundary draped across the state from SW
to NE, which will determine the threat area for strong/severe storms
by the afternoon and evening Saturday. Day 2 SPC expansion of the
Enhanced area into the CWA appears more than warranted with
expectation of a "juicy" air mass building in which may yield SBCAPE
values in excess of 3000 J/kg along/south of the surface front.
While threats Saturday will be similar to today, tornadoes and hail,
the lead threat may be more in line with hail given the increased
CAPE and potential ECAPE enhancement. As noted by previous
discussion, wind fields are less substantial in the lowest levels,
but deeper wind profiles remain more than capable of organized
convection and some tornadic potential. Initial isolated storms mid-
afternoon to evening will be of greatest concern, before anticipated
upscale growth slowly lessens severe threats and potentially
translates to possible hydro concerns with storm motions roughly
parallel to the surface boundary and continued moisture transport
lifting northward. Overall, CAMs have eased back a bit off the 3"+
of rain potential, with the boundary potentially not remaining
stationary, but will be something to continue to keep a casual eye
on into the evening/overnight Saturday.
Sunday still brings yet another potential round of strong to severe
storms, but this remains with a few uncertainties given the above
rounds of convection needing to play out. This will be tied to the
upper level wave and surface low moving out into the Plains.
Synoptic guidance is pretty well aligned, at this point in time,
moving the surface low across Iowa in/around peak heating. Aside
from that, anticipated cloud cover throughout Sunday will limit
destabilization. Regardless, another opportunity for a few strong to
severe storms.
Beginning of next week continues to look on the quieter/dry side,
before additional shortwave activity returns unsettled weather mid-
late week. Throughout this forecast period, high temperatures will
oscillate between the 60s and 70s.
&&
.AVIATION /00Z TAFS THROUGH 00Z SUNDAY/...
Issued at 633 PM CDT Fri Apr 26 2024
IFR to LIFR CIGs are expected for the next few hours at
KFOD/KMCW/KALO. Scattered to numerous showers and thunderstorms
will then move from west to east across the area from 02-06z
tonight. Localized IFR impacts are possible with any storms for
1-2 hours along with variable and gusty winds. Lingering VFR to
IFR cigs may linger behind the storms, gradually scattering out
towards morning. Additional storms are possible Saturday
afternoon, but confidence on storm coverage remains in question
at this time.
&&
.DMX WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
MESOSCALE...Fowle
DISCUSSION...Curtis
AVIATION...Fowle
Area Forecast Discussion...UPDATED
National Weather Service Quad Cities IA IL
809 PM CDT Fri Apr 26 2024
.KEY MESSAGES...
- Active pattern through the weekend with several rounds of
showers and thunderstorms with an additional 1-3+ inches of
rain likely.
- Flash Flooding is a concern for areas that receive repeated
rounds of thunderstorms Saturday night. Confidence remains low
on the placement of the heaviest rainfall.
- Severe storm risk exists through the weekend, but there
remains uncertainty as prior rounds of convection may impact
magnitude/timing/location of any severe weather threat.
&&
.UPDATE...
Issued at 809 PM CDT Fri Apr 26 2024
SPC mesoanalysis page is showing broad warm advection across
Iowa this evening in the 925 to 850 mb layer. The 00z sounding
this evening shows some destabilization in the mid levels with
most unstable CAPE values of 597 J/KG with deep layer shear
values around 50 knots. ACARs soundings to the southwest in
Missouri show warming temperatures at 850 and further cooling in
the mid levels should lead to increasing mid level instability
setting the stage for the potential for storms tonight to
produce large hail. The last 4 runs of the HRRR show shower and
storms redeveloping over the next couple of hours largely south
of a Fairfield to Freeport Illinois line and lifting
northeastward. Looking farther to the west, an arcing line of
thunderstorms stretches from Spencer to Des Moines to north of
Lamoni Iowa with multiple tornado warnings at this time. CAMs
show this activity clipping our CWA north of a Fairfield to
Dubuque line overnight with the capping increasing at 850 think
that there will be a large hail threat across this area from 4
to 8 UTC. After this lifts northeastward, quiet weather is
forecast for the rest of tonight.
&&
.SHORT TERM /THROUGH TONIGHT/...
Issued at 255 PM CDT Fri Apr 26 2024
A large area of light to moderate rain will continue to work
through the region from SW to NE into the late afternoon hours.
There have been embedded thunderstorms at times mainly
along/south of I-80, but this heavier activity has diminished
significantly over the past few hours. On the northern edge of
the rain shield, across portions of eastern Iowa into northwest
Illinois, we had a period of strong SE winds during the mid to
late morning with many locations peaking between 40 - 50 mph.
Cedar Rapids was the outlier, reaching 65 mph! These unexpected
strong winds occurred in a region of subsidence sufficient to
mix down momentum tied to a robust southeasterly LLJ. Still
gusty SE to S winds will continue through this evening into
tonight, but likely on the order of 30 to 40 mph for peak gusts.
Persistent elevated warm air advection north of a warm front
draped across northern Missouri will likely lead to another
round of scattered showers and isolated storms developing this
evening into early tonight. However, coverage with this round
does not look to be quite as widespread as earlier today. Any
threat for severe weather remains low as the better moisture is
forecast to hold south across central Missouri and the stronger
dynamics to the west near a surface low over western/central
Iowa. By late tonight, expect mostly dry conditions with breezy
S to SSW winds.
&&
.LONG TERM /SATURDAY THROUGH FRIDAY/...
Issued at 255 PM CDT Fri Apr 26 2024
Saturday:
A lull in convection is anticipated through much of the day as
low pressure shifts toward Lake Superior with the attendant
cold front/low-level boundary expected to hold to our west
across central Iowa. Gusty southerly winds developing tonight
(Friday night) will last through the day on Saturday and advect
a warm and humid air mass into the region with highs in the
upper 70s to low 80s; dewpoints rising into the 60s will make
it feel rather humid. There is a low chance for isolated storms
during the early/mid afternoon period; however, confidence is
low on activity developing that early. The better chance for
storms is Saturday evening into the nighttime as a mid-level
wave approaches from the southwest. Confidence remains low on
the exact placement for this period, but the environment will be
supportive of strong to severe storms with sufficient MUCAPE
(2000+ J/kg) and deep layer shear (35+ kts).
The primary threat into Saturday night may transition to heavy
rainfall and localized flash flooding with high PWATs up to
1.5 inches. There is also the potential for repeated rounds of
storms as mean 850-300mb flow steers the convection in a SW to
NE trajectory, as a new area of low pressure organizes over the
Central Plains. The 12Z HREF that grouped several of the CAMs
output together shows localized amounts over 3 inches in our
CWA. A Flood Watch may be needed eventually due to the potential
for an additional 1-3+ inches of rainfall through the weekend.
