Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 07/27/20
Area Forecast Discussion
National Weather Service Amarillo TX
628 PM CDT Sun Jul 26 2020
.AVIATION...
Several areas of cumulus development this afternoon in response to
afternoon heating and dewpoints in the upper 50s. Most of the
clouds are struggling to break through the cap, which mesoscale
models suggest are around 7 degrees C around 10Kft. The cap is a
bit weaker to the far northwest, and that is where we see some
convective showers beginning to develop near the TX/NM state line
just south of Clayton. Given the cap strength, would expect the
storms today to be quite confined to the north and northwest until
a front or other lifting mechanism is present.
The lifting mechanism will be the awaited cold front, currently
expected into the area early Monday. At 23Z, the cold front is
located in northwest Kansas / northeast Colorado and will be
making slow and steady progress through the evening. By mid
morning, between 12Z and 18Z Monday, there will be enough showers
or thunderstorms around to warrant at least Prob30 groups within
each terminal forecast. Thunderstorm chances will become a bit
more widespread during the day on Monday, and are expected to last
into Monday night and even Tuesday. For the short term, flying
conditions will be decent for the next six to 12 hours, before
deteriorating conditions after that.
Fox
&&
.PREV DISCUSSION... /Issued 408 PM CDT Sun Jul 26 2020/
SHORT TERM...Tonight through Monday Night...
Difficult forecast over the next 24-48 hours. Visible satellite
this afternoon shows quite a bit of cloud cover over the area with
cumulus filling in everywhere. We already have some pop up showers
over eastern Oldham/western Potter Counties. The HRRR has been on
it lately and picking up on these little pop up showers. Expect
more to pop up by 3pm through the central Panhandles and die off
around 6-7pm. Satellite is also showing the thicker cloud cover
over New Mexico associated with the tropical moisture from Hanna
as it is circulated around the mid-level high pressure over the
eastern Panhandles/western OK. The tropical moisture will continue
filling into the area and interact with disturbances rotating
around the high pressure, the mountains in New Mexico, and a cold
front that is progged to push into the area tonight. All these
features will create repeated rounds of precip for on and off
showers. We have already seen the need for several issuances of
flooding products over the last few weeks due to the rain rates
with the pop up showers, so with the PWATs running extra high and
near record with the tropical moisture, wouldn`t be surprised for
the showers to produce significant rain rates to cause flooding
issues. The front will add extra lift and any mid-level disturbances
will be an added bonus to create enhancements to the precip. The
difficult part of the forecast is what to do with the front and
the location of these enhancements. The models want to hang the
front in the middle of the Panhandles. Feel the cold pool with the
storms will likely move the front further south and not hang it
up, so tried to progress the pops Monday afternoon. The position
of the front and other mesoscale features such as how the Canadian
River Valley or being off the Caprock will play a roll in where
the higher precip totals will be. May need to do significant
updates depending on how the front plays out. Believe no matter
how the front moves, there is going to be quite a bit of precip
with significant enough rain rates that a Flash Flood Watch is
warranted for tomorrow afternoon through the night.
Beat
LONG TERM...Tuesday through Sunday.
For Tuesday and Tuesday night, plenty of moisture should continue
to reside over the forecast area. The upper level ridge of high
pressure will remain over the southwest states, placing our region
in west northwest flow aloft. A minor upper level shortwave trof
embedded in the flow pattern is progged to translate east across
the area Tuesday and Tuesday night, and should lead to another
round of showers and tstms. Highest pops were placed across the
far northwest sections with lowest values in the far southeast
Texas Panhandle during this time period. Residual showers and
tstms with far less coverage is anticipated Wednesday and Wednesday
night as the aforementioned minor upper level shortwave trof moves
east of the region.
For Thursday through Sunday, the upper level ridge of high pressure
is forecast to meander around the four corners region during this
time frame as seen in latest medium range models. At the same
time, an upper level trof of low pressure is progged to develop
over the eastern states. This is a continuation of the northwest
flow aloft, with a threat for late afternoon and nighttime showers
and thunderstorms Thursday through Sunday. The NBM pops during
this time period look reasonable and were utilized, with a slight
edge upward Thursday night as values looked a bit low given the
expected pattern.
02
&&
.AMA Watches/Warnings/Advisories...
TX...Flash Flood Watch from Monday afternoon through Tuesday morning
for the following zones: Armstrong...Carson...
Collingsworth...Dallam...Deaf Smith...Donley...Gray...
Hansford...Hartley...Hemphill...Hutchinson...Lipscomb...
Moore...Ochiltree...Oldham...Palo Duro Canyon...Potter...
Randall...Roberts...Sherman...Wheeler.
OK...Flash Flood Watch from Monday afternoon through Tuesday morning
for the following zones: Beaver...Cimarron...Texas.
&&
$$
14/11
Area Forecast Discussion
National Weather Service La Crosse WI
632 PM CDT Sun Jul 26 2020
.SHORT TERM...(This evening through Monday)
Issued at 154 PM CDT Sun Jul 26 2020
Surface analysis at 1 pm has a cold front sagging southeast,
currently extending from central WI into northeast IA. Radar
pretty quiet right now but expecting a broken line of
showers/storms to form along the cold front as it progresses
southeast through the rest of the area. So, storms this afternoon
into this evening look to be confines mainly south of a Richland
Center/Boscobel WI to Elkader IA line. MLCape is around 2000J/kg
range now and expected to top off in the 2000-3000j/kg as the
front pushes through. Bulk shear fairly modest with RAP effective
bulk shear around 20kt. So, not expecting much for severe weather
but could see a few stronger storms with higher wind gusts and
very heavy downpours given very warm/humid airmass.
