Area Forecast Discussion
Issued by NWS Bismarck, ND

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FXUS63 KBIS 180931
AFDBIS

Area Forecast Discussion
National Weather Service Bismarck ND
331 AM CST Wed Jan 18 2017

.SHORT TERM...(Today and tonight)
Issued at 330 AM CST Wed Jan 18 2017

Temperatures continue to be the main problem in the short term
period.

Currently, an upper level ridge was over the Northern Plains with a
mild and dry surface Pacific high over the central US Rockies and
Plains. A strong westerly h925, h850 and h700 wind flow was
accompanying the ongoing warm advection across the Northern Plains.
Surface winds across western and central ND were ranging from
southwest/west 5 to 20 mph. Only a few hundred feet above the
surface, stronger west winds of 35-45 mph were present. At times,
some of the higher elevation areas...mainly in southwestern ND or
along the Coteau ridge...were reporting west winds gusting to 30 mph
or more. This was creating some areas of drifting snow, and, in
turn, slippery conditions on roadways.

Today should be the one of the warmest days of the week, with h850
temperatures of +10-+12C. The deep snowpack will limit how high the
surface temperatures will reach. A recent study indicates that it is
difficult to get surface temperatures higher than 40-45F with such a
deep snowpack. Thus felt confident undercutting the model guidance
across western and central ND. It is interesting that current
temperatures in some elevated areas were in the 30s - where winds
were stronger and mixing the surface with the warmer air aloft. We
capped the max temps south and west of the Missouri River at 40-
41F...with forecast highs along and north/east of the river in the
mid to upper 30s.

Tonight the upper level ridge broadens and expands eastward as a
southern Plains low deepens and moves/expands northeastward towards
NE/IA. Meanwhile a west coast longwave trough continues to deepen.
This will result in weaker flow aloft, and the lower and mid level
flow becomes southerly. Gulf moisture begins moving northward from
the southern Plains through the central Plains...reaching into SD.
However, we may get possible fog/stratus because of the anticipated
melting of the top layers of the snowpack. Confidence is not yet
high enough for this development to put in the current forecast for
tonight, but this will be monitored as we see how warm it gets
today. The 5 to 10 mph southerly winds expected tonight should allow
temperatures to be drop to the 15-20F degree range.

.LONG TERM...(Thursday through Tuesday)
Issued at 330 AM CST Wed Jan 18 2017

The long term period will bring chances of precipitation, but no
cold blasts of arctic air.

The flow aloft over ND becomes southwesterly on Thursday as the
aforementioned west coast longwave trough expands across the
Rockies. The aforementioned central Plains low continues to
move/develop northward into the SD/IA/MN area Thursday, lifting into
Manitoba/Ontario on Friday. Meanwhile another shortwave in the
expanding longwave low/trough that encompasses the western and
central US lifts northward into the ND/SD/MN area Saturday, and into
Manitoba/Ontario on Sunday. The persistent upper level low/trough
remains over central North America through at least mid-week of next
week.

Thursday and Friday:

Expect increasing low level moisture from the south to continue
Thursday, with more widespread fog/stratus spreading west and north
across the forecast area late Thursday night and Friday.
This is when we also start to see mid level forcing lift northward
into the forecast area. The first impulses Thursday night are pretty
weak and we are quite dry above our nearly saturated lowest levels.
Any precipitation is expected to be very light with a slight chance
of precipitation for the southern James Valley but will need to
monitor precipitation type. Looking at temperatures aloft we would
expect drizzle/freezing drizzle or light rain/freezing rain.
However, an examination of wetbulb temperatures aloft would be much
more likely to yield rain or snow, depending upon the surface
temperature.  At this time will keep a mention of just rain/snow as
wetbulb temperatures aloft typically work better than temperatures
with such a dry area aloft. Chances of rain or snow Friday should be
mainly over central and eastern ND with the aforementioned
southern/central Plains low moving northward.

Saturday and Sunday:

One of the aforementioned shortwaves/lows moves northward through
the State during the weekend.  Our overall temperature profile cools
and we turn to just a chance of light snow - except a mix still
possible in the James Valley Saturday.

Monday and Tuesday:

We continue to remain on the cool side of the westerlies into early
next week. However any Arctic air remains well north of the area. A
couple of stronger upper level systems track across the continental
U.S. but at this time they track more across the central and
southern plains. Only slight chances of light snow are expected
early next week.

&&

.AVIATION...(For the 06Z TAFS through 06Z Wednesday night)
Issued at 1223 AM CST Wed Jan 18 2017

VFR at all TAF sites through the TAF period. Surface winds mainly
southwesterly at 5 to 15 knots...however there is a strong westerly
wind field beginning only a few hundred feet off the surface -
around 35-40knots. Therefore added low level wind shear at TAF sites
until later this morning or by around 18z when forecast winds aloft
at that time suggest winds aloft not as strong. At times the strong
winds aloft may break through to the surface, creating strong gusty
surface winds. Some areas of southwestern ND experiencing drifting
snow with the stronger gusts and may affect runways.


&&

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

$$

SHORT TERM...JV
LONG TERM...JV
AVIATION...JV



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