Area Forecast Discussion
Issued by NWS Grand Forks, ND

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063
FXUS63 KFGF 192118
AFDFGF

Area Forecast Discussion
National Weather Service Grand Forks ND
318 PM CST Sun Feb 19 2017

.SHORT TERM...(This evening through Monday)
Issued at 318 PM CST Sun Feb 19 2017

Precipitation timing and amounts are the main challenge for the
period.

Water vapor loop shows the upper ridge axis moving east and a
significant trough lifting from the Four Corners region
northeastward. The trough will lift into the Western Plains
tonight, which will help push the surface trough currently in the
lee of the Northern Rockies out towards the Red River Valley.
There have been a few showers out ahead of the main system today
along the mid level warm air advection, but so far very little has
been reaching the ground and precip has been mostly sprinkles so
far. However, with breezy south-southeast winds on the leading
side of the surface low continuing for much of the night, there
will be more moisture advecting into the area. Models have dew
points in the southern counties rising into the 50s and with those
kind of readings already in southeastern SD it seems feasible.
With increasing moisture, some stratus and possible fog will also
be on the increase. Winds are not very favorable for fog but with
moisture pooling along the surface trough axis early in the
morning cannot completely rule it out. Have left fog out of the
grids for now but will include some light mention in the aviation
forecasts.

The increased moisture will also help more rain reach the ground
late tonight and into tomorrow as the trough pushes eastward into
the region and the surface trough moves from the Red River Valley
off into MN. The short range models seem to be in fairly good
agreement with first showers arriving with the surface trough axis
during the early morning hours. With Showalters in the negative
numbers across the southeastern CWA for much of the morning, some
thunder is not out of the question in that area. By afternoon,
the upper trough will have arrived in the Red River Valley and
most of the showers will have transitioned off to the east, with
the models showing similar intensification of QPF just to the east
of the CWA. With the precip expected to be more shower in nature
with even a few thunderstorms possible, exact precip amounts are
difficult to pinpoint. Will keep highest values of a quarter to
third of an inch over our northeastern counties, with more spotty
further south and west. Some amounts up to a half an inch are not
completely out of the question particularly in the eastern
counties, but think that showers and the system as a whole will
be moving quickly which will keep too much water from
accumulating.

As for temperatures, the warm moist air coming up from the south
tonight will keep lows much higher than most February highs.
Readings will range from the 30s in the north to near 50 in the
south. Clouds and precip will keep the diurnal range down, so
while highs tomorrow will still be a large amount above average,
they should stay in the upper 30s north to mid 50s south.

.LONG TERM...(Monday night through Sunday)
Issued at 318 PM CST Sun Feb 19 2017

Any lingering precipitation across far eastern portions of the area
will exit Monday night as the main surface low propagates off
towards Hudson Bay. Upper zonal flow will then set up across the
region for Tuesday allowing for a brief break in precipitation as
the unseasonably warm air stays in place with one last day of near
record to record high temperatures.

Models continue to depict a compact surface low and associated wave
quickly moving through the upper flow Tuesday night and into
Wednesday but still vary considerably on the details. The 12z GFS
tracks the surface low from west to east right through the heart of
the forecast area with the greatest forcing and associated
precipitation chances along the international border. The ECMWF is
continuing to trend further south while the Canadian is somewhere in
between. Therefore, a blended solution with the greatest PoPs along
the international border and gradually trending downward towards the
I-94 corridor still seems like a reasonable approach. QPF amounts
are still quite variable in the deterministic models, along with a
fairly large range in values depicted by the GEFS Ensemble.
Regardless, impacts with this system may be a bit greater than
Monday`s all-liquid system due to colder air pushing back into the
region with some mixed precipitation and even a few tenths of snow
accumulation possible, mainly across the north.

The second half of the week will remind us that it`s still only
February as 850 mb temperatures plunge well below zero and surface
temperatures return to more seasonal values. Models continue to be
all over the place regarding a strong storm system pulling out of
the Rockies towards the end of the week. The 12z GFS pulled the main
impacts well south of the area (almost even out of South
Dakota/central Minnesota) while the ECMWF continues to impact
southern portions of our area...and the Canadian in between once
again. At this time, temperatures look to be cold enough to support
an all snow event, if we see any impacts at all.

Next weekend looks to bring some more uncertainty regarding any
precipitation chances. It won`t be nearly as warm as this past
weekend, however, with highs struggling to reach the freezing mark
and lows dipping back down into the single digits.

&&

.AVIATION...(For the 18Z TAFS through 18Z Monday afternoon)
Issued at 1243 PM CST Sun Feb 19 2017

All TAF sites are VFR with mid and high clouds over everyone but
KFAR which is seeing some sunshine. South to southeasterly winds
will continue at 10 to 20 kts into this evening and will bring
more moisture northward. The surface trough will move eastward
into the Red River Valley tonight, and think there will be some
pooling of moisture along the trough axis late tonight and
tomorrow morning. Have ceilings and visibilities coming down,
although kept true fog out for the time being. Ceilings should
drop into the MVFR and then IFR range as moisture comes in later
tonight and continues through tomorrow morning. Visibilities will
be down to 2-5SM with some areas down to 1SM or lower as winds
decrease along the trough axis. Rain showers will be moving across
the area and will improve visibility at times, but there is
enough uncertainty in placement to just include VCSH at the
current time. Winds will begin shifting to the west at the end and
after the TAF period.


&&

.HYDROLOGY...
Issued at 318 PM CST Sun Feb 19 2017

Streams and tributaries across the southern Red River Basin are
beginning to respond to local melting and runoff. Slow rises to
tributaries and the mainstem Red near Fargo, and points upstream,
are likely through the coming week. Forecast rainfall for Monday may
also contribute to river levels. Several locations are expected to
reach or exceed action stage while a few might hit flood stage or
just above. Please see RVSFGF and ESFFGF for details on these
locations.

&&

.FGF WATCHES/WARNINGS/ADVISORIES...
ND...None.
MN...None.
&&

$$

SHORT TERM...JR
LONG TERM...Lee
AVIATION...JR
HYDROLOGY...Lee



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