Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 06/22/20
Area Forecast Discussion
National Weather Service La Crosse WI
651 PM CDT Sun Jun 21 2020
.SHORT TERM...(This evening through Monday)
Issued at 305 PM CDT Sun Jun 21 2020
Atmosphere is primed and ready to go for isolated to scattered
convection this afternoon as temperatures climb through the low to
mid 80s across much of the area. Ongoing weak moisture transport
continues to nudge dewpoints upward through the 60s, promoting
MLCAPEs of 1000-2000 J/kg. Only limiting factor for more widespread
convection thus far has been a lack of robust forcing. A decaying
MCV passing through central IA did manage to trigger a few brief
vigorous updrafts just south of our area. Otherwise there is a very
weak H5 ripple that appears to be the mechanism responsible for some
scattered pulse convection across far northeast Iowa into far
southwest Wisconsin. Updraft development has been quick and robust,
but in the absence of any substantial deep layer shear they have
been unable to sustain themselves for long. Stronger cells this
afternoon will be capable of producing small hail and gusty winds
(perhaps marginally severe with a storm or two) as well as localized
downpours. In this weakly forced environment, CAMs are having a hard
time pinning down this pulse convection, but would expect it to
remain focused mainly near and west of the Mississippi River where
low level lapse rates are steepest. Seeing some agitated cu fields
across portion of southeast MN and west-central WI.
Main focus for stronger storms will be this evening as a stronger
mid-level shortwave rolls into the area ahead of a cold front. Low
level convergence associated with these features is already
promoting development of a linear complex of storms from southwest
MN into northwest WI. Juicy summerlike airmass out ahead of this
line will fuel the storms as they slowly approach our area towards
evening. CAMs show some general agreement with timing and evolution,
but there`s still enough spread to muddy the waters. Latest HRRR
might be lagging a bit behind current convective development, but it
pinpoints the line of storms entering our CWA from the northwest
around 7 PM with gradual eastward progression across the rest of the
area through roughly 1 AM. CAMs continue to favor a stronger
southern tail to this line of convection that is progged to dive
just to our south where nose of low level moisture transport will be
focused over central/southern IA. So the question is how the
northern portion of this convective line will evolve as it crosses
our CWA, where forcing and instability aren`t as favorable. Most
CAMs show a break/gap in the line as it crosses our area. The line
of convection will be arriving as instability is diminishing across
our area, so our far western counties (grazed by SPC`s slight risk)
will see the greatest chance of any strong to severe activity.
Soundings would support some gusty winds and perhaps isolated
marginally severe hail. But again, deep layer shear will be meager
so not expecting long-lived, sustained stronger storms. Localized
heavy rainfall certainly a possibility with this tropical-like humid
environment: PWATs >1.5", deepening warm cloud depths, and slow-
moving storm progression. Northeast IA into far southwest WI will be
the area of greatest concern, especially if southern flank of storms
would begin to repeat along the outflow. Earlier HRRR runs suggested
this possibility but now look a little more progressive. Something
to watch, though. HREF mean QPF suggests 0.5 to 1.5" with max QPF
on the order of locally 2 to 3+".
Moisture transport will nose into our southeast late tonight, which
may steer the weakening southern tail of convection into our
south/east counties. While storm activity will be diminishing, there
will likely be a more stratiform band of lingering rain continuing
to progress through our east into Monday morning ahead of the
approaching cold front. That front will drop in from the northwest
just after daybreak and may trigger some additional isolated
activity mainly across our southeast once it recovers from lingering
morning showers. Less instability in place than today, but steep
low level lapse rates may support a stronger storm or two.
.LONG TERM...(Monday night through Sunday)
Issued at 305 PM CDT Sun Jun 21 2020
Northwest flow aloft will dominate through mid-week as an amplified
upper trough spins across the Great Lakes region. Despite a
relatively dry, seasonable airmass, surface heating beneath cold mid-
level temps will likely generate some scattered mainly diurnal
showers/storms as weak upper waves rotate through the flow. By late
in the week, the upper trough gets kicked east with the flow
becoming more zonal. There is broad model agreement for a shortwave
trough to slide through on Friday with a chance for storms as low-
level moisture/instability increase. For next weekend, expect warmer
highs in the 80s. With the progressive zonal flow pattern, some
potential for periodic storms continues depending on timing of low
predictability shortwave troughs.
.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
Issued at 651 PM CDT Sun Jun 21 2020
Broken line of storms moving into RST at this hour and will make
it into LSE around 02Z. These storms have largely been sub-severe
but there will be an brief period of gusty winds out of the west
to northwest as the storms blow through. Upstream obs have
generally remained VFR despite the downpours, but cannot rule out
a dip to MVFR or perhaps briefly IFR. Otherwise these storms have
produced a decent amount of lightning and isolated small hail.
Once they blow through there will be some lingering showers.
Later tonight and perhaps into Monday morning may bring another
round of showers and perhaps a storm to mainly LSE. Otherwise
expect lowering MVFR ceilings towards daybreak as a cold front
approaches. Should see a return to VFR around midday. Light and
variable winds later tonight will quickly swing around to the
north-northwest by late morning once the front drops through.
Area Forecast Discussion
National Weather Service Boston/Norton MA
1029 PM EDT Sun Jun 21 2020
Summer heat and humidity continues! We continue to expect above
normal temperatures for the start of the work week. Similar to this
weekend, isolated afternoon showers or thunderstorms are
expected. A cold front passes through the area during late
Wednesday into early Thursday, which may bring a better chance
for some rainfall. Warmth continues during Friday into the
weekend, but with noticeably lower humidity.
.NEAR TERM /UNTIL 6 AM MONDAY MORNING/...
1015 PM Update...
Forecast is largely on track so made minimal changes. Notice two
areas of low clouds/fog, one along the Cape and Islands and
another area just north of Cape Ann coming down from coastal
Maine. WPC surface analysis shows a very weak pressure gradient
across our area, with winds north of the Rte 2 corridor
generally northeasterly and the winds south of Rte 2 having a
southerly component to it. Nonetheless, very light winds. Will
keep an eye on potential fog development along the immediate
South Coast and the Cape and Islands like the past few nights.
