Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 04/14/18


Area Forecast Discussion
National Weather Service Columbia SC
740 PM EDT Fri Apr 13 2018 .SYNOPSIS... High pressure centered off the coast will continue ridging into the southeastern states through Saturday. This will produce southerly flow over the region along with a warming trend. A cold front will cross the area Sunday into Sunday night bringing showers and thunderstorms. Dry weather and cooler temperatures will arrive Monday with moderating temperatures through the middle of next week. && .NEAR TERM /UNTIL 7 AM SATURDAY MORNING/... Surface high pressure situated off the Southeastern Coast will continue to promote southerly flow into the forecast area overnight. Clouds are expected to increase towards daybreak. Increasing clouds and mixing should promote mild overnight low temperatures, in the upper 50s to around 60. && .SHORT TERM /7 AM SATURDAY MORNING THROUGH SUNDAY NIGHT/... Winds out of the south on Saturday will bring additional moisture into the region through the day. PWAT readings climb to around an inch, but with model soundings still showing a good capping inversion in mid-levels, do not expect any precip through the day. Temperatures will be rather warm during the afternoon on Saturday, with readings into the middle 80s common. Saturday night should also remain mostly dry for majority of the night. For that time, models do show some rainfall around the region, but keep much of it closer to the mountains, and also along the coast. Exception will be closer to sunrise Sunday morning when isolated showers may be able to move into the forecast area. Overnight lows mainly in the middle 60s. Sunday is the day of interest. A cold front will be approaching the region from the west, while a strong upper trough will push eastward also. The upper trough appears to have a negative tilt to it west of the area by the afternoon as the front approaches. Low-level winds become rather strong, and moisture continues to increase in advance of the front. Best chance for stronger activity should be during the late afternoon and evening hours as a potential squall line moves through. SPC has the area outlooked in a Day 3 slight risk. Damaging winds will be the main threat. Will continue high pops across the cwa on Sunday, but have tried to narrow down some of the timing and movement a little bit better. Lower pops in the morning, with increasing pops during the afternoon associated with the line, then a decrease in pops Sunday night as the front moves east. && .LONG TERM /MONDAY THROUGH FRIDAY/... Behind the exiting cold front, generally fair conditions expected to persist through the longer term period. High pressure will build into the region behind the front on Monday, with the potential for windy conditions during a good portion of the day due to a tight pressure gradient over the region. Winds weaken Monday night, then become lighter for the remainder of the period. The airmass appears to remain dry at this time through the end of the week, so no rainfall expected, even with a weak cold front during the middle of the week. Temperatures will be cooler on Monday behind the front, then a warming trend begins on Tuesday, lasting through the end of the week. && .AVIATION /00Z SATURDAY THROUGH WEDNESDAY/... VFR conditions through most of the TAF period although some stratus possible early Saturday morning mainly near OGB. Pressure ridge continues offshore of the Carolinas. Cumulus clouds diminishing with loss of heating so expect mainly clear sky during the evening. Winds will diminish to south- southeast less than 10 knots. Models suggest a relatively strong low level jet...20 to 30 knots overnight which should limit fog despite modest increase in low level moisture due to onshore flow. There is some guidance mainly HRRR suggesting some stratus with IFR/MVFR possible ceilings around daybreak mainly near OGB terminal. MVFR visibility restriction also suggested at AGS/OGB although low level jet should be a limiting factor. So brief period of MVFR forecast in those areas around 12z...otherwise VFR with scattered to broken cumulus developing by late morning. South winds will increase to 10 to 15 knots Saturday afternoon. EXTENDED AVIATION OUTLOOK...Restrictions expected Sunday and Sunday night as a cold front crosses the region along with showers and thunderstorms. Strong and gusty winds expected Sunday through Monday. && .CAE WATCHES/WARNINGS/ADVISORIES... GA...None. SC...None. && $$
Area Forecast Discussion
National Weather Service Des Moines IA
711 PM CDT Fri Apr 13 2018 .SHORT TERM.../Tonight/ Issued at 426 PM CDT Fri Apr 13 2018 Bottom Line up Front... Severe Weather main threat in southern Iowa for the immediate short- term. Large hail, tornadoes, and damaging winds all possible. Transition to winter weather hazards overnight across northern to northwestern Iowa. Setup... 20z Sfc analysis has roughly a 990mb low positioned over southeastern Nebraska/northeastern Kansas. Well-advertised moisture has surged ahead of this low into the warm sector, aided by 50 to 60 kt moisture transport winds. All eyes have been on how far north the warm front (oriented from west to east) attendant to the sfc low would make it today. At present time, the boundary is draped around the southern three tiers of counties in Iowa. South of the boundary, dewpoint temperatures have climbed into the 60s. Much of southwestern Iowa had sunshine through this morning which aided in destabilization. Convective initiations is well underway from southwestern Iowa southward through Kansas. Ongoing Severe Weather... With ongoing convection, focus is on mode and longevity. Latest RAP showing widespread CAPE values of 2000 J/Kg. 0-6KM shear is upwards of 50 kts and low-level helicity is off the charts. With this moisture, sounding profile, LCL heights are more than sufficiently low for tornadoes... especially near to the boundary. Hodograph analysis has slowed down storm motion to more the 30 to 40 mph range vs the 50 to 60 mph range they were suggesting yesterday. Storms getting north of the boundary will lose their tornado potential, with elevated hail being the main convective mode. Into the overnight, boundary layer won`t decouple, so we won`t have capping issues. Instability lingers, though waning through 12z Sat. The boundary is slated to slowly