Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 07/13/21

Area Forecast Discussion
National Weather Service Denver/Boulder CO
903 PM MDT Mon Jul 12 2021 .UPDATE... Issued at 850 PM MDT Mon Jul 12 2021 There are still a few on-going showers in the mountains at this time. Rainfall from these showers is/was very light. There are several boundaries moving around the plains right now. Winds across the CWA are light and variable. Not to many changes are needed to the GFE grids this update. Satellite pictures are showing extensive deep layer smoke across, about the western one half of the Unites States right now, and certainly covering the CWA. Will leave the smoke in tonight. && .SHORT TERM...(This evening through Tuesday) Issued at 137 PM MDT Mon Jul 12 2021 Warming has been slowed today by the smoke. The slightly cooler temperatures has helped to stabilize the airmass, which wasn`t going to be all that unstable to begin with. Lowered PoPs for the rest of the day to reflect this. Expect isolated showers and storms to track south- southeast across the higher terrain. Don`t expect them to survive or form over the lower elevations and removed the mention of showers and storms from the forecast for the rest of today. An upper level trough moving across Montana will help push the ridge southwest on Tuesday. Surface low pressure will deepen over Wyoming in advance of the trough. This will cause south/southeast winds to increase across eastern Colorado and advect moisture into the area. Precipitable water values increase to around an inch across the plains. Over the higher terrain, precipitable water values climb to around three-quarters of an inch. CAPE won`t be all that impressive with 400-800 J/kg over the eastern plains and 200-600 J/kg farther west. Gusty winds to 50 mph and brief heavy rain will be the main threats with the showers and thunderstorms. Will have to see how much the smoke impacts temperatures, and thus stability Tuesday afternoon. With some smoke, still expect highs to reach the lower 90s, but if it is as thick as today. Temperatures may only reach the upper 80s and may decrease the amount of convection Tuesday afternoon/evening. .LONG TERM...(Tuesday night through Monday) Issued at 137 PM MDT Mon Jul 12 2021 Tuesday evening, isolated and high based showers and storms may come off the high terrain and bring gusty winds and light rainfall to the eastern plains. A shortwave trough will push a weak cold front over the plains early Wednesday as it moves from the northern Rockies towards the Dakotas. Wednesday should be a bit cooler behind that front, with highs back down in the mid to upper 80s across the plains. The front will also bring an increase in low level moisture and some northeasterly upslope flow into the foothills, probably around 10 knots. Wednesday should have the best moisture of the period, models are showing precipitable water values up to around 1.0 to 1.25 inches over the lower elevations and 0.5 to 0.8 inches over the higher terrain. Expect scattered to widespread showers and storms Wednesday afternoon and evening, with the best coverage and intensity over the high terrain. A few severe storms are possible given some moderate instability and shear, but the main concern should be for heavy rainfall. The greatest precipitation should occur on the east slopes of the Front Range, especially over the foothills, as those areas are favored by the upslope flow. The most recent HRRR Smoke model output suggests significant concentrations of smoke still in the air come Wednesday, which continues to make sense given the large smoke output of many active fires upstream and the transport flow aloft. However, the early cold front should help to clear some smoke from the near surface and greater moisture and precipitation should wash some of the particulate from the air as well, resulting in lesser concentrations felt in the lower levels for a little while. Thursday should see similar conditions to Wednesday, but with less moisture and therefore precipitation. Expect similar temperatures, and some models are now even suggesting that it might be just slightly cooler. A gradual warming and drying trend should set back in Thursday and Friday and persist through the weekend as a large ridge builds over the Rockies again. && .AVIATION...