Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 09/25/19

Area Forecast Discussion
National Weather Service Amarillo TX
624 PM CDT Tue Sep 24 2019 .AVIATION...00Z TAFs... VFR conditions expected through the period at all TAF sites. Very small chance for a rumble of thunder near GUY this evening, but current westward extent of thunderstorms in SW Kansas - currently between 19S and DDC - suggests that probability is very small. Otherwise, low confidence in exact wind direction tomorrow given expected development of a weak E-W surface trough, but wind speeds should remain at or below 12 knots, so impact of exact wind direction is likely to remain low. Ferguson && .PREV DISCUSSION... /Issued 343 PM CDT Tue Sep 24 2019/ SHORT TERM...Tonight through Wednesday afternoon... Water vapor imagery reveals a mid level cutoff low with center near Yuma, AZ as of 1930z. A longwave trough over central Canada was digging southeast with 70kt speed max progressing over the northern Plains. A subtle perturbation was noted in the southwest flow moving into far southeast CO while another minor shortwave moves southeast towards central CO. RAW models suggest somewhat of a phasing of these two features as a small/weak 500mb jet streak strengthens over southwest KS and our far northeast zones late this afternoon and evening. This results in just enough dynamics over the far northeast zones (in the vicinity of a right entrance region of the weak jet streak) to warrant a slight bump in the PoPs. The best chance for storms will be slightly further north, just into KS where the best overlap of dynamics and surface convergence is expected due to proximity to surface trough. Further south into the eastern Texas Panhandle, some slight chance PoPs were retained for the afternoon near the southwest extending surface trough. This area lacks much in the way of upper level support, so surface convergence will need to be strong enough to overcome warm 850mb temperatures (cap) and the persistent subsident inversion near 500mb. There was some CU trying to form some vertical extent in central Potter Co, but like yesterday these may not do much. There is better moisture compared to yesterday with warmer surface temperatures, which does support the HRRR forming an isolated cell by 22z. The best convective parameters for severe weather will reside in the northeast closer to the jet streak, as this will support better deep layer shear overall (effective shear near 35 knots). Effective shear further south will be closer to 25 - 30 knots. MLCAPE around 1500 to 2000 J/kg is likely across most of the eastern Panhandles (east of the surface trough). Any isolated cells that can form this afternoon could become strong to severe, with multicell characteristics or even transient supercell characteristics (especially near Beaver Co). If a cell does rotate, hail up to ping pong balls and strong winds would be possible. Otherwise, dime to nickel hail with generally gusty winds is more likely. Low level helicity values are progged to increase as a LLJ form this evening, with 0-1km values over 100 in eastern zones (higher in Beaver Co). Thus, if an isolated supercell exists in the 01z to 03z timeframe (unlikely), some decent updraft helicity can`t be ruled out for storms that remain surface based. Heavy rain could lead to localized flooding given PWATs around the 90th percentile. Storms should be out of the area or dissipated by 03z. For tomorrow, the upper pattern does not change too much except that the Canada trough progresses across the northern plains helping to setup weak zonal flow across the Panhandles. The cross barrier flow will support lee pressure falls in northeast NM and even extending into the western TX/OK Panhandles with an west/east extending surface trough. Short and medium term models suggest surface moisture will shift east with a lack in overall lift, so storm chances were kept below 15 percent. Ward LONG TERM...Wednesday night through Tuesday The long term forecast starts off relatively benign before potentially trending more active with increasing precip chances. The aforementioned cutoff low will be phasing back with the polar jet Thu night as a stronger wave slides in and scoops it up. The exact timing that this weakening wave crosses is still in some question, with ECMWF slower than most other model progs. After this wave skedaddles off to the NE, upper level ridging will build in the southeast CONUS as deep upr troughing carves into the western US. The Panhandles, as we so often are, will be caught in the transition zone with broad SW flow aloft taking hold beginning this weekend and continuing through mid next week. Thursday... Thursday may be the most uncertain day of the next seven as questions about the upr trough ejection and