Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 05/18/21

forecast discussion, there will be plenty of dry time as well, so
not looking like a washout by any means. Along with the southerly
flow will be increasing moisture drawn up from the Gulf of Mexico, with precipitable water exceeding 1.25" (+1 to +3 Standard Anomalies/greater than 90th percentile per NAEFS) into the weekend. With warm cloud depths also exceeding 3000m at times, there could be some heavy downpours under any storms that do form, though the lack of a stronger focus and resulting more scattered to isolated nature of convection precludes widespread heavy rainfall. There aren`t a lot of strong signals to latch on to for severe weather in the extended period, but given increasing instability Wednesday through the weekend, will have to keep an eye out for any upticks in deep- layer shear. 17.12Z GFS/Canadian/NAM are showing 30-40 kts of 0-6 km bulk shear with a wave moving through Thursday afternoon, so this might be one such time period to watch, although there are varying amounts of instability to work with in the guidance. Beyond that the flow aloft looks rather weak as eastern ridging nudges just a tad westward toward us. The ridge looks to flatten toward the beginning of next week, but timing/placement differences make predictability low. Temperatures from mid-week into the weekend look mild, with increasing humidity as well. Highs in the 70s and 80s are certainly possible, but one caveat to the warmth (and to some extent instability) will be clouds, as low-level moisture looks plentiful and the possibility of low-clouds at times could temper highs a bit (more like 60s to 70s if low clouds are more extensive than currently forecast). && .AVIATION...(For the 06Z TAFS through 06Z Tuesday night) Issued at 935 PM CDT Mon May 17 2021 Cigs: saturation will be on the increase from the south overnight as upper level shortwave trough approaches and 850 mb moisture transport kicks in. Models all suggest dropping into MVFR (potentially IFR), but differ in how soon that occurs. Consensus mostly by mid/late morning (15-18z) but certainly could be a few hours earlier. Once in, the models suggest that they could hold into Wed. Caveat to all this is the potential start out and/or improve to VFR for a period Tue afternoon. RAP/HRRR bufkit soundings favor this for KLSE, holding the lower cigs to the west/southwest (KRST) initially. For now, will stay the course with bringing MVFR in to both TAF sites at similar times, but something to watch. WX/vsby: scattered to areas of showers should start to spread toward the TAF sites btwn 15-18z, with chances persisting through the afternoon. Might be more miss than hit for much of the time, and what falls looks relatively light. Some hints that drizzle could precede the rain chances if more low level saturation/lower cloud bases could be realized. HREF not excited about vsby restrictions, but a few other models suggest some potential. Will hold onto MVFR with shra/br for the afternoon for now. With responsible shortwave trough exiting north in the evening, expect some decrease in shower activity/areal extent. Mixed messages in the models on whether fog could then become a concern. Going to stick with some MVFR reductions with low saturation and some increase in near sfc moisture (increasing Tds and possible rainfall). Winds: generally looking to hold mostly east/southeast through the period. Some uptick Tue as sfc gradient tightens. A few higher gusts possible, but low cloud cover will inhibit some of that mixing. && .ARX WATCHES/WARNINGS/ADVISORIES... WI...None. MN...None. IA...None. && $$ SHORT TERM...Zapotocny LONG TERM...Lee AVIATION...Rieck
Area Forecast Discussion
National Weather Service Caribou ME
933 PM EDT Mon May 17 2021 .SYNOPSIS... A cold front will cross the area Tuesday. High pressure will build south of the region Wednesday through Friday. A cold front will approach late Friday and stall over the region Saturday. A second cold front will push through the area Sunday. && .NEAR TERM /THROUGH TUESDAY/... 935 PM Update: Despite a lull in shwr cvrg and intensity, a lead s/wv impulse alf well ahead of the main s/wv trof slated toward morn is resulting in a re-surgence of shwrs and even isold tstms late this eve with some left ovr elevated CAPE. Subsequently, we xtnded the mention of isold thunder til mdngt. Otherwise, fcst hrly temps/ dwpts were updated into the late ngt hrs based on trends seen from latest sfc obs with no chgs to ovrngt lows posted at 5am. Prev Disc: Onshore flow tngt will result in a marine layer and the possibility of patch fog along Coastal Downeast late tngt. After midnight, a low pressure system to the north will swing a cold front into the state, starting in the NW and moving SE across the state through the early morning hours on Tuesday. Expected scattered rain showers ahead of the front. The timing of the front still has some uncertainty. NAM and RAP models are in agreement with the cold front entering the region much slower, while the GFS and Euro have the cold front passing throw much faster. Nevertheless, scattered rain showers are expected across the region while the far north should see numerous showers. By the afternoon hours, diurnal heating and instability should support the production of isolated thunderstorms. As the front passes, NW flow will return, pulling in stable, dry air and causing showers to diminish. By the evening, the majority of the shower should be out of the region. Due to the frontal passage and cloudy skies, temperatures should be slightly cooler for Tuesday for the area. Expect NW winds to increase after the front moves through. && .SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY/... This portion of the forecast will be dominated by a powerful upper ridge building over the southeastern US and resulting subsidence. The air mass will be of the dry Canadian variety which makes high temps and dew points the biggest challenge. Went on the high side of guidance for high temps on both days and on the low side of dew point guidance on both days. Fire weather is not a huge concern given light winds and the green up status. Nights will be pleasantly cool with lows in the 40s...and maybe some 30s in the North Woods, but do not foresee any significant frost issues. Offshore winds will ensure the warmer temps right to the coast on Wednesday, but the sea breeze returns Thursday. Thursday may be the warmest day of the week with readings near 80F north of Hancock and Washington counties. Can`t rule out an isolated shower or thunderstorm in the North Woods on Thursday afternoon, but not too concerned given the strong ridging. && .LONG TERM /THURSDAY NIGHT THROUGH MONDAY/... The massive upper ridge over the SE US retrogrades back towards the lower Mississippi Valley and allows northern stream shortwaves to move along the northern periphery of the ridge across Maine Friday into Sunday. The air mass will become moister as dew points rise towards the 50s by Saturday. The first shortwave will offer the risk of thunderstorms Friday afternoon and evening. Went for high temps slightly cooler than Thursday due to the moister air mass, cloud cover and an emerging onshore flow across the area. The associated surface front then stalls over the area Friday night into Saturday with enough clouds to further reduce highs on Saturday to the lower 70s and the continued risk of scattered showers and thunderstorms. A stronger shortwave arrives Sunday and could generate strong thunderstorms if the timing is right. Expect a drier and cooler