Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 09/28/24


Area Forecast Discussion
National Weather Service Birmingham AL
828 PM CDT Fri Sep 27 2024 ...New SHORT TERM... .SHORT TERM... (Tonight through Sunday) Issued at 822 PM CDT FRI SEP 27 2024 Post-tropical cyclone Helene is currently centered near Evansville, IN. Remnant tropical moisture is wrapping around the back side of the circulation, but rainfall rates are light. Steady light rain is located over our far northwest counties, while some light rain bands are weakening in our northeast counties. Still seeing some sporadic 30 to 35 mph gusts, so will keep the wind advisory going, but it should be able to expire at 10 PM. Winds will help keep temperatures up overnight. Wraparound moisture lingers over the area tonight and tomorrow, with spokes of lift rotating around the low causing light rain at times across the north. Did expand low PoPs southward tomorrow afternoon where some of the high res models indicate a band of light rain, but should be low impact. 32/JDavis Previous short-term discussion: (This evening through Saturday) Issued at 138 PM CDT FRI SEP 27 2024 This afternoon. A highly amplified pattern was analyzed over the Country early this afternoon with broad amplified ridging over much of the Southern and Central Intermountain West while a deep-layer low was over the Southern Tennessee Valley. Tropical Depression Helene was located near the far eastern extent of Kentucky/Tennessee State Line according to the latest NHC advisory. Multichannel water vapor imagery along with the 27/12z BMX sounding depicts a fairly dry airmass in the mid and upper levels over much of our area, with more moisture in the low to mid levels per RAP 13 km PWAT plots showing values near or just over 1.20 inches roughly near and northwest of the Interstate 59 corridor. Expect partly cloudy skies across the southern third of the area with dry conditions today. More clouds with chances for isolated showers are forecast for areas near and northwest of the Interstate 59 corridor roughly. The best chances for showers will be across our northwest 5 counties for this afternoon into the evening as the tropical depression is forecast to decelerate as it drifts west-northwest across South-Central Kentucky while the upper low remains just to our northwest. Windy conditions will continue to be experienced this afternoon with a wind advisory remaining in effect for generally the northern half of Central Alabama. Expect southwest winds from 15-25 mph with gusts potentially up to 35 mph in higher elevations and in open exposure locations. High temperatures will range from around 70 far northwest to the low 80s across the southern quarter of the forecast area. Tonight. Global modeling remains in solid agreement in the deep-layer low absorbing/consolidating with the remnants of Helene overnight. The upper low reflection is progged to move over eastern Tennessee then loop northwest over Southwest Kentucky overnight, resulting in a more vertically stacked system. At the surface, low pressure will be centered across West-Central Kentucky overnight while a surface trough will extend southwest from the low across the Mid- South Region. Expect partly cloudy skies with dry conditions across the southern third of the forecast area overnight. Mostly cloudy to cloudy skies will be found further to the north across our area with lingering chances for isolated shower activity generally near and northwest of the Interstate 59 corridor with scattered showers forecast across our northwest 5 counties. Winds will remain breezy as the pressure gradient slowly relaxes across the region. Expect west to southwest winds from 10-20 mph on average with decreasing speeds later into the night. Low temperatures will range from the upper 50s across the northwest and north-central quarter of the forecast area with low 60s expected elsewhere. Saturday. The deep-layer low will remain positioned over West-Central Kentucky while the surface low becomes positioned slightly northeast across North-Central Kentucky. A surface trough will continue to extend southwest of the Surface low into the Mid and Deep South Regions. Partly cloudy skies are forecast areawide Saturday with mostly cloudy skies across the northern third of the forecast area. Dry conditions are expected across the southern third of the area while isolated showers will be possible across the central third of the area with scattered activity possible across the northern third of the area. Winds will be breezy at from the west to southwest from 10-20 mph at times. High temperatures will range from around 70 far northwest to the mid 80s generally along and south of the U.S. Highway 80 corridor. 05 && .LONG TERM... (Saturday night through Thursday) Issued at 244 PM CDT FRI SEP 272024 A large, closed low centered over Kentucky, will encompass most of the eastern CONUS on Sunday. With our area on the southern side of the low, a temperature gradient is expected from north to south, in part due to cloud cover across our northern counties. As the low wobbles around, mid-level vorticity may contribute to shower activity along and north of I-20 Sunday afternoon. The low at 500 mb will begin to weaken on Monday as it shears into a weaker open wave and gains forward speed to the east. Behind the departing trough, we can expect dry and warm conditions for Monday through Thursday. 