####018004191#### FXUS63 KGRR 161900 AFDGRR Area Forecast Discussion National Weather Service Grand Rapids MI 300 PM EDT Fri May 16 2025 .KEY MESSAGES... - Scattered Showers and Storms Tonight - Gusty Winds and Lingering Rain Showers Saturday - Cooler Temperatures into Next Week && .DISCUSSION... Issued at 300 PM EDT Fri May 16 2025 - Scattered Showers and Storms Tonight Another round of showers and storms is expected to move through after 8pm tonight. Storms could be strong to severe with damaging winds being the primary hazard, but can't rule out hail or a tornado with this evenings storms. We'll need to monitor convection currently in Missouri as it tracks northeast into southern Michigan and the showers and storms that develop in Wisconsin as they move across the lake. There is some uncertainty with the exact variables in play this evening. Model solutions vary with the amount of instability available along with the LCL values as storms approach. Hence why we can't completely rule out any one hazard. There is higher confidence in the source of lift with the 500 mb positive vorticity advection with the upper level low currently over Minnesota and with the 850mb 40 to 45 knot jet also bringing with in some moisture. Showers and storms will also be moving into a more mixed out environment, meaning there is an ample amount of dry air toward the surface. Downdraft CAPE values will be in the 800 to 1000 J/kg range as storms approach leading to the higher confidence in the damaging wind potential. - Gusty Winds and Lingering Rain Showers Saturday As the previously mentioned upper level low tracks through the northern Great Lakes, low level moisture and lift will bring some lingering showers to the area Saturday. It will also bring gusty westerly winds with gusts in the 30 to 40 mph range. As the low departs Saturday night winds subside and dry conditions return. Highs Saturday are only expected to be in the 50s to low 60s. - Cooler Temperatures into Next Week Pressure heights increase Sunday into Monday with dry conditions expected. Thereafter the pattern becomes a little less certain looking at the ensemble clusters and the 500mb flow. An upper level low will be in the vicinity but the timing and placement vary based on each cluster which impacts our rain chances through the remainder of the week. It does look like most of the rain will be to our south, but the placement of the low will determine how far north rain will spread. Either way it doesn't look like a total washout, but temperatures will remain on the cooler side with highs in the 50s and 60s and lows mainly in the 40s. Sunday night and Monday night there is a chance for temperatures to drop into the mid to low 30s for areas north of I-96. These temperatures could result in frost damaging susceptible vegetation. && .AVIATION /18Z TAFS THROUGH 18Z SATURDAY/... Issued at 139 PM EDT Fri May 16 2025 Visible satellite loop shows cu developing across the region with high clouds streaming in from Wisconsin. Another round of showers/storms is expected to develop this evening in response to a wave of low pressure spinning around an upper low. Favored time frame is from 01z-05z. Gusty winds are the main threat with these storms and a few could be strong to severe. Once the storms pass through, we'll see ceilings fall to MVFR by sunrise. && .MARINE... Issued at 300 PM EDT Fri May 16 2025 Thunderstorms will be possible again tonight and may produce strong winds. Gusty southerly winds continue and become more westerly into Saturday as low pressure moves across the northern Great Lakes. Waves build into Saturday with heights of 4 to 7 feet. Winds and waves gradually subside Saturday night. Northwest winds may pick back up to Small Craft Advisory levels Sunday afternoon. && .GRR WATCHES/WARNINGS/ADVISORIES... MI...None. MARINE...Small Craft Advisory until 2 AM EDT Sunday for LMZ844>849. && $$ DISCUSSION...RAH AVIATION...04 MARINE...RAH ####018008797#### FXUS63 KDMX 161903 AFDDMX Area Forecast Discussion National Weather Service Des Moines IA 203 PM CDT Fri May 16 2025 .KEY MESSAGES... - Strong and gusty winds through this evening, with A Wind Advisory in effect across much of northern, western, and into central Iowa. - Patchy light rain through early tonight, mainly across the northern half of Iowa, and notably cooler weather through the weekend. - More active weather is forecast from late Sunday into early next week. Severe thunderstorms and heavy rain may be possible at times between Sunday night and Tuesday, but confidence in timing and details is low at this range. && .DISCUSSION... Issued at 203 PM CDT Fri May 16 2025 Things have unfolded largely as forecast today. A large gyre is spinning over northern/central Minnesota, and this morning a weak shortwave impulse rounding the base of the cyclone generated some sprinkles/light showers across central and southern Iowa but generally with only a trace of rain. Meanwhile a surface trough is moving across our forecast area like a spoke on the wheel, currently picking up on radar and approaching the Des Moines and Waterloo areas. Ahead of this trough winds are from the southwest and skies are mostly sunny with temperature climbing all the way to 82 at Oskaloosa, but behind the trough winds shift to westerly, skies become mostly cloudy with a few sprinkles/light showers, and temperatures have fallen to 49 at Estherville. Winds are strong and gusty everywhere, but particularly behind the trough and across our favored northern and western areas where a couple of