drift southward, making it into Missouri between 06z Sat and 09z Sat, which will bring an end to the SVR/Tor threat. Will have to keep an eye on storms in Kansas/Missouri moving northward... with such prolific shear profiles, storms should be able to sustain themselves into Iowa. .LONG TERM.../Saturday through Friday/ Issued at 426 PM CDT Fri Apr 13 2018 Bottom Line up Front... Winter weather hazards continue tonight through Sunday, with blizzard potential likely in northwestern Iowa. Strong winds will be major driver of impacts. Transition to snow should begin in northwestern Iowa around 12z Sat as CAA begins to infiltrate Iowa. Minor tweaks made to the forecast from the previous days... the biggest of which has been to beef up amounts slightly in northwestern Iowa. In short, there has been a trend to linger instability through Iowa as major ascent processes in play. Thundersnow remains very possible, which typically indicates upwards of 2 inch per hour rates. High confidence in winds remaining in the 25 to 35 mph range, with gusts upwards of 50 mph in northwestern Iowa. Winds will be the biggest driver of impacts, as visibility will approach zero during heavier periods of snow...likely in the Saturday Morning to Saturday afternoon timeframe. This would have significant impacts on travel, making travel very dangerous and nearly impossible in certain locations. As our sfc low pulls away to the east, snowfall intensity/rates will begin to diminish Saturday afternoon into the evening hours. Another forecast tweak has been to linger the snow into Sunday. The 12z NAM especially keeps some forcing in our eastern counties through at least 18z Sun. Winds should be around 15 to 25 mph during this timeframe, so there may still be travel impacts as visibility could drop to less than one mile at times. Monday and Beyond... High pressure moves in to melt snow and quiet the weather on Monday. Long-term models have consistently been showing the next systems to push through the upper Midwest on Wednesday and on Saturday. At this time, it appears these should be fairly low-impact systems, with rain and a possible light rain/snow mix during the overnight hours Tuesday night and Friday night. && .AVIATION.../For the 00Z TAFS through 00Z Saturday evening/ Issued at 711 PM CDT Fri Apr 13 2018 IFR conditions and strong, gusty winds are in place across northern Iowa, somewhat removed from a west to east warm front currently between KCNC and KOXV. Confidence is high that these conditions will persist and sag southward somewhat later this evening. Thunderstorms producing producing severe wind gusts at times with variable conditions will also continue from western into northern Iowa. Later tonight strong winds will persist north with strong winds continuing north leading to blizzard conditions north and west with IFR or less likely. && .HYDROLOGY... Issued at 458 PM CDT Fri Apr 13 2018 Wet period expected over the next couple days with seasonally moderate to heavy QPF expected across the northern CWA. In response, the 2-day QPF hydrograph ensembles show significant within-bank rises at many forecast points within the Cedar, Iowa and Des Moines River basins mainly along and north of US Hwy 20, with the exception being the Des Moines River at Des Moines SE 6th St where the river may come within a couple feet of flood stage. The 2-day QPF hydrograph ensembles suggest flooding is possible at a few locations in the Cedar and Des Moines River basins along and north of US Hwy 20. A Flood Warning has already been issued for the West Fork Des Moines River at Estherville. In addition, a Flood Watch has been issued for the Cedar River at Cedar Falls. && .DMX WATCHES/WARNINGS/ADVISORIES... Winter Weather Advisory from 7 AM Saturday to 1 AM CDT Sunday for IAZ025-035-036-044>047-057-058. Blizzard Warning from 7 AM Saturday to 1 AM CDT Sunday for IAZ004-005-015-023-024-033-034. Winter Weather Advisory from 7 AM Saturday to 1 PM CDT Sunday for IAZ017-026. Winter Storm Warning from 7 AM Saturday to 1 AM CDT Sunday for IAZ006-007-016. Winter Weather Advisory from 1 AM to 1 PM CDT Sunday for IAZ007- 027-028-037>039. && $$ SHORT TERM...Kotenberg LONG TERM...Kotenberg AVIATION...Small HYDROLOGY...Zogg
Area Forecast Discussion
National Weather Service Austin/San Antonio TX
1019 PM CDT Fri Apr 13 2018 .UPDATE... See Fire Weather section below for the primary update purpose. One quick note on the ZFP update is that evening post-frontal winds are stronger, and the area of storm chances late tonight was expanded a few counties westward. && .FIRE WEATHER... The cold front overtook the dry-line and generate quite a windy condition over the southern Edwards Plateau, and perhaps brought slightly stronger storms and convection inititation to expand westward. The RFW for the evening was thus extended east to include Llano, Uvalde, and Eagle Pass. Brief near critical fire weather conditions could extend east into the I-35 corridor overnight, but will be more likely after sunrise Saturday. To avoid confusion, the Fire Weather Watch will not be upgraded until after the 2am RFW is set to expire. && .PREV DISCUSSION... /ISSUED 655 PM CDT Fri Apr 13 2018/ AVIATION... /00Z TAFS/ Brief towering cumulus formed near DRT but has since waned with no new cell development expected. Along I-35, cell development over the Hill Country and rapid refresh model tracking of the propagation would suggest some impacts to reach AUS, with the model showing weaker convection forming with the fropa around SAT/SSF. Improving sky condition should occur quickly in the wake of the front, but a brief period of mvfr cigs near the front will be possible. Gusty winds are forecast after daybreak possibly over 25 knots at AUS. PREV DISCUSSION... /ISSUED 255 PM CDT Fri Apr 13 2018/ SHORT TERM (Tonight through Saturday Night)... The associated mid level shortwave, which generated the elevated convection earlier along the I-35 corridor, is continuing northeast out of the CWA. A weakening of the cap took place across the northern CWA as it passed, confirmed by aircraft soundings out of AUS, and clearing should help to continue a gradual weakening as the dry line approaches from the west. The dry line is currently nearing a Rocksprings to Del Rio line mid afternoon and will continue east through the remainder of the afternoon. CU is becoming slightly agitated across