Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 04/28/22

Area Forecast Discussion
National Weather Service Cheyenne WY
755 PM MDT Wed Apr 27 2022 .UPDATE... Issued at 755 PM MDT Wed Apr 27 2022 Early evening WV/IR imagery showed a couple of shortwave troughs, one moving into the central and southern High Plains accompanied by strong convection, and the second moving through central MT to northwest UT. A cold front stretched from northwest WY into southern NV, with a surface trough through southeast WY and far northeast CO. Some showers were developing in the vicinity of the trough over southeast WY, however very dry low levels (inverted-v sounding profiles) resulted in virga and locally gusty winds up to 45 mph. These showers will eventually dissipate with more concentrated shower activity spreading northeast across northern and northeast WY for the next several hours with the passage of the shortwave trough. The current forecast is on track, so no changes are anticipated this evening. && .SHORT TERM...(This evening through Friday) Issued at 345 PM MDT Wed Apr 27 2022 The weather pattern remains active for the next several days. The main concerns in the short term forecast are as follows: * Potential for showers and thunderstorms to develop mainly along and east of the Laramie range Thursday afternoon through the overnight hours, with a possibility for isolated severe storms. * A strong cold front will push through Friday morning, and we may be looking at yet another strong wind event for parts of SE Wyoming. * Elevated fire weather concerns continue. More details can be found in the fire weather section below. Currently, GOES satellite shows mid to high level cloud cover near the area associated with two weak upper level shortwaves shifting to the northeast amid SW flow aloft. Our area is sandwiched between the two disturbances, one of which is located over east central Colorado, while the other is located near the Yellowstone area. Elevated moisture has crept up as these systems pass by, but the lower levels remain very dry. Thus, even though some light precipitation echoes are visible on radar, this is expected to remain largely virga. A stronger system approaches on Thursday as a vigorous 500-mb vorticity maximum pushes onshore near the CA/OR border. Diffluent flow aloft on the downstream flank of the shortwave will help to support the development of some weak surface cyclogenesis in central Colorado. Pressure drops in this area will enhance the low level jet over the plains and allow for increased boundary layer moisture advection from the southeast into the western Nebraska panhandle and far eastern Wyoming by Thursday evening. Low level easterlies underneath strong mid to upper level southwesterlies as the trough pushes overhead will lead to increasing deep layer shear across the high plains. Forecast soundings show steep mid level lapse rates resulting from the cold air aloft. Thus, the possibility remains for the development of afternoon convection as vorticity advection aloft provides some enhanced lift by late in the day on Thursday. The SPC has included the Nebraska panhandle in a marginal risk for severe thunderstorms tomorrow, with wind and hail being the main threats. The boundary layer remains fairly dry, exhibiting some inverted-Vs in the forecast soundings for tomorrow. The main source of uncertainty is the extent of the instability, even amongst the hires models. The HRRR is quite a bit drier in the low levels along with decreased CAPE compared to the more moist hires NAM. Thus, the HRRR only develops isolated convection, while more widespread thunderstorms are shown in the 3km NAM solution. We will continue to watch this over the next 24 hours, but at least for now, isolated to scattered thunderstorms look likely along and east of the Laramie range starting late Thursday afternoon through the overnight hours. The cold front will push through Friday morning. Increasing 700-mb height gradients across our area behind the front may lead to another round of high winds for the wind prone areas, as early as Friday morning for some locations. Did not have the confidence to go with a watch at this time, but later shifts will need to monitor this. Strong cold air advection aloft is expected during the day on Friday as the upper level trough passes overhead. Some wraparound moisture could bring appreciable precipitation to the Nebraska panhandle, especially further north, on Friday. Some weak instability remains through the day on Friday, so there could be rumbles of thunder. Uncertainty remains quite high in this phase of the event, which will carry into the long term period outlined below. .LONG TERM...(Friday night through Wednesday) Issued at 345 PM MDT Wed Apr 27 2022 Main forecast concern in the Medium to Long Range is the evolution and movement of the Pacific upper level trough which will initially move across the northern Rockys as a progressive open wave; but recent models indicate the gradual formation of a closed low across the western Great Plains region. For now, will just monitor the evolution of this system with all models onboard...showing the surface low developing over Kansas and central Nebraska. This is a bit too far east to result in significant precip/impacts across southeast Wyoming and most of western Nebraska. However, the northern and central panhandle of NE seem to do pretty well on the backside in the TROWAL/wrap around moisture region. Kept POP highest (~70 percent) near Chadron and Alliance Nebraska with some snowfall possible Friday night. Elsewhere, not expecting all that much due to the northern trajectory of the system over Wyoming, resulting in downslope westerly winds across most of the area outside of the mountains. Very windy conditions are expected on Saturday behind the system, especially if the surface low develops quicker and intensifies rapidly. High Wind criteria are possible, especially for the Wind Prone areas and the High Plains east of Interstate 25 into western Nebraska. Increased winds near HWW criteria for these areas early Saturday morning through the afternoon hours. For late in the weekend and through the middle of next week, models show a progressive pattern with increasing jet energy near the Colorado and Wyoming border along with the western third of the United States. Expect Pacific energy to quickly move across the Great Basin Region and into the Rockys every 36 to 48 hours. The main Pacific system to watch during this time period is on Tuesday, but models are in poor agreement with the position of the upper level low. The Canadian is slower and well to the north, showing the system in Montana by late Tuesday while the GFS is much more progressive but shows a similar track compared to the Canadian. The ECMWF digs this upper low into the eastern Great Basin region and is much slower, still showing it west of Salt Lake City Tuesday evening. The ECMWF solution bares watching, but will not go too aggressive at this time due to poor support from other deterministic models and most ensemble forecasts. Kept temperatures near or slightly below normal for this time of the year with highs in the 50s and 60s. && .AVIATION...