Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 10/24/20

Area Forecast Discussion

National Weather Service La Crosse WI

 658 PM CDT Fri Oct 23 2020

.SHORT TERM...(This evening through Saturday)
Issued at 300 PM CDT Fri Oct 23 2020

Forecast concerns in the short term will be the elevated river
levels and some minor flooding, light mixed precipitation ending,
then temperatures falling back into the teens and 20s overnight.

At midday...water vapor satellite imagery, heights, and observations
showed a broad mid-level trough that extends from the Pacific
Northwest toward the Great Lakes.  The were several embedded troughs
within the broad trough.  The first has been pushing through the
local area since yesterday.  Heavy rain fell across parts of the
forecast area with localized 4 to 6 inch reports across Clayton and
Fayette Counties in northeast Iowa, and Grant and Richland Counties
in southwest Wisconsin. Additional reports of 1 to 4 inches were
common south of a line from Decorah to Black River Falls with less
than an inch farther north.  The La Crosse NWS had 0.98 inches
through 7am, the LSE airport 0.97, Galesville 0.53, and the RST
airport 0.31. See the hydrology section below for more details on
the elevated river levels and specific forecasts on our Advanced
Hydrologic Prediction Service page on our web site.

Mixed drizzle...light rain...and light snow has been pushing across
the forecast area today as the shortwave trough.  This light
precipitation will continue to exit the area mostly ending by
evening.  Surface high pressure building into the Plains will usher
in drier dewpoints, decreasing clouds, and colder temperatures.
Visible satellite imagery and observations highlight the more solid
area of MVFR clouds over central Minnesota, however there are some
patches still farther west. Look for the back edge of the low clouds
to push east overnight with lows dropping back into the teens and
20s as the winds decrease to 10kts or less. Per RAP relative
humidity forecasts...RH is already returning Saturday morning
though around 500mb lowering to 700mb by noon...thus look for mid
clouds to be advancing with the next storm system.

.LONG TERM...(Saturday night through Friday)
Issued at 300 PM CDT Fri Oct 23 2020

Accumulating snow arrives Sunday and much below normal
temperatures continue for much of the extended.

The next trough will have some lead shortwave energy that is
expected to bring thickening clouds Saturday and Saturday night.
There are a number of factors that come into play and may
complicate the snow forecast. Initially, the low levels are dry,
thus the onset becomes problematic. There is broad synoptic lift
with the approaching trough. Some interaction between the right
rear exit region of the jet and the left front exit of the jet
could affect the snow amounts. There is some frontogenesis,
however it does not appear that we have steep lase rates to work
with. It appears that the event will be mainly snow with the
colder temperatures air aloft. Do have some chance pops Saturday
night, with higher pops with snow likely spreading east across
the forecast area during the day Sunday and moving out Sunday
night. There is still a spread of in snowfall amounts and this is
likely due to the location of where the band of higher amounts
sets up. Early indications are the main snow amounts will range
from 1 to 4 inches. Some wind is expected, but mostly in the 5 to
15 mph with some local spots in unprotected areas seeing higher
winds.

Much colder temperatures for Monday and these may be record
cold highs in the 20s and 30s. Lows Monday night are forecast to
range from 10 to 20 degrees.

The rest of the week appears to be mainly dry with continued below
normal temperatures.

&&

.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
Issued at 658 PM CDT Fri Oct 23 2020

MVFR ceilings are expected tonight at both TAF sites, with VFR
conditions returning late tonight or early Saturday morning.

MVFR ceilings are expected to persist at KRST through the early
evening before higher ceilings and then clearing upstream finally
arrive from the west. At KLSE, ceilings will likely flirt with
the MVFR/VFR threshold before low clouds move out late tonight or
early Saturday morning. Trends will have to be monitored for
possible adjustments to these times, however. With high pressure
moving in, winds will be northwesterly tonight into Saturday
morning, becoming more north to northeasterly late Saturday ahead
of the next system approaching from the west. Ceilings will also
gradually lower in advance of this system during the afternoon,
though are expected to remain VFR during the day. There could also
be a few diurnal cumulus clouds that develop. Light snow will be
possible later Saturday night beyond the end of the TAF period.

&&

.HYDROLOGY...
Issued at 300 PM CDT Fri Oct 23 2020

Heavy rainfall of 2 to 6 inches fell across parts of northeast
Iowa and southwest Wisconsin. The soils have been fairly dry
recently and although flash flood warnings were issued, much of
the area has been able to handle the rainfall will mainly minor
flooding.

Heavy rainfall of 2 to 4 inches fell across the Kickapoo River basin
Thursday night. A flood watch was issued on the Kickapoo River with
rises expected especially at Readstown and Gays Mills through this
weekend.

Some minor flooding was also occurring around Burton on the Grant
River. For specific details, please refer to our latest
statements and warnings.

