Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 09/22/17


See below for an aviation forecast discussion for the 00Z TAFs.

&& .SHORT TERM...(This Evening through Friday Afternoon) Issued at 336 PM CDT Thu Sep 21 2017 High pressure has now slid well off to the east, with low pressure centered over Colorado, with a boundary extending from it northward over western South Dakota. This boundary will push very slowly eastward tonight to becoming situated from northwest Minnesota to south central South Dakota. Instability looks to increase across the far eastern CWA and into Minnesota later this evening into the overnight hours, along with a developing 45-55 knot LLJ. May see some strong thunderstorms develop at this intersection, mainly over the far northeastern CWA around or after midnight. Quiet conditions are expected during the daytime hours on Friday as the LLJ diminishes and the shear weakens. Will see a decent temperature gradient both tonight and Friday, with much cooler air behind the front. Lows tonight will range from the upper 40s over north central South Dakota, to the upper 60s over east central Minnesota. High temperatures on Friday will range from the upper 50s over north central South Dakota, to the upper 80s over northeastern South Dakota and west central Minnesota. .LONG TERM...(Friday Evening through Thursday) Issued at 336 PM CDT Thu Sep 21 2017 Fairly good agreement over the long term pattern which features a western CONUS upper low/trough and an eastern CONUS ridge. This puts us in southwest flow aloft with several distinct waves lifting into or just southeast of the CWA before the upper low opens and lifts over the area Monday. In the low levels at the start of the period we should be on the northwest side of the surface trough. That means each wave will generate generally overrunning precipitation so have minimized the mention of thunder for the most part, outside the initial round of severe weather that develops friday night. 850mb temperatures remain between +6 and +14C for the extended, so high temperatures will be stuck in the 50s and 60s for the next few days. There does looks like, with high pressure overhead and despite a trough overhead, no waves passing through, that we will see ideal radiational conditions Wednesday morning. Thus, lowered temperatures a notch below blended guidance. Otherwise no significant changes over blended guidance within the extended. && .AVIATION...(For the 00Z TAFS through 00Z Friday Evening) Issued at 631 PM CDT Thu Sep 21 2017 VFR conditions expected to persist into the overnight hours before the potential for sub-vfr stratus (perhaps even some areas of fog) sets up. Remarkably high dewpoint air exists at the surface from the James River valley eastward into MN. Once the surface trof/cold front begins to slow down over central/northeast South Dakota tonight and surface low pressure begins to deepen along it, the potential for low level saturation really ramps up, per the latest RAP Refresh output. For now, have introduced a low cloud deck at all four terminals late tonight/early Friday morning. There is also the potential for isolated/scattered elevated thunderstorms tonight at or after 06Z which may travel over/near the KATY (lesser chance at KABR) terminal before convective potential refocuses east into MN Friday morning. Low level wind shear potential exists tonight, as well, at the KATY terminal, where the nose of the low level jet will be focused. && .ABR WATCHES/WARNINGS/ADVISORIES... SD...None. MN...None. && $$ UPDATE...Dorn SHORT TERM...Parkin LONG TERM...Connelly AVIATION...Dorn
Area Forecast Discussion
National Weather Service Bismarck ND
1019 PM CDT Thu Sep 21 2017 .UPDATE... Issued at 1012 PM CDT Thu Sep 21 2017 CAMs pushed up the timing of possible convection closer to 12Z so POPs were adjusted for this. SREF t-storm probs continue to depict thunderstorm potential increasing after 09Z across southern ND then expanding northward with time. Shear profiles within the elevated instability ranges from 50-65Kts. Would not be surprised to see a few stronger storms near warning-worthy given all the ingredients in place. Time will tell. Products were updated to increase the t-storm potential wording. UPDATE Issued at 705 PM CDT Thu Sep 21 2017 Forecast through this evening remains on track. For the overnight period (after midnight), models are showing a band of precipitation forming across southwest and south central ND 9-12Z as a ribbon of instability lifts north along the frontogensis zone north of the surface low across SD. Modified POPs to better reflect this. SREF thunderstorm probs start to ramp up as well after 09Z and remains rather high through the day Friday. Coupled with SPC having the entire state in at least the general t-storm outlook, I spread isold thunder across the board Fri aft. Will take a closer look at the nocturnal showers as I may need a mention of thunder as early as 9-12Z if model MUCAPE projections are accurate. ESRL HRRR and NAMNest also trigger convection early Friday morning. The ESRL HRRR as early as 1145Z and the NAMNest 14Z. Right now I have isold thunder in the forecast starting at 15Z for the southwest and south central. && .SHORT TERM...(This evening through Friday) Issued at 307 PM CDT Thu Sep 21 2017 An upper level trough over the western U.S. into southern Canada will influence the weather over the northern plains over the next several days. Tonight, jet energy propagating through broad southwest upper flow will continue to produce an area of light showers/virga extending from south central MT into northwest and far north central ND. Associated surface low pressure from central North Dakota into southwest South Dakota will push slowly east. Strong southerly winds over the James River Valley, ahead of the surface trough, will diminish late this afternoon and evening. Capping over this same region is expected to inhibit any afternoon/evening convection despite a moderately unstable atmosphere. Moderate to strong 700-500mb frontogenesis develops tonight over a good portion of central and northwest ND north of the surface trough. Although synoptic scale forcing is not strong, it does persist over this same area. Global models have been persistent the last couple of runs in developing a band of light precipitation over western and central ND late tonight into friday morning, which is handled well with the current forecast. Continued surface and mid level forcing along the surface front, combined with upper level divergence over the region, will support an area of thunderstorms Friday, but most likely just to the south and east of the forecast area. Although we will need to monitor the southern James river valley for possible thunderstorm activity in case there is some north and/or westward shift to the surface boundary. Most of the CWA will be cooler on Friday (50s and 60s) but the southern James River Valley could see some readings near 80. .LONG TERM...