Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 02/13/19

National Weather Service Binghamton NY
912 PM EST Tue Feb 12 2019 .SYNOPSIS... A storm system moving through the Great Lakes will continue to spread mixed precipitation across NY and PA through tonight. Another storm will pull a rain and snow mix into our region early Friday. && .NEAR TERM /THROUGH WEDNESDAY/... The new NAM nest and HRRR are picking up well on a dry slot this evening that will move west to east across the area. A band of wintry mix still looks to move through the region overnight ahead of the main cold front. Precipitation chances were adjusted to match the latest trends. With the early and mid-evening updates, some adjustments were based on the latest round of mesoscale modeling. Current radar trends have shown a dry slot this evening that is gradually filling in. However, because of this QPF looks to be a bit less than anticipated tonight in NE PA and the Southern Tier. Also, the blend of mesoscale models still shows portions of the Finger Lakes having temperatures rising to around freezing in the next couple of hours. In these locations discussed above we have converted the winter storm warning to an advisory given the potential still for icing of a tenth of an inch and burst of light snow around sunrise tomorrow. 230 PM update... The changeover from snow to mixed precipitation arrived quicker than expected today, but the net result was the same. While snow totals fell, ice totals increased, creating hazardous travel conditions. The mixed precipitation line will force its way into Oneida County between 4 PM and 6 PM. Elsewhere, the sleet and freezing rain is already occurring. We expect the mixed precipitation to continue through late tonight and taper off as snow showers toward sunrise when the cold front arrives. Cold air sliding across Lake Erie could produce squalls from the Central Southern Tier and lower Finger Lakes to the I-81 corridor on Wednesday. In addition, winds will increase to 15 to 25 mph with gusts of 25 to 35 mph possible, creating blowing and drifting snow. A strong lake band is forecast to form over Lake Ontario Wednesday evening and slide into Northern Oneida County. This lake band could produce 6 to 10 inches of snow by Thursday morning. Additional warnings may be needed. 1030 AM update... Dual-pol radar depicts the mixed precipitation line entering our southwestern forecast area at this time. The NamNest is doing a good job with the changeover, and based on the latest model output we are speeding up the changeover by 1-2 hours across much of the I-81 corridor and areas northeastward. The quicker changeover necessitated we lower the snowfall amounts from the Twin Tiers southward. The latest grids have been published. && .SHORT TERM /WEDNESDAY NIGHT THROUGH THURSDAY/... Thursday through Friday... Main concerns in the short term are focused on the ending lake effect snow across mainly Oneida County Thursday morning...the next weak low pressure system expected to clip the region with a mix of light snow and rain Thursday night through Friday afternoon...and above average temperatures on Friday as well. Exiting low pressure system over Maine will continue to have enough cold air rotating around the back side of the system and favorable west winds Thursday morning to trigger an additional 1 to 3 inches of snow over portions of northern Oneida County. The period of additional lake effect snow should be short-lived as upper level ridging and backing winds lift any remaining snow to the north and dissipate it through the rest of the morning. Weather conditions will likely be fairly quiet through the rest of the day Thursday as high pressure moves through and the next system prepares to move in from the Great Lakes. Temperatures on Thursday are expected to warm into the 30s and lower 40s. Winds out of the south will combine with a weak warm air advection regime ahead of the next system to slowly warm the low levels above freezing. The leading edge of the precipitation Thursday evening/night will move west to east across the region in the form of light snow. However, the response from the warm air advecting in from the south will push much of the boundary layer above freezing and allow the snow to mix with rain into the morning hours on Friday. Continued warming on Friday will turn much of the area to all rain...with the exception to nrn Oneida and the highest elevations of the Catskills where a mix of rain and snow may persist. Rainfall amounts will generally range from a couple hundredths up to a quarter inch of liquid. && .LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/... Friday night through Monday... Area of low pressure will move from the Central Great Lakes into srn Quebec and allow a trailing cold front to sweep through the region with a minimal amt of moisture available to produce an area of light snow through Saturday morning. Snow amounts should be less than 2 inches. A period of quiet weather is expected Saturday into at least early Sunday with high pressure building across the region. Boundary layer winds out of the nw may become favorable for lake effect snow, but the limiting factors will be the lack of moisture and the shallow depth of the mixed layer on Saturday. So...will continue with chance pops Saturday and dry weather Sat night. There is some agreement among the models for a mid-Atlantic system moving by to the south Sunday and Sun night...which would brush the southern half of the forecast area with a quick hit of snow. Still quite a bit of uncertainty being 5-6 days out. Does appear that temperatures will drop back to near normal this weekend and early next week as the jet stream dips south. Highs in the 20s and 30s...and overnight lows in the teens and 20s are expected. && .AVIATION /02Z WEDNESDAY THROUGH SUNDAY/... A wedge of fairly deep low level cold air was still hanging tough early this evening with most of the terminals still indicating mainly a snow/sleet