Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 09/02/17

Area Forecast Discussion
National Weather Service State College PA
1159 PM EDT Fri Sep 1 2017 .SYNOPSIS... The remnants of what was once Hurricane Harvey will track slowly across the Ohio Valley and cross the region bringing showers this weekend. High pressure will return for early next week. && .NEAR TERM /UNTIL 6 AM SATURDAY MORNING/... High pressure continuing to keep most of the region dry even though dewpoints have crept up a couple of degrees, while clouds from what was once Harvey continue to stream into and thicken over the region. Best chance for light rain, or more likely just sprinkles into the early morning hours will continue to be the far SWRN zones. Radar showing precip splitting over the Appalachians with some drifting off to the north and the rest tracking nearly eastward, both avoiding my southern boundary. This is supported by near term HRRR and NBM forecasts. Later tonight this begins to change and light precip should fill in a bit, but PoPs through 12z may still be too high over SW third of CWA as much of this may fall as drizzle (with scattered light rain). && .SHORT TERM /6 AM SATURDAY MORNING THROUGH 6 PM SATURDAY/... Saturday looking cloudy, downright chilly and damp. Still a big question of how much it will rain with an initially very dry airmass in place. Thinking that much of the day will favor cloudy and cool conditions with perhaps some periods of light rain or a misty drizzle. The deeper we get into the day the better will be the chances for rain. I did undercut model blended high temps by several degrees. This looks like a classic warm season cold air damming scenario. With a strong high off to our north and east and an approaching low from the SW, the guidance shows a strong low level northerly component to the ageostrophic flow which will help keep us anomalously cool for the early days of September. With highs only in the mid 50s to lower 60s, these temps are 15-20F below normal. && .LONG TERM /SATURDAY NIGHT THROUGH FRIDAY/... *Wet start to holiday weekend followed by improving/rain-free conditions Sunday into Monday (Labor Day) *No significant flooding impacts expected from the remnants of Harvey *Moderating/seasonably warmer temperatures Monday-Tuesday will trend below normal Wednesday-Friday *Precipitation potential likely maximized between Tuesday- Thursday A northern stream shortwave trough over the western Great Lakes will merge with the remnants of Harvey and lift northeast through the Mid Atlantic and New England states on Sunday. Ahead of the surface system and mid level trough, models still indicate max PoPs/QPF Saturday night into early Sunday morning as a strong low level jet transports 1.50 inch PW air into central PA. Rainfall amounts on the order of 0.25 to 0.75 inches are expected with hires ARW/NMM/NamNest signaling potential for north-south training resulting in locally higher amounts up to 1.5 inches. Even the higher amounts should be offset to a degree by the recent short-term dryness, with 3hr RFC FFG values well over 2 inches. Therefore, no significant heavy rain/flooding impacts are expected. Sunday will be a transition day toward improving weather conditions, followed by a mostly sunny and pleasant Labor Day. Models/ensembles continue to agree upon a significant long wave flow pattern amplification during the second half of the period, with an anomalous full-latitude trough over the Eastern U.S. reaching maximum amplitude around the middle of next week. A well- defined cold front is fcst to sweep eastward from the Midwest and slow down as it eventually moves off the eastern Seaboard by Thursday-Friday. The front will be accompanied by precipitation but the timing/coverage/intensity will be sensitive to uncertain details aloft impacting the speed/movement of the boundary. The most likely period for rain/max PoPs is Tuesday-Wednesday with opportunity for some enhanced rain associated with one or two frontal waves. For now, next week should end on a dry note with all eyes likely turning to Hurricane Irma, forecast by GFS/ECMWF to reach a position between the northern Bahamas and Bermuda by next Sunday 9/10. && .AVIATION /04Z SATURDAY THROUGH WEDNESDAY/... VFR will continue into much of the night ahead of the remnants of Harvey. Cigs will reduce overnight and have included rain in the TAF for the southern TAF sites, though not expecting reduced conditions until late tonight or after sunrise Saturday. IFR is possible for JST after 12Z. .OUTLOOK... Sat...Lowering conditions spreading slowly northeastward with occasional light rain/drizzle. Mainly over southern areas. Sun...MVFR/IFR improving for the afternoon Mon...Mainly VFR. Tue...An approaching cold front will bring scattered showers and locally reduced conditions, especially at western terminals by afternoon. Wed...Reduced conditions as the cold front pushes through the region. && .CLIMATE... August 2017 was marginally cooler than average at Harrisburg (-1.0F) and Williamsport (-0.1F). Precipitation for the month was above average with totals of 4.67" (+1.47") at MDT and 5.76" (+1.90") at IPT. For the meteorological summer season (June-July-August), temperatures were slightly above average (around +1.0F) at both sites. More noteworthy were the 3-month precipitation totals which ranked in the top-10 wettest summers on record. Harrisburg recorded 17.76" of precipitation which was +6.35" above normal and ranked as the 8th wettest summer. Williamsport recorded 16.91" of precipitation which was +4.79" above normal and ranked as the 3rd wettest summer season. The top-10 wettest seasonal rankings are impressive in that there were no tropical systems that contributed to the precipitation totals. That said, the wettest summer at both locations was 1972, helped of course by Hurricane Agnes. && .CTP WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...La Corte/RXR NEAR TERM...La Corte/RXR SHORT TERM...La Corte/RXR LONG TERM...Steinbugl AVIATION...La Corte/Gartner CLIMATE...
