Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 05/24/21
Area Forecast Discussion
National Weather Service Binghamton NY
943 PM EDT Sun May 23 2021
.SYNOPSIS...
The cold front is currently over NE Pennsylvania and will push
through the region in the next few hours. A dry night is
expected with cool air filtering in from the north and light
winds across the area tonight. Temperatures will stay in the
60s and 70s for most areas on Monday, warmest in the Mohawk
Valley. Active weather returns midweek with possible rain
showers and thunderstorms.
&&
.NEAR TERM /THROUGH MONDAY NIGHT/...
940 PM Update
The cold front is currently sitting across an area from Sullivan
County NY to Sullivan County PA, and will make its way south as
the evening progresses. Rain showers have diminished, with a
dry night expected for the region. Winds have already begun to
weaken and should become very light overnight as the pressure
gradient over our area loosens up.
A majority of the forecast remains on track. Minor adjustments
were made to temps, winds and sky cover.
647 PM Update
The cold front is currently draped across the NY/PA border,
moving to the south. Isolated rain showers are weakening as they
progress through the Twin Tiers. Can`t rule out a rumble of
thunder over Sullivan and southern Luzerne counties as the front
moves through, but considering instability over the region is
very weak, confidence for thunderstorms is very low.
The majority of the previous forecast was unchanged. Updated
PoPs across the area as the front moves through and adjusted
temperatures a few degrees lower across CNY behind the front.
345 PM Update
Cold front is just about to push through Ithaca, Cortland, and
Norwich, while a prefrontal trough has reached the Twin Tiers.
So far, convection has been highly isolated and mostly running
ahead of the prefrontal trough, with some shallow showers and
lowering ceilings behind the cold front.
The window for stronger thunderstorms is quickly narrowing
across NY State, and while SBCAPE values (per RAP13) are highest
just south of the state line, shear is a little weaker to the
south. Still can`t rule out some gusty winds with whatever
storms manage to develop, but the focus for this has shifted
towards NE PA.
Behind the front, clouds will increase and ceilings will drop as
temperatures quickly drop into the 60s. We may see some breaks
of sun reach the Southern Tier again before sunset. Much drier
air in the low levels is also present behind the front, and with
dewpoints dropping into the 30s and 40s overnight, fog shouldn`t
be a problem, even as winds slacken after midnight.
Northwest flow aloft will continue on Monday as an upper level
ridge builds across the Midwest. Cooler temperatures will be
mainly in the 60s and 70s, warmest across the Mohawk Valley. A
weak disturbance dropping down the eastern edge of the ridge
will bring some increase in mid-level clouds to the Finger Lakes
and NE PA during the day, but any precip looks to stay well to
our southwest.
1155 AM Update
Surface obs, radar, and satellite imagery show the cold front
draped between Watertown and Rome and across Lake Ontario, with
a prefrontal trough and windshift line further to the south,
just south of Seneca Falls, just north of Cortland, and just
south of Hamilton. Both are moving quickly to the south, a
little ahead of schedule, and the front is likely to overtake
the trough at some point this afternoon.
Towering cu and a few showers are just starting to go up along
the trough. RAP analysis shows weak but increasing instability
with SBCAPE values around 500 J/Kg across the Twin Tiers,
but BUFKIT soundings also show weak to moderate capping around
700 mb, which is not likely to break without some warmer surface
temperatures and a bit of larger-scale lift.
Best chance for thunderstorms will be along the prefrontal
trough and the cold front as it catches up...once you`re behind
that, thunder chances drop considerably.
Made some update to the PoP and wx grids to go with coverage
wording (versus probability) and reduce overall coverage of
rainfall to `scattered` (PoPs 30-50). Will keep the enhanced
wording for gusty winds across the Twin Tiers and NE PA only.
&&
.SHORT TERM /TUESDAY THROUGH WEDNESDAY/...
230 pm update...
High pressure moves off to the east of the region on Tuesday
with warm SE flow behind it. Day time heating and dew points in
the upper 50s to low 60s leads to some instability Tuesday
afternoon with a few afternoon showers and thunderstorms.
Showers and thunderstorms come to an end in the early evening
with the loss of daytime heating with dry conditions expected
into Wednesday morning.
Wednesday has a better chance for widespread thunderstorms, some
of which could be severe. An upper level trough begins to move
in with increasing speed shear through the day. The region will
be under the right entrance region of a jet streak with
divergence aloft. 0-6 km shear increases to 30-40 knots by the
afternoon and falling 500 mb heights as the shortwave moves in
helps weaken the CAP. The amount of cloud cover is uncertain
with the moist SW flow at 850-500 mb. If it stays cloudy for
most of the day, it will be difficult to develop the instability
needed for severe thunderstorms and surface based
thunderstorms. As of now, the NAM keeps cloud cover under 50%
for most of the region with almost 1000-2000 J/kg of SBCAPE with
the GFS about the same but favoring the Finger Lakes region.
The NAM also has a weak surface trough out ahead of the cold
front that acts as the trigger for storms with the cold front
not moving through until later, which would result in more
discrete storm cells vs a linear storm mode along the cold
front. The GFS is too coarse to really pin point this feature
and will need to be watched as CAMs get within range of the
event.
&&
.LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/...
230 pm update...
Showers and Thunderstorms continue into Wednesday night ahead of
the cold front. Once the cold front moves through, it scours out
all the low level moisture with drier weather expected
Thursday. Beyond Thursday, uncertainty increases as zonal flow
takes over and another shortwave moves in. Models disagree with
timing of the shortwave, the location of precipitation, as well
as duration of precipitation so just stuck with the NBM beyond
Friday. Overall it is looking like an unsettled pattern for
Memorial day weekend.
&&
.AVIATION /02Z MONDAY THROUGH FRIDAY/...
Rain showers remain very isolated and continue to weaken through
the evening. A wedge of dry air is moving in from the north as
seen by the clearing on the visible satellite. This clearing
will continue to push south tonight, but likely not make it
through the entire area as the front stalls out to the south/sw.
Flight conditions will likely remain VFR through the next 24
hours after a few hours of MVFR at BGM and ELM this evening.
Weather conditions remain dry through tomorrow as high pressure
builds in from the west/nw.
North winds this evening around 5 to 12 kts...becoming variable
5 kt or less tonight, then shifting to the south/se later Monday
morning with a few gusts up to 15 kt into the afternoon.
Outlook...
Tuesday...A chance for stray showers and thunderstorms,
otherwise mainly VFR.
Wednesday...Chances for scattered showers and thunderstorms,
with associated restrictions possible.
Thursday...VFR conditions expected at this time.
Friday...A chance of rain showers with associated restrictions.
&&
.BGM WATCHES/WARNINGS/ADVISORIES...
PA...None.
NY...None.
&&
$$
SYNOPSIS...JTC/MPH
NEAR TERM...JTC/MPH
SHORT TERM...AJG
LONG TERM...AJG
AVIATION...AJG/BJT
Area Forecast Discussion
National Weather Service Denver/Boulder CO
853 PM MDT Sun May 23 2021
.UPDATE...
