sd discuss
Office: FSD
FXUS63 KFSD 260408
AFDFSD
Area Forecast Discussion
National Weather Service Sioux Falls SD
1108 PM CDT Thu Apr 25 2024
.KEY MESSAGES...
- Isolated to scattered showers and storms this afternoon. Additional
showers and storms move in tonight through Friday. Strong to
severe storms are possible tomorrow (greatest risk between 3
and 9 PM), along with locally heavy rain.
- Shower and storm chances taper off Saturday, but increase once
again on Sunday. Uncertainty remains, but those with outdoor
plans should keep an eye on the forecast.
- Through Sunday night, widespread beneficial rainfall of an
inch or more is expected. Some localized areas could see 2 or
more inches of rain in this period.
&&
.DISCUSSION...
Issued at 354 PM CDT Thu Apr 25 2024
REST OF TODAY AND TONIGHT: Isolated showers and storms continue this
afternoon and early evening with increasing clouds as the first
vorticity lobe advects north a wave ejecting out of the Rockies.
Precip has been struggling a bit with dry air below the cloud bases.
This low will begin to deepen tonight. Breezy conditions this
afternoon continue through tonight, with tightening pressure
gradient and the potential to mix into stronger winds aloft. Expect
southeasterly winds 20-30 mph, with gusts around 40 mph. Isolated
gusts as high as 45 mph have been briefly observed (as well as
sustained winds over 30 mph); however, these have been sporadic and
isolated enough in nature to preclude any wind headlines. As we lose
peak mixing later this evening and tonight, should see a slight drop
in gusts. But, we could see some 40 mph gusts overnight if there is
any mixing into the strengthening LLJ. Temperatures this afternoon
range from the upper 50s (cloudy areas along the MO River) to the
lower 70s (clear skies in SD and MN). Continued southeasterly flow
helps keep lows in the 40s and lower 50s.
Once afternoon showers/isolated storms lift north out of the area,
we'll turn our attention to the development just to our southeast in
NE through the evening hours. This activity, firing off the nose of
the LLJ and mid level vorticity lobe coincident with the WAA and
elevated warm front, will continue to lift north/northeast ahead of
the deepening low through the overnight hours. Instability is
elevated, and with values around 700 J/kg, severe weather looks
unlikely. Mid level lapse rates around 6 deg C/km could produce some
hail up to nickel sized in a stronger storm, and can't rule out a
gust or two around 50 mph overnight if showers/storms are able to
pull down any of the stronger winds. Rain amounts will be quite
variable due to the convection but areas under stronger and/or
multiple thunderstorms could see close to an inch, with the highest
amounts across northwestern IA.
TOMORROW AND TOMORROW NIGHT: Low pressure continues to deepen as it
lifts northeast through the day on Friday, lifting into the southern
MO Valley by the late afternoon/early evening hours - becoming more
stacked as it treks into our area. Strong to severe storms are
possible, although there is some uncertainty as we wait and see the
answers to these three questions: if/how quickly do clouds and
morning convection clear up during mid day, if/how quickly can the
atmosphere recover, and where does the surface warm front end up.
Stratus through the day would help to temper some of the heating and
conditional instability, and thus limit the threat somewhat (less
instability to work with). Regardless, Friday is shaping up to be a
high shear/low CAPE possible severe weather event. MUCAPE varies
between model runs, but generally is at or below 1200 J/kg. However,
0-6 bulk shear values of 35+ knots (with some higher res models
showing 50+ knots) and low level (0-1 km) shear 35-40+ knots is
enough for supercells (or mini supercells) and a tornado threat. LCL
heights are hovering around 1500 ft, which is also supportive of a
tornado threat. Mid level lapse rates also increase, especially if
we are south of the warm front and/or clear out, with values around
6.5-7.5 deg C/km supportive of the threat for large hail of half
dollar size - which is the main and most likely threat. Shear values
are more perpendicular to the front than parallel, so anticipate
that convection will be more discrete than linear. Damaging winds to
60-65 mph can't be ruled out, although would be a greater threat if
more of the conditional instability is realized. So, greatest
concern tomorrow for severe weather falls between 3-9 PM, with the
risks of large hail, tornadoes, and damaging winds. Rainfall totals
again could be around an inch or more for some in the convection,
but most could see a tenth to one half of an inch in this time.
Otherwise, clouds and breezy conditions prevail with highs in the
upper 50s to upper 60s (again, depending on how far north the front
goes and if we can clear out) Low pressure slides into southwestern
MN by the early overnight, with lingering wrap around showers and
isolated storms. Lows fall into the upper 40s and 50s.