mix rather than a phase of freezing rain/sleet. The warm air aloft will continue to surge in between 00Z-05Z thus we still expect more of an evolution toward freezing rain. Models suggest passage of the surface occluded front between 06Z-09Z with best precipitation forcing moving east. At this point, really only expecting the corridor from KELM-KITH-KSYR to experience any changeover to just rain as surface temperatures briefly nudge above freezing. Most lingering precipitation should be over by 09Z with only scattered snow/rain shower activity through morning. Ceilings should be mainly MVFR with occasional variations between VFR and IFR. A period of IFR is possible behind the surface front late tonight/early Wednesday. Dry air aloft will sweep over the region on Wednesday morning with ceilings lifting and becoming broken...then MVFR settles in on colder northwesterly flow during the afternoon. LLWS likely this evening, otherwise...moderate SE winds 15-30 knots become SW overnight, then WSW 20-30 knots on Wednesday afternoon. Outlook... Wednesday night...MVFR. Gusty winds. Localized lake effect snow in the vicinity of KRME. Thursday...Mainly VFR. Thursday night through Saturday...restrictions likely with mixed precipitation. && .BGM WATCHES/WARNINGS/ADVISORIES... PA...Winter Weather Advisory until 7 AM EST Wednesday for PAZ038>040-043-044-047-048-072. NY...Winter Weather Advisory until 7 AM EST Wednesday for NYZ015>017-022>025-044-045-055-056. Winter Storm Warning until 7 AM EST Wednesday for NYZ009-018- 036-037-046-057-062. && $$ SYNOPSIS...DJP NEAR TERM...DJP/MWG SHORT TERM...BJT LONG TERM...BJT AVIATION...JAB
Area Forecast Discussion
National Weather Service Columbia SC
1025 PM EST Tue Feb 12 2019 .SYNOPSIS... A cold front will cross the area tonight. High pressure will be over the region Wednesday and Thursday with the next in a series of systems crossing the region Friday into the weekend. && .NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/... The main line of showers ahead of the cold front has moved well east of the forecast area. Strong gusty winds were associated with these showers. Peak gusts were 56 miles an hour at Augusta Bush Field and 54 mph at Columbia Metro. We sent a public information statement with a listing of peak gusts earlier tonight. There will be lingering showers until drying occurs behind the cold front. The HRRR and radar trends support showers moving out of the area between midnight and 300 am. Winds have diminished because of less mixing. Observation trends and the GFS LAMP suggests gusts 15 to 20 knots and below the lake wind advisory criteria. The temperature guidance was close with lows in the lower to mid 40s. && .SHORT TERM /6 AM WEDNESDAY MORNING THROUGH THURSDAY NIGHT/... The cold front will be offshore at sunrise with high pressure and drier air moving into the region. With a pressure gradient remaining tight through the early afternoon winds will remain strong and gusty. As the pressure gradient relaxes through the afternoon expect winds to diminish and become light and variable overnight as an inversion develops. Skies will be mostly clear Wednesday night and combine with the subsiding winds producing excellent net radiational cooling conditions. Wednesday afternoon high temperatures will be in the upper 50s to low 60s with in overnight lows in the mid 30s for most locations. Conditions will be similar Thursday as the high moves across the region with skies remaining mostly clear and light southerly winds. Late Thursday afternoon clouds will begin increasing as the southerly flow increases and continues transporting moisture northward. Thursday night clouds will continue increasing as the next front moves through the TN Valley and into the Upstate around daybreak. High temperatures Thursday afternoon will be in the mid to upper 60s with lows Thursday night in the mid to upper 40s. && .LONG TERM /FRIDAY THROUGH TUESDAY/... Models are in good agreement with the synoptic pattern through the long term with some differences in timing and intensity. The cold front will begin Friday in the eastern TN Valley with models indicating it struggling to cross the Appalachians. As such have adjusted pops to keep highest chance in the northern Midlands with lower pops to the south. Systems beyond Friday will occur in rapid succession as the longwave trough remains over the West Coast with zonal flow over the remainder of the US. The remains of the frontal boundary will stall over the area Friday afternoon with another disturbance moving along the boundary Friday night. This system will mainly stay north of the area however with southerly flow persisting over the area expect showers to develop over the area Friday night into Saturday morning with clouds and frontal remains over the area into Saturday night. The frontal remains will move south of the area Sunday with only a brief period of high pressure building into the area before the front returns northward on Monday with increasing chances of rain for the early part of next week. Temperatures through the long term will be above normal. && .AVIATION /04Z WEDNESDAY THROUGH SUNDAY/... The main line of showers ahead of the cold front has moved well east of the terminals. There will be lingering showers until drying occurs behind the cold front. The HRRR and radar trends support the showers moving out of the area by 07z. Observation trends support VFR ceilings along the front with clouds dissipating in the dry air advection pattern behind the front during the early morning hours. The GFS LAMP indicates gusts around 18 knots through much of the 24-hour TAF period. EXTENDED AVIATION OUTLOOK...Expect VFR conditions through Thursday. A frontal system may bring widespread MVFR or IFR conditions Thursday night through Saturday. && .CAE WATCHES/WARNINGS/ADVISORIES... GA...None. SC...None. && $$ SYNOPSIS...99 NEAR TERM...99 SHORT TERM...99 LONG TERM...99 AVIATION...99
Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
