Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 04/28/17

Area Forecast Discussion
National Weather Service La Crosse WI
628 PM CDT Thu Apr 27 2017 .UPDATE... Issued at 628 PM CDT Thu Apr 27 2017 Stratus - the bane of a forecaster`s existence sometimes. Per satellite trends, clouds have gone nowhere today, courtesy of both low level chilly air (for some diurnal component) and pronounced low level cyclonic flow with low pressure departing into southeast Ontario. Given recent trends, have pushed back the clearing time for many areas (save for the far south) by a few hours, and may need to go a big longer. However, recent RAP runs seem to have a good handle on the situation, with increasingly anticyclonic flow south of I-90 through the night likely helping erode the stratus, though am intrigued to see what happens farther north where cyclonic flow remains intact overnight. Can envision some low clouds hanging tight for much of the night north of I-90. Regardless, clouds will obviously impact overnight lows but planning no changes to current Frost Advisory as current temps are already in the mid 30s to lower 40s, and it won`t take but a few hours of clearing for readings to dip. && .SHORT TERM...(Tonight through Friday night) Issued at 247 PM CDT Thu Apr 27 2017 GOES Water Vapor imagery this afternoon showing the mid-level wave responsible for snow burst east of the Mississippi River this morning now exiting into northeast WI. Radar still showing some lingering rain/snow shower activity across the area in steep low level lapse rate/cold cyclonic flow. Temperatures this afternoon were chilly with readings in the 30s. West winds 10-20 mph were adding a bite to the chilly air. For tonight, a ridge of high pressure builds in from southwest to northeast for clearing skies allowing for good radiational cooling given light airflow. Depending on how much decoupling takes place, will likely see some freezing temperatures across the area. And, given the advanced blooming of vegetation across some of the area, concerned for some plant/bloom damage. As such, have frost headlines posted for areas along the Mississippi/Wisconsin Rivers where progression of Spring/blooming has advanced. Models continue to show a mid-level wave/weak surface low rippling northeast across IA/IL Friday afternoon into Friday night. Fairly strong frontogenesis noted by the NAM/GFS centered around 700mb sliding through the region. This should be sufficient for isolated to scattered showers south of I-94, more numerous south of I-90. Otherwise, looks a bit warmer for highs with readings in the upper 40s/lower 50s. Friday night may need frost headlines again for portions of the area as temperatures dip into upper 20s to the middle 30s. .LONG TERM...(Saturday through Thursday) Issued at 247 PM CDT Thu Apr 27 2017 Looks like a dry start to Saturday but then rain chances spread south to north into the area through the day ahead of cyclogenesis over the southern Plains. Otherwise, plan on increasing clouds with highs in the upper 40s to the middle 50s. Strengthening low pressure moves out of the Southern Plains toward the region Saturday night through Monday for an increasingly wet period. GFS and NAM still showing precipitable water values in the 1- 1.25 inch with a wide-open gulf tap. Right now, looking at rainfall from Saturday night through Sunday in the 1/3 to 1 inch range with potentially another 1/2 to 1 inch through Monday. See hydrology section below for impact on area rivers. Otherwise, looks like a cold rain with highs Sunday and Monday mainly in the 40s. Look for mixing of the rain with snow later Monday night as column cools with low becoming vertically stacked. Cool cyclonic flow aloft continues through Tuesday for a chance of showers as highs top off in the upper 40s to the upper 50s. Temperatures slowly rebound Wednesday and Thursday with that closed low filling/moving off to the east. Still a couple weak waves rippling through we`ll have to keep an eye on for slight shower chances. Right now, they don`t look too impactful. && .AVIATION...(For the 00Z TAFS through 00Z Friday evening) Issued at 628 PM CDT Thu Apr 27 2017 Stubborn and widespread stratus remains draped across the region, but is gradually thinning on its western and southern fringes the past few hours. Ceilings are MVFR just about everywhere and should remain that way through late evening and early overnight, as clouds very slowly continue to erode eastward. At the present time, it appears RST will see some clearing toward 06Z while LSE will likely wait until 07-08Z per current trends. However, there is a chance that clouds could take even longer to clear, especially given plenty of remaining low level cyclonic flow near and north of I-90 overnight, and it`s not impossible that MVFR stratus could sneak back southward later tonight for a time. Even if that does occur, a return to VFR conditions is still expected everywhere on Friday, as mid and high clouds thicken through the day. Westerly winds 10-15 knots this evening will diminish overnight and then become light from mainly the north on Friday. && .HYDROLOGY...(Concerning rainfall this weekend) Issued at 247 PM CDT Thu Apr 27 2017 Looking at another very wet weather system moving through the region Saturday night through Monday. Right now looking at 1 to 2 inch of rainfall through the period. Plan on river rises but not anticipating any flooding at this time. && .ARX WATCHES/WARNINGS/ADVISORIES... WI...Frost Advisory from 1 AM to 8 AM CDT Friday for WIZ041-053>055- 061. MN...Frost Advisory from 1 AM to 8 AM CDT Friday for MNZ088-096. IA...Frost Advisory from 1 AM to 8 AM CDT Friday for IAZ011-030. && $$ UPDATE...Lawrence SHORT TERM...DAS LONG TERM....DAS AVIATION...Lawrence HYDROLOGY....DAS
