Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 05/23/23

Area Forecast Discussion...UPDATED
National Weather Service Aberdeen SD
909 PM CDT Mon May 22 2023 .UPDATE... Issued at 907 PM CDT Mon May 22 2023 Some weak shower and thunderstorm activity that developed over the past couple of hours over eastern Spink county has now dissipated. With the loss of daytime heating, do not expect any additional development. No changes made to winds or temperatures at this time. && .SHORT TERM...(This Evening through Tuesday Night) Issued at 211 PM CDT Mon May 22 2023 Smoke, pcpn chances and temperatures remain the biggest challenges for the short term. Per current sat pix, elevated smoke continues to pretty much cover the entire Northern Plains. The latest RAP data suggests this will likely occur at least through Tuesday. The bigger if is whether or not the smoke gets thick enough in the LL to cause vsby reductions. Here the RAP still highlights the western Dakotas into the overnight hours. For Tuesday am not confident in the amount of LL smoke, so will leave out of the grids for now. For this evening will continue mention of spkls. Soundings indicate elevated CAPE late this afternoon and evening, but moisture is pretty scant. An isolated shower/storm isn`t entirely out of the question. For Tuesday and Tuesday night a back-doorish looking front will slide toward the northern/ne CWA. This system is expected to stall out near the SD/ND border area. A few showers/storms are possible near this boundary, particularly late afternoon/night across far northern SD. Temperatures will remain warmer than normal for the period as H850 temps continue in the 15-20C range. .LONG TERM...(Wednesday through Monday) Issued at 211 PM CDT Mon May 22 2023 An unsettled blocky weather pattern continues for the long term with ongoing warm temperatures. GEFS/ENS ens agree on the amplified ridge with the crest well into Canada and the Northern Plains under the ridge Wednesday morning. At the same time, a high pressure system will be to our northeast. This ridge will become more positive tilted as it pushes east. This is due to a low pressure system over western Canada/Pacific Northwest along with the troughing pattern over the western US. This low will push north and reattach to the main flow well north to us in Canada. By the end of the week, this deep trough remains fairly stationary over the western US into the weekend. This will provide southerly/southwesterly winds aloft Thursday through the weekend. With this setup, several shortwave pulses will move northeastward along the right side of the trough, creating this unsettled weather. The shortwave for the end of the week looks to affect more western SD/NE and Rockies area. More of the shortwave energy will move east over our area for the weekend. Cluster ensembles are in good agreement with location and intensity of this trough/ridge setup and the split flow pattern for day 3/4. Onward, clusters disagree on the ridge/trough intensity. The good news is once our winds aloft turn southerly/southwesterly, this will help alleviate the smoke aloft! Gusty winds (up to 35-40kts) returns to the area Wednesday/Thursday afternoons on the backside of a high and in between the low causing steeper pressure gradients. Looking down at the surface, ensembles plus deterministic agree on a surface low and trough, but timing is still off a bit between the models. We really see the CWA in the warm sector between the warm and cold fronts next weekend into Monday. Most of the action stays to our west Wednesday and models have backed off on the eastward movement. As this low moves east, spotty chances of pops (15-35%) periodically for Thursday west of the Missouri and a gradual increase eastward Friday into the weekend, each afternoon per NBM/ECMWF Ens. ECMWF/GFS ensembles indicate PWAT>1 inch increases Friday-Saturday with 80-100% west of MO river to 20-90% east of Missouri river. CIPS Prob Severe Day 5-8 really keeps most of the severe chances out of the CWA with 10% prob mostly in Rapid City WFO area being hail the main concern. ECMWF/GEFS prob of CAPE>1000 is between 10-40% east of the Mo and up to 60% west river Wednesday/Thurs evening. Even looking into the weekend, CAPE and bulk shear values are not too impressive over the area. For example GFS MUcape up to 1500 which creeps into the area Friday-Sunday afternoons over the CWA. Better chances for higher CAPE look to occur early next week. With dewpoints increasing on Friday-weekend into the 50s and maybe into the lower 60s, along with lift from the boundaries, and some CAPE, thunderstorms are possible. No organized severe weather expected at this point due to the lack of instability. However, isolated severe could be possible if a few storms extend upward enough for some hail/gusty winds. && .AVIATION...(For the 00Z TAFS through 00Z Tuesday Evening) Issued at 623 PM CDT Mon May 22 2023 Terminals KABR,KATY,KPIR,KMBG VFR conditions will prevail across the area tonight and through the day Tuesday. Elevated wildfire smoke from Canada will remain over the region through the TAF period. && .ABR WATCHES/WARNINGS/ADVISORIES... SD...None. MN...None. && $$ UPDATE...Parkin SHORT TERM...TDK LONG TERM...MMM AVIATION...Parkin
Area Forecast Discussion
National Weather Service La Crosse WI
1005 PM CDT Mon May 22 2023 .DISCUSSION...(This evening through Monday) Issued at 246 PM CDT Mon May 22 2023 Key Messages: - Hazy skies expected again tomorrow across portions of the forecast area. - Low humidity is the biggest concern in the extended forecast with multiple days of very dry air in place. - Forecast continues to trend dry through Sunday with no clear signal of when precipitation will return. HAZY SKIES CONTINUE: The RAP smoke model continues to show the presence of smoke aloft over most of the forecast area through tomorrow night. The concentration of smoke in the vertical column is forecast to slowly decrease over time, but some obstruction is expected to continue. WARM AND DRY THROUGH THE WEEKEND: A longwave ridge amplifies over the central CONUS this week bringing a pattern of high pressure to the region. This will lead to light winds, warm temperatures, and low relative humidities. Wednesday is the exception with an 850mb temperature gradient setting up somewhere across the forecast area from a trough passing by to the northeast. An early look at model soundings for later in the week shows a very dry layer of air above the surface. This dry air will mix down to the surface, especially during the afternoon hours. As a result, minimum relative humidity values could bottom out in the teens and low 20s. Light winds will help mitigate the fire risk some and most places are further along in the green-up process, but with the dry air lack of recent rainfall fire conditions could become elevated. In previous forecasts there was a question about precipitation over the Memorial Day weekend, but the most recent deterministic and ensemble guidance have trended drier with upper-level ridging holding in place. && .AVIATION...(For the 06Z TAFS through 06Z Tuesday night) Issued at 1005 PM CDT Mon May 22 2023 CIGS: smoke from Canadian skies will continue to make for milky skies through Tue. Could see a few afternoon cu. Will continue to cover smoke with SCT250. Models then point to a backdoor front slipping in Wed morning, potentially bringing in a few hour period of lower VFR cigs. WX/vsby: some potential for MVFR FU vsbys Tue, but not high enough to include in the forecast. WINDS: staying light, mostly from the south. && .ARX WATCHES/WARNINGS/ADVISORIES... WI...NONE. MN...NONE. IA...NONE. && $$ DISCUSSION...KAA AVIATION.....Rieck
National Weather Service Bismarck ND
