Area Forecast Discussion
Issued by NWS Bismarck, ND

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FXUS63 KBIS 202107

Area Forecast Discussion
National Weather Service Bismarck ND
407 PM CDT Tue Mar 20 2018

.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 18Z TAFS through 18Z Wednesday afternoon)
Issued at 1224 PM CDT Tue Mar 20 2018

MFVR/IFR CIGS and VSBY through the TAF period. Low stratus will
hang on for most of the TAF period, especially for the eastern
terminals. Patchy fog will develop later this evening and remain
through most of the morning hours. Conditions improve from west to
east tomorrow.




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