Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 03/10/20

Area Forecast Discussion
National Weather Service Denver/Boulder CO
743 PM MDT Mon Mar 9 2020 .UPDATE... Issued at 743 PM MDT Mon Mar 9 2020 A few showers have formed off to the east of Denver this evening. No lightning with this activity, though it can`t be totally ruled out. The showers will track east this evening and stay east of the Urban Corridor. Adjusted Pops to reflect the current showers. No other changes to the forecast area planned. && .SHORT TERM...(This evening through Tuesday) Issued at 300 PM MDT Mon Mar 9 2020 Westerly flow aloft is going to prevail over the next 24 hours, in the wake of today`s departing weather system. A few snow showers have developed over the mountains, which should continue through tonight. Coverage of showers and snow accumulations should be pretty light. A few rain showers are forecast on the northeast plains this evening with the latest HRRR runs still showing a round of showers moving across northern Lincoln County between 7 and 10 PM. The increasing westerly flow aloft will help increase the winds over the mountains and foothills through later tonight and Tuesday. Gusts of 40 to 50 MPH will be possible. Some mid level moisture is forecast to be embedded in the westerly flow which will continue producing some light snow showers in the mountains. Once again, snow accumulations are expected to be less than a couple inches. Across the plains, temperatures are expected to rebound into the lower and mid 60s under sunny to partly cloudy skies. .LONG TERM...(Tuesday night through Monday) Issued at 330 PM MDT Mon Mar 9 2020 A shortwave trough over the Central Plains moves east of our area Tuesday night while a cut off trough slowly meanders over California. Ridging will develop over Colorado between these features on Wednesday which will lead to mainly dry conditions. The only exception will be light snow showers in the mountains with minimal accumulation expected. The downslope winds across the plains will lower minimum relative humidities to the teens but the recent rainfall will limit any fire danger. On Thursday, a shortwave trough will move southeastward out of the Pacific Northwest with the main energy passing north of Colorado. The moist, westerly flow will create snow showers in the mountains with light amounts expected. The westerly, downslope flow over the plains will keep conditions mainly dry but a shower or two cannot be ruled out especially over the far northeastern plains. A cold front will push through Colorado during the latter half of Thursday which will drop temperatures Thursday night and Friday. Highs will struggle to get above the mid 40 across the urban corridor and plains as low clouds will be persistent throughout the day. There is quite a bit of uncertainty in the models with regards to precipitation on Friday. The Euro has a much more progressive pattern with the aforementioned cutoff trough moving toward Colorado and producing widespread precipitation across our CWA. On the other hand, the GFS has a slower progression of the upper level pattern with almost no precipitation over our CWA. Right now, the national blend of models has widespread 30 to 50 PoPs which is sufficient for this time. Saturday appears mainly dry as slight ridging develops over Colorado between two troughs. Sunday and into early next week, a longwave trough will position itself over the western US with shortwave troughs rotating through it from time to time. Generally, there is medium to high confidence in early next week being colder and wetter than normal. However, it`s too early to know any details on the amount of precipitation during this period. && .AVIATION...(For the 00Z TAFS through 00Z Tuesday evening) Issued at 743 PM MDT Mon Mar 9 2020 East to southeast winds will prevail through this evening and turn a southerly direction after midnight. A few showers will form and stay to the east of Denver. Outflow from the showers may produce a brief wind shift to the south to southeast. VFR conditions are expected through Tuesday with high clouds streaming across the region. South to southwest winds are expected to shift to the northwest around 20Z behind a weak front. && .BOU WATCHES/WARNINGS/ADVISORIES... None. && $$ UPDATE...Meier SHORT TERM...Dankers LONG TERM...Danielson AVIATION...Meier
Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
