Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 07/06/17


Area Forecast Discussion
National Weather Service Albuquerque NM
541 PM MDT Wed Jul 5 2017 .AVIATION... 00Z TAF CYCLE VFR conditions should prevail over all TAF locations with the main issue over the next 2-6 hours being winds and some isolated showers west of the Central Mountain Chain. Most convection over the region is fairly high based, so the threat of gusty winds will remain through the evening hours. However due to low confidence in timing/location, it has been left out of the 00Z TAF`s. The most likely locations for any convection-related gusts will be KFMN and KGUP through about 06Z. For KSAF-KABQ, gusty east winds are still expected to develop in the 02-4Z time frame and last until about 09-10Z . Confidence in this event developing is lower than last night`s 00Z package, so winds have been reduced slightly. 54/Fontenot && .PREV DISCUSSION...321 PM MDT Wed Jul 5 2017... .SYNOPSIS... Strong high pressure aloft will remain centered in the vicinity of the Four Corners through Thursday. Strong daytime heating combined with residual moisture will support isolated showers and thunderstorms favoring the mountains and western half of the state. However, Thursday will likely be the least active day of the next seven. The upper high will shift farther west Friday before gradually weakening and drifting back toward the Four Corners this weekend into early next week. This will allow for gradual increase in storm coverage Friday through Tuesday. Daytime temperatures will remain well above average but trend closer to seasonal average this weekend and early next week. && .DISCUSSION... A strengthening and gradually expanding dome of higher pressure aloft will consolidate vicinity of the Four Corners remainder of the week. Primary centroid looks to meander around southeast UT or southwest CO through Thursday. Thereafter, models are similar with near 600 decameter 500mb height center over southern UT before the ridge slowly shifts back eastward and becomes more elongated west to east this weekend into early next week with 500mb heights decreasing every so slightly and trending closer to climo. Main concern remainder of this afternoon into the evening will be downburst potential along/west of the central mountain chain associated with isolated convection generally drifting toward the southwest. Broad plume of steep, nearly dry adiabatic lapse rates amidst a slightly more moist air mass will continue to support at least isolated virga bombs. Latest HRRR also likes isolated convection vicinity of Caprock in east-central NM within the next 1- 2 hours that could impact areas along the Pecos River Valley from Fort Sumner to Roswell. Otherwise, much less storm potential on the on the plains as compared to recent days. Thursday will likely be less if not far less active as compared to today, especially NC/NW areas, due to better developed subsidence inversion aloft and some mid-level drying. However, beginning Friday, a gradual day-to-day increase precipitable water indicated for the weekend into early next week. Combined with any subtle mid- level cooling, a general uptick in storm coverage looks reasonable for late week into the weekend as previous forecast. Steering flow considerations would favor central/western areas with predominately hot and dry weather in the east. KJ && .FIRE WEATHER... As expected, high pressure aloft has re-centered north of the Four Corners, but is broadly encompassing the Rockies. Shower and thunderstorm coverage has increased along the central mountain chain today with light easterly winds providing some weak upslope on the east faces. Despite seeing some dewpoint rises last night and this morning, drier air has mixed back over portions of the northern and central mountains this afternoon, causing storms to take on dry and gusty characteristics. The steering flow will push storm activity from a northeast to southwest trajectory. Storms will tend to be drier along and west of the Rio Grande. Temperatures have seen small drops in the eastern half of the state this afternoon with slightly lower Haines values there and small gains in humidity for most zones in the forecast area. Excellent RH recovery is expected for the northern and eastern tiers of the state, and gusty east canyon winds could redevelop. Into Thursday, slightly less storm coverage is expected as the dome of high pressure takes a temporary step to the south, back over the Four Corners. The high will strengthen, but isolated to scattered storms are still expected to develop. The footprints of true wetting rainfall will be small, and gusty outflows will accompany any showers or storms. Temperatures will climb just above average, and humidity will be lowest in the far western zones, dipping just beneath 15 percent. On Friday, Saturday, and Sunday the pattern will continue to be defined by high pressure, now shifting northwest of the Four Corners. Modest and diffuse mid to upper level subtropical moisture will yield storms over the northern mountains and secondarily over the western high terrain Friday. Storms will then increase over the central and western zones into the upcoming weekend. Temperatures will hover close to seasonal values through the weekend and humidity will make a slow trend upward day-by day. Prevailing winds will typically be from the east or south in many zones, with local storm outflows be the primary wind concerns. The dry nature of storms would also keep the threat of dry lightning going, especially in western zones. High pressure will then gradually shift more directly over the central Rockies next week, potentially allowing a better plume of moisture to invade with wetter storms. 52 && .AVIATION... 18Z TAF CYCLE Cumulus clouds are already bubbling up over the higher terrain of New Mexico, and are expected to blossom into high-based showers and thunderstorms. As isolated to scattered storms take shape, most will produce minimal rainfall due to the hot temperatures, modest surface dewpoints and meager mid level moisture owing to very dry sub-cloud layer humidity. This will elevate the gusty downburst potential with any shower or storm. The threat will be low for any significant downpours to reduce ceilings or visibility. Some showers and storms will slowly fill into lower elevation areas and valleys late this afternoon and through the early evening, but most activity should diminish by midnight. As has been the case the past several days, high density altitude will plague much of the northern and central New Mexico area this afternoon due to the hot temperatures. 52 && .ABQ WATCHES/WARNINGS/ADVISORIES... None. && $$ 41
Area Forecast Discussion
National Weather Service Bismarck ND
922 PM CDT Wed Jul 5 2017 .UPDATE... Issued at 922 PM CDT Wed Jul 5 2017 Thunderstorm potential continues across north central ND and the upper James River valley. Storms have slowly been intensifying northeast of Bismarck since 01 UTC. Visually the cumulonimbus has mainly lacked a crisp structure and has been high-based, which is suggesting that updrafts have been ingesting warm elevated mixed layer air to their overall detriment, and that they may not even be root in the boundary layer. Nonetheless, the environment that they`re in is characterized by MUCAPE around 4000 J/kg and deep- layer bulk wind differences near 50 kt in support of a continued, conditional severe risk. Moreover, upstream convection in Canada is maintaining its intensity and is on track to propagate into north central ND after 03 UTC. So, while we blended the latest radar trends into the forecast, we again are continue to carry a mention of potential severe thunderstorms in the forecast during the next several hours over north central ND into the upper James River valley. Elsewhere the risk of storms is over now that the lower atmosphere has begun to cool, yielding increasing MLCIN. UPDATE Issued at 653 PM CDT Wed Jul 5 2017 Overall, we are in a wait and see mode on thunderstorm initiation further north with a mostly flat-looking cumulus field as of 2345 UTC in northwestern ND and southeastern Saskatchewan. HRRR cycles since 20 UTC made about as drastic of a shift in solutions as any we`ve ever seen and are now silent on storms in north central ND. The presence of capping as noted by MLCIN values near -50 J/kg in RAP-based objective mesoscale analysis data could ultimately keep a literal lid on deep convection in north central ND this evening as those HRRR iterations suggest, but at the same time, we aren`t confident that the cap is truly that strong. Meanwhile, towering cumulus from Hazen and Hannover southeast toward Bismarck is more vigorous and shows signs of intensification, too. Suffice to say that the risk of severe weather remains across most of central ND this evening, so we have only made minor forecast adjustments with this update even though confidence in the more significant-severe storms in north central ND into the James River valley does appear somewhat lower than earlier thought at this moment. && .SHORT TERM...