Area Forecast Discussion
Issued by NWS Grand Forks, ND

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FXUS63 KFGF 231957

Area Forecast Discussion
National Weather Service Grand Forks ND
257 PM CDT Fri Sep 23 2016

.SHORT TERM...(This evening through Saturday)
Issued at 257 PM CDT Fri Sep 23 2016

Precipitation timing and how strong tomorrow`s convection will be
are the main challenges for the period.

Showers and thunderstorms stretch from northwestern ND into
central MN across our southwestern counties. This activity will
lift north and east throughout the rest of the afternoon into the
evening as isentropic lift along the mid level baroclinic zone
moves through. The main surface warm front is well to our south,
and the model have it moving slightly northward towards our
southern border later tonight. Both the high resolution models as
well as the synoptic runs have the most significant precip along
the mid level front and lifting north towards the Canadian border
throughout tonight. There is some weak elevated CAPE as seen on
the SPC meso page and the models have this continuing so will keep
the mention as showers with isolated thunderstorms. With the warm
front still mostly to our south there will be plenty of cloud
cover overnight and southeast winds will keep us mixed. Have some
mild low temperatures in the 50s to low 60s.

Tomorrow, the main upper low currently over the Rockies will
progress into western ND. The models are in decent agreement at
this point in the forecast and have the surface low moving up into
western to central ND during the day and starting to wrap up.
Southeasterly winds will continue for our area and the tongue of
warmer air will start to move into the southern Red River Valley.
There is still some question how much clearing there will be
during the day on Saturday, with most of the models having quite a
bit of moisture lingering in the area. At this point think there
will be at least some breaks and allow temperatures to get into
the 60s and 70s by afternoon. The NAM has a narrow band of surface
based CAPE moving into our western counties late in the day. Deep
layer bulk shear is better further west, but there could be some
30-40kts of 0-6km shear. Storms should start to redevelop by
afternoon in the western counties into the Red River Valley. Still
a lot of uncertainty, but there is enough CAPE and bulk shear
predicted by the models for a marginal risk tomorrow afternoon.

.LONG TERM...(Saturday night through Friday)
Issued at 257 PM CDT Fri Sep 23 2016

The primary challenge for the long term period will be timing and
placement of the dry slot associated with an area of low pressure
over western North Dakota.  GFS and EMCWF are in similar agreement
with 00Z Sunday spatial characteristics of the surface low,
positioned from Sakakawea area to Medora with the ECMWF slightly
southwest at 00Z.  However, GFS positions upper low further north. A
band of showers and embedded storms will develop sometime in the
late evening to overnight period.  With subtle model differences,
leaning toward SREF solution for timing and placement...which gives
likely POPs over eastern zones and a sharp transition to dry conds
westward into the dry slot.  Next challenge becomes track of upper
low and location of the wrap around moisture that should eventually
fill in western and northern zones later in the long term period.
Favored superblend solution for this portion of the system`s
evolution.  Throughout the last three shifts monitoring this system,
models have been fairly consistent with no to low CAPE values for
this time period...and have once again revert wx type grids back to
the most likely scenario, predominant rain showers with small
potential for embedded thunder.

After the upper low/trough swings through, northern tier transitions
to NW flow pattern aloft with an amplifying ridge over the Canadian
rockies that slides over the Dakotas by Tue night.  This will bring
dry weather the the middle portion of next week, with fall like
temperatures.  Chances for precip increase again near the end of
next week.


.AVIATION...(For the 18Z TAFS through 18Z Saturday afternoon)
Issued at 1242 PM CDT Fri Sep 23 2016

All sites are VFR, but showers and storms have entered the
southwestern forecast area and will be impacting KFAR shortly. The
band of showers and storms will continue to move northeastward
towards the Canadian border by this evening, then there will be a
bit of a break before more storms fire tomorrow afternoon. Think
that most ceilings will stay VFR to start with but there will be
some deterioration as more moisture moves in from the south
tonight. Think that most sites will be MVFR tonight with IFR
towards tomorrow morning. Some of the models are putting out some
fog but will keep visibilities above 6SM for now and will monitor
how things develop behind the band of showers and storms. Some
slight recovery will be possible by the end of the period.
Southeast winds have been gusty in some areas. The gusts should
settle down although sustained southeast winds will stay around
15kts. Winds will pick up a bit by the end of the period tomorrow.




LONG TERM...Speicher
AVIATION...JR is the U.S. government's official web portal to all federal, state and local government web resources and services.