Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 06/22/17
Area Forecast Discussion
National Weather Service Bismarck ND
930 PM CDT Wed Jun 21 2017
.UPDATE...
Issued at 921 PM CDT Wed Jun 21 2017
Precipitation over southern portions of the area has now pushed
well off to the east. The next batch of showers is now knocking on
the door over the northwestern portions of the area as showers
over northeast Montana continue to push to the east. Expect this
to push into the area late this evening, and continue an easterly
track overnight as an impulse rotating around an upper low located
along the Manitoba/Saskatchewan border continues its easterly
path.
UPDATE Issued at 622 PM CDT Wed Jun 21 2017
Most storms have pushed to the east of the far southern James
River Valley, though a boundary still shows up on radar that is
over the southern/eastern portions of Dickey County, which is also
denoted by some cloud growth on satellite. Therefore, will keep
some low thunderstorm chances going for another hour or so before
all pushes east.
&&
.SHORT TERM...(This evening through Thursday)
Issued at 300 PM CDT Wed Jun 21 2017
A cold frontal passage this afternoon will be followed by another
surge of cold air advection and gusty northwest winds Thursday.
We continue to downplay the potential for surface-based storms in
our area of responsibility this afternoon since the current pace
of a southeast-moving pre-frontal trough and cold frontal boundary
suggests they will be mostly east of the area by the time capping
is sufficiently eroded for convective initiation. However, there`s
been just enough run-to-run consistency in HRRR iterations through
its 18 UTC cycle to carry a slight chance of thunderstorms across
Dickey County for a brief window in the late afternoon. Forecast
soundings do suggest MLCAPE of 1000-1500 J/KG and deep-layer speed
shear of 50 kt, sufficient for marginally-severe storms, but again
we believe the probability of convective initiation in our area
is low since the primary low-level confluence region will quickly
be shifting east of the area.
Today`s global and CAM model suites suggest another frontal surge
marked by additional thermal packing in the 850 mb isotherms will
push into northwest and north central ND tonight. Vertical motion
associated with a strong but transient 140 kt 300 mb jet streak is
expected to move eastward along the international border overnight
and will likely yield a deep enough ageostrophic circulation atop
the mid-level baroclinic zone in support of scattered showers. That
frontal zone and its following cold air advection is then expected
to continue southeast across the area early Thursday, away from the
deeper forcing aloft associated with the upper-level jet streak. A
dry forecast is thus in play tonight and Thursday in southwest
and south central ND.
Forecast soundings from the 12 UTC NAM and GFS both concur that we
will have deep mixing to around 650 mb on Thursday in the cold air
advection regime. Mean mixed-layer winds will be near 30 kt and
peak speeds at its top will near 40 kt, especially northwest and
north central. We weighted forecast winds toward the consensus of
12 UTC MOS guidance, which often verifies well in these cases.
Those numbers suggest that a wind advisory may be required with a
later forecast release if model trends hold steady, especially
from Williston toward Minot Thursday afternoon.
.LONG TERM...(Thursday night through Wednesday)
Issued at 300 PM CDT Wed Jun 21 2017
Much cooler weather is still expected Friday and Saturday, but
only a low chance of showers exists.
The 00 and 12 UTC GFS and ECMWF and their ensembles held steady in
forecasting a 500 mb trough across the region with temperatures at
850 mb in the 5 to 8 C range Friday and Saturday. Thus, highs will
likely struggle to get out of the 60s F and overnight lows will be
in the 40s F this weekend. Precipitation prospects will be limited
by lackluster tropospheric moisture content, especially since it
appears a stronger 500 mb low dropping through the trough may well
pass east of the local area.
A warming trend is still on track next week as flow aloft begins
to return to a more zonal and progressive nature.
&&
.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 622 PM CDT Wed Jun 21 2017
Gusty northwest winds develop over the area on Thursday.
Otherwise, VFR conditions will prevail.
&&
.BIS WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
UPDATE...JJS
SHORT TERM...CJS
LONG TERM...CJS
AVIATION...JJS
Area Forecast Discussion
National Weather Service Hastings NE
650 PM CDT Wed Jun 21 2017
.MESOSCALE DISCUSSION...
Issued at 608 PM CDT Wed Jun 21 2017
In the interest of maintaining a flow of info...this is not the
highest confidence watch we`ve ever issued.
Updrafts are struggling to sustain themselves in an environment of
weak shear and anemic BL moisture. The altocu are moving toward
higher dwpt air...but with increased capping.
This will definitely be one of those watches in which most of the
watch is quiet. There is still potential for a couple svr tstms.
