000
FXUS63 KBIS 121735
AFDBIS

Area Forecast Discussion
National Weather Service Bismarck ND
1235 PM CDT Fri Apr 12 2024

.KEY MESSAGES...

- Warmer today and continued mild through the weekend and to
  start the work week.

- Increasing rain chances next week, especially Monday night and
  Tuesday, with greatest chances (60 to 80 percent) coming to
  central and into eastern North Dakota.

- Colder temperatures mid to late in the work week with
  lingering chances (30 to 60 percent) for rain and snow.

&&

.UPDATE...
Issued at 1235 PM CDT Fri Apr 12 2024

The forecast remains on track at this time. Wind gusts have
begun to pick up, with some stations observing gusts of around
30 miles per hour in the southwest.

UPDATE
Issued at 945 AM CDT Fri Apr 12 2024

No changes to the forecast were needed for this update. High
clouds have begun to move into the northwest at this time, but
otherwise the sky remains mostly clear. Winds are generally
light and variable.


UPDATE Issued at 556 AM CDT Fri Apr 12 2024

No changes to the going forecast. Clear and cold this morning.

&&

.DISCUSSION...
Issued at 212 AM CDT Fri Apr 12 2024

Currently, high pressure is situated over central North Dakota
with low pressure off to the east and west. Skies were mostly
clear, with some high clouds approaching from the west.

Today and through the weekend our weather will be influenced by
a northern stream zonal to slightly northwest flow pattern.
Upper level ridging early today will be flattened by a
shortwave tracking across southern Canada. Mid level forcing
combined with warm advection ahead of a warm front may produce a
few showers across the north tonight into Saturday. A weak cold
front will move through the area Saturday with little more than
a wind shift expected. Surface flow will turn northerly late
Saturday into early Sunday, then eventually easterly as the
surface high behind the front slides east of the area.

Overall we are looking for a nice weekend ahead. Highs, mainly
in the 60s today, will climb into the upper 60s to upper 70s
Saturday, and only dropping slightly on Sunday. There will be
some small precipitation chances mainly across the north
tonight into Saturday (mentioned above). Winds will be breezy
today in the west, with breezy conditions sliding east
overnight. Lighter winds are then expected through the weekend.

While we are enjoying our weekend an upper level low off the
West Coast moves onshore Sunday and then into the Southern
Rockies by early Monday. In addition, a strong northern stream
wave develops into another upper level low over western Canada
by early Monday. This will set the stage for an interesting
stretch of weather next week.

Initially Sunday night into early Monday, warm advection ahead
of developing low pressure in the lee of the Rockies, combined
with one last northern stream wave, could produce some showers
late in the day Sunday through Sunday night. The potential for
thunder looks minimal at this time but there is some elevated
instability and NBM is producing some low thunder
probabilities.

The main show (as far as qpf amounts) will be Monday through
Tuesday night as the southern system moves into the Great Lakes
Region and the northern stream upper low drops into the Northern
Rockies/Northern Plains region. The most favored timeframe for
thunder looks to be Monday afternoon through Tuesday morning.
Deterministic models show some elevated instability lifting into
southern ND Monday afternoon, and remaining over the far south
central/southeast into early Tuesday. Initially there is some
dry air remaining as we see upper level ridging over southern ND
ahead of the strong southern stream low. Eventually this
ridging gets pushed north and east, out of the area, but we also
see mid-upper level ridging behind this low and ahead of the
northern stream low. Therefore, a lot of uncertainty remains in
how much precipitation we see. The raw model ensemble surface
low positions are fairly well clustered tracking the low from
northeast Colorado, across Nebraska and into southern Minnesota.
The GEFS members may be a little north of the ECMWF. Latest
deterministic GFS/ECMWF runs are both a bit farther south than
the ensembles with the surface low position. If we are able to
get some elevated convection, we could definitely see some nice
rain accumulations. If we don`t get convection, I wonder how
widespread the non-convective precipitation will be.

A lot of that will probably depend on the interaction, or lack
thereof between the northern and southern stream systems. One
interesting note in the deterministic and DESI ensembles is the
mid level (700 mb) forcing late Monday through Tuesday looks to
be (at least partially) a result of the interaction between
these two lows. You can see the 70H low and resulting forcing
track southwest to northeast generally across central ND. This
occurs as the upper level ridging (between the two lows) pushes
from western int central ND. Not sure exactly what this means,
but it almost seems like the latter could inhibit the mid level
forcing (limiting qpf or at least the areal extent of qpf) if
the timing works out. If the mid level forcing moves through
before the upper level ridging then perhaps qpf is higher.


A cluster analysis centered on 7 PM Monday through 7 PM Tuesday
yields, from what I can tell, four separate solutions. Two with
more separation between the two systems (you can see the ridging
between them) and two without. of these two scenarios, there is
both a stronger and a weaker southern southern low. There are
also differences between the strength/position of the northern
stream low. You could possibly try and group these together
somehow, but the main thing I can see is that between the four
clusters, there is only a 10 percent difference in members
between the cluster with the most members and the one with the
least. If you could combine three somehow, you could maybe get a
better separation between solutions, but I can`t really see that
at this time. Thus at most you, if you go with two clusters you
get a 57/43 favored solution. Another thing is that if you look
at the 24 hour qpf, at 7 PM Tuesday, each cluster gives you a
completely different solutions. If anything, the south and east
would probably be favored, just looking at the 24 hour qpf from
the clusters.

UPDATE...Latest DESI guidance does look to favor south central
into eastern ND for higher qpf. Latest ECMWF SA page favors the
south central into eastern ND for higher qpf from 7 PM Monday
through 7 PM Tuesday. The GEFS ensemble SA page also favors the
I94 Corridor from around Bismarck to Jamestown for very high
PWAT values (above the 99th percentile) centered around 12 UTC
Tuesday.

As we get beyond Tuesday night, two things are apparent. Qpf is
much lighter and temperatures are much colder. Currently, the
NBM is producing high chance to likely precipitation chances
Wednesday through the day on Thursday, tapering to chance pops
Thursday night and slight chance pops Friday. Temperatures are
such that any precipitation that falls Wednesday night or early
Thursday would be at least a rain/snow mix, and possibly all
snow north and west. By Thursday evening through Friday morning,
any precipitation would likely be snow. Morning lows Thursday
and Friday will be mainly in the 20s and daytime highs in the
30s to mid 40s, quite a difference from what we will see this
weekend, so enjoy the weekend. Any accumulating snow would
probably be confined to the west and north.

&&

.AVIATION /18Z TAFS THROUGH 18Z SATURDAY/...
Issued at 1235 PM CDT Fri Apr 12 2024

VRF conditions are expected through the 18Z TAF period. South
southeasterly flow will strengthen through this afternoon,
especially across the west and portions of the south central,
including the terminals of KXWA and KDIK, where gusts could
approach 30 knots. Winds will diminish overnight. LLWS will be
possible at KMOT, KBIS, and KJMS overnight, beginning generally
around 05Z. An isolated shower or two may appear around the
northern terminals of KXWA and KMOT this evening through
Saturday morning, though chances are too low (5 to 15 percent).

&&

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

&&

$$

UPDATE...Adam/TWH
DISCUSSION...TWH
AVIATION...Adam