Area Forecast Discussion
Issued by NWS St. Louis, MO
Issued by NWS St. Louis, MO
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598 FXUS63 KLSX 240856 AFDLSX Area Forecast Discussion National Weather Service Saint Louis MO 356 AM CDT Mon Jun 24 2024 .KEY MESSAGES... - Heat Advisory looks on track for central Missouri today. Heat will expand across much of the area along and south of I-70 for Tuesday so the Heat Advisory in central Missouri has been extended, and expanded east. - A cold front is expected to move through late Tuesday night. Widespread showers and thunderstorms are expected ahead of the front Tuesday night. Current indications are that some parts of the are could get an inch or more of rain. Additionally, some of the storms could be severe with damaging winds and large hail. && .SHORT TERM... (Through Tuesday Night) Issued at 353 AM CDT Mon Jun 24 2024 High pressure centered over the Midwest this morning will drift eastward causing the wind to swing around to the south today. This will bring warmer and more humid air back into the area, particularly into parts of central Missouri. High temperatures across the area should be between 2 and 7 degrees warmer than yesterday, with a corresponding increase in dew point. This pushes heat index values in central Missouri up to right around 105, so the Heat Advisory continues to look on track for today. There could be one fly in the ointment though. Widely scattered convection has developed over Iowa and is pushing into north central Missouri. While most guidance shows this convection dissipating before it reaches our area, there are some CAMs that show weak showers persisting past 17Z across parts of central and northeast Missouri. If this happens, the clouds and precip would likely suppress temperatures enough to spoil the advisory. However, the low level jet that`s forcing this convection weakens and backs slightly this morning according to the RAP and GFS, so I don`t think that scenario is very likely. Attention turns to Tuesday as persistent southwest flow continues the warm/moist advection into Missouri and Illinois. Some guidance numbers have come in a little cooler than previous runs, but widespread mid to upper 90s continues to look likely, and St. Louis may still hit 100. Afternoon heat index values rise rise into the 105+ range generally along and south of I-70, so we`ve extended the central Missouri heat advisory, and expanded it eastward through east central and southeast Missouri into southwest Illinois. There continues to be a chance for afternoon showers and thunderstorms, which could suppress temperatures, however low level forcing to trigger convection looks weak to non-existent so the chance for storms looks very low at this time. That will not be the case on Tuesday night as a cold front drops south from Iowa across Missouri and Illinois. The CAMs that go out that far show a complex of thunderstorms developing along the front, and then moving south into Missouri and Illinois as a linear MCS. Both the GFS and RAP shows some pretty beefy CAPE values in excess of 4000 J/Kg across northern Missouri and Iowa. The GFS loses a lot of that instability between 03-06Z Wednesday, but the RAP hangs on to 3500+ J/Kg through 6Z when the run ends. Luckily the deep-layer shear isn`t that strong across our area at only 15-20kts. However with that amount of instability the storms could certainly be capable of producing damaging wind gusts and large hail, most likely across northern portions of the forecast area during the late evening, possibly extending past 06Z and farther south. The other big story with these storms is the potential for substantial rainfall. Latest WPC QPF shows most of the area getting between 0.50 and 1.10 inches of rain which is more than most of the area has seen in several weeks. Carney && .LONG TERM... (Wednesday through Sunday) Issued at 353 AM CDT Mon Jun 24 2024 The remainder of the forecast looks relatively quiet. The short wave which is driving the front is forecast to move relatively slowly into the Mid-Mississippi Valley, which will cause the front to move slowly as well. This changes late Tuesday night as another wave which will be moving across the Upper Midwest phases up with southern wave. This amplifies the pattern and finally gives the front a shove south Wednesday morning. This will bring cooler temperatures in the mid to upper 80s to the area for Wednesday and Thursday. There will probably be some lingering showers and storms on Wednesday in the vicinity of the front, primarily across southern Missouri as the the two waves come into phase. Thursday looks dry as high pressure moves across the Midwest into the Great Lakes region. Heat and humidity return Friday as the high moves farther east and low level flow swings back to the south, although current indications are that it won`t be as hot as this recent stretch. LREF mean temperatures are in the low 90s Friday and Saturday, and even the 75th percentile doesn`t break the mid 90s either day. Medium range deterministic guidance is advertising another FROPA Saturday night/Sunday morning, and the LREF seems to agree with temperatures falling back into the low to mid 80s Sunday afternoon. Carney && .AVIATION... (For the 06z TAFs through 06z Monday Night) Issued at 1049 PM CDT Sun Jun 23 2024 VFR conditions persist under clear to mostly clear skies through the period. Light and variable surface winds turn southerly and increase by mid-morning Monday, but largely remain at or below 10 knots. Maples && .CLIMATE... Issued at 353 AM CDT Mon Jun 24 2024 With hot temperatures forecast, here are some of the daily high temperature records: MON JUN 24 TUE JUN 25 ST LOUIS 102 in 1988 102 in 1954 COLUMBIA 103 in 1988 102 in 1988 QUINCY 99 in 1988 102 in 1931 && .LSX WATCHES/WARNINGS/ADVISORIES... MO...Heat Advisory from noon to 8 PM CDT Tuesday for Audrain MO- Callaway MO-Crawford MO-Franklin MO-Gasconade MO-Iron MO- Jefferson MO-Lincoln MO-Madison MO-Montgomery MO-Osage MO- Reynolds MO-Saint Charles MO-Saint Francois MO-Saint Louis City MO-Saint Louis MO-Sainte Genevieve MO-Warren MO- Washington MO. Heat Advisory from noon today to 8 PM CDT Tuesday for Boone MO- Cole MO-Moniteau MO. IL...Heat Advisory from noon to 8 PM CDT Tuesday for Bond IL-Clinton IL-Madison IL-Monroe IL-Randolph IL-Saint Clair IL- Washington IL. && $$ WFO LSX