Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 07/19/20
Area Forecast Discussion
National Weather Service La Crosse WI
1145 PM CDT Sat Jul 18 2020
.SHORT TERM...(Tonight)
Issued at 231 PM CDT Sat Jul 18 2020
Morning convection definitely complicated the heat forecast for this
afternoon. Widespread debris clouds finally gave way to clearing by
late morning, but since then have had pesky cu and stratocu
developing in their wake. Even some nuisance cells developed early
this afternoon over central WI where capping is weaker. A
southerly breeze is leading to efficient moisture advection,
pumping a rich pool of mid 70s dewpoints into the area, soupiest
generally west of the Mississippi River. A handful of observing
sites are reporting dewpoints flirting with 80 at this hour thanks
to that maturing corn crop. So while humidity is not lacking,
temperatures have been trickier to pin down this afternoon, still
mostly in the 80s across the forecast area at this hour. Thinking
bulk of the area will still have no problem exceeding 100 degree
heat indices by late afternoon to meet advisory criteria, so have
left headline untouched. Only somewhat questionable area looks to
be central WI where dewpoints still remain in the low 70s.
Heading into this evening we`ll be closely watching a cold front
dropping in from MN and northwest WI. Instability out ahead of the
front will be super favorable with MLCAPEs >3500 J/kg across the
area. Afternoon heating will gradually erode the stout capping in
place as the front approaches, and CAMs show storms erupting along
the front by late afternoon over central MN. Question then
becomes how this line of convection evolves as the front
progresses southeast, and how extensive the line of storms will be
as it pushes through our area. The HRRR didn`t handle last
night`s convection very well and seems to be the outlier again
this afternoon. So not putting much stock in it wanting to keep
bulk of storms north of I-94. Other CAMs show a broad line of
storms perhaps with some bowing segments extending through the
entire forecast area this evening into early Sunday morning,
roughly between 7 PM and 2 AM. Timing will likely need some
further refinement once convection initiates and mesoscale
influences become more dominant.
Severe potential still looks decent given the juicy airmass and fat
CAPE sounding profiles. Deep layer shear will be strongest behind
the front, but it does look like there may be ample shear in the
vicinity of the front as well. Damaging winds will likely be the
main threat, especially if storms congeal into bowing segments as
depicted by several CAMs. Isolated large hail is also possible. Low
level shear will be respectable and hodographs show favorable
curvature from 0-1km for perhaps an isolated tornado or two. The
rich low level moisture will also support rather low LCLs. Due to
the expected progressive nature of this line of storms, not
expecting a widespread significant flooding threat. That being
said, strong moisture transport out ahead of the front and deep
warm cloud depths will definitely support heavy rainfall rates.
HREF mean 24 hr QPF ending 19.12Z shows widespread 0.5 to 1" of
rainfall across the area with ensemble max QPF of 1 to 2" with
locally up to 3 inches. Barring any stalling or training storms
(not expected) or super heavy rainfall rates, latest flash flood
guidance would suggest the area should have no trouble handling
that amount of rain.
Convection will shut off from NW to SE behind the front late
tonight, but the overnight still looks rather muggy with
temperatures slowly falling only into the mid 60s to mid 70s.
.LONG TERM...(Sunday through Saturday)
Issued at 231 PM CDT Sat Jul 18 2020
Near normal temperatures and lower dewpoints return on Sunday behind
a cold front that will move through the are overnight tonight.
Expect high temperatures to range from the upper 70s to middle 80s
over the next few days, with much more comfortable dewpoints.
Surface high pressure builds in from the west going into the
beginning of the new week, keeping things mostly dry. Shower and
storm chances return Monday night into Tuesday as a shortwave trough
drops south from the Dakotas. Upper ridging builds in across the
region by the middle to end of the new week, allowing temperatures
to gradually climb by next weekend. Additional chances for showers
and storms will be possible by the end of the new week as a
shortwave trough or two move through the large scale flow aloft.
&&
.AVIATION...(For the 06Z TAFS through 06Z Sunday night)
Issued at 1045 PM CDT Sat Jul 18 2020
Line of storms along a cold front running from northern WI into
western parts of the state. Meso models doing a bit better capturing
the convection, suggesting further expansion southward along the
eastward moving front (although not as widespread as to the north).
Storms no longer looking like a "sure thing" for both TAF sites.
Cigs: MVFR potential with any storm, otherwise VFR bkn cigs into the
overnight with generally SKC/SCT conditions through Sunday.
WX/vsby: VCTS looking more appropriate for KRST now with expected
less coverage. Chances higher for KLSE, but could also be missed.
Will hold onto the brief TEMPO for KLSE now, amend if necessary.
Winds: South will swing to the northwest with passage of front
tonight, roughly in the 06-09z time frame. Strong wind gusts with
any storm not looking as likely at this time with stabilizing of the
near sfc layer.
&&
.ARX WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...None.
IA...None.
&&
$$
SHORT TERM...Kurz
LONG TERM...NMB
AVIATION...Rieck
Area Forecast Discussion
National Weather Service Des Moines IA
721 PM CDT Sat Jul 18 2020
.DISCUSSION.../Tonight through Saturday/
Issued at 229 PM CDT Sat Jul 18 2020
.Overview...After hot and humid weather today, a cold front will
pass through tonight and bring less hot weather on Sunday. This
front may also bring storms to portions of Iowa tonight with highest
chances in the northeast. Additional storm chances will be possible
and focused at night each Sunday, Monday, and Tuesday with highest
chances over southern Iowa. As the mid-level ridge builds back
northward late next week, this may bring storm chances farther north
into the state with a possible return of the heat by late next
week/weekend.
.Details...Wave of 850mb theta-e advection and nocturnal low level
jet into Iowa in concert with outflow boundary over northern Iowa
from Minnesota/Wisconsin MCS pushed showers and storms through parts
of central Iowa this morning. Those moved out of the state by late
morning and left only some patchy clouds over southern Iowa with
scattered cumulus developing this afternoon over northern Iowa.
