Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 05/23/21
Area Forecast Discussion
National Weather Service Gaylord MI
1135 PM EDT Sat May 22 2021
.UPDATE...
Issued at 931 PM EDT Sat May 22 2021
It was a good run, but the cold front that has been perched just
north of Superior for a few days is on its way south. This is
occurring as strong high pressure builds across central Canada,
and as a digging shortwave racing toward New England briefly
suppresses heights aloft. Showers are seen north of the front over
northern Superior, and a few TSRA are seen back toward Isle Royale
where the tail end of the precip area intercepts the surface
front. Closer to home, a cu field is waning in the HTL area, with
just some patchy mid/high clouds elsewhere. Plenty of haze/fog/
stratus over the colder Great Lakes though.
The front is progged to to be somewhat south of a TVC-APN axis by
8am. With the shortwave and speed max aloft racing eastward,
dynamics will be diminishing with time for us. And instability is
also decreasing. Bulk of the near- and post-frontal convection now
over Superior will stay north of eastern upper MI. However, some
showers remain possible up there, especially in Chippewa Co. RAP
continues to kick off a few showers in nw lower MI (mainly s and
sw of TVC) toward morning. This is within a marginal MuCape axis
that folds into nw lower MI out of WI late. An isolated pop there
remains fine.
Min temps from low-mid 50s in eastern upper, to the mid 60s in se
sections.
&&
.NEAR TERM...(Through Tonight)
Issued at 358 PM EDT Sat May 22 2021
High Impact Weather Potential: Minimal.
Pattern Synopsis/Forecast: Surface boundary stretches from the
front range of the Rockies northeastward through the Upper
Midwest into Ontario, then eastward into Quebec with several weak
sfc waves along the front. Boundary has made some very modest
movement S/E today, fixed between strong sfc high pressure
through the Ohio Valley and secondary strong high building across
south-central Canada.
Aloft, large scale ridging remains across the eastern CONUS,
downstream from a closed low over the far western states. Lots of
warm air in place through the eastern CONUS and Great Lakes along
with a nice plume of deep layer moisture extending from the Texas
Gulf Coast up into the Midwest and Great Lakes. Some slightly
drier air has managed to squeeze into the region (evident on water
vapor imagery). Along with late May sunshine, we finally managed
to mix out the low cloud cover from earlier in the day leading to
a SCT-BKN Cu deck across the region. But marine stratus remains
prominent on the lakes (60s dewpoint air over the cold lakes). As
anticipated, a few showers have popped across interior eastern
Upper Michigan along a narrow lake breeze convergence axis.
Deep layer ridge across the eastern CONUS is expected to meander
down toward the Gulf Coast through tonight with slightly lowering
mid level heights nosing into the northern lakes region. Sfc
boundary across the Midwest and Ontario folds down into northern
Lower Michigan by Sunday morning, in response to strong Canadian sfc
high pressure continuing to build across Ontario.
Primary Forecast Concerns: Low end shower chances along and ahead
of the boundary.
Sfc boundary and tight baroclinic zone will be sliding down
through eastern Upper Michigan into the tip of the Mitt by early
Sunday morning. Not overly impressed with shower chances with the
boundary. But given our somewhat moist environment I`ll maintain
our lower end shower chances across eastern Upper for the
overnight. Further south, RAP13/NAMNEST guidance suggests there
will be a narrow axis of MUCAPE that extends out of Wisconsin into
northern/central Lower Michigan overnight, which might kick off
additional spotty showers well ahead of the front toward morning.
Again, not overly confident that will happen...but I have added
some lower end pops to the forecast across the SW counties.
&&
.SHORT TERM...(Sunday through Tuesday)
Issued at 358 PM EDT Sat May 22 2021
High Impact Weather Potential: Possible thunder at
times...
Pattern Synopsis/Forecast:
Upper level shortwave trekking through the flow to our north will
diminish heights and therefore ridging across the Great
Lakes...giving the flow a more northwest-to-southeast oriented look
Sunday...with cooler and drier air across the northern half of the
state behind a backdoor cold front dropping in from the north.
As upstream troughing in the western US lifts northward through the
flow there...will look for ridging to build eastward across the
central US/Canada Sunday night ahead of said troughing...lifting the
cold front back north as a warm front into Monday...with potential
for some shower and thunderstorm activity. This will result in
another period of warm and somewhat humid conditions for the early
part of the week...until a more substantial cold front brings a
cooler air mass toward Michigan...leading to additional chances for
shower and thunderstorm activity into the region Tuesday...as that
shortwave moves toward us.
Primary Forecast Concerns: Precipitation/thunder chances
through the period...high temperatures through the period...
Will be watching the start of the period for some weak activity with
that backdoor cold front dropping in from the north. Broad westerly
flow aloft will likely keep things warm and somewhat moist
aloft...while surface high pressure to our north will advect cooler,
drier (RH-wise) Canadian air into the region. This may keep us from
getting too drizzly...but on the other hand...would not be surprised
if low clouds stuck around, sort of similar to today (but less
humid). As the boundary/cold front dropping in will be bridged by
high pressure on Sunday...with a surface high to our north (as
mentioned earlier) and another to our south in the Ohio Valley
region...will expect the boundary to not make too much progress
southward and ultimately stall out somewhere across lower Michigan.
Additionally...with the lifting upstream troughing lending to
organization of a surface system across southern Saskatchewan late
Sunday into Monday...will look for return flow to strengthen
again...allowing the boundary to lift back north as a warm front
Sunday night into Monday. Precipitation chances should increase with
this feature as that warm, moist air advects northward into the
area over that lingering boundary...though best chances attm look to
be just to our south. Will have to watch for the potential for some
thunder with this...perhaps best on Monday afternoon as we start to
get into the warm sector of the system as the warm front lifts
through.
The temperature forecast in the coming days will be a tad
tricky...as it will depend fairly heavily on the movement of that
boundary. For Sunday...will look for generally cooler temperatures
across the north, and slightly warmer in the south, where there is
potential for things to warm up a tad before the front dives
in...likely reaching central Lower by early afternoon...though there
is still a bit of uncertainty in the timing of this...and exactly
where it ends up stalling out across southern Lower. Will
have to watch for a little breeziness behind this front...though
winds attm don`t look excessively strong. Northeasterly winds should
keep things cooler along the Lake Huron shores especially, with the
lakes still in the 40s for water temps. Monday will again depend on
that boundary...primarily, how far north it gets...and how much
cloud cover is able to affect things. As we`ve been seeing the last
few days...the current airmass is warm enough that only a bit of sun
is necessary to turn the dial up...probably not to the proverbial
eleven, but up nonetheless. Will look for southwesterly winds to
pick up Monday night as well...lasting into Tuesday...as that
strengthening low pressure to our west begins to progress eastward.
Will therefore expect warmer lows Monday night than Sunday night,
given this relatively strong warm, moist advection pattern.
Perhaps one of the bigger concerns for the short term is the
potential for thunder on Tuesday...as a more organized, more
baroclinic system approaches from the northwest. Continued warm,
moist advection in the lower levels Tuesday ahead of the main system
will lend to instability, especially as colder air aloft approaches.
Better dynamics will perhaps stay to our west...but it is
nonetheless worth keeping an eye on...as there should be some
instability...some lift ahead of the front...moisture available
(with pwats still at the high end of climo)...and some shear with
stronger winds moving in aloft.
.LONG TERM...(Tuesday night through Saturday)
Issued at 358 PM EDT Sat May 22 2021
High Impact Weather Potential: Minimal attm...
There is some uncertainty through the extended (not entirely a
surprise), given some differences in how quickly troughing exits the
area Tuesday night into Wednesday...and how an upstream trough,
poised to head eastward toward the Great Lakes late in the period,
evolves. Initially, though...will look for precipitation/thunder
chances to hold on into the night Tuesday night and perhaps even
early Wednesday, depending on how quickly the front moves
through...with cooler temperatures rolling in behind it for the
remainder of the week...as pattern becomes more zonal. Bottom
line...it should be cooler (probably closer to normal) and perhaps a
little on the active side going into the end of the week/start of
the Memorial Day weekend.
