Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 05/26/18

Area Forecast Discussion
National Weather Service Columbia SC
946 PM EDT Fri May 25 2018 .SYNOPSIS... The region will remain moist and unstable the next few days between a ridge offshore and weak low pressure to the west. Scattered to numerous showers and thunderstorms, mainly during the afternoon and evening, are expected. Periods of heavy rain are possible Sunday and Monday as a plume of tropical moisture from Subtropical Storm Alberto is directed into the area. && .NEAR TERM /UNTIL 6 AM SATURDAY MORNING/... The deep moist southerly flow will continue through tonight associated with high pressure at the surface and aloft off the coast and low pressure to our west. Precipitable water values will remain 1.8 to 2.0 inches with weak instability. Shower and thunderstorm coverage has been greatest in the Central Savannah River Area associated with a surface trough and mid-level shortwave trough. Expect continued diminishing coverage tonight because of nocturnal cooling. The HRRR displays little shower coverage overnight. The high moisture will help hold up temperatures. As with the previous 2 nights expect lows in the upper 60s to lower 70s. && .SHORT TERM /6 AM SATURDAY MORNING THROUGH SATURDAY NIGHT/... Saturday, the moist air mass will remain over the FA through the afternoon allowing mainly diurnal showers and thunderstorms to develop. With the upper-level ridge axis shifting east of the FA there may be some weak upper-level support for thunderstorms late in the day. However 850 mb high pressure ridging into the area will help keep coverage limited. Overall the chance for rain will be lower than the past few days with a low threat of severe weather. Although we cannot rule out the possibility of a severe storm with slightly drier mid-level air in place and possible weak upper-level support. Saturday night should provide a brief break in the wet pattern. Mid-level drier air moves into the region and precipitable water values drop to below 1.5 inches. Highs will generally be in the mid to upper 80s with lows overnight in the mid to upper 60s. && .LONG TERM /SUNDAY THROUGH FRIDAY/... A surge of tropical moisture will move northward into the forecast area Sunday afternoon or Sunday night. Strong moisture transport and weak potential instability should yield widespread showers and some thunderstorms along with a heavy rain threat through Monday. Flash flooding may be possible, particularly in flood-prone areas and where heavy rainfall in the past several days have saturated soils. The CSRA and areas along and south of I-20 have received 2 to 5 inches of rain in the last seven days and may be more prone to flash flooding. A flash flood watch may be needed. The unsettled weather pattern is expected to continue through much of the extended forecast period. Moderate to heavy rainfall may be possible through the remainder of the long term, although confidence is not high enough to include heavy rain in the forecast after Tuesday mainly because of the possible track and intensity of Subtropical Storm Alberto. Nevertheless, there is high confidence in an abundantly moist air mass with precipitable water values around or above 2 inches throughout the period with persistent southerly flow off the Gulf of Mexico. There is at least a high chance of showers and thunderstorms through Thursday. High temperatures during this period will be near normal, in the mid to upper 80s, and above normal for lows, in the upper 60s to lower 70s. && .AVIATION /02Z SATURDAY THROUGH WEDNESDAY/... Shower and thunderstorm coverage should continue to diminish because of nocturnal cooling. Most of the guidance indicates IFR ceilings again developing overnight given abundant low- level moisture combined with nocturnal cooling. Fog development may be limited given a 15-knot low-level jet and weak instability. Should see improving conditions by 26/15Z because of heating and mixing. We leaned toward the GFS LAMP for the timing of IFR conditions. Showers and thunderstorms are not expected to be as widespread Saturday afternoon with a little more pronounced ridging. The thunderstorm chance was too low to include in the terminal forecasts at this time. EXTENDED AVIATION OUTLOOK...Restrictions in late night and early morning fog and stratus should develop Saturday night into early Sunday morning. Tropical moisture associated with Subtropical Storm Alberto will increase by the late Sunday into Monday, increasing the frequency and intensity of showers and associated restrictions. && .CAE WATCHES/WARNINGS/ADVISORIES... GA...None. SC...None. && $$ SYNOPSIS...99 NEAR TERM...99 SHORT TERM...99 LONG TERM...99 AVIATION...99
Area Forecast Discussion...UPDATED
National Weather Service Austin/San Antonio TX
838 PM CDT Fri May 25 2018 .UPDATE... Isolated severe storm moving into San Saba county mid evening. The storm is on track to clip Llano county and has necessitated an update to the PoP/WX forecast for this evening. The storm is shown by the HRRR to gradually weaken with loss of daytime heating/increasing convective inhibition as it clips the far northern CWA and should eventually dissipates around 11 PM. && .PREV DISCUSSION... /ISSUED 656 PM CDT Fri May 25 2018/ UPDATE... See below for the 00z aviation discussion... AVIATION... Currently VFR at all sites under mostly clear skies and light southeasterly winds. Convection across portions of northern central Texas is moving south, but should dissipate before reaching the Austin area. VFR conditions are expected to persist at all sites through the evening hours and into early Saturday morning. SAT may see ceilings lower to MVFR intermittently between 10z and 15z Saturday morning due to a stratus deck developing. Also included a scattered cloud deck at around 2500 feet at AUS and SSF during this same time period to indicate the possibility of a brief moment or two where ceilings may lower to MVFR. Any