Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 04/10/21

Area Forecast Discussion
National Weather Service Boston/Norton MA
1008 PM EDT Fri Apr 9 2021 .SYNOPSIS... High pressure centered just east and south of New England, continues to move slowly southeastward and offshore tonight into Saturday. This will allow for mainly dry weather and result in quite mild temperatures away from the coasts.Weakening low pressure passing to our south will result in a turn to much cooler temperatures on Sunday along with a period of rain at least across interior Southern New England. Cooler afternoons are on tap for much of next week with onshore flow and considerable cloudiness at times. && .NEAR TERM /UNTIL 6 AM SATURDAY MORNING/... 1000 PM Update: Regional radar mosaic shows a narrow NNW to SSE oriented line of really light showers across eastern NY into western/southwestern CT. These showers continue to fizzle with eastward approach given drier air in place over Southern New England. Will continue to see mainly mid-level clouds overspread as the night progresses. The exception is along the South Coast, Cape Cod and the Islands. Stratus has advanced from Block Island, Rhode Island Sound and Buzzards Bay landward per nighttime microphysics RGB imagery. In addition, temperatures in the low 40s near dewpoints has permitted areas of fog along these same areas. Have increased sky cover a little sooner than prior indications, using a blend of the 01z HRRR time- lagged ensemble and the 12z HREF which best captures cloud cover trends the best. RAP-based fcst soundings at EWB, HYA and OQU indicate shallow RH remains locked in, which reinforces the idea that low clouds and fog stand to persist for the balance of the overnight across these areas. Stratus may advance as far north as HFD, IJD, PVD, TAN and PYM. Temps project the coolest in these areas in the low to mid 40s. Milder lows in the upper 40s to low/mid 50s should be more common away from the South Coast and Cape Cod, with mid clouds allowing for tempered cooling. Previous discussion: Previous forecast is on track. High pressure offshore coupled with cooling boundary layer, light southerly flow and dewpoints in the 40s will result in another round of low clouds and fog developing on the south coast, Cape and Islands. Latest satellite imagery and observations already showing this occurring in Newport. So while low clouds and fog, some of which may be dense will overspread the south coast, Cape and Island over the next several hours it should not get much further north than that. South to southwest low level flow should be enough to keep it confined to mainly that region overnight. Otherwise, mid and high level cloudiness will impact the rest of the region. While dry weather will be the main story overnight, we can not rule out a few brief spot shower or two across western MA and CT. While upper level ridging is in control, there will be a shortwave shearing out will approach from the west. Subsidence should keep us mainly dry, but enough elevated instability may result in a spot shower or two in this region overnight. As for temperatures, they currently ranged from the 40s on the south coast to the 60s across much of western and northern MA. We should see most locations bottom out in the 40s by daybreak with the current large temperature spread diminishing. && .SHORT TERM /6 AM SATURDAY MORNING THROUGH SATURDAY NIGHT/... Saturday: Expect to start off the morning with considerable cloudiness, due to moisture associated with the short waves and flattening of the mid level ridge, and surface high center moving further SE from our area, placing us in return flow allowing for south coastal stratus. However mid level ridging builds back into our area to some degree, and as short wave moves out expect to see decreasing clouds and skies becoming partly to mostly sunny. Exception should be along the immediate south coasts of RI/MA, where marine stratus could linger through the day due to that continued prevailing SW flow. SW winds will also keep the south coasts of MA and RI (including Cape/Islands) cooler. Shallower mixing and onshore SW winds (which may gust into the 20-25 mph range) should keep highs in the mid- upper 50s to mid 60s in that area. However, away from the south coast, this drier/warmer trajectory will allow for warming into the upper 60s to mid 70s. Winds at H925 may be strong enough to preclude a sea breeze at Boston, and pending no sea breeze we would have highs in the low 70s there. Saturday Night: Occluded low pressure tracks into the Great Lakes Region, while high pressure slides further offshore. Warm front associated with the low moves towards our area, and S/SW flow allows for increasing moisture and hence increasing cloud cover. We could see some patchy light rain during the overnight, but bulk of rain is expected to hold off until Saturday. Mild overnight lows in the mid 40s to low 50s. && .LONG TERM /SUNDAY THROUGH FRIDAY/... Highlights... * Turning much cooler Sun into Sun night with some rain across the interior, but uncertain on