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

Area Forecast Discussion...UPDATED
National Weather Service Corpus Christi TX
935 PM CDT Sun May 20 2018 .DISCUSSION... Updated forecast based on radar trends and expected convection overnight. Not expecting much overnight maybe closer to the coast. Most of the activity well west of the Rio Grande should stay west or move south of the area overnight. Still did keep a low chance or slight chance after midnight to account for this. All forecast parameters for tonight and portions of Monday have been updated. Products are out. Made some adjustments to the marine forecast. That will be issued by 10 PM. && .PREVIOUS DISCUSSION... /Issued 659 PM CDT Sun May 20 2018/ DISCUSSION... Convective line stretches from Whitsett southward to George West with a broken line of storms extending southwestward to near Laredo. Some of these storms may be strong to possibly severe with strong to damaging winds being the primary threat. This threat should continue into the evening for a few more hours. Main reason for the update was to align pops closer to radar trends and expected movement of the storms during the evening hours. Additional updates will likely be needed. PREVIOUS DISCUSSION... /Issued 630 PM CDT Sun May 20 2018/ DISCUSSION... There will be an update coming out shortly on the evening package based on the current radar/radar trends and expected convective progress this evening and overnight. Also adjusting some other parameters as-needed to fall more in line with the observations. Update will be out shortly. See .AVIATION discussion for 00Z TAFs. AVIATION... Main issue is the convection and this set of terminals is based in part on radar and surface forcing trends (LAPS convergence), along with meso-model "trends" (meso models cannot be relied on for exact location of convection just that convection will likely be around some areas). Given that, am expecting convection to move more to the south during the evening, especially KLRD and KALI terminals, but also possibly into the KVCT terminal. Lots of surface moisture divergence near KCRP terminal at this time (thus against rain), and that is the tricky terminal but given that the models have been consistent on possibly having something proximate to the terminal this evening did also include convection here (weaker however). Best shot for convection is between 02Z and 07Z at KALI, 03Z and 08Z at KCRP, 01Z to 07Z at KLRD (possibly longer), and 01Z to 05Z at KVCT. Strongest storms (gusts greater than 30 knots likely at all but KCRP (but not that KCRP cannot get higher winds...cannot base on worst case situation). After the convection, should have MVFR CIGS develop all terminals, with some showers possibly in the vicinity of KCRP overnight. CIGS improve to VFR before by 17Z with potential for some convection during the afternoon again. For now, put in VCTS at KALI and KLRD during the afternoon with much uncertainty elsewhere. Less winds and more easterly in the forecast for tonight and Monday outside of convection. PREVIOUS DISCUSSION... /Issued 401 PM CDT Sun May 20 2018/ SHORT TERM (Tonight through Monday night)... Main forecast concern is thunderstorm potential this afternoon and evening. Convection associated with outflow boundary to the north will slowly approach the northwest and northern parts of the region over the next several hours. HRRR runs over the last few hours support this, and actually bring this area of showers and storms near the coast later this evening. MLCAPE values remain around 2000 J/kj at this time with little to no capping across South Texas. Strong storms will be possible as this activity moves into the area late this afternoon and early evening with primary threats of gusty winds and small hail. An isolated severe storm or two is not completely out of the question either. Some moderate to heavy rains may also occur with PW values around 1.7 to 1.8 inches. This area of showers and storms should slowly moves to the south and east tonight. Confidence is not that great of any redevelopment, but sufficient moisture lingering around will warrant low pops through 12z. Overnight lows will generally be in the lower to middle 70s inland with upper 70s along the coast. Any remnant boundaries coupled with an approaching upper level disturbance may result in isolated to scattered storms on Monday. Will continue with 30 to 40 pops, with best chances along the Rio Grande and western Brush Country. Highs tomorrow will be in the upper 80s to low 90s. LONG TERM (Tuesday through Sunday)... Ridging pattern will develop overhead on Tuesday. Sufficient moisture along the coast may allow for isolated showers or storms to develop and stream onshore throughout the day on Tuesday. Drier air will then push into the region Wednesday, with below normal moisture and dry conditions persisting into late in the week as mid/upper level ridging remains set overhead. A warming trend will continue through the week, with highs back near 100 degrees across the Brush Country and in the mid to upper 90s to the east by the end of the week. Over the weekend the upper level ridge will shift further to the west as a trough axis develops to the east of the region. Slightly higher moisture creeping into the coastal areas and less suppressive conditions aloft may allow for some isolated coastal convection to pop up again by the weekend. However, most locations will remain dry at the time. && .PRELIMINARY POINT TEMPS/POPS... Corpus Christi 74 88 73 90 73 / 60 30 10 20 10 Victoria 72 90 70 91 70 / 50 30 10 20 10 Laredo 75 92 74 94 74 / 20 40 10 10 10 Alice 73 91 71 93 71 / 60 30 10 10 10 Rockport 77 86 76 88 76 / 50 30 10 20 10 Cotulla 71 92 71 94 72 / 20 40 10 10 10 Kingsville 74 92 72 93 73 / 70 30 10 20 10 Navy Corpus 78 86 78 88 77 / 40 30 10 20 10 && .CRP WATCHES/WARNINGS/ADVISORIES... TX...None. GM...None. && $$ GW/86...SHORT TERM
Area Forecast Discussion
National Weather Service State College PA
1154 PM EDT Sun May 20 2018 .SYNOPSIS... A weak cold front will settle south of the area by this evening followed by drier air that will finally work into the region. During the day Monday, this same old frontal boundary will lift back northward as a warm front. Showers and scattered thunderstorms will accompany the front as it lifts north across the Commonwealth. Most of the showers and storms will be from late Monday into early Wednesday. && .NEAR TERM /UNTIL 6 AM MONDAY MORNING/... Current fcst on track. Earlier discussion below. Showers and storms south of PA as of 520 PM. Updated the grids. Afternoon discussion below. Satellite shows brightening skies, but with plenty of post frontal strato-cu over northern areas. The HRRR doesn`t make me optimistic for these clouds to mix out in time to bring much sunshine before the afternoon is over. Over the SE, still ahead of the weak front, a few showers are developing. They are still fairly squat and despite the RAP showing max CAPEs in excess of 1000J, lapse rates are not very impressive so we expect little more than some brief showers and maybe a rumble of thunder. The HRRR shuts things down fairly quickly after about 5PM. High pressure over the Upper Midwest/Northern Great Lakes will build SE and moves across Pennsylvania late tonight and Monday morning with fair/dry weather, lower humidity and light wind helping to yield cool temps. Recent rains have left conditions moist, so some late night fog looks like a fair bet. Lows tonight will vary from the upper 40s across the Northern Tier of PA to the lower 60s in the Southern Valleys. && .SHORT TERM /6 AM MONDAY MORNING THROUGH 6 PM MONDAY/... The gift that keeps on giving in the form of our cold front, will start to