IWX issues Area Forecast Discussion (AFD) at May 12, 12:07 AM EDT
254
FXUS63 KIWX 120407
AFDIWX
Area Forecast Discussion
National Weather Service Northern Indiana
1207 AM EDT Mon May 12 2025
.KEY MESSAGES...
- Very warm in the days ahead with highs in the 80s becoming
common Monday through midweek. Increasing humidity may become
more noticeable as well.
- Periodic showers and storms are possible through much of the
week, mainly during the afternoons. Later Thursday into
Thursday night has a chance for severe weather.
&&
.DISCUSSION...
Issued at 310 PM EDT Sun May 11 2025
The high pressure center keeping the area dry reaches the
northeastern US this afternoon/evening and this allows warm air
advection to begin to take over tonight into Monday. With the
weakness in the flow, upper low trapped to our south during this dry
period starting at the end of last week begins to travel northward
on Monday. Increased moisture (we're already beginning to see
pockets of 50 degree dew points this afternoon in our south),
moves in on the outer fringes of the arriving upper low. With
this in mind, am a little bit more inclined to bring in slight
to chance PoPs as early as midday in our south on Monday even
despite the antecedent dry air. Given the enhanced moisture
profiles and some modest instability, can't totally rule out
some embedded thunder Monday evening.
As the upper low pressure center moves closer to the area for
Tuesday, it appears that a dry slot works in later Monday night into
Tuesday morning. But with vorticity around from the upper low and
increasing low level lapse rates, wouldn't be surprised to see
afternoon pop showers and storms perhaps due to differential
heating, especially with our area on the northwestern end of the
moisture stream off the western Atlantic. While minimal shear is
still expected to limit overall severity of storms, slow storm
motion and convective elements of cells may allow for locally heavy
rain. For Wednesday, the upper low continues to wash out as the next
trough advances towards the area, but it still leaves enough
vorticity around to help set off more summer-like afternoon
showers/storms. High temperatures in the 70s will continue into
midweek with low 80s also being possible.
The next trough contains a deep upper low and that pushes towards
the area for Thursday. This orientation makes it much more conducive
to introducing shear to the situation so if thunderstorms are able
to form later Thu/Thu night, the severe potential is better. Mid
level ridging is notable across the area as is low to mid level RH
so there is some question about if debris clouds may be able to
limit development of convective energy during the day Thu. 7 to 8
C/km mid level lapse rates move through the area later Thursday and
vacate the area before the overnight period. DCAPE values approach
1000 J/kg. This would allow for the possibility of both wind damage
and large hail. Additionally, better effective helicity values are
being shown, which could allow for some rotation meaning a tornado
threat could exist. SPC has continued with their slight risk of
severe weather area for this period. It is interesting to see 850 mb
temperatures forecast to reach 18C Thu, which when mixing is
maximized often leads to 90F high temperatures. According to a plot
on Iowa State Mesonet's page, Rochester rarely (since 2003), sees 90
degrees in mid May so that would be early if it is realized.
With a cold front moving through later Thu night, this likely keeps
Friday devoid of showers/storms, but the front is then expected to
stall out not too far from the area. The ECMWF/GFS camp indicates
some rain/storms could be possible Friday evening scraping our
southern 1 to 2 rows of counties as a low level jet reinvigorates to
our west on the southern side of the aforementioned upper low that
slowly heads towards the upper Great Lakes.
Next weekend looks dry again as weak high pressure follows on the
heels of the departing upper low.
&&
.AVIATION /06Z TAFS THROUGH 06Z TUESDAY/...
Issued at 1206 AM EDT Mon May 12 2025
Cutoff low over cntrl LA will slowly wobble newd into the lower OH
valley by late Tue. Backing downstream low level flow will allow for
a concerted push of mid lvl moisture across the terminals toward
early aftn. This might be enough to support a few high based, light
showers. Will reaccess rain potential for 12Z fcst but prospects for
that and potential MVFR based cigs tonight much in doubt.
&&
.IWX WATCHES/WARNINGS/ADVISORIES...
IN...None.
OH...None.
MI...None.
MARINE...None.
&&
$$
DISCUSSION...Roller
AVIATION...T
Source: IWX issues Area Forecast Discussion (AFD) at May 12, 12:07 AM EDT (https://mesonet.agron.iastate.edu/p.php?pid=202505120407-KIWX-FXUS63-AFDIWX)
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