Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 07/26/20

Area Forecast Discussion

National Weather Service La Crosse WI

 1033 PM CDT Sat Jul 25 2020

.UPDATE...
Issued at 1030 PM CDT Sat Jul 25 2020

The 00Z MPX sounding had around 2.25 inches of precipitable water
and surface based CAPE around 3000 J/kg. The NAEFS Precipitable
water charts show that these values are around 4 standard
deviations above normal with return values of 30 years and Maxed
out through Sunday morning. The increasing low level jet will
continue to feed moist, unstable air into southeast Minnesota and
western Wisconsin overnight. Two to three inch rains per hour
will be possible with the storms as they repeatedly move over the
same area. MPX has had storm develop in their area and the
moisture axis is from MPX into ARX`s cwa. Some of the guidance has
the heavier rain staying north, while others develop it southward
(ARW) As ouflows develop and storms develop, it seems like the
ARX is catching on to this. The HREF has some locations picking up
3 to 6 inches. Flash flood guidance is generally in the 2 to 3
inch range and most locations can actually use 1 to 3 inches. The
pattern calls for the potential for very heavy rain, however it
will depend on how the bands of rain set up. For now will include
a handful of counties in a flash flood watch to raise the
awareness of the potential for flash flooding overnight.

&&

.SHORT TERM...(This evening through Sunday)
Issued at 201 PM CDT Sat Jul 25 2020

Currently observing scattered shower/isolated thunder activity
across northern IA/southeast MN into northwest WI. This area was
on the southeastern periphery of decent 850mb moisture transport
and along a remnant MCV. Otherwise, temperatures across the local
forecast area as of 1 pm were mostly in the 80s with a couple
sites reporting lower 90s. Dew points were oppressive...well into
the 70s with heat indices currently ranging from near 90 to 100.
A Heat Advisory is in effect until 8 pm tonight for heat indices
maxing out in the 100-105 range.

For tonight will be watching for an uptick in showers/thunderstorms
as a cold front slowly makes its way toward the region and as we are
located on the southeast periphery of increasing low level 850mb
jet/moisture transport. CAPE is ample in this very muggy airmass but
shear is modest with RAP 0-3km in the 20-30kt range. 0-1km shear was
fairly impressive though in the 25-35kt range. As such, will have to
keep an eye on some stronger/possibly severe storms. Otherwise,
overnight lows will only make it down into the low to mid 70s with
those dewpoints in the 70s...so a sticky/muggy night in store.

The cold front will continue to push south into the area Sunday for
increased shower/thunderstorm potential. Cloud cover will be the fly
in the ointment as to how much CAPE can build during the day,
NAM/GFS depicting some pockets of 4kJ/Kg but overall bulk shear
values are modest. So, thinking we`ll see a few stronger/possibly
severe mainly pulse type storms with a marginal threat for damaging
winds. With expected shower/storm activity/cloud cover, will hold
off on heat headlines as temperatures may be cooler than today.

Also for consideration tonight into Sunday will be the potential for
pockets of very heavy rainfall given high precipitable water values
pushing 2.5 inches.

.LONG TERM...(Sunday night through Saturday)
Issued at 201 PM CDT Sat Jul 25 2020

The cold front finally pushes through the area Sunday night, taking
the thunderstorms and uncomfortable heat with it. Monday will be
markedly more pleasant with highs around 80 and dew points around
60.

Upper pattern settles into northwest flow for the remainder of the
forecast period. Result will be generally dry with seasonable
temperatures.  Surface ridging during the period will be weak, so
could see some diurnal shower activity, especially later in the week
as the surface ridging becomes more diffuse.  Models diverge as we
approach next weekend, although there are suggestions of a decent
wave dropping down in the northwest flow that would bring the next
notable chance of precipitation.

&&

.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 646 PM CDT Sat Jul 25 2020

Isolated showers will continue to impact KRST and KLSE this
evening. Thunderstorms are beginning to increase over southern
Minnesota and expect this trend to continue with the low level jet
increasing. Over time, the on and off storms will sag southeast
toward KRST and KLSE. VFR conditions with MVFR/IFR ceilings and
visibilities with occasional thunderstorms. South to southeast
winds mostly 5 to 15kts will becoming northwest behind the front
later Sunday 20 to 22Z.


