Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 11/17/19

Area Forecast Discussion
National Weather Service Green Bay WI
608 PM CST Sat Nov 16 2019 Updated aviation portion for 00Z TAF issuance .SHORT TERM...Tonight and Sunday Issued at 239 PM CST Sat Nov 16 2019 The latest RAP analysis and satellite/radar imagery show high pressure exiting over the eastern Great Lakes while low pressure is moving east over southern Manitoba. Mid-level clouds continue to move east across the region above scattered to broken mvfr strato-cu. Think some of these low clouds will erode through the rest of the afternoon. Precip is developing over South Dakota and falling out of a mid-level cloud deck. As this storm system moves east, timing and accumulations of wintry precip are the main forecast concerns. Tonight...Low pressure and associated frontal system will continue to track east into Wisconsin late. Timing has slowed a bit, and the cold front may not move into northwest Wisconsin until closer to 12z Sunday. Timing of precip has slowed as a result, arriving into north-central WI in the 4 to 6 am time period. Could see up to a half inch of snow accumulations by 6 am over western Vilas county. Otherwise, will see clouds gradually thicken and lower through the night. With a mild south wind and cloud cover, temps should only fall into the middle to upper 20s. Sunday...Precipitation will continue to move east along the cold front, but gradually diminish in the process. Temps should be cold enough for precip to fall mainly as snow over central and north- central WI. This should result in an additional accumulations of up to an inch. By the time precip moves into northeast WI, including the Fox Valley, temps are forecast to warm into the middle 30s, making precip more of a rain/snow mix. With precip forecast to thin out, accumulations continue to look minor in this area, and perhaps a couple tenths are possible. Forecast soundings indicate that mid-level moisture departs during the afternoon on the trailing edge of the precipitation band. Could therefore see precip mix with or change over to freezing drizzle for a time, mainly over north-central WI where temps will be near freezing. But don`t think any freezing drizzle will lead to much impacts with temps near freezing and time of day considerations. .LONG TERM...Sunday Night Through Saturday Issued at 239 PM CST Sat Nov 16 2019 An upper level trough and associated cold front will be moving through the forecast area Sunday evening, so will keep a chance of precipitation in the east and north part of the cwa. Moisture will be shallowing out, so any lingering light snow may change to drizzle or freezing drizzle. Temperatures in eastern WI may also be warm enough for a mix of light rain/snow early. Generally dry conditions are anticipated as a ridge of high pressure moves through WI Monday and early Monday night. A warm front will impact the forecast area late Monday night into Tuesday, but will not have much moisture to work with. For now, will only carry low-end pops for light snow or freezing drizzle. A potentially stronger system is expected to arrive Wednesday night into Thursday, but there are strength and timing issues with the medium-range models. The GFS is strongest and farthest north with the surface low, and brings a significant rain to much of the cwa, while the ECMWF is farther south, colder and not as strong. Have bumped up pops to likely in the southeast part of the forecast late Wednesday night into Thursday morning. Later forecasts will be able to provide more details on the likely track and strength of the low in upcoming days, with better estimates on QPF, as well as potential snow accumulations on the colder northwest periphery of the storm. As this system exits, there will be potential for a brief period of light lake effect snow showers over north central WI Thursday night. Models diverge for the weekend, with the GFS suggesting a generally dry forecast, while the ECMWF supports a chance of snow showers as an upper trough swings through the region. && .AVIATION...for 00Z TAF Issuance Issued at 608 PM CST Sat Nov 16 2019 Some MVFR clouds persisted across portions of eastern WI late this afternoon, with mid-upper clouds across the rest of the area. Look for the MVFR clouds to continue to dissipate/exit eastern WI as winds become southerly, lingering the longest at KMTW. Flying conditions will deteriorate on Sunday as snow spreads west to east across the area. IFR CIGS and VSBYs are expected for a few hours in the heaviest precip. A period of LIFR conditions are possible as well, mainly at KAUW, KCWA, and KRHI Sunday morning. As temps climb through the day, look for the snow to mix with or change to a period of rain, especially across central and eastern WI. As the steady precip exits in the afternoon, a period of drizzle and freezing drizzle is expected. Only minor improvements in CIGS are expected in the afternoon. && .GRB WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SHORT TERM.....MPC LONG TERM......Kieckbusch AVIATION.......Bersch
