Area Forecast Discussion
Issued by NWS Bismarck, ND

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FXUS63 KBIS 160613
AFDBIS

Area Forecast Discussion
National Weather Service Bismarck ND
1213 AM CST Sat Dec 16 2017

.UPDATE...
Issued at 1208 AM CST Sat Dec 16 2017

Areas of light rain continue over western and central ND.
Fortunately temperatures were mainly in the middle and upper 30s
where rain was falling so do not anticipate problems with freezing
rain. Previous forecast shift updated pops with a blend of
persistence with the time lagged HRRR. This seemed reasonable and
will continue with the trend.

UPDATE Issued at 950 PM CST Fri Dec 15 2017

Light rain was reported in areas of western North Dakota in the
last hour. The highest radar returns were found across the
northwest, down through the Missouri River region. With that in
mind these areas will be the most likely to see light rain or
mixed precipitation over the next few hours. An observation blend
and adjustment to the PoPs were the main changes with this
update, otherwise forecast looks to be on track.

UPDATE Issued at 640 PM CST Fri Dec 15 2017

Light snow continues in much of Rolette County on the western
edge of a NW/SE oriented baroclinic zone. This zone will shift
east over the next few hours, ending the greatest chances for snow
in that area. To the west 850mb cold air advection is creating
some stronger radar returns, although a stout low level dry layer
is preventing much of any precipitation from reaching the ground.
In areas where the dry low levels is overcome tonight, a light
rain/snow mix is possible with the relatively colder air mass
moving in.

With widespread surface dew points in the 20s, a minimum
temperature adjustment was made as MOS guidance indicated lows in
the mid to upper 20s tonight.

&&

.SHORT TERM...(This evening through Saturday)
Issued at 255 PM CST Fri Dec 15 2017

Light radar returns continue over portions of western and central
ND. Light rain was observed in north central ND along with light
snow in the Rolla area. Snowfall amounts around one inch are
forecast for the far northeast CWA.

A quasi-stationary frontal boundary across north central into
eastern North Dakota will begin an eastward shift around 06Z,
diminishing chances for light precipitation in northern and eastern
areas of the CWA. The eastward shift occurs as a weak secondary cold
front from Saskatchewan slides south through western and central ND.
Associated chances for snow are possible in the far southwest
Saturday morning. The 12Z GFS/ECMWF keep QPF just south of the
border in SD, while the SREF/Canadian touch the far southwest with
light QPF. Opted to include slight chances for light snow in the
forecast. BUFKIT soundings indicate a fairly saturated column,
particularly in the lower levels though overall chances for snow
look underwhelming. Along with a few flakes, freezing drizzle may be
possible in the far southwest. Though guidance hints at the
possibility of freezing drizzle, due to lack of nuclei, opted not to
include freezing drizzle in the forecast due to overall confidence
in precipitation being low.

Cooler Canadian air will filter into state with the surface front,
bringing cooler temperatures for Saturday. Highs will be in the 30s;
still mild for this time of year.


.LONG TERM...(Saturday night through Friday)
Issued at 255 PM CST Fri Dec 15 2017

Sunday kicks off the long term with nice weather. Mild and dry
conditions with light winds and partly cloudy skies are in the
forecast Sunday. As we get into the Sunday night/Monday Morning,
another clipper/cold front is projected to move eastward across ND.
Associated chances for precipitation (mostly snow) are forecast
mainly in northern areas, at this time, through Monday morning.
breezy conditions are also expected Monday. Another system (with
potential impacts) is slated for late Tuesday night through
Wednesday. Widespread accumulating snow will be possible though much
depends on where the sfc low sets up and tracks. Once this system
departs, colder air is forecast to enter into the region. Based on
long range outlooks (MJO and ensemble runs) the colder air may
linger beyond the long term.

&&

.AVIATION...(For the 06Z TAFS through 06Z Saturday night)
Issued at 1208 AM CST Sat Dec 16 2017

A frontal boundary extended from eastern Saskatchewan to
southeastern ND to southern MN. This boundary was between cooler air
over Ontario and warmer air over the western plains and Front Range.
A series of weak upper level impulses moving west to east across the
northern plains was associated with an area of light precipitation.
Stations in western and central ND were reporting surface
temperatures in the mid 30s to lower 40s, and most precipitation
reported was in the form of light rain. Latest iterations of high
res models indicate the area of precipitation should move
south/southeast and shrink in areal coverage over the next few
hours, dissipating in southern ND by around 10-11z. There may be
brief mixing with light snow or possible freezing rain (if surface
temps dip to the freezing mark before the precip finally tapers off).

A mix of VFR and MVFR ceilings are expected at the TAF sites through
sunrise, then ceilings becoming all VFR from west to east by 18z.


&&

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

$$

UPDATE...TWH
SHORT TERM...AC
LONG TERM...AC
AVIATION...TWH



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