Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 03/29/18

Area Forecast Discussion
National Weather Service Birmingham AL
803 PM CDT Wed Mar 28 2018 .UPDATE... MESOSCALE UPDATE. && .SHORT TERM... Closely monitoring a QLCS moving across central Mississippi at this time. Warnings still ongoing over there, but have not seen many severe reports lately, which certainly does not mean storms are not severe. These storms have indicated large hail, damaging winds and rotation on the comma head feature and with additional southern flank convection. The latest convection allowing models and RAP analysis have convection weakening as it approaches the Alabama state line in more marginal instability. But these shorter term models do not have the current situation diagnosed adequately. The storms are much farther east and are indicative of stronger updrafts. These storms were forming near a weak wave along a quasi-stationary boundary/effective warm front/convergence zone that has been present all day. It appears that the storms have enhanced their own environment along the boundary as low level winds above surface winds increase. Therefore, expect some storms to make it into Central Alabama, especially Pickens, Lamar, and Marion Counties...possibly Fayette and Winston Counties. The timing appears to be after 930 pm near the state line. The main threat with the storms if they hold some strength will be wind gusts to 45 mph and some dime size hail. Will closely monitor the tornado threat as there is shear along the boundary and LCL heights will lower with time. But we need a sustained updraft and that is the question at this time. So be aware that some strong storms are possible late this evening northwest. 75 Previous short-term discussion: Central Alabama is currently positioned on the west side of an upper level ridge that extends from the eastern Gulf of Mexico northeast toward coastal North Carolina. A deep positively tilted trough at H500 was analyzed from western Kansas extending southwest into northwest Texas and into eastern New Mexico. Toward the surface, a stationary front was aligned in a southwest to northeast position from southern Texas through the Ohio River Valley Region and into western Pennsylvania. A warm front extended from a surface low in western Pennsylvania along the front to the southeast to near the entrance of the Chesapeake Bay in Virginia. Ongoing convection along the front from central Texas into western Tennessee has produced an outflow boundary that was analyzed from central Texas into northwest Louisiana and into northern Mississippi, generally from just south of Greenville to near Tupelo, and into west-central Tennessee. Satellite imagery depicts cloud cover increasing across forecast area from west to east with a southerly trajectory near the surface and a more southwest flow aloft. Radar imagery indicates generally light shower activity associated with the aforementioned outflow boundary from central Mississippi that extends northeast into far northwest Alabama and into central Tennessee. Low-level thermal and moisture advection will persist from the south winds that will remain gusty at times this afternoon and into early evening. Winds will decrease to some extent overnight as the boundary layer decouples with the loss of vertical mixing provided by daytime heating but expect the warm advection regime to continue. Cloud cover will continue to stream overhead from the west and southwest, becoming thicker across our western counties overnight and gradually increasing in coverage over our eastern counties this evening into early Thursday morning. The severe weather potential on Thursday will be provided by wind shear and helicity provided by dynamical support that has been fairly consistent in current and recent convection-allowing models (CAMs). Sufficient near-surface instability is less certain as thicker cloud cover across the area tomorrow morning through midday will help to discourage solar insolation and yield lower levels of instability. However, thermal and moisture advection will continue to help increase instability in the lower levels and overcome the impact of the cloud cover present. The biggest limiting factor will be where exactly is the outflow boundary from tonight`s activity to our west. If the outflow stays where the models indicate then the severe potential will remain possible. If it makes it further east, then the severe potential will be limited at best. What is consistent at this point in time is that sufficient dynamics exist to support strong to severe thunderstorms on Thursday with the amount of available energy remaining in question. The better potential of realizing sufficient instability remains across our southern counties and potentially across our east-central counties if cloud cover remains less dense through midday. The risk for strong to severe storms area wide will be dependent on the amount of low level instability provided by solar radiation. There is enough consistency to raise the confidence of the threat to a 2, but will keep the area of concern the same. 05/16 .LONG TERM... Friday through Tuesday. A return to quiet weather should return for Friday as the upper low swings through the north during the morning. Clearing skies by the afternoon as high pressure builds into the area and will remain through Sunday. Rain chances could start to increase on Monday into Tuesday as a front approaches from the north, but does not make it through the area at all. Temperatures in the north will be highly dependent on where the front sets up and which way it fluctuates each day as it will be quasi-stationary through midweek. 