844 PM EST Tue Feb 12 2019 .UPDATE... A region of snow now advancing across the northern half of the forecast area is generally tied to the upper level forcing along the lead edge of the mid level low now lifting toward Central Lower Mi. This region of forcing will generally advance north and east of the area later this evening into the early portion of the overnight. This will greatly diminish the chances for much additional snow north of the I-69 corridor after midnight. Ongoing low level cold air advection within a moist cyclonic flow is however supporting an uptick in the lake response across southern Lake Michigan. With the westerly flow off the lake, convergence will focus higher intensity snow showers across portions of Se Mi, mainly between the I-69 and I-94 corridors. A secondary mid level impulse pivoting around the back side of the upper low will track across far southern Lake Mi overnight, enhancing the lake response. The snow squall risk and potential for additional accumulations in this region mentioned in the previous discussion remains valid. A push of mid level subsidence and decreasing over-lake instability should diminish the lake effect activity by early Wed afternoon, even with a boost in the diurnal cycle. The better downward momentum push associated with the upper wave will occur across the Ohio Valley region tonight. The sfc low is actually forecast to weaken as it lifts into Quebec Wed afternoon. It will remain windy through Wed afternoon. Strong winds Wed will be mainly a function of mixing, which may prove a struggle to get gusts over 45 MPH during the afternoon. So the best potential for wind gusts over 40 MPH across the southern portions of the forecast area will occur tonight. Based on the above, some adjustments will be made to the end times of the current headlines. The winter weather advisory across the Saginaw Valley and thumb will end at 4 AM, with Shiawassee, Genesee and Lapeer Counties ending by 6 AM (by which time the higher intensity snow squalls should be south) and the remainder of the winter wx advisory counties will end at noon Wednesday as will the wind advisory. && .PREV DISCUSSION... Issued at 613 PM EST Tue Feb 12 2019 AVIATION... A rapid improving trend to cigs and vsby is already underway as the sfc low is now lifting into the thumb region. This is driving a more well mixed boundary layer into Se Mi. While this better mixed layer is leading to some improvement in cigs/vsby, it is bringing with it an uptick in the southwest winds. The sfc low will deepen as it traverses Lake Huron tonight, driving colder air into Se Mi. This will support a continued deepening mixed layer capable of providing some continued improvement in cigs/vsby but also an increase in the west-southwest winds through the night. While the higher intensity precip from earlier this evening is steadily lifting northeast of the terminals, deep layer moisture advancing back into the region from the west will sustain snow showers, with visibilities likely fluctuating from IFR to MVFR. There is expected to be some disorganization to the snow shower activity this evening into the early overnight. Optimal lake effect processes are expected to develop a dominate band/bands of high intensity snow showers late tonight into Wed morning. Based on the flow these are expected to be more prevalent from PTK south through metro Detroit. For DTW...Southwest winds will be on the increase through the evening with a deepening mixed layer. This mixing will actually sustain sfc temps a couple degree above freezing until late evening before low level cold air advection increases. There will be a trend toward a little more west-southwest flow overnight into Wed morning, with gusts topping 30 knots at times. There is at least a potential for the winds to turn a little more westerly, which may result in some crosswind concerns. Intense lake effect snow showers are expected to impact the area late tonight into Wed morning, with the 09-13Z time frame being the most probable time period for impacting metro. DTW THRESHOLD PROBABILITIES... * High for ceiling 5000 ft or less through the period. * High in precip type being all snow tonight and Wednesday. * Moderate in crosswind thresholds being exceeded late tonight through the day Wednesday. PREV DISCUSSION... Issued at 343 PM EST Tue Feb 12 2019 DISCUSSION... Strong PV anomaly is noted at press time lifting northeast invof the southern tip of Lake Michigan at press time. MSLP at Holland, near the center of circulation, is down to 998mb with system-relative pressure falls of 1mb/hr or slightly less progged to continue through tonight as the center of circulation moves to Georgian Bay by Wed morning. Cross-sections indicate a pronounced stratospheric intrusion into the upper portion of the frontal zone immediately adjacent to the cyclonic side of the upper jet. The attendant dry air stream ended meaningful precipitation over the CWA several hours ago. Rain and snow showers have developed beneath the dry air over eastern Illinois and central Indiana as mid-level PV advection ramps up this afternoon. Locally, radar echoes have been percolating as H5- H7 mid-level instability wakes up in advance of this leading to scattered drizzle and freezing drizzle of virtually no impact as the latter is falling into established snowpack. Convection will remain tied to mid-level forcing and will become oriented increasingly orthogonal to the thermal gradient, offering at least some potential for fgen processes to aid in organization as the band lifts toward the northern half of the CWA this evening where a quick inch will be possible west of M53 in the cold air. Probability of disorganization and/or rain as the dominant ptype along the front increases with south and eastward extent - Detroit will see rain as this feature moves through. Well-mixed WSW flow will fill in in the wake of the surface low tonight, the stronger winds filling in from south to north between about 