Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 10/01/21

Area Forecast Discussion
National Weather Service Caribou ME
1009 PM EDT Thu Sep 30 2021 .SYNOPSIS... An upper level low will remain over the region through Saturday then slowly move east on Sunday. A warm front becomes stationary southwest of the region Monday through Tuesday, while at the same time high pressure from Quebec builds across northern portions of the region. && .NEAR TERM /THROUGH FRIDAY/... 1010 pm update... Updated to increase temps slightly for the overnight as cloudy skies are keeping temps warmer than fcst acrs nrn areas. No chgs needed to pops for the overnight with more widespread showers over the north and east closer to proximity of upr low with Downeast likley in the clear after midnight. Prev discussion blo... The upper level and surface lows continue to spin to the NE of the state and should lift to the N tonight. Upper air model sounding indicate that the convergence and convective dynamics will start to weaken tonight with the exiting low. The RAP and Euro keep some light QPF all the way down to the coast after midnight while HRRR, GFS, NAM and Canadian models have QPF pulling up to just the northern half of the CWA after midnight. Model percentiles seem to be more on track with the GFS and HRRR, so adjusted the precip forecast to have rain pulling out of the south after midnight. Nevertheless, rain showers will continue for the north. Cloud cover should help keep temps from reaching into the 30s. Expect 40s across the region. By Friday, the upper level low will start to move more north, which will help push the surface low more northward. This will help keep numerous showers to the north and scattered rain showers in the south. 925-850mb model temps show that with cold air associated with the low and ample cloud cover, temps will struggle to reach into the 50s in the north. Some clearing of clouds in the south will allow some sunshine to warm temps into the upper 50s to low 60s for the day. && .SHORT TERM /FRIDAY NIGHT THROUGH SUNDAY/... Low lvl moisture and s/wv trofs alf will cont to rotate arnd a slowly exiting upper low across the Nrn Can Maritimes Fri Ngt til about Sat eve with intermittent lgt shwrs and lgt measurable 6 hrly QPFs durg this tm span. Conditions improve for some clrg late Sat Ngt into Sun with intervals of msly cldy skies and still a few isold lgt shwrs or sprinkles. Hi temps will make only a slow recovery Sat thru Sun with cld cvr keeping temps near normal, although some clrg late Sat ngt could allow for some pockets of below normal low temps across Nrn vlys under lgt sfc winds. && .LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/... A narrow sfc ridge will keep fair conditions Sun ngt, with potential of ovrngt low temps at of below frzg and front for a large ptn of the FA...if skies become and remain clr, which is a little uncertain attm. Otherwise, models are now showing anomalous Nrly component flow high alf ovr our Rgn between the departing upper low E of the Can Maritimes and very anomalous strong ridging/blocking ovr Nrn Can msly keeping moisture ahead of a warm front and a Srn upper low in the Srn Jet Stream ovr the Midwest/Srn states just SW of our FA Mon and Tue, bringing some cldnss to all of the Rgn and perhaps brushing far Swrn areas with sct shwrs Mon Ngt int Tue. Ridging alf from the NW then becomes more established for Wed and Thu with more in the way of sunshine for all of the FA. High temps will recover a little each day, becoming quite pleasant in the 60s by mid week. Ovrngt lows will remain chilly spcly across the N with drier air promoting large diurnal swings upwards to 30 deg between low and high temps. && .AVIATION /02Z FRIDAY THROUGH TUESDAY/... NEAR TERM: MVFR expected across northern terminals through the day tomorrow, with ocnl IFR cigs expected late tonight. Downeast terminals will likely remain VFR with unrestricted and/or brief MVFR showers. SHORT TO LONG TERM: Fri Ngt - Sun...all TAF sites low VFR/high MVFR clgs with intermittent lgt rn shwrs. Lgt winds. Sun Ngt - Tue...all TAF sites low VFR clgs to unlmtd VFR. Lgt winds. && .MARINE... NEAR TERM: Winds and seas will remain below SCA conditions tonight and Friday. NNW winds will increase to 10-15 kts with gusts up to 20 kts tonight, but decrease by Friday morning. Then increase again by Friday afternoon to 10-15 kts and 20 kts gusts. SHORT TO LONG TERM: Initially no hdlns for our waters, but wvs in the form of very long pd of swell from Hurricane Sam over the open Cntrl Atlc ocean will begin to arrive on Sat, reaching SCA wv hts of 5 to 6 ft Sat Ngt thru Sun Eve, then dmnshg below 5 ft late Sun ngt and contg to subside Mon into Tue. Went with blended model wv guidance for fcst wv hts with the main spectral component being very long period upwards to 14 to 16 sec radiating wv groups from Sam spcly Sat thru Sun. && .TIDES/COASTAL FLOODING... Long period swell with a peak wave period of 14-16 seconds from Hurricane Sam will reach the Downeast coast late this weekend. The swell will likely lead to rip currents and the potential for high surf. Astronomical tides are on the low side late this week and into the weekend, but higher astronomical tides are predicted for early next week. && .CAR WATCHES/WARNINGS/ADVISORIES... ME...None. MARINE...None. && $$ Near Term...Farrar/LaFlash Short Term...VJN Long Term...VJN Aviation...Farrar/LaFlash/VJN Marine...Farrar/LaFlash/VJN Tides/Coastal Flooding...