Also would monitor low clouds/fog development along the Eastern
MA coast, especially Cape Ann. Interior fog prone areas such as
in the river valleys could also see some patchy fog. Otherwise,
a mostly dry, muggy and warm night with lows in the 60s.
7 PM Update...
We`re done with the thunderstorms for this evening, as the
seabreeze that helped to kick off some slow moving storms
earlier this afternoon has progressed into central
MA/dissipated. Mesoanalysis shows the boundary moving out of
the region of greatest sfc based CAPE (eastern MA) while
convective inhibition has increased in the last hour as well
with loss of diurnal heating. The main change with this
evening`s update was to add in a chance of a few pop up showers
overnight near/after midnight for generally areas from Worcester
Another hot & humid day across much of Southern New England as many
locations recorded temperatures in the upper 80s and low 90s. We
continue to monitor BOX radar for pulse showers and thunderstorms
during the remainder of Sunday afternoon. We`ve seen much of the
convection to the north in New Hampshire and Vermont, and as of
415 pm thunderstorms had developed along the eastern MA sea
breeze boundary. Across southern New England the MUCAPE is 1000
to 2000 J/kg, greatest in the vicinity of the sea breeze
boundary, thus pop-up showers or thunderstorms remain possible
until we near sunset. Additionally with the daytime heating and
elevation of the Berkshires, like on Saturday, the Berks could
see a pop-up storm or two. Coverage of these will not be
widespread so not a washout for most locales, a few localized
spots may receive a quick inch of rainfall.
HREF continues to support the resurgence of low-level clouds night
across Rhode Island and southeast Massachusetts. As in nights
previous the fog bank will return as well to coastal RI, southeast
MA, and the valleys across northwestern MA. It`s another warm and
muggy night with lows in the 60s.
.SHORT TERM /6 AM MONDAY MORNING THROUGH MONDAY NIGHT/...
A coastal low pressure will pass to the southeast of the Cape and
Islands on Monday. While no significant rain is expected from this, a
very brief shower or two could reach eastern Cape Cod or Nantucket
during the mornings hours. The strong summer sun will once again
burn off the morning clouds at the coast, before returning to
another mostly sunny afternoon. Yes, it will be another hot and
humid day. Especially away from the coast temperatures could once
again reach the upper 80s and low 90s. We are expecting slightly
`cooler` temperatures in and around Boston in the low and mid 80s
because of the sea breeze. Dewpoints once again will be in the mid
and upper 60s.
A mostly dry day is on tap, but like the past couple of days we do
have the threat for pop-up showers or a thunderstorm. PWATs values
are in the neighborhood of 1.50", a brief downpour under these pulse
storms are possible. Many members, including the HRRR favor the
development of these pulse showers as far east as Rhode Island and
You guessed it! Monday night into Tuesday is once again mild and
muggy! A/C will be your best bet for a comfortable night sleep! Like
clockwork, coastal fog and low-level clouds will move back into the
coastal region of RI and SE MA by Tuesday morning.
.LONG TERM /TUESDAY THROUGH SUNDAY/...
* Very warm and humid conditions continue thru Wednesday, with
isolated storms near the terrain on Tuesday.
* Cold front late Wednesday/early Thursday brings better chances for
showers and storms, though timing is still unclear.
* Still warm Friday into the weekend but with noticeably lower
The weather pattern on Tuesday remains remarkably similar to the
last several days as we remain downstream of an upper low over
Ontario. Under the warm and muggy airmass (dewpoints will be in the
upper 60s) we should once again achieve several thousand J/kg of
CAPE during the afternoon allowing for some isolated showers and
thunderstorms mainly tied to the terrain. Again expecting quick
pulse storms given zero bulk effective shear. Difference from Monday
may be a lesser chance of showers over eastern/southeastern MA and
RI as brief mid level ridging provides more subsidence to keep those
The best potential for widespread rain/thunderstorms comes Wednesday
into Thursday. This is thanks to a pattern breakdown causing heights
to fall as the sfc low moves north of New England, dragging its
cold front through around Wednesday night/Thursday morning. The RRQ
of a 100 kt upper jet moves overhead during the time period
providing better synoptic lift for more widespread showers ahead of
the front arrival. Still there remains some uncertainty on the
timing of the front which will impact the potential for strong
thunderstorms. At the moment it looks like some scattered
thunderstorms are likely Wednesday afternoon and evening.
Instability will be abundant, but wind fields are marginal; around
25-30 kts of 0-6 km bulk shear which would limit severe potential.
Better shear comes in behind the front.
By Thursday and Friday southern New England is under cyclonic flow
with colder temps aloft, allowing for more instability showers and
thunderstorms before our next front/more widespread chance of
showers may come over the weekend.
Temperatures through the long term will remain above
average...moreso Tuesday and Wednesday in the upper 80s and 90s.
Things cool down behind the front late in the week but we`ll remain
in the upper 80s. Humidity will be elevated, but relatively lower
Thu/Fri, in the mid 50s to mid 60s rather than upper 60s.
.AVIATION /03Z MONDAY THROUGH FRIDAY/...
Forecaster Confidence Levels...
Low - less than 30 percent. Moderate - 30 to 60 percent. High -
greater than 60 percent.
Low CIGs/VSBYs to MVFR/IFR expanding beyond ACK into south
coastal RI/MA and Cape Cod by 06z. VFR elsewhere in the interior
MA and CT terminals, with patchy MVFR/IFR vsbys in fog. There
is a low probability of stratus along and offshore of coastal
Maine dipping southward into the North Shore and vicinity of
BOS. ESE wind around 10 kts expected 14Z Mon and on.
Any leftover MFR/IFR CIGs/VSBYs will quickly lift and dissipate,
improving to VFR. Exception will be over immediate south coasts
of MA/RI and Cape/Islands, where it may take longer in the
morning to lift and dissipate. Low probability of stratus along
far northeast MA early in the morning. Isolated to widely
scattered SHRA/-TSRA during the afternoon.
Monday night...high confidence.
Mainly VFR, with IFR/LIFR stratus/fog redevelopment possible
along south coastal MA/RI, the Cape and Islands. Also some IFR
fog possible in river valleys.
KBOS Terminal...High confidence in TAF, except moderate
confidence late tonight and early Monday. There is a low
probability of marine stratus to the N drifting S into BOS
vicinity late tonight/early Mon.