Held off for now because of the aforementioned low confidence on
placement of the heaviest rainfall. A look at the latest 1 - 3
hr flash flood guidance shows values approximately in the 1.5 to
3 inch range.
Sunday: The upper low will lift out and take a similar path to
the previous shortwave from Colorado into the Upper Midwest by
Monday morning. We`ll see widespread showers and storms occur
Sunday into Sunday night with the warm, moist advection and
increasing synoptic scale lift then followed by the cold frontal
passage Sunday night into Monday AM. The widespread
precipitation and cloud cover brings about uncertainty as to the
severe weather potential and magnitude/location, etc.
Overall, we have 2 surges of PWATs of around 1.5 inches
the first today into this evening and the second
Saturday night through Sunday. Those would be the
periods favored for locally heavy rainfall concerns.
Between both events many areas will see widespread 1
inch or more (today through Sunday) with areas/swaths of 2 - 4+
inches where rounds of convection occur that will bring a risk
of isolated flash flooding.
In the wake of the cold front, the start of next week
looks to turn quieter and drier. However, there`s signs
that an active pattern will return mid to late next week
with the flow becoming semi-zonal shuttling impulses
across the Midwest from the Pacific along a meandering
mid level baroclinic zone.
&&
.AVIATION /00Z TAFS THROUGH 00Z SUNDAY/...
Issued at 638 PM CDT Fri Apr 26 2024
Clouds linger across the area this evening with ceilings ranging
from 500ft at KDBQ to 5500ft at KBRL. Showers and potentially
thunderstorm are forecast to redevelop by 2 to 3 UTC and
continue through the overnight but confidence is lower in that
occurring at this time so they were left out of the TAFs
everywhere except CID. Other locations may see drizzle develop
with MVFR visibilities instead of rain. Look for precipitation
to end from 8 to 12 UTC across the area and ceilings to gradually
lift from 12 to 18 UTC on Saturday with potential VFR
conditions by late afternoon area wide.
&&
.DVN WATCHES/WARNINGS/ADVISORIES...
IA...None.
IL...None.
MO...None.
&&
$$
UPDATE...Cousins
SHORT TERM...Uttech
LONG TERM...McClure/Uttech
AVIATION...Cousins
Area Forecast Discussion
National Weather Service Green Bay WI
1044 PM CDT Fri Apr 26 2024
Updated aviation portion for 06Z TAF issuance
.UPDATE...
Issued at 1010 PM CDT Fri Apr 26 2024
Issued a wind advisory for the Fox Valley and Manitowoc and
Kewaunee counties for 15z until 21z Saturday, as the RAP, HRRR,
and NAM all have 35 knots of wind just around 1000 ft above the
ground and 50 knots at the top of the mixed layer. If the sun
doesn`t come out at all it won`t get as windy, but if there is any
sunshine and good mixing gusts to 50 mph could materialize.
&&
.KEY MESSAGES...
- Several systems will bring periods of showers and thunderstorms
tonight through mid-week. Storms Sunday into Sunday night
could produce periods of moderate to heavy rain, resulting in
chances for isolated flash flooding in urban and low lying
areas.
- It remains possible that conditions will support a few strong
to severe storms from mid-Saturday afternoon through early
Saturday evening over northeast Wisconsin. Large hail and
damaging winds will be the primary threats.
- Conditions hazardous to small craft will be possible at times
tonight through the weekend on the Bay and Lake.
&&
.DISCUSSION...
Issued at 216 PM CDT Fri Apr 26 2024
Short Term...Tonight and Saturday
The latest RAP analysis and satellite imagery show a Rocky
Mountain cyclone developing over Nebraska with a warm front
extending east across Missouri and far southern Illinois. Strong
isentropic ascent via 40-50kt low level jet are pushing showers
into far southwest Wisconsin early this afternoon. However, these
showers are running into a very dry airmass associated with a
receding Hudson Bay high where PWATs remain 25% of normal over far
northeast parts of Wisconsin. The strong southerly flow remains
expected to overwhelm the dry air, and push some these showers
into central and east-central WI by mid to late afternoon. As the
low tracks northeast and across the region over the next 24 hours,
precipitation trends and severe weather potential remain the
primary forecast concerns.
Precipitation trends tonight into Saturday morning...Showers will
continue to surge northeast across the region this evening.
Elevated instability will eventually move into the region, but
not until late evening into the overnight. Some models depict
elevated instability reaching up into the 500-700 j/kg range, but
with effective shear values under 20 kts, most likely looking at
sub- severe storms that could produce small hail. As the low level
jet lifts into Upper Michigan, precip will trail off late
overnight into Saturday morning across the region. Most of the
region will remain shrouded in clouds until midday.
Severe potential on Saturday afternoon...As the low pressure
system moves into the Lake Superior region on Saturday afternoon,
it will leave behind a trailing cold front across northeast
Wisconsin. This cold front could become the focus for strong or
severe storms starting around mid to late afternoon.
A conditional severe weather event remains in the cards.
Uncertainties revolve around how destabilization and mid-level
capping evolves in the afternoon. Low levels are forecast to
remain quite moisture laden, but models insist partial clearing
taking place ahead of the front by early afternoon. If clearing
occurs, models are likely under doing surface temps and mixing
which could lead to temps reaching into the middle 70s and
dewpoints in the low 60s (instead of mid 60s like some models
depict). If this were to occur, mixed layer instability of 1500
j/kg is possible, which modified soundings indicate would be
sufficient to scrape by a mid-level cap for convective initiation
by 21z.
The strength of the cap and mid-level dry air are also problematic
as mid-level subsidence will be occurring behind a departing
shortwave. Models frequently underdo the strength of the cap.
However, convective allowing models (CAMS) appear to be
indicating that the cap and mid-level RH of 40-50% will be
sufficient to prevent widespread deep/severe convection from
developing. Most CAMS show little in the way of thunderstorm
redevelopment on Saturday afternoon and precip amounts have
trended down over the past 24 hours.
That said, it`s hard to ignore the prospects of destabilization
combined with effective shear values upwards of 40 kts due to
strong winds through a deep layer. If storms develop, brief
cyclonic curvature to the hodographs suggest discrete storms and all
hazards would be possible including damaging winds, large hail,
and possibly a tornado or two in the late afternoon hours before
wind fields become more unidirectional. But dry air entrainment
and mid-level capping will likely make the threat of severe storms
isolated in coverage, if at all. It appears the greatest risk
will occur over and just west of the Fox Valley where the most
solar insolation is likely to occur and further removed from a
more stable marine layer near Lake Michigan.