Area Forecast Discussion
National Weather Service Des Moines IA
642 PM CDT Fri Sep 1 2017 .SHORT TERM.../Tonight through Saturday/ Issued at 147 PM CDT Fri Sep 1 2017 Main forecast challenge through the short term period is the chance for light showers this evening through Saturday morning. Satellite and radar imagery through the day has shown a widespread area of cloud cover and showers over the Dakotas and Nebraska. This activity will slowly into western Iowa this evening and overnight. Hi- res models have trended toward the light showers holding together to about the I-35 corridor early Saturday morning before dissipating. A shortwave passing near the Canadian border will send a weak front southward during the morning and afternoon hours, however models remain dry along the front through 00z Sunday upper level support passes north of the state. Also of note, the HRRR vertically integrated smoke product suggests the potential for more haze and air quality degradation tomorrow morning as result of significant wildfire activity out west. Previous HRRR runs did not have a good handle on the degree of smoke/haze that was observed earlier today. Cloud cover makes it difficult to discern on satellite the amount of smoke currently upstream, although the upper level pattern remains in a favorable orientation to push more Canadian/Montana wildfire smoke into our area. Confidence is too low at this time to include any mention in the forecast at this point. .LONG TERM.../Saturday night through Friday/ Issued at 147 PM CDT Fri Sep 1 2017 No significant weather of note through the long term period. Isolated storms will be possible Saturday evening along the aforementioned surface front, but minimal upper level support should keep the activity isolated and limited to areas near the MO border. A strong PV anomaly will round the Hudson Bay low and dig southeast in the eastern conus early next week. Low level response in advance of this system will advect a much warmer air mass into the CWA and put highs in the 80s to near 90 for Sunday. A strong cold front will push through the CWA Monday afternoon and evening. The timing of the front will have a significant impact on temperatures Monday. Models have come into fairly good agreement with respect to the fropa timing, so the blended forecast looks reasonable which paints highs in the 70s in our north and near 90s in the south. Despite strong baroclinicity and increasing fgen in low levels, a relative lack of moisture and mid-level cap may limit precip potential as the front slides through. Slight to low end chance pops will suffice for now. Below normal temperatures are likely through the middle and latter half of the week as a cool air mass settles into the region behind the front. Not expecting any precip during this time period as the quasi meridional flow scours out most of our available moisture. && .AVIATION.../For the 00Z TAFS through 00Z Saturday evening/ Issued at 642 PM CDT Fri Sep 1 2017 Few real concerns through period...though VFR cigs and few showers may impact KFOD/KMCW before weakening further aft 08z. Band of -shra moving into western Iowa encountering drier air. Cigs should lower to bkn035-bkn080 by 12z then thinning thereafter through 20z. Small risk that MVFR cigs may eclipse KMCW between 12 and 15z Saturday and will evaluate for 06z. Winds also mix out aft 15z Saturday with higher sw gusts at KMCW/KALO/KDSM through 21z then increasing NW winds aft 21z. /rev && .DMX WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SHORT TERM...Martin LONG TERM...Martin AVIATION...REV
Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
837 PM EDT Fri Sep 1 2017 .AVIATION... Reasonably high amplitude midlevel ridge and associated high geopotential heights is currently leading to surface high pressure and quiet weather over southeastern Michigan. Cool, dry Canadian airmass will again yield nil potential for boundary layer fog overnight. The forecast item that requires watching is the remnants of Harvey as it lifts into the Ohio River Valley on Saturday. Some fairly high model spread exists with overall likelihood to witness low-midlevel rich theta e/saturation over the Detroit TAF sites. NAM completely resides on the wet side while the RAP is significantly lacking in the amount of column moisture. Given ceiling and rainfall observation trends down south, will continue to side with the NAM in aggressive moisture advection, but remain relatively conservative with MVFR cig heights. Latest time lagged probability metrics suggest a 30-40 percent 3 hour rainfall probability for DTW after 2 PM Saturday. Given lack of steep lapse rates, activity will likely be limited to sprinkles. For DTW...The easterly flow picks up again after 12z on Saturday as ceilings develop below 5000 feet. //DTW THRESHOLD PROBABILITIES... * None && .PREV DISCUSSION... Issued at 358 PM EDT Fri Sep 1 2017 DISCUSSION... Another cool night is in store for SE Michigan, especially along and north of the I-69 corridor. This is where high clouds and surface wind will be minimal which will allow radiational cooling to send overnight temperatures well down into the 40s once again. A repeat of this morning seems reasonable where the usual sheltered locations made it down to around 40. FNT actually radiated down to 39 which broke the record of 40 for September 1 set in 1967. Records for tonight, Sept 2: MBS 38/1946, FNT 39/1994, DTW 44/1885. The track of Harvey remnants will be the primary concern for Saturday as it interacts with the northern stream upper level trough digging from central Canada into the Great Lakes. Rain potential associated with both of these features will be inhibited initially by mid level dry air between them associated with resident high pressure before it is squeezed into eastern Canada during the afternoon. There should also still be a western edge in the area where light rain is able to reach the ground with the highest chance POPs closer to the Canadian border up to near Port Huron. There may also be a larger chance POP footprint Saturday night with the upper trough axis before it moves eastward overnight. The process of squeezing high pressure eastward during Saturday will also scour out the low level thermal trough tied to our recent cooler temperatures. Also, the surface pressure trough associated with the upper wave Saturday night will act more like a warm front heading into Sunday. Model projections do not show much change in 850 mb temps but there is considerable 1000-850 mb thickness warming that reflects continued displacement of the cool boundary layer conditions. The result will be a notable warming trend through the weekend as high temperatures return to the lower and mid 70s Saturday and then mid to upper 70s Sunday. The progression of shortwaves in the northern stream upper level flow will continue into early next week. The warming trend will continue Monday as strong southwest flow develops ahead of the next frontal system. Southwest wind gusting into the 30 mph range will help boost high temps back into the 80s Monday afternoon ahead of the associated cold front which remains the subject of shower and thunderstorm potential into Monday night. The 12Z NWP is considerably less aggressive on QPF with the passage of the front which is likely due to the thermal ridge building into the area. NAM and GFS temperatures are borderline capped in the 850-700 mb layer which produces a more dramatic negative response compared to the ECMWF and GEM. Otherwise, global model solutions are in good agreement on another strong cooling trend post front into the middle of next week. MARINE... A tight pressure gradient will be maintained over the waters of Lake Erie through much of the night. This onshore flow will build significant wave heights to 3 to 5 feet with maximum wave heights up to 7 feet in the Michigan waters. Moderate wind will persist through the weekend as two systems move through and affect the Great Lakes region. Easterly winds will become southeast by late Saturday and then veer to westerly by Sunday. Stronger southwest flow will develop in advance of a strong cold front on Monday. Very warm air on Monday will keep winds in the 20 to 30 knot range for Lake Huron, but expect small craft advisory winds for all of the nearshore areas. Thunderstorms will be possible Monday and Monday night followed by developing gusty northwest flow behind the front as cooler air infiltrates the region. && .DTX WATCHES/WARNINGS/ADVISORIES... MI...Lakeshore Flood Advisory until midnight EDT tonight for MIZ076-083. Beach Hazards Statement until midnight EDT tonight for MIZ083. Lake Huron...NONE. Lake St Clair...NONE. Michigan waters of Lake Erie...Small Craft Advisory until 10 AM EDT Saturday for LEZ444. && $$ AVIATION.....CB DISCUSSION...BT MARINE.......RBP You can obtain your latest National Weather Service forecasts online at
Area Forecast Discussion
National Weather Service Wilmington NC
