Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 07/06/21

Area Forecast Discussion...UPDATED
National Weather Service Aberdeen SD
927 PM CDT Mon Jul 5 2021 .UPDATE... Issued at 924 PM CDT Mon Jul 5 2021 Forecast appears to be in fine shape, with agreement from latest HRRR model runs, so no major changes expected. Temperatures look about right. Showers/thunderstorms should continue to move across the CWA overnight as system aloft moves east/se over the region. && .SHORT TERM...(This Evening through Tuesday Night) Issued at 350 PM CDT Mon Jul 5 2021 Main challenges during the short term revolve around thunderstorm activity, both ongoing and anticipated, in terms of severe potential and QPF. The most intense thunderstorms this morning and afternoon have been in the vicinity of a stationary front, across south central South Dakota, where SBCAPE of around 3000 J/kg has combined with just enough deep layer shear for some pulsing multicell storms. Slow storm motions have led to locally heavy rain and potential flooding as well. This activity is expected to track southeast into areas of higher instability along the stationary front. Stronger forcing in the form of a shortwave aloft and a trough of low pressure at the surface is expected to trigger additional convection beginning around 6pm along and west of the Missouri River. While effective bulk shear will be in the 35 to 40kt range across north central SD, instability may be a bit lacking given prior convection (still have marginally steep mid-level lapse rates). A couple stronger storms certainly have the potential for large hail and damaging winds. By tonight, a widespread area of showers and thunderstorms is expected to track from west to east across the area. Southerly flow will continue Mean PW values of 1.5 to 1.75in are in the 97.5 to 99.5 percentile for this time of year, which aids in confidence for at least locally heavy rain potential. Ensemble guidance continues to highlight the northern CWA as having the greatest potential for the highest QPF, where over an inch could fall in some areas. Further south, a quarter to half an inch of rain plus is more likely. Precipitation will exit to the east of the forecast area Tuesday afternoon, leaving much cooler temperatures in its wake with highs in the low to mid 70s. .LONG TERM...(Wednesday through Monday) Issued at 350 PM CDT Mon Jul 5 2021 The main highlights in the out periods surround precipitation chances mainly Thursday afternoon through Saturday, as well as temperatures throughout the period. The next low pressure system to potentially impact some of most of the CWA is progged to enter the scene from the northwest, with a notable surface low pressure reflection developing into Thursday while low to mid-level waa is taking shape. When the main upper level low pressure circulation works through the region Friday into Saturday morning, additional lighter precipitation amounts will be possible. Beyond that, much of the rest of Saturday through next Monday should be dry while high pressure at the surface and aloft take up residence across the region. For much of the extended forecast period, the CWA should be experiencing temperatures near normal for early July. Perhaps the western third of the CWA (Missouri River valley westward) ends up running above climo normal Wednesday, Thursday and early next week. && .AVIATION...(For the 00Z TAFS through 00Z Tuesday Evening) Issued at 619 PM CDT Mon Jul 5 2021 Terminals KABR,KATY,KPIR,KMBG Coverage of showers and storms will gradually increase from west to east this evening and overnight. After midnight, IFR cigs are expected to develop across the area, and then linger through Tuesday morning. Some improvement in cigs will come in the afternoon. && .ABR WATCHES/WARNINGS/ADVISORIES... SD...None. MN...None. && $$ UPDATE...TDK SHORT TERM...Lueck LONG TERM...Dorn AVIATION...TDK
Southeast Alaska Forecast Discussion
National Weather Service Juneau AK
257 PM AKDT Mon Jul 5 2021 .SHORT TERM.../Through Wednesday night/...Most of the panhandle enjoyed a nice sunny day today as the marine layer clouds retreated a bit allowing Angoon, Hoonah, Gustavus, and Sitka to get in on the sunshine. The only exception is Yakutat, which remains in the marine layer with off and on drizzle and mist. Typical afternoon breezes of around 15kt formed as expected across the region, with Cross Sound a little stronger. Some folks may have noticed that the blue skies aren`t 100% blue, with a haze across the region. The HRRR Vertically Integrated Smoke product shows some smoke advecting into the region from fire activity in B.C. and Washington state. The smoke is high in the atmosphere, so not expecting any health or visibility impacts at the surface. An area of vorticity near Hyder and the Misty Fjords is on track to cross the border this evening. That combined with the heat of the day (Stewart B.C. is 81 currently) means that the convective potential is elevated in this area this evening. The 12z sounding from Annette this morning does show an area of CAPE above 7000 feet that any thermals off the higher mountains of Misty Fjords could tap into this afternoon. In light of this, the area of showers and slight chance of Thunderstorms for this afternoon and evening remains unchanged. Satellite has registered a few strikes about 50 miles to the east of Hyder, so this forecast seems on track. Overnight tonight, the marine stratus layer and ares of drizzle are expected to encroach into the inner channels again. The clouds should reach as far east as Chatham Strait before retreating again tomorrow. Any thundershowers that develop in the Hyder area are expected to dissipate toward sunset. Change starts to creep into the forecast for Tue night as the surface ridge that has been keeping most of the rain well west of the area starts to break down. Overall flow starts to become more SW rather then the NW it has been and a weak front advances on the northern gulf coast. Yakutat will see its drizzle become a chance of rain as early as Tue afternoon with the northern panhandle starting to see some chance of rain by Wednesday. The initial feature is rather weak however so any rain the does fall is expected to be rather light. The forecast changes today included fine tuning the sky cover and chance of thunderstorms in the Hyder area, matching the min/max temperatures up with the cloud cover (or lack of) and updating the drizzle and low stratus chances along the coast. Models are in good agreement with the synoptic setup for throughout the short term forecast period, but there are differences in the timing of when and how much precipitation will fall after the ridge breaks down. .LONG TERM...Models are in good agreement for an upper-level low that will support pushing moisture to Yakutat at the start of the long term. The timing of this wave of precipitation is on track to reach the northern half of the panhandle on Wednesday. Light rainfall is expected at this time, with total amounts remaining under a quarter of an inch. Confidence is increasing in the timing and location of this band of precipitation. A second band of precipitation Thursday looks like a repeat of Wednesday, but is expected to reach the southern panhandle this time around by late Thursday. The southern panhandle will likely dry out quickly, but may see a slight chance of precipitation from Friday to Saturday as onshore flow remains. The Climate Prediction Center has near-normal temperatures and below-normal precipitation in the southern panhandle and slightly below-normal temperatures and near normal precipitation in the northern portion, which matches what guidance is predicting. For the extended long term grids starting on Saturday, nudged the WPC towards the ECMWF to keep the chance/slight chance for precipitation in the forecast due to the high uncertainty. The next system in question is a surface low in the Gulf moving towards the panhandle at the start of the week after next. Low confidence in timing and the strength of the low. && .AJK WATCHES/WARNINGS/ADVISORIES... PUBLIC...None. MARINE...None. && $$ BFL/KRT Visit us at
National Weather Service Albany NY
1028 PM EDT Mon Jul 5 2021 .SYNOPSIS... A warm and humid airmass will return for Tuesday and Wednesday. Showers and thunderstorms will be likely at times, and some may be strong in the afternoon and evening. It will not be as warm Thursday with rain expected. && .NEAR TERM /UNTIL 6 AM TUESDAY MORNING/... .UPDATE...Area of convection has moved into the western part of the St Lawrence River valley late this evening. The main cluster of stronger storms has a bowing structure near the Jefferson/St Lawrence border and has had a history of producing 30-45 mph winds. It appears the apex of the bow will pass by to the north of Herkimer County, but additional cells have developed farther south along the outflow boundary and may move into the western Adirondacks and western Mohawk Valley. SPC Mesoanalysis and 00Z KALY sounding showing around 500-1000 J/Kg of MLCAPE in our forecast area with fairly weak low level lapse rates, so expect an eventual weakening trend. Increased POPs in these areas to account for activity developing upstream. Brief wind gusts around 30 mph and downpours/lightning will remain possible. Chances for convection decrease for areas farther south/east, but will still maintain slight chance if a few remnant showers or storms last well into the overnight hours with favorable environment aloft. .PREVIOUS [0757]...Made just some minor adjustments based on obs and trends this evening. Watching a cluster of convection north of Lake Ontario moving eastward. This activity is associated with a short wave trough tracking into the lower Great Lakes. Best instability expected to remain to our west, so activity should generally weaken as it approaches. However, still expecting scattered showers and thunderstorms to move across the western Adirondacks late this evening into the overnight hours. Will continue to monitor this evening. Upstream shortwave trough over Lake Superior is generating a loosely organized area of convection over Lake Huron/Georgian Bay. These storms are occurring within an area of steep midlevel lapse rates (e.g., 7.7 K/km on the 12Z KAPX sounding) in a pocket of 1.5-2.0 inch PWATs. This area of convection is expected to continue moving eastward tonight, likely moving into portions of the southern Adirondacks after midnight. There is a chance a couple of these storms could be on the stronger side as some of the steeper midlevel lapse rates fold into the area, leading to around 1000 J/kg MUCAPE. Stronger storms could contain hail, although fairly weak deep-layer shear of around 25 kt should limit the threat. An isolated gusty wind or two is possible as well despite the storms likely remaining somewhat elevated. Elsewhere, a moderate southerly wind will keep temps considerably milder than previous nights, with lows mainly in the 60s. && .SHORT TERM /6 AM TUESDAY MORNING THROUGH WEDNESDAY NIGHT/... Heat Advisory in effect for Mid-Hudson Valley 11 am to 7 pm Tuesday... An active weather period is in store in the short term with a few rounds of convection possible along with heat concerns. Tuesday, a few showers/storms may linger in the morning mainly north of I-90 associated with the midlevel impulse discussed in the near term section. This activity is expected to weaken as the wave exits. Warm advection overnight will have boosted 850 mb temps into the mid to upper teens. Southern zones, more removed from the morning clouds/showers and next round of convection, will likely be able to mix to this level, supporting high temps in the low 90s. Dewpoints may lower somewhat, but are likely to remain at least in the upper 60s, yielding heat index values of 95-100 over the Mid-Hudson Valley, prompting a Heat Advisory. Southern Litchfield County will be close to criteria Tue/Wed, but we opted not to include them in collaboration with WFOs BOX/OKX. Strong surface heating, moist low levels and respectable midlevel lapse rates are expected to combine to result in SBCAPE of 1500-2500 J/kg roughly from the Mohawk Valley/Capital District/southern VT on south during the afternoon. Point soundings off the HRRR and NAM3 indicate potential for DCAPE around 1000 J/kg as low levels steepen as well. Also, despite deep layer shear being weak at around 20 kt, there is a belt of 25-35 kt of 850-700 mb flow. These factors suggest a damaging wind threat in any stronger updrafts. However, both low and midlevel forcing are weak, and it is unclear how or if morning activity will impact the convective environment in the afternoon. CAMs show a variety of solutions with respect to how the afternoon will play out, but current thinking is that storms may form in the early afternoon along possible convergence due to an outflow boundary from the morning convection or differential heating boundary. Some CAMs suggest storms congealing into bowing segments and pushing south into the better instability, although it is unclear if this will occur in our area or to the south. Bottom line is that there is enough evidence in a damaging wind threat to upgrade the convective outlook to SLGT from the Mohawk Valley/Capital District/southern VT on south in collaboration with SPC and neighboring offices. Main threat period is 1-8 pm. Otherwise it will be a bit breezy, very warm and humid with southwesterly winds gusting to 25 mph at times. Subsidence is expected to build in Tuesday night with zonal flow overhead. Lows expected to be fairly mild mainly in the 60s. Wednesday into Wednesday night, midlevel flow strengthens and backs a bit in response to increased troughing in the Upper Midwest. Low confidence with how this period will play out. It does look like another hot and humid day from I-90 south, and additional Heat Advisories are possible. The atmosphere will again become very unstable from I-90 south. North of I-90 will be where the best chance of precipitation will be in the morning hours along a fairly tight low level baroclinic zone and beneath an equatorward entrance region of the upper jet. High pressure to the north will allow cooler air to filter in from the north, with the 12Z.05 NAM12 quite aggressive with this scenario, dropping temps 10 degrees at ALB from 18-21Z. Think this is probably overdone, but highs north of I-90 are expected to be cooler than Tuesday with lower humidity. Along and south of I-90 in the unstable airmass, a convective trigger is a question mark, but could be along the leading edge of the low-level cooler air advancing from the N/NW. MRGL risk for severe in effect which seems fine at this point until more certainty can be gained. Wednesday night, PWATs increase ahead of the approaching midlevel trough as 850 mb inflow increases modestly. Somewhat of an overrunning signal as well, and will message scattered to numerous showers and possibly an isolated thunderstorm. Lows expected to range from the upper 50s to upper 60s. && .LONG TERM /THURSDAY THROUGH MONDAY/... The main focus for the long term will be on the Thursday into Friday time frame when moisture streaming northward from the Gulf of Mexico and Tropical Cyclone Elsa could interact with an incoming trough and jet streak to produce periods of widespread rainfall. Improving conditions are expected over the weekend as the trough gradually exits the region and high pressure builds overhead. However, yet another warm front looks to return early next week increasing chances for precipitation. Read on for details. We begin the long term on Thursday with the latest guidance in good agreement that a broad shortwave trough from the Midwest will be heading eastward and southwesterly flow developing in response downstream over the Northeast. During this period, Tropical Cyclone Elsa, according to the latest National Hurricane Center forecast, is expected to