Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 07/23/20

Area Forecast Discussion
National Weather Service Cheyenne WY
743 PM MDT Wed Jul 22 2020 .UPDATE... Issued at 737 PM MDT Wed Jul 22 2020 Areas of heavy rainfall have developed across the south Laramie Range and to its east. A small stream flood advisory will remain in effect through 9:45 pm tonight in northwest Laramie County to cover the flood threat due to the large amount of radar estimated rainfall being observed. Lighter rainfall has been noted further north and west. Rainfall and thunderstorms should continue to about midnight until a shortwave embedded within a southwesterly flow aloft finally passes. A quiet night is in store for the remainder of the night, with fog possible where the heavy rainfall occurred and have made this adjustment to the forecast. && .SHORT TERM...(late this afternoon through Thursday) Issued at 200 PM MDT Wed Jul 22 2020 Compared to this time yesterday, convection early this afternoon was limited to scattered CU forming over the higher terrain. HRRR/RAP soundings revealed a capping inversion around 700mb, with upwards of -300 surface- based convective inhibition. The 18Z HRRR progs isolated thunderstorms developing along the I-25 corridor by 22Z, with a greater coverage of convection spreading northeast from western and central CO into south central WY after 00Z. Despite SBCAPEs of 2000-3000 j/kg east of the Laramie Range, around 25 kt 0-6 km shear will result in a few strong storms capable of gusty outflow winds and possibly small hail. Most shower/thunderstorm activity will wane later this evening, with isolated elevated convection possible over the northeast plains late tonight and early Thursday morning. Isolated to scattered afternoon convection develops across the southern 2/3 of the CWA Thursday. SBCAPEs are progged from 500-1000 j/kg range with weak 0-6 km shear. Severe threat will be low, with isolated strong storms with gusty winds and small hail possible. It will be warm with highs in the 70s and 80s west of I-25, and 90s to the east. .LONG TERM...(Thursday night through Tuesday) Issued at 311 AM MDT Wed Jul 22 2020 Upper level ridge will continue to persist over the intermountain west for the medium range to long range forecast. Split flow due to a weak upper level low at the the base of a shortwave trough Friday night into Saturday will help with a monsoon moisture plume surge toward the Central Rocky Mountains/Front Range/Laramie Range. 700mb temps on model guidance show pockets of lower temperatures in the 8C- 12C range most likely due to cold pooling associated with convective cell migration to the north and northeast overnight into Saturday morning. Diurnal heating coupled with modest low level southwest airflow from the 4 corners region will advect warm air into the region. Would not be surprised to see high temperatures crest 90-100 degrees east of the Laramie Range for Saturday. Continued surges of monsoon moisture and afternoon convection look to limit afternoon highs for Sunday, Monday, and Tuesday despite atmospheric ridging present in the upper levels. Overall, a fairly active weather pattern is favored for the extended period with above average temperatures for the CWA as well. && .AVIATION...(For the 00Z TAFS through 00Z Thursday evening) Issued at 509 PM MDT Wed Jul 22 2020 A few showers and storms over far se Wy this evening with vcts affecting KLAR. Other showers may move north out of Colorado for a time this evening as well. Otherwise VFR expected to prevail with monsoonal moisture resulting in fairly widespread mid and high clouds over the area through Thursday. && .FIRE WEATHER... Issued at 123 PM MDT Wed Jul 22 2020 A ridge of high pressure aloft will be situated over the central and southern Great Plains for the next several days. Clockwise flow around the ridge will draw monsoonal moisture from the Four Corners into the bi-state region. Instability combined with weak upper level disturbances will produce isolated to scattered mainly afternoon and evening showers and thunderstorms. Winds will be light to moderate, except variable and gusty near thunderstorms. && .CYS WATCHES/WARNINGS/ADVISORIES... WY...None. NE...None. && $$ UPDATE...AB SHORT TERM...MAJ LONG TERM...BMW AVIATION...RE FIRE WEATHER...MAJ
National Weather Service Sioux Falls SD
