Area Forecast Discussion
Issued by NWS Bismarck, ND

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FXUS63 KBIS 191741

Area Forecast Discussion
National Weather Service Bismarck ND
1241 PM CDT Mon Jun 19 2017

Issued at 1241 PM CDT Mon Jun 19 2017

Preliminary, non-operational imagery from GOES-16 shows well the
leading edge of ascent with the upstream shortwave trough nearing
the Estevan area at 1730 UTC, with an enhancement to clouds and
an area of greater background moistening in the low-level moisture
channel imagery. This forcing is on track to generate convection
in north central ND in the next 60 to 90 minutes. All we did with
this update was blend observational trends into the forecast, for
little overall change.

UPDATE Issued at 953 AM CDT Mon Jun 19 2017

No significant changes were made with this update, though we did
speed up the progression of showers and thunderstorms slightly in
the gridded forecast following the trend in recent CAMs. Overall,
the 11-13 UTC iterations of the HRRR and ESRL HRRR along with the
12 UTC 3-km NAM (NAM NEST) remain similar to prior cycles showing
potential for a line of strong to severe low-topped storms moving
rapidly southeast across parts of central ND in the 19 to 01 UTC
time frame. Forecast soundings show marginal bouyancy with MLCAPE
of 200-500 J/kg with surface dewpoints around 50 F, but given the
intense wind fields aloft updrafts will likely be very tilted and
the potential for momentum transfer of strong winds to the ground
will be high. Marginally-severe hail is also possible given cold
temperatures aloft and the expectation of organized, very sheared

UPDATE Issued at 647 AM CDT Mon Jun 19 2017

The HRRR and ESRL HRRR through their 09 and 10 UTC iterations
respectively, the 00 UTC NAM NEST, and to a lesser extent the 06
UTC NAM NEST, continue to suggest the potential for a line of
strong to severe thunderstorms, with perhaps a low topped
supercell or two, to propagate out of Canada around 19-20 UTC this
afternoon ahead of a strong 500mb jet streak. Instability will be
weak, however, shear will be very strong around 60-70kts. The
aforementioned CAMs within their updraft helicity forecasts have
continually highlighted the potential for organized convection
across the north central, possibly the far northwest, and into the
James River Valley through the early evening. Have coordinated
with SPC for a possible upgrade to the Day 1 Convective Outlook.
The primary threat will be damaging winds especially in light of
strong environmental mid level winds to transport to the surface.
Large hail to around quarter size is also possible.


.SHORT TERM...(Today and tonight)
Issued at 316 AM CDT Mon Jun 19 2017

The main focus for the short term is thunderstorms across the
Turtle Mountains and James Valley today.

A potent, fast-moving wave will exit southern Saskatchewan later
this afternoon. This wave will combine with diurnal heating to
provide ample lift for thunderstorm development later today.
While CAPE will be limited with 50s dewpoints and temperatures in
the 70s, there will be an abundance of shear available to support
rotating updrafts. This could lead to a few stronger storms
capable of producing hail and strong winds. Current runs of the
short-term models are hinting at stronger storms entering the
Turtle Mountains late by this afternoon and pushing southeastward
into the northern James Valley.

.LONG TERM...(Tuesday through Sunday)
Issued at 316 AM CDT Mon Jun 19 2017

Westerly/Northwesterly flow will continue to bring waves across
the Northern Plains this week and therefore continue the chances
for scattered showers and thunderstorms. It appears at this time
one such wave will swing through Wednesday and a more robust wave
late this weekend. However, with the upper level jet stream parked
nearby daily chances for showers and thunderstorms seem possible
Wednesday through Sunday.


.AVIATION...(For the 18Z TAFS through 18Z Tuesday afternoon)
Issued at 1241 PM CDT Mon Jun 19 2017

A rapidly-moving line of strong to possibly severe thunderstorms
is forecast to move southeast across north central and extreme
northwest ND into the James River Valley this afternoon, exiting
the area by 01 UTC. Localized MVFR to IFR conditions, damaging
surface winds and large hail are possible with the most intense
storms. Otherwise, VFR conditions will prevail for the 18 UTC TAF
cycle as high pressure builds into the region overnight. Gusty
northwest winds will also diminish this evening.




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