(For the 00Z TAFS through 00Z Thursday evening) Issued at 540 PM MDT Wed Apr 27 2022 VFR conditions expected through the night with some mid- to high- level clouds. Some virga showers possible during the evening, with wind gusts up to 30 kts. Winds overnight and into the morning hours will be light. && .FIRE WEATHER... Issued at 345 PM MDT Wed Apr 27 2022 Elevated to near critical fire weather conditions are present this afternoon especially along and south of the I-80 corridor, where RH has dropped to near 15%, but winds remain on the light side. With light winds expected to continue overnight, we should cool down well overnight leading to good humidity recoveries. Another round of elevated to near critical fire weather is expected Thursday. Winds will be stronger than Wednesday with gusts 20 to 25 mph possible east of the Laramie range, and up to 35 mph in parts of Carbon county. However, dewpoints will creep up compared to Wednesday which should prevent RH from dropping below critical thresholds. Isolated to scattered showers and thunderstorms are expected to develop Thursday afternoon through the overnight hours with the best probabilities along and east of the Laramie range. A strong cold front pushes through Friday morning, with strong winds and cooler temperatures likely by the afternoon. && .CYS WATCHES/WARNINGS/ADVISORIES... WY...None. NE...None. && $$ UPDATE...MAJ SHORT TERM...MN LONG TERM...TJT AVIATION...SF FIRE WEATHER...MN
Area Forecast Discussion
National Weather Service Des Moines IA
644 PM CDT Wed Apr 27 2022 ...Updated for the 00z Aviation Discussion... .DISCUSSION.../Tonight through Wednesday/ Issued at 333 PM CDT Wed Apr 27 2022 Key Messages: -Increasing threat for scattered showers and storms tonight into Thursday -Main swath of showers and thunderstorms expected Friday night into Saturday A warm front is bisecting the state this afternoon from west central Iowa to the southeast. Relatively strong east flow north of the boundary has produced somewhat brisk conditions with temperatures mostly in the 50s. South of the boundary, readings have climbed into the 70s with readings approaching 80 in the southwest corner of the state. Moisture remains lacking near the front, hence only high clouds passing over the state at this point. Theta-e advection and moisture transport increases into this evening and overnight which eventually leads to the development of scattered showers and storms in portions of the state. CAMS have indicated development this evening near the 850mb boundary across the northeast with the activity persisting overnight. In fact, both the HRRR and RAP show backbuilding across the far northeast overnight with moderate to locally heavy rainfall grazing the extreme northeast edges of the forecast area. Otherwise, there are varying solutions for scattered showers/storms overnight across mainly the west and south in the axis of low level flow into the state. The somewhat unorganized lift persists into Thursday and Thursday night with scattered precipitation continuing during these periods. The main shortwave ejects into the Plains on Friday with more organized forcing. Convection is expected to develop in eastern Nebraska and Kansas by late afternoon/evening and then press northward ahead of the upper low. The best low level instability remains in southwest Iowa where the slight risk is currently places. Elevated instability extends farther north and both GFS and Euro lift the convection into the state overnight Friday night with some threat of severe weather, mainly in southwest. Good moisture transport into the system should assist with locally heavy rainfall as well. The convection moves northeast into Saturday morning across central Iowa with diurnal weakening. There remains some small threat of marginally severe weather into Saturday afternoon across the far east and northeast portions of the forecast area where instability wraps back northwest toward the surface low. However any convection that does fire should quickly exit the forecast area to the north and east. The deformation zone of the system does wrap into the northwest half of the forecast area on Saturday night/Sunday morning with some scattered showers and cool/breezy conditions. The pattern remains relatively active into next week although timing difference are quite apparent between the medium range models. However, there does appear to be some threat of precipitation later Monday into early Tuesday with a surface low passing south of the state. Temperatures appear to remain at or below normal for much of the period with thermal trof to the north and east of the state and cloudiness as well. && .AVIATION.../For the 00Z TAFS through 00Z Thursday evening/ Issued at 644 PM CDT Wed Apr 27 2022 A warm front bisects the state this evening with easterly winds across northern Iowa and southerly winds across southern Iowa. In fact, though KDSM has south winds our office a few miles north is 10 degrees cooler with east winds. The front will move little overnight and showers/thunderstorms will develop over northern Iowa late tonight into Thursday across northern sites KMCW/KALO and perhaps into KFOD. Further south at KDSM/KOTM spotty showers may develop but thunderstorms are not anticipated. Precipitation will linger into Thursday morning. While cigs will initially remain VFR, degradation to MVFR and perhaps IFR is possible moving later into Thursday. && .DMX WATCHES/WARNINGS/ADVISORIES... NONE. && $$ DISCUSSION...Cogil AVIATION...Hagenhoff
