Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 04/06/21

Area Forecast Discussion

National Weather Service La Crosse WI

 1059 PM CDT Mon Apr 5 2021

.SHORT TERM...(Tonight and Tuesday)
Issued at 130 PM CDT Mon Apr 5 2021

Upper level trough sliding eastward along the US/Canadian boundary
tonight, dragging a sfc front along with it. Bits of shortwave
energy spit out ahead of the main trough, kicking across northern
parts of MN/WI. The better frontogenetic lift expected to hold
northward too. Ribbon of 850:700 mb moisture transports pushes
north/northeast along the front. Expect convection to kick off
across central/northern MN this evening, moving east into the
overnight. Should become elevated as it nears the local forecast
area. Meanwhile, will also run into saturation concerns as you work
southward along the boundary plus a cap roughly around 800 mb. CAMS
hold the better shower/storm threat north of I-94 as a result. Can`t
rule out some scattered/isold activity southward - maybe more of the
mid level/ACCAS variety. With the northern storms, CAPE profile is
fairly skinny via RAP Bufkit soundings and minimal shear to work
with (20-30 kts 0-3km). Invert-V shape though, and any cap appears
minimal this evening. Any storm could produce some enhanced gusts.
Some strong possible, but think any severe risk is rather low.

Overnight, the GFS more rambunctious with pcpn chances along the
southern flank of the front, which suggests more widespread rains
for most of the forecast area by 12z. This looks tied to convection
the GFS starts over NE/SD this evening, with an MCV developing in
response and shifting across the local area. CAMS models aren`t
enthusiastic with this potential, and will lean the rain chances
this way.

The cold front leans over west-east as more of a warm front on Tue
with a piece of shortwave energy moving out of the southern Rockies
and up into the local area later in the afternoon. Expect showers, a
few storms to go along and north of the front later in the
afternoon, persisting through the night. Some instability (500 to
1000 J/kg SBCAPE) to play with, but skinny sounding profile wouldn`t
support strong updrafts. With potential saturation issues across the
south along with a stout low level cap, storm/shower chances look
limited roughly south of I-90.

A caveat to consider...

The HRRR and RAP move the front farther north on Tue compared to
other models...thus much of the forecast area is in the
warmer/capped off area. Pcpn chances would be small/none for most of
the day AND evening (esp if you like the HRRR).

Again, going to side with some chances mostly along/north of I-90,
but going to have to keep a close eye on where this boundary sets
up. It would be a lot drier, and warmer day if the northern solution
pans out.

.LONG TERM...(Wednesday through Monday)
Issued at 130 PM CDT Mon Apr 5 2021

Upper level, stacked low meanders eastward across the southern
plains by mid week, progged to slowly lift northeast across the
local area by 12z Fri. The low is mostly cutoff from the mean flow,
and not expected to get a push eastward until a shortwave trough
kicks east from the PAC NW Wednesday night, driving across the great
lakes for the weekend.

With the upper level low in the vicinity of the region through much
of the work week, along with various sfc boundaries, expecting a
fairly wet week. Steady influx of low level moisture via 850 mb
moisture transport to fuel on and off rain chances...with PWS
generally around 1" (or so) through the week. EC ensemble members
suggestive of 1 1/2 to 2 rain totals through the week. GEFS similar
although with a range of outcomes per its ensemble members. Mean
though is closer to 1 3/4 with many members above that. All in all,
looks like a prolonged period with beneficial rains regionwide.
Considering how dry its been, and the several day period of rain,
don`t anticipate any water concerns. Wed/Wed night currently
trending to be the wettest period.

There does look to be some instability to play with from time to
time, and expect some storms here and there. As for whether there
would be enough instability to overlap with favorable shear for a
strong/severe storm threat isn`t clear. Wed could be interesting as
cold front shifts in from the west. If we can clear for a period
ahead of the front, and if favored timing of sliding the boundary in
toward 00z Thu plays out, there could be some low level shear to aid
storm development. Something to keep an eye on. A lot of "ifs".

