Area Forecast Discussion
Issued by NWS Bismarck, ND

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168
FXUS63 KBIS 211835
AFDBIS

Area Forecast Discussion
National Weather Service Bismarck ND
1235 PM CST Tue Feb 21 2017

.UPDATE...
Issued at 1229 PM CST Tue Feb 21 2017

Latest surface analysis indicates a weak pressure pattern over
western and central ND early this afternoon. Temperatures have
warmed nicely across the south and are again slower to warm across
the north. Have raised temperatures a little across the board, but
more over snow free areas over portions of the far southwest and
south central. Increasing reflectivities moving into the west. A
lot probably not hitting the ground but we have measured a
hundredth at both Jordan and Glendive in eastern MT. Only some
small tweaks to PoPs as they look reasonable.

UPDATE Issued at 947 AM CST Tue Feb 21 2017

We had a brief period of lower visibilities at Rolla, otherwise no
significant issues with fog. Will let the mention of fog expire at
16 UTC as advertised. Elsewhere, strong upper level jet works its
way into the region today. Light reflectivities already showing up
over eastern MT but nothing likely reaching the ground as of yet.
Made some minor adjustments to pops based on latest time lagged
HRRR output blended with our previous forecast. Overall no
significant changes. Updated products will be sent shortly.

UPDATE Issued at 650 AM CST Tue Feb 21 2017

We opted to include patchy fog in the forecast over north central
ND through 16 UTC based on small temperature-dewpoint spreads in
recent ASOS/AWOS observations, light surface winds, and forecast
soundings that suggest weak low-level turbulence this morning in
that part of the state. However, recent HRRR simulations have
been overzealous with fog development when compared to reality.
Otherwise, the remainder of the forecast is on track and only
minor changes were made. We did end up adding a slight chance of
rain slightly further south from Dickinson to Bismarck this
afternoon, though. That`s in line with the 08-11 UTC RAP and HRRR
iterations and the 06 UTC NAM and GFS forecasts, which have all
shown a slight southward shift in their precipitation simulations
as the exit region of a 115 kt 300 mb jet streak approaches the
area this afternoon and evening.

&&

.SHORT TERM...(Today and tonight)

Issued at 413 AM CST Tue Feb 21 2017

Forecast highlights in the short term period will be continued
chances for precipitation today and tonight, plus one last very
mild day today.

Currently, embedded S/WV continues to move quickly east along the
International Border with its associated surface trough moving
into central North Dakota. In the wake of the sfc trough, BKN-OVC
mid level cloud deck is trending scattered to clear, though an
increase in sky cover is noted over southeastern MT as the next
wave approaches. Light precipitation ahead of the sfc trough
remains over the Turtle Mountain region and should soon move off
to my north and east over the next hour or so. Air temperatures
near freezing though road surface temperatures are sub-freezing so
will maintain a mention of sleet/freezing rain.

Partly to mostly sunny this morning followed by increasing clouds
in the afternoon as another embedded S/WV trough moves across
Montana towards the Northern Plains. Surface low pressure over
central MT early today moves east ahead of the wave into North
Dakota this evening. Area of isentropic ascent ahead of the low
develops from southwest to northeast across western and central ND
today resulting in a band of light rain. Precipitation becomes
orientated in a west to east band across northern North Dakota
tonight along a strong cold front. As colder air mixes south will
see precipitation transition to snow with a window of freezing
rain as well where temps aloft are warmer south of the front.

Warm front moving east across western and central ND early this
morning will see one last mild day before the initial shot of
colder air arrives tomorrow. Highs today will be colder north
around 40 and warmer south where low 60s are forecast southwest.

Numerical models are indicating an increasing pressure gradient
over southwestern ND later today into tonight as the
aforementioned surface low develops eastward into central ND.
Increased winds for this reason.

.LONG TERM...(Wednesday through Monday)

Issued at 413 AM CST Tue Feb 21 2017

An active weather pattern will be in place through the long term
period, though not seeing any major storm systems for western and
central ND. Temperatures will trend colder beginning Wednesday.

Broad low pressure across Canada begins the long term with a
digging trough just off the west coast and a quasi-zonal flow
across the Northern Plains. West to east orientated baroclinic
zone/cold frontal boundary continues to slowly sag southward Wed-
Wed night maintaining a chance for rain or snow across most of the
region. We are still only forecasting light snow accumulations
generally less than one inch. Parts of western North Dakota may
see upwards of two inches. Noticeably colder on Wednesday as
colder air filters southward behind the cold FROPA. Highs are
forecast from the lower 30s north to low 40s south, coupled with a
steady north wind.

Colder air continues southward through the remainder of the week
and upcoming weekend as the upper level jet sags southward into
the southern CONUS. Forecast high temperatures will only reach the
20s by Friday and remaining so through next weekend. Each embedded
wave that moves through the region will bring reinforced shots of
colder air with precipitation type all snow. Models still do not
indicate any major storm systems impacting our region through
early next week.

&&

.AVIATION...(For the 18Z TAFS through 18Z Wednesday afternoon)
Issued at 1229 PM CST Tue Feb 21 2017

Generally VFR conditions are forecast this afternoon, with gradually
lowering ceilings from north to south beginning this evening. Rain
showers are possible west and north at KDIK and KISN...and later
this afternoon at KMOT. Expect deteriorating conditions tonight from
north to south as a large area of MVFR and IFR ceilings spreads
southward across the area after 03 UTC, with a mix of rain and snow
at first, then becoming all snow later tonight.

&&

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

$$

UPDATE...TWH
SHORT TERM...NH
LONG TERM...NH
AVIATION...JV



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