Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 03/16/21

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
1159 PM EDT Mon Mar 15 2021 .AVIATION... A narrow band of light mixed precipitation will expand across the southeast Michigan airspace through the early morning hours. Recent trends suggest primarily VFR level restrictions within this moist axis. Lowering cloud bases in the wake of precipitation 08z-09z, with precipitation potential diminishing during this time. Extensive low stratus then in place throughout the daylight period Tuesday. Predominant low MVFR, but with the potential for a period of IFR mid- late morning. Gradual improvement in ceiling heights during the afternoon and evening. prevailing east-northeast winds become northwesterly. For DTW...Lingering window for possible light freezing rain through 07z. Otherwise, cloud bases solidly below 5000 ft within extensive low stratus through Tuesday. .DTW THRESHOLD PROBABILITIES... * High for ceiling at or below 5000 ft midnight through Tuesday morning, then moderate Tuesday afternoon and evening. * Moderate for p-type initially freezing rain early this morning. && .PREV DISCUSSION... Issued at 854 PM EDT Mon Mar 15 2021 UPDATE... Formidable magnitude and depth to the low level dry layer /00z dewpoint of 3 degrees at DTW/ yielding a radar return offering simply a generous supply of virga late this evening. Upstream observational trends suggest steady top-down saturation will commence on schedule from southwest to northeast between 04z-07z as the 850-700 mb frontal slope makes steady inroads. As highlighted by the afternoon discussion, there remains a model signal within the hi res model solution space for the frontal circulation to strengthen with time overhead under increasing dcva. This places a corridor generally northeast of a Detroit-Pontiac-Owosso line more favorably to witness a brief increase /1-3 hours/ in both coverage and intensity of wintry precipitation during the early morning hours. No shift in the overall reasoning in terms of expected precipitation type, with a mix of snow/freezing rain highlighted within the M-59/I-69 corridors and primarily snow with accums upwards of a couple of inches Saginaw valley/northern thumb. A more lackluster response appears likely for points southwest of this line, simply pockets of very light precip yielding only minor qpf. Overall brevity of this event outlooked across a low travel period continues to preclude a headline consideration. Evening update forthcoming for minor adjustments based on latest radar/temperature trends. PREV DISCUSSION... Issued at 405 PM EDT Mon Mar 15 2021 DISCUSSION... A mostly light wintry mix of precipitation is on schedule for tonight with interesting twists in evolution of the system. A weakening trend in the band ongoing this afternoon leads to just trace amounts of accumulation/icing from the Ohio border northward through metro Detroit. Reintensification then occurs from the I-69 corridor northward after midnight producing a burst of higher rate snowfall. This leads to a bump in accumulation into the 1 to 3 inch range before ending Tuesday morning. Afternoon radar/satellite imagery and surface analyses indicate a textbook mid latitude cyclone positioned over the central Plains with a warm front extending into the TN valley. Strong low level moisture transport and isentropic lift has a band of heavy snow extending from the upper Midwest transitioning to a rain/snow mix over IL/IN and into the Ohio valley. The weakening trend of this band projected by the latest models appears tied to it becoming displaced from the upper wave resulting in a veering and weakening of the low to mid level wind field. This in turn results in a frontolytic weakening and reduced system relative isentropic lift as the theta-e gradient shears apart overhead. The band then reintensifies after midnight as strong short wave forcing develops eastward along the elevated front from WI across central Lower MI. Cross sections from the RAP indicate all of the usual elements for a burst of high rate precipitation; a deep layer of instability, high RH, specific humidity around 3 g/kg, and a strong ageostrophic response. Speed of the system and short duration of intensity are about the only limiting factors for advisory worthy accumulation. Model soundings north of I-69 also indicate a high and shallow DGZ and a deep layer below freezing but near zero for riming limitations on snow ratio. That being said, model consensus of 12 hour liquid equivalent QPF around 0.25 inch looks solid for accumulation toward 3 inches in the Tri Cities area before ending around 8 AM. While snow is concentrated in the Tri Cities and northern Thumb, enough warm air makes across the Ohio border to keep freezing rain in the forecast at least up to the I-69 corridor. Model soundings and mean RH projections also indicate enough mid level dry air for a struggle maintaining DGZ saturation and really even above about -10C. Lighter precipitation rate also has a lower wet bulb cooling effectiveness which allows the warm air to influence liquid precip type trends, although with just trace amounts of icing while temperatures drop toward the upper 20s and become marginal around the freezing mark in metro Detroit toward sunrise. The exception is the usual colder surface temperature bias in higher terrain areas west/north of Detroit and then farther north toward I-69. This is where some slick spots could develop on area roads before the morning commute. The system carries precipitation out of the are Tuesday morning while the surface pressure reflection lingers in Ohio. This allows some temperature recovery even as clouds hang on through much of the day. Short wave ridging aloft then brings some clearing Tuesday night in time for lows in the upper 20s outside of metro Detroit. SE MI remains between systems through Wednesday for dry and milder weather. The four corners low pressure system moves into the southern Plains Wednesday and into the Ohio valley Thursday. There is some phasing with the northern stream westerlies however the moisture pattern remains dominated by the southern stream closed low and the easterly Atlantic conveyor. The northern stream supplies strong high pressure over northern Ontario and a strong gradient across the central Great Lakes. The low level flow of dry air on gusty NE wind is expected to set up a sharp northern edge in a cold rain pattern mainly south of I-69 Thursday and Thursday night. Passage of this system eastward then allows the Quebec high pressure to settle southward for dry weather next weekend. MARINE... Moderate easterly flow continues this evening off the west end of Lake Erie and this is where Small Craft Advisories remain in effect. Low pressure brings a decrease in wind overnight at the expense of a wintry mix of precipitation through Tuesday morning. High pressure returns for the mid week period with light winds and waves until Thursday when the next low pressure system moves into the Ohio valley. The arrival of this system generates a gusty NE wind across the central Great Lakes by Thursday. The wind pattern is sub gales for now but will likely require a new round of Small Craft Advisories Thursday and Thursday night. && .DTX WATCHES/WARNINGS/ADVISORIES... MI...NONE. Lake Huron...NONE. Lake St Clair...NONE. Michigan waters of Lake Erie...NONE. && $$ AVIATION.....MR UPDATE.......MR DISCUSSION...BT MARINE.......BT You can obtain your latest National Weather Service forecasts online at
Area Forecast Discussion
National Weather Service Austin/San Antonio TX
631 PM CDT Mon Mar 15 2021 .AVIATION.../00Z TAFS/ Fair skies are expected for all areas through this evening. Well mixed air mass in the low levels will begin to saturate a few hours after midnight with both fog and low cigs possible. With onshore winds falling below 5 knots for most of the early morning, there should be some LIFR conditions developing along I-35, and there could be some areas of dense advection fog developing around daybreak. Steady improvements are expected back to IFR and MVFR in the midday hours. && .PREV DISCUSSION... /ISSUED 227 PM CDT Mon Mar 15 2021/ SHORT TERM (Tonight through Tuesday Night)... Satellite visible and WV imagery and RAP analyses indicate weak upper ridging over the four corners region between a closed low over CA and the system over the central Plains that brought impressive snow totals to the Front Range yesterday. Locally, weak surface high pressure is keeping skies mostly clear, with a few cirrus developing just to our west along a very subtle upper shortwave. Temperatures at 19Z range from the low to mid 70s over much of the Hill Country to the low to mid 80s in several spots, with highs today expected to climb to 77-88, coolest over the southern Edwards Plateau. Tonight, as sfc high pressure quickly moves east, light southerly flow will develop and moisture will pour back in from the gulf. Dew points currently in the 30s and low 40s across the region will rise into the 60s across much of the region by this time tomorrow. Late tonight, low stratus and areas of fog are anticipated and will likely become locally dense. Where moisture remains slightly lower along the Rio Grande and our northern border, fog shouldn`t be too much of an issue. Should see the fog end by late morning, but low clouds may hold on into the afternoon across much of the area and may never clear at all over the Coastal Plains and I-35 corridor Tuesday. This will keep temperatures in the upper 70s and lower 80s for the most part east in the afternoon, while mid to upper 80s are forecast along the Rio Grande. The addition of the CAMS to the model suite has given us a much better look at the environment we can expect tomorrow night. The warm, moist airmass in place along with steepening mid-level lapse rates above a relatively sharp inversion caused by low-mid-level ridging overhead tomorrow will allow for the buildup up MUCAPE in excess of 1500 J/kg and likely closer to 2000 J/kg by tomorrow night ahead of an approaching cold front and upper trough. Effective shear will also increase to 40-50 kts, and with ample frontal forcing and some mid-level ascent as the trough nears, elevated showers and storms are expected to develop in the late evening hours above the cap over the Edwards Plateau, growing upscale and crossing the region after midnight. SPC has upgraded their outlook to include Austin and San Antonio in a marginal risk of severe storms, while locations north of Rocksprings to Leakey to Blanco to Georgetown are in a slight risk (2 out of 5). At this lead time, I think this may be a bit bullish as the fast-moving front may undercut storms before they can fully organize. Nonetheless, the threat for severe weather is certainly higher than it looked this time yesterday. The primary hazard would be large hail in any rotating storms, with damaging winds or a QLCS tornado not entirely out of the question as latest model soundings indicate a small chance for the cap to erode fast enough to allow a brief period of surface rooting before the sfc front sweeps through. Latest HRRR is rather bullish with simulated reflectivity, despite being slightly slower-progressing than the rest of the CAMS, although in contrast the NAMNEST depicts development slightly further north and somewhat weaker. Most of the remaining CAMS lie somewhere between, but all of them are in general agreement in the likelihood of thunderstorm activity and the possibility some of this development becomes severe across at least the Hill Country overnight. Still two full forecast packages to refine this forecast, so stay tuned! LONG TERM (Wednesday through Monday)... The front is progged to move out of the area on Wednesday morning with clearing behind. The much drier air from the northwest will be a concern for fire weather conditions as we may reach critical thresholds. Relative humidities over the area will drop to in the teens and even single digit percentages in our far southwest counties. This dry air combined with the gusty northwest winds with gusts up to 27 mph at times may require fire weather products to be issued. Conditions will continued to be monitored. The later half of the week will be pleasant with continued northerly flow at the surface keeping the air dry, and the daytime temperatures mild and pleasant, and overnights cool. The next upper system approaches at the start of next week. && .PRELIMINARY POINT TEMPS/POPS... Austin Camp Mabry 57 81 60 78 47 / 0 20 80 20 0 Austin Bergstrom Intl Airport 56 81 59 79 47 / - 20 80 20 0 New Braunfels Muni Airport 57 81 60 82 47 / - 20 70 20 0 Burnet Muni Airport 55 81 55 74 45 / 0 10 80 - 0 Del Rio Intl Airport 56 87 56 82 48 / 0 - 20 0 0 Georgetown Muni Airport 56 81 57 77 46 / 0 20 80 10 0 Hondo Muni Airport 56 81 57 81 46 / 0 - 60 - 0 San Marcos Muni Airport 55 81 60 79 46 / 0 20 70 20 0 La Grange - Fayette Regional 60 80 63 79 48 / - 30 50 40 0 San Antonio Intl Airport 59 81 60 79 49 / 0 10 70 10 0 Stinson Muni Airport 58 80 61 80 48 / - 10 60 10 0 && .EWX WATCHES/WARNINGS/ADVISORIES... None. && $$ Short-Term/Aviation...Oaks Long-Term...05