Area Forecast Discussion
National Weather Service Dodge City KS
725 PM CDT Thu Apr 27 2017 ...Updated Aviation Section... .SHORT TERM...(This afternoon through Friday) Issued at 105 PM CDT Thu Apr 27 2017 Thick cloud cover across SW Kansas this afternoon along with breezy SE winds. HRRR model generates scattered convection across the western zones by 4-5 pm, then subsequently moving eastward across the CWA this evening. Storms may intensify some along with some linear segments, allowing for some cold pool generation and strong outflow winds. Moisture and instability are limited, but high-based thunderstorms will pose a primary risk of wind gusts of 50-60 mph through this evening. Strongest cores may have nickel to quarter size hail, but this is a secondary concern. As shortwave energy rotates through tonight, shower activity and embedded thunder will rotate NE into northern Kansas. Dry with partial clearing expected by sunrise Friday, with lows ranging from the upper 30s NW to upper 40s SE. Much of Friday will be dry, as strong closed low sinks south to the Four Corners by evening. Enough sunshine expected for the first half of the day to allow for afternoon temperatures well into the 60s. Diffluence aloft will begin increasing during the afternoon, with increasing clouds, and scattered rain showers and embedded thunder across western zones by late afternoon. Any rainfall through 7 pm Friday appears insignificant. Widespread stratiform rain, moderate to heavy at times, is expected to arrive Friday evening/night. .LONG TERM...(Friday night through Thursday) Issued at 250 PM CDT Thu Apr 27 2017 ...Strong and wet late season winter storm expected this weekend... Yet another beneficial rainfall event is on its way to SW Kansas. Widespread rain, moderate to heavy at times, is expected Friday night through Saturday morning. Warm advection/isentropic lift will be intense during this timeframe, with around an inch of rain likely during Friday night alone. SW Kansas will be entrenched in the cold conveyor belt, with not enough elevated instability to warrant a thunder mention. Still, mesoscale bands of heavy rain are expected. Minor flooding and ponding issues. Parent upper low expected to be in NW New Mexico 7 am Saturday. Upper low digs SE during the day on Saturday, ending up in SE New Mexico by 7 pm. With this more southerly track, dynamic lift will continue to support rain, albeit at gradually lessening intensity, throughout the day Saturday. While there may be a few breaks in the rain late in the day, Saturday will generally be a washout with another 0.25-0.75 of QPF. Rain may mix with wet snow at times on the higher terrain of the western counties early Saturday morning, but no accumulations are expected...yet. Unseasonably cold, with strong NE winds and cold air advection and rain holding temperatures in the 38-45 range. The record coldest high temperature at Dodge City for April 29th is 39/1994, and we won`t be much warmer than that. Strong upper low strengthens further Saturday night, ending up near Childress at 7 am Sunday. This storm track will be ideal for setting up the deformation zone over SW Kansas. With strong lift, likely pops are warranted. The much harder part of the forecast is one of thermodynamics and the expected phase change from cold rain to wet snow. Concensus of models spreads the rain/snow line eastward across the western 1/2 of the CWA through sunrise Sunday. Some accumulations expected on grassy/elevated surfaces from Dodge City westward, especially before sunrise. 12z ECMWF strongly suggests a snow changeover for the western 2/3 of the CWA, with 850 mb temperatures falling to -2/-3C. This would get snowflakes to the ground, but impacts on trees and powerlines will come down to surface air temperatures, forecasted to be in the 30-35 range. Areas with subfreezing surface temperatures in the heavy snow bands may experience significant tree/power line damage, given north winds will be gusting near 40 mph. Roads will remain wet to at most occasionally slushy; still, a winter weather headline will likely be required. Snow amount grids came up with 1-4 inches across the western counties, and was accepted as a good start for now. Strongest forcing expected Sunday morning, as upper low intensifies to near 544 dm near Medicine Lodge by 1 pm Sunday. Pops are likely, and will need to be raised to categorical. Heavy wet snow is expected to continue across the western 1/2 of the CWA for several hours Sunday morning, rain elsewhere. All models show deformation precipitation continuing, and changing back to rain, through Sunday afternoon. This will be another wet cyclone for SW Kansas, with stormtotalQPF grids for this event 1-2 inches widespread. Wraparound rain finally ends across the NE zones Sunday evening. Another cold day Sunday in the 40s, followed by near freezing temperatures Monday morning. Winter isn`t done with us just yet! Monday and Tuesday...Dry, with afternoon temperatures back in the 60s. && .AVIATION...(For the 00Z TAFS through 00Z Friday evening) Issued at 720 PM CDT Thu Apr 27 2017 Low stratus is expected to develop late this evening, affecting mainly DDC and HYS terminals. There is low confidence in duration of IFR ceiling, especially at DDC and GCK. Showers and thunderstorms will impact terminals through the evening hours, waning after midnight. && .PRELIMINARY POINT TEMPS/POPS... DDC 43 68 37 41 / 50 20 90 90 GCK 40 64 35 38 / 50 30 80 80 EHA 41 64 34 36 / 10 30 80 90 LBL 42 66 39 40 / 20 20 90 80 HYS 43 60 38 41 / 70 20 80 90 P28 48 72 44 48 / 50 10 80 90 && .DDC WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SHORT TERM...Turner LONG TERM...Turner AVIATION...Umscheid
