Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 04/24/21

Area Forecast Discussion...UPDATED
National Weather Service Amarillo TX
647 PM CDT Fri Apr 23 2021 .AVIATION... For the 00Z TAFs, a cold front has moved through the terminal sites with north winds in its wake. A few showers and tstms may impact KGUY between 01Z and 03Z this evening, and have included VCTS durg that time frame. Winds are forecast to become southerly at the TAF sites late Saturday morning into the afternoon hours. 02 && .PREV DISCUSSION... /Issued 230 PM CDT Fri Apr 23 2021/ SHORT TERM...Tonight through Saturday Night... Please see the Meso Scale Update to cover the tonight period. Late tonight into Saturday night...Cold front will be through the Panhandles after midnight, and with storms ending we can expect a prolonged dry period. Cold air will quickly exit to the east, so much that highs tomorrow will be warmer than they were today in the north (mainly due to the low clouds that held the temperatures in check). Westerly flow aloft will lead to a lee surface low in southeast Colorado tomorrow and winds will come around the clock to southerly, as drier air settles. RH values could be as low as 13 percent tomorrow with winds around 10-15 mph. This will keep the Fire Weather threat really limited to just a couple hours at best, and that`s without certainty of some areas that might pick up rain this evening, allowing some ERC`s to recover a bit. Weber MESOSCALE UPDATE... ..Severe Weather Expected Today... * Synoptic Overview: Mid level trough approaching the Panhandles will provide sufficient lift for storms this afternoon and evening. A cold front this evening will allow for potentially a second round of storms, however they are not expected to be severe. * Mesoscale: Dryline now just east of Amarillo expected to stall around Donley County as the surface trough dives southeast allowing for moisture to curl back and keeping the severe weather threat in play for the north central and southeast Panhandles. Right now Amarillo is not expected to benefit enough from this return flow to be in the severe threat, but there is still a very slim chance that storms could form this afternoon. RAP sounding (Shamrock, TX) indicate a very fairly robust CAPE values 1000-1500 J/kg across Wheeler County with very little to no capping inversion. Any capping inversion will be taken care of by large scale forcing from the mid level wave moving through. LCLs across the east could be down to 500m, with effective bulk shear in the 30-45kt range, and while the low level wind profiles are not conducive, there`s enough going on that we can`t rule out an isolated tornado. Hail and damaging wind will be the main concern, with large hail being a primary concern in the far southeast Texas Panhandle. * Threats: Hail the size of quarters to golf balls will be possible in the north central and northeast Panhandles where there`s lesser instability. However,hail size from hen egg to tennis ball (2.0"- 2.5") will be possible in the Wheeler, Donley, Collingsworth County areas, where the instability is the greatest. These areas are also the main areas to focus a tornado threat, as the wind profiles are even worse to the north and west (central to northeast Panhandles). Additionally, higher LCL`s to the areas north and west will make it even more difficult for the tornado threat. All areas under the hail threat will also be in the damaging wind threat, with wind gusts up to 60 mph. * Timing & Location: While some storms have begun to initiate east in central Oklahoma, the threat for storms to initiate over our area shouldn`t be any earlier than 3PM, however 4 to 5 PM looks more favorable. At initiation time storms should start to fire up in the northwest, closer to the cold front (non-severe), as well as just east of Amarillo (severe threat),and expand to the southeast. Right now the main coverage should be north of a Romero - Amarillo - Wayside line, where areas south and west of that line are likely to be in the drier region, and thus no storms in the forecast. The severe window may be very short lived with it starting around initiation time and likely dropping off around 8 PM. It`s possible it will continue through 10PM, but at that point it would be more isolated in nature. * Summary: Overall, severe storms expected this evening, with the best chances to the southeast. Large hail is the main threat, with some areas possibly seeing greater than 2.0" hail. Isolated tornado can`t be ruled out in the far southeast. Main timing for severe weather will be from 4 to 8 PM but can`t rule out severe weather through 10 PM. All storm activity should be out by midnight. Weber LONG TERM...Sunday through Thursday... Not much for changes in this run of models. Fire weather is still the focus of the extended with a shot for storms Tuesday into Wednesday. Sunday will be a warm day with the LLTR stemming from down in the Rio Grande area of west Texas up through the western Panhandles. Jets won`t be stacked so it will keep winds from becoming more than breezy by Panhandle standards. We will likely mix upwards of the 700mb level which has a broad area of 30-35kts for gusts. There may be a few mid level clouds in the east on Sunday according to short range model cross sections. Cross sections also show some low level folding of potential vorticity lines, which will enhance the likely of the gusts reaching the ground in the west where the folding exists. With the dryline pushing east to the OK state line, the dry and breezy conditions will lead to critical fire weather across the Panhandles. By Sunday night the mid level flow pattern starts to gain a southwesterly component as the mid-level trough comes on shore in California. For Monday, models show the southern jet stream move northward and bring the southern Plains Pacific moisture. This shift in the jet will bring high level clouds to the area. This won`t limit the high temps too much but may serve to lower some of the fire weather threat for the day, although we will still be looking for critical fire weather conditions across the area again. Jets overhead still aren`t lined up, resulting in similar wind speeds forecast for Monday. Long range models are still bouncing around the timing of the cold front on Tuesday from model to model and run to run. This is due to there continual differences with the evolution of the trough. The GFS has a closed low early on and then opens it to a progressive wave. Meanwhile the ECMWF is open and closes it off about the time the GFS opens it. The Canadian is the slowest of all the models for pushing the low across the southern Plains. The blended consensus for now is for the front to start pushing into the Panhandles Tuesday evening and be through shortly after midnight. Depending on the position of the dryline, there could be precip in our southeast in the afternoon on Tuesday through early Wednesday. Otherwise, the majority of precip chances should come on the backside of the cold front. There are several GEFS members that leave us dry as well as some EC members. However the majority of EC members are more optimistic on precip for Wednesday. Regardless of precip or not for mid-week, Wednesday looks to be the coolest day of the extended with highs in the 60s. The end of the work week looks for temps to increase and dry conditions as ridging takes over the west and troughing in the eastern CONUS. Beat FIRE WEATHER...Sunday through Thursday... Some sort of fire risk is probably each day across areas of the Panhandles. Sunday is likely to see critical fire weather across all but the far southeast TX Panhandle, which will likely be in elevated. RFTI values are expected to be 1-3 in the east and 4 to 5 with spotty areas of 6 in the west. The LLTR will extend up through the western Panhandles, but jets will be misaligned leaving the area with winds generally in the 20-30mph range with gusts upwards of 40 mph. RH values look to dip to single digits in the west and rise to lower teens in the east. Monday will be similar to