&&

.ARX WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...None.
IA...None.
&&

$$

SHORT TERM...Zapotocny
LONG TERM...Zapotocny
AVIATION...Lee
HYDROLOGY...Zapotocny



Area Forecast Discussion

National Weather Service Boston/Norton MA

 1028 PM EDT Fri Oct 23 2020

.SYNOPSIS...
High pressure will maintain dry and mild weather tonight and
Saturday. A dry cold front will move across southern New
England Saturday afternoon and evening. In wake of the front,
Canadian high pressure builds into the area Saturday night and
Sunday, ushering in dry but much cooler air. A couple waves of
low pressure and a frontal boundary will result in several
chances of showers next week. Not a washout as there will be
many hours of dry weather especially around Wednesday.
Seasonably cool temperatures expected much of next week, with
highs in the 50s to near 60 and night time lows in the 30s and
40s.

&&

.NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...
1030 pm update...

Previous forecast remains on track, thus no major changes with
this forecast update. Earlier discussion below.

==================================================================

Highlights...

* Cloudy with areas of fog. Could have some drizzle across the
  eastern slopes of the Berkshires.

Subtropical ridge axis building east of Cape Cod while a shortwave
trough lifts from Upper Michigan into southern Quebec by Saturday
morning. At the surface high pressure nudges in from the Carolinas
while a cold front slides across the eastern Great Lakes.

Will see east to southeast flow across eastern areas that will
advect in ocean stratus per RAP RH from the SFC to 925 hPa. Central
and western areas will remain cloudy due to southerly flow advecting
in moisture. This will result in a cloudy night across much of
southern New England. It will be mild as southwesterly warm air
advection of 10 to 12 degree Celsius 850 hPa moves in. Low
temperatures falling into the 50s.

The additional influx of moisture in combination with light winds
will result in areas of fog. Expect the lowest visibilities to be
concentrated across the CT River Valley. Could also see some spotty
drizzle as indicated by the NAM/ARW/NMM/CMC and ECMWF across the CT
River Valley and eastern slopes of the Berkshires.

&&

.SHORT TERM /6 AM SATURDAY MORNING THROUGH SATURDAY NIGHT/...
Highlights...

* Few light showers possible across the west, but generally a dry
  cold frontal passage on Saturday. Skies clearing out during the
  afternoon.

* Much cooler Saturday night into Sunday morning.

Shortwave trough lifts into northern Quebec on Saturday. A ridge
builds from the Northern Plains into Ontario/the central Great Lakes
late on Saturday into early Sunday. The cold front is well removed
from the upper forcing, so am anticipating a dry frontal passage on
Saturday. There may be a few light spotty showers across the far
west. Should see clearing skies during the afternoon from northwest
to southeast as high pressure builds in from the northwest. The high
will remain in place through the overnight hours.

Saturday...

A somewhat tricky temperature forecast on Saturday due to the front
sliding through in combination with colder air advecting in from
westerly flow aloft. Despite this, am expecting another above normal
temperature day across southern New England. The westerly flow will
result in some downsloping, so should see most areas getting well
into the 60s and there may even be a few readings in the low 70s
across the typical warm spots.

The cold front may bring a few spotty rain showers across western
portions of the CWA, but the front is far removed from the upper
forcing. This is backed up by the latest deterministic guidance, so
have only kept slight chances of precipitation.

Skies will clear in wake of the front. Winds will shift to the
northwest and it could be a bit breezy at times with gusts getting
up to 20-25 mph during the afternoon with the highest speeds over
the eastern slopes of the Berkshires.

Saturday Night...

Gusty winds diminishing across the interior as high pressure relaxes
the pressure gradient. However, it still may be a bit breezy along
the coastal plain.

Skies will generally be mostly clear across much of southern New
England with relatively light winds. Have nudged down the low
temperatures in the latest update toward the 20th percentile of
guidance. May need to go lower in future updates, but have held off
as there may be enough mechanical mixing to keep temperatures from
plummeting further. Low temperatures generally in the 30s across
the interior with patchy frost. Coastal areas will range from the
upper 30s to the mid 40s.

&&

.LONG TERM /SUNDAY THROUGH FRIDAY/...
Highlights...

* Fall weather returns Sunday

* Not a washout next week but multiple chances for showers

* Driest day next week may be Wednesday

Precipitation...

Confluent flow pattern sets up over or near New England much of next
week. This results in a storm track and associated frontal boundary
remaining close to our region much of the time. Thus low confidence
forecast on exact placement of this boundary and timing of low
amplitude waves traversing the front along with individual precip
shields. Although confidence is high early in the period with dry
weather expected Sunday as 1025+ mb high pressure builds into
southern Quebec and northern New England. Then the next wavy frontal
boundary impacts the region Sun ngt into Tue night. Ensembles
suggest northern stream trough may be sufficient to drive frontal
boundary south of New England midweek, offering a period of dry
weather around Wed. Then ensembles trending more bullish on trailing
frontal wave to move across the Northeast Thu/Fri, as closed low
over the dessert southwest ejects northeast. So to summarize,
multiple chances for showers next week, although not a washout with
many hours of dry weather likely, especially mid week around
Wednesday.

