Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 202028
AFDLSX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ST LOUIS MO
328 PM CDT Wed May 20 2015

.SHORT TERM:  (Through Late Tonight)
Issued at 327 PM CDT Wed May 20 2015

The shortwave causing today`s rain is nearly through the area, and
the last vestiges of the rain are now moving through east central
Missouri.  Some lingering light rain may continue past 00Z in our
far eastern Illinois counties, but should be ending shortly
thereafter.  Primary concern for tonight after the rain ends will be
clouds and temperatures.  The clearing line is way up in South
Dakota and Minnesota and doesn`t look to be moving too fast.  Think
we may see some faster clearing than what`s occuring now as the wave
moves further east and drier air funnles south into the region, but
the majority of the area will likely stay cloudy/mostly cloudy.
Stuck close to the colder guidance numbers for lows tonight.  Lows
last night back in the plains were mostly in the low 40s and upper
30s so going with the colder numbers seemed reasonable.

Carney

.LONG TERM:  (Thursday through Tuesday)
Issued at 316 AM CDT Wed May 20 2015

High pressure remains in place on Thursday and Friday. An upper
ridge also builds over the central US on Friday then amplifies on
Saturday ahead of a deepening trough over the western half of the
US. Several disturbances lift through the trough between Saturday
and Monday. These disturbances should bring a period of unsettled
weather to the forecast area, especially between Sunday and
Tuesday. Similar to the last two weekends, day to day
precipitation chances will depend both on synoptic scale
shortwaves and on any MCVs which form upstream. Refinements are
likely. Temperatures begin to warm up again on Saturday when winds
become southerly around the retreating surface high. A more
noticeable jump in warmth is expected on Sunday after a warm
frontal passage.

42

&&

.AVIATION:  (For the 18z TAFs through 18z Thursday Afternoon)
Issued at 1037 AM CDT Wed May 20 2015

Low pressure and associated rain will move east across the area
today. Rain will end gradually west to east throught the
afternoon. As the upper trof begins digging a bit to the
southeast upper flow will become northwest overight. Main question
is what will the clouds do overnight into Thursday. NAM guidance,
as usual, hits this the hardest with lots of IFR. With some
cyclonic flow aloft and light northerly winds am inclined to keep
at least MVFR ceilings overnight, although IFR is possible at
times.

Specifics for KSTL: Main question will be whether to go IFR
overnight. Rain will continue this afternoon, with the heavier
stuff ending early this afternoon and light, intermittent rain
continuing. IFR clouds have formed behind the rain back to Kansas
City and it looks that will also develop here. Right now am
leaning toward the more pessismistic NAM guidance which keeps IFR
ceilings in until about 14-15z. VFR may not return until 18z or a
little later Thursday.

JPK

&&

.CLIMATE:
Issued at 316 AM CDT Wed May 20 2015

Record cool high temperatures for May 20th are as follows.

St. Louis, MO....55/1924 (KSTL)
Columbia, MO.....57/1924 (KCOU)
Quincy, IL.......57/1967 (KUIN)
Farmington, MO...66/1954 (co-op station)


&&

.PRELIMINARY POINT TEMPS/POPS:
Saint Louis     44  64  52  74 /  10   5   0   5
Quincy          40  66  49  73 /  10   5   0   5
Columbia        43  64  48  71 /  10   5   0  10
Jefferson City  43  65  47  72 /  10   5   0  10
Salem           45  62  48  73 /  20   5   0   5
Farmington      42  62  42  72 /  10   5   0  10

&&

.LSX WATCHES/WARNINGS/ADVISORIES:
MO...NONE.
IL...NONE.
&&

$$

WFO LSX






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