While the storms and clouds held temperatures back a little this
morning, they are well into the 80s and low 90s early this
afternoon. Heat indicies are broadly in the middle 90s to around 105
with the higher indicies at AWOS sites, which are pushing 80 degree
dewpoints. Those probably are inflated by proximity to cropland with
core ASOS sites in the middle 70s as of 130pm. Regardless, it`s hot
and humid and heat advisory will remain in place through early this
evening.
As the heat wanes late this afternoon into this evening, attention
will turn to the northwest as a cold front begins to move into Iowa.
Morning forecast soundings from the RAP and HRRR for late this
afternoon into this evening show CAPE values easily topping 4000
J/kg with deep layer shear around 20 knots or so. A capping
inversion somewhere around 800mb to 775mb should keep storms from
forming until near and likely after sunset, which is supported by
much of the guidance over the last few runs. The temperature in the
inversion lowers a degree or two this evening and that along with
forcing for ascent along the front, which will also have slightly
better shear perhaps near 30 knots, may initiate storms. If the
erosion of the cap is not uniform along the front, which seems
probable at this time, this may result in less coverage of storms.
Morning convective allowing models (CAMs) such as the 11 through 17z
HRRR and 12/15z RAP show the struggle to develop widespread
convection with the exception being the 00z WRF-NMM, 06z NAM Nest,
and to a lesser extent the 12z NAM Nest. Overall, the highest chance
for storms will be over north central into eastern Iowa. Severe
concerns would be primarily focused on gusty winds and hail over
northern Iowa. There is less certainty on rainfall in southwestern
Iowa. CAM and global models show a relative minimum it would seem
over the drought stricken areas of western Iowa. The exceptions have
been the GFS, 12z WRF-NMM, and the 00z WPC QPF, which had a maximum
over this area near 1.5 inches. The 12z WPC QPF has trended down
about an inch over this area and have coordinated with Omaha to
lower even a bit more.
The front and storm chances should slip into northern Missouri
Sunday morning with less hot air settling into Iowa with highs in
mid-80s. As warm air advection interacts with the stalled boundary
south of Iowa, this should allow a round of thunderstorms with
highest chances over southern Iowa and northern Missouri Sunday
night. Additional storm chances over roughly these same areas are
expected Monday and Tuesday nights as the boundary remains with
favorable low level flow and shortwave troughs passing over this
area and being the impetus for storms. Severe weather threat looks
low each of these nights at this time given weak shear. The 850-
300mb will be quasi-parallel to this boundary and weaker at around
15 knots compared to yesterday. Precipitable water values will be
above 1.75 inches to around 2 inches with optimal warm cloud depths
for efficient rain producers. This could bring needed rainfall to
dry areas with the highest amounts at this point looking to be south
of the Iowa border through Wednesday morning.
This boundary will begin to lift northward as the mid-level ridge
builds back into the central US Wednesday into next weekend. With
shortwave troughs still passing through on the northern side of the
mid-level ridge, this could bring higher chances for storms farther
northward into Iowa late next week. Conditions may turn hot again by
late next week or weekend with highs back into the 90s.
&&
.AVIATION.../For the 00Z TAFS through 00Z Sunday evening/
Issued at 721 PM CDT Sat Jul 18 2020
Main impact will be in the first 12 hours of this TAF cycle as a
frontal boundary brings chances for isolated -shra/-tsra activity.
Its far from a sure bet, however, as preceding conditions work to
inhibit convective development. Event so, did keep mentions of
VCSH/VCTS going for all terminals for a time during the overnight.
As for timing, earliest will be at northern IA terminals and
latest for KOTM in the south. Did not drop conditions below VFR as
any decrease associated w/ -TSRA would be brief. Will continue to
monitor through the evening. Otherwise, conditions remain VFR
through Sunday with no precip chances.
&&
.DMX WATCHES/WARNINGS/ADVISORIES...
Heat Advisory until 8 PM CDT this evening for IAZ004>007-015>017-
023>028-033>039-044>050-057>062-070>075-081>086-092>097.
&&
$$
DISCUSSION...Ansorge
AVIATION...Hahn
Area Forecast Discussion
National Weather Service Quad Cities IA IL
950 PM CDT Sat Jul 18 2020
.UPDATE...
Issued at 943 PM CDT Sat Jul 18 2020
Uncertainty still exists with convective evolution, coverage and
magnitude overnight. Trends in observational data, some of hi-
res CAM output as well as newer deterministic model seemingly
point to our development potential resting primarily with weak
low amplitude wave in the plains shifting eastward in semi-zonal
flow aloft, and elevated warm advection and convergence with
veering low level jet overnight ahead of approaching front.
Appears like best potential will reside across our north half or
so, and could still be yet a few to several more hours from really
developing with main ascent still to our north and west. Coverage
remains in question, but have kept likely PoPs for a few hours in
this aforementioned area where best juxtaposition of said forcing
is being suggested. Very steep mid level lapse rates could pose
more of a hail threat than originally thought with elevated
convection. Can`t rule out though some eventual organization into
linear frontal convection with a wind threat too, though so deep
in the night poses uncertainty with magnitude.
&&
.SYNOPSIS...
Issued at 324 PM CDT Sat Jul 18 2020
This afternoon, clouds from morning convection remained
entrenched across most the area. Temperatures did not climb as
high as forecast, however dewpoints are higher than expected due
to a lack of mixing. This still resulted in head indices near or
exceeding 100 degrees across the area. These storms have left an
outflow boundary across the area that needs to be watched for
storms overnight.
&&
.SHORT TERM...(This Evening through Sunday)
ISSUED AT 324 PM CDT Sat Jul 18 2020
Key Messages:
1. Signal for night time convection continues.
2. Mesoscale features make overall evolution still uncertain at
this time.