Front and associated storms expected to push south of the area
this evening as refreshing Canadian high pressure pushes in.
Cooler/much drier airmass over the area through Monday with
northwest winds in the the 10 to 20 mph range. Look for highs
Monday in the upper 70s to lower 80s with dewpoints in the mid-50s
to near 60...ahh!
.LONG TERM...(Monday night through Sunday)
Issued at 154 PM CDT Sun Jul 26 2020
For those that did not get some rain this weekend, the prospects
are not looking good over the upcoming week. The upper level low
currently over central Manitoba will track slowly to the east
allowing the upper level ridge to build back over the northern
Rockies into the High Plains. This looks to leave the Upper
Midwest under a relatively quiet northwest flow. What little rain
chances there will be are centered on Thursday and Saturday. A
weak short wave trough may pass across the Great Lakes region
Thursday with the 26.12Z GFS showing a little bit of rain along a
weak cold front coming through with the short wave trough. The
26.12Z ECMWF is farther to the southwest with the short wave
trough which keeps the rain farther to the southwest as well. By
Saturday, another weak short wave trough and cold front look to
pass across the region. Again, some differences between the models
on the placement of the short wave trough and how much rain may
occur across the area. With the northwest flow aloft, there does
not look to be any big warmups coming in the next few days. Look
for daytime highs to generally be in the upper 70s into the 80s
with overnight lows mainly in the 50s to lower 60s.
&&
.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
Issued at 622 PM CDT Sun Jul 26 2020
The bulk of the storms have pushed off to the southeast and winds
turned to the northwest at 6 to 12kts. The cold front could
increase winds for an hour or so with some high gusts to around
15 to 20kts. Any showers/storms will be isolated with the cold
front and mvfr conditions patchy ahead of the front. Continued
deepening of the mid-level trough Monday and very steep lapse
rates favor mixing with northwest wind increasing to 12kts gust to
24kts. Some sct-bkn cumulus fl050-060 and pop-up showers possible
20-24Z.
&&
.ARX WATCHES/WARNINGS/ADVISORIES...
WI...Heat Advisory until 7 PM CDT this evening for WIZ054-055-061.
MN...None.
IA...Heat Advisory until 7 PM CDT this evening for IAZ010-011-029-030.
&&
$$
SHORT TERM...DAS
LONG TERM...04
AVIATION...Zapotocny
Area Forecast Discussion
National Weather Service Denver/Boulder CO
740 PM MDT Sun Jul 26 2020
.UPDATE...
Issued at 732 PM MDT Sun Jul 26 2020
Most of the shower and thunderstorms activity has been confined to
the southern third of the forecast area, primarily south of
Interstate 70. Have dropped the pops to mainly isolated coverage
north of the interstate, with mainly scattered coverage to the
south. Latest HRRR shows an increase in showers over the northeast
corner of the state late tonight so will keep pops going there.
Have also added fog to the northeast plains after 3 am.
&&
.SHORT TERM...(This evening through Monday)
Issued at 321 PM MDT Sun Jul 26 2020
Shower activity over the forecast area has been increasing over
the past couple hours with the heaviest showers up to this point
over Park and Lincoln Counties. The surface cold front has moved
over the Palmer Divide and will become a focus for additional
shower development through this evening. The airmass remains very
moist with precipitable waters above 1 inch and surface dew points
in the upper 50s to mid 60s. Locally heavy rain will be possible
with showers that develop over the frontal boundary. one to two
inch amounts over one to two hour periods will be possible.
Antecedent conditions should be dry enough to handle the rainfall,
so no Flash Flood watches at this point. Local advisories or
warnings may be necessary if evening thunderstorms stall. Shower
activity should be on the decrease after midnight.
Later tonight, continuing moist upslope winds will produce areas
of stratus and fog in the South Platte River Valley. Later
tomorrow, moisture is expected to linger over the mountains and
Palmer Divide, but some drying and cooling is expected over the
northeast plains as weak northeasterly flow continues in the wake
of today`s frontal passage. As temperatures remain the upper 70s
and lower 80s, the airmass will be too stable for very much
shower development.
.LONG TERM...(Monday night through Sunday)
Issued at 321 PM MDT Sun Jul 26 2020
Lingering showers and tstms Mon night will be mainly focused over
the higher terrain along and south of I-70. This activity will end
by midnight.
Looking ahead to Tue, an upper level trough will move across the
area. This feature has fairly decent mid level ascent, with it,
for this time of the year. As a result, expect widespread showers
and storms over the higher terrain with activity spreading across
the plains in the aftn and evening hours. MLCAPE over the plains
is in the 500-1000 j/kg range and with increasing shear, late in
the day, could see some stronger storms. As for highs, readings
will be in the 80s over nern CO.
For Tue night into Wed, the upper level trough will eventually
develop into a closed low over Wyoming. Cross-sections show
decreasing moisture over the higher terrain so only expect isold
to widely sct tstms. Over nern CO, a lee trough will be over the
plains with decent instability over the far nern plains. So this
area will probably have the best chc of tstms. As for highs,
readings will range from the mid 80s to lower 90s across the
plains.
