Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 07/09/21

Area Forecast Discussion
National Weather Service La Crosse WI
1040 PM CDT Thu Jul 8 2021 .SHORT TERM...(This evening through Friday) Issued at 207 PM CDT Thu Jul 8 2021 Water vapor satellite this afternoon shows a couple of short wave troughs upstream of the area. The first was over North Dakota with the second just crossing the border into northern Montana. The first wave should pass across the area this evening with just enough forcing to help keep the clouds in place but is not expected to produce any showers or storms. The second wave will generate a round of convection that should initiate this afternoon over Montana and then roll southeast across the Dakotas overnight. The hi-res meso- scale models suggest some remnants of this will hold together and move across Iowa Friday. Some uncertainty on how far north this will extend with the 12Z meso-scale models suggesting there is a decent chance for this to move across northeast Iowa. However, the latest 08.16Z HRRR looks to be taking this a little farther south and if this trend continues, it could possibly only be the very far southern sections of the area that could get some rain. For now, have trended the rain chance area farther south but have maintained some higher chances across northeast Iowa. Either way, there should be abundant cloud cover for much of the area Friday that will help hold temperatures down again. Expecting highs again to only be the 70s. .LONG TERM...(Friday night through Thursday) Issued at 207 PM CDT Thu Jul 8 2021 From Friday night into Saturday, a series of shortwave troughs will move along the northeastern and eastern periphery of the western region. Still plenty of uncertainty on the placement of this rainfall. With much of the instability well west and south of the area, thinking that the greatest risk for flooding and severe weather will remain out of the forecast area. Also kept the rain chances more in the 20 to 50 percent range. A bit concerned that the chances may be too far east and north. From Saturday night into Monday, the western ridge will build north and northeast of the forecast area. This will cause a cutoff low to develop over the Central Plains and Mid Mississippi River Valley. As shortwaves rotate around this low, some showers and storms may pivot north into northeast Iowa and southwest Wisconsin. Beyond this period, the closed low starts to open up and eventually gets picked up by the westerlies. Still plenty of uncertainty on whether any of this rain from this system will affect the area. Temperatures will range from the mid 70s to around 80 this weekend and be in the 80s next week. && .AVIATION...(For the 06Z TAFS through 06Z Friday night) Issued at 1040 PM CDT Thu Jul 8 2021 Cigs: mid level deck expected to be lowering later Fri morning with mostly MVFR cigs then expected into Friday night. WX/vsby: thunderstorm complex over the northern plains will dive southeast overnight, tracking across IA/IL early on Friday. Meso models currently favor keeping the brunt of any shra/ts chances south of the TAF sites and will leave any mention out of the TAFs. However, bits of upper level energy post the MCS could serve to trigger scattered shra/ts for early afternoon. Some hints in a few models this could occur. Will monitor and add if likelihood increases. With clouds expected to be plentiful overnight, don`t see a threat for valley fog at KLSE. Winds: sub 10 kt winds to continue with mostly a southeast direction. && .ARX WATCHES/WARNINGS/ADVISORIES... WI...None. MN...None. IA...None. && $$ SHORT TERM...04 LONG TERM...Boyne AVIATION...Rieck
Area Forecast Discussion
National Weather Service Birmingham AL
743 PM CDT Thu Jul 8 2021 .UPDATE... Evening Update and 00z Aviation. && .SHORT TERM... /Updated at 0714 PM CDT Thu Jul 08 2021/ The latest 00z BMX raob has the Precipitable Water values down to 1.3 inches, lower than the latest LAPS analysis. This also puts the Mixed Layer CAPE values lower in the 500 range. Although there is some instability, it is a bit limited this evening. There were also two boundaries around the area. One was along the gulf coast and should not be any factor over Central Alabama. The other was at the edge of the mean relative dry air, stretching west to east near the US 80 corridor. Showers and thunderstorms have developed along the axis from near Demopolis to near Prattville, moving eastward. Will keep the highest pops near this boundary south and have the activity slowly waning overnight. It appears that any boundary that approaches from the north or northwest will be very late tonight. I did leave the 20 pop north, but most of the activity will hold off until Friday afternoon. 75 Previous short-term discussion: /Updated at 1232 PM CDT Thu Jul 08 2021/ Through Friday. Showers and storms are starting to develop across the southern tier of counties early this afternoon with low level flow becoming westerly to southwesterly. Best coverage of rain should remain along the U.S. 80/I-85 corridors as we go into the afternoon and early evening hours, where the highest overall moisture currently resides. Based on RAP analysis, a PWAT gradient currently exists between north Alabama (1.5 inches) as opposed to far southern Alabama (1.9 to 2 inches). The KBMX 12z sounding came in with a PWAT of 1.8 inches with 3500 J/kg of SBCAPE. There`s certainly more dry air aloft today than what was observed on Wednesday, so we can`t rule out a storm that has some gusty winds at times later on this afternoon. It`s possible that we could see a few storm clusters develop off to our south that forms an outflow boundary moving northeast. PoPs were kept in the chance range through the evening to allow for that possibility, as well as additional mesoscale boundary interactions. Mostly cloudy skies are expected to develop once again during the overnight hours across at least the southern half of the area with muggy conditions continuing. As the weak upper trough begins to try and swing through the area on Friday, flow will shift from the northwest aloft. Upper level shortwave disturbances are expected to move southeastward, helping to trigger scattered to numerous showers and storms across the northern half of the area. We`ll have to watch the development of these storms off to our northwest, as it could be a bit more organized in the form of an MCS with gusty winds. 56/GDG .LONG TERM... /Updated at 0334 PM CDT Thu Jul 08 2021/ Friday Night through Wednesday. Low level ridging will keep afternoon storm coverage at isolated to scattered Saturday, but will see increases in coverage each afternoon through the beginning of next week. An upper level low will rotate southward into Missouri over the weekend, with weak impulses rotating around this low through the Lower Mississippi and Tennessee River Valleys. This added forcing will couple with elevated moisture to increase storm coverage, particularly during peak heating when instability is maximized. Made minor changes to coverage areas, but no significant changes needed to the extended this afternoon. 14 Previous long-term discussion: /Updated at 0309 AM CDT Thu Jul 08 2021/ Friday night through Wednesday. Low level ridging begins to amplify across the Gulf Coast Friday night into Saturday morning as the upper trough axis shift eastward. Meanwhile, another trough dips through the Upper Midwest and moves into the Mid-MS Valley later in the weekend. This should give us a brief period on Saturday where we see enough synoptic subsidence with the height rises/ridging to limit diurnal convection in Central AL. Model guidance has struggled with this, so while I think we could see a decrease in coverage, scattered thunderstorms will still be possible Saturday afternoon. The upper trough to our northwest becomes a cut-off upper level low pressure system Saturday night into Sunday, wedging Central AL between a trough to the west and ridging to the east. This will result in continued southerly moisture advection and enough synoptic lift to generate slightly higher than normal coverage of diurnal thunderstorm activity each day Sunday, Monday and Tuesday. The cut-off upper level low is expected to phase back in with the upper flow Tuesday evening into Wednesday, lifting quickly northward. This should allow for a decrease in the forcing across Central AL and therefore a relative decrease in rain/thunderstorm chances as we approach the middle of next week. With that said, the timing of when cut-off lows phase back into the overall upper level jet flow can be very difficult for models to handle, so this forecast will likely change in coming days as model guidance fluctuates on that upper low evolution. 25/Owen && .AVIATION... 00Z TAF Discussion. Have no weather mentioned at any terminals, but there is a boundary near MGM. This boundary was the dividing line between drier air to the north and tropical air to the south. A few showers/storms have developed on this boundary and will have to monitor for possible addition for MGM. The activity in the south will wane this evening. Otherwise, VFR forecast through much of the overnight hours. There should be some LIFR ceilings developing again tonight, but will be later in developing. It appears that these ceilings will be around 005, with fog not as much of an issue. The ceilings will be around generally from 10-15z. Showers and thunderstorms are anticipated on Friday. handled this activity with PROB 30 late morning and VCTS in the afternoon for starters. Winds will be westerly less than 5kts tonight and west 5-10kts on Friday. && .FIRE WEATHER... Low clouds are possible early Friday morning, with ceiling heights below 1kft across the south. These ceilings will improve through the morning hours. Scattered to numerous showers and storms are expected each day through this weekend, mainly in the afternoon and evening. A humid airmass will result in high RH values for the next several days, with light winds less than 7kts. && .PRELIMINARY POINT TEMPS/POPS... Gadsden 71 89 70 89 69 / 20 70 20 50 30 Anniston 71 87 71 88 71 / 20 70 10 50 20 Birmingham 72 89 71 89 71 / 20 70 10 50 20 Tuscaloosa 73 89 72 90 72 / 20 60 10 40 20 Calera 72 88 72 88 72 / 20 60 10 40 20 Auburn 71 87 71 87 71 / 40 60 10 40 10 Montgomery 73 90 72 92 73 / 40 60 10 40 10 Troy 72 88 72 90 72 / 30 60 10 40 10 && .BMX WATCHES/WARNINGS/ADVISORIES/... None. && $$
Area Forecast Discussion
National Weather Service Buffalo NY