make a return Monday as a warm front. The first showers could reach my SWRN Laurel Highlands zones by mid day, but more likely we will see the chance for showers ramp up from SW to NE as the afternoon progresses. Ensembles show the PWATs starting to creep up and 12Z guidance shows some erosion in the stability, so thunderstorms will be possible. Highs should be relatively pleasant topping 70 everywhere. That`s a few degrees warmer than normal for the time of year. && .LONG TERM /MONDAY NIGHT THROUGH SUNDAY/... After being suppressed to our south early next week, the chances for convection will increase once again Monday afternoon and especially Monday night into Tuesday as moisture on the northern periphery of the subtropical ridge creeps back into the region as an old frontal boundary lifts to the NE as a warm front, putting the west into the warn sector. Numerous showers along with a few thunderstorms will bring a few to several tenths of an inch of rainfall to much of the region Monday night into Tuesday before drier air makes a push in from the NW behind a weak cold front starting Wednesday. Tuesday looks like the coolest day of the week, though humidity will be highest. From there it looks like the period form Wednesday through Friday will feature some rare (of late) rain-free conditions, before the chance for a pop-up shower or storm becomes returns for Sat. Temps look to climb into the 70s each day, with Saturday the warmest as high range from the mid 70s to the lower 80s. The coolest morning will be Friday with valleys of the northern mountains dipping into the mid 40s. More active weather returns for late weekend as another period of showers and scattered thunderstorms begins. && .AVIATION /04Z MONDAY THROUGH FRIDAY/... Clearing skies, a diminishing wind and wet ground will likely lead to areas of valley fog late tonight. The weakest pressure gradient and lightest winds should be across the northern tier, where SREF prob charts and NAMnest indicate the most widespread vis reductions late tonight. However, patchy fog is possible even into southern Pa late tonight. The one airfield least susceptible to radiation fog will be KJST, due to its ridgetop location. Any fog should mix out between 12Z-14Z. After that, there is some concern of MVFR cigs in the vicinity of KJST/KAOO later Monday, due to a developing easterly flow ascending the higher terrain of south central Pa. Based on an examination of varying model guidance, believe the odds of this are slightly less than 50 pct. Much drier air working into northern Pa should ensure VFR conditions across that part of the state Monday. Outlook... Tue...AM rain/low cigs possible. PM tsra impacts possible west. Wed...AM low cigs possible W Mtns. Thu-Fri...No sig wx expected. && .CTP WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...La Corte/Martin NEAR TERM...La Corte/Martin SHORT TERM...La Corte LONG TERM...RXR AVIATION...Fitzgerald
Area Forecast Discussion
National Weather Service Cheyenne WY
523 PM MDT Sun May 20 2018 .SHORT TERM...(Tonight - Monday) Issued at 219 PM MDT Sun May 20 2018 Showers & a few thunderstorms are developing along and west of the Laramie Range this afternoon, in response to a mid-level shortwave lifting northeast across southwestern CO in advance of a deepening upper low over the western US. Limited moisture & instability will preclude a risk for strong storms, but activity may linger through much of the evening aided by ample dynamic support. Recent runs of the HRRR suggest at least isolated showers may persist through 06z or so before diminishing. Fog is possible again tonight w/ moist low-level upslope remaining in place along/east of the Laramie Range. Moisture profiles should not be quite as supportive of widespread dense fog tonight, but we could see some areas of visibilities as low as 1/4 mile. Expect to see any fog diminish by mid-morning on Monday. Convective activity will be possible once again on Mon w/southwest flow aloft ahead of a closed upper low over southern California. A bit of an issue with capping/subsidence associated w/ a short-wave ridge over the central Rockies, so expect the bulk of the activity to be confined to the higher terrain. Highs will continue to trend warmer as H7 temperatures climb to +8 to +12 deg C. .LONG TERM...(Monday Night - Sunday) Issued at 227 AM MDT Sun May 20 2018 Main highlight in the long term will be the warming temperatures through the period and afternoon shower and thunderstorm chances. The more significant coverage and intensity day of storms could be Wednesday for far east WY and moreso the NE Panhandle. By Tuesday, the H5 ridge axis will shift east in to the Central Plains as a large western CONUS closed low pivots into the Great Basin. Greater southwest flow aloft for western areas in the mountains should allow for greater spatial shower and storm coverage but instability and shear combination looks to marginal at best. Going into mid-week on Wednesday, the closed H5 low over the great basin will open up and shift northeast across the Rockies. Stronger H3 diffluent flow aloft along and instability over the High Plains (especially more so NE Panhandle) should support stronger thunderstorm development. A negating factor is wind shear as it continues to look meager in the 25-35 knot range. Strong pulse to semi- organized storms could be possible Wednesday afternoon into evening. By late week, the base of the transiting trough axis will shift north of the region. Stronger west winds will develop and shunt deeper moisture farther east into the Central Plains as drying vertical profiles occur. Friday and into the early weekend, weak northwest flow develops as the trough axis passes east and H5 ridging shifts in just west of the Rockies. Just enough impulse/vorticity difluence aid and meager instability could help scattered showers and isolated thunderstorms over the higher terrain but overall coverage will be limited and the High Plains will likely remain rain free. && .AVIATION...(For the 00Z TAFS through 00Z Monday evening) Issued at 518 PM MDT Sun May 20 2018 Mainly VFR conditions are expected at area terminals this evening and tomorrow. One area with somewhat limited confidence is the development of patchy fog tonight at KCYS. Models show CIGS falling quickly with visibility under one quarter mile. While confidence on exact visibilities are low... expect some fog and lower ceilings to develop around 10z and continue through early morning. A few VCTS are possible for KLAR tomorrow but elsewhere should remain VFR through the period. && .FIRE WEATHER... Issued at 227 AM MDT Sun May 20 2018 Despite the warmer and drier conditions, fire weather concerns will remain low as ample rain amounts have occurred over the past several days for many areas. One areas that missed out on rainfall was Carbon County. However, they should remain in the upper 20 to low 30 percentiles relative humidity wise this afternoon. A few higher terrain showers and isolated weak thunderstorms will be possible this afternoon but overall coverage will be low to zero elsewhere. A few isolated showers/storm could again be possible Monday across the Laramie Range and into the NE Panhandle. Coverage again is expected to be low. Relative humidity values will fall near 20 percent but winds should remain below critical thresholds at 15 to 20 mph from the southwest. Overall long range forecast appears to remain just moist enough during the afternoons to preclude high fire concerns at this time. && .CYS WATCHES/WARNINGS/ADVISORIES... WY...None. NE...None. && $$ SHORT TERM...CLH LONG TERM...JSA/CLH AVIATION...WFOCYS FIRE WEATHER...JSA/CLH
Please see the 00Z aviation forecast discussion below.

