Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 07/26/21


AREA FORECAST DISCUSSION
National Weather Service Albany NY
1010 PM EDT Sun Jul 25 2021 .SYNOPSIS... Isolated thunderstorms will diminish this evening, allowing for a mostly clear sky with patchy fog for tonight. High pressure will allow for dry and warm weather on Monday. The next storm system will approach for Tuesday, with some scattered afternoon showers and thunderstorms. Drier and less humid conditions should return for Wednesday. && .NEAR TERM /UNTIL 6 AM MONDAY MORNING/... As of 1010 PM EDT...Showers and thunderstorms have dissipated over the region, with any remaining isolated showers remaining south and east of the region. With nocturnal cooling taking over, all showers and storms over the region should be completely done by the next hour or two. Any clouds should also be dissipating or exiting as well as surface high pressure to the west stretches towards the area. Moist low levels remain in place and with a quickly cooling boundary layer thanks to the fairly clear skies, it looks to be a good setup for radiational valley fog overnight. The fog will be most dense for areas that saw recent rainfall for the late night hours, but should start to lift after sunrise Monday. Overnight lows will generally be upper 50s to mid 60s, with the coolest temps across the Adirondacks, Catskills and southern Vermont. && .SHORT TERM /6 AM MONDAY MORNING THROUGH WEDNESDAY/... Monday, high pressure builds overhead setting the stage for a period of dry weather into Tuesday. Partly to mostly sunny skies are expected with high temperatures warming into the upper 70s to mid 80s. Haze/smoke from the wildfires out west should also be evident from the Capital District northward throughout the day. Have added in the haze wording into the forecast to account for this (per latest HRRR smoke forecast guidance and upstream observations). Clouds begin increasing late Monday night as a cold front approaches from the Saint Lawrence River Valley. Overnight lows will be in the upper 50s to low 60s once again. Tuesday, a cold front will drop south through the forecast area, mainly during the afternoon and evening hours. There is still some timing differences between the model guidance but if the passage is coincident with peak heating, could be an active severe weather day. Model soundings indicate ample SBCAPE (>1500 J/kg), modest low level lapse rates and increasing PWATS. Given the uncertainty of the timing, we are not in an severe weather outlook from SPC quite yet and have therefore maintained just a chance for thunder (with no enhanced wording) in the forecast. With all that in mind, showers and thunderstorms are expected to traverse the forecast area from north to south throughout Tuesday afternoon/evening before exiting to the south late Tuesday night. Also dependent on the frontal passage will be afternoon high temperatures with low 70s expected to the north, and upper 80s to the south. Drier, cooler air filters in Monday night, with lows dipping into the low 50s up north to the low 60s down south. Wednesday looks like another dry and mostly sunny summer day with highs in the low to upper 70s. && .LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/... A persistent mid-to-upper level pattern will continue over the CONUS through this period with strong ridging over the Rockies and plains and northwest flow over the northeast. The main system to affect our area during this period will be a short wave trough diving southeast from Ontario across the northeast CONUS Thursday and Thursday night. The GFS and ECMWF and ensembles are in good agreement with this scenario, which would bring a good chance of showers and thunderstorms to the area Thursday into Thursday night. Enough warm air and higher dew points will likely be drawn northeastward ahead of this system so that a severe threat and localized convective heavy rain potential will exist on Thursday, although obviously with this system still several days away certainty on any details is low. High pressure will build southeast behind the short wave trough on Friday and Saturday, setting the stage for a period of dry, comfortable weather. Temperatures will be a bit below normal with highs in the 70s to near 80 and lows Friday night mostly in the 50s, with some 40s possible over higher terrain and across the north country. && .AVIATION /02Z MONDAY THROUGH FRIDAY/... Showers and thunderstorms are dissipating and moving away from the region. With a thunderstorm exiting the Pittsfield area, will continue a TEMPO for one hour at KPSF for any lingering clouds/light rain with the exiting storm, but the threat for precip looks to be ending quickly. With a humid airmass in place at low levels, will expect radiational fog to form tonight thanks to fairly clear skies and light winds. All sites have a chance at seeing some fog, but KGFL/KPSF have the best chance at a prolonged period of IFR fog after midnight. Can`t rule out IFR fog at KALB and possibly KPOU as well, but it looks to occur just for a short period prior to daybreak for those sites. Any fog/mist should dissipate shortly after sunrise, allowing for VFR conditons to return to all sites. Light southwest winds will become westerly at 5 to 10 kts. Few-sct diurnal cu around 5-6 kft will develop by afternoon, but it will remain VFR for all sites through the day with no precipitation. Outlook... Monday Night: No Operational Impact. NO SIG WX. Tuesday: High Operational Impact. Likely SHRA...TSRA. Tuesday Night: Moderate Operational Impact. Chance of SHRA...TSRA. Wednesday: Low Operational Impact. Slight Chance of SHRA. Wednesday Night: Low Operational Impact. Slight Chance of SHRA. Thursday: Moderate Operational Impact. Likely SHRA...TSRA. Thursday Night: Moderate Operational Impact. Chance of SHRA. Friday: Low Operational Impact. NO SIG WX. && .FIRE WEATHER... Dry air has quickly filtered into the region, allowing for a mostly sunny summer day. Skies will clear overnight as high pressure builds into the region, resulting in a dry period of weather Monday into Tuesday. Temperatures will be seasonable. The next chance for rain and thunderstorms arrives on Tuesday with a cold frontal passage. RH values will increase to 90 to 100 percent tonight with patchy fog forming. The RH values will decrease to 40 to 55 percent during Monday afternoon before recovering into the 85 to 95 percent range Monday night. South to southwest winds at 10 to 20 mph are expected through this evening. The winds will be west or southwest at 5 to 10 mph tonight into Monday. && .HYDROLOGY... Outside of an isolated shower or storm this afternoon, dry weather is expected through Monday night which will allow streams and rivers to lower closer to late July normals. The next chance of showers and thunderstorms will be Tuesday afternoon and also on Thursday. 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...None. MA...None. VT...None. && $$ SYNOPSIS...Frugis NEAR TERM...Frugis SHORT TERM...JLV LONG TERM...MSE AVIATION...Frugis FIRE WEATHER...JLV/Wasula HYDROLOGY...JLV/Wasula
Area Forecast Discussion
National Weather Service Burlington VT
1019 PM EDT Sun Jul 25 2021 .SYNOPSIS... Any lingering showers or thunderstorms will be ending overnight with with patchy fog developing. Monday will feature partly sunny skies, seasonal temperatures and a few isolated showers and thunderstorms in the afternoon. A cold front will bring more numerous showers and thunderstorms Tuesday, followed by high pressure and cooler temperatures on Wednesday. && .NEAR TERM /THROUGH MONDAY NIGHT/... As of 1019 PM EDT Sunday...Still hanging on to a couple isolated showers and thunderstorms with a subtle short wave trof skirting just north of the international border. They should be winding down soon. Still looking at patchy fog, especially in the river valleys of VT and where it rained. Visibility restricted in fog/haze/smoke overnight. Previous Discussion...Fairly quiet weather is expected this evening and overnight. Convection has had a hard time developing this afternoon due to the copious amount of dry air aloft. That being said, have seen a few light returns on radar recently, so still believe a light shower or two will be possible through sunset. Precipitation chances are a little better along the international border later tonight as a weak upper shortwave skirts through southern Ontario/Quebec, though coverage will remain limited by the aforementioned dry air. There will be a little elevated instability, so a rumble of thunder or two will also be possible. Moisture will be plentiful at low levels however, and with clearing skies and light winds, patchy fog is expected late tonight into early Monday, especially in the favored valley locations. Lows tonight will be on the muggy side, generally in the upper 50s to mid 60s. For tomorrow, still expect a few showers and thunderstorms to pop up in the afternoon. There`s little in the way of forcing outside of daytime heating and shear is unimpressive. The dry air at mid-levels will also remain, so coverage and intensity of any convection will be minimal. Also of concern for tomorrow is the potential for hazy conditions due to smoke drifting in from western wildfires. Smoke is clearly visible on satellite and a fair number of observations in Ontario north of the Great Lakes have been reporting visibility restrictions due to smoke and/or haze most of the day. HRRR model guidance indicates that this will drift over our region tomorrow, so anticipate we`ll see haze through a good part of the day. Highs will be in the upper 70s to mid 80s. Isolated showers/thunderstorms continue to be possible in northern sections Monday night with a cold front slowly approaching from the north. Otherwise, it should be partly cloudy with patchy fog once again. Lows will be very similar to what is expected tonight. && .SHORT TERM /TUESDAY THROUGH TUESDAY NIGHT/... As of 346 PM EDT Sunday...Main challenge for this period continues to revolve around the timing of a strong cold front. Its passage in the latest data looks a bit later on a whole, which will increase the chances of thunderstorms for central and southern areas. High temperatures also have been pushed up into the low 80s over a wider area of south central Vermont, with otherwise little change from the previous forecast. The front will be marked by a sharp low-level temperature change as winds turn northerly. Therefore, in spite of daytime heating, surface temperatures should fall behind the front. As an example, currently show temperatures falling from the mid-70s to upper 60s along the western slopes of the central Greens from noon through mid-afternoon. Still think showers and thunderstorms should be likely across our region given the strong forcing, but best chances of any stronger storms will be limited to the aforementioned southern Vermont areas. Much cooler and drier air Tuesday night will help temperatures fall into the upper 40s to low 50s in most areas with skies clearing out. && .LONG TERM /WEDNESDAY THROUGH SUNDAY/... As of 346 PM EDT Sunday...A fall-like pattern will dominate during this period as the jet stream sinks south of the area with a broad upper-level trough over the Northeast promoting shots of unseasonably cool and dry air. For those who prefer sun over clouds, you are in luck, as the upper- level low migrates well to our north, which will keep forcing for showers weak in our area aside from transient low pressure systems. We do have better clarity on timing of precipitation for this period, with both Wednesday and Friday night through Saturday morning looking dry areawide. A wave of low pressure passing to our north on Thursday is trending stronger among model guidance, with good moisture transport ahead of its accompanying cold front. For now have left out mention of thunder with progged instability low in the vicinity of 100 J/kg, but will have to keep an eye on temperature trends as greater heating could lead to more favorable parameters for thunderstorms. Behind that front we will see another shot of cool, dry air with breezy northerly or northwesterly flow. We may see a rinse and repeat over the weekend with another quick round of showers on Sunday in response to another frontal system, but no significant pattern change is evident in the global models. && .AVIATION /02Z MONDAY THROUGH FRIDAY/... Through 00Z Tuesday...Other than a thunderstorm at MPV this hour...mainly VFR over the next 24 hours, though it does look like the possibility of 5-6SM in HZ at times through the period due to wildfire smoke coming down from Canada. Otherwise the main concern will be local VLIFR/LIFR conditions in fog, especially at KSLK, KMPV, and KEFK. Have also added IFR in BR at KRUT where it rained recently. Start time of the fog a bit uncertain due rain there and expected rain at KMPV but thinking 3-5Z. Fog will lift 12-13z with VFR to prevail at all terminals through the remainder of the TAF period. South to southwest winds remain 5 to 10 kt with brief gusts to around 15 kt through 22z, then becoming light overnight before increasing out of the south- southwest after 13z Monday. Outlook... Monday Night: VFR. Slight chance SHRA. Tuesday: Mainly VFR, with areas MVFR possible. Chance SHRA, Slight chance TSRA. Tuesday Night: Mainly VFR, with local MVFR possible. NO SIG WX. Wednesday: VFR. NO SIG WX. Wednesday Night: VFR. Chance SHRA. Thursday: VFR. Chance SHRA. Thursday Night: Mainly MVFR, with local IFR possible. Chance SHRA. Friday: MVFR/IFR conditions possible. Slight chance SHRA. && .BTV WATCHES/WARNINGS/ADVISORIES... VT...None. NY...None. && $$ SYNOPSIS...Hastings/Sisson NEAR TERM...Hastings/Sisson SHORT TERM...Kutikoff LONG TERM...Kutikoff AVIATION...Hastings/Sisson
