Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 01/20/17

Area Forecast Discussion...UPDATED
National Weather Service Birmingham AL
615 PM CST Thu Jan 19 2017 .UPDATE... For 00Z Aviation. && .SHORT TERM... This Afternoon through Friday. --Significant severe weather potential on the board for this weekend-- Central Alabama was generally in the warm sector this afternoon. A developing low was located along the Mississippi River south of Memphis with a cold front extending southward. A warm front was located across northeast Alabama into central Georgia. A trough was analyzed with the more organized line of storms stretching from central to southwest Alabama. The current rap analysis has plenty of atmospheric shear near the line of storms and low LCL`s. Therefore, rotation is possible and weak rotation has already been noted in the lower levels. This area of storms did produce a tornado back in Mississippi earlier this morning. Surface based instability has been limited today due to the low clouds, fog and drizzle/showers. But the latest water vapor imagery has the upper trough beginning to turn negative with some good heating noted south. Upper level divergence will increase as well as the wind speeds. Therefore, some destabilization is anticipated the next few hours, especially south. Will continue to mention a threat of a brief tornado or some damaging winds along and ahead of the line of storms, and south of Interstate 20. This area is moving rather slowly but may pick up some speed. Due to uncertainty in speed, held the threat through midnight east. Rain chances very slowly decrease from west to east into Friday morning. Did hold onto some chance pops south a leftover boundary from the convection hangs over the area. Overnight lows will be very similar to last night mainly in the 50s. With little change in the airmass, went near record highs on Friday especially south. 75 .LONG TERM... Friday Night through Weekend. --Instances of severe weather this weekend. Significant severe weather possible across southern portions of the service area-- *Headline: Rounds of thunderstorms are expected to move through the region this weekend. Friday night to Sunday morning holds the greatest potential for severe weather. Details on threats, timing, and areas are outlined below. *Weather setup: Several impulses will emanate from a southern U.S. longwave trough, while a very strong ~125-knot jet streak moves into northern Mexico, instigating the development of an upper-level low. Our severe weather potential will be tied to the broad southwesterly flow preceding the upper low, and with associated upper- and low- level lobe impulses translating through the region. Dynamics-wise, the low-level wind field will essentially be a mishmash of comparatively laxed winds and surges of ~35-45 knots (key factors in subsequent severe activity), southwest at 850mb. Instability-wise, CAPE will be available alongside a plume of steeper lapse rates. *Forecast changes: There are no changes to threat areas or hazards. As of Thursday afternoon, we are maintaining a swath of `elevated` severe weather risk through roughly the southern-half of the service area, with a `limited` risk points north. Refer to the severe weather threat graphic on our homepage. *Impacts_Severe: There will be a risk of tornadoes, severe- caliber hail (1"+), and severe straight-line winds. Multiple rounds of thunderstorms are expected: 1) Friday night through Saturday morning as storms advance into the area from Mississippi and southern Alabama, associated with an inland- moving boundary. This could end up being the main show, focused on roughly the southern-half of the service area (and toward the immediate Gulf coast). Supercells and thunderstorms segments are expected. Forecast models are suggesting a zone of backed surface and low-level winds in the vicinity of a northward- moving maritime air mass, locally enhancing hodographs and SRH as the first low-level jet surge occurs. This will be a principal area to watch as storms interact with the boundary. A best estimate `window of concern` (this will be adjusted) appears to line up from 09Z/3AM Saturday to 18Z/noon, or so; 2) A questionable period Saturday afternoon when renewed thunderstorm development is uncertain (pending morning storm characteristics/progression, trigger), but would have severe potential if recovery is realized to the extent of some model projections; and 3) Saturday night as another impulse moves through, especially toward southeastern counties. This will be another period to watch closely as it`ll be associated with another low-level jet impulse. *Impacts_Hydro: Analysis from our senior hydrologist indicates that streamflow remains low across area rivers. It is anticipated that basins will be able to handle forecast storm total rainfall amounts of 2-4 inches. However, localized flooding could occur in poor- drainage areas or small streams, associated with any heavy downpours. 89^GSatterwhite && .AVIATION... 00Z TAF Discussion. Line of showers and thunderstorms moving across Central Alabama at this writing. Line is already through TCL/BHM/EET and about to move through ASN/ANB then MGM/TOI. Some lower cigs/reduced vsbys possible with the TS. However, expecting -RA then later transitioning to -DZ after midnight as system progresses. With IFR/LIFR cigs expected behind the rain some fog is also expected to develop and last through mid morning. 08 && .FIRE WEATHER... A wet and chaotic pattern sets up today through Sunday. Afternoon relative humidity values will generally remain above 40 percent due to the southerly winds bringing gulf moisture northward. Some strong to severe storms can be expected today, Saturday and Sunday morning. Rain amounts through Sunday will be 3 to 4 inches. && .PRELIMINARY POINT TEMPS/POPS... Gadsden 56 72 56 68 54 / 100 30 40 70 80 Anniston 59 74 59 69 56 / 100 30 50 70 80 Birmingham 58 74 59 69 56 / 90 20 60 70 80 Tuscaloosa 59 76 60 72 57 / 90 20 60 70 70 Calera 59 75 60 70 57 / 90 20 60 70 80 Auburn 60 75 61 70 59 / 90 30 60 90 80 Montgomery 60 79 62 73 58 / 90 30 90 80 80 Troy 61 78 63 73 60 / 90 30 80 90 80 && .BMX WATCHES/WARNINGS/ADVISORIES/... None. && $$ 75/89/08