&&

.AVIATION...(For the 06Z TAFS through 06Z Tuesday night)
Issued at 1059 PM CDT Mon Apr 5 2021

The main concern for the overnight hours is whether any of the
ongoing convection across Minnesota is going to move across either
site. This activity has developed ahead of a cold front as a short
wave trough moves across far southern Canada. The latest hi-res
meso-scale guidance is split on what the activity will do. The
HRRR runs have been lifting the activity to the northeast in
conjunction with the more sustained forcing from the short wave
trough. However, the 06.00Z NAMnest and NSSL WRF suggest the
possiblity of the activity developing a cold pool and moving more
east/southeast withing the CAPE axis that the RAP shows nosing
into the area overnight. While not specifically adding a mention
of any showers or storms overnight, did adjust the forecast grids
to at least acknowledge this possibility and some mention may need
to be added starting around 08Z or so. Otherwise, not a lot of
activity is expected until Tuesday afternoon tied to a short wave
trough approaching from the southwest. Most of the meso-scale
models suggest the next round may develop to the north of both
sites but based on forecast pops, was obligated to at least
include a vicinity in the late afternoon and evening hours.

&&

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

$$

SHORT TERM...Rieck
LONG TERM....Rieck
AVIATION...04



Area Forecast Discussion

National Weather Service Boston/Norton MA

 1024 PM EDT Mon Apr 5 2021

.SYNOPSIS...
Low pressure meanders south of Nova Scotia and may bring a few
showers at times to Cape Cod tonight, along with extra clouds
across eastern MA. Otherwise, dry and mild conditions persist
through most of this week with above normal temperatures,
especially away from the coast. The risk for some rain showers
may return next weekend, but confidence is very low.

&&

.NEAR TERM /UNTIL 6 AM TUESDAY MORNING/...
1025 PM Update:

Observed temperatures continue to outpace forecast values by 3-5
degrees, due to NW gradient winds ~ 10 mph and variable amounts
of cloudiness associated with distant coastal low over the
eastern Gulf of Maine and the Canadian Maritimes. Opted for a
slower cooling rate utilizing some of the bias-corrected temps
to try to capture the milder bias. While NW winds should begin
to subside into the overnight hrs, there should be enough wind
flow around even as cloudiness scatters/clears to allow for some
tempered radiational cooling. Ended up raising lows a couple
degrees into the upper 30s/around 40 across western MA/northern
CT to the mid 40s near coastal eastern MA.

Previous discussion from 8 PM:

Gusty NW winds combined with clouds overspreading most of MA, RI
and eastern CT from the retrograding low to our east have kept
temperatures ~5 degrees above forecast conditions. Much of the
area remains in the 50s away from the coast. To account for
this, temperatures were blended with the more bullish HRRR
guidance to bring lows up from widespread upper 30s to the low
40s across much of the area. As winds diminish this evening,
western MA and the CT River Valley have the greatest potential
to radiate a few hours before sunrise as clouds begin to pull
east. Otherwise, the forecast remains on track this evening.

Previous Discussion...

Far eastern zones can`t escape the influence of the low pressure
swirling over the Maritimes this afternoon. A deck of mid clouds
continues to blanket the region from Worcester east. Light returns
continue to show up on radar over the extreme east coast, but the
supremely dry air in the lowest 3,000 ft is doing a number on
moisture`s ability to make it to the ground (we`re talking dewpoint
depressions of 20 to 35 degrees). Most locations that see overcast
now won`t see much clearing at least through sunset. We`ll remain
sandwiched between the low offshore and a ridge of high pressure to
our west overnight maintaining strong but decreasing NW flow. This
means winds will come down significantly but remain breezy
overnight. It will be a rather mild night, but a few degrees colder
than last night, in the upper 30s and low 40s.

&&

.SHORT TERM /6 AM TUESDAY MORNING THROUGH TUESDAY NIGHT/...
Tuesday the low over Nova Scotia slowly but surely begins to shift
further east while surface high pressure builds overhead. As this
happens the pressure gradient slackens and the low level jet moves
away. This means winds will be quite a bit less on Tuesday which,
together will moistening low levels will dampen the fire weather
concerns that we saw today. Dewpoints on Tuesday will rise into the
low to mid 30s, with relative humidities of 30 to 45 percent outside
of the Cape and islands. Winds gust 15 to 20 mph at times. We`ll
keep the chance of mid clouds around as some weak ripples in the
flow rotate around the exiting low bringing a mix of clouds and sun;
may even see some light showers on the outer Cape early to mid
morning. Not expecting much change in the airmass overhead, so
should see highs similar to today, in the 50s and 60s. Again, Cape
Cod and the islands will be the coldest in the low 50s thanks to the
ocean influence. Overnight mid levels dry out a bit so should see
clearing skies as temperatures dip into the upper 30s and low
40s.

