####018006391#### FXUS63 KGRB 132306 AFDGRB Area Forecast Discussion National Weather Service Green Bay WI 506 PM CST Sat Dec 13 2025 Updated aviation portion for 00Z TAF issuance .KEY MESSAGES... - Bitterly cold arctic air with wind chills as low as 20 to 30 degrees below zero will remain dangerous through Sunday morning for most areas. A Cold Weather Advisory is in effect for all of northern and central Wisconsin (except Door County). - A warming trend develops Tuesday and Wednesday, followed by a potent system that brings the potential for a wintry mix, rain, fog, and strong winds Wednesday night into Thursday. && .DISCUSSION... Issued at 218 PM CST Sat Dec 13 2025 The latest RAP analysis shows low pressure spinning north of Lake Superior while arctic high pressure is building southeast from the northern Plains to the mid-Mississippi Valley. Scattered cumulus clouds developed near the U.P. border around midday, but otherwise, skies have been mostly clear across the region so far today. Lake effect snow showers and clouds streets have mostly remained north of the U.P. border so far today. Scattered clouds are pushing south across northern Minnesota and northwest Ontario, but high relative humidity profiles in model soundings suggest there should be more clouds than are currently present. Have therefore lowered cloud cover for the rest of the afternoon. Current wind chills early this afternoon range from 15 below to 25 below zero. Focus of this forecast remains on the bitter cold wind chills and subsequent cold weather headlines. Bitter Cold Temperatures and Wind Chills: Arctic high pressure will gradually slide south across the northern Mississippi Valley tonight. On the eastern flank of this arctic high, the core of the arctic airmass will drop southeast across Wisconsin tonight. Low level wind trajectories will gradually be veering, which is supportive of lake clouds and light snow showers pushing south from the western U.P. and into far northern WI. There is low confidence in how quickly this occurs and how far south the clouds reach. Considering the bias of model RH fields in arctic airmasses, errored on the lower coverage side. This impacts temperatures and wind chills, and consequently, lowered min temps and wind chills across far northern WI. This puts all of northern Wisconsin (except for Door County) into Cold Weather Advisory criteria (20 below to 30 below) into the evening. Guidance insists on rising temps overnight and can see parts of the Cold Weather Advisory cancelled prior to expiration (6 am for the north). Over central WI, minimum wind chills of 30 below to 35 below are expected, which falls just shy of Extreme Cold Warning criteria. Temperatures should warm quicker on Sunday morning than this morning with wind chills rising above advisory criteria in the 9-10 am timeframe across central and east-central WI. Otherwise, expect mostly sunny skies with highs ranging from the middle single digits over central WI to the upper teens over far northeast WI. High pressure shifting east across the Ohio Valley will promote return flow developing on Sunday night. Southwest winds will become breezy which will maintain low wind chills generally 5 below to 15 below zero. Shouldnt see much fall in temperatures while statistical guidance actually shows surface temps undergoing a slow warming trend at some locations. Light Wintry Precipitation Late Sunday Thru Tuesday: Guidance continues to show weak clipper energy producing light snow after midnight on Sunday night into early Monday morning over far northeast WI. Chances reach up to 40% near the U.P. border. Perhaps up to one half inch of snow will be possible. Light snow from additional clipper systems look to remain north of the area on Tuesday and Tuesday night. Mid-Week System and Warming Trend: Then will be monitoring a potential fast moving and potent cyclone crossing Lake Superior on Wednesday night into Thursday. This system has trended stronger over the past 48 hours of ensemble runs. Critical thickness values are projected to lift north of the Upper Peninsula border by Wednesday evening. Probability of 850mb temps reaching above freezing range from 60-90%. Surface dewpoints are expected to rise above freezing over the southern parts of the area on Wednesday night. Probabilities range from 60-80%. Therefore a wintry mix looks possible on Wednesday night. Liquid precip will have potential to freeze after sunset as the ground will be very cold. Dense fog will also have potential to develop over the southern parts of the area. Behind the system, colder air will return, but there is quite a large spread in regards to how cold the airmass will be. There is higher confidence of windy weather on Thursday in the cold advection part of the cyclone. 925mb winds are currently in the 90-95th percentile. Light snow and minor accumulations will also be possible region wide. Another system could impact the region late Friday into Saturday. By Tuesday, there is a greater than 80% chance that highs will top 32F across the entire forecast area. Global ensembles favor these more moderate temperatures sticking around into Thursday. && .AVIATION...for 00Z TAF Issuance Issued at 506 PM CST Sat Dec 13 2025 Mainly VFR conditions through the TAF period thanks to a bitterly cold arctic airmass across the region. Light snow showers will be possible at times over northern Vilas and Door Counties that could produce MVFR ceilings and brief IFR to MVFR visibilities. In general, trended more optimistic with ceilings tonight due to the dry arctic airmass. W-NW winds of 10-15 knots with gusts of 20-25 knots will occur at