The HRRR and 18Z NAM Nest still develop potent storms near the
state line in the next 3 hrs.
&&
.SHORT TERM...(This evening through Thursday)
Issued at 255 PM CDT Wed Jun 21 2017
Aloft: Basically zonal flow was over the Nrn half of the CONUS and
it will remain zonal thru tomorrow. However...a low was over Sask
and it will cont heading E across Srn Canada. The Westerlies will
begin amplifying and the zonal flow will gradually become more
cyclonic..espcly tomorrow as a shortwave trof rotates around the
low into MT/ND.
Surface: Occlude low pres was over Sask. A cool front extended
from ND back to NV...with a warm front from ND down into cntrl Neb
then heading E to near OMA and into the OH Vly. This front has
been reinforced with convective outflow. A 1005 mb low was near
TIF with a trof extending SSW along the CO/KS border. This low and
trof will be responsible for initiating sct tstms and tstm
clusters this afternoon/eve. Meanwhile...as the Canadian low conts
E it`s associated cool front will press further S and E...crossing
Neb during the daytime hrs tomorrow...and finally clearing the CWA
(N-cntrl KS) by midnight.
Now: We cont to monitor sat/radar for convective initiation within
the sfc trof from the Sandhills back into NW KS. SPC issued MD
1109 at 230 PM. Probability of watch issuance is currently 40%.
Reasoning from 943 AM version of this product has not changed.
Deep mixing and convergence within the trof should initiate a few
tstms that will be outflow dominant.
As usual...CAMs depict a wide variety of possibilities for
convective coverage and evolution.
Shear and instability are lowest within the trof. Any storms or
storm clusters that develop and move E will be moving into an
environment of increasing shear/instability.
Current indications are that sct tstms/tstm clusters will develop
and should be SE of the CWA by midnight.
Be sure to monitor for any statements/watches/warnings from this
office as well as support guidance from SPC.
Thu: Tstms should develop along the approaching cool front over
WY/SD tonight. This activity should cont E across SD during the
morning...but will probably send an outflow boundary S into the
CWA. It could trigger a few tstms during the AM N of I-80.
During the afternoon/eve...a few tstms could develop S of a line
from Beaver City-Columbus or even a little further S from
Phillipsburg-Geneva. Am highly skeptical of much tstm activity
over the NW 1/2 of the CWA as this area will be N of the front and
strongly capped. Bottom line is I think our fcst is too extensive
with tstm potential in the post-frontal environment.
Where sfc-based tstms to develop (SE 1/2)...certainly large hail
and damaging winds will be a threat.
High temps are very uncertain over S-cntrl Neb due to the frontal
passage.
.LONG TERM...(Thursday night through Wednesday)
Issued at 255 PM CDT Wed Jun 21 2017
This has been a hot month with 11 days of highs in the 90s at
GRI. The rest of the month is looking substantially cooler...with
a few days much cooler than normal.
Aloft: Amplification of the Westerlies was just beginning. Over
the next svrl days a broad trof will develop over the Nrn USA
downstream of a ridge along the W coast. This trof will gradually
shift into the Ern USA early next week with deamplification fcst
toward the middle of the week.
Surface: The cool front referenced above will sink SE across Neb
during the day tomorrow and will be completely S and E of the CWA
by midnight. Weak high pres will build over Neb/KS Fri. Meanwhile
another cool front will plunge into the Nrn Rockies. It will
arrive here and sink thru the CWA during the daytime hrs Sat. A
big chilly and very strong high for summertime will expand over
the Plns Sun-Mon from the Canadian Prairies to TX. It will then
head into the SE USA Tue with return flow developing here on the
Plns.
Temps will be cooler than normal Fri-Mon...with at least one day of
much cooler the normal Sat. Probably returning to near normal Tue
and then above normal Wed.
The cool fronts will shove the rich low-lvl moisture far S of the
CWA thru Mon. Once it advects back into the rgn Mon night into Tue
then the risk of tstms will return. A little/light rain generated
by fgen should accompany the front Fri night into Sat...and
possibly lingering into Sun S of I-80. Rainfall amts will be
minor.
&&
.AVIATION...(For the 00Z KGRI/KEAR TAFS through 00Z Thursday)
Issued at 650 PM CDT Wed Jun 21 2017
Significant Wx: LLWS tonight then WSHFT early Thu PM will
necessitate changing RWYs.