be tracking through or exiting off the coast of the Southeast U.S. While the center of Elsa should still be far to our south, the deep south-southwest synoptic flow could help advect tropical moisture northward. Guidance also shows an anticyclonic curved jet streak in place across southern Canada, placing the Northeast in the right entrance. The combination of tropical moisture in the presence of synoptic forcing has increased confidence that periods of moderate to even heavy rainfall could result Thursday into Thursday night. Therefore, we continue to show likely and even categorical POPs throughout the region for this period with some enhanced wording to highlight the potential for heavy rain at times. Some hints of a PRE (Predecessor Rainfall Event) are also in place but it is too early to make this distinction at this lead time. Favorable conditions for steady rainfall continue into Friday as our broad trough will still be upstream over the Great Lakes/southern Canada and Elsa, as per the latest NHC forecast, continues to track near or just off the NJ/Long Island coast. Depending on how much the incoming trough amplifies the downstream ridge over the western Atlantic will determine if the trough will capture Elsa and steer it closer to the coast or if Elsa will outrun it and escape out to sea. The GFS is still the most progressive, suggesting Elsa is near Cape Code and the islands by 12 UTC Friday while the CMC and ECMWF are slower and only show it off the NJ coast at this time step. However, all three pieces of guidance suggest Elsa will be close enough to the coast that strong southerly flow will be able to advect tropical moisture through at least parts of eastern NY and western New England on Friday. In addition, a cold front will be gradually pushing through the region at this time which could help focus the rainfall where there is the best low level convergence. By Saturday, Elsa should finally be out to sea, however, our broad trough looks to be overhead. West to southwest winds in place could still provide enough support for some diurnally driven showers and storms. This is why we continue to carry slight chance and chance POPs Saturday afternoon. Outside of any precipitation, temperatures should be seasonable with dew points still a bit elevated making it still feel a bit muggy. Improving conditions finally arrive Sunday as high pressure looks to build overhead and we lowered POPs compared to the blended guidance. There is a warm front positioned to our south but recent trends keep this boundary to our south until the new work week begins. && .AVIATION /02Z TUESDAY THROUGH SATURDAY/... Mainly VFR conditions expected to prevail tonight, although a brief period of MVFR cigs is possible at KPSF over the next 1-2 hours and overnight at KGFL. Otherwise, high and mid level clouds will gradually increase ahead of a convective complex approaching from just north of Lake Ontario. Showers and storms will likely not hold together long enough to reach the TAF sites, although a leftover shower may get close to KGFL/KALB so have mentioned VCSH there. Any BKN-OVC stratus clouds should dissipate to scattered coverage during the morning, with some possible mid level convective debris clouds around. The main concern for the afternoon to early evening hours is the potential for strong to severe thunderstorms. Since they are expected to occur during the last 6 hours of the TAF period, will mention PROB30 for now and can be refined in subsequent forecasts. Brief MVFR or even IFR conditions will be possible with any TSRA, as well as downpours and strong gusty winds. Winds tonight will be southerly around 5-10 kt, becoming southwest and increasing to 10-15 kt by early Tuesday afternoon with occasional gusts of around 20-25 kt. Outlook... Tuesday Night: Low Operational Impact. Slight Chance of SHRA...TSRA. Wednesday: Moderate Operational Impact. Chance of SHRA...TSRA. Wednesday Night: Moderate Operational Impact. Likely SHRA...TSRA. Thursday: High Operational Impact. Likely SHRA...TSRA. Thursday Night: High Operational Impact. Likely SHRA...TSRA. Friday: Moderate Operational Impact. Chance of SHRA...TSRA. Friday Night: Low Operational Impact. Slight Chance of SHRA. Saturday: Moderate Operational Impact. Chance of SHRA...TSRA. && .FIRE WEATHER... A very warm and humid airmass will be in place Tuesday and Wednesday with minimum RH values mostly in the 50 to 60 percent range. Scattered showers and thunderstorms are possible at times through this period, although it will not be a washout. Breezy southwesterly winds are likely on Tuesday. Rain will become more widespread Thursday. && .HYDROLOGY... Scattered showers and thunderstorms are possible tonight through Wednesday with typical summertime downpours possible and no widespread hydro issues anticipated. Rain is expected to be more widespread Thursday into Thursday night as an approaching trough interacts with tropical moisture. Urban and poor drainage flooding along with isolated flash flooding will be possible. According to MMEFS data, main stem river flooding is unlikely at this time, but this will continue to be monitored. For details on specific area rivers and lakes, including observed and forecast river stages and lake elevations, please visit the Advanced Hydrologic Prediction Service /AHPS/ graphs on our website. && .ALY WATCHES/WARNINGS/ADVISORIES... CT...None. NY...Heat Advisory from 11 AM to 7 PM EDT Tuesday for NYZ059-060- 064-065. MA...None. VT...None. && $$ SYNOPSIS...Thompson NEAR TERM...Thompson/JPV SHORT TERM...Thompson LONG TERM...Speciale AVIATION...JPV FIRE WEATHER...Thompson HYDROLOGY...Thompson
Area Forecast Discussion
National Weather Service Boston/Norton MA
952 PM EDT Mon Jul 5 2021 .SYNOPSIS... A warm front moves through tonight followed by hot and humid conditions Tuesday and Wednesday with scattered afternoon and evening showers and thunderstorms. Some of the storms on Tuesday will likely be strong to severe with damaging wind gusts and torrential downpours. A cold front will stall south of Southern New England Thursday and Friday with more showers and thunderstorms, then Elsa or its remnants is expected to track south of New England Thursday night into Friday. the front then moves through late Friday or Saturday, then stalls to our south. Expect scattered showers/thunderstorms to move along the front. && .NEAR TERM /UNTIL 6 AM TUESDAY MORNING/... 950 pm Update... Warmer and more humid tonight compared to previous nights, as southerly flow advecting dew pts in the 60s across the region. Given the increased moisture, be alert for areas of fog overnight into early tomorrow morning. Scattered showers and thunderstorms currently from just NW of Albany, to northern NY state, is associated with mid level warm front. This shows up nicely on SPC mesoanalysis with good thermal packing at 850 mb and tight PWAT gradient across New England into NY. A few of these showers/T-storms may enter our region overnight, especially across northern MA. Previous forecast captures this nicely, thus no major changes with this update. Previous Discussion... High pressure will continue to move east and further away from the region tonight. The result will be a moist southerly low level flow of air along with a scattered to broken deck of clouds. Dewpoints of 60+ will result in milder temperatures than the last few nights. Overnight low temps will bottom out mainly in the middle/upper 60s. While there is a modest LLJ that develops overnight it will be somewhat veered out. This coupled with a shortwave and its associated forcing passing well to our north should result in dry weather dominating overnight. That being said there is some modest elevated instability and a few brief showers along with the low risk for an isolated t-storm or two is possible. Opted to cover this with just low pops in the grids for now. && .SHORT TERM /6 AM TUESDAY MORNING THROUGH TUESDAY NIGHT/... Highlights... * Scattered strong-severe thunderstorms between 1 & 8 PM Tuesday * Strong to damaging wind gusts are the main risk * Brief torrential rain/localized street flooding a secondary concern Tuesday... 1) Heat & Humidity: A return to very warm/hot & humid weather arrives on Tuesday. Southwest flow around a ridge of high pressure will result in 850T climbing to around +18C. This coupled with good mixing should yield afternoon high temperatures in the upper 80s and lower 90s, except upper 70s to the middle 80s along the immediate south coast, Cape & Islands. Dewpoints near 70 will result in Heat Indices in the middle to upper 90s in many areas away from the south coast. Later shifts will have to consider Heat Advisories given the potential for these values to be reached again on Wed. The one thing that will take a little bit of an edge off the humidity om Tuesday will be gusty SW winds. Bufkit shows excellent mixing with southwest wind gusts of 20 to 30 mph and perhaps near 35 towards the southeast New England coast and the typical spots near Falmouth. 2) Severe Weather: The main concern will revolve around the likelihood of scattered strong to severe thunderstorms; roughly between 1 and 8 PM on Tuesday. This a result of an approaching shortwave in westerly flow aloft. Given heat & humidity; the SPC SREF indicates modest probabilities of MLCapes exceeding 2000 J/KG across a good portion of the region. Guidance is also forecasting steep low level lapse rates with a ribbon of 30-40 knots of flow in the 850-700 mb layer. The one limiting factor is weaker winds in the 500-600 mb layer, which keeps effective shear values lower than we normally want to see for a severe weather event. That being said, high resolution CAM simulations are pretty aggressive with impressive 2-5 KM updraft helicity swaths depicted by the 3 KM NAM and even the 18z HRRR to some extent. The 4 hour max updraft product is lit up quite a bit on the HREF too across southern New England. So in a nutshell, scattered strong to severe thunderstorms are expected to sweep across the region from northwest to southeast between 1 and 8 pm Tuesday. Steep low level lapse rates along with modest DCape values > 800 J/KG suggest strong to damaging wind gusts are the main threat with this activity. While storms will be moving, PWATs near 2 inches also support brief torrential rain/localized street flooding particularly if activity moves across urban centers. Lastly, we can not rule out an isolated large hail report or two given even modest steep ML Lapse rates. We opted to included enhanced wording in the forecast. Tuesday night... Lingering convection should come to an end by early-mid evening even along the south coast. Otherwise, dry and somewhat muggy weather is expected Tuesday night with low temperatures only dropping into the upper 60s and the lower 70s. && .LONG TERM /WEDNESDAY THROUGH MONDAY/... Big Picture... Zonal flow across the Northern USA while a 594-Dm upper ridge sits over the Desert Southwest. One shortwave in the zonal flow moves east over New England Thursday night/Friday, turning our upper flow more from the southwest. This may also affect the track of Tropical Storm Elsa as it passes offshore. After the shortwave moves past, the flow briefly turns from the northwest. West Atlantic upper ridge then builds over Srn New England Sunday and Monday. Contour heights at 500-mb are approaching their climatological max values, in the upper 570s Dm to low 580s Dm. Values are forecast to remain in that range Wednesday through Saturday, then increase to around 590 Dm by Monday. Expect seasonably warm temps during the week, except closer to the average as the trough and Elsa move past. Relatively good agreement in the mass fields through Saturday. Even after that, fair agreement on Sunday and Monday, including an approaching weather system later next Monday. Overall confidence is moderate-high, except just moderate for Sunday and Monday. Details... Wednesday... Offshore high pressure continues to bring very warm humid air into SRn New England. The airmass remains quite unstable with CAPE of around 1500 J/Kg and LI values of minus 3 to minus 5. PW values of 1.5 to 1.8 inches. Expect scattered showers/thunder, some with local downpours. Dew points will be upper 60s and lower 70s, so expect high to oppressive humidity. The mixed layer reaches to near 800-mb, with temps of 14C at that level, equiv to 19C at 850-mb. Expect max temps of 90 to 94, cooler South Coast. Based on the temperature and dew point, expect Heat Index values 90 to 95 most places, but potentially 94 to 98 in CT and parts of RI. Will hold back on a Heat Advisory for now, but will be monitoring. Thursday-Friday... Tropical air remains in place as the approaching shortwave turns the upper flow from the southwest. Cold front stalls north and west of Srn New England, but is close enough that it could generate a few thunderstorms, especially in Nrn Mass. A few local downpours are possible due to the tropical air. Meanwhile, Tropical Storm Elsa or its remnants will move up the East Coast, but looks to pass well offshore of Srn New England Thursday night..and even southeast of the 40/70 benchmark. This path, and geographical suggestions that it will be starting a mid-latitude transition, point to winds mostly on the southeast side of the system while heavy rain will be mostly on the northwest side...catching Srn New England. Expect local downpours Thursday night and Friday morning. The weekend and Monday... The stalled cold front moves south through Srn New England and then stalls again, this time offshore. Upper ridge from the ocean will maintain little push to move the front onward. Jet segments moving through the upper flow may generate showers of and on through the period. Temperatures will remain warm in the 80s. Dew points will drop back a little, but values will remain in the 60s so expect the humidity to remain noticeable. && .AVIATION /02Z TUESDAY THROUGH SATURDAY/... Forecaster Confidence Levels. Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. 02z update... Showers and T-storms currently across NY state will mainly track across central and northern NY overnight, weakening with time as well. Some of the activity may track as far south as northern MA. This is consistent with previous forecast, so no major changes with this forecast update. Earlier discussion below. ================================================================= Tonight...Moderate Confidence. VFR conditions likely dominate. There is a chance for a period of MVFR ceilings, especially eastern New England. But areal coverage and duration of any low clouds remains uncertain. A few brief showers with the low risk for a rumble of thunder are possible, but mostly this will be north of Massachusetts. The vast majority of the night will feature dry weather and VFR. South to Southwest winds 5 to 10 knots, but may become a bit stronger after midnight in the high terrain and southeast New England coast. Tuesday...High Confidence. Mainly VFR conditions in the morning. Scattered strong-severe thunderstorms are expected to sweep across the region from northwest to southeast...roughly from 17z through 00z. Localized brief strong wind gusts and torrential rainfall may result in a short period of IFR-LIFR conditions at some terminals. Otherwise, VFR conditions dominate during the afternoon but with SW wind gusts of 20 to 30 knots developing. The strongest of those wind gusts will be across southeast New England. Tuesday night...High Confidence. Any lingering showers/t-storms will depart the south coast by early-mid evening. Otherwise, mainly VFR conditions with WSW wind gusts generally less than 10 knots except a bit stronger across the Cape/Islands. KBOS TAF...High Confidence in TAF. Biggest concern is a cluster of strong-severe thunderstorms in the vicinity of and/or crossing the terminal between 18z and 22z on Tuesday. KBDL TAF...High Confidence in TAF. Biggest concern is a cluster of strong-severe thunderstorms in the vicinity of and/or crossing the terminal between 18z and 22z on Tuesday. Outlook /Wednesday through Saturday/... Wednesday: VFR with local MVFR. Chance SHRA, isolated TSRA. Local downpours. Wednesday Night: Mainly VFR, with local MVFR possible. Chance SHRA, isolated TSRA. Thursday: Mainly VFR, with areas MVFR possible. SHRA. Thursday Night: Mainly VFR, with areas IFR possible. SHRA likely. Friday: Mainly VFR, with local IFR possible. Chance SHRA. Friday Night through Saturday: Mainly VFR, with local MVFR possible. Chance SHRA. && .MARINE... Forecaster Confidence Levels. Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Tonight...High Confidence. High pressure moving east of the waters will generate SW winds of 10 to 15 knots tonight. We may see some 20-25 knot gust develop toward daybreak along with some marginal 5 foot seas across our southern waters. Overall though expect winds and seas to generally remain below small craft thresholds tonight. Tuesday...High Confidence. A modest low level jet coupled with excellent mixing over the land will generate SW wind gusts of 20 to 30 knots developing Tue morning and continuing through the afternoon. The strongest of the winds will be near shore and especially towards the southeast New England where some marginal near shore Gale force gusts can not be ruled out for Buzzards Bay and Nantucket sound areas. Regardless, small craft headlines are posted for all waters and mariners should expect gusty SW winds and choppy seas. Also, scattered strong thunderstorms during the mid-late afternoon and early evening hours may impact the waters. Frequent lightning and strong winds may impact pose a risk to those on the waters as well...especially across our near shore waters north of the Plymouth area. Tuesday night...High Confidence. Any remaining convection should dissipate/weaken across the southern waters by mid-evening. Small craft wind gusts should also diminish, but lingering 4-6 foot seas may persist across our southern outer-waters. Outlook /Wednesday through Saturday/... Wednesday: Winds less than 25 kt. Seas up to 5 ft. Slight chance of rain showers. Wednesday Night: Winds less than 25 kt. Areas of seas approaching 5 ft. Slight chance of rain showers. Thursday: Winds less than 25 kt. Seas up to 5 ft. Chance of rain showers. Thursday Night: Winds less than 25 kt. Seas up to 5 ft. Rain showers. Friday: Winds less than 25 kt. Seas up to 5 ft. Chance of rain showers. Friday Night: Winds less than 25 kt. Areas of rough seas. Chance of rain showers. Saturday: Winds less than 25 kt. Seas up to 5 ft. Chance of rain showers. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...Air Quality Alert from 11 AM to 11 PM EDT Tuesday for CTZ002>004. MA...None. RI...None. MARINE...Small Craft Advisory from 8 AM to 8 PM EDT Tuesday for ANZ230>237-251. Small Craft Advisory from 5 AM Tuesday to midnight EDT Tuesday night for ANZ250. Small Craft Advisory from 5 AM Tuesday to 8 AM EDT Wednesday for ANZ254>256. && $$ SYNOPSIS...WTB/Frank NEAR TERM...WTB/Frank/Nocera SHORT TERM...Frank LONG TERM...WTB AVIATION...WTB/Frank/Nocera MARINE...WTB/Frank
Area Forecast Discussion
National Weather Service Burlington VT
1012 PM EDT Mon Jul 5 2021 .SYNOPSIS... A warm front will produce scattered showers with a few embedded thunderstorms overnight across northern New York with the activity decreasing in areal coverage over Vermont by Tuesday morning. A warmer night with some patchy fog is possible in eastern Vermont, as temperature cool into the upper 50s to upper 60s. After a few lingering morning showers, intervals of sunshine will develop as temperatures warm back into the 80s. A few additional showers and storms are possible on Tuesday afternoon. Forecast continues to support a widespread rain event on Thursday into Friday. && .NEAR TERM /THROUGH TUESDAY NIGHT/... As of 1002 PM EDT Monday...Watching closely a cluster of showers/tstorms over Saint Lawrence County. KTYX sampling inbound winds 45+ knots at around 5000 ft just to the south of Saint Lawrence County, however RAP soundings indicating inversion below 3000 ft preventing the momentum aloft from reaching the surface. Thus, still thinking severe threat remains minimal...though some gusts up to around 30 knots and some pea sized hail are possible within the cluster. Complex will continue to weaken as it progresses eastward and instability continues to wane. Previous discussion follows. Fcst focus overnight wl be potential for convection acrs northern NY into VT, along with impacts clouds/winds have on temps. Water vapor/satellite and radar show complex showers with thunderstorms over the northern-central Great Lakes. This activity is progged to angle east-southeast toward northern NY btwn 03z-06z and into the CPV after 06z. Still some question about how well complex holds together acrs VT, so have continued with likely pops northern NY, tapering off to chc pops in VT. Have noted SPC place SLV into marginal risk overnight for svr. Feel the risk for severe is very low, but not zero, given axis of elevated CAPE of 700 to 1000 J/kg with 0 to 6 km shear of 25 to 30 knots, associated with developing 850mb to 700mb jet of 35 to 45 knots. Best potential for a stronger storm, which may require an spc would be over the SLV btwn 04z-07z tonight. The instability/shear and dynamics for weakening s/w is less acrs VT, so mainly anticipating showers with an embedded rumbles of thunder. Have noted soundings at VSF showing a shallow/sharp llvl thermal inversion developing below 925mb this evening, with nearly saturated bl conditions, supporting the idea of patchy fog btwn 03-09z, before high clouds and winds increase toward sunrise. Have patchy fog in the CT and Passumpsic Valleys. Sfc dwpts already in the lower 60s SLV and southwest winds, expecting lows near 70F SLV/CPV with coolest values in the mid/upper 50s acrs eastern VT, including the NEK. Tuesday best short wave and axis of better 850 to 700mb moisture is east-southeast of cwa by 15z, resulting in large scale subsidence/drying aloft. Soundings show a very deep dry layer btwn 850-500mb developing, with some mixing of drier air toward the sfc, lowering dwpts back into the 60s. Many of the CAM models show favorable sfc based cape profiles in the 1800 to 2400 j/kg range, while axis of best 0 to 6 km shear of 25 to 35 knts is either displayed to our north our southeast. Furthermore, sfc convergence with boundary is minimal, so general idea of decreasing pops into the 15 to 25% range on Tues aftn looks good. Tuesday wl not be a washout with very limited areal coverage of showers/storms expected. Given instability cannot completely rule out a stronger storms, but with minimal upstairs support probability is low.Temps wl warm back into the upper 70s to mid/upper 80s. A spot 90F is possible with better mixing profiles in the aftn here at BTV. Tues night wl be quiet with any showers/storm dissipating by sunset. Lows generally in the mid 50s to lower 60s. && .SHORT TERM /WEDNESDAY THROUGH WEDNESDAY NIGHT/... As of 316 PM EDT Monday...Main focus on Wednesday will be on a shallow W-E oriented cold front that is expected to bisect the North Country throughout the daylight hours. Light north to northeast surface winds and abundant low clouds are expected across the northern half of the forecast area, yielding well-below normal daytime high temperatures - only in the mid-upper 60s near the International Border, and only in the lower 70s across most of the Champlain Valley. May see a few showers within the frontal zone, but overall forcing is limited for much rainfall. Limited QPF to 0.05" or less across northern areas on Wednesday. Meanwhile, appears portions of s-central VT will remain south of the cold front, with partly sunny conditions and better surface heating. Should see south-central VT valleys warming into the upper 70s to lower 80s based on present indications. Given frontal location and strong differential heating, can`t rule out isold thunderstorm development across Rutland/Windsor counties Wednesday afternoon. Best instability mainly expected to remain south of our forecast area. As such, not expecting much of a severe tstm threat attm. Should see mostly cloudy and cool conditions continue into Wednesday night as sfc frontal zone shifts southward and stalls across e- central NY into central New England. Lows generally expected in the 50s areawide. Winds above the shallow frontal zone, in the 950-800mb layer, begin to veer south to southeasterly toward daybreak Thursday, and may begin to generate a few showers toward sunrise with isentropic ascent across the frontal sfc. The majority of the rainfall is expected to hold off until the daylight hours Thursday, but there is an increase to 30-50% PoPs, especially southern areas, after 09Z Thursday. && .LONG TERM /THURSDAY THROUGH MONDAY/... As of 316 PM EDT Monday...A widespread rainfall is still expected Thursday into Thursday night, with rainfall amounts perhaps exceeding 1" across portions of the Adirondacks and central/srn VT. Per NHC guidance, as Elsa tracks newd across the southeastern US and Mid-Atlantic coast, the global NWP guidance is consistent in showing aspects of a Predecessor Rain Event (PRE) well removed and to the NW from the tropical system. Our rainfall will be driven by right entrance region of a strong 250mb jet juxtaposed with the lingering low-level frontal zone and a 850-700mb deformation zone that is forecast to intensity during the daytime hrs. Both the 12Z GFS and NAM indicate elevated instability in the frontal zone, so may see some embedded convective elements within larger swath of precipitation expected across nrn NY and VT. In additional to 80-90% PoPs, included chance of thunderstorms for Thursday afternoon into Thursday evening given CAPE for parcels rooted near 850mb. Mesoscale details aren`t clear yet, but appears enough ingredients in place for an axis of rainfall amounts 1-1.5" across portions of the CWA. Overall, a much needed rainfall given antecedent conditions, and don`t foresee any flooding threat attm with generally light to moderate rainfall rates. We`ll monitor for any locally heavier rainfall rates in aforementioned convective elements, but with 6-hr flash flood guidance expected in the 2.5-3" range, will take a lot to yield any flood threat. High temperatures on Thursday generally expected in the upper 60s to lower 70s, with lows Thursday night 55-60F. Best large-scale forcing shifts to our east Friday morning, with decreasing chances for showers through the day, and partial clearing expected from west to east. Should see mid- late afternoon high temperatures in the mid-upper 70s. Should see near normal mid-July temperatures for the weekend into early next week. Weak surface high pressure generally in place, but with modest mid-level trough across sern Ontario into northern New England, did maintain roughly 30-40% PoPs for possible shower activity - especially afternoon periods - Saturday through Monday. && .AVIATION /02Z TUESDAY THROUGH SATURDAY/... Through 00Z Wednesday...Widespread VFR conditions to start the TAF period will deteriorate through the evening/night as an approaching shortwave spreads mid and low-level clouds through the area along with some rain/tstorms. As of 00Z, the rain/tstorms are just approaching northern NY from the west, poised to move through the Saint Lawrence Valley between 00Z and 04Z, and through the northern Adirondacks between 02Z and 06Z. The storms will generally weaken through the night as they progress eastward into Vermont. Not expecting any severe weather associated with the storms, but they may contain some gusty winds and lightning, especially at KMSS and KSLK. Have not specifically included mention of TS in TAFs due to weakening nature of the system, but will be watching closely and amend if needed. A period of MVFR ceilings/visibilities is expected overnight at most TAF sites as the precipitation moves through. Conditions will trend towards VFR after 15Z behind the departing shortwave. Winds will be from the south/southwest overnight with some gusts 15 to 20 knots possible. In addition some low level wind shear is expected overnight as a 35 to 45 knot low level jet develops. During the day Tuesday, winds will be from the southwest/west with gusts to 20 knots. Outlook... Tuesday: VFR. Chance SHRA, Chance TSRA. Tuesday Night: VFR. Slight chance SHRA. Wednesday: VFR. Chance SHRA. Wednesday Night: Mainly VFR, with local MVFR possible. Chance SHRA, Slight chance TSRA. Thursday: Mainly VFR, with areas MVFR possible. Chance SHRA, Slight chance TSRA. Thursday Night: Mainly IFR, with local MVFR possible. Likely SHRA, Slight chance TSRA. Friday: Mainly MVFR, with areas IFR possible. Chance SHRA. && .BTV WATCHES/WARNINGS/ADVISORIES... VT...None. NY...None. && $$ SYNOPSIS...Taber NEAR TERM...Duell/Taber SHORT TERM...Banacos LONG TERM...Banacos AVIATION...Duell
Area Forecast Discussion
National Weather Service Caribou ME
1132 PM EDT Mon Jul 5 2021 .SYNOPSIS... High pressure will crest south of the region this evening. A warm front will approach tonight and lift north through the area Tuesday. A cold front will cross the area early Wednesday then stall offshore on Thursday while low pressure approaches. Low pressure will pass south of the area Friday and pull away from the region Saturday. && .NEAR TERM /THROUGH TUESDAY/... 11:30 PM Update: Sky remains mostly clear except for some low clouds/fog moving in near the coast. Adjusted temps over western areas where the valleys have cooled into the upper 50s. Otherwise, no major changes this hour. Previous discussion: Clear skies this evening as high pres ridge moves across the region w/winds becoming light. As this ridge shifts to the east, S winds will set up later tonight w/increasing dewpoints and llvl moisture. Mdl soundings from the NAM, RAP and GFS show llvl moisture being trapped under an inversion below 1500`, which could allow for some low clouds and fog to develop. Some of the CAM guidance such as the NAMNEST support this set up. Therefore, decided to show low clouds moving from from s to n w/fog development expected as far Caribou and Presque Isle. The Bangor and Downeast region could see some dense fog setting up w/vsbys dropping below 1 mile by early Tuesday morning. This region did get heavy rainfall and w/clear skies and light wind, and also some cooling, fog a good bet. Attm, did not have the confidence to go w/any Dense Fog Advisory. The evening crew can assess this potential further when the updated guidance arrives. For Tuesday, low clouds and fog should lift and burn off w/some sunshine available for heating and the destabilization of the atmosphere by late morning, especially across the Maine Central Highlands. Temps across the CWA by early afternoon will reach into upper 70s to lower 80s. GFS and NAM/NAMNEST show CAPE potential of 800-1200 joules in the aforementioned area w/some decent shear of around 30 kts at 0-6km to allow some convection. Mid level lapse rates of 6.5 c/km progged to set up by early afternoon to allow for good updrafts and potential for organized convection. Given the shear and some divergence aloft, thinking that some stronger wind gusts are possible, again mainly for the Maine Central Highlands and the Bangor region and interior Downeast. PWs are forecast to be in the 1.5 to 1.8 inch range leading w/a warm cloud up through 11k and dewpoints in the mid/upper 60s for heavy rain. Coordinated w/GYX to include heavy rainfall and gusty winds in the forecast. Further n of the Millinocket-Lincoln region, lapse rates were not impressive at all w/values < 6.0c/km keeps updrafts to a minimum. Therefore, just went w/general tstms and no enhanced wording. The later shifts can assess this potential and make adjustments as