537 
FXUS63 KBIS 150622
AFDBIS

Area Forecast Discussion
National Weather Service Bismarck ND
122 AM CDT Sat Sep 15 2018

.UPDATE...
Issued at 113 AM CDT Sat Sep 15 2018

The RAP/HRRR/NBM/GFSLamp through their 05 UTC iterations continue
to depict fog formation across northwest into far north central
North Dakota through the night and into Saturday morning on the
cool side of a stationary front. A Dense Fog Advisory may be 
needed later tonight. 

UPDATE Issued at 1019 PM CDT Fri Sep 14 2018

CAM models catching on to some convection in east central North
Dakota, northward into southern Pierce county, which is north of
the current forecast. Updated pops through early morning. 

UPDATE Issued at 923 PM CDT Fri Sep 14 2018

Several CAM models showing some fog development northwest tonight
so added patchy fog there. Otherwise expect the thunderstorms to
trend down across the south east and east central this evening. 

UPDATE Issued at 638 PM CDT Fri Sep 14 2018

A single supercell has formed along an east-west mid level 
boundary across south central North Dakota. A few thunderstorms
will be active for the next 2 hours or so. Otherwise will continue
to se low level moisture and clouds pulled north along a warm 
frontal boundary this evening. Scattered showers and 
thunderstorms will slowly diminish with time around midnight. 

&&

.SHORT TERM...(This evening through Saturday)
Issued at 239 PM CDT Fri Sep 14 2018

Thunderstorm potential highlights the short term forecast.

Currently, a stationary frontal boundary extended from a surface low 
over eastern South Dakota northward across Wahpeton/Fargo into 
northwestern Minnesota. Another secondary boundary in the form of a 
cold front extended from the Turtle Mountains to near Bismarck to 
near Hettinger. At upper levels, a longwave trough over the West 
Coast was keeping a southwesterly flow aloft across the northern 
Rockies and Northern Plains today.

Upper level impulses within the flow aloft were keeping scattered 
showers across northwestern and north central ND today. And the 
coolest air remained behind the secondary cold front over far 
northwestern ND where temperatures remain in the 50s/60s this 
afternoon, while highs in the low to mid 70s were reported across 
the remainder of western and central ND.

This afternoon and tonight, the upper level west coast trough digs 
south into California, forcing the upper level energy impulses over 
northern ND farther north into Canada as h500 heights rise over our 
region. Thus scattered rain showers in northern ND are expected to 
wane with time this evening. Meanwhile, the aforementioned surface 
stationary boundary becomes more of a strengthening warm front, 
extending southwest-to-northeast from a low over Wyoming, across 
South Dakota, into southeastern ND by Saturday morning. As this 
occurs, a strengthening low level jet is forecast to develop, 
bringing chances of showers and thunderstorms to south central and 
southeastern North Dakota this afternoon and evening. Bulk shear 
values are fairly high at 50+ knots, but CAPE is weak at up to 
around 100-400 J/kg. Thunderstorms possible but severe weather not 
anticipated.

The CAMs develop scattered thunderstorms from Bismarck to Jamestown 
and south late this afternoon and evening, with the convection 
moving north and east out of central North Dakota later 
tonight...with little in the way of showers Saturday morning. 
Along with the developing low level jet, a mid-level thermal cap 
develops northeastward, building from the western high plains into
southern and eastern North Dakota later tonight and Saturday. 
This should keep showers and thunderstorm chances confined to 
northeastern North Dakota - and moreso into northern Minnesota and
southern Canada. 

Looking at a mostly cloudy day on Saturday, with low clouds in the 
morning giving way to mid level clouds in the afternoon. Thus high 
temperatures should only reach the mid 60s northwest to mid 70s 
along the South Dakota border.

.LONG TERM...(Saturday night through Friday)
Issued at 239 PM CDT Fri Sep 14 2018

A warm Sunday southwest, south central and across the James River 
Valley...followed by a cool down next week...and a chance for 
widespread rains mid-week across the area highlights the extended 
forecast.

Saturday night the Wyoming surface low lifts northward into eastern 
Montana, and the associated surface warm front moves northward to 
the Canadian border by daybreak Sunday. As this occurs, the 
northward leading edge of the low level jet moves northward as well, 
with the continuing expansion of the mid level thermal ridge. This 
should lead to confining showers and thunderstorms to mainly the 
northern half of ND. Increasing CAPE with increasing surface to h850 
dewpoints will be realized as well, but the best forcing should be 
north of the Canadian border Saturday night, and especially into 
Sunday. 

On Sunday, a small but vigorous upper level shortwave moves 
northeast across Montana into western ND and into Manitoba. In 
response, the Montana surface low develops/moves eastward across the 
Dakotas as a cold front. Gusty southerly winds ahead of the front 
will allow warmer, humid air to continue to advect into the eastern 
Dakotas. Behind the front, gusty west/northwest winds will develop, 
ushering in drier air Sunday afternoon. Sunday looks to be the last 
summer-like day across the state...at least for the next several 
days. Look for highs in the mid and upper 80s - perhaps 90F - in the 
far south central and James Valley, with highs in the 70s over 
the northwest and north central. 

Cooler weather next week as the upper level flow becomes more zonal, 
then the upper level flow develops into a western US and Rockies 
trough, with a large-scale surface low deepening over the central 
Plains. This scenario will allow plenty of showers and thunderstorms 
for the central Plains through the Mississippi Valley, and 
overrunning showers and possible thunderstorms for North Dakota 
Wednesday and Thursday. Look for high temperatures next week to be 
mainly in the 60s, with lows mainly in the mid 30s and 40s. Frost is 
possible over northwestern and north central ND beginning Monday 
night.

&&

.AVIATION...(For the 06Z TAFS through 06Z Saturday night)
Issued at 113 AM CDT Sat Sep 15 2018

MVFR stratus across far southwest and south central North Dakota,
and the James River Valley will expand across nearly all of
western and central North Dakota through the night and into
Saturday morning. IFR ceilings are possible west and south central,
especially at KDIK with easterly upsloping winds. MVFR stratus 
will remain across most of the area through the day on Saturday, 
and likely into Saturday night. Ceilings may fall towards IFR 
across western North Dakota Saturday night after sunset. IFR/LIFR 
conditions in fog are possible across northwest and far north 
central North Dakota and the Turtle Mountains late tonight into 
Saturday morning. Fog may form again across the west Saturday 
night. Scattered rain showers and thunderstorms may develop 
Saturday afternoon southwest and south central, and spread north 
into Saturday evening and night. 

&&

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

$$

UPDATE...PA
SHORT TERM...JV
LONG TERM...JV
AVIATION...PA