Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 05/24/21

Area Forecast Discussion
National Weather Service Binghamton NY
943 PM EDT Sun May 23 2021 .SYNOPSIS... The cold front is currently over NE Pennsylvania and will push through the region in the next few hours. A dry night is expected with cool air filtering in from the north and light winds across the area tonight. Temperatures will stay in the 60s and 70s for most areas on Monday, warmest in the Mohawk Valley. Active weather returns midweek with possible rain showers and thunderstorms. && .NEAR TERM /THROUGH MONDAY NIGHT/... 940 PM Update The cold front is currently sitting across an area from Sullivan County NY to Sullivan County PA, and will make its way south as the evening progresses. Rain showers have diminished, with a dry night expected for the region. Winds have already begun to weaken and should become very light overnight as the pressure gradient over our area loosens up. A majority of the forecast remains on track. Minor adjustments were made to temps, winds and sky cover. 647 PM Update The cold front is currently draped across the NY/PA border, moving to the south. Isolated rain showers are weakening as they progress through the Twin Tiers. Can`t rule out a rumble of thunder over Sullivan and southern Luzerne counties as the front moves through, but considering instability over the region is very weak, confidence for thunderstorms is very low. The majority of the previous forecast was unchanged. Updated PoPs across the area as the front moves through and adjusted temperatures a few degrees lower across CNY behind the front. 345 PM Update Cold front is just about to push through Ithaca, Cortland, and Norwich, while a prefrontal trough has reached the Twin Tiers. So far, convection has been highly isolated and mostly running ahead of the prefrontal trough, with some shallow showers and lowering ceilings behind the cold front. The window for stronger thunderstorms is quickly narrowing across NY State, and while SBCAPE values (per RAP13) are highest just south of the state line, shear is a little weaker to the south. Still can`t rule out some gusty winds with whatever storms manage to develop, but the focus for this has shifted towards NE PA. Behind the front, clouds will increase and ceilings will drop as temperatures quickly drop into the 60s. We may see some breaks of sun reach the Southern Tier again before sunset. Much drier air in the low levels is also present behind the front, and with dewpoints dropping into the 30s and 40s overnight, fog shouldn`t be a problem, even as winds slacken after midnight. Northwest flow aloft will continue on Monday as an upper level ridge builds across the Midwest. Cooler temperatures will be mainly in the 60s and 70s, warmest across the Mohawk Valley. A weak disturbance dropping down the eastern edge of the ridge will bring some increase in mid-level clouds to the Finger Lakes and NE PA during the day, but any precip looks to stay well to our southwest. 1155 AM Update Surface obs, radar, and satellite imagery show the cold front draped between Watertown and Rome and across Lake Ontario, with a prefrontal trough and windshift line further to the south, just south of Seneca Falls, just north of Cortland, and just south of Hamilton. Both are moving quickly to the south, a little ahead of schedule, and the front is likely to overtake the trough at some point this afternoon. Towering cu and a few showers are just starting to go up along the trough. RAP analysis shows weak but increasing instability with SBCAPE values around 500 J/Kg across the Twin Tiers, but BUFKIT soundings also show weak to moderate capping around 700 mb, which is not likely to break without some warmer surface temperatures and a bit of larger-scale lift. Best chance for thunderstorms will be along the prefrontal trough and the cold front as it catches up...once you`re behind that, thunder chances drop considerably. Made some update to the PoP and wx grids to go with coverage wording (versus probability) and reduce overall coverage of rainfall to `scattered` (PoPs 30-50). Will keep the enhanced wording for gusty winds across the Twin Tiers and NE PA only. && .SHORT TERM /TUESDAY THROUGH WEDNESDAY/... 230 pm update... High pressure moves off to the east of the region on Tuesday with warm SE flow behind it. Day time heating and dew points in the upper 50s to low 60s leads to some instability Tuesday afternoon with a few afternoon showers and thunderstorms. Showers and thunderstorms come to an end in the early evening with the loss of daytime heating with dry conditions expected into Wednesday morning. Wednesday has a better chance for widespread thunderstorms, some of which could be severe. An upper level trough begins to move in with increasing speed shear through the day. The region will be under the right entrance region of a jet streak with divergence aloft. 0-6 km shear increases to 30-40 knots by the afternoon and falling 500 mb heights as the shortwave moves in helps weaken the CAP. The amount of cloud cover is uncertain with the moist SW flow at 850-500 mb. If it stays cloudy for most of the day, it will be difficult to develop the instability needed for severe thunderstorms and surface based thunderstorms. As of now, the NAM keeps cloud cover under 50% for most of the region with almost 1000-2000 J/kg of SBCAPE with the GFS about the same but favoring the Finger Lakes region. The NAM also has a weak surface trough out ahead of the cold front that acts as the trigger for storms with the cold front not moving through until later, which would result in more discrete storm cells vs a linear storm mode along the cold front. The GFS is too coarse to really pin point this feature and will need to be watched as CAMs get within range of the event. && .LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/... 230 pm update... Showers and Thunderstorms continue into Wednesday night ahead of the cold front. Once the cold front moves through, it scours out all the low level moisture with drier weather expected Thursday. Beyond Thursday, uncertainty increases as zonal flow takes over and another shortwave moves in. Models disagree with timing of the shortwave, the location of precipitation, as well as duration of precipitation so just stuck with the NBM beyond Friday. Overall it is looking like an unsettled pattern for Memorial day weekend. && .AVIATION /02Z MONDAY THROUGH FRIDAY/... Rain showers remain very isolated and continue to weaken through the evening. A wedge of dry air is moving in from the north as seen by the clearing on the visible satellite. This clearing will continue to push south tonight, but likely not make it through the entire area as the front stalls out to the south/sw. Flight conditions will likely remain VFR through the next 24 hours after a few hours of MVFR at BGM and ELM this evening. Weather conditions remain dry through tomorrow as high pressure builds in from the west/nw. North winds this evening around 5 to 12 kts...becoming variable 5 kt or less tonight, then shifting to the south/se later Monday morning with a few gusts up to 15 kt into the afternoon. Outlook... Tuesday...A chance for stray showers and thunderstorms, otherwise mainly VFR. Wednesday...Chances for scattered showers and thunderstorms, with associated restrictions possible. Thursday...VFR conditions expected at this time. Friday...A chance of rain showers with associated restrictions. && .BGM WATCHES/WARNINGS/ADVISORIES... PA...None. NY...None. && $$ SYNOPSIS...JTC/MPH NEAR TERM...JTC/MPH SHORT TERM...AJG LONG TERM...AJG AVIATION...AJG/BJT
Area Forecast Discussion
National Weather Service Denver/Boulder CO
