Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 05/19/24
Area Forecast Discussion
National Weather Service Bismarck ND
951 PM CDT Sat May 18 2024
.KEY MESSAGES...
- Low to medium rain shower chances (20 to 40 percent) return
late tonight into early Sunday morning.
- There is a Marginal Risk of severe weather (level 1 out of 5)
late Sunday afternoon into the evening hours.
- High temperatures remain cool through the next work week,
mainly in the 60s. Expect daily low to medium (20 to 40
percent) chances for showers and thunderstorms through the
week.
&&
.UPDATE...
Issued at 949 PM CDT Sat May 18 2024
Clear skies and calm winds as the daytime heating driven clouds
have died. It will be a calm night before clouds and some light
showers move in early morning.
UPDATE
Issued at 643 PM CDT Sat May 18 2024
The diurnal cumulus continue to slowly die across most of the
area and will be clear skies be sunset. Winds are also relaxing
and will go calm after sunset as well. The Wind Advisory will be
allowed to expire as winds are calming now.
&&
.DISCUSSION...
Issued at 231 PM CDT Sat May 18 2024
An upper low continues to spin off to the east just north of the
Canadian border over eastern Manitoba. Associated light rain
showers continue over Bottineau and Rolette counties, but should
move out in the next hour or two.
Western and central North Dakota generally sits under the
influence of near zonal flow aloft but we will see some subtle
ridging move across the state through the rest of the day. While
visible satellite imagery shows a decent amount of fair weather
cumulus, this progressive ridging should lead to some
subsidence across the west, leading to some clearing.
The strongest cold air advection and pressure rises have mainly
moved off to the east, so while it will remain windy though the
rest of the afternoon (winds out of the west northwest), it
should very gradually diminish as we move towards sunset. Given
the tight pressure gradient, we are still expecting sustained
winds up to 30 mph and gusts to 45 mph for a few more hours.
Thus, the Wind Advisory still looks to be in good shape.
Late tonight and into Sunday morning, we will gradually
transition to southwest flow aloft as a Pacific Northwest trough
starts to approach. Warm air advection may lead to some low to
medium (20 to 40 percent) chances for hit and miss showers late
tonight into Sunday morning, mainly across the south central
and James River Valley. This activity should move north through
the morning and into the early afternoon but uncertainty remains
about how long it will be able to sustain itself.
A better chance for showers and thunderstorms (40 to 70 percent)
should start to develop over the south central and James River
Valley by late Sunday afternoon and into the evening hours. A
surface low will start to deepen over South Dakota with an
inverted surface trough extending to it`s north northeast. This
boundary should be the focus for thunderstorm development by the
late afternoon hours. Across the far south, RAP soundings
suggest the potential for up to 2000 J/kg of MUCAPE. However,
looking at MLCAPE, we generally max out in the 500 to 1000 J/kg
range. Still, with forecast deep layer shear will range from 45
to 55 knots over the same area. On paper, these parameters
should be more than enough for a strong to severe storm or two.
However, there are concerns with moisture quality and depth. It
is also worth noting that the RAP is a bit more bullish on
higher instability than most of the other short term models (but
the RAP still shows fairly "skinny" CAPE which may mean
relatively narrow updrafts). That being said, deep layer shear
vectors will mainly be orthogonal to the surface trough so
storms that do form could be discrete or semi- discrete. The
Storm Prediction Center has placed Emmons, Logan, McIntosh,
LaMoure, and Dickey counties in a Marginal Risk (level 1 of 5)
for severe weather. After analyzing soundings and the latest
CAMS, we have decided to message the marginal severe weather
potential up to Kidder, Stutsman, and Foster counties as well.
For now, we will message wind gusts up to 60 mph and hail to the
size of quarters. The one caveat is that if the RAP were to
verify, these thresholds would possibly be too low. However,
the RAP appears to be an outlier right now, maybe not mixing
out dewpoints enough.
Regarding temperatures, Sunday will be the warmest day of the
week with highs ranging from the lower 60s to the lower 70s. By
Monday we will only see lower 70s in our far southeast with
highs in the 60s elsewhere. Highs will mainly be in the 60s
through midweek. The coolest days will then be possible towards
the end of week (Thursday and Friday) when we could see some
highs in the upper 50s to lower 60s.
The active progressive flow will also continue through the week,
leading to daily low to medium (20 to 40 percent) chances of
precipitation at various locations across western and central
North Dakota. Thunderstorm potential will be limited given the
cooler temperatures but a slight chance seems warranted towards
the end of the week across the south as most models have a
potent trough moving into the region (Thursday-Friday). The
eventual track of this trough and associated upper low is still
a bit up in the air. Most models/ensemble members have this
feature but substantial uncertainty remains regarding the track
and strength. It may be worth nothing that CIPs extended analogs
suggest some severe potential across our south by the end of the
week, but CSU Machine Learning guidance is not showing the
potential at this point.
&&
.AVIATION /00Z TAFS THROUGH 00Z MONDAY/...
Issued at 950 PM CDT Sat May 18 2024
Calm winds and clear skies overnight before VFR clouds move in
early morning. Showers are possible at every terminal at some
point in the late afternoon so included VCSH. Winds will
increase to around 20kts Sunday from the southeast.
&&
.BIS WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
UPDATE...Smith
DISCUSSION...ZH
AVIATION...Smith
Area Forecast Discussion
National Weather Service Cleveland OH
1016 PM EDT Sat May 18 2024
.SYNOPSIS...
High pressure slides across the region tonight and Sunday. A
weak cold front approaches from the northwest Sunday night
before lifting well to our north as a warm front on Monday. A
cold front is expected to push through on Wednesday.
&&
.NEAR TERM /THROUGH SUNDAY NIGHT/...
9:30 PM Update...
Convection has completely dissipated, and that will allow for a
dry night as high pressure builds overhead. We just await the
development of radiation fog. Temp/dew point spreads are larger
than last night, and we mixed well this afternoon, so that will
make the fog less dense and less widespread than last night.
However, the latest RAP forecast soundings still show a low-
level inversion late tonight, especially in NE Ohio and NW PA,
and enough low-level moisture lingers to cause at least mist
with pocket of dense fog in the sheltered valleys. For these
reasons, kept patchy fog in most of the area overnight, with
areas of fog in NE Ohio and NW PA, but not enough confidence on
coverage and duration for any special weather statements at this
point. Lakeshore areas near the Islands have the best potential
for locally dense fog outside of NE Ohio and NW PA where light
NE flow will advect some lake moisture below the inversion, so a
fog bank could redevelop on the lake and affect communities
near the western and central basins. Many HREF members show high
probabilities of this, but confidence is still somewhat low due
to the overall environment being a little drier than 24 hours
ago.
6:30 PM Update...
Increased PoPs over an axis from Morrow and Knox Counties
through southern Richland, Ashland, Wayne, and Stark Counties
over the next 1-2 hours. A weak boundary associated with a
lingering mid-level vort max over eastern Ohio is generating
persistent convection along its low-level convergence where
MLCAPE of 500-1000 J/Kg is present. PWATs are only around 1 inch
in that area, but these cells have produced efficient rainfall
rates of 2 inches in 30 to 45 minutes! This is due to training
and very slow movement of around 5 kts or so. Expect this pulse
convection to finally wane after 23Z as the sun angle decreases.
The rest of the forecast remains on track.
Original Discussion...
Relatively benign weather is expected for the remainder of the
weekend. The combination of heating of a somewhat moist low-
level airmass, a subtle vort max overhead, and some low-level
convergence over the Mid Ohio region has allowed isolated
showers and thunder to develop. Expect this activity to
dissipate by around sunset. Weak high pressure then slides
through tonight and Sunday leading to partly to mostly clear
skies and dry conditions for most of the forecast area through
the rest of the near term. A weak cold front will try to
approach Northwest Ohio late Sunday afternoon / evening before
lifting north to start the week. Strong upper ridging will be
in place, though forecast soundings depict modest to moderate
and uncapped instability near Toledo late Sunday afternoon /
evening. Enough hi-res models have isolated to scattered
convection nearing Northwest Ohio late Sunday to maintain some
20-30% POPs to cover the potential. Weak shear and forcing
suggest any storms will be of the single cell or "pulse"
variety. Thermodynamics may be sufficient for a couple of cells
to produce locally gusty winds or small hail in Northwest Ohio
late Sunday, though overall am not too concerned about any kind
of organized strong to severe storm threat. Any storms that
make it into Northwest Ohio should rain themselves out by late
Sunday evening with dry weather for the rest of Sunday night.
Lows tonight will generally settle into the 50s. It will be
quite warm on Sunday, with highs in the low to mid 80s with the
exception of the eastern lakeshore where onshore flow will keep
conditions cooler. Lows Sunday night will be quite mild, ranging
from the mid to upper 50s from far eastern OH into PA to the mid
60s along and west of I-71. Some radiation fog is likely again
late tonight and very early Sunday though coverage should not be
as widespread as Friday night into early this morning. The most
widespread fog with pockets of dense fog will be from interior
eastern OH into western PA, with fog more patchy and generally
not quite as dense farther west.
&&
.SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/...
Mid to upper level ridging will gradually build east during the day
Monday before an upper trough and embedded shortwave clips Northwest
Ohio on Tuesday. For now, have low end PoPs confined to Northwest
Ohio for Monday afternoon and along and west of I-71 Tuesday
afternoon. The upper trough becomes more pronounced Tuesday night as
the surface low moves northeastward while deepening. This low will
swing a cold front toward the Ohio Valley region to end the short
term and begin the long term period.
Temperatures will rise nearly 10-15 degrees above normal Monday and
Tuesday with highs in the mid to upper 80s. Warm overnight lows
Monday and Tuesday night in the mid to upper 60s.
&&
.LONG TERM /WEDNESDAY THROUGH SATURDAY/...
The aforementioned deepening low pressure will drag a cold front east
across the local area on Wednesday and bring increased shower and
thunderstorm chances to the region. The environment continues to
look favorable for strong to severe storms develop as we`ll remain
in the warm sector with dew points in the low 60s with current
guidance suggesting roughly 1000-1500+ J/kg of MLCAPE to work with.
We will continue to monitor the severe weather potential for
Wednesday as we get more model guidance. Trended drier toward the
end of the week behind the cold front as a brief ridge of high
pressure builds northward for Friday.
Highs top out in the lower 80s ahead of the cold front on Wednesday
before returning to near normal values in the mid 70s Thursday
through Saturday. Overnight lows through the long term settle in the
mid 50s each night.
&&
.AVIATION /00Z Sunday THROUGH Thursday/...
Convection near KMFD is dissipating and should be gone by 00Z.
This will leave VFR at all sites through the evening. The main
question mark for tonight continues to be how much fog will
develop? Most areas mixed well today, so it should be less
widespread than last night. However, another inversion will
develop tonight, so think most areas should go down at least
below 5 miles, with pockets of 1/2 to 1 mile visibility in fog
as temp/dew point depressions remain small. The duration of the
most dense fog should be shorter, but KERI could still have
dense fog much of the night due to added low-level moisture
advection off of Lake Erie. Any fog/mist will gradually
dissipate by mid to late Sunday morning, but it could once again
hang on at KERI into the early afternoon.
Light N to NE winds this evening will turn light and variable
tonight before becoming N at 5-10 knots Sunday.
Outlook...Low risk for isolated thunderstorms in Northwest OH
Monday night. Somewhat greater potential for isolated to
scattered thunderstorms Tuesday afternoon and evening. Scattered
to widespread thunderstorms are likely Wednesday afternoon.
Mainly VFR is expected outside of thunderstorms.
&&
.MARINE...
Satellite imagery and local area webcams of Lake Erie indicate vast
improvement of visibilities and thus the Dense Fog Advisory was
cancelled. Moist low levels under a steep inversion overnight
tonight will likely prompt the issuance of another fog headline over
the lake. Low confidence in exact timing and placement of overnight
fog so opted to hold off on issuing a new Dense Fog Advisory for
overnight tonight with this forecast update.
High pressure persists through the weekend keeping winds light and
variable on the lake through Monday afternoon. Flow turns southerly
over Lake Erie by Monday night generally remaining between 5 and 10
knots. Deepening low pressure centered over the Great Plains will
enter the Great Lakes region by mid week and will allow for
southerly flow to increase to 15-20 knots during the day Wednesday
before a cold front crosses eastward on Wednesday evening. Southwest
flow of 10-15 knots behind the cold front continues into the end of
the week.
&&
.CLE WATCHES/WARNINGS/ADVISORIES...
