Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 06/24/23

AREA FORECAST DISCUSSION

National Weather Service Bismarck ND

 913 PM CDT Fri Jun 23 2023

.UPDATE...
Issued at 913 PM CDT Fri Jun 23 2023

02Z regional radar imagery shows a line of thunderstorms moving
through northwest South Dakota, with reflectivities greater than
50 dBZ remaining south of the common Dakota border. Reported wind
gusts on the northern edge of this activity have remained below 45
mph and it looks as though the instability gradient remains well
enough to the south to prevent severe thunderstorm gusts this
evening. Coverage of showers and some thunderstorms is still
expected to increase across southern North Dakota through Saturday
morning as the upper low crosses the state. With the lack of
MUCAPE, severe weather is not expected.

UPDATE Issued at 702 PM CDT Fri Jun 23 2023

Broad coverage of convection is currently observed across
southern Montana through northeast Wyoming. This convection is on
the leading nose of a 50 kt 500mb speed max, ejecting through a
shortwave trough over the Great Basin and Northern Rockies.
Winds upstream of this shortwave are fairly weak and water vapor
imagery shows warmer temperatures moving into the base of the
trough, indicative of a trend towards less progressive shortwave
movement. This lines up with recent guidance indicating this wave
should close off this evening, causing the low level front (and
associated instability gradient) to stall near the South Dakota
border. RAP guidance sneaks a bit of MUCAPE into far southwest
North Dakota this evening, which may allow for a small window of
strong to severe thunderstorm potential in areas near the South
Dakota border from the southwest into the south central. Radar
trends in convection to our southwest show storm modes becoming
linear, though an isolated supercell does exist north of the Black
Hills. The linear storm mode combined with easterly surface flow
into the convection could pose a damaging wind threat if adequate
instability does exist in our far south, with severe hail
possible given the low but non-zero potential for initially
discrete cells. While there is currently a Tornado Watch bordering
southwest North Dakota, again the stalling instability gradient
should keep this environment almost entirely south of the state.
In all, the primary threat tonight looks to be an isolated
potential for damaging wind in areas near the southern border as
a linear segment across these areas is likely, with uncertainty
surrounding severity as this area will be on the edge of the
instability gradient.

&&

.SHORT TERM...(This Evening through Saturday Night)
Issued at 255 PM CDT Fri Jun 23 2023

Showers and a few thunderstorms remain possible through tonight,
with the overall severe weather threat remaining low. This
morning`s showers remain in the east late this afternoon and will
continue its slow progression eastward. Behind these showers have
been a few isolated showers trying to redevelop and may continue
to do so through this afternoon. Still a conditional setup for
severe weather across the southwest and far south central
tonight. As an upper wave moves eastward out of NE WY a weak
frontal boundary does as well. This could be the focus for severe
weather, although is generally expected to impact SD more than ND.
That said there is some increased ML and MU cape tonight,
although is not particularly high. What is increased though are
the 0 to 6 KM and in some areas the 0 to 3 KM shear vectors. DCAPE
though is fairly low. So if a stronger storm can develop in ND,
strong winds will be the biggest hazard of concern with gusts up
to 60 MPH. Some hail is also possible, although with low cape
there may need to be some sort of meso present for larger hail.
Overall the confidence in the CWA getting severe weather is low
and will need to be monitored through the evening.

After this initial round of showers and thunderstorms moves
through, the upper wave and surface low will start to take over.
This will develop a broad area of showers from south to north and
continue through at least Saturday morning. How far north still
remains uncertain although NBM is starting to show heaviest rain
should be along and south of Interstate 94 to perhaps Highway 200.
Here the probabilities for over an inch of QPF are quite high, and
even over 2 inches remains modest. As the low moves eastward
during the day Saturday, showers become more scattered. There may
be enough weak instability in the south central and southeast for
a few thunderstorms, although severe weather is not expected at
this time. Many areas then see precipitation end before or during
Saturday night, with some maybe lingering through the night in the
east. Lows tonight and Saturday night will be in the 50s, while
highs Saturday will be in the 60s and 70s. The wrapped up low
could bring some breezy northeast winds on Saturday, although
should remain below wind advisory criteria.

.LONG TERM...(Sunday through Friday)
Issued at 255 PM CDT Fri Jun 23 2023

After a brief lull in precipitation to start the week, an
unsettled pattern may return next week.

Surface high on Sunday should bring generally dry conditions
except perhaps in far eastern areas. Breezy northwest winds may
linger on Sunday, with the higher winds in the east. NBM gets
close to advisory criteria for some, although confidence in winds
this high is low at this point. Temperatures under high pressure
should warm to near seasonal highs in the 70s on Sunday. High
moves eastward on Monday. This could further warm temperatures
back into the 80s and lessen the winds. Ridge riding disturbances
could bring for a few showers and thunderstorms Monday.

Ridge then looks to break down and opens the door for multiple
disturbances to pass through each day. Right now Tuesday and
Wednesday have the highest pops in the forecast, although each day
has at least chance pops. CSU-MLP right now showing minimal
chances for severe weather likely due to lower amounts of shear. Although
given the pattern and some modest instability at times isolated
strong storms cannot be ruled out. Temperatures next week look to
remain near to slightly below seasonal normals.

&&

.AVIATION...(For the 00Z TAFS through 00Z Saturday Evening)
Issued at 702 PM CDT Fri Jun 23 2023

Showers with isolated thunderstorms are expected to become
widespread across the south from late tonight and increasing in
coverage through Saturday morning. This activity should remain
south of KXWA-KMOT and impact KDIK-KBIS-KJMS. MVFR to IFR
conditions are likely within this activity while winds out of the
north/northeast will increase to 10 to 20 kts through the day.
Shower activity should end from west to east through the afternoon
and evening, though low ceilings may persist in the evening in the
south central to southeast.