SATURDAY: Low pressure moves off to the northeast Saturday, but will
likely see some lingering wrap around precipitation through the day,
especially early and along the Hwy 14 corridor. Breezy with highs in
the mid 50s west of the James to the upper 60s southeast of IA/MN
Hwy 60, where the cold front might not have fully exited until later
in the day and skies might be more clear due to the position of the
low. Lows at night fall into 40s to near 50.
SUNDAY: Pattern Sunday is oddly similar to what we're expecting
Friday and Friday night, with low pressure moving northeast out of
the Rockies into KS/NE. This low becomes stacked as it moves into
NE, with attendant warm front lifting north. More questions in the
track of this system as well as the timing, but could be another
high shear/low CAPE sort of day. This low is poised to move into the
MO River Valley a bit more quickly, during the late morning/early
afternoon Sunday. Similar questions regarding if/when we can clear
out, which would increase our conditional instability. Those with
outdoor plans should especially keep an eye on the forecast with the
chances for showers and storms. Will be keeping an eye on trends
here, with a potentially shifting severe weather risk.
When all is said and done through the weekend, beneficial rainfall
of 1-2" is possible to have fallen, as both the ECMWF and GFS
ensembles showing the entire area with an 80% chance or more of at
least an inch of rain. Mostly low (~30%) to moderate (40%) chances
of greater than 2" across the area, although there are higher
pockets in both the ensembles and the deterministic models.
EARLY/MID NEXT WEEK: Behind the low Sunday night, mid and upper flow
becomes more zonal with occasional shortwaves passing through.
Largely expect near to above normal temperatures with highs in the
upper 60s and 70s and lows in the 40s. Could see some periodic
showers or isolated storms with passing waves, but confidence is too
low to stray from the NBM at this time. Periodically breezy
conditions expected as well.
&&
.AVIATION /06Z TAFS THROUGH 06Z SATURDAY/...
Issued at 1108 PM CDT Thu Apr 25 2024
VFR ceilings have begun to deteriorate as stratus moves in, and will
continue to deteriorate to MVFR with scattered IFR for the remainder
of the period. Scattered showers and thunderstorms have begun across
the region. This first round is expected to remain sub-severe,
however dime to nickle size hail and stronger wind gusts up to 50
mph under thunderstorms are possible.
Winds are out of the southeast at 15-20 kts sustained with gusts 30-
35 kts. The highest gusts will shift from west to east during the
overnight period and will be predominate over northwestern Iowa by
Friday morning. Winds will gradually decrease through the afternoon
to less than 20 kts. There exists some concern for LLWS at KSUX near
the end of the period. Directional and speed shear may be present
between 1500 and 2000 feet AGL at 160 degrees and 45 kts.
A second, stronger round of showers and thunderstorms will develop
over northern Nebraska in the next few hours. Some of these storms
could be strong to severe with hail up to an inch and damaging wind
gusts. Several additional waves of showers and thunderstorms are
expected through Sunday as a low pressure system moves through the
area. Some of these storms could again be strong to severe.
&&
.FSD WATCHES/WARNINGS/ADVISORIES...
SD...None.
MN...None.
IA...None.
NE...None.
&&
$$
DISCUSSION...SG
AVIATION...AJP
Office: UNR
FXUS63 KUNR 260436
AFDUNR
Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
1036 PM MDT Thu Apr 25 2024
.KEY MESSAGES...
- Fairly widespread rainfall at times from Friday through much of
the weekend, especially the Black Hills and eastward.
- Warmer and drier conditions move in for much of next week.
&&
.DISCUSSION...(This Evening Through Thursday)
Issued at 228 PM MDT Thu Apr 25 2024
Current surface analysis shows low pressure over far east central
WY, with Pacific cold front stretching from far western ND to far
eastern WY. Upper level analysis shows trough over the Great
Basin to Four Corners region, with developing low pressure over
northeast AZ. Skies are variably cloudy, with the most clouds over
northeast WY and far western SD. KUDX radar shows scattered to
numerous showers and thunderstorms from northeast WY to the Black
Hills area and northwest SD as stronger energy aloft pushes
through western portions of the CWA. Temps are mostly in the 60s
and lower 70s, with some 50s over the Black Hills and rain cooled
areas. Brisk southeasterly winds are gusting to over 35 mph across
central SD, with lighter and more variable winds to the west.
Active weather pattern taking shape for the next several days as a
couple of upper level systems cross the region. Any severe weather
potential will be confined to the next several hours, with the
heaviest rain potential expected through Friday as the first upper
low approaches and passes over the region. Most favorable CAPE this
afternoon has been over and east of the Black Hills, ahead of the
front, with values around 1000 j/kg. Shear is rather weak in many
areas, so individual storms have been pulsy in nature and not very
long-lived, producing smaller hail for the most part. Various CAMS
show numerous storms continuing to develop through the afternoon
along and ahead of the front, trying to consolidate into at least a
broken line of storms along the front by late afternoon/early
evening. Marginally severe hail and strong winds would be the main
threats with stronger storms through at least late afternoon, with
gusty winds perhaps a threat into the early evening over portions of
the western SD plains if a more organized line of storms did
develop. With precipitable water values up to 150 percent of
average, heavy rain will accompany the stronger storms as well.