(For the 00Z TAFS through 00Z Tuesday evening) Issued at 850 PM MDT Mon Jul 12 2021 Easterlies are still blowing at DIA right now. Models do show normal drainage patterns by 06Z tonight. Will leave the "FU" mention in the TAFs; no way around that. There will be no ceiling issues overnight. && .HYDROLOGY... Issued at 137 PM MDT Mon Jul 12 2021 Isolated thunderstorms are expected over the mountains and foothills through early evening. Most of the rain today is expected to be light. The flash flood threat for the burn areas will be very low through tonight. Moisture will increase on Tuesday with scattered thunderstorms expected to form Tuesday afternoon. A brief period of heavy rain will accompany the stronger storms and could cause localized flash flooding if one passes over a burn area. Scattered to isolated showers and storms will persist into the evening Tuesday, but most will still be high based and produce light rain which keeps the flash flood threat low. Brief, locally heavy rainfall may still be possible with stronger storms. Better moisture Wednesday and Thursday will mean increasing shower and storm coverage with more significant precipitation. The greatest moisture and precipitation of the period is expected Wednesday. Upslope flow into the Front Range could result in stronger storms and an elevated flash flood threat for burn areas east of the Continental Divide, namely, Cameron Peak and Calwood. A similar situation with similar threat levels is possible on Thursday, though overall less moisture and precipitation are expected. A gradual warming and drying trend will likely set back in Thursday and persist through the weekend, with decreasing precipitation and impacts. && .BOU WATCHES/WARNINGS/ADVISORIES... None. && $$ UPDATE.......RJK SHORT TERM...Meier LONG TERM....EJD AVIATION.....RJK HYDROLOGY....EJD/Meier
Area Forecast Discussion
National Weather Service Caribou ME
1054 PM EDT Mon Jul 12 2021 .SYNOPSIS... High pressure will build in from the north through tomorrow. A warm front lifts north Tuesday night into early Wednesday. A cold front is expected to cross the region on Thursday. Unsettled into the weekend with a series of disturbances affecting the region. && .NEAR TERM /THROUGH TUESDAY/... Update... High pressure will cross the region overnight with mostly clear/partly cloudy skies. Could also have patchy fog Downeast late tonight. Low temperatures will range from around 50 to the mid 50s north, to the mid to upper 50s Downeast. Have slightly decreased low temperatures across portions of the region with this update. Have also updated to adjust for current conditions along with overnight clouds. Previous Discussion... Tonight...One thing to note, is that at the sfc, the high is expected to start moving east later tonight w/an ESE light flow to set up. This could begin to bring in some llvl moisture below 925 mbs(around 1500`), which could allow for some fog and low clouds to set up. Attm, the best potential looks to be right along the coast and possibly portions of interior Downeast by daybreak. The latest SREF and HRRR point to this potential. The NAM hints at the potential for some as well w/the low clouds. Therefore, decided to go w/some fog and showed some clouds moving on to the coast by around the daybreak hrs. Further n. clear to partly cloudy skies overnight. Temps are expected drop back into the mid/upper 50s. For Tuesday, looks like a rain-free day w/humidity gradually on the increase. The 12Z NAM and GFS show moisture increasing during the as that stalled frontal boundary begins to lift back to the n as a warm front. Both show the potential for some light rain showers or drizzle setting up around the western periphery of the high w/some weak forcing aloft. The GFS is more robust w/brining the rain further n, while the NAM holds it back across far southern Maine and se New Hampshire. Went w/a blend and brought 20-30% pops to the western areas late in the day and this might be overdoing it, given the lack of significant forcing aloft. && .SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY/... A warm front wl be lifting thru the region Tue night. Sfc high builds east into the Canadian Maritimes during the evening. Ridging aloft fm sern high wl slide south and east and allow s/wvs to begin to flatten ridge, especially acrs the west by Wed morning. For those areas that don`t see rainfall late Tue night an inversion wl develop and trap moisture near the sfc in the form of stratus, fog and possibly drizzle. Some question as to how far north marine layer will be able to make it Wed morning. With srly flow, extensive cloud cvr and warm advection temps wl only be able to fall to near 60 overnight. Little diurnal range is expected on