Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 12/07/20

Area Forecast Discussion
National Weather Service Caribou ME
911 PM EST Sun Dec 6 2020 .SYNOPSIS... Strong low pressure will slowly exit across the Maritimes through Monday. High pressure will cross the region Tuesday, then exit across the Maritimes Wednesday. A cold front is expected to cross the region Wednesday night into Thursday morning. High pressure is expected for Friday. && .NEAR TERM /THROUGH MONDAY/... 9:11 PM Update: Low pressure is near the western tip of PEI and it will remain quasi-stationary overnight before beginning to pull away during the day Monday. Moisture continues to wrap around the low and will produce light snow across northern and eastern sections of the FA late this evening and into the overnight hours. The light snow will transition to scattered snow shower and flurries by morning. At this point,the vast majority of the accumulating snow is over with any add`l accumulations under an inch. A gusty northwest wind and slowly falling temperatures will allow for areas of blowing and drifting snow, especially in areas that received more significant snowfall from our recent storm that is winding down. Made some adjustments to the PoPs and weather to hold on to more stratiform light snow until around 3 am. Otherwise, just very minor adjustments to the other forecast elements based on the current conditions and expected forecast trends overnight. Previous discussion: The wrapped up low in New Brunswick will still have influence on the region`s wx into tonight w/periods of snow, especially across northern and eastern areas. Still some good convergence across portions of the northern and eastern areas to keep steady snow going w/bands of enhanced snow at times into early evening. This can be seen on the latest NAM as well as HRRR streamline analysis. So, an additional 1-3 inches is possible into the evening before convergence weakens as the low slowly pulls away. Given this, decided to drop the Winter Warnings and Advisories s of Aroostook, Nrn Somerset, Nrn Piscataquis and Nrn Penobscot County. The Winter Storm warning for the northern areas is in place through 7 pm. The steady snow is expected to transition to snow showers/flurries overnight w/the loss of the convergence and sufficient forcing. Gusty NW winds will lead to blowing and drifting of snow through at least midnight as temps have cooled down to allow for more lighter snow which should be able to be lofted quite easily. The winds are expected to let up by early Monday morning w/a reduction in the blowing and drifting expected. Temps will be dropping back slowly overnight as clouds will hang on overnight. Monday will see some improvement as the low pulls even further away. There is still some risk of scattered snow shower/streamers that will be coming off the open St. Lawrence. Used a blend of the guidance for the pops which show 20-30% across the northern and western areas. Any snow accumulation will be light and less than an inch. Temps will warm some w/upper 20s across the n and w, while central and downeast areas are expected be in the lower 30s. NW winds will be much lighter than they were today. && .SHORT TERM /MONDAY NIGHT THROUGH WEDNESDAY/... Maine will remain in a quite compact pressure gradient between the exiting low and incoming high pres ridge into Tuesday. Much of the low level moisture will have moved out of the region, but clouds and some breezy conditions will remain. The NW winds will keep cool air channeling into Maine, with temps falling into the teens across the north Tues night, and lower 20s across Downeast. Clouds may prevent a greater rad cooling effect, but snow will still be on the ground for many central and northern locations. Gradient winds will finally slacken on Wednesday with a calmer day. Clouds will remain overhead, but it should remain dry as the brief sfc ridge passes overhead. The next chance of precip arrives Wednesday evening and overnight as a weak shortwave dives across New England north of a 500mb jet. The jet core is forecast to remain south and west towards the central Great Lakes, which keeps best divergence aloft in the exit region away from any deeper source of moisture. Thus, have kept only a slight chance of snow showers across the CWA overnight. && .LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/... For the second half of the week, temperatures will seasonable with little in the way of precip during the work week. The item to watch will be a large storm system developing across the central CONUS around next weekend. The aforementioned shortwave washes out on