1056 PM CDT Wed Jul 22 2020 .UPDATE... Issued at 940 PM CDT Wed Jul 22 2020 Have made some minor modifications to the forecast tonight. Have raised forecast lows across eastern South Dakota. With increasing winds, temperatures should struggle to cool substantially. In addition, have delayed pops till closer to 09Z when low level warm air advection increases. && .SHORT TERM...(This Evening through Thursday) Issued at 317 PM CDT Wed Jul 22 2020 The primary concern in the short-term is convection chances for tonight into Thursday morning. Convection over the forecast area has momentarily ended. Satellite shows some flat cumulus over Tripp county and will continue to watch that area for development. However, model soundings show a strong enough cap exists (~ -50 J/kg) to prevent convection from developing. We did keep a slight chance of thunderstorms into the evening in south central SD should cumulus break the cap. Of more significance is a combination of a weak upper level wave that will move along the SD/NE border overnight combined with strong WAA between 850 and 700 mb ahead of a developing cap. Model soundings show that parcels based between 800 and 700 mb only have a very weak cap by 09Z. Expect that lift along the mid level boundary, which will be on the nose of the LLJ, will result in convection developing between KYKN and KSUX - likely near the Missouri River - after 06Z. CAMs have been split on how widespread development will be. THe latest HRRR shows isolated convection with a few light showers while the ARW and NMM show significant convection from KFSD into much of eastern Nebraska. While MUCAPEs are 1000-1500 J/kg, am more uncertain if the cap will be as weak as shown by model soundings and that could limit coverage of convection later tonight into Thursday morning. So kept PoPs in the 30-50 percent range. Severe weather is not expected given effective shear of 20 kts or less but initial updrafts may be able to produce up to dime size hail later tonight. As the LLJ weakens Thursday morning, convection should rapidly diminish and is unlikely to make it as far east as Storm Lake. As for temperatures, high pressure will slowly move east overnight. Winds will remain in the 5-15 mph range west of I-29 and with increasing moisture, lows will remain in the upper 60s. Near Hwy 71 in Iowa and Minnesota, lighter winds and clear skies will allow lows to fall to around 60 degrees. On Thursday, south winds will continue to increase bringing warmer air northward. Highs west of I-29 will reach the lower 90s with mid to upper 80s elsewhere. With dew points at or above 70 by the afternoon, places in the James Valley could see heat indices reach 100. Given forecast heat indices are at or just above 100 for an hour or two decided to hold off on any heat advisory in case dew points do not warm as quickly as forecast. .LONG TERM...(Thursday Night through Wednesday) Issued at 317 PM CDT Wed Jul 22 2020 The heat and humidity will continue into the weekend. On Thursday night, all deterministic models now show a strong cap in place over the forecast area with convection staying to the west and north of the area where a boundary will be in place and the upper level wave tracks. Therefore have removed PoPs from the forecast from Thursday afternoon into Thursday night. With high dew points moving into the area, lows will be in the 70s. Friday and Saturday will be hot and humid across the area. Both days will see highs well into the 90s and, with dew points remaining from 70-75, heat indices in much of southeastern South Dakota into northwestern Iowa and northeastern Nebraska will be from 100 to 105 degrees. With temperatures closer to 90 in southwestern Minnesota, the forecast heat indices are from 95 to 100. However, like last weekend, it is possible dew points on one or both days could be 2 to 4 degrees higher which would likely result in heat indices closer to what was seen last weekend. Regardless, dangerous heat will be over the area so those planning outdoor activities on either Friday or Saturday should be prepared. The other question is convective possibilities. All models keep the front north and west of the area through Saturday afternoon. So convective initiation will be to the north and west of the area during the late afternoon on Friday. The question will be if storms can develop/propagate far enough southeast to impact the forecast area. On Friday night, storm motion will be northeast to east-northeast. This track should keep most storms out of the forecast area with the best chance from north of Chamberlain to Marshall Minnesota. On Saturday afternoon evening, the front will be moving toward Highway 14. This means convection is more likely to either develop or move into the area from late afternoon into the evening. MLCAPEs will be over 3000 J/kg and effective shear will be around 30 kts so there will be the potential for isolated severe storms Saturday afternoon and evening. Temperatures will return to normal Sunday and into early next week. && .AVIATION...