Area Forecast Discussion
National Weather Service Denver/Boulder CO
659 PM MST Thu Jan 19 2017 .UPDATE... Issued at 645 PM MST Thu Jan 19 2017 Satellite shows fog moving westward from Kansas into the far eastern plains at this time. The RAP and HRRR continue to show this trend overnight, with the fog primarily impacting eastern sections of Sedgwick, Phillips and Washington Counties. This fog then gets flushed east late tonight and Friday morning. Have included areas of fog in these zones tonight and also increased the cloud cover there. In the mountains, we increased the pops, but no adjustments to the snow amounts as the overall totals still appear to be on the light side. && .SHORT TERM...(This evening through Friday) Issued at 308 PM MST Thu Jan 19 2017 Models show southerly flow aloft overnight into Friday morning. The flow weakens and becomes southwesterly by afternoon. There is a weak upper trough that moves across the CWA from 09Z to 21Z on Friday. The QG Omega fields show some moderately strong upward synoptic scale energy for the CWA tonight and much of Friday. The low level wind fields have southeasterlies this evening, then weak normal drainage winds overnight. Winds are weak and downsloping for the most part on Friday. Models have moisture on the increase tonight from west to east. By 12Z Friday morning, moisture is deep over the mountains and that continues through Friday. There is plenty of moisture over the plains, but not in the lower levels on the GFS or the ECMWF. The QPF fields have limited measurable in the mountains tonight and Friday. There is a tad of measurable precipitation over the plains on Friday. For pops, will go with 50-80%s in the mountains from about 06Z tonight through Friday. Orographic enhancement is not the greatest, but there is moisture and some synoptic scale energy. Snowfall amounts do not warrant highlight criteria amounts. For the plains, will go with mostly "chance"s late tonight into Friday afternoon. For temperatures, Friday`s highs are 3-6 C cooler than this afternoon`s. .LONG TERM...(Friday night through Thursday) Issued at 308 PM MST Thu Jan 19 2017 A series of weakly organized weather systems will move across Colorado over the weekend, and then a bit stronger system will move over the state during the first half of next week. Each system will bring a little light snow to the mountains, but not necessarily affect the plains. The system that sets up over the state for the Monday through Wednesday time period will have more of a region-wide impact. The first trough, on Saturday will be diving southeastward as it produces the bulk of snowfall over the western slope and San Juan mountains. The north central mountains will see scattered afternoon snow showers. Upper ridging will build over the state Sunday with dry weather across the forecast area. Monday will be transitional as an upper trough carves out over the entire western United States. By Monday evening snow should be moving into the mountains. Then on Tuesday the ECMWF shows an upper low developing over over northeast Colorado which will lead to unsettled weather across the mountains and plains. A strong upper level jet will accompany this trough which may add to the strength of the developing system. The GFS shows a very similar solution, so we will have to watch how much moisture this system brings with it. Unsettled weather and cooler temperatures are the main story for now. && .AVIATION...(For the 00Z TAFS through 00Z Friday evening) Issued at 645 PM MST Thu Jan 19 2017 The southeasterlies should move towards normal drainage directions, south/southwest after 03Z this evening. MVFR ceilings 020-030 after 10Z Friday morning with a chance of snow showers. Ceilings should climb back above 060 by 18Z Friday, with VFR conditions in the afternoon. && .BOU WATCHES/WARNINGS/ADVISORIES... None. && $$ UPDATE...Cooper/Meier SHORT TERM...RJK LONG TERM...Dankers AVIATION...Cooper
Area Forecast Discussion
National Weather Service Duluth MN
552 PM CST Thu Jan 19 2017 .SHORT TERM...(This evening through Friday) Issued at 419 PM CST Thu Jan 19 2017 Hopefully everyone in the area got outside today, as conditions are going to get progressively worse tonight, with clouds overspreading the area from the south this evening, and then precipitation spreading in from the south as well. Stratus is currently over southwest Minnesota, eastern South Dakota and Nebraska, and spreading in our direction. It should advance into the forecast area here in 2-4 hours, continuing north during the evening. RAP 900-925 RH progs have been good indicators of this stratus during the daytime, and I expect that to continue, even showing the stratus accelerating some this evening as would be expected. Towards morning, an area of lift will rotate across the area as a shortwave and weak vort max pushes across the area, bringing a band of precipitation and warm temperatures aloft across the area during the early morning and most of the day on Friday. Of great concern are the surface temperatures, which should dip to around freezing this evening and then fluctuate around there through the night before rising again in the morning. Have concerns that the precipitation will be freezing drizzle/freezing rain instead of liquid rain/drizzle, causing icing on local roads. Road surface temperatures this afternoon are in the 40s and low 50s, with sub surface temperatures in the low- mid 30s. It will be a very near thing, and is going to depend on exact values as the precipitation moves in. In addition to all of this, the warm temperatures over the snow are going to produce copious amounts of fog again tonight. We are likely to need headlines once again, but the specific location of the lowest visibilities is uncertain still, though am favoring northwest Wisconsin for the worst conditions overnight. Friday temperatures should warm enough to bring precipitation back to liquid for most locations as the precipitation comes to an end from south to north. .LONG TERM...