Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 06/26/20

Area Forecast Discussion
National Weather Service Birmingham AL
659 PM CDT Thu Jun 25 2020 .UPDATE... For 00Z Aviation. && .SHORT TERM... /Updated at 0128 PM CDT Thu Jun 25 2020/ Through Tonight. Scattered to numerous showers and storms continue across the eastern half of Central Alabama as of early this afternoon. So far, we`ve been able to achieve modest diurnal heating with widespread clouds, but most locations have been able to rise into the lower 80s as of the 1pm hour. Coverage of showers and storms is still expected to be widespread as we go into the late afternoon and early evening hours. A few strong storms certainly can`t be ruled out, especially farther south with a bit more surface based instability and 0-6km bulk shear of 20 to 25 knots could sustain a few more updrafts. Additional showers and storms are expected to develop to our southwest and move northeast through the afternoon and evening. PoPs have been updated to reflect that thinking, keeping likely PoPs in the forecast for most locations through 10pm. At least scattered activity can be expected to continue through the overnight hours with muggy overnight temperatures. 56/GDG Previous short-term discussion: /Updated at 0340 AM CDT Thu Jun 25 2020/ Today and Tonight. Mesoanalysis depicts a longwave trough across portions of the Northeast CONUS with an upper-low spinning just south of Hudson Bay, and an associated trough axis extending into the OH and TN Valleys. Farther south, anticyclonic flow wraps around a subtropical ridge centered near the FL Peninsula. A previous shortwave trough just to our west and southwest has weakened and elongated, though a weakness in mid-level heights is still observed near this area with embedded convective vort maxes across the western Gulf. Overall, this configuration continues to provide a pipeline of tropical moisture across much of the Deep South as low-level flow trajectories remain situated to advect Gulf moisture into the area. Low overcast and patchy fog will linger into early this morning as a result. Isentropic ascent and confluent zonal flow below 500 mb will provide a corridor of showers and eventually thunderstorms across Central Alabama later this morning and into the afternoon. PWs remain in the 1.6-1.9" range as indicated by RAP mesoanalysis and recent 00Z RAOBs, with near-saturation through much of the troposphere (higher PWs are south and southwest still yet). Aided by modest diurnal heating, PoPs steadily increase into the afternoon and evening, but sporadic activity including a rumble of thunder can`t be ruled out across the area this morning as well. Low stratus overcast should inhibit convective activity until mixing can occur later today, however. Overall behavior of thunderstorms should be more tame as compared to yesterday as the environment lacks low and deep-layer kinematic support for stronger/briefly organized updrafts, as well as relatively muted buoyancy with abundant mid/upper-level cloud cover. However, there`s slightly better flow progged to stretch across the southern half of the area today. This could promote a few multicell clusters later in the convective life cycle, but this same area also remains on the lower end with CAPE/DCAPE. A few pockets of better sunshine may manifest across the area which could increase low-level lapse rates and instability a bit, but confidence/predictability on this is low. All things considered, another generous coverage of rain is forecast, with high temperatures in the 80s. I bumped temperatures down a tad overall, though any extra sunshine here and there could ruin this adjustment in spots. Shower and thunderstorm coverage and intensity should wane throughout the evening with lingering showers overnight. Lows should fall into the mid 60s to near 70. Friday afternoon. We may get a bit of a break from the day-to-day widespread rainfall on Friday as guidance suggests positioning of the subtropical ridge farther northwest, generally closer to our area. Anticyclonic flow aloft and slightly drier air has led to PoPs being truncated to <40%, with best chances north of US Hwy 80 where westerly to northwesterly flow aloft remains a little more intact, just on the northwestern periphery of the ridge. Warmer conditions are expected with slightly less cloud cover, as well as drier air above 700 mb. We`ll keep an eye on thunderstorm activity during the afternoon since this could support a few stronger convective downbursts, even though PoPs are lower. Highs are forecast in the mid 80s to lower 90s. 40/Sizemore .LONG TERM... /Updated at 0150 PM CDT Thu Jun 25 2020/ Saturday through Thursday. Overview: Expect chances for showers and thunderstorms to remain highest during the midday through early evening hours but a few lingering showers and storms will remain possible overnight through the period. Features: Upper ridging will become positioned over the Eastern Gulf of Mexico on Saturday while diffuse troughing moves into the area from the northwest. A longwave trough over the Ohio River Valley Region will move east over the East Coast portion of the country on Sunday. The height falls will help to confine the upper ridging to our southeast further south into the the South Florida and Southeast Gulf vicinity. Meanwhile, Longwave ridging will amplify and build into the Mississippi Valley from the Western Gulf Coast northward through Wisconsin and Minnesota. Expect height rises to develop over the area Sunday and persist into the day on Monday. Higher heights will develop aloft over Northeast Mexico and into South Texas Late Monday into Tuesday as heights locally begin to descend with the weakening of the ridging aloft. A closed upper low will dive southeast out of Eastern Canada into New England and height falls are expected down the spine of the Appalachians through the Carolinas and into Georgia Tuesday into Wednesday. Heights will also fall over the Mid Mississippi River Valley region in response to a potent closed low positioned over Montana Tuesday into Wednesday. Expect the area to remain under the influence of a weakness aloft into the day Wednesday and continuing into the day on Thursday. Toward the surface. expect weak high pressure toward the surface to nose into much of the area from the southeast on Saturday and persist through Monday. A weak front is progged to move south from the Ohio River Valley region into the Tennessee Valley region from Tuesday into Wednesday and may become positioned across our northern counties by Thursday next week. Forecast: Shower and storm chances will be lowest on Saturday with isolated activity across the area as the upper level ridging is in close proximity to our southeast while height falls will occur to the northwest. An increase to scattered activity Sunday through much of the upcoming work week with the gradual falling heights aloft as ridging weakens over the area. A weak surface front is forecast to move south toward the area from the Ohio River Valley Region Wednesday into Thursday, further supporting higher chances for shower and thunderstorm activity. Overnight lows will remain in the mid to upper 60s north and east to readings in the lower 70s west and southwest. Daytime highs will remain in the range from the mid to upper 80s north and northeast to values in the lower 90s south and southwest. 05 && .AVIATION... 00Z TAF Discussion. Currently, there are some scattered showers and storms across eastern portions of Central AL with a couple lines of strong to marginally severe storms moving into western AL from MS. These lines of storms should eventually merge and continue eastward across the western half of the forecast area. Visibilities may be reduced briefly due to heavy rainfall. There`s still some uncertainty as to when the line(s) break up/dissipate so have only carried VCTS at ANB/ASN/MGM/TOI for now. Amendments may be needed throughout the evening. Most of the current activity should dissipate or move out of the area by 06Z, with only some isolated activity possible in the north overnight. Widespread fog development is not anticipated, and ceilings should remain VFR through the period. 19 && .FIRE WEATHER... Tropical moisture will keep humidity and rain chances quite elevated through this evening with scattered to numerous showers and thunderstorms expected, particularly during the afternoon and early evening. Winds remain light and variable this morning though favoring the southwest and becoming 5-10 mph by the afternoon. Rain chances decrease somewhat by Friday and into the weekend, though minimum RH values remain above 50-60% with at least scattered rain activity forecast each afternoon. && .PRELIMINARY POINT TEMPS/POPS... Gadsden 68 86 66 86 67 / 50 40 10 30 20 Anniston 68 86 68 87 68 / 50 40 10 30 20 Birmingham 70 88 70 88 71 / 60 40 10 30 20 Tuscaloosa 69 88 70 87 71 / 90 30 10 30 20 Calera 69 87 68 87 69 / 70 30 10 30 20 Auburn 68 86 69 88 69 / 50 20 10 20 20 Montgomery 70 89 70 90 71 / 60 20 10 20 10 Troy 70 91 70 92 71 / 60 20 10 20 10 && .BMX WATCHES/WARNINGS/ADVISORIES/... None. && $$