Canadian air mass to follow for the beginning of next week. && .AVIATION /02Z TUESDAY THROUGH SATURDAY/... NEAR TERM: VFR this evening and tonight. Light SW winds. Possible MVFR in showers and thunderstorms. By early morning Tuesday, BHB possible IFR with patchy onshore fog. Elsewhere, VFR, possible IFR for Aroostook terminals with patchy fog in areas that had rain and mostly clear skies. By Tuesday afternoon, VFR with MVFR in rain and thunderstorms. SSW winds 10-15 kts. SHORT TERM: Tuesday night into Friday evening...Predominately VFR with light winds and just a small risk of fog near the coast Thurs night into Friday morning. There is a chance of thunderstorms Friday afternoon and evening. Friday night into Saturday morning...Chance of thunderstorms, risk of IFR fog/stratus for BHB and BGR, MVFR tempo IFR cigs further north. Light winds. && .MARINE... NEAR TERM: Winds and seas will remain below SCA criteria through Tuesday. Fog will reduce visibility at times for tonight and early morning Tuesday. SHORT TERM: No advisories are expected during the period. Fog becomes a concern Friday evening through Saturday night. && .CAR WATCHES/WARNINGS/ADVISORIES... ME...None. MARINE...None. && $$ Near Term...VJN Short Term...MCW Long Term...MCW Aviation...VJN/MCW Marine...VJN/MCW
Area Forecast Discussion
National Weather Service Austin/San Antonio TX
918 PM CDT Mon May 17 2021 .UPDATE... Quick forecast update. The main change was to adjust PoPs and QPF from now through about 1 am. The highest PoPs and QPF are now centered around Zavala and Dimmit county where ongoing convection is producing a lot of lightning and some moderate to heavy rainfall. Mesoscale models are still all over the place, but the new 00z HRRR and new 00z generally suggest that most areas other than the Rio Grande will stay dry through much of the night. Earlier model runs developed an MCS and brought it across our area during the early morning hours on Tuesday. The 00z HRRR takes the storms across northwest Texas now and forms an MCS out of them and drags that into our Hill Country counties early Tuesday afternoon. It then continues moderate to heavy rainfall across the I-35 corridor and points northward through the evening until around 11pm tomorrow night. The new NAM on the other hand creates an MCS over Mexico late tonight and moves it across Maverick, Zavala, and Dimmit Counties. The model may have picked up on whatever is causing the current convection and may just be running a few hours later. Both models generate a large MCS across the Rio Grande and/or Hill Country late Tuesday night and brings it through our area during the day on Wednesday. For this update have followed the mesoscale models and radar trends, dropping PoPs for much of the I-35 corridor and Coastal Plains through the evening. Have maintained Chance PoPs (around 30%-40%) for the early morning hours across much of the area to cover any potential new development. && .PREV DISCUSSION... /ISSUED 659 PM CDT Mon May 17 2021/ UPDATE... A Severe Thunderstorm Watch has been added for Dimmit, Frio, Maverick, and Zavala Counties. An outflow boundary from convection across the I-35 corridor earlier in the day is interacting with a very conducive environment for storms and has produced one Severe Thunderstorm already that is drifting to the southeast across the eastern portion of Dimmit County. AVIATION... A complicated forecast for the TAFs, especially when it comes to convection. Addressing the easy part in general expect VFR skies this evening across the I-35 corridor. Some localized MVFR clouds have developed over Bexar County for SAT/SSF but do not expect those to last more than an hour or two. With the moist atmosphere in place MVFR ceilings are likely at all TAF sites around 06z and should last through the mid-morning hours on Tuesday. With respect to convection have based the inclusion of PROB30 groups on a consensus of mesoscale models which show convection along the Rio Grande this evening, with a possible second round developing later tonight. These storms will generally move to the east overnight and into the I-35 corridor by the early morning hours on Tuesday. It is important to note that the convective forecast with this TAF package is very low confidence as mesoscale boundaries and small changes will have a large impact on the timing of convection tonight into Tuesday. Winds will generally continue out of the southeast. PREV DISCUSSION... /ISSUED 319 PM CDT Mon May 17 2021/ SHORT TERM (Tonight through Wednesday Night)... An upper level low was centered near the Four Corners area this afternoon. The low level flow was from the southeast and the airmass over South Central Texas remains warm and moist. A line of thunderstorms stretched across the eastern half of the area moving toward the south. These storms have been just short of severe and this activity will continue for the next several hours. The next focus will be out west where we have just issued a Tornado Watch for Val Verde County. Convection has started to initiate over West Texas and the mountains in northern Mexico. Conditions are favorable for severe thunderstorms with tornadoes possible. In addition to tornadoes very large hail is possible this evening. Convection will continue to be likely overnight. Deep moist air is in place with PW values in excess of 1.5 inches across the southern half of the area. This will start an extended period of possible locally heavy rain. The upper and lower patterns will remain virtually unchanged through Thursday morning. As the upper low moves slowly to the northeast over the next 48 hours or so, we expect multiple rounds of showers and thunderstorms Tuesday and Wednesday. There will be ample instability and sufficient deep layer shear for strong to severe storms both Tuesday and Wednesday. The better chances for severe will be Tuesday across the northeastern part of the CWA. Locally heavy rain will continue to be possible. With the multiple rounds of convection we expect rainfall totals to be eight to ten inches along I-35 from Austin through Williamson County. Outside of this area, two to six inches with locally higher amounts is possible as far west as Kerr, Medina, and Frio Counties. Lesser amounts are likely farther west. LONG TERM (Thursday through Monday)... Another upper level low will move onto the west coast Thursday keeping Texas in the unstable southwesterly upper flow through the weekend. While the low level flow will remain southeasterly, the extreme moisture will retreat to the east. This will mean the locally heavy rain threat will come to an end Thursday afternoon. However, rain chances will continue. For the end of the week convection should be more diurnally driven with higher POPs during the daytime periods and lower POPs overnight. It`s a little early for forecasting any severe potential, but this is climatologically the peak of our severe season and the threat may come into better focus over the next few days. && .PRELIMINARY POINT TEMPS/POPS... Austin Camp Mabry 86 71 83 69 79 / 40 40 90 80 80 Austin Bergstrom Intl Airport 86 71 84 69 79 / 40 40 80 80 80 New Braunfels Muni Airport 87 73 85 70 81 / 30 40 80 70 80 Burnet Muni Airport 84 69 81 68 79 / 30 40 90 60 70 Del Rio Intl Airport 94 71 93 72 86 / 10 40 20 30 60 Georgetown Muni Airport 85 70 82 68 79 / 40 40 80 70 80 Hondo Muni Airport 89 71 86 70 80 / 20 50 60 50 80 San Marcos Muni Airport 86 72 84 68 80 / 30 40 80 70 80 La Grange - Fayette Regional 86 73 86 71 81 / 50 30 80 70 90 San Antonio Intl Airport 86 72 84 70 81 / 30 40 80 60 80 Stinson Muni Airport 89 73 86 71 81 / 20 40 70 60 90 && .EWX WATCHES/WARNINGS/ADVISORIES... Flash Flood Watch through Thursday afternoon for Atascosa-Bandera- Bastrop-Bexar-Blanco-Burnet-Caldwell-Comal-De Witt-Fayette-Frio- Gillespie-Gonzales-Guadalupe-Hays-Karnes-Kendall-Kerr-Lavaca-Lee- Llano-Medina-Travis-Williamson-Wilson. && $$ Short-Term/Aviation...Treadway Long-Term...Brady