(For the 06Z TAFS through 06Z Thursday night) Issued at 1053 PM CDT Wed Jul 22 2020 VFR conditions through 08Z Thursday. Thereafter, expect elevated storms to develop south of highway 18 impacting the Yankton area, and spreading northeast through the morning. Have a period around sunrise where the I-29 corridor will be impacted south of FSD. Expect cumulus field to develop during the day on Thursday, with gusty southeast winds. && .FSD WATCHES/WARNINGS/ADVISORIES... SD...NONE. MN...NONE. IA...NONE. NE...NONE. && $$ UPDATE...BT SHORT TERM...Schumacher LONG TERM...Schumacher AVIATION...BT
National Weather Service Hastings NE
636 PM CDT Wed Jul 22 2020 .SHORT TERM...(This evening through Thursday) Issued at 321 PM CDT Wed Jul 22 2020 A well defined MCV moved through central Nebraska this morning. This brought a few showers and non-severe storms to the area. This has now moved out of the forecast area and become a little more diffuse. The main question today has been how much of a severe threat we end up having the rest of today. The severe threat is certainly looking less impressive for this evening, but there is at least still a conditional risk for a strong to marginally severe storm or two. The HRRR and RAP have been very adamant that no convection will develop behind the remnant MCV, but the NAMnest and NSSL WRF show a few scattered storms developing near warm front in southwestern portions of the area. I tend to favor the more conservative HRRR/RAP solution, as they are handling the MCV very well, but cannot totally rule out something developing. IF storms do develop, CAPE and shear are supportive of severe updrafts producing large hail and damaging wind. Later tonight, additional scattered showers and storms are expected to develop on the nose of an increasing low-level jet. The location of the jet would favor northeastern third of the forecast area. Severe storms appear unlikely at this point. Thursday is expected to be a dry and warmer day as we see rising heights aloft and increasing southerly flow near the surface. Highs are forecast to reach the low to mid 90s with southerly wind gusts of 25-30 MPH. .LONG TERM...(Thursday night through Wednesday) Issued at 321 PM CDT Wed Jul 22 2020 The warming trend continues on Friday. Although we will likely remain below advisory criteria, the humidity will push heat index values to around 100 degrees for many locations. Slight chances for thunderstorms creep into northwestern portions of the area overnight along with the next approaching trough and surface front. That said, this will likely remain primarily over the panhandle and western Sandhills. Saturday is still expected to the hottest day of the forecast period, and heat index values may approach 105 degrees in some spots. There is another chance for thunderstorms during the evening and overnight as the next trough continues to edge closer, but we still anticipate most of the local area to remain dry. Temperatures are a little more uncertain on Sunday, as a cold front is forecast to push into the area. Some locations will still likely push into the mid 90s ahead of it, though. This front will also likely bring us thunderstorms by the late afternoon and evening. Convective details remain pretty uncertain in day 5, but relatively high precipitable water and instability could lead to a few severe storms or flooding issues through Sunday night. Good chances for thunderstorms continue on Monday, but this will depend heavily on how far south the front pushes or if it stalls out in the local area. Regardless, temperatures should be around 10 degrees cooler than on Saturday. Slight PoPs continue Tuesday and Wednesday, but confidence is not high at this point. The latest ECMWF shows a drying trend, but the GFS does not have as much of a dry push behind the front, and therefore lingers precipitation in or near the area through this period. && .AVIATION...(For the 00Z KGRI/KEAR TAFS through 00Z Friday) Issued at 635 PM CDT Wed Jul 22 2020 Significant wx: Low level wind shear (LLWS) Tonight: VFR. Few lingering CU should dissipate around sunset. Have removed the VCTS through the early eve as subsidence behind departing MCV looks to quell tstm activity. However, later tonight, an incr LLJ could bring tstm chcs to near GRI, but esp points N and NE. It will also cause LLWS, esp. at EAR, through around dawn. Any convection that develops will be elevated, so only mid to high clds expected. Confidence: Medium to high. Thu: VFR. Fairly quiet conditions expected, with only issue being incr sfc winds out of the SE-SSE. Sustained winds will incr to 15-17kt, with gusts 24-26kt for the aftn. May see a few aftn CU with bases 3-4K ft. Confidence; High. && .GID WATCHES/WARNINGS/ADVISORIES... NE...NONE. KS...NONE. && $$ SHORT TERM...Mangels LONG TERM...Mangels AVIATION...Thies