00z and 09z. Wind gusts to advisory criteria will certainly be possible given borderline wind speeds within the modeled boundary layer, dynamic forcing for descent, and augmented mixing courtesy of the lake influence. Given the ongoing advertisement of blowing snow, especially across the northern third of the CWA, and the potential for lake effect snow opted to wrap a wind advisory into the WWA product for all but the southern tier of counties. A straight wind advisory for the southern tier is based solely on the expectation that lake effect is either positioned to the north or is transient in nature. See the earlier AFD for a summary of the headlines. Worth noting that blowing of snow, except perhaps Bay, Midland, and Huron Counties, will be solely dependent on fresh snowfall tonight as existing snowpack will obviously glaciate after today`s partial thaw. LES will develop after midnight tonight as theta-e lapse rates fall as low as -4C/KM over Lake Michigan. Large scale ascent and strong mostly unidirectional boundary layer flow will contribute to a potential snow squall threat focused between I-94 and I-69 between 06z and 15z before surface ridging interrupts the fetch over Lake Michigan early Wed. Favorable thermal profiles will support high ratio snow within convection while the strong ambient wind field and sufficiently cold surface will ensure dangerous travel (blowing snow, covered-roads) within any stronger bands. Timing before and during the morning commute will potentially lead to significant impacts should the threat materialize. 18z HRRR and 18z NAM suggest the favored corridor for convergence will be Livingston and Oakland Counties, but given the ongoing situation with the rapidly deepening low over the Lower Peninsula, the forecast fetch will remain subject to refinement. A breezy day expected Friday after a cold front ushers in a fresh arctic air mass. High temps will be limited to the upper 20s to mid 30s as the cold advection fights daytime heating. Some lingering isolated snow showers will be possible early in the day, but Friday looks mostly dry with ridging beginning to nudge in from the south and west. Split flow developing aloft will divert the storm track and allow for a period of relatively quiet weather through the weekend into the early week. Temperatures will be a bit below normal with highs in the 20s. The best chance for light snow will come Sunday evening as a low moves through the Ohio Valley. MARINE... Gale Warnings remain in effect across the central Great Lakes through Wednesday as a strong low pressure system tracks through Central Lake Huron this evening. High end easterly gales around 40 knots are occuring over the north half of Lake Huron through this evening, but will briefly diminish tonight as the low tracks through. Wind turning west-northwest tonight and gusting to Gales late tonight through tomorrow with additional snow. Inner Saginaw has been added to the Gale warning for tomorrow. Conditions then improve quickly with the arrival of high pressure Wednesday evening into Thursday morning. Another deepening low pressure system is then forecasted to track through northern Lake Huron Thursday evening, with westerly marginal Gales possible over northern Lake Huron on Friday as colder air sweeps back in. PREV DISCUSSION... Issued at 1212 PM EST Tue Feb 12 2019 Update... Update forthcoming to bring headlines and a fresh set of zones in closer alignment with expectations going forward. Burst of strong warm advection has nearly cleared the area by 11am LST this morning. A general 3-5" of snow was observed in the warning, 2-4" accompanied by mostly sleet and some fzra in the advisory, and around 0.3" of ice accretion in the ice storm warning. The dry slot will overspread the area for the remainder of the daylight hours limiting any additional precip going forward, so the ice storm and winter storm warnings have been cancelled. Incoming well-mixed cold airmass tonight will bring a quick shot of deep/strong convergence and dynamic support in the form of the parent 400mb PV anomaly pivoting through the CWA 21-00z. A transient burst of convective showers can be expected along the front with low vsbys possible in its wake west of the glacial ridge where precip will most likely be snow. To the east, including most of Metro Detroit, rain is expected. Weak deformation will support additional minor accums across the north tonight that wouldn`t be headline- worthy on their own merit, especially after such a prolonged break, but the potential for blowing snow, wind nearing wind advisory criteria in spots (tonight thru Wed), and typical lower- predictability lake effect response are sufficient to simply transition the WSW to an generic WW advisory. LES potential will be greatest in the climatological corridor which is already captured in the existing advisory (I-94 to I-69) and will be a focus of attention for this aftn. Poorly defined/lower probability threat near the Ohio border lends itself to just a wind headline at this time. All advisories are now scheduled to expire concurrently Wed aftn as wind guts and any blowing snow begin to diminish. Final note on the ice storm - additional power outage potential as strong winds develop tonight will be conditional on the degree of melting that occurs today as temperatures rise well into the 30s in most spots. Either complete melting of ice on power lines or even just enough melting to allow ice to break free/fall off during wind would be sufficient to limit impacts. The current expectation of light winds until 00z or later and 32+F temps is therefore a rather fortuitous outcome in terms of mitigating additional infrastructure damage. MARINE... Gale Warnings remain in effect across the central Great Lakes today through Wednesday as a strong low pressure system moves through the region. High end easterly gales around 45 knots are likely, especially across the north half of Lake Huron where the long easterly fetch over open