Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 09/04/19

Area Forecast Discussion
National Weather Service Gaylord MI
1145 PM EDT Tue Sep 3 2019 .UPDATE... Issued at 1013 PM EDT Tue Sep 3 2019 Low pressure center has pushed east into SE Ontario late this evening...with the associated cold front now extending from NE Lower Michigan to the Wisconsin/Illinois border. Last vestiges of convection have pushed off shore into Northern Lake Huron. A look at upstream satellite...radar and surface obs indicated a large area of low clouds and scattered light shower activity rotating into the Western Great Lakes region in the wake of this system. Much of our CWA is currently experiencing a temporary clearing in between the front and this wrap-around moisture. Expect these low clouds and scattered light showers will slide into our CWA overnight. Going forecast handles this no major changes needed to the near term forecast. CAA behind the front will be offset by increasing low clouds. Still expect overnight lows in the upper 40s to lower 50s. && .NEAR TERM...(Through Tonight) Issued at 311 PM EDT Tue Sep 3 2019 ...Breezy Evening Diminishing Overnight... High Impact Weather Potential...Thunderstorms sure, but severe weather, well there`s a chance. Pattern Synopsis/Forecast...Sfc low over W Upper This afternoon, with a warm front over N lower and a cold front along the Lake Michigan shoreline of Wisconsin. The last of the warm front thunderstorms is making its way out of E Upper near ANJ, at the moment with showers trailing across the warm sector. Thunderstorms are beginning to break out along the cold front along the Wisconsin shoreline. These showers and thunderstorms will move across Lake Michigan and into portions of NW Lower and cross the forecast area, between 00z and 03z/Wed. Winds will remain gusty this afternoon, and then veer NW and remain gusty until about 06z/Wed, when the winds will diminish overnight. 850 mb temperatures will cool overnight to around +5C with 850 mb moisture, will expect another round of rain showers, as the LE rain machine gets going for a short period of time. Primary Forecast Concerns...Severe potential for the rest of the afternoon and early evening. 18z/Tue upper air release (in support of Dorian) showing sfc based CAPE around 750J/kg, while the KGRB is around 2500 J/kg. The main difference is the cloud cover is still sticking into most of NW/NC lower attm. Latest satellite images showing clearing line begin to move in from Lake Michigan. Looking at the more conservative MLCAPE here it is 76J/kg, while while GRB is 1000J/KG. So the main issue will be if the clouds continue to move east, while the sunshine destabilize the boundary layer enough to get anything going. HRRR (18z) is showing that by 21z showers and thunderstorms should make it across the region, from Wisconsin, and with the LFQ of the500 mb Jet over us, will have to watch. but thinking that most of the region will have general thunder as the cloud cover continues to keep the boundary from destabilizing to its potential. && .SHORT TERM...(Wednesday through Friday) Issued at 311 PM EDT Tue Sep 3 2019 ...Cooler Wednesday; chances for showers Friday... High Impact Weather...None is expected. Primary Forecast Concerns...Pops early Wed and Thu night/Fri. Much cooler and drier air continues to advect in Wednesday. Over lake instability (the difference between 850 mb and lake temperatures is in the mid teens) would normally be sufficient for lake effect but this will be offset by the drier air (850-700 mb relative humidity falling from about 50 percent at 12z to 25 percent at 15z). The drier air should win out here squelching any lake effect rain bands in the morning (slight chance pops through 15z). High pressure then builds in Wednesday afternoon and holds through the day Thursday yielding rain free conditions. An upper level trough and associated surface cold front will then bring chances for showers Thursday night into Friday. Temperatures will be several degrees below normal Wednesday before rebounding to close to normal Thursday and Friday. .LONG TERM...(Friday night through Tuesday) Issued at 311 PM EDT Tue Sep 3 2019 ...Cool over the weekend then moderating temperatures... High Impact Weather...None is expected. West northwest flow aloft is expected to lead to cool but precipitation free conditions this weekend. Increasing warm air advection should then lead to moderating temperatures and chances for showers early next week. && .AVIATION...(For the 06Z TAFS through 06Z Wednesday night) Issued at 1145 PM EDT Tue Sep 3 2019 Low clouds and MVFR cigs will move into Northern Michigan overnight into early Wednesday morning behind the cold front. Scattered showers are also expected overnight into early Wednesday...but chances are too small to include in the TAF forecast for now. Winds will remain from the NW at 15 to 25 kts thru Wednesday. && .MARINE... Issued at 311 PM EDT Tue Sep 3 2019 tonight through Thursday...Wind will continue to be at gale force into the evening, as the cold front in Wisconsin crosses Lake Michigan, and Whitefish Bay. Winds will diminish to 10-15 knots after 06z/Wed. Lake Huron may take a little longer. High pressure then builds into the region and wind continue to be variable at less than 10 knots over most of the region. && .APX WATCHES/WARNINGS/ADVISORIES... MI...BEACH HAZARDS STATEMENT through Wednesday afternoon for MIZ016>018-020-021-024-025-030-031-036-042-099. LH...SMALL CRAFT ADVISORY until 5 PM EDT Wednesday for LHZ345>349. LM...BEACH HAZARDS STATEMENT through Wednesday afternoon for LMZ346. SMALL CRAFT ADVISORY until 5 PM EDT Wednesday for LMZ323-341-342- 344>346. LS...SMALL CRAFT ADVISORY until 5 PM EDT Wednesday for LSZ321-322. && $$ UPDATE...MR NEAR TERM...JL SHORT TERM...AS LONG TERM...AS AVIATION...MR MARINE...JL
Area Forecast Discussion
National Weather Service Cleveland OH
1023 PM EDT Tue Sep 3 2019 .SYNOPSIS... Low pressure over the upper Midwest will continue east across the northern Great Lakes today. This low will extend a cold front across the region on Wednesday. High pressure will build in behind the cold front on Wednesday night and will remain in place through Friday. && .NEAR TERM /THROUGH WEDNESDAY NIGHT/... Update...Wind chills went rogue on zone product with -120 chills but did correct, sorry. Otherwise radar now showing thunderstorms developing in southern lower MI, southwest into central IL. Expect this activity to increase over the next couple hours as a strong short wave interacts with favorable low level instability with mixed layer capes around 3000j/kg to our west. Adjusted pops based at the time mainly ion the HRRR which did show this development moving east across the area although after 06Z or so expect activity to thin and weaken. SPC has indicated a watch is possible for isolated severe threat. Original...A surface low was located just north of Michigan with a cold front extending southwest into Illinois. This cold front is forecast to rapidly move southeast, arriving in northwest Ohio later this evening. Showers and thunderstorms will move into the area just ahead of the cold front, now looking to enter the Toledo area around 9 or 10 pm, moving southeast through the area around 3 to 5 am. This timing is slightly slower compared to earlier forecasts, but the short term high res models are in good agreement so forecast confidence is pretty high. Areas generally along and west of I-71 are in a slight risk for severe weather while areas east are in a marginal risk of severe weather. Wind and hail are the main concerns, however an isolated tornado can`t be ruled out especially for northwest Ohio. Please see for additional information. Dry weather is expected by around noon tomorrow for the entire area as surface high pressure begins to build east over Ohio. Much cooler weather is expected tomorrow across the region as a result of the cold front expected tonight. Temperatures tomorrow afternoon are expected to top out generally in upper 60s to low 70s, about 10 to 15 degrees cooler compared to today. Temperatures tomorrow are expected to be between 5 and 10 degrees cooler than normal values for the beginning of September. Little change in the weather pattern through Wednesday night as surface high pressure remains the dominant weather feature. && .SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/... A relatively quiet end of the week expected as high pressure builds east across the Great Lakes region into New England/Quebec by Friday. A shortwave and attendant surface low will dive southeast through the Great Lakes on Friday, with the mid/upper wave weakening through the Great Lakes and the surface low weakening and lingering across the central