16 && .AVIATION... 00Z TAF Discussion. Attempted to give some trend of weather conditions the next 24 hours but expect updates as the mesoscale will play a prominent role in the precipitation. A QLCS over central Mississippi is moving toward the Alabama state line and should remain north of all terminals overnight. Ceilings should dive into the MVFR range by 4-5z west and spread to the remainder of the through 09z or so. Nice warm air advection hodograph and isentropic lift covers the state by morning. Expect some weakening of the storms in Mississippi, but a boundary sets up that will allow additional storms on Thursday. Mentioned light rain and VCTS as early as 15-17z north and ending before 00z with a few hour delay for southern sites. Once again, this does not mention the activity now as an expected decrease is anticipated but may need adjusting if it can hold together. Predominant MVFR ceilings on Thursday with times of IFR and VFR here an there. Most areas eventually reach VFR ceilings around 00z, but trends indicate this may not last too long. Winds south to west during the period with some gusts up to 20kts or so. 75 && .FIRE WEATHER... Shower and thunderstorm chances will slowly increase from northwest to southeast tonight, ahead of an approaching front. Low clouds and patchy fog could become possible Thursday morning as low level moisture increases. The best rain chances will be Thursday afternoon and evening, as the front moves through the area. Drier conditions are expected by Friday. There are no fire weather concerns at this time. && .PRELIMINARY POINT TEMPS/POPS... Gadsden 60 73 51 66 39 / 20 100 70 10 0 Anniston 59 75 52 68 40 / 10 90 90 10 0 Birmingham 62 75 52 67 43 / 30 100 60 10 0 Tuscaloosa 64 73 51 69 43 / 30 100 30 10 0 Calera 62 74 52 69 44 / 20 100 70 10 0 Auburn 59 74 56 69 45 / 10 70 100 10 0 Montgomery 61 78 56 72 44 / 10 80 90 10 0 Troy 61 78 57 72 45 / 10 70 100 10 0 && .BMX WATCHES/WARNINGS/ADVISORIES/... None. && $$
Area Forecast Discussion
National Weather Service Columbia SC
739 PM EDT Wed Mar 28 2018 .SYNOPSIS... High pressure offshore will continue dry weather and above normal temperatures through Thursday. The chance for showers will increase Thursday night into Friday ahead of a cold front, and thunderstorms may also be possible. The return of high pressure will bring dry weather and mild temperatures for the weekend. && .NEAR TERM /UNTIL 7 AM THURSDAY MORNING/... High pressure will remain offshore of the Carolinas overnight with southwesterly winds continuing to push moisture into the region. With the increasing moisture there will be potential for patchy fog development, however this will be offset by persistent winds between 5 and 10 mph. Expect the wind to keep the near surface layer mixed enough to prevent fog and have not mentioned fog in the overnight forecast. With the increased moisture some cloudiness will develop overnight and will help insulate the region to keep overnight lows in the mid to upper 50s. && .SHORT TERM /7 AM THURSDAY MORNING THROUGH FRIDAY/... Warm and dry condition expected Thursday. Downslope flow and compressional heating will allow temperatures to rise into the low to mid 80s. The upper level ridge will move offshore Thursday and surface high pressure ridging into the area from the western Atlantic will move out to sea Thursday night, allowing moisture to increase ahead of an approaching cold front and upper level trough. The cold front will cross the area Friday morning, then move offshore during the afternoon. The best chance for showers will be late Thursday night into Friday morning. Cannot rule out isolated thunderstorms on Friday given weak instability just ahead of the front. Rainfall amounts will average one half inch or less. High temperatures in the 80s expected Thursday with lows in the lower 60s Thursday night. Highs Friday still expected to be above the mid to upper 70s. && .LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/... Dry weather expected for the weekend with surface high pressure in control and a nearly zonal flow aloft. Near normal temperatures in the low to mid 70s Saturday will warm into the mid and upper 70s for Sunday. Nighttime lows in be in the 40s. Unsettle conditions possible Monday through Wednesday. Models indicate a progressive level pattern with a cold front affecting the area Monday and again Wednesday. Temperatures are forecast to be at or above normal with highs in the 70s and lows in the 50s. && .AVIATION /00Z THURSDAY THROUGH MONDAY/... VFR conditions expected through the TAF period. High pressure has shifted offshore and southwesterly winds are expected to prevail through the forecast period. Model forecasts of a 30 knot low level jet overnight should inhibit fog formation while helping keep a bit of wind overnight. Some indications in the MOS guidance that there could be a brief period of fog around 12z but confidence is low and latest HRRR not supporting this. Expect some high clouds overnight and then as heating takes place on Thursday a diurnal cumulus VFR cloud deck expected to form after 15z. Winds could become gusty with some gusts over 20 knots. EXTENDED AVIATION OUTLOOK...Restrictions possible Thursday night and Friday as a cold front with showers...possible thunderstorms...crosses the region. && .CAE WATCHES/WARNINGS/ADVISORIES... GA...None. SC...None. && $$
previous package. Previous forecast discussion is included below.

