Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 08/24/18

Area Forecast Discussion
National Weather Service Albany NY
1036 PM EDT Thu Aug 23 2018 .SYNOPSIS... High pressure will allow for dry and comfortable weather tonight through Saturday. It will start to turn a little more humid by Sunday, with a shower or thunderstorm possible for north and western areas. Hot and humid weather will return for next week, along with the chance for some scattered showers and thunderstorms. && .NEAR TERM /UNTIL 6 AM FRIDAY MORNING/... As of 945 PM EDT...skies remain mostly clear. In areas where winds have trended calm, temps have already dipped into the mid/upper 50s, while remaining in the lower/mid 60s where wind persists such as within portions of the eastern Mohawk River Valley and Capital Region near KALB. Latest Hi-Res models, such as the HRRR and RAP13, suggest some patchy clouds may develop across portions of the western Adirondacks after midnight, as the low level flow backs more into the west/northwest allowing some Lake moisture to become trapped beneath a lowering subsidence inversion. This is depicted by the RH fields around H925. Should this occur, the rate of falling temps across these areas may slow down after midnight. Otherwise, will expect most low temperatures to fall into the 50s, with some 40s still expected in portions of the southern Adirondacks and southern VT. Winds may not go completely calm everywhere tonight, but they should in some sheltered valleys. Where this occurs, some patchy fog will be possible, especially located close/near bodies of water. && .SHORT TERM /6 AM FRIDAY MORNING THROUGH SATURDAY NIGHT/... Dry weather is expected to continue through the majority of the short term period. High pressure will slowly shift eastward from the mid-Atlantic on Friday to offshore the eastern seaboard for Saturday. Plenty of sunshine is expected on Friday, but there could be some more clouds around by Saturday, as a southerly return flow sets up ahead of the next approaching shortwave over the Great Lakes. Humidity levels will continue to fairly be comfortable, with dewpoints in the 50s on Friday and upper 50s to low 60s for Sunday. Most areas should see max temps in the mid 70s to low 80s each day with lows in the 50s to low 60s. By Saturday night, there could be a few light rain showers that make it into the western Adirondacks by late in the night. Otherwise, it will continue to be dry with a partly cloudy sky. && .LONG TERM /SUNDAY THROUGH THURSDAY/... For Sunday, a weakening short-wave trough will be moving across SE Canada. The combination of forcing from the shortwave, and some low/mid level warm advection may lead to some isolated/scattered showers/thunderstorms for areas mainly north and west of Albany, with best chances across the Adirondacks. Highs will be a little above normal with 80-85F readings in the valleys, and mid 70s to around 80F over the hills and mtns. It will become more humid Sunday night, with lows will be in the lower to mid 60s. Monday into Tuesday...mid and upper level heights increase due to the ridging over the Southeast and western Atlantic. The mid and upper level flow will be rather flat over and north of the forecast area. A cold front initially north of the St Lawrence River Valley will try to move southward, but the timing is tricky and uncertain based on the medium range guidance and ensembles. This could be a scenario where multiple clusters of showers/thunderstorms move east across SE Canada and northern New England, and will have to watch trends for possible strong/severe thunderstorms in at least northern areas given the possibility of abundant instability and close proximity of strong mid level winds just to the north. It should be hot and humid with H850 temps 1 to 2 STD DEVS above normal and PWATS in the 1 to 2+ STD DEVS above normal based on the latest 12Z/23 GEFS. The combination of above normal temps, and high dewpts /60s to lower 70s/ may allow heat indices to reach the mid and upper 90s in the mid Hudson Valley MON and TUE afternoons. Heat Advisories may be needed for these days. Highs MON and TUE will be in the mid 80s to lower/mid 90s in the lower elevations, and upper 70s to mid 80s over the hills and mtns. Lows Monday night will be muggy in the mid to upper 60s, except possibly only around 70 in some valley areas. Tuesday night into Thursday...uncertainty increases whether the hot and humid stretch continues through the period, or is temporarily interrupted by a cold front settling southward from SE Canada. Latest 12Z/Thu model consensus favors a frontal boundary settling southward sometime Wednesday, with additional showers/thunderstorms possible into Wednesday evening. Cooler and slightly less humid conditions may arrive Wednesday night into Thursday. Highs Wednesday still mid 80s to lower 90s in valleys, and upper 70s to lower 80s for higher elevations. Wednesday night lows mainly in the 60s. Thursday highs ranging from the lower/mid 80s in valleys, to 75-80 across higher terrain. && .AVIATION /03Z FRIDAY THROUGH TUESDAY/... High pressure will build across the TAF sites through Friday. Clear skies and light to calm winds this evening may allow for some patchy radiational mist/fog to form at KPSF/KGFL, especially after 06Z. This could result in a brief period of IFR/LIFR, especially between 08Z-10Z/Fri. Some mist also possible at KPOU. After any patchy fog lifts between 10Z-12Z/Fri, expect VFR conditions throughout the day Friday. West/northwest winds at 5-10 kts early this evening will become light to calm shortly after 02Z/FRI. Light south to southwest winds should average 4-8 KT late Friday morning into the afternoon. Outlook... Friday