needed. && .SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY/... The cold front will gradually cross the area overnight. Some thunderstorms are possible before midnight ahead of the front and maintained mention of a slight chance. The cold front looks stronger than it did in the charts a day ago and have lowered low temps to the lower 50s in the Saint John Valley and mid 60s for Bangor and Downeast. It will still be a humid night for Bangor and Downeast with dew points also in the mid 60s and not falling until Wednesday morning. Steadily drier air filters in Wednesday and have reduced highs to the upper 60s to around 70F in northern Aroostook County to around 80F for Bangor and the coast. The coast will be the warm spot in the forecast area with the offshore flow. The biggest challenge for later Wednesday into early Thursday will be whether a wave of low pressure can maintain itself as it moves from the Great Lakes region towards Maine along the stalled frontal boundary. Most model guidance has backed off PoPs on this feature compared to yesterday...except ECMWF. This is mostly due to the expectation that the cold front is stronger and pushes further south than yesterday`s expectation. The wave then tends to fizzle out as it moves into dry air and the only affect is high clouds rather than precipitation. Based on that scenario, reduced PoPs and clouds in the forecast for later Wednesday into early Thursday. The stalled front will lift northward as a warm front on Thursday with thickening clouds and steadily increasing PoPs through the day. The cooler air behind Tuesday night`s cold front will be entrenched in the area by Thursday with highs only reaching the upper 60s. && .LONG TERM /THURSDAY NIGHT THROUGH MONDAY/... Heavy rainfall is possible Thursday night into Friday night as low pressure from the Great Lakes region moves northeastward along the stalled frontal boundary. The associated upper level shortwave will amplify and help pull in the remnants of Tropical Storm Elsa northward towards eastern Maine. With deep moisture, elevated instability and PWs over 1.75 inches, it`s certainly possible most of the area could see an inch or two of rainfall or more. The low pressure system will exit later Friday night. Drier and seasonable cool air is expected for next weekend and into Monday as cool Canadian high pressure builds. A blend of models leads to increasing PoPs again by later Monday into Monday night. && .AVIATION /04Z TUESDAY THROUGH SATURDAY/... NEAR TERM: VFR late this evening. Conditions will likely lower to IFR from KHUL south overnight into Tuesday morning in lower clouds and fog. Conditions should improve from north to south late morning and into the afternoon. VFR at the terminals from KPQI to KFVE with the outside chance of a little late night fog that could briefly lower conditions. Isolated to scattered thunderstorms Tue PM with brief IFR/MVFR. Light SW winds 10 kts or less becoming S. Strong and erratic wind gusts possible in/near any thunderstorms Tue PM. SHORT TERM: Tuesday night...Fog may be an issue for BHB...and more likely towards Eastport, Machias and Princeton. Otherwise VFR conditions are expected with a slight chance of a thunderstorm Tuesday evening. Wednesday into Thursday...VFR with just a small chance of a brief period of MVFR cigs north of HUL on Wednesday morning. Thursday night into Friday night...IFR cigs and tempo IFR vis in heavy rain. Embedded thunderstorms possible. Saturday...VFR outside of a chance of MVFR cigs north of HUL in the morning. && .MARINE... NEAR TERM: No headlines expected through Tue. SW winds 10 kt increasing to 10-15 kt from the S on Tue. Gusts to 20 kts are expected. Seas 3-4 ft gradually building to 4-5 ft Tue afternoon. Highest seas over the outer zones. Areas of fog through the day lowering vsbys to < 1 NM. SHORT TERM: No advisories are anticipated. Did adjust winds and seas down for Tuesday night due to stability. Fog remains the big concern Tuesday night into early Wednesday morning before the front pushes it out. The next round of fog appears likely Thursday night into Saturday morning. Have started with mention of patchy fog, but with the very humid remnants of TS Elsa, it could end up being dense on Friday. Elsa could also bring high surf and heavy rainfall Friday. && .CAR WATCHES/WARNINGS/ADVISORIES... ME...None. MARINE...None. && $$ Near Term...CB/Hewitt Short Term...MCW Long Term...MCW Aviation...CB/Hewitt/MCW Marine...CB/Hewitt/MCW
Area Forecast Discussion
National Weather Service Corpus Christi TX
642 PM CDT Mon Jul 5 2021 .AVIATION... Latest radar shows storms north and west of COT moving toward COT. Weak showers are also present across the eastern TAF sites. Weak isolated showers are expected to continue through early evening across VCT, ALI and CRP TAF sites, while sct thunderstorms continue across LRD and COT. Convection is expected to wane by late evening for a few hours, then increase to numerous once again overnight into Tue morning. Models indicate that rain chances will decrease across the northern areas by Tuesday afternoon, but remain numerous across LRD, ALI and CRP TAF sites into Tue evening. A mix of VFR and MVFR conditions will prevail tonight through Tuesday with periods of LIFR/IFR due to convection. && .PREV DISCUSSION... /Issued 348 PM CDT Mon Jul 5 2021/ SHORT TERM (Tonight through Tuesday Night)... Surface analysis at 3 PM consisted of a broad, circular outflow boundary expanding west into the Brush Country and north into the Victoria Crossroads, with generally light SE winds and quiescent conditions elsewhere. Convergence along the outflow should be greatest on its northern end for the next hour or two where the greatest PoPs remain focused, while much of the Coastal Bend remains more stable behind the outflow. A bit of a wild card exists this evening and early tonight across our western zones as storms currently over the Edwards Plateau continue trekking south in weak NW flow. Most models (including the HREF and TTU WRF) dissipate and shift this activity west of Cotulla and Laredo overnight, but the most recent HRRR has trended farther east which seems plausible. Opted to show 40-50% PoPs in our western counties tonight; however, certainty increases toward daybreak as we expect at least two larger clusters of convection to evolve - one over the western Brush Country tied to an approaching MCV, and the other near the Upper Coastal Bend courtesy of enhanced speed convergence along the coast. This latter area is favored by most CAMs to dominate the scope of our CWA by midday as outflows congeal and potentially lead to a diffuse MCS that drifts south. With PWATs around 2.4", weak steering flow, and deep warm layer rain processes, the stage is clearly primed for some heavy rain. Opted to hold off on flood headlines given rather high flash flood guidance values of 2-4", although localized flooding is likely at some point during the day tomorrow. By late Tue afternoon, conditions look to be too worked over/stabilized in the wake of these storms and this should extend into the first half of the night before another round of coastal speed convergence yields late night/early morning convection near the coast. NBM`s high temps for Tuesday look too warm for the degree of thicker clouds and widespread precip, so nudged temps lower and more in tune with the CONSSHORT output. LONG TERM (Wednesday through Monday)... Significant moisture remains in place across South Texas with PWATs ranging from 2.0-2.5" through Friday before decreasing to near 2.0" this weekend into early next week. Low to mid level support seems to be the most driving factor for convective development compared to a potential limiting upper level setting. At 250mb, the GFS has high pressure over the Gulf of Mexico push further inland over the Coastal Plains, inducing ridging by separating troughs from Mexico and the AR/LA/TX border. However, there are model disagreements as the ECMWF and CMC deepen the trough over South Texas keeping the high pressure well east over the Gulf. The latter would lead to an environment more favorable for convective development through upper level divergence. Models are in fair agreement with a mid level trough axis spanning from Deep South Texas into South Texas Wednesday through Thursday night. In addition, cyclonic flow will also be present down to the surface with speed convergence evident and greatest along the coast. Considering all the above, scattered to numerous showers and thunderstorms are expected Wednesday through Thursday night, then decrease to scattered on Friday as ridging approaches from the east. Heavy rainfall and localized flash flooding will also be possible through this time period as moisture remains near or above the 99th percentile, CAPE generally less than 1500 J/kg, and cloud layer mean wind remains slow at less than 15 knots. The WPC has all of South Texas in a marginal risk of excessive rainfall on Wednesday. Therefore, have included heavy rain for Wednesday through Thursday when conditions are most favorable. Storm total QPF through Friday ranges from 2 to 6 inches with locally higher possible. Expect the greatest coverage and rainfall over the waters, Coastal Bend, and Victoria Crossroads. High pressure from the Gulf begins to push westward into South Texas heading into the weekend, with the trough or developing closed mid- level low (ECMWF hinting) over northeast Mexico, west of the CWA, persisting into early next week. This push will likely focus rain chances to this mid-level disturbance, outside of the CWA, as ridging builds over South Texas. The GFS sticks out as an outlier this weekend as it keeps the high pressure over the north Gulf of Mexico with the mid-level trough draped over South Texas. Due to the close proximity of the disturbance, uncertainty, and high PWAT values above the 75th percentile, kept 20-40% PoPs for diurnally driven showers and thunderstorms Friday night through Monday. Tropical Storm Elsa may increase wave heights to near 7 feet and swell periods to 6-8 seconds Thursday into Saturday. This increase in swells with P-ETSS guidance indicating tide levels near 1.5 ft above MSL, could cause waters to reach the dunes as well as an increase in rip currents. High temperatures will remain below normal, ranging from the mid to upper 80s through Friday before gradually increasing through the weekend. Lows remain in the mid to upper 70s. MARINE... Light to moderate onshore flow continues tonight through Tuesday night. Scattered showers and thunderstorms this evening should expand and become numerous during the pre-dawn hours on Tuesday and continue through much of the day, before diminishing in coverage Tuesday night. Weak to moderate onshore flow will continue through Thursday before strengthening to moderate Thursday night through the weekend. Swells from Tropical Storm Elsa will likely move into the region and increase wave heights Thursday through Saturday. This may lead to periods of Small Craft Advisory conditions at times, particularly over the offshore waters. Numerous showers and thunderstorms Wednesday through Thursday, will decrease to scattered Thursday night. Rain chances will decrease to 20 to 40 percent Friday into early next week as an upper level ridge builds west into the region. && .PRELIMINARY POINT TEMPS/POPS... Corpus Christi 77 84 74 85 75 / 50 90 80 80 70 Victoria 75 85 74 84 74 / 70 80 80 80 60 Laredo 77 86 75 87 74 / 70 80 70 70 50 Alice 75 84 73 85 73 / 50 90 80 80 60 Rockport 77 83 76 86 77 / 70 90 80 80 70 Cotulla 76 88 74 88 75 / 70 70 70 70 50 Kingsville 76 85 74 85 74 / 50 90 80 80 70 Navy Corpus 78 83 77 86 78 / 60 90 80 80 70 && .CRP WATCHES/WARNINGS/ADVISORIES... TX...None. GM...None. && $$ TE/81...AVIATION
Area Forecast Discussion
National Weather Service Cheyenne WY
530 PM MDT Mon Jul 5 2021 .SHORT TERM...(This evening through Thursday) Issued at 200 PM MDT Mon Jul 5 2021 Leeside low east of the Laramie Range this afternoon. Southerly winds east of the low with dewpoints in the mid 50s to 61 at Torrington east of the Laramie Range. West of the Laramie Range...winds out of the north and 1PM dewpoints in the mid 40s. MUCAPE of 1000 to 2000 J/KG east of the Laramie Range. Starting to see convection developing along the Laramie Range and out across Albany County. To our north...a cold front is being analyzed across southern Montana near the Wyoming state line. Latest HRRR guidance showing showers and storms increasing in coverage by mid afternoon west of the Laramie Range and along the Laramie Range. Storm motions less than 10kts for the remainder of the we need to be watching for flash flooding. WPC does have a Marginal Risk for Flash Flooding across much of our CWA this afternoon. Shear begins to increase after 00Z that will help with the flash flood threat...but then we will be dealing with severe thunderstorms with the additional shear. Surface based CAPE of 2000-2500 J/KG across the northern Nebraska Panhandle...west to Lusk this evening. Would anticipate a busy evening for the evening folks. Upper shortwave associated with the surface front very slow to move through tonight. Looks to be near the northern Panhandle by 12Z Tuesday. SREF QPF coming more in line with the ECMWF in holding QPF across our southeastern zones through Tuesday afternoon. Will continue to keep chance PoPs going for that time. Warming and drying for Wednesday with the departure of that shortwave. High pressure builds back into the area with warmer temperatures and increased concerns for critical fire weather. WIll probably need some fire headlines for Thursday as GFS 700mb winds increase to 25-30kts west of the Laramie Range and afternoon humidity falls to the low teens. .LONG TERM...(Thursday night through Monday) Issued at 200 PM MDT Mon Jul 5 2021 Friday...Somewhat cooler in the wake of a cold frontal passage associated with a shortwave trough passing across the Northern Plains states. The front looks rather dry, though we may see isolated late day thunderstorms. Saturday...Even cooler and more stable in the relatively dry air in the wake of the cold front passage. With minimal low and mid level moisture, it looks dry. Sunday-Monday...Mostly dry with a warming trend as the ridge aloft builds overhead. Ridging aloft breaks down slightly on Monday as a shortwave trough moves overhead, perhaps spawning isolated late day thunderstorms due to an increase in low and mid level moisture and convergence along a north to south oriented surface trough. && .AVIATION...(For the 00Z TAFS through 00Z Tuesday evening) Issued at 520 PM MDT Mon Jul 5 2021 KRWL will continue with MVFR conditions until 01Z. Thunderstorms moving northeast across the region will impact all TAF sites this evening until 15Z Tuesday morning. KCYS and KLAR will drop to MVFR starting 0Z for KCYS and 02Z for KLAR with cloud bases trending BKN at 4k ft. Sites across the Nebraska Panhandle will experience thunderstorms until 10Z along with BKN clouds at 5k ft. There is a possibility of fog tonight for KCYS starting 07Z thus MVFR conditions are possible until 12Z. && .FIRE WEATHER... Issued at 200 PM MDT Mon Jul 5 2021 Minimal fire weather concerns today through Tuesday as a slow moving low pressure system moves through southeast Wyoming. This low will bring widespread chances for wetting rains...thunderstorms and cooler temperatures. We begin to dry out Wednesday and especially Thursday as high pressure builds in from the south. Critical fire weather conditions looking likely along/west of the Laramie Range Thursday with afternoon humidity falling below 15 percent and westerly wind gusts of 30 to 35 mph expected. These critical conditions could continue for Carbon County FWZs into Friday. && .CYS WATCHES/WARNINGS/ADVISORIES... WY...None. NE...None. && $$ SHORT TERM...GCC LONG TERM...RUBIN AVIATION...AW FIRE WEATHER...GCC
Area Forecast Discussion
National Weather Service Des Moines IA
