Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 01/11/18

Area Forecast Discussion
National Weather Service Albany NY
946 PM EST Wed Jan 10 2018 .SYNOPSIS... An approaching warm front will bring some patchy light freezing rain tonight, mainly across the southern Adirondacks and Mohawk Valley region. A brief break in the precipitation is expected Thursday, before an approaching frontal system from the west brings periods of rain Thursday night into Friday. As colder air filters in from the north, rain will gradually change to sleet and freezing rain late Friday night into Saturday morning, before ending as some snow later Saturday. Cold and windy conditions will continue for Sunday. && .NEAR TERM /THROUGH THURSDAY/... As of 930 PM EST...Precipitation was fairly light moving through the Mohawk Valley where temperatures were hovering near the freezing mark. Mesonet observations were into the 20s across the Dacks and Glens Falls area, however, temperatures were holding nearly steady elsewhere. Additional showers were evolving around the SYR-UCA-RME-ART areas which will translate east the next couple of hours where a coating of ice is expected as wet bulb processes commence. Did redo the hourly temperatures a bit per the observations and latest HRRR/RAP 2m temperatures and dewpoints. Remainder of the forecast looks in good shape at this time as the 00Z guidance is arriving... Prev Disc... Mid and high level clouds will overspread the area late this afternoon and early this evening ahead of a band of isentropic lift associated with a warm front approaching from the west. Models including the latest HRRR are in good agreement that some light precipitation will break out along the warm front this evening over the Mohawk Valley and southern Adirondacks with precipitation amounts generally less than 0.10 inches. Temperatures will be tricky; we expect a few degree drop around sunset late this afternoon then temperatures will likely drop another degree or two with evaporational cooling with the onset of any precipitation later this evening. This should allow for temperatures to be near or just below freezing over the northern half of our forecast area when the precipitation is falling later this evening. The result will be a little freezing rain over the Mohawk Valley, upper Hudson Valley and southern Adirondacks this evening into the overnight hours with ice accumulations of less than a tenth of an inch. Even if temperatures nudge just above freezing overnight the very cold ground surface conditions could still allow for some glazing on untreated surfaces. Based on this we have gone with a winter weather advisory for a light coating of freezing rain in NY from the Mohawk Valley northward. Farther south and east any spotty light glazing should be covered by a special weather statement. The area from the Catskills east to NW Connecticut should remain dry tonight with wintry precipitation passing by to the north. Most of the precipitation will be north and east of the area by Thursday morning. Temperatures will climb to the warmest levels since before Christmas with many locations getting above 40 by afternoon, although cold air may hold tough for awhile north of the Capital District. && .SHORT TERM /THURSDAY NIGHT THROUGH SATURDAY/... A slow moving cold front will gradually approach from the Great Lakes region Thursday night into Friday. Increasing low/mid level moisture and convergence will promote an increasing chance for rain later Thursday night, with periods of rain expected Friday. Moisture should become plentiful, as a combination of low level Gulf and Atlantic inflow, some of which becomes entrained from the system off the Florida coast. Rain may become heavy at times, especially late Thursday night into Friday morning. A quick one half to one inch of rainfall is possible during this time. In addition, strengthening southeast to south winds will bring milder air into the region, especially across higher elevations. Expect high temperatures to reach the lower/mid 50s for many areas south and east of Albany, and upper 40s to lower 50s to the north and west, coolest within the Mohawk Valley region and possibly upper Hudson Valley. For Friday night into Saturday, the frontal system will slowly being to settle south and east. Models suggest that shallow arctic air seeps southward in valley areas first, before gradually deepening Saturday morning. In addition, another wave of low pressure will be tracking northward along the frontal boundary, triggering another surge of moderate to briefly heavy precipitation. Will have to watch this situation extremely closely, as there is an increasing potential for freezing rain for several hours across much of the Hudson River Valley north of Albany, into the Mohawk Valley region, and adjacent to the CT River in SE VT. In these areas, there is a possibility of one quarter of an inch or more of ice accretion before precipitation transitions to mainly sleet Saturday morning, and snow by early Saturday afternoon. Across southern areas, mainly rain is expected, although can not rule out a period of freezing rain/sleet before precipitation tapers off later Saturday morning or early Saturday afternoon. Temperatures should fall into the 20s for most areas near and north of the Mohawk River by daybreak Saturday, if not even colder, with 30s to lower 40s to the south. Temperatures should fall during Saturday into the teens and 20s by sunset. All areas may be susceptible to a flash freeze situation Saturday afternoon/evening, as any lingering unfrozen water on ground surfaces potentially quickly freezes with temps rapidly plunging into the teens/20s, if not lower in some areas. && .LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/... A return to colder temperatures for the remainder of the weekend in the wake of the storm as we return toward below normal temperatures once again. There will remain a couple of weak short wave troughs to migrate through the northeast with a slight chance for snow showers for the remainder of the weekend. A period of tranquil weather is in the forecast for later Sunday night into Monday as a narrow ridge of high pressure and short wave ridging returns for dry weather but still remain chilly as per the ensemble MOS shows little variability in the temperature forecast which keeps it cold with highs mainly into the teens and 20s throughout the region. Next PV Anomaly and mid level jet max approaches Monday night from the Ohio Valley into Tuesday where a period of light snow with weak isentropic lift along with a weak surface reflection developing along the I95 corridor or along the mid-Atlantic coastline. The ECMWF is the most aggressive while the GFS is the most progressive with minimal impacts. Temperatures through the period will average below normal throughout the county warning area. && .AVIATION /03Z THURSDAY THROUGH MONDAY/... CIGS are thickening and lowering, especially north of KPOU, as band of precipitation was approaching from the northern I81 corridor. Scattered light showers of rain or freezing rain are possible tonight after 00z at GFL/ALB/PSF as the warm front moves across the area, with cigs lowering to MVFR. Thursday will be dry but mostly cloudy with cigs mainly 3-5 kft. Winds will be mostly from the south at less than 10 kts today through tonight, then south-southwest at 5 to 10 kts on Thursday. LLWS will be an issue as we will continue to mention in the TAFs at this time for the tonight period. Outlook... Thursday Night: High Operational Impact. Definite RA. Friday: High Operational Impact. Definite RA. Friday Night: High Operational Impact. Definite RA...FZRA...SLEET. Saturday: High Operational Impact. Definite SN...FZRA...SLEET. Saturday Night: No Operational Impact. NO SIG WX. Sunday: No Operational Impact. NO SIG WX. Sunday Night: No Operational Impact. NO SIG WX. Martin Luther King Jr Day: No Operational Impact. NO SIG WX. && .HYDROLOGY... Based off temperature analysis, river and lake ice is estimated between 7 and 15 inches thick. As a storm system approaches from the west, some light freezing rain is expected tonight, although amounts will generally be light, mainly under a tenth of an inch of liquid equivalent. For Thursday into Friday, temperatures will rise above normal with periods of rain expected for Thursday night into Friday. The steadiest/heaviest precip is expected on Friday morning, where locally moderate to heavy rainfall is possible. Precipitation will continue into Friday night and Saturday morning, but should start to changeover to a wintry mix or snow from north to south before ending during the day Saturday. In total, about 1.50 to 2.50 inches of precipitation is expected across the area, with the heaviest amounts in