Area Forecast Discussion
National Weather Service Denver/Boulder CO
546 PM MDT Thu Jun 25 2020 .SHORT TERM...(This evening through Friday) Issued at 324 PM MDT Thu Jun 25 2020 Becoming a relatively active thunderstorm afternoon day across Colorado, but so far storms are mainly on the weaker side with impacts of strong winds, brief rain and possibly some small hail. Surface dewpoints have mixed out into the 30s across the urban corridor and mainly 40s over the Eastern plains resulting in surface based CAPE generally under 1000j/kg. Storms will be outflow and boundary driven this afternoon with one convergence boundary draped across Lincoln and Washington counties, while several outflow boundaries have worked southward out of Weld and Larimer counties. Expect most storms to be under severe limits but can`t rule out a few severe storms with high winds over the far eastern zones. For tonight, a weak cold front will move southward across the plains from 04-07z as winds shift to the north. Increasing low level moisture is expected behind the front and even some possible low stratus late tonight through Friday morning. A few showers and storms may still be ongoing given some frontal lift expected until later tonight. For Friday, temperatures will be cooler behind the front with high temperatures around 80 degrees. The big question will be how much thunderstorm activity we get and the potential for strong or severe storms? Latest NAM soundings show very stable airmass and strong inversion 700mb until late afternoon and then most storms will be confined to elevated terrain of the Palmer Divide with near zero chances over Denver. The high resolution HRRR on the other hand is rather bullish and sending a whole line of convection marching from west to east over the whole plains after 19z. This seems excessively bullish and think it may take a while for convection to get going on the plains. For now will play a bit in the middle but focus the higher pops over higher terrain and for a mid/late afternoon target time of initiation. If and when storms do fire there will be ample CAPE of 1500j/kg and sufficient mid level flow for a few severe storms with damaging winds and hail the main threats. Moisture levels also are up with precipitable water values progged to be around an inch by late afternoon over much of the plains. .LONG TERM...(Friday night through Thursday) Issued at 324 PM MDT Thu Jun 25 2020 Model discrepancies continue Friday night as the wave of convection pushes east across the plains. Will keep the chance to likely PoPs across the plains during the evening and then exit it out after midnight. There still may be some lingering storms over the far corner into the early morning hours. Storms during the evening will continue to have the possibility of being strong to severe, east of a line from Cheyenne to Last Chance. A surface lee trough will begin to develop along the urban corridor overnight to flush out the higher dewpoints to the east. The upper trough over Utah and down into Arizona Saturday morning will move east over the state Saturday. Look for slightly drier and slightly warmer conditions across the area, with another round of afternoon and evening thunderstorms. Could still see some strong storms over the far eastern plains, as CAPES will be 1000-2000 J/kg, depending on whether you`re following the weaker GFS or stronger NAM. Hail and strong outflow gusts would be the main issues. Sunday temperatures will be increasing as flow aloft turns southwesterly from a large Pacific trough dropping into the Great Basin. Afternoon and evening storm coverage will be less, as well as the strength as the best moisture moves north and east. Likely will only see a few isolated storms over the high country and that is it. The upper trough will slow its movement Monday before it starts to lift northeast. Temperatures will likely stay similar to Sunday`s readings, and moisture will slightly increase, but still staying isolated to scattered in coverage mainly over the high terrain. The bigger concern will be fire weather as southwesterly winds will be increasing as the jet ahead of the upper trough moves overhead. Tuesday should be cooling as the upper trough will move overhead and bring lower heights. Better storm coverage but weak winds aloft will result in better chance for wetting rains. Northwesterly winds on the backside of the trough Wednesday should bring even cooler temperatures with more shower and storm coverage. Upper ridging will then move up from the south for the rest of the work week for warmer and drier conditions. && .AVIATION...(For the 00Z TAFS through 00Z Friday evening) Issued at 541 PM MDT Thu Jun 25 2020 Afternoon showers and thunderstorms have died out, with another round in the mountains to move out to near TAF sites before sunset. Multiple colliding outflow boundaries make wind forecast difficult, with low confidence in wind direction through this evening. Toward 05-06z timeframe a weak front will shift wind around to the north for a few hours, then return to south then east. Potential for MVFR cigs in the 08-12z timeframe, then improving to VFR after 12z. Afternoon showers and thunderstorms on Friday again, with variable wind and gust potential to 20 to 30 kts. && .BOU WATCHES/WARNINGS/ADVISORIES... None. && $$ SHORT TERM...Entrekin LONG TERM...Kriederman AVIATION...Hanson
Area Forecast Discussion
National Weather Service Boston/Norton MA
1009 PM EDT Thu Jun 25 2020 .SYNOPSIS... Dry weather and comfortable humidity levels are anticipated most areas tonight. A few showers/thunderstorms will be possible tonight into Friday, but dry weather will dominate. A warm front brings higher humidity levels Saturday with rain in the morning, then a potential for scattered stronger thunderstorms Saturday afternoon. Less humid Sunday, but with pop up showers and thunderstorms near the terrain, dissipating after sunset. Turning cooler with daily rain chances into midweek, but not expecting a washout on any one day. && .NEAR TERM /UNTIL 6 AM FRIDAY MORNING/... No major changes to the ongoing forecast this evening. Minor tweaks to timing for showers across southern New England tonight. Also brought temperatures back in line with observed trends. 