Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 12/04/24


Area Forecast Discussion
National Weather Service La Crosse WI
556 PM CST Tue Dec 3 2024 .KEY MESSAGES... - VERY WINDY Wed afternoon-evening. Wind Advisory for most locations west of the Mississippi river (could be expanded east). Wind gusts 35 to 45 mph for entire area with sustained from 20 to 30 mph. Winds WILL impact travel and blow lightweight objects around (holiday decorations). - BITTER COLD start to Thu with combination of wind and cold air producing 5 to 15 below wind chills. Bundle up for your commute to work/school. - SCATTERED SNOW SHOWERS Wed (20-50%). Accumulations look minimal at this time, but could provide further travel impacts with sudden reductions in visibility, some slick spots on roads. - Cold is short-lived with above normal air moving in for the weekend - back in the 40s for some! && .DISCUSSION... Issued at 215 PM CST Tue Dec 3 2024 - WED/THU MORNING: windy, colder and low end snow shower chances (20- 50%) OVERVIEW: upper level shortwave trough still on track to drop southeast out of Canada tonight, digging across the great lakes Wed night, developing a negative tilt as it drives over the new england states by thu evening. Although the associated sfc low will hold across southern Canada, a couple related sfc fronts will move across the region. Very strong cold air advection, some low level instability, and tightening pressure gradient accompany the system, promising strong/gusty winds, much colder air, and some snow shower chances. The bulk of its impacts will be shifting east with the storm Thu morning. WINDS: a lot of elements progged to come together and foster a very windy period for the region with Wed afternoon-evening likely harboring the strongest gusts for the local area. 1) Tightening sfc pressure gradient 2) Unidirectional winds (northwest) through nearly the entire column Wed aft/eve. 3) Mixing upwards of 825 mb with RAP/HRRR/NAM/GFS bufkit soundings suggesting upper 30s to around 40 kts will be brought to the sfc for the afternoon/early evening Wed. 4) Trop fold could bring even stronger winds surfaceward, with the 1.5 PV sfc reaching 750-800 mb in the NAM/GFS, but as low as 850 mb in the EC. The EC has been the most robust with this. All this has been a very consistent signal in the models the past several days. The EC (as already alluded to) has been the most bullish on strong winds. Essentially 100% of its ensemble members paint 40 mph gusts for the entire forecast area for Wed aft/eve. In its 03.12z run, 20 of the EPS members suggest 50+ mph could be attained Wed afternoon at KRST. In addition, 03.00z EFIs are 0.8+...an increase over already high values from previous runs (0.7+). The EC is "all in" for a high wind event, perhaps too much as it is running at the top end of the guidance. That said, ample support from the other short/medium range guidance that 45 mph gusts could be reached, along with periods of sustained 30 mph. Per coordination with surrounding offices, will issue a Wind Advisory for most of SE MN/NE IA for 18z Wed through 03z Fri. May need to expand this eastward - and will let further model updates, realtime observations, steer that need. Eitherway, it will be a very windy day Wed/Wed night. In addition, with how cold it is expected to get, any potential loss of power due to strong winds will have added impacts on heating. Prepare accordingly. TEMPS: don`t expect much drop in temps from the early evening through the overnight as the southerly fetch/low level warming persists. Much colder air starts to return after 12z Wed, in earnest post the second front. Highs for most will be by noon, with steady or falling through the afternoon. 850 mb temp anomalies via the NAEFS and ECMWF are around -2.5 for Wed night while determinist runs of the EC/GFS 850 mb temps fall from near 0 at 12z Wed to -15 C by 12z Thu. The Grand Ensemble places a 80-100% for single digit lows west of the Mississippi River Thu morning with less chances north of I-94 where clouds could be more prevalent. Add in the strong northwest winds and wind chills from -5 to -15 should be planned for. Bundle up early morning commuters to work/school Thu. PCPN CHANCES: a variety of lifting mechanisms will provide multiple means to force snow showers Wed into Wed evening. A loft, the upper level trough drops southeast across WI with mostly mid/upper level QG convergence with it. At the sfc, while the system`s associated low will be tracking west-east just north of Great Lakes, 2 cold fronts will stretch south/southwest of the low. The first is progged to slide southeast across the region in the early morning hours (12- 15). The second takes a similar track during the afternoon. Strong cold air advection in the low levels will promote 1000:850 mb lapse rates of +9 C/km (mostly behind the second front). Meanwhile RAP/HRRR Bufkit soundings depict weak instability through the day. Same soundings point to enough saturation to form clouds/showers. While there is initially weak, disjointed low level Fgen along both sfc fronts, CAMS modeled reflectivity depicts mostly cloud streets/convection parallel to the mean wind (not in relation to the frontal lift). RAP does become more organized and increases the low level Fgen as the second front shifts southeast of the local area, so perhaps frontal orientated convection would increase then. Short term guidance is low with its