Area Forecast Discussion
National Weather Service Goodland KS
728 PM MDT Mon May 17 2021 .UPDATE... Issued at 726 PM MDT Mon May 17 2021 Updated the Tonight to Tomorrow time period to provide a smoother transition between current conditions and storms expected to move into the area from the southwest this evening prior to lifting out of the area after midnight with some redevelopment by mid day Tuesday. && .SHORT TERM...(This evening through Tuesday night) Issued at 315 PM MDT Mon May 17 2021 Overview: A deamplifying upper level low, presently situated over the Desert Southwest, will slowly progress eastward across the southern Rockies tonight through Tuesday night. Through Tonight: An MCV (emanating from widespread convection yesterday evening), initially situated invof southern Greeley/Wichita counties at sunrise, currently (as of 21Z) situated invof Goodland.. will continue to weaken/deamplify as it lifts north toward the Nebraska border. Convection associated with this feature has steadily weakened during the past few hours, and will likely continue to weaken.. as activity progresses northward into an increasingly stable/capped airmass. Convection presently developing along the I-25 corridor in southern CO and central/ northern NM is anticipated to merge/coalesce into a NW- SE oriented line this evening.. approaching southwest portions of the area (i.e. Cheyenne county, CO and Greeley/Wichita counties, KS) around 04Z. However, the approaching convective line will encounter an increasingly unfavorable /worked-over/ airmass with northern extent.. and simulated reflectivity forecasts via the HRRR and NAM NEST suggest that rapid weakening is likely thereafter.. with activity more-or-less dissipating by 06-08Z. With the above in mind.. severe weather is not anticipated in the WFO Goodland CWA. Given that ongoing convection associated with the lingering MCV has already begin to weaken.. locally heavy rainfall /isolated flash flooding/ appears unlikely from this point onward. Tue-Tue night: Scattered convection may develop over portions of the area Tue aft/eve.. though recent runs of the HRRR and NAM NEST suggest that coverage is very much in question. Given that the thermodynamic environment upstream of the region will be altered (to some degree) by widespread convection this evening, and that forcing will, once again, largely be tied to mesoscale features (directly or indirectly) associated with convection.. considerable uncertainty persists. .LONG TERM...(Tuesday night through Monday) Issued at 332 PM MDT Mon May 17 2021 The long term period is looking drier than the start of the week with temperatures that are slightly above average. In spite of the drier pattern, chances remain nearly daily for rain and storms. Wednesday continues to see the upper level low that moved in from the west diffuse out into the larger flow as a ridge sets up in the east and a trough sets up in the west. This general upper level pattern then should persist through the remainder of the period leaving the Tri-State area in southwest flow. Near the surface, higher pressure will slowly move in through the remainder of the week. However, low pressure systems may come off the Front Range each day and could increase synoptic lift and rain chances. The air aloft looks to dry out through Friday which should lower cloud cover and chances for precip. However, guidance suggests that moisture gets pulled northward during the weekend though how much is uncertain. What this means is that Wednesday still looks to be a transition day with precip chances decreasing and cloud cover decreasing through the day. There is still a chance for storms and a few could become severe though confidence is not great in that regard. High temperatures are forecasted to be in the low 70`s. Thursday and Friday are looking drier and warmer with high temperatures reaching up into the low 80`s and sunnier skies during the day. There still could be some isolated storms that form with dewpoints reaching the upper 50`s and lower 60`s, but the low synoptic forcing and drier air aloft is expected to lower the overall coverage. Some may become severe with lapse rates approaching 8-9C and MLCAPE getting above 1000 J/KG but this is remains uncertain for now. This weekend and into Monday looks to be similar to the end of the week but with a few changes. First, moisture is expected to move in aloft from the south which would increase moisture available for storms that form though nothing producing extreme amounts. Secondly, the upper level trough is forecasted to move north and east and flatten the ridge. At the same time, lower surface pressure is forecasted to move into the northern Plains. Depending on how far south it moves, the low pressure maybe able to add some synoptic lift to the area. Finally, the cold front mentioned in previous forecasts is looking less certain on when/if it would move through the area with latest guidance suggesting Monday. Given the inconsistencies in the handling of this front and slow movement of the trough, I am currently leaning towards a warmer forecast for the weekend. Temperatures are currently forecasted in the upper 70`s but expect this to vary some as the weather pattern becomes clearer. && .AVIATION...(For the 00Z TAFS through 00Z Tuesday evening) Issued at 534 PM MDT Mon May 17 2021 The scattered showers currently extending along the northwest Kansas and southwest Nebraska border will continue lifting northward across over the next few hours with another area of more widespread showers and thunderstorms lifting northeastward out of southeast Colorado across western Kansas into southwest Nebraska between 06-12Z. Areas of fog are possible overnight. There is a lul in showers expected Tuesday morning with additional thunderstorm development expected generally after 17Z. GLD will see mainly MVFR conditions primarily due to low ceilings through 05Z. After 05Z, conditions will deteriorate and vary between IFR and LIFR due to low ceilings and visibility with fog rain showers with isolated thunder through 14Z. After 14Z, expect low ceilings and LIFR conditions to persist. MCK will drop from MVFR to IFR with intermittent LIFR between 06-19Z and thunderstorms mainly between 09-11Z. After 19Z, MVFR conditions are expected along with scattered thunderstorms. && .GLD WATCHES/WARNINGS/ADVISORIES... KS...NONE. CO...NONE. NE...NONE. && $$ UPDATE...LOCKHART SHORT TERM...VINCENT LONG TERM...KAK AVIATION...LOCKHART
Area Forecast Discussion
National Weather Service Huntsville AL
