Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 06/18/21
Area Forecast Discussion
National Weather Service La Crosse WI
656 PM CDT Thu Jun 17 2021
.SHORT TERM...(This evening through Friday)
Issued at 225 PM CDT Thu Jun 17 2021
The threat for impactful severe weather remains on tap for much
of the forecast area late this afternoon into the overnight hours.
As of 19Z, a poorly defined cold front stretched from Polk and
St. Croix counties southwestward through the southern Twin Cities
metro to south of Sioux Falls. Ahead of this baroclinic zone, a
narrow corridor of rich theta-e air exists with surface dewpoints
in the upper 60s to around 70 degrees and temperatures pushing 90+
degrees. Mid-level convection associated with the leading edge of
an upper level impulse/jet streak have been progressing into
central Minnesota and spreading cloud debris and high-based
thundershowers/virga eastward across the forecast area. There is
some uncertainty as to how this complex will affect the threat for
surface-based convection later this afternoon. However, given the
the bulk of the daytime heating haven taken place and continued
southwesterly low-level theta-e advection continuing through the
afternoon just ahead of the boundary, minimal modification of the
near-surface airmass is expected.
Impressive mid-level lapse rates coupled with the rich lower
tropospheric theta-e ribbon will yield 3000-4000 J/kg of MLCAPE at
peak heating just ahead of the boundary. Increasing H700-500 wind
speeds ahead of the approaching upper level jet will yield 30-50
kts of effective shear in the column, plus with shear vectors
oriented nearly orthogonal to the frontal slope, the initial
storms should have an appreciable off-boundary motion which would
promote discrete convection early on, but upscale growth into a
multi-cell or linear complex is expected as we head into the
evening hours.
The locations impacted by convection for this event is still a
bit nebulous given a number of factors, such as the strength of
the EML cap, the influence of the mid-level cloud shield, and the
displacement of the main jet max north of the surface front. While
earlier CAM runs were strongly suggesting that discrete cells
would form in the rich airmass of northern Iowa, there have been
signals in the HRRR that the focus for convection may actually be
in western Wisconsin and far southeast Minnesota, closer to the
upper jet. Nevertheless, forecast soundings in northern Iowa still
depict profiles with low inhibition by 00-02Z, so this area still
bears close watching given its explosive potential.
Very large hail will be a threat with any discrete cells early on
given the high NCAPE values, morphing into a damaging wind threat
as we head into the overnight hours. Localized flooding concerns
may exist with any periods of heavy rainfall or training storms
given the dry and somewhat impervious soils. The tornado potential
appears more conditional based on localized enhancements to the
near-surface wind field in far northeast Iowa and southwest
Wisconsin where winds may remain more backed to the south and SRH
values increase in the evening, but hodographs within the inflow
layer would support streamwise vorticity ingestion and possibly
torndogenesis.
The front sags southward through the overnight hours, taking the
convection southward with it. The threat for severe weather should
wane after 06Z and storms should exit the southern forecast area
by 12Z. With upper level forcing lifting out of the region, the
front should lay out and linger over central Iowa and Illinois
during the day on Friday, but any additional storms should stay
south of the area.
.LONG TERM...(Friday night through Thursday)
Issued at 225 PM CDT Thu Jun 17 2021
Look for mostly dry conditions into the weekend with increasing CAA
slowly but steadily driving temperatures downward. Highs by Saturday
fall into the upper 70s to low 80s with surface high pressure firmly
in control. The next upstream wave descends into the northern CONUS
on Sunday, lifting the near surface baroclinic zone back northward
and bringing with it the threat for rain/storms during the day. A
shot of colder Canadian air arrives for the first half of the week,
a welcome change from the record hot start we have had to the month
of June.
&&
.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 645 PM CDT Thu Jun 17 2021
Thunderstorms will continue to be in the vicinity of the
KRST/KLSE sites until the front moves through the area later
tonight; 04-06Z. Some of the storms may be strong to severe with
large hail and damaging winds. The storms are initially isolated,
but as the low level jet increases should consolidate and drop
southeast of the area. Due to the isolated nature will metwatch as
needed to include any of the higher end winds and mention of
hail.
&&
.ARX WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...None.
IA...None.
&&
$$
SHORT TERM...Skow
LONG TERM...Skow
AVIATION...Zapotocny
Area Forecast Discussion
National Weather Service Denver/Boulder CO
800 PM MDT Thu Jun 17 2021
.UPDATE...
Issued at 800 PM MDT Thu Jun 17 2021
High based showers and thunderstorms have progressed eastward
onto the eastern plains. Gusty winds have been the main feature
with this activity with gusts up to 50 mph. Doesn`t appear much
rain occurred. The showers and thunderstorms will come to an end
by midnight as the airmass stabilizes. Going forecast on track
with no major changes planned.
&&
.SHORT TERM...(This evening through Friday)
Issued at 300 PM MDT Thu Jun 17 2021
A strong ridge over the Four Corners region continues to maintain
its strength with record highs reported across much of the Desert
Southwest. Denver hit 100 degrees for the third day in a row.
Showers and storms have formed mainly over South Park and the
Palmer Divide while high level clouds are limiting storm
development farther north. Localized microbursts are possible
underneath the stronger storms as soundings show a well-mixed
boundary layer up above 500 mb. DCAPE is up to 1,700 j/kg which
would support winds up to 55 mph.