&&

.LONG TERM /WEDNESDAY THROUGH MONDAY/...
Highlights

* Dry and seasonably mild Wednesday through Friday.

* Cape Cod will remain the coolest location through the week,
  influenced by a retrograding low south of Nova Scotia.

* Next shot for showers is next weekend, however, confidence is low
  at this time. Temperatures will drop towards climatology for the
  weekend.

Wednesday through Friday...

The blocking pattern that kept low pressure nestled off our coast
earlier in the week persists, however, weak high pressure builds in
slowly from the southwest mid-week. A significant low pressure
system develops across the mid-west, but will track to our northwest
as a ridge centers itself over our area late week. Thanks to the
omega block in place, high temperatures are not expected to vary
much this week, but will remain slightly above climo norms;
widespread upper 50s and low 60s, warmest in the CT River Valley.
With the departure of the low to our east, a few shortwave features
may toss periods of cloudiness our way Wednesday, but cloud cover
will gradually decrease, yielding pleasant, partly cloudy skies
Thursday and Friday. As is typical in April, seabreeze development
is likely with low surface winds under high pressure. Temperatures
to remain in the low 50 along the eastern coast of MA, Cape Cod, and
the Islands given sea surface temps in the low to mid 40s.

The warmest day of the week looks to be Friday, where temperatures
will max out in the mid to upper 60s, especially across the CT river
valley and Metrowest. Given that winds will be from the
south/southwest across western zones, there is potential for
temperatures to overperform in these areas.

Fire weather concerns early in the week fall by the wayside by
Wednesday. A moistening boundary layer, with dewpoint temperatures
in the mid and upper 30s on Wednesday and 40s Thursday and Friday,
combined with light winds support the notion that fire weather
criteria will not be met. Widespread RH values between 40 and 60
also expected.


Friday night through Sunday...

There is agreement between guidance that the ridge that set up camp
over New England on Thursday/Friday will persist into the early
weekend. Some guidance, namely the GFS, points towards the
degradation of the blocking pattern late in the weekend, opening the
door for a low pressure system to approach from the southwest on
Sunday. Should this solution occur showers may develop, especially
for our western zones, on Sunday afternoon and evening. Given there
is considerable disagreement in the guidance in regards to chance
for precipitation late in the period, NBM guidance was used to
include a slight chance/chance of showers.

Like precipitation, there is significant disagreement in the
guidance regarding temperatures this weekend, but both the GFS and
ECMWF narrow in on Saturday being the (slightly) warmer of the two
days. Some guidance, namely the Canadian model suggests that there
may be somewhat of a back door cold front late Sunday, so NBM
temperatures were favored in the forecast given this shot of cold
air resides at the end of our forecast period.

&&

.AVIATION /02Z TUESDAY THROUGH SATURDAY/...
Forecaster Confidence Levels.

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

Tonight...High confidence.

VFR with the gusty NW winds gradually diminishing. Some
expansion of the mid to high clouds a bit further west. Cloud
bases between 4-10 kft. There could be some MVFR ceilings
pushing in to the outer Cape toward daybreak. Gusty NW winds
will diminish towards daybreak.

Tuesday and Tuesday night...High confidence in trends. Moderate
confidence in timing.

Lower clouds should continue to push west Tuesday morning, with
conditions likely towards the outer Cape and Nantucket. There
is some question as to how far west MVFR conditions make it.
MVFR conditions are not likely to affected BOS. Should see NNW
to N winds at 5-10 kts and cannot rule out a few 20 kt gusts
across Cape Cod and Nantucket. VFR continues Tuesday night with
light NW winds.

KBOS TAF...High confidence in TAF.

KBDL TAF...High confidence in TAF.

Outlook /Wednesday through Saturday/...

Wednesday: VFR.

Wednesday Night: Mainly VFR, with areas MVFR possible.

Thursday: Mainly VFR, with local MVFR possible.

Thursday Night through Friday Night: VFR.

Saturday: VFR. Slight chance SHRA.

