Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 05/15/23

in the forecast discussion today.



 Once the cold front and upper low move through cooler air will be
in place for later this week. In fact, with the growing season
officially starting tomorrow (Monday, May 15th), those cooler
temperatures will be something to monitor as we move later into
the week. Based of the latest NBM, the probabilities for
temperatures falling below freezing in western parts of the state
are generally in the 15 to 25 percent range for Thursday night /
Friday morning.

&&

.AVIATION...(For the 00Z TAFS through 00Z Monday Evening)
Issued at 626 PM CDT Sun May 14 2023

VFR conditions will prevail through the forecast period.


&&

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

$$

UPDATE...JJS
SHORT TERM...King
LONG TERM...King
AVIATION...JJS



Area Forecast Discussion

National Weather Service Columbia SC

 809 PM EDT Sun May 14 2023

.SYNOPSIS...
A series of disturbances will move over the region through the
end of the week with more summer like weather pattern expected
with daily afternoon showers and thunderstorms possible.

&&

.NEAR TERM /UNTIL 6 AM MONDAY MORNING/...
Lingering showers and isolated thunderstorms continue along a
back door frontal boundary that currently stretches from the
coastal plain up into the CSRA, with some additional activity
near the mountains. Will expect the activity to continue to
drift south and mostly dissipate later this evening, although
latest HRRR indicates some of the shower activity to the north
could possibly hold together and slip into our northern counties
later tonight.

&&

.SHORT TERM /6 AM MONDAY MORNING THROUGH TUESDAY NIGHT/...
Monday and Monday night: Appears as if guidance is trending
towards a drier day across most of the forecast area through
Monday night. Front will be across the southern counties,
possibly even south of the cwa, to start off the day. At best,
the southern Midlands and CSRA may see isolated showers from the
morning into the afternoon, while drier air settles into the
northern half of the area through the day. This drier air will
try to push further southward into Monday night, but may stall
out across the central Midlands. Most of Monday night will be
dry, with best rain chances shifting more towards the upstate of
SC. Temperatures will remain tricky, depending upon overall
cloud cover and amount of drier/cooler air that can move into
the northern counties. Still expect temperatures to be in the
upper 70s to lower 80s.

Tuesday and Tuesday night: The upper pattern will begin to
flatten out somewhat, becoming more westerly through Tuesday
night. This is in response to a digging upper trough that will
be moving towards the region Tuesday night. As low-level winds
turn more southerly again, moisture and the front south of the
area will begin to return back towards the north through the
day. There should be more coverage for showers and storms during
the afternoon and evening hours, with a low severe threat.
Temperatures bounce back once again into the mid to upper 80s
for Tuesday afternoon, while the overnight hours will be mild as
temperatures drop into the middle 60s.

&&

.LONG TERM /WEDNESDAY THROUGH SUNDAY/...
Plenty of uncertainty in the longer term in regards to timing of
upper shortwaves, and surface fronts, as they traverse through
the area. For the most part, upper trough remains over the area
through Thursday, then a deeper upper low moves Friday into the
weekend. In general, will keep chances of rain in the forecast
through much of this period, continuing with more diurnal
activity. As for temperatures, kept mostly with NBM numbers
through the period.

&&

.AVIATION /00Z MONDAY THROUGH FRIDAY/...
VFR conditions for much of the period with restrictions possible
during the early morning and sunrise hours.

Weak frontal boundary continues to slide southward through the
terminals with showers along the boundary. Overnight the
boundary will continue slowly sliding southward with potential
for some stratus and fog to develop. With rain occurring much
earlier this afternoon at CAE/CUB much of the moisture has mixed
out while at OGB/AGS/DNL higher amounts of rain later this
afternoon and evening will create a different scenario. As such
have included some MVFR cigs at AGS/DNL/OGB and will continue to
monitor rain with lower cigs and vsbys likely with future
issuances. Potential for restrictions too low to include for
CAE/CUB as slightly drier air will be moving into the area
overnight. Conditions will return to VFR by 14z with some
potential for showers at AGS/DNL Monday afternoon however the
potential is too low to include attm.

EXTENDED AVIATION OUTLOOK...Scattered afternoon thunderstorms
possible each day mainly during the afternoon and evening hours.
With abundant low level moisture in place, fog and stratus
possible during the early morning and sunrise hours each
morning.