Some of these showers and storms will continue overnight tonight
across the eastern plains. The HRRR seems to be trying to resolve
a heat burst or two on a couple runs which is unique. The
conditions seem to be prime for heat burst development due to the
inverted-V soundings, very hot daytime temperatures, and very
high-based showers so it seems believable. Winds could reach 55
mph if a heat burst or dry microburst were to occur. Otherwise,
low temperatures will be near the warmest on record with lows in
the mid to upper 60s across the plains.
The aforementioned Four Corners ridge will weaken a bit on Friday
as there will be 500 mb height falls over our CWA. A weak cold
front will move across our forecast area tomorrow morning with
northeasterly winds bringing in better moisture and cooler
temperatures. The high tomorrow will be around 90 in Denver.
Models are struggling to come into agreement as to how far west
the moisture will get and whether or not it will mix out tomorrow.
The NAM and NAM Nest have the moisture getting farther west (up to
the foothills) than the HRRR and GFS (stays east of DIA) which
would mean higher instability values and a better likelihood of
storms over the foothills and I-25 corridor. I tend to think the
NAM solutions will be closer to verification so I increased the
PoPs across the foothills and I-25 corridor tomorrow afternoon.
There will be enough instability (around 1,000 j/kg of mixed layer
CAPE) for storms to become severe although the surface to 6km
wind shear will be lacking (around 30 knots). An isolated severe
storm or two is expected with hail and wind gusts being the
primary threats.
.LONG TERM...(Friday night through Thursday)
Issued at 300 PM MDT Thu Jun 17 2021
Closer to seasonal temperatures are expected through the early
part of next week. The center of the upper level ridge will remain
over central AZ through the weekend. On Saturday, a relatively
weak westerly flow aloft will be over northern CO, with a moist
southeasterly winds at the surface. Surface dewpoints 55-60F in
the morning mixes out in the afternoon, but sufficient moisture
over the far northeast plains, around 50F for one or two
marginally severe thunderstorms with GFS forecast soundings
indicating surface based CAPES over 1000 j/kg. Less subsidence in
the mid/upper levels with the ridge shifted over the Desert
Southwest. 500 mb heights still around 585 dm over northern CO
Saturday with the highs around 90F. Elsewhere, generally gusty
winds should be the main threat from the storms. On Sunday, the
flow aloft will increase over northern CO. The models show weak qg
ascent in the mid and upper levels ahead of a short wave trough
passing out of the northern Rockies and across WY. A cold front
associated with this system will push across the forecast area
Sunday morning, with gusty north to northwest winds in the morning
transitioning to northeast in the afternoon. The models indicate
the nose of a 100 kt jet max brushing the northern border around
00z Monday. This will certainly improve the storm motions of any
developing storms, but could also elevate the threat of severe
storms depending on the timing of the cold front. The ECMWF is
slower than the GFS with this next system. The bottom line,
Monday will significantly cooler and wetter from the Front Range
eastward across the northeast plains. The threat of flooding in
the burn areas will be elevated, but increased stability may
translate more to steady stratiform rain vs convective showers. By
the middle of next week, it`s back to the 90s with a broad ridge
&&
.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 800 PM MDT Thu Jun 17 2021
Southerly winds are expected to prevail the rest of the night.
Just a slight chance of an additional wind shift from the
convection off to the east. A cold front will move through Friday
morning bringing northeast winds behind it. There will be a chance
for showers and thunderstorms after 21Z Friday. Outflow winds
gusting to 40 knots will be the main threat.
&&
.FIRE WEATHER...
Issued at 300 PM MDT Thu Jun 17 2021
Most areas will see higher moisture levels on Friday meaning
relative humidity will only bottom out around 25 percent. This
will keep fire danger on the lower side. The exception will be
North Park and the surrounding terrain that will have less
moisture as relative humidity will drop to the low teens. There
will be elevated fire danger across that area as wind gusts will
reach 25 mph.
&&
.HYDROLOGY...
Issued at 300 PM MDT Thu Jun 17 2021
Moisture will increase on Friday behind a cold front that moves
through the area. Some storms are expected to form over the burn
areas which could pose a threat for flooding. This threat is
rather limited though as precipitable water values are on the
lower side.
A modest increase in thunderstorm activity is expected for
Saturday through Monday, and more moisture will be available as
well. Storms are expected to be moving, but there could be enough
rain with the strongest storms to cause minor flooding in the new
burn areas. This low risk of flooding will continue through
Monday, then drier conditions will reduce the risk after that.
&&
.BOU WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
UPDATE...Meier
SHORT TERM...Danielson
LONG TERM...Cooper
AVIATION...Meier
FIRE WEATHER...Danielson
HYDROLOGY...Cooper
Area Forecast Discussion
National Weather Service Des Moines IA
723 PM CDT Thu Jun 17 2021
.DISCUSSION.../Tonight through Thursday/
Issued at 401 PM CDT Thu Jun 17 2021
Tonight into Friday...Elevated convection across northern Iowa
looks to continue to push eastward and although not severe attm,
there is the potential for intensification as they trickle east.
Certainly the threat of hail and winds with the elevated nature of
these storms and not concerned with the tornadic activity due to
the LCLs of 2500-3000m. Cloud bases are AOA 10kft and convection
should continue to fester north of Highway 20. The 17.18z HRRR is
not handling the current convection attm, but the FV3 and NAM Nest
has some hint of the current radar trends. The cap seems to be
strong enough (700mb temps of 12-14C) to keep these storms below
severe attm, but the latest convection has helped break the cap as
well cap does weakening further east. Plenty of CAPE present,
surface and MLCAPE, and the effective shear continues to trend
upward and the DCAPE around 1400 J/kg per latest SPC Mesoanalysis.