1151 PM EDT Mon Mar 9 2020 .AVIATION... Area surface observations indicate lowering ceilings under ongoing low level moistening within the rain. Expect this will still result in a quickly lowering ceiling height to low end MVFR or IFR within the 06Z to 08Z time frame. Area VAD wind profiles and recent RAP soundings indicate that winds in the 1-2k foot layer of 40 to 50 knots combined with the drop in sfc winds will remain supportive of low level wind shear through at least the first 2 to 3 hours of the TAFs. A cold front will traverse Se Mi early in the morning, forecast to pass through MBS around 10Z and metro Detroit around 13Z. This front will cause a wind shift to the north-northwest. Ample low level moisture along the front will sustain IFR and/or low end MVFR cloud bases in light rain/drizzle at least during the early morning hours. For DTW...The cold front is expected to pass through metro around 13Z Tues, which is when the wind shift to the north-northwest is expected. .DTW THRESHOLD PROBABILITIES... * High for ceilings at or below 5000 tonight and Tuesday morning. * High in precip being all rain tonight and Tuesday morning. && .PREV DISCUSSION... Issued at 827 PM EDT Mon Mar 9 2020 UPDATE... Widespread rain remains on target to affect the entire forecast area the latter half of this evening. Regional water vapor shows a mid level low now over nrn Illinois, with good moisture transport into Lower Mi. Deep layer moist isentropic ascent ahead of the wave will sustain the rain into the overnight. The large scale ascent is forecast to wane a bit as the wave lifts northeast across Lower Mi overnight. There has however been some decent frontal forcing noted along the sfc-925mb front, which currently extends from SE Wisconsin into NW Lower Mi. This front will traverse Se Mi late tonight/early Tues morning and will sustain at least some light rain/drizzle into the morning. Although the post frontal cold air will be shallow, upstream observations suggest there will still be a notable temp drop behind the Tues morning cold front; not quite cold enough for precip type concerns. Based on upstream conditions and 18Z guidance, some minor downward adjustments will be made to Tues AM temps. PREV DISCUSSION... Issued at 348 PM EDT Mon Mar 9 2020 DISCUSSION... Low amplitude shortwave with southern branch origins is lifting north toward Lower Michigan and will be absorbed into baroclinic westerlies over the Northeast during the next 36 hours. A transient period of right entrance dynamics is now developing in advance of the wave and is supporting a deepening frontal response that extends to the ground most notably over eastern Iowa and southwest Wisconsin at press time. The remainder of the pre-frontal precipitation shield is being driven by moist isentropic ascent in the 286-306k layer. The bulk of tonight`s rain will be associated with the latter region of forcing as right entrance support rapidly evolves northeast and deposits a weakening frontal circulation over northern Lower. The weak, transient nature of the forcing doesn`t lend much confidence in the more aggressive QPF outcomes among some of the guidance, and that has been reflected in overall model trends across the board. The dry air stream is already well-established and is aggressively eating into radar returns over central Missouri as drizzle forms beneath. The dry slot is timed to surge into the area between 03-06z suggesting the greatest potential for QPF of a few tenths of an inch will be in the Saginaw Valley where duration ahead of this feature will be maximized. Model cross-sections indicate very weakly stable air filling immediately behind the dry slot after 09z. Superposition with the advancing cold front and higher quality low-level moisture, a high coverage of showers appears likely in the 09-12z time window. Rain potential then rapidly spins down through mid-morning Tuesday as subsidence works downward through the column concurrent with post- frontal dry advection. Overnight lows ahead the front will be well above average highs for this time of year, but will likely still fall into the 40s due to wet bulbing. Zonal flow quickly reestablishes on Tuesday minimizing cold advection behind the already-weak cold front. Temperatures will have no issue rebounding back into 50s under post-frontal sun and H85 temps at 0C or warmer for most of the day. Quiet through mid-week with the only item of note being the weak shortwave presently off the coast of the Pacific Northwest. Strong consensus that this wave will quickly translate east bringing a high probability of increased clouds. Chance for rain/snow appears increasingly fleeting as duration of forcing is short and moisture quality is extremely poor. MARINE... Low pressure system located across the Midwest will continue to aim towards Michigan and will travel across lower northern Michigan tonight, producing widespread rainfall for most locations. Return