Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 05/22/21

Area Forecast Discussion
National Weather Service La Crosse WI
1050 PM CDT Fri May 21 2021 .SHORT TERM...(This evening through Saturday) Issued at 219 PM CDT Fri May 21 2021 GOES water vapor imagery continued to show a plume of deep moisture extending northward from the Gulf Coast through the Upper MS Valley on the western fringe of strong mid-level ridging across the Ohio Valley. Clouds remain extensive over the region with persistent moisture transport and precip water values over 1.6 inches. Scattered showers and a few storms will continue into early evening as a shortwave trough lifts across the region. With moist profiles/weak lapse rates and abundant cloud, instability has been slow to increase, with the RAP indicating 500+ J/kg of MLCAPE through late afternoon. Deep layer shear is quite a bit weaker today, although some 0-1 km shear is still present with the stronger low-level flow. This environment isn`t very favorable for strong/severe storms, and in fact, more showery conditions are expected than organized storms. Given the low-level shear, though, any stronger more persistent cells could at least exhibit transient rotation. As ridging builds across the area tonight into Saturday, GEFS integrated water vapor transport shows a relaxing of the moisture fetch into the area. In the absence of any coherent large scale lift signal, later tonight into Saturday looks predominantly dry. A weak shortwave trough possibly could bring a few showers to far southern areas by later Saturday, however. With potential for more sunshine on Saturday and 925 mb temps climbing into the 20-22C range, expect high temps into the 80s for much of the area. That said, if clouds do remain more stubborn, highs could hold in the 70s in some areas. .LONG TERM...(Saturday night through Friday) Issued at 219 PM CDT Fri May 21 2021 It looks like the potential for another extended period of rain chances is setting up for next week. The upper level ridging the builds over the Midwest for the weekend will get flattened as the western U.S. upper level low lifts to the north/northeast. As this low reaches southern Canada Monday and then weakens and move east, the upper level flow will transition to a quasi-zonal pattern over the Upper Midwest. This looks like it will return the pattern of several short wave troughs moving across the region, especially in the first half of the work week. At the surface, the nearly stationary boundary currently set up across the Dakotas and northern Minnesota, will sink south into the region by Sunday. An area of low pressure should develop with the upper level low and help to lift this front back to the north Monday. However, as the low moves to the east, it will quickly push a weak cold front into the region to help maintain a boundary/focus for convective development. This boundary may not exit the region until Tuesday night given the rather slow eastward movement of the parent area of low pressure across Canada. With the potential for several short wave troughs to move across the area and the presence of the surface boundaries, there will be an extended period of on and off rain chances from Sunday into Tuesday night. As of now, the periods with the best chances for some widespread rain looks to Sunday afternoon and night and Monday afternoon and night. Current indications are that any severe threat should be pretty minimal Sunday. While there may be some modest ML CAPE in place ahead of the boundary, on the order of 750 J/Kg or so, the deep layer shear will be lacking as it stays well to the north. Some heavy downpours might occur as warm cloud depths reach 3.5 to 4 km, but the moisture transport into the boundary does not look very impressive at this point. Looking out into the middle and end of next week, an area of high pressure should briefly build in from the north for some dry weather Wednesday. The should then move off to the east Thursday as another short wave trough approaches from the west to bring in a return for some additional rain. && .AVIATION...(For the 06Z TAFS through 06Z Saturday night) Issued at 1047 PM CDT Fri May 21 2021 Clouds have decreased through the evening and should see scattered clouds overnight. Moisture transport has weakened, however relative humidities are still expected to be on the high side. There may be some MVFR ceilings that spread northward around 12Z. With low confidence left the clouds scattered for now and can adjust if the ceiling develop northeastward. Low level winds of 20 to 35kts overnight should help mitigate the fog at the TAF sites. Southeast to southwest winds 5 to 15 kts with some stronger gusts at KRST Saturday. && .ARX WATCHES/WARNINGS/ADVISORIES... WI...None. MN...None. IA...None. && $$ SHORT TERM...JM LONG TERM...04 AVIATION...Zapotocny
Area Forecast Discussion
National Weather Service Denver/Boulder CO
854 PM MDT Fri May 21 2021 .UPDATE... Issued at 850 PM MDT Fri May 21 2021 Weakening thunderstorms over the northeast plains no longer warrant the Severe Thunderstorm Watch, therefore the watch has been cancelled. Also added the potential for patchy fog late tonight into Saturday morning, from the I-25 corridor eastward onto the plains. UPDATE Issued at 657 PM MDT Fri May 21 2021 Overall the timing of the thunderstorms in the grids this evening remains on track. Main line of storms over western Logan, Washington and Lincoln counties as this time, with the overall line moving slowly east this evening. No longer expect thunderstorms over Weld County this evening so I cancelled the Severe Thunderstorm Watch there. We may cancel the watch for Morgan County as well within the hour. Generally weak showers and a isolated thunderstorms over the mountains the rest of the evening, so flood threat in the burn areas will be very low the rest of tonight. Gusty south to southeast winds will persist across the northeast plains this evening, but gradually weaken further west. Only short term adjustments were made to the pops this evening, the rest of the grids look good. && .SHORT TERM...(This evening through Saturday) Issued at 323 PM MDT Fri May 21 2021 We`re still expecting strong to severe storms to develop over the eastern part of the plains on the redeveloping dryline over the next few hours. The area from east of Limon to north or northwest of Sterling looks like it`s almost warm/moist enough to break the cap. CAPEs in this area are 1000-1500 J/kg. The wind profile will favor large hail while the background 30 knots or so of low level flow will make it easier to get severe wind gusts as well. A tornado can`t be ruled out but once again some deviant motion would likely be required as there`s even less environmental helicity than yesterday. Storms should race northwards and while there may be a couple of nice focal points to start with, the environment will likely become messier with time and more likely to have linear or cluster types than quasi-supercells. There will likely still be enough CAPE/shear for large hail through early evening then later it should be mostly a wind threat as the low level flow stays brisk even as the convection weakens. The latest HRRR shows some redevelopment just after sunset. It seems possible for there to be some refocus at some point but I wouldn`t count on any of the detail. Meanwhile, the surface pressure falls near Denver delayed the south wind`s arrival, but it has spread across most of the city now. There`s still a battle going on up against the foothills around Broomfield which will likely continue. Eventually the northerly winds will wind, but this evening we`ll see conflicting forcing from the decreasing flow off the ground, the tendency for southerly drainage winds over most of the city, and a larger tendency for northerly winds as the synoptic pressure falls should shift out onto the plains a bit. By morning the cooler but moist air should have pushed southward across Denver. We prefer the models that are more aggressive with this, pushing it well south past Colorado Springs. This scenario keeps the area from Denver northwards too cool for surface based convection most of the day with northeast to east low level winds. The GFS is really aggressive with this and suggests the area will be capped all day, with a high in the mid 60s in Ft Collins. We`re not ready to go all the way with that solution and are still concerned with an intermediate solution that would be just warm enough and moist enough for the upslope winds to trigger late afternoon or evening convection that could be anchored or repetitive over the foothills presenting a flash flood threat. The convergence area south and southeast of Denver should be the focus for strong to severe convection Saturday afternoon. Models suggest this activity would likely start in El Paso and Elbert counties and then stream northward. How far north depends on the strength of the cool air surge, though the area east of Denver could be recharging as the plains southerlies push richer air into that area during the afternoon and early evening. There`s a lower threat of strong storms up along the northern border, though it will be moist enough that there is some threat if it gets warm enough. For temperatures, we`ve gone toward the cooler end of guidance across most of the area, but not as cold as the frigid GFS north of Denver. .LONG TERM...