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

Area Forecast Discussion
National Weather Service Charleston SC
1020 PM EDT Sun Oct 3 2021 .SYNOPSIS... High pressure will remain the primary feature through Monday. A complex storm system will then bring periods of unsettled weather through the end of the week. && .NEAR TERM /UNTIL 6 AM MONDAY MORNING/... Late evening observations indicated dewpoint depressions between 0 to 2 degrees across most of the SC Lowcountry. The latest round of observations line up well with recent runs of the HRRR and LAMP. The HRRR and LAMP indicates that at least patchy fog will develop across the SC Lowcountry late tonight. The updated forecast will feature the addition of patchy fog across the SC zones. Later updates may need to expand the mention of fog, possibly with dense fog. Temperatures are forecast to cool into the 60s during the pre- dawn hours. && .SHORT TERM /6 AM MONDAY MORNING THROUGH WEDNESDAY/... The upper pattern will become more amplified early to mid week as a mid level trough digs into the Lower Mississippi River Valley and eventually closes off into a low. The low will meander in this region through Wednesday. A deep moisture feed will keep anomalously high precipitable water values over the area. This pattern favors higher than normal rain chances, especially Tuesday and Wednesday. Scattered to numerous showers with isolated thunderstorms are expected. While coverage will be maximized during the day, activity could linger/persist overnight as well. High temperatures will be in the lower to mid 80s with lows in the mid to upper 60s/near 70 closer to the coast. && .LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/... The persistent mid level low over the Mississippi River Valley will lift northward and open up to a wave Wednesday night into Thursday, before the trough axis shifts east and becomes aligned over or near the East Coast. At the surface, high pressure will likely be centered north of the area while an inverted trough or weak low meanders off the Southeast coast. Given elevated shear, this low has a low chance of becoming tropical. Ample moisture and occasional upper level energy passing through will support at least scattered showers in the forecast each day. Perhaps less coverage over the weekend with models hinting that some drier air could arrive as ridging edges eastward and pushes the best moisture off the coast. Temperatures are expected to be within a few degrees of normal. && .AVIATION /02Z MONDAY THROUGH FRIDAY/... Prior to the 0Z TAFs, KCLX detected a sea breeze passing just inland of KSAV, pushing to the west. Terminals are forecast to remain VFR through the TAF period. Winds are forecast to remain steady from the SSW. Extended Aviation Outlook: The chance for periodic flight restrictions, mainly in showers, will increase Tuesday through late week. && .MARINE... Tonight: Southerly flow will prevail across the local waters, with speeds no higher than 10-15 knots. Seas are expected to average 2-3 feet. Monday through Friday: Southeast winds will persist early this week with speeds 15 knots or less. Seas will average 1-3 feet. There is still some uncertainty in the late week period but winds and seas will likely increase. The forecast will largely hinge on the position and strength of an inverted trough/weak low. At this time, conditions remain below Small Craft Advisory criteria. Rip currents: Residual swell energy from Hurricane Sam, plus an onshore flow will result in a Moderate Risk for rip currents at all beaches through Monday. && .TIDES/COASTAL FLOODING... Due to the upcoming new moon (10/6) and perigee (10/8) astronomical tide levels will steadily increase this week. Onshore winds could drive tidal departures up enough to produce minor coastal flooding as early as Monday evening. The time period of primary concern will come late in the week when the astronomical tide peak coincides with northeasterly winds. This could produce moderate coastal flooding in the late week time period, primarily in and around the Charleston area. && .CHS WATCHES/WARNINGS/ADVISORIES... GA...None. SC...None. MARINE...None. && $$ NEAR TERM...NED SHORT TERM...ETM LONG TERM...ETM AVIATION...NED MARINE...BSH/ETM TIDES/COASTAL FLOODING...