&&

.HYDROLOGY...
Issued at 1030 PM CDT Sat Jul 25 2020

Most locations could use one to three inches of rainfall, however
would not be able to take higher amounts or very high rainfall
rates of two to three inches an hour without some flash flooding.
Based on the rainfall forecasts rapid rises on rivers and streams
are possible for parts of southeast Minnesota and west central
Wisconsin as the water moves through the system or falls over the
rivers and streams.

&&

.ARX WATCHES/WARNINGS/ADVISORIES...
WI...Flash Flood Watch until 8 AM CDT Sunday for WIZ032>034.

MN...Flash Flood Watch until 8 AM CDT Sunday for MNZ079-086>088-094-
     095.

IA...None.
&&

$$

UPDATE...Zapotocny
SHORT TERM...DAS
LONG TERM...DMD
AVIATION...Zapotocny
HYDROLOGY...Zapotocny




Area Forecast Discussion

National Weather Service Grand Junction CO

 542 PM MDT Sat Jul 25 2020

.SHORT TERM...(Tonight through Sunday night)
Issued at 326 PM MDT Sat Jul 25 2020

Deep layer moisture continues to stream into much of the forecast
area today, thanks to the monsoon, and brought some widespread
rainshowers to areas south this morning. However, northwest
portions of the forecast area remained mostly clear and with the
added daytime heating, showers and thunderstorms have fired.
Upper level winds are fairly light and motion of this convection
has been very slow so some locally heavy rainfall remains
possible under the stronger, slower moving storms. Like yesterday, the
extensive cloud cover has inhibited more widespread convection but
visible satellite imagery does show breaks in the clouds down
south. The question is will the clouds get thin enough to tap
into the instability aloft. Both the HRRR and NAMNEST favor the
convection getting going with the HRRR a bit more aggressive in
its coverage while the NEST looks to place the stronger convection
on the fringes of the cloud cover and clearer skies. CAPE values
vary from about 300 to 500 J/kg up north, not much, and between
800 to 1000 J/kg for the San Juans and southern valleys so
southern areas remain favored.  Once heating ends, most
convection will die down though a few showers can`t be ruled out
for the San Juans.

For tomorrow, high pressure remains to our east while a trough
remains to the west and a wave well to our north will cause the
plume of moisture to `tilt` more to the northeast. Models are
picking up on this tilt with precip still expected for the San Juans
but then shifting to the central mountains towards Vail Pass. On the
backside of the wave, winds will bring in some drier air north of I-
70 which follows model solutions. Expect slow moving storms and
showers again tomorrow so the risk remains for some heavy rainers.

.LONG TERM...(Monday through Saturday)
Issued at 326 PM MDT Sat Jul 25 2020

Deterministic and ensemble guidance remain in excellent agreement
regarding the progression of the synoptic scale pattern over the
long term period. A mid-level ridge of high pressure will retrograde
west/southwest from the central Plains into the southern Four
Corners Monday and Tuesday. While this will effectively cut-off the
source of monsoonal moisture to our south, above normal moisture
already in place (characterized by total precipitable water values
of 0.5-1.5 standard deviations above the mean) will be trapped
underneath and continually recycled through Tuesday. Additionally, a
nearly stationary shortwave trough located over southern California
will eject northeast over the Great Basin on Monday and then across
eastern Utah and western Colorado on Tuesday. Given the enhanced
dynamical lift associated with the shortwave trough, numerous to
widespread showers and thunderstorms are likely, particularly on
Tuesday. Gusty winds, frequent lightning and heavy rain will once
again be the main threats, especially in the higher terrain.

Changes then begin to take shape on Wednesday as the aforementioned
shortwave rounds the northern periphery of the ridge and dives into
the central Plains. In its wake, 500MB heights will rise and expand
with the center of the ridge located directly over the Four Corners.
Mid and upper level flow will turn more westerly and northwesterly
in response, ushering in much drier air into the forecast area for
the middle and latter part of the week. This will result in warmer
temperatures (back to near or just above seasonal norms) and much
lower chances for afternoon showers and storms. With that being
said, weak, fast-moving disturbances moving through the
west/northwesterly flow combined with diurnal heating and any
leftover moisture may be just enough to touch off a few isolated
orographic showers and storms each day, mainly in the higher terrain
closest to the Continental Divide.

