Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 05/13/18

Area Forecast Discussion...UPDATED
National Weather Service Corpus Christi TX
651 PM CDT Sat May 12 2018 .DISCUSSION...See Aviation section for 00Z TAFs. && .AVIATION...Boundary layer moisture is higher over the coastal plains this evening where MVFR ceilings continue at this time. Expect a brief period after 02z when clouds will scatter along the coast. But expect an earlier onset of MVFR ceilings returning for coastal areas between 05-06Z. Low level flow is not expected to be as strong as last night especially over the Victoria Crossroads. Patchy fog will be possible for the inland coastal plains late tonight with IFR vsbys possible for VCT area. SREF, HRRR models along NAM model soundings indicated lower IFR ceilings possible for the coastal plains between 09-13Z. MVFR ceilings are also expected to reach LRD area earlier around 08Z. MVFR ceilings should continue through the morning hours into early afternoon when VFR conditions will be prevalent area wide. && .PREVIOUS DISCUSSION... /Issued 237 PM CDT Sat May 12 2018/ SHORT TERM (Tonight through Sunday night)... With the upper low over the North-Central Gulf of Mexico and high pressure over Texas (at least by default), we should stay high and dry (or should I say unseasonably warm and dry). Could not rule out a rogue shower here or there (here near the Rio Grande early in the short-term with the moisture axis present, then there offshore with some moisture coming in from the gulf). In any case, the main synoptic and high resolution models do not show anything of significance, and thus no rainfall will be forecast. Winds may be elevated this evening a bit as the sea-breeze pushes west (and over the coastal areas tonight), which will help to keep some temperatures up again. Could have some brief patchy fog again toward sunrise over the inland/Highway 77 corridor, but that is about the only "notable" weather in the short term. Temperature forecast has been based on the combination of a blend of Bias- Consensus MOS and All grids, with some adjustments near the coast as usual. MARINE (Tonight through Sunday night)... Will have some elevated/moderate onshore flow tonight over the southern bays/nearshore waters, and possibly Monday night given the good sea-breeze which is expected tonight and continue on Sunday night. Otherwise, weak to moderate southerly flow with no significant weather expected. LONG TERM (Monday through Saturday)... Models prog a short wave to round the northwest periphery of the ridge aloft, tapping into moisture along the Sierra Madre. However, precip is not expected to make it into the CWA. Kept 5-10 silent pops for a rogue tsra or two, mainly for the western areas. Models show embedded short waves periodically through the extended, but moisture will be very limited along with a capping inversion, thus only went with silent 5-10 pops through Sat. A gradual warming trend will continue through the week with highs nearing 100 degrees along the Rio Grande by the latter part of the week. Onshore winds will generally be weak to at times moderate through the period. && .PRELIMINARY POINT TEMPS/POPS... Corpus Christi 73 90 74 89 71 / 0 0 0 10 10 Victoria 71 92 71 91 68 / 0 10 10 10 10 Laredo 74 97 75 95 74 / 0 10 10 10 10 Alice 71 95 71 94 68 / 0 0 0 10 10 Rockport 76 88 76 86 74 / 0 10 10 10 10 Cotulla 71 96 73 95 72 / 10 10 0 10 10 Kingsville 73 94 71 93 70 / 0 0 0 10 10 Navy Corpus 78 89 78 87 76 / 10 10 0 10 10 && .CRP WATCHES/WARNINGS/ADVISORIES... TX...None. GM...None. && $$ TMT/89...AVIATION
Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
1151 PM EDT Sat May 12 2018 .AVIATION... Strengthening of inflow into the mid level frontal boundary over southern Michigan will sustain showers across the area during the first few hours of the TAF period. Showers should end prior to daybreak as some enhanced upper level subsidence expands across Se Mi with expansion of thunderstorms expected to take hold just south of the state line. With the showers, there will be some low cloud redevelopment during the night, particularly south of FNT. As has been the case over the last 24 hours, the circulation around the high pressure to the north-northeast will sustain some degree of low level dry air across the area, leading to some degree of fluctuation in cloud heights. Current indications are that any low clouds during the morning will lift in to a sct-bkn VFR cu field in the afternoon with daytime heating. For DTW...Southwest flow will force some additional moisture/instability transport into metro Detroit early in the morning, therefore supporting a chance for thunderstorms (primarily in the 07Z to 10Z time frame). .DTW THRESHOLD PROBABILITIES... * Moderate in ceilings below 5000 ft through the TAF period. * Moderate in thunderstorms overnight. && .PREV DISCUSSION... Issued at 839 PM EDT Sat May 12 2018 UPDATE... Enhanced frontal forcing along the 700-600mb front has been supporting showers all the way up toward central Lake Mi. This forcing will traverse Se Mi later this evening into the overnight. Based on radar trends, an update will be issued simply to raise pops a little higher across the northern sections of the forecast area. Increased southwesterly flow overnight is still expected to result in a little better convective development farther