Temperatures...

Much cooler Sunday with highs only in the low to mid 50s with upper
40s high terrain! Big cool down from our recent warmth. In fact
these temps are cooler than normal for late Oct, with normal highs
55-60. Although sunshine especially morning and early afternoon
Sunday combined with light winds will help take the edge off the
cooler temps. For next week, low confidence on temps given
uncertainty in exact frontal position, cool side of boundary vs warm
sector. Although given clouds, showers and proximity of frontal
boundary, temps near normal appear most likely.

&&

.AVIATION /03Z SATURDAY THROUGH WEDNESDAY/...
Forecaster Confidence Levels...

Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.

02z update...no major changes from previous TAFs. Earlier
discussion below.

===============================================================

Tonight...Moderate confidence.

Onshore flow brings MVFR to LIFR stratus, which will move in
from west to east. Areas of fog developing. Expect lowest vsbys
along the CT River Valley, ORH and BED. Could be some fog at
BOS, but once winds shift to the SW expect vsby to improve.
Light SE/S winds shift to the SW. Also think that there may be
some light drizzle across the eastern slopes of the Berkshires
into the CT River Valley.

Saturday...High confidence.

Starting off with MVFR to LIFR stratus, but will see
improvement to MVFR/VFR from west to east as a mainly dry cold
front slides through. SW winds shifting to the W and eventually
the NW as the front moves through. Speeds generally 5-10 kts.
Could see some 15-20 kt gusts during the afternoon.

Saturday night...High confidence.

Borderline MVFR/VFR ceilings across Cape Cod and the Islands.
Elsewhere will be VFR with clear skies and relatively light
winds.

KBOS Terminal...High confidence in trends, but moderate in exact
timing of IFR conditions. Possibility of LIFR ceilings between
04-12Z.

KBDL Terminal...High confidence in trends, but moderate in exact
timing of return to IFR conditions.

Outlook /Sunday through Wednesday/...

Sunday: VFR. Breezy.

Sunday Night: Mainly VFR, with areas MVFR possible. Breezy.
Slight chance SHRA.

Monday: Mainly MVFR, with areas IFR possible. Breezy. Chance
SHRA.

Monday Night: Mainly MVFR, with local IFR possible. Breezy.
SHRA likely.

Tuesday: Mainly MVFR, with local VFR possible. Breezy. SHRA
likely.

Tuesday Night: Mainly MVFR, with local IFR possible. Chance
SHRA.

Wednesday: Mainly MVFR, with areas VFR possible. Slight chance
SHRA.

&&

.MARINE...
Extended all Small Craft Advisories into Sunday morning and expanded
Small Craft Advisories to Ipswich/MA Bay, Rhode Island and
Block Island Sound due to building seas. The building seas is
due to southeasterly swell from distant Hurricane Epsilon through
Saturday. Peak long-period seas occur on Saturday with wave
heights around 9 ft across the outer waters. These long period
seas will bring building surf and an increasing risk of rip
currents to southern/eastern exposed beaches through Saturday.

While seas serve are the main focus for the small craft
advisory, northwest winds increase later Saturday into Saturday
night behind a cold front. This will reach into solid SCA
criteria on the majority of waters. Borderline Gale Force Gusts
are possible Saturday night into early Sunday across the outer
eastern waters.

Another period of low clouds and fog is expected across the
waters tonight.

Outlook /Sunday through Wednesday/...

Sunday: Winds less than 25 kt. Areas of rough seas.

Sunday Night through Monday: Winds less than 25 kt. Seas up to
5 ft. Slight chance of rain showers.

Monday Night through Tuesday: Winds less than 25 kt. Seas up to
5 ft. Rain showers likely.

Tuesday Night: Winds less than 25 kt. Areas of seas approaching
5 ft. Chance of rain showers.

Wednesday: Winds less than 25 kt. Seas up to 5 ft. Slight
chance of rain showers.

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...Small Craft Advisory until 8 AM EDT Sunday for ANZ235-237-250-
     251-254>256.

&&

$$
SYNOPSIS...Nocera/BL
NEAR TERM...BL/Chai
SHORT TERM...BL
LONG TERM...Nocera
AVIATION...Nocera/Loconto
MARINE...Nocera/Loconto



Area Forecast Discussion

National Weather Service Charleston SC

 929 PM EDT Fri Oct 23 2020

.SYNOPSIS...
Weak high pressure and a coastal trough will persist into the
weekend. A weak cold front will drop through the area Sunday
night, followed by high pressure. A storm system may affect the
area late next week.