By Thu, the upper low will move southeast into Nebraska, with
rather stg subsidence over the area. Cross-sections show some
moisture mainly over the far ern plains. Not sure why blended
solution is showing chc pops over the higher terrain based on
current data. Meanwhile, depending on the position of the upper
level low, there could be some threat of showers and storms over
the far ern plains. As for highs, a front may affect nern CO
which would keep highs mainly in the 80s.
Looking ahead to Fri, the upper level low will continue to move
slowly southeast and be over ern KS. Cross-sections show a rather
dry airmass over the area which would keep any tstm activity rather
limited. Meanwhile will keep highs near seasonal normals.
For Sat an upper level ridge will begin to build into the area from
the swrn US. This would lead to warmer temps along with only a
slight chc of tstms.
&&
.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
Issued at 732 PM MDT Sun Jul 26 2020
Weak upslope flow will probably generate areas of stratus and
possibly fog around the Denver area and up the South Platte River
valley after 4 am. IFR ceilings and visibilities may occur from
about 4 AM through 8 or 9 AM Monday morning. Southerly winds
developing after sunrise tomorrow should begin clearing out the
stratus by late morning. VFR by midday with a chance of showers in
the afternoon. Isolated thunderstorm at best so vcsh will suffice
in the terminals for Monday afternoon.
&&
.BOU WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
UPDATE...Cooper
SHORT TERM...Dankers
LONG TERM...RPK
AVIATION...Cooper
Area Forecast Discussion
National Weather Service Austin/San Antonio TX
634 PM CDT Sun Jul 26 2020
.AVIATION...
A few widely scattered showers this evening across the area as well
as occasional thunder could potentially impact the San Antonio sites
through about 02Z before the loss of daytime heating leads to these
cells dying off. Expecting VFR conditions to deteriorate to MVFR at
the I-35 sites late tonight with IFR cigs likely at AUS, and some
light fog can`t be ruled out there either. For SAT/SSF, IFR cigs are
possible but less certain, and at DRT VFR conditions are likely to
prevail although cigs may come near thresholds late tonight into
Monday morning so a brief period of MVFR cannot be completely ruled
out. Should see the usual improvement by mid- morning (15-16Z). A
few redeveloping showers will again be possible during the day
Monday.
&&
.PREV DISCUSSION... /ISSUED 219 PM CDT Sun Jul 26 2020/
SHORT TERM (Tonight through Monday Night)...
Deep tropical moisture continues to stream over South Central Texas
as Tropical Storm Hanna moves westward into northeastern Mexico.
Pwat values of 2.0 to 2.4 inches have pooled over much of the region
and daytime heating has reinvigorated the outer and far reaching
rain bands of Hanna. Storms seem to be generating along the coast
and over the Coastal Plains, likely from frictional convergence, and
push further into the CWA as light to moderate rain showers. Bands
of rain have been quick moving throughout the day. So even under the
heaviest rain showers, certain isolated areas have only picked up
about 2 inches of rain.
High resolution guidance have some disagreement on handling
convection later this afternoon with the NAM NEST showing a lull in
activity till daytime heating gets going tomorrow but the latest 18Z
HRRR and Texas Tech WRF show continued isolated activity through
this evening. Keeping rain/storm chances in the forecast for much of
the area given the sporadic nature of showers and storms the last 36
hours. Trimming back chances for rain overnight to areas along and
south of I-10 and US 90.
Moisture values remain elevated through the day on Monday but
coverage of showers and storms should be less than what was seen
today. Less cloud cover and less chances for rain will spell a bump
back up in afternoon temps into the mid 90s, far southern zones may
only make it to the upper 80s or low 90s with better chances for
rain.
Upper level pattern will remain slightly unstable with the
subtropical ridge attempting to build in from the Desert Southwest
but not close enough at the end of the long term to have any
dominate features of the weather pattern.
LONG TERM (Tuesday through Sunday)...
Afternoon rain chances continue for Tuesday and Wednesday before the
upper ridge gets hold of the area on Thursday. While under upper
ridging, the forecast becomes dry and a warming trend ensues. The the
end of the week and into the weekend, temperatures have crept back up
to the triple digits for a good part of the area.
&&
.PRELIMINARY POINT TEMPS/POPS...
Austin Camp Mabry 74 95 75 93 76 / 20 30 - 20 -
Austin Bergstrom Intl Airport 74 94 74 93 75 / 20 30 - 20 -
New Braunfels Muni Airport 74 93 74 92 74 / 30 40 10 30 -
Burnet Muni Airport 72 93 73 93 74 / 20 20 - 20 -
Del Rio Intl Airport 74 95 76 96 76 / 30 30 20 20 10
Georgetown Muni Airport 74 94 75 94 76 / 20 20 - 20 -
Hondo Muni Airport 73 94 74 95 75 / 30 30 10 30 10
San Marcos Muni Airport 74 93 74 93 74 / 20 30 10 30 -
La Grange - Fayette Regional 75 94 76 94 76 / 20 40 20 30 -
San Antonio Intl Airport 75 94 76 94 76 / 30 40 10 40 10
Stinson Muni Airport 74 93 75 93 76 / 30 40 10 30 10
&&
.EWX WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
Short-Term/Aviation...KCW
Long-Term...04
AREA FORECAST DISCUSSION
National Weather Service Sioux Falls SD
610 PM CDT Sun Jul 26 2020
.SHORT TERM...(This Evening through Monday)
Issued at 239 PM CDT Sun Jul 26 2020
Mid afternoon surface observations show a weak cold front is
situated roughly from Spencer to Sioux City Iowa and continues to
progress southeast through the region. Radar and satellite imagery
show an area of showers and storms developing with a weak shortwave
disturbance across western NE, and some scattered showers and storms
along and ahead of the front. Did keep slight chances of showers and
storms across a portion of northwest IA to account for this and/or
any additional isolated showers or storms developing before the
front progresses southeast out of the forecast area. The latest few
HRRR runs suggest activity across NE will progress eastward toward
east central NE and west central IA this evening, remaining south of
the forecast area. Suspect the majority of the region will remain
dry through the rest of the afternoon and evening with decreasing
clouds overnight.