Area Forecast Discussion
National Weather Service Goodland KS
546 PM MDT Wed Jul 22 2020 .SHORT TERM...(This evening through Thursday night) Issued at 159 PM MDT Wed Jul 22 2020 500 mb RAP analysis and satellite imagery showed an upper ridge building across the Rockies early this afternoon, with weak northwest flow over the region. An MCV from last night`s convection continued east along the Kansas/Nebraska border. Skies were sunny, with some high clouds moving in from the west as thunderstorms developed along the Front Range. At 2:00 PM MT, temperatures were in the upper 80s to mid 90s, with southerly winds gusting at 25 to 35 mph for the central portion of the area. A field of cumulus clouds was developing west of St. Francis. A few thunderstorms are forecast to develop over the northern half of the region this afternoon and evening where boundaries remain from this morning`s convection. However, confidence in storms forming/maintaining is low at this time. If thunderstorms are able to kick off, instability, shear, and hodographs suggest that a severe storm or two can develop with all modes of severe weather possible. Even a tornado cannot be ruled out. The best chance for severe weather will be along and north of Interstate 70. Thunderstorm activity should come to an end across the region by midnight MDT, as temperatures fall into the 60s and low 70s. The upper ridge moves onto the Plains on Thursday with an upper trough to its west, placing the region under southwest flow aloft. Breezy south winds are expected once again, with mostly/partly sunny skies and highs in the 90s. As moisture filters into the region from the southwest, thunderstorms may develop in the late afternoon and continue into the evening hours, mainly for locations along and west of Highway 27. At this time, severe weather is not expected. Temperatures fall back into the 60s and low 70s Thursday night, with dry conditions returning to the area by midnight. .LONG TERM...(Friday through Wednesday) Issued at 108 PM MDT Wed Jul 22 2020 For the start of the extended period not much has changed. Models are still showing the local area under the influence of a strong upper-level high and ridge over the Plains that is producing weak southwesterly flow aloft over the Central High Plains region. This pattern will produce above normal temperatures (middle 90s) and a daily chances for showers and thunderstorms through the weekend. For the start of next work week, the high will move more southwestward, towards the desert southwest, allowing for a low pressure system, and its associated front to transit south over the Great Lakes and northern High Plains regions. As of now, the models do show this front reaching the central High Plains region by Monday. If this holds, the local area will see an increase chance of showers and thunderstorms and closer to normal temperatures through the middle of next week. && .AVIATION...(For the 00Z TAFS through 00Z Thursday evening) Issued at 523 PM MDT Wed Jul 22 2020 VFR conditions are expected at MCK and GLD through the 00Z TAF period. Gusty south southeast winds will lose some gustiness after sunset with some low level wind shear developing at both locations after 04Z that continues through about 11Z before dissipating around sunrise. South winds will become gusty again by mid day on Thursday with scattered high clouds remaining across the area. && .GLD WATCHES/WARNINGS/ADVISORIES... KS...NONE. CO...NONE. NE...NONE. && $$ SHORT TERM...JBH LONG TERM...BW AVIATION...LOCKHART
National Weather Service Morristown TN