southeastern areas. The combination of rainfall and snow melt due to the milder temperatures will allow for river and stream levels to increase. This increased flows should allow some river ice to break up and potentially lead to some ice jams and possible ice jam flooding. In addition, the heavy rainfall may lead to minor flooding of urban and low lying areas, especially where snow and ice block drainage. The MMEFS suggest that there even is the potential for some flooding on main stem rivers, depending on how warm temps get and just how much rainfall occurs. Based on these factors, a Flood Watch has been issued for all of eastern NY and adjacent western New England. Runoff should start to slow down during the day Saturday into Saturday night as temps quickly fall and precip ends. Colder and drier weather is expected for Sunday into early next week. For details on specific area rivers and lakes, including observed and forecast river stages and lake elevations, please visit the Advanced Hydrologic Prediction Service /AHPS/ graphs on our website. && .ALY WATCHES/WARNINGS/ADVISORIES... CT...Flood Watch from late Thursday night through Saturday afternoon for CTZ001-013. NY...Flood Watch from late Thursday night through Saturday afternoon for NYZ032-033-038>043-047>054-058>061-063>066- 082>084. Winter Weather Advisory until 7 AM EST Thursday for NYZ032-033- 038>043-048>050-082>084. MA...Flood Watch from late Thursday night through Saturday afternoon for MAZ001-025. VT...Flood Watch from late Thursday night through Saturday afternoon for VTZ013>015. && $$ SYNOPSIS...Frugis/KL NEAR TERM...MSE/BGM SHORT TERM...KL LONG TERM...BGM AVIATION...MSE/BGM HYDROLOGY...MSE/Frugis/KL
Area Forecast Discussion
National Weather Service Caribou ME
1039 PM EST Wed Jan 10 2018 .SYNOPSIS... High pressure will move east tonight. A warm front will slowly cross the region later Thursday into Thursday night. A strong cold front will cross the area Friday night through early Saturday with low pressure moving along the front Saturday. && .NEAR TERM /THROUGH THURSDAY/... 1030 PM Update... The latest radar loop showed some light precip moving into far northern and western areas. Most of this was aloft, but some of the higher returns edging into western Piscataquis County could be some light snow or sleet. Decided to adjust the timing of the light snow and mixed precip per the radar. NAM and RAP soundings as well as the KCAR sounding showed dry below 8k ft but the column is expected to thicken and lower overnight w/precip reaching the surface. Kept the Winter Weather Advisory going into Thursday morning w/the exception of the coast. Temps have leveled off and are beginning to rise and will continue to do so overnight into Thursday. A light icing threat is expected w/this first batch of light precip. Previous Discussion... Precipitation will break out after midnight. There is a strong punch of warm advection in the H850 to H700 layer which means sleet and freezing rain should be the dominant p-types rather than light snow. Most of the precipitation will end early Thursday morning and the amounts will be just a few hundredths of an inch. The timing affects the morning commute across the forecast area and will maintain the Winter Weather Advisory. Did not include the coastal zones as temperatures will be above freezing most of the night as southerly winds increase, but it`s still possible the light rain could freeze on cold surfaces further inland in these zones. Tonight`s lows will occur this evening...followed by steady to rising temperatures all night. Temperatures will continue to slowly rise all day tomorrow into the evening such that Thursday`s high will be at the end of the afternoon. Measurable precip will end Thursday morning, but the saturated low levels may generate some drizzle through the day as the frontal inversion and cloud bases lower. Temperatures will rise above freezing across the forecast area by late morning and creep towards the upper 30s and lower 40s by late afternoon. As dew points rise above the freezing mark in the afternoon, fog will develop and likely thicken by sunset. A Dense Fog Advisory will be a consideration by evening. && .SHORT TERM /THURSDAY NIGHT THROUGH SATURDAY/... A return flow of warmer air will persist across the region Thursday night in advance of an approaching cold front. Temperatures will be near steady or slowly rise Thursday night. Rain chances will begin to increase later Thursday night. The cold front will approach northwest Maine later Friday. A disturbance will also lift across the region Friday with an area of rain. The cold front will begin to cross the region Friday night, though how rapidly this occurs is still uncertain. Rain will persist in advance of the cold front. However, temperatures will rapidly fall in the wake of the cold front. Precipitation will transition to a wintry mix across much of the forecast area inland from the coast Friday night, with mostly snow across northwest areas late Friday night. The transition to a wintry mix should reach interior Downeast areas late Friday night. The cold front will move offshore Saturday while an area of low pressure moves along the front with another area of precipitation. Precipitation will transition increasingly toward snow across northern areas Saturday with accumulations of snow, sleet and ice expected. The transition to a wintry mix will reach the coast early Saturday. A wintry mix of sleet, freezing rain and snow is then expected to persist Downeast through the remainder of the morning and afternoon. Uncertainty still exists regarding exact precipitation amounts and types later Friday night into Saturday. High temperatures will occur early Saturday then fall through the afternoon. With warm moist air across the snowpack, areas of fog will also develop Thursday night then persist into Friday night in advance of the cold front. && .LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/... The low will exit across the maritimes Saturday night with decreasing snow chances north and decreasing mixed precipitation chances Downeast. High pressure will build toward the region Sunday with decreasing clouds, along with a chance of snow showers across mostly the north and mountains. High pressure then builds across the region Monday with partly sunny skies. Low pressure could approach from the west later Tuesday with increasing clouds and a chance of snow late. The low should then track south of the region Wednesday with a chance of snow or snow showers, particularly Downeast. Temperatures should be at near normal levels Sunday, with below normal level temperatures expected Monday through Wednesday. && .AVIATION /03Z THURSDAY THROUGH MONDAY/... NEAR TERM: VFR conditions will prevail through this evening with the possible exception of BHB where some MVFR cigs are expected. LLWS will develop tonight. Late tonight, all terminals will become MVFR due to cigs and vis in freezing rain/drizzle. The freezing rain and drizzle will end Thursday morning across the area, but IFR cigs will take its place. VLIFR cigs are possible by late afternoon with drizzle. SHORT TERM: IFR/LIFR, with occasional VLIFR, conditions are expected Thursday night into Saturday. MVFR/IFR conditions are expected Saturday night. Occasional MVFR conditions are expected across the region Sunday, particularly across the north and mountains. VFR conditions are expected across the region Monday. Precipitation will be in the form of rain Thursday night into Friday. A wintry mix will then begin to transition to snow across northern areas Friday night, with a wintry mix starting to develop late Downeast. Snow or a wintry mix is expected across northern areas Saturday, with a wintry mix Downeast. Fog will also be a concern Thursday night into early Saturday. && .MARINE... NEAR TERM: Will extend the SCA through Thursday night. Have some concerns about near gale conditions tonight, but will reference a few gusts to 35 kts for tonight and early Thursday morning rather than upgrading the headline. There is decent mixing over the waters until Thursday afternoon when the stability sets in and fog begins to materialize. SHORT TERM: Gale conditions are possible Friday. Otherwise, small craft advisory conditions are expected Thursday night then again Friday night/Saturday. Visibilities will be reduced in rain and fog Thursday night through early Saturday, with a wintry mix expected later Saturday. && .CAR WATCHES/WARNINGS/ADVISORIES... ME...Winter Weather Advisory until noon EST Thursday for MEZ001>006- 010-011-015>017-031-032. MARINE...Small Craft Advisory until 7 AM EST Friday for ANZ050>052. && $$ Near Term...Hewitt
Area Forecast Discussion
National Weather Service Charleston SC
