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000
FXUS63 KBIS 251442
AFDBIS

Area Forecast Discussion
National Weather Service Bismarck ND
942 AM CDT Thu Apr 25 2024

.KEY MESSAGES...

- Above normal temperatures today, with widespread highs in the
  70s. Strong southeast winds are likely across the south and
  central.

- Showers and thunderstorms are likely (60-90%) this evening
  through Friday, with the highest probabilities across the
  southern half of the state.

- Cooler temperatures on Saturday and Sunday, with low to medium
  chances of rain showers across southern and central North
  Dakota.

- Temperatures warm up back to above normal next work week, with
  low chances for showers most days.

&&

.UPDATE...
Issued at 939 AM CDT Thu Apr 25 2024

High clouds begin to move into the southwestern portion of the
area, with more expected to move into the area from Montana
through the day. Winds are a bit slow to develop this morning,
so the only major change we`ve made with this update was
slightly decreasing winds for the next few hours. Otherwise, the
forecast remains on track.

.UPDATE...
Issued at 647 AM CDT Thu Apr 25 2024

Rain showers have moved out of the southern James River Valley,
with mostly clear skies and quiet weather to start the day, with
the exception of breezy southeast winds across our far eastern
counties. No change in thinking today, with high-res guidance
bringing scattered convection into southwest North Dakota this
afternoon, expanding north and east through the evening and
overnight hours. Main update was to freshen up winds for this
afternoon and evening, but did not make much change. Still
holding off on any potential wind headlines and will let day
shift see how things are progressing later this morning.
Otherwise going forecast looks good for the day.

&&

.DISCUSSION...
Issued at 409 AM CDT Thu Apr 25 2024

Weak ridging aloft is passing over the Northern Plains this
morning, with multiple surface lows analyzed in central
Saskatchewan, southern Montana, and northeast Colorado. A
modest surface pressure gradient is in place across central and
eastern North Dakota, with southeast winds staying breezy
through the night. Light radar returns have been persistent in
the southern James River Valley on the nose of a low-level jet, and
one lightning pulse was recently detected in LaMoure County. We
will continue carrying slight chance POPs through the early
morning.

Strong low-level warm air advection will continue overspreading
the area today, producing forecast highs in the 70s and
potentially some 80s in western North Dakota. Southeast winds
will increase through the day across the southwest and central
parts of the state, with sustained winds around 30 mph. We opted
to not issue a Wind Advisory on this shift. The latest guidance
shows the stronger push of 850mb winds from a strengthening low
level jet doesn`t reach the James River Valley area until late
in the afternoon / early evening, in the 5 to 7 PM timeframe.
Forecast soundings are showing 35 to 38 knots at the top of the
mixed layer, which is a decrease from yesterday, and being later
in the day (past peak mixing time) there is uncertainty in how
strong the winds will end up. Will leave it to the day shift to
re-evaluate the latest high-res guidance and upstream obs to see
if an advisory will end up being needed.

As flow aloft turns southwesterly later today, a leading impulse
will move from Wyoming to the western Dakotas, bringing
increasing chances for showers and thunderstorms. Forecast instability
is in the 1000-1500 J/kg range, with decreasing mid-level
heights and modestly steep lapse rates. Some forecast soundings are
advertising an inverted V sounding which would promote gusty,
erratic winds. Forecast shear was already looking like the limiting
factor to convective strength today, and latest deterministic
guidance has lowered potential shear a bit further, with some
guidance only showing 15 to 20 knots of 0-6km shear. Any stronger
thunderstorms that develop will likely be short-lived and
pulsey before collapsing on themselves due to the low shear and
weak flow aloft. So although the severe thunderstorm potential
is low, we can`t rule out some small hail and strong wind gusts
with any of the more robust storms that potentially develop. CSU
machine learning probabilities have decreased in spatial
coverage just a touch with the latest run, but still have low
probabilities of severe hail across parts of western and south
central North Dakota. We are also still only in a general
thunder risk from SPC, with the Marginal Risk (level 1 of 5)
extending across most of western South Dakota.

A warm season Colorado Low is still on track to move through the
region late tonight through Saturday morning, bringing
widespread, high chances of showers and thunderstorms to most of
the forecast area. Precipitation will start to wrap around the
north side of the low late Thursday night into Friday morning as
the low begins tracking northeast through Nebraska, deepening
as it progresses. Friday is progged to be the main washout day,
with blended POPs ranging from 20-40% in northwest North Dakota,
to 75-95% from Dickinson, to Minot, and areas east. Tonight through
Saturday, there is a medium to high chance (45 to 75%) of at
least 0.50" of rain across central North Dakota, with chances
for at least 1" generally under 30%, with the exception of the
far southeast James River Valley which will be closer to the
center of the low. Any thunderstorms or heavier rain showers
could produce locally higher rain amounts, with forecast PWATs
on the far upper end of climatology (above the 90th percentile).
As the stacked low moves into central Minnesota on Saturday,
precipitation chances will taper off through the day, with only
a 10- 30% chance of rain showers across southern North Dakota
Saturday afternoon and night.

A cold front associated with a surface low moving through the
Canadian Prairies will move south through the area on Friday,
ushering in cooler Canadian air for the weekend. Highs on Saturday
and Sunday are likely to drop into the mid 40s to mid 50s, with
mostly cloudy skies and breezy northeast winds on Saturday as well.
Overnight lows could fall into the upper 20s across northern North
Dakota where rain chances and cloud cover are lower, so at this
point not concerned with any snow chances.

Although it does still look like a secondary trough and attendant
surface low will quickly follow the initial Colorado Low, latest
guidance is favoring a bit drier of a system overall and thus rain
chances have decreased some on Sunday. POPs are still highest and
decrease to the northwest, but now, chances for rain are generally
under 20% for western and north central North Dakota. The
probability of at least 0.25" of rain is low for most of the area,
with medium chances (40-55%) in the James River Valley. But overall,
this second system is looking less impactful compared to the first.

To start next work week, there is fairly good agreement amongst
ensemble members for Sunday`s system to exit quickly and have
ridging build in its wake. This is reflected in a strong rebound
in NBM temperature percentiles, which are showing high
confidence in highs returning to the 60s across the area. From
here, however, guidance deviates pretty strongly with a few
different solutions possible. One scenario is for ridging to
break down quickly and have us return to southwest flow aloft
(30%), one is for ridging to persist and put us under mostly
zonal flow (50%), and one is for a modest shortwave to move
through midweek (20%), which brings the highest precipitation
chances of all solutions. What is consistent among these
scenarios is for above normal temperatures to continue through
next work week, with precipitation chances and timing as the
main question. For now we carry NBM POPs which keep a broad
20-30% chance of showers to start the work week, with a brief
break before additional chances late in the week.

&&

.AVIATION /12Z TAFS THROUGH 12Z FRIDAY/...
Issued at 647 AM CDT Thu Apr 25 2024

VFR conditions at all terminals to start the TAF period.
Southeast winds will increase through the day, becoming strong
across parts of the south central and southeast (primarily
impacting KJMS), with sustained winds of 25 to 30 knots. Chances
for showers and thunderstorms will increase this afternoon and
evening, starting in southwest North Dakota (KDIK) and spreading
across the area after 00Z, with prevailing showers and
thunderstorms likely at all terminals except KXWA. Ceilings will
also begin lowering after 00Z, with low MVFR to IFR ceilings
expected at all terminals except KXWA by the end of the TAF
period.

&&

.BIS WATCHES/WARNINGS/ADVISORIES...
None.

&&

$$

UPDATE...Besson
DISCUSSION...Jones
AVIATION...Jones