&&

.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 541 PM MDT Sat Jul 25 2020

Scattered to broken skies, some overcast, will be common across
the area through tonight as monsoonal moisture continues to pump
into the region. Some convection is also likely overnight so
included VCTS for many TAF sites. The main concern from storms
will be some gusty outflow winds and visibilities dropping to
below VFR conditions under moderate to heavy rain. ILS breakpoints
will be met from time to time but do not anticipate this to occur
for a prolonged period. Most convection will die down late this
evening though some rain showers will persist over the San Juans.

&&

.GJT WATCHES/WARNINGS/ADVISORIES...
CO...None.
UT...None.
&&

$$

SHORT TERM...TGR
LONG TERM...MDM
AVIATION...TGJT



Area Forecast Discussion

National Weather Service Goodland KS

 702 PM MDT Sat Jul 25 2020

.UPDATE...
Issued at 659 PM MDT Sat Jul 25 2020

Cancelled the Heat Advisory over the northeast sections of the
forecast area for today.

&&

.SHORT TERM...(This evening through Sunday)
Issued at 111 PM MDT Sat Jul 25 2020

Water vapor imagery and RAP analysis indicated CWA on western
fringe of large H5 ridge centered over southeast Kansas. At the
surface, weak convergent area noted across northwest CWA with
towering CU developing along it. Another area of speed convergence
was bisecting the CWA.

Main forecast concerns will center around precip chances through
the weekend and possible flooding impacts.

Previously mentioned convergence zones will be likely focus for
thunderstorm development this afternoon and early evening and with
PWAT values around the 90th percentile of climatology and slow
storm movement, heavy rain will once again be a threat. While
storm motions will be more parallel to forcing across eastern CWA
resulting in higher threat for heavy rainfall, confidence in this
area initiating is somewhat low. Further north, while the storm
motion may limit training of cells near the tri state border, area
still recovering from very heavy rain that occurred on Thursday
night and therefore remain especially vulnerable to flash
flooding. For the time being, think flash flood watch will
continue for this area. Given that storms are being driven more by
surface heating and near surface features think there will be a
strong diurnal trend with them. While increasing low level flow
aloft may sustain storms near approaching front into the
overnight hours, think the window for the GLD area will likely
close by 05 UTC.

For Sunday, cold front will sweep across the area resulting in
nearly 20 degree temperature gradient from southeast to northwest.
Guidance actually pretty consistent with placement of front and
temperatures, but confidence in related precipitation threat
somewhat low through the day. Best forcing will be immediately
along front, which makes a quick exit from the CWA in the late
afternoon. While there does appear to be forcing along H7 frontal
zone late in the period, have concerns that available instability
will be lacking. While a few models seem to be picking up on this
potentially drier solution, consensus still looks like bulk of the
area will see some meaningful rainfall Sunday. While there
certainly will be hydro concerns, aforementioned concerns about
precip placement keep confidence on the low side for any kind of
watch.

.LONG TERM...(Sunday night through Saturday)
Issued at 210 PM MDT Sat Jul 25 2020

Sunday Night-Monday night: Broad cyclonic flow aloft over the
Central/Northern Plains.. on the far southern periphery of an
upper level low in Manitoba.. will transition to NW flow aloft on
Mon as the aforementioned upper low progresses eastward into
Ontario and a more-pronounced upper level ridge develops over the
Intermountain West/Desert Southwest/Rockies. With the Tri-State
area situated on the southern periphery of the westerlies
/cyclonic flow aloft/ -- and a weakening /increasingly west-east
oriented/ SFC-H85 trough progressing slowly southward from
Nebraska into Kansas -- convection appears likely over the
majority of the area Sunday evening into Monday morning, with
activity gradually progressing south of I-70 during the day on
Monday. Although brief severe downbursts are possible in assoc/w
the strongest updrafts (mainly Sunday evening) -- heavy rainfall
and isolated flash flooding appear to be the primary convective
hazards -- particularly in areas hard-hit by recent heavy rain
(i.e. Yuma/Dundy/Cheyenne counties).