(Friday night through Thursday) Issued at 307 PM CDT Thu Sep 21 2017 Cool and showery weather remains through the upcoming weekend and into early next week. Highs mainly in the 50s and lows generally in the upper 30s to mid 40s. Substantial cloud cover should inhibit any widespread frost, but will certainly have to monitor the western half of ND in case we would happen to clear out more than expected. Precipitation chance wane as we head into the middle of next week but we remain at or below seasonable normals. && .AVIATION...(For the 00Z TAFS through 00Z Friday evening) Issued at 705 PM CDT Thu Sep 21 2017 MVFR ceilings will lift northward into North Dakota after 12Z Friday bringing MVFR ceilings to KJMS and KBIS by 15-18Z. MFVR ceilings will also be possible for KDIK and KMOT after 18Z. && .BIS WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...NH SHORT TERM...TWH LONG TERM...TWH AVIATION...NH
Area Forecast Discussion...UPDATED
National Weather Service Cheyenne WY
729 PM MDT Thu Sep 21 2017 .UPDATE... Issued at 729 PM MDT Thu Sep 21 2017 Winds are dropping off as the boundary layer decouples most locations. With diminishing winds and humidity rising with cooler temps, have allowed the Red Flag Warning to expire on time. No other changes at this time. && .SHORT TERM...(This evening through Saturday) Issued at 248 PM MDT Thu Sep 21 2017 Main forecast concern through the aftn will continue to be the critical fire weather conditions across lower elevations of southeast Wyoming. Deep southwesterly flow and very dry midlvls is causing dewpoints to drop well below the consensus guidance, with the HRRR really the model to capture the very low RH values (8-12 percent). The Red Flag Warning is in good shape with even some extreme Red Flag conditions to the west of the Laramie Range where gusts to 30-40 kt are occurring. Highly amplified upper trough will remain rather stationary on Friday with the axis across the Great Basin. Temps will be around 10-15 degrees cooler on Friday over the CWA, ending fire weather concerns. With increasing large scale ascent ahead of the trough during the aftn/evening, scattered showers and isolated thunder will be possible over mainly southeast Wyoming. The models continue to show excellent upper level divergence and overrunning over the llvl front by Saturday afternoon/evening. Raised PoPs to above 60 percent on Saturday aftn with the good model agreement. Wet bulb zero heights through 00Z Sunday stay mostly above 11000-11500 ft, so only the higher peaks of the Sierra Madre and Snowy Ranges will see any chance of snow through 00Z Sunday. .LONG TERM...(Saturday night through Thursday) Issued at 248 PM MDT Thu Sep 21 2017 Closed mid/upper level low will be located over southern Utah early Saturday night. To the east a broad area of upper diffluence combined with a low level frontal zone over our Panhandle counties will contribute to widespread moderate rainfall especially over the plains. Best forcing for ascent will push north and east of the area by Sunday morning with some drying aloft noted on forecast soundings. With the low level NE flow and weak overrunning, Sunday should be a cloudy and cool day with little temperature recovery continued the trend of undercutting MOS guidance a bit. Models have come into a bit more agreement in the mid level low weakening and moving to the north and east directly over central Wyoming Sunday night through Monday. This track is not typically a good one for low elevation snow in SE Wyoming. Models have continued the trend of keeping the colder air at bay to the west until the precipitation rates begin tapering off late Sunday night and Monday morning. So while a period of accumulating snowfall in much of the Snowy and Sierra Madre ranges is likely Sunday into Sunday night, accumulating snowfall in the lower elevation is becoming less likely. Still expect some rain/snow mix or maybe a brief period of all snow for the higher valleys west of the Laramie Range late Sunday night into early Monday morning but the steadier precipitation should be ending by that time and boundary layer temperatures would be marginal for much accumulation. Tuesday through Thursday look basically dry and seasonable as the upper trough pushes east and some ridging rebuilds along the west coast. && .AVIATION...(For the 00Z TAFS through 00Z Friday evening) Issued at 729 PM MDT Thu Sep 21 2017 VFR expected overnight with winds dropping off to less than 20 kts most spots with the exception of the usual late dropoff at Rawlins and the overnight increase we have been seeing the past several nights at Chadron where gusts around 25 kts will continue well into the late evening. We brought in some vicinity mention for Rawlins tomorrow afternoon for showers as the southwesterly upper flow moistens across the western zones. && .FIRE WEATHER... Issued at 248 PM MDT Thu Sep 21 2017 It will continue to be a warm, very dry, and breezy afternoon over much of southeast Wyoming. A Red Flag Warning remains in effect through the early evening for Fire Weather Zones 304, 306, 308, 309, and 310. Fire weather concerns will be minimal after this afternoon. Cooler temperatures on Friday will cause RH values to stay mostly above 25 percent. It will turn much cooler over the weekend with good chances for widespread precipitation. && .CYS WATCHES/WARNINGS/ADVISORIES... WY...None. NE...None. && $$ UPDATE...JG SHORT TERM...ZF LONG TERM...DEL AVIATION...JG FIRE WEATHER...ZF