1057 PM CDT Mon May 17 2021 .UPDATE... For 06Z TAFS. && .NEAR TERM...(Rest of tonight) Issued at 959 PM CDT Mon May 17 2021 Surface high pressure that brought the chilly weather last week has moved east of the Mid Atlantic. A southerly flow rounding its western periphery has helped continue a warmer trend, with high temps earlier today in the mid 70s to around 80. Mid evening temperatures have cooled into the upper 60s to mid 70s with light ESE winds. As of the mid evening, local and regional radars indicated light showers moving to the NE over NW Alabama. While measurable precip has not been noted yet, a trace has fallen so far at Haleyville, with 0.01" in Marion AL and Amory MS in Monroe county. HRRR and RAP output has not been handling this light precip well, as was the 00Z NAM. Radar trends have these showers heading to the NE, while on a diminishing trend. A layer of drier air above the surface was evaporating most of the precip before it reached the surface. Going with continuity and those showers, have kept lower end rain chances going mainly for areas west of I-65. Soundings instability looks too minimal for thunder, so will maintain a thunder free forecast. Lows not as cool as last night in the low/mid 60s looks fine. .SHORT TERM...(Tuesday through Wednesday) Issued at 219 PM CDT Mon May 17 2021 Tuesday looks to house the best shot at the low-end chances for rain for the area for the next 7-10 days. If we don`t see much then, it`s looking pretty bleak for the rest of the extended forecast period for the TN Valley. This is good news for those of you ready for Summer! For the rest of you pluviophiles out there (myself included), this may be the last shot for somewhat appreciable rainfall for a while as the unofficial start of Summer begins next weekend. Short-term models continue to lessen their chances for rainfall tomorrow (again, thunder was removed from the fcst), but what does fall, will dissipate as the day wears on, with the best chances by/before midday Tuesday. Otherwise, the upper ridge to the south begins building N, essentially shutting off any changes for rain while it dominates the weather pattern for the rest of the week/weekend. Temperatures for Tue/Wed will top out in the middle 80s (with morning lows starting out in the middle 60s). .LONG TERM...(Wednesday night through Sunday) Issued at 219 PM CDT Mon May 17 2021 The H5 ridge S of the CWFA begins to build Nwrd and strengthen for the remainder of the week/weekend ahead. With little in the way of rainfall expected thanks to subsidence in place across the area, temperatures will rise into the lower to perhaps middle 90s by this weekend. This is pretty close to climatology for the area, with the first 90-degree day falling somewhere in the last week (or so) of May. Either way, it looks like it should shape up to be a nice (albeit hot) Memorial Day weekend for the area. Morning lows will be mild, only falling into the lower/middle 60s each day. && .AVIATION...(For the 06Z TAFS through 06Z Tuesday night) Issued at 1057 PM CDT Mon May 17 2021 VFR flight conditions are expected to persist through the TAF period at both terminals. Some light showers were seen on radar, but expect those to dissipate by 06z. Breezy southeasterly flow will pick up during the daytime hours on Tuesday, with wind gusts as high as 20kts. Should see a thinning in cloud cover and slackening winds by the evening hours. && .HUN WATCHES/WARNINGS/ADVISORIES... AL...NONE. TN...NONE. && $$ NEAR TERM...RSB SHORT TERM...12 LONG TERM...12 AVIATION...25 For more information please visit our website at
Area Forecast Discussion
National Weather Service Wichita KS
910 PM CDT Mon May 17 2021 .UPDATE... Issued at 910 PM CDT Mon May 17 2021 Loss of afternoon heating has led to most of the diurnally driven cumulus to diminish for the late evening hours. So with loss of the heating, also think chances of diurnally driven showers or storms is diminishing to near zero as well. So plan on removing most of the pops for the evening hours, as latest RAP doesn`t show any low level moisture transport pushing back into KS until well after midnight. Next impulse to round the base of the main upper low, situated over the Rockies, will begin to lift northeast out of NM and towards KS late tonight or early on Tue morning. Lift associated with this next impulse will lead to shower and embedded thunderstorm chances increasing for early Tue morning, and certainly for the daytime hours on Tue. So after this evenings lull, will ramp back up pops for most locations for Tue morning. Ketcham && .SHORT TERM...(This evening through Thursday night) Issued at 315 PM CDT Mon May 17 2021 The periodically wet and stormy weather pattern will continue through the mid-week periods. While an a few showers and storms cannot be ruled out through this evening in the weakly unstable and uncapped airmass, better chances look to arrive late tonight into Tuesday as a more pronounced shortwave upper trof looks to rotate northeastward across the area, ahead of the main upper low moving across the southern Rockies. While timing may be nuanced, another such wave looks to move across the area late Tuesday night into early Wednesday before the main upper trof opens up and lifts northeastward across the Plains Wednesday night into Thursday. The combination of moderate instability and shear at times will give rise to a few strong and perhaps marginally severe storms the next couple of days, though localized, yet transient areas of heavy rainfall will remain the main threats. Temperatures will continue to average near or just a couple degrees below seasonal climo in the rather moist/humid airmass. Darmofal .LONG TERM...(Friday through Monday) Issued at 315 PM CDT Mon May 17 2021 Periodic chances for showers and storms will continue through the weekend and into early next week. However, chances could be squelched or shunted a bit further west for a time, as an upper ridge retrogrades across the lower Mississippi Valley into the Ozarks. This may focus the better chances for deep convection across the high Plains where better meridional flow and instability will exist to the east of the deep western conus upper low. This upper low/trof is progged to lift bodily north and then eastward across the Rockies and northern Plains Sunday night into Monday with perhaps better chances spreading into eastern Kansas again. KED && .AVIATION...(For the 00Z TAFS through 00Z Tuesday evening) Issued at 631 PM CDT Mon May 17 2021 Expect VFR conditions for the remainder of the evening hours, as diurnally driven cumulus clouds dissipate after sunset. As the overnight approaches, low level moisture is expected to increase again after midnight and towards 09-10z/Tue, with CIGS dropping to MVFR and then IFR as the next impulse on the SW flow moves NE out of OK. As this impulse moves northeast, the chance for SHRA will increase. By the daytime hours on Tue, increasing elevated instability may lead to some scattered TSRA as well. So will go with prevailing SHRA and VCTS for most locations for the daytime on Tue. Ketcham && .PRELIMINARY POINT TEMPS/POPS... Wichita-KICT 60 74 61 75 / 50 70 80 60 Hutchinson 58 73 60 75 / 50 70 80 50 Newton 58 73 61 74 / 40 70 80 60 ElDorado 59 73 61 74 / 40 70 80 70 Winfield-KWLD 60 74 61 75 / 50 70 80 70 Russell 57 71 57 76 / 50 70 70 60 Great Bend 58 71 57 75 / 50 70 70 50 Salina 59 74 60 76 / 30 70 80 60 McPherson 58 73 60 75 / 40 70 80 60 Coffeyville 61 76 63 76 / 30 70 80 80 Chanute 60 75 63 75 / 30 70 80 80 Iola 59 74 62 75 / 30 60 80 80 Parsons-KPPF 61 75 63 75 / 30 70 80 80 && .ICT WATCHES/WARNINGS/ADVISORIES... None. && $$ UPDATE...Ketcham SHORT TERM...KED LONG TERM...KED AVIATION...Ketcham
Area Forecast Discussion
National Weather Service Jacksonville FL