Discussion:
Stronger upper level wave will remain north of the area as a cold
front is dragged across the area tonight. CAMs reflectivity
guidance has been struggling to keep up with what has happened
today and are of little value this time. Looking towards actual
forcing mechanism. The best mechanism looks to be associated with
the cold front and weak H85 LLJ convergence tonight across the
area. Deep layer shear is rather weak however, the low level shear
in the HRRR looks to be strong, near 30 knots. This may lead to
strong to severe wind gusts. With the OFB in the area a tornado
threat cannot be ruled out. This needs to be watched by later
shifts.
Tomorrow will be quieter as cooler H85 temps move in with the
cold front.
.LONG TERM...(Sunday Night through Saturday)
ISSUED AT 324 PM CDT Sat Jul 18 2020
Key Messages:
1. Near to slightly below normal temperatures on Monday and Tuesday
before the heat returns for the remainder of the long term.
2. Chances of thunderstorms through the period. There is lower
confidence toward the end of next week.
There is good agreement with the overall synoptic pattern but there
are timing and placement differences for key features through the
long term period.
There will be an active zonal flow across the region through
Wednesday when a deeper trough passes to our north. In the wake of
this system, ridging rebuilds into the Northern Plains. This
places the local area under northwest flow aloft and with a
shortwave either cutting under the apex of the ridge or topping it
resulting in active weather continuing into the weekend. For
these reasons, there are daily chances of showers and thunderstorms
through the period. The period will begin with a cold front near
Interstate 80 or across northern Missouri. This feature will slowly
lift northward through the period and will be a focusing mechanism
for all of the previously mentioned shortwave energy moving across
the region. Confidence is lower for chances of storms in the wake
of the Tuesday night storm system as chances will depend on the how
far north the ridge builds and its strength as to whether it will be
wet or dry. There will definitely be dry hours in between the
different waves.
Temperature wise, Monday and Tuesday will start out below normal
with highs 80 to 84 degrees. The normal high temperatures for the
last week in July are normally 82 to 86 degrees. Low temperatures
will be in the upper 60s to near 70 which continues to be above
normal. The second half of the week will feature highs in the mid
to upper 80s which is near to slightly below normal with low
temperatures in the upper 60s to lower 70s.
&&
.AVIATION...(For the 00Z TAFS through 00Z Sunday Evening)
ISSUED AT 547 PM CDT Sat Jul 18 2020
VFR conditions will start the TAF period with gusty S/SW winds
diminishing some with sunset although occasional gusts still possible
through the evening. Expect storms to develop and/or move across
the region late this evening and overnight ahead of an approaching
cold front, with bouts of MVFR to IFR conditions. A few severe
storms with strong winds are possible. Any storms should exit
Sunday AM, with VFR conditions in their wake along with NW winds
occasionally gusty.
&&
.DVN WATCHES/WARNINGS/ADVISORIES...
IA...NONE.
IL...NONE.
MO...NONE.
&&
$$
UPDATE...McClure
SYNOPSIS...Gibbs
SHORT TERM...Gibbs
LONG TERM...Cousins
AVIATION...McClure
Area Forecast Discussion
National Weather Service Austin/San Antonio TX
526 PM CDT Sat Jul 18 2020
.AVIATION...
Isolated area of convection around the area, though not expected to
impact the terminals. Increasing clouds overnight at San Antonio
sites with MVFR ceilings, clearing up later in the morning. Winds
decreasing after sunset.
&&
.PREV DISCUSSION... /ISSUED 238 PM CDT Sat Jul 18 2020/
SHORT TERM (Tonight through Sunday Night)...
An inverted upper trough axis is located over South Texas at the
present time and is leading to some isolated to scattered shower and
thunderstorm activity across our southern counties. A higher
coverage of activity is noted on area radars closer to Corpus
Christi where the better lift and moisture is located. Some of the
high-res model guidance including the HRRR and ARW is showing a some
widely isolated showers farther north later this afternoon while
other members such as the TTU-WRF remain drier. Seeing some decent
agitation to the cumulus field in the southern Hill Country and
closer to New Braunfels with cloud tops only 5C warmer than where
showers are ongoing. Therefore, will include a mention of showers
with a 10 PoP for locations farther north of the higher coverage.
Not much accumulation will be expected out of this activity.
Otherwise, for the remainder of the afternoon, temperatures will top
out in the lower to upper 90.
The night time period is expected to be rain free, with skies
becoming partly to mostly cloudy for the typical portions of the
area. For tomorrow, the rain chances should be small again but this
time limited only to the Coastal Plains as the effects of the
inverted trough are gone. Highs tomorrow will be in the middle to
upper 90s for most locations with near 100 degrees expected closer
to the Rio Grande. Dry conditions with lows in the lower to middle
70s are expected for tomorrow night.
LONG TERM (Monday through Saturday)...
Pooled moisture and broad instability over the northern Gulf will be
moving west along the nrn Gulf Coast for much of the next week as the
upper ridge axis remains somewhat suppressed to a flat E-W axis with
localized ridge maxima over the 4 corners region and the Smokey
Mountains. Monday through Thursday should be mostly similar type of
days for South Central TX with the western counties remaining
largely dry and central areas seeing some isolated outflow-driven
convection fizzles out as it reaches the escarpment. Most of the
substantial downpour potential amounts over 1/4 inch should remain
east of I-35 each day. The increased tropical air moving inland
should at least maintain some more tolerable high temperatures for
the next several days.
By Friday the most concentrated area of moisture an instability
approaches the TX coast and could bring the convection deeper inland
and possibly bring low chances for rain in all areas. There is
another weak inverted trough associated with this moisture swell, and
it again looks most likely to favor best rain chances over areas
south of Hwy 90. However, this moisture surge looks to potentially
reach slightly farther north than the one over South TX today, and
low PoPs are included for much of the Hill Country. Friday also looks
to sport the lowest high temps of the week with parts of the Hill
Country and Central TX possibly being held to a 90 degree high.
&&
.PRELIMINARY POINT TEMPS/POPS...