1006 PM EST Wed Jan 10 2018 .SYNOPSIS... A coastal trough will shift inland tonight and Thursday. A cold front will move through Friday afternoon and evening, followed by a secondary front Saturday night. Cool high pressure will settle over the area Sunday through much of next week. && .NEAR TERM /UNTIL 6 AM THURSDAY MORNING/... Opted to nudge overnight temperatures up a degree or two for most areas per going trends. The rest of the forecast is on track. Weak isentropic lift is occurring across the offshore coastal trough and atop the inland high pressure wedge this evening. This is supporting some very light showers and patchy drizzle for some spots. The strongest lift is currently situated off the Florida east coast where more substantial shower activity is occurring. The northern fringe of this area of lift will move into Southeast Georgia overnight bringing a slightly better chance for measurable rainfall. Readjusted the axis of highest pops (up to 40%) into Southeast Georgia for this reason. The risk for some patchy fog and drizzle will continue through the night, but dense fog appears unlikely. Lows from the mid 50s north to upper 50s south look on track. && .SHORT TERM /6 AM THURSDAY MORNING THROUGH SATURDAY/... High pressure will linger east of the Northeast states on Thursday. Meanwhile, a closed upper low over eastern Florida will lift northwest as it merges with an approaching longwave trough. As a result, the coastal trough over our waters will shift inland late Thursday morning. Moist, isentropic ascent will overspread the forecast area from the southeast during the day. The strongest forcing and moisture advection will be over inland SC/GA on Thursday, shifting into interior SC late Thursday afternoon through Thursday night. This is where we have the highest PoPs. Despite extensive cloud cover throughout the day, strong low-level warm advection is expected to push Thursday high temperatures into the low 70s. Fog is expected Thursday night, likely due to stratus build-down. The upper longwave trough will weaken and lift northeast as it approaches the Eastern U.S. on Friday. An associated surface low will shift into western NC while a cold front approaches the local area. With surface temps rising into the mid 70s and dewpoints in the mid 60s, model data indicates the potential for marginal surface-based CAPE during the afternoon. Fairly widespread showers expected to move in during the afternoon, sweeping through the area Friday evening. We maintained mention of a slight chance for thunderstorms as well. Cold, dry air advection will occur Friday night into Saturday. Highs on Saturday will be considerably cooler than Friday in the 50s. && .LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/... Models are in fairly good agreement in the long term period. High pressure will build into the region on Sunday and persist into early next week. A weak cold front could cross the area on Tuesday. Overall, the period looks to be dry with temperatures a bit cooler than normal. && .AVIATION /03Z THURSDAY THROUGH MONDAY/... Primary concern: * cigs Similar to last night, it appears guidance is being too aggressive in the development of widespread IFR and LIFR cigs tonight. Generally favored the RAP soundings, which keep the axis of deeper moisture situated across Southeast Georgia through daybreak. Will show low-end VFR cigs prevailing at KCHS with just a TEMPO group for MVFR cigs roughly 11-14z. At KSAV, the risk for sub-VFR cigs will be higher. Will show prevailing MVFR through about 10z with MVFR cigs prevailing 10-14z with a return to VFR thereafter. Could see a brief period of IFR just before sunrise, so a TEMPO group will be included for high-end IFR cigs (but above alternate minimums) 11-14z. Extended Aviation Outlook: Flight restrictions likely Thursday through Saturday morning due to low ceilings and restricted visibilities. && .MARINE... Tonight: Winds will remain elevated a tad given the pressure gradient between high pressure to the north and weak low pressure to the south. Seas have been running a bit above guidance and so we have raised Advisories for the southern SC waters and northern GA waters as a result of 6+ ft seas, mainly comprised of swells. Thursday through Monday: Persistent southeast winds on Thursday will weaken slightly as directions turn to the south and the coastal trough shifts inland. However, strengthening southerly winds expected on Friday ahead of a cold front. Winds will turn offshore late Friday night but remain fairly strong into Saturday as cold air advection occurs over the waters and high pressure builds in. Small Craft Advisories continue for all waters except Charleston Harbor into Thursday night, then linger for the Charleston County near shore waters and GA offshore waters through much of Saturday due to higher seas. All waters expected to be advisory-free by Saturday night. High pressure will build into the region the remainder of the weekend and persist into early next week. Sea fog: Conditions will become favorable for sea fog as a warm and moist airmass develops over the abnormally cold shelf waters. Sea fog could develop as early as late tonight and then persist into Friday. Marine Dense Fog Advisories may eventually be needed. && .CHS WATCHES/WARNINGS/ADVISORIES... GA...None. SC...None. MARINE...Small Craft Advisory until midnight EST Thursday night for AMZ352. Small Craft Advisory until 7 PM EST Saturday for AMZ374. Small Craft Advisory until 4 PM EST Saturday for AMZ350. Small Craft Advisory until 4 PM EST Thursday for AMZ354. && $$
Area Forecast Discussion
National Weather Service State College PA
1007 PM EST Wed Jan 10 2018 .SYNOPSIS... High pressure will drift east and off the New England coast overnight. A frontal system will approach by Friday and move through the region early Saturday. Very cold air will return to the area for the weekend lasting into at least the beginning of next week. && .NEAR TERM /UNTIL 6 AM THURSDAY MORNING/... The HRRR shows just the chance of a light shower or some drizzle over the north, mainly later tonight through sunrise, with the remainder of the CWA staying dry under slowly increasing clouds. Some breaks in the clouds over the eastern half of the CWA, and winds becoming generally light from the south or SE tonight will allow temps to dip to around freezing for a low. Across the higher terrain of NW PA and the Laurels, a light to moderate southerly breeze should combine with the clouds to keep temps several degrees warmer than our eastern zones. && .SHORT TERM /6 AM THURSDAY MORNING THROUGH 6 PM THURSDAY/... a better surge of moisture and rapidly deepening cloud deck pushes NE into the region later Thurs afternoon and evening. Will maintain POPs AOB 30 pct for the most part during the day Thursday, with the best chance for a few hundredths of an inch of light rain occurring near and to the North and West of KBFD. Temps should rise nicely under the influence of south to SE flow and strengthening low to mid level WAA. The cooler air near the surface air may be tough to get rid of (especially in the eastern valleys). However, 925mb temps do climb to near +10C. So, we need to keep a sharp eye out for any periods of enhanced vertical mixing, which would lead to a big bust (being too cool) on temps. Max temps are predominately in the mid to upper 40s, though the higher terrain near and to the west of route 219 could see the mercury jump at least into the low 50s. && .LONG TERM /THURSDAY NIGHT THROUGH WEDNESDAY/... *Localized risk for poor drainage and ice jam flooding into the weekend *Late-week storm to bring mixed precipitation with heavy snow/significant ice threat focused over NW Pennsylvania *New shot of arctic air behind the late week storm will support below normal temperatures into early next week Ensemble guidance shows H5 heights building over much of the Eastern U.S supporting January thaw/mild spell through Friday. Southern stream shortwave emerging from split-flow trough over the Central U.S. will lead to surface low development over the southern Plains into the Lower MS Valley on Thursday. This low and attendant frontal system will strengthen as it lifts northeastward along/east of the Appalachians across the northern Mid-Atlantic states to the New England coast Friday and Saturday. By the end of the weekend, troughing will once again be established across the Eastern U.S. with shot of arctic air supporting below average temperatures into early next week. Winter weather details associated with the late week storm system are starting to come into focus. Issued winter storm watch for Warren and McKean Counties given increasing risk for significant/heavy snow and ice Friday night into Saturday. Thermal profiles will be the key to the forecast