Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 02/23/18

Area Forecast Discussion...UPDATED
National Weather Service Brownsville TX
629 PM CST Thu Feb 22 2018 .DISCUSSION...Updated for latest aviation discussion below. && .AVIATION...A mix of IFR/MVFR ceilings prevail across deep south Texas early this evening. A warm front is expected to move north across the region later tonight, with the light onshore flow maintaining the very moist low-level conditions. LIFR ceilings should return later this evening and overnight for all Rio Grande Valley terminals. Patchy fog reducing visibilities to IFR/LIFR will be possible late tonight, mainly between 08 to 13z. Conditions will gradually improve by mid to late morning Friday with MVFR or low-end VFR conditions Friday afternoon as southeast winds strengthen. && .PREV DISCUSSION... /issued 337 PM CST Thu Feb 22 2018/ SHORT TERM (Tonight through Friday Night): Cold front which pushed all the way through the CWA overnight has now pulled up stationary about 40 miles offshore, oriented roughly SSW-NNE. Model consensus now gradually veers the N-NW surface flow to the west of the front back around to onshore as the night goes on and weak coastal troughing ejects toward the NE. NAM (which continues as the primary basis for the first 24 hours of the forecast) is somewhat slower than the GFS to do so, but the end result will be that temperatures and dewpoints will creep up overnight, except over the northern/western Ranchlands where temps will hold more steady. Will once again have to watch convection moving off the higher terrain in Mexico in the SW flow aloft and moving across the Rio Grande, with potential impacts for roughly the area east of Hwy. 281/I-69C. 12Z GFS was pretty bullish on convection in this area, with a 0.5" precip bullseye over Zapata county driven by a weak wave aloft. HRRR has been trending weaker with the convection in this area this evening, and forecast soundings do not suggest a very favorable environment. But after the past two nights, will respect the recent trend and maintain scattered showers and isolated thunder for mainly the western three counties. Also will see areas of fog along the coast, with patchy fog forming further inland with the more soupy airmass returning with the light onshore flow. Could become dense in spots but won`t try to pin down locations just yet. Temperatures warm up to back up above normal Friday afternoon as SE flow becomes breezy with a tightened pressure gradient in place. Most areas will see 80s again during the afternoon, depending on inland penetration of the warm front. Column RH wanes so basically nil rain chances during the day. Models indicating another disturbance may initiate convection over the Sierra Madre again Friday night. Most of this activity is progged to pass north, but could clip Zapata county again so will introduce isolated showers in this timeframe. LONG TERM (Saturday through Thursday): A series of deep 500 mb troughs will dig across the southwestern and south central plains states this weekend. This will push through another pretty mild fropa on Sun. Surface convergence from the fropa in addition to better moisture advection occurring ahead of the front will increase the conv potential for this upcoming weekend. Longer range MUCAPE values ahead of the front remain pretty unstable for both Sat and Sun so will maintain the mention of thunder for both days. The overall moisture levels after the fropa never decrease that much due to pretty limited dry air advection occurring early next week. Another deep 500 mb trough will dig down south along the West Coast on Mon and Tues which will rebuild the mid level ridging over the Gulf of Mex. This will push the old cold front back northwards as a warm front during the first half of next week with the better moisture values shifting steadily north away from the RGV decreasing the conv potential later in the forecast period. This West Coast 500 mb closed low will then open up and will shift east into the south central plains states late Wed/early Thurs which will push another fairly mild cold front through the RGV. Moisture advection ahead of this next fropa will be more limited than the fropa this weekend and will maintain only some slgt chc pops towards the end of next week. Overall model agreement between the GFS and the ECMWF is pretty reasonable through Day 7 in the overall timing of the 500 mb trough progressions. The biggest disagreement shows up with the timing and the position of the last trough axis that tracks over the south central states. The GFS shows the trough tracking much farther north versus the ECMWF. So overall confidence in the longer range forecast wording is above average through Wed and then drops to average for Thurs. MARINE: (Now through Friday Night): Marine Weather Statement for visibilities of 1-3 nm in fog remains in effect for the Laguna Madre and nearshore Gulf waters through midnight tonight. If conditions worsen this evening, it may be upgraded to a Dense Fog Advisory. Otherwise, winds will veer onshore tonight as the old front moves back NW as a warm front. Moderate SE winds kick in behind the warm front for Friday, possibly increasing to SCEC levels Friday night as the pressure gradient continues to tighten. Seas build to near 6 ft. as well in the 20-60nm Gulf waters, with 4-5 ft. predominating until then. Saturday through Tuesday Night: The PGF ahead of the next fropa this weekend will increase enough on Sat to possibly push the Bay and Gulf conditions up close to SCA levels due to the stronger S-SE low level flow. Once the cold front moves through the region on Sun the PGF will then weaken somewhat with the post frontal winds allowing for fairly benign marine conditions to prevail into Mon and Tues. && .BRO WATCHES/WARNINGS/ADVISORIES... TX...None. GM...None. && $$ This product is also available on the web at: HTTP://WEATHER.GOV/RGV 63
Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
939 PM EST Thu Feb 22 2018 .UPDATE... Not planning to make any drastic changes to the forecast for tonight. Offered thoughts in aviation discussion earlier with more emphasis on potential freezing drizzle the latter half of the night versus freezing rain. Even then, low confidence in timing and coverage of drizzle exists with a lack of activity immediately upstream. Surface temperatures are expected to be very marginal with current surface temperatures this evening still running some 2 to 4 degrees above the freezing mark. Dewpoints are in the 20s across the Detroit Metro area, but wet bulb cooling potential expected to be minimal as near surface theta e content increases. From this vantage point, not expecting any significant impacts. && .PREV DISCUSSION... Issued at 658 PM EST Thu Feb 22 2018 AVIATION... The last few peeks of satellite imagery suggests that MVFR cloud that initially lifted into southeastern Michigan has been thinning and scattering out due to an increase in easterly dry air advection. Rolled back timing on MVFR/IFR by a couple of hours, although suspect that lowering of cig heights will be very rapid once low level moisture advection kicks in. The big question for tonight is both timing and overall potential for freezing rain. Looking through a collection of forecast soundings suggests some potential for drizzle development as early as 05-06Z tonight. Upstream, observations over central Illinois are reporting drizzle. Given amount of near surface saturation with IFR/LIFR conditions in central Ohio, decided to introduce TEMPO FZDZ at all sites after 06Z. Warm air advection is forecasted to be very strong around daybreak and the idea is to carry a warm rain forecast once depth of moisture increases. Confidence in areal coverage of freezing drizzle tonight is low. IFR/LIFR cigs to remain in place early Friday before lifting during the late afternoon. For DTW...Pushed back timing of MVFR/IFR a couple of hours, but suspect rapid onset of conditions late this evening. Introduced earlier timing with TEMPO for -FZDZ between 06-10Z with warm rain after 10Z. Low confidence in coverage of -FZDZ. /DTW THRESHOLD PROBABILITIES... * High for cigs aob 5kft * Moderate for -FZDZ 06-10Z. High for rain after 10z. PREV DISCUSSION... Issued at 315 PM EST Thu Feb 22 2018 DISCUSSION... Mid clouds stripped away this afternoon allowing temperatures to reach into the upper 30s to around 40 degrees across most areas. Dew pts are predominately in the mid 20s. Mid clouds should be returning this evening, limiting the diurnal fall expected tonight (upper 20s to lower 30s), as low level warm advection ramps up as well. Strong upper wave coming out of the Four Corners region, tracking through southern Minnesota late tonight, with max 6 