(Friday night through Thursday) Issued at 419 PM CST Thu Jan 19 2017 Wintry precipitation is expected Friday night through the weekend with another system moving into the region around midweek. A distorted Omega Block pattern will continue over the Plains and Upper Midwest Friday evening through the weekend. An upper low will meander northward through the region and into the Canadian Prairies by Saturday morning. Warm air aloft and near the surface will continue, leading to numerous challenges regarding precipitation type. Another shortwave trough will rotate northward into the Upper Midwest Saturday night and Sunday with precipitation chances continuing. A mix of rain, freezing rain, and snow is likely Friday night gradually switching over to a rain/snow mix and eventually all snow by Sunday night. There is a potential for around one-tenth of an inch of ice accumulation Friday night and Saturday in the high terrain along the North Shore, with less ice accumulation expected elsewhere. Surface temps will be the main governing force in precipitation type through Saturday night. If forecast temps are even a few degrees too cool, precip will likely be all rain instead of a mix. The blocking pattern aloft will continue during the first half of the week with slight chances of rain or snow. A more organized shortwave trough and slug of vorticity will move into the Upper Mississippi River Valley Tuesday night through Wednesday night. The midweek system will bring another round of rain/snow to the Northland. Temperatures will remain fairly mild through the end of the forecast period. && .AVIATION...(For the 00Z TAFS through 00Z Friday evening) Issued at 552 PM CST Thu Jan 19 2017 Largely VFR conditions have been found across the TAF sites this afternoon, but things will change considerably as the night wears on. An elongated area of low pressure and upper level shortwave will lift northward across the region overnight. Any VFR conditions are likely to give way to IFR/LIFR or even VLIFR overnight. A wintry mix of precipitation is expected, which will generally turn to rain on Friday. && .PRELIMINARY POINT TEMPS/POPS... DLH 32 37 31 37 / 30 80 50 70 INL 28 38 30 38 / 10 70 70 50 BRD 31 37 31 38 / 50 60 40 60 HYR 33 40 33 41 / 70 70 40 60 ASX 32 40 32 40 / 40 70 50 60 && .DLH WATCHES/WARNINGS/ADVISORIES... WI...None. MN...None. LS...None. && $$ SHORT TERM...LE LONG TERM...Huyck AVIATION...DAP
Area Forecast Discussion
National Weather Service Jacksonville FL
853 PM EST Thu Jan 19 2017 .UPDATE... A few showers developed on the Gulf Coast seabreeze this afternoon near the Gainesville area and these showers continue to push northeastward towards Jacksonville, weakening in the process. We also had an Atlantic seabreeze today which collided with the gulf coast seabreeze, a very unusual occurrence for this time of year. The main update was to add 20% pops to account for this activity, which should wind down completely here in the next hour or two. Parts of the Jacksonville area could get a light sprinkle but it shouldn`t amount to much. The main line of showers/storms upstream will continue to march in our direction overnight but is expected to weaken significantly as it reaches our western zones late tonight. As a result, we will continue with only slight chance pops to account for a few leftover light showers with this activity late tonight. We also backed off a little on the fog wording overnight. The transitioning state of the atmosphere is not really favorable for significant fog development tonight. Upper trough pivoting along the northern Gulf Coast will continue to nudge the upper ridge, which has had a stronghold over us this past week, eastward. This will bring a gradual increase in clouds and winds just above the boundary layer overnight, thus fog development should be held somewhat in check. Still cannot rule out the possibility of some areas of fog across our western Florida zones, mainly along and west of the I-75 corridor. && .AVIATION... Conditions tonight are not nearly as favorable for fog like they were last night. Best chance for IFR conditions will be at the GNV TAF site where the SREF shows a medium chance of some advection fog moving in from off the Gulf. The HRRR is way more aggressive with the fog bank off the Gulf, bringing it all the way into the Jacksonville area again. But so far the HRRR has been way overdone and we will side with the SREF and stick with mainly just MVFR impacts for TAF sites along and east of the I-95 corridor. The exception will be at VQQ where typical shallow ground fog will develop. && .MARINE... Relatively benign conditions will continue overnight with some patchy fog possible. No updates needed. Rip Currents: Low Risk. && .PRELIMINARY POINT TEMPS/POPS... AMG 59 78 62 72 / 20 20 20 80 SSI 58 76 62 71 / 10 20 10 60 JAX 60 81 62 77 / 20 20 10 40 SGJ 62 79 61 78 / 20 20 0 20 GNV 59 79 60 77 / 20 20 10 40 OCF 59 79 61 79 / 10 20 10 10 && .JAX WATCHES/WARNINGS/ADVISORIES... FL...None. GA...None. AM...None. && $$ Shuler/Sandrik/Shashy
Area Forecast Discussion
National Weather Service Phoenix AZ
835 PM MST Thu Jan 19 2017 .SYNOPSIS... A series of Pacific storm systems will move into the region. After a weak disturbance tonight, a stronger and wetter system will affect the region Friday through early Saturday. Snow accumulation will be above 5500 feet, with a Winter Storm Warning posted for the mountains east of Phoenix. A break in the weather is expected Saturday night and early Sunday, however another Pacific storm is expected in the region later Sunday through Monday night. Dry but cool weather will settle over the region for the middle of next week. && .DISCUSSION... The 1st in series of Pacific storm systems that will be affecting our region over the next several days is now moving across South- Central AZ at this hour. Current 88D radar imagery is showing very light shower activity moving eastward across Maricopa County, and into southern Gila county. So far, rainfall amounts with this system have been quite, light, mainly 0.10 inch or less, with many spots only seeing trace amonuts of rainfall. Latest HRRR high-res model guidance continues to show light shower activity developing through the rest of tonight over south-central AZ, but with many areas likely not seeing