&&

.MARINE...
A low pressure lingering south of Nova Scotia will continue
to generate gusty NW winds with gusts 25-30 kt this afternoon
into tonight. Seas 7-9 ft over waters east of Cape Cod. Small
Craft Advisories for all eastern waters. Winds diminish some
tonight, but rough seas continue into Tuesday and Tuesday night
across the eastern outer coastal waters. Mainly dry conditions
with good visibility. A few showers are possible tonight, with
brief reductions in visibility.

Outlook /Wednesday through Saturday/...

Wednesday through Thursday: Winds less than 25 kt. Areas of
seas approaching 5 ft.

Thursday Night: Winds less than 25 kt. Seas locally approaching
5 ft.

Friday through Friday Night: Winds less than 25 kt. Areas of
seas approaching 5 ft.

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

&&

.FIRE WEATHER...
Elevated fire parameters continue this afternoon with minimum
RH of 20-30 percent away from the immediate coast along with NW
winds gusting to 25-35 mph at times. Fire concerns diminish on
Tuesday as the low levels moisten and winds diminish.

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...Small Craft Advisory until 8 PM EDT Tuesday for ANZ250.
     Small Craft Advisory until 4 AM EDT Tuesday for ANZ231-251.
     Small Craft Advisory until 11 AM EDT Wednesday for ANZ254-255.

&&

$$
SYNOPSIS...BW/Chai/KS
NEAR TERM...Loconto/BW/KS
SHORT TERM...BW
LONG TERM...Chai/KS
AVIATION...Loconto/BW/Chai/KS
MARINE...Loconto/BW/Chai/KS
FIRE WEATHER...



Area Forecast Discussion

National Weather Service Cheyenne WY

 529 PM MDT Mon Apr 5 2021

.SHORT TERM...(This evening through Tuesday)
Issued at 240 PM MDT Mon Apr 5 2021

Forecast challenges deal with snow amounts and fire weather
issues.

Currently...Cold front on our doorstep. Currently front lays
across our northern CWA from Chadron to Glenrock...to a surface
low near Riverton. Winds have shifted northerly behind the front.
South of the front...southwest winds being reported with very warm
temperatures once again. Panhandle airports reporting low 80s with
wind gusts to near 25 mph. Rest of that zone (313) has been
staying below Red Flag criteria with Scottsbluff reporting winds
under 10 mph. Since winds are so isolated in the zone that has so
many sensors...decided to hold off on any fire headlines at this
time. Looks like front will move into the southern Panhandle by
22Z or so...roughly an hour away...so issuing now would not be
beneficial.

Around the area...CU seems to be pretty flat with afternoon CAPE
around 400-500 J/KG. Continued low chance PoPs as latest HRRR and
hires guidance continues to show convection developing through 03
to 04Z.

.LONG TERM...(Tuesday through Sunday)
Issued at 417 AM MDT Mon Apr 5 2021

An 500 mb upper level closed low will continue to drop into the
area, with colder air filtering into southeast Wyoming over the
course of the morning. By mid-morning, all precipitation will have
switched from rain to snow along and west of the Laramie Range; rain
showers will be noted to the east of the Laramie Range. Could see a
few heavier showers under thunderstorm activity in the morning along
the Pine Ridge as the frontal boundary pushes east. By the afternoon
period, a slight chance of thunderstorms will be present across both
southeast Wyoming and the west Nebraska Panhandle as the main closed
low slides across the area with a few vorticity maxima embedded
within it, increased CAPE, instability and lapse rates. By night
fall, the cold front will have made it completely across the region
to the east, with temperatures in the upper 20s and low 30s noted
across the region and snow likely at all locations. Most locations
will only a a trace to a few hundredths of snow; however, the
highest terrain and the Pine ridge will see a few inches, generally
2-3 inches, with a few isolated locations possibly noting 4-5
inches.

The upper low will drop towards the southeast and all wrap-around
moisture will taper off by Wednesday afternoon. Behind this trough,
heights will rise, and high temperatures will bounce back into the
50s. Under a shortwave ridge, should see temperatures climb into the
60s Thursday, though a quick hitting open wave 500 mb trough Friday
will bring breezy conditions as well as highs back into the 50s, our
normal for this time of year. These conditions will extend into the
weekend.