Area Forecast Discussion
National Weather Service Peachtree City GA
750 PM EDT Mon Mar 15 2021 .PREV DISCUSSION... /Issued 343 PM EDT Mon Mar 15 2021/ SHORT TERM /Tonight through Tuesday Night/... The Ides of March are upon us -- as is an active pattern throughout this week. The upper level ridge continues to move eastward away from the forecast area and toward the Atlantic coast as the short term period begins. Deep moisture is increasing over the area in the southwesterly flow behind the ridge axis. At the surface, an old frontal boundary remains stalled across central Georgia as a cold front moves into the Mississippi River Valley. Meanwhile, as high pressure over the Great Lakes Region continues to move east, a wedge will build down the spine of the Appalachians and into the northeastern portion of the forecast area. This wedge will remain entrenched over northeast Georgia into the evening Tuesday. The approaching weakening cold front will become more zonally oriented before it reaches Georgia, stalling to the north and west of the forecast area. This will provide a focus for convection and keep the CWA within the warm sector through the majority of the period. Widespread showers will enter northwest Georgia this evening and slowly spread south and east during the overnight hours and throughout the day on Tuesday. Some marginal instability is present outside of the wedge and across central and west Georgia this afternoon, which will lead to a slight chance of thunderstorms in that area as precipitation moves into the area. Some enhanced low- level shear is also present in the vicinity of the stalled boundary. While severe thunderstorms are not expected this afternoon and evening, a couple of storms along the boundary could become strong and capable of producing gusty winds and locally heavy rain. Better coverage of thunderstorms is anticipated on Tuesday. As a result of continued advection of warm and moist air into the area, relatively higher instability values will spread east into the forecast area overnight and into Tuesday. A broad area of MUCAPE values of 500-1000 J/kg will be present generally along and south of the I-20 corridor during the afternoon and evening tomorrow. This area of elevated instability will be co-located with 0-1 km shear values of 20-25 kts and deep layer bulk shear values of 35-40 kts. As a result, a few thunderstorms are anticipated to be strong to severe and capable of producing damaging wind gusts, locally heavy rain, and frequent lightning. A brief tornado cannot be ruled out. Precipitation chances will diminish Tuesday night into Wednesday morning, allowing a brief lull before the next system approaches. Rainfall totals for this system remain fairly consistent with the previous forecast run, with QPF values of 1 to 2 inches across much of western Georgia and lower amounts elsewhere in our area. Heavy rain in isolated strong storms could lead to locally heavier amounts, which could lead to some instances of localized, nuisance flooding. Widespread flooding concerns are not currently expected during the short term period, but another round of heavy rain will be coming on Wednesday as another system impacts north and central Georgia. King LONG TERM /Wednesday through Monday/... Main concern in the long term period is timing, likelihood, coverage and intensity of severe convection Wed/Thurs. Heavy rainfall and possibility of minor flooding also a concern. At the start of the period, intense upper wave centered over OK moving slowly east. Noted just a little slowing of system compared with prev runs, but mainly still seeing GFS as the faster solution while EC, CMC and NAM are slower. Using slower timing, much of Wednesday and perhaps even Wednesday evening should be mostly dry with just scattered showers ahead of the main line of convection. Have used blend of model timing for now, but suspect GFS may slip to slower timing. 12Z EC also a hair faster than previous run fwiw. Finally, model blends once we get inside 48h projections will take advantage of hires guidance like HIRESW, HRRR synoptic runs and others. Should push out by Tuesday late afternoon unless further slowing occurs. Given strong, large-scale forcing and plenty of instability and vertical wind shear, confidence/likelihood of severe storms growing though best ingredients will be in place over AL rather than GA. Even if system slows further and moderate instability develops over the area Thurs, vertical wind shear not expected to be as favorable. Model sig tor values, which combine instability, vertical wind shear, CIN and LCL, are progged to be 3-6 over AL and 1-2 mainly over Wrn GA Wed evening and overnight and again 1-1.5 Thursday. Given strong deep shear (0-6km 60-70kts) and moderate low level shear (0-1km 30-40kts), good directional shear and instability (SBCAPE 1000- 1500 J/kg), mode of convection expected to be supercells with line segments, becoming more lines of cells or QLCS on Thurs as shear becomes more uni-directional. Total rainfall 1-3" likely for the event with one round Tues with warm front/warm advection then the other Wed-Thurs. Greatest amounts expected in NW GA Wed-Thurs and even with extended dry weather last two weeks, may see rain rates exceed FFG there. Will hold off on any kind of flood outlook or watch based on uncertainty on amounts and limited runoff potential with dry soils and increasing vegetation. Rest of long-term period appears dry and mild with seasonable temps. Only very small chances of rain expected far north on Fri and Sat. SNELSON && .AVIATION... 00Z Update... Precip has moved in across NW GA and is slowly moving SE. Should begin to see SHRA at the ATL/AHN area TAF sites by 06z and they will continue through the end of the TAF period. Precip will move into the CSG/MCN areas by Tue afternoon. Winds are expected to stay easterly through the period but wind speeds are expected to diminish some. Currently wind speeds are in the 08-12kt range with gust to 20kt. These gust should subside overnight with winds 10kt or less after 09z. Ceilings are VFR right now but they will fall into the MVFR range by 04z then IFR by 09z. Ceilings should stay IFR through the rest of the period. //ATL Confidence...00Z Update... Confidence medium to high on all elements. 01 && .PRELIMINARY POINT TEMPS/POPS... Athens 45 54 50 68 / 80 80 60 80 Atlanta 51 59 54 71 / 80 90 60 80 Blairsville 42 58 47 64 / 80 70 30 80 Cartersville 48 60 51 71 / 90 80 40 90 Columbus 61 74 60 80 / 70 80 70 80 Gainesville 43 54 50 65 / 80 80 40 80 Macon 58 72 58 79 / 50 70 70 80 Rome 50 63 52 72 / 90 70 40 90 Peachtree City 55 64 55 74 / 80 90 70 80 Vidalia 59 80 62 82 / 20 50 50 60 && .FFC WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SHORT TERM...King LONG TERM....SNELSON AVIATION...01
Area Forecast Discussion
National Weather Service Grand Rapids MI
952 PM EDT Mon Mar 15 2021 LATEST UPDATE... Update .SYNOPSIS... Issued at 247 PM EDT Mon Mar 15 2021 - Snow/Wintry Mix Tonight - Another System Brings Chance for Snow/Rain Thursday - Dry Weather Returns For the Weekend && .UPDATE... Issued at 952 PM EDT Mon Mar 15 2021 The very dry air below 700 mb continues to win out vs. the incoming precip/lift aloft and only scattered trace amounts of rain/snow/sleet have been reported so far. Sfc dew points are actually still between zero and 5 above along the I-96 corridor with RHs around 25 pct. The Winter Weather Advisory issued earlier may be in trouble if this trend continues much longer but latest HRRR guidance continues to show 1-3" snow accumulations occurring north of I-96 overnight as the shortwave approaching from the southwest strengthens and becomes negatively tilted (enhancing upper divergence/lift). That would lead to slick, snow covered roads for the morning commute for at least the northern sections of the advisory area. Meanwhile, very little QPF is shown for the I-96 corridor southward overnight in the latest guidance. The concern here though is for areas of freezing drizzle developing as ceilings lower, and it doesn`t take much of that to cause slick spots and travel impacts. Will continue the Winter Weather Advisory as is for now and see how things evolve over the next few hours. && .DISCUSSION...(This evening through next Monday) Issued at 247 PM EDT Mon Mar 15 2021 - Snow/Wintry Mix Tonight - Light snow/Wintry Mix currently to our southwest will continue to move into our area this evening bringing concerns for freezing rain/wintry mix/snow. Mainly below freezing thermal profiles still indicate that primarily snow can be expected for areas across central and northern lower MI. Meanwhile, a small warm layer above a cold and dry surface layer will bring the possibility for a mixture of freezing rain and freezing drizzle for areas across southern lower MI. QPF is still relatively low with this system, however even a glazing of ice across areas along and south of I-96 may cause travel concerns. Meanwhile areas north of I-96 will be more susceptible to up to 1 inch of snow with locally higher amounts possible. By tomorrow mid to late morning this low will occlude while it exits further northeast resulting in precipitation weakening and ending. - Another System Brings Chance for Snow/Rain Thursday - Once our Monday/Tuesday system exits to our east, another low emanating from the southwest will take it`s place and bring our next chance for precipitation. Model trends still hint at a more southern track of the low across the Ohio River Valley, which would result in precipitation for the southern third portion of lower Michigan. Precipitation type will once again be a question, with a chance for rain or a rain/snow mix possible. - Dry Weather Returns for the Weekend - High pressure ridging will build back into the region following the departure of the Thursday system. This will result in the return of dry weather with sunshine and highs in the 50s for this weekend! && .AVIATION...(For the 00Z TAFS through 00Z Tuesday evening) Issued at 806 PM EDT Mon Mar 15 2021 Low confidence aviation forecast tonight in terms of cigs/vsbys as well as precip potential and precip types. The problem is that we have extremely dry air still present in the low levels which is being reinforced by easterly winds gusting up to 30 kts. (We still have sfc dew points in the single digits.) Meanwhile precipitation is breaking out aloft but struggling to reach the ground. As we go through the night however the model guidance suggests that further moistening of the atmosphere does occur causing cigs to gradually lower into MVFR category. Precipitation should have a better chance of reaching the ground by 03Z, and model fcst soundings indicate mostly snow for a period at GRR/MKG/LAN, with light FZRA/FZDZ being the primary risk at AZO/BTL/JXN. That said, there`s also a chance that dry air could still win out and very little precip occurs tonight. && .MARINE... Issued at 247 PM EDT Mon Mar 15 2021 Winds will be the primarily concern through the next couple days as waves stay low due to the offshore direction of the wind. A small craft advisory remains in effect through this evening due to wind gusts up to 25 to 30 knots. && .GRR WATCHES/WARNINGS/ADVISORIES... MI...Winter Weather Advisory until 10 AM EDT Tuesday for MIZ037>040- 043>046-050>052-056>059-064>067-071>074. LM...Small Craft Advisory until 2 AM EDT Tuesday for LMZ844>848. && $$ UPDATE...Meade SYNOPSIS...Thielke DISCUSSION...Thielke AVIATION...Meade MARINE...Thielke
Area Forecast Discussion
National Weather Service Lincoln IL
