Marine Weather and Tide Forecast for Aurelia, IA

DISCUSSION
Issued at 155 PM CDT Tue May 13 2025

THIS AFTERNOON: Temperatures again rising well into the 80s and are expected to reach the 90 degree mark in a few locations. While slightly higher surface dew points have arrived, we're going to continue to mix down drier air and keep RH values at critical thresholds into the evening.

TONIGHT: We'll begin to see a frontal boundary slowly move eastward across the Dakotas tonight. While any convection that forms is likely to remain well west of the CWA, modest moisture turn in the mid-lvls may result in a mid-lvl cloud deck developing along or west of the CWA by daybreak. Further east, breezy winds overnight are expected to hold temperatures into the upper 50s to lower 60s.

WEDNESDAY - WEDNESDAY NIGHT: All eyes have been on a deep upper trough beginning to cross the Rockies on Wednesday into Thursday. As this trough begins to influence the Plains, we'll see low-lvl return flow begin in earnest early on Wednesday. Some high based showers and thunderstorms may form along or behind this boundary in north central and the western Dakotas early in the morning, however further east ahead of the front, we'll continue to see a narrow tongue of upper 50s to even low 60 dew points nose into central SD/NE.

As inhibition is weakened and weak synoptic lift arrives, isolated to scattered convection is expected to form along and ahead of the front by 3pm. Initial storms develop within a corridor of 1500-2000 J/KG MLCAPE, but rather paltry shear (15 to 20 knots) initially. The poor shear instability balance along with the nearly parallel flow to the frontal boundary likely means initial storms produce marginally severe hail and some stronger downbursts (DCAPE nearly 1200 J/KG), but may become outflow dominant as they struggle to move east.

The environment begins to modify rather quickly through the evening as the upper trough begins to take on a bit of a negative tilt and a mid-lvl jet 50-60 knot streak moves into the Central Plains. With the emergence of the nocturnal LLJ and arrival of a plume of richer 850mb theta-e, we should begin to see additional convection develop further south along the front into the Missouri River valley and into central Nebraska. The northward draw of slightly higher instability and sharpening mid-lvl lapse rates could lead to larger hail (1.75" or greater) in initial updrafts as they develop. The increase of bulk shear and especially turning of the 0-2km shear vector more perpendicular to the orientation of the convection could lead to either stronger bowing segments within a line, or one or larger bowing MCS moving northeast to east into the Tri-State area towards the 12am timeframe and into early morning Thursday. While some uncertainties on the stability of the boundary layer remains, DCAPE may be sufficient enough to punch through pockets of stronger winds clusters move east. Can't ignore the very low probability of a quick tornado within any broken line segments despite fairly high LCLs, given increasing 0-1 KM CAPE and favorable angle of the 0-2KM shear vector. This is also being indicated in the latest HRRR probabilities for TOR/WIND which would suggest that future upgrades could be increased or expanded. Convection should weaken as it moves towards the Spirit Lake/Spencer/Storm Lake/Jackson areas given the time of arrival (after 3am), but stronger winds may continue.

CAMs have backed off slightly on the potential for renewed elevated convection on a secondary vort max spinning northeast after 4am.
While CAMS are not indicating much today, the residual elevated instability and high shear remain, so will need to monitor. Any MCS may stabilize things sufficiently to prevent this from developing.

One other thing regarding this event. Initial convection along the boundary will see nearly parallel movement to the front, resulting in slow training of storms. Given increasing PWAT values approaching 1.5", locally heavy rainfall may be possible.
Areal averages from the NBM suggest 1-1.75" over a large area, but LPMM from the HRRR suggest pockets of 3 to 5" may be possible anywhere along and west of the James. The only potential limiter further east may be the eventual progressive nature of the convection. This rain will generally not cause any flooding issue to area rivers, unless it happens to fall on an urban population.

THURSDAY: There is considerably better agreement that this upper trough will enter the Northern Plains and deepen and slow it's eastward track on Thursday. In return, we may end up with period of showers and stronger westerly winds for most of Thursday. Potential gusts over 40 mph will be possible, and future wind forecasts may increase.

FRIDAY: The upper low, now stalled over northeast Minnesota, will continue to spin bringing both a considerable amount of stratus, but eventually a secondary cold front in the afternoon with scattered showers. Optimistic highs in the mid 60s to lower 70s continue, but trends could push them lower.

SATURDAY-SUNDAY: Quiet and slightly cooler (than the past week)
conditions will move in for the weekend. No hazards anticipated.

MONDAY-TUESDAY: Probabilities of rain remain very high as we start next week (70%+) in many areas. Yet another upper low is expected to dig into the southwestern US, with strong return flow interacting with a retreating 850 mb front by early Monday. Several rounds of rain may be possible into Tuesday.

AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/
Issued at 1156 AM CDT Tue May 13 2025

VFR conditions continue into Wednesday. Breezy southerly winds are expected to turn gusty at times into early afternoon.

Isolated mid-lvl clouds to cirrus will arrive by daybreak Wednesday with southeasterly winds turning gusty again by mid- day.

FIRE WEATHER
Issued at 155 PM CDT Tue May 13 2025

Another hot, dry, and windy throughout the Tri-State area.
Current forecast remains on track, suggesting that peak fire weather conditions continue through mid-evening before winds weaken.

Relative humidity values will increase through the night, but persistent breezy conditions combined with longer duration hot/dry spell will continue to lead to less overnight recovery or at least a slightly persistent low fire danger into Wednesday morning.

Winds increase again on Wednesday as highs push the upper 80s to lower 90s. RH values however fall only to the upper 20s to lower 30 percent range, leading to near critical values, but likely fall short of red flag levels.

Widespread rain moves through by Thursday morning ending the fire danger risks in the near term.



FSD WATCHES/WARNINGS/ADVISORIES
SD...Red Flag Warning until 9 PM CDT this evening for SDZ038>040- 050-052>071.
MN...Red Flag Warning until 9 PM CDT this evening for MNZ071-072- 080-081-089-090-097-098.
IA...Red Flag Warning until 9 PM CDT this evening for IAZ001-002- 012.
NE...None.