720 PM Update... Made some minor adjustments to the going forecast to sharpen timing of onset of cloudiness/showers towards the South Coast and Cape Cod/Islands. Though generally quiet for most, there are two main focus areas tonight for shower possibilities: one is across a small area in northwest MA stemming from weakening heavy showers/storms over the Catskills into east-central NY. These storms are moving out of the better convective instability, which are also waning with daytime heating coming to an end. Most-unstable CAPE values decrease markedly with eastern extent with T-Td spreads some 30 degrees. Did increase sky cover in western MA thru 02z - light showers could briefly clip areas such as Hawley, Charlemont and Rowe but expect that by mid evening this threat is over. Didn`t think the chances necessarily are great enough to warrant mentionable PoP for this small area. The other area, with somewhat better prospects for showers, is after midnight and early-Fri AM towards the South Coast, parts of southeast MA and the Cape mainly S of Highway 44. Guidance seems to want to bring the cluster of showers/storms now over the Jersey Shore northeast ahead of the trough aloft. Dewpoints rise enough associated with this that CAPE values on the RAP accordingly rise around 500-750 J/kg; not terribly unstable, but enough to include isolated thunder or rumbles thereof for these areas. Dry conditions elsewhere with prospects for radiation fog nil. Lows will range from the mid to upper 60s across southeast and east MA into a good part of central and southern RI and the Hartford area. Upper 50s to lower 60s across the remainder of the interior. Previous discussion... Shortwave from the Great Lakes sweeps east and approaches New England. The supporting upper jet remains over the region through the night with the right entrance region over Southern New England. Cold advection at 500-mb helps destabilize the airmass. Surface dew points increase during the night. Put it all`s not terribly impressive, but enough to support scattered showers during the overnight. Stability parameters suggest a parallel chance of thunder. Aside from the scattered showers, a dry night. Dew points in the upper 50s to mid expect min temps in the upper 50s and 60s. && .SHORT TERM /6 AM FRIDAY MORNING THROUGH FRIDAY NIGHT/... Friday... The shortwave and colder air aloft move through during the morning, then move off to the east in the afternoon. A second shortwave then moves through during the mid-late afternoon. The morning shortwave will be supported by cold air destabilization and a deeper moist column. The afternoon shortwave will pass while the temps aloft are starting to warm, the moist layer is relatively shallow, and cross sections show dry air below 850 mb. Stability parameters continue to suggest a chance of thunder. The forecast will show clouds and scattered showers/tstms over Eastern MA and parts of RI during the morning. Diminishing clouds in the afternoon. The mixed layer Friday reaches to 800 mb or above. Temperatures at 800 mb are forecast at 8-10C, equiv to 13-15C at 850 mb. That suggests max sfc temps again in the 80s. The pressure gradient will be weak enough to allow afternoon sea breezes again along the coast. Friday night... Shortwave ridge moves overhead during the night, bringing a dry period much of the night. Another shortwave moves from the Great Lakes, bringing more lift late at night. Expect increasing clouds at this time. The GFS brings showers into western and central MA between 5 and 8 AM, while the GGEM and ECMWF keep the showers over NY state through 8 AM. The forecast follows the slower onset, with dry weather past sunrise early Saturday. Increasing clouds should keep min sfc temps will be in the upper 50s to mid 60s. && .LONG TERM /SATURDAY THROUGH THURSDAY/... Highlights... * Warm front brings period of rain/possible embedded thunder first part of Sat. Turning more humid, with possible strong/severe storms late Sat into early Sat night pending clearing of clouds. * More sun on Sunday with a little less humidity, but with scattered diurnal showers/storms Sunday afternoon. Isolated /limited-coverage stronger storms possible, best chance near terrain and in the coastal plain. * Turning cooler than normal for early next week with daily rain chances, though not a washout on any particular day. Details... Saturday into Saturday Night: An initial 500 mb shortwave trough/vort max associated with a surface low and related warm front in the west flow aloft moves through Southern New England during the day on Saturday. This will likely spread a round of showers, perhaps embedded with thunder due to the progged strength of the shortwave, during the first part of the day. Model spread still remains considerable on timing higher PoPs, with the GFS on the faster side and the international suite of guidance as well as the NAM being somewhat later, closer to mid- morning to early-afternoon. Ironing out those details will be critical to the potential for afternoon warm-sector strong to possibly severe storms, and more specifically on if/how quickly can warm-frontal cloudiness clear for any afternoon heating and destabilization. Across all models, 700-500 mb lapse rates are progged to be around 5.5-6.0 C/km, values which are fairly low and would limit potency of updrafts. Because the GFS brings precip in earlier than other guidance, it allows for greater cloud breaks than the other models, with progged CAPEs on the order of 2000 J/kg away from the coast. On the other hand, only a few hundred J/kg of CAPE is depicted in the other solutions, with greater progged instability over the lower Hudson Valley into western sections of MA/CT. Effective layer wind shear values are in the 35-40 kt range and would support storm organization and persistence were storms to develop. Current SPC Outlook for Saturday (as of this writing), Marginal Risk/5% severe probs over Southern New England with the Slight Risk/15% to our west, still seems reasonable. If greater cloud breaks were to materialize sooner, supporting a more unstable GFS stability depiction, then a greater coverage of stronger storms could ensue but seems too conditional at this time. As PWAT values rise to around 1.8-2", any thunderstorm would be capable of downpours but storms would be moving along at a fair clip. With current preference towards the NAM and international guidance on timing PoPs/sky cover, will be siding temperatures on the lower end of guidance - but greater cloud breaks would allow for significantly warmer temperatures. It will be quite humid though with dewpoints in the mid to upper 60s. Leftover showers or storms may linger Should have clearing by mid- evening with some potential for patchy fog in the favored spots. Sunday into Sunday Night: Troughing associated with the Quebec/eastern Ontario upper low builds southward into Southern New England later Sunday into early Sunday night. After the cloudier day anticipated for Saturday, will have considerably less cloudiness and stronger daytime heating on Sunday. With stronger heating, there`s a better chance of realizing the 1000-2000 J/kg of CAPE progged for Sunday on the GFS/NAM, with effective shear values around 30 kt. However with westerly flow there is less of a triggering mechanism outside of the terrain and perhaps in the coastal plain on the western side of sea breezes. There`s drier mid- level air on Sunday that could lead to lower dewpoints and somewhat less instability than models depict. Will continue to carry mention of thunder in the forecast for Sunday, with better chances in the interior and into the coastal plain. Still could have a few stronger storms on Sunday given forecast instability/shear parameters but the coverage may be limited by a lack of stronger forcing mechanisms. Any showers or storms should start to diminish in strength and coverage by evening. Dewpoints to slowly fall into the upper 50s to lower 60s, so also turning a little less humid. Early Next Week: Closed upper low over northern parts of ME/NH by 12z Monday projects to be the dominant driver of weather conditions really into a good part of next week. This upper level feature shifts southeast towards the southern ME coast by Tuesday and continues to at least be in the vicinity of Southern New England into Wednesday. While there are no days which appear to be a washout, scattered diurnal showers, possibly a rumble of thunder will be around. Cloud cover will tend to increase a little more on Wednesday as upper low starts to dig southward through Southern New England into the mid-Atlantic region. Temperatures will start to trend near to slightly cooler than normal with modest onshore flow. Most days will feature highs in the mid 70s to near 80 and lows in the lower 60s, with dewpoints in the upper 50s to lower 60s - noticeable humidity levels but still generally comfortable. && .AVIATION /02Z FRIDAY THROUGH TUESDAY/... Forecaster Confidence Levels... Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. 