Lacking significant deep moisture but certainly sufficient
moisture available and would not be surprised if a couple of
storms become severe around the Interstate 35 corridor north of
Highway 20. This is handled with the WW276 until 03z.
Next round looks to be late tonight into Friday morning along the
nose of the LLJ and surface boundary draped over southern MN into
northwest IA. The majority of the CAMs keep the convection east of
the forecast area, or delay the storms until past 12z Friday,
other than the latest NAM Nest. Seems more likely solution with
the LLJ increasing and the 850mb front sagging southward and
covering much of the central part of the forecast area. Deep layer
shear is sufficient to keep storms going, but the CAPE dwindles
through 12z Friday. Low confidence with severe threat but a few
storms should be around central Iowa by the morning commute.
Saturday through Monday...Surface high pressure builds into the
region Friday night into Saturday providing a cool and even less
humid airmass. Decent shortwave and surface low track across the
Central Plains into Corn Belt on Sunday. Confidence is increasing
with some convection over central to northern Iowa by Sunday
morning into the afternoon as models are in good agreement with
timing and location of system. Sharp cold front through the region
Sunday night providing a much needed cool down by Monday and
Tuesday. Cold night Monday night with lows into the 40s and 50s.
No significant system next week to help with drought conditions.
&&
.AVIATION.../For the 00Z TAFS through 00Z Friday evening/
Issued at 717 PM CDT Thu Jun 17 2021
Main concern initially will be convection at N IA terminals along
a boundary that sags south after 02z. Still some uncertainty at
the extent of the coverage, but for now confidence is highest at
KMCW and KALO, so kept TEMPO going there. Confidence is less at
KFOD, so VCTS will suffice. Going to take storms longer to sag
south along the boundary, so have added VCTS to KDSM and KOTM
after 12z to reflect this possibility. Another round of storms a
good bet across southern Iowa just beyond this TAF cycle, mainly
impacting KOTM.
&&
.DMX WATCHES/WARNINGS/ADVISORIES...
Heat Advisory until 8 PM CDT this evening for IAZ023-024-033>036-
044>050-057>062-070>075-081>086-092>097.
&&
$$
DISCUSSION...Podrazik
AVIATION...Hahn
Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
1154 PM EDT Thu Jun 17 2021
.AVIATION...
Convection west of the region late this evening will work east,
southeast into the area overnight into early Friday morning as
strong elevated warm air advection regime spreads into the lower
Great Lakes. A wedge of relatively unstable air will precede this
convection so will maintain tsras in the forecast with a TEMPO
around dawn. Activity later in the forecast in advance of a cold
front is in question given the expected influence of this early day
convective system. Given 00z HiRes model trends, it appears there
will be a window for activity to fire before shift southeast so will
include another PROB30 group for the I-94 terminals. Main period of
showers with embedded thunder will be from 08z-09z through 13z-14z
with the next round of scattered convection somewhere in the 18z-22z
time frame. Southwest winds will persist through the forecast,
veering to a more west direction late Friday with the cold front.
For DTW...00z guidance still suggests showers with some embedded
thunder seem likely in the 10z-14z time frame. This activity is
already underway over the upper midwest and expect convection to
track into the area late tonight within zone of warm air advection.
Will include PROB30 group for additional convection in the mid
afternoon, but confidence in this period is much lower.
.DTW THRESHOLD PROBABILITIES...
* Low to medium in thunderstorms with cigs aob 5000 feet impacting
the terminal early Friday morning. Low Friday afternoon as new
development may fire near/south of the terminal.
&&
.PREV DISCUSSION...
Issued at 356 PM EDT Thu Jun 17 2021
DISCUSSION...
A dry and warm is in place this afternoon under a deamplifying ridge
that will be suppressed further east through remainder of the day.
Temperatures of around 16-17C at 850 mb are contributing to the
afternoon temperatures that have climbed into the 80s for most of
southeast Michigan. Dry weather conditions with the elevated fire
danger continue through this evening before an abrupt change arrives
tonight.
Flow tonight becomes more zonal in the mid and upper levels after
the ridge is flattened with the help of a shortwave moving into the
Hudson Bay. This will usher in an impressive theta-e plume to our
west into Lower Michigan tonight through early tomorrow morning with
the dry air being replaced by PWATs greater than 1.50 inches. An MCS
is expected develop within this theta-e plume and track through
Wisconsin/far northern IL tonight. The leading edge of this MCS
should arrive to west/southwest portions of southeast Michigan after
midnight tonight with bulk of rainfall occuring between 07-15Z. The
12Z suite of models still leaves a bit of uncertainty in regards to
how far north convection will be as MCS moves E-SE into southeast
Michigan, the HRRR being the more aggressive with the further north
solution. The other scenario and slightly better consensus is for
the bulk of better convection to move across west/southwest portions
of the CWA. It does appear that the intensity of this activity will
be weakening as it outruns the corridor of greater instability.
Though, MUCAPEs of a few hundred j/kg with enough shear, jet
support, and 6-7 C/km mid level lapse rates will sustain convection
with embedded thunderstorms as it rolls through. Gusty winds will be
possible as low level winds increase to 30-35 knots. Rainfall
amounts with this system also dependent on MCS track. QPF amounts
across the majority of the CWA should be well below a half inch.
Though, amounts may need to be adjusted upward if northerly track
looks like it will play out as advertised by the Euro and HRRR.