extent of a cold frontal push bring about an array of high temperature possibilities ranging from the 60s to the 90s. Would typically lean toward the outlier NAM with its stronger front moving further south and low clouds/drizzle behind. However, there is some concern that the slower ECMWF upr trough ejection will verify and result in the cold front stalling further north. Do think the front will make it into the OK and nrn TX Panhandle and have substantially reduced highs there to at least get somewhere in the middle of the range of solutions. Considered adding some drizzle up there too, but will hold off for now given uncertainty as ECMWF and GFS solutions still provide a warm sunny day for the entire area. Friday through Sunday... Another cold front will likely affect the area on Friday, but this one looks pretty weak with only a very slight chance of a shower or storm along it. Southerly low level winds begin to bring more moisture in over the weekend, setting the stage for isolated to scattered afternoon storm possibilities once again. Temperatures over the weekend look to be above normal with highs in the 80s to around 90 common. Monday through mid next week... Continued moisture influx should result in gradually increasing rain and storm chances early next week as ripples in the SW flow aloft should be sufficient to kick off rounds of storms. The other notable impacts of increasing SW flow aloft will likely be a return to breezy afternoon conditions most days and continued above normal temps. Simpson && .AMA Watches/Warnings/Advisories... TX...None. OK...None. && $$ 77/3
Area Forecast Discussion
National Weather Service Bismarck ND
959 PM CDT Tue Sep 24 2019 .UPDATE... Issued at 954 PM CDT Tue Sep 24 2019 Much quieter late this evening as winds have diminished and convection has all but ended across western and central ND. Could be a stray thundershower far south central into the James River Valley, otherwise expect mainly a few sprinkles/showers into the early overnight hours. Once again updated pops/weather based on latest satellite and radar imagery. UPDATE Issued at 743 PM CDT Tue Sep 24 2019 We have removed the mention of severe through the rest of the evening. Any of these remaining showers or isolated thunderstorms could produce a wind gust to around 50 mph for the next couple hours, but the threat for large hail continues to diminish and the wind threat will also lessen soon with loss of daytime heating. Updated pops and sky cover base on latest radar and satellite observations. Also pushed slight chance pops south toward the SD border this evening as indicated a number of the latest CAMS. UPDATE Issued at 731 PM CDT Tue Sep 24 2019 We have removed the mention of severe through the rest of the evening. Any of these remaining showers or isolated thunderstorms could produce to around 50 mph for the next couple hours, but the threat for large hail continues to diminish and the wind threat will also lessen with loss of daytime heating. Updated pops and sky cover base on latest radar and satellite observations. Also pushed slight chance pops south toward the SD border this evening as indicated a number of the latest CAMS. UPDATE Issued at 513 PM CDT Tue Sep 24 2019 Latest CAMS indicate stronger convection along the International border remaining mainly north and east of the Forecast area. This looks reasonable given recent radar trends and latest RAP analysis which shows strongest instability just northeast of the forecast area. Convection associated with the left exit region of a strong upper jet over northeast MT and Western ND remains within an area of stronger bulk shear and decent lapse rates over northeast Montana, but both decrease as cells move into western ND. This area is also seeing increasing Convective inhibition so expect cells over Northeast MT will have a hard time surviving as they move into western ND over the next couple of hours. We did keep the mention of severe through around 7 PM. Will re-evaluate with the early evening update, but suspect if trends continue, will be able to drop the severe mention by then. We updated pops based on latest radar trends. && .SHORT TERM...