eastward extent * Cool afternoons much of next week especially across eastern MA * Need to watch offshore low pressure late next week, but whether it can bring any appreciable rain is uncertain Details... Sunday... Tricky forecast in regards to rainfall amounts across interior southern New England and how much/if any appreciable rainfall survives into eastern New England. Deep closed low over the Great Lakes will send a piece of shortwave energy into southern New England. However, this shortwave will shear out/weaken some as it enters upper level ridging in place. A band of mid level forcing and some elevated instability will survive and be competing with some dry air/subsidence especially across eastern New England. Give the reasoning above we do expect a band of rain to arrive across southwest MA and CT by late Sunday morning or afternoon. Low level dry air coming in from the northeast will be fighting this band of rain as it attempts to move northeast. While a bit of rain may survive into eastern MA; any amounts will probably be rather light. This forecast will certainly need to be fine tuned with later guidance, but highest confidence in some appreciable rain Sunday into Sunday night will be across southwest MA and northern CT. The threat for appreciable rainfall diminishes the further north and east one gets from this region. As for temperatures, high pressure across Canada and weakening low pressure passing to our south will allow the passage of a backdoor cold front by early to mid morning on Sunday. It is possible temps get into the 60s towards the CT River Valley if the backdoor cold front is delayed. Otherwise, temperatures will mainly be in the 50s perhaps even the middle to upper 40s in spots during the day Sunday. Monday through Friday... The main story for much of next week will feature a closed upper level low spinning just southeast of the Canadian Maritimes with upper level ridging to the north. The result will be an onshore flow much of the time along with a fair amount of cloudiness, but still expect periods of partial sunshine. Overall though afternoon temperatures quite a bit cooler than what we have experienced this week. High temperatures will be held mainly in the 50s although some spots may break 60 at times particularly towards the CT River Valley. Much of the week will feature little if any organized rainfall other than a few showers and perhaps some drizzle/fog at times. However, by late next week will have to watch an offshore low pressure system. If it can track close enough to the coast, there could be a more of a threat for a period of widespread rain but that remains uncertain at this time. && .AVIATION /02Z SATURDAY THROUGH WEDNESDAY/... Forecaster Confidence Levels. Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. 00Z Update... Tonight: Moderate confidence. VFR conditions expected for most airports away from RI and the South Coast. Areas near the south coast as well as the Cape Cod and ACK airports will see another round of IFR-LIFR in status and fog developing over the next several hours. Winds becoming light from the SSW. Saturday: High confidence, except Moderate confidence south coast. VFR most terminals. Exception is across south coastal MA/RI/Cape/Islands, starting out at IFR/LIFR in stratus and fog, should trend MVFR/VFR for most airports by midday. SW winds increase to around 10 kt. Strongest sustained winds across Cape Cod with gusts up to 20 kt. Saturday Night: Moderate confidence. Mainly VFR during the evening, with MVFR/IFR CIGs developing overnight. Slight chance SHRA. KBOS TAF...High confidence in TAF. During Sat expecting SW wind to prevail during the day, but there is a low probability for a brief sea breeze developing for a couple of hours during the afternoon. KBDL TAF...High confidence in TAF. Outlook /Sunday through Wednesday/... Sunday: MVFR/IFR conditions possible. Breezy. Chance SHRA, patchy BR. Sunday Night: Mainly VFR, with local IFR possible. Breezy. Chance SHRA. Monday through Tuesday: Mainly MVFR, with areas VFR possible. Breezy. Slight chance SHRA. Tuesday Night: Mainly MVFR, with areas VFR possible. Chance SHRA. Wednesday: Mainly MVFR, with areas VFR possible. Breezy. Chance SHRA. && .MARINE... Tonight and Saturday... Winds and seas are expected to remain below small craft advisory levels during tonight and Saturday. SE winds around 10 kt today will come around to S then SW late tonight and Saturday. Some increase in SW winds is expected Saturday with gusts to 20 kt. Seas in the 3-4 ft range on the offshore waters, 1 to 2 ft near shore. Areas of fog re-develop tonight with visibility locally below 1 mile, mainly along the southern waters. Fog lingers into Saturday along the southern waters. Saturday Night...SW winds 10-15 kts with gusts around 20 kts. Seas mainly 2 to 4 feet, except may build to 3 to 5 feet along the outer waters. SCA headlines may be needed. Areas of fog are possible. Outlook /Sunday through Wednesday/... Sunday: Low risk for Small Craft Advisory winds with gusts up to 20 kt. Seas up to 5 ft. Chance of rain showers, patchy fog. Local visibility 1 nm or less. Sunday Night: Low risk for Small Craft Advisory winds with gusts up to 25 kt. Areas of rough seas. Chance of rain showers, patchy fog. Monday: Moderate risk for Small Craft Advisory winds with gusts up to 25 kt. Local rough seas. Slight chance of rain showers. Monday Night through Tuesday: Winds less than 25 kt. Seas up to 5 ft. Slight chance of rain showers. Tuesday Night through Wednesday: Winds less than 25 kt. Local rough seas. Chance of rain showers. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...None. MA...None. RI...None. MARINE...None. && $$ SYNOPSIS...Frank/NMB NEAR TERM...Frank/Loconto SHORT TERM...NMB LONG TERM...Frank AVIATION...Frank/Loconto/NMB MARINE...Frank/Loconto/NMB
