Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 05/22/24
AREA FORECAST DISCUSSION
National Weather Service Wakefield VA
826 PM EDT Tue May 21 2024
.SYNOPSIS...
High pressure shifts offshore this evening. A summerlike
pattern develops by the middle of the week as high pressure
settles off the Southeast coast. A cold front approaches from
the northwest Thursday with daily chances for showers and
thunderstorms to end the week and into the weekend.
&&
.NEAR TERM /THROUGH WEDNESDAY/...
As of 800 PM EDT Tuesday...
Key message:
- Quiet overnight with patchy fog possible once again, mainly E
of I-95.
The latest analysis indicates ~1017 mb sfc high pressure
centered along the Delmarva and Carolina coast, with an upper
level ridge extending ENE from the Gulf of Mexico to the NC
coastal plain. There is a weak trough aloft not too far to the
W, across the central and southern Appalachians, but this will
have little affect of the local area overnight. Temperatures are
several degrees warmer than 24 hrs ago (along with a another day
of drying from earlier today). Still, the pattern w/ sfc high
pressure slowly drifting off the coast and a light SE flow will
be conducive to another night with at least patchy fog,
primarily further east and SE tonight given that the high has
shifted offshore. Will go with patchy fog especially SE and
south central VA, NE NC and the Eastern Shore. Lows generally
dropping back into the upper 50s/lower 60s, with some mid 50s
over the interior sections of SE VA and across the eastern
shore.
&&
.SHORT TERM /WEDNESDAY NIGHT THROUGH THURSDAY NIGHT/...
As of 330 PM EDT Tuesday...
Key Messages:
- Summerlike and more humid for Wed and Thursday with
temperatures close to 90 each day.
- Chances for storms later Thursday into Thursday evening. A
few of these storms may be strong to severe.
High pressure settles off the coast by Wednesday, leading to
south to southwest low level flow. This will allow the surge of
warmer temperatures and higher humidity levels across the area.
Despite temps approaching 90, it looks tough for any storms to
develop given the ridge axis over the region. The HRRR and
HighResFV3 suggest storms may develop over northern VA late Wed
afternoon then perhaps brush by the far northern part of the
forecast area Wed evening as the showers/storms diminish. Have
opted to include a slight chance for this time period but most
likely it will stay dry.
Scattered showers and storms are expected to develop as a cold front
approaches from the NW on Thursday. These will most likely form
later in the day (say after 3 or 4 pm) and then continue to the
coast by later Thu evening. With the ridge breaking down somewhat,
stronger mid level flow of 40 kt will move across the area during
the afternoon. This stronger mid level flow combined will help to
give 30 kt of deep shear. The kinematics combined with favorable
thermodynamics (MLCAPE 1000-1500 J/KG) may allow for some localized
severe storms especially if we can see the multicellular storms
develop into a more linear feature. The inverted-V type
sounding and some dry air aloft would suggest wind being the
main threat from any severe weather. Currently have a marginal
risk for severe weather for the majority of the area.
&&
.LONG TERM /FRIDAY THROUGH TUESDAY/...
As of 335 AM EDT Tuesday...
Key Messages:
- Remaining somewhat unsettled through the weekend with chances
for mainly afternoon/evening showers and thunderstorms.
- Forecast trending warmer for the weekend into early next
week.
Not too many changes to the underlying thinking for Friday through
the Memorial Day weekend. The slow moving cold front which will be
gradually moving through the area on Thursday will stall out nearby
for the weekend. Meanwhile, the ridge breaks down just enough to
allow stronger mid level westerly flow to remain in place across the
area through the weekend. Within this westerly flow, the models
suggest a series of short waves moving through. Timing of these is
impossible to accurately predict at this time, however. As
such, there will be chances for showers and storms for much of
the weekend. We should be able to better define timing of the
best chances as we get closer to the weekend. However, for now,
the best chances for showers/storms look to be on Friday and
again on Sunday.
The NBM has warmed up temperatures for the weekend, with most places
now in the mid to upper 80s. With lack of any significant
troughiness across the region, this makes sense and have increased
the official forecast to match.
&&
.AVIATION /00Z WEDNESDAY THROUGH SUNDAY/...
As of 800 PM EDT Tuesday...
VFR conditions this evening with a mainly clear sky and light
winds. Expect patchy fog and perhaps some low CIGs develop
after midnight, primarily from near the coast to portions of
interior SE VA and NE NC (and the VA-MD eastern shore). In
general, the flight restrictions will be less than what occurred
last night/early this morning. Will keep RIC VFR all night since
the sfc high shifted offshore is not as favorable a pattern for
fog in central VA. However, will have some mention of IFR-MVFR
restrictions at the other terminals, with the greatest coverage
expected from 05-11Z. Fog/low clouds should quickly burn off a
little faster Wed morning with all sites VFR by 13-14z. On Wed,
winds will be SW 5-10kt, except with some backing of the winds
to the SE near the coast in the aftn. Mostly sunny with SCT aftn
cumulus.
Outlook...A cold front approaches the area Thu bringing with it a
chance for showers/storms along with possible flight restrictions.
The front looks to stall in the vicinity of the region Fri-Sun,
bringing daily chances for mainly afternoon/evening showers and
storms.
&&
.MARINE...
As of 230 PM EDT Tuesday...
Key Messages:
-Moderate rip current risk continues for southern beaches today
before returning to low for all local coastal waters Wednesday.
-Marine fog will be possible again tonight. Rain and storm chances
return beginning Thursday.
High pressure remains across the local area this afternoon creating
calm marine conditions. Winds are generally variable at less than
8kt, but should become more southeasterly late this evening before
turning southwesterly during the early morning hours. Speeds are
forecast to remain between 10-15kt. Seas are 2-3ft with waves in the
Bay around 1ft. Another round of low clouds/marine fog may be
possible again tonight, particularly along the Atlantic coast.
Visibilities could be reduced to 1-2SM at times.
The area of high pressure begins to slide offshore on Wednesday
ahead of an incoming frontal system. High-resolution guidance tries
to indicate a brief uptick in southerly wind speeds to sustained 15-
19kt Wednesday afternoon. Rain and storm chances will increase on
Thursday with the front`s approach, and are forecast to persist each
day into early next week as the front stalls out across the region.
Expect the best rain chances to be likely in the afternoon/evening
hours. Currently not anticipating any wind issues with the frontal
passage itself, though strong erratic gusts will be possible with
any stronger thunderstorm during this period. Seas are forecast to
remain around 2-3ft.
A moderate risk of rip currents continues for the rest of the day
for the southern beaches. Expecting the rip forecast to return to
low for all beaches on Wednesday.
&&
.HYDROLOGY...
As of 800 PM EDT Tuesday...
The Nottoway River at Sebrell remains in minor flood, and has
been dropping slower than the previous forecast. Water levels
are expected to fall below flood stage by early Wed morning, so
the Flood Warning has been extended.
&&
.TIDES/COASTAL FLOODING...
As of 230 PM EDT Tuesday...
Another round of nuisance to minor tidal flooding is expected to
occur tonight, particularly for the middle Chesapeake Bay and tidal
portions of the Rappahannock River and southern shore of the tidal
Potomac. A Coastal Flood Statement has been issued for these
locations for tonight`s high tide cycle. A similar pattern will
likely continue again later Wednesday as the higher astronomical
high tides will remain elevated.
&&
.AKQ WATCHES/WARNINGS/ADVISORIES...
MD...None.
NC...None.
VA...None.
MARINE...None.