Issued at 852 PM MDT Sun May 23 2021
Storms are out of the area with much drier air moving over the
area. The wrinkle in tonight`s forecast is varying handling of the
cool outflow air that is now over most of northeast Colorado. The
HRRR is most aggressive with this and seems overdone in
developing fog/stratus across all of the plains in the next couple
of hours. Other models either don`t see what`s there very well,
or have intermediate solutions with some mixing out around the
edges or pushing the edge of the moist air back off the ridges and
eastward a bit overnight. We`ll try to fashion some kind of
intermediate solution with increased stratus and areas of fog on
the plains. We`ll leave Denver out of this with the expectation of
a southerly component to the winds that will likely bring some
drying over the eastern part of the city if not the really dry air
and also limit the temperature drop. We`ll need to drop the lows
a little as even the drier air looks cooler than our forecast.
Some of the mountain valleys could really have temperatures tank
overnight with the drier air. There should be teens in the colder
spots. We`ll also drop tomorrow`s highs slightly given a cooler
start and slightly cooler guidance.
&&
.SHORT TERM...(This evening through Monday)
Issued at 319 PM MDT Sun May 23 2021
A couple severe discrete severe storms have developed, with three
brief tornado touchdowns reported so far this afternoon. We`ll
likely see these severe storms continue with a threat of more
tornadoes and very large hail as they move north/northeast across
the northeastern CO plains. There will also be a damaging wind
threat as storms gradually organize into more linear structures.
HREF Paintballs of updraft helicity show clustering of greater
than 150 m2/s2 over northeast Colorado, generally centered on
Akron and points north/east. Even higher values >250 on the 90th
percentile WoFS, and agrees with what we would expect given the
increase in low level southeast winds ahead of these storms. Peak
inflow winds peaked at a whopping 55 knots (severe storm criteria)
at Limon, and up to 37 knots so far at Akron and many other
mesonet observations across northeast Colorado. Therefore, the
tornado threat will continue this evening, with a longer track
tornado still possible, in addition to very large hail and
damaging winds. Severe threat should exit the far northeast corner
by 7-8 pm.
Dryline is working down the Front Range at the present time, which
will effectively end any convection across the foothills and I-25
Corridor late this afternoon, and then from west to east across
the plains through early this evening.
Gusty winds will ease by mid evening, with lighter winds expected
overnight and Monday. Monday will feature dry conditions, mostly
sunny skies, pleasant temps (70s lower elevations), and finally
stable conditions with no thunderstorms.
.LONG TERM...(Monday night through Sunday)
Issued at 319 PM MDT Sun May 23 2021
West-southwesterly flow aloft is expected for the CWA Monday
night and Tuesday before becoming due westerly and increasing
Tuesday night into Wednesday morning. Models show southwesterly
flow aloft again the rest of Wednesday and Wednesday evening,
ahead of a weakening upper trough that moves over Wednesday
overnight. The low level winds look weak with normal diurnal wind
patterns expected through Wednesday. There may be a weak cold
front and weak upslope move into the plains Wednesday evening
with the weakening upper trough. The QG Omega fields have downward
vertical velocity for the CWA Monday night and Tuesday, then
upward motion Tuesday night into Wednesday evening.
Looking at moisture, the CWA looks pretty dry Monday night through
Wednesday night, except for some increased moisture in the very low
levels over the eastern third of the CWA Monday night, Tuesday
afternoon, and late day Wednesday. There isn`t much in the way CAPE
until Wednesday, then values are fairly decent over the eastern half
of the plains. Will leave the "scattered" pops for showers and
storms in Wednesday late in the day the eastern and northern plains.
Temperature-wise, Tuesday`s highs are 1-3 C warmer than Monday`s and
Wednesday`s readings come up another 1-2.5 C over Tuesday`s highs.
For the later days, Thursday through Sunday, upper ridging is over
the CWA Thursday and Friday, with flat upper ridging Saturday and Sunday.
There is some moisture around, especially next weekend, so will go
with minor late day pops those two days. Temperatures should be a tad
above seasonal normals all four days.
&&
.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
Issued at 852 PM MDT Sun May 23 2021
Winds are complicated in the Denver area as a surge of cool moist
air is trying to come in from the northeast while west to
southwest winds off the foothills are fluctuating. Southwest to
west winds should prevail at KAPA/KBJC for the next couple of
hours, while KDEN winds are now northeast and will likely stay
that way for a bit. The trend should be toward south to southeast
winds at KDEN and KAPA by 06z, and lighter west winds at KBJC.
Some low clouds and fog are expected to develop over the plains
after 06z. There is a chance this could affect the Denver
terminals, mainly KDEN between 08z and 14z, but we think it`s more
likely that it will remain northeast of the area. If the fog does
move in, it would probably bring IFR ceilings. The chance of LIFR
conditions for a few hours looks pretty low but not zero.
The rest of Sunday will be VFR with light winds.
&&
.HYDROLOGY...
Issued at 319 PM MDT Sun May 23 2021
Strong to severe thunderstorms will shift east across the
northeast corner of the state through early evening. There are
some linear features and training storms, so locally heavy rain
and minor flooding possible there. Meanwhile, dry conditions are
quickly building over the Front Range with no threat to burn areas
through Monday.
Mainly dry conditions for the mountains/adjacent plains expected
through the week, except a chance for showers/thunderstorms
returning on the far plains for Wednesday through Friday.
&&
.BOU WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
UPDATE...Gimmestad
SHORT TERM....Barjenbruch
LONG TERM.....RJK
AVIATION...Gimmestad
HYDROLOGY.....Barjenbruch
Area Forecast Discussion
National Weather Service Boston/Norton MA
938 PM EDT Sun May 23 2021
.SYNOPSIS...
A sharp wind shift in wake of the front could pose a
significant impact to mariners and recreational boaters early
tonight. Much cooler/seasonable temperatures to start the work
week, but the warmth returns by mid week. Showers and perhaps a
few thunderstorms possible late on Wednesday into early Thursday
associated with a cold front. This front will usher in a more
seasonable airmass late in the week and into the weekend.
&&
.NEAR TERM /UNTIL 6 AM MONDAY MORNING/...
935 PM Update...
No major changes in the latest update other than bringing things
in line with the latest observations. Did nudge down wind gusts
as the front has moved through a bit quicker. With decreasing
wind gusts we did cancel the Small Craft Advisories with the
exception of the outer waters. Otherwise a refreshing night is
on tap.
Previous discussion...
Regional radar mosaic shows scattered showers ahead of a sharp
cold front and northerly wind shift, mainly north of the
Massachusetts Turnpike. Vertical growth with these showers has
been slow and generally limited (storm tops as of 330 PM less
than 20k). However somewhat greater instability (surface-based
CAPEs around 1000 J/kg) noted per SPC mesoanalysis is common
across areas south of the Massachusetts Turnpike. Isolated to
widely scattered thunderstorms should blossom a little more than
what we`ve seen so far as they move southeast into this
slightly-more-unstable air mass, reaching the south coastal
waters through 8 PM. NAM-3km and recent HRRR runs reflect these
ideas. Not everyone will see thunder today with coverage being
no better than widely scattered, but any stronger cell could
produce gusty to locally damaging winds.
Cold front now over south-central NH/VT to surge southward and
bring about a substantial change in air mass from the very
warm/hot conditions to a more seasonable and drier air mass with
onshore flow. Sharp 3-hr pressure rises in the 4 to 6 mb
neighborhood should allow for north to north- northeast winds
to become rather breezy in the hours after FROPA (around 25-30
mph) early, then decrease a bit into the mid-evening/midnight as
winds become more northeast. Clearing and dry conditions with
ridging building back in, 925 mb temps falling from the +20 to
+22C level this afternoon down to around +7 to +9C by pre-dawn
Monday. Should see lows in the 40s to lower 50s.
