Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 10/23/17

Area Forecast Discussion
National Weather Service Caribou ME
1020 PM EDT Sun Oct 22 2017 .SYNOPSIS... High pressure will continue to move east of the region through Monday. Low pressure will approach by mid week with the potential for a widespread significant rain event Wednesday into Thursday. && .NEAR TERM /THROUGH MONDAY/... 1022 PM Update... Brought fog in across the downeast areas overnight and adjusted the temps up a tad as the clouds will keep a lid on things. The latest IR satl imagery showed low clouds moving in from the Gulf of Maine. The latest RAP guidance was doing quite well w/the low clouds and temps. It lined up well w/bringing the low clouds further n into portions of the Central Highlands overnight. Based on this assessment, decided to bring more clouds northward into the Millinocket- Lincoln region as well as into the central and southern Piscataquis region. Less clouds n of the Houlton-Millinocket region. Previous Discussion... Surface high pressure will continue to move east through the Canadian Maritime provinces tonight, while a 500 mb ridge axis crests across the region by morning. Expect mainly clear to partly cloudy skies across the region this evening. As the surface high continues to move east, expect a light southeast return flow to develop. The light southeast flow and increasing boundary layer moisture could lead to some low clouds and patchy fog by morning, especially across the upslope region of of Piscataquis county. Some of this may spread east as far north as southeast Aroostook by daybreak Monday. Otherwise, any low clouds and patchy fog early Monday should give way to mainly sunny skies and milder afternoon temperatures as the high continues to build to the south of the Canadian Maritime provinces. Lows tonight will range from the upper 30s to lower 40s north and low to mid 40s central an down east. Highs on Monday will range from the low to mid 60s across the region. && .SHORT TERM /MONDAY NIGHT THROUGH WEDNESDAY/... Dry Regime is Replaced by Wet Regime... Although steady rn will not arrive into our FA until Tue ngt, with sfc and llvl winds becoming and increasing from the S Mon ngt, oceanic ST, patchy dz and fog will initially overspread the FA by erly Tue morn. Low cldnss...patchy dz and sct shwrs will cont thru Tue as the Srly wind fetch remains in place. heavier steadier rnfl will then move W to E onto the FA Tue ngt and Wed as a deep trop atmos rvr from the trop Atlc and Caribbean Sea moves ovr the FA. Sig rnfl totals for much of the FA will be possible even by Wed eve, so max PoPs will be near 100 percent by Wed aftn. Winds will increase slowly from Tues into Wed, with possible wind adv wind speeds by Wed aftn. Both hi and spcly low temps will be well abv normal durg this ptn of the fcst. && .LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/... How much Rainfall for our Region?... Long range models show only slow E movement of the deep trop atmos rvr crossing our FA Wed ngt and Thu with PWATs in excess of 150 percent, with the potential of additional sig to hvy rnfl. We kept PoPs well into the categorical range during both of the pds. To far out to mention hvy rnfl attm, but we do indicate mdt rnfl beginning Wed and contg into Thu. If the worst case scenario rnfl pans out as we get closer to this event, we will have to entertain a flood watch for part or all of or Rgn. We will cont to monitor the latest model trends in making this decision. Otherwise, the mean consensus of long range models ends the rn Thu ngt as sct shwrs with improvement in the wx for Fri as a s/wv trof and sfc cold front from the Midwest finally kicks out the deep trop moisture E out of the Rgn. Fair and drier conditions should cont Sat and most of Sun before cldnss and shwrs from the next sfc low and associated s/wv alf from the Midwest apchs for Sun ngt and Mon. Temps will cont abv normal thru the pd even behind the cold front Thu ngt and Fri. && .AVIATION /02Z MONDAY THROUGH FRIDAY/... NEAR TERM: VFR conditions with light southeast winds this evening. There is the potential for MVFR or lower conditions toward KBGR/KBHB after 05Z in developing low ceilings. Any low clouds should dissipate after sunrise with VFR and light south winds on Monday. SHORT TO LONG TERM: Oceanic ST will overspread the FA from S to N ovrngt Mon with conditions lowering from VFR to IFR with patchy fog and dz. Some recovery to MVFR clgs are possible Tue aftn, spcly Nrn TAF sites before conditions lower to IFR Tue ngt for all sites and cont thru Thu ngt mainly in rn. Conditions should improve to MVFR on Fri with sct shwrs. && .MARINE... NEAR TERM: Winds/seas will remain below small craft advisory levels