914 PM CDT Mon May 22 2023 .UPDATE... Issued at 914 PM CDT Mon May 22 2023 Various observations across the forecast area continue suggesting near-surface smoke is reducing visibility to between 6 and 9 miles in some locations. Otherwise, a quiet evening continues before shower and thunderstorm chances work into the area Tuesday. UPDATE Issued at 637 PM CDT Mon May 22 2023 Smokey conditions continue, especially in the west where visibility has dropped to as low as 5 miles from near-surface smoke. The only other update at this time was to remove sprinkles in the south central. Any diurnal cu is east of the forecast area and is not producing any radar returns. With lots of dry air remaining off the surface and dewpoint depressions in excess of 30 degrees, it would be extremely difficult for any unorganized precipitation to reach the ground at this point in time. && .SHORT TERM...(This Evening through Tuesday) Issued at 259 PM CDT Mon May 22 2023 An upper level ridge over the Northern Rockies continues to bring weak northwest flow into the Northern Plains. Therefore, elevated smoke from the fires up in Canada continues to move through the region resulting in hazy skies. Near surface smoke has cleared out of western and central North Dakota for the moment. The RAP Near- Surface Smoke does increase smoke coverage across the west this evening as an inversion sets up. Therefore, patchy smoke remains in the grids through 12Z Tuesday. Southeasterly surface winds could limit near surface smoke across central North Dakota tonight maybe keeping smoke out over the west. The upper level ridge is going to settle over the Northern Plains tomorrow leading to temperatures in the mid 80s to lower 90s. The low level thermal ridge will span across south central North Dakota where the warmest temperatures are expected. A warm front will lift through the region tomorrow causing thunderstorms out west. A lack of shear and the storm motion will result in slow moving storms that could cause localized flooding. In addition PWATs are going to be over an inch increasing likelihood of heavy rain. The CSU severe weather machine learning has highlighted a chance for hail across much of North Dakota. Due to the lack of shear storms will pulse up and remain unorganized making the hail potential low. A back door cold front will move in tomorrow evening bringing breezy winds and maybe initiating convection in the evening. .LONG TERM...(Tuesday Night through Monday) Issued at 259 PM CDT Mon May 22 2023 An unsettled weather pattern will return Wednesday through the end of the week. Troughing across Western CONUS will continue to bring in southwesterly flow aloft to the Northern Plains. A back door cold front could keep initiating storms Wednesday morning. Much of Wednesday the area will remain dry with a few showers and spattered around. Thursday thunderstorm chances increase as another short wave moves across the western half of the state. PWATs are still forecast to remain above an inch continuing the heavy rain potential for western and central North Dakota. Another wave is forecast to move through the state Friday evening through Saturday morning. The active pattern will continue into the weekend with increased chances out west. Temperatures are forecast to sit slightly above normal in the upper 70s to lower 80s for the remainder of the week. && .AVIATION...(For the 00Z TAFS through 00Z Tuesday Evening) Issued at 637 PM CDT Mon May 22 2023 Near-surface smoke is reducing visibility to as low as 5 SM in western North Dakota. Generally speaking though, visibility remains at 6 SM or greater. Therefore, while MVFR visibility from smoke is possible at KDIK or KXWA, VFR visibility is expected to prevail. A couple showers or thunderstorms may develop in western North Dakota late tonight and into the morning hours. Precipitation chances then increase mid to late afternoon Tuesday. For the most part, left precipitation chances out of TAFs for now due to uncertainty in both timing and location of any shower and thunderstorm development. && .BIS WATCHES/WARNINGS/ADVISORIES... None. && $$ UPDATE...Telken SHORT TERM...Johnson LONG TERM...Johnson AVIATION...Telken
Area Forecast Discussion
National Weather Service Denver/Boulder CO
800 PM MDT Mon May 22 2023 .UPDATE... Issued at 800 PM MDT Mon May 22 2023 Scattered showers and thunderstorms are expected to linger another hour or two before they dissipate for the night. Small hail, gusty outflow winds, and brief heavy rain have accompanied the strongest storms. Going forecast is on track and don`t anticipate any big changes. && .SHORT TERM...(This evening through Tuesday) Issued at 245 PM MDT Mon May 22 2023 Weak convection continues to slowly develop, with limited strength and organization limited by the lack of any wind shear. We did get a few storms out around Limon earlier than expected as dew points rose into the 50s. There is a boundary moving northeast from that area that could generate more storms further west, but they should continue to be disorganized and the strength should be limited by cloud cover. We just added isolated storms from Lincoln county west to Douglas county through this evening. For Tuesday, there`s very slight warming and also probably a little less smoke, so slightly warmer temperatures look good. There`s still very little wind through the depth of the atmosphere, but probably a little tendency towards and eastward drift later in the day. We trimmed back PoPs a little in the gradient east of the mountains again. There may be a better chance of something drifting off the mountains in the evening. .LONG TERM...(Tuesday night through Monday) Issued at 245 PM MDT Mon May 22 2023 Key Messages: 1) Gradual improvement in smoke Wednesday 2) Increasing chances & coverage of showers and storms by Weds 3) Potential for locally heavy rainfall and severe storms later this week Into Wednesday, the upper level pattern transitions to SW flow aloft as an amplified 500 mb trough moves into the western CONUS. As the previous ridge pushes eastward, ensemble guidance indicates a plume of anomalous moisture (~145% of normal) moving into Colorado. An embedded shortwave in the flow will provide some upper level support for ascent thus helping initiate storms across the region in the afternoon after instability develops. MLCAPE builds with values in the 600-1100 J/kg range. With sufficient shear around (0-6 km bulk shear 20-30kts), a couple of strong storms will be supported, potentially even severe. These stronger storms may be capable of producing small hail, gusty outflow winds and localized heavy rainfall. More numerous showers and storms Thursday and Friday. In a typical pattern, the trough to the west would have moved across Colorado; however, a blocking pattern will likely slow this progression down as an upper low retrogrades back into the Tennessee Valley. This will amplify the ridge centered east of Colorado. Above normal moisture continues to shift across the mountains and into the plains. Within the SW flow aloft there will be bulk shear values 20- 30 kts with a good amount of instability forming ahead of a few embedded waves with MLCAPE 1000-2000 J/kg. This will support afternoon showers and thunderstorms with a chance for severe storms as well. Given the anomalous moisture in place and fairly weak flow aloft, slower moving storms are possible and with the capability of producing locally heavy rainfall. Into the weekend, confidence in the upper level pattern decreases given the uncertainty in the progression/evolution of the blocking pattern. WPC cluster analysis shows some eastward progression of the ridge by Sunday which would push the trough across Colorado. Overall, looking at an unsettled pattern with scattered to numerous showers and thunderstorms across the region each day. For much of the long term period, highs stay close to normal across the urban corridor/plains in the mid to upper 70s. Although this pattern calls for the threat of severe storms and local heavy rainfall/flash flooding potential, flow aloft should gradually push the wildfire smoke out after mid-week. && .AVIATION...(For the 00Z TAFS through 00Z Tuesday evening) Issued at 535 PM MDT Mon May 22 2023 Main aviation issue will continue to be smoke from the wildfires in Canada. Visibility should stay above 5sm through Tuesday, but enough smoke should be around to impact arrival slant visibility at KDEN. The southeast winds will increase a little around 02Z as outflow winds arrive from earlier storms that were off to the southeast. Winds then settle south to southwest direction around 06Z. Weak winds to prevail Tuesday morning and then become light out of the northeast around 18Z. For Tuesday afternoon/evening, the HRRR model shows westerly outflow winds from convection moving through around 00Z and triggering a few storms. This is the only model showing convection near DEN, so will leave the mention of thunder out of the TAFs for now. && .HYDROLOGY... Issued at 245 PM MDT Mon May 22 2023 For this evening and Tuesday afternoon, scattered slow moving storms are expected over the mountains. The strength and organization of the storms will keep the burn area flood threat low, but if one of the heavier storms does occur over a sensitive area there could be some flooding. There is a trend of increasing moisture, shower/storm coverage and strength mid through late week. Flow aloft will be on the lower side, supporting slower moving storms. Above normal precipitable water values will support storms capable of producing localized heavy rainfall. As a result, there will be at least a limited threat for flash flooding over the burn areas each day with even a threat over portions of the plains towards the latter end of the work week. An elevated threat is becoming likely over the burn areas Wednesday given slow storm motions and above normal moisture. For the remainder of the week, at least a limited threat with more confidence in an elevated risk for Cameron Peak Thursday and Friday. A lot of this will depend on the how the upper level pattern progresses. If it is slower to progress eastward and weaker flow remains, there may be an extended elevated threat through the weekend. && .BOU WATCHES/WARNINGS/ADVISORIES... None. && $$ UPDATE...Meier SHORT TERM...Gimmestad LONG TERM...Mensch AVIATION...Meier HYDROLOGY...Gimmestad/Mensch