Long Term...Saturday Night Through Friday
An active pattern containing a train of shortwaves and several
accompanying rain/storm chances will persist through the duration
of the extended. Main focus will be on excessive rainfall risk
with a Sunday/Monday system trailing behind Saturday`s cold front.
Periods of moderate to heavy rainfall associated with this system
may result in localized flash flooding. Attention will then turn
to a mid-week system that clips the upper Midwest, bringing
additional storm chances to the forecast area.
Saturday night through Monday... The severe weather threat should
begin to wind down Saturday evening as the cold front drops to our
south and encounters stable air near the lake. A brief lull in
precip will then set in Saturday night before next chances for
precip arrive Sunday morning. A southern stream trough will spin
up a surface low over the Texas and Oklahoma panhandles before
trekking into the Upper Mississippi Valley by Monday morning. Rain
is expected to arrive to the forecast area Sunday morning out
ahead of the warm front as it lifts north before becoming more
widespread through the afternoon and evening. Potential for severe
weather doesn`t look too impressive given a robust capping
inversion and insufficient airmass recovery time after Saturday`s
system. Any storms that do pop up would likely be elevated in
nature, with gusty winds and small hail the biggest threats.
Current ensemble guidance currently seems to be targeting portions
of central and north-central Wisconsin to receive the bulk of the
rain (~0.6 to 1" 24-hour QPF). Given an open Gulf and 1 to 1.5"
PWATs being ingested by the surface low, suspect that rainfall
amounts may trend on the higher end of what is being shown.
Tuesday through Wednesday... Better chances for thunderstorms look
to arrive with a Tuesday/Wednesday system. Another piece of
closed upper-level energy will ride the US/Canada border through
the beginning of the week, placing a surface low over Alberta
that will skim the upper Midwest by Wednesday morning. Models are
still struggling to resolve precip timing, but a broad overview
seems to suggest that some convective elements (MUCAPE, low-level
lapse rates, surface forcing due to cold FROPA) may come together
enough to warrant thunderstorm potential. However, it is still
too far out in the forecast period to ascertain storm severity.
&&
.AVIATION...for 06Z TAF Issuance
Issued at 1044 PM CDT Fri Apr 26 2024
A storm moving from Nebraska to Lake Superior will produce
showers and a few thunderstorms tonight. Saturday will be mostly
dry.
Ceilings will be largely IFR later tonight through Saturday morning
west of an IMT to STE line, and also near the Lake Michigan shore.
MVFR ceilings are expected further east. Ceilings should improve
to MVFR west of IMT to STE Saturday afternoon, with VFR further
east.
Low level wind shear is possible overnight through 15z Saturday
with southeast winds around 10 knots at the surface and southwest
around 40 knots at 2000 feet. The threat of low level wind shear
will diminish after 15z Saturday, but mechanical turbulence is
likely as southwest surface winds increase to 20 knots with gusts
to 35 knots or more by afternoon.
&&
.GRB WATCHES/WARNINGS/ADVISORIES...
Wind Advisory from 10 AM to 4 PM CDT Saturday for WIZ038>040-
048>050.
&&
$$
UPDATE.........RDM
DISCUSSION.....MPC/Goodin
AVIATION.......RDM
Area Forecast Discussion
National Weather Service Grand Rapids MI
1012 PM EDT Fri Apr 26 2024
.KEY MESSAGES...
- Showers and Thunderstorms Tonight
- Slight Risk of Severe Weather Saturday evening
- Multiple Rounds of Showers and Storms Through Mid Week
&&
.UPDATE...
Issued at 1002 PM EDT Fri Apr 26 2024
As expected the initial batch of showers weakened as it
encountered the dry low level airmass in place here in MI. It
looks like there`s a gap in the precipitation moving in however a
larger area of showers/storms was headed our way from IL. Thus
later tonight we will see the precipitation on the increase and
towards daybreak, the instability increases steadily so that is
when the potential for storms ramps up.
Looking at the rest of the weekend, there is some indications that
a potential for excessive rain could evolve. Corfidi vectors
become short and a very moist airmass with low lcl`s and thin/deep
CAPE exists at times. Also a low level jet sets up both Saturday
night and Sunday night with a low level boundary around. It does
look like the models may be catching onto this risk with the 00Z
HRRR now showing some swaths of over 2 inches of rain by 00z Mon
here in the CWA.
&&
.DISCUSSION...
Issued at 325 PM EDT Fri Apr 26 2024
- Showers and Thunderstorms Tonight
An area of isentropic ascent in strong warm advection pattern is
bringing showers and embedded thunder into northern Illinois this
afternoon and this will be moving northeast through Lower Michigan
tonight. The storms are expected to remain elevated overnight. By
Saturday morning the steadier rain is done with just isolated
showers through the day as the warm front will focus shower
activity north of the forecast area.
- Slight Risk of Severe Weather Saturday evening
Convection will be limited across much of the forecast area
through Saturday afternoon under shortwave upper ridging, with a
capping inversion noted in model soundings, but we will have to
watch the northwest zones for initiation of convection during the
evening along a prefrontal trough aligned across central or
northern Lake Michigan. There is 30 knots of shear present in this
area along with 500 to 1000 J/kg of CAPE, so any convection that
initiates could become organized enough to present a severe
threat. Main threat at this point would be hail and isolated wind.
There could be an isolated tornado threat with some model
guidance showing potential for a triple point low across the
northwest zones during the evening.
- Warm With Multiple Rounds of Showers and Storms Through Mid Week
Additional showers and storms are likely Sunday into Monday
associated with forcing from an upper-level jet streak and aided by
a frontal boundary sitting across northern Michigan and a shortwave
from the parent trough ejecting through the region. Convection will
be favored across Central Lower for our CWA closer to the warm
frontal boundary, with MUCAPE values north of 500 J/kg suggesting
there will be an attendant thunder risk. SPC currently has us in
general thunder which is reasonable given that the favored region
instability is separated from deep later shear and the highest
likelihood of showers/storms.
Widespread showers then expand into the remainder of the CWA Sunday
night and continue into early Tuesday as a cold front drifts across
the area. MUCAPEs suggest thunder chances continue. Rainfall by the
time all is said and done Monday night looks to be from 0.3-0.4
inches in the southeast CWA to 1-1.5 inches up towards Ludington.