&&

.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Issued at 525 PM MDT Mon Apr 5 2021

As a front begins to move through SE WY and W NE, the wind will be
changing to northerly with gusts 18 to 25 knots right now at many
TAF terminals. Winds may gust 25 to 35 knots tonight into tomorrow
morning. In addition, ceilings and visibilities may drop to
VFR/MVFR levels during and after the front moves through until
around 00Z tomorrow with the potential for some light rain/snow at
KCDR.

&&

.FIRE WEATHER...
Issued at 417 AM MDT Mon Apr 5 2021

A concerning, near-critical fire weather day ahead today with
LAL2 conditions paired with above normal temperatures, low
humidities in the low teens, and gusts generally up to 20 mph.
Could be a short window of dry and gusty conditions across the
upper Panhandle this afternoon, but strongest winds should occur
behind the southward- dropping front as humidities rise. Dry
thunderstorms will be the main concern today however with this
front and could be noted along and west of the Laramie Range,
extending east as they initiate along the mountains, into Platte,
Goshen and Laramie Counties this afternoon. Precipitation and
colder temperatures Tuesday and Wednesday before another round of
dry conditions under seasonable high temperatures for the
remainder of the week and next weekend.

&&

.CYS WATCHES/WARNINGS/ADVISORIES...
WY...None.
NE...None.
&&

$$

SHORT TERM...GCC
LONG TERM...AB
AVIATION...LK
FIRE WEATHER...AB



Area Forecast Discussion

National Weather Service Duluth MN

 1015 PM CDT Mon Apr 5 2021

.DISCUSSION...(This evening through Sunday)
Issued at 253 PM CDT Mon Apr 5 2021

Near critical fire weather conditions across northeast Minnesota
this afternoon, a threat for thunderstorms possibly severe this
evening, all followed by very much needed rainfall mid to late
this week highlight the forecast.

High temperatures in the 70s with relative humidity between 10 and
20 percent will continue this afternoon into the early evening
across much of northeast Minnesota away from the influence of Lake
Superior. When combined with dry fuels and southeast wind gusts to
20 mph, near critical fire weather conditions are possible.

Most of northeast Minnesota and northwest Wisconsin are in a
Marginal Risk from SPC for severe thunderstorms for this evening,
with a Slight Risk from the Brainerd Lakes area through the I-35
corridor. The threat is greatly dependent on moisture return south
of a warm front that has made its way from the Brainerd Lakes
through Hayward and Phillips as of 20 UTC. Even still dewpoints
to the south of the warm front that will continue to advect into
the Northland look even more marginal than before with values in
the lower 40s to the lower 50s. Thus, the best chance for severe
convection, and perhaps just thunderstorms themselves is from the
Brainerd Lakes area towards the I-35 corridor and into northwest
Wisconsin where moisture will be greatest. Dewpoints as low as the
teens and 20s across much of the Arrowhead of Minnesota as well
as a far inland reaching lake breeze will limit the threat for
these areas.

Regarding forcing, a cold front across northwest Minnesota will
propagate east to an International Fall to Brainerd line around 00
UTC, arriving across western Lake Superior around 06 UTC. MLCAPE
around 1000-1500 j/kg with steep mid level lapse rates and around
30-35 kts of deep layer shear largely orthogonal to the cold front
supports the conditional severe threat for scattered
thunderstorms possibly severe this evening. Again this is
dependent on moisture return from the south. The 12 UTC CAM suite
shows a large spread of solutions from very little organized
convection, to the more relatively intense HRRR and FV3-SAR. Large
hail to around half dollar size and damaging wind gusts to 60 mph
with remain the primary threats with high based discrete storms
along the cold front, with convection eventually growing upscale
as the warm front continues to propagate north, intersecting with
the cold front.

Looking ahead to Tuesday night through at least Friday, a very
slow moving and closed system will impact the Upper Midwest with a
very broad precipitation shield. This is favored to bring very
much needed widespread rainfall to the region, possibly 1 to 2
inches by Saturday.

&&

.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Issued at 649 PM CDT Mon Apr 5 2021

A warm front has moved north into far northern Wisconsin and
extended west toward a cold front that was into north central
Minnesota. Showers and thunderstorms were occurring ahead of the
cold front as far east as northern Wisconsin and the Arrowhead. We
expect these to continue and others to form along and just ahead
of the cold front this evening. Some strong to possibly severe
storms will be possible with the main threats strong wind and hail
around to just over an inch in diameter. Conditions for most areas
will remain VFR but with the stronger storms/showers, brief
periods of MVFR or even IFR will be possible. The front will
continue east overnight and clear the Arrowhead and northern
Wisconsin late tonight into early Tuesday morning. Winds will
switch to northerly behind the cold front.