756 PM CDT Mon Mar 15 2021 .SYNOPSIS... Issued at 327 PM CDT Mon Mar 15 2021 Scattered showers and a few thunderstorms will move across central Illinois tonight. In addition, areas of fog will develop overnight into Tuesday morning as winds become nearly calm. Low temperatures will range from the lower 30s near Galesburg and Lacon, to the lower 40s south of I-70. && .UPDATE... Issued at 756 PM CDT Mon Mar 15 2021 Area of showers has advanced into west central and south central Illinois early this evening, with much of the lightning strikes occurring west of the Mississippi River. RAP showing a couple hundred J/kg of MUCAPE from about Jacksonville to Paris southward through the evening, diminishing over east central Illinois after midnight. Some updates have been made to the timing of the precipitation over the next several hours, with some increase in chances south of I-70. Some concern continues with fog potential overnight. NAM forecast soundings show a rather stout inversion around 2,000 feet persisting through the night, and while the GFS is not as impressive, it does keep decent low level moisture in place below that level. HRRR and LAMP show fog expanding in the areas that don`t see precip after midnight (northern CWA and south of I-70), but do try to close off the area in between later. Not really looking for any clearing that could speed this along, but will keep the mention of fog going across most of the CWA tonight into Tuesday morning. && .SHORT TERM...(This evening through Tuesday) ISSUED AT 327 PM CDT Mon Mar 15 2021 Vigorous upper low evident on 20z/3pm water vapor imagery near Kansas City will track eastward across central Illinois tonight. Scattered convection is beginning to develop beneath the low across eastern Kansas into west-central Missouri and this activity is expected to increase in areal coverage and shift eastward into the KILX CWA this evening. HRRR/NAM have both been very consistent with showers arriving across the far SW around Jacksonville/Winchester after 00z/7pm. Based on the track of the low and where showers are currently initializing, it appears the best chance for rain will be along and south of the I-72 corridor. Forecast instability is slightly weaker than previously thought, but MUCAPEs are still progged to exceed 100J/kg across the southern half of the CWA. Will mention slight chance thunder everywhere south of a Macomb to Bloomington line accordingly. Once the low passes, showers will come to an end from west to east before dawn Tuesday. In addition to the precip, several CAMs are suggesting fog development overnight as winds become light and the boundary layer remains saturated. Based on latest RAP/GFSLAMP, have included areas of fog in the forecast across much of the area north of I-70 late tonight into Tuesday morning. Once the fog slowly dissipates, mostly cloudy skies and dry conditions will prevail on Tuesday with highs ranging from the lower 50s far north around the lower 60s south of I-70. && .LONG TERM...(Tuesday night through Monday) ISSUED AT 327 PM CDT Mon Mar 15 2021 After a brief lull on Tuesday, the next storm system will come into the picture by Wednesday as another highly amplified upper low rolls eastward out of the southern Rockies. This system will spread rain showers into central Illinois on Wednesday, with the heaviest and most widespread shower activity focusing Wednesday night into Thursday. With surface low pressure expected to track from the panhandle of Oklahoma Wednesday morning into southern Indiana by midday Thursday, central Illinois will remain mostly on the cool side of the system. As a result, am expecting widespread rain...with perhaps a few thunderstorms across the S/SE half of the CWA. Given ample deep-layer moisture from the Gulf of Mexico, this will be another efficient rain-maker, resulting in overall rainfall amounts of 1 to 1.50 inches. Once the low departs, a return to mild and dry weather is anticipated...with temperatures climbing back into the lower 60s by Sunday/Monday. && .AVIATION...(For the 00Z TAFS through 00Z Tuesday evening) Issued at 622 PM CDT Mon Mar 15 2021 IFR ceilings expected to prevail early in the forecast period, deteriorating to less than 500 feet late this evening. Some concerns about dense fog becoming widespread between 06-09Z, but there is some uncertainty at this point and will limit visibility to only a mile for now. Ceilings will be slow to improve Tuesday morning, but should gradually become MVFR early afternoon. An area of showers and isolated thunderstorms is crossing the Mississippi River north of KSTL currently, and is expected to impact the KSPI-KCMI area between 01-05Z. Have kept a VCTS mention in this corridor for this evening. && .ILX WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...Geelhart SYNOPSIS...Barnes SHORT TERM...Barnes LONG TERM...Barnes AVIATION...Geelhart
Area Forecast Discussion
National Weather Service Jacksonville FL
916 PM EDT Mon Mar 15 2021 .UPDATE... Backdoor front is basically stationary over southeast GA this evening but expected to lift north of the area late tonight. Sfc high is over the mid Atlantic but will push offshore tonight. Low to mid level ridge is located east of the FL peninsula and upper level flow is westerly, so quite a bit of veering in the 00z sounding profile. Only precip on radar is at best some sprinkles over southeast GA, and a couple of showers just to the east of the offshore coastal waters. Partly to mostly cloudy skies over the forecast area, and most of the cloudiness will likely be over most of our southeast GA zones. Some indications of patchy fog possible tonight given that dewpoints are in the lower 60s, though winds may be a bit mixy for sustained period of fog or dense fog. Main updates were to tweak min temp slightly and lower POPs over southeast GA to below 15 percent. Warmer overnight lows due to the addition of moisture/clouds to the area with lows in the upper 50s and lower 60s. .MARINE... Only minor changes for winds tonight due to the front in the southeast GA waters and for tweaks to the sea heights. Otherwise, forecast on track. && .PREV DISCUSSION [747 PM EDT]... .Near Term.../through Tuesday/... Frontal boundary will lay across SE GA this evening, then lift north of the area overnight. A few sprinkles or light showers will be possible with this boundary this afternoon and evening. This front will be just north of the forecast area through the day Tuesday. Waves will move east along this boundary Tomorrow, which may push the front a little further to the south. There is a chance for a few showers and storms over SE GA during the day Tuesday as one of these waves moves through. For NE FL, while the proximity of the front will provide added cloud cover it will remain dry. Above normal temperatures expected Tonight and Tuesday. .Short Term.../Tuesday night through Friday/... The frontal zone will remain just to the north through Tuesday night. The front then sinks south into SE GA during the day Wednesday. Expecting isolated to scattered showers and storms along the boundary. Models have trended slower with the main cold front, which is now expected to reach western counties late morning Thursday, then be east of area Thursday night. The later arrival of the front will slow the onset of precipitation with Wednesday night dry, and eastern half of area will have a dry morning. This will allow eastern counties to heat well into the 80s ahead of the front. This will create greater surface instability, increasing the potential for a few strong storms, however better chances for stronger storms to the north OF area closer to low center. High pressure will build well to the north Friday, which will push a secondary trough south toward area late in the day. At this point, looks like a dry day Friday, but cloud cover will begin to increase in the afternoon ahead of the trough. Above normal temperatures Tuesday night through Thursday night, with near normal for Friday. .Long Term.../Friday night through Monday/... Strong high pressure will build to the north Friday night, pushing surface trough south across forecast area leading to a few showers. The strong high will remain to the north over the weekend, with an inverted trough expected to develop over the coastal waters. This feature will result in the chance for showers and gusty winds, especially near the coast. The high will weaken and move toward the northeast Monday, with a dry day expected, although can not completely rule out potential for coastal showers. Temperatures will be below normal over the weekend, with highs in the 60s common north of Ocala. .AVIATION... [Through 00Z Wednesday] VFR conditions expected to prevail this period, though with a mix of some low clouds and broken mid to high clouds. A weak front is located over the central parts of parts of southeast GA but will lift back north of the area late tonight. A brief bout of some low clouds below 1 kft and some vsby restriction possible at SSI tonight based on LAV guidance and HRRR model, but uncertain on this potential at this time so just showed TEMPO 6SM and scattered clouds around 300 ft from 03z-06z. Occasional breezy northeast and southeast flow this evening for terminals, except for GNV, will settle down by midnight and become more variable and light tonight. Increases in southerly and southwest winds near 8-12 kt gusting near 20 kt expected Tuesday after about 14Z. .Marine... Frontal boundary over region will lift to the north Tonight. High pressure will build to the southeast Tuesday, with surface boundary just to the north. The high will sink further to the southeast Wednesday, with the boundary remaining just to the north. Cold front will move southeast across the region Thursday, and pass to the southeast Thursday night. Strong high pressure will build to the north Friday into Friday night, pushing a secondary trough south across area. Strong high pressure will remain to the north over the weekend, with an inverted trough over the coastal waters. The high will weaken as it builds more toward the northeast early next week. Rip Currents: SE GA: Moderate through Tuesday NE FL: Moderate through Tuesday && .PRELIMINARY POINT TEMPS/POPS... AMG 60 81 62 81 61 / 10 20 20 30 10 SSI 62 76 62 77 63 / 10 10 10 10 10 JAX 61 84 62 83 63 / 0 0 10 10 0 SGJ 64 82 62 81 63 / 0 10 0 0 0 GNV 60 83 59 85 61 / 0 0 0 0 0 OCF 59 84 61 87 62 / 0 0 0 0 0 && .JAX WATCHES/WARNINGS/ADVISORIES... FL...None. GA...None. AM...None. &&
National Weather Service Jackson KY
1201 AM EDT Tue Mar 16 2021 .UPDATE... Issued at 1201 AM EDT TUE MAR 16 2021 Rain showers have moved out of our area with the exception of some isolated activity across far southeastern Kentucky. PoPs have been lowered accordingly, based on the radar trends. The HREF had decreasing low level cloud coverage through 0900z, especially across the southern portion of the area. As such, did reduce sky cover a bit through the night. Most of the model guidance has been too aggressive with hourly temperatures warming overnight. The HRRR 0100z run grids had the best handle on a more gradual warming through dawn, as winds veer from southeasterly to more southerly. Consequently, adjusted the hourly readings towards this idea. UPDATE Issued at 828 PM EDT MON MAR 15 2021 Scattered to numerous showers will be exiting eastern Kentucky in the next 1 to 2 hours. This activity is mainly associated with a passing mid-level short wave trough, as well as moderate 850 mb moisture transport. While the mid-level support will move on, the 850 mb transport will linger a bit longer across the area, allowing for isolated shower activity to threaten through late this evening, especially across far southeastern Kentucky, where PWATs are higher. Have freshened up the PoPs through tonight, incorporating more recent radar trends. Forecast lows were also adjusted, as the surface trough/secondary warm front has been slower to lift to the north early this evening. As such, some 30s will linger north of the Mountain Parkway for another few hours, before generally warming through the rest of the night. Updates will be out shortly. && .SHORT TERM...(This evening through Tuesday night) Issued at 327 PM EDT MON MAR 15 2021 An upper level low is pressing along through the Plains this afternoon. At the surface, we see an occluded low in the Central Plains and locally a surface trough across southern Kentucky. This is leading to a strong temperature gradient from southern Kentucky compared to the Bluegrass, as low 60s are the story in southern Kentucky and mid 30s in the Bluegrass. The mid 30s are likely a result of wet bulbing from the heavier precipitation seen toward northern Kentucky. A spoke off the previously mentioned upper level is elbowing its way into the Ohio Valley helping to push a shortwave ridge east. This will aid by giving way to some mid- level forcing bring the slug of precipitation seen in central Kentucky eastward through the afternoon and evening. This will be a light QPF, as we are still trying to overcome the dry air at the surface in many cases. Therefore most locations will see less than a quarter of an inch of rain. This feature will push through most areas later this evening and perhaps some lingering showers possible in the southeast through the night. Temperatures tonight will remain above normal with lows in the mid to upper 40s. Tuesday, we see a dry day in store, with some mid and high clouds from time to time under locally zonal flow. Expect a warm one with highs around 70 for most locations and perhaps warmer (closer to the 75 percentile of the NBM) depending on the cloud cover. Tuesday night the skies should clear some and we will see slight mid-level ridging. This could lead to a slight ridge/valley split, but the question that remains is do we see some fog or low stratus develop minimizing this some. Right now leaned toward a little split, with lows in the low to mid 40s in the valleys and mid to upper 40s on the ridges. To derive the valley lows leaned toward the 5 percentile of the NBM. .LONG TERM...