87/Grantham && .AVIATION... (00Z TAFS) Issued at 621 PM CDT FRI SEP 27 2024 Light rain, low clouds, and gusty winds continue to swirl around Post-Tropical Cyclone Helene centered over Kentucky. One small band of rain with brief visibility reductions is moving through BHM/EET now. Will amend any other sites as necessary, but rain should largely lift north of the terminals this evening. Wraparound low-level moisture will cause cigs to lower to MVFR and eventually IFR by Saturday morning at the northern terminals, with a close call at MGM. Low clouds will linger on Saturday, but should lift to VFR by mid-afternoon. Southwest winds will continue to gust to 25 to 35 kts this evening, decreasing to 15 to 20 kt gusts overnight and Saturday. 32/JDavis && .FIRE WEATHER... Southwest winds of 15-25 mph will continue this afternoon, and a slow decrease in speed is expected for Saturday and again on Sunday. Additional rain showers should be confined to our northern counties, or along and north of I-20 through Sunday. Minimum afternoon RH values through Sunday will range from 45 across the south to 70 percent across the north. && .PRELIMINARY POINT TEMPS/POPS... Gadsden 63 73 60 80 / 50 30 20 20 Anniston 64 76 62 81 / 30 30 20 20 Birmingham 64 75 62 80 / 40 30 20 20 Tuscaloosa 64 78 62 83 / 30 20 10 20 Calera 65 77 63 82 / 30 20 20 10 Auburn 63 80 64 82 / 0 10 10 10 Montgomery 64 84 64 87 / 0 10 10 10 Troy 64 84 64 85 / 0 0 0 10 && .BMX WATCHES/WARNINGS/ADVISORIES... Wind Advisory until 10 PM CDT this evening for the following counties: Blount-Calhoun-Cherokee-Clay-Cleburne-Etowah-Fayette- Jefferson-Lamar-Marion-Pickens-Randolph-Shelby-St. Clair- Talladega-Tuscaloosa-Walker-Winston. && $$ SHORT TERM...32/JDavis LONG TERM....87 AVIATION...32
Area Forecast Discussion
National Weather Service Grand Rapids MI
1002 PM EDT Fri Sep 27 2024 .KEY MESSAGES... - Showers Move in Saturday - Lingering Chances for Light Rain Sunday-Tuesday - Drying Out for Wednesday Through Friday && .UPDATE... Issued at 1002 PM EDT Fri Sep 27 2024 A few showers are developing in far southeast Michigan, moving west. Latest guidance continues to suggest shower coverage increasing and nudging northward into southern Michigan by early morning, affecting mostly south of a South Haven to Lansing line. HRRR forecast soundings for the Kalamazoo area during early morning show some elevated parcels being weakly unstable up to about -15 C, so a flash or two of lightning can`t be ruled out. && .DISCUSSION... Issued at 244 PM EDT Fri Sep 27 2024 - Showers Move in Saturday Tropical Depression Helene is in the process of getting absorbed into an upper low presently across KY/TN. The pressure gradient force between this system and a high across the Upper Great Lakes will lead to gusty winds on the order of 30-40 mph across the region, especially in the 8pm-2am time frame tonight near and south of M-46. The northern periphery of Helene`s rain bands will likely make it as far north as southern Lower Michigan by Saturday. GFS/ECMWF RH layers indicate saturating conditions in the 925-700mb layer with PWAT values climbing to around 1.75", quite high for late September. Rain showers will initially develop in the early morning, moving from SE to NW, but as deep E/NE flow takes hold, a more east to west banding is likely. Model guidance is depicting narrowly forced rain bands, likely due to the limited geographical breadth of deeper moisture overhead that coincides with relatively weak frontogenetical forcing on the northern periphery of a decaying Helene. All this to say that rain amounts will be quite variable, with most areas less than 0.25" but a few distinct, very narrow bands that could produce 0.50"-1.00" or so, per the 12z HREF 24 hr LPMM through Saturday evening. The northernmost extent of rain will likely halt somewhere near I-96, so it is from that corridor to the south where the greatest likelihood for showers will be. The highest amounts will likely fall near and east of a AZO/LAN line. The Nam 3km and HRRR are showing 100-300 J/kg of MUCAPE rooted above the 700mb layer where a general lack of saturation is present, thus the threat for thunderstorms is quite low. - Lingering Chances for Light Rain Sunday-Tuesday Low level moisture and precipitable water values around an inch linger over the area into Tuesday. No one day will be a washout but any slight amount of lift will result in drizzle or rain showers. Monday`s chances are better in the afternoon as we see some diurnal instability develop with mean CAPE values of 100 to 200 J/kg. Tuesday`s chances are better as the front moves through though there is some uncertainty at the exact timing as seen in the ensembles. - Drying Out For Wednesday Through Friday Behind the front Tuesday drier air filters in with northwest flow becoming more geostrophic for the end of the work week. Temperatures will be cooler as well with highs in the 60s and lows in the 40s. With the cooler temperatures and partly cloudy to sunny skies, weatherwise it will be a fitting start to October. && .AVIATION /00Z TAFS THROUGH 00Z SUNDAY/... Issued at 722 PM EDT Fri Sep 27 2024 Moisture from Tropical Depression Helene will continue to try to move into the region tonight. Ceilings will fall throughout the night. The I-94 terminals have the best chance of seeing light rain and IFR cigs after 06z. The I-96 terminals will likely remain dry. Ceilings will gradually improve Saturday afternoon. && .MARINE... Issued at 244 PM EDT Fri Sep 27 2024 Winds over the nearshore waters are expected to gust into the 25-30 kt range across the SCA area near and south of Grand Haven, lasting into at least Saturday morning. A possible extension may be needed into Saturday afternoon depending on the persistence of the higher winds. Given the ENE flow, the highest wave action will be south of South Haven. Conditions do look to improve later Saturday into Sunday. && .GRR WATCHES/WARNINGS/ADVISORIES... MI...None. MARINE...Small Craft Advisory until 8 AM EDT Saturday for LMZ844>846. && $$ UPDATE...CAS DISCUSSION...Hoving/RAH AVIATION...04 MARINE...Hoving