Forecast Discussions mentioning any of "ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 10/15/17


Area Forecast Discussion
National Weather Service Grand Rapids MI
953 PM EDT Sat Oct 14 2017 LATEST UPDATE... Mesoscale Discussion .MESOSCALE DISCUSSION... Issued at 953 PM EDT Sat Oct 14 2017 Have extended the areal flood warning northward to include Allegan, Barry, and Eaton counties. Radar currently shows an impressive feed of showers and thunderstorms coming into this region from the Chicago area. This convection was recently able to achieve radar estimated precipitation rates well in excess of an inch per hour just north of metro Chicago. It appears that in general, DualPol / MRMS QPE values correlate best to rainfall reports we have received thus far. These radar estimates show a maximum just south of Paw Paw and Mattawan, and we have recently received a credible report of 5.9" near Mattawan. This suggests that even the DualPol/MRMS QPE might be a bit low. Aircraft soundings out of Chicago imply elevated convection rooted around the 850mb level. This would limit the wind threat for our area in spite of impressive looking bow structures seen on the LOT radar. There is little to suggest the instability plume will work its way much further east than it already has. && .SYNOPSIS... Issued at 327 PM EDT Sat Oct 14 2017 A strong fall storm system will affect the area through Sunday. This storm will bring a good deal of rain to the whole area through tonight. Some of this rain will be accompanied by embedded storms, some of which could become locally strong to severe. Winds and localized flooding will be the main threats. Strong winds will develop late tonight and last through much of Sunday as colder air flows into the area. Once lingering showers end on Sunday night, much of the upcoming week looks dry and increasingly warmer. Monday will still be a bit cool after some possible frost across Central Lower Sunday night. Highs could reach up into the 70s by the end of the week. && .SHORT TERM...(This evening through Monday night) Issued at 327 PM EDT Sat Oct 14 2017 No major changes for the forecast this afternoon as the table has been well set for all of the weather expected through Sunday. The flood watch still looks well justified, as does the wind advisory for late tonight and on Sunday. We are thinking that we have three organized waves of showers/storms that will work through the area between now and Sunday morning when the front moves through. The first is coming into the CWFA right now, the next one is south of the Quad Cities, and the third and strongest one is over NW MO and SW IA. The first two are expected to bring mainly heavy rainfall to the area with only some embedded storms. We are watching the track of these, as heavy rain has already fallen from Van Buren county to Calhoun county. If these areas see additional heavier rain, we may have to upgrade to a flood warning there. We will be watching any other areas for possible advisories/warnings if too much training over one area occurs. The third wave continues to be our main concern for tonight. This looks to arrive mid-late evening, and last into the early morning hours on Sunday. This wave is the one that is being fueled by the RRQ of the strengthening upper jet to our NW, and the resulting 60+ knot low level jet zipping up through here. Instability is limited in our area to as much as 400-500 j/kg of MU Cape. The concern is that with the strong wind fields, any downdraft reaching the sfc could bring down the 50-60 knots winds only 1500-3000 ft up. Then once the convection moves out, the concern focuses to the frontal passage, and the strong synoptic winds that will ensue. Models are fairly similar in showing the ability to mix 45 knots down from late tonight and lasting through much of Sunday. There will be a few showers on Sunday with the wind. The showers could be enhanced a bit along the lakeshore with land/lake delta t/s in the mid to upper teens C. The showers will then end late Sunday night as ridging builds in. Inland areas could see some patchy frost up in the normally colder locations toward Mt. Pleasant and Clare. After Sunday night, the weather quiets down. We will remain rather cool on Mon in comparison to the recent weeks with highs only in the 50s. .LONG TERM...