Wednesday with maxes below normal. Ridge wl be flattening as lead shortwave ejects twd the northwest. Elevated instability wl be present with a chance for thunder acrs most of the region in the afternoon and into the nighttime hrs. This type of pattern wl allow fog to persist in a warm and soupy airmass. Weak boundary wl mv thru Wed night but wl bring thru very little change in airmass. Skies wl become partly cldy and rain wl gradually come to an end Thu afternoon. This wl allow high temps to rebound twd the 80s areawide with dewpts rmn in the 60s as frontal bndry rmns north acrs srn Canada. && .LONG TERM /THURSDAY NIGHT THROUGH MONDAY/... Early in the long term, models diverge with location of front to our north, along with wave riding up along it. 12z EC and GEM indicate boundary will be located to the north of the Gulf of St. Lawrence while GFS is a little murkier with it`s location. Operational EC has the support of it`s ensemble mean. Minimal precip is expected Thu night into Friday morning before front begins to approach. Due to uncertainty in movement of sfc low riding along front and initial location of bndry hv followed NBM with chc pops for the area on Friday, though they may be able to be lowered by later shifts as models come into better agreement. Either way it appears an active pattern wl be setting up for the weekend and possibly into early next week. && .AVIATION /03Z TUESDAY THROUGH SATURDAY/... NEAR TERM: Generally VFR overnight through Tuesday. However, variable conditions possible with any fog late tonight through early Tuesday Downeast. Light and variable winds overnight. South/southeast winds around 10 knots Tuesday. SHORT TERM: Tuesday night-Thursday...Low stratus and fog likely to affect Downeast terminals Tue night and Wed night bringing LIFR restrictions each morning. Brief improvement to MVFR/VFR each afternoon and BGR and BHB. Uncertainty as to how far north IFR will make it with KHUL possibly seeing IFR but confidence is low, with northern terminals likely seeing patchy IFR fog each morning in valley fog. Cannot rule out restrictions in thunder each afternoon and evening across the north at all terminals.S 5-15kts and gusty each afternoon. Thu night-Sat...IFR possible each morning in fog before improving to VFR in the afternoon on Friday. MVFR/IFR possible in showers and storms Friday night and Saturday. Light SW Thu night increasing to S 5-10kts Fri morning. && .MARINE... NEAR TERM: Winds/seas below small craft advisory levels overnight through Tuesday. Visibilities lowering in developing fog overnight, then fog persisting Tuesday. SHORT TERM: Seas and winds to remain below SCA thresholds into Saturday. Areas of fog, perhaps locally dense at times, is expected through the end of the week. && .CAR WATCHES/WARNINGS/ADVISORIES... ME...None. MARINE...None. && $$ Near Term...Norcross/Hewitt Short Term...Farrar Long Term...Farrar Aviation...Norcross/Farrar Marine...Norcross/Farrar
Area Forecast Discussion
National Weather Service Grand Rapids MI
1056 PM EDT Mon Jul 12 2021 LATEST UPDATE... Update .SYNOPSIS... Issued at 307 PM EDT Mon Jul 12 2021 - Marginal svr and flw risk late this afternoon into tonight - Strong storms possible Tue - Organized convection Wed night to Thu night && .UPDATE... Issued at 1056 PM EDT Mon Jul 12 2021 What appears to be an MCV is moving northeast from Northeast Indiana into South Central Lower Michigan. In the wake of this feature precipitation has been on the decrease across much of Northern Indiana. This does not bode well for precipitation chances across Southwest Lower Michigan tonight. We do expect some shower and thunderstorm development tonight however as a weakening warm front lifts north into Lower Michigan along with a glancing blow from a weak 20kt or so low level jet. Feel the upper trough moving in from the west will aid in some precipitation production as well. The highest pops late tonight will remain in the northwest and west which will be in closest proximity to the upper trough. && .DISCUSSION...