The track and speed of the MCS tonight remains important for how
things play out Friday. The best forcing appears likely to be south
of Michigan associated with the modified convective boundary across
Indiana and Ohio. Greater forcing from the north with the Ontario
shortwave is also lagging in arrival ahead of a frontal boundary.
The other limiting factor to severe weather development is presence
of a capping inversion up to around 800 mb. This would effectively
suppress deep convection given the weaker forcing if it holds through
much of the day. There will be plenty of shear present with 40+
knots from 0-6 km with lapse rates again slightly greater 6 C/km.
MLCAPE values during the afternoon build up to at least 1500-2000
J/kg with up to around 3000 J/kg near the border. Thus, the set up
for tomorrow will be conditional for severe weather. The question is
if there will be enough forcing to take advantage of the favorable
environment or if the cap can erode enough for weak shortwaves to
generate convection. Several Hi-res models for Friday afternoon are
showing limited convection in our area. At the moment, the best
forcing looks to our south and north. Be sure to stay up to date
with the forecast as adjustments are still likely for tomorrow
afternoon and evening.
A trailing weak shortwave swings across the state on Saturday atop a
stationary boundary while the larger shortwave trough moves from
Ontario into Quebec. Expecting most areas to stay dry, but there
remains at least a low chance for some weak convection. The overall
airmass remains warm over the weekend with some lingering moisture.
High temperatures over the weekend are forecast to stay in the 80s.
The next appreciable chance for showers and thunderstorms may come
Sunday night/Monday ahead of cold front tracking through the region
while troughing deepens across the central CONUS.
MARINE...
South/southwesterly flow continues to increase through the evening,
with gusts topping out around 20 kts across northern Lake Huron, as
a tightened pressure gradient migrates southeast through the Great
Lakes ahead of approaching sfc trough. More widespread gusts of 20+
kts expected tomorrow in response to enhanced flow aloft and cold
frontal passage. Given uncertainty in timing/stability over the
lakes and marginal gust potential, will continue to monitor advisory
potential for the next forecast update. Approaching weather system
to also produce two rounds of shower/thunderstorm activity: tomorrow
morning and again in the afternoon/evening with main hazards being
lightning, brief periods of gusty winds/enhanced waves, and heavy
downpours. Winds behind the cold front shift northwest late Friday-
Saturday, with dry conditions expected to prevail for the weekend as
high pressure returns.
HYDROLOGY...
An area of showers and thunderstorms will be moving across
central/lower Michigan late tonight through early Friday morning. A
high degree of moisture with PWATs greater than 1.50 inches will
accompany this system. This will bring potential for some locally
heavy rainfall with any embedded stronger thunderstorms. There is
still some uncertainty in the track of this system and where heaviest
rainfall occurs. Basin average rainfall amounts will range generally
around a quarter inch with higher amounts towards Lenawee County. If
track of MCS is further north, amounts will need to be increased
slightly up towards the I-69 corridor. No significant flooding
concerns anticipated, but any localized higher amounts associated
with embedded with thunderstorms may lead to some minor flooding of
low lying and urban areas.
&&
.DTX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
Lake Huron...Small Craft Advisory from 4 AM to 4 PM EDT Friday for LHZ421-422-
441>443.
Lake St Clair...NONE.
Michigan waters of Lake Erie...NONE.
&&
$$
AVIATION.....DG
DISCUSSION...AA
MARINE.......MV
HYDROLOGY....AA
You can obtain your latest National Weather Service forecasts online
at www.weather.gov/detroit.
AREA FORECAST DISCUSSION
National Weather Service Wilmington OH
1155 PM EDT Thu Jun 17 2021
.SYNOPSIS...
A decaying system will be approaching late in the overnight and
into the early morning hours on Friday. Severe thunderstorms
will develop during the late afternoon and into the evening
hours on Friday. Heavy rainfall will also be possible.
Thunderstorm activity and the potential for severe weather will
again be possible on Saturday as the boundary remains in place
across the region.
&&
.NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
Some storms firing in west central IN/east central IL ahead of
the line of decaying showers over nrn IL/srn LMich. Took this
and a few very minor returns over nw IN and blended them into
the 12z forecast to account for movement, but no models were
showing any kind of initiation in this section at all tonight,
so this appears to be a wildcard in play that will likely affect
the forecast updates tonight, especially if the CAMs take a
while to see this and adjust.
Low temperatures overnight are expected to drop down into the
middle 50s to the middle 60s.
&&
.SHORT TERM /6 AM FRIDAY MORNING THROUGH FRIDAY NIGHT/...
An active weather pattern will be in place for Friday into
Friday night. A decaying MCS will continue to move into northern
portions of the region during the morning hours. There are some
model solutions that bring this feature further south and this
would have implications for afternoon placement of convective
development. At this point in time have a slight chance to
chance of precipitation for locations generally north of the
Ohio River with likely precipitation generally north of
Interstate 70. This feature will then likely lay out a boundary
for convective development during the late afternoon and into
the evening hours. Winds will pick up for the afternoon hours
and have wind gusts upwards of around 25 to 30 mph outside of
thunderstorms.
There are some concerning signals for a higher end damaging wind
event late Friday afternoon into Friday night. CIPS analogs
also are supportive of this and SPC has a large portion of the
region in an enhanced risk. Given shear profiles there is also
at least some tornadic and hail potential as well. Added severe
wording into the forecast
Friday night the flow becomes more west-east oriented. With this
flow orientation there will be flooding concerns as well. A
flood watch will be needed in the future, however held off for
now to try to fine tune where the axis of heaviest rainfall will
be.