(This evening through Wednesday) Issued at 233 PM CDT Tue Sep 24 2019 Latest water vapor imagery shows a northwest flow into North Dakota. A couple of shortwaves embedded within a northwest flow continue to track southeast across Alberta and Saskatchewan. Surface cold front associated with one shortwave now pushing through northwest North Dakota and will makes it way across central ND this evening. SPC mesoanalysis shows Most Unstable Cape around 500-1000 J/Kg over north central ND. Mid level lapse rates around 7.5C/Km, and deep layer shear 25kt-30kt. Ascent will increase behind the front as the upper level shortwave and the approach of an upper level jet streak/left exit region work in tandem resulting in scattered showers and isolated severe thunderstorms. Freezing levels around 7500ft agl, with low topped convection expected to around 20kft per Equilibrium levels, are in line with the the Donovan 1 inch diameter hail indicator. CAM`s reflectivity fields still maintain isolated strong cores 23z-04z, and will closely monitor through the evening. Lows tonight will be in the 40s. Precipitation will wane 04z-06z. A few more shortwaves slated for Wednesday afternoon will shift across the area, favoring northwest and north central for a slight chance of showers. Highs Wednesday will range from the upper 50s to mid 60s. .LONG TERM...(Wednesday night through Tuesday) Issued at 233 PM CDT Tue Sep 24 2019 Trend for a wet and colder pattern remains on track. The coldest air still appears to come at the end of the long term period, Tuesday. Initially, shortwaves embedded within a west to northwest flow and associated surface features will produce another round of rainshowers Thursday into Thursday night. The heaviest precipitation will be found across the north with much lower amounts in the south. Some drying occurs Friday, before the upper flow transitions to a southwesterly flow aloft. Strong upper closed low in the Pacific northwest will send another surge of moisture across western and central ND Saturday and Sunday. H85 temperatures begin a cooling trend, much quicker on the GFS verses the ECMWF. Potential of a rain/snow mix across the far north at some point over the weekend per GFS, while the EC suggests the colder air holds off until Tuesday, and by this point, the majority of precipitation has been shunted east. GEFS Plumes for snow accumulation show a very large spread across the northwest and north central ND over the weekend. Much uncertainty on this, but agreement with colder air eventually arriving sometime this weekend through next week. Highs will be warmest Thursday with upper 50s to upper 60s, with highs in the 40s to lower 50s slowly beginning to overtake western/central North Dakota Saturday through Tuesday. Potential for frost is looking more likely across the north this weekend. && .AVIATION...(For the 00Z TAFS through 00Z Wednesday evening) Issued at 954 PM CDT Tue Sep 24 2019 VFR conditions expected through the forecast period. Isolated showers and thunderstorms this evening could produce a gust to around 40-45 mph. through around 02-03 UTC. Isolated showers may linger to around 06 UTC. Otherwise diminishing west to northwest winds and diminishing VFR clouds through the night. It will become breezy to windy once again Wednesday afternoon out of the northwest. && .BIS WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...TWH SHORT TERM...KS LONG TERM...KS AVIATION...TWH
Area Forecast Discussion
National Weather Service Caribou ME
926 PM EDT Tue Sep 24 2019 .SYNOPSIS... Low pressure will move east of the region overnight followed by high pressure Thursday. A cold front will approach Wednesday night and cross the region Thursday. High pressure will briefly build in on Friday. Another cold front will approach Friday night and cross the region later Saturday. Cool high pressure will build in on Sunday. && .NEAR TERM /THROUGH WEDNESDAY/... 925 PM Update: Whats left of any tstms have crossed over into S Cntrl NB prov ovr the last hr or two as the cntr of the 500mb low crossed from SE ME into Srn NB. Subsequently, we removed tstms ovr SE ME for the the remainder of the eve and added patchy dz with sct shwrs for the remainder of the ngt. Otherwise, fcst hrly temps/dwpts into the late ngt hrs were updated using latest mid eve obsvd sfc obs trends, with no chgs to fcst ovrngt low temps posted at 7 am EDT needed attm. Prev Disc: Upper low lifting across the region this afternoon with showers lifting northward. The radar loop showed a band of showers lifting across the northern areas while another area was setting up across swrn ME and moving ene. Atmosphere across the Dover- Foxcroft and Bangor region into Downeast has destabilized w/the potential for some tstms. Lapse rates did steepen w/CAPE climbing above 700 joules thanks to the sun. GYX has issued SVRs for swrn areas w/large hail reported. Expecting tstms to move into the Penobscot Valley region and Downeast this afternoon through early evening. Some storms have the potential to deliver heavy rainfall and hail. Wind field is not that impressive through 700 mbs(<15 kt), so strong winds not a high threat. Training cells lead to concern for some urban flood issues. This will need to be monitored. Will update the Hazardous Weather Outlook for this threat. The activity will begin to wind down later in the evening as the upper low lifts ene. Leaned heavily toward