(This evening through next Monday) Issued at 307 PM EDT Mon Jul 12 2021 - Marginal svr and flw risk late this afternoon into tonight Mid to upper level low over IL opens up and lifts through Lower MI into Tuesday. Steady 500 mb height falls occur as PWAT values climb up to around 1.75 inches. So far the low clouds have limited the destabilization today. However the clouds will be breaking up from south to north allowing for a few hours of warming temperatures. Thus we could start to see a few storms developing...mainly after 22z. Bulk effective shear is shown to climb to 25 to 30 knots during the evening. Thus a few storms may become organized. However the progged ML CAPE only rises to around 500 j/kg for places like Kalamazoo to Jackson. Mid level lapse rates are weak as well. With continued height falls through the night...we will likely maintain the convection. Where the cells persist...some hydro impacts could occur. The past couple of runs of the HRRR have shown the Battle Creek to Jackson area as a location to potentially see several inches of rain through tonight. - Strong storms possible Tue Morning convection may be loosely organized given lower bulk effective shear values progged...around 20 knots and low ML CAPE values. As we go into the afternoon ML CAPE increases and could support a few pulse stronger cells...especially for eastern parts of the CWA where the bulk effective shear is forecast to be higher. A cap arrives Wednesday so for now...we are leaning toward a dry forecast. - Organized convection Wed night to Thu night A low level jet forms upstream in the Southern Plains Wednesday morning and migrates through the Northern Lower MI later Wednesday night. This could allow for elevated strong storms that may clip our NW CWA then. Models have been advertising the arrival of a mid to upper level wave Wednesday night into Thursday from the west. The latest high res euro shows the 300 mb winds increasing overhead to 70 knots around 00z Fri. Bulk 0 to 6 km shear values are shown to be around 35 to 40 knots from the high res euro but 40 to 50 knots from the GFS...thus an increased risk for organized convection could develop. At the same time a surface front is shown to be tracking through the CWA during the afternoon and evening. How much of an impact these storms result in will likely be influenced by how unstable the airmass becomes Thursday and whether the morning convection alters the setup. For now...we will feature high POPs and continue to highlight the risk in social media and the hazardous weather outlook. && .AVIATION...(For the 00Z TAFS through 00Z Tuesday evening) Issued at 815 PM EDT Mon Jul 12 2021 Weak low pressure is centered over portions of Central Illinois at 00z. A warm front extends northeast and then east from the low into portions of Northern Indiana. The low will move northeast to out over Lake Michigan tonight with the warm front lifting northward into Lower Michigan. In a weak wind / moist airmass setup, we should see low clouds expand in coverage and lower further through the night. In fact, by 12z most of the area should be below the 1,000ft level socked in with IFR clouds. The IFR conditions should lift to MVFR in the early afternoon (16z-18z). VFR weather should develop in the late afternoon (21z-00z) on Tuesday. As for the weather, we should see occasional showers and scattered thunderstorms lift north from Indiana through the TAF sites tonight. Between 06z and 12z visibilities should dip into the MVFR category at all TAF sites due to scattered showers and especially some light fog. Another round of showers and storms is likely from midday on Tuesday into the afternoon hours (17z-23z). && .MARINE... Issued at 307 PM EDT Mon Jul 12 2021 Overall through Wednesday the pressure gradient remains relatively weak which will act to keep the wind under 20 knots. The arrival of front Thursday into Thursday night could strengthen the winds out of the south to southwest. Storms at around that time could result in gusty and variable winds. && .GRR WATCHES/WARNINGS/ADVISORIES... MI...None. LM...None. && $$ UPDATE...Duke SYNOPSIS...MJS DISCUSSION...MJS AVIATION...Duke MARINE...MJS
Area Forecast Discussion
National Weather Service Lake Charles LA
942 PM CDT Mon Jul 12 2021 .UPDATE... After a fairly active late afternoon to early evening period, convection seems to finally be moving out of the area, though a few showers are still noted near Alexandria. Best chance for any future development through the night likely also remains in the north portion of the CWA, closer to the influence of the E CONUS trough... Though thinking overall PoPs will remain limited. Biggest threat for any weather would come in the form of fog/mist development after midnight, especially where some of the higher rainfall totals from earlier were. While thinking any fog that does form should largely remain patchy and shallow in nature, SREF does give ~20-40% probs of visibility less than 1 SM north of the I-10 corridor. For now, kept fog out of the WX grids, but it`ll be something to monitor overnight. Otherwise, only made minor adjustments to the gridded forecast to align with trends and short term guidance, and the remainder of the forecast looks to be in good shape. 