Sunday in temps and RH. The two main difference will be the winds may be a bit stronger in the northwest, reaching closer to 35 mph sustained winds, and the drying out that happens from Sunday will increase ERCs from around the 75th to the 85th percentile. With the slight increase in winds, the RFTI values increase in the northwest to 7 and 8. While Sunday looks to be mostly sunny, there looks to be some high level clouds develop Monday which may help, but also prevent seeing of fires on satellite. Overnight recovery Sunday into Monday and Monday into Tuesday will be dismal for those behind the dryline with RH rising to only around 30 percent. Tuesday will be slightly better for the area with RH dropping into the teens, but winds will remain breezy. Cloud cover will increase and a cold front looks to move through starting in the evening hours. Tuesday looks to be an elevated to critical fire weather day with RFTI values of 1 to 4. Post frontal conditions on Wednesday will be dependent on precip coming through the area. If not, we could again see possible elevated conditions with RFTI values of 1 to 2 but RH looks to only drop to the mid 20s. Thursday looks to have RH drop to around 20 percent area-wide with winds of 20-25mph; therefore, again may see some elevated fire weather conditions depending on ERC values. If we do get some precip Tuesday into Wednesday, this should help lower ERCs and limit some of the later week fire threats. Beat AVIATION...18Z TAFS... VFR conditions set to prevail at all TAF sites over the next 24 hours. However TS will be something of concern at all sites, more so at KDHT and KGUY, but KAMA is not completely in the clear. Right now have VCTS in the KDHT/KGUY area from the 23-04z time period, will note with amendments if it looks more favorable. KAMA should be west of the main convection early this evening, but the post frontal showers/storms currently holds a VCSH at KAMA from 03-06z, that may need to be shifted to TS, but too early to tell as it will be when we start to really stabilize. As long as storms don`t go directly over a TAF site, cigs and vis should remain well in the VFR categories, but only expect MVFR conditions if they were to impact a site. Northeast winds at KDHT and KGUY will shift more northwest after the front tonight 02-04z period, and winds currently south southwest 10-15kts will shift more west as the dryline will soon push through and become more northwesterly 10-15kts by 03-06z. Weber && .AMA Watches/Warnings/Advisories... TX...None. OK...None. && $$
Area Forecast Discussion
National Weather Service La Crosse WI
1059 PM CDT Fri Apr 23 2021 .SHORT TERM...(This evening through Saturday) Issued at 242 PM CDT Fri Apr 23 2021 GOES water vapor imagery/loop and RAP 500mb analysis showing mid- level vorticity center moving through northwest WI while a surface low/cold front lagged behind from western MN into western Nebraska. Surface observations were showing occasional very light rain showers associated with these features across southern and central MN in weak 850mb moisture transport ahead of the front. Otherwise, temperatures as of 1 pm were in the 50s to near 60. Latest CAMs showing a few more showers, albeit very light with minimal amounts this afternoon during peak heating and with the forcing along that cold front. These showers will be battling a dry sub-cloud base environment which may produce more virga than actual rainfall reaching the ground. So, not expecting much more than a hundredth of an inch or two from these passing isolated showers. Look for afternoon highs in the mid-50s to a few 60s. For tonight, the cold front will be passing through the area with better moisture convergence focused north of I-90 for a continued small-end chance of showers. Plan on lows in the mid-30s to lower 40s. Another mid-level trough pushes into the area Saturday morning for additional small-end rain chances...but again amounts look to be minimal with a trace to perhaps a couple hundredths of an inch expected. Rain chances pretty much come to an end Saturday afternoon with skies clearing from west to east as high pressure builds in from the Northern Plains. Cold air advection will hold back temperatures with highs ranging from the mid-upper 40s across portions of southeast MN into north central WI, and mid-50s to near 60 across northeast IA into central WI. .LONG TERM...(Saturday night through Friday) Issued at 242 PM CDT Fri Apr 23 2021 Surface high pressure will build in overnight with temperatures once again expected to lower into the teens, 20s, and around 30 Sunday morning. We ill continue to coordinate with our agricultural partners related to the growing season as it continues to remain mixed with some locations quite a bit further along than other areas. A ripple in the mid-tropospheric ridge may bring some showers to the region Sunday with highs in the 40s and 50s. On water vapor satellite imagery, this weather system appears to be decent looking. The NAM is dry, however the 12Z GFS still has some a little more precipitation into our area. Any precipitation locally appears it would be light per the EC EPS, generally from a trace to a tenth or two. Temperatures will be important as initially temperatures start out cold. Should it be precipitating, it would be snow changing to rain. The mid-level ridge sharpens with energy track across parts of Canada into the Upper Mississippi Valley and a 35 to 45kt 850mb jet will help to focus precipitation north of the area sunday night. Monday, a 35 to 45kt 900mb jet will track across the area while a 60 to 70kt jet across Missouri will veer toward Illinois. Forecast soundings appear to be capped with a strong inversion, so it appears to be really limiting rain chances. Some spotty activity toward the forecast area sunday night and Monday, especially north of I90 or something isolated toward DBQ Monday morning or above the cap ahead of the warm front. Will need to assess this each day as there is plenty of forcing available and areas outside of the cap with enough moisture will have shower/t-storm chances. The SREF has a 5% t-storm probability for parts of the area Sunday and Sunday night with the 10% area north into the MPX forecast area. With the warm front lifting into the area, temperatures Monday should be in the 70s. Wind gusts are currently forecast to be 25 to 35kts. Things are greening up, thus less impactful for fire danger. Lowest relative humidity values are expected to mostly in the 40s. Monday night through Thursday will bring on and off rain chances as a long wave trough over the Rockies moves toward the Ohio River Valley and a front sags into the area and takes a while before it exits the region. Tuesday into Tuesday night or Wednesday morning appears to be our best chance for showers and thunderstorms. The GEFs plumes are clustered between .25 and .5, however there are over half a dozen members that have an inch or two. The GFS has more post-frontal precipitation. The EC EPS has backed off slightly from yesterday, but still have general amounts around a half an inch. We need the rain and this would be a good pattern to pick up some of those locally higher amounts. It is a bit far out, however the Storm Prediction Center is highlighting the day 4 potential for severe weather Tuesday in the Central and Southern Plains along the dryline. The severe weather potential will need to be honed in on as we get closer. Longer range models show instability along the front with some stronger 0-3km shear vectors. Some potential there and will need to assess this when we have a better handle on where the front will be, the thermal heating/profile, and forcing for ascent. The models are not in agreement if northern stream trough for Thu, does not appear strong enough to kick the system east. The GFS is dry for Thursday, however the EC has lingering post- frontal precipitation with the trough. Temperatures will start out above normal Tuesday, drop to near normal Wednesday and Thursday, then return to above normal Friday. && .AVIATION...(For the 06Z TAFS through 06Z Saturday night) Issued at 1059 PM CDT Fri Apr 23 2021 A cold front was moving slowly east across Minnesota late this evening. This front will continue to advance east and move through both airports overnight or Saturday morning. MVFR ceilings are filling in behind the front and these should continue to expand and are expected to spread over both sites. Some signals that the ceilings could go down to IFR but confidence is not high enough to include at this time. The ceilings should stay MVFR for much of the day Saturday and then lift back to VFR either late in the afternoon or early in the evening. && .ARX WATCHES/WARNINGS/ADVISORIES... WI...None. MN...None. IA...None. && $$ SHORT TERM...DAS LONG TERM...ZAPOTOCNY AVIATION...04
