496 FXUS63 KLSX 150830 AFDLSX Area Forecast Discussion National Weather Service Saint Louis MO 330 AM CDT Mon Apr 15 2019 .SHORT TERM... (Through Late Tuesday Afternoon) Issued at 330 AM CDT Mon Apr 15 2019 Will leave the ongoing Frost Advisory as-is, although, conditions across central MO are not great. That said, the more sheltered locations should still see frost. Surface ridge axis continues to shift east early this morning. Strong low to mid level WAA is generating clouds across NW MO into IA/NEB region. This area of WAA should persist as it moves east today. While the NAM/GFS suggest dry conditions, the RAP/HRRR solutions suggest WAA that is strong enough and in lower levels that isolated to scattered showers may develop this later morning, perhaps lingering into the afternoon hours. Confidence is low that showers will develop to the point that measurable precip will reach the ground, but believe that the situation is worthy of a slight PoP. As the surface ridge continues to build east today, surface flow becomes southerly with strong WAA thru low levels. This should allow temperatures to quickly rebound into the 60s to around 70. Given the strong WAA and deep mixing, have trended toward the warmer guidance today and again Tues. Expect mixing to persist overnight tonight and have therefore also trended toward the warmer guidance. With the developing low across the Plains through Tues and the increasing pressure gradient, expect wind gusts to be around 20 kts during the late morning and afternoon hours. Tilly .LONG TERM... (Tuesday Night through Sunday) Issued at 330 AM CDT Mon Apr 15 2019 (Tuesday Night - Wednesday) A return to a more active weather pattern begins to take shape on Tuesday night. While the CWA will be in the warm sector well south of a warm front draped west to east from Nebraska through Pennsylvania, low-level moisture convergence should be strong enough to produce at least isolated elevated convection late Tuesday night into early Wednesday morning. One main limiting factor preventing more widespread coverage appears to be mid/upper level ridging and associated subsidence. Dry weather is likely Wednesday afternoon after some weakening of the low-level jet. As expected within the warm sector, temperatures are forecast to be on the mild side. Low temperatures Tuesday night should only drop into the upper 50s to near 60 degrees with high temperatures on Wednesday in the upper 70s to near 80F. These temperatures would be about 10-15 degrees above normal for the middle of April. (Wednesday Night - Thursday) The threat for showers and thunderstorms will increase quickly Wednesday night as a strong shortwave trough ejects out of the south- central Plains. At the surface, an area of low pressure is forecast to strengthen as it moves through the Upper Midwest. The cold front attendant to this low will slowly move eastward late Wednesday night and Thursday across the CWA. This slow-moving front will serve as the focus for showers and thunderstorms through the period, some of which may be strong to severe. Timing of the front is certainly not ideal for severe weather, with convection potentially weakening overnight Wednesday into Thursday morning. Storms may then re- intensify Thursday afternoon if the atmosphere is able to recover from morning convection, but this may occur just east of the CWA across the lower Ohio River Valley. However, with favorable deep- layer shear, steep midlevel lapse rates, and at least modest instability, there certainly is the potential for strong to severe thunderstorms. If the timing of this system changes slightly, the threat may further increase. Temperatures will be very mild Wednesday night ahead of the front with lows only in the upper 50s to low 60s. Highs on Thursday are fairly uncertain due to subtle differences in frontal passage and probability of convection, but the general expectation at this time is for temperatures to reach the 60s to low 70s. (Thursday Night - Sunday) A closed upper-level low is forecast to develop by medium-range guidance across the Mississippi Valley. Exactly at what latitude is the major question mark. Secondary cyclogenesis is likely to occur somewhere to our east putting the mid-Mississippi Valley on the cool side of this cyclone. Light rain is likely to the northwest of the surface low along with much cooler than normal temperatures on Friday. However, due to the high uncertainty of the track of this surface low, went with a conservative approach with highs on Friday which resulted in mid to upper 50s. Temperatures are forecast to moderate by Sunday as the closed low moves eastward toward the east coast and surface winds return out of the south. Gosselin && .AVIATION... (For the 06z TAFs through 06z Monday Night) Issued at 1144 PM CDT Sun Apr 14 2019 Still looking at the potential for radiational fog overnight into the early morning hours at KSUS, KCPS, and KUIN. Otherwise high and mid clouds will gradually spread across the area overnight and then thin/exit to the east by early Monday afternoon. Increasing south-southeast winds are expected from late Monday morning through the afternoon. SPECIFICS FOR KSTL: VFR flight conditions are expected through the forecast period with high and mid clouds gradually spread into the area overnight and then thinning/exiting to the east by early Monday afternoon. Increasing south-southeast winds are expected from late Monday morning through the afternoon. Glass && .PRELIMINARY POINT TEMPS/POPS... Saint Louis 65 56 81 59 / 0 0 0 10 Quincy 61 52 78 57 / 20 0 0 20 Columbia 71 54 80 60 / 0 0 0 20 Jefferson City 72 55 81 61 / 0 0 0 20 Salem 61 52 78 57 / 0 0 0 5 Farmington 66 53 78 58 / 0 0 0 10 && .LSX WATCHES/WARNINGS/ADVISORIES... MO...Frost Advisory until 9 AM CDT this morning for Audrain MO-Boone MO-Callaway MO-Cole MO-Crawford MO-Franklin MO-Gasconade MO- Iron MO-Jefferson MO-Lincoln MO-Madison 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-Warren MO-Washington MO. IL...Frost Advisory until 9 AM CDT this morning for Bond IL-Calhoun IL-Clinton IL-Fayette IL-Greene IL-Jersey IL-Macoupin IL- Madison IL-Marion IL-Monroe IL-Montgomery IL-Randolph IL- Saint Clair IL-Washington IL. && $$ WFO LSX