hr height fall center tracking through Lake Superior during Friday. Thus, max forcing/better isentropic ascent displaced to our northwest, but there looks to be adequate moisture advection/isentropic ascent arriving close to 12z Friday to support developing precipitation. It does not appear the surface high over Eastern Canada will put up much of a fight, and models indicating a real good surge of warm air in the 925-850 MB layer, rising into the upper single numbers to near 10 C. Thus, even if surface temperatures are marginally below freezing, it is not a given the warm drops will freeze on contact. Either way, freezing threat looks limited/brief early Friday morning, and certainly not enough confidence to issue an advisory. If anything, could see a little freezing drizzle with shallow moisture before 11z, but otherwise latest HRRR keeps it mainly dry through 11z, and then expect dew pts to rise above freezing, with temperatures climbing well into the 40s during the day. Mid level dry slot arriving Friday afternoon will shut off the rain, with low level cold air then bleeding in Friday night with northerly drainage flow. Depth of cold air and southern placement in question on Saturday as baroclinic zone aligns in west-east fashion, with high pressure (1026 MB) sliding through the northern Great Lakes. This high will tend to help maintain the low level cold feed during the day, as precipitation potentially overspreads southern lower Michigan (see 12z Canadian/Euro). A light wintry mix is not out of the question, but surface temps likely well above freezing and with the daytime timing, probably looking at mainly just a cold rain. Strong low pressure progged to be centered over the UP of Michigan Sunday morning will pull an occluded frontal boundary across Southeast Michigan early Sunday. Behind this front, a much drier air mass will quickly end precipitation as better mixing allows gusty winds to overspread the region throughout the day on Sunday. High pressure will then build into the region early next week as upper level ridging slowly rebuilds over the Eastern US. This will bring a period of dry, calm conditions to Southeast Michigan through Tuesday as temperatures remain above average with highs in the mid 40s to lower 50s while lows fall into the upper 20s to lower 30s. As the high moves to the Eastern Seaboard by midweek, return southwesterly flow will advect moisture across the region ahead of the next wave moving into the central US. Shower chances look to increase starting Wednesday as temperatures remain above average with highs in the mid 40s to near 50. MARINE... Light to moderate flow will dominate through Saturday. Strong east to southwest wind will develop on Saturday night as a deepening low lifts toward the Straits. Stability may be sufficient to probhit gusts to gales on Saturday night, but the gradient will ramp up as wind turns southwesterly on Sunday. A gale watch may eventually be needed for the waters of Lake Huron...particularly the central axis of the Lake including part or all of Saginaw Bay. HYDROLOGY... Flood warnings remain in effect for most of the primary river basins over southeast Michigan. Additional rain on Friday is not expected to contribute to additional flooding or prolong existing flooding as amounts will remain generally one quarter of an inch or less. Another round of rain will then impact the area late Saturday into Saturday night with perhaps one half of an inch of rainfall falling in some areas. This may impact river and stream levels to some degree, but should not exacerbate flooding to any great degree. && .DTX WATCHES/WARNINGS/ADVISORIES... MI...NONE. Lake Huron...NONE. Lake St Clair...NONE. Michigan waters of Lake Erie...NONE. && $$ UPDATE.......CB AVIATION.....CB DISCUSSION...SF/JD MARINE.......JVC HYDROLOGY....JVC You can obtain your latest National Weather Service forecasts online at
Area Forecast Discussion
National Weather Service Grand Forks ND
940 PM CST Thu Feb 22 2018 .UPDATE... Issued at 940 PM CST Thu Feb 22 2018 Light to moderate snow continues to move north into the forecast area. Regional radar shows the heavier bands have so far been staying to our south and east, although some heavier returns developing over northeastern SD could impact our southeastern counties in the next few hours. The 00Z run of the RAP has some pretty strong frontogenesis developing right over the southern counties by 05Z or so, recent runs have backed off on that and the negative EPV values stay mostly southeast of the CWA. Several of the high resolution models have been pretty good about matching current radar trends, so blended them in with the current QPF. This lowered the evening totals a bit but bumped them up after midnight, leaving adjusted totals fairly similar to what we had going. Will continue to leave headlines as they are for now and take another look in the next few hours. && .SHORT TERM...(This evening through Friday) Issued at 325 PM CST Thu Feb 22 2018 The snow is expanding on radars to the south, but is still down and south of Watertown SD. It will lift up into the far southern FA in the next 2 to 3 hours, then continue to expand slowly northward tonight. The initial onset of the snow is slower than yesterday, and also lingers a little later into Friday morning. However, general snow totals look about the same, with areas within the advisory expected to pick up 3-5 or 3-6 inches, with less outside the advisory. Like the previous shift noted, there may be a sharper northward border to the snow, which is a little further south than the models showed yesterday. The Grand Forks to Baudette MN corridor is along this line, so these areas may pick up a dusting or maybe not much at all. Wind speeds still look pretty light throughout this event, so blowing and drifting snow are not expected to be an impact. With the slower onset and departure times, did make some adjustments to the timing on the winter weather advisory. The snow should exit out of the eastern FA by late Friday morning, with Friday afternoon looking dry. .LONG TERM...(Friday night through Thursday) Issued at 325 PM CST Thu Feb 22 2018 The main focus for the extended outlook centers around a strong Colorado low that is expected to develop in the central Plains Saturday and propagate into the Great Lakes region Saturday night and into Sunday morning. As a robust upper level trough moves out over the Plains Saturday, lee cyclogenesis and upper level ascent along a baroclinic zone will result in a strong surface low that is expected to propagate to the northeast. While most deterministic guidance agree with the development of this storm, timing and track differences add uncertainty to the forecast. Long and medium range ensemble guidance, along with analog guidance, suggest the greatest risk area lies from northeast South Dakota through central/south central Minnesota. Frontogenetical and upper level forcing signals suggest the potential for snow banding to occur Saturday night through Sunday across the risk area. At this time, accumulating snowfall appears to be the biggest winter weather threat to the FGF CWA with the best chance for accumulation across western Minnesota and far southeastern North Dakota. Light snow will be possible further north across northwest Minnesota and northeast North Dakota, though there is much less confidence in accumulation for these regions. Winds are forecast to be relatively light until mid day Sunday when wind gusts of 20 to 25 knots will be possible on the backside of the low in response to moderate pressure rises. Beyond this weekend, relatively quiet and calmer weather is anticipated as a surface high builds over the northern Plains. Southerly return flow should return by early next week and allow for seasonal temperatures with highs in the mid to upper twenties and overnight lows in the single digits and low teens. && .AVIATION...(For the 00Z TAFS through 00Z Friday evening) Issued at 646 PM CST Thu Feb 22 2018 VFR across the forecast area as mid level clouds spread northward, but conditions will deteriorate as snow and lower stratus moves in from the south later tonight. Think snow will be in KFAR and KBJI by mid to late evening, then move into KGFK and KTVF around 06Z. KDVL will be spared and should be VFR throughout the period. The other TAF sites will see ceilings drop to the 1500-4000 ft range with visibility down to 1SM, although some 2-5SM is possible on the northern fringes. The lowered vis will continue to around 12Z before snow moves off to the east, lingering at KBJI just a bit longer. All sites should return to VFR conditions by afternoon, with the west and central sites seeing the most clearing. Winds will remain fairly light, shifting from the south to the northwest and then west, staying below 10 kts. && .FGF WATCHES/WARNINGS/ADVISORIES... ND...Winter Weather Advisory until 3 AM CST Friday for NDZ052-053. MN...Winter Weather Advisory until 6 AM CST Friday for MNZ024-028- 030>032-040. Winter Weather Advisory until 3 AM CST Friday for MNZ029. && $$ UPDATE...JR SHORT TERM...Godon LONG TERM...AM AVIATION...JR