part of the Great Lakes through Friday night. The models are showing some inconsistency with the strength and timing of the system, but most of the area should be dry during this period. A stray shower is possible downstream of the lake across northeast OH and northwest PA, but only warrants a slight chance at this point. Highs in the low 70s Thursday will warm into the mid 70s Friday. && .LONG TERM /SATURDAY THROUGH TUESDAY/... A low confidence long term period is forecast with models solution differences. A cold front will sink south across the Great Lakes Saturday night into Sunday as a surface low swing around James Bay. A stray diurnally driven shower cannot be ruled out Saturday across the snow belt with the lingering trough in the region ahead of the front. Most of the guidance is suggesting a dry fropa Saturday night into Sunday. The ECMWF suggest the front stalling out across the southern part of the area, with a shortwave bringing precip chances into the area Sunday night through Monday. The rest of the guidance clears the area of the front and keeps precip chances south and west of the area. Have opted for slight chance pops Sunday night, with a dry forecast Monday and beyond. Near normal temps Saturday will cool behind the front on Sunday, with moderating temps through Tuesday, when 80s return to the forecast. && .AVIATION /00Z Wednesday THROUGH Sunday/... Outflow boundaries to our west have initiated convection across southern MI and northern Indiana this afternoon but so far this activity has not really taken off. HRRR guidance, which has missed the initial convection, still develops convection to our northwest ahead of the approaching cold front within the next few hours and then drops it ese across the area through the early overnight. Will keep conditions VFR across the area through the evening but with convection will drop conditions, at this point, to MVFR. IFR however will be possible and with development any update may contain lower conditions. VFR expected Wednesday. .OUTLOOK...Non-VFR possible Friday night. && .MARINE... Southerly winds will increase through this evening across the lake as a cold front sinks southeast through the central Lakes. A line of storms is expected to cross the lake this evening just ahead of the front, with the front pushing across the lake overnight and moving east of the lake by Wednesday morning. Have left the headlines in tact, although winds may not ramp up to near small craft criteria until closer to 00Z. Winds will quickly shift to the west behind the storms, then increasing out of the southwest for a few hours overnight before the frontal passage. Winds will become northwest across the lake by Wednesday morning. Winds will slowly veer northerly Wedneday night to northeasterly Thursday as high pressure builds across the Great Lakes. Another weak front will cross the lake on Saturday. && .CLE WATCHES/WARNINGS/ADVISORIES... OH...Beach Hazards Statement from 5 AM EDT Wednesday through Wednesday morning for OHZ011-012-089. PA...Beach Hazards Statement from 5 AM EDT Wednesday through Wednesday morning for PAZ001. MARINE...Small Craft Advisory until noon EDT Wednesday for LEZ146>149. Small Craft Advisory until 5 AM EDT Wednesday for LEZ142>145. && $$ SYNOPSIS...Riley NEAR TERM...TK/Riley SHORT TERM...Greenawalt LONG TERM...Greenawalt AVIATION...TK MARINE...Greenawalt
Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
928 PM EDT Tue Sep 3 2019 .UPDATE... Attention this evening remains centered on the thunderstorm potential ahead of 925-850mb cold front that is now pushing onshore across far western Lower Michigan. 00Z KDTX raob highlighted the environment well with a midlevel capping inversion at 6.0 kft agl and very steep 800-600mb lapse rates. Sounding did capture lower quality boundary layer moisture that corresponds to surface dewpoints that have struggled to even hit the mid 60s. No surprise then with a somewhat slower than expected development of shower and thunderstorm activity given combination of lower boundary layer moisture and high CIN between 3.0-6.0 kft agl. HREF output places a tongue of ML instability from SW Lower Michigan to the northeast into sections of the northwest cwa that is corroborated by this evening`s RAP based mesosanalysis. The thunderstorm in Clare Co. was on the apex of this instability axis while the shower/elevated thunderstorm activity from Lansing eastward through Shiawassee/Genesee counties has been on the eastern flank. HREF solution shows that peak of instability locally will last through 02Z before shrinking/withering away with the loss of daytime heating. A strongly sheared environment remains in place with 0-3km SRH in excess of 350 m2/s2 and environmental wind of 50 knots at 2750 ft agl, see 00Z KDTX raob. Given this shear and steep midlevel lapse rates the potential still exists for strong to severe thunderstorm development before midnight. Will likely see convective updrafts weaken as the activity pushes eastward away from the main instability axis. This suggests less of a strong thunderstorm potential east and north of I 75. Low level equivalent potential temperature progs and HREF output shows strong to severe thunderstorm potential ending quickly by 4Z. && .PREV DISCUSSION... Issued at 819 PM EDT Tue Sep 3 2019 AVIATION... Strong kinematic field and resultant instability advection spreading south of strong surface low pressure system over western Lake Superior will bring a period of thunderstorm activity to Southeast Michigan in the 00-04Z timeframe. Initial thunderstorm activity developed along the front flank of 900-700mb theta e advection that will exit the forecast area by the start of the 00Z taf period. Model soundings show a stout capping inversion for a brief moment this evening before midlevel dry air punches into the cwa and steepens lapse rates aloft. The focus for the nearterm will shift to the potential for strong to possibly severe thunderstorms along the 950-800mb cold front that will impact the area before 04Z. Orientation of the trough supports similar timing for all the taf sites. Strong to severe wind gusts with large hail will be possible with thunderstorm activity this evening. Abrupt windshift to the west northwest, 290-300, expected around 05-06Z. Wednesday forecast soundings showing saturation remaining trapped below midlevel subsidence inversion. Prefer BKN030 cigs Wednesday morning transitioning to BKN050 for the afternoon. Northwest winds of 10 to 20 knots. For DTW...Timing for convection this evening remains centered on 01- 04z with strong to severe storms possible. Abrupt windshift to the northwest at approximately 06Z. DTW THRESHOLD PROBABILITIES... * Moderate for cigs aob 5000 ft late this evening, and again Wednesday morning. * Moderate for thunderstorms this evening with the most likely timing around 01-04z. PREV DISCUSSION... Issued at 337 PM EDT Tue Sep 3 2019 DISCUSSION... A high degree of effective bulk shear (60 KTS) will present a severe threat this evening. Upper level jet core (90 knots at 250 MB) tracking through northern Lower Michigan/north half of Lake Huron presenting a window of right entrance forcing over southeast Michigan around 00z, as a strong cold front tracks through this evening, with the seasonably strong low pressure system (aob 1000 MB) tracking into northeastern Ontario. Southwest winds gusting 35 mph this afternoon within the boundary layer gives a glimpse of the strong wind fields. Despite the limited destabilization over southeast Michigan thus far, seeing surface dew pts around 70 degrees over southeastern Wisconsin and good instability (MLcapes 2000+ J/KG), with pocket of steep mid level lapse rates (8 C/km) noted over northern Illinois. Latest RAP suggests this instability and steeper lapse rates will advect/work its way into southern Lower Michigan, with SBCAPES increasing to between 2000-2500 J/kg over the CWA during the mid evening hours (8- 10 PM). With 0-1 KM bulk shear 30+ knots, cells will have a tendency to rotate supporting embedded supercells capable of producing large hail, damaging winds, and even possible tornadoes before the front clears the State around/shortly after Midnight. Right now, the warm layer/cap at 750 MB (temp 12-14 C) is the biggest concern of the forecast going astray (limited activity with the front), but is expected to cool/erode as the forcing kicks in. Cold advection overnight through the day tomorrow, as 850 MB temps lower into the high single numbers (Celsius), holding maxes predominately in the lower 70s, as there will likely be a stratus deck trapped underneath the stout subsidence inversion around 850 MB. The inversion height is forecasted to lower Wednesday evening, which suggests skies will