Marine Weather and Tide Forecast for Altoona, WI

DISCUSSION
Issued at 247 AM CDT Mon Apr 20 2026

Surface analysis this early this morning shows a sprawling 1028mb high pressure area centered over MN/WI, making for a clear but chilly late-April morning with lows into the mid 20s.
Atop the high sits pronounced NW flow aloft in between a large trough emanating from a deep Hudson Bay low with its axis over the Appalachians and an amplified ridge over the Rockies.

The surface high will shift into the Ohio Valley today, making for a deep southerly surge over the Upper Midwest which will bring in noticeably warmer air along with breezy winds, albeit with a lack of moisture. This will allow highs to climb to the mid-upper 50s in western WI, and to the lower 60s to lower 70s over the MN portion of the WFO MPX coverage area. Highest temperatures will be in SW MN. However, with dewpoints only climbing into the 20s today, this combination will allow RH values to drop to the between 20-25 percent. Combined with southerly winds of 15-25mph with higher gusts, critical fire weather conditions are expected today over much of central through southwestern MN. Therefore, after collab with MN fire officials and surrounding offices, have opted to issue a Red Flag Warning for that portion of our coverage area for today.

Winds will diminish after sunset and high pressure will regain control despite the passage of a weak frontal boundary tonight which will result in little more than clearing skies. However, with western ridging continuing to slowly nudge eastward and influencing the airmass over the Upper Midwest, warmer temperatures are expected for both tonight through midweek as lows tonight bottom out in the upper 30s to lower 40s. Highs on Tuesday will climb to the upper 60s to mid 70s. The aforementioned weak frontal boundary will lift back north as a warm front Tuesday night through Wednesday, making Wednesday the warmest day of the week. Highs will jump to the mid 70s in western WI to the mid 80s in western MN, with the potential still there for highs in southwestern MN to climb to near 90.
These warm temperatures combined with a moderately breezy day on Wednesday could again produce fire weather concerns. However, latest guidance doesn't quite have the high wind speeds but, more certainly, dewpoints will be higher due to a more pronounced surge of moisture into the region from the south.
Thus, fire weather concerns for Wednesday appear to be a bit mitigated but will continue to monitor the potential for elevated fire weather conditions.

Thursday will bring the next chance for precipitation as the central CONUS ridge breaks down, allowing an impressive upper low from the eastern Pacific to trek across the country. This upper low will aid in cyclogenesis over the northern Rockies, spawning a sub-990mb occluded low over the Northern Plains on Wednesday which will shift across the Dakotas and MN Thursday into Friday. The bulk of the rainfall still looks to be in eastern MN through western WI given the synoptic orientation of this system. And although the expanse of rainfall does look pretty good, QPFs are still generally under 0.25". That said, dewpoints look to creep up to the upper 50s to possibly near 60 in advance of the cold front of this system while the upper level trough tightens up and even potentially comes negatively tilted, allowing for decent thunderstorms coverage and with higher instability and stronger jetting in the mid-levels, a growing severe risk. The better severe potential will be south of MN/WI at this point but where the upper low pivots and brings the surface low may make for better severe weather potential into the Upper Midwest on Thursday.

Once the Thursday system moves through, central NOAM troughing will then persist for the end of the week into the weekend with lower H5 heights atop an incoming western Canadian high pressure airmass. This will mean more clouds than sun for the weekend along with temperatures cooling back to near-to-below normal values for the weekend with limited chances for precipitation.

AVIATION /06Z TAFS THROUGH 06Z TUESDAY/
Issued at 1222 AM CDT Mon Apr 20 2026

Light winds overnight will turn southeasterly around daybreak and will increase to 5-10kts. Winds are forecast to turn more southerly as the morning progresses and will become breezy, especially for the western MN terminals. Afternoon gusts upwards of 25-30kts are most likely at AXN/RWF, with peak gusts between 20-25kts more common for STC/MKT/MSP. Otherwise, VFR with just high clouds moving in through the day.

KMSP...No additional concerns.

/OUTLOOK FOR KMSP/ TUE...VFR. Wind N 5-10 kts.
WED...VFR. Wind SE 10-15G25 kts.
THU.. MVFR/-RA likely, mainly PM. Wind S 10-15G25 kts.

MPX WATCHES/WARNINGS/ADVISORIES
MN...Red Flag Warning from 11 AM this morning to 8 PM CDT this evening for Benton-Blue Earth-Brown-Chippewa-Douglas- Faribault-Isanti-Kanabec-Kandiyohi-Lac Qui Parle-Martin- McLeod-Meeker-Mille Lacs-Morrison-Nicollet-Pope-Redwood- Renville-Sherburne-Sibley-Stearns-Stevens-Swift-Todd- Watonwan-Wright-Yellow Medicine.
WI...None.