1024 PM EDT Thu Jul 8 2021 .SYNOPSIS... A cold front will move across the area overnight with some fog developing and a few showers. A weak trailing system will allow for lingering chances of showers into Friday before drier weather advances into the area. Unsettled and humid conditions resume by the start of next week. && .NEAR TERM /THROUGH FRIDAY/... A frontal boundary draped across the region early this evening will finally move through as a cold front overnight. There will be a few lingering showers with this, mainly east of Lake Ontario. Otherwise, the main impact will be areas of fog which will develop across Western New York, especially near the lakeshores. Some of this fog may be locally dense. Fog already can be seen on webcams along Lake Ontario and at Dunkirk along Lake Erie. Prefer HRRR guidance which does a good job advecting and spreading this fog out overnight. The fog will linger into Friday morning. A secondary wave in NW flow aloft will traverse the area on Friday with a minimum in the H5 temperatures. This will result in showers blossoming inland from the Great Lakes and moving off to the ESE in the mean layer flow. These will be scattered in nature, and the majority of Friday is likely to be dry. && .SHORT TERM /FRIDAY NIGHT THROUGH SATURDAY NIGHT/... Surface high pressure will begin to build into our region from the west as the moist airmass continues to push off to the east Friday night. This will provide mostly dry conditions overnight, with only a chance of a lingering shower or two. Overnight low temperatures will be in the 50s to low 60s across the Lake Plains. Though most areas on Saturday should also see rain-free conditions, a few light showers may pop-up in the afternoon hours. Weak cold air advection in the mid-levels combined with daytime surface heating will steepen lapse rates as a relatively weak upper level jet passes over the area in the afternoon hours, which may provide the little bit of extra forcing to sour an entirely dry forecast. Nonetheless, very limited moisture, weak flow through the column and subsidence courtesy of surface high pressure should limit shower coverage. Temperatures on Saturday will peak near or just below climatological normals for this time of year. Any showers that develop should quickly die out as daytime heating falls off. Cloud cover should initially diminish as well, allowing for temperatures to again drop into the lower 60s and 50s across the region. However, temperatures will begin to moderate as mid and high level clouds begin to build into our region in the second half of Saturday Night. A surface warm front pushing towards our region from the South will bring another period of active weather beginning on Sunday. Rain showers along the front along with with diffluent flow aloft will gradually spread from south to north across the region. More widespread shower activity will reach the NY/PA border in the early afternoon and overspread much of the area shortly thereafter, lasting right through Sunday night. Low level warm air advection should limit lapse rates and overall CAPE, but abundant moisture with PWATs close to 2" will bring the chance for some steady rain and a possibly a few rumbles of thunder in the afternoon. Temperatures will again be near normal during the day Sunday, but a warm overnight is in store with temps in the mid 60s, a bit cooler east of Lake Ontario. && .LONG TERM /SUNDAY THROUGH THURSDAY/... An upper level ridge off the southeast U.S. coast Monday will build northward and span the eastern seaboard by mid-week. A warm front will be track from south to north across western and north central NY early in the week. Temperatures and dewpoints will increase with daily chances for showers and thunderstorms. A shortwave trough near the Upper Great Lakes is forecast to stay to the west as the strong upper level ridge stays across the Northeast through Tuesday. This should keep widespread severe risk low. The ridge should start to break down Wednesday and Thursday and the chance for showers and thunderstorms continue with an increase in southerly flow. High temperatures will average in the low to mid 80s Monday to the mid to upper 80s Tuesday-Thursday. Low temperatures will average in the mid to upper 60s. && .AVIATION /02Z FRIDAY THROUGH TUESDAY/... Low moisture will increase across the area with low stratus lowering flight conditions to IFR or lower. Lower cigs and locally dense fog are possible, with a risk of VLIFR in any dense fog. Greatest risk is between 06Z and 15Z at KBUF, KIAG, and KJHW. Fog will slowly dissipate and cigs lift on Friday, but it may not be until Friday afternoon before conditions improve to MVFR. Scattered showers and an isolated thunderstorm is possible. Outlook... Friday night...Improving to MVFR/VFR with diminishing chances for showers. Saturday...VFR. A chance of showers over the far west. Sunday...VFR. Monday...VFR/MVFR with a chance of showers and thunderstorms. Tuesday...VFR/MVFR with a chance of showers and thunderstorms. && .MARINE... A cold front will drop south of the waters with generally light winds and negligible waves overnight. There will be areas of fog on the waters, which may become dense at times. Looking ahead to the upcoming weekend...gentle to occasionally moderate winds on Saturday will be accompanied by negligible wave action. While winds and waves should not be an issue on Sunday... conditions will once again deteriorate with some showers and thunderstorms becoming likely. && .BUF WATCHES/WARNINGS/ADVISORIES... NY...None. MARINE...None. && $$ SYNOPSIS...Apffel/Fries/RSH NEAR TERM...Apffel/Fries SHORT TERM...PP LONG TERM...HSK AVIATION...Apffel/Fries MARINE...Apffel/Fries
Area Forecast Discussion
National Weather Service Cheyenne WY
750 PM MDT Thu Jul 8 2021 .UPDATE... Issued at 745 PM MDT Thu Jul 8 2021 Quick forecast update this evening with the expiration of the Red Flag Warning this afternoon. Another day of dry conditions and gusty winds are expected on Friday, but the worst conditions will shift further west. Isolated showers and thunderstorms will continue over southeast Wyoming and western Nebraska this evening, but should diminish in intensity after 900 pm. Another round of thunderstorms expected Friday with a better potential for severe with severe storms likely occurring later in the day/evening hours. && .SHORT TERM...(Tonight - Saturday Night) Issued at 155 PM MDT Thu Jul 8 2021 The main forecast concern/highlight over the next 24-48 hours will be the potential for strong to locally severe thunderstorms across portions of the area. Hot & dry today on the northern fringe of an intense upper-level ridge encompassing much of the southwestern US this afternoon. Fire weather conditions remain elevated especially along and west of the Laramie Range. KCYS radar loop shows showers and thunderstorms beginning to develop along the Laramie Range, in western Platte County. Convection should increase in coverage over the next few hours with a few stronger disturbances traversing the flow on the edge of the ridge. Dew points in the 50s, coupled with steep mid-level lapse rates are contributing to MLCAPEs up to 1500 J/kg across east central WY into the northern NE Panhandle. Expect this to be the most likely area for any severe storms later in the afternoon and this evening beneath 40-50 knots of H5 flow, helping to support effective bulk shear in excess of 40 knots which should contribute to a risk for supercell structures. We do not expect to see this activity become particularly widespread, but potential is there for an intense storm or two. Stronger mid-level short wave dives south across the CWA on Friday afternoon, yielding considerably stronger forcing than what exists currently. 50+ knots of westerly H5 flow will give way to up to 60 knots of 0-6 km shear, which could combine with CAPE values around 2000-3000 J/kg depending on the degree of boundary layer mixing in the hours before initiation. Convection may come in several rounds for different areas, but primary focus will be across east central Wyoming and the northern Nebraska Panhandle once again, first late in the afternoon and then again during the mid/late evening. High- resolution guidance including the HRRR and NAMNest have been quite consistent painting numerous supercells & linear segments, roughly between 21z and 06z. Recent westward expansion of SPCs Slight Risk looks good based on the latest data. Primary hazards will be large hail and damaging winds. High cloud bases should limit chances for an isolated tornado despite substantial directional shear near the surface. Some shower & thunderstorm activity could linger into the early to mid morning hours on Saturday. Otherwise, much cooler and drier in the wake of the cold frontal passage with highs 75-85. .LONG TERM...(Sunday - Thursday) Issued at 155 PM MDT Thu Jul 8 2021 Quieter weather expected by the late weekend into early next week as a ridge of high pressure builds across the CWA and an upper level low stalling out across the Midwest. Should begin to see a warm and dry pattern emerge with a blocking feature developing across the eastern seaboard, allowing the low to remain fixed over the Ohio Valley through Monday. An uptick in the temperatures is likely under this feature, with daytime highs projected to be in the upper 80s and even in the mid-90s for the northern portions of the CWA. With the uptick in daytime highs, and drier conditions expected, will inevitably raise fire weather concerns as the afternoon RH values drop to the mid-teens. At this time, long range model guidance has wind speeds below criteria, with in house products in good agreement of the lower wind speeds. However, will need to reevaluate later model runs to determine if any fire weather headlines will be needed. Once the overall ridging pattern begins to break down across the southwest, will see increase chances for afternoon thunderstorms through Thursday. Even though PWat values remain higher across southeastern Wyoming and the Nebraska Panhandle compared to Monday, much of the good moisture advection remains to the east. Regardless, once northwest flow sets up across the domain, combined with surface heating, 500-1000 J/kg MUCAPE, and 40-60 kt of 0-6km shear supports isolated strong to severe storms Wednesday and Thursday. && .AVIATION...(For the 00Z TAFS through 00Z Friday evening) Issued at 526 PM MDT Thu Jul 8 2021 VFR. Thunderstorms in the vicinity at Laramie, Cheyenne, Chadron, Alliance, Scottsbluff and Sidney until 01Z. Wind gusts to 37 knots at Rawlins, Laramie and Cheyenne until 02Z, then to 35 knots after 15Z Friday. && .FIRE WEATHER... Issued at 405 AM MDT Thu Jul 8 2021 Well above normal temperatures expected today with humidities dropping to 12 to 15% across Converse, Niobrara, Carbon, and Albany counties and westerly winds gusting to 35 MPH ahead of a cold front. Some shower and thunderstorm, likely dry thunderstorm, activity possible with the cold front passage. Friday looks a little bit cooler than Thursday, but for areas less impacted by the cold front, specifically areas west of the Laramie Range, humidities will remain 12 to 15% through the afternoon and evening with winds gusting to 35 MPH. Saturday will be the coolest day with higher humidity and weaker winds, but that relief is short- lived as temperatures warm back up to well above normal with humidity dropping to 12 to 20% Sunday into early next week. However, winds are currently forecast to be relatively light and variable with little to no thunderstorm activity expected. && .CYS WATCHES/WARNINGS/ADVISORIES... WY...Red Flag Warning from 11 AM to 8 PM MDT Friday for WYZ304-305- 307-308. NE...None. && $$ UPDATE...TJT SHORT TERM...CLH LONG TERM...MD AVIATION...RUBIN FIRE WEATHER...LK
Area Forecast Discussion
National Weather Service Des Moines IA