(This evening through Thursday) Issued at 358 PM CDT Wed Jul 5 2017 Potential severe thunderstorms late this afternoon through this evening are our focus with this forecast release. As of 20 UTC, high-based convection is developing in southwestern ND where intense boundary layer heating has allowed the convective temperature to be met along and ahead of a surface wind shift. We believe this initial activity will have a wind threat given very steep low- and mid-level lapse rates, surface temperature-dewpoint spreads around 50 F, and seasonably-strong mid-level flow aloft. This convection will propagate eastward into south central ND, and could further intensify as it reaches greater instability, but we are not particularly confident as to whether or not that will take place. CAMs have offered up quite dispersive scenarios with regard to convective longevity and intensity in south central ND owing to the dry boundary layer air mass from which it emanates, but if any updrafts can survive dry air entrainment eastward into the Highway 83 corridor they could be supercellular with an attendant risk of large hail along with damaging winds. This is the lower, but non- zero risk of severe weather that exists for places such as Elgin, Beulah, Bismarck/Mandan, and Linton. Meanwhile, a corridor of greater low-level moisture characterized by lower 60s F dewpoints is being maintained over central ND ahead of a subtle warm front that is lifting northeast. This is yielding MLCAPE of 2500 to 3000 J/kg along and east of a line from roughly Minot to Jamestown late this afternoon and evening. Model derived soundings and recent RAP objectively-analyzed mesoscale analysis data suggests this reservoir of significant instability is capped to boundary layer parcels, and there remains some uncertainty as to whether or not MLCIN will indeed be minimized sufficiently for surface-based convective initiation by evening. However, moisture channel imagery has suggested a weak mid-level impulse rounding the top of the ridge aloft in southern Canada which may serve as the impetus for storm development into north central ND by 00 UTC. CAMs through the 19 UTC HRRR and 18 UTC 3 km NAM, including the 12 UTC NCEP-run WRF-ARW and WRF-NMM, have been extremely consistent in advertising intense storms impacting north central ND into the upper James River valley this evening. Maximum updraft helicity values from those CAMs have also consistently been in the 100 to 150 m2/s2 range with simulated storms in those areas, indicative of potentially higher-end severe thunderstorm risk. Moreover, the projected near-storm environment is a match to many high-end hail events with peak sizes over two inches in diameter, and the NSSL WRF-ARW ensemble from 00 UTC and more recent HRRR iterations have all supported peak wind gusts of 55 to 65 kt, which is a rather noteworthy signal. Suffice to say that this could be a formidable event. MLLCL heights are forecast to be around 2000 m AGL, which should limit tornado risk, but the potential does exist given the expected intense mesocyclones driven by the CAPE and shear setup, the latter of which is driven by effective bulk wind differences around 50 kt. Upscale growth from initial supercells into a bowing complex is possible from north central ND into the James River valley given the largely unidirectional flow aloft. A cold front will then move southward across the area tonight and lead to a dry and relatively cooler day on Thursday. .LONG TERM...(Thursday night through Wednesday) Issued at 358 PM CDT Wed Jul 5 2017 The primary synoptic-scale feature of interest in the long term forecast period will remain the stout middle- and upper-level ridge centered across the western United States. The 12 UTC GFS and ECMWF stayed the course in advertising a period of northwest flow aloft across the local area through the upcoming weekend as the axis of the ridge remains near the spine of the Rockies. This will allow the air mass to be somewhat cooler - highs in the 80s and 90s F as opposed to 90s and 100s F - Friday through Monday. A seasonably strong shortwave trough may cut across the top of that ridge axis next week, which would in turn allow for another surge of hotter mid-level temperatures to push eastward into western and central ND Monday or Tuesday. A low-end thunderstorm risk may also be centered on that period given the glancing influence of that shortwave rolling across the top of the mean ridge. && .AVIATION...(For the 00Z TAFS through 00Z Thursday evening) Issued at 922 PM CDT Wed Jul 5 2017 Thunderstorms remain possible from north central ND into the upper James River valley through about 08 UTC. However, our confidence in storms impacting either KMOT or KJMS is modest at best, which means that TAF amendments will likely be driven by later trends in radar imagery. Otherwise, VFR conditions will prevail tonight and Thursday as a cool frontal boundary moves south and turns surface winds northerly by 12 UTC. && .BIS WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...CJS SHORT TERM...CJS LONG TERM...CJS AVIATION...CJS
Area Forecast Discussion
National Weather Service Burlington VT
1010 PM EDT Wed Jul 5 2017 .SYNOPSIS... High pressure will give away to a series of fronts with increasing threat for showers and thunderstorms on Thursday into the weekend. Not expecting a complete washout on any individual day or widespread heavy rainfall...but several chances for precipitation. Also...humidity levels will climb by Friday with near normal temperatures. Highs mainly mid 70s to lower 80s and lows in the upper 50s to mid 60s. && .NEAR TERM /THROUGH THURSDAY NIGHT/... As of 1007 PM EDT Wednesday...late evening refresh has no changes, other than to incorporate in the latest satellite (for clouds) and surface observation (for temperature/dewpoint) data to the first couple of hours of the forecast. The 00z HRRR indicates even lower chance of any light showers after midnight, and keeps the little bit of showers it has more to the southwest of the area. Could very well be what happens, but since the PoPs in the forecast are rather low right now, I decided to let what we have ride. Still for the most part a good night to have the windows open, though it won`t be as cool as last night. Previous comprehensive discussion from the dayshift forecaster follows... Water vapor shows large area of subsidence/dry air aloft directly over our cwa...which will provide us with clear skies and dry conditions overnight. 1020mb high pres over the CT River Valley will shift east tonight...allowing a southerly flow to develop with increasing moisture/temps by 12z Thursday. This increasing high clouds and 975mb to 925mb jet of 20 to 30 knots will limit areal coverage of fog...best chance over the CT River Valley. Temps will be 4 to 8 degrees warmer tonight...with lows ranging from the mid/upper 40s slk/northeast kingdom to lower 60s CPV/SLV. Still some uncertainty on shower/storm potential on Thursday...associated with weak 5h vort in the southwest flow aloft and weak surface trof. Most guidance is highlighting dacks into northern VT with chc pops...as best moisture and forcing is present. However...seems these showers will act to moisten up the atmosphere...especially low levels with limited qpf actually reaching the ground. Better instability develops across the SLV aft 18z...with sfc based cape values between 600-900 j/kg...but forcing is weak. So we cannot completely rule out a few showers/storms and will continue to mention slight chc to chance pops...overall threat and coverage will be limited. Temps are challenging as we have reached 84f here at BTV as of 300 PM...and progged 925mb to 850mb thermal profiles are expected to warm another degree or two. However...more clouds may offset heating some...so have mention highs mainly in the upper 70s to mid 80s...warmest cpv/slv. Thursday Night...We continue to be between systems with deeper moisture and surface low pres to our south and stronger dynamics with developing mid/upper lvl trof and sfc boundary to our nw. Very difficult to completely rule out a spot shower or rumble of thunder...given how close moisture/lift is...so continue with slight chc/chc wording. Given the lack of deep layer moisture and pws btwn 1.0 and 1.5" widespread heavy rainfall is not expected. Southerly flow in the boundary layer will help to advect higher surface dwpts into our region with some return to humidity expected. Lows mainly in the m/u 50s sheltered valleys to mid 60s cpv/slv. && .SHORT TERM /FRIDAY THROUGH SATURDAY/... As of 339 PM EDT Wednesday...The end of the work week and first half of the weekend continues to look active though quite complex and uncertain with models struggling to resolve the synoptic features and in general disagreement with the timing. Thus, a blended model approach is what follows for this forecast. Overall setup beginning Friday morning will be a developing wave of low pressure along a surface boundary near D.C. while a deepening upper trough enters into the western Great Lakes. Deepest moisture and lift from the coastal low seems to stay mainly south of the CWA, offering just a chance for a few showers across our southern zones, but the better chance for precip will come with the trough and attending cold front approaching from the west. As is typical in the North Country, the front will come through in pieces with a pre- frontal trough firing showers and thunderstorms during the Friday afternoon and evening hours before quieting for a bit during the overnight. Main surface front though will be on the doorstep of the St. Lawrence Valley come 12Z Saturday morning, swinging through the region during the day with widespread showers redeveloping, with the chance for a few thunderstorms. Overall low confidence on the areal coverage of convection on Friday, though it is the better day compared to Saturday with better instability and a brief area of enhanced PWATs swinging through. Could see a few stronger cells with the chance for gusty winds and heavy rain. On Saturday instability is weaker, along with PWATs lowering through the day so while I can`t rule out a few stronger cells, feel showers will be more prevalent. && .LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/... As of 339 PM EDT Wednesday...Large discrepancies remain amongst the deterministic guidance for the extended periods, largely from differing opinions on the evolution of a strong closed low over Hudsons Bay during the Sunday/Monday timeframe