1006 PM EDT Fri Sep 1 2017 .SYNOPSIS... A stalled front to our north will shift northward overnight and Saturday as another cold front approaches from the west and moves offshore Saturday night. Showers and thunderstorms are expected along and ahead of the front as it shifts to the coast and offshore through Saturday night. High pressure will bring dry weather to the area Sunday through Tuesday. Another cold front may bring more thunderstorms Wednesday and Thursday. Swell from Hurricane Irma will be increasing next week. && .NEAR TERM /THROUGH SATURDAY/... As of 1000 PM Friday...Tornado Watch has been cancelled and the risk for severe weather has ended. There have so far been no reports of severe weather today/this eve. All of the severe reports today have been further to the north, along a stalled front. This front is expected to retreat north through Sat. The last of the showers and a rumble of thunder was moving north across northern Bladen County and this activity should move north of Bladen County through midnight. The HRRR model is showing showers may develop offshore and skirt portions of the coast overnight and so have trended POPs accordingly. Will continue to show POPs trending below threshold for areas well inland. Low level jetting is expected to mitigate the fog potential, but low stratus may fill in, especially inland. Deep moisture will still be in place Sat ahead of a cold front. Good heating ahead of the front should allow showers and thunderstorms to develop. The highest risk for thunderstorms will be shifting to the coast with the front on Sat. Lows tonight will be in the lower to mid 70s. Highs will be in the mid 80s. && .SHORT TERM /SATURDAY NIGHT THROUGH SUNDAY NIGHT/... As of 230 PM Friday...Plume of Gulf moisture will be shifting off the coast Saturday evening ahead of fropa. A dry slot will wrap into the forecast area around the mid-level circulation associated the remnants of Harvey, which by this time will be opening up ahead of a trough swinging across the Great Lakes. Shower and thunderstorm activity will taper off from west to east Saturday evening, trailing off to nil after midnight. Clouds will scatter out late Saturday night, and should see a fair amount of sun on Sunday as dry air is ushered in with deep westerly flow. Weak surface high pressure will build across the Carolinas Sunday night and push a frontal boundary into the area. Moisture will be lacking so no PoPs will be introduced with this feature, but will trend them up towards (but still below) slight chance across the far southern zones Monday night to account for some moisture return ahead of the boundary. && .LONG TERM /MONDAY THROUGH FRIDAY/... As of 230 PM Friday...Beautiful start to the week, with high pressure overhead leading to a dry Labor Day and only a few stray showers on Tuesday, both days with seasonal temperatures. Clouds and rain chances increase Tuesday into Wednesday as a relatively strong cold front descends upon the eastern Carolinas. The front will be offshore Thursday morning, followed by cooler and dryer high pressure. The end of the week will feature dry weather with below normal temperatures. && .AVIATION /00Z SATURDAY THROUGH WEDNESDAY/... As of 00Z Saturday...KLBT will experience the brunt of thunderstorm activity through 01z. Otherwise some light showers will advect northward across the terminals. The HRRR model is showing some convective redevelopment along the coast overnight, but this remains a low confidence forecast. Showers and thunderstorms should redevelop with heating on Sat. Thunderstorms will continue to have the potential for flight restrictions to MVFR or lower. Extended Outlook...VFR conditions are expected Sun into Tue. Thunderstorms may result in flight restrictions on Wed. && .MARINE... NEAR TERM /THROUGH SATURDAY/... As of 1000 PM Friday...S to SW winds around 15 kt through Sat. Seas will be mainly 2 to 3 ft with up to 4 ft across portions of the outer waters. Showers and thunderstorms are expected to develop across the waters overnight and will become scattered to numerous through Sat night with the approach of a cold front from the W. SHORT TERM /SATURDAY NIGHT THROUGH SUNDAY NIGHT/... As of 230 PM Friday...Southwest flow and shower/thunderstorm activity will be ongoing Saturday evening ahead of a frontal boundary, which will push off the coast after midnight. The surface pressure gradient will wash out quickly behind the front, so after a period of westerly flow late Saturday night and Sunday morning, expect some degree of variability as winds lighten Sunday afternoon. A weak frontal boundary will approach from the north Sunday night, as high pressure builds across the Carolinas, and the front may reach the southern waters by sunrise Monday. Moisture will be limited, so expect no significant chance of precip with this front, expect perhaps the waters south of Murrells Inlet Sunday night. LONG TERM /MONDAY THROUGH WEDNESDAY/... As of 230 PM Friday...High pressure over the western Atlantic will keep winds from the SW at around 10 kts, with seas ranging right around 2 ft through the period. && .ILM WATCHES/WARNINGS/ADVISORIES... SC...None. NC...None. MARINE...None. && $$ NEAR TERM...RJD SHORT TERM...REK LONG TERM...REK AVIATION...RJD
Area Forecast Discussion
National Weather Service Louisville KY
931 PM EDT Fri Sep 1 2017 .Forecast Update... Issued at 931 PM EDT Fri Sep 1 2017 Remnant circulation of Harvey was located across our far southeastern counties...just northeast of Liberty KY. The center continues to move off to the northeast slowly. Radar imagery shows the bulk of the moderate to occasionally heavy rainfall continuing to shift to the north. A constant deformation band extends now from around Shepherdsville (Bullitt County) northeastward to near Cincinnati (Hamilton County OH). This band should continue into the overnight hour and shift northeastward with time. Elsewhere, light to occasionally moderate rainfall continue across the region. Rainfall rates are generally light with most locations seeing < 0.25/hr rates. Latest HRRR forecasts continue to show a little an arcing band of precipitation to continue overnight from Bowling Green northeast to Cincinnati. However, the overall rainfall amounts from each successive HRRR run have been tapering down with each run. Based on the projected forecasts, we have trimmed up the Flash Flood Watch for the overnight. We cleared out some of our far western counties, some of our southern counties, and much of our southeastern (Lake Cumberland areas). We still expect to see rainfall in these areas, but the amounts are forecast to be light and are not expected to aggravated saturated soil conditions in these areas. It appears that the most at risk ares would be our far SE IN counties and our far northern KY counties north of I-64 and west of the I-75 corridor. Though no flooding reports have been received as of this time, some minor flooding of poor drainage and low-lying areas will be possible. The remaining section of the Flash Flood Watch will remain in effect through 06Z (original expiration time). With the above changes, a few edits to the forecast were made, generally to lower PoPs slightly in the west, far south, and far southeast. Will maintain 100 PoPs across much of north and east central KY overnight. Overall additional rainfall of 0.25 to 1.25 inches are expected with a diminishing trend in the rain late tonight. Update issued at 712 PM EDT Fri Sep 1 2017 Current forecast remains on track at the moment. Remnants of Harvey continue to churn across south-central KY this afternoon. Deformation zone with the heaviest precipitation continues to stretch from Ohio County northeastward through Harrison/Clark/Floyd/Jefferson counties in southern Indiana. Precipitation has been rather heavy at times within the band. Legacy Doppler and MRMS data suggests 1-1.5 inches of rainfall in this band with the majority of it falling in Meade and Harrison (IN) counties. Deformation band is expected to continue to push slowly northward this evening...likely pushing a little north of the Ohio River by mid-late evening. The latest HRRR runs suggest a more southwestward development of the band back down into Butler and Warren counties later tonight. We can already see the beginnings of this as a heavier band seems to be developing from Breckinridge county southward into Butler and western Warren counties. Elsewhere, precipitation is generally light to occasionally moderate. This is true south and east of a line from Simpson county northeastward to Clark (KY) county. Overall, we are not seeing much in the way of additional development across our southeast this evening and into the overnight. Current thinking is the heaviest rainfall would be in an arcing band from Cincinnati-Louisville- Bowling Green with an additional 1-2 inches of rainfall. Should current trends continue, it is likely that we`ll trim a