the latest run of the HRRR and RAP for tonight. Cooler air filtering in later tonight will lead to temps dropping back into the low/mid 40s northern 1/2 of the CWA, while central and downeast areas see upper 40s to low 50s. For Wednesday, some leftover across the far north during the morning and then for the forcing weakens as the upper low pulls away. The CWA will pretty much for the most part hang on to clouds w/the cyclonic flow hanging on into the afternoon. The areas that could see some sun will be the far west and southwest areas and this looks to be in the afternoon. Daytime temps will run below normal. && .SHORT TERM /WEDNESDAY NIGHT THROUGH FRIDAY/... Surface and upper level ridge shifts east Wednesday evening as cold front tracks east toward the region from western Quebec with increasing clouds. There could be some radiational cooling across the north prior to the increase in cloud cover, as well as some patchy fog. Otherwise a few showers could make there way across northwest areas toward daybreak in the weak warm advection in advance of the approaching front. The cold front will move east across the region Thursday afternoon accompanied by showers, as a short wave and surface cold front crosses the region. Expect decreasing clouds Thursday night with any evening showers diminishing, as the front exits through the Canadian Maritimes. Fair weather returns for Friday along with seasonal temperatures. && .LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/... We will once again see increasing clouds Friday evening as yet another cold front starts to approach from the west. The front crosses the region later Saturday through Saturday evening with the chance for showers, followed by decreasing clouds later Saturday night. The air mass behind this front is considerably colder, with temperatures at both 925MB/850MB progged to be right around 0C across the St. John Valley by daybreak Sunday. Otherwise, Sunday is shaping up as a dry day with perhaps a bit patchy stratocu clouds across the north. Sunday night may see favorable radiational cooling conditions, especially for the colder northern valleys. Fair weather Monday before the next system approaches later Monday night and Tuesday with the next chance for showers. && .AVIATION /22Z TUESDAY THROUGH SUNDAY/... NEAR TERM: IFR/MVFR through tonight for all terminals. This afternoon KBGR and KBHB were seeing VFR as things improved but tstms will bring things to MVFR and then IFR. Could see some LIFR at times in the lower cigs. Winds will be light. For Wednesday, MVFR/IFR in the morning w/some improvement for KBGR and KBHB to VFR by the afternoon. Northern terminals will be MVFR through the afternoon. SHORT TERM: Wed night...VFR. Wind South 5 to 10 kts. Thu-Thu Night...MVFR possible in SHRA. Southwest wind around 10 kts. Fri...VFR. Sat...MVFR in -SHRA. Sun...VFR. && .MARINE... NEAR TERM: Dropped the SCA per coordination w/GYX w/winds and seas dropping off. Winds and seas will continue to slowly drop back overnight into Wed. Wind direction will be from the NNW tonight back to the NW on Wed w/speeds to 10-15 kts. Seas will average 4-5 ft tonight subsiding to 3-4 ft on Wed. SHORT TERM: No headlines expected although seas could approach 5 ft in advance of the approaching cold front Thursday and again on Saturday. && .CAR WATCHES/WARNINGS/ADVISORIES... ME...None. MARINE...None. && $$ Near Term...VJN Short Term...Duda Long Term...Duda Aviation...VJN/Duda Marine...VJN/Duda
Area Forecast Discussion
National Weather Service Green Bay WI
627 PM CDT Tue Sep 24 2019 Updated aviation portion for 00Z TAF issuance .SHORT TERM...Tonight and Wednesday Issued at 233 PM CDT Tue Sep 24 2019 The latest RAP analysis and satellite/radar imagery show a cold front moving into the northern Mississippi Valley early this afternoon. Outside of some rain over northern Minnesota, the front has been inactive across the region so far. After a cool morning, temps and dewpoints have been steadily rising through the day over Wisconsin, and some dewpoints approaching 65 degrees are showing up on observations over the southwest part of the state. This trend should continue through the rest of the afternoon as a 35 to 40 kt low level jet cranks up ahead of the front and advects deeper moisture to the northeast. Expectations remain that improving convective parameters will set the stage for rapid thunderstorm development from northern Iowa to western Wisconsin in the 21-00z time period. As those thunderstorms track east, severe thunderstorm potential is the main forecast concern. Tonight...The cold front will track east and across the region bringing the potential for severe weather and localized flooding. Convective parameters, with most unstable capes up to 1500 j/kg and effective shears of 