the northeast Hill Country, but so far aforementioned cap is preventing deeper convection from developing. As cap weakens through the remainder of the afternoon there is a slight chance of getting deeper convection and a storm or two ahead of the dry line across the northern CWA. A conditional severe threat for large hail exists given CAPE values of 3000-4000 J/kg and deep layer shear values in excess of 40 kts. 12Z runs of HREF members as well as recent HRRR runs develop convection later this evening near and east of I-35 as forcing from the front, catching up to the dryline, and tail end of shortwave are able overcome what is left of the weakening inversion. However, each model initiates the isolated convection in different areas along the I-35 corridor, before increasing in coverage ahead of the front east of I-35 overnight. Again, a strong to severe threat is in play with any storms that develop, with hail and straight-line winds the primary threat. Farther west, winds should be increasing through the remainder of the afternoon across the far western third of the CWA, and a critical fire danger should develop thorugh the later afternoon and into the evening in counties currently in the Red Flag Warning. Cooler, dry, and breezy to windy conditions will develop behind the front on Saturday. Elevated to near critical fire weather conditions are possible across portions of the area and will address further in the Fire Weather section below. LONG TERM (Sunday through Friday)... A cold morning on Sunday, and model guidance has trended colder on morning lows for the Hill Country now showing mid 30s in many areas. Winds speeds will play a large role in how far temps bottom out. NAM MOS, which indicates winds dropping of to nearly calm across the northern Hill Country, is indicating the potential for near freezing temperatures across Kerr and Gillespie counties. Elsewhere winds should stay up enough, but still cool in the low to mid 40s outside of the Hill Country Sunday morning. The dry air in place and clear skies should lead to a large diurnal swing in temperatures, with highs Sunday afternoon back into the 70s, and even some lower 80s along the Rio Grande. Dry and warmer conditions for Monday and Tuesday, and a breezy southerly wind could lead to elevated fire weather conditions in some areas. Increasing low level moisture will take place Tuesday night into Wednesday with a weak cold front slipping through or stalling over the area Wednesday and Wednesday night. A stronger upper level system will develop to the west Friday into Saturday with better chances for precipitation over the area as it approaches. Fire Weather... A dry-line is currently moving through Val Verde and Edwards counties and will continue east through the remainder of the afternoon and evening. Gusty west and northwest winds and very low relative humidity values will continue to develop behind it this afternoon and evening. Wind gusts around 30 mph and RH values bottoming out around 5 to 15 percent will develop through the late afternoon. When combined with dry fuels this result in critical fire weather conditions and a Red Flag Warning remains in effect for Val Verde, Kinney, and Edwards counties. A cold front is forecast to move through late tonight. Strong north winds will develop behind the front on Saturday, with drier air filtering into the rest of the region. Wind gusts to around 30 mph with minimum RH values in the teens to 20s will result in elevated to near critical fire weather conditions on Saturday. A Fire Weather Watch is in effect for areas near and west of I-35 and could be upgraded to a Red Flag Warning tomorrow. && .PRELIMINARY POINT TEMPS/POPS... Austin Camp Mabry 77 71 45 73 47 / 30 - 0 0 0 Austin Bergstrom Intl Airport 75 70 40 72 43 / 40 - 0 0 0 New Braunfels Muni Airport 75 72 41 75 45 / 40 0 0 0 0 Burnet Muni Airport 81 68 40 71 44 / 20 0 0 0 0 Del Rio Intl Airport 85 77 47 81 52 / 0 0 0 0 0 Georgetown Muni Airport 77 68 40 71 43 / 30 - 0 0 0 Hondo Muni Airport 81 76 41 80 47 / 20 0 0 0 0 San Marcos Muni Airport 76 71 41 74 44 / 40 - 0 0 0 La Grange - Fayette Regional 77 69 42 70 44 / 50 10 0 0 0 San Antonio Intl Airport 77 74 44 76 49 / 30 0 0 0 0 Stinson Muni Airport 81 75 45 77 49 / 30 - 0 0 0 && .EWX WATCHES/WARNINGS/ADVISORIES... Fire Weather Watch from Saturday morning through Saturday evening for Atascosa-Bandera-Bexar-Blanco-Burnet-Comal-Dimmit-Edwards-Frio- Gillespie-Hays-Kendall-Kerr-Kinney-Llano-Maverick-Medina-Real- Travis-Uvalde-Val Verde-Williamson-Zavala. Red Flag Warning until 2 AM CDT Saturday for Bandera-Edwards- Gillespie-Kerr-Kinney-Llano-Maverick-Real-Uvalde-Val Verde. && $$ Mesoscale/Aviation...04 Synoptic/Grids...Oaks Public Service/Data Collection...Williams
Area Forecast Discussion
National Weather Service Lincoln IL
844 PM CDT Fri Apr 13 2018 .UPDATE... Issued at 831 PM CDT Fri Apr 13 2018 Scattered showers and storms continue to track north to northeast across west central Illinois with a larger area of showers and storms over central and southern Missouri heading northeast towards our area. A frontal boundary edging slowly south into our area again this evening with the winds at Galesburg and Lacon into the east with temperatures 50 to 75 miles north of the boundary in the middle 40s. As the wave of showers and storms to our southwest tracks over our area later this evening and overnight the boundary will hold nearly steady but then, as the showers shift off to our east Saturday morning, the front will begin to drift south. Just where the boundary ends up in central Illinois will make a big difference not only in temperatures Saturday, but where the threat for severe storms sets up Saturday afternoon. Tonight`s storms could still produce some isolated gusty winds and hail but tomorrow afternoon`s threat will include an isolated tornado along the frontal boundary as weak low pressure moves along the stalled front over central Illinois. Have made some adjustments to the temperatures across the north for the rest of the evening along with increasing the POPs across the west and north where we were already seeing shower activity. We should have the update out by 9 pm. && .SHORT TERM...