50 && .PREV DISCUSSION... /issued 612 PM CDT Mon Jul 12 2021/ AVIATION...A intermittent line of showers and storms will continue east across the region through the next few hours. Gusty winds, reduced vis, and frequent lightning will be possible along with MVFR ceilings. Conditions will improve after sunset, however patchy fog may develop late tonight. More thunderstorms will be possible again Tuesday with lower vis and ceilings likely in storms. PREV DISCUSSION... /issued 330 PM CDT Mon Jul 12 2021/ DISCUSSION... SHORT TERM [Tonight through Wednesday Night] A series of disturbances wrapping around an upper level low centered over Illinois this afternoon continues to send lines of convection through the area. The next of these is presently moving through Polk and Liberty counties in southeast Texas as of this writing. Latest runs of the HRRR show this line gradually weakening as it moves across the region with the loss of daytime heating. A weak surface pressure gradient will allow winds to calm overnight and with soils remaining saturated, patchy light fog appears likely once again during the early morning hours tomorrow. Don`t expect fog to become dense enough to be anything more than a minor nuisance. Any fog that develops will quickly dissipate after sunrise. The aforementioned upper low will begin to lift off to the northeast tomorrow and while there will still be some marginal upper level support, convection tomorrow will be more diurnally driven and less well organized than has been seen the last couple of days. Wednesday`s convection will be exclusively diurnally driven with weak gradients both at the surface and aloft. With such a weak atmospheric profile, it wouldn`t be a surprise to see tropical funnel clouds develop Wednesday afternoon. Jones LONG TERM [Thursday through Monday]... Not many changes in the extended period this afternoon, as global models continue to show the region on the western flank of a low/mid level ridge that will maintain a steady and moist SE flow underneath a general weakness aloft. This will yield daily and mainly diurnally driven showers and thunderstorms with daytime highs in the lower 90s and morning lows in the lower to mid 70s. 13 MARINE... A light to moderate onshore flow will persist through the forecast period. Scattered showers and thunderstorms will be possible each day through next weekend. Locally higher winds and seas will be possible around storms. && .PRELIMINARY POINT TEMPS/POPS... AEX 72 89 73 91 / 40 50 10 30 LCH 75 89 75 89 / 30 50 10 50 LFT 74 89 75 90 / 10 60 10 50 BPT 75 90 75 89 / 30 40 10 40 && .LCH WATCHES/WARNINGS/ADVISORIES... LA...None. TX...None. GM...None. && $$
Area Forecast Discussion
National Weather Service Marquette MI
751 PM EDT Mon Jul 12 2021 .SHORT TERM...(This evening through Tuesday) Issued at 323 PM EDT MON JUL 12 2021 An overall quiet day was observed across Upper Michigan today. Temps have climbed into the 70s and low 80s across the region and with mostly clear skies, this has turned out to be a nice summer day so far. There was still some lingering haze associated with the fires to our northwest in Ontario, particularly over the lake and in the Keweenaw. As low-mid level winds shifted to be predominately southerly, GOES 16 products have observed the smoke patch lifting northward. This has matched fairly well to what the HRRR anticipated through the day. The overall synoptic picture is painting a scenario where a blocking ridge across the western Atlantic and East Coast continues to mitigate much movement of a pinched off upper level low over the middle-Mississippi River Valley. This has allowed dry air to remain over the region. Tonight though, as the low finally devolves into an open wave and begins riding the ridge top, expect cloud cover to increase in the south and east. At the same time, expecting chances of rain showers to increase. Lows look to be in the 50s across the region, with some low 60s by the lakeshores being possible. Rain showers will continue lifting from the south on Tuesday, mainly in the east. The central and west are expected to stay dry. Given the slightly warmer airmass and partly cloudy to clear skies over the west and central, expecting highs to climb into the low to mid 80s. In the east, more moisture will make it feel muggy as highs climb into the 70s. .LONG TERM...