&&

.NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...
High-res guidance continues to favor dense fog overnight across
the interior. There are still concerns on exactly how deep the
fog layer will become. Opted to introduce patchy dense fog
wording across the interior given the persistent trends noted in
the RAP, H3R, and CONShort output. The Hazardous Weather
Outlook has also been amended to include the possibility for a
Dense Fog Advisory early Saturday. Otherwise, the forecast is
largely on track.

Broad high pressure centered along the U.S. Coast will holds
its influence on the region tonight. The boundary layer is
poised to decouple quickly after sunset resulting in calm to
light winds across much of the area. The main concern tonight
centers on potential fog development as skies clear and
temperatures cool. The various statistical and high-res
operational guidance support the formation of widespread
radiation fog within a decoupled boundary layer after midnight.
Curiously, the 1000 hPA condensation pressure deficit progs off
the RAP are not overly low and model point soundings from the
NAM, GFS, RAP and H3R do not depict a saturated boundary layer
at sunrise. This suggests the radiational fog layer could be
quite shallow, but widespread. There is a potential for shallow
dense fog, especially in the Reidsville-Statesboro-Hampton-
Walterboro corridor where both the HREF dense fog probabilities
are in the 65-85% range.

&&

.SHORT TERM /6 AM SATURDAY MORNING THROUGH MONDAY/...
Weak high pressure will persist to the east on Saturday. A
shortwave will approach from the west late in the day, then move
into eastern SC by Sunday morning. Moisture will deepen ahead
of the wave with PW values increasing to around 1.5" Saturday
afternoon. A few showers will be possible across the area
Saturday afternoon through Sunday.

Although surface dewpoints will remain unseasonably high,
a slightly drier airmass will move in Sunday night and Monday
behind a weak backdoor cold front. Generally rain-free
conditions expected.

Temps will remain above normal through the period with highs in
the low/mid 80s and lows in the mid/upper 60s.

&&

.LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...
The mid-levels will consist of high pressure centered roughly over
FL on Tuesday. The high will slowly trend eastward, into the
Atlantic through Thursday. Meanwhile, a strong trough will approach
from the west on Thursday. A wedge of surface high pressure to our
north on Tuesday will shift offshore while weak coastal troughing
prevails. A stronger cold front should approach our region towards
the end of the week. Above normal temperatures with low POPs should
prevail.

&&

.AVIATION /02Z SATURDAY THROUGH WEDNESDAY/...
Fog is the main concern at both KSAV and KCHS overnight.
Soundings do not show a saturated boundary layer with high 1000
hPa condensation pressure deficits through daybreak. This
suggests the fog will be shallow, but could still be potentially
significant. Will carry prevailing MVFR at KCHS 10-13z where
fog probabilities are the lowest. For KSAV, probabilities are
considerably higher so will trend the 00z TAF more pessimistic,
but not as low as some guidance suggests. Will cap prevailing
vsbys at 3SM 09-1430z with a TEMPO of 1 1/2SM with cigs right at
airfield minimums 10-13z. VFR should return to both sites by
13z at KCHS and 1430z at KSAV. Lower conditions may be needed
for both terminals, especially KSAV, with the 06z TAF cycle as
additional data are received and better short-term trends can be
established.

Extended Aviation Outlook: Brief restrictions possible in low
clouds/fog Saturday night. MVFR/IFR stratus possible Sunday
night and Monday morning behind a weak cold front.

&&

.MARINE...
Tonight: High pressure will remain centered north of the area
and distant Hurricane Epsilon to our northeast will continue to
bring swell into the marine areas. A slightly relaxed pressure
gradient will cause winds to drop to 10 kt or less across all
waters. As winds decrease, seas will gradually subside
overnight; peaking at 4 to 5 ft in the nearshore waters out 20
nm, and up to 7 ft in the GA offshore waters where a Small Craft
Advisory remains in effect.

Saturday through Wednesday: The main issue this weekend is
continued 6 ft swells over the offshore GA waters from distant
Hurricane Epsilon. We shortened the end time on the Small Craft
Advisory by about 24 hours since wave guidance now brings seas
below 6 ft by daybreak Sunday.

A weak northeast surge is expected Sunday afternoon through
Monday as a weak cold front drops through the waters. Southerly
flow will return Tuesday or Tuesday night as high pressure
builds over the western Atlantic.

Rip Currents: Long period swells from distant Hurricane Epsilon
will gradually subside over the weekend though we`ll maintain
a Moderate Risk for rip currents due to 2-3 ft swells every
12-13 seconds.

&&

.CHS WATCHES/WARNINGS/ADVISORIES...
GA...None.
SC...None.
MARINE...Small Craft Advisory until 6 AM EDT Sunday for AMZ374.