30 to 40 kts, will likely peak this evening as the thunderstorms enter central and north-central WI around the 00-02z time period. Strengthening wind profiles with a low level jet around 50 kts, and 0-1 km/0-3 km helicities in the 200-300 range will make damaging winds the primary concern, with bowing segments possible. Large hail could also occur in the strongest storms. Given the high helicities, cannot rule out an isolated tornado as well. Instability is expected diminish relatively quickly through the evening, and HREF max reflectivity paintball show storms should be weakening as they move into northeast WI late in the evening into early overnight. Some risk that strong gusty winds and heavy rainfall could persist into northeast WI despite an overall weakening trend of the storms. Most storms should be exiting northeast WI during the 06-08z time period as winds turn to the west and remain breezy behind the front. Low temps will remain mild, and range from the mid 50s to low 60s across the region. Wednesday...The cold front is forecast to move into northern Lower Michigan by early Wednesday morning. But flattened upper troughing is expected to remain overhead through the day. Combined with 100-200 j/kg of instability that is anticipated to develop with the heat of the day, could see some showers or maybe a rumble of thunder develop during the afternoon, mostly over northern WI. West winds will be breezy with gusts to 30 mph possible. Highs ranging from the low 60s over the far north to low 70s over east- central WI. .LONG TERM...Wednesday Night Through Tuesday Issued at 233 PM CDT Tue Sep 24 2019 High pressure will track to the south of the area Wednesday night and Thursday, keeping the area dry with temperatures just below normal for this time of year. Rain chances return by the end of the work week as a low pressure system approaches the region from the west. After a brief break in precipitation early in the weekend, the unsettled pattern returns later in the weekend and into early next week as a series of low pressure systems bring several chances for additional rain showers and thunderstorms. && .AVIATION...for 00Z TAF Issuance Issued at 627 PM CDT Tue Sep 24 2019 A cold front will produce a line of showers and thunderstorms as it moves across the area tonight. MVFR conditions are expected with the arrival of the rain, with local IFR in thunderstorms. Low level wind shear is possible late this evening with south winds at 10 knots at the surface with southwest winds around 50 knots at 2000 ft agl. The cold front will exit the area early Wednesday, with gusty west winds and VFR conditions likely by noon. Good flying weather is generally expected Wednesday afternoon through Thursday. && .GRB WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SHORT TERM.....MPC LONG TERM......Kurimski AVIATION.......RDM
Area Forecast Discussion
National Weather Service Wichita KS
656 PM CDT Tue Sep 24 2019 .SHORT TERM...(This evening through Thursday night) Issued at 338 PM CDT Tue Sep 24 2019 Storms have began firing ahead of the surface cold front in an environment characterized by effective shear on the order of 30-40kt and moderate instability which should be supportive of organized, severe convection. Additionally, effective SRH of around 150 m2/s2 may tend to help in the development of rotating updrafts/supercell potential. Deep layer shear oriented perpendicular to the boundary should keep storms more discrete initially, although a mixed multicell/supercell mode is possible given the marginal shear, with storm mergers possible with time. The main threats look to be large hail and damaging wind gusts. Of note, hail up to 2" in diameter cannot be ruled out should storms remain more discrete and/or be able to develop sustained, rotating updrafts. Additionally, some enhanced stretching potential may exist in the vicinity of the cold front where steep low-level lapse rates and instability are maximized, with a tornado not out of the question. By this evening, storms may tend to weaken as they outrun the cold front and as the better large scale forcing shifts away from the area. Given all of the above, we still expect the potential for severe weather, but it remains a somewhat more conditional threat (ie. if storms can form, they will likely be severe). Martin Scattered elevated showers and storms may linger through the early morning hours tomorrow as warm moist advection looks slow to taper off. The NAM and RAP are the most generous with this idea while the GFS seems to shutdown the moisture transport more quickly. Models agree that the surface cold front will stall and stay draped along portions of south central and southeast KS throughout the day tomorrow. This stalled front and any residual outflow boundaries from