Area Forecast Discussion
National Weather Service Columbia SC
817 PM EDT Fri Apr 23 2021 .SYNOPSIS... Dry high pressure remains in place with elevated fire danger continuing through this evening. Winds pick up out of the south ahead of a strong low pressure system that will bring heavy rain and strong to severe thunderstorms throughout the day Saturday. Things clear out for Sunday as a ridge of high pressure builds in, keeping us dry and mild through mid-week. Rain chances increase late in the week as a trough and low pressure system cross the area. && .NEAR TERM /UNTIL 6 AM SATURDAY MORNING/... Despite a relatively dry air mass across the area, a few showers did develop in the south and central Midlands this afternoon associated with weak mid level short waves in west flow aloft. These showers are now east of the area along the Savannah River area. High pressure has begun sliding toward the coast and will continue moving away from the area overnight. High temperatures remain on track for the low 70s at most locations. Synoptic situation will change tonight as low pressure marches eastward across the Gulf states with moisture rapidly increasing toward daybreak with pwat values reaching 1.2 inches in the CSRA and 1 inch in the northern Midlands. This will also result in showers spreading in the CSRA and southern Midlands with lower chances of pops in the central and northern Midlands. Instability will be minimal through daybreak and although shear will be increasing do not expect any thunderstorms. Increasing clouds overnight and weak warm advection will keep overnight lows in the low to mid 50s. && .SHORT TERM /6 AM SATURDAY MORNING THROUGH SUNDAY NIGHT/... An overall tricky and still uncertain forecast for Saturday. SPC has continued their slight risk for the entire CWA, but increased the risk to our south. Again, the SPC highlights the risk for all hazards while underscoring the uncertainty in the forecast. A sharp upper level short wave and jet will spin up a strong surface low this afternoon in the southern plains. As this low slides across LA, MS, and AL this evening and overnight, southerly flow kicks up for the CWA and deep moisture return will drive PWATs over 1 inch by the Saturday morning. Isentropic lift will gradually increase throughout the morning as a warm front is pushed across the region. A weak in-situ wedge appears possible as this warm front triggers showers as it tries to move north. The uncertainty with system is primarily associated with the strength of the low level jet and therefore the northward extent of more unstable air. Hi-res guidance is split, with the HRRR and several others with a weaker jet and significantly further south solutions, reducing the severe threat over most of the CWA. The 3km NAM and others show a 60+ knot 850 mb jet that allows the entire CWA to enter the warm sector and destabilize in the afternoon. The HRRR-like solution would suggest that the majority of the severe weather stays south of the CSRA, with stratiform rain over most of the CWA. The NAM-like solution would bring stratiform morning rain along the warm front before some clearing, followed by strong thunderstorms with the cold front in the evening. Overall, the HRRR-like southern solution is similar to one we see often, intense deep convection to our south significantly cuts off moisture transport to the north. So again, the key will be the low level wind field and whether or not that verifies. The differences in these solutions become apparent fairly early in their runs (between 00z and 06z Saturday), so the picture should hopefully become clearer later this evening. Regardless of severe potential, confidence is high in a heavy rainfall event. Widespread 1-2" with spots over 3" is likely. We dry out by early Sunday morning and northwest flow will dominate the weather Sunday with highs in the upper 70s due to some downsloping, despite the cold advection behind the low. Lows overnight Sunday into Monday should stay around 50 thanks to some winds. && .LONG TERM /MONDAY THROUGH FRIDAY/... A strong upper level ridge will dominate the pattern through Wednesday. Initially to our north, the accompanying surface high will shift off the Atlantic coast and force some southerly flow. There is a good signal in the long range ensembles for temperatures warming above average with dry conditions through Wednesday. GEFS, blend, and EC members all continue to show a deep upper level trough amplifying as it moves across the US by Thursday. Consequently, rain chances increase sharply by Thursday and Friday. && .AVIATION /00Z SATURDAY THROUGH WEDNESDAY/... VFR into late tonight with restrictions likely in the morning. High pressure continues to move offshore with the next low pressure system along the Texas panhandle moving east. Just prior to daybreak, ceilings will begin to lower to MVFR along with some light showers. Showers will increase and become heavier in the afternoon with possible visibility restrictions. Thunderstorms are also possible mainly in the afternoon, however there is still uncertainty in the timing and best location for storms. Winds will become east southeasterly around 10 knots with gusts to 17 knots around 14z to around sunset. EXTENDED AVIATION OUTLOOK...Showers and thunderstorms along with associated restrictions will continue into Sunday morning as a low pressure system moves through the region. && .CAE WATCHES/WARNINGS/ADVISORIES... GA...None. SC...None. && $$
Area Forecast Discussion
National Weather Service Peachtree City GA
816 PM EDT Fri Apr 23 2021 .UPDATE... Updated for the 00Z Aviation Discussion. && .PREV DISCUSSION... /Issued 305 PM EDT Fri Apr 23 2021/ SHORT TERM /Tonight through Saturday Night/... High pressure center has moved offshore. A warm front is situated across the east Texas/western LA coasts. Further out west, low pressure is developing across eastern New Mexico/west Texas. The low pressure center will begin moving east along the northward moving warm front overnight and into tomorrow. The low pressure system should begin entering the Lower Mississippi River Valley by 12Z tomorrow and then should move quickly across north Georgia during the day dragging a cold front through. The overnight period should be fairly quiet with increasing clouds. Good easterly flow will continue to bring low level moisture in from the western Atlantic. Widespread precipitation should be on the doorstep by 10Z tomorrow. With BL winds 15-25kt overnight and early tomorrow, do think the warm front will move north, leaving much of the CWA in the warm sector tomorrow. The HRRR seems to have a reasonable handle on the situation, for now, and have stuck close for timing. Kept mention of thunderstorms out of the forecast for the overnight hours. Models have delayed the onset of precip a bit from previous runs. Models are also holding onto a weak wedge in the far NE CWA for early tomorrow. However, it is a very good possibility that any weak wedge will mix out in the afternoon as the warm front moves northward. There could be a couple of waves of convection tomorrow. The first wave should be in the early/mid morning hours. Ongoing MCS should move out of central AL into central portions of the CWA. After the morning convection, there could be a lull ahead of the 500mb