clear out as surface high (1023 MB) builds over southeast Michigan. Low temperatures in the 40s seems reasonable with the good radiating conditions expected, outside of the urban heat island of Detroit where temps hold in lower 50s. It is possible there may be enough lingering surface moisture to support some fog, but will see how well we dry out tomorrow before introducing. Still under the influence of upper level northwest confluence flow on Thursday, leading to dry and seasonably cool conditions. Passage of an upper-level trough and embedded PV anomaly in conjunction with slightly favorable jet streak dynamics, as the nose of a weak upper-level jet pushes across SE MI from the Midwest, will bring the chance for rain showers across the region Friday morning and afternoon. As a result, have increased rain chances slightly during this time frame to account for the more favorable dynamics. Otherwise, upper-level flow to turn more zonal as surface high pressure expands from the Midwest into the Ohio Valley to finish off the week. This will bring dry weather and relatively little change to day-to-day highs and lows Friday and Saturday, where slightly below normal values with hold -- Highs in the 70s and lows in the 50s. The passage of a weak cold front will then move through on Sunday, reducing temperatures slightly down into the 60s to lower 70s for a high and possibly even down into the 40s for a low temperature leading into Monday. This frontal boundary that is pushing south is set to settle across the Ohio Valley which will set up a a nice baroclinic zone, which may be the focal point for ongoing precipitation due to overruning along the front. At this time, rain and thunderstorm chances are expected to take place just south of the Michigan border, however, any slightly deviation from the projected model runs to the north could bring much higher (and extended period) precipitation chances to southern Michigan. Surface low and a weakening upper-level shortwave is projected to travel east across the northern Plains Monday into Tuesday and in turn will lift the stalled frontal boundary north across SE MI. This will be the next chance for a potential warm up in addition to rain and thunderstorm chances. MARINE... Seasonably strong low pressure is moving eastward across Lake Superior with a tightened pressure gradient set up across the central Great Lakes. Strong south and southwest winds will continue through this afternoon, weakening slightly this evening before the associated strong cold front approaches. Northwest winds then strengthen tonight after frontal passage with northwest gales expected late tonight through Wednesday morning over central and northern Lake Huron, where a Gale Warning remains in effect. Small Craft Advisories also continue tonight into Wednesday morning for the nearshore zones as winds in excess of 25 kt and increased wave action create hazardous marine conditions. Tonight`s front will also bring numerous showers and storms, some of which may be strong to severe. Storms will move out by early Wednesday morning. Winds begin to weaken late in the morning as high pressure moves into the western Great Lakes. Improved marine conditions will persist into the late week as this high moves overhead. HYDROLOGY... Numerous showers and thunderstorms are expected this evening and tonight ahead of and along a strong cold front. Storms are expected to be progressive and move west to east at about 45 mph and thus will likely not linger over one area, but precipitable water values reaching and possibly exceeding 1.50 inches will result in relatively brief but heavy downpours. Rainfall totals of a quarter to three quarters of an inch will be possible before the front clears the area by around 2am. As is usually the case with thunderstorms, total precipitation amounts will likely show a high variability across the area. The potential for flooding will be equally variable and limited to ponding of water on roads and in poor drainage areas. && .DTX WATCHES/WARNINGS/ADVISORIES... MI...Lakeshore Flood Warning until 4 AM EDT Wednesday for MIZ063-070. Lake Huron...Small Craft Advisory until 4 PM EDT Wednesday for LHZ441>443. Gale Warning until 11 AM EDT Wednesday for LHZ361>363. Small Craft Advisory until 10 AM EDT Wednesday for LHZ421-422. Lake St Clair...Small Craft Advisory until 4 AM EDT Wednesday for LCZ460. Michigan waters of Lake Erie...Small Craft Advisory until 4 AM EDT Wednesday for LEZ444. && $$ UPDATE.......CB AVIATION.....CB DISCUSSION...SF/AM MARINE.......TF HYDROLOGY....TF You can obtain your latest National Weather Service forecasts online at
Area Forecast Discussion
National Weather Service Grand Rapids MI
1022 PM EDT Tue Sep 3 2019 LATEST UPDATE... Mesoscale Discussion .MESOSCALE DISCUSSION... Issued at 1024 PM EDT Tue Sep 3 2019 The thunderstorms are now becoming more active as a shortwave rotates in on the upper level trough. The axis of MU cape is over Southwest Michigan from near Grand Rapids to South Haven at 10 pm. There is around 3000 j/kg of MU cape south of I-94 and around 2500 j/kg of MU cape over the I-94 area. The axis of the low level jet (LLJ) was from near South Bend to Detroit with the core of the LLJ near Detriot. There is around 50 knots of effective bulk shear near the front front where the storms currently are. The early inversion seen on AMDAR sounding as gone now so convection is now surface based ahead of the front. We expect the storms to continue to develop and move east. It may take till midnight now for the storms to clear our CWA. So, the area near I-94 is still at risk for severe storms till midnight. && .SYNOPSIS... Issued at 308 PM EDT Tue Sep 3 2019 - Slight risk for severe thunderstorms this evening - Cooler for Wednesday - Some showers possible for Thursday Night into Friday && .UPDATE... Issued at 754 PM EDT Tue Sep 3 2019 We are watching for development on the cold front and it is looking less and likely for severe storms. Actually it is becoming questionable that there will be much in the way of thunderstorms. I still think given the MU cape, and elevated mixed layer with a shortwave moving through with the cold front it is still possible a line of storms my form south or near I-94. No matter what this should all be done by 10 pm. && .DISCUSSION...(This evening through next Tuesday) Issued at 308 PM EDT Tue Sep 3 2019 The atmosphere continues to gradually destabilize through mid afternoon with a southwesterly flow advecting in considerable moisture. The clouds have delayed/slowed the heating somewhat. At the same time deep layer and low level shear were impressive. How much if any severe weather we see will likely be determined by the amount of destabilization from now until the cold front pushes through this evening. Based on satellite imagery there will be a window of an hour or two when decent destabilization could occur just ahead of the cold frontal passage. HRRR does forecast surface based CAPE values up over 2000 j/kg ahead of the frontal passage. Even if we end up short of these values...given the strong shear in place and lift with the wave moving in...a risk for severe weather exists. Damaging winds...large hail and a risk for tornadoes are possible. By 10 pm the main area of instability should shift southeast of the area. This is when I drop off the thunderstorm potential. A much cooler airmass moves in overnight and into Wednesday. A few showers could clip northern parts of the CWA late tonight. A weakening wave of low pressure arrives for Thursday night into Friday. We will only feature a low chance for a few showers given the weakening trend noted in the models. && .AVIATION...(For the 00Z TAFS through 00Z Wednesday evening) Issued at 754 PM EDT Tue Sep 3 2019 The threat for severe storms has decreased but it is still possible between now and say 02z that there could be a storm. Whether or not that happens, there is an area of MVFR cigs near the front. That will be cleared out by the front so by 04z or so all TAF sites are VFR. There is a secondary surge of cold air that will have an area of MVFR cigs with it and that moves through in in the 12z to 16z time frame. After that enough cool dry air moves in to once again clear the skies. Winds will not be as strong behind the cold front as it was ahead of the cold front, for the most part winds will in the 5 to 15 knot range Wednesday during the day. && .MARINE... Issued at 844 PM EDT Tue Sep 3 2019 I have downgraded our Gale Warning to a Small Craft Advisory since we have not had gales since prior to noon. We have winds of 15 to 25 knots into mid morning Wednesday and with the cold air coming in it makes sense to continue the Small Craft Advisory till late afternoon. I through it good to keep the beach hazard and flood advisory for the same time period. && .GRR WATCHES/WARNINGS/ADVISORIES... MI...Lakeshore Flood Warning until 4 PM EDT Wednesday for MIZ037-043- 050-056-064-071. Beach Hazards Statement through Wednesday afternoon for MIZ037- 043-050-056-064-071. LM...Small Craft Advisory until 4 PM EDT Wednesday for LMZ844>849. && $$ MESOSCALE...WDM UPDATE...WDM SYNOPSIS...MJS DISCUSSION...MJS AVIATION...WDM MARINE...WDM