903 PM EDT Wed Jul 22 2020 .UPDATE... EVENING UPDATE. && .DISCUSSION... Still a few storms across the area as the sun is setting. Coverage is beginning to decrease but some of these clusters of storms looks to still be capable of producing new storms from their outflow, especially in the Tri Cities are and near the NC/TN/GA border. Expect storms currently on radar to somewhat persist for a while, but overall the coverage of storms this evening should remain relatively low. Will continue with low end PoPs across most of the area with increased chances where there is currently storms on radar. Overall only a few tweaks to the forecast in the evening hours, otherwise everything else remains on track. ABM && .AVIATION... 00Z TAF DISCUSSION. Storms should continue through the rest of the evening and begin to decrease in coverage with the setting sun. If a storm does impact an airport it would likely only last briefly with strong winds and heavy rain being the main hazards. Fog is not expected overnight unless an airport receives heavy rain...And we can expect more summertime thunderstorms once again tomorrow afternoon. ABM && .PREV DISCUSSION... /ISSUED 334 PM EDT Wed Jul 22 2020/ SHORT TERM...(Tonight and Thursday) Key Messages: 1. Scattered thunderstorms through this evening capable of producing locally heavy rain, with less of a chance for isolated strong winds. 2. Marginal risk for severe thunderstorms and excessive rainfall Thursday with widespread thunderstorms expected to develop. The main impact will be localized flooding and strong winds. Discussion: This afternoon/evening... Latest water vapor and RAP analysis shows a strong shortwave progressing across the lower Great Lakes and OH Valley with a surface low near the thumb of MI extending a cold front from NW OH through central MO. This system will continue moving eastward the rest of the day further breaking down the persist SE U.S. ridge as the surface high retreats to the E. Much of the dynamics are across the eastern Great Lakes and NE U.S. associated with a 60-80 kt 300 mb jet, but some confluence aloft, lowering heights with cooling mid level temps, and low-level moisture and instability have resulted in numerous diurnally driven thunderstorms this afternoon. Much of the activity is over the plateau and eastern mountains as of 18Z, but this will fill in across the valley late this afternoon through the evening, so maintained chance to likely PoPs with the highest values over the higher terrain. The threat of severe weather has decreased. MLCAPEs are 1000-1500 J/Kg, but DCAPEs are only 400-500 J/Kg, and when combined with 0-6 Km shear generally under 10 kts, any strong downdrafts will be isolated. Localized flooding continues to be the main concern with 1.8 to 2.10 inch PWATs, and weak wind field leading to very slow storm motions. One hour Flash flood guidance is only around 1 inch across the N Plateau and NE TN and parts of SW VA, so these areas will be most susceptible. Tonight... The initial shortwave will progress into the NE U.S. with the associated cold front making its way south and eastward toward the lower OH Valley. Since the forcing remains N through the night, believe most of our convection will dissipate after 02 or 03Z as the boundary layer cools, but still kept slight chance PoPs across northern areas through the night closer to the slowly approaching boundary. Lows will remain mild in the upper 60`s/low 70`s. Thursday... A secondary shortwave looks to dive into the NE U.S. setting up a slightly cooler and drier NW flow pattern over the eastern CONUS, which will finally drive the cold front through the S Appalachians as Canadian high pressure builds across the Great Lakes. This frontal boundary will cross slowly and not clear to our S until Fri morning. Looking at the forecast details, an active day of diurnal convection is expected due to a subtle increase in wind energy aloft on the periphery of this trough and associated jet dynamics combined with increasing convergence ahead of the front. Forecast soundings show a very weak cap around 700 mb during the morning, but this will quickly break as convective temps are reached by late morning. There will be a few stray showers early in the morning, but expect most convection to develop after 15Z starting across northern areas, as well as the plateau and eastern mountains, then expanding through the afternoon. CAMS suggest this timing and location which increases confidence, so have chance PoPs in the morning increasing to likely/categorical during the afternoon. Severe chances are a bit better owing to the SPC marginal risk areawide. Shear in the 0-6 Km layer increases to around 20 kts by evening across the north half of the CWA with MLCAPE projected at 1000-2000 J/Kg, LI`s of -5 to -8, and low-level lapse rates above 7 C/Km, although DCAPE remains low at 500-800 J/Kg. The improved shear with these at least modest