275 
fxus63 kmpx 051126 
afdmpx 


Area forecast discussion 
National Weather Service Twin Cities/Chanhassen Minnesota 
626 am CDT Sat Jul 5 2008 


Discussion... 
today will be a day of transition across the region...going from dry 
to wetter pattern...as upper ridge to our west continues to flatten 
out as noted on satellite. The bottom line is that WI and Minnesota will 
be in an area prone to occasional thunderstorms with westerly jet 
trekking just to our north. Thus much of the forecast includes 
mention of storms. 


Broad area of middle and high clouds approaching Minnesota and WI. Surface ridge 
extending from eastern Iowa to New England and light southeast 
winds still prevails across most of the County Warning Area. However... strong low 
in Saskatchewan with trough extending southward into the central rockies. Tight 
gradient and winds in the higher terrain of the Buffalo Ridge in 
SW Minnesota have been gusting close to 20 knots. So winds will be on the 
increase this morning. Dew points in the upper 50s also common. 


First wave to affect the County Warning Area will be arriving tonight. Models are 
in rather good agreement with the best forcing occurring late 
tonight and Sunday morning. Plentiful moisture and there is some 
hint of a subtropical jet arriving this evening in addition to the 
stronger one just to our north. Both NAM and GFS increase the 
precipitable water to 1.9 or 2.0 inches late tonight. Instability 
also significant. Some decent speed shear as well. Could be a few 
severe entering western Minnesota late tonight. The main question for severe on 
Sunday is whether storms late tonight and Sunday morning produce 
enough cloudiness to hinder redevelopment of storms later Sunday. 
There is some hint this may happen. 


Most models suggest an end to precipitation Sunday evening as surface system 
departs and upper ridge builds slightly. GFS and to a lesser 
extent the global both show a slower front dropping out of the 
north...and hanging up across central Minnesota by Monday morning. But 
even if the GFS is correct...there is little upper support for 
precipitation late Sunday night and Monday morning. Will carry small probability of precipitation 
though. These two possible rounds of storms seem to have 
influenced model solutions for Monday. General idea seems to show 
warm front just to the south and west of Minnesota...which will likely 
lift back into the area later on Monday. So Monday afternoon 
and night will be the next best time for storms. As alluded to 
earlier...pattern will feature the continued chance of storms 
every day or two for the rest of the week. 


&& 


Aviation.../12z taf issuance/ 


Low level return flow will resume in earnest today across the taf 
sites. First...some low level wind shear /below mentionable criteria/ does exist 
looking at profiler observations...with 25-30kts at 1.5-2 kft 
early this morning. This is primarily the case over Minnesota taf sites 
and should fade somewhat quickly by 13z-14z. Some scattered middle level 
clouds will also pass over the region this morning...with cirrus 
incoming above that from convection across the northern plains last 
evening. This will have little hindrance to good mixing this 
afternoon given projected high temperatures. This combined with 
surface pressure falls moving into the region will allow for 
breezy conditions. Axn and rwf should see sustained winds near 20 
kts with gusts of 25-30 kts at times during this afternoon. Winds 
should gradually drop into this evening losing some of the stronger 
gusts from 00z-01z. Convection is expected to develop in the eastern 
Dakotas during the evening. The main propagation on this should take 
it into the northern half of Minnesota. However...another low level jet tonight will 
lead to increasing elevated instability into overnight and do 
expect isolated to scattered convection developing in ctrl and southern Minnesota. 
Axn...rwf...and stc all have a chance tonight with some of this 
potentially being near msp very late in the taf period. 
Low level wind shear...again below mentionable criteria...will be present at taf 
sites given the stronger jet. 30-35 kts predicted in the 1-1.5 kft 
layer...but with higher surface winds the change with vertical ascent 
will not be too extreme. Beyond the taf period...chances for 
convection increase at msp and WI taf sites readily for Sun 
morning. Redevelopment of isolated to scattered convection...some of it 
strong...may occur Sun afternoon with all taf sites potentially seeing 
some thunder. 


&& 


Mpx watches/warnings/advisories... 
Minnesota...none. 
WI...none. 
&& 


$$ 


Tdk/mtf