overnight convection will provide a focus for renewed convection tomorrow evening and night. Along the front, areas of south central and southeast KS will destabilize with daytime heating and low 70s dewpoints progged again. A weakening CAP is progged mainly over southeast KS in the afternoon (albeit there remain some model discrepancies of which areas hold a strong cap vs become weakly capped). Any convective initiation in this unstable environment including MLCAPE values of 2,000 to 3,000 J/kg (RAP is the most generous) and modest mid level lapse rates of 6.5 C/km combined with marginal shear of 25-30kts would support a few strong to severe storms capable of one inch hail and wind gusts of 60 mph. Widely scattered elevated storms may develop later in the evening and overnight tomorrow mainly across areas of south central and southeast KS. 310 K isentropic upglide, subtle shortwaves embedded in the mid level flow, and increasing frontal convergence will combine with 2000J/kg or greater of MUCAPE and about 20-30kts of 1-6km bulk shear to support strong to marginally severe storms overnight. While there remains some discrepancies in the degree of moisture transport, a couple models show decent moisture transport running into the front which would increases the chance of convection (GFS is again quick to shut off moisture). Have kept modest pops in the forecast. This front will lift north on Thursday before our next decent cold front arrives on Friday. Butler .LONG TERM...(Friday through Tuesday) Issued at 338 PM CDT Tue Sep 24 2019 Mid level flow switches to SW`ly on Friday as a mid level shortwave moves over the region pushing a cold front through the Central Plains. At this time, severe storms look likely along and ahead of the cold front Friday afternoon and early evening. The front then stalls over the area for the weekend before lifting north of the area on Sunday which will bring continued chances of showers and storms. We lock in southwesterly flow toward the end of the forecast period as an upper ridge builds over the Ohio and Tennessee Valleys. This pattern will leave portions of Kansas unsettled with multiple chances of showers and storms to start out next week. Expect above normal temperatures Sunday and Monday with highs in the mid to upper 80s. Butler && .AVIATION...(For the 00Z TAFS through 00Z Wednesday evening) Issued at 641 PM CDT Tue Sep 24 2019 Challenge - Timing of thunderstorms Scattered thunderstorms are impacting south central Kansas at the moment. The timing of these storms with an eastward progression was the challenge given a southeast track. Thus the confidence was not there to put a prevailing group of TSRA for KHUT and KICT. These next six hours are the key for those sites as well as KGBD which has storms just to the south. KSLN has storms just to the north. There could be thunderstorms that impact KCNU in the morning. Again the confidence was to leave the wording as vicinity for now. A gradual wind shift is expected with a front that will move through central Kansas. Thus this was relayed accordingly in the TAF. Given the nature of the next six hours which are critical, please expect that amendments may be needed if there are changes in the current tracks of the storms. && .PRELIMINARY POINT TEMPS/POPS... Wichita-KICT 68 83 62 80 / 40 20 40 20 Hutchinson 65 81 59 79 / 40 10 30 20 Newton 66 81 60 78 / 40 10 40 20 ElDorado 68 82 62 78 / 30 20 50 30 Winfield-KWLD 69 85 63 81 / 30 20 50 20 Russell 61 81 56 79 / 20 0 20 10 Great Bend 61 80 57 79 / 40 0 20 10 Salina 63 80 57 79 / 40 10 20 20 McPherson 64 80 57 77 / 50 10 30 20 Coffeyville 69 85 65 81 / 30 30 60 30 Chanute 68 83 62 79 / 40 30 50 30 Iola 68 82 62 79 / 40 30 50 30 Parsons-KPPF 69 85 64 80 / 40 30 60 30 && .ICT WATCHES/WARNINGS/ADVISORIES... None. && $$ SHORT TERM...KMB/RM LONG TERM...KMB AVIATION...VJP
Area Forecast Discussion
National Weather Service Key West FL
1045 PM EDT Tue Sep 24 2019 .DISCUSSION... The 00z KEY sounding observed a record dry (for the date) PW value of 0.99". The boundary layer was capped by a strong subsidence inversion based near 4,300 feet and topped by extremely dry air. Even the near-surface air mass is uncommonly dry, with dewpoints running near 70F across the Keys this evening. So given the dry air mass and deep northeast flow, it is little surprise that we have been precip-free this evening. However, the GFS and recent HRRR runs show a few sprinkles developing during the early overnight hours over the Lower Keys along a wind shift boundary (land breeze induced from the mainland) that will settle southwest. These showers will amount to little more than sprinkles and will struggle to measure, if they develop at all. && .COASTAL FLOODING... Tidal anomalies (the difference between astronomical tide