(Wednesday through Monday) Issued at 315 PM EDT MON MAR 15 2021 The weather in the extended will be primarily influenced by a large area of low pressure, that is forecast to move out of the Great Plains and across the Ohio and Tennessee valley regions from late Wednesday through early Friday evening. A warm front associated with the low will move through our area Wednesday and Wednesday night, with the parent low moving across the area Thursday night and Friday. Widespread rain showers will accompany this system as it moves through our part of the country. We may even see a few thunderstorms along the warm front as it moves through. Since the main time frame for thunderstorm activity appears to be Wednesday night through Thursday morning, only garden variety thunderstorms are expected at this time. This is because our weather system will be lacking in instability and a large complex of thunderstorms that is forecast to form and move through the Gulf Coast states Wednesday and Thursday, will likely rob a large amount of Gulf moisture from the storms that are able to form over our area. The lack of both instability and an uninterrupted feed of Gulf of Mexico moisture should greatly limit or even eliminate the potential for severe weather for eastern Kentucky. Temperatures will above normal to begin the period, with highs in the upper 60s to lower 70s on tap for Wednesday and Thursday. Once low pressure moves overhead, and then to our easter, cooler air will spill into the area. Once that happens, we will see more seasonable highs in the 50s on Friday and Saturday. Things should begin to warm up again over the weekend, as high pressure builds back across the region. Highs on Sunday may reach the upper 50s to lower 60s. Nightly lows should be in the 40s and 50s Wednesday and Thursday night, and in the 30s and 40s thereafter. && .AVIATION...(For the 00Z TAFS through 00Z Tuesday evening) ISSUED AT 828 PM EDT MON MAR 15 2021 Scattered to numerous showers will exit areas east of I-75 through 02z, with a few showers lingering through around 06z across far southeastern Kentucky. MVFR/low end VFR ceilings will gradually improve to VFR from southwest to northeast through this evening. VFR conditions will generally prevail thereafter, although mostly cloudy skies will continue, due mainly to passing mid and high level clouds. East southeast to east northeast surface winds of 5 to 10 kts, will gradually veer to the southeast and south through tonight, before becoming more southwest to west southwest by Tuesday afternoon. Stronger southerly winds aloft will also provide a threat of low level wind shear tonight into early Tuesday morning. && .JKL WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...BATZ/GEOGERIAN SHORT TERM...DJ LONG TERM...AR AVIATION...GEOGERIAN
Area Forecast Discussion
National Weather Service North Platte NE
628 PM CDT Mon Mar 15 2021 .SHORT TERM...(This evening through Tuesday night) Issued at 323 PM CDT Mon Mar 15 2021 The midlevel disturbance operating across the Panhandle this afternoon is showing no sign of weakening and sfc observations in that area show visiblity falling to a mile and as low as 1/4 to 1/2 mile briefly. The disturbance will move east tonight favoring the central Sandhills for the best accumulating snowfall, generally around 2 inches according to the latest forecast. The disturbance will affect ncntl Nebraska Tuesday morning. Temperatures aloft support snow with h700mb temperatures of -8C to -10C, but temperatures near h850mb will be close to 0C across the Sandhills and slightly above 0C south of the Sandhills near Interstate 80. This should set up a rain snow line along or north of the interstate. The lift shown in the RAP model is weak at the -12C-18C layer but this system will be operating below this level, closer to the ground, below h700mb where temperatures are -5C to -10C. Periods of strong lift are shown in the model in this layer for a few hours tonight. The locally higher amounts shown in the model appear to be the result of a mesoscale circulation developing in the h850-h750mb level. The strength of this circulation can be hard to predict. The snow forecast lines up well with the RAP and HRRR which suggest some local amounts of 3 or 4 inches in spots. The new QPF suggested by WPC this afternoon would seem to supports the local amounts predicted by the HRRR and RAP. The temperature forecast tonight uses the guidance blend plus bias correction for lows in the upper 20s. This is a little cooler than the deterministic blend. The cooler temperatures seem appropriate given afternoon temperatures are in the 30s. The temperature forecast Tuesday and Tuesday night also uses the guidance blend plus bias correction which in on the cooler side of the forecast envelop. .LONG TERM...(Wednesday through Monday) Issued at 323 PM CDT Mon Mar 15 2021 A storm system operating across cntl California this afternoon will sweep through the srn Rockies Tuesday and emerge onto the Colorado and Kansas plains Tuesday night and Wednesday. This will be another fairly strong system but favoring KS and sern Nebraska for the best rain. Snow will likely fall on the northern side of the storm. Earlier runs of the SREF suggested storm would curve north more sharply producing a good chance of significant snow across swrn and scntl Nebraska. The morning run of the SREF however, tracks the storm more east and keeps the better snow chance south and east of swrn and scntl Nebraska. This is in good agreement with the model consensus which show the storm dropping into far nrn Oklahoma. Slowly moderating temperatures are expected Thursday and Friday. This is the result of a storm system approaching the West Coast which will cause a sharp rise in heights aloft. The system will be deep enough to drive warmer Desert Southwest air across the Rockies and in Nebraska. This should produce highs in the 50s to near 60 Saturday and Sunday as temperatures at the h850mb level rise toward 10C. The West Coast system could begin to affect the weather across wrn and ncntl Nebraska Sunday night and Monday. && .AVIATION...(For the 00Z TAFS through 00Z Tuesday evening) Issued at 628 PM CDT Mon Mar 15 2021 Another piece of the Rocky Mountain storm system will continue to spread into western and north central Nebraska through tomorrow. Light snow is underway in the panhandle and will move east through the night, affecting most terminals. Areas of fog are also affecting north central Nebraska (KONL), which will likely stick around until the snow arrives around sunrise. Overall, expect a prolonged period of MVFR to IFR conditions due to cigs or visby (or both during snow). Winds will gradually transition to to east tonight then north tomorrow morning, with speeds generally 10 kts or less. && .LBF WATCHES/WARNINGS/ADVISORIES... Winter Weather Advisory until 1 PM CDT /noon MDT/ Tuesday for NEZ004-005-008>010-022>028-035>037-094. && $$ SHORT TERM...CDC LONG TERM...CDC AVIATION...Snively
Area Forecast Discussion
National Weather Service Louisville KY
851 PM EDT Mon Mar 15 2021 .Forecast Update... Updated at 840 PM EDT Mon Mar 15 2021 Sharp warm front is draped across southern Kentucky, with BWG sitting at 61F while it`s just 44 at EKX. Deep moisture feed and associated precip have pushed off to the east, so the rain is done for the night. Main question marks tonight will be min temps and fog potential. North of the front, we are probably at our lows for the night, and looking at steady temps until the front lifts north, then a slow rise toward morning. By daybreak Tuesday expect temps to range from the upper 40s in southern Indiana to the mid 50s in south central Kentucky. Some concern with fog, but with a respectable 30-40 kt LLJ just 2000 feet off the deck, fairly warm ground temperatures, and rising air temps, would expect most of the moisture to be lifted into a low stratus deck. Will continue to monitor through the night, especially in southern Indiana where the hi-res models hit the fog potential the hardest. If the front gets hung up, there could be an opportunity for locally dense fog the farther north you go. Updates on the way shortly to come in line with hourly trends and remove precip mention. && .Short Term...(This evening through Tuesday) Issued at 242 PM EDT Mon Mar 15 2021 Expect widespread rainfall across southern Indiana and central Kentucky through Monday evening as a shortwave trough ejects from a closed 5H low over the central US and moves through the OH Valley. Latest surface analysis continues to place the triple point of the occluded low in far western KY with the warm front extending ESE across TN. Current radar shows rainfall with embedded moderate to heavy showers moving NE through the CWA with measurable rainfall now reaching as far east as Mercer and Boyle Counties. Latest HRRR and NAM3K agree on decreasing rain rates and coverage by early evening and most if not all rain exiting east of our area before midnight. So far, heavier rainfall has reduced visibility down to less than 2 miles at BWG and HNB, though total rainfall amounts through this evening are still expected to be between 0.25 to 0.50 inches. Tuesday will remain dry yet mostly cloudy as weak surface ridging builds over the region beneath deep SW flow. Cloud cover overnight will keep temperatures mild with Tuesday morning mins in the mid to upper 40s north of the Parkways and in the low 50s south of there. WAA as a result of SW flow will result in above normal max temps Tuesday with afternoon highs in the upper 60s to low 70s. .Long Term...(Tuesday night through Monday) Issued at 322 PM EDT Mon Mar 15 2021 ============================================= Synoptic Overview ============================================= Upper air pattern at the beginning of the period will feature a broad ridge over the southeastern US with an upper level wave moving into the lee of the Rockies. The vigorous upper level wave will deep as it cross the Plains and generate a surface cyclone over Oklahoma which is then forecast to move into IL by Thursday morning and then off into southern New England by Friday morning. Widespread convection is forecast to occur ahead of this developing cyclone with a substantial risk of severe weather across the southeastern portions of the United States. Once the system moves east, upper level ridging over the Plains will move eastward and build into the Ohio Valley. Dry weather with a moderation in temperatures is expected over the weekend and into next week. ============================================= Model Discussion and Sensible Weather ============================================= In general, the models are in decent agreement with the overall pattern. By Wednesday morning we will see a surface low developing over Oklahoma with a warm front extending eastward through the TN Valley. Vigorous upper level wave is forecast to move through the Plains with the surface low moving into southern IL by Thursday morning. Attendant cold front will surge eastward and will probably be in the process of occluding as it heads through the Ohio Valley. Main forecast challenge will be how far north will the warm front surge and where the triple point of the system will be. These factors will heavily influence our chances at seeing strong/severe convection. Consensus of the current guidance suggests that the warm front will make its way northward close to the southern Ohio Valley. Model dewpoint forecasts suggest dewpoints getting into the upper 50s to possibly the lower 60s. However, model soundings still have a bit of CINH across the region with some elevated instability. Shear values still look impressive with a low-level surface ESE flow veering around to the southwest. Most likely scenario is that we`ll see an increasing amount of shower and thunderstorm activity move northward into the region Wednesday afternoon, though much of this thunderstorm activity will likely be elevated. More surface based thunderstorm development looks to remain south across AR/TN/MS/AL/GA where stronger instability will reside. As cold front heads eastward, we`ll have to be on close guard to see how much surface based instability develops northward into the region. CIPS analog guidance still has much of the severe threat contained to our south. However, by Wednesday night, we do have some steepening of lapse rates aloft and weak instability that could promote a severe hail threat across southern KY. As mentioned in this morning`s discussion, wet bulb values remain pretty low and the CIPS analogs had a few events that were hail storms across TN. Although the model soundings still show quite a bit of mid-level saturation that may limit the overall hail threat. Current SPC risk profile of a slight risk is justified across SW KY and I suspect that slight risk will be adjusted a little eastward in subsequent outlooks, though I don`t think it would come north of the BG/WK Parkways. Widespread showers along with scattered thunderstorms are expected across the region late Wednesday night and early Thursday as the occluded front works eastward through the region. With the upper trough swinging through during the day on Thursday, additional showers are expected to continue. We should start to dry out by Friday as moisture gets shunted to the east and southeast fairly quickly with a large amount of upper level ridging building into the region for the weekend and into early next week. A moderation in temperatures is expected through this time frame. As for temperatures, we`ll be quite mild on Wednesday with highs in the mid-upper 60s with lows in the 50s. Highs in the 60s are likely for Thursday as well, but we`ll see a cool down Thursday night and Friday behind the departing system. Highs Friday will likely only top out in the upper 40s to the lower 50s. Highs on Saturday should warm into the upper 50s with upper 50s and lower 60s expected on Sunday. We expect slightly warmer readings by Monday, probably in the 65-70 degree range. ============================================= Societal Impacts ============================================= A period of strong to possibly severe thunderstorms exists for Wednesday afternoon and Wednesday night. The highest risk of severe weather looks to be across the southern half of Kentucky. ============================================= Forecast Confidence ============================================= Overall storm evolution for Wed/Thu : Moderate Risk of strong/severe storms for S IN/N KY : Low Risk of strong/severe storms for S IN : Low-Moderate Drier and warming trend for weekend : Moderate && .Aviation...