Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 280604

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
1204 AM CST Mon Nov 28 2016

.SHORT TERM...  (Through Late Monday Afternoon)
Issued at 249 PM CST Sun Nov 27 2016

Low pressure strengthening over eastern Colorado and Wyoming will
move northeast over the next 24 hours ending up in southeast North
Dakota by 00Z Tuesday.  Low strengthens to 974-976mb overnight and
Monday...and the low level jet ahead of it is impressive as a
result.  Strong low level warm advection and moisture convergence
due to the jet is already producing areas of showers with a few
embedded thunderstorms over eastern Kansas and western-central
Missouri.  This convection should continue to spread east/northeast
through the evening into tonight.  Expect greatest coverage/highest
rainfall amounts to be north of the Missouri river tonight.
Temperatures won`t fall off all that much...maybe 4-5 degrees from
this afternoon`s highs during the evening...and then will
probably hold steady or rise a bit overnight due to the strong
southerly flow.

Another wave of showers will develop during the pre-dawn hours of
Monday morning in response to the mid-level trof digging into the
Great Plains.  The trof starts to take a negative tilt during the
day which will shove that wave of precip northeast through Arkansas
and much of eastern Missouri and Illinois by late morning into
early afternoon.  This will probably be our best chance at
thunderstorms as MUCAPE values max out in the 300-
500 J/Kg range during the afternoon ahead of the surface cold front
associated with this system.  Highs will likely be a bit warmer on
Monday since we`ll start the day out 10-15 degrees warmer than this
morning...but clouds and precip will likely keep temperatures
suppressed in the mid to upper 50s.


.LONG TERM...  (Monday Night through Next Sunday)
Issued at 249 PM CST Sun Nov 27 2016

Precipitation will largely be exiting stage right Monday evening as
the upper level trof axis quickly swings across the region. Given
the occluding nature of the main storm system, well removed to our
northwest, there will be almost a 24 hour delay in the cold air
arriving behind the precipitation. In fact, latest model guidance
continues to advertise temperatures climbing well into the 60s on
Tuesday ahead of the cold front.

Once the cold front does go through late Tuesday afternoon and
evening the wind will shift to the west/northwest and a steady feed
of cold air advection will guarantee that temperatures will be
closer to normal the remainder of the work week and into next
weekend with dry conditions.



.AVIATION...  (For the 06z TAFs through 06z Monday Night)
Issued at 1144 PM CST Sun Nov 27 2016

Busy fcst prd with another chance for rain and IFR conditions on
Mon. Strong storm system will not move much as it continues to
sit and spin across the ern Dakotas keeping gusty sthrly winds
going thru Mon aftn. The initial band of precip will clear the STL
metro area terminals by 7Z with ISLD SHRAs thru the rest of the
night. There could be a TSTM or two overnight as well. A few
report of LLWS have also been kept the LLWS going
thru the remainder of the night. MVFR CIGS will slowly spread E
overnight. Meanwhile, another batch of precip will move out of AR
Mon mrng and move NE impacting locations mainly along and E of
I-44 in MO and I-70 in IL. This is where the best chance for IFR
conditions exist collocated with the most persistent rain...and
possibly a TSTM. The STL metro area will be on the wrn fringe of
the precip and therefore the IFR conditions. There will also be a
small chance for ISLD TSTMs across cntrl and NE MO tomorrow aftn.
Clouds and precip clear from W to E from late tomorrow aftn into
Mon evng.


Active prd with another chance for precip and IFR/MVFR flight
conditions Mon. Main band of precip this evng has shifted E of the
terminal. Remainder of the night should feature ISLD SHRAs with
an outside chance for a rumble of thunder. MVFR CIGS will slowly
work into the terminal near 12Z. Kept LLWS going since there a few
reports across the area this evng. Another batch of precip
overspreads the STL metro area Mon mrng and continues thru much
of the aftn. The metro area will be on the wrn fringes of the
IFR conditions. It will be a close call. Conditions improve Mon
evng as the rain lifts NE and skies clear by 06Z.





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