Thursday ahead of an elongated upstream jet. The movement of this jet across the northern tier of the US will help amplify a incoming longwave trough along the western US. With the troughs arrival in the lee of the Rockies, guidance suggests the formation of a strong surface low across the Great Plains through Thurs night and Friday. The footprint of the occluded low expands, bringing the jet along the base of the trough and leaving much of the eastern US in SW WAA beginning Friday afternoon through the late weekend. EPS solutions take the low center into the Great Lakes and Southern Quebec. This space and duration of the WAA will trend daily sfc temperatures above normal. This is possible not only for Maine but a bulk of the Northeast as indicated by CPCs 6-10 day temp outlook. An anomalous surge of PWATs will also be possible into the warm region, meaning the chance for another rain event. Most long range guidance shows the development of the system across the nations midsection, but further confidence is needed before considering QPF amts, timing, and potential hydro impacts. The CWA has recently experienced a few heavy precip events, and snowpack will likely remain across locations that received significant snowfall over the past 24 hours, especially in the deep woods. Thankfully, headwaters and soil moisture Downeast will get a break during the week ahead. && .AVIATION /02Z MONDAY THROUGH FRIDAY/... NEAR TERM: MVFR late this evening for all sites, w/tempo IFR from KHUL northward. KBGR-KBHB should see VFR late this evening and holding that way into Monday. Northern TAF sites should hang on to MVFR for Monday. NW winds tonight at 10 to 20 mph w/gusts to 25-30 mph especially this evening. This will lead to areas of blowing and drifting snow, which will reduce visibilities. Improvement on the wind for Monday for all sites w/NW winds dropping back to 10-15 mph. SHORT TERM: Monday night: VFR. Light N wind. Tuesday: VFR, a brief period of MVFR possible across the north. N wind gusting up to 15 kt at BGR and BHB. Tuesday night: VFR. Light NW wind. Wednesday: VFR dropping to MVFR north, Light SW wind. Wednesday night: MVFR to VFR north, a chance of snow showers. VFR Downeast. Light SW wind. Thursday: MVFR north, VFR Downeast. Light W wind. && .MARINE... NEAR TERM: A small craft advisory is in effect through early Monday morning. Still expecting some gusts to 30 kts overnight with a brief gust or two to 35 knots, mainly over the outer zones. Seas are expected to slowly subside overnight. Winds are forecast to drop below 20 kts w/seas subsiding to 3-4 ft by midday Monday. SHORT TERM: Conditions will predominantly be below SCA criteria. The exception being Tuesday afternoon when N coastal gusts increase to around 25 kt as low pressure passes outside the Gulf of Maine, subsiding towards midnight. Winds become W through Wednesday and into Thursday. && .CAR WATCHES/WARNINGS/ADVISORIES... ME...None. MARINE...Small Craft Advisory until 4 AM EST Monday for ANZ050>052. && $$ Near Term...CB/Hewitt Short Term...Cornwell Long Term...Cornwell Aviation...CB/Hewitt/Cornwell Marine...CB/Hewitt/Cornwell
Area Forecast Discussion
National Weather Service Quad Cities IA IL
453 PM CST Sun Dec 6 2020 ...00z AVIATION UPDATE... .SYNOPSIS... Issued at 310 PM CST Sun Dec 6 2020 A mix of sunshine, patches of lingering stratocu and afternoon instability cumulus acrs the area, while the next upstream upper level low was noted on water vapor imagery dropping south acrs LK Superior. Northerly steering flow to lee of upper blocking pattern acrs the western CONUS will continue to shuttle short waves down acrs the upper Midwest and GRT LKS into early this week, before the ridge flattens and presses eastward acrs the mid CONUS for a mid week warm up. Following that, there still appears eastern Pacific upper trof energy will stride inland and possibly induce a storm system somewhere acrs the Midwest by late week. && .SHORT TERM...