31 /Issued 405 AM EDT Wed Mar 28 2018/ The long term period will start will unsettled weather as a cold front is forecast to move across the area Thursday night and possibly early Friday. The front will bring showers and a chance of thunderstorms. Instability associated with the front and a surface trough out ahead of the front, will be weakening overnight Thursday but there is decent low level shear associated as well. There will be a marginal risk for severe thunderstorms at the start of Thursday night favoring north and west GA. Strong gusty winds, frequent lightning and locally heavy rain will be the mostly likely hazards. Friday there will be some lingering shower chances with the exiting front and upper short wave. The weekend will be mostly dry with moisture from the cold front skirting mainly far n GA on Sunday. After that, the GFS and European models are Not very consistent with handling the deeper moisture in the upper flow but any shower chances look to favor n GA the most through Tuesday. Temperatures will start out above normal at the very start of the long term but return closer to normal for Friday and Saturday. Sunday through Tuesday look to have near to above normal temperatures. BDL AVIATION... 00Z UPDATE... VFR cigs around the ATL terminals have largely abated with just some BKN high clouds to contend with. This will be changing into the overnight hours however with MVFR cigs moving in from the SW by 10Z. These look to hold on well into Thu before giving way to VFR conditions during the afternoon to go along with gusty winds. SHRA to move in by 22Z to 00Z and have also added prob30 for TSRA in for ATL. //ATL CONFIDENCE...00Z UPDATE... Medium on MVFR cig timing. High on remaining elements. Deese && .PRELIMINARY POINT TEMPS/POPS... Athens 56 76 57 72 / 0 40 70 30 Atlanta 58 73 55 67 / 5 50 80 20 Blairsville 53 68 51 62 / 10 70 90 20 Cartersville 56 72 53 65 / 5 70 80 20 Columbus 59 75 59 73 / 5 50 70 10 Gainesville 56 71 55 67 / 5 50 80 20 Macon 56 79 60 74 / 0 30 70 30 Rome 57 72 53 65 / 10 80 80 20 Peachtree City 56 74 55 69 / 5 50 70 10 Vidalia 58 82 64 75 / 0 0 50 50 && .FFC WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SHORT TERM...Deese LONG TERM....Merritt AVIATION...Deese
Area Forecast Discussion
National Weather Service Grand Rapids MI
847 PM EDT Wed Mar 28 2018 LATEST UPDATE... Update .SYNOPSIS... Issued at 330 PM EDT Wed Mar 28 2018 Rain showers will develop very late tonight through Thursday as a low pressure system moves across the Ohio Valley region Thursday. High pressure will bring fair weather Friday. The next low pressure system will bring a mix of rain and snow Saturday. An unseasonably cold airmass will move in behind that system for Sunday and Monday. && .UPDATE... Issued at 847 PM EDT Wed Mar 28 2018 I increased the POP and QPF over our central CWA overnight. As it turns out there is significantly more showers going on across WI and southern Lake Michigan at 8 pm than either the 12z or 18z NAM forecast (much father north)showed or forecast. The HRRR / HRRRX runs continue to do much better in that regard, so, I update all of our GRIDs into mid morning Thursday to follow a mix of CONSHORT, HRRRTL and the latest HRRR,HRRRX and RAP13 pop and qpf. This brings likely rain to GRR overnight and increases the area of patchy fog into midday Thursday. Seems the major difference in the models (NAM compared to RAP) is he relative humidity is close to saturation below 850 farther north on the high res models than on the NAM. Since it is raining under those showers north to MKE, seems clear increased pop/qpf is warranted. Either way it is to warm for snow over all of our CWA into late afternoon. So I did not change that part of our forecast. && .SHORT TERM...(This evening through Friday night) Issued at 330 PM EDT Wed Mar 28 2018 Rain showers will develop during the early morning hours Thursday over our southern fcst area as a low pressure system moves northeast into the Ohio Valley region Thursday morning. A consensus of latest short range guidance suggests that the steadiest rain will occur over our se fcst area where a quarter to half inch of rainfall is expected. Meanwhile no rain is expected over our nw fcst area. A few wet snow flakes may mix in Thursday evening before pcpn ends. However it still looks like significantly colder air will not advect in until late Thursday night when pcpn will already have come to an end. Therefore there will be no snow accumulation. High pressure will bring fair and seasonably cool wx Friday. Some light mixed pcpn will begin to develop Friday night but most of the pcpn with the next low pressure system will hold off until Saturday. .LONG TERM...