Dry conditions then take over later Tuesday. as a high pressure
system quickly pushes through the area. Conditions then become more
active Wednesday as we see a cold front driven through Lower
Michigan by a northern stream shortwave followed by additional rain
chances into Thursday as a surface low ejects north into the upper
Ohio Valley.
Temperature wise, highs in the 70s are expected to continue into mid
week. By late week, expect highs to fall back to near normal in the
60s as a thermal trough slides into the central Great Lakes.
&&
.AVIATION /00Z TAFS THROUGH 00Z SUNDAY/...
Issued at 725 PM EDT Fri Apr 26 2024
Showers will continue to gradually develop from southwest to
northeast across the area through the mid to late evening hours.
Conditions will start out VFR but will gradually deteriorate to
primarily MVFR overnight due to lowering cigs and steadier rain
showers. Isolated thunderstorms may develop overnight with the
relatively best chance for a storm coming after midnight through
around daybreak.
SE winds will stay up around 15 to 20 kts with higher gusts to
around 25 kts overnight. MVFR cigs are likely to linger Saturday
morning before gradually improving to VFR in the afternoon. Southerly
winds will stay up at around 15 to 25 kts Saturday. A few showers
and storms may develop late Saturday afternoon and early evening
but there is not enough potential for it to include mention in any
of the terminal forecasts. The better chance for rain and convection
will hold off until after 00Z Sun.
&&
.MARINE...
Issued at 325 PM EDT Fri Apr 26 2024
Hoisted a Small Craft Advisory for later tonight through Saturday
night. Southwest winds should hit 25 knots and perhaps 30 knots at
times. Marine fog is possible as well with dew points in the mid
to upper 50s although the winds may be able to mix out the
inversion and disperse the fog to some extent.
&&
.GRR WATCHES/WARNINGS/ADVISORIES...
MI...None.
MARINE...Small Craft Advisory from 2 AM Saturday to 8 AM EDT Sunday for
LMZ844>849.
&&
$$
UPDATE...MJS
DISCUSSION...Ostuno/Thomas
AVIATION...Laurens
MARINE...Ostuno
Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
827 PM CDT Fri Apr 26 2024
.KEY MESSAGES...
- Showers and thunderstorms will redevelop over the area late
this evening into the overnight hours.
- Saturday looks summer-like with highs in the upper 70s to
lower 80s, increasing humidity levels, and eventually partly
cloudy skies.
- Showers and thunderstorms will develop toward and after sunset
Saturday night and continue through Sunday morning. A threat
for flash flooding will exist where thunderstorms train.
- Periods of showers and storms will continue through midweek,
a few of which could be strong to possibly severe on Sunday.
&&
.UPDATE...
Issued at 827 PM CDT Fri Apr 26 2024
Minor adjustments to going forecast tonight, primarily to add
detail for a period of dry weather early-mid evening, then to
increase thunder chances somewhat overnight. Overall however,
going forecast is in good shape.
Evening surface analysis depicts 992 mb low pressure over
eastern Nebraska, with a warm front extending east-southeastward
across southern IA into central IL. The low is forecast to lift
northeast into the upper Mississippi Valley by morning, in
response to a strong negative-tilt shortwave trough propagating
across the region. As this occurs, the warm front over central
IL/IN will lift north across the forecast area overnight,
pulling warmer and more humid summer-like air into the area by
morning.
While earlier rains had lifted northeast of the area late this
afternoon, another round of rain and embedded thunderstorms is
expected to develop northeastward across the area later this
evening and overnight. Strong ascent associated with the
negative-tilt short wave to our northwest will help to steepen
mid-level lapse rates, while lower-level south-southwesterly
flow increases (approaching 60 kts at 850 mb) transports
moist/unstable air into the region. Thus, the current area of
rain/embedded thunder currently noted in regional radar plots
across eastern MO/downstate IL is expected to spread
northeastward into the forecast area late this evening, likely
with some expansion of elevated convection to the north. RAP
forecast soundings depict ~600 J/kg of elevated MUCAPE across
northern IL after midnight, which along with strong
unidirectional deep layer shear may support hail up to nickel
size as well as some gusty surface winds. This would likely be
more likely if convection over central MO were to expand and
result in some upscale growth. Otherwise, the severe threat
appears generally low and SPC`s level 1/5 (marginal) risk across
our IL portion of the cwa is reasonable. Convective coverage
looks to decrease quickly toward sunrise, as the warm front
lifts north along with larger scale forcing.
Going forecast has all of this handled nicely. Did make some
adjustments to pop trends this evening for the current break in
precip, before rain spreads back into the area after 9-10 pm.
Also did increase thunder chances somewhat overnight with
forecast soundings looking more supportive. Otherwise, no
significant changes made for the overnight hours.
Ratzer
&&
.DISCUSSION...
Issued at 248 PM CDT Fri Apr 26 2024
Through Saturday Night:
Regional water vapor and visible satellite imagery, surface
observations, and radar data depict a surface low pressure
system centered along the Kansas and Nebraska borders underneath
an upper level shortwave trough lifting northeastward into the
Upper Mississippi River Valley. Bands of showers and a few
thunderstorms are evident east of the center of the low,
including severe convection across the Plains and warm-air
advection driven showers along and east of the Mississippi
River. A diffuse surface warm front is draped across southern
Illinois, and delineates summer-like moisture to the south and
more seasonable (and wet) conditions to the north.
Over the next 18 hours or so, waves of showers will parade over
northern Illinois and northwestern Indiana as broad warm air
advection continues atop the northward-surging warm front. While
coverage of thunderstorms will initially be isolated this
afternoon and evening, gradually increasing instability (by
virtual of low- level moistening and steepening mid-level lapse
rates) will support embedded thunderstorms particularly after
sunset and especially midnight. While the threat for severe
weather remains low, a localized threat for pea to nickel size
hail or gusty winds exists across much of the area through the
overnight hours, particularly if any upscale growth of any
cluster originating out of Missouri occurs overnight. The SPC
Level 1/5 threat level for the overnight hours covers the
potential well.
After daybreak, the warm front is expected to stall across
central Wisconsin as the low-level jet wanes. At the same time,
a secondary upper-level trough moving into the Southern Plains
will induce gradual mid-level height rises across the Great
Lakes. The net result should be the erosion of any remaining
shower or thunderstorm after daybreak affording a dry period
from mid-morning to mid- afternoon. As low-level stratus thins
from mid-morning onward, a "pop" of southwesterly winds gusting
40-45 mph may occur before noon as mixing builds into the waning
low-level jet. Thereafter, southwesterly gusts of 30-35 mph
will continue through the afternoon. With 850mb temperatures
climbing to +13 to +14C and prospects for even filtered
sunshine, temperatures tomorrow are poised to shoot into the
upper 70s to even lower 80s. When combined with a humid airmass
(surface dew points in the low to mid 60s and PWATs nearing
1.5"), it will feel more like late June than late April by
tomorrow afternoon!
