Area Forecast Discussion
Issued by NWS Kansas City/Pleasant Hill, MO

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FXUS63 KEAX 290546

1146 PM CST Fri Nov 28 2014

Issued at 304 PM CST FRI NOV 28 2014

Unseasonably warm weather will continue through Saturday and for
parts of the area into Sunday. But by Sunday afternoon, the bottom
will fall out as a strong cold front blasts through the area. As has
been the case the last few days, models remain consistent in moving
the front through the day, but there remains some timing differences
that then result in the potential for huge bust potential. The GFS
remains the fastest and seems like an outlier at this point given
the closer clustering of timing amongst the GEM, NAM and the ECMWF.
With that in mind, temperatures in the far southeastern portions of
the forecast area may climb into the lower 60s. A few hundred miles
to the northwest, far northwestern Missouri will likely see their
highs set before sunrise, with temperatures steady or falling
throughout the day. The forecast depicts a 30 degree temperature
spread for highs on Sunday and it`s quite possible this could be
closer to 40 degrees given the magnitude of the cold air behind the
front and the air mass it`s replacing.

The other aspect of this frontal passage will be the potential for
showers or drizzle ahead of the front and drizzle or freezing
drizzle behind the front. Forecast soundings show a very moist
low-level environment with a small amount of positive buoyancy ahead
of the front. This may result in a few showers in our far
southeastern zones. Then, in the afternoon, the front plows through,
knocking temperatures back below freezing with winds picking up from
the northwest. This could have several effects. First, the low-levels
remain saturated as they fall below freezing, and with no ice
crystals could result in a brief window of freezing drizzle. Another
possible scenario is that if there is some prefrontal precipitation
that mainly elevated surfaces could become slick as temperatures and
winds quickly cool those surfaces down.

Models are in better agreement for the first half of the week with
cold high pressure being the main player. But the inconsistencies
that have been present the last few days remain mostly the same for
the later half of the week. The GFS remains the most progressive
with zonal flow allowing an eastern Pacific trough to quickly move
ashore and move eastward into the center of the country. The GEM and
the ECMWF, while showing a similar pattern, maintain a stronger
ridge over the western CONUS and are slower to track that upper
trough to the east. The result of this continues to be that the ECMWF
and GEM are colder at the surface with high pressure through the
Upper Midwest into the Lower Missouri Valley. In contrast, with the
GFS being more progressive, it develops lee troughing and allows
warmer air and precipitation to advect northward. Confidence remains
low from about Wednesday onward given the differences in the models.


.AVIATION...(For the 06Z TAFS through 06Z Saturday Night)
Issued at 1140 PM CST FRI NOV 28 2014

Feeling is that fog development will not be prevailing through the
entire early morning period, as dry air above the surface and mixed
out boundary layer should provide enough mitigating ingredients to
prevent the widespread, prevailing fog. That being said, moisture
will make its way into the area and temperature/dew point depression
will be rather low, so will go with a mention of MVFR fog, with
perhaps some brief IFR periods. HRRR guidance through the night
indicates some patchy IFR VIS near the terminals, so will hold on to
the mention of IFR. Otherwise VFR conditions prevail.




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