&&

.BIS WATCHES/WARNINGS/ADVISORIES...
None.
&&

$$

UPDATE...AE
SHORT TERM...Anglin
LONG TERM...Anglin
AVIATION...AE



Area Forecast Discussion

National Weather Service Cleveland OH

 957 PM EDT Fri Jun 23 2023

.SYNOPSIS...
Low pressure will gradually move northeast across the area
tonight before exiting to the northeast on Saturday. High
pressure briefly returns Saturday evening into Sunday, but this
will be short-lived as a low pressure system approaches from the
west Sunday afternoon. The low will push a cold front east
across the area Sunday night into Monday.

&&

.NEAR TERM /THROUGH SATURDAY NIGHT/...
930 pm update...
The HRRR and a couple of the other high res forecast guidance
are still indicating a good potential for areas of fog and very low
stratus to form later tonight through early Saturday morning.
We think the WRF and NAM 3KM is a little too overdone with the
dense fog potential at this time. The latest HRRR seems to be
more realistic with patchy to areas of fog developing by 06z and
lifting off from near the surface around 13z or 14z in the
morning. There could be pockets of thicker fog with localized
visibility dropping to less than a mile possible. With this
update, we will maintain situational awareness and monitor
trends as we progress later in the night.

700 pm update...
We lowered hourly POPs from likely category to chances of 30 to
50 percent for the rest of this evening. We also used the
coverage wording in the evening update of the zone forecast with
to better described the nature of the scattered showers. There
should be a slow decrease in coverage of showers later this
evening, especially after sunset with the loss of daytime
instability. The chance for scattered showers will linger in our
northeastern CWA towards northwest Pennsylvania through
Saturday morning. We are seeing some potential for patchy to
areas of fog possible tonight with low stratus building
downward. We will put some mention of fog in the hourly
forecast late this evening through the mid Saturday morning.
Confidence is low on how widespread and how dense the fog
potential may be late tonight. We will look at the data over the
next couple of hours and revisit this fog potential with a
better idea with the late evening forecast update.

Previous discussion...
Upper level low over the local area will gradually shift east
through tonight, resulting in cloudy skies and unseasonably cool
weather. Scattered showers are present across the area this
afternoon and guidance is hinting at some more convective
showers with perhaps a few rumbles of thunder developing over
the next couple of hours before dissipating after 00Z this
evening. Opted to lower thunderstorm probability to slight
chance (less than 25%) due to limited instability. Showers
remain possible mainly east of I-71 overnight tonight and can`t
rule out some patchy drizzle/mist/fog across the CWA if a low
level inversion manages to develop. Expect overnight lows in the
upper 50s to lower 60s.

The low will pivot into the northeastern CONUS throughout the
day Saturday and the highest rain chances should largely shift
to the east and southeast of the local area Saturday morning.
Scattered showers may pop up during peak heating, but at this
point coverage across the area looks minimal. The low exits the
region Saturday night with dry weather returning. Saturday`s
highs should start warming up as high pressure builds into NW OH
with highs in the low to mid 80s forecast. Temps will be in the
cooler mid to upper 70s further east. Anticipate lows in the
60s Saturday night.

&&

.SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/...
The trend for the warm season has been for limited upper level
ridging over our area while dealing with a succession of upper level
closed lows and open low pressure waves that frequently affect the
region. This trend continues Sunday after a very brief period of
ridging aloft previously on Saturday night is followed by a closed
564dkm low rotates into the Great Lakes. Models are resolving a line
of convection late morning into early afternoon ahead of the main
surface frontal system moving west to east into Ohio. The current
run of models is suggesting that this line organizes with the early
destabilization of the low and mid levels of the atmosphere during
the day Sunday. For now, putting a lower confidence on the timing of
this, as well as its ability to sustain itself in its eastward track
through our CWA as it moves into progressively less supportive air,
possibly due to a now depicted weaker low level jet and weaker
shear. However that does not completely eliminate the potential for
it to push through the entire area. This line coming into the
western CWA could be refiring from the lingering nighttime
convection further west, so there are still details to be ironed
out. But for now, this looks to be the first of two waves of
convection. The second will be with the cold frontal advancement and
ultimate passage Sunday into Sunday evening which is likely going to
have better dynamics in the form of stronger low level winds/0-6km
shear. SB CAPE values high as well, even if exaggerated by the NAM
dewpoints. Brief dry slot post frontal Sunday night, but moisture
quick to return for Monday in the cold pool where scattered showers
and storms are expected to fire again. These will not be completely
diurnally driven and have high POPs continuing into the Monday night
period.

Low/mid 80s expected Sunday in southerly flow ahead of the cold
front, especially where there is increased insolation prior to
arrival of convection. Temperatures take a hit Monday behind the
cold front, likely around 10 degrees cooler and back into the 70s,
another familiar trend so far this late spring/early summer.

&&

.LONG TERM /TUESDAY THROUGH FRIDAY/...
Closed low fills, opens up, and exits late Tuesday, taking the bulk
of the POPs with it Tuesday night. Models hint at ridging aloft
through mid week, bringing reduced POPs down to patchy slight chance
coverage and a gradual warm up again in temperatures after they
bottom out for highs Wednesday with mid 60s east to mid 70s west.
Nothing organized precipitation wise after Tuesday night.