through Monday. SHORT TO LONG TERM: Initially no hdlns Mon ngt, but winds and seas increase to SCA by late Tue with a srly wind fetch and cont so thru into Fri with the highest seas Wed into Thu as wind gusts apch gale force. Winds and seas then slowly diminish Thu ngt thru Fri as winds become more wrly component ovr tm. Used a blend of WW3/NWPS for fcst wv hts with wv pds increasing from 5 to 7 sec Mon ngt to arnd 10 sec as the character of the wvs become more storm like late Wed into Thu morn when open water wv hts possibly apch 15 ft. Marine ST cld cvr and fog will start becoming an issue late Mon ngt and Tue and will likely reduce vsbys to a half mile or less Tue ngt thru Thu despite Srly strong wind speeds due to warm...moist air from the trop Atlc movg Nwrd across cold Gulf of ME waters. && .CAR WATCHES/WARNINGS/ADVISORIES... ME...None. MARINE...None. && $$ Near Term...Hewitt
Area Forecast Discussion
National Weather Service Glasgow MT
900 PM MDT Sun Oct 22 2017 .SHORT TERM...for northeast Montana...tonight through Mon... 900PM UPDATE: A second wave on convection on radar tied with a second frontal passage is currently wandering through northwest zones and will drop through the central zones before showers dissipate around 10 to midnight. NAMNest still seems to have the best handle on current conditions followed by the RAP for precipitation. However these models fail throughly at sustained wind speed with the convection being roughly 10 to 15 kts underperforming ins spots. Surface observation and RTMA field are very much play a wack-a- mole game with common sustained winds speeds of 25 kts at most recording stations interspersed with almost random jumps to near 40+ kts when convection drops by. GAH 500PM UPDATE: Changes to the forecast revolved around including the increased convection over the next 2 hours and then properly tapering it down out towards midnight. NAM model guidance seems to have the best handle on local convection where GFS and RAP appear to be placing convection in the wrong places. Therefore, went heavily on a NAM blend with tweaks towards observed data. Strong to high winds appeared to be on track. GAH PREVIOUS SHORT TERM DISCUSSION: Fairly good mixing as the jet core associated with an Alberta clipper system moves into the area. Most models are still showing winds at 50 kts at H850 and approaching 70 kts at H700. It seems that the strongest jet streaks are currently over southern Petroleum and Garfield counties, as well as over central to southern Phillips county. Winds today have already reached the High Wind criteria over parts of Phillips county. With continued increasing winds across eastern Montana along with steep lapse rates and strong wind gusts anticipated from the showers that continue to move across northeast Montana, decided to leave the High Wind Warning that is in effect until 8 PM this evening as is. Winds will still be strong overnight, especially over our southern zones where the jet core will likely be, but concerns of winds approaching 50 kts should be over by around 8 PM tonight. With the jet still moving generally eastward across the area Monday, winds will again be strong with sustained winds of 15 to 25 kts, especially south and along the North Dakota border. Some of the gusts will approach 40 kts or higher, as the steep lapse rates coincident with the jet core will still be present. However, no precipitation is expected during this period. Hickford .LONG TERM...Mon night through Sun... AFTERNOON UPDATE: A ridge of high pressure will keep the area warmer and drier Tuesday and much of Wednesday. Wednesday night and into Thursday, there is continued model agreement with the presence of a low pressure system deepening as it dives through eastern Montana from the Canadian Rockies. Any precipitation looks to begin Wednesday evening as rain, transitioning to snow some time after midnight, but I say that very cautiously as guidance could change significantly by then. Regardless, much colder air will move into northeast Montana behind this system, with highs on Thursday 20 to 30 degrees cooler than on Wednesday. Thursday night will also be very cold, with overnight lows anticipated to be in the teens and 20s. Beyond that, the Pacific ridge pushes east into the weekend, but model guidance is not consistent regarding timing or strength. Hickford PREVIOUS LONG TERM DISCUSSION: Tuesday into Wednesday, a warming and drying trend returns to the area thanks to high pressure building over the northern Rockies. Models in slightly better agreement with the next clipper diving through the Canadian prairies. Strong winds, some rain or snow showers and much colder air expected with this system Wednesday night into Thursday. Very cold