and onward. Overall I`ve trended towards a non-GFS blend similar to the previous forecaster as the GFS seems to be the outlier in the southern progression of said trough, with the ECMWF and CMC offering a more northern track and subsequently drier forecast. That said, Saturday night should turn out to be mainly dry behind the exiting cold front, and have kept some token chance PoPs along the intl border Sunday/Sunday night, with a bit more areal coverage possible Monday as the main shortwave passes north. High pressure mainly dominates then for Tuesday and Wednesday, with temperatures near seasonal normals. && .AVIATION /02Z THURSDAY THROUGH MONDAY/... Through 00z Friday...VFR expected for the next 24 hours. Potential for fog at MPV looks even less based on latest guidance, so have removed from the forecast. Could be a few light showers after 06z, but won`t cause any reduction in flight category. The chance for any shower is generally quite low, so only worth a "VCSH" mention for SLK which is where if anything falls out of the sky, it would be there. For the day on Thursday, expect isolated showers or perhaps a thunderstorm across northern NY. Again, chances are so low that have just placed "VCSH" at PBG and SLK. Surface southerly winds will be increasing late tonight with gusts up to 20 knots possible, especially in the Champlain and St Lawrence Valleys. Outlook... Thursday Night: VFR. Slight Chance SHRA...Slight Chance TSRA. Friday: VFR. Chance SHRA...Chance TSRA. Friday Night: VFR/MVFR. Likely SHRA...Chance TSRA. Saturday: VFR. Chance SHRA...Chance TSRA. Saturday Night: VFR. Slight Chance SHRA. Sunday: VFR. Slight Chance SHRA. Sunday Night: VFR. Chance SHRA. Monday: VFR. Chance SHRA. && .BTV WATCHES/WARNINGS/ADVISORIES... VT...None. NY...None. && $$ SYNOPSIS...Taber NEAR TERM...Taber/Nash SHORT TERM...Lahiff LONG TERM...Lahiff AVIATION...Nash
Area Forecast Discussion
National Weather Service Dodge City KS
634 PM CDT Wed Jul 5 2017 ...Updated Aviation Section... .SHORT TERM...(This evening through Thursday) Issued at 340 PM CDT Wed Jul 5 2017 Benign weather pattern to remain in place over the next 36 to 48 hours before the next appreciable opportunity for convection returns. A broad cu field developed early afternoon, with scattered bases around 4kft. Discounting blotted pcpn which the HRRR develops this afternoon in this cu field south and east of Dodge. These clouds should rapidly dissipate upon loss of afternoon heating as the they help cap temperatures around the 90 degree mark late this afternoon. With surface high pressure to the east, the surface winds will remain light tonight, becoming more southerly with time over the entire area into central Kansas by early Thursday morning. Another mild overnight period to follow with most raw model and mos guidance centered in the mid 60s. The light surface winds will continue on Thursday. The higher dew point air will shift east out of the area, relegating the 60`s dew points to the extreme southeastern counties by late Thursday afternoon, with dewpoints in the 40s across the western counties. This in turn will allow for quicker rising temperatures curves during the day and overall warmer highs probably in the mid 90s. .LONG TERM...(Thursday night through Wednesday) Issued at 340 PM CDT Wed Jul 5 2017 NAM/WRF shows a weak shortwave moving out of Colorado Thursday night, with potential for thunderstorm/mcs development, however the signal remains focused over far northern KS and into Nebraska. By Friday evening the NAM/WRF again develops high plains convection driven across northwest KS and tying it to a developing warm front straddling KS nw to southeast by the early the next day. This pattern is somewhat validated by the GFS20, not so much by the the ECMWF. Beyond this, the Superblend maintains mainly a dry forecast going forward, with high temperatures around 5+ degrees warmer than normal. && .AVIATION...(For the 00Z TAFS through 00Z Thursday evening) Issued at 628 PM CDT Wed Jul 5 2017 Quiet aviation weather will continue through the period. Prevailing wind will be out of the south to southeast at 5 to 10 knots. Winds should remain below 12 knots through Thursday given the weak pressure gradient as an upper high anchors in across the Desert Southwest region into the Rockies. && .PRELIMINARY POINT TEMPS/POPS... DDC 66 95 68 96 / 0 0 0 10 GCK 65 99 67 97 / 0 0 0 10 EHA 64 96 67 96 / 0 0 0 10 LBL 66 97 68 97 / 0 0 0 10 HYS 66 97 69 93 / 0 0 20 20 P28 68 95 69 96 / 0 0 0 10 && .DDC WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SHORT TERM...Russell LONG TERM...Russell AVIATION...Umscheid
Area Forecast Discussion
National Weather Service Grand Forks ND
1015 PM CDT Wed Jul 5 2017 .UPDATE... Issued at 1012 PM CDT Wed Jul 5 2017 Severe thunderstorm watch issued for counties along and north of HWY 200 in ND to Norman Co MN and west of a line from Norman Co to Roseau Co MN until 4am. Primary threats will be hail up to 2 inches in size and winds up to 70mph. Marginal severe storm approaching the western edge of the forecast area currently. Main activity to watch will be storms in Manitoba approaching. UPDATE Issued at 937 PM CDT Wed Jul 5 2017 Convective evolution for the overnight period coming into focus with strengthening activity in Manitoba drifting to the southeast. Another weaker area of convection is drifting to the ESE from central ND. Expecting storms to move into the Devils Lake basin in the next couple hours with additional storms developing as upper forcing overruns the forecast area. ML CAPE up to 4500J/kg and bulk shear values around 50kts will fuel and support convection. CAM trends are showing the activity merging into a MCS tracking across the northern valley into NW MN late tonight. && .SHORT TERM...(This evening through Thursday) Issued at 244 PM CDT Wed Jul 5 2017 Main impacts through the short term will be severe potential from late afternoon through the evening. Current surface map indicating low pressure over se Sask and weak boundary extending from nw ND to the se corner of ND then into central Mn. CAM guidance indicating this boundary may be the focus for possibly two rounds of deep convection this evening. Although upper forcing looks relatively weak and there will be some CIN to overcome Airmass sufficiently unstable with dewpoints in the 60s and bulk shear from 25 to 40kts. Favored guidance indicating potential for development initially from far se ND eastward into west central MN then shifting south and east. Better potential farther north and west with convection organizing over Sask/MB vcnty sfc low and boundary then propagating se during the late evening. HRRR indicating potential for bowing segment from N central ND pushing into se ND later tonight generally along and just north of current boundary position. Based on lack of significant upper support, stronger convection will likely be fairly widely scattered so will generally keep pops in chance/scattered ranges. Low level jet not all that impressive so confidence not real high on how long convection will last overnight. Temperatures to remain mild overnight as thermal ridge axis will be parked over the Fa during half of the overnight and dewpoints remain above 60. High pressure and drier airmass will follow departing system on Thursday for less active and a bit cooler day. .LONG TERM...(Thursday night through Wednesday) Issued at 244 PM CDT Wed Jul 5 2017 For Thursday night into Friday...surface high pressure will dominate the area with slightly cooler temperatures and a more stable airmass. Little to no precipitation is forecast at this time. By Saturday...the upper ridge remains amplified over the high plains...and model guidance indicates a bit of a stagnant pattern through the end of the period. There remains some differences in the placement of the features...but the differences are not considered significant. Therefore...will trend to a blended soln through the remainder of the period. A few minor disturbances can be expected to propagate through the flow...but not enough energy for significant precipitation although some scattered afternoon showers cannot be ruled out. Temperatures will continue to be on the warmer side with highs generally into the 80s...under a mix of sun and clouds.&& .AVIATION...(For the 18Z TAFS through 18Z Thursday afternoon) Issued at 1242 PM CDT Wed Jul 5 2017 VFR conditions expected through the period. Convection expected tonight, possibly severe, however coverage expected to be rather isolated so other than DVL not enough confidence on any storms affecting TAF sites for mention at this time. && .AVIATION...(For the 18Z TAFS through 18Z Thursday afternoon) Issued at 1242 PM CDT Wed Jul 5 2017 VFR conditions expected through the period. Convection expected tonight, possibly severe, however coverage expected to be rather isolated so other than DVL not enough confidence on any storms affecting TAF sites for mention at this time. && .FGF WATCHES/WARNINGS/ADVISORIES... ND...None. MN...None. && $$ UPDATE...JK SHORT TERM...Voelker LONG TERM...Hopkins AVIATION...JK
Area Forecast Discussion
National Weather Service Sioux Falls SD