Night: No Operational Impact. NO SIG WX. Saturday: No Operational Impact. NO SIG WX. Saturday Night: No Operational Impact. NO SIG WX. Sunday: Low Operational Impact. Isolated SHRA...TSRA. Sunday Night: No Operational Impact. NO SIG WX. Monday: Moderate Operational Impact. Scattered SHRA...TSRA. Monday Night: Moderate Operational Impact. Scattered SHRA...TSRA. Tuesday: Moderate Operational Impact. Scattered SHRA...TSRA. && .FIRE WEATHER... Dry weather is expected to continue over the next few days. RH values look to fall to 40 to 50 percent on both Friday and Saturday afternoons. Winds on Friday will be west to southwest around 5 MPH and southerly on Saturday at 5 to 10 mph. The next chance for precipitation may be Sunday into early next week, when scattered showers or thunderstorms are possible. && .HYDROLOGY... Dry weather is expected for tonight through early Sunday. River and stream levels will remain steady or slowly fall through this time. Some scattered showers or thunderstorms are possible for Sunday into next week, with the highest chance mainly for areas north and west of the Capital Region. Rainfall amounts will be variable due to the convective nature of the precipitation. For details on specific area rivers and lakes, including observed and forecast river stages and lake elevations, please visit the Advanced Hydrologic Prediction Service /AHPS/ graphs on our website. && .ALY WATCHES/WARNINGS/ADVISORIES... CT...None. NY...None. MA...None. VT...None. && $$ SYNOPSIS...Frugis NEAR TERM...Frugis/KL SHORT TERM...Frugis LONG TERM...KL/Wasula AVIATION...SND/KL FIRE WEATHER...Frugis HYDROLOGY...Frugis
Area Forecast Discussion
National Weather Service Cheyenne WY
925 PM MDT Thu Aug 23 2018 .UPDATE... Issued at 907 PM MDT Thu Aug 23 2018 A large amount of smoke from western wildfires continues to plague southeast WY and the western NE Panhandle this evening. Overall, a quiet night is expected across the region, but smoke may certainly present some forecast challenges. Numerous observations still show visibility restrictions as of 03z, and recent satellite data still shows significant amounts of smoke upstream. Overnight lows may be a few degrees warmer than earlier anticipated w/ likely impacts to radiational cooling. This was the main change for tonight. Looking ahead to tomorrow, the latest HRRR smoke products are suggesting a batch of thick smoke during the afternoon. In fact, incoming solar radiation products also indicate a reduction in solar energy. This suggests cooler highs than the majority of guidance suggests, with likely impacts to mixing and wind speeds as well. We will not make any changes to headlines and will leave the Fire Weather Watch as- is due to this uncertainty. At this time, we believe the smoke may impact conditions enough to keep things barely outside of critical thresholds. && .SHORT TERM...(This evening through Saturday) Issued at 232 PM MDT Thu Aug 23 2018 Upper low over the northeast Wy/southeast Montana area will progress east over the Dakotas overnight. Some showers and a few storms over mainly northern parts of the CWA late this afternoon will dissipate/move out early this evening leaving clear skies for the CWA overnight. Will still be some smoke lowering visibilities some but not dense. Friday will be warm and dry with a bit of a breeze as an upper ridge slips across the region. Some fire weather concerns will exist out west with marginal winds and humidities expected so have continued the Fire Weather Watch. May see a little less smoke so have left it out of the grids for now. Clear Friday night into Saturday with the upper flow gradually backing to wsw behind the upper ridge axis. Some late day convection expected as moisture increases some and a weak impulse moves across the area. .LONG TERM...(Saturday night through Thursday) Issued at 232 PM MDT Thu Aug 23 2018 Another cold front will pass through the region on Sunday with chances for showers and thunderstorms. Initial convection trends are focused on the higher terrain with some later on progressing into the high plains area, mainly far SE corner of WY and western NE Panhandle. Models trending still on fairly light pops but with warm temperatures into the upper 80s and low 90s in the high plains so not unexpected with forcing to have some storms linger past sundown with even a bit of instability remaining in the atmosphere. Some Monday afternoon showers and thunderstorms possible as well. Cold front will have Tuesday high temperatures take a dip into the low to mid 70s with some low pocket 80s across Morrill, Cheyenne, and Box Butte Counties. Another system will skirt northward over the CWFA Tuesday into Wednesday with some slight chance of showers though main precipitation and forcing will be better situated over the SD Black Hills and northeastern WY. Continued the drier pattern from previous forecast and ECMWF trend. && .AVIATION...(For the 06Z TAFS through 06Z Friday night) Issued at 907 PM MDT Thu Aug 23 2018 The main aviation concern over the next 24 hours continues to be a large amount of smoke across the region. This is resulting in some locally MVFR visibilities around 3 to 5 miles. Otherwise, VFR will prevail with several terminals experiencing frequent reductions in visibilities to around 6 to 8 miles. The smoke situation is likely to persist at least through Friday night, so will maintain FU with the TAFs through the period. && .FIRE WEATHER... Issued at 232 PM MDT Thu Aug 23 2018 Drier air will continue to spread over the area this evening as a low pressure system moves by to the north. Warm and breezy conditions are expected once again Friday and critical to near critical fire weather conditions still look possible mainly Friday afternoon over western districts. Somewhat higher moisture and less wind should return over the weekend which will lessen fire weather concerns. && .CYS WATCHES/WARNINGS/ADVISORIES... WY...Fire Weather Watch from Friday afternoon through Friday evening for WYZ302>304-309. NE...None. && $$ UPDATE...CLH SHORT TERM...RE LONG TERM...WM AVIATION...CLH FIRE WEATHER...RE