National Weather Service Sioux Falls SD
1022 PM CDT Sun Oct 3 2021 .SHORT TERM...(This Evening through Monday) Issued at 327 PM CDT Sun Oct 3 2021 A well-mixed afternoon has pushed temps into the 70s and allowed dewpoints to fall into the 40s. Winds which have been a bit breezy in areas across southwest MN and northwest IA will come down quickly this evening under the ridge axis, leading fairly strong radiative conditions until generally clear skies overnight. Small potential that some minor surface-based smoke seen across far northeast SD and southeast ND could leak in toward northern portions of southwest MN during the evening, but 12z-15z HRRR smoke guidance suggests this will be washing out within mixing conditions this afternoon before it can make any serious inroads, but some of the later guidance suggest will need to keep a watch on this area. Otherwise, will have to watch tonight for some patchy fog developing, but this should be mainly the lowest and most wind protected areas near water that run the risk of mainly very shallow fog development for a couple hours very late tonight/early Monday. After any fog dissipates early in the day, strong ridging aloft builds across the region on Monday, leading to a very pleasant fall day with the proximity of the ridge axis keeping winds fairly light. Before any real advection begins for moisture near the surface, should be able to kick temps into the mid 70s to around 80 during the afternoon. .LONG TERM...(Monday Night through Sunday) Issued at 327 PM CDT Sun Oct 3 2021 Monday night, continued westward advection to near-surface moisture beneath the stabilized pattern aloft will yield a better chance for fog and lower clouds developing in the low-level east- southeast flow at least into NW IA. Should yield at least a few more daytime stratocumulus near/east of I-29, with the stable profile and slight cooling likely taking a few degrees of highs from the prior day. Tuesday night likely to provide an environment for more lower clouds and some fog near the edge/along easterly upslope areas. Clouds likely to be even a bit more prevalent into daytime hours Wednesday as deeper easterly flow develops north of a closed low wandering south of the zonal ridge folded over through the Great Lakes. Easily may be even a shade cooler Wednesday, depending on clouds. Upper low to the south retains at least a weak tie to the western troughing, and a split dynamical filament shears across the area Thursday. Could see a spotty bit of precip from mere presence of this feature, but overall stability and somewhat lacking moisture would suggest not much for coverage. Temps above normal, but fairly similar to Wednesday with clouds in the mix and persistent southeasterly surface flow. Fairly strong consensus of another shortwave ridge present on Friday, prior to more northern stream energy driving a cold front across the area on Saturday. More dynamics north than south, and will have to knock down the capping inversion somewhat to get showers/thunder to develop. May need a but higher chance across the Highway 14 corridor along the boundary, but for now a chance seems sufficient. Both Friday and Saturday will be fairly warm, mainly 70s, but could be warmer Friday in southeast SD and Saturday across northwest Iowa given 22-25C 925 hPa temps ahead of the boundary. Have nudged temps up just slightly from initial blends to account for this. By Sunday, some lower pops remain in the forecast mainly due to timing uncertainty, but trends would surely suggest a mainly dry period, somewhat cooler, with the next threat of precipitation likely into the following week as the western trough/eastern ridge pattern throws more energy our way. && .AVIATION...(For the 06Z TAFS through 06Z Monday night) Issued at 1020 PM CDT Sun Oct 3 2021 With calm winds, can`t rule out some shallow fog later tonight, mainly in low lying areas, but chances too remote to include restrictions. Otherwise, light winds and VFR conditions expected through the period. && .FSD WATCHES/WARNINGS/ADVISORIES... SD...NONE. MN...NONE. IA...NONE. NE...NONE. && $$ SHORT TERM...Chapman LONG TERM...Chapman AVIATION...Kalin
Area Forecast Discussion
National Weather Service Grand Rapids MI
1002 PM EDT Sun Oct 3 2021 LATEST UPDATE... Update .SYNOPSIS... Issued at 330 PM EDT Sun Oct 3 2021 - Threat for swaths of locally heavy rain this evening/tonight - Rain gradually tapers off Monday into Monday night - Another round of rainfall expected Wednesday night into Friday - Warmer than normal temperatures to continue && .UPDATE... Issued at 1002 PM EDT Sun Oct 3 2021 Coverage and intensity of showers has been rather limited so far this evening and instability is now falling off. However slow moving mid level circulation evident near the MI/IN border will continue to generate areas of rain overnight. While the heavy rain threat looks to have diminished, relatively high pops are still warranted overnight. && .DISCUSSION...(This evening through next Sunday) Issued at 330 PM EDT Sun Oct 3 2021 - Threat for swaths of locally heavy rain this evening/tonight An upper low can be seen in the vicinity of Southern Lake Michigan this afternoon with a trough extending south to a vort max that is now swinging northeast into Indiana. Showers and thunderstorms have broken out in a fairly widespread fashion this afternoon in the area ahead of the upper low and trough. Southwest Lower Michigan is in line to see this activity move through this afternoon and evening especially. Surface dew points are in the mid 60s across the area with PWAT values around 1.50 inches. CAPE values have reach the 1000-2000 J/Kg range and surface based LIs are near -5 over Southwest Lower Michigan. We also are in the left exit region of a jet streak moving through around 250mb. Bottom line plenty of parameters coming together to produce showers and storms and the threat of locally heavy rain. The probability matched mean 24HR rainfall from the HREF would suggest many areas through Monday morning will see 0.50 to 1.25 inches of rain with some swaths of 2.00+ inches possible. No Flood Watch given antecedent conditions that do not favor it. Feel we will handle areas of heavy rain with short term areal Flood Advisories if we need those. Overlapping swaths of rainfall will be where advisories may be needed. A slow storm motion will aid in the chance of