lowered ceilings to MVFR should end by 15z Saturday morning with mostly clear skies persisting for the remainder of Saturday. DRT is expected to remain VFR for the entire forecast period. Winds at all sites will remain light and out of the south. PREV DISCUSSION... /ISSUED 229 PM CDT Fri May 25 2018/ SHORT TERM (Tonight through Saturday Night)... All is fairly quiet across South-Central Texas at the present hour with just some fair weather cumulus clouds around the region. Showers and isolated storms have remained well east of the CWA and think the bulk or if not all of the activity will remain out of the CWA this afternoon. Have left the mention of isolated thunder with a 10 PoP through the afternoon hours for the eastern counties. The focus then shifts to a complex of storms northeast of Dallas that continues to slide to the southeast. This main complex will remain well to our northeast and am not expecting any direct impacts from it. However, the past few runs of the HRRR develops some storms along the western end of the outflow boundary west of Fort Worth around 4 PM. The northwest flow aloft pattern we are in would eventually bring any storms in this area south to near Williamson County this evening. Have kept PoPs below 15 percent for now, but did include a mention of isolated thunderstorms for Williamson County in the 00z-03z time frame. Latest visible satellite imagery does show from agitated cu in the area the HRRR develops convection and this increased confidence slightly to warrant a mention of the iso thunder. The forecast will likely be updated closer to 00z to either increase or decrease PoPs depending on how the potential storms evolve. If a storm does develop and make it to the CWA, it could be strong. Otherwise, tonight will be warm with lows in the 70s for much of the CWA with upper 60s possible for the Hill Country. Have a rain-free forecast for the remainder of the short-term forecast as the upper ridge continues to amplify and move closer to our area from the west. Highs tomorrow will be quite warm, especially for the western CWA where highs above 100 are expected. Middle to upper 90s can be expected for the eastern counties. Lows tomorrow night will be very similar to tonight. LONG TERM (Sunday through Friday)... The long-term forecast will remain dominated by the upper level ridge. Hot and dry weather can be expected with highs in the upper 90s to 104 degree range each day with the higher values in the southwestern CWA. The GFS has come more into an agreement with the ECMWF for our area as south/southeast winds in the lower levels of the atmosphere keep temperatures from getting too out of hand. Otherwise, no rain is expected in the long-term under the ridge, Welcome to Summer 2018. && .PRELIMINARY POINT TEMPS/POPS... Austin Camp Mabry 73 96 73 96 74 / 10 10 - 0 0 Austin Bergstrom Intl Airport 72 95 72 95 73 / 10 10 - 0 0 New Braunfels Muni Airport 72 95 71 96 73 / 10 - 0 0 0 Burnet Muni Airport 71 95 71 96 72 / 10 10 - 0 0 Del Rio Intl Airport 74 104 74 103 75 / 0 0 0 0 0 Georgetown Muni Airport 72 95 72 95 73 / 10 10 - 0 0 Hondo Muni Airport 71 98 70 99 73 / 0 0 0 0 0 San Marcos Muni Airport 72 96 71 97 73 / 10 - 0 0 0 La Grange - Fayette Regional 73 94 72 94 73 / 10 10 - 0 0 San Antonio Intl Airport 72 97 72 98 74 / 10 - 0 0 0 Stinson Muni Airport 73 97 73 98 74 / 0 - 0 0 0 && .EWX WATCHES/WARNINGS/ADVISORIES... None. && $$ Mesoscale/Aviation...Williams Synoptic/Grids...Runyen
Area Forecast Discussion
National Weather Service Grand Forks ND
657 PM CDT Fri May 25 2018 .UPDATE... Issued at 655 PM CDT Fri May 25 2018 Nicely defined vort max moving toward Winnipeg at 23z. This vort responsible for enough lift to get sct t-storms going over parts of the RRV/NW MN. As for max moves east and the sun sets the threat for convection will diminsh in NW MN. On southwest side of vort we have had good mixing with drier air aloft mixing down and this has caused wind gusts into the 30-40 mph range in NE ND the last few hours. && .SHORT TERM...(This afternoon through Saturday) Issued at 321 PM CDT Fri May 25 2018 Organized forcing is mainly north of our CWA with shortwave troughs over southern Canada. Despite disorganized forcing locally, instability, mid level moisture, and several weak surface troughs/convergence zones have helped kick of isolated showers/thunderstorms over parts of our CWA. Most CAMs show isolated activity over much of our CWA, but HRRR does indicate maybe an increase in coverage over NW MN. ML CAPE is still 500-1000 J/KG limiting severe concern somewhat, but surface based parcels would still feed into a very unstable air mass, so isolated/stronger cells still can`t be ruled out. Moisture profiles (inverted-V) and DCAPE over 1000 J/KG raises concern for microburst/downdraft potential with activity, but without more organization threat should be very localized/isolated. With marginal to unfavorable mid level lapse rates and middling forcing activity should be highly diurnally driven and wind down quickly after sunset. Upper troughs are even further east on Friday, so other than Lake of the Woods region, most locations should see dry conditions. Near record or record highs are expected once again Friday with many locations around 90F or warmer (a little "cooler" in the northern RRV). As has been the case winds may also be underdone in guidance based on mixing heights, so I trended winds up a bit from standard blend towards MOS blend which has tended to be closer on wind speeds (still a little low). Winds should be low enough and RH high enough to keep us below RFW criteria, but it is worth monitoring like today (could be "near" critical again). .LONG TERM...