&&
$$
SYNOPSIS...LKB/MRD
NEAR TERM...LKB/MRD
SHORT TERM...MRD
LONG TERM...MRD
AVIATION...MRD
MARINE...JKP
HYDROLOGY...AKQ
TIDES/COASTAL FLOODING...AKQ
Area Forecast Discussion
National Weather Service Buffalo NY
1039 PM EDT Tue May 21 2024
.SYNOPSIS...
There will be showers and thunderstorms as a cold front
approaches the region on Wednesday. Some of these storms may be
strong with gusty winds possible. Cooler more comfortable
weather can be expected Thursday into the first part of the
Memorial Day weekend.
&&
.NEAR TERM /UNTIL 6 PM WEDNESDAY EVENING/...
Late this evening a mid-level wave will exit to the east and
with diminishing instability following nightfall it will be dry
and mild overnight with lows in the 60s.
Active weather day expected Wednesday with the potential for strong
to severe thunderstorms. Ahead of approaching cold frontal boundary
an increasingly unstable environment will emerge, with surface
temperatures in the mid to upper 80s and surface dewpoints getting
into the mid to upper 60s. Surface based CAPES likely nearing 2000
j/kg during peak heating. Increasing shear profiles suggesting the
potential for damaging winds and hail, with even a small corridor of
enhanced low level helicity developing into southwest New York
possibly favoring a few rotating cells. HRRR and most mesoscale
guidance brings this into Western NY around 1 p.m. then moves
the line of storm eastward to the eastern Lake Ontario region
around 6 p.m. A secondary line of less developed storms is
possible just ahead of the cold front heading into Wednesday
evening. SPC has most of the area in a slight risk for severe
weather, with the exception of portions of the Eastern Lake
Ontario region which is in a marginal risk.
&&
.SHORT TERM /6 PM WEDNESDAY EVENING THROUGH FRIDAY/...
Closed mid-level low centered over the central portions of the
Ontario province will become vertically stacked by Wednesday night
with its surface low. As this low pressure system weakens, its
associated cold front draped southward across the lower Great Lakes
will continue to progress eastward across western and north central
NY. This being said heading into Wednesday night, showers and a few
thunderstorms will linger into the evening hours, though the
potential for severe thunderstorms will diminish shortly after
sunset due to the loss in diurnal heating and instability. The front
will then cross Wednesday night and continue to support showers
inland from the lakes. By Thursday morning the vast majority of
shower activity should be to the southeast of the area, as dry air
from the next incoming surface high advances east towards the area
resulting in dry conditions across the region.
As surface high pressure pushes east across the area Thursday
through Friday, associated subsidence will support dry weather
persist. Though dry, it will be `cooler` in the wake of the cold
front Thursday and Friday with highs ranging in the 70s.
&&
.LONG TERM /FRIDAY NIGHT THROUGH MONDAY/...
The next mid-level trough over the northern Plains/Upper Midwest
will support a surface low to push northeast across the eastern
Great Lakes into southern Canada Saturday. This will support a warm
front to advance towards the region ahead of the surface low,
resulting in an increase in shower potential Friday night and last
through Saturday night.
A brief interlude in shower activity for the Memorial Day weekend on
Sunday as high pressure slides east across the region.
Showers return late Sunday night and linger through Monday as
another upper level trough and associated surface low pushes across
the Ohio Valley towards the lower Great Lakes.
Temperatures for the period will be near normal with high
temperatures ranging in the low to upper 70s for most of the area
and cooler temperatures across the higher terrain.
&&
.AVIATION /03Z WEDNESDAY THROUGH SUNDAY/...
VFR with no active weather through 15Z Wednesday. Showers and
thunderstorms will move into the area ahead of a cold front
Wednesday afternoon. Some of these could be strong with gusty
winds and hail. After this, another line of storms is possible
with the cold frontal passage Wednesday evening, however these
are not expected to be as strong.
Outlook...
Wednesday night...VFR/MVFR. A chance of showers and thunderstorms.
Thursday...Mainly VFR. A chance of showers.
Friday...Mainly VFR.
Saturday...Restrictions possible. A chance of showers and
thunderstorms.
Sunday...Mainly VFR. A chance of showers and thunderstorms.
&&
.MARINE...
Low pressure will send a cold front into the eastern Great
Lakes on Wednesday, resulting in a increasing SSW flow. But
winds and waves look like they will remain below small craft
conditions with this frontal passage and for the rest of the
work week.
&&
.BUF WATCHES/WARNINGS/ADVISORIES...
NY...None.
MARINE...None.
&&
$$
SYNOPSIS...AR/Apffel/TMA
NEAR TERM...Apffel/TMA
SHORT TERM...EAJ
LONG TERM...EAJ
AVIATION...Apffel/TMA
MARINE...AR/Apffel/TMA
Area Forecast Discussion
National Weather Service Columbia SC
734 PM EDT Tue May 21 2024
.SYNOPSIS...
High pressure will dominate the region through early Thursday
keeping fair and dry conditions in place along with warming
temperatures. A frontal boundary will approach the region
Thursday night and Friday and is expected to stall just north
of the area resulting in chances of showers and thunderstorms
Friday through next weekend.
&&
.NEAR TERM /UNTIL 7 AM WEDNESDAY MORNING/...
Weak high pressure remains in place over the area this evening.
Only forecast issue will the the chances for ground fog
overnight. The best chances will be in the eastern Midlands and
southern CSRA where the dew points are a bit higher, and also
along rivers and lakes where local moisture values are a bit
higher.
&&
.SHORT TERM /7 AM WEDNESDAY MORNING THROUGH THURSDAY NIGHT/...
High confidence in a fairly quiet period through Friday as
guidance is in good agreement on the expected pattern. Upper
level ridging is forecast to be centered across the southeastern
US by Wednesday morning, with deep troughing settling into the
OH Valley. Ensembles & operational models push the axis of this
ridge offshore by Thursday evening, with more zonal flow
emerging on its heels. The ridging will keep us warm, dry, and
sunny on Wednesday. Highs are likely to be in the low 90s during
the afternoon, with only a few clouds. A strong mid-level
inversion looks to settle in with subsidence beneath the
ridging, so chances of rain are near zero. Clear skies and lows
in the low 60s are expected Wednesday night. The zonal flow is
forecast to take over on Thursday at the same time as we begin
to see an increase in low-level moisture across the forecast
area. Surface theta-e is forecast to climb to 340-345k across
the area on the western side of the surface high across the
Atlantic, increase potential instability. However, it still
looks like a strong cap will remain in place and keep storms at
bay for most of the area. The GFS/NAM/LREF suite of members do
show a weak shortwave trough approaching by Thursday evening.
Thinking that this could break the cap in the northern FA and
spark an isolated to scattered storm across that area. Bumped
PoPs up to slight chance as a result of this. LREF probabilities
of >0.01" of rain in the period are 20-30%, which support the
idea that, while not widespread, some precip is definitely
possible with this shortwave. Highs will likely be in the lower
90s on Thursday, with overnight lows in the upper 60s.
&&
.LONG TERM /FRIDAY THROUGH TUESDAY/...
Fairly high confidence in the general pattern in the long term.