Area Forecast Discussion
National Weather Service Des Moines IA
1027 PM CDT Mon May 22 2023 ...Updated for the 06z Aviation Discussion... .DISCUSSION.../Tonight through Monday/ Issued at 242 PM CDT Mon May 22 2023 Key messaging highlights: * Little change anticipated through the week * Mainly dry and warm through at least the weekend Our current weak northwest flow pattern will give way to central CONUS upper level ridging over the next few days keeping our weather warm and dry through at least the weekend. The ridging will be persistent with little sign of breaking down until possibly early next week. A weak, compact PV anomaly continues to drift across IA this afternoon, but with limited forcing or moisture the result has been nothing beyond some mid/high level cloudiness with higher based cumulus underneath. The small short wave should drift into MO tonight with two features of note into tomorrow, upper level ridging well through the Plains into Canada, and a progressive long wave trough clipping the Great Lakes. The former feature will keep our forecast dry for at least several days, but the latter will drive an airmass change, especially in terms of moisture. The trough passage will produce a noted backdoor cool front Wed night into Thursday. Temps will drop back some, but still remain in the 70s and just above normal. The most sensible change will be significant drying through the entire column late week. Dewpoints should dip into the 30s to end the work week, and precipitable water values may reach anomalously low values for late May per NAEFS and EPS percentiles with plenty of sunshine. A bit of the guidance suggests light precip potential with the backdoor front, but confidence is certainly low and the forecast remains dry. Regarding smoke, satellite imagery shows the highest concentrations north and west of IA, and the latest RAP extension (15Z) suggests this should remain mainly north of IA. There are higher concentrations drifting northward from MO in the model, but this appears to be over-initialized. The only real forecast question will the re-introduction of precip. The latest deterministic and ensemble guidance continues to be less bullish, lowering PoPs and/or pushing things back in time. A pseudo Omega block, some form of Appalachian or OH Valley low and ridging topping it to the north, will follow the trough and keep our dry pattern locked in through at least the weekend. Low level trajectories will struggle to move beyond SSE keeping any appreciable low level moisture return at bay. Ensemble guidance does suggest some potential for better moisture and the far eastern fringe of the weak Plains southwest flow to barely nudge enough to the MO Valley to get some precip here late in the period. Would not be surprised to see the late holiday weekend chances diminish with time however if present trends continue. Recent GEFS/EPS guidance yet to be ingested in the NBM suggests the holiday weekend will mainly be dry. && .AVIATION.../For the 06Z TAFS through 06Z Tuesday night/ Issued at 1027 PM CDT Mon May 22 2023 Few changes needed to going forecast. VFR conditions expected with winds generally below 10kts. Sct to broken mid level cu expected aft 15-17z with possible more widespread deck of 150-180kft aft 01z. Otherwise, smoke aloft and sfc restrictions not expected. /rev && .DMX WATCHES/WARNINGS/ADVISORIES... NONE. && $$ DISCUSSION...Small AVIATION...REV
Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
1157 PM EDT Mon May 22 2023 .AVIATION... Light southeast to south flow around high pressure will maintain dry conditions. Wind speeds will remain generally under 10 knots with a gradual veering to a more southerly direction into Tuesday night. DTW THRESHOLD PROBABILITIES... * None. && .PREV DISCUSSION... Issued at 312 PM EDT Mon May 22 2023 DISCUSSION... Enhanced boundary layer convergence extending from the Tri Cities down to Port Huron is shown in the recent sfc observations. The moisture depth is quite shallow, which will likely inhibit any evening convection. The most recent RAP solution for vertically integrated smoke suggests the high altitude smoke overhead will remain quite thick through the night, thinning toward daybreak. The weak gradient flow and relatively dry air in the boundary layer will still offer enough radiational cooling opportunity to support min temps in the 50s. Subtle mid level height rises and a lack of moisture will ensure dry conditions on Tuesday. Sfc high pressure will become centered along the coast of New England with light southerly return flow developing over Se Mi, driving 925MB temps up toward +19C. Model soundings show mixing depths up to 6-7k feet which will support afternoon highs into the low 80s. Amplification of a mid level trough axis moving from northern Ontario into upstate New York/Quebec Tues night into Wednesday will drive a cold front south across the Great Lakes region. Deep layer FGEN will support widespread showers as this system enters the northern Great Lakes Tuesday night. The upper jet support and region of mid level height falls will track largely east of Lake Huron Tues night/Wednesday. This will result in a weakening of the deep layer FGEN as the front moves south across the forecast area Wed morning. Per the 12Z model suite, moisture depth and forcing look adequate to support a chance of showers early Wed morning across the thumb and Saginaw Valley. The FGEN is then forecast to quickly fall apart, leaving just a low level and shallow frontal circulation by the time the front passes south of metro Detroit. There will be a respectable push of cold air in the wake of this front, modified by the cold waters of Lake Huron. 925mb temps are forecast to plunge into the single digits on Wednesday. Even with a late May sun angle, high temps will most likely occur Wed morning, with afternoon temps likely falling/holding in the 50s or low 60s. The strength of the subsidence in the wake of this mid level wave will allow strong high pressure to expand across the northern Great Lakes by Thursday. A cool and very dry (continental polar airmass) will reside across the area through the end of the work week. Medium range model solutions are suggesting a rex block becoming established by this weekend, with Lower Mi under the ridge. This will ensure continued dry conditions. Modification of the airmass will allow warmer temperatures to return, leading to a warm and dry holiday weekend. MARINE... A washed out cold front retreats back toward Canada tonight as mild/weak return flow off eastern high pressure seeps into the central Great Lakes tonight and into Tuesday providing favorable marine conditions. Benign weather wanes Tuesday night as a cold front tracks due south along the long-axis of Lake Huron. It will take some time before the upper level trough forces the front across the southern waterways Wednesday, but expect prevailing winds to become uniform in the frontal wake, organizing out of the north with a modest uptick in speeds as the gradient responds. Potential continues to increase regarding the development of Small Craft Advisory criteria waves and gusts, especially for the Huron nearshores, Wednesday afternoon and early evening. Ridging then reestablishes over north-central CONUS late week supporting diminished wind/wave response into the weekend. && .DTX WATCHES/WARNINGS/ADVISORIES... MI...None. Lake Huron...None. Lake St Clair...None. Michigan waters of Lake Erie...None. && $$ AVIATION.....DG DISCUSSION...SC MARINE.......KGK You can obtain your latest National Weather Service forecasts online at
National Weather Service Hastings NE