Area Forecast Discussion
National Weather Service Hastings NE
929 PM CST Thu Feb 22 2018 .UPDATE... Issued at 928 PM CST Thu Feb 22 2018 Regarding the rest of tonight, including the Winter Weather Advisory: 1) Needless to say, light freezing drizzle hung on several hours longer than originally expected this evening across much of our coverage area (CWA), but seems to finally be letting up in coverage per the last few radar scans. Nonetheless, with automated airport stations within much of the eastern half of the CWA still reporting visibilities of 3 miles or less as of 9 PM (essentially "ground truth" that light freezing drizzle is still falling), along with actual ground truth reports of lingering light freezing drizzle per social media and law enforcement sources, opted to once again extend counties along/east of Highway 281 until Midnight. This may have been "overkill" for some areas, and some of these Advisory counties could even end up being cancelled early, but did not want to take any chances given the slower- than-expected trends this evening. No matter, confidence is actually pretty high that no Advisory will be needed past Midnight as light westerly low-level flow continues bringing light freezing drizzle to an end from west-to-east with time. 2) Once the Winter Weather Advisory is finally gone, about the only concern the rest of the night is whether "impactful" fog forms in parts of the CWA. While the prevailing light west- northwest wind direction generally strongly discourages anything more than "light fog" in our CWA, these winds are light enough that some models (including HRRR/RAP) continue hitting especially our southwestern counties fairly aggressively with fog development, mainly during the 4AM-9AM time frame. Do not have enough confidence to formally mention "dense fog" in forecast products, but do have 1-mile-or-less visibility mentioned for areas mainly southwest of a Kearney-Osborne KS line, where fog development would seem most favored. UPDATE Issued at 644 PM CST Thu Feb 22 2018 A few comments regarding our pesky ongoing combo of light snow and/or light freezing drizzle: 1) First and foremost, have extended the Winter Weather Advisory for our entire coverage area (CWA) 3 more hours until 9PM (except for the 4 northeast counties that already went until 9PM), as the slower-than-expected exit of at least light wintry precipitation rendered the original 6PM expiration too early. As of this writing, the majority of light measurable snow/freezing drizzle is within our eastern counties, but radar and ground truth suggests pesky very light freezing drizzle extending at least as far west as Highway 183, and did not feel it was prudent to drop the Advisory for these western counties yet either, as even very light freezing drizzle could pose issues. It is possible that a few of our far eastern counties may even need extended past 9PM, but this will be addressed in a few hours. Per RAP13 relative humidity progs in the lowest 1 kilometer, low level saturation deep enough to promote freezing drizzle should gradually erode from west-to- east over the next several hours, but again, a bit slower than earlier expected. 2) This has been an interesting/pesky event, as much of the CWA spent nearly all day in a "lull" with little to no precipitation in the wake of mainly light snow overnight. However, as upper forcing increased mid-late afternoon with the arrival of a fairly decent shortwave trough into the Central Plains, areas of wintry mix quickly increased in coverage, with several of especially our southern counties reporting a light glaze of ice and slick conditions, including at least a tenth of an inch of ice accumulation in Burr Oak KS per a NWS coop observer. && .SHORT TERM...(This evening through Friday) Issued at 328 PM CST Thu Feb 22 2018 Winter Wx Advisory remains as posted earlier. Hazardous Weather: A little snow or frzg drzl thru early this eve. Aloft: RAP analyses/RAOB/sat imagery show a longwave trof in the W with SW flow over the Plns. One weak shortwave trof lifted out of the base of the Wrn trof this AM was over Wrn Neb and was continuing to weaken. Another moved into the base this AM and was lifting into NM/CO. This trof will cross the CWA this eve. Heights will rise a bit in its wake as a shortwave ridge develops and crests over the rgn tomorrow. There is a potent shortwave trof diving down the backside of the Wrn trof today. As it reaches the trof base tomorrow ...the Wrn trof will begin moving E. Surface: Strong high pres over Ont/Qb extended back into the rgn. It will lose its influence as a weak sfc trof crosses the area tonight in response to the forcing aloft. Then Nrn Rockies high pres will begin building in and slide into the Nrn Plns tomorrow. Winter Wx Advisory: believe it`s shaky on verifying. It`s mainly out for frzg drzl potential and just don`t have a good feeling that it`s going to materialize. We`ve had a couple reports thru the day here and there...but predicting frzg drzl is usually difficult. Fear that we may take a hit on this Advisory...but plan is to keep it going at least to cover the evng commute "just in case" it materializes. Confidence is low. What appears more likely is a bit of snow here and there and it will come and go. Not looking at anything steady for more than 1 hr. Tonight: Cldy to start and if any precip is occurring after 00Z it should be done by 03Z. Then decreasing clds and that presents a fog problem .LONG TERM...(Friday night through Thursday) Issued at 328 PM CST Thu Feb 22 2018 Winter Storm Watch has posted for Fri night into Sat. Potentially Hazardous Weather: Snow and frzg drzl Fri night-Sat. Snow: we cont to monitor potential for a swath of svrl inches (6+) across the NW 1/4 of the CWA. This is still 36 hrs out but our current fcst offers: 6-8" from Lexington-Loup City-Greeley 3-5" Tri-Cities (and Cambridge-Columbus) 1-3" Phillipsburg-Geneva and York These totals are subject to further revisions. Believe we`ll see narrow band of snow develop and blossom in a def zone from NE CO into SW Neb Fri eve. This band will move into Wrn CWA after midnight and spread NE mainly thru S-cntrl Neb during the day. Preceding the snow (SE of the watch)...frzg drzl could be a problem due to persistent lift in the absence of deep moisture (dry DGZ). So things could ice up first before some snow moves in. The EC/NAM are the most emphatic about lower precip amts over the SE 1/2 of the CWA (basically S and E of the Tri-Cities). As always there is model variability. There can always be a narrow swath of locally higher snowfall amts than we are advertising. Models rarely agree with each other (or with themselves run-to- run) on where this occurs...especially beyond 24 hrs. So cont to monitor future fcst updates. As for the big picture: the mean trof will remain in the W thru next Thu...but discontinuous retrogression downstream over the Atlantic will eventually result in a trof also developing over the E. This will force a longwave ridge to form over the Plns. While this is a pattern change...things could still be interesting in early Mar as the pattern heads toward being blocked. Temps: below normal thru Sun...then near normal Mon-Tue. Possibly returning to below normal Wed-Thu. Precip: above normal due to Fri night-Sat event...then no significant precip foreseen thru next Thu. && .AVIATION...(For the 00Z KGRI/KEAR TAFS through 00Z Friday) Issued at 644 PM CST Thu Feb 22 2018 General overview: This is a low-confidence forecast, especially with regard to ceiling/visibility trends during the first 16 hours or so, and precipitation trends these first 2-3 hours. Beyond the first 16 hours though, confidence is overall-higher fairly high in VFR ceiling/visibility (especially visibility), although there are actually hints of an MVFR ceiling during this time as well. Surface winds will not be a big issue, with speeds averaging under 10kt throughout, and direction trending from variable this evening, to northwesterly late tonight/early Friday, then eventually northeasterly Friday afternoon. Read on for more element-specific details... Precipitation: Any lingering very light freezing drizzle and/or snow should end within the next 2-3 hours, with dry conditions expected thereafter. A very light glaze of additional ice is the main issue. Ceiling/visibility: Especially through these first 6 hours (and possibly beyond), both ceiling and visibility should fluctuate between IFR/MVFR categories, with light fog lingering even after any light precipitation ends. One of the big question marks is whether more persistent fog (perhaps LIFR) could develop late tonight/Friday morning, but confidence is low on how bad fog gets (especially with light westerly breezes) so have kept prevailing visibility no worse than IFR for now. Am currently indicating a return to VFR (both ceiling and visibility) by late Friday morning, but some models/guidance suggest that even if VFR ceiling returns for a time, an MVFR ceiling could redevelop during the day so this will need considered in later issuances. && .GID WATCHES/WARNINGS/ADVISORIES... NE...Winter Weather Advisory until midnight CST tonight for NEZ040- 041-047>049-062>064-075>077-085>087. Winter Storm Watch from late Friday night through Saturday afternoon for NEZ039>041-046-047-060-061-072-073-082. KS...Winter Weather Advisory until midnight CST tonight for KSZ006- 007-018-019. && $$ UPDATES...Pfannkuch SHORT TERM...Kelley LONG TERM...Kelley AVIATION...Pfannkuch