Area Forecast Discussion...UPDATED
National Weather Service Austin/San Antonio TX
648 PM CDT Thu Sep 30 2021 .AVIATION (00Z TAFS)... /NEW/ A complicated forecast will evolve overnight as ceilings will be tricky as thunderstorms move into the region. Overall, expect thunderstorms to develop out west first, and slowly by surely march east and southeastward through the late evening and into the early morning hours on Friday. At DRT, expect thunderstorms at the airport by 02Z and the possibility of IFR ceilings between 03Z-07Z as heavy rain and thunderstorms look like a good bet. Beyond that, expect MVFR ceilings through at least 18Z before a period of what should be VFR ceilings moves over the terminal. Next, at AUS, expect storms to arrive by 09Z and continue for a couple hours, with IFR ceilings expected along with gusty winds up to 25 kts. Ceilings finally come back up after 20Z Friday. Lastly, at SAT/SSF, heavy thunderstorms are possible between 10-14Z, with winds gusting up to 35 mph or possibly higher. IFR ceilings are expected even LIFR ceilings cannot be ruled out. Ceilings should get back into the MVFR range by 16Z with lingering light rain. Expecting things to attempt to dry out by the evening hours, but trends will need to be monitored to consider running with prevailing -SHRA through much of the 24-30 hour forecast period. && .PREV DISCUSSION... /ISSUED 251 PM CDT Thu Sep 30 2021/ SHORT TERM (Tonight through Friday Night)... The slow-moving upper level low remains over AZ/UT this afternoon with the bulk of convection associated with the low in West Texas at the present time. Additional convection can be seen along the coast and in our Coastal Plains counties and this activity is associated with a weaker disturbance on the northern periphery of an upper level ridge in the northern Gulf of Mexico. The Coastal Plains activity will continue and push a bit farther north and east through the late afternoon hours. The main concern for late this afternoon into Friday morning will be the convective evolution of the activity to the west. Latest surface analysis shows this activity is developing along a convective boundary. As this boundary moves southward through the afternoon and evening, showers and thunderstorms should be on the increase with the northwestern CWA being the first location. However, there could be some isolated to scattered showers and storms ahead of the main line and some of this activity could be strong. There are also some indications in some of the high-res models that a brief linear bowing segment could occur in Val Verde County with the initial convection along the boundary. The biggest threat with this if it were to occur would be the potential for strong winds. The main focus for the threat of heavy rainfall will occur with the potential linear activity as this boundary continues to move south. The latest run of the HRRR shows this evolution with showers and storms entering Val Verde County around 4z continuing south through the night. The main area for potential locally heavy rainfall will be in the western areas as this is where the heavier storms are expected to move through tonight with the boundary having a better surge southward there. Think areas in the northwestern CWA could see 2-3 inches of rainfall with isolated amounts up to 6 inches. The soils out west are dry due to recent dry conditions and not much falling a couple of nights ago. Therefore, do not anticipate widespread flooding issues tonight, but some isolated flooding will be possible. For tomorrow, the boundary is expected to make it as far south as out southern counties before washing out with southerly flow returning. Think the morning hours will primarily have more scattered activity lingering from the overnight convection with a possible break in activity. Redevelopment of scattered activity is expected tomorrow afternoon. Some locally heavy rainfall will remain possible. For tomorrow night, it does not appear that there will be any appreciable boundaries but some isolated heavier showers and thunderstorms could continue to produce local flooding concerns dependent on soil moisture. LONG TERM (Saturday through Thursday)... The upper level low centered across the Desert Southwest will lift northeastward into/through Saturday which helps to advance a cold front into the region out of the north. Combination of the deep column moisture with PWATS between 1.6 to 2 inches and the surface forcing ahead of the front should result in another wet day with scattered to numerous showers and thunderstorms. Activity looks to generally concentrate immediately along and ahead of the surface front. While the instability is lower on Saturday, models continue to depict the potential for more locally heavy rain