Area Forecast Discussion
National Weather Service Wilmington NC
653 PM EST Sat Nov 16 2019 .SYNOPSIS... Periods of rain, very strong wind, and unseasonably cool temperatures will prevail through the remainder of the weekend, as powerful low pressure deepens off the Carolina coast. The storm will move away from the area late Sunday, with rain and wind trending down. High pressure will follow early next week, with drier and warmer weather into mid week. A cold front is expected to move through the area late next week. && .UPDATE... WINDS: Almost all synoptic/mesoscale models show the strongest 975 mb winds (45-50 kt) affecting the coast between now and 06z. The Frying Pan Shoals buoy has gusted to 58 kt/67 mph within the past hour. Gusts on the beaches have reached 59 mph at Wrightsville Beach, and 45 mph on Topsail Island. Weatherflow station peak gusts include 51 mph at Federal Point, NC; 49 mph at Oak Island, NC; and 48 mph at Lake Arrowhead near Myrtle Beach, SC. At the Wilmington airport gusts have reached 47 mph, with 46 mph at North Myrtle Beach. The Wind Advisory was earlier expanded one tier of zones westward, and continues into Sunday. TEMPS: Temps may rise a bit along the NC coast overnight, with steady to slowly falling temps anticipated across most of northeastern South Carolina. Forecast lows are raised to around 40 on the I-95 corridor, mid 40s SC beaches, and upper 40s NC beaches. Used a raw model-based curve (non-diurnal) to calculate hourly temps through Sunday morning. POPS/WX: Used 18z NAM and 22z HRRR to nudge PoPs/Wx grids overnight. Inland rain should largely dry up around midnight, but waves of rain and some evening elevated convection will continue overnight nearer to the coast. Overall reduced QPF forecasts, especially inland. COASTAL FLOODING: Expanded the coastal flood advisory to cover the Brunswick County coast. Despite offshore winds, the offshore storm has pushed water levels high enough along the entire Carolina coastline to produce flooding during Sunday morning`s high tide. This is one to watch: the latest ETSURGE guidance has Wrightsville Beach getting within about 3 inches of moderate (warning-level) coastal flooding Sunday. && .NEAR TERM /THROUGH SUNDAY/... High Surf Advisory for Pender, New Hanover beaches ongoing through much of Sunday, as 8-13 foot breakers crash onshore. This threat will escalate with Sunday morning`s high tide, as coastal flooding and high water run-up reach peak, increasing the danger for beachgoers, especially anyone entering the surf, or venturing too close to the surf`s edge without a flotation device. Strong winds caught in the pressure grip of the potent coastal low will peak this evening, holding strong overnight, with more notable abating of wind Sunday afternoon. As a result the `Wind Advisory` for the NC coast will remain intact, with N gusts as high as 45-50 mph from Surf City to Wrightsville Beach to Carolina Beach to Fort Fisher to Bald Head Island, to eastern Brunswick county coast tonight and early Sunday. Weakened trees or large branches from Hurricane Dorian`s impacts could topple as winds peak late today, overnight, and early Sunday morning. Approximate center-line of QPf ensembles, pointing to an additional 1.5-2 inches along the NC coast, 3/4-1.25 inches along the NE SC coastal zones, and 1/3-1 inch for most of inland SE NC and NE SC. Areas west of I-95 may only see additional amounts around 1/4 inch. Do not anticipate big flooding problems, but isolated training of rain, or brief high rain-rates, could cause localized flooding, and dangerous water ponding on highways. Wind, clouds, rain, and a singular air mass, will keep temperatures at and by the coast, nearly flat-lined, whereas diurnal temperature ranges well inland will show greater spreads between max-T/min-T. && .SHORT TERM /SUNDAY NIGHT THROUGH MONDAY NIGHT/... A mid level trough will move across the area through the day Monday and guidance, although seemingly going back and forth is once again developing some light showers across the area. Have added little activity (pop) with this development and to align with adjacent offices as well. Highs Monday will be in the middle to upper 50s and lows Tuesday morning with some clearing will be a couple of degrees either side of 40. && .LONG TERM /TUESDAY THROUGH SATURDAY/... The extended period remains relatively