Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 05/13/24


See below for an aviation forecast discussion for the 00Z TAFs.

&& .SHORT TERM /THIS EVENING THROUGH MONDAY NIGHT/... Issued at 236 PM CDT Sun May 12 2024 Low pressure in eastern Canada, and high pressure in its wake, is feeding smoke out of central Canada, though the highest concentration of smoke is currently overhead and HRRR smoke products show a slow diminishment tonight/Monday with it lingering in the northeast of the state and western Minnesota though much of Monday morning. There is also a weak shortwave embedded in a northwest flow regime over the western Dakotas and eastern Montana. This feature will drift slowly southeast, overrunning the high pressure at the surface. Thus, looking at mainly high based/weak showers with little actual QPF. High pressure and upper ridging dominate Monday till we begin to see diffluent flow associated with the next wave coming in from the west for early Tuesday. A front along the gulf will block any moisture return and as such looking at mainly light QPF though with more coverage in comparison to tonight`s system. && .LONG TERM /TUESDAY THROUGH SUNDAY/... Issued at 236 PM CDT Sun May 12 2024 Clusters are in agreement with a slightly positive tilted shortwave over the Northern Rockies at 12Z Tuesday. The axis extends from southwestern MT into ID, leaving zonal flow across the area. They also indicate a separate weak shortwave pushing east across Saskatchewan into Manitoba/ND as well. The 850mb low will be over western MT/ND as this system occludes and a secondary surface low forms over ~western SD Tuesday. Through the day, this low and warm front will push east/northeast across the CWA. By Tuesday evening, both of the waves will continue to push east/northeast (and merge together) along with the surface low as models indicate the cold frontal passage early Wednesday morning across central SD and more Wednesday midday/afternoon across eastern SD into western MN as winds shift to the northwest. By the end of the week, another wave will push northwest to southeast and over the Northern Plains along with a broad mid level low in Canada. Clusters start to diverge at this point on timing and intensity of our next system. Ensembles agree well on precipitation in the form of rain moving in from the northwest and into our northwestern and central CWA by Tuesday morning. EC seems to be the quickest on the progression of this precipitation as it pushes eastward across the CWA and GEPS being the slowest so time may vary a bit. Rain will become widespread over the CWA by Tuesday evening/night. NBM shows this pattern well with our highest pops between Tuesday afternoon across central and western CWA (30-75%) and pops ranging from 40-60% Tuesday night into early Wed morning. As this low continues east, rain will end west to east Wednesday evening. Prob of QPF>0.25" from Tuesday morning through Wednesday through evening from the ensembles range from 25 to 70%, highest over our western CWA. NBM pops indicate this well with QPF up to 0.35" or so in this area. Prob of CAPE>500 j/kg per GEFS ranges from 30-50% across south central SD with 20-30kt shear out of the west Tuesday afternoon and evening in the warm sector of the low and dp`s in this area reaching the lower 50s. This could lead to some general thunderstorms with severe weather remaining low at this point. Additional slight pop chances are noted by NBM (15-30%) for the end of week with the next system, however low confidence exists. Temps will range in the lower to mid 70s Tuesday and cooler on Wednesday behind the front, with highs in the upper 60s to the lower 70s. Temps will rebound and gradually warm for the end of the week back into the mid to upper 70s/lower 80s by Friday. && .AVIATION /00Z TAFS THROUGH 00Z MONDAY/... Issued at 629 PM CDT Sun May 12 2024 Terminals KABR,KATY,KPIR,KMBG Except for the periods of time when near surface smoke concentrations are high enough to reduce visby (4-5sm FU), VFR conditions are forecast for all terminals through the TAF period. Out of any of the terminals, the highest smoke concentrations are supposed to reside over far northeast South Dakota (KATY?) through Monday evening. && .ABR WATCHES/WARNINGS/ADVISORIES... SD...None. MN...None. && $$ UPDATE...Dorn SHORT TERM...Connelly LONG TERM...MMM AVIATION...Dorn
Area Forecast Discussion
National Weather Service La Crosse WI
1052 PM CDT Sun May 12 2024 .KEY MESSAGES... - Scattered showers/storms into the evening with rain chances shifting south of I-90 Monday. Gusty winds, lightning and small hail possible through this evening. - Air quality alerts for MN/Parts of WI through Monday Morning. Extensions may be needed. - Seasonable temps with the next better chance for widespread rain Wednesday night into Thursday && .DISCUSSION... Issued at 255 PM CDT Sun May 12 2024 Overview: Showers and thunderstorms have developed this afternoon with heating with increasing 850mb moisture and warm air/theta-e advection. The HRRR seemed to pick up on these showers/storms over northeast Iowa the best. We did have a gust to 50mph near New Hampton and some small hail. The SPC had SBCAPE around 1500J/kg and very steep low level lapse rates of 9-10deg. C/km. Downdraft CAPE was 900-1100J/kg...and inverted-v soundings favor gusty winds. The effective shear has decreased from earlier today over southwest WI and is generally 25kts or less. Water vapor satellite imagery, 500mb heights, and lightning show a trough over CO/western Plain and also over the Ontario. Lightning was noted between the two systems from northern WI into parts of southern MN along the cold front and the area across northern Iowa The surface cold front at 19Z was moving through the Twin Cities. Scattered showers/storms into the evening with pcpn chances shifting south of I-90 Monday (15-85% higher toward DBQ): The storm system over the Plains does phase somewhat with the northern stream wave, however the cold front does push through areas north of I90, then slow down. We`ll see the scattered showers and thunderstorms continue per the CAMs with a southern area and an area along the cold front, generally pushing south I 90 by 03-04Z with a weakening trend there, but continuing across parts of eastern IA and southwest WI. Smoke/Air Quality Alerts Smoke from wildfires in Canada continue to affect parts of the area today. The HRRR Smoke forecast calls for the near surface smoke/integrated smoke to continue to push south with the cold front into southeast MN/much of central WI and into northern IA through Noon Monday. As a result, both MN and WI have issued air quality alerts through Monday morning. We`ll continue to monitor conditions for