Area Forecast Discussion
National Weather Service Hastings NE
1002 PM CDT Thu Aug 23 2018 .UPDATE... Issued at 1002 PM CDT Thu Aug 23 2018 A quick update from earlier thinking for overnight: Most thoughts from previous discussion remain on track, but did opt to expand a slight chance of showers/storms (20 percent) to also include KS zones, as models such as the 00Z NAMNest suggest that at least very isolated activity could brush at least slightly south of the state line overnight as well. As of this writing, we are finally starting to see some spotty weak thunderstorm activity to our NW over the Sandhills region, and some of this should eventually expand east and affect parts of our CWA. Again, cannot rule out a few stronger storms with hail potential given elevated CAPE perhaps around 1000 J/kg...but with most of this instability rooted well-up around 750 millibars. UPDATE Issued at 749 PM CDT Thu Aug 23 2018 Regarding the next 12 hours only (tonight-early Friday AM): Echoing the thoughts of preceding day-shifter, certainly a tricky forecast, especially with regard to sky cover, at least limited thunderstorm potential, and also a halfway decent chance for some fog development overnight (this is a "new twist" that was not included in the original afternoon forecast package). Will touch on these 3 items: 1) Sky cover: As of this writing, much of the western half of the CWA is partly to mostly clear, while much of the east is cloudy/mostly cloudy. Current thinking is that this eastward- advancing clearing line will stall this evening, with low clouds perhaps redeveloping back to the west as low-levels cool/saturate in the presence of light southerly breezes. Will be interesting to see how this evolves, but no matter what happens tonight we are still calling for widespread sunshine during the day Friday. 2) Thunderstorm potential: As has been suspected here for a few days now, the severe storm risk that could have perhaps materialized this afternoon-evening was highly conditional/uncertain, and in fact nothing has formed within, or even all that close to our CWA so far this evening owing to various factors (including low clouds inhibiting instability, fairly warm air aloft providing a cap, and overall lack of large- scale forcing). Based on current satellite trends and the solution of very-short term models such as the RAP13/HRRR, it`s fairly likely that the majority of the CWA will continue storm-free through the night. That being said, there are hints of at least limited, elevated convection perhaps forming across mainly our Nebraska zones during mainly the 1-9 AM time frame, in response to increased forcing along the southern periphery of the main shortwave trough tracking east through the Dakotas. As a result, have kept/expanded a slight chance (20 percent) of thunderstorms across most of our Nebraska zones through the late night hours through early-mid Friday AM. Should anything materialize (not a sure thing), severe storms seem fairly unlikely (not necessarily "zero" chance), but the combo of halfway-decent elevated instability and deep-layer shear could easily promote a few strong storms with small hail potential. 3) Fog potential: While factors such as the lack of true "calm" winds overnight, along with the fact that direction should turn more southwesterly with time typically do not bode well for widespread fog formation, we have nonetheless added either "patchy fog" or "areas of fog" to most of the CWA for the late night/early Friday AM hours. For one thing, temp/dewpoint spreads will be very low overnight, with plentiful boundary layer moisture. Secondly, fog development is often enhanced near the edge of low cloud decks (such as the one currently roughly bisecting the CWA). Not surprisingly, various models (SREF/HRRR/RAP13) are all fairly insistent on at least "some" fog development overnight, and at least limited portions of the CWA could easily see visibility drop below 1 mile. Do not have much confidence in the development of widespread dense fog (visibility 1/4 mile), but this is at least a possibility, especially near the edge of the aforementioned cloud/clearing line. && .SHORT TERM...(This evening through Friday) Issued at 243 PM CDT Thu Aug 23 2018 Difficult forecast regarding sky cover, drizzle and temperatures today as stratus is more reminiscent of late autumn rather than summer. Best chance at any strong to severe storm this late afternoon and evening will be in our far southeast close to the boundary. other than that, low ceilings and drizzle abound until we can get this to clear out behind a trough to the west. We may get enough upper level support for some thunder late tonight, but does not look impressive. I used RAP wind gusts until the surface trough gets close enough to bring less of a surface pressure gradient. Although QPF from models does not look impressive, I still went with 20 POP for most of the CWA tonight and very early Friday morning in our far east/northeast, but subsidence should quickly scour us out as mid levels finally warm with a shortwave ridge moving in and will warm us to near what is normal for this time of year, pushing well into the 80s if not 90 for highs. .LONG TERM...