Tonight: VFR multi-layered clouds before midnight mostly AOA 7K
ft. Sct SHRAs are moving in from the W and trying to become TSRAs
but they are struggling. It is unlikely they affect the terminals
...but did include VCTS/CB at EAR. Cloud debris should decrease by
midnight. S-SSW winds will average 10-15 kts and there could be
some ocnl gustiness. LLWS. Confidence: Medium
Thu: VFR with no clds AOB 10K ft until a cold frontal passage and
WSHFT occurs early afternoon. Then some stratocu could form around
4K ft. The exact timing of the WSHFT/FROPA will need some minor
refining +/- 1 to 2 hrs. Light SW winds will become vrbl then
become NE and increase to 15-20 kts with gusts up to 28 kts.
Confidence: Medium
&&
.GID WATCHES/WARNINGS/ADVISORIES...
NE...None.
KS...None.
&&
$$
MESOSCALE...Kelley
SHORT TERM...Kelley
LONG TERM...Kelley
AVIATION...Kelley
Area Forecast Discussion
National Weather Service Green Bay WI
935 PM CDT Wed Jun 21 2017
Updated aviation portion for 06Z TAF issuance
and new information added to update section
.UPDATE...
Issued at 921 PM CDT Wed Jun 21 2017
Convection has been slow to develop across the area this evening,
likely due to stable air lingering across the area. Local meso
plots indicate destabilization has occurred over about the
southwest quarter of the state. That will expand northeast during
the night, possibly quite rapidly as the LLJ increases. Storms
over northern Minnesota have weakened as they shifted east of the
main axis of instability. Increasing isentropic lift near the nose
of the LLJ still looks favorable for thunderstorms across the
area, but have delayed their onset and the highest PoPs until
later in the night. The severe risk is also somewhat uncertain.
Storms to the west have shown no sign of upscale growth. Right now
the most likely path to getting severe weather tonight would be
for a few individual storms to get strong enough to generate
severe hail after midnight.
Grids/ZFP with updated PoPs/Wx were just sent, will tweak/update
the wording of the HWO and have that out shortly.
&&
.SHORT TERM...Tonight and Thursday
Issued at 239 PM CDT Wed Jun 21 2017
The main concern for tonight and Thursday is timing of
thunderstorm activity along with the potential for severe
weather. 19z surface analysis indicated a surface warm front
draped from western Minnesota to south-central Iowa. Temperatures
on the north side of the front were in the 70s across much of our
area along with dewpoints in the middle 40s to middle 50s. To the
south of the warm front, temperatures were in the middle 80s to
lower 90s with dewpoints in the 60s.
For tonight, models depict low level jet increasing to 50 to
55 knots as the warm front lifts northward. Elevated convection
is expected to develop across central and east-central Wisconsin
during the mid to late evening hours. Some differences by a few
hours noted between the HRRR and the NAM Nest Models. The latest
RAP 13 splits the difference in timing. Models also indicated
strong 0-6 km shear of 50 to 60 knots, mid level lapse rates
around 6 c/km to support rapid development of storms. Current
thinking there would be some large hail at the onset, however
wetbulb zero heights on the bufkit soundings were near twelve
thousand feet that may lower the number of severe hail reports
over an inch. Once the storms form, damaging wind gusts are
possible as the storms organize. Most of the activity should be
out of the forecast area shortly after sunrise. Low clouds will
prevail tomorrow morning which should limit any convective
activity. Torrential rainfall can be expected with some of the
stronger storms which could lead to urban street flooding and
ponding of water on area roadways.
Did keep a small chance in the morning then increase chances
again Thursday afternoon. Some of the meso models depicts a
northern band of showers and storms heading for northern
Wisconsin while another band of showers and storms develop across
our southern forecast area and then merge late Thursday
afternoon. Some of the storms could become severe with damaging
winds and large hail, especially south of a Marshfield to Green
Bay to Algoma line. High temperatures tricky depending on how
much sunshine we get in the late morning and afternoon.
.LONG TERM...Thursday Night Through Wednesday
Issued at 239 PM CDT Wed Jun 21 2017
Focus in the long term will be ongoing convection Thursday night
and on and off chances for more showers and thunderstorms through
the forecast period.
Thunderstorms (some potentially severe) are likely to be ongoing
at 00Z Friday, especially south of a line from Marshfield to
Green Bay closer to the location of the surface cold front.
Thunderstorm chances will end from NW to SE overnight, with models
showing the front and instability moving south of the forecast
area by 12Z Friday.
The rest of Friday looks mainly quiet. Models still show a weak
shortwave to potentially produce a few showers in northern
Wisconsin during the afternoon, with perhaps isolated thunder at
best with MLCAPE and MUCAPE not more than 200 J/kg.