(Tuesday through Saturday) Issued at 327 PM EDT Sat Oct 14 2017 A steady warmup is on tap for the middle and latter portion of next week as upper level heights build and H850 warm air advection settles in. We`re looking at the warmest days likely being toward the end of the week and weekend as H500 heights surge back into the 580s dm. H850 flow will advect temps in the 14C to 16C range, or possibly higher, if the Ohio Valley ridge develops as advertised. This equates to a few things for our region. First, if this pattern materializes, high temperatures late in the week and weekend may overachieve given the anomalous pattern and the challenges that numerical models can have resolving the degree of warmth. For now, we have low 70s featured from Thursday through Saturday. Actual highs may be several degrees warmer. With average highs around 60 degrees this time of year, we are expecting temperatures to be 10 to 15 degrees above normal by late next week. Secondly, we will likely be precipitation free through Saturday with a good amount of sunshine for the region. It should be a quiet stretch. && .AVIATION...(For the 00Z TAFS through 00Z Sunday evening) Issued at 810 PM EDT Sat Oct 14 2017 Some IFR will still be possible for the I-96 TAF sites early this evening, but then MVFR will be predominate. Winds will be increasing and that will help hold ceilings and vsbys up as we work through the overnight. A round of thunderstorms is expected to roll through, mainly between 02Z and 06Z and may impact all TAF sites. After this departs much of the TAFs should remain VFR. Southwest winds will begin gusts to around 30 knots after 06Z and continue much of Sunday. These winds should finally simmer down around 22Z. && .MARINE... Issued at 327 PM EDT Sat Oct 14 2017 No changes needed to the marine headlines with this forecast package. The latest data continues to support solid gales for the waters this evening ahead of the front, through Sunday with the strong cold air advection. The chance for Storm Force winds is not zero, but looks way too low for now to consider an upgrade at this time. && .HYDROLOGY... Issued at 1217 PM EDT Sat Oct 14 2017 Multiple waves of convection, some of it training, are expected to provide the entire area with a soaking rainfall by Sunday morning. PW values will be at or above 1.5 inches for the entire day, which are about as high as they can get this time of year (based on DTX sounding climatology). With elevated instability being maintained through a thick layer of this deep atmospheric moisture, rain production will be efficient in convection. Mesoscale models have been consistent with providing 1 to 3 inches of rain to the area, but have reasonable disagreement on where the axis of heaviest rain will fall. There could be two heavy rain swaths that end up falling, as convection this morning and afternoon will focus south of I-96, then convection will tend to blossom north of I-96 later this evening and tonight. Several runs of the HRRRX have shown the potential for isolated 4 to 6 inch totals. Already southern Van Buren and Kalamazoo counties are approaching 2.0 inches in the past 6 hours. A flood watch has been issued through late Saturday night. River flood advisories or warnings may be needed if heavy rain falls in flood-prone drainage basins. With basin-average totals between 2 to 3 inches plugged into river models in the lower Kalamazoo and upper Grand basins, several river points climb above bankfull (the usual suspects: Holt, Eagle, Maple Rapids, Ionia, Hastings). && .GRR WATCHES/WARNINGS/ADVISORIES... MI...Flood Watch until 4 AM EDT Sunday for MIZ043>046-050>052-056>059- 064>067-071>073. Wind Advisory from 2 AM to 8 PM EDT Sunday for MIZ037>040- 043>046-050>052-056>059-064>067-071>074. LM...Gale Warning until 8 PM EDT Sunday for LMZ844>849. && $$ MESOSCALE...TJT SYNOPSIS...NJJ SHORT TERM...NJJ LONG TERM...Hoving AVIATION...JK HYDROLOGY...CAS MARINE...NJJ
Area Forecast Discussion
National Weather Service San Diego CA
813 PM PDT Sat Oct 14 2017 .SYNOPSIS... High pressure aloft over Southern California will bring a warming trend through Monday, when temperatures will be in the nineties from near the coast to the mountains. Surface high pressure over the Great Basin will bring periods of gusty northeast winds near the coastal foothills and below passes and canyons...mostly through Sunday morning. Weak onshore flow will return on Tuesday and strengthen on Thursday and Friday. Slow cooling will begin on Tuesday and Wednesday with greater cooling on Thursday and Friday along with a chance of precipitation and periods of stronger and gusty west winds for the mountains and deserts. && .DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE... SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO COUNTIES... ...Update... Extremely low dewpoints lie across inland locales away from the sea breeze, which has made it into western portions of the Inland Empire. Dewpoints where the sea breeze has passed are in the 50s and 60s, while ahead of the sea breeze, insanely low dewpoints in the single digits and teens prevail. In the mountains, dewpoints are even lower in the -10s to -30s! The San Diego