Area Forecast Discussion
Issued by NWS Bismarck, ND

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FXUS63 KBIS 210517

Area Forecast Discussion
National Weather Service Bismarck ND
1217 AM CDT THU JUL 21 2016

Issued at 1217 AM CDT Thu Jul 21 2016

We let the rest of the previously-extended severe thunderstorm
watch expire at 05 UTC. The thermodynamic and kinematic setting
over east central ND remains impressive at this hour with MUCAPE
around 7000 J/kg and effective bulk wind differences of 50 kt per
RAP-based SPC mesoscale analysis data. However, radar trends over
the last 60 minutes have strongly suggested mid-level capping is
prevailing, even with the possible jet-related ascent manifest as
high-based showers extending from southeast MT into southwestern
ND, where 700-MB temperatures are slightly cooler. Recent HRRR
simulations suggest little additional risk of intense convection
overnight, but we have continued mentioning the slight chance of
a severe storm in southwest and south central in our hazardous
weather outlook as the environment would certainly support large
hail or damaging winds if a storm would actually develop. There`s
just little suggestion or confidence that any will.

UPDATE Issued at 946 PM CDT Wed Jul 20 2016

Updated to remove some counties from the tornado and severe
thunderstorm watches, basically where the convection has cleared.
Continue to see strong to severe storms move through central ND.

UPDATE Issued at 655 PM CDT Wed Jul 20 2016

Updated for upgrade of severe thunderstorm watch to a tornado
watch across far north central North Dakota, where there have been
numerous reports of funnels and multiple reports of a tornado with
one of the earlier storms. Also received baseball size hail
report near Berthold. Watches go through 11 pm. SPC Meso Analysis
page continues to show 5500 J/Kg of MLCAPE across central ND with
the best 0-6km effective bulk shear of 40-55 knots across the
north central areas. Significant tornado parameter values are
maximized around 4 across the tornado watch area. 22z operational
HRRR clears convection out of our area by 04z.


.SHORT TERM...(This evening through Thursday)
Issued at 319 PM CDT Wed Jul 20 2016

Upgraded much of the Heat Advisory to an Excessive Heat Warning
across much of south central North Dakota and into the James River
Valley. Surface dewpoints in the upper 70s to the lower 80s are
observed across these areas given strong evapotranspiration. With
temperatures quickly climbing into the 90s, heat index values to
110 degrees are likely to continue to the afternoon and early
evening. While dewpoints will mix out a bit the rest of the day,
all guidance is under-doing surface dewpoints this afternoon.

Regarding the severe convective threat this afternoon and evening,
cumulus fields continue to develop across southwest and northwest
North Dakota in the vicinity of weak surface confluence as of 2015
UTC. Strong instability is in place with effective deep layer
shear of 35-50 kts. While coverage may be low, any storms that
develop are favored to become supercellular with all threats
possible. Storms through the afternoon and evening are likely to
be tied to the aforementioned boundary as it propagates east. The
19 UTC KBIS sounding still shows some capping to overcome, yet,
also supports the potential for very large hail with MU CAPE near
7000 j/kg. See the 20 UTC SPC Day 1 Convective Outlook for further

.LONG TERM...(Thursday night through Wednesday)
Issued at 319 PM CDT Wed Jul 20 2016

Cooling temperatures into the weekend and a possible severe
thunderstorm threat Friday highlights the extended forecast.

Overall, the 12 UTC suites are in agreement on the broad upper
level ridge across the CONUS flattening Friday into the weekend,
with near zonal flow into next week. This would favor a return to
near normal temperatures. The next best chance for thunderstorms
is Friday into Saturday as a wave possibly coming onshore to the
pacific northwest on Thursday propagates into the Northern Plains.
SPC has placed much of the area in a slight risk in their day 3


.AVIATION...(For the 06Z TAFS through 06Z Thursday night)
Issued at 1217 AM CDT Thu Jul 21 2016

VFR conditions will generally preval tonight and Thursday. There
remains a slight chance of a thunderstorm and attendant, localized
sub-VFR conditions overnight in southwest and south central ND.
There`s also a slight chance of low clouds forming before sunrise.
Confidence in either of those things occurring is low.


.BIS Watches/Warnings/Advisories...


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