Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 05/14/21

Area Forecast Discussion
National Weather Service La Crosse WI
1040 PM CDT Thu May 13 2021 .SHORT TERM...(This evening through Friday) Issued at 245 PM CDT Thu May 13 2021 Forecast concerns will be how far east showers will advance Friday, clouds, and temperatures. Clear skies this morning allowed a few spots to drop into the 20s (BCK and CMY), otherwise, most locations held in the 30s and 40. Scattered to broken clouds were noted on visible satellite at 18Z, however with increasing southwest winds, temperatures were all in the 60s by 18Z. The WSR-88D mosaic did show a weakening line of storms over southeast South Dakota and eastern Nebraska. Tonight, an upper level jet over Montana/Colorado will dive southeast, gradually shifting eastward across South Dakota and Nebraska toward Iowa and Kentucky/Tennessee. Meanwhile, a 40 to 50kt low level jet increases across Kansas and Nebraska and to a lesser extent around 25kts into southeast Minnesota and eastern Iowa Friday morning. Thunderstorms will re-develop over parts of South Dakota, Nebraska and Kansas and we`ll see showers develop far east along the Missouri River around 06Z. These showers will result from a shortwave dropping southeast in the northwest flow aloft in combinations with the upper level jet support and increase moisture transport with the strengthening low level jet. The stronger frontogenesis and 700 mb warm advection tracks south of the forecast area with weaker forcing across the forecast area. Timesections and soundings show moistening in the 3000-7000ft layer 12-00Z with limited lift. Will continue with isolated to scattered pops. The EC EPS 90th percentile for rain has only a trace to 0.02 west off the Mississippi River through 00Z and only of 50/50 probability of over .01 toward La Crosse. Current convective allowing models are mainly dry through 15Z. The HRRR is the most robust with greater coverage making it to the Mississippi River by 00Z while the RAP/NamNest/ARW focus more over parts of northeast Iowa. With the lack of forcing farther north, will mention sprinkles and have the higher pops over parts of northeast Iowa. The instability and shear are better north and south of the area. With more clouds Friday have highs in the 60s to around 70. South winds should be gusty at times around 20kts for parts of southeast Minnesota and northeast Iowa. .LONG TERM...(Friday night through Thursday) Issued at 245 PM CDT Thu May 13 2021 A series of shortwave energy embedded in the northwest flow aloft will produce periodic chances of showers across the forecast area Friday night into Sunday. Instability is lacking during this time frame across much of the forecast area...storm chances remain low. The 13.12z GFS/NAM show weak moisture transport/convergence and weak forcing with the shortwave energy...especially Friday night into Saturday morning. Higher chances for showers will occur during this time. QPF amounts look to be up to a quarter of an inch...mainly across northeast Iowa and southwest Wisconsin. Main forecast concern Sunday night through Thursday are precipitation chances and temperatures through the period. The 13.12z GFS/ECMWF/GEM are in decent agreement in amplifying upper level ridge over the central United States by middle of next week. With southerly winds and ridge building in over the area...warmer air is expected to advect into the forecast area by middle of next week. The 13.12z GFS/ECMWF are warming 925mb temperatures to plus 15 to plus 20 degrees celsius by 00z Wednesday. This would suggest high temperatures in the upper 70s to middle 80s potentially. However... the deterministic models suggest weak pieces of energy in the south to southwesterly flow aloft to track into the Upper Midwest Wednesday into Thursday. Depending on shower/storm activity and clouds...this may produce cooler temperatures across the forecast area...especially Wednesday into Thursday. && .AVIATION...(For the 06Z TAFS through 06Z Friday night) Issued at 1040 PM CDT Thu May 13 2021 Mostly clear skies overnight will give way to broken VFR clouds Friday as a trough of low pressure approaches the region. A few -shra are also possible after 19z west of the Mississippi (KRST) and by Saturday 00z at KLSE. Some MVFR cloudiness looks likely at KRST after Saturday at KRST. Otherwise, light south winds overnight will become a bit breezy, gusting near 20kt during the day Friday. && .ARX WATCHES/WARNINGS/ADVISORIES... WI...None. MN...None. IA...None. && $$ SHORT TERM...Zapotocny LONG TERM...DTJ AVIATION...DAS
Area Forecast Discussion
National Weather Service Dodge City KS