Area Forecast Discussion
National Weather Service Wilmington NC
1035 PM EST Thu Feb 22 2018 .SYNOPSIS... Strong high pressure aloft north of the Bahamas, will bring unseasonable warmth in the days ahead, until a cold front arrives Monday. The front will bring a chance of rain, and temperatures closer to normal early next week. A warming trend is expected next Wednesday and Thursday, as a low pressure system approaches from the west. && .NEAR TERM /THROUGH FRIDAY/... As of 1000 PM Thursday...Bermuda ridge remains in place as this atypical February pattern holds strong across the Southeast. With little change from the past few nights, the forecast challenge again remains the potential for fog as this anomalously warm and humid airmass persists. Latest RAP soundings show slightly lower moisture near the surface than the past few nights, but less wind as well. With nearly cloudless sky conditions and lack of any meaningful wind turbulence, fog is again expected, although may not be as widespread as the past few nights. Have continued with areas of fog across all areas, and while highest moisture content will be closer to the coast, better cooling and greater departures from crossoverT is expected inland. May be able to avoid any dense fog tonight, but this will be a near term challenge overnight. Do expect fog to develop after midnight and slowly spread across the area. Mins again will be in the upper 50s to around 60, about 20 degrees above normal. Relevant portion of previous discussion below: As of 332 PM Thursday...The weather pattern is nearly unchanged tonight and Friday, the differences subtle, such as, the center of the offshore surface high shifts slightly SW, moisture and SW wind flow above 850 mb increases a little as the upper ridge, is faintly dented from the NW, and local inshore water temperatures may be a degree or two warmer. All these differences however don`t appear crucial enough, to change the potential for another day of record breaking warmth in late February 2018 again Friday, where record maximums include, ILM 80 in 1975, CRE 74 in 2017, and FLO 83 in 1975. There were wide shreds of sea fog inshore this morning, and each morning as SSTs become a little warmer, we are seeing just a bit less sea fog. But this is gradual and the pattern remains highly similar, so persistence wins out, and will carry marine fog again tonight and early Friday, impacting the coastal zones. && .SHORT TERM /FRIDAY NIGHT THROUGH SATURDAY NIGHT/... As of 332 PM Thursday...The mid level ridge that has been dominating conditions this week will get suppressed to the south during this period setting the stage for some changes next week. The center of the surface high will remain more or less in the same position but weaken somewhat. This being said, weather conditions will remain essentially unchanged. One small change will be the slight chance for convective showers mostly to areas west of the coast Saturday as the mid levels become a little more conducive. Certainly don`t expect deep convection and even thunder is a stretch. Overall temperature forecast remains on track for highs in the upper 70s to possibly over 80 inland with lows in the 60s. && .LONG TERM /SUNDAY THROUGH THURSDAY/... As of 332 PM Thursday...Surface and mid-level ridging weaken Sun as they become flatter and sink south. Stacked low tracking across the western Great Lakes will drag a cold front into the area, but the front is initially moisture starved and lacks dynamics. Front moves into the area late Sun before ending up parallel to the flow aloft. The front will be stalled in the area Sun night but precip chances seem slim at best. Temperatures ahead of the front Sun will be on the order of 20 degrees above normal with lows Sun night in the low 60s, right around highs typical for late Feb. On Mon a series of shortwaves, emerging from the base of the 5h trough over the Southwest, move along the stalled boundary. Deep southwest flow helps spread moisture over the southeast while the waves aid dynamics. Anticipate an increase in precipitation in the area as the waves move overhead. Confidence on timing is on the low side as there is still some disagreement between the GFS/ECMWF solutions, but the slower ECMWF might be the way to go given the presence of a mid-level ridge. Cloud cover and precip will keep temperatures cooler than previous days but both highs and lows will remain above climo. Surface high builds over the southeast Tue into Wed as flow aloft becomes progressive at the top of a 5h ridge over the Gulf of Mexico. Quiet period is short lived as the flat 5h flow moves the remains of a stalled front into the area, which is then lifted north as a warm front Wed into Thu. Subtle amplification of the mid-level pattern late in the period will push above normal temps during the midweek period to well above normal for the end of the period with potential for convection late Thu or Thu night as a cold front moves into or across the area. && .AVIATION /04Z FRIDAY THROUGH TUESDAY/... As of 00Z...Persistent pattern continues. VFR is expected at all terminals through 06Z. Under clear skies and light winds fog is expected to develop again overnight as the previous nights. Have indicated IFR/MVFR after 07Z with tempo LIFR 09-13Z. Fog should burnoff rapidly after sunrise, initially at the coastal terminals then inland terminals by mid morning. Extended Outlook...Morning IFR/BR possible through Sat, otherwise VFR. SHRA/MVFR Sunday through Monday, becoming VFR Tues. && .MARINE... NEAR TERM /THROUGH FRIDAY/... As of 1000 PM Thursday...Little change to the overall synoptic pattern maintains a persistence type forecast for the waters tonight. 3ft/7sec swell remains dominant as light southerly winds of 5-10 kts continue. This swell will lengthen to 8-9 sec overnight but seas will remain around 3 ft all waters. Fog is again of concern again tonight, and visibilities could be reduced in areas. A dense fog advisory for the waters cannot be ruled out entirely late tonight and early Friday, but the window for this seems to be closing as water temps slowly climb. SHORT TERM /FRIDAY NIGHT THROUGH SATURDAY NIGHT/... As of 332 PM Thursday...A south to southwest flow of ten knots or less will continue across the waters through about midday Saturday. The gradient will increase slowly from that point on to increase winds to 15-20 knots through Sunday morning. This will increase the seas from the 2-3 feet which will have persisted for days to 3-5 feet by Sunday morning. LONG TERM /SUNDAY THROUGH TUESDAY/... As of 332 PM Thursday...Bermuda High remains off the coast Sun with southwest flow increasing as cold front approaches from the northwest. Pinched gradient increases winds to 15 to 20 kt Sun and Sun night before the arrival of the front drops speeds closer to 10 kt. Direction veers from southwest Sun night to north-northwest by Mon morning. Surface high builds in from the west Mon into Tue, then shifts overhead Tue afternoon. Northeast surge Mon night will peak around 20 kt close to midnight but then the gradient starts to weaken as the high moves closer. Northeast flow starts to wind down after sunrise Tue with winds slowly veering to easterly and dropping to 10 kt or less as the period ends. Seas 3 to 5 ft Sun and Sun night drop to 2 to 4 ft Mon. Northeast surge Mon night into Tue will push seas back to 3 to 5 ft for much of Tue before decreasing winds allow seas to fall to 2 to 3 ft Tue night. && .ILM WATCHES/WARNINGS/ADVISORIES... SC...None. NC...None. MARINE...None. && $$ SYNOPSIS...MJC NEAR TERM...MJC/JDW SHORT TERM...SHK LONG TERM...III AVIATION...MRR MARINE...