Area Forecast Discussion
National Weather Service Grand Forks ND
717 PM CDT Thu Sep 21 2017 .UPDATE... Issued at 712 PM CDT Thu Sep 21 2017 HRRR had indicated a few cells developing in NW MN at 00z... and there was one shower nr Waskisk that formed nr 23z. Otherwise have considerable high based stratocu in warm advection zone over the fcst area. Quite strong low level moisture push early this evening with 60 dew pts into Fargo and 70 dew pt into Elbow Lake. For Fargo this is a good 15 deg rise in the last few hours. Actual frontal boundary east of Langdon to Crary ND to Carrington and moving southeast. Low level moisture will stream northward ahead of this boundary. Low level jet cranks up 06z-09z period with nose of the jet into WC/C MN. HRRR indicates some thunderstorms in far NE SD into WC MN 08z time period...moving quickly ENE. This conforms to the fcst for now so will not change. && .SHORT TERM...(This evening through Friday) Issued at 330 PM CDT Thu Sep 21 2017 A couple areas to watch for potential pcpn tonight. One area will be mainly over northwest minnesota early this evening in zone of enhanced warm advection ahead of approaching surface boundary which will reach the northwest by early evening. Appears to be a weak impulse from water vapor over sw ND which may also assist in upper support. Convective parameters weak so may be mainly shra vs T. Of more concern will be later tonight initially over the far south spreading e-ne during the early morning. During mid- late evening a low level jet will strengthen with favored convergence vcnty tri-state border region. This area will also be under zone of maximized warm advection. Capping may initially retard development however cap weakens during the late evening. Although storms will be elevated cannot rule out a few storms reaching severe limits. Minimum temperatures will remain mild overnight over all but the far nw with thermal ridge axis in place, warm advection and low level moisture flux. On Friday, the frontal boundary will drift to a BDE-ABR line. As a mid level impulse lifts northeast during the day an associated surface low will propagate ne along the front reaching the tri- state border region by evening. Unsure at this time how much convection will be occuring during the day. Current guidance hinting that most pcpn during the day will be on the cold side of the boundary. By late afternoon with approaching wave convection should initiate vcnty boundary. Convective parameters sufficient for severe storms and with approaching surface low/triple point over the far s/se cannot rule out a tornado. .LONG TERM...(Friday night through Thursday) Issued at 330 PM CDT Thu Sep 21 2017 Storms which develop Friday afternoon should propagate e-ne through the evening as the surface low continues to lift along boundary. With front nearly stationary and precipitable h2o values of 1.5 inches or greater will have to watch for heavy rainers in addition to severe. On Saturday/Saturday night boundary sags to the far s-e forecast area. Another surface low and upper wave will lift northeast bringing a continue threat for rain mainly over the southeast half of the fa. The upper level low centered around the four corners region will keep the Dakotas largely in southwest flow aloft continuing to draw moisture up from the south. Mid level waves of energy will ride within the southwest flow over the region utilizing the available moisture. In the low levels, a southwest-northeast oriented stalled front draped over Minnesota will serve as a focal point for moisture to overrun upon. Steady rainfall will be possible for west- central and northwestern Minnesota as well as within southeastern North Dakota Sunday with a gradual tapering off of rainfall chances from north to south Monday. The upper level low is then progged to shift eastward over the region bringing another wave of energy over the area towards Tuesday, although moisture return will not be as great as Sunday`s forecast. Conditions finally start to dry around Wednesday into Thursday as a high pressure builds into the region. With the forecast area expected to remain on the northern side of this front along with northerly flow, cool and cloudy conditions are expected through at least Tuesday with highs remaining largely in the 50s. Somewhat milder temperatures return Wednesday and Thursday. && .AVIATION...(For the 00Z TAFS through 00Z Friday evening) Issued at 712 PM CDT Thu Sep 21 2017 Issue this period is wind shift with cold front sagging southeast...and development of likely low clouds overnight into early Saturday ahead of front into Fargo-Bemidji eastward. && .FGF WATCHES/WARNINGS/ADVISORIES... ND...None. MN...None. && $$ UPDATE...Riddle SHORT TERM...Voelker LONG TERM...CJ/JK/Voelker AVIATION...Riddle
Area Forecast Discussion
National Weather Service Green Bay WI
1059 PM CDT Thu Sep 21 2017 Updated aviation portion for 06Z TAF issuance .UPDATE... Issued at 932 PM CDT Thu Sep 21 2017 Updated forecast grids to include widespread dense fog over the east, lake and bay. This matches the dense fog/marine dense fog advisory areas. Also downplayed the PoPs for at least the next several hours. && .SHORT TERM...Tonight and Friday Issued at 258 PM CDT Thu Sep 21 2017 A warm front was lifting into southern MN and southwest WI this afternoon. A band of low clouds was persisting north of this boundary, and moving northward through GRB CWA. Temperatures were in the low to mid 70s within the cloud band, but in the upper 70s to lower 80s where there was sunshine. Despite SBCAPE of 1000-1500 j/kg across the region, CINH of 75-100 j/kg was capping off any convection. The warm front is expected to lift north across the region tonight and Friday morning. The front, combined with a developing 30-35 kt low-level jet, should trigger isolated elevated thunderstorms north of the boundary, as H8 LI`s of -3 to -5 C advect into the region. Storms may be a bit more numerous over north central WI, as