Forecast Discussions mentioning any of "ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 09/30/21

Area Forecast Discussion
National Weather Service Green Bay WI
1031 PM CDT Wed Sep 29 2021 Updated aviation portion for 06Z TAF issuance .UPDATE... Issued at 842 PM CDT Wed Sep 29 2021 Issued a dense fog advisory for the lake and bayshore counties. It might need to be extended further west to the Fox Valley later tonight. Satellite pictures show cirrus increasing, but these clouds are very high (35k feet based on 21z aircraft sounding at MKE and 00Z GRB radiosonde) and should not stop surface air temperatures from falling that much. Old rule of thumb is that if temperatures fall 3 or more degrees below lowest afternoon dewpoint you often get dense ground fog. That should happen tonight. Mesoscale model visibility forecasts also show fog forming in these areas tonight. && .SHORT TERM...Tonight and Thursday Issued at 238 PM CDT Wed Sep 29 2021 Fog potential late tonight into early Thursday is the main forecast concern. GRB CWA will remain on the western periphery of a large Great Lakes high pressure system. A high-amplitude upper level ridge will also be situated over the western Great Lakes region. These features will keep the area dry through Thursday, with only a gradual increase in high clouds anticipated. Mostly clear skies and light winds will lead to fog development late tonight into early Thursday morning, especially over far northeast WI. Lows tonight are expected to be in the 40s and lower 50s. Highs on Thursday should be similar to today, ranging from the upper 60s and lower 70s near Lake Michigan to 75 to 80 well inland. .LONG TERM...Thursday Night Through Wednesday Issued at 238 PM CDT Wed Sep 29 2021 The stretch of dry and quiet weather will be coming to an end late this weekend and weekend as we enter a more unsettled pattern. Pleasant fall weather looks to return sometime early next week. Temps will be well above normal through Saturday then drop back closer to normal but no real cold air in sight for the foreseeable future. Thursday night...the quiet weather continues across the area as ridging remains in control. High clouds will likely be present for much of the night. Light winds and another strong inversion could lead to some patchy ground fog. A few spots across northern WI could drop into the 40s, but most of the area look to see lows in the 50s. Friday into Saturday...the quiet/dry fall weather will come to an end as the ridge breaks down and shifts east of the region and a trough and frontal boundary approach from the west. Still some model differences on timing of the front/trough and arrival of the shower chances. Models trending toward northern WI for the best chance to see the activity Friday afternoon/evening, but the rest of the area will still see at least a chance of some shower activity. Better chances for showers will spread across the entire area Friday night into Saturday as the front and trough push across the area and PWATs climb to around 1.5" (near the 99th percentile for this time of year). Instability will be weak (skinny CAPE under 500 J/kg) and fairly weak lapse rates, but could see some isolated storms. Temps look to warm up nicely ahead of the front on Friday with most spots topping out in the middle 70s to lower 80s. We could approach a couple records. Friday night is looking mild for early October with lows in the middle 50s to lower 60s. More clouds and shower activity will hold highs on Saturday in the upper 60s and 70s but this is still above normal. Rest of the long the front pushes east of the area on Saturday night and Sunday, only a few lingering showers will be possible as one upper trough departs and another digs across the western Great Lakes. GFS the most aggressive with the second through, painting more precip over the area, but this looks to be mainly south of our area. For next week, models continue to struggle with the overall pattern as how much the closed off upper level low will retrograde west/south is handled differently. How far this system is away from the area will determine precip chances, along with cloud cover and temps. Will favor a dry solution for now. Temps will settle back near normal for early next week with more above normal readings looking likely for a period next week. && .AVIATION...for 06Z TAF Issuance Issued at 1031 PM CDT Wed Sep 29 2021 Thin Cirrus clouds will continue to move in from the west tonight. Areas of dense ground fog are expected, especially east of an IMT to STE line. Ceilings and visibilities could be below minimums at some airports. The fog should dissipate by around 1400 UTC Thursday, with good flying weather for the rest of the day and through the evening hours. Ground fog is possible again late Thursday night and early Friday. && .GRB WATCHES/WARNINGS/ADVISORIES... Dense Fog Advisory until 9 AM CDT Thursday for WIZ022-040-050- 073-074. && $$ UPDATE.........RDM SHORT TERM.....Kieckbusch LONG TERM......Bersch AVIATION.......RDM
Area Forecast Discussion
National Weather Service Phoenix AZ