&&

.AVIATION /00Z Saturday THROUGH Wednesday/...
The main aviation concerns with this TAF update will be low
stratus building downward overnight into early Saturday morning
as well as the potential for areas of fog or light mist
impacting visibilities. VFR to MVFR ceilings and conditions will
start out this TAF period for early this evening. We do expect
conditions to be less ideal as we head into the late evening and
overnight hours. Ceilings will start to drop between 03z and
06z down through low end MVFR to widespread IFR ceilings. There
is the potential for localized LIFR ceilings but not confident
enough to drop the levels that much. With this TAF update, have
most TAF sites dropping between 500 and 700 feet. MFD, CAK,
ERI, and TOL have the better potential for ceilings to drop
below 500 feet and we will take another look at the data for the
next update. There are some scattered light showers and pockets
of misty rain swirling around an area of low pressure this
evening. Most of those showers will fade away and become more
localized towards northwest Pennsylvania later tonight into
Saturday morning. We will turn our attention to the fog
potential which there is a decent indication of areas of lower
visibility will likely develop. As of this update, we have most
TAF dropping between 1sm and 3sm by 06z through about 14z
Saturday morning. There is some potential for localized areas
of fog below 1sm impacting some terminals later tonight but
again not confident enough to put that in the TAFs just yet.

The very low stratus and areas of fog or mist will slowly
improve late Saturday into the midday hours. Most locations will
see VFR or MVFR ceilings by midday or early Saturday afternoon.
Winds will be light and variable tonight become a light
northwest breeze around 4 to 7 knots on Saturday.


Outlook...Non-VFR possible with scattered chances of showers and
thunderstorms Sunday night through Wednesday.

&&

.MARINE...
Northeasterly winds 5-10kts become northwesterly by Saturday
morning, and then variable through Saturday less than 10kts with
waves two feet or less. Saturday night into Sunday, winds turn
southerly 5-15kts ahead of a cold front that will enter the western
basin of Lake Erie early Sunday night. Winds then become
southwesterly 10-20kts after the cold frontal passage Sunday night
into Monday. Wave heights increase away from shore in the
southerly/southwesterly winds 1-3ft Monday through Monday night. As
the lagging surface low passes Tuesday, winds become more westerly
10-20kts, adding more of an onshore component to the 1-3ft wave
heights for the central and eastern basin of Lake Erie.

&&

.CLE WATCHES/WARNINGS/ADVISORIES...
OH...None.
PA...None.
MARINE...None.

&&

$$
SYNOPSIS...Maines
NEAR TERM...Griffin/Maines
SHORT TERM...26
LONG TERM...26
AVIATION...Griffin
MARINE...26



Area Forecast Discussion

National Weather Service Goodland KS

 539 PM MDT Fri Jun 23 2023

.UPDATE...
Issued at 256 PM MDT Fri Jun 23 2023

A Severe Thunderstorm Watch has been issued for Cheyenne county in
Colorado and Greeley, Wichita, Wallace, and Logan counties in
Kansas until 04Z (10 pm MDT/11 pm CDT).

&&

.SHORT TERM...(This evening through Sunday night)
Issued at 220 PM MDT Fri Jun 23 2023

Across the region this afternoon, mostly sunny to sunny skies are
prevailing area-wide. Diurnal cumulus popping up ahead of a surface
low currently over southeast Colorado. A strong southerly gradient
has persisted over the area during the day, strengthening some this
afternoon. Gusts are currently in the 20-30 mph range, especially in
areas east of the Colorado border ahead of the low. Temperatures are
mainly in the 80s.

For the remainder of the afternoon on into the evening hours, the
main wx concerns will focus on the potential for strong to severe
storms to develop in two groups affecting different portions of the
cwa, and these are in Slight risks from SPC.

The first area will focus on the aforementioned surface low over
southeast Colorado. Latest HRRR is showing an area of storms
developing over the southeast side of the low around 21z-22z and
push E/NE through areas south of the Interstate for several hours
after that. The airmass is quite unstable at this time, with
southerly surface flow giving way to southwest flow at 500 mb.
SBCape values currently ranging from 3500-4500j/kg. DCape values
1200-1700j/kg. Bulk 0-3km shear from the west around 20kts. SPC
large hail parameter hinting at high values along/south of
Greeley/Wichita counties. Storms that do develop will have the
potential for wind(up to 65mph)/hail(1-2") threats, along with an
isolated tornado. Areas east of the CO border are seeing PW values
an inch or higher, especially the further east away from the
aforementioned low. Heavy rainfall is thus possible bringing about
flooding concerns.

The second area will focus in on locales along/north of Highway
34/36. The instability here in this region will interact with a
passing shortwave later tonight to trigger another round of storms.
The track of these will push northward well into Nebraska before
clearing the cwa late tonight. Instability parameters are currently
less there at this time, with a bit more cloud cover, but as the
shortwave passes tonight, the additional lift will aid in storm
formation. The Marginal risk area in between the 2 Slight risk zones
could see a few isolated storms traverse the region tonight.
Guidance is mixed for amount/areal coverage but can`t be ruled out.
locally heavy rainfall is possible along with any wind/hail threats.

For the upcoming weekend, upper ridge becomes more dominant over the
Plains region, setting the region up for a mainly dry 48 hr period.
Surface flow on Sunday is mainly northerly through most of the day,
providing a slightly cooler day compared to Saturday. Mixed guidance
for a weak shortwave to ride over the northern periphery of the
upper ridge Sunday night for a possible storm or two.

For temps, highs across the area this weekend will range mainly in
the mid to upper 80s, with a few locales east of Highway 83 around
90F. On Sunday, slightly cooler with upper 70s west into the mid and
upper 80s east. Overnight lows from tonight into Sunday night will
have a slight cooling trend. Looking for mid 50s west to mid 60s
east for tonight, but by Sunday night, a range of only mid to upper
50s.