Tomorrow afternoon, neutral height tendencies and boundary
layer heating may prove sufficient to erode capping. As a
result, isolated showers and thunderstorms may develop after 2
or 3 PM, though confidence in anything developing so early is
pretty low (equating to a 20% chance for thunderstorms).
Tomorrow evening, coverage of showers and storms will increase
markedly first across Missouri and Iowa, and later across
northern Illinois, as the next upper-level shortwave pivots
northeastward and supports the redevelopment of an expansive
low-level jet. With a steady feed of low-level moisture and
convergence along the nose of the low-level jet overnight,
showers and storms may continue more or less continuously
through daybreak Sunday along a southwest to northeast, or even
west to east, oriented axis.
While the pattern doesn`t conceptually match classic flash-
flood set- ups (as the upper-level jet will be displaced too far
to our north and west, and cells may be more broken than within
a continuous, training line), the ability for the low-level jet
to continuously feed replenishing instability and moisture into
a relatively confined band of thunderstorms over a prolonged
period of time does raise concern for a localized threat for
flash flooding mainly in urban areas. At this point, CAM
guidance (including an experimental FV3 core extended CAM
ensemble) appears to favor the axis aligning near the Illinois
and Wisconsin state line which is reflected in our forecast.
However, we would be remiss to ignore the deterministic HRRR,
RAP, and experimental RRFS, which all favor the thunderstorms
aligning somewhere near I-80 or I-88. For now, felt the course
of least regret was to collaborate a southeastward expansion of
the D2 WPC Flash Flooding Threat level 1/5 area to encompass
much of northern Illinois.
Not to be forgotten, overnight lows Saturday night will be
incredibly (record?) warm and in the low to mid 60s.
Borchardt
Sunday through Friday:
The secondary upper trough, currently over the Great Basin, is
expected to be traversing the central Plains into the upper
Midwest as a closed upper low on Sunday. This trajectory will
place the Mississippi River Valley and western Great Lakes in
the diffluent region of the trough and therefore continue to
support periods of showers and thunderstorms through Sunday
night. However, there is a notable signal amongst the mid-range
forecast guidance that a modest cap may develop Sunday morning
which could limit (if not inhibit) shower and storm development
until better forcing and destabilization arrives Sunday evening
into the overnight hours as the aforementioned trough is closest
and a low-level jet forms overhead. While it continues to look
as if the better forcing and subsequent instability should
remain near and west of I-39, 30-35 kts of effective shear are
forecast to be in place which could allow a few storms to become
better organized and be capable of producing severe weather,
primarily during the late afternoon and evening hours Sunday.
Therefore, a marginal (level 1 of 5) severe weather risk remains
for the western half of our forecast area.
As the aforementioned upper low lifts into the upper Midwest
Sunday night into Monday, a cold front is expected to move
through northeast IL and northwest IN bringing yet another
period of showers and thunderstorms. Though, the instability on
Monday does look to be notably weaker than on Sunday which
should keep the threat for any strong to severe storms to a
minimum. While temperatures are expected to cool a bit in the
wake of the front, high temperatures are forecast to remain in
the mid to upper 70s through the middle of next week.
A brief break in the active weather is expected for Monday
night and Tuesday as the upper-level pattern transitions into a
more zonal (east-west oriented) pattern. However, additional
shortwave troughs are forecast to traverse through the pattern
Tuesday night through Thursday which looks to return the threat
for periodic showers and thunderstorms. It does look as if high
pressure may try to establish over the central CONUS towards the
end of the week and into next weekend with more seasonable
temperatures as well.
Yack
&&
.AVIATION /00Z TAFS THROUGH 06Z SUNDAY/...
Issued at 705 PM CDT Fri Apr 26 2024
Key Aviation Messages:
- Isolated to scattered elevated TS late this evening and early
overnight.
- SW wind gusts over 30 knots on Saturday.
- Periods of MVFR ceilings through the period.
SE winds gusting to 20 knots early this evening will increase
to around 25 knots late this evening, then veer SSW overnight.
An area of SHRA with embedded TS across eastern Missouri early
this evening is expected to lift northeast toward the Chicago
terminals late this evening into the overnight hours. Steepening
lapse rates combined with renewed forcing ahead of trough over
western Missouri should support at least isolated to scattered
TS at ORD/MDW in the 04-08Z window. Have therefore included
TEMPO TS for this period.
Beyond roughly 08-09Z, dry conditions are expected to prevail
through the daytime hours Saturday. Winds will veer SW after
sunrise, with gusts quickly increasing to over 30 knots by mid-
morning. MVFR ceilings in the morning may lift into lower end
VFR levels or become SCT in the afternoon.
Additional isolated SHRA are expected to develop Saturday
evening, so have included VCSH at this time.
Kluber
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...None.
IN...None.
LM...Small Craft Advisory until 10 PM CDT Saturday for Winthrop
Harbor to Northerly Is. IL.
Small Craft Advisory until 10 PM CDT Saturday for Northerly
Is. IL to Michigan City IN.
&&
$$
Visit us at weather.gov/chicago
Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
648 PM CDT Fri Apr 26 2024
.KEY MESSAGES...
-Showers and a few thunderstorms are expected to continue to move across
the area through this evening. A few of these storms could
produce locally heavy downpours and gusty winds.
-Showers and thunderstorms are likely over the area on Saturday
and Sunday. A few severe thunderstorms are possible over western
parts over the area on Saturday and across the entire area on
Sunday. Large hail, damaging winds, and an isolated tornado are
possible with the strongest storms as well as a localized flash
flooding threat.
&&
.SHORT TERM... (Through Sunday)
Issued at 428 PM CDT Fri Apr 26 2024
A band of showers and scattered thunderstorms is moving northeast
across the CWA this afternoon ahead of a shortwave trough with a
band of low level moisture convergence moving northeast across
Missouri and Illinois. The latest run of the HRRR and other CAMS are
showing this batch of rain continuing to move northeast across the
CWA through the early evening before it exits the CWA. There is
also a low chance (<30%) that storms now developing over eastern
Kansas will hold together and enter central and northeast Missouri
late this evening, though only the NAMNest is showing this
possibility. Otherwise, we have stayed well north of the warm front
today in the cool air and the SPC objective analysis is showing most
of the CWA with MUCAPES of 100 J/kg or less. Expect most storms to
stay below severe limits because of this lack of instability.