&&
.AVIATION...(For the 06Z TAFS through 06Z Sunday night)
Issued at 1135 PM EDT Sat May 22 2021
IFR Sunday morning PLN/MBL/TVC.
A cold front is about to enter eastern upper Michigan, and will
drop southward across northern lower MI very late tonight into
Sunday morning. Conditions are VFR now, though marine fog/stratus
lurks over the Great Lakes. As the front passes, and w to nw winds
develop, cigs and perhaps vsbys will sharply lower. Presently
keep APN as MVFR, but the other sites are IFR for Sunday morning.
Gradual improvement Sunday afternoon, but TVC/MBL are unlikely to
improve past MVFR.
Current sw to w winds will veer nw toward morning, then n and ne
by midday Sunday.
&&
.MARINE...
Issued at 358 PM EDT Sat May 22 2021
Westerly winds today will turn sharply north/northeast late
tonight into Sunday with passage of a cold front. Some gustiness
anticipated, although winds/waves will likely remain below
headline criteria. Winds weaken and veer more east/southeast
Sunday night and southerly on Monday with winds/waves remaining
below headline criteria through the period.
&&
.APX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LH...NONE.
LM...NONE.
LS...NONE.
&&
$$
UPDATE...JZ
NEAR TERM...BA
SHORT TERM...FEF
LONG TERM...FEF
AVIATION...JZ
MARINE...BA
Area Forecast Discussion
National Weather Service La Crosse WI
903 PM CDT Sat May 22 2021
.UPDATE...Tonight
Issued at 858 PM CDT Sat May 22 2021
Radars continue to show scattered showers across south-central and
southeast Iowa. This is associated with a weak shortwave trough.
During the overnight, there will be weak 925 and 850 mb moisture
transport and isentropic lift into northeast Iowa and southwest
Wisconsin. In addition, both the HRRR and High Res FV3 support
that these showers will move across this area during this time
frame. As a result, raised the rain chances in these areas.
&&
.SHORT TERM...(This evening through Sunday)
Issued at 239 PM CDT Sat May 22 2021
Main focus will be on thunderstorm/localized heavy rain on
Sunday.
Upper level ridging is well-established over the area this afternoon
per water vapor imagery. A few weak shortwave troughs currently
indicated across KS into southern IA will slowly progress northward
through the ridge with only minor height falls into tonight. Late
this afternoon a few showers could sneak into northeast IA/southwest
WI ahead of one weak wave, but these would look to be pretty
light/scattered. Not seeing much of a moisture transport signal
tonight with CAM solutions not overly excited in their reflectivity
fields. Scattered showers/iso storms may begin to develop overnight
into Sunday morning with the approach of a shortwave trough from the
south.
Going into Sunday there will be a shallow backdoor cold front that
tries to drop south associated with a trough passing well north of
the area. Moisture transport into the boundary looks to be on the
weak side and 0-2 km moisture convergence is also weak, suggesting
areal coverage will be fairly low for precip. With minimal capping,
though, expect some shower/storm development near the boundary
through the day. Given pwat standard anomalies of 2+, SBCAPE up
around 1000 J/kg, and warm cloud depths of over 3 km with slow storm
movement/weak upper flow, any storms will likely be efficient rain
producers. Due to weak low-level/deep layer shear, expect the severe
storm threat to be low with locally heavy rain the primary threat.
Some potential for localized 1 to 3 inch rain amounts exists, with
the CAM consensus still favoring the I-94 corridor. Given the dry
antecedent conditions, don`t expect flooding to be a big concern,
but will need to keep an eye on any training slow-moving
showers/storms.
.LONG TERM...(Sunday night through Saturday)
Issued at 239 PM CDT Sat May 22 2021
Tuesday appears to be the highest chance of severe storms for the
week, although that is still marginal.
As the western CONUS longwave trough lifts through the MT/Dakotas
Sunday night, the front near I-90/I-94 will begin to lift
northward with isolated to scattered showers and storms along it,
diminishing through the night. Consensus model information
suggests very light forcing and low-level moisture transport. The
focus really shifts west toward the Dakotas and the ejecting
forcing and instability.
By late in the day Monday, forcing increases just to the northwest
but isnt particularly impressive in the northern forecast area.
MUCAPE builds over the area and there is little/no capping in
place - so any focus could work to initiate storms. Thinking that
most of the day will be dry with the `cold front / dryline` being
located roughly from Duluth to Omaha late. Convergence may still
exist in nwrn WI with increasing storm chances late. Any shortwave
trough moving over in the southerly flow Monday could cause
storms...but it appears that will not happen until Monday night.
Monday night the best QC forcing lifts through northern MN and
nwrn WI ahead of the main longwave through over southern Canada.
Through Tuesday, the longwave begins to shift east and the ridge
collapses, driving the front southeastward. By Tuesday afternoon,
the front appears it should be over the area with suggestions of
an elevated mixed layer moving over the front aloft. This provides
a breakable cap and steep lapse rates in the 900-650 layer
(8C/km) which is favorable. Deeper bulk wind shear of 35-40 kts
suggests maybe some supercells would be possible near/north of
I-90. The hodographs do show a veer-back-veer signature, not ideal
for supercell storm growth. Clouds and ongoing showers may hamper
destabilization, and lend to a lower confidence forecast in
severe storm chances as well. But consensus MLCAPE in the
deterministic models from 1500 to 2500 J/Kg by afternoon east of
a Mason City-Winona-Medford WI line. So, the potential for severe
storms looks to be there for large hail and damaging winds under
slightly better wind shear and lapse rates.
Wednesday through Saturday...The front drives south of the area
providing drier and cooler days. While there are rain chances
later in the week as a system shifts across the area, it appears
storms will be hard to come by as the front and main instability
pool remain south of the area.
&&
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 615 PM CDT Sat May 22 2021
IFR/MVFR clouds will develop around 23.08z and then continue
through much of the morning before rising up into the 3-5K range
during the late morning and early afternoon.
Scattered showers and storms will develop on Sunday afternoon
along and north of Interstate 90. At this time, the CAMS are
suggesting this precipitation will remain just north of the TAFS,
so kept them out of the forecast.
&&
.ARX WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...None.
IA...None.
&&
$$
UPDATE...Boyne
SHORT TERM...JM
LONG TERM...Baumgardt
AVIATION...Boyne
Area Forecast Discussion
National Weather Service Charleston SC
1009 PM EDT Sat May 22 2021
.SYNOPSIS...
High pressure will linger across the region through the middle
of next week.
&&
.NEAR TERM /UNTIL 6 AM SUNDAY MORNING/...
A weak lee side trough will persist, as high pressure remains
anchored over Tennessee, while a weak short wave will approach
from the north overnight. This short wave will generate varying
amounts of cirrus and cirrostratus which is expected to thin out
with time.
With light or clam winds inland, lows will get down to 60-64F
inland from US-17, while a bit of mixing and the close proximity
to the ocean will hold coastal sections to the mid and upper
60s.
There are still little signals of anything more than ground fog
late tonight. However, the NAM and to some extent the HRRR do
show somewhat more favorable condensation pressure deficits
south of Savannah over the coastal counties by around 6 AM. But
since it`ll be difficult to achieve cross-over temperatures, we
have still refrained from adding fog to the forecast.
&&
.SHORT TERM /6 AM SUNDAY MORNING THROUGH TUESDAY/...
Mid-level ridging will prevail across the region as high pressure
persists at the surface. With plentiful dry air in place, the area
is expected to remain dry. Though, some models hint at some showers
on Tuesday but with lack of forcing, have maintained a dry forecast.
With rising heights and a southwest flow, temperatures are going to
be quite warm. For Sunday and Monday, high temperatures did seem a
degree or two too warm. Therefore, lowered temps accordingly both
days. For Tuesday, far inland counties could make a run to hit 100
degrees, with low 80s along the coast.
&&
.LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/...
Mid-level ridging will prevail across the area through late week. At
the surface, high pressure will persist through mid-week before
shifting to the south. Then, rain could return by late week.