(Saturday night through Friday) Issued at 321 PM CDT Fri May 25 2018 Hot, possible record heat for Memorial Day Weekend. Cooler but still above normal temperatures Tuesday through the rest of the next work week. Chance for showers and thunderstorms in the Northern Plains throughout the next week. Upper level ridge with an upper low over the Nevada/Utah area defines the upper level pattern at the start of the period. Some embedded short waves will move over the area to help increase the chances of showers and thunderstorms. Saturday night into Sunday morning the east chance for shower and storms will be in eastern North Dakota associated with a surface low to the southwest. Sunday night the shower and rain threat increases as another surface low moves in from the west. MU CAPE late Sunday could approach 1500 to 2000 J/kg. On Monday MU CAPE could be higher with values over 3000 J/kg in the NAM and GFS. Bulk shear over 40 knots also present in the Northern Plains so there is severe potential with these storms. One of the major limiting factors here will be the amount of CIN as it is forecast to be high as well over this period. Tuesday into Wednesday high precipitable water values in the NAM and GFS are above the 90th percentile for nearby sounding climatologies (BIS, ABR, and INL). This is supported by the previous upper low becoming dislodged and the trough moving towards the Northern Plains. Dryer weather expected Thursday before another chance for rain late next week. && .AVIATION...(For the 00Z TAFS through 00Z Saturday evening) Issued at 655 PM CDT Fri May 25 2018 Gusty west winds to 30 kts in NE ND and isold tsra in NW MN will occur thru sunset. Winds will calm down under 10 kts after dark and the convection will diminish. Quite overnight into Saturday with VFR conditions. Daily CU Sat aftn likely...esp N/E. && .FGF WATCHES/WARNINGS/ADVISORIES... ND...None. MN...None. && $$ UPDATE...Riddle SHORT TERM...DJR LONG TERM...NC AVIATION...Riddle
National Weather Service Jackson KY
1107 PM EDT Fri May 25 2018 .UPDATE... Issued at 1102 PM EDT FRI MAY 25 2018 Pops have been updated based on recent radar, satellite, and convective allowing model trends. This led to a bit higher pops in parts of Pike County and McCreary County over the next hour or so with a lull for a few hours overnight. However, several of the convective allowing models including the HRRR have showers and possibly a thunderstorm moving north into the TN and VA border counties prior to dawn as the upper level trough approaches. Some slight chance pops were added during that time frame in the south. Also, coverage of fog was adjusted to add more fog in Pike County down into Letcher County where heavier rain fell. UPDATE Issued at 840 PM EDT FRI MAY 25 2018 A few showers and even a thunderstorm near the TN and KY border linger as sunset approaches. This convection is largely diurnally driven and should wane over the next 1 to 2 hours. The overnight hours should generally be dry. With the upper trough working in, some of the convective allowing models indicate the potential for an isolated shower toward dawn in the southwest part of the area. We will continue to monitor trends on this. Otherwise, outside of showers, clouds will decrease and locations that picked up heavier rainfall from showers and thunderstorms today are expected to experience more widespread fog and it may become dense. Some of these locations include Whitley County near the I 75 corridor and portions of the Big Sandy region and portions of Letcher county. More widespread coverage of fog has been added overnight in these areas. Otherwise, fog development is anticipated in the valleys. && .SHORT TERM...(This evening through Saturday night) Issued at 405 PM EDT FRI MAY 25 2018 The afternoon surface analysis shows a weak boundary across the the Tennessee Valley and a surface high pressure off the North Carolina Coast. This high pressure is continuing pump more moisture into the region this afternoon, with dewpoints climbing into the mid 60s this afternoon. The latest radar data shows some showers and perhaps a isolated thunderstorm developing across the region. Interestingly, the lack of steering flow is leading to arcing outflow boundaries this afternoon and this could make convection more difficult to nail down through the early evening. Given this will keep thunder in isolated to scattered wording this afternoon and early evening. The CAMs have the mess of convective outflows and thunderstorm complexes across western Kentucky weakening this evening. Given this and the waning convection through the evening, and did lower POPs overall given the lack of steering flow from the west and loss of daytime heating. There could be some fog tonight in the river valleys or perhaps more so where rain has fallen this afternoon. This will have to be more fine tuned this evening. Temperature splits remain possible tonight, but they should be less overall given a little more cloud cover to contend with. An upper level trough across the Midwest will slowly spill weak height falls into the Ohio Valley Saturday. This in combination with strong low level lapse rates, modest mid level lapse rates, increased moisture and MUCAPE around 2000 J/kg should yield more numerous coverage in convection mainly in the afternoon on Saturday. Given the lack of larger scale forcing or surface features to work with this will be harder to nail down exact locations. The main threats will be heavy rain and frequent lightning given the lack of shear. By later in the afternoon, this maybe driven by convective outflows to a extent, but that will have to be evaluated as we get closer to that time. This convection may linger into the evening and perhaps some showers linger into the overnight. Did add some fog again for Saturday night, but again this is hard to nail down given the uncertainty on exactly where rain will fall. The temperatures splits will likely be more limited Saturday night as well given the additional cloud cover. .LONG TERM...