some weak short-wave energy and the RRQ of 50-60 kt jet brush past later tonight. SPC still has a small part of north central WI in the Marginal risk for severe storms tonight, and this seems reasonable, as deep-layer shear is strongest there (around 30 kts). Have added patchy fog across most of the region overnight, with areas of fog in far northeast WI and on Lake Michigan, where marine fog is already occurring. The warm front will lift into the Upper Peninsula of Michigan on Friday, ending the threat of thunderstorms. The resulting clearing and gusty southwest winds will lead to strong heating, with mixing through 900-875 mb supporting high temperatures in the middle 80s to lower 90s, much above normal. .LONG TERM...Friday Night Through Thursday Issued at 258 PM CDT Thu Sep 21 2017 An amplified pattern will be in place for the conus until early next week, thanks to a deep trough over the western U.S., and a ridge over the east. The pattern does translate east, which will signal a pattern change by the middle of next week across the region. Although there are some timing differences in regards to when this pattern change occurs, models are generally in good agreement this far out, so will continue to use a multi model blend for this forecast. Friday night through Sunday...With a cold front nearly stationary over Minnesota, and a warm front extending east over Lake Superior, the entire region is expected to be located in the warm sector during this period. With mostly clear conditions and a breezy south wind, temperatures will likely range from 15 to 20 degrees above normal. Saturday should be warmer than Sunday, when a few 90s are possible in the warm spots. Heat indices in the low to mid 90s on Saturday will fall back to the upper 80s on Sunday. Rest of the forecast...Sunday night continues to look quiet and warm. Then precip chances will gradually increase from west to east on Monday and Tuesday when a cold front drifts closer to the region. Storm chances look the highest on Tuesday along this front, but its too early to assess a severe threat. More seasonable temps return behind the front for midweek. && .AVIATION...for 06Z TAF Issuance Issued at 1059 PM CDT Thu Sep 21 2017 Plenty of issues just in the short term make this a low confidence forecast. Rain that most of the synoptic scale models had reaching the area by 06Z at the latest, has not yet developed. HRRR had a few specs in central/north central Wisconsin on the simulated reflectivity product, but just for a couple of hours and then nothing moves in until around 14Z when showers and storms reach Vilas County. In the mean time mostly clear skies prevailed, but dew points were well into the 60s and it will not take much for temperatures to drop enough for fog development. IFR/LIFR conditions in dense fog prevailed close to Lake Michigan and the fog could advect farther inland overnight. Will go with mostly MVFR and/or IFR conditions in fog at most locations overnight. Some low ceilings may also develop. Plan to bring showers and storms in during the morning and continue them east into the afternoon. && .GRB WATCHES/WARNINGS/ADVISORIES... Dense Fog Advisory until 10 AM CDT Friday for WIZ022-040-050. && $$ UPDATE.........MG SHORT TERM.....Kieckbusch LONG TERM......MPC AVIATION.......MG
Area Forecast Discussion
National Weather Service San Joaquin Valley - Hanford CA
230 PM PDT Thu Sep 21 2017 .SYNOPSIS...Scattered showers will continue over the mountains through this evening as an upper trough to our east keeps unsettled conditions over the area. Winds will also be strong and gusty through and below the mountain passes into this evening. Temperatures will be cooler than normal across the area through the upcoming weekend as the trough remains over the Great Basin. A slow warming trend will take next week as highs pressure slowly builds inland into the region. && .DISCUSSION...Cold front pushed through central CA earlier today and brought widespread precipitation to our area overnight and this morning. Several locations in the Southern Sierra Nevada picked up between half and inch to an inch of rainfall with a few locations in and near Yosemite Park picking up over an inch of rain. The precipitation mainly fell as snow above 11000 feet, but the snow level lowered to 7000 feet by daybreak in the cooler post-frontal airmass. In the San Joaquin Valley a few locations measured close to 0.40 inches, but most locations picked up a tenth of an inch or less. Although the front has now moved out of our area, radar composites are indicating scattered instability showers have developed over the Southern Sierra Nevada this afternoon. Isolated thunderstorms will also be possible in the Yosemite Park area as the HRRR is showing CAPE and instability are sufficient for thunderstorm development today. The main concern through through this evening will be strong winds over the ridge tops and below the passes in the Kern County Mountains and Deserts where gusts up to 75 mph will be possible through this evening. A High Wind Warning remains in effect for these area through 1100 pm PDT this evening. Breezy conditions are also expected along the I-5 corridor and below the passes along the west side of the San Joaquin Valley through this evening as well and a Wind Advisory remain in effect until 1100 pm PDT for the west side of the San Joaquin Valley. WRF indicating a deep upper trough will remain situated over the Great Basin tonight through Satruday with a cyclonic flow aloft prevailing over Central CA through Friday Night. This will result in much below normal temperatures across our area on Friday. Other than some upslope clouds on the valley facing slopes of the mountains skies should be mostly clear on Friday. There will be a slight chance of afternoon and early evening showers over the Southern Sierra Nevada on Friday as instability remains sufficient. An upper ridge will begin to push inland on Saturday and bring about a slow warming trend across our area over the weekend. However temperatures will remain below seasonal normals as a cool northerly flow prevails over Central CA as we remain