Some low level wind shear will occur this evening, mainly
affecting KHYR but possibly KDLH briefly.

&&

.MARINE...
Issued at 1015 PM CDT Mon Apr 5 2021

Winds have diminished some from what they were earlier today.
However, showers and thunderstorms will continue to move across
western Lake Superior for the next several hours and locally
higher winds and waves will occur near them. Gusts to 40 knots
will be possible with the strongest storms and hail to nickel size
will also be possible. These storms will occur ahead of a cold
front which will move across the lake tonight switching the wind
to northerly for a time. There may also be brief gusts to 25 knots
with frontal passage.

Tuesday will be dry with winds veering to east to northeast but
remaining at or below 15 knots. An area of low pressure will bring
widespread rain into the area later Tuesday night into Wednesday.
East to northeast winds will increase and be form 15 to around 20
knots with higher gusts by Wednesday morning and they will
strengthen further Wednesday into Wednesday night. Some gales will
be possible Wednesday into Wednesday night.

&&

.PRELIMINARY POINT TEMPS/POPS...
DLH  41  55  39  44 /  40  20  90  80
INL  33  56  35  51 /  10   0  10  60
BRD  41  61  42  51 /  30  20  90  80
HYR  47  60  44  60 /  50  50  90  70
ASX  43  53  39  50 /  50  20  90  70

&&

.DLH WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...None.
LS...None.
&&

$$

DISCUSSION...PA
AVIATION...Melde
MARINE...Melde



Area Forecast Discussion

National Weather Service Northern Indiana

 737 PM EDT Mon Apr 5 2021

.SYNOPSIS...
Issued at 341 PM EDT Mon Apr 5 2021

Isolated to scattered showers and a few thunderstorms will be
possible through early this evening. Skies are expected to clear
later tonight with sunny to party cloudy conditions expected for
Tuesday. The unseasonably warm weather will continue through the
middle of the week with high temperatures in the mid to upper 70s
for Tuesday and Wednesday. Dry weather is expected Tuesday into
early Wednesday, with widespread rain and isolated thunderstorms
affecting the region late Wednesday night into Thursday.

&&

.SHORT TERM...(This Evening through Tuesday)
Issued at 341 PM EDT Mon Apr 5 2021

An outflow reinforced sfc trough axis extends from southwest Lower
Michigan into northwest Ohio this afternoon. Continued influx of
higher theta-e air southwest of this boundary continues to trigger
scattered showers north of the US 30 corridor. Persistent high cloud
cover also may be aiding in some differential heating forcing for
new shower generation over the past hour or two across northwest
Ohio. Another upstream vort max across northern Illinois should work
east-southeast across the western Great Lakes this afternoon. RAP
near term forecast progs were depicting axis of 400-800 J/kg of
surface based CAPE across northwest Indiana late this afternoon in
advance of this wave, although good cirrus coverage may be prevent
full realization of this instability. With instability now even more
in question, not as confident in second round of isolated convection
late afternoon/early evening as this short wave approaches. However,
given this increase in forcing next few hours and slow accompanying
eastward migration of steeper mid level lapse rates across northern
Illinois, will continue to carry 20-30 PoPs into early evening. Some
concern noted earlier that if more robust isolated showers could
develop in narrow window late afternoon, that very dry subcloud
layer in inverted-V type sounding could be favorable for some
isolated stronger wind gusts. However, given more questionable
instability profiles, confidence in that scenario is lower. Greatest
coverage of showers/isolated storms over next few hours will likely
remain across the far northwest where shallow cold Lake Michigan
dome may be aiding in some enhanced lift for ascending elevated
parcels.