extensions Monday. Extended: Tuesday through Wednesday we should generally be in-between weather systems with seasonable temperatures in the 60s to lower 70s. The next full latitude trough will move through Wednesday night into Thursday night. It appears to deepens as it exits the area with increasing areal coverage of precipitation, taking the higher rainfall amounts to the east. Per the European/GFS/Canadian ensembles, the probability for 0.25" for the 24hrs ending 7am Friday is 20 to 50% with the higher probabilities toward far southern WI. We have a better chance of seeing a wetting rain (0.10"), 50 to 70%. Friday should generally be dry unless the storm system slows down and precipitation chances linger across the far southern portion of the forecast area. && .AVIATION /06Z TAFS THROUGH 06Z TUESDAY/... Issued at 1053 PM CDT Sun May 12 2024 Southwest winds will continue to transition to northwest winds overnight as a cold front moves through the region. Scattered showers and thunderstorm chances are expected to diminish during the overnight hours before picking back up again Monday morning, especially in portions of northeast Iowa and southern Wisconsin. Smoke, from some Canadian wildfires, will enter the area on Monday and as a result there may be some MVFR visibility restrictions. && .ARX WATCHES/WARNINGS/ADVISORIES... WI...None. MN...Air Quality Alert until noon CDT Monday for MNZ079-086>088- 094>096. IA...None. && $$ DISCUSSION...Rieck/Zapotocny AVIATION...Cecava
Area Forecast Discussion
National Weather Service Cleveland OH
958 PM EDT Sun May 12 2024 .SYNOPSIS... High pressure over the Ohio Valley this evening will exit offshore of the Mid Atlantic coast tonight allowing a weak cold front to drop to the vicinity of Lake Erie. This front will return north as a warm front Monday as low pressure moves across the Mississippi Valley. The low will then lift across the Great Lakes Monday night and Tuesday extending a cold front into the area. && .NEAR TERM /THROUGH MONDAY NIGHT/... No changes to the forecast at this time. Previous Discussion... Clouds that lingered much of the day over NE Ohio and NW PA have cleared nicely allowing for a fair but cool afternoon as mid/upper troughing lingers over the eastern Great Lakes. We only have to look to the west and northwest to find our next weather makers though in the form of a mid/upper shortwave trough in the Upper Midwest and a southern stream closed low over the southern High Plains. Surface high pressure currently over the Ohio Valley will quickly move offshore of the Mid Atlantic coast tonight allowing the upstream shortwave over the Upper Midwest to progress across the northern and central Great Lakes. This will push a weak cold front southward into Lake Erie late tonight before stalling in response to the southern stream closed low and associated weak surface low approaching the Mid Mississippi Valley. The cold front will be displaced well south of the synoptic forcing tonight leading to very limited convergence and moisture return, so expect any showers or rumbles of thunder to be very isolated. However, with the boundary dropping into the area, have slight chance to chance PoPs for lakeshore areas late tonight and Monday morning, mainly in the 06-12Z timeframe. The boundary will likely not make it any farther south than the south shore of Lake Erie before it retreats back north as a warm front Monday morning in response to the system over the Mid Mississippi Valley. That closed low will become more of an open shortwave trough as it lifts across Missouri and into Illinois during the day Monday. Strong warm air advection ahead of this system will lead to much warmer conditions and a sharp change to well above normal temperatures Monday. NAM and RAP forecast soundings suggest a weak cap in the 850-700 mb layer Monday afternoon, so do not expect to see much in the warm sector, and low- level moisture is also slow to return limiting MLCAPE values to a couple hundred joules. However, the 3-KM NAM hints at some convection near a lake breeze boundary in far NE Ohio and NW PA in the afternoon, so it cannot be entirely ruled out. Most areas will just be warm and dry Monday though. Precipitation chances will expand east into the area Monday night as the weak surface low associated with the shortwave rides up the boundary across northern Illinois, finally supporting stronger moisture advection and isentropic ascent into the southern Great Lakes. This will support fairly widespread showers, and there will be enough elevated instability for pockets of thunder, so have likely PoPs in most areas Monday night. Lows tonight will be milder ranging from the mid/upper 50s in NW and north central Ohio to the mid 40s to low 50s in NE Ohio and NW PA. Highs Monday will rise into the upper 70s/low 80s. Lows Monday night will only fall into the upper 50s/low 60s. && .SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/... Unsettled Tuesday in southwest flow aloft, a warm front draped lengthwise along the Lake Erie axis, and the slow moving upper trough axis just to the west of the CWA. Modest instability and shear, but a drier layer sitting above 600mb in which the limited instability could still tap into could make the convective scenario slightly tricky. Will need to see how these details unfold a little more going forward. System finally moves through late Tuesday night into early Wednesday, transitioning to northeasterly flow into the region with some lingering POPs in onshore low level moisture advection. High pressure gradually builds into the Great Lakes Wednesday night, and dries out the forecast as it does so. && .LONG TERM /THURSDAY THROUGH SUNDAY/... After brief ridging in the area Thursday, the next low pressure system moves in for the end of the week and the first part of the weekend. Significant differences exist in the evolution of this system, so the details are not there right now but will carry POPs in the extended that peak in the Friday/Friday night time frame. Should get a little warmer from the short term into the long term forecast period, and too early for now to try to dive into any sort of storm threat for the long term. && .AVIATION /00Z Monday THROUGH Friday/... VFR conditions are expected through the TAF period. High pressure is in control this evening into the first part of tonight and will allow for light winds and clear conditions. A cold front will pass to the north of the region and will allow for some cirrus to enter late tonight. For NW PA and far NE OH, some mid level clouds and some scattered rain showers could enter late tonight into Monday and have a brief vicinity shower mention. Return flow will allow for southwest winds to be favored during