257
FXUS63 KBIS 071746
AFDBIS

Area Forecast Discussion
National Weather Service Bismarck ND
1246 PM CDT Fri Jun 7 2024

.KEY MESSAGES...

- Isolated to scattered showers and thunderstorms will remain
  possible through this evening. Thunderstorms are generally
  expected to be below severe limits, however, an isolated
  stronger storm is possible in southcentral and portions of
  southwestern North Dakota with small hail and gusty winds
  being the main threats.

- Isolated showers (20 percent chance for rain) are forecast for
  Saturday, mainly north and east of Minot, and then on Sunday
  (20 percent) over central and eastern North Dakota.

- With high confidence it is expected to be cooler Sunday and
  Monday, the question is how much cooler, and then warmer for
  the middle of next week with high temperatures into the 80s.

&&

.UPDATE...
Issued at 1245 PM CDT Fri Jun 7 2024

Forecast overall remains on track. SPC has added a Marginal Risk
of severe weather in southcentral and portions of southwestern
North Dakota. The threat for severe weather overall looks to
still remain very isolated today. Some HRRR CAMS are showing an
isolated stronger storm later this afternoon into this evening
across these areas. There is abundant shear in this area during
this time period. The bigger concern though is the lack of
instability. HREF ensemble data showing MUCAPE up to 500 J/KG.
While surface based CAPE is higher in some instances, the
elevated nature of today`s convection would be tough to tap
into this. A quick change from easterly flow at the surface to
westerly flow aloft could be adding some SRH and perhaps promote
weak rotation in isolated storms, yet again this would require
surface based storms. More looking into the elevated storm
environment the hodographs become more straight. This could
still help with hail production, especially given the high
amounts of shear. The concern still remains the lack of
instability. If a stronger storm can get going and pulse up,
then perhaps hail up to an inch in diameter and wind gusts up to
60 mph are possible. For now updated the HWO to match the
Marginal Risk. Messaging will remain with small hail and gusty
winds as this is where our highest confidence currently resides.

UPDATE
Issued at 1014 AM CDT Fri Jun 7 2024

Overall limited updates needed this morning. Weak returns on
the radar showing up this morning. This is likely from an
advancing wave expected to move through today. With it will
bring isolated to scattered shower activity starting in the
north and eventually spreading chances across much of the CWA.
There is some limited instability and high amounts of shear.
Severe weather is not expected, yet perhaps some small hail or
gusty winds are possible to any more organized storms. Overall
just made minor changes to PoPs based on current trends.
Expanded thunder mention in the HWO based on current SPC general
risk category.

UPDATE
Issued at 645 AM CDT Fri Jun 7 2024

The forecast is on target with showers about to move into the
northwest part of the forecast area, the Williston area, ahead
of an advancing short wave trough. CAMS continue to bring this
convection to the east and south as the morning wears on,
intensifying to isolated to scattered thunderstorms south of
Minot by this afternoon. The cloud shield associated with the
showers also continued to expand in coverage. There were a few
wind gusts, on the order of 20 mph, near showers in
Saskatchewan.

&&

.DISCUSSION...
Issued at 430 AM CDT Fri Jun 7 2024

The surface analysis as of 4 AM showed weak high pressure
centered near Bismarck with a clear sky and winds that were
light, under 10 mph, and variable in direction. An inverted
trough extended north through eastern Montana. Low pressure
aloft was drifting south through central Saskatchewan with
pockets of energy (short waves) passing through the cyclonic
flow and heading toward the international border. Clouds in
association with the waves were both moving through southern
Saskatchewan and developing there. Radars showed an increase in
reflectivity north of Glasgow, Montana, with movement to the
east and south.

For today that first wave, and the cyclonic flow, will bring
increasing weak ascent of air parcels into the forecast area.
Guidance shows an abundance of 0-6km shear forecast to be over
the area but little in the way of CAPE, at least until later
this afternoon, and mostly along and south of Interstate 94.
Because of this CAMS bring showers into the northwest this
morning and intensify them as they move south and east, but only
slightly (the intensification). By intensification we mean
going from showers to thunderstorms. Looking at the HRRR fields,
a pocket of higher MUCAPE, on the order of 300 J/kg, is forecast
to move from southwest of Bismarck to south of Jamestown during
the late afternoon and into the evening. That would be the
highest chance and most likely location for a stronger storm. In
discussion with my shift partner we are concerned on one hand
of a storm there being able to produce some small hail, but on
the other hand, with strong shear, concern goes to the updrafts
not being able to gain much altitude before being sheared off.
We`ll have to watch to see how convective parameters change
through the short term to have more confidence in the risk of
small hail.

Another wave brushes the northeast on Saturday with chances for
showers, maybe a storm, mainly east and north of Minot. Then on
Sunday, the upper low advances into the state with cooler air
and shower chances in the cyclonic flow, over the central and
east.

Sunday should be the coolest day over the next seven with that
upper low over the state, followed by warming then through
at least Wednesday. The NBM 1D Viewer shows a wide range in
possible high temperature outcomes on Sunday, but all lower than
70. The question then becomes, cool Sunday, but just how cool,
especially north. 60s at this point would be a high
expectation, but lower, mid or upper 60s will need to be
determined. The Viewer then shows narrower ranges (higher
confidence) for high temperatures for the middle of the week,
basically 80 to 85. It does look like the 80s could be
accompanied by unsettled weather as the mean H5 ridge is broken
down every 24 hours or so by short wave troughs passing through
it, and bringing chances for rain. By Thursday the ridge could
be replaced by cyclonic flow troughing (cooler and more
unsettled).

&&

.AVIATION /18Z TAFS THROUGH 18Z SATURDAY/...
Issued at 1245 PM CDT Fri Jun 7 2024

VFR conditions generally expected through the forecast period.
Isolated to scattered showers and thunderstorms could be found
through this evening. Confidence was high enough to include
shower mention to most sites. It was only high enough to include
TS mention to the KBIS and KJMS TAF site. Precipitation looks to
diminish later this evening bringing clearing skies and
continued VFR conditions. VFR conditions are then expected for
much of Saturday. Light winds will become easterly today. These
easterly winds will then become westerly tonight into Saturday.

&&

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

&&

$$

UPDATE...Anglin
DISCUSSION...JPM
AVIATION...Anglin