situated in between the trough over the Great Basin and the ridge off the CA coast. The medium range models are in good agreement with the ridge building inland next week as the the trough finally moves east toward the central CONUS. Rises in heights and thicknesses will result in a warming trend with temepratures rising to above normal levels by next Tuesday and continuing to rise through the remainder of next week. High temperatures in the San Joaquin Valley, lower foothills and the Kern county desert will be in the 90s during the second half of next week while the nights will be relatively cool (mid 50s to mid 60s). RH progs are indicating no signs of significant moisture impacting our area next week and as a result a dry forecast will remain in place. && .AVIATION...Scattered showers will produce areas of MVFR and local terrain obscurations over the southern Sierra Nevada through 03Z Friday, while lingering upslope clouds will persist along north and west facing slopes of the Kern County Mountains through 12Z Friday. Winds will gust near 35 knots along the west side of the San Joaquin Valley and near 50 knots over the Kern County mountains and deserts through 06Z Friday. Areas of MVFR and local IFR visibilities will be possible in blowing dust from the gusty winds. VFR conditions are otherwise expected over the Central CA interior during the next 24 hours. && .AIR QUALITY ISSUES...None. && .CERTAINTY... The level of certainty for days 1 and 2 is medium. The level of certainty for days 3 through 7 is medium. Certainty levels include low...medium...and high. Please visit www.weather.gov/hnx/certainty.php for additional information an/or to provide feedback. && .HNX Watches/Warnings/Advisories... High Wind Warning until 11 PM PDT this evening ABOVE 1500 FEET FOR CAZ095-098-099. Wind Advisory until 11 PM PDT this evening CAZ089-091. && $$ public...DS avn/fw...Bean synopsis...DS weather.gov/hanford
Area Forecast Discussion...UPDATED
National Weather Service Jackson MS
907 PM CDT Thu Sep 21 2017 .UPDATE... Updated for evening discussion. && .DISCUSSION... Extended pops in the Golden Triangle area for another hour as showers continue to slowly dissipate in that area currently. Otherwise, the 00z sounding showed a decrease in precipitable water and so do not expect fog to be as widespread as past mornings. /10/ Prior discussion below: SHORT TERM...Tonight through Friday... Latest RAP satellite imagery showed the area showed the region under an upper ridge which extended through the Lower Mississippi Valley as well as under a shear axis over the southern areas which extended from an upper trough over the eastern seaboard. Also a weak shortwave was pushing across the region from the east. This combined with some cooling aloft and some low level moisture had triggered isolated showers and thunderstorms across the south. With 6-7c lapse rates we may see a few strong storms with some gusty winds for the remainder of the afternoon. Expect the weak shortwave to exit the region by late tonight. The isolated showers should dissipate by 00z. For later tonight expecting another round of patchy fog prior to dawn across the northwest delta and the south which will lift by 14z. Another weak shortwave will push through on Friday. Return flow ahead of this feature will trigger isolated to scattered showers and thunderstorms mainly during the afternoon. Lapse rates look a little weaker as far as strong strong potential is concern. As far as temperatures are concern readings will continue to be above normal. Lows will be in the upper 60s to lower 70s. Highs will be in the lower 90s. Heat indices will range from the middle to upper 90s./17/ Friday night through mid week next week... Not much change in the forecast is expected over the next several days as temperatures in the region will remain above their late September averages under a humid airmass. The chances of diurnal thunderstorm activity will also be present each day during the period. There will only be slight changes in the upper level pattern over the weekend with the deep troughing over the western CONUS and ridging over the east. A broad, weak upper low will begin to develop underneath the ridge, becoming centered over the northern Gulf Coast by Sunday. At the surface, the ArkLaMiss will remain on the western periphery of a broad surface high that will encompass the eastern half of the CONUS. Pwats will range between 1.3"- 1.9" through the period. Long term models suggest a front will finally sweep through region late next week bringing with it organized chances of rain/storms and cooler temperatures in its wake. && .AVIATION... 00Z TAF discussion: Vcty SHRAs were noted at GLH at 2315Z and a few SHRAs wl come in vcty of GTR before dissipating by 01Z. VFR conds wl prevail at most sites tonight. The exception wl be in the south where MVFR vsbys wl be psbl 10Z-13Z. After 13Z VFR conds are expected to prevail Fri until around 20Z when isold TSRA activity may come in vcty of cntrl and s TAF sites. /22/ && .PRELIMINARY POINT TEMPS/POPS... Jackson 70 93 70 89 / 7 32 12 18 Meridian 70 92 69 89 / 10 34 16 18 Vicksburg 71 92 70 91 / 4 24 9 17 Hattiesburg 69 92 69 89 / 7 33 18 21 Natchez 71 92 69 89 / 5 31 13 18 Greenville 70 93 70 91 / 3 9 4 17 Greenwood 70 93 70 90 / 7 11 4 17 && .JAN WATCHES/WARNINGS/ADVISORIES... MS...None. LA...None. AR...None. && $$
Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