(This Evening through Monday) ISSUED AT 310 PM CST Sun Dec 6 2020 Tonight...Some of the banded instability CU should decay after sunset but then a more extensive stratocu deck currently extending from far southeast NE, eastern MN and NW WI/LK Superior, will look to get dragged southeastward as the above mentioned closed low to the north drops toward western lower MI by midnight, and toward IN/ northwest OH by Monday morning. This a bit further east track than indicated by model runs at this time yesterday. But this system will still utilize some higher cloud deck patches as seeder feeders to the low stratocu deck that will slide acrs the local area after mid evening. This will produce some flurries spreading in from the north as the deck approaches along with lift from the wave aloft. There may even be some bands more characterized as light snow as opposed to flurries and produce a dusting like what occurred Sat night-early Sunday morning. Bulk of model solutions including HiRes suggest most of this flurry or light snow activity to occur mainly along and east of the MS RVR and spread in from the north after 10 PM, prime window then mid nigh through 5 am from north-to-south. But higher band of seeder feeder clouds seen on the current Vis satellite loop currently acrs northwest into north central WI was pushing south-southwest. If this trend maintains, the entire CWA will be at risk for flurries later tonight. Extrapolating the ongoing band of light snow this process is producing acrs north central WI ATTM, this band would almost miss the CWA to the west or clip areas west of a Dubuque to Cedar Rapids line. No model is handling this band at all. That`s if it can maintain, and another evening of watching upstream trends so as to adjust POPs for light snow and the need to spread flurry wording further west. Lows tonight generally in the mid to upper 20s, but a mix of cloud cover and clear holes will make for quite a temperature variation. Monday...Will be stubborn with lingering cloud cover with looks like it may get trapped under post-wave ridging aloft/subsidence inversion. But the subsidence may also act as a cloud scouring agent like it did today, thus some holes or breaks also likely especially by afternoon. Then the active northerlies will look to shuttle down a weaker short wave trof down toward the area by evening. Thus more clouds/stratocu may be on the increase again from the north by late day. Will go with 75 percentile high temp potential making for widespread upper 30s to low 40s, but more insolation tomorrow than currently expected may make these values be a degree or two on the cool side. ..12.. .LONG TERM...(Monday Night through next Sunday) ISSUED AT 310 PM CST Sun Dec 6 2020 Key Messages: 1. Warmer temps to highlight most of the work week. 2. Next chance for precip will be the end of the week where differences in guidance make for a difficult forecast. Discussion: Ridging aloft begins to move into the area at the beginning of the period as WWA begins to bring in above 0 H85 temps. This will in turn lead to a few days with temperatures in the 50s, well above normal and even possibly reaching the 60s by midweek. We will get close to potential record highs. With the shift in polar temps, this set up will feature strong baroclinicity across the region and thus at the end of the week we have the potential for strong storm system. At the current time, the GFS is the strongest of the models, bringing a left entrance region into the area along with an upper level wave shifting negative across the area. This is likely currently overdone, yet is a perfect example of the potential dynamically driven system for the end of the week. All guidance has the majority of our area in the warm sector and rain for the area. Wrap around snow is possible in most guidance and looking at the ensembles the signal is for light snow. The main question is how warm do we get Friday and whether or not we see storms. The GFS would lead to quite amount of shear and potential for strong storms. The GEM and ECM would be wet rain for the area. Also there are timing differences in these systems which causes a longer period of POPs in the extended. As we get closer to the event, expect this window to get smaller as confidence increases. && .AVIATION...(For the 00Z TAFS through 00Z Monday Evening) ISSUED AT 452 PM CST Sun Dec 6 2020 Challenging TAF for this period as a stratus deck builds across the area from the north this evening. Guidance is in agreement of MVFR conditions for all terminals, with some high-end IFR ceilings even possible mainly for CID/DBQ. It becomes complex for tomorrow as some CAMs show the deck mixing out, while other models like the RAP and NAMnest keep MVFR conditions through the day. Have more confidence in the later, as those forecast soundings maintain a strong low- level inversion which is tough to mix out and often traps moisture fairly well this time of year. Therefore, will maintain MVFR ceilings through the period. Winds will be light and variable thanks to broad surface high pressure to the west. && .DVN WATCHES/WARNINGS/ADVISORIES... IA...NONE. IL...NONE. MO...NONE. && $$ SYNOPSIS...12 SHORT TERM...12 LONG TERM...Gibbs AVIATION...Speck
Area Forecast Discussion
National Weather Service Green Bay WI