&&
.SHORT TERM /6 AM MONDAY MORNING THROUGH 6 PM MONDAY/...
While mostly sunny to partly cloudy conditions (fair weather
cumulus) to prevail, the main story is the much cooler and more
seasonable air mass compared to today. High temperatures may be
some 25 degrees colder for Monday than today! In addition,
dewpoints in the 30s to lower 40s compared to the upper 50s to
lower 60s than today. Light east to southeast winds across the
interior initially to trend more southerly late, though sea-
breezes look likely near the eastern MA coast which will keep
east-coastal sites cooler than further inland. Highs in the mid
60s to lower 70s in the interior, and in the lower to mid 60s
near the coastlines.
&&
.LONG TERM /MONDAY NIGHT THROUGH SUNDAY/...
Highlights
* Temperatures on the rise into mid week, with summerlike warmth on
Wednesday. Temperatures cool to near/cooler than seasonable for
late in the week and into the weekend.
* Dry and quiet weather Monday night into Tuesday. Next shot for
more widespread shower/storm activity is later on Wednesday into
early Thursday. Late in the week and into the weekend could be
more unsettled, but confidence remains low this far out.
Monday night through Tuesday...
Ridge axis builds over southern New England Monday night and
offshore on Tuesday. A surface high will remain south of Nova Scotia
and build further offshore on Tuesday.
Dry and quiet weather expected with high pressure under control.
Aloft flow will become southwesterly due to the position of the
ridge/high. This will advect warmer air into the region with 7-8
degree Celsius air in place over the region Monday night and 10-15
degree Celsius air on Tuesday. Given the high in place, relatively
light winds and mostly clear skies did lower temps Monday night
toward the 25th percentile of guidance as am anticipating some
decent radiational cooling. Lows range from the mid 40s to the lo
50s. Held off from going cooler as mechanical mixing could be an
issue along with some cloudiness.
Should be milder (in comparison to Monday) across southern New
England on Tuesday with high temperatures ranging from the mid 60s
to the upper 70s.
Wednesday through Thursday morning...
Ridge axis offshore with cyclonic flow in place as a trough digs
into Hudson Bay/northern Ontario. Am anticipating a shortwave trough
to lift from the central Great Lakes early on Wednesday through
northern New England by Thursday morning. A warm front will lift
through early on Wednesday and we could see some showers/storms
within the warm sector, but am anticipating a better shot when the
cold front swings through later in the day into early Thursday.
Summer like warmth is expected across southern New England on
Wednesday. Will see 15-17 degree Celsius air in place over the
region. The result are high temperatures well into the 80s across
the interior and there will be some low 90 degree readings across
the Merrimack Valley and CT River Valley. Should remain a bit cooler
along the south coast given the southwesterly flow in the lower
levels, so highs will generally be in the 70s.
Have kept with the NBM precipitation chances, but knocked things
down to keep them in the chance to slight chance categories given
there is some uncertainty on the exact timing of the front moving
through. Did add a mention of thunderstorms in the latest update
given there is roughly a few hundred to about 1500 J/kg of MUCAPE if
not a bit higher. Decent moisture in place given dew points will be
in the upper 50s to lower 60s and PWATs in the 1.5 to 2 inch range.
These PWAT values are toward the max of SPC Sounding climatology for
this time of year for CHH. Mid level lapse rates are poor around 5-6
degrees Celsius per km, so this may limit sustaining/more organized
storms along with 0-6 km shear with values between roughly 20-30 km.
Will need to keep an eye on this day is a few hundred J/kg of DCAPE,
which could potentially bring gusty winds. Thinking that heavier
rainfall and gusty winds would be the main risk as this point in
time, but will need to see how guidance trends over time.
Front moves through the vast majority of the CWA by Thursday morning
and should bring an end to any shower/storm activity. Should be
relatively mild with low temperatures in the 60s across much of the
region heading into Thursday.
Thursday through Saturday...
Weak ridging in place on Thursday. This is followed by a
trough/cutoff lifting in from the Upper Midwest for late in the week
and into the weekend. High pressure weakly nudges in on Thursday.
Vast majority of guidance keeps the coastal low to the south, but
will need to see how things progress as time goes on. For now have
kept slight chance to chances of precipitation. Cooler airmass moves
in wake of the front that slides through early on Thursday.
Temperatures trending downward for the rest of the week. Highs on
Friday/Saturday generally in the 60s, but there may be a few 70
degree readings in the CT River Valley.
&&
.AVIATION /02Z MONDAY THROUGH FRIDAY/...
Forecaster Confidence Levels.
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.
Through 12Z...High confidence
Cold front is mostly through the CWA. Only have a few showers
lingering near Cape Cod and the Islands. This will move through
in the next 1-2 hrs. Gusty post frontal N/NE winds early this
evening, especially over eastern MA. Should see the gusts
diminishing as the night progresses, but speeds will be around
5-10 kts. Generally expecting VFR conditions, but could have
some brief periods of MVFR with clouds bases between 2.5-5 kft
this evening. Should see drier air punching in bringing clearing
late.
Monday...High confidence.
VFR, with a few fair weather Cu in the afternoon. Should have
cloud bases around 4-6 kft. E/ESE winds become S/SW in the
interior to around 5-10 kt, though with sea breezes near the
eastern MA coast.
Monday Night...High confidence.
VFR continues, with S/SW winds 5-10 kt.
KBOS TAF...High Confidence in TAF.
KBDL TAF...High Confidence in TAF.
Outlook /Monday Night through Friday/...
Monday Night through Tuesday Night: VFR. Breezy.
Wednesday through Wednesday Night: Mainly VFR, with areas MVFR
possible. Breezy. Chance SHRA, isolated TSRA.
Thursday: VFR. Breezy.
Thursday Night: Mainly VFR, with areas MVFR possible. Slight
chance SHRA.
Friday: Mainly MVFR, with local VFR possible. Chance SHRA.
&&
.MARINE...
Forecaster Confidence Levels.
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.
Tonight: High confidence.
* Abrupt windshift (west to northerly) with brief wind gusts of
35 to 45 knots possible between 5 and 9 PM Sunday.
Cold front will bring a risk for scattered showers/thunder to
most of the waters late this afternoon into early tonight.
Potential exists for a couple storms to become strong, though
coverage will be limited. Main concern will be during the mid-
late afternoon hours into early this evening. A strong cold
front will cross the waters with a rather strong pressure rise
couplet behind the front. NAM shows 975 MB winds at 40 knots
from the NNE, with strong sea-level pressure rises supporting a
potential (though brief) period of northerly winds in the Gale
range. This could be especially problematic to recreational
boaters caught on the water. SCAs still are in effect but will
continue the marine weather statement before its scheduled 21z
expiration.
A more rapid decrease in winds/gusts expected after mid-evening,
with northeast gusts around 15-20 kt by daybreak. Seas mainly
in the 4-6 ft range on the outer waters.
Monday into Monday Night: High confidence.
SE winds around 10-15 kt most of the day, seas around 2-4 ft.
Late in the day and more into the evening, winds to trend SW and
increase to borderline SCA level in gusts on our northeastern
waters, with seas nearing 5 ft. May need to consider SCAs for
the Monday late-afternoon into Monday evening but seems too
marginal to hoist at this point.
Outlook /Monday Night through Friday/...
Monday Night through Tuesday: Low risk for Small Craft Advisory
winds with gusts up to 25 kt. Areas of seas approaching 5 ft.