the day on Monday and some wind gusts in the 20 to 25 kt range are expected. The next system will approach late the period and have mid-level clouds returning with rain/storm chances best expected after the TAF period. Outlook...Non-VFR possible in showers and thunderstorms Monday night through Wednesday. && .MARINE... Offshore winds 10-20kts through Monday weaken to 5-15kts Monday night. Immediate nearshore waters less than a foot while the open waters will reach 1-3ft during this time frame. A low pressure system moves through Tuesday turning winds northeasterly 10-15kts, increasing to 15-20kts Wednesday. Central and western basin wave heights will be higher during this period as well where the higher winds exist, pushing 2-4ft Wednesday. Onshore winds continue through Thursday, but in lighter flows, waves subside to 1-3ft. && .CLE WATCHES/WARNINGS/ADVISORIES... OH...None. PA...None. NY...None. MARINE...None. && $$ SYNOPSIS...Garuckas NEAR TERM...Garuckas/Sefcovic SHORT TERM...26 LONG TERM...26 AVIATION...Sefcovic MARINE...26
Area Forecast Discussion
National Weather Service Grand Forks ND
707 PM CDT Sun May 12 2024 .KEY MESSAGES... - Smoke from Canadian wildfires will continue to impact the region into Monday morning. - Areas of frost are expected for areas mainly north of US Highway 2 late tonight into Monday morning. && .UPDATE... Issued at 703 PM CDT Sun May 12 2024 Clear sky tonight. Watching vsbl for some band of smoke. The initial thick band behind the front is gone and what is left are bands of smoke with vsbys 4-6SM. But upstream shows less smoke in S Manitoba and from HRRR smoke grids idea is for a slow diminish trend in smoke thru the night from the north. But it will take til daybreak in some areas. So idea of smoke in the grids looks good. Also with lesser smoke anticipated overnight in the northern fcst area makes sense to see mid 30s in that area with areas of frost. Few colder spots will likely get 33 or so. So no changes will be made to forecast or headlines. && .DISCUSSION... Issued at 327 PM CDT Sun May 12 2024 Northwest flow on the back side of a mid/upper low centered over northwest Ontario is in place currently with surface ridging building south behind the cold front (now south of our forecast area in SD/central MN). The larger scale pattern becomes progressive and quasi-zonal with broad troughing developing in Canada, which results in a series of mid level shortwave ridges and troughs passing through the Northern Plains next week. This pattern will tend to support temperatures varying from the 60s to 70s each day as ridging/troughing passes which is within a standard deviation of climate averages (basically seasonal). There will also be increasing chances for light showers (and enough instability for low non-severe thunderstorm potential). The best resolve mid level wave arrives late Monday night through Tuesday, with likely rain showers and closer a 50-70% chance for at least 0.1" rainfall during that period. Excessive rainfall and severe thunderstorms are not expected based on analogues and ensemble based machine learning during the next 7 days. Regarding smoke timing/impacts: Northwest flow continues to bring reinforcing periods of smoke into the region today, with the highest smoke concentrations closer to the frontal zone and wrapping up into the mid level low to our northwest. This smoke is originating from fires located over norther Alberta, Saskatchewan and Manitoba. Satellite (matching up with latest HRRR/RAP smoke models) indicates a period of improvement possibly arriving this evening, though additional pockets of smoke may continue to rotate into the region through Monday morning becoming trapped below the nocturnal inversion. The shift in flow as the next mid level shortwave should result in surface smoke impacts eventually ending Monday, though the back side of that system could bring smoke right back as flow shifts back out of Canada later Tuesday night. Regarding frost impacts tonight: As smoke allows for long wave radiation to escape, it will not factor into low temperatures tonight the way clouds would. As actual cloud cover should remain mostly clear and winds should decrease, we should see good radiational conditions. Surface Tds are forecast to be in the 32-35F range during peak radiational cooling across our north-northeast, so the floor for our lows will be within range for frost conditions. NBM probs are low regarding the potential for widespread lows 35 or lower, however the pattern should support our traditional colder/outlying locations dropping to the 33-36F range supporting frost formation on surfaces. Based on experience of seeing those locations drop lower than guidance in similar patterns, confidence was high enough to issue a Frost Advisory (3am-8am) along the US/Canada border and near the Hwy 2 corridor in MN (where traditional colder spots are most likely to have frost impacts). In similar patterns the immediate Red River Valley (and urban areas) tend to remain higher, but there is still potential (less than 30% chance) for frost in outlying parts of counties just south of the current advisory where Tds may be near 36F. && .AVIATION /00Z TAFS THROUGH 00Z TUESDAY/... Issued at 703 PM CDT Sun May 12 2024 Issue will be vsby in smoke this evening into the overnight. Idea will be for less smoke into the overnight/early Monday. Until then 4-6SM in smoke for many areas. North winds to diminsh quickly this evening and turn more north-northeast overnight into Monday morning at 5 to 10 kts. && .FGF WATCHES/WARNINGS/ADVISORIES... ND...Frost Advisory from 3 AM to 8 AM CDT Monday for NDZ006>008-016- 054. MN...Frost Advisory from 3 AM to 8 AM CDT Monday for MNZ004>009- 013>017. && $$ UPDATE...Riddle DISCUSSION...DJR AVIATION...Riddle
Area Forecast Discussion
National Weather Service Grand Rapids MI