(Tuesday night through Monday) Issued at 334 PM EDT MON JUL 12 2021 Although Upper Michigan will be under an unsettled pattern coming up in the long-term period, the model trends have been drier and/or more southerly, making precip chances much more hit and miss this week. Some low-end PoPs appear tomorrow night, but the better chances hold off until late Wednesday into Thursday as an amplifying trough approaches the Upper Great Lakes. Models had been trying to develop a well-defined low that followed a path reminiscent of a fall system, but the 12z GFS run has backed off on that, with the ECMWF maintaining a more robust system, and the CMC and NAM falling somewhere in the middle of these two opposing solutions. Regardless of the low`s strength, where models do have better agreement is it tracking somewhere in the vicinity of northern Lake Michigan, which would generally limit precip chances further to the west in the U.P. As the low marches off toward the NE and the parent trough keeps a progressive motion, so too go the precip chances, allowing for high pressure to build back into the region and dry conditions to prevail next weekend. Temperatures continue a slow yet steady increase from how they`ve been as of late into Wednesday before briefly dropping off in conjunction with the aforementioned system. As ridging returns later this week into the weekend, so too do the summer temps with widespread 80s. Lows will of course respond accordingly, with the warmest nights in the period looking to occur tomorrow night and then next weekend. && .AVIATION...(For the 00Z TAFS through 00Z Tuesday evening) Issued at 750 PM EDT MON JUL 12 2021 VFR conditions and light winds will continue at KIWD/KCMX/KSAW thru this fcst period. A disturbance over the Mid-Mississippi Valley will lift ne across the Great Lakes region on Tue. However, associated pcpn will most likely pass e of KSAW. If not, a few -shra may be in the KSAW vcnty late tonight/Tue morning. && .MARINE...(For the 4 PM Lake Superior forecast issuance) Issued at 323 PM EDT MON JUL 12 2021 Winds will remain below 20 knots through at least Wednesday. From there, some northeasterly to easterly winds gusts to 25 knots will be possible into Thursday night as a low moves through the Upper Great Lakes. Beyond this and through the weekend, winds are expected to remain below 20 knots. With increasing chances for rain starting Tue, fog could be a possibility, especially associated with the system Wednesday night into Thursday. Given that confidence isn`t high enough, will wait to add it to the forecast. && .MQT WATCHES/WARNINGS/ADVISORIES... Upper Michigan... None. Lake Superior... None. Lake Michigan... None. && $$ SHORT TERM...JP LONG TERM...lg AVIATION...Rolfson MARINE...JP
...Updated for 00Z Aviation Forecast Discussion...

.DISCUSSION... Issued at 410 CDT Mon Jul 12 2021 Pleasant conditions around the area this afternoon with current temps close to 80F and northeasterly winds generally under 5 knots. Canadian wildfire smoke is evident on GOES 16 loop and, to a lesser extent, just by looking out the windows here in Valley. It is notably more dense on the western periphery of the area. The 12Z run of the HRRR shows it becoming more dense tonight.. though the Canadian smoke in place now will be replaced by smoke working in from the western U.S. Temps continue to climb for Tuesday on the strength of continued sunshine and WAA on southerly flow that should drive temps up by 5-10F and equal seasonal norms. A compact and relatively weak shortwave will eject from the northern Rockies on Tuesday night and produce a chance at severe weather along the Nebraska/SD state line before diving southeast. Wouldn`t be surprised to see these storms linger a bit longer than advertised with the LLJ ramping up as it approaches Nebraska. Have boosted POPs in northern portions of the CWA. Storms are expected to be propagating along the cold pool and should have a linear mode by the time they enter this neck of the woods. They`ll primarily pose a wind threat. Sure enough, the new Day 2 convective outlook has expanded southeast to include Norfolk, Omaha, and Lincoln. Some areas will achieve their warmest temps of the week on Wednesday while areas just north will be cooler. Expect a range of near 80 north to near 90 south... with the gradient dependent on the front`s location. Determinstic forecast highs for Wednesday in Lincoln and Omaha have been inching up for the past 36 hours. Worth