(00Z TAF Issuance) Issued at 705 PM EDT Mon Mar 15 2021 Tricky forecast overnight with stratus and LLWS concerns associated with a warm front lifting north across the region. Last few showers will be moving out and/or dissipating early this evening, and then easterly winds will veer to nearly due south after midnight. There`s a narrow window of opportunity just before that for some low-level wind shear, as sfc winds will be light out of the SE while the LLJ cranks up to 35-40 kt from the SW. Will include it briefly starting at 05Z at SDF (and HNB and LEX) but it should abate by 08-10Z as the warm front kicks northward. MVFR stratus will run below 2000 feet at least through this evening, with SDF and HNB potentially on the edge of some LIFR with the warm front. As the night goes on, the cutoff between the lowest stratus and possibly even VFR conditions will sharpen, so there`s some bust potential. Will include TEMPO for IFR conditions. Warm advection on Tue morning should mix out the low levels pretty quickly, improving cigs to VFR. && .LMK WATCHES/WARNINGS/ADVISORIES... IN...None. KY...None. && $$ Update...RAS Short Term...CG Long Term...MJ Aviation...RAS
Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
909 PM CDT Mon Mar 15 2021 .UPDATE... 909 PM CDT The main band of precipitation has shifted north of the area. The focus is now on two areas of precip, the lingering drizzle across northeast IL and another band of rain showers across central IL. Continued low level lift in the lowering cloud deck will support some lingering drizzle through the evening and early overnight hours. Temperatures hover between 31 and 33 and they will likely hold here (or maybe inch up due to increasing dewpoints). Therefore while we may have some freezing drizzle obs, the impacts should be fairly limited given the marginal temperatures. Still, localized slick spots may still be possible. With the continued moist conditions, patchy fog will continue, with no obvious sign that things will drop significantly given some continued winds, cloud cover, and no large surge in moisture. The compact shortwave across Missouri will drive an area of showers across central IL tonight. The main instability axis will just graze the area to the south, thus these should overall be fairly light. KMD && .SHORT TERM... 330 PM CDT Through Tuesday night... A true spring snow system with a hodgepodge of precipitation types, gusty winds, embedded bursts of snow, and isolated lightning! Snow is tapering from south to north through the rest of the afternoon. The primary concern going forward after dark will be the potential for freezing drizzle. The strongly forced zone of precipitation associated with the left exit region of a 120+ kt jet is lifting northward through far northern Illinois and Wisconsin. Regular 1/4SM visibility within heavy snow was seen within this, along with a handful of CG lightning strikes in north central Illinois. The system dry slot nose on the aforementioned jet basically is moving northward on the back side of this, with a zone of steepened lapse rates above 800 mb helping to force isolated showers (with sleet or snow). Impacts into the evening commute will primarily be residual from what has fallen, apart from the far northern Chicago metro which will likely still see some snow activity. Beneath the dry slot, low-level moistening is occurring with some lowering cloud bases, although as of 3 PM these are still almost entirely above 1,500 ft (not ideal for drizzle). This appears to improve this evening on forecast guidance, and observational trends support that upstream with lower clouds, as well as some drizzle already east of Peoria northward toward LaSalle-Peru. There was even a social media report to WFO ILX of ice accumulation from freezing drizzle in Eureka, IL near 3 PM. This is the concern for this evening, as today`s precipitation and deep cloud cover lowered temperatures and will keep them down through sunset. The 280K isentropic surface on both the RAP and NAM show a fair amount of upglide through the evening, and model profiles show low-level omega and veering profiles in the lowest part of the column. At least patchy drizzle would seem probable in this setup, but whether or not it`s heavy enough and pavement actually becomes icy where temperatures are 32 or lower is challenging to say. This is especially true considering much of the pavement is wet and/or treated. Will be something we will need to watch though. Also some fog is possible tonight as the boundary layer moistens and with the already moist and cooler ground from today. Otherwise the strong short wave near the Kansas City metro area will move east-northeastward across central Illinois late tonight. On the northern periphery of this, some convection may clip the far southern CWA, but expecting a gradual weakening trend in this wave overnight which will limit any amplification and northward push to this, so not expecting this to be a big deal. Clouds are likely to stick around under an inversion through Tuesday. Mid-level heights only gradually rise through the day with limited cloud bearing flow. Did tweak down highs some and may have to a little further. MTF && .LONG TERM... 325 AM CDT Tuesday through Sunday... While the primary focus this morning is on our near-term impactful weather, another strong storm system is expected to affect the forecast area from Wednesday through Thursday night/early Friday. Locally heavy rainfall amounts and another round of strong gusty northeast winds are the main expected impacts, with some thunderstorm potential across the southern parts of the cwa as well during Wednesday night/Thursday period. Surface low pressure and mid-level short wave trough associated with our near-term inclement weather will exiting the are to the east on Tuesday morning. Some patchy drizzle or light freezing drizzle may linger past daybreak, though ascent atop the shallow moist layer should diminish quickly with the departure of the mid- level wave. Mid-level short wave ridging is slower to develop eastward across the region during the day, though subsidence does strengthen in the afternoon which may help to erode some of the lingering low cloud cover later in the day as the associated inversion lowers. Surface high pressure develops just to our north and northeast Tuesday night as the mid-level ridge moves overhead, with dry weather and lighter winds into early Wednesday. Lingering low clouds and likely some lingering snow cover will tend to keep temps down a bit over far north and northwest parts of the cwa Tuesday, while modest northeast onshore winds cool lakeshore areas in the Chicagoland area. Daytime temps Tuesday should be closer to mid-March averages across the southern parts of the forecast area. By Wednesday, a sense of deja vu takes hold as attention turns to yet another compact closed upper low tracking east-northeast across the central and southern Plains. Guidance has come into better agreement with the track of the mid-level vort center into southern Missouri Wednesday night, and across southern Illinois during the day Thursday, with the slight negative tilt to the mid- level axis takes the surface low just a bit farther north than some previous forecasts. Initial effects from this system will again be increasing east-northeast winds across the forecast area Wednesday, with precipitation developing Wednesday afternoon into Wednesday evening as the southerly warm/moist conveyor stream ascends north of the surface warm frontal zone within the eastern periphery of the wave. Current model guidance depicts a warmer thermal column than with our early-week system, resulting in primarily rain expected. Northeast low level flow will maintain a feed of cooler/drier air across the far northern parts of the forecast area however, where some rain/snow mix may be possible later Wednesday night and early Thursday as the column saturates. This system will have a more wide-open Gulf and stronger circulation as it transits the region, pulling warmer and higher moisture content air into the storm. P-wats of around an inch are progged into the southern parts of the cwa Wednesday night into early Thursday, which combined with relatively steep mid-level lapse rates and some elevated thunderstorm potential across our southern cwa will have the potential for producing some locally heavy rainfall amounts in the 1-1.50" range. With the slightly farther north track of the low, guidance focuses some of these higher rainfall amounts as far north as the I-80 to I-88 corridor, with late Wednesday night into early Thursday looking like the main period of the heavier rain. This coincides with the best juxtaposition of deep forcing - strong moisture advection/isentropic upglide north of the warm front and at least weak elevated instability along with indications of coupled upper jet exit/entrance regions over the western Lakes region. Forcing weakens during the day Thursday as the system occludes and passes off to our southeast. As alluded to above, with the surface low passing south of the area strong east-northeast winds are expected especially during the late Wednesday night through Thursday night period. Various model soundings and time-height sections indicate 35-40 kt winds 1000-1500 feet off the surface, supporting the potential for 30-40 mph surface wind gusts. The prolonged period of northeast winds will likely result in high waves on southern Lake Michigan, which could lead to minor lakeshore flooding issues along the Illinois and Indiana shores. Models diverge with what happens to the departing upper low across the southeastern U.S. late in the period, though are generally in agreement in developing upper ridging from the Plains into the western Great Lakes northwest Friday into Saturday. This results in sprawling surface high pressure across the Great Lakes region Friday into Friday night, with some milder return flow developing across the area Saturday as the ridge drifts off to the east. So the end of the week looks quiet, with the potential for warmer temps heading into the weekend. Ratzer && .AVIATION... For the 00Z TAFs... Primary Forecast Concerns * Lingering drizzle and freezing drizzle through the evening and early overnight hours * Expanding IFR cigs and vis and potential LIFR early Tuesday AM The primary band of heavy wintry precipitation has since lifted northeast of the area with lingering light precipitation falling mainly as light snow/drizzle/freezing drizzle. Surface temperatures in the low 30s heading into the evening hours suggests that at least some freezing drizzle will persist in areas that surface temperatures remain at or below freezing. Anything that does fall will be light, however. IFR cigs and vis are expanding in coverage this evening as the system pulls away from the area. With the fresh snow/sleet pack felt more confident to introduce a period of LIFR cigs early Tuesday morning. There remains some uncertainty with how quickly the LIFR/IFR cigs stick around into the morning hours. For now have things improving around 15Z. Winds will remain a bit gusty here this evening into the 20kt range but will gradually ease overnight. Winds then become light out of the N/NE into early Tuesday with a reinforcing lake breeze possible Tuesday afternoon. Petr && .LOT WATCHES/WARNINGS/ADVISORIES... IL...None. IN...None. LM...Small Craft Advisory...IL nearshore waters until 4 AM Tuesday. Small Craft Advisory...IN nearshore waters until 10 PM Monday. && $$ Visit us at Follow us on Facebook, Twitter, and YouTube at:
Area Forecast Discussion...UPDATED
National Weather Service Memphis TN