803 PM CST Sun Dec 6 2020 New Information added to update section .UPDATE... Issued at 803 PM CST Sun Dec 6 2020 A little more active evening than initially anticipated with freezing drizzle developing across portions of central/north- central Wisconsin. This is due to a fairly shallow layer of moisture, along with upsloping/light northwest winds into Vilas and Oneida County. This is also a result of shortwave energy passing through the area this evening. RAP soundings indicate some weak cooling of the thermal profile along with a bit deeper moisture layer toward midnight into the overnight hours, which would introduce more ice crystals into the cloud. This should effectively transition/mix any precipitation to flurries or light snow showers. In fact, have already seen this happening on webcams and surface observations in Vilas County. Have extended the Special Weather Statement farther south into Marathon County as observations continue to show some southward advancement of very light freezing drizzle or mist. && .SHORT TERM...Tonight and Monday Issued at 219 PM CST Sun Dec 6 2020 A fairly vigorous shortwave will drop through northeast Wisconsin across Lake Michigan tonight, bringing with it overcast skies and a chance for some light flurries and drizzle. Kept the mention of patchy drizzle/flurries in through the approximate timing of the shortwave, as they will likely dissipate without the upper level forcing. Areas across central and north- central Wisconsin may also see the development of patchy fog in the evening through late tonight. With the low clouds in place, temperatures tonight are not expected to drop as much as the past couple nights, with lows in the lower to middle 20s. Monday will continue the trend of cloud cover dependent temperature forecasts. At this time, expect mostly cloudy skies to remain in place over the area, which will keep highs a touch cooler than previously forecast. Highs will likely still range from the lower to middle 30s. .LONG TERM...Monday Night Through Sunday Issued at 219 PM CST Sun Dec 6 2020 Quiet and mild weather is anticipated through Thursday night, followed by a potentially significant low pressure system next weekend. Dry conditions with a return to much above normal temperatures is expected for the middle of the week. By Wednesday, highs should be in the 40s to around 50 range, which is around 15 degrees above normal. A weak cold front will move through on Wednesday, but is not expected to bring much cooling into Thursday. Although details are significantly different, medium-range models show a potentially strong low pressure system moving through the western Great Lakes region over the weekend. WAA/isentropic lift should generate some precipitation on Friday, followed by cyclogenesis as a deep upper trough/upper low moves into the region over the weekend. The ECMWF has an open upper trough that is more progressive, and tracks a deepening surface low through southeast WI and Lake Michigan late Friday night into Saturday. The GFS initially tracks a strong low to near the MN/IA border Friday and Friday night, then shifts the vertically stacked system east through WI Saturday into Saturday night. The Canadian is slower and farther west. Regardless, it appears a significant system will impact the region during days 5-7. The timing and track are very uncertain, and will ultimately determine how much rain/snow occurs, and whether winds will be a big concern. Will start to highlight the potential for possible snow accumulations in the Hazardous Weather Outlook, but refrain from making any significant changes to the blended guidance pops at this time. If similar trends continue tomorrow, will ramp up the pops and messaging accordingly. && .AVIATION...for 00Z TAF Issuance Issued at 521 PM CST Sun Dec 6 2020 MVFR and IFR conditions are expected to push into each TAF site this evening and then linger through at least Monday morning. The lowest ceilings and perhaps some fog will generally be confined to the central TAF sites, RHI/CWA/AUW. Some light flurries/snow showers are also possible, especially at RHI. Otherwise, slowly improving conditions can be expected toward Monday afternoon. && .GRB WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE.........Cooley SHORT TERM.....Uhlmann LONG TERM......Kieckbusch AVIATION.......Cooley
National Weather Service Jackson KY