LREF member means and operational models are in fairly good
agreement showing zonal flow continuing through early next
week, with multiple robust shortwaves progressing through the
flow in the long term period. At the surface, rich BL moisture
characterized by high theta-e, PWs 125-130% of normal, and
dewpoints in the upper 60s to around 70 will be in place. This
is forecast to all sit southward of a slow moving surface front
that should approach on Friday and become diffuse or weak around
the area into the weekend. Combine all of this with seasonally
warm temps in the low 90s and the stage is set for a fitting
start to the summer season and Memorial Day Weekend. So look for
highs to be 90-95F each day through early next week, with
chances for storms each afternoon as well. Given the strength of
some of these shortwaves combined with the rich low-level
moisture that is expected and there is a chance that strong
storms become a possibility each afternoon. The mesoscale
details will be important, so stay abreast of the forecast
especially if you have outdoor plans this weekend. For what its
worth, the CSU ML Probabilities are showing elevated severe
probabilities at this range on Sat/Sun/Mon, so it will be worth
watching this weekend. A more developed system and front look
likely to push in and through the region by the middle of next
week, which could cool us down if the front actually
materializes.
&&
.AVIATION /00Z TUESDAY THROUGH SUNDAY/...
High confidence in VFR conditions all terminals through 06z
then expect predawn visibility/ceiling restrictions in patchy
fog primarily at OGB and AGS. Confidence is higher for
restrictions at OGB.
High pressure remains in place across the region with a
relatively dry air mass in place. However, low level winds
overnight shift more southeasterly and may allow for some weak
onshore flow possibly leading to early morning fog/stratus over
the Coastal Plain. Guidance continues to suggest LIFR conditions
possible at OGB prior to dawn...08z-12z. The cross-over
temperature is higher at that terminal suggesting an increased
threat for fog. HRRR also supports MVFR/IFR at AGS. Brief MVFR
fog possible at CAE and CUB but overall NBM visibility
probabilities much lower than at OGB. Winds will be light and
variable overnight but favor a southeast direction. With the
ridge axis shifting east Wednesday, expect winds from a south-
southwest direction through the day less than 10 knots. High
clouds will be increasing from the west mainly in the afternoon
as the upper ridge weakens.
EXTENDED AVIATION OUTLOOK...No significant flight restrictions
are currently anticipated through Thursday outside of brief
morning fog. Low probability of restrictions during the late
week period into the weekend from afternoon and evening
convection.
&&
.CAE WATCHES/WARNINGS/ADVISORIES...
SC...None.
GA...None.
&&
$$
Forecast Discussion at weather.gov/mqt.
&&
.DLH WATCHES/WARNINGS/ADVISORIES...
MN...Flood Watch through Wednesday morning for MNZ010>012-018>021-
025-026-033>038.
Dense Fog Advisory until midnight CDT tonight for MNZ020-037.
WI...Flood Watch through Wednesday morning for WIZ001-006.
Flood Watch until midnight CDT tonight for WIZ002-007-008.
MARINE...Small Craft Advisory until 7 AM CDT Wednesday for LSZ121-147-
148.
Gale Warning from 7 AM to 7 PM CDT Wednesday for LSZ121-147-
148.
Dense Fog Advisory until 7 AM CDT Wednesday for LSZ140>143.
Gale Warning until 7 PM CDT Wednesday for LSZ140>146-150.
Dense Fog Advisory until 3 AM CDT Wednesday for LSZ144-145.
&&
$$
DISCUSSION...Melde
AVIATION...JDS
MARINE...Melde
Area Forecast Discussion
National Weather Service Kansas City/Pleasant Hill MO
623 PM CDT Tue May 21 2024
.KEY MESSAGES...
- Chances for strong to severe storms this afternoon and evening continue
across MO and KS. Storms are expected to start out as
discrete cells before merging into a line of storms. All
hazards are possible including damaging winds, large hail, and
tornadoes.
- Storm chances will be greatly influenced by the position of
the cold front and timing of storm initiation. Severe risk is
significantly reduced behind the front.
&&
.MESOSCALE...
Issued at 127 PM CDT Tue May 21 2024
Satellite imagery shows an area of agitated cumulus
overspreading much of far eastern KS and western MO.
Observations show the cold front progressing into eastern KS.
Some convection has initiated across SE Nebraska; however, the
18Z TOP sounding shows a little bit of a CAP left curtailing
development further south at this time. This CAP is expected to
erode as daytime heating continues. SPC mesoanalysis shows
nearly 1000-2000 J/kg CAPE gain in the past 3 hours mostly due
to daytime heating. Bulk shear remains above 50kts with 0-1
helicity of 100-150 m2/s2. All of these factors keep
expectations for storm modes unchanged. Initial discrete storms
are anticipated before storms congeal into a line across central
MO. All severe hazards including large hail, damaging winds,
and tornadoes are possible.
Uncertainties remain as to where the front will be when
initiation takes place; however, trends in obs and CAMs suggest
storms starting to form within the next 1-3 hours.
&&
.DISCUSSION...
Issued at 107 PM CDT Tue May 21 2024
Short Term (Today-Tonight)
A small line of elevated storms moved across far northern MO during
the morning hours. Its concentration further north and quick
progression through the region does not look to impact the short
term forecast. Warm air and moisture advection into the region
continues ahead the approaching cold front. This destabilizes the
atmosphere substantially with some CAMs already projecting CAPE
values around 3000-4000 J/kg. Bulk shear above 50kts and midlevel
lapse rates greater than 8 C/km further increase confidence in the
potentially volatile environment. Storms are already beginning to
form across far SE Nebraska. Now, it is just a matter of how fast
the cold front progresses across eastern KS and how long it takes
for storms to initiate across the cold front.
Confidence is high that storms will form within the warm sector
ahead of the front; however, exactly where the front will be as
storms initiate is still in question. Short term model guidance
varies in the timing of convective initiation and the position of
the front. Citing two, the NAMnest initiates convection across
eastern KS pushing eastward into central MO through the evening.
Conversely, the HRRR suggests the front progressing further eastward
with storm initiation possible along and east of the I-35 corridor.
If the cold front progresses further eastward, those behind the
front may not see any storms regardless if there are within the
outlined risk areas.
Where models have been persistently agreeing is in the expected
storm modes and evolution of the system. Confidence is high that
storms are expected to start as discrete cells before congealing
into a line of storms across central and eastern MO. These discrete
cells are expected to bring chances for large hail (2+ inches),
damaging winds, and tornadoes. These threats are expected to
continue even as storms begin to linearize. Once the line becomes
fully organized, the primary threat transitions to damaging winds.
However, embedded brief tornadoes remain possible. Please ensure you
have multiple methods for receiving weather information; especially
during the late evening hours.
Longer Term (Extended Forecast)
The long term forecast remains persistent. A reinforcing vort
max will move through the Midwest on Wednesday, which may keep
storm chances in our southern fringes during the
afternoon/evening. More likely, though, is that storms will stay
south of the region Wednesday and Wednesday night (70 percent
chance). After the warm weather today, temperatures will be much
more seasonal on Wednesday in the wake of the system.
The pattern late this week into this weekend remains unsettled,
with general quasi-zonal or southwesterly low-amplitude flow in
place. Multiple perturbations will eject from a broad large-
scale trough in the West, leading to multiple chances for
convection through the holiday weekend. Ensembles are gradually
converging on a relatively higher threat Thursday night and
Friday as well as Sunday. With an open Gulf and relatively fast
flow in proximity to the perturbations, at least some severe
threat exists with each of these passing systems. Notably, the
CSU machine-learning probabilities provide nearly daily chances
of severe weather from Thursday through Monday for the region.
&&
.AVIATION /00Z TAFS THROUGH 00Z WEDNESDAY/...
Issued at 618 PM CDT Tue May 21 2024
With today`s expected storms well east of the terminals this
evening, VFR conditions are expected at all the Kansas and
Missouri state line terminals through this TAF cycle. Only issue
to watch will be the strong west wind, which will be very gusty
through 03Z, then should ease up as it veers to the northwest.
&&
.EAX WATCHES/WARNINGS/ADVISORIES...