Area Forecast Discussion
National Weather Service Houston/Galveston TX
1009 PM CDT Tue Sep 3 2019 .DISCUSSION... Tropical Storm Fernand continues to move west toward the Mexican coast and it`s impacts on SE TX will be minimal and confined to mainly the marine zones. Radar is quiet at the moment but am expecting some showers to redevelop around 09z over the Gulf waters and move toward the coast prior to sunrise. The 02z HRRR is showing some of the showers clipping the coast and bumped PoPs up a bit along the immediate coast. made a few minor tweaks to MinT grids and it`s going to be a warm night across the region with low temps near 80 in Houston and mid 70`s inland. A 594 dm upper level high will build into Texas and high temps Wed/Thu/Fri look to be very hot. The calendar might say September but the thermometer is stuck in August. Water levels are near 3.0 feet at high tide but should begin to fall overnight. Water levels should reach similar values on Wednesday night. No coastal flooding is expected. A SCEC was issued earlier this evening for all of the Gulf waters and Matagorda Bay as east winds increase. 43 && .PREV DISCUSSION... /ISSUED 635 PM CDT Tue Sep 3 2019/ AVIATION [00Z TAF Issuance]... No major changes in this TAF package, with VFR ceilings expected to prevail through the TAF period. Some light showers will be possible along the coast, potentially impacting LBX and GLS in the morning hours. Mostly a wind forecast, with winds light and out of the east overnight, increasing to between 7 to 12 knots by mid morning and turning more out of the southeast. Winds could become gusty once again tomorrow afternoon as we have seen today. Otherwise, expect a scattered deck overhead once again around 6000 feet tomorrow afternoon. Hathaway PREV DISCUSSION /Issued 323 PM CDT Tue Sep 3 2019/... SHORT TERM [Tonight through Wednesday]... Convection around TS Fernand has become more robust this afternoon with at least one flare up of deep convection around the circulation. Fernand is not far from the Mexican coast and will likely make landfall tomorrow. This means impacts from Fernand for SE Texas will be minimal. The main concerns will be a far outer rainbands that happens to brush along the coast causing brief heavy rain along with gusty easterly winds, building seas, tide levels about 1 foot above normal and rip currents. Otherwise upper level ridging over the central Rockies and central Plains will provide enough subsidence to keep deep convection from forming inland. Precipitable water values are running above 2 inches just along the coast so this area may be the lone exception for deep convection for this afternoon through tomorrow. The other concern will be the hot conditions expected tomorrow. Today temperatures have reached the upper 90s in several locations but temperatures at or just above 100F will be more common tomorrow. There should be enough winds to mix the boundary layer so dewpoints should decrease in the afternoon holding heat index values in the low 100s as well. Overpeck LONG TERM [Wednesday Night through Tuesday]... Based on the current track of Fernand, its effects over SE TX (which are expected to be mainly along the coast/coastal waters) will be de- creasing further by this time frame. Hot/dry weather to prevail over much of the CWFA as the strong upper ridge lingers over the Southern Plains. While high temperatures are progged to be in the 98F to 102F range, drier air moving into the region (from the NE/E) will help to mix dewpoints out during the afternoons. This should keep heat index values just under advisory criteria(108F) for the latter half of the week. Some relief is possible by the end of the weekend/early next week as the upper ridge weakens in response to a series of strong trofs move in from the west coast across into the Northern Plains. This will be helping to re-open the Gulf to us as E/SE winds return to the area. Have kept with the mention of low POPs for next Mon/Tues. 41 MARINE... No major changes for the short-term with the development of Tropical Storm Fernand in the western Gulf. We will continue to see the outer bands associated with this system move into our coastal waters along with moderate to strong east winds and 3 to 6 foot swells. Did main- tain the SCEC for the offshore waters through tomorrow evening based on its current track into the eastern coast of Mexico. After this... seas will be slowly decreasing as winds shift briefly to the N/NE. A weak surface high building over the area will keep winds very light/ variable late Thurs through Sat. Onshore winds are set to return Sun night/early Mon. 41 && .PRELIMINARY POINT TEMPS/POPS... College Station (CLL) 75 100 74 102 75 / 0 0 0 0 0 Houston (IAH) 78 99 77 101 78 / 0 0 0 0 0 Galveston (GLS) 84 93 81 95 81 / 20 20 10 10 0 && .HGX WATCHES/WARNINGS/ADVISORIES... TX...High Rip Current Risk through Wednesday morning for the following zones: Brazoria Islands...Galveston Island and Bolivar Peninsula...Matagorda Islands. GM...SMALL CRAFT SHOULD EXERCISE CAUTION through Wednesday morning for the following zones: Coastal waters from Freeport to Matagorda Ship Channel TX out 20 NM...Coastal waters from High Island to Freeport TX out 20 NM...Matagorda Bay. SMALL CRAFT SHOULD EXERCISE CAUTION through Wednesday evening for the following zones: Waters from Freeport to Matagorda Ship Channel TX from 20 to 60 NM...Waters from High Island to Freeport TX from 20 to 60 NM. && $$ Discussion...43
Area Forecast Discussion
National Weather Service Lincoln IL
809 PM CDT Tue Sep 3 2019 .SYNOPSIS... Issued at 253 PM CDT Tue Sep 3 2019 A cold front will move across central and southeast Illinois tonight. Ahead of the front, there is a chance for strong to storms north of I-70. High pressure will push into the region in the wake of the front bringing dry and cooler weather for the next few days. && .UPDATE... Issued at 808 PM CDT Tue Sep 3 2019 Radar imagery showed the cold front pushing across the northwestern CWA, generally from near Macomb to northwest of Pontiac. Storms, or even clouds, have been struggling to get going over the last few hours, despite CAPE`s above 3500 J/kg. However, a few showers have recently starting developing along the boundary from northeast of Peoria to Chicago. Latest HRRR is starting to back off a bit from its earlier aggressive stance a couple hours ago, but increases and pushes the showers/storms across mainly the northeast half of the CWA through midnight. Latest SPC Day1 backed off on the slight risk in our area, but kept a marginal risk in an area from Peoria to Lincoln to Danville. Have worked on refining the PoP trends, and have recently sent out a grid update for it. Updated zones will follow shortly. && .SHORT TERM...(This evening through Wednesday) ISSUED AT 251 PM CDT Tue Sep 3 2019 Sounding from 18z indicates cap still in place with -60 J/kg. Abundant cloud cover north of I-72 is inhibiting heating. With 700 temp of 12C, it will likely take approach of a cold front currently from SW WI to SE IA to provide sufficient convergence to initiate significant convection. Effective bulk shear is 30-40 kts across the northern portions of the forecast area early this afternoon, which should be sufficient for rotating storms if the cap can be broken before the boundary layer decouples later this evening. The best chances for severe weather would be in our northeast forecast area which has received more insolation and is concurrent with the elevated shear. This area likely also has a antecedent boundary from this morning`s MCS. Over the remainder of the area the window should be small both spatially and temporally for any strong convection. Any isolated remnant convection should be out of the area by sunrise. Temperatures following the frontal passage on Wednesday should be about 10 degrees cooler with much lower humidity. && .LONG TERM...(Wednesday night through Tuesday) ISSUED AT 251 PM CDT Tue Sep 3 2019 Northwest flow will dominate the Midwest through the end of the week as ridging develops over the Rockies/High Plains. A reinforcing cold front is expected to move through the region Friday, but with mostly north flow over the SE US, moisture should be limited prior to the front. At this time, will be keeping Friday dry. Following the Friday front, models diverge significantly in the evolution of the ridge to our west and the upstream trof over the Great Basin. Will stick with a model blend for the weekend until we have a better idea on which way the pattern will change. && .AVIATION...(For the 00Z TAFS through 00Z Wednesday evening) Issued at 610 PM CDT Tue Sep 3 2019 VFR conditions expected the next 24 hours. Main concern will be with any thunderstorms that manage to fire this evening. Atmosphere has been struggling with getting anything going ahead of the cold front, though latest RAP/HRRR models do show some activity in the 02-04Z time frame. Don`t have confidence to go any higher than a VC mention at this point. Any convective activity should be past the TAF sites by 06Z. Winds will swing around to the northwest between 02-06Z as the front drops through the area. && .ILX WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...Geelhart SHORT TERM...Barker LONG TERM...Barker AVIATION...Geelhart