(Sunday through Friday) Issued at 405 PM EDT FRI MAY 25 2018 A large but weak upper trough axis will extend from the Great Lakes to the Gulf of Mexico at the start of the period, with a strengthening tropical system (Alberto) over the northern Gulf. The northern extent of the trough will be progressive, while the flow around the tropical system becomes more closed as it deepens. This would shear the deep moisture regime originally over our area at start the period, shunting it southeastward, and allowing drier air aloft to advance southeastward over eastern KY. This would tend to keep precip more sparse, especially over the northwest part of the area. Meanwhile, the developing col in the geopotential heights over our area would lead to weak flow and rather featureless mid/upper levels, resulting in the movement and coverage of any precip becoming more limited from Sunday into Monday. As Alberto moves inland and weakens beginning Tuesday, we will come more under its influence and deep moisture should make a comeback. Along with this would come an increase in precip coverage. Aside from this generality, there is still a lot of uncertainty. The mid week forecast depends largely on the development and demise of Alberto, and models do not agree on the timing and track of the system in its waning stages. It`s still possible for it to track north, south, or over our area. Whatever the case, it should be to our east by Friday. However, without any real change in air mass, there still could be diurnal convection which pops up on Friday. && .AVIATION...(For the 00Z TAFS through 00Z Saturday evening) ISSUED AT 835 PM EDT FRI MAY 25 2018 Much of the first 6 hours of the period should feature VFR, outside of the few locations experiencing some initial showers and or an isolated thunderstorm with brief MVFR or IFR reductions. Otherwise, valley fog with mainly MVFR reductions and spotty IFR is expected to develop by 6Z to 8Z and generally not affect the TAF sites with the exception of SJS that received rain this evening. Reductions to at least MVFR by 3Z are anticipated there and some IFR fog is anticipated from about 6Z to 12Z. Convection is expected on Saturday, possibly before 15Z with chances lingering through the end of the period. Confidence in timing of onset and thunder on station at any one location was to low for more than prevailing VCTS during the second half of the period. Winds will average light and variable outside of any thunderstorms. && .JKL WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...JP SHORT TERM...DJ LONG TERM...HAL AVIATION...JP
Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
834 PM CDT Fri May 25 2018 .UPDATE... 834 PM CDT Pattern far more reminiscent of mid-summer than May with weak synoptic forcing convection largely being driven by MCVs. One weakening MCV from last night`s convection is supporting a small cluster of showers a couple t-storms across east central IL, including our far southern CWA. This activity is likely to weaken over the next couple hours, likely dissipating by midnight as it encounters drier and more stable air mass. Upstream over NE IA and SW WI another area of convection has begun to show some signs of mesoscale organization, with a QLCS bowing toward SE. The evening sounding from DVN sampled a modestly unstable environment with CAPE around 1000 j/kg, however boundary layer is currently cooling and atmosphere is beginning to stabilize. Could see another MCV develop in the bookend of this developing bow, which could augment the weak ambient shear environment and help this activity sustain itself as it pushes into NW IL mid-late this evening. Would generally expect a weakening trend, particularly with the eastern extent of this line as it encounters a more stable and worked over air mass. GOES-16 1-min IR imagery has shown a tendency for warming cloud tops and weakening of the convection over SW WI and some cooling cloud tops (intensification) over IA where instability is greater. Will likely be a bit of battle of opposing forces the next several hours as instability axis over eastern IA would tend to support more of a southward propagation of this convection, while current storm motion and the development of a MCV would tend to favor more of a SE motion toward our CWA. At this point, planning to increase pops far western CWA late this evening to account for this activity potentially spreading in. However, given the weaker instability in our area, suspect the threat of more robust storms should remain west of our CWA, though certainly lightning and heavy downpours look quite possible. - Izzi && .SHORT TERM... 253 PM CDT Through Saturday... Scattered shower and thunderstorm trends are the main forecast concerns through this evening, with continuation of very warm summer-like weather persisting into the holiday weekend. Early afternoon surface analysis depicts weak low pressure over western IL, along a pseudo-warm front extending from along the Mississippi River into far southern IL. This weak low, and an area of thunderstorms over western IL, were associated with a mid- level short wave trough propagating across the region. The primary low level focus for storms appears to be the warm frontal trough, further enhanced by differential heating due to cloud cover, and convective outflow. These storms should continue to move slowly to the east-northeast across the forecast area through the remainder of the afternoon and early evening hours, though instability gradually decreases farther east. This, combined with weak mid- level lapse rates and weak deep-layer shear, should allow for a general decrease in intensity and coverage with eastward extent into early evening as diurnal instability diminishes with sunset. While SPC has stretched the day 1 marginal severe risk east to the IL/IN border, overall lack of deep shear and warm thermal profiles should preclude much of a severe threat, with the main concern being the potential for isolated wind gusts. Locally heavy rainfall is likely a greater threat, given slow cell movements and p-wats approaching 1.80". High-res CAM guidance continues to indicate some potential for storms currently developing over southeastern MN to develop southeastward into parts of northwest/north central IL after midnight tonight. Forecast soundings, especially from the NAM, suggest substantial elevated CAPE may be present over northwest IL during the early overnight hours, though veering of the H8 winds and overall lack of deep shear suggests that storms may struggle to push too far south. 