water enhances the wind pattern. A brief gust to storm force remains possible there while colder air remains over the remaining ice free water. The center of the system tracks across southern Lower Michigan and central Lake Huron tonight which allows a brief decrease in wind before increasing to northwest gales again through Wednesday as the system exits into Ontario and Quebec. The associated cold front moves through Lower Michigan during the evening and brings the northwest gales first to Lake Erie and Lake St Clair which have been upgraded to a Gale Warning tonight through Wednesday. An extensive break up of ice is expected over the south third of Lake Huron which may help frequent gale force gusts reach outer Saginaw Bay and the southern nearshore waters down to Port Huron. Conditions then improve quickly with the arrival of high pressure Wednesday night into Thursday. && .DTX WATCHES/WARNINGS/ADVISORIES... MI...Wind Advisory until noon EST Wednesday for MIZ082-083. Winter Weather Advisory until 6 AM EST Wednesday for MIZ060>062. Winter Weather Advisory until noon EST Wednesday for MIZ063-068>070- 075-076. Winter Weather Advisory until 4 AM EST Wednesday for MIZ047>049- 053>055. Lake Huron...Gale Warning until 4 PM EST Wednesday for LHZ361>363-421-441>443- 462>464. Gale Warning from 7 AM to 4 PM EST Wednesday for LHZ422. Heavy Freezing Spray Warning until 10 PM EST this evening for LHZ361-362. Lake St Clair...Gale Warning until 4 PM EST Wednesday for LCZ460. Michigan waters of Lake Erie...Gale Warning until 4 PM EST Wednesday for LEZ444. && $$ UPDATE.......SC AVIATION.....SC DISCUSSION...JVC/TF MARINE.......SF You can obtain your latest National Weather Service forecasts online at
Area Forecast Discussion
National Weather Service Wilmington NC
852 PM EST Tue Feb 12 2019 .SYNOPSIS... A cold front will bring scattered showers to the area tonight. Dry weather will prevail Wednesday and Thursday as high pressure migrates across the Southeast. A warm up will occur Thursday and Friday. A cold front should reach the area Friday night and may linger as low pressure develops, leaving unsettled weather for next weekend and start of next week. && .NEAR TERM /THROUGH WEDNESDAY/... As of 900 PM Tuesday...Shallow convection produced strong winds across much of the Sandhills and Pee Dee region early this evening. Gusts in the 30-50 mph range were common, with some stronger winds and wind damage reported back across central South Carolina. Surface-based instability, or more correctly the lack of it, near and east of I-95 appears to have been the determining factor for why the convection weakened as it moved east. Now feeding on meager elevated instability of 500 J/kg or less, the line should reach the Myrtle Beach metro area shortly after 9 PM, then Wilmington close to 10 PM -- still capable of producing some briefly gusty winds but no lightning given radar-measured echo tops all below 20kft. South-southwest wind trajectories have maintained dense sea fog across the coastal waters and adjacent land areas all evening. Webcams and airport weather obs from the North Myrtle Beach airport have been instrumental in helping me define the areas affected by fog this evening. Fog will clear as soon as winds turn westerly behind the shallow convective squall line. Given the current and forecast movement of the line I`ve added a couple hours onto the Dense Fog Advisory for coastal North Carolina. No other significant changes have been made to the forecast with this evening update. Discussion from 630 PM follows... A shallow convective squall line across central South Carolina is rapidly moving eastward. Linear motion estimates and the latest HRRR model runs show this feature reaching Florence and the I-95 corridor by 730 PM, the Myrtle Beach/Grand Strand area before 900 PM, and Wilmington before 1000 PM. Temperatures across much of central and southern South Carolina spiked into the upper 70s this afternoon which produced an area of surface- based CAPE in the 500-1000 J/kg range. Subsequent convection has been relatively shallow with CAE radar echo tops measured near 20-25 kft. Bulk shear across the 0-6 km layer is 50-60 knots which is helping to organize the storms into bowing segments, some of which have reportedly produced wind damage. With the loss of daytime heating, convective instability should wane over the next few hours. However this may not be fast enough to prevent strong to potentially severe storms from impacting a portion of the Pee Dee region over the next 90 minutes. Strong wind is the primary severe weather mode expected. Convection should weaken with time, and by the time of the squall line makes it down to the North Carolina coast late this evening it may not even be a solid line due to a drying mid-level atmosphere and even less elevated instability present. Dense fog continues to affect the coastal waters, and several of our off-duty meteorologists have called to report dense fog is moving inland across coastal portions of Pender and New Hanover counties. Webcams and airport obs in the Myrtle Beach area also confirm dense fog continues here. The squall line and its shift to westerly winds will likely be what clears this fog offshore between 8-10 PM. No changes have been made to forecast lows tonight, with upper 40s to lower 50s expected for most areas. This is near the upper end of the MOS guidance envelope due to overnight breezes keeping the boundary layer rather well mixed. && .SHORT TERM /WEDNESDAY NIGHT THROUGH FRIDAY NIGHT/... As of 300 PM Tuesday...Zonal flow aloft keeps surface features moving quickly from west to east during the period. High pressure over the area at the start of the period moves off the coast in the Thu afternoon. Slight amplification of the 5h pattern later Thu into Thu night shifts the center of the high northeast, but period of west-southwest flow aloft is limited. Moisture return ahead of quick moving cold front and deamplifying 5h trough is meager, and rainfall