Severe Thunderstorm Warning 250, NWS Bismarck, ND

Area Forecast Discussion
National Weather Service Bismarck ND
1245 PM CDT Sun Aug 9 2020

.UPDATE...
Issued at 1237 PM CDT Sun Aug 9 2020

A severe thunderstorm watch has been issued through this afternoon
for much of the James River Valley. The cold front continues to
push through the area, and it is now just to the east of a line
from Carrington to Linton. Ahead of the front, strong instability
remains as previously discussed with deep layer shear from around
35 to 40 knots. Therefore, any storm that does develop as the
front passes through will have the potential to become severe.
With this all said, storms should push to the east of the area by
late this afternoon, with a quiet evening ahead.

UPDATE Issued at 930 AM CDT Sun Aug 9 2020

Cold front continues to push its way through the area, and is now
oriented from near Bottineau to near Washburn to the tail of
Sioux County. Some storms continue to linger near the Turtle
Mountains, with a few little showers popping up here and there to
the south. Still expect stronger storms to flare up early this
afternoon as the front shifts into the James River Valley region.
High-res models continue to advertise strong instability in this
area during the afternoon, with CAPE values in excess of 3000
J/KG. The storms should be quick moving as the front sweeps
through, with the convection pushing to the east of our area
during the late afternoon. For mid-morning update have added
severe wording to the forecast this afternoon over the James River
Valley given the strong instability, and have adjusted
precipitation chances a bit to address the morning convection.

UPDATE Issued at 634 AM CDT Sun Aug 9 2020

At 6 am CDT, a cold front extended across western ND, from near
Stanley south to near Dickinson. A warm front extended through
north central into eastern North Dakota. The front will be the
focus for thunderstorms in central ND this morning and eastern
North Dakota this afternoon.

We have followed the CAM models so far today, and that has worked
out OK, using the HRRR. The morning convection was focused along
and north of the warm front. lated this morning and afternoon the
convection will align along the cold front as it progresses east.
Current forecast looks good.

&&

.SHORT TERM...(Today and tonight)
Issued at 332 AM CDT Sun Aug 9 2020

Confidence in CAM models has increased as they have reasonably
depicted the convection across western and north central North
Dakota this morning.

This area is in a region of isentropic lift and associated
convergence of the low level jet, with convergence along an
eastward moving cold frontal boundary as well. Cape values of 1500
and shear of 35 kts would seem to support some marginally severe
thunderstorms. However, so far the storms have not been persistent
enough, showing severe characteristics for a volume scan or two
then falling apart. So there is some potential for large hail and
gusty winds this morning, but short lived pulse storms are
expected.

The thunderstorms will fairly quickly move east with the front
today, and by early afternoon thunderstorms will be exiting the
region across the southern James River Valley.

There the low level parcels will briefly see CAPE values exceed
4000 this afternoon (by 2 pm CDT) on the NAM forecast sounding.
but they may not have residency time in this rich airmass for very
long as the cold front sweeps through by 4 pm CDT. So we will
continue to message a marginally severe potential southeast today.

Tonight skies will clear as teh cold front moves east and high
pressure builds in.

With the surface high over the region with light winds blend gives
overnight lows from teh upper 40s to mid 50s.

.LONG TERM...(Monday through Saturday)
Issued at 332 AM CDT Sun Aug 9 2020

We will transition from cyclonic flow aloft Monday into more
zonal flow, then shortwave ridging by Tuesday. Height rises aloft
should suppress widespread convection Monday and Tuesday.

The next chance for more widespread thunderstorms will be
Wednesday into the weekend, as several upper lows migrate
through southern Canada. During this process, severe shortwaves
will move through the cyclonic flows aloft keeping the period
from Wednesday through Saturday active for thunderstorms. Active
buy not widespread would be more accurate.

&&

.AVIATION...(For the 18Z TAFS through 18Z Monday afternoon)
Issued at 1237 PM CDT Sun Aug 9 2020

A cold front will continue to push through central into eastern
North Dakota this afternoon. Ahead of the front, areas of MVFR
ceilings remain. In the vicinity of the front, scattered
thunderstorms are expected to develop, with some possibly becoming
severe. This may affect the KJMS terminal. By late this afternoon
into early this evening the thunderstorms will be east of our
area, with VFR conditions prevailing.

&&

.FIRE WEATHER...
Issued at 332 AM CDT Sun Aug 9 2020

Elevated fire weather concerns will be seen for a number of days
through early next week.

A moderate westerly h500 flow across the Rockies will maintain
low dewpoints across the lee side of the mountains in Montana.
Todays cold frontal passage will be able to bring some of that
very dry air into western North Dakota. With dewpoints as low as
the mid 30s in the afternoon possible over western North Dakota
today and Monday.

Although temperatures will be cooler, the dry air will favor
minimum relative humidity around 20 percent today, and 15 to 20
percent Monday.

Today will see northwest winds of 15 to 20 mph across the west.
Monday the winds will be across the north.

Elevated fire weather conditions are expected today with minimum
RH around 20 percent with widespread winds of 20 mph across the
west.

Near critical fire weather conditions are possible Monday,
with min RH 15 to 20 percent. But the strongest winds on Monday
will be displaced to the north from the lower RH somewhat.

&&

.BIS WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

UPDATE...JJS
SHORT TERM...WAA
LONG TERM...WAA
AVIATION...JJS
FIRE WEATHER...WAA

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PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE BISMARCK ND
1021 AM CDT SUN AUG 9 2020

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0600 AM     HAIL             3 SSW ORRIN             48.05N 100.18W
08/09/2020  E1.00 INCH       PIERCE             ND   PUBLIC

&&

AE

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE BISMARCK ND
1028 AM CDT SUN AUG 9 2020

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0556 AM     HAIL             6 SSW ORRIN             48.02N 100.24W
08/09/2020  E0.75 INCH       MCHENRY            ND   PUBLIC

&&

AE

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