(Saturday night through Friday) Issued at 323 PM MDT Fri May 21 2021 A few severe storms with high winds and large hail will likely continue to race north/northeast across the plains Saturday evening. A couple showers and thunderstorms may also linger across the mountains and I-25 Corridor for a few hours in the evening due to sufficient instability, mid level moisture, and weak synoptic scale forcing. However, the primary severe threat should be pushing farther east, driven by the low level (untapped) instability axis. Some of these showers and storms may even linger past the midnight hour thanks to the above mentioned factors. Sunday will likely bring another severe storm threat, this time shifting farther east across the plains versus tomorrow. Timing will be everything here, with the latest models in fair agreement driving a well pronounced dryline east across the plains and roughly reaching a Sterling to Akron line by early to mid afternoon. Anywhere along and east of that line will see MLCAPE near 1500-2000 J/kg, coinciding with bulk shear at a whopping 45-60 knots. Hodographs are close to straight-line, with some curvature and effective Storm Relative Helicity (SRH) near 100 m2/s2. That said, a deviating storm to the east/northeast would support a rapid increase in SRH and larger tornado threat. Otherwise, very high winds and damaging/destructive hail would be the primary storm threats. Models can sometimes be too fast with the dryline, so will also watch this for any potential slowing and thus threat somewhat west of the above mentioned Sterling to Akron line. We do have higher confidence that the I-25 corridor and points west through the mountains will be dry, in fact - very dry, as the deep dry slot and downslope drying ensue the short wave/dryline passage. We`ll then see mostly dry conditions persist Monday and Tuesday. By Wednesday through the latter half of next week, we should begin to see more convective activity and stronger storms as MLCAPE builds and weak troughing is advertised by operational and ensemble averages. && .AVIATION...(For the 18Z TAFS through 18Z Saturday afternoon) Issued at 850 AM MDT Fri May 21 2021 VFR through tonight with gusty southerly winds gradually decreasing this evening. Saturday morning around 09z the models show more switch to north/northwest winds. This could result in patchy fog toward 12z but may just address this with vcfg in the next taf update. The winds are expected to become more easterly Saturday afternoon. Scattered thunderstorms are expected Saturday afternoon with a chance of wind shifts with gusts to 40 knots and localized MVFR conditions. Instrument approaches to KDEN may be needed after 18z due to ceilings and the thunderstorms. && .HYDROLOGY... Issued at 657 PM MDT Fri May 21 2021 Scattered showers and isolated thunderstorms will be possible over the mountains this evening. Just some brief light rain showers the rest of this evening so the flash flood threat will be very low the rest of tonight. On Saturday, moisture will increase but instability will be limited. If thunderstorms do develop over the foothills burn areas, heavy rain is possible. Storms are expected to be moving, but there would be potential for enough rain to cause flooding. Areas west of the divide will have a lower threat as storms should be moving faster. The main threat would be in the late afternoon through mid evening. A much drier airmass will develop across the mountains and foothills Sunday, with only a slight chance of a passing light shower over the burn areas. The far northeast corner of the state could still see locally heavy rain due to strong/severe storms. Drier weather should persist Monday and Tuesday, with scattered storms entering the picture again for Wednesday into the latter half of next week. && .BOU WATCHES/WARNINGS/ADVISORIES... None. && $$ UPDATE...Cooper SHORT TERM...Gimmestad LONG TERM...Barjenbruch AVIATION...Cooper/Gimmestad HYDROLOGY...Cooper/Gimmestad/Barjenbruch
Area Forecast Discussion
National Weather Service Caribou ME
915 PM EDT Fri May 21 2021 .SYNOPSIS... A cold front will approach overnight and slowly move across the region into Saturday night. A second cold front will move across the area Sunday. High pressure will build in through early week before another cold front approaches by the middle of next week. && .NEAR TERM /THROUGH SATURDAY/... 9:15 PM Update: A mild and muggy evening inland with dew points well into the 60s. It is much cooler along and near the coast owing to the cold ocean waters. The 00z Caribou sounding was very moist with a PWAT of 1.62" which is a daily record and not far from the May record of 1.73". Area radars showing showers pushing south across the Downeast Region and additional showers across the northern zones. No lightning has been detected in the past few hours. Made some adjustments based on the current conditions as well as for increased rain chances Downeast during the next few hours as showers move through the area. Previous discussion: Disturbance moving through the upper ridge kicking off showers and tstms this afternoon w/the most significant action being across eastern Aroostook County. Still expecting some activity to continue into the evening. Sounding data and convective parameters still showing MU CAPE Values into the evening of 500-700 joules, w/the best chance for storms from the Piscataquis region up into SE Aroostook County. Onshore wind has kept things cooler across the Bangor and Downeast region helping to negate the convective potential. As the night wears on, atmosphere is expected to stabilize which help to alleviate any further convection. The latest runs of the RAP and NAM show a pre-frontal trof apchg the region by early Saturday morning w/some upper support to set off some more showers across the far n and nw. The 12Z GFS showed this setup too. The RAP is the most robust w/the showers and placement which looks overdone as the NAM is weaker w/forcing. GFS is similar to the RAP and does show some mid level forcing to support the showers. Decided on the blend and leaned w/highest pops across the northern border and 20--40% elsewhere. Kept the mention of patchy fog in there for the Downeast areas and across the n where rainfall occurred. Some showers or perhaps drizzle expected in the morning, then a break as the trof lifts off to the e. Some partial clearing is possible which will allow for the atmosphere to destabilize by late morning, especially for the northern and central areas. This will lead to the potential for tstms w/CAPE values hitting 700-1000 joules. The steepest lapse rates are in the late morning across the Maine Highlands and Northern Maine, which would support updraft potential. However, those lapse rates shift to east as the cold front apchs and showers and storms get going. Looking at the latest Showalter Index and EHI placement, best potential looks to line up across the Southern Aroostook region down into the Piscataquis and Penobscot region by early to mid afternoon. In this region there a better chance for some heating leading to convective development. Soundings do support some hail, heavy rainfall w/the stronger storms given the PWS of >/= 1.50" WBZs around 10k ft. Inverted V in the llvls coupled w/dry air aloft leads to threat of some strong wind gusts