633 PM CDT Thu Jul 8 2021 ...Updated for 00z Aviation Discussion... .SHORT TERM.../Tonight through Friday Night/ Issued at 318 PM CDT Thu Jul 8 2021 ...Increasing Risk of Severe Storms Friday Afternoon and Night... Confidence: Medium Main challenge is increasing severe threat Friday into Friday Night. Remnants of the area of showers continues to move southeast into our area and continues to fester this afternoon. Stratus that backed into eastern and central Iowa overnight along with the fog has lifted with some clouds lingering late this afternoon due to the weakening area of showers. Meanwhile, over southeast Wyoming, the southern of two short waves will begin to lift northeast later today and tonight. A nearly stationary front this morning from a northern stream low over Montana will also begin to push northeast tonight. Increasing H850 winds and stronger thetae advection will focus an area of elevated storms along this boudoir with the initial storms over Iowa beginning around or shorter after 06z. H700 flow is east southeast and with the expected strengthening of the low level jet between 06z and 12z, the storms will attempt to ride east southeast while the main synoptic boundary lifts northeast. So, overall tonight`s focus is for the northwest/west central into northeastern and northern sections with time through 18z Friday. There is decent consensus on tonight`s evolution of the storms primarily affecting areas north of I80, but still some uncertainty on the cutoff on the southern edge as well as how far southwest an expected outflow boundary will move with the main MCS that forms later tonight into Friday. There is better consensus today that at least some semblance of the storm complex will remain ongoing through the daytime hours as it lifts into northeast Iowa tomorrow. Tonight our 0-6km shear increases to 45 to 50 kts, peaking from 06- 12z across northwest and then expanding to southeast Iowa from 18z to 00z and weakening slightly into 06z. Though there are differences in the synoptic solutions, a general focus is coming into view. The first round of convection should remain elevated with hail being the main threat over the west/northwest tonight. SPC has expanded the marginal area farther east a bit overnight to cover more of western/northern Iowa through 12z Friday. Tonight lows will be warmer with expected cloud cover and increasing southeast flow during the night hours. Mins will range from the lower 60s northeast to the mid 60s over the south/southwest. Early indications for Friday suggest that the lingering storms mainly north of I80 will lay down an outflow boundary back into central Iowa. The HRRR shows a wind shift backing west southwest and somewhat aligning/converging with the main synoptic boundary by 19- 21z. South of the boundary, daytime heating should bring highs back into the 80s just along and southwest of the boundary. Instability parameters increase to roughly 2000-2500+ J/kg MLCAPE south of the boundary with strong curvature in area hodographs, 0-1km SRH 200-300 m2/s2 and forecast SR mean wind over 40 kts in a corridor over central to southeast Iowa from mid/late afternoon through early evening. The GFS and NAM solutions are a bit more robust and farther northeast than the Euro today. At this time, it appears that there will be little if any cap by late day south. Limiting factors over a portion of south/southwest early in the event, include a warm layer of +10C at H700 which is generally back west/southwest of Des Moines. Thus the potential for a corridor strong thunderstorm activity may be confined to a more narrow region somewhere along and near the I35 corridor southeast to far southeast Iowa just along and south of a surface warm front and area of stronger sfc convergence during the afternoon and then some storms moving into the southwest later in the night. The new SWODY2 outlook for an enhanced risk covers the area pretty well with some uncertainty yet on extent of coverage. There remains some timing uncertainty on the afternoon uptick or into early evening for coverage/severity with the ongoing convection in the morning. All modes of severe are possible with a higher risk of significant hail and significant thunderstorm winds along with tornadoes. Given diurnal expectations, the most likely timeframe would be from 20-23z through mid to late evening with some hydro issues possible south into the overnight if the storms can reform along the main sfc boundary collapsing south into Missouri and propagate east. Similar to previous forecasts and also given high PWATs as well as sufficient warm cloud depths, some areas may see a quick 1 to 2 inch rainfall overnight tonight into Friday midday with a more robust rainfall signature with the afternoon/evening convection over the south into Friday night. Rainfall totals then could exceed 2 to 4 inches at some locations. For now, will not issue any hydro headlines for Friday night, given the uncertainty, but will need to evaluate again tonight or very early tomorrow morning. A lot of the forecast in the near term depends yet on the overall cloud coverage early Friday morning. Lows Friday night will drop to the mid 60s south and lower 60s north. .LONG TERM.../Saturday through Thursday/ Issued at 318 PM CDT Thu Jul 8 2021 Confidence: Low to Medium Models continue to struggle with the evolution of the H850 low and subsequent chances for storms from Saturday through Monday. The favored areas would remain over the south and east during the period. The Euro continues to emphasize a farther south track while the GFS/NAM are a bit farther north. The 12z GEFs H850 low track is farther east and south by 06z Monday than the operational GFS, but still has more northerly drift of the system into the weekend compared to the operational Euro. For now, will maintain rain/thunder chances into Monday with some expectation that the mesoscale forcing will help direct the synoptic pattern farther south with time. Overall additional rainfall of an inch or so is possible with the H850 low near our area through Monday. Temperatures will struggle Saturday and Sunday with some warming into midweek with another approaching system and cool front by Wednesday and cooler conditions into Thursday. && .AVIATION.../For the 00Z TAFS through 00Z Friday evening/ Issued at 633 PM CDT Thu Jul 8 2021 VFR conditions at present, but that will be changing as the first wave of showers and storms moves over northern Iowa after 6z. MCW and ALO have highest chances of keeping showers and storms around after this first wave passes with lower chances at the other terminals. This resulted in long periods of VC wording across the northern terminals, but tried to limit TS mention to when confidence was higher. Stronger storms are expected to develop in the mid-afternoon hours with the most likely terminals impacted being DSM and OTM and perhaps FOD and ALO. && .DMX WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SHORT TERM...REV LONG TERM...REV AVIATION...Ansorge
National Weather Service Hastings NE
838 PM CDT Thu Jul 8 2021 ...Short Term and Aviation Update... .UPDATE... Issued at 836 PM CDT Thu Jul 8 2021 Some comments on our limited (but non-zero) rain/thunderstorm chances later this evening-overnight: - Overall, only cosmetic changes made thus far to the evening- overnight forecast inherited from day shift. See excellent previous discussion below for more assessment of our small (but non-zero) chance for spotty and most likely non-severe activity late tonight into early Friday. - About the only change made to previous forecast was to delay any mentionable (20+ percent) PoPs/chances into our far western/northern zones until midnight (and then expanding to more of the area thereafter), as previous forecast had small PoPs creeping into our far west as early as 9-10 PM...which radar/satellite/model trends now confirm will not occur that early. - Echoing some previous forecaster thoughts from below, clearly the "main show" for late-night activity within the low level jet exit region should focus pretty clearly to our north-northeast in the general NE/SD/IA border area, but just enough limited and very-elevated instability (mainly 700-600 millibar layer) will exist directly over our CWA to perhaps promote isolated to scattered shower/storm development particularly near/after 3 AM. Needless to say, this is far from a "sure thing", as even short term/hi-res models still show quite a bit of disparity, ranging from a fair amount of scattered late-night/early morning activity (per the HRRR) to practically nothing (per the 18Z NamNest). && .DISCUSSION...(This evening through Thursday) Issued at 425 PM CDT Thu Jul 8 2021 Main concerns revolve around heat indices Friday afternoon, then thunderstorm chances late Friday and into the weekend. Warm and breezy conditions in place this afternoon under fully sunny skies. S winds gusting 20-30mph have provided some relief from the warm, muggy conditions as highs have climbed into the upper 80s to low 90s amidst Tds as high as upper 60s in spots. Expect similar conditions to continue thru the eve. Latest WV imagery shows our next upper disturbance, quite clearly as a tight/compact spin, moving SE out of S Canada into N MT. Otherwise, remnants of Elsa can be seen moving NE along E Coast, with another upper trough noted over the Pac NW, which will be our disturbance for Fri night that will eventually carve out a nice trough over the Midwest this weekend. Tricky PoP forecast begins tonight as a small, but non-zero, chance for at least a few tstms exists nearly all night. The first low end potential is for remnants of High Plains convection to move in from the W towards HWY 283 after dark and before midnight. Several HRRR runs have shown this scenario. Not completely sold this activity will be able to hold together, though, due to incr CINH and fact that primary LLJ convergence should set up well N/NE of the area. Another potential catalyst for weak convection will be from lift on the S fringes of aforementioned MT shortwave after midnight within highly elevated zone of instability, generally between H7 and H5. NE half of CWA, or so, will have best potential given track of shortwave well NE of the area, and some of this activity may persist into Fri AM. Attention then turns to heat and humidity for Fri aftn. Have coordinated with neighbors to issue a Heat Advisory for KS zones given potential for peak heat index values around 105-107F. These areas will remain warmest tonight on steady S wind, have least chc to be impacted from overnight convection/clds, and likely see warmest air temps in the low 100s ahead of a sfc trough. Areas S of this sfc trough may still see some decent Srly breezes, so tough to gauge how much near-sfc moisture will mix out...but even mid 60s Tds will add a few deg to the feels like temp. Further N, the aforementioned sfc trough will likely lead to much weaker mixing and promote pooling of sfc moisture. Air temps won`t be as warm, generally low to mid 90s, but less mixing and better evapotranspiration will likely lead to higher Tds in the upper 60s to low 70s. It doesn`t appear actual heat indices will exceed 105F N of the state line, but lesser wind will make it feel just as uncomfortable as warmer S zones. Forecast focus then shifts to potential for svr tstms, perhaps as early as early Fri eve, but more likely late eve into overnight. Models