ahead of the front Fri into Fri night is looking like less of a possibility. Have dialed back precip chances during the second half of the period, but further reduction may be required. Temperatures above climo Thu and Thu night will run well above climo Fri and Fri night as first strong warm advection kicks in and then clouds arrive overnight. && .LONG TERM /SATURDAY THROUGH TUESDAY/... As of 300 PM Tuesday...Progressive mid-level pattern will keep a front stalled in the area through the weekend. Low pressure exiting the the Mid-Atlantic coast late in the weekend will push the stalled boundary southeast of the forecast area into the middle of next week. -A series of weak waves will travel northeast along the stalled front this weekend, maintaining elevated rain chances into Sun afternoon. -Rain will be on and off through the weekend with cloudy skies and relatively narrow diurnal ranges. Highs will be near climo with lows well above climo. -High pressure briefly builds in from the north late Sun through Mon night before expanding 5h ridge over the western Atlantic helps push the boundary back into the region. At the same time increasing southern stream energy taps into moisture, spreading rain across the area Tue. && .AVIATION /00Z WEDNESDAY THROUGH SUNDAY/... As of 00Z...Currently VFR conditions inland with MVFR at ILM and LIFR and the Myrtles, courtesy of sea fog pushing inland. Expect visibilities at the Myrtles to be decreased next couple hours. A line of showers associated with an approaching cold front is moving in from the west. This line should reach Florence and Lumberton shortly after start of TAF period, and the coastal sites by 2-3z. Some higher gusts may be associated with the front line. Precipitation to continue behind line for few hours. Look for coastal terminals to improve to VFR by around 6z, with scattered high clouds likely rest of period. Current southerly winds to shift westerly behind front, and remain westerly around 10kts into tomorrow. Extended Outlook...VFR conditions will develop Wed through Thu as high pressure ridges over the region. A warm front will push north across the area on Fri with MVFR conditions and rain possible into Sat and Sun. && .MARINE... As of 900 PM Tuesday...Dense fog continues to affect the coastal waters of the Carolinas. Earlier satellite imagery showed dense fog likely developing 10-15 miles offshore, then streaming northward with the low-level winds. A line of showers approaching Myrtle Beach from the west should move offshore between 8 and 9 PM, veering winds to the west and rapidly improving visibility. Given the current and forecast movement of this line of showers, I`ve added a couple hours onto the Dense Fog Advisory for the coastal waters of southeastern North Carolina. Assuming my forecasts on the movement of the showers are correct, all locations, even those east of Cape Fear, should be clear of fog by 11 PM. Buoy-reported seas continue to build and are now 4-5 feet on the CORMP/NDBC buoys near Cape Fear. Discussion from 630 PM follows... Webcams, late afternoon visible satellite data, and even nearshore airport observations confirm that widespread dense fog covers most of the nearshore coastal waters as rich subtropical moisture touches our cold ocean waters. Fog should continue up until the arrival of a line of showers between 8-10 PM. Gusty west winds developing with these showers should push the fog offshore, with rapidly improving visibilities expected overnight. Before these showers arrive, south to southwest winds will increase to a solid 20-25 kt with seas building to 5-7 ft. Discussion from 300 PM follows... Marine fog/stratus mixing out somewhat gradually. DFA has been extended slightly in time into the evening. Mariner headaches will not clear up with the visibility however as winds and seas will ramp up to Small Craft Advisory levels with tonight`s frontal passage. A sharp veer to NW will accompany the front late tonight and then abating winds/seas slated for all of Wednesday as high pressure builds in to our west. The center of the high remains over GA/AL so winds may have a tough time dropping below the 10-15kt range. Extended period of south to southwest flow Thu through Sat as high pressure overhead Thu morning shifts east-northeast. Light winds Thu morning will steadily increase through the end of the week, peaking on the high end of the 15 to 20 kt range Sat. Seas will build to 3 to 5 ft later Sat due to increased winds. Weak cold front moves across the water Sat night and ends up stalling over the waters briefly Sun morning. Front returns north Sun as weak low passes to the northwest. The passage of the low drives the front back south, across the waters, stalling southeast of the area as the period ends. Erratic wind directions over the weekend coupled with speeds under 15 kt Sat night through Sun night will drop seas in the 3 to 5 ft range Sat evening to 2 to 3 ft Sun and Sun night. && .ILM WATCHES/WARNINGS/ADVISORIES... SC...Dense Fog Advisory until 9 PM EST this evening for SCZ054-056. NC...Dense Fog Advisory until 9 PM EST this evening for NCZ110. Dense Fog Advisory until 11 PM EST this evening for NCZ106-108. MARINE...Dense Fog Advisory until 9 PM EST this evening for AMZ254-256. Small Craft Advisory until 7 AM EST Wednesday for AMZ250-252- 254-256. Dense Fog Advisory until 11 PM EST this evening for AMZ250-252. && $$ SYNOPSIS...III NEAR TERM...TRA SHORT TERM...III LONG TERM...III AVIATION...21
Area Forecast Discussion...UPDATED
National Weather Service Baltimore MD/Washington DC
