Marine Weather and Tide Forecast for Necedah, WI

DISCUSSION
Issued at 210 AM CST Mon Dec 9 2024

- PRECIPITATION CHANCES INTO WED: Light rain/snow chances north of I- 90 today (minimal if any accumulations). Increasing chances for widespread light snow showers/flurries for Wednesday, with only minor amounts expected.

Upper level shortwave trough shifting west-east across the region today into tonight. Weak sfc boundary reflects at the sfc with a little Fgen associated with it. Upper/mid level QG convergence holds across northern MN/northern WI. Cold air a loft increases 1000:850 mb lapse rates of 8-9 C/km in the RAP for the afternoon. HRRR/RAP bufkit soundings also indicate weak instability for the afternoon, which could/would promote some shower chances. Saturation is the sticking point. North-south running RAP x-sections show an increase in low saturation upwards of 700 mb down to the I-90 corridor moving through the afternoon holds most of the low saturation north of I- 94, reflected in both the RAP and HRRR soundings. Little QPF produced in the short term guidance, so pcpn chances are too low for the setup. Will increase chances down through the I-94 to I-90 corridor for the afternoon hours. Temps would support rain or snow with minimal/trace amounts.

Next shortwave trough is set to drop southeast out of Canada, moving across the region late Tue night through Wed. Strong cold air advection will promote low level instability. More for saturation with this shortwave per west-east running x-sections. Pretty much all the EPS members drop very light QPF across the region with nearly all the GEFS doing the same. Again, models suffering from the low QPF nature of the setup and pcpn chances are too low. Have increased to 30-50% for most of the area overnight Tue through Wed, and if trends continue, these chances will need to be increased.
Again, amounts look minimal at this time, but much of the area could/would experience light snow/flurries.

- BLAST OF COLD AIR MID WEEK! Highs could struggle to warm out of the single digits Thu.

Long range guidance continues to carve out a sharper, more anomalous 500 mb trough across the upper mississippi river valley for mid week. WPC clusters have shown this trend over the past few days depicting a slower, deeper trough across the region - with only minor variances in strength. No favorite cluster in the GEFS or EPS as they have members in all 4 of the clusters. EFIs via the EC continue to paint -0.8 for highs while NAEFS and EC 850 mb anomalies hover near -2.5. As noted yesterday, the spread in the 10 to 90 percentiles for temps in the Wed and Thu time frame have tightened up, indicating model members are coming into more agreement than not. The 08.12z run of the LREF has a "zero" percent chance for temps above 15 degrees at 18/00z Fri, although that does miss the mid afternoon hours where temps will likely peak. Same LREF run suggests a 80 to 100% chance that highs won't climb out of the single digits for southeast MN into north-central WI. BRRRR.

Winds do look blustery during the day Wed with gusts currently forecast in the mid 20s to around 30 mph. This will push daytime wind chills into the negative teens. However, those winds look to be slackening as high pressure builds in from the west Wed night, and Thu morning wind chills could drop into the lower 20s below zero.
Cold weather advisory criteria is -25 (wind chill or ambient air temp) so we could get close to headlines, depending on how this shakes out. Bitter cold start to the day Thu anyway you slice it for early Dec.

- BUT...SEASONABLE TEMPS RETURN FOR THE WEEKEND. Temps looking to rebound to at/above freezing.

While the stronger, slightly slower trough has been a consistent signal in the models the past several days, so has been the suggestion for shortwave ridging/broad zonal flow moving into the weekend and early next week. Expect moderating temps in this scenario. Plenty of spread in possible temps in the GEFS and EPS suites, but the 25-75% is only about 10 degrees and around the early Dec normals. Also, all 4 WPC clusters show ridging. So, whether highs "only" top out in the upper 20s, or potentially climb to 40, it's not looking like that cold will stick around for more than a couple days.

AVIATION /06Z TAFS THROUGH 06Z TUESDAY/
Issued at 1025 PM CST Sun Dec 8 2024

Mid-level clouds continue to move through the region tonight as a surface low passes through southeastern Minnesota. Winds will increase towards daybreak with increasing gusts by the afternoon as deeper mixing ahead of an incoming cold front will aid in momentum transfer of higher gusts of around 25-30 kts across southeast MN and northeast IA with prevailing winds in the 15-20 kt range during the afternoon from the west/northwest.
As the front approaches, low-level saturation and weak lift may instigate some brief, light rain/snow (15-30% chance). Consequently, have included a prob30 group at both KLSE and KRST to account for this potential. Regardless, no category reductions would be expected with any rain/snow that does occur.
After the cold front passes through, lingering low-level saturation will aid in spreading MVFR cigs (70-100% chance in the 09.00z HRRR)
from west to east across the entire region during the late afternoon and evening hours.

ARX WATCHES/WARNINGS/ADVISORIES
WI...None.
MN...None.
IA...None.