624 PM CDT Mon Jul 5 2021 ...Updated Aviation... .DISCUSSION.../Today through Sunday/ Issued at 218 PM CDT Mon Jul 5 2021 Forecast Highlights: -- A few storms possible over northern Iowa this afternoon/early evening -- Scattered showers and storms Tuesday night into Wednesday -- Cooler and turning dry later Wednesday into Thursday -- Growing confidence in strong to severe storm chances including locally heavy rain in the region Friday perhaps into Saturday Details: For this afternoon into early this evening, 18z SPC mesoanalysis shows over 2000+ J/kg of MLCAPE with deep layer shear less than 25 knots with a weak boundary around the Iowa/Minnesota border. There are weak perturbations in the mid-level flow, but this weak lift is displaced from the instability axis. The NAM, RAP, and HRRR forecast soundings show a weak warm layer that persists through daytime heating that will likely limit convection this afternoon. 1 minute GOES-East visible imagery has shown this cap in the way of developing cumulus over eastern Hamilton County that were showing slight vertical development. However, a short time later these clouds were suppressed. Examining the 5/00z and 5/12z HREF members, the ARW has been the most aggressive with storm development this afternoon. However, the NSSL WRF and FV3 show less storms than 24 or even 12 hours ago and even the ARW has backed off, perhaps owning to better resolving the cap and weak forcing. SPC morning update removed the marginal and all guidance here is supportive of such removal. Any storms that do form will be isolated, but could pose a risk of downburst winds given inverted V soundings and perhaps hail in the updraft stage of a storm. Any storms would diminish shortly after sunset. With the boundary being pushed back northward tonight, Iowa will be well within the warm sector on Tuesday. As a shortwave trough moves across the Dakotas and into Iowa by later in the day, this will bring the boundary/front into the state. Timing continues to look late in the afternoon if not the evening hours for reaching our northwestern forecast area. Most of the scattered storms will be behind the surface front and instability is lowering into the overnight hours. The deep layer shear is better than this afternoon so a few strong storms may result late in the afternoon or evening hours. Precipitable water values around 2 inches will pool near and behind the slow moving boundary, but the 850-300mb flow is not parallel to the boundary. While storms may be slow moving, not seeing a concern for flash flooding with 3 hour flash flood guidance values around 2 inches and expected rain amounts. The scattered showers and storms will push through by later Wednesday afternoon with cooler air arriving. Temperatures Wednesday afternoon and Thursday morning will average 5 or so degrees below normal with highs in the 70s to around 80 degrees and lows in the 50s to around 60 degrees with the lowest of those temperatures in northern Iowa. The lower temperatures will be accompanied by lower dewpoints for a short period late Wednesday into a good portion of Thursday. Attention will turn upstream as a strong shortwave trough will be arriving over the Pacific Northwest and British Columbia province of Canada Wednesday and moving over the Canadian Rockies later Thursday. Another shortwave will undercut this shortwave and phasing of these two is being shown in both the ECMWF and GFS. This would help to strengthen and could cause the merged shortwaves to close off and slow down as it moves southeastward toward the upper and middle Mississippi Valley. Storms may arrive overnight Thursday into early Friday into parts of the state, but later Friday is when there is likely to be favorable instability and deep layer shear. This environment would be supportive of strong to severe storms chances somewhere in the region later in the day. 5/00z CIPS analog has a 50- 60% of at least 1 severe report over much of western into portions of central Iowa and points immediately west of Iowa with the recent 12z run focusing these probabilities farther southwest with the 12z GFS track of the shortwave farther southwest. Indeed, the idea of a severe risk is also being highlighted in SPC`s day 5 outlook. If the slower solution results, then portions of our forecast area may have another round of storms on Saturday and with the closed low nearby, this could result in a favorable environment for tornadoes northeast of wherever the low moves. There is also a signal for heavy rainfall as the ensemble mean precipitable water values from the GEFS and EC ensemble show over 1.75 to at times above 2 inch values with favorable warm cloud depths for efficient rainfall later Friday into Saturday. The 850- 300mb flow at this time looks a bit on the fast side for ideal training storms, but given the high PWs, locally heavy rainfall looks possible in the region. 5/00z CIPS top 15 analogs for the period ending 10/00z shows over an inch in portions of the state with the more recent 12z run shifting the heavier rainfall into southwestern Iowa and adjacent areas of neighboring states. Meanwhile the 5/00z WPC cluster analysis shows a half an inch over southern Minnesota. While a half an inch is not impressive, it is the mean of 100 members from the deterministic and ensemble solutions of the CMC, GFS, and ECMWF. Subjectively examining the ensemble members, there are more members that have around or more than 2 inches amounts than yesterday. Deterministic solutions, of course, can have higher 6 hour maximums, though not as extreme as one solution from yesterday`s 12z run. Further looking at deterministic solutions as they relate to the 100 year annual return interval, the GFS and ECMWF extreme precipitation forecast table highlights areas of Minnesota into parts of north central or northeastern Iowa Friday night into Saturday with generally 30 to 50% for 6 hours and about 20 to 30% higher for the 24 hour period. While rainfall deficits are greater over northern Iowa looking at 30 and 60 day departures and soil moisture percentile, as we saw in southern Iowa a few weeks ago this does not preclude water issues. Indeed, yesterday`s and today`s National Water Center`s prototype National Hydrologic Discussion mentions the medium range forecast is signaling bankfull and rapid onset flooding on Friday or Saturday possible in parts of the region. An important note is that the National Water Model`s precipitation is driven by a single model (GFS) so that signal in the medium range will shift with the deterministic weather model. All of this said about the heavy rainfall and severe potential late this week into perhaps the first part of this weekend will hinge on if the shortwaves merge, if they close off, if they slow down, which has an impact on timing and placement of key features. While confidence is growing in severe weather and heavy rainfall later Friday into Saturday in or around Iowa, the details and what that will mean for a certain area or city will remain in flux for at least several more days. && .AVIATION.../For the 00Z TAFS through 00Z Tuesday evening/ Issued at 623 PM CDT Mon Jul 5 2021 VFR conditions prevail through the current TAF period. Isolated TSRA likely in north central Iowa this evening. Coverage should remain sparse enough to not warrant mention in the forecast. Additional TSRA late day Tuesday should hold off until around or after 00z. && .DMX WATCHES/WARNINGS/ADVISORIES... NONE. && $$ DISCUSSION...Ansorge AVIATION...Martin
Area Forecast Discussion
National Weather Service Austin/San Antonio TX
630 PM CDT Mon Jul 5 2021 .AVIATION... The bulk of the thunderstorm activity has shifted west of the I35 sites, with moderate rainfall and some thunder continuing at DRT. Things should slowly calm down through the night, but some of the high-res model guidance shows a bit more overnight activity than previous nights especially for the San Antonio sites. Will hold onto a VCSH group there overnight. Another round of afternoon storms appears likely for tomorrow and will handle that with a -SHRA VCTS group for now. Some MVFR ceilings will be possible overnight. && .PREV DISCUSSION... /ISSUED 208 PM CDT Mon Jul 5 2021/ SHORT TERM (Tonight through Tuesday Night)... Widespread showers and thunderstorms are already ongoing across South Central Texas this afternoon as a mid-level impulse works its way south into the the Southern Edwards Plateau. This, combined with the effects of convective outflow boundaries as a result of the sea breeze, will result in locally heavy rain and occasional cloud to ground lightning. Showers and storms that have formed east of I-35 and the I-37 corridor are mostly multicellular in nature, with little in the way of deep layer shear to work with. Given this lack of meaningful shear with height, expect storms to be very pulse-like in nature, and with PWATs in excess of 2" across the board, along with sfc dewpoints well into the 70s, it`s no wonder rainfall rates could exceed 1-2" per hour at times with the heaviest cells. Some brief gusty winds are possible as well along any outflow boundaries, but the bigger threat for perhaps an isolated wind gust to 50mph will be out west over the Rio Grande Plains and Southern Edwards Plateau, where some shear will be present this afternoon and evening. Along with the mid-level impulse and MLCAPE of 2000-3000 J/kg, 0-6km bulk shear will actually be in the 20-25 kt range, leading to the slight possibility of a couple gusty winds from storms. Storms should push southward towards Del Rio this evening posing the risk for some gusty winds and locally heavy rainfall. Storm coverage should decrease after sunset out west, but hi-res guidance, in particular the HRRR and TT WRF, are indicating that showers and perhaps a rumble of thunder could develop over the Coastal Plains and the I-35 corridor after midnight. Have bumped up PoPs to the high chance threshold in anticipation of this threat. Tuesday will be yet another active day, however, more diurnally driven storm activity is once again expected, as the lack of a mid- level shortwave disturbance will result in chaotic storm motion and outflow boundaries by mid-afternoon. With PWATs still nearly off the charts for this time of year in the 2.1-2.3" range, along with sfc dewpoints in the 70s, expect yet another shot at locally heavy rain to continue with any storms that can sit over any location for more than 30 minutes. While the flash flooding threat will be very localized, it is not out of the question that we could start seeing more flash flooding threats, especially in locations that have received 1-3" or more in the last couple of days. LONG TERM (Wednesday through Monday)... Overview: The well advertised cool, wet pattern will continue mid to late week with a slight southward trend noted in the guidance for the best rain (and particularly heavy rain) chances Wednesday through Friday. Considerable uncertainty remains in the forecast this weekend into early next week but some rain chances will continue for at least portions of the area. Details: Wednesday morning, the tail end of available high resolution guidance paints a picture that the "center" of the somewhat disorganized upper level height falls will be to our south or southeast with a potential surface reflection noted in the model pressure and wind fields centered over deep south TX. Rain chances in the morning will thus be higher across our southern counties, especially the Coastal Plains as increased onshore flow/convergence seems likely. Rain chances will spread northward through the day, and although coverage will diminish overnight as usual, some lingering isolated activity may remain. A very similar story is forecast Thursday. Locally heavy rain could occur anywhere within the CWA these days, but probabilities are notably higher south of I- 10/US-90. As we head through Friday and beyond, the global models begin to disagree significantly as they have the past several model cycles with little signs of converging on any one solution. The Euro continues to shift the main area of energy to the west into Mexico, then northward along the terrain which would allow for our northeastern areas to see much lower rain chances while our western counties would become the focus area for convection. The GFS and its ensemble members are generally less defined with any system organization and keep the primary POPs closer to the Gulf Coast. And the Canadian continues it`s way-out-there high QPF over south- central TX through the weekend. While the amounts can certainly be discounted, the potential for a wetter solution than the GFS/Euro are currently spitting out cannot. It remains to be seen how this will play out but we will have to remain cognizant of continued low risk for locally heavy rain through the rest of the long term. Hopefully additional clarity will come over the next 24-36 hours. PREV DISCUSSION... /ISSUED 1248 PM CDT Mon Jul 5 2021/ AVIATION (18Z TAFS)... /NEW/ Bottom line: Widespread showers with isolated thunderstorms are expected to continue over the next 24-30 hours, making this a rather difficult forecast. Trying to pick out and decipher any particular prevailing weather will be tough given a moist and unstable airmass with very weak steering flow leading to chaotic storm motions and storm interaction. Expect CIGs to fluctuate between MVFR and VFR throughout the day at all sites, most notably AUS/SAT/SSF. Have gone with a TEMPO group at those three sites for early afternoon to early evening for thunderstorms with visibility and ceilings down to IFR. Meanwhile at DRT, a complex of storms looks to be organizing to the north and should arrive between 22Z-02Z, hence the TEMPO for that time period. Overnight, rain chances continue, but the thunder threat should be reduced with rain showers possible at all sites through tomorrow. IFR ceilings are expected to form after 09Z at all three I-35 sites and continue through 15Z. Morris PREV DISCUSSION... /ISSUED 414 AM CDT Mon Jul 5 2021/ SHORT TERM (Today through Tuesday)... Another active day is in store with scattered to numerous showers and thunderstorms expected mainly this afternoon and evening. However, we could see some showers and maybe an isolated thunderstorm before noon across the Coastal Plains and the northern part of the Hill Country. For this afternoon and early evening, the weather scenario looks interesting as an upper level impulse pushes down into our area. This feature is forecast to generate showers and thunderstorms as it moves into the Hill Country and Edwards Plateau. A second feature that is forecast to play a big role on today`s weather is the seabreeze. Between these features, in addition to outflow boundaries, the combination brings the potential for localized heavy rain. Why heavy rain? First, dewpoint temperatures are likely to range from the mid to upper 70s under a rich tropical airmass in place. Second, PWATs are likely to range between 2.1 to 2.25 inches based on GEFS and as high as 2.5 inches per GFS. These values are between +2SD and +3SD for this time of the year. Third, mean wind flow is expected to be around 10 mph allowing storms to slowly move forward. All of these components when put together bring the potential for impressive rain rates and therefore the potential for minor flash flooding. For the past two days, localized rainfall amounts of 3 to 4 inches have occurred and today will be another day for some areas across the Hill Country, Edwards Plateau, along I-35 and/or the Coastal Plains to experience these types of isolated rainfall amounts. Therefore, average storm totals rainfall amounts for today are one tenth to one inch over most areas with maximum values of 3 to 5 inches. The Weather Prediction Center Excessive Rainfall Outlook for Day One has areas along and north of Highway 90 under a slight risk of