Initial activity with the cold front should shift east of the
forecast area toward midnight.
Upper low moves into the central Plains later tonight and somewhere
across central NE/eastern SD on Friday. Showers and some embedded
thunderstorms will wrap north-northwestward into the forecast area
late tonight and Friday, especially for the Black Hills area and
eastward. There appears to be at least a slightly further south and
east trend to the low track for Friday in the EC and now the latest
GFS, which would shift the heavier rainfall potential a bit further
east onto the western SD plains Friday. Right now, probabilities are
40 to 70 percent for an inch or more of rainfall Friday into Friday
night for the northern Black Hills and much of the west central to
south central SD plains. It will be breezy and cooler Friday, with
highs in the 50s and lower 60s. Lingering areas of lighter rainfall
can be expected Friday night into Saturday, especially for the Black
Hills area. Even cooler air pushes in for the weekend, with highs
only in the mid 40s to mid 50s, 40s over the Black Hills. As the
first upper low weakens and departs the region, a second one
develops over the central Rockies Saturday and moves northeast
across nearly the same areas as the first one Saturday night and
Sunday. This one looks to be somewhat quicker moving and its pcpn
shield not quite as big. Best chances for more significant rainfall
later Saturday night into Sunday will be across south central SD,
with mostly light rainfall elsewhere. Not much, if any, thunder
expected with the second system. There could be a little bit of snow
across the higher Black Hills Saturday night into Sunday, but any
accumulations look to be very minor. Breezy north to northeast winds
will persist through the weekend.
After this system exits the region Sunday night, near zonal flow is
expected to develop early next week. Above average temps will
quickly return to the area Monday and likely persist through the
week. Another low pressure system is progged to develop over the
northern Rockies and track north of the region Monday night and
Tuesday. There will be chances for showers and a few thunderstorms
late Monday into Tuesday, mainly across the Black Hills and northern
portions of the CWA. A building ridge behind this system should
bring mild and mainly dry conditions midweek, with the possibility
of a cold front passage in the Friday timeframe.
&&
.AVIATION...(For the 06Z TAFS Through 06Z Friday Night)
Issued At 1033 PM MDT Thu Apr 25 2024
Widespread MVFR/local IFR conditions expected tonight with an
expanding area of stratus on the SD plains. Showers and isolated
thunderstorms will linger over south central SD through the night.
Northerly winds will increase to 15-25 kts with gusts around 35
kts Friday morning with showers continuing on the SD plains,
shifting to more isolated activity to the west. Mainly VFR conds
expected over northeast WY.
&&
.UNR WATCHES/WARNINGS/ADVISORIES...
SD...None.
WY...None.
&&
$$
DISCUSSION/KEY MESSAGES...26
AVIATION...JC
Office: ABR
FXUS63 KABR 260549 AAC
AFDABR
Area Forecast Discussion...UPDATED
National Weather Service Aberdeen SD
1249 AM CDT Fri Apr 26 2024
.KEY MESSAGES...
- Winds will remain breezy out of the southeast with gusts of 35
to near 45 mph, and slowly diminish from west to east into
Friday morning.
- Weak thunderstorms will remain possible through Friday night.
Periodic soaking rains will continue into Saturday morning.
Another round of rain showers will move in Sunday, with a focus
over our southern and eastern counties.
&&
.UPDATE...
Issued at 1244 AM CDT Fri Apr 26 2024
Aviation discussion updated below for the 06Z TAFs.
UPDATE Issued at 839 PM CDT Thu Apr 25 2024
Have updated PoPs this evening to keep up with the latest trends
on radar. Rain should continue to push east and north through the
night, but especially on Friday as upper low gets closer to the
forecast area.
&&
.SHORT TERM /THIS EVENING THROUGH FRIDAY NIGHT/...
Issued at 401 PM CDT Thu Apr 25 2024
Elevated winds remain a concern over the next 1-3 hours, before
slowly diminishing. Several SD DOT and other locations have peaked
with wind gusts of 40-48 mph with a couple of locations briefly
around 50 mph. Winds will continue to be highlighted in our HWO and
other products through the evening hours.