613 PM CDT Thu May 13 2021 ...Updated aviation discussion... .SHORT TERM...(This afternoon through Friday night) Issued at 1145 AM CDT Thu May 13 2021 Pressure gradients are increasing as of midday, as the cool surface ridge finally exits, and return flow establishes. South winds will gust in the 30-40 mph range this afternoon and early evening. The warming trend continues, with all locations within a few degrees of 70 at max heating, about 10 degrees warmer than Wednesday. All grids are dry for all zones through 7 pm. High based thunderstorm development is expected across Nebraska early this evening, which organizes into a complex with a consolidated cold pool over south central Nebraska and north central Kansas by late evening. Latest HRRR iterations and 12z NAM suggest this activity may clip the far northeast reaches of our zones, and kept some low/slight chance pops in for these locales through the night to cover this possibility. Outflow from this small MCS may pose a strong wind threat tonight (particularly in the Hays/Ellis vicinity), and it will be monitored. Agree with SPC`s reduction in marginal wind/hail probability on the 1630z update, favoring only the I-70 corridor tonight. Elsewhere, south/southeast winds will remain elevated and gusty overnight with a strong low level jet keeping the boundary layer mixed. As such, the warming trend in the minimum temperatures will continue, with most locations near 50 Friday morning. Convective instability finally returns Friday, with warmer afternoon temperatures near 80, and continued moist advection pushing dewpoints well into the 50s. 12z NAM continues to develop MUCAPE around 2000 J/kg by late afternoon. Even though instability returns Friday afternoon, with no triggers for initiation available, all grids are dry through 7 pm. Guidance is in good agreement that convection will need the higher terrain of eastern Colorado to initiate, and then subsequently move southeast into SW KS in the WNW flow aloft. Moderate instability and modest shear will support marginally severe wind/hail from the strongest activity Friday evening, per 5% wind/hail SPC probability. High end/significant severe is not expected. Highest pops remain focused on Friday evening. The warming trend continues with min temperatures sunrise Saturday in the lower to mid 50s. .LONG TERM...(Saturday through Thursday) Issued at 215 PM CDT Thu May 13 2021 There is no shortage of rainfall opportunities in the long term, and a very wet regime is expected with numerous rounds of either stratiform rain/showers and periods of thunderstorms. 12z ECMWF maintains great continuity from its previous runs, keeping the closed cyclone in the vicinity of California Saturday through Sunday. Moisture and instability will be sufficient to support convection both days this weekend, but with the better mid level flow and effective bulk shear displaced well westward, there continues to be kinematic concerns regarding the severity of the expected storms. Although modest for May, the ingredients appear sufficient to support at least marginally severe wind/hail both Saturday and Sunday afternoon/evening. Chance to likely pops from the NBM were accepted, but organization will be a struggle for many storms, with outflow dominant tendencies and heavy rain potential (given the relatively weak flow/slow storm movement). Afternoon highs in the upper 70s and lower 80s, with lows in the 50s over the weekend. 12z GFS/ECMWF continue to show a slow drift eastward of the weak closed low, still over western New Mexico Tuesday morning. At least a transient Rex block attempts to develop, with 12z ECMWF building a 580-582 dm upper high near South Dakota Tuesday. This will slow the cyclone`s ejection to a crawl and encourage a southward track, with ECMWF placing the cyclone near Midland, Texas 7 pm Tuesday. GFS and its ensembles are aligning with this thinking, with its cyclone also in west Texas late Tuesday. This track would clearly keep the warm sector and its associated severe risks well south of SW KS, with any rainfall in our region more stable/stratiform in nature. Healthy pops from the NBM early next week were retained, considering the proximity of the cyclone and its deformation. Afternoon temperatures from NBM/MEX are also trending cooler, given the expected clouds and rainfall. && .AVIATION...(For the 00Z TAFS through 00Z Friday evening) Issued at 613 PM CDT Thu May 13 2021 A cluster of storms over western Nebraska is expected to track southeast into tonight. While there is some uncertainty, some of the latest short term model guidance moves the southwest edge of this cluster through the Hays terminal by around 04-06z. For now will include VCTS along with a tempo group with variable, gusty winds. The southwest Kansas terminals should see southerly winds continue overnight with LLWS developing. Winds at GCK/DDC could also become northeasterly later tonight if outflow from the northern Kansas thunderstorms can make it that far southwest. && .PRELIMINARY POINT TEMPS/POPS... DDC 50 81 55 80 / 10 20 50 40 GCK 49 81 53 78 / 10 10 50 20 EHA 50 83 53 81 / 10 10 30 20 LBL 48 82 53 83 / 10 20 40 20 HYS 50 78 55 74 / 20 20 60 50 P28 51 78 58 80 / 20 20 60 50 && .DDC WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SHORT TERM...Turner LONG TERM...Turner AVIATION...Gerard
Area Forecast Discussion
National Weather Service Gray ME