rainfall exceeding flash flood guidance. As a friendly reminder, 6 inches of fast moving water can knock an adult off their feet and 12 inches of rushing water could carry away most cars. Turn Around, Don`t drown if flooded roadways are encountered. Shower and thunderstorm activity is expected to decrease late tonight into Tuesday morning. Then the activity picks up in the afternoon once again with the western half of South Central Texas favored for pockets of heavy rains in the afternoon. LONG TERM (Tuesday Night through Sunday)... A broad mid and upper level low/trough is forecast on Wednesday to be positioned from Deep South Texas northeast up the Texas coast. The focus for the heaviest rainfall should remain over the Coastal Plains on Wednesday. Nevertheless, southeasterly boundary layer flow will maintain elevated precipitable water values across the region Wednesday, especially the southern half of the area, and there should be a diurnal pattern of scattered showers and thunderstorm development inland through the afternoon and early evening. There are indications that the trough will shift slightly west and inland on Thursday, potentially bringing some higher rain chances farther north into the CWA. Beyond Thursday there are some significant differences in the upper level pattern between the 00Z operational runs of the GFS, ECMWF, and CMC. The ECMWF and CMC close and tighten the upper level low up and drift it northwest Friday through Saturday, with the CMC bringing it into western areas of the CWA and the ECMWF into Coahulia, Mexico. Both also have a surface low reflection. A scenario like this could bring much greater rain chances Friday into the weekend than are currently advertised, especially across the southwest and western CWA, which would include nocturnal convection. Some may also continue to notice the very high run total QPF from the CMC and ECMWF solutions. While these are currently outliers, they can`t be completely discounted in terms of the general potential for pockets of higher QPF amounts Friday into the weekend. With respect to the operational run of the GFS, this solution maintains a broad trough, but does shift it northwest indicating continued broad rain chances. With that said, in general 2-4" of rainfall is advertised this week across the CWA, favoring southern and western areas. Pockets of higher amounts up to 6" inches are likely, and a caveat that if GFS and the GEFS trend toward the ECMWF and CMC then the pockets could be even higher. These isolated pockets could occur in a short period of time. Thus, we will continue to advertise a threat for localized flooding concerns through the week. With respect to temperatures, forecast max temperatures will continue to remain below normal for this time of year, welcome news for most given it`s July. && .PRELIMINARY POINT TEMPS/POPS... Austin Camp Mabry 73 87 72 88 73 / 50 70 40 60 20 Austin Bergstrom Intl Airport 72 87 71 87 71 / 50 70 30 60 20 New Braunfels Muni Airport 74 87 72 87 72 / 60 70 40 70 20 Burnet Muni Airport 71 85 71 86 71 / 50 60 30 50 20 Del Rio Intl Airport 75 88 74 91 74 / 60 70 40 50 50 Georgetown Muni Airport 72 86 72 87 71 / 50 60 30 60 20 Hondo Muni Airport 73 85 72 86 71 / 60 70 50 70 40 San Marcos Muni Airport 72 87 72 87 71 / 50 70 40 70 20 La Grange - Fayette Regional 75 87 74 89 73 / 50 70 40 70 20 San Antonio Intl Airport 74 84 73 86 73 / 60 80 50 70 20 Stinson Muni Airport 76 86 74 87 74 / 70 80 50 70 30 && .EWX WATCHES/WARNINGS/ADVISORIES... None. && $$ Short-Term/Aviation...Hampshire Long-Term...YB
Area Forecast Discussion
National Weather Service Grand Forks ND
934 PM CDT Mon Jul 5 2021 .UPDATE... Issued at 934 PM CDT Mon Jul 5 2021 A nearly stationary W-E oriented frontal boundary has sagged south of the Highway 2 corridor this evening... with showers still trying to inch eastward along that line. Deeper convection now increasing in western SD is associated with a deepening surface low there... and should continue to track east-northeastward into s-cntrl and eastern ND during the overnight... effectively pushing that frontal boundary back north a bit, before it finally slides through the area on Tuesday. Lots if players in this game tonight, with southeastern ND and west-central MN likely to be the biggest precipitation winners. Still expect some frontal overrunning precip up into the Highway 2 corridor and GF areas as well. The latest 00z and 01z RAP13 runs support this, though the recent 23z, 00z, and now 01z SPC HRRR runs are still quite variable convection evolution. Long story short... not planning any significant changes to the current evening and overnight forecast package. UPDATE Issued at 715 PM CDT Mon Jul 5 2021 An updated Aviation Discussion is attached below. && .SHORT TERM...(This evening through Tuesday night) Issued at 319 PM CDT Mon Jul 5 2021 The showers moving east thru the far northern parts of ND continue to weaken as they move into Cavalier-Langdon-Cando. Main focus will be the coverage of showers and thunderstorms tonight and rainfall amounts. Next wave over northern Wyoming and south central Montana will move east and be in the Aberdeen/Jamestown area 12z Tuesday with sfc low just a tad south of this. 850 mb low tracks along the SD/ND border and best warm advection and isentropic lift looks to be south of Hwy 200 overnight peaking prior to 12z. PWATs near 1.50 inches so some good rainfall rates seem likely in this zone. Average amounts look to run around 1.25-1.50 inch near the SD border thru 12z Tues then a bit more after before it ends. Farther north rainfall amounts will be less as sfc pressure rises as high moves south into central Manitoba. This will limit how far north rain will get overnight and amounts. Clearing will work quickly southeast behind the system Tuesday, with last area for rain to end and skies to clear being west central MN by late aftn. Cooler Tuesday with highs mid 60s to low 70s. Skies mainly clear Tuesday night in the mid 40s to low 50s. .LONG TERM...(Wednesday through Monday) Issued at 319 PM CDT Mon Jul 5 2021 Wednesday into early Thursday...surface high pressure continues to retreat and return flow will bring warmer temperatures and breezy conditions ahead of the next system. Energy aloft will propagate through the flow helping to trigger showers and storms by Thursday and Friday bringing another round of measurable precipitation. The system will reorganize farther south late Friday and Saturday resulting in drier conditions over the area...with continued seasonal temperatures. Pleasant conditions will persist through the end of the forecast period. && .AVIATION...(For the 00Z TAFS through 00Z Tuesday evening) Update at 934 PM CDT Mon Jul 5 2021 Generally VFR conditions across the FA with sct rainshowers and isolated thunderstorms moving eastward into eastern ND along a nearly stationary W-E oriented frontal boundary laying currently lying along the Highway 2 corridor. An approaching low pressure system will bring areas of showers and scattered MVFR CIGS and VSBYS in thunderstorms into eastern ND from 05z through 11z... becoming more numerous and overspreading northwest and westcentral MN through 14z. Conditions will improve from the north from 16z through 20z as the frontal boundary sags further southward. && .FGF WATCHES/WARNINGS/ADVISORIES... ND...None. MN...None. $$ UPDATE...Gust SHORT TERM...Riddle LONG TERM...Hopkins AVIATION...Gust
Area Forecast Discussion
National Weather Service Goodland KS
934 PM MDT Mon Jul 5 2021 .SHORT TERM...(This evening through Wednesday night) Issued at 140 PM MDT Mon Jul 5 2021 Satellite and 500 mb RAP analysis showed near northerly flow aloft this afternoon, with the region on the eastern side of an area of high pressure. A shortwave trough could be seen rounding the northern periphery of the high, exiting the Great Basin. Skies were clear across the western CWA; however, fields of cumulus were billowing into the region from the southeast. No thunderstorm development was associated with these clouds at this time. At 1 PM MT, temperatures ranged from the low 80s to the low 90s, with southeast winds at 10 to 15 mph. Thunderstorms developing along the Front Range this afternoon are expected to push east into the evening hours as the upper trough approaches the High Plains. This disturbance brings a slight chance for showers and thunderstorms to areas west of a line from Stratton, NE to Sharon Springs, KS late this evening. At this time, confidence in storms making it to the region before dissipating is quite low, resulting in the lowering of precipitation chances for tonight. If activity does make it into the area, severe weather is not anticipated. Otherwise, temperatures fall into the 60s region-wide. Tuesday looks to be a bit more active in terms of storms. The cold front associated with our aforementioned disturbance pushes across the region throughout the day, becoming a focus for thunderstorm development as early as the morning hours. Of course better chances come in the afternoon and evening as daytime heating cranks things up (highs in the 80s/low 90s) and storms increase in coverage. It appears that a likely scenario is one or two linear clusters form and track across the area from northwest to southeast. Again this is just one scenario, and where such storms would set up is uncertain. Moisture will be plentiful, with PWATs near 1.5" by the afternoon. Additionally, moderate instability, lapse rates of 6-7C/km, and shear maybe up to 30 knots suggests that a few strong to severe thunderstorms will be possible (mainly in the afternoon and evening). Primary threats with these storms include damaging winds, large hail, and locally heavy rainfall which could create flash flooding issues. Storms should exit the region to the southeast overnight as temperatures fall into the upper 50s to mid 60s. Thunderstorms pass to our east Wednesday morning while drier air moves into the High Plains. Quiet weather is anticipated, with highs in the 80s behind Tuesday`s cold front as ridging builds east across the western CONUS. Temperatures fall into the upper 50s to low 60s under clear skies Wednesday night. .LONG TERM...(Thursday through Monday) Issued at 123 PM MDT Mon Jul 5 2021 The extended period begins with high pressure located over the Four Corners region and a trough located over the Great Lakes. The majority of the day Thursday is expected to remain dry. I have introduced low end pops for areas north of Highway 34 as a subtle shortwave emanates off the Rockies in northern Colorado/Southern Wyoming. The better forcing may remain north of the CWA in the Nebraska panhandle but felt it was worth addressing the potential. High temperatures for the day will be in the 90s across the area with lows in the mid 60s to low 70s. Friday, a ridge begins to take shape over the western CONUS as an upper level low moves southeast from the northern plains into the Great Lakes. A cold front will be associated with the upper level low and is currently forecasted to move through the CWA during the afternoon to late evening. Before the cold front arrives, warm to hot temperatures are expected with daytime highs in the in the low 90s across Colorado to approaching triple digits to the east, some heat indices could approach 100 degrees during the afternoon. Regarding the timing of the cold front, model discrepancies exist with either a afternoon passage or a late evening passage which could have an impact on how warm it will actually get. Showers and storms appear possible during the afternoon and evening as well with the better chances currently looking to be south of Interstate 70. Some guidance has been hinting at gusty to perhaps strong winds with the passage of the front, confidence is not high enough currently to raise wind gusts but is something that will continue to be monitored. Saturday and Sunday, will be relatively cooler in the wake of the cold front passage as afternoon highs in the 80s are expected. Low temperatures each morning will be in the mid 50s across east Colorado to the mid 60s across eastern portions of the CWA.Saturday will feature a low chance for afternoon showers/storms as a weak disturbance moves down the eastern periphery of the ridge still situated over the western CONUS; however the better forcing looks to remain off to the east across central Kansas. && .AVIATION...(For the 06Z TAFS through 06Z Tuesday night) Issued at 934 PM MDT Mon Jul 5 2021 VFR conditions will prevail at KGLD and KMCK terminals through the forecast period. Southerly winds around 6-10kts will transition to the west overnight and into tomorrow morning. Winds will shift to the northwest as a cold front moves through the region. Showers and thunderstorms will be possible in the vicinity of the terminals by 18Z, tapering off by 00Z. && .GLD WATCHES/WARNINGS/ADVISORIES... KS...NONE. CO...NONE. NE...NONE. && $$ SHORT TERM...JBH LONG TERM...TT AVIATION...AW
Area Forecast Discussion...UPDATED
National Weather Service Jackson MS
923 PM CDT Mon Jul 5 2021 .UPDATE... Updated for evening discussion. && .DISCUSSION... This evening`s shower and thunderstorm activity has mostly faded after the sea breeze storms` outflow boundary reached just north of the I-20 corridor. A cluster of storms near Meridian is about all that is left to wind down, but can`t rule out a few stray showers overnight. An area of upper-level low pressure is centered over the central Gulf Coast tonight, and this should help to steer more moisture and wrap rain chances farther across our forecast area by tomorrow afternoon. Updated POPs and weather through the afternoon tomorrow to account for trends in latest short-term guidance. The first showers and storms of the day will likely be in the Pine Belt again, which should keep temperatures from climbing too quickly there. Otherwise, most locations should see a range of normal lows tonight and normal highs tomorrow. /NF/ Prior discussion below: Tonight & Tuesday... Tonight: With showers moving to the NW closer to I-20 corridor & a little better moisture, any remnant showers/storms will wind down within an hour or so after sunset. The boundary is progged to continue lifting N, bringing increasing moisture depth & in the boundary layer. This will help more cloudiness to spread N overnight & higher sfc dewpoints in the low 70s. Lows will remain near normal in the low 70s. Tuesday: Tropical Storm Elsa will be moving off of N Cuba by Tuesday morning & will straddle the western FL Peninsula but will remain no threat to the N Gulf Coast. As the front stalls, deeper moisture near 2 inch PWs will advect NW. A broad upper low over the TX coast & areas of PV in the region will help convection to spread W-NW. Coverage will be more scattered-numerous along & S of the I-20 corridor & highest in the Hwy 84 corridor. Shear will be subtle but 500mb temps could be slightly cooler, leading to a little better lapse rates. Some strong storms are possible but severe looks unlikely. Light backbuilding flow will bring some potential for quick heavy downpours. Heat will be a little less due increasing convective coverage, but warmer in the west. /DC/ Tuesday night through early next week: By Tuesday night into Wednesday morning, an upper trough will have begun ejecting Tropical Storm Elsa north and east, which should let it go away from the area with very little local effect. Afternoon isolated to widely scattered showers and thunderstorms will be possible each day this week, though the best chances may come Wednesday and Thursday afternoon and evening when an upper trough glances by to the north. Temperatures will also begin to warm and moisture increases through the week: Lows warm from the lower 70s F by early week into the middle 70s F by late week while highs will rise from the middle 80s F into the lower and middle 90s F. By Friday, the upper trough responsible for the scattered showers earlier in the week will be just east of the area, placing the ArkLaMiss under convergent upper flow and increasing upper heights. This will dramatically lower rain chance as we head into the weekend with only isolated showers and storms in the evening. An additional upper trough will approach the area by late in the day Sunday which should bring increased rain chances and perhaps a marginal reduction in afternoon high temperatures to close out the week. Day 7 and beyond, we venture a bit into the unknown as a complex pattern could evolve with an upper low in retrograde or stalled across Texas which could block the pattern somewhat with flow to the north of the cut off low becoming zonal or a bit ridged. This will likely lead to near or above average temperatures and near to slightly below average rain chances as we start next week with the late-Sunday trough lifting out to the east. /86/ && .AVIATION... 00Z TAF discussion: Mainly VFR conditions reported in the short term...with a broken line of thunderstorms lifting through JAN/HKS this afternoon. Showers and thunderstorms will be ending soon...and dissipating as they move northward. Llvl moisture will contribute to LIFR cigs in PIB/HBG...and IFR for HKS/JAN/MEI/GTR in the overnight. SREF and HRRR as well as other guidance is in good agreement about the northern extent...if not necessarily about the magnitude. However, persistence will side on LIFR in the southeast in the predawn hours. Another day with showers and thunderstorms and light se winds for tomorrow. && .PRELIMINARY POINT TEMPS/POPS... Jackson 72 88 72 86 / 24 73 46 82 Meridian 70 85 69 86 / 29 82 46 81 Vicksburg 73 90 72 88 / 18 68 45 79 Hattiesburg 72 85 71 86 / 29 86 50 82 Natchez 72 88 71 85 / 26 77 53 82 Greenville 71 89 71 88 / 11 32 28 73 Greenwood 71 90 71 88 / 11 43 31 74 && .JAN WATCHES/WARNINGS/ADVISORIES... MS...None. LA...None. AR...None. && $$ NF/HJS/DC/LP