(Saturday through Wednesday) Issued at 330 PM EDT Wed Mar 28 2018 A strengthening low pressure system will move east across the northern Great Lakes region Saturday and bring a mix of rain and snow. There is still some uncertainty with regard to the exact track of the low pressure system which has large implications on potential for accumulating snow. At this time we will continue to fcst a mix of rain and snow and potential for light snow accumulations mainly over our northern fcst area. Strong nw flow caa will occur behind this system Saturday night. H8 temps will plummet to -15 to -17 C by 12Z Sunday yielding delta t/s in the lower 20`s. Therefore nw flow lake effect snow showers will develop Saturday night and continue into Sunday. It will be unseasonably cold Sunday with high temps only reaching the lower to perhaps middle 30`s. The active wx pattern will continue early next week as another low pressure system moves east across our region Monday into Tuesday. This system will bring potential for mixed pcpn once again from Monday afternoon through Monday night into Tuesday. && .AVIATION...(For the 00Z TAFS through 00Z Thursday evening) Issued at 742 PM EDT Wed Mar 28 2018 I have gone with the high resolution model forecast for just how far north the rain gets tonight into Thursday. This would suggest meaningful rain may get as far north as MKG in the 09z to 15z time frame. The I-69 TAF sites will get solid IFR cigs/vsby from 09z through 15z (more or less). All areas should see improving cigs/vsby in the 18z to 21z time frame. && .MARINE... Issued at 330 PM EDT Wed Mar 28 2018 Wave heights will ramp up Thursday afternoon through Thursday evening as northerly winds increase to the north of the Ohio Valley low pressure system. Therefore we will issue a small craft advisory for all our nearshore zones from Thursday afternoon through Thursday night. && .HYDROLOGY... Issued at 1021 AM EDT Wed Mar 28 2018 Rivers are experiencing small rises due to the recent rain, but flooding is not expected. Several chances for rain and/or snow are on tap this week, with under a half inch tonight into Thursday night. Additional light rain/snow is possible Saturday and early next week. This precipitation is not expected to lead to flooding. && .GRR WATCHES/WARNINGS/ADVISORIES... MI...None. LM...Small Craft Advisory from noon Thursday to 6 AM EDT Friday for LMZ844>849. && $$ UPDATE...WDM SYNOPSIS...Laurens SHORT TERM...Laurens LONG TERM...Laurens AVIATION...WDM HYDROLOGY...63 MARINE...Laurens
Area Forecast Discussion
National Weather Service Houston/Galveston TX
902 PM CDT Wed Mar 28 2018 ...LOCALLY HEAVY RAIN POSSIBLE TONIGHT... .DISCUSSION... Concern is increasing that heavy to excessive rain will persist/develop overnight. At the surface a weak area of low pressure was noted near Alice with a weak trough of low pressure extending to the north to near Tyler. G 00z sounding showed PW values around 1.80 inches with CAPE values between 2500-4500 J/Kg and unstable lapse rates. GOES-R PW field show values between 1.80 and 2.00 inches and this matches up well model progs and soundings. 00z 300 MB wind analysis shows a splitting jet structure over East Texas with a speed max rotating around the base of the upper trough. SE TX will lie in the RRQ of a 140 kt between 06-09z and feel there will be a period of heavy rainfall with training of cells along the Highway 59 corridor late this evening into the overnight. Some of the latest short term guidance is becoming quite generous with rainfall amounts tonight with some 3 to 6 inch totals possible. PoPs were already high tonight but have increased the QPF over the area for the possible training of cells later tonight. Tornado Watch will be allowed to expire and the Flash Flood Watch will be maintained as is with the north expiring at 100 AM and areas to south at 7 AM Thursday. 43/11/08 && .PREV DISCUSSION... /ISSUED 651 PM CDT Wed Mar 28 2018/ AVIATION... Radar imagery currently shows the worst of the thunderstorms located east of CXO and IAH, but anticipating redevelopment this evening for TAF sites at HOU and northward. HRRR shows the possibility for showers and isolated thunderstorms moving across the northern TAF sites at CLL between 02-05z. The main line of precip will continue to sag southward impacting CXO until 09Z and pushing south of GLS between 12-13Z. Light and variable winds are anticipated Thursday morning, and ceilings should begin to lift eventually clearing out by 18Z across all TAF sites. Southwesterly flow around 5-8 kts will prevail by the afternoon hours. Hathaway PREV DISCUSSION... /ISSUED 354 PM CDT Wed Mar 28 2018/ DISCUSSION... Active day across Southeast Texas today as a line of thunderstorms continues to slowly drift to the southeast. Expectations for severe and flooding potential through tonight have changed little from earlier. Once any lingering rain tomorrow morning clears out, look for fair weather until early next week. Threat Summary: Flooding - Individual storms continue to train to the northeast while the entire line drifts slowly southward. This creates continued potential for flash flooding into tonight, following the drift of the line. Widespread rains of 1-3 inches are still expected, but localized rains of 4-7 inches are possible. In general, this will be most impactful on streets and areas of poor drainage. Street flooding will become increasingly more dangerous after sunset, as it will become even more difficult to determine the true state of roads in the dark. As always, never attempt to travel on any water-covered roads, and it may simply be best to find a safe place