unchanged with the mid level trough moving across early in the week transitioning to a somewhat progressive mid level ridge. A broad split flow wants to develop late although there are timing differences with the guidance. A cold front, mainly associated with the northern branch moves across very late in the period. Not necessarily a significant system but low pops are warranted. No significant changes to the temperature forecast which offers little deviation from climatology until late when warmer readings develop. && .AVIATION /0Z SUNDAY THROUGH THURSDAY/... Predominantly MVFR this TAF period, with chance for IFR ceilings overnight into tomorrow morning. As strong nor`easter offshore slowly moves northeastward, abundant low level moisture and tight pressure gradient will keep ceilings mainly around 1500 ft across the area with strong northerly winds. Light rain will slowly taper off across NE SC, and linger in coastal NC areas through tomorrow afternoon. Included IFR ceilings at ILM overnight where confidence is higher, but IFR possible elsewhere as well. Strongest winds will be between now and 12z, sustained between 15 and 20 kts inland and 20-25 kts along the coast, with gusts mainly between 25 and 30 kts. Gusts up to 40 kts at times possible at coastal sites overnight. Have included low-level wind shear at ILM due to forecasted winds at 2 kft over 50 kts overnight. Wind shear at MYR and CRE will be close to criteria with 2 kft winds near 50 kts. Extended Outlook...Sub-VFR ceilings could linger Sunday into Monday afternoon, mainly along the coast and SE NC. Becoming VFR Monday through Thursday, with chance for fog Tuesday morning. && .MARINE... Dangerous marine conditions, venturing out and especially offshore is highly discouraged. Storm Force winds will rip across the NC waters and buoy 41013 has already reported gusts to 51 knots, or about 59 mph. Gale force winds will rake the SC waters, with a few storm force gusts possible beyond 15 nm tonight and early Sunday. Noticeable lessening of winds will be seen by Sunday afternoon, but still dangerous as large seas propagate through the waters. Seas made up of NE waves 9-14 every 10-12 seconds, with lashing N chop in the mix on top of these large waves. If all this were not convincing enough to stay in port, isolated TSTMs are possible offshore, mainly beyond 10 NM through this evening. No real significant systems to drive winds and seas too high for basically the short and long term period. More variability in the winds, which is typical if anything. A decent northwest flow of 10-15 knots will be in place initially associated with the waning impacts from this weekend`s coastal storm. Weak high pressure will dominate the mid week period with a weak boundary moving across later Tuesday to kick up the winds briefly. A decent and prolonged (at least for the winter season) return flow develops late and increases gradually in magnitude. Could see some 15-20 knot speeds here. Significant seas basically follow the winds with 2-4 feet with maybe an increase late with the better fetch. && .TIDES/COASTAL FLOODING... Dangerous beach conditions through Sunday morning. Tidal flooding will combine with large storm-waves, to bring significant coastal flooding and sea-water run-up at areas beaches. The offshore wind at Brunswick county will help stem the reach and advance of water there, and to a lesser extent at east facing beaches. Erosion will occur Sunday morning, as water levels approach the more rare `moderate` flooding threshold, possibly breaching low dune spots, with exception of Brunswick county. Right now, predicted water levels to make the upper reaches of `minor` category, but this could change to moderate with any increases in predicted levels. The lower Cape Fear river also to experience significant water rises Sunday morning, especially with all the rain run-off, and river levels also approach moderate stages, resulting in much more extensive impacts to residents affected by high water levels on the lower Cape Fear river, and adjacent roadways. && .ILM WATCHES/WARNINGS/ADVISORIES... SC...Wind Advisory until noon EST Sunday for SCZ054. Coastal Flood Advisory until 2 PM EST Sunday for SCZ054-056. NC...Wind Advisory until noon EST Sunday for NCZ105>110. High Surf Advisory until 6 PM EST Sunday for NCZ106-108. Coastal Flood Advisory until 2 PM EST Sunday for NCZ106-108- 110. Coastal Flood Advisory from 10 AM to 2 PM EST Sunday for NCZ107. MARINE...Gale Warning until noon EST Sunday for AMZ254-256. Storm Warning until 6 AM EST Sunday for AMZ250-252. && $$ SYNOPSIS...SHK UPDATE...TRA NEAR TERM...MJC SHORT TERM...SHK LONG TERM...SHK AVIATION...VAO MARINE...MJC/SHK TIDES/COASTAL FLOODING...