trough and cold pool. Afternoon convection would heavily depend upon how well the airmass recovers from the early morning convection. It`s Springtime, so strong heating may be able to occur, especially if the overcast skies begin to break. Do think the afternoon activity will be more scattered in nature than the morning activity. Plenty of surface instability will be available for the early morning convection, especially south of the warm front. In the afternoon, available surface instability will depend upon how well the airmass recovers...but steeper mid level lapse rates with the cold pool aloft are expected. Good shear values will be present all day. So multiple storm modes will be likely tomorrow. In the morning, the MCS should contain a more linear type of convection with the potential for bowing segments. The primary hazards with this convection should be damaging wind gusts with the potential for a brief tornado. The afternoon convection should be more cellular in nature, with the primary hazards being large hail, damaging wind gusts and the continued potential for tornadoes. Think the greatest potential for severe thunderstorms with the morning convection should be south of the Interstate 20 corridor. For the afternoon convection, anywhere south of where the warm front sets up, probably south of a Rome to Athens line. In addition to the severe thunderstorm potential, heavy rainfall will be likely. For now the current axis of heavy rainfall is along and south of the Fall line...across the sandier soils of the state. There is some potential for training of storms, especially if the atmos is able to de-stabilize for the afternoon. On average 1 to 2 inches of rainfall are likely, with some locally higher amounts of 3+ inches possible, especially south of the I-20 corridor. NListemaa LONG TERM /Sunday through Friday/... Picking up on Sunday morning with the potential for some lingering showers across the CWA as the shortwave trough pushes off the Delmarva coast. Otherwise, the extended remains mostly dry with a surface high sinking in over the Carolinas under a broad upper level ridge. Near the end of the extended, model guidance continues to prog a deep trough developing over the Four Corners region by Tuesday evening, pushing eastward and eventually deepening into an upper low over the midwest by Wednesday night. It`s still a ways out, but models have started to come into better agreement in regards to spatial coverage of precip over the CWA in the latter half of the extended. However, great disparity remains on the timing of the system, with the GFS staying the more progressive and faster of the solutions while the Euro has continually showed a slowing trough. Regardless, this low is expected to bring a sweeping cold front through the CWA and thus, increased PoPs to mid-range Chance with slight change thunder across the CWA on Thursday into Friday. Also, time to put away the flannel, warm weather fans will enjoy this extended with high temps reaching into the low to mid 80s by midweek thanks to being parked under the broad ridge, which is around 5-6 degrees above avg for this time of year. Morgan && .AVIATION... 00Z Update... VFR conditions are in place across north and central Georgia as the period begins, with mostly mid to upper level clouds in place. Ceilings are expected to lower to MVFR between 08-10Z as precipitation becomes more widespread. IFR ceilings are also possible after 12Z and through the morning hours. Hi-res guidance continues to indicate two waves of convection on Saturday, with the first during the morning and the second later in the afternoon. A TEMPO for TSRA has been introduced from 12-16Z at the metro ATL sites, and another will likely be needed in ensuing updates for the afternoon convection as confidence increases on timing. E to SE winds overnight and tomorrow morning will increase to 10-14 kts with gusts up to 25 kts, then shift to SW during the mid afternoon hours. //ATL Confidence...00Z Update... Medium confidence on all elements. King && .PRELIMINARY POINT TEMPS/POPS... Athens 51 67 52 76 / 70 80 40 0 Atlanta 53 70 54 73 / 80 90 40 0 Blairsville 46 61 47 69 / 70 80 30 0 Cartersville 50 72 49 73 / 70 80 30 0 Columbus 57 76 55 78 / 100 100 60 0 Gainesville 50 64 52 74 / 70 80 30 0 Macon 55 73 56 79 / 80 100 60 0 Rome 51 72 52 74 / 80 80 30 0 Peachtree City 52 72 52 74 / 80 100 40 0 Vidalia 58 75 61 80 / 50 100 60 0 && .FFC WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SHORT TERM...NListemaa LONG TERM....Morgan AVIATION...King
Area Forecast Discussion
National Weather Service Fort Worth TX
750 PM CDT Fri Apr 23 2021 ...New Short Term, Aviation... .SHORT TERM... /NEW/ /Through Saturday/ Ongoing convection continues to move eastward this evening along the I-35 corridor. This area appears to be along the fringes of approaching large-scale ascent, but is actually starting to move away from the greater instability immediately east of the dryline. As a result, I expect a gradual weakening trend of convection as it ventures farther east away from I-35. With the lack of greater instability, loss of daytime heating and high probability that earlier day convection has stabilized the airmass east of I-35 also making it a less than ideal environment for strong/severe storms. Farther west...satellite imagery (billow clouds to even clear skies) corroborates with RAP 310K isentropic progs which shows strong downglide/sinking motion just ahead of the dryline. While high based CU was noted farther west, forecast soundings near KABI show a very hostile environment for renewed convective development across our Big Country counties and thus I think any renewed convection here will be short-lived, though I cannot completely discount a strong storm or two given the instability. Across western North Texas near the triple point, a cluster of showers and storms continues within an environment characterized by CAPE in excess of 2000 J/kg, mid-level lapse rates of 8-9 C/km and 0-6/0-8km bulk wind differences in excess of 50 knots. While the near surface will likely attempt to stabilize, it seems reasonable that this convection will eventually try to grow upscale and develop a fortified cold pool. Even with a stable near surface layer, a strong cold pool will have no trouble assisting parcels upward toward their LFCs to realize the instability aloft. While typically overzealous with cold pool generation, the NSSL WRF and NCEP WRF ARW core tend to perform better in these types of environments and I`ve tailored the short term forecast to their output some. This equated to keeping 70-90 PoPs along the Red River after about 10-11 pm with a tight PoP gradient toward the I-20 corridor. The big question will be how far south convection will build as it moves through North Texas. Low-level flow should veer with the approach of the complex/front and so I believe this will limit the amount of convergence on the southern end of the developing complex. It is possible that a damaging wind threat may materialize for parts of this region (specifically west of I-35 north of HWY 380), especially if storms develop a solid cold pool. Storms may linger to just before sunrise Saturday as a cold front sweeps southward through the area. Bain && .LONG TERM... /Issued 152 PM CDT Fri Apr 23 2021/ /Sunday onward/ The long-term forecast period will begin with an upper-level ridge axis across the central CONUS, and an upper-level trough moving into the western CONUS by Monday. As this trough digs into the West, surface cyclogenesis will take place along the lee of the Central Rockies. The combination of subsidence from the ridge aloft and southerly low-level flow in response to the cyclogenesis across CO/WY will lead to warm temperatures on Monday. Maximum temperatures on Monday will rise into the mid to upper 80s for much of North and Central Texas, with a few spots near and west of U.S. Highway 281 forecast to approach 90 F. Despite the warm and breezy conditions, relative humidity should stay near or above 30 percent for most