concerning ptypes which will dictate how much snow/ice falls. Arctic air will continue to wrap southeast and undercut the warm layer aloft, which will foster precipitation northwest of the low track to transition from rain to freezing rain, then to a period of sleet and ultimately snow as the cold air deepens through the column. Anticipate a ptype transition to progress southeast with time with a period of ice then snow advancing to the I-81 corridor by Saturday afternoon. Temperatures should drop below freezing rather quickly which raises the concern for rapid freeze-ups on untreated surfaces. Minimum wind chills will drop into the positive and negative single digits Saturday night into Sunday. A drastic temperature swing is expected with temperatures falling 40-50 degrees between Friday`s highs and Sunday night`s lows. Cold but tranquil weather to start next week with some light snow possible into Tuesday with weak clipper type system. && .AVIATION /03Z THURSDAY THROUGH MONDAY/... A bkn-ovc shield of VFR to MVFR Stratocu (topped by some alto cu) will continue to drift east acrs the commonwealth overnight. MVFR will continue at BFD overnight. Overall, looking at mainly dry conditions. Perhaps some patchy light drizzle tonight and thursday...mainly across the northern and western mtns of the state. LLWS was included at KBFD late tonight through at least 18Z Thursday as the eastern edge of a swrly Low-Level jet of 40-45 kts moves over NW PA. As moisture drifts from the southeast, conditions will continue to degrade late Thursday afternoon and through Thursday evening. This will drop cigs and vsbys from the Southeastern TAF sites and spreading westward. This will bring MVFR to IFR cigs and vsbys Thursday night into tomorrow. Outlook... Thu night...Period of rain/low cigs likely. Fri...Periods of rain/low cigs possible. A change to freezing rain or sleet is likely across the NW Mtns of PA late Friday, then Sleet and Snow Friday night. Sat...Rain/low cigs possible across the Susq Valley. Mixed precip or snow (with IFR to LIFR Cigs and Vsbys) tapering off by the early afternoon. Sat night and Sunday...Windy and much colder with areas of IFR cigs and vsbys in frequent snow showers across the NW mtns and Laurel Highlands (KJST to KBFD), and more brief IFR to MVFR in isolated to sctd snow showers elsewhere. Monday...VFR with morning sunshine followed by increasing afternoon clouds. && .HYDROLOGY... A brief January thaw with mild temperatures is expected through Friday. Despite low streamflow levels, the warm surge combined with melting snow and periods of rain will support a localized risk for poor drainage and ice jam flooding through the weekend. Another shot of arctic air with very cold temperatures may reinforce ice jams into early next week. && .CTP WATCHES/WARNINGS/ADVISORIES... Winter Storm Watch from Friday afternoon through Saturday afternoon for PAZ004-005. && $$ SYNOPSIS...La Corte NEAR TERM...La Corte SHORT TERM...Dangelo LONG TERM...Steinbugl AVIATION...Lambert/Ceru HYDROLOGY...
Area Forecast Discussion
National Weather Service Des Moines IA
943 PM CST Wed Jan 10 2018 .UPDATE... Issued at 937 PM CST Wed Jan 10 2018 Have adjusted max snow axis and made some minor headline changes to account for persistent south and east shift in heavy snow axis as depicted by 18z and new 00z guidance. Confidence remains low however even as the event nears with a fairly wide range in model spread. The latest NMM core suite of the NAM, NAMNest and HRW- NMM are all fairly similar placing the max axis along a Greenfield/Boone/Charles City line. However the unsettling 02z RAP and HRRR runs are even more aggressive than that, going to the southeast Des moines metro with the axis. Thus the evening update is hopefully headed in the right direction with a few warning counties added to better fit the 4 inch snow amount as mentioned below and attempt to blend into adjacent offices for a consistent WWA map. Although amounts have dimnished on the NW side of the warning, 2 to 4 inch amounts may still occur with considerable blowing and drifting and significant travel impacts. Further changes in amounts and headlines with the midnight packages may very well occur too, hopefully with better model consensus. && .SHORT TERM.../Tonight through Thursday/ Issued at 410 PM CST Wed Jan 10 2018 The primary forecast challenge remains the winter storm that will impact the area late tonight into Thursday. Areas of fog will continue over northern Iowa through this evening with then the lowest visibilities due to fog will be situated just ahead of the surface cold front as it moves southeast into Iowa. Visibilities may drop near to below one quarter mile at times. As of now, an SPS likely will be able to handle the situation if visibilities do drop. An area of low pressure continues to organize and deepen over southeast Colorado this afternoon as a vigorous short wave/PV anomaly moves across Arizona and New Mexico. This system will eject northeast tonight through Texas and Oklahoma and be over eastern Kansas by 12z Thursday. A surface low pressure will accompany the system as it lifts north through eastern Iowa. A deformation band of snow will develop along the western edge of the low pressure track late tonight into Thursday morning. This deformation band will have strong forcing through the dendritic layer with higher snow ratios of 12-15 to 1 expected and snowfall rates exceeding 1 inch per hour at times. Expecting a band of 4 to 6 inches of snow, which could potentially become higher should the deformation band maintain a steady position. General trends continues to be a more easterly from near Mason City southwest through Audubon. In addition, a strong push of Arctic air will arrive as a cold front sweeps through the state. This boundary will bring strong northwest winds of 20 to 30 mph with gusts approaching 35 to 40 mph. A strong inversion above 900 mb will limit the overall mixing potential with peak mixed layer winds in the low to mid 30s kts. The strong cold advection will enhance the momentum transfer of winds so much of this should be realized at the surface. A brief period of stronger pressure gradient and higher pressure rises will move east through Iowa between 09-18z and may enhance winds further. At this time, expect significant blowing and drifting of snow that may create significant travel impact but conditions should remain below blizzard criteria. Have upgraded a large portion of the watch to Winter Storm warning based on expected impacts and generally outlined an area with 4+ inches of snow combined with the winds. The snow will diminish during the afternoon though low level temperatures will drop within the dendritic layer by the afternoon and may keep light snow going. Finally, warm temperatures in the 30s to 40s ahead of the precipitation may cause wet conditions initially as precipitation begins as rain or a wintry mix before transitioning to snow in addition to snow melting until pavement temperatures lower. The arrival of the Arctic air with temperatures falling into the teens by mid morning will cause flash freezing of any wet surfaces and may cause very icy conditions. Due to the flash freeze potential and expected wintry mix over central Iowa, have added a Winter Weather Advisory along the southeast periphery of the warning. An additional expansion to the southeast maybe required should an icing potential develop. Finally, wind chills will fall to near 20 below zero over northern Iowa by the afternoon then expand south to near Highway 30 overnight. Likely will need wind chill headlines once the current headlines expire. .LONG TERM.../Thursday night through Wednesday/ Issued at 410 PM CST Wed Jan 10 2018 Cold temperatures will persist through much of the forecast period as strong northerly flow continues through at least Tuesday. This will lead to several periods with wind chills dropping to 20 below zero or less each night. Two strong short waves to watch arrive Friday night and Sunday afternoon and night. Light snow is possible with the Friday night system and at this time looks to have minimal impact. The Sunday/Sunday night system may have a bigger impact as a stronger system arrives. This system will feature a deep dendritic layer from near the surface to around 13 kft. This system may produce a widespread 1 to 3 inches of snow. In addition gusty northwest winds may produce additional impacts. && .AVIATION.../For the 00Z TAFS through 00Z Thursday evening/ Issued at 554 PM CST Wed Jan 10 2018 VFR conditions had lifted northward to essentially Interstate 80 by 00z but MVFR to LIFR conditions persisted farther north. These conditions are expected to changed little through the evening but IFR/LIFR conditions will become more widespread to the south and east as a cold front begins moving through the state and precipitation begins. The precipitation should initially be rain but transition to a FRZA/PL mix before switching to all snow area wide into midday. This will be followed by gusty NW winds to 25-35kts and considerable blowing snow in areas with appreciable accumulations. At least MVFR conditions due to ceilings and/or blowing snow should persist through 00z. && .DMX WATCHES/WARNINGS/ADVISORIES... Winter Weather Advisory from 6 AM to 6 PM CST Thursday for IAZ027-028-038-039-048-049-059>061-071>074-081>084-092>095. Winter Storm Warning from 3 AM to 6 PM CST Thursday for IAZ005>007-015>017-023>026-033>037-044>047-057-058-070. Winter Weather Advisory from 3 AM to 6 PM CST Thursday for IAZ004. && $$ UPDATE...Small SHORT TERM...Donavon LONG TERM...Donavon AVIATION...Small