640 PM CDT Mon May 22 2023 ...Aviation Update... .DISCUSSION...(This evening through Monday) Issued at 355 PM CDT Mon May 22 2023 Key Messages: * Mainly dry with mild temperatures through midweek. * Better chances for showers and thunderstorms may arrive Thursday and continue into the weekend. However, latest model trends are for majority of activity to remain W and SW of the Tri Cities - over/along the High Plains. The latest forecast for the holiday weekend likely sounds worse/wetter than what will happen, and risk for organized severe weather appears low at this time. * Smoke for Canadian fires will impact the region again this week, but latest indications are that it should remain mostly elevated and not be as impactful at the surface as last week. Forecast Details: Latest WV and upper air analysis reveals more of a summer-like, split flow/weak pattern in place across the CONUS relative to a "normal" mid-late May pattern. The primary belt of westerlies runs from a trough in the Pac NW then well N into Canada due to strong upper ridging across the N Plains, with any other subtle enhancements due to small/compact perturbations and/or vorticity maxima. One such vort max can be seen clearly on regional sat/rad over SW KS. Another vort max is apparent on WV along IA/MO border. Subsidence behind this wave is making it tough for more than high clouds to advect northward from the KS wave. As a result, appears most convective chcs tied to this wave will remain S/SW of the CWA. However, did maintain some slgt chc PoPs in our KS zones due to band of agitated CU beneath a swath of implied weak ascent denoted by cirrus. This probably won`t develop into anything given aforementioned battle with incr mid level dry air/subsidence, but if we do get anything this eve, this is where it would be. CAPE/shear are far too limited for anything severe. Other than the KS vort max "washing out" and drifting SE, the overall pattern changes little Tue into Wed as upper ridging dominates majority of central/northern Plains into Upper MS Valley and Great Lakes region. Thus, expect similar conditions to this aftn to persist - highs in the upper 70s to 80s, lows in the 50s, and just some aftn fair wx cumulus. Only modest S/SE sfc wind should make for very pleasant wx by mid/late May standards. Fires continue to burn over portions of Canada (quite intensely, in spots) and generate plentiful smoke. Fortunately, latest RAP forecast smoke output continues to indicate that while smoke will be noticeable visually next couple of days (at least), the impacts at the surface to visibility and health look to be minimal...or at least significantly less than compared to last week (Thu). Pattern could trend "more active" as we head into the upcoming Memorial Day holiday weekend...however want to emphasize that the weekend does not appear to be a "washout" as there will be plenty of dry time and current forecast may sound worse than what will really occur. Overall predictability on day-to-day details/features is fairly low - owing to aforementioned summer- like pattern and weak mid to upper flow - but it appears that convection will be a daily occurrence over the High Plains where there is a favorable combination of E/SE upslope sfc flow and weak capping. This type of pattern tends to favor diurnally driven convection that peaks in coverage/intensity W of our CWA, but can occasionally still make it in during the late eve and overnight hrs, particularly with the help of a robust MCV. These features are notoriously difficult to predict beyond 12-18 hrs, but would tend to favor W/SW/S zones given placement/proximity of main instability axis. And even if robust convection develops over the High Plains, progged weak 0-3km and 0-6km shear vectors argue for lack of organization and declining intensity with eastern extent during the eve/night hours. Further illustrating this point is distinct trend in last few deterministic EC runs of placing sharp drop-off in QPF from W to E across KS/NE...such that NE/E zones could see very little to no appreciable QPF through the weekend. Not good for drought stricken areas locally, but at least those just S/SW of here should see some much need relief from ongoing drought in those areas. Perhaps this could pave the way for better moisture return later in the spring/early summer. Otherwise, temperatures look to remain quite steady through the weekend and not too dissimilar to the next couple of days. Perhaps additional cloud cover over the weekend could knock a few deg off, but not expecting substantial low level cloud cover at this time. && .AVIATION...(For the 00Z KGRI/KEAR TAFS through 00Z Wednesday) Issued at 637 PM CDT Mon May 22 2023 VFR conditions persist at both terminals through the forecast period. Expect a few mid-level clouds this evening and into tonight, with ceilings expected to lower, but remain at VFR levels around midnight. Southeasterly winds 5-10kts this afternoon become southerly tonight. Southerly winds persist through the rest of the TAF period, increasing to around 10-15kts by mid-morning. There will be a chance of a few thunderstorms across north central Kansas tomorrow afternoon, but these are not expected to reach impact either TAF site. && .GID WATCHES/WARNINGS/ADVISORIES... NE...NONE. KS...NONE. && $$ DISCUSSION...Thies AVIATION...Wekesser
Area Forecast Discussion
National Weather Service Grand Junction CO
545 PM MDT Mon May 22 2023 .SHORT TERM...(Tonight through Tuesday night) Issued at 235 PM MDT Mon May 22 2023 Rinse and repeat story today as widespread, anomalously high moisture has led to another round of scattered to numerous showers and thunderstorms. Coverage has been enhanced by the passage of a weak, midlevel low pressure system across the southern tier of our forecast area this afternoon. Dynamics associated with said low has led to some slightly stronger storms across the Four Corners region with SBCAPE sitting near 1000 J/kg. However, weak shear has prevented storms from being long-standing and, while it`s not quite the "pop-and-drop" variety, the lifespan has been relatively short. Precipitable water (PWAT) values remain elevated at 150 to 200% of normal across the region with localized areas approaching 250% of the norm in southwest Colorado. As has been the trend the last several days, brief heavy rain will be the primary threat from any stronger storms with secondary threats of gusty winds to 40 mph or less as well as small hail. The midlevel wave will exit east of the Divide tonight, seeing convection largely dissipate by 9 PM, though the HRRR in particular is pinging on some lingering showers over the central mountains through midnight or so. Tuesday will see the upper level trough centered over the Pacific Northwest elongate along the West Coast. Meanwhile, a ridge of high pressure will build over the Great Plains. As a result, look for flow aloft across eastern Utah and western Colorado to shift to the southwest on Tuesday. Additional moisture will advect into the region ahead of the trough in this pattern shift, seeing PWATs reach 180 to 200% of normal (or more) by the afternoon. A weak ripple in the flow also looks to quickly slide overhead across eastern Utah and far western Colorado on Tuesday. The uptick in moisture paired with weak support from this shortwave will result in more widespread showers and thunderstorms Tuesday afternoon and evening. Given the earlier days of moderate to heavy rain, most notably down south, localized runoff concerns will be possible if any stronger convective cells develop. Drier air will begin to infiltrate the Four Corners late Tuesday evening and overnight as the Pacific trough dives farther south towards Baja. The originally projected cutoff low over California is not as favored in the latest models but, regardless, dry air will spread northeast in the southwest flow. In response, showers over the southern zones will come to an end earlier than previous evenings with activity gradually tapering off elsewhere into the midnight hour. Partly to mostly clouds skies will persist into Wednesday. High temperatures on Tuesday will moderate by a couple of degrees compared to today`s values. Overnight lows both tonight and Tuesday night will follow suit. Either way, low temperatures will sit 4 to 8 degrees above normal while Tuesday`s highs will trend 3 to 6 degrees above normal across eastern Utah and northwest and west- central Colorado. The southern zones will sit a couple degrees below normal due to increased clouds and showers. .LONG TERM...(Wednesday through Monday) Issued at 235 PM MDT Mon May 22 2023 Models still struggle to handle the complex weather pattern with little jet support to steer the systems, so there is low confidence in the extended forecast. That being said, the latest runs have a low over eastern Montana with deep troughing down into the Great Basin, a high over the Northern Plains to the Great Lakes and a low over the southeastern US in a weak omega block that hangs around into Friday before the Arctic jet drops down into the Pacific Northwest to eject the Montana low and Northern Plains high east, setting up a longwave trough across the Western US. With troughing in the Great Basin and ridging over the Central Plains, look for breezy southwest winds Tuesday, peaking Wednesday and tapering off going into the weekend pulling a drier, near seasonal normal airmass up from the southwest. Through the weekend into early next week, a couple shortwave systems track across Utah and Western Colorado with a return of a moister airmass and unsettled weather to the Utah and Colorado mountains. The weather across the region will have continued widespread afternoon and evening showers and thunderstorms across the higher elevations of Colorado and northern Utah Wednesday. Beyond Wednesday, the dry air intrusion will reduce the convective activity to isolated to scattered showers and thunderstorms over the northern Utah mountains, and along and east of the Divide in Colorado. Sunday into early next week will see scattered showers and thunderstorms slowly creep back south and west across the region as the longwave trough allows shortwave systems to pass over the region. && .AVIATION...