Additional showers and thunderstorms will be possible during the day
on Saturday, though the coverage is not expected to be as extensive
as a shortwave ridge will be building as it moves across the area.
The best chances (around 50%) will be across southeast Missouri into
southwest Illinois where a weak mid-level impulse will combine with
925-850mb moisture convergence to bring a chance of showers and
thunderstorms. Another area will be across northeast Missouri into
west central Illinois which will be closer to a surface front with
little capping. There will be an increased chance for showers and
thunderstorms Saturday night into Sunday as another shortwave trough
rounds the Great Plains upper low and increases mid-level lift at
the same time that the low level jet increases in speed on Saturday
night. Expect to see a gradual increase showers and thunderstorms
that will move into the area from the west on Saturday night. This
will continue to move east across the day on Sunday as both the
NAM/GFS are showing a maximum in mid-level ascent/low level moisture
convergence moving across the the CWA. This goes along well with the
LREF showing a band of high probabilities (>90% for 0.01" precip)
moving across the CWA from Saturday night into Sunday night in
concert with the NAM/GFS forcing. A few severe thunderstorms remain
possible mainly during the late afternoon and evening hours when
heating will be maximized. Saturday`s threat will mainly be over
the western part of the CWA and be limited somewhat by weaker deep
layer shear compared to Sunday which will cover much of the CWA and
have stronger deep layer shear. While most of the global models
show the shortwave trough moving across Missouri and Illinois during
the evening and early overnight hours, the surface front does not
move into the area until Monday.
Britt
&&
.LONG TERM... (Sunday night through Next Friday)
Issued at 428 PM CDT Fri Apr 26 2024
Global models are showing the front getting hung up over Missouri
and Illinois next week in quasi-zonal flow aloft. There will be
some instability available along the front which will allow
showers and thunderstorms to develop along it each day. CIPS and
CSU guidance are showing some low probabilities for a few strong
to severe thunderstorms over the area into next week. Temperatures
will remain above normal as 850mb temperatures will be in the
10-15C range.
Britt
&&
.AVIATION... (For the 00z TAFs through 00z Saturday Evening)
Issued at 640 PM CDT Fri Apr 26 2024
Persistent rain and embedded thunderstorms will impact much of the
region this evening before it moves off to the east. While the
rest of the night and Saturday morning likely will stay dry,
cannot rule out an isolated shower/storm.
During the rain this evening, MVFR visibilities will be most
prevalent, but some short periods of IFR conditions will also be
possible. Otherwise, expect fairly gusty southerly winds through
the night and into Saturday morning, mainly around 25 knots.
Gosselin
&&
.LSX WATCHES/WARNINGS/ADVISORIES...
MO...None.
IL...None.
&&
$$
WFO LSX
Area Forecast Discussion
National Weather Service Marquette MI
806 PM EDT Fri Apr 26 2024
.KEY MESSAGES...
-Elevated fire weather conditions continue into this evening
with minimum relative humidity around 20-30 percent over much
of the area accompanied by gusty south to southeast winds to
20-30 mph.
-Low pressure systems bring light to moderate rain tonight into
Saturday.
-Marginal risk for a few strong thunderstorms capable of hail
and gusty winds south-central and east Saturday afternoon and
evening, but confidence is low.
-Active pattern continues, with multiple low pressure systems
bring chances of precipitation virtually all of Saturday night
through next Thursday night.
-The WPC has issued a Marginal Risk of Excessive Rainfall
Sunday into Monday for around an inch of rainfall across the
UP.
&&
.SHORT TERM /THROUGH SATURDAY/...
Issued at 432 PM EDT Fri Apr 26 2024
Visible satellite shows high clouds continuing to filter in ahead of
the next low pressure system currently centered over NE as noted on
RAP analysis and WV imagery. Lingering mid level ridging and the
departing high pressure to our east set up another day of above
normal temps in the 50s to low 60s. While some spots in the west
could warm an additional degree or two into the mid 60s with
downsloping flow, peak afternoon temps will occur within the next
hour. The mixing this afternoon has brought southwest gusts to 20-30
mph across the UP with RHs in around 20-25% over the west with 25-
40% over the east and in the Keweenaw. This will continue elevated
fire weather conditions into the early evening.
The 4/26 12z HREF has the sfc low around 992 mb over northeast NE at
0z Saturday, continuing northeast tonight toward northwest WI by 12z
Saturday as it weakens to around 1000mb. Isentropic ascent will
eventually support showers lifting northeast across the UP this
evening once the dry air is eroded. Better PVA arriving after 6z
Saturday with the mid level shortwave reinvigorates showers and
possibly weak elevated convection tonight. MUCAPE peaks around 250-
500 j/kg and bulk shear is around 30 kts as a LLJ lifts into the
area, so no severe weather is expected. Lows are expected in the 40s.
The sfc low continues to weaken on Saturday as it moves northeast
across Lake Superior to northeastern Ontario. Moisture surges north
from the Gulf of Mexico into the Upper Great lakes moisture, mid
level lapse rates approach 7 C/km, MLCAPE is around 300-600 j/kg
(the NAM is higher around 600-1200 j/kg), and bulk shear of 50-60
kts. This set up is more than adequate for organized updrafts and
stronger storms. That being said, there are a few problems regarding
storm development. Destabilization may be negated by a mid-level
capping inversion, especially with lingering showers and cloud
cover. Also, the consensus of CAMs show the stronger convection
developing along the cold front once the frontal boundary is already
southeast of the UP. Overall confidence in severe thunderstorms in
our CWA is low, but the best chances are located along Lake
Michigan. Highs are expected above normal in the 60s to low 70s, but
could get higher over the south central given more clearing during
the day. Gusty southwest winds to 20-30 mph are also expected in the
afternoon and evening.
&&
.LONG TERM /SUNDAY THROUGH FRIDAY/...
Issued at 407 PM EDT Fri Apr 26 2024
The active weather pattern of late shows no signs of stopping
through the next week. By Saturday night, a handful of 500mb troughs
of various lengths are expected over the CONUS, which of most note
to interests in Upper Michigan are a departing trough over Lake
Superior and the next upstream trough, an anomalously deep (-13 dam
per 12Z GEFS) trough over the Four Corners region. Lagging showers
from the departing system will keep low PoPs in the forecast
Saturday night before the western trough negatively tilts and races
northeast to the Upper Great Lakes basin for the end of the weekend
and the beginning of next week. Attention then turns westward again
as an anomalous trough races along the USA/Canada border through the
early week and has ramifications on the precipitation pattern for
the middle of next week and beyond.