locally heavy rainfall. - Rain gradually tapers off Monday into Monday night The upper low gradually moves south of the area on Monday and fills into Monday night. So, the heavy rain threat will be tapering off with time. Based on the 6HR probability matched mean rainfall values from the HREF not expecting heavy rain tomorrow. It should come to an end overnight tonight. Plenty of low clouds hang on for Monday and Monday night, so the dreary weather will likely continue. - Another round of rainfall expected Wednesday night into Friday We look to be dry for a bit from Tuesday into Wednesday as high pressure nudges into the area from the north. A drying northeast to east flow at the surface is expected. Another round of rainfall is forecast though from Wednesday night at least into Friday as an upper low moves our direction from Arkansas and Missouri mid to late week. By Thursday the low/upper trough will be moving in and by Friday it should be overhead. Showers and a few thunderstorms can be expected during the latter half of the work week. So, overall we will be in an active pattern for awhile with a short respite on Tuesday/Wednesday. It appears there could be more rain into the weekend with a cold front moving our direction from the plains. - Warmer than normal temperatures to continue Normal highs this time of year should be dipping back into the lower to middle 60s. 850mb temperatures do not change much the next 7 day, roughly staying between +11C and +14C. We should see a fair amount of days with highs in the 70s. && .AVIATION...(For the 00Z TAFS through 00Z Monday evening) Issued at 758 PM EDT Sun Oct 3 2021 MVFR cigs/vsbys becoming more widespread this evening then conditions trending down further overnight to widespread IFR with areas of LIFR. Cigs gradually lifting back to MVFR levels by Monday afternoon. Scattered rain showers continuing tonight and Monday but have left thunder out of the TAFs since the coverage should remain very isolated. && .MARINE... Issued at 330 PM EDT Sun Oct 3 2021 We have issued a fairly short duration Small Craft Advisory for Monday afternoon and evening north of Grand Haven. The worst of the conditions, winds around 20 knots and 3-5 footers, will be found up near Big and Little Sable Points. Winds in the higher resolution models like the HRRR and the WRF-ARW have the best handle on this event. North flow wind event will be driven by a surface high in the Northern Great Lakes and a low in Northern IN/OH. Otherwise, there is the potential for areas of fog over the lake as well with surface dew points (mid 60s) which are higher than the lake surface water temps (lower 60s). Winds pick up a bit out of the north tonight which may tend to temper the fog a bit, but we will have to monitor lakeshore webcams tonight. Winds after Monday evening look to be off shore much of the time and below SCA criteria. So the marine concerns are essentially in the first two periods tonight (fog) and Monday (waves/wind). && .GRR WATCHES/WARNINGS/ADVISORIES... MI...None. LM...Small Craft Advisory from 2 PM to 11 PM EDT Monday for LMZ847>849. && $$ UPDATE...Meade SYNOPSIS...Duke DISCUSSION...Duke AVIATION...Meade MARINE...Duke
Area Forecast Discussion
National Weather Service Gray ME
1056 PM EDT Sun Oct 3 2021 .SYNOPSIS... Persistent clouds and scattered showers will continue tonight as a frontal boundary remains stationary over the area. This boundary will waver some on Monday and Tuesday for continued mostly cloudy skies with chances for showers primarily over southern areas. High pressure slowly builds in from the north towards midweek for mostly dry and mild weather the second half of the week. && .NEAR TERM /OVERNIGHT/... 11PM UPDATE... Made some adjustments to POP forecast based on latest radar trends. Southern NH will get rain most of the night although the northern edge will continue to get squeezed by the dry air advancing from the north. 9PM UPDATE... Just some small tweaks to the forecast based on current radar and satellite trends. Drier air has pushed in from Waldo County to Rangeley with some breaks in the cloud cover, but cloud deck is making slow progress now, with not much clearing expected further south. Rain will be on the increase over the next few hours across southern NH, while the small area of showers across Maine begins to pull off the coast with maybe some patchy drizzle across SW Maine tonight, but should remain mostly dry for the remainder of the forecast area. 5PM UPDATE... Have updated the forecast early this evening to adjust pops over northern New Hampshire and central portions of Maine where periods of light rain will continue. Second area of rainfall remains over southern New Hampshire. This region will receive rain throughout the night and into Monday per latest mesoscale models. Otherwise, just minor tweaks to the ongoing near term portion of the forecast. ORIGINAL DISCUSSION... The latest HRRR and HREF solutions depicts the stationary front will begin to retreat southward to some extent overnight as slightly drier air returns from the north. The focus for periods of light rain will shift mainly to southern areas overnight with rain likely over southernmost New Hampshire and scattered showers elsewhere. There will be patchy fog developing during the overnight hours, most likely more than last night. Temperatures will bottom out in the 40s north to the 50s south however there will be some temperatures in the 30s over the far northern mountains with scattered frost. && .SHORT TERM /MONDAY THROUGH MONDAY NIGHT/... An upper level trough and associated weak area of low pressure at the surface will advance eastward on Monday and Monday night. While light rain will be confined to southern New Hampshire Monday morning, moisture will make another push towards the north and east. This will allow for periods of rain and some fog to advance into central New Hampshire and extreme southwest Maine by late in the day. The low cloud cover will prevent temperatures from climbing higher than the upper 50s to lower 60s for afternoon high temperatures in most areas. The coolest readings will be over New Hampshire where the lowest cloud deck will be in place with lower 60s over eastern areas where some sunshine will remain. 