Area Forecast Discussion
National Weather Service State College PA
1126 PM EDT Fri Apr 9 2021 .SYNOPSIS... An unsettled weather pattern will plague central Pennsylvania through the upcoming weekend, bringing more clouds than sun and periods of showers. Temperatures will remain mild/above average into early next week. && .NEAR TERM /THROUGH SATURDAY/... Radar loop at 03Z shows scattered showers lifting across Lancaster County in region of minimal elevated CAPE ahead of mid level shortwave. Radar trends and latest HRRR suggest the showers should clear the forecast area by 06Z. Large scale subsidence behind the departing shortwave should ensure an uneventful and largely precipitation-free conditions late tonight. However, will maintain the chance of spotty drizzle, mainly on the windward slopes, through late tonight along and southeast of I-81, where model soundings continue to indicate a nearly saturated 0-1km layer. Southeast flow off of of the Atlantic should keep the entire region blanketed under stratus overnight. The overcast skies and plenty of low level moisture should result in only very slowly falling temperatures tonight, with lows mostly in the lower 50s. && .SHORT TERM /SATURDAY NIGHT/... Most places start off cloudy and damp early Saturday. The question will be how much sunshine can break through the low clouds. Model guidance remains most optimistic on the northern and western fringes of the CWA, where mostly sunny skies appear likely by midday. Across the southeast half of the forecast area, stratus will be more persistent. However, model soundings and latest HREF suggest partly sunny skies are likely by mid afternoon. Based southeast flow/cold air damming signature, will continue to undercut NBM temps in favor of the cooler Superblend east of the mountains. Strong April sunshine should push readings to near 70F east of the mountains and well into the 70s across the northwest mountains. The CAD will remain in place with only weak E/S wind picking up a little through the day on Sat. But, the system advancing from the west will likely not bring rain in until after sunset in the west. Held just a low PoP for the SW before 00Z Sun. Clouds invade/lower/thicken through the evening with 100 PoPs o/o. Excellent moisture feed, but only for 3-6 hrs at any one location. Some convective elements should be able to develop since we will destabilize before the forcing arrives. But, nighttime could turn them elevated or squash any thunder before it gets more than 40-50mi into the CWA. QPF of 0.50-0.75" still looks good. This should continue to help reduce the wildfire/spread threat. RHs are expected to remain above 30pct for the weekend and into next week. && .LONG TERM /SUNDAY THROUGH FRIDAY/... Latest model guidance shows potential for some convection to develop Sunday afternoon (in the wake of morning rain) over the eastern part of the area. Sunday should be the warmest day of the long-range period south and east of the Allegheny Front, where highs should reach the low to mid 70s. Expect cooler temperatures for next work-week, as upper-level low pressure continues to slowly progress from the Great Lakes across the northeastern United States. This will also maintain a daily chance of showers, with the highest POPs during peak heating of the afternoon as GEFS plumes show. && .AVIATION /03Z SATURDAY THROUGH WEDNESDAY/... Expect the MVFR cigs to lower to IFR overnight across the region overnight with moist SE llvl flow. Some DZ and FG is expected late tonight, especially along the windward slopes. Some improvement is expected during the day Saturday. Dry air from the west will mix down thanks to mid April sun angle/heating and most areas will see VFR conditions in the afternoon. The exception may be KMDT and KLNS where low clouds could hang on longer into the late afternoon. Outlook... Sun...AM IFR/SHRA east, then improvement to VFR in most locations from west to east thru the rest of the day. Mon-Wed...Lingering -SHRA and MVFR conds poss N; otherwise VFR. && .CLIMATE... The high temperature of 77F at Bradford on Thursday 4/8 broke the previous record high of 76F set in 2001. && .CTP WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Dangelo NEAR TERM...Fitzgerald SHORT TERM...Fitzgerald/Dangelo LONG TERM...Fitzgerald/Evanego AVIATION...Dangelo/Travis CLIMATE...