GFS, ECMWF, and Canadian all depict an upper level trough over
Ontario and the Great Lakes dominating the pattern across
Wisconsin from Saturday through early next week. This flow will
continue to bring mid- level shortwaves across the area and result
in scattered shower and thunderstorm chances. Models are in less
agreement on the exact timing and location of these shortwaves.
The best chances seem to be in the Saturday afternoon/Saturday
night and Monday afternoon/Monday night time periods. Stuck with a
blended model solution which features chance and slight chance
PoPs that coincide well with when the best energy moves though.
On Tuesday the upper level trough moves east as an upper level
ridge builds over the Upper Midwest. This is accompanied by high
pressure at the surface and the best-looking day to see dry
weather at the moment. Models continue to diverge on timing and
track of a surface frontal system to approach the area around
midweek. Continued with the blended model solution for now which
brings in higher PoPs Wednesday.
Temperatures will be running below seasonal normals through most
of the long term period, especially across northern Wisconsin
where highs will be about 10 degrees below normal Saturday and
Sunday. Temps moderate some for the start of next week.
&&
.AVIATION...for 06Z TAF Issuance
Issued at 921 PM CDT Wed Jun 21 2017
The main aviation forecast concern continues to be the
thunderstorm potential overnight and Thursday. It still looks like
2 rounds of storms are likely, but the onset of the first round
has been delayed a bit by lingering stable air across the area.
Will continue to try and indicate the most likely time for storms
in the TAFs, though it certainly is possible those may need to be
adjusted as the storm development unfolds.
&&
.HYDROLOGY...
Issued at 239 PM CDT Wed Jun 21 2017
Another round of heavy rain expected tonight into Thursday night.
Average rainfall totals of 1 to 2 inches are possible south of a
Merrill to Sturgeon Bay line. Locally higher amounts are possible
if thunderstorms train over the same area.
&&
.GRB WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
UPDATE.........Skowronski
SHORT TERM.....Eckberg
LONG TERM......KLB
AVIATION.......Skowronski
HYDROLOGY......Eckberg
Area Forecast Discussion
National Weather Service Lincoln IL
910 PM CDT Wed Jun 21 2017
.UPDATE...
Issued at 910 PM CDT Wed Jun 21 2017
A shortwave will continue to trigger showers and isolated storms
across our northern counties the rest of the evening, and the
HRRR is finally catching up with that scenario. Many other high
res models are missing the boat with this wave. The stabilizing
boundary layer has already limited cloud to ground lighting, as
well as in-cloud lightning. However, a few strikes could still
occur this evening, so isolated thunder was left in the forecast.
Have increased our overnight clouds, especially in the south from
Tropical Storm Cindy and in the north from ongoing convection. The
clouds will increase lows a few degrees, and have adjusted up
slightly in the south and north.
Updates this evening have been to PoP/Wx, Sky, and temps. The
latest forecast info is already available.
&&
.SHORT TERM...(This evening through Thursday)
ISSUED AT 240 PM CDT Wed Jun 21 2017
Weak convection today and associated cooling has kept the warm
front from redeveloping north of the forecast area as originally
expected. Isolated storms may still be possible near the boundary
that extends from near Springfield east to near Paris through the
remainder of the afternoon. However, ridging will once again build
into the area overnight and the delayed translation of the warm
front into Wisconsin is likely to occur late tonight or Thursday
morning as strong insolation should assist in mixing. Temps should
be higher across central Illinois compared to today due to the sun
early on. Low-level moisture will increase as southerly flow
becomes more prominent during the day but with 700mb temps
progged to climb 4-5C in 24 hours and moving well above 10C
capping of significant convection seems likely. We will keep any
chc pops confined to near I-70 and southeastward.
.LONG TERM...(Thursday night through Wednesday)
ISSUED AT 240 PM CDT Wed Jun 21 2017
Model suite from 12z continues to push frontal system southeast
into the forecast area late Thursday Night in conjunction with a
short wave expected to move across the upper Mississippi Valley.
The approach of the front should correspond with the period of best
moisture advection from the remnants of Cindy and may lead to a
brief period of heavier rain along and behind the front across
central Illinois between midnight and Friday morning. Still some
uncertianty of the evolution of the front and its interaction with
the tropical moisture particularly across southeast Illinois
Friday. Will retain likely PoPs southeast of I-57 with an
diminishing trend from northwest to southeast as the front sags
southeast and remnant circulation center moves far enough east to
cut off overrunning potential.