12Z guidance consensus suggests periods of light rain will be limited mainly to southern New Hampshire Monday night as the rain shield once again is on the move, this time drifting south as a weak disturbance begins to exit the region. QPF/Locally Heavy Rainfall: The rainfall may be heavy at times tonight through Monday night over southernmost New Hampshire. Currently, the ongoing forecast for one to two inches mean basin average appears reasonable. With the precipitation falling over a two day period, these amounts should not cause any issues. However, minor flooding is possible and this portion of the Granite State remains as a marginal risk in the excessive rainfall outlook. Echoes should be fast moving, however training is a possibility as the flow remains parallel to the front. Also PW values will remain on the high side in this region as well. && .LONG TERM /TUESDAY THROUGH SUNDAY/... High pressure is set to move in quickly behind the exiting system Tuesday morning. Along with it returns dry air. This should shut off precip rather early Tuesday, with skies on a thinning trend. NE areas will undergo this by mid-afternoon, with the remainder of the CWA thinning by mid evening. The clearing trend Tues night across central ME will lead to temps falling into the lower 40s north of Augusta, with mid 30s possible in the northern valleys with the chance of some frost. To the south, have kept temps a bit warmer as long as clouds do stick around, even then, it may just be a thin cirrus shield remaining with mid clouds increasing into central New England. Dry weather is then expected Wed through late week. The region will be dominated by high pressure overhead. This keeps temps on the mild side with highs warming towards 70 in the coastal plain and overnight lows in the upper 40s to around 50. With relatively calm winds and mostly clear skies under the high, rad cooling could help drop temps a couple of degrees cooler than current forecast/guidance. But even then, many areas will keep frost free outside of the far northern valleys early this week. The next chance for area precip comes late this weekend. Sunday, the slowly exiting high pressure will slide out of New England. Whether it takes a more easterly slip or dips further south is the debate between guidance. A more easterly drive would allow return flow to combine with SW flow, introducing the slight chance of showers amid good moisture transport. A southerly dip would mean keeping this at bay. Plenty of time for this to evolve given the complex blocking patterns, and have kept precip chances low. && .AVIATION /03Z MONDAY THROUGH FRIDAY/... Short Term...Cigs will lower overnight with most terminals dropping to IFR/LIFR. Overcast skies and occasional -ra will continue Monday with a mix of MVFR and VFR cigs. Lowest cigs in the south. Conditions lowering once again to IFR/LIFR most areas Monday night. Long Term...Remaining MVFR Tues morning will trend VFR through at least Sat night. The exception will be any nightly valley fog that develops in the CT valley near KLEB and KHIE. Winds light and variable. && .MARINE... Short Term...Long period swell from distant tropical activity has entered the Gulf of Maine with seas topping out around 4 to 5 ft. A stationary front draped west to east across New England will lead to to easterly winds tonight through Monday night with gusts topping out around 20 kts Monday. Patchy fog will restrict visibilities at times, mainly during the night. Long Term...Waves briefly increase Tuesday night, before a northerly wind shift takes them down, 2 to 3 ft. Winds and waves are expected to remain below SCA through the period under high pressure. The exception will be breezy winds in the afternoon up to 15 kt. && .GYX WATCHES/WARNINGS/ADVISORIES... ME...None. NH...None. MARINE...None. && $$ NEAR TERM UPDATE...Kimble SHORT TERM...Cannon LONG TERM...Cornwell
National Weather Service Jackson KY
1159 PM EDT Sun Oct 3 2021 .UPDATE... Issued at 1159 PM EDT SUN OCT 3 2021 Trimmed PoPs across the southwest as convection took a sudden downturn in intensity and coverage. Otherwise, the forecast remained generally on track. Only needed to tweak grids to incorporate latest hourly obs. Updated zones and grids have been issued. UPDATE Issued at 1027 PM EDT SUN OCT 3 2021 Have been watching a broken line of showers and thunderstorms pushing eastward across south central Kentucky and convection has held together nicely. HRRR is currently showing this activity holding together long enough to affect portions of our southwest, though there continues to be a weakening trend in guidance overall. However, HRRR has shown a tendency to weaken this activity too rapidly through the evening, at least until the last run or so. Beefed PoPs back up across the far southwest but did trend PoPs lower as the activity moves through our southern zones during the overnight. Increased QPF just a bit across the southwest as well. Updated zones have been issued. Grids will be sent shortly. No other changes at this time. Convection is expected to continue to wane through the overnight as patchy fog and lower clouds develop across the area. UPDATE Issued at 805 PM EDT SUN OCT 3 2021 Seeing a general downward trend in shower and thunderstorm activity across the area. However, still watching a band, or at times, line of scattered showers and thunderstorms associated with a surface cold front moving eastward into central Kentucky. Model solutions and guidance suggest a general decrease in activity as the line pushes eastward into eastern Kentucky, along with a slowing of the front and eventual stalling out across central portions of the Commonwealth. However, convection may hold together just long enough to affect some of our most western zones. Will watch and make necessary adjustments to the forecast if the activity holds together longer than expected. Otherwise, adjusted grids for latest hourly trends. Updated grids sent and zones will be out shortly. && .SHORT TERM...