south along the frontal slope. When this occurs, the precip farther north along mid level front will likely wane. The latest HRRR continues to suggest the higher intensity convection occurring later in the night along/south of the MI/OH border, closer to better low level convergence and instability. So the expectation continues to be that the heaviest overnight rainfall will occur across Lenawee/Monroe Counties and points south, south of the region which received the heaviest rainfall earlier today. PREV DISCUSSION... Issued at 304 PM EDT Sat May 12 2018 Flood advisory will be allowed to expire at 330 PM as showers have just about exited the area at press time. Subtle upper level ridging building over the upper Mississippi River Valley leading to northwest Confluent flow over the Central Great Lakes, with expansive high pressure (1022-1024 MB) over Lake Superior-Lake Huron. Low level northeast winds has subsequently advected drier air into southeast Michigan late this afternoon, with the 850 MB front/moisture axis now just south of the Michigan border, with the surface boundary and instability axis well south over the southern Ohio Valley. Surface low pressure approaching Iowa this evening will provide the focus for yet another complex to develop and roll east, tracking close to the southern Michigan border tonight. It appears the low level jet will be veering quickly to west-east direction, limiting the moisture/instability return into the state, and still appears bulk of heavy rainfall will be along and south of Michigan border. Still, 700 MB moisture axis/FGEN over hanging the southern Michigan border should assure at least some shower activity and possible thunderstorm activity south of M- 59, supported by latest HRRR. Lenawee/Monroe counties have missed out on the heavier rain over the past 24 hours, so should be able to handle 1+ inches ok. Obviously, if this heavier activity makes it into Washtenaw/Wayne it will be a different story, and considered issuing a flood watch, but was just not finding much support to get heavier activity that far north. 12z Euro is about the only solution, but Euro is not handling this lead wave currently over Illinois. 12z HiRes-ARW looks like a more reasonable solution for tonight. The frontal boundary and moisture axis will be hanging over the northern Ohio Valley Sunday-Monday, making for a low confidence forecast, as any ripple/wave riding along the front could lead to shower/thunderstorm development activity toward the southern Michigan border, despite being within the backdrop of the flat 500 MB ridge. Confidence in the temperature forecast Sunday/Monday is also not high due to the dependence of low clouds, as NAM indicating high degree of RH/moisture at 925 MB level through the period. An active period of weather will continue through the extended with a few chances for precipitation. As far as temperatures, highs are expected to remain in the 70 degree range through the remainder of the week and into the start of next weekend. Multiple waves will continue to move along the flow and just to the south of the CWA. Models are showing the best chances for rain/storms on Tuesday and then possibly again late Thursday night into the Friday timeframe. MARINE... High pressure over the northern Great Lakes will build slowly south into tonight, but a stalled front across the southern Great Lakes will be slow to exit the region. The front will remain active with showers across lake St Clair and Lake Erie through Sunday morning before finally drifting far enough south to allow drier air to move in. Stable boundary layer will keep wind gusts generally less than 15 knots through the next few days. The exception will be Lake Erie where wind speeds may approach 20 knots within easterly gradient flow around this high on Sunday. HYDROLOGY... One more round of rainfall is expected tonight as another disturbance tracks along a nearly stationary frontal boundary. This wave is expected to track further south and affect mainly areas from I-94 southward. Rainfall amounts will be lighter than last night, but still possibly range from around one quarter of an inch near the I-94 corridor to one inch near the Michigan state line. Most of the new rainfall will fall just south of ongoing flood issues and should not exacerbate the situation tonight. PREV DISCUSSION... Issued at 301 PM EDT Sat May 12 2018 && .DTX WATCHES/WARNINGS/ADVISORIES... MI...NONE. Lake Huron...NONE. Lake St Clair...NONE. Michigan waters of Lake Erie...NONE. && $$ AVIATION.....SC UPDATE.......SC DISCUSSION...SF/SP MARINE.......DG HYDROLOGY....DG You can obtain your latest National Weather Service forecasts online at
Area Forecast Discussion
National Weather Service Grand Forks ND