KBDL Terminal...High confidence in TAF.
Outlook /Tuesday through Friday/...
Tuesday through Tuesday Night: VFR. Slight chance SHRA,
Wednesday: VFR. Breezy. Chance SHRA, chance TSRA.
Wednesday Night: VFR. Breezy. Slight chance SHRA, isolated
Thursday: VFR. Chance SHRA, slight chance TSRA.
Thursday Night: VFR. Slight chance SHRA, slight chance TSRA.
Friday: VFR. Slight chance SHRA, isolated TSRA.
Tonight and Monday...
An offshore, non-tropical low with a center located about 250 miles
southeast of Nantucket will track northeastward during tonight and
Monday. This system is passing far enough offshore to keep
winds/seas below SCA thresholds for the southern New England coastal
waters. Seas building to 2 to 4 feet on the outer coastal waters.
S/SW winds 10 to 15 kts tonight and Monday, except winds becoming SE
around 10 kts for Monday along east coastal MA and Cape Cod Bay.
Areas of fog develop tonight, areas with visibility below 1 mile at
times especially for the southern waters. Visibility improves
during Monday morning, though patchy fog may linger during the
Monday Night...Seas diminish to 2-3 ft as the offshore low pulls
further away from our area. Winds become SW around 10 kts.
Outlook /Tuesday through Friday/...
Tuesday: Winds less than 25 kt. Slight chance of rain showers,
Tuesday Night: Winds less than 25 kt. Seas locally approaching
5 ft. Slight chance of rain showers, isolated thunderstorms.
Wednesday: Winds less than 25 kt. Areas of seas approaching
5 ft. Chance of rain showers, chance of thunderstorms.
Wednesday Night: Winds less than 25 kt. Areas of seas
approaching 5 ft. Slight chance of rain showers, isolated
Thursday through Thursday Night: Winds less than 25 kt. Areas
of seas approaching 5 ft. Chance of rain showers, slight chance
Friday: Winds less than 25 kt. Seas locally approaching 5 ft.
Slight chance of rain showers.
Area Forecast Discussion
National Weather Service Dodge City KS
624 PM CDT Sun Jun 21 2020
...Updated Aviation Discussion...
.SHORT TERM...(This afternoon through Monday)
Issued at 113 PM CDT Sun Jun 21 2020
...Significant Severe Weather Episode This Afternoon/Evening...
WFO DDC is preparing for severe weather operations early this
afternoon. Nearly full insolation has heated a very moist boundary
layer through midday, with mesoanalysis of up to 6000 J/kg SBCAPE
in SW KS. Shear has modestly improved, with effective bulk shear
to near 35 kts. As NWly flow aloft increases this afternoon, and
an embedded shortwave/associated forcing for ascent arrives,
explosive thunderstorm development is expected. Convection will
fire quickly across the northern zones by 3 pm. Have coordinated
with SPC on the upgrade to moderate risk probability. HRRR has
shown strong consistency with storms quickly organizing into a
severe squall line, and then marching out of the SE zones around
10 pm. Damaging winds are likely with this squall line, with gusts
of 60-70 mph common. Some gusts to near hurricane force may occur,
given a linear configuration and tremendous CAPE axis. Large hail
will be focused across the initial northern storms. That said,
will be watching for discrete supercell development on the tail
end of the squall line (tail end Charlie) or just ahead of the
squall line. If a discrete supercell can be maintained through 5-7
pm, then giant hail and a tornado risk would occur. There is some
CAM consensus that this threat would focus on the Dodge-Garden-
Liberal triangle vicinity 5-7 pm. MCS will clear the SE zones by
midnight, with all zones dry after midnight. There is some
potential for another round of convection amid the continued NW
flow aloft Monday afternoon/evening, but much of the atmosphere
will be strongly worked over through tonight. As such, any
thunderstorms Monday PM will likely favor the Oklahoma border
region, where reasonable instability will have the best
opportunity to reload.
.LONG TERM...(Monday night through Sunday)
Issued at 125 PM CDT Sun Jun 21 2020
Weak disturbances will continue to move down through the northwest
flow aloft through at least the late part of the week. This will
bring a chance of storms across portions of western Kansas in the
late afternoon to evening hours. Otherwise expect partly cloudy
skies and winds generally from a southerly direction. As for
temperatures, highs will start out in the mid 80s Tuesday with low
to mid 90s for the remainder of the long term period.
.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
Issued at 605 PM CDT Sun Jun 21 2020
A line of strong to severe thunderstorms will cross in the Dodge
City and Liberal areas through 02z Monday. Wind gusts in excess
of 30 knots and reduced visibilities due to heavy rain will be
possible for the next hour or two with these storms near these two
locations. Ceilings will be as low as 3000ft AGL. Behind these
storms ceilings will improve and an easterly wind will develop at
10 knots or less. Between 10z and 14z Monday some patchy fog and
areas of ceilings in the 500ft to 1000ft AGL level will be
possible across southwest Kansas.
.PRELIMINARY POINT TEMPS/POPS...
DDC 62 88 60 85 / 50 20 30 10
GCK 61 88 60 85 / 80 20 30 20
EHA 62 92 61 84 / 20 40 50 30
LBL 63 91 61 86 / 30 30 50 10
HYS 61 86 59 84 / 80 20 20 10
P28 66 90 63 87 / 90 30 30 0
AREA FORECAST DISCUSSION
National Weather Service Kansas City/Pleasant Hill MO
620 PM CDT Sun Jun 21 2020
Issued at 231 PM CDT SUN JUN 21 2020
Today`s forecast became much more challenging with the formation of
the convection along an isentropic surface over central KS this
morning. This convection was not picked up in any guidance well and
CAMs are still struggling with this development 6 hours later. The
main impact of these storms was the massive cold pool and cirrus
shield that has developed throughout the day. Central Nebraska was
not able to get into the 90s which would have built a large MLCAPE
or MUCAPE reservoir in that corridor. This has delayed convective
initiation over this region and also shifted that development
further west in KS and further north in Nebraska. A small ridge of
MLCAPE was able to develop along the warm front over northeast
Nebraska with convective initiation going on there right now as of
2PM. Western KS has also joined the party with severe storms quickly
developing near a surging dryline. Going into the overnight hours
the thoughts were that two main areas of storms would form in north
central KS and NE, but the morning convection has altered that
solution. Now it appears there will be three different regions of
convection this afternoon, western KS, central KS, and northern NE.
