Monday Night: Mostly clear. Low: 45
Tuesday: Scattered clouds, isolated PM showers/T-storms. High: 76
Tuesday Night: Mostly cloudy. Low: 56
Wednesday: Partly cloudy, possible PM showers. Breezy. High: 79
Wednesday Night: Cloudy and breezy. Showers/T-storms late. Low: 62
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Discussion: After a quiet start to the week, the chance for rain returns. Tuesday will certainly not be a wash out, but very isolated showers and thunderstorms will be possible in the afternoon. Rain chances begin to increase again Wednesday afternoon, with showers and thunderstorms moving through Wednesday night into Thursday.
-Shaw ================================================================
Forecasters: Shaw, Russell
Date Issued: 4/17/2023 5:00PM CDT
Technical Discussion:
Sensible weather is off to a quiet start this week in the wake of Saturday's severe weather. Modest ridging looks to set up across the Mississippi River Valley Tuesday and Wednesday before low pressure ejects off of the inter-mountain West, bringing unsettled conditions in by Thursday morning. Currently have three periods of interest for precipitation: one Tuesday afternoon associated with a weak shortwave, one Wednesday afternoon associated with diurnal heating, and a more well-defined band Thursday along and ahead of the cold front. Generally speaking, the GFS trends the upper-level low further south than the EURO or NAM, resulting in more liberal moisture advection and precipitation totals. As such, the EURO and NAM were relied upon more for this forecast period.
At the start of the period, the closed low responsible for our weekend storms is occluding over southern Ontario, ushering in northwesterly flow across MO. Ridging in all levels begins to slide in early Tuesday morning, with a weak but defined warm front setting up across southern MO during this time. By early afternoon, this front should be draped north of Columbia, bringing in increased moisture and warm air advection. By the afternoon, a subtle shortwave in the mid and upper levels may provide just enough of a kick to initiate isolated showers and storms in the vicinity of the front, but coverage is expected to be quite low across the region, especially due to lackluster mid-level moisture. Thus, most areas will stay dry on Tuesday.
As the ridge axis passes through Wednesday morning, flow at all levels turns more southwesterly, further enhancing low and mid-level moisture return. At the same time, a closed surface low will eject into the TX and OK Panhandle region, also contributing to our S/W flow regime. Consequently, the LLJ will ramp up Wednesday morning. By Wednesday afternoon, surface temperatures will be in the upper 70s, with dew points in the low 60s. It is possible, given this airmass, that isolated showers and thunderstorms could form across central MO; however, a capping inversion will significantly hinder the likelihood for convection. Current guidance suggests that Wednesday will stay dry, though precipitation chances are not zero. Additionally, surface winds will begin to pick up Wednesday afternoon as the pressure gradient tightens across the central US with the deepening low. Gusts could reach into the upper 20mph range, especially by Wednesday evening.
Heading into early Thursday morning, upper-level low pressure over MT will push the jet stream south across western MO. Concurrently, the surface-low located over NW MO will continue to drive rich moisture into the region. Still, some uncertainty exists regarding the timing of precipitation, with the GFS bringing showers and thunderstorms into central MO by 12z and the NAM/EURO trending slightly later. Model soundings indicate that conditions will be in place for marginal severe weather Thursday morning, with nicely veered wind profiles, LI of -8, and CAPE over 1000J/kg present ahead of the cold front. Future shifts will want to monitor the progression of these features to nail down timing and possible impacts of this round. Forecast rain totals by the end of the period (14z Thursday) are between .3-.5", though precipitation will still be ongoing at this time.
At the start of the period, the closed low responsible for our weekend storms is occluding over southern Ontario, ushering in northwesterly flow across MO. Ridging in all levels begins to slide in early Tuesday morning, with a weak but defined warm front setting up across southern MO during this time. By early afternoon, this front should be draped north of Columbia, bringing in increased moisture and warm air advection. By the afternoon, a subtle shortwave in the mid and upper levels may provide just enough of a kick to initiate isolated showers and storms in the vicinity of the front, but coverage is expected to be quite low across the region, especially due to lackluster mid-level moisture. Thus, most areas will stay dry on Tuesday.
As the ridge axis passes through Wednesday morning, flow at all levels turns more southwesterly, further enhancing low and mid-level moisture return. At the same time, a closed surface low will eject into the TX and OK Panhandle region, also contributing to our S/W flow regime. Consequently, the LLJ will ramp up Wednesday morning. By Wednesday afternoon, surface temperatures will be in the upper 70s, with dew points in the low 60s. It is possible, given this airmass, that isolated showers and thunderstorms could form across central MO; however, a capping inversion will significantly hinder the likelihood for convection. Current guidance suggests that Wednesday will stay dry, though precipitation chances are not zero. Additionally, surface winds will begin to pick up Wednesday afternoon as the pressure gradient tightens across the central US with the deepening low. Gusts could reach into the upper 20mph range, especially by Wednesday evening.
Heading into early Thursday morning, upper-level low pressure over MT will push the jet stream south across western MO. Concurrently, the surface-low located over NW MO will continue to drive rich moisture into the region. Still, some uncertainty exists regarding the timing of precipitation, with the GFS bringing showers and thunderstorms into central MO by 12z and the NAM/EURO trending slightly later. Model soundings indicate that conditions will be in place for marginal severe weather Thursday morning, with nicely veered wind profiles, LI of -8, and CAPE over 1000J/kg present ahead of the cold front. Future shifts will want to monitor the progression of these features to nail down timing and possible impacts of this round. Forecast rain totals by the end of the period (14z Thursday) are between .3-.5", though precipitation will still be ongoing at this time.
-Shaw
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