Area Forecast Discussion
Issued by NWS Bismarck, ND

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FXUS63 KBIS 212359

Area Forecast Discussion
National Weather Service Bismarck ND
659 PM CDT Wed Mar 21 2018

Issued at 646 PM CDT Wed Mar 21 2018

For the early evening update we lowered sky cover across the CWA
this evening. Fog and stratus that lingered into the afternoon
finally dissipated except for a few areas remaining over the north
central and into the Turtle Mountains. Otherwise skies were clear.
This will likely set the stage for another round of fog/stratus
developing later this evening and overnight across northwest and
central ND.


.SHORT TERM...(This evening through Thursday)
Issued at 146 PM CDT Wed Mar 21 2018

Short term highlights include patchy fog overnight and the
oncoming winter storm beginning Thursday night.

Synoptically a ridge axis was centered over the northern Rockies
with northwesterly flow over the northern Plains. A surface high
remains in place under anticyclonic flow aloft. Light winds
associated with the high pressure and continuing snowpack
sublimation were enough to continue patchy fog in the forecast for

Thursday mid-level winds turn southerly in response to an upstream
trough approaching from the west. Warm air advection, focused to
the southwest, will bring surface highs into the low to mid 40s
across our west/southwest.

.LONG TERM...(Thursday night through Wednesday)
Issued at 146 PM CDT Wed Mar 21 2018

Overnight Thursday a potent shortwave ejects out of the deep
Pacific trough. Strong mid-level southerly winds reaching 50 kts
will amplify moisture transport ahead of the wave as NAEFS
guidance has been consistent on anomalous precipitable water
values reaching the 99th percentile with this system. Strong lift
associated with deep frontogenesis under broad synoptic ascent
above will create a swath of moderate to at times heavy precipitation
across northwest to south-central and southeast ND.

Precipitation type will be heavily dependent on the surface
temperature and ice presence within the atmospheric profile. A
thermal gradient oriented along the band of precipitation will
cause rain to be the dominant precipitation in the southwest with
a transition to snow towards the Missouri River and eastward.
Uncertainty in accumulation totals along and west of the Missouri
River through Lake Sakakawea exist with surface temperatures
around or above freezing early Friday morning.

The greatest snowfall accumulations continue to be favored across
north central North Dakota through the James River Valley where
thermal profiles will be coolest under the coupling of intense
synoptic/mesoscale forcing. As this band of snow passes to our
east late Friday the threat for freezing drizzle on the back end
arises with ice loss aloft.

The 12Z global model suite continues to indicate additional
opportunities for accumulating snow Saturday night into early next
week under an active southwesterly flow pattern, with uncertainty
in intensity and exact location of precipitation.


.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 646 PM CDT Wed Mar 21 2018

VFR conditions to begin the 00Z TAF period. It appears KDIK will
have the best chance of remaining VFR through the night, although
some of the mesoscale models indicate KDIK could be near the low
stratus/fog late tonight into Thursday morning. Otherwise KISN,
KBIS and especially KMOT and KJMS are expected to develop
fog/stratus late this evening or overnight. Once fog does develop
IFR to LIFR ceilings and visibilities would be expected to linger
through mid to late morning on Thursday, before slowly improving
to MVFR Thursday afternoon. A light east to southeast flow is
expected tonight and Thursday morning, with an increasing
southeast flow Thursday afternoon.


Winter Storm Watch from Friday morning through Saturday morning
for NDZ002>005-010>013-021>023-025-035>037-047-048-050-051.



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