Due to the low level forcing mechanisms these storms will likely
become multicellular and eventually linear as the cold pools start
to develop. As the shortwave and surface features progress the MBE
vectors will start to shift from westerly to northwesterly around
sunset. So any MCSs that develop from these areas will start to take
a more southeast direction, becoming even more southerly as the LLJ
develops (if central KS storms don`t impede that) and LL winds shift
more SW. Due to that nature of storm movement, our area would need
an MCS to form up more over central NE for the KC Metro and eastern
NE for northern Missouri. Based on the latest satellite and radar
trends the central NE storms may not even happen, but the eastern NE
storms look likely to be a player. If this does develop into a MCS
then it would reach NW Missouri around midnight and push through
central Missouri. What may hurt the chances of severe weather is
that the cirrus blow off from the current storms in central KS has
keep our MUCAPE availability lower than it would have and more
confined to IA and right along our border. This may provide enough
fuel to keep the MCS going, but it will likely weaken as it enters
Missouri, but the LLJ may aid in a more balanced outflow boundary.
We currently like the overall trend of the HRRR and RAP where a MCS
moves through northern Missouri, but weakens over time. There is a
real possibility the KC Metro and our western areas don`t see a rain
drop, unless something can get going over central Nebraska before
sunset if it can recover in time. A constant mesoanalysis will be
necessary to keep the forecast accurate with timing and intensity
tonight as things play out to our west and northwest.
How everything plays out overnight tonight will have quite a bit of
implications to Monday`s forecast. As stated above, the thought is
that storms may not develop as robust as previously thought over
central Nebraska which will possibly limit the MCS effects going
into Monday morning. If that is the case, then there is a better
chance of more substantial instability building into our area ahead
of the cold front which will be over NW Missouri by noon. This would
develop a corridor of potential convective development along and
east of I-35 with 1000-2000 J/kg (all depends on MCS remnants or
not) and effective shear of 35-40kts. Due to the strong synoptic
forcing, storms would likely become linear quickly which would limit
the large hail threat, but increase the damaging wind threat. If an
MCS does push through Monday morning then that will delay our
ability to heat up and build that instability. This may either cause
the storms to develop later and further east, or stay capped and not
develop at all. There is a lot of uncertainty in tomorrows forecast
based on what happens this afternoon and overnight.
Things become much less complicated Tuesday on the backside of the
cold front with a cooler airmass moving into the region.
Temperatures will be very comfortable for late June with highs in
the upper 70s to lower 80s and dewpoints in the 50s! Wednesday
continues the trend of cooler weather with highs slightly higher in
the low to mid 80s. Wednesday night a LLJ over KS may develop some
elevated showers and storms over eastern KS and western MO through
the early morning timeframe. Unfortunately, our cool and dry pattern
starts to break down on Thursday as southerly flow returns to the
Central Plains ahead of an incoming shortwave trough over the
Rockies. We`ll climb back into the 90s with dewpoints in the upper
60s to lower 70s which may also allow some pulse-like convection to
occur over central Missouri in the afternoon. A cold front will
develop ahead of the previously mentioned shortwave trough which may
become the focus for storms late Friday afternoon into the evening
over northern Missouri. Guidance starts to vary on how the front
will progress into Saturday leaving some uncertainty for how wet or
dry the weekend may be. NMB PoPs trend in the uncertain direction as
well with 30-40 percent over much of the region.
.Aviation...(For the 00Z TAFS through 00Z Monday Evening)
Issued at 616 PM CDT SUN JUN 21 2020
Could be a tricky aviation weather night. VFR conditions will
continue through sunset, towards 06Z, expect scattered
thunderstorms to move into portions of the region from the west.
Introduced VCTS around this time, as coverage remains a question
mark. Believe the best chance for storms will be in northeastern
Kansas and northwestern Missouri, primarily effecting KSTJ, but
cannot rule out activity farther south. Winds will begin to shift
more westerly through sunrise and shower chances return midday,
through the end of the period.
AREA FORECAST DISCUSSION
National Weather Service Eureka CA
331 PM PDT Sun Jun 21 2020
.SYNOPSIS...The first full official week of summer will bring an
extended stretch of hot, dry and sunny weather to interior
northwest California, while cool onshore breezes and marine layer
clouds keep most coastal areas seasonably cool.
.DISCUSSION...While the big story for the upcoming week will
remain hot inland temperatures, most of the area is actually
running several degrees cooler compared to this time yesterday.
That still puts the warmest valley locations into the low 90s, but
the deeper marine air has clearly taken the edge off. Persistent
cloudiness socked in around the lower Eel River basin has made for
a more dramatic change compared to yesterday for places. With the
building ridge and warming temperatures aloft, along with light
onshore flow in the boundary layer, it will be tough to get rid of
the stratus and fog particularly around Humboldt Bay over the
next couple of days. Still, have continued to advertise some
afternoon clearing, even though in some lucky locations it will
still be tough to come by, as we have seen Sunday afternoon.
As far as the heat goes, little has changed with the overall
forecast, message and impacts. That said, have swapped the
Excessive Heat Watch for a Head Advisory. This was the best
compromise for a unified message with our neighboring offices, and
matches up well with the levels of heat risk that the bulk of our
area is forecast to see. There will be some locations that will
have a higher heat risk that could have been deserving of an
excessive heat warning, like around Weaverville, Douglas City, and
eastern Lake County where temps may reach 103 to 105...but the
majority of our valleys will see more typical summer-time warmth
in the mid 90s to low 100s. That said, do not take this heat for
granted, especially if you haven`t acclimated yet this year or are
from out of the area. The risk of heat related illnesses will be
real during the peak afternoon hours. Try to spend more time in
the shade, drink plenty of fluids, and take care care of your very
young and elderly family members and neighbors.