Austin Camp Mabry 75 97 76 94 75 / - - - 10 10
Austin Bergstrom Intl Airport 73 96 74 93 75 / - - - 20 10
New Braunfels Muni Airport 73 96 74 94 75 / - 10 - 20 10
Burnet Muni Airport 73 96 73 94 73 / 0 0 0 10 10
Del Rio Intl Airport 76 101 77 102 78 / - - 0 - -
Georgetown Muni Airport 74 98 75 95 75 / - - 0 10 10
Hondo Muni Airport 73 99 73 99 75 / 0 - 0 10 -
San Marcos Muni Airport 73 97 74 94 75 / - 10 - 20 10
La Grange - Fayette Regional 75 98 76 95 76 / 0 10 - 30 20
San Antonio Intl Airport 75 98 76 96 76 / - - - 20 10
Stinson Muni Airport 75 97 76 96 76 / - - - 20 10
&&
.EWX WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
Short-Term/Aviation...YBVP
Long-Term...04
AREA FORECAST DISCUSSION
National Weather Service Hastings NE
635 PM CDT Sat Jul 18 2020
.SHORT TERM...(This evening through Sunday)
Issued at 414 PM CDT Sat Jul 18 2020
Heat has been the main issue today and it`s right on track. Highs
reaching to the century mark and beyond in some instances with
dewpoints generally in the 70 to 75 degree range. Heat indices
above 100 are common across the area as of this issuance. The
front/wind shift is through Albion to Holdrege and southwest.
Winds are veering as the front approaches and the westerly
component is helping temps soar and for some who are far enough
behind the boundary...the dewpoints to drop some. Regardless, the
heat headline looks good with no changes, expecting it to expire
this evening. Some areas out west may be able to be let go early,
but will allow the next shift to watch and take care of it.
The thunderstorm concern for today has been the main question. The
high-res guidance has continued to show development along the
front since yesterday...but during the day today the development
has trended slightly later and further south than before. This
makes sense with the quicker frontal movement. The latest runs of
the HRRR and NAMNest have also trended the development to be more
along the KS/NE border and be closer to 00z for it entering the
forecast area. Instability is abundant...why wouldn`t it be with
the heat and moisture we have, but shear remains marginal.
Thunderstorms are expected to move southeast with the front into
the evening and overnight hours...mainly impacting the southern
and southeast portions of the area. A question is how will the
overnight hours evolve in Nebraska. The latest HRRR runs indicate
that there is a potential for some development across
central/south central Nebraska towards Sunday morning.
Sunday:
What is going to happen Sunday? That is the question. Most models
indicate the potential for some scattered activity in the morning
hours and through the day, but confidence in any one solution is
low as they all are different for areal extent and location. So
covered it with low slight chances for now. The better chance for
thunderstorms Sunday will be Sunday night across much of the area.
With the frontal passage today, temps for Sunday will be much
cooler...highs in the 80s for most are expected.
.LONG TERM...(Monday through Saturday)
Issued at 414 PM CDT Sat Jul 18 2020
The first half of the work week remains under northwesterly upper
level flow aloft with weak disturbances moving across the area.
This will bring continued precipitation chances. Highs in the 80s
are expected.
Upper level ridging builds in for the second half of the work-
week. But the latest guidance indicates a decent disturbance
moving into the region late Wednesday into Thursday. This will
bring additional rain chances. Beyond that...while there are some
small chances in the forecast, think it will be dry for most.
Highs will begin to increase into the 90s for the remainder of the
work-week.
&&
.AVIATION...(For the 00Z KGRI/KEAR TAFS through 00Z Monday)
Issued at 635 PM CDT Sat Jul 18 2020
The cold front is through both terminals as of this TAF issuance.
Winds are northerly and will briefly gust over 20-25kts. Further
behind the front winds will be 10-15kts and remain northerly until
early Sunday when they become more easterly. Some thunderstorms
are possible, but confidence in timing is low. Think the primary
concern in the short term is storms south of the front which
should keep the terminals dry...but later tonight into
Sunday...there are small chances throughout the whole period.
Because confidence is not overly high, have kept VCTS to a short
period in the TAFs tonight and they will need to be watched and
amended as necessary.
&&
.GID WATCHES/WARNINGS/ADVISORIES...
NE...Heat Advisory until 8 PM CDT this evening for NEZ048-049-062>064-
073>077-082>087.
KS...Heat Advisory until 8 PM CDT this evening for KSZ005>007-017>019.
&&
$$
SHORT TERM...Billings Wright
LONG TERM...Billings Wright
AVIATION...Billings Wright
Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
903 PM CDT Sat Jul 18 2020
.UPDATE...
900 PM CDT
Dewpoints remain impressively elevated in the upper 70s to near 80
degrees early this evening, but with the loss of insolation, air
temperatures continue to slowly fall here. As a result, we
formally let the Heat Advisory go early at 8 PM, although it will
remain quite humid this evening.
Main focus for the rest of the evening and overnight is on
potential convective trends which still remain somewhat nebulous.
The KMPX sounding sampled extraordinary instability (6100 J/kg of
MUCAPE) but also still somewhat robust capping inversion around
800 mb. Since then, have started to see some renewed storm
development as the effects of continued low-level warm advection
and attendant cooling and moistening of the near-surface layer.
Guidance continues to remain split on just how expansive
convective coverage becomes up that way, and this would likely
impact the degree of cold pool amalgamation and this is important
since expansive convection could eventually support a deep enough
cold pool to allow an MCS to sag southward towards the IL/WI state
line very late tonight. Less convection would likely keep things
farther north.
A potential second area we`re monitoring is out across Iowa within
the core of the impressively steep mid-level lapse rate plume.
KOAX sampled nearly 9 C/km lapse rates in the 700-550 mb layer.
Davenport likewise sampled the eastern periphery of these lapse
rates, but also indicating rather dry air between 850 and 700 mb.