3km WRF, HRRR and ARW runs all weaken these storms as they spread into IL during the pre-dawn hours, and have generally limited mention to low chance pops for these. Primary mid-level trough passes across the region early Saturday, with weak height rises developing during the day. While low level wind fields turn light westerly behind the trough, air mass remains very warm and moist. While no significant forcing is noted, an isolated shower or thunderstorm can`t be ruled out during the peak heating hours of the afternoon where weak low level convergence of subtle mid-level vort may interact, however most areas will likely remain dry. With at least partly sunny conditions, temps should again reach the upper 80`s/around 90 degrees, with a weak lake breeze likely keeping areas along the immediate Lake Michigan shore a little cooler. Ratzer && .LONG TERM... 231 PM CDT Saturday night through Friday... Surface high pressure will be across the area Saturday night while upper ridging to the west slides into the area into Sunday night. Overnight lows will remain warm with mid and upper 60s while the heart of the Chicago metro see lows around 70, if not warmer. With the upper ridge pushing in Sunday low and mid level warming peaks with 850 mb temps around 20C. This supports low 90s with a few mid 90s possible given that sunshine should be abundant. Limiting factor from reaching mid 90s may be weak low level winds. This weak flow will also allow a lake breeze to develop which should provide some relief from the hottest temps near the lake. Main question will be how high temps peak before some modest cooling into the mid/upper 80s in the afternoon. Peak heat index values should be around 95 away from the lake. The upper ridge broadens for Monday with surface high pressure still in place so may not see much change from Sunday and may need to bump high temps up a couple degrees similar to the forecast for Sunday. Expect either a weak easterly flow on the west side of the high or a lake breeze to develop keeping lakeshore areas cooler. The upper ridge starts shifting east Tuesday and an upper trough will move east across the northern plains. The current sub tropical low is expected to move into the Gulf coast states by Wednesday will have an impact on pattern evolution and may phase the northern plains trough. Quiet a few things need to occur before mid week so confidence in details is low but the area may get into some precip chances as early as Tuesday and could continue through mid week. Am fairly confident that a warm pattern, though not as warm as the next few days, will continue with highs generally in the 80s. The pattern may favor an easterly flow or lake breeze development so lakeshore areas look to be cooler through much of the week. MDB && .AVIATION... For the 00Z TAFs... VFR conditions expected through the forecast period. S/SW winds will remain generally under 10kts at all sites. A weak lake breeze should pass ORD/MDW late Saturday afternoon into the early evening. At RFD, a cluster of TSRA currently over far southeast MN is expected to remain just west of the terminal, but a few showers may brush the terminal between 03-07Z. Kluber && .MARINE... 231 PM CDT South to southwest winds will prevail across the open waters through the weekend with the strongest winds occurring into this evening. A weaker flow pattern will allow winds to ease Saturday and Sunday and will also favor the development of onshore flow across the Illinois and Indiana nearshore waters each day. A weak front drops down the lake later Monday bringing at least a temporary shift to northeasterly flow. After that the pattern becomes less certain with the sub tropical system currently off the Yucatan Peninsula moving into the Gulf coast states early next week. This may interact with a trough moving across the northern Plains but this is not certain. Do not foresee any major wind producing systems affecting the lake but wind speed and direction details from Tuesday onward may change. MDB && .LOT WATCHES/WARNINGS/ADVISORIES... IL...None. IN...None. LM...None. && $$ VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE) FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT: WWW.FACEBOOK.COM/NWSCHICAGO WWW.TWITTER.COM/NWSCHICAGO WWW.YOUTUBE.COM/NWSCHICAGO
This extended forecast discussion will be focused on two weather
items. The first will be the strength of a southwest to northeast
oriented, vertically stacked, high pressure ridge to suppress convective activity on Monday (Memorial Day), and secondly, the impacts of the subtropical named circulation Alberto on parts of the WFO PAH forecast area between Tuesday and Thursday of next week. For Monday and Monday night(Memorial Day), subsidence associated with the ridge should suppress any convection (showers and thunderstorms during the morning and evening hours. A few storms may develop during the heating of the day in the afternoon, so a small chance of storms was added during this time period. Heat index values will likely reaching into the 90 to 95 degree range during the afternoon outside of any rain areas. The 12z ECMWF is a little more robust about developing afternoon convection over the WFO PAH forecast area on Monday, but kept the WFO PAH forecast area dry to reflect the collaborative input from surrounding offices and to keep within the regional model guidance initialization. For Tuesday through Friday, given the range of forecast possibilities associated with the current subtropical storm Alberto, plan to keep the local forecast close aligned to the