926 PM CDT Wed Jul 5 2017 .UPDATE... Issued at 923 PM CDT Wed Jul 5 2017 Made an important update to include like to high end scattered pops dropping southeastward through the night, but keeping it west of Sioux Falls and Sioux City. Convection has currently blossomed into a line in central SD along with more scattered activity in east central SD and northeast SD. With a stabilizing boundary layer, not sure if the scattered activity to the east of the line will maintain overnight. However the latest HRRR has latched onto the line in central SD, and moves it southeast right across our entire southwest zones overnight. The reflectivity`s are not overly strong with the line, but enough to warrant some TSRA mention. The grids should be uploaded shortly but again, so far have the pops west of I 29, west of Sioux Falls and Sioux City with the convection`s current trajectory. && .SHORT TERM...(This evening through Thursday) Issued at 332 PM CDT Wed Jul 5 2017 Convective development continues to be the largest challenge to the short range forecast - perhaps more so if it can even occur over the next 24 hours. Strong Rockies ridge in place, and will see a wave move over the ridge downstream into northern Minnesota by Thursday morning. Continual gradual warming to temperatures aloft will increase the cap strength across the region from the west. At mid afternoon, have readings around 100 in south central SD, but also with mixing of moisture to knock dewpoint readings back to around 60 degrees. Elsewhere, not quite as hot, but still seeing the dewpoint readings drop into the lower to mid 60s. Result has been maintenance of strong ML cap of 100-200 J/kg through the afternoon. Again, will have to look well upstream toward north central SD or south central ND for development, closer to the lower-level convergence. Problem for this development will be the attempt to progress into the warm and dry layer aloft, which would likely work to diminish activity before making much of what would be a slow progression into the highway 14 corridor during the evening. As the jet streak/wave punches toward MN late night, likely that another small MCS could develop well north of the area, with a very small chance that a tail of trailing convection could develop toward southwest MN, and have put a very small threat up around KMML for late night to cover, although odds are strongly against it. Convective development in weak forcing is by far not the strong suit of the high resolution CAMS, and that is the situation with each HRRR run showing almost random locations for development, but with the general theme mentioned above. By Thursday, will again have to focus on the heat. Cold front driven by the wave in MN will push southward, indications on latest runs a bit quicker than earlier model runs. This should not have a significant impact on warming, with good west to southwest flow ahead of the front, and far from strong cooling behind. Combination of heat and some humidity will push the apparent temperature to around 100 degrees from the lower Missouri River valley eastward toward KSLB. Not warm enough for a heat advisory, but definitely uncomfortable and deserving of applying heat safety practices. Otherwise, cap will be very strong again tomorrow as boundary sinks southward, and expect mainly a quiet frontal passage. In the event there is slightly better moisture convergence or a slight dynamic lift cooling in the warm layer, have a very limited temporal threat for storms mainly south of Iowa Highway 3 and south of highway 20 in Nebraska. Threat only for an hour or two around mid to late afternoon, with the threat ending as frontal boundary sinks past area prior to 00z. .LONG TERM...(Thursday night through Wednesday) Issued at 332 PM CDT Wed Jul 5 2017 The extended appears to be characterized by the summer doldrums with upper level ridge building across the western half of the country. This should result in mild conditions, with limited chances of precipitation. Behind the cold front on Thursday night, could see temperatures cool quite nicely with good radiative conditions in a dry environment. Looking at a warming trend Friday through Sunday. On Monday, ECMWF shows a strong ridge rider tracking across the area, while the GFS has little to nothing in terms of a mid level wave. Left the skittish pops Monday-Wednesday, but the prevailing conditions appear to be hot and dry. && .AVIATION...(For the 00Z TAFS through 00Z Thursday evening) Issued at 633 PM CDT Wed Jul 5 2017 Added some VCTS to the KHON TAF site due to TSRA drifting southward from northeast SD through 02Z this evening. A lot of this activity is likely heating based so it may not last much longer after sunset. One question mark is winds for KHON if outflow is produced from the TSRA. In that area, observations are not overly abundant and area radars could shoot over outflow boundaries. So erratic winds could occur at KHON early this evening with not a lot of lead time. Otherwise expecting VFR through the TAF period. && .FSD WATCHES/WARNINGS/ADVISORIES... SD...None. MN...None. IA...None. NE...None. && $$ UPDATE...MJ SHORT TERM...Chapman LONG TERM...BT AVIATION...MJ
Area Forecast Discussion
National Weather Service Hastings NE
633 PM CDT Wed Jul 5 2017 .SHORT TERM...(This evening through Thursday) Issued at 317 PM CDT Wed Jul 5 2017 Satellite and observations show a few cumulus have formed across the forecast area. There are not very many of them and so there is plenty of sunshine to warm temperatures this afternoon. The forecast models all have an upper level ridge in the western CONUS and there are a few waves that move around the ridge. The deterministic models are dry for the afternoon and into tonight, but a few of the short term models, including the HRRR, have some convection during the late afternoon and evening that takes off along the sand hills, just to the northwest of the forecast area. Have left some low PoPs in the far northwest for this. The problem is that the HRRR also brings another round of storms later this evening into the area from the north. At this time, have left this period dry since there is only a couple of models that have this. On Thursday, there will be a cold front that moves into the forecast area during the day. The morning should be dry, but during the afternoon there could be a few thunderstorms developing along and north of the front. .LONG TERM...(Thursday night through Wednesday) Issued at 317 PM CDT Wed Jul 5 2017 The upper level ridge in the western CONUS drifts to the east through the period. There are several upper level waves that move over the ridge and into the forecast area. Most of these are fairly weak, but there are a few that are a little stronger. The first wave during the period will be Thursday night. There will be a few thunderstorms developing along the front during the later afternoon, but during the evening as the upper wave moves in, the chance continues and spreads across the forecast area. This is not a strong wave, so chances are fairly small. There could be a few thunderstorms that linger into Friday morning, but should come to an end during the morning. The upper level wave that moves in Friday afternoon and night will be a little stronger wave and the chances for thunderstorms will be a little better, mainly during the overnight hours. There could be some lingering into Saturday morning and with a wave in the afternoon the small chances for thunderstorms continues. These are smaller chances and not for the entire area. Sunday through most of Tuesday is dry at this time. There are still some weak upper level waves that move over the ridge, but none of them are strong enough to get too excited about. During this time, the ridge is edging a little east and temperatures are warming up. Tuesday afternoon into Wednesday there will be a few waves over the ridge and there are some small chances for small part of the forecast area. && .AVIATION...(For the 00Z KGRI/KEAR TAFS through 00Z Thursday) Issued at 633 PM CDT Wed Jul 5 2017 VFR conditions are expected through the TAF period. Winds will be fairly light out of the south and southeast. Although a couple short term models still suggest we could see at least some light precipitation this evening, have kept things dry and expect skies remain mostly clear overnight. As temps warm up tomorrow afternoon some scattered cu could develop across the area. A cold front approaches from the north late in the afternoon with slight chances for isolated thunderstorms to develop along it. The timing of the frontal passage is close to 00Z, so have held off on including a VCTS mention at this time. && .GID WATCHES/WARNINGS/ADVISORIES... NE...None. KS...None. && $$ SHORT TERM...JCB LONG TERM...JCB AVIATION...Petr
Area Forecast Discussion
National Weather Service Grand Rapids MI
728 PM EDT Wed Jul 5 2017 LATEST UPDATE... Aviation .SYNOPSIS... Issued at 250 PM EDT Wed Jul 5 2017 An area of high pressure located over New England will continue to track east away from the region. Southwest winds on the backside of this departing system will draw up an increasingly moist airmass tonight and into Thursday. A cold front will push southeastward through the Great Lakes region Thursday night resulting in some rain. A reinforcing shot of cooler air is expected to move in over the weekend resulting in a cooling trend. && .SHORT TERM...(This evening through Friday night) Issued at 250 PM EDT Wed Jul 5 2017 The main challenge in the short term deals with the timing of any showers and thunderstorms. Overall there appears to be not much potential until Thursday Night. To start...confidence is lower than normal as far as the precipitation potential goes over the next couple of days. The main reason for this is that the models have done a rather poor job with the handling of the convection located in Wisconsin. Considering that there is more storms out there upstream than forecasted...I will add a small potential for a few storms this evening toward Ludington. Then later tonight...earlier runs of some of the High Res models were trying to bring down a convective complex after 09z. The latest runs have backed off on this scenario. Will only go with a small chance for this to happen. Then for Thursday...lots of instability builds during the day...but deep layer shear remains weak during the day. Forecast soundings show some negative area for surface based lifted parcels. Thus if some storms did go...it appears they would be pulse in nature. Thursday night the cold front drops down from the northwest. A decent wind shift is noted along with instability that would be supportive of stronger convection. Deep layer shear increases somewhat...so a risk for organized convection does exist. PWAT values are forecasted to climb to over 1.5 inches...with some models showing closer to 2 inches. Thus heavier downpours are possible which could lead to some urban and poor drainage flooding. .LONG TERM...