Area Forecast Discussion
Issued by NWS Wilmington, OH

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000 FXUS61 KILN 151953 AFDILN Area Forecast Discussion National Weather Service Wilmington OH 253 PM EST Wed Feb 15 2017 .SYNOPSIS...
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Weak high pressure will briefly build into the area late tonight into Thursday. A warm front will develop across the region Thursday night and lift north of the area Friday. This will mark the beginning of an extended period of very warm temperatures.
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&& .NEAR TERM /THROUGH TONIGHT/...
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Cold air advection will become neutral with northwest flow persisting. So stratocumulus deck across about the eastern two thirds of the forecast area this afternoon will persist through much of the night. Clouds should keep temperatures from falling too far and have generally shaded towards warm side of MOS guidance.
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&& .SHORT TERM /THURSDAY THROUGH THURSDAY NIGHT/...
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Weak high pressure will build into the area on Thursday and low level temperature advection will turn warm. This should result in stratocumulus diminishing during the day. However, a short wave dropping into the region in northwest flow will bring a mid deck across the region Thursday afternoon into Thursday night, with these clouds moving out late Thursday night. Highs will be a few degrees higher than today. Lows will likely be reached Thursday evening with steady or even slowly rising temperatures late Thursday night.
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&& .LONG TERM /FRIDAY THROUGH TUESDAY/...
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Very high confidence that this period begins an anomalous stretch of warmth that becomes impressive by all February measures in terms of magnitude and duration. Also high confidence in weekend rainfall potential being insignificant /amounts/ focusing along and south of the Ohio River /Saturday/...and that appreciable threat of any more significant sensible weather holds off until Tuesday night/Wednesday. But all the talk will most definitely revolve around the stretch of late February warmth which begins Friday and likely goes all the way through next Friday /Day 9/. In the details...at 12Z on Friday there is strong deterministic and ensemble agreement in a deep longwave trough over Nova Scotia and compact/closed low in the active southern stream over Texas...which will be in the process of opening up/shearing northeastward into a generally unfavorable regime to support it /confluent flow/. Residual cold air with the departing longwave trough over the northeast will have long since vacated the Ohio Valley...with large pool of above normal temps set to push in as heights rise over the eastern U.S. downstream of the aforementioned trough in TX. By Saturday...agreement remains strong in the data that TX trough continues to open up/weaken as it shifts through the middle/lower MS valley...while even deeper/sharper srn stream energy digs thru southern California and old Mexico. Heights will continue to rise into Saturday morning before the remnants of the rapidly weakening upper trough reverse that trend...which will induce a threat of light rain/showers along and south of the Ohio River /nearest the maximum of pv advection aloft and height fall center/ Saturday and Saturday evening as these weak dynamics /and rather anemic moisture transport/ shift through. By 12Z Sunday...wave continues to significantly deamplify as it shifts through the Mid-Atlantic...with no sense of appreciable cold advection in its wake given srn stream origin. Attention then turns to very deep/sharp/anomalous mid/upper level trough shifting through Mexico...with impressive /climatologically significant/ height rises downstream into the Ohio Valley Sunday thru Tuesday. All manner of climo-based tools /including NAEFS standardized anomalies...NAEFS climate percentiles...etc/ suggest the mid/upper level ridge will be in the 95-99%ile in magnitude...if not outside the 30 year analysis used in these products. Not surprisingly...GEFS/ECMWF temp anomalies are running 1.5 to 2.0 sigma above climo at 925/850mb. This is a strong signal which has been duplicated over many days of ECMWF/GFS ensemble runs. A long-duration period of February warmth is expected...rivaling similar Feb. warm stretches from 2000...1976...1930...and 1880. Starting on Friday...a 5 to 7 day stretch of high temperatures averaging out in the upper 50s /central Ohio/ to lower 60s /Ohio River/ is highly likely. The warmth will peak on Monday/Tuesday before clouds with approaching moisture ahead of the now-ejecting srn stream trough temper things a little bit by Wednesday. Monday and/or Tuesday may feature a 70F reading or two along and south of the Ohio River. Latest ILN forecast is already forecasting a record high minimum temp at CVG for Tuesday /Day 6 - 51 degrees/ which is indicative of the confidence/magnitude of this warm stretch. But it is worth mentioning that upcoming warmth does not appear `record breaking` in magnitude over multiple days or with the more-often higher visibility max temperature -- as daily max temp records are near/above 70. Instead...the upcoming period appears more significant in terms of length/duration of anomalous Feb warmth. Noting that 2000 was the last /and perhaps most significant of all Feb warm spells/ it was not at all surprising to see the 15.12Z CIPS analogs suggesting the GFS-forecast pattern for late this weekend has high correlation to the pattern of late Feb/early Mar 2000. Lower confidence is noted in precipitation chances Tues/Wed of next week given speed /not so much depth/ of the srn stream trough as it ejects out of deep south TX into the wrn Gulf. All NWP solutions have a deep system...but speed /longitude/ of the trough axis is highly variable by Day 7...suggesting a general increase in rain chances is warranted in the forecast...but far too early to determine significance/coverage/timing. Given this is a strong srn stream system...with further energy again digging into the western CONUS...the warmth will likely continue well past mid-week into early next weekend.
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&& .AVIATION /20Z WEDNESDAY THROUGH MONDAY/... Stratocumulus will prevail through much of the period. The exception will be in the Cincinnati area which will be near the edge of the cloud deck, so it will be broken variable scattered there. Nonetheless, expect VFR conditions to prevail with the clouds, although cannot completely rule out a brief drop to MVFR ceilings from KDAY to KCMH/KLCK. Northwest winds will gust up to 25 kt through the daylight hours then diminish slightly overnight. Speeds will decrease to less than 10 kt on Thursday as winds back slightly. OUTLOOK...No significant weather is expected. && .ILN WATCHES/WARNINGS/ADVISORIES... OH...None. KY...None. IN...None. && $$ SYNOPSIS... NEAR TERM... SHORT TERM... LONG TERM...Binau AVIATION...

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