856 PM EDT Mon May 17 2021 ...WARMING TREND UNDER BREEZY EASTERLY FLOW CONTINUES... .UPDATE... Breezy onshore flow will continue over the local area through Tuesday with more low level cloudiness and a low chance of spotty, light coastal showers near the Golden Isles and possibly Flagler/St. Johns counties into Tuesday where a couple of convergent bands may set-up. A general warming trend will continue with seasonably warm temperatures ranging from lows in the low 60s coast to upper 50s across inland SE GA, to highs in the low/mid 80s inland to near 80 coast. Shallow patchy ground fog may develop in a few inland locations where wind decouple after midnight tonight, but elevated boundary layer winds and passing clouds will prevent significant fog development. && .MARINE... High pressure ridge will remain to the north of the waters through the week. A long fetch of strong easterly winds will persist with seas remaining elevated. Updated the offshore waters this evening to Exercise Caution due to winds of 15-20 kts and there could be some light showers nearing our outer GA waters later tonight into Tuesday as a convergent band sets up. Rip Currents: High to moderate risk expected through the upcoming week. && .FIRE WEATHER... Elevated dispersion near 20 units will continue near a late afternoon wildfire that developed near Colee Cove in inland St. Johns county (noted on IR imagery this evening). Smoke from this fire will continue stream westward across Clay county. && .PREV DISCUSSION [804 PM EDT]... .NEAR TERM [Tonight through Tuesday]...Easterly flow will persist with high pressure situated to the north. Dry weather will continue with gusty winds especially near the coast. Temperatures will continue to be slightly below average. .SHORT TERM [Tuesday night through Thursday Night]... Deep layer of high pressure will strengthen to the north of the area. A breezy onshore flow will persist and increase bringing a slight increase in low level moisture. Rain chances will be too low to mention as models show a low potential for coastal showers. .LONG TERM [Friday Through Monday]... High pressure ridge at the surface and aloft located to the north on Friday will retrograde southwest through the period. The dry pattern will continue as the airmass remains too dry for precipitation. Near average temperatures will become above average by early next week with daily highs reaching the lower 90s. .AVIATION... [Through 00Z Wednesday] Prevailing VFR conditions under breezy easterly flow will continue through the forecast period under passing cumulus moving onshore with cloud bases primarily 4-5 kft. There could be brief periods of 2-3 kft bases late night and early morning near coastal terminals as well as spotty, light coastal showers, with latest HRRR suggesting this potential near SSI around 10-14z Tue morning. Given low potential of occurrence, refrained from VCSH in the forecast at this time. Gusty easterly flow 20-25 kts picks-up mid-morning Tue, continuing to spread inland toward VQQ/GNV into the afternoon and early evening before weakening after sunset. .FIRE WEATHER...Strong easterly winds will produce high dispersions the next few days. The dry weather pattern will continue with minimum RH values remaining above critical levels. && .PRELIMINARY POINT TEMPS/POPS... AMG 59 83 60 83 59 / 0 10 0 10 10 SSI 68 81 68 81 67 / 10 10 10 10 10 JAX 63 81 65 81 66 / 0 10 10 10 10 SGJ 66 79 67 79 67 / 0 10 10 10 10 GNV 61 84 61 84 61 / 0 10 10 10 10 OCF 61 86 64 85 63 / 0 10 10 10 10 && .JAX WATCHES/WARNINGS/ADVISORIES... FL...None. GA...None. AM...None. &&
National Weather Service Morristown TN
905 PM EDT Mon May 17 2021 .UPDATE... EVENING UPDATE. && .DISCUSSION... Radar shows a few weakening showers/sprinkles still around. The best chance for any measurable rain still looks north. Will leave PoPs/Wx as they are as the diminishing trend depicted in the forecast still looks to be on track. Will just tweak hourly temps and dew points with this update. && .AVIATION... 00Z TAF DISCUSSION. A few showers will be around at times, especially early and late in the period at TRI. Will include vcsh during these times for TRI. If precipitation actually occurs at TRI this evening, then fog will be more likely, but for now will keep the fog out given uncertainty of any precipitation there. Otherwise, there will be varying amounts of mainly high and mid clouds during the period all sites. VFR conditions forecast all sites for the period. LW && .PREV DISCUSSION... /ISSUED 329 PM EDT Mon May 17 2021/ SHORT TERM...(Tonight and Tuesday)... Key Messages: 1) Isolated to scattered afternoon showers and possibly a thunderstorm over the far northeast, but otherwise dry with near normal temperatures. Discussion... Afternoon water vapor imagery along with RAP analysis places a deep low near the four-corners with a shortwave progressing out of the central plains. Further east, weak amplitude ridging continues across the local area. At the surface, a weak front was noted to the north of the area. Despite previous guidance depicting isolated showers and thunderstorms developing, the strength of the H70-H50 ridge likely has inhibited this development thus far. However, continued moisture pooling along with further boundary layer heating could still yield at least a slight chance of shower development through the afternoon hours. GOES16 RGB`s have shown recent increases in cloud tops over the past hour. Can`t rule out a thunderstorm given some weak instability present. This activity will be confined to far NE portions of the forecast area. Tonight will remain quiet as ridging continues across the Southern Appalachians while a weak shortwave lifts quickly NE into the Ohio Valley. Overnight temperatures will be mild with lows in the mid 50s to low 60s. Moisture aloft will continue to promote mostly cloudy skies through the night. On Tuesday, conditions look mainly dry as heights continue to increase over the area. However cannot rule out an isolated shower or two mainly north and east of the Knoxville area. Tomorrow looks like another warm day with highs approaching the upper 70s to low 80s. Diegan LONG TERM...(Tuesday night through Monday)... Key Messages: 1. Mostly dry weather through the extended with just a very small chance of isolated convection across the higher elevations. 2. Anomalously strong ridging will bring much above normal temperatures and many areas getting into the 90s by the weekend. Discussion: The extended period begins with surface ridging centered across the Southern Appalachians and Mid-Atlantic regions with a strong upper ridge across the Southeast. This ridge will become stronger through the week with 500mb heights of 592 to 594 dam centered across the Tennessee Valley by the weekend. This anomalous ridging is near the NAEFS 99th percentile to maximum of the climatological record for this time of year which indicates a reasonable chance of approaching record max temperatures by the weekend. Record max temperatures for the week ahead are below: Daily Record High Maximum Temperatures Date Chattanooga Knoxville Tri-Cities Oak Ridge 05-17 93(1962) 92(1962) 91(1962) 91(1957) 05-18 96(1962) 94(1962) 92(1962) 93(1996) 05-19 96(1962) 93(1962) 91(1962) 93(1962) 05-20 97(1962) 93(1941) 89(1962) 92(1998) 05-21 95(1962) 95(1941) 93(1941) 94(1948) 05-22 96(1941) 96(1941) 94(1941) 92(1962) 05-23 93(1953) 92(1903) 91(1953) 91(1962) 05-24 94(1953) 92(1904) 88(2019) 93(2019) 05-25 95(1953) 93(2011) 90(1953) 93(1953) 05-26 95(2019) 94(1926) 91(2012) 92(2019) With strong subsidence across the area, precip chances will be too low to mention throughout the extended with only a very small (<10%) chance of a few isolated showers across the higher elevations. JB && .PRELIMINARY POINT TEMPS/POPS... Chattanooga Airport, TN 62 80 63 85 62 / 10 20 0 0 0 Knoxville McGhee Tyson Airport, TN 60 79 60 83 59 / 10 20 0 10 0 Oak Ridge, TN 58 79 58 83 58 / 10 20 0 10 0 Tri Cities Airport, TN 57 76 55 81 55 / 20 30 0 10 0 && .MRX WATCHES/WARNINGS/ADVISORIES... NC...NONE. TN...NONE. VA...NONE. && $$
...Updated Aviation Forecast Discussion...