.LONG TERM...(Monday through Friday)
Issued at 224 PM MDT Fri Jun 23 2023

At the start of the long term period, forecast models show an upper
air ridge over the CWA with an upper air low over the Great Lakes
region and another low over WA/OR on Monday morning. This pattern
looks to stay in place through the rest of the day while an upper
air shortwave disturbance passes through the flow over the CWA
during the evening. On Tuesday, model guidance projects the ridge
axis to pass over the CWA in the morning and turn the upper air flow
more west-southwesterly during the evening when another shortwave
disturbance makes an appearance. For Wednesday, models have a trough
over the western CONUS that makes its way slightly eastward over the
Rockies by the evening hours when a shortwave disturbance passes
over the CWA. For Thursday and Friday, long term models start to
depart in how the project the western trough progresses going
forward with the ECMWF shows a quicker progression than the GFS as
the ECMWF has the axis of the trough passing over the CWA late
Thursday night with the GFS keeping the trough west of the CWA
throughout Thursday and Friday. Will monitor future model runs for
better agreement in the evolution of this trough in the latter parts
of the long term period going forward.

At the surface, models continue to show daily chances for showers
and thunderstorms going through the long term period starting with
the shortwave disturbances seen Monday through Wednesday. On
Thursday, models hint at possible cold front passing through the CWA
though the timing differs due to the upper air pattern differences,
but there may be better chances for precipitation in the CWA
compared to the previous days during the evening because of it. On
Friday, the GFS is showing more widespread precipitation chances
compared the ECMWF during the evening hours as it shows a shortwave
disturbance along with the CWA being underneath an inflection point
in the jetstream. Upon looking at convective parameters for the long
term period, SBCAPE values currently look to be on the low side with
the exception of those on Tuesday. 0-6km bulk shear values look to
be around 30 kts or above on each day. Based on this: Tuesday might
be the best day for possible convection at this point, but will
continue to monitor for this potential going forward. Fire weather
continues to not be a concern for the CWA with minimum RH values
staying above criteria.

For the temperature forecast, the CWA expects daytime highs in the
middle 80s to lower 90s on Monday and Tuesday followed by
Wednesday`s highs in the upper 80s to middle 90s. Thursday`s daytime
highs look to be in the middle 80s to middle 90s while Friday sees
highs in the upper 70s to lower 90s range. Overnight lows for the
first three nights of the long term period range between the upper
50s and middle 60s with the remainder of the period seeing overnight
lows between the middle 50s and middle 60s.

&&

.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
Issued at 536 PM MDT Fri Jun 23 2023

VFR conditions forecast for the TAFs. The main impact will be the
LLWS for both sites tonight. Otherwise am anticipating the storm
activity to remain far enough from either TAF site to not need a
mention.

&&

.GLD WATCHES/WARNINGS/ADVISORIES...
KS...NONE.
CO...NONE.
NE...NONE.
&&

$$

UPDATE...CC
SHORT TERM...JN
LONG TERM...076
AVIATION...JTL



Area Forecast Discussion

National Weather Service Green Bay WI

 1041 PM CDT Fri Jun 23 2023

Updated aviation portion for 06Z TAF issuance

.SHORT TERM...Tonight and Saturday
Issued at 256 PM CDT Fri Jun 23 2023

Precipitation and smoke trends will be the main forecast
concerns, along with temperatures.

Precipitation Trends: Scattered showers and thunderstorms
were ongoing across NC/far NE WI this afternoon, in response to
the arrival of a weak cold front, daytime heating, and SBCAPE of
500-1500 j/kg. Deep layer shear is very weak (5-10 knots), so
storms have been short-lived and not very strong, but inverted-v
soundings support brief gusty winds as the storms collapse. In
addition, PWATs of 1-1.25 inches and the slow movement of the
storms will lead to brief heavy rainfall in localized areas. The
storms will taper off after sunset, with little precipitation
expected overnight into Saturday morning. Additional convection is
expected to fire in far N WI Saturday afternoon, in the vicinity
of the stalled frontal boundary. Most of the precipitation with
the incoming upper trough will stay west of the forecast area
until Saturday night, which makes sense given the blocky pattern
in place.

Smoke trends/impacts: thicker smoke over eastern WI will spread
west later this afternoon into tonight, and eventually cover most
of the forecast area. This may result in minor reductions in
visibility, especially tonight into early Saturday. Made some
adjustments to haze trends and sky cover to account for the
thicker smoke. Air Quality Advisories remain in effect through
late Saturday evening.

Rest of the Forecast: Patchy fog is expected to develop over parts
of NC/far NE WI late tonight, in the shallow cool air mass behind
the frontal boundary, and especially where rain occurs this
afternoon/early evening. Otherwise SCT-BKN cloud cover will
prevail through the period. Lows will fall into the upper 50s and
lower 60s in most locations tonight. Highs on Saturday will be in
the upper 70s to lower 80s lakeside, lower to middle 80s in
northern WI, and upper 80s to lower 90s in C/EC WI.

.LONG TERM...Saturday Night Through Friday
Issued at 256 PM CDT Fri Jun 23 2023

As advertised, a 500mb closed low will move across Wisconsin
Saturday night and Sunday, then east of the state Sunday night
and Monday. 500mb ridging will build into the western Great
Lakes by mid week with the next 500mb trough swinging across
the region Friday into Saturday.

For Saturday night, will start out with smoke/haze concerns. The
latest HRRR smoke forecast has the area improving during the day
Saturday, thus will not have any smoke or haze in the forecast
during the evening. It is interesting the HRRR model takes a
plume of smoke from Ontario and swings it westward across northern
Minnesota, southwest through North Dakota, southward into South
Dakota and then southeast into Iowa at the end the HRRR smoke
forecast period. Pretty much the smoke is being wrapped around
the upper low. As for rainfall trends, there will be some isolated
to scattered convection early in the evening that should wane.
Otherwise, there is some significant differences in the arrival
of the rain from the west. Took a blend of the slower ECMWF/NAM80,
the quicker Canadian/GFS and coordination with surrounding
offices. It is possible the rain may not make into Door County
until after midnight. Rain is expected on and off through the
day. High temperatures somewhat tricky. If there is a steadier
rain through the day, highs my only be in the 60s,, especially
across the north. Just a few breaks in the rain with a few peaks
of the sun could bump temperatures into the 70s across the north.