Area Forecast Discussion
National Weather Service Grand Forks ND
709 PM CST Wed Jan 10 2018 .UPDATE... Issued at 705 PM CST Wed Jan 10 2018 Forecast on track so no changes. Continue to monitor short term trends. Heaviest snow area Grand Forks to Bismarck via radars...and moving NE. Within this band snowfall rates 1/2 to 1 inch per hour. But with winds, so difficult to measure. Highest winds in the RRV as anticpated as there is a favorable 340-350 degree wind. Gusts to 35-40 kts at GFK for the highest. DVL basin not as bad and thus vsbys more like 3/4 to 1SM vs the 1/4 at GFK and CKN. So overall the blizzard vs warning area working out well. As we go thru the evening issue will be snow into NW MN (esp TVF) where advisories are out and possiblity exists for 6 inches of snow (on high end) and need to upgrade to warning. Right now though the latest HRRR indicates a general snowfall in NW MN with not quite as high rates but close call to warning criteria. Also Fargo area Snow moving in and winds there gusty as well...will see how things evolve to see if upgrade to Blizzard is needed there. && .SHORT TERM...(This evening through Thursday) Issued at 340 PM CST Wed Jan 10 2018 Confidence in snowfall totals, wind speeds, and winter weather impacts has increased enough to have a pretty good idea of what is going to happen. Current conditions indicate a band of snowfall from central North Dakota extending into the northern Red River Valley related to mesoscale forcing being aided by synoptic scale forcing. Latest CAM/High Resolution guidance indicates QPF totals within this band of 0.40 to 0.60 inches, which would lead to an area of 5 to 8 inches of snow (given stronger winds snow ratios should be toward the lower end of the spectrum). Given the forcing mechanisms involved, trust these models and will increase snowfall totals into this range (expanded the winter storm warning westward). Will need to monitor observations and incoming guidance for the eastern extent of this heavier snowfall. The strongest synoptic forcing will move through the region by this evening which will then spread lighter QPF into the SE ND and west central MN, although snowfall amounts will be less compared to the northern areas. Winds and blowing snow the other concern. Issued a blizzard warning for the area that will experience the strongest winds and heaviest snowfall (central/northern Red River Valley). Before the snow started the current winds were already causing patchy areas of 1/4 mile visibility. The coverage of these conditions has deteriorated as the snow has begun to fall. As the snow continues to accumulate, expect these conditions to further deteriorate. Wind speeds expected to be 25-30mph with gusts to 35-40mph, which will likely mean more of an open country type blizzard. Will need to monitor other areas, but thinking is that either wind speeds or snowfall amounts will limit the blowing snow impacts to near blizzard conditions in open country (areas that are currently winter storm warning). Conditions will improve after sunrise tomorrow. .LONG TERM...(Thursday night through Wednesday) Issued at 340 PM CST Wed Jan 10 2018 In the wake of the mid week snow and wind event, Arctic air will continue to build into the Northern Plains. High pressure overhead Fri night will offer optimum radiative cooling conditions and resultant low temps colder than 20 below throughout the forecast area. This will bring apparent temps close to 40 below even as wind speeds remain at 5 mph or lower. Some warm air advection Sun will allow for daytime highs edging over the zero degree mark as a trough swings down within the NW flow aloft. Then back to frigid weather and more dangerous apparent temp values for Sun night through Mon night. Two systems with migrate through the NW flow through the weekend. The first round is slated for Fri and a southerly track is First still favored as guidance products converge to this solution. This will be followed by a second instance of potential snowfall for Sun, associated with the previously mentioned upper trough and modest warm air advection. Light accumulations would be the most likely result. By Wed western ridging will edge closer to our area, bumping temps up toward or beyond seasonal expectations. && .AVIATION...(For the 00Z TAFS through 00Z Thursday evening) Issued at 705 PM CST Wed Jan 10 2018 For most areas IFR conditions thru the night, worst at GFK, as snow system moves through. IFR either with vsby or ceilings. Conditions will improve gradually Thursday daytime. Gusty north winds 20-35 kts, highest in the RRV. && .FGF WATCHES/WARNINGS/ADVISORIES... ND...Winter Storm Warning until 9 AM CST Thursday for NDZ007-014-015- 024-026-028-038-039-049-052>054. Blizzard Warning until 9 AM CST Thursday for NDZ008-016-027-029- 030. Winter Weather Advisory until 9 AM CST Thursday for NDZ006. MN...Winter Storm Warning until 9 AM CST Thursday for MNZ003-029. Winter Weather Advisory until noon CST Thursday for MNZ005-006- 008-009-013>017-022>024-027-028-030>032-040. Blizzard Warning until 9 AM CST Thursday for MNZ001-002-004-007. && $$ UPDATE...Riddle SHORT TERM...TG LONG TERM...WJB AVIATION...Riddle
Area Forecast Discussion...UPDATED
National Weather Service Fort Worth TX
638 PM CST Wed Jan 10 2018 .AVIATION... /00Z TAFs/ Several forecast challenges this cycle, with the immediate issue being the resumption of MVFR/IFR conditions at the TAF sites this evening/overnight. A large swath of MVFR ceilings currently extends from the Bonham/Paris area southward to Corsicana and Palestine. Scattered elements of this cloudiness already encompass part of the Metroplex, and expect MVFR conditions to redevelop in the 03-05z timeframe as low level moisture advection and isentropic lift proceed. Went ahead and included a period of IFR ceilings at KDAL and KACT from around 09-15z, closer to the deeper moisture feed that will exist across central and eastern Texas by daybreak Thursday. In keeping with the latest HRRR and SREF solutions, believe there`ll be a marked east-west gradient of low cloudiness overnight. I was not confident about including any IFR conditions from KDFW/KGKY westward. As surface low pressure intensifies across the Texas Panhandle overnight, south winds of at least 15 knots (and perhaps higher) will persist across North and Central Texas. Stayed pretty close to the latest HRRR/3km NAM guidance on the timing of Thursday`s frontal passage, with 16-17z being the estimated time period for FROPA in the Metroplex. The wind shift at KACT should occur around 18z. Winds at all locations will veer to a southwesterly direction for a few hours Thursday morning prior to FROPA, with a sharp swing to the northwest at speeds of 25 knots once the front passes. We could briefly see some crosswind issues at KDFW in the 17-20z timeframe if post-frontal winds jump up in speed yet don`t veer as much as expected. By mid-afternoon, wind direction should be in the 320-330 degree range, which should preclude significant crosswind problems. Still see a relatively brief, yet robust period of mid-level lift associated with the strong shortwave that will be transiting the region tomorrow afternoon. This in turns still suggests the possibility of some brief scattered snow showers, or a mix of sleet and snow, across the far northwestern and northern counties of Texas Thursday afternoon. While it`s not out of the realm of possibility that a few flakes or sleet pellets could reach the I-20 corridor and the Metroplex TAF sites, confidence is not high enough at this time to include a mention of these precipitation types in the 00z TAFs. This will need to be monitored closely for possibly inclusion with later packages, however. Steady improvement in ceilings should occur from west to east across the region after 23z Thursday, with some VFR conditions likely developing area-wide by the evening hours. North winds