Sunrise 5:51 AM   Sunset 7:48 PM Moonrise 7:50 PM   Moonset 5:35 AM

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LMZ521 Green Bay South Of Line From Cedar River To Rock Island Passage And North Of A Line From Oconto Wi To Little Sturgeon Bay Wi- Green Bay South Of Line From Oconto Wi To Little Sturgeon Bay Wi- 107 Am Cdt Tue Apr 23 2024
.small craft advisory in effect from 1 pm cdt this afternoon through Wednesday morning - .
Overnight - SW wind 10 to 20 kts with a few gusts to around 25 kts. Partly cloudy. Waves 1 to 3 ft. Today - SW wind 10 to 15 kts veering nw 15 to 25 kts with gusts to around 30 kts in the afternoon. A slight chance of rain showers in the morning, then rain showers likely and a slight chance of Thunderstorms in the afternoon. Waves 1 to 3 ft building to 3 to 5 ft late in the afternoon. Tonight - N wind 15 to 25 kts with gusts to around 30 kts. Partly cloudy in the evening then clearing. Waves 4 to 7 ft subsiding to 3 to 5 ft early in the morning. Wednesday - NE wind 10 to 20 kts with gusts to around 25 kts veering E 5 to 10 kts in the afternoon. Sunny. Waves 2 to 4 ft subsiding to 1 to 3 ft in the late morning and afternoon.

LMZ500
No data

FXUS63 KGRB 230855 AFDGRB

Area Forecast Discussion National Weather Service Green Bay WI 355 AM CDT Tue Apr 23 2024

Forecast discussion for routine morning forecast issuance

KEY MESSAGES

- There is a chance of thunderstorms this afternoon into early this evening, but severe storms are not expected.

- Elevated fire weather conditions are possible Wednesday and Thursday due to relative humidities ranging from 15 to 25 percent. However, lighter winds and temperatures mainly in the 50s will keep conditions below critical levels.

- Thunderstorms are possible Friday afternoon through Sunday evening. It is too early to determine whether they might be severe.

DISCUSSION
Issued at 355 AM CDT Tue Apr 23 2024

Short Term
Today
Tonight...and Wednesday

Some thunderstorms are expected this afternoon as a strong secondary cold front approaches. Gusty winds and small hail would be the primary hazards. Though the Day1 Marginal Risk has shifted back across southeast WI, no severe storms are expected at this time for our forecast area.

Leading cold front is working across WI this morning. A few showers and even some isolated thunder has occurred over north- central WI. These showers will shift out of far northeast WI shortly after daybreak. Rest of the morning will be pretty quiet as shortwave trough axis reaches Lake Superior to southern MN while secondary cold front drops across northern MN. Ahead of the front, a thermal ridge will result in soaring temps, especially over east-central WI where readings by early afternoon will be well into the 60s if not nearing 70. As the secondary cold front draws closer, limited instability ahead of the front (low sfc Td offset somewhat by steep mid-level lapse rates over 8c/km) will begin to allow scattered showers and some thunderstorms to blossom mid to late afternoon. These gusty showers and storms will then sweep southward into the early evening as the front crosses the region from the north. Even with the mid-level instability, limited low-level moisture and majority of stronger effective shear shunted farther south and east should limit potential for severe storms, though cannot rule out an isolated severe storm late this afternoon south of highway 29 where heating and insolation will be maximized.

Front moves through this evening with temperatures quickly falling off from north to south. Readings by late evening will already have fallen below freezing over north-central (with maybe a bit of light snow) and will be heading down to the upper 30s to lower 40s elsewhere. So, after a day with highs near 70 degrees in parts of the forecast area, readings all areas by daybreak on Wednesday will be at or below freezing.

Long Term...Wednesday Night Through Monday

Precipitation...Dry conditions are expected to continue Wednesday night through Thursday night, as dry air from a departing surface high and a trailing upper-level ridge reside over the region.

Attention turns to Friday through Monday, with a couple rounds of rainfall and thunderstorms expected to impact the region from two southern stream systems. Both systems are beginning to take shape with very similar paths from the central Plains to the Upper Mississippi Valley northeast across WI. However, for both systems there are still crucial timing and placement differences that will ultimately determine rainfall amounts, including where the heaviest rain will occur, and thunderstorm potential, including severe potential.

The first system looks to bring precip to the forecast area sometime Friday afternoon/evening through Saturday evening, with the heaviest rain occurring Friday evening/night when PWATs around 1.25 inches are present. There is potential for some elevated thunderstorms Friday night, but a better chance for surface-based storms looks to occur on Saturday when the surface low's cold front sweeps across the warm sectored forecast area. Although some guidance is supporting the potential for strong/severe storms, cannot say for certain there will be some given a slight shift in timing of the cold frontal passage could change that.

Following the frontal passage Saturday evening, a small window with no precip appears to occur Saturday night before precip from the next system arrives sometime Sunday morning and exits sometime on Monday. The timing of this system is even less certain than the previous since there is still uncertainty with the first system.
But, a general consensus still has a strong signal for another round of healthy rainfall amounts and some thunderstorms with this system.

Temperatures...As low-level winds turn southerly on Thursday, temperatures will begin to increase to slightly above normal with highs ranging from the mid 50s to low 60s. Similar temperatures are anticipated on Friday before the precip arrives. Saturday's temperatures will be a challenge to determine this far into the forecast and given the uncertainty of the cold frontal passage.
However, many models are indicating the forecast area will be in the warm sector, which could result in highs in the mid 60s to even mid 70s.

AVIATION
for 06Z TAF Issuance Issued at 1002 PM CDT Mon Apr 22 2024

Evening showers will shift east of the forecast area by issuance time, followed by a dry period and partial clearing overnight into early Tuesday. Surface winds will subside and LLWS will gradually end from west to east overnight.

On Tuesday, a strong cold frontal passage will generate numerous showers and scattered thunderstorms in a marginally unstable air mass, especially in the afternoon and early evening. Will continue to highlight the best two-hour window for thunderstorms at all of the TAF sites, except RHI. Ceilings may drop to MVFR behind the cold front in far northern WI, but models have backed off a bit on the low ceilings.

West to northwest winds will gradually increase on Tuesday, then abruptly turn north and become gusty as the cold front moves through during the afternoon and early evening. The strongest winds will likely occur in the Fox Valley and lakeshore areas.

FIRE WEATHER
Issued at 355 AM CDT Tue Apr 23 2024

Ahead of a stronger cold front today, elevated fire weather conditions could develop from mid morning through early afternoon as temperatures rise well into the 60s, RH values lower to 25-35 percent and southwest-west winds increase to around 15 mph. The conditions will be brief and limited to mainly east-central WI.

Another period of elevated fire weather conditions is possible Wednesday and Thursday, as a dry airmass moves into the region.
Afternoon RH values of 20 to 30 percent are possible on Wednesday, but cooler temps are anticipated in the lower 40s lakeside to the low 50s inland. On Thursday, RH values will be slightly higher between 25 to 35 percent, and temps will also be slightly higher in the mid 50s to low 60s. But, due to the proximity of the prevailing high pressure system, winds will be below critical levels on both days.

GRB WATCHES/WARNINGS/ADVISORIES
None.

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