flow behind the low will result in the veering of wind direction from the southwest to northwest throughout early Tuesday morning, and the cooler air in conjunction with a stronger pressure gradient will result in a window of increased winds speeds across Lake Huron. Gusts around 25 knots, isolated 30 knots and elevated wave heights have resulted in the issuance of Small Craft Advisories for the Outer Saginaw Bay and Lake Huron shoreline on Tuesday. High pressure will then quickly fill in behind the cold front and will bring back a period of calm to light winds by Wednesday. HYDROLOGY... Low pressure will bring rain tonight as PWAT values increase to around 1.00 inch. Favorable synoptic forcing along with this moisture will result in total rain around 0.25", except 0.3" in the Saginaw Valley and Thumb where some ponding on poorly drained roads may be possible. && .DTX WATCHES/WARNINGS/ADVISORIES... MI...Lakeshore Flood Advisory from 8 AM to 10 PM EDT Tuesday for MIZ049- 055-063. Lake Huron...Small Craft Advisory from 8 AM to 10 PM EDT Tuesday for LHZ421- 441>443. Lake St Clair...NONE. Michigan waters of Lake Erie...NONE. && $$ AVIATION.....SC UPDATE.......SC DISCUSSION...JVC MARINE.......AM HYDROLOGY....JVC You can obtain your latest National Weather Service forecasts online at
Area Forecast Discussion
National Weather Service Goodland KS
522 PM MDT Mon Mar 9 2020 .SHORT TERM...(This evening through Tuesday night) Issued at 300 PM MDT Mon Mar 9 2020 Today-Tonight: Expect decreasing cloud cover this afternoon, in association with subsidence /height rises/ in the wake of a shortwave progressing eastward from Kansas into Missouri. Meanwhile, upstream in Colorado, marginal diurnal destabilization (~100 J/kg mlcape) is currently underway -- as evidenced by the development of scattered diurnal Cu on the southern flank of the Palmer Divide -- where simulated reflectivity forecasts via the HRRR and RAP suggest that isolated convection may develop invof Limon late this afternoon and early this evening (23-01Z). If convection develops, activity may progress eastward (via westerly steering flow) into portions of Yuma/Kit Carson counties this evening (01-04Z). However, with weak forcing and a meager /diurnally driven/ thermodynamic environment, confidence is low with regard to whether or not activity will (1) develop and (2) persist after sunset. Convection allowing guidance also suggests that isold showers may develop in northwest Kansas overnight -- presumably in assoc/w the onset of low-level warm advection -- though confidence is very low. Tue-Tue night: With southerly flow on the eastern periphery of a developing lee cyclone, expect temperatures to rebound into the mid-upper 60s to lower 70s during the day on Tue. The approach of a northern stream shortwave -- and a period of low-level warm advection /frontogenesis/ on the N-NE periphery of the associated lee cyclone -- may result in the development of elevated convection invof I-70 in northwest KS late Tue afternoon and evening (23-05Z). .LONG TERM...(Wednesday through Monday) Issued at 215 PM MDT Mon Mar 9 2020 At the start of the period, an upper closed low spins off the California coast as a shortwave over the northern Plains continues to push east. West to northwest flow develops over the region behind the exiting wave on Wednesday, with dry weather anticipated. With relative humidities forecast as low as 16 to 22 percent and southwest winds gusting around 20 mph in the afternoon, elevated fire weather conditions could develop in eastern Colorado. A weak disturbance may generate some light rain late Wednesday night into early Thursday for eastern portions of the area. Meanwhile, a low pressure system crosses southern Canada with its cold front looking to sweep through the region sometime Thursday. A fairly active pattern is expected for the extended timeframe. The California closed low comes onshore by Friday and progresses to the Plains through the weekend, becoming an open wave. This disturbance produces precipitation chances Thursday night through Saturday. Precipitation type is diurnally driven, with light rain changing over to light snow during nighttime periods each night. As the aforementioned California disturbance impacts the High Plains, another closed low strengthens over the Pacific Northwest and digs along the west coast. Some disagreement remains on how this system will play out. But at this point, will keep a mention of light precipitation on Sunday and Monday (mainly along and north of I-70) as the low progresses. Temperatures peak at the start of the long term period, with highs in the upper 60s to low 70s Wednesday. A cooling trend is expected thereafter, with highs in the 50s/low 60s on Thursday and in the 40s/low 50s Friday through Monday. Low temperatures fall from the 30s/low 40s Wednesday night to the 20s/low 30s for the rest of the period. && .AVIATION...