bit of the Flood Watch off in our southeast sections by mid-evening. In the meantime, we`ll continue to watch for high water within the deformation band across far northern KY and southern Indiana. Update issued at 514 PM EDT Fri Sep 1 2017 A couple of real quick updates. First, we have dropped the Wind Advisory as of 500 PM. Our current thinking is that the wind gusts of 40-45 MPH are over with. However, we could see some continued gusts into the 20-25 MPH range for a few more hours as the remnants of Harvey continue to wind down. Second, we are going through and contacting counties with regards to flooding conditions. Our plan is to let the areal flood warnings die off with their respective expiration times this evening. Digital forecast grids and forecasts text products have been updated to reflect the dropping of the Wind Advisory. In terms of current weather expectations...The latest model solutions suggests that the heaviest rainfall will continue to move northward into southern Indiana and far northern Kentucky this evening. In general, the heaviest rainfall looks to stay mainly along and north of the I-64 corridor. The 01/18Z NAM and 01/20Z HRRR runs support this thinking. However, both models are suggest more development on the back side of Harvey`s circulation as it treks northeastward across the state. Generally speaking, a swath of 1-2 inches of additional rainfall may affect areas west of I-65 this evening, extending from Louisville back down into the Bowling Green area. Lesser amounts of rainfall are expected over our far southeastern counties, down in the Lake Cumberland area. Should these trends hold steady, we may drop the Flash Flood Watch for our southeast areas in the next few hours. The severe weather threat associated with Harvey looks to be more confined to our east over far eastern KY where arcing bands of convection are moving east of Jackson/Hazard and toward Paintsville and Pikeville. && .Short Term...(This evening through Saturday night) Issued at 255 PM EDT Fri Sep 1 2017 Widespread light to moderate rain, with a few heavier pockets, will continue tonight as Harvey`s low slowly crosses central Kentucky. Another general inch of rain is expected, primarily across north central Kentucky and the northern Blue Grass. Slightly enhanced amounts will be possible where bands train over a certain spot, which would be most likely to happen over the Blue Grass. Southern Kentucky, where the flooding has been the most severe, should see only light additional amounts. After talking with JKL and ILN, will keep the FFA in place for now since there is ongoing flooding and rain is still falling...though the threat of significant widespread flooding is diminishing and the watch will likely be dropped, or at least significantly trimmed back, this evening. Showers will taper off from west to east Saturday as what was once Harvey weakens significantly and moves off into Ohio. Saturday night high pressure will build into the Tennessee Valley. A weak cold front will approach from the northwest, but the high should keep us dry. .Long Term...(Sunday through Friday) Issued at 230 PM EDT Fri Sep 1 2017 On Sunday, dry northwest flow aloft will take over across the Great Lakes and Ohio Valley. Expect fair and warmer weather with highs in the upper 70s to lower 80s. Labor Day Monday also will be dry with high temperatures in the lower and mid 80s. By Tuesday, a significant shortwave trough aloft is progged to dig southeast across the Great Lakes and mid Mississippi Valley before amplifying across the Ohio Valley mid week. The GFS and ECMWF show a sharper trough than the GEM as the trough moves into the Ohio Valley. This would result in scattered to numerous showers and thunderstorms along and ahead of an accompanying surface cold front Tuesday and Tuesday night, some with brief heavy rainfall. The GEM, on the other hand, would bring scattered showers Monday night and Tuesday morning. The blended forecast favors best chances for rain Tuesday. Models suggest isolated diurnal showers may occur Wednesday under cool air aloft. Surface temperatures and humidity levels will be lower Wednesday and Thursday behind the cold front with afternoon highs in the upper 60s to mid 70s. By late next week, high pressure takes control with pleasant dry early September weather. && .Aviation...(00Z TAF Issuance) Issued at 721 PM EDT Fri Sep 1 2017 The remnants of tropical storm Harvey will continue to track northeast across the region tonight and off to the northeast through the day tomorrow. Mainly IFR ceilings are expected through the night and into the morning hours tomorrow at SDF, LEX, and BWG. Steady rain and/or rain showers will continue through the night with generally 2-4 mile visibility through at least 06Z. Thereafter there could be some occasional improvements. HNB is in the edge of the system and ceilings are expected to remain higher than sites to the east. MVFR cigs should prevail through the night. Ceilings will likely be slow to improve tomorrow. However, all but LEX should improve to VFR by mid to late afternoon. The ceilings should improve at LEX towards the end of the TAF period, but will likely remain MVFR. The gusts are expected to diminish through the overnight hours. Wind direction will slowly swing around as the low shifts northeastward. && .Hydrology... Updated at 257 PM EDT Fri Sep 1 2017 Light to moderate rain will continue in most locations tonight, but amounts should be generally less than an inch. Flood Warnings have been issued for Rochester and Woodbury on the Green River. Rises can be expected at Alvaton on Drakes Creek, Boston on the Rolling Fork, and Dundee on the Rough River, but as of this writing those points are expected to stay below flood stage. && .LMK WATCHES/WARNINGS/ADVISORIES... IN...Flash Flood Watch until 2 AM EDT Saturday for INZ079-090>092. KY...Flash Flood Watch until 2 AM EDT /1 AM CDT/ Saturday for KYZ024- 025-027>043-045>049-053>055-062>065-071-074-076. && $$ Update.......MJ Short Term...13 Long Term....13 Aviation.....EER Hydrology....13
829 PM PDT Fri Sep 1 2017 .SYNOPSIS... Hot weather will continue through Saturday. The remnants of a tropical system may track close enough to bring some showers and thunderstorms to portions of the region Sunday afternoon through Monday, along with some cooling. Temperatures will remain above normal through late next week. && .SHORT TERM...(FRI-MON) As expected, another very hot day occurred across the forecast area. Surprisingly the majority of the Central Coast trended higher over 20 degrees in several locations. Lompoc was up 27 degrees from yesterday`s hi of 76 degrees to a whopping 103 degrees this afternoon. Both Santa Maria and San Luis Obispo were over 20 degrees. The big difference was due to the stronger broad upper level easterly flow that reinforced the offshore surface gradients. This synoptic pattern is going to continue through tomorrow with continued offshore flow. The seabreeze will kick in late tomorrow, but should see a near repeat of high temps across the Central Coast before some cooling late in the afternoon. Showers and a few embedded thunderstorms did develop across the LA/VTU/SBA County Mtns and spilled over into the valleys late this afternoon. There were a few showers across the Oxnard Plain as well early this evening. The convective parameters were not nearly as explosive as yesterday. A few rogue showers cant be ruled out tonight, especially SBA county where both the HRR and RAP high resolution models focus best moisture and lift. In evening update, we will be expanding the slight chance of showers and tstms to coastal areas of SBA county. As far as high temps tomorrow, the 00Z NAM WRF continues to show an eddy spin up across the SoCal Bight overnight. This should bring some cooling across the coastal areas of LA/VTU and SBA South Coast. In fact, the marine layer depth could rise to 1000 ft which should bring a few degrees of cooling to the coastal valleys as well. At this point, not expecting much in the way of stratus, but would not be surprised if some low clouds developed off the Orange County Coast and moved north into LA County. *** From previous discussion *** Tomorrow looks somewhat less favorable for convection and best chances would be in the eastern San Gab mtns. Forecast gets quite complicated Sunday into Monday as we start to see the moisture moving in from TS Lidia. What`s left of the the circulation center is expected to remain well southwest of the area, however moisture wrapping around it from the southeast should impact at least the southern half of the forecast area Sunday and Sunday night and likely reach SLO county. Pwats increase to over 2" Sunday afternoon and with some instability with it there`s a decent chance, assuming the forecast track is reasonably close, that we`ll see some showers and thunderstorms by Sunday afternoon. And chances are pretty equal everywhere, though somewhat better towards the south closer to the remnant low. The temperature forecast will be very tricky as we`ll still be dealing with offshore gradients and some better easterly support aloft with what`s left of Lidia, but then likely plenty of clouds and potential showers/storms. Even with fairly thick clouds a scenario like this could still see highs in the 90s for inland coast/valleys with some lower 100`s possible. But if there`s widespread precip than temps will definitely be cooler. Obviously quite a but more humid with the tropical air mass in place so any cooling would likely be offset but the muggier air. Going into Monday the moisture will start to exit to the west as the remnant low shoots out over the Pacific. Still some lingering shower/storm chances in the morning, especially northern and western areas, then for the afternoon just some small chances over the interior. Temperatures still quite warm and muggy, though decent onshore trends should bring some relief to at least the coast/valley areas. .LONG TERM...