Area Forecast Discussion
National Weather Service Indianapolis IN
1151 PM EDT Tue Sep 3 2019 .UPDATE... The AVIATION section has been updated below. && .SYNOPSIS... Issued at 137 PM EDT Tue Sep 3 2019 A quick moving cold front will sweep across Indiana this evening and Overnight. This may result in isolated to scattered showers and thunderstorms to Central Indiana overnight. High pressure is then expected to build across Indiana for the middle of the week...bringing dry weather and slightly below normal temperatures for the rest of the work week. Rain chances...albeit small...will return this weekend with continued cool temperatures. && .NEAR TERM /Tonight/... Issued at 915 PM EDT Tue Sep 3 2019 Slowed down timing of PoPs a couple hours based on trends and updated the Weather Story and Hazardous Weather Outlook due to the Storm Prediction Center pulling the Slight Risk out of our area and taking the Marginal Risk near and north of Muncie and Crawfordsville. Previous discussion follows... Issued at 137 PM EDT Tue Sep 3 2019 Surface Analysis early this afternoon shows SW flow in place across Indiana between High pressure over SE OH and an approaching cold front across Wisconsin and Iowa. Radar shows a convective cluster within the SW flow aloft over NW Indiana. HRRR advects the convective cluster slightly southeast and gradually results in dissipation within the next few hours. Still some minimal chances for showers this afternoon across the north forecast area appear prudent at this juncture. The GFS and NAM bring a weak short wave aloft along with the surface cold front across Indiana late tonight. Timing for daytime heating appears unfavorable...with a late overnight passage. HRRR suggests light scattered precip overnight with the frontal passage. Moisture with this system continues to be a problem. Time heights and forecast soundings never really show deep moisture available. Deep gulf moisture remains cut off by high pressure in place over Tennessee and the deep south. However some lift remains as the front passes and dew point temps are in the 60s. Thus will keep some low chance pops for very light rain amounts overnight. Given the rain and expected change in air mass will trend lows close to the NBM. && .SHORT TERM /Wednesday through Friday/... Issued at 137 PM EDT Tue Sep 3 2019 The GFS and NAM keep and similar and stable weather pattern in place on Wednesday through Friday. Strong ridging is indicated aloft over the Western United States...resulting om NW flow from the northern plains into the Ohio Valley. This lee side flow also result in subsidence and drying across the region. the result at the surface is a rather large area of high pressure in place across the upper midwest...great lakes and Ohio Valley. Generally northerly flow will be in place through at least Thursday night...allowing cooler Canadian air to spill across Indiana. This will also continue to prevent any gulf moisture from arriving in Central Indiana. Finally through Thursday night...forecast soundings show a dry column with unreachable convective temperatures through Friday. Thus will trend toward mostly sunny days and mostly clear nights through Thursday night. Will generally stick close to the NBM on temps. Forecast soundings are hinting at some lower level moisture arriving on Friday with a passing area of surface low pressure within the NW flow. Again moisture remains a problem here as the NW flow aloft remains prevalent. Thus confidence for pops on Friday is low and will try to trend toward a dry forecast. && .LONG TERM (Friday Night Through Tuesday)... Issued at 205 PM EDT Tue Sep 3 2019 Models are close enough that the National Blend of Models initialization was accepted for most items. Much of the long term will be quiet. A cold front will move through Friday night but have no moisture to work with, so went dry. High pressure will keep Saturday dry, but as alluded to yesterday, an upper disturbance will now bring chances for rain around Sunday. Have some low PoPs in around then. A warm front will be in the area on Monday and Tuesday, but heights will be rising during that period. Thus, without upper support, kept those days dry for now. Below normal temperatures at the start of the long term period will give way to above normal readings by the end of the period. && .AVIATION (Discussion for the 040600Z TAF Issuance)... Issued at 1151 PM EDT Tue Sep 3 2019 Good confidence any convection and brief MVFR or worse conditions in thunderstorms will be south of the terminals after 07z-08z. Then, should see VFR conditions the remainder of the TAF period per the SREF and GFS LAMP. Winds will start off northwest at LAF and southwest elsewhere to near 10 knots and then shift to northwest and north in the wake of the cold front after 07z-08z. && .IND WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...Puma NEAR TERM...Puma/MK SHORT TERM...Puma LONG TERM...50 AVIATION...MK
Area Forecast Discussion
National Weather Service Key West FL
1025 PM EDT Tue Sep 3 2019 .DISCUSSION...In the middle and upper levels(700-200 MB), latest available satellite imagery overlaid with model streamline analysis as of 900 pm, depict the axis of a middle and upper trough extending from Lake Superior down to the Tennessee Valley. South of that, a northwest to southeast oriented ridge is centered over the Western Gulf near 28N 94W, with the eastern flank of the ridge poking SE into the Florida Straits and Central and Western Cuba attm. Well east of that feature the western flank of a ridge centered over the Central Tropical Atlantic pokes northwest to just east of the Carolina Outer banks. In betwixt these large scale features sits Hurricane Dorian, located as of 800 pm, at 28.1 N, 78.8 W, or about 110 miles east of Cape Canaveral, moving NW at 6 mph. At the surface and in the lower to middle levels(Surface to 700 mb), latest available land and marine surface observations and analysis as of 900 pm, detail Tropical Storm Fernand over the far Southwest Gulf of Mexico, and of course aforementioned Hurricane Dorian. The Florida Keys remain in the far southwest circulation of departing Hurricane Dorian. && .CURRENTLY...As of 900 pm, skies are partly to mostly cloudy across the islands and surrounding waters. Radar detects isolated showers with an occasional thunderstorms that are confined to banding features that are moving across the Florida Straits attm. Maybe some sprinkles would be impacting a few of the islands at best attm. Temperatures across the Keys are in the middle to upper 80s with dewpoints in the middle to upper 70s. C-man stations along the Florida Reef are strongest over the Upper Keys with Alligator Reef and Carysfort Reef with near near 20 knot west southwest to west winds with higher gusts. Traveling down the Reef, winds are 15 to 20 or near 20 knots at Sombrero Key, and near 15 knots off the Lower Keys and 10 to 15 knots out at the Dry Tortugas. As a result, the 00Z evening sounding illustrated a quite moist with columnar PWAT at 2.27 inches and moderate to west west to northwest flow off the surface to 500 mb, indicative of confluent lower to middle level flow typical of the outermost circulation of a category 2 Hurricane well to the northeast of the Florida Keys. .SHORT TERM...Overnight and Wednesday, Hurricane Dorian will continue to pull away from the Keys, reaching approx 100 miles east of the GA/FL line by 800 pm Wed. The Keys will remain in the circulation of this storm, however, much drier air may already mixing down from above 500 mb this evening. Local/Caribbean HRRR is still indicating slightly more robust banding features could impact the Keys with heavier showers (within redeveloping rainbands again after 0600Z). However, overall coverage has been isolated to