(For the 00Z TAFS through 00Z Tuesday evening) Issued at 516 PM MDT Mon Mar 9 2020 Widely scattered rain showers will move out of southeast Colorado tonight and across northwest Kansas/southwest Nebraska...but confidence is low in directly impacting either terminal, so will not mention in the TAFs at this time. Overnight...may see lower ceilings develop towards 12z at KMCK with IFR conditions possible. The ceilings are not expected to impact KGLD at this time. For Tuesday...after any low ceilings clear at KMCK, expecting VFR with occasionally breezy surface winds up to 20kts in the afternoon. && .GLD WATCHES/WARNINGS/ADVISORIES... KS...NONE. CO...NONE. NE...NONE. && $$ SHORT TERM...VINCENT LONG TERM...JBH AVIATION...024
Area Forecast Discussion
National Weather Service Los Angeles/Oxnard CA
900 PM PDT Mon Mar 9 2020 .SYNOPSIS...09/805 PM. A low pressure system to our west will move through the region bringing rain to the area over the next few days. Thunderstorms are possible Tuesday and Tuesday night, and will bring moderate to heavy downpours and possibly small hail. Some lingering showers are possible Thursday. Mostly dry weather is expected for Friday and Saturday. && .SHORT TERM (MON-THU)...09/839 PM. A cutoff upper low has moved very little since this morning, still near 30n/128w. For this evening, a significant influx of mid and high level clouds continues across the region. Doppler radar is indicating increasing shower activity streaming in from the south, mostly south of Catalina Island as of 8 pm. This area of showers is associated with an increasing upper level diffluent area developing across the region tonight. As the upper level low pressure system starts to track east overnight, there will be increasing chances of showers, with the best chances in the mountains. Models in pretty good agreement placing the center of the upper low about 600mi west of LAX around noon Tuesday. Widespread light rain should be developing early Tuesday morning south of SLO County, then turning heavier and affecting the entire forecast area late morning through evening. While the main atmospheric river axis with this storm will stay well south of our area, there is still ample moisture being pulled into our region tomorrow, with precipitable values maxing at around 1.0 inch. The main concern with this system will be the convective threat, especially from late Tuesday morning through Tuesday evening when the left front quadrant of a strong 120 knot jet core is over the region, along with a continued area of upper level diffluence. In addition, lapse rates become more unstable during the afternoon and evening as the cold upper low approaches the region, with 500 mb temperatures falling as low as -24 degrees celsius by Tuesday evening. The NAM 12 and RAP models both indicating impressive convective parameters with a large area of negative lifted index values (as low as -5 to -7) and CAPE values ranging between 500-1000 J/kg which is notable for a winter storm system. Will be issuing a Special Weather Statement to highlight the thunderstorm threat across Southwest California on Tuesday. Any thunderstorms that develop on Tuesday will have the potential to produce brief heavy downpours (with rainfall rates locally up to 1 inch per hour), small hail, and gusty winds. In addition, conditions are also favorable for isolated waterspouts on Tuesday, which can potentially come ashore as small tornados. Potential impacts due to the convective threat include roadway flooding, minor mud/debris flows in recent burn areas, rock/mudslide activity on canyon roads, and beach lightning. Projected rainfall amounts still look on track for the storm. *** From previous discussion *** Rainfall rates up to an inch per hour are possible with thunderstorms, though steering flow is pretty strong at 30-40kt from the south during the peak of the event so storms will be moving pretty quickly. Will not be issuing flash flood watches at this time as even those rates for short bursts are not expected to generate widespread flash flooding. Most coast/valley locations are now expected to receive amounts in the 1-2" range (highest south of Pt Conception and where thunderstorms form) and up to around 3" in the mountains. Minimal snow impacts with this system as snow levels will be at or above 7500` for the vast majority of the event. The resorts will likely see decent accumulations but not much, if any on