Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 142322

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
522 PM CST Tue Feb 14 2017

.SHORT TERM...  (Through Late Wednesday Afternoon)
Issued at 307 PM CST Tue Feb 14 2017

Weak frontal boundary continues to slowly slide south this
afternoon, eventually washing out over southern Missouri tonight. In
the meantime, most of area to remain dry, but could see some light
rain creep back into far southern portions of forecast area briefly
this evening. With northwest to north winds, colder air to filter in
with lows in the upper 20s to lower 30s under clearing skies.

Surface ridge to build in to our southwest on Wednesday, so light
north to northwest winds to persist. Despite northerly flow,
temperatures will still rebound under mostly sunny skies into the
40s with warmest temps along and south of I-70 corridor in Missouri.


.LONG TERM...  (Wednesday Night through Next Tuesday)
Issued at 307 PM CST Tue Feb 14 2017

The synoptic pattern at the start of the long term period will
feature a developing Rex Block pattern, with an amplified ridge
across the western CONUS, and a weak trough undercutting this ridge
well to the south across northern Mexico.  This ridge will build
into the central CONUS by late this week into early next week,
providing a prolonged period of mostly dry and unseasonably warm

A strong eastern trough will be moving of the Northeast Coast on
Thursday, allowing heights to build across the Midwest.  At the
surface, a high pushing off to the southeast and a low pressure
system developing in the Northern Plains will place the Midwest
within southwesterly surface flow.  These southwesterly winds
coupled with plenty of sunshine and dry soils will likely lead to
overachieving temperatures once again, thus have gone above the
guidance consensus for high temperatures.  This puts readings in
the mid to even upper 60s.

The same regime continues for Friday, with even higher low-level
thicknesses.   Therefore, think temperatures will be even warmer
than Thursday, likely rising into the upper 60s and low 70s Friday
afternoon! Will have to keep an eye on the weak southern stream
trough as it slides northeast Saturday into Sunday.  It could
provide just enough weak ascent to bring some showers to southeast
MO and southern IL. Additionally, it could also spread some some
thicker cloud cover into the area, especially on Saturday, helping
to keep temperatures "only" in the mid to upper 60s.  Otherwise,
temperatures Sunday and Monday will climb into the upper 60s/low
70s.  This is a really impressive stretch of warmth we are about to
experience for mid-February.

Yet another piece of energy will cut off over TX/Mexico early next
week while the northern stream remains active. Given the strong
ridging/blocking pattern in place, suspect this system will continue
to slow down as we have seen in the past few model runs. Therefore,
have delayed pops until Monday night, and even this may be too
early. We will have to watch how this system evolves as we could
be split by the better PV anomalies passing to our north and to
our south, which would cause us to miss out on some much needed
rainfall. Stay tuned!



.AVIATION...  (For the 00z TAFs through 00z Wednesday Evening)
Issued at 521 PM CST Tue Feb 14 2017

VFR with northwesterly to northerly winds through the period.





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