locations, keeping the fire weather threat low. By Tuesday, the upper-level trough axis will move further east into the Rocky Mountains, deepening the surface low over eastern CO. To the south of this low, a dryline will sharpen across West Texas with dewpoints in the warm sector forecast to increase well into the 60s. Strong ascent from the approaching upper-level trough, large instability within a robust low-level warm-air advection regime, and strong wind shear from a 120+ KT jet streak will support a risk for severe thunderstorms. While there remain some timing differences between major global models (with the GFS being faster/earlier and the ECMWF being slower/later), we feel confident at this time that a potential for a severe weather episode is likely to exist somewhere in the Southern Plains by late Tuesday and into Tuesday night. For Wednesday and beyond, the forecast will be highly dependent upon how quickly the upper-level trough exits our region. The slower ECMWF solution would lead to higher precipitation chances continuing into Wednesday as well as cooler temperatures. The GFS solution on the other hand would lead to decreasing precipitation chances on Wednesday. Regardless, it does appear that by the end of the week, precipitation chances should end and a return to normal to above normal temperatures can be expected as upper-level riding builds back in across the western CONUS. Godwin && .AVIATION... /NEW/ /00 UTC TAF Cycle/ Concerns---Convection and Ceiling trends. A band of TSRA continues to move to the east of D10 TAFs with TSRA likely to split KACT in the next 1-2 hours. While TSRA may not explicitly occur at a given TAF site over the next 2-4 hours (except at DAL), impacts will continue as the eastbound departures and traffic along the Bowie, Bonham, and Cedar Creek cornerposts experience TSRA. MVFR/IFR cigs will continue through the overnight hours with FROPA a few hours after midnight at D10 TAFs and around sunrise at Waco. We are watching an area of upstream TSRA just south of KFDR. Current indications are that this will develop into a line of TSRA and move southeastward toward D10 TAFs. Confidence is high enough to maintain VCTS near 0600 UTC. If activity upstream shows more pronounced organization, TEMPO TS will be needed. Bain && .PRELIMINARY POINT TEMPS/POPS... Dallas-Ft. Worth 58 76 54 83 62 / 60 0 0 0 0 Waco 57 76 51 84 59 / 60 0 0 0 0 Paris 58 72 51 78 58 / 100 5 0 0 0 Denton 56 74 49 81 59 / 80 0 0 0 0 McKinney 58 73 51 80 60 / 90 0 0 0 0 Dallas 59 76 56 84 64 / 70 0 0 0 0 Terrell 59 74 51 80 59 / 70 0 0 0 0 Corsicana 59 76 54 82 59 / 60 0 0 0 0 Temple 55 78 51 84 59 / 50 0 0 0 0 Mineral Wells 55 75 49 85 60 / 30 0 0 0 0 && .FWD WATCHES/WARNINGS/ADVISORIES... None. && $$
Area Forecast Discussion
National Weather Service Houston/Galveston TX
655 PM CDT Fri Apr 23 2021 .AVIATION [00Z TAF Issuance]... Initial round of severe weather is through, leaving numerous showers and a handful of storms in its wake. Activity should lull late this evening, but severe storms along the I-35 corridor near San Antonio may try to push in overnight. Considerable uncertainty exists whether these storms will persist to impact our TAF areas, so stick with VCSH/VCTS for now, and will revisit with amendments and/or the 06Z cycle as needed. Beyond that, once cold front is through, look for clearing sky and gusty offshore winds. && .PREV DISCUSSION /Issued 319 PM CDT Fri Apr 23 2021/... .SHORT TERM [Remainder of This Afternoon Through Saturday Night]... Conditions are increasingly favorable for strong to severe thunderstorm development during the remaining afternoon through early evening hours, and SPC has parts of our area (mainly along and north of the I-10 corridor) under a Tornado Watch 9 PM. Large hail, damaging winds and isolated tornadoes are all possible if storms do go severe in and around the Watch area, and maybe especially focusing in and around SPC`s Day One Severe Weather Outlook enhanced risk area (mainly Houston, Trinity and Polk counties) where greatest divergence aloft looks to possibly set up. Most recent HRRR and WoFS guidance is pointing toward areas to the north of the Houston area near/along surface boundaries as it moves northward. In addition to the severe risk, parts of SE TX (again, mainly north of I-10 and especially around and to the north of the Conroe area) are at risk for locally heavy rainfall where training storms could dump a quick 2 to 3 inches (locally higher amounts possible). Bottom line for those in and around the Houston area is to keep a close eye on how everything unfolds over the next couple of hours to make sure the higher risk stays to the north. In case it edges southward, make sure you are prepared for the storms and can make it safely through them. Once everything moves off to our east this evening, there could be some lingering showers and maybe some fog across the area before the cold front moves on through during the day on Saturday and helps to clear everything out. The rest of Saturday and on through Saturday night look mostly clear and quiet. Low temperatures tonight will range from the lower to mid 60s inland to around 70 at the coast. Saturday will be on the warm side with highs in the low to mid 80s for much of the area. It will finally cool back down Saturday night when we have lows in the mid to upper 50s inland and in the low to mid 60s at the coast. 42 .LONG TERM [Sunday Through Friday]... A surface high pressure and upper-level ridge will settle in across Texas on Sunday. Onshore flow will resume, helping to increase cloud cover and moisture across SE Texas through mid-week next week. Daytime highs will be in the mid-80s Sunday through Tuesday. Increased cloud cover overnight as well as warm and humid onshore flow will slowly drive overnight lows into the low 70s by Tuesday night. Our next chance of rain returns Tuesday through Thursday next week as a leeside low will strengthen across The Central Plains late Tuesday and invigorate a surface front that will push through Texas on Wednesday. Ahead of the front, a decent low-level jet will help advect Gulf moisture across SE Texas, driving up temperatures and moisture. PWATs will climb to 1.5-1.9". Spotty showers are possible on Tuesday ahead of the FROPA on Wednesday. Global models depict this front pushing reaching our CWA on Wednesday and pushing offshore and out of our CWA by Thursday. Some uncertainty still remains in its duration with the GFS pushing this front out faster than most other models. Behind the front, high pressure builds back in again. KBL .MARINE... Winds and seas will be elevated through tonight as a storm system passes across the region. Will carry caution flags in the bads and advisories off the coast. A weak cold front will move into the waters on Saturday and will bring a brief period of offshore winds. High pressure will quickly move to the east allowing onshore winds to resume on Sunday. Winds and seas will increase going into the middle of next week in advance of the next weather system and will likely require caution and/or advisories. 42 && .PRELIMINARY POINT TEMPS/POPS... College Station (CLL) 63 81 55 86 60 / 50 0 0 0 0 Houston (IAH) 68 84 59 84 62 / 60 0 0 0 0 Galveston (GLS) 71 82 67 77 69 / 40 10 0 0 0 && .HGX WATCHES/WARNINGS/ADVISORIES... TX...None. GM...Small Craft Advisory until 4 AM CDT Saturday for the following zones: Galveston Bay...Matagorda Bay. SMALL CRAFT SHOULD EXERCISE CAUTION from 4 AM CDT Saturday through Saturday morning for the following zones: Galveston Bay...Matagorda Bay. Small Craft Advisory until 10 AM CDT Saturday for the following zones: Coastal waters from Freeport to Matagorda Ship Channel TX out 20 NM...Coastal waters from High Island to Freeport TX out 20 NM...Waters from Freeport to Matagorda Ship Channel TX from 20 to 60 NM...Waters from High Island to Freeport TX from 20 to 60 NM. && $$ SHORT TERM...42 LONG TERM...KBL AVIATION...Luchs MARINE...42
Area Forecast Discussion
National Weather Service Northern Indiana