most of our major mountain roads. It`s not certain where the upper low will be after Tuesday but most of the models are suggesting just a scattered shower regime Wednesday. Can`t rule out thunderstorms but probability is too low to add at this time. Additional precip amounts expected to be on the light side (a quarter inch or less except in thunderstorms). Thursday is potentially interesting as northeast flow develops across the area behind the upper low which is expected to be moving into northern Baja. Some models are showing moisture returning to LA/Ventura Counties and possibly some light precip but very low confidence in this and impacts pretty minimal either way. Snow levels are still at or above 7000`. .LONG TERM (FRI-MON)...09/216 PM. Models differ on how fast to move the low east but all of them have out of CA Friday night. However, there`s still a non-zero threat of light precip eastern areas Friday. On Saturday there is a strong onshore push and the GFS is showing a rapidly deepening marine layer. If this happens there could be some drizzle or light showers, mainly south of Pt Conception. The ECMWF ensembles are almost unanimous showing light precip so Saturday may end up being a little wetter than what is currently indicated in the forecast but amounts would likely be very light and best chances would likely be eastern LA County. Then we turn our attention to a system approaching from the north Sunday into Monday. Being a northerly system models are at odds with how much moisture it will have with the ECMWF definitely the wetter of the two but certainly warrants a chance of rain in the forecast. && .AVIATION...10/0001Z. At 2355Z, there was no marine inversion at KLAX. Overall, moderate confidence in 00Z TAF package. High confidence in VFR conditions for all sites through this evening. For Tuesday, rain will gradually spread over the area with conditions lowering to MVFR levels. High confidence in rain developing with gusty east-southeast winds, but still some uncertainty in timing of steady rain and associated MVFR conditions, however highest probability after 16z. Indicated 30 percent probability of thunderstorms on Thursday afternoon for TAF sites south of Pt Conception. KLAX...Overall, moderate confidence in 00Z TAF. High confidence in VFR conditions through tonight. For Tuesday, high confidence in light-moderate rain developing after 14Z, but low confidence in timing of steady rain and development of MVFR conditions. 30 percent chance of thunderstorms near KLAX in the afternoon. Moderate confidence in southeast winds around 10 knots after 08Z, with brief gusts as high as 15 knots possible Tuesday morning. KBUR...Overall, moderate confidence in 00Z TAF. High confidence in VFR conditions through tonight. For Tuesday, high confidence in light-moderate rain developing after 14Z, but low confidence in timing of steady rain and development of MVFR conditions. 30 percent chance of thunderstorms near KBUR in the afternoon. && .MARINE...09/856 PM. For the Outer Waters, moderate to high confidence in current forecast. Have issued SCA for Tuesday for SE to E winds across zones 673/676 with a 30 percent chance of SCA conditions for zone 670. For Wednesday and Thursday, winds and seas are expected to drop below SCA levels. On Friday, there is a 50% chance of SCA level northwest winds. For the Inner Waters north of Point Sal, moderate to high confidence in current forecast. Other than a 30% chance of SCA level southeast winds on Tuesday, winds and seas are expected to remain below SCA levels through Saturday. For the Inner Waters south of Point Conception, have issued a SCA for zones 650/655 due to E-SE winds. Otherwise, winds and seas are expected to remain below SCA levels through Saturday. With the gusty southeast winds tonight and Tuesday, steep short- period seas will be likely. Additionally, there is the possibility of thunderstorms Tuesday and Tuesday night with the potential for waterspouts. && .LOX WATCHES/WARNINGS/ADVISORIES... CA...Beach Hazards Statement in effect from 7 AM PDT Tuesday through Tuesday afternoon for zones 40-41-87. (See LAXCFWLOX). PZ...Small Craft Advisory in effect from 3 AM to 3 PM PDT Tuesday for zones 650-655-673-676. (See LAXMWWLOX). && .HAZARD POTENTIAL OUTLOOK (THU-MON). No significant hazards expected. && $$ PUBLIC...Gomberg/MW AVIATION...Gomberg MARINE...Gomberg/RAT SYNOPSIS...Phillips
Area Forecast Discussion
National Weather Service Nashville TN
