Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Wilmington Ohio
1000 am EST Friday Dec 20 2013
a warm...southerly flow will bring increased moisture to the Ohio
Valley into the weekend. A frontal boundary will be the focus with
significant rainfall expected to occur Saturday into Saturday
night. Colder conditions will move in behind a cold front for
Sunday and Sunday night and the first part of next week.
Near term /until 6 PM this evening/...
two bands of showers affecting the forecast area this morning. One
band moving through the southeast counties should move out over
the next few hours. Other band is lifting northeast through
Indiana and impacting the northwest counties. Expect showers to
continue off and on across this area well into the afternoon.
Elsewhere appears that showers will be scattered at most. Mild
temperatures to start should only increase modestly at best given
extensive cloud cover. But did bump up highs slightly were
readings were running a little warmer than forecast.
Short term /6 PM this evening through Sunday/...
focus continues to be on heavy rain and flood potential. With the
passage of todays surface wave there looks to be a general lull in
precipitation activity this evening. Have trimmed back probability of precipitation to
chance category for most of the night.
Regarding the placement of the heavy rain axis...some uncertainty
still exists with the NAM/European model (ecmwf) solutions trending further northwest
with this axis from central Indiana through Northwest Ohio. The GFS solution is
an outlier with the heaviest rain axis centered on Cincinnati.
06z GFS run has trended toward the ECMWF/solns. Have used a blend
of previous forecast with 00z European model (ecmwf) and NAM. Have heaviest rain axis west
of I-71...from east central Indiana through Dayton and northwest side of cmh. Will
continue Flood Watch for all but the far southeast. Have storm total
rainfall from 1.5 inches in the far southeast to 3.7 over east central
Looking at the details...surface frontal boundary looks to slip into
Northwest Ohio with next surface wave rippling northeast through Ohio late
tonight into Saturday. 50 knots 800 mb jet increases to 60kts during the
day Saturday with very favorable low level convergence developing.
Precipitable water/S increase to 1.5 inches or over 300 percent of normal during the
day Saturday. Models are also bringing in some instability...with
the NAM being the most unstable into the far south. Have continued
mention a chance of a rumble of thunder mainly across the S early
Sat. Will mention heavy rain late tonight. Temperatures stay mild with
lows from the lower 40s northwest to the lower 50s southeast.
During the day light hours on Saturday there will likely be a break in
precipitation across the southeast the the main focus across east central Indiana and west
central Ohio. Have heavy rain mention across northwest half of iln/S forecast area.
Have bumped up temperatures in the southeast with highs in the middle 60s to the
middle 40s far northwest.
As middle level flow phases...southern short wave to lift NE from Southern Plains
late Sat night through the Great Lakes Sunday. In response to this
short wave main surface wave to track to our west across Indiana Sat night into
the Great Lakes Sunday. Models show instability across southeast ahead of approaching
cold front late Sat night/early Sunday. Therefore...have included
another chance of thunder. Precipitation expected to diminish from west
to east Sunday morning with the passage of associated cold front.
Have continued to allow for redevelopment of precipitation into the northwest
late due to warp around. Have non-diurnal temperatures Sunday with the
early frontal passage...with highs ranging from the upper 40s northwest to the
lower 60s southeast.
Long term /Sunday night through Thursday/...
weak upper system/trough comes through Sunday night with
scattered light rash/snsh as colder air works in. Still may be
some flurries or light snow showers on Monday and Monday evening
as cold air flows over lakes but left probability of precipitation out for now. Ridge
moves over area Tuesday and Wednesday with dry conditions and near
seasonably cold temperatures. Models indicating a weak system for late
Wednesday night into Thursday evening which probably produces a
light snow event. Will include low chance probability of precipitation for now. Temperatures tricky
for Sunday depending on any sunshine and strength of cold air advection. Should a
see a small rise before a slow fall in the afternoon. Near
guidance on temperatures for rest of forecast period.
Aviation /15z Friday through Tuesday/...
scattered showers will affect the terminals through the day. MVFR
ceilings will prevail and may lower to below 2000 feet before 00z.
Heavier rain with IFR is forecast starting at 03z Saturday. Rain
is expected to continue through the end of the forecast and beyond
as moisture is replenished on a very strong low level jet. South
winds will gust over 2o knots during the afternoon.
Outlook...IFR will persist Saturday into Sunday. Conditions will
likely improve to MVFR on Sunday with MVFR ceilings lingering
Sunday night into Monday.
Ohio...Flood Watch from late tonight through Sunday morning for
Kentucky...Flood Watch from late tonight through Sunday morning for
In...Flood Watch from late tonight through Sunday morning for