Area Forecast Discussion
Issued by NWS Sioux Falls, SD
Issued by NWS Sioux Falls, SD
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771 FXUS63 KFSD 271130 AFDFSD Area Forecast Discussion National Weather Service Sioux Falls SD 630 AM CDT Mon May 27 2024 .KEY MESSAGES... - Scattered showers and thunderstorms near and east of a line from Huron to Sioux Falls to Storm Lake this afternoon and evening. An isolated stronger storm east of MN/IA State Highway 60 could produce wind gusts to 60 mph and hail to quarter size, but overall severe risk remains very low. - Isolated showers and storms are possible again Tuesday for the same locations, but most stay dry. Otherwise, more widespread rain and storm chances return Wednesday night into the weekend. - Temperatures largely near average for this time of year with periodic breezy conditions. Strongest winds expected today and Thursday. && .DISCUSSION... Issued at 304 AM CDT Mon May 27 2024 TODAY: First wave of the day continues to move east across the area early this morning, with showers and brief heavy rainfall. Amounts this morning have generally been around or less than a tenth of an inch. This continues to move east through mid morning, although some isolated showers may linger in southwestern MN into mid morning. Showers are occasionally mixing down some stronger wind gusts to around 30 mph. Temperatures through this morning remain in the 50s. Next wave poised to impact the area is currently evident on water vapor across southwestern ND and northwestern SD. This tracks southeast through the day. Surface low pressure swings across southern MN through the afternoon hours, tightening the surface pressure gradient (SPG). We`ll see breezy conditions today not only from the strengthening SPG, but also as we mix into stronger winds aloft. Sustained northwesterly winds will reach as high as 25 mph, with gusts around 35 mph (although a few gusts to 40 mph are possible if mixing is a bit deeper into the stronger and colder air aloft). Scattered showers and storms are possible with this wave, mainly along and east of a Huron to Sioux Falls to Storm Lake line. Deterministic models and soundings have increased the amount of expected instability, with anywhere from 500 to 1500 J/kg of CAPE. Severe risk remains very low given overall lack of shear (less than 30 knots) and instability, but can`t rule out a stronger storm or two which may produce wind gusts to 60 mph or quarter sized hail. Greatest concern with any storm, especially a stronger storm, would be the potential for strong wind gusts as high as 60 mph given the stronger and colder air aloft. Freezing levels around or less than 6kft could support hail to the very isolated instances of quarter sized hail. Rainfall amounts less than a tenth of an inch for most, although 0.25" is possible with thunderstorms. Highs today in the upper 60s to mid 70s. TONIGHT THROUGH WEDNESDAY: Shower and storm chances taper off through the evening hours, as do the stronger winds. Lows tonight fall into the mid/upper 40s. By Tuesday morning, another mid level wave drops through MN, bringing isolated showers and storms to the same areas Tuesday morning into the afternoon. Coverage should be more isolated given the wave being a bit further off to the northeast and weaker than today`s wave. Rainfall amounts less than a tenth of an inch expected. With less instability to work with, severe weather is not expected. Highs will be a couple degrees cooler on Tuesday with the next push of CAA and northwesterly flow. Quick moving ridge and surface high slide overhead into Wednesday, with dry and warmer conditions prevailing. Winds increase west of the James River late in the day as the next system ejects out of the Rockies. WEDNESDAY NIGHT ONWARD: Aforementioned system ejects out of the Rockies Wednesday night into Thursday. This will continue to move northeast through the latter part of the week, keeping shower and storm chances in place. Additional short waves are progged to move through late week into the weekend, although past mid day Friday, solutions vary too widely to stray from the NBM for timing/location/strength of any system. Ensembles continue to show low (< 40%), but non-zero chances for severe weather late week into the weekend; however, very low confidence given the model uncertainty. Ensemble guidance shows a moderate to high chance (> 60%) of rainfall totals along/west of I-29 exceeding 0.25" Thursday into Friday. Regardless of storm chances, periodic breezy conditions with temperatures near normal. && .AVIATION /12Z TAFS THROUGH 12Z TUESDAY/... Issued at 623 AM CDT Mon May 27 2024 Area of showers and isolated storms will exit the KCKP/KSLB/KSPW region by 13z. Will begin to see another area of showers move into the KHON area by 12-13z; however, with more sparse coverage, will leave as VCSH for now. Additional showers and isolated storms are expected to develop this afternoon and evening along and east of a KHON to KFSD to KSLB line. However, given sparse nature and uncertainty in coverage, will omit from KHON and KFSD TAFs for now. Winds with storms could gust around or over 45 knots and produce small hail. Although risk is low, a stronger storm could produce winds near 50 knots and quarter sized hail (risk greatest along/east of MN/IA State Hwy 60). Have seen some patchy CU around 1500 ft this morning; however, expect these to remain FEW but will monitor trends. Otherwise, outside of brief heavy rain dropping visibility to MVFR categories, VFR conditions are expected to prevail. Northwesterly winds increase through the morning. Sustained winds around 20 knots and gusts to 30 knots prevail outside of any convection. Winds and gusts taper off after sunset. && .FSD WATCHES/WARNINGS/ADVISORIES... SD...None. MN...None. IA...None. NE...None. && $$ DISCUSSION...SG AVIATION...SG