temperatures expected for Thursday night with Canadian high clearing skies and weakening winds. Pacific ridge pushes east into the weekend for rebounding temperatures and dry weather. Ebert && .AVIATION... MICROBURST POTENTIAL: Convective showers with strong winds aloft are also bringing about the chances for microbursts between now - 04Z. LLWS: As cold air slips in under the strong winds, surface winds will lightening and lend more toward a threat for LLWS through the evening. FLIGHT CAT: VFR SYNOPSIS: An Alberta clipper moving through the area will bring very strong west winds through the early evening. As the cold air enters the area and winds reduce at the surface and a very strong jet core aloft will lend toward wind shear concerns. SFC WIND: Out of the West and slowly calming to 20 kts by the late evening, then increasing to 20 to 30 kts Monday afternoon. GAH && .GLASGOW WATCHES/WARNINGS/ADVISORIES... High Wind Warning until 10 PM MDT this evening for Central and Southeast Phillips...Central and Southern Valley...Dawson... Garfield...McCone...Northern Phillips...Petroleum...Prairie... Richland...Southwest Phillips...Wibaux. Lake Wind Advisory until 6 PM MDT Monday For Fort Peck Lake for Central and Southeast Phillips...Central and Southern Valley... Garfield...McCone...Petroleum. && $$
Area Forecast Discussion...UPDATED
National Weather Service Huntsville AL
741 PM CDT Sun Oct 22 2017 .NEAR TERM...(Tonight) Issued at 740 PM CDT Sun Oct 22 2017 Regional radar and satellite show two main areas of precipitation. One being the MCS producing very heavy rainfall across south AL into the western panhandle of FL. The MCS was feeding off very moist inflow air (PWs around 2 inches and dew points 70+) and was slowly shifting eastward. The northern stratiform rainfall was spreading northward into central AL, but was encountering drier air limiting its progression. Other separate bands of showers were advancing northeast through eastern MS and western TN along and ahead of a cold front. Thus far, we have not noticed any lightning activity. RAOBS indicate very little CAPE to work with. However, water vapor imagery shows the strong trough from MO through AR and LA which will negatively tilt and eject east-northeast through the region late tonight into early Monday as an upper/mid level jet and dry slot accelerate the trof passage. The resulting divergence aloft will enhance UVVs and should maintain and possibly expand the area of showers while entering the I-65 corridor and points east. Recent runs of HRRR reflectivity show one main band of showers reaching I-65 from 07-08z, and exiting northeast AL/Franklin Co TN by 13-14Z. Thus, prolonged heavy precipitation is not anticipated for our western counties. Have lowered our QPF thru 06z, with resulting totals of around 1/2-3/4 inch west of I-65, and 1-1.5 inches further east. There is a good amount of veering of the wind profile which will also accelerate later tonight in our eastern counties in advance of the system. The 1km SRH value at 00Z from the BMX RAOB was 230 m2/s2. The limited convective instability should prohibit any sustained rotating updrafts in even shallow convection. .SHORT TERM...(Monday through Tuesday night) Issued at 222 PM CDT Sun Oct 22 2017 The axis of the upper trough will move into northwest Alabama Monday morning, with the surface cold front over northeast Alabama. Lingering showers will begin to taper off by the late morning hours, with much of the precip expected to be out of the area by the afternoon. There is still some uncertainty with the timing of the front. Additionally, wrap around moisture associated with the upper low will move through the area during the day, so kept in isolated to scattered light rain into the afternoon hours. Lingering cloud cover, along with the lowering heights will keep temperatures on Monday in the mid to upper 60s. Dry air will quickly filter into the area Monday night, with dewpoints dropping into the low to mid 40s. Skies will also clear through the overnight hours and combine with light winds to create good radiational cooling conditions. Overnight lows will drop into the mid to upper 40s, which is roughly 10 to 15 degrees cooler than those expected tonight. A reinforcing front is also expected to move through late Monday night/early Tuesday morning as a second upper trough digs southward and through the area. This will send even cooler and drier air into the area, with strong cold air advection during the day Tuesday keeping high temps in the upper 50s to lower 60s despite plenty of sunshine. Another good radiational cooling night on Tuesday will send temperatures down into the upper 30s. Will have to watch for the potential frost development across portions of the area early Wednesday morning. .LONG TERM...