00z TAF Update: Tonight: High confidence. Generally VFR for most of the TAFs. Approaching disturbance aloft may bring ongoing showers/storms toward the South Coast, Cape and Islands tonight. Possible short-lived MVFR visibilities in showers, from PVD-PYM southeast towards the Cape and the Islands. Carried as VFR showers for now with TEMPOs as needed. WSW-SW winds 4-8 kt. Friday...High confidence VFR. Widely scattered showers and thunderstorms possible across RI and eastern MA, best chances generally within a few miles either side of I-95. SW winds around 5 to 10 kts. Friday night... High confidence. VFR with light wind. KBOS Terminal...High confidence in TAF/trends. Sea breeze around 16z Fri, possible SHRA/-TSRA ~16-20z. KBDL Terminal...High confidence in TAF/trends. Outlook /Saturday through Tuesday/... Friday Night: VFR. Saturday: Mainly MVFR, with areas VFR possible. Breezy. SHRA likely, slight chance TSRA. Saturday Night: Mainly VFR, with areas MVFR possible. Breezy. Slight chance SHRA, isolated TSRA. Sunday: Mainly VFR, with areas MVFR possible. Chance SHRA, isolated TSRA. Sunday Night: VFR. Monday: Mainly VFR, with areas MVFR possible. Slight chance SHRA. && .MARINE... Winds and seas generally remain below Small Craft Advisory thresholds. Seas may approach 5 feet on the eastern outer waters Friday afternoon and evening. Widely scattered showers/thunderstorms late tonight into Friday with slight lowering of visibility. Outlook /Saturday through Tuesday/... Friday Night: Winds less than 25 kt. Seas locally approaching 5 ft. Saturday: Winds less than 25 kt. Areas of seas approaching 5 ft. Chance of rain showers, isolated thunderstorms. Saturday Night: Winds less than 25 kt. Seas up to 5 ft. Chance of rain showers, isolated thunderstorms. Sunday: Winds less than 25 kt. Areas of seas approaching 5 ft. Chance of rain showers, isolated thunderstorms. Sunday Night: Winds less than 25 kt. Areas of seas approaching 5 ft. Monday: Winds less than 25 kt. Seas locally approaching 5 ft. Slight chance of rain showers. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...None. MA...None. RI...None. MARINE...None. && $$ SYNOPSIS...WTB/Loconto NEAR TERM...WTB/Belk/Loconto SHORT TERM...WTB LONG TERM...Loconto AVIATION...WTB/Belk/Loconto MARINE...WTB/Loconto
Area Forecast Discussion
National Weather Service Caribou ME
912 PM EDT Thu Jun 25 2020 .SYNOPSIS... An upper low will drop southward from Canada over the weekend into early next week with a series of upper level disturbances affecting the region. && .NEAR TERM /THROUGH FRIDAY/... 9:12 pm Update: Satellite pictures show an upper low to the east of James Bay with mid level water vapor showing drier air across Maine. This dry air was evident on the KCAR 00z sounding with a PWAT of 0.80" which compares with a PWAT of 1.89" this time last night. There are still a few showers ahead of the upper low in eastern Quebec, although no lightning has been detected all evening. Will make some adjustments to cut back on the PoPs, not that they were any higher than isolated, but even that looks like it can be trimmed back for the remainder of the night. Otherwise, the forecast remains on track with a much drier air mass at low and mid levels across the area and a much more comfortable night. Lows by morning will mostly be in the 50s, and even some 40s are possible in the normally colder northwest valleys. Previous discussion: An upper trof seen on the 12Z UA was moving into Quebec. This feature is picked well on the visible and wv satl imagery. A nice 35-40 kt jetstreak is associated w/this feature. RAP soundings do show the column moistening up to 700mbs this evening across far northern and western areas. The RAP and HRRR have been consistent w/bringing some light showers across the far northern areas during the evening hrs up through midnight. Decided to go w/20-30% pops and just showers. Much cooler overnight w/temps in the 50s. The exception will be across far n and nw areas w/some upper 40s. SW winds will be dropping off this evening as the gradient weakens. Some fog is possible overnight especially across the Downeast coast. The latest RAP and NAM support the fog development. Across northern areas, there is potential for some patchy fog w/the cooldown and temp/dewpoint being w/in few degrees. Fog that is around in the morning, will quickly dissipate. A sfc trof/pre-frontal boundary is forecast to slide into the region late Friday morning into the afternoon. Dewpoint pooling along and just ahead of the boundary is noted by the 12z NAM and even the GFS. The best moisture convergence appears to be across the interior Downeast nosing up into Nrn Washington and SE Aroostook County. Mdl soundings show SB CAPE 500-900 joules in this area. Mid level lapse rates are marginal, but llvl lapse rates are shown to hit 8.0 c/km which would aid in allowing for buildups. PWs around 1.0". 0-6KM shear is around 20 kt which should be enough to allow for convection to fire and keep going. Inverted sounding supports potential for some gusty winds w/any tstms. Attm, confidence is not high enough to include any enhanced wording in the forecast. Afternoon temps should be able to hit 80 and higher across the region w/the warmest temps across the Maine Central Highlands down to the Downeast region. && .SHORT TERM /FRIDAY NIGHT THROUGH SUNDAY/... Large upper low just east of James Bay Friday night gradually drifts to over Maine late Sunday. As this upper low approaches, it will send several shortwave troughs through our area with shots at showers and storms. One shortwave trough will be exiting to the east Friday evening, thus expect showers and storms to die off quickly after dark. Enough of an onshore component that there should be some fog again mainly Downeast but possibly up to Houlton and Millinocket. Later Saturday, another shortwave trough approaches. Dynamics could be strong enough to allow a weak surface low to form near the Maine coast, and if this happens, could see some rain. Not a done deal though. Raised PoPs to around 60 percent Downeast late Saturday and Saturday evening. High chance to low likely PoPs in Northern Maine late Saturday with perhaps some storms as well. Then late Sunday the upper low nears the area and with the colder air aloft, should see an increase in showers and storms again. With the colder air aloft with the upper low, could be a good setup for small hail. Not as warm with highs in the 70s. There are some slight differences with model timing of shortwaves, but nothing major and overall fairly confident in the forecast. && .LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/... Tough call Monday and Tuesday what happens to the upper low after being over us late Sunday. Tentatively, it looks like it will weaken a bit and drift slowly SW of the area. Enough cold air aloft and instability Mon/Tue that kept a mention of thunder those days, though coverage probably will be less than Sunday. Pleasant temps Mon/Tue with highs in the 70s. Models in poor agreement on what happens after Tuesday. Some build a decent upper ridge in from the NW with a similar warm blocking pattern to what we had a week ago, while others keep us under unstable NW flow. && .AVIATION /01Z FRIDAY THROUGH TUESDAY/... NEAR TERM: VFR from KBGR northward. Some IFR cigs are possible at KBHB overnight into the early morning hrs on Friday. SHORT TERM: Friday Night...Mainly VFR except for some IFR with fog Downeast. Light wind. Saturday through Sunday Night...Mix of VFR and MVFR. Generally MVFR outside of showers and storms, but MVFR in showers and storms which are possible through the period. Fairly light wind. Monday and Tuesday...Mainly VFR with light wind. && .MARINE... NEAR TERM: No headlines. The main deal will be the fog over the waters developing overnight into Friday morning causing some navigation issues for the mariners. SSW winds around 10 kts w/seas 2-3 ft, building to 3-4 ft. SHORT TERM: Pretty quiet on the waters with seas and winds below small craft. Main issue will be some fog lingering into Saturday night. && .CLIMATE... Today was the 10th consecutive day with a high of 80 degrees (F) or warmer in Caribou, Maine. This ties with August 2015 for the longest consecutive stretch of 80 degrees on record. Weather records in Caribou date back to 1939. && .CAR WATCHES/WARNINGS/ADVISORIES... ME...None. MARINE...None. && $$ Near Term...CB/Hewitt Short Term...Foisy Long Term...Foisy Aviation...CB/Hewitt/Foisy Marine...CB/Hewitt/Foisy Climate...