&&

$$



Area Forecast Discussion

National Weather Service Lincoln IL

 735 PM CDT Fri Oct 23 2020

.SYNOPSIS...
Issued at 735 PM CDT Fri Oct 23 2020

Much cooler weather will prevail over central and southeast
Illinois this weekend, with high temperatures both Saturday and
Sunday in the 40s and 50s. After a few lingering showers exit
areas south of I-70 during the evening, dry weather is on tap
through early Sunday. After that, the next storm system will bring
rain to the region Sunday afternoon into Monday, heaviest in areas
south of I-70.

&&

.UPDATE...
Issued at 735 PM CDT Fri Oct 23 2020

Just a few lingering showers south of I-70 early this evening in
the wake of the strong cold front from earlier today.
Stratocumulus is widespread across Illinois and adjacent areas.
Satellite imagery showing breaks pushing south across eastern
Wisconsin and northwest Iowa, though there is also a higher cloud
deck streaming northeast toward northern Illinois, and it is
unclear how much of this clearing may make it this far south. HRRR
is fairly optimistic in its solution, but we`re getting into the
time of year where it can be harder to get rid of the lower cloud
decks, so the forecast will remain mostly cloudy through the
night. With this cloudier trend, temperatures were bumped up a
degree or two overnight, especially west of I-55.

&&

.SHORT TERM...(This evening through Saturday)
ISSUED AT 319 PM CDT Fri Oct 23 2020

The cold front that quickly pushed through the local area has
exited southeast Illinois, and is pushing into the Ohio River
Valley as of this afternoon. Showers and storms tracked through
the region, with even some strong and severe storms occurring
across southern Illinois this afternoon. Behind fropa, gusty
northwest winds have slid into central Illinois, and now into
southeast Illinois as CAA is arriving. This windy trend will
continue through the evening and into the overnight, before winds
decrease after midnight. Temperatures will begin falling after
sunset...however cloud coverage will inhibit a major reduction
overnight. Some spots across far nw CWA will likely dip below
freezing, with a few locations possibly reporting upper 20s by
morning.

Quiet weather arrives Saturday, as the upper level flow turns
zonal for a brief period. This will allow for slight temperature
increases during the day, with highs climbing into the 40s and
50s. Winds for Saturday will come out of the ne around 8-12mph,
which will slowly erode the clouds lingering during the early
morning.

&&

.LONG TERM...(Saturday night through Friday)
ISSUED AT 319 PM CDT Fri Oct 23 2020

To end the weekend, the upper level pattern slants to a more sw-ne
flow, as a Low pressure system across central Canada works through
the northern Plains into the Rockies. This will setup the next
weather system to bring precipitation chances to the Midwest
heading into next week. As the system works southward Sunday, a
chance for precip arrival occurs across northern Illinois during
the late afternoon and evening. Models at this time are indicating
some colder temperatures, which will allow for a wintry mix
precipitation to develop. Not expecting much in terms of
accumulation at this time, as ground temperatures remain above
freezing, and with mixed precip, it should allow for quick
melting. This system will track through the area Sunday night into
Monday. For southern Illinois, this system will mostly occur as
rainfall, however some light mix could be possible as far south as
the I-70 corridor Monday morning.

As the developing upper Low in the Rockies becomes cut-off, it
will create a zonal flow though the first half of next week. This
trend will lead to chances of precipitation through Tuesday night,
before weak High pressure slips dry conditions overhead mid-week.
However, heading into the second half of the week, the Low will
track through southern US, leading a sfc Low across the southern
portion of the CONUS. This system looks to remain mainly south of
the area, however some precipitation activity is forecast to slide
into southern Illinois on Thursday. Model uncertainty exists with
the exact track of this system, but there has been a noticeable
southward trend of the system over the last 24 hours.

&&

.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
Issued at 608 PM CDT Fri Oct 23 2020

Widespread ceilings below 2,000 feet in the wake of the cold front
earlier, and these should persist into early Saturday. Models
suggest some improvement toward mid-late morning as clouds begin
to scatter out, though a northeast flow off Lake Michigan has
potential to cause some additional ceilings in the afternoon from
KPIA-KCMI. Northwest wind gusts will begin to drop off later this
evening, but sustained winds above 10 knots still likely much of
the night. Expect winds to turn more northeast Friday morning.


&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

UPDATE...Geelhart
SYNOPSIS...Geelhart
SHORT TERM...Baker
LONG TERM...Baker
AVIATION...Geelhart




Area Forecast Discussion

National Weather Service Louisville KY

 1054 PM EDT Fri Oct 23 2020

.Forecast Update...
Issued at 1054 PM EDT Fri Oct 23 2020

Other than an isolated rumble of thunder in the Lake Cumberland
region over the next hour, stormy weather has come to an end. Clouds
will persist through the night as evidenced by expanse of low
overcast reaching back into the Midwest and Great Lakes. Some patchy
light drizzle will be possible towards morning primarily south of
the Ohio River.