(Friday night through Thursday) Issued at 243 PM CDT Thu Aug 23 2018 General warming continues into the weekend and beyond as a western trough develops in the west and sends us into southwest flow, with intermittent chances of precip/storms, especially late Saturday night when we may have some support for strong to severe storms. && .AVIATION...(For the 00Z KGRI/KEAR TAFS through 00Z Friday) Issued at 749 PM CDT Thu Aug 23 2018 General overview: This is a tale of two 12-hour blocks essentially, as the first half of the period will likely feature MVFR/possibly IFR conditions much of the time, while the latter 12 hours features a fairly high confidence return to VFR conditions and mostly sunny skies. Precipitation-wise, there is a slight chance of a brief passing shower/thunderstorm mainly during the 07-12Z time frame, but this chance has been deemed low enough to not even warrant a generic "vicinity" mention. Surface winds should average at-or- below 11KT through the period, but direction will shift from south-southeasterly tonight to west-northwesterly behind a passing surface trough on Friday. Read on for more details regarding ceiling/visibility... Ceiling/visibility: Honestly, confidence is a bit shaky regarding these first 12 hours, as the primary two question marks involve: 1) Does the MVFR cloud deck continue to scour out from west-to-east, or does it fill back in this evening and perhaps lower to IFR levels?...2) Does visibility drop to at least MVFR in fog, and perhaps IFR-or- worse for at least a brief time? Regarding the ceiling questions, KEAR could temporarily scatter out on the far western edge of a clearing line this evening, but overall am expecting an MVFR ceiling to hang tough before perhaps finally departing for good late in the night. At KGRI, odds of a temporary scattering this evening are lower, but like KEAR, a return to VFR is anticipated toward sunrise. That is, assuming that a very low ceiling in fog does not also develop. While wind speeds/direction are not all that favorable for dense fog, various models/guidance are fairly insistent that at least MVFR visibility will be common overnight, and perhaps IFR-or-worse. Did not go too pessimistic at this time, but did at least introduce low-end MVFR visibility to the TAFs for the 06-14Z time frame. The bottom line: expect at least a few amendments to ceiling/visibility trends during these next 12 hours. && .CLIMATE... Issued at 749 PM CDT Thu Aug 23 2018 ..Grand Island and Hastings (airports) have had their longest AUGUST stretch of 75-degrees-or-cooler in 14 years.. See our social media posts/graphic for more details, but Thursday (somewhat unexpectedly) marked the 5th-consecutive day of 75-or- cooler at Grand Island and Hastings (our primary long-term climate data sites). Although this is not unprecedented during August by any means, it is quite rare. In fact, the last time this happened during August was 14 years ago, when there was a similar 5-day stretch from Aug. 10-14, 2004. The "all-time" August record for consecutive days of 75-or-cooler at Grand Island/Hastings is 7 days. This record will not be threatened this time around, as high temperatures Friday should easily climb well into the 80s, thus ending the current cool stretch at five days. && .GID WATCHES/WARNINGS/ADVISORIES... NE...None. KS...None. && $$ UPDATE...Pfannkuch SHORT TERM...Heinlein LONG TERM...Heinlein AVIATION...Pfannkuch CLIMATE...Pfannkuch
Area Forecast Discussion
National Weather Service Goodland KS
605 PM MDT Thu Aug 23 2018 .UPDATE... Issued at 600 PM MDT Thu Aug 23 2018 The latest Rap, GFSLamp and NAM indicate fog and stratus backing into the far northeast and eastern forecast area (generally from McCook to near Oberlin and Hill City) by early to mid evening and continuing overnight before dissipating shortly after sunrise Friday morning. Have introduced some "patchy" and "areas" wording at this point with the possibility of having dense fog if visibility forecasts verify. && .SHORT TERM...(This evening through Friday) Issued at 221 PM MDT Thu Aug 23 2018 An upper-level low with ridging on either side is tracking across the northern plains and brings an associated surface trough across the area this afternoon into this evening. A well-defined dry line is centrally-located over the AOR and the source of lift will come with passage of the surface trough, possibly inducing storms along and east of the dry line boundary. The majority of available moisture and CAPE will remain confined to the eastern sector. As the low begins to track eastward and intersect with the dry line, the timing will not exactly align to produce high confidence in severe potential. As of current model runs, however, an isolated severe cell or two is possible. 40-45 mph of 0-6 km bulk shear is present over the area, a tight SBCape gradient exists over extreme NW Kansas ranging from 900 j/kg to 3100 j/kg at 18Z and tracking eastward as to be expected from the diurnal cycle and its effects on the dry line. Downdraft CAPE values range significantly between the GFS, NAM, and the RAP, with the RAP showing much lower confidence than the GFS and NAM which both indicate values up to 1750 j/kg over the KS/CO border as of 00Z. For these reasons, severe potential cannot be ruled out, however, the likelihood of any development will largely depend on what time the trough passes and the degree to which the atmosphere has become unstable due to surface convergence and afternoon heating. If convection does occur on or east of the dry line, storms are expected to be spotty and not survive very long the farther they track away from the dry line boundary. This event will largely be diurnally-driven and as to be expected, PoPs do not extend beyond 04Z before fading out. The main threats would be hail of up to 1" and T-Storm wind gusts of up to 60 mph. Once thunderstorm potential subsides, skies will gradually begin to clear out and the upper-level pattern will begin to shift toward ridging as the predominate pattern for the remainder of the forecast period. No precipitation or thunderstorm potential is in the forecast for Friday. .LONG TERM...