Area Forecast Discussion
National Weather Service Buffalo NY
1020 PM EDT Sun Jul 25 2021 .SYNOPSIS... High pressure across the Mid-West will gradually move eastward across Ohio, keeping our area mostly rain-free through Monday night. A cold front will drop across the region on Tuesday with some showers and thunderstorms possible. High pressure will then build back across the area providing dry weather for Wednesday. && .NEAR TERM /THROUGH MONDAY NIGHT/... The axis of a ridge of high pressure centered to our west will ridge across the region tonight. This will maintain dry weather and mostly clear skies. This will support fairly good radiational cooling, especially across interior valleys where temperatures should drop into the 50s tonight. Fog may develop across the Southern Tier valleys. Mainly dry again on Monday as the surface high moves closer and provides mostly sunny skies south of Lake Ontario. The St. Lawrence Valley will be closer to a mid-level trough, perhaps enough to support a stray showers or thunderstorm along the lake breeze boundary northeast of Lake Ontario. Otherwise, it will be a bit warmer than today with highs in the upper 70s to mid 80s. Visible satellite and observations show near surface smoke from the western wildfires across Northeastern Ontario this evening. HRRR guidance depicts this area moving near northern NY Monday which may produce hazy conditions across north central NY. A cold front will approach late Monday night, but model consensus keeps any precipitation associated with the front to our north and west. Fair radiational cooling with partly to mostly clear skies. Lows in the upper 50s to mid 60s. && .SHORT TERM /TUESDAY THROUGH THURSDAY/... There will be two systems that impact our region this period, both occuring with a west to northwest flow aloft. The first system will arrive Tuesday. Two shortwaves aloft will help to push a cold front across the region...with the first shortwave near the Saint Lawrence Valley and a second shortwave later across Western New York. Showers and thunderstorms blossoming along the cold front and ahead of the shortwaves will likely first be concentrated east of Lake Ontario by early afternoon Tuesday...and then later in the afternoon and early evening across WNY. There continues to be sufficient instability ahead of this front, along with 0-6km bulk shear values 35 to 40 knots to support the potential for a few stronger storms. As the cold front pushes across our region from northwest to southeast, showers and thunderstorms will taper down Tuesday Night. Much drier air aloft will push into the North Country by early evening, and then across WNY through the night. Lingering low level moisture could bring some patches of fog late Tuesday Night. Weak high pressure near the region Wednesday should bring a dry day with a mix of clouds and sunshine. Wednesday Night the next system will impact our region, mainly during the second half of the night. A mid level shortwave will cross our region, bringing renewed chances for showers and thunderstorms. PWAT values a little higher with this second system...nearing 1.75 inches could allow for heavier downpours...though at this time, an earlier timing in the day Thursday of convection could lower the threat for severe potential. With a decent amount of clouds around, especially Tuesday and Thursday high temperatures will be near or just below normal...while overnight lows dip to near normal levels. && .LONG TERM /THURSDAY NIGHT THROUGH SUNDAY/... In the wake of the cold front, high pressure builds east across the lower lakes bringing cooler and drier air to the region. The high will maintain dry conditions through Saturday. An area of low pressure moving across Ontario will bring the risk of some showers Saturday night and Sunday. Highs Friday will be in the upper 60s to low 70s, about 5 to 10 degrees below normal, followed by a slow warming trend with temperatures within a few degrees of the norm by Sunday. Overnight lows too will start cool with some interior sections of the southern tier and north country seeing lows in the 40s Friday night gradually moderating to near normal upper 50s to low 60s Saturday night. && .AVIATION /02Z MONDAY THROUGH FRIDAY/... Mainly clear tonight will support mainly VFR flight conditions. Fog is likely to develop across the Southern Tier Valleys, with a period of IFR likely at KJHW. Any fog will dissipate quickly on Monday. Prevailing VFR flight conditions expected during the day however haze from upstream smoke may track into the region. This may cause MVFR conditions at KROC and KART through the afternoon. Outlook... Monday night...VFR. Tuesday and Tuesday night...VFR/MVFR with showers and thunderstorms possible. Wednesday...VFR. Thursday...VFR/MVFR. A chance of showers and thunderstorms. Friday...VFR. && .MARINE... High pressure will build across the lower Great Lakes tonight and Monday. Pressure gradient will relax some across Lake Erie with lowering winds and waves, while winds remain somewhat elevated on Lake Ontario keeping choppy conditions in place, however waves should be less than 2 feet. && .BUF WATCHES/WARNINGS/ADVISORIES... NY...None. MARINE...None. && $$ SYNOPSIS...Apffel NEAR TERM...Apffel/HSK SHORT TERM...Thomas LONG TERM...Levan AVIATION...Apffel/HSK MARINE...Apffel/JM
Area Forecast Discussion
National Weather Service Caribou ME
1127 PM EDT Sun Jul 25 2021 .SYNOPSIS... A warm front will lift across the area tonight. A cold front will cross the area on Tuesday. High pressure will build over the area Wednesday. Low pressure will approach on Thursday. && .NEAR TERM /THROUGH MONDAY/... 11:30 PM Update...A line of showers and embedded thunderstorms can be seen moving toward the northwestern part of our area from the west. Increased pops and put isolated thunderstorms in as this moves through. However, anticipate it may weaken overnight as it moves across. Otherwise, no major changes this hour. Prev Disc: The warm front and transition to a more humid air mass is the dominant feature tonight into Monday morning with fog developing across the entire area tonight. A Dense Fog Advisory may be needed but will hold off for now. Rain will taper off by early evening ahead of the warm front, but light rain and drizzle is certainly possible throughout the night. Later tonight, an upper level shortwave will cross the area. This shortwave is currently associated with thunderstorm activity in southern Ontario and western Quebec. Although not all guidance shows it holding together across the northern half of the forecast area later tonight, some CAMS output has shown it for days and continues to do so. There`s some decent cooling aloft while a low level thermal ridge builds at the top of the frontal inversion tonight. This generates some elevated CAPE later tonight and shear also increases. Will maintain mention of isolated thunderstorms across Aroostook County late tonight into early Monday morning. Low clouds and fog will slowly burn off Monday morning. By this time the occluded front has moved across the area, leaving a much warmer and humid air mass. The morning low clouds will slow production of SBCAPE, but eventually there should be sufficient instability for isolated to scattered afternoon thunderstorms. The best CAPE and shear will be in southern Penobscot County and interior Downeast for a brief time in the early to mid afternoon. Shear looks marginal for strong storms. There`s also the remnants of the washed out occluded front in that area. There`s several factors inhibiting convection such as very dry air aloft, lack of a decent upper level shortwave like earlier in the day, and a cap near 500mb. Will mention thunderstorms across the area in the afternoon, but hold off on enhanced wording. Smoke is the other emerging issue for Monday. Have not added smoke or haze in the gridded forecast database at this time, but HRRR guidance and METSAT imagery shows smoke from Manitoba and Ontario fires heading this way...and it may mix towards the surface by Monday morning. That usually generates a lot of confusion and concern from the public. By the time clearing occurs later Monday morning into the afternoon, the smoke will likely be more noticeable. && .SHORT TERM /MONDAY NIGHT THROUGH WEDNESDAY/... Area wl be split btwn two fronts on Mon evening. Cannot rule out lingering showers over srn and nrn areas with an isold tstm still possible but coverage wl likely be on the decrease with loss of diurnal htg. Given moist and humid airmass still in place wl likely see areas of fog acrs the area Mon night. Depending on how quickly high pressure builds south out of Canada Tue morning wl determine where storms wl develop in the aftn as s/wv heads south and east out of Canada. This wl allow storms to develop along front dropping thru the CWA and shud allow storms to develop across central and srn zones aft 18z. Given the uncertainty have hesitated to call it chc showers and tstms and hv only worded it as isold tstms until details can be better ironed out. Secondary front wl mv offshore Tue evening with showers winding down aft midnight along the coast. Patchy fog expected to develop acrs the north as skies clear but drier dwpts may prevent fog to increase in coverage drg the overnight. Downeast coast may see patchy fog as well as humid airmass rmns in place, however skies wl still be cldy and prevent more widespread coverage. Sfc high pressure wl be building into nrn New England with cool northerly flow draining out of Canada. Skies will be mocldy on Sunday with nw winds ocnly gusting drg the afternoon. && .LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/... Flow rmns out of the nw aloft thru Wed night and wl gradually transition to a s/wv ridge acrs Maine Thu morning. Sfc high pressure wl be building well offshore Wed night and with skies clearing and light winds cannot rule out areas acrs the northwest dipping into the mid-40s. Next system wl be heading in fm the west and guidance fairly consistent in bringing showers, possibly stratiform rain, in wrn areas on Thu afternoon. Rain continues Thu night with showers expected especially across the north on Friday as upr lvl trof mvs thru Quebec into the Maritimes. Temps likely to be below normal thru the end of the long term and into next weekend. && .AVIATION /04Z MONDAY THROUGH FRIDAY/... NEAR TERM: Conditions to continue to deteriorate this evening to IFR and then LIFR due to low cigs, drizzle and fog. Fog is most likely for GNR towards HUL and points south...especially on the coast. FVE will also have fog. LLWS is expected late this afternoon into the early evening. Thunderstorms are possible north of HUL and GNR after midnight into early Monday morning. Isolated afternoon thunderstorms are expected Monday afternoon after morning fog and low clouds dissipate. SHORT TERM: Mon night...Potential IFR in areas of fog developing late at all terminals. Light WSW wind. Tue...Becoming VFR late morning with localized MVFR restrictions in -tsra, mainly at HUL and BGR. W 5-10kts. Tue night...VFR early, decreasing to localize IFR in fog late. NW 5 kts. Wed-Wed night. VFR. NW 5-10kts Wed becoming light SW Thu morning. Thu-Fri...Lowering to MVFR/IFR in rain and fog. S 5-10kts, becoming SW Fri morning. && .MARINE... NEAR TERM: Fog will thicken and become more widespread tonight and slowly move offshore Monday afternoon...returning again in the evening. S Wind Gusts will reach as high as 20 kts ovrngt before subsiding by daybreak, but will fall short of advisory criteria. These south winds will generate south seas reaching up to 4 feet by late tonight, then subsiding durg the day Mon. SHORT TERM: Winds and seas to remain below SCA thresholds through the week. Expect that humid airmass will bring areas of fog to the waters Mon night and Tue night before a cold front crosses the waters Wed morning. && .CAR WATCHES/WARNINGS/ADVISORIES... ME...None. MARINE...None. && $$ Near Term...VJN/MCB Short Term...Farrar Long Term...Farrar Aviation...VJN/Farrar Marine...VJN/Farrar
