Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 10/24/21
Area Forecast Discussion
National Weather Service Des Moines IA
658 PM CDT Sat Oct 23 2021
...Updated for the 00z Aviation Discussion...
.SHORT TERM.../Tonight through Sunday/
Issued at 252 PM CDT Sat Oct 23 2021
While weak ridging is pushing across the state today and has
fostered a seasonably cool day with light easterly winds, this
will change this evening. This is signaled in the GOES-East upper
level water vapor imagery, which shows a switch to more westerly
or southwesterly flow approaching from the west. This flow and a
weak shortwave trough interacting with a surface boundary
initiated a convective cluster over eastern Kansas that has been
moving through the Ozarks today. This boundary will lift northward
as a warm front this evening as surface low pressure moves out of
eastern Colorado into central Kansas. With increasing theta-e
advection tonight, saturation in the atmospheric column will also
be increasing from southern into central Iowa. However, this will
likely be slower than models are showing due to the low level, dry
easterly flow with forecast soundings from the NAM and GFS
showing dry air remaining below 900mb. This dry air will be
eventually be overcome and result in numerous showers and storms
as increasing QG convergence spreads over the region. There is a
low risk of severe weather over southern Iowa, likely toward and
after midnight tonight. Forecast soundings at LWD and OTM show
that instability grows above an inversion, which will be
reinforced by the low level thermal lift. That instability is
initially around 500 J/kg by around midnight, but grows with the
HRRR, NAM, and RAP showing above 1500 J/kg of elevated instability
by daybreak. In addition, 0-6km deep layer bulk shear is around
50 knots, more than sufficient for storm organization. With this
environment, the main severe concern will be hail tonight with the
inversion likely preventing any wind gusts to reach the surface.
Rain and elevated storms will continue on Sunday, particularly over
southern and central Iowa, but expand into northern Iowa. The
northward progress of the rain will be tempered through the night by
a mid-level closed low centered over Hudson Bay that has a cyclonic
spin over southeastern Canada, the Great Lakes region, and the
northeastern US. This closed low will lose its influence on our area
on Sunday as a lead shortwave trough ejects ahead of the parent
longwave trough over the western US and Canada. This will allow for
showers and storms to push into northern Iowa as the surface low
moves eastward out of Kansas and near or just south of the
Iowa/Missouri border. This movement will be slow as low pressure
becomes stacked in the atmosphere with most locations experiencing a
9 to 15 hour period of a high chance of rain and/or storms. This
prolonged period of rainfall, starting tonight and lasting into
Sunday, along with precipitable water values topping an inch over
northern Iowa to 1.5 inches over southern Iowa and high for October
warm cloud depths over 3000m will lead to efficient rainfall. The
00z ECMWF extreme forecast index for tonight through Sunday
afternoon is showing a very unusual event based on it 20 year model
climatology for this time of year with the shift of tails around 2
indicating an anomalous event. The CMC and FV3 both show the
highest amounts amongst the deterministic models of around or over
4" in parts of our southeastern forecast area. Looking at
ensemble guidance, the 12z HREF localized probability matched
mean shows the 3" QPF contour over southern Davis and Appanoose
counties for time period ending 00z Sunday with the event total
probability matched mean of 3" QPF contour along and south of
Highway 34 and east of I- 35. The 12z GEFS spread is 1.5 to 2.5"
while the 6z EPS spread is 1.75 to 3" for the 25th and 75th
percentiles at OTM. Further, this southeast forecast area has
about a 30 to 40% chance of exceeding 3" of rainfall through 6z
Monday according to NBM v4.1. So, there is high confidence in the
highest rain totals over our southeastern forecast area and likely
eclipsing 2" in many of those areas and perhaps 3" in a few of
those areas. These amounts and over a prolonged period are less
concerning from a flash flood standpoint given that most areas
south of Highway 30 have a 3"+ over 6 hour flash flood guidance.
Further, contingency hydrographs over southern Iowa show below
action stage rises on rivers with OTMI4 5` below flood stage,
MOLI4 2` below flood stage, and CHTI4 3.5` below flood stage given
maximum rainfall. Given the prolonged nature of the rainfall and
high flash flood guidance along with a buffer in the contingency
hydrographs, have held off on issuing a flood watch. Rises on
streams and rivers and ponding in low lying and poor drainage
areas seems likely and could be exasperated in localized areas if
harvested field stubble clogs culverts/drainage ditches.
Another severe risk may evolve ahead of the low pressure as it
tracks just south of the Iowa/Missouri border with the warm front in
the vicinity of the same border. Most soundings solutions from
the 9z/12z runs of the HRRR, RAP, NAM, and GFS show the surface
inversion remaining, meaning that the warm front does not make it
or does not make it far into southern Iowa. This would mitigate
concerns about surface based storms and tornadoes. Did come across
one sounding that showed a one or two hour window with surface
based potential at OTM with 2000 J/kg of instability and 40 knots
of deep layer shear, but this seems like an outlier case given the
preponderance of guidance. Finally, winds from the east will
increase and be gusty on Sunday, especially over northern Iowa, as
the low pressure passes over northern Missouri. As the low
pressure moves into northern Illinois, rain showers will wrap
around on the back side of the low. Initial guidance showed an
hour or two of a rain-snow mix over north central Iowa, but it is
likely that drier air will arrive before the air is cold enough to
support it.
.LONG TERM.../Sunday night through Saturday/
Issued at 252 PM CDT Sat Oct 23 2021
The long term weather pattern remains active. Monday will start
out quiet and cooler than normal as ridging moves across the
state, followed by a slight rebound to near normal Tuesday as low
level return flow sets up.
The next weather-maker is on tap for mid week. Deterministic
forecast models are in general agreement that the low now over the
Pacific will continue to dig and deepen as it pushes eastward across
the CONUS and into the midwest around mid week. With the energy
still well off the west coast, confidence remains low in forecast
timing and details from Tuesday night into Thursday, since small
changes in the track of the surface low and associated fronts will
cause notable differences in the sensible weather. Thus the general
thinking is that there will be a round or two of precip mid week and
seasonable temperatures.
&&
.AVIATION.../For the 00Z TAFS through 00Z Sunday evening/
Issued at 652 PM CDT Sat Oct 23 2021
Deteriorating conditions during the period as cigs lower and
precipitation increases from south to north. This evening will
remain primarily VFR but possibly IFR conditions will reach
KDSM/KOTM prior to 12z followed by lowering conditions at the
other sites. East wind overnight will become breezy to even gusty
at times Sunday.
&&
.DMX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SHORT TERM...Ansorge
LONG TERM...Dubberke
AVIATION...Donavon
Area Forecast Discussion
National Weather Service Goodland KS
850 PM MDT Sat Oct 23 2021
.UPDATE...