where a quick inch or two may fall resulting in additional flooding concerns. WPC highlights a marginal risk on the latest day 3 excessive rainfall outlook from 12Z Saturday to 12Z Sunday over the eastern 2/3rds of the CWA. Rain chances then push southward into the southern zones from Saturday night into Sunday along the front. Moisture and cloud cover keeps the afternoon highs slightly cooler while the morning lows remain on the mild and humid side. Drier and more comfortable conditions arrive behind the front as winds become north-northeasterly and surface high pressure builds across the region from later Sunday through midweek. While the afternoon highs are to remain rather seasonable, expect for cool nights with overnight lows that lower into the 50s and 60s across the majority of the region. && .PRELIMINARY POINT TEMPS/POPS... Austin Camp Mabry 71 85 72 84 69 / 40 70 50 60 30 Austin Bergstrom Intl Airport 70 85 70 84 67 / 40 70 50 60 30 New Braunfels Muni Airport 71 85 70 86 69 / 50 70 60 60 30 Burnet Muni Airport 69 82 69 83 65 / 60 70 60 70 20 Del Rio Intl Airport 71 86 71 86 70 / 80 70 80 50 30 Georgetown Muni Airport 70 84 70 83 67 / 50 70 60 70 30 Hondo Muni Airport 71 85 70 86 67 / 60 70 70 60 40 San Marcos Muni Airport 70 85 69 84 67 / 50 70 50 60 30 La Grange - Fayette Regional 73 86 72 85 71 / 40 60 30 70 30 San Antonio Intl Airport 72 84 72 85 70 / 50 70 60 60 30 Stinson Muni Airport 74 86 73 87 71 / 50 70 60 60 30 && .EWX WATCHES/WARNINGS/ADVISORIES... None. && $$ Short-Term/Aviation...Morris Long-Term...Hampshire
National Weather Service Hastings NE
625 PM CDT Thu Sep 30 2021 ...AVIATION UPDATE... .DISCUSSION...(This evening through Thursday) Issued at 252 PM CDT Thu Sep 30 2021 The main issues for this forecast will be chances from this afternoon through Friday, and into Saturday. Overall trends are for lowered POPs this afternoon and tonight as NBM continues to overdo in this category and cold front is east of the CWA, although slowing down and possibly stalling. Some wrap around moisture from the surface low along the front could help give us a slight jump in POPs later tonight, but not by much. General consensus among hi-res models that coverage should be spotty, and support for drizzle will be in place for this afternoon and into tonight for a good chunk of the area. Maybe enough instability to maintain some thunder in our far east through this evening. HRRR is pointing toward some fog in parts of our CWA late tonight and early Friday, especially north half/east CWA, but I`m keeping this out for now given the unfavorable wind direction from the north northwest and lack of clearing expected, and also the SREF does not hit the fog nearly as hard. Still enough for some mention of thunder at times for Friday/Saturday, but not enough support for severe weather. Trends still toward drier for Friday with some shortwave ridging in advance of a shortwave trough approaching from the southwest and continue to go in that direction, but still non-zero POPs for Friday/Friday night for now, and continue to decrease. For Saturday, trends from previous runs are also farther south for precip compared to previous 00Z runs of both operational models and ensembles, but ensembles still indicate a decent shot at some precip for much of the CWA, with higher chances in our south and kept robust POPs in for Saturday for now. Operational are definitely trending dry for the north half of the CWA with higher QPF tending farther south. After the trough passes, Sunday and beyond are forecast as dry and cool as has been the general gist for the past few forecasts. && .AVIATION...(For the 00Z KGRI/KEAR TAFS through 00Z Saturday) Issued at 613 PM CDT Thu Sep 30 2021 Cigs continue to straddle the line between MVFR and IFR, sitting right about 1,000 ft. This will continue to be the case for a few more hours before cigs then come down into IFR territory for the overnight hours through the early morning hours. Then cigs will lift back to MVFR till the afternoon hours when the cloud deck will begin to break up and should lift to VFR as well. Winds will remain relatively light, less than 10 kts, and will be generally out of the north but will shift to more northwesterly late in the period. && .GID WATCHES/WARNINGS/ADVISORIES... NE...NONE. KS...NONE. && $$ DISCUSSION...Heinlein AVIATION...Shawkey
Area Forecast Discussion
National Weather Service Goodland KS