1043 PM EST Sun Dec 6 2020 .UPDATE... Issued at 1041 PM EST SUN DEC 6 2020 Rain showers have spread into eastern KY near the Mtn Parkway corridor from Central KY. Measureable rain has fallen in Central KY per KY Mesonet stations and KLEX and KFFT ASOS stations upstream. With clouds in place, temperatures generally remain mild with temperatures above freezing at this point even in the high terrain. However, as an upper level disturbance drops across the region overnight, showers are expected to increase in coverage over the southeastern portions of the area and as cold air moves into the area and wetbulbing occurs, this should change to snow on the ridgetops first not long after midnight. Some light accumulationsare still anticipated with the SPS wording of a dusting to a quarter of an inch for lower elevations and upwards of an inch on the higher ridges in the southeast still on target. Minor adjustments have been made to bring in chance and slight chance pops a bit earlier and account for recent observations. UPDATE Issued at 650 PM EST SUN DEC 6 2020 Other than minor adjustments based on hourly temperature trends no changes were needed at this time. Recent guidance including the HRRR continues to support the previous forecast. && .SHORT TERM...(This evening through Monday night) Issued at 521 PM EST SUN DEC 6 2020 The current upper level pattern features ridging stretched from the Eastern Pacific through Southern California, before stretched northward across the Rockies and into south central Canada. Troughing remains positioned from the Great Lakes/New England down through the Mississippi Valley, with embedded vorticity centers noted across the Upper Great Lakes, Ohio Valley, and Lower Mississippi Valley. At the surface, high pressure generally controls for most west of the Mississippi River. Weaker high pressure is seen across portions of the Great Lakes/Ohio Valley, with broad low pressure stretched from the Central Appalachians down through the Tennessee Valley. Despite the foggy start to the day, and clouds on the increase across Eastern Kentucky into this afternoon, temperatures managed to make into the mid to upper 40s across the northern half of the area, with upper 40s to lower 50s having occurred in the south. A more decisive cool down will take place across the Ohio and Tennessee valleys through the short term. This will be accompanied by some light snow that will move in late tonight and through the day on Monday, before gradually tapering to flurries Monday night. The models are in good agreement through the short term, with the trough becoming more amplified across the Eastern CONUS. This occurs in response to the Great Lakes upper level vorticity lobe dropping south, while the Ohio Valley vort max shifts east with time. By Monday night, a deeper upper level low will be established across the Delmarva region, before shifting towards the Western Atlantic by early Tuesday morning. At the surface, low pressure will deepen as it heads towards the Carolinas tonight, before bombing out as it moves out over the Western Atlantic Monday into Monday night. For Eastern Kentucky, clouds will increase and lower tonight, as moisture deepens with the approach of the short wave trough axis from the eastward progressing upper level low across the Ohio Valley. The models have trended up on the moisture associated with this feature, with a mix of sprinkles/flurries initially later this evening across the area, before column cooling allows for a changeover to some snow showers overnight tonight and into early Monday morning. The highest PoPs will be more focused across the southeastern half of our area. Given the warm ground temperatures in place, snow impacts will be more limited to elevations above 1500 feet, and especially along the typically favored highest elevations along Pine and Black Mountains, where temperatures will cool off much quicker, given the colder start. The snow showers will gradually become more confined to far southeastern Kentucky during the day on Monday, as deeper moisture exits. Snow amounts will range from a dusting to a quarter of a an inch for elevations near and below 1500 feet, mainly on grassy and elevated surfaces. For elevations above 1500 feet, snow amounts of up to an inch are expected. As such, have hoisted a Special Weather Statement for the southeastern half of our area. Temperatures will trend below normal through the period. Lows tonight will range from the mid to upper 20s north, and the upper 20s to lower 30s south. Mostly cloudy skies, cold air advection, and ongoing flurries/light snow showers will keep temperatures from moving much on Monday, with highs generally in the low to mid 30s. Skies may be a bit more stubborn to clear Monday night, given the upslope flow in place at the low levels. Lows will range from the low to mid 20s. .LONG TERM...