Area Forecast Discussion
Issued by NWS Springfield, MO
FXUS63 KSGF 022351
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SPRINGFIELD MO
551 PM CST Mon Dec 2 2013
.SHORT TERM...(This Evening through Wednesday)
Issued at 255 PM CST MON DEC 2 2013
A rather nice day for early December unfolded across the region
after morning clouds and fog. The relatively mild weather will
continue tonight into Tuesday as southerly winds increase.
Areas of stratus and fog will likely develop again tonight.
However with a little more mixing overnight I do not expect the
fog to be as dense as this morning.
Mild temperatures are in store for Tuesday as southerly winds
increase ahead of a cold front pushing across the Plains. Highs
Tuesday will reach the lower to middle 60s.
Temperatures will remain mild Tuesday night as the front
approaches. The cold front will enter far southwestern Missouri by
day break Wednesday then push across southern Missouri during the
day. Temperatures will steady off then fall following the frontal
Some patchy drizzle and perhaps a few light showers may develop
across south central Missouri Tuesday night into Wednesday as a
result of deepening moisture. However little precipitation is
expected with the frontal passage.
.LONG TERM...(Wednesday Night through Monday)
Issued at 250 PM CST MON DEC 2 2013
By Wednesday evening, much colder air is expected to be in the
process of advecting southeast into the forecast area in the lower
levels of the atmosphere. Aloft, southwest flow will continue, with
an upper level jet streak strengthening considerably across the
central Great Plains into the Great Lakes region. This jet position
will place the Ozarks well within the right entrance region of the
upper jet, which will combine with a subtle mid level shortwave
moving northeast from the southern Plains to produce large scale,
rather deep ascent across the region Thursday morning.
Precipitation should begin fairly rapidly Thursday morning, though
precipitation type remains difficult to pin down at this juncture.
Current indications are that the surface freezing line should be
roughly along a line from Branson to Salem, thus anything falling
over the northern two-thirds of the forecast area would be frozen or
freezing, with a small area over south central Missouri where just
rain would be favored, at least for a short time before colder air
builds south. Along with the surface temperature, the temperature
profile aloft will obviously be key to the precipitation type.
For areas north of I-44, it appears likely that 850 MB temps will
remain cold enough to either result in no melting of hydrometeors,
or just partial melting. In the low levels over this area,
temperatures will be cold enough for anything that (partially)
melts to completely refreeze, thus snow or a mix of snow or sleet
would be expected. By Thursday evening, any sleet should change
over entirely to snow.
Further south, along and south of I-44, things are a bit more
complicated. Temperatures around 850 MB will get progressively
warmer as one goes south, suggesting that the potential for partial
or complete melting of hydrometeors will become more likely further
south. At the surface and very lowest levels of the atmosphere,
there should be an axis where the low level cold air is cold enough
to refreeze anything that melts aloft before it hits the surface,
resulting in a mix of snow and sleet. If any precipitation melts
aloft and makes it down to the surface, and surface temperatures are
at or below freezing, then freezing rain would result.
It is important to note that precipitation type and amounts will
depend entirely on differences in temperatures at the surface and
aloft of just a couple of degrees, differences that are extremely
difficult to resolve this far in advance. With that said, it is best to
not focus on specific precipitation types or amounts for a given
location at this time, but instead just be aware of the potential
for accumulating wintry precipitation later this week. As the storm
system of interest and associated air masses are better sampled by
the surface and upper air observation network, specific details will
become more clear in the coming days.
Thankfully, by Thursday evening, any remaining precipitation should
simply change over to all snow as the colder low level air mass
continues to build in from the north. By Friday morning, the upper
level jet will realign itself from roughly Dallas to Toronto, and
strengthen considerably. Ascent within the right entrance region of
the jet should help produce another round of precipitation over the
region, especially the southern half of the forecast area, Friday.
The atmosphere is expected to be cold enough across the entire area
to result in all snow, with the potential for at least a few inches
of accumulating snowfall across the area by Friday evening.
As we head into the weekend, the core of the very cold Canadian
air mass will move south into the area, resulting in very cold
temperatures Friday/Friday night through Sunday. Lows will be in
the teens and single digits, with wind chills approaching zero.
Readings may need to be adjusted down a few degrees.
Finally, it appears that by next Sunday, yet another round of wintry
precip will move through the area as a stronger but much more
progressive shortwave swings across the area. Along with the
potential for some additional snowfall, it should bring a
reinforcing shot of cold air to the region, with temps likely
staying below freezing heading into the next workweek.
.AVIATION...(For the 00Z TAFS through 00Z Tuesday Evening)
Issued at 539 PM CST MON DEC 2 2013
For the KSGF/KJLN/KBBG tafs: The main concern is fog redevelopment
over the next few hours. A moist lower atmosphere remains in place
over the region. Unlike last night, somewhat stronger low level
south winds may help limit fog, at least early tonight, with overall
better chances along and south of the higher elevations of the MO
Ozarks plateau. The SREF progs have the highest probability for
dense fog and low stratus after 09z along and south of a
Pineville to Springfield to Rolla line. Will maintain IFR fog at
KSGF and KBBG with somewhat lower chances at KJLN. Any fog will
burn off between 15z-18z with moderately gusty south winds