too. Another item to be mindful is that since it is the weekend, folks being out on area lakes/streams and still relatively colder water temps led to the issuance of a Special Weather Statement for cold water temperatures. && .SHORT TERM /SATURDAY NIGHT THROUGH MONDAY/... The first cold front will slowly exit the area Saturday evening with a few lingering thunderstorms possible and most precip should be over by later in the evening. Conditions will remain quite humid overnight with dew points near 60F and that will limit low temps...and perhaps generate some fog. Fog would be most likely in the coastal Downeast region. The next cold front will be arriving in the Saint John Valley early Sunday morning and sweep southward across the forecast area by mid-afternoon. It appears to be an anafrontal set up with a baroclinic zone lagging behind the surface front. This structure and the early timing will limit convective potential in northern zones. Have maintained a chance of thunderstorms in the southern half of the forecast area for a narrow window from the midday into mid afternoon. There`s still some guidance suggesting a more robust convective environment with strong wind gusts as shear will be favorable, but most guidance favors the cooler and more stable scenario. The cold front will rapidly bring much cooler air into the area later Sunday and northeasterly winds will be gusting as high as 40 mph in the afternoon. A 1028mb high in Canada quickly builds overnight and suggests winds will die off enough to produce some frost later Sunday night. This will be mostly in the northern half of the area and the lowest temps will be in the North Woods where the frost/freeze program is not in effect. Monday looks like a sunny day with very low humidity and pleasant temperatures in the 60s. Did make some efforts to lower dew points below guidance. && .LONG TERM /MONDAY NIGHT THROUGH FRIDAY/... Temperatures will likely cool off fairly quickly Monday evening in the cool air mass, but may warm later in the night as the high moves offshore and warming southwest winds commence. Highs on Tuesday will be around 10F warmer than Monday and a strong pressure gradient generating gusty southwest winds. Gusts could reach up to 30kt. In the absence of any significant rainfall this weekend, fire weather would be a prime concern on Tuesday. The strong winds continue Tuesday night and keep lows from dropping out of the 50s. Guidance suggests some shower or thunderstorm activity in northern zones on Tuesday night along a thermal ridge axis, but could be just convective debris moving into very dry air over the state. Temps warm back towards the upper 70s to lower 80s on Wednesday ahead of another cold front. Timing will be critical for convective activity as the spread on frontal passage currently ranges from Wednesday afternoon to later Wednesday night. Once again, this front will bring a fresh supply of cool Canadian air and a return to seasonable temps and dry weather for late week into the Memorial Day weekend. && .AVIATION /01Z SATURDAY THROUGH WEDNESDAY/... NEAR TERM: VFR late this evening. There is a threat for MVFR and possible IFR by early Saturday morning, especially for KBGR and KBHB. S winds 5-10 knots overnight. For Saturday, some IFR cigs in the morning, and then conditions improving to VFR by mid to late morning mainly n of KHUL. Further s. MVFR hangs on longer. SHRA/TSRA possible in the afternoon for the region w/potential for MVFR and TEMPO IFR. SHORT TERM: Saturday night...VFR except a chance of IFR fog towards the coast to include BHB. Isolated thunderstorms possible in the evening. Light winds. Sunday...VFR with the exception of MVFR cigs in rain north of PQI in the morning. Isolated afternoon thunderstorms south of MLT and HUL. Winds becoming NW gusting to 25kt. Sunday night through Wednesday...VFR. Isolated thunder possible north of GNR and HUL on Tuesday night. Southwest winds gusting to 25kt on Tuesday. && .MARINE... NEAR TERM: Beach Hazards Statement issued per collaboration w/USCG and GYX. This will most likely be needed again for Sun. SCA in effect for swells of 5-6 ft for the outer waters into Sun morning. SSW winds 10-15 kt w/ocnl gusts hitting 20+ kts by late Sat w/the apch of the cold front. SHORT TERM: Fog expected Saturday night into Sunday morning. Can`t rule out an isolated thunderstorm Sunday evening. Long period SE swell will be diminishing Saturday night into Sunday with seas maxing out around 4 ft. A Small Craft Advisory seems likely to develop Tuesday and carry into Wednesday spite of stable conditions and little gustiness under an inversion. && .CLIMATE... The high of 85F in Caribou today was the warmest temperature since August 14, 2020. && .CAR WATCHES/WARNINGS/ADVISORIES... ME...Beach Hazards Statement from 8 AM EDT Saturday through Saturday evening for MEZ029-030. MARINE...Small Craft Advisory from 4 AM Saturday to 4 AM EDT Sunday for ANZ050-051. && $$ Near Term...CB/Hewitt Short Term...MCW Long Term...MCW Aviation...CB/Hewitt/MCW Marine...CB/Hewitt/MCW Climate...CB
Area Forecast Discussion
National Weather Service Grand Forks ND
921 PM CDT Fri May 21 2021 .UPDATE... Issued at 921 PM CDT Fri May 21 2021 The front is being picked up by the radar, with the latest image showing it along a line from Thief River Falls to Hillsboro to Cooperstown. The north winds to the north of the boundary have been fairly gusty, which has limited the fog so far. If the front keeps moving as it has been, it should push down into the Fargo Moorhead area in the next couple of hours, and could well continue even further southward. This has been bringing low clouds and north winds behind it, as well as falling temperatures. This southward push is a bit faster than expected, which will play into Saturday`s forecast too. The new model guidance for Saturday is looking cooler, with north winds across the entire FA. High resolution model guidance continues to show the precipitation developing over western South Dakota right now....lifting north- northeast overnight, mainly into the Devils Lake region, so that remains on track. UPDATE Issued at 655 PM CDT Fri May 21 2021 Tricky forecast again tonight, due to fog, spotty showers and storms, the possibility of an area of showers and storms moving into the Devils Lake region after midnight, and wind speeds and directions. The surface front sits along a Jamestown to Grand Forks to Warroad line, with south winds on one side and north winds on the other. Like last night at this time, there are some 4 to 5 mile visibilities already developing north of the boundary. This gives a little more confidence to fog developing again overnight, but not sure if it will become dense, or it will just stay in the 2 to 5 mile range. Did add the mention of fog to some areas behind the boundary. Spotty showers and storms continue to form along the boundary as well. After dark last night, they became elevated well north of the surface boundary, and that may happen again this evening. Already had some low precipitation chances along and north of highway 2, just spread them a little more eastward. Finally, high resolution models still show a more organized band of showers and storms forming over the western Dakotas and lifting up toward the Devils Lake region around or after midnight. If this occurs, it would finally bring a little more widespread rain to that parched area. However, convection is variable, and a lot could happen between now and then. && .SHORT TERM...