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Area forecast discussion...updated aviation 
National Weather Service St Louis MO
509 am CST Fri Mar 6 2015

Short term: (through late this afternoon)
issued at 313 am CST Fri Mar 6 2015

Some mid level cloudiness across the western half of Iowa ahead of a
northwest flow shortwave and in a region of low-mid level warm air
advection will move eastward through parts of northeast MO and west
central Illinois this morning. Warmer temperatures can be expected this
afternoon as the surface ridge extending from northeastern Arkansas
northeast through southern Illinois moves southeastward and the surface
wind becomes south-southwesterly across our forecast area. The
models shift the zero degree c 850 mb isotherm eastward to the
Mississippi River by 00z Saturday. Went closer to the warmer GFS
MOS guidance for high temperatures today, particularly in areas
without snow cover from central MO eastward through the St Louis
Metro area.


Long term: (tonight through thursday)
issued at 313 am CST Fri Mar 6 2015

The trend to more typical early March temperatures should
continue to be the primary forecast trend as we head into the
weekend and early next week. As upper air flow regime over all but the
extreme southern Continental U.S. Takes on a west-northwest look, the cold
air that has been locked over the eastern half of the country for
the past few weeks will begin retreating into southeast Canada and
New England, allowing a more moderate air mass to spread from the
plains to the mid- Mississippi Valley. Shortwaves embedded in the
west- northwest flow will make several attempts to bring some
cooler air our way, but with the pattern blocking any strong
southward intrusion of cold air these cool Downs should be
relatively minor.

Believe that the warmup and strong sunshine that occurs today will
be a "snow eater" in many parts of the cwa, so by Saturday any
impacts of existing snow cover on temperatures will likely be
fairly minimal and confined to our far southeast counties. With a
westerly wind component advecting temperatures from the snow-free
areas of western MO and lots of sunshine, forecast highs for
Saturday will continue to lean towards the warm side of guidance.
I've placed the warmest temps (55-60) along the thermal ridge
progged along and just south of the i70 corridor in Missouri, with
highs in the upper 40s and lower 50s elsewhere.

A bit of cooler air oozing into the region on Sunday along with
additional high cloudiness should keep highs near their average
early March levels, with similar readings expected on Monday.


00z guidance continues to indicate a pronouced (and for most, a
welcomed) warmup in the offing for the mid-Mississippi Valley
heading into the middle of next week as heights build across the
central U.S. Initial surge of warmth on Tuesday should push most
areas west of the Mississippi to around the 60 degree mark, with
highs in the 60s over most of the region by Wednesday and

Precipitation chances should remain quite low through the middle
of next week. However, there appears to be some agreement in
medium range solutions that remnants of southwest U.S. Upper level
low will drift our way by the end of the period, and have added
some low pops to southeast sections of the forecast area for Thursday and
Thursday night.



Aviation: (for the 12z tafs through 12z Saturday morning)
issued at 452 am CST Fri Mar 6 2015

VFR conditions this forecast period with just some mid-high level
clouds expected. The NAM MOS guidance appears overdone with its
boundary layer moisture and low level clouds its forecasting for
uin this evening. S-sely surface winds with strengthen and become
swly late this morning and early this afternoon as surface ridge
extending from northeastern Arkansas northeast through southern Illinois moves
southeastward. Swly surface winds will continue tonight.

Specifics for kstl: just some mid-high level clouds this forecast
period. S-sely surface winds will strengthen late this morning and
become swly. Swly surface winds will continue tonight and Saturday



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