OH...None.
PA...None.
NY...None.
MARINE...None.
&&
$$
SYNOPSIS...Sullivan
NEAR TERM...Garuckas/Sullivan
SHORT TERM...Iverson
LONG TERM...Iverson
AVIATION...Garuckas
MARINE...Iverson
Area Forecast Discussion
National Weather Service State College PA
1124 PM EDT Sat May 18 2024
.SYNOPSIS...
An upper trough overhead will slide east through the late
evening with showers decreasing by late tonight. High pressure
will start to build into the region on Sunday accompanied by
generally rain-free conditions that are expected to hold through
the middle of next week. A storm system should arrive late
Wednesday into Thursday bringing the next chance of showers and
thunderstorms to the area.
&&
.NEAR TERM /UNTIL 6 AM SUNDAY MORNING/...
Isolated open cellular showers continue to roam areas from the N
Central Mountains to the WC Mountains late this evening as upper
low upper low tracks off the coast and drier air works southward
behind the upper trough axis. Showers will taper by late tonight
with clearing skies and light winds allowing areas of fog to
form overnight. Some fog could become locally dense in the
predawn hours. Lows will range from the mid 50s to around 60.
&&
.SHORT TERM /6 AM SUNDAY MORNING THROUGH TUESDAY NIGHT/...
High pressure rolls in for Sunday. Clouds/fog in the AM clear
out nicely. However, just enough instability develops and enough
moisture lingers to pop a couple of SHRA. Literally just a few
with the highest probability (30pct) over the SErn hill tops.
Maxes in the 70s will be pretty normal. We are likely to see
some areas of fog again Sunday night with the sky clearing out
better, but dewpoints not dipping out of the m50s.
A decent and mostly rain-free stretch of weather is expected
Monday through Wednesday morning, with high pressure dominating
the sensible weather conditions and bringing the driest weather
we`ve seen in a few weeks. We are timing the next weather system
into central PA by Wednesday afternoon. Scattered showers and
thunderstorms may approach western areas by late Wednesday
afternoon, but it looks like most areas stay dry until after 00z
Thurs.
&&
.LONG TERM /WEDNESDAY THROUGH SATURDAY/...
Late evening update holds minor changes to the long-term
forecast, most notably have capped PoPs at Chc Wednesday
evening into Thursday as both GFS/ECMWF models have
showers/thunderstorms along the cold front breaking up as they
enter central PA. Ensemble plumes still outline higher chances
of PoPs in this timeframe so have decided to just cap instead of
trim PoPs at this time.
Prev...
By the middle of next week, upper troughing will move
across Pennsylvania and support a better chance for showers and
thunderstorms. At the surface, there remains plenty of model
uncertainty about the timing of a cold front. The mean timing is
Wednesday afternoon, but individual models bring rain as late
as Thursday morning. If the front moves through Wednesday
afternoon or evening, it could produce the first threat for
severe weather in some time given the aforementioned WAA
bringing greater instability.
After the front moves through, considerable uncertainty exists
in terms of how much and how frequent rain will be. A chance of
showers remains in place through the end of the week despite
zonal flow aloft providing little in the way of synoptic
forcing. The next chance for a widespread soaking rain will come
during the weekend with a center of low pressure developing
across the Ohio Valley by Friday afternoon.
&&
.AVIATION /03Z SUNDAY THROUGH THURSDAY/...
03Z Update: Minimal changes outside of slightly later (1-2hr)
later on fog development overnight with generally the same time
for mixing out. A period of MVFR cigs possible tomorrow compared
to earlier guidance but VFR expected by the afternoon hours.
Prev...
The main concern overnight will be fog formation at all
airfields across central PA. The bulk of recent guidance
outlines IFR conds in the 04-07Z timeframe, with most likely
timing between 05-06Z where the potential for calm/light winds
becomes slightly higher. This is echoed in recent RAP model
soundings, thus have these restrictions in with moderate
(50-60%) confidence. There is some uncertainty in regards to
which airfields go down to 1/4SM vsbys and VV cigs after during
the early morning hours Sunday morning. Highest confidence
(40-50%) remains at AOO/UNV/IPT, with some potential for these
conds at JST/BFD. Further to the SE, cannot rule out some lower-
level clouds (below 300ft AGL) to bring LIFR conds to LNS with
moderate (40-50%) confidence while retaining IFR conds at MDT
based on a combination of RAP/GLAMP guidance.
After sunrise, some lingering low cigs/vsbys remain possible
through 14Z Sunday before rapid improvement (in a 1-2 hour
period) towards VFR is expected by the late morning. Once conds
prevail to VFR, expect these conditions to continue through 00Z
Monday.
Outlook...
Mon...Patchy AM fog possible. Otherwise, becoming VFR.
Tue...Predominantly VFR, w/ no sig wx expected.
Wed...Sct to widespread SHRA/TSRA return.
Thu...Chc of TSRA.
&&
.CTP WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
SYNOPSIS...Lambert/DeVoir
NEAR TERM...DeVoir/Dangelo
SHORT TERM...DeVoir/Dangelo
LONG TERM...NPB/Bowen
AVIATION...NPB
Area Forecast Discussion
National Weather Service Dodge City KS
1034 PM CDT Sat May 18 2024
...Updated Aviation/Key Messages...
.KEY MESSAGES...
- Hot temperatures in the 90s and strong south winds are
expected Sunday afternoon.
- Scattered thunderstorms are expected Sunday afternoon and
evening. Some storms are expected to be severe with large
hail and damaging winds.
- The highest risk of straight line wind damage will be east of
Dodge City Sunday evening, where gusts of 60-80 mph are
probable.
&&
.SHORT TERM /THROUGH SUNDAY NIGHT/...
Issued at 200 PM CDT Sat May 18 2024
18Z observations and upper air analysis shows a cold front
located from central Kansas to around Liberal which is slowly
progressing to the south and east. Winds behind the front have
increased to 20-30 mph. A 1006 mb surface low is located in the
Texas panhandle in association with an upper level shortwave
while mid level winds are generally zonal.
Tonight the main feature of interest is a forecast MCS to
develop in northeast Colorado around sunset. Ahead of the storm
complex a 700 mb shortwave and surface low will develop and the
present cold front will lift back to the north as a warm front
which should allow the return of more robust moisture as the
winds switch back to the southeast. Through the evening and
overnight hours BUFKIT soundings in northwest and northcentral
Kansas show the storm will be quite elevated and the main threat
would be downburst winds up to 60 mph and as a result there is a
marginal risk of severe weather. These storms will likely affect
areas along an north of a Syracuse to Hays line through sunrise
Sunday morning.
Sunday there should be a brief outflow boundary from the
overnight convection which will stabilize the atmosphere
through mid morning. Afterwards as the winds turn back to the
southeast we will have growing moisture and instability ahead of
a developing dryline along the Kansas-Colorado border. Mid level
temperatures will be quite warm at 10-11(C) however with
forecast highs reaching to the mid 90s around the dryline this
should be warm enough to erode any cap we have. A 700 mb
shortwave should move into the vicinity of the dryline around
20-21Z and thunderstorm initiation should quickly result around
the Kansas/Colorado border. If we do have any supercells they
will quickly evolve into a linear squall line within a couple
hours. With short term models forecasting 3,000 J/kg or more
CAPE these storms will have plenty of energy to work with as the
progress eastward. Main threat for severe weather on Sunday will
be straight line winds as the 12Z HRRR has hints of wind gusts
approaching 75-80 kts once the line gets into the most robust
moisture along and east of highway 183. Secondary threat with
any squall line could be some brief QLCS spin up tornadoes
embedded in the line. Hail threat will be the most with initial
storm development and then lessen as the storms become more
linear. The bulk of the line should be through by Sunday
evening.
Sunday evening as the main line of storms moves into central
Kansas HRRR models hint at a secondary line of storms developing
on an outflow/frontal boundary along K-96. If there is any
instability left after the initial line this could certainly be
a possibility. Storms look to fester between K-96 and I-70
through close to sunrise on Monday.
&&
.LONG TERM /MONDAY THROUGH SATURDAY/...
Issued at 205 PM CDT Sat May 18 2024
Monday medium range ensembles have a large longwave trough in
the western CONUS and southwest winds at 700 mb will push a
shortwave into western Kansas by 00Z. With how the track of the
surface to 850 mb the majority of the rain and storms will be
concentrated in northwest and north central Kansas into
Nebraska.
Tuesday into Wednesday the longwave trough will be concentrated
in the northern plains with a strong cold front moving into
Kansas Tuesday. High temperatures on Wednesday will be in the
70s.
A warming trend will return towards the end of the week as highs
get into the middle 80s. The more active part of the jet stream
looks to be in the northern plains.
&&
.AVIATION /06Z TAFS THROUGH 06Z MONDAY/...
Issued at 1034 PM CDT Sat May 18 2024
Outside of the influences of any convection, VFR is expected to
continue through this TAF period. KDDC radar at 0330z showed
strong thunderstorms near the CO/KS line well west of GCK. These
storms are expected to track primarily north of GCK/HYS through
12z Sun, so kept any mention out of this set of TAFs. Light east
winds will prevail overnight. After 15z Sun, south winds will
increase quickly at all airports, gusting 30-35 kts. Scattered
thunderstorms are expected to initiate on a dryline near US 83
(GCK-LBL) around 21z Sun, then rapidly spread eastward to impact
DDC/HYS through 00z Mon. Using 00z ARW as a guide, only
mentioned VCTS/CB for now, with the expectation that TEMPO
groups will eventually be required, once the expected squall
line is trackable on radar. Some thunderstorms Sunday are
expected to be severe, with the primary risk to aviation being
outflow wind gusts in excess of 50 kts.
&&
.DDC WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
SHORT TERM...Tatro
LONG TERM...Tatro
AVIATION...Turner
Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
1154 PM EDT Sat May 18 2024
.KEY MESSAGES...
- Patchy fog, locally dense at times, will be possible tonight.
- Warm and muggy conditions continue through early next week with
daytime highs in the 80s.
- Chance for showers and thunderstorms tomorrow afternoon and
evening favored toward the lakeshores. Locally heavy rainfall and
strong thunderstorm winds will be possible.
&&
.AVIATION...
Will maintain a mention of fog KYIP/KDTW/KDET within light southeast
flow from Lake Erie, but will temper the degree of lower stratus as
late evening satellite trends do not support much stratus at this
point. Winds veer to the southwest and then west as a weak frontal
boundary settles into the area. This front, combined with a number
of lake breeze boundary, will be the focus for widely scattered to
scattered showers/thunderstorms late in the day, mainly KPTK south.
Wind will shift to northeast tomorrow night behind the front and
then basically become light/variable.
For DTW/D21 Convection...There will be a chance for scattered
thunderstorms Sunday afternoon as a weak frontal boundary interacts
with lake breeze(s) serving as the focus. Isolated heavy downpours
may bring visibility restrictions.
DTW THRESHOLD PROBABILITIES...
* Low for ceilings aob 5kft late tonight.
* Low for thunderstorms Sunday afternoon.
&&
.PREV DISCUSSION...
Issued at 423 PM EDT Sat May 18 2024
DISCUSSION...
Lower clouds supported by lake moisture under the strong inversion
this morning has mixed out this afternoon bringing mostly clear
skies. Warm and muggy airmass in place today. The 12Z DTX RAOB came
in with 925mb temperatures in the mid teens (C). This is supporting
the temperatures into the 80s this afternoon. Daytime heating and
low level moisture has brought a scattered field cumulus, but high
pressure and ridging should largely limit any shower activity with
instability lacking and very weak forcing. Higher dewpoints,
southeast flow off Lake Erie, and mostly clear skies will bring
potential for patchy fog development again tonight.
An unstable airmass residing across Michigan tomorrow will set the
stage for scattered shower and thunderstorm potential. The RAP
offers 1000-1500 J/kg of MLCAPE developing by 18Z tomorrow across
much of southeast Michigan with increased mid level lapse rates of
6.5-7.0 C/km and low level lapse rates to around 9 C/km. A northern
stream shortwave will drive a weakening cold front into southeast
Michigan tomorrow. Shear over much of the area will be weak though
with best flow off to the north. Bulk shear from 0-6 km is mostly
below 20 knots with the exception across portions of the Tri-Cities
and Thumb. The northern stream shortwave will push a weakening cold
front into southeast Michigan during the late morning/early
afternoon while stronger surface heating will likely lead to the
development of multiple lake breezes during the afternoon. This
brings several opportunities for surface convergence to force
convection initiation, especially if the front tracks further into
southeast Michigan and meets up with any lake breeze. The weaker
flow leads to mainly a pulse type thunderstorm mode that form
initially on either of the aforementioned boundaries with
thunderstorm outflow also driving additional updrafts. Current Hi-
res model suite wants to place greater probability for initiation
across Port Huron to the Detroit Metro area and down to Monroe
County along the lake breezes. Though, some capping in the forecast
soundings could also put a damper on some thunderstorm development.