Tropical Prediction Center/National Hurricane Center (TPC/NHC) and the Weather Prediction Center (WPC) forecasts. Those with specific interests associated with this circulation should refer to these NOAA/NWS websites for more information. A this time, the TPC/NHC forecast most closely aligns with the 00z ECMWF guidance with the position and general intensity of the expected remnants of Alberto, as it is forecast to move through eastern Mississippi, western Tennessee, and near the Pennyrile region of West Kentucky. The latest 12z Friday model run of the ECMWF places the center of the circulation near the Todd/Muhlenberg County KY by 7 pm Wednesday. At this point, frictional effects of the circulation over land, the diurnal expansion and contraction of the dynamic precipitation core with the circulation, and the interaction with the surrounding ridge may play havoc with the timing, location, and intensity of the circulation and attendant precipitation. From a QPF (rainfall amount) perspective, a majority of the rainfall associated with the circulation is expected to fall during the afternoon/evening hours on Tuesday, Wednesday, and Thursday. With this forecast package (subject to many changes the next several days), rainfall amounts are forecast to range from 0.6" to 1.00" across the Pennyrile region of West Kentucky and into southwest Indiana. WPC`s seven day forecast of QPF, suggests 1.5" to 2.00" over the same area, but this includes any and all forecast rain from today (Friday) through next Friday, June 1st. This would suggest that at least half of the rainfall next week may likely be associated with the remnants of Alberto, assuming it maintains a similar track. Again, there will be some uncertainty as to the eventual track and impact of Alberto for our area. Temperatures next week will remain coolest (lower 80s) in the vicinity of the greatest rainfall and cloud cover expected with subtropical storm Alberto. However, after the passage of this system, temperatures will be on the rise with subsidence behind the circulation. This will likely generate heat index values in the upper 90s on May 31st, with some locations see heat index values around 100 during the afternoon on June 1st. && .AVIATION... Issued at 622 PM CDT Fri May 25 2018 With the loss of daytime heating, convective intensity will dwindle through the evening hours. However, the atmosphere is very moist, and there is a disturbance in the upper levels of the atmosphere. These factors will likely keep some isolated showers going overnight. Where heavy rain fell today, some fog is likely during the overnight hours. The fog could become rather dense if skies cleared out totally, but mid level clouds are forecast to be rather persistent. On Saturday, quite a bit of sun in the morning will give way to lots of cumulus clouds and more scattered storms in the afternoon. Any storms will again have the potential for heavy rain. && .PAH WATCHES/WARNINGS/ADVISORIES... IL...None. MO...None. IN...None. KY...None. && $$ SHORT TERM...DRS LONG TERM...Smith AVIATION...MY
Area Forecast Discussion
National Weather Service Blacksburg VA
833 PM EDT Fri May 25 2018 .SYNOPSIS... High pressure offshore will maintain a moist southerly flow of air across the region into the weekend. Subtropical Storm Alberto moving into the Gulf of Mexico this weekend will move ashore and wobble over the lower Mississippi Valley early next week. Tropical moisture will stream northward into the region with a return of showers and storms especially during the afternoons and evenings over the next few days. && .NEAR TERM /THROUGH SATURDAY/... As of 800 PM EDT Friday... A quick update to reduce pops, cloud cover, and bring temperatures into line with current readings. No major changes though. Convective activity, just showers so far, with outer fringes of tropical moisture very widely scattered so far and confined to areas west of the Blue Ridge. HIRES HRRR and NAMNest suggest this activity will dissipate quickly after sunset, but showers may drift back into the area later in the night. Cloud cover is also quite scattered at this point, so reduced the percentages about 20% across the board at this time. As of 230 PM EDT Friday... Seeing small clusters of convection develop within southeast flow along the southern Blue Ridge and foothills as well as across the far western ridges where an axis of higher instability off to the west prevails. Latest short term guidance continues to focus most convergence across the far western/southwest counties through sunset with added clusters/bands of at least shallow convection espcly along the I-77 corridor. Otherwise expect only isolated coverage at best elsewhere over the southern/western tier and just some leftover cumulus across the northeast where residual ridging lingers. Appears will see most coverage fade with loss of heating this evening given lack of support with the boundary well to the south, so trimmed back pops to isolated or low chance mainly west which may be generous into the overnight. However combination of increasing southwest flow and deeper moisture may lead to added showers espcly south before daybreak where forecast soundings show a rather saturated column late. Should also see some fog around in the valleys and where earlier rain occurred but likely limited via cloud cover so keeping coverage patchy at this point. Lows again mainly in the 60s with some cooler 50s western valleys. Upper heights continue to slowly decrease on Saturday as the surface high slides farther offshore. This in conjunction with increasing southwest flow and a surge in moisture, per PWATs rising to above 1.5 inches, should allow for more widespread convective coverage by afternoon. Appears initial coverage along the southern Blue Ridge and points west by midday per forecast 85h theta-e axis/southwest flow, with showers/storms spilling east into better forecast instability east of the ridges in the afternoon as weak