Saturday night, the trough affecting the weather earlier in the day
will be lifting into northern Ontario, leading to height rises over
the Upper Peninsula. This will act against any ongoing lingering
showers, but enough remaining shortwave energy and orographic uplift
from the northerly flow will keep some slight chance PoPs (15-30%)
in the forecast. GEFS mean precip in that time period is only a
couple of hundredths, so any showers that linger will be light in
nature.
Sunday morning, ahead of a 500mb trough exiting the Rockies, a near-
1000mb low pressure will be over the Central Plains. Isentropic
upglide ahead of the lifting warm front will bring gradually
increasing PoPs throughout the day. The warm front of the low should
arrive around Sunday evening with the cold front passing Monday
evening as the low transits through the Upper Great Lakes at around
1005 mb. Following strong 850mb CAA in the morning, Sunday will be
the coldest day of the week, with gridded MOS guidance showing highs
only in the 40s and lower 50s. ECMWF EFI SoT between 0 and 1 by
Monday indicates the potential for an unusually high
precipitation total potential. The NAEFS climatology percentiles
for vapor transport, PWAT, and humidity are all in the
90-99.5th percentile range through late Monday, leaving the
ingredients for some higher QPF forecasts. Ensemble forecasts do
have a somewhat high spread, but the range of plausible
forecasts (80% probability) is between a half inch of rain and 2
inches of rain by Monday night, leading to the WPC issuing a
Marginal Risk of Excessive Rainfall. A few rumbles of thunder
are also possible, with the GEFS and Canadian ensemble showing
generally up to 700 J/kg of SBCAPE especially on Monday.
Ensemble spread increases significantly following the passage of the
system by Tuesday, but the general idea is that a trough passing
along the USA/Canada border will support a low pressure tracking
just north of Lake Superior which should support rain showers
roughly in the late Tuesday/early Wednesday timeframe. Another
system could pass in the Thursday timeframe, but NBM PoPs of only 15-
30% highlight the uncertainty in the timing and location of such a
system. Confidence is increasing that ridging will build over the
region for next weekend, giving at least some period of time for the
UP to dry out. Soils could be particularly soggy by then, as the
GEFS accumulated QPF by the end of next week ranges from 1 to 4
inches.
&&
.AVIATION /00Z TAFS THROUGH 00Z SUNDAY/...
Issued at 805 PM EDT Fri Apr 26 2024
VFR to continue through at least Sat 06Z at all TAF sites before
rain (possible thunderstorms at IWD) start overspreading the area
with an approaching low pressure system. At that point, IWD and SAW
will quickly deteriorate to MVFR followed by CMX. From mid
morning to early afternoon tomorrow, also cannot rule out a
period of IFR with low confidence LIFR. Slight improvement can
be expected by tomorrow afternoon, but nothing above MVFR
levels. Meanwhile, LLWS will be a threat at all TAF sites in the
Sat 06-18Z time frame due to an associated low level jet. And,
strong southeasterly surface winds (becoming southwesterly
tomorrow afternoon) will gust to 28 kts.
&&
.MARINE...
Issued at 530 AM EDT Fri Apr 26 2024
Southeast winds gusting up to 25 mph are occurring early this
morning with the strongest winds across the east half of the lake.
Southeast winds increase up to 30 knots across the eastern lake
Friday afternoon. A few gale force gusts up to 35 knots are possible
near the tip of the Keweenaw and the international border through
Saturday morning. A low pressure tracks across Lake Superior on
Saturday resulting in a period of light and variable winds. Cold air
advection increases Saturday night resulting in northerly winds
gusting up to 30 kts across north-central portions of the lake.
Another low pressure approaches Lake Superior on Sunday causing
winds to back northeasterly and increase to gales across the far
western lake. Winds back easterly Sunday night as gales spread
across all but far eastern Lake Superior. A local office tool
indicates 60-90% chances for 40-45 kt gales across the far
western lake Sunday afternoon and evening with lower 25-50%
chances across the north-central lake. Gales are forecast to
subside on Monday as the low`s center lifts across Lake
Superior. Winds become west- southwesterly Monday night while
decreasing to 20 to 25 knots. Light winds less than 20 knots
prevail Tuesday then another system moving through Tuesday night
and Wednesday increases west winds to around 25 kts.
Thunderstorms are possible over portions of Lake Superior tonight
through Saturday evening then again Sunday evening through Monday
evening.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
None.
Lake Superior...
Gale Watch from Sunday morning through Monday morning for
LSZ162.
Gale Watch from Sunday evening through Monday afternoon for
LSZ242>246-264>266.
Small Craft Advisory until 6 PM EDT Saturday for LSZ244-245-
249-250.
Small Craft Advisory until 2 PM EDT Saturday for LSZ246.
Small Craft Advisory until 8 AM EDT Saturday for LSZ248.
Small Craft Advisory until 8 PM EDT Saturday for LSZ251.
Gale Watch from Sunday afternoon through Monday afternoon for
LSZ263.
Lake Michigan...
Small Craft Advisory from 5 AM to 8 PM EDT Saturday for LMZ221.
Small Craft Advisory from 7 AM Saturday to 5 AM EDT Sunday for
LMZ248.
Small Craft Advisory from 5 AM Saturday to 5 AM EDT Sunday for
LMZ250.
&&
$$
SHORT TERM...Jablonski
LONG TERM...GS
AVIATION...TDUD
MARINE...GS
Area Forecast Discussion
National Weather Service Springfield MO
647 PM CDT Fri Apr 26 2024
.KEY MESSAGES...
- Thunderstorm chances continue into this evening with the
better potential for severe storms occuring over southeast
Kansas to along the western Missouri border.
- After a break Saturday, periodic thunderstorm chances resume
Saturday evening into Monday. A Flood Watch has been issued
for Saturday night into Monday as anticipated heavy rain falls
on regions that recently received excessive rains.
- The unsetteled pattern continues with additional storm chances
mid to late next week.
&&
.SHORT TERM /THROUGH SATURDAY NIGHT/...
Issued at 301 PM CDT Fri Apr 26 2024
Atmosphere to remain unsettled through much of the short term as a
negatively tilted upper low moves into Iowa and associated
diffluence aloft aids upper vertical motion.