Area Forecast Discussion
National Weather Service Cheyenne WY
458 PM MDT Sun Jul 25 2021 .SHORT TERM...(This evening through Monday) Issued at 158 PM MDT Sun Jul 25 2021 Latest satellite displaying cumulus field across good majority of the forecast area as Td depressions over SE WY remain about 40-50 degrees. Ongoing pockets of isolated to scattered convection remains along and nearby elevated terrain in Albany and Carbon Counties early this afternoon. With growing cumulus field, expect to see some enhancement in overall coverage. Wind shear is lacking this afternoon over ongoing convection to limit and reduce any severe convection potential. A few brief gusty winds and moderate rainfall may be possible in the strongest of storms but overall precipitable water values hovering around 0.7 inches. Some storms late this afternoon into early evening may move off the higher terrain into portions of the high plains in SE WY. High pressure continues to build over the region as upper level low near the Four Corners continues to spin moisture northward aiding in our shower and thunderstorm potential today. Area haze on webcams from distant fires across the west continue to warrant inclusion in the forecast grids with high pressure building centered on us Monday should keep skies hazy and sunrise/sunset picturesque. Lows tonight front he upper 50s into middle 60s. Highs Monday a few degrees warmer into the upper 80s and middle 90s for SE WY and middle 90s to low 100s for the NE Panhandle. .LONG TERM...(Monday night through Sunday) Issued at 158 PM MDT Sun Jul 25 2021 Overall ridging pattern persists into midweek as midlevel trough digs into the west coast and slowly erodes the ridge as it drifts eastward. Warm and dry conditions continue Tuesday as subsidence continues though models have begun some trend to some western-based convection Wednesday across the southern mountains as pockets of vorticity and monsoonal moisture are advected in. Continued warm temperatures into the upper 90s and low 100s Wednesday for the Panhandle and upper 80s to upper 90s across SE WY. Long-range models continue consensus of weather pattern shift late in the week going into the next weekend as better moisture flow enters the region with elevated precipitable water values around an inch or so. Backdoor cold front expected to stall over the region in same timeframe with more widespread showers and thunderstorms. Severe threat late in the week remains fairly low as surface-based CAPE around 500 J/kg with some pockets of CIN available. Lapse rates in the low levels remain fairly weak under 7 degrees/km. Concern as stated by previous forecast remains with heavy precipitation and flooding potential that will have to be monitored over the next few days. Cold front though will usher in some cooler temperatures into the weekend from the upper 70s into low 90s across much of the forecast region. && .AVIATION...(For the 00Z TAFS through 00Z Monday evening) Issued at 453 PM MDT Sun Jul 25 2021 VFR conditions likely through the forecast period for all terminals. Minimal concerns outside of some gusty conditions around 20 to 25 knots, and some lingering convection from some outflow boundaries pulsing through the region. Will likely see shower and thunderstorm potentials drop off after 01z. Looking ahead into tomorrow, the HRRR is hinting at some convective development across Wyoming. However, confidence is low at this time as subsidence is expected to prevail. && .FIRE WEATHER... Issued at 126 PM MDT Sun Jul 25 2021 Fire weather concerns remain fairly limited through the week with isolated to scattered chances of showers and thunderstorms ahead of monsoonal moisture and widespread precipitation chances heading into next weekend. Min RH values will generally range from 10 to 20 percent though wind speeds are not expected to exceed criteria for any immediate headline concerns. Seasonably warm temperatures to persist. && .CYS WATCHES/WARNINGS/ADVISORIES... WY...None. NE...None. && $$ SHORT TERM...WM LONG TERM...WM AVIATION...MD FIRE WEATHER...WM
Area Forecast Discussion
National Weather Service Des Moines IA
547 PM CDT Sun Jul 25 2021 ...Updated for 00z Aviation Discussion... .DISCUSSION.../Tonight through Sunday/ Issued at 259 PM CDT Sun Jul 25 2021 Today through Early Monday Morning: Surface high pressure has been developing along the NE-KS state line this morning as the remnants of the convective cluster from last night dissipate. Low-level flow across the High Plains and Front Range will be southerly on the back side of the high pressure. This will result in strong WAA and will amplify the ridge. For Iowa, this will switch the mid and upper-level flow back to northwesterly. Low- level flow will be rather weak as the high pressure centers over the area, thus no overly strong temperature advection for Iowa today. Expect more smoke/haze to be in the skies this afternoon through evening with the northwesterly upper-level flow, which may provide some limitation to insolation, as well as the clouds emanating from tops of remnant convection over the central Plains. However, still expecting warm air temperatures today as the airmass is now slightly drier and will heat up more efficiently. The lower dewpoints though will keep heat index values close to the air temperatures. This evening, low-level jet develops over the Central Plains providing strong theta-e advection into the region. There is not much at the surface or low-levels other than the LLJ itself, but there is a signal for some convergence in southern South Dakota right where the H5 height gradient becomes stronger. Expect elevated convection to develop late in the evening, and will begin to move toward the southeast. There is potential for a cluster of thunderstorms move into northern potions of the forecast area overnight or by early Monday morning. The HRRR has been the most robust CAM thus far, attempting to bring weak showers to around Hwy. 20. However, not entirely convinced the instability and moisture needed to maintain a thunderstorm cluster will be present over Iowa at this time. Thus, will keep slight chances POPs along and north of the Hwy. 18 corridor. At this time, there does not appear to be any severe weather potential for the forecast area. Prior to any rain shower or convection activity, areas of fog may develop as dewpoint depressions may drop in an environment with weak winds. Heat Through Midweek: A subtle short-wave trough across the western Great Lakes Monday through Tuesday will provide a weak block to the ridge, while persistent WAA on the backside of the surface high pressure across the central Plains will further amplify the H5 ridge, with heights likely reaching 597dam! Temperatures will steadily rise throughout the week. The surface high pressure will need to slide a bit further eastward before this truly ramps up for the forecast area, but by Tuesday late afternoon and through Wednesday, the stronger axis of WAA/theta-e advection will arrive, and the ridge axis will also slide eastward across the Central Plains and into the upper Midwest. This will send temperatures into the mid 90s on Tuesday, with dewpoints in the upper 60s to lower 70s. Wednesday is still looking to be the warmest day for Iowa, with air temperatures in the upper 90s and dewpoints in the low to mid 70s. This will send heat index values to 105, and may be able to reach 110 in some places. These heat conditions will be hazardous for outdoor activities. There is some uncertainty regarding the maximum extent of dewpoint temperatures for the middle of this week. GFS soundings have been showing a prominent EML, and stronger flow on the backside of the high pressure. During the afternoon, lower dewpoints may be able to mix down closer to the surface. It will be a battle between evapotranspiration from the crops, and mixing down. If the mixing ends up being weaker, then the dewpoints will be able to surge considerably in the middle of the weak. For the exception of early Monday morning (discussed in previous section), there is no definite signal for precipitation activity through Wednesday, as any forcing is shoved way northward during this time. There will be some forcing in portions of southern Minnesota and southwest Wisconsin, but current thinking is the amplifying ridge will keep this out of Iowa. Thursday and Beyond: Thursday afternoon the amplified ridge will still be present, with the axis centered over the High and Central Plains, but a short-wave perturbation will begin to travel through the northwest flow over Iowa and will allow a thermal boundary to move through the area. This will finally introduce more considerable precipitation chances into the forecast, as well as provide some relief from the heat. This will continue into Friday, with chances for at least some shower activity, and cooler temperatures. The northwest flow pattern across the upper Midwest will remain active into Saturday, with another short-wave or two that will travel through the flow. These short-waves will be moving over a warm moist air mass, thus it won`t take all too much forcing to generate a shower. At this time, it is hard to pinpoint if any of these short-waves will pose a severe weather risk. These northwest flow perturbations tend to generate a decent amount of forecast uncertainty beyond just a few days, and that is the case again with this setup. If one of these short-waves pairs up with some kind of surface feature, one of these setups could produce some stronger storms. But at this time, that call cannot be made. && .AVIATION.../For the 00Z TAFS through 00Z Monday evening/ Issued at 547 PM CDT Sun Jul 25 2021 While official TAFs are VFR with SCT250 for high level smoke, there are two concerns that will bear watching this evening. First, fog development is once again possible after midnight tonight over southeastern Iowa. At this time, it looks to be east of OTM. Second, thunderstorms are expected to move into southern Minnesota, but are expected to weaken as they move into northern Iowa and its terminals. With low confidence on impacts, have left out any mention. Will monitor trends this evening and address if needed at 6z. Wind will be light overnight, but become from the south or southwest at 7 to 13 knots at all but OTM by Monday afternoon. && .DMX WATCHES/WARNINGS/ADVISORIES... NONE. && $$ DISCUSSION...Krull AVIATION...Ansorge
AREA FORECAST DISCUSSION
National Weather Service Sioux Falls SD