Area Forecast Discussion
National Weather Service Lincoln IL
904 PM CST Thu Feb 22 2018 .UPDATE... Issued at 904 PM CST Thu Feb 22 2018 One initial concern this evening is the potential for dense fog. While most observations in our forecast area are above one quarter mile visibility (dense fog), reports in between OBS have indicated some dense fog has developed across central and southeast IL. HRRR and RAP guidance are projecting that the coverage and timing of dense fog looks to be generally spotty and shifting northward with time. Those trends appear tied to the onset of rains and an increase in surface winds overnight. Will not issue a dense fog advisory at this point, and have covered the situation with an SPS. Will monitor fog trends closely. The rest of the night will see rains become widespread from S-SW to N-NE, fueled by a steady stream of moisture with some tropical sources involved. An extended period of waves of rain is setting up for the end of the week and into the weekend, especially across our southeast counties. Clouds and rains tonight will limit the diurnal temperature swing, as lows range from the mid 30s near Galesburg to the mid 40s toward Lawrenceville. Made some updates to weather to match expected trends, with minor adjustments to temps and winds. The latest forecast info should be available. && .SHORT TERM...(This evening through Friday) ISSUED AT 137 PM CST Thu Feb 22 2018 Some welcome dry weather is occurring across the forecast area early this afternoon, and temperatures in the 30s and 40s have melted off the lingering ice. Next surge of rain is currently approaching the western border of Missouri, with the upper wave moving northeast from the Oklahoma area. Forecast soundings show a dry wedge in the mid levels that lingers for a time this evening, so PoP`s have been adjusted downward a bit to slow the onset of the rain by a few hours. All areas will have at least categorical PoP`s for a time, though, but rain chances by Friday morning should be limited to areas south of I-70. A few rumbles of thunder possible in that area after midnight, with a few hundred joules of elevated MUCAPE. While most of the area will be dry by morning, the clouds won`t be in any hurry to leave, due to a persistent low level inversion. With little cold air behind the boundary that passes by early tomorrow, temperatures in the 50s still seem reasonable east of I-55, with mid-upper 40s west. .LONG TERM...(Friday night through Thursday) ISSUED AT 137 PM CST Thu Feb 22 2018 Main focus for heavy rain into the weekend remains focused across the southeast CWA. The frontal boundary will be hanging up from the Ohio Valley into the southern Plains on Friday. Several waves of energy will ride northeast, culminating in a strengthening storm system over the central Plains this weekend. The track of the surface low from this system will take it into Wisconsin late Saturday evening, with the trailing cold front crossing us Saturday night. Once that passes, a few welcome days of dry weather are on tap. In regards to the timing and details, rain will be spreading into the area once again Friday evening, though locations north of I-72 will see it arrive later in the night. With the colder northeast surface low persisting into early Saturday, a transition to some sleet, freezing rain or snow is possible on the northern periphery of the rain shield. Current indications are that areas north of a Quincy to Bloomington line are most favored for this transition zone. Any icing there will be short lived, as temperatures rise to near 50 degrees on Saturday. Precipitation chances remain very high until the passage of the front. Regarding the heavy rain, precipitable water will frequently be in the 1-1.5 inch range across the southeast CWA into Saturday evening. An upper wave riding northeast into the Ohio Valley will help enhance thunder chances as well as heavy rain potential. Current thinking is for 2-2.5 inches south of I-70 for the period from tonight through Saturday evening. May need a flood watch down there eventually, but will hold off for now as the rain tonight should be an inch or less. Temperatures through the period should remain on the milder side, with no significant cold surges expected. && .AVIATION...(For the 00Z TAFS through 00Z Friday evening) Issued at 558 PM CST Thu Feb 22 2018 Widespread IFR and LIFR ceilings have developed, with the onset of drizzle at the TAF sites, and those cloud conditions should continue overnight and into Friday morning. Visibility conditions are generally IFR due to drizzle and light fog, with LIFR vis only at PIA to this point. Forecast soundings show that vis could become dense (VLIFR) at PIA and BMI tonight, before steady rains arrive and help with some mixing of the boundary layer. Have kept the forecast more pessimistic with clouds overnight, despite MAV guidance pointing toward some MVFR cloud heights during the period of rains later tonight. Rain/drizzle should diminish Friday morning, with cloud ceilings rising to MVFR by early afternoon, then VFR by late afternoon. Winds will start out east-southeast at less than 10kt, then become southwest by Friday morning, and eventually west Friday afternoon after a cold frontal passage. Speeds will generally remain in the 8-12kt range. && .HYDROLOGY... Issued at 137 PM CST Thu Feb 22 2018 Many of the rivers are in flood at the moment, courtesy of the 2.5 to 5 inches of rain that has fallen this week. Danville (Vermilion River) has crested at its 3rd highest level on record, and the highest value since 1994. Moderate flooding is projected on the Illinois and Wabash Rivers. The crest on the Illinois River is currently near La Salle, with areas downstream rising into the weekend. Heaviest precipitation over the next few days will be focused more on the areas along and south of I-70, with potential for 2-2.5 inches through Saturday evening. That will be more of an impact for the Wabash, Embarras and Little Wabash Rivers. && .ILX WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...Shimon SHORT TERM...Geelhart LONG TERM...Geelhart AVIATION...Shimon HYDROLOGY...Geelhart
Area Forecast Discussion
National Weather Service Louisville KY
837 PM EST Thu Feb 22 2018 .Forecast Update... Issued at 835 PM EST Thu Feb 22 2018 Currently, a frontal boundary is weakly defined over southern KY, mostly by a notable dew point gradient. Given the recent heavy rainfall and the light and variable winds beneath a strengthening low level inversion, we are seeing a couple spotter reports and obs showing dense fog formation. Don`t like the idea of combining flooded roadways and dense fog so will need to monitor this closely over the next few hours. At this point, have only see a couple of isolated instances, and overall think the threat will be short-lived as the aforementioned boundary strengthens and quickly lifts north as a warm front around and after Midnight. The mixer low levels should improve vis at that time. Nevertheless, will keep monitoring and issue a Special Weather Statement if dense fog reports become more numerous/widespread. ...Axis of Heavy Rain Expected Along/North Ohio River Tonight... The other issue will be the next round of rain set to arrive around Midnight, lasting through the overnight hours. Already seeing a blob of moderate to heavy rain near the Mississippi/Ohio River confluences, which is situated on the nose of a strengthening low level jet. Given the strong moisture transport beneath increased lift in the right entrance region of an upper jet, feel we see a similar setup to what we saw last night. The main difference is that the heavy rainfall axis will be displaced more NW than last night, putting the heaviest swath along and mainly just north of the Ohio River. PWATs should approach 1.6 inches through the column, and given some training think the axis of 1 to 2 inches is a good call across the southern IN and far N central KY counties. Bumped up QPF a bit in the southern IN counties given increased confidence offered by hi-res models. Given the overachievement of last night, and a similar setup in store tonight local amounts of 3 inches can`t be ruled out. Flash Flooding will be a concern along with areal and ongoing river flooding. If it were falling over the same heavy swath as last night, we would be very concerned. That area does look to get the focus of the heaviest rain later into the day on Friday so that will need to be watched when the time comes. && .Short Term...(This evening through Friday night) Issued at 400 PM EST Thu Feb 22 2018 ...MULTIPLE ROUNDS OF RAINFALL CONTINUING INTO THE WEEKEND... ...FLOOD WATCH FOR ALL OF SOUTHERN INDIANA AND MUCH OF CENTRAL KENTUCKY THROUGH SATURDAY NIGHT... (Tonight - Friday Night) - Rain continues and intensifies at night. Expect river flooding. Currently, light rain continues across southeastern Kentucky with the northern edge of this rain stretched across a line from Logan County through the Bluegrass. This rain is expected to continue for the rest of the day as the low level jet continues to overrun the stationary front. The rest of southern Indiana and central Kentucky will continue to sit under cloudy skies. With the front running horizontally through Kentucky, southeastern Indiana is seeing mid 40s as southeastern Kentucky sees mid 60s. (Tonight - Friday Night) - Rain chances increase bringing heavier rain to southern Indiana with a gradient dropping through Kentucky. Near 0z the stationary front in northern Tennessee will begin to push north with a 50 knot lower level jet with precipitable water around 1.5". During this general time the CWA will remain in the right entrance of the upper level jet. Several global models have the axis of heaviest rain setting up through south central Indiana. The HRRR is showing precipitation further south. Based on recent rainfall trends, it is believed the axis of highest rain will fall in northwestern Kentucky near Henderson and Daviess Counties through southern Indiana near Crawford and Perry Counties. Around an inch is possible between 6-12z along this axis. Rain amounts will fall off further north, south, or east. The rain is expected to move into the area shortly after 6z from the southwest. As the warm front continues north, the heavier rain is expect to run into Saturday afternoon. Along that axis of heaviest rainfall another 0.5 - 1" is expected. Winds from the south are expected to be 10-15 mph with gusts near 25 mph in central Kentucky. The warm front will occlude and settle across central Kentucky. Friday night, the upper level trough axis along with a cold front begins to move east from Utah. This will be the force that pushes the rain chances out of the area. Confidence is high that the area will see 1-2" near and north of the Ohio River tonight and tomorrow. Expect local rivers to react the this additional rainfall. && .Long Term...