(This evening through Saturday) ISSUED AT 241 PM CDT Fri Apr 13 2018 Warm front has drifted about 10 miles north of the far northern CWA border early this afternoon, roughly aligned just south of I-80. Showers and scattered thunderstorms have continued to push northeast, and were largely contained to areas north of I-72 at 2:30 pm. A lull in the rain is anticipated into early evening, as the convection ahead of the front in Missouri starts to get organized. NAM and the ARW/NMM have this arriving shortly after sunset, while the HRRR favors more of a late evening approach. As the surface low move into northern Missouri overnight, the bulk of the rain will be confined to the east half of the forecast area. The front should drift back southward late in the night, remaining quasi-stationary from about Quincy-Bloomington most of the day. Have cut back on thunder chances Saturday north of this boundary, but kept showers and storms further south. Latest SPC Day2 outlook keeps the slight risk of severe storms over the eastern CWA. GFS progs show surface CAPE of around 1500 J/kg in that area by early afternoon, though the NAM has dialed things back considerably. With the front over the northern CWA, a fairly sizable temperature gradient will be in place. Far northern CWA should stay fairly steady in the mid 40s on Saturday, while the south gets close to 70. .LONG TERM...(Saturday night through Friday) ISSUED AT 241 PM CDT Fri Apr 13 2018 Large upper low with this storm system will be in no particular hurry to exit the area, with the synoptic models centering it somewhere near the southern Michigan border by early Monday. Scattered showers will continue through the weekend as this feature passes, most numerous from about Peoria northward. Cold air being drawn in behind the low still looks to be sufficient to cause a changeover to snow Sunday night, though amounts should be negligible. Temperatures should be down into the 20s by Monday morning, threatening any gardens that have been planted in the recent mild spell. Mid week storm system has trended a bit further south, though the models do have decent agreement in much of the precipitation staying north of the low track. Have included a chance of showers north of I-74 Tuesday night, but conditions should be largely dry next week, once the upper low exits. A cooler period is expected in the wake of the mid week system, not especially cold but enough that some frost may be a concern. && .AVIATION...(For the 00Z TAFS through 00Z Saturday evening) Issued at 602 PM CDT Fri Apr 13 2018 Main forecast challenge this period will be timing of showers and thunderstorms into the forecast area later this evening and how quickly cigs drop to MVFR and IFR, especially across the north in PIA and BMI. A frontal boundary is expected to slowly edge south tonight with IFR cigs to the north of the boundary while MVFR and low VFR cigs dominate to the south. Question is how far south this boundary will go later tonight into Saturday morning as low pressure approaches from the west. Most of the operational models suggest it will move to south of a BMI to PIA line and approach CMI and AAA by Saturday morning. The surface low will track right along the boundary tomorrow with our northern TAF sites possibly staying in MVFR to IFR while further south, we may see cigs pop up to low VFR for a time. Shower timing looks to be in the 02z to 05z time frame from southwest to northeast with a lull in the precip around 12z Saturday with chances low enough during the day to continue with VCSH at this time. The gusty southerly winds will gradually back into a east to southeast direction later this evening in PIA and BMI and after 09z in our southern TAF sites. Depending on where the front actually ends up tomorrow, winds will vary from east to northeast at PIA and BMI and southeasterly at SPI, DEC and CMI. Wind speeds tonight will range from 12 to 17 kts with gusts up to 25 kts at times, especially in SPI, DEC and CMI. Wind gusts should start to settle down after 03z across the north and by 08z in our southern TAF sites. && .ILX WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...Smith SHORT TERM...Geelhart LONG TERM...Geelhart AVIATION...Smith
Area Forecast Discussion
National Weather Service Jackson MS
1024 PM CDT Fri Apr 13 2018 ...SEVERE STORMS AND FLASH FLOODING TONIGHT THROUGH SATURDAY... .UPDATE... Updated for evening discussion. && .DISCUSSION... Showers and thunderstorms will continue moving into the region tonight in association with a strong cold front. All modes of severe weather will be possible, along with flash flooding. The current forecast is in good shape with no changes needed. /27/ Prior discussion below: Tonight through Saturday night... Satellite imagery and RAP analysis shows a digging trough exiting out of the Desert Southwest and into the Southern Plains with large scale ascent overspreading a large portion of the Great Plains/Midwest. This trough and associated closed mid/upper-level low and strong cold front will be the driver for the expected severe weather tonight through Saturday. Dry weather will persist across the vast majority of the ArkLaMiss the rest of this afternoon into the early evening hours. As previously mentioned yesterday, guidance has continued to hone in on the slower timing with ongoing convection over the ArkLaTex progged to enter the Delta between 10pm and midnight. Severe threat tonight: deep layer shear of 40-50kts, strong 0-1km shear and helicity, and ample SBCAPE up to 1500 J/kg will support all modes of severe weather as convection enters the Delta. 