507 PM MST Wed Sep 29 2021 .UPDATE...Updated Aviation discussion. && .SYNOPSIS... A weather system will provide slight to moderate chances for showers and isolated thunderstorms later today and into Thursday, especially from Phoenix eastward. After continued below normal temperatures through Friday, increasing high pressure over the weekend should bring readings back to around normal by Sunday. && .DISCUSSION... Water vapor imagery shows the southern extension of a trough over the eastern Great Basin through the lower Colorado River Valley. Area of cloudiness and modest ascent is resulting some weak showers across central Arizona this afternoon. Although some drying has occurred over the past 48 hours, surface dewpoints are holding in the 50s across the lower deserts, and objective analysis and ACARS soundings are showing PW values near or just under one inch over the southern half of Arizona. A few showers and thunderstorms are possible across La Paz/western Maricopa Counties this afternoon and evening closer to a low-level moisture access, but coverage should remain fairly limited. More widespread activity is expected to develop overnight, primarily from the Phoenix metro area eastward, as the upper trough continues to progress eastward. Latest HREF and HRRR runs are very consistent in highlighting this area overnight, with the main uncertainty being how far westward the area of showers and thunderstorms will extend. Precipitation amounts on average should range between 0.10 and 0.25 of an inch, but the HREF maximum precip fields suggest some isolated locations could receive over 0.50 of an inch. Gusty outflow winds are also possible in the vicinity of any thunderstorms, with the HREF highlighting a 10-30% chance that 30 kt winds affect the Phoenix area overnight. This may be enough to kick up some localized blowing dust in Pinal County. By daybreak Thursday, the bulk of the activity should shift eastward primarily into southern Gila County, with drier air overspreading the lower deserts. Wrap around moisture accompanying the main upper-level circulation may spread southward off the higher terrain towards northern Maricopa County during Thursday afternoon, but expecting any additional precipitation to remain isolated. The upper low will begin to accelerate late Thursday east of the region, bringing modest height rises to the Southwest by Friday. Temperatures will remain below normal and only expected to reach the upper 80s through Friday in Phoenix, and lower to mid 90s in southeast California. Temperatures will gradually warm through the weekend closer to seasonal normal, reaching the upper 90s in many locations Sunday and Monday. NBM guidance is even suggesting there`s some chance for triple-digit readings, peaking Monday at 19% in Phoenix and 32% in El Centro. The next feature of interest will be an intense and well-defined cutoff low near the coast of northern Baja California, that is forecast to rapidly shift northeastward across the Southwest Tuesday and Wednesday of next week. The orientation of this feature is not expected to be too favorable for significant moisture advection and precipitation across the lower deserts, but perhaps moreso across northern Arizona. However, given the potential intensity of this system, some outlying members are highlighting higher QPF amounts. The 95th percentile 24-hour QPF values of the NBM range between 0.25-0.5 inch for south-central Arizona, while the 50th percentile values are 0. Trends will certainly be worth monitoring. Otherwise, a slight decrease in temperatures into the low 90s along with breezier afternoons can be expected by mid-week. && .AVIATION...Updated at 0000Z South-Central Arizona including KPHX, KIWA, KSDL, and KDVT: Showers and thunderstorms are expected to develop overnight across portions of south-central Arizona. Latest radar and model trends are suggesting a more active late evening and overnight period, and 00z TAFs were adjusted to include VCTS and ceilings down to 7k feet for the Phoenix sites beginning around 07z. Severe storms are not anticipated, however the strongest storms will be be capable of producing wind gusts above 35 kt. Conditions are expected to improve during the 12z-15z period as the trough axis pushes slowly eastward through the Valley. Southeast California/Southwest Arizona including KIPL and KBLH: No aviation weather impacts expected. Mostly clear skies and northerly winds occasionally up to 12 kt will prevail through Thursday at KIPL and KBLH. && .FIRE WEATHER... Friday through Tuesday: Conditions will dry out and warm up through the weekend and early next week. Sunday will be the hottest and driest day with afternoon highs reaching the mid to upper 90s while minimum RH`s drop into the 15-25% range. Min RH`s will be slightly wetter on other days. Overnight RHs will rise into the 40-60% range for most areas on most nights. Otherwise, winds will be fairly light with directions favoring local diurnal/terrain influences. && .SPOTTER INFORMATION STATEMENT... Spotters should follow standard reporting procedures. && .PSR WATCHES/WARNINGS/ADVISORIES... AZ...None. CA...None. && $$ DISCUSSION...Rogers AVIATION...Hirsch FIRE WEATHER...12