widely scattered at best this evening. Hence, have already lowered rain chances down to 40%, middle of the road, for the overnight period for the islands. Better low level confluence may be available Wednesday morning thru Wednesday afternoon, as ridging south of Cuba begins to pull northwards across the Straits. As for local breezes tonight, they will continue to vary greatly across the region, with the highest winds in the upper Keys, and the lowest across the Lower Keys and out at the Dry Tortugas, which are more distant from the gradient of Hurricane Dorian. && .MARINE...A Small Craft Advisory remains in effect for the eastern coastal waters of the Florida Keys due to southwest to west winds 20 to 25 knots. Hurricane Dorian will continue to the northwest and track east of, and parallel to the Florida east coast overnight. Moderate to fresh, southwest to west breezes are expected across the coastal waters of the Florida Keys overnight and Wednesday. Confused seas can be expected off the Upper Keys due to locally driven wind waves and long period swells emanating southward from Dorian. Winds and seas will begin to subside Wednesday night and Thursday && .AVIATION...VFR conditions will prevail at both the Key West and Marathon terminals overnight and through tomorrow morning. There is a possibility of isolated quickly moving showers passing over either terminal, and this will be reflected by the inclusion of vicinity showers in the terminal forecast. If showers do cross the terminals, they should bring only very brief MVFR conditions. Any showers that do develop will be moving towards the east at 15 to 20 knots. Surface winds will be out of the west near 10 knots, with occasional gusts near 15 knots. && .COASTAL FLOODING... High tides are expected to run about a half foot to a foot above the predicted tides, including the Lower, Middle, and Upper Florida Keys. The total water level at high tide will result in minor saltwater flooding in the Florida Keys. 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 is almost certain to be saltwater. Reports from the Bayside communities of the Upper Keys indicate some of the low- lying neighborhoods have about a foot of water over the streets. These conditions likely will persist through Wednesday night. && .KEY WATCHES/WARNINGS/ADVISORIES... FL...None. GM...Small Craft Advisory until 6 AM EDT Wednesday for GMZ042-043-052- 053-072-073. && $$ Public/Marine...Futterman Aviation/Nowcasts....Devanas Upper Air/Data Collection/Social Media......DR/KL/Devanas Visit us on the web at Follow us on Facebook and Twitter at:
Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
620 PM CDT Tue Sep 3 2019 .MESOSCALE DISCUSSION... 500 PM CDT Convective evolution continues to be monitored, with capping from the morning convection and lingering clouds severely impeding any mature development thus far. This will likely prevent any rapid development and may very well keep any development that can occur isolated, such as has been the case. A conditional severe risk does exist though if any sustained mode can develop. Convection in the southeast CWA over the past hour to hour and a half will have moved mainly east of the area by 530 pm. This activity is along an old outflow boundary and pseudo warm front advancing higher theta-e air into the area. While this convection has fair potential to be supercellular, it has struggled to be mature and sustaining thus far, likely owing to the cap. Further northwest along the cold front -- our now best chance for storms -- convection has been isolated in southern Wisconsin with agitated cumulus struggling along the boundary. Aircraft soundings from across northern Illinois and even into Wisconsin show capping around 850 mb, that had weakened little since ILX`s 18Z sounding. In Wisconsin there are more noteworthy height falls and associated cooling with the ascent that looks to only just graze far northern Illinois. This is why we think development is likely only to be isolated at least for the next few hours. Observational trends indicate the front is slower than forecast trends, and so did slow the forecast timing of chances slightly, along with lower them some. The nature of development should continue to be discrete given the orthogonal flow and shear with respect to the front. Given the values of deep layer shear (50+ kt) and CAPE, including in the low-levels thanks to the high moisture ahead of the front, supercellular mode is still favored and a conditional severe threat if sustained enough. If convection can grow more scattered into early evening as the front works into eastern Illinois and northwest Indiana, it`s possible some segments/clustering may develop and have a little more potential for wind. MTF && .SHORT TERM... 300 PM CDT Wednesday... Primary concern for Wednesday will focus on winds. As high pressure continues to slide into the Upper Missouri Valley and the deep low and associated cold front continue to push to the east, an area of moderate pressure rises and deep layer cold advection will continue the strengthening north winds. the gradient should be strongest over Lake Michigan and a little weaker over land. So, while winds over land should remain in the 5-10 mph range, winds over the lake should be in the 15 to 20 mph range, with an occasional higher gust. Winds along the Lake County IL shore should be mainly along shore while winds approaching the Cook County and Lake/Porter Counties should be more directly on shore, generating higher waves and a greater rip current threat. So, have issued a Beach Hazard Statement for Cook County IL and Lake County IN for the late morning through early evening hours and a bit longer for Porter County IN, from early morning through early evening. Otherwise, conditions Wednesday will be dry with below normal temperatures. Lows in the morning should be in the middle to upper 50s, and low 60s for the Chicago area urban heat island. Highs will, generally, be in the lower 70s, except along the lake where temperatures should only reach the middle to upper 60s. && .LONG TERM... 203 PM CDT Wednesday Night through Tuesday... Main weather concerns this period include a chance of showers and storms with a cold front late Thursday and/or early Friday... followed by a possible additional period of high swim risk at Lake Michigan beaches Friday in the northeast flow behind the front. Then possibly an unsettled pattern with periodic thunderstorm chances Saturday night through Tuesday. Sprawling high pressure moves overhead Wednesday night bringing light winds and mainly clear skies along with very September like temperatures with overnight lows in the upper 40s to lower 50s for locations outside of the Chicago metro. Thursday sees a return to a milder southerly flow but only marginally increased moisture ahead of a cold front expected to move across the area late Thursday or early Friday. Rain/storm chances are better north coincident with stronger upper level forcing... with central and southern sections of the CWFA quite possibly staying dry. Northeast surface flow on the back side of this cold front may set up yet another period of waves sufficient to produce a high swim risk at Lake Michigan beaches before high pressure riding moves over the area Friday night into Saturday. Models then continue to diverge in solutions for Saturday night through Tuesday with the GFS bringing a stronger area of surface high pressure southeast out of the Canadian prairies and into the northern Great Lakes Sunday into Monday. Meanwhile the Canadian takes a more northward track of this high... and the ECMWF even more so. Both hence shift the ribbon of shortwave energy in the northwest flow aloft farther north... to include northern IL and northwest IN. This would place the area under periodic chances of thunderstorms Saturday night through Monday... until most of the area comes under the warm sector with low pressure tracking along the U.S.