Diurnal cooling and eastward push of steeper mid level lapse rates
should effectively cap things for surface and elevated parcels late
evening into the overnight. Mid level heights to build slightly on
Tuesday with lack of any discernible forcing mechanisms for
additional precip and likely maintenance of convective inhibition
given mid level subsidence reinforcing cap. Tuesday will feature
warm conditions once again with relatively deep mixing as surface
boundary should mix northward across the Great Lakes. Building
heights should also be accompanied by secondary increase in low
level theta-e advection during the afternoon. Have not made many
changes to previously forecasted highs in the mid to upper 70s with
dry conditions persisting Tuesday.

&&

.LONG TERM...(Tuesday Night through Monday)
Issued at 341 PM EDT Mon Apr 5 2021

Medium range models continue to exhibit better convergence in
solutions for the Wed-Thu period as blocking pattern across eastern
CONUS/western Pacific results in slow progression of main central
CONUS upper low. Guidance has trended to some increasing negative
tilt with the upper low as we head into late Wednesday night into
Thursday. Above factors still appear to support forecast trends over
last several cycles of slowing onset of higher PoPs Wednesday.
Greatest delay in PoPs likely to take place across the far northeast
including south central Lower Michigan due to negative tilt
evolution and a more delayed onset to deeper moisture across these
locations. While longwave pattern is slow to evolve, stronger vort
max rotating around parent low should be progressive in nature
resulting in progressive occluded front late Wednesday night into
Thursday. Total rainfall amounts may be somewhat limited given a
relatively short residence time of deeper moisture profiles locally
in this pattern. Forecast soundings do indicate this increase in
large scale forcing may be enough Wednesday to at least raise the
base of the mid level inversion to possibly overcome any weak
capping issues for some weak surface based instability. Thus, have
maintained iso thunder mention during the day Wednesday with a
potential of smaller scale perturbations progressing through the
flow downstream of primary upper trough. No change from previous
forecast in focusing likely/categorical PoPs for overnight Wednesday
into Thursday. Otherwise, much above normal temperatures to continue
Wednesday in the warm sector.

Confidence is still on the relative low side for timing and extent
of precip chances post-Thursday. Some consistent signals are
developing in medium range models for another significant eastern
Pacific trough to dig across the northern Rockies by Friday.
Guidance consensus still not indicating great phasing of this system
with slowly departing mid-week upper low, but this should provide
some renewed rain shower chances toward the early weekend period.
Temperature forecast becomes a bit more muddled for Days 5 through 8
as mid/upper level pattern evolution could yield fairly strong
thermal gradient across the Great Lakes/MS Valley region. With low
confidence have generally yielded to consensus high temps in the 60s.

&&

.AVIATION...(For the 00Z TAFS through 00Z Tuesday Evening)
Issued at 735 PM EDT Mon Apr 5 2021

Quasi-stationary boundary has dropped just south of both TAF sites
resulting in a light E/SE flow to begin this cycle. Boundary also
focus for a few areas of light rain showers that may briefly
impact KFWA at the outset but both ceilings and visibilities will
remain at VFR. Boundary lifts back north of the area overnight
which will bring winds back around to the southwest. Surface
gradient will support sustained winds of 12-15kts and forecast
soundings indicating potential to mix down 20-25kt gust Tuesday
afternoon.

&&

.IWX WATCHES/WARNINGS/ADVISORIES...
IN...NONE.
MI...NONE.
OH...NONE.
LM...NONE.
&&

$$

SYNOPSIS...Marsili
SHORT TERM...Marsili
LONG TERM...Marsili
AVIATION...JAL


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Area Forecast Discussion

National Weather Service Marquette MI

 820 PM EDT Mon Apr 5 2021

.SHORT TERM...(This evening through Tuesday)
Issued at 400 PM EDT MON APR 5 2021

Potential record high at IWD, up to 79 at the airport (record of 75,
1912) this afternoon as Upper Michigan remains under a broad ridge.
Latest RAP soundings suggest deep mixing through roughly 700 to
600mb, leading to some pretty dry dew points and RHs this aftn, thus
the firewx potential will continue through the evening hours. 30kt
winds at the top of this mixed layer aren`t quite making it to the
sfc, though, so thankfully it hasn`t gotten too breezy where the
temperatures are the warmest.