The axis of the upper trough tracking east through the Canadian
prairie provinces will progress through the Northern Plains tonight,
spreading notably drier air into the region for a pleasant Monday.
The passage of the upper trough places the region in drier and
milder northwest flow aloft. Dew points will fall to a more
comfortable mid 50s to lower 60s by morning (vs 70s from the
weekend). Surface high pressure will build through the forecast area
overnight, resulting in lighter winds for at least early Monday.
Expect a mild day with highs to reach the 80s for most locations
under abundant sunshine.
.LONG TERM...(Monday Night through Sunday)
Issued at 239 PM CDT Sun Jul 26 2020
No impactful weather is expected until at least Wednesday as drier
northwest flow aloft persists. For Tuesday and Wednesday, southerly
flow and weak warm air advection develop, continuing high
temperatures in the 80s to near 90 degrees. These days may gradually
feel warmer as dew points creep back into the mid to upper 60s and
perhaps lower 70s.
For Wednesday night through Friday, there is good model agreement in
a broad upper level trough digging into the central U.S. in
northwest flow aloft. This system brings increased cloud cover and
periodic chances for showers and storms, but there is significant
uncertainty in the timing and general progression of the system.
Ensemble guidance favors lower rainfall amounts for the late week
period, less than a quarter inch on any given day for most
locations. Some solutions have very little to no rain during this
period. Thus late in the work week doesn`t look to be a total wash
by any means, as the bulk of the precipitation is favored to track
well south of the forecast area this point. Temperatures late week
are expected to remain near normal values with highs in the 80s, but
cloud cover and timing of the precipitation will bring some day to
day subtle variations.
&&
.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
Issued at 610 PM CDT Sun Jul 26 2020
VFR conditions expected through the period. North-northwest winds
will prevail at or below 10kt through mid-morning Monday, with
occasional gusts nearing 20kt in southwest Minnesota at times
Monday afternoon.
&&
.FSD WATCHES/WARNINGS/ADVISORIES...
SD...NONE.
MN...NONE.
IA...NONE.
NE...NONE.
&&
$$
SHORT TERM...BP
LONG TERM...BP
AVIATION...JH
Area Forecast Discussion
National Weather Service Goodland KS
538 PM MDT Sun Jul 26 2020
.SHORT TERM...(This evening through Monday)
Issued at 1259 PM MDT Sun Jul 26 2020
18Z Surface observations and RAP analysis indicated pre frontal
trough across the southeast corner of the forecast area.
Observations as well as visible satellite indicate cold front
steadily advancing south and was located between Wray and St
Francis.
Main concern will center around heavy rain through this evening
and potential for localized flooding.
Morning raobs continue to indicate near record values of
precipitable water in place all around the area. The ample
moisture combined with relatively deep warm layer and slow storm
motions some what parallel to initial forcing provides a good set
up for very efficient, heavy rain producing thunderstorms.
Already have convective initation along trough and with continued
forcing along front expect storms to steadily increase in
coverage through the afternoon. While the initiation points are
somewhat apparent, CAM`s suggest that once storms start, new
development will be heavily driven by new outflows which will
really lower the predictability with respect to location as storms
evolve. Stayed closely to HREF mean representation of
precipitation evolution but expect the details will remain
somewhat murky. With very favorable environment and low FFG
values, flash flood watch looks to be in good shape with the most
likely area highlighted. Rest of the area should be on lookout for
flash flooding as well as environment favorable over much of the
area.
As colder air works into area tonight, expect storms to gradually
shift to the south through the overnight and morning hours.
Atmosphere remains unstable to near sfc parcels through the night
however, so storms may linger much longer than usual. Fog, low
stratus and cooler temperatures will build into the area in the
morning which will diminish precipitation threat. Atmosphere
becomes capped through at least 22Z, so do not expect a lot of
redevelopment, if any, until late afternoon.
.LONG TERM...(Monday night through Sunday)
Issued at 135 PM MDT Sun Jul 26 2020
Long range guidance suggests that WNW to NNW flow aloft will
prevail over the Central/Northern Plains in this period -- on the
N-NE periphery of an amplifying upper level ridge over the Desert
Southwest/Intermountain West. A variety of small amplitude waves
and/or convectively generated features may be present within WNW-
NNW flow aloft over the Central/Northern Plains this week... none
of which can confidently be anticipated at this range. With the
above in mind, significant forecast uncertainty persists...
particularly with regard to precipitation chances (i.e. location/
timing/coverage/evolution of convection).
&&
.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
Issued at 508 PM MDT Sun Jul 26 2020
Expect TSRA at GLD through about 07Z with a transition from VFR to
MVFR due to low ceilings and visibility by 07Z that may include
intermittent LIFR due to lower ceilings between 11-13Z. MVFR
conditions will improve to VFR again after 19Z Monday.