Clouds and cold advection behind the front should keep temps
noticeably cooler Friday. The cool weather should persist into
early next week as the area remains in cool northwest flow and 850
mb temps drop into the single digits through Monday prior to
recovering by midweek. Several weak shortwaves will move through
the northwest flow bringing periodic clouds and maybe a slight
chance of a shower, but overall dry weather should dominate the
are from the weekend into midweek.
&&
.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 646 PM CDT Wed Jun 21 2017
A weak shortwave over eastern Iowa appears poised to push an area
of showers into central Illinois this evening. HRRR is the main
high resolution model indicating precip will progress across the
I-74 corridor, with others keeping showers north the I-74 TAF
sites. Based on radar and satellite trends, have added a VCSH for
a few showers to affect PIA and BMI this evening. A steady
decline in instability later this evening should preclude CMI from
experiencing rain. Beyond that VFR conditions are expected to
persist, under a veil of high clouds from tropical storm Cindy in
the Gulf of Mexico.
There are several models indicating a northward surge of low
level moisture tomorrow afternoon, triggering MVFR cloud ceilings
to develop from south to north. Have included that scenario in the
00z TAFs.
Winds will generally remain S-SW over the next 24 hours. Wind
speeds will increase tomorrow morning, with gusty conditions
developing after 15z. Gusts should reach between 20-25kt at times
on Thursday.
&&
.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
UPDATE...Shimon
SHORT TERM...Barker
LONG TERM...Barker
AVIATION...Shimon
Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
1025 PM CDT Wed Jun 21 2017
.UPDATE...For 06z Aviation discussion below
&&
.SHORT TERM...(This evening through Thursday)
Issued at 332 PM CDT Wed Jun 21 2017
Visible satellite shows very little cu this afternoon across the
vast majority of the area with the remnants of the morning MCS
maintaining mid level cloud cover across far southern Minnesota.
Chances for thunderstorms tonight will be focused in two areas,
although those probabilities have also decreased. One area will be
this evening over west central and possibly extending east into
central Minnesota by late evening. A line of cu has formed along
the cold front over North Dakota, which is progged to continue
pushing southeast tonight to southern Minnesota by Thursday
morning. A few storms may fire along it this evening in an
environment characterized by MUCAPE of 1000 J/kg before they
reach a much more stable airmass further east across Minnesota mid
evening. The other area will be across southeastern MN and into
central WI late this evening with the development of a LLJ. Given
where the nose of this LLJ is expected to be around 06Z tonight,
over southern WI, the most concentrated activity will be across
central and eastern WI - east of our CWA. Maintained chc PoPs for
both these areas, and a dry forecast from southwest to east
central MN. CAMs have consistently been showing this all day and
believe the global models are way too overdone with developing
convection locally, especially the GFS which shows widespread
precip occurring across southwestern MN this afternoon.
As the front sags south into South Dakota overnight, additional
storms may develop as it encounters deeper moisture. This activity
will spread east Thursday across central and southern MN behind
the front. Forecast soundings are quite stable behind the
boundary with poor lapse rates and a cool boundary layer. Further
south across southern MN, the close proximity to the EML and
deeper low level moisture/higher thetaE should allow for
widespread thunderstorms by afternoon. A few of them may become
severe with 50-60 kts in the mid levels, but the best probability
will be south of I-90 where the quasi-stationary front should be
for much of the day.
.LONG TERM...(Thursday night through Wednesday)
Issued at 332 PM CDT Wed Jun 21 2017
Overall the long term period will be cool and fairly quiet as we
will be under northwest flow with the main jet to our south.
Saturday will bring a chance for showers and isolated thunderstorms
with an upper level shortwave moving through the region. A warming
trend appears to be on tap for early to middle of next week, which
could bring more thunderstorm chances to the region.
By tomorrow evening, the thunderstorm activity across our area will
be pushing to the east, with most of the area drying out in the
evening. Storms could linger from south central Minnesota through
parts of west central Wisconsin. A few of these could be strong but
the main severe threat looks to be in the short term period (during
the day). All storms should be east of the forecast area by the
overnight period.
Behind this activity, the flow becomes northwesterly as the cold air
advection ensues from the northwest. 850H temps will fall during
the day Friday down to around 5 to 8 degrees C. At the surface,
expect highs in the upper 60s to lower 70s. The cool northwest flow
will continue through the weekend so highs will continue to be
cooler than normal right through the weekend. On top of that, a
compact shortwave will move through Saturday and spark showers and
possible thunderstorms mainly during the afternoon. Continued to
follow the GFS primarily for this evolution, but the ECMWF is slower
and slightly farther north with this wave.