generally depict the CWA in shortwave ridging/subsidence behind tonight/Fri AM departing wave, so in the absence of some sort of remnant MCV or strong outflow bndry (which seems unlikely attm), think lack of upper forcing and relatively warm mid level temps (H7 temps 12-14C) will keep most, if not all, of the CWA dry Fri aftn. I think best chcs for aftn sfc based convection will be E of the CWA within better zone of low level forcing/moisture/instability and less capping. Appears our primary concern will be for convection to develop over the central High Plains, within zone of moist upslope flow and strong effective shear, organize into an MCS, then propagate E/SE along mid-level thermal gradient towards W portions of the CWA around 02-03Z. The question then becomes how organized will the MCS become by the time it reaches the CWA, and well will it maintain intensity into the overnight? Not sold it is a slam dunk severe weather chc for our CWA for a few reasons: 1) models suggest there may be a minimum in instability over central Neb., E of the zone of initiation and W of the CWA, where Tds remain in the 50s. 2) the timing of the MCS into this zone of lesser instability may be around sunset and be too much incr CINH for the MCS to persist through, and 3) models have trended the primary convergence zone associated with LLJ further S and removed from the approaching MCS. On the flip side, IF the MCS can persist into south central Neb., model depict a significant reservoir of strong MUCAPE for the MCS to work with, in the midst of moderate to seasonably strong deep layer shear of 35-45kt. Needless to say, confidence on exact evolution remains pretty low. Would think the primary concern locally would be dmg wind gusts up to 70mph given expected storm mode, but strong shear would also support some embedded supercells and associated large hail threat, as well. PWAT values briefly incr to near 2" could also support some locally hvy rn. Tstm chcs will continue through the day on Sat, owing to continued influence from deepening upper low, as well as moist low level airmass beneath much cooler mid level temps and less capping. This should allow for any breaks in rain/clouds to only promote stronger instability and renewed iso-scat tstm development by early aftn. In fact, some models prog aftn SBCAPEs of 1500-2000 J/kg with nearly 30kt of bulk shear, which could be just enough for some marginally severe hail given seasonably low WBZ levels. So overall, Sat could be a bit of washout for some, and can`t rule out iso/transient strong/marginally severe storms capable of brief bouts of nickel-quarter size hail. Should see gradually decr instability and PoPs with time Sat eve into overnight. Sun looks to be pick day of the weekend as current forecast is dry. May eventually need a slgt chc PoP for E portions of CWA for aftn, but regardless, overall tstm chcs appear much lower than Sat and airmass will be pleasantly mild and less humid. Dry conditions are forecast Mon-Tue before next chc for shwrs/tstms arrives towards middle of next week as temps return to the 90s. && .AVIATION...(For the 00Z KGRI/KEAR TAFS through 00Z Saturday) Issued at 836 PM CDT Thu Jul 8 2021 Ceiling/visibility/precipitation: High confidence in VFR ceiling/visibility through the period, with the lowest clouds likely consisting of a possible scattered to perhaps broken deck as low as around 12K ft, particularly late tonight into Friday morning. That same late night/early morning time frame also contains the main (albeit highly-uncertain) window of opportunity for hit-or-miss thunderstorm activity in the area. As a result, have maintained a basic "vicinity thunderstorm" (VCTS) mention, but have confined it to the 08-12Z time frame as this looks most favorable. Severe storms are not anticipated, but should storms develop, suppose some gusty winds cannot be ruled out. Please note that much better chances for thunderstorms (potentially severe) look to arrive shortly beyond this current valid period (Friday evening-overnight). Winds (including low level wind shear/LLWS): Surface winds will be strongest right away this evening, averaging southerly around 15KT/gusts 20+KT. However, these slightly-breezy southerlies will gradually back off through the late night/early morning hours. Then by mid-day Friday, a period of fairly light winds (mainly sustained under 10KT) will be established in the vicinity of a slowly-southward-sinking front, resulting in wind direction perhaps becoming variable for a time but likely more easterly by mid-late afternoon. As for low level wind shear this evening into early Friday morning, have largely maintained the mention from previous issuances with only minor tweaks. This latest rendition contains LLWS from 04-13Z, as speeds within roughly the lowest 1,500 ft. AGL will accelerate to around 45KT from the south-southwest, setting up around 30-35KT of overall shear magnitude between the surface and this level. && .GID WATCHES/WARNINGS/ADVISORIES... NE...NONE. KS...Heat Advisory from 1 PM to 8 PM CDT Friday for KSZ005>007- 017>019. && $$ UPDATE...Pfannkuch DISCUSSION...Thies AVIATION...Pfannkuch
Area Forecast Discussion
National Weather Service Grand Rapids MI
923 PM EDT Thu Jul 8 2021 LATEST UPDATE... Update .SYNOPSIS... Issued at 248 PM EDT Thu Jul 8 2021 - Some drying into Friday night - Risk for Showers and Thunderstorms returning Sunday into next week && .UPDATE... Issued at 923 PM EDT Thu Jul 8 2021 I have added scattered showers to our forecast for tonight, mostly for areas south of Route 20 and east of US-131. The latest surface analysis at 9 pm shows a surface trough from near MKG to Lansing. There is surface wind convergence on this trough (shown nicely by our MSAS analysis tool). Meanwhile at the mid to upper levels, on the water vapor loop, it is clear that there is a series of shortwaves moving across lower Michigan early tonight. The combination of the surface trough, shortwaves and cold air aloft associated with the digging upper level trough over our are helping to cause the light showers we are seeing develop on radar between Grand Rapids and Jackson. These showers will not amount to much but since they are there it seem reasonable to put them in the forecast. The HRRR is showing the area of showers slowly sinking south with time this evening. The showers should be out of this area by midnight or so. && .DISCUSSION...(This evening through next Thursday) Issued at 248 PM EDT Thu Jul 8 2021 - Some drying into Friday night An area of high pressure will build in from the northwest into Friday. North to northwest winds ahead of this feature will advect in a drier airmass. This will support the clouds breaking up. Visible satellite imagery shows this trend underway around Grand Rapids and Muskegon and points upstream. This drier airmass will support lower than normal temperatures at night. Bufkit RH overviews suggest we could see some diurnal clouds developing on Friday...but they will likely be scattered to broken. Mid level moisture starts to increase on Saturday so clouds may thicken up then. - Risk for Showers and Thunderstorms returning Sunday into next week A mid level trough digs down from the northwest Sunday into Monday with the feature expected to close off to the southwest of the CWA on Monday. Considerable uncertainty exists where this feature closes off which will play a big role in terms of how much rain we see. For now with steady height falls and increasing moisture...we should see an increase in the shower and thunderstorm activity...which we will feature in the forecast. Eventually for the middle to end of next week this feature lifts through the CWA. Given the moist axis that will exist out ahead of this feature...above normal precipitation looks likely to occur. && .AVIATION...(For the 00Z TAFS through 00Z Friday evening) Issued at 730 PM EDT Thu Jul 8 2021 Expect low MVFR cigs more or less at all of our TAF sites through the night tonight. As dry air moves in from the north the clouds should thin out by mid morning Friday. Most of our TAF sites should be mostly clear by mid afternoon. It would not be out of the question there could be an isolated shower this evening at any of the TAF sites but the risk is low and even if it did happen the precipitation should be very light and not impact visibilities. && .MARINE... Issued at 248 PM EDT Thu Jul 8 2021 The small craft advisory and beach hazard conditions will continue into tonight as a the drier airmass advects in from the northwest. Waves out in the mid part of the lake were around 5 feet at the buoy. Gust of around 20 knots are occurring as well. The pressure gradient weakens later tonight into Friday...which will support lowering of the winds and waves. && .GRR WATCHES/WARNINGS/ADVISORIES... MI...Beach Hazards Statement until 5 AM EDT Friday for MIZ056-064-071. LM...Small Craft Advisory until 5 AM EDT Friday for LMZ844>846. && $$ UPDATE...WDM SYNOPSIS...MJS DISCUSSION...MJS AVIATION...WDM MARINE...MJS
Area Forecast Discussion
National Weather Service Gray ME
1100 PM EDT Thu Jul 8 2021 .SYNOPSIS... Tropical Storm Elsa will approach the region tonight with showers and thunderstorms overspreading the area. As this storm passes just south of the region on Friday...very heavy rain is expected across the region with flash flooding possible. Some gusty winds are possible along the coast along with large breaking waves. The remnants of the tropical storm will depart the region Friday night and Saturday with seasonable temperatures and dry weather expected this weekend. && .NEAR TERM /UNTIL 6 AM FRIDAY MORNING/... 