Issued at 850 PM MDT Sat Oct 23 2021
The latest short range guidance has come around to the GFSLamp
guidance in producing visibilities of 1/4 mile or less in dense
fog for all but Hitchcock and Red Willow counties. Have gone ahead
and issued a Dense Fog Advisory that is in effect until 11z. KITR
(Burlington, CO) reported 1/4sm in dense fog about 20 minutes ago.
&&
.SHORT TERM...(This evening through Sunday)
Issued at 315 PM MDT Sat Oct 23 2021
A fairly difficult forecast unfolded for today as persistent low
clouds and dense fog hung around all morning and thus far into the
afternoon. Visibility is very slowly improving at KOEL and KCBK
with 1/2 mile now being reported by their AWOS. This lingering
cloud cover has severely impacted afternoon highs for west Kansas
and Nebraska as highs have been lowered into the 50s. RAP
analysis and visible satellite show an advancing low pressure
system moving off of the Rockies with additional clover emanating
onto the Colorado Plains. The low is expected to be fairly quick
moving as it will be out of the area around 18Z tomorrow. As the
low approaches the chances for light rain increases starting late
this afternoon and into the night. The best potential for rain
showers appears to be along and east of Highway 83 with less than
0.05" expected. Confidence has also increased in the development
of fog again. Guidance indicates areas of fog could begin
developing as early as 03Z and becoming more widespread throughout
the night and through the morning. Locally dense areas may occur
as the atmosphere is more moist and with convergence from the
approaching low. It also was hard to ignore the fact that Colby,
Oakley and Scott City all were below 1 mile visibility for the
majority of the day. A Dense Fog Advisory may be needed by the
upcoming shifts but held off for now until more certainty in the
magnitude comes into focus. Overnight lows for tonight will be
warmer than the past nights in part to the cloud cover and
rainfall potential. Overnight temperatures look to be in the mid
40s to low 50s across the area.
Sunday, rain showers come to an end around 18Z as clouds and any
lingering fog dissipate. The afternoon looks to be mainly clear
as temperatures are forecasted to rise into the 60s to 70s. If the
clouds do hang around longer then a similar situation to today
may play out with cooler high temperatures being realized. Breezy
to gusty winds look likely in wake of the low with sustained winds
of 15-20 knots and and perhaps wind gusts up to 30 knots,
potentially higher at times. The clear skies persist into Sunday
night which will allow radiational cooling to lower temperatures
into the 30s again with frost again possible. Sunday night into
Monday morning, some guidance has again been hinting at a window
for fog development, have left out of the forecast for now due to
lack of confidence.
.LONG TERM...(Monday through Saturday)
Issued at 305 PM MDT Sat Oct 23 2021
The upper ridge moving over the High Plains on Monday continues
east over the Plains states on Tuesday. The pattern over the
central and western U.S. becomes more amplified as the trough
moving through the Intermountain west deepens into a closed low
over the southern Rockies Tuesday night, emerges over the
Panhandle region Wednesday morning, and moves across Oklahoma by
Wednesday evening. Timing and location differences in the position
of the upper low start to show up on Thursday as the low moves
into the Mississippi valley area with ridging returning to the
central High Plains Thursday night and Friday ahead of the next
upper trough moving into the Rockies by Saturday.
Monday into Tuesday morning will be dry across the forecast area
with the ridge in place aloft and high pressure at the surface
moving to the east.
As the upper pattern amplifies and is reflected at the surface by
a low developing over eastern Colorado Monday morning, the
pressure gradient and winds speeds begin increasing across the
central High Plains on Tuesday with sustained southerly winds
around 20 kts and gusts near 35kts by mid day. Expect the surface
trough to move across the area Tuesday evening followed by a cold
front with winds turning northwest and showers moving across the
forecast area with a few thunderstorms possible across mainly the
eastern sections of the forecast area Tuesday evening. Some of
those thunderstorms could become severe mainly over the far
eastern sections of the forecast area east of a line from McCook,
Nebraska to Quinter, Kansas.
Temperatures on Wednesday will be 10-15 degrees cooler with
showers continuing eastward with the low pressure system along
with gusty winds on the back side of the low. Showers move out of
the area Wednesday night and winds diminish as the system
continues to the east.
Dry and cooler conditions remain through Thursday with dry and
slightly warmer daytime temperatures on Friday and Saturday. With
mostly clear skies and lighter winds, expect early morning
temperatures Friday and Saturday morning to dip into the lower 30s
for possible areas of frost/freeze.
&&
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 735 PM MDT Sat Oct 23 2021
KGLD...sub VFR conditions are expected from taf issuance through
15z under stratus and fog. Winds begin the period from the
northeast under 10kts backing to the north then northwest at
similar speeds through sunrise Sunday morning. Northwest winds
gusting 25kts or so are expected shortly after sunrise with VFR
conditions expected.
KMCK...sub VFR conditions are expected from taf issuance through
15z under stratus and fog. Winds begin the period from the east
under 10kts backing to the northeast then north at similar speeds
through sunrise Sunday morning. Northwest winds gusting 25kts or
so are expected by mid to late morning with VFR conditions
returning.
&&
.GLD WATCHES/WARNINGS/ADVISORIES...
KS...Dense Fog Advisory until 5 AM MDT /6 AM CDT/ Sunday for
KSZ001>004-013>016-027>029-041-042.
CO...Dense Fog Advisory until 5 AM MDT Sunday for COZ090>092.
NE...Dense Fog Advisory until 5 AM MDT Sunday for NEZ079.
&&
$$
UPDATE...99
SHORT TERM...TT
LONG TERM...LOCKHART
AVIATION...99
Area Forecast Discussion
National Weather Service Hanford CA
215 PM PDT Sat Oct 23 2021
.SYNOPSIS...
Northwesterly breeze across the district today as northwest
flow aloft continues. A very strong and wet storm system
will approach the region on Sunday. Breezy to gusty conditions
are possible along the coastal range Sunday afternoon through
the morning on Monday. Heavy rain below 8,000 feet and snow above
8,000 feet will begin impacting the area late Sunday, and will
continue through Monday afternoon. Residual, upsloping showers may
persist along the Sierra Nevada and Tehachapi mountains Tuesday.
Drier and warmer pattern Wednesday and afterwards.
&&
.DISCUSSION...
Cooler than normal conditions continue today after the passage of
yesterday`s cold front. Latest observations indicate that most
areas won`t get much above 70 degrees this afternoon, which is
several degrees below average. Starting tonight, a robust storm
system will begin to dive out of the Gulf of Alaska and approach
the area tomorrow morning. This storm system will feature an
impressive fetch of moisture along the cold frontal boundary,
forming an Atmospheric River. Ahead of the cold front, breezy
conditions may occur starting mid day Sunday through Monday
morning along the Coastal Range, so a Wind Advisory has been
issued for wind gusts up to 45 mph.