measurable rainfall between now and Friday morning. Further to the east, the rainfall should turn to snow above 5500 feet, with a few inches still possible over the highest peaks of our cwa between now and early Friday. For the short term, have adjusted POPS downward through the rest of this evening and up a bit overnight over the lower deserts to reflect updated high-res model forecasts, and also made some adjustments to hourly temp/dewpoint/wind grids to better reflect current trends. && .PREVIOUS DISCUSSION... Tonight through Saturday... A series of Pacific weather systems has begun to move into the region. The first one, a minor one, moved through southwest and south central AZ this morning, followed by another system late this afternoon and evening. Most showers through tonight will be on the light side, except in the upslope areas of southern Gila county where rain and snow should be a little heavier. With the passing systems tonight through Saturday, snow levels will rise and fall with each system. For example, in the area where we have a Winter Storm Warning in southern Gila County, snow levels fall to near 5500 feet late tonight, lift to 6000 feet Friday evening, then fall to 5000 feet by Saturday morning. In general the Winter Storm Warning in southern Gila County is posted above 5500 ft where storm total accumulations by Saturday afternoon could reach nearly a foot in the highest elevations. With the cold frontal passage Friday night, low level winds at 5000 feet begin to approach 45-60 mph in a belt from just east of Yuma to Phoenix. Rainfall and isolated thunderstorms could tap this momentum to develop gusty surface winds in the 30 to 45 mph range, higher near thunderstorms. A Wind Advisory is posted for southwest and south central AZ Friday night. Sunday... A break in the weather will develop Sunday afternoon, but with cloudy skies and a slight chance of showers over the mountains of southeast CA ahead of the next weather system for Sunday night and Monday. Sunday night and Monday... Another Pacific weather system will move into the region this period. The character of precipitation will be light. Additional snowfall is expected in southern Gila County above 5800 feet Monday afternoon and evening with perhaps an inch or two. Tuesday through Thursday... Partly cloudy, drier and colder weather is expected this period under northerly flow aloft from Nevada and Utah. && .AVIATION... South-Central Arizona including KPHX, KIWA,and KSDL: Expecting sct-bkn ceilings to in the 3-5k foot range to continue this evening. Showers are approaching from the west and should begin to affect terminals as early as 22Z, persisting through 06-07Z. Rain should become more spotty after this period across south-central AZ, with some improvements in ceilings possible to around 8k feet. Easterly winds around 5 kt should be maintained through late evening as well, before a shift towards the southwest is anticipated after 06Z. More widespread rainfall is anticipated late Friday evening and Saturday morning and will be associated with another period of increased cloud cover. Winds will also strengthen during this time as a cold front approaches, shifting from southerly to westerly by early Saturday morning. Southeast California/Southwest Arizona including KIPL and KBLH: Areas of sct-bkn ceilings as low as 7k feet, along with scattered showers, have developed across southeast California into the lower Colorado River Valley. Otherwise, expect sct clouds with bases near 10-12k ft this afternoon and overnight. Gusty west winds are still anticipated to develop across the Imperial Valley this afternoon, before weakening around 03Z. Periods of more widespread showers are possible across the area Friday afternoon, and will be associated with an increase in westerly winds. Aviation discussion not updated for amended TAFs. && .FIRE WEATHER... Saturday through Wednesday: After a brief respite from the rain Saturday evening through Sunday morning, precipitation associated with another low pressure system will develop Sunday afternoon and evening across the Desert Southwest. Additional rainfall is likely Monday along with breezy to windy conditions. High pressure will gradually rebuild across the area Tuesday and Wednesday, resulting in a drying trend though temperatures will remain below normal. Fire danger will remain low through the period due to the persistent and anomalously moist conditions. && .SPOTTER INFORMATION STATEMENT... Spotter reports of rain and snow will likely be needed later this week. && .PSR WATCHES/WARNINGS/ADVISORIES... AZ...Winter Storm Warning from midnight tonight to 11 AM MST Saturday for AZZ024. CA...None. && $$ Visit us on Facebook...Twitter...and at DISCUSSION...Percha/Vasquez AVIATION...Hirsch FIRE WEATHER...Hirsch
Area Forecast Discussion
National Weather Service Blacksburg VA
1104 PM EST Thu Jan 19 2017 .SYNOPSIS... High pressure centered over our region this afternoon will shift east to the coast tonight as a warm front lifts north from the Gulf Coast states into the southern Appalachians. The warm front will swing north across Virginia and into the mid-Atlantic Friday, before stalling. Another storm system moving across the southern U.S. will impact our region Sunday into Monday. && .NEAR TERM /THROUGH FRIDAY/... As of 1100 PM EST Thursday... Adjustment to the forecast address to main features, overnight low temperatures and timing of arrival of precipitation. Several locations over parts of Southside Virginia and neighboring portions of north central North Carolina are already experiencing temperatures in the upper 30s. Forecast lows were in the lower 40s. Have adjusted forecast lows to reflect readings not too much lower than the ongoing readings, allowing for additional slow cooling into the early morning hours before a slight rise in temperatures before sunrise as weak warm air advection starts. Have slowed the arrival of rain into the region from west to east. This amounted to not a whole lot of changes across the western portions of the area, but for eastern areas, the arrival of the main area of rain looks delayed until a little after sunrise Friday. As of 