sites have sporadically reached High Wind Warning criteria, but the majority of the area/time have remained solidly within Wind Advisory criteria. As such, no changes have been made to the ongoing advisory which remains in effect through 9 PM. As the large cyclone moves eastward into the Great Lakes region and continues to slowly fill in tonight, winds will gradually diminish after sunset and any lingering light rain will move out. A high pressure ridge will then build in from the north Saturday and Saturday night, leading to mostly clear skies by Saturday afternoon along with cooler temperatures through the weekend. On Saturday temperatures will remain in the 60s despite good insolation late in the day, and in the north closer to the ridge axis and where clouds may linger longer through the morning, temperatures may not even reach 60 degrees. After sunset temperatures should then fall quickly Saturday night, especially in areas where winds go very light or calm, and Sunday morning lows are forecast in the mid to upper 30s in our northern counties and mid-40s in the south. At this time the lowest forecast temps are 37-38 and winds are expected to stay light (rather than calm) with the core of the ridge over Minnesota, so have not included any frost in the forecast. However, it is possible isolated, sheltered locations in our northwest could see a light frost by sunrise Sunday. The general scenario for early next week has not changed appreciably since yesterday, but with some increase in confidence levels regarding the details of the evolution. By Sunday morning a trough will have dug into the western U.S., with a two-phase appearance of vorticity maxima, one near the Utah/Arizona border and the other over Washington state. During the day Sunday the northern vortmax will sink south southeastward while the southern one lifts slowly northeastward, and thereafter the two will do-si-do and eventually congeal into one large mid/upper low over the High Plains by Monday evening. The entire system will then move slowly eastward over Iowa before passing to the east around Wednesday night. At the surface, the aforementioned high pressure ridge will lie across the Upper Midwest and Iowa Sunday morning ahead of the storm system, with cool and dry conditions in place. By Sunday evening however, things will begin to change as the western storm system approaches, turning steering flow over Iowa to the southwest with warm air/moisture advection aloft surging in. Forecast soundings show this rapid warming/saturating aloft, but also maintain a dry near-surface layer consistent with easterly surface flow out of the retreating ridge. While some deterministic model runs paint copious QPF across our forecast area Sunday night, others (most notably the NAM) are more bearish as a result of this low-level dry air. Regardless of whether precipitation is widespread or more scattered, and how early Sunday night it is able to commence, model soundings are nearly unanimous in depicting increasing instability aloft, especially in our southwestern counties where MUCAPEs will increase to around 2000-2500 J/Kg by late Sunday night. While shear in the elevated layer is not overly strong, it is enough combined with the strong instability to support a hail threat during this time, again mainly in our southwest, and this is well illustrated by the D3 Marginal Risk from SPC. During the day on Monday, surface cyclogenesis will result in a deepening low over the OK/TX panhandle and the development of a warm front arcing across northeastern KS and northern MO. North of this boundary, over Iowa, convective evolution during the day is uncertain as warm air advection continues aloft but is undercut by cooler surface flow from the east northeast, and broad but nebulous forcing overhead is unfocused by a lack of surface boundaries/heating. This should result in a relative lull in precipitation for most of the day, but with a maintenance of POPs in the forecast to account for scattered rain/storms especially with the degree of saturation just above the surface. By late in the day Monday thunderstorms should develop rapidly near the surface warm front, perhaps just to our southwest, and move northeastward into our service area in the deeper steering flow. As the mid/upper low moved in Monday night and mean winds back around into it, storm motion will slow and high POPs will be maintained right across Iowa. This will lead to a potential for slowing/erratic motion of individual convective elements and prolonged potential for heavy rain, leading to an increasing concern of hydrologic impacts. However, these are mitigated by the very dry antecedent conditions, and limited by a relative lack of confidence in such details 3-4 days out. In addition, there is certainly some potential for severe thunderstorms late Monday/Monday night, however, if the surface warm front does stay south of our area then any storms would likely be elevated for us, and with profiles saturated the threat of any hail/wind would appear fairly low and mostly confined to our southern counties. That being said, we are still several days out from this system and any northward shift in the location of the boundary would have a significant effect on our severe weather probabilities, so the situation definitely bears watching over the next few days. By Tuesday the large storm system will be filling in and gradually weakening, then moving off to the east, with any precipitation in our area diminishing in intensity on Tuesday and ending