Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 03/28/18

Area Forecast Discussion
National Weather Service Boston/Norton MA
951 PM EDT Tue Mar 27 2018 .SYNOPSIS... Very light and widely scattered showers may lead to light icing mainly across W MA and W CT late tonight into early Wednesday morn. Expect improving conditions through the day on Wednesday. Warmer air moves north on Thursday, then a cold front sweeps across the region Friday. Expect mild air and showers during this time. Another cold front may bring another round of precipitation sometime early next week. && .NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/... 10 pm update... Indications per progression of 0z upper air soundings W to E, low- level dry air deeper E, further top down saturation W, and notably surface high dewpoint depressions. Attendant suppressive environment, anti- cyclonic flow, tough for observed precipitation per WSR-88D to advance E. Dual-pol included, indications of mixed sleet and rain, whether as freezing rain depends if its reaching the ground and if temperatures are sub-freezing. Isentropic shield progresses along 290-310K surfaces, pressed against the cut-off low S of Nova Scotia, in-between sinking, drier air. Per RAP model, watching moisture below H7 which should increase chances of precip reaching the ground, especially sleet. Trends echoed with chance PoPs. Greater outcomes after midnight and mainly W MA / W CT as top down saturation proceeds slowly E against aforementioned suppressive environment. Lift remains weak, outcomes light overall. Presently, above freezing, but a diurnal cooling trend plus wet-bulbing is expected lending to marginal sub-freezing temperatures, especially over the deeper snow pack high terrain. Again, outcomes light given circumstances noted above. Will keep the SPS through the morning as a precaution. && .SHORT TERM /6 AM WEDNESDAY MORNING THROUGH 6 PM WEDNESDAY/... Wednesday... Risk for precipitation ends as the moisture dissipates rather rapidly through the day, likely thanks to the synoptic- scale enhanced subsidence provided between the two systems mentioned above. This should lead to some breaks in the clouds through the day as well. The continuation of modest low- mid lvl WAA will lead to H85 temps approaching +4C, with an isothermal layer down to H92. Given this, mixing should allow temps to approach the upper 40s across much of the region, with the likelihood of more widespread low-mid 50s especially where the sun is observed. Generally a pleasant day after a damp start. Wednesday night... Warm front will be approaching from the S, which will lead to a combination of increasing moisture and resulting cloud cover through the overnight hours. Not expecting any precip as the overruning is very weak and the moisture is confined mainly well above the sfc. However, the clouds will lead to a milder night than recent nights with min temps likely only dropping into the mid 30s to around 40 in most spots. && .LONG TERM /WEDNESDAY NIGHT THROUGH TUESDAY/... Big Picture... The weather over North America will be dominated by a closed upper low over Hudson`s Bay and vicinity. This will direct several shortwaves through the flow and up across the St Lawrence Valley or Northern New England. The flow across us will be fast-moving, leading to uncertainty in exactly timing the passage of individual shortwaves. The upper jet placement and storm track near or up the St Lawrence Valley suggests a milder than normal late week for our area. Upper heights are also above normal for this period. Heights quickly lower to normal or a little below behind the Friday-Friday night shortwaves, so expect temps cooling to around normal. Model mass and thermal fields are in general agreement through Saturday, then diverge early next week. Confidence is moderate-high through Saturday, and low due to timing issues Sunday through Tuesday. Details... Thursday to Saturday... Weak high pressure overhead Thursday with stalled front over PA-NJ. As the upper ridge shifts east of us and shortwaves approach through the Great Lakes, we expect the westerly upper flow to turn from the southwest. This will nudge the front north as a warm front. The warm fropa should generate some light rain/showers Thursday, followed by mild and humid air. The surface low passes west of us Thursday night and north of us Friday. This will swing a cold front through the region Friday. Expect a chance of showers in the warm sector during this time, tapering off Friday afternoon/evening. A 50-60 knot southwest low level jet moves over the top during this time, with the potential for surface wind gusts as high as 30-35 mph. Surface high pressure moves over us Saturday and should bring dry weather. Warm advection in the warm sector Thursday will limit the depth of mixing, but temps at 950 mb and 1000 mb show potential for max sfc temps near 60 in the interior and 45-50 along the coast. If clouds are thick and showers frequent, then 55 inland and 40-45 coast may work better. We compromised, going a little higher than guidance but lower than full potential. Friday will have a better chance of 60 degrees inland with 50s along the coast. Deep mixing Saturday in cold advection, but temps aloft support max sfc temps in the 50s. Sunday to Tuesday... Less confidence in timing within this part of the forecast. Consensus of the models would suggest a cold front moving through on Sunday. The ECMWF stalls the front close enough to our south to bring a trailing precip shield along the front and reaching to the South Coast and Islands Sunday. The GGEM brings is slower with this precip and brings it to all of Southern New England on Monday. Another shortwave may affect us with showers Tuesday. Timing questions of shortwaves in a fast flow, although it is a reasonable scenario that one or two shortwaves could bring showers during this period. We used a blend of model values. && .AVIATION /02Z WEDNESDAY THROUGH SUNDAY/... Forecaster Confidence Levels... Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Short Term /through Wednesday Night/... Tonight... VFR, lowering MVFR over W CT / W MA with -RA/-FZRA/-PL. Spotty. Looking to remain dry with little to no ice accretion. Light winds. Wednesday into Wednesday night... Spotty morning precipitation, then improving, CIGs lifting. VFR. Winds becoming SW, increasing. KBOS Terminal...High confidence in TAF. KBDL Terminal...Spotty -SHRA/-PL towards Wednesday morning push. May not be enough to wet runways. Little to no impacts. MVFR to low-end MVFR CIGs after midnight into Wednesday morning possible. Outlook /Wednesday Night through Sunday/...Moderate Confidence. Thursday Night: MVFR/IFR conditions possible. Breezy. Chance SHRA, patchy BR. Friday: Mainly VFR, with local IFR possible. Windy with local gusts to 30 kt. Chance SHRA. Friday Night: VFR. Breezy. Slight chance SHRA. Saturday: VFR. Breezy. Saturday Night through Sunday: VFR. Breezy. Slight chance SHRA. Sunday Night: VFR. Monday: Breezy. Slight chance SHRA. && .MARINE... Short Term /through Wednesday/... Through the overnight hours...High confidence. Diminishing NE winds, likely dropping below Small Craft thresholds by midnight as they shift to the S-SW. However, with an offshore storm still churning south of Nova Scotia, swells will continue to impact the waters with 9-11ft seas on the open ocean. Small Craft Advisories will therefore continue, in spite of the weakening winds. Wednesday and Wednesday night...High confidence. Winds become variable at times, but predominantly W-SW and mainly below 15kt. Swells continue, with 10+ ft seas beginning the day on Wed, gradually lowering through the overnight. Small Craft Advisories linger due to these higher seas. Outlook /Wednesday Night through Sunday/...Moderate Confidence. Thursday Night: Winds less than 25 kt. Areas of seas approaching 5 ft. Slight chance of rain showers. Friday: Winds less than 25 kt. Areas of rough seas. Chance of rain showers. Friday Night: Winds less than 25 kt. Areas of rough seas. Slight chance of rain showers. Saturday: Low risk for Small Craft Advisory winds with gusts up to 25 kt. Local rough seas. Saturday Night: Winds less than 25 kt. Areas of rough seas. Slight chance of rain showers. Sunday: Low risk for Small Craft Advisory winds with gusts up to 25 kt. Areas of rough seas. Chance of rain showers. Sunday Night: Winds less than 25 kt. Areas of seas approaching 5 ft. Monday: Winds less than 25 kt. Slight chance of rain showers. && .EQUIPMENT... Due to our move to the new forecast office in Norton, MA, we are still trying to resolve some communication issues. The following NOAA Weather Radio transmitter is back on the air... Somers, CT transmitter........WXJ41.....162.475 MHz However, the following NOAA Weather Radio transmitters are not yet on the air... Johnston, RI transmitter......WXJ39.....162.400 MHz Gloucester, MA transmitter....WNG574....162.425 MHz Blue Hill, MA transmitter.....KHB35.....162.475 MHz Hyannis, MA transmitter.......KEC73.....162.550 MHz Paxton, MA transmitter........WXL93.....162.550 MHz && .BOX WATCHES/WARNINGS/ADVISORIES... CT...None. MA...None. RI...None. MARINE...Small Craft Advisory until 8 PM EDT Wednesday for ANZ232. Small Craft Advisory until 2 PM EDT Wednesday for ANZ235-237. Small Craft Advisory until 8 AM EDT Thursday for ANZ250-251. Small Craft Advisory until 5 AM EDT Thursday for ANZ254-255. Small Craft Advisory until midnight EDT Wednesday night for ANZ256. && $$ SYNOPSIS...WTB/Doody NEAR TERM...WTB/Doody/Sipprell SHORT TERM...Doody LONG TERM...WTB AVIATION...WTB/Doody/Sipprell MARINE...WTB/Doody EQUIPMENT...WFO BOX Staff