On Monday into Monday night, showers and a few storms will
continue, with the rain diminishing or ending Monday night.
An unusual gusty wind event for late June is possible
as north/northwest winds are expected at 15 to 25 mph with
a few gusts over 30 mph. A lingering chance of showers on Tuesday
with dry conditions expected most of the day. Dry conditions are
expected Tuesday night and Wednesday. Low temperatures Wednesday
could approach 40 degrees across the north due to the cool dry
Canadian high pressure system. The next system should bring a
chance of rain Thursday into Friday. High temperatures should
return closer to normal by the end of the next work week.

Eckberg.
&&

.AVIATION...for 06Z TAF Issuance
Issued at 1041 PM CDT Fri Jun 23 2023

Smoke will affect the forecast area through much of Saturday. The
smoke will likely mix down to the surface at times and produce
visibilities of 4 to 6 miles. In addition, patchy IFR fog may
develop across northern WI late tonight, especially at locations
that received rain. Otherwise, SCT-BKN mid-level clouds will
cover the region.

Scattered showers are expected to dissipate overnight over central
and north-central Wisconsin with more showers and storms developing
near the frontal boundary in far northern Wisconsin Saturday
afternoon. A push of steadier showers and thunderstorms will track
through the area Saturday night as a low pressure system
approaches the western Great Lakes region.
&&

.GRB WATCHES/WARNINGS/ADVISORIES...
None.
&&

$$

SHORT TERM.....Kieckbusch
LONG TERM......Eckberg
AVIATION.......Kurimski



Area Forecast Discussion...Updated

National Weather Service Lincoln IL

 817 PM CDT Fri Jun 23 2023

.SYNOPSIS...
Issued at 817 PM CDT Fri Jun 23 2023

Hot and dry conditions will prevail during the daytime hours of
Saturday. Shower and storm chances increase Saturday night into
Sunday as a weather system pushes a cold front through the area. A
few strong to severe storms will be possible at times over west-
central IL late Saturday night and over eastern and southeast IL
Sunday afternoon.

&&

.UPDATE...
Issued at 817 PM CDT Fri Jun 23 2023

Forecast is on track this evening with no significant changes
needed. High pressure will settle across central Illinois
overnight resulting in light and variable or calm winds. Temps
are expected to fall into the lower to mid 60s under mostly clear
skies.

Deubelbeiss

&&

.DISCUSSION...
Issued at 321 PM CDT Fri Jun 23 2023

Forecast highlights:

1) A MCS will bring a broken line of thunderstorms to the area late
Saturday night into early Sunday morning (8 pm to 3 am). A few of
the storms could be strong to severe posing a threat for damaging
winds west of I-55. Additional thunderstorm development will be
possible across eastern and southeast IL Sunday afternoon, once
again posing a threat for severe storms.

2) Breezy northwest winds will develop behind the frontal passage
late Sunday afternoon into Monday, bringing gusts upwards of 30-35
mph.

An upper-level low continues to lift into the eastern Great Lakes
Region as a ridge of high pressure centered over the eastern Plains
states approaches from the west. Mid-level moisture associated with
the upper low has allowed diurnal cumulus to develop this afternoon.
A few widely scattered showers may form in eastern IL over the next
few hours, but chances of this occuring in a given location is less
than 15%.

Higher concentrations of elevated wildfire smoke originating from
Quebec is working into the region this afternoon, creating a
hazy/milky look to the sky. The HRRR and RAP smoke model shows small
amounts of smoke possibly mixing down to the surface through this
evening, but it shouldn`t lead to any reductions to surface
visibilities.

Upper ridging will become situated overhead on Saturday as a
shortwave trough works through the northern Plains states. Surface
flow will become southerly to start the weekend, which will pump in
much warmer temperatures and eventually higher dewpoints for the
weekend. High temperatures on Saturday will be unseasonably warm
with values in the low to middle 90s. Attention then turns to
Saturday night when a decaying MCS approaches from the northwest.
Instability and shear doesn`t appear to be particularly strong, but
should be favorable enough to sustain a few organized storms capable
of damaging wind gusts late Saturday night into the early morning
hours of Sunday. CAMs show the line of thunderstorms becoming very
broken as it moves through the area, eventually pushing into Indiana
prior to 12Z Sunday.

The aforementioned shortwave trough will work into the western Great
Lakes Region going into Sunday. At the surface, a cold front will
work through the area positioning itself near the IL River Valley
Sunday morning. Temperatures will once again be unseasonably warm on
Sunday though locations west of the front should be in the middle to
upper 80s. Much higher dewpoints spread northward as well, reaching
the 60s to even low 70s in southeast IL by the afternoon hours. This
will send heat indices into the upper 90s to near 100 in southeast
IL by the afternoon. Strong instability is expected to build over
eastern/southeast parts of the state with SBCAPE values possibly
exceeding 2000+ J/kg. A 60 kt mid-level jet rounding the base of the
upper trough will increase shear with 0-6 km bulk values expected to
be around 40 kts by Sunday afternoon. Forecast soundings show a
capping inversion will be present much of the day on Sunday with
locations near and east of I-57 being the most likely to break the
CAP by mid afternoon. There still remains some differences and
uncertainty on what will be the forcing mechanism for new storm
development (cold front vs. outflow boundary). With that being said,
there are still some timing differences with the cold front passage.
The GFS and ECMWF are the faster solutions with the NAM being a
slower outlier. A faster frontal passage could mean new storm
development may be just outside of our area on Sunday afternoon.

