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000
FXUS63 KBIS 241448
AFDBIS

Area Forecast Discussion
National Weather Service Bismarck ND
948 AM CDT Wed Apr 24 2024

.KEY MESSAGES...

- Above normal temperatures today and Thursday, with widespread
  highs in the 70s on Thursday.

- Strong southeast winds are likely across the south and
  central on Thursday.

- Showers and thunderstorms are likely (60-90%) Thursday 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. The highest chances are across the
  south.

&&

.UPDATE...
Issued at 945 AM CDT Wed Apr 24 2024

High clouds continue to stream across the southwest from
Montana, and will continue to do so throughout the day today.
Winds are still forecast to increase through the day as the
small impulse moves across the state, with near critical fire
weather still possible in the southwest and south central
portions of the area today. As such, no major changes have been
made with this update. Just blended the current observations
into the forecast.

.UPDATE...
Issued at 640 AM CDT Wed Apr 24 2024

Quiet weather continues this morning, with many locations
across the south and central seeing current temps in the mid 20s
with calm winds. Satellite imagery shows some high clouds
beginning to drift in from Montana, with more widespread cloud
cover upstream associated with an impulse embedded in mean
zonal flow. No major changes needed with this update.

&&

.DISCUSSION...
Issued at 355 AM CDT Wed Apr 24 2024

This morning, a shallow ridge aloft was beginning to build over
the northern Rockies, while at the surface a broad high pressure
was centered to our east across Ontario into the Great Lakes
region. Quiet weather will continue through the morning, with
light winds, clear skies, and temperatures in our normal cool
spots dropping into the mid to upper 20s.

Expecting warmer temperatures today, with highs from the mid
60s to mid 70s. Southeasterly return flow will be increasing,
with breezy winds forecast across the southwest and south
central. Near critical fire weather conditions are possible
across southwest and south central North Dakota this afternoon,
with minimum relative humidity in the lower to mid 20 percent
range and breezy southeasterly winds. Humidity values are
forecast to be lower across northern North Dakota, but winds
will be lighter in this area.

A mid-level wave moving through midday will bring an increase
in cloud cover, but a dry near-surface layer will prevent any
precipitation. High-res guidance is beginning to pick up on
another weak wave moving up from South Dakota tonight, so we
are carrying 20% POPs across the southern James River Valley.

Thursday is still the primary day to watch for potential strong
thunderstorms. As the upper ridge breaks down, a surface low and
attendant warm front will be in the vicinity of eastern Montana
and the western Dakotas. Flow aloft is expected to turn
southwesterly through the day, with a leading shortwave moving
through and increasing precipitation chances through the
afternoon and evening across much of the forecast area.
Deterministic guidance is still advertising up to 1000 J/kg of
MUCAPE Thursday afternoon and evening as mid-level height falls
overspread the area, with modestly steep lapse rates (around 7
degrees C/km). Shear continues to look like the limiting factor
in any substantial convective development, with forecast bulk
shear only around 20-25 knots in the area of highest instability.
CSU machine learning is advertising low probabilities of severe
hail to include most of western and parts of south central
North Dakota, which is an expansion since the previous run. The
latest SPC Day 2 outlook does have a Marginal Risk (level 1 of
5) extending across much of western South Dakota, so approaching
the southwest corner of our forecast area.

Thursday will also be the warmest day of the next week, with
widespread highs in the 70s, and wouldn`t be surprised if a few
spots out west hit 80 degrees. Southeast winds will also be
strong across the south and central, with forecast soundings
showing 35 to 40 knots at the top of the mixed layer.

Chances for showers and thunderstorms from this initial system
don`t have a chance to end before another system approaches the
area. GEFS and EC ensemble members are starting to agree more on
the track of a warm-season Colorado Low progged to move through
the region this weekend, with members advertising the low
progressing from southwest Nebraska late Thursday night, to
southeast South Dakota Friday night, into central Minnesota on
Saturday. Blended POPs have increased further with this update,
producing the highest chances through the day Friday. Areas from
Bowman to Garrison to Harvey and south/east have an 80-95%
chance of rain showers and a few thunderstorms on Friday, with
decreasing chances to the northwest. Through Friday night and
into Saturday, rain chances very slowly decrease, with the
spatial pattern of highest POPs not changing (highest southeast
/ lowest northwest). During the 24-hour period covering Friday
and Friday night, there is a medium chance (40-60%) for at least
0.50" of rain across the south central and southeast, with a
low probability of exceeding 1" of rain.

While the deep low is circulating to our south, a cold front is
forecast to drop south from a separate, weaker low pressure. This
will lead to seasonably chilly temperatures this weekend, with highs
dropping into the mid 40s to mid 50s on Saturday and Sunday.
Precipitation chances linger across the south (20-40%) on Saturday
as the Colorado Low exits to our east, but a second trough is likely
to quickly follow, with ensemble cluster scenarios all advertising
this solution. NBM POPs increase on Sunday with higher chances
again in the southeast while the northwest is favored to stay
mostly dry. Ensemble member MSLP values are not as deep as the
first system, with QPF probabilities subsequently lower (only
low chances of exceeding 0.50" Sunday and Sunday night).

Upper level flow is favored to rebound quickly from these systems,
becoming much more zonal to start the work week. NBM temperature
percentiles respond accordingly, with a warmup back to near normal
highs on Monday with precipitation chances ending early. The active
period continues, however, with broad, 20 to 30% POPs returning
midweek, although with continued warmer than normal temperatures.

&&

.AVIATION /12Z TAFS THROUGH 12Z THURSDAY/...
Issued at 640 AM CDT Wed Apr 24 2024

VFR conditions expected at all terminals through the TAF period.
Light and variable winds will be turning southerly through the
morning, with breezy southeast winds expected across the west
and south central through the day. Winds will stay elevated at
10 to 15 knots through the night tonight. High clouds will be
increasing through the day before clearing tonight.

&&

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

&&

$$

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