936 PM CDT Sat May 12 2018 .UPDATE... Issued at 933 PM CDT Sat May 12 2018 No changes to the going forecast. Sprinkles over the southern counties have dissipated as expected. The showers over south central ND have been weakening as they move east and think they will be completely gone or not reaching the ground by the time they get into our southwestern counties. Temps have been staying in the 50s to low 60s so far, but think as we get further past sunset we should start dropping faster and continued to keep lows in the 40s to upper 30s. && .SHORT TERM...(This evening through Sunday) Issued at 305 PM CDT Sat May 12 2018 Weak high pressure exists from the Great Lakes east through northern MN and ND this afternoon. A weakening upper level disturbance moving thorugh SD and far southern ND may bring a few sprinkles/light showers to far SE ND this afternoon. All in all, not expecting much from these showers before they dissipate. Tonight, some left over mid and high clouds will linger across the region, helping keep temps up into the evening hours. Skies should clear across much of the area by Sunday morning, save the south. On Sunday, expect a westerly breeze by the afternoon...along with dry conditions in the north. Temps should make it into the 70s across the entire area...and maybe near 80 in the far northern Red River Valley. .LONG TERM...(Sunday night through Saturday) Issued at 305 PM CDT Sat May 12 2018 Sunday night through Wednesday... An H5 blocking pattern sets up firmly over the intermountain west on Sunday and produces a split flow pattern over the Northern Plains region through the early part of the work week. Expect generally fair and warm conditions through Wednesday... with temperatures ranging near 10 degrees above long term averages. Light northerly winds are expected Sunday night and Monday... with dry, near critical, fire weather conditions likely to persist. Tuesday will see winds swing out of the south... and with an increasing southerly flow from Tuesday into Wednesday... humidity levels should rise a bit. Wednesday night through Friday... Models are consistent in showing a breakup of the western U.S. block followed by a potentially damp late week period... as a series of weak impulses roll across the Northern Plains. High temperatures cool from the 70s on Thursday into the 60s on Friday... with intermittent showers possible both days. A predominantly southerly flow on Thursday should swap out of the north by Friday... leading to a somewhat cooler and drier weekend. For now... Saturday looks to end up mainly sunny and dry through the morning, with increased clouds and a risk for showers across the southern Red River Valley in the afternoon. && .AVIATION...(For the 00Z TAFS through 00Z Sunday evening) Issued at 647 PM CDT Sat May 12 2018 Conditions are VFR at all sites and will remain so throughout the period. Light and variable winds will pick up out of the west- southwest by late tomorrow morning, mostly staying below 12 kts. && .FIRE WEATHER... Issued at 305 PM CDT Sat May 12 2018 Sunday afternoon is shaping up to be a near critical fire weather day across northeast ND and northwest MN. Highs should be in the 70s to near 80 degrees. The HRRR model has done well with humidity/dew points recently and are hinting at dew points in the 30s across the north tomorrow. The rest of the models are forecasting more low 40 dew points. The other element of concern is winds...which may be around 14 to 18 mph with gusts of 20 to 25 mph tomorrow afternoon. Most models don`t support anything higher than 25 mph. However, if some areas mix all the way to 700 mb/3000 ft AGL, there could be more +25 mph gusts and will be something for the next forecast shift to monitor/evaluate. Conditions will improve quickly in the evening as winds decrease and humidity recovers. && .FGF WATCHES/WARNINGS/ADVISORIES... ND...None. MN...None. && $$ UPDATE...JR SHORT TERM...Knutsvig LONG TERM...Gust AVIATION...JR FIRE WEATHER...Knutsvig
Area Forecast Discussion
National Weather Service Green Bay WI
1053 PM CDT Sat May 12 2018 Updated aviation portion for 06Z TAF issuance .UPDATE... Issued at 840 PM CDT Sat May 12 2018 Similar scenario to Friday evening again tonight with disorganized band of very light shower activity that had developed in weak WAA zone north of frontal boundary over Illinois and ahead of shortwave impulse passing across the forecast area. HRRR did a rather lousy job capturing the shower activity earlier this but finally seems to have handle albeit a little too late. 00Z Green Bay sounding shows very dry air roughly below 3 km thus precipitating cloud bases are pretty high around 7 to 9 kft. As last evening, precipitation is again waning as it impinges on increasingly dry air over northeast Wisconsin. Precipitation a bit more widespread south of highway 10...but even there not much more than a car spotter or perhaps an isolated hundredth of an inch. Bumped up POPs for the next few hours generally south of a GRB to ISW line to reflect current trends. After midnight mainly mid to high clouds and dry conditions. && .SHORT TERM...Tonight and Sunday Issued at 257 PM CDT Sat May 12 2018 An area of showers and thunderstorms should pass south of the forecast area late this afternoon/early this evening as a mid level short wave continues to move east and an east-west stationary front remains across central Illinois. Mesoscale models showed some activity to the west dissipating as it reaches central Wisconsin. Have left some slight chance, and low end chance, PoPs across the southern tier of counties for a few hours during the evening to be on the safe side. Expect mid and high clouds around for the night, but temperatures are still likely to fall into the 30s across much of the area. Would think frost will develop due to the light winds and chilly temperatures. A narrow surface ridge is forecast to be over Wisconsin on Sunday, helping to keep the area dry for at least the daytime