Issued at 930 PM EDT Fri Oct 23 2020

Worst of the storms this evening along the I-75 corridor this hour
continuing their way eastward. Cold front now crossing the SDF/BWG
line, continuing eastward and bringing in a quick chill. HNB now in
the 40s. HRRR soundings tonight still showing saturation in the low-
levels for several overnight hours, so drizzle/light rains still on
track. No zone update planned at this time.

Issued at 533 PM EDT Fri Oct 23 2020

...Strong to Severe Storm Threat Ongoing...

Scattered storms continue in the broad warm sector out ahead of the
front, with more linear storms lining up along the front. We`ve had
some strong to severe storms, with a few supercellular structures
over southern IN. For now, the supercell on the Clark/Floyd county
line appears outflow dominant as the low level RFD undercuts the
updraft a bit. Will continue to closely monitor.

Back to the west, the line of storms appears to be sub severe at the
moment as we only measure 25-35 mph from several sources (including
spotters) across Dubois county. Overall, it appears the outflow has
outpaced the main line a bit which seems to have limited the
immediate severe gust threat. However, will watch for new
development (forward propagation) along the leading edge as ML CAPE
values remain moderately strong out ahead of the line.

Not out of the woods yet by any means, and expect that storms will
have the ability to stay strong to severe for another 2 to 3 hours
before the best instability is lost, and the best deep layer shear
diminishes to the NE.

&&

.Short Term...(This evening through Saturday)
Issued at 255 PM EDT Fri Oct 23 2020

...Strong storms Possible This Afternoon & Evening...

Scattered showers and storms are ongoing across the CWA in the pre-
frontal warm advection regime. Have seen a steady uptick in coverage
and intensity early this afternoon, and expect that trend to
continue through the late afternoon and early evening as the cold
front approaches and quickly pushes through. The cold front is
currently positioned from NE Indiana, southwestward down through the
Wabash River Valley, and into the Missouri Bootheel, and this
feature is forecast to push east through our area by Midnight EDT.
Ahead of this feature, we`ve warmed to the upper 70s and low 80s
with mid to upper 60s Td`s. This has allowed for 1500-2000 J/KG of
ML CAPE just ahead of the front, however mid level lapse rates are
only around 6-6.5 C/Km. In addition to the meager lapse rates, 0-6
km shear is only around 25-30 knots at best. Given the weak lapse
rates (especially above 20 K feet) and the marginal deep layer
shear, only expect a severe threat with the strongest updrafts, and
even those may be limited by the factors mentioned above.
Nevertheless, if storms are able to briefly organize isolated
instances of damaging wind with multicell clusters and brief bowing
segments or perhaps some marginally severe hail would be possible
mainly between 4 and 9 PM EDT.

Behind the front will be a notable airmass change with temperatures
falling into the 40s over much of the area by dawn. Models aren`t
picking up on much QPF behind the front, however a look at time
heights shows a different picture with trapped low level moisture
between the surface and ~700 mb. Expecting that lingering patches of
drizzle will hang around through portions of Saturday, especially
along and south of the I-64 corridor. In fact, have added notable
chances of measuring along and southeast of a Bowling Green, KY to
Lexington, KY line.

Given the steady cold advection and virtually 100% sky cover across
the areas mentioned above on Saturday, liked the previous forecast
idea of going low for highs on Saturday. Expect a less than 10
degree diurnal climb from morning lows which will only put highs in
the 50s. Our NE may only see highs around 50!

.Long Term...(Saturday night through Friday)
Issued at 312 PM EDT Fri Oct 23 2020

Dreary conditions will continue into the long term period as cooler
temperatures and drizzly conditions look to persist into the later
hours of Sunday. Model soundings show a classic drizzle signature
with a robust subsidence inversion at 700mb with a saturated profile
underneath. Given the thick low level cloud cover and precipitation,
decided to go below guidance on temperatures Sunday. Expect to see
Sunday morning mins in the low 40s across southern Indiana and
increasing southward into the upper 40s in south central KY. Highs
will struggle to reach into the low to mid 50s in southern Indiana
and into the upper 50s to low 60s across central and south central
KY.

Monday will see two shortwaves, one in the northern stream rotating
around Lake Huron and another fast moving wave shooting NE from the
southern Rockies towards the Great Lakes. The latter will send a
cold front toward the OH Valley that appears to stall out over the
area, while the other helps to provide moisture. PWATs will increase
into the 1.00 to 1.30 inch range during this period. Soundings
advertise lapse rates on the stable side, so really not expecting
much thunder chances with this system. But depending on exactly
where the front stalls out, which currently looks like right along
and north of the OH River, this will determine where most of the QPF
occurs. As of now, accumulation estimates for the Monday/Tuesday
timeframe are roughly 1-1.5 inches along and near the boundary and
around a quarter inch for those south and east of there.

The boundary appears to stick around for much of Tuesday, which
continues to place our CWA in the warm, moist sector to its south.
Will keep mention of slight chance to chance PoPs for all on
Tuesday. Rain chances will wane and give way to dry conditions
Wednesday. Expect to see cooler conditions Tuesday with lows in the
40s to low 50s and highs in the 50s to low 60s. Wednesday will be a
bit warmer with highs in the upper 50s to low 60s.