sometime around Tuesday night or so. This will be followed a brief period of deep-layer ridging that should provide a respite of quieter weather roughly around Wednesday through Thursday or so, followed by an establishment of relatively brisk west northwesterly 500 mb flow later next week which may lead to a return of intermittent precipitation chances and a prevention of any significant warming. && .AVIATION /18Z TAFS THROUGH 18Z SATURDAY/... Issued at 1224 PM CDT Fri May 16 2025 Strong winds are spreading across the area and will persist through most of the TAF period, resulting in frequent crosswinds of greater than 20 KT particularly on north-south runways. Low clouds and light showers are also coming in from the northwest this afternoon, and will result in prevailing MVFR ceilings at most terminals from later today through tonight, with brief IFR ceilings possible at MCW/FOD but not probable enough to include in the 18Z TAFs. Any visibility restrictions from -SHRA will generally be MVFR and limited to the northern terminals. && .DMX WATCHES/WARNINGS/ADVISORIES... Wind Advisory until 9 PM CDT this evening for IAZ004>007- 015>017-023>026-033>037-044>048-057>060-070>072-081-082-092- 093. && $$ DISCUSSION...Lee AVIATION...Lee ####018004680#### FXUS64 KSJT 161904 AFDSJT Area Forecast Discussion National Weather Service San Angelo TX 204 PM CDT Fri May 16 2025 ...New SHORT TERM... .KEY MESSAGES... - Isolated potential for a severe thunderstorm this afternoon and early evening from Brownwood to Brady to Mason and east. - Increasing chances for showers and thunderstorms Saturday through early next week. Strong to severe storms will be possible in the afternoons/evenings. && .SHORT TERM... (This evening through Saturday) Issued at 132 PM CDT Fri May 16 2025 SPC has added a slight risk of severe thunderstorms from Brownwood to Brady to Mason today. While storms are conditional, the slight risk looks good, as the instabilities in that area have increased with MUCAPES in the 4000 J/KG range. A cumulus field was also developing from Junction to Mason. If storms develop, very large hail of 3 inches+ are possible. Most of this activity should ending by 7 PM CDT, but carried it over for a few hours past 7 PM. A similar situation will exist for Saturday afternoon as a dryline forms along a Sonora to San Angelo to Abilene to Throckmorton line, with very unstable air with dew points in the lower 70s to the east. SPC again has a slight risk/along and east of the dryline, Storm activity may be conditional, depending on breaking the cap, but it develops, very large hail and damaging winds will be possible. Mild temperatures in mid 60s to lower 70s are expected tonight, with highs in the mid and upper 90s Saturday. && .LONG TERM... (Saturday through Thursday) Issued at 224 AM CDT Fri May 16 2025 Upper level trough axis will settle into the Southern Rockies through early in the week, allowing the dryline to slosh back and forth into West Central Texas each afternoon. Models do show a shortwave in advance of the trough, moving across the Southern Plains on Saturday and likely setting the stage for fairly widespread strong to severe convection across Texas during the afternoon and evening hours. How much of this develops across our are and how much farther east into central and north central Texas is a question, so will lean towards the latest CAMs for a first guess. CAMs show 70+ dewpoints spreading into the area during the morning hours, with the dryline mixing east by noon to near an Abilene to San Angelo line. If this holds, then best chances for storms will be across the Heartland, eastern Big Country, and the Northwest Hill Country and will reflect this idea in the forecast. Will want to keep a close eye of the dryline however. Not uncommon for the dryline to have trouble mixing east with that much moisture in place with storms then developing closer to Abilene and San Angelo. Dryline moves back west Saturday night, with some chance of convection developing overnight along the retreating dryline as well. Otherwise, repeat performance for Sunday afternoon. SPC has already added the northern Big Country into a Slight Risk and would not be surprised if it ends up farther south once the high resolution models can extend out that far and confirm the low level moisture and dryline position. Some chance of storms again Monday afternoon, although dryline looks like it will mix a little farther east and keep the best chances for convection across the far eastern counties. Dry conditions return for Tuesday as a weak cold front moves through the area and shifts the low level moisture well east of the area. Otherwise, temperatures will remain above normal through Monday, before the front cools readings off closer to normal values for TUesday and Wednesday. && .AVIATION... (18Z TAFS) Issued at 1229 PM CDT Fri May 16 2025 Light haze will be affecting KJCT through the period as moist air with dew points in the lower 70s advects northward. Otherwise VFR next 24 hours. A weak cold front will bring light Northwest to north winds to KABI and KSJT this afternoon, but winds should weaken further and become variable overnight. && .PRELIMINARY POINT TEMPS/POPS... Abilene 68 96 69 92 / 0 20 20 30 San Angelo 67 98 69 96 / 0 20 10 20 Junction 70 99 68 98 / 10 30 10 20 Brownwood 68 96 68 92 / 10 40 20 40 Sweetwater 67 95 69 95 / 0 10 10 20 Ozona 70 96 71 95 / 0 20 10 10 Brady 71 97 70 95 / 10 40 20 30 && .SJT WATCHES/WARNINGS/ADVISORIES... None. && $$ SHORT TERM...04 LONG TERM....07 AVIATION...04