A mid week disturbance will bring a lull in the heat; limiting
most interior valleys to the 90s on Wednesday. Friday and Saturday
have the potential to be the hottest days of the entire forecast
period as the ridge rebuilds and amplifies over our area, with 850
temps possibly reaching 27 to 30C and H5 heights in the low to
mid 590s. Would not completely rule out a stray mountain
thunderstorm over the Trinity Alps or Yolla Bollys on Wednesday
afternoon, but for now have left out of the forecast. That gives
us a dry next 7 or 8 days. /AAD
.AVIATION...By midday, remnant bands of the coastal stratus layer
were continuing to stream over Coastal terminals with mostly MVFR
ceilings. Into the afternoon, coastal terminals cleared to VFR.
Satellite imagery shows the inland valley fog has been slower to
erode as well. Overnight, KACV should see the stratus fill back in,
potentially to LIFR levels. There is growing support from HRRR and
high-resolution wind guidance that some of the stratus layer may be
transported north to KCEC in the early morning hours via a coastal
wind eddy. The reach to KCEC may be brief, and the conditional
nature to generate the lower Cigs prompts only moderate confidence
at this time. Conditions are anticipated to begin improving through
midday, eventually to VFR. KUKI will remain VFR. /JJW
.MARINE...Northerly winds and steep seas will continue to increase
this evening, and will remain elevated, especially in the northern
waters. A few gale force gusts will be possible in isolated areas,
including downwind of Cape Mendocino and Pt St George, but are not
expected to be widespread enough to warrant a gale warning. Steep
seas will build to 7 to 11 feet in the outer waters and south of
Cape Mendocino. There is also a 1 to 2 foot southerly swell around
16 seconds and a 2 to 3 foot swell at 10 seconds that will persist
through the week, along with continued steep seas with the northerly
winds. The latest guidance shows the steep seas of over 5 feet and
winds over 20 kt only briefly pulsing into northern inner waters at
times, so will not issue a small craft advisory. However, it will be
close to these conditions and it may be needed. /JJW
CA...Heat Advisory from noon Monday to 10 PM PDT Tuesday for CAZ105-
NORTHWEST CALIFORNIA COASTAL WATERS...Small Craft Advisory until
3 AM PDT Wednesday for PZZ470-475.
Small Craft Advisory until 5 AM PDT Monday for PZZ455.
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Area Forecast Discussion
National Weather Service Indianapolis IN
1143 PM EDT Sun Jun 21 2020
The AVIATION section has been updated below.
Issued at 208 PM EDT Sun Jun 21 2020
A pair of upper level weather disturbances are expected to push
across Indiana over the next few days...providing daily chances
through Tuesday. Rain amounts with these systems will be light.
High pressure is expected to arrive across the area by
Wednesday...providing dry weather for mid week. Chances for
showers and storms will return next weekend.
.NEAR TERM /Tonight/...
Issued at 700 PM EDT Sun Jun 21 2020
Extended small PoPs over the east through 06z to match adjacent
Previous discussion follows...
Issued at 208 PM EDT Sun Jun 21 2020
Water vapor imagery across the area shows a short wave trough in
place IL and KY...pivoting into Indiana. Radar shows showers and
storms over central Indiana...ahead of this system progressing
across the state. Associated cloud cover has also prevented much
heating and instability.
Models suggest the short wave responsible for the rain will
quickly exit to the east late this afternoon and early this
evening...bringing ongoing rain to a quick end. Forecast soundings
overnight indicate a drying trend and HRRR shows dry weather
overnight. Mid levels show dry air arriving amid subsidence. Thus
will trend for some pops through 00Z late tonight...otherwise a
dry forecast will be expected Overnight. Given the little change
in the overall air mass and decreasing clouds expected through
the night...will not veer far from the NBM on temps.
.SHORT TERM /Monday through Wednesday/...
Issued at 208 PM EDT Sun Jun 21 2020
The models continue to indicate broad cyclonic flow in place aloft
through Wednesday. Yet another shorty wave within the flow is
expected to push across Indiana on Monday afternoon and Monday
Night. Forecast soundings at that time show pwats over 1.83 inches
with attainable convective temperatures but limited CAPE. Thus
enough forcing and moisture is expected for some pops and isolated
tsra. Will mainly focus precipitation chances during the
afternoon and evening as the short wave passes. Given the expected
sunshine and heating early on in the day...will trend highs at or
above the NBM.
The Short wave quickly exits the area on Monday night...and
forecast soundings show subsidence and drying within the column
through Tuesday. Cyclonic flow aloft remains and forecast
soundings show limited instability. Thus will try to trend toward
a dry forecast on Tuesday as confidence in diurnally driven storms
is low given the dry air aloft. Will stick close the NBM temps
The flow aloft remains cyclonic through Wednesday as Ridging
builds across the Plains states. This continues to place Indiana
within an area favorable for subsidence. Meanwhile at the surface
high pressure is expected to build across the Ohio valley from the
Central plains. Thus will trend toward a dry forecast on
Wednesday and Thursday with temps near the NBM.
.LONG TERM /Wednesday Night through Sunday/...
Issued at 218 PM EDT Sun Jun 21 2020
Surface high pressure will continue building into the area
Wednesday night to Thursday, allowing for dry conditions in that
time frame. There is a small chance for light rain at times
Thursday. Models are in pretty good agreement for the start of the
long term, but varies more into next weekend and thus lowering the
confidence in the forecast, particularly with timing of any
weather. Did go with guidance as it looked good given the model
variations in the long term. Generally though, models hint at a
system approaching the area while a high sits to the SE, off the
Atlantic coast. This will likely allow Gulf air into the Ohio
Valley and thus rain chances for the weekend. Best PoPs at the
moment look to be Friday night through Saturday. Temperatures will
start out slightly below normal, but will trend to above normal by
.AVIATION /Discussion for the 22/06Z TAF Issuance/...
Issued at 1143 PM EDT Sun Jun 21 2020
Convective allowing models and radar trends suggest dry conditions
until after 15z, when shower and thunderstorms will be possible and
increase during the afternoon.
GFS LAMP suggest MVFR or worse fog and ceilings possible mainly 09z-
13z. MVFR ceilings will again be possible after 00z Tuesday.
Winds will be light and variable overnight and southwest to 12 knots
Area Forecast Discussion...UPDATED
National Weather Service Chicago/Romeoville, IL
930 PM CDT Sun Jun 21 2020
930 PM CDT
Earlier local storms have all faded with the diurnal weakening of
instability in an atmosphere void of any appreciable shear.