1042 PM EDT Thu May 13 2021 .SYNOPSIS... A band of showers will cross portions of the region through this evening and again Friday afternoon. Thereafter, warming weather will continue but and we will have to dodge a daytime rain showers and thunderstorms over the weekend as the morning sunshine provides some instability. High pressure will move off the coast early next week before a cold front approaches from the northwest on Tuesday. Cooler conditions will arrive midweek. && .NEAR TERM /TONIGHT/... 1045PM UPDATE... Primary adjustments with this update were to overnight lows. Clouds and showers have dissipated pretty quickly and temperatures will be on their way down again. Not expecting temperatures to get as cold as last night, but we will likely see a run at the freezing mark again in the northern valleys. Outside of there, some upper 30s are possible. 645PM UPDATE... Made some minor adjustments to temperature, sky cover, and precipitation chances. Shower activity is quite sparse and unlikely to get much more numerous. Thunderstorm threat is quite low, so this was removed. Afternoon cumulus has already shown signs of decay, so sky cover has been adjusted downward as well. ORIGINAL DISCUSSION... A weak disturbance will continue to bring a few scattered showers to the region through this evening with the best chance over the mountains. The atmosphere will continue to be unstable with a slight chance for a thunderstorm with gusty winds as well. This precipitation will weaken as we head through the night with the latest HRRR ending any showers after 06Z. Temperatures will drop into the 30s in the mountains with 40s for overnight lows expected over southern and central areas. && .SHORT TERM /FRIDAY THROUGH FRIDAY NIGHT/... A weak short wave will cross the forecast area once again on Friday. This will lead to a few scattered showers and possibly a thunderstorm, mainly with the aid of daytime heating, modest destabilization and CAPE values around 200 J/KG. Heights aloft will be slow to rise during this period. However, H8 temperatures will top out above +4C during the afternoon. With partly sunny conditions, this will allow surface temperatures to reach the lower to mid 70s in most locations. There will be a seabreeze during the afternoon hours as the gradient becomes weak, especially along the Midcoast region of Maine where temperatures will be confined to the 60s for highs. Very dry conditions will continue on Friday with surface dew points in the 20s and 30s. An increasing gradient aloft and increased mixing during the daytime hours will allow for gusty winds as well. Nightfall will once again allow for stabilization and a weakening/dissipation of the showers. We will likely be frost free across much of the region with upper 30s in the north and 40s in the south. && .LONG TERM /SATURDAY THROUGH THURSDAY/... This weekend, broad surface high pressure crests the East Coast, pushing out over the Atlantic early next week with warm and pleasant temperatures. While high pressure provides a fairly quiet weather pattern for a large portion of the eastern CONUS, upper level disturbances crossing to our north through the weekend will provide support for diurnally driven showers and storms. Next week, the main question will be if/when upstream blocking over the Atlantic breaks down and allows for a more amplified patten to develop. Starting Saturday...cumulus and the first showers of the day will pop by mid-morning with strong mixing while temperatures warm through the 60s on their way to the mid-70s over the southern interior, near 70 elsewhere. Between strong mixing and moderately steep lapse rates aloft leading to a few hundred J/kg of tall+skinny CAPE, there will be adequate thermodynamic forcing to produce thunderstorms... especially over the mountains with additional convergence there in the weak-flow regime. Speaking of weak flow, there won`t be much dynamic support for sustained updrafts with 0-6 bulk shear clocking in at 15-25 kts at best. So, am expecting short-lived showers and storms with the stronger cells having potential to produce briefly gusty winds in outflow as storms collapse through a deep mixing layer. Sunday is almost a repeat with the only real difference being a little more upper level support... which should lead to greater coverage of showers that last into the early overnight hours. One mesoscale component to keep an eye on as we near the weekend will be the behavior of the seabreeze... weak surface flow will allow a strong sea breeze to develop, which may then become a focus for convection inland. Elevated instability doesn`t look strong enough to overcome the stability of the sea breeze, so am expecting overall a pretty nice day along the coast - albeit with a cooler breeze coming off the waters. With high pressure settling east out over the waters, a moist onshore flow develops by Monday. The moisture availability could lead to another round of diurnally driven showers and a few afternoon thunderstorms. Beyond that, the model suite is beginning to hone in on a common solution WRT a shortwave tracking across Canada and diving southeastward toward the eastern maritimes early next week. This wave pushes a cold front southeastward across New England around the Tuesday timeframe with rain showers. After that... models diverge greatly when it comes to bringing in another ridge with warming for the second half of the week or keeping cool troughing overhead. && .AVIATION /00Z FRIDAY THROUGH TUESDAY/... Short Term...Mainly VFR conditions tonight. Similar conditions expected on Friday with mainly diurnally driven showers and possibly a thunderstorm bringing MVFR conditions to a few locations. Long Term...VFR prevails at all terminals through the long range with chances for restrictions in afternoon -SHRA/TSRA, mainly Saturday and Sunday but possibly Monday as well. This will be most likely for KHIE/KLEB... and least likely for coastal terminals. Light and variable