will remain quite strong, however, averaging 20-30 knots with higher gusts. Bradshaw && .SHORT TERM... /Issued 340 PM CST Wed Jan 10 2018/ /Tonight through Thursday Night/ An upper level trough located to our west will swing through the Southern Plains tonight through Thursday night bringing notable weather changes to the region. The surface low currently in southeastern Colorado will move southeast overnight, and this will maintain breezy south winds tonight. With the aid of the breezy south winds, low level moisture will continue to increase, especially across the eastern half of the region. In these areas, dense cloud cover will prevail and temperatures are expected to remain nearly steady and/or rise some overnight. Across our western counties, where clearer skies are expected, temperatures will fall into the mid and upper 40s. As the lead impulse within the upper level trough moves northwest of the region this evening, some light rain may occur in our far northwestern counties. In addition, with the help of warm air advection overnight, some patchy drizzle may occur east of Interstate 35/35E after midnight. With the breezy winds, do not think there will be much of a fog potential, but light fog may occur east of Interstate 35/35E where better moisture advection is expected, and in particular where drizzle/mist may be observed. The lead disturbance within the trough will move north of the region by daybreak, with a secondary disturbance dropping across the state during the day Thursday. A strong cold front will enter our CWA from the northwest in the morning hours and proceed southeast through the day, exiting the region by mid afternoon. Falling temperatures and very strong winds are expected behind the front. Sustained winds of 20-30 mph, possibly higher in some places, with wind gusts up to 40-45 mph will occur behind the front. Have hoisted a Wind Advisory for all but our southeastern counties from 9 AM-Midnight. This advisory could have been piece- mealed with various start times as the front progresses through the area, but the main message is it will be very windy tomorrow, on top of turning much colder! The cold and blustery conditions on Thursday and Thursday night will be the main highlight for all of North and Central Texas, but many people are likely more excited for the wintry mix potential. I`ll start out by saying any accumulations are expected to be very minor with very little, IF ANY, in the way of travel impacts. However, temperatures behind the front will likely fall into the lower 30s Thursday afternoon north and northwest of the DFW Metroplex, and this is where there could be minor accumulations and impacts. It is possible the howling winds may cool elevated and exposed surfaces enough for some slick spots on roads the area northwest to north of the DFW Metroplex. An in depth analysis of soundings, frontogenesis, lift, humidity, instability and more continue to suggest the most likely location of wintry precipitation is northwest of the DFW Metroplex. However, based on the latest data, I did expand the mention of a sleet and snow mix to north of a Goldthwaite to Hillsboro to Athens line, and also extended the mention into the evening hours. The sleet mention was retained during the afternoon hours before the column cools completely below zero supporting a transition to all snow, but surface temperatures will likely still be above freezing and most of this sleet should melt. Whether the frozen precipitation occurs in small bands, or as a larger coverage area, we may not know until the event unfolds, but this is a fast moving system, and we do not expect the sleet/snow to last more than a few hours at any one particular location. Where surface temperatures remain above freezing, most of the frozen precipitation will melt, but the strong winds may also have a factor in potential minor accumulations. Again, we do not expect significant impacts from this event! Thursday night will be a cold and breezy night with low temperatures in the 20s. Wind chill values will be in the teens Friday morning. If anyone wants to wrap outside pipes, today or tomorrow before the front is the best time to complete that task. JLDunn && .LONG TERM... /Issued 340 PM CST Wed Jan 10 2018/ Fairly tricky forecast in today`s extended periods, with dry and cool weather occurring first, followed by additional changes next week. Friday through Sunday, the weather will be relatively quiet. Temperatures will be below normal, as highs will remain in the 40s during the afternoon hours, while overnight lows will also be below normal. However, the weekend is expected to remain dry. By Monday, the moisture will be slowly creeping back into north and Central Texas, and rain chances return to the forecast late Monday and into Tuesday morning. During nearly any other time of year, this would be your typical 20-30% chance of rain. However, with temperatures dropping near and below 32 degrees, this does introduce the changes for a few hours worth of light rain or light freezing rain during the overnight hours. The chances for rain remain Monday night and Tuesday, and return again on Wednesday. The mid week precipitation chances are far from certain, however. The ECMWF is suggesting a slightly stronger short wave trough moving across North Texas on Wednesday than the GFS. While the deterministic GFS remains dry, about half of the GFS ensemble members suggest some sort of precipitation during the middle of next week. Have therefore kept at least a slight chance of rain mentioned for Tuesday/Wednesday. Expect this to change somewhat as the details get ironed out over the next few days. Fox && .PRELIMINARY POINT TEMPS/POPS... Dallas-Ft. Worth 54 54 28 45 27 / 10 30 30 0 0 Waco 55 58 28 50 28 / 10 10 10 0 0 Paris 52 59 23 43 25 / 10 30 20 5 0 Denton 51 52 24 45 25 / 10 30 30 0 0 McKinney 52 56 25 44 25 / 10 30 30 0 0 Dallas 54 56 27 46 27 / 10 20 30 0 0 Terrell 54 60 26 45 25 / 10 20 20 0 0 Corsicana 54 61 27 45 27 / 10 20 10 0 0 Temple 55 60 29 51 29 / 10 10 5 0 0 Mineral Wells 47 47 25 48 24 / 10 30 20 0 0 && .FWD WATCHES/WARNINGS/ADVISORIES... Wind Advisory from 9 AM Thursday to midnight CST Thursday night for TXZ091>095-100>107-115>123-129>135-141>146-156>159. && $$
Area Forecast Discussion
National Weather Service Grand Rapids MI
937 PM EST Wed Jan 10 2018 LATEST UPDATE... Update .SYNOPSIS... Issued at 330 PM EST Wed Jan 10 2018 Warmer air surging into the area over the snowpack will continue to create areas of fog into Thursday. The fog may become dense in some locations late today and tonight. Drizzle will also persist through the night, while temperatures rise. Breezy and very warm conditions are expected on Thursday, with high temperatures reaching into the 50s. Rain is also likely ahead of a cold front. The front will then push through the area Thursday night, changing rain to snow. Accumulations Thursday night into Friday are expected to remain less than an inch. && .UPDATE... Issued at 937 PM EST Wed Jan 10 2018 I made two changes to our ongoing forecast. I have expunged the eastern 2/3rd of our fog advisory on a diagonal from near Kalamazoo to Evart. I also increased our forecast high to the mid to upper 50s based on how our current temperature has already reached the upper 40s at GRR and that matches the ECE mos with gives GRR a high of 59 Thursday. As for the fog advisory, both the HRRR and RAP model visibility forecast and CONSHORT in GFE show the area of lowest visibilities lifting north with time through midnight, then after midnight is seems a marine layer seems to come in and lower temperatures so an area west of a line from Kalamazoo to Evart have air temperatures in the lower to mid 40s while area east of that after midnight are in the mid 50s! So, since those models are doing nicely now, I am assuming that they will continue to do well. This would lead to fog reformation. Which is why I am holding onto the fog advisory. It should be pointed out that the HRRR does have air temperatures in the mid to upper 50s east of US-131 Thursday afternoon. This is also supported by my 1000/925 mb thickness tool temperature forecasts. Bottom line is most of the snow on the ground, over most of our CWA will be gone by Thursday evening. Areas close to Lake Michigan, where it does not get quiet so warm Thursday and there was more snowfall in the first place, some of the snow is likely to remain on the ground there. && .SHORT TERM...