-Canadian border into the northern Great Lakes by late Tuesday. Will continue to carry low pops in the forecast pending further inter-model consistency. Ed F && .AVIATION... For the 00Z TAFs... The primary aviation weather concerns through the period revolve mainly around a brief window of TS potential with a cold front followed by breezy northwesterly winds. A cold front is about to pass through RFD and will be through ORD and MDW around 0130 and 0200 respectively. Recent AMDAR soundings out of ORD and MDW indicate capping remains in place with a plume of warm air in the 850-700 mb layer. Thus far, convection near the state line has struggled to maintain itself in this very strongly sheared and capped environment. However, the Cu field remains agitated entering our CWA, and RAP forecast soundings reveal a rather quick lifting/cooling of the aforementioned warm nose shortly after 00z as the front makes its approaches to the Chicago-area terminals. As a result, convective initiation remains possible, although still conditional on erosion of the remaining warm layer just off the surface. It may be that storms begin to initiate more cohesively as the front begins to pass the Chicago area terminals as better height falls overspread the region through the mid- evening hours. As a result, will be maintaining a VCTS mention at ORD, MDW, and DPA up through FROPA, and will continue a TEMPO for TSRA at GYY. Any TS potential should be relatively short-lived, however, as much drier air will invade the region quickly behind the front. Northwesterly breezes will gradually abate through the night, with winds trending to light northerly on Wednesday. A modest push off the lake will turn the winds more northeasterly at ORD and MDW through the afternoon. Carlaw && .LOT WATCHES/WARNINGS/ADVISORIES... IL...Beach Hazards Statement...ILZ014...11 AM Wednesday to 7 PM Wednesday. IN...Beach Hazards Statement...INZ001...11 AM Wednesday to 7 PM Wednesday. Beach Hazards Statement...INZ002...7 AM Wednesday to 7 PM Wednesday. LM...Small Craft Advisory...nearshore waters until 10 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
Area Forecast Discussion...Updated
National Weather Service Saint Louis MO
946 PM CDT Tue Sep 3 2019 .UPDATE... Issued at 936 PM CDT Tue Sep 3 2019 The cold front was located near a Chicago to Quincy to Kansas City line at 02z. Warm air aloft was resulting in signficant capping and the only convection was located just ahead of the front across NE IL where CIN was much less. The cold front will continue to move southward through the remainder of the CWA tonight. The chances of surface-based storms appears pretty remote given the current CIN and forecast CIN. I can`t completely rule out the possibility of an isolated and short-lived elevated shower or storm forming associated with increasing clouds/moisture in the 850-700 layer spanning the frontal zone, but even that chance seems rather low at this point. Glass && .SHORT TERM... (Through Late Wednesday Night) Issued at 335 PM CDT Tue Sep 3 2019 Latest surface analysis indicates that the front extends from eastern Iowa into far northwest Missouri. Satellite trends continue to show extensive mid clouds along the front, but a limited cumulus along the front with the only thunderstorms over northeast Illinois and Indiana. Convective development farther westward as been hindered by stout cap shown well by the RAP soundings today, and this trend is expected to continue into this evening. CAMS have kept shower/thunderstorm development over Illinois tonight, so will do the same. Have only isolated showers and thunderstorms over west/south central Illinois during the evening hours. If updrafts are stout enough to develop and remain upright, then there will be sufficient CAPE/shear parameters for a few severe storms, particularly over Illinois. These storms will be capable of producing large hail and damaging winds. The cold front will push south of the CWA late tonight. Then dry weather is expected Wednesday and Wednesday night as a surface ridge moves in from the upper Midwest and the atmosphere becomes dry through a deep layer. Highs on Wednesday will be cooler behind front with cold air advection. Britt .LONG TERM... (Thursday through Next Tuesday) Issued at 335 PM CDT Tue Sep 3 2019 Expect mainly dry weather from Thursday into Saturday as a large surface high moves across Missouri and Illinois under generally dry northwesterly upper flow aloft. This will change by Saturday night into early next week as the deterministic global models and GEFS mean show a pair of shortwave troughs dropping southward out of the Northern Plains. These troughs will combine with a stalled front over southern Missouri and Illinois to bring a chance a showers and thunderstorms late in the period. Temperatures will be close to normal on Thursday, but will then warm up above normal on Friday ahead of a cold front with 850mb temperatures close to 20C. Temperatures behind the front will likely be at or below normal behind the cold front with a chance rain, but the spread on the GEFS ensemble temperatures is showing an increasing spread which lowers the confidence in the overall forecast in early next week. Overall trend in guidance is showing temperatures going back above normal by next Tuesday. Britt && .AVIATION... (For the 00z TAFs through 00z Wednesday Evening) Issued at 659 PM CDT Tue Sep 3 2019 A cold front currently stretches from northwest IL across southeast IA into northwest MO early this evening. This front will move southward tonight and will be accompanied by a increasing swath of VFR clouds with bases from 4,000 to 5,000 feet. Precipitation chances with the front look iffy and if a shower or thunderstorm does develop this evening, then the coverage should be rather isolated. The TAFs reflect the wind shift with the cold front and clouds, and are void of any precipitation given the aforementioned low probability. SPECIFICS FOR KSTL: A cold front currently stretches from northwest IL across southeast IA into northwest MO early this evening. This front will move southward tonight and should move through the terminal around 05-06z. The front will be accompanied by VFR clouds with bases from 4,000 to 5,000 feet. Precipitation chances with the front look iffy and if a shower or thunderstorm does develop this evening, then the coverage should be rather isolated. The TAF reflects the wind shift with the cold front and clouds, and are void of any precipitation given the aforementioned low probability. Glass && .LSX WATCHES/WARNINGS/ADVISORIES... MO...None. IL...None. && $$ WFO LSX
Area Forecast Discussion
National Weather Service San Francisco Bay Area
855 PM PDT Tue Sep 3 2019 .SYNOPSIS...Monsoonal moisture arriving from the south late tonight and Wednesday will result in a slight chance of thunderstorms on Wednesday and Wednesday evening, mainly across northern portions of our forecast area. Temperatures are not expected to change much through Wednesday, meaning warm conditions will persist inland. A gradual inland cooling trend is then forecast from Thursday on through the weekend as the marine layer slowly deepens and onshore flow increases. && .DISCUSSION...As of 8:55 PM PDT Tuesday...Primary forecast concern in the short term continues to be the possibility of showers and/or thunderstorms tomorrow and tomorrow evening, especially the potential for dry lightning. Monsoon moisture continued to flow across southern California today, resulting in widespread thunderstorms across southern California as well as the southern Sierra Nevada. Both the NAM and GFS continue to forecast scattered light precipitation in the SF Bay Area tomorrow and tomorrow evening (mostly across the North Bay) as an approaching upper trough interacts with the plume of monsoon moisture flowing in from our south. Forecast soundings indicate that most of the moisture will be above 10K feet, with dry air below. Thus, any thunderstorms that may develop could produce dry lightning as much of the rainfall will likely evaporate before reaching the ground. Shower/thunderstorm potential will end by Wednesday night as the flow aloft takes on a more westerly component, bringing in a drier airmass. It should be noted that neither the HRRR or ECMWF forecast precipitation on Wednesday. Thus, slight chances for showers and thunderstorms seems sufficient. The Fort Ord profiler shows that the marine layer remains shallow this evening with a depth of only about 1000 feet. The profiler also indicates recent warming of the airmass above the marine layer. Model guidance indicates little change in temperatures through Wednesday, which seems reasonable given current conditions. Cooling is then likely on Thursday, especially inland, as the upper trough finally reaches the coast, enhancing onshore flow and bringing with it a slightly cooler airmass. Little change is forecast for Friday, but then additional cooling is expected over the weekend as a second upper trough sweeps across California. Inland temperatures over the weekend are forecast to be 7 to 15 degrees cooler than they were today. The trough forecast for the weekend looks to be strong enough to mix out the marine layer which will mean more sun and thus warmer temps in coastal areas, especially on Sunday. It`s looking less likely that moisture from Hurricane Juliette will have any impact on our weather. Both the GFS and ECMWF now forecast Juliette`s moisture to mostly remain south of 30N and not be drawn northward ahead of the weekend