(TUE-FRI) After the leftovers of Lidia exit the area Monday we should see a slow climb in temperatures through the rest of the week as high pressure strengthens over the Great Basin. The ECMWF wasn`t quite as far west with the expansion of the high as it had shown in earlier runs and now looks pretty similar to the GFS, so while some warming is expected highs aren`t expected to be quite as hot as they were and certainly not like they`ve been the last couple days. The other big difference being a fairly persistent onshore flow which is expected to strengthen as we go through the week so we should also see a return of some marine lyr clouds to coastal areas. There`s still a favorable upper level flow pattern to allow monsoon moisture in from the southeast so will keep the slight chances of showers and storms over the mountains and Antelope Valley going each day. && .AVIATION...01/2350Z. At 2330Z, there was no marine layer at KLAX. VFR conditions are expected throughout the period. There is a 20% chance for VLIFR to LIFR conds across the central coast. Also with an eddy circulation developing overnight. There will be a 30% chance for IFR to low MVFR cigs developing across LA/VTU county coast after 10z tonight. KLAX...VFR conditions are expected throughout the period. There will be a 40% chance for SE or easterly wind component over 10 kt between 11z-16z Sat morning. There is a 10 percent chance of VLIFR to LIFR conditions between 12Z and 15Z. KBUR...VFR conditions are expected throughout the period. No wind issues are expected at this time. && .MARINE...01/800 PM. Conditions are expected to remain below SCA levels through Sunday, and possibly through Tuesday. There is a chance of isolated gusts to 25 knots during the afternoon and evening hours through the weekend, especially over the San Pedro Channels. Shower and thunderstorm activity should increase over the weekend as Tropical Storm Lidia moves north into the offshore coastal waters. The cyclone, currently over Southern Baja California, or about 650 miles southeast of Point Conception could bring showers and thunderstorms to the Coastal Waters. The storms will likely be capable of producing heavy downpours, gusty erratic winds, and cloud- to- ocean lightning. && .LOX WATCHES/WARNINGS/ADVISORIES... CA...Heat Advisory in effect until 10 PM PDT Saturday for zones 34-35-39-40. (See LAXNPWLOX). Excessive Heat Warning in effect until 10 PM PDT Saturday for zones 36>38-41-44>46-51>54-59-88-547. (See LAXNPWLOX). PZ...NONE. && .HAZARD POTENTIAL OUTLOOK...(MON-FRI) No significant hazards expected. && $$ PUBLIC...Kaplan/Gomberg AVIATION...CK MARINE...Smith SYNOPSIS...Smith
Area Forecast Discussion
National Weather Service Miami FL
732 PM EDT Fri Sep 1 2017 .UPDATE...Showers and storms are ongoing over the western half of South Florida this evening, with prevailing south-southeast winds focusing the strongest storms just to the north of the lake. RUC analysis shows cooler temperatures aloft encroaching from the west as a large area of disturbed weather along a broad trough slides across the eastern Gulf. With these features in place, models suggest that the weather will remain unsettled overnight. Expect overall coverage to decrease through the evening hours, though showers and a few storms will linger, mainly over the local waters. Depending on how far east the Gulf activity gets, coverage may be a little higher. No significant changes to the ongoing forecast for tonight. && .AVIATION... A few thunderstorms and showers will remain in the vicinity of APF through around 02Z for which a TEMPO remains in place for MVFR cigs/vis. After 02-03Z VFR is expected to prevail at all terminals through late Saturday morning. Winds will become light an variable later tonight. Another round of VCTS is expected Saturday afternoon as sea breezes push inland. Winds will turn to the SE at around 10 knots, except APF where westerly onshore flow will develop with the afternoon seabreeze. && .PREV DISCUSSION... /issued 428 PM EDT Fri Sep 1 2017/ DISCUSSION... THIS AFTERNOON AND TONIGHT: The Gulf breeze has been more active as it`s moved into inland Collier/Glades/Hendry with an active line of showers and storms going up along it. Mesoscale models suggest that this will kick off an outflow boundary, along with steering flow becoming more south-southwesterly that will interact with a diffuse seabreeze over the interior through the afternoon and early evening hours. Convection wanes through the late evening hours. With an approaching disturbance from the Gulf and cooler temperatures aloft, some storms may linger through the overnight, especially over the local waters. A few models are a little more bullish with convective coverage overnight with a faster approach of the disturbance over the Gulf, and have split the difference, with storms becoming scattered towards daybreak. HOLIDAY WEEKEND: Post-Tropical Cyclone Harvey is expected to continue to move northeast across the OH/TN valleys over the next 24 hours. It then becomes absorbed into the trough swinging through the Great Lakes, lifting out into New England and the Canadian Maritimes into Monday. This evolution will erode the western side of the western Atlantic ridge, allowing a trailing boundary and associated disturbance over the eastern Gulf into the state over the next two days. Steering flow will veer more south- southwesterly, tapping back into an area of tropical moisture to our southwest. Models show a few impulses moving from SW to NE within this flow, with temperatures aloft little cooler at -7C to -8C. Shower and storm chances look above normal again on Saturday, starting earlier in the day as the feature from the Gulf helps get activity started. Conditons will remain favorable for a few stronger storms with gusty winds. Coverage is expected to diminish closer to normal on Sunday as the boundary washes out and a little stronger easterly flow brings in some drier air, with the direction focusing activity more towards the interior and Gulf coast. Stronger easterly flow on Monday should push most storms towards the Gulf coast, where models hint that the Gulf breeze may not even develop. NEXT WEEK: Models continue to show a large upper level trough digging across the eastern half of the US into mid next week. This pattern is expected to drive a low level frontal boundary through OH/TN valley and into the east coast as we enter the latter half of the week. While both the GFS and ECMWF have the same basic pattern, the exact impacts to local weather, as always, is in the details. While the GFS` trough is stronger, the ECMWF shows a more split pattern with a stronger vort pattern along the southern side of the trough as it moves east. These differences affect the timing of the when the trough may move off the east coast and weaken the western Atlantic ridge, which has implications as to how far east or west Hurricane Irma may track. Regardless, it looks like an unsettled weather pattern returns to the region with scattered to numerous showers and storms each day. It is important to remember that track errors for tropical systems are around 200 miles at 5 days, and this is in the day 7 to 9 timeframe with continuing run to run and model differences. While Irma will remain a system to watch over the next week, it is far to early to speculate as to if Irma will impact South Florida. MARINE...Weak boundary moving into the state briefly weakens the western Atlantic ridge as we move into Saturday, with south- southeasterly winds continuing around 10 knots. High pressure is expected to re-strengthen to the west early next week, with winds becoming east at 10-15kts. Both seabreezes are expected to develop through the holiday weekend, with winds becoming southwesterly over the Gulf waters each afternoon. Stronger east flow may hold off Gulf breeze developing into next week. A 1-2ft 10-12 sec NE swell is expected to continue across the local Atlantic waters through the holiday weekend, with seas 3-5ft, especially off the Palm Beach coast. The swell is expected to slowly diminish by mid next week. Scattered to numerous showers and storms can be expected over the area through the weekend, becoming more scattered into early next week. BEACH FORECAST...A 1-2ft long period NE swell as already reached the local Atlantic waters this afternoon. Local beach patrol has already reported an increase in rip currents. A moderate risk of rip currents this afternoon is expected to become high at all Atlantic beaches through the holiday weekend. && .PRELIMINARY POINT TEMPS/POPS... West Palm Beach 78 91 77 93 / 20 50 20 10 Fort Lauderdale 79 91 79 92 / 30 40 20 10 Miami 79 90 78 93 / 30 40 20 10 Naples 77 91 76 92 / 20 50 30 30 && .MFL WATCHES/WARNINGS/ADVISORIES... FL...None. AM...None. GM...None. && UPDATE...88/ALM AVIATION...17/AR