MO...None.
KS...None.
&&
$$
MESOSCALE...Pesel
DISCUSSION...Pesel/CMS
AVIATION...Cutter
Area Forecast Discussion
National Weather Service Grand Rapids MI
915 PM EDT Tue May 21 2024
.KEY MESSAGES...
- Severe Weather Potential Tonight
- Dry for Wednesday and Thursday; Rain Chances Return Friday
- Rain Chances Linger Through the Holiday Weekend
&&
.UPDATE...
Issued at 915 PM EDT Tue May 21 2024
No significant fcst changes are needed or planned this evening. A
consensus of latest CAMs continues to indicate that severe
thunderstorms to our west across Wisconsin will gradually congeal
into a QLCS and cross Lake MI between around 03Z and 04Z.
Potential for severe wx still exists mainly west of US-131 between
around 04Z and 05Z.
However it is noted that overall trends in latest CAMs and the 12Z
HREF as compared to the 00Z run yesterday evening show less in
terms of potential for severe wind gusts this far east into our
area. This includes a consensus of latest probabilistic guidance
for higher end wind gusts. Latest trends in the HRRR continue to
support this notion.
Will continue to monitor very closely as a well organized squall
line or QLCS can overperform. However latest model trends do not
show this as the most likely outcome. If there is any severe wx
across our area damaging wind gusts are the primary svr wx threat
west of US-131 and particularly near Lake MI.
&&
.DISCUSSION...
Issued at 350 PM EDT Tue May 21 2024
- Severe Weather Potential Tonight
Not expecting more than scattered showers and thunderstorms
through this evening before a squall line moves across Lake
Michigan from Wisconsin and reaches the western zones around
midnight.
Flat shortwave ridging at mid-levels is apparently suppressing
afternoon convection today, but heights will begin to fall as
a negatively-tilted shortwave trough closes off over Minnesota
accompanied by sfc cyclone tracking into Canada with a cold front
advancing into Lower Michigan overnight.
An analysis of model soundings and other model-generated severe
weather probability guidance suggests the greatest chance for
severe weather tonight will be across the western forecast area
near the Lake Michigan shore. A line of storms in western Iowa at
330 PM EDT is progged to expand and move east, crossing Lake
Michigan. Main threat for our nearshore waters and western
forecast area is for downburst winds but transient QLCS
mesocyclone circulations cannot be ruled out, resulting in
enhanced swaths of higher winds and even a quick tornado.
Model soundings suggest instability decreases as the storms move
east and some of the model guidance show a corresponding weakening
of the line of storms before they reach Grand Rapids.
The front becomes more parallel to the environmental winds on
Wednesday slowing and stalling near or south of the forecast area
with lingering showers possible near JXN during Wednesday.
- Dry for Wednesday and Thursday; Rain Chances Return Friday
Good forecast certainty remains for a dry Wednesday and Thursday and
this will be accompanied by much more seasonal highs in the 70s.
Humidity will be substantially less oppressive too with dewpoints
dropping into the 50s and then 40s by Thursday.
GOES satellite water vapor channels show an upper PV maximum
currently diving southward into the Pacific Northwest region. This
feature will eventually emerge as a cyclonically breaking upper wave
over the Upper Mississippi valley region Friday afternoon/evening.
Strong upper divergence with this feature will support a solid
coverage of showers and storms pushing eastward into our forecast
area Friday night, although the best QG forcing should remain well
northwest of our area. This combined with nocturnal stabilization
should limit the threat for severe thunderstorms.
- Rain Chances Linger Through the Holiday Weekend
Unfortunately, forecast details for Memorial Day weekend remain
quite uncertain. A brief lull in precipitation for at least part of
Saturday seems probable, but that`s about as definitive as I want to
get right now. Starting Saturday afternoon, PoPs for the rest of the
holiday weekend look to be in the neighborhood of 20 percent, which
is right around climatology. High temperatures will be quite close
to climatology as well in the neighborhood of low 70s.
&&
.AVIATION /00Z TAFS THROUGH 00Z THURSDAY/...
Issued at 748 PM EDT Tue May 21 2024
This set of terminal forecasts features a fairly significant
change from previous thinking with regards to thunderstorms
later tonight. This change is dropping thunder wording altogether
at all of the sites except KMKG, where we went with a VCTS.
Convection is not as widespread or strong as thought earlier. The
latest model trends give us increasing confidence that the
convection out to our west may just clip the NW portion of our
area. It will be a close call at KMKG, thus the reason with VCTS
there.
The biggest impact will likely be some MVFR cloud cover that will
move in near the cold front late tonight and first thing Wednesday
morning. A few showers will be possible with the actual front,
then just clouds. The clouds will then lift and break up Wednesday
afternoon.
Winds will increase late this evening from the SSW with gusts up
to 25 to 30 knots. The winds will generally stay up most of the
rest of the forecast period, becoming more from the SW on
Wednesday.
&&
.MARINE...
Issued at 350 PM EDT Tue May 21 2024
No changes to the Small Craft Advisory. In addition to strong
southwest winds from the tightening pressure gradient, there could
be gusts over 50 knots tonight as a squall line moves across Lake
Michigan, arriving in the nearshore area around midnight.
&&
.GRR WATCHES/WARNINGS/ADVISORIES...
MI...None.
MARINE...Small Craft Advisory until 8 PM EDT Wednesday for LMZ844>849.
&&
$$
UPDATE...Laurens
DISCUSSION...Ostuno/TJT
AVIATION...NJJ
MARINE...Ostuno/Thielke
Area Forecast Discussion
National Weather Service Gray ME
1152 PM EDT Tue May 21 2024
.SYNOPSIS...
Scattered thunderstorms are expected across New Hampshire and
interior Maine through this evening, with a few strong to severe
storms possible. Very warm and increasingly humid conditions
will follow through Thursday. A cold front will cross Thursday
and will bring potential for thunderstorms with the potential
for a couple to become strong to severe. It will remain warm
Friday into the weekend weak systems bringing low chances for
showers late in the weekend.
&&
.NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
1145 PM Update... Remnant and weakening convection is crossing
over the CT River Valley into NH with a cold pool helping to
maintain this region of light to moderate rainfall and
occasional lightning. There remains some uncertainty in how far
east this area of rain will make it into NH and possibly
western ME as latest CAM runs continue to struggle but no
further strengthening is expected as this activity remains
elevated in nature. Nevertheless, did increase PoPs to account
for this rain and made some minor adjustments to
temperatures/dewpoints through the overnight hours. Patchy fog
is already beginning to develop as well and it could become
locally dense so please use caution if traveling.
800 PM Update... An area of thunderstorms is continuing to
weaken as it moves east over the Seacoast of NH as it interacts
with the marine layer and a stout inversion. There is another
area of convective showers over Coos county NH but decreasing
shear and increasing CIN is helping to keep this weak. This will
continue to be the trend over the next few hours as the threat
for severe storms has ended. The main changes with this forecast
update were to tighten up PoPs as well as remove enhanced
wording from the forecast.
Previously...
A convectively induced short wave associated with a remnant MCS is
tracking across southern Ontario this afternoon. This wave has
already triggered convection across Upstate NY and VT that has
spilled into NH. The 12Z HREF suggests that thunderstorms cannot be
ruled out across the entire area while the best juxtaposition of
shear and CAPE will be across NH and to a lesser extent into the
western Maine mountains. Latest RAP analysis shows ML CAPE is now up
1000J/kg and will build up to 1500J/kg across southern and western
NH with effective shear to 25-30 kts. Farther east, cool onshore
flow will limit instability across the NH Seacoast and along the
coastal plain of Maine. CAMs generally fire storms through 00Z with
convection waning afterwards. A notable trend within the 12Z CAM
suite has been for increased coverage in storms across southern NH
and interior SW Maine with these storms holding together as the
approach the coast. Both strong to damaging winds and marginally
severe hail will be a threat with storms with the greatest
threat for strong storms across central and southern NH where
the best instability will be.
