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-- Discussion containing changed information from previous version are highlighted. --
000
FXUS63 KBIS 050334
AFDBIS

Area Forecast Discussion
National Weather Service Bismarck ND
934 PM CST Thu Mar 4 2021

.UPDATE...
Issued at 934 PM CST Thu Mar 4 2021

There are some hints of fog developing in northwest North Dakota,
and to the south and west of the Devils Lake Basin. Based on
previous nights` model vs. observation performance of low-level
moisture fields, we are very reluctant to increase messaging of
fog potential until we see something more prominent. The greatest
potential for impactful visibility reductions is across the 4
northwestern-most counties of North Dakota, where snow cover
still exists and dense fog is climatologically more common (at
Stanley and Tioga).

Model consensus for sky cover remains very poor. It is
under-performing on high clouds across southwest North Dakota and
over-performing on low clouds across northern North Dakota,
although there are signs of developing fog in some similar
locations. The first several hours were adjusted to more closely
follow observed trends.

UPDATE Issued at 622 PM CST Thu Mar 4 2021

Some minor adjustments were made to the coverage of patchy fog
tonight through tomorrow morning. The HRRR and RAP visibility
fields were relied upon, as they have been trending well with
observed surface dewpoints. However, it`s worth noting that all
guidance, especially non-HRRR/RAP solutions, has been far too
aggressive with both the coverage and duration of low stratus and
fog the past few nights. For this reason, we also trended sky
cover down with this update. Even though our forecast grids will
contain 30-70% sky cover for much of the area, think that most
locations will either be completely overcast or completely clear
at any given time.

&&

.SHORT TERM...(This evening through Friday)
Issued at 113 PM CST Thu Mar 4 2021

Low stratus and fog tonight and continued mild temperatures
tomorrow highlight the short term forecast.

Tonight, easterly surface flow will bring in a shallow layer of
moisture (enhanced by continued snow pack melting) across central
and eastern ND. Forecast sounds depict low stratus between
500-1000 feet AGL and some fog as a result. There is some
uncertainty as to the extent and duration of the stratus/fog. Some
short-term models want to take it as far west as Dickinson and
leave Jamestown clear, while the majority maintain a further east
solution.

How long clouds/fog persist will play a significant
role in temperatures tomorrow. We still maintained a warmer
forecast than what the NBM is providing due to its continued cold
bias, but we elected to go below the higher end thresholds we`ve
been trending with as of late. We still expect the southwest will
see temperatures in the 60s tomorrow, but further east where cloud
cover is more likely and more likely to linger longer,
temperatures could struggle to get out of the 40s to lower 50s.

.LONG TERM...(Friday night through Thursday)
Issued at 113 PM CST Thu Mar 4 2021

Mild and dry conditions continue through much of the long term
before a potentially more active pattern sets up next week.

Saturday will likely be the warmest day through the next week as
an upper-level ridge axis moves directly overhead. Therefore,
maintained higher than straight NBM temperatures which brings
widespread upper 60s into portions of the west and widespread
upper 50s to low 60s everywhere else, except for the Turtle
Mountains. This is slightly cooler than the previous forecast as
the cold front appears to be slightly delayed. This means
compressional warming will be maximized a bit further west and a
southeasterly (which doesn`t mix down as well as southwesterly)
wind will be favored all day. Winds will be quite breezy Saturday
afternoon with southeasterly winds around 25 mph gusting to 35
mph. This may lead to near critical fire conditions across the
southwest Saturday afternoon where temperatures will be in the
upper 60s, relative humidity around the low 20s and winds around
30 mph. Sunday will not be as warm, but highs should remain well
above normal with widespread readings in the upper 40s to upper
50s.

The flow becomes more zonal on Monday as a broad western trough
approaches Tuesday into Wednesday. This could be the start of a
more active period. The 12z suite of deterministic global models
have trended towards the flow staying split over the Dakotas
before phasing across the Great Lakes, keeping the strongest
cyclogenesis well to our east. Still, warm air advection
associated with the northern wave stream would still bring us a
brief period widespread precipitation in this scenario, but the
impacts would be fairly tempered. The 12z ensemble guidance has
shifted their favored storm track a bit north and lowered their
expectations of more meaningful precipitation. Overall,
expectations remain low in this system producing impacts or much
needed rain, but a great deal of uncertainty remains so there is
still the possibility however small it might be.

&&

.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 622 PM CST Thu Mar 4 2021

Patchy fog with associated LIFR ceilings may develop across much
of western and central North Dakota tonight through Friday
morning. Confidence in impacts at any given terminal remains low,
so have opted to include VCFG and SCT003 mentions for this set of
TAFs. Otherwise, VFR conditions and light easterly winds are
expected through the forecast period.


&&

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

$$

UPDATE...Hollan
SHORT TERM...AJ
LONG TERM...AJ
AVIATION...Hollan