Tuesday-Saturday: Long range guidance suggests that an exceedingly
complex synoptic pattern will evolve over the Central/Western
CONUS in this period, lending *significant* uncertainty to
forecast specifics -- particularly with regard to chances for
precipitation/convection. With this in mind, the long range
forecast will be steered toward climatology.

&&

.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 553 PM MDT Sat Jul 25 2020

VFR conditions are expected at MCK and GLD through the 00Z TAF
period. Thunderstorms are expected in the vicinity of both sites
through about 05Z tonight. Thunderstorms are expected to develop
across the area again on Sunday. With a cold front pushing through
the area, thunderstorms coverage is expected to be more extensive
and have introduced thunderstorms as a prevailing condition at
both sites from about 21Z and beyond Sunday afternoon.


&&

.GLD WATCHES/WARNINGS/ADVISORIES...
KS...Flash Flood Watch until 7 AM CDT Sunday for KSZ001.

CO...Flash Flood Watch until 6 AM MDT Sunday for COZ090.

NE...Flash Flood Watch until 6 AM MDT Sunday for NEZ079.

&&

$$

UPDATE...LOCKHART
SHORT TERM...JRM
LONG TERM...VINCENT
AVIATION...LOCKHART




Area Forecast Discussion

National Weather Service Lincoln IL

 852 PM CDT Sat Jul 25 2020

.SYNOPSIS...
Issued at 320 PM CDT Sat Jul 25 2020

A muggy night is on tap tonight, under mostly clear skies across
central Illinois. Hot and humid conditions on Sunday will push
heat index readings between 100 and 105 degrees. A cold front
will trigger showers and storms later Sunday night and Monday.
A few storms could be strong with gusty winds and locally heavy
rain on Monday.

&&

.UPDATE...
Issued at 852 PM CDT Sat Jul 25 2020

No significant updates needed this evening. Although some shallow
fog is possible overnight, sounding profile showing moisture
dropping off quickly above the surface should promote dew over
fog, while at least a light wind in many areas, especially the
western half of the state, could help promote mixing and diminish
fog possibility. Nevertheless, will continue to monitor for fog
potential, mainly I-57 eastward, where combination of light wind
and high surface moisture will be best. Otherwise, lows in the low
70s and mostly clear skies continue to look good for tonight.

&&

.SHORT TERM...(This evening through Sunday)
ISSUED AT 320 PM CDT Sat Jul 25 2020

The latest surface analysis shows high pressure centered over the
Great Lakes with a ridge axis extending back across central
Illinois. Southerly return flow around that high was pushing
afternoon dewpoints up into the low to mid 70s in a majority of
our CWA, with the highest readings generally west of I-55. Heat
indices have remained below 100F so far, with Jacksonville at 99F
at 230 pm.

The HRRR and RAP continue to show a cluster of storms developing
from Schuyler to Scott counties late this afternoon. Satellite
pics show agitated CU closer to the Mississippi River, but not
significantly towering at the moment. Shallow CU continued to
bubble up in our counties. Still feeling the dry mid-level air
will suppress storm chances in our counties, along with subsidence
under the surface ridge axis. Therefore, will not add PoPs late
this afternoon/early eve.

The muggy air mass will help keep low temps in the lower 70s
tonight, under mostly clear skies. There could be another round of
late night shallow fog in our eastern counties, but confidence not
high enough to include in the forecast.

Sunday will be our hottest day of the next week, with dewpoints
likely to climb into the mid to upper 70s, as high temps climb
into the lower 90s. That will push heat index readings into the
100-105F range, just below our heat advisory criteria. Can`t rule
out a couple locations possibly reaching 106F, but it is not
expected to be widespread enough to trigger a headline for heat in
our counties. Plus, some afternoon convection just northwest of
our CWA could push a dense cirrus overcast into C IL, which would
definitely limit high temps and lower the H.I. Will continue with
an SPS for the heat.