flow this weekend will yield to onshore breezes each afternoon, certainly impacting coastal terminals but possibly impacting as far inland as MHT/CON/AUG this weekend. && .MARINE... Short Term...Winds and seas will remain below SCA thresholds tonight through Friday night. Long Term...High pressure builds into the waters by the weekend, departing east over the Atlantic next week. Thus winds and seas are expected to remain below SCA thresholds. One exception to the fairly quiescent conditions is the low probability of a stray shower or storm forming over land and tracking out over the waters with the ability to produce briefly gusty winds. The greatest chance of that will be Sunday as a weak cold front drops southward through the region. && .GYX WATCHES/WARNINGS/ADVISORIES... ME...None. NH...None. MARINE...None. && $$ NEAR TERM UPDATE...Kimble SHORT TERM...Cannon LONG TERM...Casey
Area Forecast Discussion...UPDATED
National Weather Service Miami FL
839 PM EDT Thu May 13 2021 .UPDATE... A cold front will continue to move southward through South Florida this evening and should be in the Florida Keys by early Friday morning. This will allow for the ongoing showers and storms over the southern areas of South Florida to slowly dissipate through rest of the evening hours. The weather should remain dry through the overnight hours over South Florida, except for some showers and a few storms over the Atlantic waters. Therefore, POPs will continue over South Florida for the evening hours before going dry for the overnight hours. Rest of the forecast looks good at this time and no other changes are planned. && .AVIATION(00Z TAFS)... VCSH will continue for all of the TAF sites, except for KAPF taf where VCTS will remain until 02Z. After 02Z until 18Z Friday the weather will remain dry, then VCTS for rest of Friday afternoon. The only exception is KAPF where it will remain dry for Friday. Ceiling and Vis will remain in VFR conditions but could fall into MVFR or even IFR conditions with any showers or thunderstorms. && .PREV DISCUSSION... (Issued 354 PM EDT Thu May 13 2021) Mesoscale Discussion (valid through this evening)... Bottom Line: Isolated strong to locally severe storms capable of producing strong gusty winds, heavy rainfall/localized flooding, and small hail will be possible along the east coast metros this afternoon, though large uncertainty remains. Present indications are that this threat will be maximized between 2PM and 8PM today. Technical Discussion: A frontal boundary continues to slowly progress southward across central Florida early this afternoon, with dense cloud coverage mainly confined to areas north of South Florida -- where mid-level height falls/large-scale ascent are being maximized amidst the surface boundary. Ahead of the surface frontal zone, rich boundary- layer moisture (lower 70s dewpoints) will be maintained, and pockets of cloud clearing/thinning will result in diurnal destabilization of the moist PBL -- yielding around 2000 J/kg MLCAPE across South Florida, especially along the east coast where onshore flow will continuously reinforce the inland boundary-layer with moist ocean- modified air. Current mid-level water vapor loops and RAP analysis show strengthening mid/upper-level westerly flow associated with an eastward-advancing low-amplitude upper-trough, and this feature will allow for both continued peripheral adiabatic cooling across South Florida (increasing deep-layer instability and ascent) and strengthening deep-layer wind shear as well. The strengthening deep- layer shear (nearing 35 to 45 knots on the east coast) combined with the above mentioned increasing buoyancy will support loosely organized convection this afternoon -- primarily along the east coast metros -- where strong gusty winds, heavy rainfall/localized flooding, and small hail will be possible. Present indications are that locally backed NNE low-level flow (on the backside of a weakly developing surface low over the Atlantic waters) below the strengthening westerly flow aloft will act to elongate hodographs along the east coast, and these hodographs will remain generally straight through the convective layer. The primarily straight hodographs should support splitting cells and associated cell mergers/messy storm modes, though one noteworthy feature in the forecast hodographs is a slight anticyclonic bow in the low-levels (associated with the NNE low-level flow) which may tend to favor left-movers over right-movers upon cell splits. The presence of both left and right moving cells will introduce the potential for undercutting, which could reduce convective residence time in the favorable surface-based effective inflow layer air. However, if any cells can remain discrete within the favorable surface-based buoyancy, the above mentioned hazards will become more likely. In addition, the cell interactions could also yield localized upscale growth (supported by favorable vertical wind shear) which may also result in locally gusty winds as convective cold pools amalgamate. The above mentioned cell mergers, rich moisture/minimal CINH, and tall buoyancy profiles will support locally heavy rainfall which could lead to isolated flooding along the east coast metros into the evening hours -- especially with repeated rounds of convection. The WPC has placed portions of