As the upper low dips south and then to the east on Sunday,
upsloping snow showers will begin at very high elevations along
the Sierra Nevada. Snow levels will start initially around
10,000-11,000 feet on Sunday afternoon ahead of the cold front.
Light rain may also begin at lower elevations of the forecast
area, including the norther San Joaquin Valley by late in the
afternoon Sunday. The cold front is progged to trek southward
through the evening Sunday evening and Sunday night, bringing
moderate precipitation rates just ahead of it. The system overall
has been trending slower, so we did push back the start times for
our products. The new start of the Flash Flood Watch for the
Creek Fire Burn Scar will be 5 PM Sunday, with the Flash Flood
watch for the KNP, Windy, French, and SQF Burn Scars/Fires now
starting at 11 PM Sunday. The Winter Storm Watch for the Sierra
Nevada above 8,000 feet has also been upgraded to a Winter Storm
Warning, with a 5 PM start time on Sunday. See our Winter Storm
Warning for more details.
The most intense rainfall/snowfall rates will come with the cold
front itself which is forecast to pass through the region very
late Sunday night into Monday morning. Some high resolution model
guidance such as the HRRR and the ensemble HREF are showing that
rainfall rates of around 1" per hour are possible in the Sierra
Nevada below the snow line early Monday morning along the cold
front. Intense rainfall of 1"/hour pose a risk to recent burn
scars, with debris flow flooding possible. Lesser rainfall rates
around .5" an hour are predicted for the San Joaquin Valley and
the coastal range as the cold front passes through. Some flooding
along the Coalinga Foothills may be possible as well as nuisance
flooding in the San Joaquin Valley Monday morning. Heavy rain
will continue in the Sierra Nevada as the front pushes southward
through Fresno County sometime early to mid morning on Monday. As
the front pushes even further south later in the morning rainfall
and snowfall rates should diminish as moisture along the front
gets wrung out over the Sierra Nevada.
The front should exit the region late on Monday. Rainfall totals
for the valley may range from 1-2 inches in the northern SJ
valley to .5-1 inches in the southern SJ Valley. Rainfall totals
in the Sierra Nevada below 8,000 feet may reach 4-6 inches Fresno
County and northward, with 2-3 inches in the Sierra Nevada in the
Tulare County Mountains. Up to 1 inch of rain may fall in the Kern
County mountains through Monday afternoon. Snowfall totals of 2-4
feet are also predicted for the Sierra Nevada above 8,000 feet
through Monday evening, with the most snow falling in Marpiosa
and Madera Counties. There are some indications that a rumble of
thunder or two will be possible in the SJ valley Monday afternoon
associated with post-frontal instability. We`ll see how that
threat evolves with upcoming model runs.
After Monday, residual, upsloping-natured showers are favored across
the north and western facing slopes in northwest flow. A ridging
pattern looks to emerge after Tuesday in the Eastern Pacific. This
will lead to a warming and drying trend across the region, however
blended model guidance is still favoring below average temperatures
for the region.
&&
.AVIATION...Areas of MVFR in low clouds and precipitation with
local mountain obscuring IFR over the Sierra Nevada north of Kings
Canyon, extending south over the Tehachapi mountains through 0z
Sunday. IFR visibility in heavy rain and snow in the Sierra Nevada
after 18z Sunday. Otherwise, VFR conditions will prevail across
the central CA interior for the next 24 hours.
&&
.AIR QUALITY ISSUES...
None.
&&
.CERTAINTY...
The level of certainty for days 1 and 2 is high.
The level of certainty for days 3 through 7 is medium.
Certainty levels include low...medium...and high. Please visit
www.weather.gov/hnx/certainty.html for additional information
an/or to provide feedback.
&&
.HNX WATCHES/WARNINGS/ADVISORIES...
Flash Flood Watch from Sunday evening through Monday evening for
CAZ322-329>331.
Flash Flood Watch from Sunday afternoon through Monday evening
for CAZ318-320-325>327.
Winter Storm Warning from 5 PM Sunday to 11 PM PDT Monday for
CAZ323-326>331.
Wind Advisory from 11 AM Sunday to 11 AM PDT Monday for CAZ300-
304-308.
&&
$$
public...Bollenbacher
aviation....Bollenbacher
weather.gov/hanford
Area Forecast Discussion
National Weather Service Wichita KS
642 PM CDT Sat Oct 23 2021
.SHORT TERM...(This evening through Sunday)
Issued at 324 PM CDT Sat Oct 23 2021
...Updated for the 00Z Aviation Forecast...
FORECAST HIGHLIGHTS:
* Conditional isolated strong/severe storm threat this evening
across portions of central and south-central Kansas.
* Strong/severe storm threat far eastern Kansas Sunday afternoon.
* Potential for widespread rain and embedded thunderstorms Tuesday
night through Wednesday night.
THIS EVENING-TONIGHT...Cannot rule out a stray thunderstorm this
evening, generally along/west of the Flint Hills and south of I-70,
in vicinity of a dryline/warm front triple point, and also near a
remnant outflow boundary from convection early this morning. Latest
RAP, NAM, and HRRR suggest boundary layer heating/moistening may be
just enough to weaken the cap sufficiently for a rogue storm or two
to form. However, there are some negatives, namely lack of large
scale mid/upper forcing, along with mid-level temperatures warming
with time this evening. If deep moist convection can indeed breach
the cap, sufficient combination of instability/shear would support
an isolated large hail/damaging wind threat. Will continue to
monitor observational trends.
Otherwise, thinking brunt of widespread showers/thunderstorms
overnight will be well northeast of the forecast area, within a zone
of strong/deep warm advection and moisture transport north of the
warm front. However, thinking a smattering of isolated to widely
scattered showers/storms could increase for locations generally
along/east of I-135 after midnight, within a zone of rich mid-level
moisture amidst increasing large scale ascent ahead of the
approaching shortwave. This activity will likely remain below strong
or severe levels.
SUNDAY...Still thinking the greatest severe threat Sunday afternoon-
evening will be just east of the forecast area across far eastern
Kansas and Missouri, as a powerful shortwave and associated stout
mid/upper speed max overspreads a moist/unstable warm sector. The
cold front reaches the Flint Hills by about lunchtime, with storms
possibly initiating as early as 2-3pm. Consequently, will hold onto
a conditional severe threat as far west as Yates Center-Fredonia-
Independence. Strong/deep wind fields in concert with moderate to
strong instability will be supportive of severe weather. Long
clockwise-turning hodographs and lower LCLs may also support a
tornado threat, even if storms tend to go more mixed mode and/or
linear with time. But once again, the greatest threat will be
probably be just east of the forecast area.