predictions and what is actually being observed) continue to run about one foot above predictions. This will lead to a resumption of minor coastal flooding around the time of the next high tide cycle on Wed morning. Through at least Wednesday, minor saltwater flooding of low elevation streets and lots is likely. Some storm drains will overflow and some seawalls and docks will be overtopped. Motorists should remember, persistent puddles around the times of high tide are almost certain to be saltwater. Wednesday morning`s high tides likely will be a few inches higher than Tuesday morning`s high tides. && .MARINE... Weak high pressure will remain situated across Florida. Through Wednesday, this will allow only light and gentle breezes to prevail. Gentle to moderate easterly breezes are then forecast from Wed night through Sunday. && .AVIATION... VFR conditions will prevail at both terminals. Dry air associated with high pressure will continue to limit almost all clouds. Winds will be light and variable overnight, returning to light northeast to east winds and remaining less than 10 knots. && .KEY WATCHES/WARNINGS/ADVISORIES... FL...Coastal Flood Advisory for FLZ077-078. GM...None. && $$ Public/Marine/Fire...Haner Aviation/Nowcasts....Chesser Data Collection......NB Visit us on the web at Follow us on Facebook and Twitter at:
Area Forecast Discussion...UPDATED
National Weather Service Chicago/Romeoville, IL
917 PM CDT Tue Sep 24 2019 .UPDATE... 915 PM CDT No change to the forecast details or primary message for the next 12-18 hours. Scattered early morning showers with possibly a couple storms will move across the area while experiencing a continued weakening trend as they do. The regional radar mosaic is aglow to our west this evening with convection from the U.P. of Michigan through the Kansas/Oklahoma border. The activity truly upstream from the CWA...that is near the IA/MN positioned on the leading edge of a 135+ kt jet sampled in eastern MT this evening. A leading edge wave, now convectively enhanced, is moving across western Wisconsin. The quicker prorogation of the front in this area, along with steering flow orientation has allowed storms to merge and propagate east or even a tad north of east (away from the CWA). Further southwest along the front into central and western Iowa, prorogation speed of the front has been slower, and convergence more limited. Just in the past hour convection has acquired some more segment/less discrete mode but forward speed remains sluggish. The overall mode along the upstream portion of the front is expected to remain in this semi-discrete to segmented mode given the shear vector orientation more perpendicular than not to the front, as well as weakening instability ahead of the front late tonight resulting in weakening and fragmentation of any linear activity. Tough to say exactly the coverage of activity late tonight, but feel the going message of 40 percent or so in northern Illinois and 20-30 percent in northwest Indiana after daybreak looks very reasonable. A couple HRRR runs have shown a split between these two upstream areas noted in the above paragraph continuing to grow and move over areas north of I-80. It`s probably unlikely to pan out completely dry over that much of the area likely those couples run, as there is ample moisture transport in a few hour window ahead of the front and still fairly good forcing for ascent. The severe weather threat with any storms should ease across the Upper Midwest. High confidence exists in that because of the lack of any widespread elevated mixed layer ahead of the front (as noted on the 00Z DVN sounding) that would help sustain cold frontal deep convection during the longer nights this late in the warm season. Otherwise just southerly winds picking up late tonight into the morning, well covered in the going forecast. MTF && .SHORT TERM... 240 PM CDT Through Wednesday night... The only noteworthy forecast concern through Wednesday night is the threat for showers and a few thunderstorms late tonight into Wednesday morning ahead of a cold front. A pleasant and breezy late afternoon and early evening is in store prior to to any showers moving into the area late tonight. Large scale forcing will increase ahead of the cold front late this evening into the overnight, with stout warm advection aloft in response to a strong 40+ kt low level jet at ~1500 ft to 3000 ft AGL. There should be sufficient forcing for scattered type coverage shower activity to break out and shift west to east or west-northwest to east-southeast across the area through mid Wednesday morning. However, any embedded thunderstorms are of lower confidence due to left-over dry air in 800-700 mb layer, which may make it tough to tap into relatively steep lapse rates