<html><head></head><body><div class="yahoo-style-wrap" style="font-family:Arial, Helvetica, sans-serif;font-size:16px;"><div dir="ltr" data-setdir="false"><font size="3">Mpls NWS discussion regarding the weekend: (WWA = warm air advection)</font></div><div><font size="3"><br></font></div><div><font size="3"><br></font></div><blockquote style="margin: 0 0 0 40px; border: none; padding: 0px;"><div dir="ltr" data-setdir="false"><div><div><i><font size="3">A pseudo-</font><span style="font-size: medium; letter-spacing: -0.02em;">stationary boundary will enter the region today and will be the </span><span style="font-size: medium; letter-spacing: -0.02em;">locus of what will be multiple rounds of showers and storms over the </span><span style="font-size: medium; letter-spacing: -0.02em;">weekend, with the location of the boundary going to be a key focal </span><span style="font-size: medium; letter-spacing: -0.02em;">point of the forecast in terms of where the heaviest rainfall will </span><span style="font-size: medium; letter-spacing: -0.02em;">end up.</span></i></div></div></div><div dir="ltr" data-setdir="false"><div><div><font size="3"><i><br></i></font></div></div></div><div dir="ltr" data-setdir="false"><div><div><i><font size="3">Heat and humidity will build today ahead of a plume of lower </font><span style="font-size: medium; letter-spacing: -0.02em;">mid level warm air and moisture that will arrive with the boundary </span><span style="font-size: medium; letter-spacing: -0.02em;">later today, with heat indices peaking in the mid to upper 90s this </span><span style="font-size: medium; letter-spacing: -0.02em;">afternoon and again tomorrow afternoon. We may see a brief hour or </span><span style="font-size: medium; letter-spacing: -0.02em;">two of heat indices exceeding heat advisory criteria, however the </span><span style="font-size: medium; letter-spacing: -0.02em;">duration for now looks to be short enough such that an advisory may </span><span style="font-size: medium; letter-spacing: -0.02em;">not be needed, especially if cloud cover and convective debris end </span><span style="font-size: medium; letter-spacing: -0.02em;">up knocking down the high temperatures just a bit. Ensemble guidance </span><span style="font-size: medium; letter-spacing: -0.02em;">shows a fairly high likelihood of highs in the upper 80s for a large</span><span style="font-size: medium; letter-spacing: -0.02em;"> portion of the MPX CWA, with dew points increasing into the mid 70s </span><span style="font-size: medium; letter-spacing: -0.02em;">within the primary warm air advection zone south of the boundary. </span><span style="font-size: medium; letter-spacing: -0.02em;">Right now, there is still not a clear consensus within the suite of </span><span style="font-size: medium; letter-spacing: -0.02em;">guidance to pinpoint the location of the boundary, however for now </span><span style="font-size: medium; letter-spacing: -0.02em;">it looks to favor near or north of the Twin Cities which would place </span><span style="font-size: medium; letter-spacing: -0.02em;">most of the CWA within the WAA zone. Potential for severe weather </span><span style="font-size: medium; letter-spacing: -0.02em;">will largely be confined to the immediate area near the boundary as </span><span style="font-size: medium; letter-spacing: -0.02em;">shear will be locally maximized, however a lower-mid level cap as </span><span style="font-size: medium; letter-spacing: -0.02em;">well as high PWATs are making this event seem more like a flooding </span><span style="font-size: medium; letter-spacing: -0.02em;">threat than a large scale severe weather threat. CFSR climatology </span><span style="font-size: medium; letter-spacing: -0.02em;">from the ECMWF shows a plume of 99th or higher percentile PWATs over </span><span style="font-size: medium; letter-spacing: -0.02em;">a large portion of the area beginning this evening and continuing </span><span style="font-size: medium; letter-spacing: -0.02em;">through Tuesday morning, with both the CFSR ECMWF and NAEFS showing </span><span style="font-size: medium; letter-spacing: -0.02em;">PWATS in excess of 2 inches for the next few nights. There is high </span><span style="font-size: medium; letter-spacing: -0.02em;">confidence in significant moisture being present with the highest </span><span style="font-size: medium; letter-spacing: -0.02em;">overall areal coverage in terms of the percentiles being Sunday </span><span style="font-size: medium; letter-spacing: -0.02em;">night into Monday morning after a few days of consistent low level </span><span style="font-size: medium; letter-spacing: -0.02em;">WAA and moisture advection take place. Stay tuned for further </span><span style="font-size: medium; letter-spacing: -0.02em;">details including the location of the boundary and most likely area </span><span style="font-size: medium; letter-spacing: -0.02em;">for localized flooding as we see more CAMs come into play that will </span><span style="font-size: medium; letter-spacing: -0.02em;">capture the full event over the next 24-36 hours.</span></i></div></div></div></blockquote><div dir="ltr" data-setdir="false"><font size="3"><br></font></div><div><br></div></div></body></html>