Will maintain the chance PoPs in the forecast here. Main threats
with activity will be strong downburst winds, hail, and brief
heavy rainfall with the PWATs of 1.25" to 1.35". Heavy rainfall
and slow storm motions bring some potential for localized flooding
of prone spots, especially in the urban footprint in and around
Detroit for any areas that experience a longer duration of
thunderstorm activity. Shower and thunderstorm activity will
weaken and eventually come to an end in the evening with the loss
of instability.
The next shortwave lifts out of the central plains and through the
southwest flow between the Canadian troughing and the ridging
through the Appalachian Mountains. A weak surface reflection is
forecast to travel across WI and northern Lake Michigan. A plume of
theta-e will support scattered showers and thunderstorms with a
boost in larger scale ascent from the shortwave. Greater forcing and
placement of the higher moisture axis puts higher PoPs towards the
Tri-Cities. Active stretch of weather remains as the above normal
temperatures and moist airmass remain over Michigan into the middle
of the week helping field additional showers and thunderstorms. Long
range models are mostly in agreement with a Tuesday night into
Wednesday system as shortwave energy originating off the Baja Coast
shoots northeast within the flow of the southern and northern stream
jets. Frontal timing will ultimately decide severe weather potential
mid-week. The well above normal temperatures with daytime highs in
the 80s will carry continue Sunday through Tuesday with overnight
lows in the upper 50s to mid 60s. Cooler temperatures will arrive
behind frontal system mid-week bringing highs back down into the 70
degree range for the late week period.
MARINE...
High pressure dominates local conditions this weekend with light
southeasterly winds generally 10 knots or below through the rest of
today, veering south tonight. Very warm and humid air in place keeps
areas of fog across marine areas, with potential for dense fog to
redevelop tonight. Will continue to monitor observations and reissue
a marine Dense Fog Advisory if/where conditions warrant. Models do
show a slightly stronger gradient picking up overnight which may
disperse any more dense fog before sunrise Sunday. A weak cold front
moves into the region on Sunday with a few showers and storms
possible, mainly in the nearshore waters. An area of low pressure
then tracks in from the Midwest late Monday into Tuesday, bringing
the next likelihood for showers and storms. Winds and waves are
expected to remain below Small Craft Advisory criteria outside of
any localized higher winds within any thunderstorms.
HYDROLOGY...
Scattered to numerous showers and thunderstorms are possible, mainly
tomorrow afternoon and evening with favored areas along the lake
breezes across Port Huron through Metro Detroit to Monroe County.
Locally intense rainfall rates are possible with any thunderstorms
that can develop with the high moisture environment. Forecast
average rainfall amounts are a quarter to half inch with locally
higher amounts of 1 inch or more possible. Several areas may remain
dry, but the slow moving nature of the scattered thunderstorms will
bring potential for these localized higher rainfall totals. Main
concern would be for localized flooding of prone urban areas across
the Detroit Metro if any of these thunderstorms develop and linger
over parts of the metro region.
&&
.DTX WATCHES/WARNINGS/ADVISORIES...
MI...None.
Lake Huron...None.
Lake St Clair...None.
Michigan waters of Lake Erie...None.
&&
$$
AVIATION.....DG
DISCUSSION...AA
MARINE.......TF
HYDROLOGY....AA
You can obtain your latest National Weather Service forecasts online
at www.weather.gov/detroit.
Area Forecast Discussion
National Weather Service Quad Cities IA IL
707 PM CDT Sat May 18 2024
.KEY MESSAGES...
- Scattered showers and storms will wane after sunset tonight.
There is a Marginal risk (level 1 of 5) of severe weather
today west of the Mississippi River.
- Boundary stalls south of the area as temperatures again reach
well into the 80s as chances for thunderstorms return late.
- Active pattern through the long term with chances of strong to
severe storms through Tuesday. Tuesday is the best day for
severe weather in the next 5 days.
&&
.UPDATE...
Issued at 705 PM CDT Sat May 18 2024
Cold front approaching the nw part of the forecast area had
briefly flared up a few thunderstorms along the front, but since
then they have weakened rapidly. The bulk of the thunderstorms,
some severe, have been across Wisconsin and western Upper MI
where the stronger shear/forcing exists. In our forecast area,
the SPC mesoanalysis showed weak shear (<20 kt) along with weak
forcing, while the SBCAPE was about 1500 J/kg. In addition, the
00z/19 DVN sounding showed a decent capping inversion above 800
mb. Being that we are past peak heating it appears that the
threat for any severe storms has diminished. However, still
can`t rule out an isolated storm or two this evening until the
front moves through.
&&
.SHORT TERM /THROUGH TONIGHT/...
Issued at 109 PM CDT Sat May 18 2024
Temperatures well into the 80s today were found area-wide.
Dewpoints in the upper 50s to low 60s made it feel somewhat
nicer than the middle of July. To the west of the area, a cold
front was located across the center of Iowa. A shortwave passing
north of the area today will drag this front through the area
this afternoon and into the evening. The boundary will then
stall out across southern portions of the area. This boundary
on Sunday will separate the higher moisture air from the drier
air. Nonetheless, we will see highs again in the 80s, but with
drier air than today. With that boundary in place across the
south, we could see some thunderstorms redevelop along the front
later in the day and move east towards us late.
Most of the impactful weather will likely be ongoing at 00z
tonight as the cold front moves through the area. Guidance has
CAPE building ahead of the front to around 2000 J/kg this
afternoon. Shear looks very weak, so updraft organization is not
expected. Pulse like storms are expected if they develop. The
main question today is forcing. The main upper level forcing is
way north, so the front and daytime heating will be the main
drivers for thunderstorm development. CAMs have either a broken
line of storms or not much with the exception of the highway 20
corridor. Dprog/Dt of the HRRR shows run to run variability with
some having convection down to highway 30 the rest further
north. The NAMnest has convection all the way through the CWA.
Think the best chance for storms is highway 20 north. In a nod
to the NAMnest, did keep schc south through I80. Am not too big
on severe today. Could see near severe wind gusts and hail,
especially due to the steeper lapse rates, but don`t expect
cells to have much longevity to really get going.
&&
.LONG TERM /SUNDAY THROUGH SATURDAY/...
Issued at 251 PM CDT Sat May 18 2024
Extremely active pattern with a mid-summer like pattern is
expected to last through most of the period as a stalled out
boundary resides just south of the CWA. This boundary will
separate the area between Tds in the 50s, to the more robust
deep moist Tds in the 60s and 70s to the south. A series of weak
waves and possibly MCVs/convective induced waves/ move over the
boundary later Sunday into Monday evening. A strong wave, with
better shear is expected to approach the area into Tuesday. A
deepening surface low with this wave will help to bring this
boundary north as a warm front Tuesday. This will bring higher
Tds into the area ahead of the wave and increased shear. Then
the boundary is sent south again as a cold front later Tuesday.
After this point, there are questions about where the boundary
will be and additional chances for thunderstorms.
Closer look at the guidance for Sunday evening suggests a MCV
rolling into the area after 00z. The 12Z HRRR has convection
firing with this wave like feature across the area. In fact, the
HRRR suggests some of these storms could be supercellular in
nature. As mentioned before, shear looks to be weak, however, if
this truly is a MCV, then the shear may actually be stronger
than forecast. With Tds lower tomorrow, think that these
supercells would be hailers and possibly HP in nature and a
wind threat. That said, other guidance keeps us clear. We will
need to keep an eye on convection upstream to see if this forms.
So there is a conditional risk for severe weather tomorrow
afternoon and evening.
Monday, another possible day with severe weather as the wave
induces height falls and the sfc boundary moving north again.
The NAMnest depicts yet another MCV moving through our area
Monday with redevelopment of showers and storms in the
afternoon. This is yet another potential case where we could see
higher shear than forecast. With clouds possibly keeping Ts
lower, our T/Td spread may be lower as well. Llvl winds looked
back so if we develop afternoon showers and storms monday they
could be severe as well. We currently have a mrgl for this day
as well, but could see this day updated to a slight if the MCV
comes true.
So after the next two days with conditional severe weather
outlooks we get to Tuesday when a better wave makes its way into
the area. This one will bring better shear into the area
Tuesday. Storm Mode: 0-6km shear vectors are perpendicular to
the forcing and around 40kts. This would suggest supercells and
they will likely form first west of the CWA. However, upper
level flow is weak so expect convection to quickly become cold
pool dominated. Expect a mature/ing bow to enter the area in
late afternoon. Severe Hazards: 0-3km shear vectors of 40kts
will help the production of mesovorts with localized higher wind
gusts and possible tornadoes. The LLJ is impressive for the
afternoon, and even more so after sunset, so this thing could
really ramp up later in the evening. With weak upper-level flow,
the overall system should not be moving all that fast. Some hail
is possible early on, but think this is rain/strong wind/tornado
event. Heavy Rain: In addition, some heavy rainfall will be
possible with this event, with PWs around 1.5 to 1.7 inches,
which would be above the 90th percentile for this time of year.
Wednesday On...additional showers and storms will be possible
late week. However, model timing differences in shortwaves
moving through the flow precludes changing the PoPs, which are
in the 15 to 30 percent range for each 6 hr period through
Friday. There will be some dry hours, but when this will occur
is still in question. Temperatures will return to more
seasonable values by late week, with highs in the 70s and lows
in the 40s.
&&
.AVIATION /00Z TAFS THROUGH 00Z MONDAY/...
Issued at 705 PM CDT Sat May 18 2024
VFR conds through this taf cycle. An isolated shower or storm is
still possible along a cold front, but coverage too low to
mention in the TAFs. Winds will turn northwest overnight then
become northeast to east on Sunday.
&&
.DVN WATCHES/WARNINGS/ADVISORIES...
IA...None.
IL...None.
MO...None.
&&
$$
UPDATE...Haase
SHORT TERM...Gibbs
LONG TERM...Gibbs
AVIATION...Haase
Area Forecast Discussion
National Weather Service Kansas City/Pleasant Hill MO
631 PM CDT Sat May 18 2024
.KEY MESSAGES...
- A few brief, isolated storms remain possible this evening.
- Active Pattern Sunday Night through Tuesday Night. Severe
thunderstorms possible each day.
- High temperatures well into the 80s, around 10 degrees above
normal, through Tuesday.
&&
.DISCUSSION...
Issued at 254 PM CDT Sat May 18 2024
19Z surface analysis reveals a modest surface trough stretched from
northern Iowa southwest through northwest Missouri into Kansas.
Behind the surface boundary, winds are gusting around 20 to 25 mph.
Visible satellite reveals some minor cu development in southwest
Iowa toward S. Joe and into northeast Kansas. The latest runs of the
HRRR have been less bullish with convective development along this
boundary as it advances toward the KC Metro and lower Missouri
Valley through the late afternoon and early evening. Forecast
soundings suggest a rather deep, 5 to 6kft, mixing layer and rather
weak wind profiles. Elevated instability will be sufficient, but
given the lack of supportive shear, organized updrafts are looking
difficult to come by. Regardless, will keep a low PoP mention going
through the evening, with the best window between 5 and 8 PM CDT. If
any one updraft can tap into the 1000 to 1500 J/Kg MLCAPE, an
isolated bout of severe hail or wind cannot be ruled out.
Positively tilted mid-level ridging will continue to strengthen
aloft across the region through Sunday morning. Overnight tonight, a
complex of thunderstorms is expected to develop with support from a
weak, open, H500 short wave trough traversing the larger flow
pattern along the northern Kansas and southern Nebraska. Through
sunrise, whatever remains of this activity will slide begin to slide
across northwestern Missouri and continue east through the day along
the MO/IA border. Most precipitation chances will exist along and
north of the US-36 corridor during the day. South of this activity,
modest return flow will persist ahead of a developing surface trough
over the western High Plains. Low to mid 60s surface dew points will
develop through the late afternoon. Convection is forecast to fire
in central Kansas by mid-afternoon near the triple point, with
convection growing upscale into a line or broken line of storms as
it moves into far eastern Kansas and western Missouri by late in the
evening. Some of this line may be strong to severe as it arrives
with damaging winds and hail and flash flooding the primary
concerns. Storms are expected to lower in intensity as they move
east through early Monday morning, with localized flooding a
lingering concern.