934 PM MDT Thu Sep 30 2021 .SHORT TERM...(This evening through Friday night) Issued at 219 PM MDT Thu Sep 30 2021 Satellite imagery and 500mb RAP analysis showed almost southerly flow above the High Plains today on the eastern side of an upper trough. This trough appeared to be digging into the Desert Southwest, closing off into a low in the process. At 1 PM MT, cloud cover had shifted off to the northeast and south, allowing clearing across the central portion of the region. Northerly winds continued at the surface, gusting around 30 mph at times, with temperatures in the 60s. For tonight, south to southwest flow persists aloft as the aforementioned low pushes further into the southwestern CONUS. Dry weather is anticipated with low temperatures in the 40s to low 50s. Cloud cover may creep back into the area ahead of the disturbance as early as the overnight hours. On Friday, the system ejects towards southwestern Kansas, resulting in rain showers and perhaps a few thunderstorms moving into the region from the south. While there is a chance for precipitation south of I-70 in the afternoon, the better opportunity for the entire area will be Friday night as the disturbance draws nearer to the High Plains. Severe weather is not expected with any thunderstorms that develop. This should tend to be more of a steady rain rather than convective, so am not anticipating flash flooding issues at this time. High temperatures are currently forecast in the mid 60s to low 70s. However, with cloud cover building in through the day, this may be a little warm. This is followed by dropping to the mid 40s to mid 50s for Friday night. .LONG TERM...(Saturday through Thursday) Issued at 132 PM MDT Thu Sep 30 2021 Precipitation will be fairly widespread during the morning hours at the start of the period with H5 low to the south of the area lifting northeast through the day. Eastern CWA remains in favorable WAA/Isentropic upglide with respect to low circulation through 18z, so expect a fairly persistent area of precipitation to develop. As system moves away from the area Div Q fields indicate strong forcing for subsidence and with limited residual instability, expect a pretty rapid decline in precipitation after 18z. H5 low will continue to the east and merge with another system forming new closed low system over the southeastern CONUS. Ridge will amplify across the area in response to this system and one approaching the four corners in an omega like pattern. While this pattern will be transient and not an Omega block, net result will be area once again under the influence of upper level ridge and associated warmth and generally quiet conditions. Although temperatures will be above normal, highs will generally be seasonal in the mid 70s. && .AVIATION...(For the 06Z TAFS through 06Z Friday night) Issued at 920 PM MDT Thu Sep 30 2021 KGLD and KMCK expect to see VFR conditions throughout the 06Z TAF period. KGLD starts with westerly winds around 5 kts before becoming light and variable at 16Z. At 00Z, KGLD winds become southerly around 5 kts then turn west-southwesterly with vicinity showers possible at 02Z. KMCK begins with northwesterly winds at 5 kts before becoming northerly around 7 kts at 18Z. At 20Z, KMCK winds become northeasterly around 6 kts then turn easterly by 23Z. KMCK may also see showers possible just beyond the TAF period. && .GLD WATCHES/WARNINGS/ADVISORIES... KS...NONE. CO...NONE. NE...NONE. && $$ SHORT TERM...JBH LONG TERM...JRM AVIATION...076
Area Forecast Discussion
National Weather Service North Platte NE
636 PM CDT Thu Sep 30 2021 .SHORT TERM...(This evening through Friday night) Issued at 355 PM CDT Thu Sep 30 2021 The main forecast challenges through the end of the week revolve around remnants from Wednesday night`s storm system, the next wave of moisture slated to arrive Saturday, and temperature in the meantime. This evening and tonight... A batch of rain showers continues to slowly drift west across north central Nebraska with some backbuilding or continuous development on the eastern edge. Some of the rain has been moderate at times, with KANW recording 0.30" of moisture since this morning. Adjusted PoP to maintain chance wording through the overnight hours, primarily along and north of Hwy 20 from KVTN to KONL. Used a blend of recent CAMs guidance for timing and location. Synoptically, the surface low is centered over northeast Neb near KOFK as of 20z, while the mid/upper trough axis cuts through the Sandhills into central Nebraska. Deep isentropic upglide exists on the backside of the surface low and ahead of the upper trough axis. This added lift corresponds with continued low level moisture advection. Have not observed any thunder with this activity today, and RAP mesoanalysis indicates marginal instability at best with MUCAPE around 100 j/kg. Removed all thunder mention and left as general rain showers through this period. Northerly winds have also been relatively gusty today with 20+ kt flow at H85 being mechanically mixed to the surface. These winds weaken tonight and some of the thick stratus clouds will clear out of the