12z hi- res CAM guidance has come into better agreement with respect to convective evolution with a slow moving broken line of storms being the primary storm mode. Potential will also exist for discrete/scattered supercells ahead of the line with embedded supercell structures in the line itself. Given the aforementioned environment, all modes of severe weather including tornadoes, some of which could be strong, hail up to golf ball size, and damaging winds up to 70mph are expected. The greatest potential for a strong tornado will be with any discrete supercells ahead of the line. There is also indication that the northern portion of the line could accelerate along and north of the Hwy 82 corridor with an associated damaging wind threat extending slightly further east. This convection will be aided by a surge of 850mb ThetaE, however the ThetaE minimum in its wake will also help to limit eastward progression overnight. Given the slow progression, expect convection to be located in the vicinity of a line from Grenada to Natchez by sunrise Saturday morning. After collaboration with SPC, the ongoing enhanced risk appears well placed and the only changes will be to update the timing to reflect the slower solution. Severe threat Saturday: the slower timing will allow for severe storms to persist through the day Saturday with convection located in the vicinity of the aforementioned line by sunrise. A ThetaE minimum will be located ahead of the ongoing line of storms during the early morning hours, however another surge of higher ThetaE air (upwards of 340 K) and renewed ascent will quickly overspread south and east portions of Mississippi by the mid morning hours. This will help to reinvigorate convection with the severe threat quickly increasing. Multiple hi-res CAM families indicate the potential for discrete/scattered supercell development ahead of the line during the mid to late morning hours roughly along and southeast of the Natchez Trace corridor. The environment will remain very favorable for severe weather with a stout 50 to near 60kt low-level jet in place which will help to enhance/enlarge hodographs. Once again, all modes of severe weather including tornadoes, some of which could be strong, hail up to golf ball size and damaging winds up to 70mph are expected. These storms are progged to congeal into a broken line by the early afternoon hours before finally exiting the area into Alabama by late afternoon/early evening. The ongoing enhanced area is also well placed to cover the threat with the only changes to update the timing. Flash flooding threat: anomalous deep moisture and multiple surges of 850mb ThetaE will combine with slow moving/training storms with high precipitation rates and will result in widespread 3-5" of rainfall with locally higher amounts. This will lead to flash flooding concerns across the ArkLaMiss tonight through Saturday. There are two main areas of focus for the heaviest rainfall, the first is tonight over northwest portions of the Delta generally along and northwest of a line from Richland Parish to Sunflower County. Strong consideration was given to upgrading this area to a significant threat in the HWO/graphics, however guidance has struggled spatially with the exact placement of highest totals so held off on any upgrades for now. The second area of concern will be Saturday along and east of a line from Brookhaven to Columbus. After collaborating with WPC and neighboring offices, a portion of this area will be added to a moderate risk for excessive rainfall. A significant threat for flash flooding was also considered for this area but once again, spatial uncertainties with exact placement of the higher amounts precluded an upgrade with this forecast issuance. However, if confidence in placement of a swath of higher totals becomes apparent an upgrade to the HWO/graphics could be needed later tonight. Storms and rain should slowly exit the area into Alabama by late afternoon to early evening on Saturday. Cooler and drier air will advect in behind the cold frontal passage with low temperatures dropping off into the low to mid 40s across much of the area by Sunday morning. /TW/ Sunday through next Thursday: Overall in the wake of the significant cold front & severe weather, expect much cooler and drier conditions. As the cold front & longwave trough digs through the region on Sunday morning, expect continued cold air advection and some cloud lingering over the east- northeastern areas on Sunday. Due to colder thermal profiles, highs will only reach the mid 50s-low 60s. This is some 15-20 degrees below normal and could reach the top 5 coolest high temperatures for Sunday. As strong surface high builds into the region and troughing builds to the east, expect lows to fall well below normal into the mid- upper 30s (~15 degrees below normal) and possibly into the top 5 coolest low temperatures. In addition, if the gradient can be a little lighter, we may be able to get some patchy frost. This would mainly be confined along and north of I-20 and east of I-55. For now, due to some gradient & winds around, will only mention in the weather grids but hold off on anything in the HWO/graphics. But will monitor trends as we go forward. As the surface high and mid-level ridging build into the area by early-mid week (Tuesday-Thursday), expect efficient mixing and warmer temperatures. We could warm well into the mid-upper 70s to near low 80s by midweek. In addition, a weak cold front will move through the region on Wednesday but with limited moisture (PWs only around an inch to an inch and a quarter_ only a few showers & increasing clouds may be possible. Capped off PoPs at slight chance as it moves through on Wednesday. As the trough digs to our northeast & weak frontal boundary moves through on Wednesday, expect surface ridging to build in the wake and clouds to clear out. Due to slightly cooler thermal profiles, expect temperatures to be slightly cooler but still near normals. /DC/ && .AVIATION... 00Z TAF discussion: Ceilings will steadily lower this evening in advance of a cold front moving in from the west. As thunderstorms increase, MVFR/IFR conditions will develop and linger for a few hours as storms slowly move through. Post storm showers will keep conditions at MVFR, but improving conditions will be seen thereafter as the front moves through. Southerly winds ahead of the boundary will generally range from 10 to 20 knots with gusts 30 to 35 knots./26/ && .PRELIMINARY POINT TEMPS/POPS... Jackson 70 72 43 58 / 28 100 44 5 Meridian 69 75 46 61 / 30 97 85 9 Vicksburg 68 70 42 59 / 67 83 22 4 Hattiesburg 71 76 48 63 / 23 99 83 6 Natchez 67 71 41 60 / 60 89 28 2 Greenville 66 69 42 55 / 92 72 19 3 Greenwood 68 70 42 55 / 83 94 34 5 && .JAN WATCHES/WARNINGS/ADVISORIES... MS...Flash Flood Watch through Saturday evening for MSZ018-019- 025>066-072>074. LA...Flash Flood Watch through Saturday evening for LAZ007>009-015- 016-023>026. AR...Flash Flood Watch through Saturday evening for ARZ074-075. && $$
Area Forecast Discussion
National Weather Service Lake Charles LA