&&

.CAE WATCHES/WARNINGS/ADVISORIES...
GA...None.
SC...None.

&&

$$



Area Forecast Discussion

National Weather Service Grand Junction CO

 545 PM MDT Sun May 14 2023

.SHORT TERM...(Tonight through Monday night)
Issued at 320 PM MDT Sun May 14 2023

GOES East water vapor imagery shows a pronounced mid-level low
pressure spinning over northern Nevada this afternoon. To the east
of this feature, southerly flow across eastern Utah and western
Colorado is supplying a tap of sub-tropical moisture...
characterized by precipitable water values roughly 100 to 200
percent of climatological normals. Meanwhile, partial sunshine has
contributed to strong surface heating this afternoon. Combined
with the moist air mass in place, 500 to 1000+ j/kg of surface
based CAPE has developed which is a clear indicator of boundary
layer destabilization. The CWA lies a little too far to the east
of the low and the resulting wind shear for any meaningful severe
convection, but very favorable low and mid-level lapse rates
exceeding 8-9 C/km and at least a little flow aloft will make for
an environment that is conducive to scattered pulse storms. These
storms will be capable of producing brief moderate to heavy rain,
gusty winds, and small hail. The HRRR and the NAMNEST have done a
good job highlighting this potential so leaned on those pieces of
guidance heavily with this package. As has been the case for the
past several days, the higher terrain will have the highest odds
of seeing the most robust shower and storm activity, though the
adjacent valleys won`t be totally out of the clear either.

After the sun sets and surface heating wanes, shower and storm
activity will gradually diminish for most of the region overnight.
The one exception may be across southwest Colorado and the San
Juans where a trailing vort max passing through may keep showers
going past midnight and into the pre-dawn hours. Despite the wave,
large scale forcing will be weakening as the low over Nevada
moves farther away. Thus, wouldn`t expect much more than light to
moderate rain showers and occasional rumbles of thunder with this
lingering activity.

Strengthening high pressure over the southern Four Corners states
and the diminishing influence of the low spinning far to our
northwest will shift the prevailing flow from southerly to
westerly and eventually northwesterly as the day progresses on
Monday. This changing wind direction should cut off the flow of
moisture into the forecast area, but with nothing to really flush
out the moisture already in place yet, we`ll be dealing with
another day of scattered afternoon showers and thunderstorms.
Similar to before, convection will first fire along the higher
terrain before drifting into the adjacent valleys later on. Once
again, the main threats will be brief heavy rain, gusty winds, and
small hail. Showers and storms will dissipate after sunset and
give way to a quiet Monday night.

Given clouds and precipitation around the next couple of days,
temperatures will generally be near or just below seasonal
averages during the day, and near to above seasonal averages at
night.

.LONG TERM...(Tuesday through Sunday)
Issued at 320 PM MDT Sun May 14 2023

Shortwave energy will eject out of the previously retrograding
low over the Pacific Northwest as it gets pinched by a Rex Block
high over British Columbia and a ridge of high pressure trying to
build in across the Four Corners. Meanwhile, a cut off low over
the Baja will try to draw sub-tropical moisture northward through
the Desert Southwest. This is a complicated setup but in terms of
meaningful weather for our CWA, we will basically be stuck between
these features on Tuesday and Wednesday with a zonal flow
overhead. Drier air will try to work in from the north which will
result in a reduction in precipitable water values with the best
moisture residing near the Four Corners as residual moisture
becomes trapped under this high. There looks to be a downturn in
storm coverage Tuesday and Wednesday compared to previous days
with best chances across the south, favoring the high terrain
where the better moisture resides. Elsewhere, expect partly sunny
skies and high temperatures about 5 to 10 degrees above normal.

A more active period with more widespread coverage of storms
looks to be in store Thursday through the coming weekend as a more
robust trough drops in from the northwest, breaking that Rex
Block high, and driving several shortwaves through the area from
Thursday through the coming weekend. Regardless of more or less
moisture and amount of forcing through this coming week, it looks
to remain fairly unsettled with best chances of widespread storms
late in the week. This warm up in temperatures in addition to
potential for moderate to heavy rainfall with storms could lead to
accelerated snow melt or at least an increase in flows on the
rivers as indicated by some river forecasts. So, this will have to
be monitored through the week.