1041 PM CDT Sun Jul 25 2021 .SHORT TERM...(This Evening through Monday Night) Issued at 246 PM CDT Sun Jul 25 2021 Spotty convective chances are the main challenge for the near-term. On the larger scale, we have an area of low pressure in western SD, with a weak boundary extending east-northeast into northeast SD. Meanwhile, a subtle upper level wave is seen in water vapor entering the western Dakotas. This wave may interact with the boundary by early evening, bringing a small chance of storms into our northwest this evening, and if this occurs, inverted-V soundings and DCAPE values above 1000J/kg would support an isolated strong wind threat. Slightly greater potential for a few storms appears to be in far north to northeast portions of the forecast area later tonight, as a modest southwesterly low level jet develops across the area. Nose of the jet focused near/northeast of the Buffalo Ridge, and will carry higher pops for the overnight period in this area. DCAPE values not quite as strong with this activity, but still quite a deep layer of dry sub-cloud air to accelerate the low level jet to the surface, so an isolated strong wind threat will continue. The convective forecast becomes more muddled for Monday, dependent on whether activity linger across northeast portions of our forecast area into the later morning hours, as depicted by several HRRR runs today. Tend to think this projection is overdone, as the waning LLJ convergence should be pushing off to the northeast, so have trended pops downward through the morning hours. Could still be a few weak boundaries lingering from overnight convection, but diurnal mixing should reestablish a primarily southerly flow across the forecast area, with consensus showing the main warm front again from central SD into central MN by late Monday into Monday night. Cannot totally rule out a few stray storms into southwest MN Monday night, but as with later tonight, think main focus for activity will be off to our north/northeast. Aside from these uncertain convective chances, the next 24-36 hours will feature modest humidity levels with dew points largely in the 60s tonight through Monday night. Abundant smoke aloft as indicated by HRRR Smoke model will have a continued impact on high temps, and have nudged readings for Monday down a few degrees from previous forecast. .LONG TERM...(Tuesday through Sunday) Issued at 246 PM CDT Sun Jul 25 2021 Heading into midweek, Tuesday-Wednesday continue to look like our period of greatest concern with regard to excessive heat/humidity. Very strong upper ridge builds into the northern Plains, with both NAEFS and ECMWF ensembles depicting 500mb heights across eastern SD/northeast NE near the highest in the climatological period by early Wednesday morning. Heat begins to build into our western CWA in earnest on Tuesday, before extending eastward on Wednesday as the thermal ridge is flattened by an approaching cold front. Low level temperature projections support highs in the mid 90s to low triple digits, though question remains if we mix high enough to attain these temperatures, how will the dew points respond. With evapotranspiration nearing its peak, overnight/morning dew points in the upper 60s to lower 70s seem reasonable. But soundings show plenty of dry air aloft, so suspect these may drop off a bit more than indicated. Confidence not quite high enough to adjust these values 2-3 days out, but will be something to consider in later forecasts. Almost certainly will see some variety of excessive heat headlines for these days, but given the uncertainty in dew points/humidity levels, still unsure whether that headline will be an advisory or warning. Relief comes in Wednesday night through the end of the week, as the upper ridge is flattened in response to a stronger jet diving southeast from the Canadian Prairies into the western Great Lakes. Transition to northwest flow may bring a somewhat more active pattern for the latter half of the week, with temperatures cooling off to much closer to normal && .AVIATION...(For the 06Z TAFS through 06Z Monday night) Issued at 1039 PM CDT Sun Jul 25 2021 Remnant scattered showers and isolated thunderstorms continue to move across portions of the area west of I-29, now moving south/southeasterly. Could see some more redevelopment of showers and thunderstorms along and north of the highway 14 corridor through tomorrow morning, but confidence not high enough to include in the HON TAF at this time. Winds will become gusty tomorrow morning predominantly from the south, with gusts in the 15-25 mph range throughout the afternoon. && .FSD WATCHES/WARNINGS/ADVISORIES... SD...NONE. MN...NONE. IA...NONE. NE...NONE. && $$ SHORT TERM...JH LONG TERM...JH AVIATION...APT
Area Forecast Discussion
National Weather Service Green Bay WI
639 PM CDT Sun Jul 25 2021 Updated aviation portion for 00Z TAF issuance .SYNOPSIS... Issued at 250 PM CDT Sun Jul 25 2021 Very warm and humid through the middle of the work week, with a few rounds of thunderstorms from Monday evening through Wednesday night. A little cooler and drier for the latter part of the work week. A strong band of westerlies will persist across the northern CONUS and southern Canada throughout the period. A longwave ridge position will be in the west, with a trough in the east. The westerlies will initially be quite flat, but gradually gain amplitude during the period. The pattern favors very warm temperatures through the middle of the upcoming work week, with a little cooling thereafter as the upper flow tilts more northwesterly. The reservoir of very humid air will shift back into the area for a few days, then get shunted south again. As typical during the summer when precipitation is almost exclusively convective, the 7-day total is tough to estimate. The best guess is for AOA amounts. && .SHORT TERM...Tonight and Monday Issued at 250 PM CDT Sun Jul 25 2021 The latest RAP analysis and satellite/radar imagery show high pressure stretching across the northern Plains into the mid- Mississippi Valley early this afternoon. Quiet conditions thanks to a very dry airmass (pwat of 0.74 inch of the 12z GRB sounding) remain in place with only some fair weather clouds over far northern WI. Looking west, quiet conditions remain present over Minnesota, but pressure falls along a developing warm front will likely lead to thunderstorm development over South Dakota later today. As this frontal boundary lifts northeast, thunderstorm and severe weather chances are the main forecast concerns on Monday afternoon. Tonight...High pressure will be sliding southeast across the middle Mississippi Valley as the warm front lifts northeast across the northern Plains. Focus for thunderstorm activity will therefore remain well west of the region closer to the warm front. The airmass will moisten somewhat, but probably not enough to influence temps very much under a mostly clear sky. Warmer lows ranging from the mid 50s to mid 60s. Monday...Backing low level flow to the southwest will push the warm front into northern Minnesota and near the U.P./Wisconsin border by the afternoon. Some uncertainty exists where this front will lay out by the time of peak heating, when mixed layer instability upwards of 1500 j/kg is forecast to develop. In addition to the position of the front, some guidance indicates deep mixing taking place over northern WI that could bring down dewpoints and diminish instability. While upper support is negligible, surface pressure falls and increasing low level convergence leads to a general consensus of thunderstorms developing around mid-afternoon over northern WI to the Upper Peninsula. Deep layer shear of 35-40 kts and mid-level lapse rates of 7-7.5 c/km are supportive of the potential for large hail and damaging winds. Highs will again range from the mid 80s to low 90s. .LONG TERM...Monday Night Through Sunday Issued at 250 PM CDT Sun Jul 25 2021 There has not been much change to the forecast scenario since yesterday. A weak boundary will shift toward northern Wisconsin Monday, providing a focus for convective development during the evening/overnight hours. The more organized the convection becomes, the farther south/southeast it will probably propagate into the warm/unstable air mass across the forecast area. The expected combination of shear and buoyancy will be sufficient for severe storms, with the best chance for severe across the north closer to the front. The greatest uncertainty early in the week will be the weather conditions on Tuesday. The possible presence of an outflow boundary across/near the area and perhaps some rain-cooled air from Monday night storms will impact temperatures as well as the possibility for additional thunderstorm development. On the large scale, forcing Tuesday will be subtle at best so the day may end up being rain-free unless low-level convergence near a boundary can kick something off. The next round of storms will probably be Wednesday afternoon through Wednesday night when a cold front accompanied by some forcing crosses the area. The large scale pattern certainly seems supportive of another risk for severe storms and possibly heavy rainfall. The very humid air mass across the area will raise the risk of heat-related issues, especially Monday and Wednesday afternoon/evening. Heat indices are not expected to be sufficient to warrant a headline, but will mention the possible hazard in the HWO. && .AVIATION...for 00Z TAF Issuance Issued at 639 PM CDT Sun Jul 25 2021 Will continue to see VFR flying conditions through the TAF period at most locations. The main feature will be wind gusts to 20 knots, which will continue to subside over the next hour or two this evening. West winds increase again late Monday morning with afternoon gusts to 20 knots. Rain and thunderstorms are possibly across north-central WI late Monday afternoon which could result in lowered cigs and vsbys. Confidence on timing was too low to include in KRHI this TAF issuance. Rain and thunderstorms are possible area wide Monday evening (after 00Z) and overnight. && .GRB WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS.......Skowronski SHORT TERM.....MPC LONG TERM......Skowronski AVIATION.......KLJ
Area Forecast Discussion
National Weather Service Gray ME
1016 PM EDT Sun Jul 25 2021 .SYNOPSIS... A frontal system will continue to cross New England through this evening with scattered showers and isolated thunderstorms possible. Weak high pressure will build into the region on Monday before a cold front approaches from the west on Tuesday bringing scattered showers and thunderstorms. High pressure then briefly builds back in on Wednesday before a series of fronts return to the area through the end of next week. && .NEAR TERM /THROUGH MONDAY/... 10:00 PM Update...Quick update this evening to increase POPS across Northern NH as cells continue to fire along an approaching vort max and associated jet streak. MUCAPE is beginning to trend down as the cells move further east towards ME, so feel the storms should begin to weaken as they move into Carroll County. Further north across the boundary mountains, chance for storms will continue through most of the night. Patchy fog is beginning to form and that should be the trend for the remainder of the night. 