Area Forecast Discussion
National Weather Service Cheyenne WY
523 PM MDT Fri Apr 9 2021 .SHORT TERM...(This evening through Sunday night) Issued at 320 PM MDT Fri Apr 9 2021 Current KCYS radar loop shows rain/snow showers and flurries across the mountains and along the I-25 corridor this afternoon which was advertised well on this morning`s HRRR 15z run. With temperatures in the mid 30s to low 40s or higher, any snowfall is not expected to amount to anything with brief reduction in visibility possible into this evening. Models show a shortwave ridge axis quickly pushing into the region from the west on Saturday. Temperatures will rebound quickly Saturday afternoon with highs in the 60s along/west of the I-25 corridor and upper 60s to low 70s across western Nebraska. This warming trend will be very brief as another Pacific cold front will be quick to follow the fast moving ridge axis. All models show this front moving across the area midnight late Saturday night through early Sunday morning. Morning high temperatures may briefly nudge into the mid 50s to around 60 southeast of a Cheyenne to Alliance line before the front moves across the eastern plains by noon Sunday. Temperatures on Sunday will be much colder with highs generally in the 40s northwest of a Cheyenne to Alliance line. Expect temperatures to lower slightly in the afternoon as the colder air moves into the region under partly to mostly cloudy skies. Precipitation and snowfall should be minimal since the system will be moving rapidly; plus dynamics and moisture will be limited across the area. Best chance for snowfall will be north of I-80 across Carbon and Albany counties, and west of I-25 across Platte and Converse counties early Sunday. Any precipitation should push east and diminish in intensity Sunday afternoon. Clearing skies will result in temperatures 10 to 15 degrees below freezing Sunday night across the whole area, which is around 10 degrees below normal for this time of the year. .LONG TERM...(Monday through Thursday Night) Issued at 145 PM MDT Fri Apr 9 2021 Ridging out in the Pacific will funnel shortwave energy down the Olympic Mtns. and into OR before taping into an evolving zonal jet stream moving east into our region behind exiting shortwave that will pass through during the weekend. Model solutions maintain trend from 00z group overall with development of closed upper low. Both latest GFS and EURO maintain a slow eastward progression that as stated in previous discussion will need to be monitored as solution differences hopefully are reconciled between models. Overall though, a slow eastward progression with decent moisture tap from the Gulf of Mexico would aid in drought reduction for the region. Initial thoughts at this time are for periods of heavy snowfall banding particularly in the overnight with cold enough temperatures. Main concern with the delay in movement is the increased chance and likelihood of more WAA and warm temperature overrunning limiting daytime snowfall amounts and restricting precipitation type to rain. Either way, any precipitation to add to the region is welcomed. Temperatures will remain more early springlike with daytime highs into the middle 40s for places east of the Laramie Range and about 10-15 degrees cooler to the west. Overnight lows will be below freezing so for avid gardeners enjoying their spring blooms, some action will need to be taken to ensure their flowers can survive the temps and freezing precipitation. && .AVIATION...(For the 00Z TAFS through 00Z Saturday evening) Issued at 521 PM MDT Fri Apr 9 2021 Wyoming TAFS...VFR. Wind gusts to 32 knots until 02Z, then to 35 knots after 15Z Saturday. Nebraska TAFS...VFR. Wind gusts to 40 knots until 02Z. && .FIRE WEATHER... Issued at 159 PM MDT Fri Apr 9 2021 Although fire weather concerns are pretty low overall, elevated conditions are possible along and west of I-25 Saturday afternoon due to low relative humidities and windy conditions. Fuels are not critical in these areas, but there is some concern due to a combination of the winds and low RH. Further east, the fuels are ready across western Nebraska, but winds will be relatively light. Minimal fire weather concerns expected through next week as more high elevation snow and low elevation rain is possible for several days. && .CYS WATCHES/WARNINGS/ADVISORIES... WY...None. NE...None. && $$ SHORT TERM...TJT LONG TERM...WM AVIATION...RUBIN FIRE WEATHER...TJT
Area Forecast Discussion...UPDATED
National Weather Service Austin/San Antonio TX
853 PM CDT Fri Apr 9 2021 .UPDATE... The dry line has stalled just west of Austin to San Antonio, with the sea-breeze meeting up with it. The cap held and what little convection developed earlier quickly dissipated. The cold front is moving quickly south through west-central Texas, and will arrive into the northern Hill Country just before midnight and into the I-35 corridor around 1-2AM. Breezy and gusty conditions will develop behind it. There was some dust along the front in west Texas and can`t rule out some of that reaching the northwest CWA. && .PREV DISCUSSION... /ISSUED 651 PM CDT Fri Apr 9 2021/ AVIATION (00Z TAFs)... VFR conditions outside of any stray or isolated SHRA or TSRA that has a low chance of developing through 02Z near and north of AUS. So far the cap has resulted in only short-lived convection just to the north. Due to the low probability, and radar trends, we have elected to keep TSRA mention out of AUS TAF. Main