Attention continues on Monday. It`s still too early for
observational trends to provide much insights into specifics for
Monday, so much of the Short Term AFD is very representative of
the expectations, the conditional severe weather potential, and
the plentiful uncertainties on precise evolution. One thing we
will note is that the chances for some showers and potentially
storms into north central Illinois sometime during the morning
has increased some, though by no means a definite.
Quiet conditions through at least early overnight look to prevail
across the area. There might be patches of shallow fog in the
locales that saw showers late in the day due to very low
temperature-dew point spreads in a high moisture boundary layer.
A mesoscale convective system (MCS) across the WI/MN/IA border
region is moving east this evening at about 50 mph, driven by
convectively-enhanced short wave that is moving slightly north of
east. On its trailing edge in north central to northeast Iowa, the
low-level jet of near 30 kt is largely offsetting a quick
progression there, which would be closer or into our latitude.
This means that the current timing of any rain chances later in
the night and primarily over north central Illinois or near the
Wisconsin border look good, with some outflow from this feature
potentially sparking scattered development. The organized
development through daybreak looks likely to remain to our
northwest and north, potentially not by very far though.
Further west, scattered convective development is likely over
western into much of central Iowa overnight, and seeing signs of
this over Nebraska as an approaching short wave nears and the
favorable inherent environment sampled by the 00Z OAX sounding.
How widespread this convection becomes and how it organizes with
the aforementioned current northern Iowa regenerating activity is
uncertain, though still at least a loose MCS is more favored than
not moving eastward over the Mississippi River by daybreak, and
as mentioned some scattered activity could be ahead of that into
north central Illinois. Also an important feature is likely the
well-organized MCV over central Kansas. The driving short wave and
the MCV itself from this is seen on several guidance solutions,
including the 00Z NAM and especially multiple RAP runs,
progressing toward the northern Illinois region by midday.
Obviously with so many mesoscale influences that have a domino
effect and several of which are still maturing or even yet to
develop, it makes Monday`s forecast very tricky. However the
likelihood of thunderstorms, quite possibly a couple rounds worth,
is favored over a decent amount of the area Monday and Monday
evening. Maturity of any morning activity and influence on timing
will likely dictate the conditional severe threat area and types,
with MCVs playing a role to where there will be pockets of
sufficient shear for better storm to mesoscale organization.
317 PM CDT
Through Monday night...
Showers and storms are percolating mainly across the southeastern
half of our CWA at this hour within a ribbon of maximized low-mid
level moisture in the wake of yesterday`s activity. The
diurnally-bubbling cumulus field gets progressively flatter with
north and westward extent towards the Wisconsin/Illinois state
line where instability drops off as dewpoints have mixed out into
the upper 50s and lower 60s. Continue to confine the `highest`
PoPs this afternoon generally east of I-55/57, but have also
dragged some very low (20%) chances farther west and south of
I-88 as somewhat lumpier Cu/towering Cu has developed west of
I-39. Deep layer shear is very low and storms are exhibiting
classic pulse type characteristics and cores are raining
themselves out within 30-45 minutes. Surface-700 mb theta-e
deficits are fairly high given the presence of some pretty dry air
in the mid-levels, so can`t rule out some gusty winds as cores
exhaust themselves. In addition, storms are moving very slowly
(less than 15 mph) so a threat for locally heavy rainfall does
exist. Storms will diurnally wane with the loss of heating this
The main focus during the short term portion of this forecast
remains squarely focused on Monday which continues to feature what
looks to be quite a messy forecast. This period also continues to
exhibit higher-than-normal uncertainty at this relatively short
range with the evolution of storms chances and the attendant
severe weather threat tied to subtle mesoscale processes which
remain fairly nebulous at this point. That said, a conditional
threat for some severe weather does exist tomorrow but does depend
on things evolving in a particular manner through the morning
A fairly sharp shortwave has translated east of the Continental
Divide and is now progressing out across the central Great Plains.
As this feature encounters an increasingly unstable and uncapped
environment, showers and thunderstorms are expected to develop
across Nebraska and northeastward into Minnesota along a cold
front. Storms should then congeal into a forward-propagating MCS
through this evening and overnight and track generally eastward
across Iowa. Confidence through this part of the forecast (through
tonight) remains fairly high as a result, but begins to degrade
pretty quickly thereafter. Overall, the MCS parameter space
doesn`t appear all that impressive, with generally weak deep layer
shear and also directed somewhat parallel to the anticipated MCS
orientation at our latitude. This should work against the
regenerative development of new/robust updrafts at the leading
edge of the accelerating cold pool and would, as a result, expect
a gradual weakening trend as outflow is exhausted from the
convective carcass by and just after daybreak. At that point, it
looks like this complex may be sneaking into our CWA at early
Monday morning in its weakening phase although can`t rule out some
lingering gusty winds with the anticipated outflow.
Depending on exactly how early or late in the morning that this
feature moves into the area, subsidence and the associated
convectively-processed airmass could keep thunderstorm chances to
a relative minimum through the morning or even into the early
afternoon hours. If this feature is lingering overhead by midday,
the subsequent strong-severe weather threat may stay pretty muted
in the afternoon as temperatures will have limited time to recover
ahead of the next shortwave. It`s just too early to tell how this
will shake out as the convective complex hasn`t taken shape yet.
If we are able to clear out a bit through the late-morning and
early-afternoon, a threat for strong-severe storms will then be
possible as the next shortwave drops southward out of
Minnesota/Iowa with convection potentially developing on any
leftover outflow. A second area of thunderstorms could
conceivably develop on a cold front off to our west potentially
yielding two corridors of initial storm development. Outside of
any mid-level flow augmentation near any remnant MCV`s, deep layer
shear looks to once again remain pretty weak which should temper
storm organization. As a result, and given weak mid-level lapse
rates, would expect the main threats to be from strong to
potentially damaging wind gusts--especially if storms can develop
and then congeal into another complex. Obviously lots of
uncertainties here, and it`s pretty difficult to highlight a
favored corridor for these severe threats at this point, although
latest indications are that this *may* maximized locally east and
south of I-55 through the afternoon.
Will hold onto relatively high PoPs through Monday evening as well
as guidance does suggest additional development on the incoming
cold front although would envision the severe weather threat with
this activity may remain more muted.