Monday, lingering showers and thunder may be ongoing across portions
of the area, likely ending through midday. At the same time, a long
wave trough will strengthen across the western CONUS, with another
surface trough developing over the western High Plains of CO/KS.
With better access to return flow and a more robust synoptic pattern
setting up to the west, recovery is expected in the wake of any
lingering precipitation in the morning. The good news for now is
that the better focus forcing looks to be in western Nebraska to
central Kansas, nearer the low center and focused along the warm
front, which the latest mid-range guidance has a bit farther north.
However, as the low level jet increases through the evening and the
region well within the warm sector, some organized convection is
expected and could result in some strong to severe updrafts.
Tuesday could be the more significant day for severe convection
across the region. It goes without saying, but any morning
precipitation would influence recovery, but with a more negative
tilt to the H500 shortwave trough ejecting across Nebraska in the
morning, strong WAA will persist, with ample recovery more than
likely ahead of the surface trough as it pushes east into the
afternoon. With steep mid-level lapse rates and surface dew points
nearing 70 F, MLCAPE between 1500 and 2500 is possible. However,
forecast soundings through the afternoon from the NAM suggest a
sizable capping inversion and given 700mb southwest flow, it`s
likely the inversion will hold off initiation until the arrival of
the surface front. Latest guidance has the line lighting up around
00Z from northwest Missouri southward toward the KC Metro. Timing of
the boundaries arrival will be key and a primary forecast focus as
step through the next two days. 0-6km shear orientation suggests
initial convection would be isolated, supercellular in nature, but
quickly developing into a line as the surface front surges south-
southeast through the evening. Damaging winds and hail and a tornado
or two cannot be ruled out with storms Tuesday evening/night.
Precipitation will clear out through Wednesday with surface ridging
briefly holding on before another trough arrives into Friday from
the west.
&&
.AVIATION /00Z TAFS THROUGH 00Z MONDAY/...
Issued at 623 PM CDT Sat May 18 2024
A cold front is currently draped across NW Missouri and into NE
Kansas, but so far only a few small and brief showers have
formed along the front. The terminals will likely remain clear
of any showers or storms, but if anything does get going in the
area it would be between now and around 2z. Winds will turn
northwesterly and then northerly behind the front tonight, with
winds turning southerly by tomorrow morning as the boundary
lifts back to the north. VFR conditions are expected through the
period.
&&
.EAX WATCHES/WARNINGS/ADVISORIES...
MO...None.
KS...None.
&&
$$
DISCUSSION...Kurtz
AVIATION...BMW
Area Forecast Discussion
National Weather Service Hastings NE
635 PM CDT Sat May 18 2024
.KEY MESSAGES...
- Scattered showers and thunderstorms move in late tonight and
continue into Sun AM. Most likely non-severe, but small hail
and gusty winds will be possible in strongest cores.
- Off and on thunderstorms are expected Sun PM through Tue,
some of which could be strong to severe and pose risks for all
severe hazards. However, confidence on details is only low to
medium as each round will have significant impact on
subsequent rounds` severity, timing, and placement.
- Cold front sweeps through the area and brings somewhat cooler
and less active weather for Tue night into Thu.
- Temperatures most days will peak in the 70s-80s, though mainly
mid 60s-70s are expected Tue-Wed. Lows will be mainly 50s-
60s, except for cooler 40s Tue/Wed nights.
&&
.DISCUSSION...
Issued at 208 PM CDT Sat May 18 2024
Expect increasingly pleasant conditions late this aftn and into the
evening as wind speeds gradually decr and temps remain mild. Short
term CAMs are in pretty good agreement that elevated convection will
develop over the central High Plains 03-06Z as 45kt LLJ noses into
the region, then shift E/NE into our area 06-09Z. Peak MUCAPE will
increase to around 1500-2000 J/kg for parcels lifted from H7-H8
amidst steep mid level lapse rates. However, the bulk of the veering
in the wind profile is below the MUCAPE layer, so effective shear is
rather marginal at mainly 25-30kt. This could yield some "pulsey"
elevated hailers, generally of the low-end variety (penny to half
dollar size), and perhaps some gusty winds around 40-50 MPH. Recent
HRRR runs and HREF seem to focus the majority of the activity along
and S of the Platte River, which is a bit of southward shift from
where previous forecast placed the highest PoPs. Seems probable (60-
70%) that at least scattered activity will persist into the mid to
late AM hrs Sunday as the LLJ slowly veers and weakens, though the
lingering activity will probably have a lesser hail risk.
Pattern recognition and general model guidance would suggest a dry
period, or at least a lull in coverage/intensity, from around midday
Sunday through AT LEAST mid aftn. Thereafter, details for
additional convection become quite a bit more murky owing to
uncertainties left by the earlier round, such as location of
outflow boundaries, cloud cover that will affect ability to
destabilize, and quality/depth of BL moisture. The overall upper
pattern will feature only modest height falls, but most
guidance has several weak disturbances in moderately fast SWrly
mid-upper flow, and the AM round may actually help to suppress
the strongest mid level capping to our S. As it stands now,
there appears to be two scenarios of convective potential:
1) Seems plausible that enough recovery will occur to allow for
a narrow window of sfc based development along lingering
outflow boundary that will probably be located somewhere between
the NE/KS border and I-70 corridor around 22Z-02Z. After that,
cooling BL will probably become capped along this boundary in
the absence of stronger forcing. It is a highly conditional, and
probably isolated, threat...but if something does pop up, it
will likely be supercellular with all modes of severe possible -
including tornadoes - given tendency for backed low level flow
and perhaps some pooling moisture. Worth noting, however, that
forecast soundings suggest moisture quality/depth will not be
great during the late aftn/early eve period and subject to
mixing out - so would really need some pooling and backed flow
to get low enough LCLs for tors. Greatest risk would likely be
large to very large hail given very steep mid level lapse rates
and bulk shear values of 40-50kt in the presence of clockwise
curved hodographs, along with damaging wind gusts.
2) The other scenario - which is more probable and likely more
impactful because of coverage - will be for tstms to develop along a
N-S corridor along the High Plains from the NE Panhandle southward
to TX/OK Panhandles within warm/hot, deeply mixed environment with
little to no capping and beneath slightly stronger height falls.
This activity would have a tendency to become outflow dominate given
inverted-V thermodynamic profiles and more forward propagating due
straighter hodographs. Since it`s developing further W, this threat
would likely be a bit later, generally after 00Z, but severe will
still be a risk as this activity will actually be moving into pool
of greater instability, and LLJ again increases to 40-50+kt. Would
tend to favor W/S zones the most, but if a mature MCV develops then
local dynamical forcing could overcome incr capping after 03Z to
persist the severe threat longer and further E. Heavy rain is
not a concern attm given isolated/conditional nature of scenario
1, and likely progressive nature of scenario 2.
Thunderstorms remain possible into Monday, and the entire area is
outlooked in either a Marginal or Slight Risk of severe weather
(levels 1 and 2 on a scale of 5) on SPC Day 3 outlook. As there are
uncertainties on Sun due to earlier convection, the uncertainties
are even higher on Monday. In general, upper troughing still resides
to the W and we`ll remain in diffluent (but kinda weak) SWrly upper
flow. At least one or two upper waves will likely be ejecting NE out
of the broader trough, which could enhance the upper flow late in
the day and moreso into Mon night. Sfc mass fields suggest a triple
point over central KS, with previous outflow boundaries possibly
augmenting and/or narrowing the primary instability axis to the E of
this triple point and southward trailing dry line. I have a tendency
to doubt we`ll have much sfc-based activity in our CWA prior to
sunset as mid level temps appear to be 1-2 deg warmer, though
mesoscale details will be important. Would think the later arrival
of upper support would favor activity moving off the High Plains
after sunset and/or new development ahead of possible northward
moving warm front in response to incr LLJ. This would provide more
of a wind/hail threat and lesser of a tornado threat, but again,
plenty of details to work out.
Trough moves through on Tuesday, and timing will be key for severe
weather chances in our area. At this time, appears it will be just
fast enough to keep primary risk to our E/SE, but any slowing trend
and our chcs will incr. Continued cloud cover and shwr chcs behind
departing system amidst NWrly low level flow will likely keep temps
considerably colder in the 60s, esp N/W of the Tri-Cities. Flow
turns more zonal late in the week and into the start of the holiday
weekend, which should support seasonable temperatures and off and on
pcpn chances.
&&
.AVIATION /00Z TAFS THROUGH 00Z MONDAY/...
Issued at 625 PM CDT Sat May 18 2024
A cluster of showers and thunderstorms is expected to move
through central Nebraska early Sunday morning, with near-term
models showing additional scattered showers and storms redevelop
later Sunday morning.
In addition to the thunderstorms, ceilings could dip to MVFR
Sunday morning. The probability for this occurring is a bit
higher at EAR compared to GRI.
Another round of stronger thunderstorms is possible Sunday
evening, just beyond this TAF period.
&&
.GID WATCHES/WARNINGS/ADVISORIES...
NE...None.
KS...None.
&&
$$
DISCUSSION...Thies
AVIATION...Mangels
Area Forecast Discussion
National Weather Service Goodland KS
516 PM MDT Sat May 18 2024
.KEY MESSAGES...
- Thunderstorms will progress eastward from CO into western KS
late this evening and overnight. A few severe storms are
possible, mainly between ~7 PM and ~3 AM MDT.
- Severe storms capable of producing very large hail and
damaging winds are possible in northwest KS and southwest NE
Sunday afternoon, mainly between 3-9 pm MDT / 4-10 pm CDT.
Latest guidance suggests that the severe weather threat in the
Goodland CWA will be isolated in nature (i.e. not widespread).
Thunderstorm coverage and severe weather potential increases
with eastern extent into central KS. In other words, locations
along/east of Highway 283 appear to be most at-risk.
- Cooler with frost concerns mid week.
- Active weather may return next weekend (Memorial Day Weekend)
&&
.SHORT TERM /THROUGH SUNDAY NIGHT/...
Issued at 245 PM MDT Sat May 18 2024
Through Noon on Sunday: Southern stream shortwave energy
presently located invof the southern CA/AZ border will track ENE
across the 4-Corners and central Rockies (tonight) and adjacent
portions of the High Plains (Sunday morning). Current and
recent runs of the HRRR and NAM NEST suggest that scattered
diurnal convection developing along the Palmer Divide this
afternoon will progress eastward to the CO/KS border this
evening.. continuing eastward across northwest KS overnight.
Guidance suggests that convection will increase in both coverage
and intensity this evening and overnight.. aided and assisted
(presumably) by DPVA attendant the aforementioned shortwave
energy (approaching from the SW-WSW) and strengthening low-level
(SFC-H85) warm advection over western KS.. when modest (albeit
increasing) airmass destabilization and strengthening deep layer
shear appear supportive of severe weather.. especially if
forcing is favorably/further augmented by convection itself
(e.g. an MCV).. mainly in the 03-09 UTC time frame. Wind gusts
up to 65 mph, quarter size hail and torrential rainfall appear
to be the primary hazards.
Sun PM-Sun night: Challenging forecast. Early morning
convection may significantly alter environmental conditions over
the Tri-State area during the day on Sunday, esp. in a pattern
characterized by a rather weak/broad/ill-consolidated lee
cyclone in southeast CO. Latest available guidance indicates a
scenario characterized by little/low convective coverage over
northwest KS and southwest NE Sunday afternoon, suggesting that
severe weather in the Goodland CWA may be isolated in nature
(i.e. not widespread).. and largely confined to the 21-03 UTC
time frame. Very large hail and damaging winds appear to be the
primary hazard(s). Broadly speaking, guidance continues to
indicate that convective coverage and severe weather potential
increases with eastern extent into central KS. In other words,
locations along/east of Highway 283 appear to be most at-risk.
&&
.LONG TERM /MONDAY THROUGH SATURDAY/...
Issued at 140 PM MDT Sat May 18 2024
The latest from the GFS/ECMWF continues to show potential for
rainfall/storms to impact mainly the northern portion of the CWA
from late Monday on into the end of next week.