MCK will see a few light showers and thunderstorms with VFR
conditions through 09Z. Ceilings will lower to produce MVFR
conditions after 09Z with intermittent IFR conditions between
11-14Z. Expect a return to VFR conditions after 18Z Monday.
&&
.GLD WATCHES/WARNINGS/ADVISORIES...
KS...Flash Flood Watch through Monday morning for KSZ003-004-014>016-
028-029.
CO...NONE.
NE...NONE.
&&
$$
SHORT TERM...JRM
LONG TERM...VINCENT
AVIATION...LOCKHART
Area Forecast Discussion
National Weather Service Indianapolis IN
1134 PM EDT Sun Jul 26 2020
.UPDATE...
The AVIATION section has been updated below.
&&
.SYNOPSIS...
Issued at 400 PM EDT Sun Jul 26 2020
A cold front will move into the region Monday, bringing showers
and thunderstorms to the area. This boundary will settle into the
Ohio Valley and remain there for much of the week, producing
chances for thunderstorms many days, with the highest chances in
the south. The front will bring a welcome reprieve from the recent
heat to the area.
&&
.NEAR TERM /Tonight/...
Issued at 400 PM EDT Sun Jul 26 2020
Most of the night should be quiet across central Indiana. There is
some hint from the HRRR that weakening convective activity could
sneak into northwestern portions of the area late tonight, and
will carry some very low pops to account for this. Otherwise,
expect mainly a gradual increase in mid and high cloud overnight.
NBM temps appear reasonable and were generally accepted. Should
see temps drop only into the low 70s overnight owing to increasing
cloud cover and high dewpoints.
&&
.SHORT TERM /Monday through Wednesday/...
Issued at 400 PM EDT Sun Jul 26 2020
Main focus during the short term will be on Monday. Expect
widespread convective activity along the front as it slowly moves
through the area tomorrow. Instability should be plentiful, but
shear will be quite modest at best. Primary convective mode should
be disorganized multicell clusters...and the primary threat will
be isolated downbursts/damaging wind gusts. Precipitation
efficiency should be fairly high with a freezing level around
14kft and precipitable water values potentially in excess of 2
inches...or nearing plus 2 standard deviations for the time of
year. Given the relatively weakly sheared environment, there will
be a threat for flooding.
Most thunderstorm activity will be south of the area by Tuesday
morning. Will have to maintain low pops Tuesday but this is
primarily on the chance that some activity near the boundary
manages to sneak into our far south. Looks as though most of the
area will be dry Tuesday into Wednesday.
Temps look reasonable and required only minor adjustments through
the period.
&&
.LONG TERM /Wednesday Night Through Sunday/...
Issued at 212 PM EDT Sun Jul 26 2020
The frontal system that is expected to move through the area
tomorrow and stall Tuesday will slowly meander for much of the
week. This front will interact with several weak upper level waves
to bring isolated to scattered showers and thunderstorms.
Confidence is fairly low in precipitation at any time, but is
highest in the southern counties where the frontal system is more
likely to be based on latest model guidance.
A more substantial upper level wave is possible this weekend which
could bring more widespread rain to the area. With northwesterly
flow through the week, temperatures will be below average.
&&
.AVIATION /Discussion for 27/06Z TAF Issuance/...
Issued at 1134 PM EDT Sun Jul 26 2020
A cold front is expected to approach KLAF from the northwest after
21z. The front will interact with a hot and humid air mass and
result in numerous MVFR or worse thunderstorms after 14z. Otherwise,
good confidence in dominated VFR conditions tonight.
Winds will start off southwest tonight and shift to the west after
21z. Wind speed with be around 10 knots much of the time with higher
gusts in thunderstorms.
&&
.IND WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SYNOPSIS...Nield
NEAR TERM...Nield
SHORT TERM...Nield
LONG TERM....White
AVIATION...MK
Area Forecast Discussion...UPDATED
National Weather Service Chicago/Romeoville, IL
958 PM CDT Sun Jul 26 2020
.UPDATE...
955 PM CDT
The loosely-defined, more outflow-driven MCS has gradually
weakened as it has progressed southeast in our area. Some gusts
with the outflow moving over far northwest Indiana and the
southern Chicago suburbs are still 30+ mph, but these will
continue to ease as they approach the Kankakee River Valley. On
the southwestern periphery of this once MCS, there has been re-
developing convection where 25-30 kt of 850-925mb flow (as sampled
on the 00Z DVN sounding) is offsetting the weakening cold pool
push. This has resulted in training convection over southern Lee
and northern LaSalle Counties. Radar estimates of over 2 inches of
rain, and at least one private gauge, has indicated this since
830 pm. Some flash flood guidance values are over 100 percent for
parts of that area, but considering the more rural area and not
extremely wet recently, have issued a Flood Advisory for now for
mainly expected localized/minor flooding impacts. This should
gradually sag east-southeastward after 11 PM.
Otherwise going into the overnight, some warm advection aloft
above 850 mb will continue impinging on and above the outflow
boundary. The air mass will remain moist as the cold front is
still well upstream (not passing until late morning/early
afternoon), and there will be ample MUCAPE (>1500 J/kg). In
addition there will be general lift from the right entrance region
of a 100+ kt upper jet over the northern Great Lakes. However,
there is not a well defined short wave, and the true low-level jet
looks to be largely cut off by the broad swath of convection over
Kansas into southern Nebraska and southwest Iowa.
MTF
&&
.SHORT TERM...
208 PM CDT
Through Monday night...