(Wednesday through Saturday) Issued at 222 PM CDT Sun Oct 22 2017 A rather complicated and potentially messy pattern to persist into the extended period. By mid week, the medium range guidance is in fair agreement with a rather deep trough positioned across the eastern CONUS with generally northerly flow across the Tennessee Valley. This will pull down rather cool and dry air though it`s often hard to time/predict cloud cover in that type of flow regime. Either way, expect temperatures will be quite a bit below normal on Wednesday with some recovery expected on Thursday ahead of the next upstream system. The pattern gets quite interesting toward the end of the week as you have a rather potent northern stream system diving southeast across the Midwest and toward the Ohio Valley. This will aid in cyclogenesis across the Great Lakes and help push a cold front toward the area in the Friday/Saturday time frame. The medium range guidance is not exactly on the same page with the GFS pushing the front through on Friday night with the Euro slower with more energy noted in the southern stream. To add to the confusion, the Canadian has similar timing to the GFS but essentially a dry front with the primary energy off the Florida coast. For now have trended with essentially a blend of the GFS/Euro for timing and discounted the dry Canadian solution. Also trended temps down a notch for Saturday/Sunday given the expected cloud cover with the upper trough passage. Have also kept thunder out of the forecast given the rather limited gulf return and overall cool statically stable lower troposphere ahead of the approaching front. && .AVIATION...(For the 00Z TAFS through 00Z Monday evening) Issued at 610 PM CDT Sun Oct 22 2017 Bands of light shower activity will occur this evening before a more solid band arrives after 04Z at KMSL and 06Z at KHSV. This is when VFR ceilings of 040-080 will drop to around 015agl (MVFR). Winds will shift from southeast to southwest or west after this rain band and cold front move through. Low clouds around 015agl will likely last into much of Tuesday, but with the probability of showers dropping through the day. && .HUN WATCHES/WARNINGS/ADVISORIES... AL...NONE. TN...NONE. && $$ NEAR TERM...17 SHORT TERM...73 LONG TERM...15 AVIATION...17 For more information please visit our website at
Area Forecast Discussion
National Weather Service Newport/Morehead City NC
1027 PM EDT Sun Oct 22 2017 .SYNOPSIS... High pressure will extend into the region from the northeast through Monday. A strong cold front will approach from the west Monday night and move across the area through Tuesday night. High pressure will build over the area Wednesday through Friday. Another cold front will approach next weekend. && .NEAR TERM /UNTIL 6 AM MONDAY MORNING/... As of 1025 PM Sunday...The latest sfc analysis continues to show sfc high pressure dominating the area this evening with scattered clouds moving along the coast, meanwhile high clouds are streaming through. Winds are now light to calm across ENC and will continue through the overnight. Expect some patchy fog to develop over the NW sections of Eastern NC. Made minor tweaks to the overnight lows with this update based on warmer trends, but expect lows in the upper 50s to mid 60s along the coast. && .SHORT TERM /6 AM MONDAY MORNING THROUGH 6 PM MONDAY/... As of 330 PM Sunday...SE-S flow and approaching strong short wave trough will produce increasing shower threat during the day with enough instability to warrant tstm mention late afternoon. Will have slight chance of showers along and east of Hwy 17 during the morning, then mainly chance POPs of showers/isolated tstms all zones in afternoon. Better chance of showers/storms and marginal threat of severe will be Monday night with better dynamics. Low level thicknesses increase to around 1390 meters but increased cloud cover expected to keep max temps near 80 inland to mid-upper 70s Outer Banks. && .LONG TERM /MONDAY NIGHT THROUGH SUNDAY/... As of 345 PM Sunday...A strong cold front will bring a good threat of showers with a few thunderstorms Monday night through Tuesday followed by another shot of seasonably cool air for mid to late next week. Monday night through Tuesday night...A deep upper trough and strong cold front will move through the region this period bringing periods of heavy rain and a marginal threat of severe storms. Vorticity advection increases as models depict dampening shortwave trough pivoting through the TN/Ohio valleys, and will spur sfc cyclogenesis in the southern Appalachians acting to increase dynamics and strengthening southerly flow on 40-50 kt LLJ. Dewpoints will be quite high in the 60s and would be