853 PM MDT Sun May 23 2021 .UPDATE... Issued at 852 PM MDT Sun May 23 2021 Storms are out of the area with much drier air moving over the area. The wrinkle in tonight`s forecast is varying handling of the cool outflow air that is now over most of northeast Colorado. The HRRR is most aggressive with this and seems overdone in developing fog/stratus across all of the plains in the next couple of hours. Other models either don`t see what`s there very well, or have intermediate solutions with some mixing out around the edges or pushing the edge of the moist air back off the ridges and eastward a bit overnight. We`ll try to fashion some kind of intermediate solution with increased stratus and areas of fog on the plains. We`ll leave Denver out of this with the expectation of a southerly component to the winds that will likely bring some drying over the eastern part of the city if not the really dry air and also limit the temperature drop. We`ll need to drop the lows a little as even the drier air looks cooler than our forecast. Some of the mountain valleys could really have temperatures tank overnight with the drier air. There should be teens in the colder spots. We`ll also drop tomorrow`s highs slightly given a cooler start and slightly cooler guidance. && .SHORT TERM...(This evening through Monday) Issued at 319 PM MDT Sun May 23 2021 A couple severe discrete severe storms have developed, with three brief tornado touchdowns reported so far this afternoon. We`ll likely see these severe storms continue with a threat of more tornadoes and very large hail as they move north/northeast across the northeastern CO plains. There will also be a damaging wind threat as storms gradually organize into more linear structures. HREF Paintballs of updraft helicity show clustering of greater than 150 m2/s2 over northeast Colorado, generally centered on Akron and points north/east. Even higher values >250 on the 90th percentile WoFS, and agrees with what we would expect given the increase in low level southeast winds ahead of these storms. Peak inflow winds peaked at a whopping 55 knots (severe storm criteria) at Limon, and up to 37 knots so far at Akron and many other mesonet observations across northeast Colorado. Therefore, the tornado threat will continue this evening, with a longer track tornado still possible, in addition to very large hail and damaging winds. Severe threat should exit the far northeast corner by 7-8 pm. Dryline is working down the Front Range at the present time, which will effectively end any convection across the foothills and I-25 Corridor late this afternoon, and then from west to east across the plains through early this evening. Gusty winds will ease by mid evening, with lighter winds expected overnight and Monday. Monday will feature dry conditions, mostly sunny skies, pleasant temps (70s lower elevations), and finally stable conditions with no thunderstorms. .LONG TERM...(Monday night through Sunday) Issued at 319 PM MDT Sun May 23 2021 West-southwesterly flow aloft is expected for the CWA Monday night and Tuesday before becoming due westerly and increasing Tuesday night into Wednesday morning. Models show southwesterly flow aloft again the rest of Wednesday and Wednesday evening, ahead of a weakening upper trough that moves over Wednesday overnight. The low level winds look weak with normal diurnal wind patterns expected through Wednesday. There may be a weak cold front and weak upslope move into the plains Wednesday evening with the weakening upper trough. The QG Omega fields have downward vertical velocity for the CWA Monday night and Tuesday, then upward motion Tuesday night into Wednesday evening. Looking at moisture, the CWA looks pretty dry Monday night through Wednesday night, except for some increased moisture in the very low levels over the eastern third of the CWA Monday night, Tuesday afternoon, and late day Wednesday. There isn`t much in the way CAPE until Wednesday, then values are fairly decent over the eastern half of the plains. Will leave the "scattered" pops for showers and storms in Wednesday late in the day the eastern and northern plains. Temperature-wise, Tuesday`s highs are 1-3 C warmer than Monday`s and Wednesday`s readings come up another 1-2.5 C over Tuesday`s highs. For the later days, Thursday through Sunday, upper ridging is over the CWA Thursday and Friday, with flat upper ridging Saturday and Sunday. There is some moisture around, especially next weekend, so will go with minor late day pops those two days. Temperatures should be a tad above seasonal normals all four days. && .AVIATION...(For the 00Z TAFS through 00Z Monday evening) Issued at 852 PM MDT Sun May 23 2021 Winds are complicated in the Denver area as a surge of cool moist air is trying to come in from the northeast while west to southwest winds off the foothills are fluctuating. Southwest to west winds should prevail at KAPA/KBJC for the next couple of hours, while KDEN winds are now northeast and will likely stay that way for a bit. The trend should be toward south to southeast winds at KDEN and KAPA by 06z, and lighter west winds at KBJC. Some low clouds and fog are expected to develop over the plains after 06z. There is a chance this could affect the Denver terminals, mainly KDEN between 08z and 14z, but we think it`s more likely that it will remain northeast of the area. If the fog does move in, it would probably bring IFR ceilings. The chance of LIFR conditions for a few hours looks pretty low but not zero. The rest of Sunday will be VFR with light winds. && .HYDROLOGY... Issued at 319 PM MDT Sun May 23 2021 Strong to severe thunderstorms will shift east across the northeast corner of the state through early evening. There are some linear features and training storms, so locally heavy rain and minor flooding possible there. Meanwhile, dry conditions are quickly building over the Front Range with no threat to burn areas through Monday. Mainly dry conditions for the mountains/adjacent plains expected through the week, except a chance for showers/thunderstorms returning on the far plains for Wednesday through Friday. && .BOU WATCHES/WARNINGS/ADVISORIES... None. && $$ UPDATE...Gimmestad SHORT TERM....Barjenbruch LONG TERM.....RJK AVIATION...Gimmestad HYDROLOGY.....Barjenbruch
Area Forecast Discussion
National Weather Service Boston/Norton MA
938 PM EDT Sun May 23 2021 .SYNOPSIS... A sharp wind shift in wake of the front could pose a significant impact to mariners and recreational boaters early tonight. Much cooler/seasonable temperatures to start the work week, but the warmth returns by mid week. Showers and perhaps a few thunderstorms possible late on Wednesday into early Thursday associated with a cold front. This front will usher in a more seasonable airmass late in the week and into the weekend. && .NEAR TERM /UNTIL 6 AM MONDAY MORNING/... 935 PM Update... No major changes in the latest update other than bringing things in line with the latest observations. Did nudge down wind gusts as the front has moved through a bit quicker. With decreasing wind gusts we did cancel the Small Craft Advisories with the exception of the outer waters. Otherwise a refreshing night is on tap. Previous discussion... Regional radar mosaic shows scattered showers ahead of a sharp cold front and northerly wind shift, mainly north of the Massachusetts Turnpike. Vertical growth with these showers has been slow and generally limited (storm tops as of 330 PM less than 20k). However somewhat greater instability (surface-based CAPEs around 1000 J/kg) noted per SPC mesoanalysis is common across areas south of the Massachusetts Turnpike. Isolated to widely scattered thunderstorms should blossom a little more than what we`ve seen so far as they move southeast into this slightly-more-unstable air mass, reaching the south coastal waters through 8 PM. NAM-3km and recent HRRR runs reflect these ideas. Not everyone will see thunder today with coverage being no better than widely scattered, but any stronger cell could produce gusty to locally damaging winds. Cold front now over south-central NH/VT to surge southward and bring about a substantial change in air mass from the very warm/hot conditions to a more seasonable and drier air mass with onshore flow. Sharp 3-hr pressure rises in the 4 to 6 mb neighborhood should allow for north to north- northeast winds to become rather breezy in the hours after FROPA (around 25-30 mph) early, then decrease a bit into the mid-evening/midnight as winds become more northeast. Clearing and dry conditions with ridging building back in, 925 mb temps falling from the +20 to +22C level this afternoon down to around +7 to +9C by pre-dawn Monday. Should see lows in the 40s to lower 50s. && .SHORT TERM /6 AM MONDAY MORNING THROUGH 6 PM MONDAY/... While mostly sunny to partly cloudy conditions (fair weather cumulus) to prevail, the main story is the much cooler and more seasonable air mass compared to today. High temperatures may be some 25 degrees colder for Monday than today! In addition, dewpoints in the 30s to lower 40s compared to the upper 50s to lower 60s than today. Light east to southeast winds across the interior initially to trend more southerly late, though sea- breezes look likely near the eastern MA coast which will keep east-coastal sites cooler than further inland. Highs in the mid 60s to lower 70s in the interior, and in the lower to mid 60s near the coastlines. && .LONG TERM /MONDAY NIGHT THROUGH SUNDAY/... Highlights * Temperatures on the rise into mid week, with summerlike warmth on Wednesday. Temperatures cool