Area Forecast Discussion
National Weather Service Louisville KY
1003 PM EST Sat Nov 16 2019 .Forecast Update... Issued at 1002 PM EST Sat Nov 16 2019 A quiet night is in store. Skies will be mostly clear, other than some scattered cirrus high overhead. Atmospheric cross-sections show very light winds by dawn from the surface to about 800mb, and temperatures will fall toward crossover temperatures. However, today was the fourth dry day in a row and most guidance keeps surface dew point depressions of a few degrees at dawn, so will continue with forecast of patchy fog...with the best fog chances in the usual river valleys...which generally agrees with RAP and NARRE progs. && .Short Term...(This evening through Sunday) Updated at 315 PM EST Sat Nov 16 2019 Surface high pressure beneath flat upper level ridging over the region continues to provide sunny skies and dry conditions across the Ohio Valley. Current satellite shows some mid and high clouds streaming across IL, which should provide a beautiful sunset for many this evening. Clearing skies overnight may result in some patchy fog early Sunday morning, mainly north of the parkways and within river valleys. Sunday will start off cold with temps in the mid 20s. Expect to see increased mid and high level clouds throughout the day Sunday ahead of a cold front that will be positioned N-S along the Mississippi Valley. Clouds will do little toward impeding diurnal warming; therefore, expect to see max temps reach into the upper 40s to low 50s. .Long Term...(Sunday night through Saturday) Updated at 340 PM EST Sat Nov 16 2019 Sunday Night through Tuesday Night... Upper level pattern looks to remain in a ridge west, trough east type pattern through this period. Our region will sit within a mean trough axis with several weaker perturbations moving through the region. Model proximity soundings are still rather meager with the overall moisture over our region. However, there may be just enough forcing to get some light precipitation at times. The first perturbation will move through the region late Sunday night and early Monday. With the system moving through overnight, model soundings suggest that we could have a mix across southern Indiana where near term surface temps very close to freezing. Highs on Monday look to rebound thorugh into the upper 40s to around 50. Another weak system looks to move through late Monday night and early Tuesday. Again model soundings are suggestive that some mixed precip could occur. However, morning lows Tuesday morning look to be slightly warmer than Monday morning. Overall forcing with this system looks a little weaker, so precipitation would be rather light and very scattered. Highs again will rebound into the upper 40s and lower 50s. Lows Tuesday night will drop back into the 33-35 degree range. Wednesday through Saturday... Global models are in good agreement with a period of ridging for Wednesday. Given the good model agreement and rather consistent signaling here, yields a higher confidence forecast of dry and pleasant conditions for Wednesday. Afternoon highs look to top out in the low-mid 50s over southern Indiana and far northern Kentucky. Highs across the southern half of the state look to warm into the upper 50s to around 60. Wednesday night lows look to cool back into the upper 30s to the lower 40s. For the Thursday through Saturday period, forecast confidence drops to below normal for a few reasons. First, we will have a split flow pattern setting up across the CONUS. Dynamical models struggle highly in a split flow regime. Secondly, we will have to watch two features within the pattern that could potentially impact us for the late week period. First feature is a fairly potent mid-level trough within the northern stream and the second feature is a cut off low over the southwest US. Earlier in the week, the global models were suggesting that these two features would eject out similarly and phase as they headed across the country. Yesterday, there was ample agreement that the northern stream system would dive down and dig faster leaving the southern stream system behind. Today`s Euro and CMC models continue this line of thinking keeping the systems unphased with ample ensemble