Temperatures will be quite warm each day and some inland areas could
come close to 100 degrees, mainly on Wednesday and Thursday. By
Saturday, temperatures should be back in the upper 80s to mid
90s.
&&
.AVIATION /02Z SUNDAY THROUGH THURSDAY/...
VFR will prevail through 00Z Monday.
A brief period of ground fog is possible at all three sites from
about 09-12Z Sunday, but no restrictions are expected.
Extended Aviation Outlook: VFR conditions are expected.
&&
.MARINE...
Surface high pressure will build over the Deep South tonight as
a trough settles over the Midlands. Winds will shift from the
S and SW early on, more toward the to W late as land breeze
influences form. Speeds will hold at no more than 5 or 10 kt.
Seas will average 3 to 5 ft, and highest on the outer Georgia
waters.
Extended Marine: High pressure will prevail across the region as
Subtropical Storm Ana, far east in the Atlantic, enhances swell
energy. On Sunday, there will be an uptick in seas. For the outer
Georgia waters, seas could approach 6 feet and a Small Craft
Advisory could be needed through Sunday night. Otherwise, SSW winds
will be 10 to 15 knots.
Rip Currents: On Sunday, an east-northeast swell with an initial
period around 15-16 seconds is forecast to move through our waters.
Hence, a Moderate Risk of rip currents is in effect for Sunday.
Depending on how quickly the swell subsides, an elevated risk could
continue on Monday. Though, as of now, a Low Risk is in place.
&&
.FIRE WEATHER...
Afternoon relative humidities are expected to be critical to near-
critical inland Sunday through the middle of the week. Fine
fuels are dry and will only get drier. However, generally light
winds should limit the overall wildfire risk.
&&
.TIDES/COASTAL FLOODING...
Coastal flooding will be possible during the evening high tides next
week due to the combination of astronomical forces and onshore
winds, primarily along the SC coast. A lunar perigee and full moon
will occur on Wednesday.
&&
.CHS WATCHES/WARNINGS/ADVISORIES...
GA...None.
SC...None.
MARINE...None.
&&
$$
NEAR TERM...
SHORT TERM...RAD
LONG TERM...RAD
AVIATION...
MARINE...MTE/NED
FIRE WEATHER...
TIDES/COASTAL FLOODING...
AREA FORECAST DISCUSSION
National Weather Service Sioux Falls SD
1054 PM CDT Sat May 22 2021
.SHORT TERM...(This Evening through Sunday)
Issued at 230 PM CDT Sat May 22 2021
Surface boundary as of mid afternoon is draped roughly from
slightly east of Ainsworth northward to a bit east of Huron. In the
warm sector east of it, temperatures have risen into the upper 70s
to 80s depending on the extent of cloud cover at any one location.
Behind it, temperatures remain stuck in the 50s and 60s with a
northwest wind and occasional elevated showers/embedded storms.
This boundary will be the focus (or lack thereof) for any shower
or thunderstorm activity into the evening hours. RAP mesoanalysis
suggests a narrow corridor of around 1000 J/kg of MLCAPE along and
just ahead of this boundary with similar values of elevated
MUCAPE behind it. Effective deep layer shear is generally on the
weaker side, or roughly 20-30 kts weighted post-frontal with the
more favorable values displaced well southwest of our immediate
region. The big question for any convective activity is a forcing
mechanism as downstream modified observed 12z soundings suggesting
persistent/established CI from reaching a convective temperature
unlikely. The more likely scenario is that we continue to see
festering of current elevated post- frontal activity with perhaps
a few struggling updrafts across the warm sector through the
remainder of the afternoon hours. A better shortwave embedded
within an elongated meridional flow is evident in WV satellite
imagery nudging toward the NE Panhandle and this will likely help
to expand thunderstorm coverage to our southwest as we move
through the evening hours. Even so, its trajectory may keep the
bulk of the activity just west of our coverage area, perhaps
clipping counties west of the James River. All of this to say, the
severe weather threat is obviously conditional on the existence
of established deep convection (which is somewhat doubtful), and
even at that, the convective parameter spaces are generally on the
lower end of the spectrum. In terms of threats, large hail to the
side of half dollars would be the main threat.
Further into the overnight hours, a second vort max glides northward
through western IA into SW MN by Sunday morning. Some weak
instability on the order of 500-1000 J/kg exists so would expect at
least isolated to perhaps scattered elevated showers/storms to
develop into early Sunday morning. Deep layer shear is largely non-
existent however so this activity should remain very pulsy. The
overnight hours will also likely feature an expanding cloud field
once again along with fairly mild low temperatures.
Not much of a change in the sensible weather for Sunday. Western
flank of the surface boundary becomes reinforced and lifts back
north, particularly across western SD. With the entirety of our
coverage area in the warm sector and guidance more optimistic on
scattering out any morning cloud cover by afternoon, should see
widespread 80s for afternoon highs. Outside of lingering morning
elevated convection across SW MN, the bulk of the daytime hours
should be primarily dry. The potential caveat to this is forecast
soundings show SBCAPE is only weakly capped and thus wouldn`t
completely discount a few late afternoon pop-up storms. The lack of
any meaningful forcing should keep this fairly isolated however.
The main thunderstorm risk will develop well to our west across the
western Dakotas and Nebraska Panhandle. A likely robust area of
strong to severe thunderstorms will develop over this area by mid to
late afternoon with initially slow progression eastward. A better
eastward push should commence through the evening with eventual
upscale growth as deep layer shear vectors have a strong boundary
parallel component. The main vort lobe rotates northeastward toward
ND, which combined with less favorable shear/instability parameters
with eastward extent, should result in a diminishing trend in
activity as it approaches our counties west of the James River. With
this said, still certainly feasible that enough strength remains in
this activity to result in a wind threat which is highlighted by a
Day 2 Slight Risk from SPC.
.LONG TERM...(Sunday Night through Saturday)
Issued at 230 PM CDT Sat May 22 2021
The forecast for Monday and Tuesday are highly dependent on boundary
location which becomes much more muddled at these timescales this
time of year. At least some broad agreement that the boundary Monday
will stretch from northeast NE into south central MN with a recent
model trend to keep it somewhat stationary through much of Tuesday
as well. This means that in terms of convection chances both days,
areas along and ahead of this boundary continue to run the risk of
afternoon/evening storms. Should storms develop either day,
instability and shear profiles suggest at least some severe risk
with large hail and wind the primary risk with fairly unidirectional
shear profiles. Again, this is fully conditional on the existence of
convective development which is uncertain. Boundary location will
also have some impact on temperatures and cloud cover with locations
behind the boundary likely to see more sunshine than those ahead of.
In either case, blended guidance of upper 70s to mid 80s seems like
a good starting point for afternoon highs for each day.
Middle of the week continues to look benign with a brief period of
shortwave ridging and temperatures in the 70s to near 80s. Wednesday
night thru Thursday night could bring another period of active
weather as a pronounced shortwave traverses the Northern Plains. At
this time, the risk for severe weather looks low with the better
instability south of our area.
&&
.AVIATION...(For the 06Z TAFS through 06Z Sunday night)
Issued at 1054 PM CDT Sat May 22 2021
The first area of showers/storms has lifted north of the NE/SD
border, but remains west of the MO River. Based on latest radar
trends and short-term models, think the majority of nocturnal
convective activity should remain west of TAF airfields and will
maintain a dry forecast. MVFR ceilings are still on track to reach
KHON by 23.10Z, KSUX by 23.09Z, and KFSD by 23.11Z. Some guidance
suggests ceilings could drop below 1000 ft agl by near sunrise
Sunday morning, but not enough confidence at this time to go that
low. Will monitor conditions and amend as necessary. Cloud bases
still expected to lift back into the VFR range by late Sunday
morning or early afternoon.
Winds will be light through the period, perhaps variable
overnight, before turning to the south-southeast for much of
Sunday. A few afternoon gusts approaching 20 kts are possible,
especially at KHON and KFSD.
&&
.FSD WATCHES/WARNINGS/ADVISORIES...
SD...NONE.
MN...NONE.