Area Forecast Discussion...UPDATED
National Weather Service Corpus Christi TX
1031 PM CDT Tue Mar 27 2018 .DISCUSSION...Convection continues to increase over the western Brush Country along surface trough axis. MLCAPE is in the 1500-2000 J/kg over this region with effective bulk shear of 60 knots. Threat for severe will continue into the overnight hours. Latest HRRR model depicts possible decreasing trend late tonight. Forecast update for new Severe Thunderstorm Watch for Webb, La Salle, and McMullen Counties until 08Z. && .PREVIOUS DISCUSSION... /Issued 636 PM CDT Tue Mar 27 2018 by National Weather Service Houston/Galveston TX/ AVIATION... Low level moisture will continue to stream into the region beneath a capping inversion. MVFR ceilings are expected to develop shortly after 00z and prevail for much of the night. A weak short wave will bring showers and thunderstorms to the southern TAF sites between midnight and 6 AM with a break in precipitation over the eastern TAF sites. An upper level trough will bring additional showers and storms Wednesday afternoon. Ceilings will likely remain MVFR or may briefly mix out to low VFR cigs in the early afternoon. 43 && .PRELIMINARY POINT TEMPS/POPS... Corpus Christi 72 80 65 84 60 / 30 60 80 20 10 Victoria 70 81 62 82 54 / 40 70 80 20 10 Laredo 72 84 63 89 57 / 50 40 60 0 0 Alice 71 83 65 86 57 / 50 60 70 10 0 Rockport 72 77 67 79 62 / 30 60 80 20 10 Cotulla 69 83 59 87 56 / 50 60 40 0 0 Kingsville 73 82 65 85 58 / 30 60 80 20 10 Navy Corpus 72 77 68 80 63 / 20 50 80 30 10 && .CRP WATCHES/WARNINGS/ADVISORIES... TX...None. GM...Small Craft Advisory until 7 AM CDT Wednesday For the following zones: Coastal waters from Baffin Bay to Port Aransas out 20 NM...Coastal waters from Port Aransas to Matagorda Ship Channel out 20 NM. Small Craft Advisory until 1 AM CDT Thursday For the following zones: Waters from Baffin Bay to Port Aransas from 20 to 60 NM...Waters from Port Aransas to Matagorda Ship Channel from 20 to 60 NM. && $$ TMT/89...SHORT TERM
Area Forecast Discussion
National Weather Service Austin/San Antonio TX
813 PM CDT Tue Mar 27 2018 .EVENING UPDATE... Opted to issue a Flash Flood Watch for a locations east of the Edwards escarpment for tonight and overnight. Throughout the evening, continued increases in QPF production in the hi-res model suite have been noted, specifically in the HRRR and TTU-WRF output. These models have generally been performing well with ongoing convection along a slow moving outflow boundary draped across the I-35 corridor. Reasonable confidence has been placed on these models. Each continues to indicate an enhancement of precip coverage over the Del Burro mountains in Mexico and spreading northeast towards the aforementioned outflow boundary. 00Z KDRT sounding is already showing PWAT values of 1.36 inches with moistening mid levels and elevated instability to go along with 50+ kts of 0-6 km bulk shear. As this area of convection progresses eastward, PWATs should increase even further. The outflow currently sluggishly pushing southeast is expected to continue to slow and potentially stall just east of the I-35 corridor, which could set the stage for additional surface based lift. Thus, the concern for some locations along and near the I-35 corridor reaching flash flood guidance values is increasing despite the favorable antecedent conditions (lack of significant rainfall lately). This is mostly a concern for the metro areas of San Antonio and Austin that are more susceptible to 1-2 inch per hour rain rates, however, localized flooding may occur farther east, especially if the outflow indeed stalls. && .PREV DISCUSSION... /ISSUED 716 PM CDT Tue Mar 27 2018/ AVIATION... Tumultuous flying and airport operation forecast expected through the overnight hours and into Wednesday as multiple rounds of showers and thunderstorms look to impact all sites. KAUS/KSAT/KSSF will have greater impacts as KDRT will miss the possible second round early Wednesday morning. Light -SHRA is ongoing near KAUS/KSAT/KSSF as of 00Z. TSRA is expected to then develop over Mexico and spread northeast from 05Z-12Z into the TAF sites. KDRT will be near or under TSRA near 02Z-07Z. TSRA could be strong to severe at times along with very heavy rainfall. Visibilities will be reduced to 2-4SM and likely lower if strong storms are right over the airport. Turbulence and around the stronger storms is to be expected. General low-end MVFR and high-end IFR will occur but brief LIFR conditions will be possible. SHRA/TSRA should exit east of the TAF sites by 21Z Wednesday afternoon as another round of storms develops in the Coastal Plains and points heat towards KHOU/IAH and KVCT. VFR will return Wednesday afternoon. PREV DISCUSSION... /ISSUED 256 PM CDT Tue Mar 27 2018/ SHORT TERM (Tonight through Wednesday Night)... Key Messages: - Widespread showers and storms develop late tonight through Wednesday morning. - 1-2 inches of rainfall appears likely along the I-35 corridor counties as well as points east that are north of I-10. Localized pockets up to 4 inches are possible. - Despite the likelihood of localized heavy rainfall, widespread flash flooding is currently not expected given the recent dry conditions. However isolated pockets of flooding can`t be ruled out, especially in areas prone to more rapid runoff such as urban areas. - Some storms tonight and Wednesday could become severe, containing large hail and damaging straight-line winds. - Conditional risk of strong to severe storms near and east of I-35 Wednesday afternoon and evening. Early convective outflow boundaries and cool pool to the north have pushed the weak surface boundary southeast to just south of a Llano Fredericksburg to Del Rio line. The boundary per HRRR will slow southward movement through the afternoon and early evening. Aircraft soundings at SAT and AUS continue to indicate cap between 800-700mb, although weakening since late this morning. Isolated streamer showers will continue beneath the weakening cap through the afternoon. Can`t rule out an isolated storm or two through early evening near the aforementioned surface boundary and across Central Texas. Bigger concerns to the forecast come tonight into Wednesday morning. Convection is forecast to rapidly develop upstream across the higher terrain in northern Coahuila by early evening in response to height falls ahead of a strong ejecting shortwave impulse. The showers and storms should expand in coverage as they cross into the southwest CWA between 02Z-04Z near what`s left of the aforementioned boundary. Deep layer shear vectors parallel to the boundary should allow the convection to organize into clusters on the cool side of the boundary, which in turn will help push the boundary southeast. Models indicate increased divergence aloft as 110 kt 300mb jet streak noses into the region, and deep omega values spreading northeast through the area, and the convection could expand significantly in coverage overnight to the northeast, becoming widespread through portions of the eastern Hill Country, I-35 corridor, and portions of the Winter Garden and Brush Country regions. Upwards of 1500-2000 J/Kg of MUCAPE could still be present in portions of the warm sector coinciding with bulk shear values of 60-70 kts. This will support a risk of severe storms with large hail and damaging straight-line winds tonight. We have included this mention in the grids and zones. PWATs are progged to climb to around 1.4-1.7 inches tonight, near record values for this time of year. Could be some pockets of training given the evolution of storms expected above. 