6:45 PM Update...A few cells are firing across VT at this hour as a jet streak aloft begins to move into the region along with general cyclonic 500mb flow. SPC surface analysis is still showing CAPE around 500 to 1000 J/KG, kept isold 20 pops in the region as a stray thunderstorm is still possible before midnight. In addition, smoke is beginning to stream in aloft, with some visibility restrictions being reported currently in upstate New York, won`t be an issue tonight, but could have some haze tomorrow morning at sunrise. Have also put in patchy fog after midnight with elevated dewpoints in the 60s and mostly clear skies expected with light winds. Should have valley and low-lying shallow fog across most of the forecast area. Warm front moved through the region today leaving 1/4 to 1/2" of rain in its wake. SKies have started to clear across NH and will continue to clear across Maine over the next few hours. Upstream there are two features we`ll be tracking into the area. First is thunderstorms which have initiated along a line extending from Val D`or to Georgian bay associated with a cold front. These storms will slowly move towards the northern portion of our area overnight. Between that front and our CWA is a broad warm sector with temperatures in the mid 70s and dewpoints in the 60s. This puts SBCAPE around 1000 j/kg widespread to our west. Additionally Bulk shear of up to 40kts makes the airmass favorable for convection. Had expected at least a few cells within this warm sector but none have initiated yet, and CAMs continue to push back any convective initiation for this afternoon leaving the threat of thunderstorms smaller and smaller. What is visible on satellite in the thunderstorm-less warm sector is smoke. A solid haze is discernible on visible satellite imagery and GOES smoke detection also shows a broad swatch of smoke. Surface observations show this haze is thick enough to decrease visibility to around 6SM, and it may also be enough to dampen any convection from popping in the warm sector this afternoon. && .SHORT TERM /MONDAY NIGHT/... Overnight the thunderstorms and front will move southeast, reaching the Canadian border after midnight where a chance for thunder remains in the forecast. Elsewhere the main concern overnight will be fog as dewpoints remain in the mid 60s overnight along with the overnight lows. With this kind of widespread rain it feels like a fog type night and have added it especially to the coastal plain and all valleys where dense fog is possible. Tomorrow expect fog to linger in the valleys but ultimately lift within 2hrs of sunrise, however that won`t be the end of the obscuration. The haze currently in Quebec will drift southeast ahead of the front and HRRR Smoke indicates it being widespread across most of our area during the day tomorrow. I can think of very few times including haze in a forecast but with such a clear smoke plume on satellite already reflected in the surface obs and supported by the models have opted to add it for the area tomorrow. Have additionally hedged a bit lower on the high temperatures due to this haze, although even a degree or two lower, most of the area will see the upper 70s to low 80s. && .LONG TERM /TUESDAY THROUGH SUNDAY/... Overview: Broad troughing over New England will continue through at least the end of the upcoming week as a series of passing shortwaves and embedded frontal systems bring multiple chances for unsettled weather. Temperatures will be near to slightly below normal through next weekend. Impacts: No significant weather impacts are currently expected. Forecast Details: A frontal system and shortwave trough will approach from the north and west on Tuesday with increasing chances for scattered showers and isolated thunderstorms during the afternoon and evening. There are some differences in the timing of this front, which will play a large role in determining the likelihood for thunderstorm activity. A slower arrival of the front would favor more thunderstorm coverage, especially if it aligns with peak daytime heating. While widespread severe weather currently looks unlikely, steep low-level lapse rates and high DCAPE suggest that any stronger thunderstorms would have the potential to produce locally gusty winds. For now, have kept general thunder wording into the grids, especially across the north. southwesterly winds at the surface will allow Tuesday to be the warmest day of the week with many locations reaching the lower to middle 80s. Behind the front, a cooler and drier airmass will move in on Wednesday with high temperatures only reaching the 60s to 70s from north to south. This will then be quickly followed by the arrival of another shortwave trough from Canada on Thursday, which will once again bring increased chances for showers and possibly isolated thunderstorms. A 300 mb jet streak will be located nearby, which would support lift for convection, but given the low surface dew points and temperatures severe weather does not currently look likely. A few lingering showers will then persist through Friday, especially across the north where there will be upslope flow. High temperatures on Thursday and Friday will primarily be into the 70s with 60s across the north and mountains. Another system may then arrive by Sunday but forecast confidence remains low at this time. && .AVIATION /02Z MONDAY THROUGH FRIDAY/... Short Term... Ceilings will improve across NH and western Maine through sunset as the band of rain associated with the warm front exits the area. Continued low level moisture overnight will bring a return of fog and IFR for both the coast and river valleys. Tomorrow will be clear, but haze will be widespread with visibility dropping to 5-6SM in HZ possible. Long Term...VFR conditions expected through the entire period outside of any SHRA or TSRA, which could result in brief MVFR/IFR conditions. The best chances for precipitation currently looks to occur on Tuesday afternoon and Thursday. Some patchy fog will also be possible on Tuesday night, especially across the valleys. && .MARINE... Short Term...SCA remains in effect through 11pm, will likely be able to end early as front is already pushing into New Hampshire and will clear the waters early this evening. Behind it winds decrease and become more westerly. Long Term...Winds and seas are expected to remain below SCA criteria through Friday. A cold front will cross the waters on Tuesday afternoon or evening with southwest winds turning northwesterly late. Another system will arrive on Thursday with increased chances for scattered showers. && .GYX WATCHES/WARNINGS/ADVISORIES... ME...None. NH...None. MARINE...None. && $$ SYNOPSIS...Curtis/Tubbs NEAR TERM...Curtis/Dumont SHORT TERM...Curtis LONG TERM...Tubbs AVIATION...Curtis/Tubbs MARINE...Curtis/Tubbs
Area Forecast Discussion
National Weather Service Jackson MS
904 PM CDT Sun Jul 25 2021 .UPDATE... Updated for evening discussion. && .DISCUSSION... Tonight`s temperature forecast was slightly adjusted to be higher due to observations being warmer than forecasted for central MS. Otherwise, no major updates were made. Overnight lows will be ranging in the mid to upper 70s, allowing for another warm and muggy night. Light winds and enhanced surface RH will allow for some patchy fog to develop in the region in the early morning hours. Similar to this morning, the patchy fog is expected to dissipate by daybreak. /AJ/ Prior discussion below: Tonight and tomorrow... Weak surface high pressure under a broad upper level ridge dominates the weather map again today. Afternoon showers and possible thunder continue to reinforce llvl moisture in a hot and humid airmass. Winds very light/calm on obs across the area this afternoon enhancing the impacts of the high heat index values across the region. Same lack of flow is causing most showers to be stationary...and areas under the few showers out there are locally seeing some rain...but the bulk of the region is seeing very little relief from the heat. Overnight tonight, the enhanced llvl RH will result in some patchy fog in low lying areas...best chances will be the same area that gets any precip today. Tomorrow will bring much of the same, and temps and heat indices on par with todays forecast with the airmass largely unchanged. Starting with the area with the greatest chances for exceeding heat advisory criteria...roughly along and west of a line from Greenwood to Columbia. But tomorrow`s Heat Advisory will likely get updated with the newest guidance... expect more of the same muggy conditions from the weekend. HRRR coverage of the showers and thunderstorms tomorrow seem to focus more in the south and east...and slightly more convection overall in a relatively stagnant airmass. /HJS/ Monday night through Wednesday: As the East Coast upper trough amplifies through midweek, the mid/upper ridge will retreat at least temporarily. While this trough will bring a weak front into the Mid South, it will not be potent enough to keep the front together through our area. Instead, the remnants of the front will serve as a focus for convergence and deep moisture, resulting in higher rain chances Tuesday and Wednesday. The added clouds/rain may also help to knock a few degrees off our high temps, perhaps offering a slight reprieve from the recent heat stress concerns. Still with moisture levels remaining high, any areas that receive a good bit of sun could still possibly reach advisory thresholds during this time frame. Thursday through next weekend: The ridge will begin to build back in late Wednesday into Thursday, with richer deep layer moisture pushing south. This will begin to limit rain chances, especially in the northern portion of the area, and usher in a return of warmer conditions with high temps again into the upper 90s and possibly pushing triple digits in a few spots and heat indices into the triple digits areawide, continuing to push heat advisory criteria. Yet another dip in the East Coast upper trough and accompanying moisture return may cause rain chances to creep back up heading into next weekend. However, otherwise warm and muggy conditions will continue through the end of the forecast period. /DL/ && .AVIATION... 00Z TAF discussion: VFR conditions will prevail through the forecast period with the exception of potential brief impacts from diurnally driven isolated/scattered TSRA, and possibly from early morning IFR/MVFR category fog given light surface wind, mostly clear skies, and humid boundary layer. /EC/ && .PRELIMINARY POINT TEMPS/POPS... Jackson 76 93 76 94 / 17 65 22 68 Meridian 75 94 75 94 / 17 60 21 71 Vicksburg 77 95 77 95 / 16 51 18 55 Hattiesburg 76 94 75 95 / 17 51 15 60 Natchez 76 93 75 93 / 17 55 17 51 Greenville 76 94 76 92 / 13 47 19 54 Greenwood 76 95 75 93 / 14 55 21 64 && .JAN WATCHES/WARNINGS/ADVISORIES... MS...Heat Advisory from 10 AM to 7 PM CDT Monday for MSZ018-019-025- 034>036-040>043-047>049-053>055-059>064-072. LA...Heat Advisory from 10 AM to 7 PM CDT Monday for LAZ007>009-015- 016-023>026. AR...Heat Advisory from 10 AM to 7 PM CDT Monday for ARZ074-075. && $$ AJ
Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
645 PM CDT Sun Jul 25 2021 .SHORT TERM... 227 PM CDT Through Monday night... Much more tranquil and less humid conditions have prevailed across the area today after Saturday`s scattered thunderstorms. Daytime mixing has tapped into significantly drier air aloft across northern Illinois, allowing dew points to lower well into the 50s and locally upper 40s (more than 20F lower than 24 hours ago). So while the overall airmass that arrived behind the cold front early this morning is slightly cooler in the lower half of the troposphere, the drier air has allowed temps to climb into the upper 80s and locally low 90s even as thinning upper-level cirrus spreads over the area. The drier air has also resulted in a noticeable reduction in haze, though some western wildfire smoke continues to advect into the region. The surface high, currently centered over south-central Iowa, will drift ESE to central Indiana through Monday night. Resulting light and sometimes calm winds tonight amid lower dew points will support generally seasonable temps under mostly clear skies. Light north winds will prevail on Monday amid another dry and mostly sunny day. Low-level thermal profiles support max temps solidly in the low 90s provided somewhat thicker smoke aloft over the northern Great Plains does not filter over the area. Otherwise, an early- arriving lake-enhanced boundary will limit temps to the mid 80s along the shore. Monday night is expected to remain dry as convection initiating over the north half of Minnesota Monday evening encounters increased capping and the noted dry air mass over Wisconsin. Kluber && .LONG TERM... 248 PM CDT Tuesday through Sunday... Hot summertime weather is expected to continue across the area through Wednesday. Increasing dewpoints for Tuesday and especially Wednesday will make for increasingly uncomfortable conditions as heat indices rise well into the 90s (possibly around 100 degrees on Wednesday). Fortunately a welcome break from this heat and humidity should occur for the later part of the week following a cold frontal passage expected sometime on Thursday. Shower and thunderstorm chances during the period will be the greatest Wednesday night and Thursday as this cold front approaches and moves into the area, but there is a low possibility for some storms shifting into parts of the area from the northwest both Tuesday and Wednesday. Following the eastward passage of the surface high moving across the area on Monday winds will turn back to the southwest on Tuesday. This will in turn allow a much more humid airmass to return