snow chances - perhaps more reflective of their low QPF output. The forcing, however, says chances should be higher. Will increase above the model blend with this in mind. Where snow falls, amounts do look relatively minor. That said, if parallel bands do form, very localized snow could drop for a longer period of time - and thus, higher amounts could be realized. A lot of "ifs" here, but its a scenario to monitor. - WEEKEND: warming up! Change in the upper level pattern moving into the weekend with the zonal/broad ridging taking over. Latest deterministic runs have 850 mb temps climbing from the teens below zero at 12z Thu to the single digits above for Sat-Mon. High temps in EPS suite of ensemble members have placed 75% of its members in the low/mid 40s for highs Sun, just a few degrees cooler either side of that day. A very consistent signal in the EPS. The GEFS has been cooler than the EPS, but has shown some increase over its past few runs. Either way, all trends point to at/above normal temps moving in for the weekend and the start of the new work week. The change in the pattern could allow for bits of shortwave energy to spin near/across the region. Current outlay of the ensembles suggest the higher pcpn probabilities would lie north/south of the forecast area. && .AVIATION /00Z TAFS THROUGH 00Z THURSDAY/... Issued at 552 PM CST Tue Dec 3 2024 We are looking at VFR conditions with southerly winds between 10 and 15 knots for tonight. In the wake of a strong cold front on Wednesday morning, winds will shift to the northwest. Sustained winds will be 20 to 30 knots with gusts of 30 to 45 knots. In addition to the strong winds, there will be MVFR ceilings. && .ARX WATCHES/WARNINGS/ADVISORIES... WI...None. MN...Wind Advisory from noon to 9 PM CST Wednesday for MNZ079-086- 087-094-095. IA...Wind Advisory from noon to 9 PM CST Wednesday for IAZ008>010- 018-019-029. && $$ DISCUSSION...Rieck AVIATION...Boyne
Area Forecast Discussion...UPDATED
National Weather Service Brownsville TX
713 PM CST Tue Dec 3 2024 ...New UPDATE, AVIATION, MARINE... .UPDATE... Issued at 654 PM CST Tue Dec 3 2024 Interesting evening underway, as weak surface low pressure (inverted trough) was hugging the coast with a sharp wind shift between Bayview/South Padre and Brownsville. That same wind shift showed a sharp difference in temperatures, from the low to mid 70s on the coast where east winds continued, to the low to mid 60s in the Brownsville/Harlingen area...and around 60 in the mid Valley and upper 50s across the Brush Country. Bands of overrunning rain continued to roll across eastern Cameron County (especially), where daily totals were nearing 2 inches (1.8" unofficially) at Brownsville/South Padre Int`l Airport. The trough has also cranked up seas and swells above originally forecast, and web cams showed both rough/high/confused surf but also run-up toward the dune line just before sunset. Based on local guidance for the incoming swell as well as adjusted model forecast tide levels, have hoisted a Coastal Flood Advisory to continue through pre-dawn Wednesday. Tides may begin to run out a little sooner...but elected to add a buffer of around 6 hours after high tide (859 PM) based on the expected incoming easterly swell which may keep a prolonged buffer of water to or just into the dunes. Based on the surf and swells, hoisted a high surf advisory for the overnight. While unlikely that many will be venturing into the dangerous surf, the water temperatures remain above average (75 degrees) so decided to be prudent and add to the mix of coastal hazards. Expect a gradual recision of run up and high surf on Wednesday, so these hazards will likely expire...but rip currents will remain through at least sunset. && .SHORT TERM... (Tonight through Wednesday night) Issued at 215 PM CST Tue Dec 3 2024 The latest radar and satellite imagery depicts overcast skies and isolated to scattered showers across Deep South Texas and the Gulf waters this afternoon. The highest coverage of showers remains mainly along the immediate coast and Gulf waters, which coincides with the highest precipitable water values and proximity to a weak coastal low and associated frontal features. Surface observations and the latest RAP analysis indicate the center of the coastal low to be near or just south of the mouth of the Rio Grande River as of this writing. Unsettled weather will continue into tonight as the aforementioned surface features translate north along the Lower Texas coast, with the highest precipitation chances (40-70%) residing mainly along and east of the I-69 corridor through midnight. Pockets of locally heavy rainfall cannot be ruled out as moisture content remains high, but the axis of rainfall should shift further north of the Lower Rio Grande Valley over through the evening and tonight. After midnight, we should begin to see activity begin to taper off from south to north along the immediate coast as the coastal low translates north. Precipitation chances are somewhat lower (30-40%) west of I-69 tonight, but light to moderate showers cannot be ruled out. Otherwise, expect overcast skies and lows falling into the 50s region wide, with the exception along the immediate coast with lows in the low 60s. Most precipitation chances on Wednesday and Wednesday night will be confined over the Gulf waters and Lower Texas beaches, where the slightly higher moisture content will reside. For