IA...NONE.
NE...NONE.
&&
$$
SHORT TERM...Kalin
LONG TERM...Kalin
AVIATION...Rogers
Area Forecast Discussion
National Weather Service Gray ME
1037 PM EDT Sat May 22 2021
.SYNOPSIS...
Sunday will start out warm and humid, but a strong cold front
will cross the region during afternoon which will bring about
much cooler and drier air to start the new work week. After a
seasonable and sunny Monday, a warming trend and precipitation
chances over the mountains return by mid-week. More cool weather
returns by the end of the week as Canadian high pressure builds
into New England.
&&
.NEAR TERM /UNTIL 6 AM SUNDAY MORNING/...
1035 PM Update...Little change to the forecast specifics. Have
hoisted a beach hazard statement for tomorrow. Otherwise,
blended in some MOS guidance for low temperatures tomorrow night
which yields colder low temperatures. Depending on wind and
sky conditions we may need a frost advisory for a few of our
northern zones tomorrow night. The entire forecast area has
officially started the growing season, with the last of our
mountain zones started on May 21st.
625 PM Update...Most shower activity (as little as it is) is
currently moving across southeasternmost NH and will be offshore
shortly. Otherwise, we note some showers near the Montreal area
that should dissipate as they move southeastward, but will still
keep a slight chance PoP in the north for the next few hours in
the mountains. Have taken any mention of thunder out of the
forecast. Otherwise, raised waves on the lakes to 2 to 3 feet
for tomorrow afternoon based on increasing and gusty NW winds
during the afternoon hours.
Previously...
GOES water vapor imagery shows a weak short wave crossing the
rooftop of Maine with surface analysis showing a pressure trough
over the area. Despite plenty of high and mid level clouds much of
the area has warmed well into the 80s with dewpoints into the low
60s. Latest RAP analysis shows upwards of 500 J/kg of SBCAPE, but
with forcing for ascent fairly weak expecting the areal coverage of
showers and thunderstorms to be isolated to scattered at best
through this evening.
Precipitation chances drop off this evening with the loss of heating
and the surface trough sliding offshore. As the surface trough
slides offshore tonight skies will become partly to mostly clear
with winds shifting offshore for the entire area including the
coast. Lows tonight will be in the 60s and the offshore flow will
keep the Mid-Coast from being as cool as last night with lows here
in the upper 50s. There still will be enough low level moisture
for areas of patchy fog near the coast and in northern valleys.
&&
.SHORT TERM /6 AM SUNDAY MORNING THROUGH SUNDAY NIGHT/...
The story on Sunday will be the passage of a sharp cold front as a
short wave crosses northern Maine during the afternoon. As
mentioned in previous discussions FROPA looks to happen before peak
heating leading to poor overlap of instability and shear with more
favorable mid-level lapse rates confined to southern New hampshire
into southern New England. CAMs have been fairly consistent in
showing a line of showers with embedded convection approaching the
International Border around 14Z with this line washing out as in it
tracks south through the area. The front looks to clear through
the Maine coast around 18Z and southern New Hampshire by 20Z
with areal coverage looking to be widely scattered with some
towns missing out on any precipitation. PWATs will be high,
around 1.5 inches so those that due experience a strong shower
or thunderstorm could see briefly heavy rain.
The overall potential for strong to severe thunderstorms continues
to look tempered by the early FROPA and the poor overlap of
convective ingredients as well as a warm layer between 850 and 700
mb. Also, the washing out look from the latest CAMs suggests
that run of the mill thunderstorms may be limited as well. Have
continued a slight chance for thunder tomorrow and will continue
to monitor for a slower FROPA and better overlap of convective
ingredients.
Temperatures will warm early tomorrow morning into the 80s
south of the mountains with west to southwest winds ahead of the
front inhibiting a sea breeze. Behind the front northwest to west winds
will pick up tomorrow afternoon with gusts between 20 to 30
mph. Temperatures and dewpoints drop substantially behind the
front with lows dropping into the 30s north to 40s south.
&&
.LONG TERM /MONDAY THROUGH SATURDAY/...
Cool, Canadian high pressure will begin to recede off the coast on
Monday. Monday night will not be overly cold as compared to Sunday
night as warm air advection begins around the periphery of the
departing high under a southwesterly flow. Most areas will drop down
into the 40s.
Strong warm air advection continues on Tuesday with H8 temperatures
topping out at +13C in some areas by the end of the day. This will
allow temperatures to reach the 70s to lower 80s in most locations.
Along the Midcoast region, an onshore flow will keep temperatures in
the 60s for afternoon highs.
There may be a shower or an isolated thunderstorm late in the day
and during the overnight hours in the northern mountains.
12Z guidance remains in relatively good agreement with the passage
of a prefrontal trough on Wednesday ahead of an approaching cold
front. This may allow for a low chance of showers and possibly a
thunderstorm in all locations. A few more showers may accompany the
passage of a cold front Wednesday night, however this system will be
relatively moisture starved.
More Canadian high pressure will follow late in the week with dry
and cold conditions once again.
&&
.AVIATION /03Z SUNDAY THROUGH THURSDAY/...
Short Term...Mainly VFR through midnight tonight, although -SHRA
may bring brief restrictions. Later tonight patchy fog and low
cigs will likely bring IFR conditions along the Maine mid-coast
to KAUG and possibly south to KPWM. Cold front cross tomorrow
with mainly VFR expected other than brief period of restrictions
in scattered SHRA and -TSRA. VFR likely prevails behind the
front tomorrow night.
Long Term...High pressure will build in on Monday with dry
conditions and VFR holding through Tuesday. Tuesday will bring
increasing cloud cover in a southwesterly flow as a cold front
approaches as perhaps a shower to KHIE. The cold front will cross
the region late Wednesday night with scattered showers and
thunderstorms impacting all terminals. More dry conditions with
Canadian high pressure will follow for late in the week.
&&
.MARINE...
Short Term...Seas will continue to run high through Sunday from
a system well offshore. Southwest winds tomorrow morning ahead
of a cold front will shift out of the west to northwest tomorrow
afternoon with gusts 25 to 30 kts. A stray thunderstorm may
track over the waters early tomorrow afternoon with the front
bringing brief strong winds, but widespread thunderstorms are
not expected over the waters.
Long Term...High pressure will build into the waters on Monday with
gusty northwesterly winds before diminishing. A southwesterly flow
will develop on Tuesday bringing gusts to near SCA thresholds. A
cold front will cross the waters late Wednesday or early
Thursday.
&&
.GYX WATCHES/WARNINGS/ADVISORIES...
ME...Beach Hazards Statement from 8 AM EDT Sunday through Sunday
evening for MEZ023>028.
NH...Beach Hazards Statement from 8 AM EDT Sunday through Sunday
evening for NHZ014.
MARINE...Small Craft Advisory until 2 AM EDT Monday for ANZ150>154.
&&
$$
NEAR TERM...Ekster
Area Forecast Discussion
National Weather Service Indianapolis IN
1145 PM EDT Sat May 22 2021
...Updated Aviation Discussion...
.Forecast Update...
Issued at 952 PM EDT Sat May 22 2021
Forecast is in excellent shape with high pressure remaining in
control. Expect some mid and high cloud overnight which will
generally keep min temps in the low to mid 60s as currently
depicted, which is well in line with latest HRRR and LAMP guidance.
Cannot entirely rule out a few outlying areas dropping below 60,
primarily southeast, but the difference is negligible.
&&
.Short Term...(This evening through Sunday night)
Issued at 313 PM EDT Sat May 22 2021
Warm summerlike temperatures continue this weekend as high pressure
persists, centered over the Ohio and Tennessee Valleys. Current
satellite imagery shows a mix of cirrus and afternoon Cu. The high
clouds are expected to continue through the period with Cu returning
tomorrow afternoon. The presence of the mid and high level clouds
could at times filter the sun and may limit temperatures slightly
from reaching full potential Sunday when upper 80s are expected.
Overnight lows will range from the low to mid 60s.