to near/cooler than seasonable for late in the week and into the weekend. * Dry and quiet weather Monday night into Tuesday. Next shot for more widespread shower/storm activity is later on Wednesday into early Thursday. Late in the week and into the weekend could be more unsettled, but confidence remains low this far out. Monday night through Tuesday... Ridge axis builds over southern New England Monday night and offshore on Tuesday. A surface high will remain south of Nova Scotia and build further offshore on Tuesday. Dry and quiet weather expected with high pressure under control. Aloft flow will become southwesterly due to the position of the ridge/high. This will advect warmer air into the region with 7-8 degree Celsius air in place over the region Monday night and 10-15 degree Celsius air on Tuesday. Given the high in place, relatively light winds and mostly clear skies did lower temps Monday night toward the 25th percentile of guidance as am anticipating some decent radiational cooling. Lows range from the mid 40s to the lo 50s. Held off from going cooler as mechanical mixing could be an issue along with some cloudiness. Should be milder (in comparison to Monday) across southern New England on Tuesday with high temperatures ranging from the mid 60s to the upper 70s. Wednesday through Thursday morning... Ridge axis offshore with cyclonic flow in place as a trough digs into Hudson Bay/northern Ontario. Am anticipating a shortwave trough to lift from the central Great Lakes early on Wednesday through northern New England by Thursday morning. A warm front will lift through early on Wednesday and we could see some showers/storms within the warm sector, but am anticipating a better shot when the cold front swings through later in the day into early Thursday. Summer like warmth is expected across southern New England on Wednesday. Will see 15-17 degree Celsius air in place over the region. The result are high temperatures well into the 80s across the interior and there will be some low 90 degree readings across the Merrimack Valley and CT River Valley. Should remain a bit cooler along the south coast given the southwesterly flow in the lower levels, so highs will generally be in the 70s. Have kept with the NBM precipitation chances, but knocked things down to keep them in the chance to slight chance categories given there is some uncertainty on the exact timing of the front moving through. Did add a mention of thunderstorms in the latest update given there is roughly a few hundred to about 1500 J/kg of MUCAPE if not a bit higher. Decent moisture in place given dew points will be in the upper 50s to lower 60s and PWATs in the 1.5 to 2 inch range. These PWAT values are toward the max of SPC Sounding climatology for this time of year for CHH. Mid level lapse rates are poor around 5-6 degrees Celsius per km, so this may limit sustaining/more organized storms along with 0-6 km shear with values between roughly 20-30 km. Will need to keep an eye on this day is a few hundred J/kg of DCAPE, which could potentially bring gusty winds. Thinking that heavier rainfall and gusty winds would be the main risk as this point in time, but will need to see how guidance trends over time. Front moves through the vast majority of the CWA by Thursday morning and should bring an end to any shower/storm activity. Should be relatively mild with low temperatures in the 60s across much of the region heading into Thursday. Thursday through Saturday... Weak ridging in place on Thursday. This is followed by a trough/cutoff lifting in from the Upper Midwest for late in the week and into the weekend. High pressure weakly nudges in on Thursday. Vast majority of guidance keeps the coastal low to the south, but will need to see how things progress as time goes on. For now have kept slight chance to chances of precipitation. Cooler airmass moves in wake of the front that slides through early on Thursday. Temperatures trending downward for the rest of the week. Highs on Friday/Saturday generally in the 60s, but there may be a few 70 degree readings in the CT River Valley. && .AVIATION /02Z MONDAY THROUGH FRIDAY/... Forecaster Confidence Levels. Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Through 12Z...High confidence Cold front is mostly through the CWA. Only have a few showers lingering near Cape Cod and the Islands. This will move through in the next 1-2 hrs. Gusty post frontal N/NE winds early this evening, especially over eastern MA. Should see the gusts diminishing as the night progresses, but speeds will be around 5-10 kts. Generally expecting VFR conditions, but could have some brief periods of MVFR with clouds bases between 2.5-5 kft this evening. Should see drier air punching in bringing clearing late. Monday...High confidence. VFR, with a few fair weather Cu in the afternoon. Should have cloud bases around 4-6 kft. E/ESE winds become S/SW in the interior to around 5-10 kt, though with sea breezes near the eastern MA coast. Monday Night...High confidence. VFR continues, with S/SW winds 5-10 kt. KBOS TAF...High Confidence in TAF. KBDL TAF...High Confidence in TAF. Outlook /Monday Night through Friday/... Monday Night through Tuesday Night: VFR. Breezy. Wednesday through Wednesday Night: Mainly VFR, with areas MVFR possible. Breezy. Chance SHRA, isolated TSRA. Thursday: VFR. Breezy. Thursday Night: Mainly VFR, with areas MVFR possible. Slight chance SHRA. Friday: Mainly MVFR, with local VFR possible. Chance SHRA. && .MARINE... Forecaster Confidence Levels. Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Tonight: High confidence. * Abrupt windshift (west to northerly) with brief wind gusts of 35 to 45 knots possible between 5 and 9 PM Sunday. Cold front will bring a risk for scattered showers/thunder to most of the waters late this afternoon into early tonight. Potential exists for a couple storms to become strong, though coverage will be limited. Main concern will be during the mid- late afternoon hours into early this evening. A strong cold front will cross the waters with a rather strong pressure rise couplet behind the front. NAM shows 975 MB winds at 40 knots from the NNE, with strong sea-level pressure rises supporting a potential (though brief) period of northerly winds in the Gale range. This could be especially problematic to recreational boaters caught on the water. SCAs still are in effect but will continue the marine weather statement before its scheduled 21z expiration. A more rapid decrease in winds/gusts expected after mid-evening, with northeast gusts around 15-20 kt by daybreak. Seas mainly in the 4-6 ft range on the outer waters. Monday into Monday Night: High confidence. SE winds around 10-15 kt most of the day, seas around 2-4 ft. Late in the day and more into the evening, winds to trend SW and increase to borderline SCA level in gusts on our northeastern waters, with seas nearing 5 ft. May need to consider SCAs for the Monday late-afternoon into Monday evening but seems too marginal to hoist at this point. Outlook /Monday Night through Friday/... Monday Night through Tuesday: Low risk for Small Craft Advisory winds with gusts up to 25 kt. Areas of seas approaching 5 ft. Tuesday Night: Moderate risk for Small Craft Advisory winds with gusts up to 25 kt. Seas up to 5 ft. Wednesday: Moderate risk for Small Craft Advisory winds with gusts up to 25 kt. Seas up to 5 ft. Slight chance of rain showers, isolated thunderstorms. Wednesday Night: Low risk for Small Craft Advisory winds with gusts up to 25 kt. Seas up to 5 ft. Chance of rain showers, isolated thunderstorms. Thursday through Thursday Night: Winds less than 25 kt. Areas of seas approaching 5 ft. Slight chance of rain showers. Friday: Winds less than 25 kt. Seas up to 5 ft. Chance of rain showers. && .TIDES/COASTAL FLOODING... Tide data shows that the May astronomical high tide will take place at midweek, with highest levels on the midnight high tide. Boston, for example, will peak at 12.2 feet Wednesday night. Nantucket will peak at 4.3 feet. Providence will peak at 6.2 feet. These values do not include any residuals. Expecting a southwest wind of 15 kt sustained and gusts to 25 kt. These winds will push water up against the south and southwest-facing coasts. The midweek tides will be monitored for potential high water levels. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...None. MA...None. RI...None. MARINE...Small Craft Advisory until 6 AM EDT Monday for ANZ250-254>256. && $$ SYNOPSIS...BL/Loconto NEAR TERM...BL/Loconto/Gaucher SHORT TERM...Loconto LONG TERM...Loconto AVIATION...BL MARINE...BL/Loconto/Gaucher TIDES/COASTAL FLOODING...
