Area Forecast Discussion
Issued by NWS Bismarck, ND

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FXUS63 KBIS 241742

Area Forecast Discussion
National Weather Service Bismarck ND
1242 PM CDT Mon Jul 24 2017

Issued at 1146 AM CDT Mon Jul 24 2017

For this update, added some slight chances of showers and
thunderstorms to the northwest. Radar echoes with occasional cloud
flashes have been noted close to the international border and in
northeastern Montana. Also lowered high temperatures and increased
sky coverage across the south central and southeast due to
lingering cloud cover that will likely stick around for a while
longer. Finally, increased winds through the afternoon using a
blend of CONSMOS and the previous forecast. Otherwise, just
blended the latest observations to the updated forecast.

UPDATE Issued at 823 AM CDT Mon Jul 24 2017

No major changes required for this update. Showers and isolated
thunderstorms across far south central North Dakota will continue
to push eastward this morning along the ND/SD border.

UPDATE Issued at 640 AM CDT Mon Jul 24 2017

Main issue is ongoing weak convection right along the southwest
border with South Dakota as upper level shortwave continues to
move through the region. Current forecast looks to be handling it
well with local radars showing echos slowly moving northward
across the border as overall area of convection continues in an
east/northeast direction. Latest CAM solutions also support
forecast with these scattered showers and isolated thunderstorms
pushing into southern portions of ND, but generally remaining
south of the I-94 corridor. Otherwise, also nudged winds up
slightly in the near term to better match latest obs.

No changes with afternoon/evening pops either, as models continue
to target convective initiation along the front around 23Z across
the west, with some uncertainty remaining due to strength of cap
and better large scale forcing focused toward the north.


.SHORT TERM...(Today and tonight)
Issued at 416 AM CDT Mon Jul 24 2017

Weather highlight is isolated severe thunderstorms favoring the
north central this evening into tonight.

Latest water vapor imagery shows two shortwaves of interest this
short term period. The first was located over northeast Wyoming
and southeast Montana, with showers/thunderstorms nearing our
southwest border counties. The GFS has these shortwaves
initialized well this morning, and continues to migrate them along
the southern border and into the southern James River Valley by
21z. The HRRR/RAP continue to trend measurable precipitation into
south central ND and the James River Valley. With satellite
showing a large cloud canopy moving from southwest ND into south
central, have trimmed high temperatures down from the mid 90s to
around 90. This area will be a complicated temperature forecast
through the day today as it will be cloud/precipitation dependent.
The end result is scattered showers and isolated thunderstorms
across the southern counties, moving from west to east through the
afternoon. Not expecting these thunderstroms to reach severe
levels at this time.

The second shortwave of interest, was located over southern
Alberta, rotating through a closed upper low/trough in western
ALberta this morning. A 60kt-80kt, 500mb-300mb speed max was also
rounding the base of the the upper trough. Being reflected at the
surface was a cold front, snaking through eastern Alberta and into
The Idaho panhandle. This cold front will be serve as enhanced
convergence later this afternoon as it passes through northwest ND
between 21z-00z. The shortwave and associated jet streak will
move east through this evening, with forcing becoming maximized
over north central ND between 23z and 06Z. The SHARPpy Minot
Sounding per NAM/RAP shows vertical motion increasing 00z-04z
with Mixed Layer Cape around 2400 J/kg, Effective Shear around
27kt, and Downdraft Cape of 1600 J/Kg. Damaging winds and Large
Hail remain as the main threats. Significant Hail Parameter
indicates maximum hail between a quarter and half dollar size.
It would appear that thunderstorm initiation begins between 23z
and 00z. The SREF 3 hour calibrated severe thunderstorm potential
is also indicative of a marked increase for isolated severe
thunderstorms between 21z Monday and 00z Tuesday in north central
ND. Farther south, continued capping will limit the development
of thunderstorms from Bismarck and into Jamestown through the
early evening.

The surface cold front slowly sags through south central
ND/Bismarck by 09z, and eventually through the southern James
River Vally by 15z Tuesday. Expect pockets of thunderstorms to
continue through the night along and ahead of the cold front, but
the threat for severe thunderstorms should diminish after 06z, as
the strongest forcing remains north of the border, and showers/thunderstorms
stay pretty much tied to the cold front farther south.

High temperatures in advance of the cold front will soar into the
mid and upper 90s today, except mid to upper 80s from the Turtle
Mountains south into the James River Valley.

.LONG TERM...(Tuesday through Sunday)
Issued at 416 AM CDT Mon Jul 24 2017

The front resides over central South Dakota Tuesday afternoon. A
Couple shortwaves riding through southern North Dakota during the
day will lead to a chance of showers/thunderstorms. The highest
cape/shear exists in the southern James River Valley until 21z,
then shifts south of our forecast area. There could be a couple
severe thunderstorms popping up along/near our southern border and
into the southern James River Valley prior to the strongest
cape/shear departing. Highs Wednesday will not be as hot, with
highs in the low to mid 80s.

Wednesday and Thursday will be dry and warm for most of western
and central ND as 700mb-500mb heights begin to rise once again.
Return flow sets up in the west Thursday with perhaps some slight
chances of showers/thunderstorms in the afternoon. A better chance
for showers/thunderstorms Thursday night, with dry conditions elsewhere.
Highs mainly in the 80s both days.

For Friday through Sunday, warming up a bit with highs in the 80s
to lower 90s. Periodic shortwaves shift through, but heights
continue to slowly rise as well. Thus not a whole lot of areal
coverage expected in terms of precipiation at this time, mainly
spotty with a lot of dry time in between.


.AVIATION...(For the 18Z TAFS through 18Z Tuesday afternoon)
Issued at 1146 AM CDT Mon Jul 24 2017

A cold front will push through today/tonight from northwest to
southeast. Isolated showers and thunderstorms develop along the
front, beginning around 23z between KISN and KMOT. However,
confidence is low and therefore nothing more than a VCTS is being
used for this potential. Large hail and damaging winds could
accompany any thunderstorms that do develop. Outside of
thunderstorms, expect VFR through the period.




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