Tuesday Night: Moderate risk for Small Craft Advisory winds
with gusts up to 25 kt. Seas up to 5 ft.
Wednesday: Moderate risk for Small Craft Advisory winds with
gusts up to 25 kt. Seas up to 5 ft. Slight chance of rain
showers, isolated thunderstorms.
Wednesday Night: Low risk for Small Craft Advisory winds with
gusts up to 25 kt. Seas up to 5 ft. Chance of rain showers,
isolated thunderstorms.
Thursday through Thursday Night: Winds less than 25 kt. Areas
of seas approaching 5 ft. Slight chance of rain showers.
Friday: Winds less than 25 kt. Seas up to 5 ft. Chance of rain
showers.
&&
.TIDES/COASTAL FLOODING...
Tide data shows that the May astronomical high tide will take place
at midweek, with highest levels on the midnight high tide. Boston,
for example, will peak at 12.2 feet Wednesday night. Nantucket will
peak at 4.3 feet. Providence will peak at 6.2 feet. These values
do not include any residuals. Expecting a southwest wind of 15
kt sustained and gusts to 25 kt. These winds will push water up
against the south and southwest-facing coasts. The midweek tides
will be monitored for potential high water levels.
&&
.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...Small Craft Advisory until 6 AM EDT Monday for ANZ250-254>256.
&&
$$
SYNOPSIS...BL/Loconto
NEAR TERM...BL/Loconto/Gaucher
SHORT TERM...Loconto
LONG TERM...Loconto
AVIATION...BL
MARINE...BL/Loconto/Gaucher
TIDES/COASTAL FLOODING...
AREA FORECAST DISCUSSION
National Weather Service Sioux Falls SD
642 PM CDT Sun May 23 2021
.SHORT TERM...(This Evening through Monday)
Issued at 248 PM CDT Sun May 23 2021
Fairly expansive cumulus field as of mid afternoon with a few
showers and thunderstorms. Most focused area of convection is along
the Buffalo Ridge where better surface convergence has allowed for
greater coverage. RAP mesoanalysis confirms effective deep layer
shear is weak however with with MLCAPE values around 1000 J/kg,
can`t rule out the possibility of a storm or two pulsing to near
strong/severe levels. Additionally, given the presence of a
boundary, a non-zero (although extremely low) chance of a brief
funnel although RAP analyzed surface vorticity is far from
impressive. This will continue to progress northeastward thru the
late afternoon.
As we move through the evening, a pronounced wave ejecting out of
the Rockies will continue to allow for expanding thunderstorm
coverage across western SD and NE Panhandle with eventual upscale
growth owing to a strong boundary parallel component of deep layer
shear vectors. Previously mentioned wave pivots northeastward away
from our coverage area and, combined with weaker instability and
shear parameters with eastward extent, should result in a weakening
trend of this convection as it approaches the MO River. This
decrease in strength is reflected well in latest HREF guidance. With
all of this said, not out of the question that areas west of the
James River still stand the risk of borderline severe wind gusts
before an eventual transition to more showers/embedded thunderstorms
east of the James River late tonight.
The eastward extent of overnight convection will have at least some
impact on the forecast for Monday via influence on the eastward
progression of the surface boundary and remnant outflow boundaries.
This will be important as forecast soundings show fairly minimal
convective inhibition and thus suspect we will likely see a fairly
early agitation to the cumulus field once better solar insolation
commences by late morning. Distinct mid/upper level forcing is again
tough to come by but weak surface convergence along the main
synoptic boundary (as well as any established outflow boundaries)
should be enough to tap into the roughly 1500 J/kg of MLCAPE.
Perhaps a bit better environment by late afternoon as the region
starts to receiving a bit more help to finalize any needed
environmental preconditioning as the right entrance region from a
departing jet streak enters the picture.
All of this to say that current indications are weak radar echos
could very well be possible near and just ahead of the surface
boundary by as early as late morning Monday with likely more
established deep convection by mid to late afternoon. Better deep
layer shear is again weighted post-frontal with effective shear in
the warm sector generally in the 20-35 kt range. This will likely
result in largely multicell clusters with perhaps some borderline
supercell characteristics. With this lack of better deep layer
shear, the severe threat may remain somewhat tempered although
initial suspicion is that at least a couple severe level storms seem
possible. Large hail up to ping pong size appears to be the primary
threat with any organized cluster also posing a damaging wind
threat. These threats are highlighted by a Day 2 Marginal from SPC.
Temperatures a few degrees either side of 80 look reasonable for
Monday with more sunshine for locations behind the boundary.
.LONG TERM...(Monday Night through Sunday)
Issued at 248 PM CDT Sun May 23 2021
Surface boundary looks to get pushed into NW IA by midday Tuesday
although if Monday`s convection is less than progged, this could be
a bit slower (the opposite could also be said). This would result in
continued shower/storm chances ahead of this boundary for areas
toward the Hwy 20 corridor in NW IA although a bit more suitable
forcing may be displayed to the south/east of our coverage area.
Temperatures again in the upper 70s to mid 80s look reasonable with
westerly winds.
Brief period of shortwave ridging is expected by Wednesday with
northeasterly winds helping to usher in cooler temperatures in the
70s and lower dewpoints.
Next shortwave will be quick behind however and looks to provide a
fairly good shot at widespread precipitation Wednesday night into
Thursday. Better instability continues to look to be be mainly
bottled up south of our area so probably more of a shower with
embedded lightning setup. This would also keep temperatures rather
cool on Thursday with upper 50s to mid 60s.
Shortwave ridging returns for Friday and Saturday along with dry
conditions and gradually warming temperatures.
&&
.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
Issued at 642 PM CDT Sun May 23 2021
23.2330Z regional radars show a solid line of showers with
embedded thunderstorms across western SD extending southward into
the Nebraska panhandle. These storms will slowly move eastward
this evening, eventually impacting TAF airfields. Storms are
expected to weaken as they move toward the MO River, but still
enough confidence to include thunder at KHON/KFSD. Short-term
model run-to-run consistency has been excellent with timing, so
only minor adjustments were needed. Expect showers and storms at
KHON by 24.05Z and at KFSD by 24.07Z. Showers should be the
dominant mode at KSUX by 24.08Z.
Prior to showers and thunderstorms, expect VFR conditions with
southerly breezes. Then, MVFR conditions are expected with any
convective activity. Cloud bases should rise back above 3000 ft
agl after rain moves out. Winds will veer slightly to the southwest
by Monday afternoon with some gusts up to 25 kts.
There is a chance for another round of showers and thunderstorms
mid-late Monday afternoon, potentially impacting KFSD and KSUX,
but confidence in timing/coverage too low at this time to include
in 00Z TAFs. Will address this potential with 06Z update.
&&
.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 Indianapolis IN
1136 PM EDT Sun May 23 2021
...Updated Aviation Discussion...
.Forecast Update...
Issued at 956 PM EDT Sun May 23 2021
Removed thunder and any measurable PoPs from the forecast for the
rest of the night. Forcing is better to the north, even with the
front sagging into the northern parts of the forecast area, and high
resolution model output shows very little development here. Given
the presence of the front and a couple of light echoes showing up on
radar loop in the northernmost counties, though, went ahead and
inserted isolated sprinkles across the north through the night,
generally along and north of the projected frontal location. End
result is a few northern locations could see a few raindrops
overnight, but don`t expect it to measure and don`t expect much
given the temperature inversion.