.LONG TERM...(Monday through Saturday)
Issued at 324 PM CDT Sat Oct 23 2021
TUESDAY-THURSDAY...Attention then turns to the mid-week period, as
model consensus progresses another deep/potent upper trough east
across Mid-America. Timing and amplitude of this next system is
still in question, with run-to-run and model-to-model consistency
issues abounding. The GFS remains the faster solution, supporting
lower rainfall totals, and rain chances only Tuesday night through
Wednesday morning. In contrast, the ECMWF and to some extent the
Canadian model remains slower and deeper, supporting a more
prolonged rain event Tuesday night through Thursday, with much
greater rainfall totals. Furthermore, while the overall synoptic
pattern favors at least a mention of strong to severe storms,
suspect the big limiting factor will be limited moisture return
and associated instability. Stay tuned for later forecasts.
FRIDAY-SATURDAY...Building upper ridging and associated large scale
subsidence should support mostly quiet weather Friday through next
weekend.
&&
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 635 PM CDT Sat Oct 23 2021
MVFR cigs are expected to expand into central KS this evening as a
warm front lifts northward across the area. The best chance to see
reduced flight categories tonight will be along the I-70 corridor
where IFR/LIFR are anticipated with some drizzle developing in a
moist upslope regime. As the front moves eastward during the
morning hours on Sunday, flight categories will improve from west
to east as drier and more subsident air overspread the region. We
could see some transient showers or perhaps an isolated storm impact
south central and southeast KS tonight as we remain within the
warm sector with some increasing large-scale forcing for ascent as
the shortwave trough approaches but the bigger concern will be
widespread LLWS impacting all of south central and southeast KS
through the overnight and early morning hours. VFR will return
from west to east during the morning hours on Sun.
&&
.PRELIMINARY POINT TEMPS/POPS...
Wichita-KICT 66 73 43 65 / 30 10 0 0
Hutchinson 64 69 40 64 / 20 10 0 0
Newton 65 71 42 63 / 30 10 0 0
ElDorado 66 73 43 63 / 30 10 0 0
Winfield-KWLD 68 77 45 67 / 30 10 0 0
Russell 52 64 37 62 / 20 20 0 0
Great Bend 53 66 38 63 / 20 10 0 0
Salina 58 66 39 63 / 30 20 0 0
McPherson 64 68 40 62 / 20 10 0 0
Coffeyville 69 79 46 66 / 30 30 10 0
Chanute 68 77 45 63 / 30 30 0 0
Iola 66 76 45 62 / 30 30 0 0
Parsons-KPPF 69 78 45 65 / 30 30 10 0
&&
.ICT WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
SHORT TERM...ADK
LONG TERM...ADK
AVIATION...MWM
Area Forecast Discussion
National Weather Service Lincoln IL
903 PM CDT Sat Oct 23 2021
.SYNOPSIS...
Issued at 240 PM CDT Sat Oct 23 2021
Moderate to heavy rain with a potential flooding threat especially
north of I-72 will impact central Illinois from very late tonight
through early Monday morning. In addition, severe thunderstorms
may impact central Illinois, especially Sunday evening. Another
storm system is expected in the middle of the week.
&&
.UPDATE...
Issued at 902 PM CDT Sat Oct 23 2021
Some spotty light rain showers have been detected on radar over
east central and southeast IL this evening in weak isentropic lift
aloft. However, the significant precipitation should develop
toward midnight from NW MO to southern IL as a low level jet
strengthens ahead of a strong surface low moving into SW KS. This
precipitation should continue to intensify and expand
northeastward into the central IL forecast area overnight, along
with some thunderstorms developing in elevated instability
aloft. Have made some minor updates to PoPs to delay initial
arrival of precipitation slightly, as well as to account for
earlier evening showers/sprinkles. Otherwise, lows ranging from
mid 40s north of I-74 to mid 50s south of I-70 look on track.
&&
.SHORT TERM...(This evening through Sunday)
ISSUED AT 240 PM CDT Sat Oct 23 2021
Light rain is detected on radar and via observations south of
I-70 near Flora and Olney as the first wave of rain along the warm
frontal zone moves east. A sharpening warm front is most
noticeable in the north-south dew point gradient as well as the
surface pressure field as extensive cloudiness and convection has
muddled the temperature field somewhat. Expect on and off rain
showers south of I-70 with perhaps a break in the late evening
before the first prominent round of steady rain begins to move
into central Illinois late tonight/early Sunday morning as isentropic
upglide serves to expand the area northward while the warm front
moves little. Additionally, the 12z HREF indicates an area of
elevated MUCAPE impinging on areas mainly south of I-72 where a
hail threat will accompany the morning activity.
Some areas may see a brief break during the early afternoon as
the warm front moves northward through Illinois. This will allow
unstable air in the warm sector to enter into central Illinois
with the latest HRRR indicating 1500-2000 J/kg of SBCAPE south of
the front until diurnal cooling starts and values slowly decrease.
Exactly how far the warm front lifts northward will be a major
factor not only in who might see the greatest tornado threat
should a surface-based storm initiate along this boundary, but
also how much of central Illinois is overspread by unstable air in
the warm sector and might be prone to a greater severe wind
threat in the evening in association with convection ahead of the
surface cold front. Current timing has a pre-frontal line of
convection crossing the CWA late Sunday evening. The severe threat
should end during the early morning hours on Monday.
Back to the rainfall...once rain re-strengthens north of the warm
frontal boundary a swath of fairly continuous moderate to heavy
rainfall is forecast predominantly north of I-72. Combining the
early morning rainfall, the afternoon rainfall, and the rain ahead
of the cold front Sunday evening, fairly widespread totals of 1-3
inches are expected north of I-72 while some locations may see
totals of up to 4-5 inches. A Flash Flood Watch has been issued
for this area in coordination with neighboring offices. Lower
rainfall totals are expected south of this line with potentially
more of a break between periods of rain, but totals of 1-2 inches
will still be common.
.LONG TERM...(Sunday night through Saturday)
ISSUED AT 240 PM CDT Sat Oct 23 2021
The severe and heavy rain threats are expected to wind down by
around 3 am Monday, with the surface low moving across north
central Illinois Monday morning. Breezy north winds and slightly
below normal temperatures are expected during the day on Monday
as the surface high moves into the Midwest. Another fairly cool
day is anticipated Tuesday with light winds before the next system
approaches the central US. WPC clusters show noticeable
differences in timing and location of the next trough with about
20% of members indicating the base of the trough moving through
Illinois on Thursday, while the other clusters show weaker
solutions over the southern Plains or a still deep but farther
south/closed solution. At any rate, since differences in
timing/strength still exist will go with the blended solution for
precip chances other than slowing progression of precip Wednesday
in coordination with neighboring offices. It`s still uncertain
whether a closed low will continue to influence central Illinois
into late week (65%) or we`ll be in dry northwest flow (35%).