The high will finally start to push south at the end of the short
term. This will weaken the subsidence some for the far northern
portion of the forecast area, allowing for a chance of isolated
showers during the afternoon to early evening hours on Sunday with
the strongest diurnal heating. Otherwise, the rest of central
Indiana is expected to remain dry this weekend.
&&
.Long Term...(Monday through Saturday)
Issued at 313 PM EDT Sat May 22 2021
During the long term, a series of upper disturbances will gradually
break down the upper ridge across the area and allow the flow to
become quasi-zonal. This will result in a front meandering across
the area at the surface with no strong push to get it out of the
vicinity until maybe next weekend. Thus, expect chances for rain at
times for much of the period.
Dry weather will continue on Monday with the ridge still in control,
but the first upper disturbance will bring rain chances on Tuesday.
The initial energy will be weak, so only expect some low PoPs then.
Better chances for rain will arrive mid-week when the surface front
initially moves into the area and has some upper support with it. As
the upper support moves off, the front will linger on Thursday.
An upper level low will move into the Great Lakes area around
Thursday night, creating a wave along the surface front. This will
bring another round of higher PoPs. Uncertainties on timing lead to
only chance PoPs with this feature for now.
The same uncertainty will keep low PoPs in for Saturday as the
surface wave/front location could conceivably still be in the area.
Well above normal temperatures early in the period will give way to
near normal readings by the end of the week thanks to clouds/rain
and cooler air behind the front.
&&
.Aviation...(06Z TAF Issuance)
Issued at 1145 PM EDT Sat May 22 2021
IMPACTS:
* VFR - no significant operational impacts during the period.
DISCUSSION: High pressure will remain the dominant force across the
region during the period. Winds will be less than 10KT throughout,
generally from 240-270 degrees. Expect some scattered mid and
high cloud overnight with some scattered cumulus based around 4kft
developing midday Sunday and midlevel cloud becoming broken.
There is a very low chance Sunday afternoon for an isolated shower
or thunderstorm in the warm and humid airmass, primarily north of
HUF/IND, but this chance at any one point is far too low for
inclusion.
&&
.IND WATCHES/WARNINGS/ADVISORIES...None.
&&
$$
Update...Nield
Short Term...KH
Long Term...50
Aviation...Nield
Area Forecast Discussion
National Weather Service North Platte NE
611 PM CDT Sat May 22 2021
.SHORT TERM...(This evening through Sunday night)
Issued at 355 PM CDT Sat May 22 2021
A Canadian cold front has dropped through the Panhandle and part of
ncntl Nebraska this afternoon. The front will be the focus for heavy
thunderstorms some which could be severe with large hail and wind
damage. The RAP and NAM suggest brief severe weather potential but
the HRRR suggests several hours, perhaps until 9 or 10 pm. Winds
aloft are strongly sheared but mostly unidirectional. This should
support storm splitting and multicell behavior with somewhat less
severe potential.
The combination of the front, deep moisture with subtropical origins
and strong shear opens up the specter of heavy rainfall from cell
training tonight. It is hard to imagine all models are lifting the
cold front north as a warm front Sunday; opening up a warm sector
for another round of storms Sunday evening. If the front remains
stationary across the Sandhills tonight as suggested by the RAP
model, heavy rainfall should develop and the models are suggesting
totals of 1 to 3 inches by Sunday morning.
The models are favoring the srn Panhandle and the Sandhills for the
heaviest rainfall; WPC has followed the model consensus placing the
heavy rain center, near 1.5 inches in this region. The forecast
leans on WPC but if the forecast adjusts for the frontal location,
further south and east than the models projected, heavy rain may
fall across southwest Nebraska.
Sunday morning presents wrn and ncntl Nebraska with easterlies at
the sfc and south winds 850-700mb. The srn flank of a large upper
low stretching from WA to California this afternoon should lift
northeast and drive a strong Pacific cold front through wrn and
ncntl Nebraska Sunday night. Winds aloft will veer supporting
supercells. The model consensus suggests storm activity would
commence across the Panhandle late in the afternoon or early in the
evening and sweep rapidly east overnight.
.LONG TERM...(Monday through Saturday)
Issued at 355 PM CDT Sat May 22 2021
The storm activity Sunday night should be mostly out of wrn and
ncntl Nebraska Monday morning. The Pacific front will get hung up
across ern and scntl Nebraska supporting a thunderstorm chance
across srn Nebraska. Winds aloft at h500mb will be strong at
40-55kt but moisture and instability will be modest suggesting a
marginal severe thunderstorm chance. The forecast is dry Tuesday.
Strong winds aloft at 40-55 kts Wednesday and Thursday along with
increasing moisture with dew points in the 50s will support
thunderstorm chances again. Wednesday will be the better chance for
storm development. A fairly strong short wave will be moving through
the nrn Plains- SD, for upper level support during this time. Rain
chances continue Thursday but temperatures have cooled into the 60s
and 70s lessening instability the thunderstorm chances.
Friday and Saturday are expected to be mostly dry with isolated to
perhaps scattered showers and thunderstorms possible at times.
&&
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 611 PM CDT Sat May 22 2021
The primary aviation weather concern this evening revolves around
thunderstorms. Clusters of storms will continue spreading
north/northeast across much of the forecast area through at least
23/06z. Brief drops in visby along with gusty erratic winds up to
40 kts are possible, along with hail. After the bulk of the
activity dissipates, stratus clouds will result in MVFR to IFR
ceilings through mid-morning. Gusty southeast winds this evening
will somewhat wane overnight, then restrengthen mid-morning with
gusts exceeding 20 kts.
&&
.LBF WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
SHORT TERM...CDC
LONG TERM...CDC
AVIATION...Snively
Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
1055 PM CDT Sat May 22 2021
.SHORT TERM...(This evening through Sunday night)
Issued at 302 PM CDT Sat May 22 2021
The main messages of the forecast for today and tomorrow are chances
for thunderstorms on Sunday along a frontal boundary. This frontal
boundary will separate warm and humid air to the south, and cooler
air to the north. There is marginal risk for severe storms with
damaging wind and large hail as the primary threat.
Today and tonight - Afternoon cloud cover exceeded expectation, and
for that reason our afternoon highs were a couple of degrees cooler
than forecast. Given the ample boundary layer moisture, opted to add
patchy fog to the weather grids overnight.
A cold front will approach the region, but the low level convergence
along the front is fairly week so not anticipating widespread
showers and thunderstorms. Still have about at 30-40% chance, which
seems reasonable. A few storms could produce large hail or damaging
wind across northwest into north central Minnesota, but the
saturated mid-levels and festering cumulus should put a low ceiling
on the severe weather potential.
Sunday and Sunday night - The aforementioned frontal boundary will
slowly sag across the region and become oriented more east/west.
Areas to the south will be warm and humid with highs in the lower to
mid 80s, while areas to the north will struggle to reach the 60s.
This type of temperature gradient usually raises concern for storms,
but the wind field is very light, on the order of 5 to 15 knots in
the lower levels, so that should limit the severe weather potential.
In addition, mid level lapse rates are still fairly moist, so that
will also limit the severe weather potential. Overall expect
scattered showers and thunderstorms, with the marginal risk for
severe storms.
.LONG TERM...(Monday through Saturday)
Issued at 302 PM CDT Sat May 22 2021
The upper level low that was present over the western CONUS over the
previous few days looks to move northeastwards into Canada, dragging
a series of frontal boundaries across the region Monday into
Tuesday. These boundaries will provide enough lift for scattered
showers and thunderstorms Monday afternoon and evening along the
warm front, and again later on Tuesday as the system occludes and
the front wraps back around the surface low pressure. There is
enough instability to support some severe thunderstorms especially
Monday evening, however the amount of cloud cover and heating ahead
of the front is key to how much instability we can tap into. Another
concern is lower level winds not giving us low level shear to
support lower level updrafts, meanwhile the overall shear profile is
favorable for some stronger storms. Scattered to even widespread
precipitation is expected along the front, but the thunderstorm
potential is still muddied behind some of the finer details.