Temperatures are slow to drop, and think going lows in the low to
middle 60s are on track.
&&
.Short Term...(This evening through Monday night)
Issued at 321 PM EDT Sun May 23 2021
Scattered to broken cumulus were across central Indiana this
afternoon, but the radar was quiet. Temperatures were in the lower
to middle 80s.
A weak front/wind shift will sink into northern Indiana later this
afternoon into early evening, but should remain north of the
forecast area. Weak instability will be across the northern forecast
area. The front may be close enough to spark an isolated shower or a
thunderstorm across this area late this afternoon into the early
evening. The HRRR continues to back up this thinking with isolated
(weak) convection. Will keep some slight chance PoPs across the far
north until 01Z, but with low confidence given lack of decent
instability.
Loss of heating this evening will allow the cumulus to dissipate,
leaving behind some passing high and mid clouds. Thus will go dry
and partly cloudy for the remainder of the tonight period.
On Monday, the upper ridge and surface high will expand a bit across
the area. Warmer air will move in at the mid levels during the day,
and this should cap off any convection. Also, increased subsidence
should reduce the amount of cumulus. Thus will keep the area dry on
Monday. These conditions should also allow for temperatures to get a
little warmer than today, with highs nearing 90 for some locations.
Dry conditions will continue Monday night with high pressure still
in control.
&&
.Long Term...(Tuesday through Sunday)
Issued at 321 PM EDT Sun May 23 2021
The ridge will weaken and move off to the southeast at the beginning
of the long term period. Troughing and a more active weather pattern
will then take over for much of the week. While there is a daily
chance of showers and thunderstorms with this pattern, better
chances will come midweek and again end of the week with more robust
waves. A frontal system looks to bring thunderstorms late Tuesday
into Wednesday as the upper trough axis swings across the
regions. Cooler air behind the front will allow temperatures to
drop from the mid to upper 80s Tuesday to the low to mid 80s
Wednesday.
Brief ridging will then return in the wake of the trough axis
passing by with the front stalling off to the east early Thursday.
This will likely bring a decrease in convection across the region
Wednesday night.
The next system will then arrive Thursday night to Friday as a
surface low tracks across the area from the central plains. More
widespread showers and thunderstorms are expected with this low and
models are showing a nocturnal low level jet forming along the
leading edge. This could provide energy for stronger storms
associated with this system but its still too early to say for sure
and will continue to monitor as we approach the end of the week.
Temperatures will finally drop to near normal for Friday as a cooler
airmass moves in.
The models have some variability going into the weekend but at the
moment looks like things will be drier compared to the the rest of
the period with high pressure building in. Will keep in the slight
to chance PoPs for now given uncertainties as a trailing upper
low could set up a boundary and trigger some storms.
&&
.Aviation...(06Z TAF Issuance)
Issued at 1135 PM EDT Sun May 23 2021
IMPACTS:
- Light and variable winds become southwesterly at 4 to 8 kts by
midmorning.
DISCUSSION: Scattered to broken mid and high clouds expected through
the night, and these should help prevent fog development. Few to
scattered VFR cu should develop during the afternoon.
&&
.IND WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
Update...CP
Short Term...50
Long Term...KH
Aviation...CP
Area Forecast Discussion
National Weather Service North Platte NE
620 PM CDT Sun May 23 2021
.SHORT TERM...(This evening through Monday night)
Issued at 205 PM CDT Sun May 23 2021
Deep southerly flow continues across wrn and ncntl Nebraska this
afternoon. A Pacific cold front has cleared the Colorado front range
and the Laramie Ranges triggering thunderstorm activity which will
carry east into wrn Nebraska this evening. There is also a small
zone of warm air advection across sern Colorado triggering storms
south of Pueblo Colorado. The storm activity across ern WY and Colo
should grow upscale into the deep moisture across wrn Nebraska this
evening producing at least scattered storms and a solid line of
storms appears likely north of Interstate 80.
A couple of hindrances may limit the magnitude of the severe
weather across wrn Nebraska tonight. Winds aloft, although very
strong, are unidirectional supporting storm splitting and the warm
air advection ahead of the Pacific cold front appears limited to
sern Colorado- aimed at nwrn KS and swrn Nebraska. The RAP model
suggests the shear is too strong to sustain supercells.
On the other hand, the RAP shows two distinct meso circulations
forming across swrn Nebraska and swrn SD which could maintain severe
storm evolution. These circulations are being fed by strong moist
low level winds below 700mb. There is also a well defined h700mb dry
slot or intrusion associated with the storms moving east through wrn
Nebraska and this should produce a cold pool and enhance wind damage
potential. So there are competing forces both in favor or in
disfavor for severe storm development. The severe weather forecast
follows the SPC which, given the strong backing low level winds this
evening, all modes of severe weather, including tornadoes are
possible.
The POP forecast leans on the short term model blend for likely to
definite pops tonight generally along and west of highway 83. East
of highway 83, chance POPs are in place. Some models like the ECM
and SREF weaken the storm activity quickly while other models like
the HREF and NAM maintain storm activity throughout ncntl Nebraska.
WPC suggested up to 1 inch of QPF tonight which locally, could
result in a few 2 inch totals. This is in line with the HRRR which
suggests a few HP storms which could produce a quick 1 to 1 and 1/2
inches of rainfall followed by additional rainfall from weaker storm
activity. All of this storm activity should be east of ncntl
Nebraska by 12z Monday with just and isolated shower chance in the
morning.
SPC has hung a marginal severe weather risk Monday afternoon and
evening across parts of swrn and ncntl Nebraska. This is the result
of the front hanging up across cntl Nebraska. A check on the RAP
model shows this front stationary late Monday but winds at the lower
levels are not backed. Thus the best severe weather potential would
appear to be just to the east of the front as suggested by the SPC.
For these reasons, just a slight chance of thunderstorms are in
place across parts of swrn and ncntl Nebraska.
.LONG TERM...(Tuesday through Sunday)
Issued at 205 PM CDT Sun May 23 2021
An excellent opportunity for severe weather may present itself
Wednesday afternoon and Wednesday night. The NAM shows a warm
front lifting north through wrn Nebraska during the afternoon and
the GFS and NAM show westerly winds h500mb increasing to 40 to 50
kts. The NAM shows some sort of convective complex developing
across nwrn Nebraska by 00z which will likely move east and grow
upscale. Chance to likely POPs are in place Wednesday afternoon
and Wednesday night.
Thunderstorms chances are in place next Saturday. The potential for
severe weather is uncertain given the distance time away from this
rain event. The rest of the forecast is generally dry.
&&
.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
Issued at 620 PM CDT Sun May 23 2021
Multiple aviation weather concerns exist during the forecast
period, including severe thunderstorms, strong surface winds, and
low ceilings. A line of strong to severe storms will cross the
region this evening into tonight, which will be capable of very
large hail and damaging winds with gusts exceeding 50 kts. Ahead
of these storms, south/southeast winds will continue to gust
around 30 kts. In the storms wake, surface winds will lighten but
stratus clouds set in, especially in southwest Neb (KLBF). Expect
MVFR to locally IFR ceilings early morning, but should return to
VFR after daybreak.
&&
.LBF WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
SHORT TERM...CDC
LONG TERM...CDC
AVIATION...Snively
Area Forecast Discussion
National Weather Service Lake Charles LA
917 PM CDT Sun May 23 2021
.UPDATE...