Rainfall totals through Monday morning still look to be around 0.25"
or so, though slightly higher amounts will be possible within any
thunderstorms, especially over northwest IL where the line of storms
will be more organized before breaking apart Saturday night. In
fact, the 23.12Z LREF Grand Ensemble (CMC, GEFS, EPS) has shown an
increase in precipitation probabilities especially over northern
parts of the the CWA. There is now a 20-40% chance of 0.50" (highest
north of I-74), a 40-70% chance of 0.25", and a 70-90% chance of at
least 0.10".

Breezy northwest winds develop behind the front Sunday afternoon
into Monday, with gusts approaching 30-35 mph at times. Upper
ridging builds over the Plains states early next week as northwest
flow sets up aloft here. The upper trough that will bring our
weekend storms will get kicked into the eastern Great Lakes Region
as  it becomes vertically stacked with the surface low. A few bits
of energy rotating along the western fringes of the system may
support occasional chances (20-50%) for showers and storms Monday
and possibly Tuesday, but additional precipitation amounts will
be pretty minimal. The upper ridge over the Plains states will
get shunted east by the middle to end of the new week as a
longwave trough moves onshore the western CONUS. Flow aloft will
transition to more zonal/low meridional as the ridge breaks down,
which would open the door for more shortwaves/weather systems to
work through the area by the end of next week into next weekend.

NMA

&&

.AVIATION...  (For the 00z TAFs through 00z Saturday Evening)
Issued at 645 PM CDT Fri Jun 23 2023

A weak ridge of high pressure is in place along the Mississippi
River Valley this evening and will gradually shift east across
Illinois while low pressure takes shape over the Great Plains
late tonight into Saturday. Light northerly winds in place
currently will become variable overnight with passage of the ridge
axis, then set up out of the S/SW during the day Saturday. VFR
conditions should prevail through the period, but couldn`t rule
out some smoky conditions settling south from northern Illinois
reducing vsby.

Deubelbeiss

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
None.
&&

$$



Area Forecast Discussion

National Weather Service Louisville KY

 715 PM EDT Fri Jun 23 2023

...Updated Aviation Discussion...

.Short Term...(This evening through Saturday)
Issued at 300 PM EDT Fri Jun 23 2023

The upper low which has lingered across the eastern one-third of the
CONUS over most of this past week is evident on latest WV imagery
centered over Lake Erie and NE Ohio. Tonight, this feature will
continue to gradually pivot northeastward, with NE flow aloft and
high pressure at the sfc over the TN valley contributing to the
development of mostly clear skies and light winds across the region.
With enough near-sfc moisture remaining in place, patchy fog is
expected after midnight tonight, especially in river valleys and
other sheltered locations. Low temperatures should settle into the
low-to-mid 60s by sunrise tomorrow, with a few upper 50s possible in
cooler outlying areas.

Tomorrow should see a return to much more typical summertime weather
as ridging attempts to build across the Mississippi Valley.
Increasing sfc-850 mb thicknesses will lead to considerably warmer
temperatures Saturday afternoon, with H85 temps 6-7 deg C warmer
than this afternoon. Accordingly, will go 10-12 degrees warmer
across the board tomorrow afternoon, which produces highs in the
upper 80s and lower 90s. Slightly greater low-level moisture across
the KY Bluegrass and Lake Cumberland regions will foster the
development of a diurnal cu field as well as isolated showers and
thunderstorms tomorrow afternoon, though these will largely be
confined to Eastern KY. Nevertheless, will include a slight chance
PoP along and east of I-75, and temperatures will likely only reach
the mid-80s given the additional cloud cover. One additional thing
not included in the forecast to watch out for is the return of
somewhat hazy conditions. Latest HRRR and RAP smoke guidance suggest
that a diffuse plume of smoke may try to overspread the region
tomorrow afternoon from NNW to SSE. Forecast smoke concentrations
are lower than a week ago, an upstream obs over Wisconsin and
Illinois this afternoon are generally 7 miles or greater.

.Long Term...(Saturday night through Friday)
Issued at 315 PM EDT Thu Jun 22 2023

...Strong to Severe Storms Possible Sunday...

Key Messages

* A couple waves of showers and storms will be possible Sunday,
  first wave in the morning with the second wave in the late
  afternoon to evening
* Best chances for strong to severe storms will be with the second
  wave in the late afternoon and evening
* All severe hazards on the table, with damaging winds being the
  greatest threat

Saturday Night - Sunday...

At the start of the extended period, upper low will be pushing into
the Upper Midwest then slowly moving through the Upper Great Lakes
Region. An associated surface low will push through MN/WI and send a
surface cold front through the mid MS Valley into the OH Valley late
Sunday into Monday. Expect to see a couple waves of showers and
storms ahead of and along the system, with some of the storms
potentially becoming strong to severe.

The first wave of showers and storms will come Sunday morning,
potentially continuing into the early afternoon across east-central
KY. Still a fair amount of uncertainty with even this first wave,
with model guidance indicating the potential for an MCS or line of
showers/storms to move through the area. Depending on storm mode and
timing of this first wave, some stronger storms may be able to
develop, but confidence remains low. Gusty winds would be the main
threat.

Evolution of the first wave of precip will impact the rest of the
day, with uncertainty around the degree of clearing and potential
for residual boundaries as we move into the afternoon. In general,
expect a lull in activity before storm chances increase by late
afternoon into early evening with peak heating. Model soundings
indicate temperatures warming into the mid 80s to lower 90s with
dewpoints in the upper 60s and lower 70s. This would result in
moderate to strong destabilization across the area with SBCAPE in
the 2500-3500+ J/kg range. Additionally, expect sufficient shear to
be in place, with Effective Bulk Shear values of 35-45+ kts. Ahead
of and along the cold front, strong to severe storms are possible
with the main threats being damaging winds and hail, although a
tornado or two cannot be ruled out. Timing still remains a big
question mark, but in general expect the severe threat to wind down
as we move into Sunday night.