&&

.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
Issued at 536 PM MDT Sun May 14 2023

VFR conditions will prevail for most areas the evening with VCSH
or VCTS at many TAF sites this evening. Isolated to scattered
showers and thunderstorms continue through about 03Z in the lower
elevations and through about 06Z in the mountains with gusts to 35
kts, brief light to moderate rain with possible small hail and
lower ceilings. Look for quiet weather overnight and scattered
showers and thunderstorms to return again by about 18Z Monday.
Coverage will be slightly less than today.

&&

.GJT WATCHES/WARNINGS/ADVISORIES...
CO...None.
UT...None.
&&

$$

SHORT TERM...MDM
LONG TERM...MDA
AVIATION...DB



Area Forecast Discussion

National Weather Service North Platte NE

 632 PM CDT Sun May 14 2023

...Updated Aviation Discussion...

.SYNOPSIS...
Issued at 204 PM CDT Sun May 14 2023

Key Messages:

- Dreary conditions continue through Monday morning with mild
temperatures expected.

- Temperatures climb back into the at or above normal range by the
middle of the week.

- Isolated rain showers with a few rumbles of thunder are possible
  Tuesday afternoon/evening for areas primarily west of Highway
  61.

- A system will cross the area Wednesday bringing increased chances
for scattered showers and thunderstorms to the area for Wednesday
and Thursday.

Recent GOES-16 WV and RAP 500-mb analysis showed a broad ridge of
high pressure across the southeastern CONUS. Further northwest of
this feature, an upper-level low pressure system was retrograding
from northern Nevada into the PNW. Just south of this feature, an
upper-level shortwave was apparent across the Baja Peninsula into
portions of western Mexico. An upper-level ridge of high pressure
has continued to hold strong across Alberta, encompassing much of
the Canadian Provinces. Closer to home, a weakening low pressure
system has stalled out across portions of the northern Plains into
the Midwest. At the surface, associated low pressure was noted
across far northwest Missouri with two stationary fronts
accompanying it. One is extending southwest across the southern
Plains while the other is extending northeast across the Mid-
Mississippi Valley. Broad surface high pressure was noted across
much of Canada, pushing south into portions of the northern
Plains. A moisture plume surging north out of the Gulf of Mexico
was evident and ample low-level moisture continuing on the
backside of the weakening low pressure system. This has resulted
in a dreary and breezy day with the entire area encompassed by
low-level clouds with areas of light rain showers and drizzle
developing across portions of the Sandhills into north central
Nebraska. As of 2 PM CT, temperatures ranged from 50 degrees at
Gordon to 57 degrees at Imperial.

&&

.SHORT TERM...(This evening through Monday night)
Issued at 204 PM CDT Sun May 14 2023

The aforementioned system currently impacting the region takes
it`s time to exit resulting in persistent light rain
showers/drizzle tonight into Monday morning. Deep layer moisture
continues into Monday which is depicted by NAEFS and ENS ensemble
guidance continuing to suggest that the mean PWAT will meet or
exceed the 99th percentile across much of the area. These rain
showers/drizzle will taper off through the late morning/early
afternoon on Monday as the previously mentioned Canadian surface
high pressure pushes further south into the High Plains. Total
rainfall amounts will be much less than the area has seen the past
few days of only a tenth of an inch to near three tenths of an
inch. Subsidence behind the system will lead to gradually
clearing skies Monday evening into Monday night.

In regards to temperatures, overnight lows Sunday and Monday will be
in the above normal range in the 40s and 50s. Mild daytime highs in
the upper 50s to low 60s is forecast for Monday.

.LONG TERM...(Tuesday through Sunday)
Issued at 204 PM CDT Sun May 14 2023

Isolated rain showers with a few rumbles of thunder are possible
Tuesday afternoon and evening for areas primarily west of Highway
61. Meager MLCAPE values nearing 500 J/kg and mid-level lapse rates
approaching 7 C/km will likely result in rumbles of thunder across
the area. The severe potential remains low given the lack of forcing
for ascent with minimal rainfall amounts anticipated of a trace to
maybe a few hundreths of an inch.

Warm temperatures return for a brief period on Tuesday and Wednesday
with highs climbing into the upper 70s to low 80s across the region.
These temperatures are 5 to 10 degrees above the climatological
normal for the middle of May.

