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Area forecast discussion 
National Weather Service Grand Forks ND
1146 PM CDT Tuesday Aug 19 2014

issued at 1145 PM CDT Tuesday Aug 19 2014

No changes from previous update.


Short term...(this evening through Wednesday night)
issued at 320 PM CDT Tuesday Aug 19 2014

Main forecast challenge will be precipitation chances and heavy rain
threat. NAM looks to be the odd model out with main surface low
too far north followed by Gem with farther south GFS/European model (ecmwf) in
pretty good agreement and will use later for forecast.

For tonight surface and middle level short wave ridge to shift east
setting up weak return flow. Eastern forecast area will be closest to surface
ridge axis and will have the best potential for fog and will
include in forecast. Temperatures currently a few degrees warmer
than yesterday so minimums should follow.

Southwest middle level flow gradually takes shape late tonight into
Wednesday as ridge shifts east. Surface low pressure organizes
across the central/northern High Plains during the day. Main low
will over Central High plains with developing east-west warm front and
this likely to be the focus for convective development. At peak
heating boundary depicted by most models from east central South Dakota into S
Minnesota with development along and north of boundary. So at this point
best potential looks to be across the southern forecast area. North-S oriented
inverted trough looks to be mainly west of the forecast area so left lower
probability of precipitation going across the dvl basin. Temperatures will depend on cloud
cover however column warm so any breaks will boost temperatures.

As initial short wave lifts northeast Wednesday night T should
continue to become more widespread. Models differ somewhat on how
far north warm front will lift and this will have a big bearing on
where heaviest rain will fall. GFS/European model (ecmwf) focus heavier rain
potential from ND/SD/MN border south and eastward while Gem/NAM
farther north. Southern forecast area has seen recent heavy rainfall so if
southern solution does pan out may need some headlines. With split
solutions will hold off for now.

Long term...(thursday through tuesday)
issued at 320 PM CDT Tuesday Aug 19 2014

Rain will gradually push east during the day Thursday. Will likely
see some degree of cloud cover persisting so maximum temperatures
to be a few degrees colder.

Forecast area should be between systems Thursday night into part of the day
Friday for generally dry conditions. Temperatures will again hinge
on cloud cover.

Longwave pattern deamplifies this period with longwave ridge/trough
over the eastern Pacific/western North America and pattern shifts
east this period. GFS is fast with lead short wave at 84 hours
compared to the other models. Then the GFS becomes slower than the
European model (ecmwf) toward the end of the period. GFS and the European model (ecmwf) have trended
farther west/northwest with last couple model runs. Will prefer the
European model (ecmwf).

Threw out probability of precipitation from the GFS. Reduce probability of precipitation in northern 2/3 of forecast
area for Friday night. Increased probability of precipitation east and decreased probability of precipitation
northwest/west on Sat night/sun. Decreased probability of precipitation in the south and
increased probability of precipitation north on Monday.

Little change to temperatures...a degree or two higher for Sat...a degree
or two lower for change thereafter.


Aviation...(for the 06z tafs through 06z Wednesday night)
issued at 1145 PM CDT Tuesday Aug 19 2014

There could be some patchy fog overnight mainly in the east...but
something to monitor even in the valley locations. Southerly winds
will increase on Wednesday...along with VFR middle clouds moving in by late
afternoon. There will be increasing chances for convection after
00z Thursday...and have started to mention some thunderstorms in the vicinity at all
sites...with timing still a bit in question.


Fgf watches/warnings/advisories...

short term...voelker
long term...hoppes/voelker

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