the rest of Deep South Texas, the combination of cloudy skies and generally light winds will promote a pleasant day with highs mostly in the low to mid 70s, slightly lower than seasonal normals for early December. Winds will gradually shift to the south through Wednesday afternoon, which will result in slightly warmer low temperatures Wednesday night ranging from the upper 50s across the Rio Grande Plains to upper 60s and low 70s across the Lower Rio Grande Valley and immediate coast. Along the Lower Texas beaches, a high risk of rip currents will continue through Wendesday evening as winds and seas remain elevated in response to the northward-moving coastal low. && .LONG TERM... (Thursday through next Tuesday) Issued at 215 PM CST Tue Dec 3 2024 Upper level troughing over the western continental U.S. will bring southwesterly flow aloft and coax a coastal low to meander north early in the long term. As the coastal low pushes northward Thursday, it will bring chances of rain, with highest chances expected Thursday evening over the Gulf Waters before backing off over the weekend. PoPs drop to less than 20% for the region, bar along the coast, for the weekend and early next week. The fate of next week lies in the timing and strength of a cold front associated with the CONUS trough, which at this time are uncertain, but continue to be monitored. European vs. North American guidance both agree this trough will evolve into a cut- off low over AZ/western Sonora by the weekend, however timing and trajectory vary between each. Temperatures start off near-seasonal in the beginning of the period, with northern ranchlands highs near 70 and lows in the 50s, and lower valley/coastal highs in the 70s - nearing 80 - and lows in the 60s. Temps may creep up early next week as 850hpa winds advect the shallow moisture remaining in the lower atmosphere. A tightening pressure gradient ahead of the coastal low late Thursday/early Friday will increase winds and return elevated seas, leading to a likely chance of increased rip current risk for the local beaches Friday. && .AVIATION... (00Z TAFS) Issued at 654 PM CST Tue Dec 3 2024 Wind shift to the northwest behind the slowly departing coastal trough has brought the relatively cooler air with it...as well as IFR to LIFR ceilings for most. CAMs and NAM-12 are the better models...but even they were tardy to the low ceiling party, so had to fly by the observations to start the period. With just a slow drop in temperatures and dewpoints expect ceilings to remain or flirt between the IFR/LIFR line at Brownsville and Harlingen overnight, with slightly higher levels at McAllen with a slightly higher mixing layer below the stout inversion. Visibility is dependent on rain...with a few more shower bands through mid evening at Brownsville/Harlingen before they should taper down. Still expecting some periods of 4-5 mile visibility overnight. Ceiling will be slow to lift on Wednesday. Raised to low VFR at McAllen for the afternoon, but held low MVFR during the same time for Harlingen and Brownsville. && .MARINE... Issued at 654 PM CST Tue Dec 3 2024 Aforementioned rise in seas/swell to 10 feet and 9 second period at buoy 42020 enough to both raise the values in the Coastal Waters Forecast and the Small Craft Advisory hazard. Extended the Advisory through noon Wednesday (seas) and may need to extend longer for at least the 20-60 nm leg but perhaps all of the waters, depending on swell direction by afternoon. A continued east to east-southeast direction would push at least 7 foot waves into the 10-20 nm portion of the nearshore, enough to extend all Gulf waters through 6 PM. && .MARINE... Issued at 215 PM CST Tue Dec 3 2024 Tonight through Wednesday night...Adverse marine conditions will prevail through late Wednesday night, with Small Craft Exercise Caution to Small Craft Advisory conditions existing for the Laguna Madre and Gulf waters. The Small Craft Advisory for the Gulf waters will likely need to be extended for elevated seas through at least Wednesday evening, although winds should begin to subside Wednesday afternoon. Otherwise, expect scattered showers and isolated thunderstorms through the period, which may result in locally enhanced winds and seas. Thursday through next Tuesday...Thursday evening through Friday night, winds and seas may become elevated once again with potential for Small Craft Exercise Caution conditions possible. Seas and winds will diminish Saturday, leaving favorable light conditions. However, a meandering coastal low will keep rain chances elevated in the beginning of the period, with the greatest chance of rain Thursday night at 70%. Moderate rain chances persist over the weekend, primarily in the northern Gulf waters, before diminishing to early next week. && .PRELIMINARY POINT TEMPS/POPS... BROWNSVILLE 61 75 67 80 / 60 20 10 40 HARLINGEN 57 73 63 80 / 50 10 10 40 MCALLEN 57 73 64 80 / 30 0 10 30 RIO GRANDE CITY 52 72 60 75 / 30 0 0 30 SOUTH PADRE ISLAND 67 74 71 77 / 70 30 20 50 BAYVIEW/PORT ISABEL 60 74 65 78 / 60 20 20 50 && .BRO WATCHES/WARNINGS/ADVISORIES... TX...High Rip Current Risk through Wednesday afternoon for TXZ451-454- 455. Coastal Flood Advisory until 5 AM CST Wednesday for TXZ451-454- 455. High Surf Advisory until 7 AM CST Wednesday for TXZ451-454-455. GM...Small Craft Advisory until noon CST Wednesday for GMZ150-155-170- 175. && $$ SHORT TERM/MARINE/AVIATION Update...52-Goldsmith