trough. && .AVIATION...As of 4:45 PM PDT Tuesday...Enough stratus has cleared from the coast to prevent early intrusion into the SFO Bay Area. Ft Ord Profiler shows marine layer is shallow at 1000 feet which also works against the stratus. Latest tafs have delayed the cigs over SFO and the approach until after 06Z but it could be even later than that. Vicinity of KSFO...VFR conditions through at least 06Z. Becoming IFR with bases 800-1000 feet sometime after 06Z. West winds to 20 kt decreasing after 04Z. SFO Bridge Approach...Similar to KSFO. Monterey Bay Terminals...A patch of stratus is developing off Point Pinos and forming a wave cloud. This cloud is expected to push into MRY by 04Z then spread into SNS after 06Z. && .FIRE 2:16 PM PDT Tuesday...A noted above the biggest concern over the next 36 hours is possible dry lightning for portions of NorCal, including the Bay Area. Dry lightning is always tricky to forecast and this slight chance is no different. However, unlike the last dry lightning event (which resulted in no lightning for the Bay Area) this one has a better trigger (jet streak). That being said, it is not a slam dunk and will not issue a Red Flag Warning at this time. If thunderstorms do develop dry lightning seems pretty certain with how dry the low levels will initially be. Gusty winds may also be possible with the right outflow boundary. Lastly, fuels are definitely dry and will be receptive to allow for possible fire starts. Persons with fire weather interests should monitor the forecast over the next day. && .MARINE...As of 8:49 PM PDT Tuesday...Northwesterly winds will strengthen over the coastal waters through mid-week, with the strongest winds occuring in the afternoon and evening hours. Long period forerunners will enter the coastal waters from the northwest on Tuesday. A shorter period southerly swell will mix in through the remainder of the week. && .MTR WATCHES/WARNINGS/ADVISORIES... .Tngt...SCA...SF Bay until 9 PM SCA...Mry Bay until 9 PM SCA...Pigeon Pt to Pt Pinos 0-10 nm until 9 PM SCA...Pigeon Pt to Pt Piedras Blancas 10-60 nm until 9 PM SCA...Pt Arena to Pigeon Pt 10-60 nm SCA...Pt Pinos to Pt Piedras Blancas 0-10 nm SCA...Pt Arena to Pt Reyes 0-10 nm SCA...Pt Reyes to Pigeon Pt 0-10 nm until 3 AM && $$ PUBLIC FORECAST: Dykema AVIATION: W Pi MARINE: W Pi Visit us at Follow us on Facebook, Twitter, and YouTube at:
Area Forecast Discussion
National Weather Service Phoenix AZ
413 PM MST Tue Sep 3 2019 .UPDATE...aviation discussion. && .SYNOPSIS... Very limited storm activity is expected over the region through Saturday. Temperatures will be above normal during this time. The warmest day looks to be Wednesday. In fact, Excessive Heat conditions are expected on Wednesday over south-central Arizona. A change in the weather pattern early next week will lead to a cooling trend. It lead to an uptrend in storm activity over Arizona. && .DISCUSSION... Rest of Today and Tonight... Modest storm activity is in progress as of mid-afternoon. Of note, surface dew points are running higher than initially projected given the 12Z PSR sounding. SPC mesoanalysis shows 1000+ J/kg of MLCAPE over the south-central AZ deserts (500-1000 elsewhere) and 1800+ J/kg DCAPE (seems overdone given dew points). Plus, there is about 15kts of easterly steering flow. But there is also noteworthy CIN to be dealt with. HRRR has been depicting isolated to scattered storms moving across Gila County and into far northeast Maricopa and northern Pinal County before dissipating. But not without spreading some outflow wind into at least eastern portions of the metro area. Other CAMs are supportive of this scenario with the 18Z NAM Nest trending closer to that than what the 12Z run was depicting. Given the mesoanalysis, this scenario is reasonable. Dry advection advertised by the RAP should help preclude storms from maintaining/regenerating themselves all the way across the metro area. Wednesday through Friday... There is good model agreement on dry advection from the east on Wednesday. This will lead to warmer temperatures Wednesday. Expect temperatures to reach high Heat Risk levels over portions of south-central AZ and thus Excessive Heat Warning remains in effect. On Thursday, the center of the ridge drifts eastward a little bit and temperatures cool slightly - just enough to dip below excessive heat thresholds. A bit better moisture remains over southwest AZ and southeast CA. By Friday, a trough approaching the West Coast begins a change to southwesterly flow aloft. Still a very low grade Monsoon situation due to lack of moisture. Little change in temps. Meanwhile, Hurricane Juliette will have no discernible effect on our forecast area. There is also an inverted trough moving through northern Mexico during this time which may help to reinforce moisture levels over Sonora. Saturday through Tuesday... There`s somewhat better operational and ensemble member agreement depicting a progressive, and rather deep northern stream trough depressing the ridge axis into northern Mexico late in the weekend, then sweeping into the four corners and Great Basin early next week. While the increased strength and depth of westerly flow would typically dislodge moisture from the forecast area, substantial incoming height and pressure falls may actually create stronger low level southerly flow and transport better moisture profiles northward ahead of a frontal boundary. Add in cooling aloft with this trough and shortwave, along with dynamical forcing, and forecast soundings actually look quite enticing for the eastern portions of the CWA during this transition season type event. Details regarding timing and depth of this system remain somewhat elusive preventing a more resounding POP mention for any given time frame, but certainly the signals are present that a more convectively active day may be in the offing sometime early next week. Regardless, there is consistency that much lower heights and cooling will spread into the region allowing temperatures to finally fall near or below average (and many lower elevation communities possibly not even hitting 100F for a day or two). && .AVIATION...Updated at 2315Z. South-Central Arizona including KPHX, KIWA, KSDL, and KDVT: Storms will continue to develop in Gila and extreme eastern Pinal/Maricopa counties this afternoon. Although storm activity is still not anticipated to actually make its way into the terminals (better chances at SDL), it is now looking likely that outflows from these storms will switch the winds to east- northeast around 01Z at SDL and DVT and between 0130Z and 02Z at PHX and IWA, with gusts as high as 20-25 kts possible. Given the wind direction, do not think blowing dust will be an issue, except possibly at KIWA. There`s a lot of uncertainty as to what the wind direction will be after the possible outflow boundary moves through, but guidance is suggesting that winds will try to veer to the south/southwest before completely switching back to the east after 07-09Z. Easterly winds will then persist through most, or all of Wednesday. FEW mid-level clouds through this afternoon should become SCT-BKN this evening with bases around 10k feet. Southeast California/Southwest Arizona including KIPL and KBLH: KBLH will favor a southerly to southerly wind through the TAF period, with speeds mainly aob 10 kts. KIPL should see a southwesterly wind before switching to the southeast after midnight with speeds aob 8 kts. A vicinity shower or thunderstorm cannot be ruled out at KIPL in the afternoon, but activity should stick mostly to the mountains to the west. Chances are better to see brief gusty outflow winds from the west in the early evening hours. FEW-SCT mid-level clouds and cumulus are expected though the TAF period with bases remaining aoa 10 kft. Aviation Discussion not updated for amended TAFs. && .FIRE WEATHER... Friday through Tuesday: Expect low grade Monsoon conditions Friday and Saturday along with high temperatures several degrees above normal. Humidities trend down over southeast California on Saturday with little change east of there. Sunday through Tuesday, high pressure weakens as a low pressure system moves through the western CONUS. Temperatures trend down and humidities trend upward. This will also lead to an uptrend in storm potential for south-central Arizona. && .SPOTTER INFORMATION STATEMENT... Spotters should follow standard reporting procedures. && .PSR WATCHES/WARNINGS/ADVISORIES... AZ...Excessive Heat Warning from 10 AM to 8 PM MST Wednesday for AZZ530-532-534-536-537-540>544-546-548-550-551-553-555-556. CA...Excessive Heat Warning from 10 AM to 8 PM PDT Wednesday for CAZ567-569-570. && $$ DISCUSSION...AJ/MO AVIATION...Hernandez FIRE WEATHER...AJ