1100 PM Update... There are very few changes to the track or forecast philosophy in terms of TC Elsa this evening (see latest updates from the National Hurricane Center). The surface pressure within the storm has dropped 4 mb in the last 6 hours and a portion of the storm will continue to emerge over water late this evening. Well ahead of this system, showers and isolated thunderstorms continue to move northeast across the region. Much of the precipitation weakened during the evening hours as it entered New Hampshire and western Maine, however as we head into the overnight period, more significant shower activity will enter the region from southern New England per latest HRRR solution. Made some minor adjustments to pops, dew points, winds and lowered temperatures a tad per latest conditions and near term mesoscale models. Temperatures will remain relatively steady throughout the night and may actually rise over some areas. Otherwise, very little in the way of changes to this updated forecast package. Prev Disc... High pressure over Quebec will shift into the Canadian Maritimes tonight while a stalled boundary over southern New England lifts northward as a warm front. Warm frontal ascent will be aided by dynamic lift from the right rear entrance of an upper jet along with an approaching mid/upper level trough. Some elevated instability along with warm cloud depths will aid in rainfall efficiency with periods of moderate to heavy rain expected overnight with embedded thunderstorms. The axis of heaviest rainfall tonight still looks to remain to our northwest with current QPF forecasts of around 1 inch in the mountains to half an inch towards the coast before the remnants of Elsa track through the area Friday morning. However, given the convective nature of precipitation through this evening locally heavier amounts are possible in thunderstorms. Lowering ceilings and increasing low level moisture will lead to areas of reduced visibility in fog and moderate to heavy rain. Lows tonight will range from the 50s north to 60s south. && .SHORT TERM /6 AM FRIDAY MORNING THROUGH FRIDAY NIGHT/... Remnants of Tropical Storm Elsa Brings Heavy Rain to the Region... Tropical Storm Elsa will undergo extra-tropical transition as the system crosses southern New England around mid-day tomorrow. The primary threat with this system as it tracks into the Gulf of Maine tomorrow afternoon will be very heavy rainfall across the region focused along the foothills through the coast. Heavy rain is expected to move into southern New Hampshire around 11 AM with rainfall rates approaching 1 inch per hour. The system will accelerate northeastward spreading heavy rain into southern Maine between 12 pm to 2 pm with rainfall rates exceeding 1 inch per hour. This heavy rain will continue to spread northeast into the Capital District of Maine around 4 PM while the back edge of the rain will be clearing through New Hampshire. Between 6 to 8 PM the system will be pulling away from the area as it accelerates towards the Canadian Maritimes. There is a strong likelihood that some areas will experience rainfall rates of 1+ inches per hour for more than one hour. This can be seen well in the 3 hour QPF products within the 12Z HREF. The ensemble max 3 hour rainfall, which is a ballpark worse case scenario, paints a broad area south of the mountains with 3 hour max QPF in the 1.5 to 3 inch range with local amounts to 4-5 inches. The ensemble mean 3 hour QPF paints a more narrow area of 1 to 2 inches in 3 hours while the probability matched mean 3 hour QPF hones in on the coast with 2 to 3 inches to locally 4 inches. Thus, the concern remains that areas currently within the Flash Flood Watch could see upwards of 3 inches of rain in a 3 hour period, which will exceed flash flood guidance in some areas, particularly urban centers. The one factor that will help mitigate flooding concerns is that the remnants of Elsa are expected to accelerate through the area minimizing the duration of heavy rainfall rates. There remains good consensus within the 12Z model suite that the heaviest rain from Elsa will stay south of the mountains with no current changes to the Flash Flood Watch. Total QPF from tonight through Friday night will range from 1.5 to 2 inches in the mountains with locally high amounts along southeast facing slopes. From the foothills to the coast total QPF will range from 2 to 3.5 inches with local amounts approaching 4-5 inches. Winds: Given the slight southward shift in the NHC track for Elsa /and the consensus of the guidance/ the potential for significant wind gusts is reduced. Current forecast package depicts gusts remaining below 30mph along the coast throughout the event as the direction remains from the northeast. A northward change to storm track would bring the potential for a period of stronger /30-40 mph gusts/ along the Midcoast for a period late Friday morning through mid afternoon. However...this is not currently the most likely outcome. Elsa pulls away from the area Friday evening with rain ending by sunset and relatively light northwest winds behind the system. Relatively light winds and ample low level moisture will make for areas fog Friday night. && .LONG TERM /SATURDAY THROUGH THURSDAY/... High Impact Weather Potential: * Confidence too low to pinpoint severe weather potential...but thunderstorm potential increases for the second half of the long term forecast period /Tuesday-Thursday/. * Building heat and humidity by Wednesday-Thursday of next week. --Pattern and Implications-- Broad troughing over the eastern United States will open the period but give way to a cutoff low over the Mid Mississippi Valley which will allow high pressure over the central Atlantic to build west into early next week with the mean flow trajectory over our area backing from northwesterly to southwesterly. This should allow for a moderating trend through the period with a seasonable summer pattern unfolding. By the end of the period...the cutoff well to our west ejects north and east...which will increase the potential for unsettled weather to end the period. --Daily Details-- Saturday - Sunday: High pressure builds over the region under northwest flow aloft with PWATs falling below 1" on Saturday with the high largely remaining in control through Sunday. Temperatures look to be seasonable if not a bit below normal on Saturday /mid-upper 70s/....warming a few degrees into Sunday. Sunday night - Monday. As mid level low cuts off south of the Great Lakes...northern stream shortwave passes north of the region Sunday night into Monday...coaxing lift over stalled frontal boundary south of our region. This will increase the potential for showers to build north along the front with additional showers along the cold front north of our region associated with the shortwave. Temperatures on Monday look similar to Sunday with increased cloud cover offsetting a slow increase in temps aloft. Certainly an increase in humidity will occur over southern sections. Tuesday - Wednesday: As the east coast ridge begins to build..the potential exists for shower/storm activity in association with a northward lifting warm front. Given building heights...forcing will overall be weak so am not confident in significant convective coverage. Certainly doesn/t look like a washout through this period with the bigger story being increasing heat/humidity under warm advection with high temperatures moving above seasonal norms by Wednesday /lower 80s north - mid 80s south/. Thursday: Guidance solutions diverge with their handling of the cutoff low over the middle of the United States...but are in general agreement that the ridge over our area will flatten with more northern stream influence with the potential for shortwave energy in the westerly flow aloft to bring a round of showers/storms to end the forecast period. Any end to the warming trend will likely not reach the region until after this forecast period ends...with the potential for a hot/humid day on Thursday. && .AVIATION /03Z FRIDAY THROUGH TUESDAY/... Short Term...Conditions will deteriorate to IFR/LIFR tonight in lowering cigs and reduced visibility in heavy rain and fog. IFR/LIFR will continue through early Friday afternoon across the area with improving conditions from SW to NE through Friday evening. The remnants of Tropical Storm Elsa will track along the Maine coast tomorrow afternoon possibly bringing periods of wind shear with greatest chances occuring at KHIE and KRKD. Fog may develop Friday night bringing restrictions again across much of the area. Long Term...VFR likely for Saturday-Sunday. Potential for restrictions in SHRA and embedded TSRA Sunday night / Monday for southern NH terminals up to PWM. This chance spreads north to all terminals for Tuesday. Winds are expected to be light through the period. && .MARINE... Short Term...Will hold on to gale watches this cycle given the fact that the southward adjustment in Elsa/s track has reduced the threat for gale force winds...even over the outer waters. The current forecast would favor the need for SCAs...but will allow the evening/overnight shift to make the final call in case there is a northward adjustment in track. Long Term...Lingering seas associated with Elsa will fall below SCA levels during the day on Saturday with headline free conditions likely on the waters beyond this through Tuesday. && .HYDROLOGY... NAEFS ensemble shows a 1000 kg /m/s Atmospheric river associated with remnants of Tropical Storm Elsa moving into the region by 06Z Friday. This is far above normal (near 30 year return based on climatology) and more than sufficient moisture to produce flooding. That said, research has consistently shown that the AR is insufficient in an of itself to result in flooding. While the abundant moisture is there, the flow remains from southwest to northeast, up the coast, keeping it largely perpendicular to the terrain. For the Whites, the main threat is training storms as multiple rounds of precipitation move along this river. What barriers might this moisture encounter to help ring it out? Most straight forward is the Camden hills, which are easily exposed to this flow direction, and a hot spot for flash flooding along the coast. The largest barrier is of course the White mountains and extending into western Maine. As the low approaches on Friday winds will tend to curl around and into the terrain, especially further east in Maine in the upper Kennebec. Rainfall totals have generally increased in this region with 2-3 inches now widespread. The third place to watch for a focus of rainfall is along the coastal front. The existing stationary front stretching from ME/NH border out into the Gulf of Maine will try to lift northwards, and as the low develops south of Block Island, the reinforcing NEly flow will tend to strengthen the front. The combination of lifting along the front and convergence as the wind decelerates off the water makes the coastal corridor a place to watch for flooding as well. This is nicely highlighted by both the HREF and the Excessive Rainfall outlook. Here 4-5 inches is possible in a narrow band. River flooding: River flows are starting off well below average, which helps to minimize the risk. Currently guidance from the Northeast RFC shows the upper Pemi at Woodstock reaching action stage, and certainly this is one of the flashier basins so the threat seems reasonable if possibly a bit underdone. Further south across southern NH the only potential focus for rainfall is along the coastal boundary where conditions are driest and terrain flat thus low chance for river issues there. Moving into Maine there are a few potential areas to highlight. As noted above the upper Kennebec basin will be a target of continued upslope flow, and the 4.2 inch flood guidance at Skowhegan is certainly within reach. Along the coastal front the potential for 4-5 inches throws the Presumpscot river at Westbrook into play for flooding. Flash Flood Watch: While there are some isolated river flooding possible, the main threat is for flash flooding with very efficient rainfall processes, and thus a Flash Flood watch has been issued. Rainfall rates in excess of 3"/hr are possible within convective bands over the next few days, which will quickly overwhelm even the driest conditions. && .GYX WATCHES/WARNINGS/ADVISORIES... ME...Flash Flood Watch from 8 AM EDT Friday through Saturday morning for MEZ012>014-018>028-033. High Surf Advisory from 5 PM Friday to 11 AM EDT Saturday for MEZ023>028. NH...Flash Flood Watch through Friday evening for NHZ003>015. High Surf Advisory from 5 PM Friday to 11 AM EDT Saturday for NHZ014. MARINE...Gale Watch from Friday afternoon through late Friday night for ANZ150>152-154. && $$ SYNOPSIS... NEAR TERM...Cannon SHORT TERM...Cannon LONG TERM...Arnott AVIATION... MARINE... HYDROLOGY...