1-2 inches of rainfall average appear likely along the I-35 corridor counties and east of I-35 and north of I-10. Localized pockets up to 4 inches are possible through this region, and indicated by GFS, Canadian, and Texas Tech 4 km WRF. We have added locally heavy rainfall into the forecast grids and zones. Given the recent drought conditions and difficulty pinpointing exactly where the heavier pockets fall, we will hold off on a Flash Flood Watch at this time. Nevertheless, some localized areas of flooding could occur, especially in urban areas. The thunderstorm evolution during the day on Wednesday and into Wednesday evening afternoon remains difficult to pin down. It will be highly dependent on how progressive and widespread showers and storms are in the morning that potentially stabilize the atmosphere. The Texas Tech WRF, which is the most robust with overnight and early morning convection, does stabilize things across the region mid morning through early afternoon. An uptick in convective development is noted near and east of I-35 late Wednesday afternoon by most global models, than NAM12, and Texas Tech WRF as conditions de-stabilize ahead of the cold front and main forcing in the base of the trough swings through. Should storms re-develop late Wednesday afternoon, can`t rule out some of these storms being strong to severe, producing hail and damaging straight-line winds, given the steep mid level lapse rates and strong bulk shear values. Precipitation should end west to east overnight into Thursday morning. LONG TERM (Thursday through Tuesday)... Drier air will shift into the region Thursday and Friday. A return flow will setup Saturday and strengthen through the weekend, becoming breezy at times and producing warmer temperatures and an eventual return of clouds by Sunday. The ECMWF continues to indicate a frontal passage Monday and disturbance aloft producing a chance for precipitation. The GFS is farther north with the front but does show a disturbance in the southwest flow aloft generating precipitation over the region Monday, while the Canadian stalls the front over the area. Confidence in the temperature and PoP forecast is currently low at this time for Monday and will continue with 20 PoPs. && .PRELIMINARY POINT TEMPS/POPS... Austin Camp Mabry 65 74 57 81 53 / 100 90 40 - 0 Austin Bergstrom Intl Airport 65 76 56 81 51 / 100 90 40 - 0 New Braunfels Muni Airport 66 78 57 82 52 / 100 90 40 - 0 Burnet Muni Airport 61 71 51 77 48 / 90 70 20 0 0 Del Rio Intl Airport 63 84 53 86 54 / 70 20 - 0 0 Georgetown Muni Airport 61 72 53 79 50 / 100 90 40 0 0 Hondo Muni Airport 67 80 54 86 52 / 100 60 30 0 0 San Marcos Muni Airport 65 77 56 82 52 / 100 90 40 - 0 La Grange - Fayette Regional 69 78 59 81 54 / 90 90 70 10 0 San Antonio Intl Airport 68 78 59 83 53 / 100 90 40 0 0 Stinson Muni Airport 68 79 59 84 54 / 100 90 40 - 0 && .EWX WATCHES/WARNINGS/ADVISORIES... Flash Flood Watch through Wednesday evening for Bastrop-Bexar- Blanco-Burnet-Caldwell-Comal-Fayette-Gonzales-Guadalupe-Hays- Kendall-Lavaca-Lee-Travis-Williamson-Wilson. && $$ Mesoscale/Aviation...Allen Synoptic/Grids...TB3 Public Service/Data Collection...Treadway
Area Forecast Discussion
National Weather Service Grand Forks ND
956 PM CDT Tue Mar 27 2018 .UPDATE... Issued at 956 PM CDT Tue Mar 27 2018 00Z NAM as well as the RAP and HRRR have been trending towards the less impressive side with our precip tonight. Slowed down the onset of precip and lowered POPs just a bit, as not all of the radar returns seen to our west have been reaching the ground. Temps have stayed fairly steady in the mid 30s, and road temps are progged to stay near or even above freezing for much of the night. Think that precip will be mostly rain, although a tiny bit of snow or freezing rain mixing in is not out of the question. Amounts look light and impacts minimal. && .SHORT TERM...(This evening through Wednesday) Issued at 306 PM CDT Tue Mar 27 2018 Diffluent flow aloft is beginning to spread into western ND ahead of an approaching shortwave trough. Temperatures over eastern ND/NW MN have reached the low to mid 40s at some locations, whit all of our CWA above freezing. WAA is shown to remain in place through most of the night with wetbulb profiles remaining above freezing through most of the period of peak lift/moisture advection. Increasing low level winds and cloud cover will also help keep above freezing surface temperatures in place. This sets the stage for rain being the favored precip type. Best chance for the surface layer to drop to freezing will be in our northwest where stronger CAA spreads into the region first. As CAA spreads further east Wednesday morning measurable precipitation should be tapering off. I still can`t rule out a rain/snow mix or pockets of freezing rain/sleet, but unless a surface is at or below freezing or lower impacts may be low. This seems unlikely after the amount of warming observed today. Windy conditions are expected during the day Monday with stronger CAA and daytime temperatures may hold steady or even fall a little through the day. Any lingering measurable or non measurable precip should end by midday as subsidence/drying overspreads our CWA from the west. .LONG TERM...(Wednesday night through Tuesday) Issued at 304 PM CDT Tue Mar 27 2018 Quiet weather to start this period before a cold front moves across the Northern Plains Thursday evening into Friday. This will bring colder temperatures, higher winds, and light snow. The colder weather will be here to stay into at least early next week. Below normal temperatures with highs in the upper twenties to low thirties and lows into the single digits are expected. The next chance for precipitation will arrive Friday evening into Saturday. There is still a high amount of uncertainty with this system as model guidance still varies significantly. The ECMWF is developing a shortwave while the GFS keeps northwesterly flow aloft. At the surface the ECMWF has a well developed low move across the Northern Plains while the GFS keeps much of the precipitation to the south as it does not develop a similar surface low. The NAM is more similar to the ECMWF and the CMC is somewhere between the GFS and ECMWF. Future runs will be needed to increase confidence. After the system on Saturday passes we will enter a quieter period with a chance for some light snow Monday. The main story Sunday to Tuesday will be the below normal temperatures with apparent temperature in the single digits above and below zero overnight. && .AVIATION...(For the 00Z TAFS through 00Z Wednesday evening) Issued at 704 PM CDT Tue Mar 27 2018 VFR conditions throughout the forecast area with increasing high and mid level clouds. Southwest winds at 40kts at the 925mb level could bring some LLWS to portions of the forecast area later tonight, so included a mention for all but KDVL. Rain moving into the area will be mostly near the Canadian border, but included a TEMPO group mention at KDVL and KGFK. Stratus will move in behind the precipitation with a cold front, dropping ceilings to the MVFR category. Winds will increase out of the southwest ahead of the front to the 15 to 25 kt range, and even stronger out of the northwest by early morning, with gusts above 25 kts possible. MVFR conditions and breezy northwest winds will continue for much of the day tomorrow with some slight improvements by the end of the period. && .FGF WATCHES/WARNINGS/ADVISORIES... ND...None. MN...None. && $$ UPDATE...JR SHORT TERM...DJR LONG TERM...NC AVIATION...JR
Area Forecast Discussion
National Weather Service Fort Worth TX