sufficient for marginal instability, and the combination of significant wind shear and marginal instability will spell a high shear/low CAPE scenario for strong or severe storms. Any heavy showers or isolated thunderstorms could produce strong gusty winds due to momentum transfer to the sfc from strong winds aloft. There remains some uncertainty with the timing of the heavier precip/stronger storms as 22/12z models are not in best agreement but they have continued to trend a little faster with onset Monday night. The GFS is on the faster side of guidance bringing in heavier precip Monday evening while the NAM is on the slower side delaying onset until early Tuesday morning. The ECMWF and CMC are between these solutions. Due to the amplifying nature of the upper trough digging into the eastern CONUS the front will be slow to move across the region and expect descent rain chances to continue through the day Tuesday, especially east of highway 17, and continuing along the coast Tuesday night into Wednesday morning. Temps will be mild Monday night and Tuesday with strong southerly flow ahead of the front. Lows Monday night expected around 65-70 with highs Tuesday in the mid to perhaps upper 70s. Much cooler Tuesday night as the front pushes offshore and expect lows in the lower 50s inland to around 60 coast. Wednesday through Friday....Continued drying and cooling expected Wednesday as the front will have pushed well off the coast by early morning. Have retained the small PoPs for Wednesday though confined them to the extreme eastern areas mainly the OBX as the deep upper low moves through E NC with lingering deep layer moisture across the OBX. Dry WNW flow on Thursday as upper low finally exits off the Mid Atlantic coast and high pressure builds into the region. Temps will be much cooler for the mid week period with Wednesday and Thursday both in the mid 60s to near 70 for highs. High pressure slides offshore Friday with return flow bringing gradually warming temps with highs around 70s. Low temps fall back into the 40s inland and low/mid 50s beaches for Thursday/Friday mornings. Saturday and Sunday...The high moves offshore next weekend with another highly amplified upper trough and surface cold front approaching from the west. Models remain in poor agreement with the timing and details with the system but there will likely be another good shot of precip and perhaps a period of strong storms sometime next weekend as there will be increasing jet dynamics with a moisture feed from the tropics into the region. Temps will likely be near to a little above normal. && .AVIATION /03Z MONDAY THROUGH FRIDAY/... Short Term /through 18Z Monday/... As of 730 PM Sunday...High confidence of VFR conditions will dominate most of the TAF period. An increase of high clouds will stream through the area as low clouds increase along the coast. Models are showing a mix signal with fog developing across ENC. Guidance continues and now the RAP forecast sounding indicates the best potential for fog development will be over NW sections and therefore forecasted a TEMPO period of IFR at KPGV and KISO 08Z-12Z. Conditions will improve in the the morning as winds increase from SE around 10 knots gusting up to 20 knot by the afternoon. Showers/isolated thunderstorms chances increase in the afternoon ahead of the approaching cold front. Long Term /Monday night through Friday/... As of 4 PM Sunday...Periods of MVFR/IFR ceilings and vsbys are likely with fairly widespread showers and perhaps a few thunderstorms Monday night through the day Tuesday. The precipitation should move east of the TAF sites by Tuesday evening with much drier air moving in behind a strong cold front. VFR conditions should prevail Wednesday through Friday, although some decent radiational cooling conditions could lead to some fog, especially around KPGV and KEWN both Wednesday and Thursday mornings. && .MARINE... Short Term /through Monday/... As of 1025 PM Sunday...Current marine forecast in great shape. The latest buoy observations are showing mostly easterly winds 5-10 knots north of Diamond Shoals and SE winds south. Seas 2 to 3 ft. Pre Dis...High pressure extending over area from NE will continue to move offshore tonight and Monday. NE-E winds around 10 kt will become E-SE 10-15 KT overnight, and then SE-S 15-20 KT with gusts to 25 KT by late afternoon. Initiated SCA for waters south of Oregon Inlet starting 5 PM Monday. Seas will build with increasing winds late tonight and Monday, with heights 4-6 feet expected outer southern and central waters by late in the day. Long Term /Monday night through Friday/... As of 415 PM Sunday...A strong cold front approaches the region Monday night and Tuesday, then pushes through the