(Friday night through Thursday) Issued at 140 PM MDT Thu Aug 23 2018 Friday night through the weekend: An upper trough enters the Upper Midwest from the northern Plains, with ridging building in behind over the tri-state region. Southwesterly flow develops aloft as a result. A wave moves through the flow Saturday, generating shower and thunderstorm chances during the afternoon and evening hours. The potential for severe weather remains uncertain due to the dry air that will be in place, but a storm or two capable of marginally severe hail and wind cannot be ruled out at this time. Another opportunity for precipitation comes for the eastern portion of the forecast area on Sunday night when a disturbances crosses the region. Southwest flow sharpens early next week as an upper trough travels east from the Pacific Northwest to the northern Rockies. This system is anticipated to push ridging to the east with a cold front passing through the High Plains by late Tuesday. A generally dry frontal passage is expected, with the main effect being cooler temperatures. Beyond Tuesday, high pressure reorganizes over the southern CONUS leading to broad ridging across the country, with quasi-zonal flow for the area. Mainly dry weather is anticipated; however, shortwaves in the pattern produce spotty shower and thunderstorm chances Wednesday and Thursday east of Highway 25. High temperatures gradually fall from the 90s on Saturday to the 80s by Wednesday as cooler air filters into the region, followed by a slight rebound to the mid/upper 80s region-wide on Thursday. Low temperatures range from the mid 50s to low 70s throughout the period. && .AVIATION...(For the 00Z TAFS through 00Z Friday evening) Issued at 440 PM MDT Thu Aug 23 2018 For KGLD and KMCK, vfr conditions through the period. Light and variable winds at taf issuance will become southwesterly by 05z at speeds under 7kts and continue through sunrise before slowly veering to the west at similar speeds. Northwest winds around 11kts with some gusts near 17kts or so expected in the late morning and early afternoon hours before falling below 10kts toward the end of the period. && .GLD WATCHES/WARNINGS/ADVISORIES... KS...NONE. CO...NONE. NE...NONE. && $$ UPDATE...99 SHORT TERM...SANDERSON LONG TERM...JBH AVIATION...99
Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
1059 PM CDT Thu Aug 23 2018 .SHORT TERM... (Through Late Friday Afternoon) Issued at 426 PM CDT Thu Aug 23 2018 High pressure over the Ohio valley will continue sliding to the east-northeast this evening toward the northeast US. A complex of showers with embedded thunderstorms will move into central Missouri this afternoon and then track southeast through Missouri this evening. This complex is associated with a weakening short wave ahead of a mid level trough over the northern Plains. There will likely be a lull of precipitation this evening into the late night. A short wave will approach the area from the west riding around the periphery of a mid level trough as it moves east across the northern Plains late tonight into Friday morning. Additionally, a southwesterly low level jet of 30 to 40 knots will ramp up late tonight into early Friday morning across the area. Chances for showers and thunderstorms will increase ahead of the feature and become likely over central Missouri around midnight in response to the shortwave and strengthening low level jet, then move across the morning through Friday morning. There will another lull in showers and thunderstorms from late Friday morning through the afternoon hours over the forecast area. Convection will develop again over portions of northeast Missouri and western Illinois in response to the upper trough moving east toward the Great Lakes region on Friday afternoon and evening. The environment ahead of the trough will feature CAPE values in 1500 J/kg to 2000 J/kg range with 30 to 40 knots of bulk shear leading to a mix of convective modes with most likely multicell thunderstorms and perhaps a few supercells. The primary hazards on Friday afternoon and evening will be damaging winds and large hail. Temperatures on Friday morning will be in the lower to mid 60s across the forecast area, highs on Friday will range from the lower to mid 80s in central Missouri to the lower 70s over western and southwestern Illinois on Friday. Kelly .LONG TERM... (Friday Night through Next Thursday) Issued at 426 PM CDT Thu Aug 23 2018 Scattered showers and thunderstorms will continue across the area on Friday night into Saturday morning as the upper trough over the mid Mississippi valley moves toward the Great Lakes. Hot and humid conditions will return to the region on Saturday and persist through early next week with mid level ridging from southeast builds into the area. Parts of the St Louis Metro Area could see heat index values near 105 from Sunday through Monday. The ridge will allow for persistent south-southwest flow over the area through early next week. The ridge will begin to shift to the east on Monday night allowing a cold front to sweep into the mid Mississippi Valley from the Plains late Tuesday. The front should be into northwest Missouri by late Tuesday afternoon/early evening. Guidance is developing precip ahead of the front Tuesday night with a broad area of QPF