&&
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 645 PM CDT Sat Oct 23 2021
Decreasing cigs and vsbys are expected to spread from south to
north overnight as a strong storm system and associated warm
front approach the area. Expect MVFR cigs at KSPI and KDEC by
02Z-03Z, and northward to KPIA and KBMI by 05Z-06Z. Rain with a
few thunderstorms will develop by a few hours later, bringing MVFR
vsbys as well. Expect conditions to further deteriorate by
morning, with IFR cigs expected by around 12Z. Showers and a few
possible thunderstorms will continue through the day, however the
I-72 terminals KSPI-KDEC-KCMI could see some improvement in cigs
to MVFR and a few more breaks in precipitation after the warm
front lifts through the area by around 21Z. A strong line of
thunderstorms is likely to arrive shortly after 00Z at these
terminals, deteriorating conditions again.
&&
.ILX WATCHES/WARNINGS/ADVISORIES...
Flash Flood Watch from 1 AM CDT Sunday through Monday morning
for ILZ027>031-036>038-040>048.
&&
$$
UPDATE...37
SYNOPSIS...AAT
SHORT TERM...AAT
LONG TERM...AAT
AVIATION...37
Area Forecast Discussion...UPDATED
National Weather Service Chicago/Romeoville, IL
910 PM CDT Sat Oct 23 2021
.UPDATE...
909 PM CDT
No significant evening changes to the forecast for the stout
autumn system moving in Sunday and persisting into Monday, and no
changes to the Flash Flood Watch or Lakeshore Flood Advisory. New
00Z model data is just starting to arrive, and full evaluation of
that will be done by the overnight shift.
Just a few notes here. A Wind Advisory will need to be considered
by the overnight shift for not only lakeshore counties of
Illinois but even inland along/north of I-88. The pressure
gradient is strong over that area much of tomorrow night. It`s
the region on the north side of a quick moving low pressure
around 1001 mb (lowest 5th percentile for the time of year in the
central Illinois area). Forecast soundings from many models show
40+ knot speeds within 1,500 ft of the ground and the low-levels
being somewhat mixed. The 00Z HRRR also has several hours of
40-45 mph gusts in the northern third of the CWA tomorrow night.
Advisory or not, the key message is consistently windy late day
Sunday through Monday A.M., and continuing all Monday on the shore.
The 18Z guidance and the 00Z guidance that has arrived remains
consistent on the low pressure path across the southern CWA. The
strongest moisture convergence on the nose of a 60 kt low-level
jet, and at least transient frontogenesis at and above this level,
is generally just ahead of this low path in the warm advection.
The Flash Flood Watch covers this area of numerous hours of heavy
rainfall well, though do think at least minor/poor drainage type
flooding in parts of the metro further north are a good bet too
given the low path and time of year (leaves impacting efficient
drainage). Will need to keep an eye on potential for exceeding 2
inches of rainfall into Kane, DuPage, and all of Cook Counties.
The 00Z HRRR, much like the 18Z long range run, continues to
show the surface warm sector knocking on the door to the southern
CWA. We still have strong doubts on whether the effective air
mass can get into the far southern CWA, but the kinematic
parameter space is quite noteworthy. The threat gradient for
severe weather may end up being quite sharp somewhere in central
Illinois and the details of where may not be able to fully emerge
until convective effects are resolved into the day tomorrow.
Finally, this evening`s river forecasts from the North Central
River Forecast Center (NCRFC) do take into account the full
forecast QPF of this system. This is bringing multiple river
points in the southern CWA to flood stage. At this time these are
all to the minor flood category, but any boost in QPF may result
in possibly an uptick -- namely the Vermilion, Kankakee,
Iroquois, and Little Calumet River basins.
MTF
&&
.SHORT TERM...
235 PM CDT
Through Monday...
Synopsis:
A powerful autumn storm system will take shape over the next 24
hours and eventually bring a multitude of inclement and
potentially hazardous weather to the area Sunday into Monday.
Water vapor imagery early this afternoon depicts a powerful
Pacific jet stream beginning to crash onshore the west coast. This
strong jet stream (130-150kt at 250mb) will translate eastward
into the central Plains tonight resulting lee cyclogenesis in the
left exit region of this jet. This cyclone will intensify and
close off a mid-upper level circulation as it moves east toward
the mid Mississippi Valley Sunday night into early Monday.
Southerly winds are already transporting moisture northward from
the Gulf of Mexico north into the southern and getting into the
central Plains. Strong low level jet (>50kt @ 850mb) will develop
tonight in response to the developing lee cyclone and help
accelerate the northward transport of moisture in advance of the
system.
Early this afternoon, a warm front at the surface extends from
central Kansas east to downstate IL. As the cyclone develops
tonight, look for warm front to begin lifting northward with
strengthening low level jet resulting in significant low level
theta-e advection into strengthen low-mid level frontal system.
The strengthening low-mid level frontogenesis combined with the
strong theta-e advection should result in a blossoming area of
showers and thunderstorms to the north of the sfc warm front.
This activity will lift north into the our CWA late tonight into
tomorrow morning, with this likely to be the first of multiple
rounds of showers and some thunderstorms as the system moves
rather slowly eastward across the region.
Hydrology:
Models continue to advertise near record levels of moisture
availability with precipitable water values near or above 1.5
inches pooling near and north of the quasi-stationary boundary.
The slow moving nature of the east west boundary combined with at
least waves of strong forcing, at first via theta-e advection and
frontogenesis and eventually from the DCVA with the cyclone
itself, should be quite effective at translating this abnormally
moist atmosphere into effective heavy rainfall production.
Higher resolution models continue to advertise narrower swaths of
well over 4" inches of rain in spots mainly south of I-80. Even
the lower resolution guidance has widespread 2-3"+ rainfall
amounts south of I-80 and one inch plus over most of the CWA.
While exact locations in the various models vary, the idea of
swaths of >4" of rain is a pretty consistent and concerning
signal in the convective allowing guidance. SREF probabilities of
2" of rain in 6 hours are in the 30-80% range over a sizable
portion of our southern CWA Sunday evening, which is close to the
6 hourly flash flood guidance (which isn`t taking into account
antecedent rainfall during the day Sunday).
A preponderance of the evidence supports issuing a flash flood
watch for our southern CWA. Not uncommon for warm sector
convection to our south to sometime retard the northward moisture
transport in these strong systems, reducing rainfall totals to the
north. In this case, round one of will occur tonight and into
Sunday, prior to any meaningful convection in the warm sector.
Widespread convection is expected to develop tomorrow
afternoon/evening across Missouri, however backing low-mid level
flow owing to the closing off of the mid-level low should actually
drive the weakening remnants of the Missouri convection north
into our CWA.