1008 PM CDT Tue Mar 27 2018 .UPDATE... A deep upper trough digging through southern New Mexico continues to set off round after round of convection across the Southern Plains. A broad surface low is positioned across southwestern Texas with a slow-moving front draped to the northwest toward Abilene, Graham, and Ardmore, Oklahoma. A consolidated outflow boundary from the previous several rounds of convection has surged southward through the entire forecast area into Central Texas which has stabilized the boundary layer while keeping surface winds generally easterly. Elevated thunderstorms with a threat for hail will still be possible as MUCAPE of up to 1000 J/kg remains in place across some of our southern counties. The main concern continues to be the potential for heavy rain and some flooding concerns, especially across our southern and eastern zones. The next round of widespread heavy rain will be taking shape over the next ~6 hours, and the greatest flooding risk generally lies south of I-20 and along/east of I-35. Lift should be enhanced by the front as it finally sinks southward toward Central Texas by daybreak. Rainfall totals could reach as high as 3-5" (in very localized areas) in a short amount of time overnight, and a Flash Flood Watch remains in effect though tomorrow. With this update, have only trimmed a few of the western/northern counties from the Watch as rainfall is expected to be lighter and less widespread in these areas through the remainder of the event. Products for this update have already been sent. -Stalley && .AVIATION... /Issued 708 PM CDT Tue Mar 27 2018/ /00z TAFs/ Waves of showers and isolated thunderstorms will continue to affect TAF sites through this evening and overnight. Convective activity will be due to lift from numerous shortwaves pivoting through the deep upper trough centered over AZ/NM, along with aided ascent from a slow-moving frontal boundary currently located through North Texas. In addition, an outflow boundary has surged southward into Central Texas which is leading to isolated showers and storms south and east of the Waco TAF site. The trend over the past few hours has been for thunderstorms to develop southwest of the DFW Metroplex in an area of slightly higher elevated instability. As they move northeastward, they encounter increasingly stable air and become predominantly showery activity with a very limited TS potential. For this reason, have not included TS in the Metroplex TAFs for this evening, but will amend if trends suggest otherwise. In the meantime, cigs/vsbys will vary drastically between VFR and IFR, with the poorest conditions occurring within heavier rain showers. There should be a relative lull in precipitation late this evening and through part of the overnight hours, but widespread low stratus should prevail throughout this time. Several hours of IFR/MVFR cigs seem likely at all TAF sites. The slow-moving cold front will also continue sinking southward, and light NE winds will become more northerly. The combination of the front and another impulse aloft should result in another large wave of showers and thunderstorms affecting much of the area beginning around midnight. The thunder potential will continue to be low in the DFW area, but will keep some TS at Waco with more favorable instability forecast to be present. Another lull in rainfall should occur through midday Wednesday, but IFR/MVFR conditions are expected to prevail at all airports through the entire day. -Stalley && .SHORT TERM... /Issued 347 PM CDT Tue Mar 27 2018/ /Through Tonight/ Scattered to numerous showers and thunderstorms continue across North Texas this afternoon as a large upper low remains to the west sending waves of ascent across the region. In addition, an outflow boundary is surging southward through the region and is now helping to ignite new convection across our southeast counties. A cold front remains across the northern half of the area, just south of the Red River. The front will actually slide farther south tonight and be the main focus for additional showers and thunderstorms through the overnight hours. For the remainder of the afternoon and evening, the main area of concern will be across the southeast counties where afternoon heating has resulted in a narrow corridor of instability. A few strong to marginally severe storms could develop through the evening hours in this area. Otherwise, as the front slides southward tonight, the upper low to the west will edge closer. Stronger height falls will again overspread North Texas with the right entrance region of a 130 kt upper jet becoming positioned across the region. With the increase in upper divergence associated with the jet and strengthening low level convergence along the frontal boundary, we should see reinvigorated convection late tonight from Central Texas into northeast Texas. The potential for heavy rainfall and some flooding issues will continue mainly along and east of I-35. We`ll have high PoPs through the overnight across much of the area, but precipitation should become concentrated along the frontal boundary later tonight. For now, we`ll leave the Flash Flood Watch intact but some western counties may be trimmed later this evening. Dunn && .LONG TERM... /Issued 347 PM CDT Tue Mar 27 2018/ /Wednesday through next Monday/ The main highlight in the first part of the long term forecast period will be the potential for rain and storms through Thursday. Conditions should be drier and warmer for most locations late Thursday at least through Saturday evening. A front will slide southward through the area through the day on Sunday resulting in the return of some rain chances and perhaps another round of thunderstorms. Rain chances will linger thereafter into early next week. Wednesday and Thursday---Another batch of showers and thunderstorms is expected to develop Tuesday night into Wednesday morning across the Big Country and western North TX. This activity should slowly push eastward, but the overall maintenance of this convection is unknown. For now, given the moist environment and broad troughing to the west, I`ll maintain some likely PoPs even as far west as our Big Country and western Red River counties. The more certain area for widespread showers and thunderstorms on Wednesday morning will be across eastern and southeastern parts of our area down across the Brazos River Valley. This area will technically remain in the warm sector and so thunderstorms are more probable here. With the front slowing due to the largely parallel flow through a deep portion of the atmosphere, there will be the potential for training of showers and thunderstorms, especially east of I-35. Given that a majority of the heavier rain activity will likely remain to the east and southeast, we contemplated pulling the Flash Flood Watch for parts of the area. For now, we will let the evening/overnight shifts examine radar/satellite trends as well as new hi-res guidance. before making any refinements. As it pertains to the severe weather risk on Wednesday, some model guidance advertises a fair amount of instability of around 1000 J/kg along with deep layer wind shear of around 50 knots. This would be supportive of strong to possibly severe storms. While these instability values are currently being suggested by RAP guidance for this afternoon, outflow from this morning`s convection may sweep southward and temper instability on Wednesday. This outflow could further re-establish itself should any new convection develop along the true front. If this occurs outflow may be re-invigorated and surge southward which would likely halt the northward progression of richer instability. If instability does surge northward and storms can become surface-based, there could be a window for a few strong to severe storms Wednesday morning and early afternoon. I`ll keep high rain chances during the afternoon hours as large scale ascent from an approaching strong mid-level jet streak overspreads the area from the southwest. Rain chances will decrease some during the evening hours on Wednesday as the true front finally slides eastward thanks to the progression of the upper trough. I won`t completely clear our area from the rain chances as the potent upper trough still remains to the west of the area. Conditions should be relatively drier on Thursday, but a potent shortwave trough is advertised to translate to the east very quickly near and just north of the Red River Valley. Interestingly, there`s not a lot of guidance that actually outputs precipitation with the exception being the latest NAM NEST and ECMWF output. Given the vigor of the vorticity lobe and likely large scale ascent, I wouldn`t be surprised to see some showers or maybe even a rumble of thunder or two, mainly near and north of I-20 on Thursday afternoon. If the column dries out very quickly, it`s possible that only a high based cumuliform clouds result, but for now, I`ll advertise a low chance for PoPs on Thursday across North TX. The aformentioned upstream vorticity lobe should be efficient and bringing down some cooler and eventually less humid area on Thursday and I`ve nudged high temperatures down by a few degrees. Most areas will likely remain in the 60s to near 70 degrees. If NAM guidance is to verify, it