Area Forecast Discussion
National Weather Service Grand Forks ND
922 PM CDT Thu Apr 27 2017 .UPDATE... Issued at 921 PM CDT Thu Apr 27 2017 Water vapor loop indicated an upper level trough from lower MI to western Ontario. Wrap around continued to back into western Ontario or just across the MN border as seen on Canadian radar. Will keep precip over the far northeast zones overnight. Drier air forecast to move in from the north overnight. Will decreased overnight lows a degree or two...mainly west. UPDATE Issued at 603 PM CDT Thu Apr 27 2017 Freshened up cloud cover with this update. The rest of the forecast looks on track at this time. && .SHORT TERM...(This evening through Friday) Issued at 154 PM CDT Thu Apr 27 2017 Forecast challenge through the short term will be mainly temperatures. Upper low over far northern Mn will continue to lift NE into Ontario overnight. A lobe of energy rotating around the low will swing through the NE tonight so will maintain some low pops as weak returns showing up on Canadian radar. Overall only minimal accumulations expected. Temperatures will be somewhat tricky overnight. Coldest air aloft will be east of the valley however clouds a good part of the overnight will hold temperatures up. Driest air and less clouds will be west of the valley however they escaped the snow so overall temperatures may end up fairly uniform in the 20s. A quiet day for Friday as high pressure builds into the region. Not much in the way of warm advection however with plenty of solar and less snow cover temperatures should be able to recover into the 40s to around 50 in the west. .LONG TERM...(Friday night through Thursday) Issued at 154 PM CDT Thu Apr 27 2017 Fairly decent weekend on tap with high pressure keeping conditions quiet. Although temperatures will remain a bit below normal (mostly in the 50s), they should feel quite nice compared to readings over the course of the past week. The main concern throughout the period will be the next storm system poised to impact at least portions of the area at the tail end of the weekend and starting the new work week. An upper low developing across the southern Plains late in the weekend is progged to deepen as it propagates to the north and east by Monday morning. With the current track, the area looks to be in the cold sector of the surface low once again. Models are actually in pretty decent agreement with timing and location of many of this system`s features for this far out but there is still plenty of time for things to change. As of now, the eastern half of the forecast area looks to see the most impacts, generally along and east of the Red River Valley. Temperature profiles suggest some tricky precipitation types which will need to be watched as they could be influenced by any big shifts in timing of the precipitation (more supportive of a mix/snow overnight Sunday before warming on Monday). Ultimately, any changes to the low track could bring big changes to the forecast so stay tuned. As the upper low continues to propagate off to the north and east, northwest flow will set up across the region through the remainder of the period. Models hint at a few weaker waves passing through the upper flow for the midweek period providing on and of chances for precipitation. Temperatures look to remain just a bit below normal but should be warm enough for no real chances for measurable snow after Monday`s system. && .AVIATION...(For the 00Z TAFS through 00Z Friday evening) Issued at 603 PM CDT Thu Apr 27 2017 MVFR ceilings are expected to continue at BJI for the next several hours. However, the NAM bufr data show a sounding capable of SCT to BKN clouds at around 3500 ft by 09Z or so...after being at IFR at 06Z. The GFS bufr/MOS are much more pessimistic with IFR cigs possible for several hours tonight and early tomorrow. With the HRRR model closer to the GFS...will side closer to the pessimistic scenario. VFR conditions are expected at the rest of the TAF sites with TVF just reaching VFR in the last hour, with VFR cigs upstream and dissipating clouds expected. Models continue to keep visibility concerns at bay. && .FGF WATCHES/WARNINGS/ADVISORIES... ND...None. MN...None. && $$ UPDATE...JH SHORT TERM...Voelker LONG TERM...Lee AVIATION...Knutsvig
Area Forecast Discussion...Corrected
National Weather Service Wilmington NC
958 PM EDT Thu Apr 27 2017 .SYNOPSIS... High pressure offshore will bring a warming and drying trend late this week through the weekend. A weakening cold front will bring a few showers or a thunderstorm tonight inland and early Friday at the coast. A stronger frontal system will bring a chance of rain late Monday and early Tuesday. Another storm system may impact the region with a soaking rain next Thursday. && .NEAR TERM /THROUGH FRIDAY/... As of 1000 PM Thursday...Low stratus is developing along the South Carolina coast a few hours faster than anticipated. Have increased sky cover forecasts and adjusted hourly temperature curves appropriately as this is interfering with radiational cooling. The line of showers across central and western South Carolina is slower to move east than anticipated. Latest HRRR runs show only spotty coverage as it enters the Pee Dee region after midnight, but still shows a resurgence as it approaches Cape Fear just before daybreak Friday. The HRRR is developing surface-based CAPE near 3000 J/kg late tonight along the coast-- something I was going to immediately dismiss until I started adjusting NAM soundings using the observed temp/dewpoint at Frying Pan Shoals buoy (75/73) and easily got 2600 J/kg. Hmmmm... PoPs have been bumped up to 30 percent in the Myrtle Beach/Cape Fear region after 3 AM. Discussion from 730 PM follows... Isolated showers and maybe