224
FXUS63 KBIS 072352
AFDBIS

Area Forecast Discussion
National Weather Service Bismarck ND
652 PM CDT Sun Jul 7 2024

.KEY MESSAGES...

- Another round of scattered showers and thunderstorms continue
  this evening. Some storms may once again produce funnel
  clouds, with a weak landspout tornado possible through early
  this evening.

- The daily potential for showers and storms will focus more
  over eastern North Dakota Monday and Tuesday, with coverage
  becoming more isolated.

- A warming trend is expected this week, with widespread highs
  in the 90s likely on Friday.

&&

.UPDATE...
Issued at 645 PM CDT Sun Jul 7 2024

Isolated to scattered showers and thunderstorms, with the
greatest coverage further east and south, continue over the
area. Even through the SPC non-supercell tornado parameter
primarily over central North Dakota remains elevated (around 3),
we have not heard of any funnel activity as we had the past few
days. With that said, concern for that remains for about
another hour before the loss of daytime heating will bring an
end to those concerns.


&&

.DISCUSSION...
Issued at 216 PM CDT Sun Jul 7 2024

A persistent cyclonic flow pattern continues to sit over the
Northern Plains this afternoon, with embedded mid to upper level
circulations rotating around the base of a longer wave trough.
While the longwave trough axis has shifted slightly eastward,
now from central Nebraska to western Ontario, western and
central North Dakota still lie under the influence of the
embedded impulses which have generated yet another round of
afternoon showers and thunderstorms. As has been the case for
the past several days, atmospheric conditions including an
unstable and buoyant boundary layer, very weak deep layer shear,
and surface vorticity are once again favorable for the
development of funnel clouds, with a brief weak landspout
tornado possible. The highest chance for funnel clouds and a
landspout are shifted farther east, but they still cannot be
ruled out with any storm across the entire state. Showers and
storms should gradually dissipate through the evening. Highs
this afternoon are forecast around 75 to 80, with northwest
winds around 10 to 15 mph.

We will finally start to see a more notable pattern shift Monday and
Tuesday as the downstream trough slides further east and deamplifies
over the Great Lakes while a strong western CONUS ridge begins to
expand and tilt eastward. Diurnally driven showers and storms remain
in the forecast along and east of Highway 83 on Monday and Tuesday,
but with lower coverage expected and possibly (hopefully) a lower
risk for funnel clouds. This pattern shift will allow temperatures
to begin warming back closer to normal, especially in the west. By
Tuesday, highs in the 80s are forecast for all of western and
central North Dakota. Ensemble guidance shows the upper ridge
continuing to build over the Rockies and High Plains Wednesday and
Thursday, with a weak surface flow pattern. This should promote a
break from daily showers and thunderstorms and continue the warming
trend. By Thursday, the NBM is advertising mid 80s east to mid 90s
southwest.

For Friday into next weekend, ensembles are pointing toward a
possible flattening of the ridge that could result in an active
zonal flow over the Northern Plains. The NBM favors Friday to be the
hottest day of the week as the ridge flattening process is just
beginning, with current projections around 90 to 95 statewide and
possibly approaching 100 in the far southwest. But Friday could also
mark the return of thunderstorm chances lasting through the weekend.
This may include prospects for severe weather given the enhanced
flow aloft, warm surface temperatures, and NBM dewpoints in the 60s.
CSU machine learning guidance confirms this thinking, with low
severe probabilities spread across the state Friday through Sunday.
Given timing and spatial uncertainty, the NBM is only carrying low
PoPs for now. Temperatures are likely to remain above normal (which
is mid 80s for highs) next weekend, but there is larger ensemble
spread due to lower confidence in the evolution of a closed upper
low moving across central Canada.

&&

.AVIATION /00Z TAFS THROUGH 00Z TUESDAY/...
Issued at 645 PM CDT Sun Jul 7 2024

Isolated to scattered showers and thunderstorms continue through
later this evening with the greatest coverage over central North
Dakota. VFR conditions then prevail overnight before the threat
for isolated thunderstorms returns primarily to central North
Dakota Monday afternoon.

&&

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

&&

$$

UPDATE...JJS
DISCUSSION...Hollan
AVIATION...JJS