and stay in for the night. Rivers and bayous are expected to rise, but most should stay within their banks. However, flooding in some channels may be possible and flows even for streams within their banks will be faster than normal. Hail - Severe hail is possible with the strongest storms. High freezing heights/wet bulb zeroes will limit potential size of hail below two inches. Luchs MARINE... South winds 15 to 20 knots and gusty will be on tap the remainder of the afternoon then should gradually diminish as outflow from storms over SETX expands toward the coast. Strong to severe thunderstorms possible in the bays and nearshore waters this evening. This long fetch has seas of 5-9 feet pushing through the area toward shore. Elevated tides and runup continues with moderate south winds. Minor flooding around 87 near High Island possible. Outflow should reach the coast tonight making for more chaotic winds. A cold front should finally push through early Friday morning with offshore flow but only short lived as winds come back around to the east and southeasterly by Saturday morning. Southeasterly flow then continues through at least Tuesday. Some differences with respect to the next front (GFS washing out in SETX Wednesday afternoon and ECMWF outflow possibly nearing the coast Thursday morning) so confidence low at that time but fortunately the marine forecast only goes out to Monday night. 45 CLIMATE... As of 3pm CDT, Easterwood Field in College Station has recorded 3.12 inches of rain. This already exceeds the record rainfall of 2.87 inches, which was set in 2006. Rain has not yet begun in earnest at any of the other main climate sites, but for what it is worth, the forecast rainfall for the City of Houston (IAH) and Hobby Airport are near their record values. Luchs && .PRELIMINARY POINT TEMPS/POPS... College Station (CLL) 61 80 54 76 54 / 60 10 0 0 0 Houston (IAH) 65 82 57 78 54 / 90 10 0 0 0 Galveston (GLS) 67 75 63 74 62 / 100 30 0 0 0 && .HGX WATCHES/WARNINGS/ADVISORIES... TX...Flash Flood Watch until 1 AM CDT Thursday for the following zones: Austin...Brazos...Burleson...Colorado...Grimes... Houston...Madison...Montgomery...Polk...San Jacinto... Trinity...Walker...Waller...Washington. Flash Flood Watch until 7 AM CDT Thursday for the following zones: Brazoria...Chambers...Fort Bend...Galveston... Harris...Liberty...Matagorda...Wharton. GM...SMALL CRAFT SHOULD EXERCISE CAUTION until 1 AM CDT Thursday for the following zones: Galveston Bay...Matagorda Bay. SMALL CRAFT SHOULD EXERCISE CAUTION until 7 AM CDT Thursday for the following zones: Coastal waters from Freeport to the Matagorda Ship Channel out 20 NM...Coastal waters from High Island to Freeport out 20 NM. Small Craft Advisory until 7 AM CDT Thursday for the following zones: Waters from Freeport to the Matagorda Ship Channel from 20 to 60 NM...Waters from High Island to Freeport from 20 to 60 NM. && $$ Discussion...43
Area Forecast Discussion...UPDATED
National Weather Service Huntsville AL
838 PM CDT Wed Mar 28 2018 .NEAR TERM...(Tonight) Issued at 837 PM CDT Wed Mar 28 2018 Clusters of showers and thunderstorms associated with a slow moving cold front are now at our doorstep as they slowly progress ENE across Mississippi. Thanks to the strengthening 50-60 kt 850 mb jet along the AL/MS border, this activity has been able to organize into two distinct clusters and broken line segments. The northern line, located from near Bolivar, TN to near Pontotoc, MS should lift ENE into far Northwest Alabama around 0230z. The second line to the southwest is located roughly from Oxford, MS to Durant, MS, which may approach Franklin County by 3:30z. While both lines possess the capability for locally heavy rainfall and gusty winds, this southern line has been notably stronger and maintained a couple of strong mesocyclones across over the past 2-3 hours. The thermodynamic environment across Northwest Alabama (and especially east of there) is more stable, with only 300 J/kg of MLCAPE observed near the MS/AL border. A more backed surface flow has helped maintain a slightly drier boundary layer, with dewpoints in the upper 50s to around 60 degrees. However, as this LLJ lifts northeast, low-level and bulk shear will become more favorable for the maintenance for these organized strong to marginally severe line segments. Thus, a localized damaging wind gust cannot be ruled out with any of this activity. Also, a diffuse, but remnant outflow boundary over this area and the good low-level directional shear means a brief, isolated, weak tornado cannot be ruled out -- though the probability is very low. The peak severe threat will likely be confined to Northwest Alabama, and generally in the 03-06z window, tied to this LLJ feature. The overall lack of instability will keep a vast majority of this activity from getting too strong. Of greater concern is the potential for heavy rainfall and localized flash flooding in the Flood Watch area of Northwest Alabama. PWATs are currently around 1.5". With the advection of richer moisture (thanks to the LLJ), a slow moving boundary, and the mean flow parallel to this boundary, the environment will be