FXUS63 KBIS 261745

AFDBIS



Area Forecast Discussion

National Weather Service Bismarck ND

1245 PM CDT Thu Jun 26 2025



.KEY MESSAGES...



- An isolated strong to severe thunderstorm could impact far 

  northwest North Dakota this evening. Expected hazards include 

  hail as large as quarters and damaging wind gusts as high as 

  60 mph.



- Patchy fog is possible Friday morning over south central North

  Dakota into the James River Valley. 



- Scattered severe thunderstorms (risk level 2 out of 5) could 

  develop across central North Dakota Friday afternoon and 

  evening. Expected hazards include hail as large as tennis 

  balls, damaging winds as high as 70 mph, and a tornado or two 

  possible.



- Near to slightly above average high temperatures in the 80s

  are forecast Friday through next week. Friday will also be

  humid for all but far western North Dakota.



&&



.UPDATE...

Issued at 1245 PM CDT Thu Jun 26 2025



While fog has lifted by the time of this mid day update, low

stratus lingers over much of western and central North Dakota.

Some erosion of this stratus layer is evident on satellite 

imagery across the west, though this is is somewhat slow going.

With this in mind, have slightly lowered temperatures across 

central North Dakota this afternoon. Otherwise, for forecast 

updates, have opted to add patchy fog across portions of south 

central North Dakota into the James River Valley early tonight 

through the mid morning hours Friday. An interrogation of BUFKIT

model soundings during this period leads me to expect this fog 

to be somewhat shallow, and should lift pretty readily after 

dawn. No other adjustments to the forecast were performed with 

this update. 



UPDATE

Issued at 950 AM CDT Thu Jun 26 2025



Low stratus and some stubborn patchy fog can be found over much

of the forecast area at the time of this morning update.

Visibility has gradually improved over the last few hours,

especially in the southwest where it had fallen as low as 1/2

mile or less at times. Fog is expected to generally lift across

over the next hour or so. Low stratus has begun to move eastward

this morning, and will continue to do so through the late

morning and early afternoon. There may be some need to lower

high temperatures across the James River Valley this afternoon

where the residence time of this low stratus is expected to be

the longest, though will hold off until the mid day update for

now. Overall, the forecast remains on track. 



UPDATE Issued at 653 AM CDT Thu Jun 26 2025



Widespread low stratus producing drizzle, mist, and fog 

continues to plague most of western and central North Dakota 

early this morning. Recent observations show the fog is becoming

more dense in southwest parts of the state. Will continue to 

monitor for potential need for enhanced fog messaging. 

Meanwhile, radar shows light showers developing and moving into 

southeast parts of our forecast area, east of Highway 83 and 

along and south of Interstate 94. PoPs have been updated through

the morning to reflect observed trends.



&&



.DISCUSSION...

Issued at 432 AM CDT Thu Jun 26 2025



The Northern Plains are under a broad southwesterly upper level flow 

pattern early this morning, and are forecast to remain so through at 

least Saturday. RAP analysis shows a weak 700-500 mb cyclonic 

circulation over North Dakota with a moist easterly flow underneath 

driven by broad high pressure over eastern Canada. This has promoted 

widespread low stratus across most of western and central North 

Dakota, with observed northwest expansion still ongoing. Drizzle and 

mist have been common underneath the low stratus, and a few webcams 

have suggested fog, but not dense.



Most of western and central North Dakota will remain free from 

showers and thunderstorms through this afternoon. The aforementioned 

mid level cyclonic circulation is forecast to deepen over the 

central Dakotas this morning, which could bring some light showers 

into the James River Valley through mid afternoon. The low clouds 

and light drizzle/mist/fog are likely to scatter/lift in a northwest 

to southeast fashion through the afternoon behind the deepening wave 

as low level flow turns more southerly. The timing of the clearing 

of clouds will highly influence the high temperature outcome for 

today. Our current expectations range from the lower and mid 80s 

along the Montana border to around 70 in the James River Valley, 

where cloud cover could hold on into the evening.



Isolated to widely scattered convection is forecast to initiate 

along a lee trough across eastern Montana late this afternoon, with 

forcing also supported by mid level height falls with upstream 

cyclonic vorticity maxima embedded in the main flow. A few of these 

storms could move into far western parts of the state this evening, 

with higher probabilities northwest compared to southwest on account 

of stronger lift from DCVA and WAA. The atmosphere is forecast to 

only be marginally supportive of lower-end severe convection, with 

MUCAPE around 1000 J/kg and 0-6 km bulk shear increasing from around 

30 to 40 kts through the evening in the northwest. There is forecast 

uncertainty in storm mode, with vector orientation to the boundary 

ranging from nearly perpendicular for deep layer shear to nearly 

parallel for anvil level SR flow. This uncertainty is reflected in 

the 00Z suite of CAMs, whose reflectivity fields depict a mixed/ 

cluster mode. Given this uncertainty and the lower-end CAPE/shear 

parameter space, we will continue to advertise baseline severe 

hazards of quarter size hail and 60 mph gusts in far northwest North 

Dakota this evening. A few clusters of showers and isolated 

thunderstorms could persist across northwest and spread into north 

central North Dakota through tonight, but the the threat of stronger 

storms should end near or shortly after midnight and remain confined 

to the far northwest.