Area Forecast Discussion
National Weather Service Cheyenne WY
933 PM MDT Thu Jun 25 2020 .UPDATE... Issued at 933 PM MDT Thu Jun 25 2020 It was a active late afternoon and early evening with scattered strong to severe thunderstorms over parts of southeast WY and western NE. The most intense convection developed over northeast Sioux and western Dawes counties, with several reports of 2 to 3 inch diameter hail in and around Crawford NE. Wind gusts of 58 mph were measured at Douglas WY. A cold front was moving south across the I-80 corridor this evening. Winds shifted to northerly and were gusting to 35 kt with fropa. Behind the front, scattered showers and isolated thunderstorms lingered. The threat for strong convection has ended, however brief heavy rain and gusty winds will be possible through late this evening. Shower coverage will decrease overnight. && .SHORT TERM...(This evening through Saturday night) Issued at 210 PM MDT Thu Jun 25 2020 Tonight...The Storm Prediction Center slight risk outlook from Glenrock to Chugwater to Sidney looks good based on best instability axis and shear outlook. Approaching shortwave trough aloft will help generate scattered to numerous showers and thunderstorms through the afternoon and early evening as depicted on the HRRR model, with strong winds the primary threat, along with a secondary threat for large hail. Storms will be slow to decrease in areal coverage overnight. Friday...Best chances for afternoon and evening showers and thunderstorms will shift to our southern counties where moisture and lift will be most pronounced. Shear and instability look less favorable for strong to severe thunderstorms. Cooler temperatures in the wake of a cold front and with more cloud cover. Friday night...Showers and thunderstorms will decrease in areal coverage in the evening with the loss of daytime heating. Saturday...With a low level trough axis expected from Casper to Cheyenne, and adequate low and mid level moisture remaining, will see isolated to scattered afternoon and evening thunderstorms mainly south of a Wheatland to Alliance line. Warmer temperatures as 700 mb temperatures rise to near 15 Celsius. Saturday night...Showers and thunderstorms will likely end quickly in the early evening. Not as cool as Friday night with the warmer airmass in place. .LONG TERM...(Sunday through Thursday) Issued at 210 PM MDT Thu Jun 25 2020 Attention this period will be on the upper trough/low that will be over the northwest part of the country, weakening slowly through mid-week. Convection looks to be rather isolated over the CWA Sunday behind a weak shortwave that will be moving east of the area. It then appears convection will gradually increase over the CWA Monday through Thursday as the upper trough edges a little closer to the CWA with several weak impulses likely to lift northeast and over the region on the front side of the trough. A cold front should pass across the CWA Tuesday which would aid in convective development. Less convective activity seen for Thursday as the weakening trough axis moves across the area. && .AVIATION...(For the 00Z TAFS through 00Z Friday afternoon) Issued at 535 PM MDT Thu Jun 25 2020 VFR will prevail through the period. Scattered SHRA/TSRA will move across the region through late this evening. Gusty erratic winds and brief MVFR visibilities can be expected with the stronger convection. && .FIRE WEATHER... Issued at 210 PM MDT Thu Jun 25 2020 Minimal concerns for Friday based on expected afternoon relative humidities. Lower humidities Saturday through Monday will increase concerns. && .CYS WATCHES/WARNINGS/ADVISORIES... WY...None. NE...None. && $$ UPDATE...MAJ SHORT TERM...RUBIN LONG TERM...RE AVIATION...MAJ FIRE WEATHER...RUBIN
Area Forecast Discussion
National Weather Service Grand Forks ND
1010 PM CDT Thu Jun 25 2020 .UPDATE... Issued at 1010 PM CDT Thu Jun 25 2020 Cold front is still moving into our CWA with warm sector slowly sliding east. ML CAPE within warm/moist air mass is still within 1000-2000 J/KG according to SPC RAP analysis, with much lower values 500 J/KG or less behind the front. Effective shear and DCAPE are both very low. This type of air mass no longer supports organized severe weather, though small hail can`t be ruled out with any storms that develop. Beside frontal zones large scale ascent is disorganized and as stable post frontal air mass spreads east we would expect any shower/storm potential to end, which is matched by current CAMs/radar trends. I lowered coverage of showers/storms and adjusted timing for activity ending around midnight in ND and around 09Z in MN based on observed and expected trends. Patchy fog may develop for a brief period as moisture pools near the frontal zone in MN late tonight/Sunday morning, but the window for this is brief as front moves east and coverage likely patchy. && .SHORT TERM...(This evening through Friday night) Issued at 344 PM CDT Thu Jun 25 2020 Convective chances and strength continue to be the forecast challenge for the period. The festivities have gotten an early start as the surface trough axis enters the Devils Lake and James river valleys. Warm front has been lifting across our central CWA with the cold front further west over central ND. While there were worries about how much we would destabilize due to clouds and early showers, there has been a lot of clearing across the southern RRV and ML CAPEs have managed to top 2000 J/kg. While the effective bulk shear is not huge, up to 35 kts has been sufficient enough for several supercells and multicells to develop early this afternoon. The storms will push eastward into far western MN late this afternoon and evening, with some weakening expected as the storms move into more stable air. Will have to watch additional development in south central ND that will push into our counties later tonight, as there could be additional marginally severe cells as the front moves eastward. Think that most of our severe threat should be over by late evening, with the loss of daytime heating and winds shifting to the northwest behind the low pressure system. Later tonight, lingering showers and a few thunderstorms should taper off, with portions of the western CWA clearing out. Clouds will clear out of the rest of the region during the day on Friday, with northwesterly flow aloft and surface high pressure building in. Cold air advection behind the system is pretty weak and will be offset by sunshine that some areas are not getting today, so highs will be in the 80s across much of the CWA. The fairly quiet weather will continue into Friday night with brief upper ridging between systems. .LONG TERM...(Saturday through Thursday) Issued at 344 PM CDT Thu Jun 25 2020 Impactful weather opportunities will still be found during the latter part of the extended period, principally during Tue-Thu when strong to severe tstms will be possible. Upper flow will transition from zonal to an upper ridge during the weekend, allowing for warmer temps and dry conditions. Look for highs in the mid 80s to low 90s during this time, with overnight lows mostly in the balmy 60s. A more southwesterly regime kicks in for late weekend into early next week. An upper low will transit into the Northern Rockies at this time, edging closer to the Northern Plains. PWATS will be on the rise along with instability, but an inspection of 700mb ensemble temp projections indicates a potentially stout cap in place, at least for Mon. The approach of an upper wave/500 mb trough by Tue could provide the de-stabilization/forcing necessary for organized strong to severe convection. There is a decent chance though that this approach could be delayed until Wed, making Wed/Thu the better days for more focused convective activity. && .AVIATION...(For the 00Z TAFS through 00Z Friday evening) Issued at 705 PM CDT Thu Jun 25 2020 Clusters of showers/thunderstorms continue to track over west central/northwest MN with brief IFR/MVFR conditions where heavier rain showers or thunderstorms track. Most activity isn`t severe but we can`t rule out stronger storms through 03Z. Further west west in ND activity as actively transitioned east with only one lingering storms near KFAR which should move east around the valid TAF time at 00Z. After a lull additional scattered showers/storms should develop back into eastern ND and northwest MN as a cold front shifts east before lingering showers/storms ends 06-07Z in MN. There is still some guidance that shows potential for MVFR conditions across MN 10-15Z period, but with westerly flow arriving behind cold front this may support clearing and trends toward prevailing VFR. && .FGF WATCHES/WARNINGS/ADVISORIES... ND...None. MN...None. $$ UPDATE...DJR SHORT TERM...JR LONG TERM...JR AVIATION...DJR
Area Forecast Discussion
National Weather Service Goodland KS