thermodynamics favors some multicell clusters and faster storm movement leading to potential areas of wind damage. Wet bulb zero heights generally over 13,000 ft will continue to limit hail potential. Additionally, most of the area is under a marginal risk for excessive rainfall. Just like today, this will be the biggest threat with PWATs in excess of 2 inches (90th percentile) and fairly warm cloud depths supporting efficient rainfall. As mentioned, storm motions will be faster keeping the flooding threat localized, but areas of training will need to be monitored, especially where heavy rain has occurred the past couple of days. Highs will generally range from the upper 80`s/low 90`s. Garuckas LONG TERM...(Thursday Night through Wednesday) The main story during the extended continues to be the oppressive heat and primarily diurnal thunderstorms. Model guidance indicates a subtle shortwave tracking SE across the forecast area on Thursday night and Friday morning. This will result in higher PoPs and chances of some rain and thunderstorms. With models indicating PW of around 2.0 inches, locally heavy downpours will be likely producing a risk of localized flash flooding in flashy areas and locations that have already received heavy rain this week. Believe the severe risk will be very low on Friday afternoon with the shortwave axis forecast to be moving east of the forecast area by Friday afternoon. Isolated damaging microburst winds will continue to be possible with the strongest storms. Subsidence behind the departing shortwave is expected to be more pronounced on Saturday bringing lower PoPs to most of our forecast area. Highest PoPs on Saturday will be across the southern and southwestern counties near a weak boundary around the periphery of the ridge. With upper ridging bringing 591 to 593hpa 500mb heights to the area through early next week, only isolated pulse convection is anticipate late weekend through early next week. Above normal temperatures and heat indices of 100 to 105 will be probable for many locations. The GFS and ECMWF both indicate a shortwave tracking eastward across the Great Lakes next Tuesday with an associated surface low and frontal boundary. Larger differences exist mid-week. The GFS takes the trough axis eastward and builds in strong ridging across the Gulf Coast while the ECMWF weakens the ridge and results in longwave troughing across the Appalachians. While this adds to uncertainty next week, a general increase in convection as heights lower and the front approaches is forecast for Tuesday and Wednesday. JB && .PRELIMINARY POINT TEMPS/POPS... Chattanooga Airport, TN 74 93 73 92 73 / 40 50 20 60 20 Knoxville McGhee Tyson Airport, TN 73 91 72 90 71 / 30 70 30 60 20 Oak Ridge, TN 72 91 71 91 70 / 40 60 30 60 20 Tri Cities Airport, TN 69 88 68 86 67 / 30 70 40 60 20 && .MRX WATCHES/WARNINGS/ADVISORIES... NC...NONE. TN...NONE. VA...NONE. && $$
Area Forecast Discussion...Updated
National Weather Service Phoenix AZ
520 PM MST Wed Jul 22 2020 .UPDATE...Updated aviation discussion. && .SYNOPSIS... The combination of increasing moisture levels and a Pacific upper-level low pressure system will bring better chances for showers and thunderstorms on Thursday and Friday over all of south central Arizona including the Phoenix metro, but southwest Arizona and southeast California will generally remain dry. Lingering thunderstorm chances may continue into Saturday before rain chances decrease for Sunday into the first half of next week. Temperatures will be below normal for most locations on Thursday through the weekend before warming back up above normal for the first half of next week. && .DISCUSSION... Hi-res models continue to show that thunderstorm chances will be limited to higher terrain locations north, east, and south of the Phoenix metro through tonight. The biggest reason for this is that dynamic forcing that helped generate virga and thunderstorm activity the past couple of days is generally lacking today as the region remain in a "col" pattern with little to no dynamic lift. Essentially, the region is sandwiched between a pair of mid-to- upper level ridges centered over northern Baja California and the TX-OK panhandles and a pair of troughs moving into southern California from the west and Sonora from the southeast. Should any outflows make it into the Valley this afternoon and evening, there would be a chance isolated storms could develop. However, confidence in outflows moving into the Valley currently remains low. with the latest HRRR making