agreement as well. Today`s GFS/FV3 solution attempts to phase the streams, but have given more weight to the Euro/CMC OP/Ens solutions here. With that thinking, we`ll swath of widespread rain showers move into the region late Wednesday and continue through the day on Thursday. Some colder air may get in on the back side of that system by Friday morning allowing for a possibility of a change over to snow before ending. As always, it will be a race to see if the cold air can catch the back side of the precipitation shield. Today`s data suggest that a secondary northern stream wave is forecast to dip out of Canada and into the Plains. This secondary wave may end up phasing with the slower southern stream system bringing another storm system through the region on Saturday. Depending on the evolution of the upper level features, the track of this system is highly uncertain and will likely change a bit over the next week. && .Aviation...(00Z TAF Issuance) Issued at 627 PM EST Sat Nov 16 2019 Overall, aviation concerns should be minimal over the next 24-30 hours. Some light fog could lower conditions to MVFR, especially between 11-14z, at HNB/SDF/LEX. Otherwise, VFR conditions likely. Mainly clear skies overnight with just brief SCT cirrus. Northeast winds around 5 kts are forecast to diminish to nearly calm by 09-12z Sun. Winds will remain light throughout Sunday with a baggy gradient in between weather systems. We`ll see a substantial increase in high level cloud cover during the afternoon and evening hours. && .LMK WATCHES/WARNINGS/ADVISORIES... IN...None. KY...None. && $$ Update...13 Short Term...CG Long Term...MJ Aviation...EBW
Area Forecast Discussion
National Weather Service Marquette MI
527 PM EST Sat Nov 16 2019 .SHORT TERM...(This evening through Sunday) Issued at 418 PM EST SAT NOV 16 2019 WV imagery and RAP analysis indicated an upstream mid/upper level trough from Manitoba into western North Dakota and eastern WY. At the surface, southerly winds prevailed through the Upper Mississippi Valley and northern Great Lakes between a trough through the eastern Dakotas and high pressure over the St. Lawrence Valley. The WAA pattern through the region supported mid clouds into Upper Michigan. Although there were weak radar returns from MN into Upper Michigan, no pcpn was observed given the very dry 925-700 mb layer. Tonight, as the trough advances toward the region, moisture advection toward Upper Michigan will increase as a sw low level jet also approaches. Even with some time to saturate the dry layer, expect light snow to develop over the west between 09z-12z with some minor accumulations up to a half inch. Otherwise, increasing clouds and mixing with the southerly winds will keep temps from falling past the upper 20s. Sunday, the mid level trough with weak to moderate 700-300 qvector conv and a band of isentropic lift will bring pcpn through the rest of Upper Michigan. Wet-bulb zero height forecasts suggest that most of the pcpn will fall as snow, except over portions of the central and east, especially for locations of with low level flow southerly flow of the warmer waters of Lake Michigan. Overall amounts should be fairly light with snowfall totals to around an inch possible. As is often the case with WAA events, locations near Lake Superior should see lower amounts with downsloping. Forecast soundings also show enough drying at the top of the moist layer for the possibility of freezing drizzle as the pcpn diminishes. .LONG TERM...(Sunday night through Saturday) Issued at 323 PM EST SAT NOV 16 2019 Sunday night, ongoing light precipitation will be associated with a slow moving shortwave and cold front that will become negatively tilted and eventually phase with a developing coastal low riding up the Atlantic. Following that, a relatively progressive pattern will be in place through next week with a couple passing shortwaves from the W/WNW. On Thursday, confidence is beginning to increase that a deepening sfc low will pass close enough to the southeast to bring more significant precipitation, mainly over the east half, but exact track and subsequent p-type and amounts remain in question at this time. Except for a briefly colder airmass passing across the region behind