605 PM MDT Thu Jun 25 2020 .SHORT TERM...(This evening through Friday Night) Issued at 102 PM MDT Thu Jun 25 2020 19 UTC Water vapor imagery and RAP analysis indicated short wave trough axis bisecting the CWA with some pronounced drying/subsidence noted near its axis. At the surface, storms starting to develop behind the upper level feature along surface trough from KIML to KLIC, in area of persistent convergence. To the south of the trough, very warm conditions dominated with temperatures in the upper 90s to low 100s. Main forecast concerns are going to be thunderstorm chances through the evening, followed by another round on Friday evening. Thunderstorms have already initiated along surface trough just to the west of the area. With high LCL`s weak overall shear and MLCAPES between 500-1500 j/kg, not expecting to see very organized storms. However, the high LCL`s and dry inflow air will likely create strong downdrafts which will pose a microburst threat as well as allow a strong cold pool to form and further initiate storms downstream across the CWA. Convective allowing models all seem to be following this evolution which increases confidence. The combination of strong winds,high cloud bases and lots of evaporation may increase the risk of lightning induced fires, although there is a lot of uncertainty with respect to how much precipitation will reach the ground. Cold front will sweep across the area overnight and may bring a brief period of gusty winds, although current timing and pressure rises estimates seem to indicate winds will not get out of hand as it passes. Will likely see little if any precip chances through the day Friday as cooler air builds into the area shifting instability axis to the south of the area, with capping very strong to the north of front even if instability present. Think the most likely scenario will be thunderstorms developing in the easterly flow behind front along higher terrain. Shear profiles certainly support organized storms and with the 0-3km shear orientation and likelihood of strong cold pools, expect MCS to roll across the area during the evening hours, perhaps bringing an organized damaging winds threat. .LONG TERM...(Saturday through Thursday) Issued at 212 PM MDT Thu Jun 25 2020 For the extended period, the models start out showing the Plains being between an upper air trough and ridge on Saturday due to an localized upper air low over UT/NM. During this period, a shortwave trough will move through the local area. On Sunday, models both show an upper level low traveling in from Pacific Northwest U.S. while another upper level low persists in the Northeastern U.S. This setup causes an upper air ridge to reside over the Plains for the beginning of next week. The GFS model shows the Pacific Northwest low moving more southeastward on Tuesday evening causing a negatively tilted upper air trough to move over the CWA. However, the ECMWF model keeps the low in the Pacific Northwest making this trough stay more over the Rockies and starting to tilt negatively by Thursday. This situation will be monitored as the timing of the middle of next week`s weather system relies on how this plays out. On the surface, a chance of showers and thunderstorms are expected on Saturday in the CWA due to the shortwave trough aloft. For the beginning of next week, dry conditions are expected throughout the CWA. However, isolated showers and thunderstorms cannot be ruled entirely at this time Sunday and Monday. Chances of showers and thunderstorms return Tuesday evening and these chances increase on Wednesday across the CWA. Thursday`s forecast also shows a slight chance of showers and thunderstorms. Fire weather also cannot be ruled out entirely for the western counties of the CWA for Sunday through Tuesday as forecasted RH values begin to drop Sunday below 20% with models show wind gust speeds expected to reach up to 25 mph. Saturday`s high temps for the CWA are expected to be in the lower 90s as precipitation cools things in the area. Sunday and Monday should see a return of highs reaching the upper 90s across the CWA with some parts hitting possibly 100 degrees. Middle 90s are the expected Tuesday`s high temps. Wednesday and Thursday`s high temps for the CWA will return to the upper 80s and lower 90s as precipitation cools the area. Overnight low temps are forecasted to stay in the upper 50s to middle 60s for the western counties of the CWA throughout the forecast period with the eastern counties of the CWA low temps ranging from the lower 60s to lower 70s. && .AVIATION...(For the 00Z TAFS through 00Z Friday evening) Issued at 600 PM MDT Thu Jun 25 2020 For KGLD, vfr conditions expected through the period. Winds will veer to the northwest at speeds around 10kts after midnight as a cold front moves through. Winds continue to veer to the north with gusts around 20kts from shortly after sunrise through late morning then decrease below 12kts and veer to the northeast and east through the afternoon. For KMCK, ongoing thunderstorms at taf issuance will move east of the terminal by 01z with isolated to scattered showers producing erratic wind gusts to 40kts through about 02z. After 03z a similar scenario as KGLD regarding timing and winds after midnight through the day Friday. && .GLD WATCHES/WARNINGS/ADVISORIES... KS...NONE. CO...NONE. NE...NONE. && $$ SHORT TERM...JRM LONG TERM...MRC AVIATION...99
Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
837 PM CDT Thu Jun 25 2020 .UPDATE... 837 PM CDT No changes to the going forecast this evening. Weak lake breeze across parts of the Chicago metro area will dissipate through late evening, with winds becoming light southwest across the region overnight ahead of a warm front which will move into the area Friday morning. Warm advection will strengthen aloft overnight ahead of the front, with isentropic ascent and moistening eventually allowing the development of scattered convection from west central IL back into central and eastern IA after midnight. Recent high-res CAM guidance continues to indicate elevated showers/thunderstorms spreading into the cwa toward/sunrise Friday morning, with western parts of the forecast area seeing higher potential prior to gradual weakening as activity moves farther east after sunrise. Light southwest surface winds and gradually increasing low level moisture/dew points will allow for milder overnight temps in the low-mid 60`s in most spots. Recent CAM guidance continues to suggest the potential for additional thunderstorm development across parts of northern IL by late morning/midday, in association with a convectively enhanced (from MCS activity across the Plains to our west tonight) circulation or MCV. Increasing chance pops north of the I-80/88 corridors across northern IL by midday in going forecast appear reasonable based on this scenario. MCS evolution overnight should allow for further refinement in temporal/spatial distribution of thunder chances. Ratzer && .SHORT TERM... 256 PM CDT Through Tonight... Most of tonight will be quiet and milder. After midnight and especially toward daybreak, warm advection/isentropic ascent on the nose of a modest veering low level jet is expected to cause scattered higher based convection to break out from central Illinois to northwest Illinois after midnight and then gradually spreading northeast toward and after daybreak. Main short-wave forcing passing to the north, relatively dry profiles, fairly weak mid- level lapse rates, and resultant minimal elevated instability, should keep coverage and intensity in check. That said, there should be enough MUCAPE (250-500+ j/kg) to tap into above capping around 650 mb to allow for some isolated to widely scattered thunderstorms. Not expecting severe weather due to the modest instability despite decent deep layer shear. Castro Friday through Saturday Night... An active Friday and Friday night is expected across the Great Lakes region, including both a scattered severe thunderstorm and potential zone of a flash flood threat. Confidence is highest in thunderstorms occurring along and north of I-80 late day into the evening. This area thus has a greater potential for severe weather and heavy rain than south of I-80 in an otherwise background Slight Risk (Level 2 of 5). Scattered showers and probably some storms should be ongoing Friday morning in the warm advection across southern Wisconsin and northern and possibly central Illinois. These will be on the leading edge of stronger elevated instability shifting eastward. As noted above, the instability is not forecast to be particularly robust, but the 2-6 km shear of 30 kt may yield a couple stronger storms. A positively-titled upper level short wave presently over eastern Montana will be a key forcing feature for later Friday as it translates east-southeast in the upper level westerlies. An ongoing MCS or convective clusters by midday across central to southern Wisconsin will likely be intersected by this wave`s forcing. The signal in 12Z guidance is fairly pronounced for upscale convective growth as an MCS along the warm/stationary front into eastern/southeastern Wisconsin during the afternoon and into Michigan Friday evening. This is where the greatest likelihood of severe weather due to organized convective modes and 45-60 kt of deep layer shear is expected, and given the close proximity there is wiggle room that the MCS threat impinges into far northeast Illinois mid-afternoon into early evening. More likely though is that convection develops along the periphery outflow or composite outflow/front into northern Illinois during mid or late afternoon. This will align well with peak heating, with forecast highs near or to 90, and surface dew points along the boundary to near 70. There are noteworthy variances in forecast timing though, with the global solutions much more progressive with the Wisconsin MCS or developing MCS, thus resulting in its outflow moving more rapidly southward through the northern half of the CWA during the mid-late afternoon and evening. This is important because it would limit the otherwise decent signal for training convection along the general west-east composite boundary with a moisture feeding 40 kt low-level jet. Those