806 PM EST Tue Feb 12 2019 .SYNOPSIS... Low pressure and its associated cold front will pass through the area late tonight. High pressure will build south of the area Thursday. Another cold front will cross the area late Friday. && .NEAR TERM /UNTIL 7 AM WEDNESDAY MORNING/... Low pressure will move northeastward through the eastern Great Lakes through tonight with its attendant cold front crossing the area overnight. For most locations, widespread light to moderate rain and drizzle will continue to move across the region out ahead of the front. The exception will be portions of central/western Maryland and eastern WV where temperatures remain near or below freezing in the sheltered valleys and mid- elevations. There, the Winter Storm Warnings were extended until 11 PM. Also watching some convective elements developing across central VA and southern MD, where some bursts of heavy rain and even some gusty winds are possible. A weak convective fine line is also possible, as currently being shown by the HRRR and members of the HREF. Partial clearing and increasing winds are expected overnight following frontal passage with gusts up to about 30 mph. The exception is over the higher elevs where 850 mb winds are expected to increase substantially and may be able to mix down more easily. There is potential for up to 50 kt winds at the highest elevations of Grant and western Pendleton Counties where 850 mb winds are fcst to peak at 60 knots. This combined with all the ice that has accumulated on trees the past two days may cause significant tree damage and power lines to come down. Some upslope snow showers are also expected to develop towards morning along/near the Allegheny Front. && .SHORT TERM /7 AM WEDNESDAY MORNING THROUGH THURSDAY NIGHT/... Windy and mainly dry Wednesday under a tight pressure gradient. The exception will be some upslope snow showers along/near the Allegheny Front with a light accumulation likely. It`s also possible some snow showers/flurries make it downwind of the mountains across eastern WV and northern Maryland as suggested by NAM12 Snow Squall Parameter and >2 Froude numbers. Most gusts should stay in the 35 to 40 mph east of the Blue Ridge with 50-60 mph at the highest elevations. Dry Wed night through Thu evening with rain chances increasing again late Thu night ahead of another low pressure moving through the Great Lks. && .LONG TERM /FRIDAY THROUGH TUESDAY/... Overall, a potentially active long term period, characterized by high forecast uncertainty. A trough and associated area of low pressure will track across the Great Lakes on Friday. The area of strongest forcing for ascent will be displaced off to our north, so very little precipitation is expected as the system passes to our north. High temperatures on Friday will max out in the mid-upper 50s. We`ll have a largely dry cold frontal passage Friday evening, which will allow cooler air to filter back into the area Friday Night. Beyond Friday Night, forecast confidence decreases. Many of the deterministic models (12z GFS, 06z FV3, 12z Euro) produce a period of snow during the day Saturday ahead of an approaching mid-level shortwave/within the poleward exit region of a zonally elongated upper jet stretching across the CONUS. However, this solution doesn`t have much support from the EPS and limited support from the GEFS. Then on Sunday, the deterministic guidance has another round of snow across the region as a second shortwave approaches from the Ohio Valley. The GFS is currently the most aggressive in producing snow, but the FV3 and Euro produce at least some snow as well. Again, there is lesser (but non-zero) ensemble support for a snow event. The pattern evolution as a whole is quite complex across the CONUS leading up to the event, so uncertainty is still high. Drier conditions are expected on Monday as high pressure starts to build in from the northwest. && .AVIATION /01Z WEDNESDAY THROUGH SUNDAY/... IFR/LIFR conditions through 06Z tonight in rain and drizzle. Cigs lifting rapidly after 06Z with frontal passage. Becoming breezy with gusts up to 25 kt. Stronger winds tomorrow under better mixing with gusts up to around 30 kt. A few showers on Friday could produce brief and intermittent sub-VFR conditions. Moving into the weekend, the pattern looks active, but forecast uncertainty remains high. && .MARINE... Winds will strengthen tonight and tomorrow as they veer from NE to WSW overnight. Gale Warning issued for upper Chesapeake Bay waters and upper Potomac through tomorrow. A cold front crossing the waters Friday will likely bring SCA gusts. Winds relax Friday Night and stay low through the weekend. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...None. MD...Wind Advisory from 4 AM to 6 PM EST Wednesday for MDZ501-502. Winter Storm Warning until 11 PM EST this evening for MDZ003- 004-501-502. VA...Wind Advisory from 4 AM to 6 PM EST Wednesday for VAZ025-026- 503-504-507-508. WV...Wind Advisory from 4 AM to 6 PM EST Wednesday for WVZ050-055- 503-504-506. Winter Storm Warning until 11 PM EST this evening for WVZ050- 051-503-504. High Wind Warning from 4 AM to 6 PM EST Wednesday for WVZ501- 502-505. MARINE...Small Craft Advisory from 3 AM to 6 AM EST Wednesday for ANZ530>532-538>540. Gale Warning from 6 AM to 6 PM EST Wednesday for ANZ530>532- 535-538>540. Small Craft Advisory from 3 AM to 6 PM EST Wednesday for ANZ533-534-537-541>543. Small Craft Advisory from 6 AM to 6 PM EST Wednesday for ANZ536. && $$ SYNOPSIS...LFR NEAR TERM...MM/LFR SHORT TERM...MM/LFR LONG TERM...KJP AVIATION...MM/LFR/KJP MARINE...MM/LFR/KJP