A somewhat continuous stream of mid level shortwave energy embedded 

in the southwest flow aloft is forecast over the region Friday, with 

surface/low-level lee troughing shifting into western North Dakota. 

The air mass downstream of the lee trough is forecast to contain 

surface dewpoints in the 60s combining with 80s high temperatures to 

yield SBCAPE around 2000 to 3000 J/kg. The lack of a strong forcing 

mechanism and favored presence of mid level capping introduces 

uncertainty to the convective initiation forecast. Still think the 

most likely outcome is for enough low level convergence combined 

with weak mid level height falls sufficiently eroding CIN to allow 

at least a few thunderstorms to develop across central North Dakota 

during the late afternoon/early evening hours on Friday. There is 

larger forecast spread in the amount of deep layer shear, ranging 

from as little as 30 kts to as high as 50 kts, but most 

deterministic models and ensemble systems do show shear increasing 

over time. The lack of strong forcing and deep layer shear/wind 

vector orientation to the boundary strongly point toward an initial 

discrete supercell mode, with possible upscale growth later in the 

evening primarily driven by cold pool propagation if the coverage of 

discrete supercells ends up being more scattered than isolated. The 

expected storm mode combined with the higher ends of the CAPE/shear 

forecast distribution lead to very large hail (up to tennis ball 

size) being the primary expected hazard, but clustering storms later 

in the evening could have access to waning, but sufficient DCAPE and 

strong 0-3 km shear to maintain a damaging wind threat (gusts as 

high as 70 mph). The risk for tornadoes is more uncertain. The 03Z 

RAP in particular is quite bullish on a favorable tornado setup, 

including STP in the 1 to 3 range and model hodographs favoring 

strong streamwise vorticity. However, the 00Z HREF only has a low to 

medium probability of STP exceeding 1 by the end of its run early 

Friday evening, and its hodographs are not as looped or concave in 

the lowest 1-2 km. Given this, and the lower confidence in storm 

coverage, we will continue to advertise a tornado or two possible. 

But a reasonable worst-case scenario could be any supercell that 

develops carrying a tornado risk. 



Most of the storms that develop Friday afternoon and evening should 

push off to the south and east by late Friday night. However, an 

intensify low level jet could lead to convective maintenance or 

perhaps even new development. Should this occur, training convection 

within a warm and moist deep layer could introduce an excessive 

rainfall risk. Low chances for thunderstorms remain in the forecast 

on Saturday under continued southwest flow aloft and with a NE-SW 

frontal boundary stalling across the region. The Storm Prediction 

Center has introduced a Marginal Risk (level 1 out of 5) for severe 

storms across south central and eastern North Dakota on Saturday, 

but any convection on Saturday could be greatly influenced by how 

storms evolve in the preceding 12 to 24 hours.



Longer range ensembles favor a trough digging into the Great Lakes 

region early next week as an upper ridge becomes amplified over the 

western CONUS, placing the Northern Plains in a prevailing northwest 

flow regime. Temperatures are favored to be near to slightly above 

average through next week, for which late June is highs in the lower 

80s. Ensembles favor a period of drier weather to the start the 

week, with shower and thunderstorm chances increasing back to medium 

levels by mid week. At this time, GEFS-based machine learning 

guidance does not contain any strong signals for severe storms for 

the first half of next week.



&&



.AVIATION /18Z TAFS THROUGH 18Z FRIDAY/...

Issued at 1245 PM CDT Thu Jun 26 2025



Low stratus is causing MVFR to IFR ceilings across the forecast

area at the time of this mid day update. As this stratus deck 

continues to move eastward through the afternoon, ceilings are 

expected to broadly improve to VFR conditions from west to east.

KJMS may remain under MVFR ceilings through the early evening 

hours. Later this evening, chances for showers and thunderstorms

are expected to increase across northwestern North Dakota, 

including around the KXWA terminal. Some of these storms may 

become strong to severe, with large hail up to quarters (1 inch)

in size and wind gusts up to 60 MPH. These thunderstorms 

expected to generally diminishing through the late evening into 

the early overnight period, though scattered showers may linger 

across the north. Confidence is too low to include mentions of 

showers or thunderstorms anywhere except for KXWA at this time. 

Friday morning, patchy fog is possible across portions of south 

central North Dakota into the James River Valley. Have included 

visibility reductions at KJMS with this update. Currently, this 

fog is expected to be somewhat shallow, and should readily lift 

by the mid morning hours. Otherwise, Light east to southeasterly

winds are anticipated throughout the TAF period. 



&&



.BIS WATCHES/WARNINGS/ADVISORIES...

None.



&&



$$



UPDATE...Adam/Hollan

DISCUSSION...Hollan

AVIATION...Adam