Monday - Friday...

The stacked low will gradually wobble through Michigan into the
Lower Great Lakes Monday and Tuesday before eventually lifting
across the Northeast through the end of the week. As mid-level
energy rotates around the low pressure, will likely see some showers
and storms pass through the area Monday into Tuesday. Dry weather is
then expected by Wednesday as the low moves out of the area and
ridging builds in from the west. Uncertainty increases for the end
of the week, but for now will have chance PoPs Thu/Fri as a couple
of disturbances rotating through the periphery of the ridge may
bring showers and storms to the area.

Temperatures are expected to be in the upper 70s to mid 80s Mon-Wed
before gradually warming for the end of the week into the upper 80s
and lower 90s.

&&

.Aviation...(00Z TAF Issuance)
Issued at 715 PM EDT Fri Jun 23 2023

Isolated to scattered light showers will come to an end over the
next couple of hours as the sun sets and give way to dry conditions
overnight. Clouds will also gradually clear or partially clear out
overnight and with light winds and fairly moist soils/ground in
place, we could see some fog develop toward sunrise. Best chances
for fog will be toward KLEX, but KBWG/KHNB may have some patchy fog
as well.

Any morning fog should quickly burn off after sunrise. Light winds
and mostly clear skies are expected going into Saturday.

&&

.LMK WATCHES/WARNINGS/ADVISORIES...
IN...None.
KY...None.
&&

$$

Short Term...CSG
Long Term...JML
Aviation...DM



Area Forecast Discussion

National Weather Service Marquette MI

 1015 PM EDT Fri Jun 23 2023

.UPDATE...
Issued at 1015 PM EDT FRI JUN 23 2023

With the sunset update, only some isolated showers and rumbles of
thunder remain across the far western UP. A weakening MCS currently
heading into northern MN may scrape the western UP with more showers
and rumbles of thunder late tonight into the pre-dawn hours of
Saturday, but current radar trends indicate that much of this may
stay out over Lake Superior. Even the CAMS, which typically seem
enthusiastic to bring in more precipitation, largely have us missing
out on additional rain chances for tonight.

Otherwise, temperatures are already dropping into the upper 60s
across most of the area, and seem in good shape to bottom out in the
lower to mid 50s area-wide while more clouds fill in across the
western half of the UP.
&&

.SHORT TERM...(This evening through Saturday)
Issued at 259 PM EDT FRI JUN 23 2023

An upper level low over the eastern CONUS is lifting north into the
Lower Great Lakes today, weakening the ridge aloft. In junction with
diurnal heating and a Lake Superior lake breeze, a subtle shortwave
and associated weak surface cold front is helping initiate
convection in the central UP and interior west UP this afternoon.
SPC RAP Mesoanalysis shows a region of 2,000 J/kg of SBCAPE in the
central to western UP, helping give updrafts plenty of strength for
lightning. PWAT values increasing to an inch to 1.25 inches are
allowing for some occasional torrential downpours, though recent dry
weather and lack of strong synoptic forcing is keeping any flash
flood considerations at bay. With sufficient lift and moisture and
plentiful instability, the only missing piece is shear, of which
there is virtually none. Most model soundings have less than 10
knots of flow in any layer of the atmosphere below 350mb. Therefore,
updrafts are struggling to maintain themselves and the first
thunderstorm of the day displayed a near-perfectly symmetrical
outflow boundary and divergent velocity signature at the lowest
tilt. Expecting "popcorn" thunderstorms to continue this afternoon
with little to no severe potential.

Tonight, in the wake of the front and post-convection, fog is
expected to form for the interior locations of the central and
eastern UP. Additionally, visibility may further be hampered in the
west by the arrival of a fairly dense smoke plume from fires in
northwestern Ontario. In a post-frontal nocturnal environment, a
fair amount of the smoke could be trapped in the surface layer,
potentially creating unhealthy conditions for sensitive groups.
Precipitation chances rise once again late in the short term period
ahead of a 1003 mb low in South Dakota by 12Z Saturday per the 12Z
GEFS, though QPF will be fairly limited.

.LONG TERM...(Saturday through Friday)
Issued at 330 PM EDT FRI JUN 23 2023

Upper air pattern consists of a 500 mb closed low in the northern
plains 12z Sat which moves into the upper Great Lakes on Sun and
into the lower Great Lakes on Mon. There will be a slow progression
of pops to the east this forecast period with the highest pops
coming in Sunday night. This is handled well by the going forecast
and did not make too many changes to the going forecast.

In the extended, the GFS and ECMWF show a 500 mb closed low and
trough over the lower Great Lakes 12z Tue with a trough in the
western U.S. and a ridge across the plains. Pattern changes little
through 12z Fri with a sfc front just to the south of the area.
Temperatures will be below normal for this forecast period. Pcpn
looks to hang on into Tue and then dry for Wed before some low pops
in for late Wed night into Thu with low chance pops in for Fri as a
warm front approaches from the south.
&&

.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
Issued at 824 PM EDT FRI JUN 23 2023

VFR conditions will continue at all sites through this evening. Fog
development tonight likely will being IFR vis to all TAF sites after
midnight, with some potential for CMX to drop to lower vis. Vis may
also be degraded from Canadian wildfire smoke originating in
northwest Ontario, but certainty is low on the exact degree of
impact it will have on vis. Tomorrow morning, an approaching
disturbance will bring rainshowers to the vicinity of IWD and CMX
with possible showers and storms developing near all sites tomorrow
afternoon, however confidence remains low to include TS at this time.
&&

.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 330 PM EDT FRI JUN 23 2023

Expect winds below 20 knots through Saturday morning, increasing to
25 knots over western Lake Superior out of the northeast by Saturday
afternoon.  As a system moves across the lake over the weekend,
widespread 20 to 30 knot winds out of the east will also impact
central and eastern portions of the lake.  Winds will eventually
back to the north Monday and Tuesday.  After that, winds will fall
below 20 kts through the remainder of the week. Thunderstorms are
possible especially across the western part of the lake through most
of this forecast period.
&&

.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
None.
Lake Superior...
  Dense Fog Advisory until 10 AM EDT /9 AM CDT/ Saturday for
     LSZ162.

