596 
FXUS63 KLSX 061727
AFDLSX

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
1127 AM CST Sun Nov 6 2022

.SHORT TERM...  (Through Late Monday Afternoon)
Issued at 230 AM CST Sun Nov 6 2022

A longwave upper-level trough now dominates the flow pattern across 
the western two-thirds of the CONUS, and the very dynamic system 
that brought widespread beneficial rain and strong gusts over the 
last 36 hours is far to our north in southeast Canada. At the 
surface, the Mid-Mississippi Valley has already returned to 
southwest flow in the wake of a strong cold front. This wind 
direction and 850mb around 10-12C will aid in bolstering 
temperatures today nearly 10F above normal for those along and
south of I-70 in Missouri and Illinois. North of I-70, temperatures
will be slightly cooler as a weak cold front drops south this 
afternoon. With no appreciable upper-level support and pitiful 
moisture return ahead of the boundary, the front will traverse the
CWA without precipitation. The only evidence of the front's 
passage will be a wind shift to the north through the afternoon 
and evening.

Weak north/northeast winds tonight into tomorrow will keep 
temperatures near normal, which deviates from previous forecasts 
that depicted warmer than normal temperatures. A majority of 
guidance now suggests the northerly/northeasterly winds will 
suppress temperatures more than previously forecast. The latest 
HREF struggles to find temperatures warmer than 60F across most of
the CWA, with the exception of far southeast Missouri and 
southwest Illinois. Winds will gradually take on a more easterly 
direction as the surface high across the Northern Plains slowly 
slides east Monday.

MRB

.LONG TERM...  (Monday Night through Saturday)
Issued at 230 AM CST Sun Nov 6 2022

Key messages through next weekend:

1) Abnormal warmth returns to the region Wednesday and Thursday, 
with temperatures approaching record highs.

2) A robust cold front brings renewed precipitation chances areawide 
Thursday night into Friday, but indications are that amounts will be 
light.

3) Much colder temperatures (likely the coldest of the season so 
far) are likely behind the front next weekend.

The upper-level flow pattern begins to amplify on Tuesday in 
response to a deepening trough in the Pacific Northwest, which will 
aid the low-level wind field in becoming more southeasterly (and 
eventually southerly) with time. Temperatures will likely be 
marginally warmer on Tuesday with the southerly wind component, 
but mixing appears rather shallow during the afternoon and we 
likely won't be able to tap into warmer temperatures aloft to 
raise surface temperatures further. The low precipitation chances
across central Missouri are even lower still with this forecast. 
While some low-level moisture does move north during the 
afternoon and evening on Tuesday, mid-level moisture is at a 
premium where better forcing exists. As such, PoPs were removed 
and the CWA will likely remain dry.

Ensemble and deterministic guidance is in fair agreement that 
mid-level heights will reach record values compared to 
climatology Tuesday into Wednesday, along with more southerly low-
level winds on Wednesday throughout the boundary layer. 850mb 
temperatures will warm above the 90th climatological percentile as
a result, which will likely send temperatures into the mid-70s 
(just below records) across most of the region. The ECMWF Extreme 
Forecast Index continues to support high temperatures at or above 
the 90th climatological percentile Wednesday, and now indicates a 
low potential for near-record temperatures in central Missouri. 
Thursday now appears to be almost as warm ahead of a strong cold 
front, though cloud cover will likely prevent Thursday from being 
warmer than Wednesday.

Better consensus among the available guidance now exists regarding 
the timing and position of a cold front that will bring a decisive 
end to the abnormally-warm weather. The trough across the western 
CONUS will move east through mid-week, approaching the Mid-
Mississippi Valley by late Thursday. Cluster analysis guidance 
depicts a majority (~85%) of the ensemble members now show a less-
amplified mid-level trough in our region, restricting the more 
impressive dynamics further to our north. Upper-level jet dynamics 
are also rather unimpressive as depicted by deterministic guidance, 
which would stifle widespread lift (and thus precipitation) along
and ahead of the cold front. While parts of the CWA will see 
rain, likely late Thursday through Friday morning, it doesn't 
appear that rainfall totals will be notable in the absence of 
strong upper- level dynamics. Ensemble probabilities of exceeding 
0.5" are ~20-30% at most, and those highest probabilities are 
restricted to northeast/central Missouri and west-central Illinois
where the best forcing will exist. It's also unlikely that any
wintry precipitation will accompany the front, despite the cold 
air behind it, given the lack of much moisture for the cold air 
with which to interact. While brief rain/snow mix in northeast 
Missouri and west-central Illinois cannot be ruled out as the 
front passes, accumulations are very unlikely.

The more notable aspect of the cold front will be the much-cooler 
air that will be ushered into the region behind it. Confidence in 
below-normal temperatures is high given the consistency among the 
ensemble guidance. CIPS Extended Analogs from Saint Louis University 
also highlights the region for a high likelihood of below-normal 
temperatures, and suggests high temperatures up to 10F below 
normal Friday into the weekend. Exactly how cold it will be 
remains far from a certainty, with ensemble guidance differing 
regarding 850mb temperatures during that period. However, it is 
likely that this cold front will be the harbinger of a pattern 
shift and bring the coldest air of this season to our region.

MRB

&&

.AVIATION...  (For the 18z TAFs through 18z Monday Afternoon)
Issued at 1103 AM CST Sun Nov 6 2022

Dry and VFR conditions are expected through the period. South to
southeast winds will turn out of the north late this afternoon and
this evening as a cold front moves southeast across the area.
Winds will increase out of the northeast and become gusty on
Monday morning.

Britt

&&

.CLIMATE...  
Issued at 1103 AM CST Sun Nov 6 2022

Wednesday (11/9) High Maximums

Columbia   78 (1999)
Quincy     76 (1999)
St. Louis  78 (2020)

Thursday (11/10) High Minimums

Columbia   58 (2012)
Quincy     59 (2012)
St. Louis  62 (1902)


&&

.LSX WATCHES/WARNINGS/ADVISORIES...
MO...None.
IL...None.
&&

$$

WFO LSX