(For the 00Z TAFS through 00Z Tuesday evening) Issued at 540 PM MDT Mon May 22 2023 Scattered showers and thunderstorms will persist this evening. Storms will fire on the terrain and drift into adjacent valleys. Terminals will remain mostly VCTS with these storms. A few may make it into the valley with a brief heavy shower and strong outflow gust, as well as brief reduction of visibility thanks to rainshowers. Showers will subside after sunset and quiet conditions should prevail into tomorrow morning. This pattern is expected to hang on another day and storms should initiate again by lunchtime Tuesday across the region with similar impacts as today: small hail, lightning, gusty outflows, and brief heavy downpours. && .HYDROLOGY... Issued at 235 PM MDT Mon May 22 2023 Daily showers and thunderstorms blossoming atop mountain peaks will continue to influence snowmelt and a limited threat for flash flooding across saturated or impervious terrain. Stronger storms are capable of producing periods of heavy rainfall, thus, accelerating runoff in very localized basins. Determining which basin is still difficult to pin point each day, so there remains that window of uncertainty in terms of spikes in river forecasts. However, the next system driving into the Great Basin tomorrow will result in a shift in weather patterns through the holiday weekend. Deep troughing over the western CONUS will set up southwest flow upstream the Four Corners Tues night into Wed, and essentially nudge the moist airmass overhead out of the forecast area. As a result, this will reduce storm coverage spatially and temporally through the latter half of the week. Flashy spikes in water levels will be reduced in tandem, however, spring runoff season is in full swing, and clearing skies with warm/dry southwest flow will still efficiently melt snow via radiational processes. Forecast hydrographs continue in an upward fashion for many of the main stems across the Western Slope. Be sure to keep an eye on river conditions and updated forecasts this week, especially if holiday weekend plans involve close proximity to these swift moving channels. Campground closures are probable, if not already in effect, as well as several road closures due to inundated crossings or damaged roadways. && .GJT WATCHES/WARNINGS/ADVISORIES... CO...None. UT...None. && $$ SHORT TERM...MMS LONG TERM...DB AVIATION...LTB HYDROLOGY...ERW
For this long-term forecast discussion, an active weather pattern is
still anticipated across the Tri-State Region, beginning Wednesday and
going into the holiday weekend. It wouldn`t quite be Memorial Day around here without the threat of thunderstorms, including some strong to severe. However, there is some uncertainty with this forecast as the overall upper level pattern just isn`t terribly conducive to larger thunderstorm events yet most forecast guidance continues to provide high chances for precipitation and also the potential for heavy rainfall for some of the forecast period. Early in the forecast period, it is also difficult to identify the potential locations of the surface features the storms will fire upon, so that is another point of uncertainty...exactly where storms will fire and who will be under the highest threat. Either way, the key message for this forecast period is that a prolonged threat for thunderstorms, including potential severe storms and heavy rainfall, is expected Wednesday into the holiday weekend. To begin, the upper level pattern should remain consistent through this stormy time period. A large ridge of high pressure is projected to build across the Great Plains, bordered by troughs of low pressure on either situated over the eastern third of the United States, and the second centered along to just onshore from the Pacific Coast. Into the weekend, the trough of low pressure slowly advances east across the Rockies, and several spokes energy ejecting over the Plains during that time frame. This energy, in the form of shortwave troughs, are what will support the development of precipitation/thunderstorm activity each afternoon and evening. One thing to note about this entire forecast period is that the mid-level winds are fairly week, which should limit the maximum magnitude of available wind shear each day for storms to work with. This may limit the potential severe weather events compared to many others observed in the month of May. As for the surface pattern, consistency is also anticipated here. Initially, southeast flow, bringing in warm, moist air from the Gulf of Mexico, is expected to extend all the way to the Rockies for at least Wednesday and perhaps Thursday as well. As the upper level low slowly migrates east, a surface trough of low pressure should form in lee of the Rockies. This should help bring in some drier air into the Front Range region, which will serve to sharpen a dryline in eastern Colorado for Friday into the weekend. There may also be a temperature gradient/pseudo-frontal boundary for Wednesday and Thursday in the region, likely stemming from temperature differences caused by persistent cloud cover in some areas versus breaks in the cloud cover further west. Starting with Wednesday, overall it appears that the severe weather potential may be limited to parts of eastern Colorado, or as currently highlighted by the marginal risk issued by the Storm Prediction Center this morning. A shortwave trough will move over the plains, but with a surface pattern that does not contain an easily identifiable feature for storms to fire, i.e. a dryline, it`s quite possible that this may be one of the days where we watch storms fire on the Rockies and await their arrival in the High Plains later that evening. Storms are certainly possible to fire in our area within the warm sector, especially on any thermal boundaries that form. Instability seems to be limited, generally 750-1250 j/kg of SBCape and poor lapse rates ranging from 5-7 C/km. Shear is also poor for most of the region, although guidance is coming into agreement that winds should strengthen over east central to more southeast Colorado, resulting in up to 35 kts 0-6 km bulk shear. Based on all of this, think we`ll see storms potentially fire in the warm sector over our area, but more likely along the Rockies, slowly moving east over the plains and possibly entering southwest portions of the forecast area (Cheyenne County Colorado, and Wichita and Greeley counties in Kansas). Severe weather would be possible, although there`s always the question of how long storms will maintain their intensity after sunset. Overall, it does appear probable that widespread non-severe thunderstorm activity may be realized across the area, which will help start to saturate the soils for future thunderstorm days and potential flash flooding. On Thursday, a more favorable setup for thunderstorm activity is anticipated, including one that favors severe storms. Winds increase enough at the lower and mid levels to cause shear to become relatively impressive considering the pattern, topping out at 40kts 0-6 km bulk shear in some guidance members. Further, a notable uptick in instability is also anticipated with SBCape increasing to 1500-2500 j/kg for a large portion of the area, and lapse rates climbing into the 6-8 C/km range. Forecast guidance indicates there may be two areas of storms that impact the area...the first forming right over us in the High Plains, and the second in the form of an MCS moving into the region later that originally formed on the Rockies. With multiple rounds of rain and slow storm movement anticipated, the flash flooding risk should ramp up for Thursday as well, especially if widespread rain is received on Wednesday. One concern with Thursday`s forecast, in addition to the previously mentioned concerns with the general pattern, is that rising heights aloft may be realized, which means that upper level support isn`t the best for thunderstorm initiation. This may serve to keep thunderstorms more scattered than widespread, at least initially until a potential MCS is able to develop. For Friday, yet another shortwave looks to move out over the High Plains. Further, this is the first day with some semblance of a sharpening dryline to the west. The question remains of how much will the environment be altered from the previous day`s storms. It does seem like instability will build once again along the dryline, so feeling comfortable in continuing precipitation/storm chances but wondering if they may be currently overdone. As mentioned yesterday, it can be difficult to get multiple days of higher-end severe storm days in a row without a significant upper level pattern causing it, and we just don`t have that for these potential events. Going into the weekend, the pattern remains fairly consistent with a dryline sharpening over eastern Colorado, serving as the focus for storm development as shortwaves move out over the Plains. Model differences are causing issues with the projections on instability and wind shear, and when those would be maximized. However, that being said, it currently appears that we no longer can expect a front moving in from the north. Instead, any potential front would stall well to the north, or arrive early to middle of next week, therefore no longer being a concern for this long-term forecast period. Therefore, confidence is growing in the surface pattern that should be anticipated, and therefore once minor model timing/location differences are resolved, we`ll be able to more comfortably and confidently provide a holiday weekend severe weather outlook. For now, the key message/takeaway for the weekend forecast is that there remains potential for strong/severe storms and heavy rainfall throughout the weekend, so those with plans, particularly outdoors, should keep a close eye on the forecast and outlooks. && .AVIATION...