(Saturday through Wednesday) Issued at 250 PM EDT Wed Jul 5 2017 Overall, the long term period looks to feature cooler than normal weather by July standards and periodic chances for some showers/thunderstorms. The operational GFS and ECMWF remain a bit at odds with one another on the finer detail of the forecast. They agree in general on upper troughing and cooler weather, but diverge on timing of upper shortwaves and surface fronts. Guidance numbers look a bit skewed towards climatology in the long term. The GFS MOS guidance for instance has highs around 80 each day. Given the 850mb temps and troughing wonder if we will not be a bit cooler in the 70s for highs which is what some of the raw model output shows. As for timing of fronts and better chances for precipitation hard to nail things down given the model disparity in play. Rolled with model blends and neighboring offices in regard to precip. Overall, would say the precipitation forecast in the long term is low confidence given the spread in the models. Both the ECMWF and GFS have chances for precipitation on Sunday. The ECMWF dries things out Sunday night into Monday night, whereas the GFS lingers the front and hence the precip chances. Sticking close to models blends until more of a trend and consensus develops. && .AVIATION...(For the 00Z TAFS through 00Z Thursday evening) Issued at 721 PM EDT Wed Jul 5 2017 Showers and thunderstorms developed over Wisconsin this afternoon. Many of the short range models did not depict this area of precipitation...but the HRRR and Canadian-Regional models have a handle on it. Radar trends in the past hour or so have indicated the showers dissipating as they move over the lake...which is consistent with the model output...so will keep the 00Z TAFs dry. VFR conditions will continue through 00Z Friday. High clouds will be the most plentiful...with mid clouds encroaching Thursday after 12Z as deeper moisture returns to West Michigan. Rain chances will increase significantly after 00Z Friday. && .MARINE... Issued at 250 PM EDT Wed Jul 5 2017 Outflow from the upstream convection in Wisconsin has been slipping southeast with time. This feature was just west of Green Bay. Current indications are this boundary will not move into the nearshore zones tonight...remaining just to the north and west. This will need to be monitored going through the evening as the computer models have struggled with it through the day. The waves will be building on Friday as a northwest flow strengthens. Will need to monitor this period for possible headlines. Currently we have the waves just under the criteria. && .HYDROLOGY... Issued at 225 PM EDT Wed Jul 5 2017 Area rivers are below bankfull and falling. The river systems in Central Lower Michigan are mostly above normal, while the southern river systems are around normal. Up to around a half inch of rain is expected Thursday through Friday. This could lead to minor river rises, but most river levels will continue to fall through the weekend. Additional rain chances are expected Sunday into mid week. && .GRR WATCHES/WARNINGS/ADVISORIES... MI...None. LM...None. && $$ SYNOPSIS...MJS SHORT TERM...MJS LONG TERM...Duke AVIATION...MWS HYDROLOGY...63 MARINE...MJS
Area Forecast Discussion
National Weather Service Huntsville AL
949 PM CDT Wed Jul 5 2017 .NEAR TERM...(Rest of tonight) Issued at 949 PM CDT Wed Jul 5 2017 Small mesoscale convective system ongoing across middle Tennessee arrived a little ahead of schedule but has produced only a few small showers across northwest Alabama so far this evening, with the bulk of the activity remaining well to our north. Satellite data suggest that a subtle vortmax may be responsible for the convection, coupled with a localized enhancement of shear noted in the 00Z Nashville sounding. Mesoanalysis data suggest that there is ample surface-based instability over north Alabama but significant convective inhibition. With such low coverage occurring right now, will there still be any storms overnight? Convection-Allowing Models are mixed; the 00Z 3km NAM is very dry, whereas the 01Z HRRR still attempts to fire storms along an outflow boundary a little farther behind this activity. Given how readily storms have developed in this moist environment (precipitable water ~2 inches) it seems unwise to lower PoPs much. So the forecast will be tweaked only slightly, maintaining the highest PoPs to the northwest closer to outflow from the middle TN MCS, tapering lower to the southeast where CIN is the highest. Temperatures are right on track, and rapidly-shrinking dewpoint depressions with generally little cloud cover lends itself to fog formation earlier than usual. If storms do not get going overnight, this could become problematic for the morning commute. .SHORT TERM...(Thursday through Friday) Issued at 115 PM CDT Wed Jul 5 2017 On Thursday, expect perhaps a carbon copy of today with slightly higher areal coverage as the upper wave and attendant front make a slow approach from the west. The instability, and associated coverage, will depend on overnight/early morning activity however. For now, will continue with likely PoPs most areas with maximum probabilities between late morning and mid afternoon. Have debated back and forth about a Flash Flood Watch for Thursday but given that most of today`s activity has had some flow to it and overall amounts at any given location have not been enormous will likely hold off for now. Expect storms to hold on a bit longer Thursday evening/night given additional upper level support and have trended PoPs that direction. Would not be surprised to see an isolated very strong/severe storm on Thursday given enhanced flow and a bit more CAPE to work with. Some initial subsidence is noted behind the upper wave on Friday and have trended PoPs down a tad accordingly. However, the notably drier air is still well to the north so we won`t feel much in the way of relief until later in the weekend. In terms of temperatures, have not made too many adjustments to the previous forecast. The combination of high humidity levels and afternoon convection will technically keep temps just below climo levels. But the relatively high "heat index" values certainly will make up for that. .LONG TERM...(Friday night through Tuesday) Issued at 204 PM CDT Wed Jul 5 2017 As this drier air continues to move into the Tennessee Valley Friday morning, models continue to push the front into central Alabama. However, they continue to keep at least some light QPF over much of northern Alabama into early Friday afternoon. With the boundary possibly not far to the south, kept isolated to widely scattered chances of showers/storms through Friday afternoon. Temperatures should rebound west of I-65 especially due to insolation into the mid to upper 80s. Expect these chances to decrease more Friday night, but model guidance does quickly push another weak frontal boundary toward the area Friday night, so kept isolated pop in then. Dewpoints don`t seem to drop much based on guidance behind the front on Friday night. Thus lows around 70 degrees will hang on even Friday night. Rain chances increase ahead of the next frontal boundary on Saturday, as some weak shear arrives with the front. Based on DCAPE values and instability, think stronger to marginally severe storms capable of producing frequent lightning, gusty winds to around 60 mph, and isolated flash flooding are possible. Despite cloud cover and precipitation, warm 925 mb temperatures should still allow highs to climb into the mid 80s at least. This majority of this activity should push to our southeast Saturday night, but isolated to widely scattered showers/storms could hold on in southwestern counties during the evening hours especially. The drier air should make temperatures a bit more tolerable Saturday night through Monday morning, as lower to mid 60 degree dewpoints are become entrenched behind the departed front. By Monday into Tuesday, southwesterly flow will bring more moisture northward again from the Gulf of Mexico ahead of another weak frontal boundary over the Ohio Valley. This will bring more humid conditions back into the area. 925 mb temperatures also climb back into the 22 to 25 degree Celsius range. This should push highs back into the upper 80s to lower 90s. && .AVIATION...(For the 00Z TAFS through 00Z Thursday evening) Issued at 637 PM CDT Wed Jul 5 2017 VFR conditions are expected through 06-07Z, at which point uncertainty increases. Short-range models suggest that the line of storms over west Tennessee will spark off additional showers/storms at KMSL, then KHSV, and this seems feasible based on the last few days. The TAFs will include VCTS to account for this, with additional amendments to follow to fine-tune impacts/timing. Once these storms are clear of the area, there is a good chance of at least MVFR fog development; visibility could drop further if the storms do not materialize, or fog could hold off if clouds/storms persist longer. Scattered showers and storms should redevelop once again mid-late morning tomorrow. && .HUN WATCHES/WARNINGS/ADVISORIES... AL...NONE. TN...NONE. && $$ NEAR TERM...BCC SHORT TERM...15 LONG TERM...KTW AVIATION...BCC For more information please visit our website at weather.gov/huntsville.