The main focus in the long term period surrounds the potential for
scattered showers and thunderstorms impacting the region Wednesday
into Thursday as a northern stream trough tracks southeast into the
far northern Plains. Model solutions continue to suggest isolated
severe thunderstorms possible across the Panhandle into portions of
the western Sandhills Wednesday afternoon and evening. Long range
model solutions continue to signal an increase in instability and
shear across those areas, however, weak flow aloft may limit the
potential for any organized storm. As the low advances across the
Upper Midwest, an accompanying cold front will track south across
the region resulting in increased frontogenetical forcing along
and behind the FROPA. This will result in increased precipitation
chances again during the day on Thursday. However, meager
instability should limit any severe potential for Thursday, though
rumbles of thunder cannot be ruled out. Given that this is in the
Day 4 and Day 5 range, cannot hone in on exact details, however,
this will be the time period to keep an eye on in the coming days.

Beyond Thursday, the Canadian cold front will sweep across the area
with surface high pressure building in behind it. Somewhat "cooler"
temperatures are anticipated on Friday before climbing back into the
well-above normal range into the weekend.

&&

.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
Issued at 631 PM CDT Sun May 14 2023

Few showers located across northern zones heading southwestward
with most areas seeing a VSBY restriction in the SHRA of 3-5SM
along with MVFR to IFR CIGS. Would expect the showers to drift
south through the evening and although won`t amount to much
precip, will reduce VSBYs somewhat and trend toward IFR to LIFR
conditions as the showers end and areas of fog develop. Would
expect any fog to develop first over the north central areas and
have introduced lower VSBY with this TAF cycle at KVTN, then KLBF
toward daybreak. Have used the NBM VSBYs as it best aligns with
somewhere between the 10th and 25th percentiles of HREF VSBYs
which seemed to handle the idea best.

&&

.LBF WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

SYNOPSIS...Viken
SHORT TERM...Viken
LONG TERM...Viken
AVIATION...Stoppkotte



Area Forecast Discussion

National Weather Service Louisville KY

 944 PM EDT Sun May 14 2023

.Forecast Update...
Issued at 944 PM EDT Sun May 14 2023

A broad surface boundary stretches roughly from Owensboro to
Tompkinsville this evening, and will drift slowly southwestward to
around an Evansville-Bowling Green line by morning. The best
convective chances overnight will be west of this boundary in an air
mass of greater moisture and instability. The vigorous convection
from southern Illinois into western Kentucky this evening will slide
to the southeast, but has already shown signs over the past hour of
becoming less organized and weaker. The convection should continue
to weaken as instability wanes overnight, but we still may see some
showers and a few thunderstorms tonight west of I-65. The most
likely region to see a stronger storm is west of the Natcher Parkway.

&&

.Short Term...(This evening through Monday)
Issued at 222 PM EDT Sun May 14 2023

Current (18z) surface analysis reveals a weak NW to SE oriented
frontal boundary across the region. While the temperature gradient
near the frontal boundary is fairly weak, there is about a 10 degree
F dewpoint spread between our southwest CWA (low 70s dewpoints) to
the northeast CWA (low 60s dewpoints). It is slowly but steadily
advancing southwestward. The boundary has become fairly evident on
satellite imagery over the last few hours, as a strato-cu field has
developed generally within the warm sector of the boundary in the
higher low-level Td air. The higher dewpoints have also aided in
destabilization of the atmosphere, and while little to no CIN exists
within the warm sector, the convergence along the frontal boundary
appears to be too weak to help initiate any convection at this time
as visible satellite imagery shows a `flat` cumulus field.

Areas north and east of the boundary ("cool" side) should stay dry
through the remainder of the day. Conversely, most folks will likely
stay dry on the other side (warm sector) within the region, though
we could see very localized showers or storms initiate near or on
the boundary late this afternoon into the early evening hours. Some
of the latest HRRR runs suggest this, mainly toward the vicinity of
the BWG area points westward. A more organized convective threat
will develop out west (Missouri, Illinois), and eventually dive
southeast into Kentucky, but it may not be until well after sunset
that we`d have any shot of seeing showers/storms in our neck of the
woods. Current forecast highlights the "best" (~20%) chance for
showers/storms mainly west of I-65 and south of I-64 overnight into
early tomorrow morning. A couple of the storms could be strong,
possibly marginally severe, if they arrive in our CWA, though the
overall severe threat would be very low. Gusty winds and small hail
would be the main threats with any stronger storm.