1015 PM CDT Fri Apr 13 2018 .DISCUSSION... Wx map shows sfc low over N MO, with cold front extending southward across eastern KS/OK and C to N TX. Radar only showing showers across inland SE TX and C LA this evening. The stronger storms remain across NE TX/N LA. Latest HRRR guidance on track to push the front and developing line of strong to severe TSRA approaching our warning area of Inland SE TX by 1-2 AM, pushing through the remainder of SE TX/C and S LA. Severe threat with this convection still present. SPC has issued TORNADO WATCH 45 until 6 AM CDT Saturday for Hardin, Jasper, Newton and Tyler counties in SE TX, and Rapides, Beauregard, Vernon parishes in Western and Central Louisiana. Short term updates to forecast, mainly for temp/dewpoint refresh, but otherwise on track. Rainfall amounts, and timing of greatest chances of showers and thunderstorms remain on track. DML && .PREV DISCUSSION... /issued 608 PM CDT Fri Apr 13 2018/ AVIATION...MVFR ceilings are expected through midnight with IFR ceilings possible during the early morning. Ceilings will improve a few hours after FROPA Saturday Morning. Showers and storms have begun across the area, but mainly in SETX and CenLA. Chances will increase across the remainder of the area through the evening. Coverage will decrease from west to east through the morning. South winds will quickly veer NW with the front. PREV DISCUSSION... /issued 411 PM CDT Fri Apr 13 2018/ SYNOPSIS... -Scattered to numerous severe storms will be possible overnight through Saturday as a cold front moves across the region -Damaging winds will be the primary threat with overnight thunderstorms, but tornadoes and large hail will also be possible. -There will be a 10-20% chance of flash flooding overnight and Saturday, with the greatest chance across far eastern Acadiana -Storm total of rainfall of 1-3 can be expected with isolated higher totals of 5+. DISCUSSION... Short TermTonight and Saturday... Radar and satellite imagery over the past several hours show convection has developed across portions of the Lower Mississippi River Valley and Central Plains. These strong to severe thunderstorms are expected to continue to develop through this evening as a the combination of a dryline and cold front pushes eastward into the Arklatex region. Deep layer shear in excess of 40 knots aligned parallel to the front/dryline should result in upscale growth of initial convection into an organized line. The latest round of 12Z HREF guidance depicts such an evolution with a line of thunderstorms moving through the CWA overnight tonight and exiting Acadiana Saturday afternoon. As far as timing of this event, the greatest potential for strong to severe thunderstorms across portions of the area will be as follows: Interior Southeast Texas/Piney Woods: 11 PM 4 AM Alexandria Lake Charles Beaumont: 3 AM 7 AM Acadiana: 6 AM Afternoon SPC has most of the area highlighted in a Slight Risk of severe of severe thunderstorms tonight and through tomorrow. The far southeastern portion of the CWA is highlighted in an Enhanced Risk based on the potential for restrengthening of thunderstorms tomorrow afternoon. The primary threat with thunderstorms tonight will be damaging winds. In addition to damaging winds, 0-1 km and 0-3 km storm relative helicity in excess of 200 m2/s2 will supportive of tornadoes with any bowing portions of the QLCS/LEWP that develop. While large hail cannot be ruled out, based on the predominant linear convective mode, it should be the least likely of the severe weather threats. The best chance for large hail will be with any isolated cells that can develop ahead of the main line late tonight across SE Texas/Central Louisiana or across far eastern Acadiana/Southeast Louisiana on Saturday. This morning`s 12Z LCH and model forecast soundings all indicate that a deep warm cloud layer will be in place over the region which will be supportive of efficient precipitation production. While the squall line should be fairly progressive, a widespread 1"-3" of rainfall is expected with local amounts in excess of 5 inches possible. Currently, 3-hour flash flood guidance across the region ranges from 3.5-5 inches. The 12Z HREF guidance had a 10%-30% chance of rainfall exceeding these values across portions of southeastern Acadiana tomorrow and this corresponds well with the Slight Risk of Excessive rainfall issued by WPC. At this point, while flash flooding will be possible tomorrow, the threat does not appear to be widespread enough to warrant a Flash Flood Watch at this time. Rainfall is expected to gradually come to an end from west to east Saturday afternoon as the cold front exits the region. Behind the front much cooler, drier air will filter in on brisk northerly winds Saturday into Sunday. Long TermSunday through Friday... An upper level ridge will build across the central CONUS in the wake of the trough that will bring tonight`s cold front. Surface high pressure will result in dry conditions and cooler temperatures on Sunday and Monday. Temperatures will begin to moderate through the middle part of the week but conditions should remain predominately dry with relatively zonal 500 hPa flow in place over the central US. The next substantial shortwave trough is expected to approach the region next weekend brining another chance for showers and thunderstorms. MARINE... Strong onshore flow will persist through the evening in advance of an approaching cold front. A broad line of thunderstorms is expected tonight into Saturday with the frontal passage. Strong offshore flow will develop in the wake of the front late Saturday. Northerly winds of 20-25 knots with gusts to 35 knots and seas of 4-8 feet with seas up to 10 feet will be possible. Strong offshore flow will persist into Sunday before relaxing on Monday afternoon as high pressure once again settles over the region. Therefore, the Small Craft Advisory currently in effect through Saturday night will likely be extended. && .PRELIMINARY POINT TEMPS/POPS... AEX 64 70 42 63 / 90 60 10 0 LCH 65 71 45 66 / 90 60 10 0 LFT 68 72 44 63 / 50 90 20 0 BPT 62 70 43 66 / 90 40 0 0 && .LCH WATCHES/WARNINGS/ADVISORIES... LA...None. TX...None. GM...Small Craft Advisory until 1 AM CDT Sunday for GMZ450-452-455- 470-472-475. Small Craft Exercise Caution through late Saturday night for GMZ430-432-435. && $$ PUBLIC...08
Area Forecast Discussion
National Weather Service Saint Louis MO