mid level wave also tracks east. This along with slow movement given forecast steering of around 10 knots or less likely to result in a heavy rain concern with even some stronger pulse storms possible within bands. Therefore expecting a quick diurnal increase in convection from chance pops west early to likelys most locations in the afternoon with even categorical in spots along the eastern slopes of the Blue Ridge. Otherwise still warm and quite muggy with highs low/mid 80s east and mostly 70s mountains. && .SHORT TERM /SATURDAY NIGHT THROUGH MONDAY NIGHT/... As of 300 PM EDT Friday... Northern stream trof will move east through New England this holiday weekend as Subtropical Storm Alberto slowly moves up the eastern Gulf and into the Southeast. Please refer to the latest advisory or statements from the NHC on Alberto. Unsettled weather is expected during the period with a flow of deep moisture into the Appalachians. A series of weak shortwaves will rotate up from the south and spark good coverage of diurnally showers and thunderstorms for the weekend. It will not be raining the whole time, and most should be able to work in a holiday picnic. Potential tropical system will remain near the Gulf Coast Monday through Wednesday between upper ridge over the southwest then central United States and the off the southeast coast. Thursday the low opens and fills and moves northeast. Models have come into better agreement taking this feature into the Tennessee Valley by Thursday morning. ECMWF has the deeper moisture over Virginia and North Carolina again Wednesday and Thursday. SPC keep our forecast area in general thunderstorms on the convective outlook. However, the instability looks healthy but deep shear is lacking. The combination of recent rains and high PWATs will support heavy rainfall and set up the possibility of flooding with training convection, along with some degree of severe threat with the most vigorous storms. Saturday evening convection will taper off to isolated to scattered showers Saturday night. Low temperatures Saturday night will range from the upper 50s in the mountains to the mid 60s in the piedmont. The best chances of thunderstorms on Sunday will be along and west of the Blue Ridge mountains. High temperatures will vary from the lower 70s in the mountains to the mid 80s in the piedmont. On Sunday night, Alberto lifts northward along the Gulf coast as the upper trof over the northeast pulls out. This may stretch dynamic forcing out and may keep the highest precipitation in the south. Low temperatures Sunday night will generally be from the lower 60s in the west to the upper 60s in the east. Unfortunately, there a good to likely chance of showers and thunderstorms for Monday. Highs will vary from the lower 70s in the mountains to around 80 degrees in the piedmont. Kept scattered showers and isolated thunderstorms in for Monday night with low temperatures from the lower 60s to the upper 60s. Will continue to highlight the region for potential hydro issues in the HWO and wait for a more specific region to declare itself in time before considering any watches. && .LONG TERM /TUESDAY THROUGH FRIDAY/... As of 300 PM EDT Friday There is the potential for periods of heavy rain during the medium range with Alberto and its track. Please refer to the latest advisory from the NHC on Alberto. By mid to late week, remnants of the tropical system could bring tropical moisture and heavy rains to our region. Flooding potential will depend on the track of the system and how much rainfall is accumulated from the showers and thunderstorms earlier in the week. The latest NHC track places Alberto in southern Mississippi by Tuesday morning, then its lifts northward into the Tennessee valley on Wednesday. The timing of the ECMWF was quicker and further north and west (Ohio Valley) compared to the GFS which was slower and more compacted (along the Appalachians. By Thursday and Friday, the low will open up and weaken as it moves northeast. There is a continued threat for showers and thunderstorms into the end of the week. Urban and small stream flooding risk will be highest early in the week with river flooding possibly by the end of the week depending on actual rainfall totals. && .AVIATION /01Z SATURDAY THROUGH WEDNESDAY/... As of 800 PM EDT Friday... Generally VFR conditions in place across the CWA and at all TAF sites at this hour. Would expect this to continue through the next several hours as the atmosphere above 850mb remains quite dry. Outer fringes of tropical moisture from Alberto beginning to encroach on the area and isolated light to moderate showers developed along the Blue Ridge this evening. The immediate activity will likely dissipate, but with tropical moisture increasing through the period, additional showers are possible along and west of the Blue Ridge overnight. Main thing of note is increasing layers of clouds as tropical moisture spreads north from the Gulf of Mexico through the period. Would expect a trend to MVFR ceilings by morning west of the Blue Ridge, but most likely remaining VFR to the east. Fog potential is limited, given expected cloud cover, but MVFR BR seems plausible at BCB and LWB during the early morning hours. Winds will be SSE to SSW through most of the period at speeds of 5-8 mph, slightly higher during the daytime Saturday with low end gusts possible east of the Blue Ridge. As of 1250 PM EDT Friday... MVFR conditions across southern/western sections will continue to slowly improve to VFR as cigs scatter out and lift this afternoon. However sub-VFR cigs likely to remain along the Blue Ridge southwest of KROA where a few showers appear likely along the KHLX-KMWK-KUKF corridor. A few storms will also be close enough to KBLF, mainly along and west of the Interstate 77 corridor this afternoon to warrant a VCTS or TEMPO group, while keeping out mention elsewhere except for perhaps a VCSH at KBCB for now. Still looks like showers