Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

FXUS63 KIWX 291023

Area Forecast Discussion
National Weather Service Northern Indiana
623 AM EDT Thu Jun 29 2017

Issued at 355 AM EDT Thu Jun 29 2017

An isolated shower or storm is possible across northern Indiana and 
northwest Ohio from late morning through early afternoon. Better 
prospects for showers and thunderstorms is expected this evening 
especially over northwest Indiana and southwest Michigan where some 
locally heavy rainfall could fall. Highs this afternoon will range 
in the low to mid 80s with increasing humidity. Drier and pleasant 
weather is expected this weekend.


.SHORT TERM...(Today and Tonight)
Issued at 355 AM EDT Thu Jun 29 2017

Immediate upstream MCS ovr lake MI continues to weaken this morning 
in response to swwd wall of convection across nrn MO. Downstream 
progression of shra curtailed though with much more stable airmass 
in place with swd extent through IN and this will not change until 
after daybreak as LLJ finally veers more wrly. That said early day 
heating and ewd theta-e ridging should promote isold-sct storm 
development by late morning into early aftn cntrl/sern areas in 
association with low level ascent plume tied to LLJ core.

Otherwise increasing mass flux/convergence expected late this aftn 
into this evening as resurging LLJ backs invof remnant outflow 
boundary which should be stalled somewhere over nrn IN. While 
marginally favorable parameter space overlaps present...severe risk 
looks quite limited given dissolution of upstream flank of plains 
based eml and lack of coherent forcing mechanism. 

Aftn based sct convection expected to weaken/die out this evening 
away from outflow boundary given absence of larger scale forcing 
which again resides well west. In fact expect another severe MCS 
will develop across IA into nrn MO again and decay with ewd extent 
overnight Thu. Will generally cut pops with e/se extent as a result 
as blend derived pops are wholefully too high.


.LONG TERM...(Friday through Wednesday) 
Issued at 355 AM EDT Thu Jun 29 2017

Nrn plains based upper trough considerably dampened in latest 00Z 
guidance cycle and as a result indicates much weaker forcing 
extending swd along ewd shifting frontal zone Fri/Fri night. In fact 
a focused convective signal is now largely absent across the srn 
lakes Fri and had shifted into the lower MS valley along nrn edge of 
most significant low level theta-e reservoir/moisture flux. Thus no 
surprise seeing continued erosion of MOS based pop guidance and will 
cut accordingly Fri aftn-Sat.

Otherwise outside a low end risk for a shower early Sat weekend 
looks dry and pleasant as low amplitude ridge builds in across the 
lakes. Thereafter a series of generally low amplitude/hard to time 
nrn stream based sw troughs to shift through srn Canada. General 
intensification of four corners based upper ridge likely to setup an 
active baroclinic zone inbetween yet deterministic placement and 
handling of individual sw troughs helter skelter. Blended pops 
across the board are much too high again and truncated in full 
throughout the remainder of the period in preference of favoring a 
lower bound chance mention versus ridging with ridiculous 
likelies at this range given scope of model irregularity.


.AVIATION...(For the 12Z TAFS through 12Z Friday Morning)
Issued at 617 AM EDT Thu Jun 29 2017

Overnight showers/storms have either moved NE or fallen apart.
High clouds reminded but should thin out with cu developing by 
late morning. Forecast not any clearer since last issuance with 
variable signals in the models regarding development of additional
convection this afternoon into tonight. 

Scenario still appear to be setup for at least isol-sct 
convection to occur at either site this afternoon with greatest 
focus possibly KFWA closer to better expected moisture and remnant
boundaries. Better chances will exist from expected upstream 
convection to move out of Iowa and Missouri this evening. 
Uncertainty regarding coverage/intensity of the activity warrants 
holding with VCSH for the time being. Convection may move out and 
end well before 12Z, but will keep simple for now. 


MI...Beach Hazards Statement until 2 PM EDT this afternoon for MIZ077.

LM...Small Craft Advisory until 2 PM EDT this afternoon for LMZ043-




Visit us at

National Weather Service Glossary of Abbreviations