out ahead of it through Wednesday morning. Current indications are that the front may get hung up over the Ozarks Wednesday and remain nearly stationary through Thursday. This will keep precip chances going for Wednesday and Thursday as well. Temperatures will remain above climatological values for morning lows and afternoon highs through the middle of next week. Kelly && .AVIATION... (For the 06z TAFs through 06z Friday Night) Issued at 1042 PM CDT Thu Aug 23 2018 Latest HRRR and Exp HRRR have slowed down precipitation development just a bit, but not enough to make major changes to the taf timing. Feel that thunderstorms to be scattered as complex moves through region, so have predominent showers with vicinity thunderstorms for all tafs. VFR conditions to lower to MVFR cigs and vsbys with onset of showers and storms. Activity to diminish by 16z-20z timeframe with cigs/vsbys improving to VFR once again. Will see another round of activity after 00z Saturday for KUIN and metro area tafs, so have added vicinity TS mention during this period. As for winds through the forecast period, they will remain southerly. Do expect some gustiness at KCOU and KUIN during the afternoon hours. SPECIFICS FOR KSTL: Latest HRRR and Exp HRRR have slowed down precipitation development just a bit, but not enough to make major changes to the taf timing. Feel that thunderstorms to be scattered as complex moves through region, so have predominent showers with vicinity thunderstorms for STL taf. VFR conditions to lower to MVFR cigs and vsbys with onset of showers and storms. Activity to diminish by 19z timeframe with cigs/vsbys improving to VFR once again. Will see another round of activity after 03z Saturday, so have added vicinity TS mention during this period. As for winds through the forecast period, they will remain southerly. Byrd && .LSX WATCHES/WARNINGS/ADVISORIES... MO...None. IL...None. && $$ WFO LSX
Area Forecast Discussion
National Weather Service Medford OR
238 PM PDT Thu Aug 23 2018 .DISCUSSION...Current satellite observations are showing that the overall marine stratus push is dissipating slowly across the Umpqua Basin while remaining quite strong over the coast. This is likely due to elevated wildfire smoke above the stratus deck keeping it from burning off. Elsewhere, the satellite is showing smoke across all of southern Oregon and northern California-- including the plumes from the Stone, Watson Creek, Natchez, Ramsey Canyon, and Klondike fires. Above the smoke, a few cumulus are occurring in a couple of bands. The main band stretches from Portland south and west over the ocean, and this is likely the demarcation for the dry cold front poised to arrive this evening and tonight. This dry cold front will create breezy conditions this afternoon, which could be problematic for firefighting purposes, but the fire weather discussion will have more information on that. This dry cold front will overall help lower temperatures and blow some of the smoke out, and we should see some temporary improvement west of the Cascades with the improvement being slower to occur east of the Cascades. The 12Z HRRR smoke model is showing that significant improvement occurring tomorrow morning. For the Rogue Valley, however, the Ramsey Canyon fire could create an issue with the improving conditions since the smoke could easily drain into the Rogue Valley--especially if the atmosphere decouples overnight. The aforementioned trough will be a dry one, as is typical for late summer or (very) early fall, but the overall troughy pattern will continue through the weekend. This will help break down the persistent summer ridge in the area and allow subsequent troughs to bring in more precipitation. Unfortunately, the troughy pattern has continued to trend drier, and have continued with the silent 10 percent chances where necessary. Models are signifying an increase in temperatures in the extended forecast before the next trough comes in to cool things down and bring more rain. Went with a blend of the ECMWF and GFS as they both are showing a similar pattern out to day 7. That being said, have very little confidence in any precipitation in the extended forecast or even the far extended forecast (out to 240 hours). Despite the models showing precipitation at some point in the far extended forecast, the models degrade quickly and come in general disagreement. It will need to be monitored, but at this point, do not see any reason why we should see rain with what the models have indicated at this time. -Schaaf && .AVIATION...For the 23/18Z TAFs...Over the coastal waters and along the coast...Widespread MVFR/IFR cigs with areas of MVFR vsbys in stratus and fog will persist through Friday morning, but some portions of the coast may briefly clear to VFR Thursday afternoon. Over the Umpqua Basin...Areas of MVFR cigs will clear to VFR by Thursday afternoon. More widespread MVFR cigs will return tonight and persist into Friday morning before clearing to VFR again. Over the rest of the area...Areas of MVFR vsbys and local IFR vsbys due to wildfire smoke will persist through Friday. && .MARINE...Updated 200 PM PDT Thursday 23 August 2018...A thermal trough will develop this afternoon, strengthen on Friday, then persist into Saturday. This will bring gusty north winds and steep, choppy wind-driven seas, especially south of Cape Blanco. Gale force gusts are possible south of Cape Sebastian Friday afternoon into Friday evening. Gusty winds and steep seas will persist south of Cape Blanco on Saturday. The thermal trough will weaken on Sunday, but small craft advisory level winds and seas may linger south of Gold Beach into Wednesday due to a combination