Area forecast discussion
National Weather Service Indianapolis in
1223 am EDT sun may 19 2013
Update...
The aviation section has been updated below.
&&
Synopsis...
issued at 200 PM EDT Sat may 18 2013
A weak area of low pressure will exit the Ohio Valley tonight
bringing chances for showers and thunderstorms to an end. A weak
ridge of high pressure will build across the area on
Sunday...keeping dry and warm weather across central Indiana through
the beginning of the work week. A few stormy days are possible
during the middle of the week as a stronger area of low pressure
develops over the plains states and allows more favorable conditions
for storms across Indiana.
&&
Near term /rest of tonight/...
issued at 956 PM EDT Sat may 18 2013
Isolated showers continue across central Indiana this evening with
some instability and weak convergence. As instability wanes for the
rest of the evening...the showers should dissipate. Have continued
isolated mention through midnight.
Looks like patchy fog will form overnight with a moist airmass and
some clearing. Best chances for fog will be in areas that saw rain
today. Have added patchy fog to the forecast and the hazardous
weather outlook.
Only made minor changes to temperatures.
&&
Short term /Sunday through Tuesday/...
issued at 200 PM EDT Sat may 18 2013
Main forecast challenge during this period will be temperatures.
Through Monday...GFS and NAM both suggest strong ridging building
across the area. Forecast soundings show a good middle level
inversion in place which should limit convection each afternoon.
Good warm air advection during the afternoon hours show 700mb
temperatures reaching 10c by 00z Monday. Thus will trend toward a dry
forecast. NAM does hint as some upper support pushing out of the
developing low over the Central Plains into Northwest Indiana on
Monday afternoon...however confidence in this feature is not great
at this time...and GFS appears to be a bit slower.
850 mb temperatures look to soar to near 14-16c on Sunday and Monday.
Even though some afternoon cumulus will be expected...plenty of sun
should be seen under the ridge. Thus will trend highs on Sunday
and Monday at or above guidance. Monday may feel like July with
highs near 90 at many locations. Given the warm air mass will also
trends lows at or above guidance...especially in the urban heat
island.
GFS and NAM suggest the strong upper low over the plains states
will push closer to Indiana on Monday night and Tuesday...ejecting
short waves into Indiana. A warm and moist air mass will be in
place at the surface with dew points in the middle 60s. Meanwhile
the NAM suggests a warm front setting up over northern
Indiana...providing a focus for convection. Forecast soundings show
great amounts of cape...over 2000 j/kg on Monday night and
Tuesday...with very favorable Li/S indicating a steep lapse rates.
18z Tuesday convective temperatures appear to be in the upper
80s...but fall as the afternoon progresses. Should the cap be
broken...Tuesday could be a severe weather day. Thus will
continue with chances for thunderstorms and rain both on Monday night and Tuesday.
Again with the very warm air mass in place will trend highs and
lows at or above guidance.
&&
Long term /Wednesday through Saturday/...
issued at 200 PM EDT Sat may 18 2013
Ensembles are in fairly good agreement on the upcoming weather
pattern over the second half of next week. Upper low initially over
the plains at the tail end of the short term is expected to slowly
shift east across the area during this period. Ensembles are a
little slower with this feature than they were yesterday...with a
few members lingering the effects of the upper low into Friday. Will
continue to hit the probability of precipitation hardest on Wednesday...but if current
trends continue...may need to increase probability of precipitation on Thursday as well.
Will also keep some chance probability of precipitation on Friday to cover the potential for
the slower solutions.
Will go with a dry forecast by next Saturday as the upper low
continues to shift east...however there are a few members that
suggest the tail end of the upper trough may cutoff over the Ohio
Valley next weekend. Not the more likely solution at this
point...but something to watch.
&&
Aviation /discussion for the 19/06z tafs/...
issued at 1223 am EDT sun may 19 2013
Rapid refresh suggests the showers should be over by issuance
time...and ridging should keep the terminals dry through the taf
period. However...cumulus development forecasts suggest scattered to broken
borderline MVFR/VFR diurnal cumulus after 15z.
Should see more MVFR and tempo IFR fog and or stratus after 06z with
light to calm east to southeast winds. Winds will be south on Sunday
less than 10 knots and south 4 to 8 knots Sunday night as pressure
gradient begins to tighten a bit ahead of an approaching plains
frontal system.
&&
Ind watches/warnings/advisories...none.
&&
$$
Synopsis...puma
near term...50
short term...puma
long term....jas
aviation...mk
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