this system on Thursday night/Friday that will bring a return to some LES, near normal temperatures are expected through the period. Early Sunday night, 850 temps of -2 to -4C will allow just enough of a delta-T for a brief period of enhancement off of Lake Michigan, but overnight qpf should still top out around 0.10". Early on, some snow accumulations of up to 1" are possible east, however forecast soundings do show ample mid level drying behind the front, with a deep saturated low level profile that may remain warmer than -10C. This indicates the chance of a changeover to a period of drizzle/light rain that will possibly begin to freeze to some elevated surfaces as temperatures dip into the upper 20s to near 30. Although any ice accumulation would max out at a couple hundredths of an inch, it could lead to some slick roadways especially over the east half for the morning commute. Cant rule out some lingering flurries or dz/fzdz during the day Monday and into Tuesday as well, but little to no accumulation is expected. 850 temps bottoming out near -5C will be too warm for any sustained or significant lake effect snow. A shortwave and associated rapidly weakening sfc trough will approach from the NW Tuesday. Some light mixed precip is possible but there is some uncertainty in timing and location. Only a dusting of snow or a hundredth or so of drizzle/ice would squeeze out with a dry airmass in place and very weak forcing. Wednesday looks mainly dry as well, but an approaching upper trough will bring colder air and increasing precipitation chances overnight. There remains a rather large spread in ensemble solutions but some synoptically forced precip is possible as a strengthening sfc low pushes through lower MI, with the best chances currently over the far east. Depending on the track, this could fall mainly as rain, or bring measurable heavy wet snow to parts of the area, but it`s also still within the envelope of GEFS solutions that significant precipitation skips the UP entirely. Current deterministic GFS is much slower and further west than other models as well as the GEFS mean, so not buying into that much wetter soln. Could be some lake enhancement component to this as well later Thursday. Will continue to hone in on the details and impacts with subsequent forecasts. There is much higher certainty in a brief period of N to NW flow lake effect behind this system Thursday night and Friday as a pocket of -12 to -15C 850 temps pushes through, but the colder air will be exiting through the daytime and winds should be diminishing as well, so Friday night into Saturday will have better chances of being drier. That said, the latest ECMWF brings a closed low out of Ontario Sat, thus slight chance to low end chance POPs remain in the forecast. && .AVIATION...(For the 00Z TAFS through 00Z Sunday evening) Issued at 527 PM EST SAT NOV 16 2019 An approaching trough and tightening pressure gradient will bring gusty south winds to all sites through Sun morning. As low level moisture increases along with light snow, expect conditions to drop to MVFR overnight or early Sunday and to IFR Sunday morning. && .MARINE...(For the 4 PM Lake Superior forecast issuance) Issued at 418 PM EST SAT NOV 16 2019 A strong pressure gradient ahead of an approaching trough will support southerly winds between 20 and 30 knots. A few gusts up to 35 knots are possible into this evening, mainly at higher observation platforms. The strongest winds are expected north and along the Keweenaw and east towards the Canadian waters and Michipicoten Island. Winds will veer more northwesterly and decrease through the day on Sunday, relaxing below 20 knots by Sunday night. Winds will remain relatively calm through Wednesday night as high pressure remains across the region. Some models suggest a low pressure system will develop across the Central Plains before traversing northeast and cross Lake Superior Thursday night into Friday. This will bring the next chance at winds approaching 30 knots. && .MQT WATCHES/WARNINGS/ADVISORIES... Upper Michigan... None. Lake Superior... None. Lake Michigan... None. && $$ SHORT TERM...JLB LONG TERM...KCW AVIATION...07 MARINE...JLB
...Updated Aviation Forecast Discussion...