(This evening through Monday night) Issued at 512 PM EDT SUN OCT 3 2021 An upper level trough was over much of the eastern CONUS on Sunday afternoon, with its axis over the upper Great Lakes, and a shortwave trough rotating around it over the mid Mississippi and lower Ohio Valleys. A surface low was over Lake Michigan, with a cold front extending down the Mississippi Valley. Abundant moisture was flowing north and northeast over our region, and being acted upon by the shortwave and an associated upper level jet max to bring rounds of showers and thunderstorms. Models agree on the trough amplifying and closing off an upper low over the lower Mississippi Valley during the period. The frontal boundary will slowly advance southeast into KY, restricted in movement by the stagnant upper air pattern. The shortwave trough and jet affecting our area will move past on Monday. Another round of showers/thunderstorms could affect the region as it moves through, with the NAM being the most bullish on this late tonight into Monday. After this, while precip can`t be ruled out, support will be less and the POP will be considerably lower Monday night, especially with loss of heating. .LONG TERM...(Tuesday through Sunday) Issued at 320 PM EDT SUN OCT 3 2021 The weather will remain unsettled Tuesday through the end of the work week as an upper level low over the deep south slowly drifts north during the week and eventually opens up into a broader trough towards the end of the week into the weekend. This will keep the chances of daily showers and thunderstorms in the forecast Tuesday through Friday, with the highest chances for thunderstorms being during the afternoon and evening each day. Rain chances finally begin to diminish over the weekend as the trough axis moves east of the area into New England and the Mid Atlantic. High temps will be near seasonal norms Tuesday through Friday in the low to middle 70s, before warming up to the mid and upper 70s for the weekend. Overnight lows remain mild and above normal starting off in the lower 60s Tuesday and Wednesday night and retreating a bit to the upper 50s by the end of the week into the weekend. && .AVIATION...(For the 00Z TAFS through 00Z Monday evening) ISSUED AT 805 PM EDT SUN OCT 3 2021 Seeing a general downward trend in shower and thunderstorm activity across the area. However, still watching a band, or at times, line of scattered thunderstorms associated with a surface cold front tracking eastward across central Kentucky. Model solutions and guidance suggest a continued decrease in activity as the line pushes eastward, along with a slowing of the front and eventual stalling out. However, convection may hold together just long enough to affect SME, less so LOZ but that is not out of the realm of possibilities. Flight conditions worsen through the overnight as mainly CIGS lower into MVFR, and for a short period of time around dawn into IFR territory before lifting and scattering out toward the end of the forecast window. Some light mist leading to MVFR VSBYS will be possible as well. Winds will generally be light and variable through the period. && .JKL WATCHES/WARNINGS/ADVISORIES...NONE. && $$ UPDATE...RAY SHORT TERM...HAL LONG TERM...CMF AVIATION...RAY
Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
836 PM EDT Sun Oct 3 2021 .SYNOPSIS... Broad upper level low over the Ohio valley will migrate southward through midweek as high pressure develops across our north. The combination of the two will yield a stationary front across the area throughout most of the upcoming week. As a result, daily chances for showers and thunderstorms will persist as temperatures remain slightly above average. && .NEAR TERM /UNTIL 6 AM MONDAY MORNING/... Latest analysis shows a broad area of low pressure residing over the Great Lakes region this evening as high pressure remains banked off the Carolina coastline. As a result, an increase in humidity continues thanks to a light southerly flow. Latest satellite imagery depicts increasing high clouds across the Alleghenies that continue to propagate eastward. Meanwhile, latest radar loop shows a few showers continuing to move northward out of north-central MD into southern PA while a second batch of showers moves into southern Nelson county. Latest runs of the HRRR have matched up well with current obs, and indicate mostly dry conditions overnight for areas mainly east of the Blue Ridge. Elsewhere, weak shortwave advection will persist which will allow scattered showers to continue through the overnight hours, albeit expecting shower activity to remain light in nature. Patchy fog is expected to develop overnight into the early morning hours Monday with overnight lows in the mid to upper 60s for most, cooler across the higher terrain. && .SHORT TERM /6 AM MONDAY MORNING THROUGH TUESDAY NIGHT/... With the aforementioned low pressure system tracking further southeastward, stronger forcing will be available which will help usher in better chances for showers and a few isolated thunderstorms on Monday. Temperatures will be a few degrees cooler with an extended period of increased clouds expected before. Latest guidance continues to depict a line of potentially convective storms by 18 to 21z on Monday, extending from the Mason-Dixon line to our SW areas along and west of the Blue Ridge Mountains and should persist further east over the course of the afternoon into the early evening hours before the loss of diurnal heating ceases the bulk of the convective activity. As we continue into Tuesday, forecast confidence diverges as guidance solutions struggle to grasp the interaction of the low residing across our southwest and high pressure to our north. The Rex Blocking pattern appears to keep us more under the influence of the high than the low, which would keep the CWA drier than previously anticipated. However, given the uncertaintyof the forecast, have kept the mention the showers and thunderstorm chances status quo for the time being, until greater confidence can be obtained. Temperatures will remain on the mild side with highs in the upper 70s to low 80s both days and overnight lows in the 60s. && .LONG TERM /WEDNESDAY THROUGH SUNDAY/... A cold front is forecast to move through our area sometime on Wednesday and become stalled to the south of our region through the second half of our week. An upper low positioned over the southern US on Wednesday is forecast to shift back north along the Mississippi River area. High pressure positioned to the northeast of the upper level low over the NE US will lead to a persistent on- shore flow in our region. This onshore flow pattern will lead to increase advection of moisture into our region. Skies will likely remain mostly overcast through most of the long term period with the possibility for periods of overnight advection fog especially along the Chesapeake