Area Forecast Discussion
Issued by NWS Wilmington, OH

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000 FXUS61 KILN 271347 AFDILN Area Forecast Discussion National Weather Service Wilmington OH 947 AM EDT Thu Oct 27 2016 .SYNOPSIS... Low pressure and a cold front will move across the Great Lakes and Ohio Valley today with a few showers and mostly cloudy skies...and cooler temperatures. High pressure building quickly into the area tonight will break up the clouds and lead to warmer temperatures and some sunshine on Friday. Much warmer air will spread across the Ohio Valley on Saturday under a mix of clouds and sun and breezy southwest winds. After a small threat for showers Saturday night...a very warm and dry period is expected for much of next week. && .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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The cold front is pushing east across our area this morning and is currently just about to the I-71 corridor. Scattered light shower activity is continuing along and ahead of the front. This will continue to taper off across our southeast through late morning/early afternoon. Otherwise, in developing low level caa, clouds should hang in through much of the day with temperatures steadying out or possibly even dropping off a bit behind the front. ...Previous discussion... GOES water vapor loops this morning clearly show compact vort max/shortwave trough across nrn lower Michigan this morning churning east...on the backside of large scale ridging centered in the Rockies. Mesoanalysis data places surface low pressure in nrn Indiana with warm front east across central Ohio...and a sharp cold front extending from the low across Indiana to very near St. Louis. Strong warm advection is ongoing across the WFO ILN forecast area as of this hour...with time trends showing temps/dwpts on the rise...and 1km winds on various radar VWPs now exceeding 50kts out of the southwest. MRMS and regional radar mosaics showing an area of showers over central/northern OH in the isentropic ascent attendant to the aforementioned low level jet...and a narrow fineline of shra along the cold front in Indiana. GOES 11-3.9 micron difference channel indicates ample stratus and stratocumulus in the cold advection regime over wrn Indiana/Illinois/Wisconsin where temps fall off into the 40s. For today...expect batch of warm advection induced showers to continue to lift northeast out of the forecast area through sunrise...and be replaced by slowly expanding fineline of showers along the cold front. But shallowing of moisture after sunrise should mitigate coverage of rain somewhat...thus 30-50% chances through the morning hours. By afternoon...cold front will have cleared the forecast area. Steepening 1000-850mb lapse rates among the higher RH could promote a few sprinkles or light showers through early afternoon...but sharpness of subsidence inversion should limit vertical growth of any showers so by afternoon not expecting much in beyond a stray shower or sprinkle. Temperatures will rise slowly this morning ahead of the cold front...peaking mid morning...and as the cold front passes will steady out or begin a slow fall during the remainder of the daylight hours. So high temperatures were lowered over the previous forecast in large part due to the expected widespread nature of low clouds trapped underneath the rather strong/sharp subsidence inversion in the wake of the front. Breezy too...especially in central Ohio where some 25 mph gusts could be seen that will add a little chill to the air.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH SUNDAY NIGHT/... Heights will quickly begin to rise tonight into Friday as the shortwave progresses into New England the large ridge over the west builds/expands eastward into the Mississippi Valley. Surface high pressure should bring clearing skies later tonight via strong subsidence thus have temps dropping into the mid/upper 30s north of the Ohio River. A touch of frost possible in typical central Ohio cool spots but not enough to raise messaging on given this late in the growing season. Plenty of sunshine expected Friday but with weak southeasterly low level flow warming will be a little slower than previously thought so trended temps back just a bit. Otherwise - should be a beautiful autumn day with highs in the 60s. Warming really takes off as swly low level jet increases again as shortwave energy races across southern Canada...laying a slowing cold front out across MI/WI/IA. Very warm air aloft rockets into the area on breezy/gusty dry swly low level flow Saturday afternoon...pushing temperatures well into the 70s. If full sunshine is realized /not likely due to some anticipated high clouds/ temperatures may need further boosting - but regardless will be a very warm late October day with gusty winds. Originally the aforementioned front was expected to penetrate the forecast area and stall along the Ohio River...but recent 27.00Z guidance