.DISCUSSION... Issued at 230 PM CST Sat Nov 16 2019 The main forecast concerns are precipitation chances tonight into Sunday morning, chances Sunday night into Monday, and then again from Wednesday afternoon into Wednesday night and Thursday. The last event in that list could have some thunder Wednesday evening, then rain changing to snow. Some snow accumulations possible, but way too early to start looking at specific amounts. Short term...Tonight through Tuesday. A fairly strong shortwave trough and an associated cold front will continue to push eastward across the region tonight into Sunday. This trough had 12 hour height falls of 50 to 100 meters from WY up into Saskatchewan and Manitoba at 12Z. There was also decent upper level jet support. Cold front will continue to push through the area overnight, with precipitation chances developing with mid level lift associated with large scale forcing. Trough axis will not be through the forecast area by 12Z and so had added some POPs for Sunday morning with an update earlier today. Most model guidance is picking up on the precipitation development in IA, but favored the RAP and some of the other short range CAMs for precipitation later tonight into mid morning Sunday across southeast NE (and southwest IA). This looks to be mostly a rain event, with a light wintry mix at least possible. Another fast moving, but weaker, shortwave trough will bring a chance for light precipitation late Sunday night into Monday morning. This also looks to be mainly rain, with some brief freezing rain or sleet possible. Look for highs Sunday in the mid 40s to lower 50s, mainly 50s Monday and Tuesday. Long term...Tuesday night through Saturday. At the start of this period we should be under the influence of weak mid level ridging with a couple of troughs to our west. One will be over Baja, with another stretching from the Pacific NW into northern CA. This will transition to more of a split flow by Wednesday, as a 500 mb low tries to close off near the CA coast. Will start increasing chances for rain Wednesday afternoon, with some thunder possible by Wednesday evening. The 12Z GFS model showed some CAPE by that time across parts of southeast NE and it does fit a common pattern. Several things will be coming together for a moderate precipitation event for our area, with the heaviest amounts likely farther south of our area, with better/deeper moisture. Cold air moving in should bring a transition of rain to snow, with details yet to be worked out. Just how fast the cold air works in will help determine snow amounts. Best chances for precipitation being in the form of snow are in northeast NE, but at this time that is also where precipitation amounts (water equivalent) are expected to be the lowest. There are some fairly large model differences (GFS versus ECMWF) for Thursday. The 12Z ECMWF has a much stronger shortwave trough in the northern stream (and is colder) compared to the 12Z GFS. The period from Thursday afternoon into Friday looks mainly dry, with chances for rain and snow increasing again toward Friday night and Saturday. Temperatures should be fairly mild Wednesday, ranging from near 50 at the SD border to lower 60s at the KS border. Thursday will be noticeably cooler with highs in the upper 30s to mid 40s. Highs Friday and Saturday should be mostly in the 40s. && .AVIATION...(For the 00Z TAFS through 00Z Sunday evening) Issued at 531 PM CST Sat Nov 16 2019 Expect a wind shift across the area this evening and overnight as a front moves across eastern Nebraska. In addition some lower ceilings, MVFR, may occur along after midnight. At this point we are not anticipating any visiblity issues as any precipitation that does form will be very light and the wind gradient will remain strong enough to keep any fog from forming. && .OAX WATCHES/WARNINGS/ADVISORIES... NE...None. IA...None. && $$ DISCUSSION...Miller AVIATION...Pearson
Area Forecast Discussion
National Weather Service Riverton WY
158 PM MST Sat Nov 16 2019 .SHORT TERM...(This evening through Sunday Night) Storm system continues to move through the area this afternoon, with the heaviest precipitation at 1 PM extending from around Lander to Beaver Rim and eastward into Natrona County. HRRR is showing the bulk of the precipitation moving southeast out of the area by around 4 PM. Certainly some heavier rain and snow occurred today than expected, with more snow due to adiabatic cooling from southern Johnson County into Natrona County and across southern Fremont County. Next couple of hours will see precipitation continue across central WY and impact activities and travel. Clearing and brisk north to northwest wind to the northwest of the system is showing nicely on radar, satellite, and webcams, though unstable mid layers with so-so moisture could give rise some scattered showers. Skies