Light showers may move in from the north a little before dawn Monday
and could persist through the morning and afternoon hours, though
overall coverage should be isolated to scattered at best. Additional
storm development is possible near the TN border where some
lingering instability could fuel a few storms. Highs Monday will be
a tad cooler in the post-frontal airmass with clouds, ranging from
low 70s in southern IN to low 80s in southern KY.

.Long Term...(Monday night through Sunday)
Issued at 320 PM EDT Sun May 14 2023

---------------------------------------------------------------------
Key Messages...

- Increasing chance for showers and thunderstorms on Tuesday; an
isolated strong-to-severe storm cannot be ruled out across south
central KY. Locally heavy rainfall and isolated flooding is also
possible.

- Drier weather returns Wednesday into Thursday with seasonable
highs and cool morning lows.
---------------------------------------------------------------------

Monday Night - Tuesday Night...

At the beginning of the extended forecast period Monday night,
ridging aloft over the southeastern U.S. will begin to recede as a
mid- and upper-level shortwave slides across the top of the
retreating ridge. At the surface, an open wave sfc low will slide
from west to east across the Ohio Valley, with latest guidance
shifting this track farther north along the I-64 corridor. South of
the sfc low track, low-level warm and moist advection will promote
increased instability, with latest guidance depicting a swath of
upper 60s and lower 70s dewpoints Tuesday afternoon across south
central Kentucky. While ensemble mean CAPE values remain limited,
14/12Z NAM and GFS deterministic runs paint a swath of 1500+ J/kg
SBCAPE along and south of the Parkways during the day on Tuesday. As
a result, there is growing concern for strong to potentially severe
storms in these areas which are able to destabilize on Tuesday.
Additionally, stronger flow aloft is resulting in 30-35 kt effective
bulk shear, which will enhance the ability of convection to become
organized. Wind profiles look fairly unidirectional in the low-
levels, with modest low-level SRH, while low (7-7.5 C/km) and mid-
level (6-6.5 C/km) lapse rates are marginal to slightly favorable.
Taking all of this into consideration, would not be surprised if the
severe threat is increased across south central KY in upcoming SPC
outlooks, with damaging winds and severe hail being the main threats.

Outside of the severe potential, heavy rainfall and flash flooding
threats will also have to be monitored, with PW values approaching
90th-95th percentile. With stronger flow aloft, storm motions aren`t
too concerning; however, if heavier cells train over the same areas,
isolated swaths of 2-3 inches of rainfall and localized flash
flooding would be possible. Along and north of the sfc low track,
which at this time would appear to be north central KY and southern
IN, rain is still likely on Tuesday, with cooler air near the sfc
limiting instability and thunderstorm potential. Widespread
precipitation totals of 0.25+" would be favored, though this could
yet change based on later trends in guidance. The sfc low is
expected to clear the region early Wednesday morning, with drier air
moving through in its wake.

Wednesday and beyond...

By Wednesday morning, the shortwave aloft will have cleared the
area, with high pressure across the Great Lakes attempting to work
southward during the day on Wednesday. Some medium-range guidance
tries to develop isolated precipitation along the edge of the sfc
high Wednesday afternoon across western KY; however, will advertise
silent PoPs for now given the expected dry air mass. By Thursday,
another mid- and upper-level disturbance will begin to descend
southeastward from central Canada into the upper Midwest. While
direct impacts from this disturbance shouldn`t arrive until Friday,
weak low-level return flow may be just sufficient for a low-end
chance of afternoon showers/storms across portions of southern KY.
As this return flow strengthens on Friday into Friday evening,
increasing moisture will promote enhanced precipitation chances area-
wide, with showers and thunderstorms developing ahead of an
approaching sfc cold front. At this time, the front is progged to
move through late Friday night into Saturday morning, with another
shot of cooler and drier air arriving in its wake for the second
half of next weekend. However, forecast confidence at this range
remains limited, to stay tuned as further guidance comes in later
this week.