even a thunderstorm will develop overnight as a dying cold front approaches from the west. The meager surface-based instability is becoming capped off due to the cooling boundary layer, however elevated instability based around 5000-7000 feet AGL will continue overnight. PoPs range from 10-30 percent, lowest near Georgetown and highest west of I-95. The last several HRRR runs and some of the recent RUC model runs also suggest late- night showers could develop near the Brunswick County coast, although I am not certain what mechanism is in play. No significant changes have been made to forecast low temperatures, expected to range from the mid 60s near and west of I-95 to the lower 70s on the beaches. This is exceptionally warm for late April, about 15 degrees above normal. && .SHORT TERM /FRIDAY NIGHT THROUGH SATURDAY NIGHT/... As of 300 PM Thursday...Bermuda High will take hold of the area with ridging all the way up through the mid and upper levels. This will maintain a deep southerly return flow with very mild summer-like weather. Plenty of dry air and subsidence through the mid levels will maintain a cap on convection although shallow low level moisture will be quite rich. Overnight winds should prevent fog, but sounding data shows potential for a few hours of saturated column up to 1500 ft or so and greater potential Sat night into Sun morning. Therefore may see some stratus around overnight but will dissipate as sun rises Sat morning. Should also see some cu develop right along sea breeze boundary as it pushes inland Sat aftn. Temps will run about 10 to 15 degrees above normal with plenty of sunshine on Sat. Both Fri night and Sat night lows will near or around 70 degrees with daytime highs soaring through the 80s to around 90 in many spots inland. && .LONG TERM /SUNDAY THROUGH THURSDAY/... As of 300 PM Thursday...Western Atlantic High Pressure will maintain deep southerly flow on Sun. Although a shower along the seabreeze can`t be ruled out, subsidence on the periphery of the ridge should keep afternoon convection to a minimum, except along the inflection point, will keep POPs out of the forecast at this time. Surface and mid level ridge will weaken and drift east Mon, allowing a cold front to approach from the W. Low pressure and associated strong dynamics and upper level support will be well dislocated from the Carolinas as a cold front moves across the area Mon night. This suggests convection weakening as it moves into the eastern Carolinas. Current timing brings the likelihood for showers and thunderstorms later Mon and Mon night. As the front moves off the coast Tue morning, high pressure along the Gulf Coast will slide east and then offshore to our S during Wed. This should bring a dry period. Deep low pressure will move out of the mid south and Gulf coast states Wed, lifting slowly to the NE. Its associated cold front will move into the Southeast states Thu-Thu night, bringing the risk for robust thunderstorms. && .AVIATION /02Z FRIDAY THROUGH TUESDAY/... As of 00Z Friday...Isolated convective showers associated with a dying cold front may move into eastern North and South Carolina later this evening. Odds of precipitation occurring at any of the airports are 20 percent or less, and flight category restrictions are unlikely. Perhaps of greater concern is the potential that low stratus will develop late this evening as very moist air gathering just offshore moves inland. Ceilings as low as 600-800 feet are possible, with IFR restrictions forecast in the TAFs for ILM, MYR, and CRE beginning around 05Z. It is worth noting the NAM model has much greater potential for low ceilings than the GFS or RUC models. Any low ceilings will either burn off just after sunrise, or push back offshore as wind directions veer more southwesterly late tonight. VFR conditions are expected for all areas after 13-14Z Friday. Extended outlook...VFR through Sunday. Periods of IFR/MVFR conditions are possible in thunderstorms late Monday into early Tuesday. && .MARINE... NEAR TERM /THROUGH FRIDAY/... As of 730 PM Thursday...The afternoon seabreeze is beginning to wind down as temperature contrasts across the beaches relax. Wind gusts as high as 27 knots occurred at Wrightsville Beach, 24 knots at Topsail Beach, and 21 knots reported at the Georgetown, SC airport. South-southwesterly winds 10-15 knots are expected for the remainder of the night. Seas consist of choppy 4-5 second wind waves overlaid with a 9 second southeast swell, totaling 3-4 feet, and little change is anticipated overnight. SHORT TERM /FRIDAY NIGHT THROUGH SATURDAY NIGHT/... As of 300 PM Thursday...Southerly return flow will persist around the periphery of the Bermuda High which will keep a stronghold on the local waters through the period. Winds will run 10 to 15 kt with gusts to 20 to 25 kt possible especially the nearshore waters during the afternoon sea breeze. Seas will run 2 to 4 ft, but may see some 5 fters in outer waters. LONG TERM /SUNDAY THROUGH TUESDAY/... As of 300 PM Thursday...Western Atlantic High Pressure will bring increasing S winds ahead of a cold front. S winds Sun and Sun night will be increasing to 15 to 20 kt. Seas will increase to 4 to 6 ft by early Mon morning. S to SW wind speeds will increase further Mon and Mon night, up to 20 to 25 kt as seas build to 5 to 8 ft. Then in the wake of the front Tue, developing offshore winds will trend lower. The offshore trajectories will knock seas down and we should drop below Small Craft Advisory levels by Tue eve. && .ILM WATCHES/WARNINGS/ADVISORIES... SC...None. NC...Coastal Flood Advisory until 1 AM EDT Friday for NCZ107. MARINE...None. && $$ SYNOPSIS... NEAR TERM...TRA SHORT TERM...RGZ LONG TERM...RJD AVIATION...TRA MARINE...