National Weather Service Sioux Falls SD
642 PM CDT Sun May 23 2021 .SHORT TERM...(This Evening through Monday) Issued at 248 PM CDT Sun May 23 2021 Fairly expansive cumulus field as of mid afternoon with a few showers and thunderstorms. Most focused area of convection is along the Buffalo Ridge where better surface convergence has allowed for greater coverage. RAP mesoanalysis confirms effective deep layer shear is weak however with with MLCAPE values around 1000 J/kg, can`t rule out the possibility of a storm or two pulsing to near strong/severe levels. Additionally, given the presence of a boundary, a non-zero (although extremely low) chance of a brief funnel although RAP analyzed surface vorticity is far from impressive. This will continue to progress northeastward thru the late afternoon. As we move through the evening, a pronounced wave ejecting out of the Rockies will continue to allow for expanding thunderstorm coverage across western SD and NE Panhandle with eventual upscale growth owing to a strong boundary parallel component of deep layer shear vectors. Previously mentioned wave pivots northeastward away from our coverage area and, combined with weaker instability and shear parameters with eastward extent, should result in a weakening trend of this convection as it approaches the MO River. This decrease in strength is reflected well in latest HREF guidance. With all of this said, not out of the question that areas west of the James River still stand the risk of borderline severe wind gusts before an eventual transition to more showers/embedded thunderstorms east of the James River late tonight. The eastward extent of overnight convection will have at least some impact on the forecast for Monday via influence on the eastward progression of the surface boundary and remnant outflow boundaries. This will be important as forecast soundings show fairly minimal convective inhibition and thus suspect we will likely see a fairly early agitation to the cumulus field once better solar insolation commences by late morning. Distinct mid/upper level forcing is again tough to come by but weak surface convergence along the main synoptic boundary (as well as any established outflow boundaries) should be enough to tap into the roughly 1500 J/kg of MLCAPE. Perhaps a bit better environment by late afternoon as the region starts to receiving a bit more help to finalize any needed environmental preconditioning as the right entrance region from a departing jet streak enters the picture. All of this to say that current indications are weak radar echos could very well be possible near and just ahead of the surface boundary by as early as late morning Monday with likely more established deep convection by mid to late afternoon. Better deep layer shear is again weighted post-frontal with effective shear in the warm sector generally in the 20-35 kt range. This will likely result in largely multicell clusters with perhaps some borderline supercell characteristics. With this lack of better deep layer shear, the severe threat may remain somewhat tempered although initial suspicion is that at least a couple severe level storms seem possible. Large hail up to ping pong size appears to be the primary threat with any organized cluster also posing a damaging wind threat. These threats are highlighted by a Day 2 Marginal from SPC. Temperatures a few degrees either side of 80 look reasonable for Monday with more sunshine for locations behind the boundary. .LONG TERM...(Monday Night through Sunday) Issued at 248 PM CDT Sun May 23 2021 Surface boundary looks to get pushed into NW IA by midday Tuesday although if Monday`s convection is less than progged, this could be a bit slower (the opposite could also be said). This would result in continued shower/storm chances ahead of this boundary for areas toward the Hwy 20 corridor in NW IA although a bit more suitable forcing may be displayed to the south/east of our coverage area. Temperatures again in the upper 70s to mid 80s look reasonable with westerly winds. Brief period of shortwave ridging is expected by Wednesday with northeasterly winds helping to usher in cooler temperatures in the 70s and lower dewpoints. Next shortwave will be quick behind however and looks to provide a fairly good shot at widespread precipitation Wednesday night into Thursday. Better instability continues to look to be be mainly bottled up south of our area so probably more of a shower with embedded lightning setup. This would also keep temperatures rather cool on Thursday with upper 50s to mid 60s. Shortwave ridging returns for Friday and Saturday along with dry conditions and gradually warming temperatures. && .AVIATION...(For the 00Z TAFS through 00Z Monday evening) Issued at 642 PM CDT Sun May 23 2021 23.2330Z regional radars show a solid line of showers with embedded thunderstorms across western SD extending southward into the Nebraska panhandle. These storms will slowly move eastward this evening, eventually impacting TAF airfields. Storms are expected to weaken as they move toward the MO River, but still enough confidence to include thunder at KHON/KFSD. Short-term model run-to-run consistency has been excellent with timing, so only minor adjustments were needed. Expect showers and storms at KHON by 24.05Z and at KFSD by 24.07Z. Showers should be the dominant mode at KSUX by 24.08Z. Prior to showers and thunderstorms, expect VFR conditions with southerly breezes. Then, MVFR conditions are expected with any convective activity. Cloud bases should rise back above 3000 ft agl after rain moves out. Winds will veer slightly to the southwest by Monday afternoon with some gusts up to 25 kts. There is a chance for another round of showers and thunderstorms mid-late Monday afternoon, potentially impacting KFSD and KSUX, but confidence in timing/coverage too low at this time to include in 00Z TAFs. Will address this potential with 06Z update. && .FSD WATCHES/WARNINGS/ADVISORIES... SD...NONE. MN...NONE. IA...NONE. NE...NONE. && $$ SHORT TERM...Kalin LONG TERM...Kalin AVIATION...Rogers
Area Forecast Discussion
National Weather Service Indianapolis IN
1136 PM EDT Sun May 23 2021 ...Updated Aviation Discussion... .Forecast Update... Issued at 956 PM EDT Sun May 23 2021 Removed thunder and any measurable PoPs from the forecast for the rest of the night. Forcing is better to the north, even with the front sagging into the northern parts of the forecast area, and high resolution model output shows very little development here. Given the presence of the front and a couple of light echoes showing up on radar loop in the northernmost counties, though, went ahead and inserted isolated sprinkles across the north through the night, generally along and north of the projected frontal location. End result is a few northern locations could see a few raindrops overnight, but don`t expect it to measure and don`t expect much given the temperature inversion. Temperatures are slow to drop, and think going lows in the low to middle 60s are on track. && .Short Term...(This evening through Monday night) Issued at 321 PM EDT Sun May 23 2021 Scattered to broken cumulus were across central Indiana this afternoon, but the radar was quiet. Temperatures were in the lower to middle 80s. A weak front/wind shift will sink into northern Indiana later this afternoon into early evening, but should remain north of the forecast area. Weak instability will be across the northern forecast area. The front may be close enough to spark an isolated shower or a thunderstorm across this area late this afternoon into the early evening. The HRRR continues to back up this thinking with isolated (weak) convection. Will keep some slight chance PoPs across the far north until 01Z, but with low confidence given lack of decent instability. Loss of heating this evening will allow the cumulus to dissipate, leaving behind some passing high and mid clouds. Thus will go dry and partly cloudy for the remainder of the tonight period. On Monday, the upper ridge and surface high will expand a bit across the area. Warmer air will move in at the mid levels during the day, and this should cap off any convection. Also, increased subsidence should reduce the amount of cumulus. Thus will keep the area dry on Monday. These conditions should also allow for temperatures to get a little warmer than today, with highs nearing 90 for some locations. Dry conditions will continue Monday night with high pressure still in control. && .Long Term...