the east coast metros in a marginal risk of excessive rainfall to account for this flooding threat. At this time, the risk for isolated strong to severe storms appears most likely along the east coast metros from Broward through Miami- Dade County, though if left-movers become established and dominant (as discussed above), Palm Beach County and inland areas could also be at risk of seeing the previously mentioned convective hazards. There is plenty of uncertainty in the convective forecast for today, so be sure to keep up with the latest from NWS Miami. SHORT TERM... Scattered showers and thunderstorms will redevelop during the overnight and early morning hours on Friday over the Atlantic waters. A couple of these showers and storms may affect portions of the east coast metro areas, however, most of the activity should remain offshore. As the surface frontal boundary slowly moves through the region on Friday, mid to upper level winds will start to shift to a west northwesterly direction as the mid level trough axis starts to shift into the western Atlantic. There will still be plenty of lower level moisture to work with on Friday which will allow for scattered showers and thunderstorms to redevelop during the afternoon and early evening hours. The greatest chances of showers and thunderstorms will continue to remain across the east coast metro areas as well as portions of the interior. High temperatures on Friday will generally range from the lower 80s across the east coast metro areas to around 90 over the western half of South Florida. LONG TERM... (Friday Night Through Monday)... High pressure will slowly move eastward from the Southeastern United States into the Western Atlantic Waters as a the stationary front remains over the Florida Straits. This will keep the moderate to breezy easterly wind flow over South Florida during this time leading to some showers over the east coast and the adjacent Atlantic Coastal waters. The only exception to this is on Saturday where the models are showing some deeper moisture working around the high and across the region. This will lead to an increase in moisture across South Florida which in turn will lead to an increase in shower coverage especially over the east coast metro areas. At this time, it still looks to be showers only as the moisture will be in the low levels of the atmosphere. Highs will be in the lower to mid 80s east coast metro areas to upper 80s west coast metro areas each day this weekend with lows in the 60s except around 70 east coast metro areas. (Rest Of Next Week)... The long range models are showing the high to become nearly stationary over the Western Atlantic waters, as the stationary front starts to move slowly northward towards South Florida. At the same time, there could be a broad weak low developing along the front over the Florida Straits and moving northwest into the Southern Gulf of Mexico. This will allow for deeper moisture to work northward into South Florida especially for the middle to end of next week leading to scattered showers and thunderstorms over the region. The long range models are also showing the PWAT values increasing to around 2 inches by end of next week which is at the maximum PWAT values for this time of year. Therefore, there could be some heavy rainfall across South Florida late next week if this trend plays out. Therefore, continue to monitor the latest forecast through the weekend into middle of next week for the potential of heavy rainfall for late next week across South Florida. Highs will be in the mid 80s east coast metro areas to around 90 west coast metro areas each day next week with lows in around 70 except lower to mid 70s east coast metro areas. Heat indices next week will be in the around 90 east coast metro areas to mid 90s west coast metro areas. AVIATION(18Z TAFS)... A frontal boundary will slowly move through the local waters this afternoon through Friday. Scattered showers and thunderstorms will be possible throughout this time frame which could lead to locally higher winds and waves. Marine conditions will gradually deteoriate later tonight and through the upcoming weekend as a northeasterly wind flow develops and increases. At the same time, a northeasterly swell will be moving into the Atlantic waters and will remain in place throughout the weekend. Seas over the Atlantic waters could reach 7 feet through the first half of the upcoming weekend. MARINE... A frontal boundary will slowly move through the local waters this afternoon through Friday. Scattered showers and thunderstorms will be possible throughout this time frame which could lead to locally higher winds and waves. Marine conditions will gradually deteoriate later tonight and through the upcoming weekend as a northeasterly wind flow develops and increases. At the same time, a northeasterly swell around 2 feet will be moving into the Palm Beach Atlantic waters and will remain in place throughout the weekend. Seas over the Atlantic waters could reach 7 feet in the Palm Beach Atlantic waters through the first half of the upcoming weekend. Therefore, an SCA has been issued for the Atlantic waters of Palm Beach County through Saturday evening. BEACHES... The risk of rip currents along the Atlantic Coast beaches will start to increase on Friday and it will remain elevated through