Tuesday will see a continuation of scattered showers mainly over
western Wisconsin, as the front occludes and slides a bit too the
east, with relatively dry and cool air pushing into MN behind the
system. Tuesday will remain relatively warm, but the cooler
temperatures will be noticeable with highs near 70 on Wednesday and
in the lower 60s for Thursday.
Another wave looks to enter the area late Wednesday through
Thursday, bringing another chance for more widespread precipitation
and potential thunderstorms. Deterministic models are still out of
phase and timing will rely on the upper level wave manifesting a
surface response, so stay tuned for details about the later part of
next week. For now, kept NBM PoPs which lie in the 30-40% range.
&&
.AVIATION...(For the 06Z TAFS through 06Z Sunday night)
Issued at 1055 PM CDT Sat May 22 2021
This remains a low confidence TAF period and have not seen anything
different from the 00z models rolling in to change much of what we
are currently forecasting. The problem remains the same, we`ll have a
moist and weakly forced environment over us on Sunday. Where the
front ends up Sunday, we will likely see scattered showers and storms
develop as instability pools along it. None of the CAMs show much
organization to the activity and with the NAM and NSSLwrf showing the
front down from MKT to LSE and the HRRR more Twin Cities to EAU,
decided to stick with a dry forecast at all terminals, though as
confidence increases on where this pop-up convection will fire, it is
expected to eventually need some form of shra/tsra mention, mostly
likely at MKT, MSP, RNH, or EAU. On the cigs front, with the front
stalling out in the area, do expect stratus to become more prevalent,
especially for any site that remains north of the boundary.
KMSP...Have kept MSP dry, though mainly because the chance of precip
is still not high enough to include in a spot forecast such as a TAF.
Starting as early as 15z, we could be seeing showers popping up near
the Twin Cities, but rather than have something like 8 to 10 hours of
some sort of precip mention for MSP, decided on the dry route until
we can better pin down a window for seeing better precip chances.
Kept cig forecast similar, though we may still be a bit too
pessimistic. with lots of spread in the CAMs with cigs.
/OUTLOOK FOR KMSP/
Mon...MVFR mrng, VFR aftn. SHRA/TSRA likely, mainly PM. Wind SW
10-20kts.
Tue...VFR. Wind WSW 15G25 kts.
Wed...VFR. Wind NW 5-15 kts.
&&
.MPX WATCHES/WARNINGS/ADVISORIES...
MN...None.
WI...None.
&&
$$
SHORT TERM...JRB
LONG TERM...TDH
AVIATION...MPG
Area Forecast Discussion
National Weather Service Marquette MI
813 PM EDT Sat May 22 2021
.SHORT TERM...(This evening through Sunday)
Issued at 319 PM EDT SAT MAY 22 2021
GOES 16 Water vapor imagery highlights an amplified pattern with
CONUS feeling the full effects of the current omega block; more
specifically, the UP is feeling the effects of being on the
western and northwestern edge of the ridge sitting over the
middle-Mississippi River Valley region. This southerly flow
pattern has kept the warm and moist conditions across our
forecast area today. Cloud cover over most of the region began
scattering out in the late morning hours due to height rises and
increasing subsidence. In the east, dinural driven CU aided by
enhanced low level convergence along the lake breeze boundary off
Lake Michigan has been observed and were even able to get a light
rain shower over Chippewa County. Given the continued clearing
trend thats expected this afternoon, expect temps to continue
climbing to near 80F across much of the forecast area. Some
exceptions will be along the immediate lakeshores of Lake
Michigan, where onshore flow is capping temps in the 60s.
Overnight a cold front will drop south into the region. Upstream
over Ontario and the Arrowhead, surface based instability around 1500
j/kg will feed convection and a line of showers and thunderstorms
are expected to move into Lake Superior. Looking upstream now,
shower activity has already started, but convective plumes are
fighting to overcome the cap in place. The lack of a pronounced LLJ
in the western parts of the lake should limit the thunderstorm`s
ability to transition to elevated storms, but the recent HRRR runs
do suggest some 850mb 30kt winds may help maintain some of the
activity`s organization over parts of the lake, at least enough to
bring a chance of showers and thunderstorms to the Keweenaw and
parts of Ontonagon and Gogebic counties. Post frontal precip across
eastern Minnesota may sustain shower activity a little longer in the
far west. With the passage of the cold front, winds will shift
northeast and overnight lows should fall into the 40s for most.
Parts of southern Menominee may be able to stay in the low 50s and
some lakeshore areas could see some high 30s.
The cold front is expected to stall out over northern Wisconsin as
another shortwave rounds the ridge. The better forcings look to
stay south of our forecast area but some scattered shower
activity across central and southern Upper Michigan looks
possible. A dramatic change in high temps is expected compared to
what we`ve observed the past few days. Many locations near Lake
Superior should top out in the mid- 40s. Further south and east,
50s are generally expected.
.LONG TERM...(Sunday night through Saturday)
Issued at 342 PM EDT SAT MAY 22 2021
Taking a broad look at the medium to extended forecast over the
forecast region will encompass several weather features affecting
the cwa with continued chances of rain showers and anomalously
warm/cool temperatures. A mid-latitude cyclone will occlude over the
Northern Plains, bringing another surge in warm surface temperatures
on Monday and Tuesday as the warm sector reaches the Great Lakes
once again. The secondary cold front from the occluded surface low
over northern Ontario will reach Upper Michigan by mid-week. This
will cause afternoon highs to be closer to seasonal averages from
mid-week to Friday, with gradual warming expected for a trend by
next weekend.
A strong, negatively tilted 500mb longwave trough will be positioned
over the Northern Rockies by Sunday evening, with strong upper level
ridging extending from the Mississippi Valley to the northwest over
Manitoba and Saskatchewan as it is on the downstream end of the
longwave trough. The upper level ridge axis will be to the west of
the Northern Great Lakes Sunday night, but the nose of warm air
aloft will be present from 700mb-850mb only. Mixing down to the
surface is not anticipated. At the surface, a 1030mb dome of High
pressure will be positioned over northern Ontario, creating
northeast to easterly flow overnight Sunday from the lake. A strong
nocturnal inversion will take place as the cool and moist flow from
the lake keeps surface temperatures comfortable across Upper
Michigan. It will make for a great night to leave your windows open
with regard to sleeping weather as the area has had several days of
anomalous humid conditions for mid to late May thus far.
This surface High will weaken by Monday morning as it quickly
propagates to Quebec. As this occurs, the semi-stationary cold front
that moved through Upper Michigan Sunday is expected to halt over
Lower Michigan, and begin to retreat back to the north. The upper
level ridge axis is anticipated to propagate over the northern Great
Lakes by Monday afternoon. Warm, southerly flow will begin to advect
toward Upper Michigan by Monday afternoon, causing a nice rebound in
afternoon highs compared to the chilly temperatures that will be
observed on Sunday. 850mb temperatures are in decent agreement with
+14C to +16C expected over Upper Michigan by Monday afternoon. As
this warm front propagates over Upper Michigan, upper level dynamics
will become slightly more favorable for showers/isolated
thundershower development, albeit the signal remains low for
atmospheric forcing at this time. As of Saturday afternoon, the SPC
keeps the mention of a Marginal Risk for convective weather further
to the west, and outside of our cwa.
With the southerly flow expected to continue Monday night into
Tuesday, we will see humid conditions as overnight lows look to
decrease to near 60 degrees. This is in response to the occluded
surface low over the northern Manitoba/Ontario region. Scattered
showers to possible thundershowers are anticipated to continue
overnight Monday into early Tuesday as a weak cold front moves
through the area behind the warm front that approached the area on
Monday. The modified air mass will keep the area moist, and low
level clouds may take a short while to burn off by early afternoon.
Temperatures look to still be anomalously warm Tuesday afternoon as
850mb temperatures between +14C to +17C mix down to the surface via
southerly flow.
The more potent cold front will arrive between Tuesday afternoon
into early Wednesday as a strong surface low over northern Ontario
is modeled by 12Z Wednesday. We will continue to monitor this
weather system as it is appears to be modeled in good agreement with
medium range guidance at this time of inspection. Widespread showers
and convective initiation ahead of this cold front is favorable.