(Tuesday through Sunday) Issued at 321 PM EDT Sun May 23 2021 The ridge will weaken and move off to the southeast at the beginning of the long term period. Troughing and a more active weather pattern will then take over for much of the week. While there is a daily chance of showers and thunderstorms with this pattern, better chances will come midweek and again end of the week with more robust waves. A frontal system looks to bring thunderstorms late Tuesday into Wednesday as the upper trough axis swings across the regions. Cooler air behind the front will allow temperatures to drop from the mid to upper 80s Tuesday to the low to mid 80s Wednesday. Brief ridging will then return in the wake of the trough axis passing by with the front stalling off to the east early Thursday. This will likely bring a decrease in convection across the region Wednesday night. The next system will then arrive Thursday night to Friday as a surface low tracks across the area from the central plains. More widespread showers and thunderstorms are expected with this low and models are showing a nocturnal low level jet forming along the leading edge. This could provide energy for stronger storms associated with this system but its still too early to say for sure and will continue to monitor as we approach the end of the week. Temperatures will finally drop to near normal for Friday as a cooler airmass moves in. The models have some variability going into the weekend but at the moment looks like things will be drier compared to the the rest of the period with high pressure building in. Will keep in the slight to chance PoPs for now given uncertainties as a trailing upper low could set up a boundary and trigger some storms. && .Aviation...(06Z TAF Issuance) Issued at 1135 PM EDT Sun May 23 2021 IMPACTS: - Light and variable winds become southwesterly at 4 to 8 kts by midmorning. DISCUSSION: Scattered to broken mid and high clouds expected through the night, and these should help prevent fog development. Few to scattered VFR cu should develop during the afternoon. && .IND WATCHES/WARNINGS/ADVISORIES... None. && $$ Update...CP Short Term...50 Long Term...KH Aviation...CP
Area Forecast Discussion
National Weather Service North Platte NE
620 PM CDT Sun May 23 2021 .SHORT TERM...(This evening through Monday night) Issued at 205 PM CDT Sun May 23 2021 Deep southerly flow continues across wrn and ncntl Nebraska this afternoon. A Pacific cold front has cleared the Colorado front range and the Laramie Ranges triggering thunderstorm activity which will carry east into wrn Nebraska this evening. There is also a small zone of warm air advection across sern Colorado triggering storms south of Pueblo Colorado. The storm activity across ern WY and Colo should grow upscale into the deep moisture across wrn Nebraska this evening producing at least scattered storms and a solid line of storms appears likely north of Interstate 80. A couple of hindrances may limit the magnitude of the severe weather across wrn Nebraska tonight. Winds aloft, although very strong, are unidirectional supporting storm splitting and the warm air advection ahead of the Pacific cold front appears limited to sern Colorado- aimed at nwrn KS and swrn Nebraska. The RAP model suggests the shear is too strong to sustain supercells. On the other hand, the RAP shows two distinct meso circulations forming across swrn Nebraska and swrn SD which could maintain severe storm evolution. These circulations are being fed by strong moist low level winds below 700mb. There is also a well defined h700mb dry slot or intrusion associated with the storms moving east through wrn Nebraska and this should produce a cold pool and enhance wind damage potential. So there are competing forces both in favor or in disfavor for severe storm development. The severe weather forecast follows the SPC which, given the strong backing low level winds this evening, all modes of severe weather, including tornadoes are possible. The POP forecast leans on the short term model blend for likely to definite pops tonight generally along and west of highway 83. East of highway 83, chance POPs are in place. Some models like the ECM and SREF weaken the storm activity quickly while other models like the HREF and NAM maintain storm activity throughout ncntl Nebraska. WPC suggested up to 1 inch of QPF tonight which locally, could result in a few 2 inch totals. This is in line with the HRRR which suggests a few HP storms which could produce a quick 1 to 1 and 1/2 inches of rainfall followed by additional rainfall from weaker storm activity. All of this storm activity should be east of ncntl Nebraska by 12z Monday with just and isolated shower chance in the morning. SPC has hung a marginal severe weather risk Monday afternoon and evening across parts of swrn and ncntl Nebraska. This is the result of the front hanging up across cntl Nebraska. A check on the RAP model shows this front stationary late Monday but winds at the lower levels are not backed. Thus the best severe weather potential would appear to be just to the east of the front as suggested by the SPC. For these reasons, just a slight chance of thunderstorms are in place across parts of swrn and ncntl Nebraska. .LONG TERM...(Tuesday through Sunday) Issued at 205 PM CDT Sun May 23 2021 An excellent opportunity for severe weather may present itself Wednesday afternoon and Wednesday night. The NAM shows a warm front lifting north through wrn Nebraska during the afternoon and the GFS and NAM show westerly winds h500mb increasing to 40 to 50 kts. The NAM shows some sort of convective complex developing across nwrn Nebraska by 00z which will likely move east and grow upscale. Chance to likely POPs are in place Wednesday afternoon and Wednesday night. Thunderstorms chances are in place next Saturday. The potential for severe weather is uncertain given the distance time away from this rain event. The rest of the forecast is generally dry. && .AVIATION...(For the 00Z TAFS through 00Z Monday evening) Issued at 620 PM CDT Sun May 23 2021 Multiple aviation weather concerns exist during the forecast period, including severe thunderstorms, strong surface winds, and low ceilings. A line of strong to severe storms will cross the region this evening into tonight, which will be capable of very large hail and damaging winds with gusts exceeding 50 kts. Ahead of these storms, south/southeast winds will continue to gust around 30 kts. In the storms wake, surface winds will lighten but stratus clouds set in, especially in southwest Neb (KLBF). Expect MVFR to locally IFR ceilings early morning, but should return to VFR after daybreak. && .LBF WATCHES/WARNINGS/ADVISORIES... None. && $$ SHORT TERM...CDC LONG TERM...CDC AVIATION...Snively
Area Forecast Discussion
National Weather Service Lake Charles LA