possible mainly southwest of a BLF- BCB line this evening, with broken deck of mainly high end MVFR to low end VFR cigs. Potential for fog is there, but only putting in where its typical and where it may rain. Cloud cover will limit the fog coverage outside of where rainfall occurred. Any fog or low cigs will slowly improve on Saturday but likely to see at least periods of MVFR cigs persist with deeper moisture in place. This should also lead to more in the way of showers/storms espcly over the mountains by midday, and across much of the region during the afternoon. This supports a VCSH mention at most locations outside of KLYH. .Extended Aviation Discussion... Wet pattern with periods of at least diurnally driven sub-VFR conditions in convection will take place into the middle of next week. Fog at night is possible if we clear enough due to wet ground conditions and rain. Worse conditions heading south to the Gulf Coast states, as a tropical system moves into the that area Monday or Tuesday. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...None. NC...None. WV...None. && $$ SYNOPSIS...JH NEAR TERM...JH/RAB SHORT TERM...KK LONG TERM...KK AVIATION...JH/RAB/WP
Area Forecast Discussion
National Weather Service Shreveport LA
919 PM CDT Fri May 25 2018 .AVIATION... For the 26/00Z terminals forecast will prevail with mostly VFR with lingering showers and thunderstorms associated with several outflow boundaries reducing flight categories briefly to MVFR. Could see visibility restrictions in rain and possibly mist/BR through 26/04Z. Later overnight after 26/09Z-26/12Z MVFR flight categories will be returning with patchy mist/BR. Will enter mention of convection earlier in the day Saturday with the position of the upper trough of low pressure across the Central and Eastern sections of the Four State Region. Surface winds will be light and variable less than 7 knots through most of the forecast period with a period of Southwest to West speeds near 7 knots early on Saturday from mid morning to mid afternoon. /06/ && .PREV DISCUSSION... /issued 253 PM CDT Fri May 25 2018/ SHORT TERM.../Tonight through Saturday Night/ A line of showers and thunderstorms that developed along an outflow boundary from a southeastward moving MCS across southeast OK earlier this morning, has slightly loss its perfectly linear look late this aftn. Though scattered showers and thunderstorms continued to affect portions of southeast OK, northeast TX and southwest AR, with isolated showers and thunderstorms elsewhere. Earlier this aftn, portions of the line of storms across McCurtain County did reach strong levels as it interacted with rather moist low levels /dewpoints in the upper 60s to lower 70s/ with hail, wind gusts and brief moderate rainfall being the main results, but have since become sub-severe. Can not rule out the occasional wind gusts that could warrant a Significant Weather Advisory or even a Warning but a widespread severe weather threat is low. As we continue to approach sunset, high-res solutions such as the HRRR exhibited a waning trend though with lingering precip as we head into the overnight hours. Thereafter, northwest flow aloft persists and another embedded impulse could once again ignite an MCS across southern OK, hence the mean-flow will propagate it to across the northwest zones aoa sunrise. Will once again have to look out for an outflow boundary that could aid in the generation of additional isolated showers and thunderstorms that model solutions sometimes struggle to pick up on. Elsewhere, daytime destabilization and plentiful moisture will yield isolated showers and thunderstorms. Just like what is expected tonight, the convection will gradually dissipate several hours after sunset tomorrow night. MOS guidance overnight temps is over-doing it a bit as persistence over the last several nights have been a few degrees cooler than what guidance have depicted. Furthermore, guidance is also a few degrees cooler during the day than what actually occurs. Will therefore continue to manually tweak both the overnight and daytime temps accordingly /overnight lows in the upper 60s to lower 70s and daytime highs mainly in the lower 90s/. Side Note: We continue to monitor the newly upgraded Subtropical Storm Alberto as it continues to become better defined just east of the Yucatan Peninsula. The National Hurricane Center still has a track that shows Alberto making landfall somewhere between southeast LA and the FL Panhandle Monday/Tuesday. The Weather Prediction Center still has the heaviest rainfall /4-7 inches/ across extreme southeast LA and eastward to the remaining Gulf coast States. /29/ LONG TERM.../Sunday through Thursday/ Alberto will be approaching the northern Gulf Coast while the ArkLaTex will still be under the influence of surface high pressure coupled with an upper level ridge. Our region will be on the west side of Alberto through about Wednesday before Alberto begins to pull out of the southeast US to the northeast. With this current forecast track, only far eastern portions of the area will see showers and thunderstorms from Alberto. Being on the west side of Alberto and under the influence of the ridge aloft will allow for the area to experience compressional heating from subsidence. The extended timeframe will see some 10 to 15 degree high temperature readings well above normal. Some locations will be experiencing near record high temperatures towards the latter part of the extended, if not flirting with triple digit readings. Long range guidance keeps the area dry throughout the period. /35/ && .PRELIMINARY POINT TEMPS/POPS... SHV 70 92 69 93 / 30 30 20 20 MLU 69 91 70 90 / 30 40 20 40 DEQ 69 91 67 92 / 30 30 10 10 TXK 69 90 68 91 / 30 30 20 20 ELD 69 89 68 91 / 30 40 20 30 TYR 72 92 72 93 / 30 20 10 10 GGG 71 92 71 92 / 20 30 10 20 LFK 71 93 72 93 / 10 20 10 20 && .SHV WATCHES/WARNINGS/ADVISORIES... AR...None. LA...None. OK...None. TX...None. && $$ 06/29/35