Area Forecast Discussion
National Weather Service Pendleton OR
814 PM PDT Mon Jul 5 2021 .SHORT TERM...It was another hot and dry day with highs in the mid-80s to mid-90s for most of the forecast area--95 to 100 over the Lower Columbia Basin. Temperatures today were very similar to the highs observed on the 4th. Tuesday will likely be several degrees warmer as the inverted surface thermal trough strengthens east of the Cascades, and heat risk graphics place the area under moderate to high risk for those sensitive to heat. Since this is a one-day advisory situation, and people know it`s hot, I will not issue any Heat Advisories for tomorrow. The focus will be fire weather and the probability of new fire starts due to lightning as well as the increasing wind Tuesday night and Wednesday. Fire Weather Watches were issued for the forecast area from Tuesday afternoon through Wednesday evening. There are a lot of challenges with the upcoming shortwave trough late Tuesday and Wednesday. The center of the trough is currently about 500 miles west of the northern CA coast and will weaken as it lifts northward along the OR coast on Tuesday. This will force the upper level ridge and inverted surface thermal trough eastward. The breakdown of the upper ridge will increase instability. However, cooler marine air with a strengthening onshore flow will provide some stability at the surface Tuesday night and Wednesday. The instability will be aloft. The question is the amount of moisture which is quite limited. For Tuesday night, some of the CAMS models (particularly HRW) advertise weak radar reflectivity over Grant, Union, and Wallowa Counties. Thunderstorms will mostly be isolated Tuesday night. On Wednesday morning, as the upper level trough tracks northeast across WA, the upper level dynamics will play a role in high based thunderstorms over south central WA. Models show very little to no QPF which is disconcerting when looking at the elevated instability. Those in the Lower Columbia Basin and surrounding valleys could wake up to several hours of thunderstorms and possible new fire starts. Confidence isn`t high at this point, so will keep the watch going for now and see what future CAMS models have in store. The marine push will improve humidity values but winds will cause problems for fire spread on Wednesday. Wildfires have increased in numbers since Thursday night storms. The upper flow from the southwest will push smoke from fires in northern CA over central and southeast OR, but the HRRR and USFS Blue Sky show this as more elevated smoke and not extensive at the surface. Air quality monitors for both eastern WA and OR remain good. Current forecast indicates haze for our eastern OR zones, and patchy smoke was added to the John Day Basin where the Dixie Creek, Lewis Rock, Bologna, and Lovlett Corral are in the vicinity. Wister && .PREV DISCUSSION... /issued 420 PM PDT Mon Jul 5 2021/ LONG TERM...Thursday through Monday...Deterministic and ensemble guidance are in good agreement through the extended period and continue to indicate that the hot and dry trend will persist into the weekend. Thursday, guidance depicts a second, weaker, shortwave trough moving across the forecast area, and exiting by the evening. Though weaker, the shortwave trough will reduce temperatures another 1 to 3 degrees compared to Wednesday, and likely bringing the coolest day over the next week with highs in the upper 80s to 90s. At the surface, tight cross Cascade pressure gradients with a mid- level jet will produce another day of breezy winds across the forecast area, especially through the Gorge and the Kittitas valley. Behind the departing shortwave trough, upper level ridging will build back over the region while the thermal trough pushes north into southeast Oregon. Conditions will continue to be dry across the forecast area with warming temperatures under the ridge and thermal trough while winds will mostly be light with an occasional light breeze in the Gorge and the Basin. Saturday, ridging over the area will be muted and a westerly flow aloft setups as a shortwave trough dropping out of the Gulf of Alaska into central BC suppresses the upper high pressure over the Southwest. Meanwhile, the thermal trough centered over central NV will support a warming trend Saturday, with temperatures across the Basin likely breaking the triple digits in the afternoon. Breezy westerly winds will develop as well in the afternoon and evening Saturday as surface pressure gradients tighten across the Cascades. Sunday and beyond, deterministic and ensemble guidance begin to come into a strength and timing disagreement with the next synoptic feature to impact the area. The general trend amongst guidance is that the shortwave trough moving into central BC will clip the forecast area. The GFS deterministic and ensemble mean depict the shortwave trough strengthening and shifting south, producing breezy conditions through the Cascade gaps and cooler temperatures Sunday afternoon. However, ECMWF deterministic and ensemble mean shows the feature weaker and further north, which would still result in low end breezy conditions, but not as great of a cooling trend. Confidence is moderate that the feature will produce breezy conditions and a slight cooling trend, however, the intensity of each brings low confidence, so have elected to to keep NBM temperatures as it falls between the ECMWF and GFS outcomes and have increased winds for Sunday. Lawhorn/82 AVIATION...00Z TAFs...Clear skies will prevail at the terminal airports through Tuesday afternoon, but high-based cumulus buildups will develop after 21Z. Bases around 12K-14K expected. Winds will primarily be light and terrain driven, although there will be evening gusts at 15-20 kts. Wister FIRE WEATHER DISCUSSION...Upper ridge building over the region tonight into Tuesday. Meanwhile an upper low will be approaching the California coast. This low will move across Oregon into Washington Tuesday night and Wednesday. Thunderstorms are expected to develop over central Oregon Tue afternoon and evening, then move across northern Oregon into southern Washington overnight and Wednesday morning. Gusty westerly winds will then develop as this system departs on Wednesday. It will remain breezy into Thursday. FIRE WEATHER WATCH IN EFFECT FROM LATE TUESDAY AFTERNOON THROUGH WEDNESDAY EVENING FOR ABUNDANT LIGHTNING FOLLOWED BY WIND AND LOW RELATIVE HUMIDITY FOR FIRE WEATHER ZONES OR610, OR611, OR639, OR640, OR641, OR642, OR643, OR644, OR645, WA639, WA641, WA643, WA645, WA675, AND WA681. && .PRELIMINARY POINT TEMPS/POPS... PDT 60 99 66 92 / 0 0 20 20 ALW 65 102 70 94 / 0 0 20 20 PSC 66 102 67 97 / 0 0 20 20 YKM 60 100 68 94 / 0 0 20 20 HRI 63 103 70 96 / 0 0 20 20 ELN 61 98 65 87 / 0 0 20 20 RDM 54 98 55 89 / 0 10 20 10 LGD 59 97 61 89 / 0 0 20 20 GCD 61 98 61 90 / 0 10 20 10 DLS 64 100 67 85 / 0 0 20 20 && .PDT WATCHES/WARNINGS/ADVISORIES... OR...Fire Weather Watch from Tuesday afternoon through Wednesday evening for ORZ610-611-639>645. WA...Fire Weather Watch from Tuesday afternoon through Wednesday evening for WAZ639-641-643-645-675-681. && $$ SHORT TERM...85 LONG TERM....82 AVIATION...85
Area Forecast Discussion...UPDATED
National Weather Service Portland OR
852 PM PDT Mon Jul 5 2021 Updated Aviation discussion .SYNOPSIS...Typical summer weather pattern prevails, with only minor changes expected over the next week. Onshore flow will maintain coastal low clouds, which will spread inland to varying degrees each night and morning before clearing back to the coast for sunny afternoons inland. Temperatures remain near to above normal, with little to no precipitation expected. Tuesday appears to be the warmest day this week, followed by a cooldown Wednesday and Thursday as a weak upper trough moves onshore and deepens the marine layer. && .SHORT TERM...This evening through Thursday...With little changing in the synoptic pattern, the coverage of stratus tonight and early tomorrow is likely to be similar to today. The main difference will be the depth of the marine layer, which should be a little lower tonight thanks to a weaker gradient across the area. Observations last night revealed a +6-8mb pressure gradient from Spokane to North Bend, while forecasts (which, of course, are just that - imperfect attempts to ascertain the future) from the GFS and NAM for tonight`s gradient are slightly weaker at around +4-7mb. As a consequence, the tops of clouds, which (according to approximations based on current Satellite) are around 2,500-3,000 ft, should be slightly lower tomorrow. To account for this, tomorrow`s cloud forecast was made to be essentially a repeat of this morning`s forecast, minus elevations over around 2,000 ft (which, being above the marine layer, are expected to remain cloud-free). Heights continue to rise across the area through tonight as a strong ridge builds to our southeast across the Great Basin and Desert Southwest. The GFS, ECMWF, NAM, and UWWRF agree that thereafter a shortwave trough and its associated vorticity maximum will approach the Oregon and Washington coasts from the southwest. This feature bears watching to evaluate thunder potential for the Tuesday night timeframe. Several high resolution models - including the NAMNest, HRW, and HRRR - depict composite reflectivities indicative of elevated convection impacting areas (which vary from one model to another) from the central Willamette Valley north and east into the north Oregon and south Washington Cascades from about 10 p.m. Tuesday to 6 a.m. Wednesday. Forecast soundings from various models suggest the presence of elevated instability, which, if recognized, could prove sufficient for convection capable of lightning. Because this highly elevated (NAM soundings suggest the LFC is at upwards of 14,000 feet) instability is above a deep layer of convective inhibition, lifting parcels to this level of the atmosphere is a challenge. If the LFC should be lower than what models suggest, orographic forcing may be sufficient to trigger free convection; if not, storms are less likely, but still possible via another mechanism. The NAM and GFS are both portraying a lowering of the dynamic tropopause ahead of the approaching trough. If this materializes, the mass of stable, sinking air may serve as a wedge to lift air parcels into the unstable tier of the atmosphere. With the freezing level present in this unstable layer, a mix of liquid and frozen water droplets would result - yielding sufficient charge separation for a few lightning strikes. Given this (low, but not nonexistent) chance for thunder, along with SPC`s addition of a thunder outlook for the northeastern third of our CWA, we have decided to include a mention of it in our forecast for parts of the area. By mid-morning Wednesday, any remaining convection will have exited our area to the northeast. In west-southwesterly 500hPa flow behind the trough, and with a strengthening gradient across the area, a strong marine push will likely overspread the region with clouds and result in some drizzle along the coast. However, the next system, right on the heels of its predecessor, will swing ashore Wednesday night and cross the area early Thursday. This system is currently progged to be dry, but will serve to keep the entire area seasonably cool Thursday with highs in the low 80s across the Willamette Valley and 60s along the coast. /Bumgardner .LONG TERM...Thursday night through Monday...In the wake of the aforementioned low, heights begin to rise Thursday night into Friday before another low approaches from the Gulf of Alaska. Deterministic runs of the GFS, Euro, and CMC each depict this system, but differ considerably on its shape, size, location, and timing of possible arrival. Interestingly enough, WPC cluster analysis solutions, while not all the same, are not drastically different from one another - the general trend being for weak ridging to zonal flow over the area. The shortwave trough depicted by the deterministic models might be getting washed out by the cluster analysis trends, but regardless the chances for seeing precipitation (especially wetting precipitation) seem low at this time. /Bumgardner && .AVIATION...At 0345Z Tuesday, marine stratus remained over the south WA/north OR coast and the Willapa Hills. Stratus was also beginning to push into KONP. Expect stratus to continue along the coast through 18-19Z Tuesday before scattering out. The exception to this will be at KAST, where stratus will have the potential to linger through the day like it has the past couple of days. That said, model guidance does suggest there will be a brief break at KAST between 21-00Z before stratus moves right back in. Confidence is low that this break will actually materialize, so for now will assume stratus will last through the day since the overall pattern will be very similar to the past couple of days. Similar to last night, stratus will once again push down the Columbia River into Clark County and the northern Willamette Valley towards 12Z Tuesday. This should affect KPDX and KTTD, but is not expected to affect KHIO or KUAO. KSLE and KEUG should also remain clear tonight. Stratus should scatter out by 16-17Z for inland locations. For detailed regional Pac NW aviation weather information, go online to: KPDX AND APPROACHES...Expect marine stratus to return around 12Z Tuesday with cigs around 1100-1400 feet, before scattering out around 16Z. -TK && .MARINE...Will continue to see high pressure centered offshore combine with low pressure will inland to result in a general northwest to north wind across the waters. Strongest winds will occur inside of 30 NM and over the central coastal waters this afternoon and evening. Otherwise, pressure gradients will ease for the next couple days with winds gusting 15-20 kts, strongest in the afternoons and early evenings. Seas are generally expected to remain in the 4 to 6 ft range with a dominant northwesterly fresh swell component. Choppy seas can be expected at times, especially during the afternoons and evenings as wind waves build. /JBonk && .PQR WATCHES/WARNINGS/ADVISORIES... OR...None. WA...None. PZ...Small Craft Advisory until 7 AM PDT Tuesday for Waters from Cascade Head to Florence OR from 10 to 60 NM. Small Craft Advisory until 11 PM PDT this evening for Coastal waters from Cascade Head to Florence OR out 10 NM. && $$ Interact with us via social media:
