Area Forecast Discussion
Issued by NWS Bismarck, ND

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FXUS63 KBIS 182005

Area Forecast Discussion
National Weather Service Bismarck ND
305 PM CDT Sun Jun 18 2017

.SHORT TERM...(This evening through Monday)
Issued at 305 PM CDT Sun Jun 18 2017

Scattered showers and isolated thunderstorms through this evening,
with some concern for weak funnels and/or a landspout in north
central ND. Another round of showers and isolated thunderstorms
are forecast Monday afternoon central ND.

For the near term, now through this evening, the latest SPC
mesoscale analysis indicates Non-Supercell Tornado Parameter
values between 2 and 4 centered over north central ND.
Contributions coming from strong surface vorticity combined with
surface based CAPE of 1000 J/Kg, steep low level lapse rates, and
little to no 0-6km shear. Will continue to monitor as isolated
showers/thunderstorms continue to develop over southeast Saskatchewan
and move into this environment. Except in the southwest, most
unstable Cape this afternoon is between 500-1000J/Kg with mid
level lapse rates at 6.5C/km. Effective Shear is weak, less than
20kt across all of western and central ND, which is expected to
remain that way for the rest of the afternoon per BUFKIT RAP
soundings. Thus, outside of the potential for weak funnels/landspout
in the north central mentioned above, expect pulse type/ordinary
showers/thunderstorms through the afternoon/evening east of
Highway 83, and also across southwest ND. The bulk of the
precipitation will wane after sunset. Some of the CAM`s suggest an
isolated shower may linger past midnight.

Latest water vapor imagery shows an upper ridge parked over
southern Nevada and an upper low circulating over Ontario. In
between, a northwest flow continues to dominate the northern high
plains. Upstream, another shortwave trough now over northern
Alberta will scoot southeast tonight through Monday. Large scale
ascent from the aforementioned shortwave and also by a 100kt 300mb
jet, per NAM/GFS Q-vector Divergence Field will shift from
central and northern ALberta into northern and central ND 12z
Monday-06z Tuesday. Scattered showers/isolated thunderstorms are
expected to initially develop across far north central ND 12z-18z
Monday, then shift southeast, mainly along and east of Highway 83
and into the southern James River Valley through 00Z Tuesday.
Instability Monday shows most unstable CAPE of around 500 J/kg
with 0-6Km Bulk Shear between 60kt-70kt. This low cape/high shear
environment may possibly favor isolated low-topped but highly
tilted thunderstorms.

.LONG TERM...(Monday night through Sunday)
Issued at 305 PM CDT Sun Jun 18 2017

Upper level flow transitions from northwesterly to zonal Monday
night into Wednesday, then back to northwesterly Thursday through
Sunday. Warm air advection increases Tuesday through Tuesday
night, ahead of a fast moving surface low and associated cold
front  and riding along the northern border. A low level jet
briefly sets up Tuesday night per 850mb southerly winds of 40kt to
50kt. A high shear environment with 0-6km bulk shear of 60kt and
70kt and low CAPE becomes evident Tuesday night per GFS BUFKIT
soundings. A strengthening EML develops Tuesday night via
southwest to westerly winds between 5kft and 10kft. Enough of a
capping inversion below the EML, limited moisture through the
column and weak most unstable cape, will limit the threat of
elevated thunderstorms. For now, isolated thunderstorms are
favored in the southern James River Valley. Elsewhere, expect
isolated to scattered showers ahead of a cold front Tuesday night
from west to east, with the highest pops from the Turtle Mountains
into the James River Valley between 06z- 15z Wednesday. Expecting
a breezy to windy day Wednesday. The NAM is weaker with the winds
behind the cold front, while the GFS has a much stronger
northwest wind developing. Used a blend of the given guidance and
CONSMOS for now. Future shifts can evaluate this with the newer
data. Warmest air Tuesday will reside in the southwest with highs
in the mid 80s. This will shift into south central and southeast
ND Wednesday, with 70s across the north

For Thursday through Sunday, periodic showers and thunderstorms
with several shortwaves rotating through the northwest flow.
Cooler with highs in the upper 60s to lower 70s fro most of the


.AVIATION...(For the 18Z TAFS through 18Z Monday afternoon)
Issued at 305 PM CDT Sun Jun 18 2017

MVFR cigs with scattered showers and thunderstorms across the
James River Valley and Turtle Mountains today, with a slight
chance southwest. Cigs elsewhere should remain mainly VFR.




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