Area Forecast Discussion
National Weather Service Marquette MI
759 PM EDT Thu Apr 27 2017 .SHORT TERM...(This evening through Friday) Issued at 357 PM EDT THU APR 27 2017 12Z raobs/latest wv imagery and RAP analysis show closed lo centered over nw MN, with shrtwv embedded in sly flow alf to the e of this feature moving n into scentral Upr MI. The steadiest pcpn has fallen over the w half of the cwa on the cyc side of the shrtwv passage. Since the dynamic cooling associated with the enhanced uvv under the sharper dpva on this side of the shrtwv track has eroded the elevated warm lyr, the pcpn has changed to mainly just sn over the w half, with just some sct rain showers over the warmer e half under dry slotting within the jet surge region. Late Today/Tngt...Arrival of dnva/deep lyr qvector dvgc/subsidence in the wake of shrtwv passing to the n of Upr MI by 00Z Fri wl result in diminishing pcpn s-n late this aftn/evng. Although quite a bit of mid lvl dry air is progged to surge into the area thru the ngt, lingering cyc wly flow and h85 temps falling as lo as -10C over the w, cold enuf for les, wl maintain hier likely pops over the nw cwa. As for going headlines, wl maintain the headline thru 00Z for the Keweenaw Counties as well as Baraga and Iron Counties, 21Z for Gogebic/Ontonagon, but canx the headline for Marquette County. Fri...Although Upr MI wl remain under a cyc flow alf on the sw flank of exiting shrtwv/sfc lo pres toward James Bay, dry air in the mid lvls and a tendency for the near sfc flow to become more acyc as a weak rdg of hi pres builds into the area during the aftn as well as some llvl drying/daytime heating and mixing wl grdly end pcpn chcs. But a good deal of clds wl linger, especially over the hier terrain of the nw half. The day wl be a cool one over the nw cwa with max temps having a hard time rising much above 40. With downsloping flow into the scentral, expect warmer temps into the 50s. .LONG TERM...(Friday night through Thursday) Issued at 357 PM EDT THU APR 27 2017 Main weather concern in the extended will be below normal temperatures along with a stronger system possible with a wintry mix Sunday through Tuesday. Friday night through Saturday: A surface ridge and drier air is expected to build into the area during this time period allowing skies to become partly cloudy with only minor chances for rain and snow showers, again, the main focus would be early in the day Friday over the Keweenaw Peninsula. Temperatures are expected to be slightly below normal through this time period. Saturday night through Tuesday: Low pressure is expected to develop over the Southern Plains late Saturday night and slide through the Upper Great Lakes Sunday through Tuesday. Models are coming into better agreement on the details of the system as it slides through the area; however, some timing and placement differences continue with the solutions. The GFS/Canadian have similar tracks and timing; however, the GFS is deeper with the surface low and upper level low. Each of the models each have the low moving out of the area Tuesday afternoon. The latest run of the EC is keeping the surface low and 850mb low farther west, taking the low over the western U.P. If the GFS/Canadian are correct there could be substantial accumulating snowfall across portions of the west half of the U.P.; however, if the EC solution is correct, then most areas may end up seeing mainly rain with maybe even some dry slotting expected over the east half. 850mb temperatures are progged to be as high as 8 to 9C with the EC, while the GFS/Canadian have 850mb tempeatures over the west half as low as -4 to -5C. Until better sampling occurs with this system it is likely that there will continue to be variances in the models, with improvement expected by Friday as the wave of energy is better sampled. Consensus is still the way to go at this point in the extended due to the reduced confidence in the system track. This will give a continued mix of rain and snow central, rain changing to snow west and mainly rain east. Tuesday night through the extended: High pressure and drier air will slide into the area Tuesday night through Wednesday, which will allow skies to become clear to partly cloudy and temperatures to slowly moderate to near or slightly above normal. A weak system may slide through the area Thursday; however, moisture looks to be fairly limited only bringing isolated rain showers to the area. && .AVIATION...(For the 00Z TAFS through 00Z Friday evening) Issued at 722 PM EDT THU APR 27 2017 Main axis of pcpn has lifted ne of the TAF sites this evening. Snow showers could linger a bit longer this evening at KCMX under cyclonic upslope westerly flow. Otherwise expect MVFR cigs to linger tonight into Fri morning with improvement to VFR at all sites by Fri afternoon as drier air filters in from the west. && .MARINE...(For the 4 PM Lake Superior forecast issuance) Issued at 357 PM EDT THU APR 27 2017 Expect nw winds slowly backing to the wsw to run as hi as 30 kts into Fri under the tight pres gradient on the southern flank of deep lo pres moving from northern Lake Superior toward James Bay. The strongest winds later tonight thru Fri will persist in the area between Isle Royale and the Keweenaw, where the land topography enhances the wsw flow. Winds will then diminish to 25 kts or less Saturday into Sunday as high pressure slides across Lake Superior. A fairly strong low pressure system will slide from the Central Plains into the Upper Great Lakes region from Sunday night through Tuesday morning allowing northeast winds of 30 kts to gust as high as 40 knot gales over mainly the western half of Lake Superior. High pressure will build in once again for Wednesday into Thursday allowing winds decrease to less than 25 knots. && .MQT WATCHES/WARNINGS/ADVISORIES... Upper Michigan... Winter Weather Advisory until 8 PM EDT /7 PM CDT/ this evening for MIZ001-003-004-010-084. Lake Superior... None. Lake Michigan... None. && $$ SHORT TERM...KC LONG TERM...KEC AVIATION...Voss MARINE...KC