issue are the winds. There should be a reduction in wind speeds temporarily after sunset. Then the cold front will move through the area between 04Z-08Z, with north winds over the Hill Country and along and east of the I-35 corridor, including SAT/AUS, increasing to around 15KT with gusts around 25KT. PREV DISCUSSION... /ISSUED 544 PM CDT Fri Apr 9 2021/ UPDATE... The dry line is now moving into the I-35 corridor counties. Recent aircraft soundings out of AUS show the cap has weakened, although still there. Earlier convection that try to go up along the dry- line just north of the CWA quickly weakened. Recent visible imagery indicates the Cu looking better across Burnet County. There remains a small window over the next couple of hours for isolated convective development across the far northeast CWA, as additional low level moisture convergence is encountered between the dry line and slightly backed winds east of it. Should any deeper convection develop, it has the potential to quickly go strong to severe given the CAPE and shear parameters in place. But this is all highly conditional on the cap. FIRE WEATHER... We have expanded to Red Flag Warning another row of counties eastward and extended through 8PM. Critical fire weather conditions are ongoing across the Hill Country and southern Edwards Plateau, with localized extreme fire weather conditions along the Rio Grande, where RH values around 5% and wind gusts between 30 and 40 mph are occurring. Wind speeds will begin to decrease temporarily after sunset. However, a north wind shift will occur late in the evening and overnight behind a cold front with gusty winds re-developing. A brief period of critical fire weather conditions may re-develop west of I-35 to the Rio Grande as this happens, before cooler temperatures allow RH values to recover. PREV DISCUSSION... /ISSUED 249 PM CDT Fri Apr 9 2021/ SHORT TERM (Today through Saturday Night)... After an overcast start to the day, clouds are finally beginning to lift for areas along and east of I-35 as a clearing line makes it`s way over the area. Dryline that has now made it into the western Hill Country will continue to progress eastward this afternoon. The timing and extent of this eastward progression will have impacts for how far east the fire weather threat will be and how high temperatures can climb behind it. Critical fire weather will be in place for the Hill Country, Edwards Plateau, and Rio Grande Plains through this evening and has prompted a Red Flag Warning for these areas through 700 PM. Potentially record setting temperatures will occur this afternoon for western areas with Del Rio`s record of 102 for April 9th likely being matched or broken. Depending on how far the dryline can make it, could near record high temperature for SAT as well. Looking at the big picture, upper level longwave troughing is in place across much of the CONUS with a pair of upper level lows embedded, one over the Great Lakes and the other moving across the Central Plains today. This has led to a surface low developing in the northern portion of the state that is currently being analyzed to be centered over Wichita Falls. This feature will bring a front across the region during the overnight period with a strong northerly windshift and cooler temperatures for Saturday. There is a substantial amount of instability in place across northeastern zones this afternoon with SFC CAPE nearing 4500 J/kg. Forecast soundings show a decent cap in place though across the entire area with high resolution models suggesting this cap will hold. The HRRR was showing a few isolated supercells initiating over Williamson and Travis County on some early model runs this morning but has backed off now. Current thinking is that we will remain capped and will see little to no convective activity this afternoon. However, if an isolated cell is able to initiate, it will likely turn severe very quickly with large hail and damaging winds being the main hazards. Will have to keep a close eye on high res model and radar trends this afternoon. Overnight, best estimate for FROPA is reaching the northern CWA by 05Z, reaching San Antonio by 07Z and exiting the CWA by 09Z. Near seasonal temperatures for much of the area on Saturday but still remaining above normal for southwestern zones. Upper 70s to mid 80s for Hill Country and I-35 corridor and upper 80s to low 90s for southwestern zones. Mostly clear skies with winds gradually becoming northeasterly then easterly and returning to southeasterly by the end of the short-term period. FIRE WEATHER... Critical fire weather conditions are in store this afternoon and evening across the Rio Grande plains, southern Edwards Plateau and western Hill Country. A dryline that is currently progressing eastward out of the Rio Grande Plains and into the Western Hill Country has led to well above normal heat and much drier air. Breezy west to northwest winds and very low humidities to the above mentioned areas will continue through the afternoon. A Red Flag Warning is in effect for the Rio Grande plains, southern Edwards Plateau and western Hill Country until 7 PM today. Temperatures will begin to decrease after sunset, but dry air remains intact for areas generally west of the Interstate 35 corridor. A brief period of near critical fire weather conditions may occur west of I-35 as a cold front brings an abrupt northerly wind shift. LONG TERM (Sunday through Thursday)... As noted at the end of the short