721 PM EDT Fri Apr 23 2021 .SYNOPSIS... Issued at 305 PM EDT Fri Apr 23 2021 Clouds expand back across the area during the evening and overnight hours tonight as our next rain chance approaches. Times of rain start tonight especially after midnight and continue through much of Saturday, but it certainly won`t be a wash out. Rain dissipates Saturday evening and dry weather takes over for Sunday through Tuesday with a trend during that period as well. Highs in the 80s are in store for Tuesday. && .SHORT TERM...(This Evening through Saturday) Issued at 305 PM EDT Fri Apr 23 2021 RAP model analysis showed as much as 40 degree 700 mb dew point depressions overhead this morning that will need to be overcome before we can precipitate across the area. Those are expected to be overcome by this evening as more moist air comes in. However, the surface relative humidity values are also very low especially east of IN-15, so would expect much of the precipitation to stay west of that road. West of IN-15 is also where the better forcing and dynamics reside tonight. Within this warm air advection wing/isentropic lift area moving in tonight, expect mostly spotty rain with the disorganized forcing and minimal omega values present, especially when collocated with the dry 0-2km RH values. As a whole though, warmer/moister theta-e air than what`ve had, does come in tonight, so expect the floor for low temperatures tonight to stay in the 40s. With the low pressure system tracking south of the area, continue to see the better moisture advection cutoff from the area. This provides a cap for precipitation amounts at 0.35", which have been lowered over the past few forecast issuances as the drier air and much more sporadic forcing has been realized. With the drier air around on Saturday east of IN-15, where the precipitation may even hold off until the afternoon, warmer temperatures and a little bit of a breeze between 15 and 20 mph could be seen, especially east of I-69. Highs on Saturday stay in the mid 50s west and between the upper 50s and 60 degrees east. && .LONG TERM...(Saturday Night through Friday) Issued at 305 PM EDT Fri Apr 23 2021 Behind the low pressure system for Saturday, a secondary cold front actually stalls out across the area Saturday night, so while cooler temperatures in the low 40s to possible upper 30s may be able to approach, feel the winds will be high enough to keep us above frost thresholds. As a low pressure system ejects off the Rockies, the aforementioned stalled out front never really washes out and some mid level moisture is noticeable in models as the low pressure system approaches. Low level moisture may be able to scrape northwestern areas, but on the whole, expect the area to remain dry on Sunday especially with rising heights. Behind the high pressure system vacating the eastern seaboard and a developing trough in the western US, a baroclinic zone sets up allowing for a warm advection pattern across the area. This generates a warming trend from Sunday to Tuesday with temperatures reaching the 70s on Monday and 80s on Tuesday with dry weather continuing. Used a blend of 75th percentile of available guidance with NBM 50th percentile and NBM guidance to come up with highs for Mon- Wed period. The next chance for rain will be mid to late week next week as a trough associated with a PV hook helps to deepen a low pressure system across the Midwest. This has slowed up some when compared to recent forecast models and may wait until late next week to even track through the forecast area, which was what the not-really- reliable GEM showed yesterday and continues to indicate today. With the track of the low to the west of our area and the warm temperatures for Tuesday, will continue to mention thunder for this late week time period, but the lack of forcing and timing differences don`t lend a lot confidence. The 850 Tds greater than 10C overhead would point towards a potential heavy rain event, but again with timing differences and the need for these ingredients to line up just right, do not have any real confidence in that hazard either this far out. && .AVIATION...(For the 00Z TAFS through 00Z Saturday Evening) Issued at 711 PM EDT Fri Apr 23 2021 There is high confidence in VFR ceilings at the TAF sites to start the night. Confidence wanes some at KSBN as rain showers approach/develop near daybreak Saturday. The saturation of the atmospheric profile gradually improves through the morning hours, and precipitable water values increase. However, guidance remains split on how low ceilings will go. It seems IFR ceilings are an outlier. For consistency, I will carry the OVC025 at KSBN but delay it until the improved saturation arrives. Confidence is perhaps higher at KFWA which avoids much of the rain until late in the TAF period. The low-level moisture profile there maxes out near 70-80%, leading me to believe VFR conditions are favored there. Rain showers may move out of the area at the extreme tail end of this TAF period. && .IWX WATCHES/WARNINGS/ADVISORIES... IN...NONE. MI...NONE. OH...NONE. LM...NONE. && $$ SYNOPSIS...Marsili SHORT TERM...Roller LONG TERM...Roller AVIATION...Brown Visit us at Follow us on Facebook...Twitter...and YouTube at:
Area Forecast Discussion
National Weather Service North Platte NE
636 PM CDT Fri Apr 23 2021 .SHORT TERM...(This evening through Saturday night) Issued at 311 PM CDT Fri Apr 23 2021 A disturbance embedded within an upper trough across the Northern Plains will move across north central Nebraska tonight. Model differences remain, with the GFS the most bullish on QPFs, followed by the NAM. The latest HRRR and RAP are virtually dry. Will keep POPs low at 20 to 30 percent. Temperatures and dewpoints will be cold enough for snow showers across the north. Precipitation amounts overnight will be light, from a trace to around 0.05 of an inch. Any snow accumulations will be light at a dusting to half inch, mainly on grassy surfaces. Skies will become overcast across the area with surface high pressure building in. Lows from the upper 20s northwest to the lower 30s southeast. Mainly cloudy skies Saturday morning, with some breaks of sun in the afternoon. Easterly wind in the morning will veer to the south and southeast in the afternoon. Went lower on highs Saturday, with mid to upper 50s most locations. The exception will across far southwest, from near 60 to the lower 60s. A warm front will lift across northern NE Saturday night as a weak disturbance moves across a flattened upper ridge. This will bring a chance for rain showers to north central NE. .LONG TERM...(Sunday through Friday) Issued at 311 PM CDT Fri Apr 23 2021 Monday night into Tuesday, a deep trough will move into the region. This will bring high temperatures back into the 50s to low 60s. Precipitation chances will return. The best chances will be Tuesday into Tuesday night. Regarding medium range models, the ECMWF is slower with the advancement of the upper trough than the GFS, which supports chances lingering into Wednesday. Will continue to monitor for the possibility of thunderstorm activity with this system. Upper ridging will build in Thursday into Friday with a warming trend. Highs by Friday should range in the 70s. && .AVIATION...(For the 00Z TAFS through 00Z Saturday evening) Issued at 635 PM CDT Fri Apr 23 2021 A cold front will continue to push into northern and central Nebraska, stalling out across southern Nebraska toward 12z Saturday. Low clouds will build into the area behind the front with some IFR ceilings possible at the KVTN terminal by 12z Saturday. MVFR ceilings are possible at the KLBF terminal overnight and will persist into midday Saturday. Winds at both terminals will be from the northeast and east tonight, shifting to the southeast during the day on Saturday. && .FIRE WEATHER... Issued at 311 PM CDT Fri Apr 23 2021 Elevated fire weather conditions are expected across the Sandhills and southwest Nebraska Sunday. The hazard is afternoon humidity between 15 and 20 percent and wind gusts up to 20 mph from the southwest. Near critical fire weather conditions Monday. Highs temperatures will reach the upper 70s to near 85. Lowest humidity from 12 to 15 percent near and south of Highway 2. Winds will be west to southwest 10 to 20 mph with gusts to 25 mph possible. && .LBF WATCHES/WARNINGS/ADVISORIES... None. && $$ SHORT TERM...Roberg LONG TERM...Roberg AVIATION...Buttler FIRE WEATHER...Roberg