National Weather Service Hastings NE
641 PM CDT Wed Apr 27 2022 .DISCUSSION...(This evening through Wednesday) Issued at 517 PM CDT Wed Apr 27 2022 -- Highlights/primary concerns of the entire 7-day forecast in chronological order: 1) Spotty strong to PERHAPS severe storm potential both this evening and then again late Thursday afternoon-evening: While am not overly-concerned about truly severe storm tonight, Thursday is a bit more of a "mystery" unfortunately, and depending on how model solutions trend, would not be surprised to see later SPC outlooks expand the official Marginal Risk to more of our our coverage area (CWA). 2) A seemingly more "synoptically-evident"/pronounced risk of severe storms Friday afternoon-evening: A fairly stout upper level low pressure system and associated surface low swings through the region, driving a strong cold front/dryline through in the process. SPC`s Day 3 outlook (issued early this AM) placed most of our CWA in a Marginal-Slight risk of severe, with the northwest edges of Enhanced Risk (level 3 of 5) clipping our extreme southeast zones. Although still plenty of "finer details" still need to be worked out, and obviously there are still 2 more days of SPC outlook refinements to come, the overall-scenario still seems to be supported. Based on various 12/18Z models, the southern half of the CWA appears overall-most favored for surface- based severe storms/possible supercells in closet proximity to the surface low, with a more multicell/slightly- elevated storm threat extending farther northward into the CWA, where plentiful cloud cover is more favored to keep temps and resultant low-level instability down a bit more. Although it`s simply too soon to "bank on" any one model solution or buy too much into details, it is worth noting that the latest NAMNest depicts a somewhat "messy" storm mode (even in our south), and the 15Z SREF shows an interesting lack of fanfare over our CWA in its "Significant Tornado Ingredients" parameter. So the bottom line is that while a severe storm threat certainly exists, it`s important not to get too carried away with its magnitude just yet. 3) Strong northwest gradient winds on the back-side of the system late Fri night and especially Saturday daytime: Confidence continues to grow that Saturday will be the overall- windiest day of the next week, with sustained speeds commonly at least 25-35 MPH/gusts 40-55 MPH (overall strongest in our western half). EPS ensemble continues to suggest that at least limited potential for High Wind/severe-criteria gusts of 58+ MPH could ultimately clip especially our far western CWA, but the overall- strongest gusts should favor areas to our west-northwest within western/north central NE. 4) Although things "settle down" a bit beyond Saturday, it`s odd to say that Sunday is truly the only "guaranteed dry" day in the forecast, as at least small-medium rain chances/PoPs re-enter the picture by Monday and linger through mid-week. That being said, the ECMWF/GFS models have a LOT of disparity in especially the timing of upper waves and resultant rain chances early-mid next week, so plenty of adjustments will likely be necessary. -- Other items of note/interest: 1) In a BIG change from recent weeks, we actually are NOT talking about any upcoming days with truly-concerning fire weather potential! While the threat will certainly not be "zero" (especially the main windy day such as Saturday), various factors such as increasing rain chances, most days not looking overly- windy (except Saturday) and no truly hot days will keep fire parameters at least somewhat in check compared to lately. 2) Finally some MUCH-NEEDED, more widespread rain? Although amounts will surely vary considerably within the CWA, WPC is currently calling for most of our CWA to measure somewhere between 0.50-1.50" over the course of the next week (most of which would likely fall Thurs-Sat). If anything, our north would be more favored for the higher amounts than our south, but as it turns out our far northern zones (Valley/Greeley area) have truly been among the overall-driest the past several months, so hopefully some decent amounts indeed materialize there. -- With the "big picture" and most important points covered, will conclude with some fairly brief day-to-day comments/additional details (including temperatures), focused mainly shorter term: - Current/recent weather scene as of 430 PM: No big surprises today, although if anything fairly decent coverage of high-level cirrus looks like it will help limit most of especially our northern/western zones to high temps only mid- upper 70s, while southern/eastern zones have managed greater coverage of low-mid 80s. As expected, the overall-strongest southerly wind today have affected our southeast 1/3 to 1/2 of the CWA (gusts commonly 25-35 MPH), while much lighter winds (generally sustained no more than 10-15 MPH) have prevailed in northern/western zones closer to this trough axis. - This evening-overnight: Have held off any mentionable (20+ percent) chance of convection until at least 7 PM this evening, and have overall-decreased POPs slightly from previous forecast. While modest instability/CAPE (RAP mixed-layer CAPE up to around 1000 J/kg in our southern zones this evening) will be present, the overall coverage of convection looks rather spotty per latest HRRR/NAMnest runs, with better potential for scattered storms/perhaps a loosely-organized MCS tracking to our south (mainly near/south of I-70 in KS). That being said, will maintain a mention for the possibility for a few stronger storms in our Hazardous Weather Outlook (HWOGID), mainly near/south of the state line. Although most areas north of the state line are likely dry through the night, very spotty weak convection within a modest low level jet axis cannot be totally ruled out and thus have slight PoPs going all but far northern zones. Steady south to southeast breezes most areas overnight will keep low temps well into the 50s most areas (Ord area most favored for upper 40s). Thurs-Thurs night: For only being 24 hours out, honestly plenty of question marks regarding thunderstorm chances. While most of the area is covered with low-end PoPs especially during the afternoon-evening, models show widely varying solutions on