Area Forecast Discussion
Issued by NWS Grand Forks, ND

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FXUS63 KFGF 151524

Area Forecast Discussion
National Weather Service Grand Forks ND
1024 AM CDT Tue Aug 15 2017

Issued at 1024 AM CDT Tue Aug 15 2017

Not planning many updates for today until more consensus among
model forecasts can be observed. Current HRRR/HRRRexp suggest
deeper convection expected to the south of the forecast this
afternoon will `rob` moisture advection to the north, and weaken
activity across the this region. Not sure exactly if this will
cause less widespread showers, or just lower expected rainfall
amounts. Other guidance still indicates the 1-2 inches possible.


.SHORT TERM...(Today and tonight)
Issued at 332 AM CDT Tue Aug 15 2017

The main forecast challenge is the next pcpn event, which is
mainly contained within this time range. Models had been showing
the potential for another round of 1 to 2 inches of rain across
the southern half of the FA. Latest runs have been pushing the
heavier rainfall south of the FA now, more so from southeast SD
into southern and eastern MN. Still could see amounts around an
inch or so, mainly south of a line from Valley City to Bemidji.
After coordinating with adjacent offices and WPC, reduced the
overall rainfall amounts to match this further south solution and
dropped the marginal risk for excessive rainfall from our FA. The
overall lack of much instability in our FA will limit the overall
thunder chances, and without organized thunderstorms there is
generally a reduced heavy rain threat. So will be putting out our
various products with this message. There is not a threat of
severe weather and the reduced expected rainfall should not cause
any issues for the area. The event also looks to occur over a
shorter time range than the models were showing yesterday too. So
looking at mainly a tonight event for the steadier rainfall
amounts, then more so in MN by Wed.

Other than the rainfall, there is also some morning fog. At this
point, it is not dense, but will have to monitor. The fog so far
has been over the eastern and southwest FA. High clouds spreading
in from the west may limit the fog from being as extensive as
yesterday morning. These clouds will continue to spread into the
FA today, with pcpn chances slowly spreading from west to east.
Think through most of the day, this rain will stay west of the Red

.LONG TERM...(Wednesday through Monday)
Issued at 332 AM CDT Tue Aug 15 2017

Some of the above mentioned rain will linger into Wed and Wed
night, but mainly over the MN portion of the FA. This will hold
down high temps on Wed, while clouds decrease from west to east
Wed night. With light winds again, there may be some fog around
again Wed night, however will hold off on mentioning it at this
point. Thu looks like a pretty nice day, with mild highs and
continued low wind speeds. Next chance of pcpn will spread into
the FA Thu night.

For Friday through Monday...High pressure moving toward eastern
Minnesota Thu night will be replaced by advancing sfc
boundary/digging short wave early Fri. Severe potential may be
minimal, with weak shear coupled with moderate instability at
best, during Fri morning.

The weekend looks warmer and dry, owing to building high pressure
both at the surface and aloft. The next threat for convection would
most likely arrive with the approach of a short wave on Mon. The GFS
and ECMWF closely agree on the timing of these features.

Temps will be near seasonal Fri, rising to the low and mid 80s for
the weekend and beyond.


.AVIATION...(For the 12Z TAFS through 12Z Wednesday morning)
Issued at 640 AM CDT Tue Aug 15 2017

Fog is being reported around most TAF sites, but web cams show it
being fairly shallow and not widespread. Will keep a mention of
fog through about 13Z, and see what happens by then. Like
yesterday, think it should go away fairly quickly this morning.
Otherwise expect increasing high clouds this morning, with some
lowering of the clouds into the mid range by afternoon/evening.
Added a mention of showers from west to east, mainly by afternoon
at KDVL and early evening at KGFK/KFAR. Will take longest to reach
KTVF and KBJI. As the steadier showers move in, ceilings will
finally lower into the MVFR range.




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