term southerly flow returns by Sunday morning. Sunday will be another hot day with afternoon highs well above normal under sunny skies. Monday will follow suite but a surface low moving across North Texas will help drive a cold front through the state late in the day on Monday. Forecast soundings show decently dry air at the surface as well as a capping inversion across the I-35 corridor. These factors may limit the overall coverage of showers and thunderstorms, but with the front providing extra lift at least isolated showers and storms are possible. If a storm is able to get going, especially across the Rio Grande Plains, there could be a wind threat associated with it. The front stalls out somewhere between the I-10 corridor and the coast. Upper level flow becomes generally west-south westerly thanks to a large trough of low pressure sitting across the Mountain West for much of next week. With the washed out front and a series of weak disturbances, moving through the WSW flow rain chances look to stick around through much of next week. While moisture stays pooled across the area, surface flow will be light and northerly or easterly through much of the week. While rain chances are present for basically Monday through Thursday the big question will be rainfall amounts. The 12z ECMWF came in much drier and closer in line with the GFS that generally only shows 1/10 to 1/4 inch across the I-35 with as much as 1/2 to 3/4 of an inch across the Rio Grande Plains. The Canadian is still the wettest of the models with more widespread 1/2 to 1.5 inch totals by the end of next week. With no real defined sources of good lift most areas may only see generally light or more isolated precipitation. Will have to monitor the trends over the weekend, but for now it does seem like a slightly wetter pattern. Along with the rainfall temperatures behind Monday`s front will be on a slow decline with near normal afternoon highs by Wednesday, while lows remain mild and above normal. && .PRELIMINARY POINT TEMPS/POPS... Austin Camp Mabry 58 81 53 90 62 / 10 0 0 0 0 Austin Bergstrom Intl Airport 58 81 51 91 61 / 10 0 0 0 0 New Braunfels Muni Airport 60 84 53 92 61 / 10 0 0 0 0 Burnet Muni Airport 54 79 52 89 61 / 10 0 0 0 0 Del Rio Intl Airport 61 88 61 96 66 / 0 0 0 0 0 Georgetown Muni Airport 56 80 51 90 61 / 10 0 0 0 0 Hondo Muni Airport 61 87 54 94 63 / 0 0 0 0 0 San Marcos Muni Airport 58 82 51 91 60 / 10 0 0 0 0 La Grange - Fayette Regional 61 80 52 90 61 / 10 0 0 0 0 San Antonio Intl Airport 61 84 56 92 64 / - 0 0 0 0 Stinson Muni Airport 62 85 55 92 64 / - 0 0 0 0 && .EWX WATCHES/WARNINGS/ADVISORIES... None. && $$ Short-Term/Aviation...Runyen Long-Term...05
Area Forecast Discussion
National Weather Service New Orleans LA
958 PM CDT Fri Apr 9 2021 .UPDATE...Main concern is the severe threat for tonight. So far not much has changed in the thinking however did make some adjustments to the current forecast. Pretty much brought all sites up to 100% chance of rain from the I-10 corridor north. That is the least of the issues. Severe potential is still looking pretty strong but there are a lot of question marks still and that is mainly to how many rounds of storms we see. Over the last 6 hours many of the CAMs were hinting at a line of storms trying to pop over SELA and southern MS during the late evening hours. This apparently looked to be associated with an old outflow boundary and increasing LL convergence. Already it looks like a band of showers is trying to develop in this area along I-55. Looking at WV there appears to be a very subtle increase in lift approaching from the southwest. Whether that gets into SELA or not is still in question but it could be the kick needed to get that area to really pop and if it does then the potential for severe storms capable of producing large hail and tornadoes will increase. Why large hail well the mid level lapse rates are expected to remain in the 7-8 C/km range through the night while the cape is pretty high in the 0 to -20C column (thick fat cape). The LL shear is also expected to increase over the next few hours in response to the developing LL jet. 0-1 km helicity in the region is already around 100-150 s2/m2 and is expected to increase to 200 or greater, 0-3km could approach 300-350. Already have 50-60kt of 0-6km bulk shear in place and that should remain like that until just before the main line gets here. So if any storms can become rooted between 3-8z along and east of I-55 and north of I-10 they will have the potential to produce all modes of severe weather. This includes heavy rain, thunderstorms are already efficient rain producers but given PWs of 1.5" which is expected to increase and increasing divergence aloft the efficiency will increase. They may not quite lead to flash flooding but could obviously prime a few rivers with more rainfall than initially expected. Now the issue has been can storms develop in that area ahead and so far in our region the answer has been no but that subtle increase in lift over the northwestern Gulf may be the catalyst. As for the line, still have some questions about it and whether it is one or two lines. What is suppose to be the main line is already developing in eastern OK and should continue to build down into eastern TX over the next few hours. This line will race to the southeast through the overnight hours. However, what about the convection ahead of of it in northern and west-central LA. overall that convection