ingredients, along with PWATs of over 1.75 inches, will be plenty for convection and we will need to monitor closely if a flash flood risk becomes more apparent. The boundary and/or outflow composite will likely be the focus, as further to the south and southeast in the warm sector is likely to be capped through at least early evening. Convective modes of multicell clusters and small scale segments or bows are favored with sufficient deep layer shear. The severe threat with this setup would be primarily wind. If the outflow push from the north is not as quickly and the boundary(ies) becomes stalled, any cells along this mainly late day/early eve could have a rotating supercell threat of hail and a tornado or two. Activity should slowly be sinking southward Friday overnight into Saturday morning, likely with a diminishing footprint. Another lower amplitude short wave is forecast to pass northern to central Illinois Saturday, interacting with the boundary and instability to foster thunderstorm chances. This would likely be more of the scattered thunderstorm variety. The trend continues to support drying for north of I-80 by later day and Saturday evening/night. MTF && .LONG TERM... 330 PM CDT Sunday through Thursday... Little changes made to this period, with quite a bit of uncertainty on Sunday and Monday, as the aforementioned frontal boundary should begin moving northward over the mid-Mississippi Valley. Heights are also likely to be building though, so that should limit the amount of thunderstorm coverage especially further northeast in the region (such as the Chicago area). So have limited PoPs from what the blend provided during Sunday-early Monday. Conditions look warm and muggy away from the lake this coming week. MTF && .AVIATION... For the 00Z TAFs... Aviation forecast concerns: * Potential for three periods of SHRA/TSRA through Friday evening. Greatest potential for widespread and likely more impactful TSRA appears to be Friday evening. * Strong southwest winds Friday, with gusts 30+ kts possible especially late afternoon. Quiet aviation weather is expected to persist through this evening. Lake breeze has moved inland with east winds at ORD/MDW, with winds expected to become light west-southwest after lake breeze dissipates mid-late evening. Warm front is expected to lift northeast across the forecast area Friday morning. Elevated convection is forecast to develop ahead of the warm front late tonight, and spread into northern IL toward sunrise. KRFD looks to have the highest chance of seeing elevated SHRA/TSRA around sunrise, with various high-res model guidance weakening this activity as it moves east through mid-morning. Can`t rule out a few SHRA making it to the Chicago area terminals, though coverage is expected to decrease significantly farther east. Latest CAM guidance is hinting at another period of potential convection mid-day, originating from a convectively enhanced circulation (MCV) which is progged to develop from storms currently developing across the Plains. Recent runs of the HRRR maintain scattered TSRA threat across the area into early afternoon as the mid-level vort passes. As several different models have picked up on this over the last several hours, feel it`s worthy of a prob30. Guidance then remains in good agreement in a more widespread strong thunderstorm threat Friday evening, ahead of a cold front sagging southeast from WI. Of course any potential convection and associated cloud cover earlier in the day may have impacts on the evolution of these trends through late Friday, though confidence is fairly decent that organized convection will affect the terminals Friday evening. Outside of thunderstorms, southwest winds will become strong and gusty by Friday afternoon after the warm front lifts north of the area. Forecast soundings support gusts near/above 30 kt during the afternoon, particularly the late afternoon as 35-40 kt low level jet develops ahead of an approaching upper trough. Magnitude of peak gusts may be modulated by earlier convection/residual cloud cover, so have stayed a bit conservative at this distance, but if good low level mixing does develop, gusts of 30-35 kts are possible during the late afternoon hours. Ratzer && .LOT WATCHES/WARNINGS/ADVISORIES... IL...None. IN...None. LM...Small Craft Advisory...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744- LMZ745...1 PM Friday to 10 PM Friday. && $$ Visit us at Follow us on Facebook, Twitter, and YouTube at:
Area Forecast Discussion...UPDATED
National Weather Service Mobile AL
942 PM CDT Thu Jun 25 2020 .NEAR TERM /Now Through Friday night/...An upper trof over the eastern states moves off into the western Atlantic through Friday while an upper ridge remains in place over the northern Gulf. A less well defined upper trof is also currently located from eastern Texas into southern Arkansas, and remains close to this position through Friday night. A series of shortwaves are ejected from this feature and advance eastward (within the westerly flow north of the Gulf upper ridge) and move across the forecast area through the period. A surface ridge which extends from the western Atlantic to along the northern Gulf coast gradually shifts into the north central Gulf coast states through Friday night. This results in light southerly surface winds over the forecast area becoming southeasterly over the southern portion of the area on Friday with a southwesterly flow expected further inland. For the remainder of this evening, an area of rain with some embedded storms will affect the northernmost counties while elsewhere isolated convection is possible. Have gone with mainly dry conditions for the late night hours. For Friday, despite the series of shortwaves set to move across the area, model soundings show significant drying will have occurred within the 900-650 mb layer, likely due to subsidence effects from the nearby Gulf upper ridge. This should be a fairly significant impediment for convective development though have opted to stay with slight chance pops for the afternoon hours for now. Lows tonight and Friday night range from around 70 well inland to the mid to upper 70s at the immediate coast. Highs on Friday will be mostly in the lower 90s and afternoon heat index values look to be near 100. A low risk of rip currents is expected from tonight through Friday night. /29 && .PREV DISCUSSION... /issued 621 PM CDT Thu Jun 25 2020/ NEAR TERM UPDATE /Now Through Friday night/...An upper trof over the eastern states moves off into the western Atlantic through Friday while an upper ridge remains in place over the northern Gulf. A less well defined upper trof is also currently located from eastern Texas into southern Arkansas, and remains close to this position through Friday night. A series of shortwaves are ejected from this feature and advance eastward (within the westerly flow north of the Gulf upper ridge) and move across the forecast area through the period. A surface ridge which extends from the western Atlantic to along the northern Gulf coast gradually shifts into the north central Gulf coast states through Friday night. This results in light southerly surface winds over the forecast area becoming southeasterly over the southern portion of the area on Friday with a southwesterly flow expected further inland. For this evening, a mesoscale convective system, manifesting as a broken line of convection, currently located mainly over south central Mississippi is expected to advance east- northeastward across interior southeast Mississippi and interior southwestern Alabama. Some isolated convection will also be present over south central Alabama this evening. MLCAPE values of 2500 J/kg, possibly higher, will be present initially early this evening then gradually diminish to 500-1000 J/kg by midnight. While shear appears to be very low, HRRR model soundings show mid level dry air near 700 mb which will continue to enhance downdraft production as the line of convection progresses across the interior portions of the forecast area. Expect that strong to marginally severe wind gusts are possible. Have updated to go with likely to categorical pops early this evening over the northwestern third of the area due to the convection to move across this portion and made other minor adjustments. For the after midnight to pre dawn hours, the potential for any convective development looks sufficiently limited to continue with a dry forecast for that time period. For Friday, despite the series of shortwaves set to move across the area, model soundings show significant drying will have occurred within the 900-650 mb layer, likely due to subsidence effects from the nearby Gulf upper ridge. This should be a fairly significant impediment for convective development though have opted to stay with slight chance pops for the afternoon hours for now. Lows tonight range from around 70 well inland to the mid to upper 70s at the immediate coast. Highs on Friday will be mostly in the lower 90s. Lows Friday night range from the lower 70s inland to the mid to upper 70s at the coast. A low risk of rip currents is expected from tonight through Friday night. /29 AVIATION... 