panhandle. Thinking the clouds will hang around over central Neb in the vicinity of the surface low. Forecast lows reflect this with values ranging from near 40F far west to mid 50s far north central. The overall change from the previous forecast is generally 2 to 3 degrees cooler where clearing is expected to little/no change in the east. Friday and Fri night... The surface low and cool front finally exit the state, but the mid/upper trough lags behind and still drapes across eastern Neb. The bulk of the forcing and moisture convergence should lie east of the forecast area, but cannot rule out a few light rain showers or sprinkles east of Hwy 281. Kept schc PoP through the day, but clouds may extend as far west as Hwy 61 as virtually the entire CWA lies in north/northwest flow at H85. Weak WAA occurs late in the day as low level flow begins to transition to southerly, mainly in the panhandle. Nevertheless, used the cool end of guidance for max temps as cloud cover should limit overall diabatic heating potential. Forecast highs are right around 70F areawide, which is just a hair below normal. .LONG TERM...(Saturday through Thursday) Issued at 355 PM CDT Thu Sep 30 2021 The main synoptic features in the extended period deal with the upper level pattern. This weekend, a closed low moves out of the Four Corners and cuts northeast across the central Plains before getting absorbed into the main northern stream somewhere around Nebraska. A separate closed low then dives south along the Mississippi River Valley to start the workweek, then gets hung up near the Ohio Valley. The first system will likely have the greater effect on western Nebraska as forcing and moisture availability will be more in proximity. Guidance is in general agreement with precipitation brushing the southern and eastern portions of the CWA, although discrepancies exist regarding the western extent and timing. Temperature-wise, values will remain seasonable in the lower to mid 70s the next several days as a weak upper ridge builds along the Rockies and a broad high pressure settles in at the surface. && .AVIATION...(For the 00Z TAFS through 00Z Friday evening) Issued at 636 PM CDT Thu Sep 30 2021 For the KLBF terminal, expect some broken mid level clouds overnight with ceilings around 5000 FT AGL. Expect some higher clouds after daybreak on Friday. For the KVTN terminal: Expect broken ceilings around 4000 FT AGL overnight with some clearing after sunrise Friday. On Friday, expect scattered clouds ranging from 6000 to 7000 Ft AGL. Winds for both terminals, will generally be from the north or northwest at under 10 KTS over the next 24 hours. && .LBF WATCHES/WARNINGS/ADVISORIES... None. && $$ SHORT TERM...Snively LONG TERM...Snively AVIATION...Buttler
Area Forecast Discussion...CORRECTED
National Weather Service Lake Charles LA
1002 PM CDT Thu Sep 30 2021 .UPDATE... Evening update. && .DISCUSSION... A few showers are currently present over southwestern portions of the outer offshore areas. The shower and thunderstorm activity from earlier in the day has dissipated with low and mid-level clouds persisting over the region. The current forecast is mostly on track. However, PoPs were reduced slightly for the next several hours to account for current radar activity and the latest run of the HRRR (00Z) showing limited shower and thunderstorm development over the next several hours and likely remaining offshore. Storm chances will be expected to increase (especially for western portions of our area) near sunrise and expand eastward as the morning progresses. The possibly for patchy fog has been adjusted as well, with expectations being for 07Z through 14Z primarily for inland counties and parishes. 55 && .PREV DISCUSSION... /issued 721 PM CDT Thu Sep 30 2021/ DISCUSSION... For the 10/01/21 0000 UTC TAF package. AVIATION... Convection has largely come to an end across the area save for some isolated light shower activity, mainly over parts of central and south central LA. Considerable cloud cover remains, however, chiefly in the form of a dense cirrus canopy though there are some clouds beneath it per SFC Obs. Nevertheless, VFR is currently prevailing at all terminals, though some low clouds may be starting to form at the Acadiana terminals. Couple of concerns to contend with tonight, with the initial one centered around low stratus and/or fog formation. Guidance is a bit all over the place in that regard, so using a blend of this guidance and persistence, showed MVFR developing most sites later tonight, though will have to continue monitoring trends at KLFT and KARA for the potential of an earlier onset and/or lower category. Next item is convective potential, with CAM guidance pointing toward some overnight and FRI morning activity developing/moving across SE TX. PROB30 was inserted at KBPT for this potential, with the rest of the coastal terminals likely to see activity more scattered in nature late morning or early afternoon. 