Bay. The combination of the stalled boundary to the south along with the upper low moving off to the west of our region will lead to continued chances for rain each day in the long term. Based on the positioning of the upper low as it moves off to the west and the continued easterly flow, the heaviest precipitation will likely be focused west of the Blue Ridge Mtns near the Allegheny front. There remains some uncertainty on the strength of the onshore flow along with the track the upper low will take as it shifts back northward. If the upper low tracks further eastward, the heaviest rain would shift over the metro areas where extended periods of rain could lead to a flooding threat. As the flow will be mainly onshore and skies will be overcast, think there is potential that statistical models could overforecast on high temperatures this week and the raw models will handle temperatures a little better. This would argue highs in the 70s for the second half of the week with lows in the upper 50s and into the 60s. && .AVIATION /00Z MONDAY THROUGH FRIDAY/... A light southerly flow continues across the terminals this evening with mostly VFR conditions. A few showers may arise overnight over MRB and CHO. Otherwise, mostly dry conditions are expected. Patchy fog is expected to develop overnight. However confidence remains low if any of the terminals will be subject to any low end CIG/VSBY restrictions overnight. Mainly VFR conditions and a southerly wind continue throughout the morning hours Monday. However, the development of showers and thunderstorms are expected Monday afternoon into Monday evening which may briefly result in CIG/VSBY restrictions. There`s a better signal for more widespread fog overnight into Tuesday with an increase in moisture and near calm winds. Additional periods of sub-VFR conditions are possible on Tuesday. However, confidence remains low at this time. An onshore easterly flow will form on Wednesday as a front stalls to the south of the region and high becomes positioned over the NE US. Low stratus decks may lead to sub-VFR conditions Wednesday through the end of the week. Rain will be possible each afternoon at all terminals with CHO and MRB having the highest threat at this time to receive the heaviest rain. && .MARINE... Increased winds overnight over the lower Chesapeake Bay and the lower Potomac River as high pressure pushes further offshore to our SE, yielding a SCA for these areas through Monday morning. A few SMWs may be possible Monday afternoon if any isolated thunderstorms make it to the waters. Otherwise, no other marine hazards expected for the short term period. High pressure over the NE US along with an upper level low to the southwest of our region will lead to persistent onshore flow through the second half of this week. The onshore flow will lead to the threat for some marine fog Wednesday and Thursday. Sub-SCA conditions expected at this time. && .TIDES/COASTAL FLOODING... Elevated water levels will persist through much of the week with southerly flow initially and then easterly/onshore flow by the middle portion of the work week. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...None. MD...None. VA...None. WV...None. MARINE...Small Craft Advisory from 11 PM this evening to noon EDT Monday for ANZ533-534-537-541>543. && $$ SYNOPSIS...SOUZA NEAR TERM...SOUZA SHORT TERM...SOUZA/ADM LONG TERM...JMG AVIATION...SOUZA/JMG MARINE...ADM/JMG TIDES/COASTAL FLOODING...ADM
Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
706 PM CDT Sun Oct 3 2021 .UPDATED for 00Z Aviation Discussion... Issued at 654 PM CDT Sun Oct 3 2021 && .SHORT TERM...(This evening through Monday night) Issued at 253 PM CDT Sun Oct 3 2021 Surface analysis this afternoon shows high pressure across the Rockies starting to make its way eastward as a surface cold front just east of the Mississippi River continues to move off to the east in conjunction with a sharp upper level trough. A dome of high pressure aloft over the Four Corners region is also nudging its way northeast. Over the next 24-36 hours, these deep ridging features will slide east northeast, moving atop the Upper Midwest tonight through Monday night. As the trough exits to the east, the lingering stratus deck over extreme eastern MN into western WI will gradually erode to the east and diminish, allowing clear skies to prevail late tonight through tomorrow night. In addition, winds will diminish tonight through late tomorrow morning, become light and variable during the day tomorrow, then become nearly calm once again tomorrow night through Tuesday. Combined with highs in the low-mid 70s today and tomorrow and lows in the mid 40s to lower 50s, these conditions would seemingly be ideal for the first week of October. Not to say they aren`t but there is one blemish with this synoptic setup - the appreciable potential for dense fog overnight through Monday morning and fog again Monday night into Tuesday morning. Plentiful rainfall over eastern MN into northwest WI yesterday, generally in the range of 1/4 to 3/4 inch with localized spots over 1 inch of rain, along with the stoic low stratus not allowing for daytime evaporation will maintain plenty of low level moisture across the eastern half of the WFO MPX coverage area overnight. This moisture will become trapped underneath the nightly inversion, occurring during what will be nearly ideal radiational cooling conditions tonight. These conditions will promote fog, and potentially dense fog, development overnight through Tuesday morning over and areas from roughly Little Falls to Mankato and points eastward to the WI state line, including the non-urban portions of the Twin Cities metro. HRRR progs also advertised the dense fog potential. Therefore, have opted to issue a Dense Fog Advy for late tonight for much of east-central into south-central MN, and a bit of west-central WI. There is some potential again for dense fog Monday night into Tuesday morning but will evaluate how conditions go tonight plus see what models do with that potential before heightening the messaging for dense fog tomorrow. .LONG TERM...