&&
.LONG TERM /SATURDAY THROUGH THURSDAY/...
Long term period begins with potential storm complex in the
south as the upper energy heads east along a mostly stationary
front. Guidance varies as to how long the convection persists,
with the 3-km NAM on the drier side and the HRRR keeping
convection going until it exits into southeast Ohio late
Saturday morning.
While warm muggy conditions continue Saturday into Sunday, forcing
looks to be rather weak as the frontal boundary dissipates. Expect
PoPs to decrease considerably during this time with isolated diurnal
convection remaining in the grids due to conditional instability.
High temperatures will peak in the mid to upper 80s each day, with
lows in the upper 60s.
For Monday, a stronger, more progressive cold front dives southeast
through the region. Uncertainty is high as far as timing the front.
ECMWF and its ensemble are slower, with FROPA occurring Tuesday
morning, and the GFS system quicker with FROPA on Monday evening.
Uncertainty is amplified by the slow progression of tropical
remnants moving through the southeast United States Sunday into
Monday. Despite uncertainty, there is certainly some concern about
strong to severe storms firing along and ahead of the front
beginning Monday afternoon into the evening.
Behind the front, decreasing clouds and cooler, drier air arrives
with surface high pressure starting to build in after noon on
Tuesday. In fact, model blend has dewpoints dropping into the upper
40s to lower 50s Tuesday night and Wednesday. Highs stay in the low
to mid 70s.
The high shifts to the east on Thursday with max temperatures
returning to near 80.
&&
.AVIATION /04Z FRIDAY THROUGH TUESDAY/...
Southerly winds will be 5-8kt this overnight period with the
exception of Lunken which may see some few vsby restrictions
towards daybreak and will decouple and go calm in the next 2-3
hours.
Tomorrow will see this south-southwest wind increase to 12-15kt
in the morning and begin gusting to 25kt or so by noon, becoming
a little stronger in the late day. Guidance on timing of rain
still runs a wide variety of spectrums in how they play out
tomorrow`s forecast. Near as I am able to discern, activity will
be north of the TAF sites through 18z but there are indications
that an outflow boundary from upstream storms may cross the
northern sections of the CWA and could be enough to initiate
some few showers ahead of the main body of storms that are still
expected to remain to the north of the CWA and TAF sites through
this time.
After 18z, storms will likely be knocking on the door to west
central Ohio and could skirt KDAY. Did not add vcsh during this
time until 20z at CMH, but do have VCTS at DAY/CMH/LCK starting
at 22z, and at 05z for the extended CVG TAF.
Mechanisms are in place to see significant storms in the evening
and overnight Friday along the I-70 corridor and then dropping
southward.
Kept VFR conditions over the TAF sites with the exception of the
last 2 hours in the CMH forecast. Hopefully the model depictions
will begin to coalesce into one or two better probability
scenarios tonight that may present more of an opportunity to
include a better timing and stronger sense of area affected, at
least to begin the showers and storms.
While chances of rain at ILN and southward aren`t high enough to
include for tomorrow afternoon, they aren`t low enough to
discount the possibility entirely. Evolving forecast will
continue to hone in on what is the most likely tomorrow as time
progresses.
.OUTLOOK...Thunderstorms are possible through Saturday and again
on Monday.
&&
.ILN WATCHES/WARNINGS/ADVISORIES...
OH...None.
KY...None.
IN...None.
&&
$$
SYNOPSIS...Novak
NEAR TERM...Franks
SHORT TERM...Novak
LONG TERM...Hogue
AVIATION...Franks
Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
319 PM CDT Thu Jun 17 2021
.SHORT TERM...(This evening through Friday night)
Issued at 317 PM CDT Thu Jun 17 2021
Weak showers with very isolated thunder have been making attempts at
getting some precipitation to the ground, but we have been pretty
strongly capped, and they are encountering drier air as they move
east. A weak cold front is passing through the Twin Cities as I
write, but the main change with the FROPA is a shift in the winds to
the northwest. The front will continue to slowly move to the
southeast through the afternoon and evening. A surge of instability
will move northeastward this afternoon into southern Minnesota as
the front moves into these areas. The front should erode the CIN
along the front late this afternoon and with bulk shear values 40-50
kts and steep lapse rates there could be explosive convective
growth, but the HRRR keeps pushing back the storm initiation and it
looks like the best chance for strong to severe storms will be on
the periphery of our forecast area along I-90 and southern portions
of west central Wisconsin. The SPC day 1 outlook has southeast
Minnesota in an enhanced risk for severe storms with Slights and
Marginals extending north of there, with the marginal risk just
south of the Twin Cities Metro area. The main threats are large hail
and damaging winds, but a tornado can not be ruled out. Any storms
that do develop in our area should move southeast quickly. There
won`t be much change in temperature with the this FROPA until later
tomorrow when a stronger front comes through the area. Brisk
northwest winds will gust to 25-30 MPH behind the front before
relaxing overnight. These gusty winds and RH values falling into the
teens and 20s will lead to critical fire weather conditions which
may require a headline. Behind this secondary front, temperatures
tomorrow night will be very comfortable for sleeping with low
temperatures falling into the 50s with the CAA.