Latest runs suggest the rainfall with the trowel on the back side
of this system later Sunday night into Monday will probably be
mostly north of the areas most likely to see heavy and potentially
flooding rainfall on the "front" side of the storm. However,
thermodynamics would suggest a potential for a lake enhancement to
the rainfall over northeast Illinois Sunday night into Monday. So
while during and intensity of the rain stands a lower probability
of producing substantial flooding in northeast IL north of I-80,
could still see problems with standing water, particularly in poor
drainage areas. Probably a flood advisory type situation, if
anything.
Convection:
Some thunderstorms are likely very late tonight into Sunday
morning in the warm air advection regime over mainly our southern
CWA, though weak instability should result in mainly a heavy
rainfall threat. It appears very likely that our CWA will remain
safely north of the warm front with minimal severe weather threat
in our area. As the sfc low track east near I-80 the warm sector
could briefly make it into the southern portions of our CWA later
Sunday night, but instability is likely to be too weak that time
of day for a meaningful severe weather threat. However, could see
a bit of an uptick in lightning activity later Sunday night as
upper low approaches and we briefly poke into the warm sector.
Winds/Waves/Lakeshore Flooding:
Tightening pressure gradient in advance of the surface low will
result in gradually increasing easterly winds, particularly
starting late Sunday afternoon into Sunday evening. Over land,
mixing is not expected to be particularly efficient in the
easterly flow, but given the strong pressure falls and tightening
gradient it should be breezy/windy Sunday night over northern IL.
Of greater concern, relatively chilly air mass in place north of
the warm front flowing over the record warm Lake Michigan water
will result in very efficient mixing of the higher momentum air to
the surface over the lake and along western shores of the lake.
Bufkit forecast soundings from most models suggest sustained winds
over the lake of around 30kt Sunday night into Monday morning with
deep mixing in the marine boundary layer likely to transport down
gusts of 40-45kt.
These strong easterly winds will should result in large battering
waves along the Illinois shore Sunday night into Monday. While the
wind direction initially will not be favorable for a big storm
surge, the magnitude of the winds should result in some response
in lake levels which combined with the large waves will result in
a lakeshore flood threat. Winds will back to northerly and begin
to slowly ease, but likely continue at gale force until later
Monday afternoon. So while the winds may begin to ease slowly
Monday, the wind direction will result in a more favorable fetch
probably continuing the lakeshore flood threat. Will be hoisting
a lakeshore flood advisory for this time frame.
- Izzi
&&
.LONG TERM...
300 PM CDT
Monday Night through Saturday...
The main concern in the medium-long range is the potential for
another period of wet weather Thursday into Friday, though
confidence is very low. Temperatures will average near normal.
On Monday night, 850 mb temps will cool to near or below 0C, which
will set up respectable lake induced thermodynamics with 850 mb to
lake deltas up to 17C, equilibrium levels of 6-7kft, and a couple
hundred J/kg of CAPE. Drying and subsidence should push in from
the west later overnight or Tuesday morning, but before that,
think some lake effect showers are a decent bet. Unidirectional
brisk north-northeast flow from the surface to well aloft entails
very little wind shear and decent inland penetration of lake
effect showers. Introduced lower chance PoPs for this.
Weak high pressure ridging will bring a quiet and seasonable
Tuesday and Tuesday night. Attention then turns to the next strong
short-wave trough ejecting across the high Plains area, with lee
cyclogenesis Tuesday. Global guidance is in good agreement in
sharp short-wave ridging across the western Great Lakes on
Wednesday in response to the digging trough to the west, and
continued dry surface high pressure influence. As such, there has
been a decided drier trend on Wednesday, so continued to trend
PoPs downward.
Model variance grows substantially after the Wednesday daytime
period, greatly lowering confidence and predictability. The
southern Plains short-wave is forecast to close off at the mid and
upper levels over the Mid South on Wednesday, with strong
secondary cyclogenesis possible over the lower-mid MS Valley. Key
word here is possible cyclogenesis, as the operational ECMWF is
much farther south and slower with the key mass fields than the
GFS and CMC. There are some ECMWF ensemble members still similar
to the much more robust GFS and CMC suites, though the mean
generally supports the operational. While vice versa is true for
the other guidance, spread is massive.
What this all entails is that greatly disparate outcomes remain
plausible for later Wednesday night through Friday, ranging from
another wind driven soaking rain (GFS and CMC) to a period of
lighter rain later Thursday into Friday and much less wind (ECMWF
operational). Trended PoPs lower Wednesday evening when model
consensus is primarily dry, but then maintained NBM thereafter,
with PoPs peaking at likely on Thursday PM. Coming off the
significant rain event tomorrow into Monday, another soaker would
increase hydro concerns. Suffice to say, it will take some time to
resolve the model variance, so stay tuned. Turning ahead to
Halloween weekend, medium-long range guidance trends point toward
seasonable to slightly above normal temperatures and drier
conditions, with a surge of chilly air possibly waiting in the
wings to start November.
Castro
&&
.AVIATION...
For the 00Z TAFs...
Concerns in this period are the expected deteriorating conditions
Sunday morning as several waves of RA move over the area through
Sunday night. VFR conditions will continue for all sites tonight,
with wind speeds under 10 knots and directions VRB but mainly
between NNE and ESE.
Mid-level clouds will quickly thicken toward daybreak, followed a
few hours later by an increasingly lower low-level cloud deck.
Low- end MVFR ceilings should become common by late morning, with
widespread IFR ceilings during the afternoon and evening. The
potential exists for a period of LIFR ceilings Sunday evening.
Precip may begin as spotty -SHRA prior to mid-morning, but
quickly increase in coverage and intensity during the late
morning. Frequent periods of MVFR visibility are expected. The RA
will become more convective in nature Sunday evening, with a few
embedded TS possibly nearing ORD/MDW from the south.
Beginning around daybreak, winds will remain E/ENE through Sunday
night while strengthening. Frequent gusts to 30 knots and
sporadically to 35 knots are expected Sunday evening.
Kluber
&&
.MARINE...
235 PM CDT
Upgrading the gale watch to a gale warning. The gale threat
appears most substantial in the Illinois nearshore waters, but
will be upgrading Indiana as well even though gales appear very
marginal there until Monday. Confidence is high in 40-45kt
easterly gales Sunday night into Monday morning, with a couple of
the more aggressive models even hinting at a threat of a couple
brief low end storm force gusts. Winds should begin to slowly
subside Monday as they back to more northerly direction.
- Izzi
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...Flash Flood Watch...ILZ019-ILZ020-ILZ021-ILZ023-ILZ032-ILZ033-
ILZ039-ILZ105-ILZ106-ILZ107-ILZ108...4 PM Sunday to 10 AM
Monday.
Lakeshore Flood Advisory...ILZ006-ILZ103-ILZ104...7 PM Sunday to
7 PM Monday.
IN...Flash Flood Watch...INZ001-INZ002-INZ010-INZ011-INZ019...4 PM
Sunday to 10 AM Monday.
LM...Gale Warning...LMZ740-LMZ741-LMZ742-LMZ743...5 PM Sunday to 9 PM
Monday.