(Saturday through Thursday) Issued at 330 PM EST Thu Feb 22 2018 ...SIGNIFICANT FLASH FLOODING POSSIBLE SATURDAY NIGHT AND SUNDAY... ...STRONG TO SEVERE THUNDERSTORMS POSSIBLE SATURDAY EVENING THROUGH SATURDAY NIGHT... A warm frontal boundary is likely to be draped somewhere over the area Saturday morning. The upper pattern will continue to be dominated by western troughing and strong ridging over the Gulf and southwestern Atlantic. The highly anomalous and persistent stream of Gulf moisture will continue over the Ohio Valley. The latest 12z GFS guidance features PWATs of 1.4-1.5 during the day. Widespread showers are likely in addition to scattered thunderstorms. Areal flooding is certainly a possibility on Saturday, especially after whatever rain falls Friday and Friday night. River flooding will only continue to worsen over the weekend. 12-hour QPF looks to range between 0.25-0.75 through 00z Sunday, with the highest totals along the Ohio River and in southern Indiana. Saturday night, the upper level trough slides east a bit with a modest boost in the upper level jet. A strong 500 mb wave ejects northeast into the Upper Midwest, taking on an increasingly negative tilt. This will allow a surface cyclone to strengthen and track from near Missouri/Iowa to northern Wisconsin Saturday night, shoving a potent cold front through central Kentucky and southern Indiana. This is a very potent system, with the latest models hinting at a 70 kt LLJ. This LLJ may be able to push surface dewpoints into the 60s along and just ahead of the front, with PWATs up to around 1.6. Strong deep layer shear and marginal (but sufficient?) CAPE may result in a squall line with a damaging wind threat. At this time, MLCAPE could even reach 200-300 J/kg, but confidence in the details is low at this point. However, given flooded soils, trees will be quick to topple in the face of relatively less wind. So we could see quite a few trees come down Saturday night. Given our ongoing, significant prolonged rainfall/river flooding event, flash flooding is the other primary threat Saturday night and Sunday. Significant flash flooding is possible. Given a strong convective environment, excessive rain rates are likely. Additional rapid rises on small creeks and streams are also likely. Dry weather looks to finally return Sunday and early next week. However, the Ohio River and other rivers will continue to rise. Additional rainfall will be possible on Wednesday and Thursday, but details and amounts are uncertain. && .Aviation...(00Z TAF Issuance) Issued at 605 PM EST Thu Feb 22 2018 IFR ceilings across the board as we approach sunset, and LEX and HNB are already on the edge of LIFR. Expect a slight build-down this evening, so will be down to 400-500 ft ceilings until the low-level jet kicks in around midnight. With a 40 kt LLJ developing we expect wind shear as well, and that will continue through about mid-morning. Another impulse will bring in numerous rain showers, which will add a vis restriction to the low ceilings. Wind shear mixes out and we get a little stronger SSW breeze during the day Friday, but rain and IFR cig/vis will persist. Finally look for some lifting of ceilings and rain tapering off late in the day as this wave pushes to our east. && .Hydrology... Updated at 335 PM EST Thu Feb 22 2018 Minor flooding continues along the Ohio River at Louisville and Cannelton, with moderate flooding expected. Tell City is in moderate flood. Synoptic models continue to advertise an additional 2 to 4 inches of rainfall through Saturday night across much of the region. This range has been very consistent over the past few days. As with any convective, long term event, some locally higher amounts will be possible depending on where multiple axes of heavier precipitation develop. The most likely geographical area to get the most rain will be those locations along and either side of the Ohio River. This rainfall combined with already saturated soils will lead to excessive runoff through the period. This will result in flooding issues in the typical low-land and flood prone areas and potentially some flash flooding. In addition, ongoing river flooding will become worse with time as the runoff makes its way into the rivers. Current river forecasts are based on forecasts that contain 72 hours of future rainfall. Thus, the current forecasts capture rainfall through Sunday morning. The forecasts that are being issued now are able to incorporate all of the expected rainfall for this prolonged event. Some of the following stage information comes from various ensemble model packages, and is likely to change as new data are ingested by those models. Other data is based on current official forecasts. **Also remember that some of the rain that will be responsible for the rises on the rivers hasn`t even fallen yet, so significant river stage forecast changes should be expected over the coming days.** ...Ohio River... The river from Louisville to Tell City is forecast to reach moderate flood levels. Tell City has just reached moderate flood, and Cannelton is expected to do so later this evening. McAlpine Upper is expected to go into moderate flood by early Saturday morning, with McAlpine lower going into moderate flood by Sunday afternoon. Clifty Creek will likely enter minor flood later this evening and is expected to get into moderate flood by Monday morning. ...Green River and Rough River... At Dundee, minor flooding is occurring, with moderate flooding possible. Minor flooding is occurring at Woodbury today and expected at Rochester by midday Friday. Munfordville and Alvaton will approach flood stage, but are not forecast to hit flood stage at this time. ...Rolling Fork River... Boston is forecast to rise to minor flood stage by early this evening and has a chance to rise to moderate. ...Kentucky River... Minor flooding may be possible at Lockport this evening and again late this weekend. Peaks Mill on Elkhorn Creek is a smaller, flashier stream and is more difficult to predict very far in advance but it is in minor flood now and may go into minor flood again late this weekend as well. Given the consistent and consecutive heavy rainfall forecasts from the guidance, a Flood Watch is in effect for the northwestern 2/3rds of KY and all of southern Indiana for the duration of the overall event, through Saturday night. Residents of southern Indiana and central Kentucky should remain alert this week for flooding. Stay tuned for the latest forecasts and updates through the week. && .LMK WATCHES/WARNINGS/ADVISORIES... IN...Flood Watch through Sunday morning for INZ076>079-083-084- 089>092. KY...Flood Watch through Sunday morning for KYZ023>043-045>049- 053>055-061>065-070>074. && $$ Update...BJS Short Term...KDW Long Term...EBW Aviation...RAS Hydrology...EER/BJS
Area Forecast Discussion
National Weather Service Newport/Morehead City NC
1058 PM EST Thu Feb 22 2018 .SYNOPSIS... A cold front will sag south into northern portions of eastern North Carolina late tonight and early Friday then lift back north Friday afternoon. High pressure will continue offshore over the weekend with continued very warm temperatures. A cold front will move through the area Sunday night into early Monday, followed by high pressure Tuesday into Wednesday. && .NEAR TERM /UNTIL 6 AM FRIDAY MORNING/... As of 1030 PM Thursday...fairly major update to indicate faster and stronger backdoor frontal push into area overnight. Latest HRRR and NAM12 have better handle than 12Z/18Z global models and have adjusted forecast accordingly wtih wind shift expected all the way to southern counties by Friday morning. Temps have dropped 10-20 degrees with frontal passage northern outer banks and lowered min temps for mainly northern sections. Added thicker cloud cover and fog and chance of drizzle with frontal passage as well. /Previous discussion/ As of 215 PM Thursday...Sct Cu inland will diminish toward evening with loss of heating. Mostly clr skies thru the evening will give way to increasing clouds late in combo of developing stratus and clouds behind a backdoor cold front that will sag S thru nrn tier. Deeper moisture looks to remain N of region so will cont with no pops in fcst. With low lvls remaining saturated good bet for fog to form again tonight...always tricky to determine how widespread the fog will be...there is the potential for some dense fog. Overnight lows will be slightly cooler than the past 2 nights mainly cpl dgrs either side of 55. && .SHORT TERM /6 AM FRIDAY MORNING THROUGH 6 PM FRIDAY/... As of 215 PM Thursday...The backdoor front is fcst to bisect the region early with it weakening and lifting back N later in the day. Clouds/fog in morn shld grad diminish