.LONG TERM...(Saturday through Thursday)
Issued at 317 PM CDT Thu Jun 17 2021
Saturday should be a very nice day as the forecast has highs in the
upper 70s to mid 80s, clear skies, and light westerly winds. Low
relative humidities signal that elevated fire weather conditions
will be possible, especially in western MN where RHs of 20-25% are
forecast. Precipitation chances begin late Saturday night as an
amplifying upper-level trough approaches from the west. Showers and
thunderstorms will develop across western MN early Sunday morning
along a warm front. This activity will spread and travel eastward
during Sunday as the open wave system matures. Redevelopment of
showers and thunderstorms is possible Sunday afternoon and evening
in eastern MN/western WI ahead of the approaching cold front.
However, warm sector recovery is highly uncertain at this time due
to the likelihood of convective debris over the region.
Additionally, differences between models exist in how much the
trough amplifies while crossing the Northern Plains: the NAM and GFS
showing a much more amplified, narrower trough while the ECMWF and
GEM`s troughs are broader and flatter. Thus, the timing and amount
of synoptic-scale forcing is also rather uncertain with the American
model suite being the most aggresive. Thus, while there is a chance
for some stronger thunderstorms later Sunday, too much uncertainty
remains to dig into the finer details.
A cool down is forecast Monday into Tuesday as northwesterly flow
moves over the Northern Plains proceeding the trough. Have adjusted
both Monday and Tuesday`s highs downward as guidance has trended
much cooler than the NBM over the last several runs. Also, the very
warm temperatures as of late means that the NBM is likely biased too
warm for this brief cool spell. NBM`s temperatures for early next
week have been slowly decreasing with time but have opted to "cut to
the chase" and not wait for the likely inevitable. Currently have
highs in the low to mid 60s on Monday while Tuesday is in the upper
60s to lower 70s. Also, Monday night`s lows could be quite chilly
with our northern counties dropping to near 40.
Otherwise, the workweek next week looks mostly dry as slight ridging
tries to work its way into the central CONUS. Temperatures are
forecast to moderate back into at least the 80s by Thursday.
&&
.AVIATION...(For the 12Z TAFS through 12Z Friday morning)
Issued at 540 AM CDT Thu Jun 17 2021
Thunderstorm development will be possible this afternoon and evening
at southern/eastern sites as a cold front sags southeast across the
area. Otherwise, VFR conditions will prevail with scattered to broken
mid and high clouds.
KMSP...Thunderstorms will quite possibly develop south and east of
KMSP, but there was still enough concern to warrant a Prob30 group
for this afternoon.
/OUTLOOK FOR KMSP/
Fri...VFR. Wind WNW 15-20G30 kts.
Sat...VFR. Wind NW 5 kts.
Sun...VFR, chc MVFR. -TSRA likely. Wind SE becoming NW 10-15G25 kts.
&&
.MPX WATCHES/WARNINGS/ADVISORIES...
MN...None.
WI...None.
&&
$$
SHORT TERM...CEO
LONG TERM...CTG
AVIATION...LS
Area Forecast Discussion
National Weather Service Paducah KY
603 PM CDT Thu Jun 17 2021
.SHORT TERM...(Tonight through Saturday night)
Issued at 233 PM CDT Thu Jun 17 2021
The latest HRRR is dry for the rest of the afternoon and evening
out in southeast Missouri. After our rogue strong storm over in
Carter and Ripley counties this morning, satellite shows a
scarcity of cumulus over there with an obvious convergence zone
west of our area. Will keep a very small PoP over there just in
case more rogueness develops.
Upper-level energy will spread east southeast into the Great Lakes
tonight into Friday, and that will suppress the upper ridge over
the Quad State. With the associated surface boundary remaining
well to our north Friday, we will be heading for a bad hair day
over most of the region. Temperatures will climb into the mid and
upper 90s with the warmest air expected in the northwest. Humidity
will also be on the increase with the highest dewpoints (low-mid
70s) also in the northwest. This will lead to heat indices
reaching 100 by 11 AM and maxing out at 105-109 over at least the
northern two rows of counties in southern Illinois as well as
Perry county Missouri eastward to Williamson County Illinois. Will
be issuing a Heat Advisory for those areas with this forecast.
The Advisory may need to be expanded into southwest Indiana, but
will let the midshift take another look at that.
In addition to the heat advisory, we will be right near Lake Wind
Advisory criteria across the northern half of the area. Will give
the winds a mention in the HWO, but will hold off on an Advisory
at this time.
The 12Z HREF keeps convection Friday night to our north, with the
exception of the ARW which does bring some convection into
southwest Indiana overnight. Will have a swath of 20-30% PoPs
along the I-64 corridor mainly overnight just in case. Certainly
could not rule out some strong winds with any storms that do reach
the area.
By Saturday, the active surface boundary may be close enough to
our area to allow renewed convection to make it into southern
Illinois and the Tri State. As a result will have 50% PoPs in the
far northeast and bring slight chances all the way south to KCGI
and KPAH in the afternoon and evening. Temperatures will not be
quite as warm as Friday and it appears that the moisture will mix
out a bit more as well, but 2000-2500 J/kg of surface-based CAPE
will be possible. Expect a few strong updrafts, but mostly a pulsy
mode. Cannot rule out some isolated damaging winds, but lightning
and locally heavy rainfall should be the primary concerns.
Saturday night will be mostly dry as our attention turns back to
the south with the tropics on our minds.
.LONG TERM...(Sunday through Thursday)
Issued at 233 PM CDT Thu Jun 17 2021
The developing tropical system in the Gulf will be the main weather
influence Sunday. Pre-genesis tropical cyclones are notoriously
difficult to model and there is quite a bit of spread amongst the
operational and ensemble guidance in the placement of this system.