(This evening through Friday night) Issued at 245 PM EST Wed Jan 10 2018 Deep southerly flow stretching from the Gulf of Mexico through the Great Lakes will persist through Thursday in advance of an amplified upper trough that spans much of central North America. This will keep us in a persistent pattern of warm air advection dominated by drizzle, fog, and mild temperatures. Freezing temperatures are not expected until Thursday night, and no further ice development is expected on roads. Main concern will be visibilities as 40+ degree dewpoints over extreme southwest Michigan and Indiana seep further north tonight and Thursday. The high dewpoint/warmer air flowing over the snowpack and frozen ground may create areas of dense fog later today and tonight, and cannot rule out an advisory being needed. Temperatures are expected to warm through the night, with areas of drizzle persisting. Better surge of moisture (PW values reaching near an inch) will occur tomorrow ahead of a cold front and as the upper trough moves closer. Breezy conditions and a weaker inversion should allow some more warmer air moving in aloft to be realized, even with the snowpack, and expect to see temperatures rise into the low/mid 50s. Best chance for rain showers tomorrow will be during the afternoon and through the evening in advance of the cold front. Model cross-sections are indicating a little convective instability, but lapse rates do not look too strong on forecast soundings, so left thunder mention out of the forecast. Cannot rule out an isolated rumble of thunder however ahead of or along frontal passage. Cold front will sweep through during the very late evening and early overnight hours, allowing rain to change to snow. There is a small chance for a brief changeover to freezing rain, but impacts should be mitigated by wet and warm roads. Snow accumulations behind the front look to be less than an inch before drier air arrives and sweeps the DGZ of ice crystals. Colder temperatures are expected Friday/Friday night. Northerly flow looks to limit coverage of lake effect snow, while inversion heights around H850 and lake-H850 temperature differences remain in the teens. This should keep any snow that does fall along the immediate lakeshore light. .LONG TERM...(Saturday through Wednesday) Issued at 245 PM EST Wed Jan 10 2018 Arctic air dominates the weekend into next week with 850 mb temps in the minus 15C to minus 20C much of that time. Saturday morning could start off colder than guidance if northerly flow allows any clearing. Lake effect snow showers are expected to gradually move onshore by Sunday as the flow goes more westerly. A clipper moving through Monday and Monday night will bring the potential for some widespread snow but accums will be limited by quick moving storm and the DGZ being close to the ground. Lake effect snow showers in northwest flow following the clipper will taper off on as sfc ridging builds in on Wednesday. && .AVIATION...(For the 00Z TAFS through 00Z Thursday evening) Issued at 640 PM EST Wed Jan 10 2018 The good news is temperatures are well above freezing and will stay that way though 00z Friday. Otherwise expect IFR or LIFR ceilings and visibilities through 00z Friday. Scattered rain showers are expected, some this evening, but mostly Thursday during the day. The greatest concentration of rain showers will be north and west of Grand Rapids through 21z Thursday. After that an are of showers assoicated with the cold front will move east across the CWA. Visibilities may go up briefly during rain some of the rain showers but will go back down once the shower passes through. There will also be a considerable amount of wind shear for the next 24 hours. Between 10000 ft agl and 2000 ft agl winds will be in the 45 kt to 55 kt range through 00z Friday. Surface winds only 15 to 25 knots, which of course creates the low level wind shear. The good new there is the direction of the wind does not change much, mostly 180 degrees at the surface to 210 degree at 3000 ft agl. && .MARINE... Issued at 245 PM EST Wed Jan 10 2018 Strong southerly flow will continue to allow large waves to build north of Holland, with heights generally between 5 and 8 feet tonight through Friday morning. Winds will increase and turn northerly on Friday, remaining strong through the day and keeping waves large. The Small Craft Advisory was extended through Friday afternoon. Additional Small Craft Advisories will likely be needed from Holland to South Haven Thursday evening through at least Friday night as the winds increase and turn north. && .HYDROLOGY... Issued at 1054 AM EST Wed Jan 10 2018 Snowmelt is expected through Thursday, as warm moist air invades the region. We could see great reductions in the snow pack. Not all of the melt water will make it into the river system before the cold air moves back in and locks it down. Snow water equivalent of the snowpack ranges from around 0.5 inch near Lansing to around 2 inches in the lake effect belts west of Highway 131. Fortunately, at this time, no excessive rainfall is expected with the warmup and amounts should be generally under one half inch through the warm period. This implies mainly just some minor nuisance flooding will occur with the snowmelt, however the rivers will need to be closely monitored for ice breakup and potential ice jam flooding. && .GRR WATCHES/WARNINGS/ADVISORIES... MI...Dense Fog Advisory until 10 AM EST Thursday for MIZ037>039- 043>045-050-051-056-057-064-071. LM...Dense Fog Advisory until 10 AM EST Thursday for LMZ844>849. Small Craft Advisory until 5 PM EST Friday for LMZ846>849. && $$ UPDATE...WDM SYNOPSIS...Duke SHORT TERM...HLO LONG TERM...Ostuno AVIATION...WDM HYDROLOGY...63 MARINE...HLO
Area Forecast Discussion
National Weather Service Memphis TN
932 PM CST Wed Jan 10 2018 .UPDATE... Update to remove dense fog and adjust p-types for Thursday night into Friday. && .DISCUSSION... A complex winter weather system expected to impact the Mid South Thursday night into Friday. First off, expect very mild and moist conditions ahead of an arctic cold front that will move through Thursday night. Light rain, drizzle, and fog will continue through Thursday across much of the region with well above average temperatures. Quickly changing weather is expected Thursday night and Friday. Temperatures will quickly fall behind a cold front Thursday night. This will result in rain changing over to freezing rain and sleet, then eventually snow through Friday. Latest guidance suggests that a more prolonged period of freezing rain will occur over the Winter Storm Watch area with lighter snow and sleet accumulations. At this time, it appears that over the Winter Storm Watch area there will be the potential for up to one quarter of an inch of ice along with 1 to 3 inches of snow and sleet. The greater snow and sleet accumulations should remain across northwest Tennessee. In addition to the winter weather potential, it appears that several hours of strong northwest winds will occur behind the frontal passage with latest guidance suggesting up to a 10 mb pressure change across a 100-150 mile distance across the front. This is likely due to the extreme temperature differences expected on either side of the frontal boundary. This should result in a period of very strong winds with a few hours behind the frontal passage with sustained winds possibly up to 30 mph, with gusts up to 50 mph possible. These type of winds could result in some downed trees and power outages. This system will be quite dynamic and additional forecast adjustments will be possible. Please continue to monitor the latest forecast for up to date details. JLH && .PREV DISCUSSION... /issued 334 PM CST Wed Jan 10 2018/ Winter is expected to return during the end of the work week, a Winter Storm Watch has been issued for all of West TN, the Missouri Bootheel, as well as portions of North Mississippi and East Arkansas. A dense fog advisory remains in effect across East Arkansas. The HRRR has done a good job with this hazard...and gradually shifts it into Central Arkansas later this evening. We may be able to expire the advisory a bit earlier than 6 PM when is set to expire. The latest guidance from WPC focuses more on ice accumulation from freezing rain and less on significant amounts of snow. However there is still a large amount of uncertainty with regard to both the timing...and amount of accumulation. The area of most concern is generally along the Interstate 40 Corridor Northeast of Memphis. SREF plumes from the Jackson, TN area range from zero to a high of 7 inches...with the mean right around one inch. A bit farther North, values are a bit higher...but the mean remains under two inches. However, the main threat from this system may end up being accumulating freezing rain and sleet resulting in dangerous roadways. We do not anticipate major ice accumulations capable of widespread damage at this time but once again, roadways could become treacherous. Precipitation is expected to begin as widespread rain late tonight continuing through the day tomorrow. Rainfall totals may approach one inch before a strong cold front approaches the Mississippi River late tomorrow. High temperatures tomorrow will likely climb into middle 60s...but temperatures will tumble Tomorrow night with morning lows near to below freezing everywhere across the Midsouth with the exception of portions of Northeast Mississippi. Rain will transition over to freezing rain after midnight, then likely a sleet snow mix around sunrise Friday...and transition to all snow midday Friday. Temperatures will likely remain below freezing Friday across most of the Midsouth. Any freezing or frozen precipitation will likely remain with us well into he weekend. A reinforcing cold front is expected to sweep across the area Saturday night. Sunday morning lows will likely be in the teens area wide. There is the potential for another round of Wintry weather early next week, but guidance remains very uncertain. If it materializes it appears it would be a "mostly snow" event as opposed to a Wintry mix. 30 && .AVIATION... 