Area Forecast Discussion
Issued by NWS Sioux Falls, SD
Issued by NWS Sioux Falls, SD
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692 FXUS63 KFSD 170706 AFDFSD Area Forecast Discussion National Weather Service Sioux Falls SD 206 AM CDT Mon Jun 17 2024 .KEY MESSAGES... - Heavy rain continues to move through the Tri-State area this morning, with fairly widespread 1-3" totals expected and locally higher amounts. - Severe weather risk has diminished somewhat, with a more narrowed focus for large hail and some gusty winds along the Missouri River and then portions of northwest Iowa and southern Minnesota. - Continued uncertainty for severe weather risks for Monday, given cloud cover, lingering showers, and warming low-lvl temperatures. Lingering elevated hail risks may continue through the morning hours, with some renewed potential later this afternoon. - A progressive front moves through on Tuesday, bringing yet another risk for strong storms and locally heavy rainfall. - An unsettled week is ahead, with numerous thunderstorm risks into next weekend. The risk for locally heavy rainfall will be possible each day, with slightly more muted severe weather risks with lower shear. && .DISCUSSION... Issued at 204 AM CDT Mon Jun 17 2024 TONIGHT: Convection continues to track east across the Tri-State area. Generally the severe weather risks have lessoned as the strong mass convergence really gave no opportunity for storms to stay very discrete. Most guidance has also been focused far too north through the night, with the true effective low-lvl front focused south of I-90. Perhaps some residual severe weather risks will be possible along the Missouri River and then into portions of NW Iowa into Southern Minnesota, where instability is a bit higher, DCAPE remains nearly 1000 J/KG, and effective shear is AOA 40 KTs. However the greatest risk tonight will remain in the form of heavy rainfall. At this point, see no reason why convection will jog northward as some of the high resolution guidance suggests. Also, stronger shortwave energy continues to approach north central Nebraska, which will travel along the elevated boundary and continue the focus for heavy rain along and just north of the Missouri River and then further east into northern Iowa through 12Z. TODAY: We`ll need to wait for the Nebraska shortwave to slide east before some weakening of deeper lift takes place. This may not happen until nearly mid-morning. However, with broad southwest flow and continued overrunning of the elevated boundary, persistent shower and thunderstorm development may continue north of the surface front through at least early to mid afternoon. Speaking of that surface front, it`s current location south of the CWA may remain stationary until afternoon when some gradual retreat will begin in the afternoon. Convection risks later this afternoon and evening remain extremely conditional, partially due to continued capping over the CWA through the day, and the absence of deep synoptic lift. For now, will keep PoPs lower into the late afternoon hours, and temperatures cooler through the day due to cloud cover. TONIGHT: With the increase of the LLJ early in the evening, this could pose a risk for convection to develop along and north of the retreating warm front over northeastern SD. An additional focus point would be along a north to south oriented cold front in central South Dakota. However, unless a subtle wave sneaks through the Plains (ala the ECMWF) the best synoptic forcing is likely to take shape northwest of the CWA, so will only maintain a low chance PoP. The return of southerly surface flow behind the retreating warm front is likely to keep overnight low temperatures very warm and humid through the region. TUESDAY AFTERNOON-WEDNESDAY NIGHT: Uncertainty on where the surface cold front ends up Tuesday afternoon, but most guidance keeps this in our area (along/east of I-29) with the main surface low off to the north. Plenty of convergence along the front with lift by the evening hours as mid level wave and upper jet begin to track over the eastern half of the forecast area. Lots of warm and moist air ahead of the surface front; however, soundings show a fairly capped environment so afternoon/evening convection may be more elevated and tied to either the 850 mb or 700 mb front. Regardless, storms during Tuesday afternoon through night could be strong to severe. Main threats would be large hail and heavy rainfall. Can`t rule out strong wind gusts, but this looks to be a secondary threat especially if storms are elevated. Prevailing storm motion is essentially parallel to the front so training storms could be a concern if the front is more slow moving. PWATs approach 2" which with days of rainfall, additional heavy rain could quickly pose issues with flooding. Stay weather aware. Showers and storms linger through Wednesday night as a couple of weak waves pass across the southwesterly flow regime and are supported by the right entrance of the upper jet. Some uncertainty with the subtle waves moving through the overall flow pattern. Not much in the way of instability during this time, so severe weather Wednesday into Wednesday night currently looks unlikely. Cooler temperatures look to prevail. THURSDAY ONWARD: Unsettled continues to be the theme of the forecast into next weekend with the blocking high remaining in place over the Mid Atlantic to TN Valley. Numerous waves/troughs swing through the mid level pattern, with the upper jet either overhead or just north. Models vary in the timing/location of each wave, but generally expect shower/storm chances to continue. Temperatures near normal.&& .AVIATION /06Z TAFS THROUGH 06Z TUESDAY/... Issued at 1127 PM CDT Sun Jun 16 2024 Storms have developed as of 17.04z from just north of KFSD stretching southwest into northwestern NE. Expect storms to continue developing and slowly moving northeast through the overnight hours. Large hail and heavy rainfall are possible. Expect MVFR and lower conditions with any storms. MVFR to possibly IFR stratus expected tomorrow with additional rounds of showers and storms through the period. Lower confidence in convective timing after daybreak Monday. Winds shift to more southerly through the period with gusts up to 30 knots. Could see some low level winds shear area wide after sunset Monday (18.01-02z) but given the expected gusts have omitted for now. && .FSD WATCHES/WARNINGS/ADVISORIES... SD...None. MN...None. IA...None. NE...None. && $$ DISCUSSION...Dux/SG AVIATION...SG