times through the weekend. Low level wind shear will be possible late tonight into Sunday morning over parts of north-central and northeast WI that may impact RHI and GRB. && .GRB WATCHES/WARNINGS/ADVISORIES... Cold Weather Advisory until 6 AM CST Sunday for WIZ005-010>013- 021-073-074. Cold Weather Advisory until 10 AM CST Sunday for WIZ018>020-030- 031-035>040-045-048>050. && $$ DISCUSSION.....MPC AVIATION.......Kurimski ####018005749#### FXUS62 KMFL 132306 AFDMFL Area Forecast Discussion National Weather Service Miami FL 606 PM EST Sat Dec 13 2025 ...New AVIATION... .KEY MESSAGES... Updated at 604 PM EST Sat Dec 13 2025 - Showers and thunderstorms will spread from south to north tonight and early Sunday, with best chances of rain over metro SE Florida. Heavy rainfall and localized flooding is possible. - High risk of rip currents through late tonight for all Atlantic beaches. && .SHORT TERM... (Rest of today through Sunday) Issued at 1205 PM EST Sat Dec 13 2025 Very tricky rainfall forecast for tonight into Sunday across South FL. Low level moisture is expected to increase this evening as the flow becomes more E/SE and a weak low in the SE Gulf eventually moves over the far southern peninsula early Sunday, riding along a weak frontal boundary that will slowly lift north across Southern FL. At the upper levels, there is a deep trough that will dig through the eastern US with the trough axis expected to move across FL sometime late Sunday night. This will also help push a cold front through the area overnight Sunday into early Monday morning. Given the weak surface features involved, not a surprise that the hi- res guidance is all over the place regarding rainfall amounts over the next 24 hours. 25th percentile amounts are generally a couple tenths of an inch, where the 90th percentile precip amounts show pockets of 1-3 inches across the east coast metro. HREF PWAT values peak at 1.5-1.8 inches, with the highest PWAT values centered over far SE FL. Given the high end potential if all the ingredients come together, WPC has introduced a marginal risk of excessive rain across the east coast metro which is reasonable given that if the higher end numbers occur, there would be a limited urban flood threat across typical poor drainage locations. Bulk of the showers and thunderstorms should be tonight and into early Sunday across South FL, with diminishing PoPs as the day progresses on Sunday with the weak low moving off to the east. Residual low level moisture will keep a chance of scattered showers and thunderstorms in the forecast on Sunday until the cold front arrives late Sunday night. Temperatures this weekend will be slightly above normal with highs in the lower 80s. Low temps tonight will range from the lower 60s around the lake to upper 60s across the east coast metro. && .LONG TERM... (Sunday night through Friday) Issued at 300 AM EST Sat Dec 13 2025 Global solutions remain in good agreement in bringing sprawling high pressure across the region in the wake of a FROPA for much the work week. Robust northerly flow will bring colder/drier air advection across the Florida peninsula. Wind gusts could reach the 30 mph range along the Atlantic coast at times on Monday and Monday evening. POPs also drop back to single digits on Monday, although latest NBM insists in keeping just a sliver of slight chances of showers right along the Atlantic coast through the afternoon hours. Afterwards, the dry air makes a final push and brings POPs to near zero through the rest of the long term. Therefore, expect generally benign and pleasant weather to prevail through the rest of the forecast period. Coolest days should be Monday and Tuesday with afternoon highs in the mid-upper 70s. Coldest morning should happen Tuesday before sunrise, with lows dipping into the low-mid 50s around Glades and northern Hendry counties. Warming trend then follows on Wednesday with highs back into the upper 70s to low 80s. && .AVIATION... (00Z TAFS) Issued at 604 PM EST Sat Dec 13 2025 Light ESE winds 5-10 kts tonight. Scattered showers and thunderstorms expected overnight into early Sunday morning. Winds becoming WNW 10-15 kts Sunday morning through the remainder of the period. SCT to BKN MVFR ceilings expected overnight, with some IFR ceilings possible over APF early Sunday morning. && .MARINE... Issued at 300 AM EST Sat Dec 13 2025 Moderate easterly winds continue through tonight, then winds shift northerly and increasing behind a frontal passage. Conditions will likely reach advisory levels by Monday morning with the stronger winds. Meanwhile, conditions should remain fairly benign through the this afternoon, then showers and thunderstorms will begin increasing tonight and through Sunday. Brief periods of rough seas and gusty wind will accompany any thunderstorm that may form. && .BEACHES... Issued at 300 AM EST Sat Dec 13 2025 A High Risk of Rip Currents is in effect for all Atlantic beaches until later tonight. Another round high risk is likely early next week with the passage of another frontal system. && .PRELIMINARY POINT TEMPS/POPS... Miami 69 81 65 74 / 70 50 20 20 West Kendall 65 81 62 75 / 70 40 10 20 Opa-Locka 67 81 64 75 / 70 50 20 20 Homestead 67 81 64 75 / 70 50 20 20 Fort Lauderdale 68 80 66 73 / 70 50 20 20 N Ft Lauderdale 68 80 66 72 / 70 50 20 20 Pembroke Pines 67 81 64 75 / 70 50 20 20 West Palm Beach 67 81 65 72 / 60 50 20 20 Boca Raton 68 81 66 74 / 70 50 30 20 Naples 67 79 59 75 / 50 40 0 0 && .MFL WATCHES/WARNINGS/ADVISORIES... FL...High Rip Current Risk until 1 AM EST Sunday for FLZ168-172-173. AM...None. GM...None. && $$ SHORT TERM...CMF LONG TERM....17 AVIATION...CMF