Area Forecast Discussion
Issued by NWS Bismarck, ND

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FXUS63 KBIS 270235
AFDBIS

Area Forecast Discussion
National Weather Service Bismarck ND
935 PM CDT Thu Apr 26 2018

.UPDATE...
Issued at 935 PM CDT Thu Apr 26 2018

The forecast is on track, so only minor adjustments were made with
this update. A surface low is located near Winnipeg at 02 UTC and
that has placed western and central ND in the warm sector of that
cyclone with a north-south-oriented warm frontal zone extending to
the south of the low across the James River valley region. An area
of mid-level clouds associated with the warm front will continue
to exit the area as the surface low continues moving eastward, and
a trailing dry cold front will move southward across the area from
06 to 12 UTC. Upstream observations behind the front suggest that
initial post-frontal cooling is not very robust, so we made little
in the way of change to forecast lows overnight.

UPDATE Issued at 715 PM CDT Thu Apr 26 2018

Quick update to let the Red Flag Warning expire. Although winds
and humidity values are still in warning criteria at some RAWS,
ASOS, and AWOS stations as of 00 UTC, we still expect conditions
to improve quickly in the next 60 to 90 minutes as the boundary
layer begins to cool and decouple.

UPDATE Issued at 604 PM CDT Thu Apr 26 2018

Only minor changes were made with this update based on observed
trends and recent rapid-refresh model guidance, most notably of
which was increasing cloud cover in the Rolla and Rugby areas
through early this evening given satellite trends. Otherwise,
model-simulated soundings offer a strong consensus in calling for
the boundary layer to decouple sufficiently for surface winds to
decrease quickly by about 01 UTC, which in turn means we expect to
be able to let the Red Flag Warning expire as planned at 00 UTC.

&&

.SHORT TERM...(This evening through Friday)
Issued at 216 PM CDT Thu Apr 26 2018

Fire weather issues are the main short term concerns

Near full sunshine this afternoon with temperatures climbing into
the 60s. We don`t have an overly strong pressure gradient over the
state today, but with a well mixed atmosphere, expect gusty
northwest winds into the early evening. Dormant vegetation and low
humidities of 15 to 20 percent across most of the forecast area.
However, with a little stronger gradient across the north, we
expect critical fire weather conditions in much of the northwest
and north central. Near critical fire weather conditions will
remain through the afternoon southwest and south central, but
winds are a little lighter in these areas and afternoon minimum
humidities are expected to be a bit higher over the James River
Valley.

Winds will diminish early this evening with mostly clear skies and
cool temperatures expected again. A dry cold backdoor cold front
will make its way through the forecast area tonight. Lows will
range from the mid 30s to lower 40s, not quite as cool as last
night.

Another sunny day on Friday, but slightly cooler behind the cold
front, especially northeast. With cooler temperatures and lighter
northerly winds, critical fire weather conditions are not
expected. We could see near critical fire weather conditions in
the southwest, where forecast afternoon humidities are expected to
be lowest (near 20 percent). However, with north winds of 10 to
15 mph, fire weather conditions are probably not going to reach
critical values. But we will continue to monitor. We did use a
blend of drier short range HRRR dewpoint guidance Friday, with
our given guidance which lowered afternoon humidities quite a bit
in the southwest.

.LONG TERM...(Friday night through Thursday)
Issued at 216 PM CDT Thu Apr 26 2018

Dry weather with above average temperatures will continue through
the weekend with chances for precipitation returning for Monday
and Tuesday, in the form of showers and thunderstorms.

The 12z iteration of the NAM and GFS continue to show a high
amplitude ridge building into North Dakota Friday night, with the
ridge axis located over central North Dakota by Sunday. Expect a
warming trend as this ridge moves eastward, with temperatures in
the lower 70s on Saturday across western North Dakota and mid 60s
across central North Dakota. Temperatures will peak on Sunday when
the entire state looks to be in the 70s, with many spots
approaching 80 degrees in western and central North Dakota. The
latest suite of model guidance appears to have a good handle on
the forecast temperatures this weekend as model snow depth is now
representative of current observations, which show all leftover
snowpack has melted across North Dakota. In addition, the bias
corrected model guidance appears to have finally caught onto the
recent pattern change to warmer weather.

A large upper level low will begin moving into western and central
North Dakota Sunday night, bringing with it sufficient moisture,
lift and instability for showers and thunderstorms Sunday night
through Tuesday. Chances for severe thunderstorms Monday afternoon
and evening look like a possibility in south central North Dakota
near the border of South Dakota. Both the GFS and the ECMWF show
forecast CAPE values in excess of 1000 J/kg in this region,
collocated with low CIN and 0-6km bulk shear values between 30
and 40 kts along an axis of high equivalent potential
temperatures. Uncertainty still remains high regarding the threat
for severe hail and wind given the marginal conditions, however
this threat will need to be monitored closely leading up to the
event.

&&

.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 935 PM CDT Thu Apr 26 2018

VFR conditions are expected across western and central ND tonight
and Friday, though there is a chance that brief low VFR to MVFR
ceilings could occur Friday morning in the Turtle Mountain region
behind a southward-moving cold front. Impacts from that dry front
will be minimal elsewhere and relegated to a switch to northerly
surface winds. Gusts to around 25 kt are expected Friday in east
central ND, including at the KJMS terminal.

&&

.FIRE WEATHER...
Issued at 935 PM CDT Thu Apr 26 2018

A dry cold front will pass through late tonight and will shift
winds to a northerly direction for Friday. However, post-frontal
gusty winds across east central ND are not currently expected to
overlap with lower humidities of 15 to 20 percent in western ND,
so no headlines are in order at this time. This will be monitored
closely though.

&&

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

$$

UPDATE...CJS
SHORT TERM...TWH
LONG TERM...TK
AVIATION...CJS
FIRE WEATHER...CJS


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