Tonight will be mild and humid with patchy fog likely along the
coastal plain and interior valleys. The will be lingering
instability overnight that could allow for isolated
thunderstorms across the north. Lows tonight will be in the
upper 50s to low 60s.
&&
.SHORT TERM /6 AM WEDNESDAY MORNING THROUGH THURSDAY/...
Wednesday looks to be the warmest day of the week with highs in
the upper 80s to low away from the coast and south of the
mountains. Mid level ridging will try to build over the area
while disturbances traversing to top of the ridge will bring
chances for showers and thunderstorms across the north.
Southwest to south winds will advect some cooler marine air into
the coast that will keep highs here in the 70s to near 80
degrees.
Wednesday night will be warmer than tonight with lows only
dropping into the low to mid 60s. An approaching cold front will
bring increasing chances for showers, and perhaps some thunder
across northwestern zones by Thursday morning.
&&
.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
A shortwave stemming from an upper low north of the Great Lakes is
set to cross New England during the day Thursday while sending a
cold front through. This front will provide focus for showers and
storms during the day as the environment out ahead it will be warm
with temperatures in the 70s and 80s, and dewpoints will be in the
mid 50s to lower 60s. A few strong to severe storms are not out of
the question as bulk shear could surpass 30-35 kt while temperatures
aloft will be cold, supporting the potential hail, and low-level
lapse rates will be steep, supporting locally strong to damaging
winds. However, the timing of the front is key here, and if it
is quicker to move through, then the overall threat will be
lower for strong/severe storms.
Skies quickly clear out behind the front Thursday evening into
Thursday night as drier air works into the area. Overnight lows
remain mild with mid 50s to lower 60s expected. It`s possible some
of the valleys see fog develop late and toward daybreak, and if any
develops it should quickly clear up within an hour or two after
sunrise. The dry air stays around for Friday providing mostly sunny
skies with no rain in the forecast. It will again be quite warm with
temperatures reaching the upper 70s to mid 80s away from the
coast.
The warmth continues over the weekend, but a couple of weak waves
aloft will cross the area, bringing a chance of showers each day.
With how things look right now, the higher shower chances will be
across the interior and farther north and mainly during the daytime
hours. High temps are forecast to reach the 70s to low 80s for much
of the area, but prevailing southerly flow/seabreeze will keep
things cooler along the coast. Will also have to watch for marine
fog/stratus during the nighttime hours.
The next opportunity for more widespread precip arrives early next
week as global models are in decent agreement showing a more
amplified trough and potentially a deepening coastal low moving into
the Northeast.
&&
.AVIATION /04Z WEDNESDAY THROUGH SUNDAY/...
Short Term...Scattered TSRA will bring potential for brief
restrictions with the greatest chance for TSRA at KLEB and KCON
and cannot be ruled out at KHIE, KMHT, and KPSM. There will be
patchy fog tonight that will bring potential for IFR along the
coast and CT Valley. Mainly VFR is expected Wednesday with
potential for patchy fog again Wednesday night.
Long Term...Marine fog/stratus may produce IFR/LIFR conditions into
Thursday morning, but this would be more likely at RKD. Otherwise, a
cold front will bring another chance of showers and storms from late
Thursday morning into the afternoon with the highest potential
generally south and east of a LEB-AUG line. These will be
capable of brief instances of IFR to MVFR restrictions, but
conditions should remain VFR outside of precipitation on
Thursday. Drier air and high pressure brings mostly VFR Friday
into early Saturday, but another low pressure will bring more
chances for showers and flight restrictions the rest of the
weekend. Southerly flow will also keep the potential of marine
fog/stratus for the coastal sites over the weekend.
&&
.MARINE...
Short Term...Winds and seas remain below SCA thresholds tonight
through Wednesday night. There will be scattered thunderstorms
over land through this evening that will approach the waters
around sunset with storms expected to weaken as they move into
the waters.
Long Term...South to southwest winds will precede a cold front on
Thursday, with fog remaining a threat prior to the front`s passing.
The front is currently forecast to cross the waters by late
afternoon or early evening with a wind shift to northerly into
Thursday evening/night. Winds are expected to remain below SCA
levels. Additional weak low pressures will move through over the
weekend and with southerly flow generally remaining, will probably
see additional fog over the waters.
&&
.GYX WATCHES/WARNINGS/ADVISORIES...
ME...None.
NH...None.
MARINE...None.
&&
$$
NEAR TERM...Tubbs
Area Forecast Discussion...Updated
National Weather Service Lincoln IL
908 PM CDT Tue May 21 2024
.KEY MESSAGES...
- Strong south winds will gust up to 40 mph into early this
evening. This will create blowing dust in spots where fields
have recently been plowed.
- There is a level 4 of 5 (moderate) risk for severe weather this
evening west of the Illinois River, with gradually lower chances
further east. While all severe hazards are in play, the greatest
risks will be damaging wind gusts and brief tornadoes. A level 1
of 5 (marginal) risk will linger south of I-70 tomorrow
afternoon.
- An active pattern continues into this weekend with another risk
of severe storms on Sunday.
&&
.UPDATE...
Issued at 858 PM CDT Tue May 21 2024
The blowing dust conditions have dominated the late afternoon and
evening so far. Frequent wind gusts over 40 mph will continue
until the cold front pushes through Illinois. Therefore, we have
continued with a Blowing Dust Warning until midnight for the
central portion of the CWA. Accidents have occurred and major
highways remain closed, to prevent accidents in some cases.
As for our severe weather potential, the 00z ILX sounding
confirmed that a capping inversion is present across central
Illinois this evening. That warm layer aloft has clearly
diminished the updraft potential so far this evening. HRRR was
advertising this type of a scenario during the day today, but
others High Res guidance still pointed toward intense storms
hitting our area. That is the difficulty with days we expect to
break the cap. We still have somewhat of an inverted-V sounding
feature and steep low level lapse rates, so some downburst wind
potential will be present as the complex of storms south of
Sangamon County progresses into southeast Illinois. Areas south of
I-72 will remain under a wind threat as some northward expansion
of that complex is indicated in the HRRR. We have trimmed PoPs
north of I-72, and advanced likely PoPs mainly south of I-70.
Possible clearing of the Tornado Watch or portions of the Watch will
be coordinated with SPC soon.
After cold FROPA we will see skies clearing out and westerly winds
develop by sunrise across our CWA.
Shimon
&&
.DISCUSSION...
Issued at 211 PM CDT Tue May 21 2024
18z surface map placed 996 mb low pressure over extreme southeast
Nebraska, which is forecast to deepen as it tracks northeast into
northern WI tonight. Well within the warm sector this afternoon,
central IL is being bathed in summertime heat and humidity with
temperatures in the upper 80s and dewpoints in the mid 60s as of 1
pm. A tight MSLP gradient will promote 30-40 mph southerly winds
gusts into early this evening. Dry top layers of soil and active
farming activity will lead to blowing dust in spots through late
afternoon.