&& .AVIATION... A complex of thunderstorms will continue to shift east and south of the region, with most activity expected to remain to the east of our TAF sites for the remainder of this evening. However, based on current radar trends, we did mention VCTS at SAT and TSRA at SSF through 01Z. The wind direction at SAT and SSF will be very complicated due to MCV formation ongoing over southern Bexar county and a wake low over Medina county. Will go with some gusty north winds at SAT and SSF for the next few hours given winds will primarily be influenced by the departing convection. Winds should then generally trend to a more east to southeast direction through late evening. Low clouds should also re-develop given recent rains and some brief clearing of high clouds. We expect MVFR cigs around 06Z along I-35, with IFR clouds and fog developing closer to 09Z. Slow improvement is then in store along I-35 tomorrow afternoon. At DRT, MVFR should develop around 09Z and continue through the morning hours. Improvement back to VFR is then expected by early afternoon. && .PREV DISCUSSION... /ISSUED 602 PM CDT Sun May 20 2018/ UPDATE... Made some adjustments to the PoP/Wx/QPF grids through 12Z tomorrow based off evolution of radar trends and latest HRRR runs. This remaining line of heavy rainfall should progress east southeast producing rainfall rates of over an inch per hour but in western areas, a well worked over atmosphere is likely preventing re- development. Much farther west, convection is taking place over the Mexican mountains but just about all hi-res models keep this activity well west of the Rio Grande. Thus lowered PoPs substantially after 00Z in the west while exiting the current system mostly out of the CWA by 03Z. PREV DISCUSSION... /ISSUED 308 PM CDT Sun May 20 2018/ SHORT TERM (Tonight through Monday Night)... Showers and thunderstorms continue as a slow moving outflow boundary continues to move southward and provide lift for further cell development. Currently, the boundary appears to be located south of Del Rio, to San Antonio and extended northeast to just south of La Grange. The majority of convection has been either confined to the boundary or developed ahead of the boundary as is the case currently. The most significant complex, located in Uvalde county as of 245PM, is riding the aforementioned boundary as well as producing its own healthy outflow, which is providing focused lifting along the interaction point of both boundaries. Ahead of this complex a gradually increasing PWAT environment (~1.6-1.8") exists as well as convergent 850 mb flow and moisture flux. The hi-res suite has largely whiffed on depicting this part of the line of convection today and only the most recent runs of the HRRR (16-17Z) have begun to resolve this feature. While still overdoing convection, it continues this complex along the southward moving boundary, missing San Antonio metro to the south, and progressing southeastward into CRPs CWA. This is largely due to a weakening low level flow regime as well as diminishing instability availability, yet the high moisture content and continued convergent orientation to the low level flow regime should keep this as a heavy rainfall concern throughout the rest of its passage through the southern CWA. Farther east, stronger southerly 850 mb flow will continue and shift to develop a more eastward component into the evening hours which will continue strong convergence along the outflow oriented more southwest to northeast in that area. Additionally, even higher PWATs of over 2" east of the I-35 corridor will continue the possibility of heavy rainfall well into the evening. While heavily leaning on the recent HRRR runs for short term guidance, the ensemble precip accumulation zeroes in on Lee/Fayette counties and eastward seeing the most rainfall through 12Z tomorrow morning. Looking at radar trends as of 3PM, this would seem reasonable as further cell development continues to the southeast and trains over this area. Ensemble guidance shows 4-5 inches for a storm total in these areas which could produce some minor flooding concerns but should stay below FFG values in those areas thankfully. As a result, believe a further 1-3 inches are possible for a line from Eagle Pass to San Antonio to Giddings with isolated amounts of 5+ inches still possible for Lee/Fayette counties as well as parts of Dimmitt, Zavala, Frio, Medina, and Atascosa counties. North of the boundary, the majority of the rainfall should be completed for the evening. Some CAMs are continuing to produce convection on the Mexican side of the Rio Grande but the well worked over environment from the boundary passage should keep any additional development at bay. Thus, overnight, have PoPs gradually decreasing through midnight, and decreasing substantially after midnight with only low end chance PoPs for the extreme southeast zones. Also PoPs for Monday will depend on destabilization efficiency and most likely be isolated, thus have kept in a broad brush 30 PoP with a slight preference to the Rio Grande Plains. LONG TERM (Tuesday through Sunday)... A much more benign pattern is in store for the extended as a ridge axis builds over the central United States and blocks energy from impacting the region from a broad low out west. With afternoon highs in the upper 80s and 90s and dewpoints in the 60s throughout the week, can`t rule out isolated afternoon showers and thunderstorm possibilities but chances should be pretty low as the ridge continues to build and dry out our air mass. Only included slight chance or sub-20 percent chances throughout the week beyond Monday. && .PRELIMINARY POINT TEMPS/POPS... Austin Camp Mabry 70 88 70 90 70 / 30 20 10 10 0 Austin Bergstrom Intl Airport 70 89 69 90 68 / 30 20 10 20 0 New Braunfels Muni Airport 70 88 69 89 68 / 50 30 10 10 - Burnet Muni Airport 67 86 67 88 68 / 20 20 10 10 0 Del Rio Intl Airport 71 88 71 89 72 / 30 30 20 10 - Georgetown Muni Airport 68 88 68 89 69 / 20 20 10 10 0 Hondo Muni Airport 70 88 69 90 69 / 20 30 10 10 - San Marcos Muni Airport 69 88 69 90 69 / 50 20 10 10 0 La Grange - Fayette Regional 71 89 71 90 70 / 50 20 10 20 - San Antonio Intl Airport 71 88 71 89 71 / 50 30 10 10 - Stinson Muni Airport 72 89 71 90 71 / 60 30 10 10 - && .EWX WATCHES/WARNINGS/ADVISORIES... None. && $$ Mesoscale/Aviation...24 Synoptic/Grids...09 Public Service/Data Collection...YB
Area Forecast Discussion
National Weather Service Lincoln IL
1104 PM CDT Sun May 20 2018 .UPDATE... Issued at 830 PM CDT Sun May 20 2018 Complex of thunderstorms over central Missouri continues to track east and northeast towards our area. Instability not that great to its east early this evening so we expect the storms to weaken some before they get into our area towards Midnight. The storms are associated with a weak upper level wave over west central Missouri and that feature will continue to track northeast towards the lower Great Lakes on Monday. Current forecast seems to have a good handle on the timing of the storms late this evening through the early morning hours. May need to fine tune the arrival time over our far west and southwest counties, but overall, the current forecast is in good shape. Not planning on any ZFP update at this time. The upper level wave and the associated showers and storms should push off to our east by afternoon but models were slow to get the cool front to our east until tomorrow night. As a result, there is the chance for storms to redevelop tomorrow afternoon, especially along and east of I-55. However, if clouds and rain linger longer than expected, any redevelopment may take place just to our east and southeast late tomorrow afternoon. With a weak frontal boundary stretched from west to east across the heart of the forecast this evening, quite a contrast in temperatures and dew points with temperatures over our far northern counties in the low 60s while along the I-70 corridor, temperatures were near 80 degrees. Coolest readings across the north tonight as the front will not make any significant track to the north overnight, with rather mild readings expected across the south where the mercury may not get much lower than the upper 60s. Highs Monday afternoon will range from the middle 70s north of I-74 to the middle 80s over southeast Illinois. && .SHORT TERM...