.LONG TERM...(Sunday night through Saturday)
ISSUED AT 320 PM CDT Sat Jul 25 2020

A cold front will approach from the NW Sunday night, increasing
PoPs to Likely in our NW counties after midnight. The front could
even progress as far as a line from Rushville to Bloomington by
12z/7 am Monday, as suggested by the GFS. Still enough evidence in
the consensus to keep the timing a little slower for now, which
puts the bulk of the showers and storms in our counties on Monday.
Have kept the categorical PoPs along and ahead of the front as it
pushes southeast through C IL. PWAT values of 2-2.3" point toward
heavy rainfall from the complex of storms. Model instability has
dropped off from previous runs, with MUCAPEs now in the 2500-3200
range for areas east of I-55 and south of I-72. A Marginal Risk
for severe storms extends only into our far eastern counties on
Monday, while a Marginal Risk for excessive rainfall covers our
entire CWA. A slower forward progression of the front in the
latest models would tend to favor flooding as a higher concern for
our area.

The cold front is expected to advance to our far SE counties by
00z/7pm Monday, with rain/storm chances lingering mainly SE of
I-70 overnight. A few showers could continue Tuesday morning along
Highway 50, otherwise dry conditions are expected on Tuesday. Less
humid air will help make the mid-week portion of the forecast more
comfortable for late July. A few shortwaves are progged to
trigger storms across the southern half of Illinois as early as
Thursday, but there is quite of bit of uncertainty in the far
extended forecast due to model differences. The 12Z ECMWF keeps
our area dry for the Tues to Saturday time frame, save for a few
storms in our far SE 3 counties on Thursday.

Besides one warmer day on Wednesday (Highs in the mid to upper
80s), high temps for Tues to Saturday look to be in the 80 to 85
degree range with lows in the low to mid 60s.

&&

.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 630 PM CDT Sat Jul 25 2020

VFR conditions expected to be predominant over the upcoming 24
hours at all central IL terminals. Patchy fog could affect
terminals around 11-12Z, especially KDEC and KCMI, and isolated
TSRA possible after 20Z, however probability of occurrence is too
low for mention in current TAFs. Winds S 4-8 kts then becoming SSW
around 10 kts with gusts around 15 kts after 17Z.


&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

UPDATE...37
SYNOPSIS...Shimon
SHORT TERM...Shimon
LONG TERM...Shimon
AVIATION...37




AREA FORECAST DISCUSSION

National Weather Service Jackson KY

 1100 PM EDT Sat Jul 25 2020

.UPDATE...
Issued at 1100 PM EDT SAT JUL 25 2020

Sure enough just as soon as the pops were gone from the grids,
a few showers started to show up on radar within the last couple
of hours. These didn`t result to much, with only a flash or two of
lightning, but a couple have persisted for quite some time and
are finally dissipating at the end of the 2Z hour. Went ahead and
increased pops again to isolated coverage across much of the CWA
for the next couple of hours, at once point hopefully instability
will have dissipated enough that no redevelopment will occur.
But...as was the case last night...may end up just having to watch
the radar and update as warranted. Also loaded in the latest
observations for temps and winds across the CWA. All updates have
been published and sent to NDFD/web. A new set of zones and HWO
have also been sent to reflect changes to the pops/weather.

UPDATE Issued at 755 PM EDT SAT JUL 25 2020

Ended up reducing pops quite substantially from the afternoon
package based on the current radar trends. There are still enough
mesoscale boundaries around, and the instability is still high
enough, that a few showers and thunderstorms can`t be ruled out
throughout the rest of the evening, mainly south of Jackson.
However, anything that develops has been diminishing almost as
quickly as it forms, with maybe only a couple lightning strikes. This
lowering of pops continued into the overnight and tomorrow
morning, with a period of the overnight likely going dry based on
the latest CAMS and neighboring offices as well.

Pops should then ramp back up during the mid-morning hours. With
conditions very similar to that of today, expect that coverage
will generally be isolated to scattered. This is also in line with
what the models are giving. Ended up lowering the pops from likely
across the southern CWA back down to scattered as a result. This
also lined up better with all of our neighboring offices.

&&

.SHORT TERM...(This evening through Sunday night)
Issued at 400 PM EDT SAT JUL 25 2020

Another warm afternoon out there today. Dewpoints are running a
degree or two lower than the past few days in most areas, but
still a good amount of moisture pooling across southern KY.
Evidence all remains of the washed out boundary laying out east to
west across the state. Slightly better moisture resides along and
just to the south of the boundary. Convection today has been much
weaker with updrafts not as sustained from what we have seen over
the past few days. There are also a few rogue cells to the north.
The threat for showers and a few storms will continue into this
evening.