A warm layer aloft centered near 775 mb should keep convection
suppressed in the warm sector this afternoon, and our attention is
focused on the cold front trailing south of the low, which is
forecast to fill in with convection over the next few hours. With
the better kinematic fields lifting northeast along with the
surface low, mesoanalysis suggests the more significant severe
weather potential (long track tornadoes, very large hail,
widespread wind damage) affecting areas to our northwest across
IA, far northwest IL, and southern WI into this evening. We do
maintain a risk of severe storms this evening locally,
particularly west of I-55 in a 7 to 11 pm window. As the
line of storms moves into this area, strong deep layer shear and
moderate instability will favor damaging straight line wind gusts
in the more intense line segments. While instability will decrease
with time and eastward extent, a 925-850 mb jet will strengthen
overhead, which may keep the severe threat going toward midnight
or a little later than the CAMs have been trending. The tornado
risk will mainly be tied to QLCS tornadoes, based on favorable
0-3km shear vectors northwest of the IL River.
Behind the front, a more typical May airmass will filter into most
of central later tonight and Wednesday with cooler highs in the
70s and lower humidity. The exception will be south of I-70 where
the front is slower to clear, leading to another warm day and a
few afternoon storms. The severe weather risk is much reduced in
this area from previous forecasts with higher instability (CAPEs
1000+ J/kg) suppressed near and south of the Ohio River based on
the 12z HREF. Still a couple strong afternoon storms can`t be
ruled out given 30 kt deep layer shear and SPC has a Marginal risk
(level 1/5) near/south of I-70.
For Thursday through early next week an active pattern will remain
in place across the region, with shortwaves shown crossing the
Midwest every 36-48 hours. Significant uncertainty in the
forecast details exist given differences in timing and placement
of these features, however Friday and Sunday look to be the
favored periods for more widespread showers and storms and this is
where higher PoPs have been placed. For severe weather prospects,
Sunday is currently the most concerning, especially if the 21/12z
ECMWF verifies with low pressure deepening just to our northwest.
Again, widely varying solutions are noted in the ensemble
envelope, so keep updated on later forecasts as the pattern
evolves.
25
&&
.AVIATION... (For the 00z TAFs through 00z Wednesday Evening)
Issued at 641 PM CDT Tue May 21 2024
South winds will gust 30-40 kt into this evening ahead of a cold
front. A broken line of TSRA is expected to cross the central IL
terminals this evening, and have a 3-hr tempo for IFR conditions
and gusty winds associated with the storms. Winds veer west behind
the frontal passage and lose gustiness. Patchy MVFR ceilings
could develop behind the front, primarily at KBMI-KDEC-KCMI and
have added a scattered cloud group there for the overnight hours.
Shimon
&&
.ILX WATCHES/WARNINGS/ADVISORIES...
Blowing Dust Warning until midnight CDT tonight for ILZ037-038-
042>045-053.
&&
$$
Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
1022 PM CDT Tue May 21 2024
.KEY MESSAGES...
- Severe thunderstorms likely this evening, with potential for
widespread, and potentially significant, damaging winds and
tornadoes
- Non-thunderstorm winds could gust over 40 mph from the south
this evening, then from the southwest in the wake of the
storms later tonight
- There will be dry breaks at times, but an active pattern for
showers and storms returns Friday through early next week
&&
.MESOSCALE...
Issued at 1022 PM CDT Tue May 21 2024
Recent radar and satellite trends new convection filling in just
east of the Mississippi River from just east of Quad Cities south
to just east of Quincy. These storms are seemingly forming on a
pre-frontal convergence axis evident on the velocity data on DVN
WSR-88D.
Evening RAOB from ILX and recent ACARs soundings from Chicago
show presence of stout capping inversion in the warm sector,
however strong ascent in association with the approaching upper
trough is progged to continue lifting/cooling the inversion this
evening resulting in weakening cap/inhibition. RAP objective
depicts an axis of 1000-2000 J/kg of MLCAPE over western IL, which
should largely maintain itself as strong winds limit nocturnal
cooling and dewpoints remain steady or even rise a bit. Near term
RAP suggests that continued ascent should continue to erode the
inhibition as the axis of strongest instability shifts eastward
coincident with the cold front and upper trough.
Assuming inhibition does indeed erode as progged, then recently
developing convection along the convergence axis would have the
potential to maintain itself and even intensify as it spreads
eastward into our CWA. While it isn`t clear this will be the case,
should sustained, strong convection maintain itself wind profiles
remain exceptionally favorable for damaging winds and even a
tornado threat. While convection hasn`t been particularly intense
in our CWA up to this point, given the exceptionally favorable
wind profiles and at least the potential for weakening inhibition
it is still a little early sound the all clear on the severe
threat tonight.
Strong synoptic winds have been gusting to and in some cases over
45 mph, so going to shoot out a short fused wind advisory.
- Izzi
&&
.DISCUSSION...
Issued at 327 PM CDT Tue May 21 2024
Through Wednesday:
All eyes are on developing convection along a cold front
extending from western Iowa through far eastern Kansas this
afternoon. Low-level capping from previous WAA and some PBL
mixing/drying continues to support dry conditions through at
least 6-7pm in our area. Meanwhile, the spread in potential
solutions from near-term CAM guidance is far higher than desired
at this point, with guidance ranging from little/no convection
over most of the CWA to an expansive squall line with
significant damaging winds and an increased tornado threat well
into the forecast area. Explosive growth of convection across
eastern Kansas and far northwest Missouri supports maintaining a
more aggressive approach with organized convection surviving
well into the area, so we again made only some tweaks to the
overall forecast and messaging with this update.
Overall expectations are for the ongoing upscale growth of the
convection along the KS/MO line, ultimately developing a robust
cold pool that will erode remaining capping and maintain
organized convection across the MS River and into at least the
western CWA around the 7-8pm window. Convection should then
gradually weaken with eastward extent as the line becomes
farther removed from the prime kinematic environment to the
north. With that said, the highest coverage of potential
significant winds favors areas roughly north of a line from
LaSalle to Cook counties and especially in the northwest CWA
toward the Rockford area.
All severe hazards are possible as the convection crosses the
area this evening, but favors a transition to primarily damaging
winds with eastward extent. Any convection, particularly
linear/bowing segments and especially any QLCS, will support a
damaging wind threat with the potential for swaths of
significant wind gusts (75mph+) through the evening. Even
decaying convection will support a significant damaging wind
risk owing to substantial low-level shear profiles and a pre-
convective pool of DCAPE up to around 1500J/kg.
The tornado risk will remain highly conditional on both storm
evolution and coverage, with the most notable threat occurring
with any QLCS/bowing structures owing to an impressive low-level
wind profile with highly elongated hodographs and only a weakly
decoupled nocturnal PBL. In fact, there may be a brief increase
in tornado potential during the mid-evening as EHI values
maximize with the increasing LLJ and slight increase in low-
level moisture. As noted in earlier discussions, strong
tornadoes (EF2) cannot be ruled out with any well-formed line
segment.
Behind the convection just ahead of and behind the convection
overnight, strong and gusty south to southwest synoptic winds
will potentially gust to 40+mph for several hours, with some
gusts possibly even reaching 50mph.
Cooler and dry conditions are expected Wednesday behind this
system.
Kluber
Wednesday Night through Tuesday:
Models are starting to key in on the clearer conditions
allowing for better heating to develop Thursday and potentially
Friday. Previous forecasts capped temperatures in the 70s
through the weekend, but now it looks like there is a better
chance for temps to return to the 80s for much of the area for
Thursday and Friday as a warm front lifts northward from
Central Illinois (more on this in a second). Unmentionable PoPs
south of I-80 along and south of the warm front were kept in the
forecast with only a few low end slight chances (15 to 20
percent) on Thursday afternoon. With little capping, perhaps a
pulse shower pops up in southern Ford or Iroquois Counties, but
confidence is low and kept the forecast mostly dry through
Friday morning.