918 PM CDT Thu Sep 21 2017 .UPDATE... 918 PM CDT Going forecast largely on track with just some mainly cosmetic changes. Did nudge temps up just a hair tomorrow. Forecast thermal profiles tomorrow are actually similar, to if not a hair warmer than, today. Cloud cover won`t be an issue over western CWA tomorrow, so look for highs several degrees warmer than today. Eastern half of the area, including Chicago area should see temps similar to Thursday if not a degree or so warmer. Afternoon lake breeze should provide some cooling near the lake in the afternoon, but highs away from the lake should climb into the mid 90s, likely breaking another record and tallying up another day in the ongoing streak of consecutive 90 degree days. - Izzi && .SHORT TERM... 224 PM CDT Through Friday... Late September heat remains the main focus of the forecast in the near term. New record high temp already set today at O`Hare with a 94 degree reading there. Midwest remains along the periphery of highly amplified upper level ridge axis, downstream of a deep long wave trough across western NOAM. 12Z RAOB from DVN indicated 850 mb temp of +20C, and a 925 mb temp of +26C, resulting in low-mid 90 degree temps across the region. Residual high cloud cover from decaying MCS over southeast IA/northeast MO has kept temps slightly lower across western parts of the cwa, though a decrease in the denser cirrus has temps approaching 90 there as well this afternoon. Of course the weak surface pressure gradient in the vicinity of the stationary front just north of the cwa has allowed a lake breeze to push inland across far northeastern IL, keeping temps in the mid-upper 80`s for areas near the lake. Recent runs of the HRRR indicate the potential for isolated thunderstorm development across mainly the southern parts of the cwa late this afternoon. Experimental ESRL HRRR also hints at this though with much lower coverage. It appears these models may be focusing on a remnant MCV from the IA/MO convection, though no distinct circulation is noted in water vapor imagery. While current RAP mesoanalysis depicts 3000 J/kg of MLCAPE and little cin across the southern tier of cwa counties, weak flow and fairly shallow cu field per GOES-16 vis imagery suggests these models may be quite overdone with thunderstorm potential. Maintained less than 20 percent pops through sunset, but may have to add an isolated mention if cu field becomes more impressive or something pops. Another mild night is in store for the region with persistent light south winds and unseasonably high dew points. Overnight mins should remain in the 70`s in most locations, which will also give a warm head start for temps on Friday. Less cloud cover and similar low level thermal field should allow highs in the low 90`s in most spots again Friday afternoon, again at or near record levels for September 22nd. (records for tomorrow are 92 for Chicago, 93 for Rockford) Weak southeasterly lake breeze should again keep temps in the 80`s right along the lake. Ratzer && .LONG TERM... Friday night through Thursday... 218 pm...The models continue to show slight thermal cooling this weekend but this will likely have little if any noticeable affects as overnight lows remain in the 60s...low 70s downtown...and highs in the upper 80s/near 90 Saturday/Sunday. Bumped temps up a few degrees to near current guidance values. Lake breezes are possible both days which will keep the immediate lakeshore areas cooler but confidence is low regarding how strong these lake breezes may be and how far inland they will move. Forecast highs are cooler near the lake but trends will need to be monitored as these time periods approach. Highs may still reach the upper 80s before temps cool and winds shift off the lake. There is still some potential that the models are cooling the airmass too fast and if that were to occur...highs could still be a few degrees warmer than currently expected this weekend. However by early next week it does appear that the entire airmass will cool enough for highs to remain in the 80s. Additional cloud cover...perhaps a more broken afternoon cu field...may also help put a lid on high temps...keeping them in the 80s. A cold front will move across the area Tuesday night into Wednesday next week. While an isolated shower is possible any afternoon from Sunday onward next week...this front will be the next best chance of rain for the entire area. However...not confident on how widespread precip will become and its possible just scattered precip in a narrow time window moves across the area ahead of the front. Though a slower front...that arrives later into Wednesday could allow for more daytime heating and thus better precip coverage. This front will allow much cooler air to spread across the area with highs back into the 70s. A second push of colder air is possible late next week. cms && .AVIATION... For the 00Z TAFs... Lake breeze came close to ORD, but has begun to retreat and no longer poses much of a threat of making it through this evening. Will probably be another lake breeze tomorrow, but opting to go with persistence for now and not include a wind shift at the terminals. Otherwise, other than possibly some patchy ground fog/MVFR VSBY at DPA early Friday morning, not anticipating any significant weather at the terminals through this TAF cycle. - Izzi && .MARINE... 218 pm...A weak cold front has stalled over south/central portions of Lake Michigan this afternoon. This front will lift back north as a warm front tonight...shifting light winds back southerly. A large trough of low pressure will remain nearly stationary over the plains through early next week maintaining southerly winds over the lake. This trough/front will move across the Great Lakes region Tuesday night into Wednesday shifting winds northwest with a period of 15-25 kts expected. cms && .LOT WATCHES/WARNINGS/ADVISORIES... IL...None. IN...None. LM...None. && $$ VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE) FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT: WWW.FACEBOOK.COM/NWSCHICAGO WWW.TWITTER.COM/NWSCHICAGO WWW.YOUTUBE.COM/NWSCHICAGO
Area Forecast Discussion
National Weather Service Midland/Odessa TX