waters Tuesday night. Southerly winds increase drastically Monday night and Tuesday, peaking around 20-30 kt with some gale force gusts possible. Seas build to 6-9 ft Monday night and 7-11 feet Tuesday. Have initiated an SCA starting late Monday/Monday evening for all waters except the inland rivers with this package. The front pushes through the region Tuesday night with winds becoming W/NW around 10-15 kt through Wednesday. Seas gradually subside Tuesday night to around 4-6 ft Wednesday. Gradients tighten some Wednesday night into Thursday and the upper trough axis swings through and expect NW winds around 10-20 kt with seas continuing around 4-6 ft. By late Thursday expect winds to diminish to below 15 kt with seas dropping below SCA criteria. Light southerly winds around 5-10 kt expected Friday with seas around 2-4 ft. && .MHX WATCHES/WARNINGS/ADVISORIES... NC...None. MARINE...Small Craft Advisory from 10 PM Monday to 10 PM EDT Tuesday for AMZ135. Small Craft Advisory from midnight Monday night to 6 PM EDT Tuesday for AMZ130-131. Small Craft Advisory from 5 PM Monday to 6 PM EDT Thursday for AMZ152-154. Small Craft Advisory from 5 PM Monday to 10 AM EDT Thursday for AMZ156. Small Craft Advisory from 8 PM Monday to noon EDT Thursday for AMZ150. Small Craft Advisory from 5 PM Monday to 10 AM EDT Wednesday for AMZ158. && $$ SYNOPSIS...JBM NEAR TERM...JBM/BM SHORT TERM...JBM LONG TERM...SK AVIATION...SK/BM MARINE...JBM/SK/BM
Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
1047 PM CDT Sun Oct 22 2017 .UPDATE... Issued at 1041 PM CDT Sun Oct 22 2017 Updated to include 06z aviation discussion below. && .SHORT TERM...(This evening through Monday) Issued at 308 PM CDT Sun Oct 22 2017 Clouds from our system yesterday are slowly moving out of western WI, but clouds are already rapidly approaching western MN out ahead of our next wave, which is currently moving across the Montana/Saskatchewan border. This wave will come at us in two waves, this first late tonight into Monday morning, with a second wave dropping through in the afternoon. Both waves will have associated cold fronts, with the second one actually having cold air with it this time around. For precip, if we see anything it will be very light, with the bigger issue being winds behind the second boundary. Looking at forecast soundings and obs back in ND, this first wave will just result in clouds moving in up around 10k ft. There are returns on the BIS radar, though rainfall obs are lacking, indicating it`s mainly virga. The HRRR shows potential precip with this wave reaching western MN around 6z. This will probably be light rain/sprinkles and may actually not be enough to measure, but will be moving across western WI by 12z Friday. Precip chances look better in the afternoon with the second wave, though that is due in part to strong CAA, which looks to create steep low level lapse and a favorable environment for developing showers with peak daytime heating. Coverage looks to be isolated to scattered, with amounts being fairly light once again (under 0.05"). As for winds, it`s behind the second boundary that we will see those pick up quickly. Pretty good deal of spread though between the GFS and NAM with how much wind we will see, and the differences come down to winds in the h9-h8 layer (where we will be mixed up to and through). The NAM shows winds in this layer in the 30-40 kt range, with the GFS out in western MN showing 40-50 kts. The heart of the isallobaric high (with 6 hr pressure rises on the order of +10-12 mb) will be heading into northwest MN, so kept our winds more tempered toward the NAM. We should see gusts up near 40 mph out in west central/southwest MN. Though strong, wind advy criteria is sustained 30 mph/gusts to 45 mph and at the moment we look to stay just below that level, but did add the strong wind mention to the HWO. .LONG TERM...(Monday night through Sunday) Issued at 308 PM CDT Sun Oct 22 2017 We will definitely see a change in the weather this week, with things autumn-like and even slightly wintry across the area. The guidance is in good agreement on the big picture, with a deep upper trough across the east and ridging out west. Over the course of the week we see a few shortwave features drop into our area, resulting in brief warm advection periods followed by reinforcing shots of colder air. The guidance has come into better agreement with a more significant system in the Thursday/Friday time frame, but at this point most solutions point toward it having its greatest impacts north of our area. We will see ridging build in from the west Monday night and Tuesday, which will bring any lingering shower activity associated with the upper low and low-level cyclonic flow to an end. Some