(For the 00Z TAFS through 00Z Wednesday evening) Issued at 531 PM MDT Mon May 22 2023 For KGLD, VFR through 06z Tuesday, then conditions drop as fog develops. Ceilings will drop to less than OVC010 through 17z then MVFR. Visibility in fog will range mainly 3-6sm but a period down to 2sm or less is possible. Winds mainly south-southeast around 10kts. Light/variable possible 06z-17z Tuesday. For KMCK, mainly VFR conditions for much of the forecast period. Several hours of MVFR/IFR ceilings around BKN009-015 are possible from 11z-18z Tuesday. Winds, mainly southeast around 10kts. Light/variable possible from 02z-18z Tuesday. && .GLD WATCHES/WARNINGS/ADVISORIES... KS...NONE. CO...NONE. NE...NONE. && $$ UPDATE...JN SHORT TERM...076 LONG TERM...RRH AVIATION...JN
Area Forecast Discussion
National Weather Service Marquette MI
1200 AM EDT Tue May 23 2023 .SHORT TERM...(Through tonight) Issued at 1238 PM EDT MON MAY 22 2023 A 1028 mb surface high in southern Quebec is downstream of broad ridging over the central CONUS today, leading to mostly clear skies with the exception of some midlevel cu over northern Lake Superior due to a subtle shortwave. This afternoon, the NAM 4k, WRF FV3 and NSSL WRF have convection popping up across northern WI and the interior of the UP, though the low level and upper levels struggle to saturate per BUFKIT soundings and GOES-16 water vapor imagery. With the majority of other CAMs not showing convection, limited PoPs this afternoon to only sprinkles mentions. SPC RAP Mesoanalysis shows 500 J/kg of SBCAPE over the central UP, so it isn`t out of the realm of possibility if enough moisture is present and convection initiates that some thunder is possible, but left it out of the grids due to the high uncertainty in initiation. Sustained warm advection in the low to mid levels will help temperatures recover into the 70s today despite sustained smoke aloft from wildfires in Canada. RH`s fall into the 30s and upper 20s especially across the interior west, though sustained winds around 5 mph and gusts up to 10-15 mph should keep fire weather concerns mostly limited. Overnight, skies should remain mostly clear besides a few clouds over Lake Superior and the far east and the ever-present smoke, allowing temperatures to fall to near 50. Winds over Lake Superior do begin to increase ahead of an approaching front from the north, but widespread PoPs do not enter the region until Tuesday. .LONG TERM...(Tuesday through Monday) Issued at 255 PM EDT MON MAY 22 2023 Upper air pattern consists of a 500 mb trough on the west coast, a trough over Hudson Bay and a broad ridge over the northern and central plains 12z Tue. The ridge amplifies over the plains 00z Thu while troughing amplifies in the western U.S. and troughing moves onto the east coast and the pattern changes little through 00z Fri. Cold front moves through Tue night with a narrow band of moisture and 850-500 mb q-vector convergence. Tue night looks to be the only chance for rain for this forecast. In the extended, the GFS and ECMWF shows 500 mb troughs in the western and eastern U.S. and a ridge across the plains into the upper Great Lakes 12z Fri. The ridge remains over the upper Great Lakes 12z Sat with a rex block setting up 12z Sun with the ridge still over the upper Great Lakes and a closed low in the sern U.S. which remains into Mon. Temperatures look to be above normal for this forecast period. One problem with temperatures though will continue to be smoke from fires in western Canada and this could knock temperatures down a few degrees. Will continue dry for this forecast. && .AVIATION...(For the 06Z TAFS through 06Z Tuesday night) Issued at 1200 AM EDT TUE MAY 23 2023 VFR will prevail thru this aftn at IWD/CMX/SAW as dry air lingers in the lower levels. A cold front will then drop s into Upper MI late aftn/evening, followed by low MVFR cigs. IFR is possible, mainly at SAW where postfrontal nne winds will be more directly upsloping at that terminal. A few -shra will also be possible after fropa at all terminals during the evening hrs. SW to W winds ahead of the front will shift to n to ne after fropa. The westerly winds today at CMX will be gusty to around 20kt, and postfrontal n to ne winds will be gusty to around 20kt at all terminals this evening. An elevated smoke layer, probably at around 10kft, originating from forest fires in western Canada will persist thru today. Expect rapidly improving conditions to VFR at all terminals just beyond this fcst period as much drier air arrives. && .MARINE...(For the 4 PM Lake Superior forecast issuance) Issued at 255 PM EDT MON MAY 22 2023 Winds will remain below 20 knots through Tue morning. Behind a cold front late Tue afternoon, north to northeasterly gusts at up to 25 to 30 knots Tuesday evening through Wednesday afternoon with the highest winds mainly over the west half of Lake Superior. Ridging settling over the area and then the lower and eastern Lakes will keep winds below 20 knots from Thursday through the Holiday weekend. && .MQT WATCHES/WARNINGS/ADVISORIES... Upper Michigan... None. Lake Superior... None. Lake Michigan... None. && $$ SHORT TERM...GS LONG TERM...07 AVIATION...Rolfson MARINE...07
Area Forecast Discussion
National Weather Service San Francisco CA
851 PM PDT Mon May 22 2023 ...New UPDATE, MARINE... .SYNOPSIS... Issued at 1229 PM PDT Mon May 22 2023 Warm temperatures today inland as highs in the interior valleys reach into the 80s. Coastal areas remain cool with stratus at the immediate coast. Cooling starts tomorrow as an upper level trough builds, with temperatures slightly below seasonal averages for the end of the work week before a slight recovery for the beginning of next week. && .UPDATE... Issued at 850 PM PDT Mon May 22 2023 The North/South pressure gradient continues to diminish, now below 6 mb heading toward below 5 mb. The ocean is once again free of clouds west of the Sonoma Coastline, while the Monterey Bay is under a heavy swath of stratus clouds with bases just over 600 feet. Winds remain onshore and breezy around 10 mph. The longwave trough moves southward from the Pacific Northwest on Tuesday and takes of residence for the better part of the week. With it, cold air advection will help cool temperatures compared to the weekend. With its onset on Tuesday, a very weak boundary will pass over the Bay Area. Its strongest signal is in the NAM, but even the most recent HRRR run shows a very, very weak tuft of potential for rain Tuesday morning. There is still low confidence in rain materializing, if it does it will most likely be a drizzle or a sprinkle, and accumulations will be limited. Otherwise, the forecast listed below will persist. DK && .SHORT TERM... (This evening through Tuesday) Issued at 1229 PM PDT Mon May 22 2023 Coastal stratus lingers in patches on the Marin coast and across the coast south of Half Moon Bay, including extensive inland coverage in the Monterey Bay region. Clearing will continue across the region for the rest of the day, but any clearing near the immediate coast will be short lived with stratus building once again this evening, with stratus expected to return quite far inland overnight. The early clearing will enhance daytime heating, and for the last day in the foreseeable future, temperatures will reach the low to mid 80s for the inland valleys, with the most interior areas seeing highs close to 90 degrees. The coastal regions will see highs in the low to mid 60s with the San Francisco Bayshore and higher elevations reaching into the low 70s. An upper level trough starts building along the coast on Tuesday, causing a mild cooldown across the region. Tomorrow`s high temperatures drop to the mid 70s to lower 80s in the inland valleys, with temperatures at the Bayshore dropping to the mid 60s to lower 70s and remaining at the low 60s along the coast. Tonight`s lows will be from the upper 40s to the lower 50s, dropping to the mid 40s in the higher elevations. Model output today shows a very slight chance for