(This evening through Saturday night) Issued at 315 PM CDT Fri May 21 2021 Frontal placement will continue to play havoc with sky cover and temperatures/winds into Saturday. South-southeast winds have made up to near a Hallock-Grafton-Devils Lake line at mid aftn. Winds have turned back north at KDVL at 20z. HRRR and blended model solutions indicate north winds dropping back southward as the front moves south behind exiting wave now in eastern Manitoba. Airmass in warm sector thru SE/EC ND into MN is quite warm and humid with man sites in the 80s and dew pts in the low-mid 60s. There have been some elevated shower/t-storms within the warm sector along the NE SD/SE ND/MN border region but they are diminishing. A narrow region of t-storms in NW MN, north of TRF to Roseau associated with southern edge of upper level wave in Manitoba will exit in the next few hours. Overall for most of the area a quiet start to the evening. Upper level wave and sfc low is progged to move north on the east side of the larger 500 mb low in Nevada. This system will showers and t-storms into south central and southwest ND this evening with a complex moving NE or ENE thru central and into NE ND and southern Manitoba overnight, exiting Saturday AM. Severe risk seems quite low but some gusty wind threat does exist into the DVL basin overnight. Behind this wave the north winds will drop south thru most areas Saturday as a front moves south. Scattered t-storms are possible along the front during the day Saturday as it moves into WC MN and SE ND in the aftn. Risk of a strong storm or two at that time, but upper ridge in place and lack of wind shear should prevent organized supercells from developing. Weak high will build into the north Saturday afternoon and evening. A chc for showers or psbly a t-storm continues over SE ND and WC MN Sat night. .LONG TERM...(Sunday through Friday) Issued at 315 PM CDT Fri May 21 2021 SUMMARY...Primary headline is the severe potential on Sunday night into Monday morning, primarily over the western CWA. The primary question to resolve is placement of the surface cyclone and connected warm front, as model guidance has been variable on positioning along the North Dakota-South Dakota border. The rest of the long term period is characterized by progressive shortwaves embedded within zonal flow and variable temperatures. SUNDAY THROUGH MONDAY...An interesting dynamic is setting up for Sunday. Ridging begins to deamplify and push eastward, allowing the strong cutoff low spinning over the northwest to push northward. This will provide for a very broad area of synoptic ascent over the northern high plains, facilitating surface cyclone development. Ensemble guidance has struggled with the position of this surface cyclone, which unfortunately puts warm frontal placement in a precarious situation, ranging from as far north as the south RRV to east central South Dakota. Isentropic ascent north of the warm front will likely facilitate cloud cover over the area, inhibiting boundary layer destabilization and limiting opportunities for thunderstorms, although showers north of the warm front cannot be ruled out, especially as ensemble members show the potential for weak shortwave troughs aloft in advance of the upper low Sunday morning. A very warm and relatively moist warm sector will set up south of the warm front, with dewpoints in the 50s and 60s with southerly flow. Within the warm sector, guidance suggests MLCAPE within the range of 1000-2500 J/kg. North of the warm front, elevated instability does exist, with lapse rates aloft in the range of 7 K/km. CI will likely occur upstream, so the primary question will be how far east ongoing convection gets and how far north it gets with the warm front. As the cold front sweeps through the area, convection will push eastward and diminish Monday morning into the afternoon. A dry clear day is expected behind the front, with increasing winds as mixing brings rather stout momentum down to the surface. TUESDAY THROUGH FRIDAY...Another breezy day on Tuesday is expected as strong flow aloft will mix down once again to the surface. Shortwave ridging will prevent any further activity on Wednesday, although guidance varies in the strength of this shortwave ridge, which will play a role in the evolution of Thursday and Friday. For now, leaving NBM due to high uncertainty in upper air evolution towards the end of the period. && .AVIATION...(For the 00Z TAFS through 00Z Saturday evening) Issued at 655 PM CDT Fri May 21 2021 Have stuck with the 18z TAF idea of fog and stratus forming again tonight into Saturday morning. Exact timing and locations when this happens is always hard to nail down, but went with the best trends and will adjust as need be. There have been isolated showers and weak storms along and north of the frontal boundary from Jamestown to Grand Forks Warroad this evening. There are some high resolution models that continue to show isolated shower and storm activity from where it is now all the way to the Canadian border this evening. However, coverage is not enough to warrant mention in any of the TAFs. The best chance for more organized showers and storms looks to arrive around or after midnight at KDVL. This may only last for a few hours before it continues to lift north-northeast into Canada. Not looking likely that the MVFR or IFR ceilings will lift on Saturday. && .FGF WATCHES/WARNINGS/ADVISORIES... ND...None. MN...None. $$ UPDATE...Godon SHORT TERM...Riddle LONG TERM...Perroux AVIATION...Godon
Area Forecast Discussion
National Weather Service Goodland KS
559 PM MDT Fri May 21 2021 .UPDATE... Issued at 434 PM MDT Fri May 21 2021 A severe thunderstorm watch is currently in effect for Yuma, Kit Carson, and Cheyenne counties until 10 PM MDT. Possible hazards include large hail and damaging winds. && .SHORT TERM...(This evening through Saturday night) Issued at 231 PM MDT Fri May 21 2021 500mb RAP analysis and satellite imagery showed southwest flow above the region this afternoon as a large closed low spun over western Nevada with upper ridging across the eastern half of the country. At the surface, a dryline extended from north to south along the Front Range in Colorado with some low to mid level clouds developing in its vicinity. Generally the region is under mostly sunny skies midday, with windy conditions as south winds gust up to 50 mph along a tight pressure gradient. At 2 PM MT, temperatures ranged mainly in the low to mid 80s. A north-south oriented line of thunderstorms is anticipated to initiate along the aforementioned dryline mid afternoon in north central/northeast Colorado. This line should enter the western portion of our area in the late afternoon and progress eastward into the evening hours. Am not anticipating this line to make it very far into southwest Nebraska and northwest Kansas before dissipating this evening. At this point, have kept thunderstorm chances in eastern Colorado and the first western tier of Kansas and Nebraska counties. Severe parameters including very steep mid level lapse rates, shear of 30 to 40 knots or so, and CAPE nearing 2000 J/kg support a potential for severe weather. While the threat exists along and west of Highway 27, the area of most concern will be Yuma and Kit Carson counties in Colorado where the mentioned severe parameters are at the highest levels. This setup suggests that large hail and damaging winds will be the main threats. Also cannot rule out a tornado or two with any initial discrete thunderstorms that develop this afternoon before they congeal into the line. Otherwise for tonight, south winds stay breezy through the evening, slightly tapering off early Saturday morning. Temperatures fall into the mid 50s to low 60s under mostly cloudy skies. On Saturday, the system over the western CONUS progresses very little, with the closed low lingering near Nevada. Southwest flow prevails aloft while breezy southerly winds gust around 30-35 mph. As temperatures rise into the mid 70s to mid 80s, we could see a little break in cloud cover before thunderstorms develop and clouds increase once again. Timing for thunderstorm initiation is uncertain at this point, with some guidance showing early development (around Noon MT) and others following similar timing to today. What is throwing me off is that we could see some thunderstorm activity billowing up from southeastern Colorado midday, which will then intensify as daytime heating is underway in the afternoon. Not sure which solution is correct, so this will have to be monitored. Nevertheless, thunderstorms look to form along the dryline once again in the afternoon, starting out as discrete cells and merging into a line or two through the evening. While severe weather will be possible across the entire region, the area that appears to have the higher threat is west of a line from Trenton, NE to Tribune, KS (roughly) due to the upper ridging pushing in from the east. Hazards are large hail, damaging winds, and a tornado or two. Dry weather should return to the region by midnight, with temperatures falling into the mid 50s to low 60s. .LONG TERM...