will go from partly cloudy to mostly clear overnight with mid-level northwest flow. Sounds like a good pattern for areas of fog after midnight in the places that have received the most precipitation. High- to mid-level clouds will start moving back into NW WY by early Sunday morning as weak energy overtops the upper level ridge over the western US. Models are indicating that low- to mid-level moisture will increase enough over NW WY for light snow showers Sunday morning. This enhancement appears to be due to a shortwave trough moving through the flow over Montana and NE WY. Sunday afternoon will thus see the surface pressure gradient increase from west to east and help west to southwest wind increase across southern and south-central WY. The wave will also bring precipitation to northeast WY where the Bighorns and Johnson County will see another round of precipitation and wind shift to the north. With 700mb temperatures back to around 0C, precipitation should be rain in the lower elevations with snow levels around 8000 feet. Some showers may make it down into eastern Natrona County as will late Sunday afternoon. This moderately moist northwest flow will continue Sunday night to allow light snow showers over the northwest mountains through Monday morning. .LONG TERM...(Monday through Saturday) A weak ridge axis will build from west to northeast across the forecast area to start out the work week. The southwest low to mid level flow into the area will result in a couple of above normal temp days with generally dry weather into Tuesday. Winds will pick up again on Tuesday especially in the wind corridor from Sweetwater into Natrona counties and will have to be watched to potentially have to highlight these areas. The next storm system will arrive late Tuesday and affect northwest Wyoming first, as the upper flow splits over the Pacific northwest. This will result in an upper low being pushed south to California, while the main mid level trough moves to the north of Wyoming. An associated cold front will move southeast into the forecast area by late Tuesday night, and will spread widespread precipitation into the region through Wednesday. The GFS and ECMWF models continue to disagree involving the precip amounts with the next system. The GFS model continues to produce more overrunning precip along the cold front, compared to the drier solution of the ECMWF model. Still leaning more toward the ECMWF model solution, which is more in line also with WPC QPF guidance, which would result in more of a snow/rain mixture in the valley locations and higher snow amounts in the northern toward central mountains. This storm system has more of a pacific air component, so do not expect very cold air in the wake of this system. High pressure By Friday, the slow moving frontal boundary should finally be south of the state, with weak high pressure expected to build into the forecast area through the upcoming weekend. && .AVIATION...(For the 00Z TAFS through 00Z Sunday evening) West of the Continental Divide...KRKS, KJAC, KBPI, KPNA Terminal sites: Skies will be clearing across the area to start tonight`s forecast period with all TAF sites expecting VFR conditions through the entire forecast period through Sunday afternoon. Winds should begin to relax somewhat by tonight after 03Z at most locations with the exception of KRKS. Have increased winds at KRKS and KBPI after 17Z Sunday. East of the Continental Divide...KCPR, KLND, KRIW, KCOD, KWRL Terminal sites. Skies will be clearing across the area to start tonight`s forecast period with most locations expecting VFR conditions through the entire forecast period through Sunday afternoon. Winds should begin to relax somewhat by tonight after 03Z at most locations with the exception of KCPR. Due to the increased moisture available and snowfall amounts especially at KLND and KCPR, will add in a mention of fog overnight at these locations from 03Z-14Z Sunday. && .FIRE WEATHER... Storm system exiting the forecast area this afternoon, with precipitation continuing across Natrona County, southern Fremont County, and eastern Sweetwater County through about 4pm. Behind the system, winds are north-northwest about 10 to 15 mph with higher gusts. Skies will be partly cloudy to mostly clear overnight. A weak system in northwest flow will skim north-central WY from midday Sunday through Monday morning, bringing some showers to the northwest mountains and the Bighorns, along with showers over Johnson and eastern Natrona counties. Sunday will also see slight warming over southwest WY with breezy west wind. Weak high pressure will be over the area Monday and Tuesday for continued breezy conditions and above normal temperatures. && .RIW WATCHES/WARNINGS/ADVISORIES...NONE. && $$ SHORT TERM...McDonald LONG TERM...Troutman AVIATION...Troutman FIRE WEATHER...McDonald