Still a bit far out to fine tune the possibility of weather strong
thunderstorms are favorable at this however.
Behind the cold front on Wednesday, much cooler conditions can be
expected. The exact placement of the coldest air at 850mb is still
not modeled well, with the GFS being the most aggressive. The Euro
and Canadian deterministic models appear to have the air mass
modified slightly as it treks over Lake Superior. This is not
uncommon, but the chilly air aloft at 850mb could reach 0C or
potentially even colder. This would keep the area slightly cooler as
compared to previous model runs 24 hours ago, with high temperatures
struggling to reach 60 degrees for Thursday and Friday as multiple
shortwaves will be riding along the upper level flow aloft between
Wednesday afternoon and next weekend. Will continue to adjust the
medium to extended forecast on the conservative side, but we could
see a rain/snow mix on Thursday night, with a brief period of light
snow showers over the interior west of Upper Michigan by Friday
morning if model agreement and timing of shortwaves next week.
Temperatures could get near or below the freezing mark for overnight
lows for the interior west to end this coming week, before a gradual
warming trend begins by next weekend.
&&
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 752 PM EDT SAT MAY 22 2021
VFR conditions will continue through much of this evening but then
a cold front will move across Lake Superior and Upper Michigan
later tonight and bring deteriorating conditions to all terminals
overnight. Some scattered showers will be possible as well, mainly
at KIWD and KCMX, with maybe an outside shot at a VCTS at KCMX.
With this cold front, a quick shift of the wind to the north or
northeast is expected. With this shift, expect conditions to
deteriorate to LIFR at KSAW and KIWD and IFR at KCMX late tonight,
but then slowly improve during the day on Sunday reaching MVFR in
the afternoon.
&&
.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 319 PM EDT SAT MAY 22 2021
Some shower and thunderstorm activity will be possible tonight as a
cold front moves through the region. South to southwesterly winds
will quickly become north to northeasterly. With the CAA and sharp
pressure rises that are expected, these northerly winds will
increase to near 30 knots by early Sunday morning across the north
and western parts of the lake. There`s some uncertainty in how much
of these stronger winds will reach the surface, but higher reporting
platforms could see a few gale force gusts. Winds should settle
through the day, with the return to light winds below 20 knots by
Sunday evening. Winds are expected to increase again mid-week with
the passage of another cold front. At the moment, northwest gusts
near 30 knots are looking possible.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
None.
Lake Superior...
None.
Lake Michigan...
None.
&&
$$
SHORT TERM...JP
LONG TERM...BW
AVIATION...Voss
MARINE...JP
Area Forecast Discussion
National Weather Service Pocatello ID
152 PM MDT Sat May 22 2021
.SHORT TERM...Tonight through Monday.
A low pressure system roughly over northern Nevada will swing
through eastern Idaho tonight and Sunday. Expect showers and a few
thunderstorms to redevelop late this afternoon and increase in
coverage overnight. Showers look more widespread across eastern
Idaho into the Lemhi region and not so much across the Magic
Valley into the Sawtooth region. Model soundings show that snow
levels are much lower than initially thought. Snow levels are
likely to fall to 6000-7000 feet overnight and into Sunday
morning as an associated cold front kicks through the region. The
lower snow levels combined with impressive QPF forecast suggests
that areas such as Island Park, Spencer, and Willow Creek Summit
could see 1 to 3 inches of snow late tonight and early Sunday
morning. There`s even a possibility Driggs down to Wayan and Soda
Springs may even pick up an inch or so on grassy and elevated
surfaces. Rainfall totals are impressive for the eastern highlands
with up to an additional inch possible, up to half an inch across
the Snake Plain, but only a quarter of an inch less for the Magic
Valley into the Sawtooth region. Winds are expected to be brisk
behind the front, likely reaching lake wind criteria for the
American Falls Reservoir by afternoon. Most of the precipitation
will come to an end Sunday night with residual light showers
mainly across the high country likely for Monday.
13
.LONG TERM...TUESDAY THROUGH NEXT SATURDAY...
Next low pressure system remains forecast to bring widespread
showers/afternoon t-storms to SE Idaho Tue/Wed as it slowly tracks
east across the CWA, but with not terribly impressive wind/QPF
impacts (totals less than 0.25 inches). The latest model runs more
definitively push the cold front/trough axis east of the CWA Wed
night and may be trending toward shortwave ridging/a break Thurs.
This is NOT yet 100% set in stone, as 2 ensemble clusters in 500mb
height analysis still favor a continued throughing signature...hard
to tell if this is related to the next approaching system (uncertain
timing) or lingering effects of the Tue/Wed system, but point being
no "break" is advertised, so...either a continued showery pattern OR
a dry break for about 24-36 hours are possible. If the shortwave
ridging verifies, a slight warmup is possible too with temps
potentially making a run at 70F at lower elevations for the first
time in the 7-day forecast! By Fri afternoon, another system may
start to reintroduce showers/t-storms to the forecast, but some
uncertainty exists here too, both in potential strength/amplitude of
the system and with timing. (One ensemble cluster...a least likely
scenario...actually features no system at all!) For now, allowed
some light/broadbrushed NBM PoPs to stand Fri/Sat with the
expectation that another system is likely...the usual scenario of
showers and afternoon/eve t-storms tied to daytime heating. All
things considered, high-impact wx does not appear likely throughout
the long-term portion of the forecast at this juncture. - KSmith
&&
.AVIATION...
While many terminals are seeing just a mix of mid/high-level clouds
and sunshine early this afternoon, showers/iso t-storms are forecast
to redevelop with daytime heating. Consensus of high-res CAMs favor
the KBYI/KSUN corridor for greatest potential (with some wrn WY
activity perhaps making at run at KDIJ) and a relative dry corridor
in between up across KPIH/KIDA, but given recent moisture/heating/
proximity of the offending low, we`ll maintain a low-end VCTS even
at these two latter terminals with a late 23z/5pm start time.
Overall, regional coverage should be less than Fri. Winds will be a
bit on the breezy side at the Snake Plain terminals. Tonight as the
low begins to spin ENE across our forecast area, most high-res
guidance develops a N-S zone of widespread rain/showers across
cntrl/ern portions of the CWA between 03-05z/9-11pm affecting
KPIH/KIDA/KDIJ, gradually lifting the bulk of that activity
northward Sun AM (but with sct showers/t-storms developing behind it
by Sun afternoon). Thus, carry -SHRA and MVFR cigs for these
terminals (an "upgrade" to predominant -RA is possible), while
holding KSUN/KBYI at VCSH and VFR cigs on the wrn fringes of this
zone. Lots of debate/anguish on SCT vs. BKN for that lowest MVFR
cloud layer tonight/Sun AM...MOS/NAMNest guidance descends solidly
into the soup, while the HRRR stays significantly higher on cloud
bases. Given widespread projected rain/showers on most models, did
lean BKN with the 18z TAFs. We also noted that the HRRR/RAP seem to
be consistently favoring that main corridor of rain targeting wrn WY
instead of ern ID. This solution seems to be an outlier, but might
signal some uncertainty in exact placement of this zone, so it bears
watching for possible forecast adjustments. Finally, WSW winds
should trend higher Sun starting after sunrise for KPIH/KIDA/KBYI,
peaking as high as 20G30kts Sun afternoon. - KSmith
&&
.PIH WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
Area Forecast Discussion
National Weather Service Pueblo CO
658 PM MDT Sat May 22 2021
.UPDATE...
Issued at 653 PM MDT Sat May 22 2021
Dropped the Tornado Watch for Pueblo, El Paso and Huerfano
Counties. Still a svr/tor risk farther east as storm east of
Trinidad is showing some rotation, with hail covering the ground
along I-25 over Raton Pass on CDOT web-cams.
&&
.SHORT TERM...(This evening through Sunday)
Issued at 245 PM MDT Sat May 22 2021
...Strong to severe storms remain possible into tonight over the
eastern plains...
Currently...
