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Area forecast discussion 
National Weather Service Grand Forks ND
322 PM CDT Thursday Aug 21 2014

Short term...(this evening through Friday night)
issued at 320 PM CDT Thursday Aug 21 2014

The main forecast challenge concerns precipitation chances and
temperatures. NAM/RUC initialized best however NAM looks to be
the odd model out in later periods and discarded. Operational
models continue to over forecast precipitation across the region
significantly. About the only thing models agree on is that the
region will persist in SW flow aloft through the period.

For tonight surface low along ND/SD/MN border area will continue
to drift east. Trailing surface boundary will roughly bisect forecast area
from NW-se. Water vapor loop indicating weak impulse moving into
the central Dakotas which will lift NE tonight. With impulse and
boundary will maintain some modest probability of precipitation through the evening. Once
the wave lifts NE later tonight a ridge of high pressure nosing in
should keep most areas dry. Clouds most areas at least part of the
night and elevated dewpoints will keep minimums generally in the
60s.

Weak surface high pressure will continue across the forecast area on
Friday/Friday night. Aloft in SW flow another weak wave will to lift
NE. Potentially the most active area will be to our west however
some precipitation may clip dvl basin so will maintain some low probability of precipitation.
Remainder of the forecast area should for the most part be dry. Temperatures
will hinge on cloud trends so held pretty close to current values.

Long term...(saturday through thursday)
issued at 320 PM CDT Thursday Aug 21 2014

Poor model agreement through Sunday as upper low crosses northern
rockies into the northern High Plains. All showing different
solutions on track/timing of upper low and associated surface
features. General thought is that low pressure will organize over
the Central Plains/High Plains and lift NE through the later half
of the weekend. With differing solutions on low level features
trying fine tune favored locations for significant precipitation very
difficult at this time. As a result made minimal changes to probability of precipitation
in later periods. Little change in thermal profiles so again
temperatures will hinge on cloud cover but likely to remain below
average.

For Sunday night through Wednesday...models coming into better
agreement at this point...but GFS surface features and precipitation become the
outlier. Therefore...a blended European model (ecmwf)/Gem solution is preferred at this time.
Otherwise...surface low pressure developing over the upper Midwest is
expected to lift to the NE. Upper level trough looks to cross the area
bringing cooler air behind the system...and frontogenetical forcing
to trigger -shra/-tsra along and ahead of the low. Sufficient ll
moisture available to wrap behind the system...keeping skies mostly
cloudy. As the upper trough digs in...look for cooler temperatures to round
out the period.

&&

Aviation...(for the 18z tafs through 18z Friday afternoon)
issued at 1249 PM CDT Thursday Aug 21 2014

Pattern resembles more of a late fall regime with persistent lowered
ceilings and visibility. Surface analysis shows low pressure located over eastern ND
with abundant low level moisture present. Observation show widespread MVFR
ceilings...with spots with scattered cloud cover. Expecting some solar to
penetrate during the afternoon hours raising ceilings a bit...but 925mb
and 850mb forecast moisture fields indicate that ceilings will be
persistent through the taf period. Therefore...raised ceilings a bit for
the first part of the period toward VFR criteria. However...loss of
heating after sunset will allow ceilings to fill in...and will drop down
to the MVFR/IFR category again. Some areas of patchy fog can be
expected...but not looking to be predominant at the taf sites at this time.



&&

Fgf watches/warnings/advisories...
ND...none.
Minnesota...none.
&&

$$

Short term...voelker
long term...Hopkins/voelker
aviation...Hopkins

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