00Z issuance...Numerous showers and storms will affect interior southeast Mississippi and interior southwestern Alabama this evening along with mainly isolated convection expected over south central Alabama. IFR conditions along with strong wind gusts can be expected with the convection. Dry conditions are expected over the entire area by 06Z which continues through early Friday morning, after which isolated convection is possible. VFR conditions are expected to prevail outside of the convection except for the potential for MVFR visibilities mainly due to dust. Southerly winds 5 to 10 knots at the beginning of the period become light and variable tonight. For Friday, expect a southeasterly flow at 5 to 10 knots over the southern portion of the area while further inland will see a light southwesterly flow. /29 PREV DISCUSSION... /issued 357 PM CDT Thu Jun 25 2020/ NEAR TERM UPDATE /Now Through Friday/...Forecast for this afternoon basically on track, isolated showers and thunderstorms are beginning to develop over portions of interior southwest Alabama. Current forecast calls for likely PoPs by later this afternoon, and although coverage may not end up as widespread as originally thought, mesoscale analysis indicates a quite unstable airmass in place (MLCAPE 2500-3000 J/KG and areas with SBCAPE up to over 4000 J/KG) so coverage (and intensity) of storms could very well increase this afternoon. Unlike yesterday though, atmospheric shear is much lower, so the severe threat is lower (especially with regard to tornadoes). However, the previously advertised Saharan Air Layer, and associated dust and dry mid level dry air, has arrived along the central Gulf coast and the drier air aloft could result in some stronger downdrafts with the stronger storms this afternoon. Our microburst checklist procedure came up with a Moderate threat of downbursts today. Also heating up this afternoon, a few degrees above expected in some locations, with heat indices in the upper 90s and even into the 100-105 range in some locations over the southern third of our forecast area. For tonight, expect at least isolated to scattered convection to continue until mid evening, especially over inland areas. By late evening most of this activity should end, but some lingering showers or storms could last all night long as the low level airmass remains moist and weak disturbances continue to move across the area on the backside of the upper trough that will be departing off to the east of the area. Lows tonight remaining quite muggy, mainly in the lower 70s over inland areas and mid to upper 70s closer to and along the coast. On Friday, the weather pattern begins to change somewhat as weak deeper layer ridging begins to develop across our area. Plenty of low level moisture with a continued east to southeast flow off of the Gulf (PWATs in the 1.7 to 1.9 inch range), combined with daytime heating, should allow for some isolated to scattered daytime showers and thunderstorms, but overall coverage should continue to be decreased as compared to the last couple of days. Will continue to be hot and a little hazy (due to the dust in the air) on Friday. High temperatures will primarily be in the upper 80s and lower 90s across the entire area, with the cooler temps over the far northwest and also along the immediate coast (where even a few mid 80s for highs will be possible). Heat indices on Friday will again be quite warm, mainly in the upper 90s to 100-105 degree range once again. /12 SHORT TERM /Friday night Through Sunday night/...A flat upper level ridge is progged to be positioned from the southwest Atlantic westward into the Gulf into the weekend. North of the ridge, mid-level impulses with varying degrees of amplitude amongst the guidance migrate eastward Saturday. Some indications that the nose of the Gulf upper ridge will extend more northward over the area into the day Sunday, bounded by a two upper level trofs. One over the Mid-Atlantic to its east and the other over the Plains to its west. No appreciable change to environmental moisture depth is noted through the weekend with PWATs ranging from 1.8-2.0 inches. Considering this along with daytime instability and the passage of mid-level impulses looks to aid in the initiation of mainly daytime scattered showers and storms Saturday. Even though more ridging aloft would suggest a lower chance of storms Sunday, will maintain a modest chance of storms out of respect for impulses riding down the southwest side of Mid- Atlantic trof. As for temperatures, latest guidance shows warm, muggy nights with night-time lows ranging in the lower/mid 70s interior. Mid to upper 70s likely to the south and closer to the coast. Highs Saturday are anticipated to be in the mid to upper 80s northwest of I-65 and along the coast. Upper 80s to lower 90s along and southeast of I-65 to I-10. Highs Sunday 87 to 92 range area-wide. /10 EXTENDED TERM /Monday Through Thursday/...Gulf upper ridge looks to continue nosing northward into the Lower MS River Valley to start the new work week. An upper low over the northeast US Monday eases southwest over the New England states by the middle of next week. A potentially active high level northwest flow pattern looks to setup between this northeast US upper trof/low and the southern US ridge. These types of flow patterns support southeastward propagating convective complexes which can produce strong winds. Considering this potential, little change in deep moisture as mentioned in the short term discussion, daytime heating and instability, showers and storms look to become likely each day. Before storms bring a cool off, heat indices of 98 to 103 possible in some locations through the middle of next week. Low level/surface pressure ridge remains anchored over the FL Peninsula with little change in highs and lows. /10 MARINE...No significant impacts expected over the marine area through the period. Seas generally 2 feet or less, enhanced slightly near shore by afternoon sea breeze and also around isolated to scattered showers and thunderstorms. /12 && .MOB WATCHES/WARNINGS/ADVISORIES... AL...None. FL...None. MS...None. GM...None. && $$ This product is also available on the web at:
Area Forecast Discussion
National Weather Service Tucson AZ
340 PM MST Thu Jun 25 2020 .SYNOPSIS...The heat will slowly subside over the next few days as high pressure weakens over the area. A moisture increase from the south will bring a chance of afternoon and evening thunderstorms to the area Saturday afternoon into early next week before another drying trend by mid week. && .DISCUSSION...High pressure overhead with temperatures running 7 to 8 degrees above climatology today. First 109 of the season so far at Tucson International with 110 not out of the question this afternoon. With a weak trough digging into the region over the next 36 hours, we`ll see some moderation in the temperature as heights and thicknesses fall back toward climo by Saturday. In the mean time, pressure differentials are enhancing a southerly flow up the Gulf with a moisture surge just beginning. HRRR trends are grabbing onto this nicely with elevated surface and near surface moisture beginning to spread into the lower deserts tonight and Friday morning. HREF ensemble moisture probabilities suggest surface dew points in excess of 50 degrees pushing in from the south late Friday into Saturday morning, 1 inch precipitable water values pushing from central to northern Sonora as early as Friday evening. While initial surge depth will be on the shallow side, NAEFS mean integrated water vapor transport percentiles suggest some depth by Saturday afternoon and evening. In addition, we are looking at the proximity of a significant remnant weakness in the flow providing some potential shear and organization to any storms that might develop Saturday afternoon. Main concerns will be strong, gusty and erratic outflow winds and potential dry lighting. Storm cores should be tight with relatively narrow (but not inconsiderable) rain shafts and prime microburst conditions. We`ll keep a chance of thunderstorms into Monday or Tuesday, but ultimately a very late season trough should push a dry westerly flow back over the area by Wednesday. Some early signs of what might end up being even stronger and hotter high pressure around the July 4th weekend. Stay tuned. && .AVIATION...Valid through 27/00Z. FEW-SCT clouds AOA 15K ft MSL thru the forecast period, with occasional periods of BKN clouds possible mainly north of KTUS. Surface wind WLY/NWLY at 11-16 kts with gusts near 26 kts through 26/03Z, then becoming 12 kts and variable in direction at other times through about 26/17Z. SWLY/WLY winds resume thereafter at 10- 18 kts with gusts up to around 27 kts. Aviation discussion not updated for TAF amendments. && .FIRE WEATHER...Dry conditions will continue across much of the area through Friday. An increase in lower to mid level moisture will result in isolated to scattered mainly afternoon and evening showers and thunderstorms Saturday through Tuesday mainly for areas from Tucson south and eastward. These thunderstorms will be capable of producing gusty and erratic outflow winds. Brief downpours are possible with the stronger storms but widespread wetting rain is not expected. Otherwise, expect elevated southwest to west winds 20- ft winds through Tuesday, with the strongest winds expected Sunday and Monday. Wind speeds may briefly approach critical fire weather thresholds Sunday and Monday. Minimum humidity levels will remain low with poor overnight recoveries tonight. Some improvement with overnight recoveries is expected this weekend and early next week. Haines 5 & 6 conditions mainly from Tucson eastward through Friday. && .TWC WATCHES/WARNINGS/ADVISORIES... None. && $$ Public...Meyer Aviation...Lader Fire Weather....Lader Visit us on Facebook...Twitter...YouTube...and at