coverage/likelihood. Of greatest concern is the last few HRRR runs, which depict a broken line of storms developing mainly in our northern CWA along a weak frontal boundary. Should this occur, at least a limited severe threat seems plausible given MLCAPE progged around 1500-2000 J/kg along with 30-40KT of deep layer shear, but overall upper forcing appears fairly weak and other models (NAM/NAMNest) are mostly dry. Something to watch. In other areas, generally south-southeast winds of 10-20 MPH through the day. Temps a little uncertain depending on how efficiently (or not) any lower level clouds vacate, but have them aimed from mid 70s east to low 80s west. Lows Thurs night again well into 50s most areas. Fri-Fri night: See paragraph above for various comments on the thunderstorm/severe potential. Certainly the potential for some severe, but how much so still in question. From a large scale perspective, at least ECMWF/GFS/NAM all in pretty good agreement on strength/track of upper system and associated surface low. High temps Friday again vary dependent on low cloud trends any clearing south into a possible dry slot, but for now upper 60s far north to mid 80s far south. Sat-Sat night: Not a very nice day, especially given aforementioned strong northwest winds with widespread gusts at least 40-55 MPH (highest west), along with a decent chance for wrap-around rain showers especially north of I-80. Most areas roughly 20 degrees cooler than Friday (low 50s far north to low-mid 60s far south). Lows Sat night as cold as mid-upper 30s, but winds likely well too strong for frost concerns. Sun-Sun night: Pretty high confidence in a dry day with brief ridging in between systems and lighter winds (compared to Saturday anyway). High temps mainly 60s. Already Sunday night though, small PoPs return to the area as the next quick-moving disturbance approaches. Lows again possibly as cold as mid-upper 30s, but frost concerns fairly minimal mainly due to increasing clouds. Mon-Mon night: Either another good chance of rain (mostly without thunder potential due to lack of instability) per ECMWF, or a mostly dry day most areas per GFS solution. Question marks abound. Temps aimed around 60. Tues-Wed: Various small PoPs continue here or there, but timing differences abound, with GFS favoring Tues-Tues night and slower ECMWF more so favoring Wed daytime. At least for now, instability appears fairly limited. Temps remain fairly seasonable if not a touch- cool for early May, with highs aimed into the 60s both days. && .AVIATION...(For the 00Z KGRI/KEAR TAFS through 00Z Friday) Issued at 636 PM CDT Wed Apr 27 2022 VFR conditions prevail through the early evening at KGRI and KEAR terminals. Winds will be from the southeast for much of the evening at 5-10kts. A few scattered showers and thunderstorms will be possible in the vicinity of the terminal this evening with chances decreasing toward sunrise. Ceilings are expected to lower to MVFR around 12-15Z. Areas receiving rainfall overnight may experience some patchy fog, however confidence in this solution remains low for the time being due to lack of widespread coverage of rain. Conditions improve late tomorrow morning at KEAR with ceilings returning to VFR. && .GID WATCHES/WARNINGS/ADVISORIES... NE...NONE. KS...NONE. && $$ DISCUSSION...Pfannkuch AVIATION...Wekesser
Area Forecast Discussion
National Weather Service Grand Junction CO
804 PM MDT Wed Apr 27 2022 .UPDATE... Issued at 804 PM MDT Wed Apr 27 2022 The Red Flag Warning has been allowed to expire at 8 PM MDT. Winds have subsided for most locations while relative humidity has recovered above critical levels thereby ending the threat of extreme fire behavior. && .SHORT TERM...(Tonight through Thursday night) Issued at 144 PM MDT Wed Apr 27 2022 Both the HRRR and NAMNEST did a great job today picking up on the convection. Both models showed some minor convection firing just before noon, which it did, and then continuing over the San Juans and shifting a bit north over the central mountains. Did see a few lightning strikes near Crested Butte so, all in all, a good show by those models. This convection is in response to a shortwave that is moving overhead with the support of a weak 70kt jet streak. This support, along with some midlevel instability, was enough to get this convection going. Satellite and radar imagery show this convection shifting to the Front Range though the NAMNEST is highlighting some weak returns across central portions of CO through about 6PM. Might see a quick sprinkle from a stronger cell but with such dry lower levels of the atmosphere in place, this will be few and far between. Deeper mixing has also allowed some gusty winds to mix to the surface with gusts of 25 to 35 mph being common across the CWA. Red Flag Warnings remain in effect for the combination of gusty winds, low humidities and critical fuels (for those areas where fuels are deemed critical). Expect some high clouds overnight ahead of the next system, especially for UT and far western CO, where they`ll be under some weak upper level support. Heading into Thursday proper, a trough will be just to our west and while the best support and moisture remains to the north, we`ll still feel the effects in the form of gusty winds and continued warm temperatures. With increasing southwesterly flow and a tightening surface pressure gradient ahead of the trough, gusty surface winds will form again and look to be stronger than those seen recently. Gusts look to range from 30 to 40 mph across the region with stronger winds north, less so south. While we will see variable cloudiness throughout the day, some spotty showers are also possible but these look to be very isolated in nature. In fact, the NBM is only highlighting some light precip over the Uintas and Park Range and is in agreement with the NAMNEST and other models for tomorrow afternoon and evening. However, chances will start to increase early Friday morning as the base of the trough and associated cold front starts to move through...more on that below. .LONG TERM...