944 PM EDT Sun May 12 2024 .KEY MESSAGES... - Small Window for Aurora This Evening Before Clouds Move In - Shower and Thunderstorm Chances Tonight through Monday Night - Rain Ends Tuesday - Additional Chances of Rain Late Week| && .UPDATE... Issued at 935 PM EDT Sun May 12 2024 As expected, a few thunderstorms have moved out of Wisconsin and across Lake Michigan. The first of these storms has just move onshore near Ludington. Additional showers and embedded storms are expected over the next several hours, generally along and north of the I-96 corridor. Small hail and gusty winds are the main concerns with some of the stronger storms this evening. && .DISCUSSION... Issued at 334 PM EDT Sun May 12 2024 - Small Window for Aurora This Evening Before Clouds Move In For those looking to view the Northern Lights tonight we remain in an active period as a X class flare (the highest level, although there are varying degrees of X class flares) came off the sun at midday. kP index values and magnetometers from across the mid latitudes show limited activity as this time. With additional flares inbound though, aurora remains a possibility tonight. The issue is like Friday evening, clouds are pushing in from the northwest after dark. There may be a window from roughly 1000pm to midnight or so where clouds have not yet obscured the sky. That window only becomes relevant though if we increase aurora activity from current relatively low levels. Stay tuned...or look skyward. - Shower and Thunderstorm Chances Tonight through Monday Night The main focus of the next day or two is the chances for showers and thunderstorms tonight, Monday and Monday night. Two main upper shortwaves of note during this time frame, one is passing well to our north across Ontario. The other lifts into the Plains from the Central Rockies tonight. A cold front associated with the Ontario wave will push into the area from the north tonight. As the Ontario low pulls away to the east the boundary stalls over the area on Monday as the plains system approaches. It is not until Monday night into Tuesday before the boundary sags south of the area. Assessing thunderstorm chances each period beginning with tonight...showers and storms will rapidly increase this evening over Wisconsin and Northern Lake Michigan where a Slight Risk has been issued by the Storm Prediction Center (SPC). Storms will try to advect in across Central Lower Michigan this evening after 800pm and continue roughly through about 300am. The 3km NAM tries to push MUCAPE values into the area that are over 1000 j/kg this evening. That may be a bit high. HRRR MUCAPE is much lower, on the order of a few hundred joules. We are in a marginal risk from the SPC, but feel severe weather is a low risk in our forecast area tonight. Storms will be very much diurnally driven and with limited CAPE to work with in the first place it will be tough to produce strong storms. Cannot rule out some small hail if a stronger storm can survive into our area given steep mid level lapse rates. Updraft helicity swaths tell the tale tonight with best chances at severe in Wisconsin and weakening storms as they move our direction. The HREF has a good flare up of convective activity in our area Monday afternoon, especially near and south of Interstate 96. We are likely looking at around 1,000 j/kg of MUCAPE tomorrow with potentially a bit more if we can develop breaks in the cloud cover located near the stalled front. Deep layer shear is only 20-30 knots where storms will be located so organization and severe threat remains on the low side. The front remains in place for Monday night slowly sagging south with time. Once we get beyond the evening hours, where some embedded thunderstorms remain, we transition into more of a synoptic scale rain. The Plains upper low and its surface reflection will be moving into the Ohio Valley Monday night. Regarding rainfall...the HREF probability matched mean is showing all areas seeing 0.25 to 0.75. Pockets of 1.00 to 1.50 inches will be possible in heavier swaths. We are not expecting any significant hydro concerns with this rainfall. - Rain Ends Tuesday Rain chances will end from north to south as the day progresses on Tuesday. This will be driven by a mid-level trough driving the frontal boundary responsible for our precipitation south of the state, with northerly flow behind it. This northerly flow keeps West Michigan in the 60s for highs Tuesday. Surface ridging and a return to southerly flow Wednesday causes highs to return to the 70s. The surface high pressure system paired with upper-level ridging and the exiting of low-level moisture means dry conditions are favored Wednesday and much of Thursday. There may even be decent sunshine given the lack of moisture. - Additional Chances of Rain Late Week Precipitation returns to the forecast late Thursday into Friday as a mid-level wave approaches the state. Confidence in precipitation is higher than 24 hours ago with the Euro/EPS trending towards the GFS/GEFS suggesting troughing arriving by Friday. Ensemble forecasts suggest that a surface low develops in association with this trough but the position and strength of this feature varies. Given the favorable synoptic setup for rain but still spread in where the best rainfall axis will be, feel the NBM broad 40-55 percent PoPs are reasonable. As the amplitude and tilt of the trough and associated location and strength of the surface low refine in the coming days, POPs may increase across the region, particularly where the synoptic setup provides the best setup for rainfall. Signals for additional precipitation exist into the weekend, but considerable spread remains in the mid-level pattern in whether troughing persists into the weekend or a period of ridging takes over. Given the weaker signal for precipitation under the less certain synoptic conditions, will leave the broad slight chance to low end chance (25-35 percent) chances of precipitation for Saturday in the outgoing forecast. && .AVIATION /00Z TAFS THROUGH 00Z TUESDAY/... Issued at 635 PM EDT Sun May 12 2024 VFR conditions are expected at all the terminals tonight. However low level wind shear is forecast late this evening and overnight as west southwest winds at 2 kft agl ramp up to around 40 kts. Scattered showers will develop overnight but conditions should remain VFR. There is not enough potential for isolated thunderstorms to warrant inclusion in any of the terminal forecasts overnight as the better chance for convection will remain well to the north to nw of all the terminals. Scattered showers will redevelop on Monday particularly in the afternoon and evening but conditions at all the terminals should remain VFR. && .MARINE... Issued at 935 PM EDT Sun May 12 2024 No significant changes to forecast compared to previous discussion. Small craft advisory winds continue near Big Sable and Little Sable points this evening, but have started to trend downward. A few thunderstorms are likely this evening, which will bring local changes to expected winds, but overall southwest winds will continue through the morning before shifting around to the northwest at less than 15 knots tomorrow. && .GRR WATCHES/WARNINGS/ADVISORIES... MI...None. MARINE...Small Craft Advisory until 2 AM EDT Monday for LMZ848-849. && $$ UPDATE...AMD DISCUSSION...Duke/Thomas AVIATION...Laurens MARINE...AMD
Area Forecast Discussion
National Weather Service Gray ME