412 PM CDT Fri Apr 13 2018 .SHORT TERM... (Through Late Saturday Afternoon) Issued at 411 PM CDT Fri Apr 13 2018 Deep closed low aloft over the northwest Kansas is winding its way slowly to the east. The surface low is now over southeast Nebraska with the trailing cold front/dryline moving into eastern Kansas. Several clusters of thunderstorms have formed along and ahead of the front in Kansas, Oklahoma and Arkansas. After some divergence earlier in the day, the CAMs are mostly centered around the idea that the thunderstorm clusters will solidify into line that will move through lower and mid Mississippi Valley this evening. RAP CAPE forecasts this evening really fall off after 02-03Z...so not sure how much potential for severe weather there is...and fairly substantial surface based CINH remains in place into the evening. Therefore, think the storms will be weakening as they move into our CWFA after 00-01Z. That being said, ~1000 J/Kg MUCAPE and 45+kts of deep layer shear is plenty for a few severe storms. Will have to initially watch for both damaging wind and large hail, but the wind threat should diminish as the evening progresses and the boundary layer stabilizes. The stratiform precip region behind the line of convection may linger over our eastern Illinois counties and southeast Missouri til near daybreak on Saturday morning, but much of the CWFA should be dry. The cold front will continue moving east on Saturday morning and should be through central Missouri by 15-16Z. Another round of thunderstorms is possible along and ahead of the cold front Saturday...and there is another severe threat over parts of central Illinois near the tipple-point just ahead of the low where mid level lapserates approach 9C. Think the primary threat will be large hail due to the steep lapserates, but 0-6km shear is approaching 50kts and the the cold/warm front interface will be near there as well which will add additional low level vorticity. Will have to watch closely for possible supercell development. Carney .LONG TERM... (Saturday Night through Next Friday) Issued at 411 PM CDT Fri Apr 13 2018 An upper trough and low pressure system will move across north central Missouri and western Illinois on Saturday night into Sunday. Some wrap around moisture and strong cold air advection will provide for a chance of a brief rain/snow mix over the northern two thirds of the forecast area on late Saturday night into Sunday morning. The precipitation type will then be all liquid shortly after sunrise on Sunday. All precipitation will exit the forecast area by Sunday night. High pressure will move into the Central Plains immediately behind the exiting upper trough by late Sunday night into Monday morning. The weather will remain dry on Monday as high pressure moves away from the forecast area. A cold front and attendant low will approach the forecast area on Tuesday night into Wednesday. At this time, it appears only scattered showers will be possible in far north central Missouri on Tuesday night into Wednesday. The cold front is expected to clear the area by Wednesday afternoon. High pressure will move south from the Northern Plains into the Central Plains, then to the Ohio Valley by Friday afternoon. Temperatures will climb from below climatological average at the end of the weekend to at or above normal values through the middle of next week. Kelly && .AVIATION... (For the 18z TAFs through 18z Saturday Afternoon) Issued at 1249 PM CDT Fri Apr 13 2018 Showers and a few thunderstorms will continue to move north- northeast across northeast Missouri and west central/south central Illinois this afternoon. The rain is very light at this time, so expect VFR conditions to prevail across most of the area. The exception is southeast Missouri and parts of southwest Illinois where an MVFR cloud deck developed earlier in the day and will likely persist this afternoon into the evening. Heavy thunderstorms are expected to develop over the southeast Plains later this afternoon and move northeast into Missouri and Illinois this evening. Guidance suggest that the thunderstorms will move from southwest Missouri into east central Missouri sometime between23-02Z...and may bypass central Missouri altogether...however cannot totally rule out storms in central Missouri at this time. Storms should be exiting the forecast area into eastern Illinois between 08-10Z. Another round of showers and a few storms is possible on Saturday...mainly over Illinois. SPECIFICS FOR KSTL: VFR flight conditions and some isolated showers are expected to prevail at Lambert through the afternoon. A wave of heavy thunderstorms which will bring MVFR and possibly IFR cigs/vsbys to Lambert is expected between 02-05Z. Lingering rain showers may continue to impact the terminal through 08-10Z. Ceilings should lift Saturday morning, but not very confident in timing at this time. Carney && .PRELIMINARY POINT TEMPS/POPS... Saint Louis 58 70 40 47 / 80 40 20 30 Quincy 56 64 37 41 / 50 40 30 40 Columbia 52 61 35 41 / 60 20 20 40 Jefferson City 52 61 36 42 / 60 20 20 40 Salem 59 71 42 50 / 80 40 40 30 Farmington 57 68 37 46 / 90 30 20 20 && .LSX WATCHES/WARNINGS/ADVISORIES... MO...None. IL...None. && $$ WFO LSX
Area Forecast Discussion
National Weather Service Nashville TN
641 PM CDT Fri Apr 13 2018 .UPDATE... FOR 00Z AVIATION DISCUSSION. && .DISCUSSION... Model spread has improved slightly in regards to precip amounts for Saturday, but have some localized areas they highlight individually. The upper low is currently over the central Plains, and remains very strong. It looks to intensify slightly overnight, and remain a closed low for the duration of its impacts on the mid state. Early chances for precip will move in just after midnight and spread eastward across the I-65 corridor before 12Z. A few short term models such as the NAM want to place the first wave of heavy rain in the northwest zones, while model consensus has mainly a half inch up to an inch west of I-65 by 18Z. Thats supported by PWAT values above 1.5 inches for that area during the morning hours, as well as a 50-60 knot LLJ through the morning hours as well. Getting into the early afternoon hours, most models and especially short term models have a bit of a break in regards to heavy precipitation. The first initial shortwave that will bring heavy rain to western zones will weaken slightly and move northeast out of the area. However, by mid afternoon onward, a second shortwave develops as the cold front moves eastward across the MS River Valley. It`s during this time