700 PM EST Thursday... Incoming moisture is hitting a wall of dry air this evening, therefore slowed the arrival of rain entering the forecast area until after midnight. Otherwise no major changes to previous forecast. As of 200 PM EST Thursday... Upper Ridge over our region this afternoon will slide east tonight into Friday. Warm advection high clouds this afternoon will be followed by increasing mid clouds starting to roll into the southwest by dusk. Low pressure over western Tennessee this afternoon will lift northeast into the Ohio Valley tonight and reach Lake Erie by Friday afternoon. A warm front trailing from the low will lift northward tonight into Friday. Isentropic lift increases this evening across the mountains of North Carolina and shift to the rest of the forecast area overnight. With a dry airmass in place, slowed down the onset of the rain this evening. Used a blend of HRRR and HiResW-arw-east for pops this evening, then utilized a mix of NAM and Continuity with pops tonight into Friday. The best chance for rain is in the mountains with lower threat in the Piedmont. Lower dewpoints in the evening combined with increasing moisture may allow for temperature drop once the rain starts to fall tonight. However, it should remain mild with low temperatures ranging from the upper 30s in the Alleghanys and portions of the Greenbrier Valley to upper 40s to about 50 degrees in Mountain Empire. On Friday, the best lift will push quickly northeast through the region. An upper level shortwave ridge will build over the Mid- Atlantic region. The bulk of the rain will have moved northeast of the area by the early to mid afternoon. Added the mention of fog to isc grids. Lowered high temperatures a few degrees especially in the north Friday with clouds and rain. High temperatures Friday will vary from the upper 40s in the mountains to the lower 60s in the south. Rainfall amounts overall will average around a quarter inch with locally higher in the western mountains of Southwest Virginia and North Carolina. && .SHORT TERM /FRIDAY NIGHT THROUGH SUNDAY/... As of 300 PM EDT Thursday Even with limited sunshine on Saturday the air mass will be unseasonably warm, 15 to 25 degrees above normal. Deep moisture begins to arrive back into the area from the southwest on Saturday afternoon. But Bufkit not showing a saturated sounding until closer to Sunday morning. Models forecasting good lift Sunday with a strong vorticity maximum crossing the central and southern Appalachians along with upper diffluence. Winds at 850MB back to the southeast by 12Z/7AM Sunday with good upslope and increasing inflow off the Atlantic first along the Appalachians in northern North Carolina on the Sunday morning gradually shifting north of Roanoke by the end of the day. More significant differences in the guidance in the amount of instability across southern Virginia and northern North Carolina on Sunday all related to the location of the warm front. 12Z NAM/GFS and latest RAP indicating enough of a secondary low developing over eastern North Carolina that with the precipitation there should be strong in-situ wedging. Large spread in location of heaviest rain also so will lean toward WPC guidance. Wedge and precipitation will keep temperatures on the cool side/or below guidance for Sunday. Have added slight chance of thunder from extreme southern Virginia into northern North Carolina but confidence is low. && .LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/... As of 200 PM EDT Thursday Precipitation will remain in the area through Monday with the highest rain amounts on Sunday night and Monday, mainly along and east of the Blue Ridge. Experimental hydrologic ensembles showed at least a small potential for 1 to 3 inches of rain. Localized minor flooding is possible if this amount of precipitation is realized. Once the surface low is off the coast on Monday night and Tuesday, precipitation will be confined to favored western upslope areas. Enough colder air comes in Monday night that we will have snow in the forecast from southeast West Virginia into northwest North Carolina. Winds will also increase Monday night and Tuesday. There may be enough of a low level jet along with cold air advection and pressure rises for wind gusts in the 40 to 50 mph range. By Wednesday and Thursday a long wave positively tilted upper trof will extend from the Great Lakes across the central United States. Prevailing deep southwest flow over the Mid Atlantic region during this time frame results in differences among the models in how fast any front will progress east. For now WPC has surface front crossing the region Wednesday and Wednesday night. Behind this system is a much colder air mass. More upslope snow showers in the mountains are possible. At this time the models are showing snow showers for Thursday night. && .AVIATION /04Z FRIDAY THROUGH TUESDAY/... As of 650 PM EST Thursday... Fast moving negatively tilted short wave will rotate through the region late tonight/early Friday, followed by an extended period of southwest flow preceding another short wave during the weekend and a deep low pressure area slated to move through the southeast U.S. early next week. This system will be in/out fairly quickly, but will leave low clouds, drizzle, fog in its wake given the persistence of southwest flow aloft remaining in place. It appears that the timing of this system is a little slower than previously thought, with the main wave of rain coming through in the 12Z-16Z time frame as opposed to 08Z-14Z time frame. Current VFR ceilings will quickly deteriorate to MVFR/IFR after the rain spreads into the region, then settle into an IFR/LIFR condition during the afternoon in fog, drizzle, low clouds. Visibility will drop into the MVFR category, occasionally IFR during the rainfall, then settle mainly into MVFR during the afternoon in fog and drizzle. Winds will be mostly east-southeast 3-5kts this evening, becoming southeast 4-8kts as the rain moves into the region. Some low end gusts are possible at KBLF with the southeast flow. Winds will become light and variable or calm east of the Blue Ridge after the rain moves out of the