Area Forecast Discussion
Issued by NWS Grand Forks, ND

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FXUS63 KFGF 110819
AFDFGF

Area Forecast Discussion
National Weather Service Grand Forks ND
319 AM CDT Sun Apr 11 2021

.SHORT TERM...(Today through Monday)
Issued at 319 AM CDT Sun Apr 11 2021

Precip chances and type will be the main headaches for the period.

Water vapor loop shows the main cut off low well to our southeast
over IL, with a northern branch trough digging down out of Canada.
The is good model agreement on that northern system cutting off
today as it moves towards the MT/ND border. At the surface, a weak
trough currently over western ND will move into our CWA today,
then starting to phase with the low to our southeast later
tonight. The cut off upper low will continue to spin over the
Dakotas and into MN tonight into Monday, wrapping some moisture
and cold air up into the system. This will make for a very messy
forecast with uncertain impacts for the early part of the work
week.

While PWAT values are not hugely impressive due to moisture
taking the scenic route into our area, thanks to the upper system
wrapping up over us there will be fairly long period of synoptic
lift over the region. 850mb frontogenesis also has some banding
potential tonight into Monday as the system wraps up. Precip
probabilities look high, mainly across our north but even the
southern counties should see a little bit.

The biggest question will be temperatures, both air and surface,
which will determine precip type and impacts. Fortunately there
does not appear to be much of a warm layer aloft as the upper
system wraps up, and model soundings show enough moisture in the
dendritic growth zone for DZ/FZDZ potential to be pretty minimal.
Will continue to keep mostly rain and snow as precip types. There
will be a decent amount of cold air advection tonight and into
tomorrow, although starting out from the 50s this afternoon will
take a bit to get down to below freezing. Precip should mostly
start out as rain, both coming in from the west as the upper
system approaches and some retrograding precip coming into the
northeastern CWA as the surface low phases with the system over
the Great Lakes and moisture wraps up. Cold air advection should
start some change over to snow in the Devils Lake Basin after
midnight, spreading south and eastward towards tomorrow morning.
Think there will be some flakes falling, and depending on rates at
least some sticking on grassy surfaces. However, temperatures on
pavement will be quite a bit warmer, and impacts as far as
accumulation on roads are still very uncertain. Agree with
previous shift that quite a bit of snow will be melting as it
falls, with accumulations on surfaces less than the total amount
of snow we see during the event.

With uncertainty in the impacts, will hold off on any headlines
for the time being, and will message a wet start to the coming
week with accumulating snow possible.

.LONG TERM...(Monday night through Saturday)
Issued at 319 AM CDT Sun Apr 11 2021

Impacts continue into Monday night and Tuesday as our H5 upper low
occludes in central Minnesota. The forward progression will be
rather slow, thus the residence time of snowfall is expected to
persist through the day and at least into the late evening hours.
Confidence in the track has increased, with blended guidance now in
agreement with both ECMWF and GEFS ensemble suites. The disagreement
remains when we bring timing into the equation, with the GFS based
guidance being a bit more progressive. This will play into the
expected brief change over to rain during the day Tuesday, primarily
for the region east of the Red River Valley as temperatures climb
above the freezing mark. The GEFS members bring a 925 mb warm nose
into the area during the afternoon and evening hours, just as
precipitation would presumably come to an end. This is in contrast
to the slower ECMWF, with it`s cooler 925 mb and 850 mb
temperatures, which would keep most of the precipitation falling as
snow.

Regarding potential snowfall amounts, confidence is increasing;
however, with a bit of disagreement remaining between the ensemble
suites, there is still some uncertainty. The highest snowfall
potential will be along and just south of the International Border
in northeastern North Dakota and the northern Red River Valley.
Further east, temperatures will be warmer, which will cut into the
accumulations, especially Monday afternoon. This being said, there
is a >50% chance of snow accumulations exceeding 3 inches for the
Devils Lake basin and the northern Red River Valley, to include the
greater Grand Forks area. Some of this snow will inevitably melt due
to warm ground temperatures; however, with below freezing temps
expected through the morning hours Monday and Tuesday, there will be
a potential for travel impacts. Some areas could see higher amounts,
with a reasonable scenario of 6 or more inches along the
International Border in North Dakota.

Snow will come to an end slowly as the H5 occluded low weakens and
pushes off to the east. Lingering light snow and flurries are
expected through Tuesday night and Wednesday morning. Slow clearing
takes place on Wednesday, allowing our temperatures to recover into
the upper 30s to mid-40s. We may even see 50 degrees in the Red
Lakes region.

Thursday brings another chance for rain and snow to eastern North
Dakota in association with another upper trough. There is a large
spread of potential solutions at this time, thus confidence is low
in specific details; however, beneficial moisture could be in store
for central and eastern North Dakota Thursday and Friday.

&&

.AVIATION...(For the 06Z TAFS through 06Z Sunday night)
Issued at 1155 PM CDT Sat Apr 10 2021

VFR conditions and light winds 5kt or less are expected across
eastern ND and northwest MN through this evening, with southeast
winds 10-15kt at KDVL early in the TAF period. Winds become
somewhat erratic during the day Sunday as low pressure sits over
the Red River Valley, with sustained winds variable near the
center, from the west-northwest on the western extent and from
the east-northeast on the other side of the low pressure. VFR may
prevail near the center of low pressure, but on either side low
stratus will begin to develop and eventually over spread most
terminals in MN and the DVL area by midday Sunday. KGFK and KFAR
are most likely to remain VFR through Sunday afternoon before
conditions deteriorate with the main system arriving Sunday
evening (along with potential rain).


&&

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

SHORT TERM...JR
LONG TERM...Lynch
AVIATION...DJR



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