Area Forecast Discussion
Issued by NWS Twin Cities, MN
Issued by NWS Twin Cities, MN
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480 FXUS63 KMPX 170002 AFDMPX Area Forecast Discussion National Weather Service Twin Cities/Chanhassen MN 702 PM CDT Sun Jun 16 2024 .KEY MESSAGES... - Showers and thunderstorms overnight, with elevated storms posing a risk for severe hail (1" or more). - Scattered showers & storms over the next few days with an increased risk of flooding due to training storms. Exact amounts will vary based on orientation of training thunderstorms. && .DISCUSSION... Issued at 315 PM CDT Sun Jun 16 2024 Temperatures have struggled to realize the 90s so far this afternoon due to persistent cloud cover leftover from morning showers and storms, followed by enough strengthening of the upper level wave to continue to produce scattered to broken ceilings of cumulus through the afternoon. The warmest heat index as of 230pm sits in the low 90s in northern Scott County, so while the 95 threshold for the Advisory may verify briefly, we did not end up with the heat that was expected yesterday at this time. Despite this, the air outside is still quite humid and is not likely to change so plan accordingly if doing anything outdoors for the rest of the day. As we move through the overnight hours, another round of showers and thunderstorms is expected to develop as low to mid level warm air & moisture advection continues with an upper level wave producing a 1- 2 PVU PV anomaly shortwave as an upper level jet sits north of the MPX coverage area. The main player overnight will remain the low level jet with efficient moisture transport, with another round of late night thunder to contend with. Low level lapse rates are quite poor, however mid to upper level lapse rates are good enough such that a few storms could be capable of producing severe hail overnight. There is a degree of low level helicity such that some spinning lower level storms are also possible, however with the poor lapse rates and large moisture content, the tornado chances remain non-zero but also quite low. What is likely is another round of soaking rainfall equaling an additional inch or two across much of the area, with some isolated higher amounts depending on where the thunderstorms set up. Coupled with last night`s rainfall, we are quickly saturating our soils and swelling area water features such that flooding begins to become a larger concern this week. Tomorrow has quite a bit of uncertainty regarding what will happen especially for the second half of the day as it depends a considerable amount on how quickly the morning showers and storms push across the region. CAM guidance including the SPC HREF diminishes shower activity between roughly 13-15z, but keeps lighter showers and storms around throughout much of the day as CAMS continue to differ on placement and timing of further showers and storms. Should we trend towards the first line of showers exiting later by around 15z, it becomes less likely that we maintain an environment for stronger storms by the afternoon. However, most guidance continues to intensify the already blistering low level jet, with GFS/CFS deterministic solutions favoring a significant continued influx of low to mid level moisture and forcing. This jet will remain the focal point for additional showers and storms with the environment remaining static through much of Tuesday before the jet finally pushes over the Great Lakes by Wednesday morning. Although there are significant hydrologic concerns due to the anomalous PWAT values and multiple rounds of showers/storms, the positioning of the features has shifted enough over the last 12-24 hours within most of the guidance such that confidence in a specific area seeing enough to cause widespread flooding issues is low at this time. The main takeaway should be additional showers and storms are likely over the coming days, but unless we see multiple rounds training over a specific location, the flash flooding/areal flooding concerns are uncertain at best. River flooding is a different story, with enough rain falling over a large enough portion of the CWA that rises in area rivers will likely result in several new or upgraded river flood warnings over the coming days. A pattern shift mid-week with brief surface high pressure on the heels of the departing jet will give us a break from significant rainfall on Wednesday alongside a couple days of cooler temperatures, however deterministic guidance once again points to a strengthening low level jet amidst zonal to southwest flow aloft, once again favoring multiple rounds of scattered showers, thunderstorms, and areas of rainfall. Uncertainty will remain high given the scope of the short-term forecast and how that will end up modifying the overall environment later in the week. && .AVIATION /00Z TAFS THROUGH 00Z TUESDAY/... Issued at 635 PM CDT Sun Jun 16 2024 Main forecast concern through the TAF period will be with the arrival and persistence of widespread rain and storms overnight. Not much change in the expected arrival time of convection, with the main question still with regards to how quickly rain and thunderstorms depart the forecast tomorrow morning. Have continued the theme of prevailing -TSRA for the initial arrival of thunderstorms and then switched over to PROB30`s Monday morning where the greatest uncertainty remains. Winds will eventually turn more southerly during the day as a front lifts north through the state. KMSP...Dry weather continues for the start of the period as winds turn more northerly into this evening. Have -TSRA prevailing at 10z and lasting a few hours prior to thunderstorm chances becoming more uncertain. Despite this, rain will remain likely through the mid-morning hours. Winds turn out of the east around daybreak and then continue to turn more southerly by late morning/into the afternoon. /OUTLOOK FOR KMSP/ TUE...VFR/MVFR, TSRA/SHRA likely, chc IFR. Wind S 15-20G30-35kts. WED...VFR/MVFR, chc -TSRA/-SHRA. Wind N 5-10kts. THU...VFR/MVFR, chc -TSRA/-SHRA. Wind NE 5-10kts. && .MPX WATCHES/WARNINGS/ADVISORIES... MN...Flood Watch from Monday afternoon through late Tuesday night for Anoka-Benton-Carver-Chippewa-Chisago-Dakota-Douglas- Hennepin-Isanti-Kanabec-Kandiyohi-McLeod-Meeker-Mille Lacs-Morrison-Pope-Ramsey-Renville-Scott-Sherburne-Sibley- Stearns-Stevens-Swift-Todd-Washington-Wright. WI...Flood Watch from Monday afternoon through late Tuesday night for Barron-Polk-St. Croix. && $$ DISCUSSION...TDH AVIATION...Strus