It`s definitely a hot and humid one out there this afternoon with
dewpoints pretty homogeneously in the 74-77 degree range, although
quite a bit lower across the more urbanized Chicago corridor owing
to the increased/deeper mixing there. With the injection of this
additional moisture (and through a not unsubstantial depth),
cumulus has been percolating over the last hour or two. Noting a
few areas of somewhat more agitated development where near-surface
convergence is maximized, as well as an area from near Lincoln to
Fowler where moisture is even a bit higher (dewpoints in the
upper 70s to near 80 degrees). We`ll get some area-wide 20% PoPs
going here by 3-4 PM, although coverage at least through 5 PM or
so across most of the area may remain more of the 10-20% variety
when taken as a whole.
An outflow boundary exhausted from overnight/early-morning
convection to our north has washed out quite a bit with the strong
mixing chewing away at the shallow cold pool. Still, this feature
appears to be evident in visible satellite imagery approaching a
Cedar Rapids-Madison line with another more defined convergence
axis about 30 miles farther northwest from there. We are
effectively uncapped area-wide now, so any subtly enhanced
convergence near these approaching boundaries or more developed
Horizontal Convective Rolls could serve as a focus of initial
isolated-scattered thunderstorm development through the rest of
the afternoon. Latest thinking here is that we like the look of
the 12z 3 km NAM, but just sped up by an hour or two based on the
location of the upstream convergence axes with the other hires
members trending more towards a solution we`d expect given the
amount of instability present--even though we`re somewhat lacking
in the large scale forcing for ascent department. 18z SPC
Mesoanalysis plots depict DCAPE values have diurnally-built north
of 1000 to almost 1500 J/kg in spots. This, combined with 0-3 km
theta-e deficits approaching 35 K will support at least an
isolated gusty/damaging wind threat into this evening. Should
convection amass into a sufficiently robust complex to our north
(and latest indications do point to that being a distinct
possibility), this could locally enhance the gusty wind potential
for our northwestern locales northwest of a La Salle to Evanston
line and this is nicely demarcated by the most recent SPC Day 1
outlook.
Given the dearth of faster mid-level flow (and any deep layer
shear really oriented boundary-parallel), any hint at cold pool
development would allow an outflow boundary to relatively quickly
surge south and eastward this evening with limited potential for
additional storm organization. As such, any localized severe
threat should wane with time towards the midnight hour, and
thunderstorm chances will commensurately follow on a downward
trend.
What happens very late tonight and into Monday morning remains a
little unclear given the most recent CAM guidance. Coarse-
resolution guidance is in good agreement that upper jet divergence
will actually start to increase towards 5-7 AM on Monday within a
still richly-moist airmass with the cold front probably just
entering northwest Illinois. RAP guidance develops quite a bit of
dry air in the 850-700 mb layer, while the ECMWF and others remain
more saturated during this period. As such, suspect we may see
some renewed development or at least some "festering" of lingering
showers/storms. Don`t necessarily like the look of the NAM trying
to lay out convection west-to-east during this period but, unlike
the situation south of Minneapolis last night where training
convection produced upwards of 6-8" of rain, we really don`t see
indications of the 925-850 mb flow strengthening or backing
sufficiently to support a big blob of low-level warm advection
atop whatever composite outflow/frontal boundary may be nearby.
With this in mind, have attempted to inflate PoPs a bit very late
tonight and into Monday morning with a continued message of a
threat for locally heavier rainfall corridors.
Drier air will finally invade through the afternoon hours, but
we`ll likely continue with showers/storms at least south and east
of I-55 into the mid-afternoon hours. Main instability axis looks
to push just southeast of our area, likely limiting any severe
threat but sporadic gusty winds will certainly be possible within
any more precip-loaded downdrafts.
Clearing and more quiescent conditions roll in for Monday night. A
lingering slight breeze through the night may ultimately help hold
temperatures up a bit, but wouldn`t be surprised to see some mid-
upper 50 degree readings near out outlying/typical cool spots.
Carlaw
&&
.LONG TERM...
229 PM CDT
Tuesday through Sunday...
Generally dry conditions with more seasonable temperatures are
expected through much of this period as broad troughing drifts
east across Ontario and Quebec this week. Weak low-level WAA from
northern Iowa into northern Ohio late Tuesday afternoon through
Wednesday will act on a pocket of Pacific moisture with some
enhancement from the Gulf of Mexico. Have opted to keep the
forecast dry during this time with the expectation of very low
coverage with enhanced cloudiness.
A more pronounced trough axis rotating south around the eastern
Canadian trough will interact with a group of troughs meandering
across the Rockies and southern Great Plains, including some of
the remnants of/moisture from Hurricane Hanna, will interact with
the northern trough across the Ohio River Valley by Thursday. The
northern fringes of the resultant system may affect southern
portions of the CWA late Wednesday night into Thursday night.
Meanwhile, stronger north to northeast winds in a weakly stable
environment over Lake Michigan Thursday into Friday will promote
increased wave action and potentially dangerous swim conditions
for the IL/IN beaches.
Troughing then builds back into the region for the weekend with
the potential for a weak embedded shortwave bringing a focused
period of precip chances, but given model differences and an
increasingly complex pattern across the CONUS, targeting a
specific period (if there is one) is not possible at this time.
Kluber
&&
.AVIATION...
For the 00Z TAFs...