(This evening through Monday) ISSUED AT 302 PM CDT Sun May 20 2018 Many mesoscale features making for a very complicated forecast in the short term, made worse by the lack of clarity between models. The 500mb shortwave to the west that was progged to slowly move out over the region is slowing further still, limiting the upper support for the MCS remnants as they drift into the region. The same lack of support seen overnight as well as in the day time today may continue...suppressing severe threat somewhat. A lack of steep lapse rates in the midlevels as well as a lack of deep shear are so far dulling convection. CAPEs even limited throughout the day from blow off cloud cover/remnant precip from western MCS activity. Short term models are a mess, with the HRRR providing some of the better solutions to work with. Forecast is vague at best, trying to follow the trend in the HRRR of a break in the activity this evening, then the remnants of a developing MCS to the west moving in after 06z tonight. Lack of support should keep the thunderstorms in check, but how recharged the atmosphere is over Central IL is a bit of a question mark considering the moisture and warm air advection, coupled with limited daytime heating. BUFKit soundings do not look promising, and NAMNest, admittedly off at initiation, is marginal at best. Have several complicating factors in place with a weak sfc low, mesoscale boundaries, and moisture convergence...but little dynamics to initiate or sustain. Hopefully 00Z runs will provide more detail. With the potential for the precip not materializing before midnight, have added a patchy fog mention as the sfc dwpts in the 60s already, and continuity from the last couple nights. Tomorrow is another conflict with ending precip early, but chances continue throughout the day with boundaries and plenty of buoyant air in place. Very vague mention of potentially higher pops to the north as the wind fields back up a passage of a weak low to the north and northeast in the afternoon hours. .LONG TERM...(Monday night through Sunday) ISSUED AT 302 PM CDT Sun May 20 2018 Once the weak upper low clears out of the region tomorrow night, 500mb ridge starts to develop over the Plains, keeping the axis just to the east of the Miss River Valley. This results in a dry period at least through midweek until the next low dives into a more northerly stream aloft, skirting the US/CAN border and driving precip slowly into the region to wrap up the week. With the ridge axis just to the west, weak NW flow does not cut off the region from some moderate WAA from the desert SW. Midlevels maintain access to the warmer temps of the swrn CONUS through the end of the forecast, keeping temps about 10F above seasonal norms. Very low pops work into the forecast about Thursday as that open upper wave drifts into the Upper Midwest. Higher pops in place with approach Friday through Saturday. && .AVIATION...(For the 06Z TAFS through 06Z Monday night) Issued at 1100 PM CDT Sun May 20 2018 Timing of showers and thunderstorms into the forecast area over the next several hours and affect on cigs and vsbys into the early morning hours the main forecast concerns this period. Complex of weakening showers and thunderstorms was tracking northeast into west central Illinois and should continue to move across the remainder of the forecast area into the early morning hours. As the upper wave that is responsible for the precipitation moves across the area on Monday, showers and low (mainly MVFR) cigs and vsbys will prevail through the morning with a gradual improvement in cigs and vsbys expected for the afternoon to low VFR early in the afternoon, with cigs lifting or even scattering out towards 00z. Surface winds will be mostly easterly tonight at 8 to 13 kts with winds veering into a southerly direction by Monday afternoon with speeds in the 10 to 15 kt range. && .ILX WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...Smith SHORT TERM...HJS LONG TERM...HJS AVIATION...Smith
Area Forecast Discussion...UPDATED
National Weather Service Jackson MS
901 PM CDT Sun May 20 2018 .UPDATE... Updated for evening discussion. && .DISCUSSION... The day`s diurnal storms are still going tonight. At this point, they seem to be feeding mostly off the energy from outflow boundaries rather than diurnal heating. Some of these storms may have some small hail in them and may be producing some gusty winds at times, but they should all remain below strong and severe storm criteria. This activity will persist for another few hours before completely dissipating around midnight or so. Conditions will remain muggy and overnight temps will fally only to the upper 60s. Mainly just updated the pops for this forecast update. /10/ Prior discussion below: Tonight and Monday: Convection has been slow to materialize this afternoon, but has finally initialized in the high 0-3km theta-e zone from northeast LA into north central MS. The HRRR is indicating that convection will continue to fire in this zone as it spreads to the southeast with time. Though overall convection will begin winding down during the evening, intersecting cold pool boundaries will keep keep some convection continuing until around midnight. Weak mid level ridge will continue to break down during this time period as cold core system over the northeastern Gulf of Mexico is absorbed by more prominent westerlies to the immediate west of the forecast area. The resulting cool air aloft will lead to more in the way of scattered convection Monday given expected temps/dewpoints. Weak mid and and deep layer shear vectors suggest slow storm movements which will lead to very localized heavy rainfall as PWs rise to above 1.75 inches. Despite the cool air aloft, deeper moisture looks to prevent lapse rates from becoming too steep, keeping strong/severe potential down a bit./26/ Monday night through Saturday: The primary focus will be for a summer like pattern with diurnal convection through the period. There will be some ridging followed by some troughiness with weak flow over the forecast area through the period. Pwats will range from 1.4 to around 1.7 inches combined with daytime heating for scattered daytime convection, which will be followed by isolated convection during the evening as we lose the heat of the day. This will change some as we start to get a better inflow of moisture for Friday night through Saturday. With all this instability we could have some microburst potential with an isolated severe storm with gusty winds that can not be ruled out for each day along with some brief downpours. Where the convection develops will depend of leftover outflow boundaries from the previous day combined with weak disturbances that will track across the region during the heat of the day. Daily highs will be in the upper 80s to the lower 90s. Heat indices will creep up to the upper 90s to around 100 on Wednesday and Thursday. Nightly lows will be around the middle 60s to the lower 70s./17/ && .AVIATION... 00Z TAF discussion: Isold to Sct TSRA wl cont in vcty of most TAF sites through 03Z before dissipating. Away from TSRA activity, VFR conds wl cont until after 09Z when MVFR cigs and vsbys wl be psbl over east MS. Cigs should improve to VFR areawide by 16Z. Sct to numerous TSRA activity is expected to develop Mon aftn and last into the evening. /22/ && .PRELIMINARY POINT TEMPS/POPS... Jackson 68 87 68 90 / 37 59 22 42 Meridian 67 86 66 89 / 43 47 23 42 Vicksburg 69 89 68 91 / 34 64 23 45 Hattiesburg 68 87 67 90 / 32 55 26 52 Natchez 68 89 68 90 / 26 64 24 42 Greenville 70 89 70 89 / 43 65 22 43 Greenwood 69 88 68 90 / 43 56 19 49 && .JAN WATCHES/WARNINGS/ADVISORIES... MS...None. LA...None. AR...None. && $$
National Weather Service Jackson KY