Despite cloud debris from an MCS that formed over Oklahoma and
spread across the forecast area today...elevated convection
continues to form upstream of the Ozarks under the cloud cover.
18z KSGF RAOB depicting significant CIN with model soundings
depicting even less instability farther east...thus severe
threat to be limited Highway 65 east.
Farther west...sunshine will support destabilizaton over southeast
Kansas with storms forming southeast of ICT suggestive of the
beginnings of the next round of storms. Leaned on the ML CAPE
from the HREF and HRRR to however anticipate that any storms
that may form to have a tough time propagating much into western
Missouri this evening. Before then however hail to the size of
tennis balls and damaging winds will be the primary threat for
the storms that reach far southeast Kansas. The tornado threat
will be somewhat reduced by veering surface winds and
diminishing instability but the threat will need to be
monitored.
Rain chances will diminish this evening with minimal support for
much of the day Saturday before diffluence induced uplift increases
once again as the next waves moves across the Plains Saturday
night.
&&
.LONG TERM /SUNDAY THROUGH FRIDAY/...
Issued at 301 PM CDT Fri Apr 26 2024
Precipital water that had increased to around 1.3 Thursday
before dropping to 0.8 inches on the 18z SGF RAOB, will once
again surge northward to over 1.75 ahead of the next wave
compliments of a 50 knot north orientated low level jet Saturday
night. The resultant rainfall coupled with it falling on
grounds already impacted by recent excessive rains raises an
elevated to significant flood threat into Sunday.
The next western wave will be more progressive as it tracks
eastward along the Canadian border on Tuesday. Questions exists
on how far south its influence will extend though moisture
convergence along an attendant cold front will be enough to
offer a limited potential for additional thunderstorms as it
slowly sags southward late in the work week.
&&
.AVIATION /00Z TAFS THROUGH 00Z SUNDAY/...
Issued at 642 PM CDT Fri Apr 26 2024
Expect VFR conditions to persist through tonight, albeit with
LLWS and gusty surface winds. For Saturday, MVFR ceilings are
expected during the day, then potential for widespread showers
and thunderstorms exists late in the day into Sunday.
&&
.CLIMATE...
Issued at 1225 PM CDT Thu Apr 25 2024
Record High Minimum Temperatures:
April 27:
KSGF: 67/1899
April 28:
KSGF: 68/1896
&&
.SGF WATCHES/WARNINGS/ADVISORIES...
KS...Flood Watch from Saturday evening through Sunday afternoon for
KSZ073-097-101.
MO...Flood Watch from Saturday evening through Sunday afternoon for
MOZ055-056-066>069-077>080-088>090-093>095-101>103.
&&
$$
SHORT TERM...Runnels
LONG TERM...Runnels
AVIATION...Titus
CLIMATE...Price
Area Forecast Discussion
National Weather Service Topeka KS
654 PM CDT Fri Apr 26 2024
.KEY MESSAGES...
- Several rounds of thunderstorms are forecast through Sunday.
- Severe weather with large hail, damaging winds and even tornadoes
are possible with the greatest risk on Saturday.
- Additional rounds of heavy rainfall may lead to flooding over east
central and northeast Kansas.
&&
.UPDATE...
Issued at 654 PM CDT Fri Apr 26 2024
The Tornado Watch has been cancelled. The threat for severe storms
this evening has diminished. Another round of severe storms is
possible tomorrow.
&&
.DISCUSSION...
Issued at 145 PM CDT Fri Apr 26 2024
An upper low was seen on the 18Z water vapor imagery with a
shortwave trough rotating through the base of the low towards
northeast KS. At the surface, A warm front has lifted mostly
through the forecast area with a dryline extending south through
central KS. Towering CU and a couple thunderstorms have formed
along the dryline.
The question with thunderstorms this evening is the extent to
the south storms form along the dryline. There are mixed results
from the various CAMs with some failing to develop storms as
far south as I-70 and others showing more widespread storms over
northeastern KS. MUCAPE around 3000 J/kg 0-6km shear of 50KT
will be supportive of supercell storms. These storms are
expected to swing to the north and east quickly this evening
which may limit the tornado risk for our area since storms would
be exiting as the low level jet and SRH increase.
The models show a continued warm air advection pattern persisting
through the night allowing the dryline to return west. RAP and NAM
show a narrow east to west axis of isentropic assent developing
overnight within the moisture return. So have continued with some
small POPs through the early morning to account for the chance some
elevated storms develop. Forecast soundings still show around 2000
J/kg of elevated CAPE with 40KT of bulk shear. So there may be a
hail and/or damaging wind risk through the early morning hours.
Confidence in elevated storms is low since CAMs don`t really support
the RAP and NAM forecasts.
Saturday looks to be complicated by warm sector development ahead of
the dryline. Forecast soundings show little in the way of inhibition
by the afternoon as height falls spread east. So storm mode
could be complicated by this activity if it develops. The
environmental conditions look to remain favorable for supercell
storms with plenty of CAPE and shear. So we continue to message
the risk for severe weather including tornadoes which may have
the opportunity to be strong. There is a little more confidence
in another round of heavy rainfall over eastern parts of the
forecast area through Saturday night. A few river points went
into flood this morning and the additional rainfall will
probably may flooding a more widespread concern. With this in
mind, went ahead and posted a flood watch for Saturday afternoon
through Sunday morning.
The storm system responsible for all of the weather is progged
to remain over the central plains Sunday with another shortwave
trough rotating through eastern KS. A diffuse boundary is
forecast to still be over eastern KS through peak heating so
there remains a chance for one more round of thunderstorms
Sunday afternoon and into the early evening.
&&
.AVIATION /00Z TAFS THROUGH 00Z SUNDAY/...
Issued at 537 PM CDT Fri Apr 26 2024
Looks like the terminals will miss the TS this evening. There is
an outside chance for an isolated TS to develop overnight.
Probabilities of 20 to 30 percent are to low to include in the
forecast at this time. LLWS looks to be mitigated by a mixed
boundary layer and unidirectional winds. Biggest impact from the
weather will be the MVFR stratus returning towards 06Z and
after. Similar to earlier, this should scattered out and lift
above 3 KFT by early afternoon.
&&
.TOP WATCHES/WARNINGS/ADVISORIES...
Flood Watch from Saturday afternoon through Sunday morning for
KSZ011-KSZ012-KSZ023-KSZ024-KSZ026-KSZ037-KSZ038-KSZ039-KSZ040-
KSZ054-KSZ055-KSZ056-KSZ058-KSZ059.
&&
$$
UPDATE...Jones
DISCUSSION...Wolters
AVIATION...Wolters