(Tuesday through Sunday) Issued at 505 PM EST SUN DEC 6 2020 The long-term starts off chilly on Tuesday, but a pleasant warming trend will send our temperatures to near the 60 degree mark for Thursday and Friday. Unsettled weather and more seasonable temps follow by the weekend. Upper level troughing will initially be in place over the eastern CONUS Tuesday morning with upper level ridging over most of the west. An ~556 dam low will also be found west of Baja California. Closer to eastern Kentucky, some weak northwest upslope flow and an upper level vort max will likely keep low-level clouds over the area through at least the first half of the day Tuesday. By late in day, southwest flow develops along the northern fringes of a surface high passing over the Deep South/Gulf of Mexico. This should cause the cloud deck to erode and gradually move out of the area. Given the widespread cloud cover through much of the day, highs are only expected to reach the upper 30s to lower 40s for most locales. Clear skies and light winds Tuesday night should allow for a ridge-valley temperature split with lower 20s in the valleys and upper 20s over the ridgetops. An upper level trough and surface cold front drops into Great Lakes on Wednesday. The trough will be deflected back to the north on Thursday as a sharpening trough digs into the western CONUS, captures the cutoff low near California, and pumps up a compensating ridge over the Ohio Valley. Clouds will increase over northern Kentucky on Wednesday ahead of the front but will later retreat as heights rise and surface high pressure becomes well established over the area by Thursday. Temperatures will warm into the lower 50s for most areas Wednesday afternoon and then near the 60 degree mark under mostly sunny skies on Thursday. The nighttime ridge-valley temperature split will redevelop each night, ranging from the upper 20 to mid 30s Wednesday night and into the lower 30s to near 40 Thursday night. Meanwhile, a lee cyclone will develop over along the eastern Rockies Thursday and then lift toward the Great Lakes Friday into Sunday, sweeping a cold front through the Commonwealth in the process. The front and its associated precip are expected to cross eastern Kentucky sometime between Friday night and Saturday night, but plenty of uncertainty remains as the models struggle with the storm system`s evolution. Clouds will increase and thicken ahead of the front on Friday, but mild southerly flow, early day sunshine, and continued dry weather should still allow temps to near 60 degrees. The front will bring a good chance for rain during the early part of the weekend. Behind the boundary, temperatures will only reach the 40s at best Sunday while some wraparound moisture and westerly flow could lead to some upslope precipitation. && .AVIATION...(For the 00Z TAFS through 00Z Monday evening) ISSUED AT 710 PM EST SUN DEC 6 2020 Mid level clouds and stratocu are spreading southeast across the region with VFR reported at present across East KY though some MVFR is reported in portions of central KY. Overall, clouds are still expected to generally thicken and lower from northwest to southeast between 0Z and 6Z, as an upper level disturbance currently over IN moves through the area followed closely by another disturbance. This system to LOZ will bring some light snow to the area, with most locations along and southeast of a line from KSJS to KJKL to KLOZ to KSME seeing a period of IFR ceilings and perhaps visibilities for a period between 06 and 15z. Light snow showers/flurries will continue to linger across southeastern into the last 12 hours of the period. Most of the IFR visibility restrictions should generally be more confined to the higher elevations towards the Virginia border, or south of a KSJS to KJKL line by the 12Z to 18Z period. Winds will average around 5 kts or less through the period out of the northeast to northwest. && .JKL WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...JP SHORT TERM...GEOGERIAN LONG TERM...GEERTSON AVIATION...JP
Area Forecast Discussion
National Weather Service Miami FL