A bit of uncertainty heading into tonight as models suggest a sfc
trof lifting from the Dakotas into wern UP after 00Z tonight. At the
same time, a shortwave and associated sfc trof and cold front to the
N through Canada will pass by to the N of Lake Superior, as the sfc
front passes over the lake late tonight/tomorrow morning. Theta-e
adv through the day today and into tonight will build a decent
amount of elevated CAPE across Upper Michigan tonight, which these
trof features will interact with between3 and 9Z tonight. Question
is, will there be enough instability to kick off some tsra or will
it remain as mostly rain? Some models ave up to 1000 j/kg of MUCAPE
tonight, lifting from around 700mb in the RAP, little over 1000J
from NAM a little lower down as well. Trends through the day from
RAP have been trending away from rain and tsra tonight across the
UP, whereas the HRRR has been trending a bit further towards. Most
of the UP is under a deep forcing for ascent lul, so convection
chances are based on this elevated instability. Going to want to
monitor the trends and nowcast a bit into tonight as CAMs have some
disagreements in timing and placement. With elevated instability and
CAPE up to 1000J/kg possible, main hazard would be hail, but other
kinematics aren`t overly impressive.

For tomorrow, cold front stalls out over wern Upper Michigan as
associated shrtwv pulls away to the NE. Despite ridging remaining
overhead, northerly winds should keep temperatures cooler than they
are today as 850mb temps drop back down to roughly 7C...but still 10
to 15 degrees abv normal.

.LONG TERM...(Tuesday night through Monday)
Issued at 338 PM EDT MON APR 5 2021

Beginning Tuesday night, an upstream upper level low over the
Central Plains will begin impacting the area. This system`s warm
front will first swing through the region from the south to the
north. Moisture and isentropic lift will increase through the night
as the boundary lifts northward through the region. Guidance is
mixed on the convective signal, with the NAM appearing to be the most
bullish with elevated MUCAPE of 500-1000j/kg. With PWATS increasing
to around an inch through the night, if the convective potential is
realized along the boundary, a thunderstorm with some brief
downpours can`t be ruled out as the showers lift through the region.
Guidance appears to shift a dry slot over the forecast area by
Wednesday afternoon. Lows should be near 40F across the region, with
some high 30s possible in the north half. Highs Wednesday should top
out near 60 in the south half and closer to 50 by Lake Superior.

From there, downstream blocking is expected to really pump the
breaks on this low`s northeastward progression through the region.
In fact, GEPS and GEFS position the various members over the western
portion of the CWA to northeastern MN. The result of this slow
motion will be multiple waves of rain showers lifting northward
through the remainder of the work week. 12z guidance suggests higher
rain probabilities across the western half of the CWA due to the
enhanced convergence along the system`s inverted trough, but
scattered rain showers can`t be ruled out from this system in the
central and east through Friday.

Upstream on Friday, a shortwave is progged to eject out of the
northern Rockies. As the upstream ridge over the northeast looks to
persist, guidance suggests this shortwave could boomerang north
through the Upper Great Lakes. While guidance varies on timing and
structure of the system, these suggest shower potential will persist
through the weekend.
&&

.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Issued at 820 PM EDT MON APR 5 2021

An approaching front and disturbance will bring the potential for
showers and a few thunderstorms across Upper Michigan tonight.
Although confidence in the coverage and timing was still limited,
the probability was high enough to warrant mention of VCTS. Low
level moisture will increase overnight, especially if more
widespread rain develops. MVFR cigs/vsby later tonigh may also drop
to IFR at KCMX and KSAW Tuesday morning into the afternoon.
&&

.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 400 PM EDT MON APR 5 2021

A few gusts to around 30 knots from the SE into this evening across
eastern Lake Superior before an approaching trof weakens as it moves
across Lake Superior tonight and Tue. In fact, the trof will
dissipate soon after reaching far eastern Lake Superior later Tue
aftn. As this trof arrives over western Lake Superior, winds over
the w will diminish to blo 20kt tonight, then remain under 20kt Tue.
Winds will then diminish to blo 20kt Tue. NE winds over western Lake
Superior and e to se winds over eastern Lake Superior will be on the
increase late Tue night thru Thu as low pres organizing over the
central Plains Tue night lifts toward the Upper Mississippi Valley
on Thu. Winds will likely increase back into the 20-30kt range over
much of Lake Superior, beginning first over western Lake Superior.
Winds should fall back a little on Fri as the low moves closer and
pres gradient weakens some.
&&

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

$$

SHORT TERM...JAW
LONG TERM...JP
AVIATION...JLB
MARINE...JAW