Area Forecast Discussion
Issued by NWS Bismarck, ND

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FXUS63 KBIS 201139
AFDBIS

Area Forecast Discussion
National Weather Service Bismarck ND
639 AM CDT Tue Sep 20 2016

.UPDATE...
Issued at 636 AM CDT Tue Sep 20 2016

Showers with a few thunderstorms continue to push off to the east.
For early morning update have trimmed precipitation chances off
over much of the west, and tapered chances down over central
locations. Broader area of showers with a thunderstorm or two
continue over the southern James River Valley, though these will
also be gradually diminishing as the morning moves on. Updates
have been sent.

&&

.SHORT TERM...(Today and tonight)
Issued at 300 AM CDT Tue Sep 20 2016

Main highlight today is the ongoing scattered showers and isolated
thunderstorms southwest through south central this morning. Latest
regional and local radar shows scattered showers and isolated
thunderstorms continuing to migrate across south central ND and
into the James River Valley. This is in association with frontogenetical
forcing in the 850mb-700mb layer per RAP/NAM. This forcing continues
to translate through the James River Valley by mid morning. The
HRRR continues to advertise stronger convection developing between
11z and 15z this morning for the far south central and southern
James River Valley, most likely due to better interaction of the
850mb southerly jet. Behind this precipitation, expect partly to
mostly sunny and dry conditions developing from west to east today
with highs in the upper 60s north to mid 70s south.

For this evening/tonight, clouds will quickly increase again this
evening west, and spread east overnight as two shortwaves - one
ejecting out from Montana and the other from Wyoming move across
western and central ND. Forcing for ascent increases overnight
per 850-700mb frontogenesis and 700-500mb Q-vector/negative
divergence field, as it slides from west to east. Followed the NAM
for instability parameters which results in another round of showers,
and a slight chance for thunderstorms central and south tonight.

.LONG TERM...(Wednesday through Monday)
Issued at 300 AM CDT Tue Sep 20 2016

Water vapor imagery shows nearly a zonal flow into and across ND
early this morning, with a gradual transition to southwest flow
seen upstream. This is in advance of an upper level low circulating
off the pacific northwest coast, which is forecast to become a
closed circulation around 00z Wednesday.

The closed slowly low will slowly sag along the northwest California
coast Wednesday and then into the Great Basin Thursday. In doing
so, the upper flow transitions from zonal to southwest across ND
with models continuing to indicate a couple of additional shortwaves
ejecting through the flow and into ND. This will result in a continued
chance of showers and slight chance for thunderstorms.

Thursday through Sunday, southwest flow transitions to southerly
as the closed low crosses into central ND Sunday. The best
moisture prospects/qpf still looks like the northwest per GEFS
Mean QPF for Friday into Saturday. The ECMWF is much wetter than
the GFS, and we have seen back and forth qpf changes in both
models the last few days. Hence, will not to confident on any
solution at this time. WPC extended forecast discussion also hints
at what both the EC and GFS are advertising, which is to separate
and stretch the upper trough with two distinct lows forming, one
ejecting out with the northern branch, and the other stuck in the
southern branch into New Mexico. So, the overall trend for showers
to fill in and overspread western and central ND Friday into
Friday night continues, with a potential dry slot punching up into
central ND Saturday, limiting precipitation amounts. A surface
cold front will sweep through Saturday night and Sunday with some
showers behind the front. Drier weather is forecast Sunday night
through Monday.

&&

.AVIATION...(For the 12Z TAFS through 12Z Wednesday morning)
Issued at 636 AM CDT Tue Sep 20 2016

Scattered showers with isolated thunderstorms will gradually
diminish this morning over south central into southeast North
Dakota. Precipitation chances gradually return tonight from west
to east...with a few thunderstorms possible south. Otherwise...VFR
conditions expected.

&&

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

$$

UPDATE...JJS
SHORT TERM...KS
LONG TERM...KS
AVIATION...JJS



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