640 PM EST Sun Dec 6 2020 .Aviation... Generally VFR conditions will prevail throughout the early evening hours. Sub VFR conditions are possible during the overnight hours as shower and thunderstorm activity increases out ahead of an approaching cold front. Short fused amendments will likely be needed as periods of IFR or LIFR are possible. Conditions will begin to improve on Monday afternoon as a breezy northwest wind moves in behind the front. && .Update... The shower and thunderstorms chances will begin to increase from west to east later this evening and into the overnight hours out ahead of an approaching cold front. The latest short range hi res model guidance continues to suggest there will be enough instability to support a couple of stronger thunderstorms during the overnight hours. Because of this, the Storm Prediction Center keeps most of South Florida in a marginal risk for severe thunderstorms during this time frame. With the chance of heavy downpours, as well as training thunderstorms over the same areas, there is a risk for localized flooding during the overnight hours with the highest chances along the east coast metro areas. The strongest thunderstorms could also contain gusty winds. Showers and thunderstorms will continue through Monday morning as the front moves through the region. Conditions should start to improve on Monday afternoon as drier air works in behind the front. && .Prev Discussion... /issued 330 PM EST Sun Dec 6 2020/ ..Concerns for localized flooding and tornados with strong storms overnight... ..Chilly days ahead behind an early week cold front... Discussion... Short Term (Today through Monday): The retreat of the surface warm front back into the region has allowed for a recovery of area dewpoints with most of South Florida in the 60s and even some lower 70s sneaking back in. Some portions of Southwest Florida did briefly experience some enhanced mixing which allowed dewpoints to drop into the 50s late this morning. The mid-level trough will continue to progress eastward across the Gulf today and tonight, pushing the associated surface cold front through the region on Monday. Ahead of the cold front, we continue to have concern for the development of a surface low or vigorous trough which could enhance convection. The question of available instability remains a crucial determinant for the quality and quantity of convection for tonight. For a more in- depth look at the mesoscale environment for tonight`s potential strong to severe storm concern, please see the previous mesoscale and hydrology discussions included below for your convenience. The Weather Prediction Center has much of the east coast metro in the marginal risk for excessive rainfall and the Storm Prediction Center has most of South Florida in the marginal risk of severe weather tonight. As the front pushes through the region on Monday, convection will begin to clear out from west to east. The majority of the moist air should be out into the Atlantic by Monday afternoon. Drier, colder air will settle into the region for the late afternoon and evening with the cloud cover eventually eroding which will allow the first of several chilly nights on Monday night/Tuesday morning. Temperatures dropping into the 60s across most of the region except around the western portions of the Lake Okeechobee region where upper 50s are possible. 10 to 15 mph winds could create wind chills in the upper 30s and lower 40s in Glades and Hendry with 40s sneaking as far as the Palm Beaches and the Alligator Alley corridor. Long Term (Monday night - Saturday): Models depict the onset of a robust cold air advection event starting Monday night in the wake of a FROPA, as high pressure establishes over the SE CONUS. Expect morning lows to dip into the 40s over interior areas, and even into the upper 30s over areas west of Lake Okeechobee. Coastal areas will likely remain in the upper 40s to lower 50s through Thursday. The afternoon highs should not surpass the mid-upper 60s Tuesday and Wednesday, and climbing into the low 70s by Thursday. With relatively dry air aloft and dominant subsidence in place, very little to no rain is expected during the long term with POPs remaining in single digits each day. Models gradually migrate the aforementioned high towards the Atlantic seaboard, which will veer the winds across SoFlo to a more easterly flow by Friday afternoon. No significant moisture rebounds should take place, keeping PoPs below 10 percent. Main changes will be warmer temperatures for the end of the period. Temperatures Friday morning rise to the low-mid 50s for interior areas, and into the low 60s near the coast. Afternoon highs should climb back into the upper 70s to low 80s for the upcoming weekend as the easterly flow modifies the air mass. Marine... Strong northwesterly flow behind a vigorous cold front will create hazardous marine conditions in the Atlantic and Gulf for small craft early this week. A Small Craft Advisory is already in effect for the offshore waters off Palm Beach County which will likely need to be expanded to include all of the Atlantic waters off South Florida along with the Gulf waters. Conditions should begin to improve by mid-week in the Gulf though some