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Area forecast discussion 
National Weather Service Bismarck ND
109 am CST sun Nov 29 2015


Issued at 109 am CST sun Nov 29 2015

Temperatures continues to drop where the sky is clear...increasing
across the south where clouds are increasing into. Adjusted
temperatures to account for this.

Thus far still waiting for fog to develop north and west. Scaled
back on the timing but did keep this in the forecast for now.
Latest hrrr not as dire with the fog either.

Low probability of precipitation are good to go across the south as doubtful much is
reaching the ground. Dry air associated with a ridge of high
pressure is winning the battle.

Update issued at 920 PM CST Sat Nov 28 2015

Clear skies and light winds have created good radiational cooling
across much of the area this temperatures have been
dropping more quickly and further than earlier anticipated. The
forecast has been updated to reflect those we now have
lows of 0 to 10 above f in many parts the area. Observations thus
far this evening have shown dewpoints dropping just as quickly as
the temperatures...thus delaying fog development...but hrrr model
output continues to support its formation after 06 UTC. Based on
the trends in hrrr simulations...we did expand the mention of fog
a bit further south into the Harvey and Carrington areas.

Otherwise...light snow is indeed weakening as it approaches the
ND and South Dakota border...but we did adjust probability of precipitation a bit over far southwest
and south central ND tonight based on radar trends and time-lagged
ensemble hrrr guidance.

Update issued at 548 PM CST Sat Nov 28 2015

No significant changes were made with this update. Light snow over
western South Dakota would appear a bit more robust than most model guidance
would have US believe...but it is indeed weakening with northward
movement like model simulations suggest so we will hang onto only
low probability of precipitation near the South Dakota border overnight. The other issue tonight is
going to be potential fog development...which the most recent hrrr
run from 22 UTC suggests could be more widespread /further south/
with lower visibility than its prior few iterations. We will be
monitoring trends the next few hours to see if any expansion of
our fog mention is necessary in the forecast.


Short term...(this evening through sunday)
issued at 222 PM CST Sat Nov 28 2015

Current surface analysis places high over the Midwest bringing
very light southwesterly winds to the region. Upper level analysis
places persistent upper low near the Great Basin with leading
wave bringing snow to western South Dakota. Quiet weather
continues over our area.

For tonight...aforementioned wave will lift into the area
overnight with cloud cover increasing over southern locations.
With that said...models continue to agree on a mainly dry solution
overnight...and have actually dried things out more in the latest
run. Therefore...will only keep low chances along our far southern
tier. Towards the north...forecast soundings along with high-res
models suggest fog forming over the far north overnight and
spreading southerly in areas that remain mainly clear. Have added
areas of fog to the forecast and will have to keep an eye on this
to see if coverage needs to be adjusted.

On Sunday...upper low stretches towards northeast Wyoming keeping
many parts of the area...especially the south...cloudy through the
day. This will keep temperatures on the cooler side while winds
remain light and southerly.

Long term...(sunday night through saturday)
issued at 222 PM CST Sat Nov 28 2015

The main focus for the long term is snow chances Monday into

A closed low over the mountain west will slowly propagate eastward
over the next several days. The exact track of this low will
determine how much or little snow portions of North Dakota
receive. Models continue to vary with respect to the track of the
low by a hundred miles or so. The European model (ecmwf) and Canadian bring the low
near Sioux Falls and through Minneapolis. This track favors snow
accumulation for southern North Dakota. Meanwhile the GFS and sref
push the low further east into Iowa and Wisconsin. This track
would leave most of western and central North Dakota with very
little precipitation. Utilized a blend of ensembles and
deterministic guidance for this forecast. This yielded snowfall
amounts around half an inch around I-94 and closer to 4 inches
across far southern James Valley. While the greatest amounts are
expected to remain south of I-94...these amounts could change
drastically over the next day or so as this system evolves.


Aviation...(for the 06z tafs through 06z Sunday night)

Issued at 109 am CST sun Nov 29 2015

Low VFR to MVFR ceilings developing over southwest and south central
North Dakota late tonight through Sunday morning including kbis-
kjms. Areas of fog and low ceilings remain possible north with IFR or
LIFR conditions mainly impacting kisn-kmot tonight and Sunday


Bis watches/warnings/advisories...



Update...New Hampshire
short term...jjs
long term...aj
aviation...New Hampshire

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