hours. Warmer temperatures are in store, with upper 60s to lower 70s at most locations away from Lake Michigan. .LONG TERM...Sunday Night Through Saturday Issued at 257 PM CDT Sat May 12 2018 Upper flow pattern over Wisconsin will be mostly confluent through the middle of next week, helping to keep the Hudson Bay high to our northeast. Dry air in the low levels will keep rain mostly to our south through midweek. An upper trough approaching from the central Plains towards the end of the week will help cause upper winds to back to the southwest, and some moisture to return in the low levels from the south. So the best chance of rain is late in the week. Temperatures will be a little above normal for the next few days, and closer to normal later in the week. && .AVIATION...for 06Z TAF Issuance Issued at 1052 PM CDT Sat May 12 2018 Weak lift north of a warm front and embedded weak disturbances aloft will continue to generate a few scattered light showers mainly across the southern third of Wisconsin and south of the GRB TAF sites overnight. Lower levels remain dry with cloud bases generally above 10kft. VFR conditions to prevail through the remainder of the TAF period with mainly middle to high clouds traversing the area from time to time. && .FIRE WEATHER... Issued at 257 PM CDT Sat May 12 2018 Low relative humidities and warmer temperatures will produce elevated fire weather conditions over central and northern WI through the middle of next week. Sunday through Tuesday should have temperatures in the 70s and low 80s with relative humidities in the upper teens and 20s across northern WI. Winds are forecast to remain pretty light through the middle of next week. && .GRB WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE.........ESB SHORT TERM.....MG LONG TERM......RDM AVIATION.......ESB FIRE WEATHER...RDM
Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
941 PM CDT Sat May 12 2018 .UPDATE... 932 PM CDT Showers and thunderstorms once again the primary forecast challenge late this evening into the overnight hours. Broad region of over-running is focused from far northwestern Iowa across southern Wisconsin where showers and thunderstorms are ongoing and will likely continue until after midnight tonight, then begin to diminish in coverage as mid level southwest flow veers to westerly. Some of these showers may dip into the northern tier of counties in Illinois, but most will stay north of the state line. Farther south, modest 35-40kt speed max is located over far NE MO per latest RAP and sampled by GOES-16 derived motion winds. Moisture convergence on the nose of this jet is focused across far SE IA into west central IL this evening where there has been a modest uptick in shower coverage along with a lone isolated thunderstorm. RAP indicates that this small speed max will weaken beyond the next couple hours as winds begin to veer. Meanwhile, MUCAPE of 500-1000 J/kg over the CWA should also begin to wane after roughly midnight tonight. Conditions seem to be peaking now and over the next couple hours for new development so prefer to monitor upstream trends for another hour before any more large-scale changes to the forecast. Barring any more robust development in that time, though, and given the expected weakening instability and forcing beyond the next couple hours, will have to consider further reducing PoPs and QPF along with canceling the remainder of the Flash Flood Watch. Deubelbeiss && .SHORT TERM... 310 PM CDT Through Tonight... Additional showers and storms are expected through tonight. A stationary boundary has settled over central IL and additional upper level waves will pass over the region. Expecting convection to blossom over the forecast area late this afternoon, but storms should not be severe due very little CAPE to work with. PWAT values are 1.3-1.6 inches, so the main threat from storms will be heavy rain. If CAPE values increase, especially south of I-80, a couple of storms could produce large hail. Additional showers will develop this evening with the best coverage between I-88 and I-80. The radar estimates that up to 1.5 inches of rain has already fallen in this area, and up 2 inches is forecast to fall through tonight. As such, issued a flash flood watch for this corridor due to the prolonged period of thunderstorms. Some models shift the heavy rain axis a bit further north or south, but the operational HRRR has been very consistent and accurate thus far today. Therefore opted to follow it`s guidance and also focus the watch on the heavy rain core. Showers and storms finally end from west to east Sunday morning. JEE && .LONG TERM... 105 PM CDT Sunday through Saturday... Main forecast concerns/challenges will continue to be with periods of showers and thunderstorms, some of which could be strong/severe and also be capable of producing additional heavy rainfall. At the start of the period, expected thunderstorms tonight should be exiting to the east southeast. However, a few storms may persist along and south of the I-80 corridor a few hours before departing. During this time, LLJ will continue to veer though remain on the stronger side. Also, large scale ascent with surface reflection moving through will be in place, in the presence of decent elevated instability. This could support a continued strong to severe threat, with hail the main