A weaker (relative to the short term forecast above) upper
level trough will move out of the Plains and toward Ontario
Friday night into Saturday. The associated surface low still
gradually move northward through Iowa on Friday, lifting the
previously mentioned warm front with it before a cold front
sweeps across the area in the evening. Notably, models have
sped of the progression of this system from a Saturday morning
event to now more of a Friday event. Model soundings are
starting suggest better mid level lapse rates with sufficient
instability aloft. With additional forcing from the cold front,
showers and thunderstorms have a chance to develop. One
limiting factor is the projected wind shear values along the
line do not look very impressive, limiting the severe
potential. Additionally, the forecast kept likely PoPs for
Friday afternoon for areas southwest of I-39, but only chance
PoPs for the rest of the area because it is currently expected
to move east over the area after sunset and therefore have
weaker instability without the diurnal heating component. But
given how models have changed, there is a lot of uncertainty in
the exact timing of the frontal passage.
Other than lingering showers Saturday morning, brief ridging
should allow for a slightly drier Saturday afternoon through the
start of Sunday. Both Euro and GFS ensembles are suggesting two
weak waves next week, one moving northward from St. Louis
Sunday night, as well as a slightly deeper one over the
northern Plains arriving over Illinois sometime between Monday
and into Tuesday. While there will certainly be breaks, it is
hard to argue with the NBM`s minimal slight chance PoPs through
next week. While PoPs are higher as models take their best
guess at timing at this range of the forecast will probably need
to be adjusted in the coming days. The main takeaway is that
regardless of the magnitude, it looks like a fairly active
pattern will remain in place through the end of the forecast
period.
DK
&&
.AVIATION /00Z TAFS THROUGH 06Z WEDNESDAY/...
Issued at 619 PM CDT Tue May 21 2024
Key aviation messages:
- Strong S to SSW winds this afternoon with gusts to 30-40kt
- Line of TSRA expected to move through late evening. Medium to
high confidence in a period of severe winds at KRFD, lower
confidence in the strength of winds at KORD/KMDW.
- Line may become broken as it approaches KORD/KMDW, but medium-
high confidence in thunder
- Strong SW to W winds develop in wake of TSRA with gusts to
30-37kt
There are no big changes to the 0z TAF cycle. Gusty south winds
will continue ahead of the line/broken area of thunderstorms now
approaching the Mississippi River.
Confidence is high in these storms maintaining themselves into
KRFD and KDPA. Confidence is also high in near severe or severe
level winds (60 mph) reaching KRFD, with chances diminishing
toward the Chicago terminals. Therefore holding gusts to 50 mph
at ORD/MDW for now, and we will monitor how well the southern
portion of the line of storms holds together. More will
certainly be known in the coming hours.
Also, the current timing for TS at ORD/MDW does appear to be
closer to 03z, but if any individual cells develop ahead of the
current activity - it could be closer to 0230z or so, and this
will be an area we will keep a close eye on as well.
Gusty SW to W winds in the mid 30 kt range will continue in the
late evening and early overnight hours. MVFR conditions will
arrive, though in pockets overnight into early Wednesday, but
fairly low confidence in arrival timing and how long these will
last. Winds will be closer to W then SSW on Wednesday with gusts
more so in the 20 kt realm than the 30 kt like today.
KMD
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...Wind Advisory until 2 AM CDT Wednesday for ILZ004-ILZ005-
ILZ006-ILZ011-ILZ012-ILZ013-ILZ019-ILZ020-ILZ021-ILZ023-
ILZ032-ILZ033-ILZ039-ILZ103-ILZ104-ILZ105-ILZ106-ILZ107-
ILZ108.
IN...Wind Advisory until 2 AM CDT /3 AM EDT/ Wednesday for INZ001-
INZ002-INZ010-INZ011-INZ019.
LM...Gale Warning until 4 AM CDT Wednesday for the IL and IN
nearshore waters.
&&
$$
Visit us at weather.gov/chicago
Area Forecast Discussion
National Weather Service Marquette MI
634 PM EDT Tue May 21 2024
.KEY MESSAGES...
- First round of showers and thunderstorms are already ongoing
and will lift north over the west half of the UP potentially
bringing small hail and stronger winds.
- Second round of thunderstorms moves from west to east this
evening into tonight, bringing mainly some heavy rain showers
and winds; there is a slight chance for all severe weather
threats along this line.
- Windy conditions develop behind the system on Wednesday. Wind
gusts of 50 to 60 mph are possible along the western lakeshore
and Keweenaw.
&&
.SHORT TERM /THROUGH TONIGHT/...
Issued at 319 PM EDT Tue May 21 2024
This afternoon brings the first wave of showers and possibly some
isolated thunderstorms to the UP with a second and more noteworthy
round expected this evening into tonight. A slight risk from the SPC
over the south-central seems to fit well for the going forecast with
potential for all severe weather threats accompanying the second
line of thunderstorms.
Latest WV imagery and RAP analysis has the first shortwave currently
over MN and northwest WI which is lighting up the radar data over
the western UP. This will continue to expand north and east over the
west half of the UP as the shortwave and mid level warm front lift
north, aided by isentropic ascent. With current RAP analysis showing
SBCAPE around 100 j/kg with mid level lapse rates below 6.5 C/km and
the 5/21 12z HREF mean SBCAPE holding around this through the
afternoon as the boundary lifts north, some isolated thunderstorms
are possible to bring some small hail. Severe weather is expected to
hold off until the second round.
The more vigorous shortwave is currently situated over east NE with
the associated sfc low over west IA. This shortwave trough will take
on an increasingly negative tilt as it lifts north-northeast through
the Upper MS Valley this evening and then across northern MN and
into Ontario later tonight. The associated sfc low will rapidly
deepen today aided by strong upper divergence from a coupled upper
jet structure (right entrance region of a 130 kt jet max over
northern Ontario and the left exit region of a 110 kt jet max over
the Southern/Central Plains). The most recent HREF mean has the low
deepening to around 984 mb near the MN/Canadian international border
by 12Z Wed as the center tracks just west of Lake Superior later
tonight. With this more northwest sfc low trend in the last 24 hours
has increased the severe weather potential. CAMs are in fairly good
agreement on this second round developing a QLCS over the western UP
this evening, quickly tracking east into tonight. With bulk shear
around 45-50kt, MUCAPE up to 1000 j/kg, and mid level lapse rates
around 7C/km, some severe thunderstorms are possible. With strong
LLJ around 60-70 kts, this should contain the severe weather threats
to winds. That said, mid level lapse rates could support hail up to
1 inch and low LCLs around 1kft with some low level helicity does
leave a low chance (~2% chance along WI state line) for a quick
tornado spin up. The limiting factor for severe weather is the
timing of the storms, as we progress into the evening and lose
daytime heating, storms are expected to weaken. Another factor in
limiting severe potential for the eastern UP is onshore flow off
Lake Michigan.
Most locations will see between half an inch to inch of rainfall
from this system with the highest amounts west. Models show shower
coverage diminishing significantly late tonight as we get into the
dry slot behind the front along with q-vector divergence/subsidence
as the system continues to lift north. Lows tonight will stay mild
in the 50s, cooler in the west.
&&
.LONG TERM /WEDNESDAY THROUGH TUESDAY/...