could be even cooler with highs in the 50s and 60s. At this time, the NAM remains a colder outlier and for now, I`ll trend warmer. It`ll also be a tad breezy on Thursday with northerly winds of 10 to 15 MPH. Friday and Saturday---The start of the weekend appears largely uneventful in terms of the sensible weather elements as northwest flow aloft develops. It`ll turn warmer and breezier as well on Friday and Saturday as surface winds increase to the 15 to 20 MPH range and become more southerly. Afternoon high temperatures will be above normal with temperatures in the 70s and 80s. Sunday and beyond---Sunday presents the next challenge as model guidance has become a bit more aggressive with the passage of a cold front. The GFS model still appears to be the fastest guidance and places the front across our western Red River counties as early as 00 UTC Sunday (Saturday evening). The ECMWF and Canadian are a tad slower with FROPA closer to 06 UTC Sunday. The big difference between the two model camps, however, is that the GFS quickly lifts the front to the north, while the Canadian and ECMWF blast the front southward through the area. The zonal flow aloft would support a stalling frontal boundary, but closer examinations of surface pressure tendencies and forecast CPC temperature anomalies would argue that there should be a decent push southward with this front. I`ve trended cooler (towards the Canadian/ECMWF guidance) and continued the mention of precipitation on Sunday. At this time, I don`t think it`ll be a complete washout, but it`s possible that there could be some impacts to Sunday morning activities. The weather pattern for Monday and beyond will likely remain active as return flow re-establishes itself across the region. Mostly zonal mid-level flow precludes any specific orientation of PoPs and I`ve gone with some slight chance to chance broad- brushed PoPs with near seasonal temperatures due to generally weak forcing. 24 && .PRELIMINARY POINT TEMPS/POPS... Dallas-Ft. Worth 54 65 52 69 49 / 70 70 30 20 10 Waco 59 66 52 75 47 / 100 90 20 5 10 Paris 55 64 52 67 43 / 80 80 40 20 10 Denton 53 63 49 68 42 / 60 70 30 20 10 McKinney 54 63 50 68 44 / 70 80 30 20 10 Dallas 56 63 53 70 49 / 70 80 30 10 10 Terrell 58 66 51 70 46 / 90 90 40 10 10 Corsicana 60 68 53 73 49 / 100 100 30 5 10 Temple 59 67 53 76 47 / 100 90 10 5 5 Mineral Wells 53 62 47 68 42 / 60 50 20 20 10 && .FWD WATCHES/WARNINGS/ADVISORIES... Flash Flood Watch through Wednesday evening for TXZ093>095- 103>107-118>123-133>135-144>148-157>162-174-175. && $$ 26/82
Area Forecast Discussion
National Weather Service Grand Rapids MI
1001 PM EDT Tue Mar 27 2018 LATEST UPDATE... Update .SYNOPSIS... Issued at 311 PM EDT Tue Mar 27 2018 A cold front will push east of the region this evening taking the rain with it. A break in the precipitation will occur on Wednesday as a weak area of precipitation moves in. Another storm system heads on our direction for Thursday. Rain will spread into the area. Temperatures will fall on the backside of this departing storm. && .UPDATE... Issued at 1001 PM EDT Tue Mar 27 2018 I have increased the cloud over overnight as our latest enhanced night time image loops show low clouds building out into central Lake Michigan as of 9:45 pm. The HRRR cloud forecast is matching this best so that suggests the clouds will hold on most of the night into the mid morning hours. This would decrease the chance of dense fog but I still kept the fog in the forecast as winds will be light and thus fog is still possible. && .SHORT TERM...(This evening through Thursday night) Issued at 311 PM EDT Tue Mar 27 2018 Clouds have remained relatively thick through the day while the axis of rain has shifted east of the region. If we do see extensive clearing...fog could become widespread. However...high level clouds will move in as the lower clouds move out. Thus the risk for widespread fog looks low at this time. Will maintain the patchy fog wording in the forecast for now. There is still considerable uncertainty with the next storm system with regards to the timing...strength and type of precipitation Thursday. The GFS would support falling temperatures on Thursday with snow in the afternoon and evening...with the NAM similar. The latest High Res Euro keeps this system as mainly a rain event...with perhaps a brief period of mix towards the end on Thursday night. The timing of the arrival of the colder air into the system would have to be just right for this to end up as a snow event...which looks like a low potential. Will continue to feature a forecast closer to the Euro...more of a rain scenario. I did lower temperatures on Thursday. .LONG TERM...(Friday through Tuesday) Issued at 311 PM EDT Tue Mar 27 2018 Next up is the storm potential for Saturday. Again there is considerable uncertainty on this one. The GFS draws down a very cold airmass from central the storm system will be pulling through. This would allow for steady accumulating snow on Saturday. The High Res Euro shows little or no chance for this to happen. I will blend the two scenarios. Low POPs Friday night could be snow...then a rain event followed by a potential for some mixed precipitation at the end for Saturday night. Will need to monitor this one closely. && .AVIATION...(For the 00Z TAFS through 00Z Wednesday evening) Issued at 718 PM EDT Tue Mar 27 2018 Dense fog is possible overnight into the early morning hours of Wednesday. In fact as I write this AZO and BTL have just gone IFR in fog. No matter happens tonight we should see enough dry air come in so that all areas should improve to MVFR cigs by midday Wednesday. If things go really well, we may even see mostly sunny skies by afternoon. The cold front has come through the area by late afternoon. Normally that would bring in enough dry air to clear the skies. However this time there is not all that much push behind the cold front that came through. It is not entirely clear to me that the low clouds will really clear. If they do not clear, then dense fog is much less likely. If, on the other hand, they do clear out by say, 06z or so, then even with the dense cirrus overcast tonight we would likely have dense fog due to light winds an wet ground from the 1/4 to 1/2 inch of rain that fell today. For now I when conservative with the TAF forecasts but we will have to watch this closely. && .MARINE... Issued at 311 PM EDT Tue Mar 27 2018 Overall the pressure gradient remains relatively weak through Wednesday night...limiting impacts to mariners. On Thursday the winds will be on the increase behind the departing wave of low pressure. Small Craft Advisories may be needed then. && .HYDROLOGY... Issued at 311 PM EDT Tue Mar 27 2018 Rain amounts Monday night through 11AM Tuesday generally ranged between 0.3 and 0.5 inches. While runoff from this rainfall will cause a minor rise in river levels through the middle of the week, flooding is not expected. Dry weather is expected tonight and Wednesday. Low pressure tracking through the area will provide a good chance for additional rain Thursday and Thursday night, with amounts possibly reaching about a half-inch. This is also not expected to cause flooding. && .GRR WATCHES/WARNINGS/ADVISORIES... MI...None. LM...None. && $$ UPDATE...WDM SYNOPSIS...MJS SHORT TERM...MJS LONG TERM...MJS AVIATION...WDM HYDROLOGY...HLO MARINE...MJS
Area Forecast Discussion
National Weather Service Houston/Galveston TX