(Sunday through Friday) Issued at 200 PM MDT Fri May 21 2021 Upper low will be over the northern Rockies on Sunday with negatively tilted shortwave trough moving over the central High Plains Sunday afternoon and evening. Front/surface trough appears to be likely location for convective initiation, which will be roughly along/just east of the Kansas/Colorado border area. Environment will be strongly sheared, up to 60 kts, with weak to moderate instability forecast. The set up would suggest severe storms likely, with still some uncertainty on exact locations for greatest risk, and perhaps some uncertainty due to lack of better instability. Nonetheless, SPC slight risk seems appropriate, might even bump it up a category due to the strong shear. Storms will continue into Sunday evening before weakening/moving east out of the area by midnight or so. Also expecting breezy to windy south winds Sunday afternoon, with gusts of 40-50 mph in Colorado and west of Highway 25 in Kansas/Nebraska. Front slowly moves through the area on Monday and becomes nearly stationary in central/eastern part of the forecast area. Exact location will ultimately determine where storms initiate in the afternoon. Another shortwave trough will be moving through the base of the upper low now in the northern plains. Deep layer shear/instability forecasts continue to support organized convection along/east of the front for Monday afternoon and evening, with shear forecast at 40-60 kts, with another round of severe storms possible. Upper flow becomes more zonal on Tuesday but appears to be another impulse coming out of the central Rockies in the afternoon. In addition, old surface front may still be in the area, but difficult to say where as mesoscale influences from previous days convection will have an influence. Deep layer shear continues to be around 40-50 kts, although some question on amount of instability if models forecasts are correct. Appears eastern areas will be favored due to timing of upper wave and where better instability currently forecast, but confidence in timing and location details is not that great at this time. For the Wednesday through Friday time period, very persistent upper pattern with southwesterly flow over the plains and embedded impulses. Instability and deep layer shear will be sufficient for severe storms should they develop. Surface pattern will basically feature a moist southeasterly flow each day, with perhaps a hint of a dry line on Thursday which may dry out southwestern areas. However, surface pattern highly uncertain at this time range. Temperatures will continue to be above normal through the long term period, with highs in the 80s and lows mainly in the 50s. && .AVIATION...(For the 00Z TAFS through 00Z Saturday evening) Issued at 550 PM MDT Fri May 21 2021 KGLD expects see VFR conditions to begin the forecast period with south-southeasterly winds at 28G37 kts. At 04Z, KGLD winds look to turn more southerly and slow to 23G30 kts with southerly LLWS of 45 kts introduced at 2 kft. At 09Z, KGLD winds slow to 18G23 kts as LLWS expects to end. MVFR conditions begin at KGLD by 13Z as the cloud ceiling drops to 2400 ft followed by VFR conditions returning at 14Z when the cloud ceiling rises to 5 kft. KMCK begins the forecast period with VFR conditions and south- southeasterly winds at 21G33 kts. At 04Z, KMCK winds expect to slow to 15G25 kts with southerly LLWS of 45 kts introduced at 2 kft. By 11Z, MVFR conditions begin at KMCK as cloud ceilings drop to 1700 ft with wind shear ending and winds slowing to 12 kts. At 15Z, KMCK winds turn southerly and increase to around 14G22 kts before VFR conditions return at 17Z with cloud ceilings rising to 3500 ft. KMCK winds then turn back south-southeasterly and slow to around 17 kts. && .GLD WATCHES/WARNINGS/ADVISORIES... KS...NONE. CO...NONE. NE...NONE. && $$ UPDATE...076 SHORT TERM...JBH LONG TERM...024 AVIATION...076
Area Forecast Discussion
National Weather Service Gray ME
1028 PM EDT Fri May 21 2021 .SYNOPSIS... Warm conditions will continue Saturday away from the coast. A cold front will cross the region on Sunday bringing a line of showers and thunderstorms. Canadian high pressure will build in to start next week bringing much cooler conditions to the region. Another warm up will arrive next week. && .NEAR TERM /UNTIL 6 AM SATURDAY MORNING/... 1025 PM Update...Little change to the going forecast at this time. Most scattered shower activity should remain over eastern zones for the next couple of hours then move offshore. Otherwise, a mostly cloudy and relatively warm night. 615 PM Update...Scattered showers continue in them mountains and foothills as well a portions of Grafton County NH early this evening. Have kept isolated in for the next couple of hours as a strike or two will be possible. Otherwise, just some minor adjustments to the going forecast at this time with the forecast remaining on track. Previously... Weak upper wave passing over the top of an upper ridge over the eastern CONUS will bring a slight chance of showers and isolated thunderstorm through this evening. Current satellite imagery shows cumulus building over the mountains with radar showing some convective showers over Aroostook County and southeast Canada. Latest RAP analysis shows a few hundred J/kg of SBCAPE over the mountain and foothills, but overall expectations are for showers to be limited in coverage with best chances across the mountains. Chances for any thunder will wane after sunset with the loss of heating. Tonight there will be slight chances for showers across eastern zones as the weak upper wave tracks into the Canadian Maritimes. It will be a mild night with lows staying in the 60s away from the coast with mostly cloudy skies. Closer to the coast lows will dip into the 50s and with plenty of low level moisture there will be areas of patchy fog near the Mid-Coast through the Capital District of Maine. && .SHORT TERM /6 AM SATURDAY MORNING THROUGH SATURDAY NIGHT/... Another upper wave passes over the top of the ridge Saturday. Despite mostly cloudy skies it will be warm away from the coast with highs into the 80s and parts of southern New Hampshire climbing to near 90F. Closer to the coast onshore winds will keep temperatures in the 70s with the Mid-Coast likely staying in the 60s. Due to the warm weather expected and water temperatures still in the 50s will be issuing a Beach Hazard Statement and Special Weather Statement to highlight the dangers of cold water. Dewpoints will climb to near 60F during the day and CAMs continue to show several hundred J/kg of SBCAPE developing over much of the area with the exception being the Mid-Coast. As the upper wave passes to our north scattered showers on thunderstorms will develop near the International Border and mountains just after noon and will track southeast across the area. Mid-level lapse rates will generally be less the 6C/km and effective shear looks to be around 25 kts so the overall severe threat looks low. PWATs will be will above normal for this time of year around 1.5 inches so there is potential for some heavy downpours with stronger cells. Showers and thunderstorms will diminish around sunset with another mild night expected. Parts of southern New Hampshire will only drop into the mid 60s with the rest of the area dropping to near 60F. && .LONG TERM /SUNDAY THROUGH FRIDAY/... A strong cold front will approach New England from Canada to start out the long term portion of the forecast on Sunday. Ahead of this front, an increasing southwesterly gradient will allow for a warm and moist atmosphere in the region. H8 readings top out near +14C. With good mixing, warm temperatures will make it to most of the region including the southwest coast of Maine and the Seacoast of New Hampshire where readings will be in the 80s in most locations outside the mountains. The southwesterly flow will allow for cooler readings along the Midcoast as winds will remain onshore. A strong and fast moving upper level trough will cross region Sunday. This will aid in thunderstorm development, some of which may contain gusty winds as dew point values climb into the lower 60s during the morning. CAPE values climb into the 500-1000 J/KG range aiding in the development of convection along and near the front. Timing is critical for the FROPA however as it may cross the region a little on the early side on Sunday. Canadian high pressure