was suppose to continue to slide east-southeast and eventually be overtaken by the line as it approached southwest MS and SELA but it is already ahead of where the latest HRRR said it would be and if this line solidifies it could cold pool and race out ahead moving into the area between 6 and 12z with the second now weaker line between 10-15z. Not quite ready to bite off on that scenario yet as the southwestern portions of the line are still struggling to solidify so still feel like we are looking at the second line being the main squall line. Everything still suggest a really good rear inflow jet behind the squall line which should lead to scattered if not widespread strong to damaging winds. All grids and zones have been udpated and sent. /CAB/ && .PREV DISCUSSION... /issued 643 PM CDT Fri Apr 9 2021/ AVIATION...00Z TAF Package...Main issues for the next few hours will be low cigs as convection likely holds off till closer to 5/6z. Convection is the main concern this and likely the next 2 TAF packages. We should begin to see a few storms impact a few terminals like MCB/HDC/ASD around 5/6z but the main line of storms will move through the area from 8z-13z. Very strong winds out of the northwest are expected with this squall line and am carrying a 2 hr tempo window in all TAFs for this line. Will refine the timing as the line finally develops and solidifies. Winds could easily gust over 40kts with the line and am showing 45 to even 50 kts at most terminals. Conditions should quickly improve late tomorrow morning. /CAB/ PREV DISCUSSION... /issued 351 PM CDT Fri Apr 9 2021/ SYNOPSIS... Main low near the west end of Lake Superior this afternoon, with a cold front southwest to a second low over north central Texas. Aloft, an upper low over Wisconsin with a shortwave moving southward along the east slopes of the Rockies around the low, and another moving eastward along the Red River. Locally, onshore flow well established, but there is an area of low level convergence near the Pearl River where outflow from convection to the southeast is merging with the synoptic scale flow. There have been a few cells of convection developing along this convergence band, but nothing has gotten out of hand at this point. as temperatures between 850 and 700 mb have warmed since this morning. Temperatures have over-achieved a bit with many areas in the mid 80s, and won`t be surprised to see one or two stations report upper 80s for a max today. Dew points running from the upper 60s to mid 70s in most areas. SHORT TERM (through Sunday night)... Main forecast concerns will be in the first 18-24 hours of the forecast. Multiple opportunities for severe weather in this period, as Red River shortwave shift eastward, scattered convection could develop across the area this evening in a very unstable airmass. The main concern, however, is convection only now beginning to develop over Oklahoma ahead of the cold front. How the two areas of convection interact is still in some question, but certainly, instability and shear don`t appear to be issues. While there is potential for scattered severe storms with the lead shortwave, all signs point to an MCS moving southeastward into the area late tonight, probably entering the CWA around 08-09z and moving rapidly southeast. Potential for significant damaging winds appears to be greatest across the extreme northern portion of the area, per SPC`s SWODY1. The other thing of concern is that some model solutions slow down the west end of the boundary and lay it east-west across some portion of our area Saturday morning. At this time, our forecast doesn`t reflect this solution, but if this occurs, there will be the potential for excessive very heavy rainfall to develop across some portion of the CWA, but the majority of solutions right now carry the convection out into the Gulf of Mexico. Even so, a quick 2-3 inch rain dump is not out of the question. Once the rain exits the area, remainder of the weekend should be dry. Will accept the blended temperatures for now. 35 LONG TERM (Monday and beyond)... Northern stream shortwaves try to lay out a boundary near the coast early next week. As weak shortwaves move overtop of a southern Gulf of Mexico upper ridge, there will be several potential rounds of convection that would produce heavy rainfall. Confidence in specific timing of these shortwaves is obviously fairly low, but there will be mention of the chance of thunderstorms as early as Monday afternoon, continuing each day through the end of the workweek. Blended temperatures will suffice until wet/dry periods become more defined. 35 MARINE... Will keep current headlines, although a few elevated observations near convection may already be near Small Craft Advisory criteria in excess of 20 knots. Main concern will be convection overnight, then conditions should subside later in the day with no major issues through most of the remainder of forecast period. 35 && .PRELIMINARY POINT TEMPS/POPS... MCB 65 80 53 80 / 100 40 0 0 BTR 67 81 54 81 / 100 40 0 0 ASD 67 82 57 81 / 100 80 10 10 MSY 70 82 63 81 / 100 90 10 10 GPT 67 79 59 80 / 90 100 10 10 PQL 64 78 59 80 / 90 100 10 10 && .LIX WATCHES/WARNINGS/ADVISORIES... LA...None. GM...Small Craft Advisory until 4 PM CDT Saturday for GMZ532-536-538- 550-552-555-557-570-572-575-577. MS...None. GM...Small Craft Advisory until 4 PM CDT Saturday for GMZ536-538-550- 552-555-557-570-572-575-577. && $$
Updated for 00Z aviation forecast discussion.

