Area Forecast Discussion
Issued by NWS Sioux Falls, SD
Issued by NWS Sioux Falls, SD
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599 FXUS63 KFSD 051739 AFDFSD Area Forecast Discussion National Weather Service Sioux Falls SD 1239 PM CDT Sun May 5 2024 .KEY MESSAGES... - Conditions will continue to trend warmer into the early part of the week with highs returning to upper 60s and low 70s for today and Monday. - Winds may near advisory levels on Monday afternoon in areas along and west of I-29. - A few strong to severe storms will be possible Monday afternoon and evening, with the greatest severe threat currently focused along and south of the lower Missouri River corridor into parts of northwestern IA. - Periodic rain chances continue for much of the upcoming week, with highs in the 60s to lower 70s. && .DISCUSSION... Issued at 400 AM CDT Sun May 5 2024 Look for a pretty decent day ahead as surface high pressure continues to exert its influence across the region. While the surface ridge axis is located directly over our area this morning, it will shift eastward during the day - into the Mississippi Valley by this evening. Winds will be southerly in a weak warm air advection regime on the backside of the high, and this will result in warmer temperatures for today. With 850 mb temperatures of 7 to 10 degrees across the area, look for highs in the upper 60s to lower 70s. A deepening surface trough over eastern MT and WY will result in an increasing surface pressure gradient (SPG) across our area, and this will result in increasing winds by the afternoon. This will be most pronounced west of Interstate 29 where the SPG is tighter and winds at the top of the mixed layer are higher. Tonight will see an increase in cloudiness - this as the aforementioned surface trough continues to deepen and shift into western SD, as an upper level low moves out of the Four Corners region into eastern WY and CO overnight. As the SPG continues to tighten over our area, winds will remain breezy during the night time hours. With the breezy conditions and warm air advection, it will be a mild night for this time of year with lows in the upper 40s to lower 50s. The upper level low lifts through western NE and western SD/ND on Monday and Monday night, while the surface low shifts northward through the western Dakotas - pulling a warm front northward across the region. With that, showers and thunderstorms will return to our area for Monday and Monday night. There remains a potential for strong to severe storms over the area on Monday afternoon/evening - as outlined in the SPC Day 2 convective outlook (a Slight risk [level 2 of 5] through the lower MO River Valley/northeast NE/parts of northwest IA and a Marginal risk [level 1 of 5] north to around the I-90 corridor). There are caveats however, with most models indicating instability on the lower side - generally less than 1000 J/KG. At the same time, ensembles continue with low probabilities of CAPE greater than 1000 J/KG - at only 10-20% over our area. The latest CSU machine learning probabilities are on the lower side for severe weather, with CIPS analog probabilities also on the lower side - 10-15%. There is however plenty of 0-6 bulk shear (around 40-50 kts) with strong winds through the low to mid levels. So in summary, while this in not a slam dunk for severe weather in our area, cannot rule out the potential for at least a few stronger storms. Related, with the strong winds aloft, it will be a windy day with sustained winds of 20-30 mph and gusts of 40 to 45 mph. It will be a relatively warm day with highs in the upper 60s to lower 70s. Any storms on Monday will exit our area very early Tuesday morning. We could again see moderate to heavy rain with the system, with latest ensembles indicating around a 70% probability of receiving at least half an inch of rain. For Tuesday through Friday, small to moderate (20-50%) rain chances linger through the period. This as the aforementioned upper level low rotates back to the northwest into the northern Rockies on Tuesday, then back into the Northern Plains on Wednesday. It then only slowly shifts to the east on Thursday and Friday, with perhaps a drying trend toward next weekend. Highs through the period will be mainly in the 60s with lows in the 40s. It looks to be a breezy each day. && .AVIATION /18Z TAFS THROUGH 18Z MONDAY/... Issued at 1238 PM CDT Sun May 5 2024 VFR conditions are expected to largely prevail this TAF cycle. Latest satellite imagery shows mostly sunny skies with a bit of cu starting to develop across across NW Iowa. Should see cu become more widespread this afternoon with the aid of diurnal heating. In regard to winds, look for S/SE to continue this afternoon, with gusts between 20 to 25 MPH possible in areas along and west of I-29. Otherwise, look for stratus to gradually build in from the west overnight and breezy winds to become more widespread, with gusts between 30 to 50 MPH possible after daybreak. Showers and storms will be possible for much of the day Monday, resulting in periods of reduced cigs and vsbys. && .FSD WATCHES/WARNINGS/ADVISORIES... SD...None. MN...None. IA...None. NE...None. && $$ DISCUSSION...JM AVIATION...SST