Weather

504 
fxus63 kfgf 281930 
afdfgf 


Area forecast discussion 
National Weather Service Grand Forks ND 
230 PM CDT Thursday Aug 28 2008 


Short term... 
forecast challenge initially is storms firing in bji-bde areas and how 
soon they will exit forecast area. And then mostly temperatures for the 
weekend and progression of next front early next week. 


Currently...vsbl sateillite loop shows vorticity maximum moving through 
Bemidji area into Itasca County. This vorticity prognosticated to move east 
toward dlh area by 00z. -20c 500 mb temperature along with surface temperatures near 
70 and dew points near 50 creating convective available potential energy 600 to 1000 j/kg in far eastern 
forecast area as of 18z. Scattered storms firing on west side of vorticity at this time 
from Lake of The Woods area toward Bagley/bji areas and this will 
continue as entire system moves east. Current gridds have chance through 
23z and this looks good with no weather mentioned past 00z as vorticity will 
be east of the area. Surface trough also associated with vorticity with 19z observation 
indicating it from west of Roseau-to east of Fosston to just west 
of Park Rapids also moving east. 


Otherwise tonight cumulus will dissipate at sunset leaving a 
mostly clear sky for most of the night. Exception is the far north 
late tonight into Friday morning as a vorticity maximum and associated surface trough 
now over central Alberta moves east-southeast through Manitoba to northwest 
Ontario Friday midday. Thicker middle clouds and possible showers will 
skirt along the Canadian border 06z-12z in NE ND and 12-18z in northwest 
Minnesota. Coordinate with other offices led to not mentioning showers at this 
time in the far north as most models keep the main vorticity 
sufficiently north of the border closer to yqk-ywg-ybr line. 


With fairly dry airmass and light winds overnight areas that 
remain pretty clear will drop to the upper 40s or around 50 for lows. 


High pressure to build in Friday behind surface trough and then 500 mb 
ridge begins to build over the area Saturday as strong upper vorticity 
dives into the northern rockies/Great Basin region out west. 500 mb 
ridge pumps up along with large rise in 850 mb temperatures Sat-sun on 
gusty south winds. Warm advection most pronounced Sat night as 50 knots low 
level jet develops aiming for southeast Manitoba/northwest Ontario with thunderstorm 
development just north of the area looking probable. GFS wants to 
paint some precipitation along northern border late Sat night-Sun morning but 
again coordination led to no weather at this time. 850 mb temperature 
thermal ridge over western 1/2 of forecast area suggest 90+ surface temperatures very 
likely northwest 1/2 of forecast area. With ridge overhead looks pretty clear 
most areas through the weekend outside of middle level altocumulus castellanus north Sat 
night-Sun morning. 




Long term... 
Sunday night through Thursday. 12 UTC GFS/European model (ecmwf) in relatively 
good agreement Sunday night through Tuesday morning...diverging 
somewhat thereafter with the evolution of a strong Pacific 
shortwave trough. GFS places 500 hpa low center across southern 
Manitoba Wednesday morning...whereas the European model (ecmwf) is a bit slower 
with the system and farther north across central Saskatchewan. 
Latest Canadian model run more closely resembles European model (ecmwf) solution 
and HPC guidance also favors slower European model (ecmwf). As such... slowed west 
to east onset of chance probability of precipitation and associated wind shift/ cooler 
temperatures across the forecast area Sunday night through 
Wednesday. At this time...best chance for measurable rainfall 
looks to be Monday night into Tuesday. Daytime high temperatures 
Tuesday will likely be 10 to 20 degrees cooler than the near 90 
degrees forecast Sunday. 


&& 


Aviation... 


Expect VFR conditions to persist at all taf sites the next 24 hours. 
Scattered-broken cumulus expected to remain at or above 4000 feet the rest of 
the afternoon...quickly dissipating after sunset. Isolated 
thunderstorms across northwest Minnesota within cumulus cloud deck 
will stay northeast of a line from Hallock to Bemidji. Gusty 
afternoon winds will decrease this evening...generally maintaining 
westerly component flow. 


&& 


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


$$ 
Riddle/Rogers