There is clearly a low amplitude shortwave out that way per water
vapor loops, and rather robust isentropic upglide has been
analyzed by the RAP along the 305-310 K theta surfaces. As this
warm advection continues to slowly lift and cool the layers
immediately under 750 mb, it`s conceivable that this allows
parcels to breach their LFC`s later this evening resulting in the
development of elevated convection. Think that a lot of the
disparity we`re seeing between the more aggressive guidance such
as the 18z/incoming 00z 3km NAM and less aggressive HRRR/RAP
stems from subtle differences in the forecast temperatures between
800-700 mb and the degree of cooling/lifting that occurs in
associated with the forecast warm advection.
All this taken together to say that things still really aren`t
clear cut at this point. Perhaps getting less concerned about an
upstream MCS charging at us from Wisconsin and more focusing on
scattered to potentially widespread (elevated) convection
developing near the river and peeling eastward into the region
very late tonight (likely well after midnight). There would
actually be a hail threat if activity does manage to develop to
our northwest given the steep lapse rate environment and
sufficient deep layer shear for storm organization, at least
initially, before storms congeal/grow upscale given the noted
boundary-parallel storm-relative anvil level and cloud-bearing
flow.
Carlaw
&&
.SHORT TERM...
301 PM CDT
Through Sunday night...
The main forecast concerns are:
- Heat indices at 100-110 through the remainder of daylight hours
(hottest south)
- Complex of storms most likely after midnight tonight with a
scattered severe/flash flooding threat through mid-morning
- Drying conditions Sunday afternoon
Gritty Details:
Currently, temperatures are in the upper 80s to around 90 with dew
points in the upper 70s. Indeed, it`s pretty muggy out there with
heat indices in the upper 90s to lower 100s at press time. The
exception is roughly along and north of I-88 where an impressively
strong MCV maintained of a complex of storms along the IL/WI border
(and even a brief supercell in De Kalb county), leading to a heavy
canopy of clouds and swath of rain-cooled air. However with no more
robust convective activity on the radar scopes (and little potential
for renewed development with strong capping in place), the low-level
cool airmass will soon mix away returning oppressive heat northward.
So while parts of the area may not reach 105-110 F levels as
previously thought, it will still feel oppressively hot with the
extreme dew points in place. All parties are strongly encouraged to
limit time outdoors, take frequent breaks, and hydrate frequently to
lessen the risk of developing heat- related illnesses.
Attention then turns to the potential for a round of showers and
storms after dark. Visible satellite and surface observations reveal
that the boundary layer is recovering aggressively across northern
Iowa and southern Minnesota as strong southerly winds advect a plume
of mid- to upper-70 degree dew points northward. At the same time, a
compact shortwave trough seen easily on water vapor imagery is
moving eastward over North Dakota. As the increasing synoptic-scale
forcing catches up to the aforementioned destabilizing airmass
across Minnesota in proximity to a surface stationary front,
vigorous renewed thunderstorm development is likely this evening.
Similar to last night, convection will likely grow upscale into a
large complex or two of heavy rain and strong wind-producing
thunderstorms in eastern Minnesota and western Wisconsin. With mid-
level thickness continues sloped south/southeastward from Wisconsin
to northern Illinois tonight, we believe initially eastward-moving
storms will make a right turn southward toward our neck of the
woods. Exact timing is still not immediately clear and will depend on
exactly how the convection develops upstream tonight, but we
anticipate storms could approach as early as midnight.
The overall severity of the storms tonight will, again, depend on
how the convection develops upstream. However, a southerly storm
motion would be less favorable for a widespread severe weather
threat given the upper-level flow will be more zonal. Even so, an
unstable low-level airmass will still promote a scattered severe
wind threat mainly with stronger embedded cores. While the
thunderstorms are expected to be relatively progressive, a localized
heavy rain/flash flooding threat may also materialize given PWATS >
2", a replenishing 40 kt low-level jet oriented right into the
complex of storms, and plenty of CAPE to enable updrafts to
squeeze out as much moisture from the atmosphere as they can.
Should the storms move southward slower than anticipated, training
echoes are a possibility.
We expected the convective activity to continue pushing southward
(in a weakening state) through the entire CWA Sunday morning
reaching Livingston/Ford/Iroquois/Benton counties before noon.
Renewed thunderstorm development is possible by early afternoon but
most likely south and east of our area as the front continues
sagging south. Thereafter, Sunday should feature decreasing cloud
cover and dry conditions. We`ll have to keep an eye on the potential
for gusty winds to develop along the backside of the thunderstorms
Sunday morning (e.g. wake low).
Borchardt
&&
.LONG TERM...
315 PM CDT
Monday through Saturday...
Less humid and a bit cooler conditions are expected over the area
in the wake of this front for Monday. Onshore winds will result
in temperatures in the low 80s near the lake, with mid 80s
inland. The threat of any storms should be primarily well to the
south of the area in closer proximity to the surface front.
The threat for more showers and thunderstorms looks to return to
the area Tuesday (perhaps later Monday night for parts of the
area) into Wednesday as the humid airmass to our south begins to
shift back to the northward in association with the approach of
another mid-level impulse. Thereafter, forecast guidance suggests
that the heat may make a return to the area to close out the work
week and into next weekend as heights aloft build back over the
the Mississippi Valley.
It looks like the late work week into weekend period would be
favored to be dry much of the time. However, similar to how
capping was not enough to prevent convection this weekend, heights
may not build quite enough late next week either. There`s a
signal for a decent short-wave to emerge to track from the
northern Plains to northern Great Lakes Thursday night through
Friday. If mid-level heights north of ridge center remain flatter
and oriented toward southeast, could make way for a greater
threat for thunderstorms into next weekend for at least portions
of the CWA, possibly including a strong/severe t-storm and
flooding risk. On the other hand, stronger ridging aloft would
keep potential MCS path to our north. Given inherent uncertainty
in this pattern, have periodic chance PoPs Thursday through Saturday.
Castro/KJB
&&
.AVIATION...
For the 00Z TAFs...