The GFS and EC agree that the flow will become progressive next week
and shift the west coast ridge to the east, displacing the deep
longwave trough east of our area and beginning a warming trend into
the middle of the week as southwest flow develops. With this, more
low chances for thunderstorms are sprinkled into the forecast.
&&
.AVIATION...(For the 06Z TAFS through 06Z Thursday night)
Issued at 1025 PM CDT Wed Jun 21 2017
Model preference is a combo of the HRRR and NAMnest models, which
feature a squeeze play of showers and thunderstorms moving into
the area overnight from eastern SD and northern IA. Both feature a
fairly rain morning for most of the sites, with embedded
thunderstorm potential as well. Afternoon convective
redevelopment (of stronger storms) still looks to be shifted
south/east of most TAF sites (with the exception of possibly
KEAU). MVFR cigs/vsbys are possible with thunderstorms, and also
with/behind the frontal passage, but expect to be VFR by 00z
Friday. Winds shift to the northwest behind the front.
KMSP...
There is a small threat for thunder early in the period, but the
more widespread showers (with embedded thunder) holds off until
around/after 10z. The morning looks to have activity around
throughout, and then we scatter out during the mid afternoon.
/OUTLOOK FOR KMSP/
Fri...VFR. Wind NW 10 kts.
Sat...Mainly VFR. Slight chc -TSRA/MVFR. Wind NW 5-10 kts.
Sun...Mainly VFR. Slight chc -TSRA/MVFR. Wind NW 5-10 kts.
&&
.MPX WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...None.
&&
$$
SHORT TERM...BORGHOFF
LONG TERM...SPD
AVIATION...LS
Area Forecast Discussion
National Weather Service Norman OK
619 PM CDT Wed Jun 21 2017
.AVIATION...
0Z TAFs - Some storms could move into portions of NW OK later this
evening. If storms do move into area, gusty variable winds could
be possible. Otherwise, mid and high level clouds from the storms
will stream across portions of the area tonight with high clouds
around T.S. Cindy affecting other portions of the area later
tonight into Thursday. T.S. Cindy could also affect winds at some
TAF sites Thursday.
&&
.PREV DISCUSSION... /issued 346 PM CDT Wed Jun 21 2017/
DISCUSSION...
A persisting upper high across the southwestern U.S will continue
to bring northwest flow across the southern plains, rolling in
another round of showers and thunderstorms off the central high
plains. Latest HRRR and Texas Tech WRF models suggest a few storms
begin moving into far northwest Oklahoma around 10 pm, and not
advancing very far before dissipating by early Thursday morning.
So far, the risk for these storms is marginal, with up to golfball
size hail and strong to severe wind gusts possible.
The remainder of Thursday is expected to be dry with seasonably
normal temperatures, with chances for more widespread TSRA
returning on Friday through the weekend as a series of short wave
disturbances in the upper flow come through. For Friday into
Friday night, the storm and rain chances increase as an advancing
surface boundary will interact with an upper wave. For this
weekend, both GFS and ECMWF suggest additional storms possible as
a few more short waves pass through, but uncertain with the timing
or moisture available, so POPs will remain low until we get
closer in time. One thing for sure, unseasonably cooler air
lagging behind Friday`s cold front passage should be arriving by
Saturday night. Temperatures for Sunday are expected to 10 to 15
degrees cooler than normal for early Summer.
&&
.PRELIMINARY POINT TEMPS/POPS...
Oklahoma City OK 68 92 71 88 / 0 0 0 30
Hobart OK 67 94 70 90 / 0 0 10 30
Wichita Falls TX 66 94 72 94 / 0 0 0 20
Gage OK 67 96 66 85 / 20 0 30 20
Ponca City OK 67 91 70 85 / 0 0 0 30
Durant OK 70 89 72 91 / 0 10 0 20
&&
.OUN WATCHES/WARNINGS/ADVISORIES...
OK...None.
TX...None.
&&
$$
30/25/25
Area Forecast Discussion
National Weather Service Reno NV
845 PM PDT Wed Jun 21 2017
.UPDATE...
Convection is decreasing across western Nevada this evening and
has ended in the Sierra. A few showers and storms are hanging on
from Lyon County east into the far northern part of Mineral
County and eastern Churchill County. This activity is associated
more with a weak trough that has focused the activity since about
630 pm. With the loss of heating we should see the activity end by
around 10 pm.
LAtest model guidance is in line with the previous guidance and
shows activity developing again Thursday...but covering a smaller
area mainly in the Sierra.
Updates will be out shortly.