will bring much cooler and drier air into the region Sunday night into Monday. In fact, frosts may occur in the northern mountains where the growing season has begun. Temperatures will be seasonable as winds switch out of the west on Tuesday. A couple showers may clip northern areas during the day. More warmth and moisture arrives on Wednesday as a strong southwesterly gradient sets up throughout the atmosphere, both at the surface and aloft. Readings will once again climb into the 80s in all areas including much of the coastline. The Midcoast region will be cooler do to an onshore component. Scattered showers and possibly a thunderstorm may accompany this warm air advection pattern. Another strong cold front will cross the region late Wednesday night and early Thursday morning. A few strong storms may accompany this system as wind fields once again increase over the region. However the time of day should minimize significant activity. && .AVIATION /03Z SATURDAY THROUGH WEDNESDAY/... Short Term...Mainly VFR through tonight with perhaps the exception being KRKD where low cigs will bring periods of IFR late tonight through sunrise. Scattered SHRA and -TSRA will develop across the mountains tomorrow just afternoon and will track southeastward bringing brief periods of restrictions. Long Term...A cold front will cross the region on Sunday, with thunderstorms moving through briefly dropping conditions to MVFR or IFR. High pressure will build in Sunday night into Monday with the next potential for rainfall on Tuesday night. Another strong frontal system will cross the region Wednesday night. && .MARINE... Short Term...Winds generally stay at or below 25 kts through the weekend while a subtropical system well offshore send in building swells tonight. Sea build to 5 feet tonight and will be in the 5-7 ft range through Saturday night. Long Term...Swell from a subtropical storm near Bermuda will continue over our waters late this weekend and into early next week. A strong cold front will also allow for gusty northwesterly winds Sunday night, possibly exceeding SCA thresholds. Seas will build also Tuesday night into Wednesday as a southwesterly gradient strengthens over the waters. && .GYX WATCHES/WARNINGS/ADVISORIES... ME...Beach Hazards Statement from 8 AM EDT Saturday through Saturday evening for MEZ023>028. NH...Beach Hazards Statement from 8 AM EDT Saturday through Saturday evening for NHZ014. MARINE...Small Craft Advisory from 2 AM Saturday to 8 AM EDT Sunday for ANZ150-152-154. && $$ NEAR TERM...Ekster/Schroeter SHORT TERM...Schroeter LONG TERM...Cannon
Area Forecast Discussion
National Weather Service North Platte NE
631 PM CDT Fri May 21 2021 .SHORT TERM...(This evening through Saturday night) Issued at 221 PM CDT Fri May 21 2021 Today the CWA remains with an upper level low to its west and a high pressure system to its east. At the sfc, there is an inverted trough over eastern WY that will move into the area with an accompanied frontal boundary and be the initiator for storms this evening. Also, there continues to be southeasterly flow which is advecting Gulf moisture into the state with PWATs reaching ~1-1.5". Given the abundance of moisture, it is possible for up to an inch of rainfall, especially in Sheridan county which the models agree will see the heaviest amounts. Additionally, if there are any slow moving storms, they may end up causing some areas of heavier rainfall. The area of concern for tonight is primarily the Panhandle and western Sandhills as here some of these storms may turn severe. Both the RAP and HRRR are showing SCP around 4-6 in the Panhandle where there are steep lapse rates (~8-9deg/km) and about 1000 J/kg of MUCAPE. There is also some decent 0-6km bulk shear near 40kts or so. As such, expecting some supercells to develop with the primary concerns being hail, strong winds, and locally heavy rainfall. As with previous fcsts, expecting most of the storms to stay west of HWY 83. Storms are expected again tomorrow afternoon and evening, with the area of concern again being the Panhandle and Sandhills. There is strong FGEN at 850 and 700mb, which is expected to be the basis for these storms, as the moisture advection continues from the SSE. There is a chance tomorrow night as well for up to an inch of rainfall over the northern Sandhills, and locally heavier amounts if storms stall out over an area. The severe threat is being monitored as there seems to be ample 0-6km bulk shear (40-50kts) and over 60kt winds at 700mb. ATTM the main concern is heavy rainfall and strong winds, but this will continue to be evaluated with new model runs. .LONG TERM...(Sunday through Friday) Issued at 221 PM CDT Fri May 21 2021 The potential for storms will return again Sunday evening and into the overnight. Into the day Sunday, the closed upper level low will move over the Rockies and lift northeastward to the WY/Nebraska border. By this time, it is expected to have developed an associated sfc cold front due to some lee FGEN IVO the Rockies. This will be the main initiator for storms, along with support from a small upper level jet. At this time, the region will still be in southeasterly flow at the surface, and receiving a good amount of moisture from the Gulf, resulting in PWAT values near 1-1.5". Given the lift provided, and the ample moisture via advection, there is potential for some localized areas of heavy rainfall (near 1+") or more. Additionally, there is a chance that some of these storms may become severe, with the biggest area of concern being the Panhandle and western Sandhills ATTM. There is looking to be near 70kts of 0-6 km of bulk shear, steep lapse rates, and moderate DCAPE...all which would support the storms turning severe. The severe potential will continue to be monitored through the weekend. The front seems to stall out in eastern Nebraska, and may linger for a few days. No present wx impacts are detected, but something to keep an eye on as confidence in location is low. Into the early morning Monday, winds will shift to southwesterly, pushing storms northeastward and bringing some drier SW air into western Neb. This will help fend off storms and keep skies clear through Tuesday. As this low treks into Canada by Wednesday, the Plains will be left in an area of ridging at upper levels, with a sfc high pressure system working its way through from the northwest. This will bring moisture advection back into the area, and increase PWATs once again. && .AVIATION...(For the 00Z TAFS through 00Z Saturday evening) Issued at 631 PM CDT Fri May 21 2021 Multiple aviation weather concerns exist for western Nebraska, including thunderstorms and gusty winds this evening, low ceilings overnight into the morning, and another round of precipitation for Saturday. The ongoing strong south/southeast winds will continue into the early overnight hours with frequent gusts over 30 kts. Once surface speeds begin to wane, low level wind shear conditions will likely arise, then subside by daybreak. Scattered thunderstorms will affect the panhandle and western terminals (KOGA to KVTN) this evening, with some being capable of large hail and wind gusts 40+ kts. A stratus deck will also build into the area to coincide with the lighter surface winds. Most terminals will drop to MVFR or IFR ceilings. Northern terminals (KVTN) may remain in stratus for much of Saturday, while southern terminals (KLBF) will break mid-morning with increasing thunderstorm chances heading into the afternoon. && .LBF WATCHES/WARNINGS/ADVISORIES... None. && $$ SHORT TERM...Meltzer/Sinclair LONG TERM...Meltzer/Sinclair AVIATION...Snively
National Weather Service Raleigh NC
