Area Forecast Discussion
Issued by NWS Bismarck, ND

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FXUS63 KBIS 170246

Area Forecast Discussion
National Weather Service Bismarck ND
946 PM CDT Sun Jul 16 2017


Issued at 946 PM CDT Sun Jul 16 2017

Competing forces right now between the low level jet and a cooling
boundary layer over north central ND continues to see pulse
thunderstorms approaching marginal severe thresholds. Our
thinking is once further cooling occurs storms should taper down
in strength between now and midnight CDT. Until then, large hail
and strong winds approaching severe limits will remain possible.

Over southwestern North Dakota, very high pressure rises in the
wake of showers/storms has generated peak wind gusts of 45 to 55
MPH at both Baker and Glendive. These winds appear to last maybe
up to an hour before tapering off.

The red flag warning was allowed to expire with RH values coming
up and gusty southerly winds winding down.

Issued at 647 PM CDT Sun Jul 16 2017

Modifications were made to POPs bases on latest radar and high res
model output. Continue to get pop-up thunderstorms that quickly
die off along a ling from McKenzie county east-northeast through
the western Devils Lake Basin area. Enough ingredients as
mentioned in previous discussion that a few of these may become
strong to severe if they can maintain their updrafts. Main forcing
will not arrive until after 01Z, closer to 02Z west when a
vigorous S/WV moves into eastern MT.


.SHORT TERM...(This evening through Monday)
Issued at 219 PM CDT Sun Jul 16 2017

Latest water vapor imagery loop and regional radar shows multiple
mid level/700mb-500mb shortwaves progressing through a southwesterly
flow into western North Dakota. Isolated light rainshowers north
central ND, with thunderstorms beginning to initiate over south
central Montana. The latest surface analysis shows a surface warm
front through western ND, with an advancing cold front into central
MT moving east with time. In between, an 850mb thermal ridge with
increasing temperatures and instability. Honing in on a 700mb-500mb
shortwave moving from southwest Montana into central Montana this
afternoon. This shortwave in conjunction with the advancing cold
front is where the thunderstorms are developing as mentioned above.
This shortwave gradually slides into western ND tonight and into
central ND Monday morning. Height falls are underway, with RAP13
soundings indicate an inverted-V type scenario/high based convection.
SHARPpy soundings show moderate instability with mixed layer
Cape/1200 J/kg, weak to modest deep layer shear (20kt to 30kt),
along with a high Downdraft Cape of 1500 to 1700 J/kg, will lead
to isolated severe thunderstorms with damaging winds and/or large
hail this evening. The CAM`s continue to show increasing coverage
of showers/thunderstorms developing in the west, (precipitation
coming in from Montana), between 21z and 00z. This lines up along
and ahead of the advancing aforementioned cold front as it shifts
through western into central ND overnight.

The cold front limps from south central ND early Monday morning
into the southern James River Valley Monday afternoon. The southern
James River Valley will be the primary focus for severe thunderstorms
Monday afternoon and evening. SPC continues with a Slight Risk in
this area as deep layer shear increases and cape.

.LONG TERM...(Monday night through Sunday)
Issued at 219 PM CDT Sun Jul 16 2017

A more active long term period with a quasi zonal flow and
multiple shortwaves traversing across western/central ND. This
will result in periodic/nearly daily showers/thunderstorm chances.
Perhaps the strongest shortwave may be in the Friday to Saturday
timeframe, as a closed low advertised on both the GFS/EC slides
across southern Canada. However the location and timing differ on
both models, so will continue to watch the trends. Otherwise, with
a flatter/more zonal flow, high temperatures will mostly be in the
80s Tuesday through Sunday.


.AVIATION...(For the 00Z TAFS through 00Z Monday evening)

Issued at 647 PM CDT Sun Jul 16 2017

Scattered thunderstorms possible tonight, with some storms
remaining possible over central and eastern portions of North
Dakota into Monday morning. Latest forecast models suggest the
west and north will see the best chance tonight. Otherwise, VFR
conditions expected.


Issued at 219 PM CDT Sun Jul 16 2017

The red flag warning remains on track. Gusty southerly winds and
lowering relative humidities this afternoon will create critical
fire weather conditions along and west of the Missouri River.
Please see for additional information.




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