that heavy precipitation will begin to ramp up again, as well as the time for best chances for severe storms. Model consensus puts 500-1000 J/kg of MLCAPE as well as 40-60 knots of deep layer shear. A few models even hint at MUCAPE getting near 1500 J/Kg as well. PWAT values remain at or above 1.5 inches across the area, and with the upper low/cold front approaching, the LLJ will increase in speed to 60 knots over the area. All of these indicators point to the potential for some strong to severe cells embedded within a line of storms that could put out some damaging winds. With 0-1km shear at 30 knots, and even 0-3km helicity around 300-400 m2/s2, isolated tornadoes can not be ruled out, but main focus for any stronger cells will be damaging wind gusts. Towards the late afternoon and into the evening hours, both the NAM and GFS indicate a slight break in the LLJ over the mid state. This looks to create an area of convergence over the area ahead of the front, and looks to help rain development along and east of I-65. As these storms develop and train over eastern zones, rainfall totals look to hit the 1-2 inch range just from the late afternoon into the early morning hours Sunday. The severe threat looks to weaken in the evening with instability decreasing, so mainly looking at a heavy rain threat for the evening hours for the mid state along and east of I-65. By sunrise on Sunday, the area looks to get between 2 to 4 inches, with the higher precip axis around 3 to 4 inches possible west of the Plateau and east of I-65. Locally higher amount could be possible elsewhere across the mid state if training impacts localized areas, and the frontal progression slows a bit. Light showers may continue on the backside of the front on Sunday, and moving east over the Plateau Sunday afternoon. Temperatures look to cool off into the 30s for lows by Monday morning, and even getting close to freezing should skies clear earlier in the overnight hours. The next chance for precip may be on Wednesday as another upper low moves through the Midwest and drags a cold front through the area. Amounts look very low as this looks to be a dry system, so only have slight chance pops in during the day on Wednesday. Temperatures will cool off again Wednesday night through Thursday, but ridging moves in ahead of another strong low for Friday so temperatures will rebound before next weekend. && .AVIATION... 00Z TAF DISCUSSION. BNA/MQY/CKV/CSV...Middle Tennessee finds itself in the maritime tropical sector of a developing low pressure system this evening, with the onset of showers and storms still hours away. Winds will remain gusty overnight, but the HRRR doesn`t bring any cells across the Tennessee River until just before 12Z. So will bring this line of storms with a broad area of rain behind the initial line of cells from west to east during the morning. Ceilings will drop to MVFR several hours after onset of showers. && .OHX WATCHES/WARNINGS/ADVISORIES... NONE. && $$ DISCUSSION......Barnwell AVIATION........08
Area Forecast Discussion
National Weather Service Tucson AZ
247 PM MST Fri Apr 13 2018 .SYNOPSIS...Gusty winds this afternoon will diminish overnight. Freezing temperatures are likely late tonight and Saturday morning for the coldest eastern and southern valleys. High pressure will bring a rapid warming trend over the weekend before another system brings gusty winds to the area Monday afternoon followed by yet another windy system late next week. && .DISCUSSION...Today`s trends continue with cooler and drier air in place. Our temperature trends are down 15-20 degrees compared to yesterday. Dew point changes are even more impressive; down between 30 and 40 degrees which puts them below zero. Winds are not as strong in most locations, but strong enough when added to the very dry air mass to yield critical fire weather conditions. Colder temperatures tonight with lows bottoming out between 5 and 15 degrees below average. One problem will be winds. They will drop off overnight, but could still be strong enough in some valley locations to keep the atmosphere mixed, which would moderate overnight lows. Latest HRRR trends go light and variable in some colder valley locations including Sulphur Springs Valley and San Pedro River Valley (much of Cochise and portions of Graham county). We converted those areas and portions of Santa Cruz county northeast of Nogales to a warning. far southeast Pinal and areas west of Nogales were dropped, with winds staying a little stronger and keeping things mixed. If winds stay about 1 to 3 mph stronger than our current forecast, then the warning areas may miss out too. A rapid warmup over the weekend with high pressure building in from the west. The active higher energy pattern will continue with another system pushing through the region north of us Monday, but not as deep as this system. Gusty winds again the main story. A stronger and deeper system may impact the area later next week. That one also looks pretty windy, but likely dry this far south. && .AVIATION...Valid through 15/00Z. Mostly clear. SFC wind wly/nwly at 15-25 kts and gusts between 35-40 kts in most locations thru the early evening hours tonight. SFC wind slowly diminishing aft 14/03Z with normal trends Saturday, generally less than 10kts. Aviation discussion not updated for TAF amendments. && .FIRE WEATHER...Strong winds will continue across the area today on the backside of an exiting system. Even though it`s much cooler, the air mass is extremely dry with dewpoints dropping below zero in many areas. A Red Flag Warning remains in effect through 7 pm MST this evening. Saturday and Sunday will be relatively quiet wind-wise as an upper level ridge builds over the area. The air mass will remain very dry with minimum RHs in the single digits and poor overnight recoveries. Another storm system will likely bring areas of critical fire weather conditions to portions of southeast Arizona Monday, followed by lighter, but still breezy winds Tuesday and Wednesday. Yet another storm system is expected late next week. && .TWC WATCHES/WARNINGS/ADVISORIES... Red Flag Warning until 7 PM MST this evening for AZZ150>153. Freeze Warning from 2 AM to 9 AM MST Saturday for AZZ503-507>509. Wind Advisory until 7 PM MST this evening for AZZ507>509. && $$ Meyer Visit us on Facebook...Twitter...YouTube...and at weather.gov/Tucson