(Friday through Wednesday) Issued at 144 PM MDT Wed Apr 27 2022 The system that dived out of the Pacific Northwest will begin to impact eastern Utah and western Colorado on Friday as it scoots by to the north across the northern Rockies and Intermountain West. At the surface, a strong cold front will surge in from the west late Thursday night and early Friday morning. Aloft, a 110 knot 250mb jet coupled with a sharp shortwave will punch in from the northwest. Large scale forcing for ascent will increase as a result, particularly within the left exit region of the jet over northeast Utah and northwest Colorado. Moisture with this system isn`t all that impressive with progged PWAT anomalies only near or slightly above normal. That said, the frontal forcing and dynamics aloft combined with the meager moisture will be enough to squeeze out some showers for mainly the higher terrain in the northern half of the forecast area. Most of this shower activity will subside by midday, but orographic upslope showers will likely linger across the central and northern Divide mountains through the remainder of the day and possibly night. All in all, QPF/snow amounts look light and sub-advisory with 1 to 3 inches expected in the highest elevations. Other than precip, the other big weather stories on Friday will be the cooler temperatures (by as much as 10 to 15 degrees), gusty winds and fire weather. While highs on Thursday will be in the 70s and 80s for the lower desert valleys and in the 50s and 60s in the mountain towns and high valleys, highs will only reach the mid 60s in the lower valleys, 30s & 40s in the mountain towns and 50s for the high valleys. Quite a stark contrast from just the day before. Gusty winds up to 40 mph and fire weather are also concerns, especially south of I-70. As mentioned above, PWATs across the north will only be nearly or slightly above normal. The opposite is true across the south where PWATs are near 50% of normal. Where fuels are critical (CO fire zones 290, 292 and 207 below 7000 feet), we have another Fire Weather Watch in effect. Similar to how things were handled on day 3 yesterday, we`re going to let that ride for now and let the midnight shift make the decision to upgrade to a warning. More details can be found in the Fire Weather discussion below. Beyond Friday, a transient ridge builds in across the Great Basin and Four Corners on Saturday. This will lead to a dry and mostly sunny day with less wind and slightly warmer temperatures. Dry weather lingers into Sunday, but another quick-moving and shallow storm system will be on the doorstep Sunday afternoon. Southwest flow will increase out ahead of this system, so we may have additional fire weather concerns. Showers likely develop Sunday afternoon and evening especially in the higher terrain. Most showers will end Monday morning, but a few may linger way up high. After a brief reprieve Monday afternoon through maybe Tuesday morning, yet another system is in the pipeline for later Tuesday into Wednesday. Details on this system are still fuzzy given a lack of model agreement, but regardless, it`s still looking like an active start to the week, especially, again, in the higher terrain. Drier weather then likely returns to round out next week with temperatures hovering near seasonal norms. && .AVIATION...(For the 00Z TAFS through 00Z Thursday evening) Issued at 532 PM MDT Wed Apr 27 2022 Instability showers over the central and southern Colorado mountains may bring strong and unpredictable wind gusts to adjacent TAF sites through 02Z. Aside from wind, this convective activity will not degrade VFR conditions prior to dissipating later this evening. Drainage winds become established by midnight, though deep mixing during the afternoon will bring another round of gusty southwest winds to TAF sites across the region on Wednesday. && .FIRE WEATHER... Issued at 144 PM MDT Wed Apr 27 2022 Gusty southwest winds have combined with low relative humidities and caused critical fire weather conditions to occur across many of the lower elevations of eastern Utah and western Colorado today. This trend looks to continue each afternoon through the end of the week. However, as most fuels are not deemed critical, fire weather highlights are only in effect for portions of southwest Colorado. Red Flag Warnings remain in effect for today and tomorrow while the Fire Weather Watch also remains in effect for Friday. Above normal temperatures will persist through Thursday. Cooler temperatures are expected Friday behind a cold front that will also bring scattered showers, mainly across the north, Friday into Saturday. && .GJT WATCHES/WARNINGS/ADVISORIES... CO...Red Flag Warning from noon to 9 PM MDT Thursday for COZ207-290- 292. Fire Weather Watch from Friday morning through Friday evening for COZ207-290-292. UT...None. && $$ UPDATE...NL SHORT TERM...TGR LONG TERM...MDM AVIATION...NL FIRE WEATHER...TGJT
Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
620 PM CDT Wed Apr 27 2022 .SHORT TERM... Issued at 301 PM CDT Wed Apr 27 2022 Through Thursday night... This evening will be another cool one with temperatures dropping into the 30`s area-wide by around midnight, but likely much earlier for those in the Chicagoland metro. A fair breeze will pull wind chills down into the 20`s and lower 30`s for the latter half of the evening, being especially cool closer to the lake as onshore flow will persist through the night. By early tomorrow morning, temperatures across the CWA will have fallen into the middle and upper 30`s. Just about everyone should remain above freezing, perhaps with the exception of some more open and rural areas. Meanwhile, a few showers are attempting to fall just west of the CWA, but a lack of low level moisture won`t allow them to reach the surface just yet. However, a plume of moisture advancing down the lee side of a midlevel trough sitting just to our west will continue to advect beds of altocumulus and altostratus clouds into the CWA from the northwest. This means the majority of the sunshine will continue to be obstructed for the remainder of our Wednesday. Moderate low level moisture advection thanks to a low level high to our SSE, with the help of some evaporating rainfall, will work to moisten up the low levels over the next several hours making it possible to see some rain later this evening. The rain chances will move in from the west as early as 7-8 PM and continue through the night while being primarily confined to areas north of I-80. There is a good chance that light rain may even become mixed with some snowflakes as temperatures