lingering swell in the Atlantic could cause improvement of conditions to be slightly slower. Beach Forecast... Improving conditions along the area beaches will be short-lived as the vigorous cold front will bring strong northwesterly wind which could cause an elevated rip current threat to develop along the Gulf beaches early to mid week. Swell from an Atlantic low pressure system could allow an elevated rip current risk to return to some of the Palm Beaches this week as well, which could persist for several days. Prev Discussion... /issued 1020 AM EST Sun Dec 6 2020/ Mesoscale Discussion... A mid/upper-level low over TX will deamplify into an open wave today, as it phases with an additional mid-level impulse diving southward into the middle Mississippi Valley. This evolution of the mid/upper-level flow pattern will support the development of a long- wave trough over the eastern states, and broad/enhanced mid-level cyclonic flow increasing across the South Florida CWA into the evening/overnight hours. As the large-scale pattern continues to consolidate today, an upper- level jet streak will develop over the SE CONUS -- providing upper- level divergence and weak forcing for ascent across the region. At the surface, a remnant quasi-stationary frontal boundary is evident via the latest RAP mesoscale analysis -- extending from the southern Gulf of Mexico eastward across portions of South Florida. South of this surface boundary, rich boundary layer moisture is evident (characterized by dewpoints in the upper 60s to lower 70s). As the above mentioned enhanced mid/upper-level cyclonic flow increases over the area, a weak frontal wave/surface low should develop over the eastern Gulf of Mexico (along the quasi-stationary surface boundary). As the frontal wave develops, the aforementioned rich boundary layer moisture will gradually spread northward across South Florida, coincident with weak WAA and associated isentropic ascent over the boundary. In addition, the latest high resolution model guidance depicts the development of a southwesterly low-level jet across South Florida, further enhancing mesoscale ascent, moisture advection, and vertical shear profiles across South Florida. All of the above mentioned factors will introduce a risk of excessive rainfall and localized flooding during the overnight hours -- supported by regenerative convection amid rich moisture/weak persistent ascent. Thermodynamic profiles will be supportive of locally heavy rainfall, though training/backbuilding of convective cells will exacerbate the flooding risk. There will also be a conditional risk of brief tornadic activity, as enhanced deep-layer shear (near 45 knots) overspreads the CWA amid rich surface moisture and elongating/veering hodographs. The primary factor regarding tornadic potential will be the ability for convection to become rooted at/near the surface -- where the rich moisture will be located. We will be closely monitoring the evolution of the aforementioned surface boundary and rich boundary layer moisture. There is currently plenty of uncertainty regarding storm mode/evolution/intensity -- owing to the weak large-scale forcing regime in place and anticipated marginal buoyancy over land areas. A reasonable-worst case scenario involves the development of a few rotating discrete cells amongst a larger area of rain, in addition to locally heavy rain and flooding. Present indications are that the greatest risk will be focused across the southern and eastern portions of South Florida, including the Gulf Coast metro areas. Keep up with the latest information from NWS Miami. Hydrology... South Florida has experienced little in the way of wetting rainfall since the departure of Eta in early November. This will help with the mitigation of flooding at the immediate surface over areas which have drained or are not lower-lying. However, the ground water levels across South Florida continue to be elevated due to the wet year so far and Lake Okeechobee continues to sit well over a foot above normal for this time of year. Releases from Lake Okeechobee have allowed the lake level to slowly drop but that has kept area canals and water conservation areas holding excess levels of water which could make drainage of excessive rainfall more difficult. && .Preliminary Point Temps/PoPs... West Palm Beach 64 75 49 65 / 80 70 0 0 Fort Lauderdale 67 78 52 67 / 80 70 0 0 Miami 69 78 53 67 / 80 70 0 0 Naples 64 74 52 65 / 90 60 0 0 && .MFL WATCHES/WARNINGS/ADVISORIES... FL...None. AM...Small Craft Advisory from 7 PM Monday to 10 AM EST Tuesday for AMZ670. GM...None. && Update...55/CWC Aviation...55/CWC