1038 PM EDT Sun May 12 2024 .SYNOPSIS... High pressure gradually builds in and moves offshore through tomorrow. A warm front stalls through central New England on Tuesday, then a slow moving cold front stalls on Wednesday. Low pressure passing south of New England spreads moisture and showers in from late Tuesday into Thursday. Conditions dry out late in the week as New England sees a period between systems, and then likely turns unsettled again by late next weekend. && .NEAR TERM /UNTIL 6 AM MONDAY MORNING/... 0238Z Update... Temperatures continue to fall through the 40s in most areas, albeit at a slower rate than the last several nights. Patchy fog will likely develop later tonight, however its extent will be driven by the amount of cloud cover over the region. Patchy fog will mainly be confined to the northern mountains tonight, somewhat different than the last couple chilly nights over southern areas. Update...Showers continue over the forecast area as of 2130Z per latest radar imagery and surface observations. However, with large surface dew point depressions, some of the echoes are not reaching the ground with plenty of dry air in the mid levels in the latest GYX sounding. In any case, have upped pops across portions of the region, especially in Maine. In western Maine, the latest HRRR has showers expanding through about 00Z before dissipating overnight. Have nudged temperatures downwards for the overnight lows, especially in the Midcoast region where clear skies may allow for temperatures to drop into the 30s. Have introduced patchy frost into the forecast for the early morning and early afternoon hours. Will continue with patchy fog and may need to expand to areas that receive rainfall this evening. Prev Disc... Weak sfc high just tour S, with cool upper level closed low overhead, and very weak forcing in the mid levels, has allowed for some showers to develop, mainly over the mtns early this afternoon, but they will move S during the mid to late afternoon. I think calling them sct or isolated is probably the best way to describe them, and they are all light, producing generally a few hundredths of an inch at best. I do think some of the clouds clear out tonight, but also with mid level forcing, I dont think they clear out completely until late, and Tds are higher than Sat night. So frost is not expected in activated zones. Otherwise lows will drop into the upper 30s in the mtns and mostly the low 40s in the S. && .SHORT TERM /6 AM MONDAY MORNING THROUGH TUESDAY/... On Mon, we manage to squeeze into weak ridging at all levels above the sfc, with a more SW flow at the sfc, as we sit between systems. We should a mainly sunny morning, with more clouds in the afternoon, but still a fair amount of sun. The SW flow is weak, so so coastal zones S of Casco Bay will likely a partial onshore component to the wind, but won;t be that much cooler than inland except near the midcoast. Highs range from around 60 on the mid coast to the low mid 60s inland, and near 70 in S NH. Monday night will see clouds and showers move in during the evening and overnight as a warm front moves in. Mins will be milder and mostly in the 40s. && .LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/... Overview... A warm front brings warm temperatures to parts of the forecast area on Tuesday. A cut off low gradually moves through the Ohio River Valley and south of New England Wednesday and Thursday. A short wave ridge passes through on Saturday, and then another system approaches New England by next Sunday. Details... As a cut off low lingers across western Quebec, the warm front associated with the low makes progress into New Hampshire and parts of western Maine on Tuesday. The front likely stalls somewhere near central Maine without fully clearing the area during the daytime. With this, temps warm into the 70s to near 80 across southern New Hampshire, while parts of the MidCoast and northwestern zones may fail to make it past the upper 50s. This forecast holds with the NBM temps for now, but the gradient is likely to be a little stronger than what it currently being shown. The big question is just how far northeastward the front makes it, with the MidCoast, Central Maine, and all northern areas standing the best chance for the front not to make enough progress for warmth. A cold front sags southward late Tuesday through Wednesday, with showers expanding along this front as a slow moving low tracks south of the area and sends moisture northward. Showers become likely by the afternoon across northern areas on Tuesday, and gradually increase as the front moves southward into coastal areas by Wednesday. The bulk of the moisture stays south of the region, but the slowing front serves to focus shower activity on Wednesday, and possibly into Thursday as well. The front stalls, likely through the middle of the forecast area from east to west. There will be wet periods during this timeframe into Thursday, but coverage looks to gradually lessen as the forcing weakens. Some showers still can`t be ruled out on Friday as the low tracks out to sea. A quick shortwave ridge likely passes through on Saturday, but the next system will be quick on it`s heals with moisture spreading in from the southwest. It`s still unclear whether this ridge will pass through during the day on Saturday, or if it moves through a bit more quickly and allows showers to move in by the afternoon hours. We`ll need to wait a little longer to iron out these details, but that looks like the set up at this point. && .AVIATION /02Z MONDAY THROUGH FRIDAY/... Short Term...VFR will persist through Monday and into Monday evening, but cigs and vis will drop in ?SHRA overnight, at least to MVFR, and maybe some periods of IFR. Long Term...VFR conditions are expected across southern and western terminals on Tuesday, but some MVFR conditions are likely across coastal terminals during the day, especially at RKD where IFR conditions are possible in marine fog. Ceilings lower at all terminals with showers Tuesday night, with MVFR conditions likely and periods of IFR possible. These conditions continue on Wednesday, and then gradually improve into the day on Thursday. VFR likely doesn`t return fully until Friday and lasts into Saturday. Restrictions likely return again with showers Saturday night and Sunday. && .MARINE... Short Term...Winds/seas stay below SCA criteria into Monday, but could approach weak SCA winds by Mon evening. Long Term...A cold front slowly approaches the waters on Tuesday, and stalls near the coast by Wednesday. A slow moving low pressure system passes south of the waters Wednesday and Thursday. These two features bring freshening southerly flow, becoming easterly by Wednesday and Thursday, with SCA conditions possible during this time frame. This system slowly moves eastward on Friday, with waves likely lingering near 5ft on Friday. && .GYX WATCHES/WARNINGS/ADVISORIES... ME...None. NH...None. MARINE...None. && $$ NEAR/SHORT TERM...Cannon LONG TERM...Clair