&&

.Aviation...(00Z TAF Issuance)
Issued at 725 PM EDT Sun May 14 2023

Widespread convection developed this afternoon from the western Gulf
of Mexico to the lower Missouri Valley to the Southeast in a ring of
fire around the periphery of an upper high over the lower
Mississippi Valley. Storms in Missouri and southern Illinois are
expected to drift to the east and southeast tonight, weakening as we
get deeper into the night. Will account for this with some VCSH at
our western TAF sites, HNB and BWG, after midnight. With humid air
in the Bowling Green region, along with very little wind, some MVFR
BR may form at BWG around sunrise.

On Monday instability will develop in the afternoon south of an east-
west boundary, leading to the possibility of some scattered showers
or thunderstorms in the BWG area.


&&

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

$$

Update...13
Short Term...DM
Long Term...CSG
Aviation...13



Area Forecast Discussion

National Weather Service Chicago/Romeoville, IL

 848 PM CDT Sun May 14 2023

.UPDATE...
Issued at 848 PM CDT Sun May 14 2023

Only minor adjustments made to going forecast this evening,
mainly to add hourly detail to pop grids as showers decrease in
coverage, as well as to remove thunder mention from our far
southern counties.

Weakening surface low pressure was analyzed near Kansas City this
evening, with a sharp quasi-stationary front extending southeast
through southern IL and western KY. Farther north, an elongated
area of seasonably strong high pressure stretched from the
northern Plains through the northern Great Lakes region. Within
the gradient region across northern IL/northwest IN, somewhat
blustery northeast winds continued to bring cooler air into the
area with temperatures currently in the low-mid 50s across much of
the forecast area. Light rain/showers have persisted area since
this afternoon, driven largely by frontogenetic forcing (most
notably in the 700-500 mb layer) within the elevated baroclinic
zone north of the stationary front along with some aid from upper
level divergence in the right rear entrance region to an upper
level jet streak to our east. High- res model guidance depicts
both of these forcing mechanisms weakening tonight as the upper
jet streak peels off to the east- southeast, and the elevated
baroclinic zone weakens as the surface front sags south. The
result will be a continued decrease in shower coverage through
late evening, especially across the northern half of the forecast
area. Farther south, some lingering f-gen forcing in the 925-850
mb layer may allow for some isolated showers to persist at times
into the overnight hours mainly south of the I-80 corridor.

With these trends already evident in regional radar imagery, have
made some tweaks to pops across the area to depict gradually
decreasing coverage of showers across the north, and maintained
low pops (20 percent) overnight in the south. RAP mesoanalysis and
forecast soundings indicate all convective instability has
shifted south of the forecast area into central IL, and thus
removed any lingering mention of thunder along our LOT/ILX border.

Updated digital/text forecast products available.

Ratzer

&&

.SHORT TERM...
Issued at 235 PM CDT Sun May 14 2023

Through Monday...

A broad region of showers is ongoing early this afternoon in
areas generally northwest of I-55. This will continue to slowly
drift southeast the rest of the afternoon. So far it has struggled
to make inroads over the city thanks to much drier low levels
indicated by O`Hare and Midway dewpoints near 40F. At times,
cloud tops have grown tall enough to see an few lightning strikes
embedded in the showers, though so far this has been limited to
locales along and west of I-39. Think the potential for lightning
the rest of the afternoon into early evening will be limited to
areas in Illinois along and south of a Mendota to Kankakee line.

Hi-res guidance begins to thin out the area of showers into a
narrower band with isolated showers that persists through the
overnight hours. Exactly where this band ends up remains somewhat
in question so it felt prudent to carry a mention for isolated
showers for most areas overnight. Think in general these showers
will be on a diminishing trend toward daybreak, though cannot rule
out a few light showers/sprinkles through the day mainly south of
I-80.

Depending on how long these light showers continue and greater
cloud coverage it could slow our warming on Monday. Left the
temperature forecast mostly unchanged with upper 60s to lower 70s.
Northeast winds and an afternoon lake breeze will keep
temperatures near the shore in the upper 50s to lower 60s.

Taking a broader look at the region, showers are ongoing across
Oklahoma and Kansas on the western side of the upper ridge. Model
guidance suggests this activity will continue to lift and
ultimately round the ridge into central Illinois. The northern
edge of these showers may sneak into areas south of I-80 late
Monday night. More details about shower chances Monday night into
Tuesday are provided in the Long Term Discussion below.