the weekend, as a northeasterly flow increases and a northeasterly swell develops in the Atlantic waters. The threat of rip currents should also continue into most of next week, due to the easterly wind flow over South Florida waters. && .PRELIMINARY POINT TEMPS/POPS... Miami 75 84 73 84 / 50 50 30 40 West Kendall 74 85 71 86 / 60 50 40 30 Opa-Locka 74 84 71 85 / 50 50 30 40 Homestead 73 84 72 84 / 60 50 40 40 Fort Lauderdale 75 83 73 84 / 40 50 30 40 N Ft Lauderdale 74 83 73 82 / 30 50 30 40 Pembroke Pines 73 84 71 84 / 50 50 30 40 West Palm Beach 73 84 70 82 / 20 50 30 40 Boca Raton 74 83 72 84 / 20 50 30 40 Naples 72 88 68 90 / 30 20 10 10 && .MFL WATCHES/WARNINGS/ADVISORIES... FL...None. AM...Small Craft Advisory from 6 AM Friday to 8 PM EDT Saturday for AMZ650-670. GM...None. && $$ Update/Aviation...BNB Tonight/Friday and Marine...CWC Friday Night through Thursday...BNB Visit us at Follow us on Facebook and Twitter at:
Area Forecast Discussion
National Weather Service Newport/Morehead City NC
1026 PM EDT Thu May 13 2021 .SYNOPSIS... High pressure remains the dominant feature through early next week. && .NEAR TERM /THROUGH FRIDAY/... As of 1025 PM Thu...Mid-level stratocu continues to stubbornly hug coastal locales late this evening. RAP 700mb analysis suggests this is being driven by weak mid-level Fgen right along the Carolina coastline. Again raised sky cover trends in the short term, expecting only slow clearing now per the HRRR. Temperatures now dropping precipitously with good radiational cooling, and T forecast is on track. Prev disc...Varying amounts of cloud cover now with mid clouds still hugging the coast from coastal Onslow County through the central Outer Banks. Meanwhile, farther inland where most of the day was sunny, a wide area of strato cu has formed with much colder air aloft. The overall trend will be to clear the sky as the clouds along the coast move offshore and the strato cu diminish with the loss of daytime heating. With a clearing sky, very dry air in place and light winds, temps will fall fast this evening and bottom out in the lower to middle 40s inland with 50s along the coast. && .SHORT TERM /FRIDAY NIGHT THROUGH 6 PM FRIDAY/... As of 345 PM Thu...After a chilly start, high pressure across the Ohio Valley will control our weather Friday with plenty of sunshine expected. With a very dry air mass in place (dewpoints in the 40s), temps will recover quite nicely with highs into the middle 70s. && .LONG TERM /FRIDAY NIGHT THROUGH THURSDAY/... As of 345 PM Thursday...High pressure will build south and east from the Ohio Valley Friday into Saturday as weak low pressure remains well to the south of the area. Mid-level heights will build as well. With deeper moisture shunted to our south, skies will become mostly sunny for Friday through the weekend with high temperatures warming well into the 70s, however lows will be chilly, mainly in the mid/upper 40s Friday and Saturday night, then into the 50s by Sunday night. High pressure slides offshore early next week allowing for warmer temperatures and increased humidity levels. Highs by midweek will be into the lower and middle 80s. Despite the increased moisture, the best mid/upper level forcing will remain generally north of eastern NC, and most precipitation will likely be driven by the daily sea breeze. Have opted to just slight chance PoPs for early/middle next week. && .AVIATION /02Z FRIDAY THROUGH TUESDAY/... SHORT TERM /through 00Z Saturday/... As of 745 PM Thu...High confidence in VFR conditions through the period. Scattered cu deck dissipating with loss of heating, leaving clear skies apart from a stubborn mid-level deck hovering over Outer Banks and Crystal Coast. NE winds at 10 kt will become light and variable overnight, and could see some patchy fog mainly south of the Albemarle Sound with moisture advecting off the waters. Cu deck redevelops tomorrow late morning with NE winds around 10 kt or so, gustier closer to the coast. LONG TERM /Friday through Monday/... As of 320 AM Wednesday...High pressure building south from the Ohio Valley will lead to generally clear skies and VFR conditions through the weekend. Deeper moisture will lead to increased cloud cover for Monday, but ceilings should continue at or above 3000 feet. && .MARINE... SHORT TERM /Through Friday afternoon/... As of 345 PM Thu...SCA continues for the ctrl/srn waters. N/NE winds 15-25 kt will through tonight, strongest south of Hatteras, with seas 3-5 ft north and 4-6 ft south. Northeast winds continue Friday 15 to 20, as seas subside a bit by afternoon. LONG TERM /Friday night through Tuesday/... As of 320 AM Thursday...For the coastal waters south of Ocracoke Inlet, winds will be NE at 15 to 20 knots with gusts to 25 knots Friday with seas 4-6 feet. Winds then drop Friday night through the weekend and will be NE 10-15 knots with seas mostly 2-4 feet as high pressure settles along the East Coast. As the high moves offshore Monday, winds will veer to mostly SE, but remain fairly light. && .MHX WATCHES/WARNINGS/ADVISORIES... NC...None. MARINE...Small Craft Advisory until 5 AM EDT Friday for AMZ154-156. Small Craft Advisory until noon EDT Friday for AMZ158. && $$ SYNOPSIS...MHX NEAR TERM...EH/MS SHORT TERM...EH LONG TERM...CTC AVIATION...CTC/MS MARINE...EH/CTC/TL
...Updated Aviation Forecast Discussion...