Area Forecast Discussion
National Weather Service Melbourne FL
933 PM EDT Fri Sep 1 2017 .UPDATE... Tonight...Quite active boundary driven convection has lingered into late evening. There is also some large scale ascent across the area from a vort max that is lifting northward out ahead of a trough dug in over the southeast states. The HRRR has been showing the bulk of this convection lifting out by midnight, but it hints at some lingering shower chances overnight, as does the local WRF model. This is already shown in the current forecast, so don`t plan any significant changes. && .AVIATION... Quite a bit of shower/storm activity was lingering this evening and providing brief IFR-MVFR. After midnight, conditions look like they will be VFR, but widely scattered showers could produce local MVFR. The atmosphere will be very moist on Saturday, so slow heating through considerable debris cloudiness will ignite scattered to numerous showers and storms from the afternoon into evening. && .MARINE... Tonight-Saturday...High pressure ridge over the Atlantic is shown providing about a 10 knot southerly wind flow. The latest buoy observations show seas around 2 feet at the coast and a little over 3 feet offshore. This is a little lower than what our current forecast was showing so will make slight adjustments. Expect a chance for lingering showers/storms over the waters early Sat and a chance for stronger storms moving offshore in the afternoon and evening. && .MLB WATCHES/WARNINGS/ADVISORIES... FL...None. AM...None. && $$ Forecasts...Lascody Impact Wx...Sedlock/Combs
Area Forecast Discussion
National Weather Service Marquette MI
642 PM EDT Fri Sep 1 2017 .SHORT TERM...(This evening through Saturday) Issued at 359 PM EDT FRI SEP 1 2017 WV imagery and RAP analysis indicated a mid/upper level ridge near the west coast resulting in wnw flow from BC toward the nrn plains. A vigorous upstream shortwave trough was located over wrn Manitoba. At the surface, srly winds were increasing over the upper MS valley and wrn Great Lakes ahead of a trough extending from ne Manitoba to the cntrl Dakotas. WAA ahead of the trough supported a band of showers through wrr MN. Tsra had also developed farther to the north through se Manitoba with the stronger forcing and higher mid level lapse rates ahead of the shrtwv. Tonight, although the dry airmass still lingers over the area, the combinaton of increasing high clouds and srly winds will keep temps from falling off nearly as much as the previous couple nights. Expect lowest inland readings around 40 with lower 50s where downslope ssw winds prevail. Short range models suggest that the showers may move into the far west late, mainly aft 09z. Saturday, showers supported by moderate to strong qvector conv ahead associated with the shortwave and upper level div with the left exit of a 120 knot 250-300 mb jet will spread from west to east. Although the models were in good agreement with the timing, the WAA initial pcpn may be fairly light and slowed by time to saturate low level dry air. Similar to what was observed upstream today, MUCAPE values and tsra chances are expected to lag the initial band with TS chances mainly in the far west into the west half by midday and over the rest of the area by mid to late afternoon as the shrtwv moves in. .LONG TERM...(Saturday night through Friday) Issued at 412 PM EDT FRI SEP 1 2017 Over the last 24hrs, medium range model guidance has slightly increased the speed of progression of features thru the middle of next week, but the overall large scale picture remains the same. Currently, a low amplitude ridge is over the western CONUS with max positive height anomaly along the Pacific NW coast. Shortwave now rounding the ridge will track across the Great Lakes region over the weekend. Early next week, the western ridge will amplify sharply thru western Canada with 500mb height anomalies peaking around 250mb above the long term early Sept avg. This will in turn force a deepening trof downstream over the Great Lakes region Mon thru Thu. In the 7-10 day time frame, the western ridge is fcst to deamplify and progress slowly with positive height anomalies gradually spreading downstream to the Upper Lakes, causing weakening and progression of the eastern trof. These large scale changes will lead to temps rising above normal on Sun ahead of a cold front passing early Mon. Transition day on Mon will be followed by much cooler conditions for Tue/Wed as 850mb temps bottom out at 1-3C. New change seen in guidance today is the potential of another shortwave to drop sse into the Great Lakes region on Thu, helping to maintain deeper troffing across the area thru Thu and delaying a more sustained warming trend until next weekend. Farther out, trend toward somewhat above normal heights into the following week should support normal to above normal temps into the mid Sept time frame. As for pcpn over the next 7 days, shortwave/associated sfc trof arriving on Sat will push a band of shra across Upper MI. Dry weather will follow on Sun. Shra chc will then return Sun night/Labor Day with next cold front. Expect unsettled weather for Tue/Wed as amplified trof and chilly air mass support plenty of cloud cover and at least some diurnally aided isold/sct shra. There may even be a lake component to shra Tue night into Wed morning. With the new depiction of a possible shortwave arriving on Thu, there may be some chc of -shra into Thu before a period of dry weather likely settles in thru next weekend as warming trend begins. Beginning Sat night, lingering shra associated with passing shortwave/sfc trof will end from w to e. Enough instability is present to maintain a mention of thunder in the evening. On Sun, expect a dry day under passing weak sfc high pres ridge. In fact, it should be a nice late summer/early fall day with mostly sunny skies and high temps well into the 70s for much of the area. A few spots may reach 80F. Sharp ridge amplification over western N America will force next shortwave to dig into the Upper Mississippi Valley/western Great Lakes on Labor Day. As previously mentioned, model trend over the last 24hrs has been to increase the progression of features slightly. So, it appears now that the cold front associated with the shortwave may exit the fcst area by mid morning. This would favor a more optimistic Labor Day fcst with limited risk of more shra development in the wake of the cold front. However, additional shortwave energy in the amplifying trof may be sufficient to generate some isold aftn -shra on Labor Day even though this energy is dropping more so into the northern Plains rather than the Upper Lakes. Expect high temps to be mostly in the upper 60s/lwr 70s. With trof amplifying thru the Great Lakes, much cooler/fall conditions will follow Tue under n to nw winds/mostly cloudy skies and isold/sct shra. Wed will be similar to Tue, but with lighter winds. Timing periods of better shra chc on Tue/Wed will be dictated by any shortwaves dropping into the trof over the Great Lakes, and models haven`t shown great consistency on that point. In any event, would expect some diurnal component to pcpn coverage on both days with aftn hrs more favorable for isold/sct -shra. Not out of the question that there could be a lake component to -shra during the min of the diurnal cycle late Tue night/Wed morning. Max temps Tue/Wed will likely hold to the 50s across much of the w and n. Lower 60s expected s central. Depending on track/strength of a shortwave dropping into the Great Lakes on Thu, there may be some potential of -shra at that time. Dry weather and a warming trend will then get underway Fri as trof shifts e and heights rise. && .AVIATION...(For the 00Z TAFS through 00Z Saturday evening) Issued at 642 PM EDT FRI SEP 1 2017 As high pressure slowly shifts to the east, VFR conditions are expected through tonight with lingering dry air over the region. A front moving into the area from the west will bring showers into the west Saturday morning that should be heavy enough to drop cigs into the MVFR range by mid to late morning at KIWD and KCMX. KCMX will briefly go IFR Sat afternoon. KSAW will go MVFR by Sat afternoon. && .MARINE...(For the 4 PM Lake Superior forecast issuance) Issued at 359 PM EDT FRI SEP 1 2017 Southwest winds will increase to 20 to 30 knots tonight into Saturday ahead of a front. Behind the front, winds will become westerly at around or less than 15 knots on Sunday. Another cold front is expected to move through the region and will increase winds to 20 to 30 knots Monday through the middle of next week. && .MQT WATCHES/WARNINGS/ADVISORIES... Upper Michigan... None. Lake Superior... None. Lake Michigan... None. && $$ SHORT TERM...JLB LONG TERM...Rolfson AVIATION...07 MARINE...JLB