noting, though, is the wide spread in ensemble temps. Get this: Wednesday has a greater percentage of members hitting 88F at Omaha than on Tuesday. At the same time, Tuesday has more members than Wednesday hitting 87F at the same location. It`s all riding on that front`s placement. Those temps certainly matter for Wednesday as low-level lapse rates will climb due to some mid-level cooling. Expect some convection along both the warm and cold front with Wednesday`s shortwave working west to east. The bulk of mid-level frontogenesis will be in South Dakota and Minnesota. But if the front were to have trouble pushing north, the threat for severe weather would be displaced into the heart of OAX. A marginal threat of heavy rain and flash flooding has been progged for the northern portions of eastern Nebraska / northern Iowa on Tuesday night and Wednesday with PWATs running in the 90th percentile with values nearing 2.0". I`m sure some of the farmers in this area would take their chances with the heavy rains as the drought`s greatest impacts overlap this region. Thursday will be cooler in the system`s wake as heights fall and 850 temps lose about 10C. As we head into the weekend, the western ridge remains strong and may expand north and east. Regularly ejecting shortwaves riding the ridge will work to try to keep it at bay, but ensembles suggest it may be futile as the threat of warmer weather increases with time. && .AVIATION...(For the 00Z TAFS through 00Z Tuesday evening) Issued at 610 PM CDT Mon Jul 12 2021 There is some smoke around, mostly aloft, and that probably will not have a huge impact on aviation. Should see VFR conditions through the period. && .OAX WATCHES/WARNINGS/ADVISORIES... NE...None. IA...None. && $$ DISCUSSION...Nicolaisen AVIATION...Miller
For frequently asked questions about the Area Forecast Discussion
Area Forecast Discussion
National Weather Service Las Vegas NV
745 PM PDT Mon Jul 12 2021 .SYNOPSIS...As the major heat wave wanes, monsoon storms will increase across parts of southeast Nevada, northwest Arizona and far eastern San Bernardino County tonight and again Tuesday night. Gusty winds and heavy rain leading to flash flooding are the primary concerns. Conditions are forecast to dry out by late in the week but monsoon moisture looks to return to northwest Arizona and parts of the Mojave Desert Sunday and Monday. && .UPDATE...Best thunderstorm activity this evening has been mainly over Lincoln and Nye counties, which have been slowly drifting southeast. The question through the rest of the evening will be if the current storms persist into the over night or if they dissipate quickly. The area south of the current activity in Clark and Mohave counties did currently show decent MUCAPEs and high moisture, which would be a decent environment for convection to continue, but now CIN was beginning to increase through that region as well. Some of the HI-Res models show at least isolated activity continuing through the night in Clark County and western Mohave County, with HRRR and FV3 models being the most bullish through the first part of the night and showing a similar situation to last night with storms congealing in northeast Clark County. While that may be a bit overdone given the general trend of things now, leaning towards less convection than last night but still some thunderstorms around through at least the first part of the night. HREF continues to show MUCAPE at 500-1000 J/Kg through the overnight hours and PWATs are very high, so with any possible outflow from storms dying to the north we could still see some additional storms. With PWATs over 1 inch over much of the region, heavy rain is possible with isolated flooding concerns where storms congeal and stall. Today should be the last day for extreme heat for southeast Nevada, eastern San Bernardino County, and Mohave County as moisture continues to push into the region. Temperatures will be lower tomorrow and heat risk decreases for these areas, so will let the excessive heat warning expire. One more day of high heat risk is likely further to the west as moisture will be lacking and the high will still be centered overhead, so will let that continue through Tuesday. && .PREVIOUS DISCUSSION...300 PM PDT Mon Jul 12 2021 .DISCUSSION...Anticipating an active evening and again tomorrow evening with gusty winds and heavy rainfall being the primary concern. Recent burn areas in Mohave County will be very susceptible to flash flooding and debris flows Tuesday night. Center of