.DISCUSSION... Issued at 309 PM CDT Thu May 13 2021 Early afternoon analysis showed a weak shortwave trough sliding through the northwest flow aloft, bringing some light showers to portions of northeast Nebraska. These have been on a dissipating trend all day and will continue to do so through the remainder of the afternoon. At the surface, southerly flow/warm air advection was in full swing on the back side of surface high pressure departing to the east. Temperatures as of 3 PM were generally in the mid to upper 60s, though a few spots had cracked that 70 degree mark. Tonight, another shortwave trough will slide southeast through the area, with the nose of the low level jet/moisture transport pointed into central and then eastern Nebraska. This will lead to additional shower development, along with potentially a few thunderstorms given perhaps a few hundred J/kg of MUCAPE sneaking into the forecast area. Would think with such little instability, especially this far east, it would be tough to get much in the way of strong storms, much less severe, but the HRRR has remained persistent in producing some 35 to 45 kt gusts on the northern edge of the convection. While forcing seems decent between the aforementioned low level jet/moisture transport and shortwave energy, along with continued warm air advection, would really expect to see a stronger moisture transport signal or higher MUCAPE values given the strength of the convection depicted by the HRRR (and most of the other CAMs). One "positive" going for potential stronger winds is steep low level lapse rates, but by the time the storms get this far east it may be tough to get any of those stronger winds through the surface inversion. Something to definitely keep an eye on though as we go through the evening. We`ll remain in an unsettled, but warmer pattern through the remainder of the forecast period. A closed low will move onshore in the Friday/Saturday timeframe and shift into the Desert Southwest over the weekend. Meanwhile, a surface boundary looks to set up west to east somewhere near or south of the KS border, oscillating north and south each day while various bits of shortwave energy eject out of the aforementioned low and interact with the boundary to produce showers and storms. Really the name of the game in forecasting the heaviest precip will be finding where that boundary sets up each day, which will likely be impacted by the previous night`s/morning`s convection. Model consensus suggests it stays south of the forecast area, which means we`ll have a tough time getting much in the way of instability this far north. Therefore, wouldn`t anticipate much for a severe weather threat, but will likely see periodic showers with occasional thunderstorms, though no day looks like a washout through at least Tuesday. Otherwise, temperatures look to consistently top out in the 70s for most of the area from Saturday onward. && .AVIATION...(For the 00Z TAFS through 00Z Friday evening) Issued at 625 PM CDT Thu May 13 2021 Showers and thunderstorms expected to move through the area late this evening and overnight, though generally expect VFR conditions to prevail until Friday morning. T-storms, while isolated, could lead to brief MVFR conditions. Powerful downdrafts are possible. Ceilings will trend downward Friday morning and are expected to become MVFR at KOFK. Showers could linger at KLNK and KOMA through the morning, with guidance persistent in developing some visibility reductions near and east of the Missouri River. Otherwise, winds will remain southerly/southeasterly at about 9kts, gusting in the 20 to 25 kt range Friday morning. && .OAX WATCHES/WARNINGS/ADVISORIES... NE...None. IA...None. && $$ DISCUSSION...CA AVIATION...Nicolaisen
Area Forecast Discussion
National Weather Service Riverton WY
448 PM MDT Thu May 13 2021 .SHORT TERM...(This evening through Friday night) Issued at 135 PM MDT Thu May 13 2021 Today continues in the transition pattern between the longwave trough to our east and the ridge to our west. A weak shortwave moving across the north today is bringing virga showers and some cloud flashes across parts of Johnson County and some more organized storms across Montana. Some convective showers and virga showers have also developed along the spine of the Wind River Mountains early this afternoon. Otherwise, not much to discuss in the forecast through tonight. Latest runs of the HRRR have brought increased chances of isolated showers across the north overnight, but there is not much confidence in exact location or timing of these showers. Breezy winds at the usual areas this afternoon will continue until around sunset. Temperatures will continue to be slightly above normal today and tomorrow. Tomorrow, breezy