The concerns for the Chicago area airports are:
- Gusty storms for a 1-2 hour evening period, with the likelihood
of gusty outflow reaching 30-60 minutes prior to the storms
- Gusty southwest winds turning northwest with the storms, then
becoming light west-southwest into overnight before turning
northwest on Monday late morning
- Chance for showers and MVFR ceilings Monday morning
- Chance for a lake breeze at MDW later Monday afternoon
An area of semi-organized storms in southern Wisconsin to
northwest Illinois will move slowly southeast through the evening
and is expected to have a gradual weakening trend. This is
outflow-dominant, in that it is pushing rain-cooled air out ahead
of it, with gusts to 25+ kt possible with just this outflow.
Underneath the storms themselves some gusts to 35 kt are possible
at ORD and MDW and likely at RFD. Also rainfall rates under any of
these storms, despite weakening, should present some brief
visibility into the IFR category. Confidence on storm trends and
timing in the TAFs is medium-high.
Behind the main area of storms, scattered showers are likely to
linger. There are signs that showers may pick up some very late
tonight into early-mid Monday morning. Confidence on that is low,
but the signal for thunder during that time is also on the lower
end. Patches of MVFR ceilings seem probable tonight into Monday
morning, but the signal has diminished.
After the wind effects of the evening storms, winds will turn
west-southwest for a period overnight and mainly light. With a
cold frontal passage Monday morning, the winds will then turn
northwest with some sporadic gusting likely in the afternoon. A
lake breeze will develop, mainly into northwest Indiana, but some
of northeast Illinois within a few miles of the shore will see the
wind shift and it may reach MDW later in the afternoon.
MTF
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...None.
IN...None.
LM...None.
&&
$$
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Area Forecast Discussion
National Weather Service Paducah KY
522 PM CDT Sun Jul 26 2020
.UPDATE...
Issued at 518 PM CDT Sun Jul 26 2020
Updated Aviation discussion for 00Z TAF Issuance.
&&
.SHORT TERM...(Tonight through Tuesday night)
Issued at 308 PM CDT Sun Jul 26 2020
Convection got off to an early start today, and as expected the
thunder has been most prevalent over west Kentucky this afternoon.
It should push east of our area by 21Z. A few light showers will
remain across the region, and an isolated thunderstorm cannot be
ruled out through sunset.
We should be dry and mostly clear tonight, but HRRR runs have been
consistently trying to bring some convection eastward along I-64
in southern Illinois toward sunrise. Confidence is not high enough
to add it to the forecast right now.
The cold front is still expected to reach the area generally after
21Z Monday. Not sure how much convection there will be ahead of
it, but figure on widely scattered showers and storms possibly
beginning before noon, especially across the north. The flow will
be weak, so any storms will be of the pulse variety and should not
lead to any damaging winds or significant flooding issues.
The hi-res guidance has consistently shown a major downward trend
in coverage and intensity as the frontal-related convection moves
south through the northern half of our region in the 21Z-03Z time
frame. The shear will remain weak and instability will not be much
better than we have had recently, so severe storms would be quite
the stretch, but a stray downburst cannot be ruled out, especially
along I-64 in the late afternoon. Also should not see much of a
heavy rainfall and flooding concern.
Not sure how much, if any, convection will make it into southern
portions of the area heading into the overnight hours, but PoPs
will drop to chance levels by late evening and remain there
overnight.
Not sure where the actual synoptic boundary will be Tuesday
morning, but it is not likely to clear west Kentucky. Given the
uncertain convective coverage overnight, the outflow may not even
clear the area. Regardless, convection is likely to develop in
the vicinity of the cold front and any outflow boundaries by late
Tuesday morning. This will be the best chance for convection over
the southeast half of the area. Once again, there will not be
enough shear to organize it, so more non-severe, pulsy storms are
expected. Given a nearly stationary boundary, the heavy rainfall
threat will be a bit higher Tuesday.
Far northern portions of the region should be dry Tuesday afternoon,
but will leave a small chance just in case the cold front holds
up a bit farther north than expected. The convection Tuesday
should be widespread enough to push the effective surface boundary
south of the area by Tuesday night, so most if not all of the
region will be dry Tuesday night.
Temperatures Monday will feel similar to the last few days, with
high temperatures around 90 and heat indices topping out near 100.
With the front and associated convection and cloud cover, Tuesday
will be noticeably less hot, especially across the north.
.LONG TERM...(Wednesday through Sunday)
Issued at 308 PM CDT Sun Jul 26 2020
The extended forecast period looks rather unsettled. However, the
details regarding the timing and duration of significant POPs remain
murky at this time. Forecast confidence is high to start the
period, but declines for next weekend.
From Wednesday through at least Friday, a stalled surface boundary
will be positioned along the southern border of the CWA. Aloft, the
region will be under the influence of northwest flow, with pieces of
energy disseminating from a trough digging into the Northern Rockies
bringing chances of scattered thunderstorms. By Thursday and Friday,
a surface inflection will organize over the Southern Plains and
traverse along the stationary boundary. This system could bring
multiple rounds of locally heavy rain to the CWA. Ensemble guidance
shows PWATs above the 90th percentile during much of this period, so
efficient rainfall processes are possible. Latest QPF shows
widespread 2-3+" totals by Saturday evening. This is still subject
to change at this range, however.
Deterministic model guidance has trended wetter for Saturday
(possibly into Sunday as well). This is due to the progged
development of a secondary area of low pressure along the stationary
boundary. We thought the NBM solution of chance POPs for Saturday
was an acceptable solution for now.