917 PM CDT Sun May 23 2021 .UPDATE... A trof continues to extend from the Texas gulf coast inland this evening streaming very high atmospheric moisture west of the Sabine River. This has maintained scattered light showers over southeast Texas through the evening. The 00Z KLCH sounding observed much drier mid level air over southwest Louisiana where periods of sun were observed earlier today for the first time in a week (but who`s counting). Latest few runs of the HRRR continue to maintain light showers over southeast Texas for another two to three hours before diminishing them for a short period late tonight. The updated PoPs reflects this expectation with precipitation reinitializing once again after sunrise tomorrow. Extended the coastal flood advisory through 00Z Tuesday based on the latest extra tropical surge guidance and it`s likely it will need to be extended further through mid week if not longer as the long southeasterly fetch is forecast to persist across the northern gulf. Jones && .PREV DISCUSSION... /issued 612 PM CDT Sun May 23 2021/ AVIATION... Radar is indicating rains moving onshore of southeast Texas at this time generally west of BPT. BPT will see periods of rains/showers this evening and into the overnight hours with ceilings lower at times in and near the showers. Otherwise... TAF lctns in srn Louisiana are expected to remain VFR. K. Kuyper PREV DISCUSSION... /issued 256 PM CDT Sun May 23 2021/ SHORT TERM [Today through Monday Night]... GOES-16 WV showing moisture sliding northward along a trough axis stretching from the Texas Gulf coast northward this afternoon. In conjunction with this, more widespread cloud coverage and a few showers are noted over the SE TX zones, with more appreciable precipitation towards Houston and the I-45 corridor. At the same time, broad and deep ridging centered over the TN valley is resulting in drier air and suppression of activity in the eastern 1/2 of the CWA. To that end, RAP sfc analysis depicts quite the moisture gradient, with PWATS ~2.00 inches west of the Sabine River, and PWATS closer to 1.00 to 1.25 inches east. As such, the best potential for rain will continue to be in SE TX for the remainder of the day. Overnight into Monday, ridge slides off a bit more to the east while the west Gulf mid level trough begins to lift more inland. The result is deeper moisture across a bit more of the region, as well as some increased lift. Combined with diurnal enhancement, expect precip to be a bit more widespread tomorrow with best chances in SE TX and W LA. Precip along with cloud cover will help keep afternoon temps in check once again, with highs forecast slightly below climatological normal. With loss of heating, the bulk of activity expected to diminish moving into Tuesday night, though an isolated shower or two will remain a possibility. 50 LONG TERM [Tuesday through Sunday]... Tuesday and Wednesday the region will remain between a ridge aloft to the east and weakness to the west while a plume of tropical moisture continues to stream in from the gulf over Texas. On Wednesday the weakness will have shifted more eastward toward LA, however weakening as this occurs. This will keep isolated to widely scattered showers in place, but mainly in the afternoons. Thursday and into Friday a ridge will briefly build aloft cutting off rain, however by the weekend another upper disturbance will approach the region allowing for isolated to widely scattered mainly diurnal storms to redevelop. 05 MARINE... Modest east to southeast winds and elevated seas will continue today into tonight before easing a bit on Monday. A few showers and t-storms will be possible, primarily south of Sabine Pass. A light to modest onshore flow will then prevail through midweek and into next weekend. 50 && .PRELIMINARY POINT TEMPS/POPS... AEX 67 84 67 85 / 0 10 10 30 LCH 70 82 70 84 / 30 40 10 30 LFT 68 83 68 84 / 0 10 0 20 BPT 71 82 71 84 / 60 60 20 40 && .LCH WATCHES/WARNINGS/ADVISORIES... LA...Coastal Flood Advisory until 7 PM CDT Monday for LAZ041-052-073- 074. TX...Coastal Flood Advisory until 7 PM CDT Monday for TXZ215-216. GM...Small Craft Exercise Caution until 5 AM CDT Monday for GMZ450- 452-455-470-472-475. && $$
Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
1103 PM CDT Sun May 23 2021 .SHORT TERM...(This evening through Monday night) Issued at 228 PM CDT Sun May 23 2021 The key messages of the forecast in the short term is the reduced threat for severe weather today. The risk for isolated heavy rainfall remains. On Monday there is a Marginal Risk of severe weather, with the primary threats being large hail and damaging wind. There is also a risk of localized heavy rain. Today - The weak winds and lack of shear are the limiting factor for strong to severe storms the rest of today. In addition, the moist mid levels with H700-500 lapse rates around 5 to 6 C/km are also a limiting factor. The combination of the two is the reasoning behind removing the Marginal Risk for today. However, PWATs remain around 1.5 inches, and the storm motion is very slow, so isolated heavy rainfall remains possible through the evening. Tonight - Scattered showers and thunderstorms should decrease in coverage overnight across the region. Meanwhile an impressive line of thunderstorms should be ongoing across the Dakotas and moving eastward. As it approaches Minnesota, it will lose instability and should weaken. By the time it reaches western Minnesota Monday morning it should be nothing more than scattered showers with maybe a few lightning strikes. Monday - On Monday a shortwave trough will move eastward along the International border. This should tighten up a frontal boundary that is most noticeable in the dewpoint gradient from southwest Minnesota through northern Wisconsin. As alluded to in the previous discussion, there will be a ribbon of 1000 to 2000 J/kg of MLCAPE on the warm side of this frontal boundary. In addition the upper level jet should increase Monday evening and the right entrance region should favor ascent. Mid level lapse rates are still fairly low, on the order of 6.5 to 7 C/km. Deep layer shear is stronger, but it is unidirectional. Put it all together and you have the Marginal Risk of severe storms with damaging wind and large hail as the primary threats. Give the shear is oriented along the boundary, there is also a threat for heavy rain with training thunderstorms. .LONG TERM...(Tuesday through Sunday) Issued at 228 PM CDT Sun May 23 2021 The long term period picks up with the front from the short term continuing to move through the area, bringing scattered showers and thunderstorms at this point mainly to western WI. The upper level trough is strongest farther to the north near the Canadian border, with the remnants of the front occluding as we head into Wednesday which should bring most of the showers to an end. Guidance is keeping any wrap around showers closer to the surface low and trough, which keeps it confined to northern MN Wednesday morning. We won`t feel the temperature impact of the front until Tuesday night and Wednesday morning, with highs in the mid 80s on Tuesday dropping into the upper 40s to mid 50s overnight. With the front moving through early on Wednesday cutting off the stream of warmth and moisture that was observed over the previous week, we will struggle to warm back up to the 80s for the remainder of the period. The coldest day will be Thursday with highs in the low 50s to near 60 expected, otherwise generally looking at 60s and low 70s through next weekend. We do have a few more chances for rainfall as well, with a quick moving 500mb trough swinging through Thursday night into Friday morning, targeting southern MN with the heavier rainfall in central Iowa. Another potential front then arrives on Sunday, however this is less certain and has a greater chance of missing due to the front stretching down a significant way from central Canada. Kept NBM PoPs for now which show about 30-40% Sunday during the afternoon while the front moves through, which is even a bit ambitious right now. && .AVIATION...