Area Forecast Discussion...Updated
National Weather Service Lincoln IL
754 PM CDT Sun May 12 2024 .KEY MESSAGES... - In the Monday to Tuesday timeframe, there is a 40-60% chance for more than an inch of rainfall. This rain will contribute to area rivers and streams already running high, increasing the risk for localized inundation near riverbanks. This could perhaps also further delay planting and inhibit germination of agricultural seedlings. - Another system will bring rain to the area late Thursday into Friday, though at this time rainfall totals from that system are forecast to be lower than those with the first one. Chances for more than an inch are only around 10-20%. && .UPDATE... Issued at 754 PM CDT Sun May 12 2024 Fairly quiet as we approach sunset, with some mid and high clouds on the fringes of the forecast area. A more substantial increase in cloud cover is expected after midnight, ahead of the storm system currently over the central Plains. Our evening sounding is pretty dry below 10,000 feet, so any precipitation before sunrise should be rather sparse. More of a substantial increase in rain chances is expected after mid morning. Geelhart && .DISCUSSION... Issued at 133 PM CDT Sun May 12 2024 After yet another dry and pleasant spring day in central Illinois, precipitation chances will increase tomorrow with the arrival of a low pressure system from the west. Visible satellite at 130pm shows the cirrus shield associated with that system drifting eastward across Missouri, with a few gusty thunderstorms to our northwest across Iowa where mesoanalysis suggests over 1500 J/kg SBCAPE has materialized despite a rather dry and deep mixed layer. Deep mixing this afternoon across our neck of the woods has kept us even drier with dewpoints in the 40s, but low level moisture will increase overnight into tomorrow with 80-100% of the HREF ensemble bringing PWATs to over 1.3" (the 90th percentile from SPC`s sounding climatology) by tomorrow afternoon. This, together with tall, "skinny" CAPE profiles conducive to warm cloud processes, will increase potential for efficient rain producing showers and thunderstorms tomorrow afternoon/night, particularly north of I-70 where MUCAPE values (700-1200 J/kg, per the HRRR) are highest and the HREF`s LPMM is well over an inch in spots. The same ensemble shows spread in rain totals through Tuesday morning will be considerable given the convective nature of this precip, though; the ensemble max, a reasonable high-end amount which one or two locations could see if there`s any training of the heavier cells, is upwards of 3 inches in a few spots, while the 10th percentile (which should be representative of the many locations which get missed by the heavier showers) is only several hundredths. While the risk for widespread hydrological issues is negligible (less than 2%), many rivers and streams across the region are already running on the high side, so localized inundation near riverbanks could occur with the more flashy rivers (in addition to the ongoing flooding near Havana and Beardstown along the Illinois River). This rain could also delay planting even further for farmers, and could inhibit germination of already-sown seedlings. On the bright side, given weak shear (15-25 kt, per HREF mean) and weak instability (with low NCAPE values indicating slow updraft parcel accelerations), severe weather is not a concern at this time. Once we`re rid of this pesky system Wednesday morning, ridging will attempt to build back in but will be rushed out by another trough on its heels, southwest flow ushering in moisture and rain chances once again by late Thursday as an ill-defined surface low passes to our north. This system will be a bit more progressive than the Monday- Tuesday night one, so initial thinking is rainfall won`t be overly troublesome. However, a large component of shear in the cloud bearing layer will be parallel to the southeastward-moving cold front favoring some training of showers and storms, and EPS mean brings PWATs back up to 1.2 to 1.3 inches, so some locations could certainly see an inch or more of precip once again (NBM probabilities are around 10-20%) to once more delay seedling germination and raise river levels. Cluster analysis suggests there`s not a whole lot of model spread in the upper pattern this upcoming weekend and beyond, with middle of the road guidance suggesting 500mb flow turns rather zonal. This may be washing out potential shortwaves due to model timing/amplification differences, but there`s certainly not a strong signal for a large and dynamic system at the end of the forecast period. Bumgardner && .AVIATION... (For the 00z TAFs through 00z Monday Evening) Issued at 618 PM CDT Sun May 12 2024 Main forecast concerns will be after 12Z, as a storm system begins to spread showers and scattered thunderstorms northeastward into central Illinois. HRRR guidance suggests a few hour window for thunderstorms with the leading edge of the showers, and a PROB30 group will be included for this potential. Later convection may produce thunder as well, but there is a lower probability at this point for inclusion. Ceilings will steadily deteriorate Monday morning, and chances of widespread MVFR heights increase to around 50-60% by mid to late afternoon. Geelhart && .ILX WATCHES/WARNINGS/ADVISORIES... None. && $$
Area Forecast Discussion
National Weather Service North Platte NE
642 PM CDT Sun May 12 2024 .KEY MESSAGES... - Three storm systems will cross the cntl/nrn Plains during the next 7 days- One tonight and Monday, then Tuesday night and Wednesday followed a third Thursday night and Friday. - The risk of anything more than an isolated strong or severe thunderstorm during the next 7 days is low at this time. && .SHORT TERM /THROUGH MONDAY NIGHT/... Issued at 318 PM CDT Sun May 12 2024 The area of deformation and rain operating across scntl and swrn Nebraska this afternoon should shift south and east as the upper low across Colo moves east into KS tonight. The rain forecast uses the short term model blend plus the NAM and HREF. Rain processes have been top-down and this suggests lapse rates have moistened up. Nonetheless, isolated thunderstorms are underway across the Sandhills and south of Interstate 80. The forecast continues isolated thunderstorm chances overnight. The thunderstorms are mainly for the early evening hours as suggested by the HRRR echo tops product. A warm sector has opened up across the Sandhills, ncntl and swrn Nebraska this afternoon supporting instability. Sfc obs show this underway and an approaching cold front from the