an attempt to move them in from the NE 1st, then from from the Ajo and Gila Bend areas, that might be too far southwest of the metro to send a decent outflow into the Valley this evening. Much better shower and thunderstorm chances begin as early as overnight tonight and more likely by Thursday afternoon as the afomentioned shortwave moves in from the west and the inverted trough over Sonora moves northwest into southeast Arizona. Ahead of this inverted trough, an increase in midlevel moisture should help increase surface-based instability close to 2000 J/kg with little convective inhibition and PWATs into the 1.6-1.9" range, along with good mid-level diffluence ahead of a rather deep (for late-July) upper low approaching the central CA coast. Latest hi- res model runs have definitely become more bullish on developing a rather coherent line/cluster of storms moving into the PHX metro from the southeast and east. The main impacts will be strong winds, blowing dust, and small hail across the lower deserts and locally heavy rains across the higher terrain of South-Central AZ. Although storm motion will be rather rapid for late July (20-30 mph), there is potential for training in areas of favored orographic lift across southern Gila County. Thus, a Flash Flood Watch has been issued for the Bush Fire Burn Scar. Also, WPC still has the region under a marginal risk of excessive rainfall for Thu/Fri. Dynamic forcing associated with the inverted trough and the relatively moist environment should support lingering shower and isolated thunderstorm activity into the overnight hours on Thursday into early Friday during which heavy rainfall would be the primary threat. Friday and Saturday`s forecast is uncertain given it will depend upon how convection evolves on Thursday afternoon into the overnight hours, but the setup will still be favorable for isolated to scattered thunderstorms in the Valley and greater coverage over the higher terrain provided we remain unstable without overcast conditions. As synoptic features expand and contract, there will be fluctuations in how far west the richer moisture gets with the moisture gradient remaining over western Arizona. Disturbances within the southwesterly flow aloft could possibly aid storm development but timing/track/strength of any of those features that would make a difference is difficult at the current moment. Regardless, the broader model ensemble is becoming more confident in a drying and warming trend that will begin on Sunday and last into the first half of next week as PWAT values have generally dropped about 0.2-0.3" from what they were in the previous model cycle for Sunday. Temperatures should increase back to seasonal normals or slightly above for Monday and Tuesday with isolated thunderstorm chances confined to the higher terrain of Gila County. && .AVIATION...Updated at 0020Z. South-Central Arizona including KPHX, KIWA, KSDL, and KDVT: For the remainder of the afternoon and through the evening, aviation impacts should be on the low side; most convection should remain well southeast or east of the terminals. Expect FEW-SCT decks generally aoa 10k feet overnight tonight. Cannot rule out an isolated shower or storm making it into the Phoenix area, but confidence too low to mention in the TAFs. Winds will tend to favor the southwest or west through midnight, but there will likely be quite a bit of light/variable or variability due to weak outflows moving in from distant convection. Overall, winds should tend to transition back to the east after about 08z. More significant aviation impacts expected by mid afternoon on Thursday as steering flow becomes stronger and more southerly and a weather disturbance will be moving in from the south. Expect clouds to thicken with SCT-BKN decks aoa 10k feet after 14z along with SCT decks developing around 8k feet. After about 21z, expect isolated showers or storms to develop and as such have added VCTS to the TAFs to account for this. At KPHX added a PROB30 for showers, with VCTS during the evening hours. Potential will develop for stronger outflow winds into the terminals Thursday late afternoon and evening, favoring south to southeast, but confidence is a bit too low and the long time range means those impacts will be left out of the TAFs with the afternoon package. Southeast California/Southwest Arizona including KIPL and KBLH: Conditions look to stay dry over the western deserts with skies generally clear through Thursday afternoon. Winds will favor the southeast at KIPL for most