&&
.PREVIOUS DISCUSSION... /Issued 246 PM PDT Wed Jun 21 2017/
SYNOPSIS...
High pressure will bring much above average temperatures through the
weekend, with cooler temperatures possible next week. Isolated to
scattered thunderstorms are expected today near and south of
Interstate 80, with isolated storms in Mono County Thursday through
Saturday. Flooding will continue for the creeks and streams in
Mono County and for portions of the Walker River.
SHORT TERM...
A weak upper trough axis is dropping south through western NV and
the northern Sierra this afternoon. This, along with a weak surface
trough extending through Mono/Mineral Counties, is providing focus
for developing convection this afternoon. So far convection remains
meek but this is expected to change as heating maximizes into the
early evening. Recent HRRR runs have pegged the initial cell
locations (eastern Mono County and out in central NV) better than
the NAM/GFS.
The HRRR shows isolated showers and thunderstorms congealing into
scattered coverage this evening south of Highway 50 in western NV
and over eastern Churchill County...with activity moving north
(likely on outflows from earlier storms). Still, while confidence
in the HRRR is growing due to its fairly consistent and so-far
accurate depiction of convective location, steering flow is very
light so storm motion will be driven by smaller-scale features
such as storm outflows. These can be quite chaotic and unpredictable.
Therefore, a broad-brush approach to evening storms (especially
north of Highway 50) was taken to allow for possible locations for
evening showers and thunderstorms. In any case, large surface
temperature-dewpoint spreads should once again allow for storm
outflow wind gusts over 50 mph out in the Basin and Range, with
areas of blowing dust possible. As far as rainfall, with light
storm motions stronger storms will be capable of dropping cores of
moderate rain, although they could be rather narrow with the dry
lower levels evaporating much of the precipitation on the edges
of storms.
Thursday, the upper level trough axis will move south into the
central Sierra and the southern half of Nevada. This is expected
to kick the focus for showers and storms down into Mono County and
points south for a quieter day as far as afternoon showers and
thunderstorms.
Friday, the upper ridge settles back overhead for a rising temperature
trend once again. With well above average temperatures and only
minor subsidence aloft a few thunderstorms cannot be ruled out in
the higher terrain near the Mono County crest. Therefore, a slight
chance of storms was added to the forecast there.
Over the weekend, the strong upper ridge remains overhead for highs
well above average...in the mid 90s to low 100s for lower valleys
and mid 80s to lower 90s for Sierra valleys. Thunderstorms will
continue to be possible with daytime heating in Mono County both
days. However, on Sunday simulations are also beginning to show
convection spreading into northeast CA and western NV as a weak
impulse moves into northern CA (and induces a zephyr) on the
periphery of the upper ridge. This makes sense and is shown in
many simulations so storms were expanded out into western NV and
up into northeast CA.
LONG TERM...Monday through Wednesday...
Next week, models continue to show a weakening of the upper ridge
for an end to thunderstorms, increasing breezes, and a gradual
cool down towards average high temperatures. Snyder
Fire Weather...
Another very hot and dry day today with thunderstorms developing
this afternoon and moderate to poor mid slope recoveries for the
next several nights. Thunderstorms are currently forming over the
high Sierra in Alpine/Mono Counties and may move into the Sierra
Front and the Basin and Range during the late afternoon/early
evening along gust fronts from the initial thunderstorms in the
Sierra. Thunderstorms should generally be of the wet variety since
storm motions are expected to be slow, but lightning strikes can
always happen outside of rain cores.
Winds will be generally light out of the north today until
thunderstorms form, then a quick change to south winds will be
possible with gusts of 40 to 50 mph along thunderstorm outflows.
Localized Red Flag conditions could easily occur for 1-2 hours as
the gusts fronts from thunderstorms move into western Nevada.
Hot and dry conditions are expected over the weekend with afternoon
thunderstorms a possibility each day, however, storms are expected
to be more confined to the Sierra after today. A trough is forecast
to approach the west coast early next week which would cause an
increase in thunderstorm activity and increased potential for
critical fire weather conditions Monday and/or Tuesday as winds
increase. -Zach
AVIATION...
&&
.REV Watches/Warnings/Advisories...
NV...None.
CA...None.
&&
$$
For more information from the National Weather Service visit...
http://weather.gov/reno
...Update to aviation forecast discussion...