A trof continues to extend from the Texas gulf coast inland this
evening streaming very high atmospheric moisture west of the
Sabine River. This has maintained scattered light showers over
southeast Texas through the evening. The 00Z KLCH sounding
observed much drier mid level air over southwest Louisiana where
periods of sun were observed earlier today for the first time in
a week (but who`s counting). Latest few runs of the HRRR continue
to maintain light showers over southeast Texas for another two to
three hours before diminishing them for a short period late
tonight. The updated PoPs reflects this expectation with
precipitation reinitializing once again after sunrise tomorrow.
Extended the coastal flood advisory through 00Z Tuesday based on
the latest extra tropical surge guidance and it`s likely it will
need to be extended further through mid week if not longer as the
long southeasterly fetch is forecast to persist across the
northern gulf.
Jones
&&
.PREV DISCUSSION... /issued 612 PM CDT Sun May 23 2021/
AVIATION...
Radar is indicating rains moving onshore of southeast Texas at
this time generally west of BPT. BPT will see periods of
rains/showers this evening and into the overnight hours with
ceilings lower at times in and near the showers. Otherwise...
TAF lctns in srn Louisiana are expected to remain VFR.
K. Kuyper
PREV DISCUSSION... /issued 256 PM CDT Sun May 23 2021/
SHORT TERM [Today through Monday Night]...
GOES-16 WV showing moisture sliding northward along a trough axis
stretching from the Texas Gulf coast northward this afternoon. In
conjunction with this, more widespread cloud coverage and a few
showers are noted over the SE TX zones, with more appreciable
precipitation towards Houston and the I-45 corridor. At the same
time, broad and deep ridging centered over the TN valley is
resulting in drier air and suppression of activity in the eastern
1/2 of the CWA. To that end, RAP sfc analysis depicts quite the
moisture gradient, with PWATS ~2.00 inches west of the Sabine
River, and PWATS closer to 1.00 to 1.25 inches east. As such, the
best potential for rain will continue to be in SE TX for the
remainder of the day.
Overnight into Monday, ridge slides off a bit more to the east while
the west Gulf mid level trough begins to lift more inland. The
result is deeper moisture across a bit more of the region, as well
as some increased lift. Combined with diurnal enhancement, expect
precip to be a bit more widespread tomorrow with best chances in SE
TX and W LA. Precip along with cloud cover will help keep afternoon
temps in check once again, with highs forecast slightly below
climatological normal. With loss of heating, the bulk of activity
expected to diminish moving into Tuesday night, though an isolated
shower or two will remain a possibility.
50
LONG TERM [Tuesday through Sunday]...
Tuesday and Wednesday the region will remain between a ridge aloft
to the east and weakness to the west while a plume of tropical
moisture continues to stream in from the gulf over Texas. On
Wednesday the weakness will have shifted more eastward toward LA,
however weakening as this occurs. This will keep isolated to widely
scattered showers in place, but mainly in the afternoons.
Thursday and into Friday a ridge will briefly build aloft cutting
off rain, however by the weekend another upper disturbance will
approach the region allowing for isolated to widely scattered mainly
diurnal storms to redevelop.
05
MARINE...
Modest east to southeast winds and elevated seas will continue
today into tonight before easing a bit on Monday. A few showers
and t-storms will be possible, primarily south of Sabine Pass. A
light to modest onshore flow will then prevail through midweek and
into next weekend.
50
&&
.PRELIMINARY POINT TEMPS/POPS...
AEX 67 84 67 85 / 0 10 10 30
LCH 70 82 70 84 / 30 40 10 30
LFT 68 83 68 84 / 0 10 0 20
BPT 71 82 71 84 / 60 60 20 40
&&
.LCH WATCHES/WARNINGS/ADVISORIES...
LA...Coastal Flood Advisory until 7 PM CDT Monday for LAZ041-052-073-
074.
TX...Coastal Flood Advisory until 7 PM CDT Monday for TXZ215-216.
GM...Small Craft Exercise Caution until 5 AM CDT Monday for GMZ450-
452-455-470-472-475.
&&
$$
Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
1103 PM CDT Sun May 23 2021
.SHORT TERM...(This evening through Monday night)
Issued at 228 PM CDT Sun May 23 2021
The key messages of the forecast in the short term is the reduced
threat for severe weather today. The risk for isolated heavy
rainfall remains. On Monday there is a Marginal Risk of severe
weather, with the primary threats being large hail and damaging wind.
There is also a risk of localized heavy rain.
Today - The weak winds and lack of shear are the limiting factor for
strong to severe storms the rest of today. In addition, the moist
mid levels with H700-500 lapse rates around 5 to 6 C/km are also a
limiting factor. The combination of the two is the reasoning behind
removing the Marginal Risk for today. However, PWATs remain around
1.5 inches, and the storm motion is very slow, so isolated heavy
rainfall remains possible through the evening.
Tonight - Scattered showers and thunderstorms should decrease in
coverage overnight across the region. Meanwhile an impressive line
of thunderstorms should be ongoing across the Dakotas and moving
eastward. As it approaches Minnesota, it will lose instability and
should weaken. By the time it reaches western Minnesota Monday
morning it should be nothing more than scattered showers with maybe
a few lightning strikes.
Monday - On Monday a shortwave trough will move eastward along the
International border. This should tighten up a frontal boundary that
is most noticeable in the dewpoint gradient from southwest Minnesota
through northern Wisconsin. As alluded to in the previous
discussion, there will be a ribbon of 1000 to 2000 J/kg of MLCAPE on
the warm side of this frontal boundary. In addition the upper level
jet should increase Monday evening and the right entrance region
should favor ascent. Mid level lapse rates are still fairly low, on
the order of 6.5 to 7 C/km. Deep layer shear is stronger, but it is
unidirectional. Put it all together and you have the Marginal Risk
of severe storms with damaging wind and large hail as the primary
threats. Give the shear is oriented along the boundary, there is
also a threat for heavy rain with training thunderstorms.
.LONG TERM...(Tuesday through Sunday)
Issued at 228 PM CDT Sun May 23 2021
The long term period picks up with the front from the short term
continuing to move through the area, bringing scattered showers and
thunderstorms at this point mainly to western WI. The upper level
trough is strongest farther to the north near the Canadian border,
with the remnants of the front occluding as we head into Wednesday
which should bring most of the showers to an end. Guidance is
keeping any wrap around showers closer to the surface low and
trough, which keeps it confined to northern MN Wednesday morning. We
won`t feel the temperature impact of the front until Tuesday night
and Wednesday morning, with highs in the mid 80s on Tuesday dropping
into the upper 40s to mid 50s overnight.
With the front moving through early on Wednesday cutting off the
stream of warmth and moisture that was observed over the previous
week, we will struggle to warm back up to the 80s for the remainder
of the period. The coldest day will be Thursday with highs in the
low 50s to near 60 expected, otherwise generally looking at 60s and
low 70s through next weekend. We do have a few more chances for
rainfall as well, with a quick moving 500mb trough swinging through
Thursday night into Friday morning, targeting southern MN with the
heavier rainfall in central Iowa. Another potential front then
arrives on Sunday, however this is less certain and has a greater
chance of missing due to the front stretching down a significant way
from central Canada. Kept NBM PoPs for now which show about 30-40%
Sunday during the afternoon while the front moves through, which is
even a bit ambitious right now.