623 PM...Forecast concerns include...
Chance of thunderstorms overnight/Sunday morning.
Isolated showers early this evening.
Gusty southerly winds tonight.
Gusty west/northwest winds Sunday.
There are a few showers moving across far northeast IL late this
afternoon and this activity is expected to end/shift east in the
next few hours. Attention then shifts to convection that will
continue to develop across southeast MN/western WI and its timing
into northern IL early Sunday morning. There still remains
uncertainty regarding timing and intensity. Thunderstorms are
expected to be in a slow weakening phase as they arrive into the
terminals...though may still have a strong outflow ahead of them.
Current time window of 08Z-12Z seems reasonable but the actual
duration is likely to only be 1-2 hours and some refinement to
this time can be expected as trends emerge this evening. Once this
activity ends Sunday morning...the rest of the period appears dry
for the terminals with any new thunderstorm activity Sunday
afternoon expected to be east and south of the terminals.
South/southwest winds are expected to remain gusty into tonight
though gusts may end by late evening. Winds will shift westerly
Sunday morning and likely more west/northwest Sunday afternoon
with gusts into the lower 20kt range expected. Speeds/gusts will
diminish with sunset Sunday evening. cms
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...None.
IN...None.
LM...None.
&&
$$
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Area Forecast Discussion
National Weather Service Lubbock TX
642 PM CDT Sat Jul 18 2020
.AVIATION...
VFR conditions will prevail at all three terminals for the next
24 hours, with any TSRA activity remaining to the northwest of
KLBB and KPVW. SE surface winds at 7pm/00 UTC will gradually
swing around to the S-SW by early Sunday morning, then back to the
SE Sunday afternoon.
&&
.PREV DISCUSSION... /issued 254 PM CDT Sat Jul 18 2020/
SHORT TERM...
Chances for storms in our area are ever so slightly better...for the
northwestern South Plains. Unfortunately the rest of the forecast
area will remain dry. Dewpoints range from the mid 50s across the
western South Plains to low 60s across the northern Rolling Plains
with a broad and weak surface trough in eastern New Mexico. Main
question remains cap strength as the models are all over the place;
the RAP has no cap, the HRRR has a weak cap, and the NAM has a
fairly strong cap with all the other models showing various
strengths across the range. Even with a cap in place, there are
several models that generate convection in eastern New Mexico and
push this north and east into the northwestern South Plains. Visible
satellite is already showing some high-based CU developing between
Portales and Lovington indicating that there is a bit better surface
convergence and/or lift compared to this time the past several days.
Will continue with a low end chance PoP across the counties along
the TX/NM state line for this evening and slight chance PoP from
west of Brownfield to west of Tulia line. All models that do
generate precipitation are holding on to activity past midnight and
potentially into the mid early morning hours.
The ridge continues to slowly break down which will help cool highs
a few more degrees compared to today. Expect mid 90s across the
Caprock and upper 90s to near 100 for the Rolling Plains. The weak
surface trough will remain over eastern New Mexico and with the
ridge breaking down, showers and thunderstorms will once again be
possible in the late afternoon across the northwestern South Plains.
Models are a bit more robust in generating convection tomorrow
afternoon so will carry chance PoPs across the far southwestern
Texas Panhandle in the afternoon as opposed to holding off until the
evening hours.
Jordan
LONG TERM...
The weakness in the upper level ridge will persist through the
middle of the upcoming week which will help to sustain more
seasonable temperatures (mid to upper 90`s) across the area. Rain
chances for the upcoming week will be tied to Monsoonal moisture
interacting with a surface trough in NM. This feature will be
present through midweek before the ridge begins to strengthen back
towards the forecast area, shunting the better precipitation chances
farther west. Therefore, each evening from Sunday through Wednesday
there is at least a slight chance of showers and thunderstorms
across the southwest Texas Panhandle and western South Plains. As
would be expected under a ridge, shear values will be quite meager
however surface based CAPE values will range between 1-2k J/Kg.
Therefore, a few isolated stronger thunderstorms would be possible
with strong downburst winds as the primary threat. As stated above
for the latter part of the week, the ridge will begin to strengthen
back towards the forecast area which will lead to a slight warming
trend. How warm that warming trend will be though is dependent on
how strong the ridge becomes overhead. Yesterday the center of high
pressure was forecasted to be much farther east than models are
progging it today so obviously a bit of uncertain remains in the
extended forecast. /WCI
&&
.LUB WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
33
Area Forecast Discussion
National Weather Service Mobile AL
1022 PM CDT Sat Jul 18 2020
.NEAR TERM /Now Through Sunday night/...As the saying goes big
bubble no trouble as we remain stuck under an expansive upper
ridge of high pressure over the southeastern US. Embedded in
rather weak easterly flow is a subtle easterly wave that will move
across the area tonight into tomorrow. With the presence of this
disturbance, coverage will likely be a little more than what we
have seen over the past couple of days. Luckily, the best support
will be over our Marine areas during the morning hours with
showers and thunderstorms likely beginning off the coast. By mid
afternoon, the seabreeze will begin its slow and steady march
inland. The HRRR model appears to be the most bullish with
convection tomorrow afternoon but Master Yoda might have once said
"If one model you trust, wrong you may be." Luckily the rest of
the model guidance does support a scenario where storms will
likely initiate along the seabreeze then spread inland and west
throughout the afternoon. A strong storm cannot be ruled out
because well it`s summer, we have instability and slightly better
moisture. Storms will likely begin to subside by sunset but a few
could linger over southeastern Mississippi.
Temperatures will continue to be just awful. Highs will remaining
the mid to upper 90s across the area. The worst part is with the
upper disturbance moving through, theres slightly better moisture
which could prevent us from mixing out keeping dewpoints in the
mid 70s rather than low 70s. This means our heat index values will
likely remain around 100 to 105 through the afternoon. The only
relief tomorrow will come in the way of any storms that do
develop. Lows will remain in the mid to upper 70s. Also a little
sidenote for the nerds like me reading this. If storm cooperate
and you have clear skies to your northwest, find a dark area away
from city lights and you might catch a glimpse of comet Neowise.