to the area. High temperatures are likely to be in the upper 80s to the low 90s both Tuesday and Wednesday. However, with increasing dewpoints into the lower to mid 70s, we are likely to see heat index readings well into the 90s for Tuesday, and potentially topping 100 on Wednesday. This will make for very uncomfortable and increasingly hazardous heat conditions for the area, and we could be close to heat advisory criteria (heat index 105+) Wednesday. While the threat of showers and storms looks fairly low for Tuesday and much of the day on Wednesday, we will have to keep a close eye on convective trends to our north across parts on MN and northern WI Monday night into Tuesday and again Tuesday night into Wednesday. Any well organized MCS`s that develop there could try to propagate southeastward along the northeastern periphery of the large upper ridge centered over the central Plains. If it does so, the 850-300mb thickness gradient suggests it could get steered in our direction into Tuesday. Its really just a question of if increasing capping will prevent these storms from shifting this far south. For this reason we will have to watch for the possibility of storms and/or an outflow boundary moving into parts of southern WI and possibly far northern IL on both Tuesday and Wednesday. Confidence remains low on this scenario, but if it occurs temperatures would be cooler than currently forecast across parts of northern IL Tuesday into Wednesday. The later Wednesday night through Thursday period remains the roughly 24 hour window where guidance is providing the strongest signal for convection in the area along the southward-shifting frontal zone. There is potential for some form of MCS late Wednesday night in the western to central Great Lakes that could be shifting southeast near or into the area, but this remains far too uncertain yet. The 00Z GFS and slightly slower ECMWF both show a not-so-favored diurnal time for the frontal passage in terms of maximizing strong convection and heavy rain potential. Obviously, plenty of time for things to shift some though. Behind the front, northeast winds look to pick up and steer in drier air fairly quickly. These forecast winds presently have the pattern to provide a high swim risk period for Lake Michigan beaches from approximately Thursday afternoon through Friday morning. The drier air mass looks to bring precipitation-free conditions for Friday and potentially most of the day Saturday. For Saturday, it looks to depend on how far southwest the frontal zone moves on Friday. This zone is forecast to be active Saturday and Saturday night, and this could remain southwest of the CWA. KJB/MTF && .AVIATION... For the 00Z TAFs... Aviation Forecast Concerns: * Wind directions in otherwise light surface flow through period. Early evening surface analysis depicts high pressure centered to the west of the forecast are cross the mid-Missouri River Valley. With the surface ridge axis extending eastward into our region, the weak surface pressure gradient has allowed light, generally west to northwest surface winds across the terminals through the late afternoon hours. A lake breeze has moved through GYY, but only came up to the very east side of the field at MDW and did not approach ORD. Thus, wind directions should remain generally westerly at all but GYY this evening. High-res model guidance has generally trended toward a more westerly direction for a good portion of the night as well, shifting more north-northwest toward sunrise. With the relatively warm/dry air mass we should decouple quickly this evening with the approach of sunset, so light/less than 10 kt conditions are expected. On Monday, the surface ridge slides south of the area. Within the light gradient, winds are expected to shift northeast by mid- morning across ORD/MDW and GYY, with a more easterly lake breeze push developing in the afternoon. Winds for these locations should then veer southeast Monday evening. Farther west, winds should eventually back more westerly at DPA and RFD, and eventually southwesterly in the afternoon at RFD. Again, speeds should generally remain less than 10 kts. Forecast soundings maintain dry moisture profiles across the region through Monday evening in the vicinity of the high pressure ridge, with the only exception being some high cirrus occasionally streaming into the region from the southwest from convection across the Plains. Skies will continue to appear milky aloft due to smoke from western wildfires, though 18Z HRRR forecasts suggest a decrease in near-surface smoke due to northerly flow above the boundary layer. Thus no horizontal surface visibility issues are expected. Ratzer && .LOT WATCHES/WARNINGS/ADVISORIES... IL...None. IN...None. LM...None. && $$ Visit us at weather.gov/chicago Follow us on Facebook, Twitter, and YouTube at: www.facebook.com/NWSChicago www.twitter.com/NWSChicago www.youtube.com/NWSChicago
Area Forecast Discussion
National Weather Service Lubbock TX
619 PM CDT Sun Jul 25 2021 .AVIATION... Scattered thunderstorms may affect KLBB and/or continue to affect KPVW through 26/03Z. Pilots should expect strong downburst winds beneath cloud base, confirmed by a surface gust of 42 kt by the KPVW METAR at 2235Z. PIREP from 2305Z out of KLBB reported moderate chop at FL340, and a convective SIGMET remains in effect through 26/0055Z for all three terminals. A few cumulonimbi may have maximum tops to 50 kft with hail up to 1 inch aloft. Thunderstorms should quickly wane in intensity and coverage after dark, with VFR prevailing otherwise for the TAF period. Sincavage && .PREV DISCUSSION... /issued 221 PM CDT Sun Jul 25 2021/ SHORT TERM... Westerly surface winds across the South Plains early this afternoon should back to the south by 21z. Weak inhibition should erode allowing widely scattered showers/thunder to develop as advertised by CAMS taking advantage of around 1000 J/KG MLCAPE. Favored area of concentration according to the HRRR and the 12z Tech WRF run is from the Caprock Canyon/nrn Rolling Plains region, developing farther south/southwest along an axis through the central South Plains into areas S/SW of Lubbock as cap erodes around 21z (4 pm). Given weak winds aloft and fairly high PWATs (1.3 - 1.7 inches), isolated cells could produce some brief heavy rain. along with gusty winds and occasional lightning. Activity should decrease rapidly with loss of heating around 01-02z (8-9 pm), although did keep slight chance pops across the SE Panhandle overnight. Similar situation with slightly less coverage on Monday, and much less activity across the northeast where pops fall below mentionable. Temperatures/dewpoints near persistence, which are also very near climatological averages. James LONG TERM... We`ll keep a slight chance of showers and t-storms going Monday evening, as models continue to show some kind of convectively induced mesoscale vortmax sliding southwest from the Panhandles into eastern NM by evening, and this may generate enough lift despite evening stabilization to maintain any ongoing activity. Tuesday appears to be mostly dry however, with the upper high in close proximity and the mid-level moisture plume shunted farther north into the plains. Tuesday`s highs should climb a few degrees area-wide with mid to upper 90s on the Caprock and upper 90s to around 103 or 104 in the Rolling Plains. By Wednesday, the center of the upper-high should be in the central plains and this should place our forecast area more squarely under easterly flow aloft. Thus we expect daytime temperatures to back off some from Tuesday`s readings. In addition, a weak disturbance undercutting the ridge will bring some mid-level moisture back into the area. The ECMWF is a little weaker and farther south than the GFS with this westward-moving wave, and the forecast remains dry for now, but there is a chance that we might need to raise PoPs across the south. Beyond Wednesday, the upper-ridge looks like it will expand south and east, becoming centered roughly over north-central Okla by Friday. This should bring hot (the heat does not appear exceptional at this time) and mostly dry weather to the forecast area to close out July. && .LUB WATCHES/WARNINGS/ADVISORIES... None. && $$ 09
Area Forecast Discussion
National Weather Service Medford OR
859 PM PDT Sun Jul 25 2021 .DISCUSSION...Just a couple of tweaks to the forecast this evening. The radar shows a few returns mainly across Modoc and Lake counties and earlier this evening there was a report of sprinkles in Lakeview. Therefore the forecast has been updated this evening for a slight chance of showers in these areas, and then a slight chance of showers overnight across mainly Siskiyou County based on the SREF model. Otherwise, we hope for rain over the next two days but with little to no thunderstorms. Sandler && .AVIATION...For the 26/00Z TAF Cycle...Along the coastal areas, expect LIFR/IFR conditions to return again early this evening and persist through late Monday morning. For inland areas, expect periods of MVFR visibilities due to wildfire smoke tonight east of the Cascades then local MVFR visibilities in smoke on Monday. A few cumulonimbi may be possible Monday morning as well as isolated thunderstorms Monday afternoon along portions of northern California and along and east of the Cascades. -Schaaf/CC && .MARINE...Updated 800 PM PDT Sunday, 25 July 2021...High pressure offshore and a thermal trough near the coast will persist into Monday. This patten will result in gusty north winds and steep to very steep wind-driven seas. Very steep and hazardous warning level seas are expected from Gold Beach southward, with north gales expected mainly beyond 5 nm from shore. North of Gold Beach, advisory level conditions will continue into Monday. Winds will ease some Monday and overall conditions will improve Monday night into Tuesday, though seas will likely remain steep south of Cape Blanco through Tuesday morning. The thermal trough pattern will be disrupted Tuesday into Wednesday, then likely return late Wednesday into Thursday. Although not as strong as the current event, gusty north winds are expected to return by Thursday and persist into next weekend. Conditions will likely become hazardous to small craft then, especially south of Cape Blanco. -Schaaf/CC && .PREV DISCUSSION... /Issued 247 PM PDT Sun Jul 25 2021/ DISCUSSION...The majority of our team`s focus today was on thunderstorms and communicating their potential, mainly because of lightning and the potential for wildfire starts, given how extremely dry the vegetation is. In general, we do expect a slight chance (15 percent) for lightning starting late tonight through Tuesday morning, and we`re communicating that directly with partner agencies mainly because it`s uncommon for us to forecast nighttime or morning thunderstorms. That said, there aren`t the ingredients coming together for an abundant lightning event through Tuesday. Smoke coverage is once again extensive across the forecast area, and it`s generally being transported from south to north aloft. At the surface, smoke that has collected in some valleys should be pushed off to the east this afternoon as daily afternoon breezes kick in. The same general daily cycle of smoke should continue tomorrow, but the latest HRRR smoke model run suggests surface smoke trending slightly lower tomorrow compared to today. Models suggest enough instability and moisture aloft tonight to support a slight chance for thunderstorms. Any storms that form will be mostly dry. That said, 500mb-300mb lapse rates, midlevel moisture depth, and trigger, all indicators for how significant overnight/morning storms can be, are marginal at best. So we generally expect less than 50 cloud to ground lightning flashes across the entire CWA through Monday morning. Tomorrow afternoon conditions will be somewhat more favorable for storms, but again not expecting abundant lighting. Instability is moderate, and our most reliable post-processed guidance and high- resolution model data are suggesting isolated storms, so that`s what we`re forecasting. The best chance for storms is east of the Cascades. Smoke is a variable that could limit surface heating and subsequent storm development, but we don`t think it