Issued at 350 PM EDT Tue May 21 2024
The extended forecast is dominated by two low pressure troughs
during the period, one west of Thunder Bay and north of the
Arrowhead of Minnesota by Wednesday morning, and another over the
Seattle area Wednesday morning making its way across the Upper
Midwest Friday afternoon through Friday night. While the first low
will be northwest of Lake Superior Wednesday, strong winds from
behind the first low will be the main story for the long term,
creating windy conditions across the area (especially the west
where a High Wind Watch and Wind Advisories were issued).
As an impressively deep 986mb low continues lifting northwest from
just west of Thunder Bay towards James Bay Wednesday, a strong low-
level jet from between 5 and 30 thousand ft will move across Upper
Michigan, allowing for windy conditions to develop over the U.P.,
particularly the west where the strongest winds of the LLJ reside.
While 70 mph is the highest possibility (<10% chance), winds up to
50 to 60 mph are expected across the western U.P. along the
lakeshores and the Keweenaw. This will cause unsecured items to the
lofted away and for driving to become hazardous in spots. Therefore,
a High Wind Watch and a Wind Advisory have been issued for Ontonagon
and Gogebic counties Wednesday. While I`m confident that Ontonagon
will see wind gusts up to 45 mph, I`m only around 60% confident that
Ironwood and northward will see gusts up to that high. Likewise, I`m
only 70% confident that northern Houghton and Keweenaw counties will
see wind gusts up to around 60 mph Wednesday too. The main concern
is how well we will mix the higher winds down to the surface across
the area Wednesday; with low-level stratus looking to hang on until
the afternoon hours, we have have a more difficult time doing so.
Nevertheless, the friction that the land will cause along the
lakeshores (as well as the increase in elevation) will help to
increase the wind speeds too. As we move into Wednesday night, we
will lose the diurnal mixing from the sunlight, and thus more stable
air in the boundary layer will prevent the higher winds aloft from
mixing down. While we will likely (80+% chance) see breezy
conditions continue over the Keweenaw Wednesday night, expect
calmer winds across the rest of the U.P. by midnight.
Besides the winds Wednesday, there is a 20% chance that we will see
some light rain showers moving through the central and east
Wednesday before more light rainfall from moisture that`s wrapped
around the low returns and brings isolated showers and thunderstorms
back over the western half by the afternoon hours. As the low
continues to pull away Wednesday night, some of the CAMs hint at a
line of light rain showers moving over the western half late as a
secondary shortwave rotates around the low over us. However, the
shower activity is expected to die out Thursday morning as weak
ridging begins to build back into the area. With warm air advection
returning to the area Thursday, expect highs in the 60s near the
Great Lakes to the 70s in the interior areas. With mostly sunny
skies being over the area Thursday, we could see some strong
dewpoint depressions develop, possibly getting min RHs down into the
low 30 percents in the interior west. There is a chance that some
convection will pop up during the afternoon hours Thursday as a
localized sfc low moves through the U.P.. Whether this occurs or not
will depend if this sfc low materializes, and if so where it tracks.
As it stands right now, I think the NBM`s 30% handles these rain
chances fairly well.
Our second big low of the period looks to impact us around the
Friday through Friday night time period. While we are looking to be
initially dry Friday, especially over the east where min RHs could
dip into the lower 30 percents, rain showers and thunderstorms from
the approaching low look to move into the west by no later than the
afternoon. I lowered thunderstorm chances from likely to chance
wording over the interior west late Friday afternoon into early
Friday evening as guidance could change rapidly over the next 3 days
in regards to the track of the low (and thus thunder chances). That
being said, should everything come into place and the low track just
right, we could see some severe weather return to the western half
as MUCAPEs could get over 1000 J/kg and 0-6 km bulk shear be around
40 to 50 knots. As the cold front of the low moves over the U.P.
Friday night and Saturday morning, expect the rain chances to cease
behind it.
Dry weather returns for this weekend as ridging builds across our
area. For the beginning of next week, model guidance begins to
significantly diverge; we could see dry conditions and ridging
continue, or we could see a Colorado low lift through the Plains
into the Great Lakes and bring more rainfall to the area.
&&
.AVIATION /00Z TAFS THROUGH 00Z THURSDAY/...
Issued at 634 PM EDT Tue May 21 2024
As a strengthening low pressure system currently over southern MN
lifts north into northern MN tonight, another round of showers and
thunderstorms will move though the area with it. A line of stronger
thunderstorms is expected to accompany a front lifting through the
area this evening into tonight. TSRA arrives first at IWD then the
line progresses to CMX and SAW after 2-3Z Wednesday. MVFR conditions
are expected to accompany these showers and storms tonight. Gusts to
25-30 kts are expected at all sites tonight into Wednesday. LLWS is
also expected this evening and tonight as a strong low level jet
moves across the area. With fast moving system, changes at the sites
will be rapid.
While windy conditions continue on Wednesday behind the low pressure
system, expect vis and cigs to return to VFR through the day.
&&
.MARINE...
Issued at 412 PM EDT Tue May 21 2024
East-northeasterly winds are increasing to gales of 35 to 40 knots
this afternoon into this evening over the far western lake as an
impressively strong low pressure lifts from Iowa into northern
Ontario tonight. As this occurs, expect winds to pick up over the
central and eastern portions of the lake to east to southeasterly
gales of 35 to 40 knots as winds in the far west slacken. However
the winds pick up over the western half of the lake again Wednesday
as a low-level jet moves over. Southwest to westerly gales of around
40 knots are expected over the west half Wednesday, with a few high-
end gales to 45 knots possible near Isle Royale and a few storm-
force gusts up to 50 knots possible near the Keweenaw. As we move
into Wednesday night, more stable conditions develop in the
atmosphere, dropping the winds over Lake Superior to below gales by
midnight. The winds continue to diminish into Thursday afternoon,
when light winds of 20 knots or less return to the area. The light
winds continue until Friday, when another low pressure lifting from
the Northern Plains towards Lake Winnipeg brings northeasterly winds
of 20 to 30 knots back across the western half of the lake. West to
southwesterly winds of 20 to 25 knots could be seen over the western
half from late Friday night through Saturday behind the passage of
the low and its cold front. Behind this, expect light winds of 20
knots or less across Lake Superior for the rest of this weekend as
high pressure ridging moves over the area.
As for thunder chances over Lake Superior for the next several days,
thunder chances continue to develop from the far western lake this
afternoon throughout the rest of the lake tonight before ending
Wednesday. While it`s not expected, we could see some severe hail
and winds with these thunderstorms. Therefore, mariners should watch
the radar and keep up with the latest forecasts in order to avoid
the possibility of hitting those conditions. We could see
thunderstorms return near the southern lakeshore Thursday afternoon
as a weak sfc low moves looks to move through Upper MI. The
thunderstorm chances again return Friday as the second low pressure
system moves north with time. The thunder chances with this low
continue until Saturday morning, when the cold front finally pushes
through the eastern lake.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
High Wind Watch from 6 AM EDT Wednesday through Wednesday
evening for MIZ001-003.
Wind Advisory from 9 AM EDT /8 AM CDT/ to 10 PM EDT /9 PM CDT/
Wednesday for MIZ002-009.
Lake Superior...
Gale Warning until 8 PM EDT /7 PM CDT/ Wednesday for LSZ162.
Gale Warning from 7 AM EDT /6 AM CDT/ to 8 PM EDT /7 PM CDT/
Wednesday for LSZ240-241.
Gale Warning from 10 PM this evening to 11 PM EDT Wednesday
for LSZ242>244-263-264.
Gale Warning from 2 AM to 11 AM EDT Wednesday for LSZ245>251-
265>267.
Lake Michigan...
None.
&&
$$
SHORT TERM...Jablonski
LONG TERM...TAP
AVIATION...07
MARINE...TAP