north supports thunderstorms this evening. All of this rain should be south and east of the area by mid morning Monday. Drier air will move in aloft for partly cloudy skies. The temperature forecast Monday uses the short term model blend plus the NBM 50th. Wrn/ncntl Nebraska will be under a WAA zone Monday afternoon and this will support highs in the mid 70s. && .LONG TERM /TUESDAY THROUGH SUNDAY/... Issued at 318 PM CDT Sun May 12 2024 The next item of interest is the prospect of showers and thunderstorms Tuesday afternoon and Tuesday night. The models show an upper level disturbance off the coast of British Columbia moving east through the nrn Plains during this time. Only the NAM and GEMreg models show storms developing across ncntl Nebraska Tuesday afternoon. The concern is winds aloft at h500mb will be strong, 30-45kt, K-indices well in the 30s to near 40 and perhaps 1500 J/KG of MLCAPE will be in place. The models are in good agreement showing this disturbance off of BC moving through the Dakotas during the afternoon for upper level support. All of this could support an isolated strong or severe thunderstorm chance across ncntl Nebraska. Additional shower and thunderstorm chance is in place for a cold front moving through Tuesday night with rain chances lasting into Wednesday. A storm system south of the Aleutians will track south and east, perhaps crossing the nrn Plains Thursday or Friday, according to the ECM. The GFS tracks the system through the central provinces of Canada. The forecast is for isolated thunderstorms with this system but it`s worth noting the ECM with it`s srn storm track suggests significant post-frontal convection Friday night. && .AVIATION /00Z TAFS THROUGH 00Z TUESDAY/... Issued at 641 PM CDT Sun May 12 2024 Isolated showers and thunderstorms will continue to impact the Sandhills and into southwest Nebraska through the evening. Small hail, wind gusts up to 40 mph and briefly heavy rainfall will cause some minor aviation concerns as visibility restrictions are also possible. Showers will diminish during the wee hours of Monday morning with VFR conditions returning to the region through the afternoon. && .LBF WATCHES/WARNINGS/ADVISORIES... None. && $$ SHORT TERM...CDC LONG TERM...CDC AVIATION...Kulik
Area Forecast Discussion
National Weather Service Memphis TN
910 PM CDT Sun May 12 2024 ...New UPDATE... .UPDATE... Issued at 907 PM CDT Sun May 12 2024 GOES-18 Water Vapor satellite this evening shows an upper-level low over the Central Plains with a shortwave embedded within southwest flow aloft moving trough the Lower Mississippi Valley. This is resulting in rain showers as close as southern Arkansas and west central Mississippi per regional METAR observations. Temperatures as of 8 PM CDT range from the upper 60s to lower 70s. Short-term models including CAMs indicate the best potential for scattered rain showers for the remainder of the night will be mainly over portions of east Arkansas (south of I-40) and over north Mississippi. Overall potential for thunderstorms remains very low due to limited instability. Tonight`s forecast will be updated to account for precipitation trends. Otherwise, the remainder of the forecast is in good shape. CJC && .SYNOPSIS... Issued at 252 PM CDT Sun May 12 2024 Most days over the next week feature seasonably warm temperatures and at least a 30% chance of showers and thunderstorms, especially Monday evening. Some storms in the Mississippi Delta may become strong to severe with the potential for gusty winds and small hail late Monday into Tuesday. Another system Thursday afternoon into Friday will bring more widespread showers, thunderstorms, and the potential for 1-2 inches of rain that could cause localized flooding issues. && .DISCUSSION... (This evening through next Saturday) Issued at 252 PM CDT Sun May 12 2024 An ongoing wave of convection is currently approaching from the ArkLaTex region. The rest of the afternoon should remain mostly dry, though PoPs and cloud cover are both on the rise in anticipation of these storms. NBM PoP guidance came in quite bullish for this evening, originally suggesting over 80% chance of rain overnight. This is likely heavily weighted by the HRRR which has a much wetter solution, but the majority of the other CAMs are significantly drier and have continued to trend drier with each subsequent run. These PoPs were undercut for the overnight period, especially in north Mississippi. Coverage of showers and thunderstorms tonight looks to start off sporadic and eventually transition to more widespread rain by early tomorrow morning. After the overnight shortwave clears the area tomorrow, an upper low will churn as it makes its way up through northern Missouri. Most areas will see at least a slight chance (>15%) of rain tomorrow as a few scattered showers rotate around the upper low. The main story in the short term is the swath of showers and thunderstorms that is expected to surge up through the Mississippi Delta late tomorrow evening. After sunset, CAMs depict a loosely organized system of showers and thunderstorms almost resembling an MCS trekking across the ArkLaMiss region in the open warm sector of the aforementioned low pressure system. The period of maximum coverage and intensity of these storms looks to be in the 10PM-4AM time frame overnight Monday into Tuesday. Hi-res model soundings depict a marginal severe threat in which the general setup is high shear / low CAPE. However, the environment also looks largely capped in that same time period. This will contribute to a low confidence, conditional threat of severe thunderstorms featuring a main threat of damaging winds and perhaps some large hail through early Tuesday morning. Medium range model guidance suggests the parent upper low will continue to churn across the Tennessee River Valley on a gradually eastward trajectory on Tuesday. As a result, Tuesday will feature PoPs in the 50-70% range all day as showers continue to wrap around the back side of the system. Temperatures look to remain seasonable in the upper 70s through midweek. We should catch a very brief break in between systems on Wednesday, so enjoy the dry and warm conditions while they last. Another surface low looks to eject from the central Plains on Thursday, deepening and occluding as it approaches the Mid-South. Showers and thunderstorms will pick up throughout the day Thursday as its warm front sweeps north across the region. More widespread and periodically heavy rain looks to arrive on Friday as the parent low crosses over southern Missouri. The area with the most favorable setup (PWATs nearing 2 inches, saturated column, training storms) for heavy rainfall is north Mississippi. QPF for Friday