Sunrise 5:44 AM   Sunset 8:07 PM Moonrise 2:43 AM   Moonset 1:46 PM

  Print   HELP   Reset   Save   Recall

FXUS63 KARX 030834 AFDARX

Area Forecast Discussion National Weather Service La Crosse WI 334 AM CDT Fri May 3 2024

KEY MESSAGES

- Areas of fog this morning. This fog may be localized dense. As drier air moves into the region and diurnal mixing occurs, this fog should burn off rapidly between 8 and 10 AM.

- Rain and scattered storms are expected late tonight and Saturday. This rain will likely only last up to 6 hours in any location. With better forcing and moisture transport into the region, rainfall amounts were increased. They now look to range from a tenth to a half-inch. Highest rain totals look to be west of the Mississippi River where the forcing and moisture transport is the best.

- For early next week (Tuesday and Tuesday night), there appears to be risk of severe weather. While the shear looks good, still some uncertainty of the amount of instability.

DISCUSSION
Issued at 334 AM CDT Fri May 3 2024

This Morning - Areas of fog - potentially dense

The combination of clearing skies, light winds, and recent rainfall will result in the development of fog across much of the area early this morning. There may be even some localized dense fog. As drier air moves into the region and diurnal mixing develops this fog should quickly dissipate between 03.13z and 03.15z.

Late Tonight through Saturday - Rain and scattered storms

The 05.03z models are in good agreement that a longwave trough will move east through the forecast area from late tonight into Saturday. Ahead of this wave, a 40 to 50-knot 850 mb jet will increase the moisture transport across the area. Precipitable water values will increase into the 1 to 1.4 inch range. The highest values will be south of Interstate 90. This is higher than the past couple of days. Due to this the precipitation totals were increased. They now range from a tenth of an inch to a half-inch. The highest values will be likely west of the Mississippi River where the forcing and moisture transport will be the strongest.

The CAMs show that the rain and scattered storms will likely only affect an area up to 6 hours. Used the CONSShort and the CAMs to try and add some timing to this precipitation. Even by doing this, still likely holding onto this precipitation a bit too long.

While the 0-6 km shear increases into the 40 to 50 knot range (highest north of Interstate 90), the 0-4 km most-unstable CAPES remains below 100 J/kg, so not anticipating any severe weather from these storms.

Monday Night into Tuesday Night - Another round of showers and storms

The models continue to show that a closed 500 mb low will lift out of the desert southwest and move into the Northern Plains on Monday. A negatively-tilted shortwave trough will move northeast through the area on Tuesday. This will likely result in a line of showers and storms. Both the deterministic GFS and ECMWF suggest the potential for the 0-6 km shear will be in the excess of 40 knots. The main question continues to be the timing differences with this system which greatly impacts the amount of instability that will be found across the region.
Colorado State severe probability still shows a 15 to 30% chance in northeast Iowa and southwest and central Wisconsin.

AVIATION /06Z TAFS THROUGH 06Z SATURDAY/
Issued at 958 PM CDT Thu May 2 2024

With increasing probabilities of IFR fog over northeast Iowa, it appears the Miss river valley could also see some MVFR fog by morning as well. Through the past several hours, most of the probabilities in the NBM guidance are consistent with some fog at KLSE. Have decided to add MVFR fog as a trend. With winds above the boundary layer at inversion height still 20 kts, think the valley fog scenario is unlikely. It would be more of a synoptic fog with possibly a slight preference for the valleys to have lower visibility with cool air drainage under the surface ridge axis.

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

Full Color Weather Map

Link to Loop


Other links: GEOS-West     Contential US     Full GOES-East

La Crosse, WI,