859 PM CDT Tue Mar 27 2018 .DISCUSSION... At 800 PM, a cold front extended from just north of Shreveport to Centerville to north of San Antonio. A pre-frontal trough extended just south of the front and this feature is helping to generate scattered to numerous showers and thunderstorms over the northern third of the region. Some of the short term guidance is bullish with rainfall totals overnight and if the HRRR is correct, some spots north of a Brenham to Trinity line could receive between 4 and 6 inches of rain overnight. Have expanded the FFA to include Wharton and Colorado counties tonight and started the Watch at 03z (1000 PM). WPC has expanded the moderate risk for flash flooding into the CWA and slight risk for flash flooding now extends north of a Columbus to New Waverly to Livingston line. GOES-R derived PW values show PWATs near 1.80 inches over the the NW corner of SE TX. 300 MB winds are broadly divergent over East Texas. 850 MB moisture is is present with 850 mb Tds between 13-15 C. Moisture flux convergence is targeting areas north of a Brenham to Trinity line as well so all the ingredients are in place for a heavy rain event tonight as storms train along the weak front tonight. Have bumped PoPs up over the north and sped up the onset but the previous forecast was on the right track. 43 && .PREV DISCUSSION... /ISSUED 701 PM CDT Tue Mar 27 2018/ AVIATION... IFR/MVFR ceilings in place at all TAF sites for the 00Z package. Radar imagery this evening shows a line of showers continuing to move southeastward and will first impact CLL. VCTS should become TSRA around 02Z at CLL, and the possibility for TSRA will hold through the morning hours as the frontal boundary continues to slowly move into SE TX with this first round of precip. UTS will lag behind about an hour or two this evening, but should see similar conditions. CXO is also dealing with RA which should transition to VCSH through the overnight hours. Short term guidance such as the Texas Tech WRF shows a short break in precip for the northern TAF sites mid morning until the early afternoon, and second round of thunderstorms will fill in around 19Z. Expecting TSRA to continue through the TAF period for these sites. IAH and southward begin to see showers associated with the first round of precipitation by the early afternoon hours, transitioning to TSRA around 20-21Z. This precip will also continue through the TAF period for these southern sites. Have began to hint at the arrival of the second round of TSRA for IAH in the early evening hours. Across all sites, expecting southeasterly winds to stay up around 10 kts this evening, until becoming more southerly tomorrow morning. These southerly winds will increase in speed to around 15 kts tomorrow afternoon. Occasional gusts could be possible at times underneath thunderstorms. Hathaway PREV DISCUSSION... /ISSUED 334 PM CDT Tue Mar 27 2018/ DISCUSSION... .Heavy rainfall and strong to severe thunderstorms possible early Wednesday morning through midnight... In the short term warm southeasterly flow in place feeding into the showers and thunderstorm that stretch from near Sanderson in a broad swath through Stephenville to northern Arkansas. Temperatures will remain above normal this evening with the WAA and should start to see the band shifting east and southeast throughout the night. Rain chances ramp up quickly starting around midnight near College Station and Crockett with scattered storms. As the s/w over Baja rotates east then northeast around the upper trough axis expecting to see a flare up in the overall coverage and intensity around 3 am moving into the College Station area and tracking eastward with more storms developing all along the band. Sounding support periods of heavy rainfall with the storms and 2"/hr rainfall rates. SPC has the area highlighted with a slight risk of severe and model soundings show a favorable profile mainly in the afternoon Wednesday. The associated boundary is slow to move through the region and Wednesday at noon the boundary will only be getting close to College Station. This will keep the area in an increasingly unstable atmosphere with deep layer shear and abundant moisture. The primary mode of severe weather will probably be hail and gusty winds winds across the north and closer to the coast the threat of tornadoes increases especially in the 1 pm to 6 pm window Wednesday on the incoming nose of the 850 speedmax. SRH 1km 125-200/MUCAPE 1400-2700j/kg with the higher end conditions closer to the coast. Some of the high res guidance also indicating long lived supercell characteristics mainly along and south of the I-69 corridor. At this point expect to see some strong/severe thunderstorms lined up from Jackson county along the 69 corridor with greater instability focused toward the Jackson/Matagorda area. The band should continue to shift slowly southward and the heavy rain threat after 10 pm-midnight should be tailing off along the 69 corridor and shift to the coast. Widespread rainfall of 1-3 inches looks likely with narrow bands of 4 to 5 inches. Have issued a Flash Flood Watch for the northern areas beginning at 1 am and the southern areas at 7 am. Pared off the southwest counties based on the drier SPoRT LIS data and the recent lack of rainfall across those areas (Colorado/Wharton/Matagorda/Jackson)...they will likely get heavy rainfall but the threat for flash flooding should be lower there. Looking at the Return Interval for the current suite of guidance indicates we may be approaching 25 to 100 year return qpf for this time of year. Thursday by 7 am the deeper and stronger convection should be mainly over the nearshore waters with residual showers still possible across the area until the dry air filters in Thursday afternoon. High pressure builds south out of the Plains Friday and SETX should have very pleasant weather Thursday night through Saturday. The high moves eastward with light east winds Thursday and the modified return flow from the Gulf impinging on the area Saturday with a second cold front dropping south to move through the area Monday/Monday night. Clouds should increase and may get some over- running rain fall though the models aren`t in good agreement yet and so for now have favored the ECMWF Monday and beyond in the guidance. 45 MARINE... Moderate onshore winds and elevated seas will prevail into Wednesday. A small craft advisory remains in effect for the Gulf waters. Conditions are borderline for the nearshore waters, but kept the SCA going for the next couple of hours. Caution flags will be in effect for the nearshore waters with a Small Craft Advisory remaining in effect for the offshore waters through tomorrow evening. A high risk of rip currents continues for the rest of today and has been extended into tomorrow as swells and higher surf will still be around. A Beach Hazards Statement is in effect through tomorrow evening. Unsettled wx, with periods of showers and thunderstorms are expected ahead of and along a weak frontal boundary that`ll be sagging toward the coast Wednesday afternoon before pushing off the coast sometime around early Thursday morning. A brief period of offshore winds can be expected in the wake of the front, but they will become onshore again late Thursday. 11 AVIATION... Several small showers have erupted across the area this afternoon from ARM to just south of CLL and UTS. These showers are quickly moving north and not expected to produce much, if any, accumulation. Have added VCSH to all TAFs from SGR/HOU northward for the rest of the afternoon for these low impact showers. Have made no other changes at this time to the rest of the forecast period. Luchs && .PRELIMINARY POINT TEMPS/POPS... College Station (CLL) 69 75 60 77 52 / 80 90 90 10 10 Houston (IAH) 70 80 66 81 56 / 40 90 90 30 10 Galveston (GLS) 71 76 68 75 63 / 30 40 90 60 0 && .HGX WATCHES/WARNINGS/ADVISORIES... TX...Flash Flood Watch through late Wednesday night for the following zones: Austin...Brazos...Burleson...Colorado...Grimes... Houston...Madison...Montgomery...Polk...San Jacinto... Trinity...Walker...Waller...Washington. Flash Flood Watch from 7 AM CDT Wednesday through Thursday morning for the following zones: Brazoria...Chambers...Fort Bend...Galveston...Harris...Liberty...Matagorda...Wharton. GM...SMALL CRAFT SHOULD EXERCISE CAUTION until 1 AM CDT Wednesday for the following zones: Galveston Bay...Matagorda Bay. SMALL CRAFT SHOULD EXERCISE CAUTION through late Wednesday night for the following zones: Coastal waters from Freeport to the Matagorda Ship Channel out 20 NM...Coastal waters from High Island to Freeport out 20 NM. Small Craft Advisory until 1 AM CDT Thursday for the following zones: Waters from Freeport to the Matagorda Ship Channel from 20 to 60 NM...Waters from High Island to Freeport from 20 to 60 NM. && $$ Discussion...43
Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