Area Forecast Discussion
National Weather Service Wilmington NC
947 PM EDT Wed Jul 5 2017 .SYNOPSIS... Isolated to scattered thunderstorms will continue through the forecast period, with hot and humid conditions through Saturday. A weak cold front will bring slight cooling Sunday, with near normal temperatures through early next week, along with an increase in rain chances as several waves of low pressure track along a stalled coastal front. && .NEAR TERM /THROUGH THURSDAY/... As of 945 PM Wednesday...A synoptic front is nearly stationary across northern North Carolina extending from just north of Hatteras to Greenville, Raleigh, and Greensboro. South of the front we`ve had a predominant westerly wind today which held the seabreeze at bay and led to the hottest day of the year so far in Wilmington (95 degrees) and in North Myrtle Beach (96 degrees). Thunderstorms erupted this afternoon along a weak boundary across eastern South Carolina. This activity has largely dissipated with the loss of heating and through convective overturning which has dropped surface temperatures into the 70s from Myrtle Beach and Conway through Marion and Florence. In fact 9 PM temps were actually a degree or two BELOW our forecast lows in a few spots, necessitating a forecast update. I don`t anticipate given the very warm airmass and high moisture content of the boundary layer that temperatures will slip much in the cool spots the remainder of the night. After missing the initial round of convection across South Carolina, the latest few HRRR runs have performed quite well, and show activity diminishing rapidly over the next few hours with dry conditions overnight. I`ve extrapolated current convection on radar ahead 2-3 hours and indicated a weakening/clearing trend progressing. && .SHORT TERM /THURSDAY NIGHT THROUGH FRIDAY NIGHT/... As of 300 PM Wednesday...The pattern remains essentially the same for most of the period with some slight mid level height falls by late Friday night. There will still be intervals of higher precipitable water moving across and this when combined with strong daytime heating, the sea breeze and Piedmont troughs warrants some mention of pops through the period. Late Thursday into the early morning hours of Friday may be the exception when most guidance is showing a dry forecast. For temperatures I continued to opt for the warmer overnight lows and slightly higher daytime highs. && .LONG TERM /SATURDAY THROUGH WEDNESDAY/... As of 300 PM Wednesday...Showers and TSTMS chances will prevail through the extended period. Hot and humid conditions Saturday will see slight relief Sunday onward as a weak cold front is slated to push through early Sunday. Low amplitude upper trough upstream will cause a frontal boundary to stall along or just off the coast through early next week. Several waves of low pressure along this front will increase rain chances across NE SC and SE NC, particularly as column moisture deepens, and aids in boosting precipitable water values to near 2 inches. && .AVIATION /00Z THURSDAY THROUGH MONDAY/... As of 00Z...A cluster of showers and t-storms will approach the Myrtle Beach area between 00-01Z this evening. The best potential for impacts on airport operations will be at CRE where the storm cores have a better chance of pushing overhead. Activity should be offshore after 0100-0130Z here. We`re also watching convective activity near CLT moving southeastward, potentially affecting the LBT airport in the 0130-0400Z timeframe. The setting sun may reduce the intensity of these storms before their arrival in Lumberton. Otherwise VFR conditions should prevail over the next 24 hours in a hot and humid weather pattern. Extended Outlook...Brief MVFR/IFR conditions are possible mainly during the afternoons and evenings in scattered thunderstorms Thursday through Monday. The potential should be largest Sunday and Monday as a weak cold front moves into this portion of the Carolinas. && .MARINE... NEAR TERM /THROUGH THURSDAY/... As of 945 PM Wednesday...A stalled front across northern North Carolina should move very little through the night, with light southwesterly winds anticipated to continue along our portion of the coastline. While there is still a very small chance of a pop-up shower or t-storm overnight, latest high-resolution models indicate dry conditions. Southwest winds 10-15 knots and seas near 3 feet should continue. SHORT TERM /THURSDAY NIGHT THROUGH FRIDAY NIGHT/... As of 300 PM Wednesday...Winds will be a little more elevated than normal summertime values through the period via enhancement of the inland trough. Expect a southwest flow of 15-20 knots. This flow will lead to somewhat higher seas as well with an overall range of 2-5 feet. A SCEC headline may be needed for most of the period. LONG TERM /SATURDAY THROUGH MONDAY/... As of 300 PM Wednesday...Cautionary marine conditions may linger into Saturday as a surface trough inland interacts with Bermuda high pressure offshore. Seas of 3-5 feet are expected through at least Saturday morning, but a subsiding trend in wind and seas is anticipated by late Saturday as the trough nears the coast and weakens. As a result, Sunday and Monday should see SW 15 KT or less with seas of 2-3 feet. && .ILM WATCHES/WARNINGS/ADVISORIES... SC...None. NC...None. MARINE...None. && $$ SYNOPSIS...MJC NEAR TERM...TRA SHORT TERM...SHK LONG TERM...MJC AVIATION...TRA
AREA FORECAST DISCUSSION
National Weather Service Jackson KY
1102 PM EDT Wed Jul 5 2017 .UPDATE... Issued at 1102 PM EDT WED JUL 5 2017 JKL continues to be precip free late this evening. However we are tracking an area of storms currently moving through central TN. These storms have resulted in multiple convective warnings through this point, and should continue its track ENE towards southeast KY over the next 4 to 6 hours. That being said, it has shown some signs of weakening as the main line starts to break apart. Also the latest CAMs continue to support it weakening substantially by the time it reaches our CWA between 8 and 10Z. If the HRRR pans out, we may be lucky to get any thunder out of it, while the ARW and NMM show only isolated convection potential. That being said, made several updates throughout the evening to both lower pops over the next few hours, as well as to better time in the next system. Kept with only scattered mentioned and did broadbrush a bit based on uncertainty. There was some concern about flash flood potential in the Lake Cumberland region of the CWA based on low flash flood guidance and the potential for some of these showers moving in to be heavy and produce over an inch of rain in a short period of time. Based on the latest CAMs not completely sure that this will in fact occur. Rather it should prime conditions further for potential flash flooding to occur with heavier storms tomorrow afternoon. That being said, after some coordination with our western offices, decided to go with an SPS and mention the isolated potential for flash flooding overnight. UPDATE Issued at 754 PM EDT WED JUL 5 2017 Lowered pops for late this afternoon/evening based on the current radar trends with the best precip now having moved east of our CWA. Another round of showers and thunderstorms that was over south-central KY a few hours ago has quickly dissipated as it propagated eastward towards our region, now only light and isolated in nature. In fact, pops may need to be further lowered to account for this continued dying trend. Based on the forecast soundings, did still see the potential for some overnight instability, so added thunder mention back into grids. That being said, if current weakening trends persist, it might be hard to have anything develop regardless of environment. Will continue to monitor weather and adjust pop/weather as needed. Also loaded in the latest observations for temps, dew points, and winds, to make sure the near term forecast was on track with current conditions. All grids have been published and sent to NDFD/web. A new zone package will be sent out to reflect thunder addition. && .SHORT TERM...(This evening through Thursday night) Issued at 328 PM EDT WED JUL 5 2017 Unsettled weather pattern will continue through Thursday night as a shortwave slowly passes across the region. Showers and thunderstorms will plague the area with greatest coverage this afternoon and early evening, and again tomorrow afternoon and evening. In fact, continued to advertise categorical PoPs for tomorrow afternoon into tomorrow evening as the trough axis and weak surface reflection make their transition across the forecast area. Atmospheric moisture remains high with PWATs near 2" so will continue to advertise locally heavy rainfall, but storms will be progressive which should keep the flash flood threat isolated in nature. On the other hand, storms may tend to get better organized tomorrow afternoon, and carry a marginal threat for strong wind gusts, as models indicate more favorable shear values developing with 850 mb winds increasing to 30-40 kts late in the day. Similar to last night, any breaks in the clouds will be met with fog development. However, also similar to last night, expect cloud cover to remain rather prolific keeping fog patchy in nature at the surface. Temperatures will remain muted due to cloud cover and shower activity. Temps tonight and Thursday night should only fall into the upper 60s to around 70, and then top out around 80 tomorrow. .LONG TERM...(Friday through Wednesday) Issued at 437 PM EDT WED JUL 5 2017 A weakening shortwave trough (being absorbed into the larger scale flow) will be exiting the region to the southeast as the period starts. A bit of precip may be lingering in the southeast part of the area Friday morning, but should be winding down. Another impulse flowing through and amplifying the larger scale eastern CONUS trough will support a cold front approaching from the northwest by late Friday. The front will pass through late Friday night or Saturday morning. Low level moisture will still be in place when the cold front arrives, but the mid-upper levels should be dried out. It may be a little more difficult to develop and sustain convection along the front with the drier air, but slight chance and chance POPs are still in order. Once the front moves through, high pressure building in from the northwest will provide a drier and somewhat cooler air mass through the rest of the weekend. The lower dew points will support lows in the 50s for much of the area. As the new work week starts, models begin to show more discrepancy. The ECMWF is much faster than the GFS to bring another cold front south. As a result, the ECMWF has precip returning on Monday, while the GFS has nothing until Tuesday (and minimal then). With poor model agreement, have used low POPs for a mention of precip Monday through Wednesday. && .AVIATION...(For the 00Z TAFS through 00Z Thursday evening) ISSUED AT 804 PM EDT WED JUL 5 2017 Isolated showers and thunderstorms are ongoing across portions of eastern KY this evening, and will persist into the overnight, if not increase somewhat in coverage late tonight into tomorrow morning as another wave begins moving in from the west. In the meantime, much like last night, we will have to deal with the development of llvl stratus and fog where is rain is not ongoing. Anticipate most locations dropping to LIFR or worse at some point overnight in a similar fashion to last night. Unfortunately the specifics of exact impacts and timing are still quite low confidence. Will have to see how the fog/stratus begins setting up overnight, along with showers and thunderstorms, and make updates/adjustments as needed. The stratus/fog will be slow to burn off tomorrow, but as it does, expect showers and thunderstorms to increase in coverage through the morning, becoming likely into the afternoon. These showers and thunderstorms could result in heavy downpours that temporarily reduce visibilities, as well as gusty winds. && .JKL WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...JMW SHORT TERM...ABE LONG TERM...HAL AVIATION...JMW