.DISCUSSION... Issued at 245 PM CDT Mon May 17 2021 The main forecast concerns are precipitation chances for the next several days. The following features were noted with the large scale pattern from the 12Z upper air plots. At 300 mb winds were around 70 knots from southern CA into west TX. At 500 mb there was a closed low centered over northern AZ, and there were 12 hour height falls of up to around 60 meters southeast of the circulation. The mid level flow in our area was quite weak (700 mb winds were calm and both KOAX and KLBF this morning) so there was not much in the way of vertical shear. There was a cool pocket at 850 mb over the Great Lakes with slightly warmer air back over the Rockies. Skies have pretty much remained cloudy so far today, and where any breaks have developed, they mostly filled back in fairly quick. Spotty to scattered showers are likely to continue into the early evening, then the coverage should slowly decrease. RAP forecast soundings suggest just enough instability for isolated thunder. Some fog and drizzle could redevelop again tonight, but exactly how low visibilities will get is not certain. We should have winds from 4-8 mph overnight most spots. A weak circulation is expected to be over northwest MO toward sunrise Tuesday, and that may stir up some showers, mainly in southwest IA. More showers could pop up again Tuesday afternoon, but probably with lower coverage than what we expected today. Look for highs Tuesday mostly from about 70 or the lower 70s - possibly 75 at a few spots. By Tuesday evening, the closed low at 500 mb over AZ should have tracked into northeast NM. Models show that system filling as it tracks northeast through mid week, but a decent piece of energy may enhance large scale lift in our area late Tuesday night into Wednesday morning. Will keep POPs fairly high for that scenario. Another weaker area of lift may move across the area late Wednesday night into Thursday morning. By Thursday evening, the 500 mb pattern is expected to feature a ridge over the eastern US and a trough in the west, putting our area in southwest flow aloft. The ridge is expected to retrograde westward a bit toward the Mississippi River valley, with the low remaining out over NV. That increases our heights and puts our mid level flow more south/southwest. Stronger flow will remain farther west until late Sunday or Monday (that seems to be our highest chance of any organized severe weather the next week). After that, the flow trends to more zonal by Tuesday May 26. Highs Wednesday should be mostly 75-80 then look for mainly highs in the upper 70s and lower 80s Thursday through Monday. A few days in there could have some mid 80s. && .AVIATION...(For the 00Z TAFS through 00Z Tuesday evening) Issued at 616 PM CDT Mon May 17 2021 Scattered showers affecting the TAF locations at issuance time with MVFR at KOFK and VFR at KOMA/KLNK. Coverage and certainty of showers diminishes by 02-05z, with IFR conditions developing. LIFR conditions develop 05-10z, and then back to MVFR by 17-19z. && .OAX WATCHES/WARNINGS/ADVISORIES... NE...None. IA...None. && $$ DISCUSSION...Miller AVIATION...DeWald
Area Forecast Discussion
National Weather Service Pendleton OR
845 PM PDT Mon May 17 2021 .UPDATE...Minor edits this evening as forecast remains on track. Breezy conditions to continue tonight and tomorrow as the front passes. Expanded shower potential tonight to cover a larger portion of the Blues, the Blues foothills down into the northern portions of Ochoco/John Day Highlands as the RAP and HRRR are showing some QPF with the front. Otherwise, the big forecast highlight will be the much cooler temps behind the front and with the approaching cold upper level low. Temps Tuesday will be 15-20 degrees cooler than Monday with highs in the upper 50s to 60s in the low elevations and mid 40s to 50s in high elevations. Even cooler as we head towards Wed/Thu. Low temps Tue and Wed night are likely to drop below freezing across portions of the forecast area and Freeze warnings may be needed. && .AVIATION...06Z TAFs...Increasing high level clouds through the evening, ahead of approaching system that pushes through tonight. Skies will become sct-bkn 5-8 kft late this evening and overnight. A few showers could approach the terminals as well, esp DLS/PDT/ALW. Expect variable mid to high level cloudiness tomorrow, with a few afternoon cu buildups. Elevated winds will be persistent 12-20g22-30kts through Tuesday early evening, before decreasing Tuesday night. PREV DISCUSSION... /issued 239 PM PDT Mon May 17 2021/ SHORT TERM...Tonight through Wednesday...Thermal/pressure gradient firmly in place across the Cascades this early afternoon has continued to produce breezy westerly winds through the Cascade gaps and across the Basin into Central OR. Weak cold front pushing ahead of approaching upper level trough will sustain breezy winds through the overnight hours. Initial frontal passage this evening and overnight will bring showers across the Cascades, with chances dropping off steeply east into the lower elevations of the east slopes. Behind the frontal boundary, cooler air will start to filter into the forecast area, with overnight lows dropping into the 40s to lower 50s. As the frontal boundary continues to march east early tomorrow morning, the Blues may see a slight chance of showers, though precipitation will likely be less than 0.05 inches at any point. Shower chances will continue across the Cascades and diminish across the Blues Tuesday as trough axis crosses over the forecast area. Upper level trough overhead will also produce enough instability over western WA and the WA Cascades for a slight chance of thunder in this area. Cooler air will continue to filter into the region with trough passage tomorrow, with snow levels steadily dropping and afternoon temperatures mainly in the upper 50s to 60s. Breezy westerly winds will persist as well Tuesday as tight pressure gradients continue over the forecast area. By late Tuesday, a closed low will begin to form over the PacNW and drop south along the WA/OR coast. Precipitation chances will initially diminish across the forecast area overnight Tuesday, however as upper low pushes south Wednesday morning, shower chances will increase again across the Cascades and northeast mountains. Snow levels will be low enough in the mountains for high elevation snow flurries Wednesday, with accumulations through Wednesday afternoon generally less than half an inch. Wednesday afternoon temperatures will continue the cooling trend and will be a coupled degrees cooler than Tuesday. By late Wednesday, center of the closed low will have moved to the CA/OR border, which will diminish precipitation chances across most of the mountain zones. Lawhorn/82 LONG TERM...Thursday through Monday...Models continue to be in good agreement about the pattern in the long term period with just some minor differences about the location and strength of various features. An upper low and trough will be the dominant player in bringing cool and unsettled weather for the late week into the weekend. Thursday will see the trough overhead with the upper low moving from southern Oregon into Northern California. There will be a chance of light rain showers mainly over the mountains and breezy winds are expected in the afternoon. Friday will see the trough continuing over the area with the upper low moving into central Nevada. There will be a chance of showers in the mountains and a slight chance in the lower elevations with the Columbia Basin mainly dry. Rain amounts will be less than a tenth of an inch. Saturday will see the weakening upper low moving back north into eastern Oregon. The eastern mountains and Blue Mountain Foothills will have a slight chance of rain showers. Sunday will see the upper low weakening further and moving into Idaho and Montana. Rain will be confined to the northern Blue Mountains and Wallowa county. Have added a slight chance of thunderstorms to Wallowa county on Sunday with rain amounts of up to two tenths of an inch. On Monday the upper low will be in Alberta and another upper low will be along the northern British Columbia coast. This will give us a west to northwest flow over the area and dry weather is expected. Snow levels through the long term will rise from around 5000 feet Thursday to around 7000 feet over the weekend. Those venturing into the higher mountains of eastern Oregon could see several inches of snow through the period. Temperatures will start out in the 60s with 50s in the mountains on Thursday then warm a few degrees each day ending up in the mid 70s to lower 80s with mid 60s to lower 70s in the mountains for Sunday and Monday. Perry && .PRELIMINARY POINT TEMPS/POPS... PDT 46 63 40 61 / 20 20 0 10 ALW 50 67 42 65 / 0 20 0 10 PSC 53 70 44 68 / 0 0 0 0 YKM 44 66 34 64 / 10 10 0 10 HRI 49 68 42 67 / 0 0 0 0 ELN 42 60 35 60 / 20 10 10 10 RDM 40 61 32 56 / 10 10 10 10 LGD 44 60 38 55 / 10 20 10 20 GCD 45 63 37 57 / 0 10 10 20 DLS 49 64 41 64 / 40 20 10 20 && .PDT WATCHES/WARNINGS/ADVISORIES... OR...None. WA...None. && $$ UPDATE.......84 SHORT TERM...82 LONG TERM....83 AVIATION.....84