region, but become SSW-SW 4-8kts with again some low end gusts at KBLF during the afternoon Friday. Medium confidence in ceilings and visibilities through the TAF valid period. Medium confidence in wind speed/direction through the TAF valid period. Extended Aviation Discussion... As noted above southwest flow aloft will persist ahead of a deep upper low that will develop across the southeast states over the weekend, then move off the southeast U.S. coast Monday. Low clouds, drizzle, and fog are likely to persist Friday night with additional waves of rain moving into the area late Saturday and persisting into Monday. At this point it appears that the only period of potential VFR cigs would be Saturday afternoon. Otherwise, much of the period will be characterized by MVFR or worse ceilings and visibilities. Winds will become strong and gusty from the northwest Monday night into Tuesday as the major weather system moves up the east coast. Ceilings and visibilities should finally improve east of the Blue Ridge after Tuesday, but likely persist with MVFR and upslope flow west of the Blue Ridge. && .CLIMATE... As of 305 PM EST Thursday... Record warm Mins for January 21 Blacksburg....42 in 1954 Bluefield.....47 in 1999 Danville......56 in 1954 Lynchburg.....51 in 1927 Roanoke.......51 in 1959 Record highs for January 21 Blacksburg....59 in 1954 Bluefield.....60 in 1999 Danville......68 in 1959 Lynchburg.....72 in 1932 Roanoke.......74 in 1932 && .RNK WATCHES/WARNINGS/ADVISORIES... VA...None. NC...None. WV...None. && $$ SYNOPSIS...KK NEAR TERM...DS/KK/RCS SHORT TERM...AMS LONG TERM...AMS AVIATION...KK/RAB CLIMATE...AMS
Area Forecast Discussion
National Weather Service San Diego CA
539 PM PST Thu Jan 19 2017 Updated SKYWARN section. .SYNOPSIS... A very stormy pattern will continue across Southern California through Monday. The first of several waves of stormy weather will continue to move across the region today bringing isolated light showers and mountain snow. The next wave will move through Friday with heavier rain and mountain snow, possible flooding and stronger, potentially damaging winds for portions of the region and scattered thunderstorms. On Sunday the next system arrives and continues into Monday, possibly bringing the heaviest precipitation of the event. Dry weather is expected by midweek. && .DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE... SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO COUNTIES... The first in a series of storms has moved through the region today, bringing moderate and locally briefly heavy showers mainly to areas over and west of the mountains. Over the last 18 hours, the coast and valleys have seen generally 0.50-0.75 inches, while the coastal slopes have seen about 0.75-1.5 inches, and about 0.05-0.15 inches in the deserts. Radar shows that showers have diminished for the most part, with just some isolated post- frontal light showers, with the snow level around 5500-6000 ft. Snow levels will likely stay at around that level today. Latest HRRR shows mainly isolated showers continuing through the rest of the day. On water vapor satellite, the current trough can be seen moving east across the region. On Friday a strong short-wave trough and accompanying 130 kt jet noses its way into Southern California, bringing a round of heavier precipitation than we`ll have today. For this storm, showers start to increase early Friday morning, with widespread moderate to heavy precipitation mid-Friday morning through Friday afternoon. Showers then diminish gradually Friday night into Saturday morning except in mountains where some showers may linger through the day Saturday in westerly flow aloft. As far as thunderstorm chances goes, the NAM12 and WRF show 500-1000 J/KG of most unstable CAPE and up to 30 kt of low level wind shear late Friday morning and afternoon. Given these parameters, would not be surprised if we see a few strong thunderstorms producing severe wind gusts tomorrow. In addition, 850 mb winds increase to 35-50 kt out of the southwest late Friday morning and afternoon, which will not only increase the potential for higher orographic precipitation along the coastal mountain slopes, but also bring strong winds not only to the mountains and deserts but also the coast and valleys. Hi-res models show sustained winds reaching 20-30 kt over the coastal and valley areas Friday morning and afternoon as the cold front moves through, which translate to wind gusts of 35-45 mph and locally stronger. This, in addition to the likely strong convective downburst that will move through the area, has led to the issuance of a High Wind Warning for the coasts, valleys and Santa Ana Mountains/foothills, with damaging wind gusts possible. Meanwhile, the San Diego county deserts look to have a bit stronger mountain wave activity Friday and Saturday than the other desert locations, so the High Wind Watch was converted to a High Wind Warning for those areas while a Wind Advisory was issued for the other deserts. Meanwhile, strong wind gusts of 70 mph or greater will be possible along the mountain ridges and desert slopes. A large, broad trough will move down off the coast of California on Sunday, directing an atmospheric river into Southern California, with precipitable water increasing to 1.4 inches. This moisture, in addition to southwest 850 mb winds increasing to 50 kt, will bring widespread moderate to heavy precipitation, higher snow levels, and strong winds to the region. The trough then drops down into Southern California on Monday, bringing colder air with it, and less intense precipitation. For rain and snow forecast amounts and flooding potential for the next couple storms, please see the HYDROLOGY section below. Long-range models indicate some slight instability on Monday, so perhaps thunder will be a possibility that day as well. There`s the possibility that another short-wave will move through the region on Tuesday, with the slight chance for some showers that day. Warming and dry weather expected starting next Wednesday as a ridge aloft builds over the west. && .AVIATION... 