756
FXUS63 KBIS 211809
AFDBIS

Area Forecast Discussion
National Weather Service Bismarck ND
1209 PM CST Fri Feb 21 2025

.KEY MESSAGES...

- Temperatures will rise back to near to above normal today,
  with highs in the mid 20s to mid 30s.

- Well above normal temperatures and breezy this weekend through
  much of next week. Southwest and south central North Dakota
  could have multiple days of highs in the 50s.

- Periodic low to medium chances (20 to 40 percent) for light
  mixed precipitation Sunday through the middle of next week.

&&

.UPDATE...
Issued at 1200 PM CST Fri Feb 21 2025

Temperatures continue to warm across the state with the western
half of the state climbing into the upper 20s. No updates are
needed at this time.

UPDATE
Issued at 853 AM CST Fri Feb 21 2025

Winds are beginning to veer out of the west across much western
and central North Dakota this morning. Which should aid
increasing temperatures especially out west this afternoon.
Temperatures is southeastern Montana are already climbing into
the 20s. No updates are needed at this time as the forecast
remains on track.

UPDATE
Issued at 557 AM CST Fri Feb 21 2025

The forecast remains in good shape. Current conditions and
trends were blended in for this update.

&&

.DISCUSSION...
Issued at 335 AM CST Fri Feb 21 2025

Anticyclonic flow resides over the Northern Plains early this
morning, with a surface/low level warm front embedded in a trough
axis extending from eastern Saskatchewan through the western
Dakotas. The end of below normal temperatures is almost here. Early
morning readings are a few degrees either side of zero and are not
expected to cool much further as the warm front continues to push
eastward through the morning. The change in wind direction to
westerly should provide strong mixing/heating of the boundary layer
this afternoon, allowing temperatures to recover into the mid 20s
east to mid 30s southwest. It will be interesting to see how big of
an influence the snowpack has on temperatures this afternoon. We
utilized the median of the NBM distribution for the high temperature
forecast today, which is a few degrees warmer than the deterministic
NBM projection. In the absence of an appreciable snowpack, a
westerly wind at this time of year would be reliable to reach the
warmest quartile of guidance, so feel confident the median is
attainable even with the snow.

The rapid warmup continues through the weekend as milder Pacific air
continues to flow down the slopes of the Northern Rockies in an
anticyclonic flow regime. The high temperature forecast for Saturday
was also raised to the median of the NBM distribution for similar
reasons as stated above, which brings highs around freezing near the
Turtle Mountains to the lower and mid 40s in southwest and south
central North Dakota. Temperatures then look to take another jump on
Sunday when there is high confidence in (75 to 90 percent chance of)
highs in the mid 30s north central to around 50 southwest and south
central. The median of the NBM distribution gives widespread lower
and mid 50s to southwest and south central North Dakota on Sunday,
but temperatures this warm become harder to achieve with snow on the
ground, and it is uncertain how much snow will have melted by then.
Similar temperatures are in the forecast for Monday and Tuesday, and
by that time any lingering snow should have little to no effect on
diurnal heating. However, there could be other factors that limit
high temperatures those 2 days (clouds, precipitation, etc.). The
westerly component of the low level wind field does not look to be
changing any time soon, so any areas that see full or even filtered
sunshine either of these days could easily reach the NBM 75th
percentile that ranges from the upper 30s near the Turtle Mountains
to around 55 to 60 in the southwest and south central.

A series of shortwaves is forecast to cross the northern CONUS/
southern Canada Sunday through Wednesday. The first distinguishable
shortwave is an Alberta clipper that crosses southern Saskatchewan
and Manitoba on Sunday. This could bring some light rain showers to
northern parts of the state during the day Sunday, possibly mixed
with snow or freezing rain should it fall in the morning. The more
likely impact for all of western and central North Dakota on Sunday
is strong westerly winds that could gust as high as 40 mph, which
should also assist with erosion of the snowpack. The NBM shows at
least breezy conditions continuing through Sunday night, which may
keep overnight temperatures near or even above freezing. On Monday,
a stronger shortwave is forecast to take a more southerly trajectory
from northwest Montana into the Dakotas. There is some timing and
placement uncertainty with this system, but the NBM has increased
precipitation chances to 30 to 40 percent across northwest, central,
and southeast North Dakota. There are still signs in deterministic
models and ensemble members that this system could produce mesoscale
banded precipitation, but the split in ensemble members that show
this potential vs. those that do not is about 50/50. If the
mesoscale banding scenario occurs, there is at least a low
probability of dynamic cooling changing rain to snow where rates are
highest. Outside of banding though, rain is the expected type given
surface/low level thermal profile projections well above freezing.
The potential for strong winds in southwest North Dakota will also
need to be monitored for the system on Monday as all ensemble
clusters show a westerly low level jet around 40 to 50 kts crossing
that part of the region in the afternoon, and the ECMWF EFI
continues to show a shift-of-tails in its wind gust output.

The next disturbance appears to be more of the split-flow/open wave
variety Tuesday into Wednesday, for which the NBM contains a 30 to
40 percent chance of precipitation for almost the whole state late
Tuesday/early Wednesday. There is higher confidence in this being a
lower-QPF event, with probabilities for exceeding a tenth of an inch
only around 10 to 20 percent, and there is only one ensemble cluster
with just 20 percent membership that exceeds those probabilities.
The passage of this wave will likely drag a relatively cooler air
mass into the region temporarily, though still much warmer than
earlier this week. In fact, it still may barely just become cold
enough for any precipitation to change over to snow Tuesday night.
From mid to late next week, ensemble spread increases in a typical
fashion for all parameters and aspects of the forecast, but there is
still high confidence in above normal temperatures persisting
through the end of the month.

&&

.AVIATION /18Z TAFS THROUGH 18Z SATURDAY/...
Issued at 1200 PM CST Fri Feb 21 2025

VFR conditions will continue across the region with westerly
winds. There is a low chance that patchy fog forming in the
valleys tomorrow morning.

&&

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

&&

$$

UPDATE...Johnson
DISCUSSION...Hollan
AVIATION...Johnson