(For the 06Z TAFS through 06Z Monday night) Issued at 1102 PM CDT Sun May 23 2021 Two issues this TAF period are evolution of stratus (and potential fog for central MN) and shra/ts chances Monday afternoon. For the clouds, kept it simple, so long as a site remains north of the wavy boundary across southern MN, they get stratus. Some fog concern for STC, though vis restrictions have been much slower to materialize this evening than the HRRR has been showing, so kept a bit more optimistic vis forecast. Main question for tonight is how quickly does the stratus retreat back to the north. MSP is on the edge of it right now, but do expect the stratus to crawl back north of the field by Monday morning. Same could happen at RNH. For storms, convergence along the front is almost non-existent, with it being nothing more than a moisture gradient. As such, only expect scattered convection to develop near the moisture gradient as diurnal instability builds. At this point, kept all TAFs dry tomorrow as confidence in storms occurring at any one location is not high enough to include in the TAFs at this point. Really, the only airport you can probably completely rule out of a rain chance Monday/Monday night is AXN. KMSP...As the boundary that push just south of MSP goes back north late tonight, can`t completely rule out a brief shower, but expect mainly dry conditions to prevail. For TS chances later Monday, it again looks like we are waiting until after 00z before chances really pick up with the front off to the west, but with little agreement in the CAMs in how precip may, or may not develop Monday afternoon/evening, went with a TAF without any precip mention at this point. /OUTLOOK FOR KMSP/ Tue...VFR. Wind WSW 15G25 kts. Wed...VFR. Wind NW 5-10 kts. Thu...MVFR/RA Likely. Chc IFR/TSRA. Wind E at 10G20. && .MPX WATCHES/WARNINGS/ADVISORIES... MN...None. WI...None. && $$ SHORT TERM...JRB LONG TERM...TDH AVIATION...MPG
Area Forecast Discussion
National Weather Service Marquette MI
732 PM EDT Sun May 23 2021 .SHORT TERM...(This evening through Monday) Issued at 337 PM EDT SUN MAY 23 2021 The weather experienced today across the U.P varied greatly with temperatures over the interior east reaching the 60s while locations in the central and west, particulary near Lake Superior, were much cooler with highs in the 40s. RAP upper air analysis and water vapor imagery showed a closed upper level low over the Great Basin with a strong downstream upper level ridge extending from the Gulf Coast north into the northern plains and southern Canada. Weak FGEN and convergence at 850mb along with weak instability was just enough to result in a few showers and thunderstorms over the west and central late this afternoon which could linger though the early evening. Tonight the upper level low pressure and associated surface low pressure will move from the Great Basin into the Northern Rockies. A surface high pressure over Ontario will push east into Quebec. This will bring returning southerly flow to the area with low temperatures likely occurring this evening followed by slowly rising temperatures overnight. A bit steeper mid-level lapse rates will begin to advect into the area on Monday along with increasing surface dewpoints. This will bring increasing instability with the possibility for showers and thunderstorms developing over northern WI and reaching the southern and western portions of the U.P by late in the afternoon. Large scale forcing looks to be relatively weak during the afternoon and MUCAPE generally less than 500 J/kg along with shear of around 25 knots or less, not expecting any strong storms at this point with the better instability and shear remaining south of the U.P. Fire weather concerns will remain low with afternoon minimum humidity remaining above 50 percent. .LONG TERM...(Monday night through Sunday) Issued at 439 PM EDT SUN MAY 23 2021 The frontal boundary that moved through the area this morning is expected to lift north as a warm front on Monday. The same warm and muggy air mass that invaded our area late last week will vist Monday afternoon through Wednesday morning. A potent cold front moves through Tuesday night into Wednesday morning with temperatures likely to fall below normal through the remainder of the long-term. However, the cooler air mass will also be dry resulting in warm sunny days and clear cool nights. The warm and sultry air mass will already be overhead at the beginning of the extended period (00Z Tuesday). Thunderstorms may be ongoing along the MI/WI border on Monday evening that may persist overnight given a respectable 40-45 knot LLJ. The main threat with these storms appears to be heavy rain, lightning, and perhaps some small hail. Tuesday appears to be a busy day with WAA persisting all day resulting in deep mixing and the potential for strong, gusty downslope winds near Lake Superior. I`m not confident on the depth of mixing considering morning convection and remnant cloud cover, but some operational guidance indicates gusts approaching wind advisory criteria. Thunderstorms may develop by Tuesday afternoon when the near-storm environment should be supportive of marginally severe hail and wind threats. The main source of uncertainty is timing and location of the frontal boundary, but 12z guidance indicates the fropa entering the west between 21-00z and exiting around 06-09Z. This is a favorable diurnal timing for thunderstorms and we definitely need the rain ... A cooler air mass is expected behind the initial frontal boundary, but a reinforcing cold front moves through early Wednesday morning. There seems to be a brief, but intense period of cold air advection behind this reinforcing cold front. 850 mb temperatures appear cool enough to result in lake-induced mixing of stronger winds aloft for a few hours on Wednesday. While it currently seems unlikely there`s a non-zero chance of a few gale force gusts over Lake Superior Wednesday morning. Thus, Wednesday will not be particularly pleasant with a chilly north wind off Lake Superior and potential for a non- diurnal temperature curve with temperatures falling during the day. By Wednesday night the chilly air mass will be in place across our CWA and it seems likely to dominate our weather through the end of the week. This means there will be chances of frost on at least Wednesday and Thursday night and perhaps Friday too. The good news is we should see the sun on a regular basis during the upcoming cool weather, which will take the edge off the chilly air mass. A weak warming trend is possible this weekend as the chilly surface ridge slides east-southeast on Saturday. && .AVIATION...(For the 00Z TAFS through 00Z Monday evening) Issued at 721 PM EDT SUN MAY 23 2021 IFR conditions at KIWD in lingering showers should improve to MVFR later this evening as showers end, and then will stay MVFR through much of Monday. Otherwise, expect VFR conditions at KCMX and KSAW to lower to MVFR stratus later tonight under a developing moist se-e upslope flow and should stay that way through much of Monday. && .MARINE...(For the 4 PM Lake Superior forecast issuance) Issued at 337 PM EDT SUN MAY 23 2021 Winds over the west will diminish overnight to less than 15kt. Winds will remain under 20kt through Tuesday afternoon before the next cold front arrives. Winds begin to increase Tuesday night to 25kt across the lake and then up to 30kt over eastern Lake Superior on Wed, with diminishing winds in the west. Winds will diminish for Thu, but there could be somewhat stronger ne winds locally gusting to 25kt down western Lake Superior as high pres builds over northern Ontario. && .MQT WATCHES/WARNINGS/ADVISORIES... Upper Michigan... None. Lake Superior... None. Lake Michigan... None. && $$ SHORT TERM...NL LONG TERM...EK AVIATION...Voss MARINE...NL
Area Forecast Discussion...UPDATED
National Weather Service Portland OR