Much like the past few nights, some weak moisture transport is
forecast to develop again on the NAM and RAP and this could bring
some shower activity to the area, especially late tonight. The RAP
appears to the most aggressive, but given the fact we nearly had
stuff all night last night under a similar pattern, opted to carry
some slight and chance pops through much of the night. I wouldn`t
rule out a very isolated storm, but for now will keep thunder
limited through the overnight period.

Sunday will feature more of the same as moisture remains pooled
across southern and southeast Kentucky which should aid in more
shower and storm development. Thunder should be more limited,
similar to today, but a few storms cannot be ruled out given the
instability in play. No shear will keep thunderstorm mode in the
pulse category. Highs should again reach into the upper 80 to
around 90.

Sunday night, the better moisture transport should shift into West
Virginia and this may allow for a lull in precipitation chances
through the overnight hours. Some patchy fog may be possible in
the river valleys assuming we clear out.

.LONG TERM...(Monday through Saturday)
Issued at 441 PM EDT SAT JUL 25 2020

Model agreement is good through day 4 but is fair to poor from days
5 through 7. Mid/upper level low over Ontario will track just south
of Hudson Bay and eastward into Quebec by Dy5 Wed. Energy in the
form of a positively tilted shortwave lobe ahead of additional
upstream energy rotating through the base of the parent low will be
driven south and eastward into the Ohio Valley by late Monday into
Tuesday. Additional disturbances and/or at least one main short wave
trough will roll into the lower to middle portions of the Ohio by
the end of the period. A surface cold front associated with the
initial system aloft will drop southeast close to the Ohio River by
Late Tuesday is not sooner. There continues to be considerable
differences with the operational runs in the timing and southward
extent of this surface front. The ECMWF continues to be slower
and stalls further north, just south of the Ohio river. However,
the 12Z trend does appear to be slightly further south than
previous runs. The GFS continues to take the front south of
Kentucky, just south of the state line into the TN Valley. The
Canadian, which is more often than not a compromise solution of
the other two brings the front as far south as the Commonwealth,
and with a west to east orientation effectively bisects our CWA
before stalling out. Thus sought out ensemble solutions for some
clues. GFS ensemble mean MSLP bisects eastern Kentucky as well.
NAEFS and ECMWF ensemble H500 and H850 height anomalies of 1-2
standard deviations do reach well south of the Great Lakes and
into the Ohio Valley, suggesting enough push to get the boundary
at least into if not just south of our area. Interestingly the
ECMWF ensemble anomalies reach further south than the NAEFS.
Therefore ensembles support the idea of the frontal zone making
it at least as far south as our forecast area by Tuesday night or
Wednesday, which also matches up well with the NBM`s
initialization.

Sensible weather features a summer like, hot and muggy start to the
extended on Monday with highs once again climbing to around 90
degrees. But a frontal boundary moving into the area combined with
additional cloud cover and the increase in the threat of showers and
thunderstorms will drop our afternoon highs from there into the 80s.
Overnight lows will range from around 70 down into the mid 60s.
Still could not rule out some lower 60s in some of our typically
cooler locations should the front make it as far south as the
Tennessee Valley.

&&

.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
ISSUED AT 808 PM EDT SAT JUL 25 2020

VFR conditions should prevail at the TAF sites through the period.
A few showers and a stray thunderstorm are still ongoing across
eastern KY away from the TAF sites, however convection should
continue diminishing as we head into the late evening/overnight
hours with the loss of daytime instability. Valley fog is expected
once more tonight, but should continue to trend lesser than the
previous night. Since TAF sites really didn`t see much in the way
of impact from this fog last night, went ahead and removed any
mention of it for tonight`s forecast. That being said, can`t rule
out a very brief lowering of VIS or CIG right around daybreak if
valley fog is present and lifting near the TAF site. A very
similar airmass and setup for convection to that of today will be
in place tomorrow as well, so expect generally isolated to
scattered convection across eastern KY during the afternoon hours.
Best chances (SCT) will be in the south portion of the state, so
did include some VCTS at KSME and KLOZ. However, with only
isolated chances farther north, confidence was too low to mention
in TAFS at this time. Winds should generally be light and
variable, under 5 kts, through the period, outside of any
thunderstorms that do occur.