13 PREV DISCUSSION... /issued 325 PM CDT Thu Sep 30 2021/ SHORT TERM [Tonight through 12Z Sunday]... Another wet day ongoing across the CWA with scattered to widespread convection noted on radar this afternoon. Much of this convection has been very slow moving today, resulting in some localized flash flooding issues across parts of south-central LA. This looks like it will continue to be a concern through the next few hours as some of these showers look to not be going anywhere fast. Fortunately, short term guidance begins to fizzle these showers out around 00-01Z, with general dry and cloudy weather expected thereafter as we head into the overnight hours. Only exception to this may be the coastal waters and coastal parishes where some convection may persist overnight. Elsewhere, main issue overnight looks to be another round of patchy fog, particularly across the Lake Area. This fog will likely persist through sunrise, before burning off through the morning hours. Tomorrow, another shortwave/vort max looks to rotate around the western CONUS trof and towards SE TX/SW LA, while at the same time some mid-level ridging tries to build northward across the north-central Gulf Coast. This weak ridging may help to hold POPs down slightly across the eastern periphery of the CWA, however, it looks like the shortwave will win out elsewhere. As a result, expect scattered convection to begin to redevelop through the early morning, particularly across SE TX, spreading eastward from there. Coverage may be a bit most widely scattered across Acadiana tomorrow, but for the most part we are expecting another wet and muggy day. Unfortunately, it looks like Saturday will be much of the same in a long string of wet days, with scattered to widespread convection once again expected. However, it does look like we may finally see a break in this pattern just beyond the end of the short term, so hopefully we don`t have to wait too much longer for some sunshine. 17 LONG TERM [Sunday through Friday]... A shortwave trough and sfc cold front in east Texas will progress eastward through the day on Sunday. Look for numerous showers and thunderstorms on Sunday ahead of the front at this time... the main issue will be from heavy rains at times... and cloud to ground lightning. This activity will shutdown as the cold front pushes through and this will slowly push the gulf moisture that is over the region off to the east and south late Sunday into Monday with rain chances tapering back and moving over the coastal waters. As the cool front exits eastward along with the upper level trof... drier and somewhat cooler air will gradually make it`s presents felt Tuesday morning with low temperatures in the mid 60s and mid 80s for afternoon high temperatures. From Wednesday onward into the weekend the cool and dry pattern will become established as a broad 1015 High over Texas will sit off to the northwest establishing a northerly flow at surface. As the pressure gradient is not expected to be become tight winds in the coastal waters will average around 10 to 13 knots with seas around two feet nearshore and two to three offshore. K. Kuyper MARINE... A moderate onshore flow around 10-15 kts, with higher gusts, will continue through the end of the week, while seas will run near 1-4 feet. Winds and seas will relax a bit as we head into the weekend, while remaining east to southeast. Scattered to widespread showers and thunderstorms will continue each day through the weekend as well. Frequent cloud to water lightning will be possible within some of these stronger storms, while winds and seas will also be locally higher near any thunderstorms. By early next week, a cold front is forecast to sweep through the region. As a result, winds become offshore behind the front and rain chances begin to lower by a fair amount. 17 && .PRELIMINARY POINT TEMPS/POPS... AEX 70 84 70 85 / 30 50 10 50 LCH 71 83 72 83 / 40 70 30 70 LFT 71 85 72 85 / 20 50 10 60 BPT 71 84 72 84 / 40 70 40 80 && .LCH WATCHES/WARNINGS/ADVISORIES... LA...None. TX...None. GM...None. && $$
Area Forecast Discussion
National Weather Service Phoenix AZ