Area Forecast Discussion...UPDATED
National Weather Service North Platte NE
622 PM CDT Wed Jul 5 2017 .SHORT TERM...(This evening through Thursday) Issued at 336 PM CDT Wed Jul 5 2017 Latest water vapor imagery shows northwest mid-level flow aloft across the Central High Plains as a upper-level ridge builds across the western CONUS, stretching from the Four Corners region into British Columbia and Alberta. Elsewhere, a weak shortwave trough was moving across Saskatchewan into southwestern Manitoba. Latest visible satellite shows cu developing across northern NEB, NEB Panhandle, and southwest NEB. Of which, the cu field has been most enhanced over the northern Sandhills into south central NEB. Latest surface plot showed a broad surface low near eastern MT/western ND with a central pressure near 1012 mb and a weak trough extending south into the Central High Plains. Rest of this afternoon-evening: There is at least a remote risk for widely isolated thunderstorms. Best chances north of I-80 and east of NE Highway 61, albeit with low confidence. Moderate instability is expected (ranging MLCAPES 1000-2000 J/kg) across the southeastern half of the CWA based on guidance/model soundings with little-scant convective inhibition. Primary fly in the ointment revolves around low-level forcing and strength of given the uncertainty. Of which, any development is expected to diminish this evening with the loss of daytime heating. Another hot day tomorrow with most places outside of northwest NEB expected to see highs 98-101 degrees. There is a risk for isolated strong to briefly severe thunderstorms tomorrow afternoon and evening. Some uncertainty involved with respect to coverage, but isolated storms are the most likely. .LONG TERM...(Thursday night through Wednesday) Issued at 336 PM CDT Wed Jul 5 2017 Thursday night through Tuesday night...A ridge of High pressure will remain in place over the western CONUS through early next week giving us a mostly dry and warm air mass over the high plains. That being said there are some isolated chances for thunderstorms over the next several days however confidence in thunderstorm development is low for most days with the exception of Thursday evening into overnight. Although confidence is a little better for Thursday evening/overnight, timing of thunderstorm development is uncertain as models have discrepancies in timing. Some models suggest development by late afternoon and continuing through the evening hours and some suggest thunderstorm development will take place after 00z. Tending to lean more to late afternoon/evening development of storms as the main driving force for initiation will be the weak cold front that moves across Thursday late afternoon and evening in combination with strong daytime heating. After the front passes temperatures will cool slightly with highs in the mid to upper 80s Friday and Saturday. Temperatures warm back into the 90s Sunday through Tuesday. && .AVIATION...(For the 00Z TAFS through 00Z Thursday evening) Issued at 622 PM CDT Wed Jul 5 2017 The forecast uses the HRRR model but places the thunderstorms about 60 miles or so west of the model. This follows the latest radar trends which shows the thunderstorms developing southward near highway 61, versus the model which shows the storms developing in a southeast direction toward KVTN. Storm activity, if it develops, could continue for several hours, perhaps past midnight. The low level jet tonight should veer off to the east toward morning and this will cause the storms to dissipate, if not sooner. && .LBF WATCHES/WARNINGS/ADVISORIES... None. && $$ SHORT TERM...ET LONG TERM...Gomez AVIATION...CDC
Area Forecast Discussion...UPDATED
National Weather Service Twin Cities/Chanhassen MN
1101 PM CDT Wed Jul 5 2017 .UPDATE... Issued at 809 PM CDT Wed Jul 5 2017 Despite an extremely unstable airmass with uncapped SBCAPE of greater than 5000 J/kg thanks to dewpoints in the low to mid 70s, the lack of forcing has greatly limited the thunderstorm potential this evening. A developing LLJ may be enough to spark a few storms after midnight, primarily across central MN, but the best chance will be further north with a stronger short wave. Even the cu field is largely non-existent across northeast ND and northern MN this evening, but there are some hints at better development near Minot, ND and especially across southern Canada. Already reduced PoPs earlier, but will need to take them out for at least the next several hours until the developing complex well to the north spreads activity southeastward. This may not occur until Thursday morning. && .SHORT TERM...(This evening through Thursday) Issued at 332 PM CDT Wed Jul 5 2017 The short term concerns remain convective/severe potential tonight and thursday. Water vapor imagery showing the back end of upper trough exiting eastern MN at this time. Some mid cloud trying to develop along/ahead of the western fringe...but latest mesoanalysis shows decent capping remains to the east. We may yet see some redevelopment associated with this feature...but should be mainly into west central WI. Then HIRES models have continued to trend some redevelopment to the northwest cwa late this afternoon/evening. Main boundary is farther north but the RUC and water vapor imagery suggests a weak short wave moving through eastern NODAK now. This may be enough to generate at least some widely scattered convection mainly this evening to the northwest. Then the HRRR tries to develop something farther to the west as the cold front moves across North Dakota and drops that into central MN after 06z. We will trend PoPs up to high end chance for now after 06z and spread them southeast through 12z. SPC Day1 looks good for the overnight. Activity is conditional but if it does develop it would likely become severe with high cape and decent shear expected. It will definitely have to be monitored this evening. The front is progged into eastern MN by 18z THU and redevelopment is still a question...especially if we do get any outflow from overnight activity. We will continue to play the chance PoP scenario over the eastern area through the day. Expected temperatures will still warm through the lower 90s into sc MN ahead of boundary .LONG TERM...(Thursday night through Wednesday) Issued at 332 PM CDT Wed Jul 5 2017 Not much change to the extended part of the forecast. Northwest flow Thursday night will lead to subsidence and surface high pressure building in for the weekend, meaning cooler and drier air starting Friday. As of now, the best chance for showers and thunderstorms is Sunday night into Monday where the GFS/GEM/ECMWF 05.12 all depict an MCS moving across southern Minnesota into western Wisconsin. Beyond that, there will be a few additional chances for showers and thunderstorms heading into next week. Friday will have breezy northerly winds as high pressure moves into the area. Forecast soundings show a thin sliver of elevated instability, but large-scale subsidence should win out. There is a compact PV anomaly, but it should be east of the region by Friday afternoon so any pops associated with is will be across eastern Wisconsin. Saturday will be sunny with light winds and dewpoints in the upper 50s to the north and lower 60s to the south. Moisture will try to return on Sunday, which will lead to around 2000-3000 J/kg of MUCAPE by late afternoon. Deep layer shear will be around 40 to 50 kts, so should see organized storms grow upscale into a squall line that moves across the region overnight. Temperatures beyond Sunday will be near the seasonal average for mid July. A few shortwave troughs could bring showers and thunderstorms at times next week, but timing and placement of these features is unrealistic at this point in the forecast, so continued with blended model guidance which carries slight chances for showers and thunderstorms across parts of the region Tuesday and Wednesday. && .AVIATION...(For the 06Z TAFS through 06Z Thursday night) Issued at 1101 PM CDT Wed Jul 5 2017 Clear skies at taf issuance time, with increasing potential for thunderstorms overnight mainly north of I-94. More storms may develop near EAU Thursday, but it appears the best chance will be to the east across central Wisconsin. KMSP...No concerns this evening. The risk of storms overnight appears to be diminishing a bit, with the best chances north. /OUTLOOK FOR KMSP/ Fri...VFR. Wind NW at 10G15kts. Sat...VFR. Wind S at 5 kts. Sun...VFR. Wind SW 5-10 kts. && .MPX WATCHES/WARNINGS/ADVISORIES... WI...None. MN...None. && $$ UPDATE...BORGHOFF SHORT TERM...DWE LONG TERM...JRB AVIATION...BORGHOFF
Area Forecast Discussion
National Weather Service Marquette MI