Petr

&&

.LONG TERM...
Issued at 235 PM CDT Sun May 14 2023

Tuesday through Sunday...

Over the next few days, the persistent upper-level anticyclone
centered over the southeastern United States will begin to break
down as substantial upper-level troughing develops over the
northeastern United States. As mid-level anticyclonic steering flow
decays, it will lift a diabatic generated low pressure system
currently in central Texas roughly toward Joplin, MO to Springfield,
IL, and eventually Lexington, KY by Tuesday night. Along and north
of the path of the low, a narrow shield of rain is poised to develop
along the remnant baroclinic zone draped across the middle
Mississippi River Valley. At this point, it appears the rain shield
may lift as far north as a line from Pontiac to Rensselaer, though
confidence is lower than average owing to the convective origin of
the low (e.g. model guidance may not by fully resolving the
structure of the low). At any rate, chances for rain appear to be
increasing across central Illinois Tuesday morning.

Meanwhile, confidence continues to increase in the passage of a Lake
Michigan pneumonia front Tuesday afternoon across northeastern
Illinois. Pattern recognition suggests temperatures may drop some 15
to 20 degrees in the span of an hour or two particularly close to
the Lake Michigan shoreline! Steep low-level lapse rates ahead of
the front may support a few showers, particularly near the Wisconsin
state line. However, the most notable impact of the front will be
the plummeting temperatures. After sunset, a surface high will
quickly build into the Great Lakes leading to clearing skies and
slackening winds. Lows Tuesday night may approach the 40 degree mark
close to the Wisconsin State line.

With the surface high parked overhead Wednesday and Thursday,
generally quiet conditions will prevail with gradually warming
temperatures, light winds, and plenty of sun. The next chance of
rain will arrive Friday as an upper-level wave and associated cold
front move across the Great Lakes. With limited moisture return
ahead of the wave, ensemble model guidance advertises only a a 50-
60% chance that 12-hour rainfall amounts exceed 0.1" of an inch...So
any rain that occurs won`t be soaking.

Ensemble meteograms provide signals for dry and seasonable weather
from May 21-25 with a trend toward warmer temperatures and perhaps
chances for thunderstorms thereafter.

Borchardt

&&

.AVIATION...
For the 00Z TAFs...

629 PM...Primary forecast concern is rain end time this evening.
Light rain will continue through mid evening, as it slowly
dissipates and shifts southeast of the terminals. Still some
uncertainty for an exact end time and have maintained previous
timing, 03z for the Chicago terminals. There may still be some
sprinkles or isolated showers after this time.

Northeast winds will continue through early Monday evening. Some
gusts to 20kts are possible early this evening then speeds are
expected to diminish under 10kts overnight, increasing back
toward 10 kts on Monday. Winds are expected to shift light
westerly Monday evening. cms

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...None.
IN...None.
LM...None.
&&

$$

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Area Forecast Discussion

National Weather Service Marquette MI

 1202 AM EDT Mon May 15 2023

.SHORT TERM...(This evening through Monday)
Issued at 330 PM EDT SUN MAY 14 2023

Water vapor imagery and RAP analysis show a strong mid-level
anticyclone centered over Alberta. Downstream of this mid-level
ridge a shortwave is dropping slowly south through Upper Mi this
afternoon, but given how very dry the air mass is over the area
no pcpn is associated with this wave, only high cloudiness. This
high cloud cover will push south of the area this evening with the
shortwave and high pressure will dominant all levels tonight.

With diurnal mixing through this very dry airmass this afternoon
dew points have dropped into the teens to lower 20s across much of
the interior. These dew points combined with high temp readings
mostly in the 60s have resulted in min RH percent values in the
teens to lower 20s. Fortunately, NE-E winds have stayed in check
for the most part with gusts generally staying blo 15 mph. The
very dry conditions and low RHs will warrant keeping the ongoing
SPS for elevated fire danger in effect through early evening.

Given the very dry airmass in place and the sfc high pressure moving
over the area this evening into the early overnight, ideal
radiational cooling conditions could yield min temps on the lower
end of guidance. It`s a good bet temps could dip blo freezing later
tonight across a good portion of the interior west where patchy
frost will be possible, so anyone with sensitive potted plants may
want to cover them or bring them inside tonight.