Area Forecast Discussion
National Weather Service Pittsburgh PA
908 PM EDT Fri Sep 1 2017 .SYNOPSIS... Temperatures will remain cold this weekend with the remnants of Harvey bringing rain through Sunday. Heavy rainfall totals are not expected. && .NEAR TERM /THROUGH SATURDAY/... Northeasterly flow is continuing to feed dry air down into the CWA even as the remnants of Harvey trudge northeastward into it. This was again well reflected in the 00z sounding this evening. This flow combined with increasing shear over Harvey as well show Harvey weakening rapidly between now and this time on Saturday. The ingestion of dry air can already be noticed on region radar mosaics as higher reflectivity returns have rapidly diminished in the past several hours. The 18z GFS, latest HRRR runs, and hi-res NMM/ARW all indicate a continued rapid erosion of the increasinly ragged rain shield moving northward ahead of Harvey. While Harvey transitions from a barotropic structure currently noted to an open upper/mid-level wave through the day tomorrow while maintaining a decent low-level center, it does seem that the precipitation field is set to bifurcate likewise with a swath following the upper support, which a second area remains concentrated with the low level warm air advection that will maximize in Ohio. PoPs were built to favor this which will likely mean a local minimum in precipitation in western Pennsylvania. QPF was summarily reduced because of this, not to mention low level easterly flow is not particularly conducive to significant QPF over much of western Pennsylvania. With all this in mind, it is certain that clouds will hold sway through the day tomorrow, and thus temperatures will be unlikely to drop much tonight, nor substantially rise tomorrow. This will mean largely below normal readings will continue. Fries && .SHORT TERM /SATURDAY NIGHT THROUGH MONDAY/... Showers will continue Saturday night and linger east of Pittsburgh early on Sunday before conditions dry out for the rest of the Labor Day weekend. High temperatures will leap about 10 degrees on Sunday and rise to seasonable values by Monday, which should be the warmest day of the upcoming seven days. && .LONG TERM /MONDAY NIGHT THROUGH FRIDAY/... A cold front crossing the region Tuesday and Tuesday night will bring another round of showers to all locations, with showers lingering into Wednesday and possibly Thursday. Temperatures will drop below normal again behind the cold front, with cooler weather continuing for several days. While today`s normal high temperature is 78, highs will likely remain in the upper 60s and lower 70s in most locations Wednesday, Thursday, and Friday. && .AVIATION /01Z SATURDAY THROUGH WEDNESDAY/... Dry low level ENE flow on the northern side of approaching low pressure should maintain VFR conditions tonight, though mid level clouds and a few showers are possible. There is some LLWS wind shear potential overnight with a marginal low lvl jet, though with sfc winds near 10kt thought LLWS values would remain under criteria. Rain and condition deterioration to MVFR, and eventual IFR, is expected Saturday afternoon as the low advances across the OH Valley region. Gusty SE winds are expected with a tight pressure gradient during the day toward the higher terrain ports. .Outlook... Restrictions are expected through Sunday morning as low pressure exits. Restriction potential returns with a Tue/Wed cold front. && .PBZ WATCHES/WARNINGS/ADVISORIES... MD...None. OH...None. PA...None. WV...None. && $$
Area Forecast Discussion
National Weather Service Blacksburg VA
906 PM EDT Fri Sep 1 2017 .SYNOPSIS... Low pressure that was once Harvey will track into Ohio through Saturday morning, then into the eastern Great Lakes Saturday afternoon. A cold front enters the mountains late tonight, and exits the piedmont early Saturday afternoon. Sunday and Monday high pressure will cover the region. && .NEAR TERM /THROUGH SATURDAY/... As of 855 PM EDT Friday... Deep wedge for early Sept remains in place tonight with soundings showing quite a stable layer below 850 mb which has kept more surface based convection just south of the area. This along with strong east/northeast flow has pushed temps into the 50s with even a few 40s across the far northwest. Otherwise bands of showers and isolated storms continue to redevelop south of the region in an area of strong upper diffluence aided by low level theta-e ridging. Expect this scenario to persist until around midnight when the tail of the passing speed max aloft finally exits. Still expect any remaining convection to be quite elevated above the chilly cool pool with heavy rainfall possibly the main issue across southeast sections that saw earlier downpours. Thus have tweaked pops up espcly south to continued likely/categorical until around midnight with chance or higher pops elsewhere. Latest HRRR then finally shifts most showers east during the early morning hours, but still enough residual band potential around the remnant Harvey low to keep in some low pops into Saturday morning. Already adjusted lows down to just below current readings as only expecting another degree or two of cooling given clouds, and breezy easterly flow which should also limit fog to the higher ridges overnight. Previous discussion as of 255 PM EDT Friday... Early this afternoon, low pressure which was Harvey was located northeast of Nashville, TN. A frontal boundary extended northeast into eastern KY, then southeast into far SW VA/NW NC, then east along I-40 in central NC. This boundary is the zone of concern for potential severe storms this afternoon. Already seeing warnings for severe and tornadoes south of our CWA toward Charlotte, NC. High-res models continue to paint a picture of the wedge front sagging southward through early evening such that severe potential remains low over our forecast area. Still given strong upper forcing and shear, could see isolated damaging wind/tornado threat into early evening, especially southeast of a line from South Boston to Yadkinville, but again better threat will be along/south of the I40/85 corridor in NC. Another concern will be heavy rain/localized flash flooding as rainfall rates from this airmass will exceed 2-3 inches at times. However, we have been relatively dry with high flash flood guidance values over the southeast CWA where the heavier rain is expected. Will have to watch for training cells, as movement is fast enough to keep flooding to a minimum. Also urban areas like Danville/South Boston/Reidsville could experience some local flooding thru this evening. Still not enough to warrant a flood watch. So as we head into the overnight the upper flow becomes more confluent with the closed low over KY, so rainfall should back off somewhat while a dry slot pushes into southern WV/far SW VA. The sfc low weakens Saturday as it shifts to Ohio while a secondary wave forms over northeast VA into the mid-Atlantic. Should see drying trend continue east of the Blue Ridge, but upper low opens to trough and vort tracking over WV will bring another round of showers in the mountains Saturday. Still cannot completely dry out it in the east given the strength of the upper trough/vort. As for temps already starting on the cool side this afternoon with rain/wedge, so lows tonight with clouds and rain will fall about 4-8 degrees into the 50s, with lower 60s far SW VA into the NC foothill/piedmont and southside VA. Saturday wedge breaks and flow turns more southwest ahead of the trough and cold front. Anticipating more sunshine over the southeast CWA by afternoon, so highs should be close to 80, while the mountains warm into the 60s, with 70s in between. && .SHORT TERM /SATURDAY NIGHT THROUGH MONDAY NIGHT/... As of 300 PM EDT Friday... The remnants of Harvey are expected to weaken and lift northeast into Saturday night. Refer to the latest statement from WPC on Harvey. The upper trough axis will rotate east across the region Saturday night into Sunday. Winds will become northwest and create downslope subsidence, while in the west upslope pattern continues with clouds and scattered showers. Low temperatures Saturday night will