411 PM MST Thu Sep 30 2021 .UPDATE...Updated Aviation Discussion. && .SYNOPSIS... An early autumn weather system begins to slowly exit the region today providing a last chance of showers and thunderstorms through this evening. Much of the activity will become focused over higher terrain areas north and east of Phoenix. Building high pressure into the weekend will allow temperatures to rebound back to near and above normal late this weekend and next week. Another weather system may sweep across the region during the first half of next week resulting in another period of unsettled weather. && DISCUSSION... The RAP 500mb analysis depicts a large elongated low pressure system over the Desert Southwest with a series of embedded vort max`s just to the E, NE and NW of the area. WV imagery shows very dry air pushing in with NNW flow aloft on the rear flank of the low. Mostly clear skies with an area of rear trough PVA were positioned to the west and northwest of the area with a large area of nimbus cloud decks off to the east. An H5-H3 northerly jet streak was entering the area from NNW with an area of H3 divergence over E AZ and NM. ACARS sounding showed some moisture left in the BL and lower mid levels with PW of 0.71-0.89" and skinny MUCAPE of 713 j/kg. Early afternoon radar showed some modest showers and isolated storms forming along the RIM in N-Cent AZ and additional isolated convection in SE AZ. The HREF members are in good agreement on the timing of isolated to scattered thunderstorms from mid-late afternoon into the early evening, to later evening for Phoenix and the lower deserts. Although high terrain areas northeast of the Valley floor are favored. The latest HREF also favors a 10-20% chance of 35 mph outflow/thunderstorm wind gusts in the late afternoon and early evening. Because of this a few areas of patchy blowing dust can not be ruled out either. Although there is a low chance of burn scar flash flooding in the high country, QPF with PM storms is anticipated to be mostly very light to modest. From this evening and into the weekend models agree on the low pressure system gradually ejecting as high pressure builds in over the Desert southwest. As a result a warming and drying trend will be in control through the weekend and into very early next week with highs topping out in the mid 90s by late this weekend and early next week. However, there are currently no tripple digit highs in the forecast for the coming week with temperatures much closer to normal. For Sunday to Tuesday ensembles favor a cut-off low pressure system positioned just offshore from N Baja ejecting and filling as it moves into the CWA by Tuesday. Some ensembles show light accumulated QPF over the deserts with more moderate amounts over the E AZ high terrain and E-Cent AZ. GEFS Plume QPF Show an ensemble mean of 0.15 storm total QPF for Phoenix with quite a bit of model spread and uncertainty also remaining at this time. && .AVIATION...Updated at 2310Z. South-Central Arizona including KPHX, KIWA, KSDL, and KDVT: Light west to southwest flow is present across the Phoenix TAF locations. Meanwhile, shower/thunderstorm coverage north of the terminals is increasing. Although showers will tend to weaken as the move off of the higher terrain, some of these showers will likely move into the Phoenix area. The most likely terminals to see rain or lightning would be KSDL and KDVT, with a lesser chance for KPHX and KIWA. Any remaining showers should weaken by around 4-5Z this evening. Model guidance is also showing a wind shift between 1-2Z to the northeast as these showers move in with recent radar scans confirming a developing outflow boundary. For most locations we will see gusts of 15-20 kts, but an isolated gust to 25 kts is possible. SCT coverage between 080 and 120 kft will develop as the showers and thunderstorms move through but should clear out overnight. No weather concerns are expected for Friday. Southeast California/Southwest Arizona including KIPL and KBLH: No major weather impacts will exist through Friday under clear skies. North winds will be preferred for most of the period though some backing to westerly will occur. Speeds may occasionally reach into the 10-15kt range this evening but these speeds will diminish overnight. && .FIRE WEATHER... Saturday through Wednesday: Above normal temperatures over the weekend and early next week will cool closer to the seasonal average by midweek as dry high pressure likely becomes replaced by a somewhat more unsettled pattern. Minimum afternoon humidity levels will mostly fall into the teens at lower elevations and closer to 30% over higher terrain. Slightly more moisture could return during the middle of next week. Overnight recovery will vary widely across the districts ranging from 25-50% in lower deserts and above 70% across mountains. Winds will mostly be light and follow typical diurnal tendencies, however may become locally gusty next week with the approach of a weather disturbance. && .SPOTTER INFORMATION STATEMENT... Spotters should follow standard reporting procedures. && .PSR WATCHES/WARNINGS/ADVISORIES... AZ...None. CA...None. && $$ DISCUSSION...Sawtelle AVIATION...Hodges/Percha FIRE WEATHER...18