600 PM CDT Thu Sep 21 2017 .AVIATION... 00Z TAF issuance Convection across the area will diminish over the next hour. VFR conditions will prevail through most of tonight before low cigs move in across the Permian Basin. Have included FM groups and tempos for MVFR and IFR conditions everywhere except KCNM and KFST. VFR conditions will return late Friday morning along the gusty southeast winds. && .PREV DISCUSSION... /issued 204 PM CDT Thu Sep 21 2017/ DISCUSSION... Mid level flow across the desert SW continues to back in response to an approaching trough. Meanwhile across W TX/SE NM se surface winds have been increasing on the periphery of the mid level height falls. Increased moisture is evident on 12Z MAF soundings with a 24hr change in PW from .84" to 1.1". Still low level moisture is shallow and even though the instability axis will be farther w today there will be some CINH to overcome. 12Z NAM12 is downplaying convection while HRRR does show diurnally driven initiation across PB from around Girvin-ODO/MAF-Lamesa around 21Z, which we tend favor with T/Td (M90s/N60). A few strong storms are again possible. By Fri PM SW mid level flow will have pulled up a theta-e ridge axis which will become increasingly rich. Showers/storms will light up within this axis Fri, especially from GDP Mtns-Eddy Co Plains and they will have a good chance to persist into the morning. Local heavy rain will be possible there. Into the Sat the mid level flow/theta-e ridge will have an especially long fetch while edging farther e to encompass much more of the Trans Pecos/SE NM, which will be the favored area for rain, again some heavy rain even thru thru Sat night. Sunday with mid level moist plume now stretching from the BB Region thru the Panhandle the PB have much a better chance for rain. PWs within the moist axis will be +1 to +2 standard deviations and heavy rain will be possible, if not favored and flash flood watches are likely to eventually be warranted? The slow movement of the moist axis will favor the interaction with a cold front that is expected to arrive late Mon PM or early Tue AM. Even the ECMWF which typically doesn`t produce much nocturnal precip is very wet Mon night/Tue AM. On Tue there is the potential for very favorable positioning of the upper jet to exacerbate heavy rain/flooding concerns. Of course hard to say just where that precip will be maximized, but SE NM-SW parts of the S Plains-PB are all in the mix. By Sunday the recent hot spell will be a distant memory and high temps will be normal to below normal into next week. && .PRELIMINARY POINT TEMPS/POPS... Big Spring 72 92 70 88 / 20 0 10 20 Carlsbad 68 93 66 86 / 10 30 50 70 Dryden 74 92 72 89 / 20 0 10 10 Fort Stockton 71 93 70 88 / 20 10 10 30 Guadalupe Pass 67 87 64 81 / 10 30 50 50 Hobbs 66 90 64 84 / 10 10 20 50 Marfa 60 90 61 85 / 20 20 10 50 Midland Intl Airport 72 92 70 88 / 20 0 10 20 Odessa 71 92 70 88 / 20 0 10 30 Wink 71 95 69 89 / 20 10 10 40 && .MAF WATCHES/WARNINGS/ADVISORIES... NM...None. TX...None. && $$ 99/99/29
Area Forecast Discussion
National Weather Service Medford OR
804 PM PDT Thu Sep 21 2017 .DISCUSSION... Forecast is on track with isolated showers still lingering from what KMAX can see. The more tricky part of tonight`s forecast is the possibility of fog in the valleys. There appears to be sections of clearing given what the infrared satellite was showing near the Willamette valley. However, latest guidance suggests that the dew point depression, difference between temperature and dewpoint, will just be too large to support shallow fog. Part of this is probably because of the high level clouds lingering around. Because of this, we removed fog from the forecast. Other than the fog, models show showers still lingering on the east side tonight. It`s looking very isolated as there appears to be broad atmospheric decent in northern Oregon at the moment. See previous discussion for more information on the upcoming weather pattern change. -Smith && .AVIATION...21/18Z TAF CYCLE...VFR will prevail into late this evening and partial terrain obscurations will persist and local MVFR is possible in rain showers. IFR/MVFR ceilings and visibilities will be possible tonight but confidence is not as high as previously thought due to persistent cloud cover tonight. If IFR cigs do develop late tonight, they are expected to lift quickly to VFR by mid Friday morning. -FB && .MARINE...Updated 730 PM PDT Thursday, 21 September 2017... Steep seas will return this evening for areas beyond 10 nm of the coast. Winds will be light today as weak low pressure drifts southward through the coastal waters bringing with it more showers. Late Friday afternoon and evening, north winds and seas will begin to build with small craft advisory level conditions expected for much of the area south of Cape Blanco by Friday evening. This will begin a prolonged period of northerlies that will maximize in strength each afternoon and evening as thermal troughing returns. /FB && .PREV DISCUSSION... /Issued 500 PM PDT Thu Sep 21 2017/ DISCUSSION...The upper trough axis is east of area which has allowed things to quiet down considerably compared to this time yesterday. However, there is a weak disturbance that is moving down along the coast. Most, if not all the precipitation should stay offshore, but could not rule out isolated through this evening. The HRRR high res model does not much of anything through this evening. Therefore we`ll keep isolated showers in the forecast with very light QPF amounts. Plenty of cloud cover remains and that will be the case through this evening. If we don`t get any breaks in the cloud cover, there`s a chance we could set a new record for the all time record low max temperature which is 61 set back in 1945. Right now were at 58 degrees. Most locations and hours will be dry tonight. Cloud cover should dissipate some, but not a lot. Despite the cloud cover, were still expecting temperatures to drop near or below freezing tonight east of the Cascades and a freeze warning and frost advisory remains in effect. Also could not rule out patchy fog in some westside valley locations late tonight if there`s enough clearing. Friday will be a transition day as the upper trough shifts east with a dry northerly flow. Still could not rule out a few showers along the northern Cascades and eastside, but they should be the exception. Another cold night is expected Friday night east of the Cascades and there will be less cloud cover and wind. So a freeze watch and frost advisory will be issued, but this time it will only be for southwest Klamath County, northeast Siskiyou and northwest Modoc counties. Please see NPWMFR for details on the locations of warnings, advisories and watches for tonight and again Friday night. Dry and warmer