947 PM CDT Mon Mar 15 2021 .UPDATE... 9 PM / 02Z surface analysis showed a stationary front across central MS, curving northeast to near Monroe county. Dewpoints in the Aberdeen and Columbus areas prevailed in the lower 60s, while further north, lower 30s dewpoints were common across the border in west TN. Isolated severe thunderstorms that formed over central MS along the front earlier this evening have weakened and moved into AL. Short range convection-allowing models (CAMs) - earlier HRRR runs excepted - kept thunderstorms out of northeast MS overnight. Latest HRRR have fallen in line, keeping storms over east central MS and AL, where a stronger low level jet will set up. Low PoPs remain in order for northeast MS overnight, given the proximity of the stationary front. Areas of fog will be possible over north MS and portions of west TN near the TN River toward morning, as the stationary front begins to lift north as a warm front. Early look at 00Z guidance for Wednesday shows instability, steep lapse rates and directional shear are likely to be in bountiful supply. All severe weather modes, including tornadoes, appear to be possible. PWB && .PREV DISCUSSION... /issued 622 PM CDT Mon Mar 15 2021/ UPDATE... Updated for the 00Z Aviation Discussion PREV DISCUSSION... /issued 338 PM CDT Mon Mar 15 2021/ DISCUSSION... The primary focus in today`s forecast is the midweek severe weather potential. Guidance continues to highlight a multi- hazard threat Tuesday night through Wednesday evening affecting much of the Mid-South. At this time, the main question is how far north the warm front will lift, representing the northern extent of the primary threat area. The current Enhanced Risk is the first for the Memphis County Warning Area (CWA) since May 3, 2020. The occluded low over the central CONUS will meander over the Plains into the midweek period as the shortwave currently over CA carves out a deeper trough across the Southern Plains Tuesday into Wednesday. In the meantime, the front that moved through the CWA today will stall just south of the area. Warm advection over the top of this boundary may result in scattered showers and thunderstorms tonight, mainly south of Tupelo. Any instability will be elevated, but these storms could produce small hail and heavy downpours. Elsewhere, generally dry weather is expected across the Mid-South overnight with fog possible (mainly along and south of I-40). The potential for a few storms will continue on Tuesday along the southern boundary of the CWA but otherwise warm and dry weather is expected. The warm front is expected to lift north Tuesday night, providing the impetus for elevated convection during the overnight period. Strong forcing for ascent downstream of the approaching trough will steepen lapse rates, enhancing the instability aloft. Hodographs show a good amount of helicity in the elevated layer and could support a marginal supercell environment with hail being the primary concern. The warm front will continue to lift north during the day, putting a large chunk of the Mid-South within the warm sector by peak heating. Most of the messy convection is expected to lift north with the warm front, but if the warm sector is contaminated, it could limit instability. However, at this time we expect SBCAPE exceeding 1000 J/kg throughout the Enhanced Risk area. Low-level wind shear will be strong area wide with 0-6 km bulk wind difference in the range of 50- 60 kts. This will be more than favorable for rotating storms, especially any discrete cells that develop within the warm sector. All modes of severe weather remain on the table, including large hail, damaging winds, and tornadoes (perhaps some strong). The warm front will represent the northern extent of the severe weather risk, so this risk will expand northward if this front lifts more aggressively. The cold front will swing across the area late in the day through the evening hours. Storms are likely to line up along the front as it moves across the Mid-South with a shear vector oriented roughly orthogonal to the boundary. Given low-level hodographs and strong line-normal shear, a QLCS with tornado and damaging wind potential will be possible. This convection will move easter into the Wednesday night period but should be east of the area before sunrise. The parent upper-level cyclone will move across the OH Valley on Thursday. Most guidance keeps this low just north of the CWA, though the ECMWF favors a slightly farther south solution. Strong westerly, post-frontal winds are expected on the southern periphery of this low. Ensemble guidance indicates a zonal component of the 1000 mb wind in the 97th+ percentile, which pushes wind speeds up near Wind Advisory criteria. There are still plenty of moving parts, but we`ll be keeping an eye on this potential. Cooler and drier air will settle over the region Thursday through the weekend. However, some wrap-around light rain is possible through Thursday, mainly in the northern half of the CWA. Dry conditions are expected Friday through Sunday. Temperatures will take a step back to slightly below normal Friday and Saturday but are expected to begin a warming trend by Sunday. Finally, we`re still not to our normal last freeze date but a lot of vegetation is beginning to bloom. With that in mind, we`ll be watching the potential for a light frost over the weekend within the cool, dry air mass. That said, the surface anticyclone may be too far removed to the north. MJ && .AVIATION... VFR conditions will be found across much of the Mid-South for the entire forecast period. Low clouds will move into portions of northeast Mississippi overnight producing MVFR ceilings and maybe some patchy areas of fog. The low clouds should exit the region by mid-morning on Tuesday. Winds will be mainly from the south at around 10 knots this evening before diminishing to around 5 knots overnight. Winds will shift to the west on Tuesday. ARS && .MEG WATCHES/WARNINGS/ADVISORIES... AR...None. MO...None. MS...None. TN...None. && $$
Area Forecast Discussion
National Weather Service Mobile AL
1022 PM CDT Mon Mar 15 2021 .Overnight /Now Through Sunrise Tuesday/...Through sunrise Tuesday, deep convection is expected to re-develop over portions of interior SE MS and Inland SW Alabama sometime just after midnight and generally along an axis from Wayne Co., MS to Choctaw Co., AL). Individual updrafts are forecast to move northeast. This axis seems to be shifting subtly southeastward with each latest model run and we continue to monitor. The ongoing cluster of deep convection over SE LA has produced outflows that are observed to be propagating northward and this will aid in the initiation later tonight (along with deep moisture flux convergence that is already operating to actively pool low level water vapor in a regional warm sector that will remain synoptically steady-state overnight). SPC SREF forecasts mean MLCAPE of at least ~1000 J kg-1 through 06-09 UTC, so instability will not be an issue. The ambient pre-storm environment at the time of initiation will be characterized by the greatest low- level vertical wind shear below about 1.5 km, which is seen to be contributing most of the clockwise curvature to the forecast regional hodographs (and producing Effective SrHel values of 200-250 m2 s-2, and this is close to what already is being observed as of this writing.) Straight-line VWS above ~1.5 km with lots of storm-relative flow which promotes updraft longevity, tends to favor the right-moving member of splitting updrafts (as we have already observed with a pre-cursor updraft earlier this evening) and also aids developing hail embryos as they move through the hail growth zone. There is also sufficient CAPE forecast to be in the hail growth zone at that time to support perhaps up to 1.5" diameter hail. A brief short-lived tornado and damaging wind gust cannot be ruled out. The SPC has maintained a Marginal Risk through 7 AM CDT, and we concur locally. So, areas generally west of I-65 and mainly north of Highway 84 are the areas of concern in the wee hours of Tuesday morning). /23 JMM .NEAR TERM /Tuesday Through Wednesday Night/...The pattern on Tuesday is not expected to be too different from that of Monday, with a conditional threat of severe weather associated with any stronger thunderstorms that develop and SPC maintains the Marginal Risk of severe storms over the northern half of our forecast area on Tuesday. Expect to have ongoing convection during the early morning hours on Tuesday morning, primarily over the northwestern portions of the forecast area. Leftover convection from the pre- dawn activity will become more widespread over the northern half of the forecast area during the course of the day in association with the lingering convergence zone just to the north of our area in conjunction with some weak shortwave activity in the west- southwest flow aloft. With daytime heating, MLCAPE values will increase to be between 500-1000 J/kg by Tuesday afternoon, with the higher instability values up to near 1600 J/kg over our northern counties. Also, 0-6 KM bulk shear values will be around 35-45 knots across much of the area during this time, along with 700-500 mb lapse rates around 6.0-6.7 C/km and 0-1km SRH generally between 100-200 m2/s2 (especially Tuesday morning). There will be some weak capping between 700-600 MB, and similar to Monday, this could have a limiting affect on the convection at times. But sufficient daytime heating and deep layer moisture could aid in eroding the cap and lead to increased chances for thunderstorms (especially over southeast Mississippi and inland southwest and south-central Alabama), and some of these storms could be strong to severe (as previously mentioned. Curved low-level hodographs could also result in some rotating cells. Thus, the main threats anticipated are damaging winds and hail; but, a tornado or two cannot be ruled out. By late Tuesday afternoon through Tuesday night convection diminishes somewhat, although an isolated to scattered storm will still be possible overnight (especially over the northern portions of the forecast area). At this time, it does not appear that there will be much of a severe threat with those. High temperatures on Tuesday will range from the mid and upper 70s over most of the forecast area, but a pocket of lower 80s will be possible over interior south central Alabama and part of the interior western Florida panhandle. Tuesday night low temperatures primarily in the low to mid 60s across the entire area. A HIGH RISK of rip currents continues along the beaches for Tuesday and Tuesday night. /12 An active severe weather day looks to unfold on Wednesday into Wednesday night. An upper level trough centered over the south- central Plains states takes on a negative tilt into the night Wednesday as it shifts east into the east-central Plains and Midwest. Upper level ridging amplifies in response over the far southeastern U.S. and western Atlantic during the period. Uncertainty remains in model guidance on exact evolution of the upper level trough, and southeastern periphery of best upper level difluence. Despite some questions on overall magnitude of large scale forcing for ascent over our CWA, ample wind shear and CAPE will be available in advance of an eastward moving cold front. During the day Wednesday, forecast models are in general agreement on developing 1,500 to 2,000 J/kg of SBCAPE, with similar MLCAPE values nearer 1,500 J/kg. Some hi- res guidance like the HRRR suggests higher SBCAPE and MLCAPE values could be realized, and is something to keep an eye on as we near Wednesday. CAPE values taper off in the evening somewhat, remaining more than adequate for severe storms with 1,000 J/kg MLCAPE and 1,500 J/kg of SBCAPE. Very steep low level lapse rates look probable nearer 7C/km, with mid-level lapse rates approaching 8C/km. Shear will undoubtedly be supportive of severe thunderstorms, including supercells. Elongated, curved hodographs with deep layer shear around 40kts will be present during the day Wednesday, strengthening into the evening and overnight to over 50kts as the nocturnal low level jet begins to crank upwards of 50kts. This will in turn help to enlarge hodographs and increase Storm Relative Helicity values appreciably after dark in excess of 300 to 400m^2/s^2 from afternoon values around 200 m^2/s^2. All hazards of severe weather are possible Wednesday late afternoon into the overnight hours, with damaging winds, tornadoes (some strong), and large hail (up to golf ball size) possible. A potential limiter for day time convective coverage would be the presence of a healthy EML (Elevated Mixed Layer) located at the 700mb level. This will help to keep the environment capped until better forcing can move in or daytime heating can overcome the EML. It is important to note/reiterate the uncertainty in where best forcing will align with the aforementioned ingredients along with timing of better forcing. This will affect overall timing of better severe weather potential. The first round of isolated to scattered convective potential appears to potentially develop during the early to mid afternoon hours across much of the CWA. This would likely be in the form of isolated to scattered discrete to semi-discrete thunderstorms capable of all severe hazards that move and develop from southwest to northeast across the area. A better threat for strong to severe thunderstorms will likely evolve from west to east during the late evening into the overnight hours along the cold front as a line of strong to severe thunderstorms pushes eastward across the region. Convection quickly tapers off behind the front during the late overnight into early morning hours, with the front exiting the CWA prior to or near daybreak Thursday. Outside of the severe threat, high temperatures look to peak in the upper 70`s to lower 80`s during the afternoon, with lows Wednesday night in the middle to upper 50`s west of I-65, and lower 60`s to the east of I-65. Best rain and thunderstorm chances appear to be late afternoon into the late night hours, waning from west to east following the frontal passage during the overnight hours. In addition to the severe risk Wednesday, strong wind gusts are possible ahead of the front over the open warm sector during the afternoon into night time hours. Wind gusts of 30 to 35mph appear probable amidst strong southerly low level flow, and would not be surprised if a Wind Advisory becomes necessary for parts of the CWA during the period. A HIGH RISK of rip currents continues through the day Wednesday into Wednesday night. MM/25 && .MOB WATCHES/WARNINGS/ADVISORIES... AL...High Rip Current Risk through Friday morning for ALZ265-266. FL...High Rip Current Risk through Friday morning for FLZ202-204-206. MS...None. GM...None. && $$ This product is also available on the web at:
next weekend. The upcoming forecast discussions and packages will
focus more on this storm system with additional details after the
current system exits the region. && of 6:00 PM PST Monday...For the 00Z TAFs. KMUX radar shows widely scattered to scattered showers over the southern half of the cwa. Metar observations show VFR and gusty west to northwest winds, ceilings briefly lowering to MVFR with passing showers. With the loss of diurnal warming expect clearing tonight and surface winds decreasing. VFR tonight and Tuesday. Vicinity of KSFO...VFR, northeast wind 5 to 10 knots, wind shifting to west 10 to 20 knots by mid evening then decreasing overnight. West wind 10 to 15 knots Tuesday. SFO Bridge Approach...Similar to KSFO. Monterey Bay Terminals...VFR, west to northwest winds 10 to 20 knots until mid to late evening the decreasing overnight. East to southeast cold air drainage winds at 5 to 10 knots developing late tonight and early Tuesday morning. West to northwest winds 10 to 15 knots Tuesday afternoon and early evening. && of 01:11 PM PDT Monday...As the cold front has passed over the waters, scattered showers continue and are expected through this evening, with a slight chance for an isolated thunderstorm. The bigger impact to mariners will be the strong and gusty, gale force northwest winds that are forecast to continue on through tonight, generating very steep combined seas of 15 to 20 feet at roughly 10 to 12 seconds. These very steep seas and gusty winds can capsize small vessels and bring other hazardous conditions across the seas. Winds look to start to calm down in the bays this afternoon, with coastal waters following around sunset. Outer waters will remain gale force through most of the night tonight. Seas are expected to subside late on Tuesday. && .MTR WATCHES/WARNINGS/ADVISORIES... .Tngt...Frost Advisory...CAZ506-516-528 GLW...Pt Arena to Pt Reyes 0-10 nm until 9 PM GLW...Pt Reyes to Pigeon Pt 0-10 nm until 9 PM GLW...Pigeon Pt to Pt Pinos 0-10 nm until 9 PM GLW...Pt Pinos to Pt Piedras Blancas 0-10 nm until 9 PM GLW...Pigeon Pt to Pt Piedras Blancas 10-60 nm until 9 PM GLW...Pt Arena to Pigeon Pt 10-60 nm until 3 AM SCA...Mry Bay until 3 AM && $$ PUBLIC FORECAST: DRP AVIATION: Canepa MARINE: Dhuyvetter Visit us at Follow us on Facebook, Twitter, and YouTube at:
Area Forecast Discussion
National Weather Service Pocatello ID
704 PM MDT Mon Mar 15 2021 .UPDATE...Added precipitation along the Utah border and in the Central mountains for early this evening. Little, if any, precipitation is expected to hit the ground. Also adjusted this coming mornings lows slightly up. Wyatt && .PREV DISCUSSION... /issued 152 PM MDT Mon Mar 15 2021/ SHORT TERM...Tonight through Wednesday night. Deep narrow trough shifting through coastal states continuing to split. Southern closed low tracks well south of Idaho through the rest of today and tonight. A few very spotty showers/virga still possible this afternoon and evening, but confidence is extremely low as models continue to trend drier over East Idaho. Best chances COULD be over the northwest portion of Custer county and along the Southern Sawtooth region, then along the Wyoming border overnight and into early Tuesday. HRRR develops a stronger downvalley gradient overnight, mainly across the INL, but guidance keeps winds low. As low tracks through Utah during the day Tuesday, wrap around moisture could impact areas in the southeast corner. This carries a higher confidence with greater model consensus. Otherwise the short term looks rather dry and remaining above normal for temperatures. DMH LONG TERM...Thursday through Monday night. Dry, mild and delightful late-winter conditions will punctuate conditions on Thursday as southerly flow gradually increases in advance of an incoming low pressure trough and attendant surface cold front. Speaking of this incoming system, the NBM continues to trend faster with the precipitation onset by a few hours. Did not adjust this offering as the NBM is well within the realm of possible scenarios. At this time, ensemble cluster analysis still favors a slightly slower solution, albeit by only a few hours. Current NBM will represent the official forecast, and as such a quickly blossoming area of precipitation is depicted across the central Idaho mountains during the morning, followed by an eastward expansion during the afternoon and early evening. As mentioned, a slightly slower onset may come to fruition, but only by a few hours. Ensemble and deterministic models continue to support the development of an organized NE-SW oriented band of precipitation Friday evening. There are some differences with regard to timing and placement, with possible scenarios ranging from the band developing across the central Idaho mountains, southern Snake Plain, eastern Magic Valley and points south towards the NW UT/NE NV. An alternate scenario depicts the band developing across the eastern highlands, also on Friday evening. The NBM does a nice job of adequately representing both scenarios with a blended approach. Valley rain and mountain snow appears increasingly likely by late Friday afternoon/early evening beneath this band. Snow levels are initially forecast in the 7,000-8,000 foot range, but the combination of diabatic cooling and modest cold advection will result in a gradual decrease in snow levels through Friday night. The above-mentioned precipitation band is shown moving out of the area Saturday morning on faster scenarios, limiting potential snow accumulations to high-elevation eastern highland valleys. The slower scenario is a bit more interesting, as thermal profiles may be cold enough for snow in the Snake Plain Saturday morning, assuming moisture and lift remains to support precipitation. At this point, either scenario is possible. Either way, much welcome rain and snow is looking like a good bet with this system. Precipitation should become more showery in nature by Saturday afternoon with activity becoming more focused across higher terrain areas. The most likely scenario currently depicts a drying trend for Sunday before another system spreads rain and snow across the area for Monday. Many detail differences remain, but the overall trend would favor an increase in precipitation chances during this time. AD AVIATION...Mid to high level clouds are forecast to continue allowing for VFR ceilings for much of the period. Some lower cloud decks are expected to work their way into the region overnight into Tuesday morning with a chance for showers/virga in the vicinity, mainly at KBYI and KDIJ. Low-level winds will increase as the pressure gradient tightens in response to a pair of nearby low pressure systems, the stronger of which passing through the southern Great Basin and the weaker one meandering through central Oregon. As a result, low-level N-NE winds will increase across the region tonight into Tuesday morning. Forecast soundings indicate NE winds increasing into the 25-35kt range between roughly 1kft-1.5kft around 09Z at KPIH and KIDA. Should surface winds slacken with the loss of daytime heating (as indicated on soundings) wind shear would meet thresholds, and as such have added a WS mention from about 09-15Z at KPIH and KIDA. Surface winds are then shown to switch to the west Tuesday morning (mainly after sunrise). Given KBYI`s location relative to a nearby wind-shift line, WS may need to be added here as well. AD && .PIH WATCHES/WARNINGS/ADVISORIES... None. && $$
Area Forecast Discussion
National Weather Service Reno NV
131 PM PDT Mon Mar 15 2021 .SYNOPSIS... Snow showers and gusty northwest winds are expected this evening as the atmosphere remains somewhat unstable. High pressure will move into the region Tuesday leaving the forecast dry through Wednesday and early Thursday. A warmer Pacific storm will bring mountain snow, light valley rain showers, and gusty winds Thursday night through Friday. The long range forecast for next week is leaning drier than normal, although storms can`t entirely be ruled out. && .DISCUSSION... * Somewhat unstable airmass coupled with deformation aloft will continue to yield snow showers into this evening. Latest HRRR and HREF bring more of an organized band of showers through W Nevada, Tahoe, and the eastern Sierra between 0z-6z evening which could drop from a dusting up to 1". As temperatures fall this could result in areas of icy roads later in the evening, overnight, and Tuesday morning. We`ve actually had quite a bit of snow today from Cedarville to Lovelock to east of Fallon - probably 2" or more based on webcams. But most has stuck only to non-paved surfaces with NDOT sensors indicating pavement temps well into the 40s. But anything that falls after sundown could be more problematic. Classic March snow. * Next item of interest is a Pacific storm projected to impact the area Thursday night through Friday. This one is warmer than today`s and has more of moisture tap, but not an atmospheric river. Latest ECMWF and GFS ensemble guidance showing most members with a low-moderate end precip event in the Sierra, with only 1 in 10 indicating more than 1" SWE at the crest (mainly GFS members). NBM snowfall also indicating a low-moderate end event along the crest - 4-9" at Donner and 1-5" for Mammoth in the 50th-75th percentiles. For W Nevada the ensemble guidance is pretty pronounced with the shadow so just light rain showers expected along with breezy winds especially Friday. Not a high wind scenario but enough for typical road and aviation travel impacts. * Long range ensemble guidance is leaning toward a less active and warmer pattern for next week with high pressure ridge along the coast becoming a dominant feature. No large storm signals in the ensembles or AR landfall probability charts, but there are members that bring a low-end system through Monday-Tuesday next week with a few rain or snow showers. All in all our snowpack will get a minor boost this Friday, otherwise it`s pretty much locked in as is for the rest of the month. -Chris && .AVIATION... Through mid-afternoon, occasional SHSN or pellets may bring short periods of MVFR/IFR conditions to the main terminals. There is a possibility of a more steady snow area developing around the Tahoe and far western NV terminals around 22-23Z, and continuing until 02-03Z around KTRK/KTVL and 04-05Z around KRNO/KCXP/KMEV/KRTS. Farther south at KMMH, separate snow shower bands are most likely between 21-01Z. While runway accumulations are less likely due to most of this snow falling before sunset, some patchy slush could develop in areas where snow lingers after dusk. Cloud cover and just enough NW-N wind after the snow ends may hold temperatures above freezing long enough to allow sufficient drying and limit ice formation on pavement overnight, although this would depend on how much moisture collects during the snow band. Otherwise, the other possible effect of evening snow is whether skies clear out overnight and allow for patchy FZFG and/or low stratus. Current projections on the blended guidance keep enough cloud cover in place to limit fog, although the HREF indicates some clearing between 10-12Z which could lead to some AM fog. Aside from tonight`s activity, we`re looking at generally VFR conditions (except possible early Wed AM FZFG at KTRK) through Thursday morning, then another storm will bring increased aviation-related wind and rain/snow impacts from Thursday afternoon through Friday. MJD && .REV Watches/Warnings/Advisories... NV...Lake Wind Advisory until 2 AM PDT Tuesday for Lake Tahoe in NVZ002. Lake Wind Advisory until 5 AM PDT Tuesday for Pyramid Lake in NVZ004. CA...Winter Weather Advisory until 5 PM PDT this afternoon CAZ071. Winter Weather Advisory until 5 PM PDT this afternoon CAZ070. Winter Weather Advisory until 5 PM PDT this afternoon CAZ073. Lake Wind Advisory until 2 AM PDT Tuesday for Lake Tahoe in CAZ072. && $$ For more information from the National Weather Service visit...
