Severe Thunderstorm Warning 116, NWS Bismarck, ND

Area Forecast Discussion
National Weather Service Bismarck ND
328 PM CDT Thu Jul 2 2020

.SHORT TERM...(This evening through Friday)
Issued at 327 PM CDT Thu Jul 2 2020

The main concern for the short term period is chances for severe
thunderstorms.

Closed upper low continues to spin over central Alberta with a
positively tilted ridge axis from the Great Lakes to Texas. A pre-
frontal surface trough is analyzed from near Mohall to Buffalo, SD,
and is a bit farther west than previously expected. Convection
initiation appears to be underway along/just ahead of the surface
trough in southwest North Dakota where SBCIN is eroding. SPC
mesoanalysis places up to 5000 J/kg SBCAPE and around 40 kts
effective bulk shear over the area. Initial storms should remain
discrete. Upscale growth into clusters/linear segments is possible,
but not a certainty due to weaker mid/upper level forcing, and right-
moving Bunkers vectors would likely move discrete supercells away
from the surface boundary. The main hazard is expected to be very
large hail, with damaging winds also possible. The tornado threat is
marginal at best, mainly due to relatively high LCLs, but still
greater than zero. It is unclear how far north and east the threat
for severe weather may expand, mainly due to capping concerns.

Further to the east, sub-severe convection has been percolating over
central North Dakota along a corridor of strong low level southerly
flow. Much greater CIN and weaker shear will likely keep this
activity below severe limits.

There is potential for the development of additional convection
overnight from southwest into central North Dakota on the nose of a
low level jet and associated low to mid level moisture transport.
Forcing may be aided by mid level shortwave energy. This potential
is likely highly contingent on the latitudinal placement of the
LLJ/moisture transport, which may be influenced by remnant outflow
boundaries from convection this afternoon and evening. MLCIN will
obviously be present at this time of day. But interestingly, the RAP
does show a weakening trend in the cap after midnight CDT. If air
parcels are able to break through the EML, MUCAPE and effective bulk
shear would promote a severe threat, which may continue into Friday
morning.

Details on timing and location of convection Friday and Friday night
remain murky at best. There is general agreement for active
southwest flow aloft topping a Central Plains ridge, with strong
moisture advection in low level southerly flow. The trend in CAMs
has been for mostly dry weather during the afternoon, while some
global models suggest meandering MCSs through the day. The potential
for early morning convection further complicates the picture and
decreases predictability. However, the environment over this time
period will generally contain steep lapse rates, CAPE greater than
2000 J/kg, effective shear greater than 30 kts, and precipitable
water greater than one inch. Any storm/complex of storms will be
capable of producing large hail, damaging wind, and torrential
rainfall. Of particular concern is the potential for training
convection as Corfidi vectors are oriented perpendicular to moisture
transport vectors, with mean 700-300 mb winds less than 30 kts.

.LONG TERM...(Friday night through Thursday)
Issued at 327 PM CDT Thu Jul 2 2020

Above normal temperatures and chances for thunderstorms, some severe
with heavy rain, highlight the long term period.

Long range guidance continues to favor a stagnant weather pattern
through the middle of next week, with persistent Pacific Northwest
troughing and broad ridging from the Southern Plains to the Upper
Mississippi River Valley. This leaves the local area in an active
southwest to quasi-zonal flow pattern, with mostly above normal
temperatures, humid conditions, and daily chances for thunderstorms.
The hottest day is expected to be Independence Day, with afternoon
heat indices in the mid to upper 90s from south central North Dakota
into the James River Valley.

Forecast instability and shear parameters along with climatology
suggest any round of thunderstorms has the potential to include
severe weather. This thinking is supported by CIPS analogs, which
bring relatively higher probabilities (at least 15 percent) of
severe weather into at least part of North Dakota every single day.
Of greater concern may be the potential for heavy rain. Periods of
strong low level moisture transport are forecast to intercept east-
northeastward propagating MCSs in an environment with above normal
precipitable water and deep warm-cloud layers. This potential threat
looks to be maximized Saturday afternoon through Sunday night.

&&

.AVIATION...(For the 18Z TAFS through 18Z Friday afternoon)
Issued at 115 PM CDT Thu Jul 2 2020

Scattered thunderstorms are possible through the forecast period,
mainly across southwest and central ND. Beyond this evening,
predictability of timing and location of storms is too low to
include a mention in the TAFs. Expect periods of IFR to LIFR
visibility, sporadic gusty winds, and possibly hail within
thunderstorms. Outside of storms, VFR conditions should prevail.
Southerly winds around 15-20 kts, gusting near 30 kts will
continue across central ND this afternoon, with lighter westerly
winds to the west. Winds will become light and variable overnight,
then southeasterly around 10 kts by Friday afternoon.

&&

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

SHORT TERM...Hollan
LONG TERM...Hollan
AVIATION...Hollan

Hazardous Weather Outlook
National Weather Service Bismarck ND
334 PM CDT Thu Jul 2 2020

NDZ003>005-010>013-017>023-025-031>037-040>048-050-051-032045-
Renville-Bottineau-Rolette-Mountrail-Ward-McHenry-Pierce-McKenzie-
Dunn-Mercer-Oliver-McLean-Sheridan-Wells-Foster-Golden Valley-
Billings-Stark-Morton-Burleigh-Kidder-Stutsman-Slope-Hettinger-
Grant-Bowman-Adams-Sioux-Emmons-Logan-La Moure-McIntosh-Dickey-
334 PM CDT Thu Jul 2 2020 /234 PM MDT Thu Jul 2 2020/

This Hazardous Weather Outlook is for portions of north central
North Dakota, northwest North Dakota, south central North Dakota,
southeast North Dakota, and southwest North Dakota.

.DAY ONE...This Afternoon and Tonight

There is a chance of thunderstorms this afternoon through tonight.
Some storms may be severe across the southwest and central, with
large hail up to golf ball size and damaging winds to 70 mph.

.DAYS TWO THROUGH SEVEN...Friday through Wednesday

Numerous thunderstorms are forecast across western and central
North Dakota Friday through Sunday. Heavy rain is possible with
any storm, especially across central parts of the state. Severe
weather is also possible.

Daily chances for thunderstorms continue Monday through
Wednesday. Some storms may be severe.

.SPOTTER INFORMATION STATEMENT...

Spotters are encouraged to report severe weather, including heavy
rainfall, to the National Weather Service in Bismarck.

NDZ001-002-009-032045-
Divide-Burke-Williams-
334 PM CDT Thu Jul 2 2020

This Hazardous Weather Outlook is for portions of northwest North
Dakota.

.DAY ONE...This Afternoon and Tonight

The probability for widespread hazardous weather is low.

.DAYS TWO THROUGH SEVEN...Friday through Wednesday

Numerous thunderstorms are forecast across western and central
North Dakota Friday through Sunday. Heavy rain is possible with
any storm, especially across central parts of the state. Severe
weather is also possible.

Daily chances for thunderstorms continue Monday through
Wednesday. Some storms may be severe.

.SPOTTER INFORMATION STATEMENT...

Spotters are encouraged to report severe weather, including heavy
rainfall, to the National Weather Service in Bismarck.

Hollan

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