primed for training overnight. In the heavier cores, rainfall rates of 0.75" to 1" per hour are possible. It is conceivable that 2"/3-hr flash flood guidance may be exceeded in a few spots in this watch area overnight. The latest runs of the HRRR continue to resolve this and paint a heavier band of 2-3" of rain along the AL/MS border overnight, just clipping far western Colbert and Lauderdale Counties. Have bumped in QPF slightly given these trends and will certainly need to monitor the flash flood threat closely in areas where training does occur. Due to the nature of slow moving boundary, areas east of I-65 will likely only see scattered showers (at best) and may stay dry all together. Thus, a tight precipitation gradient will exist from west to east. Have maintained this thinking in the forecast, with 90-100% across our far western areas and 20-30% along the AL/GA border. .SHORT TERM...(Thursday through Friday) Issued at 232 PM CDT Wed Mar 28 2018 Latest model runs are showing the mid level ridge breaking down slightly quicker than previous forecasts which means the upper level trough will be able to swing through and push that cold front east into N. AL quicker. This more progressive solution means less overall rainfall as the rain, which will actually be along a prefrontal trough/leftover surface low, will move through faster on Thursday. By 18z, the leading edge should be over Huntsville and in NE AL by 21z. By 00z, the GFS/CMC clear out NW AL with the ECMWF/NAM a little later and not drying NW AL until 06z. It was also noted that some guidance is showing a bullseye of higher QPF along the Gulf coast and into central AL which would help slow the moisture stream over N AL and lower the rainfall amounts. Total rainfall amounts have therefore continued to decrease to a little over 2 inches in NW AL to half an inch to an inch in NE AL and southern middle TN. Outside of NW AL, the bulk of the rain will fall after 15z Thursday. In terms of thunderstorms, it`s quite tricky and not certain. It looks like by 17-18z ish, we do realize a few hundred J/KG of CAPE, coupled with bulk shear values of 50-60kts and low level shear of 20-30kts. The deep layer lift will be more than sufficient so the only thing that is questionable is the instability and moisture. We are only forecasting dew points around 60-63 and temps around 70, and if we get cut off by gulf convection, both of these could be even lower. The surface based CAPE mentioned above is based on high temperatures getting to a least 70 so that could be an uncertainty point. Model reflectivity is consistent in showing a QLCS/line of storms strengthening as it reaches Huntsville around 17-18z. So I do think there`s a window of 18-22z where a few severe storms could occur with damaging wind gusts being the highest threat. The bulk of the rain/pre-frontal trough should be out by 12z at the latest in NE AL and the front will be starting to get through NW AL by 6-9z, shifting winds to the NW. There will probably be a few showers accompanying the front as it moves across the area. Guidance is trying to clear out the clouds fairly quickly on Friday but this forecast package did push that back a little to be slightly more pessimistic. The front itself may not even get through Huntsville until 12-15z and there is lingering low level moisture and light showers with it. Soundings are showing drying and subsidence at the mid levels on Friday which creates a low level inversion, trapping the low level moisture. So by the end of the afternoon there will likely be some sun but don`t expect a fully sunny day! In terms of temps, Thursday highs will be in the upper 60s near 70 and cooler highs on Friday behind the front, only around 60. Lows Thursday night will be around 50. .LONG TERM...(Friday night through Tuesday) Issued at 232 PM CDT Wed Mar 28 2018 Friday Night through Saturday Night will be quiet and dry with high pressure, a departing trough, and fairly seasonable temperatures. After what might be a frosty start Saturday morning (given good radiational cooling, temps in the mid-upper 30s, and a small dewpoint depression), Saturday looks like a pretty nice day with highs rebounding to near 70 and mostly sunny conditions. The forecast goes downhill from Sunday onward due to a low- predictability pattern, despite solid agreement among medium-range models & ensembles. A weak front (and associated showers) will push into the area Sunday and stall out/wash out as it begins paralleling the mid /upper-level flow. Another mid-level shortwave will make a run at driving the front through early Monday with little success. None of these days look like a washout, but there is little confidence in dry days either. Middle-of-the-road chance PoPs (30-50%) are reasonable, focused for now on Sunday and Monday, though this could change. Temperatures through this time period will likely be depressed by clouds and scattered showers, though ensemble mean/blended guidance is preferred since the position of the front will dictate how cool (or warm) things get. Models agree well on a broader, deeper trough pushing into the eastern CONUS for Days 6-7, but diverge in the details. As is typical, the GFS is a fast and dry outlier whereas the ECMWF and CMC are slower and wetter. Blended guidance splits the difference and this works for such a far-ranging time period. Again, temperatures will depend on the speed of the front, so it is hard to deviate much from blends. && .AVIATION...