Models generally agree on moving a cut-off low from TX/OK through
the lower OH Valley Thursday and Friday, which will set up a rainy
end to the work week. Will keep an eye on this feature as new data
become available.

&&

.Aviation...(00Z TAF Issuance)
Issued at 745 PM EDT Fri Oct 23 2020

A strong cold front is progressing through the region at this hour,
and has already passed HNB, SDF, and is passing BWG now. Expect it
to pass through LEX an hour or two before midnight EDT. Ahead of
this feature, still seeing a line of showers and thunderstorms. Time
those out of BWG/SDF/LEX, but will will then almost immediately go
to fuel alternate low ceilings. Perhaps some IFR will mix in at
times as well. The best chance for some drizzle overnight will be at
BWG and LEX with low clouds likely not clearing out of those TAF
sites until late in this forecast cycle, if at all. A bit more
optimistic at HNB and SDF where improvement is expected by late
morning or midday. Steady NW winds will gradually veer to a NE wind
in the post-frontal airmass.


&&

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

$$

Update...RJS/BJS/13
Short Term...BJS
Long Term...CG
Aviation...BJS



Area Forecast Discussion

National Weather Service Marquette MI

 637 PM EDT Fri Oct 23 2020

.SHORT TERM...(This evening through Saturday)
Issued at 345 PM EDT FRI OCT 23 2020

Water vapor imagery and RAP analysis show a shortwave rounding the
base of a mid-level trough axis and moving through the Upper Great
Lakes this afternoon. Q-vector convergence and some weak mid-level
fgen along and ahead of this shortwave providing some enhancement to
north to northeast flow lake effect snow showers this afternoon.
Webcams indicate 1-2 inches of snow has fallen around the Ironwood
area today and around an inch of snow has fallen at the NWS
Marquette office since late morning. Deep moisture noted on NAM
soundings and continued enhancement from shortwave suggest another 1
to maybe 2 inches of wet snow may be possible for higher elevations
through 5-6 pm this evening before deeper moisture with departing
system cuts out and flow begins to back nnw and becomes
anticyclonic. Will keep the current advisory going for Marquette-
Baraga counties through 5 pm.

As the shortwave and associated synoptic system push east this
evening, a lake effect regime will set up which will result in 1 to
locally 3 inches of additional lake effect snow for the west to
northwest wind snowbelts of western Upper Michigan mainly late
tonight into Saturday. Greatest amounts will likely be over the
higher terrain of Ontonagon and Houghton counties where the passage
of a weak shortwave and increasing low-level convergence should help
to focus more organized LES bands. Expect the rest of the wnw snow
belts west and east to see an inch or less snow accumulation.
Building sfc high pres ridge into the interior west half and south
central should result in mostly dry conditions for these areas
through the period and maybe some partial clearing later tonight.

Lows tonight may dip into the high teens interior west with mostly
20s elsewhere. Lows hovering near 30F are expected by the lakeshores.
Expect highs Sat generally ranging from the lower 30s west half to
mid to upper 30s east half.

.LONG TERM...(Saturday night through Friday)
Issued at 433 PM EDT FRI OCT 23 2020

Troffing will continue to dominate Canada thru the middle of next
week with this trof extending into the northern tier of the Lower
48. Both the NAO and AO will be trending from negative to
predominantly positive, and the implications for negative height
anomalies to trend toward consolidating at higher latitudes is
suggestive of some moderation of the blo normal temps that have been
prevailing across Upper MI for more than a week. At a minimum, will
start to see a little more temp fluctuation (periods of
warming/cooling) beginning later next week as the jetstream/storm
track drifts northward somewhat from where it has been. As for pcpn,
while it will still be on the active side with a progression of
shortwaves, pcpn frequency/amounts will be trending downward due to
lower amplitude shortwaves affecting the Upper Lakes combined with a
southern stream that will capture Gulf moisture transport and
prevent it from reaching these northern waves. Lake effect will be
a daily concern thru the early part of next week.