Area Forecast Discussion
National Weather Service Houston/Galveston TX
714 PM CDT Thu Jul 8 2021 .AVIATION [00Z TAF Issuance]... With the messy wet forecast continuing into tonight, have tried to best time the bands of SHRA (isolated TSRAs) through the overnight period...all strongly influenced by the latest HRRR guidance. And, with that being said, aviation interests should continue to expect a slew of amendments as conditions change throughout the night. As we head into tomorrow afternoon, the weakening upper low and upper ridge trying to build back into the region from the W/NW should be heralding the onset of a slightly drier pattern. 41 && .PREV DISCUSSION... /ISSUED 239 PM CDT Thu Jul 8 2021/ ..Locally Heavy Rain Possible over Parts of SE TX... SHORT TERM [Tonight Through Friday Night]... A broad upper level low over South Texas and a weak surface low in roughly the same area of South Texas and a weak coastal trough of low pressure will focus periods of showers and thunderstorms near the middle and upper Texas coast through Friday. The surface low retreats to the southwest by early Friday but the position and orientation of the upper level feature will keep SE TX in a favorable region for additional rain. The low level jet (LLJ) increases to 30-35 knots between 03-06z tonight and the nose of the jet targets the area around Matagorda Bay so feel the heaviest rain should develop across Matagorda, Jackson and Wharton counties. SOme of the models expand the precip into Harris but feel this is overdone based on the orientation of the LLJ. The Flash Flood Watch was expanded earlier to include Wharton and Ft Bend counties and have some concern that Colorado county needs to be included as well. Will advise the next shift and will monitor rainfall trends in that area closely. Jet dynamics not looking as impressive as it did yesterday but upper level winds still show a split across the region but the speed max is no longer a significant player. As for rainfall tonight, still looking for an additional 4 to 8 inches of rain in the watch area with isolated totals between 10-12 inches. Further north, 1 to 3 inches of rain possible over the central zones and less than an inch over the northern zones. Significant river flooding will be possible over the Lavaca Navidad, Tres Palacios and San Bernard watersheds. On Friday, locally heavy rain will probably persist over much of the area during the morning but the upper low and surface low both retreat to the W-SW and moisture levels begin to drop with PW values falling to around 2.00 inches by mid-afternoon. Forecast soundings show some drying in the 850-700 mb layer as well. There should be a decrease in precipitation during the afternoon with drier conditions to the E-NE and wetter to the W-SW. Upper level ridging will try to expand into SE TX Friday night, but moisture trapped beneath the ridge should allow for some isolated to scattered showers to persist. Clouds and rain cooled air should keep MaxT values a little below climo but overnight lows should remain near climo for the next couple of days. 43 LONG TERM [Saturday Through Thursday]... "Here comes the sun, do do do do!" Saturday will essentially be our transition day from the widespread coastal rains associated with the previous low pressure system in South Texas to diurnally driven scattered afternoon showers and thunderstorms that interact with the seabreeze. This is due to the moisture transport decreasing as the low dissipates with PW values finally dropping below 2" over the weekend. As moisture fades away throughout the day on Saturday, locations north of I-10 will be able to see more blue skies than gray skies. This will be temporary models are still in consensus on an upper-level low embedded in a longwave trough digging down into the Central Plains on Sunday. A corresponding surface low will form in the Upper Midwest and attempt to push a surface cold front into Southeast Texas. I say attempt won`t quite make it (sorry y`all). The GFS still takes the front the furthest south of all of the solutions into the Brazos Valley before it washes out. Meanwhile, the ECMWF washes the front out to the north of the CWA. The positioning of the front is a key factor into the rain chances on Sunday/Monday. With the consistency of the models in keeping the front mostly north of the CWA, higher PoPs will be relegated over our northern counties due to increased moisture convergence with PW values approaching 2" and more favorable jet mechanics. For now, going with 50-60% PoPs Sunday through Monday afternoon. Following Monday, we return back to our regularly scheduled programming of afternoon showers and thunderstorms. With the decreasing coverage of rain, temperatures will be able to climb back into the 90s. Fortunately, model trends still indicate that high temperatures will remain slightly below normal through next week with highs in the low 90s inland and upper 80s closer to the coast. Looking further ahead, there are no strong signals of a return to upper-level ridging, so the below normal high temperature trend appears that it will continue into next weekend. Overnight temperatures will hold steady in the mid-to-upper 70s throughout the forecast period, which is right around normal. Batiste HYDROLOGY... Heavy rain is expected to develop tonight, especially over the SW zones. If heavy rain does develop, there will likely be some significant rises on the Lavaca Navidad, Tres Palacios, and San Bernard watersheds. Based on current QPF forecasts, the Tres Palacios could reach major flooding. Rainfall rates could reach 2-3 inches per hour with additional rainfall totals of 4 to 8 inches possible in the Flash Flood Watch area. 43 && .PRELIMINARY POINT TEMPS/POPS... College Station (CLL) 74 83 75 90 75 / 80 80 20 30 10 Houston (IAH) 74 82 76 90 76 / 90 80 40 50 10 Galveston (GLS) 78 84 82 89 80 / 90 70 40 50 20 && .HGX WATCHES/WARNINGS/ADVISORIES... TX...High Rip Current Risk until 9 PM CDT this evening for the following zones: Bolivar Peninsula...Brazoria Islands... Galveston Island...Matagorda Islands. Flash Flood Watch through Friday evening for the following zones: Bolivar Peninsula...Brazoria Islands...Coastal Brazoria...Coastal Galveston...Coastal Jackson...Coastal Matagorda...Fort Bend...Galveston Island...Inland Brazoria...Inland Galveston...Inland Jackson...Inland Matagorda...Matagorda Islands...Wharton. GM...Small Craft Advisory until 7 AM CDT Friday 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...Galveston Bay...Matagorda Bay... 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. && $$ Discussion...99 Aviation/Marine...99
Area Forecast Discussion
National Weather Service North Platte NE
615 PM CDT Thu Jul 8 2021 .SHORT TERM...(This evening through Friday night) Issued at 321 PM CDT Thu Jul 8 2021 A blend of the RAP, HRRR and HREF models is the basis for isolated thunderstorm chances across wrn and ncntl Nebraska tonight. These models suggest storm development across the Black Hills, Pine Ridge and Cheyenne divide late this afternoon which would carry east this evening and overnight. Winds aloft at h500mb should increase to 35 to 50 kts supporting isolated storms given the limited moisture- PWAT around 1 inch. SPC suggested a marginal severe weather risk and this is consistent with the strong winds aloft and limited moisture across Nebraska. The better focus will be across SD where a warm front will be positioned. The warm front will drop south through wrn and ncntl Nebraska tonight and the models are in very good agreement dropping the front through swrn Nebraska by Friday morning. Wrn and ncntl Nebraska will be post frontal Friday in a belt of easterlies. Moisture should pool behind the front across the Panhandle and especially northwest Nebraska where storm development appears probable by late afternoon. There is little change in the winds aloft predicted by the models. Winds at h500mb - h300mb should increase to 45 to 65kts by late Friday afternoon and 0-6km/ 0-8km shear increases to 50kts, 60kts, and perhaps even to 70kts depending on the timing of the arrival of the stronger winds aloft. The NAM and GFS continue to show a rather intense HP type storm/cluster developing across northwest Nebraska late in the afternoon which moves east or southeast into and through the Sandhills during the evening. PWAT has increased to near 1.25 inches by this time and given the very strong shear, the potential for significant wind or hail is a concern as suggested by the SPC severe weather outlook for Friday. The POP forecast Friday and Friday night leans on the short term model blend which places the best thunderstorm chances across Sandhills as suggested by the NAM and GFS. Thunderstorm activity, not necessarily severe, should continue overnight as heights aloft fall with the approach of a developing upper level low. .LONG TERM...(Saturday through Thursday) Issued at 321 PM CDT Thu Jul 8 2021 The models are in very good agreement developing a h500mb cut- off low across Iowa Saturday. The upper low may remain nearly stationary across the Midwest through the weekend and into early next week. Shower and thunderstorm chances continue Saturday but given the cool temperatures in the 70s, the risk of severe weather appears low. The forecast is dry Sunday and Monday; the upper low across Iowa stalls. Meanwhile, a strong subtropical high will remain anchored across the Desert Southwest. The result is strong north winds aloft and subsidence at the sfc across Nebraska. Winds aloft will become west-northwest with the approach of a disturbance Tuesday. The GFS and ECM are in good agreement suggesting the potential for strong or perhaps severe thunderstorms Tuesday-Tuesday night. An upper level disturbance will drop through the nrn Plains and this should cause winds aloft at h500mb to increase to 35-45kts. Both models suggest some sort of compact rain maker; presumably a severe storm or cluster of storms affecting the Sandhills or ncntl Nebraska. Chance POPs are in place Tuesday-Tuesday night for this system. && .AVIATION...(For the 00Z TAFS through 00Z Friday evening) Issued at 615 PM CDT Thu Jul 8 2021 Isolated to scattered thunderstorms will traverse the forecast area this evening and tonight. VFR is primarily expected, although brief drops in visby/cigs will accompany any storm that affects a terminal. Most activity will have waned by 09/06z, then clear conditions will run through Friday afternoon. Gusty south winds this evening will lighten tonight, then transition to east for tomorrow. && .FIRE WEATHER... Issued at 321 PM CDT Thu Jul 8 2021 The short term models or CAMS, continue to suggest intense daytime heating across the Panhandle will cause isolated thunderstorm development late this afternoon. These storms would move east into wrn Nebraska this evening. Dry lightning fire starts are the concern and the HRRR wind gust product suggests the potential for gusty winds with the thunderstorm activity. The potential for dry lightning will continue Friday evening as intense storms develop across northwest Nebraska and the Sandhills. Minimum afternoon less than 30 percent is expected along and west of highway 61. && .LBF WATCHES/WARNINGS/ADVISORIES... None. && $$ SHORT TERM...CDC LONG TERM...CDC AVIATION...Snively FIRE WEATHER...CDC
Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
654 PM CDT Thu Jul 8 2021 .UPDATE... Issued at 612 PM CDT Thu Jul 8 2021 Post-cold frontal advection of drier air upon northwesterly low- level flow has been slow and gradual into the CWA so far this evening with dewpoints remaining in the upper 60s to low-70sF, outside of northeastern MO and west-central IL. Advection of dry air is only anticipated to weaken through the remainder of the evening into overnight as an inverted surface pressure ridge settles southeastward near the Mississippi River Valley. The resulting combination of winds becoming light, residual boundary layer moisture, and efficient radiational cooling from mostly clear skies has increased concerns for at least patchy radiation fog development overnight into Friday morning. Currently, fog appears most favored in proximity to the Mississippi River near and south of the St. Louis metro and into southeastern MO, where the overlap of greatest boundary layer moisture and lightest winds is forecast. Dense fog also cannot be ruled out, especially in river valleys. Pfahler && .SHORT TERM... (Through Late Friday Night) Issued at 306 PM CDT Thu Jul 8 2021 A slow-moving cold front continues to drift southeast across parts of Missouri and Illinois this afternoon. The front is expected to stall late tonight near the Missouri/Arkansas border. The short wave currently over the Montana/Saskatchewan border is forecast to move southeast into the Upper Mississippi Valley by Friday afternoon. This will attenuate the ridge back over the Great Plains and deepen the trough over the eastern U.S. somewhat, and the Mid Mississippi Valley will end up in deeper northwest flow. The next short wave in line, which is now moving onshore over Washington and Oregon, will begin coming into phase with the longwave over eastern North America on Friday over the Great Plains. This will force low level cyclogenesis over the Plains and turn the flow back to the south across Arkansas, Texas, and Oklahoma. The southerly flow will push the front back to the north as a warm front Friday afternoon. Short range deterministic guidance as well as the HREF is in good agreement that precip tonight will stay along and south of the cold front, and current indications are that the front will be southeast of our forecast area by 00Z. Will therefore continue the dry forecast for tonight. By 18Z Friday guidance shows the front near a line from Hannibal to St. Louis to Chester, with some CAMs developing scattered convection as early as 21Z in the vicinity of the front. Deterministic guidance shows SBCAPE in excess of 2000 J/Kg along and west of the Mississippi with 40+ kts of 0-6km shear. This is more than enough shear/instability to support severe thunderstorms during the afternoon, but the main severe threat will likely come Friday evening as an area of convection which is likely to develop over Iowa congeals into a line and rushes southeast. Several CAMs show this QLCS moving into northeast Missouri after 02Z Saturday, and this scenario looks very reasonable in conjunction with the deterministic guidance. The RAP shows a ribbon of 2500+ J/Kg MUCAPE persisting through much of the night in the vicinity of the Mississippi River to maintain storms. Initially, the storms will pose a hail and wind threat, and then shift to more of a wind threat...with a few tornadoes also possible. Carney .LONG TERM... (Saturday through Next Thursday) Issued at 306 PM CDT Thu Jul 8 2021 The aforementioned second short wave digs through the Missouri Valley into the Mississippi Valley Saturday into Sunday. The wave becomes highly amplified as it comes into phase with the long wave trough over eastern N. America, and then it cuts off over the Midwest. Both the GFS and ECMWF keep this cut off low spinning over the region through at least Tuesday morning. The GFS is a bit faster filling in the low and moving it out Tuesday, but both models keep a troughy pattern over the Midwest through Thursday. The end result will be several rounds of showers and thunderstorms for Saturday through Tuesday. Some locally heavy rain looks likely Saturday and Sunday as well since P-Wats will be around 2 inches, which is up near the 90th percentile according to the NAEFS. With clouds and precip in the forecast, temperatures should be mild, with highs Saturday in the low to mid 80s, and Sunday and Monday`s highs will struggle to reach 80 in most locations. Should see a warmup as the upper level low finally exits Tuesday into Wednesday. Carney && .AVIATION... (For the 00z TAFs through 00z Friday Evening) Issued at 653 PM CDT Thu Jul 8 2021 Fog will be likely across portions of the area overnight into Friday morning, with KSUS and KCPS the most favored terminals to be impacted. As such, MVFR visibilities have been introduced, with further temporary reduction to IFR flight conditions also possible at KSUS. Otherwise, predominantly dry and VFR flight conditions should continue into Friday. A few thunderstorms could develop as early as late Friday afternoon along a nearby warm front; however, low confidence in occurrence precluded inclusion of thunderstorms with this TAF issuance. The exception is KSTL`s extended TAF period with VCTS portraying increasing thunderstorm chances through Friday evening. Pfahler && .PRELIMINARY POINT TEMPS/POPS... Saint Louis 68 89 71 84 / 0 40 80 80 Quincy 64 82 69 79 / 0 60 80 70 Columbia 66 89 72 83 / 0 40 60 80 Jefferson City 67 91 73 85 / 0 40 50 80 Salem 66 86 70 84 / 0 40 80 80 Farmington 67 89 70 87 / 5 40 50 70 && .LSX WATCHES/WARNINGS/ADVISORIES... MO...None. IL...None. && $$ WFO LSX
Area Forecast Discussion
National Weather Service Memphis TN
856 PM CDT Thu Jul 8 2021 .UPDATE... A line of showers and thunderstorms is moving southeast toward the Memphis area. This activity has developed along a prefrontal trough ahead of the main cold front. The front is moving into northeast AR and the Bootheel at this time but isn`t expected to progress much farther south. The evolution of the ongoing convection is the main forecast question for tonight. We have seen outflow boundaries extending farther from the updrafts, indicating it is moving into a less favorable environment of shear/instability balance. Some of the recent guidance (HRRR/RAP) suggests this activity will eventually stall along the I-40 corridor. A 30 kt low-level jet is forecast to develop across the area overnight and could assist in maintaining or redeveloping convection along the prefrontal trough overnight. This could result in some training of showers and thunderstorms tonight. However, confidence isn`t all that high given the lack of agreement in the short-term model solutions. The primary concern would be localized heavy rainfall. PoPs/QPF were adjusted accordingly for the tonight period. Only minor changes were needed for other elements. MJ && .PREV DISCUSSION... /issued 254 PM CDT Thu Jul 8 2021/ Fairly progressive pattern for July as weak northwest flow across the Northern Plains to the Ohio Valley is forcing boundaries to push into our region. Currently a weak front is the focus for convection occurring across southern MO/Northern AR. Expect this area to sink mainly across northern portions of our service area along with pop up storms almost anywhere before dying out later this evening. Little overall change in the flow into Saturday as convective systems threaten north of the forecast area. They may creep into the Mid-South along with diurnal storms that continue to pop up almost anywhere. The big change in the flow begins later Saturday into early next week as an upper low develops across the mid-section of the country. A strong chance for thunderstorms is expected on Sunday as a surface front pushes across our area. This upper level system pulls out by mid-week leaving a continuation of progressive westerlies across the north tier of the US. The risk for diurnally forced storms will still continue in the wake of the upper low. Temperatures overall through the period will begin fairly typical, except lowering to below normal levels under the influence of the upper low, producing clouds and precipitation. Temperatures will recover to more normal as the upper low lifts out. Belles && .AVIATION... 00Z TAF Set VFR conditions expected through the period. Although, scattered convection continues to fire up along a weak boundary. The boundary will gradually sink south to the TN/MS border overnight. Latest HRRR keeps showers developing in the vicinity of the front. Will introduce VCTS wording at KMEM and KMKL through 3Z then convert to VCSH after sunset through the overnight hours. Will reintroduce VCTS wording at 19Z at KMEM, KMKL, and KJBR. Expect most of the activity to stay north of KTUP, but did throw in a VCSH during the afternoon. S-SW winds of 5-10 KTS expected through the period. KJBR could see some higher speeds during the afternoon hours. KRM && .MEG WATCHES/WARNINGS/ADVISORIES... AR...None. MO...None. MS...None. TN...None. && $$
...Updated Aviation Forecast Discussion...