cool through the night, though no accumulations are anticipated. Heading into late tomorrow morning/early afternoon, more rain showers are expected to pop up to our southwest along a quasi- stationary frontal boundary and advect into the CWA. The chance for on and off showers and sprinkles will then last through the remainder of tomorrow and into Friday morning. Guidance doesn`t have the greatest grasp on the exact coverage of the rainfall, but it should be scattered enough to where some spots may not see any rainfall tomorrow while other may see rain come and go for several rounds. Additionally, the occasional moderate shower is just about as heavy as the rain is expected to get. As far as tomorrow`s temperatures go, the outlying areas should be similar to today with highs in the middle and upper 50`s. This lake-effect cold pool we`re seeing today shouldn`t be nearly as prominent come tomorrow. Therefore, the metro, especially areas near the lake, will see a notable warmup with highs in the middle 40`s to lower 50`s. Efficient low level warm air advection overnight, along with overcast skies, should keep conditions relatively mild with Friday morning highs expected to be in the middle to upper 40`s. Doom && .LONG TERM... Issued at 243 PM CDT Wed Apr 27 2022 Friday through Wednesday... As noted in the previous discussion, this period is looking to be fairly active with a progressive flow pattern setting up into next week. Upper ridging will be cresting the mid and upper Mississippi River valley and amplify as it does so thanks to a trough moving east into the Rockies. With the mid level thermal gradient tightening between the amplifying ridge and the approaching trough, persistent isentropic ascent/warm advection will set up and gradually spread northeastward through the day. Waves of scattered showers in the southwest part of the area to start the day will spread northeastward through the afternoon with the greatest coverage across the southwest half or so of the area. Warm advection and southerly winds will help highs to moderate with readings in the upper 50s to around 60, though the Illinois shoreline will likely be cooler thanks to an easterly component to the south wind. Moist ascent persists Friday night with the low level flow increasing as the advancing low closes off over Nebraska. This will provide more support for showers and possibly some thunderstorms as elevated instability spreads north and east toward or into the area. By Saturday, the surface low associated with the upper low is expected to be slowly moving from northern Nebraska into southwest Minnesota. An associated cold front will move eastward and looks to occlude through the day as it does so. At this point its tough to say how far north the warm sector of the system will spread, at least in terms of one being clear enough to realize more than limited instability. It will be something to keep an eye for potential severe weather which at this point would be favored south of the area. Otherwise, periods of showers/rain are expected. Expect warmer conditions across the area, though an easterly wind component may remain in place keeping northeast sections of Illinois int the 50s with mid 60s to near 70 degree temps spread elsewhere. Another trough digging into the west will help the closed upper low over the local region eastward Sunday and Sunday night. Modestly cooler air will spread in as this occurs and there will likely be enough ascent for scattered showers Sunday, mainly across northern sections of the area. Beyond that, several more systems look to cross the area through midweek bringing periodic shower and maybe thunder chances. Temperatures look to remain on the cool side of normal with highs in the 50s and 60s depending on the day. MDB && .AVIATION... For the 00Z TAFs... Primarily VFR conditions are expected to prevail through the TAF period. As warm air advection increases atop a stalled frontal boundary draped across central Iowa and northern Illinois this evening, showers will blossom and regenerate more or less in the same place through late Thursday morning. At least some convective processes may occur with the showers as well mainly toward the northwestern ZAU airspace, given RAP 700-500 mb lapse rates exceeding 7 K/km, "bumpiness" in visible satellite imagery, and recent convective-looking radar returns near KDVN. However, closer to the Chicago terminals, a dry low-level airmass from about 3500-10000 feet (as sampled by a recent descending flight into MDW) may chew away raindrops as they fall toward the ground, keeping radar echoes as largely virga through the night. Chances for rain to reach the surface should increase toward and especially after daybreak as the frontogenetical forcing and low- level WAA peaks in intensity. For now, opted to maintain the inherited TEMPO groups this evening and introduce a PROB30 group at the Chicago terminals after daybreak, though in reality raindrops may hit the ground really anytime from sunset through noon tomorrow. Cigs and visbys are expected to remain above 3000 feet and 6 miles, respectively, in the showers so no impacts beyond wet runways are anticipated. Coverage of showers should wane tomorrow afternoon as frontogenetical forcing decreases, leaving behind a BKN080 cloud deck. Winds through the TAF period will maintain an easterly component, first out of the east- northeast this evening and the east-southeast tomorrow. Borchardt && .MARINE... Opted to hoist a small craft advisory this morning through mid evening. Unseasonably cold air mass resides over the lake with a couple of ship obs well offshore reporting air temps in the mid 30s. Water temps have warmed well into the 40s, resulting in a rather unusually unstable marine boundary layer for this time of year. As high pressure moves east the strengthening synoptic pressure gradient should be strengthened by the lake-land breeze circulation today. Only ran the small craft advisory through 02Z, but it is possible winds and/or waves are slower to come down than forecast and the advisory may need to be extended. - Izzi && .LOT WATCHES/WARNINGS/ADVISORIES... IL...None. IN...None. LM...Small Craft Advisory...nearshore waters until 9 PM Wednesday. && $$ Visit us at Follow us on Facebook, Twitter, and YouTube at:
Area Forecast Discussion