Area Forecast Discussion
National Weather Service Phoenix AZ
410 PM MST Mon Jul 5 2021 .UPDATE... Updated Aviation && .SYNOPSIS... Drier conditions will settle into the area, likely persisting through the majority of the week. Daily isolated storms will still be likely across the eastern Arizona high terrain, while the lower deserts will mostly remain dry. Temperatures will warm to a few degrees above normal for much of the coming week with highs mostly in a 109 to 112 degree range across the lower deserts. A slight boost in moisture is likely later this week, but this alone is not likely to be enough to bring back rain chances for the lower deserts. && .DISCUSSION... Latest water vapor imagery reveals drier air aloft overspreading the Desert Southwest, however conditions remain quite moist in the lower levels with dewpoints in the 50s and even lower 60s. Total PWATS are near 1.5 inches in Phoenix but are steadily decreasing. Meanwhile, RAP streamline analysis indicates the Monsoon High has taken up residence near the Four Corners, while the 700 mb ridge is positioned across southwestern Arizona. This is resulting in a weak north-northwesterly steering flow across the higher terrain well east of Phoenix, where there is more instability and convection is more likely to initiate. Consensus from the CAM ensemble indicates only isolated storms will develop across Gila County this afternoon, before drifting southward. There is also a very low probability of an outflow boundary with gusty winds reaching the Valley this evening. NBM PoPs remain less than 5 percent across the Valley this evening, owing to widespread convective inhibition. This is largely due to a well-defined subsidence inversion around 800 mb evident on the latest ACARS sounding. Latest HREF depicts debris clouds lingering overnight, which will likely result in temperatures a few degrees above normal. && .PREVIOUS DISCUSSION... Looking at the large scale pattern throughout the coming week, model ensembles have shifted the positioning of the building ridge. Currently, the upper level (250/300mb) ridge center is situated just south of Arizona. There is now better agreement in this ridge slowly shifting to the northwest late this week while strengthening, becoming another anomalously strong ridge over the Western U.S. Previous runs were fairly similar, but there was at least a strong sign of a moist easterly return flow later in the week. This is still somewhat true, but a likely stronger ridge and a subtle shift in the winds will likely only give us a brief window of moisture return, mostly involving shallow Gulf of California moisture surges Wednesday into Thursday. After limited storm chances over the eastern Arizona high terrain through Wednesday, Thursday could possibly bring a few isolated storms to the south-central Arizona deserts with the help of the GoC surge, but it is looking much less likely due to the lack of deeper moisture. Friday is likely to be similar to Thursday, but NBM PoPs continue to back off on rainfall chances over the lower deserts (now at 10% for Phoenix, down from 20%). PoPs for next weekend are also considerably lower than the previous few forecast packages as the shift in the high center to our west northwest is likely to bring more pronounced northerly dry flow. We will have to wait and see if the potential moisture return later this week will be enough for a return of storm chances for some of the lower deserts. A warming trend is definitely on the way over the next couple days as the boundary layer dries out. Highs are still forecast to warm to around 110 degrees across the western deserts today and then over the south-central Arizona deserts starting Tuesday. From Tuesday through the coming weekend, NBM guidance shows little variability in forecast highs mostly ranging from 109-111 degrees across the Phoenix area to 110-113 degrees across the western deserts. As the ridge strengthens later this week, these temperatures will mostly be dependent on how much boundary layer moisture is present. If we end up being drier than forecast, temperatures very well could reach excessive heat levels in some areas. The highest probabilities of this occurring looks to be during the Friday-Sunday time period when the ridge is likely peaking in intensity. && .AVIATION...Updated at 2310Z. South-Central Arizona including KPHX, KIWA, KSDL, and KDVT: Westerly winds will weaken this evening with speeds falling below 10 kts. Guidance shows easterly winds struggling to take hold overnight. Chances for convection in Phoenix this evening is low (< 10%) and model guidance do not support outflows reaching the terminals. West winds should return quickly be late Tuesday morning. FEW-SCT clouds aoa 10 kft are forecast through the period. Southeast California/Southwest Arizona including KIPL and KBLH: Mostly clear skies are expected through the TAF period. South winds will be expected at KBLH with NBM showing speeds as high as 12kt. West winds at KIPL should become SE again Tuesday morning with NBM showing a few gusts up to 20kt this evening. && .FIRE WEATHER... Thursday through Monday: Somewhat drier than normal conditions will generally confine the threat of storms to the higher terrain north and east of Phoenix. Strong high pressure affecting the region will also result in slightly above normal temperatures. Min RH values will generally be in a 15-20% range over the lower deserts and 20-30% across the eastern Arizona high terrain. Max RHs will recover into the 35-45% range for lower deserts locations to 50-60% across the high terrain. Wind patterns should follow diurnal patterns for much of the period with daily afternoon gusts to around 20 mph likely. && .SPOTTER INFORMATION STATEMENT... Spotters should follow standard reporting procedures. && .PSR WATCHES/WARNINGS/ADVISORIES... AZ...None. CA...Excessive Heat Watch from Saturday morning through Sunday evening for CAZ560-561-570. && DISCUSSION...Hirsch PREVIOUS DISCUSSION...Kuhlman AVIATION...Smith/18 FIRE WEATHER...Kuhlman/Hirsch
Area Forecast Discussion
National Weather Service Pueblo CO
904 PM MDT Mon Jul 5 2021 .UPDATE... Issued at 901 PM MDT Mon Jul 5 2021 The Flash Flood Watch has expired. There is still a chance for some lingering showers this evening, but severe and flash-flood potentials have dwindled significantly. && .SHORT TERM...(This evening through Tuesday) Issued at 328 PM MDT Mon Jul 5 2021 1) The threat for heavy rain and flash flooding across the burn scars continues this evening, along with the potential for scattered strong to severe storms along and west of I-25. 2) More widespread showers and storms are expected across the eastern mountains and plains on Tuesday, with the flash flood risk for area burn scars along with the potential for strong to severe storms also returning. Showers and thunderstorms continue this afternoon, continuing to focus over and near the mountains. The main hazard so far this afternoon has been heavy rain with possible flash flooding across the burn scars. Radar trends along with short term guidance all are pointing toward an increase in coverage of storms around the burn scars here in the near term, and likely persisting through mid evening. Given these trends, have not made any adjustments to the current Flash Flood Watch in effect. Still anticipate thunderstorm development away from the mountains towards the I-25 corridor this afternoon into early evening, with the potential for some of these to become strong to severe. Once again, no change in this thinking, but do think the severe threat may be more isolated. Latest RAP analysis showing weakening trends with instability and shear, and with short term guidance indicating this might continue into the evening. So, while storms will remain possible along the I-25 corridor into this evening, think only a few storms will be strong to severe. Overall coverage of showers and storms will diminish by mid to late evening, with the threat of heavy rain/flash flooding lowering. However, weak west/northwest flow aloft will remain in place along with the potential for some weak mid level waves to move overhead. This may keep the precip development occurring across Lake and Chaffee counties, but think the intensity of any additional showers or a few storms will be much lower. So, have not extended the Watch for this area at this time. With this northwest flow remaining in place on Tuesday, a boundary is expected to push south across CO early Tuesday. This setup and boundary along with a steady and deep push of east northeast winds will help support thunderstorm development across the plains and eastern mountains on Tuesday. This support will be in place rather early in the day, and expect thunderstorm development to be early in the day across both the mountains and plains. Instability and shear expected to increase in the afternoon, supporting a risk for strong to severe storms over much of the plains. Additionally, persistent and strong focus across the eastern mountains will support another day of higher potential for burn scar flash flooding. .LONG TERM...(Tuesday night through Monday) Issued at 328 PM MDT Mon Jul 5 2021 ...On Tuesday, a chance of thunderstorms will be possible over most of the CWA during the afternoon and evening afternoon and evening, some of these storms could become severe, especially over the central and southeast plains. On Wednesday, slight chance of a thunderstorm during the morning hours over the far southeast plains. Isolated thunderstorms will be possible later in the day, mainly during the afternoon, over the mountains. On Thursday...a slight chance of thunderstorms will be possible during the afternoon and evening over the mountains. On Friday and Saturday, thunderstorms will be possible over the mountains and plains, with the best chance being over the southern Sangre de Cristo Mountains, Raton Mesa, and southeast plains in the evening for both days. On Sunday and Monday, thunderstorms will be possible in the afternoon for both days, with a better chance on Monday... Tuesday... A weak perturbation in the longwave pattern overhead to the north coupled by some monsoonal flow around the plateau high with the upper level ridge in place over the southwest CONUS will allow for there to be some moderate instability over the area a bring a chance of thunderstorms over most of the CWA, with a possibility of strong to severe thunderstorms over the plains. Greatest areas that there looks to be a severe potential will be over the I-25 corridor and over the central and southeast plains, due to a weak convergence boundary and also the possibility of a weak lee-side meso-low cyclogenesis over the southern I-25 corridor as some models are indicating. MLCAPE and MUCAPE values are appearing to be highest over the central and eastern plains, with an area of relatively high CAPE right along the I-25 corridor of more than 1500 J/kg, although this is all relatively skinny CAPE, whereas the values of over 2000 J/kg over areas of the eastern plains yield a little more fatter of a CAPE in the profile sounding, along with some helicities between 150 and 200 m^2/s^-2 showing up on the ARW and WRF models, which will give this area more of a favorable environment for rotating updrafts. The NAM 3km does have an area of very strong bulk sheer with most of this being between 0-3km and values in excess of 55 kts over the central portion of the I-25 corridor at around 1600L, this area is just southeast of the Wet Mountains and if this model holds true, there could also be potentially severe storms forming in this region as well. Main threat due to the CAPE being more of a skinnier profile, would be strong downdraft winds, but there could also be some hail of 1 inch or greater and a very slight chance of a weak tornado, yet the greater chance of an isolated tornado occurring would be over the central and southeast plains. Storms are likely to develop elsewhere and could possibly still become strong to severe, especially over the southern Sangre de Cristo Mountains and Raton Mesa area. Burn scars will could also experience flash flooding as well, yet if there is enough shear in the mid levels, it could help to prevent the storms from becoming too stationary and hopefully bring down the risk, yet with heavy rain in a brief period of time associated with some of these thunderstorms, even the storm not being stationary could still have an impact. Winds will become predominantly out of the northeast later over the plains and cooler as well tomorrow with the trough overhead, with high temperatures around 5 degrees cooler than the seasonal average for most locations. Rain showers and some thunderstorms will continue into the evening hours and overnight for the southeastern portion of the CWA. Only some clearing will take place further west and lows for Tuesday night will fall into the mid 50s to low 60s for the plains, to the 40s and low 50s for the mountain valleys and generally the 40s for the mountains and 30s for the highest peaks. Wednesday and Thursday... The upper level ridge axis over southwest CONUS is going to continue to slightly propagate further west and become squished by a trough deepening over the northwest in the longwave pattern, this will allow for relatively cooler and drier air to move in from the west over the Pacific upstream, and help to dry out of mid level monsoonal moisture for both of these days and hinder much in the way of thunderstorm development for both of these days. There will be a slight chance due to some residual moisture along a weak boundary associated with the trough downstream for there to be a few morning shower or thunderstorms over the southeast plains, otherwise only some isolated thunderstorms will develop during the afternoon and early evening over the mountains on Wednesday. On Thursday, isolated thunderstorms will be possible again over the mountains, with the central mountains having the best chance for this day. The troughing upstream will enhance the mid-level flow out of the west with an adiabatically warming downsloping wind, coupled with southerly flow over the plains, will result in hot and dry conditions for most of the region and above the seasonal average high temperatures for most locations on Thursday. && .AVIATION...(For the 00Z TAFS through 00Z Tuesday evening) Issued at 328 PM MDT Mon Jul 5 2021 VFR conditions will be predominant throughout the forecast period for all TAF sites, CIGs will remain fairly high based although they could come down a bit in SHRA or TSRA in the vicinity of all terminals for the rest of this evening. Keep in mind that outflows can also cause wind shifts to occur in the vicinity of anyone of these terminals. Some of the higher wind gusts in the lower levels near KALS later in the day could also result in some light to moderate CAT near the surface. Winds at KALS will be primarily light and variable and then become NW`ly and then back to the NE and increase a little with some gusts as high as 22 kts, they will weaken later in the evening and become East to SE`ly and return to light and variable by tomorrow morning. At KCOS and KPUB, SE`ly winds will eventually shift out of the NW later this evening and then remain from that direction throughout the rest of the forecast period. && .PUB WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...GARBEROGLIO SHORT TERM...RODRIGUEZ LONG TERM...STEWARD AVIATION...STEWARD