With a blocking upper ridge over the eastern portion of the
country through the midweek timeframe, a strong trough will
swing east out of the north central Rockies late Monday, making
a slow trek eastward due to the blocking effects of the eastern
ridge. This system will eventually lift northeast along the
western periphery of the block. This will be followed by a
second shortwave taking a similar track although a bit more
easterly as guidance breaks down the ridge for the latter
portion of the week. Another amplified ridge build into the
Plains region for Thursday, shifting east to end the week. This
will be ahead of an elongated trough stretching through the
northern/central Rockies.
At the surface, low pressure sets up across southern Kansas
late Monday into Tuesday, lifting northeast with an associated
front. The position/track of this low will allow for a moist,
easterly upslope flow from the surface to 850mb and eventually
going northerly by Tuesday as the low lifts east. A similar
setup will occur late Tuesday into Wednesday for the second
system, although a bit further south based on both the
GFS/ECMWF. High pressure traverses the CWA Thursday/Thursday
night, with southerly flow setting up increased warmth/moisture
ahead of the end-of-week upper system. A surface low does work
off the Front Range in tandem with the upper system.
As a result, the main wx concerns are going to focus on the
potential for showers and storms. QPF/track through midweek puts
the best chances for rain north of the Interstate, especially
along/north of Highway 36. For Fri/Sat, the coverage is ahead of
the low/front that moves off the Front Range, but for areas
closest to the surface low.
The chances for storms will be focus mainly for the Mon-Tue
timeframe with the passage of the aforementioned shortwaves. The
end of week system does differ with timing/placement of
storms/QPF, but these could be problematic.
Decent instability along with increasing PW values from west to
east on Mon-Tue, will afford the potential for strong to severe
storms, especially Monday. SPC currently has a Marginal risk
for most locales east of the Colorado border. The surface low
passages to the south will bring in PW values of an inch plus,
especially east of Highway 83 which is closest to the surface
trough/front that extends into central Kansas. So, besides a
hail/wind threat, heavy rainfall/flooding potential will also be
high. Monday looks to be the main focus, with WPC having a
Marginal risk area out for locales north of highway 36 Mon
night-Tue. Please refer to the Hydro section below for more
details.
The passage of the second system Tuesday night into Wednesday
will bring about some cooler/colder air into western locales.
Areas in Colorado could see some frost potential, but will be
highly dependent on the extent of clearing from the exiting
system. Right now, western portions of Kit Carson/Cheyenne
counties are most prone.
For temps, with a cold front settling through the region during
the first portion of next week, looking for a downtrend in
daytime highs before rebounding for the latter portion of the
week. On Monday, mid 70s north through the mid 80s south are
expected. A wide range for Tuesday with mainly 60s north of the
Interstate and 70s south will give way to lower and mid 70s
area-wide for Wednesday. 80s Thursday drops to the mid 70s
through the lower 80s to end off the week.
Lows during this time will mainly range from the mid 40s west
through the lower and mid 50s east. Tuesday night will be the
coldest, with lower to mid 40s east of the Colorado border, with
upper 30s to around 40F for northeast Colorado.
&&
.AVIATION /00Z TAFS THROUGH 00Z SUNDAY/...
Issued at 500 PM MDT Sat May 18 2024
For KGLD... A mix of VFR and IFR conditions are forecast along
with chances for thunderstorms through the period. A line of
storms was entering western Kit Carson county as of 23Z.
Currently expecting these storms to progress and move through
the terminal around 0130Z. They currently are moving slowly and
if they don`t speed up as forecast, then it would move in around
4Z. When the line passes, VFR conditions are forecast for a few
hours until moisture advection and cooling temperatures
saturated the lowest 1000ft around 09Z. Unless additional storms
form, the lower ceilings should break a few hours after sunrise
and allow for VFR conditions. Storms are then possible again
around the last 3 hours of the period. Currently, the storms are
forecast to form near, but not over the terminal tomorrow
afternoon, look for updates.
For KMCK... VFR to MVFR ceilings are forecast at times through
the period, but the main concern will be storms and rain.
Currently expecting a line of storms around the Western Yuma
county line (as of 23Z) to move east through the evening. Based
on current forecast and timing, the storms and rain should move
over the terminal around 04Z. The main uncertainty is whether
storms will redevelop near the terminal through the night due
to an MCV/low, or if the storms will progress and leave the
terminal. Once the storms end, stratus clouds are forecast to
develop around 1000-1500ft. There is a 20% chance that the cloud
layer could be below 1000ft. By around noon, ceilings should
lift and VFR conditions are expected for the afternoon.
&&
.HYDROLOGY...
Issued at 226 AM MDT Sat May 18 2024
Some potential does exist for torrential rainfall and isolated
flash flooding starting Saturday night/Sunday morning into early
portions of the new work week. The majority of the area,
especially western and southern portions have seen a lack of
rainfall in recent weeks and worsening drought conditions.
Overall main concern for any hydro issues lies to the east of
Highway 83 in Kansas where portions of Gove county for example
received 1-3 inches of rainfall earlier in the week. PWATS will
rapidly increase tonight around 1.25 inches and remain above 1
inch for the duration of the weekend. Overall widespread
flooding potential is relatively low as overall systems should
be fairly quick moving with fast Corfidi Vectors. The overall
main concern for any hydro related issues lies in multiple
rounds of heavy rainfall and any potential training locales.
&&
.GLD WATCHES/WARNINGS/ADVISORIES...
KS...None.
CO...None.
NE...None.
&&
$$
SHORT TERM...BV
LONG TERM...JN
AVIATION...KAK
HYDROLOGY...Trigg
Area Forecast Discussion
National Weather Service Grand Rapids MI
1039 PM EDT Sat May 18 2024
.KEY MESSAGES...
- Warm Weekend Continues
- Unsettled Weather at Times Monday through Wednesday
- Drier and cooler Thursday and Friday
&&
.UPDATE...
Issued at 1038 PM EDT Sat May 18 2024
Cold front is moving east through Wisconsin at 1030pm and can
clearly be seen in regional radar loops. Convection on the front
has trended down (fading diurnally), but it has not come to an
end. There is enough instability on the front that storms
continue. MUCAPE values at present are on the order of 1000-2000
j/kg in Wisconsin. The front makes steady progress eastward
tonight and moves through much of the forecast area between
midnight and 800am. The 3km NAM shows MUCAPE values remaining
around 1,000 j/kg through the night in Southwest Lower Michigan.
Consensus of short term models suggest we need an
isolated/scattered chance (20-30 pct) for showers and storms
through the night. Most places will likely not see any
precipitation but the front is strong enough and instability great
enough to warrant the chance. The HREF that is now coming in
suggests an uptick in showers and storms near and after 500am. It
will be a warm night with lows in the lower 60s in many areas. The
normal low at GRR tonight is 50.
&&
.DISCUSSION...
Issued at 258 PM EDT Sat May 18 2024
- Warm Weekend Continues
"Cold" front over Wisconsin slips our way tonight but it is
really nothing more than a wind shift line. High temps will
actually be similar or even a few degrees warmer on Sunday
despite its passage.
A band of showers and thunderstorms along the front in WI weakens
considerably as it drifts southeast and arrives in our area later
tonight, and may even dissipate completely before getting here.
Will maintain 20-30 pops toward/after midnight for areas
north/west of GRR but latest CAMs look to be decreasing the threat
of convection since the shortwave stays well northwest of us over
the Lk Superior region and instability wanes quickly.
A few showers and storms may redevelop by Noon Sunday south and
east of GRR where the frontal boundary stalls out and sfc
instability rebuilds. RAP has SBCapes rising to near 2000 J/KG
where sfc dew pts near 60 will be present along with some weak
sfc convergence. Pops only 20-40 pct again (highest near JXN),
and any storms will be the pop-up/pulse-variety in weakly sheared
environment. Any diurnal showers/storms will dissipate with
sunset although returning warm front late Sunday night could touch
off a few storms again by daybreak Monday.
- Unsettled Weather at Times Monday through Wednesday
The ridge that will be over the area on Sunday will slip east of
the area by Monday. This occurs as a long wave trough will dig and
amplify across the western half of the country. Our area will end
up under deep flow from the SSW which usually results in a warm
and humid/wet period. This period looks about as expected with
periods of showers/storms, although it will not be raining all of
the time by any means.
The first chance of rain will come as early as Monday as the
leading short wave ejecting from the long wave trough skirts by to
our NW. Ahead of this wave, we will see a surge of warm and moist
air ahead of it with a low level jet. Showers and storms look
like a decent bet into Monday night before that wave moves away
from the area.
We are expecting another more significant wave to lift NE around
the long wave trough in the Tue/Wed time frame. A front will
remain over the southern half of the area behind the Mon system,
and will then move back north as a warm front on Tue ahead of the
stronger wave. This will bring additional chances of
showers/storms. This system is the center of the SPC DY4 outlook
that clips the area. It appears that the main threat may stay SW
of the area with the entire system wrapping up a bit to the west.
We will remain out ahead of the cold front on Wednesday, leaving
the area in the warm sector for at least a part of the day.
Getting out that far, details are a bit gray. Timing of features
with this system with respect to peak heating as late as Wed may
ultimately determine the severe weather threat. The potential does
exist with some strong wind fields aloft and plenty of warm and
humid conditions present.
- Drier and cooler Thursday and Friday
It does look like the front should sweep out the heat and
humidity by late Wednesday, leaving a mild and drier air mass in
it`s wake. The instability and showery weather with the cold pool
aloft should stay north, while the front moves SE of the area.
This leaves some ridging in place, and it looks likely to stay dry
through at least Friday. There remains some small chances of rain
in the NBM, but we are thinking it is more likely to stay dry.
Rain chances will increase some by Saturday, but nothing
significant is on the horizon yet for the beginning of the
upcoming holiday weekend.
&&
.AVIATION /00Z TAFS THROUGH 00Z MONDAY/...
Issued at 747 PM EDT Sat May 18 2024
VFR prevails across the area with clear skies. Expect continued
VFR through the forecast period with no major forecast concerns to
note. Wind will be primarily southerly through much of this
evening and early overnight, then a dry front will pass through
resulting in a wind shift to the northwest between 06 and 12z
Sunday. A line of 5 to 7k ft clouds will accompany the front then
clouds will scatter out after sunrise. Diurnal cumulus is
expected to develop tomorrow afternoon.
&&
.MARINE...
Issued at 258 PM EDT Sat May 18 2024
Winds and waves remaining below advisory levels through the
remainder of the weekend, although a frontal boundary slipping
through tonight will shift the winds from southerly this afternoon
and tonight to northwesterly on Sunday. There may be a period
Sunday afternoon where the NNW winds increase to near 15 kts or
so for a time. The fog threat appears to have ended over the lake.
&&
.GRR WATCHES/WARNINGS/ADVISORIES...
MI...Air Quality Alert until midnight EDT tonight for MIZ050-056-057-
064-071.
MARINE...None.
&&
$$
UPDATE...Duke
DISCUSSION...Meade/NJJ
AVIATION...Thielke
MARINE...Meade
Area Forecast Discussion...UPDATED
National Weather Service Jackson MS
952 PM CDT Sat May 18 2024
...New MESOSCALE UPDATE...
.MESOSCALE UPDATE...
Issued at 943 PM CDT Sat May 18 2024
The potential for any severe storms in our CWA has ended and the
probability of any measurable rain was coming to an end as well.
Local radars had a few very light showers over eastern Clarke
county and back to the west across southern Scott county. These
light showers were along a nearly diffuse cold front that will
continue to sag south of Interstate 20 and near Highway 84 the
remainder of tonight. Some patchy fog may develop across our
southeast as a result. /22/
&&
.DISCUSSION...
Issued at 242 PM CDT Sat May 18 2024
The rest of today through tomorrow: Radar imagery shows mostly
showers and some storms developing in the Golden Triangle Region
this afternoon. A boundary associated with a low pressure moving
eastwards across the MS/AL line is enabling storm development and
will continue through the late afternoon. RAP mesoanalysis shows
an estimated 2000 - 3000 J/kg of SBCAPE and low level lapse rates
between 6.5 -7 C/km, which has allowed for some strong shallow
updrafts to develop so far this afternoon. Mid-level lapse rates
continue to be lackluster, which will make it difficult for any
deep cores to develop through the remainder of the evening.
Despite this, a Marginal Risk (1/5) will continue through the late
evening with the main risks being isolated severe storms with
hail up to quarter size and damaging wind gusts up to 60 mph. By
tonight, rain chances are expected to diminish and maintain a dry
overnight period. in the southeast, lingering moisture is expected
to generate some patchy fog across the Pine Belt, but diminish by
daybreak.