Storms are currently moving S-N over and just west of the I-25
corridor, moving NE fairly quickly. Several reports of sub-severe
hail have come in, and between radar and observations, near-severe
wind gusts and locally heavy rain remain possible under these
storms.
Today and tonight...
Plains and I-25:
Severe weather is the main concern for the rest of today as the
broad upper trough/low west of Colorado ejects to the northeast. In
the process, this system will be wrapping around tropical Pacific
moisture and strong southerly flow over most of the region.
Synoptically prevailing conditions today will be warm and breezy
thanks to that upper low, with afternoon gusts over the plains
hitting around 40 knots and high temperatures expected to be
seasonably warm, if a few degrees cooler than yesterday, with mid
70s-80s expected.
Severe threat:
A moisture gradient has pushed west from KS into our area this
afternoon. With dewpoints at some places across the plains already
in the low-50s, if the moisture is able to stay in place storms
could get ramped up pretty quickly. While a few of the short-term
models had El Paso County and some of our other northern areas
drying out a bit in the earlier parts of the day, model agreement
and forecast confidence have both increased greatly on more moisture
staying in central and east El Paso through tonight, with dewpoints
of 45-55 sticking around into the late afternoon.
Convective parameters are still looking favorable for further severe
development as well. Current mesoscale analysis is showing over 1000-
1500 J/kg of CAPE up the I-25 corridor to Colorado Springs, with
strong southerly winds turning more easterly near the surface as
storms pass nearby, further enhancing low-level directional shear.
Winds are already gusting to around 40 mph, and will likely get
stronger as the day goes on. While there is still some CIN in place
over the area, storms have already begun to grow in intensity and
there is little remaining concern than convective activity will be
limited for the day. Some of the high-red models are indicating
that there could be as much as 2000 J/kg of CAPE over parts of the
eastern plains by this evening. Bulk shear will also be sufficient
for supporting thunderstorm enhancement, with 30-35 knots EBS
sitting over the area this afternoon, which is expected to increase
to near 50 knots over some areas by tonight. However, the main
challenge with the severe forecast will be the speed shear. If
storms are moving too quickly and flow aloft is too fast, storms
will be unable to get properly organized before they fall apart,
possibly limiting the severe potential.
Ongoing convective development will likely progress similarly the
rest of this afternoon. Storms are expected to continue to quickly
move up from the south, likely either staying scattered in nature or
forming brief lines oriented north-south. Storms are expected to
continue moving over the area surrounding the I-25 corridor this
afternoon, with storm motion expected to be NNE around 40 mph. High-
res ensemble and deterministic forecasts from this morning seem to
be holding true so far for the most part, so it could be expected
for these storms to continue popping up through evening, slowly
moving more eastward in the process where the better dynamics and
shear could potentially increase the threat of tornadic storms and
larger hail. Luckily, this means that the burn scars are at somewhat
less risk from individual storms, as they will be moving too fast
for flash-flooding to be concerning. However, if multiple storms
manage to all train over a single burn scar things could get
concerning pretty fast, so monitoring of any lines of training
storms will be paramount. The main severe threats for today and
tonight will be wind gusts of 70 mph, hail up to 2 inches, and an
isolated tornado or two if storms are able to get properly rotating,
given the shear and rapid storm movement.
Finally, later this evening after 5-6pm or so, many of the short-
term models have storms a bit more organized and linear, moving more
to the east across the plains into later tonight. The last several
runs of the HRRR have been very consistent with developing this
feature, and confidence in it has increased since morning. This
potential linear storm mode will also increase wind speeds over the
plains, likely leading to more severe gusts. It is also expected
that storms will be present in the area, moving ENE across the
plains and/or coming up from the Raton Mesa, late into tonight,
potential sticking around until about midnight or even a few hours
later.
Snow over the mountains:
The eastern San Juan Mountains have been seeing a lot of
precipitation over the last few days. However, as the low continues
to track northeast, precipitation over the area should wane. Snow
levels remain high into tomorrow morning, and should stay relegated
to the higher mountains peaks. Overall, another inch or two are
possible over the peaks of the eastern San Juans, with a little more
rain possible at lower elevations.
Tomorrow:
Tomorrow is expected to be much drier than today as the upper
forcing lifts north and east away from our area. A few lingering
showers could persist overnight, especially over the southeast
mountains, but they are expected to fade by mid-morning at the
latest. However, the upper trough axis will still be centered near
the region, and flow aloft will still be strong from the SSW. A
modest moisture gradient will be set up right around the CO-KS
border, and with over 1500 J/kg of CAPE possible around the line,
thunderstorm development seems likely. However, as opposed to the
last 2 days, development is currently slated to be later in the day,
21Z at the earliest between the short-term guidance, and storms will
likely move east out of our area rather quickly, so impacts are
expected to be pretty minimal. However, given the models`
inconsistency on the exact placement of drylines, it is possible
that some storms could form just a bit further west, possibly as far
west as the La Junta to Kim line. Given the expected initial
scattered to isolated nature of the storms, as well as available
CAPE and shear, some storms will be well supported enough to become
strong to severe, especially later into the evening hours. Precip
chances should diminish quickly mid-late evening. High temperatures
should be just a bit warmer than today, with 50s-60s expected west
into the mountains and mid 70s-80s expected over the plains.
.LONG TERM...(Sunday night through Saturday)
Issued at 245 PM MDT Sat May 22 2021
Monday... Starting the long term period, a trough will be lifting to
the NE, but the southern fringe of it will still influence the area.
With this some upper level synoptic support will be present, with
decent southwesterly flow aloft and areas of vorticity maximums
flowing around the trough perimeter. Given this, increased
divergence aloft will be present and will aid in the development of
a surface lee cyclone. This cyclone will force a weak cold front
south over the area during the afternoon, and a dryline to the east
near the CO and KS border. As the surface cyclone lifts to the NE in
conjunction with the strongest upper level flow, the cold front will
push southward toward the the CO and NM border, and on the dryline,
thunderstorms will likely begin forming. Given the location of the
dryline, thunderstorms should move off into KS before they begin
intensifying. Otherwise, expect dry and relatively clear skies over
the Pueblo CWA.
Tuesday - Wednesday... Mid week, the GEFS and EPS ensembles bring in
a weak upper level ridge. This ridge should bring quiet weather to
the Pueblo CWA, with dry and clear conditions expected given the
synoptically sinking air over the area.
Thursday - Saturday...Heading into the end of next week, the
ensembles begin digging a trough into the western US and pushing it
eastward towards the Pueblo CWA. This would increase precipitation
chances, especially near the end of the period, over the area as
lift and moisture increase in response to the approaching upper
level system.
&&
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 245 PM MDT Sat May 22 2021
KALS...VFR conditions are expected through the forecast period.
Winds will be strong from the south today, with gusts of 35-40 knots
expected through later tonight.
KCOS...Thunderstorms will continue to persist in the immediate area
through later tonight, and while confidence on a storm moving
directly over the terminal has gone down, it is still possible. It
is also possible that an outflow boundary could impact the terminal
at some point this afternoon, although that too is fairly low in
confidence at this time. Prevailing winds will continue to be
strong, gusting to 25-30 mph from southeast, although if a storm
makes it close to the terminal outflow winds could gust over 40 mph.
Storms are expected to leave the immediate area around 23-00Z
tonight, although a few showers could linger in the vicinity for a
few hours longer. After that, VFR should return for the rest of the
period.
KPUB...Thunderstorms will persist in the immediate area through
later tonight, and are expected to periodically pass over or close
to the terminal several times between now and about 01Z. Prevailing
winds will be out of the southeast, gusting to about 35 knots, while
thunderstorm winds will be variable and could gust to 45 knots or
more briefly. Brief periods of moderate to heavy rain under stronger
storms could also limit vis to short-lived MVFR-IFR conditions.
Lightning and wind are very likely under any storm impacting the
terminal, and some hail is also possible. Storms should stick around
in the area until around 06Z tonight, after which VFR should return.
&&
.PUB WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
UPDATE...PETERSEN
SHORT TERM...GARBEROGLIO
LONG TERM...SIMCOE
AVIATION...GARBEROGLIO