alone is also approaching 2 inches for our southern CWA. This will need to be monitored for flooding potential based on the axis of heaviest rain. Next weekend looks quite warm; NBM probabilistic guidance even has a few pixels of low probabilities for temperatures above 90 degrees next Sunday. CAD && .AVIATION... (00Z TAFS) Issued at 631 PM CDT Sun May 12 2024 Main TSRA track will remain to our south tonight, though TUP may see a few lightning strikes near the far northern periphery of an overnight convective system. Otherwise, scattered -SHRA will develop toward morning, with gradually lowering CIGs. Midsouth TAF sites will remain in the warm sector Monday, making CIG forecasts somewhat challenging. Guidance (NBM, LAMP) appear too pessimistic in maintaining IFR through the afternoon. Briefly considered adding a chance of TSRA Monday evening at MEM, but given lack of guidance consensus, have held off. Convective coverage and the magnitude of above-surface instability remain in question. Will reevaluate for the 06Z TAFs. PWB && .MEG WATCHES/WARNINGS/ADVISORIES... AR...None. MO...None. MS...None. TN...None. && $$ PUBLIC FORECAST...CAD AVIATION...PWB
Area Forecast Discussion...CORRECTED
National Weather Service Marquette MI
808 PM EDT Sun May 12 2024 .KEY MESSAGES... - Scattered thunderstorms into early evening, especially south central. There is a slight risk (15%) of large hail and/or damaging winds south central. - Dry weather returns by Monday, continuing through Wednesday afternoon. Next chance for rain will be Wednesday night into Thursday. && .SHORT TERM /THROUGH TONIGHT/... Issued at 429 PM EDT Sun May 12 2024 Water vapor imagery and RAP analysis show a well-defined mid-level low spinning over northern Ontario. Cold front associated with feature has pushed into western Upper MI, aided by lake breeze component. Ahead of front, shra/tsra have developed as expected. Latest RAP analysis show MLCAPE of 100 to near 500j/kg across the w half of Upper MI, maximized in eastern Gogebic County and eastern Marquette County. Deep layer shear is running 30-35kt to support storm organization. However, so far, nothing particularly strong has developed. Deep mixing and lack of full green up for evapotranspiration have worked to hold dwpts down today, and thus instability has been held in check despite temps rising well into the 70s and lwr 80s ahead of front and to the e of Lake MI marine modified air across roughly the e half of Upper MI. Over the next several hrs, the shra/tsra will continue to push e and se thru central and eastern Upper MI. There is still the potential of isold svr storms to develop across central Upper MI, s central in particular, but that will depend on whether instability can increase further over the next few hrs. Expect the shra/tsra to exit s central/se fcst area by midnight. Wildfires are off and running again in portions of s central and western Canada. First batch of smoke of the year is following the cold front. Hazy skies will develop after fropa, and based on webcams on Isle Royale, the smell of smoke will be in the air as the evening progresses, at least across the w half of Upper MI. && .LONG TERM /MONDAY THROUGH SATURDAY/... Issued at 243 PM EDT Sun May 12 2024 A couple beautiful weather days are forecast to start off the coming work week. Behind tonight`s cold front, drier and cooler air will filter into the region as high pressure at the surface and mid-level ridging gradually build across the region. Before then though, a weak mid-level shortwave moving through from the west and another system moving eastward well south of us may support some cloud cover late Monday into Tuesday. Otherwise, ridge axis moving through on Tuesday should support mostly clear skies. Under mostly northerly flow, lakeshore areas both days should top out near 50F with low-mid 60s across central and southern portions of the forecast area. Overnight lows both days look to be in the 30s for most of the area. Best places for bottoming out in the 40s will be the southern portions of Menominee County. Upstream smoke observed on GOES 16 imagery and surface cameras in Minnesota, is expected to filter into the region behind today`s cold front. The HRRR Vertically Integrated Smoke product does suggest some of this may produce a hazy sky Monday. An upstream shortwave will press closer to the region on Wednesday while a surface low moves into western Minnesota, allowing for increasing cloud cover from west to east. By Wednesday night, the low looks to press into western Wisconsin, allowing weak theta-e and moisture advection to eventually spread showers into the region. By Thursday, increasing left exit jet dynamics may support more widespread shower activity, but notable timing differences can be seen among the deterministic suite, suggesting the showers may be confined to the west half until Thursday night/Friday morning. Another wave looks to press into the region Friday night/Saturday. && .AVIATION /00Z TAFS THROUGH 00Z TUESDAY/... Issued at 727 PM EDT Sun May 12 2024 Showers have cleared the terminals this evening with the passage of the cold front. Other than some smoke from Canadian wildfires which could lead to occasional MVFR vsbys tonight at CMX and maybe IWD, expect VFR conditions through the rest of the forecast period. && .MARINE... Issued at 243 PM EDT Sun May 12 2024 Warm sector draped across central Lake Superior this afternoon is producing winds of 25-30 knots is some places. Some of this appears to be a mix of outflow/downdrafts from lingering showers in the east and a stronger low level jet overhead behind the warm front then every model suggested. A cold front is currently stretched southwestward across western Lake Superior. Ahead of this front, some showers and some lightning have been observed mainly north of the Keweenaw, but much of this isn`t likely reaching the surface. As this front pushes east this afternoon/evening, winds should shift to northwest post frontal, but a significant wind increase isn`t expected unless there`s thunderstorms. Thunderstorm development should be confined to the interior portions of Upper Michigan and into Lake Michigan, but if something develops over Baraga/Marquette County this afternoon, its possible this may stretch into Lake Superior east of Marquette near the lakeshores. Stronger storms will be capable of producing erratic winds and some hail. Behind the front, high pressure will settle over the lake, supporting a few days of mostly 20 kts or less over the lake through at least midweek. && .MQT WATCHES/WARNINGS/ADVISORIES... Upper Michigan...None. Lake Superior...None. Lake Michigan...None. && $$ SHORT TERM...Rolfson LONG TERM...JTP AVIATION...Voss MARINE...JTP