&&
.AVIATION...(For the 06Z TAFS through 06Z Monday night)
Issued at 1102 PM CDT Sun May 23 2021
Two issues this TAF period are evolution of stratus (and potential
fog for central MN) and shra/ts chances Monday afternoon. For the
clouds, kept it simple, so long as a site remains north of the wavy
boundary across southern MN, they get stratus. Some fog concern for
STC, though vis restrictions have been much slower to materialize
this evening than the HRRR has been showing, so kept a bit more
optimistic vis forecast. Main question for tonight is how quickly
does the stratus retreat back to the north. MSP is on the edge of it
right now, but do expect the stratus to crawl back north of the
field by Monday morning. Same could happen at RNH. For storms,
convergence along the front is almost non-existent, with it being
nothing more than a moisture gradient. As such, only expect scattered
convection to develop near the moisture gradient as diurnal
instability builds. At this point, kept all TAFs dry tomorrow as
confidence in storms occurring at any one location is not high enough
to include in the TAFs at this point. Really, the only airport you
can probably completely rule out of a rain chance Monday/Monday
night is AXN.
KMSP...As the boundary that push just south of MSP goes back north
late tonight, can`t completely rule out a brief shower, but expect
mainly dry conditions to prevail. For TS chances later Monday, it
again looks like we are waiting until after 00z before chances really
pick up with the front off to the west, but with little agreement in
the CAMs in how precip may, or may not develop Monday
afternoon/evening, went with a TAF without any precip mention at this
point.
/OUTLOOK FOR KMSP/
Tue...VFR. Wind WSW 15G25 kts.
Wed...VFR. Wind NW 5-10 kts.
Thu...MVFR/RA Likely. Chc IFR/TSRA. Wind E at 10G20.
&&
.MPX WATCHES/WARNINGS/ADVISORIES...
MN...None.
WI...None.
&&
$$
SHORT TERM...JRB
LONG TERM...TDH
AVIATION...MPG
Area Forecast Discussion
National Weather Service Marquette MI
732 PM EDT Sun May 23 2021
.SHORT TERM...(This evening through Monday)
Issued at 337 PM EDT SUN MAY 23 2021
The weather experienced today across the U.P varied greatly with
temperatures over the interior east reaching the 60s while locations
in the central and west, particulary near Lake Superior, were much
cooler with highs in the 40s. RAP upper air analysis and water vapor
imagery showed a closed upper level low over the Great Basin with a
strong downstream upper level ridge extending from the Gulf Coast
north into the northern plains and southern Canada. Weak FGEN and
convergence at 850mb along with weak instability was just enough to
result in a few showers and thunderstorms over the west and central
late this afternoon which could linger though the early evening.
Tonight the upper level low pressure and associated surface low
pressure will move from the Great Basin into the Northern Rockies. A
surface high pressure over Ontario will push east into Quebec. This
will bring returning southerly flow to the area with low
temperatures likely occurring this evening followed by slowly rising
temperatures overnight. A bit steeper mid-level lapse rates will
begin to advect into the area on Monday along with increasing
surface dewpoints. This will bring increasing instability with the
possibility for showers and thunderstorms developing over northern
WI and reaching the southern and western portions of the U.P by late
in the afternoon. Large scale forcing looks to be relatively weak
during the afternoon and MUCAPE generally less than 500 J/kg along
with shear of around 25 knots or less, not expecting any strong
storms at this point with the better instability and shear remaining
south of the U.P.
Fire weather concerns will remain low with afternoon minimum
humidity remaining above 50 percent.
.LONG TERM...(Monday night through Sunday)
Issued at 439 PM EDT SUN MAY 23 2021
The frontal boundary that moved through the area this morning is
expected to lift north as a warm front on Monday. The same warm and
muggy air mass that invaded our area late last week will vist Monday
afternoon through Wednesday morning. A potent cold front moves
through Tuesday night into Wednesday morning with temperatures
likely to fall below normal through the remainder of the long-term.
However, the cooler air mass will also be dry resulting in warm
sunny days and clear cool nights.
The warm and sultry air mass will already be overhead at the
beginning of the extended period (00Z Tuesday). Thunderstorms may be
ongoing along the MI/WI border on Monday evening that may persist
overnight given a respectable 40-45 knot LLJ. The main threat with
these storms appears to be heavy rain, lightning, and perhaps some
small hail.
Tuesday appears to be a busy day with WAA persisting all
day resulting in deep mixing and the potential for strong, gusty
downslope winds near Lake Superior. I`m not confident on the depth
of mixing considering morning convection and remnant cloud cover,
but some operational guidance indicates gusts approaching wind
advisory criteria. Thunderstorms may develop by Tuesday afternoon
when the near-storm environment should be supportive of marginally
severe hail and wind threats. The main source of uncertainty is
timing and location of the frontal boundary, but 12z guidance
indicates the fropa entering the west between 21-00z and exiting
around 06-09Z. This is a favorable diurnal timing for
thunderstorms and we definitely need the rain ...
A cooler air mass is expected behind the initial frontal boundary,
but a reinforcing cold front moves through early Wednesday morning.
There seems to be a brief, but intense period of cold air advection
behind this reinforcing cold front. 850 mb temperatures appear cool
enough to result in lake-induced mixing of stronger winds aloft for
a few hours on Wednesday. While it currently seems unlikely there`s
a non-zero chance of a few gale force gusts over Lake Superior
Wednesday morning. Thus, Wednesday will not be particularly pleasant
with a chilly north wind off Lake Superior and potential for a non-
diurnal temperature curve with temperatures falling during the day.
By Wednesday night the chilly air mass will be in place across our
CWA and it seems likely to dominate our weather through the end of
the week. This means there will be chances of frost on at least
Wednesday and Thursday night and perhaps Friday too. The good news
is we should see the sun on a regular basis during the upcoming cool
weather, which will take the edge off the chilly air mass. A weak
warming trend is possible this weekend as the chilly surface ridge
slides east-southeast on Saturday.
&&
.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
Issued at 721 PM EDT SUN MAY 23 2021
IFR conditions at KIWD in lingering showers should improve to MVFR
later this evening as showers end, and then will stay MVFR
through much of Monday. Otherwise, expect VFR conditions at KCMX
and KSAW to lower to MVFR stratus later tonight under a developing
moist se-e upslope flow and should stay that way through much of
Monday.
&&
.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 337 PM EDT SUN MAY 23 2021
Winds over the west will diminish overnight to less than 15kt. Winds
will remain under 20kt through Tuesday afternoon before the next
cold front arrives. Winds begin to increase Tuesday night to 25kt
across the lake and then up to 30kt over eastern Lake Superior on
Wed, with diminishing winds in the west. Winds will diminish for
Thu, but there could be somewhat stronger ne winds locally gusting
to 25kt down western Lake Superior as high pres builds over northern
Ontario.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
None.
Lake Superior...
None.
Lake Michigan...
None.
&&
$$
SHORT TERM...NL
LONG TERM...EK
AVIATION...Voss
MARINE...NL
Area Forecast Discussion...UPDATED
National Weather Service Portland OR
811 PM PDT Sun May 23 2021
Updated Aviation Discussion
.SYNOPSIS...A weak cold front moves in late Sunday night and
Monday bringing more chances for rain, followed by showers lasting
into Tuesday. An upper level ridge will bring dry weather Wednesday,
another cold front brings chances of rain back into the forecast
Thursday
&&
.SHORT TERM...Tonight through Tuesday...A weak line of showers is
moving east over the Willamette Valley as of 20Z. Accumulations have
been minimal with the northern Oregon coast and Coast Range recieving
less than 0.10 of an inch. Westerly flow coupled with low level
moisture will keep a slight chance for showers along the Coast and
Cascade Range this evening.
