429 FXUS63 KBIS 181943 AFDBISArea Forecast Discussion National Weather Service Bismarck ND 243 PM CDT Thu Sep 18 2025
.KEY MESSAGES...
- Showers, along with a few rumbles of thunder, remain in the forecast through Friday. The highest rain chances are over south central and southeastern parts of the state this evening. Then Friday the highest chances will be along and east of the James River Valley.
- Severe weather is not expected, though periods of heavy rain may bring some localized minor flooding at times.
- High temperatures will be mainly in the 50s and 60s Friday, then warming into the 70s and low 80s by Sunday. Low temperatures will be in the 40s to mid 50s.
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.DISCUSSION... Issued at 240 PM CDT Thu Sep 18 2025
Currently a double barrel upper low is positioned over the Northern Plains. The western low is over northern Montana, while the second and stacked low is over northeast South Dakota. This entails the surface low is also in northeast South Dakota. The two upper lows are slowly rotating counter- clockwise around each other, so the surface low in SD is slowly moving north.
At the surface, multiple rains bands are spiraling counter- clockwise through in the southern and eastern half of North Dakota. As the surface low slowly progresses north and slightly east, the rain bands will slowly expand north and east. This trend will continue overnight. Aloft the double lows will combine over the Dakotas and begin the eastward progression out of here tonight. Friday the rain will end west to east naturally as the low moves east. High temperatures while being in the backside of this system will remain below average in the 60s in the central and east. The western part of the state will be in the upper 60s as a shortwave ridge moves in. This weekend will be dry and at or above average for temperatures with highs in the 70s and 80s once again.
The weak ridging pattern will break down Monday when an upper low dives south from Canada into Idaho. North Dakota will briefly be in weak southwest flow Monday. Showers and maybe a thunderstorm will then be possible across the southwest and south central Monday from this. That low then could move east through the Central Plains and produce more rain in the southern half of the state later next week. Long term models and the CPC are showing continued above average temperatures through the end of October.
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.AVIATION /18Z TAFS THROUGH 18Z FRIDAY/... Issued at 240 PM CDT Thu Sep 18 2025
LIFR CIGs are present in the south and east, especially in the rain bands. MVFR to VFR elsewhere. Bands of rain will move east to west across most of the state through Friday morning. A few thunderstorms are possible in the east this evening. Winds will stay around 12kts, except in the southeast where gusts around 25 are possible from the east. CIG raise towards the end of the period.
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.BIS WATCHES/WARNINGS/ADVISORIES... None.
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DISCUSSION...Smith AVIATION...Smith
NWS BIS Office Area Forecast Discussion