Temperatures will trend cooler through the forecast period, owing
to the ample cloud coverage and precipitation chances. High
temperatures will generally be in the lower to middle 80s, with
overnight lows in the upper 60s. Dew point temperatures will not
come down much, so it will still feel quite humid outdoors.
&&
.AVIATION...
Issued at 518 PM CDT Sun Jul 26 2020
Widely scattered convection continues in the late day heat, and
will remain a vicinity possibility until sunset or shortly
thereafter. Will let latest radar trends dictate its inclusion.
Otherwise, another scattering of VFR skies tonight is expected,
with a repeat (diurnal) scenario tmrw as cu field develops by
mid-late morning. Short res models suggest we might see early
convection coming in from the northwest, so included vicinity
mention with VFR cigs/bases at KMVN for this writing.
&&
.PAH WATCHES/WARNINGS/ADVISORIES...
IL...None.
MO...None.
IN...None.
KY...None.
&&
$$
Area Forecast Discussion
National Weather Service Pueblo CO
1002 PM MDT Sun Jul 26 2020
.UPDATE...
Issued at 1002 PM MDT Sun Jul 26 2020
Updated the forecast to add another flash flood watch for tomorrow
afternoon and evening for the area burn scars. With the monsoonal
moisture in place, we are expecting for another round of slow
moving thunderstorms tomorrow afternoon. This will combine with
areas of saturated soils from previous days precipitation for the
potential of flash flooding once again, especially for the burn
scars.
&&
.SHORT TERM...(This evening through Monday)
Issued at 237 PM MDT Sun Jul 26 2020
Currently
Scattered thunderstorms and numerous showers were noted over the
forecast area at 2 pm. The strongest storms were noted in the KTAD
area and across eastern Baca County. Other showers and storms
were noted over the mtns/plains interface. A cool front was on the
Palmer Divide and was about to move into El Paso county.
Rest of Today and into Tonight...
Main concern is what is going to happen in the next several hours.
Cool front will continue to push south in the unstable airmass over
southeast CO. Between 500 and 2000 J/kg of mixed CAPE were noted
over the region with the most unstable air over the far SE Plains.
HRRR continues to indicate (as it has been doing since I got into
the WFO at 8 AM) to show the strongest activity in the mtns is going
to occur over the mtns/plains interface. In addition, storms over S
Lincoln County have put out a boundary and it was pushing west and
south, and storms in the KTAD area are likely going to push a
boundary northward. Likewise, I would not be too surprised to see
some strong storms fire in the Pueblo County area and eventually
push east later this afternoon. Based on the HRRR guidance, a
significant flash flood threat is still possible for all of the
burn scars along the Wets and Sangre mtns, especially once the
main front moves down into that region.
For the rest of the period, storms will slowly subside over the
higher terrain this evening while a cluster of storms slowly pushes
east across the plains. These storms may linger well into the
evening and early morning hours.
We will likely see quite a bit of clouds with areas of low cigs over
the plains tonight.
Tomorrow...
Main change to the fcst is the potential for less precip over most
of the region tomorrow. Temps are going to be rather cool tomorrow
70s and 80s plains) and this is likely going to stabilize the
atmosphere. I have cut back pops quite a bit on the plains, but
later shifts may need to cut them back even more. In the mtns,
especially along the contdvd, the threat of locally heavy rain will
still be with us and kept high pops over this region. /Hodanish
.LONG TERM...(Monday night through Sunday)
Issued at 237 PM MDT Sun Jul 26 2020
On Tue the upper level ridge is expected to be centered near the
southern CA coast, while an upper disturbance moves thru WY and
northern CO. There will be a little less moisture over the area
Tue, but still plenty around for scattered showers/storms over and
near the mtns, then spreading over the plains in the evening hours.
Wed the upper ridge becomes centered over AZ, with northwest flow
aloft over the forecast area. Moisture is expected to be lacking on
Wed, but the far eastern plains may have the best moisture and some
isolated storms may be possible. There could also be some isolated
showers/storms over some of the mtns as well.
A disturbance moves into KS on Thu, while the upper ridge becomes
centered near the Four Corners. Little moisture is expected over
the area on Thu but there could again be some isolated
showers/storms, especially near the eastern border.
Fri and Sa the upper ridge center is expected to be over northeast
AZ and a little more moisture is expected over the mtns, especially
the eastern mtns, so maybe scattered showers/storms may form over
the mtns and portions of the I-25 corridor in the afternoon and
possible over the southern plains in the evening.
Sun the upper ridge may shift westward and the models show a
disturbance affecting the area and potentially bringing better
chances for precip.
&&
.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
Issued at 237 PM MDT Sun Jul 26 2020
Thunderstorms, some with very heavy rain, are still a threat for
later this afternoon and evening at all 3 taf sites, KPUB, KALS and
KCOS. The heaviest rain threat will be at KCOS and KPUB. Another
concern will be low cigs tonight given the abundant low level
moisture over the plains. Storm threat for tomorrow afternoon is
decreasing at all 3 taf sites as more stable air is fcst to move
into the region.
&&
.PUB WATCHES/WARNINGS/ADVISORIES...
Flash Flood Watch until midnight MDT tonight for COZ061-062-
072>075-077-079-080-087.
Flash Flood Watch from Monday afternoon through Monday evening
for COZ061-062-072>075-077-079-080-087.
&&
$$
UPDATE...MW
SHORT TERM...HODANISH
LONG TERM...28
AVIATION...HODANISH