&& .SHORT TERM...(Tonight through Sunday night) Issued at 310 PM CDT Fri Apr 9 2021 A few showers have developed from an area of agitated cumulus from the Ozark Foothills northeast along a confluence zone across southern Illinois and into Gibson county Indiana. Instability is fairly limited east of the Mississippi, so would expect some bubbling to continue with possibly a stray lightning strike, but the stronger showers and any storms should have a hard time sustaining themselves for long. SPC`s mesoanalysis indicates that there is around 1000J/kg of mixed-layer CAPE over much of southeast Missouri, but it may still be struggling with a cap. Therefore the cu field is locked to the better terrain for now. A broken band of thunderstorms is lifting northeast into southwest/south central Missouri along a progressive outflow. The 0-3KM bulk shear and SRH is not great, so not thinking that there will be much organization of the convection through the early evening. The HRRR lifts a few cells into southeast Missouri through 00Z, and then tries to push them eastward into west Kentucky this evening. Meanwhile, storms are expected to fire along the cold front over eastern Kansas and Oklahoma around 00Z. This convection is likely to become organized as it primarily dives east southeast into Arkansas through the evening. The northward extent of this development is in doubt, but cannot rule out a few stronger cells with wind or hail in our southwest counties after 06Z tonight. The overall signal is for the frontal convection to do a split with a mean-looking MCS diving to our south and more disorganized convection lifting north with the surface low. Not sure if there will be much convection left by 12Z as it attempts to push east of the Mississippi. The cold front will reach the Mississippi by 15Z Saturday and then clear the entire area by 21Z. At least scattered showers will continue along and ahead of it. A few storms will also be possible until the front passes. A few wraparound showers may skirt the northwest and northern edges of the forecast area late Saturday and Saturday night, but most of this activity will stay northwest/north of the region. .LONG TERM...(Monday through Friday) Issued at 310 PM CDT Fri Apr 9 2021 The next work week still looks rather uneventful. Generally dry conditions are forecast through the period. Temperatures compared to this week will be cooler, with highs mainly in the 60s. The longer term global models have been strongly hinting at a major cooldown, but they have delayed the timing of the cooldown. As a result, forecast temps will remain constant through the week. Highs will be warmest on Monday ahead of a cold front, ranging from the mid 60s to mid 70s. Otherwise, expect highs in the 60s with lows in the 40s through Friday. As far as precip chances, very little if any precip is expected. There is a slight chance of showers with the cold front passage Monday and Monday night. Tuesday appears dry behind the front. Beyond Tuesday, the ensembles continue to depict a broad area of negative 500 mb height anomalies over the northern states. These negative height anomalies are forecast to slowly sink south and increase late in the week. However, there is really not much of a signal for precip despite the falling 500 mb heights and lack of a strong surface high. The national model blend has littered the forecast with 20 percent pops starting Wednesday. Given the model differences in the large area of upper-level troughing approaching our region, it is tough to rule out a few showers. && .AVIATION... Issued at 645 PM CDT Fri Apr 9 2021 00Z tafs reflect ongoing convection, which should be weakening over the next hour or two. Our attention then turns to a band of showers, possibly some storms, that is expected to move eastward across the region overnight into Saturday morning. Not sure if there will be much impact on visibilities, but certainly cannot rule out MVFR conditions in the showers, possibly IFR at times. Winds will be light out of the south or southeast tonight, and then pick up and become gusty from the southwest behind the cold front Saturday morning and especially into the afternoon, when gusts of 30 to 35 mph will be possible. && .PAH WATCHES/WARNINGS/ADVISORIES... IL...None. MO...None. IN...None. KY...None. && $$