showers could linger across the east on Tuesday, with a few snowflakes certainly possible, but with no accumulation. The next shortwave embedded in northwest flow looks to drop southeast through the region Tuesday night and Wednesday, but things have trended east with this feature, keeping any rain mostly out of our area. After that we`ll await the arrival of a more significant upper wave that will emerge into the northern High Plains Wednesday night, and drive a surface low east across central/northern Minnesota during the day on Thursday. This looks to bring decent precipitation, including the possibility of snow, to northern Minnesota, but for our area much will depend on the exact track of the system and how much precipitation will wrap south in the wake of the surface low in association with the upper trough and deformation zone. Although the guidance is in good agreement on the larger scale pattern, there are definitely some differences in these details. For now, mostly chance PoPs Thursday through Friday are the wisest course of action, with the best time frame for snow coming on the backside of the system on overnight Thursday night into Friday. The deterministic GFS is much more aggressive in bringing heavier precipitation (which would at least be a mix of snow if not all snow) southward into our area in comparison to the ECMWF and the GEFS. The GFS is essentially outside of the envelope the GEFS in terms of precipitation across our area, so won`t get too excited about things at this point. However, it does appear that we should at least have a shot at many locations see their first snow of the season, even if it isn`t able to accumulate. Needless to say, it will be something to keep an eye on through the week, as we will sometimes see successive shortwaves in these patterns drop a bit farther south than initially progged. Any lingering precipitation should exit by Saturday with ridging looking to hold on into Sunday (although there is quite a bit of spread in the solutions at that point). && .AVIATION...(For the 06Z TAFS through 06Z Monday night) Issued at 1041 PM CDT Sun Oct 22 2017 High clouds will move into the region tonight in advance of a cold front due to pass through the region during the day tomorrow. High ceilings will lower into the mid-levels but remain solidly in the VFR range. A few isolated showers are possible from time to time but nothing that should impact operations to any great degree. Main issue will be shifting and strong/breezy winds. Winds will shift from S to W overnight then to NW during the day tomorrow. Speeds at the surface will remain around 10 knots while winds in the 1-2 kft layer may climb to around 30 knots, close to LLWS criteria but looks to be more turbulence at this point so will leave out LLWS mention. After daybreak, deep mixing will allow the stronger WNW winds to mix down to the surface, resulting in speeds around 15-20G30kts. KMSP...Pre-frontal boundary will move across the area close to daybreak, potentially creating crosswinds on the 12/30s through the morning push, with wind speeds around 10 knots. Winds then will continue veering to WNW by the evening push. Gusts will commonly run in the low 20s knots but could hit 30 knots at times. /OUTLOOK FOR KMSP/ Tue...VFR with MVFR possible. Wind NW 15-20kts gusting to 30 kts. Wed...VFR. Wind NW 5-10 kts. Thu...VFR with MVFR late. Wind S 5-10kts becoming NW. && .MPX WATCHES/WARNINGS/ADVISORIES... WI...None. MN...None. && $$ UPDATE...JPC SHORT TERM...MPG LONG TERM... AVIATION...JPC
Area Forecast Discussion
National Weather Service Marquette MI
732 PM EDT Sun Oct 22 2017 .SHORT TERM...(This evening through Monday) Issued at 342 PM EDT SUN OCT 22 2017 Water vapor imagery and RAP analysis show a shortwave trough moving east across the central CONUS. Associated cold front extending south from sfc low over northern Manitoba has also moved east across Upper Mi today providing a focus for numerous showers this afternoon into central and eastern portions of the cwa. Showers will continue to diminish or end over the west half later this afternoon and should be out of the eastern fcst area by midnight tonight. Considerable high cloudiness will linger after the pcpn ends, but skies should generally clear from w, late this afternoon into evening beginning in the w. The next shortwave trough will dig into the Northern Plains tonight. Narrow zone of waa/isentropic ascent ahead of the this feature may generate some showers that could reach western Upper MI by 12z Mon, but given the antecedent dry air mass pcpn chances appear minimal. Will continue to carry dry fcst during the overnight. Expect cooler min temps with lows ranging from the mid 30s over the typical interior cool spots