325 PM CDT
Tuesday through Sunday...
Monday night`s cold front passage will usher in a cooler and drier
low level air mass that will be with us through Wednesday night.
Most of that time will be dry, but isolated to perhaps widely
scattered diurnally driven instability PM showers will be possible
on Tuesday and Wednesday. Upper level low pressure will set up
south of James Bay and then slowly translate eastward through
Thursday night. In the northwest flow on the southwest periphery
of the troughing influence of the upper low, occasional short-wave
impulses may touch off the aforementioned diurnally driven showers
as lower level lapse rates steepen. Tuesday`s instability looks
quite meager, enough so that thunderstorms continue to appear
unlikely. Wednesday may have a bit more, but still low instability
to enable a few isolated thunderstorms amidst widely scattered
afternoon showers. On Thursday, as the upper low finally kicks
east, temperatures will warm to around normal low-mid 80s, though
humidity will still be low. Any afternoon convection should be
widely isolated, with minimal instability and less forcing.
The main timeframe to watch this week after Monday`s potentially
widespread convection is Friday into the weekend. A warm front
will lift north Thursday night into Friday, with warm and more
moist advecting in with a lead short-wave possibly kicking off
showers and thunderstorms toward morning. Depending on how the
morning evolves with regard to effects of possible morning storms
on daytime heating and destabilization, there may be another
round on Friday afternoon into at least the evening. Thermally,
temps in the upper 80s will be possible, if not warmer, but a
messy convective evolution would likely limit things a bit.
Ensemble mean PWAT approaching 1.75" and operational solutions
offering up potentially nearing 2" PWATs would support a heavy
rain and flooding risk with Friday`s likely storms. Meanwhile,
there may be enough west to west-northwest mid-level flow on
Friday PM for some strong/severe risk. A weak cold front could try
to shift the instability axis a bit southward over the weekend,
though possibly still in the CWA, so the muggy and unsettled
weather could continue with occasional shower and thunderstorm
chances, with above normal temps).
For the 00Z TAFs...
Quiet conditions are expected through the overnight hours at all
sites as widely isolated diurnally-assisted activity over northern
Illinois quickly diminishes over the next hour or two. Winds will
settle at S/SSW under 10 knots overnight.
The forecast becomes quite complex by mid-morning Monday. Developing
convection from northeast Nebraska into southwest Minnesota is
expected to move eastward through tonight, reaching northern
Illinois in a decaying mode Monday morning. Uncertainty with how
quick this decay occurs complicates the forecast for the remainder
of the day at the Chicago metro sites, though some SHRA and possible
TS should survive to around RFD. There are two scenarios that could
unfold for the Chicago area sites on Monday:
1) Overnight convection weakens considerably, producing little
impact in the Chicago area Monday morning. New convection will then
quickly develop on the remnant outflow over the metro early in the
afternoon. After an early evening lull, scattered convection is
possible on a cold front arriving late in the evening.
2) Overnight convection is slow to weaken, bringing residual SHRA
and gusty west winds through the Chicago area mid-morning. The
stabilizing effect and farther SE push of the outflow could keep
most afternoon convection southeast of DPA/ORD/MDW. Evening
convection will remain possible along the cold front.
A better idea of which scenario will unfold likely will not be
realized until the overnight hours once convective trends over Iowa
become more clear.
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Area Forecast Discussion
National Weather Service Shreveport LA
1013 PM CDT Sun Jun 21 2020
The evening mosaic radar imagery continues to indicate a broad MCV
spinning between FSM and RUE, with convection having become
enhanced across the very moist and unstable environment to its SSE
over the Nrn sections of SW and SCntrl AR, where PW`s near 2" and
MLCapes of 1500-2000 J/KG persist. With the air mass becoming
stabilized with the increasing convection, the primary threat
tonight will focus to a heavy rain and potential flood threat, as
a 20-30kt SWrly low level flow continues to feed into the MCV as
drifts slowly E overnight. Whereas the 12Z and 00Z global models
have been underdoing the QPF thus far, a few of the latest CAMs
including the HRRR, ARW, and RAP suggest that widespread 2-5+ inch
QPF are likely across portions of SW and SCntrl AR, although each
vary in the exact location of the higher totals. The highest
confidence though for seeing the potential for flash flooding is
only across a small area from Howard to Hempstead and Nevada
Counties, as well as Union County, but these areas have remained
drier than normal over the last month and should be able to take
most of these rains and thus, a Flash Flood Watch will not be
issued with the forecast update.
Also of note is the ongoing MCS across NW OK, which is quickly
advancing SE across Wrn into Ncntrl OK attm, with the 00Z CAMs
suggesting that this complex will hold together (although in a
weakened state) mainly NW of I-30 into extreme NE TX/SE
OK/adjacent SW AR by and just prior to 12Z. With this complex
moving across much of Cntrl and Ern OK overnight which remains
more stable than areas to the SSW over Srn OK/NW TX, this MCS
should weaken as it approaches the region, and should remain
progressive enough such that the flash flood potential over
McCurtain County should be reduced in wake of the widespread 2.5-5
inches of rain that fell earlier today.
For the evening update, did raise pops considerably to
categorical/likely over the Nrn sections of SW AR, while also
beefing up pops to likely/high chance farther WNW after 06Z for SE
OK/extreme NE TX. Given the uncertainties of the NW OK MCS late
tonight, did not make any changes to the pops Monday, although a
cold pool/outflow boundaries from this convection should help
focus at least sct convection during the day farther SE across the
remainder of the region.
Did lower min temps a bit tonight across the rain cooled areas of
SE OK/SW AR, while also removing pops for Lower E TX/much of N LA
where the seabreeze convection has diminished and the air mass
Zone update already out...grids will be available shortly.
.PREV DISCUSSION... /issued 728 PM CDT Sun Jun 21 2020/
VFR conditions will continue this evening, with the sct convection
winding down for the most part with the stabilizing air mass.