convection over the northern reaches of Napa and Sonoma Counties later this afternoon, and again Tuesday afternoon. The NAM has been the most potent model in terms of convection potential with surface cape values in northern Sonoma and Napa counties reaching 1000-2000 J/kg or above. However, the NAM is alone in reaching such elevated values. ECMWF and GFS output suggests that CAPE values will struggle to exceed 500 J/kg. In addition, all models suggest that dry conditions aloft and at the surface will inhibit convective activity. Based on those factors, the likelihood of any convection is limited. At most, a 5-10% probability of convection on both days near Mount Saint Helena and the mountains of far northern Napa County. && .LONG TERM... (Tuesday night through next Sunday) Issued at 1229 PM PDT Mon May 22 2023 The upper level trough continues to build throughout the week with a continued cooldown in temperatures as a result. By the end of the work week, high temperatures should bottom out at or slightly below the seasonal averages. Expect highs around the upper 50s to low 60s along the coast, and the upper 60s to mid 70s inland. Then a modest rebound could see highs in the interior valleys climbing to the upper 70s by the beginning of next week. For the next week, CPC outlooks suggest that, while the signals are weak, the signals we do have suggest a lean towards lower temperatures and higher precipitation than seasonal averages, keeping in mind that for this time of year, climatology would dictate that any measurable precipitation would effectively be above average for our area. The European, American, and Canadian ensemble model outputs all suggest that the trough pattern could persist well into the first week of June. && .AVIATION... (00Z TAFS) Issued at 507 PM PDT Mon May 22 2023 The marine layer depth has compressed a bit since this morning and is now around 1300 feet at Bodega Bay to 1600 feet at Fort Ord per profiler data. With that compression coupled with the northerly pressure gradient increasing again, we`re seeing a thinning out of stratus north of Half Moon Bay airport to the Golden Gate Bridge with no stratus along much of the North Bay coastline. With the incoming trough on Tuesday, there`s a bit of a challenge on timing and height of the lowest cigs overnight. The hi-res NAM model indicates some patchy drizzle possible, primarily along coastal areas including SFO, OAK, MRY, and SNS overnight into Tuesday morning. Vicinity of SFO...VFR expected this evening. As the upper level trough arrives tonight, the marine layer should deepen and bring a return of MVFR stratus arriving sometime between 06-10z then continuing through about 21z...although cigs will gradually increase on Tues morning. Expecting VFR Tuesday afternoon and evening. SFO Bridge Approach...Similar to SFO. Monterey Bay Terminals...MVFR Stratus persists near MRY and lingers just north of SNS. Forecast is for cigs to impact SNS sometime between 03-06z and then both airports will have persistent MVFR into Tuesday afternoon. Patchy light drizzle possible. && .MARINE... (Tonight through next Saturday) Issued at 841 PM PDT Mon May 22 2023 Continued gales impact the northern waters with breezy to gusty winds elsewhere including across the bays each afternoon and evening. Hazardous seas for small craft due to wind driven waves. A series of southerly swells continue, with heights of 2 to 3 feet and periods of 14 to 16 seconds until mid week. Upper level troughing moves into the region tonight and lingers for much of this week. && .MTR WATCHES/WARNINGS/ADVISORIES... CA...None. PZ...Small Craft Advisory from 9 AM to 9 PM PDT Tuesday for PZZ530. Gale Warning until 3 AM PDT Tuesday for PZZ540. Small Craft Advisory until 3 AM PDT Tuesday for PZZ545. Gale Warning until 3 AM PDT Wednesday for PZZ570. Small Craft Advisory until 9 PM PDT Tuesday for PZZ575. && $$ SHORT TERM...DialH LONG TERM....DialH AVIATION...JBB MARINE...JBB Visit us at Follow us on Facebook, Twitter, and YouTube at:
Area Forecast Discussion
National Weather Service Tallahassee FL
1003 PM EDT Mon May 22 2023 ...New NEAR TERM, MARINE, AVIATION, HYDROLOGY... .SYNOPSIS... Issued at 418 PM EDT Mon May 22 2023 A stationary front will continue to support an abundance of shower and thunderstorm activity through Tuesday. The front will start to push south on Tuesday evening, with showers and thunderstorms lingering over the southeast Big Bend on Wednesday. The air mass will be dry enough areawide on Thursday for little if any shower activity. Over Memorial Day weekend, a drier air mass and northeast winds will support little if any rain, and temperatures should run a little below normal, especially at night. && .NEAR TERM... (Through Tuesday) Issued at 1004 PM EDT Mon May 22 2023 Over the past few hours, we have watched easterly surface winds spread all the way west through the Alabama Wiregrass and Northwest Florida. We now have shallow cool air in place. Is interesting to watch the multi-cell cluster of thunderstorms now crossing I-65 between Evergreen and Greenville Alabama. EOX radar shows broad rotation around the 10,000-foot level, which could help sustain this during the late evening and overnight hours as it cross Southeast Alabama and makes headway into Southwest Georgia. Am reluctant to trim back the Flood Watch until we have a chance to see how this round of convection will behave overnight. Though recent runs of the HRRR show it weakening in the hours ahead, am reluctant to bit off on that given the mid-upper level support. By Tuesday afternoon, a stronger push of high pressure down the coastal plain of the Carolinas and Georgia will finally start to push the back door front more squarely south through out Florida counties and into the Gulf on Tuesday evening. The sharpening of the front as it crosses our FL counties will support the heaviest rain there on Tue afternoon. After pockets of heavy rain today, our FL counties will be the focus of flash flood concerns by Tuesday afternoon. Meanwhile to the north over Alabama and Georgia, the push from the northeast will start to advect a deeper layer of drier and somewhat cooler air. Rain chances will be in the process of dropping north of U.S. 84 on Tue afternoon. && .SHORT TERM... (Tuesday night through Wednesday night) Issued at 418 PM EDT Mon May 22 2023 A stationary back door cold front is currently located from near Eufaula AL to Camilla GA to Lake Park GA. On Tuesday evening, this boundary will start to push south, driven south in part by developing surface low pressure off the Southeast U.S. coast. After another active day of convection on Tuesday, Precipitable Water (PW) values will start a sustained drying trend on Tuesday evening, falling in most places below 1.5 inches by sunrise Wednesday. The main exception will be over the SE Big Bend, where that will take until about Wed evening. So the SE Big Bend is the one place where convective coverage on Wednesday will continue to warrant likely PoPs. Elsewhere to the northwest, rain chances will drop off into the 20-40 range for Wednesday. As drier air finally makes it to Cross City on Wed evening and surface dewpoints areawide drop into the 55F-65F range, rain chances will diminish further. && .LONG TERM... (Thursday through Monday) Issued at 418 PM EDT Mon May 22 2023 A blocking pattern will hold a 500 mb low over the Tennessee Valley from Thursday through Sunday, then wandering east across the southern Appalachians on Memorial Day. 500 mb heights over the tri-state area will hover in the 5740-5800 meter range. For reference, 5790 meters is in the 10th percentile of the moving average for this week of the year in the SPC Sounding Climatology. So upper heights will be unseasonably low, and mid-level temps will be cool. We will be under cyclonic flow aloft for most of the weekend. However, the air mass will be fairly dry, with PW values hovering in the 0.8-1.2 inch range. This is typically not high enough to support deep, moist convection, but the low heights and cyclonic flow make it impossible to rule out a weak, low- topped shower, especially in the afternoon hours. Will hold onto chicken 10-15 PoPs for the afternoon hours through the weekend. However, the main message for Memorial Day weekend will be how pleasant it will be. Temperatures will run a couple degrees below normal, especially at night given the drier air mass. Sunshine and fair weather cumulus will dominate the days, with little more than a stray, weak shower. && .AVIATION... (00Z TAFS) Issued at 1004 PM EDT Mon May 22 2023 Overnight, heavy rain over southwest Alabama may move east and affect the DHN terminal. Shallow cool air near the surface will set the stage for low stratus overnight areawide, likely with IFR cigs and possibly with fog. Drizzle is possible at VLD. After sunrise, low clouds will start to lift, albeit more slowly than usual due to northeast winds at the surface. Thunderstorms will develop as soon as late