835 PM CDT Mon Mar 9 2020 .UPDATE... FOR EVENING DISCUSSION. && .DISCUSSION... Scattered echoes are finally showing up in Middle Tennessee, and the showers have had a difficult time becoming established given the dry surface-based layer in place. Dew points near the Tennessee River have risen dramatically just in the last few hours, so it looks like the boundary layer is finally becoming saturated there. The 00Z sounding from OHX still shows a dry surface-based layer, and we`re seeing no CAPE and a +8 lifted index. However, some destabilization will occur as we experience additional evaporation below the cloud base and dew points increase correspondingly. Don`t know if it will be enough to produce convection, but we`ll leave mention of TS in the forecast for after midnight, as the HRRR does suggest some pockets of higher reflectivity later on. Will update the public forecast in a little while to remove the "early evening" wording. && .AVIATION... 00Z TAF DISCUSSION. BNA/MQY/CKV/CSV...Mid and high clouds have spread across Middle Tennessee with an increased southerly flow and increasing low- level jet (contributing to significant LLWS during the next several hours). Dew point spreads are still relatively large (15-20F), but there are a few echoes now showing up east of the Tennessee River, and look for this moisture to gradually work its way down to the surface during the evening. So we can expect ceilings to lower to MVFR for most of tonight and tomorrow in addition to widespread showers. In addition, there may be just enough CAPE for at least isolated thunderstorms with this weather system coming through. The chance of TS isn`t great enough to warrant mention in the TAF`s, but please be aware of the possibility of convection and CB`s. && .OHX WATCHES/WARNINGS/ADVISORIES... NONE. && $$ DISCUSSION......08 AVIATION........08
To quote yesterday`s long term forecast discussion in regard to the
upcoming winter storm on Thursday and Friday , "At this point in
time, there is high certainty that a high impact winter storm will bring heavy snow to the mountains and there is medium certainty that there will be heavy wet snow developing over the lower elevations." Well, I now have lower confidence... Model diagnostic discussions from the WPC discuss how the GFS is an outlier and to rely and the ECMWF, which I agree with. The GFS and the EC were in agreement yesterday, but the deterministic GFS now gives southern Colorado mountain snow, but nothing over the lower elevations. The EC still brings snowfall to the lower elevations, but the latest run resolves a weak shortwave trough, as compared to the closed low resolved yesterday. Ensemble forecasts don`t appear to be much helps either, as the GEFS is flip-flopping much like its deterministic sibling. Now for a time line of the forecast. Thursday will have another round of instability snow showers confined over the mountain tops of the Continental Divide. A front associated with a shortwave located to the north of Colorado will develop overhead, cooling down temperatures, primarily over the plains during Thursday afternoon or evening. The main low pressure system will begin to impact southern Colorado early Friday morning, bringing snowfall over the mountains first, spreading east with time. Similar to yesterday`s forecast, the initial surge of precipitation over the plains should be rain with a few rumbles of thunder, but as the day progresses temperatures will cool and there will be a messy forecast of where the rain-snow line is. Places like Teller, northern El Paso County, and the mountains should be below freezing throughout the event, therefore only snow is expected there. So, to summarize, there is still high confidence for heavy mountains snow, but less confidence for the impacts on the lower elevations. This forecast was ECMWF- heavy per guidance from WPC. After the storm passes, the upper flow will be from the southwest, promoting dry conditions with isolated snow showers over the higher elevations. All of this is dependent on how the first storm develops across the region. && .AVIATION...(For the 00Z TAFS through 00Z Tuesday evening) Issued at 308 PM MDT Mon Mar 9 2020 KCOS and KPUB are expected to have VFR conditions the next 24 hrs, with periods of clouds. There could be some showers in the vicinity of KCOS late this evening or into the very early morning hours. Winds should generally be 12 kts or less through midday Tue, then winds are expected to be southwesterly and gusty, with gusts of 20- 25 kts being possible. KALS will also have periods of clouds, but conditions should be VFR. Winds at KALS should mostly be under 12 kts, but will increase late Tue morning from the southwest, and could be gusty through the afternoon. Gusts could be 20-25 kts. && .PUB WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SHORT TERM...28 LONG TERM...SKELLY AVIATION...28