west and central to the lower to mid 40s far west due to increasing clouds later tonight ahead of approaching Plains trough and for well-mixed locations along Lake Superior in downsloping sw flow. On Monday, the Northern Plains trough will begin to push east into the Western Great Lakes region. Weak q-vector convergence and mid- level moistening ahead of this feature combined with steepening lapse rates from sfc to 700 mb should generate isolated to scattered showers into Upper Mi especially into the afternoon hours with the best chance of rain over the west half. Expected highs Monday in the mid to upper 50s will still be above normal but a bit more typical of mid to late October readings. .LONG TERM...(Monday night through Sunday) Issued at 401 PM EDT SUN OCT 22 2017 Focus continues to be on the potential for a very strong fall storm system with strong winds, large waves on Lake Superior, and possibly heavy rain late Monday night into Tuesday night. Significant forecast model spread continues with phasing of a central Canadian trough and Gulf Coast trough. The CMC and ECMWF continue to produce a much stronger surface low than the GFS, though multiple members of the GEFS are more in line with the stronger solution. At this time, significant spread in model solutions supports continuing with a slightly conservative forecast when compared to the stronger CMC solution. However, did trend closer to the strongest solution given CMC run-to-run continuity and GEFS members showing a stronger storm. This solution yields northerly wind gusts as high as 50mph and some beach erosion along the Lake Superior shore and wind gusts to 35mph inland on Tuesday. However, it should be noted that the CMC solution would produce substantial impacts to Upper Michigan on Tuesday, with winds gusts possibly to 60mph and considerable beach erosion along the Lake Superior shore from the Keweenaw Peninsula to the east. Heavy rain would also occur with this solution across the north central and east, with storm total rainfall surpassing 2". Lastly, some colder air arriving Tuesday night may switch rain over to snow across the interior, but little to no accumulation is expected as deeper moisture will be departing. Scattered rain/snow showers will linger into Wednesday before brief ridging brings dry conditions Wednesday night. Guidance is then in good agreement on a clipper system dropping southeastward across the Upper MS Valley Thursday into Friday. The bulk of the precip, will occur Thursday night into Friday, with a chance of minor snow accumulations across the interior west Thursday night. Beyond this point model solutions begin to diverge considerably, so maintained blended forecast for now. However, depending on the track of the aforementioned clipper system Friday Night/Saturday, accumulating snow could be possible for portions of western Upper Michigan. && .AVIATION...(For the 00Z TAFS through 00Z Monday evening) Issued at 731 PM EDT SUN OCT 22 2017 With strong drying over the area in the wake of the cold front, VFR conditions are expected tonight into Monday afternoon. Another disturance moving in later Monday could support isold/sct -shra along with cigs dropping to near MVFR over the west half. && .MARINE...(For the 4 PM Lake Superior forecast issuance) Issued at 342 PM EDT SUN OCT 22 2017 West-southwest winds of 20-30kt strongest over the west and north central portions of Lake Superior will continue to diminish into the evening hours in the wake of the cold frontal passage, but should pick up again slightly over the west and north central ahead of the next approaching low pres trough. Southwest winds will then generally be in the 15-25kt range on Mon strongest west half. A deepening low pres lifting north from the Ohio Valley on Mon and reaching a position near Drummond Island on Tue morning will result in increasing winds on Lake Superior. Northerly gales of 40-45kt will develop from w to e Mon night through Tue. If the sfc low ends up deeper than currently expected, winds could up being storm force over the east half on Tue. With the low quickly exiting to the nne, winds will fall back to under 20kt on Wed. Look for increasing se winds again on Thu ahead of the next low pres trough moving across the Plains. && .MQT WATCHES/WARNINGS/ADVISORIES... Upper Michigan... None. Lake Superior... Gale Watch from Tuesday morning through Tuesday evening for LSZ251-267. Gale Watch from late Monday night through Tuesday evening for LSZ243>250-264>266. Gale Watch from late Monday night through Tuesday afternoon for LSZ162. Gale Watch from late Monday night through Tuesday evening for LSZ240>242-263. Lake Michigan... None. && $$ SHORT TERM...Voss LONG TERM...Kluber AVIATION...JLB MARINE...Voss