192130Z...SCT/BKN low cloud will continue across the region, with bases from 1300-4500 ft MSL. SHRA and isolated TSRA will continue through tonight. VIS will lower to 1-3 SM BR in showers. The bulk of the precip will move out of the region by late morning. Widespread RA will develop Friday morning and into the afternoon. Mountain tops will be obscured at times through the period. SW to W wind gusts of 50-60 kt will continue over the mountains, desert mountain slopes and into adjacent deserts and through Friday. Severe UDDFS will be possible on the lee side of the mountains through the period. && .MARINE... Several storms moving across the region will continue unsettled conditions through Tuesday. Winds are currently gusting at 19 kt and seas have risen to 8 ft at the San Clemente Bouy. The Small Craft Advisory will continue over the waters through early Friday, then Gale force winds will develop Friday, Saturday and possibly again on Monday. See the Small Craft Advisory and Gale Warning (LAXMWWSGX) currently in effect for additional details. && .BEACHES... High surf is likely along the beaches through Tuesday. The largest and potentially damaging surf is likely to occur late Friday through Saturday, and again Monday into Tuesday. Strong rip currents and large surf will make swimming conditions very dangerous. A High Surf Warning remains in effect through the period. Coastal flooding and beach erosion are possible as highest sets to 16 ft occur Friday night through Saturday coincident with times of high tide. Highest tide during highest surf is 4.6 ft at La Jolla 435 AM Saturday. High Surf will diminish by the middle of next week. && .HYDROLOGY... A series of storms will move into Southern California over the next 5 days, possibly bringing the heaviest precipitation seen here since 2010. The storms will bring significant amounts of rain, with heavy snow accumulations at elevations above 5000 ft. Some areas could receive 5 to 10 inches of total rainfall between through Monday night, possibly as much as 12 inches along the coastal slopes. This has the potential to create an extended period of enhanced runoff into streams and main-stem rivers. Over time, the soil will have decreasing capacity to absorb rainfall resulting in increasing runoff. Flash flooding will also be possible, especially during periods of heavier rainfall. For the Friday storm, snow levels will likely be around 5500-6000 feet or so, with 1-2 feet of snow possible above 6000 feet and 6 inches to a foot between 5000 and 6000 feet. A Winter Storm Warning continues for the San Bernardino and Riverside county mountains through 6 am Saturday...and a Winter Storm Warning was issued for the San Diego county mountains for areas above 5000 foot elevation. Storm total precipitation forecast for Friday looks to be: Coast and Valleys: 1-2 inches Mountains: 2-4 inches High Deserts: 0.15-0.40 inches Lower Deserts: 0.10-35 inches A Flash Flood Watch has been issued for areas over and west of the mountains on Friday due to the likely heavy rainfall rates and thunderstorms. For the Sunday-Monday storm, it will be a warmer storm initially so snow levels look to be initially high around 7000-8000 ft Sunday then lowering quickly to 4000 ft Monday. Storm total precipitation forecast for Sunday-Monday looks to be: Coast and Valleys: 2-3 inches Mountains: 3-6 inches High Deserts: 0.50-1.5 inches Lower Deserts: 0.25-1 inch With precipitation amounts this heavy, more flooding issues look likely, especially considering the precipitation amounts and saturated Ground from previous rainfall. When all is said and done, we could see a total of: Coast: 3-5 inches Valleys: 4-6 inches Mountains: 6-12 inches High Deserts: 1-3 inches Lower Deserts: 1-2 inches && .SKYWARN... Skywarn activation is requested Friday morning-afternoon and again on Sunday. Threats: Damaging winds and flash flooding and extreme mountain snowfall. && .SGX WATCHES/WARNINGS/ADVISORIES... CA...Flash Flood Watch from Friday morning through Friday evening for Orange County Coastal Areas-Orange County Inland Areas- Riverside County Mountains-San Bernardino County Mountains- San Bernardino and Riverside County Valleys-The Inland Empire-San Diego County Coastal Areas-San Diego County Mountains-San Diego County Valleys-San Gorgonio Pass Near Banning-Santa Ana Mountains and Foothills. Wind Advisory until 4 AM PST Friday for San Diego County Deserts- San Diego County Mountains. Winter Storm Warning from 4 AM Friday to 6 AM PST Saturday for San Diego County Mountains. High Wind Warning from 4 AM Friday to 10 PM PST Saturday for San Diego County Deserts. Wind Advisory until 10 PM PST Saturday for Apple and Lucerne Valleys-San Gorgonio Pass Near Banning. Winter Storm Warning until 6 AM PST Saturday for Riverside County Mountains-San Bernardino County Mountains. High Wind Warning from 7 AM to 10 PM PST Friday for Orange County Coastal Areas-Orange County Inland Areas-San Bernardino and Riverside County Valleys-The Inland Empire- San Diego County Coastal Areas-San Diego County Valleys- Santa Ana Mountains and Foothills. Wind Advisory from 10 AM Friday to 10 PM PST Saturday for Coachella Valley. High Surf Warning until 10 PM PST Tuesday for Orange County Coastal Areas-San Diego County Coastal Areas. PZ...Small Craft Advisory until 10 AM PST Friday for Coastal Waters from San Mateo Point to the Mexican Border and out to 30 nm- Waters from San Mateo point to the Mexican Border Extending 30 to 60 nm out including San Clemente Island. Gale Warning from 10 AM Friday to 4 PM PST Saturday for Coastal Waters from San Mateo Point to the Mexican Border and out to 30 nm-Waters from San Mateo point to the Mexican Border Extending 30 to 60 nm out including San Clemente Island. && $$ PUBLIC...Harrison AVIATION/MARINE...JJT
Area Forecast Discussion
National Weather Service Tallahassee FL