912 PM EDT Tue Mar 27 2018 .SYNOPSIS... A developing warm front will approach from southern West Virginia overnight, then oscillate over the area through Friday. Low pressure moving from the Ohio Valley to the eastern Great Lakes will drag a cold front across the Mid-Atlantic Friday. Canadian high pressure will return for the middle of the weekend before another storm system approaches from the Great Lakes by early next week. && .NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/... A warm front will move north and east toward our area overnight. The warm front will likely remain draped across the Appalachians into southern Virginia and North Carolina overnight. Our area will remain on the cool side of the boundary, but a southerly flow will allow for noticeably milder conditions compared to recent nights. In fact, temperatures for most areas will remain nearly steady and even rise along the ridges. With the warm front approaching, anticipating overcast skies with spotty light rain. Weak forcing will be north of the warm front. This would place the best chance for intermittent/spotty light rain over the Allegheny and Potomac Highlands toward northern Maryland. Patchy light rain or drizzle is possible elsewhere as well. && .SHORT TERM /6 AM WEDNESDAY MORNING THROUGH THURSDAY NIGHT/... Pretty much all model guidance is trying to lift the warm front north to near the Potomac, perhaps even a touch further north on Wednesday. I`m skeptical of this given the unseasonably strong wedge of high pressure in place. Boundary layer winds may increase to 10-15 kts by Wednesday afternoon which could aid the front lifting northward some. To the south of the boundary, temperatures should reach well into the 60s to near 70 with breaks in the cloud cover. Meanwhile, it will be stuck in the 50s under overcast skies and spotty light rain north of the warm front. Any northward progress of the front should be halted by Wednesday evening. A small disturbance riding along the front will cause a batch of light rain to move west to east across the region, reinforcing the warm front and possibly forcing it back south a bit. Patchy fog is possible in the wake of evening light rain overnight Wednesday. Guidance has persistently been trending very warm for Thursday (into the 70s). But low level winds remain rather weak until late in the afternoon, making it seem a little unlikely the warm front will push too far north. If the aforementioned perturbation is a little stronger than currently forecast, subsidence in its wake could result in some clearing/increased mixing through Thursday morning, resulting in slightly stronger boundary layer winds and aid in northward progress of the warm front. Model guidance has high temperatures ranging anywhere from around 60 to close to 80 on Thursday. For now, stuck with SuperBlend and took a middle of the road approach for highs. Lift will increase ahead of an approaching upper trough/surface cold front late Thursday night resulting in a re-generation of showers. A rumble or two of thunder is possible given a little elevated instability. && .LONG TERM /FRIDAY THROUGH TUESDAY/... An area of low pressure will pass off to the northwest of the forecast area on Friday. It`s trailing cold front will work its way across the area from west to east late Thursday Night through Friday Morning. In association with that front, rain showers (possibly with a couple rumbles of thunder) are likely for most locations Friday morning. The bulk of the precipitation will end by early afternoon. However, some lingering showers will still be possible in eastern portions of the area, as well as west of the Allegheny Front where some upslope precipitation could occur. High pressure will build into the area from the southwest on Saturday. Another cold front will slowly approach the area from the west later in the weekend. Model guidance differs on the exact timing of the front, but some precipitation will be possible out ahead of the front in the Sunday through Monday time period. Following the passage of this front, model guidance differs significantly with the evolution of the pattern early next week, casting uncertainty on the forecast for that time period. && .AVIATION /01Z WEDNESDAY THROUGH SUNDAY/... MVFR cigs have developed over the terminals this evening. Forecast confidence is low for cigs/vsbys overnight given the fact that the warm front is to our south but a southerly flow may usher in drier air at the low-level just off the deck. Did lean toward the LAMP and HRRR ensemble which shows IFR conditions developing overnight across KBWI and KMTN where weak isentropic lift will remain north of the warm front. However, cigs may lift farther to the south and west overnight as the low-level flow backs from the southeast to the southwest. Looking upstream, VFR conditions are in place. However, patchy fog may develop overnight most likely causing MVFR vsbys with perhaps IFR across the northern terminals. VFR should return briefly by late tomorrow morning as the warm front slowly lifts north. Spotty light rain will be possible, mainly near MRB during the first part of the day, then pressing eastward during the afternoon. MVFR/IFR possible tomorrow night, with VFR more likely Thursday. More restrictions possible Thursday night as a cold front moves in from the west. Sub-VFR conditions will be possible on Friday as a cold front moves through the area. Conditions will improve to VFR as high pressure builds in Friday Night through Saturday. Sub-VFR conditions will likely return Sunday as a slow moving cold front approaches the area from the west. && .MARINE... Brief/marginal SCA conditions are possible in southerly channeling this overnight. Left the SCA for lower MD Chesapeake Bay/Tangier Sound waters for a few hours this evening. Gradient/winds should remain light enough to preclude any marine headlines Wednesday into Wednesday night. Southerly gradient increases markedly late Thursday with SCA becoming more likely during this time. On Friday, winds will be near the SCA threshold, therefore an advisory is possible. Winds will decrease Friday Night into Saturday, and are expected to remain below the SCA criteria for the remainder of the weekend. && .TIDES/COASTAL FLOODING... Tides will come close to minor thresholds at Annapolis/Straits Point tonight, but this high tide cycle is the lower of the two. Therefore, held off on headlines for now. Water levels will remain elevated until a cold front crosses late in the week. && .CLIMATE... Dulles Airport had its 20th consecutive day with a low temperature at or below freezing this morning. This is the longest such streak this late in the season for this site, where records began in 1960. Lows tonight will likely stay above freezing, ending the streak at 20 days. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...None. MD...None. VA...None. WV...None. MARINE...Small Craft Advisory from 1 AM to 4 AM EDT Wednesday for ANZ534-543. && $$ SYNOPSIS...BJL/DHOF NEAR TERM...BJL/DHOF SHORT TERM...DHOF LONG TERM...IMR AVIATION...BJL/IMR/DHOF MARINE...BJL/IMR/DHOF TIDES/COASTAL FLOODING...DFH/BJL CLIMATE...DHOF
Area Forecast Discussion
National Weather Service Memphis TN
957 PM CDT Tue Mar 27 2018 .UPDATE... Light to occasionally moderate rainfall has been a little slower to develop east this evening, persisting mainly west of the MS River. Latest HRRR and RAP guidance depicted increased rain rates lifting into the I-40 corridor from southern AR overnight, focused along and north of a slow moving cold front and aided by a strengthening low level jet. Regional radar mosaic showed this scenario may getting underway. Most recent forecast update included a slight delay in eastward expansion of rain for the late evening, and reduction in rain chances over northeast MS overnight. PWB && .PREV DISCUSSION... /issued 653 PM CDT Tue Mar 27 2018/ UPDATE... Updated to include 00Z aviation discussion below. PREV DISCUSSION... /issued 351 PM CDT Tue Mar 27 2018/ DISCUSSION... A split flow pattern persists across the CONUS this afternoon. A northern stream trough is moving east across the northern tier states with a downstream ridge building up the East Coast. A southern stream trough continues to spin over the Four Corners area this afternoon with a cold front is located to our north, extending across southeast MO into northeast TX. This boundary will sag slowly south over the next 1-2 days, providing a focus for widespread showers with occasional thunderstorms. The warm conveyor belt downstream of the Four Corners trough will shift eastward over the Mid-South tomorrow with precipitable water increasing to around 1.75" along and ahead of the aforementioned cold front. This is a good 2-3 standard deviations above climatology and will set the stage for heavy rainfall over the next 36 hours. The first wave of heavy rain is expected late tonight into Wednesday morning and there may be a lull Wednesday afternoon. However, another round of heavy rainfall is expected Wednesday night before tapering off on Thursday and Thursday night as drier air advects into the CWA. In addition to the heavy rainfall potential, a few strong to severe storms are possible tomorrow late afternoon and evening, primarily south of I-40. Models are in better agreement today in pulling the upper-level support and moisture east of the area Thursday night. Thus, PoPs were removed for Friday. Temperatures will be a bit cooler on Friday with highs in the low/mid 60s. A brief dry period is anticipated area wide Friday and Friday night in the wake of the departing trough, but light rain showers are back in the forecast on Saturday across the northern portion of the CWA. The synoptic pattern will be more quasi-zonal by this time and a fast-moving shortwave trough is progged to be approaching the Ohio Valley during the weekend. This will drive another cold front south into the area Saturday night. This front is then forecast to lift back north on Sunday and Sunday night as the next trough approaches the region. Yet another trough is progged to affect the area on Tuesday, bringing rain chances back to the Mid-South through early Wednesday. Temperatures will be a bit below normal Sunday through Tuesday, with highs generally in the low/mid 60s and overnight lows in the 40s. Johnson && .AVIATION... 