&&

.JKL WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

UPDATE...JMW
SHORT TERM...KAS
LONG TERM...GEERTSON/RAY
AVIATION...JMW



...Updated for 00Z Aviation Forecast Discussion...



 .DISCUSSION...
Issued at 307 PM CDT Sat Jul 25 2020

Heat index values at 3 pm were running 101 to 106 degrees, and
thus no changes to the heat advisory that continues through 8 pm.

Focus then shifts to potential convection overnight into Sunday
night as a slow moving cold front moves through the region. There
does appear to be a weak wave moving through the central Rockies.
Scattered strong and possibly severe storms will likely develop
across western and central NE within the area of the pre-frontal
surface trough. This activity will be well west of the forecast
area, so lowered the pops in northeast NE this evening. Believe
the best scenario is for some nocturnal convection in our area
after midnight, which would generally be along and north of I80,
and that could linger into Sunday morning. While widespread severe
storms aren`t expected, a storm or two could contain gusty winds
and some small hail perhaps.

The cold front will get a decent push into the area Sunday from a
reinforcing upper wave coming out of the Rockies. We should see
increasing areal coverage of thunderstorms as the front moves into
the area during peak heating. This will result in cooler temps in
the 80s behind the front, but still hot and oppressive ahead of
the front, and southwest IA/southeast NE could again reach heat
index criteria near 105. Thus may need another heat advisory south
of I80 Sunday afternoon, but will let the night shift take a look
with the later model runs. Secondary concern Sunday afternoon and
evening will be potentially strong to severe thunderstorms along
and south of the frontal boundary. There will a chance of damaging
wind gusts, but the potential for heavy precip will also exist
with 1-3" of rain still looking possible for southeast NE and
southwest IA. While the storms will be moving, PW values will be
quite high. 3-hour flash flood guidance values are running
2.25-3.0. WPC has placed much of the region in a slight risk for
excessive heavy rainfall, but am optimistic we won`t have
widespread flooding problems. Many areas need the rain badly.

There may still be a few lingering showers south of I80 Monday,
but overall, the heaviest rains by then should be pushing south
into KS and MO. Much more comfortable weather expected with highs
in the lower to mid 80s.

The seasonable and even slightly below normal temps continue
through the remainder of the week. Rain chances back into the
forecast Wednesday through Saturday.

&&

.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 620 PM CDT Sat Jul 25 2020

Latest thoughts are that thunderstorms could spread into parts of
northeast NE by 11 pm to midnight, and these could possible affect
the KOFK TAF by 05Z. Mid level clouds should increase over all of
the area and recent runs of the ESRL HRRR 1 km radar reflectivity
output seem reasonable, producing scattered precipitation
spreading toward KOMA and KLNK 08Z-11Z. Will just include a VCSH
group for that now. Mid level clouds are likely to linger much of
Sunday, with TSRA developing and becoming more widespread. Tried
to keep PROB30 groups into the main times where activity was
likely. Could see MVFR or lower ceilings in TSRA and IFR
visibilities.

&&

.OAX WATCHES/WARNINGS/ADVISORIES...
NE...Heat Advisory until 8 PM CDT this evening for NEZ011-012-015>018-
     030>034-042>045-050>053-065>068-078-088>090.

IA...Heat Advisory until 8 PM CDT this evening for IAZ043-055-056-069-
     079-080-090-091.

&&

$$

DISCUSSION...DeWald
AVIATION...Miller




Area Forecast Discussion

National Weather Service Phoenix AZ

 450 PM MST Sat Jul 25 2020

.UPDATE...
Updated Aviation

&&

.SYNOPSIS...
Chances for showers and thunderstorms will generally favor the
higher terrain north and east of Phoenix this weekend. Southwestern
Arizona and southeastern California will remain dry as the moisture
remains farther east. High pressure will build across Arizona next
week, resulting in a return to above normal temperatures and below
normal precipitation chances.