(For the 00Z TAFS through 00Z Thursday evening) Issued at 618 PM CDT Wed Mar 28 2018 VFR conditions this evening will gradually give way to MVFR to IFR conditions overnight as a cold front and associated showers and storms slowly track toward the region. Have added prevailing TSRA at KMSL from 04-08z to account for better confidence of thunder there, but have left it out of KHSV. The actual cold front will move through the region tomorrow. Ahead of the boundary, gusty SW winds will prevail, before switching to the NW in wake of the front. Additionally, a second line of showers and isolated storms will move through the region during the afternoon, so have maintained a mention of VCTS. Late in the period, precip will taper off, but low ceilings will remain in place through Thursday evening. && .HUN WATCHES/WARNINGS/ADVISORIES... AL...Flood Watch through Thursday evening for ALZ001>003. TN...NONE. && $$ NEAR TERM...AMP.24 SHORT TERM...LN LONG TERM...BCC AVIATION...AMP.24 For more information please visit our website at
National Weather Service Jackson KY
1104 PM EDT Wed Mar 28 2018 .UPDATE... Issued at 1104 PM EDT WED MAR 28 2018 The relative lull in shower activity is starting to relent in the northern half of the area. There appears to be a mesoscale boundary aligned from approximately Paintsville to Mount Vernon, as scattered showers have been forming along this fairly distinct line over the past hour. On the SPC mesoanalysis page, there is some subtle convergence at 925 mb. Meanwhile, further south, a convective line is currently moving east across TN/MS. The HRRR has been suggesting some of this activity making it into our area overnight, with some of this focusing somewhere near the aforementioned boundary, with much of the Bluegrass areas getting more cutoff from the better moisture. The 00z NAM continues to shift the heavier QPF further northwest with time, although it does show more modest QPF further southeast compared to the 18z run. Given that the HRRR has been fairly consistent with the convective trends, have allowed for a strip of three quarters to an inch of QPF along the boundary, with still around a half inch or so across the Bluegrass counties. All of this will fall within the Flood Watch area, so updates planned for the headline. Have also included some patchy dense fog through the overnight, as there have been some reports of this in places. Updates have been sent. UPDATE Issued at 806 PM EDT WED MAR 28 2018 Moderate showers have diminished to light showers through early this evening, as forcing gradually relaxes across the area. The higher rainfall amounts occurred along a corridor from Salyersville to Mount Vernon, where an inch to an inch and a quarter fell. The 18z model suite as well as some of the shorter term model guidance has shifted the better QPF coming in late tonight and into Thursday a bit more northwest. The HRRR has been fluctuating between further northwest and right across the southeastern portion of the watch area. For now, have only made some POP adjustments, mainly to allow for more of a lull in the activity until after midnight. Will continue to monitor model trends and reassess things in a few hours. Also freshened up the hourly temperatures and dew points through the rest of the evening, with readings remaining in the 50s and 60s, closer to normal highs for this time of year. && .SHORT TERM...(This evening through Thursday night) Issued at 304 PM EDT WED MAR 28 2018 We will maintain the flood watch in its current configuration, with the watch beginning this evening at 8 PM and running through 8 AM Friday morning. Latest event total QPF forecast, including some QPE from today`s rain generally has 1.5 to 3 inches of rain in the flood watch through 8 AM Friday, with generally 0.5 to 1.5 inches outside the flood watch area. The total rainfall forecast for the flood watch area remains very similar to the previous forecast amounts. Current satellite and radar imagery shows the wave that brought today`s rain exiting off to the northeast. The next wave to affect the area will emerge from the lower MS valley this evening, with rain ramping back up later tonight. Another lull in the rain looks to be in store Thursday morning into the afternoon before the final round of showers and possible thunderstorms occurs from Thursday afternoon into Thursday night. At the surface a stationary front remains draped from northern AR to western KY into western PA. As the last mid level wave in a series of waves moves northeast on Thursday, the final wave of surface low pressure will move northeast as well, and into western PA Thursday evening. This will result in the surface front moving east across our area as a cold front Thursday night. Some of the high resolution models such as the HRRR had a good handle on the rain that occurred today and have followed the HRRR idea with rain chances diminishing late this afternoon and then ramping back up from the southwest after 02Z this evening. The axis of heaviest rain tonight should be over the far west and northwestern part of the forecast area. Rain from Friday afternoon into the Friday night should mainly occur in a band with the approaching cold front, but with shower and thunderstorm activity likely diminishing as it moves east Friday night, so that rainfall amounts in the east end up being less than the rainfall amounts in the west for the Thursday into Thursday night. .LONG TERM...