1056 PM EDT Sun May 20 2018 .UPDATE... Issued at 1056 PM EDT SUN MAY 20 2018 The last of the storms that threatened from the north have dissipated. Expect a quiet rest of the night, with partly cloudy to mostly clear skies and areas of fog forming once again. The fog should be more confined to the deeper river valleys compared to last night. Forecast lows in the low to mid 60s look on target and have only made a few adjustments based on the latest trends in observations. Updates have been sent. UPDATE Issued at 805 PM EDT SUN MAY 20 2018 Eastern Kentucky remains precipitation-free at the moment, as short wave ridging has kept most convection at bay. A cluster of storms is moving in from around the Ohio River, but these should dissipate as they move into a less favorable environment across the Bluegrass, which recent runs of the HRRR supports. Will maintain the dry forecast through the night, and have mainly freshened up the diurnal temperature drop off through this evening. Will assess temperatures and fog a bit later. Updates will be out shortly. && .SHORT TERM...(This evening through Monday night) Issued at 407 PM EDT SUN MAY 20 2018 Have seen a few showers pop this afternoon across the Big Sandy region as a summertime airmass interacts with the higher terrain. Temperatures in the mid 80s combined with dewpoints in the mid-upper 60s have created enough instability, that when combined with even subtle lift, is enough for a pulse type storm to quickly develop. Have actually seen dewpoints mix down into the upper 50s to lower 60s in the Lake Cumberland region nearer the core of relatively drier air. Additional showers and isolated storms will remain possible this afternoon, mainly in far eastern Kentucky where southwesterly low level winds will provide greater upslope lift. None of these will last long given the lack of available shear for storm-scale organization. Upper ridging currently over much of the southeastern U.S. and extending into eastern Kentucky will gradually flatten tonight into Monday as a shortwave trough migrates out of the Great Plains and toward the Great Lakes. Dry conditions should largely prevail locally through tonight and early Monday as an overnight complex of storms remains confined to mainly north of the Ohio River. Valley fog will be a good bet given crossover temperatures in the mid 60s or so, but this should be less prevalent than last night due to an overall lack of rain today. Rain chances will ramp back up Monday afternoon as upper heights eventually fall southeast of the above mentioned upper impulse. A surface low will follow a similar track, surging precipitable water values back to the 1.5 inch range. A frontal boundary initially near the lower Ohio Valley will lift north through the morning and afternoon, but any height falls aloft will be enough to spark scattered to numerous showers/storms throughout the afternoon given abundant instability. Anemic deep layer shear will keep strong to severe storms at bay, other than perhaps a few cell mergers and resultant brief upticks in updraft strength. These could produce isolated small hail and wind gusts to 40 mph or so. Rain chances will continue into the evening and overnight as a cool front slides southeast toward the lower Ohio Valley. .LONG TERM...(Tuesday through Sunday) Issued at 300 PM EDT SUN MAY 20 2018 In the extended we can expect chances for showers and storms Tuesday through late Wednesday. The best chances for rain during this initial round of precipitation will be Tuesday afternoon and evening. The rain should then taper off very quickly late Tuesday night into early Wednesday morning. The last few showers or storms should be out of the area by late Wednesday afternoon. After that, we should see a period of dry weather from Wednesday evening through early Friday morning, as a ridge of high pressure temporarily takes hold across the region. A series of low pressure systems are then forecast to bring periods of showers and storms back to eastern Kentucky from Friday through Saturday night. Temperatures during the period will likely be above normal, with daily highs in the low to mid 80s and nightly lows in the low to mid 60s expected. && .AVIATION...(For the 00Z TAFS through 00Z Monday evening) ISSUED AT 805 PM EDT SUN MAY 20 2018 Expect VFR conditions to prevail through the majority of the period. Fog will likely form again late tonight, but expect the IFR or worse conditions to be more confined to the deeper river valleys, given the lower crossover temperatures as well as lack of precipitation coverage through the day. Have included a 2 to 4 hour window of MVFR fog at the TAF sites, generally between 09 and 13z. Storm coverage looks to be better on Monday, and will include VCTS at all sites during the afternoon hours. Winds will remain at around 5 kts or less through the period. && .JKL WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...GEOGERIAN SHORT TERM...GUSEMAN LONG TERM...AR AVIATION...GEOGERIAN
Area Forecast Discussion
National Weather Service Marquette MI
752 PM EDT Sun May 20 2018 .SHORT TERM...(This evening through Monday) Issued at 346 PM EDT SUN MAY 20 2018 Water vapor imagery and RAP analysis show a split flow pattern over the western CONUS with a wnw confluent flow aloft into the Upper Great Lakes region and sfc high pressure dominating. Lake breezes have kept conditions cooler this afternoon near the Great Lakes shores (40s and lower 50s) while much farther inland under sunny skies and deeper mixing temps have risen in the upper 60s/lower 70s along the WI border. Winds will diminish to calm/near calm tonight, setting the stage for a chilly night as dry air mass (precipitable water as low as one- quarter to one-third inch) aids radiational cooling potential. Will continue to favored the lowest of available guidance, bias corrected mos guidance and bias corrected CMC global which is normally a superior performer on radiational cooling nights. Traditional interior cold spots should fall into the upper 20s/around 30F. Sfc high pressure will remain in control continuing the dry conditions on Monday. With the center of the high moving east southeast gradient winds will increase near 10 mph with gusts reaching over 15 mph at times over the west half of the fcst area. The winds combined with high temps reaching into the lower 70s and minimum RHs lowering into the 20 to 25 percent range will contribute to elevated fire weather concerns especially over the west half. Shortwave lifting ne from the Central Plains could bring some mid- high clouds into s central portions in the afternoon, although any showers associated with this system should remain south on Monday. .LONG TERM...(Monday night through Sunday) Issued at 356 PM EDT SUN MAY 20 2018 The main weather concern through the middle of the week will be elevated wildfire potential, especially inland from the Great Lakes where dewpoints in the afternoon hours will drop into the 20s. A thermal trough is expected to develop across the interior during the afternoon hours as temperatures heat up into the 70s and lower 80s across the interior and lake breezes dominate the low-level wind fields. The development of this thermal trough inland of the Great Lakes will be reinforced on Wednesday as a weakening, dry backdoor cold front drops south. Compressional along this trough axis should allow for another day with well-above normal temperatures on Wednesday. Thursday through early parts of the Memorial Day Weekend will become much more active weather wise with increasing chances for showers and thunderstorms. As result temperatures will be a bit more difficult to forecast based on how cloud cover and precipitation evolve. With the main shortwave associated with this pattern change lifting northeast from the southwest into the northern Plains, this track will favor good moisture transport this far north as the Gulf of Mexico is progged to be open for days in advance. As this axis of low to mid-level moisture gets into Upper Michigan on Thursday, we will start to see chance for showers and storms increase across the west half of Upper Michigan. With this convection well removed from the main upper-level forcing, thinking the primary area of concern will be along lake breeze boundaries and the far eastern edge of the warm front, associated with a developing surface low in the northern Plains. On Friday and Saturday, the surface low will track towards the Arrowhead of Minnesota and then drop south across Wisconsin. This should allow the warm front to gradually lift north across Upper Michigan and allow for better chances for showers and thunderstorms on Friday in the vicinity of the frontal boundary, as well as lake breeze boundaries. On Saturday, as the low pressure system tracks just to our south, this will allow for additional chances for showers and thunderstorms. Towards the tail end of the weekend, as the surface low continues to track south of the area we should see a cool down, but lingering showers are not out of the question. Right now it is difficult to say whether or not we will see any strong to severe storms during this time period. However, with a weakening, yet still impressive elevated mixed layer progged to track across the region on Friday, this would favor a better environment for stronger updrafts. Based on the current instability axis and deep-layer shear profiles it appears that at least pesky pulse-type thunderstorms won`t be out of the question. Overall, if you have outdoor activities planned towards the end of the work week and the Memorial Day Weekend you`ll definitely want to keep an eye on the weather. Even if we don`t see stronger storms, remember lightning is always a hazard with thunderstorms. && .AVIATION...(For the 00Z TAFS through 00Z Monday evening) Issued at 750 PM EDT SUN MAY 20 2018 With high pressure and a very dry air mass dominating, VFR conditions will prevail at KIWD/KCMX/KSAW through this forecast period. && .MARINE...(For the 4 PM Lake Superior forecast issuance) Issued at 346 PM EDT SUN MAY 20 2018 Sfc high pres ridge over the Upper Lakes has led to winds under 15kt today across most of Lake Superior this afternoon. However, with the ridge axis setting up across southern Lake Superior, sw winds over the n central part of the lake could gust as high as 20kt late this afternoon. High pres will then remain over the Great Lakes region into Tue, resulting in winds mostly under 15kt. Although a cold front will drop s across Lake Superior Tue night/Wed morning, it will be weak, and winds will likely remain mostly under 15kt thru Wed and into Thu. && .MQT WATCHES/WARNINGS/ADVISORIES... Upper Michigan... None. Lake Superior... None. Lake Michigan... None. && $$ SHORT TERM...Voss LONG TERM...Ritzman AVIATION...JLB MARINE...Voss