has halted the progression of the front considerably...keeping it north of the forecast area all day Saturday and Saturday evening...and bringing the dying/weakening boundary into the area Saturday night. Thus...pulled rain chances for Saturday...and delayed them until later Saturday evening/night with a focus on central Ohio. There`s still some uncertainty on a weak frontal wave which may develop along the front Saturday night which may enhance shower potential...but kept rain chances pretty low. The presence of the weak front stalling in the area on Sunday means slightly cooler temperatures than Saturday...but southern areas will need to be watched for another potential very warm day depending on how far south the boundary settles and how much sunshine develops. This part of the forecast will need to be fine-tuned in coming days. && .LONG TERM /MONDAY THROUGH WEDNESDAY/... The big message next week is a high-confidence period of much above normal temperatures...which may approach early November records. At 12Z anomalous mid/upper level ridge will be located over the eastern 1/2 of the CONUS...with the ridge axis just east of the Mississippi River. 500mb standardized anomalies per ECMWF/GEFS/CMC ensembles will be 1.5 to 2.0 sigma above climatology...strongest in the ECMWF ensemble data. Attendant 850mb/925mb temp anomalies will also be 1.0 to 1.5 sigma above climo. This ridge will shift east and build in strength on Tuesday into Wednesday...centering more in the Ohio Valley /Tuesday/ and then expanding/elongating in east/west fashion across the entire east CONUS again by Wednesday. This is a high confidence pattern in the ensemble deterministic runs should add detail and be trusted even at this time range. Latest /27.00Z/ deterministic guidance from the GFS/CMC/ECMWF all point to even stronger ridging/warmer temp anomalies than parent ensemble means...which is no surprise given ensemble means smoothing out the gradients/maximums at this time range. New 27.00Z ECMWF is bullish on warming for Tuesday...with +15C at 850mb across OH/IN/KY and around 20C at 925mb along the Ohio River. Mixing conservatively to 925mb /which should easily be attained in dry wswly boundary layer flow on Tuesday yields highs well into the 70s...and likely approaching 80F along/south of the Ohio River. Very interesting...considering this would be November 1st...and there have only been 6 November days at CVG in the entire POR where max temps have hit 80F in November. Anomalies...pattern...and boundary layer setup all suggest this could boosted high temperatures on all three of these days. Wednesday could easily be just as warm as reservoir of very warm air remains anchored over the TN valley and flow continues out of the SW. Prototype/experimental ECMWF MOS is already pegging upper 70s at CVG and mid 70s elsewhere on Tuesday...with all three of these days into the 70s across the entire CWA. Putting this into context...using CVG forecast data as proxy for the rest of the CWA...this pattern looks to be the warmest early November pattern since 2003...when CVG went 71/77/77/79 to start the month of November. And if the 27.00Z ECMWF is any indication...high temps on Wed will need boosting in future updates...with anomalous warmth through the entire week. High confidence also in Monday/Tuesday being dry...and likely into Wednesday too but confidence in rain chances begins to break down by Wednesday due to timing of a shortwave trough cresting the upper ridge in the Wed/Thu/Fri timeframe. This will likely be targeted for Thur/Fri instead of Wednesday. && .AVIATION /14Z THURSDAY THROUGH MONDAY/... Cold front is working it way through the tafs, as it has already past DAY. With the fropa, cigs there have fallen to MVFR. Have the front timed to I-71 right at 12Z, so that will make first hour of the rest of the tafs tricky. If the front hasn`t quite made it, cigs will be VFR, if fropa has occurred they will be MVFR like DAY. Went ahead and made everyone MVFR to start the forecast period, as that should be the prevailing condition for the hour. Latest observations are still showing a band of IFR cigs just behind the front. Kept an hours worth of below 1kft cigs at all the tafs, generally between 13-15Z. Cigs should recover to MVFR by late morning and stay there for the rest of the day. Winds will pick up and turn to the west behind the front as caa begins to affect the region. It doesn`t look like the MVFR cigs will begin to break up until after 00Z as surface high pressure will slowly builds in overnight. Since the low level moisture will be trapped due to the low clouds and winds will be light tonight, added some MVFR fog between 09-12Z. OUTLOOK...MVFR cigs possible Sunday. && .ILN WATCHES/WARNINGS/ADVISORIES... OH...None. KY...None. IN...None. && $$ SYNOPSIS...Binau NEAR TERM...JGL SHORT TERM...Binau LONG TERM...Binau AVIATION...Sites is the U.S. government's official web portal to all federal, state and local government web resources and services.