501 
FXUS63 KBIS 120511
AFDBIS

AREA FORECAST DISCUSSION
National Weather Service Bismarck ND
1211 AM CDT Tue Sep 12 2023

.UPDATE...
Issued at 1156 PM CDT Mon Sep 11 2023

One lone shower remains just west of Ashley in McIntosh county.
Otherwise shower activity has exited the forecast area. Otherwise
expect mostly clear skies, but with fog developing around the
James River Valley and possibly up the Hwy 52 corridor towards
Minot. Fog has already developed at the Jamestown Airport, but
from satellite imagery and webcams, seems patchy in nature at
least for now. Also vsby beginning to lower at KMOT. Will adjust
area and timing of fog to account for current conditions.

UPDATE Issued at 924 PM CDT Mon Sep 11 2023

A few returns producing light rain persist in the southern James 
River Valley of ND. These should continue to dissipate/move out of
the forecast area within the next hour or two. Otherwise, models 
maintain strong indications of patchy fog developing mainly in 
the JRV tonight. Further fog development north and west of the JRV
is not out of the question either, but may be hindered by
stronger near-surface winds. 

UPDATE Issued at 629 PM CDT Mon Sep 11 2023

As of now, thunderstorms have either ended or moved out of the
forecast area, although a few showers remain mainly in the south
central. Remaining showers should continue to diminish as the
sun sets. Thus tweaked PoPs slightly over the next couple hours 
based on the latest radar trends. Also made slight adjustments to 
cloud cover where thicker low level stratus persists, especially 
along and just east of the Missouri Coteau. 

&&

.SHORT TERM...(Today through Tuesday) 
Issued at 240 PM CDT Mon Sep 11 2023

Forecast highlights in the short term period will be ongoing
showers and isolated thunderstorms today along with continued
cooler temperatures through the short term period. 

Currently, upper level ridge extends from the Great Basin
north/northeast through central Saskatchewan, with an upper level
trough over the Great Lakes region. This puts north/northwesterly
flow aloft over the Northern Plains region today. An embedded S/WV
continues to rotate south through the eastern Dakotas, resulting
in areas of showers and isolated thunderstorms. Expect this
activity to slowly end north to south during the day today as the
aforementioned forcing departs to the south and we lose daytime
heating after 00Z. 

Another chilly night ahead with lows in the 40s, and may see a 
handful of locations dropping into the 30s, especially northeast 
where winds will be lightest. Areas of fog look probable, over the
James River valley, as suggested by both the RAP13 and HRRR. Opted
to add in patchy fog for now and see how models trend. Elsewhere
tonight, some models suggest low stratus development over some
areas west due to a southeasterly upslope flow regime, and did 
reflect this somewhat in the sky grids.

For Tuesday, ridge axis moves overhead, with increasing return
flow across the Dakotas. Winds will become breezy west with peak
winds within the mixed layer around 20-25kts, thus sub-advisory.
Best WAA holds off to the west one more day, so expect similar 
afternoon temperatures on Tuesday as we are seeing today. 

.LONG TERM...(Tuesday Night through Monday)
Issued at 240 PM CDT Mon Sep 11 2023

Ridge is flattened on Wednesday as a mid level S/WV moving into 
the Pacific NW Tue night approaches the Northern Rockies during 
the day Wednesday. Increasing southerly return flow ahead of this
feature on Wed will advect a warmer airmass into the local area,
with highs Wednesday in the mid 70s to lower 80s.

This wave will continue to track east Wed night through Thursday,
along with an associated frontal boundary moving across western
and central ND. Both of these features will result in an increase
in precipitation chances during this period, with the frontal
boundary the main focus for showers and a few thunderstorms as it
progresses slowly southeast across our region through Thu night.
Cooler temperatures on Thu also forecast with the expected
increase in cloud cover and cooler air filtering in behind the 
FROPA. 

Thereafter, global ensembles favor upper level ridging across the
western CONUS into the Rockies redeveloping for this coming
weekend, then eventually into the Northern Plains region early
next week. Resultant weather will be mainly dry conditions 
coupled with a slow warming trend, yet overall with near normal 
highs and lows for the middle of September.

&&

.AVIATION...(For the 06Z TAFS through 06Z Tuesday Night)
Issued at 1156 PM CDT Mon Sep 11 2023

Areas of fog, dense at times is expected around the James river
Valley early this Tuesday morning, including KJMS. KJMS already at
1/4SM FG just prior to the 06Z TAFS. Based on satellite it looks
patchy in nature and may vary at time 06-10-12 UTC before becoming
more dense around sunrise and continuing through 15-17 UTC. KMOT
also dropping a little down to 6SM prior to 06 UTC TAFS, but here
will not be as pessimistic with visibilities through mid morning,
probably starting off with tempo down to MVFR and will go from
there. 

Otherwise, after fog dissipates this morning only high level
clouds expected with a southeast surface flow through the period.
Southeast flow breezy at times west this afternoon and evening.

&&

.BIS WATCHES/WARNINGS/ADVISORIES...
None.
&&

$$

UPDATE...TWH
SHORT TERM...NH
LONG TERM...NH
AVIATION...TWH