of wind-driven seas and building fresh northwest swell. && .FIRE WEATHER...Updated 100 PM PDT Thursday 23 August 2018...A dry cold front will push through the forecast area this evening and overnight. Winds will increase ahead of this front and humidity will still remain low as the region hangs on to a dry air mass. This will create near critical fire weather conditions for much of the forecast area this afternoon. One area that we have high confidence in meeting critical fire weather criteria is Modoc County. A Red Flag Warning is in effect due to gusty winds and low humidities today across much of Fire Weather Zone 285. Tonight, humidity recoveries will trend significantly higher than last night (by 10% or more) along and west of the Cascades. After the cold front moves through, general winds will turn more northerly on Friday and Saturday west of the Cascades (and northeasterly towards the coast as a thermal trough develops), and breezy afternoon winds are expected. Humidity will trend higher though compared to today. From the Cascades east, expect breezy west to northwest winds each afternoon and evening on Friday and Saturday. A cooler trend is expected for later this week into early next week as an upper trough deepens over the region. There is also some possibility of light rainfall over far northwest portions of the area Sunday night and Monday morning, mainly for Coos and northwest Douglas county. Confidence is low in the details of this portion of the forecast due to variability on the strength and track of the upper trough over the region. However, the consensus of data suggests that wetting rains are unlikely for the next 7 days over the forecast area. SK/CC && .MFR WATCHES/WARNINGS/ADVISORIES... OR...None. CA...Red Flag Warning until 8 PM PDT this evening for CAZ285. Pacific Coastal Waters...Small Craft Advisory from 5 PM this afternoon to 11 PM PDT Saturday for PZZ356-376. $$
Area Forecast Discussion
National Weather Service Melbourne FL
937 PM EDT Thu Aug 23 2018 .UPDATE... Current-Tonight...Daytime heating generated convection ended around sunset and considerable debris clouds will gradually diminish with skies becoming partly cloudy after midnight. The GFS shows a fair amount of precip overnight. The HRRR model has been showing some convection sticking around past 06z but is too aggressive right out of the box. A weak upper level shortwave trough is shown dropping into northern sections and precipitable water is forecast 1.8 to 2.0 inches. There is also a weak low level trough just to our north. However, the ECMWF and local WRF don`t generate much precip overnight. It`s possible that there are a few weak outflow boundaries lingering, but as night stability sets in, won`t forecast a regeneration of convection. && .AVIATION... Conditions look VFR overnight. Above normal moisture with daytime heating and boundary interactions will lead to scattered-numerous storms again in the afternoon/evening. Slow south to north storm motion will allow for some local heavy rain amounts. && .MARINE... Tonight-Friday...A south gradient wind around 10 knots tonight will become southeast Fri afternoon as a low level trough to our north slowly lifts northward. Seas will continue benign at 1-2 feet. There should be isolated to scattered marine showers/storms overnight and on Fri. The strong afternoon storms that form inland will move slowly but gusty outflow winds could push back to the intracoastal waters. && .MLB WATCHES/WARNINGS/ADVISORIES... FL...None. AM...None. && $$ FORECASTS...Lascody IMPACT WX...Weitlich
Area Forecast Discussion
National Weather Service San Francisco Bay Area
854 PM PDT Thu Aug 23 2018 .SYNOPSIS...Temperatures will remain near to below seasonal averages through the forecast period as a broad upper level trough remains over the West Coast. Widespread night and morning low clouds will continue with clearing conditions each afternoon over inland areas while partial clearing is possible near the coast. && .DISCUSSION...As of 8:50 PM PDT Thursday...Smoke from wildfires to our north, primarily the Mendocino Complex Fire, had drifted offshore over the past few days. Today that smoke moved inland across most of our forecast area and also managed to mix to near the surface, resulting in poor air quality, especially across the SF Bay Area. The HRRR Smoke model indicates near-surface smoke concentrations will peak this evening, remain relatively high overnight into Friday morning, and then gradually decrease Friday afternoon and evening. Thus, expect better air quality by late Friday evening. Smoke acted to deflect incoming sunlight today, resulting in slightly cooler temperatures across most of our area. Afternoon highs were anywhere from 3 to 10 degrees cooler than seasonal averages. A large eddy circulation formed in the status cloud field offshore west of San Francisco today between light southerly flow near the Central California Coast and northerly flow in the northern California offshore waters. This circulation helped draw low clouds away from coastal areas from Santa Cruz County southward this afternoon. However, satellite imagery this evening shows low clouds are rapidly filling in along the coast and already developing inland. Expect widespread low clouds to develop once again by Friday morning. The models agree that the longwave upper trough position will remain near the West Coast through the weekend and well into next week. Thus, we can expect inland temperatures to remain slightly cooler than average through the forecast period. Coastal temperatures are a more difficult call. On the one hand, a deep marine layer should help maintain widespread low cloud cover in coastal