The good news is that it will become higher and brighter in the
sky this week so keep on the lookout and keep the storms away.
BB/03
&&
.PREV DISCUSSION... /issued 635 PM CDT Sat Jul 18 2020/
NEAR TERM UPDATE /Now Through Sunday night/...A broad deep layer ridge of
high pressure continues to extend across the Tennessee Valley and
southeastern states this afternoon. Visible satellite imagery
shows a fairly extensive cumulus field across our region within
the moist low levels of the atmosphere. Convergence along the
seabreeze is allowing for the development of a few showers and
thunderstorms near the coast. Isolated to locally scattered
convection is expected to develop northward along the seabreeze
boundary through the afternoon and will maintain POPs around 30%
coverage into the interior northwest FL panhandle and adjacent
portions of southwest/south central AL. Forecast soundings from the
NAM/RAP indicate that MLCAPE values between 2000-3000 J/KG will be
in place along southern portions of the CWA this afternoon, while
DCAPE values may locally exceed 1000 J/KG. Isolated storm cells
could still be capable of producing brief strong/gusty winds.
Isolated cells may linger until around or shortly after sunset early
this evening, before dry conditions are anticipated overnight. The
exception could be the development of isolated showers near the
immediate coast toward daybreak.
Short range models continue to indicate a shortwave trough moving
across the northern Gulf and adjacent southwest AL/southeast MS
Sunday on the southern and southwestern periphery of the mid
level ridge axis Sunday. Moisture associated with this feature may
be a bit more enhanced across southern and southwestern portions
of our forecast area Sunday, with precipitable water values
projected to rise around or slightly above 2" over these areas.
Convective coverage may be a little more enhanced over far
southeast MS into far southwest AL along the seabreeze Sunday
afternoon, and for now will raise POPs to 40-50% over the above
mentioned areas, with 20-30% coverage further inland. The seasonably
hot and humid conditions will otherwise continue through Sunday.
Lows tonight range in the lower to mid 70s inland and in the upper
70s to around 80 near the coast and beaches. Highs Sunday should
once again range in the lower to mid 90s over interior portions of
the region and around 90 degrees near the immediate coast and
beaches. Maximum heat indices continue to range between 100-105
degrees. /21
AVIATION...
00Z issuance...VFR conditions will continue across the area with
an isolated shower or thunderstorm lingering into the early
evening hours before dissipating. Gusty winds could be possible in
the vicinity of any storms. Winds will remain light out of the
south becoming variable tonight. BB/03
PREV DISCUSSION... /issued 328 PM CDT Sat Jul 18 2020/
NEAR TERM UPDATE /Now Through Sunday/...A broad deep layer ridge of
high pressure continues to extend across the Tennessee Valley and
southeastern states this afternoon. Visible satellite imagery
shows a fairly extensive cumulus field across our region within
the moist low levels of the atmosphere. Convergence along the
seabreeze is allowing for the development of a few showers and
thunderstorms near the coast. Isolated to locally scattered
convection is expected to develop northward along the seabreeze
boundary through the afternoon and will maintain POPs around 30%
coverage into the interior northwest FL panhandle and adjacent
portions of southwest/south central AL. Forecast soundings from the
NAM/RAP indicate that MLCAPE values between 2000-3000 J/KG will be
in place along southern portions of the CWA this afternoon, while
DCAPE values may locally exceed 1000 J/KG. Isolated storm cells
could still be capable of producing brief strong/gusty winds.
Isolated cells may linger until around or shortly after sunset early
this evening, before dry conditions are anticipated overnight. The
exception could be the development of isolated showers near the
immediate coast toward daybreak.
Short range models continue to indicate a shortwave trough moving
across the northern Gulf and adjacent southwest AL/southeast MS
Sunday on the southern and southwestern periphery of the mid
level ridge axis Sunday. Moisture associated with this feature may
be a bit more enhanced across southern and southwestern portions
of our forecast area Sunday, with precipitable water values
projected to rise around or slightly above 2" over these areas.
Convective coverage may be a little more enhanced over far
southeast MS into far southwest AL along the seabreeze Sunday
afternoon, and for now will raise POPs to 40-50% over the above
mentioned areas, with 20-30% coverage further inland. The seasonably
hot and humid conditions will otherwise continue through Sunday.
Lows tonight range in the lower to mid 70s inland and in the upper
70s to around 80 near the coast and beaches. Highs Sunday should
once again range in the lower to mid 90s over interior portions of
the region and around 90 degrees near the immediate coast and
beaches. Maximum heat indices continue to range between 100-105
degrees. /21
SHORT TERM /Sunday night Through Tuesday night/...Strong upper
level high pressure centered over the Tennessee River Valley and
Southeast remains in place, weakening a bit as a series of upper
level shortwave systems pass to the north and south though the
period. A surface ridge continues to stretch west over the Southeast
through the period, bringing general southeasterly flow to the
forecast area and nearby. Guidance is advertising moisture levels
remaining at or above seasonal norms, ranging from 1.5"-2". With the
upper ridge remaining in control through Tuesday, below seasonal
chances of rain are expected each day, with isolated to scattered
afternoon showers and thunderstorms. A few may become strong to
severe, with afternoon MLCapes topping out around 2000 J/kg and DCape
values rising into the 900-1200 J/kg range each day. Add in some dry
layers above 500mb, and we will have to monitor for damaging
downburst winds.
Subsidence from the persistent upper ridge and high moisture levels
will continue to bring temperatures generally above seasonal norms.
High temperatures ranging from the mid to upper 90s inland, around
90 along the coast are expected. Low temperatures in the low to mid
70s inland, upper 70s along the coast are expected.