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710 PM PST Tue Feb 12 2019 .SYNOPSIS...Moisture associated with our next system will reach the southern Sierra Nevada tonight. The moisture will continue to stream eastward across the region Wednesday and Thursday with good chances of mountain snow and valley rain. Additional storms systems over the weekend will keep the region cooler than normal along with a threat of rain and snow showers. && .UPDATE...Increasing mid and high clouds are currently streaming in off the Pacific ahead of our next weather system approaching the area. HRRR and high resolution models suggest increasing precipitation spilling over the Sierra crest by daybreak Wednesday, with additional light shower activity traversing eastward through the day. Overall, rainfall amounts look fairly light outside of the Owens Valley/Sierra tomorrow, but moderate rainfall rates will be possible in the Owens Valley and near Bishop through the day. Of additional concern is rising snow levels, with forecast soundings suggesting the snow level rising to between 8-9k feet by Wednesday afternoon. Periods of moderate rainfall on the substancial snowpack in the higher terrain could lead to periods of enhanced runoff and stream flow in the Sierra/Owens Valley and parts of the Spring Mountains. The current forecast is in good shape and no significant updates have been made this evening. -Outler- && .SHORT TERM...through Friday. The focus of the short term remains a developing atmospheric river event, which could prove to be significant with inland penetration across the region. Microwave satellite imagery already shows impressive poleward transport of tropical moisture, already as far as 30N over the eastern Pacific. Trends are expected to continue as upper-level trough will continue to sag south out of the Gulf of Alaska and phase with low pressure currently just east of Hawaii. The fire hose of moisture will take aim first at Northern California, then work southward and intensify as it does so. Precipitation will begin in the Sierra by Wednesday morning and intensify through the day. Wet-bulb effects might briefly lower snow levels to around 5500` to start the event, but should quickly rise through the day Wednesday, potentially to 9000` or above with the heaviest precipitation. This could limit major accumulations to above 8000` with transition zone of moderate amounts down to 7000`. Just where that snow level ends up will have impacts on any rain-on- snow runoff and flooding concerns, but minor flooding is possible with over QPF amounts over an inch forecast for the Owens valley, and in excess of 3-5" liquid/liquid equivalent in the Sierra, with snow amounts of 1-3 feet above 8000`, and in excess of 3-5 feet for the crest. The AR will continue to slide southward on Wednesday, with quite a few models indicating moisture funneling inland around the south of the Sierra and Tehachapis, producing some precipitation chances in the southern Great Basin and local mountains on Wednesday. Fairly low confidence for precipitation and amounts in those areas for that time frame. The AR continues sinking south under cyclonic flow and strengthening Wednesday night into Thursday, and attention turns to the southern California mountains. PWATs are forecast to be near or at records for several hours. It looks like 18Z -00Z Thursday is the best window for maximum precipitation for the mountains in/around San Bernardino county, with plenty of spillover into places like Morongo Valley and Yucca Valley. Flooding becomes a concern for these areas and eastward with the progression of the AR Thursday. Decided to hoist a flash flood watch for southern portions of San Bernardino and Mohave counties for Thursday for the heavy rain and runoff risk. General amounts across the Mojave desert look to be around 0.25", but amounts closer to or in excess of 1" are possible if not likely in areas of the Flash Flood Watch. Would not be surprised to see areas like Las Vegas receive very little rain, while the mountains receive plentiful rain. Snow levels will likely rise above the 8000` mark on Thursday, which will limit accumulation in areas like Kyle Canyon in the Spring Mountains. Snow amounts there have been cut/shifted upward once again. Lee Canyon may pick up significant snow, so current advisory still in good shape. Areas of concern if the moisture plume wobbles a bit further north would be the Virgin and Muddy River basins. Anyone with concerns in these basins are not out of the woods, and should continue to monitor forecasts for updates. The area really starts to shut off Thursday night and Friday as the AR gets shoved even further southward, with only lingering shower activity in the mountains from colder air taking back over. However, it may take some areas several days to respond to the mountain rainfall, like the Big Sandy River in southern Mohave county. .LONG TERM...Friday night through Tuesday. A trough axis is forecast to swing through our area Friday night on the southern periphery of the big, cold low over the Pacific Northwest. This will provide enough forcing to wring out some more precip over the Sierra and the higher terrain of the southern Great Basin, possibly extending as far south as northern Mohave County. It will also kick up westerly winds, and cannot rule out needing a wind advisory for the places prone to enhanced west winds such as Barstow. Behind the trough axis, precip chances should mostly come to an end Saturday. The next storm is forecast to roll southward through California Sunday, bringing another round of precip chances to much of our area. Depending on how quickly it moves out, precip chances should end either Monday or Tuesday. Temperatures will be below normal through the period under the influence of long wave troughing. && .AVIATION...For McCarran...Clouds will slowly lower and thicken through Wednesday, with ceilings possibly falling to 8000 feet or below along with a slight chance of showers Wednesday afternoon. A stronger storm is expected to bring worse conditions Thursday afternoon into Friday morning, with low ceilings and visibilities possible along with gusty south to southwest winds. For the rest of southern Nevada, northwest Arizona and southeast California...Precip chances will begin in the Sierra this evening and spread across much of the area by Wednesday afternoon. Expect lowering ceilings with mountain obscurations. After a brief lull Wednesday night, a stronger storm will bring deteriorating conditions Thursday into Friday morning, with widespread valley rain and high mountain snow, leading to significant terrain obscuration. && $$ SHORT TERM...........STEELE LONG TERM/AVIATION...MORGAN For more forecast information...see us on our webpage: or follow us on Facebook and Twitter