811 PM PDT Sun May 23 2021 Updated Aviation Discussion .SYNOPSIS...A weak cold front moves in late Sunday night and Monday bringing more chances for rain, followed by showers lasting into Tuesday. An upper level ridge will bring dry weather Wednesday, another cold front brings chances of rain back into the forecast Thursday && .SHORT TERM...Tonight through Tuesday...A weak line of showers is moving east over the Willamette Valley as of 20Z. Accumulations have been minimal with the northern Oregon coast and Coast Range recieving less than 0.10 of an inch. Westerly flow coupled with low level moisture will keep a slight chance for showers along the Coast and Cascade Range this evening. A weak upper ridge will push across the Pacific NW tonight into tomorrow. This will making way for an upper level trough that will increase low to mid level moisture across the region Monday and Tuesday. This brings increasing chances for rain spreading into the region late tonight from the west. As the upper trough moves in Monday, models have consistently shown a cold front moving east across the region during the daylight hours. Time-height cross sections of relative humidity show relatively deep moisture available with the front, so will continue to carry categorical pops for most of the area Monday. Air behind the front not particularly cold however, so snow levels expected to remain above Cascade passes through the most widespread and heaviest precipitation. Quarter of an inch accumulations looks likely for inland valleys, with heavier amounts in the mountains and along the coast. Behind the front late Monday into Tuesday, low levels expected to remain moist. As the coolest air aloft moves across Monday night and Tuesday, models indicate low level instability which will keep showers going. Deeper instability immediately behind the front over the southern half of the Willamette Valley and adjacent Cascades around the time of peak heating will bring a slight chance of thunderstorms Monday afternoon and evening. The moist onshore flow over the next few days will generally keep daytime temperatures a little cooler than normal. .LONG TERM...Tuesday night through Saturday...No major changes to previous discussion. A progressive pattern will continue through most of the week. An upper ridge will bring a period of dry weather late Tuesday through Wednesday for most of the region. Models remain fairly consistent in bringing the next trough through during the last half of the week, with a cold front arriving along the coast early Thursday and making its way across the region by Thursday evening. Chances for showers follow Friday into Saturday, but with models favoring the core of the cool air aloft passing by to the north, chances will be on the low side and tend to favor the northern part of the forecast area. && .AVIATION...MVFR conditions along the coast and VFR conditions inland expected to persist through the next few hours. This evening a disturbance is expected to bring showers along the coast around 06Z to 08Z Monday, along with IFR/LIFR conditions. These showers will also move inland bringing low end VFR/ high end MVFR conditions to the Willamette Valley around 09Z to 11Z Monday. Inland locations could see some periods of IFR but confidence is low at this time. Expect MVFR conditions to become widespread after 18Z Monday for all areas, which will likely persist through 00Z Tuesday. There is also a slight chance of thunder for the southern Willamette Valley and the southern Oregon Cascades starting at 21Z Monday. For detailed regional Pac NW aviation weather information, go online to: KPDX AND APPROACHES...Predominately VFR conditions through 09Z Monday. After 09Z Monday expect showers and low end VFR/high end MVFR conditions. These conditions are expected to persist through 00Z Tuesday. /42 && .MARINE...Fairly benign marine conditions through early Thu. Wind speeds generally 10 kt or less, but increase overnight into early Mon morning. Models in good agreement showing the wind backing to S to SW this evening ahead of the next frontal system. The 12Z NAM, GFS and 4km WRF-GFS show a narrow band of 20-25 kt boundary layer wind speeds Mon morning. However, the higher-resolution RAP and HRRR show slightly lower wind speeds. Not expecting small craft advisory wind with this system, but would not be surprised if there were a few gusts to 25 kt. The 12Z HREF 10m ensemble mean wind gust output indicates 25-30 kt gusts Mon morning. This lends some concern regarding the need for an advisory. Will let the next couple of shifts scrutinize a little more for possible small craft advisory highlights. Wind speeds decrease Mon afternoon. Models agree that a surface trough will reside over the waters Mon night into Tue morning. High pressure returns to the waters by 18Z Tue and holds through Wed. Another frontal system is forecast to move through the waters Thu. The ECMWF appears to be weaker with this system compared to the GFS. However, the small craft advisory potential for this system looks greater. Wave heights generally 4-6 ft through early Thu. The latest wave guidance indicates seas at or very close to 10 ft Thu and then easing back into the 5-8 ft range late in the week and over the weekend. Weishaar && .PQR WATCHES/WARNINGS/ADVISORIES... OR...None. WA...None. PZ...None. && && .PQR WATCHES/WARNINGS/ADVISORIES... OR...None. WA...None. PZ...None. && && $$ Interact with us via social media:
Area Forecast Discussion
National Weather Service Pueblo CO
309 PM MDT Sun May 23 2021 .SHORT TERM...(This evening through Monday) Issued at 304 PM MDT Sun May 23 2021 ...Convection continues this evening over the eastern plains... ...Some severe storms possible close to the Kansas border Monday afternoon and evening... .Tonight...low level jet develops this evening along the Kansas border. HRRR suggests over 1000 J/kg of CAPE persists well into the evening. Have kept scattered PoPs on the far eastern counties well into the overnight period. HRRR and NAMNest keep echoes until around 08Z near the border. Otherwise, it will be a generally quiet night over the forecast area. Temperatures will be cooler than normal over the mountains with the cooler air aloft associated with the trough. .Monday...Trough moves to the north of the region with dry southwest flow aloft. Anticipate a dry and mild day over most of the CWA. An approaching weak trough will turn winds southeasterly near the Kansas border allowing for some low level moisture to advect westward into the CWA. Current SPC day 2 has marginal risk over eastern Colorado close to the Kansas border. Models suggest up to 1500 J/kg of CAPE in this region with bulk shears around 40 knots. Current grids have silent PoPS over much of the plains given the potential for low coverage of any convection. --PGW-- .LONG TERM...(Monday night through Sunday) Issued at 304 PM MDT Sun May 23 2021 ...Pattern change with more westerly flow aloft... ...Suggestions for some storms late int he week into the weekend... .Tuesday...Dry and mild westerly flow aloft continues over the region with dry and warm weather expected. A weak front may move into the eastern plains bringing a modest increase in low level moisture. Models suggest some CAPE on the plains but it looks to be capped with the warmer air aloft. .Wednesday and Thursday...Next trough moves into the northern and central Rockies on Wednesday staying mostly to our north on Thursday. Currently looks like the best low level moisture will stay to the north of the region. NBM grids are mostly dry these two days. Will have to watch for critical fire weather conditions mainly in the mountains and high valleys Wednesday with the stronger southwest flow aloft. .Friday into Sunday...Trough to the east of the region on Friday will bring high pressure to the high plains with the potential for upslope flow on Friday into Saturday. Another trough may reinforce the upslope on Sunday. With the increase in low level moisture on the plains, will have to watch for some severe weather. Currently with a mean ridge loft, shears may be marginal. But, given it is late May, it does not take much to produce some severe weather. --PGW-- && .AVIATION...(For the 00Z TAFS through 00Z Monday evening) Issued at 304 PM MDT Sun May 23 2021 VFR all TAF sites. Gusty south to southwest winds continue through mid evening at the TAF sites. Some gusty southwest winds will develop at KALS during Monday afternoon. Low level moisture remains to the east of the I 25 corridor with very low threat for diurnal convection at KPUB and KCOS. --PGW-- && .PUB WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SHORT TERM...PGW LONG TERM...PGW AVIATION...PGW