00z TAFs Next 24 hours consist of gusty southerly flow and mainly vicinity showers, with the main frontal passage just getting in range of the KMEM 30 hour TAF. Expecting mainly MVFR to IFR ceilings, with not as much visibility issues in this set. KTUP being the main exception with LIFR ceilings and some fog possible through the morning hours. Showers will not prevail until after the frontal passage, which looks to be around at around 04z tomorrow. WLC && .MEG WATCHES/WARNINGS/ADVISORIES... AR...Winter Storm Watch from late Thursday night through Friday evening for Clay-Craighead-Crittenden-Cross-Greene- Mississippi-Poinsett-St. Francis. MO...Winter Storm Watch from late Thursday night through Friday evening for Dunklin-Pemiscot. MS...Winter Storm Watch from late Thursday night through Friday evening for Alcorn-Benton MS-DeSoto-Marshall-Tippah- Tishomingo. TN...Winter Storm Watch from late Thursday night through Friday evening for Benton TN-Carroll-Chester-Crockett-Decatur-Dyer- Fayette-Gibson-Hardeman-Hardin-Haywood-Henderson-Henry-Lake- Lauderdale-Madison-McNairy-Obion-Shelby-Tipton-Weakley. && $$
Area Forecast Discussion
National Weather Service Tampa Bay Ruskin FL
812 PM EST Wed Jan 10 2018 .UPDATE (Overnight through Thursday morning)... 01Z water vapor and H4 RAP analysis shows shows a cutoff mid/upper level low continuing to spin over south Florida and the Florida Straits. The majority of the synoptic lift and resulting surface reflection forcing precipitation is off to the east of our area this evening. A few instability showers under the upper low cool pool migrated toward Fort Myers a few hours ago...but have since diminished with the loss of diurnal heating. Regional radars shows this energy forcing a large area of rain off the FL east coast...but the bulk of this activity (if not all of it) stays confined to the FL east coast overnight into Thursday morning. The main forecast concern for our area overnight and Thursday morning will be the development of locally dense fog. The fog and widespread lower clouds ceilings will mostly be a concern to the aviation community, but may become dense enough in spots to impact the early morning commute as well. Overall...these conditions will make for a dreary/cloudy start to the morning for a lot of the region. In addition...will watch the potential for some of this fog to drift over the coastal waters...including Tampa Bay and Charlotte Harbor late tonight. This occurred early Wednesday as well...and had a significant impact on the shipping route in and out of Tampa Bay. Will be watching the fog development and evolution closely over the next 3-6 hours in case any dense fog advisories, or marine dense fog advisories become necessary. && .AVIATION... Winds becoming light and variable with possible -SHRA near FMY and RSW ending by 02Z. Confidence is high for a widespread fog event with MVFR vsby/cigs by 05Z across all TAF sites. IFR conditions are likely to set in by 08Z with possible LIFR impacting some locations overnight, especially across our southern terminals. Conditions should improve by 15Z although low cigs may still linger for a couple of hours as daytime heating works to lift and burn off the stratus. Prev Discussion... /issued 252 PM EST Wed Jan 10 2018/ SHORT TERM (Today and Thursday)... A potent upper trough continues to dig in across the Southern Rockies, generating widespread wintry weather to the Rocky Mountains. Downstream from this feature, broad ridging exists from the Southern Plains into the Mid Atlantic region. Within this upper ridge, a weak cutoff low continues to spin over southern Florida. At the surface, weak high pressure remains anchored across the Mid Atlantic and Northeast, maintaining light easterly flow across the region. Though it took some time to mix out of the low clouds and fog this morning, we are well on our way to a warm afternoon with middle and upper 70s report across much of southwest Florida. Just like last night however, low clouds and fog will begin to build back in overnight tonight. This is due to a rather deep layer of dry air atop a shallow moist layer near the ground. This will set up a subsidence inversion, favoring fog formation as well as low stratus with the moisture coming off the Atlantic Ocean. The fog may be locally dense, but widespread dense fog is not expected at this time. Mild overnight lows generally in the 60s can be expected as dewpoints remain relatively high with several days of east to southeast flow off the Atlantic. We will start the day off gray and dreary on Thursday, much like we did today. Expansive fog and low clouds will likely linger into late morning and perhaps midday in some areas. With enough surface heating, we should eventually erode that stable surface layer and get the fog and low clouds out of here, after which another warm one is expected. Some areas will likely climb into the lower 80s with middle and upper 70s common elsewhere. Long Term (Thursday night-Wednesday)... A weak trough at the surface and aloft will be in place across the state to start the period with an approaching cold front back to the NW over the Lower MS Valley region. The front gradually moves through the area later Friday into early Saturday with scattered showers and a few thunderstorms possible along and ahead of it Thursday night through early Saturday. Cooler and drier high pressure then builds into the area behind the front for the rest of Saturday through Monday night, with a dry reinforcing front moving through the area later Tuesday. Lows Thursday night will be in the upper 50s to upper 60s, then cooling to the mid 40s north to around 60 south Friday night. The colder air then moves in for Saturday night and Sunday night with lows near freezing north to the mid 40s south. Monday night and Tuesday night will then see some moderating, with lows in the upper 30s north to around 50 south. Highs follow a similar trend, starting in the lower 70s north to lower 80s south on Friday, then mid 50s north to upper 50s south Saturday, lower 50s north to mid 60s south Sunday, and moderating Monday to the upper 50s north to around 70 south. Highs Tuesday and Wednesday in the lower 60s north to the lower 70s south. MARINE... Weak high pressure north of the waters will maintain light east to southeast flow over the next few days. Patchy sea fog will be possible both tonight and tomorrow night as fog moves off land and over water. As winds become southerly ahead of a cold front Friday, a prolonged sea fog event may unfold. Winds will increase sharply behind the front as it passes late Friday into Saturday, bringing drier air and removing fog potential. Cautionary to advisory winds and seas will be likely for a few hours Friday night into early saturday. As strong high pressure builds in north of the waters, periods of cautionary to advisory level conditions may occur at times through the weekend and into early next week. FIRE WEATHER... Weak high pressure will remain north of the area with light easterly flow persisting. Warm and somewhat humid conditions will persist through Friday. A cold front will move through the area Friday night into saturday, bringing breezy winds and cooler drier conditions for the weekend. Humidities look to remain well above critical thresholds through the weekend and no fire weather concerns are expected. && .Preliminary Point Temps/PoPs... TPA 61 76 65 77 / 0 20 20 50 FMY 62 79 67 81 / 30 20 20 30 GIF 62 79 65 80 / 10 20 20 50 SRQ 61 74 64 77 / 0 10 20 40 BKV 60 78 60 77 / 10 20 20 50 SPG 61 75 64 75 / 10 20 20 50 && .TBW WATCHES/WARNINGS/ADVISORIES... FL...None. Gulf waters...None. && $$ UPDATE...Mroczka Aviation...Norman Previous Discussion...Austin/Hubbard