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Area forecast discussion...updated 
National Weather Service Aberdeen South Dakota 
931 PM CDT Thursday Jul 3 2008 


Update... 
lowered cloud cover a bit across the north where skies have pretty 
much cleared. Also left the mention of more cloud cover across the 
southwest and the far east where clouds have been slow to clear. 
No other changes made to the forecast at this time. New aviation 
discussion below. 




&& 
Previous discussion... 
short term...tonight through Saturday night 
biggest challenge facing the short term deals with convection 
chances Saturday evening/night...along with warming temperatures. 


Models continue to advertise rising 500 mb heights heading into the 
Holiday weekend...as western Continental U.S. Ridge builds and slides east into 
the region through Sunday morning. There is a minor wave that is 
sliding southeast across ND and northestern South Dakota this evening...and some light 
virga/rain showers were seen on the kbis 88d earlier. With dry air 
currently in place across the County Warning Area...don't expect much more than 
slight increase in middle clouds for the NE tonight. Did bump up probability of precipitation 
to 14 percent...but kept dry conds going. 


Attention then turns toward Saturday evening/night for next round 
of potential rainfall. Upper ridge passes east through the 
Dakotas...with developing pre-frontal trough moving east across 
South Dakota late in the day Saturday. There is some discrepancy 
between the models in just how warm the 7h layer is supposed to 
get...but generally from +12 to +14 celsius by 00z Sunday is 
forecast. GFS and NAM soundings are also very dry...with ample cin 
in place by 00z. There is also some differences when evaluating 
the nocturnal jet influence Saturday night. The NAM is showing 
30+kts at 850 mb ahead of the surface trough...while the GFS is only 15 
to 20 kts. Envision precipitation developing across western/central ND during the 
early evening...then drifting southeast into the northern sections of the County Warning Area 
overnight. BUFKIT shows storm motion from the northwest at 15 to 20 
kts...so chances will linger through the night. Based on such warm 
middle-layer temperatures...have pulled chance probability of precipitation a bit further north and 
gone with slight chance to the south. 


Temperature wise...things begin to get warm in a hurry heading into the 
weekend. This morning..85h temperatures were +8 to +11 celsius across the 
County Warning Area. With southerly flow setting up by Friday...temperatures climb to +21 
to +28 celsius by 00z Sunday. Have tempered readings just a bit 
during the day Saturday...as they will be dependant upon just how 
much moisture can advect northward. By 00z Sunday...NAM shows 
widespread area of 70+ dewpoints across the region...which if that 
does indeed pan out...temperatures may be just a bit lower than currently 
forecast. Likewise...if drier air is in place since 
evaportranspiration won't really be going strong...then temperatures 
could be a bit higher. Either way...looks to be a warm and muggy 
weekend coming up. 


Long term...Sunday through Thursday 
period begins with weak shortwave exiting northeast corner of 
forecast area Sunday morning. Could see some lingering activity in 
the northeast but elsewhere should be dry and have removed mention 
of precipitation for the morning hours. Bigger impact of aforementioned 
shortwave may be surface boundary that it pushes into the area. 
Boundary expected to stall somewhere across the region by midday 
Sunday as it becomes more parallel to upper flow. Models showing 
that moisture expected to pool along this boundary /dew points 
possibly approaching 70 degrees/ will weaken what would otherwise 
be a decent cap across the area and could result in some 
thunderstorm development Sunday afternoon/evening. For now have 
left slight chance probability of precipitation across entire area until confidence grows 
in low-level pattern. By late Sunday night decent shortwave pushes 
into western South Dakota and moves across through the morning 
hours. Models have been consistent with thunderstorm complex 
signature associated with this wave and push it right along the 
surface boundary. Bumped up precipitation chances a bit and kept best 
chances across south...but again exact movement will likely depend 
on where surface boundary sets up. 


For the rest of the week ridge builds across the western half of 
the country. Behind Sunday night system thermal ridge gets knocked 
back so expect Monday to be coolest day before very warm temperatures 
aloft build in toward late in the week. If it does not happen 
Saturday forecast area could possibly see first triple-digit 
temperature Wednesday or Thursday West River. Did not go quite 
that warm for now since there is not complete agreement on 
amplification of upper ridge. Kept rest of period dry for now. May 
need to revisit Tuesday night on next forecast update...but at 
this time looks like best chance stays well north of the area. 
Temperatures aloft later in the week pretty much guarantee a cap over the 
area with no system seen that was strong enough to break it. 




&& 


Aviation... 
a broken-overcast deck of clouds around 7k feet will persist over the 
southwestern County Warning Area...affecting kpir...through around 05z. A scattered-broken 
deck between 5k-6k feet will track southward over the far eastern 
County Warning Area...affecting Katy...during the rest of the evening as well. The 
rest of the County Warning Area will see clear skies...with the entire County Warning Area 
expected to be VFR under clear skies after 06z. Visibilities will be 
unrestricted. 




&& 


Abr watches/warnings/advisories... 
South Dakota...none. 
Minnesota...none. 
&& 


$$ 
Update...Parkin 
short term...Hintz 
long term...zeltwanger 
aviation...Parkin 


Weather.Gov/Aberdeen