Gale Warning...LMZ744-LMZ745...8 PM Sunday to 9 PM Monday.
&&
$$
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Area Forecast Discussion
National Weather Service Pendleton OR
829 PM PDT Sat Oct 23 2021
.UPDATE...Scattered light showers developed this evening across
south central WA and north central OR, and showers will track
northeast and out of the forecast area over the next few hours.
Any additional showers the remainder of tonight until around 3 AM
will be isolated in a southwest flow aloft. Meanwhile,
precipitation associated with a deep low off the eastern Pacific
will spread inland. Between 3-5 AM, precipitation will develop
along the OR Cascades and as far east as Bend and Warm Springs.
Surface gradients will also tighten for increasing southerly winds
and breezy/windy conditions between midnight and sunrise.
High wind warnings and wind advisories were issued across most of
eastern OR and far southeast WA from 5 AM to 5 PM Sunday. The wind
advisory was expanded to include the John Day Basin. The low
offshore is impressive with a surface low possibly as deep as
944mb tomorrow! This could be one of the lowest surface pressures
in the northern Pacific in history. Strong southerly pressure
gradients combined with a low level jet around 55kts at 850mb will
bring strong winds to portions of the area. The area likely to
receive the strongest winds will be along the Oregon Blue Mountain
Foothills where several different high resolution models are
showing sustained winds of 40-45 mph with gusts 60-70 mph.
Downsloping winds off the Eagle Caps may also create similar gusts
in Joseph.
Precipitation amounts of 0.25-0.5 inch are expected for most of
the area Sunday and Sunday night. Although rainfall amounts are
not significant, the moist ground will lead to better potential
for fallen trees with weak roots.
Forecast looks good, and only minor updates were made. Again, the
John Day Basin was added to the Wind Advisory. Wister/85
&&
.PREV DISCUSSION... /issued 450 PM PDT Sat Oct 23 2021/
SHORT TERM...
Tonight through Sunday night...Broad westerly flow will remain
over the region early before the flow becomes more southwesterly
tonight. The gradient will tighten in advance of a very strong low
off the Oregon and Washington coasts that will move northeastward
toward the British Columbia coast by Monday morning.
The tightening gradient coupled with strong low level jet support
will bring increasing south winds on a southwest to northeast
axis from central Oregon across the Blue Mountain foothills, the
Blue Mountains and into portions of Wallow County.
The ECMWF Extreme Forecast Index (EFI) depicts this area well,
with a broad area between 0.8 and 0.9 across eastern Oregon and
smaller areas between 0.9 and 0.95, especially near the Blue
Mountains.
The latest NBM 4.1 continues to show very strong wind gusts in
these areas and also across portions of Wallowa County. The NBM
continues to be supported well overall by the HRRR guidance. As a
result, the previously issued high wind watches will be upgraded
to high wind warnings and portions of Wallowa County have been
added to the warning as well.
Additionally the same NBM 4.1 and HRR Guidance also supports
strong winds across central Oregon, though with values not quite
as high, so wind advisories have been issued for these areas.
By Sunday evening, the strongest winds should be subsiding.
As far as rain chances, there will not be much for the remainder
of today into tonight. However, as jet support increases and
several short waves move through, there will be an increasing
chance of showers during the day on Sunday, from west to east,
with rain chances decreasing during the late evening and overnight
hours. Most locations will end up with 0.25 inches or less,
though some of the higher terrain could receive upward of 0.50
inches with locally higher amounts.
High temperatures on Sunday will range from the lower 50s to
around 60, with overnight lows mainly in the 40s tonight and
Sunday night, except in the 30s across central Oregon.
LONG TERM...
Monday through Saturday...A series of troughs moves across the
Pacific Northwest through the end of the week keeping us windy and
wet. The strongest conditions in the extended period look to be
on Tuesday when the heaviest precipitation and strongest winds
should occur. Widespread QPF totals of 0.1-0.25 inch are possible,
with local amounts exceeding 0.5 inch, with gusty winds 20-30 mph
also expected. Into Thursday a brief period of weak ridging
coupled with southwesterly flow will slightly warm up the region,
with widespread mid to upper 60`s possible. Another trough behind
that though will drop us again on Friday, with slightly below
average highs then expected on Saturday. But a stronger ridge is
forecast to build in on Saturday, which should help to finally dry
us out and calm the weather pattern down by the end of the long
term and just beyond. Goatley/87
AVIATION...00Z TAFs...The deep low pressure system off the eastern
Pacific will have a large impact on the weather east of the
Cascades, and there are aviation hazards with it. A strong low
level jet will likely result in LLWS with 40-55kt winds just above
the surface for most of the TAF sites on Sunday. Surface winds will
also be considerably stronger tomorrow at the terminal airports,
especially along the Blue Mtn Foothills and Central OR. While
downsloping winds will keep CIGS high with little precipitation at
ALW and PDT, the other sites may have MVFR or less. Strong low
level upslope near the Yakima Valley may keep CIGs and VSBY low at
YKM for most of the day. Wister/85
&&
.PRELIMINARY POINT TEMPS/POPS...
PDT 43 61 43 60 / 40 50 80 20
ALW 46 60 46 62 / 40 50 70 30
PSC 45 60 43 63 / 40 70 70 20
YKM 41 56 38 57 / 20 90 20 40
HRI 45 61 42 63 / 40 60 60 20
ELN 38 52 37 54 / 20 90 40 40
RDM 40 60 33 55 / 50 90 30 20
LGD 44 55 41 56 / 20 70 60 40
GCD 43 55 42 57 / 30 80 70 30
DLS 45 57 42 60 / 20 90 20 60
&&
.PDT WATCHES/WARNINGS/ADVISORIES...
OR...Wind Advisory from 5 AM to 5 PM PDT Sunday for ORZ505-506-511.
High Wind Warning from 5 AM to 5 PM PDT Sunday for ORZ049-050-
502-503-507-508.
WA...High Wind Warning from 5 AM to 5 PM PDT Sunday for WAZ029-030.
&&
$$
SHORT TERM...85
LONG TERM....87
AVIATION...85
Area Forecast Discussion
National Weather Service Pueblo CO
246 PM MDT Sat Oct 23 2021
.SHORT TERM...(This evening through Sunday)
Issued at 240 PM MDT Sat Oct 23 2021
Currently...
A flat short wave trough was located over the central Rockies early
this afternoon. Quite a few showers were noted with it over NW CO.
Over most of the NWS PUB area, lots of wave clouds were noted,
leading to mostly cloudy skies over the region. Temps over the
region varied quite a bit, with L80s over far SE plains to U60s over
the Palmer Divide. Over the mtns and valleys, temps ranged from the
40s to L60s. Winds were still relatively light as it was breezy over
the higher terrain, and the gap flow area in the greater Walsenburg
region.