Area Forecast Discussion
National Weather Service Pueblo CO
911 PM MDT Mon May 17 2021 .UPDATE... Issued at 908 PM MDT Mon May 17 2021 ...SEVERE THUNDERSTORM WATCH HAS BEEN CANCELLED FOR PUEBLO, HUERFANO, AND LAS ANIMAS COUNTIES. THE WATCH STILL REMAINS IN EFFECT FOR CROWLEY, OTERO, BENT, PROWERS, AND BACA COUNTIES... -Steward && .SHORT TERM...(This evening through Tuesday) Issued at 344 PM MDT Mon May 17 2021 Main Forecast Concerns/Challenges: 1) Continued flash flooding risk for all the burn scars into this evening. 2) Strong to severe storms will remain possible into the evening, with the highest risk of storms still appearing to be along and south of the HWY 50 corridor. An isolated stronger storm can`t be ruled out to the north though, for the Pikes Peak region and Kiowa county. 3) Increasing chances for snow across the higher terrain through the period. Thunderstorms for much of this afternoon have remained tied to the higher terrain and adjacent locations. Development has remained sub- severe so far, with only a few stronger storms. However, the location of his development has been concerning for the flash flood potential across the burn scars. Think this will continue to be concerning for the remainder of the afternoon into this evening, as focus/moist upslope flow persists. While Decker and Hayden Pass could see some stronger storms with higher rainfall rates, think the most at risk will continue to be the Junkins and especially the Spring Burn scar. Strongest development has been focused right in these areas, and this looks to continue well into the evening. The overall risk should lower later this evening into the overnight hours as the main convective activity pushes to the east. As the upper level system pulls overhead tonight, do think steady light rain will continue over the burn scars but the rates should not be enough to produce any flooding at this time. As noted above, most of the convection has been sub-severe and mainly tied to the higher terrain. However, have begun to note development across the far I-25 corridor. Think this is the beginning of an eastward push of this development, as upper level system and more vigorous mid level energy lifts across the region. Surface trough and boundary are evident across far southern CO, where upper 40s to around 50 degree dewpoint air is located. Meanwhile, an abundance of sunshine and daytime heating has occurred, with steepening low level lapse and increasing MLCAPE values the trend this afternoon. As thunderstorm expands east over the next couple of hours, think any storm along and south of HWY 50 will quickly become strong to severe. Steep mid level lapse rates will continue to support large hail, with an axis of higher DCAPE values situated right along the border supporting damaging winds. Additionally, the highest shear is analyzed here, with latest RAP analysis showing values in the 30-35 kt range. Still think there is a chance for a few weak tornadoes into this evening, as boundary in place could once again serve as an area of enhanced low level helicity. RAP analysis is showing a maximized area of 0-3km MLCAPE and surface vorticity along and east of Walsenburg to Trinidad into far SE CO. This looks to be a persistent signal into early evening, and something to keep an eye on for support of tornadic development. Lastly, upper low moves overhead tonight into Tuesday, and will support decent chances for widespread precip across southern CO. Did increase pops and qpf to reflect this thinking, however, may not be high enough for both. As this system moves overhead, think snow chances will increase across the higher terrain. Did increase snow totals but once again, could be on the lower side. Chances for showers and thunderstorms return on Tuesday, though the severe threat does not appear to be as high. However, instability and moisture look to linger and can`t rule out isolated strong to severe storms Tuesday afternoon across the far southern plains. .LONG TERM...(Tuesday night through Monday) Issued at 344 PM MDT Mon May 17 2021 Main Forecast Concerns/Challenges 1) Dryline scenario eastern plains Friday through Sunday Tuesday night through Thursday...The upper low will be located along the CO/NM border Tue evening, then weaken and gradually lift to the north-northeast through the day Wed. The next storm system to affect the region drops south out of the Pacific NW and into northern CA and NV through Thu. Models indicate that Tue evening there will still be around 1000 j/kg of CAPE across the far eastern plains, so convection will probably linger late into the night before tapering off. On Wed as the low begins to lift, CAPE and shear really drop off, but feel that there will be sufficient available moisture for another round of aftn and evening convection, mainly tied to the higher terrain, and more scattered for the plains. Strong southwesterly flow aloft settles in across the Four Corners for Thu, with a rapid warm-up in max temps and just isolated convection expected. Plan on highs in the mid 60s to mid 70s for most locations on Wed, then 70s for the high valleys and 80s for the plains on Thu. Friday through Sunday...Extended models continue to point to a deep trough setting up over the western third of the US, with the closed upper low remaining nearly stationary over NV over the weekend. This will produce deep southerly flow aloft across the state, with a healthy tap of moisture feeding into CO. The dryline will develop over the eastern plains near the eastern border, but may actually pull west back into CO. This will serve as the focus for strong thunderstorms each aftn and eve. Meanwhile, multiple disturbances within the flow will help fire isolated to low-end scattered convection each aftn across the higher terrain and high valleys. Plan on highs around 70F each day for the high valleys, and in the 70s to around 80F for the eastern plains. This will potentially be another very busy period of weather for southeast and south central CO. Monday...Long range models agree on finally moving the upper low to the northeast, shifting the flow aloft across the Four Corners to a more southwest direction. The dryline should kick east as conditions dry out, with just isolated convection at best forecast. Temps will climb into the lower 70s for the high valleys, and mid 70s to lower 80s for the plains. Moore && .AVIATION...(For the 00Z TAFS through 00Z Tuesday evening) Issued at 344 PM MDT Mon May 17 2021 Active weather will continue across all the sites, as showers and storms and low ceilings will remain possible. As an upper level system approaches, expect showers and storms to continue to develop out ahead of it. Showers with a few thunderstorms have already moved across ALS and think similar trends are possible going into the evening. Thunder chances do look to lower for ALS later tonight, however, do think rain showers will persist for much of the period. Additionally, this added moisture could support some lowering of ceilings through the period. Similar trends expected at COS, however, COS may observe some stronger thunderstorms into the evening. The highest confidence for more prevailing and longer in duration thunder is still at PUB, where stronger storms are expected to occur into early evening. The strongest storms, possibly severe, are once again expected at PUB. Thunderstorm activity should diminish later this evening, though the upper level system will move overhead through the remainder of the period and likely provide a longer duration of light rain for all the sites. In this rain, think MVFR ceilings are possible, especially across COS. Some possibility for IFR ceilings, but confidence is low at this time. && .PUB WATCHES/WARNINGS/ADVISORIES... Flash Flood Watch until midnight MDT tonight for COZ072>075-079- 080. && $$ UPDATE...STEWARD SHORT TERM...RODRIGUEZ LONG TERM...MOORE AVIATION...RODRIGUEZ
National Weather Service Raleigh NC
