Area Forecast Discussion
Issued by NWS Bismarck, ND

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FXUS63 KBIS 210552

Area Forecast Discussion
National Weather Service Bismarck ND
1252 AM CDT Wed Mar 21 2018

Issued at 1239 AM CDT Wed Mar 21 2018

The forecast for the overnight remains on track and blended to
observed trends through 05 UTC. Fog is expected to develop first
across western North Dakota where skies are clear, taking longer
to expand across central North Dakota through Wednesday morning
underneath the stratus. This is well depicted by the
RAP/HRRR/NBM/GFSLAMP visibility forecasts through their 04 UTC
iterations. A Dense Fog Advisory may be needed at some point.
Patchy freezing drizzle is possible, however, impacts are not
expected to be large at this time. This will be monitored.

UPDATE Issued at 945 PM CDT Tue Mar 20 2018

Made some minor adjustments to pops and ProbIce grids for the
late evening update.

An area of light precipitation lingers over the Turtle Mountains
and has expanded southward into south central ND from Bismarck to
Jamestown. Precipitation remains light snow at Rolla, but sensors
in Rugby and Harvey have been reporting unknown precipitation.
Made a few calls and it does not look like precipitation has
not resulted in any significant impacts as of yet, but a little
drizzle noted here at the Bismarck Airport confirms that there is
likely a bit of drizzle out there this evening. Previous forecast
had a good handle on this and we already had a mention of freezing
drizzle in the forecast. We did adjust some IceAloft grids to push
the mention of drizzle a little farther east, into Rugby and
Harvey. Although a call returned from Rugby indicated
precipitation had turned to snow.

Basically a mix of light snow or freezing drizzle from the Turtle
Mountains into the James River Valley where IceAloft remains, with
drizzle central where ice has been lost.

Temperatures look reasonable and no other changes were made to the
going forecast. Updated text products will be sent shortly.

UPDATE Issued at 622 PM CDT Tue Mar 20 2018

For the early evening update we added some light snow over the
Turtle Mountains area for a few hours this evening. This are of
light reflectivities produces some light snow in Minot late this
afternoon. Otherwise no significant changes to the going forecast.


.SHORT TERM...(This evening through Wednesday)
Issued at 248 PM CDT Tue Mar 20 2018

Light wintry mix and patchy fog headline the short term forecast
for tonight.

Water vapor imagery depicted several shortwaves embedded in
northwest flow south of a closed low over the southern Canadian
prairies. Initial shortwave passing through central ND was the
source of our light snow and cloud cover this afternoon. A second
shortwave currently moving into northern Montana will be the
source of light precipitation overnight. Forecast soundings
indicate saturation confined below the dendritic growth zone,
depicting a freezing drizzle potential as this passes. High-
resolution guidance indicates just scattered coverage with this
overnight precipitation so PoPs were kept low. A shallow moisture
layer, largely attributed to our fresh snowpack, and an inversion
signature from the forecast soundings was enough to continue
fog in the forecast tonight. Uncertainty in low level flow and
associated turbulent mixing was enough to limit coverage to

.LONG TERM...(Wednesday night through Tuesday)
Issued at 248 PM CDT Tue Mar 20 2018

Northwest flow sets in over the Northern Plains on Wednesday with
upper level ridging over the Rockies and broad low pressure over
the eastern CONUS. A transition to westerly mid-level winds and
warm air advection begins a gradual warming trend with high
temperatures reaching the upper 30s to low 40s. Through Thursday
the upper level ridge shifts over the Northern Plains with a
surface low setting up over eastern Montana/Wyoming and a
transition to south/southeasterly surface flow in North Dakota.
Temperatures reach the mid 40s and upper 30s once again across our

As we get into Thursday night and Friday the well advertised
Pacific trough axis begins to cross the west coast. Southerly 850
mb flow intensifies as heights fall rapidly to the west. Ensemble
guidance continues to show anomalous moisture transport ahead of
the leading wave as NAEFS guidance indicates precipitable water
values up to the 99th percentile reaching the Northern Plains. QPF
placement remains somewhat uncertain as the 12Z GFS/ECMWF retain
highest values to the north-central part of the state while recent
runs of the NAM, producing more of a closed low, keep highest
precipitation totals to the south-central. A blend of guidance
keeps a large swath of precipitation centered from the north-
central down southeast through the upper James River Valley with
most areas outside of the far southwest receiving some sort of
precipitation. Precipitation type continues to be the challenge
with the forecast as a northwest to southeast oriented thermal
gradient will create a transition zone from more rain/snow to the
southwest to heavy snow as you move northeast. Where this gradient
sets up will have a large impact on snow totals and will need to
be monitored for potential headline-worthy snowfall over parts of
the area.

Looking into the weekend and early next week, global models
struggle to find consistency in how the western trough develops
eastward. However agreement in some form of southwest and active
flow over our region continues the forecast theme of additional
chances for rain and snow through Monday.


.AVIATION...(For the 06Z TAFS through 06Z Wednesday night)
Issued at 1239 AM CDT Wed Mar 21 2018

Widespread stratus across northwest and central North Dakota will
likely continue for most of the 06 UTC TAF period. MVFR
visibility in light snow will continue across the Turtle Mountains
through the James River Valley tonight. MVFR/VFR ceilings central
and northwest will lower to MVFR/IFR late tonight into Wednesday
morning, with slow improve Wednesday afternoon. IFR/LIFR
conditions in freezing fog are expected to develop tonight across
western North Dakota, potentially impacting KISN/KDIK. Freezing
fog is forecast to develop Wednesday morning across cental North
Dakota. Patchy freezing drizzle is possible.




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