morning and coalesce into clusters during the afternoon. && .MARINE... Issued at 1004 PM EDT Mon May 22 2023 Buoys over the northeast Gulf are observing light breezes and seas of less than 1 foot. Over the next 24 hours, the main concern will be strong thunderstorm outflow wind gusts on Tuesday afternoon, particularly closer to shore. From CWF synopsis...A nocturnal surge of moderate easterlies is spreading across Apalachee Bay this evening. Late Tuesday, a back door cold front will spread across the waters. Following the front, low pressure off the Georgia and Carolina coast will maintain moderate northeasterly breezes through Friday night, occasionally becoming fresh during nighttime hours. && .FIRE WEATHER... Issued at 418 PM EDT Mon May 22 2023 A very wet pattern is expected through Tuesday night with widespread showers and thunderstorms throughout the day and into the evening. Storms could produce erratic gusty winds along with lightning and locally heavy rainfall. Gradually improving mixing heights and transport winds will lead to fair dispersions in our AL and GA districts but, will remain low for the FL districts during the day Tuesday. As rain chances decrease during the day Wednesday, it appears that dispersion indices will begin to increase by the end of the term as the mixing heights are also expected to increase. && .HYDROLOGY... Issued at 1004 PM EDT Mon May 22 2023 Many pockets of heavy rain occurred on Monday. Overnight and early Tuesday morning, the main focus for heavy rain will be across Southeast Alabama into Southwest Georgia, generally west of Albany. By Tuesday afternoon, the heavy rain threat will focus further south... over our Florida and far southern Georgia counties. More pockets of 2-4 inch rainfall can be expected, with flash flooding being a concern. Thunderstorms should settle down on Tuesday night and Wednesday. By Wednesday night, a turn to mostly dry weather will occur, with no additional hydrologically significant rain through Memorial Day weekend. Heavy rain will not be widespread enough for river flooding, through rises within river banks can be expected over the next couple days. && .SPOTTER INFORMATION STATEMENT... Spotter activation is not requested. However, spotters are always encouraged to safely report significant weather conditions when they occur by calling the office or tweeting us @NWSTallahassee. && .PRELIMINARY POINT TEMPS/POPS... Tallahassee 69 79 65 79 / 50 80 40 40 Panama City 71 82 65 80 / 40 60 30 30 Dothan 68 73 61 76 / 70 70 30 30 Albany 67 72 61 76 / 70 70 40 30 Valdosta 68 77 63 77 / 80 70 40 40 Cross City 69 84 66 80 / 50 70 40 70 Apalachicola 74 81 68 78 / 50 70 40 40 && .TAE WATCHES/WARNINGS/ADVISORIES... FL...Flood Watch through late Tuesday night for FLZ007>019-026>029- 034-108-112-114-115-118-127-128-134. GA...Flood Watch through late Tuesday night for GAZ120>131-142>148- 155>161. AL...Flood Watch through late Tuesday night for ALZ065>069. GM...None. && $$ NEAR TERM...Haner SHORT TERM...Haner LONG TERM....Haner AVIATION...Haner MARINE...Haner FIRE WEATHER...Montgomery HYDROLOGY...Haner
Area Forecast Discussion
National Weather Service Las Vegas NV
802 PM PDT Mon May 22 2023 .SYNOPSIS...Showers and storms focus on our northern areas the next couple of days before dry conditions return everywhere on Thursday. An area of low pressure will bring stronger gradient winds to the area on Tuesday and Wednesday. Above normal temperatures will continue through midweek then become more seasonal for the end of the week. && .UPDATE...Thunderstorm activity continues to diminish this evening, with most of the activity confined to areas north of I-15. The remaining storms will continue to decrease through the evening and should end by midnight. Scattered thunderstorms are expected tomorrow, although coverage should be less than what was seen today and be mainly over northern and far western areas of the CWA. The current forecast looks good, and no updates are needed to the forecast grids this evening. && .PREV DISCUSSION... 318 PM PDT Mon May 22 2023 .DISCUSSION...Tonight through Wednesday. An elongated area of low pressure over Washington State evolves into 3 separate disturbances by early Tuesday. Tonight, the low over Washington is forecast to lift northward into Canada while a second shortwave moves south on the backside of this initial low and into Oregon Tuesday morning. A third weaker disturbance is forecast to be near the central California coast by midday Tuesday. While the 2 northern most systems remain nearly anchored in their respective places into Tuesday night, the southern most disturbance is forecast to move into central California and then could combine with a secondary feature spinning off the low over Oregon. This combined system/trough determines weather conditions over the Southwest through the rest of the work week although uncertainty increases as we approach next weekend. Models maintain a connection between the anomalous moisture over our area and a pool of anomalous moisture along the southern California coast. This moisture connection remains continuous over the next 48 hours although the breadth of the connection shrinks as the trough, as a whole, moves east. So what does this actually mean? Well, officially the thunderstorm coverage area for Tuesday is limited to the far northern fringes of our CWA. However, the HRRR is forecasting showers and possibly a few isolated thunderstorms developing Tuesday afternoon across Death Valley and in parts of western San Bernardino County within this aforementioned moisture band. Officially, showers are not in the forecast for these areas but this will need to be looked at when the 00z model data suites arrive. Especially if the vorticity max moving into California near Point Conception Tuesday afternoon can act as a forcing mechanism in these areas. By Wednesday, models forecast the connection between these 2 anomalous moisture regions thinning or separating. The southern most moisture band is still forecast to have PWATs of 120-150% of normal over the Colorado River Valley and Mohave County. The difference being there are no discernible sources of forcing to lift the moisture. Winds are the primary concern for both Tuesday and Wednesday and it needs to be determined whether they will be strong enough to warrant headlines. It`s apparent from the 12z data that widespread windy conditions will develop on Tuesday with gusts in the 20-40 mph range. Wednesday is similar but areas covered by stronger 30-40 mph gusts expands. For either day however, areas where gusts meet or exceed 40 mph remain very localized. Based on the current data, neither day would require a headline. Otherwise, temperatures both days change little compared to what we see today. && Thursday through Monday... Very large differences remain in the model forecasted pattern evolution during the long term, especially heading into the weekend. The NBM has temperatures cooling Thursday into Friday with Friday being the coolest day. A minor warming trend is then forecast over the weekend into the beginning of next week. This trend is largely unchanged from what I was looking at yesterday. Apparently, there wasn`t any clear signal to move away from the previous forecast. && .AVIATION...For Harry Reid...Prevailing southwest winds are expected for the remainder of the afternoon with speeds generally between 10- 20 kts. There will be isolated thunderstorms, mainly over the higher terrain, through the afternoon which could potentially bring varying outflow winds into the valley with gusts up to 30 kts possible. It`s also not out of the question that a thunderstorm could pop over the valley between 21-23z this afternoon, but confidence is too low to include in the TAF. Convection is expected to diminish after 01z with FEW clouds around 10k feet. Thunderstorm coverage Tuesday is expected to be less than today with most of the activity remaining north of the Las Vegas Valley. For the rest of southern Nevada, northwest Arizona and southeast California...South-southwest breezes, primarily for areas along and south of I-15. This results in drier conditions for the Colorado River Valleys. Here, afternoon breezes are expected to be around 10- 15 kts from the south, with gusts of 15-20 kts possible. Isolated thunderstorms are possible elsewhere through the afternoon with gusty outflow winds up to 35 kts and FEW-SCT clouds around 8-10k feet. Otherwise, typical diurnal winds are expected at these sites, with gusty west-southwest winds at KDAG this afternoon. Thunderstorm coverage will be less Tuesday with areas across Nye and Lincoln Counties seeing the better chances. && .SPOTTER INFORMATION STATEMENT...Spotters are encouraged to report any significant weather or impacts according to standard operating procedures. && $$ UPDATE...Planz DISCUSSION...Salmen AVIATION...Gorelow For more forecast information...see us on our webpage: or follow us on Facebook and Twitter