However, the exception will remain over the Nrn and NE sections of
SW/Scntrl AR, near and E of an MCV that will drift E into SCntrl
AR overnight. Thus, sct convection will remain prevalent near and
N of the ELD terminal tonight, and thus have continued VCTS
mention here through much of the overnight period. Otherwise,
elevated convective debris will linger overnight, with low
MVFR/possibly IFR cigs develop around or just prior to 12Z Monday
areawide, which look to linger through much of the morning before
becoming VFR by late morning/early afternoon. However, some
uncertainty with the duration of these cigs exist as a SE moving
convective complex (MCS) over Srn KS/NW OK will slide SE through
OK overnight, which may enter SE OK/portions of NE TX by/shortly
before 12Z Monday as it decays. Thus, a cold pool from this
decaying convection may shift SE across the region by mid to late
morning, thus focusing at least sct convection with the aid of
diurnal heating. An earlier cold pool/outflow bndry would tend to
quickly scatter/lift any low cigs Monday morning, with sct
convection primarily affecting Deep E TX/N LA/SCntrl AR during the
afternoon. Have added VCTS to all but the TYR/GGG/TXK terminals
Monday afternoon. S winds 6-12kts tonight will become SSW 10-15kts
with higher gusts after 15Z. /15/
.PRELIMINARY POINT TEMPS/POPS...
SHV 75 91 74 84 / 10 40 40 90
MLU 72 91 74 87 / 20 50 30 90
DEQ 69 87 69 85 / 60 60 80 80
TXK 72 88 71 81 / 50 50 80 90
ELD 70 89 71 82 / 70 40 70 90
TYR 75 91 71 84 / 10 40 50 80
GGG 75 91 71 85 / 10 30 40 90
LFK 74 92 73 87 / 10 40 20 90
Area Forecast Discussion
National Weather Service Tulsa OK
925 PM CDT Sun Jun 21 2020
The forecast was updated based on the latest short term data and
recent obs trends. See discussion below.
As has been anticipated for at least a couple days now, an MCS has
evolved out of cluster of severe storms over western KS this
afternoon. Over the past couple hours, some trends have been noted
in area radar data, and suggest that the last few runs of the HRRR
are painting a reasonable idea of how this will evolve. The
initial MCS split in two, with the eastern flank surging out
toward Wichita to the south of a book end vortex. This convection
has since become very disorganized and no longer is severe. The
storms on the western flank were more intense and have now evolved
into what looks like the main show for the overnight across
northwest Oklahoma. The CAMs take this MCS southeast overnight,
tracking into east central and southeast Oklahoma toward the early
morning hours on Monday. While the environment over much of
eastern Oklahoma is far from ideal for convection, some
improvement in conditions is possible down toward the Red River
overnight ahead of the MCS as effects from the MCV over the
Arklatex continue to wane as it shifts east. Based on the latest
radar and CAM data trends, PoPs have been adjusted to focus the
higher numbers from east central down into southeast Oklahoma
after midnight. Damaging winds remain the primary severe threat,
though with some uncertainty regarding the environment over
eastern OK ahead of it, have toned down the wording just a bit.
Updated products and graphics have been sent.
.PREV DISCUSSION... /Issued 652 PM CDT Sun Jun 21 2020/
CONCERNING TAF SITES KTUL/KRVS/KBVO/KMLC/KXNA/KFYV/KFSM/KROG.
Increasing high level clouds and winds between east and south
should remain common across the CWA this evening. Overnight...
attention turns to the MCS ongoing across Western Kansas. Latest
short term guidance continues to indicate this complex diving
more southerly through Western/Central Oklahoma before reaching
Southeast Oklahoma late tonight. Thus...will trend this set of
TAFs in that direction and hold onto VCTS for a period in
Northeast Oklahoma with thunderstorms and tempo groups for
Southeast Oklahoma. Across Northwest Arkansas...there is still a
chance of a few storms and will continue with VCTS/tempos early
Monday morning. Otherwise...there could be the potential for some
MVFR ceilings during this time period. Within the
convection...MVFR conditions along with gusty winds will be
possible. During the day Monday...precip chances look to decrease
by mid/late morning with prob30 groups covering the afternoon
hours. Scattered to broken mid and high clouds and winds becoming
westerly are also forecast during the day Monday over the CWA.
PREV DISCUSSION... /Issued 201 PM CDT Sun Jun 21 2020/
Almost looks like we have two MCVs drifting across
southeast Oklahoma this afternoon. These features
continue to produce scattered showers and thunderstorms
across southeast Oklahoma into western Arkansas
this afternoon. This activity is expected to diminish
as we move closer to sunset. With MLCAPE values running
around 2000 J/KG, these storms could become briefly strong
to marginally severe.
We will then focus our attention to the north this evening
as thunderstorms are expected to develop across western
Kansas in the vicinity of a surface boundary in the lee of
the Rockies this afternoon and spread to the southeast.
This activity is expected to coalesce into a MCS and move
into northeast Oklahoma as we approach the midnight hour and
then across the remainder of the area through the night into
Monday morning. The main concern with this thunderstorm complex
as it moves through the area will be damaging winds and heavy
The chances of showers and thunderstorms persist through the
Monday afternoon and into Tuesday morning time-frame in the
vicinity of any residual outflow boundaries and in the area
of any MCV type features. This activity will also be enhanced by
a synoptic cold front moving into the area as a mid-level
shortwave trof plows across the Plains. There is expected to
be adequate instability and deep layer shear for any these storms
to become severe with damaging winds and large hail the concern.
Tuesday night into Wednesday appear to be mostly dry as high
pressure builds into the region behind a reinforcing cold
front. More showers and thunderstorms are possible late
in the week as a the front moves back to the north and east
across the area.
Still looking at the potential for another 1 to 3 inches of
rain through Tuesday with locally higher amounts possible.
Localized flooding of low lying areas will be possible.
Stayed close to NBM temperatures through the forecast period.
.PRELIMINARY POINT TEMPS/POPS...
TUL 69 86 67 85 / 50 50 60 10
FSM 68 86 70 87 / 50 60 90 40
MLC 69 85 68 84 / 60 60 80 40
BVO 68 85 65 84 / 40 50 50 0
FYV 66 82 65 82 / 30 60 80 30
BYV 66 83 65 82 / 10 60 70 30
MKO 69 86 67 84 / 40 60 80 20
MIO 67 84 65 84 / 40 60 50 10
F10 68 86 67 84 / 50 50 80 20
HHW 69 86 70 84 / 80 60 80 60