(Friday through Wednesday) Issued at 357 PM EDT WED MAR 28 2018 An active weather pattern will continue through the long term portion of the forecast with several frontal passages and waves of low pressure bringing repeated rounds of precipitation. As a result precipitation will be in the forecast just about every day of the forecast. After the cold frontal passage Thursday night, cooler air will spread into the area for the end of the week. Surface high pressure will slide across the area Friday night, and with mostly clear skies and light winds, temperatures will fall into the middle 30s, with frost possible. This was already highlighted in the HWO and we will continue to highlight the frost threat for Friday night into Saturday morning. With high pressure slipping to our east by Saturday morning, and a cold front approaching from the northwest Saturday afternoon a nice warm up will occur, with highs Saturday in the 60s. However the cold front will move across the area on Saturday night with another round of showers, and then much cooler weather for Easter Sunday. A mid level wave will move across the OH and TN valleys Sunday night. The ECMWF is much colder than the GFS across our forecast area, with the GFS having 850mb temperatures from 6 in the south to -1 in the north by 12Z Monday, and the ECMWF having 850 temperatures from -1 in the south to -6 in the north at the same time. It is possible that some snow may mix with rain or even change to all snow in some spots late Sunday night into Monday morning. At this time no impacts are expected and will not mention in the HWO. Another cold front looks to move across the area Tuesday night with more rain chances and then another mid level wave keeping rain chances in the area into mid week. && .AVIATION...(For the 00Z TAFS through 00Z Thursday evening) ISSUED AT 806 PM EDT WED MAR 28 2018 Low pressure will ride up along a stationary frontal boundary positioned just northwest of the area late tonight and into Thursday. This will bring an additional round of widespread showers to most locations along and northwest of a line from JKL to SME, with MVFR/IFR conditions prevailing for most of the period, especially after 06z. Mainly VFR conditions will hold on across far southeastern Kentucky through most of the period, besides during periods of passing showers. An increasing low level jet moving in from the Tennessee valley will provide a threat of low level wind shear across eastern Kentucky generally between 08 and 14z. Southwest winds will average around 5 kts through the mid- morning hours on Thursday, before increasing to around 10 kts, with gusts of 15 to 20 kts. A cold front will approach the area towards the end of the period, with perhaps a few thunderstorms to contend with at times. && .JKL WATCHES/WARNINGS/ADVISORIES... Flood Watch through Friday morning for KYZ044-050>052-058>060- 068-069-079-080-083-104-106>109-111-112-114. && $$ UPDATE...GEOGERIAN SHORT TERM...SBH LONG TERM...SBH AVIATION...GEOGERIAN
Area Forecast Discussion
National Weather Service Norman OK
927 PM CDT Wed Mar 28 2018 .UPDATE... Lift from approaching wave and some increase in isentropic lift have resulted in development of scattered showers and thunderstorms across the Texas panhandle into far western Oklahom and western north Texas this evening. Have increased precip chances through the night time period based on this as well as agreement in last several runs of HRRR and 00Z NAM. Expect to see this activity continue to increase in areal extent as it moves east into the area. Still do not anticipate any severe weather, but a few strong storms may occur. && .PREV DISCUSSION... /issued 652 PM CDT Wed Mar 28 2018/ DISCUSSION... Please see the 00Z aviation discussion below. AVIATION... Flight conditions will deteriorate quickly tonight as very low cigs and FG/BR develop. Expect at least IFR to apply over most terminals for 3-5 hours tonight. Thunderstorms will also develop over WWR around 03Z and move southeastward close to OKC/OUN during the early morning hours. A wind shift from the north will result in some improvement to flight conditions after 12-14Z for most terminals, but still expect MVFR to IFR cigs through most of Thursday. && .PRELIMINARY POINT TEMPS/POPS... Oklahoma City OK 47 58 39 67 / 60 20 10 0 Hobart OK 46 61 37 69 / 30 20 10 0 Wichita Falls TX 47 62 41 70 / 20 20 10 0 Gage OK 41 58 36 68 / 40 20 10 0 Ponca City OK 46 57 35 66 / 40 20 10 0 Durant OK 51 68 44 70 / 30 20 10 0 && .OUN WATCHES/WARNINGS/ADVISORIES... OK...None. TX...None. && $$ 30/03