mid-level ridge forecast to lies across southern California the next two days. Area of broad divergence aloft is forecast along the northeast/eastern quadrant of the high across southern Nevada, northwest Arizona and the lower Colorado River Valley. SPC HREF has been consistent showing thunderstorms and associated outflow surging south across Clark County southward into the Lake Mead Natl Rec Area and western Mohave County late this evening. Main concern tonight looks to be gusty winds with localized heavy rainfall. Similar setup for Tuesday evening into Wednesday morning. However, this time both gusty winds and heavy rainfall are the concern as storms surge south all the way through the lower Colorado River Valley and southern Mohave County. Hourly rainfall rates of 1 to 1.5 inches are possible Tuesday night. Collaborated a Flash Flood Watch with surrounding offices with ours running from 2 pm Tuesday - 5 am Wednesday morning. Our major heatwave will continue across the western zones through Tuesday while most area will be allowed to end later this evening. Temperatures will continue to drop on Wednesday with highs closer to what we would expect this time of year. Moisture lingers and showers and storms continue across mainly Lincoln and Mohave counties. Heat will moderate from mid week through the weekend with no additional heat headlines anticipated. On Thursday, high pressure ridging is suppressed with weak troughing setting up near the west coast. Seasonal temperatures will continue through the weekend with the deeper moisture shifting eastward and focusing any remaining storm chances over or near eastern Mohave County. The Four Corners high rebuilds sometime over the weekend and storm chances expand west across much of Mohave County on Sunday. && .AVIATION...For McCarran...Southeast winds are expected this afternoon with occasional gusts to around 15-20 knots. There is still a potential of storms developing in and around the Las Vegas Valley this evening bringing erratic and gusty outflow winds. Also, there is still the potential of outflow winds moving in from northeast and northwest with storms that develop to the north. Low confidence on magnitude of these outflow winds at this time. If outflow winds do develop there is still the potential they could exceed 35 knots, again low confidence however. Cloud bases with convection will range from 7-10kft AGL. Storm chances decrease by 10- 12Z overnight tonight. Another round of storms are possible again tomorrow, initially developing along the higher terrain in the afternoon with a similar wind threat in the evening. For the rest of southern Nevada, northwest Arizona and southeast California...Generally light winds are expected across most TAF sites through this afternoon. Storms will be possible near KBIH through this afternoon, with potentially erratic and gusty outflows to around 30-40 knots. Slight chance for storms moving through Clark and Mohave Counties to make it to KIFP and KEED overnight tonight. If storms do develop down the Colorado River Valley TAF sites, gusts to around 25-35 knots are possible. Cloud bases with convection will range from 7-10kft AGL. Storm chances decrease from north to south 10-12Z overnight tonight. However, there`s a non-zero chance of storms near KDAG early Tuesday between 11-14Z. Another round of storms are possible again tomorrow, initially developing along the higher terrain in the afternoon with a similar wind threat in the evening. && .CLIMATE...Listed below are a few climate locations showing both the record high maximum and high minimum temperature for each location and the year the record was last set for Monday and Tuesday. LOCATION MON-JULY 12 TUE-JULY 13 (HIGH MAX) Record(year) Record(year) Las Vegas NV 114(2003) 115(1939) Bishop CA 108(2020) 107(2020) Barstow CA 115(2020) 115(1972) Needles CA 124(1925) 123(2005) Kingman AZ 111(2020) 110(2005) Desert Rock NV 111(2020) 111(2014) Death Valley CA 130(1913) 131(1913) LOCATION MON-JULY 12 TUE-JULY 13 (HIGH MIN) Record(year) Record(year) Las Vegas NV 94(2020) 93(2020) Bishop CA 69(1990) 68(2002) Barstow CA 87(2012) 84(2020) Needles CA 92(2019) 95(2020) Kingman AZ 83(1925) 83(2007) Desert Rock NV 81(2003) 89(2020) && .SPOTTER INFORMATION STATEMENT...Spotters are encouraged to report any significant weather or impacts according to standard operating procedures. && $$ UPDATE...Nickerson DISCUSSION...Pierce AVIATION...Peters For more forecast information...see us on our webpage: or follow us on Facebook and Twitter