Area Forecast Discussion
National Weather Service Morristown TN
935 PM EDT Thu Apr 27 2017 .DISCUSSION... Front has moved east of the area with associated pcpn finally out of SW VA. Latest HRRR indicates end of pcpn chances for tonight, so removed POPs for SW VA for remainder of tonight, but have added in patchy fog there as some places are already reporting vsby less than a mile at times. Also added patchy fog to other low lying areas beginning after midnight and persisting to sunrise in the morning. Otherwise, tweaked temperatures in line with latest observations, but kept morning lows as remainder of overnight fcst is on track. && .PRELIMINARY POINT TEMPS/POPS... Chattanooga Airport, TN 57 85 66 87 / 10 20 10 10 Knoxville McGhee Tyson Airport, TN 55 84 65 88 / 10 10 10 10 Oak Ridge, TN 55 87 66 88 / 10 10 10 10 Tri Cities Airport, TN 52 87 59 87 / 10 10 10 20 && .MRX WATCHES/WARNINGS/ADVISORIES... NC...None. TN...None. VA...None. && $$ EJH
Area Forecast Discussion
National Weather Service Raleigh NC
840 PM EDT Thu Apr 27 2017 .SYNOPSIS... A cold front will over the Mountains this evening will drift into the central Piedmont overnight, then dissipate. A strong high pressure will build off the southeast coast Friday and linger into Saturday. A moist southerly return flow on the western periphery of the strengthening Bermuda high will prevail Friday through the weekend. && .NEAR TERM /THROUGH TONIGHT/... As of 748 PM Thursday... Central and eastern parts of our region, essentially east of the Triad region eastward are in the clear for now, and expected to be so for the evening. The air mass continued to be rather stable and not favorable for convective development. To the west, as previously mentioned the cold front was drifting into the Mountains. Conditions were more unstable and favorable for convective showers/iso thunderstorms in this region. However, the most unstable air did reside along the boundary over the Mountains and the forecast is for the boundary layer east of the mountains to cool and stabilize further as the the evening unfolds. Therefore, the scattered showers and isolated thunderstorms tracking NE over the Mountains, Foothills, and western Piedmont should weaken with time this evening. We will maintain the highest POP (likely) over the Winston- Salem area, with lower POP (chance of shower) from Greensboro and Lexington eastward to Burlington for the next few hours. Otherwise, no POP in the east. Then later tonight and early in the morning, the cold front will slowly advance east toward the central Piedmont. As this occurs, the latest HRRR and other hi-res models suggest only a low chance of showers associated with the front. Otherwise, simply a partly cloudy evening and overnight with warm temperatures. Lows should be in the mid to upper 60s (or a good 15-18 degrees above normal). && .SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/... As of 330 PM Thursday... In the wake of the upper wave lifting through the Great Lakes, the sub-tropical ridge will expand across the Southeast Friday into the weekend. Strong heating, with thicknesses approaching 1420m on Saturday, will leave to highs in the upper 80s Friday and upper 80s/low 90s on Saturday. A strong cap will limit any convection to the seabreeze on Friday, where the cap will be weaker owing to strong heating, but dry air will ultimately limit the coverage storms. Lows Friday night in the mid to upper 60s. Strong instability will develop on Saturday as an elevated mixed layer advectS across the region, deflect to the north a bit by the mid-level ridge. MLCAPE as high as 3000 J/KG is forecast by both the NAM and GFS. The threat of severe storms will be conditions upon convective development, which will be hindered by dry mid-level air (which will also support 1000 J/KG of DCAPE) and the lack of a focus, other than the terrain induced differential heating. Models do indicate a shallow tropopause disturbance/jet emerging off the GOMEX saturday, which given the strong instability could be enough to offer some forcing. However, confidence is low at this point. Lows Sat night will be in the upper 60s. && .LONG TERM /SUNDAY THROUGH THURSDAY/... As of 330 PM EDT Thursday... The subtropical ridge will retreat a bit on Sunday and especially Monday as an upper low lifts of the southern Plains. the associated cold front and convection are forecast to move into central NC Monday night, later than in prior forecasts, with limited instability and and forcing as it moves east. The front will also serve to knock temps back to more seasonal values, with highs in the 70s and lows in the 50s for midweek. Some uncertainty develops midweek, as the front is forecast to stall over the region and may be the focus for some unsettled weather as another shortwave or two swing through the longwave trough generally over the eastern US. && .AVIATION /00Z FRIDAY THROUGH TUESDAY/... As of 840 PM Thursday... 24 Hour TAF Period: A cold front will slowly move into the area this evening/tonight, while dissipating. KGSO/KINT stand the best chance of see sub-VFR conditions and thunderstorms from 00-04Z this evening. Further east, from 02-08Z VFR/MVFR conditions in showers will be possible. IFR/MVFR cigs will be possible early Friday morning through around mid/late morning-early afternoon as well. VFR conditions are expected to return Friday afternoon as strong high pressure aloft expands over the region. Outlook: A very summer-like pattern through the weekend with sub-VFR stratus possible during the early morning hours, scattering out by 15Z, and isolated afternoon convection being focused mainly around GSO/INT. Otherwise, expect the best overall potential for convection Monday evening/night in assoc/w a cold front /squall line/ progged to track eastward through the Carolinas. && .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Badgett NEAR TERM...Badgett SHORT TERM...SMITH LONG TERM...SMITH AVIATION...BSD/SMITH