areas, even into the afternoon hours. However, the marine layer may mix out from time to time, resulting in afternoon clearing. Also, sea surface temperatures have warmed into the lower 60s along much of our coast which will help to boost coastal temperatures, especially during the overnight hours. A forecast update earlier this evening included increasing coastal overnight lows by 3 to 5 degrees over the next three nights. && of 4:30 PM PDT Thursday...Main concern today is the smoke which is reducing visibilities to 3-5 miles. Latest HRRR model indicates smoke continuing to blow over the area through Friday. There may be some improvement tonight then worsening again on Friday. As for stratus...the clouds have pulled further back from the coast compared to yesterday. Latest taf forecasts a return of MVFR cigs at 04Z for SFO but it could be later than that. Vicinity of KSFO...Vsbys 3-5 miles in haze improving slightly tonight. MVFR cigs after 04Z but confidence is low as it may come in later. West winds to 15 kt through 03Z. SFO Bridge Approach...Same as KSFO. Monterey Bay Terminals...Stratus has pulled further back from the bay today so MVFR cigs for MRY delayed until 05Z and SNS until 06Z. Hazy conditions with vsbys 3-5 miles improving slightly tonight. && of 04:36 PM PDT Thursday...Light to moderate winds will prevail over the coastal waters through this evening and through Friday. Northwesterly winds are forecast to increase over the outer waters overnight tonight and will continue through the day on Friday. Winds will also be breezy through the Golden Gate Gap and along the Big Sur coast tomorrow afternoon and evening. Light northwest swell around 3 to 6 feet anticipated through the forecast period. && .MTR WATCHES/WARNINGS/ADVISORIES... .Tngt...SCA...Pt Arena to Pigeon Pt 10-60 nm from 3 AM && $$ PUBLIC FORECAST: Dykema AVIATION: W Pi MARINE: BAM/Rowe Visit us at Follow us on Facebook, Twitter, and YouTube at:
Area Forecast Discussion
National Weather Service Tucson AZ
313 PM MST Thu Aug 23 2018 .SYNOPSIS...Abundant moisture will remain over much of the area through Saturday resulting in scattered thunderstorms, some producing heavy rains and local gusty winds. Afternoon temperatures will remain on the cool side through Saturday. Then a gradual drying and warming trend will begin to develop Sunday well into next week. && .DISCUSSION...Wow, impressive morning and early afternoon as the atmosphere did a great job utilizing the available energy. Plenty of water hit the ground with Nogales taking the brunt of it thus far. We still have several flood products out and will leave the Flash Flood Watch as is for now even though we are fairly well worked over as we still have a large area of upper level divergence over the area and new development popping up here and there. The overnight period again has a threat of being somewhat active (for nighttime hours) as we remain wet and unstable and the HRRR and UA WRFNAM, which did reasonably well with today`s convection, highlight more activity approaching from the north late tonight. Tweaked pops up for the overnight period. Friday has the potential to be another active day if we can manage enough sunshine early on. We will remain in a very moist regime with PWs similar to what we have today from eastern Pima county eastward and plenty of instability. A lot will depend on leftover clouds and vortices from current and overnight convection. It won`t take much to get storms and with them significant rains. Basically, anytime through early Friday night we are under an enhanced threat of localized heavy rainfall and flooding. Temperatures will remain on the cool side. There is a bit of question by the time we get to Saturday as we are gradually transitioning to a SW flow in response to a deep trough in the Pacific NW. The question is how quickly do we begin to erode the moisture over the region. At the moment the GFS is quicker to lower PW values, ~1.50" Saturday evening, while the NAM hangs in there with 1.80" at the same time in the Tucson area. Considering the trend over the last few days I am leaning toward the slower scouring and have trended wetter in the afternoon forecast package. Therefore I increased pops and cloud cover and lowered max temps a bit. I didn`t get to spend much time on the longer range however we do look to reduce PW values closer to late August averages with plenty of instability on Sunday so thunderstorms will still develop, just with more typical amounts of rainfall. Then westerly flow will continue to exert it influence next week with continued drying and warming afternoon temperatures. && .AVIATION...Valid through 25/00Z. Scattered SHRA/TSRA with mostly BKN-OVC clouds with bases around 5k- 10k ft AGL from KTUS toward the east through the evening. Conditions then improve overnight before another round of SHRA/TSRA develops again Friday afternoon. Surface winds remain less than 12 kts through the period with the exception of stronger gusts near TSRA. Aviation discussion not updated for TAF amendments. && .FIRE WEATHER...Deep moisture continues to provide favorable conditions for thunderstorm development into the weekend. Some storms will be capable of producing very heavy rainfall in a short period of time. The pattern then shifts next week allowing for drier conditions with warmer temperatures. Terrain driven 20-ft winds persist at less than 15 mph, except in and around thunderstorms where strong outflows may occur. && .TWC WATCHES/WARNINGS/ADVISORIES... Flash Flood Watch until 8 PM MST this evening for AZZ502>515. && $$ PUBLIC...Cerniglia AVIATION....Howlett FIRE WEATHER...Howlett Visit us on Facebook...Twitter...YouTube...and at