On Sunday morning guidance varies in placement from central MS to
central GA. The same idea applies to our weather as the previous
packages with a more westward final solution being rainier and a
more eastward destination drier. For now, continued mainly afternoon
slight chance/chance shower and thunderstorm pops in line with NBM
but uncertainty remains high.
Monday still appears to be the best chance for rain as an upper
trough pushes a fairly strong cold front into the area. GFS/GEFS
seems more amplified and progressive with the trough and faster with
the front, while the ECMWF is a bit slower. Kept likely
shower/thunderstorm chances for the day Monday and into Monday night
and kept a lingering chance for showers/rain Tuesday morning in the
east owing to the slower ECMWF solution. The synoptic pattern will
be at least somewhat favorable for a strong to severe storm or two
but the finer details of this threat or lackthereof will likely
become clearer in the coming days. Locally heavy rainfall also
appears possible although net QPF appears to be trending downward as
column moisture decreases a bit from past guidance.
Behind the front on Tuesday looks pretty spectacular, with highs in
the upper 70s and lows in the mid 50s amid mostly sunny skies.
Wednesday will likely be warmer and slightly more humid as ridging
slides eastward. Introduced shower/thunder chances again on Thursday
as low level winds increase from the south ahead of the next upper
disturbance moving through the plains.
&&
.AVIATION...
Issued at 603 PM CDT Thu Jun 17 2021
VFR conditions, with generally unrestricted ceilings and
visibilities should dominate the WFO PAH TAF locations for the 00z
Friday forecast. Cannot rule out some scattered to locally broken mid-
level clouds developing between 11z-15z Friday over the
KPAH/KEVV/KOWB TAF sites, as moisture near 10kft agl is lifted
along the mid-upper level shear axis of an west to east oriented
ridge. This ridge becomes more suppressed further south across the
WFO PAH TAF sites during the late morning and early afternoon on
Friday, in advance of a shortwave moving east across the area.
At this point in time, have low confidence in seeing anything
other than VFR conditions through the forecast period.
&&
.PAH WATCHES/WARNINGS/ADVISORIES...
IL...Heat Advisory from 1 PM to 7 PM CDT Friday for ILZ075>078-
080>085.
MO...Heat Advisory from 1 PM to 7 PM CDT Friday for MOZ076.
IN...None.
KY...None.
&&
$$
SHORT TERM...DRS
LONG TERM...99
AVIATION...Smith
Area Forecast Discussion
National Weather Service Tampa Bay Ruskin FL
729 PM EDT Thu Jun 17 2021
.AVIATION...
Prevailing VFR conditions will return after RA and low clouds
move away from TPA/PIE terminals over the next couple of hours.
Southeast winds by late morning, shifting onshore at coastal TAF
sites courtesy of the west coast sea breeze. VCTS introduced by
17Z-20Z tomorrow afternoon.
&&
.Prev Discussion... /issued 624 PM EDT Thu Jun 17 2021/
UPDATE...
Showers with the occasional embedded thunderstorm continues to
gradually push northward this evening with the bulk of rainfall
now north of Tampa - across Tarpon Springs and Brooksville. This
convective activity is propagating along an outflow boundary
being driven north with the help of low-level southerly flow
around 10 knots. RAP analyses suggests MLCAPE of 800-1200 J/kg
along and north of I-4 will support the reformation of
showers (and perhaps a thunderstorm) as we head through the
remainder of the evening hours. Farther south, light stratiform
rain remains over Lee county and is slowly dissipating across the
area. This evening`s updates consist of PoP adjustments through
the next 9 or so hours to account for latest radar trend and
mesoanalysis... The remainder of the forecast remains on track.
In other news, NHC has began issuing advisories on Potential
Tropical Cyclone 3 in the SW Gulf of Mexico this afternoon. This
disturbance is expected to become a Depression or Storm as it
moves towards the LA coast during the next couple of days. No
direct impacts are anticipated across West Central and Southwest
FL.
&&
.Preliminary Point Temps/PoPs...
TPA 75 90 76 90 / 20 40 10 30
FMY 74 91 74 93 / 30 40 0 30
GIF 73 90 73 93 / 30 40 10 40
SRQ 74 89 74 92 / 10 40 10 20
BKV 70 90 72 92 / 40 40 10 40
SPG 77 89 77 90 / 20 40 10 30
&&
.TBW WATCHES/WARNINGS/ADVISORIES...
FL...None.
Gulf waters...None.
&&
$$
Update/Aviation...Norman
Decision Support/Upper Air...Oglesby
Area Forecast Discussion
National Weather Service Las Vegas NV
146 PM PDT Thu Jun 17 2021
.SYNOPSIS...
Dangerous heat will continue through the weekend as temperatures
continue to approach record values. Early next week temperatures
will begin to decrease but are still expected to remain above
normal. Isolated thunderstorms producing dry lightning and strong
winds will be possible on Friday.
&&
.SHORT TERM...Today through Saturday.
The heat wave continues with another few days of well above
normal temperatures challenging records in many areas through
early next week. A cloud shield this morning helped insulate us
overnight with a morning low at McCarran of 90 degrees. This may
limit us from approaching all-time record highs as we have the
past couple of days. With this being said, it will still be very
hot with triple digit temperatures in many locations. No changes
are needed to the Excessive Heat products which now go through
Sunday.
