746 
FXUS63 KLSX 011142
AFDLSX

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
642 AM CDT Sat Apr 1 2023

.SHORT TERM...  (Through Late Sunday Afternoon)
Issued at 346 AM CDT Sat Apr 1 2023

Deep low pressure over Lake Michigan will move east-northeast into 
New England today.  High pressure currently over the northern Plains 
will move into the Midwest by late this afternoon/early evening. The 
pressure gradient between these two systems remains quite strong, 
and a secondary cold front is now moving quickly southeast through 
the forecast area, and should be through southeast 
Missouri/southwest Illinois by 13-15Z this morning.  Wind will 
increase from the west-northwest once again behind the front, and 
will stay strong and gusty at least through late morning.  All 
deterministic guidance points to sustained winds between 25-30kts 
across central through east central and northeast Missouri into west 
central and southwest/south central Illinois.  Even the 25th 
percentile HREF show these high values for sustained wind.  NBM 10th 
and 25th percentile are likewise showing 25+kts sustained this 
morning, so confidence is high in the Wind Advisory in these areas. 
Farther south across the eastern Ozarks the sustained winds will be 
a little lower, but forecast soundings from GFS/NAM/RAP indicate 
gusts in excess of 40kts are likely, and this agrees well with 
NBM/HREF 25th-75th percentile forecasts.  Have therefore reissued 
the Wind Advisory for our southeast Missouri counties and Randolph 
Illinois.  Strong cold advection behind the front will suppress 
temperatures this morning, and a broad area of low stratus will also 
move over the area behind the front, limiting insolation and further 
suppressing the normal diurnal warm up.  Clouds are forecast to 
scatter and move east this afternoon, and wind is still expected to 
diminish as the pressure gradient slackens, so we should still see 
an afternoon bump up in temperatures into the 50s in most locations.

As the high moves across the Midwest tonight, wind will become light 
and variable.  With the daytime stratocu gone, the clear sky should 
produce excellent radiational cooling conditions for much of the 
night across the area.  However, as the ridge axis crosses east of 
the Mississippi River after midnight, the wind will pick back up 
from the south which will likely bring the falling temperatures to a 
halt in the mid 30s well before sunrise Sunday morning.  The next 
upstream short wave trough will move across the northern Plains near 
the US/Canada border on Sunday, producing another rather deep 
surface low as it goes.  The pressure gradient between the ridge to 
our east and the low to the northwest tightens back up on Sunday and 
15-20kt wind with gusts up to 30kts look likely according to 
deterministic model soundings, particularly across central and 
northeast Missouri into west central Illinois.  HREF and NBM 25th-
75th wind gust forecasts also support another breezy to windy day 
for Sunday.  Strong warm advection/insolation with mostly sunny sky 
will allow temperatures to rebound into the upper 60s to low 70s in 
most locations.

Carney

.LONG TERM...  (Sunday Night through Friday)
Issued at 346 AM CDT Sat Apr 1 2023

The weather pattern still looks active into next week.  Sunday's 
shortwave and attendant surface low drags a cold front through most 
of the Midwest where it stalls near the Missouri/Iowa border into 
central Illinois Sunday night. Low level moisture return south of 
the front could produce some showers and a few thunderstorms across 
parts of the area Sunday night through Monday night.  Meanwhile, 
another long wave trough is forecast to dig across the eastern 
Rockies into the western Plains early Tuesday.  LREF cluster 
analysis products are showing increasing variance with respect to 
timing and amplitude of this trough as it closes off Tuesday morning 
and ejects northeast Tuesday night into early Wednesday.  That being 
said, the deterministic GFS and ECMWF handle this system very 
similarly on the 00Z run, and it looks very similar to the storm 
system which we just dealt with yesterday...potentially could be 
stronger.  Current solutions show the stacked low moving across the 
central Plains into the Upper Midwest Tuesday evening, with the cold 
front sweeping through our area between 06Z-12Z Wednesday.  Wind 
shear and instability ahead of the front looks sufficient for severe 
thunderstorms, potentially significantly severe.  Again...take all 
this with a large grain of salt, especially the timing, due to the 
uncertainties indicated in the cluster analysis.  After a windy 
Wednesday behind the front, it looks like Thursday and Friday will 
be tranquil as high pressure moves from the Great Plains across the 
Mississippi Valley.

Carney

&&

.AVIATION...  (For the 12z TAFs through 12z Sunday Morning)
Issued at 633 AM CDT Sat Apr 1 2023

Strong west-northwest wind sustained in around 25kts with gusts in
excess of 40kts will continue this morning. This will cause
crosswind issues on north-south oriented runways. Winds will
diminish slowly from late morning through the afternoon, and 
gusts should be about done by 23-01Z. Light wind tonight will turn
to the south Sunday morning as a ridge axis moves east of the 
area. Otherwise, the stratus deck over central and northeast 
Missouri and west central Illinois will continue to spread 
southeast this morning. Expect most of the MVFR to be confined to 
northeast Missouri and west central Illinois this morning. 
Ceilings will lift and scatter from west to east this afternoon. 
Expect a clear sky for most of the area by late afternoon/early 
evening.

Carney

&&

.PRELIMINARY POINT TEMPS/POPS...
Saint Louis     53  37  67  53 /   0   0   0  20 
Quincy          51  33  67  48 /   5   0   0  20 
Columbia        55  36  71  50 /   0   0   0  30 
Jefferson City  56  36  72  51 /   0   0   0  20 
Salem           50  33  62  50 /   0   0   0  20 
Farmington      54  34  66  50 /   0   0   0  20 

&&

.LSX WATCHES/WARNINGS/ADVISORIES...
MO...Wind Advisory until 1 PM CDT this afternoon for Audrain MO-Boone 
     MO-Callaway MO-Cole MO-Crawford MO-Franklin MO-Gasconade MO-
     Iron MO-Jefferson MO-Knox MO-Lewis MO-Lincoln MO-Madison MO-
     Marion MO-Moniteau MO-Monroe MO-Montgomery MO-Osage MO-Pike 
     MO-Ralls MO-Reynolds MO-Saint Charles MO-Saint Francois MO-
     Saint Louis City MO-Saint Louis MO-Sainte Genevieve MO-
     Shelby MO-Warren MO-Washington MO.

IL...Wind Advisory until 1 PM CDT this afternoon for Adams IL-Bond IL-
     Brown IL-Calhoun IL-Clinton IL-Fayette IL-Greene IL-Jersey 
     IL-Macoupin IL-Madison IL-Marion IL-Monroe IL-Montgomery IL-
     Pike IL-Randolph IL-Saint Clair IL-Washington IL.

&&

$$

WFO LSX