weather returns this weekend as an upper ridge builds over the eastern Pacific. At the surface, a thermal trough will develop with increasing offshore flow in Southeast Oregon and Western Siksyou County. Confidence is high we`ll remain dry for all of next week with above normal temperatures. The upper ridge is expected to gradually move over our area Tuesday through Wednesday with continued dry weather and max temperatures averaging close to 10 degrees above normal. The models are in general agreement showing the ridge axis shifting east late next week with some cooling as a weak front approaches the coast. -Petrucelli FIRE WEATHER...Updated 200 PM PDT Thursday, 21 September 2017.... The cold upper level trough that brought the wet, unsettled weather over the area earlier this week will gradually move into the Great Basin and the Intermountain West over the next 24- 48 hours. Mostly light to moderate northerly flow will persist on the back side of this trough, and while this is generally a dry flow for the area, isolated to scattered showers will persist. Showers will be most numerous near the coast, inland west of the Cascades, and in southern Lake and Modoc Counties through this evening, then tend to diminish after midnight. Isolated showers are still possible Friday and Friday evening, but any amounts will be very light. Meanwhile, high pressure offshore will begin to build into the area. This will result in a thermal trough developing along and near the coast. Light northeast winds associated with the development of the surface thermal trough may begin as early as late tonight/early Friday morning over the SW Oregon coast range and western Siskiyou County mountains, but humidity recovery should again be very good. The thermal trough will strengthen this weekend and result in east to northeast winds each night and morning through at least Tuesday. Nighttime humidity recoveries will gradually worsen and afternoon humidity will likely lower to 20-30% across most of the forecast area. Temperatures are expected to be 5 to 10 degrees above normal and warmth will likely reach all the way to the coast (mainly south of Cape Blanco) each afternoon. With recent rainfall, models may be somewhat overdoing the amount of drying, at least initially. So, for this weekend we`ve leaned toward the consensus guidance rather than seeking the drier solutions (as we were doing prior to the significant rainfall). We have lowered minimum RH values slightly across the area early next week. At midweek, the thermal trough is expected to weaken and move north/inland. As such, the northeast winds will abate and we`ll expect more of a marine influence along the coast Wednesday onward. It will remain dry and warm inland. Extended model guidance is hinting at a potential (mostly dry) frontal passage late next week, which could result in stronger afternoon winds, especially over the east side. We`ll continue to monitor this for any trends. CPC`s 8-14 day outlook as well as weeks 2-4 on the CFSv2 continue to indicate enhanced probabilities of above normal temperatures and below normal precipitation. So, a steady and long-duration warm and dry period is expected, albeit tempered by the declining sun angle associated with the changing of the seasons. Spilde/BTL && .MFR WATCHES/WARNINGS/ADVISORIES... OR...Frost Advisory from 2 AM to 9 AM PDT Friday for ORZ029>031. Freeze Warning from 2 AM to 9 AM PDT Friday for ORZ029>031. Frost Advisory from 2 AM to 9 AM PDT Saturday for ORZ029. Freeze Watch from late Friday night through Saturday morning for ORZ029. CA...Frost Advisory from 2 AM to 9 AM PDT Friday for CAZ084-085. Freeze Warning from 2 AM to 9 AM PDT Friday for CAZ084-085. Frost Advisory from 2 AM to 9 AM PDT Saturday for CAZ084. Freeze Watch from late Friday night through Saturday morning for CAZ084. Pacific Coastal Waters...Small Craft Advisory for hazardous seas until 11 AM PDT Friday for PZZ370-376. $$ CZS/MAP/FJB
Area Forecast Discussion
National Weather Service Melbourne FL
925 PM EDT Thu Sep 21 2017 .DISCUSSION... Tonight...The models show a weak inverted trough over the Atlantic pushing west and reaching the coast late. Low level northeast flow is forecast to become more easterly while a band of higher moisture pushes ashore. The HRRR model has been showing a batch of showers arriving in the pre-dawn hours. The GOES total precipitable water product does show this ribbon of higher moisture, but is followed by an area with lower values. The 18z GFS actually did a fine job in depicting this scenario and only generates sparse coverage while MOS has a max of 20 PoPs along the coast. Don`t plan to make any changes to our 30 PoPs for the coast though, as the GFS shows the bulk of precip after 09z and the next forecast package can account for higher rain chances. Prospects for higher coverage look to be a good bet on Fri as a trough aloft dropping into the northeast Gulf of Mexico provides destabilization while east flow spreads deeper moisture across the entire area. && .AVIATION...Generally VFR conditions expected outside of isolated/ scattered showers approaching coastal terminals from the Atlantic through the overnight hours. Friday looks like a more active day for convection, with scattered showers and isolated storms. Coastal terminals would have the main chances in the morning and early afternoon, then inland terminals should have the highest chances in the afternoon. && .MARINE... Tonight-Fri...The pressure gradient will continue to tighten between high pressure over the eastern U.S. and Hurricane Maria which will be gaining latitude near the 71W longitude line. Northeast-east winds 10-15 knots should become easterly closer to 15 knots Fri afternoon. The exercise caution threshold probably won`t be met overnight, but will leave statements in the forecast since we`re on the doorstep of a long period of small craft advisory conditions from Maria swells and peripheral winds, starting by Friday night. There will be an increase in showers on Fri and also expect isolated storms. && .MLB WATCHES/WARNINGS/ADVISORIES... FL...None. AM...None. && $$ Lascody/Sedlock/Combs