into the aftn. Temps over srn tier will be similar to today around 80...bit cooler nrn tier with front in area with highs in the 60s nrn cst. && .LONG TERM /FRIDAY NIGHT THROUGH THURSDAY/... As of 315 AM Thursday...Strong high pressure at the surface and aloft offshore will continue to provide a warm southwest flow into the region into the weekend. An approaching cold front coupled with deep moisture will lead to an increased rain threat Sunday into Monday before another cold front brings a return to dry weather Tuesday. Friday Night and Saturday...Near-record high temperatures expected given southwest flow and unusually high 500 mb heights over the region. High temperatures will be well into the 70s with a few spots reaching the lower 80s Saturday. GFS/ECMWF show the development of a few showers Saturday given an increase in precipitable water ahead of next front. Sunday through Monday night...Deeper moisture will be drawn north into the eastern Carolinas ahead of cold front as ridge to the east weakens and moves east. Continued high chance PoPs Sunday night and especially Monday when deepest moisture and best lift is in place. Continued very warm Sunday in warm sector ahead of front with highs well into the 70s, but as front moves offshore later Sunday night, highs on Monday will range mostly in the upper 50s to lower 60s with more widespread precipitation expected. Tuesday and Wednesday...Dry high pressure will build across the region with cooler temperatures, but still above normal under mostly clear skies. Highs will generally be in the 60s with lows in the 40s, still about 10 degrees above normal for this time of year. Wednesday Night and Thursday...An increase in deep moisture ahead of low pressure crossing the Mississippi and Ohio Valleys will lead to another round of showers Wednesday night into Thursday. Have high chance PoPs in the forecast. Temperatures will remain mild, despite the precipitation however. && .AVIATION /04Z FRIDAY THROUGH TUESDAY/... Short Term /through Fri/... As of 645 PM Thursday...Mainly VFR thru this evening with mostly clear skies prevailing. Weak backdoor front will push in from N-NE overnight but generally expected to stall near KPGV-KEWN line near morning and then lift back north on Friday. Low stratus and fog will develop ahead of and behind front at TAF sites late tonight with IFR expected most sites poss dropping to LIFR at times. Appears srn tier will quickly see fog/st dissipate with VFR by mid/late morn. Nrn tier may hold onto lower clouds and vsbys til late morn or early aftn with VFR all areas later in aftn. Long Term /Friday Night through Monday/... As of 325 AM Thursday...VFR conditions will prevail Friday night and Saturday as high pressure continues to circulate warm air into the region on S/SW winds. Some periods of sub-VFR conditions, likely MVFR, are expected Sunday into Monday as an approaching frontal system will bring more numerous showers, especially behind the cold front on Monday. && .MARINE... Short Term /through tonight/... As of 1030 PM Thursday...Major update for overnight into Friday morning as backdoor front pushing down stronger and faster than previous forecast. Now expect wind shift to NE all the way down into southern waters by morning with 10-15 KT gusting to 20 KT at times for northern half. Still expect winds to return to southerly during Friday but slower than previous forecast. Also added more widespread fog and chance of drizzle in wake of front and dense fog advisory may be needed. /Previous discussion/ As of 215 PM Thursday...SSW winds 5 to 15 kts thru the evening with 3 to 4 foot seas in long period swell. Late tonight a weak cold front will cross nrn tier with winds become N to NE mainly from about Hatteras N with light WSW winds S of the front. Once again will likely see fog develop and will have to monitor trends overnight for poss dense fog advisory. The front will grad weaken and lift N Fri with winds becoming SSW below 15 kts all waters later in the day with fog diminishing. Cont longer period swells will keep seas mainly in the 3 to 4 foot range Fri. Long Term /Friday night through Monday/... As of 325 AM Thursday...Not alot of change in the latest marine forecast. S/SW winds will cont Friday night and Saturday. Expect 10-15 knot winds for this period with seas of 2-4 feet. Small Craft Advisory conditions still look like a given on Sunday ahead of the cold front with gusty SW winds of 20-25 knots and seas building to as high as 6-7 feet, south of Oregon Inlet. Winds subside again Monday behind the front as winds become northerly. && .MHX WATCHES/WARNINGS/ADVISORIES... NC...None. MARINE...None. && $$ SYNOPSIS...RF NEAR TERM...RF/JBM SHORT TERM...RF LONG TERM...CTC AVIATION...CTC/JBM MARINE...RF/CTC/JBM CLIMATE...MHX
Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
603 PM CST Thu Feb 22 2018 .SHORT TERM...(This evening through Friday) Issued at 327 PM CST Thu Feb 22 2018 Snow is advancing northeastward into southwestern Minnesota this afternoon. It will reach just about all of the southern half of Minnesota and western Wisconsin by 6 or 7 PM. Light to moderate snow will persist area wide through midnight, then begin to end from southwest to northeast. The steady snow will end in southwest MN around 1 AM and the I-94 corridor by around 4 AM. During this process of drying in the mid levels, there could be a period of freezing drizzle following the end of accumulating snow due to continued saturation in the low levels. However, this will be brief and little or no ice accumulation is expected. Models are in pretty good agreement with QPF tonight. There could be some mesoscale banding in places and hi-res guidance is hinting at streaks of higher QPF/snowfall. However, on a widespread basis we should expect about 3 inches across southern MN where the period of accumulating snow will be shortest, to 4 to 6 inches across the remainder of the forecast area. The current Winter Weather Advisory configuration looks good, so no changes were needed to that. Drier air will make for a relatively pleasant day Friday with some decrease in clouds possible. .LONG TERM...(Friday night through Thursday) Issued at 327 PM CST Thu Feb 22 2018 Friday night and early Saturday look good, but the next system is fast on the heels of tonight`s system and will begin arriving Saturday afternoon. This system will be neutrally tilted to start Friday night over the Plains, but will trend more negative Saturday and Saturday night as it passes across the Upper Midwest. This lends to a higher confidence event with widespread significant snow accumulations. 12Z GFS is most bullish/quickest with the mid level wave closing off and results in a strong cyclone centered over the southeast corner of MN late Saturday evening. Models have been slowly trending toward this solution. In addition, the GFS deterministic run is right in the middle of the spread of SLP/QPF in the GEFS solutions, with the lowest member still showing at least 0.6" of QPF at MSP. Thus, confidence in 6 inch amounts is pretty high from south central MN to northwest WI and totals could approach 12 inches somewhere in that corridor. Snowfall rates will be impressive with an inch or two per hour possible during the height of the event. As for wind, the rapidly deepening low center passing by could be occurring a little too late for the wind to respond and increase to critical levels for blizzard conditions. Therefore, blizzard conditions are still questionable, but certainly not impossible if gusts can increase 5 to 10 mph above what is currently forecast. Given that we`re within a 48 hour window of the snow beginning, and the degree of confidence present, have issued a Winter Storm Watch for most of the CWA except for far western MN. It`s possible those counties will be included later if confidence increases for greater than 6 inches. All told, it`s likely most of the CWA will see over 12 inches between tonight`s snow and Saturday`s, and some could exceed 15 inches. Much more tranquil weather follows for early next week, but there are signs of another system for late next week that will need to be watched. && .AVIATION...(For the 00Z TAFS through 00Z Friday evening) Issued at 547 PM CST Thu Feb 22 2018 Snow has been battling the dry air this afternoon, hence it`s later than advertised arrival, but the dry layer is quickly being eaten away, with snow hitting the ground. Only had minor changes to the going TAFs, with timing lined up similar to what the HRRR is showing. Main change is looking at upstream obs, 3/4sm is the prevailing vis, with some scattered 1/2sm vis, so trended the TAFs that direction with prevailing 3/4sm and tempo 1/2sm vis. Still expecting a widespread 3-5 inches, with snow mostly done by 12z. Lower confidence with cig trends behind the snow, but we could certainly clear out faster than TAFs currently indicated, but played the improvements a bit more conservative until we have a better feel of how quickly skies will improve in the wake of the snow. KMSP...Based on the HRRR, looks like the vast majority of the snow, along with the potential rates of around 3/4" per hour will come between 4z and 7z. This is also the window where some vis down to 1/2sm will be possible. Friday morning, skies may go VFR shortly after the winds go SW and we could see VFR conditions as early as 15z. /OUTLOOK FOR KMSP/ Sat...VFR early. Then IFR/SN with LIFR possible in aftn and overnight. Significant snow accums possible. Wind ENE 5-15 kts. Sun...CHC MVFR cigs. Wind W 10-20 kts. Mon...VFR. Win SW 5-10 kts. && .MPX WATCHES/WARNINGS/ADVISORIES... WI...Winter Storm Watch from Saturday afternoon through late Saturday night for WIZ014>016-023>028. Winter Weather Advisory until 9 AM CST Friday for WIZ014>016- 023>028. MN...Winter Weather Advisory until 6 AM CST Friday for MNZ041-042- 047>049-051-057>060-062-066>070-076>078-085. Winter Storm Watch from Saturday afternoon through late Saturday night for MNZ043>045-049>053-057>063-066>070-076>078-084- 085-093. Winter Weather Advisory until 9 AM CST Friday for MNZ043>045-050- 052-053-061-063. Winter Weather Advisory until 3 AM CST Friday for MNZ054>056-064- 065-073>075-082>084-091>093. Winter Storm Watch from Saturday afternoon through late Saturday night for MNZ056-064-065-073>075-082-083-091-092. && $$ SHORT TERM...BORGHOFF LONG TERM...BORGHOFF AVIATION...MPG