threat. Additional heavy downpours will also be possible. By mid morning, this precip/convection should be east of the CWA. Guidance does vary with regards to additional shower/thunderstorm chances for the remainder of the day Sunday. Most hires guidance indicating a lull in the activity for much of the day, while other pieces of guidance depict additional development along surface boundary and reflection still in place across the southern CWA. Can`t completely rule out additional precip chances in this location Sunday afternoon, as it will be possible for additional upstream mid level energy to move overhead. Given the uncertainty, will continue going forecast of slight chance to low chance pops mainly for locations south of I-80. With some slight warming to the air mass along with the possibility for the sun to break out in some locations Sunday, expect temps to be warmer than today. Additional chances for thunderstorms remain Sunday night into Monday morning, with another period of strong to severe storms possible. With mid/upper level forcing supportive of steering a stronger surface low north into the region, surface boundary will have a chance to lift north during this time. This coinciding with a strengthening LLJ, will once again support thunderstorm development to our west. There is some uncertainty as to exactly where this will initiate, along with where this will track. Some guidance would indicate much of northern IL and northwest IN observing these thunderstorms. However, I wonder if more southerly track would be favored, following instability axis. If this were to occur, then locations south of I-88 would have the highest chances for thunderstorms. Given the change in the overall pattern and with increasing instability, a hail and now a damaging wind threat would be the hazards. Similar pattern into mid week will support additional thunderstorm chances, with similar hazards also possible. Night time development appears to be the more favored periods, however, day time development will also be possible. Rodriguez && .AVIATION... For the 00Z TAFs... The main forecast concerns tonight and Sunday for ORD and MDW are: - Scattered showers near and north of the airports through mid- eve, followed by a 4-6 hour period of thunderstorms at least near the airports into the overnight - IFR ceilings returning, likely not long after dark, and increasing potential for LIFR ceilings (possibly down to 300 ft) during Sunday morning - Potential for drizzle/fog Sunday morning with visibility as low as 3/4SM possible In the wake of the earlier rain, IFR ceilings had developed at Chicago area airports and have since mixed out at most. However, these are not far away and will likely creep back in not long after dark. In addition, scattered showers will continue in the region early this evening. Deeper convection is anticipated to develop across central/eastern Iowa into northwest Illinois by mid-eve and spread east-southeast late this eve into overnight. This looks like a setup that will bring periodic storms for as much as six hours to some locations of northern Illinois, and ORD and MDW are in the favored axis. However, confidence on where exactly this will set up and how wide of a storm axis is low-medium. Confidence on timing is higher and this should be after peak demand time tonight and before that of the morning. The Sunday morning operations do look to be impacted though, mainly by low ceilings and the potential for low visibility in drizzle/fog. While not climatologically favored in mid-May, northeast winds combined with the moist low levels in the wake of the rain and increased dew points are a regime to support LIFR ceilings. Confidence is medium in these occurring and they could be even lower than the 500 ft presently forecast. There could be scattered showers continuing further into the morning, and if that were to happen, it may disrupt some of the lower ceilings at least temporarily. Patchy drizzle certainly is a possibility too and that would lower visibility in tandem with the lower ceilings. Ceilings should inch their way up into the afternoon while northeast winds remain fairly light. Showers and some storms are likely to increase in coverage across the region later Sunday night. MTF && .MARINE... 349 PM CDT A persistent pressure pattern will remain over the lake through early next week. An elongated ridge from the central Plains to the northeast will slowly shift south early next week. An elongated trough extending from the central Plains to just north of the Ohio River will dissipate early next week. North winds become easterly tonight, and 10-20 kt winds are expected over the southern half of the lake. As the ridge shifts south, light and variable winds are expected across the lake. Winds turn southwest over the northern end of the lake Sunday night followed by another period of light and variable winds. Winds become northeast across the lake as a series of surface highs shift from Manitoba to Quebec Monday night through late next week. JEE && .LOT WATCHES/WARNINGS/ADVISORIES... IL...Flash Flood Watch...ILZ013-ILZ014-ILZ022 until 10 AM Sunday. Flash Flood Watch...ILZ008-ILZ010-ILZ011-ILZ012-ILZ019-ILZ020- ILZ021 until 7 AM Sunday. IN...Flash Flood Watch...INZ001-INZ002 until 10 AM Sunday. LM...None. && $$ 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