Area Forecast Discussion
National Weather Service Nashville TN
847 PM CDT Sun May 20 2018 .DISCUSSION... Another magical evening at the Weather Service. Skies were mostly sunny with only isolated storms in the Mid-State at 4 pm, then *POOF*, between 5 pm and 6 pm, thunderstorms popped up all over the place between Clarksville, Dickson, Springfield, Nashville and Gallatin. A few storms became severe, with damaging winds and quarter size hail. Localized flooding was also reported. This makes the second day in a row with that sort of *POOF* convection in our northwest and north- central areas. Our late afternoon LI of -6 and -7 these last few days certainly has not been lacking in potential, that`s for sure. and, guess what? the GFS pegs the same general area with late afternoon LI`s of -5 to -7 late tomorrow afternoon. So, maybe we can go for Round 3? We should continue to see convection exhibit an evening slow down over the next several hours. However, the HRRR keeps convective potential running overnight across our western sections, so believe our chance PoPs for the late night hours is certainly warranted. The most widespread wind damage this evening seems to have been confined mainly to southwestern Davidson County, just southwest of Nashville, in the Belle Meade, Green Hills and Bellevue areas. Numerous trees were blown down, some onto houses, some onto cars and some onto powerlines. && .AVIATION... 00Z TAF DISCUSSION. BNA/MQY/CKV/CSV...Thunderstorm complex is currently affecting the Nashville Metro & Clarksville areas and this is reflected in the first period of the TAF`s. Expect things to subside within the next couple of hours. Do not expect widespread radiation fog overnight due to a mid-level cloud deck, and also there was very little fog reported last night. Very little air mass change is expected during the next 24 hrs., so have included PROB30 remarks for scattered afternoon convection again Monday. && .PRELIMINARY POINT TEMPS/POPS... Nashville 69 86 67 86 68 / 30 50 20 40 20 Clarksville 67 83 66 84 65 / 60 50 40 40 10 Crossville 63 79 62 78 62 / 20 60 30 50 20 Columbia 66 84 65 84 65 / 30 50 20 40 20 Lawrenceburg 65 83 64 83 64 / 30 50 20 50 20 Waverly 68 83 67 85 67 / 60 50 30 40 10 && .OHX WATCHES/WARNINGS/ADVISORIES... NONE. && $$ DISCUSSION......19 AVIATION........08
Area Forecast Discussion
National Weather Service Paducah KY
852 PM CDT Sun May 20 2018 .UPDATE... Issued at 852 PM CDT Sun May 20 2018 Similar to last night we are expecting the convective line over central Missouri to weaken as it approaches southeast Missouri and southern Illinois. However, we don`t expect the line to completely dissipate. Given the steep mid-level lapse rates over much of our region, as revealed in LAPS soundings this evening, we should see an increase in showers and thunderstorms over southeast Missouri late this evening, and then farther east overnight. There will be a weakening trend in coverage and intensity as the convection spreads east across the region into the overnight hours. Plenty of clouds and a persistent south wind should be enough to prevent any significant fog formation tonight. UPDATE Issued at 708 PM CDT Sun May 20 2018 Updated aviation discussion. && .SHORT TERM...(Tonight through Tuesday night) Issued at 312 PM CDT Sun May 20 2018 Main convective line moving through southern Illinois and the delta region of west Kentucky being supported by 2500-5000 j2/kg2 LAPS surface based CAPE stretching from the Mississippi River near New Madrid, then arcing northeast into northwest Kentucky south of KEHR and KOWB at 20z. Updraft/cold pool flow balance is episodic with parts of the line seeing gust front extension ahead of the line. Cleared a few counties from Severe Thunderstorm Watch behind the line of thunderstorms. There will be a few hours of boundary layer stabilization before the flow returns southerly across the area, priming the pump for later tonight into Monday over western sections of southeast Missouri and southwest Illinois. Although there is some timing issues for the resumption of new showers and thunderstorms behind the current line of convection, both the RAP and CMC model guidance suggest new convection will fire back further west into Missouri and slowly work east back into our area overnight and during the day on Monday. Channeled vorticity in the southwest flow aloft will help to maintain periodic lines of showers and thunderstorms from Monday night into Tuesday, with the main activity shifting east with the front. .LONG TERM...(Wednesday through Sunday) Issued at 312 PM CDT Sun May 20 2018 Fairly high confidence of an unseasonably warm pattern Wednesday through Friday with little if any precipitation coverage most of the time. A nearly stationary mid/upper level high pressure ridge will be the main weather influence through the lower and mid MS River Valley through that time frame, with little low level forcing/triggers. Expect daily highs well into the 80s each afternoon. Temps will cool back into the 60s at night. As we head into next weekend, a system over the northern Gulf of Mexico is expected to drift slowly north into the southern Gulf Coast states. At the same time, a mid level trof and associated weak surface front should be working east/southeast toward the Ms River and lower OH river Valleys. This would lead to increasing shower/thunderstorm chances on Saturday into Sunday, especially during the heat of the day. Conditions should also remain quite warm and humid through the weekend. It will be interesting to see how well, if any, the two systems can merge into one deep elongated trof by that time. && .AVIATION... Issued at 708 PM CDT Sun May 20 2018 The stabilization of the atmosphere due to diminishing shower and tstm activity will yield VFR cigs across the region into the overnight hours. However, short-lived MVFR cigs are expected to be associated directly with scattered shower/tstm activity that will eventually pop up again during the 00Z TAF period. Best guess is that this scattered activity may occur mainly late in the night/ early Sun morning north of the OH River, and in the late afternoon mainly east of the MS River. Winds outside of tstms will be light and variable overnight, picking up to less than 10 kts out of the south-southwest after daybreak. Winds just off the surface will lessen the likelihood of significant fog formation. && .PAH WATCHES/WARNINGS/ADVISORIES... IL...None. MO...None. IN...None. KY...None. && $$ UPDATE...DRS SHORT TERM...Smith LONG TERM...GM AVIATION...DB
Area Forecast Discussion
National Weather Service Pueblo CO