915 PM EDT Mon May 17 2021 .SYNOPSIS... A series of weak shortwave troughs will move through the area tonight through tomorrow, resulting in periods of cloudy skies as well as a few sprinkles. By Wednesday however, conditions will turn drier and much warmer with temperatures steadily increasing through the weekend. Warm/dry weather should persist into early next week. && .NEAR TERM /TONIGHT/... As of 915 PM Monday... Forecast is on track. Considerable mid and high clouds will continue to streak southeastward over the area, thickest over the NW, all within the right entrance region of the upper jet to our NE and E and along a weakening mid level shear axis. The latest surface analysis shows the core of high pressure still sitting off the Delmarva, while a weaker mesohigh sits just E of the mountains, over W VA into the NW Piedmont/Foothills of NC, separated from the offshore high by a weak inverted trough extending from central SC NE through the I-95 corridor. This weak mesohigh is setting up an in situ wedge event, with enhanced NE flow (albeit weak) over the Triad. Model signals of the degree of stratus and/or fog tonight is varied, but the GFS has sufficient low level saturation and moist upglide through the 290k-295k depth late tonight over the Triad region for patchy lower clouds. With nighttime dewpoints continuing to creep up and continued light surface winds, shallow fog remains possible, mainly over and N of the Triad to RDU, locations that saw a few sprinkles in the last several hours, and over bodies of water. The general muted forcing for ascent and still somewhat limited moisture below 800 mb favors isolated sprinkles or light showers at most for the next few hours over the far N and NW, so minimal changes needed there. Still expect lows from the mid 50s to around 60. -GIH Earlier discussion from 243 PM: Early afternoon water vapor imagery continues to show WNW flow across the Mid Atlantic with a weak embedded shortwave trough making its way through western VA. Regional radar imagery, vis satellite, and surface obs indicate light rain ahead of the trough approaching the NW Piedmont as of 18Z (relatively close to previous HRRR and HREF projections for this time of day). Conditions remain dry elsewhere but cloud cover has started re-developing area-wide. For the rest of the afternoon/evening hours, thermodynamic parameters are largely unsupportive of convection across the area, although a few sprinkles or light showers cannot be ruled out. Surface and mixed layer instability is virtually non-existent given relatively dry air in the boundary layer and cooler than normal temperatures from extensive cloud cover. While there is some elevated instability to work with, it is meager at best (100-200 J/KG MUCAPE) and is mainly south and west of the area (well displaced from the trough). While it`s possible that there could be a rumble or two of thunder, that should be the exception and not the rule. Despite the less than favorable BL, showers presently across VA should be able to make it into NC late this afternoon/evening, but will struggle to hang on. I will maintain the idea of 30-40 PoPs mainly along and north of I-85, with only 10-20 PoPs elsewhere. While some guidance is suggesting isolated showers overnight, lack of a strong forcing mechanism should limit areal coverage after midnight. Where rain does occur this afternoon/evening, moisture pooling along with light/vrb winds could allow for patchy fog development. We should have enough low/mid cloud cover overnight to preclude widespread/dense fog but I felt it was worth a mention in the forecast nonetheless. Temperatures tonight should bottom out in the mid/upper 50s. && .SHORT TERM /TUESDAY AND TUESDAY NIGHT/... As of 243 PM Monday... WNW flow aloft will continue on Tuesday with yet another weak shortwave trough forecast to move through the flow and into the Mid Atlantic. Similar to today, thermodynamic parameters are largely unfavorable tomorrow afternoon and the areal coverage of showers that develop should be even less than today. Mid level height rises and increasingly warm temperatures aloft should further preclude widespread shower/thunderstorm development. Opting to include only a slight chance mention of showers tomorrow afternoon along and west of I-85, but barely (15-20 percent PoPs at most). Any showers that make it into the area should quickly dissipate by evening, with gradually eroding cloud cover overnight. Temps tomorrow should generally hit the mid/upper 70s, with lower 80s to the south. Lows should once again fall into the mid/upper 50s. && .LONG TERM /WEDNESDAY THROUGH MONDAY/... As of 243 PM Monday... In the upper-levels, a large omega ridge will spread from the Southeast to the Great Lakes region through the end of the work week. The ridge will then weaken across the Carolinas and build towards the Mid-Mississippi Valley this weekend, providing northerly flow across our region, and then weaken early next week, shifting flow to more northwesterly. At the surface, high pressure along the Mid-Atlantic/NC coast Wednesday will slowly move across NC and into the TN Valley by Friday. The ridge will weaken over the lower Mississippi Valley into early next week as a coastal trough develops along the NE/Mid- Atlantic Coast. The aforementioned pattern will yield increasing temperatures and dry weather from ridging and subsidence aloft, with highs increasing from the low to mid 80s on Wednesday to the upper 80s to low 90s by Saturday and possibly the low to mid-90s by Monday. Although the increasing temperatures will make for quite hot weather, dewpoints in the 50s will prevent it from feeling too muggy and help lows radiationally cool to the 50s for the end of the work week and the 60s for the weekend into early next week. Precipitation may return for the middle of next week, however confidence remains low at this time. && .AVIATION /00Z TUESDAY THROUGH SATURDAY/... As of 840 PM Monday... VFR conditions at all sites for most of the TAF period. A few scattered showers may try and make it into INT/GSO as well as RDU tonight, but precip intensity should be light enough not to affect vsbys. Any showers that manage to develop near INT/GSO will likely remain elevated and not reach the ground. Elsewhere at RWI/FAY, confidence is not high enough to include a mention of showers at all, so those sites have been left dry. Any showers that develop should be over with by 08Z. For those sites that do manage to get showers tonight (INT/GSO/RDU), there is a low possibility of MVFR fog/stratus early Tuesday morning. Extensive cloud cover should prevent conditions from dropping below MVFR but some haze is certainly possible before daybreak. Conditions will improve to VFR by 15z Tuesday morning. Looking beyond 18z Tue, there is a possibility of non-VFR weather early Wednesday morning due to lingering fog. Mainly VFR weather expected Wednesday afternoon through Saturday. && .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Leins NEAR TERM...Hartfield/Leins SHORT TERM...Leins LONG TERM...JJT AVIATION...Leins/GIH/AS
Area Forecast Discussion
National Weather Service Tucson AZ
257 PM MST Mon May 17 2021 .SYNOPSIS...A storm system will bring cooler temperatures and gusty afternoon winds today, along with a chance of thunderstorms with most favorable locations in the mountains northeast of Tucson. High pressure will heat things back up Wednesday before another system brings gusty winds and a few degrees of cooling to end the week. && .DISCUSSION...A low pressure system currently near the 4 corners region has brought some gusty winds and unseasonably mild temperatures to SE AZ today. It`s also generating some thunderstorm activity along the Mogollon Rim north of the area. Over the next 24 hours the low will slowly push across northern New Mexico with surface winds relaxing toward normal diurnal trends and temperatures already climbing back toward seasonal values for mid May. Meanwhile, a modest moisture increase combined with a weak impulse rotating around the back side of the low from the north will bring a decent chance of thunderstorms to the mountains of Graham and Greenlee county Tuesday afternoon. Most larger scale deterministic models don`t do much as far west as Tucson, however it should be noted that HRRR and University of AZ WRF runs are showing a chance through the Tucson area as well. Ensembles appear to be tamping this down too much so we`re going to blend 10 to 15 percent chances into eastern Pinal and Pima counties as well. By Wednesday a shortwave ridge will push temperatures back to several degrees above average. Another system digging into the Great Basin the second half of the week will bring back gusty winds Thursday and Friday, along with a few degrees of cooling Friday. It looks like this one is going to remain further north as a strong broad ridge takes hold across much of the southern tier of states and the storm track retreats northward. && .AVIATION...Valid through 19/00Z. FEW-SCT mid level clouds W and N/NE of KTUS until 18/04z otrw SKC thru 18/14z. SCT mid level clouds once again aftr 18/15z with a slight chc of -shra. Winds W/NW 10-15 kts gusting 20-25 kts thru 18/04z then again aft 18/15z. Winds at other times terrain driven with speeds 5-10 kts. Aviation discussion not updated for TAF amendments. && .FIRE WEATHER...A weather system lingering over the area through mid-week will bring a chance of mainly dry thunderstorms to the White mountains this evening and then again Tuesday and Wednesday afternoon. Elsewhere from Tucson east there is a slight chance of showers on Tuesday. Winds will be breezy today and Tuesday mainly from Tucson eastward. Wednesday winds will be elevated to the west and east of Tucson. Wind speeds pick back up Thursday into Saturday with brief and localized fire weather conditions possible in Cochise County Friday and Saturday. Minimum RH values will be 10-15 percent for most locations through Thursday then drop into the single digits Friday into the weekend. && .TWC WATCHES/WARNINGS/ADVISORIES... None. && $$ Visit us on Facebook...Twitter...YouTube...and at