00Z TAF Set Mainly VFR conds to start with developing IFR/LIFR conds later tonight. A cold front is already through JBR at this hour, with a windshift to the north being reported on site. This front is expected to push through MEM in the 06-08Z timeframe, with a significant windshift to the west and eventually north. The front is expected to slow down and possibly stall just to the south of MEM. This will create obstructed VSBYS, lowered CIGS, and push flight rules into LIFR and possibly VLIFR along and north of the boundary. Confidence beyond about 12Z is low at this time, due to considerable model differences on where the frontal boundary stalls out. Decided to use a VCSH north of the front, as each model depicts scattered activity beyond 14Z. To the south of the boundary VCTS was placed at TUP, where greater instability will exist. AC3 && .MEG WATCHES/WARNINGS/ADVISORIES... AR...Flood Watch from 1 AM CDT Wednesday through Thursday morning for Clay-Craighead-Crittenden-Cross-Greene-Lawrence-Lee AR- Mississippi-Phillips-Poinsett-Randolph-St. Francis. MO...Flood Watch from 1 AM CDT Wednesday through Thursday morning for Dunklin-Pemiscot. MS...Flood Watch from 1 AM CDT Wednesday through Thursday morning for DeSoto-Tunica. Flood Watch from Wednesday afternoon through Thursday afternoon for Alcorn-Benton MS-Calhoun-Chickasaw-Coahoma-Itawamba- Lafayette-Lee MS-Marshall-Monroe-Panola-Pontotoc-Prentiss- Quitman-Tallahatchie-Tate-Tippah-Tishomingo-Union-Yalobusha. TN...Flood Watch from 1 AM CDT Wednesday through Thursday morning for Benton TN-Carroll-Chester-Crockett-Decatur-Dyer-Fayette- Gibson-Hardeman-Haywood-Henderson-Henry-Lake-Lauderdale- Madison-Obion-Shelby-Tipton-Weakley. Flood Watch from Wednesday afternoon through Thursday afternoon for Hardin-McNairy. && $$
Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
1033 PM CDT Tue Mar 27 2018 .SHORT TERM...(This afternoon through Wednesday) Issued at 1156 AM CDT Tue Mar 27 2018 Surface analysis this afternoon shows high pressure centered over the Central Plains, extending NE into MN/WI and SW into eastern CO. One cold front is now well off to the east, into the Ohio Valley and mid-Mississippi River Valley regions while a second cold front lingers to the north over south-central Canada. The high pressure area will be the prevailing feature through the overnight hours as skies continue to clear out from eastern MN into western WI this afternoon and remain mostly clear across the entire coverage area for much of tonight. Conditions do look conducive to producing some patchy fog, particularly over far southern MN into southwestern WI, closer to the center of the high. By daybreak, the aforementioned northern cold front will drop through the Dakotas and into far northwestern MN. A spoke of the main upper level trough originating in central Canada will nudge a developing low pressure center just north of the international border from southern Manitoba into southwestern Ontario. The cold front of this system will quickly slide southeast through much of MN and northwestern WI by late day. Not much in the way of deep moisture will accompany the front as the bulk of the moisture will be concentrated near the low pressure center. Yet, enough frontal lift plus the pivoting of the upper trough may produce some isolated light rain/snow showers across much of the area tomorrow. Only about a hundredth or two of QPF is expected with any shower. The main impact will be a minor surge of warmer air in advance of this front for the area which will be realized in the form of highs ranging from the lower 40s in western MN, which will have the cold frontal passage first, to highs in the lower 50s in far eastern MN into western WI. Because of the clear skies tonight, lows will again drop to the upper 20s to lower 30s. .LONG TERM...(Wednesday night through Tuesday) Issued at 244 PM CDT Tue Mar 27 2018 Once the cold front of Wednesday drops through the region, this will commence a period lasting through early next week of colder than normal temperatures, including occasional chances for light snow going into the start of April and lows into the teens. Low level flow will become more predominantly west to northwest as a series of fronts are expected to pass through the region, namely Friday into Saturday then Monday into Tuesday. In conjunction with these frontal passages, the prevailing upper level low rotating generally over Hudson Bay will maintain a longwave trough over eastern NOAM with northwest flow aloft. Within this flow, several shortwave trough axes will aid in not only pushing the aforementioned cold fronts through the region but also bringing down chunks of arctic air, in a modified fashion, into the Upper Midwest which will contribute to keeping below normal temperatures in place. With the first frontal passage, the best chances for precipitation will come Friday morning through Saturday morning, most of which will come as light snow though some light rain could mix in. Not a lot of moisture is associated with this frontal passage so will look for snow amounts in the 1-2 inch range for much of the area, over this 24-36 hour period. With the second frontal passage, the best chances for precipitation will come Sunday into Monday. Again, moisture will be relatively limited, so will not look for much in the way of accumulation but the majority of this precipitation will come as light snow (with some occasional mixing with light rain). There are still some uncertainties to iron out due to the transitional season nature of these systems and the strong temperature gradients involved but the overall lack of deep moisture gives the thinking that QPF and hence snow accumulations will be on the lower side of the spectrum. && .AVIATION...(For the 06Z TAFS through 06Z Wednesday night) Issued at 1033 PM CDT Tue Mar 27 2018 Keeping an eye on the potential for fog tonight, with MKT/EAU already dropping down to a 6sm vis. We look to keep a gradient and wind in place through the night, so that should keep fog from getting out of hand. Still think greatest potential for fog will be over the snowpack that comes up out of IA into southwest and south central MN, with MKT having the greatest potential for fog, though EAU down by the river will have potential as well. FROPA timing has not changed much from 00z TAFs. Maintained dry TAFs as well, with nothing more than sprinkles expected. Also favor the HRRR/RAP idea with MVFR cigs coming in behind the front, likely down in the 2k-3k foot range, which is what we are seeing now up in southern Alberta and Saskatchewan. The LAV continue to downplay the post frontal cloud threat, but forecast soundings from the GFS/NAM continue to support the post frontal cloud idea. KMSP...Still a threat for some problematic cross winds in the morning and upped winds a bit in the morning hours looking at the HRRR and GFS forecast soundings for MSP. May get a sprinkle or two with the fropa around 19z, but nothing more than that. Confidence is high we will see MVFR cigs behind the front, coming in as early as 20z. Less confidence on when they will dissipate, but could be as early as 2z, or they could hang tight most of the night. /OUTLOOK FOR KMSP/ THU...VFR. Wind NW 5-10 kts. FRI...MVFR chc IFR. Chance mrng -RASN. Wind SW bcmg nw 5-10 kts. SAT...Chance MVFR/-SN early. VFR by aftn. Wind NW 10-20 kts. && .MPX WATCHES/WARNINGS/ADVISORIES... WI...None. MN...None. && $$ SHORT TERM...JPC LONG TERM...JPC AVIATION...MPG