winds will once again occur across the usual areas as the ridge pushes into the region. Winds will not be as breezy as today. Another shortwave will bring chances of scattered showers and thunderstorms through the afternoon. Tomorrow will certainly see greater chances of showers and thunderstorms than today. SPC is going with a general thunderstorm outlook across the region, with the exception of the far southwest part of the state. These showers and thunderstorms will be isolated in nature, so it is difficult to pin down exact locations of the showers. Went with a blend of CAMS and the HRRR to get general PoPs and some greater PoPs across the north to account for showers coming off of the Absarokas and Bighorns. Shower and thunderstorm activity will diminish after sunset when diurnal heating ends. Overnight, mostly cloudy skies and lows staying pretty well above freezing for most areas. .LONG TERM...(Saturday through Thursday) Issued at 135 PM MDT Thu May 13 2021 The northern portion of a splitting trough will pull across the Northern Rockies Saturday and Saturday night. The southern portion will be a cut off low which is progged to settle into southern California by 12Z Sunday. The associated weak cold front is expected to pull across the forecast area Saturday night. A shortwave pulling across the area in the northern stream trough in combination with the right-entrance region of an upper jet and weak instability will give good chances of convection across the area Saturday afternoon and evening. The Convective Available Potential Energy (CAPE) is tall, but skinny which would suggest updrafts would not be too impressive. Overall forcing will much weaker Sunday as the upper low over southern California shifts slowly east into the southern Great Basin. However there enough instability for some diurnal convection especially over and near the mountains. The GFS is most aggressive with convection, but the drier NAM and ECMWF seems to be more reasonable. The southern low will gradually shift east into the Four Corners Region or tad south of that by 12Z Tuesday, and then expected to push into the southern High Plains Tuesday. At the same time the forecast area looks to be in a light and chaotic flow in the mid- upper levels both Monday and Tuesday. There could be a light easterly flow over the east with a weak convergence zone over the far eastern zones. In addition there is also relatively weak instability so diurnal convection remains possible both days, but again the GFS seems to be overdoing the coverage of convection. Late Tuesday into Tuesday night, global models show a trough pushing into the Pacific Northwest. On Wednesday and Wednesday night this trough is expected to swing eastward across the northern Intermountain West and extreme northern Rockies. There is disagreement on how far east/southeast the associated cold front will push across the forecast area, but overall there looks to be chances of convection Wednesday, with possibly dry slotting on Thursday on the southern part of this trough. && .AVIATION...(For the 00Z TAFS through 00Z Saturday) Issued at 430 PM MDT Thu May 13 2021 Very isolated early evening showers are expected across the area with the best chance over the north. Confidence is not high enough to mention at any terminal at the moment. Otherwise, VFR conditions with scattered to broken mid-level cloudiness are expected through Friday morning. Some models show the possibility of showers overnight into Friday morning over the north, but again coverage and confidence is not high enough to include VCSH at KCOD or any other terminal. A much better chance of showers and a few thunderstorms are expected Friday afternoon. Will have VCSH at all terminals Friday afternoon to account for this activity. Breezy west to north winds this afternoon across much of the area will weaken around sunset. && .FIRE WEATHER... Issued AT 135 PM MDT Thu May 13 2021 Smoke dispersal will be good through this afternoon with breezy winds in the usual areas. Tomorrow will see much of the same, though winds won`t be quite as breezy. RHs tomorrow will be between 15 and 20 percent across the south with RHs above 25 percent across the rest of the region. A few isolated showers today mainly across the Wind River mountains and Johnson County off of the Bighorns. Tomorrow will see greater chances of showers and thunderstorms, especially across the north tomorrow afternoon. Saturday will see more widespread showers across the region. Ridging with embedded scattered showers and possibly thunderstorms will continue to be the story into the beginning of next week. && .RIW WATCHES/WARNINGS/ADVISORIES...NONE. && $$ SHORT TERM...Fisher LONG TERM...Murrell AVIATION...Murrell FIRE WEATHER...Fisher