sounding this evening shows -20s to -30F dewpoint at the level of the ob (~8000FT), so looks reasonable. The extremely dry air will remain in place on Sunday. Dewpoints are 60-65F along the coast with ACARS data showing a surface inversion developing. This presents the potential of patchy fog developing along the coast, so have added this to the forecast. Confidence is very low on dense fog. Fog could not form at all, but given a possibility, patchy fog mention near the coast is prudent. ...Previous Discussion (Issued at 152 PM PDT Sat Oct 14 2017)... Mostly clear this afternoon, except for a few high clouds. Sfc pressure gradients are now -11.3 mb SAN-TPH, and the offshore winds are surfacing in the I.E. So far today, the strongest gust reported is 45 mph at Highland Springs last hour. Highland Springs is at 2233 ft, a few miles south of Beaumont. The driest conditions west of the mtns are in the northern I.E. where relative humidities are less than 10 percent. A ridge of high pressure aloft will strengthen over Southern California into Monday with surface high pressure over the Great Basin. This combination will bring a warming trend with very dry conditions and periods of gusty northeast to east winds. The offshore winds will continue through Sunday morning before weakening Sunday Afternoon. The strongest winds will be near the coastal foothills and below passes and canyons where gusts to 45 mph will be possible. Monday will likely be the warmest day, with 90+ degree temps from within 1-2 miles of the coast inland to the foothills. The very warmest locations for inland coastal areas into the western valleys could have high temperatures near 100 on Monday. For Tuesday and Wednesday...the high pressure aloft over Southern California will begin to weaken in response to a low pressure trough moving in from the northwest. This will bring a return of onshore flow which slowly strengthens. Temperatures will begin to decrease near the coast and spread inland with night and morning coastal low clouds and fog returning and spreading farther inland later in the week. For Thursday and Friday...Temperatures continue to decrease and onshore flow strengthens as the approaching trough deepens off the California coast. The increasing onshore flow could bring periods of gusty west winds to the mtns and adjacent desert areas. Medium-range deterministic models show a chance for some precip on Fri. This is dependent on whether or not moisture from the sub- tropics gets entrained as the trough absorbs an upper level low currently located at about 35N 140W. Chances of precip should end next Saturday as the trough axis moves east. && .AVIATION... 150300Z...Areas of east to northeast winds 15-25 KT will continue through 18Z Sunday with local surface gusts 30-40 KT through/below passes and canyons of the San Bernardino and Riverside County Mountains and Santa Ana Mountains producing MDT-STG UDDFS and LLWS over and west of the mtns, including near KONT and KSBD. Winds will be mostly below 25 KT after 18Z Sunday. Near the coast, there is a small chance of fog with visibilities below 1 mile 05Z-13Z Sun. This could occur near KSAN and KCRQ though confidence is low. Otherwise, skies will be clear with unrestricted vis through Sun evening. && .MARINE... No hazardous marine weather is expected through Thursday. && .FIRE WEATHER... High pressure aloft will strengthen over Southern California bringing a warming trend through Monday. Mostly weak offshore flow will continue into Sunday. Winds will then weaken late Sunday into Monday. Lowest daytime humidities will be 5 to 10 percent each afternoon through Monday...with Sunday being the driest day. Overnight recovery will be poorest near the coastal foothills where mixing from winds continues overnight. Periods of gusty northeast to east winds near the coastal foothills and below passes and canyons will continue at times through Sunday morning. The stronger winds are expected to be in the Inland Empire below the Cajon and Banning Passes and near the coastal foothills of the Santa Ana Mountains. The strongest gusts will be mostly around 45 mph. && .SKYWARN... Skywarn activation is not requested. However weather spotters are encouraged to report significant weather conditions. && .SGX WATCHES/WARNINGS/ADVISORIES... CA...Red Flag Warning until noon PDT Sunday for Orange County Inland Areas-San Bernardino County Mountains-Including The Mountain Top And Front Country Ranger Districts Of The San Bernardino National Forest-San Bernardino and Riverside County Valleys -The Inland Empire-Santa Ana Mountains- Including The Trabuco Ranger District of the Cleveland National Forest. PZ...NONE. && $$ PUBLIC...Gregoria (Update)/PG(Previous Discussion) AVIATION/MARINE...Maxwell