329 PM MDT Sun May 20 2018 .SHORT TERM...(This evening through Monday) Issued at 251 PM MDT Sun May 20 2018 Upper disturbance moving through the 4 corners region is helping to spark thunderstorms across the mountains this afternoon. As these encounter sufficient low level moisture which has penetrated westward into the valleys due to deep upslope flow from last night, they have been tapping around 500 to a little under 1000 j/kg of CAPE. This has allowed a few to strengthen as they hit these pockets of higher instability. However, shear has been the limiting factor today and this has kept storms more on the pulsey side of things. Thus not anticipating much in the way of a severe threat. But could see some small hail, local wind gusts to 40 mph and brief heavy rainfall. Will have to monitor the burn scars closely, particularly the Hayden Pass burn scar, where there has been more sun today to destabilize the atmosphere. Meanwhile, persistent low clouds have remained banked up along the I- 25 corridor much of the day and expect this will continue into the mid-late afternoon. This has delayed heating, resulting in a more stable atmosphere across the plains. As storms develop and move eastward, suspect they will decrease in intensity as they encounter this cooler airmass. The exception to this will be along the Raton Mesa region where latest HRRR runs continue to indicate the possibility of a thunderstorm developing and moving eastward through the evening hours. This could be forced by a developing low level jet, so can`t discount it and have spread some isolated pops across Las Animas and Baca counties for now. Elsewhere, expect convection to decrease diurnally with pops diminishing quickly towards midnight. Should be another relatively cool night across the area, though with increasing southwest flow aloft, do not think we will see a repeat of widespread stratus redevelopment across the southeast plains. -KT .LONG TERM...(Monday night through Sunday) Issued at 251 PM MDT Sun May 20 2018 Upper level low remains over the swrn U.S. Mon night into Tues, with rather deep sly flow ahead of the system bringing a modest amount of moisture northward into CO through the period. As a result, expected isolated to scattered -shra/-tsra over the region Mon night/Tue/Tue night, as weak upper level energy occasionally ejects from the swrn low. 0-6km wind shear remains on the low side (30 kts or less) through the period, as wind profiles are rather unidirectional and speeds rather light, so threat of severe storms looks rather low. Best chance for a stronger storm would be along the NM border Tue afternoon/evening, where instability/shear will be greatest. Max temps Tue should drift upward another couple degf versus Mon as sly flow continues. Swrn low then lifts northward through the Great Basin into the nrn Rockies Wed/Thu, with upper level ridging developing over the western U.S. as deep low develops offshore of the Pacific Coast. As pattern shifts, drier swly flow develops across srn CO, shunting most moisture eastward both days. Still some low level moisture/instability near the KS border ahead of the surface trough/dryline, so will keep some low pops in place each afternoon to account for this possibility. Could see some marginal critical fire weather conditions in a few spots both days as well, though given mix of fuels greening up and at least spotty precip, tough to pinpoint any particular area at this point. Max temps will push back into the 80s/90s at many lower elevations, as heights rise and mixing deepens. Upper wave then crests the ridge and drops into the Midwest from Fri into next weekend, pushing a cold front south through CO Fri, followed by surface high pressure dropping south through the central plains. Should see at least a modest upturn in convective chances increase through the period over the eastern mountains and adjacent plains, as low level upslope winds develop and transport moisture back westward into the area. && .AVIATION...(For the 00Z TAFS through 00Z Monday evening) Issued at 251 PM MDT Sun May 20 2018 Residual MVFR cigs along the lower eastern slopes of the southeast mountains will continue to lift and break late this afternoon as evening showers and thunderstorms roll off the mountains. Thunderstorms should decrease in intensity as they encounter cooler more stable air east of the mountains, and have restricted precipitation chances to a VCSH group for COS this evening to reflect this. KALS will have a window for thunderstorms this afternoon with erratic gusts to around 35-40 kts near thunderstorms. Thunderstorms will diminish over the mountains after 02-03z with clearing skies expected overnight. Increasing southwest flow aloft should help prevent the widespread formation of stratus across the plains so have kept TAFs VFR for now. -KT && .PUB WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SHORT TERM...KT LONG TERM...PETERSEN AVIATION...KT
Area Forecast Discussion
National Weather Service Springfield MO
706 PM CDT Sun May 20 2018 .SHORT TERM...(This evening through Monday) Issued at 158 PM CDT Sun May 20 2018 In a bit of a lull right now with morning convection having stabilized conditions. Convection is firing along a distinct outflow boundary over northeast AR. The boundary becomes less distinct has farther to west into NW AR. Another shortwave that extends form south central KS into central OK will shift northeast with lift increasing over the area, especially the western cwfa late this afternoon and this early this evening. MLCAPE values off the HRRR reach 1000-1500 j/kg with around 30kts 0-6km bulk shear which would support multicell or possibly supercells with a large hail and damaging wind risk for a few hours before the wave lifts off to the northeast. Questions still consist of how long convection will linger into the eastern counties overnight. Have raised rain chances using a blend of cams/short term guidance. In general, Monday looks more quiet with weak mid level height rises. .LONG TERM...(Monday Night through Sunday) Issued at 158 PM CDT Sun May 20 2018 Mid level shortwave ridging and height rises are expected through midweek as an upstream closed upper low moves into the western CONUS. Can`t rule out some diurnally driven isolated pulse convection through midweek, but coverage looks limited. The western upper trough opens up and lifts well northwest of the area. Late in the week a blocking upper level pattern develops with a slow moving upper low moving north out of the Gulf of Mexico and another moving east from the western CONUS. Chaotic upper level flow doesn`t generate much confidence in the forecast. May see an uptick in diurnal convection late in the period, but no major systems are expected. && .AVIATION...(For the 00Z TAFS through 00Z Monday evening) Issued at 637 PM CDT Sun May 20 2018 Pilots can expect variable flight conditions tonight into Monday. Storms will push east of the terminal sites this evening. A front will move across the region late tonight and Monday morning bringing a wind shift and lowering ceilings. Expect MVFR to potentially IFR ceilings spreading west to east late tonight and Monday morning. Improving flight conditions can be expected by Monday afternoon. && .SGF WATCHES/WARNINGS/ADVISORIES... MO...NONE. KS...NONE. && $$ SHORT TERM...DSA LONG TERM...DSA AVIATION...Foster
Area Forecast Discussion
National Weather Service Shreveport LA
929 PM CDT Sun May 20 2018 .UPDATE... Shifted likely-definite POPs to across portions of central LA tonight, as that is where the lingering showers /with intermittent thunderstorms/ have been occurring. Light scattered showers were noted nearing deep east TX and across southeast OK, but all of the precipitation activity has been waning as expected. Otherwise, forecast is largely on track with slight/slim chances of isolated showers developing overnight. Tweaked the surface temperatures to reflect current trends and subsequently adjusted the dewpoint temperatures and relative humidity values. && PREV DISCUSSION... /issued 632 PM CDT Sun May 20 2018/ AVIATION... Isolated to scattered -SHRA/-TSRA have intermittently affected the western terminals, whilst nearing the remainder terminals early this evening. This has caused winds to have a variable wind direction, as well as briefly experiencing gusts when a storm directly affects a terminal. This makes for a complicated TAF forecast but have tried to best time when the convection will begin and end. For the most part, should see the precipitation taper off later this evening but will of course amend as necessary. Otherwise, CIGS should remain VFR throughout the TAF cycle, though there could be a brief period of MVFR CIGS and VFR- MVFR fog at a few sites if the winds are able to drop off. Any lingering low clouds/fog should dissipate by Monday mid-morning and isolated -SHRA/-TSRA could make a return by the afternoon. Felt confident enough to insert a VCTS at all but keld and kmlu tomorrow afternoon at this time. PREV DISCUSSION... /issued 354 PM CDT Sun May 20 2018/ SHORT TERM.../Tonight through Monday Night/ The Ewd moving outflow bndry has slowed but continues to be reinforced by convection this afternoon, and has reached E of a JDD/TYR/JSO/DKR line as of 2030Z. Additional sct convection has fired ahead of this bndry over extreme Ern TX along an axis of theta-e advection within a moderately unstable air mass characteristic of SBCapes of 1500-2000+ J/kg, just ahead of an upper trough axis extending from Cntrl KS S into the Srn Plains. The ongoing convection should begin to wind down