Lake Michigan...
None.
&&

$$

UPDATE...LC
SHORT TERM...GS
LONG TERM...07
AVIATION...Jablonski
MARINE...07



Area Forecast Discussion

National Weather Service Portland OR

 300 PM PDT Fri Jun 23 2023

.SYNOPSIS...Onshore flow is expected Saturday through Thursday with
mainly dry weather and seasonable to slightly above average
temperatures.

&&

.SHORT TERM...Friday afternoon through Saturday night...At 245 PM PDT
Friday, satellite and radar observations showed isolated showers and
thunderstorms beginning to develop over the south WA/north OR
Cascades and the north OR Coast Range. This is generally on track
with what hi-res models have been suggesting for over 24 hours now.
This helps boost confidence for additional showers and thunderstorms
later Friday afternoon into the early evening hours. There is now a
15-30% chance of thunderstorms over the northern Willamette Valley
into Clark County, as well as over the Columbia River Gorge and south
WA/north OR Cascades and foothills. It appears the cells currently
anchored over the higher terrain of the coast range will not move
much until the diurnal sea breeze pushes far enough inland to
interact with these cells. This is likely why the HRRR does not
simulate any convection over the Portland metro until 5-6 PM. Not
expecting any severe storms given the very weak environmental shear
in place, however there is more than enough instability to suggest
small hail will occur with the strongest cells. Expect any showers or
thunderstorms lingering Friday evening to quickly diminish by
approximately 7 PM with the loss of daytime heating.

Similar to Friday morning, expect marine stratus at the coast to push
into the Eugene area Saturday morning, as well as down the lower
Columbia towards Woodland. The rest of the Willamette Valley will
most likely remain clear, however the HREF does show a 10-30% chance
of low cloud cover over the northern and central Willamette Valley.
Forecast NAM soundings continue to suggest the marine layer will be
deep enough to support patchy light drizzle along the south WA/north
OR coast from roughly 3-10 AM Saturday. Decided to increase NBM PoPs
to 15% along the north coast to ensure patchy light drizzle is
mentioned in the forecast. Expect high temperatures will be very
similar on Saturday when compared to Friday, with highs in the upper
70s to lower 80s inland and upper 50s to mid 60s at the coast.-TK


.LONG TERM...Sunday morning through Thursday night...On Sunday, the
GEFS/EPS/CMC ensemble means continue to show a weak ridge over the
far northeast Pacific with very weak northerly flow over northwest OR
and southwest WA. The aforementioned ridge then flattens out Sunday
night into Monday while weak flow remains in place over the Pacific
Northwest. The 500 mb flow regime then becomes more westerly Tuesday
into Wednesday, albeit still very weak. At the surface, varying
degrees of onshore flow are evident. Overall, there is not much to
latch onto in regards to the synoptic scale pattern throughout the
long term forecast. Expect this benign setup will maintain dry and
seasonable weather across the area, with high temperatures mainly in
the low 80s inland and 60s at the coast.

Expect somewhat breezy west to northwest winds in the late afternoon
each day as the diurnal sea breeze pushes inland, with the strongest
winds occurring downwind of the coast range gaps. It is also worth
mentioning that the marine layer will likely be deep enough to
support patchy light drizzle along the coast during the morning hours
each day, especially north of Tillamook. NBM PoPs are picking up on
this potential, and only minor adjustments were needed to ensure the
coast has a mention of drizzle in the forecast. On Thursday, about
66% of members from the WPC cluster analysis hint at ridging building
in the PacNW, which could result in warmer temperatures. The NBM is
showing a 10-25% chance of inland high temperatures above 90 degrees
on Thursday while the chance of highs above 100 degrees is at only
0-1%.  -TK/Alviz

&&

.AVIATION...High pres remains anchored offshore through Friday.
This will maintain persist marine stratus along the coast, with
CIGS 0700 to 1200 ft, though CIGS will lower a bit overnight.

Farther inland, weak disturbance moving across region will combine
with some mid-level moisture and instability this afternoon. As
such, will have scattered showers and a few thunderstorms over
the Cascades, perhaps as far west as the interior lowlands of
Clark County and north Willamette Valley (affecting KPDX and
KTTD, perhaps KUAO) for through early this evening. Otherwise,
mostly clear tonight again, with areas of stratus spreading over
more of the region later tonight into early Sat.

For detailed Pac NW aviation weather information, go online to:
http://weather.gov/zse

KPDX AND APPROACHES...VFR  today and tonight. But, do have enough
instability and moisture aloft to support a few showers or
thunderstorms in/around KPDX and eastward for late this afternoon
into early evening. Probability of such at KPDX still low
(15-25%), but much higher (80% or higher) over the Cascades and
foothills through 9 pm this evening.  /Rockey

&&

.MARINE...Little change, as high pressure remains anchored
offshore. Thermal low pressure will remain over far south Oregon
coast into northwest Calif. As such, gradients not all that
strong, with winds 10 to 15 kt. May have some gusts to 20 kt in
the afternoons/evenings this weekend. Seas generally stay in the 2
to 5 ft range.

&&

.PQR WATCHES/WARNINGS/ADVISORIES...

OR...None.
WA...None.
PZ...None.

&&

$$

www.weather.gov/portland

Interact with us via social media:
www.facebook.com/NWSPortland
www.twitter.com/NWSPortland