above 650 mb. Higher chance for thunder, while still lower confidence, appears to be along and west of I-39 where slightly higher MUCAPE with minimal capping may be realized. Mitigating factors above for thunderstorm coverage will likely also preclude a risk for any stronger storms. Temperatures tonight will be propped up by breezy to at times gusty south- southwest winds. The cold front will sweep across the area through Wednesday morning, flipping winds to west/west-northwest, ending any lingering showers east/southeast as drier air filters back in. Air mass behind the front will not be much cooler, so along with mild start to the today, high temps should easy tag about 75-80 degrees. Surface ridging from high pressure off to the west will nose in on Wednesday night, dropping winds enough for good radiational cooling. Likely keeping temps from dropping much more though is cloud cover from a moisture starved but stout short-wave trough that will eject across the region. Most locations should see lows in the lower-mid 50s, except upper 50s in/near Chicago. Castro && .LONG TERM... 226 PM CDT Thursday through Tuesday... High pressure will be over the area Thursday providing a temporary relief from the late (almost out of) season warmth and humidity. The reprieve looks to be short lived as the high is progged to push east of the area and allow for a deep southerly flow to develop and re-advect the abnormally moist air mass back into the region late in the week. Concurrently, a shortwave trough and associated sfc cyclone tracking across the northern tier of states will push a front southward into the lower Great Lakes region. As the front pushes south it should slow as it become aligned with the mid-upper level flow and runs into the anomalous southeastern U.S. upper ridge. The slow movement of the front combined with abnormally moist air mass in place will certainly warrant attention for potential heavy rainfall late Thursday night through Friday night time frame. The severe t-storm threat is a bit more nebulous as lapse rates will likely be weak and widespread cloud cover/precip likely limiting destabilization. However, given seasonably strong flow aloft and respectable wind shear, will have to watch for any local pockets of clearing and greater stabilization for any potential localized severe threat Friday afternoon/early evening. GFS and ECMWF suggest a brief shot of cooler and less humid conditions Saturday into early Sunday before warmth and moisture surge back north as southeastern upper ridge is progged to significantly amplify heading into early next week. There some threat of showers/storms associated with the northward surging moisture/warmth. At this juncture, operational runs of GFS and ECMWF would suggest the upper ridge will build far enough north that we could see precip chances decrease early next week with just abnormally warm and humid conditions. - Izzi && .AVIATION... For the 00Z TAFs... Main concerns for the period will be gusty swly winds overnight and then shifting wly tomorrow morning and a chance for some scattered showers early tomorrow morning. Gusty swly winds will persist through the night as a cold front/trough move slowly across the Upper/Middle Mississippi Valley. Latest forecast soundings suggest that the boundary layer will remain well mixed through the night, allowing some of the stronger winds aloft to mix down. A strong swly-wly low-level jet of 35-45kt at the top of the boundary layer could provide enough wind veering and speed sheer to set up LLWS, though with gusty winds at the surface, conditions would likely be more of a low- level turbulence situation than true LLWS. The cold front is expected to cross the area tomorrow morning, bring sct shra and the wind shift to wly. there is a chance for lowering cigs/vis invof any shra, but the latest guidance is suggesting that pcpn coverage with the front will become more sparse as it crosses nrn IL, so have gone with a short tempo for pcpn. Increasing low level moisture could also yield a period of cu/stratocu in the 2-2.5 kft range. While there is a chance that mvfr cigs could develop, the more sparse pcpn coverage lends to lower confidence in mvfr cigs as a prevailing or tempo condition. SHRA activity by an hour or two. As the cold front shifts across the area tomorrow morning, winds will veer to wly-wnwly with gusts in the 20-25kt range. && .LOT WATCHES/WARNINGS/ADVISORIES... IL...None. IN...None. LM...Small Craft Advisory...IL nearshore waters until 4 PM Wednesday. Small Craft Advisory...IN nearshore waters until 4 PM Wednesday. && $$ VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE) FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT: WWW.FACEBOOK.COM/NWSCHICAGO WWW.TWITTER.COM/NWSCHICAGO WWW.YOUTUBE.COM/NWSCHICAGO