Given the strong winds, the storms currently over
Meade/Perkins/Ziebach Counties (where winds are currently gusting
around 30 mph) will not take much to bring down near severe wind
gusts. We'll continue to monitor the storms as they move into a less
favorable area. MLCAPE values near 1400J/kg will shift to central SD
by 00Z Thursday and diminish. While most storms will have a mainly
easterly component, any right moving supercells that could develop
would be shifting to the southeast. Bowing segments or outflows
still show up on the latest HRRR runs, and we will continue to
monitor for that potential with gusty winds pushing out away from
storms.
The main wave of precipitation, with embedded weak thunderstorms,
will shift overhead overnight. There is significant enough
differences in the CAMs and other models to reduce confidence in
overall rainfall totals. Friday may end up with significant dry
periods between the Missouri River and James River, especially
during the afternoon hours as rain bands rotate through. There end
up being a couple of maximums with this initial wave into Saturday,
over central SD and far eastern SD/west central MN.
Overall, the surface low will shift northeast from Colorado to
Kansas and Minnesota Saturday morning, pushing a wetting rain across
the region. The initial surge of rain showers will overspread the
area during the evening and overnight hours. While there will be
breaks in the showers they will continue through at least Friday
night. The rain showers may be accompanied by thunderstorms/mainly
just rumbles of thunder (after our initial storms this evening over
north central SD) through Friday evening.
&&
.LONG TERM /SATURDAY THROUGH THURSDAY/...
Issued at 401 PM CDT Thu Apr 25 2024
This period kicks off at 12Z Saturday with one low pressure system
departing while the next one organizes right on the heels of the
first one to our southwest. Lingering rain shower activity will be
possible Saturday morning, especially across our eastern zones as
the upper low circulation and its sfc reflection lift northeast
across MN into the western Great Lakes. Any additional rainfall will
be minimal with up to around a tenth of an inch of accumulation
possible during the morning. Otherwise, our forecast area could
sneek in a period of dry conditions at least by midday and afternoon
before the next surge of moisture moves into the region. Daytime
high temperatures will be on the cool side as we're expecting
extensive cloud cover and 950mb temps between about +5C and +10C.
During the course of the day on Saturday, the 2nd in the series of
500mb low pressure systems will be organizing across the Four
Corners region of the CONUS.
Deterministic and ensemble guidance has a fairly good handle on this
system. They prog it to track northeastward out into the Central
Plains by Saturday night. It will continue to take a northeastward
track into NE during the day Sunday and end up somewhere around the
eastern SD/western MN border region by Sunday night before lifting
across northern MN and Ontario on Monday. The sfc low is expected to
be somewhat more displaced farther southeast from the upper features
compared to the first system that moves through tomorrow and
Saturday. Guidance takes this system's sfc low through the Omaha, NE
area and central IA by midday Sunday and Sunday afternoon and then
on up toward the Twin Cities and western Great Lakes on Monday. The
first surge of moisture with this system is forecast to make it
northward into our forecast area by late Saturday night/early Sunday
morning. This activity should become more prevalent and widespread
during the daytime as the upper wave circulation moves closer into
our region. It appears at this time our far southern and eastern
zones will have the greatest potential to see the steadier rain
shower activity and higher rainfall potential by the time this
system winds down early Monday.
NBM QPF probabilities for seeing a quarter of an inch or more in a
24-hour period ending at 12Z Monday range from 30-70 percent with
this highest values(>50%) from the James Valley and east into west
central MN. Bumping up the probs to at least a half inch or more
within that same time frame prog our eastern zones(James Valley and
points east) between a 40-50 percent range. Farther west,
probabilities drop off considerably to between 10-30 percent. By 12Z
Monday, most of the PoPs associated with this system will be exiting
our far eastern zones. A dry period can be expected thereafter until
late Monday into early Tuesday with another mid-lvl wave traverses
the region from west to east. Only light rain shower activity and
minimal rainfall is expected at this time. Drier conditions will
return for the end of the period by the middle of next week.
Temperatures will remain rather cool on Sunday with highs struggling
to reach 50 degrees. It will be brief however as a warming trend is
expected during the course of the first half of next week.
Temperatures at or above normal will be possible with daytime
temperatures in the 60s and 70s and overnight lows in the 30s and 40s.
&&
.AVIATION /06Z TAFS THROUGH 06Z FRIDAY/...
Issued at 1244 AM CDT Fri Apr 26 2024
Terminals KABR,KATY,KPIR,KMBG
Periods of -SHRA/SHRA and isolated -TSRA will continue to
overspread the region through the TAF period. In areas of heavier
SHRA, MVFR/IFR VSBY is possible. CIGs are forecast to drop into
MVFR/IFR as well.
&&
.ABR WATCHES/WARNINGS/ADVISORIES...
SD...None.
MN...None.
&&
$$
UPDATE...TMT
SHORT TERM...KF
LONG TERM...Vipond
AVIATION...TMT/TDK