.LONG TERM...(Monday night through Sunday)
Issued at 252 PM EDT SUN MAY 14 2023

Key Messages:
-Warm and dry Monday
-A dry cold front Tuesday brings more normal temps, cool overnight
-Quiet Wednesday before light rain Thursday/Friday
-Ridging Saturday, keeping an eye on a trough nearby Sunday

The long term forecast starts with a 1032 mb high pressure stretched
broadly across the Upper Midwest coinciding with 500 mb height
anomalies of +28 dam. NAEFS geopotential height and SLP are all in
the 99th percentile to maximum of climatology for 12Z Monday. This
dry air and subsidence should keep precip (and clouds, for that
matter) out of the forecast, especially with NAEFS PWAT in the
bottom 10 percent of climatology. The big forecast focus for Monday
will be on the fire weather conditions as mixing the boundary layer
from the CMC model output gives surface dew points in the 20s and
teens only recovering to the 30s while the prime radiation heating
leads to highs in the 70s and high 60s. The wind forecast begins
with light westerlies, but throughout the morning, winds increase to
10-15 mph with gusts up to 20 mph as the pressure gradient increases
between the high over the Midwest and Northern Plains and a
deepening low over the Canadian Maritimes. While the winds alone are
not critical, the minRH`s in the 20`s% range and lower in some areas
along with highs around 70 lead to borderline critical fire weather
conditions.

Tuesday, the surface high weakens and sags south as 500mb anomaly
erodes back towards 0. A shortwave trough is expected to pass north
to south through the region midday Tuesday, though it will quickly
be replaced by a high pressure in its wake for Wednesday. No precip
is expected with the cold front passage as even the NBM 95th
percentile has no measurable precip in the forecast area. The cold
fropa will bring Tuesdays high temperatures down 10+ degrees from
Monday`s highs, bringing highs back in line with the climatological
averages. Additionally, with the cold fropa and expected clear skies
for radiational cooling, lows Tuesday night could reach sub-freezing
in some interior locations.

A quiet Wednesday is expected as ridging will dominate the forecast
before the next 500mb trough digs southeast through Ontario and the
Upper Great Lakes vicinity Thursday. The 12Z GEFS has much higher
certainty than this time yesterday that the low center will be
around 1000-1005mb passing along the northern shores of Lake
Superior. However, the range of QPF solutions has increased, with
the 25th percentile being around 0.05-0.2 inches and the 75th
percentile being half to 3/4 of an inch of rain. Despite the
increasing trend in QPF, impacts are still expected to be fairly low
as thunder coverage is only expected to be isolated at most in the
interior west and with rivers receding after the most recent
snowmelt, hydro concerns are not particularly high. The NBM does
have a 5 percent chance of snow for the highlands of Baraga and
Marquette counties with lingering precip Friday, but temperatures
should be far too high for that solution.

A brief ridge will take hold of the region Saturday, though Sunday`s
weather will be hard to pin down as the next feature of note is a
trough over the Hudson Bay on the 12Z GFS. Some ensemble members
bring the trough far enough south to bring precip to the region, but
model spread (and thus, uncertainty) is high at this forecast time.
&&

.AVIATION...(For the 06Z TAFS through 06Z Monday night)
Issued at 1202 AM EDT MON MAY 15 2023

A dry airmass and surface high pressure continue to result in VFR
conditions for the duration of TAF period.  Winds will become
primarily southwesterly around mid morning at all TAF sites, and
strong at CMX this afternoon with sustained speeds of 12 to 15 kts
and gusts to 24 kts.

&&

.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 252 PM EDT SUN MAY 14 2023

Winds are below 20 kt through Monday afternoon, when a cold front
from the north brings southwest winds up to 30 kt. A gale force gust
or two cannot be ruled out Monday evening, especially in the central
portions of the lake near the Keweenaw Peninsula. Winds shift to the
north Tuesday evening and gusts remain around 20 kt through Tuesday
evening. A brief high pressure will help bring winds below 20 kt
Wednesday before an approaching low pressure will bring southerly
gusts of 20 to 25 kt overnight into Thursday, becoming westerly from
west to east throughout the evening. Friday, winds become northerly,
still remaining around 20 to 25 kt.
&&

.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
None.
Lake Superior...
None.
Lake Michigan...
None.
&&

$$

SHORT TERM...Voss
LONG TERM...GS
AVIATION...TDUD
MARINE...GS