National Weather Service Lubbock TX
607 PM CDT Wed Apr 27 2022 .AVIATION... VFR conditions will prevail at all terminals. There is a very slim chance for a shower or thunderstorm to impact PVW and/or LBB between 11 PM and 1 AM tonight, but confidence is extremely low at this time. There is also a slight chance for MVFR CIGs at CDS around sunrise, but confidence is low and will also be kept out of this TAF cycle. && .PREV DISCUSSION... /issued 220 PM CDT Wed Apr 27 2022/ SHORT TERM... 18Z upper air analysis depicts a shortwave trough beginning to eject across the west-central Great Plains with a corresponding baroclinic leaf present over eastern Colorado and western Kansas. A pair of mid/upper-level cyclones were located over the Pacific Northwest and northeastern U.S., resulting in weak blocking of the low-amplitude ridge encompassing most of the central Great Plains. At the surface, lee cyclogenesis is underway across southeastern Colorado with a diffuse dryline extending south-southwestward which is draped across east-central New Mexico/along the Sangre de Cristo and Sacramento Mountains and a secondary surface trough arcing southeastward into the Texas Panhandle and Rolling Plains, evident from recent METAR and West Texas Mesonet data. Pressure falls were weak across the CWA, near -1 mb/3 hr to locally -2 mb/3 hr as the cyclone gradually deepens with a current pressure near 1008 mb based off nearby METARs fixed to the low center. This has resulted in breezy, southerly winds between 15-25 mph area-wide as the pressure gradient begins to tighten. Cyclogenesis is expected to continue through the rest of the afternoon as the shortwave trough ejects north of the CWA, though deepening will continue to be gradual as it rotates through the low-amplitude ridging overhead. The southerly fetch has advected heavily modified moisture from the Gulf of Mexico into the region, characterized by surface dewpoints in the lower-middle 50s across the Caprock an/99/99d Rolling Plains, respectively. A differential diabatic heating boundary, oriented in a north-to- south direction and juxtaposed to the diffuse surface trough, was also analyzed across the east-central Rolling Plains based off of visible satellite imagery and theta-e advection magnitudes on the West Texas Mesonet. Diurnally-driven convection has formed along the immediate leeward side of the mountains in New Mexico as the shortwave trough nears and as convective temperatures have been reached amidst minimal mixed-layer convective inhibition, which was observed on the 27/12Z RAOBs from ABQ and EPZ. Weak geopotential height falls will continue to contribute to the advection of a tall and skinny EML over the CWA as mid-level lapse rates steepen to near 7.5 deg C/km, with around 1,000 J/kg of CAPE for surface-based parcels evolving later this afternoon across the western South Plains/TX PH based off of recent RAP analysis which is further confirmed by the observed RAOBs this morning. As multi-cells near the TX/NM state line, the initial storm movement governed by advection may transition into a spatiotemporal window for discrete propagation as straight hodographs and effective bulk wind differences (EBWDs) near 30 kt to locally 35 kt support the potential formation of weak, mid-level mesocyclones for left- and right-moving supercells. A dry, well-mixed sub-cloud layer with LCLs near 700 mb across the western South Plains/TX PH will facilitate cold downdrafts with wind gusts up to 60 mph possible beneath the deepest cores. A hail event or two up to 1 inch in diameter will be possible as well; however, the weak EBWDs and skinny updrafts should limit the potential for severe-caliber hail. There exists uncertainty on how far east cells will propagate, and coverage will be limited to a few cells with the best potential mainly west of the I-27 corridor. Thunderstorm coverage will wane altogether after dark as MLCINH increases and the boundary-layer stabilizes. Surface winds will gradually veer overnight while remaining breezy as the cyclone drifts towards the Raton Mesa and OK/TX PH region, resulting in boundary-layer moistening once again as the low-level jet (LLJ) strengthens to near 35 kt beneath the dampening shortwave trough over central Kansas. The development of a low stratus deck will be possible prior to sunrise Thursday, especially across the Rolling Plains owing to the terrain-influenced, deeper PBL as T/Td spreads near 0 deg near the top of the LLJ with decreasing potential for saturation with westward extent onto the Caprock. After sunrise, intense dry-bulbing and vertical mixing is expected as the dryline mixes eastward into the eastern Rolling Plains as large-scale forcing for ascent gradually increases compared to today due to a shortwave trough pinching off and digging southward from the parent mid/upper-level cyclone over western Canada and the Pacific Northwest. Temperatures will soar into the middle 90s across most of the CWA, excluding the extreme southwestern TX PH where temperatures in the upper 80s are expected, in wake of the dryline. Breezy, southwesterly winds between 15-25 mph are expected despite vertical mixing heights ascending into the mid-levels in the dry sector as the jet streak remains displaced over the southern Great Basin. The dryline is forecast to stall while also sharpening (i.e. a dewpoint gradient of nearly 20 deg F over >=30 miles depending on various locales) across the western vicinity of the 100th meridian, keeping the far eastern Rolling Plains from near Childress southward to Aspermont in the moist sector. Vertical thermodynamic profiles in the moist sector will be similar to today with straight hodographs favoring an initial multi-cellular storm mode with the potential for discrete propagation for left- and right-moving supercells fostering the possibility of low-end, severe-caliber hail and wind reports before convection moves east of the CWA. Sincavage LONG TERM... Increased fire weather concerns will occur later this week with a chance of widespread thunderstorms late in the weekend. The increased fire weather concerns will come on Friday. An upper trough centered over the central Rockies on Friday morning will emerge onto the Central Plains Friday afternoon and will sharpen up as this occurs. The upper level jet streak associated with this short wave will track