The clouds will lead us to the other weather topic for today and
tomorrow which is the potential for high based showers and storms
with an influx of mid-level moisture. Currently, there are light
radar returns over much of the area as a weak wave rotates around
the the high which is still centered to the east over the Four
Corners region. Today instability is pretty much limited to Inyo
County and the Sierra but a few moderate updrafts are being
indicated over southern Clark County and central Mohave County
later on today on the last few HRRR runs. Showers and any isolated
storms will be very capable of producing strong outflow winds.
Even light activity this morning has already seen a measured gust
of 50 mph out of a weak shower over Kingman. This is further
supported by DCAPE values of 1000-2000 J/kg and very dry low
levels indicated on this mornings sounding. Activity should
decrease this evening with potential for pre-sunrise showers over
southeast California and Esmeralda and Nye counties. Instability
will be more widespread on Friday across much of southern Nevada
and northeast Arizona which will support potential for convective
development Friday afternoon. Threats remain similar to today in
dry lightning, strong outflow winds, and lofted dust.
By Saturday, the ridge shifts southwestward cutting off our
southeast flow which will limit chances for any shower or storm
activity but continue the very hot temperatures across the
region.
.LONG TERM...Sunday through Wednesday.
Sunday`s high temperatures are expected to be a few degrees below
highs on Saturday which should bring an end to record challenges for
the time being. With that said, Sunday morning low temperatures will
still be very warm and provide little relief while the slightly
cooler daytime temperatures on Sunday will remain around 10 degrees
above normal. Since heat risk changes little Sunday and will remain
quite elevated, went ahead and extended all heat products through
Sunday evening.
A cooling trend brings more tolerable temperatures to the area Monday
through Wednesday even though summer officially begins on Monday.
Any moisture that was lingering around the area to begin the
weekend is flushed out Sunday with very dry conditions forecast
through Wednesday. Looking further out, the Climate Prediction
Center forecasts the probability of seeing above normal
temperatures across the NWS Las Vegas CWA in the 8-14 day period
at 40-60 percent.
&&
.FIRE WEATHER...
Heat wave continues through early next week with the addition of
isolated, dry thunderstorms today and tomorrow. These storms will
also be capable of producing strong, erratic wind gusts in and
around the area up to near 50 mph. The higher terrain will see
more favorable chances for this activity both days with Friday
being a slightly more active day than today. As a result, went
ahead and upgraded the Fire Weather Watch to a Red Flag Warning
with the addition of Fire Weather Zone 227 in eastern Inyo County.
RH values will drop below critical values each afternoon through
early next week.
&&
.CLIMATE...Listed below are a few climate locations showing both the
record high maximum and high minimum temperature for each location and
the year the record was last set for this Wednesday, Thursday and Friday.
LOCATION THU-JUNE 17 FRI-JUNE 18SAT-JUNE 19
(HIGH MAX) Record(year) Record(year)Record(year)
Las Vegas NV 113(1940) 115(1940) 114(1940)
Bishop CA 104(2017) 107(1985) 107(2015)
Barstow CA 110(2017) 112(1985) 115(2017)
Needles CA 120(1917) 119(2017) 123(2017)
Kingman AZ 108(1917) 109(2017) 111(2017)
Desert Rock NV 106(2017) 108(2017) 110(2017)
Death Valley CA 122(1917) 124(2017) 125(2017)
Laughlin NV* 113(2017) 117(2015) 117(2017)
Lake Havasu City AZ* 115(1985) 115(1985) 117(2017)
* Not climate sites, but state temperature record holders.
LOCATION THU-JUNE 17 FRI-JUNE 18SAT-JUNE 19
(HIGH MIN) Record(year) Record(year)Record(year)
Las Vegas NV 87(2008) 86(2017) 88(2017)
Bishop CA 65(2002) 69(2017) 67(2017)
Barstow CA 78(1971) 79(1971) 79(2017)
Needles CA 88(2000) 90(1988) 87(2017)
Kingman AZ 79(1949) 73(2000) 75(1945)
&&
.AVIATION...For McCarran...Persistence wind forecast for the rest of
this afternoon so sticking with an easterly component up to 10 kts.
However, any passing area of virga could bring a sudden shift and
gustiness to the wind. Confidence in any of those scenarios is low
so did not mention in the forecast. Typical down valley wind up to 8
kts will develop overnight, although there is some indication that a
more northwesterly wind may develop after midnight. Looking at an
easterly wind up to 10 kts developing again Friday. Any isolated
shower or thunderstorm over the higher terrain Friday could bring
higher gusts to the valley. No significant clouds expected below 12
kft. Temperatures will remain in the 113 to 115 range over the next
few days with temperatures exceeding 100 by 11 AM.
For the rest of southern Nevada, northwest Arizona and southeast
California...Outside of any convective influence wind at terminal
sites the rest of this afternoon should be light and variable. Any
nearby shower or thunderstorm could bring on a sudden shift and
gustiness. Look for typical downvalley winds to develop overnight
with speeds less than 10 kts. The exception will be around KDAG
where sustained speeds will be 10-15 kts. Typical afternoon winds
expected across the region Friday, but any isolated shower or
thunderstorm over the higher terrain Friday could bring higher gusts
to a terminal. No significant clouds expected below 12 kft.
&&
.SPOTTER INFORMATION STATEMENT...Spotters are encouraged to report
any significant weather or impacts according to standard operating
procedures.
&&
$$
SHORT TERM/FIRE WEATHER...Guillet
LONG TERM...Salmen
AVIATION...Pierce
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