910 PM EDT Fri May 21 2021 .SYNOPSIS... High pressure will strengthen over the Carolinas and southern Appalachians through Saturday. A strong high pressure aloft will continue to dominate the pattern for our region Sunday through next week with predominately hot and dry conditions. && .NEAR TERM /THROUGH TONIGHT/... As of 910 PM Friday... Current forecast on track for the overnight period. High pressure over far eastern VA will move southwestward into central NC overnight, resulting in excellent radiational cooling. Lowered minimum temperatures a few degrees with generally mid to upper 50`s and some lower 50`s in the typical colder spots. Some high clouds will drift into the area by the early morning hours as a mid-level ridge over the Ohio Valley drifts south into the Tennessee Valley. Latest guidance from the SREF and HRRR show potential for some fog across the far eastern Coastal Plain, perhaps clipping Rocky Mount and southern Sampson County as some low-level moisture, currently present near Kitty Hawk, drifts southwestward under the easterly flow. Any fog would be patchy and lift by sunrise. && .SHORT TERM /SATURDAY AND SATURDAY NIGHT/... As of 350 PM Friday... A mid/upper shortwave rotating around the ridge centered over the Deep South will move south from the Great Lakes region into the Mid- Atlantic on Saturday and Saturday night. At the surface, an associated trough will develop along the East Coast, shunting the high pressure system farther west over the Deep South. While no precipitation is expected in central NC with this shortwave, it will likely result in increased cloudiness during the day and into Saturday night. With 1000-850mb thicknesses around 1400-1410m (roughly 15m higher than Friday), and the flow shifting to a more westerly direction, temperatures on Saturday will climb into the upper-80s to near 90 (5-10 degrees above normal). Increased clouds will help keep lows Saturday night warmer than previous nights as well, in the lower-to-mid-60s. && .LONG TERM /SUNDAY THROUGH THURSDAY/... As of 240 PM Friday... ...Record hot temperatures possible for part of next week (mainly Wednesday, May 26 and possibly Thursday, May 27). ...Little if any short term relief from the abnormally dry conditions through the next 7-10 days. Strong upper level high pressure is expected to weaken slightly and drift slowly westward (retrograde) but still located just to our west, over the TN Valley region Sunday into Monday. Our moisture sources will be cut off with strong ridging to our west. The mean flow will be from the NW-N aloft which will be susceptible to remnant/decayed convection well to our NW (Great Lakes etc...). However, there should be some periods of mid/upper level cloudiness with any of these remnant vort maxes. The surface flow will be light from the west (downslope) which will aid drying and heating during the day. Highs both days should be in the upper 80s to lower 90s. These temps may have to be adjusted at any point given the chance of mid/high clouds affecting temps especially early Sunday, then again late Monday. The chance of any convection looks meager, at best. Lows will be in the mid to upper 60s. A backdoor cool front may make a run into NC from the NE later Monday into Tuesday. This may allow it to be a few degrees cooler in the NE Tuesday with some additional cloudiness. Other than a slight chance of a shower or thunderstorm near the front, expect dry conditions. Highs Tuesday should range in the mid 80s NE to lower 90s south. The hottest days during this late May heat wave should be Wednesday and Thursday as the ridge remains strong with little in the way of cloudiness to inhibit heating. Highs Wednesday should soar into the lower 90s NW, mid 90s for the central areas, and upper 90s in the Sandhills. If this forecast holds, new daily record highs will have a potential to be tied or broken in some areas. Finally, some relief should develop late week with the approach of a cold front from the NW-N as the ridge aloft weakens somewhat. However, the chance of thunderstorms still remains questionable with the lack of low level moisture. Convection may remain isolated to widely scattered even with the front on Friday. We will keep POP very low until the pattern shows some definitive signs of changing. Highs should drop back 4-7 degrees into the upper 80s to lower 90s by Friday. && .AVIATION /00Z FRIDAY THROUGH WEDNESDAY/... As of 737 PM Friday... 24 hour TAF period: Aside for a brief period of some sub-VFR conditions in fog/stratus at KRWI between 10 to 12z Sat, expect VFR predominately VFR conditions through the forecast period. Otherwise, high clouds/cirrus is expected to increase late tonight through Saturday. Looking beyond 18z Saturday: VFR conditions will continue through Sunday, with partly to mostly sunny skies. There is a low chance of showers and storms from Monday through Wednesday, with sub-VFR conditions also possible. The best chance will be across the northern Piedmont. && .CLIMATE / ...Possible high temperatures that have a chance to be broken next week. Raleigh: Wednesday, May 26, (94 set in 2019) Thursday, May 27, (96 set in 1916) Greensboro: Wednesday, May 26, (95 set in 1926). Fayetteville: Wednesday, May 26 (100 set in 1953) .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Badgett NEAR TERM...Kren/Danco SHORT TERM...Danco LONG TERM...Badgett AVIATION...CBL/Danco CLIMATE...Badgett
Area Forecast Discussion
National Weather Service Riverton WY
513 PM MDT Fri May 21 2021 .SHORT TERM...(This evening through Saturday night) Issued at 128 PM MDT Fri May 21 2021 Cold front pushed south overnight and is now stalled essentially along the continental divide from Yellowstone to Dubois to South Pass to south of Casper. North of the front temperatures are well below normal with low clouds over the lower elevations, and fewer clouds over the higher elevations. Southwest of the front, temperatures are more seasonal to below normal (farther north), though instability is greater, so showers this morning are becoming heavier and more numerous this afternoon. Latest model guidance has widespread precipitation occurring from Sweetwater County northwest into Sublette, Lincoln, and Teton Counties. The heaviest amounts are expected along the west side of the Wind River Mountains with the strong southerly flow converging along the divide. SPC has introduced an area of marginal risk of severe thunderstorms across eastern ID and barely into western WY. The slightly stronger storms look most likely late this afternoon as the dry slot over UT moves north and noses into SW WY for the storm from Star Valley to the Tetons. Late this afternoon and early evening, the showers over SW WY are expected to move NNE over the dome of cooler air to bring showers to areas east of the divide. The convective activity looks to diminish after midnight over much of the area, with isolated chances through the morning. Counter to model suggestions yesterday, the warm dry southerly flow is not likely to push the stationary front northward, so below normal temperatures with low clouds are likely east of the divide into Saturday. The upper level low over west central Nevada will move toward NW Nevada Saturday morning, tightening the gradient from NE Utah into SW WY. Easterly flow will continue east of the divide, while SW WY should again see strong dry southerly flow with gusts 30-40 mph. Saturday morning from 6am to noon looks to be mostly quite precipitation wise. In this situation, thunderstorms are expected to develop early Saturday afternoon along the boundary and move northward. The northern Wind Rivers and Absarokas as well as around the Bighorns appear to be the most favorable locations. Some areas may see 0.25 to 0.50" of precipitation during the afternoon and early evening, with a couple of inches snow in the highest elevations. The HRRR is suggesting that the cold air will push over the divide Saturday evening and move into SW WY as the strong southerly flow subsides. Moderate precipitation should continue Saturday evening into Sunday morning as the upper level low becomes negatively tilted to provide much better mid and upper level support. Saturday night could see some areas see up to an inch of precipitation as the upper level low becomes more negatively tilted and the 300 mb jet gets focused from south central WY toward NW WY. With the low moving toward NW WY early Sunday morning, winds across southern and central WY may be gusty as 700mb winds over 40 kts start to move in. Overall, another very active short term period the next 48 hours to bring precipitation to western and central WY. Temperatures will either be quite cool or near normal, depending on the location! .LONG TERM...