of the period, with some southwest wind possible later this evening into Thursday morning. Speeds should generally stay 12kt or less. Winds to favor the south at KBLH with gusty conditions into the evening both today as well as Thursday afternoon. Peak gusts to exceed 20kt at times. && .FIRE WEATHER... Saturday through Wednesday: Monsoonal moisture and isolated to scattered thunderstorms with below normal temperatures are expected east of the Lower Colorado River Valley on Saturday, with the best chances over south central Arizona. Southeast California will remain dry with near normal temperatures during this time while temperatures over the lower deserts of Arizona remain below normal. Minimum relative humidity values will generally be in the 20-30% range across the lower deserts through Saturday with values in the teens over southeast California and above 30% over the higher terrain of Gila County. Overnight recovery above 30% is expected for all locations with values above 50% over the higher terrain of Gila County. A drying and warming trend will begin on Sunday through the Wednesday across the entire region, with only isolated thunderstorms expected over Gila County. Diurnal winds are generally expected aside from any gusty outflows associated with thunderstorms. && .SPOTTER INFORMATION STATEMENT... Spotters should follow standard reporting procedures. && .PSR WATCHES/WARNINGS/ADVISORIES... AZ...Flash Flood Watch (Bush Fire Bush Scar) from Thursday afternoon through Thursday evening for AZZ547-556-557. CA...None. && $$ DISCUSSION...Percha/Hopper AVIATION...CB FIRE WEATHER...Hopper
Area Forecast Discussion
National Weather Service Shreveport LA
1005 PM CDT Wed Jul 22 2020 .SHORT TERM.../Tonight/ The convection has diminished this evening, a bit sooner than what was observed 24 hrs ago, with the bndry lyr having quickly cooled near the remnants of a weak shear axis over portions of Srn AR and N LA. The earlier runs of the global models as well as the latest 00Z NAM continue to suggest that isolated convection may redevelop overnight near this weak shear axis over SE OK/portions of extreme NE TX/SW AR/extreme Nrn LA, with even the latest run of the HRRR suggesting this as well, and thus have retained slight and low chance pops tonight across these areas to account for this possibility. Unfortunately, the rain may be harder to come by Thursday as this shear axis dissolves in response to the amplifying upper ridge over the Srn Plains which will expand E to the Mid-South region, thus suppressing most convection development while in turn, resulting in an increase in the heat. Did not make much adjustments to the forecast min temps tonight, with temps expected to range from the lower to mid 70s once again. While the heat will return Thursday, convection should increase across portions of E TX/N LA/Srn AR Friday N of newly formed TD 8 in the Cntrl Gulf, which will continue W towards the TX coast through the weekend. Zone update already out...grids will be available shortly. 15 && .PREV DISCUSSION... /issued 644 PM CDT Wed Jul 22 2020/ AVIATION... VFR conditions should continue through much, if not all of the 23/00Z TAF period. The convection continues to quickly diminish across the region early this evening, although convective debris will linger through the overnight hours. Some isolated SHRA redevelopment will be possible though overnight across portions of extreme NE TX/SW AR/NW LA near a weak disturbance aloft, but low confidence precludes mention in the SHV/TXK terminals attm. Some patchy FG/BR will be possible late tonight in areas that received rain earlier today, with brief IFR/low MVFR cigs possible around/shortly after daybreak Thursday before scattering out by mid-morning. A sct cu field is expected by late morning through the afternoon, with isolated convection possible across portions of extreme NE TX/SE OK/SW AR near the weakening upper level disturbance, as well as across the Srn sections of Ncntrl LA well N of a slowly developing low pressure system drifting W across the Cntrl Gulf. Any convection though should diminish by early evening. Lt/Vrb winds tonight will become SE 4-8kts after 15Z. /15/ && .PRELIMINARY POINT TEMPS/POPS... SHV 75 93 76 91 / 10 20 0 50 MLU 75 95 75 92 / 20 30 10 60 DEQ 73 90 73 92 / 30 30 0 20 TXK 73 91 75 90 / 20 20 0 20 ELD 72 94 73 92 / 20 20 10 30 TYR 75 93 75 90 / 10 10 0 30 GGG 74 93 75 91 / 10 10 0 40 LFK 74 93 76 90 / 10 10 10 70 && .SHV WATCHES/WARNINGS/ADVISORIES... AR...None. LA...None. OK...None. TX...None. && $$ 15