.SHORT TERM...(This evening through Thursday)
Issued at 307 PM CDT Wed Jun 21 2017
A subtle upper level wave moving through central Nebraska helped
spark scattered showers and thunderstorms over far NE Kansas and
locations further north and east late this morning. This wave and
the associated shower activity will push east of the area by the mid
afternoon hours, with a second wave nipping at the departing
system`s heels over SE Wyoming. A dryline across western Kansas will
once again be the focus for thunderstorm development later this
afternoon and evening. Given the lack of steering flow aloft,
convection will not move terribly quickly off the dryline, and have
hence slowed the arrival of POPs in the forecast after 21Z. This
idea matches most of the CAM solutions such as the HRRR and high-res
ARW/NMM cores.
The main threats from this event would be large hail and damaging
winds in the far western CWA given the SB/MLCAPE values over 4000
J/kg and near adiabatic low-level lapse rates from the surface to
above 800 mb. Deep shear values will be lacking, thus the convective
clusters will likely be non-steady state and new convection will be
driven by previous convective cold pools. Steep mid-level lapse
rates above a 30-40 kt LLJ may drive elevated convection into the
night over central portions of the CWA, but the lack of deep shear
should once again keep the severe threats to a minimum.
The upper level pattern will amplify over the northern Rockies
during the day on Thursday as a longwave trough digs southward from
western Canada. As this wave approaches, the cold front over
Nebraska will begin to shift ESE and reach the NW corner of the CWA
at the end of the period. High temperatures on Thursday will be near
what they reached yesterday and today--reaching the low 90s east to
upper 90s west. Heat indices will push 100 degrees in most locations.
.LONG TERM...(Thursday night through Wednesday)
Issued at 307 PM CDT Wed Jun 21 2017
Thursday night into Friday morning, broad cyclonic flow resides over
the northern tier of the CONUS. A deep upper level closed low will
amplify short wave energy over the Northern Rockies and eventually
send this impulse into the Northern and Central Plains. The closed
low will begin to fill into the overnight and thus weaken as it
shifts east into the Northern Great Lakes. Best forcing for large
scale ascent stays north of the forecast area and leaves
northeastern KS under a capped environment much of the day with a
strong EML in place. NAM and GFS solutions are more consistent with
higher moisture set up and a well mixed boundary layer in place but
also strong CINH in place. Both solutions focus gradient of
instability along the front as it moves through southern NE late
afternoon and into the northeastern KS by early evening. MLCAPE and
SBCAPE on the order of 1500-2000 J/kg as it makes its way into
northeast KS within marginal deep layer shear with best deep layer
shear lagging well behind the front should lead to isolated to
widely scattered storms probably at best. Most CAM solutions that
go out far enough to include this forecast period are suggesting
that any discrete multicells that do develop quickly become a
disorganized cluster or quasi linear set up into the evening. The
ECMWF solution is similar to the overall concept that the NAM and
the GFS arrive at, but slow the overall progression of the cold
front slightly with overall less moisture pooling to help
initiate activity in the first place. All this being the case, it
leads to a low probability set up that severe storms will be long
lasting or maintained. The threats that do exist would be possibly
some large hail and mainly a wind threat lasting for a short time
frame (before boundary layer stabilzation takes place) where
storms can break the cap and get going. Therefore, have gone with
slight to some chance POPs in the early evening on Thursday.
On Friday day time frame high pressure ridge noses into the area and
should leave a nice day in place with subsidence aloft. Temps will
be in the 80s with dew points in the 50s.
Saturday, there may be some showers and storms that make their way
into portions of the area coming off the high plains associated with
another impulse rotating around the broad cyclonic flow aloft that
just continues to skirt the area once again. It`s a low chance set
up and one that won`t have a lot of support but too much model
variance at this point to determine one way or the other.
Latter part of the weekend into the first half of the upcoming week,
the pattern becomes more progressive with a low amplitude ridge
working into the area and activating the lee trough. This will
bring some return flow of moisture back into the area and possibly
lead to a couple on and off chance of precip with isentropic lift
developing and advecting over the area. All in all, temperatures
will be more near normal and comfortable compared to recent heat.
&&
.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 625 PM CDT Wed Jun 21 2017
VFR prevails at terminals with main concern being the low level
wind shear and dissipating convection across western Kansas. Sfc
winds are expected to become light around 5 kts aft 01Z with the
low level jet increasing around 1000 feet up to 40 kts. This is
expected to persist through sunrise before southerly sfc speeds
increase above 10 kts near 14Z. Current convection in western
Kansas is expected to weaken as it shifts east and southeast.
There is a slight chance for a few thunderstorms to reach KMHK by
11Z, hence the VCTS mention.
&&
.TOP WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SHORT TERM...Skow
LONG TERM...Drake
AVIATION...Prieto