(Sunday through Friday) Issued at 1248 PM MDT Fri May 21 2021 Sunday through the beginning of next week, the trough to the west of the region begins to lift as the trough negatively tilts and the low center moves east. The trough will lift over the Cowboy State through the day Sunday and Monday. This will increase the pressure gradient and bring very strong winds into the region beginning Sunday morning. Will likely need some kind of wind highlights Sunday morning through Monday afternoon where the SSW flow will be strongest along the pressure gradient. MOS Guidance is pushing winds sustained 30+ kts from Rock Springs to Buffalo, especially Sunday afternoon. 50 to 60kt 700mb winds will also be present across Sweetwater county Sunday morning, moving east into Natrona and Johnson County by early afternoon, where it will stall into Monday morning. Despite southerly flow, the wind will keep temperatures moderated through the early part of the week. By Tuesday morning, the low should finally have lifted up and out of the region. Warmer zonal flow will fill in behind it, bumping temperatures back into the 70s east of the Divide by later in the week. In terms of precipitation, models show a good bit of uncertainty through the second half of the week. In general, looks like zonal flow with weak ridging that could bring shortwaves across the region. Will likely see scattered convection throughout the week as the instability and generally active pattern continues. && .AVIATION...(For the 00Z TAFS through 00Z Sunday) Issued at 510 PM MDT Fri May 21 2021 Rain showers (and snow showers for the higher terrain) will continue over the region into the evening hours, with far west-central WY (including KJAC) having the best chance of isolated thunderstorms before 22/0500z. Expect lower ceilings and some visibility reduction when showers move through. Winds are expected to decrease after sunset, with most valleys decoupling. Those sites close to terrain (e.g. KPNA) may continue to see some gusts, but less than the winds seen during the daytime hours. After midnight, precipitation decreases across the region. Light north and northeast flow resumes east of the Divide. Winds increase late morning for those west of the Divide on Saturday morning. Showers and isolated thunderstorms are again possible during the afternoon hours Saturday. Please see the Aviation Weather Center and/or CWSU ZDV and ZLC for the latest information on icing and turbulence forecasts. && .FIRE WEATHER... Issued AT 137 PM MDT Fri May 21 2021 A very unsettled pattern the next 2-3 days over western and central WY As a large upper level low pressure system over Nevada moves toward Montana. A cold front aught up on the continental divide is complicating the situation. Much of the area will see showers and thunderstorms, with some areas seeing strong storms and heavy precipitation. This afternoon and evening, the strong southerly flow across SW WY will focus the precipitation into the Wind Rivers and western mountains. Showers will continue through midnight. Temperatures are below normal east of the divide and near normal over SW WY. Saturday morning looks to be fairly quite, with more showers and thunderstorms developing over central WY early in the afternoon. Stronger storms and showers with moderate precipitation is expected from the Wind Rivers into the Absarokas and NW WY Saturday afternoon and evening, with some areas likely seeing 0.50" to 1.0" of precipitation. Look for strong southwest winds Sunday for much of the state as the core of the system goes over Yellowstone. && .RIW WATCHES/WARNINGS/ADVISORIES...NONE. && $$ SHORT TERM...McDonald LONG TERM...Fisher AVIATION...VandenBoogart FIRE WEATHER...McDonald
Area Forecast Discussion
National Weather Service Las Vegas NV
425 PM PDT Fri May 21 2021 .SYNOPSIS...A large low pressure system will circulate over our region today and Saturday bringing considerably cooler temperatures with scattered showers across the southern Sierra and south central Nevada with light snow accumulations possible above 6000 feet. Winds diminish Saturday and Sunday, though temperatures will remain below normal as the system slowly lifts away to the north. Near normal temperatures and dry conditions will return early next week. && .SHORT TERM...Today through Sunday. The broad upper-level trough currently centered over southwest NV will continue to dig southeast through Saturday. However, the board low will continue to circulate overhead through Sunday morning before it lifts northeast. As a result, breezy west to southwest winds are expected again tomorrow, with gusts to around 15-25 mph. Slightly stronger winds will be possible across western San Bernardino County near Barstow tomorrow afternoon, where gusts to around 30 mph will be possible. As the low shifts southeast through tomorrow, moisture associated with the low center will also push south, similar to today, leading to another day of isolated to scattered light showers/high elevation snow showers. Precipitation is expected to again be light tomorrow, but elevations above 7000-7500 feet may see some light dusting of snow where temperatures will be cold enough and showers are expected. Otherwise, accumulating snow is only expected above 9500 feet. An additional 1-3 inches will be possible along the higher elevations of the eastern Sierra and up to 1-2 inches along the higher elevations of the Spring Mountains tomorrow. Decent instability associated with the low center will also be in place tomorrow afternoon, so isolated thunder will be possible with some of the stronger updrafts that develop. Smoke plume associated with the Cherrywood fire is expected to overspread across parts of western Lincoln County this afternoon, per the latest HRRR smoke runs. By Sunday, the low will begin to wrap up and lift northeast, allow for height increase, resulting in increasing temperatures. Though, a weak piece of energy along the backside of the trough will move across central NV, leading to a slight increase in pressure gradients, creating breezy west winds across Lincoln County. .LONG TERM...Height fields will be rising fairly rapidly during the day Monday and in turn so will surface temperatures. Generally zonal flow and some additional warming taking place on Monday, bringing temperatures back to closer to their seasonal normals. WPC Clusters indicate another weak upper low moving into northern California on Tuesday which, at this point looks to have only very modest impacts to the Great Basin and Mojave Desert. Southwest winds may increase a bit ahead of the approaching system and temperatures will climb a few more degrees in most locations. The upper level trough will be slow to make much progress on Wednesday and Thursday, basically keeping the status quo with temperatures at or slightly above their normals, which in Las Vegas is in the lower 90s, along with breezy and dry conditions. && .FIRE WEATHER...A belt of west to southwest winds gusting 35 to 45 mph will combine with low relative humidity to create another round of critical fire weather conditions over the San Bernardino County deserts up across the Lake Mead National Recreation area and northwest Arizona. A Red Flag Warning is in effect for these areas until 8 PM this evening. && .AVIATION...For McCarran...Continued minor to moderate impacts to the terminal through about sunset as isolated showers continue to occur in the vicinity of the Valley. While there could be brief shifts to the west, southwest direction is favored through the overnight period with a stark drop off in wind gusts after 03Z. Relatively light and variable winds expected early tomorrow morning before another round of isolated showers bring virga and outflow concerns again tomorrow afternoon and more westerly wind gust potential. PIREP solicitation is recommended through at least 12Z due to low level turbulence up to 12kft. For the rest of southern Nevada, northwest Arizona and southeast California...Continued gusty winds and isolated -SHRA expected across much of the region through the first few hours of the TAF period. By sunset, winds and showers should diminish resulting in a relatively quiet night overall. Winds will increase again tomorrow afternoon but much less than the last couple days. Isolated -SHRA again possibly tomorrow afternoon for KBIH and the LV Valley. && .SPOTTER INFORMATION STATEMENT...Spotters are encouraged to report any significant weather or impacts according to standard operating procedures. && $$ Short Term...Peters Long Term...Czyzyk Aviation...TB3 For more forecast information...see us on our webpage: or follow us on Facebook and Twitter