range from the lower 50s in the mountains to the lower 60s in the Piedmont. On Sunday, clouds and scattered showers associated with the upslope flow will decrease in coverage as the day progresses as the 850 mb flow decreases and backs slightly. High temperatures on Sunday will vary from the mid 60s in the northwest mountains to the lower 80s in the Piedmont. High pressure to our southwest will build across the region Sunday night. Low temperatures Sunday night will generally be from the lower 50s in the west to near 60 degrees in the east. High pressure will be overhead Monday, then it will slide east Monday night. High temperatures will be near normal Monday with readings from the lower 70s in the mountains to the mid 80s in the Piedmont. A cold front will approach the area from the northwest Monday night into Tuesday. Low temperatures will feature values from the mid 50s in the west to the lower 60s in the east. && .LONG TERM /TUESDAY THROUGH FRIDAY/... As of 300 PM EDT Friday... Upper trough digs south from the Great Lakes Region into the Tennessee Valley through Midweek, then it travels eastward into the weekend. There remains some model differences in extended as too how far east the trough axis moves, in relation to strength and position of upper ridge over the western Atlantic. Ahead of the cold front, Tuesday will be a warm and humid day. The frontal boundary will reach the mountains by Tuesday evening with scattered showers and a few thunderstorms along and ahead of it. The timing of the moisture and the front is faster on the ECMWF compared to GFS. By Wednesday, most solutions generates scattered showers and thunderstorms. Frontal boundary slows down per ridge offshore with waves of low pressure setting up along it. There will be a good chance for convection from Midweek into Thursday. High across the Ohio Valley will build east across our region Thursday night into Friday. Meanwhile, a shortwave will rotate around the upper trough to our north. A cooling trend is expected from Tuesday into the end of the week. && .AVIATION /01Z SATURDAY THROUGH WEDNESDAY/... As of 650 PM EDT Friday... Poor flying conditions to persist overnight as a strong wedge of cool air keeps low cigs in place for the most part with periods of passing showers/rain through at least late this evening. This should result in widespread MVFR, with areas of IFR and perhaps LIFR espcly over the mountains outside of rainfall. Vsbys a bit more tricky with MVFR at times within rainfall while overall VFR this evening before perhaps trending MVFR late as perhaps patchy fog develops along the ridges. Gusty northeast/east wind to also linger overnight as the gradient between high pressure to the north and remnants of Harvey to the west continues. Expect may even see gusts to 20-25 kts espcly along and east of the Blue Ridge overnight. Even though showers should become less widespread Saturday, except across the northwest where will be closer to the passing remnant low of Harvey, appears the wedge will hold for the most part. This will allow low cigs to linger with some gradual improvement to MVFR during the day, although cant totally rule out periods of VFR in the east by late in the day. With best chances of showers basically across the northwest, will be keeping in a VCSH mention excluding KLYH/KDAN at this point Saturday afternoon. Extended Aviation Discussion... The remnants of Harvey will track northeast into the Ohio Valley Saturday night, before becoming absorbed in the northern stream upper trof. Sunday into early next week will see improving conditions to mostly VFR as high pressure moves southeast into the region. The exception will be late night/early morning patchy dense fog at the usual locations, KLWB and KBCB. Shower chances increase again ahead of a front Wednesday, so sub VFR is possible. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...None. NC...None. WV...None. && $$ SYNOPSIS...WP NEAR TERM...JH/WP SHORT TERM...KK LONG TERM...KK AVIATION...AMS/JH/RAB/WP
Area Forecast Discussion
National Weather Service Tucson AZ
836 PM MST Fri Sep 1 2017 .SYNOPSIS...Increased moisture from Tropical Storm Lidia will bring a chance of showers and thunderstorms mainly west to south of Tucson this weekend. Expect isolated to scattered afternoon and evening thunderstorms next week. && .DISCUSSION...Yet another quiet afternoon/evening throughout southeast Arizona. Such is life with dewpoints in the 30`s and a PW of 0.5". However, change is on the horizon due to TS Lidia. Outer bands of cirriform clouds associated with the tropical system continue to expand south to north across the international border. The latest NHC Advisory #13A showed Lidia currently moving up the western coastline of Baja California Sur, gradually weakening as it interacts with mountainous regions and cooler Pacific waters. Good agreement among the model suite keeps Lidia drifting away toward the northwest, but moisture in our area will be increasing tonight into tomorrow. Slight chance of light precip along the southern border in Santa Cruz County tonight before more organized measurable rainfall arrives tomorrow morning. The 02/02Z HRRR shows a band of showers reaching the border around 15Z, slowly expanding toward the north. This solution holds in line with the earlier guidance and the forecast appears to be in good shape. No changes are necessary at this time. Please see previous discussion for further details. && .AVIATION...Valid thru 03/06Z. Surface winds ely/sely less than 12 kts through tonight. Increasing clouds mainly above 10k ft AGL from south to north across the area late tonight into Saturday. Isolated -SHRA mainly near international border and KOLS Saturday morning. Scattered -TSRA/-SHRA mainly west of KTUS Saturday afternoon into evening. Winds remain ely/sely tomorrow with gusts to 20 kts during afternoon. Aviation discussion not updated for TAF amendments. && .FIRE WEATHER...Isolated showers south of Tucson late tonight into Saturday morning, then scattered showers and thunderstorms mainly west of Tucson Saturday afternoon into Sunday. Expect isolated to scattered afternoon and evening thunderstorms Monday into next Friday. 20-foot winds will generally be from the east to southeast at 5-15 mph with occasional gusts to 25 mph through much of the forecast period. && .PREV DISCUSSION /245 PM MST/...Measurable rainfall is not expected to occur this evening. Have opted for a slight chance of showers (with no thunder) mainly near the International border adjacent Santa Cruz/southern Pima Counties late tonight. Isolated showers with a slight chance of thunderstorms Saturday morning should be confined south of an Ajo-Green Valley-Douglas line. As noted in the morning discussion, the 01/12Z NAM MOS guidance and especially the 01/12Z GFS MOS guidance suggest markedly reduced measurable precip chances from Tucson northward/eastward versus solutions from 24 hours ago. However, precip potential remained similar versus model solutions from 24 hours ago for locales west to south of Tucson. The high resolution models such as the 01/12Z Univ of AZ WRF-NAM and WRF-GFS suggest that scattered showers/tstms will develop Saturday afternoon mostly across western/central Pima County. However, the WRF-GFS remained more robust versus the WRF-NAM by depicting a potential for showers/tstms to occur Saturday afternoon and evening further eastward and southeastward to include portions of the Tucson metro area into Santa Cruz County. The WRF-NAM and WRF-GFS were then similar with limiting shower/tstm potential to mainly western/central Pima County Saturday evening. At any rate, the official forecast continues with scattered showers/ tstms mainly west-to-south of Tucson Saturday afternoon into Saturday night, and isolated showers/tstms for the Tucson metro area. Lidia is forecast by the National Hurricane Center to decay to a remnant low just west of the northern Baja California coast Sunday morning. The models suggest that dry conditions will occur from Tucson eastward Sunday, but adequate moisture will justify at least a slight chance of showers/tstms across western sections. Thereafter, the 01/12Z GFS/ECMWF/CMC deterministic solutions continued to depict strong high pressure aloft to remain over the western CONUS Monday into next Friday. A fairly low grade shower/ tstm potential exists daily Monday through Friday. However, a cold front moving westward across southern New Mexico and encroaching upon eastern sections, as well as enhanced northeasterly mid-level steering flow, may provide increased shower/tstm coverage area-wide Tuesday afternoon/evening. High temperatures this forecast period will mainly be quite close to seasonal normals. The exception appears to be Monday and Tuesday when daytime temps may average a few degrees above normal. && .TWC WATCHES/WARNINGS/ADVISORIES...None. && $$ Howlett/Francis Visit us on Facebook...Twitter...YouTube...and at