718 PM EDT Wed Jul 5 2017 .SHORT TERM...(This evening through Thursday) Issued at 438 PM EDT WED JUL 5 2017 WV imagery and RAP analysis indicated a prominent mid/upper level ridge over the cntrl/srn Rockies and a srn stream trough over MO leaving mainly zonal flow through the nrn CONUS and srn Canada. Mid/high clouds leftover from the the MCS this morning remained over Upper Michigan with the more signifcant convection well to the south over srn WI where MLCAPE values were over 2k J/Kg. At the surface, ssw flow prevailed between high pres over the ern Great Lakes and a trough from west of James Bay into nw MN. This has helped push temps into the lower 80s (west half) with dewpoints in the mid 60s. Tonight, with SBCAPE values into the 1000-1500 J/Kg range this afternoon and some weak boundaries off of the Great Lakes or from differential heating near the area of clouds, some isold/ shra/tsra may develop late this afternoon into this evening. However, the short range high res models do not show any clear signals for a more signficant area of shra/tsra through most of tonight. Given the amount of instability and shear (0-6km 20-25 knots), any storms that develop may produce some gusty winds or small hail but are not expected to become svere. Thursday, shrtwvs upstream over srn Saskatchewan or srn Manitoba were relatively weak. However, as the trough moves closer and the low level jet strengthens from the ern Dakotas into MN additional areas of tsra or an MCS are likely to develop that again should slide ese toward the cwa toward daybreak. Although the shra/tsra may again weaken, expect a better chance of pcpn with the trough moving through the area and greater instability already in place. With 0- 6km shear values closer to 40 knots and MUCAPE values to at least 2k J/Kg, a few severe storms will also be possible with potential for damaging winds and small hail. If the morning convection pushes the boundary more quickly to the se the greater shra/tsra coverage and higher severe risk would be mainly over the se half. .LONG TERM...(Thursday night through Wednesday) Issued at 247 PM EDT WED JUL 5 2017 Long term guidance continues to advertise a persistent large-scale pattern of ridging across the western CONUS and a broad mid-level low over eastern Canada well into next week. With this pattern, there will be several chances for scattered showers and some thunderstorms with several weak troughs rounding the larger eastern low. Determining timing is quite difficult with this set-up, so will focus on a couple of better opportunities to see precip. Otherwise, temperatures will vary a decent bit by mid-summer standards, with the coolest conditions expected on Friday and warmest conditions expected toward the middle of next week. Thursday night into Friday: Ongoing convection is expected across mainly the central and eastern CWA at the start of the period. Some of this convection may be severe during the evening hours if initial convection in the late afternoon remains organized. The primary threat would be strong winds from organized bowing multi-cell clusters by mid-evening. Activity will quickly end from NW to SE through the night as the trough and associated surface front clear the CWA. A secondary trough shifting southward across the CWA Friday afternoon may generate a some diurnally enhanced showers in the afternoon. Though instability will be limited, low freezing levels around 8kft could support small hail in any stronger showers/isolated storms across the south-central. Saturday afternoon through Sunday evening: A stronger trough embedded in the large-scale flow will track SE across the CWA Saturday night. However, modest shear and MLCape would support strong to marginally severe storms in the afternoon and evening conditional upon development along lake breeze boundaries south- central. With limited instability outside of peak heating, only scattered showers and possibly a few thunderstorms would be expected with the trough passage Saturday night. Sunday afternoon may end up being a repeat of Saturday afternoon, mainly across the southeast half, if enough clearing occurs post-trough. Again, only modest shear and instability would be present, with any activity remaining focused to lake breezes. && .AVIATION...(For the 00Z TAFS through 00Z Thursday evening) Issued at 711 PM EDT WED JUL 5 2017 Mainly VFR conditions are expected through the forecast period. There is a chance of showers and possibly a thunderstorm late tonight into Thursday morning as a cold front approaches the area. However, confidence is too low for mention of TS in the TAF. && .MARINE...(For the 4 PM Lake Superior forecast issuance) Issued at 438 PM EDT WED JUL 5 2017 Wind conditions across the lake should remain tranquil through the forecast period with winds staying below 20 knots. With dewpoints surging into the 60s through Thursday and the prospects of scattered convection that might move out of the lake...areas of fog will likely develop and persist through much of Thursday. && .MQT WATCHES/WARNINGS/ADVISORIES... Upper Michigan... None. Lake Superior... None. Lake Michigan... None. && $$ SHORT TERM...JLB LONG TERM...Kluber AVIATION...Voss MARINE...JLB
Area Forecast Discussion
National Weather Service Paducah KY
1023 PM CDT Wed Jul 5 2017 .UPDATE... Issued at 1023 PM CDT Wed Jul 5 2017 Made some PoP/Weather adjustments to reflect ongoing convective activity over the southern Pennyrile, as main core of MCV/bookend mesocyclone will move along and just south of KHPX before 345z. RAP guidance within tolerance, but lowered rain chances across most of the WFO PAH foreast area for the remainder of tonight. May still be too high, as 12z Canadian, 12z NAM-WRF (NMM), and 12z ECMWF suggest some ridging/capping east-southeast of low over central Missouri this evening. Main convection will be focused just ahead of the closed low in Missouri (into Southeast Missouri) and departing from the southern Pennyrile for the rest of tonight. Kept a thin strip of higher PoPs oriented southwest to northeast, mainly over the West Kentucky Pennyrile region to reflect some enhanced precipitation chances with a narrow deformation zone later tonight, otherwise kept overall rain chances lower across the WFO PAH forecast area. UPDATE Updated aviation section for 00z taf issuance && .SHORT TERM...(Tonight through Friday night) Issued at 215 PM CDT Wed Jul 5 2017 Upper Low/trof drifting across area is trigger for tapping high theta/unstable air...though weakly sheared trop with minimal winds aloft resulting only in gusts 20-30 mph. Main impact is locally heavy rainfall and lightning, and this will continue to be the case until the Low/trof drifts completely out of the area. Will keep model/blended Pops, which are reasonably high, until then. Afterward, models still try to bring a cold front across/make passage Friday afternoon/evening, and that offers our next (marginal) risk of strong storms. Otherwise it`s locally heavy rain/lightning as the continuing impact wx, including Friday. The cold front`s passage will offer welcomed change for the weekend/beginning of the long term portion of the forecast. .LONG TERM...(Saturday through Wednesday) Issued at 215 PM CDT Wed Jul 5 2017 To start out the weekend, most of the area should be dry as high pressure builds in behind the aforementioned cold fropa. If any location has a very small chance for any lingering precipitation, it would be extreme southern parts of the area on the AR/TN borders. We should see a small cooldown for Saturday behind a front that passes through Friday/Friday night. This will be noticed most in our northeastern counties or the Evansville Tri State region, where 850mb temperatures drop down into the lower teens vs the upper teens we have seen recently. This should mean high temperatures in the mid 80s up there. However, very little change in temperatures will occur farther southwest into southeast MO, far west KY and southwest IL, where highs on Saturday will only drop into the upper 80s. But there will be a drop in humidity area wide, as dew points fall back into the low to mid 60s. Winds will be northerly on Saturday but quickly shift back to southerly by Sunday as the weak high pressure system moves east. This will mean that more humid weather will evnetually return. We will see highs on Sunday in the mid to upper 80s and mainly upper 80s for early next week. Dew points will rise back into the upper 60s to around 70 degrees by the end of the day Sunday, but rain chances do look minimal for now. However, daily chances for mainly afternoon storms still looks on target with this increase in moisture. Models are not in great agreement on synoptics or even the timing and strength of any upper level energy. Therefore, it would be wise to keep POPs low/minimal at this juncture. && .AVIATION... Issued at 615 PM CDT Wed Jul 5 2017 Primary aviation concerns are the potential for low stratus clouds later tonight into early Thursday, then possible thunderstorms on Thursday. A very humid atmosphere will promote the development of low clouds tonight. Winds will become nearly calm late tonight as a surface low pressure center weakens into an open trough of low pressure over our region. The light winds and high moisture will be conducive for areas of ifr conditions, especially during the early morning hours. On Thursday, cloud heights will tend to rise by midday as solar heating begins. However, cigs will be slow to improve to vfr. Some thunderstorms may develop along the weakened trough of low pressure during the midday and afternoon. Mention of vcts was included in most tafs. && .PAH WATCHES/WARNINGS/ADVISORIES... IL...None. MO...None. IN...None. KY...None. && $$ UPDATE...Smith AVIATION...MY
Area Forecast Discussion
National Weather Service Shreveport LA
920 PM CDT Wed Jul 5 2017 .UPDATE... Difficult update this evening as several variables coming into play for renewed convective development overnight with the million dollar question being exactly where. KSHV WSR-88D radar trends over the last hour has been for some isolated shower/thunderstorm development mainly south of the I-20 Corridor across portions of Deep East Texas into West Central Louisiana. GOES-16 FOG [10.3-3.9um] Imagery showing this slightly elevated cu field growing in coverage and intensity as far north as the I-20 Corridor of NE TX into NW LA as well. Several surface boundaries remain in this general region from earlier daytime convection as well. Looking to our west, consistent scattered convection across N Central TX has a history of excessive, flood producing rainfall is beginning to move eastward now after being nearly stationary across Tarrant County, Tx earlier. Latest HRRR and new 00z NAM output is honing in on renewed convective development along and north of the I-20 Corridor overnight, or in the vicinity of the 500mb trough axis with only isolated convection where we are currently seeing renewed development south of the corridor. Forecast for the most part is in good shape but did reorganize pops somewhat trending pops higher across our northern zones through the remainder of the overnight hours. Also adjusted sky cover slightly to mimic current and expected overnight trends. Temps and all other grids are in good shape so no changes needed elsewhere. Updated zone package out shortly...13. && .PREV DISCUSSION... /issued 830 PM CDT Wed Jul 5 2017/ AVIATION... For the 06/00Z terminal forecast, VFR will prevail until around 06/07Z-06/10Z when MVFR flight categories will return with lower clouds developing and spreading across the area. A convective complex may develop and help with scattered showers and thunderstorms after 06/06Z and additional development with residual outflow boundaries in the early morning around 06/11Z-06/15Z. Could see a lowering to IFR over parts of Deep East Texas affecting KLFK between 06/10Z-06/14Z. VFR flight categories will be returning in the mid to late morning hours. Surface winds will be light and variable to light South overnight becoming South to Southwest during the early morning 5-10 knots with a shift to the west during the mid morning to early afternoon Thursday. /06/ && .PRELIMINARY POINT TEMPS/POPS... SHV 76 91 75 92 / 30 30 20 20 MLU 76 92 75 92 / 20 30 30 30 DEQ 70 89 70 92 / 40 20 10 10 TXK 74 88 73 90 / 40 30 10 20 ELD 73 88 73 91 / 40 30 20 30 TYR 76 90 75 91 / 30 20 20 20 GGG 75 90 74 91 / 30 30 20 20 LFK 74 94 74 93 / 20 30 20 30 && .SHV WATCHES/WARNINGS/ADVISORIES... AR...None. LA...None. OK...None. TX...None. && $$ 06/13