Area Forecast Discussion
National Weather Service Tampa Bay Ruskin FL
851 PM EDT Thu Apr 27 2017 .UPDATE... 00Z water vapor and H4 RAP analysis shows the beginning stages of upper ridge building over the eastern Gulf of Mexico and FL peninsula have commenced. This upper ridge will be the dominant player in our weather through the upcoming weekend, as it protects the forecast area from any real inclement weather attempting to move eastward from upstream. This ridge will be complimented by a surface ridge axis extending from the Atlantic, across the peninsula and into the Gulf of Mexico. Overall, we are looking at a very summer-like synoptic pattern, and will be certainly seeing summer-like temperatures. The sea-surface temperatures are still generally in the 70s, so unlike the pure summer, dewpoints will not be as high, and it will not feel overly oppressive. On the flip side of the coin, the lack of low level moisture and strong subsidence aloft will likely almost completely prevent any chances for sea-breeze showers/storms. The chances will not be zero, but just very low at any one location to see a passing storms. One lone thunderstorm was able to break through the hostile air aloft this evening as sea-breezes collided over Highlands County. A renegade similar type storm is possible again late Friday, however, it will be fighting even greater thermodynamic hostility aloft as the upper ridge continues to strengthen. So...the main thing to take from the forecast the next few days, so that it will be hot. Even the beaches will get pretty toasty by early afternoon, and then settle back down through the 80s as the sea-breeze kicks in and turns winds off the relatively cooler shelf waters. Those shelf waters are continuing to warm, and it will not be too long before they cross a crucial threshold, and add yet one more ingredient to the start of the summer storm season. && .AVIATION (28/00Z through 29/00Z)... The synoptic situation has not changed significantly since early Thursday morning, and therefore areas of shallow field fog are possible once again between roughly 07-11Z at KLAL/KPGD/KFMY/KRSW. Have included MVFR vis, but a period of IFR is not out of the question given what occurred last night. Although some guidance has been bullish with fog near the coast later tonight, have disregarded this as unlikely and kept restrictions out of KTPA/KPIE/KSRQ. Any fog is gone very early Friday morning...followed by prevailing VFR the remainder of the day. Just a slight chance of an isolated shower along the sea-breeze after 21Z, but potential low enough to leave mention out of the TAFs at this point. && .Prev Discussion... /issued 247 PM EDT Thu Apr 27 2017/ SHORT TERM (Tonight - Friday)... An upper level low sits over southwestern Ontario with broad troughing extending over the central U.S. Upper level ridging continues to hold over the Florida peninsula and will further build through the short term period. On the surface, an area of low pressure just north of the Great Lakes extends a cold front over the eastern Great Lakes region and further southward along the Appalachian mountain chain. The trailing edge of this front dissipates over southern Georgia/northern Florida as high pressure continues to ridge across the peninsula through the end of the week and into the weekend. This will keep a southeast through southwest wind flow over the area which will result in above average temperatures. The coastal counties will top out in the upper 80`s, while the inland counties will see daytime highs in the 90`s. Rain free conditions will continue through the end of the week. MID/LONG TERM... Strong mid-level ridge will keep us hot and dry into the weekend. H5 heights of 591+ DM will support high temps soaring well above normal Saturday and again on Sunday with widespread 90s expected with some mid 90s possible across interior zones. Some record high temperatures will certainly be possible. The location of the Atlantic surface ridge will keep a SE wind flow in place through the weekend. The ridge will break down at the start of next week as a low pressure system develops across the central U.S. This system will gradually move towards the Great Lakes region while an associated frontal boundary approaches the area Monday. Upper-level support looks to diminish as the front moves towards the area. GFS continues to show the front moving through at least the Bay area while the ECMWF keeps it draped across the Nature Coast. Forecast continues to lean more towards the Euro solution for now but either way, low end PoPs continue in the forecast for Monday and Tuesday with warm temperatures continuing. Late in the forecast period, and just beyond, models continue to show a major pattern change across the CONUS with deep upper-level troughing developing across the eastern U.S. Will see how this plays out over time as it is still over a week from now and much can change between now and then. Stay tuned. AVIATION... The stratus/fog from this morning has dissipated and a CU/SC cloud deck has developed over the region. Even with the CU/SC clouds, conditions are expected to remain VFR through late tonight. Some