this evening with the loss of heating, but did retain low chance pops this evening areawide, with mid chance pops over lower E TX per the consensus amongst the HREF and HRRR in maintaining convection a little longer over these areas. Am reluctant to take pops out completely after 06Z, thus did keep slight chance pops going overnight as the tail end of the upper trough/shear axis becomes removed from the primary shortwave over Wrn NE as it lifts NE into the Midwest late. This shear axis will linger over SW AR/N LA/extreme Ern TX Monday, and will again be the focus for mainly afternoon sct convection, especially over the Ern half of the region. Have raised pops to mid and high chance, especially over Scntrl AR/N LA, with additional development primarily tied to outflow interactions within a moderately unstable but weakly sheared air mass. Did trend max temps a little warmer than MOS given the fact that most areas this afternoon trended a little warmer than guidance. The convection should again gradually diminish during the evening Monday with the loss of heating, and thus kept slight chance to low chance pops going in the evening in VC of the shear axis. This feature should again play a role in sct convection development Tuesday as it become trapped beneath an amplifying dirty upper ridge over the Srn Plains and Mid MS Valley. 15 LONG TERM.../Tuesday through Sunday/ A broad upper lvl ridge pattern with moisture in weak easterly flow and diurnal nature of convection brought on by instability through the workweek. Positioning of ridge will determine day by day location of scattered, versus more isold convection, which will tend to develop along peripheries of diffuse ridge center. Weak wind shears will limit svr potential for storms, although gusty winds and locally heavy rainfall will remain a possibility. An upper lvl trough may try to organize over the central Gulf and drift nwd towards the coast, which may enhance rainfall by the holiday wknd, particularly if coupled by weak front which will attempt to move swd towards the region. Increased overall cloud cover will bring aftn temps back into upper 80s to around 90 on average, with overnight lows expected to continue to prevail either side of 70 degrees. Winds will remain mostly lgt and vrb for much of the week. /07/ && .PRELIMINARY POINT TEMPS/POPS... SHV 70 89 70 89 / 30 40 20 30 MLU 69 90 69 89 / 30 50 30 40 DEQ 65 87 66 89 / 50 30 20 20 TXK 68 88 68 87 / 40 30 20 30 ELD 67 90 67 89 / 30 50 30 30 TYR 67 89 70 88 / 20 20 10 30 GGG 67 89 69 89 / 20 20 10 30 LFK 68 90 68 89 / 30 20 10 30 && .SHV WATCHES/WARNINGS/ADVISORIES... AR...None. LA...None. OK...None. TX...None. && $$ 29/07/15
Area Forecast Discussion
National Weather Service Las Vegas NV
835 PM PDT Sun May 20 2018 .SYNOPSIS...A low pressure system will bring unsettled weather to the region through Tuesday. Isolated to scattered showers and thunderstorms will be possible for areas north of Interstate 40 on Monday and Tuesday. Temperatures across the region will drop a few degrees early next week. A warming trend is expected from mid week into Memorial Day weekend. && .UPDATE...Tight cyclonic circulation associated with an upper low is presently over SW Oregon/NW California. The low is progged to slide south into central California Monday. Some of the new 00z guidance along with hourly rapid refresh output suggests that we may see some light precipitation breakout around Las Vegas Monday morning, between 8 am and 11 am. As instability increases the threat transitions to thunderstorms after 11 am. Lower levels of the atmosphere stay dry which means gusty winds will be the primary concern around Las Vegas. Closer under the low over Inyo County stronger storms could produce small hail. Updated to tweak POPs for the rest of tonight and Monday. && .AVIATION...For McCarran...Increasing clouds above 10kft are expected through the night and on Monday, with overcast skies around 15kft by Monday morning. Winds on Monday will favor a south- southeast direction with sustained winds up to 10 kts. There may be light rain showers around the valley between 8 am and 11 am Monday morning. Isolated thunderstorms, favoring the higher terrain along the western foothills possible Monday afternoon and evening. Primary concern at the terminal from thunderstorms will be gusty winds along with varying wind directions. For the rest of southern Nevada, northwest Arizona and southeast California...Showers and a few thunderstorms are possible tonight across Inyo County. West winds will increase overnight across western San Bernardino County where wind gusts between 30-35 kts will be possible. Scattered showers and thunderstorms are possible across much of the area on Monday, with the best chances over San Bernardino, Inyo, Esmeralda, Nye and Central Clark County...however anticipate scattered precipitation coverage to be more widespread and farther south than what we have seen the past few days. && .SHORT TERM...Tonight through Tuesday. Current IR and visible imagery indicates a band of cirrus moving across southern NV and northwest arizona and another broken band of cirrus pushing eastward over the Sierra crest. A clearing between these cirrus decks has allowed a broader area of cumulus to develop across Esmeralda and central Nye Counties along with the Spring Mountains. Though moisture is limited, insolation should promote a few showers with embedded thunderstorms possible. Per RAP guidance, the best instability through the afternoon will be across the Sierra and Esmeralda. Expect any convective activity that develops quickly diminish around sunset. Another round of unsettled weather is expected early this work week as an upper low closes off across central California and slowly tracks eastward across the Mojave Desert and southern Great Basin Monday and Tuesday. As it does, mid and upper level moisture will overspread the region. Moisture coupled with forcing will result in precip chances mainly for areas north of Interstate 40. Although guidance introduces marginal instability on Monday, diurnal heating should be minimal due to a thick cirrus shield in place. High-based showers will be favored over thunderstorms; however, cannot rule out thunderstorms based on available instability and associated dynamics. Clouds begin to break up more on Tuesday as dry air works around the backside of the low. This should allow more diurnal heating and higher a chance for convection, especially along differential-heating boundaries. Dry low levels will limit rain totals to a a few hundreths to half an inch, outside of the Sierra where totals may be closer to an inch precip. The only adjust made to the forecast was an increase to PoPs across northwest AZ Tuesday afternoon as instability combined with diurnal heating may lead to high chance of shower and thunderstorm generation. By late Tuesday the upper low will pull to the north and begin to fill. A stable air mass will push in from the south and limit shower activity to the far northern zones Tuesday night. Temperatures will drop a handful of degrees Monday as a result of limited mixing, cooling temperatures aloft, and abundant cloud cover. Temperatures will warm slightly Tuesday with slightly less cloud cover. .LONG TERM...Wednesday through Sunday. The weather pattern from the middle of the week into Memorial Weekend is looking mostly dry for our region, but afternoon winds could become gusty Saturday and Sunday due to an Eastern Pacific low moving inland and lifting across northern California and northwest Nevada. The medium range models are in fairly good agreement with the synoptic pattern, though confidence decreases with the placement of the upper low late in the weekend which would affect wind speeds depending on how close the base of the system brushes it brushes our region. The ECMWF is a little farther south and slower with it than the GFS. The only day where showers look possible enough to mention is Wednesday over the southern Sierra behind the early week low pressure system lifting away to the north. After that, a ridge amplifies over a region ahead of the Eastern Pacific Low and temperatures will climb each day and now highs near or in the triple digits look likely across much of the the Mojave Desert Region Friday through Sunday. && .SPOTTER INFORMATION STATEMENT...Spotters are encouraged to report any significant weather or impacts according to standard operating procedures. && $$ UPDATE...Pierce SHORT TERM...Boothe LONG TERM...Adair AVIATION....Wolf For more forecast information...see us on our webpage: or follow us on Facebook and Twitter