(Tuesday through Sunday) Issued at 253 PM CDT Sun Oct 3 2021 As mentioned above, areas of fog are possible early Tuesday before we see more sunshine and temperatures once again warming into the low to mid 70s. Ridging will be in full swing with winds slowly becoming southeasterly through the day as the surface high pulls away to the east over Quebec. Much of the same is in store for Wednesday before we see our next set of systems approach the area Thursday. The first comes in the form of a 500mb cutoff low moving up from the mid Mississippi Valley towards the Great Lakes. While the majority of impacts from this feature will be felt well to our southeast, our western Wisconsin counties and eastern Minnesota have a slight chance of seeing some afternoon showers lingering into the overnight hours. On the heels of this system is a stronger, negatively tilted trough that will swing through late Friday into Saturday. WAA looks to be strong ahead of it, allowing for one last run at 80 degrees. The limiting factor will likely be cloud cover with an abnormally moist airmass in place. Model PW values are running well above 1" from late Thursday through Saturday evening. There are still some timing differences regarding the onset of precip and the overall strength of the surface low, but feel comfortable with widespread slight to chance PoP values from Friday evening into early Sunday morning. As of now, highest rainfall totals look to be across central and northern Minnesota due to the proximity of the best forcing. By the end of the period, more fall-like weather will settle in behind the front with highs in the mid 60s and a few lingering showers through Sunday. The more active pattern will continue into early next week, but there are still no temperatures below freezing in sight. Our normal first freeze date typically falls sometime during the first two weeks of October. && .AVIATION...(For the 00Z TAFS through 00Z Monday evening) Issued at 654 PM CDT Sun Oct 3 2021 VFR conditions at KAXN and KRWF, but areas of dense fog is expected to develop tonight at the rest of the TAF sites. As of now it appears that LIFR conditions are most likely at KMKT, KSTC, and KRNH. The winds will be light, and that will make it difficult to mix out the fog if it does form, so have it lasting into the late morning. No precipitation is expected. KMSP... The clear skies this evening should give way to fog development overnight. Guidance continues to suggest as low as LIFR conditions, so have trended the tafs down a bit but kept the visby at 3/4 mile. It is certainly possible it could be lower early Monday morning. The fog should break up by late morning. /OUTLOOK FOR KMSP/ Tue...VFR. Wind SE 5-10 kts. Wed...VFR. Wind SE 5-10 kts. THU...VFR. Wind SE 5-10 kts. && .MPX WATCHES/WARNINGS/ADVISORIES... MN...Dense Fog Advisory from 11 PM this evening to 9 AM CDT Monday for Anoka-Benton-Carver-Chisago-Dakota-Hennepin-Isanti-Kanabec-Le Sueur-McLeod-Meeker-Mille Lacs-Morrison-Nicollet-Ramsey-Rice- Scott-Sherburne-Sibley-Stearns-Washington-Wright. WI...Dense Fog Advisory from 11 PM this evening to 9 AM CDT Monday for Barron-Polk-St. Croix. && $$ SHORT TERM...JPC LONG TERM...Dye AVIATION...JRB
Area Forecast Discussion
National Weather Service Marquette MI
755 PM EDT Sun Oct 3 2021 .SHORT TERM...(This evening through Monday) Issued at 340 PM EDT SUN OCT 3 2021 The pattern remained blocked with RAP analysis 500mb heights showing a rex block over eastern Canada with our area remaining under the influence of an upper level trough moving under the northern ridge. A weakening MCV remained nearly stationary over the west today bringing several hours of rain, sometimes heavy, particularly in Houghton and Keweenaw counties. Showers were forming along a boundary in the central U.P where skies had broken and allowed for additional destabilization. Though Monday the blocking over Eastern Canada breaks down and the ridge shifts east. Additional ridging begins to build into the central US, extending from the eastern Rockies / High Plains to MN by Monday evening. Meanwhile, weak troughing over the Great Lakes today begins to cut off under the building ridge and sink south. For the rest of the afternoon and evening we will continue to see areas of showers with a few thunderstorms in the southeast. The forcing mechanisms look like they will continue to decrease in the area of the MCV with models showing isentropic ascent and fgen weakening and shifting east. It looks like there will still be enough lift to promote additional areas of showers over the central and east, all with rather slow movement under weak steering flow. With PWATs remaining high showers or thunderstorms could produce heavy rainfall. Fog will be a concern again tonight with onshore, upslope flow along with rainfall promoting fog development. We should see drier air and better mixing over the area tomorrow with fog dissipating though the morning hours. .LONG TERM...(Monday night through Sunday) Issued at 433 PM EDT SUN OCT 3 2021 The extended forecast will consist of a occluded upper level low meandering to the southeast from the Great Lakes, and a building ridge pattern causing above average temperatures dry weather across the area through most of the week. Toward the end of the week, the weather regime looks to pick up and become more active once again, bringing multiple opportunities for rainfall across Upper Michigan. Monday night will see the broad, surface low pressure slowly meander south-southeast. This is the same weather system that has plagued the Great Lakes with multiple rounds of showers over the last couple of days. As this broad, low pressure slowly moves to the south, surface high pressure will overtake the Upper Great Lakes. We anticipate that sky cover will quickly dissipate as dry air from the midlevels is brought toward the surface Monday night into Tuesday morning. This will be most apparent in the west half where the cloud cover will dissipate the quickest. Overnight lows will bottom out in the upper 30s to lower 40s over the interior west, with the remainder of the area remaining in the 40s. The upper level ridge pattern will build across the Central and Northern CONUS on Tuesday through Thursday. This ridge pattern will continually bring WAA to the area, despite surface high pressure bringing onshore flow along the Lake Superior shoreline, and cooler temperatures localized to these areas. Temperatures will be above average across the interior, mainly in the middle 60s to middle 70s. Due to surface high pressure being over the area from Tuesday through Thursday, and WAA at 850mb creating nocturnal inversions, patchy fog will be possible for several mornings. By Thursday night into the weekend, the upper level ridge will break down. Multiple shortwave troughs will brings chances for rainfall to the area. This will be welcomed relief to areas that are experiencing drought conditions across Upper Michigan. A strong cold front will be moving through the region by the end of next weekend, and into the beginning of next week. && .AVIATION...