patchy fog and low clouds will be possible once again tonight that may bring some MVFR/IFR conditions to the terminals early Friday morning. Predominant wind flow will be out of the southwest this afternoon/evening, then becoming more southeast overnight. No other aviation impacts expected. MARINE... High pressure will continue to ridge from the Atlantic into the eastern Gulf of Mexico through the weekend. A weak front washing out over the northern Gulf today will produce a tight pressure gradient, with cautionary headlines needed for the Gulf waters north of Tarpon Springs for the remainder of the day. Winds will increase again to around exercise caution levels Sunday and Monday as another front moves into the region. FIRE WEATHER... Dry and rain free conditions continue across west central and southwest Florida into the weekend. Relative humidity values may briefly drop below 35 percent over the inland counties today, but should not be below 35 percent for more than a couple of hours, so no Red Flag Warning will be needed. With that being said, drought conditions continue across the region and county burn bans remain in place for many counties. Humidity values will be on the rise into the weekend and a chance of rain will occur on Monday and Tuesday next week which will briefly reduce the risk of wildfires. && .Preliminary Point Temps/PoPs... TPA 73 91 74 91 / 10 20 10 0 FMY 72 92 73 91 / 0 20 0 0 GIF 71 96 72 93 / 0 10 10 0 SRQ 71 87 72 86 / 10 20 10 0 BKV 67 95 69 93 / 0 20 10 0 SPG 73 90 75 90 / 10 10 10 0 && .TBW WATCHES/WARNINGS/ADVISORIES... FL...None. Gulf waters...None. && $$ UPDATE/AVIATION/MARINE...14/Mroczka UPPER AIR...99 DECISION SUPPORT...99
Area Forecast Discussion
National Weather Service Topeka KS
623 PM CDT Thu Apr 27 2017 ...AVIATION UPDATE... .SHORT TERM...(This evening through Friday) Issued at 256 PM CDT Thu Apr 27 2017 Isentropic lift and moisture depth will gradually increase this afternoon ahead of our next weather system for tonight and tomorrow. Currently seeing widespread 20-30 dBZ echoes across central Kansas, but based on surface obs/high res soundings, only a fraction of this is reaching the ground as rain. Did start with light POPs for this afternoon given this off chance of a shower lifting northward, with increasing POPs into the night as the deeper lift and saturation arrive. An elevated ribbon of MUCAPE will manifest itself above the H850-H750 front lifting northward between 03-09Z, bringing with it the chance for convection/scattered thunderstorms. The upper level dry slot will punch across the area Friday mid-morning and should bring precipitation to an end except in the far northern CWA. However, low clouds should linger through much of the day, especially north of the warm front which will bisect the CWA from E- W by 18Z. .LONG TERM...(Friday night through Thursday) Issued at 256 PM CDT Thu Apr 27 2017 The Friday night through Sunday forecast really has not changed much from previous periods. The broad long wave trough will remain to our west for the majority of this time frame, kicking out a steady stream of upper level short wave troughs into a very moist environment across the Plains. It remains likely that the local forecast area will remain on the cool side of the storm system with only periodic bouts of elevated instability present to support occasional bouts of thunderstorms embedded within the otherwise rain shower environment. Severe thunderstorms appear very unlikely in the local area at this time due to limited instability and a stable boundary layer. The heart of the upper trough is expected to trek over northeast KS on Sunday with a well-organized deformation zone and TROWAL on the northwest to west side of the upper trough. The end result is that over the entirety of the period now through Sunday still points to 1.50 to 3 inches for the entire forecast area, but it should be mostly spread out over time to limit the flooding potential. Some RFC guidance suggests potential for generally minor river flooding so will monitor this potential closely but looks like minimal impacts at this time. On the cold side of the system, ample cold air will be pulled into the storm system and may actually support a band of rain mixing with snow across north central and perhaps northeast KS. The limiting factor will be surface temperatures in the mid 30s but may be sufficient for a quick bout of snow accumulating on grassy areas. Beyond this period, northwest flow and generally cool temperatures will prevail through the long term. Another storm system is forecast to develop over the Plains by mid week but is currently expected to be focused south of the forecast area so have generally low end pops at this time. && .AVIATION...(For the 00Z TAFS through 00Z Friday evening) Issued at 623 PM CDT Thu Apr 27 2017 Deteriorating conditions are forecast overnight as a surface low transitions from southwest CO into the plains. Low level moisture advection is expected to increase and bring some MVFR and IFR CIGS into the region along with periodic rain showers as the terminals remain north of a pseudo warm front. Instability is not great but mid level lapse rates are steep enough to keep a mention of VCTS during the overnight. Biggest uncertainty is with how low CIGS get and for how long they linger over the area. The RAP soundings suggest any IFR CIGS may be brief with the surface low lifting into NE KS through the afternoon. Have stayed with the model consensus and will monitor trends, but in any case it looks like there is some chance for CIGS to lift to VFR by the mid afternoon. && .TOP WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SHORT TERM...Skow LONG TERM...Barjenbruch AVIATION...Wolters