Area Forecast Discussion
National Weather Service Tallahassee FL
940 PM EDT Mon Mar 15 2021 .NEAR TERM [Through Wednesday]... Light to moderate southerly low-level flow lies beneath fast westerly flow aloft. In the confluent southerly low-level flow, CAMS guidance shows shower activity blossoming overnight south of the Walton and Bay County coastline. Showers should then move to the north-northeast onshore around sunrise, then move inland and across southeast Alabama, curling northeast across southwest Georgia. It will probably take until this cluster is curving northeast in the afternoon to start producing lightning. Otherwise, low stratus is already moving onshore out near Destin, so it seems reasonable to that low stratus or fog will lift north through the Panhandle late tonight, then up across southeast Alabama and counties near the Chattahoochee early in the morning. For the evening update, have lowered PoPs for the rest of tonight, most notably across SE Alabama. Raised rain chances a little early in the morning around Bay County for the showers that are expected to move onshore. && .PREV DISCUSSION [758 PM EDT]... .SHORT TERM [Tuesday Night Through Wednesday Night]... The loss of daytime heating should reduce the threat for any isolated severe storms for the overnight period Tuesday night. For Wednesday, the forecast area will be in a warm advection pattern within the warm sector with highs in the lower 80s and dew points in the mid 60s. Isolated to scattered severe storms will be possible during the afternoon. However, the main event should be in the form of a squall line ahead of an approaching cold front. That should begin impacting our western counties after midnight with impact weather advancing eastward ahead of the front. Most of the weather should be east of the area Thursday afternoon. The primary threats will be damaging straight line winds and isolated tornadoes. .LONG TERM [Thursday Through Monday]... This period should be dry and cooler, albeit not really cold. Overnight lows will generally be in the 40s with highs in the 60s or 70s. The coolest afternoon looks to be Saturday with highs ranging from the upper 50s between Albany and Valdosta to the upper 60s for the southern Big Bend counties. By Monday, everyone will be back in the 70s. .AVIATION... [Through 00Z Wednesday] Fog and low stratus will again be a concern late tonight through a couple hours after sunrise on Tuesday morning in low-level southerly flow. Already, beachfront locations such as Destin are already reporting ceilings of 500 feet or less, so the marine soup is poised to spread inland late this evening and overnight, with VLD the most likely terminal to miss out. Recent runs of the HRRR show a cluster of low-topped shower activity lifting north across the coast near ECP soon after sunrise on Tuesday, eventually affecting DHN and possibly ABY later in the morning. .MARINE... Light to moderate onshore winds will increase to cautionary levels from Wednesday afternoon through Friday night. A wind shift from southwest to northwest will occur from Wednesday night through Thursday night and it is during this period where winds will reach small craft advisory criteria at times. .FIRE WEATHER... The best chance for a wetting rain will be Wednesday into Thursday. Dense fog is possible tomorrow morning in the Florida Big Bend. Elsewhere, fog will be patchy. Otherwise, there are no fire weather concerns. .HYDROLOGY... The Suwannee River at Rock Bluff will gradually recede and drop below flood stage sometime Wednesday or Wednesday night. Rainfall with the next system is not expected to be sufficient for flooding concerns as forecast totals have come down. Heavier rain is expected north of the area. There may be implications down stream in our area if rainfall in the northern part of the ACF basin is excessive. .SPOTTER INFORMATION STATEMENT... Spotter activation is not requested. However, spotters are always encouraged to safely report significant weather conditions when they occur (while following all local, state, and CDC guidelines) by calling the office or tweeting us @NWSTallahassee. && .PRELIMINARY POINT TEMPS/POPS... Tallahassee 62 78 64 80 66 / 10 20 10 20 30 Panama City 65 75 65 77 66 / 20 40 20 30 60 Dothan 63 78 64 80 65 / 20 70 20 60 70 Albany 61 78 64 81 65 / 10 60 30 50 50 Valdosta 59 80 63 83 63 / 0 20 10 20 10 Cross City 60 80 62 82 63 / 0 0 10 10 10 Apalachicola 64 73 64 74 65 / 10 20 10 20 30 && .TAE WATCHES/WARNINGS/ADVISORIES... FL...High Rip Current Risk until 10 PM EDT /9 PM CDT/ this evening for Coastal Bay-Coastal Gulf-South Walton. GA...None. AL...None. GM...None. && $$ NEAR TERM...Haner SHORT TERM...Wool LONG TERM...Wool AVIATION...Haner MARINE...Wool FIRE WEATHER...Montgomery HYDROLOGY...Wool
Area Forecast Discussion
National Weather Service Tampa Bay Ruskin FL
745 PM EDT Mon Mar 15 2021 .UPDATE... Existing forecast on track with no changes necessary. Warm temps continue with overnight lows in the lower 60s and afternoon highs in the lower 80s along the immediate coast thanks to the sea breeze and mid/upper 80s elsewhere. Fog appears to be less of an issue tonight although a few areas may see development of late night/early morning fog. && .AVIATION... VFR expected through period. Light/variable winds overnight increase out of the S/SE during morning, veer SW during afternoon, decrease to light/variable during evening. && .Prev Discussion... /issued 145 PM EDT Mon Mar 15 2021/ Synopsis... 17Z water vapor and H4 RAP analysis showing broad and protective mid/upper ridging continue in place of the eastern Gulf of Mexico and Florida peninsula. Shortwave energy ejecting through the TN valley and the associated inclement weather is being kept well removed from our region...and will remain so for a couple more days. The 12Z sounding from KTBW indicated a well-defined subsidence inversion located at around connection with the aforementioned ridging aloft. PW values are not unseasonably low at around 0.75", but it is dry enough to prevent any of the sea-breezes today from being able to support shower development. That time of year is just around the corner though. At the surface...high pressure extends down the eastern seaboard and over the peninsula. The pattern as a whole is providing us with dry, benign and warm conditions. Temperatures early this afternoon are into the 80s away from the coastline, and are generally holding in the mid/upper 70s at the beaches as the diurnal sea-breeze kicks in and transports some "cooler" air off the shelf waters of the eastern Gulf of Mexico. SHORT TERM (Tonight through Wednesday)... The overall synoptic pattern will not be changing much through the mid-week period, and hence neither will be forecast philosophy. Mid/upper ridging holding in place will keep our forecast dry and increasingly warm. Will likely see temperatures (especially inland) creep up by a couple of degrees each day, and will not be surprised to see a few spots flirt with 90 on Wednesday afternoon. LONG TERM (Thursday through the upcoming weekend)... Progressive shortwave energy ejecting out of the southern Plains on Wednesday will eventually cut off as it moves over the MS/TN valleys Thursday into Thursday night. Good agreement in the ensemble guidance that this energy will finally be able to break down the protective ridge. A cold front trailing from an area of low pressure over the Ohio Valley later Thursday will reach the northern FL peninsula Thursday evening and then slowly sink southward into Friday morning, and then clearing into the Florida Straits Friday afternoon/evening. The best height falls/synoptic support to support organized frontal convection and the potential for strong storms appears as though it will sneak just to our north during the second half of Thursday. However, it will be a close call for the Nature coast zones and will need to keep a close eye on the potential for a stronger storm to move ashore off the Gulf. The best potential for measurable precipitation will also be to the north of the I-4 corridor, although amounts do not look impressive. Likely 1/4" or less. The frontal support only lessens with time and southern progress Thursday night and expect just a broken band of showers (maybe a thunderstorm) for areas along and south of the I-4 corridor Thursday night/early Friday). Friday and Friday night are looking cooler (not cold) and dry in the post-frontal environment. Beyond Friday night, the forecast is of lower confidence. The upper level pattern becomes rather complex, with varying degrees of cut-off energy interacting with the baroclinic zone of the Gulf Stream off the GA/NE Florida coast. Have kept the forecast dry for the weekend as of now, in line with the majority of the ensemble guidance. MARINE... High pressure keeps winds below 15 knots and seas on the low side through the middle of the week. Look for afternoon sea-breezes to turn winds onshore after 1-2pm each day. Stronger flow to cautionary levels is expected from the south ahead of an approaching cold front during Thursday, then shift to the northwest, and remain near cautionary levels Thursday night and Friday in the wake of the front. FIRE WEATHER... Dry and warm conditions continue through the middle of the week. Despite temperatures well into the 80s away from the coast the next several days, increasing low level moisture should help keep relative humidity generally above critical levels. A cold front will bring a chance for a wetting rainfall later Thursday into Thursday night, with best potential for measurable rainfall to the north of the I-4 corridor. Expect cooler and drier weather with a wind shift to the north and northeast for the end of the week behind this front. && .Preliminary Point Temps/PoPs... TPA 66 83 67 84 / 0 0 0 0 FMY 65 85 64 86 / 10 0 0 0 GIF 65 88 64 89 / 0 0 0 0 SRQ 64 82 65 83 / 0 0 0 0 BKV 59 87 59 87 / 0 0 0 0 SPG 68 80 68 81 / 0 0 0 0 && .TBW WATCHES/WARNINGS/ADVISORIES... FL...None. Gulf waters...None. && $$ UPDATE/AVIATION...Hurt UPPER AIR/DECISION SUPPORT...Sobien