Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Wilmington Ohio
138 am EDT sun Mar 29 2015
high pressure will settle over central Ohio tonight and West
Virginia by daybreak Sunday. A cold front will cross the Ohio
Valley on Monday evening/overnight and should bring a shot of rain
to the region. Brief high pressure will build into the area Monday
and another low will traverse the Great Lakes and eastern Ohio
Near term /until 6 am this morning/...
high pressure overhead will shift southeast overnight allowing for
some light southerly winds in the western counties late. Skies
will remain clear with overall excellent radiational cooling
conditions. Forecast has this well handled. So only blended in
Short term /6 am this morning through Monday night/...
after a chilly start to the day southerly flow should kick in and
provide for a cool but nice Spring day. Highs in the upper 40s to
lower 50s could place higher with more sun than not and a stronger
southerly flow during the day. This would be a 35-40 degree departure
from morning lows. While these diurnal differences are larger than
typically expected...the strong southerly push ahead of the next front
suggest such a scenario.
The next cold front will push enough warm air ahead of it to wring
out available moisture starting in the later afternoon Sunday in
the west and by evening in the east. A round of showers is
expected although discontinuities in the models suggest that while
most areas see some...a few spots could miss out or only see very
little rain Sunday evening as the system works east. Have put in
around .1 to .15 inches of rain in the expected quantitative precipitation forecast from shower
activity that could be scattered as it works east through the Ohio
Valley. 500 mb dynamics are well behind/northwest of the surface front
so that thunder should not play a part in the Ohio Valley.
In the wake of the cold front west winds will only usher in low
temperatures Sun night that are in the middle 30s...a marked uptick from
this morning and tonights lows. High pressure will build into the
Ohio Valley Monday for another nice day in the 50s...potentially
higher if sun lasts longer than the clouds streaming in from the
west later in the day.
Models are all noting a decently strong surface low making a southeast
push from the Great Lakes Monday night to the middle Atlantic on
Tuesday. European has increased the threat for rain with this
system overnight and a low chance of rain has been added to northestern
County Warning Area Monday night.
Long term /Tuesday through Saturday/...
much higher confidence in days 3-4 /tues and Wednesday/ before
confidence unravels rather quickly for the end of the work week -
which is a bit unsettling as there are indications of an active
period of weather either Thursday or Friday...or both.
Tuesday begins with a rather amplified pattern still in place across
the Continental U.S. /Wrn ridge and eastern trough/ with a decent shortwave sliding
down through the Great Lakes on Tuesday morning. Good agreement that
the surface cyclone attendant to this system will slide southeast
through Northern Ohio into the middle Atlantic which puts most of our area
in strong low level warm advection through the first part of the
day. Winds will become gusty /southwest/ and increased winds
somewhat this forecast with high into the 50s and 60s. Per bufr
soundings /GFS and NAM/ expect that isentropic ascent in this
portion of the open warm sector will need to overcome rather anemic
precipitable water /below normal/ so current thinking is that bulk
of saturation and better rain potential will be along/north of track
of the low...though some scattered/light activity is possible in
cntl Ohio Tuesday morning into afternoon. A dry/breezy day for the rest
of the area.
Weak bubble high builds in the wake of this system for Tuesday
night/Wednesday with a brief bout of cold advection which will
likely temper wednesdays highs somewhat...though plenty of sunshine
will help US back into the 50s /north/ and 60s /south/ by days end
as flow begins to rapidly turn around by Wednesday evening. This
downstream of a more substantial/sharp shortwave digging through the
Montana/ND area...which will induce height rises over the Ohio Valley as
the western ridge breaks down and is shunted east. May see some shower
threat spread into the area later Wednesday night...but not an overly good
signal as forcing seems to have slowed to point to better chances
Gets interesting Thu/Fri...as initial shortwave deamplifies as it
slides east along the US/Canadian border north of the Great Lakes.
Depending on how fast system deamplifies will tell how far south
front pushes. May be a lower-end threat for a strong/severe storm Thursday
if a stronger frontal surge occurs /GFS/...but deamplifying nature
of the shortwave and slowing front...or potential for clouds to be
spreading in early Thursday limiting heating could be factor - either
way - way too early to say - and latest European model (ecmwf) is hinting front may
struggle to even make it into the area before stalling Thursday evening.
Did allow temperatures to warm nicely Thursday ahead of front on good low level
warm air advection signal /60s and 70s/.
Admittedly there is more interest/concern for Friday albeit at this
time range there are huge inconsistencies and variabilities that
will take many days to gain clarity on - but another shortwave
moving east through the nation/S midsection may pair up with stalled
front from Thursday to bring more shower/storm threats. 28.00z and
28.12z European model (ecmwf) runs are concerning in that a deepening cyclone runs NE
through the Great Lakes Friday afternoon/evening with very strong flow fields
amidst a moist warm sector as stalled front lifts north as warm
front over Ohio/Indiana. Similar runs of GFS are flatter with a cold
rain threat for the Ohio Valley as surface low pulls to the south of the
area along the further south displaced front and warm sector
remaining south. Either way - appears a deepening system will be
moving through the Ohio Valley with strong flow and baroclinicity
and potential for active weather. Given big ensemble spread /plumes
of temperature which are proxy of varying surface low tracks/...just keeping
rain chances moderate for Friday with no thunder mention until
clarity is gained...but this time period will need to be watched in
coming days given aforementioned forcing/thermal gradient.
Aviation /06z Sunday through Thursday/...
high pressure is currently located over the area allowing for calm
winds and VFR conditions. High pressure will pull to the east this
afternoon though as the next upper level disturbance approaches
from the west. Winds will be gusty today as models continue to
advertise an impressive low level jet this afternoon. Rain looks
to start in our western counties early this evening and spread
east this evening. The new NAM is about 2 to 4 hours slower
starting the precipitation than the other global models. For now will
lean with the consensus. Ceilings will also be slowly lowering through
the day today and will eventually reach MVFR by the end of the taf period.
Outlook...MVFR ceilings and visibilities possible on Thursday.