will preclude seeing some lightning tomorrow. Tomorrow night will feature more significant moisture and trigger, so we are forecasting a slight chance for storms again, in a similar area as tonight. On Tuesday a well-defined disturbance will move from south to north through the area and will be accompanied by a lot of moisture--with precipitable water values 300% of normal for areas east of the Cascades. What this means is that we`ll likely see lots of shower activity with some embedded thunderstorms possible. The latest European model ensemble suggests a 30-50 percent chance of 0.1 inches of rainfall from the Cascades eastward from Tuesday through Tuesday evening. Temperatures Tuesday across the forecast area will likely be below normal because of increased cloud cover. Wednesday through Friday`s weather will feature a warming trend, with temperatures jumping to 5 to 10 degrees above normal. Deep southerly flow continues through the week, and as a result, thunderstorm chances continue as well (though generally 20 percent chance or less) from the Cascades and Siskiyous eastward. Keene AVIATION...For the 25/18Z TAF Cycle...VFR will prevail for much of the area away from the coast and away from area wildfires. Along the coast and in the Coquille Basin, stratus is burning off the beaches bringing VFR to the coast through this afternoon. Expect LIFR/IFR conditions to return again early this evening. Expect periods of MVFR visibilities due to wildfire smoke this afternoon, especially east of the Cascades. A few cumulonimbus may be possible tomorrow morning along portions of northern California and along and east of the Cascades. -Schaaf MARINE...Updated 200 PM PDT Sunday, 25 July 2021...A typical summer weather pattern of high pressure offshore and a thermal trough near the coast will persist into Monday. This patten will result in gusty north winds and steep to very steep wind-driven seas. Very steep and hazardous warning level seas are expected from Gold Beach southward, with north gales expected beyond 5 nm from shore. North of Gold Beach, advisory level conditions will continue into Monday. Winds will ease some Monday and overall conditions will improve Monday night into Tuesday, though seas will likely remain steep south of Cape Blanco through Tuesday morning. The thermal trough pattern will be disrupted Tuesday into Wednesday, then likely return late Wednesday into Thursday. Although not as strong as the current event, gusty north winds are expected to return by Thursday and persist into next weekend. Conditions will likely become hazardous to small craft then, especially south of Cape Blanco. -Schaaf/BR-y FIRE WEATHER...Updated 200 PM Sunday 25 July 2021...The upper level ridge east of the area continues to weaken and our focus is shifting to the potential for thunderstorms over the next several days. Water vapor imagery is showing southerly flow aloft taking hold allowing monsoon moisture -- mostly over the Desert Southwest for the past several days -- to surge northward across California. This is evident with some high cirrus moving in and even some mid-level cumulus/altocumulus across the south and east. We`ll see an area of elevated instability move into the area tonight pushing north across the area Monday morning. Forcing for convection is weak and we don`t think there`ll be a lot of lightning (if any), but some of the hi-res guidance is indicating a slight chance of high-based showers and perhaps a stray CG flash or two developing after 09z. Any rain will be minimal. Hi-res guidance continues to show mid-level moisture increasing with modest instability persisting into Monday afternoon/evening. Right now, we`re not expecting widespread/abundant lightning. We`re continuing to forecast isolated thunderstorms mainly east of a line from the Jack Fire to the Illinois Valley. Best instability in the guidance is being depicted from around Chemult/Crescent to the Bootleg Fire down to around the Warner Mountains. In these areas, however, instability may be somewhat limited by wildfire smoke. Due to the dry air mass in place ahead of this, storms that do form could be dry initially, but then get wetter with time due to the increase in precipitable water (PW) to around 1.00 inch. Elevated instability Monday night could result in nocturnal activity in advance of another healthier disturbance arriving on Tuesday, but again, activity appears to be isolated. Recent models are still showing a fairly robust upper short wave moving northward across California Monday night, then across the forecast area Tuesday. PWs surge to and reach a peak of 1.00-1.50 inches during this time period. With much more cloud cover expected, expect this to be more widespread showers with embedded and isolated thunderstorms, though any thunderstorms will be effective rain- producers. Given the high PWs, we`ve increased our chances of wetting rain (>=0.10") to around 30-50% in a corridor east of the Cascades from eastern Siskiyou County to much of Klamath County and into western Lake County, which would include the Bootleg Fire. Wednesday-Saturday, it will heat up again. Since we`ll mostly remain on the western periphery of the upper ridge axis to the east, we`ll be under southerly flow aloft. Instability should be present each afternoon/evening during this time period, and convective activity will be dictated by short waves coming northward in the flow. We`ve continued with a slight chance of pm/eve thunderstorms, mainly from the Cascades eastward, but these areas can change, so keep checking back. -Spilde && .MFR WATCHES/WARNINGS/ADVISORIES... OR... CA...None. Pacific Coastal Waters...Small Craft Advisory until 11 PM PDT Monday for PZZ350-356-370-376. Gale Warning until 11 PM PDT Monday for PZZ356-376. $$ RES/RES/RES
AREA FORECAST DISCUSSION
National Weather Service Morristown TN
925 PM EDT Sun Jul 25 2021 .UPDATE... EVENING UPDATE. && .DISCUSSION... Radar shows the convection over the area has been waning with the loss of heating as expected. However, given the very moist air mass over the area will need to keep at least slight chance to low chance PoPs in for showers/possible thunderstorms overnight. Will make some tweaks to temps/dew points to better fit latest observations, but overall forecast for tonight generally looks to be on track. && .AVIATION... 00Z TAF DISCUSSION. There will be mainly scattered convection around at times, especially early and again late in the period. Will try to time the higher probability times for thunder with VCTS/prob30 groups. Fog development will be possible later tonight, with highest chance for vsby restriction to MVFR or lower being at TRI. Will include MVFR vsby at TRI but keep vsby no lower than 6SM at CHA/TYS for now, but lower conditions are possible. Outside of convection and any fog, conditions are expected to be mainly VFR with light winds. LW && .PREV DISCUSSION... /ISSUED 321 PM EDT Sun Jul 25 2021/ SHORT TERM...(This Afternoon through Monday)... Key Messages: 1. Another weak wave in northwest flow aloft will bring another round of scattered storms across the Plateau (especially northern) and western Tennessee valley this evening. Isolated strong storm with torrential rains, gusty winds up to 45 mph and frequent lightning. 2. Increasing coverage of storms Monday, especially in the afternoon/early evening due to daytime heating/destabilization. Again, Isolated strong storm with torrential rains, gusty winds up to 45 mph and frequent lightning. Discussion: Through this evening, another area of scattered storms over south-central Kentucky is associated with a weak wave in northwest flow aloft. MLCAPES from the RAP shows values of 1500-2200 over most of the area, DCAPES of 700-900 and PWs of 1.6 to near 2 inches. This environment could produce isolated strong storms with torrential rains, gusty winds up to 45 mph and frequent lightning. Very localized flash flooding can not be ruled out. For Tonight, diurnal convection waning and weak wave moving east will diminish coverage and intensity. However, vertical profile is very moisture so can not rule out isolated/widely scattered convection almost anywhere. High moisture content will also produce some fog. For Monday, a frontal boundary will approach/move into the area in the afternoon. Another weak wave in the upper flow along with the boundary will focus the moist/marginal unstable airmass to produce areas of convection. Airmass will remain very moist with MLCAPEs again between 1500-2000. Again, isolated strong storms can be expected producing torrential rains, gusty winds up to 45 mph and frequent lightning. Very localized flash flooding can not be ruled out. LONG TERM...(Monday Night through Sunday)... Key Messages: 1. Increasing heat this week peaking in the mid/upper 90`s Wed through Fri, but cooling still expected next weekend. 2. Scattered convection will continue Tues, especially S of I-40, but mainly dry Wed and Thurs before chances for convection slowly increase Fri into the weekend. Discussion: Monday Night through Tuesday... The cold front will continue to sag S and SW during this time as a couple of mid/upper shortwaves progress across the Great Lakes and NE CONUS, effectively deepening longwave troughing over the NE CONUS. The S Appalachians will remain SW of the main trough axis, so expect the boundary to stall and washout over our southern counties as it runs into a building mid/upper ridge across the Plains and MS Valley. The weak boundary in the area, some mid-level PVA, weak upper diffluence, and heating of a moist boundary layer characterized by Td`s in the low/mid 70`s and PWATs of 1.50 to 2.00 inches will allow for widespread convection during the afternoon and evening as MLCAPES build to around 2000-2500 J/Kg. However, expect a sharp gradient in the best coverage of convection with most of the activity S of I-40 closer to the boundary. This is where pooling low- level moisture will yield the highest Td`s and PWATs, and therefore, the greatest instability. Forecast soundings suggest PWATs dropping below 1.50 inches from the middle Valley northward into SW VA during the afternoon as surface high pressure dropping into the OH Valley allows for drier northerly low-level flow behind the front, so convective coverage will be much less in those areas. Due to the limited upper support with the main jet well to the N, do not expect much organization to the convection with a pulse nature being the most likely outcome. Locally heavy rain and gusty winds will accompany the strongest cores, but still cannot rule out an isolated severe cell with damaging winds due to high DCAPE values. Highs Tues will reach the upper 80`s/low 90`s with morning lows in the upper 60`s/low 70`s. Tuesday Night through Friday... The big story in this period will be a few days of significant heat with heat indices getting close to advisory criteria, especially in the southern Valley. The aforementioned mid/upper ridge over the Plains and MS Valley will strengthen to an impressive 598 DAM by Wed and expand/elongate eastward across the TN Valley and deep South through the end of the week. H5 heights peak at 592-594 DAM over the S Appalachian region Wed and Thurs with an 850 mb thermal ridge sliding into our region too. The building mid-level and thermal ridge combined with low-level WAA will boost 850 mb temps to 20-21 C Wed and 21-23 C Thurs, with the ECMWF being the warmest of the guidance. Stout mid-level capping thanks to an EML tongue advecting E should allow for mostly sunny skies and very limited convection outside of the highest terrain, and since we are in the climatologically warmest weeks of the year, feel that NBM highs of mid 90`s Wed and mid/upper 90`s Thurs are realistic. If rainfall coverage is less than expected early this week, then ECMWF highs near 100 in a few places are possible. Regardless, Td`s in the low 70`s combined with the heat will yield heat indices near the 105 degree advisory threshold, especially over the S Valley, so those outdoors will need to take frequent breaks and stay hydrated. By Thurs night and Fri, shortwave energy will carve out a deepening longwave trough over the Great Lakes and NE CONUS allowing a cold front to approach from the N. Deterministic and ensemble guidance agree on this, but timing of the fropa is low confidence. Will have scattered showers/storms increasing from N to S late Thurs night and Fri. The lowering heights and gradually cooling 850 mb temps, along with possibly more cloud cover, will cap highs in the low/mid 90`s Fri, but heat indices could still be near 105 in southern areas. Low temps for mid and late week will be uncomfortably warm and muggy struggling to fall out of the low 70`s, with some mid 70`s in the S Valley. Friday Night through Sunday... The heat will diminish to more seasonable levels for the weekend as a series of shortwaves deepen a broad trough across the Great Lakes and NE CONUS leading to W/NW flow aloft and a cold front settling into the TN Valley and S Appalachians. The front will likely stall in this region, but tough to say exactly where this far out. Continued low-level moisture and instability beneath lower heights and the front in the vicinity will allow for scattered convection each day, peaking during the diurnal cycle. Highs Sat will stay in the upper 80`s/low 90`s with generally upper 80`s Sun. && .PRELIMINARY POINT TEMPS/POPS... Chattanooga Airport, TN 74 91 74 90 73 / 20 60 20 70 10 Knoxville McGhee Tyson Airport, TN 73 90 72 92 72 / 30 60 20 50 10 Oak Ridge, TN 73 89 72 90 71 / 30 70 20 40 10 Tri Cities Airport, TN 69 87 68 90 66 / 40 70 10 40 10 && .MRX WATCHES/WARNINGS/ADVISORIES... NC...NONE. TN...NONE. VA...NONE. && $$