On Sunday, drier conditions look to prevail as an upper trough
ejects out of the Southeast region onto the eastern coast. Deep
ridging will begin to build into the Lower Mississippi Valley,
allowing for temperatures to increase and cloud cover to dissipate.
Sunday highs look to be in the upper 80s to near 90, with mostly
sunny skies across the region. /AJ/
Next week...
Early-midweek (Monday-Wednesday): As the mid-level ridge amplifies
over the Bay of Campeche & Mexico, the low-level ridge axis is
progged to build across the area through mid-week. Sfc high pressure
is progged to build across the region, with an active upper level
jet ejecting across the Central Plains. This will drive a strong low
pressure system out of the Plains into the Mid West to Great Lakes.
A dry pattern is progged to persist through early week, with
increased warm advection/low-level temps into the upper teens to low
20s degree C at 850-925mb layers. Expect highs to moderate to
seasonably warm into the low 90s & lows in the upper 60s southeast
of the Natchez Trace to low 70s to the northwest. Heat & humidity
will be on the rise around midweek with heat indices climbing into
mid-upper 90s, but heat stress shouldn`t be much of an issue. Low-
level return flow won`t pick back up until by midday Tuesday through
midweek, with rain & storm chances picking back up around late
Wednesday aftn to evening, mainly northwest of the Natchez Trace.
Late week (Thursday-Friday): As the trough swings into the Great
Lakes to Hudson Bay, expect the ridge axis to relax & gradual height
falls to occur across the Gulf Coast region. This keep continued
heat & humidity but increased scattered rain & storm chances to
build into the region from the north. During this time, there could
be enough westerly zonal flow for some organized convective & strong-
severe potential into late week. There are some indications in long
term convective outlooks & CSU machine learning probs for some
isolated strong-severe potential, but this remains too far in the
extended timeframe to introduce in HWO graphics for now. Seasonably
warm conditions in low 90s on Wednesday will tamper down into the
upper 80s to near 90 degrees south of I-20 by late week. Heat &
humidity will be slightly less oppressive but still heat indices in
the low-mid 90s, with less potential for heat stress. /DC/
&&
.AVIATION...
(00Z TAFS)
Issued at 643 PM CDT Sat May 18 2024
Isold SHRA may come in vcty of MEI by 02Z and reduce flying
conditions. Elsewhere VFR conditions wl prevail until 10Z. After
10Z a brief period of MVFR/IFR vsby wl be psbl at MEI-PIB-HBG
until 13Z. After 13Z VFR conditions wl prevail areawide through
the end of the TAF period. /22/
&&
.PRELIMINARY POINT TEMPS/POPS...
Jackson 65 87 66 89 / 10 0 0 0
Meridian 64 88 64 90 / 30 10 0 0
Vicksburg 67 89 68 91 / 0 0 0 0
Hattiesburg 67 89 66 91 / 10 0 0 0
Natchez 66 89 68 90 / 0 0 0 0
Greenville 67 89 70 91 / 0 0 0 0
Greenwood 65 89 68 91 / 10 0 0 0
&&
.JAN WATCHES/WARNINGS/ADVISORIES...
MS...None.
LA...None.
AR...None.
&&
$$
AJ/DC/22
Area Forecast Discussion
National Weather Service North Platte NE
632 PM CDT Sat May 18 2024
.KEY MESSAGES...
- An active weather pattern brings a variety of impacts,
including severe weather and heavy rainfall Sunday through
Tuesday.
- A limited threat for late season frost, but cannot rule out a
localized threat following a cool down mid week.
- The pattern remains active through the week, brining the
potential for precipitation nearly every day. Confidence on
daily precipitation chances remains relatively low, due to
uncertainty in exactly how the upper level pattern evolves.
&&
.SYNOPSIS...
Issued at 235 PM CDT Sat May 18 2024
Upper air analysis and satellite imagery this morning reveal an
upper level low over north central North Dakota, and a developing
shortwave over western Washington. At the surface, a low pressure
system is located over Winnipeg, Manitoba this morning, with a cold
front extending south through north central Kansas. High pressure is
observed over the Nebraska Panhandle.
&&
.SHORT TERM /THROUGH SUNDAY NIGHT/...
Issued at 235 PM CDT Sat May 18 2024
Tonight, the stage becomes set for several days of active weather.
As surface high pressure ejects to the east, a weak surface boundary
may be the focus for some showers and thunderstorms this evening
through Sunday morning, particularly across southwest Nebraska. As
the nocturnal low level jet settles in, a plume of warm, moist air
advects into the region. While this is happening, a low
pressure system over Wyoming is expected to form and mature,
developing a warm front and cold front before it heads east.
The main forecast challenge in the short term will be how long these
showers and thunderstorms linger, which sets up two main scenarios
for Sunday evening. If the storms exit the region more quickly, as
seen in HRRR guidance, there is a greater period of daytime heating,
and as such a greater severe weather threat Sunday afternoon and
evening. These solutions are presenting decent surface based CAPE
and generally initiate storms along a line through most of the
region. On the other hand, there is some slower guidance such as the
NAM Nest, which holds the cloud cover from showers and storms a bit
longer, limiting the daytime heating. These slower solutions limit
the surface based CAPE, keeping storms more elevated in nature, and
in some cases wipes the thunderstorm threat out by tomorrow evening.
What does remain consistent is the plume of moisture ahead of the
approaching system. Additionally, forecast soundings all tend to
show a potential severe weather environment tomorrow evening, with
ample CAPE and shear profiles. If the daytime heating can erode the
capping layer, and storms can tap into the surface based layer, the
environment seems primed to produce large hail and damaging winds.
If the cap remains in place, then convection likely remains
elevated, still with large hail potential, but may end up being
hindered unless it can tap into the surface moisture.
&&
.LONG TERM /MONDAY THROUGH SATURDAY/...
Issued at 235 PM CDT Sat May 18 2024
Showers and thunderstorms Sunday night begin to taper off after
midnight, giving a brief dry period on Monday morning. By the
afternoon, another batch of showers and thunderstorms develops to
the west and begins to track across the forecast area. Overnight
Monday into Tuesday continues to be highlighted as the peak intensity
of this precipitation event. Current guidance suggests that forecast
precipitable water values will exceed the climatological 90th
percentile. To further back this, ensemble guidance is now
highlighting portions of north central Nebraska and the Sandhills
with a 60 percent chance of exceeding 1 inch of rain in 24 hours. As
for expected amounts, followed with the Weather Prediction Center
guidance which calls for storm total rainfall around 1 to 3 inches
across the region from tonight through early Wednesday morning.
Currently, the highest amounts are expected across the Sandhills,
but with the convective nature of the rain, locally higher amounts
are possible.
The next concern comes with a mid week cool off Wednesday morning.
The latest forecast sees temperatures trending up slightly, however
some of the lower end guidance brings mid to lower 30s across
southern portions of the Panhandle. Will continue to keep an eye on
temperature trends over the next several days, as temperatures in
the mid to lower 30s could cause some late season frost concerns
across the southern Panhandle. At this time, the chances seem
somewhat limited, but again, will be worth keeping a close eye on.
Mid week through the end of the week, the upper level pattern
remains fairly active. A series of shortwave and upper level lows
persist across the Northern Plains, with variations in the placement
of surface systems and associated rainfall. Precipitation chances
remain through the end of the week, however, it is a bit difficult
to nail down a precise timing right now. Certainly, the synoptic
forcing will be there, so it will also be worth keeping an eye on
how the upper level pattern evolves over the next several days to
more precisely time precipitation chances through the week. For now,
will continue to stick with general chances of showers and
thunderstorms through the week, however, follow on forecasts may be
able to refine the timing as models resolve the pattern later this
week.
&&
.AVIATION /00Z TAFS THROUGH 00Z MONDAY/...
Issued at 625 PM CDT Sat May 18 2024
VFR conditions will continue through the overnight period,
though clouds will begin to fill in and lower as rain showers
develop Sunday morning. MVFR to locally IFR ceilings are likely
for southern terminals after sunset, impacting KLBF. Winds will
strengthen out of the south with gusts exceeding 25 knots.
Clouds will begin to scatter out towards the end of the valid
period. Confidence on timing and specific impacts from the rain
showers is rather low at this time, thus future amendments and
inclusions will be possible.
&&
.LBF WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
SYNOPSIS...Richie
SHORT TERM...Richie
LONG TERM...Richie
AVIATION...Viken
Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
907 PM CDT Sat May 18 2024
.KEY MESSAGES...
- Small chance (~20%) for some isolated/widely scattered
showers/storms later this evening as a weak cold front moves
into the area.
- A few additional isolated showers and storms possible Sunday
afternoon and early evening, mainly south of the Illinois and
Kankakee River Valleys.
- Summer-like warmth expected through Tuesday night,
interrupted only by lake cooling Sunday; then during any
showers/storms Monday and Tuesday.
- Scattered thunderstorms likely Monday afternoon and evening
across portions of northern Illinois, a few of which could be
strong, and capable of causing heavy downpours and ponding
- Scattered (mainly non-severe) thunderstorms possible Tuesday
morning and then after a break, widespread thunderstorms in
the evening, including a severe threat for parts of the area
&&
.UPDATE...
Issued at 859 PM CDT Sat May 18 2024
This evening, we find a weak cold front draped across eastern
IA and up through central WI propagating eastward toward
northern IL. Clusters of strong thunderstorms can be found ahead
of the front across central and northern WI where there is
notably better forcing for ascent, both along the face of the
front and from features aloft. What little activity we had
brewing out to our west a bit earlier this evening has fizzled
away meaning areas upstream are rain-free for the time being.
While most high res guidance has dry conditions prevailing along
the front, if not producing just a few sprinkles, the RAP and
HRRR have consistently been resolving a little bit of
shower/storm redevelopment along the line within the next few
hours just prior to reaching the CWA. Some low level deformation
appears to be the primary driver behind this redevelopment as
it looks to stretch the low level vort lobe and provide us with
a little uptick in pre-frontal forcing over the next few hours.
With dry low level air in place, LFCs across northern IL are
pushing 10,000+ ft AGL, which equates to around 700 mb, with
more and more MUCIN building up as the evening progresses. And
with such shallow moisture to work with beneath awfully dry mid
level air, it`s going to be tough to overcome these dampers and
produce any precip, even with the added forcing. If anything
does manage to go up, chances are seemingly greatest across far
north central IL late this evening with the environment becoming
even less favorable to support precip as the front moves into
the Chicago metro later tonight. The current forecast brings
slight chances across our northern CWA with the front, and that
seemed appropriate still. That being said, the short term
forecast remains very much on track.
Doom
&&
.DISCUSSION...
Issued at 315 PM CDT Sat May 18 2024
Through Sunday Night:
Very warm and somewhat more humid weather has set up across the
area this afternoon in advance of an approaching cold front
across the Upper Midwest. While there have recently been a few
attempts at thunderstorm development across northwestern IN where
weaker capping exists, no more than some isolated sprinkles or
light showers are expected east of I-57 this afternoon. Elsewhere,
partly cloudy and warm conditions will persist the remainder of
the afternoon as inland temperatures top out in the mid 80s.
Slightly cooler conditions are expected near the IL Lake Michigan
shores due to an onshore southeasterly wind component.
Diurnal heating and destabilization in advance of the approaching
cold front to our west-northwest is expected to foster scattered
thunderstorm development across parts WI and northeastern IA later
this afternoon. While this activity should persist into this
evening as the cold front begins to approach northwestern IL, a
gradual weakening trend is expected through the evening as the
boundary layer stabilizes. Nevertheless, I opted to add some
slight chance POPs (20%) along the front across northern IL later
this evening. Areas in and around the Rockford area stand the best
chance to have a few of these weakening showers and storms in the
10pm to midnight timeframe.
The cold front is expected to stall out over my southern counties
in central IL and IN on Sunday. North of the boundary, a drier
airmass will filter into the area on east-northeasterly winds.
Accordingly, a less humid day is expected for much of interior
sections of northern IL (especially north of I-80). Temperatures
will be the coolest near the lake, where readings will hold in the
upper 60s to around 70. Farther inland, temperatures will top out
in the low to mid 80s.
Much of the area will be precipitation free on Sunday due to the
drier easterly winds. However, a moist and unstable airmass will
remain in place to the south near the stalled frontal boundary
across central IL and IN. Therefore, as capping weakens in the
afternoon, some isolated showers and thunderstorms cannot be ruled
out, especially south of the Kankakee and Illinois River Valleys.