/16
EXTENDED TERM /Wednesday Through Saturday/...The upper ridge over the
Southeast shifts west to over the eastern Plains/Mississippi River
Valley and builds as an upper trough develops off the East
Coast. Wednesday through Thursday, guidance continues to
advertise an upper level trough moving west over the Gulf of Mexico,
on the southern periphery of the upper ridge. Today`s guidance is
advertising a bit more southerly track of the trough, with the GFS
more so than the ECMWF. Have shifted the higher likely PoPs south
as a result, placing them mainly over the open Gulf waters. Have
continued to generally place the higher PoPs over the southern
portions of the forecast area, closer to the passing system. Have
also continued to keep the lower daytime temperatures for
Wednesday and Thursday closer to the coast, with higher cloud
coverage and weaker subsidence from the passing upper trough. High
temperatures ranging from around 90 to the low 90s expected south
of Highway 84, around to upper along and north each day. Lows
remains pretty much status quo Wednesday night, with low to mid
70s expected inland, upper 70s along the coast.
Thursday night through Saturday, the ECMWF builds the upper high
farther east (along the east side the Mississippi River Valley) than
GFS (over the eastern Plains). With the 00z ECMWF ensembles and 12z
GFS ensembles advertising an in-between solutions, have went with
a blended approach. Temperatures above seasonal norms due to the
presence of the building upper ridge nearby. High temperatures
ranging from the mid to upper 90s, and around 90 along the coast
are expected, with low temperatures in the low to mid 70s inland,
upper 70s along the coast. Have went around seasonal with the
PoPs, with an upper level weakness present near the forecast area
in either solution.
/16
MARINE...No impacts forecast except winds and waves higher near
isolated to scattered thunderstorms. /21
&&
.MOB WATCHES/WARNINGS/ADVISORIES...
AL...None.
FL...None.
MS...None.
GM...None.
&&
$$
This product is also available on the web at:
http://weather.gov/mob
...Updated Aviation Forecast Discussion...
.DISCUSSION...
Issued at 305 PM CDT Sat Jul 18 2020
The main forecast concerns are potential thunderstorms over the next
few days. Heat headlines will be allowed to expire at 8 pm for
most of the area, but trimmed out parts of northeast NE to end at
6 pm where it will cool off a bit faster.
Water vapor satellite imagery, in combination with recent RUC
model initializations, showed a mid tropospheric ridge over the
southern US and a trough from Saskatchewan down toward western SD.
There was some monsoonal moisture headed our way from CO and
parts of western NE. Surface analysis showed the cold front, which
will be pushing through the area tonight, extending from a low
pressure center over southeast SD back southwest into northeast CO.
Dewpoints ahead of the front were in the 70s, but a little lower
than they were yesterday - due to mixing and more of a downslope
component of the southwest winds.
Tonight.
Will keep some slight chance to chance category POPs going for the
area. Will decrease these late this evening in northeast NE but
then go back to a slight chance after midnight. There is a fairly
large spread of model outcomes looking at the various high
resolution model output. Mid level temperatures remained quite
warm from the 700 mb 12Z plot this morning (values 13-17 C across
NE and southern SD). Some mid level cooling will take place as
the shortwave trough to our north tracks eastward tonight. The
atmosphere will be quite moist, with Precipitable Water (PW)
values around 2 inches or more along and ahead of the cold front.
Severe weather chances look fairly low, with SPC keeping us in the
Marginal risk - and that seems appropriate. Low temperatures
should be in the mid to upper 60s in northeast NE, but upper 60s
to mid 70s for southeast NE and southwest IA.
Various model solutions exist for potential showers and
thunderstorms on Sunday. Confidence is average to below average.
Based on output from RAP13, High Res ARW and some others, will
keep low POPs in southern and western parts of the area at least
in the morning. Highs Sunday afternoon should reach 84 to 89.
Sunday night into Monday night.
As mentioned yesterday, this should be a wetter period than what
we have had for a while. Frontal boundary to our south will try to
lift north Sunday night with deeper moisture and a weak to
moderate low level jet. Will increasing rain chances from south to
north during the night. Rain amounts could reach up to half an
inch. Continued advection of a warm and moist airmass on Monday
may lead to pockets of heavy rain and this should keep afternoon
temperatures down, with highs in the upper 70s and lower 80s.
A continued unsettled pattern continues for Monday night into
Tuesday. The 12Z GFS keeps the strongest low level jet across KS
and tries to focus heavy rain potential mainly in southeast NE and
southwest IA. Kept highest POPs in those areas, with a decrease
down into the 20 to 30 percent range for Tuesday afternoon. Highs
Tuesday are expected to reach the lower and mid 80s.
Wednesday into Saturday.
It still appears that a mid level ridge will try to rebuild over
the south central and southeast US for the mid and later part of
the week. This will shift the higher chances for rain to the
north of our area. Temperatures should slowly warm, reaching back
into the lower and mid 90s by Friday into Saturday.
&&
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 622 PM CDT Sat Jul 18 2020
VFR conditions are expected through much of the TAF period with a
cold front bringing a wind shift to the northwest behind it. This
front has already passed through KOFK and is forecast to move
through KOMA and KLNK by 03z. Gusts behind the front up to 15 to
20 kts can be expected but should diminish after 06z.
Scattered showers may move across the TAF sites through the period
but this is still somewhat uncertain as much of the radar returns
remain aloft with little to no precipitation hitting the ground. A
few isolated thunderstorms are possible south of KLNK after 04Z
but are not expected to impact the TAF site.
&&
.OAX WATCHES/WARNINGS/ADVISORIES...
NE...Heat Advisory until 8 PM CDT this evening for NEZ015-018-031>034-
042>045-050-051-065-078-088>093.
Excessive Heat Warning until 8 PM CDT this evening for NEZ052-
053-066>068.
IA...Heat Advisory until 8 PM CDT this evening for IAZ043-055-056.
Excessive Heat Warning until 8 PM CDT this evening for IAZ069-
079-080-090-091.
&&
$$
DISCUSSION...Miller
AVIATION...Kern