close to the 37th parallel keeping any large scale ascent well north of the region. The rapid movement of the system onto the Plains Friday afternoon will easily shove a dryline east of the Rolling Plains with strong lee surface cyclogenesis in western Kansas. Winds directly overhead will not be that impressive on Friday during the daytime. However, the approach of the short wave will allow the surface pressure gradient to tighten significantly which will bring strong westerly winds and warm temperatures. A cold front will follow late Friday into early Saturday. This will bring temperatures closer to seasonal averages for Saturday. Short wave ridging will be moving overhead in advance of the next short wave to affect the area on Sunday. Return flow will be quick to establish itself beginning early Sunday in advance of this short wave moving across the Great Basin region. An upper level jet streak will be more squarely overhead providing better large scale ascent on top of a sharp dryline near the Texas/New Mexico state line. However, at this forecast range the devil is in the details with regards to any minor short waves in the flow and there remains much uncertainty. Analog guidance indicates the potential for severe storms on Sunday afternoon and evening over a widespread area of West Texas. FIRE WEATHER... Critical fire weather conditions are expected across the Caprock, particularly along and west of the I-27 corridor, tomorrow afternoon. A Red Flag Warning is in effect between noon and 9 PM CDT. Breezy, southwesterly winds between 15-25 mph with gusts up to 35 mph will combine with hot temperatures and very low relative humidity, resulting in favorable conditions for the growth and spread of fires. Southwesterly breezes will persist overnight but decrease to around 10-15 mph with RH recovery near 100 percent across the region. && .LUB WATCHES/WARNINGS/ADVISORIES... Fire Weather Watch from Friday morning through Friday evening for TXZ021>044. Red Flag Warning from noon to 9 PM CDT Thursday for TXZ021>023- 027>029-033>035-039>041. && $$ 51
Area Forecast Discussion
National Weather Service San Diego CA
855 PM PDT Wed Apr 27 2022 .SYNOPSIS... Cooler weather with a greater influence from the marine layer is expected through Thursday. Gusty westerly winds across the mountains and deserts will be boosted by a trough of low pressure moving through the region. Low clouds and fog will spread inland to the mountains tonight into Thursday, including patchy drizzle early Thursday. As the trough departs a weak ridge will help temperatures rebound into Saturday. More troughs of low pressure appear early next week, for occasional winds and cool weather. && .DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE... SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO COUNTIES... Update: Marine layer low cloudiness lies along all but parts of the northern Orange County coast this evening. However, this likely will fill in this evening and move well into the inland valleys overnight. Patchy drizzle is even possible overnight through Thursday morning given the deepening marine layer. The forecast has this handled well, so no changes to the forecast were needed this evening. Previous Discussion: .SHORT TERM...(Today through Saturday)... A coastal eddy continues to spin over the California Bight, where clouds have eroded away off the coast. An approaching trough off the Pacific will enhance the marine layer, where it will become deepest tonight this week. Most areas west of the mountains will see low clouds filter in later this evening through tomorrow morning. HRRR picking up possible drizzle late tonight into Thursday morning for areas west of the mountains. The marine layer will be deep and saturated to support this. This pattern will also bring much cooler weather and windy conditions. NBM/HRRR/WRF blend depicts desert slopes gusting 45 to 55 MPH Thursday afternoon and night, while deserts will gust near 30 to 40 MPH at times. Gusty winds and blowing dust will be a concern for drivers out on the roads during this time. A weak ridge will come into the area by Friday, introducing less low cloud coverage west of the mountains, warmer temperatures, and less wind. Saturday will see further warming for all areas. && .LONG TERM...(Sunday through Tuesday)... Models diverge a bit on what will happening by Sunday and early next week. A trough will enter the Pacific Northwest on Saturday. Depending on the strength and position of this feature, will determine how cool and windy we get next week. ECMWF/Canadian are more aggressive with the system as the GFS shows it a bit weaker. Model clusters still uncertain, but consensus leans toward zonal to a slight troughing pattern, which would lead to near or slightly below average temperatures with continued dry weather. && .AVIATION... 280310Z...Coast/Valleys...BKN/OVC low clouds will spread farther inland overnight with current bases of 1500-2000 ft MSL eventually rising to 2000-2500 FT MSL, and tops to 3500 ft MSL with areas of higher terrain obscured in clouds, and local vis 2-4 miles in BR in the valleys. Most areas will clear by 18-19Z Thu. Mountains/Deserts...Mostly clear skies with mostly unrestricted VIS will continue through Thursday. Areas of west surface winds will continue through Thursday from the mountain crests east through the desert slopes and into the deserts with gusts 25-35 knots, locally 35-45 knots Thursday afternoon, along with areas of strong up/downdrafts, LLWS and local vis restriction below 3 miles in blowing dust. && .MARINE... Wind gusts of 20 knots, locally greater, are likely Thursday through Thursday evening, especially in the outer coastal waters. Local seas of 6-8 seconds with a period around 8 seconds will create choppy seas in the outer coastal waters at times through Thu night. && .SKYWARN... Skywarn activation is not requested. However weather spotters are encouraged to report significant weather conditions. && .SGX WATCHES/WARNINGS/ADVISORIES... CA...Wind Advisory from 1 PM Thursday to midnight PDT Thursday night for Riverside County Mountains-San Diego County Deserts-San Diego County Mountains-San Gorgonio Pass Near Banning. PZ...NONE. && $$ PUBLIC...Gregoria (Update)/APR (Previous Discussion) AVIATION/MARINE...Adams
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