A weak upper ridge will push across the Pacific NW tonight into
tomorrow. This will making way for an upper level trough that will
increase low to mid level moisture across the region Monday and
Tuesday. This brings increasing chances for rain spreading into the
region late tonight from the west. As the upper trough moves in
Monday, models have consistently shown a cold front moving east
across the region during the daylight hours. Time-height cross
sections of relative humidity show relatively deep moisture
available with the front, so will continue to carry categorical pops
for most of the area Monday. Air behind the front not particularly
cold however, so snow levels expected to remain above Cascade passes
through the most widespread and heaviest precipitation. Quarter of an
inch accumulations looks likely for inland valleys, with heavier
amounts in the mountains and along the coast.
Behind the front late Monday into Tuesday, low levels expected to
remain moist. As the coolest air aloft moves across Monday night and
Tuesday, models indicate low level instability which will keep
showers going. Deeper instability immediately behind the front over
the southern half of the Willamette Valley and adjacent Cascades
around the time of peak heating will bring a slight chance of
thunderstorms Monday afternoon and evening. The moist onshore flow
over the next few days will generally keep daytime temperatures a
little cooler than normal.
.LONG TERM...Tuesday night through Saturday...No major changes to
previous discussion. A progressive pattern will continue through most
of the week. An upper ridge will bring a period of dry weather late
Tuesday through Wednesday for most of the region. Models remain
fairly consistent in bringing the next trough through during the last
half of the week, with a cold front arriving along the coast early
Thursday and making its way across the region by Thursday evening.
Chances for showers follow Friday into Saturday, but with models
favoring the core of the cool air aloft passing by to the north,
chances will be on the low side and tend to favor the northern part
of the forecast area.
&&
.AVIATION...MVFR conditions along the coast and VFR conditions
inland expected to persist through the next few hours. This
evening a disturbance is expected to bring showers along the
coast around 06Z to 08Z Monday, along with IFR/LIFR conditions.
These showers will also move inland bringing low end VFR/ high
end MVFR conditions to the Willamette Valley around 09Z to 11Z
Monday. Inland locations could see some periods of IFR but
confidence is low at this time. Expect MVFR conditions to become
widespread after 18Z Monday for all areas, which will likely
persist through 00Z Tuesday. There is also a slight chance of
thunder for the southern Willamette Valley and the southern
Oregon Cascades starting at 21Z Monday.
For detailed regional Pac NW aviation weather information, go
online to: https://weather.gov/zse
KPDX AND APPROACHES...Predominately VFR conditions through 09Z
Monday. After 09Z Monday expect showers and low end VFR/high end
MVFR conditions. These conditions are expected to persist
through 00Z Tuesday. /42
&&
.MARINE...Fairly benign marine conditions through early Thu. Wind
speeds generally 10 kt or less, but increase overnight into early
Mon morning. Models in good agreement showing the wind backing
to S to SW this evening ahead of the next frontal system. The 12Z
NAM, GFS and 4km WRF-GFS show a narrow band of 20-25 kt boundary
layer wind speeds Mon morning. However, the higher-resolution RAP
and HRRR show slightly lower wind speeds. Not expecting small craft
advisory wind with this system, but would not be surprised if there
were a few gusts to 25 kt. The 12Z HREF 10m ensemble mean wind
gust output indicates 25-30 kt gusts Mon morning. This lends
some concern regarding the need for an advisory. Will let the
next couple of shifts scrutinize a little more for possible small
craft advisory highlights.
Wind speeds decrease Mon afternoon. Models agree that a surface
trough will reside over the waters Mon night into Tue morning.
High pressure returns to the waters by 18Z Tue and holds through
Wed. Another frontal system is forecast to move through the
waters Thu. The ECMWF appears to be weaker with this system
compared to the GFS. However, the small craft advisory potential
for this system looks greater.
Wave heights generally 4-6 ft through early Thu. The latest wave
guidance indicates seas at or very close to 10 ft Thu and then
easing back into the 5-8 ft range late in the week and over the
weekend. Weishaar
&&
.PQR WATCHES/WARNINGS/ADVISORIES...
OR...None.
WA...None.
PZ...None.
&&
&&
.PQR WATCHES/WARNINGS/ADVISORIES...
OR...None.
WA...None.
PZ...None.
&&
&&
$$
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Area Forecast Discussion
National Weather Service Pueblo CO
309 PM MDT Sun May 23 2021
.SHORT TERM...(This evening through Monday)
Issued at 304 PM MDT Sun May 23 2021
...Convection continues this evening over the eastern plains...
...Some severe storms possible close to the Kansas border Monday
afternoon and evening...
.Tonight...low level jet develops this evening along the Kansas
border. HRRR suggests over 1000 J/kg of CAPE persists well into the
evening. Have kept scattered PoPs on the far eastern counties well
into the overnight period. HRRR and NAMNest keep echoes until around
08Z near the border. Otherwise, it will be a generally quiet night
over the forecast area. Temperatures will be cooler than normal over
the mountains with the cooler air aloft associated with the trough.
.Monday...Trough moves to the north of the region with dry
southwest flow aloft. Anticipate a dry and mild day over most of the
CWA. An approaching weak trough will turn winds southeasterly near
the Kansas border allowing for some low level moisture to advect
westward into the CWA. Current SPC day 2 has marginal risk over
eastern Colorado close to the Kansas border. Models suggest up to
1500 J/kg of CAPE in this region with bulk shears around 40 knots.
Current grids have silent PoPS over much of the plains given the
potential for low coverage of any convection.
--PGW--
.LONG TERM...(Monday night through Sunday)
Issued at 304 PM MDT Sun May 23 2021
...Pattern change with more westerly flow aloft...
...Suggestions for some storms late int he week into the weekend...
.Tuesday...Dry and mild westerly flow aloft continues over the
region with dry and warm weather expected. A weak front may move
into the eastern plains bringing a modest increase in low level
moisture. Models suggest some CAPE on the plains but it looks to be
capped with the warmer air aloft.
.Wednesday and Thursday...Next trough moves into the northern and
central Rockies on Wednesday staying mostly to our north on
Thursday. Currently looks like the best low level moisture will
stay to the north of the region. NBM grids are mostly dry these
two days. Will have to watch for critical fire weather conditions
mainly in the mountains and high valleys Wednesday with the
stronger southwest flow aloft.
.Friday into Sunday...Trough to the east of the region on Friday
will bring high pressure to the high plains with the potential for
upslope flow on Friday into Saturday. Another trough may reinforce
the upslope on Sunday. With the increase in low level moisture on
the plains, will have to watch for some severe weather. Currently
with a mean ridge loft, shears may be marginal. But, given it is
late May, it does not take much to produce some severe weather.
--PGW--
&&
.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
Issued at 304 PM MDT Sun May 23 2021
VFR all TAF sites. Gusty south to southwest winds continue through
mid evening at the TAF sites. Some gusty southwest winds will
develop at KALS during Monday afternoon. Low level moisture
remains to the east of the I 25 corridor with very low threat for
diurnal convection at KPUB and KCOS. --PGW--
&&
.PUB WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SHORT TERM...PGW
LONG TERM...PGW
AVIATION...PGW