Beginning Sat night thru Mon...On Sat night, high pres will ridge
eastward into the northern Great Lakes from a strong high pres
center settling s into MT. As the ridge builds into the area, nw low-
level flow to start Sat night will diminish and become more land
breeze dominated by Sun morning. By Sun evening, a positively tilted
trof will be setup from Hudson Bay across the Northern Plains to the
Great Basin. Shortwave within this trof will aid in developing an
inverted trof extending generally n up Lake MI to eastern Lake
Superior on Sun. This trof then lingers until early Mon when the
northern part of the positively tilted mid-level trof breaks
eastward, leaving the southern part over the sw states. This period
of lighter winds featuring an inverted trof and nighttime enhanced
land breezes will set the stage for lake effect concerns. 850mb
temps of -7 to -10C will be the rule during this period, cold enough
to support the lake effect pcpn. Light nw flow lake effect to start
Sat evening should tend to reorganize into the land breeze
convergence zones by Sun morning. Depending on the lingering
strength of the nw flow over the lake, this lake effect pcpn should
mostly affect areas close to the shore. In this type of land breeze
driven pattern, more persistent lake effect should tend to setup
btwn Marquette/Munising and vcnty of the Porcupine Mtns toward the
Portage Canal by Sun morning. Then, Sun into Sun evening, deepening
moisture profile and modest deep layer forcing will lead to some -sn
developing across the area. While that won`t be of any importance
(snow accumulations generally not much more than 1 inch), the
synoptic forcing/deep moisture will set the stage for potentially
some locally mdt or even hvy LES with the key word being locally.
Inverted trof location on Sun and then sharpening of the convergence
along the trof as land breeze component strengthens Sun night will
be the area to monitor. Right now, it appears somewhere btwn Big Bay
and Grand Marais would be the area that may be impacted. Those
details won`t be known until we get closer to that time. Out w,
convergence won`t be as focused, but that area will also be inline
for some LES accumulations given the more favorable synoptic setup
for a time. LES will wind down on Mon as high pres ridge builds into
the northern Great Lakes. Any lingering LES will end Mon evening as
winds back sw. Passing high pres ridge will allow temps to plummet
Mon night. Traditional cold spots over the interior w may slip blo
10F. A quick check of a few sites in the climate database indicates
that record lows will be challenged Mon night.

Shortwave tracking across s central Canada to northern Ontario will
lead to increasing sw winds on Tue. Pcpn associated with this wave
should pass mostly n of Upper MI. A couple of shortwaves will pass
over or n of the fcst area thru mid and late week. For now, none of
these waves look to generate any noteworthy pcpn. Pcpn would be
light and generally scattered at most.
&&

.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
Issued at 637 PM EDT FRI OCT 23 2020

Lake enhanced snow showers will diminish this evening. IWD will stay
MVFR until late Sat afternoon with lake effect clouds remaining in
the area and some snow showers overnight tonight. CMX will gradually
get to VFR conditions with snow showers moving back in later
tonight. CMX will return to MVFR on Sat morning with lake effect
clouds around. SAW will gradually get to VFR this evening as snow
showers will let up.
&&

.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 345 PM EDT FRI OCT 23 2020

1034 mb high pressure is building into the Dakotas today as
deepening low pressure lifts northeast from Lake Huron into Quebec
tonight. The resulting pressure gradient and CAA and deeper mixing,
will result in continued northeasterly to northerly winds near 30kts
across the lake. Gale force gusts will be possible, particularly for
high reporting platforms like Stannard Rock. As the low lifts out,
winds will become northwesterly while settling back down to 25kts or
less. Expect winds to remain below 25 kts through the weekend.

The next notable system on the horizon looks to be Tuesday. Low
pressure will skirt through Manitoba and Ontario, resulting in
increasing southwesterly winds to possible minimal gales to 35 kts
mainly over the western half and north central sections of the lake
Tuesday. Winds should settle down back below 25kts late Tuesday
night.
&&

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

$$

SHORT TERM...Voss
LONG TERM...Rolfson
AVIATION...07
MARINE...Voss




Area Forecast Discussion

National Weather Service Nashville TN

 829 PM CDT Fri Oct 23 2020

.UPDATE...
FOR EVENING DISCUSSION.

&&

.DISCUSSION...

Latest surface observations show cold front has passed Clarksville
with temperatures already down into the upper 40s across western
Kentucky. After reaching the low to mid 80s across much of the
area today, this front will bring a chilly 25 to 35 degree
temperature drop by Saturday morning. Radar shows a line of
showers and thunderstorms continues ahead of the front and
currently stretches from Waynesboro to Jamestown. This activity
will continue slowly eastward through the night and by mostly
east of the Plateau by 3am or so per HRRR and CONSShort models,
but additional showers are expected to develop late tonight into
tomorrow as a secondary shortwave crosses the area. However, no
more strong or severe storms are anticipated due to the loss of
daytime heating and activity having moved east of the higher
instability axis. Have adjusted temperatures and pops
significantly based on latest obs and short term guidance. Rest
of forecast remains largely on track.

&&

.AVIATION...
00Z TAF DISCUSSION.

A cold front will move across the area tonight bringing showers/
storms, which will reduce VSBYs briefly, and later this evening a
low deck is expected to follow. Heavy rain will end before
midnight but low clouds and light showers/area of drizzle will
will keep conditions MVFR/IFR late tonight well into Saturday.
VSBYS likely to improve but CIGs expected to stay quite low.


&&

.OHX WATCHES/WARNINGS/ADVISORIES...
NONE.

&&

$$

DISCUSSION......Shamburger
AVIATION........07