While weak flow through the troposphere will curtail any threat
for organized storms, any showers or storms that do manage
to develop Sunday afternoon will be very slow moving at 10 mph or
less. This could thus promote some very localized instances of
heavy rainfall.
These isolated storms should diurnally weaken after sunset Sunday
evening, thus setting up a relatively quiet night for the area. We
will have to keep an eye on convective trends to our west late
Sunday night, however. Numerous thunderstorms are expected to
develop and convectively enhance a mid-level disturbance across
the Plains Sunday afternoon and evening. The decaying remnants of
these thunderstorms are expected to shift east-northeastward
across the Corn Belt Sunday night, and it is possible that some of
them make it into northern IL into early Monday morning. We thus
continue to carry some low end chances (~20%) west of I-39 late
Sunday night to account for this possibility.
KJB
Monday through Saturday:
On Monday, a lead short-wave and its associated surface low
lifting into the upper MS Valley will drag a warm front north of
the area. While the strongest forcing will pass north of our area,
the southern flank of the short-wave will provide some weak height
falls. With strong heating bringing temps up into the mid-upper
80s and dew points into the 60s amidst 6.5-7.0 C/km mid-level
lapse rates, looking at up to 1500 J/kg of MLCAPE. Areas
near/northwest of I-55 or I-57 should see enough erosion of CIN
(capping) that combined with the modest large scale forcing,
expecting scattered thunderstorms to develop toward mid day and
especially in the afternoon over the western or northwestern half
or third of the CWA and then track northeast.
Marginal (less than 30 kt) of deep layer shear and the modest
mid-level lapse rates appear to be limiting factors for a more
appreciable severe threat, though fairly steep low level lapse
rates and seasonably high PWATs may contribute to wet downbursts
with 50 to perhaps 60 mph gusts across the northwest CWA, in line
with the SPC day 3 level 1 (marginal) severe risk. Our official
forecast holds onto likely PoPs north of I-80 in the evening and
overnight, though with weak flow aloft, diurnal loss of
destabilization, and minimal large scale forcing, the highest
thunderstorm coverage may in reality be confined to only an hour
or two after sunset.
Looking into Tuesday, global guidance has been consistent in
bringing a lead short-wave northeastward across the mid-MS Valley
during the morning hours. There may be enough of a MUCAPE
reservoir for scattered showers and thunderstorms during this
time, focused near/northwest of I-55, where we have 30-50% PoPs in
our forecast. Morning timing and marginal deep layer shear suggest
primarily non-severe thunderstorms, with maybe a chance of an
isolated marginally severe hail or wind producer. Similar to our
previous discussion, Tuesday afternoon continues to look like a
gap in the convection that should support temps at least in the
mid to upper 80s, and possibly tagging 90F if clouds really scour
out. Southerly winds will gust up to 30-35 mph.
The powerhouse cyclone for late May that has exhibited an overall
slowing trend vs. a few days ago will have the surface low
northwest of Des Moines early Tuesday evening (around 00z).
Initial supercells initiating west of the MS River may tend to
congeal into a squall line or bowing segments into the evening,
with a coherent but possibly weakening severe MCS tracking
eastward across the area during the evening. Given the slightly
later and less favorable timing, areas of the CWA within the 30%
probs area in the SPC Day 4 outlook correspondingly appear to have
the highest severe chance. With this said, strong dynamics and
strengthening southerly low-level flow may offset diurnal
stabilization enough to keep the severe (mainly wind) threat going
farther east, overall fitting the 15% area on the outlook.
Thunderstorm coverage should wind down overnight Tuesday night
and then expecting the cold front to clear the area by Wednesday
morning. Barring a slightly slower trend in the cold frontal
passage, Wednesday will be a breezy, cooler (highs in low-mid
70s), and dry day for most of the area. In this scenario
(slightly slower cold front), the best chance for any showers
and a thunderstorm will be southeast of I-55, where chance PoPs
were maintained. Dry and pleasant weather Thursday, with highs
in the mid to upper 70s, may very well persist through the day
on Friday, before shower and thunderstorm chances possibly
return at the end of the period. An early glance at Memorial Day
Weekend points toward seasonable temps and some potential for
showers and thunderstorms at times, but that`s about all that
can be said this far out.
Castro
&&
.AVIATION /00Z TAFS THROUGH 06Z SUNDAY/...
Issued at 614 PM CDT Sat May 18 2024
Key Aviation Messages:
- Slight (<20%) chance of a shower or thunderstorm late tonight
with a cold front moving through the area.
- South-southwest winds will shift north-northwest behind the
front pre-dawn Sunday, then northeast around/after sunrise.
Surface low pressure was over far western Ontario early this
evening, with a cold front trailing through western WI into
eastern IA. South-southwest winds (with a few 15-20 kt gusts
prior to sunset) will prevail ahead of the cold front into the
overnight hours, before shifting north-northwest behind the
front which should move through KRFD 06-07Z and KORD/KMDW
09-10Z. Isolated to widely-scattered showers and thunderstorms
were occurring ahead of the front currently, but are expected to
diminish in coverage with the loss of diurnal heating after
sunset. High-res CAM guidance suggests most of these would
dissipate before reaching the Chicago terminals later tonight.
KRFD has a little better chance, but probability is too low for
TAF mention.
Winds will shift northeasterly early Sunday morning, and will
remain from that direction through the day, before trending more
easterly Sunday evening. VFR conditions should prevail through
the period.
Ratzer
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...None.
IN...Air Quality Alert until midnight CDT tonight for INZ001-INZ002-
INZ010-INZ011.
LM...None.
&&
$$
Visit us at weather.gov/chicago
Area Forecast Discussion
National Weather Service Marquette MI
657 PM EDT Sat May 18 2024
.KEY MESSAGES...
- Increasing threat for severe thunderstorms capable of
damaging winds and large hail across western Upper Michigan
late this afternoon into the evening hours.
- Borderline elevated fire weather conditions on Sunday with
very dry conditions, but winds on the lighter side.
- Frequent periods of showers Monday through late week, but
mainly focused on Monday and also Tuesday afternoon and
Tuesday night.
- Above normal temperatures early in the week falling to below
normal late week.
&&
.SHORT TERM /THROUGH EARLY THIS EVENING/...
Issued at 309 PM EDT Sat May 18 2024
Forecast is mostly on track early this afternoon except for a few
pesky rain showers that continue to percolate across the Copper
Country on the cool side of a ~40 kt low level jet. There was some
thunder/lightning with this activity before it moved into our area,
but has just been showers since then. Looking around local weather
stations indicates morning rainfall has been difficult to measure,
probably due to the deep inverted-v signature evaporating most of
the droplets. Otherwise temperatures have warmed into the 70s and
80s in line with the morning forecast with the warmest spots being
L`Anse, Harvey, and Covington that all observed 84F around 2PM.
Relative humidity values decreased to 28% at Baraga Plains, Golden
Lake, and Michigamme sites with everywhere else staying at or above
30% at this time. The eastern edge of lower RHs appears to be a
subtle Lake MI lake breeze with a subtle wind shift from SSW to SSE
and dew points a few degrees warmer.
The main forecast challenge going through this evening continues to
be thunderstorm chances as a cold front sweeps east across Upper
Michigan. Many different observation platforms reveal a cold front
extending south from the MN arrowhead toward La Crosse, WI. A lake
breeze boundary over the Bayfield Peninsula is also apparent on DLH
radar with SPC mesoanalysis of surface vorticity and divergence
highlighting these features well. The latest 18z mesoanalysis also
shows SBCAPE around 1500 J/kg along the MN/WI state line beneath 0-6
km bulk shear of 30-40 kts, which is conducive to marginally severe
thunderstorms. Large hail and damaging winds are the most likely
hazards and deep inverted-vs with DCAPE of similar magnitude as
MUCAPE suggests damaging winds may be more prevalent. Several recent
HRRR/NAM nest runs have shown gusts at or near severe thresholds
with the most common location being near and northeast of the
Porcupine Mountains.
Satellite/radar imagery shows orphan anvils over northern WI
indicating updrafts are trying to get going, but have so far failed
to persistently break a mid level capping inversion. However, HREF
guidance indicates rapid initiation over northern WI around 20Z/4PM
eastern with coverage increasing as it moves into Gogebic County by
22Z/6 PM eastern then well into the western UP by 00z/8 PM eastern.
Thunderstorm activity is expected to be weakening as it moves into
the central UP due to the loss of surface heating. However, the
threat doesn`t end until the cold front moves through and the
frontal boundary apparent on DLHs area is about 5 hours away
according to the time of arrival tool. This is a fair amount slower
than CAMs implying storms may be outflow-dominant, surging ahead of
the boundary. As far as rain totals ensemble guidance favors a quick
0.10-0.20in of rain for the most part, but there is a chance (30-
40%) for heavier amounts up to a half inch in any heavier downpours.
Skies quickly clear from west to east behind the front while winds
veering westerly before becoming light and variable under surface
ridging.
&&
.LONG TERM /TONIGHT THROUGH SATURDAY/...
Issued at 551 PM EDT Sat May 18 2024
An active pattern will continue across the U.S. during this week.
Troffing currently over western Canada into the northern U.S.
Rockies will amplify over the next few days, leading to western
Canada/western U.S. troffing this week. A series of shortwaves
dropping into this trof from the N Pacific will then eject e and ne
across the U.S., supporting the active pattern. For Upper MI, the
result will be several opportunities of rainfall this week. The
first is just beginning and continues into tonight. The second
follows late Sun night thru Mon evening, the third Tue aftn thru
Wed, possibly lingering into Thu, associated with the strongest low
pres of the week, and finally the fourth at some point Fri thru the
weekend. Models are in overall good agreement thru midweek. Timing
of the last system is most uncertain, but that`s expected given the
farther time range out in the model runs. So, expectation is for
overall above normal pcpn across Upper MI over the next 7 days. This
will work to ease still lingering drought over portions of western
Upper MI where, per the 5/16 U.S. Drought Monitor, severe drought
was still indicated, centered around the Porcupine Mtns, and also in
eastern Upper MI where moderate drought was still indicated from
eastern Delta to western Mackinac counties. As for temps, above
normal readings will be the rule thru Mon, warmest on Sun. Temps
will then trend downward to blo normal Thu/Fri, due to the flow
around the deep low that passes across the area midweek. A return
toward normal expected over the weekend.
Beginning tonight, a mostly narrow band of convection associated
with cold front still currently w of Upper MI will continue
progressing eastward with a tendency to diminish with time once it
reaches central Upper MI due to loss of daytime heating and
resulting waning instability. Risk of damaging winds/large hail
exists across roughly the w half of Upper MI owing to 500-1000j/kg
of MLCAPE over the next few hrs and deep layer shear of 30-40kt.
Last of the diminishing shra/tsra will exit the eastern fcst area 06-
09z. Skies will quickly clear from w to e after fropa. Expect lows
generally in the upper 40s to lwr 50s F across the area.
On Sun, sfc high pres ridging will move to the Upper Great Lakes
along with and an associated very dry air mass. Full sun thru the
morning will give way to some mid/high clouds arriving from the w in
the aftn. Strong insolation will result in deep mixing into
extremely dry mid-levels. NAM shows late morning dwpts at
800mb/~5kft AGL ranging from -20 to -40C, though this is the low end
of the model guidance. Moisture aloft does increase during the aftn,
but mixing potential still supports sfc dwpts falling thru the 30s
F. Some locations will see upper 20s F. The low dwpt potential is
evident thru local mixed dwpt tool and simply in raw model guidance,
HRRR most dramatically (it often captures mix down drying quite
well). With high temps in the mid/upper 70s F across the interior,
the low dwpts will drive RH down to around 20pct across much of
Upper MI Sun aftn. The good news is winds will be on the lighter
side, though a little higher than previously expected. Sustained
winds will be around 10 mph with gusts to around 15 mph. Winds will
be strongest across the Keweenaw with gusts to around 25mph there.
Will need to monitor for lightning strike started fires, especially
if rainfall from storms is more limited tonight. Lake breeze
development will limit fire wx concerns close to the Great Lakes
shorelines due to cooling conditions (temps falling into the 60s F),
and higher dwpts, resulting in higher RH.