Area Forecast Discussion
National Weather Service Lake Charles LA
630 PM CDT Fri Apr 23 2021 .DISCUSSION... 00Z 24APRIL21 TAFs && .AVIATION... Storms on radar as a warm front moves north ahead of another front moving east. Winds will remain elevated along with VCTS until the second front moves east out of the area near the end of this period. && .PREV DISCUSSION... /issued 325 PM CDT Fri Apr 23 2021/ SHORT TERM [From Today through early Sunday]... Warm front beginning to creep further north with 70 degree dew points noted in SE TX. Radars beginning to show some convective activity over our area...but warm frontal lift and increasing PVA ahead of the shortwave will lead to more widespread coverage developing in the coming hours. This is further supported by the special 18Z LCH sounding, which shows the 700mb capping layer has eroded significantly. Convection developing near the warm front will have a favorable environment to work with. Favorable wind fields will be further in enhanced in the low levels with the warm front in vicinity, and instability will be more than sufficient for strong updrafts. Tornadoes and damaging wind gusts will be possible with these, and while mid level lapse rates aren`t particularly steep per 18Z LCH sounding, large hail will still remain a threat as well. Upscale convective growth will likely favor a mix of semi discrete cells and bowing linear segments towards the evening, and with a strong low level jet developing, damaging wind and tornado threat will persist into the overnight hours. PoPs remain elevated, but do slowly taper off gradually after midnight, though trailing cold FROPA not expected until the day Saturday. Aside from the possibility of severe weather, heavy rain and flooding potential is also a concern. PWATS of 1.64" already noted on 18Z LCH sounding, and this will likely further increase as deep moist advection continues while the warm front lifts north. With modest instability and a good axis of moisture convergence, storms will produce rainfall efficiently, and training cells will be possible. 12Z HREF suite depicts a somewhat narrow east-west oriented PMM QPF corridor of 3-6", with individual members resolving this in slightly different areas around the CWA. That said, the signal is one that will need to be monitored going forward when/if such a training scenario develops. Latest HRRR runs also show the potential for a somewhat stationary trailing inflow band developing on the back end of the event overnight, which could further exacerbate any prior flooding if it were to develop. Given all that, a Flash Flood Watch will be issued with the afternoon forecast package. Thanks neighboring offices/WPC for all the collaboration this afternoon. Weak cold front/surface trough slides through on Saturday, and with no appreciable CAA, temperatures actually look to be quite mild with highs in the low to mid 80s. With a lack of good forcing, expecting dry conditions with the FROPA. Once northerly winds do develop, slightly drier air works in overnight with lows Sunday morning near seasonal normals. 50 LONG TERM [Sunday through Friday]... Ridging developing aloft and sfc high pressure sliding ewd will lead to dry weather for late in the weekend and early part of the new work week. Building heights will lead to slightly warmer temps for Sunday afternoon across the TX zones...however the good dry air in place will allow good radiating Sunday night, leading to mins around seasonal values Monday morning. The warming trend then overspreads the remainder of the forecast area on Monday as heights further build and return flow begins ushering in warmer air off the Gulf, with highs Tuesday expected to warm well into the 80s all but the coastal zones. A series of shortwaves will dig a trof over the wrn CONUS into mid-week. The first disturbance rounding the base will begin spreading lift across the wrn Gulf region Tuesday night. Convective coverage will gradually increase through Wednesday morning while PWAT values climb to around 2 inches, with scattered showers/storms in the forecast for Wednesday afternoon/evening as a pre-frontal trof looks to sweep through the area. Convection will largely end with the passage of this feature, although some lingering showers could continue into Thursday when our next sfc cool front passes, followed by the mid-level trof axis. Cooler/drier weather then looks on tap for the end of the forecast period with daytime highs generally in the 70s and overnight lows in the 50s. 25 MARINE... Strong srly winds are developing on the coastal waters today as the gradient tightens ahead of deepening low pressure over the Plains...and SCA/SCEC headlines continue. Winds will relax later tonight as the low fills/ejects ewd. Winds behind the first frontal passage are not expected to be too elevated with the lack of cold air moving over the nwrn Gulf. With a progressive pattern in place, an elevated onshore flow can be expected again late in the period ahead of the next frontal passage. 25 && .PRELIMINARY POINT TEMPS/POPS... AEX 64 82 57 80 / 100 10 0 0 LCH 68 84 61 82 / 80 10 0 0 LFT 68 82 59 80 / 70 10 0 0 BPT 69 85 59 81 / 70 0 0 0 && .LCH WATCHES/WARNINGS/ADVISORIES... LA...Flash Flood Watch through Saturday morning for LAZ027>033. TX...Flash Flood Watch through Saturday morning for TXZ180-259-260. GM...Small Craft Advisory until 3 AM CDT Saturday for GMZ450-452-455- 470-472-475. Small Craft Exercise Caution from 3 AM CDT Saturday through Saturday morning for GMZ450-452-455-470-472-475. Small Craft Exercise Caution until 3 AM CDT Saturday for GMZ430- 432-435. && $$ AVIATION...87
Area Forecast Discussion
National Weather Service Marquette MI
810 PM EDT Fri Apr 23 2021 .SHORT TERM...(This evening through Saturday) Issued at 350 PM EDT FRI APR 23 2021 GOES imagery and RAP analysis show a shrtwv lifting NE through WI this afternoon, weakening on its approach to the UP. A few scatterers showing up on adjacent radars (MQTs down through mid next week), but abundant dry air ahead of the wave is limiting this rain to virga, perhaps a few sprinkles at best. As this wave continues to lift to the NE, Upper Michigan will become overcast skies, which will limit add`l warming, after temperatures climbed abv guidance quite early this morning. After climbing into the low 60s across the central and east, Marquette Proper is back into the low 50s as a lake breeze has moved through. Included sprinkles to the fcst through the rest of the afternoon evening as GOES imagery suggest cloud ice is present in these mid-level clouds, but still haven`t seen anything hit the spares webcam network. Tonight, a cold front will approach Upper Michigan bringing rain showers across the west half late tonight/early tomorrow morning as the column saturates. After a few hours, these showers will begin to mix in with snow, before model soundings suggest pcpn becoming all snow. Not expecting any accumulation by sunrise tomorrow, but the changeover to snow should begin just before. The cold front will reach western UP around sunrise or just before. This will leave high temperatures for the day across the west being right near sunrise; however, there will be a little time to warm up across the south and east. Therefore, temperatures will reach around 50 across the south and across the east, with 40s across the central and 30s across the west...falling through the day as the front moves through. Snow showers across the west will last 6-8 hours or so, before models suggest column saturation and ice nuclei end. Could see a sloppy inch or two across the west, especially in the higher terrain where some lake-enhancement is expected. .LONG TERM...