847 PM EST Thu Jan 19 2017 .NEAR TERM [Through Tonight]... A line of storms stretches along central AL and the western FL Panhandle. With the loss of daytime heating, instability ahead of the line of storms has fallen greatly. The 00Z RAP analyzes MLCAPE values to be around 250 J/kg in southeast AL and southwest GA, with values approaching 500 J/kg along the northern Gulf waters. Our 00Z sounding reflects these paltry values with SBCAPE of 225 J/kg and mid-level lapse rates around 5 C/km. The low level jet that was featuring values up to around 60 kts earlier has weakened to around 35-45 kts. RAP forecasts for 0-1 km shear have fallen to 15-20 kts, though 0-6 km shear remains fairly high at around 50 kts. Overall, these storms and the environment are looking less and less favorable for severe thunderstorms overnight, though there remains a marginal risk for some isolated damaging wind gusts or a brief tornado. Timing for the storms however, still appears to be on track, with our western zones beginning to see showers and thunderstorms over the next few hours, then storms dissipating as they head further east through the night. && .PREV DISCUSSION [624 PM EST]... .SHORT TERM [Friday Through Sunday]... The aforementioned trough will be moving through the Tennessee and Ohio valleys through tomorrow afternoon with southerly flow prevailing at the surface on the western edge of high pressure. A scattering of light to moderate showers are expected on Friday as weak low-level (300K) isentropic ascent sits over the region. These showers should come to an end by the evening. The main concern in the short term period will be for the potential for severe weather over the weekend. The northern stream longwave trough will continue to amplify and move eastward across the central CONUS in response to a few shortwaves; most notably a strong shortwave moving through the Four Corners region. As the broad longwave forcing moves along the Gulf Coast, a coastal trough/low is expected to develop; thus increasing low-level forcing and the low-level wind field. Deep layer shear will be plenty from the northern stream trough and very steep lapse rates are expected to be in place as well. This will favor discrete storm development through the day across the Tri-State region with all modes of severe weather possible. Saturday night into Sunday, the potent shortwave that was over the Four Corners will move into the southern Mississippi Valley and result in even more low-level and upper-level forcing across the region. Lapse rates will still be quite steep, though dampening a bit. However, a decent increase in low/deep layer shear should compensate for the slight reduction in lapse rates. With this second wave, a more organized squall line is expected with the primary threats being tornadoes and damaging winds, though severe hail can`t be ruled out along the line as well. The local area currently resides under a Slight Risk by the SPC for Saturday, and have a 15-30% risk on Sunday. Those type of outlooks that far into the future tend to indicate a fair amount of confidence in severe weather unfolding across the region. The main variable will be the timing of the waves of severe weather and whether the first will end up interfering with the evolution of the squall line. Folks are urged to pay close attention to the forecast over the next 24-36 hours. For information on expected rainfall totals, see the hydrology discussion below. .LONG TERM [Sunday Night Through Thursday]... As the system moves away from the region, some showers may linger into Monday but the chance of severe weather should begin to diminish. Also, fast offshore winds (20-30 kt) are expected to decrease by Monday night. Afterwards, a cooler and dry air mass filters in and stays over the CWA for a few days allowing temps to cool down closer to the seasonal average. On Wednesday night into Thursday, a low pressure system moves over Michigan into the Northeastern seaboard while its corresponding cold front moves into our area. There is some disagreement between the global models as to the timing of the frontal passage. The ECWMF has the front moving through the region by the end of Thursday which is quicker compared to the GFS. However, both bring rain to the CWA beginning Wednesday night. .AVIATION [Through 00Z Saturday]... Conditions would once again be primed for widespread fog and low cigs overnight, but the consensus of NWP models are in good agreement in an area of SHRA/TSRA moving east across the region tonight. This convection will "turn over" the PBL and scour out any dense fog. KDHN and KECP will have rain between 04Z and 08Z, followed by KTLH and KABY between 07Z and 11Z, with a weakening area of rain reaching KVLD by daybreak. However, between 03Z and 08Z there will be enough of a window of quiet weather for LIFR Vis/cigs to develop at KTLH and KVLD, before the convection dissipates the fog. Low cigs (generally below 1k ft) are likely at all sites Friday morning, followed by VFR cigs by late morning. .MARINE... Winds will begin to ramp up to Advisory levels late Friday night ahead of a strong low pressure system. Advisory levels will prevail through early next week, with Gale force gusts and possibly sustained winds Sunday night through Monday. Seas could climb as high as 15 feet well offshore by Monday afternoon. .FIRE WEATHER... No concerns. .HYDROLOGY... Beginning tonight, 2 to 4 inches of rain are expected to fall across the Tri-State region through Sunday night. Isolated amounts around 6 inches will be possible as well. These amounts will most likely fall over a long enough period that flash flooding wont be a concern. While rises are naturally expected on area rivers, with widespread average amounts probably wont force area rivers into flood stage. Should the locally higher amounts fall over Kinchafoonee Creek or the Choctawhatchee River minor flooding could be possible there. && .PRELIMINARY POINT TEMPS/POPS... Tallahassee 62 76 66 70 65 / 70 50 40 90 80 Panama City 64 73 68 72 66 / 80 50 50 90 80 Dothan 61 75 64 72 62 / 100 40 60 90 80 Albany 60 76 65 72 63 / 70 40 50 90 80 Valdosta 60 76 66 71 64 / 50 40 30 90 80 Cross City 59 75 65 72 65 / 40 40 20 70 80 Apalachicola 65 73 67 71 66 / 70 50 50 90 80 && .TAE WATCHES/WARNINGS/ADVISORIES... FL...High Rip Current Risk until 11 PM CST this evening for South Walton. GA...None. AL...None. GM...None. && $$ NEAR TERM...Moore SHORT TERM...Harrigan LONG TERM...Harrigan/Chaney AVIATION...Fournier MARINE...Harrigan FIRE WEATHER...Fournier HYDROLOGY...Harrigan