Out of the amplifying mid-level trof over the western CONUS, next
shortwave will lift to the Upper Great Lakes on Mon, accompanied by
a surge of precipitable water up to ~190pct of normal. This increase
in moisture along with increasing isentropic ascent will lead to
shra/isold tsra and a widespread wetting rain across much of the
fcst area. EPS ensemble probabilities show much of the area, except
the Keweenaw, with a 30-50% chance of seeing 0.5 inch of rain from
this system. Shra will arrive late Sun night and end most areas Mon
evening. After a period of drier weather late Mon night thru Tue
morning, a notably stronger shortwave ejecting from the western trof
will reach the Upper Mississippi Valley Tue night. With this wave
potentially closing off a mid-level low, it may be slower to exit
across Upper MI into Ontario Wed/Thu. The GFS has been and continues
to be on the faster edge of the model solutions. This fcst leans
toward the slower consensus. Associated deepening sfc to 985-990mb
range will be in the vcnty of western Lake Superior Wed morning.
While the low track passing to the w of Upper MI will support the
widest coverage of heaviest rainfall to the w of Upper MI, mdt to
locally hvy rainfall will still be possible across the fcst area
during the period of strong isentropic ascent/strong 850mb theta-e
advection to the e of the low Tue night. Precipitable water
increases to ~200pct of normal as well. Expect widespread rainfall
across the area. EPS probabilities show a 30-70% chance for at least
a half inch of rainfall from this system with the highest
probabilities se and w. Shra coverage will diminish significantly
for Wed, some areas may slip in dry weather for much or all of the
day, especially e half. As the low lifts across northern Ontario,
isold/sct shra may linger under cyclonic flow on Thu.
Timing shra potential Fri/Sat is uncertain. For now, of the 2 days,
Fri has the better shot at being a dry day.
&&
.AVIATION /18Z TAFS THROUGH 18Z MONDAY/...
Issued at 657 PM EDT Sat May 18 2024
VFR conditions prevail thru this fcst period. A brief 2 hour window
through 02z at SAW and CMX could see some thunderstorms when a cold
front sweeps east across Upper Michigan. Cloud cover also rapidly
diminishes behind the front with skies becoming clear by Sunday
morning.
&&
.MARINE...
Issued at 325 AM EDT Sat May 18 2024
Stable conditions will lead to light winds of generally 20 knots or
less prevailing over the lake into early next week, except for some
20-25 kt southeast gusts today over the east half ahead of an
approaching cold front. Thunderstorms are possible today into
tonight as the cold front marches across the lake. These storms may
contain small hail, gusty and erratic winds, and frequent lightning.
More thunder chances return late Sun night into Monday and then
again late Tuesday into Tuesday night as a series of disturbances
track northeast across the Upper Great Lakes region. Models and
ensembles indicate winds will ramp up Tue night into Wed as a
stronger low pressure center tracks across the western and northern
portions of the lake. Ensemble probabilities show a 40-60 pct chance
of gale force gusts to 35 knots late Tue night into Wed across
western and northern sections of the lake.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
None.
Lake Superior...
None.
Lake Michigan...
None.
&&
$$
SHORT TERM...EK
LONG TERM...Rolfson
AVIATION...07
MARINE...Rolfson
Area Forecast Discussion
National Weather Service Omaha/Valley NE
621 PM CDT Sat May 18 2024
.KEY MESSAGES...
- Several rounds of strong to severe thunderstorms will be
possible across our region tomorrow through Tuesday afternoon.
All modes of severe weather including flash flooding will be
possible.
- There will be another chance for thunderstorms Thursday night.
Overall risk of severe weather appears low at this time.
&&
.DISCUSSION...
Issued at 159 PM CDT Sat May 18 2024
Today through Tomorrow Night...
A warm and dry air mass will be in place this afternoon in
association with a high pressure that has taken residence across
our area. Clear skies and high temperatures in the upper 70s to
mid 80s will be on tap for us before temperatures start cooling
after sundown this evening.
Tonight will begin a prolonged period of rain and thunderstorm
chances, lasting through Tuesday afternoon. Aloft, models have
consistently resolved a deepening longwave trough over the
western CONUS. While this main upper-level disturbance is not
expected to eject out into the Plains until later Monday night,
a series of subtle shortwaves are anticipated to eject out into
our area downstream of this feature in the days prior.
The first in this series of disturbances is going to be a low-amplitude
negatively tilted shortwave that should kick out into the
central High Plains by 7 PM this evening. Scattered showers and
thunderstorms should develop in response to the forcing
associated with this disturbance, and generally grow upscale as
the system propagates towards the northeast overnight tonight.
With surface dew points in the 40s, this convection is expected
to remain elevated. However, short term CAMs depict a cold pool
maturing under this cluster of storms owing to evaporative
cooling from the deep and dry low-levels. As such these storms
will pose a low-end wind threat through the early morning hours
tomorrow morning. Storms should moved into portions of east-
central Nebraska by 3 AM in the morning, with the US-30 corridor
an approximate center line for the region of highest rain and
strong wind chances. Wind gusts of 45 to 55 mph are possible,
with a severe wind gust up to 60 mph not out of the question.
These storms should move into central Iowa by 9 AM tomorrow
morning.
Additional showers and thunderstorms are expected to trail this
initial round of storms, bringing cloud cover and rain to much
of eastern Nebraska and western Iowa through the morning hours
tomorrow. This will act to delay recovery and destabilization of
the atmosphere until the afternoon hours. By early afternoon
tomorrow, winds are expected to become south/southeasterly as a
warm front slowly advances north across the area. This will
help advect gulf moisture back into our region from the south,
with short term guidance bringing dew points in the low 60s up
to the I-80 corridor by 7 PM tomorrow. This front will be the
focus for a conditional threat for isolated severe thunderstorms
tomorrow. All CAMs have trended towards eroding the capping
inversion by 4 to 5 PM, with MLCAPE ranging from 1500 to 2250
J/kg. Aloft, a 500 mb jet is expected to be in place over our
area, bringing 45 to 60 knots of bulk shear over portions of
southeast Nebraska and southwest Iowa. 0-1 km shear will be on
the weaker side with shear magnitudes under 20 knots and 0-1km
SRH around or under 100 m2/s2. This will support a large hail
and damaging wind threat with any storm that can develop. The
tornado risk appears to be much lower with these storms, but
non-zero. Further to our southwest, scattered thunderstorms are
expected to develop along a dryline in western Kansas and
Nebraska. These storms will quickly grow upscale into an MCS and
track east across the central Plains. These storms are not
expected to reach our area until after 7 PM tomorrow evening.
The primary threat for these storms will be strong damaging
winds. With lowering LCLs and a strengthening low-level jet
tomorrow after sundown, a spin-up tornado or two cannot be ruled
out. The highest risk for severe weather will be south of I-80
sometime between 9 PM and midnight.
There will be a more conditional threat for strong winds with
another potential cluster of storms that may track across
northeast Nebraska tomorrow night. The pre-storm environment in
this region will be less favorable as the warm front will
struggle to get this far north in addition to the environment being
more worked over by convection tonight into tomorrow morning.
Nonetheless, a few CAM solutions depict a second cluster of
storms that will weaken as they traverse east across northeast
Nebraska. These will also pose a risk for strong winds tomorrow
night, with the time frame of highest risk being between 10 pm
and 1 am. The risk for severe hail and tornadoes with this
particular cluster of storms appears low at this time.
Monday through Tuesday Night...
The aforementioned longwave trough out west will approach our
area on Monday. Synoptic scale forcing for ascent and height
falls will aid in surface cyclogenesis in the central Plains.
The favored area for surface low development seems to be
southwest Kansas at this point in time. Extending northeastward
out of this developing low pressure, a warm front will arc
across central and northeast Nebraska, with a moderately
unstable airmass to the south and east of the boundary. Surface
dew points by Monday evening will likely range from the mid 60s
across east-central Nebraska and western Iowa, to around 70
degrees in southeast Nebraska. Model trends over the last day
have been to weaken the capping inversion over our area Monday
afternoon as well. As such, with periods of substantial forcing
as low-amplitude shortwaves eject into the Plains downstream
from the main disturbance, the potential for scattered strong to
severe thunderstorms Monday evening is increasing (30 to 50
percent at this time). Uncertainty with regards to the magnitude
of destabilization and exact strength of the capping inversion
will remain until Monday becomes in range for short term CAMs.
This will preclude any further discussion on coverage details.
Nonetheless, GFS and EURO both show an airmass with 2000 to 2500
J/kg of surface based CAPE under 10 to 20 J/kg of CIN across
much of eastern Nebraska and western Iowa. For what it`s worth,
the 18Z run of the HRRR leaves southeast Nebraska uncapped by 1
PM on Monday. Furthermore, SREF probabilities for CAPE at or
greater than 3000 J/kg range from 50 to 75 percent south of the
I-80 corridor. The limiting factor to organized convection, at
least early Monday afternoon will be weak shear over our area.
Bulk shear values will remain under 30 knots until around mid-
afternoon. As the evening progresses and flow aloft strengthens
with the approach of the trough out west, the dynamic
environment should improve to better support organized
convection. All in all, this will all support an isolated
threat for strong to severe thunderstorms, with large hail being
the primary hazard Monday late afternoon and evening.
By Monday night, the environment is expected to look very
different than the one in place over our region Monday
afternoon. Aloft, a speed max is expected to eject out into the
Plains as the axis of the main trough moves to the east of the
Rockies. With much stronger flow aloft, bulk shear across our
region will range anywhere from 40 to 60 knots by midnight
Monday night. At the surface, the aforementioned surface low
will track north-northeast, likely in the vicinity of south-
central Nebraska/north-central Kansas by Tuesday morning. With
the development of a strong low-level jet (flow by 4 AM Monday
at 850 mb may exceed 50 knots), all modes of severe weather will
become increasingly likely for any convection that can persist
into the overnight hours. The one complicating factor to this
set up is there is still substantial uncertainty with how much
the nocturnal boundary layer will cool across our region. Strong
mixing from the low-level jet in conjunction with strong
advection of warm air and moisture at the surface from the
south will mitigate nocturnal cooling (and by correlation
minimizing CIN that can develop ahead of any pre-existing
storms). On the other hand, strong southwesterly flow in mid-
levels may advect much warmer temperatures that may develop a
capping inversion above the boundary layer, helping weaken
storms into the early morning hours. Regardless, there may be
sufficient forcing for ascent driven by the strong dynamics at
play Monday night to overcome this. These uncertainties should
be ironed out over the next few forecast issuances. Until then,
will refrain from any further discussion on timing, coverage,
and threat details.
Tuesday morning. A surface low is expected to be somewhere in
northeast Nebraska or southeast South Dakota. A cold front will
extend to the south-southwest of this front through central
Nebraska into central Kansas. The airmass ahead of this front
will destabilize very quickly, with convection initiating on the
front as early as the late morning hours. While there is still
uncertainty with the exact placement and timing of the system at
this point, odds are increasing for rapid development of
thunderstorms along the cold front in eastern Nebraska by around
noon, with strong to severe thunderstorms exiting our region by
mid afternoon. Surface based CAPE may exceed 3000 J/kg by noon,
particularly across southwest Iowa. Bulk shear will also be very
strong, with magnitudes 50 to 65 knots possible. Hodographs
Tuesday appear to be fairly straight line at this time which
would limit the tornado risk, at least until these storms move
east of our region. As such, large hail and damaging winds will
be the primary risk, with a low but non-zero tornado risk slowly
increasing as the afternoon progresses. The highest risk for
severe weather at this time appears to be southwest Iowa in the
early to mid afternoon hours.
Lastly, due to multiple rounds of heavy rain traversing our
region, there will be a threat for flooding across all of
eastern Nebraska and western Iowa through Tuesday afternoon.
This risk appears to be maximized across northeast Nebraska and
west-central Iowa where storm total rainfall amounts will range
from 1 to 2 inches, with local amounts of 3 to 4 inches
possible.
Wednesday through Friday...
The pattern should quiet down after our main system moves east
on Tuesday. Another round of thunderstorms appears possible
Thursday night, however the potential for severe weather is low
at this time.
&&
.AVIATION /00Z TAFS THROUGH 00Z SUNDAY/...
Issued at 621 PM CDT Sat May 18 2024
VFR conditions will likely prevail through the forecast period
with increasing shower and thunderstorm chances late tonight
into Sunday morning. Measurable precipitation appears most
probable at KOFK where prevailing -SHRA will be indicated Sunday
morning. At KOMA and KLNK, TEMPO -TSRA groups will be included
for a 2-3 hr period Sunday morning. Otherwise, southeast winds
are expected to increase to 12+ kt by mid-morning at KOFK, and
midday or early afternoon at KOMA and KLNK.
&&
.OAX WATCHES/WARNINGS/ADVISORIES...
NE...None.
IA...None.
&&
$$
DISCUSSION...Darrah
AVIATION...Mead