Area Forecast Discussion
National Weather Service Reno NV
128 PM PDT Sun Jul 25 2021 .SYNOPSIS... Light westerly winds will continue to pour smoke into the region from the large Dixie Fire through at least Monday. Monsoon moisture will overspread the region leading to an increase in thunderstorm chances each afternoon much of this coming week. After a hot day Monday, temperatures will cool notably Tuesday before warming back up again late week. && .DISCUSSION... * Smoke: Well, earlier there was some hope we`d see a (very) gradual improving trend in the smoke out our window. That`s pretty much dashed with worsening AQI as a likely smoke layer aloft mixes down into the valley around Reno. Super light westerly winds should kick in later today but the temperature gradient to drive those winds will be made even weaker by the thick smoke over W Nevada. In the end, based on HRRR Smoke Model there may be some evening improvement but extra-low confidence on extent. * Similar situation Monday with light W/NW flow at night bringing in Dixie Fire smoke to much of the region by daybreak, with mixed confidence on improving conditions for late day, modulated by t-storm outflows. The one area that escapes the thick smoke is the E Sierra with more S/SE wind monsoonal trajectories developing Monday. * Thunderstorms: Respectable monsoon moisture push into the region this week with a large high centered over the Four Corners and Rockies. Thunderstorm probabilities will remain elevated with precipitable water values rising to near 1" by Tuesday afternoon in most ECMWF EPS members. Monday afternoon looking active with slow moving storms in latest HRRR and HREF guidance, and a wave lifting north out of SoCal could keep faster moving t-storms going into the pre-dawn hours Tuesday. Some possibility subsidence behind this wave + "too high PW" could keep storm coverage down Tuesday PM but low confidence on that this far out. * We`ll really need to be on our toes with flash flood and debris flow risks on the newer burn scars such as Beckwourth, and even the ongoing Tamarack Fire especially on steeper slopes just west of Hwy 395 + steep terrain of Alpine County. It only takes 5-10 minutes of heavy rain to cause major flooding on recent high intensity burns. Will defer to the overnight shift to decide on flash flood watch issuances each day, as flood flood environments have limited predictability in our region more than 12-18 hours out. * Most of the EPS guidance has drier air working in Wednesday while some members keep moisture values high enough for a continued storm risk. PW values rise again Thursday into the weekend so better confidence of storms there. GEFS has a rather robust QPF signal for Thursday, something to watch. We`re definitely in a pattern over the coming week where at some point over the next seven days, most areas will see some rainfall and some could see rather heavy downpours. Now`s a good time to ensure drainages are cleared out, and people near recent fires are prepared for possible flooding. -Chris && .AVIATION (through Monday)... Widespread smoke covering the area today mainly from the Dixie Fire in NE California. Some aircraft holds into RNO due to low visibility this afternoon. Any improvements will be very gradual due to afternoon westerly winds being on the light side. HRRR smoke shows some late afternoon and evening improvements for TVL/TRK and possibly RNO/CXP/MEV, though confidence is only medium as there is just a ton of smoke both at the surface and aloft to move around. Air flow turns more W/NW again tonight with smoke coming back in overnight into Monday morning - MVFR to IFR conditions again well into Monday. Highest risk of thick smoke is for SVE-RNO-NFL-CXP areas, with less risk for TRK/TVL. Main exception to this will be MMH where wind trajectories favor only minimal smoke or haze impact through Monday. Thunderstorms become more of a factor starting today with a solid monsoon push working north into the region. Based on NBM and HREF guidance, the best chances through this evening are between TVL/MEV and MMH in the E Sierra. Somewhat slow moving storms with areas of MVFR-IFR in heavy rain and outflows to 35 kts. For Monday afternoon t-storms are more expansive ahead of an approach wave aloft, including RNO and TRK/TVL and NFL vicinities. Outflows in HREF look stronger, possibly up to 50 kts. T-storms of at least isolated coverage will last into the evening and possibly overnight to daybreak Tuesday. -Chris && .FIRE WEATHER... The main concern for fire weather this week will be the increase in thunderstorm activity that is expected to last throughout the week as increasing monsoon moisture moves into the region from the southeast. New fire starts in very dry fuels, along with gusty erratic outflow winds and the potential for flash flooding on current/recent fires are all hazards that could create issues with the ongoing fire fights. Today looks like a fairly typical thunderstorms day with build ups beginning to develop late this morning along the higher terrain of the eastern Sierra, with continued development and a few relatively weak storms, expected through early evening. Monday is a little more concerning as an upper-level wave brings additional forcing while increasing moisture continues to flow into the region. Stronger thunderstorms will be likely tomorrow with the with elevated nocturnal convection possible lasting overnight. Overnight storms are not clear cut at this point, but the enough forcing and instability could be left over from to keep some storms going after dark. Currently expecting a mix of wet and dry storms tomorrow with the best chances for drier storms north of highway 50 along the edge of the better increasing PWATs, where storm motions will be faster with less available moisture. Storms will continue to transition to the wetter variety on Monday (south of I-80), and throughout the region later in the week. This will create flash flooding concerns, mainly in the more vulnerable areas with fresh burn scars, especially near on the Tamarack fire where considerable amounts of complex terrain has burned near and above roadways. Storms will continue throughout the week with varying degrees of coverage and intensity. As moisture levels increase chances for more widespread wetting rains will be possible this week, with the best chances from Tahoe southward. -Zach && .REV Watches/Warnings/Advisories... NV...None. CA...None. && $$ For more information from the National Weather Service visit... http://weather.gov/reno
Area Forecast Discussion
National Weather Service Las Vegas NV
207 PM PDT Sun Jul 25 2021 .SYNOPSIS...A moist weather system will bring widespread shower and thunderstorm activity to the region today and Monday before drier conditions resume Tuesday and Wednesday. Thereafter, another uptick in monsoonal moisture is expected with increasing thunderstorm activity through the weekend. Temperatures through the week will be near to slightly below normal. && .DISCUSSION...through next weekend. As of 2 pm, convection was beginning to fire along the higher terrain of Mohave county while working swiftly westward. 500-700mb mean flow of 20-30 knots has resulted in a quick storm motion, with storms moving at near 25 mph from northeast to the southwest. Meanwhile, SPC mesoanalysis indicates surface based CAPE values of 1500-2500 j/kg pooled from southern Nevada southward towards the Colorado River Valley. All in all, conditions are primed for some robust thunderstorm development through the afternoon and evening hours. HRRR and HREF guidance has been quite consistent in developing the strongest storms across northern/central Mohave County with storms congealing and developing westward towards far southern Clark county and the Mojave Preserve through the evening. Storms may then eventually work west into the Western Mojave Desert and Morongo Basin. While chances exist for storm activity in the Las Vegas Valley this evening, the best signal for storms is mainly south of the Vegas metro area. Given 25-35 knots of effective shear, some storms could be severe with damaging winds and even some quarter sized hail. Torrential rainfall is also a possibility given highly anomalous precipitable water creeping into the region, but quick storm motion will mitigate the risk somewhat this evening. Inverted trough will push into California tomorrow, with precipitable water values peaking at 200% of normal or greater across our western zones. Additionally, storm motion vectors will slow down and shift to a more southerly direction, which will favor both slower storm movement and the potential for training near terrain features. Given the highly anomalous moisture in play and signals from ensemble guidance for locally heavy rainfall, issued a Flash Flood Watch for most of San Bernardino County, Inyo, Esmeralda, Nye, and far western and southern Clark counties through Monday evening. Coverage and intensity of activity Monday will be dependent on how much instability can be realized amongst the thick cloud cover in the moisture rich airmass, but it won`t take a lot of heating to convect. The inverted trough will weaken and lift north along the Pacific coast on Tuesday and Wednesday with a drier and more stable airmass working into the region. Drier conditions with only very sparse thunderstorm activity are expected on these days along with gradually warming temperatures. Thereafter, additional monsoonal moisture and perhaps another weak inverted trough will push into the region with thunderstorm activity increasing through the weekend. && .AVIATION...For McCarran...East to northeasterly wind around 10kt will become more southeasterly this afternoon. Thunderstorm activity in Mohave County will send east or southeast outflow wind toward KLAS, but low confidence in timing and magnitude at this time. Expect onset no sooner than 22Z. A change to southerly wind gusting 15-20kt with lowering CIGS aoa 8kft after 03Z is expected. Cannot rule out a thunderstorm near the terminal later the evening. For the rest of southern Nevada, northwest Arizona and southeast California...Storms will move southwest this afternoon and evening from SW Utah and Mohave County potentially bringing heavy rain and strong outflow winds to southern NV and along the Colorado River Valley, directly affecting KEED and KIFP and potentially KDAG later in the evening. Lowering CIGS can be expected from east to west across the area tonight with CIGS aoa 10kt expected. && .SPOTTER INFORMATION STATEMENT...Spotters are encouraged to report any significant weather or impacts according to standard operating procedures. && $$ DISCUSSION...Outler AVIATION...Berc For more forecast information...see us on our webpage: https://weather.gov/lasvegas or follow us on Facebook and Twitter