Tonight...
Progressive wave will move across the region bringing some light
snow to the higher terrain, with the brunt of it falling after
midnight. Best chance of some light accumulating snow will be over
the CONTDVD, with the central mtns being favored.
Breezy conditions will keep up across the region and this will
allow temps to be rather mild tonight, with lows on the in the 40s
across the plains and 20s in the mtns and valleys. West slopes
will see the (relative) warmest temps due to downslope flow.
Tomorrow...
Overall expect a very nice day. A few showers may still be lingering
early in the day across the central mtns. It may be a bit breezy
early but winds should decrease by late morning nearly all areas.
Temps tomorrow will be several degrees cooler than today and we
should see more Sun tomorrow across the region. /Hodanish
.LONG TERM...(Sunday night through Saturday)
Issued at 240 PM MDT Sat Oct 23 2021
...Strong system moves across Tuesday...
Significant Pacific storm system will affect the region starting
late Monday and last into Wednesday. This system will likely bring a
period of snow to all of the mountains, with the CONTDVD region
being most favored. I`d expect to see amounts of 3 to 6 inches
with locally heavier amounts on the west slopes of the divides.
Give the strong winds that will accompany this Pacific weather
system we will likely need some highlights for some of the higher
terrain areas for the Tuesday time frame.
Winds will be concern with this system all areas. By Tuesday
afternoon expect winds of 20 to 30 mph with gusts to 40 mph over the
plains. RH values will approach critical values and near critical
to critical (RED FLAG) conditions will be possible on Tuesday. It
will also be quite gusty over the mtns and valleys, with stronger
winds over the passes.
NBM guidance came in with some scattered POPs across all of the
plains Tuesday night and this is a change from earlier guidance.
Although the GFS still is rather progressive with this system (and
keeps a westerly component to all of the winds), the EC is much more
amplified and indicates some wrap around precip with this system.
Looking at the individual ensemble members from the EC and GFS,
there area several members that show some healthy qpf along the I-25
corridor, especially down in the greater Raton Mesa region
(However there are several members that show NO precip at all).
Given that this is a rather very dynamic system, I would not be
surprised if a stronger solution verifies with this event. This
system is rather warm so any precip on the plains that falls
Tuesday night will likely be liquid, with some snowflakes possible
over the Palmer Divide in the evening hours.
Wednesday...
System will be slow to push east,, however expect brunt of precip
will be out of the region by Wednesday morning, with just some
lingering showers in the C mtns and far eastern plains early. The
primary concern will be winds on Wednesday as the system will rap
up over the central plains and this will lead to strong gusty NW
winds over the region during the daylight hours. RH values may be
rather low and this may lead to some near critical fire weather
conditions once again over the plains.
Thursday into Saturday...
Dry with mild temperatures.
Sunday...
Another system will move across the region, this system will be
dropping out of Canada, so we may see some cooler air move into the
region for Sunday. Ensemble temp data shows a very large spread in
the member values, so some rather cool air will be possible with
this system. /Hodanish
&&
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 240 PM MDT Sat Oct 23 2021
VFR conditions are expected during the next 24 hours at all 3 taf
sites, KPUB, KALS and KCOS. Breezy conditions will last into the
early evening hours with winds then weakening.
&&
.PUB WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SHORT TERM...HODANISH
LONG TERM...HODANISH
AVIATION...HODANISH
For frequently asked questions about the Area Forecast Discussion
visit...
http://weather.gov/saltlakecity/general/afd_faqs.php
Area Forecast Discussion
National Weather Service Tulsa OK
702 PM CDT Sat Oct 23 2021
.DISCUSSION...
A quiet but unseasonably warm evening is underway across the
region. South winds will stay up thru the night as low pressure
continues to organize over the southern High Plains. The winds and
higher dewpoints (in the 60s) will yield rather toasty overnight
lows for tonight. In fact, with a forecast low of 70 on Sunday
morning at TUL, this would be only the 2nd year on record with a
low of 70 or higher on Oct 24th, the other year being 1939 with
the record of 71. There is an elevated storm over the eastern TX
Panhandle, giving some credence to the latest HRRR runs, which
suggest a small cluster of elevated storms will spread across
northwest and north central OK later tonight. Some of this
activity may graze our area as well and have thus stuck close to
the previous forecast of slight chances across northeast Oklahoma
north of I-44 after midnight tonight.
&&
.PREV DISCUSSION... /Issued 617 PM CDT Sat Oct 23 2021/
AVIATION...
CONCERNING TAF SITES KTUL/KRVS/KBVO/KMLC/KXNA/KFYV/KFSM/KROG.
Initial VFR conditions will give way to a period of MVFR cigs as
low level wind fields increase and bring increased moisture to the
region. That said, will continue with WS remarks overnight and into
tomorrow morning. Cigs will likely come up a little to low VFR by late
morning/early afternoon. A cold front will move through the NE OK sites
mid afternoon, however any TSRA chances will be east of those sites.
AR sites and KMLC have better chances for a period of TSRA, however
that looks to be at or after 00z- just beyond the scope of this
issuance.
PREV DISCUSSION... /Issued 256 PM CDT Sat Oct 23 2021/
DISCUSSION...
Convection continuing to straddle OK/KS/MO borders this afternoon
but is diminishing, slowly but surely. Attention for the forecast
now turns to the potential for severe weather Sunday afternoon
and evening.
Warm and moist airmass continues to stream north this afternoon
and will remain in place ahead of a potent low-amplitude wave
moving across the western U.S. and its attendant cold front.
Overnight lows tonight will remain much above normal, only a few
degrees below normal highs for the date. Most of the available
CAM guidance hints at some elevated showers or possibly a t-storm
developing late tonight into Sunday morning in WAA regime across
northeast OK.
Cold front is expected to push into northeast OK around 18z
Sunday, with scattered storms eventually developing along the
boundary by mid afternoon. In addition, 3km NAM and to a lesser
extent the HRRR hint at open warm sector convection well ahead of
the front from far eastern OK into western AR. Should any of this
manage to root in the boundary layer, they would pose a threat
for all modes of severe given the impressive low level shear.
Storms that develop along the front also would likely be severe,
though low level shear is less favorable by later part of the day
and especially by 00z. Eventual transition to a more linear storm
mode through the evening implies damaging winds become more
prevalent.
Front will sweep southeast through the area Sunday night with
more seasonable temps for Monday. Moisture should begin to surge
back north tuesday ahead of another potent upper system. Model
differences remain significant in handling the system with the
ECMWF continuing to depict a deeper cutoff low moving across Texas
Wed into Thu. Blended guidance will continue to be followed with
highest thunderstorm chances Tuesday night into Wednesday,
followed by cooler and breezy conditions late in the week with at
least a small chance of lingering showers into Thursday.
&&
$$
Lacy