(Saturday night through Friday) Issued at 251 PM EDT FRI APR 23 2021 Upper air pattern will consist of a closed low off the Pacific NW coast and a trough in the upper Great Lakes 00z Sun. After the trough moves by, shortwave ridging will build into the upper Great Lakes. A deep trough will move into the western U.S. 00z Tue with a amplified ridge over the eastern U.S. Deeper moisture and 850-500 mb q-vector convergence moves into the area Sun night and remains into Mon. Did not make too many changes to the going forecast. In the extended, the GFS and ECMWF show a deep 500 mb trough over the Rockies 12z Tue with a ridge over the ern U.S. This trough moves slowly east 12z Wed and will be moving into the plains then. The trough then moves into the upper Great Lakes 12z Thu with a shortwave heading towards our area and the trough remains into 12z Fri. This will mean a slow sfc pattern for movement of fronts and systems and temperatures going back below normal along with wet weather. && .AVIATION...(For the 00Z TAFS through 00Z Saturday evening) Issued at 807 PM EDT FRI APR 23 2021 VFR conditions will prevail through this evening, before dropping to MVFR overnight. As a cold front approaches late tonight, light rain will begin before changing to snow. IFR cigs are expected to accompany this front with some IFR vsbys as the snow begins. Cigs may also fall to or near LIFR late tonight/early Saturday morning at IWD. Conditions should improve to MVFR or near MVFR by late Saturday afternoon. && .MARINE...(For the 4 PM Lake Superior forecast issuance) Issued at 350 PM EDT FRI APR 23 2021 A cold front will pass over Lake Superior late tonight, with northerly winds gusting up to 30 knots as the front moves through. Models suggest a few gale force gusts are possible across the north central and east right as the front moves through, otherwise winds across the west will relax blo 15 knots, as 30 knots continue across the east. Winds relax for Sunday before Lake Superior lies between a high pressure across Quebec and an approaching low pressure through the Northern Plains on Monday, with southeasterly winds gusting up to 30 knots across the east. Winds fall blo 20 knots by Tuesday and are expected to remain there through the rest of the fcst period. && .MQT WATCHES/WARNINGS/ADVISORIES... Upper Michigan... None. Lake Superior... None. Lake Michigan... None. && $$ SHORT TERM...JAW LONG TERM...07 AVIATION...JLB MARINE...JAW
National Weather Service Morristown TN
932 PM EDT Fri Apr 23 2021 .UPDATE... EVENING UPDATE. && .DISCUSSION... Previous forecast on track with very minor adjustments. Adjusted hourly POPs based on the latest HRRR guidance. This adjustment slowed the onset of precip by a few hours with precip not expected to reach our southern areas until around 3 AM EDT. Then, precip will continue to spread northeast into our area through sunrise with showers possibly reaching the central TN Valley between 6 and 7 AM EDT. Otherwise, just a few hourly temp and dewpoint adjustments with this update. SR && .AVIATION... 00Z TAF DISCUSSION. Clouds increase overnight along with lowering CIGs as our next system approaches. Conditions will eventually lower to IFR at CHA by late morning and then TYS and TRI by afternoon. LLWS in at CHA later tomorrow morning. Conditions will improve to VFR at CHA near the end of the period but with TYS and TRI remaining MVFR/IFR. SR && .PREV DISCUSSION... /ISSUED 319 PM EDT Fri Apr 23 2021/ SHORT TERM (Tonight through Sunday)... Spotty light rain showers today are winding down and expect a mostly dry night in lieu of a rainy day on Saturday. An H5 shortwave over the southern plains will be the catalyst for the formation of widespread showers across the lower Mississippi Valley tonight. This rain area will move eastward with the shortwave`s progress, and the rain will be moving from southwest to northeast, impacting the southern Valley and southern Plateau probably before sunrise, then reaching SW VA later in the morning. The rainfall will hopefully help ease the few wildfires. However, conditions are favorable for a mountain wind event Saturday as well, and downsloping winds help to limit precip. The best amounts of rainfall for this Saturday-Saturday night event will be across the southern counties - upwards of an inch of rain, while the lowest amounts will be along the typical rain-shadowed areas down from the mountains, where event totals may average around a half an inch for the event. Isolated thunderstorms are possible mostly during the day and mostly south of I-40 on Saturday. Lingering mountain showers are possible Sunday morning, but elsewhere Sunday looks pleasant as high pressure begins to build in once more. GC LONG TERM (Sunday Night through Friday)... Key Messages: 1. Dry with very mild temperatures expected for the first half of the week. Much of the area will reach into the 80s Tuesday and Wednesday. 2. Rain chances return heading into Thursday and Friday with high uncertainty in the development and track of a system to impact the central and eastern U.S. Sunday Night through Tuesday To start the period, quasi-zonal flow will be in place with subtle ridging over the Great Plains and troughing into the Atlantic. Another trough will be moving onshore from the Pacific with a very strong upstream jet. At the surface, broad, weak high pressure will be in place over southern Appalachia and the Great Lakes up into Canada. With this initial setup, increasing upper-level amplification will be noted due to digging of the west coast trough and more notable amplification of ridging as it moves into the eastern CONUS. This is coincident with significant height rises and subsequent thermal ridging locally as we move into the week with surface high pressure setting up over the Atlantic Coast. As a result, southerly flow at the surface and significant increases in 1,000-500mb thickness values will yield WAA and a notable warming trend. Based on ensemble and deterministic indications for strongly positive 500mb height anomalies and 850mb temperature anomalies, much of the area will likely reach well into the 70s on Monday with 80s across much of the area on Tuesday. Wednesday through Friday Later in the week, the evolution of the trough/system is a lot less known with the GFS suggesting more of a deep trough and the CMC deterministic yielding a cutoff low. The ECMWF suggests a slower but similar solution to the GFS. In any case, very mild temperatures will remain in place on Wednesday with continually increasing thickness values and southerly winds. The overall trend with this system has been slower with cyclogenesis possibly taking place on Wednesday. But again, the evolution of the system remains highly uncertain with the consensus being for the surface low to track towards the Great Lakes on Thursday, then into Canada. In line with what the GFS suggests, a deep surface low could develop yielding forcing, and instability sufficient for severe weather across the Great Plains and perhaps further east. But with the other solutions, this potential is a lot lower with weaker frontogenetic forcing. The ECMWF, for example, develops two weaker surface lows. Regardless of the model solution, confidence is at least moderate for increasing rain chances Thursday into Thursday night with a dropoff by later on Friday. With the arrival of the trough and associated cold front in any form, notably cooler temperatures will likely return by Friday. This is also due to potential lingering showers and cloud cover as well as significantly lower heights. BW && .PRELIMINARY POINT TEMPS/POPS... Chattanooga Airport, TN 51 69 51 73 47 / 70 90 40 10 0 Knoxville McGhee Tyson Airport, TN 48 66 50 69 44 / 40 80 40 10 0 Oak Ridge, TN 47 64 48 70 45 / 40 80 40 10 0 Tri Cities Airport, TN 43 62 48 65 41 / 10 90 50 10 0 && .MRX WATCHES/WARNINGS/ADVISORIES... NC...NONE. TN...High Wind Watch from 8 AM EDT Saturday through Saturday evening for Blount Smoky Mountains-Cocke Smoky Mountains-Sevier Smoky Mountains-Southeast Carter-Southeast Greene-Southeast Monroe-Unicoi. VA...NONE. && $$