.DISCUSSION... Issued at 325 PM CDT Thu Jul 8 2021 Bottom line: some isolated strong/severe storms are possible tonight along NE/SD border. Greater severe weather threat will be sometime Friday afternoon/night, though lots of questions remain on how things will pan out so overall forecast confidence is on the lower side. Clouds and even a few showers associated with a weak shortwave sliding southeastward stuck around a little longer than planned today which held temperatures down a few degrees. 3 PM readings across the area were generally in the mid 70s to lower 80s. Otherwise, of note in water vapor imagery were the upper level high over the Desert Southwest along with a pair of along the Montana/Canada border and another just coming onshore in the Pacific Northwest...that will play large roles in our weather Friday into the weekend. Also playing a large role will be a surface warm front currently analyzed from northwest Nebraska south/southeastward into south-central Kansas. The general idea heading into tonight is that the surface boundary will lift northward while a low level jet ramps up and leads to thunderstorm initiation somewhere near/along the NE/SD border late this evening. Storms are unlikely to be surface-based given timing, but a decent amount of shear and instability could allow for some organized storms with large hail and perhaps some gusty winds. Storms will push southeastward through the early morning hours Friday, with additional development expected across southeast SD, southern MN, and into IA as the aforementioned MT/Canada shortwave slides through. Strength of these storms (and associated cold pools), as well as exact location will play a key role in where the warm front (and greater severe weather threat) sets up during the day Friday. In general, would think that cool outflow would hold the warm front farther southwest than depicted in much of the guidance. In addition, latest RAP guidance suggests fairly strong isentropic ascent continuing in the warm sector through at least mid-day, leading to cloud cover at the very least, and possibly some additional showers and storms which most CAMs are suggesting. Should these pan out, instability could be limited a bit and an already expected stout cap could be that much stronger. They could also help from a temperature standpoint, as mid to upper 90s are currently forecast for portions of southeast Nebraska (though dewpoints in the upper 60s to lower 70s will still make it feel pretty uncomfortable). On the other hand, if these warm sector storms don`t occur, or clear out earlier in the day, MLCAPE values could approach 4000 J/kg per latest RAP guidance and the cap could erode a bit, allowing storm development near the warm front. Should this happen, supercells capable of all severe weather threats would be possible, owing to the aforementioned instability and looping hodographs in vicinity of the front, especially as the low level jet ramps up by early evening. While this scenario would need a lot of things to come together just right, it`s not completely out of the question. However, the more likely scenario is that we wait for some energy associated with the Pacific NW shortwave to approach the area and assist with storm initiation in western NE/SD. General idea is that those would eventually congeal to form an MCS (or multiple) and slide through the area overnight, bringing mainly a damaging wind and locally heavy rain threat. So again, lots of questions remain, even being just 1 day out, but the potential is definitely there for some impactful weather heading into the weekend. While the severe weather threat should exit the area by the early morning hours on Saturday, expect showers and some storms to linger in the area through the day as troughing continues to dig into the Lower Missouri River Valley. Eventually expect a cutoff low to form, the track of which will determine our weather for Sunday into early next week. Should it hang around the area for a while, would expect continued lingering showers and a few storms Sunday and possibly into the very least would expect more cloud cover. As a result, daily highs will be in the 70s and lower 80s, with the coolest day being Saturday. Still quite a bit of spread between various ensemble members regarding timing and track, however, so low confidence in how it`ll pan out. Eventually expect the troughing/low to push off into the Great Lakes region, allowing us to gradually warm back into the upper 80s and lower 90s by Tuesday or Wednesday. Also some hints at another shortwave trough and associated precip sliding through sometime mid-week, but lots of spread on exact timing, with solutions depicting anything from Tuesday through Thursday. && .AVIATION...(For the 00Z TAFS through 00Z Friday evening) Issued at 628 PM CDT Thu Jul 8 2021 VFR conditions are forecast throughout the period. winds will be veering from south-southeast to northwest throughout the day on Friday. Some thunderstorms are possible near KOFK after 0600Z, KOMA after 1000Z and KLNK after 1200Z. Some brief MVFR conditions may impact KOMA, KOK, and KLNK if a storm moves right across the field. && .OAX WATCHES/WARNINGS/ADVISORIES... NE...None. IA...None. && $$ DISCUSSION...CA AVIATION...Smith
Area Forecast Discussion
National Weather Service San Angelo TX
612 PM CDT Thu Jul 8 2021 ...New AVIATION... .SHORT TERM... (This evening through Friday) Issued at 111 PM CDT Thu Jul 8 2021 Visible satellite imagery this afternoon shows a nice field of scattered cumulus having developed across West Central Texas. However, RAP forecast soundings indicate that there will be enough convective inhibition and subsidence from the expanding and strengthening upper level ridge across the Southwest CONUS to inhibit shower/thunderstorm development this afternoon, except for possibly one or two isolated cells. With the stronger upper level ridge and warming of the 850 mb thermal ridge, temperatures as of 1 pm are at least a few degrees warmer than 24 hours ago. Expect highs today a few degrees warmer than yesterday, with highs in the 86-92 degree range. Low clouds are likely to develop across the region from southeast to northwest tonight through the early morning hours Friday morning as a short-wave disturbance rotates into the Hill Country around a mostly stationary upper low over South Texas. This disturbance may also bring some isolated to scattered showers and thunderstorms to the I-10 corridor and Northwest Hill Country late tonight through Friday afternoon. With the increase in cloud cover brought about by this disturbance and the associated enhanced, moist easterly to southeasterly flow, expect slightly cooler temperatures (highs in the 84-90 degree range) Friday despite the stronger 500 mb ridge aloft. Meanwhile, lows tonight will be mild once again, and perhaps a little warmer than last night due to the aforementioned clouds/moisture (lows in the upper 60s/low 70s). && .LONG TERM... (Friday night through next Thursday) Issued at 158 PM CDT Thu Jul 8 2021 Other than an isolated thunderstorm across the I-10 corridor, high pressure will largely keep scattered thunderstorms from developing through Saturday. However, a low pressure system moving across the Great Plains will swing a cold front into the region on Sunday. This will add support for additional thunderstorms to develop across all of West Central Texas on Sunday and Sunday night. Highs will likely remain in the upper 80s to middle 90s. && .AVIATION... (00Z TAFS) Issued at 612 PM CDT Thu Jul 8 2021 MVFR conditions developing after midnight, lowering to IFR around sunrise. IFR to MVFR ceilings will persist through at least midday at far southern terminals. A few showers are also possible tomorrow afternoon for these locations. && .PRELIMINARY POINT TEMPS/POPS... Abilene 69 88 72 92 / 0 5 5 5 San Angelo 69 88 72 92 / 0 10 10 10 Junction 70 84 72 89 / 10 40 30 20 Brownwood 70 86 73 92 / 5 10 10 10 Sweetwater 69 88 71 91 / 0 0 0 5 Ozona 68 87 71 89 / 5 20 20 10 && .SJT WATCHES/WARNINGS/ADVISORIES... None. && $$ SHORT TERM...SJH LONG TERM....41 AVIATION...SK