Area Forecast Discussion
National Weather Service Nashville TN
656 PM CST Thu Feb 22 2018 .UPDATE... FOR EVENING DISCUSSION. && .DISCUSSION... Fog has developed along the frontal boundary and has been dense in some spots. Zones were updated to include areas of fog along and north of the current boundary position. As the boundary lifts northward over the next few hours, fog may dissipate along the southern fringes. Pops were also adjusted to reflect the thinking of high res models which keeps rain concentrated in the northwest overnight. && .AVIATION... 00Z TAF DISCUSSION. Stationary boundary is currently draped just north of CKV with LIFR to MVFR cigs at CKV, BNA, and MQY. Cigs should improve overnight as the boundary drifts farther north with the exception of a period of MVFR cigs at CSV. HRRR shows rain impacting CKV overnight while staying north of BNA and MQY. Most of the daylight hours for BNA, MQY, and CSV will be VFR while CKV will have MVFR cigs closer to the frontal boundary. Southerly winds will increase overnight to the 10 kt range and turn southwesterly after 15z. && .OHX WATCHES/WARNINGS/ADVISORIES... Flood Watch through late Saturday night for Cheatham-Davidson- Dickson-Hickman-Houston-Humphreys-Lewis-Maury-Montgomery-Perry- Robertson-Stewart-Sumner-Williamson. && $$ DISCUSSION......Reagan AVIATION........Reagan
Area Forecast Discussion
National Weather Service Shreveport LA
930 PM CST Thu Feb 22 2018 .UPDATE... 03z Sfc Analysis showing our returning warm front situated from near Houston and Lufkin, Texas to near Natchitoches, Louisiana and Vicksburg, Miss. This boundary has moved very little since 4 pm but should at least move further north along its eastward flank, moving north of Monroe and near or just south of El Dorado by 6 am Friday Morning. So far this evening, most of the activity as been going on across Deep East Texas spreading north northeastward into NW LA and SW AR and this is along a deformation zone which has set up across this same general area. 00z NAM output along with the current run of the HRRR has nailed this activity thus far and really begins to focus renewed activity north and west of the returning warm front or across our northwest zones for the remainder of the night. This activity should orient itself along an elevated 850mb theta-e axis which should be near or along a line from near TYR to TXK and LZK later tonight. Already seeing an uptick in convective coverage across these regions and therefore the ongoing forecast has a good handle on this likelihood through the remainder of the overnight hours. Did add areas of fog however through the overnight grids as if you are void of the mixing effects of the convection, you will likely see some fog overnight. Overnight min temp forecast is very difficult as we could see rising temperatures across our eastern zones and near steady to slightly falling temperatures out west in and out of rain activity. Therefore made only very slight adjustments to temperatures overnight. Prelims to follow...13. && .PREV DISCUSSION... /issued 555 PM CST Thu Feb 22 2018/ AVIATION... For the ArkLaTex, a warm front stretches from KLFK to KRSN/KMLU and continues lifting Northward. VLIFR-IFR for most sites attm except KMLU now well behind the boundary. Cigs/vsby issues will linger well into daylight on Friday with models showing more TSTM activity along the warm frontal boundary currently affecting KGGG and soon for KTXK/KTYR. Warm front will lift past terminals with MVFR/VFR expected late period and L/V winds. Outlook is for more TSTMS for Sat and the next weak cold front drying us for 2/3 days. /24/ && .PRELIMINARY POINT TEMPS/POPS... SHV 53 71 63 76 / 100 70 40 90 MLU 58 78 65 81 / 40 60 40 50 DEQ 47 60 55 71 / 100 100 80 90 TXK 47 63 59 73 / 100 100 50 90 ELD 48 67 60 76 / 100 100 40 90 TYR 45 68 62 73 / 100 90 50 90 GGG 51 69 62 74 / 100 80 40 90 LFK 53 75 66 77 / 70 50 30 90 && .SHV WATCHES/WARNINGS/ADVISORIES... AR...Flash Flood Watch through Friday evening for ARZ050-051-059>061- 070>073. LA...Flash Flood Watch through Friday evening for LAZ001>006-010>014- 017>022. OK...Flash Flood Watch through Friday evening for OKZ077. TX...Flash Flood Watch through Friday evening for TXZ096-097-108>112- 124>126-136>138-149>153-165>167. && $$ 24/13
Area Forecast Discussion
National Weather Service Sacramento CA
329 PM PST Thu Feb 22 2018 .SYNOPSIS... A cold system will bring low elevation snow to the mountains into early Friday, which could impact travelers. A few showers are possible in the Valley. Below normal temperatures will continue. Additional systems likely next week. && .DISCUSSION... Vort max that was along the CA/OR coast dropping SSEwd, mainly along the Wrn side of the CWA. Clouds and scattered showers will spread SEwd over the CWA into this evening. Very low WBZs will result in low snow levels dropping into the foothills. AT press time, the snow level had dropped to Applegate around 2 kft. SPC SREF plumes suggest the Srn portion of the CWA will be more unstable, roughly from SMF Swd into the Nrn SJV where isolated storms are possible through late afternoon, than the Nrn portion of the CWA. This is due to the timing of the vort max dropping Swd this afternoon. Effective Shear indicates the potential for some mid level rotation/rotating storms. The limiting factor is the elevated instability forecast in the Bufkit forecast soundings and not surface based convection. Central Valley rotating storms are rooted in the boundary layer with low LCLs. Dewpoints in the 30s makes this more problematic. Can`t rule out a possible funnel cloud, but less likely there would be an actual touchdown. Looks as if the HRRR suggests some isolated cells in the extreme Srn Sac, Solano Co, Nrn SJV areas this afternoon. The 12z NAM 3 km keeps the precip in frozen form and basically out of the Valley. Timing of the snow advisory looks good with precip winding down around 06z. Precip amounts will be light with this system due to a dry air mass with PWs ranging from .13 at REV to .34 at MFR and .44 at OAK. These values are below average. AMSU data also indicate very low PW over the region. However, good dynamics and cold temps will result in some brief periods of heavy showers with high snow ratios. For example for BLU, using the max temp in the profile, a snow ratio of 16:1 to 18:1 is calculated for today. The average SLR is 9:1. Don`t expect normal snow water equivalents with these next few systems in the short term. After the wx system/trof moves through the area tonite, dry Nly winds will increase over the CWA, weakening Fri afternoon. Winds may continue to mix the Nrn and Wrn zones overnite, while decoupling will occur on the E side of the Valley. With clearing skies overnite, it will be another cold nite, with a brisk Nly wind on the W side of the Vly/lee-side of the Coastal Range. A couple more wx systems are forecast to drop out of the GOA in the highly amplified pattern along the W Coast of NOAM in the short term. The next system on Sat, followed by another late Sun into Mon. These systems will be similar, cold with relatively low QPF. The WR US West Coast AR Landfall tool (Probability of IVT) is virtually "bone dry" for the next 16 days. What moisture there is will be spilling over the Pac Ridge and eroding as it hits the Pac NW and spreads inland into our CWA. Even though Norcal will have the continuation of a cold, showery pattern, the QPF will be relatively low, albeit with high snow ratios. Some modest modification in temps is expected later in the weekend and into early next week. JHM && .EXTENDED DISCUSSION (Monday THROUGH Thursday) Models show a continuation of the wet pattern as several shortwaves dive southward from the Gulf of Alaska. Compared to this week`s systems, the upcoming storms have the potential to pull in some moisture from the Pacific before spreading precipitation inland. Given the cold nature of these systems, snow levels will remain low. Models are showing better agreement compared to previous forecast runs, though differences remain in terms of timing and precipitation amounts. The first system moves in Monday into Tuesday. Early precipitation estimates suggest 0.10-0.30 inches across the Valley, and around 0.25-0.65 inches over the mountains, though these amounts will likely change as we get closer to the event. A brief break is expected late Tuesday into Wednesday as weak upper ridging builds in. Then, a stronger and wetter storm will move across the area late Wednesday into Friday. Precipitation will initially impact the northern mountains on Wednesday before spreading across the forecast area on Thursday. Stay tuned to see how these systems develop as model uncertainty remains. Temperatures will remain below average as cold air continues to filter in. && .AVIATION... VFR conditions expected next 24 hours except local MVFR vicinity scattered showers and thunderstorms 22Z-02Z and widespread IFR over the northern Sierra with snow showers thru about 03Z Friday. && .STO WATCHES/WARNINGS/ADVISORIES... Winter Weather Advisory until 10 PM PST this evening for Burney Basin / Eastern Shasta County-Motherlode-Northeast Foothills/Sacramento Valley-West Slope Northern Sierra Nevada- Western Plumas County/Lassen Park. && $$