(For the 00Z TAFS through 00Z Monday evening) Issued at 743 PM EDT SUN OCT 3 2021 Very moist airmass remains in place across Upper Michigan, ensuring LL stratus and fog persists at all three terminals. Drier air will slowly make its way into the area from west to east, but not until tomorrow. Even then, model soundings struggle to depict any sort of drastic, immediate improvement, so some SCT stratus could linger, particularly at KSAW where it appears to be slower to clear out. Generally light N to NNE winds will prevail through the TAF period. && .MARINE...(For the 4 PM Lake Superior forecast issuance) Issued at 340 PM EDT SUN OCT 3 2021 The wind stays at or below 20 knots through the forecast period. Dense fog could remain an issue tonight though somewhat drier and less stable air will filter into at least the western portion of the lake which could mitigate the fog threat. Kept the dense fog headlines but confidence has become lower. && .MQT WATCHES/WARNINGS/ADVISORIES... Upper Michigan... None. Lake Superior... Dense Fog Advisory until 8 AM EDT /7 AM CDT/ Monday for LSZ162- 240>251-263>267. Lake Michigan... Dense Fog Advisory until 9 AM EDT Monday for LMZ221-248-250. && $$ SHORT TERM...NL LONG TERM...BW AVIATION...lg MARINE...NL
Area Forecast Discussion
National Weather Service Reno NV
209 PM PDT Sun Oct 3 2021 .SYNOPSIS... Warm and dry conditions continue into the start of the week with a slight uptick in winds starting Monday. A weather pattern change then appears likely midweek onward with some afternoon breezes, increased clouds, and a cooling trend. Precipitation chances may also return later in the week into next weekend. && .SHORT TERM... No appreciable changes to the ongoing forecast with a couple more mild and very dry days on tap. There will be a slight uptick in winds Monday and Tuesday afternoon across northeast CA and northern Nevada with gusts of 20-30 mph possible. Single digit RH values on Monday will increase by about 5% Tuesday, with further increases into midweek. There are enhanced fire weather concerns Mon/Tues, however widespread critical conditions are not expected. The only other concern through Tuesday would be smoke and haze, primarily from the KNP Complex near Sequoia National Park. We already can see the haze aloft today, with thicker near-surface smoke likely to drift northward into southern Mono County this evening, based on HRRR smoke models. Southerly flow may continue to bring an increase in haze along the western Nevada Sierra front overnight into Monday as well. Increasing afternoon breezes Monday should push smoke further into western Nevada, with similar patterns for Tuesday. -Dawn .LONG TERM...Wednesday through next weekend... The evolution of the weather pattern change later in the week continues to be in flux, with the latest guidance favoring Thursday and Friday having the best overall precip chances, and the coolest temperatures from Thursday-Saturday. More details on the highlights: * RAIN/SNOW: While not all ensemble members are on board, an increasing percentage are showing an improved moisture tap on Thursday, even with the main trough splitting near the northern CA coast. While overall totals still look modest, there could be some bands of moderate rainfall producing low end wetting amounts (0.10"-0.25") even for lower elevation sites. Then from late Thursday night through Friday, the better precip chances appear to favor areas south of US-50. By this time, snow levels could fall to near 7500 feet, with best potential for light accumulations near the crest in Alpine and Mono counties. * WINDS: Not a big wind producer with the peak gusts expected for Wednesday (around 30 mph, maybe a few sites seeing gusts to 35 mph), followed by lighter winds from Thursday onward. Humidity values will be on the rise Wednesday, which will limit fire weather concerns. * TEMPERATURES: A sharp cooling trend will begin Wednesday with highs in the lower-mid 70s for western NV valleys and 60s for eastern CA communities. Then from Thursday-Saturday, highs are only projected to reach the lower-mid 60s for lower elevations and 50s for Sierra valleys, then rebounding slightly on Sunday. Potential for freezing temperatures in areas that have yet to see a fall freeze will increase by next weekend. * EVEN COLDER EARLY NEXT WEEK?: After a break in most precip activity for Saturday night-Sunday, the medium range guidance has a reasonable agreement this far out for a reinforcing cold front dropping in from the north for the Monday-Tuesday (October 11-12) time frame, with some moisture and lift potentially bringing a rain-snow mix even down to some lower valleys by next Monday night. Although there is plenty of time and variance in the ensemble guidance, this is an early "heads-up" for a potential touch of winter weather early next week for parts of eastern CA-western NV. MJD && .AVIATION... Pleasant flying conditions today into the start of the week, though haze is present across the Sierra and western Nevada Sierra front due to the KNP Complex wildfire. Southerly flow is likely to bring thicker smoke to southern Mono County this evening with potential terrain obstruction and surface visibility reductions for KMMH. This flow pattern may transport thicker haze northward into Monday as well, but afternoon winds will clear haze for most areas north of US-50. Light winds this afternoon will increase a bit for areas north of I-80 Monday-Tuesday, then across the region Wednesday as a colder system moves into the west. At this point, most gusts should remain near or below 20-25 kts for terminal sites. This system could bring rain and snow showers to the region by the end of the week or possibly next weekend with falling snow levels and much colder temperatures. -Dawn && .REV Watches/Warnings/Advisories... NV...None. CA...None. && $$ For more information from the National Weather Service visit...