Area Forecast Discussion
Issued by NWS Bismarck, ND

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FXUS63 KBIS 270538

Area Forecast Discussion
National Weather Service Bismarck ND
1238 AM CDT Thu Oct 27 2016

Issued at 1237 AM CDT Thu Oct 27 2016

Latest iterations of the HRRR were indicating an area of fog
beginning in the Devils Lake Basin...and expanding to include much
of the areas along and east of the Coteau. Currently Rugby was down
to 1/4 mile in that would suggest the HRRR is capturing the
fog in its solution. However, there is a large area of mid level
clouds that extended from Saskatchewan/Montana/southwestern ND/much
of SD. This area of clouds is forecast to continue moving eastward.
This should act to inhibit radiational cooling and, in turn, fog
(especially dense fog) from continuing or expanding. Have mention of
areas of fog along and east of the Coteau with patchy dense fog
mention. Will continue to monitor the fog and may be issuing a dense
fog advisory later this morning.

Otherwise adjustments to lower min temps tonight. Radiational
cooling along the northern tier of counties had allowed temperatures
to drop into the lower 30s. Expect that the mid cloud cover should
keep temps from dropping too much farther.

Issued at 911 PM CDT Wed Oct 26 2016

Updated the forecast earlier to add low POPs for an area of
showers moving through south central into southeastern ND, and
will maintain isolated-scattered mention for another couple of
hours. Have had light rain reports at both KDIK and KBIS.
Otherwise, the forecast remains in good shape for tonight.

Issued at 653 PM CDT Wed Oct 26 2016

For the early evening update, expanded fog wording a bit in aerial
coverage and developed sooner based on observations and the last
few hours of the high res model guidance, which indicates fog
developing after sunset for all but the southwest initially.
Already seeing zero T/Td spreads east of Highway 83 along with a
few observing sites already indicated visibility restrictions.
Otherwise the forecast remains in good shape for tonight.


.SHORT TERM...(This evening through Thursday)
Issued at 302 PM CDT Wed Oct 26 2016

At 3 pm CDT, a cold front extended from surface low pressure in
eastern Saskatchewan, through northwest North Dakota. A warm
front extended across central North Dakota. Low clouds and fog
that formed along and east of the warm front earlier Wednesday
have been slowly eroding east at 5 to 10 mph through the day.

This pattern will continue this evening with the low clouds
retreating east across east central North Dakota with the warm
front. Meanwhile the cold front across the northwest will move
through the region after midnight. The HRRR model runs show
shallow cool northwest flow behind the cold front that will
likely support stratus and some possible fog back into the north.
Finally some fog is also possible south central where diurnal
cooling in the moist boundary layer will set up a fog scenario.

On Thursday with a complete airmass exchange in the wake of the
cold front expect partly to mostly sunny skies that will allow
good mixing. As a result mild temperatures are forecast well into
the low to mid 70s southwest to the 60s central.

.LONG TERM...(Thursday night through Wednesday)
Issued at 302 PM CDT Wed Oct 26 2016

A generally progressive flow will continue through the extended
with several shortwave troughs flattening the broad h500 ridge
across the central and northern plains. This will bring several
chances for rain with a cooling trend from this weekend into next
week. The best chances for precipitation will be Saturday, and
again sunday night and monday. The flow aloft remains progressive
and the latest ECMWf, which earlier exhibited a closed low over
the northern plains Monday, now looks closer to the more open wave
and progressive GFS early next week. This may reduce the chances
for widespread rainfall on Monday.

The remainder of the forecast, Tuesday and Wednesday, looks dry
with seasonable temperatures.


.AVIATION...(For the 06Z TAFS through 06Z Thursday night)
Issued at 1237 AM CDT Thu Oct 27 2016

The forecast challenge for the 06Z TAF period is fog. KDIK and KISN
are expected to have prevailing VFR conditions, while fog is
forecast to impact KJMS...KMOT and perhaps KBIS. Dense fog was
already reported in the Devils Lake Basin including Rugby/Devils
Lake and eastward. Short term high res HRRR model indicates fog
expanding this morning to encompass along and east of the
Coteau...thus KMOT and KJMS are included. However...inhibiting the
fog is a large area of mid level clouds over southwestern ND moving
east. Thus confidence is low regarding the areal coverage and timing
of any light or dense fog at KMOT/KBIS/KJMS. Have a hint of light
fog at KMOT/KBIS but put MVFR/IFR vsbys at KJMS. Expect KJMS to
become vfr around 18z.




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