&&

.DISCUSSION...
Latest water vapor imagery reveals a well-defined PVD across Sonora,
with deeper moisture displaced north and east of the vort max across
eastern Arizona. Further west, another closed low is evident across
California. Ahead of this system, relatively dry Pacific air is
being transported into southern California and western Arizona.
Latest ACARS soundings confirm the drying around 850 mb, which is
beginning to make its way to the surface across the lower deserts.
Meanwhile, further aloft at 700 mb, the latest RAP streamline
analysis depicts a weak anticyclonic flow, resulting in
light north and northwesterly winds from Maricopa County eastward.

General consensus amongst the HREF CAMs is that the best chance for
showers and thunderstorms this afternoon will remain confined to the
higher terrain of southern Gila County in the vicinity of the
deeper moisture, and along the moisture gradient across northeastern
Maricopa County. Main concern for today will be slow-moving cells
that have the potential to produce heavy rain and perhaps even
isolated flash flooding near the burn scars.

With the aforementioned northerly component to the flow, storm
motion will generally be southward towards the foothills and lower
deserts. CAPE may be high enough for isolated storms to survive
into the foothills, however the environment remains unfavorable for
convection in the lower deserts with the warm layer near 450 mb
yielding weak mid-level lapse rates. Even the most aggressive CAMs
indicate little potential for outflows to reach the Valley and
consequently PoPs remain below 5 percent for the Phoenix area.

&&

.PREVIOUS DISCUSSION...
The forecast for tomorrow looks conceptually similar to today but
with slightly lower PoPs over the higher terrain and just
minuscule chances for the lower desert as drier air continues to
overtake more of the region. Guidance trends consistently support
this evolution, but as always the case with convection, the
outcomes from the previous day`s events can change the forecast
from day-to-day. Drier conditions will eventually solidify by
early next week confining most thunderstorm activity over the
higher terrain well east of Phoenix, and over southeastern
Arizona.

The GEFS and EPS are both in pretty good agreement with the
subtropical ridge re-centering over Arizona, which is not the most
ideal location for monsoon rains. Given this, most ensemble members
from both sets of guidance are very bearish regarding rain chances
in Phoenix and most everywhere else in the forecast area beyond this
weekend. If the guidance is off, and the ridge positions closer to
the Four Corners area instead, we might be able to realize a more
favorable monsoonal pattern. Another wrinkle to consider is the
potential implications from Tropical Storm Hanna but confidence in
any particular development is very low at this time.

Otherwise, drier conditions combined with increasing atmospheric
thickness underneath the ridge will support a warming trend.
Forecast highs will approach 110 degrees Sunday/Monday, and remain
in the 108-113 degree range for much of next week. As of now, no
heat watches or warnings are planned but the increased heat risk
will require monitoring.

&&

.AVIATION...Updated at 2350Z.

South-Central Arizona including KPHX, KIWA, KSDL, and KDVT:
With SHRA/TS remaining well east of Phoenix through Sunday evening,
identifying wind shifts will be the primary forecasting challenge.
Storm outflows should be far less defined this evening versus
previous days, and chances of distinct wind shifts are only remote.
A wind shift to the traditional overnight easterly may be more
delayed than usual, and a switch at KPHX may not occur until after
sunrise Sunday, if at all. Otherwise, light westerly winds will
settle over the region by early afternoon with a somewhat better
chance of a more organized easterly outflow boundary later Sunday
evening.

Southeast California/Southwest Arizona including KIPL and KBLH:
No substantial aviation issues will exist through Sunday night under
clear skies. Trends in wind shifts will be similar to the past
several days with directions oscillating between SE and SW, and in
many cases variable for extended periods.


&&

.FIRE WEATHER...
Tuesday through Saturday:
High pressure will build across Arizona, resulting in a return to
above normal temperatures and below normal precipitation chances.
Nevertheless, moisture will be sufficient for at least isolated
storms each day, particularly across the higher terrain north and
east of Phoenix. Min RHs will generally fall into the teens each
afternoon. Meanwhile, winds will be light and diurnal each day,
except in the vicinity of with thunderstorms.

&&

.SPOTTER INFORMATION STATEMENT...
Spotters should follow standard reporting procedures.

&&

.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...None.
CA...None.

&&

$$

DISCUSSION...Hirsch
PREVIOUS DISCUSSION...Deems
AVIATION...MO
FIRE WEATHER...Hirsch